3066	----	University, and Alev Akman THE RED MAN'S CONTINENT A CHRONICLE OF ABORIGINAL AMERICA By Ellsworth Huntington NEW HAVEN: YALE UNIVERSITY PRESS TORONTO: GLASGOW, BROOK & CO. LONDON: HUMPHREY MILFORD OXFORD UNIVERSITY PRESS 1919 PREFACE In writing this book the author has aimed first to present in readable form the main facts about the geographical environment of American history. Many important facts have been omitted or have been touched upon only lightly because they are generally familiar. On the other hand, special stress has been laid on certain broad phases of geography which are comparatively unfamiliar. One of these is the similarity of form between the Old World and the New, and between North and South America; another is the distribution of indigenous types of vegetation in North America; and a third is the relation of climate to health and energy. In addition to these subjects, the influence of geographical conditions upon the life of the primitive Indians has been emphasized. This factor is especially important because people without iron tools and beasts of burden, and without any cereal crops except corn, must respond to their environment very differently from civilized people of today. Limits of space and the desire to make this book readable have led to the omission of the detailed proof of some of the conclusions here set forth. The special student will recognize such cases and will not judge them until he has read the author's fuller statements elsewhere. The general reader, for whom this book is designed, will be thankful for the omission of such purely technical details. CONTENTS I. THE APPROACHES TO AMERICA II. THE FORM OF THE CONTINENT III. THE GEOGRAPHIC PROVINCES OF NORTH AMERICA IV. THE GARMENT OF VEGETATION V. THE RED MAN IN AMERICA BIBLIOGRAPHICAL NOTE THE RED MAN'S CONTINENT CHAPTER I. THE APPROACHES TO AMERICA Across the twilight lawn at Hampton Institute straggles a group of sturdy young men with copper-hued complexions. Their day has been devoted to farming, carpentry, blacksmithing, or some other trade. Their evening will be given to study. Those silent dignified Indians with straight black hair and broad, strong features are training their hands and minds in the hope that some day they may stand beside the white man as equals. Behind them, laughing gayly and chattering as if without a care in the world, comes a larger group of kinky-haired, thick-lipped youths with black skins and African features. They, too, have been working with the hands to train the mind. Those two diverse races, red and black, sit down together in a classroom, and to them comes another race. The faces that were expressionless or merely mirthful a minute ago light up with serious interest as the teacher comes into the room. She stands there a slender, golden-haired, blue-eyed Anglo-Saxon girl just out of college--a mere child compared with the score of swarthy, stalwart men as old as herself who sit before her. Her mobile features seem to mirror a hundred thoughts while their impassive faces are moved by only one. Her quick speech almost trips in its eagerness not to waste the short, precious hour. Only a strong effort holds her back while she waits for the slow answers of the young men whom she drills over and over again in simple problems of arithmetic. The class and the teacher are an epitome of American history. They are more than that. They are an epitome of all history. History in its broadest aspect is a record of man's migrations from one environment to another. America is the last great goal of these migrations. He who would understand its history must know its mountains and plains, its climate, its products, and its relation to the sea and to other parts of the world. He must know more than this, however, for he must appreciate how various environments alter man's energy and capacity and give his character a slant in one direction or another. He must also know the paths by which the inhabitants have reached their present homes, for the influence of former environments upon them may be more important than their immediate surroundings. In fact, the history of North America has been perhaps more profoundly influenced by man's inheritance from his past homes than by the physical features of his present home. It is indeed of vast importance that trade can move freely through such natural channels as New York Harbor, the Mohawk Valley, and the Great Lakes. It is equally important that the eastern highlands of the United States are full of the world's finest coal, while the central plains raise some of the world's most lavish crops. Yet it is probably even more important that because of his inheritance from a remote ancestral environment man is energetic, inventive, and long-lived in certain parts of the American continent, while elsewhere he has not the strength and mental vigor to maintain even the degree of civilization to which he seems to have risen. Three streams of migration have mainly determined the history of America. One was an ancient and comparatively insignificant stream from Asia. It brought the Indian to the two great continents which the white man has now practically wrested from him. A second and later stream was the great tide which rolled in from Europe. It is as different from the other as West is from East. Thus far it has not wholly obliterated the native people, for between the southern border of the United States on the one hand, and the northern borders of Argentina, Chile, and Uruguay on the other, the vast proportion of the blood is still Indian. The European tide may in time dominate even this region, but for centuries to come the poor, disinherited Indians will continue to form the bulk of the population. The third stream flowed from Africa and was as different from either of the others as South is from North. The differences between one and another of these three streams of population and the antagonisms which they have involved have greatly colored American history. The Indian, the European, and the Negro apparently differ not only in outward appearance but in the much more important matter of mentality. According to Brinton * the average brain capacity of Parisians, including adults of both sexes, is 1448 cubic centimeters. That of the American Indian is 1376, and that of the Negro 1344 cubic centimeters. With this difference in size there appears to be a corresponding difference in function. Thus far not enough accurate tests have been made upon Indians to enable us to draw reliable conclusions. The Negro, however, has been tested on an extensive scale. The results seem to leave little doubt that there are real and measurable differences in the mental powers of races, just as we know to be the case among individuals. The matter is so important that we may well dwell on it a moment before turning to the cause of the differences in the three streams of American immigrants. If there is a measurable difference between the inherent brain power of the white race and the black, it is practically certain that there are also measurable differences between the white and the red. * D. G. Brinton. "The American Race." Numerous tests indicate that in the lower mental powers there is no great difference between the black and the white. In physical reactions one is as quick as the other. In the capacity of the senses and in the power to perceive and to discriminate between different kinds of objects there is also practical equality. When it comes to the higher faculties, however, such as judgment, inventiveness, and the power of organization, a difference begins to be apparent. These, as Ferguson * says, are the traits that "divide mankind into the able and the mediocre, the brilliant and the dull, and they determine the progress of civilization more directly than do the simple fundamental powers which man has in common with the lower animals." On the basis of the most exhaustive study yet made, Ferguson believes that, apart from all differences due to home training and environment, the average intellectual power of the colored people of this country is only about three-fourths as great as that of white persons of the same amount of training. He believes it probable, indeed, that this estimate is too high rather than too low. As to the Indian, his past achievements and present condition indicate that intellectually he stands between the white man and the Negro in about the position that would be expected from the capacity of his brain. If this is so, the mental differences in the three streams of migration to America are fully as great as the outward and manifest physical differences and far more important. * G. O. Ferguson. "The Psychology of the Negro," New York, 1916. Why does the American Indian differ from the Negro, and the European from both? This is a question on which we can only speculate. But we shall find it profitable to study the paths by which these diverse races found their way to America from man's primeval home. According to the now almost universally accepted theory, all the races of mankind had a common origin. But where did man make the change from a four-handed, tree-dwelling little ape to a much larger, upright creature with two hands and two feet? It is a mistake to suppose that because he is hairless he must have originated in a warm climate. In fact quite the opposite seems to be the case, for apparently he lost his hair because he took to wearing the skins of slain beasts in order that he might have not only his own hair but that of other animals as a protection from the cold. In our search for the starting-place of man's slow migration to America our first step should be to ascertain what responses to physical environment are common to all men. If we find that all men live and thrive best under certain climatic conditions, it is fair to assume that those conditions prevailed in man's original home, and this conclusion will enable us to cast out of the reckoning the regions where they do not prevail. A study of the relations of millions of deaths to weather conditions indicates that the white race is physically at its best when the average temperature for night and day ranges from about 50 to 73 degrees F. and when the air is neither extremely moist nor extremely dry. In addition to these conditions there must be not only seasonal changes but frequent changes from day to day. Such changes are possible only where there is a distinct winter and where storms are of frequent occurrence. The best climate is, therefore, one where the temperature ranges from not much below the freezing-point at night in winter to about 80 degrees F. by day in summer, and where the storms which bring daily changes are frequent at all seasons. Surprising as it may seem, this study indicates that similar conditions are best for all sorts of races. Finns from the Arctic Circle and Italians of sunny Sicily have the best health and greatest energy under practically the same conditions; so too with Frenchmen, Japanese, and Americans. Most surprising of all, the African black man in the United States is likewise at his best in essentially the same kind of weather that is most favorable for his white fellow-citizens, and for Finns, Italians, and other races. For the red race, no exact figures are available, but general observation of the Indian's health and activity suggests that in this respect he is at one with the rest of mankind. For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race. Such a characteristic must have become firmly fixed in the human constitution before primitive man became divided into races, or at least before any of the races had left their original home and started on their long journey to America. On the way to this continent one race took on a dark reddish or brownish hue and its hair grew straight and black; another became black skinned and crinkly-haired, while a third developed a white skin and wavy blonde hair. Yet throughout the thousands of years which brought about these changes, all the races apparently retained the indelible constitutional impress of the climate of their common birthplace. Man's physical adaptation to climate seems to be a deep-seated physiological fact like the uniformity of the temperature of the blood in all races. Just as a change in the temperature of the blood brings distress to the individual, so a change of climate apparently brings distress to a race. Again and again, to be sure, on the way to America, and under many other circumstances, man has passed through the most adverse climates and has survived, but he has flourished and waxed strong only in certain zones. Curiously enough man's body and his mind appear to differ in their climatic adaptations. Moreover, in this respect the black race, and perhaps the red, appears to be diverse from the white. In America an investigation of the marks of students at West Point and Annapolis indicates that the best mental work is done when the temperature averages not much above 40 degrees F. for night and day together. Tests of school children in Denmark point to a similar conclusion. On the other hand, daily tests of twenty-two Negroes at Hampton Institute for sixteen months suggest that their mental ability may be greatest at a temperature only a little lower than that which is best for the most efficient physical activity. No tests of this sort have ever been made upon Indians, but such facts as the inventiveness of the Eskimo, the artistic development of the people of northern British Columbia and southern Alaska, and the relatively high civilization of the cold regions of the Peruvian plateau suggest that the Indian in this respect is more like the white race than the black. Perhaps man's mental powers underwent their chief evolution after the various races had left the aboriginal home in which the physical characteristics became fixed. Thus the races, though alike in their physical response to climate, may possibly be different in their mental response because they have approached America by different paths. Before we can understand how man may have been modified on his way from his original home to America, we must inquire as to the geographical situation of that home. Judging by the climate which mankind now finds most favorable, the human race must have originated in the temperate regions of Europe, Asia, or North America. We are not entirely without evidence to guide to a choice of one of the three continents. There is a scarcity of indications of preglacial man in the New World and an abundance of such indications in the Old. To be sure, several skulls found in America have been supposed to belong to a time before the last glacial epoch. In every case, however, there has been something to throw doubt on the conclusion. For instance, some human bones found at Vero in Florida in 1915 seem to be very old. Certain circumstances, however, suggest that possibly they may not really belong to the layers of gravel in which they were discovered but may have been inserted at some later time. In the Old World, on the contrary, no one doubts that many human skulls and other parts of skeletons belong to the interglacial epoch preceding the last glacial epoch, while some appear to date from still more remote periods. Therefore no matter at what date man may have come to America, it seems clear that he existed in the Old World much earlier. This leaves us to choose between Europe and Asia. The evidence points to central Asia as man's original home, for the general movement of human migrations has been outward from that region and not inward. So, too, with the great families of mammals, as we know from fossil remains. From the earliest geological times the vast interior of Asia has been the great mother of the world, the source from which the most important families of living things have come. Suppose, then, that we place in central Asia the primitive home of the thin-skinned, hairless human race with its adaptation to a highly variable climate with temperatures ranging from freezing to eighty degrees. Man could not stay there forever. He was bound to spread to new regions, partly because of his innate migratory tendency and partly because of Nature's stern urgency. Geologists are rapidly becoming convinced that the mammals spread from their central Asian point of origin largely because of great variations in climate. * Such variations have taken place on an enormous scale during geological times. They seem, indeed, to be one of the most important factors in evolution. Since early man lived through the successive epochs of the glacial period, he must have been subject to the urgency of vast climatic changes. During the half million years more or less of his existence, cold, stormy, glacial epochs lasting tens of thousands of years have again and again been succeeded by warm, dry, interglacial epochs of equal duration. * W. D. Matthew. "Climate and Evolution," N. Y. Acad. Sci., 1915. During the glacial epochs the interior of Asia was well watered and full of game which supplied the primitive human hunters. With the advent of each interglacial epoch the rains diminished, grass and trees disappeared, and the desert spread over enormous tracts. Both men and animals must have been driven to sore straits for lack of food. Migration to better regions was the only recourse. Thus for hundreds of thousands of years there appears to have been a constantly recurring outward push from the center of the world's greatest land mass. That push, with the consequent overcrowding of other regions, seems to have been one of the chief forces impelling people to migrate and cover the earth. Among the primitive men who were pushed outward from the Asian deserts during a period of aridity, one group migrated northeastward toward the Kamchatkan corner of Asia. Whether they reached Bering Sea and the Kamchatkan shore before the next epoch of glaciation we do not know. Doubtless they moved slowly, perhaps averaging only a few score or a hundred miles per generation, for that is generally the way with migrations of primitive people advancing into unoccupied territory. Yet sometimes they may have moved with comparative rapidity. I have seen a tribe of herdsmen in central Asia abandon its ancestral home and start on a zigzag march of a thousand miles because of a great drought. The grass was so scanty that there was not enough to support the animals. The tribe left a trail of blood, for wherever it moved it infringed upon the rights of others and so with conflict was driven onward. In some such way the primitive wanderers were kept in movement until at last they reached the bleak shores of the North Pacific. Even there something--perhaps sheer curiosity--still urged them on. The green island across the bay may have been so enticing that at last a raft of logs was knotted together with stout withes. Perhaps at first the men paddled themselves across alone, but the hunting and fishing proved so good that at length they took the women and children with them, and so advanced another step along the route toward America. At other times distress, strife, or the search for game may have led the primitive nomads on and on along the coast until a day came when the Asian home was left and the New World was entered. The route by which primitive man entered America is important because it determined the surroundings among which the first Americans lived for many generations. It has sometimes been thought that the red men came to America by way of the Kurile Islands, Kamchatka, and the Aleutian Islands. If this was their route, they avoided a migration of two or three thousand miles through one of the coldest and most inhospitable of regions. This, however, is far from probable. The distance from Kamchatka to the first of the Aleutian Islands is over one hundred miles. As the island is not in sight from the mainland, there is little chance that a band of savages, including women, would deliberately sail thither. There is equally little probability that they walked to the island on the ice, for the sea is never frozen across the whole width. Nevertheless the climate may at that time have been colder than now. There is also a chance that a party of savages may have been blown across to the island in a storm. Suppose that they succeeded in reaching Bering Island, as the most Asiatic of the Aleutians is called, the next step to Copper Island would be easy. Then, however, there comes a stretch of more than two hundred miles. The chances that a family would ever cross this waste of ocean are much smaller than in the first case. Still another possibility remains. Was there once a bridge of land from Asia to America in this region? There is no evidence of such a link between the two continents, for a few raised beaches indicate that during recent geological times the Aleutian Islands have been uplifted rather than depressed. The passage from Asia to America at Bering Strait, on the other hand, is comparatively easy. The Strait itself is fifty-six miles wide, but in the middle there are two small islands so that the longest stretch of water is only about thirty-five miles. Moreover the Strait is usually full of ice, which frequently becomes a solid mass from shore to shore. Therefore it would be no strange thing if some primitive savages, in hunting for seals or polar bears, crossed the Strait, even though they had no boats. Today the people on both sides of the Strait belong to the American race. They still retain traditions of a time when their ancestors crossed this narrow strip of water. The Thilanottines have a legend that two giants once fought fiercely on the Arctic Ocean. One would have been defeated had not a man whom he had befriended cut the tendon of his adversary's leg. The wounded giant fell into Bering Strait and formed a bridge across which the reindeer entered America. Later came a strange woman bringing iron and copper. She repeated her visits until the natives insulted her, whereupon she went underground with her fire-made treasures and came back no more. Whatever may have been the circumstances that led the earliest families to cross from Asia to America, they little recked that they had found a new continent and that they were the first of the red race. Unless the first Americans came to the new continent by way of the Kurile and Aleutian Islands, it was probably their misfortune to spend many generations in the cold regions of northeastern Asia and northwestern America. Even if they reached Alaska by the Aleutian route but came to the islands by way of the northern end of the Kamchatkan Peninsula, they must have dwelt in a place where the January temperature averages -10 degrees F. and where there are frosts every month in the year. If they came across Bering Strait, they encountered a still more severe climate. The winters there are scarcely worse than in northern Kamchatka, but the summers are as cold as the month of March in New York or Chicago. Perhaps a prolonged sojourn in such a climate is one reason for the stolid character of the Indians. Of course we cannot speak with certainty, but we must, in our search for an explanation, consider the conditions of life in the far north. Food is scanty at all times, and starvation is a frequent visitor, especially in winter when game is hard to get. The long periods of cold and darkness are terribly enervating. The nervous white man goes crazy if he stays too long in Alaska. Every spring the first boats returning to civilization carry an unduly large proportion of men who have lost their minds because they have endured too many dark, cold winters. His companions say of such a man, "The North has got him." Almost every Alaskan recognizes the danger. As one man said to a friend, "It is time I got out of here." "Why?" said the friend, "you seem all right. What's the matter?" "Well," said the other, "you see I begin to like the smell of skunk cabbage, and, when a man gets that way, it's time he went somewhere else." The skunk cabbage, by the way, grows in Alaska in great thickets ten feet high. The man was perfectly serious, for he meant that his mind was beginning to act in ways that were not normal. Nowhere is the strain of life in the far north better described than in the poems of Robert W. Service. Oh, the awful hush that seemed to crush me down on every hand, As I blundered blind with a trail to find through that blank and bitter land; Half dazed, half crazed in the winter wild, with its grim heartbreaking woes, And the ruthless strife for a grip on life that only the sourdough knows! North by the compass, North I pressed; river and peak and plain Passed like a dream I slept to lose and waked to dream again. River and plain and mighty peak--and who could stand unawed? As their summits blazed, he could stand undazed at the foot of the throne of God. North, aye, North, through a land accurst, shunned by the scouring brutes, And all I heard was my own harsh word and the whine of the malamutes, Till at last I came to a cabin squat, built in the side of a hill, And I burst in the door, and there on the floor, frozen to death, lay Bill. * * From "Ballads of a Cheechako." The human organism inherits so delicate an adjustment to climate that, in spite of man's boasted ability to live anywhere, the strain of the frozen North eliminates the more nervous and active types of mind. Only those can endure whose nerves lack sensitiveness and who are able to bear long privation and the strain of hunger and cold and darkness. Though the Indian may differ from the white man in many respects, such conditions are probably as bad for him as for any race. For this reason it is not improbable that long sojourns at way stations on the cold, Alaskan route from central Asia may have weeded out certain types of minds. Perhaps that is why the Indian, though brave, stoical, and hardy, does not possess the alert, nervous temperament which leads to invention and progress. The ancestors of the red man unwittingly chose the easiest path to America and so entered the continent first, but this was their misfortune. They could not inherit the land because they chose a path whose unfavorable influence, exerted throughout centuries, left them unable to cope with later arrivals from other directions. The parts of America most favorable for the Indian are also best for the white man and Negro. There the alerter minds of the Europeans who migrated in the other direction have quickly eliminated the Indian. His long northern sojourn may be the reason why farther south in tropical lands he is even now at a disadvantage compared with the Negro or with the coolie from the East Indies. In Central America, for instance, it is generally recognized that Negroes stand the heat and moisture of the lowlands better than Indians. According to a competent authority: "The American Indians cannot bear the heat of the tropics even as well as the European, not to speak of the African race. They perspire little, their skin becomes hot, and they are easily prostrated by exertion in an elevated temperature. They are peculiarly subject to diseases of hot climates, as hepatic disorders, showing none of the immunity of the African. Furthermore, the finest physical specimens of the race are found in the colder regions of the temperate zones, the Pampas and Patagonian Indians in the south, the Iroquois and Algonkins in the north; whereas, in the tropics they are generally undersized, short-lived, of inferior muscular force and with slight tolerance of disease." * "No one," adds another observer, "could live among the Indians of the Upper Amazon without being struck with their constitutional dislike to heat. The impression forced itself upon my mind that the Indian lives as a stranger or immigrant in these hot regions." * * Thus when compared with the other inhabitants of America, from every point of view the Indian seems to be at a disadvantage, much of which may be due to the path which he took from the Old World to the New. * D. G. Brinton, "The American Race," pp. 34, 35. * * H. W. Bates, "The Naturalist on the River Amazons." vol.II, pp. 200, 201. Before the red man lost his American heritage, he must have enjoyed it for thousands upon thousands of years. Otherwise he never could have become so different from his nearest relative, the Mongol. The two are as truly distinct races as are the white man and the Malay. Nor could the Indians themselves have become so extraordinarily diverse except during the lapse of thousands of years. The Quichua of the cold highlands of Peru is as different from the Maya of Yucatan or the Huron of southern Canada as the Swede is from the Armenian or the Jew. The separation of one stock from another has gone so far that almost countless languages have been developed. In the United States alone the Indians have fifty-five "families" of languages and in the whole of America there are nearly two hundred such groups. These comprise over one thousand distinct languages which are mutually unintelligible and at least as different as Spanish and Italian. Such differences might arise in a day at the Tower of Babel, but in the processes of evolution they take thousands of years. During those thousands of years the red man, in spite of his Arctic handicap, by no means showed himself wholly lacking in originality and inventive ability. In Yucatan two or three thousand years ago the Mayas were such good scientists and recorded their observations of the stars so accurately that they framed a calendar more exact than any except the one that we have used for the last two centuries. They showed still greater powers of mind in inventing the art of writing and in their architecture. Later we shall depict the environment under which these things occurred; it is enough to suggest in passing that perhaps at this period the ancestors of the Indians had capacities as great as those of any people. Today they might possibly hold their own against the white man, were it not for the great handicap which they once suffered because Asia approaches America only in the cold, depressing north. The Indians were not the only primitive people who were driven from central Asia by aridity. Another group pushed westward toward Europe. They fared far better than their Indian cousins who went to the northeast. These prospective Europeans never encountered benumbing physical conditions like those of northeastern Asia and northwestern America. Even when ice shrouded the northern part of Europe, the rest of the continent was apparently favored with a stimulating climate. Then as now, Europe was probably one of the regions where storms are most frequent. Hence it was free from the monotony which is so deadly in other regions. When the ice retreated our European ancestors doubtless followed slowly in its wake. Thus their racial character was evolved in one of the world's most stimulating regions. Privation they must have suffered, and hardihood and boldness were absolutely essential in the combat with storms, cold, wild beasts, fierce winds, and raging waves. But under the spur of constant variety and change, these difficulties were merely incentives to progress. When the time came for the people of the west of Europe to cross to America, they were of a different caliber from the previous immigrants. Two facts of physical geography brought Europe into contact with America. One of these was the islands of the North, the other the trade-winds of the South. Each seems to have caused a preliminary contact which failed to produce important results. As in the northern Pacific, so in the northern Atlantic, islands are stepping-stones from the Old World to the New. Yet because in the latter case the islands are far apart, it is harder to cross the water from Norway and the Lofoten Islands to Iceland and Greenland than it is to cross from Asia by way of the Aleutian Islands or Bering Strait. Nevertheless in the tenth century of the Christian era bold Norse vikings made the passage in the face of storm and wind. In their slender open ships they braved the elements on voyage after voyage. We think of the vikings as pirates, and so they were. But they were also diligent colonists who tilled the ground wherever it would yield even the scantiest living. In Iceland and Greenland they must have labored mightily to carry on the farms of which the Sagas tell us. When they made their voyages, honest commerce was generally in their minds quite as much as was plunder. Leif, the son of that rough Red Eric who first settled Greenland, made a famous voyage to Vinland, the mainland of America. Like so many other voyagers he was bent on finding a region where men could live happily and on filling his boats with grapes, wood, or other commodities worth carrying home. In view of the energy of the Norsemen, the traces of their presence in the Western Hemisphere are amazingly slight. In Greenland a few insignificant heaps of stones are supposed to show where some of them built small villages. Far in the north Stefansson found fair-haired, blue-eyed Eskimos. These may be descendants of the Norsemen, although they have migrated thousands of miles from Greenland. In Maine the Micmac Indians are said to have had a curious custom which they may have learned from the vikings. When a chief died, they chose his largest canoe. On it they piled dry wood, and on the wood they placed the body. Then they set fire to the pile and sent the blazing boat out to sea. Perhaps in earlier times the Micmacs once watched the flaming funeral pyre of a fair-haired viking. As the ruddy flames leaped skyward and were reflected in the shimmering waves of the great waters the tribesmen must have felt that the Great Spirit would gladly welcome a chief who came in such a blaze of glory. * * For this information I am indebted to Mr. Stansbury Hagar. It seems strange that almost no other traces of the strong vikings are found in America. The explanation lies partly in the length and difficulty of the ocean voyage, and partly in the inhospitable character of the two great islands that served as stepping-stones from the Old World to the New. Iceland with its glaciers, storms, and long dreary winters is bad enough. Greenland is worse. Merely the tip of that island was known to the Norse--and small wonder, for then as now most of Greenland was shrouded in ice. Various Scandinavian authors, however, have thought that during the most prosperous days of the vikings the conditions in Greenland were not quite so bad as at the present day. One settlement, Osterbyden, numbered 190 farms, 12 churches, 2 monasteries, and 1 bishopric. It is even stated that apple-trees bore fruit and that some wheat was raised. "Cattle-raising and fishing," says Pettersson, "appear to have procured a good living.... At present the whole stock of cattle in Greenland does not amount to 100 animals." * In those days the ice which borders all the east coast and much of the west seems to have been less troublesome than now. In the earliest accounts nothing is said of this ice as a danger to navigation. We are told that the best sailing route was through the strait north of Cape Farewell Island, where today no ships can pass because of the ice. Since the days of the Norsemen the glaciers have increased in size, for the natives say that certain ruins are now buried beneath the ice, while elsewhere ruins can be seen which have been cut off from the rest of the country by advancing glacial tongues. * O. Pettersson, "Climatic Variations in Historic and Prehistoric Times." Svenska Hydrogrifisk--Biologiska Kommissioneur Skrifter, Haft V. Stockholm. Why the Norsemen disappeared from the Western Hemisphere we do not exactly know, but there are interesting hints of an explanation. It appears that the fourteenth century was a time of great distress. In Norway the crops failed year after year because of cold and storms. Provinces which were formerly able to support themselves by agriculture were obliged to import food. The people at home were no longer able to keep in touch with the struggling colony in Greenland. No supplies came from the home land, no reenforcements to strengthen the colonists and make them feel that they were a part of the great world. Moreover in the late Norse sagas much is said about the ice along the Greenland coast, which seems to have been more abundant than formerly. Even the Eskimos seem to have been causing trouble, though formerly they had been a friendly, peaceable people who lived far to the north and did not disturb the settlers. In the fourteenth century, however, they began to make raids such as are common when primitive people fall into distress. Perhaps the storms and the advancing ice drove away the seals and other animals, so that the Eskimos were left hungry. They consequently migrated south and, in the fifteenth century, finally wiped out the last of the old Norse settlers. If the Norse had established permanent settlements on the mainland of North America, they might have persisted to this day. As it was, the cold, bleak climate of the northern route across the Atlantic checked their progress. Like the Indians, they had the misfortune of finding a route to America through regions that are not good for man. Though islands may be stepping-stones between the Old World and the New, they have not been the bringers of civilization. That function in the history of man has been left to the winds. The westerlies, however, which are the prevailing winds in the latitude of the United States and Europe, have not been of much importance. On the Atlantic side they were for many centuries a barrier to contact between the Old World and the New. On the Pacific side they have been known to blow Japanese vessels to the shores of America contrary to the will of the mariners. Perhaps the same thing may have happened in earlier times. Asia may thus have made some slight contribution to primitive America, but no important elements of civilization can be traced to this source. From latitude 30 degrees N. to 30 degrees S. the tradewinds prevail. As they blow from the east, they make it easy for boats to come from Africa to America. In comparatively recent times they brought the slave ships from the Guinea coast to our Southern States. The African, like the Indian, has passed through a most unfavorable environment on his way from central Asia to America. For ages he was doomed to live in a climate where high temperature and humidity weed out the active type of human being. Since activity like that of Europe means death in a tropical climate, the route by way of Africa has been if anything worse than by Bering Strait. By far the most important occurrence which can be laid at the door of the trade-winds is the bringing of the civilization of Europe and the Mediterranean to the New World. Twice this may have happened, but the first occurrence is doubtful and left only a slight impress. For thousands of years the people around the Mediterranean Sea have been bold sailors. Before 600 B.C. Pharaoh Necho, so Herodotus says, had sent Phenician ships on a three-year cruise entirely around Africa. The Phenicians also sailed by way of Gibraltar to England to bring tin from Cornwall, and by 500 B.C. the Carthaginians were well acquainted with the Atlantic coast of northern Africa. At some time or other, long before the Christian era, a ship belonging to one of the peoples of the eastern Mediterranean was probably blown to the shores of America by the steady trade-winds. Of course, no one can say positively that such a voyage occurred. Yet certain curious similarities between the Old World and the New enable us to infer with a great deal of probability that it actually happened. The mere fact, for example, that the adobe houses of the Pueblo Indians of New Mexico are strikingly like the houses of northern Africa and Persia is no proof that the civilization of the Old World and the New are related. A similar physical environment might readily cause the same type of house to be evolved in both places. When we find striking similarities of other kinds, however, the case becomes quite different. The constellations of the zodiac, for instance, are typified by twelve living creatures, such as the twins, the bull, the lion, the virgin, the crab, and the goat. Only one of the constellations, the scorpion, presents any real resemblance to the animal for which it is named. Yet the signs of the zodiac in Mediterranean lands and in pre-Columbian America from Peru to southern Mexico are almost identical. Here is a list showing the Latin and English names of the constellations and their equivalents in the calendars of the Peruvians, Mexicans, and Mayas. * * See S. Hagar, "The Bearing of Astronomy on the Problems of the Unity or Plurality and the Probable Place of Origin of the American Aborigines, in American Anthropologist," vol. XIV (1912), pp. 43-48. Sign English Peruvian Mexican Maya -------------------------------------------------------- Aries Ram Llama Flayer -- Taurus Bull (originally Stag) Stag Stag or Deer Stag Gemini Twins Man and Woman Twins Two Generals Cancer Crab Cuttlefish Cuttlefish Cuttlefish Leo Lion Puma Ocelot Ocelot Virgo Virgin (Mother Goddess of Cereals) Maize Mother Maize Mother Maize Mother Libra Scales (originally part of Scorpio) Forks Scorpion Scorpion Scorpio Scorpion Mummy Scorpion Scorpion Sagittarius Bowman Arrows or Spears Hunter and War God Hunter and War God Capricornus Sea Goat Beard Bearded God -- Aquarius Water Pourer Water Water Water Pisces Fishes(and Knot) Knot Twisted Reeds -- Notice how closely these lists are alike. The ram does not appear in America because no such animal was known there. The nearest substitute was the llama. In the Old World the second constellation is now called the bull, but curiously enough in earlier days it was called the stag in Mesopotamia. The twins, instead of being Castor and Pollux, may equally well be a man and a woman or two generals. To landsmen not familiar with creatures of the deep, the crab and the cuttlefish would not seem greatly different. The lion is unknown in America, but the creature which most nearly takes his place is the puma or ocelot. So it goes with all the signs of the zodiac. There are little differences between the Old World and the New, but they only emphasize the resemblance. Mathematically there is not one chance in thousands or even millions that such a resemblance could grow up by accident. Other similarities between ceremonies or religious words in the Old World and the New might be pointed out, but the zodiac is illustration enough. Such resemblances, however, do not indicate a permanent connection between Mediterranean civilization and that of Central America. They do not even indicate that any one ever returned from the Western Hemisphere to the Eastern previous to Columbus. Nor do they indicate that the civilization of the New World arose from that of the Old. They simply suggest that after the people of the Mediterranean regions had become well civilized and after those of America were also sufficiently civilized to assimilate new ideas, a stray ship or two was blown by the trade-winds across the Atlantic. That hypothetical voyage was the precursor of the great journey of Columbus. Without the tradewinds this historic discoverer never could have found the West Indies. Suppose that a strong west wind had blown him backward on his course when his men were mutinous. Suppose that he had been forced to beat against head winds week after week. Is there one chance in a thousand that even his indomitable spirit could have kept his craft headed steadily into the west? But because there were the trade-winds to bring him, the way was opened for the energetic people of Europe to possess the new continent. Thus the greatest stream of immigration commenced to flow, and the New World began to take on a European aspect. CHAPTER II. THE FORM OF THE CONTINENT America forms the longest and straightest bone in the earth's skeleton. The skeleton consists of six great bones, which may be said to form a spheroidal tetrahedron, or pyramid with a triangular base, for when a globe with a fairly rigid surface collapses because of shrinkage, it tends to assume this form. That is what has happened to the earth. Geologists tell us that during the thousand million years, more or less, since geological history began, the earth has grown cooler and hence has contracted. Moreover some of the chemical compounds of the interior have been transformed into other compounds which occupy less space. For these reasons the earth appears to have diminished in size until now its diameter is from two hundred to four hundred miles less than formerly. During the process of contraction the crust has collapsed in four main areas, roughly triangular in shape. Between these stand the six ridges which we have called the bones. Each of the four depressed areas forms a side of our tetrahedron and is occupied by an ocean. The ridges and the areas immediately flanking the oceans form the continents. The side which we may think of as the base contains the Arctic Ocean. The ridges surrounding it are broad and flat. Large parts of them stand above sea-level and form the northern portions of North America, Europe, and Asia. A second side is the Pacific Ocean with the great ridge of the two Americas on one hand and Asia and Australia on the other. Next comes the side containing the Indian Ocean in the hollow and the ridges of Africa and Australia on either hand. The last of the four sides contains the Atlantic Ocean and is bounded by Africa and Europe on one hand and North and South America on the other. Finally the tip of the pyramid projects above the surrounding waters, and forms the continent of Antarctica. It may seem a mere accident that this tip lies near the South Pole, while the center of the opposite face lies near the North Pole. Yet this has been of almost infinite importance in the evolution not only of plants and animals but of men. The reason is that this arrangement gives rise to a vast and almost continuous land mass in comparatively high latitudes. Only in such places does evolution appear to make rapid progress. * * W. D. Matthew, "Climate and Evolution," N. Y. Acad. Sci., 1915. Evolution is especially stimulated by two conditions. The first is that there shall be marked changes in the environment so that the process of natural selection has full opportunity to do its work. The second is that numerous new forms or mutants, as the biologists call them, shall be produced. Both of these conditions are most fully met in large continents in the temperate zone, for in such places climatic variations are most extreme. Such variations may take the form of extreme changes either from day to night, from season to season, or from one century to another. In any case, as Darwin long ago pointed out, they cause some forms of life to perish while others survive. Thus climatic variations are among the most powerful factors in causing natural selection and hence in stimulating evolution. Moreover it has lately been shown that variations in temperature are one of the chief causes of organic variation. Morgan and Plough, * for example, have discovered that when a certain fly, called the drosophila, is subjected to extremes of heat or cold, the offspring show an unusually strong tendency to differ from the parents. Hence the climatic variability of the interior of large continents in temperate latitudes provides new forms of life and then selects some of them for preservation. The fossils found in the rocks of the earth's crust support this view. They indicate that most of the great families of higher animals originated in the central part of the great land mass of Europe and Asia. A second but much smaller area of evolution was situated in the similar part of North America. From these two centers new forms of life spread outward to other continents. Their movements were helped by the fact that the tetrahedral form of the earth causes almost all the continents to be united by bridges of land. * Unpublished manuscript. If any one doubts the importance of the tetrahedral form, let him consider how evolution would have been hampered if the land of the globe were arranged as isolated masses in low latitudes, while oceans took the place of the present northern continents. The backwardness of the indigenous life of Africa shows how an equatorial position retards evolution. The still more marked backwardness of Australia with its kangaroos and duck-billed platypuses shows how much greater is the retardation when a continent is also small and isolated. Today, no less than in the past, the tetrahedral form of the earth and the relation of the tetrahedron to the poles and to the equator preserve the conditions that favor rapid evolution. They are the dominant factors in determining that America shall be one of the two great centers of civilization. If North and South America be counted as one major land mass, and Europe, Asia, and Africa as another, the two present the same general features. Yet their mountains, plains, and coastal indentations are so arranged that what is on the east in one is on the west in the other. Their similarity is somewhat like that of a man's two hands placed palms down on a table. On a map of the world place a finger of one hand on the western end of Alaska and a finger of the other on the northeastern tip of Asia and follow the main bones of the two continents. See how the chief mountain systems, the Pacific "cordilleras," trend away from one another, southeastward and southwestward. In the centers of the continents they expand into vast plateaus. That of America in the Rocky Mountain region of the United States reaches a width of over a thousand miles, while that of Asia in Tibet and western China expands to far greater proportions. From the plateaus the two cordilleras swing abruptly Atlantic-ward. The Eurasian cordillera extends through the Hindu Kush, Caucasus, and Asia Minor ranges to southern Europe and the Alps. Then it passes on into Spain and ends in the volcanoes of the Canary Islands. The American cordillera swings eastward in Mexico and continues as the isolated ranges of the West Indies until it ends in the volcanoes of Martinique. Central America appears at first sight to be a continuation of the great cordillera, but really it is something quite different--a mass of volcanic material poured out in the gap where the main chain of mountains breaks down for a space. In neither hemisphere, however, is the main southward sweep of the mountains really lost. In the Old World the cordillera revives in the mountains of Syria and southern Arabia and then runs southward along the whole length of eastern Africa. In America it likewise revives in the mighty Andes, which take their rise fifteen hundred miles east of the broken end of the northern cordillera in Mexico. In the Andes even more distinctly than in Africa the cordillera forms a mighty wall running north and south. It expands into the plateau of Peru and Bolivia, just as its African compeer expands into that of Abyssinia, but this is a mere incident. The main bone, so to speak, keeps on in each case till it disappears in the great southern ocean. Even there, however, it is not wholly lost, for it revives in the cold, lofty continent of Antarctica, where it coalesces once more with the other great tetrahedral ridges of Africa and Australia. It is easy to see that these great cordilleras have turned most of the earth's chief rivers toward the Atlantic and the Arctic Oceans. That is why these two oceans with an area of only forty-three million square miles receive the drainage from twenty million square miles of land, while the far larger Indian and Pacific Oceans with an area of ninety-one million square miles receive the rivers of only ten million square miles. The world's streams of civilization, like the rivers of water, have flowed from the great cordilleras toward the Atlantic. Half of the world's people, to be sure, are lodged in the relatively small areas known as China and India on the Pacific side of the Old World cordillera. Nevertheless the active streams of civilization have flowed mainly on the other side--the side where man apparently originated. From the earliest times the mountains have served to determine man's chief migrations. Their rugged fastnesses hinder human movements and thereby give rise to a strong tendency to move parallel to their bases. During the days of primitive man the trend of the mountains apparently directed his migrations northeastward to Bering Strait and then southeastward and southward from one end of America to the other. In the same way the migrations to Europe and Africa which ultimately reached America moved mainly parallel to the mountains. From end to end of America the great mountains form a sharp dividing line. The aboriginal tribes on the Pacific slope are markedly different from those farther east across the mountains. Brinton sums the case up admirably: "As a rule the tribes of the western coast are not connected with any east of the mountains. What is more singular, although they differ surprisingly among themselves in language, they have marked anthropologic similarities, physical and psychical. Virchow has emphasized the fact that the skulls from the northern point of Vancouver's Island reveal an unmistakable analogy to those from the southern coast of California; and this is to a degree true of many intermediate points. Not that the crania have the same indices. On the contrary, they present great and constant differences within the same tribe; but these differences are analogous one to the other, and on fixed lines. "There are many other physical similarities which mark the Pacific Indians and contrast them with those east of the mountains. The eyes are less oblique, the nose flatter, the lips fuller, the chin more pointed, the face wider. There is more hair on the face and in the axilla, and the difference between the sexes is much more obvious. "The mental character is also in contrast. The Pacific tribes are more quiet, submissive, and docile; they have less courage, and less of that untamable independence which is so constant a feature in the history of the Algonquins and Iroquois." * * D. G. Brinton, "The American Race," pp. 103-4. Although mountains may guide migrations, the plains are the regions where people dwell in greatest numbers. The plains in the two great land masses of the Old World and the New have the same inverse or right- and left-handed symmetry as the mountains. In the north the vast stretches from the Mackenzie River to the Gulf of Mexico correspond to the plains of Siberia and Russia from the Lena to the Black Sea. Both regions have a vast sweep of monotonous tundras at the north and both become fertile granaries in the center. Before the white man introduced the horse, the ox, and iron ploughs, there prevailed an extraordinary similarity in the habits of the plains Indians from Texas to Alberta. All alike depended on the buffalo; all hunted him in much the same way; all used his skins for tents and robes, his bones for tools, and his horns for utensils. All alike made him the center of their elaborate rituals and dances. Because the plains of North America were easy to traverse, the relatively high culture of the ancient people of the South spread into the Mississippi Valley. Hence the Natchez tribe of Mississippi had a highly developed form of sun-worship and a well-defined caste system with three grades of nobility in addition to the common people. Even farther north, almost to the Ohio River, traces of the sun-worship of Mexico had penetrated along the easy pathway of the plains. South of the great granaries of North America and Eurasia the plains are broken, but occur again in the Orinoco region of South America and the Sahara of Africa. Thence they stretch almost unbroken toward the southern end of the continents. In view of the fertility of the plains it is strange that the centers of civilization have so rarely been formed in these vast level expanses. The most striking of the inverse resemblances between America and the Old World are found along the Atlantic border. In the north of Europe the White Sea corresponds to Hudson Bay in America. Farther toward the Atlantic Ocean Scandinavia with its mountains, glaciers, and fiords is similar to Labrador, although more favored because warmer. Next the islands of Great Britain occupy a position similar to that of Newfoundland and Prince Edward Island. But here again the eastern climate is much more favorable than the western. Although practically all of Newfoundland is south of England, the American island has only six inhabitants per square mile, while the European country has six hundred. To the east of the British Isles the North Sea, the Baltic, and Lakes Ladoga and Onega correspond in striking fashion to the Gulf of St. Lawrence, the river of the same name, and the Great Lakes from Ontario to Superior. Next the indented shores of western France and the peninsula of Spain resemble our own indented coast and the peninsula of Florida. Here at last the American regions are as favored as the European. Farther south the Mediterranean and Black seas penetrate far into the interior just as does the Gulf of Mexico, and each continent is nearly cut in two where the canals of Suez and Panama respectively have been trenched. Finally in the southern continents a long swing eastward in America balances a similar swing westward in Africa. Thus Cape Saint Roque and Cape Verde are separated by scarcely 16 degrees of longitude, although the extreme points of the Gulf of Mexico and the Black Sea are 140 degrees apart. Finally to the south of the equator the continents swing away from one another once more, preserving everywhere the same curious inverse relationship. Even more striking than the inverse resemblance of the New World to the Old is the direct similarity of North and South America. In physical form the two continents are astonishingly alike. Not only does each have the typical triangular form which would naturally arise from tetrahedral shrinking of the globe, but there are four other cardinal points of resemblance. First, in the northeast each possesses an area of extremely ancient rocks, the Laurentian highlands of Quebec and Labrador in North America and the highlands of Guiana in South America. Second, in the southeast lie highlands of old but not the most ancient rocks stretching from northeast to southwest in the Appalachian region of North America, and in the Brazilian mountains of the southern continent. Third, along the western side of each continent recent crustal movements supplemented by volcanic action on a magnificent scale have given rise to a complex series of younger mountains, the two great cordilleras. Finally, the spaces between the three mountain masses are occupied by a series of vast confluent plains which in each case extend from the northern ocean to the southern and bend around the southeastern highlands. These plains are the newest part of America, for many of them have emerged from the sea only in recent geological times. Taken as a whole the resemblance between the two continents is striking. If these four physiographic provinces of North and South America lay in similar latitudes in the respective continents we might expect each pair to have a closely similar effect on life. In fauna, flora, and even in human history they would present broad and important resemblances. As a matter of fact, however, they are as different as can well be imagined. Where North America, is bathed by icy waters full of seals and floating ice South America is bathed by warm seas full of flying-fish and coral reefs. The northern continent is broadest in the cool latitudes that are most favorable for human activity. The southern expands most widely in latitudes whose debilitating monotony of heat and moisture is the worst of handicaps to human progress. The great rivers of the northern continent correspond very closely to those of the southern. The Mackenzie, however, is bound in the rigid bands of winter for eight months each year, while the Orinoco, the corresponding South American river, lies sweltering under a tropical sun which burns its grassy plains to bitter dust even as the sharp cold reduced the Mackenzie region to barren tundra. The St. Lawrence flows through fertile grain fields and the homes of an active people of the temperate zone, but the Amazon winds its slow way amid the malarious languor of vast tropical forests in which the trees shut out the sky and the few natives are apathetic with the eternal inertia of the hot, damp tropics. Only when we come to the Mississippi in the northern continent and the Rio de la Plata in the southern do we find a pair of rivers which correspond to any degree in the character of the life surrounding them, as well as in their physiographic character. Yet even here there is a vast difference, especially in the upper courses of the river. Each at its mouth flows through a rich, fertile plain occupied by a progressive, prosperous people. But the Rio de la Plata takes its rise in one of the world's most backward plains, the home of uncivilized Indians, heartless rubber adventurers, and the most rapacious of officials. Not infrequently, the degenerate white men of these regions, yielding to the subtle and insidious influence of the tropics, inflict the most outrageous abuses upon the natives, and even kill them on slight provocation. The natives in turn hate their oppressors, and when the chance comes betray them or leave them to perish in sickness and misery. The upper Mississippi, on the other hand, comes from a plain where agriculture is carried on with more labor-saving devices than are found anywhere else in the world. There States like Wisconsin and Minnesota stand in the forefront of educational and social progress. The contrasts between the corresponding rivers of the two Americas are typical of the contrasts in the history of the two continents. CHAPTER III. THE GEOGRAPHIC PROVINCES OF NORTH AMERICA The four great physical divisions of North America--the Laurentian highland, the Appalachian highland, the plains, and the western cordillera--are strikingly different in form and structure. The Laurentian highland presents a monotonous waste of rough hills, irregular valleys, picturesque lakes, and crooked rivers. Most of it is thinly clothed with pine trees and bushes such as the blueberry and huckleberry. Yet everywhere the ancient rock crops out. No one can travel there without becoming tiresomely familiar with fine-grained, shattered schists, coarse granites, and their curiously banded relatives, the gneisses. This rocky highland stretches from a little north of the St. Lawrence River to Hudson Bay, around which it laps in the form of a V, and so is known as the Archaean V or shield. Everywhere this oldest part of the Western Hemisphere presents unmistakable signs of great age. The schists by their fine crumpling and scaly flakes of mineral show that they were formed deep in the bowels of the earth, for only there could they be subjected to the enormous pressure needed to transform their minerals into sheets as thin as paper. The coarse granites and gneisses proclaim still more clearly that they must have originated far down in the depths of the earth; their huge crystals of mica, quartz, hornblende, feldspar, and other minerals could never have been formed except under a blanket of rock which almost prevented the original magmas from cooling. The thousands or tens of thousands of feet of rock which once overlay the schists and still more the granites and gneisses must have been slowly removed by erosion, for there was no other way to get rid of them. This process must have taken tens of millions of years, and yet the whole work must have been practically completed a hundred or perhaps several hundred million years ago. We know this because the selfsame ancient eroded surface which is exposed in the Laurentian highland is found dipping down under the oldest known fossiliferous rocks. Traces of that primitive land surface are found over a large part of the American continent. Elsewhere they are usually buried under later strata laid down when the continent sank in part below sea-level. Only in Laurentia has the land remained steadily above the reach of the ocean throughout the millions of years. Today this old, old land might be as rich as many others if climate had been kind to it. Its soil, to be sure, would in many parts be sandy because of the large amount of quartz in the rocks. That would be a small handicap, however, provided the soil were scores of feet deep like the red soil of the corresponding highland in the Guiana region of South America. But today the North American Laurentia has no soil worth mentioning. For some reason not yet understood this was the part of America where snow accumulated most deeply and where the largest glaciers were formed during the last great glacial period. Not once but many times its granite surface was shrouded for tens of thousands of years in ice a mile or more thick. As the ice spread outward in almost every direction, it scraped away the soil and gouged innumerable hollows in the softer parts of the underlying rock. It left the Laurentian highland a land of rocky ribs rising between clear lakes that fill the hollows. The lakes are drained by rapid rivers which wind this way and that in hopeless confusion as they strive to move seaward over the strangely uneven surface left by the ice. Such a land is good for the hunter and trapper. It is also good for the summer pleasure-seeker who would fain grow strong by paddling a canoe. For the man who would make a permanent home it is a rough, inscrutable region where one has need of more than most men's share of courage and persistence. Not only did the climate of the past cause the ice to scrape away the soil, but the climate of the present is so cold that even where new soil has accumulated the farmer can scarcely make a living. Around the borders of the Laurentian highland the ice accomplished a work quite different from the devastation of the interior. One of its chief activities was the scouring of a series of vast hollows which now hold the world's largest series of lakes. Even the lakes of Central Africa cannot compare with our own Great Lakes and the other smaller lakes which belong to the same series. These additional lakes begin in the far north with Great Bear Lake and continue through Great Slave Lake, Lake Athabasca, and Lake Winnipeg to the Lake of the Woods, which drains into Lake Superior. All these lakes lie on the edge of the great Laurentian shield, where the ice, crowding down from the highland to the north and east, was compressed into certain already existent hollows which it widened, deepened, and left as vast bowls ready to be filled with lakes. South and southwest of the Laurentian highland the great ice sheet proved beneficial to man. There, instead of leaving the rock naked, as in the Laurentian region, it merely smoothed off many of the irregularities of the surface and covered large areas with the most fertile soil. In doing this, to be sure, the ice-cap scoured some hollows and left a vastly larger number of basins surrounded in whole or in part by glacial debris. These have given rise to the innumerable lakes, large and small, whose beauty so enhances the charms of Canada, New England, New York, Minnesota, and other States. They serve as reservoirs for the water supply of towns and power plants and as sources of ice and fish. Though they take land from agriculture, they probably add to the life of the community as much in other ways as they detract in this. Moreover glaciation diverted countless streams from their old courses and made them flow over falls and rapids from which water-power can easily be developed. That is one reason why glaciated New England contains over forty per cent of all the developed water-power in the United States. Far more important, however, than the glacial lakes and rivers is the fertile glacial soil. It comes fresh from the original rocks and has not yet been exhausted by hundreds of thousands of years of weathering. It also has the advantage of being well mixed, for generally it is the product of scrapings from many kinds of rocks, each of which contributes its own particular excellence to the general composition. Take Wisconsin as an example. * Most parts of that State have been glaciated, but in the southwest there lies what is known as the "driftless area" because it is not covered with the "drift" or glacial debris which is thickly strewn over the rest of the State. A comparison of otherwise similar counties lying within and without the driftless area shows an astonishing contrast. In 1910 the average value of all the farm land in twenty counties covered with drift amounted to $56.90 per acre. In six counties partly covered with drift and partly driftless the value was $59.80 per acre, while in thirteen counties in the driftless area it was only $33.30 per acre. In spite of the fact that glaciation causes swamps and lakes, the proportion of land cultivated in the glaciated areas is larger than in the driftless. In the glaciated area 61 per cent of the land is improved and in the driftless area only 43.5 per cent. Moreover, even though the underlying rock and the original topography be of the same kind in both cases, the average yield of crops per acre is greater where the ice has done its work. Where the country rock consists of limestone, which naturally forms a rich soil, the difference in favor of the glaciated area amounts to only 1 or 2 per cent. Where the country rock is sandy, the soil is so much improved by a mixture of fertilizing limestone or even of clay and other materials that the average yield of crops per acre in the glaciated areas is a third larger than in the driftless. Taking everything into consideration it appears that the ancient glaciation of Wisconsin increases the present agricultural output by from 20 to 40 per cent. Upwards of 10,000,000 acres of glaciated land have already been developed in the most populous parts of the State. If the average value of all products on this area is reckoned at $15 per acre and if the increased value of agricultural products due to glaciation amounts to 30 per cent, then the net value of glaciation per year to the farmers of Wisconsin is $45,000,000. This means about $300 for each farmer in the glaciated area. * R. H. Whitbeck, "Economic Aspects of Glaciation in Wisconsin", in "Annals of the Association of American Geographers," vol. III in (1913), pp. 62-67. Wisconsin is by no means unique. In Ohio, for instance, there is also a driftless area. * It lies in the southeast along the Ohio River. The difference in the value of the farm land there and in the glaciated region is extraordinary. In the driftless area the average value per acre in 1910 was less than $24, while in the glaciated area it was nearly $64. Year by year the proportion of the population of the State in the unglaciated area is steadily decreasing. The difference between the two parts of the State is not due to the underlying rock structure or to the rainfall except to a slight degree. Some of the difference is due to the fact that important cities such as Cleveland and Toledo lie on the fertile level strip of land along the lake shore, but this strip itself, as well as the lake, owes much of its character to glaciation. It appears, therefore, that in Ohio, perhaps even more than in Wisconsin, man prospers most in the parts where the ice has done its work. * William H. Hess, "The Influence of Glaciation in Ohio," in "Bulletin of the Geographical Society of Philadelphia," vol. XV (1917), pp. 19-42. We have taken Wisconsin and Ohio as examples, but the effect of glaciation in those States does not differ materially from its effect all over southern Canada and the northern United States from New England to Kansas and Minnesota. Each year the people of these regions are richer by perhaps a billion dollars because the ice scraped its way down from Laurentia and spread out over the borders of the great plains on the west and of the Appalachian region on the east. We have considered the Laurentian highland and the glaciation which centered there. Let us now turn to another highland only the northern part of which was glaciated. The Appalachian highland, the second great division of North America, consists of three parallel bands which extend southwestward from Newfoundland and the St. Lawrence River to Georgia and Alabama. The eastern and most important band consists of hills and mountains of ancient crystalline rocks, somewhat resembling those of the Laurentian highland but by no means so old. West of this comes a broad valley eroded for the most part in the softer portions of a highly folded series of sedimentary rocks which are of great age but younger than the crystalline rocks to the east. The third band is the Alleghany plateau, composed of almost horizontal rocks which lie so high and have been so deeply dissected that they are often called mountains. The three Appalachian bands by no means preserve a uniform character throughout their entire length. The eastern crystalline band has its chief development in the northeast. There it comprises the whole of New England and a large part of the maritime provinces of Canada as well as Newfoundland. Its broad development in New England causes that region to be one of the most clearly defined natural units of the United States. Ancient igneous rocks such as granite lie intricately mingled with old and highly metamorphosed sediments. Since some of the rocks are hard and others soft and since all have been exposed to extremely long erosion, the topography of New England consists typically of irregular masses of rounded hills free from precipices. Here and there hard masses of unusually resistant rock stand up as isolated rounded heights, like Mount Katahdin in Maine. They are known as "monadnocks" from the mountain of that name in southern New Hampshire. In other places larger and more irregular masses of hard rock form mountain groups like the White Mountains, the Green Mountains, and the Berkshires, each of which is merely a great series of monadnocks. In the latitude of southern New York the crystalline rocks are compressed into narrow compass and lose their mountainous character. They form the irregular hills on which New York City itself is built and which make the suburbs of Westchester County along the eastern Hudson so diverse and beautiful. To the southeast the topography of the old crystalline band becomes still less pronounced, as may be seen in the rolling, fertile hills around Philadelphia. Farther south the band divides into two parts, the mountains proper and the Piedmont plateau. The mountains begin at the Blue Ridge, which in Virginia raises its even-topped heights mile after mile across the length of that State. In North Carolina, however, they lose their character as a single ridge and expand into the broad mass of the southern Appalachians. There Mount Mitchell dominates the eastern part of the American continent and is surrounded by over thirty other mountains rising to a height of at least six thousand feet. The Piedmont plateau, which lies at the eastern foot of the Blue Ridge, is not really a plateau but a peneplain or ancient lowland worn almost to a plain. It expands to a width of one hundred miles in Virginia and the Carolinas and forms the part of those States where most of the larger towns are situated. Among its low gentle heights there rises an occasional little monadnock like Chapel Hill, where the University of North Carolina lies on a rugged eminence which strikingly recalls New England. For the most part, however, the hills of the Piedmont region are lower and more rounded than those in the neighborhood of Philadelphia. The country thus formed has many advantages, for it is flat enough to be used for agriculture and yet varied enough to be free from the monotony of the level plains. The prolonged and broken inner valley forming the second band of the Appalachians was of some importance as a highway in the days of the Indians. Today the main highways of traffic touch it only to cross it as quickly as possible. From Lake Champlain it trends straight southward in the Hudson Valley until the Catskills have been passed. Then, while the railroads and all the traffic go on down the gorge of the Hudson to New York, the valley swings off into Pennsylvania past Scranton, Wilkesbarre, and Harrisburg. There the underlying rock consists of a series of alternately hard and soft layers which have been crumpled up much as one might wrinkle a rug with one's foot. The pressure involved in the process changed and hardened the rocks so much that the coal which they contain was converted into anthracite, the finest coal in all the world and the only example of its kind. Even the famous Welsh coal has not been so thoroughly hardened. During a long period of erosion the tops of the folded layers were worn off to a depth of thousands of feet and the whole country was converted into an almost level plain. Then in the late geological period known as the early Tertiary the land was lifted up again, and once more erosion went on. The soft rocks were thus etched away until broad valleys were formed. The hard layers were left as a bewildering succession of ridges with flat tops. A single ridge may double back and forth so often that the region well deserves the old Indian name of the "Endless Mountains." Southwestward the valley grows narrower, and the ridges which break its surface become straighter. Everywhere they are flat-topped, steep-sided, and narrow, while between them lie parts of the main valley floor, flat and fertile. Here in the south, even more clearly than in the north, the valley is bordered on the east by the sharply upstanding range of the crystalline Appalachians, while on the west with equal regularity it comes to an end in an escarpment which rises to the Alleghany plateau. This plateau, the third great band of the Appalachians, begins on the south side of the Mohawk Valley. To the north its place is taken by the Adirondacks, which are an outlier of the great Laurentian area of Canada. The fact that the outlier and the plateau are separated by the low strip of the Mohawk Valley makes this the one place where the highly complex Appalachian system can easily be crossed. If the Alleghany plateau joined the Adirondacks, Philadelphia instead of New York would be the greatest city of America. Where the plateau first rises on the south side of the Mohawk, it attains heights of four thousand feet in the Catskill Mountains. We think of the Catskills as mountains, but their steep cliffs and table-topped heights show that they are really the remnants of a plateau, the nearly horizontal strata of which have not yet been worn away. Westward from the Catskills the plateau continues through central New York to western Pennsylvania. Those who have traveled on the Pennsylvania Railroad may remember how the railroad climbs the escarpment at Altoona. Farther east the train has passed alternately through gorges cut in the parallel ridges and through fertile open valleys forming the main floor of the inner valley. Then it winds up the long ascent of the Alleghany front in a splendid horseshoe curve. At the top, after a short tunnel, the train emerges in a wholly different country. The valleys are without order or system. They wind this way and that. The hills are not long ridges but isolated bits left between the winding valleys. Here and there beds of coal blacken the surface, for here we are among the rocks from which the world's largest coal supply is derived. Since the layers lie horizontally and have never been compressed, the same material which in the inner valley has been changed to hard, clean-burning anthracite here remains soft and smoky. In its southwestern continuation through West Virginia and Kentucky to Tennessee the plateau maintains many of its Pennsylvanian characteristics, but it now rises higher and becomes more inaccessible. The only habitable portions are the bottoms of the valleys, but they are only wide enough to support a most scanty population. Between them most of the land is too rough for anything except forests. Hence the people who live at the bottoms of the valleys are strangely isolated. They see little or nothing of the world at large or even of their neighbors. The roads are so few and the trails so difficult that the farmers cannot easily take their produce to market. Their only recourse has been to convert their bulky corn into whisky, which occupied little space in proportion to its value. Since the mountaineer has no other means of getting ready money, it is not strange that he has become a moonshiner and has fought bitterly for what he genuinely believed to be his rights in that occupation. Education has not prospered on the plateau because the narrowness of the valleys causes the population to be too poor and too scattered to support schools. For the same reason feuds grow up. When people live by themselves they become suspicious. Not being used to dealing with their neighbors, they suspect the motives of all but their intimate friends. Moreover, in those deep valleys, with their steep sides and their general inaccessibility, laws cannot easily be enforced, and therefore each family takes the law into its own hands. Today the more rugged parts of the Appalachian system are chiefly important as a hindrance to communication. On the Atlantic slope of the old crystalline band there are great areas of gentle relief where an abundant population can dwell. Westward on the edges of the plateau and the plains beyond a still greater population can find a living, but in the intervening space there is opportunity for only a few. The great problem is to cross the mountains as easily as possible. Each accessible crossing-place is associated with a city. Boston, as well as New York, owes much to the low Mohawk-Hudson route, but is badly handicapped because it has no easy means of crossing the eastern crystalline band. Philadelphia, on the other hand, benefits from the fact that in its vicinity the crystallizes are low and can readily be crossed even without the aid of the valleys of the Delaware and Schuylkill rivers. It is handicapped, however, by the Alleghany escarpment at Altoona, even though this is lower there than farther south. Baltimore, in the same way, owes much of its growth to the easy pathways of the Susquehanna on the north and the Potomac on the south. Farther south both the crystalline band and the Alleghany plateau become more difficult to traverse, so that communication between the Atlantic coast and the Mississippi Valley is reduced to small proportions. Happy is New York in its situation where no one of the three bands of the Appalachians opposes any obstacle. The plains of North America form the third of the four main physical divisions of the continent. For the most part they lie between the great western cordillera on one side and the Laurentian and Appalachian highlands on the other. Yet they lap around the southern end of the Appalachians and run far up the Atlantic coast to New York. They remained beneath the sea till a late date, much later than the other three divisions. They were not, however, covered with deep water like that of the abysmal oceans, but only with shallow seas from which the land at times emerged. In spite of the old belief to the contrary, the continents appear to be so permanent that they have occupied practically their present positions from the remotest geological times. They have moved slowly up and down, however, so that some parts have frequently been submerged, and the plains are the parts that remained longest under water. The plains of North America may be divided into four parts according to the character of their surface: the Atlantic coastal plain, the prairies, the northwestern peneplain, and the southwestern high plains. The Atlantic coastal plain lies along the Atlantic coast from New York southward to Florida and Alabama. It also forms a great embayment up the Mississippi Valley as far as the Ohio River, and it extends along the shore of the Gulf of Mexico to the Rio Grande. The chief characteristic of this Atlantic and Gulf coastal plain is its belted nature. One layer of rocks is sandy, another consists of limestone, and a third of clay. When uplifted and eroded each assumes its own special topography and is covered with its own special type of vegetation. Thus in South Carolina and Georgia the crystalline Piedmont band of the Appalachian province is bordered on the southeast by a belt of sandstone. This rock is so far from the sea and has been raised so high above it that erosion has converted it into a region of gentle hills, whose tops are six hundred or seven hundred feet above sea-level. Its sandy soil is so poor that farming is difficult. The hills are largely covered with pine, yielding tar and turpentine. Farther seaward comes a broad band of younger rock which forms a clayey soil or else a yellow sandy loam. These soils are so rich that splendid cotton crops can be raised, and hence the region is thickly populated. Again there comes a belt of sand, the so-called "pine barrens," which form a poor section about fifty miles inland from the coast. Finally the coastal belt itself has emerged from beneath the sea so recently and lies so nearly at sea-level that it has not been greatly eroded, and is still covered with numerous marshes and swamps. The rich soil and the moisture are good for rice, but the region is so unhealthy and so hard to drain that only small parts are inhabited. Everywhere in the coastal plain this same belted character is more or less evident. It has much to do with all sorts of activities from farming to politics. On consulting the map showing the cotton production of the United States in 1914, one notices the two dark bands in the southeast. One of them, extending from the northwestern part of South Carolina across Georgia and Alabama, is due to the fertile soil of the Piedmont region. The other, lying nearer the sea, begins in North Carolina and extends well into Alabama before it swings around to the northwest toward the area of heavy production along the Mississippi. It is due to the fertile soil of that part of the coastal plain known as the "cotton belt." Portions of it are called the "black belt," not because of the colored population, but because of the darkness of the soil. Since this land has always been prosperous, it has regularly been conservative in politics. The Atlantic coastal plain is by no means the only part of the United States where the fertility of the soil is the dominant fact in the life of the people. Because of their rich soil the prairies which extend from western Ohio to the Missouri River and northward into Canada are fast becoming the most steadily prosperous part of America. They owe their surpassing richness largely to glaciation. We have already seen how the coming of the ice-sheet benefited the regions on the borders of the old Laurentian highland. This same benefit extended over practically the whole of what are now the prairies. Before the advent of the ice the whole section consisted of a broadly banded coastal plain much older than that of the Atlantic coast. When the ice with its burden of material scraped from the hills of the north passed over the coastal plain, it filled the hollows with rich new soil. The icy streams that flowed out from the glaciers were full of fine sediment, which they deposited over enormous flood plains. During dry seasons the winds picked up this dust and spread it out still more widely, forming the great banks of yellow loess whose fertile soil mantles the sides of many a valley in the Mississippi basin. Thus glaciers, streams, and winds laid down ten, twenty, fifty, or even one hundred feet of the finest, most fertile soil. We have already seen how much the soil was improved by glaciation in Wisconsin and Ohio. It was in the prairie States that this improvement reached a maximum. The soil there is not only fine grained and free from rocks, but it consists of particles brought from widely different sources and is therefore full of all kinds of plant foods. In most parts of the world a fine-grained soil is formed only after a prolonged period of weathering which leaches out many valuable chemical elements. In the prairies, however, the soil consists largely of materials that were mechanically ground to dust by the ice without being exposed to the action of weathering. Thus they have reached their present resting-places without the loss of any of their original plant foods. When such a soil is found with a climate which is good for crops and which is also highly stimulating to man, the combination is almost ideal. There is some justification for those who say that the north central portion of the United States is more fortunate than any other part of the earth. Nowhere else, unless in western Europe, is there such a combination of fertile soil, fine climate, easy communication, and possibilities for manufacturing and commerce. Iron from that outlier of the Laurentian highland which forms the peninsula of northern Michigan can easily be brought by water almost to the center of the prairie region. Coal in vast quantities lies directly under the surface of this region, for the rock of the ancient coastal plain belongs to the same Pennsylvanian series which yields most of the world's coal. Here man is, indeed, blessed with resources and opportunities scarcely equaled in any other part of the world, and finds the only drawbacks to be the extremes of temperature in both winter and summer and the remoteness of the region from the sea. Because of the richness of their heritage and because they live safely protected from threats of foreign aggression, the people who live in this part of the world are in danger of being slow to feel the currents of great world movements. The western half of the plains of North America consists of two parts unlike either the Atlantic coastal plain or the prairies. From South Dakota and Nebraska northward far into Canada and westward to the Rocky Mountains there extends an ancient peneplain worn down to gentle relief by the erosion of millions of years. It is not so level as the plains farther east nor so low. Its western margin reaches heights of four or five thousand feet. Here and there, especially on the western side, it rises to the crest of a rugged escarpment where some resistant layer of rocks still holds itself up against the forces of erosion. Elsewhere its smooth surfaces are broken by lava-capped mesas or by ridges where some ancient volcanic dike is so hard that it has not yet been worn away. The soil, though excellent, is thinner and less fertile than in the prairies. Nevertheless the population might in time become as dense and prosperous as almost any in the world if only the rainfall were more abundant and good supplies of coal were not quite so far away. Yet in spite of these handicaps the northwestern peneplain with its vast open stretches, its cattle, its wheat, and its opportunities is a most attractive land. South of Nebraska and Wyoming the "high plains," the last of the four great divisions of the plains, extend as far as western Texas. These, like the prairies, have been built up by deposits brought from other regions. In this case, however, the deposits consist of gravel, sand, and silt which the rivers have gradually washed out from the Rocky Mountains. As the rivers have changed their courses from one bed to another, layer after layer has been laid down to form a vast plain like a gently sloping beach hundreds of miles wide. In most places the streams are no longer building this up. Frequently they have carved narrow valleys hundreds of feet deep in the materials which they formerly deposited. Elsewhere, however, as in western Kansas, most of the country is so flat that the horizon is like that of the ocean. It seems almost incredible that at heights of four or five thousand feet the plains can still be so wonderfully level. When the grass is green, when the spring flowers are at their best, it would be hard to find a picture of greater beauty. Here the buffalo wandered in the days before the white man destroyed them. Here today is the great cattle region of America. Here is the region where the soul of man is filled with the feeling of infinite space. To the student of land forms there is an ever-present contrast between those due directly to the processes which build up the earth's surface and those due to the erosive forces which destroy what the others have built. In the great plains of North America two of the divisions, that is, the Atlantic coastal plain of the southeast and the peneplain of the northwest, owe their present form to the forces of erosion. The other two, that is, the prairies and the high plains, still bear the impress of the original processes of deposition and have been modified to only a slight extent by erosion. A similar but greater contrast separates the mountains of eastern North America and those of the western cordillera--the fourth and last of the main physical divisions of the continent. In both the Laurentian and the Appalachian highlands the eastern mountains show no trace of the original forms produced by the faulting of the crust or by volcanic movements. All the original distinctive topography has been removed. What we see today is the product of erosion working upon rocks that were thousands of feet beneath the surface when they were brought to their present positions. In the western cordillera, on the contrary, although much of the present form of the land is due to erosion, a vast amount is due directly to so-called "tectonic" activities such as the breaking of the crust, the pouring out of molten lavas, and the bursting forth of explosive eruptions. The character of these tectonic activities has differed widely in different parts of the cordillera. A broad upheaval of great blocks of the earth's crust without tilting or disturbance has produced the plateaus of Arizona and Utah. The gorges that have been rapidly cut into such great upheaved blocks form part of the world's most striking scenery. The Grand Canyon of the Colorado with its tremendous platforms, mesas, and awe-inspiring cliffs could have been formed in no other way. Equally wonderful are some of the narrow canyons in the broadly upheaved plateaus of southern Utah where the tributaries of the Virgin and other rivers have cut red or white chasms thousands of feet deep and so narrow that at their bottoms perpetual twilight reigns. It is a curious proof of the fallibility of human judgment that these great gorges are often cited as the most striking examples of the power of erosion. Wonderful as these gorges certainly are, the Piedmont plain or the northwestern peneplain is far more wonderful. Those regions had their grand canyons once upon a time, but now erosion has gone so far that it has reduced the whole area to the level of the bottoms of the gorges. Though such a fate is in store for all the marvelous scenery of the western cordillera, we have it, for the present at least, as one of the most stimulating panoramas of our American environment. No man worthy of the name can sit on the brink of a great canyon or gaze up from the dark depths of a gorge without a sense of awe and wonder. There, as in few other places, Nature shows with unmistakable grandeur the marvelous power and certainty with which her laws work out the destiny of the universe. In other parts of the great American cordillera some of the simplest and youngest mountain ridges in the world are found. In southern Oregon, for example, lava blocks have been broken and uplifted and now stand with steep fresh faces on one side and with the old surface inclining more gently on the other. Tilted blocks on a larger scale and much more deeply carved by erosion are found in the lofty St. Elias Mountain of Alaska, where much of the erosion has been done by some of the world's greatest glaciers. The western slope of the Wasatch Mountains facing the desert of Utah is the wall of a huge fracture, as is the eastern face of the Sierra Nevadas facing the deserts of Nevada. Each of these great faces has been deeply eroded. At the base, however, recent breaking and upheaval of the crust have given rise to fresh uneroded slopes. Some take the form of triangular facets, where a series of ridges has been sliced across and lifted up by a great fault. Others assume the shape of terraces which sometimes continue along the base of the mountains for scores of miles. In places they seem like bluffs cut by an ancient lake, but suddenly they change their altitude or pass from one drainage area to another as no lake-formed strand could possibly do. In other parts of the cordillera, mountains have been formed by a single arching of the crust without any breaking. Such is the case in the Uinta Mountains of northwestern Utah and in some of the ranges of the Rocky Mountains in Colorado. The Black Hills of South Dakota, although lying out in the plains, are an example of the same kind of structure and really belong to the cordillera. In them the layers of the earth's crust have been bent up in the form of a great dome. The dome structure, to be sure, has now been largely destroyed, for erosion has long been active. The result is that the harder strata form a series of concentric ridges, while between them are ring-shaped valleys, one of which is so level and unbroken that it is known to the Indians as the "race-course." In other parts of the cordillera great masses of rock have been pushed horizontally upon the tops of others. In Montana, for example, the strata of the plains have been bent down and overridden by those of the mountains. These are only a few of the countless forms of breaking, faulting, and crumpling which have given to the cordillera an almost infinite variety of scenery. The work of mountain building is still active in the western cordillera, as is evident from such an event as the San Francisco earthquake. In the Owens Valley region in southern California the gravelly beaches of old lakes are rent by fissures made within a few years by earthquakes. In other places fresh terraces on the sides of the valley mark the lines of recent earth movements, while newly formed lakes lie in troughs at their base. These Owens Valley movements of the crust are parts of the stupendous uplift which has raised the Sierra Nevada to heights of over 14,000 feet a few miles to the west. Along the fault line at the base of the mountains there runs for over 9.50 miles the world's longest aqueduct, which was built to relieve Los Angeles from the danger of drought. It is a strange irony of fate that so delicate and so vital an artery of civilization should be forced to lie where a renewal of earthquake movements may break it at any time. Yet there was no other place to put it, for in spite of man's growing control of nature he was forced to follow the topography of the region in which he lived and labored. On the southern side of the Mohave Desert a little to the east of where the Los Angeles aqueduct crosses the mountains in its southward course, the record of an earthquake is preserved in unique fashion. The steep face of a terrace is covered with trees forty or fifty years old. Near the base the trees are bent in peculiar fashion. Their lower portions stand at right angles to the steeply sloping face of the terrace, but after a few feet the trunks bend upward and stand vertically. Clearly when these trees were young the terrace was not there. Then an earthquake came. One block of the earth's crust was dropped down while another was raised up. Along the dividing line a terrace was formed. The trees that happened to stand along the line were tilted and left in a slanting position on the sloping surface between the two parts of the earth's crust. They saw no reason to stop growing, but, turning their tips toward the sky, they bravely pushed upward. Thus they preserve in a striking way the record of this recent movement of the earth's crust. Volcanoes as well as earth movements have occurred on a grand scale within a few hundred years in the cordillera. Even where there is today no visible volcanic activity, recent eruptions have left traces as fresh as if they had occurred but yesterday. On the borders of the Grand Canyon of the Colorado one can see not only fresh cones of volcanic ash but lava which has poured over the edges of the cliffs and hardened while in the act of flowing. From Orizaba and Popocatepetl in Mexico through Mount San Francisco in Arizona, Lassen Peak and Mount Shasta in California, Mount Rainier with its glaciers in the Cascade Range of Washington, and Mount Wrangell in Alaska, the cordillera contains an almost unbroken chain of great volcanoes. All are either active at present or have been active within very recent times. In 1912 Mount Katmai, near the northwestern end of the volcanic chain, erupted so violently that it sent dust around the whole world. The presence of the dust caused brilliant sunsets second only to those due to Krakatoa in 1883. It also cut off so much sunlight that the effect was felt in measurements made by the Smithsonian Institution in the French provinces of North Africa. In earlier times, throughout the length of the cordillera great masses of volcanic material were poured out to form high plateaus like those of southern Mexico or of the Columbia River in Oregon. In Utah some of these have been lifted up so that heavy caps of lava now form isolated sheets topping lofty plateaus. There the lowland shepherds drive their sheep in summer and live in absolute isolation for months at a time. There, as everywhere, the cordillera bears the marks of mountains in the making, while the mountains of eastern America bear the marks of those that were made when the world was young. The geysers and hot springs of the Yellowstone are another proof of recent volcanic activity. They owe their existence to hot rocks which lie only a little way below the surface and which not long ago were molten lava. The terraces and platforms built by the geysers are another evidence that the cordillera is a region where the surface of the earth is still being shaped into new forms by forces acting from within. The physical features of the country are still in process of construction. In spite of the importance of the constructive forces which are still building up the mountains, much of the finest scenery of the cordillera is due to the destructive forces of erosion. The majestic Columbia Canyon, like others of its kind, is the work of running water. Glaciers also have done their part. During the glacial period the forces which control the paths of storms did not give to the cordillera region such an abundance of snow as was sifted down upon Laurentia. Therefore no such huge continental glaciers have flowed out over millions of square miles of lower country. Nevertheless among the mountains themselves the ice gouged and scraped and smoothed and at its lower edges deposited great moraines. Its work today makes the cliffs and falls of the Yosemite one of the world's most famous bits of scenery. This scenery is young and its beauty will pass in a short time as geology counts the years, for in natural scenery as in human life it is youth that makes beauty. The canyons, waterfalls, and geysers of the cordillera share their youth with the lakes, waterfalls, and rapids due to recent glaciation in the east. Nevertheless, though youth is the condition of most striking beauty, maturity and old age are the condition of greatest usefulness. The young cordillera with its mountains still in the making can support only a scanty population, whereas the old eastern mountains, with the lines of long life engraved upon every feature, open their arms to man and let him live and prosper. It is not enough that we should picture merely the four divisions of the land of our continent. We must see how the land meets the sea. In low latitudes in both the Old World and the New, the continents have tended to emerge farther and farther from the sea during recent geological times. Hence on the eastern side of both North and South America from New Jersey to Brazil the ocean is bordered for the most part by coastal plains, uplifted from the sea only a short time ago. On the mountainous western side of both continents, however, the sea bottom shelves downward so steeply that its emergence does not give rise to a plain but merely to a steep slope on which lie a series of old beaches several hundred and even one thousand feet above the present shore line. Such conditions are not favorable to human progress. The coastal plains produced by uplift of the land may be fertile and may furnish happy homes for man, but they do not permit ready access to the sea because they have no harbors. The chief harbor of Mexico at Vera Cruz is merely a little nick in the coast-line and could never protect a great fleet, even with the help of its breakwater. Where an enterprising city like Los Angeles lies on the uplifted Pacific coast, it must spend millions in wresting a harbor from the very jaws of the sea. In high latitudes in all parts of the world the land has recently been submerged beneath the sea. In some places, especially those like the coasts of Virginia and central California which lie in middle latitudes, a recent slight submergence has succeeded a previous large emergence. Wherever such sinking of the land has taken place, it has given rise to countless bays, gulfs, capes, islands, and fiords. The ocean water has entered the valleys and has drowned their lower parts. It has surrounded the bases of hills and left them as islands; it has covered low valleys and has created long sounds where traffic may pass with safety even in great storms. Though much land has thus been lost which would be good for agriculture, commerce has been wonderfully stimulated. Through Long Island Sound there pass each day hundreds of boats which again and again would suffer distress and loss if they were not protected from the open sea. It is no accident that of the eight largest metropolitan districts in the United States five have grown up on the shores of deep inlets which are due to the drowning of valleys. Nor must the value of scenery be forgotten in a survey such as this. Year by year we are learning that in this restless, strenuous American life of ours vacations are essential. We are learning, too, that the love of beauty is one of Nature's greatest healers. Regions like the coast of Maine and Puget Sound, where rugged land and life-giving ocean interlock, are worth untold millions because of their inspiring beauty. It is indeed marvelous that in the latitude of the northern United States and southern Canada so many circumstances favorable to human happiness are combined. Fertile soil, level plains, easy passage across the mountains, coal, iron, and other metals imbedded in the rocks, and a stimulating climate, all shower their blessings upon man. And with all these blessings goes the advantage of a coast which welcomes the mariner and brings the stimulus of foreign lands, while at the same time it affords rest and inspiration to the toilers here at home. CHAPTER IV. THE GARMENT OF VEGETATION No part of the world can be truly understood without a knowledge of its garment of vegetation, for this determines not only the nature of the animal inhabitants but also the occupations of the majority of human beings. Although the soil has much to do with the character of vegetation, climate has infinitely more. It is temperature which causes the moss and lichens of the barren tundras in the far north to be replaced by orchids, twining vines, and mahogany trees near the equator. It is rainfall which determines that vigorous forests shall grow in the Appalachians in latitudes where grasslands prevail in the plains and deserts in the western cordillera. Forests, grass-lands, deserts, represent the three chief types of vegetation on the surface of the earth. Each is a response to certain well-defined conditions of climate. Forests demand an abundance of moisture throughout the entire season of growth. Where this season lasts only three months the forest is very different from where it lasts twelve. But no forest can be vigorous if the ground habitually becomes dry for a considerable period during which the weather is warm enough for growth. Desert vegetation, on the other hand, which consists primarily of bushes with small, drought-resistant leaves, needs only a few irregular and infrequent showers in order to endure long periods of heat and drought. Discontinuity of moisture is the cause of deserts, just as continuity is the necessary condition of forest growth. Grasses prevail where the climatic conditions are intermediate between those of the forest and the desert. Their primary requisite is a short period of fairly abundant moisture with warmth enough to ripen their seeds. Unlike the trees of the forests, they thrive even though the wet period be only a fraction of the entire time that is warm enough for growth. Unlike the bushes of the desert, they rarely thrive unless the ground is well soaked for at least a few weeks. Most people think of forests as offering far more variety than either deserts or grass-lands. To them grass is just grass, while trees seem to possess individuality. In reality, however, the short turfy grass of the far north differs from the four-foot fronds of the bunchy saccaton grass of Arizona, and from the far taller tufts of the plumed pampas grass, much more than the pine tree differs from the palm. Deserts vary even more than either forests or grass-lands. The traveler in the Arizona desert, for example, has been jogging across a gravelly plain studded at intervals of a few yards with little bushes a foot high. The scenery is so monotonous and the noon sunshine so warm that he almost falls asleep. When he wakes from his daydream, so weird are his surroundings that he thinks he must be in one of the places to which Sindbad was carried by the roc. The trail has entered an open forest of joshuas, as the big tree yuccas are called in Arizona. Their shaggy trunks and uncouth branches are rendered doubly unkempt by swordlike, ashy-yellow dead leaves that double back on the trunk but refuse to fall to the ground. At a height of from twelve to twenty feet each arm of the many-branched candelabrum ends in a stiff rosette of gray-green spiky leaves as tough as hemp. Equally bizarre and much more imposing is a desert "stand" of giant suhuaros, great fluted tree-cacti thirty feet or more high. In spite of their size the suhuaros are desert types as truly as is sagebrush. In America the most widespread type of forest is the evergreen coniferous woodland of the north. Its pines, firs, spruces, hemlocks, and cedars which are really junipers, cover most of Canada together with northern New England and the region south of Lakes Huron and Superior. At its northern limit the forest looks thoroughly forlorn. The gnarled and stunted trees are thickly studded with half-dead branches bent down by the weight of snow, so that the lower ones sweep the ground, while the upper look tired and discouraged from their struggle with an inclement climate. Farther south, however, the forest loses this aspect of terrific struggle. In Maine, for example, it gives a pleasant impression of comfortable prosperity. Wherever the trees have room to grow, they are full and stocky, and even where they are crowded together their slender upspringing trunks look alert and energetic. The signs of death and decay, indeed, appear everywhere in fallen trunks, dead branches, and decayed masses of wood, but moss and lichens, twinflowers and bunchberries so quickly mantle the prostrate trees that they do not seem like tokens of weakness. Then, too, in every open space thousands of young trees bank their soft green masses so gracefully that one has an ever-present sense of pleased surprise as he comes upon this younger foliage out of the dim aisles among the bigger trees. Except on their southern borders the great northern forests are not good as a permanent home for man. The snow lies so late in the spring and the summers are so short and cool that agriculture does not prosper. As a home for the fox, marten, weasel, beaver, and many other fur-bearing animals, however, the coniferous forests are almost ideal. That is why the Hudson's Bay Company is one of the few great organizations which have persisted and prospered from colonial times to the present. As long ago as 1670 Charles II granted to Prince Rupert and seventeen noblemen and gentlemen a charter so sweeping that, aside from their own powers of assimilation, there was almost no limit to what the "Governor and Company of Adventurers of England trading into Hudson's Bay" might acquire. By 1749, nearly eighty years after the granting of the charter, however, the Company had only four or five forts on the coast of Hudson Bay, with about 120 regular employees. Nevertheless the poor Indians were so ignorant of the value of their furs and the consequent profits were so large that, after Canada had been ceded to Great Britain in 1763, a rival organization, the Northwest Fur Company of Montreal, was established. Then there began an era that was truly terrible for the Indians of the northern forest. In their eagerness to get the valuable furs the companies offered the Indians strong liquors in an abundance that ruined the poor red man, body and soul. Moreover the fur-bearing animals were killed not only in winter but during the breeding season. Many mother animals were shot and their little ones were left to die. Hence in a short time the wild creatures of the great northern forest were so scarce that the Indians well-nigh starved. In spite of this slaughter of fur-bearing animals, the same Company still draws fat dividends from the northern forest and its furry inhabitants. If the forest had been more habitable, it would long ago have been occupied by settlers, as have its warmer, southern portions, and the Company would have ceased to exist. Aside from the regions too cold or too dry to support any vegetation whatever, few parts of the world are more deadening to civilization than the forests of the far north. Near the northern limit of the great evergreen forest of North America wild animals are so rare that a family of hunting Indians can scarcely find a living in a thousand square miles. Today the voracious maw of the daily newspaper is eating the spruce and hemlock by means of relentless saws and rattling pulp-mills. In the wake of the lumbermen settlers are tardily spreading northward from the more favored tracts in northern New England and southern Canada. Nevertheless most of the evergreen forests of the north must always remain the home of wild animals and trappers, a backward region in which it is easy for a great fur company to maintain a practical monopoly. Outliers of the pine forest extend far down into the United States. The easternmost lies in part along the Appalachians and in part along the coastal plain from southern New Jersey to Texas. The coastal forest is unlike the other coniferous forests in two respects, for its distribution and growth are not limited by long winters but by sandy soil which quickly becomes dry. This drier southern pine forest lacks the beauty of its northern companion. Its trees are often tall and stately, but they are usually much scattered and are surrounded by stretches of scanty grass. There is no trace of the mossy carpet and dense copses of undergrowth that add so much to the picturesqueness of the forests farther north. The unkempt half-breed or Indian hunter is replaced by the prosaic gatherer of turpentine. As the man of the southern forests shuffles along in blue or khaki overalls and carries his buckets from tree to tree, he seems a dull figure contrasted with the active northern hunter who glides swiftly and silently from trap to trap on his rawhide snowshoes. Yet though the southern pine forest may be less picturesque than the northern, it is more useful to man. In spite of its sandy soil, much of this forest land is being reclaimed, and all will some day probably be covered by farms. Two other outliers of the northern evergreen forest extend southward along the cool heights of the Rocky Mountains and of the Pacific coast ranges of the United States. In the Olympic and Sierra Nevada ranges the most western outlier of this northern band of vegetation probably contains the most inspiring forests of the world. There grow the vigorous Oregon pines, firs, and spruces, and the still more famous Big Trees or sequoias. High on the sides of the Sierra above the yuccas, the live oaks, and the deciduous forest of the lower slopes, one meets these Big Trees. To come upon them suddenly after a long, rough tramp over the sunny lower slopes is the experience of a lifetime. Upward the great trees rise sheer one hundred feet without a branch. The huge fluted trunks encased in soft, red bark six inches or a foot thick are more impressive than the columns of the grandest cathedral. It seems irreverent to speak above a whisper. Each tree is a new wonder. One has to walk around it and study it to appreciate its enormous size. Where a tree chances to stand isolated so that one can see its full majesty, the sense of awe is tempered by the feeling that in spite of their size the trees have a beauty all their own. Lifted to such heights, the branches appear to be covered with masses of peculiarly soft and rounded foliage like the piled-up banks of a white cumulus cloud before a thunderstorm. At the base of such a tree the eye is caught by the sharp, triangular outline of one of its young progeny. The lower branches sweep the ground. The foliage is harsh and rough. In almost no other species of trees is there such a change from comparatively ungraceful youth to a superbly beautiful old age. The second great type of American forest is deciduous. The trees have broad leaves quite unlike the slender needles or overlapping scales of the northern evergreens. Each winter such forests shed their leaves. Among the mountains where the frosts come suddenly, the blaze of glory and brilliance of color which herald the shedding of the leaves are surpassed in no other part of the world. Even the colors of the Painted Desert in northern Arizona and the wonderful flowers of the California plains are less pleasing. In the Painted Desert the patches of red, yellow, gray-blue, white, pale green, and black have a garish, almost repellent appearance. In California the flame-colored acres of poppies in some places, of white or yellow daisylike flowers in others, or of purple blossoms elsewhere have a softer expression than the bare soil of the desert. Yet they lack the delicate blending and harmony of colors which is the greatest charm of the autumn foliage in the deciduous forests. Even where the forests consist of such trees as birches, beeches, aspens, or sycamores, whose leaves merely turn yellow in the fall, the contrast between this color and the green tint of summer or the bare branches of winter adds a spice of variety which is lacking in other and more monotonous forests. From still other points of view the deciduous forest has an almost unequaled degree of variety. In one place it consists of graceful little birches whose white trunks shimmering in the twilight form just the background for ghosts. Contrast them with the oak forest half a mile away. There the sense of gracefulness gives place to a feeling of strength. The lines are no longer vertical but horizontal. The knotted elbows of the branches recall the keels of sturdy merchantmen of bygone days. The acorns under foot suggest food for the herds of half-wild pigs which roam among the trees in many a southern county. Of quite another type are the stately forests of the Appalachians where splendid magnolia and tulip trees spread their broad limbs aloft at heights of one hundred feet or more. Deciduous forests grow in the well-balanced regions where summer and winter approach equality, where neither is unduly long, and where neither is subject to prolonged drought. They extend southward from central New England, the Great Lakes, and Minnesota, to Mississippi, Arkansas, and eastern Texas. They predominate even in parts of such prairie States as Michigan, Indiana, southern Illinois, and southeastern Missouri. No part of the continent is more populous or more progressive than the regions once covered by deciduous forests. In the United States nearly sixty per cent of the inhabitants live in areas reclaimed from such forests. Yet the area of the forests is less than a quarter of the three million square miles that make up the United States. In their relation to human life the forests of America differ far more than do either grass-lands or deserts. In the far north, as we have seen, the pine forests furnish one of the least favorable environments. In middle latitudes the deciduous forests go to the opposite extreme and furnish the most highly favored of the homes of man. Still farther southward the increasing luxuriance of the forests, especially along the Atlantic coast, renders them less and less favorable to mankind. In southern Mexico and Yucatan the stately equatorial rain forest, the most exuberant of all types of vegetation and the most unconquerable by man, makes its appearance. It forms a discontinuous belt along the wet east coast and on the lower slopes of the mountains from southern Yucatan to Venezuela. Then it is interrupted by the grasslands of the Orinoco, but revives again in still greater magnificence in the Guianas. Thence it stretches not only along the coast but far into the little known interior of the Great Amazon basin, while southward it borders all the coast as far as southern Brazil. In the Amazon basin it reaches its highest development and becomes the crowning glory of the vegetable world, the most baffling obstacle to human progress. Except in its evil effects on man, the equatorial rain forest is the antithesis of the forests of the extreme north. The equatorial trees are hardwood giants, broad leaved, bright flowered, and often fruit-bearing. The northern trees are softwood dwarfs, needle-leaved, flowerless, and cone-bearing. The equatorial trees are often branchless for one hundred feet, but spread at the top into a broad overarching canopy which shuts out the sun perpetually. The northern trees form sharp little pyramids with low, widely spreading branches at the base and only short twigs at the top. In the equatorial forests there is almost no underbrush. The animals, such as monkeys, snakes, parrots, and brilliant insects, live chiefly in the lofty treetops. In the northern forests there is almost nothing except underbrush, and the foxes, rabbits, weasels, ptarmigans, and mosquitoes live close to the ground in the shelter of the branches. Both forests are alike, however, in being practically uninhabited by man. Each is peopled only by primitive nomadic hunters who stand at the very bottom in the scale of civilization. Aside from the rain forest there are two other types in tropical countries--jungle and scrub. The distinction between rain forest, jungle, and scrub is due to the amount and the season of rainfall. An understanding of this distinction not only explains many things in the present condition of Latin America but also in the history of pre-Columbian Central America. Forests, as we have seen, require that the ground be moist throughout practically the whole of the season that is warm enough for growth. Since the warm season lasts throughout the year within the tropics, dense forests composed of uniformly large trees corresponding to our oaks, maples, and beeches will not thrive unless the ground is wet most of the time. Of course there may be no rain for a few weeks, but there must be no long and regularly recurrent periods of drought. Smaller trees and such species as the cocoanut palm are much less exacting and will flourish even if there is a dry period of several months. Still smaller, bushy species will thrive even when the rainfall lasts only two or three months. Hence where the rainy season lasts most of the year, rain forest prevails; where the rainy and dry seasons do not differ greatly in length, tropical jungle is the dominant growth; and where the rainy season is short and the dry season long, the jungle degenerates into scrub or bush. The relation of scrub, jungle, and rain forest is well illustrated in Yucatan, where the ancient Mayas reared their stately temples. On the northern coast the annual rainfall is only ten or fifteen inches and is concentrated largely in our summer months. There the country is covered with scrubby bushes six to ten feet high. These are beautifully green during the rainy season from June to October, but later in the year lose almost all their leaves. The landscape would be much like that of a thick, bushy pasture in the United States at the same season, were it not that in the late winter and early spring some of the bushes bear brilliant red, yellow, or white flowers. As one goes inland from the north coast of Yucatan the rainfall increases. The bushes become taller and denser, trees twenty feet high become numerous, and many rise thirty or forty feet or even higher. This is the jungle. Its smaller portions suggest a second growth of timber in the deciduous forests of the United States fifteen or twenty years after the cutting of the original forest, but here there is much more evidence of rapid growth. A few species of bushes and trees may remain green throughout the year, but during the dry season most of the jungle plants lose their leaves, at least in part. With every mile that one advances into the more rainy interior, the jungle becomes greener and fresher, the density of the lower growths increases, and the proportion of large trees becomes greater until finally jungle gives place to genuine forest. There many of the trees remain green throughout the year. They rise to heights of fifty or sixty feet even on the borders of their province, and at the top form a canopy so thick that the ground is shady most of the time. Even in the drier part of the year when some of the leaves have fallen, the rays of the sun scarcely reach the ground until nine or ten o'clock in the morning. Even at high noon the sunlight straggles through only in small patches. Long, sinuous lianas, often queerly braided, hang down from the trees; epiphytes and various parasitic growths add their strange green and red to the complex variety of vegetation. Young palms grow up almost in a day and block a trail which was hewn out with much labor only a few months before. Wherever the death of old trees forms an opening, a thousand seedlings begin a fierce race to reach the light. Everywhere the dominant note is intensely vigorous life, rapid growth, and quick decay. In their effect on man, the three forms of tropical forest are very different. In the genuine rain forest agriculture is almost impossible. Not only does the poor native find himself baffled in the face of Nature, but the white man is equally at a loss. Many things combine to produce this result. Chief among them are malaria and other tropical diseases. When a few miles of railroad were being built through a strip of tropical forest along the coast of eastern Guatemala, it was impossible to keep the laborers more than twenty days at a time; indeed, unless they were sent away at the end of three weeks, they were almost sure to be stricken with virulent malarial fevers from which many died. An equally potent enemy of agriculture is the vegetation itself. Imagine the difficulty of cultivating a garden in a place where the weeds grow all the time and where many of them reach a height of ten or twenty feet in a single year. Perhaps there are people in the world who might cultivate such a region and raise marvelous crops, but they are not the indolent people of tropical America; and it is in fact doubtful whether any kind of people could live permanently in the tropical forest and retain energy enough to carry on cultivation. Nowhere in the world is there such steady, damp heat as in these shadowy, windless depths far below the lofty tops of the rain forest. Nowhere is there greater disinclination to work than among the people who dwell in this region. Consequently in the vast rain forests of the Amazon basin and in similar small forests as far north as Central America, there are today practically no inhabitants except a mere handful of the poorest and most degraded people in the world. Yet in ancient times the northern border of the rain forest was the seat of America's most advanced civilization. The explanation of this contradiction will appear later. * * See Chapter 5, Aztecs. Tropical jungle borders the rain forest all the way from southern Mexico to southern Brazil. It treats man far better than does the rain forest. In marked contrast to its more stately neighbor, it contains abundant game. Wild fruits ripen at almost all seasons. A few banana plants and palm trees will well-nigh support a family. If corn is planted in a clearing, the return is large in proportion to the labor. So long as the population is not too dense, life is so easy that there is little to stimulate progress. Hence, although the people of the jungle are fairly numerous, they have never played much part in history. Far more important is the role of those living in the tropical lands where scrub is the prevailing growth. In our day, for example, few tropical lowlands are more progressive than the narrow coastal strip of northern Yucatan. There on the border between jungle and scrub the vegetation does not thrive sufficiently to make life easy for the chocolate-colored natives. Effort is required if they would make a living, yet the effort is not so great as to be beyond the capacity of the indolent people of the tropics. Leaving the forests, let us step out into the broad, breezy grass-lands. One would scarcely expect that a journey poleward out of the forest of northern Canada would lead to an improvement in the conditions of human life, yet such is the case. Where the growing season becomes so short that even the hardiest trees disappear, grassy tundras replace the forest. By furnishing food for such animals as the musk-ox, they are a great help to the handful of scattered Indians who dwell on the northern edge of the forest. In summer, when the animals grow fat on the short nutritious grass, the Indians follow them out into the open country and hunt them vigorously for food and skins to sustain life through the long dreary winter. In many cases the hunters would advance much farther into the grass-lands were it not that the abundant musk-oxen tempt the Eskimo of the seacoast also to leave their homes and both sides fear bloody encounters. With the growth of civilization the advantage of the northern grass-lands over the northern forests becomes still more apparent. The domestic reindeer is beginning to replace the wild musk-ox. The reindeer people, like the Indian and Eskimo hunters, must be nomadic. Nevertheless their mode of life permits them to live in much greater numbers and on a much higher plane of civilization than the hunters. Since they hunt the furbearing animals in the neighboring forests during the winter, they diminish the food supply of the hunters who dwell permanently in the forest, and thus make their life still more difficult. The northern forests bid fair to decline in population rather than increase. In this New World of ours, strange as it may seem, the almost uninhabited forest regions of the far north and of the equator are probably more than twice as large as the desert areas with equally sparse population. South of the tundras the grass-lands have a still greater advantage over the forests. In the forest region of the Laurentian highland abundant snow lasts far into the spring and keeps the ground so wet and cold that no crops can be raised. Moreover, because of the still greater abundance of snow in former times, the largest of ice sheets, as we have seen, accumulated there during the Glacial Period and scraped away most of the soil. The grassy plains, on the contrary, are favored not only by a deep, rich soil, much of which was laid down by the ice, but by the relative absence of snow in winter and the consequent rapidity with which the ground becomes warm in the spring. Hence the Canadian plains from the United States boundary northward to latitude 57 degrees contain a prosperous agricultural population of over a million people, while the far larger forested areas in the same latitude support only a few thousand. The question is often asked why, in a state of nature, trees are so scarce on the prairies--in Iowa, for instance--although they thrive when planted. In answer we are often told that up to the middle of the nineteenth century such vast herds of buffaloes roamed the prairies that seedling trees could never get a chance to grow. It is also said that prairie fires sweeping across the plains destroyed the little trees whenever they sprouted. Doubtless the buffaloes and the fires helped to prevent forest growth, but another factor appears to be still more important. All the States between the Mississippi River and the Rocky Mountains receive much more rain in summer than in winter. But as the soil is comparatively dry in the spring when the trees begin their growth, they are handicapped. They could grow if nothing else interfered with them, just as peas will grow in a garden if the weeds are kept out. If peas, however, are left uncared for, the weeds gain the upper hand and there are no peas the second year. If the weeds are left to contend with grass, the grass in the end prevails. In the eastern forest region, if the grass be left to itself, small trees soon spring up in its midst. In half a century a field of grass goes back to forest because trees are especially favored by the climate. In the same way in the prairies, grass is especially favored, for it is not weakened by the spring drought, and it grows abundantly until it forms the wonderful stretches of waving green where the buffalo once grew fat. Moreover the fine glacial soil of the prairies is so clayey and compact that the roots of trees cannot easily penetrate it. Since grasses send their roots only into the more friable upper layers of soil, they possess another great advantage over the trees. Far to the south of the prairies lie the grass-lands of tropical America, of which the Banos of the Orinoco furnish a good example. Almost everywhere their plumed grasses have been left to grow undisturbed by the plough, and even grazing animals are scarce. These extremely flat plains are flooded for months in the rainy season from May to October and are parched in the dry season that follows. As trees cannot endure such extremes, grasses are the prevailing growth. Elsewhere the nature of the soil causes many other grassy tracts to be scattered among the tropical jungle and forest. Trees are at a disadvantage both in porous, sandy soils, where the water drains away too rapidly, and in clayey soil, where it is held so long that the ground is saturated for weeks or months at a time. South of the tropical portion of South America the vast pampas of Argentina closely resemble the North American prairies and the drier plains to the west of them. Grain in the east and cattle in the west are fast causing the disappearance of those great tussocks of tufted grasses eight or nine feet high which hold among grasses a position analogous to that of the Big Trees of California among trees of lower growth. It is often said that America has no real deserts. This is true in the sense that there are no regions such as are found in Asia and Africa where one can travel a hundred miles at a stretch and scarcely see a sign of vegetation-nothing but barren gravel, graceful wavy sand dunes, hard wind-swept clay, or still harder rock salt broken into rough blocks with upturned edges. In the broader sense of the term, however, America has an abundance of deserts--regions which bear a thin cover of bushy vegetation but are too dry for agriculture without irrigation. On the north such deserts begin in southern Canada where a dry region abounding in small salt lakes lies at the eastern base of the Rocky Mountains. In the United States the deserts lie almost wholly between the Sierra Nevada and the Rocky Mountain ranges, which keep out any moisture that might come from either the west or the east. Beginning on the north with the sagebrush plateau of southern Washington, the desert expands to a width of seven hundred miles in the gray, sage-covered basins of Nevada and Utah. In southern California and Arizona the sage-brush gives place to smaller forms like the saltbush, and the desert assumes a sterner aspect. Next comes the cactus desert extending from Arizona far south into Mexico. One of the notable features of the desert is the extreme heat of certain portions. Close to the Nevada border in southern California, Death Valley, 250 feet below sea-level, is the hottest place in America. There alone among the American regions familiar to the writer does one have that feeling of intense, overpowering aridity which prevails so often in the deserts of Arabia and Central Asia. Some years ago a Weather Bureau thermometer was installed in Death Valley at Furnace Creek, where the only flowing water in more than a hundred miles supports a depressing little ranch. There one or two white men, helped by a few Indians, raise alfalfa, which they sell at exorbitant prices to deluded prospectors searching for riches which they never find. Though the terrible heat ruins the health of the white men in a year or two, so that they have to move away, they have succeeded in keeping a thermometer record for some years. No other properly exposed, out-of-door thermometer in the United States, or perhaps in the world, is so familiar with a temperature of 100 degrees F. or more. During the period of not quite fifteen hundred days from the spring of 1911 to May, 1915, a maximum temperature of 100 degrees F. or more was reached on five hundred and forty-eight days, or more than one-third of the time. On July 10, 1913, the mercury rose to 134 degrees F. and touched the top of the tube. How much higher it might have gone no one can tell. That day marks the limit of temperature yet reached in this country according to official records. In the summer of 1914 there was one night when the thermometer dropped only to 114 degrees F., having been 128 degrees F. at noon. The branches of a peppertree whose roots had been freshly watered wilted as a flower wilts when broken from the stalk. East and south of Death Valley lies the most interesting section of the American desert, the so-called succulent desert of southern Arizona and northern Mexico. There in greatest profusion grow the cacti, perhaps the latest and most highly specialized of all the great families of plants. There occur such strange scenes as the "forests" of suhuaros, whose giant columns have already been described. Their beautiful crowns of large white flowers produce a fruit which is one of the mainstays of the Papagos and other Indians of the regions. In this same region the yucca is highly developed, and its tall stalks of white or greenish flowers make the desert appear like a flower garden. In fact this whole desert, thanks to light rains in summer as well as winter, appears extraordinarily green and prosperous. Its fair appearance has deceived many a poor settler who has vainly tried to cultivate it. Farther south the deserts of America are largely confined to plateaus like those of Mexico and Peru or to basins sheltered on all sides from rain-bearing winds. In such basins the suddenness of the transition from one type of vegetation to another is astonishing. In Guatemala, for instance, the coast is bordered by thick jungle which quickly gives place to magnificent rain forest a few miles inland. This continues two or three score miles from the coast until a point is reached where mountains begin to obstruct the rain-bearing trade-winds. At once the rain forest gives place to jungle; in a few miles jungle in its turn is replaced by scrub; and shortly the scrub degenerates to mere desert bush. Then in another fifty miles one rises to the main plateau passing once more through scrub. This time the scrub gives place to grass-lands diversified by deciduous trees and pines which give the country a distinctly temperate aspect. On such plateaus the chief civilization of the tropical Latin-American countries now centers. In the past, however, the plateaus were far surpassed by the Maya lowlands of Yucatan and Guatemala. We are wont to think of deserts as places where the plants are of few kinds and not much crowded. As a matter of fact, an ordinary desert supports a much greater variety of plants than does either a forest or a prairie. The reason is simple. Every desert contains wet spots near springs or in swamps. Such places abound with all sorts of water-loving plants. The deserts also contain a few valleys where the larger streams keep the ground moist at all seasons. In such places the variety of trees is as great as in many forests. Moreover almost all deserts have short periods of abundant moisture. At such times the seeds of all sorts of little annual plants, including grasses, daisies, lupines, and a host of others, sprout quickly, and give rise to a carpet of vegetation as varied and beautiful as that of the prairie. Thus the desert has not only its own peculiar bushes and succulents but many of the products of vegetation in swamps, grasslands, and forests. Though much of the ground is bare in the desert, the plants are actually crowded together as closely as possible. The showers of such regions are usually so brief that they merely wet the surface. At a depth of a foot or more the soil of many deserts never becomes moist from year's end to year's end. It is useless for plants to send their roots deep down under such circumstances, for they might not reach water for a hundred feet. Their only recourse is to spread horizontally. The farther they spread, the more water they can absorb after the scanty showers. Hence the plants of the desert throttle one another by extending their roots horizontally, just as those of the forest kill one another by springing rapidly upward and shutting out the light. Vegetation, whether in forests, grasslands, or deserts, is the primary source of human sustenance. Without it man would perish miserably; and where it is deficient, he cannot rise to great heights in the scale of civilization. Yet strangely enough the scantiness of the vegetation of the deserts was a great help in the ascent of man. Only in dry regions could primitive man compete with nature in fostering the right kind of vegetation. In such regions arose the nations which first practised agriculture. There man became comparatively civilized while his contemporaries were still nomadic hunters in the grasslands and the forests. CHAPTER V. THE RED MAN IN AMERICA When the white man first explored America, the parts of the continent that had made most progress were by no means those that are most advanced today. * None of the inhabitants, to be sure, had risen above barbarism. Yet certain nations or tribes had advanced much higher than others. There was a great contrast, for example, between the well-organized barbarians of Peru and the almost completely unorganized Athapascan savages near Hudson Bay. * In the present chapter most of the facts as to the Indians north of Mexico are taken from the admirable "Handbook of American Indians North of Mexico," edited by F. W. Hodge, Smithsonian Institution, Bureau of Ethnology, Bulletin 30, Washington, 1907, two volumes. In summing up the character and achievements of the Indians I have drawn also on other sources, but have everywhere taken pains to make no statements which are not abundantly supported by this authoritative publication. In some cases I have not hesitated to paraphrase considerable portions of its articles. In the northern continent aboriginal America reached its highest development in three typical environments. The first of these regions centered in the valley of Mexico where dwelt the Aztecs, but it extended as far north as the Pueblos in Arizona and New Mexico. The special feature of the environment was the relatively dry, warm climate with the chief rainfall in summer. The Indians living in this environment were notable for their comparatively high social organization and for religious ceremonials whose elaborateness has rarely been surpassed. On the whole, the people of this summer rain or Mexican type were not warlike and offered little resistance to European conquest. Some tribes, to be sure, fought fiercely at first, but yielded within a few years; the rest submitted to the lordly Spaniards almost without a murmur. Their civilization, if such we may call it, had long ago seen its best days. The period of energy and progress had passed, and a time of inertia and decay had set in. A century after the Spaniards had overcome the aborigines of Mexico, other Europeans--French, English, and Dutch--came into contact with a sturdier type of red man, best represented by the Iroquois or Five Nations of central New York. This more active type dwelt in a physical environment notable for two features--the abundance of cyclonic storms bringing rain or snow at all seasons and the deciduous forest which thickly covered the whole region. Unlike the Mexican, the civilization of the Iroquois was young, vigorous, and growing. It had not learned to express itself in durable architectural forms like those of Mexico, nor could it rival the older type in social and religious organization. In political organization, however, the Five Nations had surpassed the other aboriginal peoples of North America. When the white man became acquainted with the Iroquois in the seventeenth century, he found five of their tribes organized into a remarkable confederation whose avowed object was to abolish war among themselves and to secure to all the members the peaceful exercise of their rights and privileges. So well was the confederation organized that, in spite of war with its enemies, it persisted for at least two hundred years. One of the chief characteristics of the Iroquois was their tremendous energy. They were so energetic that they pursued their enemies with an implacable relentlessness similar to the restless eagerness with which the people of the region from New York to Chicago now pursue their business enterprises. This led the Iroquois to torture their prisoners with the utmost ingenuity and cruelty. Not only did the savages burn and mutilate their captives, but they sometimes added the last refinement of torture by compelling the suffering wretches to eat pieces of flesh cut from their own bodies. Energy may lead to high civilization, but it may also lead to excesses of evil. The third prominent aboriginal type was that of the fishermen of the coast of British Columbia, especially the Haidas of the Queen Charlotte Islands. The most important features of their environment were the submerged coast with its easy navigation, the mild oceanic climate, and the dense pine forests. The Haidas, like the Iroquois, appear to have been a people who were still advancing. Such as it was, their greatness was apparently the product of their own ingenuity and not, like that of the Mexicans, an inheritance from a greater past. The Haidas lacked the relentless energy of the Iroquois and shared the comparatively gentle character which prevailed among all the Indians along the Pacific Coast. They were by no means weaklings, however. Commercially, for instance, they seem to have been more advanced than any North American tribe except those in the Mexican area. In architecture they stood equally high. We are prone to think of the Mexicans as the best architects among the aborigines, but when the white man came even the Aztecs were merely imitating the work of their predecessors. The Haidas, on the contrary, were showing real originality. They had no stone with which to build, for their country is so densely forested that stone is rarely visible. They were remarkably skillful, however, in hewing great beams from the forest. With these they constructed houses whose carved totem poles and graceful facades gave promise of an architecture of great beauty. Taking into account the difficulties presented by a material which was not durable and by tools which were nothing but bits of stone, we must regard their totem poles and mural decorations as real contributions to primitive architecture. In addition to these three highest types of the red man there were many others. Each, as we shall see, owed its peculiarities largely to the physical surroundings in which it lived. Of course different tribes possessed different degrees of innate ability, but the chief differences in their habits and mode of life arose from the topography, the climate, the plants, and the animals which formed the geographical setting of their homes. In previous chapters we have gained some idea of the topography of the New World and of the climate in its relation to plants and animals. We have also seen that climate has much to do with human energy. We have not, however, gained a sufficiently clear idea of the distribution of climatic energy. A map of the world showing how energy would be distributed if it depended entirely upon climate clarifies the subject. The dark shading of the map indicates those regions where energy is highest. It is based upon measurements of the strength of scores of individuals, upon the scholastic records of hundreds of college students, upon the piecework of thousands of factory operatives, and upon millions of deaths and births in a score of different countries. It takes account of three chief climatic conditions--temperature, humidity, and variability. It also takes account of mental as well as physical ability. Underneath it is a map of the distribution of civilization on the basis of the opinion of fifty authorities in fifteen different countries. The similarity of the two maps is so striking that there can be little question that today the distribution of civilization agrees closely with the distribution of climatic energy. When Egypt, Babylonia, Greece, and Rome were at the height of their power this agreement was presumably the same, for the storm belt which now gives variability and hence energy to the thickly shaded regions in our two maps then apparently lay farther south. It is generally considered that no race has been more closely dependent upon physical environment than were the Indians. Why, then, did the energizing effect of climate apparently have less effect upon them than upon the other great races? Why were not the most advanced Indian tribes found in the same places where white civilization is today most advanced? Climatic changes might in part account for the difference, but, although such changes apparently took place on a large scale in earlier times, there is no evidence of anything except minor fluctuations since the days of the first white settlements. Racial inheritance likewise may account for some of the differences among the various tribes, but it was probably not the chief factor. That factor was apparently the condition of agriculture among people who had neither iron tools nor beasts of burden. Civilization has never made much progress except when there has been a permanent cultivation of the ground. It has been said that "the history of agriculture is the history of man in his most primitive and most permanent aspect." If we examine the achievements and manner of life of the Indians in relation to the effect of climate upon agriculture and human energy, as well as in relation to the more obvious features of topography and vegetation, we shall understand why the people of aboriginal America in one part of the continent differed so greatly from those in another part. In the far north the state of the inhabitants today is scarcely different from what it was in the days of Columbus. Then, as now, the Eskimos had practically no political or social organization beyond the family or the little group of relatives who lived in a single camp. They had no permanent villages, but moved from place to place according to the season in search of fish, game, and birds. They lived this simple life not because they lacked ability but because of their surroundings. Their kayaks or canoes are marvels of ingenuity. With no materials except bones, driftwood, and skins they made boats which fulfilled their purpose with extraordinary perfection. Seated in the small, round hole which is the only opening in the deck of his canoe, the Eskimo hunter ties his skin jacket tightly outside the circular gunwale and is thus shut into a practically water-tight compartment. Though the waves dash over him, scarcely a drop enters the craft as he skims along with his double paddle among cakes of floating ice. So, too, the snowhouse with its anterooms and curved entrance passage is as clever an adaptation to the needs of wanderers in a land of ice and snow as is the skyscraper to the needs of a busy commercial people crowded into great cities. The fact that the oilburning, soapstone lamps of the Eskimo were the only means of producing artificial light in aboriginal America, except by ordinary fires, is another tribute to the ingenuity of these northerners. So, too, is the fire-drill by which they alone devised a means of increasing the speed with which one stick could be twirled against another to produce fire. In view of these clever inventions it seems safe to say that the Eskimo has remained a nomadic savage not because he lacks inventive skill but partly because the climate deadens his energies and still more because it forbids him to practice agriculture. Southward and inland from the coastal homes of the Eskimo lies the great region of the northern pine forests. It extends from the interior of Alaska southeastward in such a way as to include most of the Canadian Rockies, the northern plains from Great Bear Lake almost to Lake Winnipeg, and most of the great Laurentian shield around Hudson Bay and in the peninsula of Labrador. Except among the inhabitants of the narrow Pacific slope and those of the shores of Labrador and the St. Lawrence Valley, a single type of barbarism prevailed among the Indians of all the vast pine forest area. Only in a small section of the wheat-raising plains of Alberta and Saskatchewan have their habits greatly changed because of the arrival of the white man. Now as always the Indians in these northern regions are held back by the long, benumbing winters. They cannot practice agriculture, for no crops will grow. They cannot depend to any great extent upon natural vegetation, for aside from blueberries, a few lichens, and one or two other equally insignificant products, the forests furnish no food except animals. These lowly people seem to have been so occupied with the severe struggle with the elements that they could not even advance out of savagery into barbarism. They were homeless nomads whose movements were determined largely by the food supply. Among the Athapascans who occupied all the western part of the northern pine forests, clothing was made of deerskins with the hair left on. The lodges were likewise of deer or caribou skins, although farther south these were sometimes replaced by bark. The food of these tribes consisted of caribou, deer, moose, and musk-ox together with smaller animals such as the beaver and hare. They also ate various kinds of birds and the fish found in the numerous lakes and rivers. They killed deer by driving them into an angle formed by two converging rows of stakes, where they were shot by hunters lying in wait. Among the Kawchodinne tribe near Great Bear Lake hares were the chief source of both food and clothing. When an unusually severe winter or some other disaster diminished the supply, the Indians believed that the animals had mounted to the sky by means of the trees and would return by the same way. In 1841 owing to scarcity of hares many of this tribe died of starvation, and numerous acts of cannibalism are said to have occurred. Small wonder that civilization was low and that infanticide, especially of female children, was common. Among such people women were naturally treated with a minimum of respect. Since they were not skilled as hunters, there was relatively little which they could contribute toward the sustenance of the family. Hence they were held in low esteem, for among most primitive people woman is valued largely in proportion to her economic contribution. Her low position is illustrated by the peculiar funeral custom of the Takulli, an Athapascan tribe on the Upper Frazer River. A widow was obliged to remain upon the funeral pyre of her husband till the flames reached her own body. When the fire had died down she collected the ashes of her dead and placed them in a basket, which she was obliged to carry with her during three years of servitude in the family of her husband. At the end of that time a feast was held, when she was released from thraldom and permitted to remarry if she desired. Poor and degraded as the people of the northern forests may have been, they had their good traits. The Kutchins of the Yukon and Lower Mackenzie regions, though they killed their female children, were exceedingly hospitable and kept guests for months. Each head of a family took his turn in feasting the whole band. On such occasions etiquette required the host to fast until the guests had departed. At such feasts an interesting wrestling game was played. First the smallest boys began to wrestle. The victors wrestled with those next in strength and so on until finally the strongest and freshest man in the band remained the final victor. Then the girls and women went through the same progressive contest. It is hard to determine whether the people of the northern pine forest were more or less competent than their Eskimo neighbors. It perhaps makes little difference, for it is doubtful whether even a race with brilliant natural endowments could rise far in the scale of civilization under conditions so highly adverse. The Eskimos of the northern coasts and the people of the pine forests were not the only aborigines whose development was greatly retarded because they could not practice agriculture. All the people of the Pacific coast from Alaska to Lower California were in similar circumstances. Nevertheless those living along the northern part of this coast rose to a much higher level than did those of California. This has sometimes been supposed to show that geographical environment has little influence upon civilization, but in reality it proves exactly the opposite. The coast of British Columbia was one of the three chief centers of aboriginal America. As The Encyclopaedia Britannica * puts it: "The Haida people constituted with little doubt the finest race and that most advanced in the arts of the entire west coast of North America." They and their almost equally advanced Tlingit and Tsimshian neighbors on the mainland displayed much mechanical skill, especially in canoe-building, woodcarving, and the working of stone and copper, as well as in making blankets and baskets. To this day they earn a considerable amount of money by selling their carved objects of wood and slate to traders and tourists. Their canoes were hollowed out of logs of cedar and were often very large. Houses which were sometimes 40 by 100 feet were built of huge cedar beams and planks, which were first worked with stone and were then put together at great feasts. These correspond to the "raising bees" at which the neighbors gathered to erect the frames of houses in early New England. Each Haida house ordinarily had a single carved totem pole in the middle of the gable end which faced toward the beach. Often the end posts in front were also carved and the whole house was painted. Another evidence of the fairly advanced state of the Haidas was their active commercial intercourse with regions hundreds of miles away. At their "potlatches," as the raising bees were called by the whites, trading went on vigorously. Carved copper plates were among the articles which they esteemed of highest value. Standing in the tribe depended on the possession of property rather than on ability in war, in which respect the Haidas were more like the people of today than were any of the other Indian tribes. * 11th Edition, vol. XXII, p. 730. Slavery was common among the Haidas. Even as late as 1861, 7800 Tlingits held 828 slaves. Slavery may not be a good institution in itself, but it indicates that people are well-to-do, that they dwell in permanent abodes, and that they have a well-established social order. Among the more backward Iroquois, captives rarely became genuine slaves, for the social and economic organization was not sufficiently developed to admit of this. The few captives who were retained after a fight were adopted into the tribe of the captors or else were allowed to live with them and shift for themselves--a practice very different from that of the Haidas. Another feature of the Haidas' life which showed comparative progress was the social distinctions which existed among them. One of the ways in which individuals maintained their social position was by giving away quantities of goods of all kinds at the potlatches which they organized. A man sometimes went so far as to strip himself of nearly every possession except his house. In return for this, however, he obtained what seemed to him an abundant reward in the respect with which his fellow-tribesmen afterward regarded him. At subsequent potlatches he received in his turn a measure of their goods in proportion to his own gifts, so that he was sometimes richer than before. These potlatches were social as well as industrial functions, and dancing and singing were interspersed with the feasting. One of the amusements was a musical contest in which singers from one tribe or band would contend with one another as to which could remember the greatest number of songs or accurately repeat a new song after hearing it for the first time. At the potlatches the children of chiefs were initiated into secret societies. They had their noses, ears, and lips pierced for ornaments, and some of them were tattooed. This great respect for social position which the Haidas manifested is doubtless far from ideal, but it at least indicates that a part of the tribe was sufficiently advanced to accumulate property and to pass it on to its descendants--a custom that is almost impossible among tribes which move from place to place. The question suggests itself why these coast barbarians were so much in advance of their neighbors a few hundred miles away in the pine woods of the mountains. The climate was probably one reason for this superiority. Instead of being in a region like the center of the pine forests of British Columbia where human energy is sapped by six or eight months of winter, the Haidas enjoyed conditions like those of Scotland. Although snow fell occasionally, severe cold was unknown. Nor was there great heat in summer. The Haidas dwelt where both bodily strength and mental activity were stimulated. In addition to this advantage of a favorable climate these Indians had a large and steady supply of food close at hand. Most of their sustenance was obtained from the sea and from the rivers, in which the runs of salmon furnished abundant provisions, which rarely failed. In Hecate Strait, between the Queen Charlotte Islands and the mainland, there were wonderfully productive halibut fisheries, from which a supply of fish was dried and packed away for the winter, so that there was always a store of provisions on hand. The forests in their turn furnished berries and seeds, as well as bears, mountain goats, and other game. Moreover the people of the northwest coast had the advantage of not being forced to move from place to place in order to follow the fish. They lived on a drowned shore where bays, straits, and sounds are extraordinarily numerous. The great waves of the Pacific are shut out by the islands so that the waterways are almost always safe for canoes. Instead of moving their dwellings in order to follow the food supply, as the Eskimo and the people of the pine forest were forced to do, the Haidas and their neighbors were able without difficulty to bring their food home. At all seasons the canoes made it easy to transport large supplies of fish from places even a hundred miles away. Having settled dwellings, the Haidas could accumulate property and acquire that feeling of permanence which is one of the most important conditions for the development of civilization. Doubtless the Haidas were intellectually superior to many other tribes, but even if they had not been greatly superior, their surroundings would probably have made them stand relatively high in the scale of civilization. Southward from the Haidas, around Puget Sound and in Washington and Oregon, there was a gradual decline in civilization. The Chinook Indians of the lower Columbia, beyond the limits of the great northern archipelago, had large communal houses occupied by three or four families of twenty or more individuals. Their villages were thus fairly permanent, although there was much moving about in summer owing to the nature of the food supply, which consisted chiefly of salmon, with roots and berries indigenous to the region. The people were noted as traders not only among themselves but with surrounding tribes. They were extremely skillful in handling their canoes, which were well made, hollowed out of single logs, and often of great size. In disposition they are described as treacherous and deceitful, especially when their cupidity was aroused. Slaves were common and were usually obtained by barter from surrounding tribes, though occasionally by successful raids. These Indians of Oregon by no means rivaled the Haidas, for their food supply was less certain and they did not have the advantage of easy water communication, which did so much to raise the Haidas to a high level of development. Of the tribes farther south an observer says: "In general rudeness of culture the California Indians are scarcely above the Eskimo, and whereas the lack of development of the Eskimo on many sides of their nature is reasonably attributable in part to their difficult and limiting environment, the Indians of California inhabit a country naturally as favorable, it would seem, as it might be. If the degree of civilization attained by a people depends in any large measure on their habitat, as does not seem likely, it might be concluded from the case of the California Indians that natural advantages were an impediment rather than an incentive to progress." In some of the tribes, such as the Hupa, for example, there existed no organization and no formalities in the government of the village. Formal councils were unknown, although the chief might and often did ask advice of his men in a collected body. In general the social structure of the California Indians was so simple and loose that it is hardly correct to speak of their tribes. Whatever solidarity there was among these people was due in part to family ties and in part to the fact that they lived in the same village and spoke the same dialect. Between different groups of these Indians, the common bond was similarity of language as well as frequency and cordiality of intercourse. In so primitive a condition of society there was neither necessity nor opportunity for differences of rank. The influence of chiefs was small and no distinct classes of slaves were known. Extreme poverty was the chief cause of the low social and political organization of these Indians. The Maidus in the Sacramento Valley were so poor that, in addition to consuming every possible vegetable product, they not only devoured all birds except the buzzard, but ate badgers, skunks, wildcats, and mountain lions, and even consumed salmon bones and deer vertebrae. They gathered grasshoppers and locusts by digging large shallow pits in a meadow or flat. Then, setting fire to the grass on all sides, they drove the insects into the pit. Their wings being burned off by the flames, the grasshoppers were helpless and were thus collected by the bushel. Again of the Moquelumne, one of the largest tribes in central California, it is said that their houses were simply frameworks of poles and brush which in winter were covered with earth. In summer they erected cone-shaped lodges of poles among the mountains. In favorable years they gathered large quantities of acorns, which formed their principal food, and stored them for winter use in granaries raised above the ground. Often, however, the crop was poor, and the Indians were left on the verge of starvation. Finally in the far south, in the peninsula of Lower California, the tribes were "probably the lowest in culture of any Indians in North America, for their inhospitable environment which made them wanderers, was unfavorable to the foundation of government even of the rude and unstable kind found elsewhere." The Yuman tribes of the mountains east of Santiago wore sandals of maguey fiber and descended from their own territory among the mountains "to eat calabash and other fruits" that grew beside the Colorado River. They were described as "very dirty on account of the much mescal they eat." Others speak of them as "very filthy in their habits. To overcome vermin they coat their heads with mud with which they also paint their bodies. On a hot day it is by no means unusual to see them wallowing in the mud like pigs." They were "exceedingly poor, having no animals except foxes of which they had a few skins. The dress of the women in summer was a shirt and a bark skirt. The men appear to have been practically unclothed during this season. The practice of selling children seems to have been common. Their sustenance was fish, fruits, vegetables, and seeds of grass, and many of the tribes were said to have been dreadfully scorbutic." A little to the east of these degraded savages the much more advanced Mohave tribe had its home on the lower Colorado River. The contrast between these neighboring tribes throws much light on the reason for the low estate of the California Indians. "No better example of the power of environment to better man's condition can be found than that shown as the lower Colorado is reached. Here are tribes of the same family (as those of Lower California) remarkable not only for their fine physical development, but living in settled villages with well-defined tribal lines, practising a rude, but effective, agriculture, and well advanced in many primitive Indian arts. The usual Indian staples were raised except tobacco, these tribes preferring a wild tobacco of their region to the cultivated." * * Hodge, "Handbook of American Indians." This quotation is highly significant. With it should be compared the fact that there is no evidence that corn or anything else was cultivated in California west of the Rio Colorado Valley. California is a region famous throughout America for its agriculture, but its crops are European in origin. Even in the case of fruits, such as the grape, which have American counterparts, the varieties actually cultivated were brought from Europe. Wheat and barley, the chief foodstuffs for which California and similar subtropical regions are noted, were unknown in the New World before the coming of the white man. In pre-Columbian America corn was the only cultivated cereal. The other great staples of early American agriculture were beans and pumpkins. All three are preeminently summer crops and need much water in July and August. In California there is no rain at this season. Though the fall rains, which begin to be abundant in October and November, do not aid these summer crops, they favor wheat and barley. The winter rains and the comparatively warm winter weather permit these grains to grow slowly but continuously. When the warm spring arrives, there is still enough rain to permit wheat and barley to make a rapid growth and to mature their seeds long before the long, dry summer begins. The comparatively dry weather of May and June is just what these cereals need to ripen the crop, but it is fatal to any kind of agriculture which depends on summer rain. Crops can of course be grown during the summer in California by means of irrigation, but this is rarely a simple process. If irrigation is to be effective in California, it cannot depend on the small streams which practically dry up during the long, rainless summer, but it must depend on comparatively large streams which flow in well-defined channels. With our modern knowledge and machinery it is easy for us to make canals and ditches and to prepare the level fields needed to utilize this water. A people with no knowledge of agriculture, however, and with no iron tools cannot suddenly begin to practice a complex and highly developed system of agriculture. In California there is little or none of the natural summer irrigation which, in certain parts of America, appears to have been the most important factor leading to the first steps in tilling the ground. The lower Colorado, however, floods broad areas every summer. Here, as on the Nile, the retiring floods leave the land so moist that crops can easily be raised. Hence the Mohave Indians were able to practice agriculture and to rise well above their kinsmen not only in Lower California but throughout the whole State. In the Rocky Mountain region of the United States, just as on the Pacific coast, the condition of the tribes deteriorated more and more the farther they lived to the south. In the regions where the rainfall comes in summer, however, and hence favors primitive agriculture, there was a marked improvement. The Kutenai tribes lived near the corner where Idaho, Montana, and British Columbia now meet. They appear to have been of rather high grade, noteworthy for their morality, kindness, and hospitality. More than any other Indians of the Rocky Mountain region, they avoided drunkenness and lewd intercourse with the whites. Their mental ability was comparatively high, as appears from their skill in buffalo-hunting, in making dugouts and bark canoes, and in constructing sweat-houses and lodges of both skins and rushes. Even today the lower Kutenai are noted for their water-tight baskets of split roots. Moreover the degree to which they used the plants that grew about them for food, medicine, and economical purposes was noteworthy. They also had an esthetic appreciation of several plants and flowers--a gift rare among Indians. These people lived in the zone of most stimulating climate and, although they did not practice agriculture and had little else in their surroundings to help them to rise above the common level, they dwelt in a region where there was rain enough in summer to prevent their being on the verge of starvation, as the Indians of California usually were. Moreover they were near enough to the haunts of the buffalo to depend on that great beast for food. Since one buffalo supplies as much food as a hundred rabbits, these Indians were vastly better off than the people of the drier parts of the western coast. South of the home of the Kutenai, in eastern Oregon, southern Idaho, Nevada, Utah, and neighboring regions dwelt the Utes and other Shoshoni tribes. In this region the rainfall, which is no greater than that of California, occurs chiefly in winter. The long summer is so dry that, except by highly developed methods of irrigation, agriculture is impossible. Hence it is not surprising to find a traveler in 1850 describing one tribe of the Ute family as "without exception the most miserable looking set of human beings I ever saw. They have hitherto subsisted principally on snakes, lizards, roots." The lowest of all the Ute tribes were those who lived in the sage-brush. The early explorer, Bonneville, found the tribes of Snake River wintering in brush shelters without roofs merely heaps of brush piled high, behind which the Indians crouched for protection from wind and snow. Crude as such shelters may seem, they were the best that could be constructed by people who dwelt where there was no vegetation except little bushes, and where the soil was for the most part sandy or so salty that it could not easily be made into adobe bricks. The food of these Utes and Shoshonis was no better than their shelters. There were no large animals for them to hunt; rabbits were the best that they could find. Farther to the east, where the buffalo wandered during part of the year and where there are some forests, the food was better, the shelters were more effective, and, in general, the standard of living was higher, although racially the two groups of people were alike. In this case, as in others, the people whose condition was lowest were apparently as competent as those whose material conditions were much better. Today, although the Ute Indians, like most of their race, are rather slow, some tribes, such as the Payutes, are described as not only "peaceful and moral," but also "industrious." They are highly commended for their good qualities by those who have had the best opportunities for judging. While not as bright in intellect as some of the prairie tribes whom we shall soon consider, they appear to possess more solidity of character. By their willingness and efficiency as workers they have made themselves necessary to the white farmers and have thus supplied themselves with good clothing and many of the comforts of life. They have resisted, too, many of the evils coming from the advance of civilization, so that one agent speaks of these Indians as presenting the singular anomaly of improving by contact with the whites. Apparently their extremely low condition in former times was due merely to that same handicap of environment which kept back the Indians of California. Compare these backward but not wholly ungifted Utes with the Hopi who belonged to the same stock. The relatively high social organization of the latter people and the intricacy and significance of their religious ceremonials are well known. Mentally the Hopi seem to be the equal of any tribe, but it is doubtful whether they have much more innate capacity than many of their more backward neighbors. Nevertheless they made much more progress before the days of the white man, as can easily be seen in their artistic development. Every one who has crossed the continent by the Santa Fe route knows how interesting and beautiful are their pottery, basketry, and weaving. Not only in art but also in government the Hopi are highly advanced. Their governing body is a council of hereditary elders together with the chiefs of religious fraternities. Among these officials there is a speaker chief and a war chief, but there seems never to have been any supreme chief of all the Hopi. Each pueblo has an hereditary chief who directs all the communal work, such as the cleaning of the springs and the general care of the village. Crimes are rare. This at first sight seems strange in view of the fact that no penalty was inflicted for any crime except sorcery, but under Hopi law all transgressions could be reduced to sorcery. One of the most striking features of Hopi life was its rich religious development. The Hopi recognized a large number of supernatural beings and had a great store of most interesting and poetic mythological tales. The home of the Hopi would seem at first sight as unfavorable to progress as that of their Ute cousins, but the Hopi have the advantage of being the most northwesterly representatives of the Indians who dwell within the regions of summer rain. Fortunately for them, their country is too desert and unforested for them to subsist to any great degree by the chase. They are thus forced to devote all their energy to agriculture, through which they have developed a relatively high standard of living. They dwell far enough south to have their heaviest rainfall in summer and not in winter, as is the case in Utah, so that they are able to cultivate crops of corn and beans. Where such an intensive system of agriculture prevails, the work of women is as valuable as that of men. The position of woman is thus relatively high among the Hopi, for she is useful not only for her assistance in the labors of the field but also for her skill in preserving the crops, grinding the flour, and otherwise preparing the comparatively varied food which this tribe fortunately possesses. From northern New Mexico and Arizona to Mexico City summer rains, dry winters, and still drier springs, are the rule. Forests are few, and much of the country is desert. The more abundant the rains, the greater the number of people and the greater the opportunities for the accumulation of wealth, and thus for that leisure which is necessary to part of a community if civilization is to make progress. That is one reason why the civilization of the summer rain people becomes more highly developed as they go from north to south. The fact that the altitude of the country increases from the United States border southward also tends in the same direction, for it causes the climate to be cooler and more bracing at Mexico City than at places farther north. The importance of summer rains in stimulating growth and in facilitating the early stages of agriculture is noteworthy. Every one familiar with Arizona and New Mexico knows how the sudden summer showers fill the mountain valleys with floods which flow down upon the plain and rapidly spread out into broad, thin sheets, often known as playas. There the water stands a short time and then either sinks into the ground or evaporates. Such places are favored with the best kind of natural irrigation, and after the first shower it is an easy matter for the primitive farmer to go out and drop grains of corn into holes punched with a stick. Thereafter he can count on other showers to water his field while the corn sprouts and grows to maturity. All that he needs to do is to watch the field to protect it from the rare depredations of wild animals. As time goes on the primitive farmer realizes the advantage of leading the water to particularly favorable spots and thus begins to develop a system of artificial irrigation. In regions where such advantageous conditions prevail, the people who live permanently in one place succeed best, for the work that they do one year helps them the next. They are not greatly troubled by weeds, for, though grasses grow as well as corn in the places where the water spreads out, the grasses take the form of little clumps which can easily be pulled up. In the drier parts of the area of summer rain, it becomes necessary to conserve the water supply to the utmost. The Hopi consider sandy fields the best, for the loose sand on top acts as a natural blanket to prevent evaporation from the underlying layers. Sometimes in dry seasons the Hopi use extraordinary methods to help their seeds to sprout. For instance, they place a seed in a ball of saturated mud which they bury beneath several inches of sand. As the sand prevents evaporation, practically all the water is retained for the use of the seed, which thereupon sprouts and grows some inches by the time the first summer floods arrive. The Indians of the Great Plains lived a very different life from that of the natives of either the mountains or the Pacific coast. In the far north, to be sure, the rigorous climate caused all the Indians to live practically alike, whether in the Rockies, the plains, or the Laurentian highland. South of them, in that great central expanse stretching from the latitude of Lake Winnipeg to the Rio Grande River, the Indians of the plains possessed a relatively uniform type of life peculiar to themselves. This individuality was due partly to the luxuriant carpet of grass which covered the plains and partly to the supply of animal food afforded by the vast herds of buffaloes which roamed in tens of thousands throughout the whole territory. The grass was important chiefly because it prevented the Indians from engaging in agriculture, for it must never be forgotten that the Indians had neither iron tools nor beasts of burden to aid them in overcoming the natural difficulties in the way of agriculture. To be sure, they did occasionally pound meteoric iron into useful implements, but this substance was so rare that probably not one Indian in a hundred had ever seen a piece. The Indians were quite familiar with copper, but there is not the slightest evidence that they had discovered any means of hardening it. Metals played no real part in the life of any of the Indians of America, and without such tools as iron spades and hoes it was impossible for them to cultivate grassland. If they burned the prairie and dropped seeds into holes, the corn or beans which they thus planted were sure to be choked by the quickly springing grass. To dig away the tough sod around the hole for each seed would require an almost incredible amount of work even with iron tools. To accomplish this with wooden spades, rude hoes made of large flakes of flint, or the shoulder blades of the buffalo, was impossible on any large scale. Now and then in some river bottom where the grass grew in clumps and could be easily pulled up, a little agriculture was possible. That is all that seems to have been attempted on the great grassy plains. The Indians could not undertake any widespread cultivation of the plains not only because they lacked iron tools but also because they had no draft animals. The buffalo was too big, too fierce, and too stupid to be domesticated. In all the length and breadth of the two Americas there was no animal to take the place of the useful horse, donkey, or ox. The llama was too small to do anything but carry light loads, and it could live only in a most limited area among the cold Andean highlands. Even if the aboriginal Americans could have made iron ploughs, they could not have ploughed the tough sod without the aid of animals. Moreover, even if the possession of metal tools and beasts of burden had made agriculture possible in the grass-lands, it would have been difficult, in the absence of wood for fences, to prevent the buffalo from eating up the crops or at least from tramping through them and spoiling them. Thus the fertile land of the great plains remained largely unused until the white man came to the New World bringing the iron tools and domestic animals that were necessary to successful agriculture. Although farming of any sort was almost as impossible in the plains as in the dry regions of winter rains farther west, the abundance of buffaloes made life much easier in many respects. It is astonishing to see how many purposes these animals served. An early traveler who dwelt among one of the buffalo-hunting tribes, the Tonkawa of central Texas, says: "Besides their meat it [the buffalo] furnishes them liberally what they desire for conveniences. The brains are used to soften skins, the horns for spoons and drinking cups, the shoulder blades to dig up and clear off the ground, the tendons for threads and bow strings, the hoofs to glue the arrow-feathering. From the tail-hair they make ropes and girths, from the wool, belts and various ornaments. The hide furnishes... shields, tents, shirts, footwear, and blankets to protect them from the cold." * *See Hodge, "Handbook of American Indians," vol. II, p. 781. The buffalo is a surprisingly stupid animal. When a herd is feeding it is possible for a man to walk into the midst of it and shoot down an animal. Even when one of their companions falls dead, the buffaloes pay no attention to the hunter provided he remains perfectly still. The wounded animals are not at first dangerous but seek to flee. Only when pursued and brought to bay do they turn on their pursuers. When the Indians of an encampment united their forces, as was their regular habit, they were able to slaughter hundreds of animals in a few days. The more delicate parts of the meat they ate first, often without cooking them. The rest they dried and packed away for future use, while they prepared the hides as coverings for the tents or as rugs in which to sleep. Wherever the buffaloes were present in large numbers, the habits of the Indians were much the same. They could not live in settled villages, for there was no assurance that the buffalo would come to any particular place each year. The plains tribes were therefore more thoroughly nomadic than almost any others, especially after the introduction of horses. Because they wandered so much, they came into contact with other tribes to an unusual degree, and much of the contact was friendly. Gradually the Indians developed a sign language by which tribes of different tongues could communicate with one another. At first these signs were like pictographs, for the speaker pointed as nearly as possible to the thing that he desired to indicate, but later they became more and more conventional. For example, man, the erect animal, was indicated by throwing up the hand, with its back outward and the index finger extending upward. Woman was indicated by a sweeping downward movement of the hand at the side of the head with fingers extended to denote long hair or the combing of flowing locks. Among the plains Indians, the Dakotas, the main tribe of the Sioux family, are universally considered to have stood highest not only physically but mentally, and probably morally. Their bravery was never questioned, and they conquered or drove out every rival except the Chippewas. Their superiority was clearly seen in their system of government. Personal fitness and popularity determined chieftainship more than did heredity. The authority of the chief was limited by the Band Council, without whose approbation little or nothing could be accomplished. In one of the Dakota tribes, the Tetons, the policing of a village was confided to two or three officers who were appointed by the chief and who remained in power until their successors were appointed. Day and night they were always on the watch, and so arduous were their labors that their term of service was necessarily short. The brevity of their term, however, was atoned for by the greatness of their authority, for in the suppression of disturbances no resistance was suffered. Their persons were sacred, and if in the execution of their duty they struck even a chief of the second class they could not be punished. The Dakotas, who lived in the region where their name is still preserved, inhabited that part of the great plain which is climatically most favorable to great activity. It is perhaps because of their response to the influence of this factor of geographical environment that they and their neighbors are the best known of the plains tribes. Their activity in later times is evident from the fact that the Tetons were called "the plundering Arabs of America." If their activities had been more wisely directed, they might have made a great name for themselves in Indian history. In the arts they stood as high as could be expected in view of the wandering life which they led and the limited materials with which they had to work. In the art of making pictographs, for instance, they excelled all other tribes, except perhaps the Kiowas, a plains tribe of Colorado and western Kansas. On the hides of buffalo, deer, and antelope which formed their tents, the Dakotas painted calendars, which had a picture for each year, or rather for each winter, while those of the Kiowas had a summer symbol and a winter symbol. Probably these calendars reveal the influence of the whites, but they at least show that these people of the plains were quickwitted. Farther south the tribes of the plains stood on a much lower level than the Dakotas. The Spanish explorer, Cabeza de Vaca, describes the Yguases in Texas, among whom he lived for several years, in these words: "Their support is principally roots which require roasting two days. Many are very bitter. Occasionally they take deer and at times fish, but the quantity is so small and the famine so great that they eat spiders and eggs of ants, worms, lizards, salamanders, snakes, and vipers that kill whom they strike, and they eat earth and all that there is, the dung of deer, things I omit to mention and I earnestly believe that were there stones in that land they would eat them. They save the bones of the fish they consume, the snakes and other animals, that they may afterward beat them together and eat the powder." During these painful periods, they bade Cabeza de Vaca "not to be sad. There would soon be prickly pears, although the season of this fruit of the cactus might be months distant. When the pears were ripe, the people feasted and danced and forgot their former privations. They destroyed their female infants to prevent them being taken by their enemies and thus becoming the means of increasing the latter's number." East of the Great Plains there dwelt still another important type of Indians, the people of the deciduous forests. Their home extended from the Great Lakes to the Gulf of Mexico. As we have already seen, the Iroquois who inhabited the northern part of this region were in many respects the highest product of aboriginal America. The northern Iroquois tribes, especially those known as the Five Nations, were second to no other Indian people north of Mexico in political organization, statecraft, and military prowess. Their leaders were genuine diplomats, as the wily French and English statesmen with whom they treated soon discovered. One of their most notable traits was the reverence which they had for the tribal law. The wars that they waged were primarily for political independence, for the fundamental principle of their confederation was that by uniting with one another they would secure the peace and welfare of all with whom they were connected by ties of blood. They prevented blood feuds by decreeing that there should be a price for the killing of a co-tribesman, and they abstained from eating the flesh of their enemies in order to avoid future strife. So thoroughly did they believe in the rights of the individual that women were accorded a high position. Among some of the tribes the consent of all the women who had borne children was required before any important measure could be taken. Candidates for a chiefship were nominated by the votes of the mothers, and, as lands and houses were the property of the women, their power in the tribe was great. The Iroquois were sedentary and agricultural, and depended on the chase for only a small part of their existence. The northern tribes were especially noted for their skill in building fortifications and houses. Their so-called castles were solid wooden structures with platforms running around the top on the inside. From the platforms stones and other missiles could be hurled down upon besiegers. According to our standards such dwellings were very primitive, but they were almost as great an advance upon the brush piles of the Utes as our skyscrapers are upon them. Farther south in the Carolinas, the Cherokees, another Iroquoian tribe, stand out prominently by reason of their unusual mental ability. Under the influence of the white man, the Cherokees were the first to adopt a constitutional form of government embodied in a code of laws written in their own language. Their language was reduced to writing by means of an alphabet which one of their number named Sequoya had devised. Sequoya and other leaders, however, may not have been pure Indians, for by that time much white blood had been mixed with the tribe. Yet even before the coming of the white man the Cherokees were apparently more advanced in agriculture than the Iroquois were, but less advanced in their form of government, in their treatment of women, and in many other respects. In general, as we go from north to south in the region of deciduous forests, we find that among the early Indians agriculture became more and more important and the people more sedentary, though not always more progressive in other ways. The Catawbas, for instance, in South Carolina were sedentary agriculturists and seem to have differed little in general customs from their neighbors. Their men were brave and honest but lacking in energy. In the Muskhogean family of Indians, comprising the Creeks, Choctaws, Chickasaws, and Seminoles, who occupied the Gulf States from Georgia to Mississippi, all the tribes were agricultural and sedentary and occupied villages of substantial houses. The towns near the tribal frontiers were usually palisaded, but those more remote from invasion were unprotected. All these Indians were brave but not warlike in the violent fashion of the Five Nations. The Choctaws would fight only in self-defense, it was said, but the Creeks and especially the Chickasaws were more aggressive. In their government these Muskhogean tribes appear to have attained a position corresponding to their somewhat advanced culture in other respects. Yet their confederacies were loose and flimsy compared with that of the Five Nations. Another phase of the life of the tribes in the southern part of the region of deciduous forests is illustrated by the Natchez of Mississippi. These people were strictly sedentary and depended chiefly upon agriculture for a livelihood. They possessed considerable skill in the arts. For instance, they wove a cloth from the inner bark of the mulberry tree and made excellent pottery. They also constructed great mounds of earth upon which to erect their dwellings and temples. Like a good many of the other southern tribes, they fought when it was necessary, but they were peaceable compared with the Five Nations. They had a form of sun-worship resembling that of Mexico, and in other ways their ideas were like those of the people farther south. For instance, when a chief died, his wives were killed. In times of distress the parents frequently offered their children as sacrifice. Many characteristics of the Natchez and other southern tribes seem to indicate that they had formerly possessed a civilization higher than that which prevailed when the white man came. The Five Nations, on the contrary, apparently represent an energetic people who were on the upward path and who might have achieved great things if the whites had not interrupted them. The southern Indians resemble people whose best days were past, for the mounds which abound in the Gulf States appear to have been built chiefly in pre-Columbian days. Their objects of art, such as the remarkable wooden mortars found at Key Marco and the embossed copper plates found elsewhere in Florida, point to a highly developed artistic sense which was no longer in evidence at the coming of the white man. It is interesting to see the way in which climatic energy tended to give the Five Nations a marked superiority over the tribesmen of the South, while agriculture tended in the opposite direction. There has been much discussion as to the part played by agriculture among the primitive Americans, especially in the northeast. Corn, beans, and squashes were an important element in the diet of the Indians of the New England region, while farther south potatoes, sunflower seeds, and melons were also articles of food. The New England tribes knew enough about agriculture to use fish and shells for fertilizer. They had wooden mattocks and hoes made from the shoulder blades of deer, from tortoise shells, or from conch shells set in handles. They also had stone hoes and spades, while the women used short pickers or parers about a foot long and five inches wide. Seated on the ground they used these to break the upper part of the soil and to grub out weeds, grass, and old cornstalks. They had the regular custom of burning over an old patch each year and then replanting it. Sometimes they merely put the seeds in holes and sometimes they dug up and loosened the ground for each seed. Clearings they made by girdling the trees, that is, by cutting off the bark in a circle at the bottom and thus causing the tree to die. The brush they hacked or broke down and burned when it was dry enough. There is much danger of confusing the agricultural condition of the Indian after the European had modified his life with his condition before the European came to America. For instance, in the excellent article on agriculture in the "Handbook of American Indians," conditions prevailing as late as 1794 in the States south of the Great Lakes are spoken of as if typical of aboriginal America. But at that time the white man had long been in contact with the Indian, and iron tools had largely taken the place of stone. The rapidity with which European importations spread may be judged by the fact that as early as 1736 the Iroquois in New York not only had obtained horses but were regularly breeding them. The use of the iron axe of course spread with vastly greater rapidity than that of the horse, for an axe or a knife was the first thing that an Indian sought from the white man. In the eighteenth century agriculture had thus become immeasurably easier than before, yet even then the Indians still kept up their old habit of cultivating the same fields only a short time. The regular practice was to cultivate a field five, ten, and sometimes even twenty or more years, and then abandon it. * *Ordinarily it is stated that this practice was due to the exhaustion of the soil. That, however, is open to question, for five or ten years' desultory cultivation on the part of the Indian would scarcely exhaust the soil so much that people would go to the great labor of making new clearings and moving their villages. Moreover, in the Southern States it is well known today that the soil is exhausted much more rapidly than farther north because it contains less humus. Nevertheless the southern tribes cultivated the land about their villages for long periods. Tribes like the Creeks, the Cherokees, and the Natchez appear to have been decidedly less prone to move than the Iroquois, in spite of the relatively high development of these northern nations. What hindered agriculture most in the northern part of the deciduous forest was the grass. Any one who has cultivated a garden knows how rapidly the weeds grow. He also knows that there is no weed so hard to exterminate as grass. When once it gets a foothold mere hoeing seems only to make it grow the faster. The only way to get rid of grass when once it has become well established is to plow the field and start over again, but this the Indians could not do. When first a clearing was made in the midst of the forest, there was no grass to be contended with. Little by little, however, it was sure to come in, until at length what had been a garden was in a fair way to become a meadow. Then the Indians would decide that it was necessary to seek new fields. One might suppose that under such circumstances the Indians would merely clear another patch of forest not far from the village and so continue to live in the old place. This, however, they did not do because the labor of making a clearing with stone axes and by the slow process of girdling and burning the trees was so great that it was possible only in certain favored spots where by accident the growth was less dense than usual. When once a clearing became grassy, the only thing to do was to hunt for a new site, prepare a clearing, and then move the village. This was apparently the reason why the Iroquois, although successful in other ways, failed to establish permanent towns like those of the Pueblos and the Haidas. Their advancement not only in architecture but in many of the most important elements of civilization was for this reason greatly delayed. There was little to stimulate them to improve the land to which they were attached, for they knew that soon they would have to move. Farther south the character of the grassy vegetation changes, and the condition of agriculture alters with it. The grass ceases to have that thick, close, turfy quality which we admire so much in the fields of the north, and it begins to grow in bunches. Often a southern hillside may appear from a distance to be as densely covered with grass as a New England hayfield. On closer examination, however, the growth is seen to consist of individual bunches which can easily be pulled up, so that among the southern tribes the fields did not become filled with grass as they did in the north, for the women had relatively little difficulty in keeping out this kind of weed as well as others. In this survey of aboriginal America we have been impressed by the contrast between two diverse aspects of the control of human activities by physical environment. We saw, in the first place, that in our own day the distribution of culture in America is more closely related to climatic energy than to any other factor, because man is now so advanced in the arts and crafts that agricultural difficulties do not impede him, except in the far north and in tropical forests. Secondly, we have found that, although all the geographical factors acted upon the Indian as they do today, the absence of metals and beasts of burden compelled man to be nomadic, and hence to remain in a low stage of civilization in many places where he now can thrive. In the days long before Columbus the distribution of civilization in the Red Man's Continent offered still a third aspect, strikingly different both from that of today and from that of the age of discovery. In that earlier period the great centers of civilization were south of their present situation. In the southern part of North America from Arizona to Florida there are abundant evidences that the Indians whom the white man found were less advanced than their predecessors. The abundant ruins of Arizona and New Mexico, their widespread distribution, and the highly artistic character of the pottery and other products of handicraft found in them seem to indicate that the ancient population was both denser and more highly cultured than that which the Europeans finally ousted. In the Gulf States there is perhaps not much evidence that there was a denser population at an earlier period, but the excellence of the pre-Columbian handicrafts and the existence of a decadent sun worship illustrate the way in which the civilization of the past was higher than that of later days. The Aztecs, who figure so largely in the history of the exploration and conquest of Mexico, were merely a warlike tribe which had been fortunate in the inheritance of a relatively high civilization from the past. So, too, the civilization found by the Spaniards at places such as Mitla, in the extreme south of Mexico, could not compare with that of which evidence is found in the ruins. Most remarkable of all is the condition of Yucatan and Guatemala. In northern Yucatan the Spaniards found a race of mild, decadent Mayas living among the relics of former grandeur. Although they used the old temples as shrines, they knew little of those who had built these temples and showed still less capacity to imitate the ancient architects. Farther south in the forested region of southern Yucatan and northern Guatemala the conditions are still more surprising, for today these regions are almost uninhabitable and are occupied by only a few sickly, degraded natives who live largely by the chase. Yet in the past this region was the scene of by far the highest culture that ever developed in America. There alone in this great continent did men develop an architecture which, not only in massiveness but in wealth of architectural detail and sculptural adornment, vies with that of early Egypt or Chaldea. There alone did the art of writing develop. Yet today in those regions the density of the forest, the prevalence of deadly fevers, the extremely enervating temperature, and the steady humidity are as hostile to civilization as are the cold of the far north and the dryness of the desert. The only explanation of this anomaly seems to be that in the past the climatic zones of the world have at certain periods been shifted farther toward the equator than they are at present. Practically all the geographers of America now believe that within the past two or three thousand years climatic pulsations have taken place whereby places like the dry Southwest have alternately experienced centuries of greater moisture than at present and centuries as dry as today or even drier. During the moist centuries greater storminess prevailed, so that the climate was apparently better not only for agriculture but for human energy. At such times the standard of living was higher than now not only in the Southwest but in the Gulf States and in Mexico. In periods when the deserts of the southwestern United States were wet, the Maya region of Yucatan and Guatemala appears to have been relatively dry. Then the dry belt which now extends from northern Mexico to the northern tip of Yucatan apparently shifted southward. Such conditions would cause the forests of Yucatan and Guatemala to become much less dense than at present. This comparative deforestation would make agriculture easily possible where today it is out of the question. At the same time the relatively dry climate and the clearing away of the vegetation would to a large degree eliminate the malarial fevers and other diseases which are now such a terrible scourge in wet tropical countries. Then, too, the storms which at the present time give such variability to the climate of the United States would follow more southerly courses. In its stimulating qualities the climate of the home of the Mayas in the days of their prime was much more nearly like that which now prevails where civilization rises highest. From first to last the civilization of America has been bound up with its physical environment. It matters little whether we are dealing with the red race, the black, or the white. Nor does it matter whether we deal with one part of the continent or another. Wherever we turn we can trace the influence of mountains and plains, of rocks and metals from which tools are made, of water and its finny inhabitants, of the beasts of the chase from the hare to the buffalo, of domestic animals, of the native forests, grass-lands, and deserts, and, last but not least, of temperature, moisture, and wind in their direct effects upon the human body. At one stage of human development the possibilities of agriculture may be the dominant factor in man's life in early America. At another, domestic animals may be more important, and at still another, iron or waterways or some other factor may be predominant. It is the part of the later history of the American Continent to trace the effect of these various factors and to chronicle the influence that they have had upon man's progress. BIBLIOGRAPHICAL NOTE Although many books deal with the physical features of the Western Hemisphere and many others with the Indians, few deal with the two in relation to one another. One book, however, stands out preeminent in this respect, namely, Edward John Payne's "History of the New World Called America," 2 vols. (1892-99). This book, which has never been finished, attempts to explain the conditions of life among the American aborigines as the result of geographical conditions, especially of the food supply. Where the author carries this attempt into the field of special customs and religious rites, he goes too far. Nevertheless his work is uncommonly stimulating and deserves the careful attention of the reader who would gain a broad grasp of the relation of geography to the history of the New World. Two other good books which deal with the relation of geography to American history are Miss Ellen C. Semple's "American History and its Geographical Conditions" (1903) and A. P. Brigham's "Geographic Influences in American History" (1903). Both of these books interpret geography as if it included little except the form of the land. While they bring out clearly the effect of mountain barriers, indented coasts, and easy routes whether by land or water, they scarcely touch on the more subtle relationships between man on the one hand and the climate, plants, and animals which form the dominant features of his physical environment on the other hand. In their emphasis on the form of the land both Semple and Brigham follow the lead of W. M. Davis. In his admirable articles on America and the United States in "The Encyclopaedia Britannica" (11th edition) and in The International Geography edited by H. R. Mill (1901), Davis has given an uncommonly clear and vivid description of the main physical features of the New World. Living beings, however, play little part in this description, so that the reader is not led to an understanding of how physical geography affects human actions. Other good descriptions of the North American continent are found in the following books: I. C. Russell's "North America" (1904), Stanford's "Compendium of Modern Geography and Travel," including the volumes on Canada, the United States, and Central America, and the great volumes on America in "The Earth and its Inhabitants" by Elise Reclus, 19 vols. (1876-1894). Russell's book is largely physiographic but contains some good chapters on the Indians. In Stanford's "Compendium" the purpose is to treat man and nature in their relation to one another, but the relationships are not clearly brought out, and there is too much emphasis on purely descriptive and encyclopedic matter. So far as interest is concerned, the famous work by Elise Reclus holds high rank. It is an encyclopedia of geographical facts arranged and edited in such a way that it has all the interest of a fine book of travel. Like most of the other books, however, it fails to bring out relationships. As sources of information on the Indians, two books stand out with special prominence. "The American Race," by D. G. Brinton (1891), is a most scholarly volume devoted largely to a study of the Indians on a linguistic basis. It contains some general chapters, however, on the Indians and their environment, and these are most illuminating. The other book is the "Handbook of American Indians North of Mexico," edited by F. W. Hodge, and published by the United States Bureau of Ethnology (Washington, 1897, 1910, 1911). Its two large volumes are arranged in encyclopedic form. The various articles are written by a large number of scholars, including practically all the students who were at work on Indian ethnology at the time of publication. Many of the articles are the best that have been written and will not only interest the general reader but will contribute to an understanding of what America was when the Indians came here and what it still is today. 
28274	----	generously made available by The Internet Archive/American Libraries.) THE BEAUTIES OF NATURE [Illustration: _Frontispiece._ GROUP OF BEECHES, BURNHAM. _Page 167._] THE BEAUTIES OF NATURE AND THE WONDERS OF THE WORLD WE LIVE IN BY THE RIGHT HON. SIR JOHN LUBBOCK, BART., M.P. F.R.S., D.C.L., LL.D. New York MACMILLAN AND CO. AND LONDON 1892 _All rights reserved_ COPYRIGHT, 1892, BY MACMILLAN AND CO. TYPOGRAPHY BY J. S. CUSHING & CO., BOSTON, U.S.A. PRESSWORK BY BERWICK & SMITH, BOSTON, U.S.A. CONTENTS CHAPTER I PAGE INTRODUCTION 1 Beauty and Happiness 3 The Love of Nature 5 Enjoyment of Scenery 14 Scenery of England 19 Foreign Scenery 21 The Aurora 33 The Seasons 34 CHAPTER II ON ANIMAL LIFE 39 Love of Animals 41 Growth and Metamorphoses 43 Rudimentary Organs 45 Modifications 48 Colour 50 Communities of Animals 57 Ants 58 CHAPTER III ON ANIMAL LIFE--_continued_ 71 Freedom of Animals 73 Sleep 78 Senses 84 Sense of Direction 93 Number of Species 96 Importance of the Smaller Animals 97 Size of Animals 100 Complexity of Animal Structure 101 Length of Life 102 On Individuality 104 Animal Immortality 112 CHAPTER IV ON PLANT LIFE 115 Structure of Flowers 128 Insects and Flowers 134 Past History of Flowers 136 Fruits and Seeds 137 Leaves 138 Aquatic Plants 144 On Hairs 148 Influence of Soil 151 On Seedlings 152 Sleep of Plants 152 Behaviour of Leaves in Rain 155 Mimicry 156 Ants and Plants 156 Insectivorous Plants 158 Movements of Plants 159 Imperfection of our Knowledge 163 CHAPTER V WOODS AND FIELDS 165 Fairy Land 172 Tropical Forests 179 Structure of Trees 185 Ages of Trees 188 Meadows 192 Downs 194 CHAPTER VI MOUNTAINS 201 Alpine Flowers 205 Mountain Scenery 206 The Afterglow 213 The Origin of Mountains 214 Glaciers 227 Swiss Mountains 232 Volcanoes 236 Origin of Volcanoes 243 CHAPTER VII WATER 249 Rivers and Witchcraft 251 Water Plants 252 Water Animals 253 Origin of Rivers 255 The Course of Rivers 256 Deltas 272 CHAPTER VIII RIVERS AND LAKES 277 On the Directions of Rivers 279 The Conflicts and Adventures of Rivers 301 On Lakes 312 On the Configuration of Valleys 323 CHAPTER IX THE SEA 335 The Sea Coast 337 Sea Life 344 The Ocean Depths 351 Coral Islands 358 The Southern Skies 365 The Poles 367 CHAPTER X THE STARRY HEAVENS 373 The Moon 377 The Sun 382 The Planets 387 Mercury 388 Venus 390 The Earth 391 Mars 392 The Minor Planets 393 Jupiter 394 Saturn 395 Uranus 396 Neptune 397 Origin of the Planetary System 398 Comets 401 Shooting Stars 406 The Stars 410 Nebulæ 425 ILLUSTRATIONS FIG. PAGE 1. Larva of Choerocampa porcellus 53 2. Bougainvillea fruticosa; natural size. (After Allman) 107 3. Do. do. magnified 108 4. Do. do. Medusa-form 109 5. Medusa aurita, and progressive stages of development. (After Steenstrup) 110 6. White Dead-nettle 124 7. Do. 125 8. Do. 125 9. Salvia 127 10. Do. 127 11. Do. 127 12. Primrose 131 13. Do. 131 14. Arum 135 15. Twig of Beech 140 16. Arrangement of leaves in Acer platanoides 142 17. Diagram to illustrate the formation of Mountain Chains 216 18. Section across the Jura from Brenets to Neuchâtel. (After Jaccard) 219 19. Section from the Spitzen across the Brunnialp, and the Maderanerthal. (After Heim) 221 20. Glacier of the Blümlis Alp. (After Reclus) 228 21. Cotopaxi. (After Judd) 237 22. Lava Stream. (After Judd) 239 23. Stromboli, viewed from the north-west, April 1874. (After Judd) 242 24. Upper Valley of St. Gotthard 257 25. Section of a river valley. The dotted line shows a slope or talus of debris 260 26. Valley of the Rhone, with the waterfall of Sallenches, showing a talus of debris 261 27. Section across a valley. _A_, present river valley; _B_, old river terrace 262 28. Diagram of an Alpine valley, showing a river cone. Front view 263 29. Diagram of an Alpine valley, showing a river cone. Lateral view 265 30. Map of the Valais near Sion 266 31. View in the Rhone Valley, showing a lateral cone 267 32. Do. showing the slope of a river cone 268 33. Shore of the Lake of Geneva, near Vevey 269 34. View in the district of the Broads, Norfolk 271 35. Delta of the Po 273 36. Do. Mississippi 274 37. Map of the Lake District 281 38. Section of the Weald of Kent, _a, a_, Upper Cretaceous strata, chiefly Chalk, forming the North and South Downs; _b, b_, Escarpment of Lower Greensand, with a valley between it and the Chalk; _c, c_, Weald Clay, forming plains; _d_, Hills formed of Hastings Sand and Clay. The Chalk, etc., once spread across the country, as shown in the dotted lines 283 39. Map of the Weald of Kent 284 40. Sketch Map of the Swiss Rivers 291 41. Diagram in illustration of mountain structure 296 42. Sketch Map of the Aar and its tributaries 299 43. River system round Chur, as it used to be 308 44. River system round Chur, as it is 309 45. River system of the Maloya 311 46. Final slope of a river 317 47. Do. do. with a lake 318 48. Diagrammatic section of a valley (exaggerated). _R R_, rocky basis of a valley; _A A_, sedimentary strata; _B_, ordinary level of river; _C_, flood level 329 49. Whitsunday Island. (After Darwin) 359 50. A group of Lunar volcanoes; Maurolycus, Barocius, etc. (After Judd) 380 51. Orbits of the inner Planets. (After Ball) 388 52. Relative distances of the Planets from the Sun. (After Ball) 389 53. Saturn, with the surrounding series of rings. (After Lockyer) 395 54. The Parallactic Ellipse. (After Ball) 413 55. Displacement of the hydrogen line in the spectrum of Rigel. (After Clarke) 416 PLATES BURNHAM BEECHES _Frontispiece_ WINDSOR CASTLE. (From a drawing by J. Finnemore) _To face page_ 13 AQUATIC VEGETATION, RIO. (Published by Spooner and Co.) 145 TROPICAL FOREST, WEST INDIES. (After Kingsley) 179 SUMMIT OF MONT BLANC 203 THE MER DE GLACE, MONT BLANC 229 RYDAL WATER. (From a photograph by Frith and Co., published by Spooner and Co.) 247 WINDERMERE 253 VIEW IN THE VALAIS BELOW ST. MAURICE 264 VIEW UP THE VALAIS FROM THE LAKE OF GENEVA 268 THE LAND'S END. (From a photograph by Frith and Co., published by Spooner and Co.) 334 VIEW OF THE MOON NEAR THE THIRD QUARTER. (From a photograph by Prof. Draper) 371 CHAPTER I INTRODUCTION If any one gave you a few acres, you would say that you had received a benefit; can you deny that the boundless extent of the earth is a benefit? If any one gave you money, you would call that a benefit. God has buried countless masses of gold and silver in the earth. If a house were given you, bright with marble, its roof beautifully painted with colours and gilding, you would call it no small benefit. God has built for you a mansion that fears no fire or ruin ... covered with a roof which glitters in one fashion by day, and in another by night.... Whence comes the breath you draw; the light by which you perform the actions of your life? the blood by which your life is maintained? the meat by which your hunger is appeased?... The true God has planted, not a few oxen, but all the herds on their pastures throughout the world, and furnished food to all the flocks; he has ordained the alternation of summer and winter ... has invented so many arts and varieties of voice, so many notes to make music.... We have implanted in us the seed of all ages, of all arts; and God our Master brings forth our intellects from obscurity.--SENECA. CHAPTER I INTRODUCTION The world we live in is a fairyland of exquisite beauty, our very existence is a miracle in itself, and yet few of us enjoy as we might, and none as yet appreciate fully, the beauties and wonders which surround us. The greatest traveller cannot hope even in a long life to visit more than a very small part of our earth, and even of that which is under our very eyes how little we see! What we do see depends mainly on what we look for. When we turn our eyes to the sky, it is in most cases merely to see whether it is likely to rain. In the same field the farmer will notice the crop, geologists the fossils, botanists the flowers, artists the colouring, sportsmen the cover for game. Though we may all look at the same things, it does not at all follow that we should see them. It is good, as Keble says, "to have our thoughts lift up to that world where all is beautiful and glorious,"--but it is well to realise also how much of this world is beautiful. It has, I know, been maintained, as for instance by Victor Hugo, that the general effect of beauty is to sadden. "Comme la vie de l'homme, même la plus prospère, est toujours au fond plus triste que gaie, le ciel sombre nous est harmonieux. Le ciel éclatant et joyeux nous est ironique. La Nature triste nous ressemble et nous console; la Nature rayonnante, magnifique, superbe ... a quelque chose d'accablant."[1] This seems to me, I confess, a morbid view. There are many no doubt on whom the effect of natural beauty is to intensify feeling, to deepen melancholy, as well as to raise the spirits. As Mrs. W. R. Greg in her memoir of her husband tells us: "His passionate love for nature, so amply fed by the beauty of the scenes around him, intensified the emotions, as all keen perception of beauty does, but it did not add to their joyousness. We speak of the pleasure which nature and art and music give us; what we really mean is that our whole being is quickened by the uplifting of the veil. Something passes into us which makes our sorrows more sorrowful, our joys more joyful,--our whole life more vivid. So it was with him. The long solitary wanderings over the hills, and the beautiful moonlight nights on the lake served to make the shadows seem darker that were brooding over his home." But surely to most of us Nature when sombre, or even gloomy, is soothing and consoling; when bright and beautiful, not only raises the spirits, but inspires and elevates our whole being-- Nature never did betray The heart that loved her; 'tis her privilege, Through all the years of this our life, to lead From joy to joy: for she can so inform The mind that is within us, so impress With quietness and beauty, and so feed With lofty thoughts, that neither evil tongues, Rash judgments, nor the sneers of selfish men, Nor greetings where no kindness is, nor all The dreary intercourse of daily life, Shall e'er prevail against us, or disturb Our cheerful faith, that all which we behold Is full of blessings.[2] Kingsley speaks with enthusiasm of the heaths and moors round his home, "where I have so long enjoyed the wonders of nature; never, I can honestly say, alone; because when man was not with me, I had companions in every bee, and flower and pebble; and never idle, because I could not pass a swamp, or a tuft of heather, without finding in it a fairy tale of which I could but decipher here and there a line or two, and yet found them more interesting than all the books, save one, which were ever written upon earth." Those who love Nature can never be dull. They may have other temptations; but at least they will run no risk of being beguiled, by ennui, idleness, or want of occupation, "to buy the merry madness of an hour with the long penitence of after time." The love of Nature, again, helps us greatly to keep ourselves free from those mean and petty cares which interfere so much with calm and peace of mind. It turns "every ordinary walk into a morning or evening sacrifice," and brightens life until it becomes almost like a fairy tale. In the romances of the Middle Ages we read of knights who loved, and were loved by, Nature spirits,--of Sir Launfal and the Fairy Tryamour, who furnished him with many good things, including a magic purse, in which As oft as thou puttest thy hand therein A mark of gold thou shalt iwinne, as well as protection from the main dangers of life. Such times have passed away, but better ones have come. It is not now merely the few, who are so favoured. All those who love Nature she loves in return, and will richly reward, not perhaps with the good things, as they are commonly called, but with the best things, of this world; not with money and titles, horses and carriages, but with bright and happy thoughts, contentment and peace of mind. Happy indeed is the naturalist: to him the seasons come round like old friends; to him the birds sing: as he walks along, the flowers stretch out from the hedges, or look up from the ground, and as each year fades away, he looks back on a fresh store of happy memories. Though we can never "remount the river of our years," he who loves Nature is always young. But what is the love of Nature? Some seem to think they show a love of flowers by gathering them. How often one finds a bunch of withered blossoms on the roadside, plucked only to be thrown away! Is this love of Nature? It is, on the contrary, a wicked waste, for a waste of beauty is almost the worst waste of all. If we could imagine a day prolonged for a lifetime, or nearly so, and that sunrise and sunset were rare events which happened but a few times to each of us, we should certainly be entranced by the beauty of the morning and evening tints. The golden rays of the morning are a fortune in themselves, but we too often overlook the loveliness of Nature, because it is constantly before us. For "the senseless folk," says King Alfred, is far more struck At things it seldom sees. "Well," says Cicero, "did Aristotle observe, 'If there were men whose habitations had been always underground, in great and commodious houses, adorned with statues and pictures, furnished with everything which they who are reputed happy abound with; and if, without stirring from thence, they should be informed of a certain divine power and majesty, and, after some time, the earth should open, and they should quit their dark abode to come to us; where they should immediately behold the earth, the seas, the heavens; should consider the vast extent of the clouds and force of the winds; should see the sun, and observe his grandeur and beauty, and also his creative power, inasmuch as day is occasioned by the diffusion of his light through the sky; and when night has obscured the earth, they should contemplate the heavens bespangled and adorned with stars; the surprising variety of the moon, in her increase and wane; the rising and setting of all the stars, and the inviolable regularity of their courses; when,' says he, 'they should see these things, they would undoubtedly conclude that there are Gods, and that these are their mighty works.'"[3] Is my life vulgar, my fate mean, Which on such golden memories can lean?[4] At the same time the change which has taken place in the character of our religion has in one respect weakened the hold which Nature has upon our feelings. To the Greeks--to our own ancestors,--every River or Mountain or Forest had not only its own special Deity, but in some sense was itself instinct with life. They were not only peopled by Nymphs and Fauns, Elves and Kelpies, were not only the favourite abodes of Water, Forest, or Mountain Spirits, but they had a conscious existence of their own. In the Middle Ages indeed, these spirits were regarded as often mischievous, and apt to take offence; sometimes as essentially malevolent--even the most beautiful, like the Venus of Tannhäuser, being often on that very account all the more dangerous; while the Mountains and Forests, the Lakes and Seas, were the abodes of hideous ghosts and horrible monsters, of Giants and Ogres, Sorcerers and Demons. These fears, though vague, were none the less extreme, and the judicial records of the Middle Ages furnish only too conclusive evidence that they were a terrible reality. The light of Science has now happily dispelled these fearful nightmares. Unfortunately, however, as men have multiplied, their energies have hitherto tended, not to beautify, but to mar. Forests have been cut down, and replaced by flat fields in geometrical squares, or on the continent by narrow strips. Here and there indeed we meet with oases, in which beauty has not been sacrificed to profit, and it is then happily found that not only is there no loss, but the earth seems to reward even more richly those who treat her with love and respect. Scarcely any part of the world affords so great a variety in so small an area as our own island. Commencing in the south, we have first the blue sea itself, the pebbly beaches, the white chalk cliffs of Kent, the tinted sands of Alum Bay, the Red Sandstone of Devonshire, Granite and Gneiss in Cornwall: inland we have the chalk Downs and clear streams, the well-wooded weald and the rich hop gardens; farther westwards the undulating gravelly hills, and still farther the granite tors: in the centre of England we have to the east the Norfolk Broads and the Fens; then the fertile Midlands, the cornfields, rich meadows, and large oxen; and to the west the Welsh mountains; farther north the Yorkshire Wolds, the Lancashire hills, the Lakes of Westmoreland; lastly, the swelling hills, bleak moors, and picturesque castles of Northumberland and Cumberland. There are of course far larger rivers, but perhaps none lovelier than The crystal Thamis wont to glide In silver channel, down along the lee,[5] [Illustration: WINDSOR CASTLE. _To face page 13._] by lawns and parks, meadows and wooded banks, dotted with country houses and crowned by Windsor Castle itself (see Frontispiece). By many Scotland is considered even more beautiful. And yet too many of us see nothing in the fields but sacks of wheat, in the meadows but trusses of hay, and in woods but planks for houses, or cover for game. Even from this more prosaic point of view, how much there is to wonder at and admire, in the wonderful chemistry which changes grass and leaves, flowers and seeds, into bread and milk, eggs and cream, butter and honey! Almost everything, says Hamerton, "that the Peasant does, is lifted above vulgarity by ancient, and often sacred, associations." There is, indeed, hardly any business or occupation with reference to which the same might not be said. The triviality or vulgarity does not depend on what we do, but on the spirit in which it is done. Not only the regular professions, but every useful occupation in life, however humble, is honourable in itself, and may be pursued with dignity and peace. Working in this spirit we have also the satisfaction of feeling that, as in some mountain track every one who takes the right path, seems to make the way clearer for those who follow; so may we also raise the profession we adopt, and smooth the way for those who come after us. But, even for those who are not Agriculturists, it must be admitted that the country has special charms. One perhaps is the continual change. Every week brings some fresh leaf or flower, bird or insect. Every month again has its own charms and beauty. We sit quietly at home and Nature decks herself for us. In truth we all love change. Some think they do not care for it, but I doubt if they know themselves. "Not," said Jefferies, "for many years was I able to see why I went the same round and did not care for change. I do not want change: I want the same old and loved things, the same wild flowers, the same trees and soft ash-green; the turtle-doves, the blackbirds, the coloured yellow-hammer sing, sing, singing so long as there is light to cast a shadow on the dial, for such is the measure of his song, and I want them in the same place. Let me find them morning after morning, the starry-white petals radiating, striving upwards up to their ideal. Let me see the idle shadows resting on the white dust; let me hear the humble-bees, and stay to look down on the yellow dandelion disk. Let me see the very thistles opening their great crowns--I should miss the thistles; the reed grasses hiding the moor-hen; the bryony bine, at first crudely ambitious and lifted by force of youthful sap straight above the hedgerow to sink of its weight presently and progress with crafty tendrils; swifts shot through the air with outstretched wings like crescent-headed shaftless arrows darted from the clouds; the chaffinch with a feather in her bill; all the living staircase of the spring, step by step, upwards to the great gallery of the summer, let me watch the same succession year by year." After all then he did enjoy the change and the succession. Kingsley again in his charming prose idyll "My Winter Garden" tries to persuade himself that he was glad he had never travelled, "having never yet actually got to Paris." Monotony, he says, "is pleasant in itself; morally pleasant, and morally useful. Marriage is monotonous; but there is much, I trust, to be said in favour of holy wedlock. Living in the same house is monotonous; but three removes, say the wise, are as bad as a fire. Locomotion is regarded as an evil by our Litany. The Litany, as usual, is right. 'Those who travel by land or sea' are to be objects of our pity and our prayers; and I do pity them. I delight in that same monotony. It saves curiosity, anxiety, excitement, disappointment, and a host of bad passions." But even as he writes one can see that he does not convince himself. Possibly, he admits, "after all, the grapes are sour"; and when some years after he did travel, how happy he was! At last, he says, triumphantly, "At last we too are crossing the Atlantic. At last the dream of forty years, please God, would be fulfilled, and I should see (and happily not alone), the West Indies and the Spanish Main. From childhood I had studied their Natural History, their Charts, their Romances; and now, at last, I was about to compare books with facts, and judge for myself of the reported wonders of the Earthly Paradise." No doubt there is much to see everywhere. The Poet and the Naturalist find "tropical forests in every square foot of turf." It may even be better, and especially for the more sensitive natures, to live mostly in quiet scenery, among fields and hedgerows, woods and downs; but it is surely good for every one, from time to time, to refresh and strengthen both mind and body by a spell of Sea air or Mountain beauty. On the other hand we are told, and told of course with truth, that though mountains may be the cathedrals of Nature, they are generally remote from centres of population; that our great cities are grimy, dark, and ugly; that factories are creeping over several of our counties, blighting them into building ground, replacing trees by chimneys, and destroying almost every vestige of natural beauty. But if this be true, is it not all the more desirable that our people should have access to pictures and books, which may in some small degree, at any rate, replace what they have thus unfortunately lost? We cannot all travel; and even those who can, are able to see but a small part of the world. Moreover, though no one who has once seen, can ever forget, the Alps, the Swiss lakes, or the Riviera, still the recollection becomes less vivid as years roll on, and it is pleasant, from time to time, to be reminded of their beauties. There is one other advantage not less important. We sometimes speak as if to visit a country, and to see it, were the same thing. But this is not so. It is not every one who can see Switzerland like a Ruskin or a Tyndall. Their beautiful descriptions of mountain scenery depend less on their mastery of the English language, great as that is, than on their power of seeing what is before them. It has been to me therefore a matter of much interest to know which aspects of Nature have given the greatest pleasure to, or have most impressed, those who, either from wide experience or from their love of Nature, may be considered best able to judge. I will begin with an English scene from Kingsley. He is describing his return from a day's trout-fishing:-- "What shall we see," he says, "as we look across the broad, still, clear river, where the great dark trout sail to and fro lazily in the sun? White chalk fields above, quivering hazy in the heat. A park full of merry hay-makers; gay red and blue waggons; stalwart horses switching off the flies; dark avenues of tall elms; groups of abele, 'tossing their whispering silver to the sun'; and amid them the house,--a great square red-brick mass, made light and cheerful though by quoins and windows of white Sarsden stone, with high peaked French roofs, broken by louvres and dormers, haunted by a thousand swallows and starlings. Old walled gardens, gay with flowers, shall stretch right and left. Clipt yew alleys shall wander away into mysterious glooms, and out of their black arches shall come tripping children, like white fairies, to laugh and talk with the girl who lies dreaming and reading in the hammock there, beneath the black velvet canopy of the great cedar tree, like some fair tropic flower hanging from its boughs; and we will sit down, and eat and drink among the burdock leaves, and then watch the quiet house, and lawn, and flowers, and fair human creatures, and shining water, all sleeping breathless in the glorious light beneath the glorious blue, till we doze off, lulled by the murmur of a thousand insects, and the rich minstrelsy of nightingale and blackcap, thrush and dove. "Peaceful, graceful, complete English country life and country houses; everywhere finish and polish; Nature perfected by the wealth and art of peaceful centuries! Why should I exchange you, even for the sight of all the Alps?" Though Jefferies was unfortunately never able to travel, few men have loved Nature more devotedly, and speaking of his own home he expresses his opinion that: "Of all sweet things there is none so sweet as fresh air--one great flower it is, drawn round about; over, and enclosing us, like Aphrodite's arms; as if the dome of the sky were a bell-flower drooping down over us, and the magical essence of it filling all the room of the earth. Sweetest of all things is wild-flower air. Full of their ideal the starry flowers strained upwards on the bank, striving to keep above the rude grasses that push by them; genius has ever had such a struggle. The plain road was made beautiful by the many thoughts it gave. I came every morning to stay by the star-lit bank." Passing to countries across the ocean, Humboldt tells us that: "If I might be allowed to abandon myself to the recollection of my own distant travels, I would instance, amongst the most striking scenes of nature, the calm sublimity of a tropical night, when the stars, not sparkling, as in our northern skies, shed their soft and planetary light over the gently heaving ocean; or I would recall the deep valleys of the Cordilleras, where the tall and slender palms pierce the leafy veil around them, and waving on high their feathery and arrow-like branches, form, as it were, 'a forest above a forest'; or I would describe the summit of the Peak of Teneriffe, when a horizon layer of clouds, dazzling in whiteness, has separated the cone of cinders from the plain below, and suddenly the ascending current pierces the cloudy veil, so that the eye of the traveller may range from the brink of the crater, along the vine-clad slopes of Orotava, to the orange gardens and banana groves that skirt the shore. In scenes like these, it is not the peaceful charm uniformly spread over the face of nature that moves the heart, but rather the peculiar physiognomy and conformation of the land, the features of the landscape, the ever-varying outline of the clouds, and their blending with the horizon of the sea, whether it lies spread before us like a smooth and shining mirror, or is dimly seen through the morning mist. All that the senses can but imperfectly comprehend, all that is most awful in such romantic scenes of nature, may become a source of enjoyment to man, by opening a wide field to the creative power of his imagination. Impressions change with the varying movements of the mind, and we are led by a happy illusion to believe that we receive from the external world that with which we have ourselves invested it." Humboldt also singles out for especial praise the following description given of Tahiti by Darwin[6]:-- "The land capable of cultivation is scarcely in any part more than a fringe of low alluvial soil, accumulated round the base of mountains, and protected from the waves of the sea by a coral reef, which encircles at a distance the entire line of coast. The reef is broken in several parts so that ships can pass through, and the lake of smooth water within, thus affords a safe harbour, as well as a channel for the native canoes. The low land which comes down to the beach of coral sand is covered by the most beautiful productions of the inter-tropical regions. In the midst of bananas, orange, cocoa-nut, and breadfruit trees, spots are cleared where yams, sweet potatoes, sugar-cane, and pine-apples are cultivated. Even the brushwood is a fruit tree, namely, the guava, which from its abundance is as noxious as a weed. In Brazil I have often admired the contrast of varied beauty in the banana, palm, and orange tree; here we have in addition the breadfruit tree, conspicuous from its large, glossy, and deeply digitated leaf. It is admirable to behold groves of a tree, sending forth its branches with the force of an English Oak, loaded with large and most nutritious fruit. However little on most occasions utility explains the delight received from any fine prospect, in this case it cannot fail to enter as an element in the feeling. The little winding paths, cool from the surrounding shade, led to the scattered houses; and the owners of these everywhere gave us a cheerful and most hospitable reception." Darwin himself has told us, after going round the world that "in calling up images of the past, I find the plains of Patagonia frequently cross before my eyes; yet these plains are pronounced by all to be most wretched and useless. They are characterised only by negative possessions; without habitations, without water, without trees, without mountains, they support only a few dwarf plants. Why then--and the case is not peculiar to myself--have these arid wastes taken so firm possession of my mind? Why have not the still more level, the greener and more fertile pampas, which are serviceable to mankind, produced an equal impression? I can scarcely analyse these feelings, but it must be partly owing to the free scope given to the imagination. The plains of Patagonia are boundless, for they are scarcely practicable, and hence unknown; they bear the stamp of having thus lasted for ages, and there appears no limit to their duration through future time. If, as the ancients supposed, the flat earth was surrounded by an impassable breadth of water, or by deserts heated to an intolerable excess, who would not look at these last boundaries to man's knowledge with deep but ill-defined sensations?" Hamerton, whose wide experience and artistic power make his opinion especially important, says:-- "I know nothing in the visible world that combines splendour and purity so perfectly as a great mountain entirely covered with frozen snow and reflected in the vast mirror of a lake. As the sun declines, its thousand shadows lengthen, pure as the cold green azure in the depth of a glacier's crevasse, and the illuminated snow takes first the tender colour of a white rose, and then the flush of a red one, and the sky turns to a pale malachite green, till the rare strange vision fades into ghastly gray, but leaves with you a permanent recollection of its too transient beauty."[7] Wallace especially, and very justly, praises the description of tropical forest scenery given by Belt in his charming _Naturalist in Nicaragua_:-- "On each side of the road great trees towered up, carrying their crowns out of sight amongst a canopy of foliage, and with lianas hanging from nearly every bough, and passing from tree to tree, entangling the giants in a great network of coiling cables. Sometimes a tree appears covered with beautiful flowers which do not belong to it, but to one of the lianas that twines through its branches and sends down great rope-like stems to the ground. Climbing ferns and vanilla cling to the trunks, and a thousand epiphytes perch themselves on the branches. Amongst these are large arums that send down long aerial roots, tough and strong, and universally used instead of cordage by the natives. Amongst the undergrowth several small species of palms, varying in height from two to fifteen feet, are common; and now and then magnificent tree ferns send off their feathery crowns twenty feet from the ground to delight the sight by their graceful elegance. Great broad-leaved heliconias, leathery melastomæ, and succulent-stemmed, lop-sided leaved and flesh-coloured begonias are abundant, and typical of tropical American forests; but not less so are the cecropia trees, with their white stems and large palmated leaves standing up like great candelabra. Sometimes the ground is carpeted with large flowers, yellow, pink, or white, that have fallen from some invisible tree-top above; or the air is filled with a delicious perfume, the source of which one seeks around in vain, for the flowers that cause it are far overhead out of sight, lost in the great over-shadowing crown of verdure." "But," he adds, "the uniformity of climate which has led to this rich luxuriance and endless variety of vegetation is also the cause of a monotony that in time becomes oppressive." To quote the words of Mr. Belt: "Unknown are the autumn tints, the bright browns and yellows of English woods; much less the crimsons, purples, and yellows of Canada, where the dying foliage rivals, nay, excels, the expiring dolphin in splendour. Unknown the cold sleep of winter; unknown the lovely awakening of vegetation at the first gentle touch of spring. A ceaseless round of ever-active life weaves the fairest scenery of the tropics into one monotonous whole, of which the component parts exhibit in detail untold variety of beauty." Siberia is no doubt as a rule somewhat severe and inhospitable, but M. Patrin mentions with enthusiasm how one day descending from the frozen summits of the Altai, he came suddenly on a view of the plain of the Obi--the most beautiful spectacle, he says, which he had ever witnessed. Behind him were barren rocks and the snows of winter, in front a great plain, not indeed entirely green, or green only in places, and for the rest covered by three flowers, the purple Siberian Iris, the golden Hemerocallis, and the silvery Narcissus--green, purple, gold, and white, as far as the eye could reach. Wallace tells us that he himself has derived the keenest enjoyment from his sense of colour:-- "The heavenly blue of the firmament, the glowing tints of sunset, the exquisite purity of the snowy mountains, and the endless shades of green presented by the verdure-clad surface of the earth, are a never-failing source of pleasure to all who enjoy the inestimable gift of sight. Yet these constitute, as it were, but the frame and background of a marvellous and ever-changing picture. In contrast with these broad and soothing tints, we have presented to us in the vegetable and animal worlds an infinite variety of objects adorned with the most beautiful and most varied hues. Flowers, insects, and birds are the organisms most generally ornamented in this way; and their symmetry of form, their variety of structure, and the lavish abundance with which they clothe and enliven the earth, cause them to be objects of universal admiration. The relation of this wealth of colour to our mental and moral nature is indisputable. The child and the savage alike admire the gay tints of flowers, birds, and insects; while to many of us their contemplation brings a solace and enjoyment which is both intellectually and morally beneficial. It can then hardly excite surprise that this relation was long thought to afford a sufficient explanation of the phenomena of colour in nature; and although the fact that-- Full many a flower is born to blush unseen, And waste its sweetness on the desert air, might seem to throw some doubt on the sufficiency of the explanation, the answer was easy,--that in the progress of discovery man would, sooner or later, find out and enjoy every beauty that the hidden recesses of the earth have in store for him." Professor Colvin speaks with special admiration of Greek scenery:-- "In other climates, it is only in particular states of the weather that the remote ever seems so close, and then with an effect which is sharp and hard as well as clear; here the clearness is soft; nothing cuts or glitters, seen through that magic distance; the air has not only a new transparency so that you can see farther into it than elsewhere, but a new quality, like some crystal of an unknown water, so that to see into it is greater glory." Speaking of the ranges and promontories of sterile limestone, the same writer observes that their colours are as austere and delicate as the forms. "If here the scar of some old quarry throws a stain, or there the clinging of some thin leafage spreads a bloom, the stain is of precious gold, and the bloom of silver. Between the blue of the sky and the tenfold blue of the sea these bare ranges seem, beneath that daylight, to present a whole system of noble colour flung abroad over perfect forms. And wherever, in the general sterility, you find a little moderate verdure--a little moist grass, a cluster of cypresses--or whenever your eye lights upon the one wood of the district, the long olive grove of the Cephissus, you are struck with a sudden sense of richness, and feel as if the splendours of the tropics would be nothing to this." Most travellers have been fascinated by the beauty of night in the tropics. Our evenings no doubt are often delicious also, though the mild climate we enjoy is partly due to the sky being so often overcast. In parts of the tropics, however, the air is calm and cloudless throughout nearly the whole of the year. There is no dew, and the inhabitants sleep on the house-tops, in full view of the brightness of the stars and the beauty of the sky, which is almost indescribable. "Il faisait," says Bernardin de St. Pierre of such a scene, "une de ces nuits délicieuses, si communes entre les tropiques, et dont le plus abile pinceau ne rendrait pas le beauté. La lune paraissait au milieu du firmament, entourée d'un rideau de nuages, que ses rayons dissipaient par degrés. Sa lumière se répandait insensiblement sur les montagnes de l'île et sur leurs pitons, qui brillaient d'un vert argenté. Les vents retenaient leurs haleines. On entendait dans les bois, au fond des vallées, au haut des rochers, de petits cris, de doux murmures d'oiseaux, qui se caressaient dans leurs nids, réjouis par la clarté de la nuit et la tranquillité de l'air. Tous, jusqu'aux insectes, bruissaient sous l'herbe. Les étoiles étincelaient au ciel, et se réfléchissaient au sein de la mer, qui répétait leurs images tremblantes." In the Arctic and Antarctic regions the nights are often made quite gorgeous by the Northern Lights or Aurora borealis, and the corresponding appearance in the Southern hemisphere. The Aurora borealis generally begins towards evening, and first appears as a faint glimmer in the north, like the approach of dawn. Gradually a curve of light spreads like an immense arch of yellowish-white hue, which gains rapidly in brilliancy, flashes and vibrates like a flame in the wind. Often two or even three arches appear one over the other. After a while coloured rays dart upwards in divergent pencils, often green below, yellow in the centre, and crimson above, while it is said that sometimes almost black, or at least very dark violet, rays are interspersed among the rings of light, and heighten their effect by contrast. Sometimes the two ends of the arch seem to rise off the horizon, and the whole sheet of light throbs and undulates like a fringed curtain of light; sometimes the sheaves of rays unite into an immense cupola; while at others the separate rays seem alternately lit and extinguished. Gradually the light flickers and fades away, and has generally disappeared before the first glimpse of dawn. We seldom see the Aurora in the south of England, but we must not complain; our winters are mild, and every month has its own charm and beauty. In January we have the lengthening days. " February " the first butterfly. " March " the opening buds. " April " the young leaves and spring flowers. " May " the song of birds. " June " the sweet new-mown hay. " July " the summer flowers. " August " the golden grain. " September " the fruit. " October " the autumn tints. " November " the hoar frost on trees and the pure snow. " December " last not least, the holidays of Christmas, and the bright fireside. It is well to begin the year in January, for we have then before us all the hope of spring. Oh wind, If winter comes, can spring be long behind?[8] Spring seems to revive us all. In the Song of Solomon-- My beloved spake, and said unto me, Rise up, my love, my fair one, and come away. For, lo, the winter is past, The rain is over and gone; The flowers appear on the earth; The time of the singing of birds is come, The voice of the turtle is heard in our land, The fig tree putteth forth her green figs, And the vines with the tender grape give a good smell. "But indeed there are days," says Emerson, "which occur in this climate, at almost any season of the year, wherein the world reaches its perfection, when the air, the heavenly bodies, and the earth make a harmony, as if nature would indulge her offspring.... These halcyon days may be looked for with a little more assurance in that pure October weather, which we distinguish by the name of the Indian summer. The day, immeasurably long, sleeps over the broad hills and warm wide fields. To have lived through all its sunny hours, seems longevity enough." Yet does not the very name of Indian summer imply the superiority of the summer itself,--the real, the true summer, "when the young corn is bursting into ear; the awned heads of rye, wheat, and barley, and the nodding panicles of oats, shoot from their green and glaucous stems, in broad, level, and waving expanses of present beauty and future promise. The very waters are strewn with flowers: the buck-bean, the water-violet, the elegant flowering rush, and the queen of the waters, the pure and splendid white lily, invest every stream and lonely mere with grace."[9] For our greater power of perceiving, and therefore of enjoying Nature, we are greatly indebted to Science. Over and above what is visible to the unaided eye, the two magic tubes, the telescope and microscope, have revealed to us, at least partially, the infinitely great and the infinitely little. Science, our Fairy Godmother, will, unless we perversely reject her help, and refuse her gifts, so richly endow us, that fewer hours of labour will serve to supply us with the material necessaries of life, leaving us more time to ourselves, more leisure to enjoy all that makes life best worth living. Even now we all have some leisure, and for it we cannot be too grateful. "If any one," says Seneca, "gave you a few acres, you would say that you had received a benefit; can you deny that the boundless extent of the earth is a benefit? If a house were given you, bright with marble, its roof beautifully painted with colours and gilding, you would call it no small benefit. God has built for you a mansion that fears no fire or ruin ... covered with a roof which glitters in one fashion by day, and in another by night. Whence comes the breath which you draw; the light by which you perform the actions of your life? the blood by which your life is maintained? the meat by which your hunger is appeased?... The true God has planted, not a few oxen, but all the herds on their pastures throughout the world, and furnished food to all the flocks; he has ordained the alternation of summer and winter ... he has invented so many arts and varieties of voice, so many notes to make music.... We have implanted in us the seeds of all ages, of all arts; and God our Master brings forth our intellects from obscurity."[10] FOOTNOTES: [1] _Choses Vues._ [2] Wordsworth. [3] Cicero, _De Natura Deorum_. [4] Thoreau. [5] Spenser. [6] Darwin's _Voyage of the Beagle_. [7] Hamerton's _Landscape_. [8] Shelley. [9] Howitt's _Book of the Seasons_. [10] Seneca, _De Beneficiis_. CHAPTER II ON ANIMAL LIFE If thy heart be right, then will every creature be to thee a mirror of life, and a book of holy doctrine. THOMAS À KEMPIS. CHAPTER II ON ANIMAL LIFE There is no species of animal or plant which would not well repay, I will not say merely the study of a day, but even the devotion of a lifetime. Their form and structure, development and habits, geographical distribution, relation to other living beings, and past history, constitute an inexhaustible study. When we consider how much we owe to the Dog, Man's faithful friend, to the noble Horse, the patient Ox, the Cow, the Sheep, and our other domestic animals, we cannot be too grateful to them; and if we cannot, like some ancient nations, actually worship them, we have perhaps fallen into the other extreme, underrate the sacredness of animal life, and treat them too much like mere machines. Some species, however, are no doubt more interesting than others, especially perhaps those which live together in true communities, and which offer so many traits--some sad, some comical, and all interesting,--which reproduce more or less closely the circumstances of our own life. The modes of animal life are almost infinitely diversified; some live on land, some in water; of those which are aquatic some dwell in rivers, some in lakes or pools, some on the sea-shore, others in the depths of the ocean. Some burrow in the ground, some find their home in the air. Some live in the Arctic regions, some in the burning deserts; one little beetle (Hydrobius) in the thermal waters of Hammam-Meskoutin, at a temperature of 130°. As to food, some are carnivorous and wage open war; some, more insidious, attack their victims from within; others feed on vegetable food, on leaves or wood, on seeds or fruits; in fact, there is scarcely an animal or vegetable substance which is not the special and favourite food of one or more species. Hence to adapt them to these various requirements we find the utmost differences of form and size and structure. Even the same individual often goes through great changes. GROWTH AND METAMORPHOSES The development, indeed, of an animal from birth to maturity is no mere question of growth. The metamorphoses of Insects have long excited the wonder and admiration of all lovers of nature. They depend to a great extent on the fact that the little creatures quit the egg at an early stage of development, and lead a different life, so that the external forces acting on them, are very different from those by which they are affected when they arrive at maturity. A remarkable case is that of certain Beetles which are parasitic on Solitary Bees. The young larva is very active, with six strong legs. It conceals itself in some flower, and when the Bee comes in search of honey, leaps upon her, but is so minute as not to be perceived. The Bee constructs her cell, stores it with honey, and lays her egg. At that moment the little larva quits the Bee and jumps on to the egg, which she proceeds gradually to devour. Having finished the egg, she attacks the honey; but under these circumstances the activity which was at first so necessary has become useless; the legs which did such good service are no longer required; and the active slim larva changes into a white fleshy grub, which floats comfortably in the honey with its mouth just below the surface. Even in the same group we may find great differences. For instance, in the family of Insects to which Bees and Wasps belong, some have grub larvæ, such as the Bee and Ant; some have larvæ like caterpillars, such as the Sawflies; and there is a group of minute forms the larvæ of which live inside the eggs of other insects, and present very remarkable and abnormal forms. These differences depend mainly on the mode of life and the character of the food. RUDIMENTARY ORGANS Such modifications may be called adaptive, but there are others of a different origin that have reference to the changes which the race has passed through in bygone ages. In fact the great majority of animals do go through metamorphoses (many of them as remarkable, though not so familiar as those of insects), but in many cases they are passed through within the egg and thus escape popular observation. Naturalists who accept the theory of evolution, consider that the development of each individual represents to a certain extent that which the species has itself gone through in the lapse of ages; that every individual contains within itself, so to say, a history of the race. Thus the rudimentary teeth of Cows, Sheep, Whales, etc. (which never emerge from their sockets), the rudimentary toes of many mammals, the hind legs of Whales and of the Boa-constrictor, which are imbedded in the flesh, the rudimentary collar-bone of the Dog, etc., are indications of descent from ancestors in which these organs were fully developed. Again, though used for such different purposes, the paddle of a Whale, the leg of a Horse and of a Mole, the wing of a Bird or a Bat, and the arm of a Man, are all constructed on the same model, include corresponding bones, and are similarly arranged. The long neck of the Giraffe, and the short one of the Whale (if neck it can be called), contain the same number of vertebræ. Even after birth the young of allied species resemble one another much more than the mature forms. The stripes on the young Lion, the spots on the young Blackbird, are well-known cases; and we find the same law prevalent among the lower animals, as, for instance, among Insects and Crustacea. The Lobster, Crab, Shrimp, and Barnacle are very unlike when full grown, but in their young stages go through essentially similar metamorphoses. No animal is perhaps in this respect more interesting than the Horse. The skull of a Horse and that of a Man, though differing so much, are, says Flower,[11] "composed of exactly the same number of bones, having the same general arrangement and relation to each other. Not only the individual bones, but every ridge and surface for the attachment of muscles, and every hole for the passage of artery or nerve, seen in the one can be traced in the other." It is often said that the Horse presents a remarkable peculiarity in that the canine teeth grow but once. There are, however, in most Horses certain spicules or minute points which are shed before the appearance of the permanent canines, and which are probably the last remnants of the true milk canines. The foot is reduced to a single toe, representing the third digit, but the second and fourth, though rudimentary, are represented by the splint bones; while the foot also contains traces of several muscles, originally belonging to the toes which have now disappeared, and which "linger as it were behind, with new relations and uses, sometimes in a reduced, and almost, if not quite, functionless condition." Even Man himself presents traces of gill-openings, and indications of other organs which are fully developed in lower animals. MODIFICATIONS There is in New Zealand a form of Crow (Hura), in which the female has undergone a very curious modification. It is the only case I know, in which the bill is differently shaped in the two sexes. The bird has taken on the habits of a Woodpecker, and the stout crow-like bill of the cock-bird is admirably adapted to tap trees, and if they sound hollow, to dig down to the burrow of the Insect; but it lacks the horny-pointed tip of the tongue, which in the true Woodpecker is provided with recurved hairs, thus enabling that bird to pierce the grub and draw it out. In the Hura, however, the bill of the hen-bird has become much elongated and slightly curved, and when the cock has dug down to the burrow, the hen inserts her long bill and draws out the grub, which they then divide between them: a very pretty illustration of the wife as helpmate to the husband. It was indeed until lately the general opinion that animals and plants came into existence just as we now see them. We took pleasure in their beauty; their adaptation to their habits and mode of life in many cases could not be overlooked or misunderstood. Nevertheless the book of Nature was like some missal richly illuminated, but written in an unknown tongue. The graceful forms of the letters, the beauty of the colouring, excited our wonder and admiration; but of the true meaning little was known to us; indeed we scarcely realised that there was any meaning to decipher. Now glimpses of the truth are gradually revealing themselves, we perceive that there is a reason, and in many cases we know what the reason is, for every difference in form, in size, and in colour; for every bone and every feather, almost for every hair.[12] COLOUR The colours of animals, generally, I believe, serve as a protection. In some, however, they probably render them more attractive to their mates, of which the Peacock is one of the most remarkable illustrations. In richness of colour birds and insects vie even with flowers. "One fine red admiral butterfly," says Jefferies,[13] "whose broad wings, stretched out like fans, looked simply splendid floating round and round the willows which marked the margin of a dry pool. His blue markings were really blue--blue velvet--his red and the white stroke shone as if sunbeams were in his wings. I wish there were more of these butterflies; in summer, dry summer, when the flowers seem gone and the grass is not so dear to us, and the leaves are dull with heat, a little colour is so pleasant. To me colour is a sort of food; every spot of colour is a drop of wine to the spirit." The varied colours which add so much to the beauty of animals and plants are not only thus a delight to the eye, but afford us also some of the most interesting problems in Natural History. Some probably are not in themselves of any direct advantage. The brilliant mother-of-pearl of certain shells, which during life is completely hidden, the rich colours of some internal organs of animals, are not perhaps of any direct benefit, but are incidental, like the rich and brilliant hues of many minerals and precious stones. But although this may be true, I believe that most of these colours are now of some advantage. "The black back and silvery belly of fishes" have been recently referred to by a distinguished naturalist as being obviously of no direct benefit. I should on the contrary have quoted this case as one where the advantage was obvious. The dark back renders the fish less conspicuous to an eye looking down into the water; while the white under-surface makes them less visible from below. The animals of the desert are sand-coloured; those of the Arctic regions are white like snow, especially in winter; and pelagic animals are blue. Let us take certain special cases. The Lion, like other desert animals, is sand-coloured; the Tiger which lives in the Jungle has vertical stripes, making him difficult to see among the upright grass; Leopards and the tree-cats are spotted, like rays of light seen through leaves. An interesting case is that of the animals living in the Sargasso or gulf-weed of the Atlantic. These creatures--Fish, Crustacea, and Mollusks alike--are characterised by a peculiar colouring, not continuously olive like the Seaweed itself, but blotched with rounded more or less irregular patches of bright, opaque white, so as closely to resemble fronds covered with patches of Flustra or Barnacles. Take the case of caterpillars, which are especially defenceless, and which as a rule feed on leaves. The smallest and youngest are green, like the leaves on which they live. When they become larger, they are characterised by longitudinal lines, which break up the surface and thus render them less conspicuous. On older and larger ones the lines are diagonal, like the nerves of leaves. Conspicuous caterpillars are generally either nauseous in taste, or protected by hairs. [Illustration: Fig. 1.--_Choerocampa porcellus._] I say "generally," because there are some interesting exceptions. The large caterpillars of some of the Elephant Hawkmoths are very conspicuous, and rendered all the more so by the presence of a pair of large eyelike spots. Every one who sees one of these caterpillars is struck by its likeness to a snake, and the so-called "eyes" do much to increase the deception. Moreover, the ring on which they are placed is swollen, and the insect, when in danger, has the habit of retracting its head and front segments, which gives it an additional resemblance to some small reptile. That small birds are, as a matter of fact, afraid of these caterpillars (which, however, I need not say, are in reality altogether harmless) Weismann has proved by actual experiment. He put one of these caterpillars in a tray, in which he was accustomed to place seed for birds. Soon a little flock of sparrows and other small birds assembled to feed as usual. One of them lit on the edge of this tray, and was just going to hop in, when she spied the caterpillar. Immediately she began bobbing her head up and down in the odd way which some small birds have, but was afraid to go nearer. Another joined her and then another, until at last there was a little company of ten or twelve birds all looking on in astonishment, but not one ventured into the tray; while one bird, which lit in it unsuspectingly, beat a hasty retreat in evident alarm as soon as she perceived the caterpillar. After waiting for some time, Weismann removed it, when the birds soon attacked the seeds. Other caterpillars also are probably protected by their curious resemblance to spotted snakes. One of the large Indian caterpillars has even acquired the power of hissing. Among perfect insects many resemble closely the substances near which they live. Some moths are mottled so as to mimic the bark of trees, or moss, or the surface of stones. One beautiful tropical butterfly has a dark wing on which are painted a series of green leaf tips, so that it closely resembles the edge of a pinnate leaf projecting out of shade into sunshine. The argument is strengthened by those cases in which the protection, or other advantage, is due not merely to colour, but partly also to form. Such are the insects which resemble sticks or leaves. Again, there are cases in which insects mimic others, which, for some reason or other, are less liable to danger. So also many harmless animals mimic others which are poisonous or otherwise well protected. Some butterflies, as Mr. Bates has pointed out, mimic others which are nauseous in taste, and therefore not attacked by birds. In these cases it is generally only the females that are mimetic, and in some cases only a part of them, so that there are two, or even three, kinds of females, the one retaining the normal colouring of the group, the other mimicking another species. Some spiders closely resemble Ants, and several other insects mimic Wasps or Hornets. Some reptiles and fish have actually the power of changing the colour of their skin so as to adapt themselves to their surroundings. Many cases in which the colouring does not at first sight appear to be protective, will on consideration be found to be so. It has, for instance, been objected that sheep are not coloured green; but every mountaineer knows that sheep could not have had a colour more adapted to render them inconspicuous, and that it is almost impossible to distinguish them from the rocks which so constantly crop up on hill sides. Even the brilliant blue of the Kingfisher, which in a museum renders it so conspicuous, in its native haunts, on the contrary, makes it difficult to distinguish from a flash of light upon the water; and the richly-coloured Woodpecker wears the genuine dress of a Forester--the green coat and crimson cap. It has been found that some brilliantly coloured and conspicuous animals are either nauseous or poisonous. In these cases the brilliant colour is doubtless a protection by rendering them more unmistakable. COMMUNITIES Some animals may delight us especially by their beauty, such as birds or butterflies; others may surprise us by their size, as Elephants and Whales, or the still more marvellous monsters of ancient times; may fascinate us by their exquisite forms, such as many microscopic shells; or compel our reluctant attention by their similarity to us in structure; but none offer more points of interest than those which live in communities. I do not allude to the temporary assemblages of Starlings, Swallows, and other birds at certain times of year, nor even to the permanent associations of animals brought together by common wants in suitable localities, but to regular and more or less organised associations. Such colonies as those of Rooks and Beavers have no doubt interesting revelations and surprises in store for us, but they have not been as yet so much studied as those of some insects. Among these the Hive Bees, from the beauty and regularity of their cells, from their utility to man, and from the debt we owe them for their unconscious agency in the improvement of flowers, hold a very high place; but they are probably less intelligent, and their relations with other animals and with one another are less complex than in the case of Ants, which have been so well studied by Gould, Huber, Forel, M'Cook, and other naturalists. The subject is a wide one, for there are at least a thousand species of Ants, no two of which have the same habits. In this country we have rather more than thirty, most of which I have kept in confinement. Their life is comparatively long: I have had working Ants which were seven years old, and a Queen Ant lived in one of my nests for fifteen years. The community consists, in addition to the young, of males, which do no work, of wingless workers, and one or more Queen mothers, who have at first wings, which, however, after one Marriage flight, they throw off, as they never leave the nest again, and in it wings would of course be useless. The workers do not, except occasionally, lay eggs, but carry on all the affairs of the community. Some of them, and especially the younger ones, remain in the nest, excavate chambers and tunnels, and tend the young, which are sorted up according to age, so that my nests often had the appearance of a school, with the children arranged in classes. In our English Ants the workers in each species are all similar except in size, but among foreign species there are some in which there are two or even more classes of workers, differing greatly not only in size, but also in form. The differences are not the result of age, nor of race, but are adaptations to different functions, the nature of which, however, is not yet well understood. Among the Termites those of one class certainly seem to act as soldiers, and among the true Ants also some have comparatively immense heads and powerful jaws. It is doubtful, however, whether they form a real army. Bates observed that on a foraging expedition the large-headed individuals did not walk in the regular ranks, nor on the return did they carry any of the booty, but marched along at the side, and at tolerably regular intervals, "like subaltern officers in a marching regiment." He is disposed, however, to ascribe to them a much humbler function, namely, to serve merely "as indigestible morsels to the ant thrushes." This, I confess, seems to me improbable. Solomon was, so far as we yet know, quite correct in describing Ants as having "neither guide, overseer, nor ruler." The so-called Queens are really Mothers. Nevertheless it is true, and it is curious, that the working Ants and Bees always turn their heads towards the Queen. It seems as if the sight of her gave them pleasure. On one occasion, while moving some Ants from one nest into another for exhibition at the Royal Institution, I unfortunately crushed the Queen and killed her. The others, however, did not desert her, or draw her out as they do dead workers, but on the contrary carried her into the new nest, and subsequently into a larger one with which I supplied them, congregating round her for weeks just as if she had been alive. One could hardly help fancying that they were mourning her loss, or hoping anxiously for her recovery. The Communities of Ants are sometimes very large, numbering even up to 500,000 individuals; and it is a lesson to us, that no one has ever yet seen a quarrel between any two Ants belonging to the same community. On the other hand it must be admitted that they are in hostility, not only with most other insects, including Ants of different species, but even with those of the same species if belonging to different communities. I have over and over again introduced Ants from one of my nests into another nest of the same species, and they were invariably attacked, seized by a leg or an antenna, and dragged out. It is evident therefore that the Ants of each community all recognise one another, which is very remarkable. But more than this, I several times divided a nest into two halves, and found that even after a separation of a year and nine months they recognised one another, and were perfectly friendly; while they at once attacked Ants from a different nest, although of the same species. It has been suggested that the Ants of each nest have some sign or password by which they recognise one another. To test this I made some insensible. First I tried chloroform, but this was fatal to them; and as therefore they were practically dead, I did not consider the test satisfactory. I decided therefore to intoxicate them. This was less easy than I had expected. None of my Ants would voluntarily degrade themselves by getting drunk. However, I got over the difficulty by putting them into whisky for a few moments. I took fifty specimens, twenty-five from one nest and twenty-five from another, made them dead drunk, marked each with a spot of paint, and put them on a table close to where other Ants from one of the nests were feeding. The table was surrounded as usual with a moat of water to prevent them from straying. The Ants which were feeding soon noticed those which I had made drunk. They seemed quite astonished to find their comrades in such a disgraceful condition, and as much at a loss to know what to do with their drunkards as we are. After a while, however, to cut my story short, they carried them all away: the strangers they took to the edge of the moat and dropped into the water, while they bore their friends home into the nest, where by degrees they slept off the effects of the spirit. Thus it is evident that they know their friends even when incapable of giving any sign or password. This little experiment also shows that they help comrades in distress. If a Wolf or a Rook be ill or injured, we are told that it is driven away or even killed by its comrades. Not so with Ants. For instance, in one of my nests an unfortunate Ant, in emerging from the chrysalis skin, injured her legs so much that she lay on her back quite helpless. For three months, however, she was carefully fed and tended by the other Ants. In another case an Ant in the same manner had injured her antennæ. I watched her also carefully to see what would happen. For some days she did not leave the nest. At last one day she ventured outside, and after a while met a stranger Ant of the same species, but belonging to another nest, by whom she was at once attacked. I tried to separate them, but whether by her enemy, or perhaps by my well-meant but clumsy kindness, she was evidently much hurt and lay helplessly on her side. Several other Ants passed her without taking any notice, but soon one came up, examined her carefully with her antennæ, and carried her off tenderly to the nest. No one, I think, who saw it could have denied to that Ant one attribute of humanity, the quality of kindness. The existence of such communities as those of Ants or Bees implies, no doubt, some power of communication, but the amount is still a matter of doubt. It is well known that if one Bee or Ant discovers a store of food, others soon find their way to it. This, however, does not prove much. It makes all the difference whether they are brought or sent. If they merely accompany on her return a companion who has brought a store of food, it does not imply much. To test this, therefore, I made several experiments. For instance, one cold day my Ants were almost all in their nests. One only was out hunting and about six feet from home. I took a dead bluebottle fly, pinned it on to a piece of cork, and put it down just in front of her. She at once tried to carry off the fly, but to her surprise found it immovable. She tugged and tugged, first one way and then another for about twenty minutes, and then went straight off to the nest. During that time not a single Ant had come out; in fact she was the only Ant of that nest out at the time. She went straight in, but in a few seconds--less than half a minute,--came out again with no less than twelve friends, who trooped off with her, and eventually tore up the dead fly, carrying it off in triumph. Now the first Ant took nothing home with her; she must therefore somehow have made her friends understand that she had found some food, and wanted them to come and help her to secure it. In all such cases, however, so far as my experience goes, the Ants brought their friends, and some of my experiments indicated that they are unable to send them. Certain species of Ants, again, make slaves of others, as Huber first observed. If a colony of the slave-making Ants is changing the nest, a matter which is left to the discretion of the slaves, the latter carry their mistresses to their new home. Again, if I uncovered one of my nests of the Fuscous Ant (Formica fusca), they all began running about in search of some place of refuge. If now I covered over one small part of the nest, after a while some Ant discovered it. In such a case, however, the brave little insect never remained there, she came out in search of her friends, and the first one she met she took up in her jaws, threw over her shoulder (their way of carrying friends), and took into the covered part; then both came out again, found two more friends and brought them in, the same manoeuvre being repeated until the whole community was in a place of safety. This I think says much for their public spirit, but seems to prove that, in F. fusca at least, the powers of communication are but limited. One kind of slave-making Ant has become so completely dependent on their slaves, that even if provided with food they will die of hunger, unless there is a slave to put it into their mouth. I found, however, that they would thrive very well if supplied with a slave for an hour or so once a week to clean and feed them. But in many cases the community does not consist of Ants only. They have domestic animals, and indeed it is not going too far to say that they have domesticated more animals than we have. Of these the most important are Aphides. Some species keep Aphides on trees and bushes, others collect root-feeding Aphides into their nests. They serve as cows to the Ants, which feed on the honey-dew secreted by the Aphides. Not only, moreover, do the Ants protect the Aphides themselves, but collect their eggs in autumn, and tend them carefully through the winter, ready for the next spring. Many other insects are also domesticated by Ants, and some of them, from living constantly underground, have completely lost their eyes and become quite blind. But I must not let myself be carried away by this fascinating subject, which I have treated more at length in another work.[14] I will only say that though their intelligence is no doubt limited, still I do not think that any one who has studied the life-history of Ants can draw any fundamental line of separation between instinct and reason. When we see a community of Ants working together in perfect harmony, it is impossible not to ask ourselves how far they are mere exquisite automatons; how far they are conscious beings? When we watch an ant-hill tenanted by thousands of industrious inhabitants, excavating chambers, forming tunnels, making roads, guarding their home, gathering food, feeding the young, tending their domestic animals--each one fulfilling its duties industriously, and without confusion,--it is difficult altogether to deny to them the gift of reason; and all our recent observations tend to confirm the opinion that their mental powers differ from those of men, not so much in kind as in degree. FOOTNOTES: [11] _The Horse._ [12] Lubbock, _Fifty Years of Science_. [13] _The Open Air._ [14] _Ants, Bees, and Wasps._ CHAPTER III ON ANIMAL LIFE--_continued_ An organic being is a microcosm--a little universe, formed of a host of self-propagating organisms, inconceivably minute and numerous as the stars of heaven. DARWIN. CHAPTER III ON ANIMAL LIFE--_continued._ We constantly speak of animals as free. A fish, says Ruskin, "is much freer than a Man; and as to a fly, it is a black incarnation of freedom." It is pleasant to think of anything as free, but in this case the idea is, I fear, to a great extent erroneous. Young animals may frolic and play, but older ones take life very seriously. About the habits of fish and flies, indeed, as yet we know very little. Any one, however, who will watch animals will soon satisfy himself how diligently they work. Even when they seem to be idling over flowers, or wandering aimlessly about, they are in truth diligently seeking for food, or collecting materials for nests. The industry of Bees is proverbial. When collecting honey or pollen they often visit over twenty flowers in a minute, keeping constantly to one species, without yielding a moment's dalliance to any more sweet or lovely tempter. Ants fully deserve the commendation of Solomon. Wasps have not the same reputation for industry; but I have watched them from before four in the morning till dark at night working like animated machines without a moment's rest or intermission. Sundays and Bank Holidays are all the same to them. Again, Birds have their own gardens and farms from which they do not wander, and within which they will tolerate no interference. Their ideas of the rights of property are far stricter than those of some statesmen. As to freedom, they have their daily duties as much as a mechanic in a mill or a clerk in an office. They suffer under alarms, moreover, from which we are happily free. Mr. Galton believes that the life of wild animals is very anxious. "From my own recollection," he says, "I believe that every antelope in South Africa has to run for its life every one or two days upon an average, and that he starts or gallops under the influence of a false alarm many times in a day. Those who have crouched at night by the side of pools in the desert, in order to have a shot at the beasts that frequent it, see strange scenes of animal life; how the creatures gambol at one moment and fight at another; how a herd suddenly halts in strained attention, and then breaks into a maddened rush as one of them becomes conscious of the stealthy movements or rank scent of a beast of prey. Now this hourly life-and-death excitement is a keen delight to most wild creatures, but must be peculiarly distracting to the comfort-loving temperament of others. The latter are alone suited to endure the crass habits and dull routine of domesticated life. Suppose that an animal which has been captured and half-tamed, received ill-usage from his captors, either as punishment or through mere brutality, and that he rushed indignantly into the forest with his ribs aching from blows and stones. If a comfort-loving animal, he will probably be no gainer by the change, more serious alarms and no less ill-usage awaits him: he hears the roar of the wild beasts, and the headlong gallop of the frightened herds, and he finds the buttings and the kicks of other animals harder to endure than the blows from which he fled: he has peculiar disadvantages from being a stranger; the herds of his own species which he seeks for companionship constitute so many cliques, into which he can only find admission by more fighting with their strongest members than he has spirit to undergo. As a set-off against these miseries, the freedom of savage life has no charms for his temperament; so the end of it is, that with a heavy heart he turns back to the habitation he had quitted." But though animals may not be free, I hope and believe that they are happy. Dr. Hudson, an admirable observer, assures us with confidence that the struggle for existence leaves them much leisure and famous spirits. "In the animal world," he exclaims,[15] "what happiness reigns! What ease, grace, beauty, leisure, and content! Watch these living specks as they glide through their forests of algæ, all 'without hurry and care,' as if their 'span-long lives' really could endure for the thousand years that the old catch pines for. Here is no greedy jostling at the banquet that nature has spread for them; no dread of each other; but a leisurely inspection of the field, that shows neither the pressure of hunger nor the dread of an enemy. "'To labour and to be content' (that 'sweet life' of the son of Sirach)--to be equally ready for an enemy or a friend--to trust in themselves alone, to show a brave unconcern for the morrow, all these are the admirable points of a character almost universal among animals, and one that would lighten many a heart were it more common among men. That character is the direct result of the golden law 'If one will not work, neither let him eat'; a law whose stern kindness, unflinchingly applied, has produced whole nations of living creatures, without a pauper in their ranks, flushed with health, alert, resolute, self-reliant, and singularly happy." It has often been said that Man is the only animal gifted with the power of enjoying a joke, but if animals do not laugh, at any rate they sometimes play. We are, indeed, apt perhaps to credit them with too much of our own attributes and emotions, but we can hardly be mistaken in supposing that they enjoy certain scents and sounds. It is difficult to separate the games of kittens and lambs from those of children. Our countryman Gould long ago described the "amusements or sportive exercises" which he had observed among Ants. Forel was at first incredulous, but finally confirmed these statements; and, speaking of certain tropical Ants, Bates says "the conclusion that they were engaged in play was irresistible." SLEEP We share with other animals the great blessing of Sleep, nature's soft nurse, "the mantle that covers thought, the food that appeases hunger, the drink that quenches thirst, the fire that warms cold, the cold that moderates heat, the coin that purchases all things, the balance and weight that equals the shepherd with the king, and the simple with the wise." Some animals dream as we do; Dogs, for instance, evidently dream of the chase. With the lower animals which cannot shut their eyes it is, however, more difficult to make sure whether they are awake or asleep. I have often noticed insects at night, even when it was warm and light, behave just as if they were asleep, and take no notice of objects which would certainly have startled them in the day. The same thing has also been observed in the case of fish. But why should we sleep? What a remarkable thing it is that one-third of our life should be passed in unconsciousness. "Half of our days," says Sir T. Browne, "we pass in the shadow of the earth, and the brother of death extracteth a third part of our lives." The obvious suggestion is that we require rest. But this does not fully meet the case. In sleep the mind is still awake, and lives a life of its own: our thoughts wander, uncontrolled, by the will. The mind, therefore, is not necessarily itself at rest; and yet we all know how it is refreshed by sleep. But though animals sleep, many of them are nocturnal in their habits. Humboldt gives a vivid description of night in a Brazilian forest. "Everything passed tranquilly till eleven at night, and then a noise so terrible arose in the neighbouring forest that it was almost impossible to close our eyes. Amid the cries of so many wild beasts howling at once the Indians discriminated such only as were (at intervals) heard separately. These were the little soft cries of the sapajous, the moans of the alouate apes, the howlings of the jaguar and couguar, the peccary and the sloth, and the cries of (many) birds. When the jaguars approached the skirt of the forest our dog, which till then had never ceased barking, began to howl and seek for shelter beneath our hammocks. Sometimes, after a long silence, the cry of the tiger came from the tops of the trees; and then it was followed by the sharp and long whistling of the monkeys, which appeared to flee from the danger which threatened them. We heard the same noises repeated during the course of whole months whenever the forest approached the bed of the river. "When the natives are interrogated on the causes of the tremendous noise made by the beasts of the forest at certain hours of the night, the answer is, they are keeping the feast of the full moon. I believe this agitation is most frequently the effect of some conflict that has arisen in the depths of the forest. The jaguars, for instance, pursue the peccaries and the tapirs, which, having no defence, flee in close troops, and break down the bushes they find in their way. Terrified at this struggle, the timid and distrustful monkeys answer, from the tops of the trees, the cries of the large animals. They awaken the birds that live in society, and by degrees the whole assembly is in commotion. It is not always in a fine moonlight, but more particularly at the time of a storm of violent showers, that this tumult takes place among the wild beasts. 'May heaven grant them a quiet night and repose, and us also!' said the monk who accompanied us to the Rio Negro, when, sinking with fatigue, he assisted in arranging our accommodation for the night." Life is indeed among animals a struggle for existence, and in addition to the more usual weapons--teeth and claws--we find in some animals special and peculiar means of offence and defence. If we had not been so familiarised with the fact, the possession of poison might well seem a wonderful gift. That a fluid, harmless in one animal itself, should yet prove so deadly when transferred to others, is certainly very remarkable; and though the venom of the Cobra or the Rattlesnake appeal perhaps more effectively to our imagination, we have conclusive evidence of concentrated poison even in the bite of a midge, which may remain for days perceptible. The sting of a Bee or Wasp, though somewhat similar in its effect, is a totally different organ, being a modified ovipositor. Some species of Ants do not sting in the ordinary sense, but eject their acrid poison to a distance of several inches. Another very remarkable weapon is the electric battery of certain Eels, of the Electric Cat Fish, and the Torpedoes, one of which is said to be able to discharge an amount of electricity sufficient to kill a Man. Some of the Medusæ and other Zoophytes are armed by millions of minute organs known as "thread cells." Each consists of a cell, within which a firm, elastic thread is tightly coiled. The moment the Medusa touches its prey the cells burst and the threads spring out. Entering the flesh as they do by myriads, they prove very effective weapons. The ink of the Sepia has passed into a proverb. The animal possesses a store of dark fluid, which, if attacked, it at once ejects, and thus escapes under cover of the cloud thus created. The so-called Bombardier Beetles, when attacked, discharge at the enemy, from the hinder part of their body, an acrid fluid which, as soon as it comes in contact with air, explodes with a sound resembling a miniature gun. Westwood mentions, on the authority of Burchell, that on one occasion, "whilst resting for the night on the banks of one of the large South American rivers, he went out with a lantern to make an astronomical observation, accompanied by one of his black servant boys; and as they were proceeding, their attention was directed to numerous beetles running about upon the shore, which, when captured, proved to be specimens of a large species of Brachinus. On being seized they immediately began to play off their artillery, burning and staining the flesh to such a degree that only a few specimens could be captured with the naked hand, and leaving a mark which remained a considerable time. Upon observing the whitish vapour with which the explosions were accompanied, the negro exclaimed in his broken English, with evident surprise, 'Ah, massa, they make smoke!'" Many other remarkable illustrations might be quoted; as for instance the web of the Spider, the pit of the Ant Lion, the mephitic odour of the Skunk. SENSES We generally attribute to animals five senses more or less resembling our own. But even as regards our own senses we really know or understand very little. Take the question of colour. The rainbow is commonly said to consist of seven colours--red, orange, yellow, green, blue, indigo, and violet. But it is now known that all our colour sensations are mixtures of three simple colours, red, green, and violet. We are, however, absolutely ignorant how we perceive these colours. Thomas Young suggested that we have three different systems of nerve fibres, and Helmholtz regards this as "a not improbable supposition"; but so far as microscopical examination is concerned, there is no evidence whatever for it. Or take again the sense of Hearing. The vibrations of the air no doubt play upon the drum of the ear, and the waves thus produced are conducted through a complex chain of small bones to the fenestra ovalis and so to the inner ear or labyrinth. But beyond this all is uncertainty. The labyrinth consists mainly of two parts (1) the cochlea, and (2) the semicircular canals, which are three in number, standing at right angles to one another. It has been supposed that they enable us to maintain the equilibrium of the body, but no satisfactory explanation of their function has yet been given. In the cochlea, Corti discovered a remarkable organ consisting of some four thousand complex arches, which increase regularly in length and diminish in height. They are connected at one end with the fibres of the auditory nerve, and Helmholtz has suggested that the waves of sound play on them, like the fingers of a performer on the keys of a piano, each separate arch corresponding to a different sound. We thus obtain a glimpse, though but a glimpse, of the manner in which perhaps we hear; but when we pass on to the senses of smell and taste, all we know is that the extreme nerve fibres terminate in certain cells which differ in form from those of the general surface; but in what manner the innumerable differences of taste or smell are communicated to the brain, we are absolutely ignorant. If then we know so little about ourselves, no wonder that with reference to other animals our ignorance is extreme. We are too apt to suppose that the senses of animals must closely resemble, and be confined to ours. No one can doubt that the sensations of other animals differ in many ways from ours. Their organs are sometimes constructed on different principles, and situated in very unexpected places. There are animals which have eyes on their backs, ears in their legs, and sing through their sides. We all know that the senses of animals are in many cases much more acute than ours, as for instance the power of scent in the dog, of sight in the eagle. Moreover, our eye is much more sensitive to some colours than to others; least so to crimson, then successively to red, orange, yellow, blue, and green; the sensitiveness for green being as much as 750 times as great as for red. This alone may make objects appear of very different colours to different animals. Nor is the difference one of degree merely. The rainbow, as we see it, consists of seven colours--red, orange, yellow, green, blue, indigo, and violet. But though the red and violet are the limits of the visible spectrum, they are not the limits of the spectrum itself, there are rays, though invisible to us, beyond the red at the one end, and beyond the violet at the other: the existence of the ultra red can be demonstrated by the thermometer; while the ultra violet are capable of taking a photograph. But though the red and violet are respectively the limits of our vision, I have shown[16] by experiments which have been repeated and confirmed by other naturalists, that some of the lower animals are capable of perceiving the ultra-violet rays, which to us are invisible. It is an interesting question whether these rays may not produce on them the impression of a new colour, or colours, differing from any of those known to us. So again with hearing, not only may animals in some cases hear better than we do, but sounds which are beyond the reach of our ears, may be audible to theirs. Even among ourselves the power of hearing shrill sounds is greater in some persons than in others. Sound, as we know, is produced by vibration of the air striking on the drum of the ear, and the fewer are the vibrations in a second, the deeper is the sound, which becomes shriller and shriller as the waves of sound become more rapid. In human ears the limits of hearing are reached when about 35,000 vibrations strike the drum of the ear in a second. Whatever the explanation of the gift of hearing in ourselves may be, different plans seem to be adopted in the case of other animals. In many Crustacea and Insects there are flattened hairs each connected with a nerve fibre, and so constituted as to vibrate in response to particular notes. In others the ear cavity contains certain minute solid bodies, known as otoliths, which in the same way play upon the nerve fibres. Sometimes these are secreted by the walls of the cavity itself, but certain Crustacea have acquired the remarkable habit of selecting after each moult suitable particles of sand, which they pick up with their pincers and insert into their ears. Many insects, besides the two large "compound" eyes one on each side of the head, have between them three small ones, known as the "ocelli," arranged in a triangle. The structure of these two sets of eyes is quite different. The ocelli appear to see as our eyes do. The lens throws an inverted image on the back of the eye, so that with these eyes they must see everything reversed, as we ourselves really do, though long practice enables us to correct the impression. On the other hand, the compound eyes consist of a number of facets, in some species as many as 20,000 in each eye, and the prevailing impression among entomologists now is that each facet receives the impression of one pencil of rays, that in fact the image formed in a compound eye is a sort of mosaic. In that case, vision by means of these eyes must be direct; and it is indeed difficult to understand how an insect can obtain a correct impression when it looks at the world with five eyes, three of which see everything reversed, while the other two see things the right way up! On the other hand, some regard each facet as an independent eye, in which case many insects realise the epigram of Plato-- Thou lookest on the stars, my love, Ah, would that I could be Yon starry skies with thousand eyes, That I might look on thee! Even so, therefore, we only substitute one difficulty for another. But this is not all. We have not only no proof that animals are confined to our five senses, but there are strong reasons for believing that this is not the case. In the first place, many animals have organs which from their position, structure, and rich supply of nerves, are evidently organs of sense; and yet which do not appear to be adapted to any one of our five senses. As already mentioned, the limits of hearing are reached when about 35,000 vibrations of the air strike on the drums of our ears. Light, as was first conclusively demonstrated by our great countryman Young, is the impression produced by vibration of the ether on the retina of the eye. When 700 millions of millions of vibrations strike the eye in a second, we see violet; and the colour changes as the number diminishes, 400 millions of millions giving us the impression of red. Between 35 thousand and 400 millions of millions the interval is immense, and it is obvious that there might be any number of sensations. When we consider how greatly animals differ from us, alike in habits and structure, is it not possible, nay, more, is it not likely that some of these problematical organs are the seats of senses unknown to us, and give rise to sensations of which we have no conception? In addition to the capacity for receiving and perceiving, some animals have the faculty of emitting light. In our country the glow-worm is the most familiar case, though some other insects and worms have, at any rate under certain conditions, the same power, and it is possible that many others are really luminous, though with light which is invisible to us. In warmer climates the Fire-fly, Lanthorn-fly, and many other insects, shine with much greater brilliance, and in these cases the glow seems to be a real love-light, like the lamp of Hero. Many small marine animals, Medusæ, Crustacea, Worms, etc., are also brilliantly luminous at night. Deep-sea animals are endowed also in many cases with special luminous organs, to which I shall refer again. SENSE OF DIRECTION It has been supposed that animals possess also what has been called a Sense of Direction. Many interesting cases are on record of animals finding their way home after being taken a considerable distance. To account for this fact it has been suggested that animals possess a sense with which we are not endowed, or of which, at any rate, we possess only a trace. The homing instinct of the pigeon has also been ascribed to the same faculty. My brother Alfred, however, who has paid much attention to pigeons, informs me that they are never taken any great distance at once; but if they are intended to take a long flight, they are trained to do so by stages. Darwin suggested that it would be interesting to test the case by taking animals in a close box, and then whirling them round rapidly before letting them out. This is in fact done with cats in some parts of France, when the family migrates, and is considered the only way of preventing the cat from returning to the old home. Fabre has tried the same thing with some wild Bees (Chalicodoma). He took some, marked them on the back with a spot of white, and put them into a bag. He then carried them a quarter of a mile, stopping at a point where an old cross stands by the wayside, and whirled the bag rapidly round his head. While he was doing so a good woman came by, who seemed not a little surprised to find the Professor solemnly whirling a black bag round his head in front of the cross; and, he fears, suspected him of Satanic practices. He then carried his Bees a mile and a half in the opposite direction and let them go. Three out of ten found their way home. He tried the same experiment several times, in one case taking them a little over two miles. On an average about a third of the Bees found their way home. "La démonstration," says Fabre, "est suffisante. Ni les mouvements enchevêtrés d'une rotation comme je l'ai décrite; ni l'obstacle de collines à franchir et de bois à traverser; ni les embûches d'une voie qui s'avance, rétrograde, et revient par un ample circuit, ne peuvent troubler les Chalicodomes dépaysés et les empêcher de revenir au nid." I must say, however, that I am not convinced. In the first place, the distances were I think too short; and in the second, though it is true that some of the Bees found their way home, nearly two-thirds failed to do so. It would be interesting to try the experiment again, taking the Bees say five miles. If they really possess any such sense, that distance would be no bar to their return. I have myself experimented with Ants, taking them about fifty yards from the nest, and I always found that they wandered aimlessly about, having evidently not the slightest idea of their way home. They certainly did not appear to possess any "sense of direction." NUMBER OF SPECIES The total number of species may probably be safely estimated as at least 2,000,000, of which but a fraction have yet been described or named. Of extinct species the number was probably at least as great. In the geological history of the earth there have been at least twelve periods, in each of which by far the greatest number were distinct. The Ancient Poets described certain gifted mortals as having been privileged to descend into the interior of the earth, and exercised their imagination in recounting the wonders thus revealed. As in other cases, however, the realities of Science have proved far more varied and surprising than the dreams of fiction. Of these extinct species our knowledge is even more incomplete than that of the existing species. But even of our contemporaries it is not too much to say that, as in the case of plants, there is not one the structure, habits, and life-history of which are yet fully known to us. The male of the Cynips, which produces the common King Charles Oak Apple, has only recently been discovered, those of the root-feeding Aphides, which live in hundreds in every nest of the yellow Meadow Ant (Lasius flavus) are still unknown; the habits and mode of reproduction of the common Eel have only just been discovered; and we may even say generally that many of the most interesting recent discoveries have relation to the commonest and most familiar animals. IMPORTANCE OF THE SMALLER ANIMALS Whatever pre-eminence Man may claim for himself, other animals have done far more to affect the face of nature. The principal agents have not been the larger or more intelligent, but rather the smaller, and individually less important, species. Beavers may have dammed up many of the rivers of British Columbia, and turned them into a succession of pools or marshes, but this is a slight matter compared with the action of earthworms and insects[17] in the creation of vegetable soil; of the accumulation of animalcules in filling up harbours and lakes; or of Zoophytes in the construction of coral islands. Microscopic animals make up in number what they lack in size. Paris is built of Infusoria. The Peninsula of Florida, 78,000 square miles in extent, is entirely composed of coral debris and fragments of shells. Chalk consists mainly of Foraminifera and fragments of shells deposited in a deep sea. The number of shells required to make up a cubic inch is almost incredible. Ehrenberg has estimated that of the Bilin polishing slate which caps the mountain, and has a thickness of forty feet, a cubic inch contains many hundred million shells of Infusoria. In another respect these microscopic organisms are of vital importance. Many diseases are now known, and others suspected, to be entirely due to Bacteria and other minute forms of life (Microbes), which multiply incredibly, and either destroy their victims, or after a while diminish again in numbers. We live indeed in a cloud of Bacteria. At the observatory of Montsouris at Paris it has been calculated that there are about 80 in each cubic meter of air. Elsewhere, however, they are much more numerous. Pasteur's researches on the Silkworm disease led him to the discovery of Bacterium anthracis, the cause of splenic fever. Microbes are present in persons suffering from cholera, typhus, whooping-cough, measles, hydrophobia, etc., but as to their history and connection with disease we have yet much to learn. It is fortunate, indeed, that they do not all attack us. In surgical cases, again, the danger of compound fractures and mortification of wounds has been found to be mainly due to the presence of microscopic organisms; and Lister, by his antiseptic treatment which destroys these germs or prevents their access, has greatly diminished the danger of operations, and the sufferings of recovery. SIZE OF ANIMALS In the size of animals we find every gradation from these atoms which even in the most powerful microscopes appear as mere points, up to the gigantic reptiles of past ages and the Whales of our present ocean. The horned Ray or Skate is 25 feet in length, by 30 in width. The Cuttle-fishes of our seas, though so hideous as to resemble a bad dream, are too small to be formidable; but off the Newfoundland coast is a species with arms sometimes 30 feet long, so as to be 60 feet from tip to tip. The body, however, is small in proportion. The Giraffe attains a height of over 20 feet; the Elephant, though not so tall, is more bulky; the Crocodile reaches a length of over 20 feet, the Python of 60 feet, the extinct Titanosaurus of the American Jurassic beds, the largest land animal yet known to us, 100 feet in length and 30 in height; the Whalebone Whale over 70 feet, Sibbald's Whale is said to have reached 80-90, which is perhaps the limit. Captain Scoresby indeed mentions a Rorqual no less than 120 feet in length, but this is probably too great an estimate. COMPLEXITY OF ANIMAL STRUCTURE The complexity of animal structure is even more marvellous than their mere magnitude. A Caterpillar contains more than 2000 muscles. In our own body are some 2,000,000 perspiration glands, communicating with the surface by ducts having a total length of some 10 miles; while that of the arteries, veins, and capillaries must be very great; the blood contains millions of millions of corpuscles, each no doubt a complex structure in itself; the rods in the retina, which are supposed to be the ultimate recipient of light, are estimated at 30,000,000; and Meinert has calculated that the gray matter of the brain is built up of at least 600,000,000 cells. No verbal description, however, can do justice to the marvellous complexity of animal structure, which the microscope alone, and even that but faintly, can enable us to realise. LENGTH OF LIFE How little we yet know of the life-history of Animals is illustrated by the vagueness of our information as to the age to which they live. Professor Lankester[18] tells us that "the paucity and uncertainty of observations on this class of facts is extreme." The Rabbit is said to reach 10 years, the Dog and Sheep 10-12, the Pig 20, the Horse 30, the Camel 100, the Elephant 200, the Greenland Whale 400 (?): among Birds, the Parrot to attain 100 years, the Raven even more. The Atur Parrot mentioned by Humboldt, talked, but could not be understood, because it spoke in the language of an extinct Indian tribe. It is supposed from their rate of growth that among Fish the Carp is said to reach 150 years; and a Pike, 19 feet long, and weighing 350 lbs., is said to have been taken in Suabia in 1497 carrying a ring, on which was inscribed, "I am the fish which was first of all put into the lake by the hands of the Governor of the Universe, Frederick the Second, the 5th Oct. 1230." This would imply an age of over 267 years. Many Reptiles are no doubt very long-lived. A Tortoise is said to have reached 500 years. As regards the lower animals, the greatest age on record is that of Sir J. Dalzell's Sea Anemone, which lived for over 50 years. Insects are generally short-lived; the Queen Bee, however, is said by Aristotle, whose statement has not been confirmed by recent writers, to live 7 years. I myself had a Queen Ant which attained the age of 15 years. The May Fly (Ephemera) is celebrated as living only for a day, and has given its name to all things short-lived. The statement usually made is, indeed, very misleading, for in its larval condition the Ephemera lives for weeks. Many writers have expressed surprise that in the perfect state its life should be so short. It is, however, so defenceless, and, moreover, so much appreciated by birds and fish, that unless they laid their eggs very rapidly none would perhaps survive to continue the species. Many of these estimates are, as will be seen, very vague and doubtful, so that we must still admit with Bacon that, "touching the length and shortness of life in living creatures, the information which may be had is but slender, observation is negligent, and tradition fabulous. In tame creatures their degenerate life corrupteth them, in wild creatures their exposing to all weathers often intercepteth them." ON INDIVIDUALITY When we descend still lower in the animal scale, the consideration of this question opens out a very curious and interesting subject connected with animal individuality. As regards the animals with which we are most familiar no such question intrudes. Among quadrupeds and birds, fishes and reptiles, there is no difficulty in deciding whether a given organism is an individual, or a part of an individual. Nor does the difficulty arise in the case of most insects. The Bee or Butterfly lays an egg which develops successively into a larva and pupa, finally producing Bee or Butterfly. In these cases, therefore, the egg, larva, pupa, and perfect Insect, are regarded as stages in the life of a single individual. In certain gnats, however, the larva itself produces young larvæ, each of which develops into a gnat, so that the egg produces not one gnat but many gnats. The difficulty of determining what constitutes an individual becomes still greater among the Zoophytes. These beautiful creatures in many cases so closely resemble plants, that until our countryman Ellis proved them to be animals, Crabbe was justified in saying-- Involved in seawrack here we find a race, Which Science, doubting, knows not where to place; On shell or stone is dropped the embryo seed, And quickly vegetates a vital breed. We cannot wonder that such organisms were long regarded as belonging to the vegetable kingdom. The cups which terminate the branches contain, however, an animal structure, resembling a small Sea Anemone, and possessing arms which capture the food by which the whole colony is nourished. Some of these cups, moreover, differ from the rest, and produce eggs. These then we might be disposed to term ovaries. But in many species they detach themselves from the group and lead an independent existence. Thus we find a complete gradation from structures which, regarded by themselves, we should unquestionably regard as mere organs, to others which are certainly separate and independent beings. [Illustration: Fig. 2.--Bougainvillea fruticosa; natural size. (After Allman.)] Fig. 2 represents, after Allman, a colony of Bougainvillea fruticosa of the natural size. It is a British species, which is found growing on buoys, floating timber, etc., and, says Allman, "When in health and vigour, offers a spectacle unsurpassed in interest by any other species--every branchlet crowned by its graceful hydranth, and budding with Medusæ in all stages of development (Fig. 3), some still in the condition of minute buds, in which no trace of the definite Medusa-form can yet be detected; others, in which the outlines of the Medusa can be distinctly traced within the transparent ectotheque (external layer); others, again, just casting off this thin outer pellicle, and others completely freed from it, struggling with convulsive efforts to break loose from the colony, and finally launched forth in the full enjoyment of their freedom into the surrounding water. I know of no form in which so many of the characteristic features of a typical hydroid are more finely expressed than in this beautiful species." [Illustration: Fig. 3.--Bougainvillea fruticosa; magnified to show development.] Fig. 4 represents the Medusa or free form of this beautiful species. [Illustration: Fig. 4.--Bougainvillea fruticosa, Medusa-form.] If we pass to another great group of Zoophytes, that of the Jelly-fishes, we have a very similar case. For our first knowledge of the life-history of these Zoophytes we are indebted to the Norwegian naturalist Sars. Take, for instance, the common Jelly-fish (Medusa aurita) (Fig. 5) of our shores. The egg is a pear-shaped body (_1_), covered with fine hairs, by the aid of which it swims about, the broader end in front. After a while it attaches itself, not as might have been expected by the posterior but by the anterior extremity (_2_). The cilia then disappear, a mouth is formed at the free end, tentacles, first four (_3_), then eight, and at length as many as thirty (_4_), are formed, and the little creature resembles in essentials the freshwater polyp (Hydra) of our ponds. [Illustration: Fig. 5.--Medusa aurita, and progressive stages of development.] At the same time transverse wrinkles (_4_) are formed round the body, first near the free extremity and then gradually descending. They become deeper and deeper, and develop lobes or divisions one under the other, as at _5_. After a while the top ring (and subsequently the others one by one) detaches itself, swims away, and gradually develops into a Medusa (_6_). Thus, then, the life-history is very similar to that of the Hydroids, only that while in the Hydroids the fixed condition is the more permanent, and the free swimming more transitory, in the Medusæ, on the contrary, the fixed condition is apparently only a phase in the production of the free swimming animal. In both the one and the other, however, the egg gives rise not to one but to many mature animals. Steenstrup has given to these curious phenomena, many other cases of which occur among the lower animals, and to which he first called attention, the name of alternations of generations. In the life-history of Infusoria (so called because they swarm in most animal or vegetable infusions) similar difficulties encounter us. The little creatures, many of which are round or oval in form, from time to time become constricted in the middle; the constriction becomes deeper and deeper, and at length the two halves twist themselves apart and swim away. In this case, therefore, there was one, and there are now two exactly similar; but are these two individuals? They are not parent and offspring--that is clear, for they are of the same age; nor are they twins, for there is no parent. As already mentioned, we regard the Caterpillar, Chrysalis, and Butterfly as stages in the life-history of a single individual. But among Zoophytes, and even among some insects, one larva often produces several mature forms. In some species these mature forms remain attached to the larval stock, and we might be disposed to regard the whole as one complex organism. But in others they detach themselves and lead an independent existence. These considerations then introduce much difficulty into our conception of the idea of an Individual. ANIMAL IMMORTALITY But, further than this, we are confronted by by another problem. If we regard a mass of coral as an individual because it arises by continuous growth from a single egg, then it follows that some corals must be thousands of years old. Some of the lower animals may be cut into pieces, and each piece will develop into an entire organism. In fact the realisation of the idea of an individual gradually becomes more and more difficult, and the continuity of existence, even among the highest animals, gradually forces itself upon us. I believe that as we become more rational, as we realise more fully the conditions of existence, this consideration is likely to have important moral results. It is generally considered that death is the common lot of all living beings. But is this necessarily so? Infusoria and other unicellular animals multiply by division. That is to say, if we watch one for a certain time, we shall observe, as already mentioned, that a constriction takes place, which grows gradually deeper and deeper, until at last the two halves become quite detached, and each swims away independently. The process is repeated over and over again, and in this manner the species is propagated. Here obviously there is no birth and no death. Such creatures may be killed, but they have no natural term of life. They are, in fact, theoretically immortal. Those which lived millions of years ago may have gone on dividing and subdividing, and in this sense multitudes of the lower animals are millions of years old. FOOTNOTES: [15] Address to Microscopical Society, 1890. [16] _Ants, Bees, and Wasps_, and _The Senses of Animals_. [17] Prof. Drummond (_Tropical Africa_) dwells with great force on the manner in which the soil of Central Africa is worked up by the White Ants. [18] Lankester, _Comparative Longevity_. See also Weismann, _Duration of Life_. CHAPTER IV ON PLANT LIFE Flower in the crannied wall, I pluck you out of the crannies, I hold you here, root and all, in my hand, Little flower--but _if_ I could understand What you are, root and all, and all in all, I should know what God and man is. TENNYSON. CHAPTER IV ON PLANT LIFE We are told that in old days the Fairies used to give presents of Flowers and Leaves to those whom they wished to reward, or whom they loved best; and though these gifts were, it appears, often received with disappointment, still it will probably be admitted that flowers have contributed more to the happiness of our lives than either gold or silver or precious stones; and that our happiest days have been spent out-of-doors in the woods and fields, when we have ... found in every woodland way The sunlight tint of Fairy Gold.[19] To many minds Flowers acquired an additional interest when it was shown that there was a reason for their colour, size, and form--in fact, for every detail of their organisation. If we did but know all that the smallest flower could tell us, we should have solved some of the greatest mysteries of Nature. But we cannot hope to succeed--even if we had the genius of Plato or Aristotle--without careful, patient, and reverent study. From such an inquiry we may hope much; already we have glimpses, enough to convince us that the whole history will open out to us conceptions of the Universe wider and grander than any which the Imagination alone would ever have suggested. Attempts to explain the forms, colours, and other characteristics of animals and plants are by no means new. Our Teutonic forefathers had a pretty story which explained certain points about several common plants. Balder, the God of Mirth and Merriment, was, characteristically enough, regarded as deficient in the possession of immortality. The other divinities, fearing to lose him, petitioned Thor to make him immortal, and the prayer was granted on condition that every animal and plant would swear not to injure him. To secure this object, Nanna, Balder's wife, descended upon the earth. Loki, the God of Envy, followed her, disguised as a crow (which at that time were white), and settled on a little blue flower, hoping to cover it up, so that Nanna might overlook it. The flower, however, cried out "forget-me-not, forget-me-not," and has ever since been known under that name. Loki then flew up into an oak and sat on a mistletoe. Here he was more successful. Nanna carried off the oath of the oak, but overlooked the mistletoe. She thought, however, and the divinities thought, that she had successfully accomplished her mission, and that Balder had received the gift of immortality. One day, supposing Balder proof, they amused themselves by shooting at him, posting him against a Holly. Loki tipped an arrow with a piece of Mistletoe, against which Balder was not proof, and gave it to Balder's brother. This, unfortunately, pierced him to the heart, and he fell dead. Some drops of his blood spurted on to the Holly, which accounts for the redness of the berries; the Mistletoe was so grieved that she has ever since borne fruit like tears; and the crow, whose form Loki had taken, and which till then had been white, was turned black. This pretty myth accounts for several things, but is open to fatal objections. Recent attempts to explain the facts of Nature are not less fascinating, and, I think, more successful. Why then this marvellous variety? this inexhaustible treasury of beautiful forms? Does it result from some innate tendency in each species? Is it intentionally designed to delight the eye of man? Or has the form and size and texture some reference to the structure and organisation, the habits and requirements of the whole plant? I shall never forget hearing Darwin's paper on the structure of the Cowslip and Primrose, after which even Sir Joseph Hooker compared himself to Peter Bell, to whom A primrose by a river's brim A yellow primrose was to him, And it was nothing more. We all, I think, shared the same feeling, and found that the explanation of the flower then given, and to which I shall refer again, invested it with fresh interest and even with new beauty. A regular flower, such, for instance, as a Geranium or a Pink, consists of four or more whorls of leaves, more or less modified: the lowest whorl is the Calyx, and the separate leaves of which it is composed, which however are sometimes united into a tube, are called sepals; (2) a second whorl, the corolla, consisting of coloured leaves called petals, which, however, like those of the Calyx, are often united into a tube; (3) of one or more stamens, consisting of a stalk or filament, and a head or anther, in which the pollen is produced; and (4) a pistil, which is situated in the centre of the flower, and at the base of which is the Ovary, containing one or more seeds. Almost all large flowers are brightly coloured, many produce honey, and many are sweet-scented. What, then, is the use and purpose of this complex organisation? It is, I think, well established that the main object of the colour, scent, and honey of flowers is to attract insects, which are of use to the plant in carrying the pollen from flower to flower. In many species the pollen is, and no doubt it originally was in all, carried by the air. In these cases the chance against any given grain of pollen reaching the pistil of another flower of the same species is of course very great, and the quantity of pollen required is therefore immense. In species where the pollen is wind-borne as in most of our trees--firs, oaks, beech, ash, elm, etc., and many herbaceous plants, the flowers are as a rule small and inconspicuous, greenish, and without either scent or honey. Moreover, they generally flower early, so that the pollen may not be intercepted by the leaves, but may have a better chance of reaching another flower. And they produce an immense quantity of pollen, as otherwise there would be little chance that any would reach the female flower. Every one must have noticed the clouds of pollen produced by the Scotch Fir. When, on the contrary, the pollen is carried by insects, the quantity necessary is greatly reduced. Still it has been calculated that a Peony flower produces between 3,000,000 and 4,000,000 pollen grains; in the Dandelion, which is more specialised, the number is reduced to about 250,000; while in such a flower as the Dead-nettle it is still smaller. The honey attracts the insects; while the scent and colour help them to find the flowers, the scent being especially useful at night, which is perhaps the reason why evening flowers are so sweet. It is to insects, then, that flowers owe their beauty, scent, and sweetness. Just as gardeners, by continual selection, have added so much to the beauty of our gardens, so to the unconscious action of insects is due the beauty, scent, and sweetness of the flowers of our woods and fields. Let us now apply these views to a few common flowers. Take, for instance, the White Dead-nettle. The corolla of this beautiful and familiar flower (Fig. 6) consists of a narrow tube, somewhat expanded at the upper end (Fig. 7), where the lower lobe forms a platform, on each side of which is a small projecting tooth (Fig. 8, _m_). The upper portion of the corolla is an arched hood (_co_), under which lie four anthers (_a a_), in pairs, while between them, and projecting somewhat downwards, is the pointed pistil (_st_); the tube at the lower part contains honey, and above the honey is a row of hairs running round the tube. [Illustration: Fig. 6--White Dead-nettle.] Now, why has the flower this peculiar form? What regulates the length of the tube? What is the use of the arch? What lesson do the little teeth teach us? What advantage is the honey to the flower? Of what use is the fringe of hairs? Why does the stigma project beyond the anthers? Why is the corolla white, while the rest of the plant is green? [Illustration: Fig. 7.] [Illustration: Fig. 8.] The honey of course serves to attract the Humble Bees by which the flower is fertilised, and to which it is especially adapted; the white colour makes the flower more conspicuous; the lower lip forms the stage on which the Bees may alight; the length of the tube is adapted to that of their proboscis; its narrowness and the fringe of fine hairs exclude small insects which might rob the flower of its honey without performing any service in return; the arched upper lip protects the stamens and pistil, and prevents rain-drops from choking up the tube and washing away the honey; the little teeth are, I believe, of no use to the flower in its present condition, they are the last relics of lobes once much larger, and still remaining so in some allied species, but which in the Dead-nettle, being no longer of any use, are gradually disappearing; the height of the arch has reference to the size of the Bee, being just so much above the alighting stage that the Bee, while sucking the honey, rubs its back against the hood and thus comes in contact first with the stigma and then with the anthers, the pollen-grains from which adhere to the hairs on the Bee's back, and are thus carried off to the next flower which the Bee visits, when some of them are then licked off by the viscid tip of the stigma.[20] [Illustration: Fig. 9.] [Illustration: Fig. 10.] [Illustration: Fig. 11.] In the Salvias, the common blue Salvia of our gardens, for instance,--a plant allied to the Dead-nettle,--the flower (Fig. 9) is constructed on the same plan, but the arch is much larger, so that the back of the Bee does not nearly reach it. The stamens, however, have undergone a remarkable modification. Two of them have become small and functionless. In the other two the anthers or cells producing the pollen, which in most flowers form together a round knob or head at the top of the stamen, are separated by a long arm, which plays on the top of the stamen as on a hinge. Of these two arms one hangs down into the tube, closing the passage, while the other lies under the arched upper lip. When the Bee pushes its proboscis down the tube (Fig. 11) it presses the lower arm to one side, and the upper arm consequently descends, tapping the Bee on the back, and dusting it with pollen. When the flower is a little older the pistil (Fig. 9, _p_) has elongated so that the stigma (Fig. 10, _st_) touches the back of the Bee and carries off some of the pollen. This sounds a little complicated, but is clear enough if we take a twig or stalk of grass and push it down the tube, when one arm of each of the two larger stamens will at once make its appearance. It is one of the most beautiful pieces of plant mechanism which I know, and was first described by Sprengel, a poor German schoolmaster. SNAPDRAGON At first sight it may seem an objection to the view here advocated that the flowers in some species--as, for instance, the common Snapdragon (Antirrhinum), which, according to the above given tests, ought to be fertilised by insects--are entirely closed. A little consideration, however, will suggest the reply. The Snapdragon is especially adapted for fertilisation by Humble Bees. The stamens and pistil are so arranged that smaller species would not effect the object. It is therefore an advantage that they should be excluded, and in fact they are not strong enough to move the spring. The Antirrhinum is, so to speak, a closed box, of which the Humble Bees alone possess the key. FURZE, BROOM, AND LABURNUM Other flowers such as the Furze, Broom, Laburnum, etc., are also opened by Bees. The petals lock more or less into one another, and the flower remains at first closed. When, however, the insect alighting on it presses down the keel, the flower bursts open, and dusts it with pollen. SWEET PEA In the above cases the flower once opened does not close again. In others, such as the Sweet Pea and the Bird's-foot Lotus, Nature has been more careful. When the Bee alights it clasps the "wings" of the flower with its legs, thus pressing them down; they are, however, locked into the "keel," or lower petal, which accordingly is also forced down, thus exposing the pollen which rubs against, and part of which sticks to, the breast of the Bee. When she leaves the flower the keel and wings rise again, thus protecting the rest of the pollen and keeping it ready until another visitor comes. It is easy to carry out the same process with the fingers. [Illustration: Fig. 12. Fig. 13. Flower and Pollen of Primrose] PRIMULA In the Primrose and Cowslip, again, we find quite a different plan. It had long been known that if a number of Cowslips or Primroses are examined, about half would be found to have the stigma at the top of the tube and the stamens half way down, while in the other half the stamens are at the top and the stigma half way down. These two forms are about equally numerous, but never occur on the same stock. They have been long known to children and gardeners, who call them thrum-eyed and pin-eyed. Mr. Darwin was the first to explain the significance of this curious difference. It cost him several years of patient labour, but when once pointed out it is sufficiently obvious. An insect thrusting its proboscis down a primrose of the long-styled form (Fig. 12) would dust its proboscis at a part (_a_) which, when it visited a short-styled flower (Fig. 13), would come just opposite the head of the pistil (_st_), and could not fail to deposit some of the pollen on the stigma. Conversely, an insect visiting a short-styled plant would dust its proboscis at a part farther from the tip; which, when the insect subsequently visited a long-styled flower, would again come just opposite to the head of the pistil. Hence we see that by this beautiful arrangement insects must carry the pollen of the long-styled form to the short-styled, and _vice versâ_. The economy of pollen is not the only advantage which plants derive from these visits of Insects. A second and scarcely less important is that they tend to secure "cross fertilisation"; that is to say, that the seed shall be fertilised by pollen from another plant. The fact that "cross fertilisation" is of advantage to the plant doubtless also explains the curious arrangement that in many plants the stamen and pistil do not mature at the same time--the former having shed their pollen before the pistil is mature; or, which happens less often, the pistil having withered before the pollen is ripe. In most Geraniums, Pinks, etc., for instance, and many allied species, the stamens ripen first, and are followed after an interval by the pistil. THE NOTTINGHAM CATCHFLY The Nottingham Catchfly (Silene nutans) is a very interesting case. The flower is adapted to be fertilised by Moths. Accordingly it opens towards evening, and as is generally the case with such flowers, is pale in colour, and sweet-scented. There are two sets of stamens, five in each set. The first evening that the flower opens one set of stamens ripen and expose their pollen. Towards morning these wither away, the flower shrivels up, ceases to emit scent, and looks as if it were faded. So it remains all next day. Towards evening it reopens, the second set of stamens have their turn, and the flower again becomes fragrant. By morning, however, the second set of stamens have shrivelled, and the flower is again asleep. Finally on the third evening it reopens for the last time, the long spiral stigmas expand, and can hardly fail to be fertilised with the pollen brought by Moths from other flowers. THE HEATH In the hanging flowers of Heaths the stamens form a ring, and each one bears two horns. When the Bee inserts its proboscis into the flower to reach the honey, it is sure to press against one of these horns, the ring is dislocated, and the pollen falls on to the head of the insect. In fact, any number of other interesting cases might be mentioned. BEES AND FLIES Bees are intelligent insects, and would soon cease to visit flowers which did not supply them with food. Flies, however, are more stupid, and are often deceived. Thus in our lovely little Parnassia, five of the ten stamens have ceased to produce pollen, but are prolonged into fingers, each terminating in a shining yellow knob, which looks exactly like a drop of honey, and by which Flies are continually deceived. Paris quadrifolia also takes them in with a deceptive promise of the same kind. Some foreign plants have livid yellow and reddish flowers, with a most offensive smell, and are constantly visited by Flies, which apparently take them for pieces of decaying meat. [Illustration: Fig. 14.--Arum.] The flower of the common Lords and Ladies (Arum) of our hedges is a very interesting case. The narrow neck bears a number of hairs pointing downwards. The stamens are situated above the stigma, which comes to maturity first. Small Flies enter the flower apparently for shelter, but the hairs prevent them from returning, and they are kept captive until the anthers have shed their pollen. Then, when the Flies have been well dusted, the hairs shrivel up, leaving a clear road, and the prisoners are permitted to escape. The tubular flowers of Aristolochia offer a very similar case. PAST HISTORY OF FLOWERS If the views here advocated are correct, it follows that the original flowers were small and green, as wind-fertilised flowers are even now. But such flowers are inconspicuous. Those which are coloured, say yellow or white, are of course much more visible and more likely to be visited by insects. I have elsewhere given my reasons for thinking that under these circumstances some flowers became yellow, that some of them became white, others subsequently red, and some finally blue. It will be observed that red and blue flowers are as a rule highly specialised, such as Aconites and Larkspurs as compared with Buttercups; blue Gentians as compared with yellow, etc. I have found by experiment that Bees are especially partial to blue and pink. Tubular flowers almost always, if not always, contain honey, and are specially suited to Butterflies and Moths, Bees and Flies. Those which are fertilised by Moths generally come out in the evening, are often very sweetly scented, and are generally white or pale yellow, these colours being most visible in the twilight. Aristotle long ago noticed the curious fact that in each journey Bees confine themselves to some particular flower. This is an economy of labour to the Bee, because she has not to vary her course of proceeding. It is also an advantage to the plants, because the pollen is carried from each flower to another of the same species, and is therefore less likely to be wasted. FRUITS AND SEEDS After the flower comes the seed, often contained in a fruit, and which itself encloses the future plant. Fruits and seeds are adapted for dispersion, beautifully and in various ways: some by the wind, being either provided with a wing, as in the fruits of many trees--Sycamores, Ash, Elms, etc.; or with a hairy crown or covering, as with Thistles, Dandelions, Willows, Cotton plant, etc. Some seeds are carried by animals; either as food--such as most edible fruits and seeds, acorns, nuts, apples, strawberries, raspberries, blackberries, plums, grasses, etc.--or involuntarily, the seeds having hooked hairs or processes, such as burrs, cleavers, etc. Some seeds are scattered by the plants themselves, as, for instance, those of many Geraniums, Violets, Balsams, Shamrocks, etc. Our little Herb Robert throws its seeds some 25 feet. Some seeds force themselves into the ground, as those of certain grasses, Cranes'-bills (Erodiums), etc. Some are buried by the parent plants, as those of certain clovers, vetches, violets, etc. Some attach themselves to the soil, as those of the Flax; or to trees, as in the case of the Mistletoe. LEAVES Again, as regards the leaves there can, I think, be no doubt that similar considerations of utility are applicable. Their forms are almost infinitely varied. To quote Ruskin's vivid words, they "take all kinds of strange shapes, as if to invite us to examine them. Star-shaped, heart-shaped, spear-shaped, arrow-shaped, fretted, fringed, cleft, furrowed, serrated, sinuated, in whorls, in tufts, in spires, in wreaths, endlessly expressive, deceptive, fantastic, never the same from foot-stalk to blossom, they seem perpetually to tempt our watchfulness and take delight in outstepping our wonder." But besides these differences of mere form, there are many others: of structure, texture, and surface; some are scented or have a strong taste, or acrid juice, some are smooth, others hairy; and the hairs again are of various kinds. I have elsewhere[21] endeavoured to explain some of the causes which have determined these endless varieties. In the Beech, for instance (Fig. 15), the leaf has an area of about 3 square inches. The distance between the buds is about 1-1/4 inch, and the leaves lie in the general plane of the branch, which bends slightly at each internode. The basal half of the leaf fits the swell of the twig, while the upper half follows the edge of the leaf above; and the form of the inner edge being thus determined, decides that of the outer one also. [Illustration: Fig. 15.--Beech.] The weight, and consequently the size of the leaf, is limited by the strength of the twig; and, again, in a climate such as ours it is important to plants to have their leaves so arranged as to secure the maximum of light. Hence in leaves which lie parallel to the plane of the boughs, as in the Beech, the width depends partly on the distance between the buds; if the leaves were broader, they would overlap, if they were narrower, space would be wasted. Consequently the width being determined by the distance between the buds, and the size depending on the weight which the twig can safely support, the length also is determined. This argument is well illustrated by comparing the leaves of the Beech with those of the Spanish Chestnut. The arrangement is similar, and the distance between the buds being about the same, so is the width of the leaves. But the terminal branches of the Spanish Chestnut being much stronger, the leaves can safely be heavier; hence the width being fixed, they grow in length and assume the well-known and peculiar sword-blade shape. In the Sycamores, Maples (Fig. 16), and Horse-Chestnuts the arrangement is altogether different. The shoots are stiff and upright with leaves placed at right angles to the branches instead of being parallel to them. The leaves are in pairs and decussate with one another; while the lower ones have long petioles which bring them almost to the level of the upper pairs, the whole thus forming a beautiful dome. For leaves arranged as in the Beech the gentle swell at the base is admirably suited; but in a crown of leaves such as those of the Sycamore, space would be wasted, and it is better that they should expand at once, so soon as their stalks have carried them free from the upper and inner leaves. [Illustration: Fig. 16.--Acer platanoides.] In the Black Poplar the arrangement of the leaves is again quite different. The leaf stalk is flattened, so that the leaves hang vertically. In connection with this it will be observed that while in most leaves the upper and under surfaces are quite unlike, in the Black Poplar on the contrary they are very similar. The stomata or breathing holes, moreover, which in the leaves of most trees are confined to the under surface, are in this species nearly equally numerous on both. The "Compass" Plant of the American prairies, a plant not unlike a small sunflower, is another species with upright leaves, which growing in the wide open prairies tend to point north and south, thus exposing both surfaces equally to the light and heat. Such a position also affects the internal structure of the leaf, the two sides becoming similar in structure, while in other cases the upper and under surfaces are very different. In the Yew the leaves are inserted close to one another, and are linear; while in the Box they are further apart and broader. In other cases the width of the leaves is determined by what botanists call the "Phyllotaxy." Some plants have the leaves opposite, each pair being at right angles with the pairs above and below. In others they are alternate, and arranged round the stem in a spiral. In one very common arrangement the sixth leaf stands directly over the first, the intermediate ones forming a spiral which has passed twice round the stem. This, therefore, is known as the 2/5 arrangement. Common cases are 1/2, 1/3, 2/5, 3/8, and 5/13. In the first the leaves are generally broad, in the 3/8 arrangement they are elliptic, in the 5/13 and more complicated arrangements nearly linear. The Willows afford a very interesting series. Salix herbacea has the 1/3 arrangement and rounded leaves, Salix caprea elliptic leaves and 2/5, Salix pentandra lancet-shaped leaves and 3/8, and S. incana linear leaves and a 5/13 arrangement. The result is that whether the series consists of 2, 3, 5, 8, or 13 leaves, in every case, if we look perpendicularly at a twig the leaves occupy the whole circle. In herbaceous plants upright leaves as a rule are narrow, which is obviously an advantage, while prostrate ones are broad. [Illustration: AQUATIC VEGETATION, BRAZIL. _To face page 145._] AQUATIC PLANTS Many aquatic plants have two kinds of leaves; some more or less rounded, which float on the surface; and others cut up into narrow segments, which remain below. The latter thus present a greater extent of surface. In air such leaves would be unable even to support their own weight, much less to resist the force of the wind. In still air, however, for the same reason, finely-divided leaves may be an advantage, while in exposed positions compact and entire leaves are more suitable. Hence herbaceous plants tend to have divided, bushes and trees entire, leaves. There are many cases when even in the same family low and herb-like species have finely-cut leaves, while in shrubby or ligneous ones they more or less resemble those of the Laurel or Beech. These considerations affect trees more than herbs, because trees stand more alone, while herbaceous plants are more affected by surrounding plants. Upright leaves tend to be narrow, as in the case of grasses; horizontal leaves, on the contrary, wider. Large leaves are more or less broken up into leaflets, as in the Ash, Mountain-Ash, Horse-Chestnut, etc. The forms of leaves depend also much on the manner in which they are packed into the buds. The leaves of our English trees, as I have already said, are so arranged as to secure the maximum of light; in very hot countries the reverse is the case. Hence, in Australia, for instance, the leaves are arranged not horizontally, but vertically, so as to present, not their surfaces, but their edges, to the sun. One English plant, a species of lettuce, has the same habit. This consideration has led also to other changes. In many species the leaves are arranged directly under, so as to shelter, one another. The Australian species of Acacia have lost their true leaves, and the parts which in them we generally call leaves are in reality vertically-flattened leaf stalks. In other cases the stem itself is green, and to some extent replaces the leaves. In our common Broom we see an approach to this, and the same feature is more marked in Cactus. Or the leaves become fleshy, thus offering, in proportion to their volume, a smaller surface for evaporation. Of this the Stonecrops, Mesembryanthemum, etc., are familiar instances. Other modes of checking transpiration and thus adapting plants to dry situations are by the development of hairs, by the formation of chalky excretions, by the sap becoming saline or viscid, by the leaf becoming more or less rolled up, or protected by a covering of varnish. Our English trees are for the most part deciduous. Leaves would be comparatively useless in winter when growth is stopped by the cold; moreover, they would hold the snow, and thus cause the boughs to be broken down. Hence perhaps the glossiness of Evergreen leaves, as, for instance, of the Holly, from which the snow slips off. In warmer climates trees tend to retain their leaves, and some species which are deciduous in the north become evergreen, or nearly so, in the south of Europe. Evergreen leaves are as a rule tougher and thicker than those which drop off in autumn; they require more protection from the weather. But some evergreen leaves are much longer lived than others; those of the Evergreen Oak do not survive a second year, those of the Scotch Pine live for three, of the Spruce Fir, Yew, etc., for eight or ten, of the Pinsapo even eighteen. As a general rule the Conifers with short leaves keep them on for several years, those with long ones for fewer, the length of the leaf being somewhat in the inverse ratio to the length of its life; but this is not an invariable criterion, as other circumstances also have to be taken into consideration. Leaves with strong scent, aromatic taste, or acrid juice, are characteristic of dry regions, where they run especial danger of being eaten, and where they are thus more or less effectively protected. ON HAIRS The hairs of plants are useful in various ways. In some cases (1) they keep off superfluous moisture; in others (2) they prevent too rapid evaporation; in some (3) they serve as a protection against too glaring light; in some (4) they protect the plant from browsing quadrupeds; in others (5) from being eaten by insects; or, (6) serve as a quickset hedge to prevent access to the flowers. In illustration of the first case I may refer to many alpine plants, the well-known Edelweiss, for instance, where the woolly covering of hairs prevents the "stomata," or minute pores leading into the interior of the leaf, from being clogged up by rain, dew, or fog, and thus enable them to fulfil their functions as soon as the sun comes out. As regards the second case many desert and steppe-plants are covered with felty hairs, which serve to prevent too rapid evaporation and consequent loss of moisture. The woolly hairy leaves of the Mulleins (Verbascum) doubtless tend to protect them from being eaten, as also do the spines of Thistles, and those of Hollies, which, be it remarked, gradually disappear on the upper leaves which browsing quadrupeds cannot reach. I have already alluded to the various ways in which flowers are adapted to fertilisation by insects. But Ants and other small creeping insects cannot effectually secure this object. Hence it is important that they should be excluded, and not allowed to carry off the honey, for which they would perform no service in return. In many cases, therefore, the opening of the flower is either contracted to a narrow passage, or is itself protected by a fringe of hairs. In others the peduncle, or the stalk of the plant, is protected by a hedge, or chevaux de frise, of hairs. In this connection I might allude to the many plants which are more or less viscid. This also is in most cases a provision to preclude creeping insects from access to the flowers. There are various other kinds of hairs to which I might refer--glandular hairs, secretive hairs, absorbing hairs, etc. It is marvellous how beautifully the form and structure of leaves is adapted to the habits and requirements of the plants, but I must not enlarge further on this interesting subject. The time indeed will no doubt come when we shall be able to explain every difference of form and structure, almost infinite as these differences are. INFLUENCE OF SOIL The character of the vegetation is of course greatly influenced by that of the soil. In this respect granitic and calcareous regions offer perhaps the best marked contrast. There are in Switzerland two kinds of Rhododendrons, very similar in their flowers, but contrasted in their leaves: Rhododendron hirsutum having them hairy at the edges as the name indicates; while in R. ferrugineum they are rolled, but not hairy, at the edges, and become ferrugineous on the lower side. This species occurs in the granitic regions, where R. hirsutum does not grow. The Yarrows (Achillea) afford us a similar case. Achillea atrata and A. moschata will live either on calcareous or granitic soil, but in a district where both occur, A. atrata grows so much the more vigorously of the two if the soil is calcareous that it soon exterminates A. moschata; while in granite districts, on the contrary, A. moschata is victorious and A. atrata disappears. Every keen sportsman will admit that a varied "bag" has a special charm, and the botanist in a summer's walk may see at least a hundred plants in flower, all with either the interest of novelty, or the charm of an old friend. ON SEEDLINGS In many cases the Seedlings afford us an interesting insight into the former condition of the plant. Thus the leaves of the Furze are reduced to thorns; but those of the Seedling are herbaceous and trifoliate like those of the Herb Genet and other allied species, subsequent ones gradually passing into spines. This is evidence that the ancestors of the Furze bore leaves. Plants may be said to have their habits as well as animals. SLEEP OF PLANTS Many flowers close their petals during rain; the advantage of which is that it prevents the honey and pollen from being spoilt or washed away. Everybody, however, has observed that even in fine weather certain flowers close at particular hours. This habit of going to sleep is surely very curious. Why should flowers do so? In animals we can better understand it; they are tired and require rest. But why should flowers sleep? Why should some flowers do so, and not others? Moreover, different flowers keep different hours. The Daisy opens at sunrise and closes at sunset, whence its name "day's-eye." The Dandelion (Leontodon) is said to open about seven and to close about five; Arenaria rubra to be open from nine to three; the White Water Lily (Nymphæa), from about seven to four; the common Mouse-ear Hawk-weed (Hieracium) from eight to three; the Scarlet Pimpernel (Anagallis) to waken at seven and close soon after two; Tragopogon pratensis to open at four in the morning, and close just before twelve, whence its English name, "John go to bed at noon." Farmers' boys in some parts are said to regulate their dinner time by it. Other flowers, on the contrary, open in the evening. Now it is obvious that flowers which are fertilised by night-flying insects would derive no advantage from being open by day; and on the other hand, that those which are fertilised by bees would gain nothing by being open at night. Nay it would be a distinct disadvantage, because it would render them liable to be robbed of their honey and pollen, by insects which are not capable of fertilising them. I have ventured to suggest then that the closing of flowers may have reference to the habits of insects, and it may be observed also in support of this, that wind-fertilised flowers do not sleep; and that many of those flowers which attract insects by smell, open and emit their scent at particular hours; thus Hesperis matronalis and Lychnis vespertina smell in the evening, and Orchis bifolia is particularly sweet at night. But it is not the flowers only which "sleep" at night; in many species the leaves also change their position, and Darwin has given strong reasons for considering that the object is to check transpiration and thus tend to a protection against cold. BEHAVIOUR OF LEAVES IN RAIN The behaviour of plants with reference to rain affords many points of much interest. The Germander Speedwell (Veronica) has two strong rows of hairs, the Chickweed (Stellaria) one, running down the stem and thus conducting the rain to the roots. Plants with a main tap-root, like the Radish or the Beet, have leaves sloping inwards so as to conduct the rain towards the axis of the plant, and consequently to the roots; while, on the contrary, where the roots are spreading the leaves slope outwards. In other cases the leaves hold the rain or dew drops. Every one who has been in the Alps must have noticed how the leaves of the Lady's Mantle (Alchemilla) form little cups containing each a sparkling drop of icy water. Kerner has suggested that owing to these cold drops, the cattle and sheep avoid the leaves. MIMICRY In many cases plants mimic others which are better protected than themselves. Thus Matricaria Chamomilla mimics the true Chamomile, which from its bitterness is not eaten by quadrupeds. Ajuga Chamæpitys mimics Euphorbia Cyparissias, with which it often grows, and which is protected by its acrid juice. The most familiar case, however, is that of the Stinging and the Dead Nettles. They very generally grow together, and though belonging to quite different families are so similar that they are constantly mistaken for one another. Some Orchids have a curious resemblance to insects, after which they have accordingly been named the Bee Orchis, Fly Orchis, Butterfly Orchis, etc., but it has not yet been satisfactorily shown what advantage the resemblance is to the plant. ANTS AND PLANTS The transference of pollen from plant to plant is by no means the only service which insects render. Ants, for instance, are in many cases very useful to plants. They destroy immense numbers of caterpillars and other insects. Forel observing a large Ants' nest counted more than 28 insects brought in as food per minute. In some cases Ants attach themselves to particular trees, constituting a sort of bodyguard. A species of Acacia, described by Belt, bears hollow thorns, while each leaflet produces honey in a crater-formed gland at the base, as well as a small, sweet, pear-shaped body at the tip. In consequence it is inhabited by myriads of a small ant, which nests in the hollow thorns, and thus finds meat, drink, and lodging all provided for it. These ants are continually roaming over the plant, and constitute a most efficient bodyguard, not only driving off the leaf-eating ants, but, in Belt's opinion, rendering the leaves less liable to be eaten by herbivorous mammalia. Delpino mentions that on one occasion he was gathering a flower of Clerodendrum, when he was himself suddenly attacked by a whole army of small ants. INSECTIVOROUS PLANTS In the cases above mentioned the relation between flowers and insects is one of mutual advantage. But this is by no means an invariable rule. Many insects, as we all know, live on plants, but it came upon botanists as a surprise when our countryman Ellis first discovered that some plants catch and devour insects. This he observed in a North American plant, Dionsea, the leaves of which are formed something like a rat-trap, with a hinge in the middle, and a formidable row of spines round the edge. On the surface are a few very sensitive hairs, and the moment any small insect alights on the leaf and touches one of these hairs the two halves of the leaf close up quickly and catch it. The surface then throws out a glutinous secretion, by means of which the leaf sucks up the nourishment contained in the insect. Our common Sun-dews (Drosera) are also insectivorous, the prey being in their case captured by glutinous hairs. Again, the Bladderwort (Utricularia), a plant with pretty yellow flowers, growing in pools and slow streams, is so called because it bears a great number of bladders or utricles, each of which is a real miniature eel-trap, having an orifice guarded by a flap opening inwards which allows small water animals to enter, but prevents them from coming out again. The Butterwort (Pinguicula) is another of these carnivorous plants. MOVEMENTS OF PLANTS While considering Plant life we must by no means confine our attention to the higher orders, but must remember also those lower groups which converge towards the lower forms of animals, so that in the present state of our knowledge the two cannot always be distinguished with certainty. Many of them differ indeed greatly from the ordinary conception of a plant. Even the comparatively highly organised Sea-weeds multiply by means of bodies called spores, which an untrained observer would certainly suppose to be animals. They are covered by vibratile hairs or "cilia," by means of which they swim about freely in the water, and even possess a red spot which, as being especially sensitive to light, may be regarded as an elementary eye, and with the aid of which they select some suitable spot, to which they ultimately attach themselves. It was long considered as almost a characteristic of plants that they possessed no power of movement. This is now known to be an error. In fact, as Darwin has shown, every growing part of a plant is in continual and even constant rotation. The stems of climbing plants make great sweeps, and in other cases, when the motion is not so apparent, it nevertheless really exists. I have already mentioned that many plants change the position of their leaves or flowers, or, as it is called, sleep at night. The common Dandelion raises its head when the florets open, opens and shuts morning and evening, then lies down again while the seeds are ripening, and raises itself a second time when they are ready to be carried away by the wind. Valisneria spiralis is a very interesting case. It is a native of European rivers, and the female flower has a long spiral stalk which enables it to float on the surface of the water. The male flowers have no stalks, and grow low down on the plant. They soon, however, detach themselves altogether, rise to the surface, and thus are enabled to fertilise the female flowers among which they float. The spiral stalk of the female flower then contracts and draws it down to the bottom of the water so that the seeds may ripen in safety. Many plants throw or bury their seeds. The sensitive plants close their leaves when touched, and the leaflets of Desmodium gyrans are continually revolving. I have already mentioned that the spores of sea-weeds swim freely in the water by means of cilia. Some microscopic plants do so throughout a great part of their lives. A still lower group, the Myxomycetes, which resemble small, more or less branched, masses of jelly, and live in damp soil, among decaying leaves, under bark and in similar moist situations, are still more remarkably animal like. They are never fixed, but in almost continual movement, due to differences of moisture, warmth, light, or chemical action. If, for instance, a moist body is brought into contact with one of their projections, or "pseudopods," the protoplasm seems to roll itself in that direction, and so the whole organism gradually changes its place. So again, while a solution of salt, carbonate of potash, or saltpetre causes them to withdraw from the danger, an infusion of sugar, or tan, produces a flow of protoplasm towards the source of nourishment. In fact, in the same way it rolls over and round its food, absorbing what is nutritious as it passes along. In cold weather they descend into the soil, and one of them (Oethalium), which lives in tan pits, descends in winter to a depth of several feet. When about to fructify it changes its habits, seeks the light instead of avoiding it, climbs upwards, and produces its fruit above ground. IMPERFECTION OF OUR KNOWLEDGE The total number of living species of plants may be roughly estimated at 500,000, and there is not one, of which we can say that the structure, uses, and life-history are yet fully known to us. Our museums contain large numbers which botanists have not yet had time to describe and name. Even in our own country not a year passes without some additional plant being discovered; as regards the less known regions of the earth not half the species have yet been collected. Among the Lichens and Fungi especially many problems of their life-history, some, indeed, of especial importance to man, still await solution. Our knowledge of the fossil forms, moreover, falls far short even of that of existing species, which, on the other hand, they must have greatly exceeded in number. Every difference of form, structure, and colour has doubtless some cause and explanation, so that the field for research is really inexhaustible. FOOTNOTES: [19] Thomson. [20] Lubbock, _Flowers and Insects_. [21] _Flowers, Fruits, and Leaves._ CHAPTER V WOODS AND FIELDS "By day or by night, summer or winter, beneath trees the heart feels nearer to that depth of life which the far sky means. The rest of spirit, found only in beauty, ideal and pure, comes there because the distance seems within touch of thought." JEFFERIES. CHAPTER V WOODS AND FIELDS Rural life, says Cicero, "is not delightful by reason of cornfields only and meadows, and vineyards and groves, but also for its gardens and orchards, for the feeding of cattle, the swarms of bees, and the variety of all kinds of flowers." Bacon considered that a garden is "the greatest refreshment to the spirits of man, without which buildings and palaces are but gross handyworks, and a man shall ever see, that when ages grow to civility and elegancy men come to build stately sooner than to garden finely, as if gardening were the greater perfection." No doubt "the pleasure which we take in a garden is one of the most innocent delights in human life."[22] Elsewhere there may be scattered flowers, or sheets of colour due to one or two species, but in gardens one glory follows another. Here are brought together all the quaint enamelled eyes, That on the green turf sucked the honeyed showers, And purple all the ground with vernal flowers. Bring the rathe primrose that forsaken dies, The tufted crow-toe, and pale jessamine, The white pink and the pansy freaked with jet, The glowing violet, The musk rose, and the well attired woodbine, With cowslips wan that hang the pensive head, And every flower that sad embroidery wears.[23] We cannot, happily we need not try to, contrast or compare the beauty of gardens with that of woods and fields. And yet to the true lover of Nature wild flowers have a charm which no garden can equal. Cultivated plants are but a living herbarium. They surpass, no doubt, the dried specimens of a museum, but, lovely as they are, they can be no more compared with the natural vegetation of our woods and fields than the captives in the Zoological Gardens with the same wild species in their native forests and mountains. Often indeed, our woods and fields rival gardens even in the richness of colour. We have all seen meadows white with Narcissus, glowing with Buttercups, Cowslips, early purple Orchis, or Cuckoo Flowers; cornfields blazing with Poppies; woods carpeted with Bluebells, Anemones, Primroses, and Forget-me-nots; commons with the yellow Lady's Bedstraw, Harebells, and the sweet Thyme; marshy places with the yellow stars of the Bog Asphodel, the Sun-dew sparkling with diamonds, Ragged Robin, the beautifully fringed petals of the Buckbean, the lovely little Bog Pimpernel, or the feathery tufts of Cotton Grass; hedgerows with Hawthorn and Traveller's Joy, Wild Rose and Honeysuckle, while underneath are the curious leaves and orange fruit of the Lords and Ladies, the snowy stars of the Stitchwort, Succory, Yarrow, and several kinds of Violets; while all along the banks of streams are the tall red spikes of the Loosestrife, the Hemp Agrimony, Water Groundsel, Sedges, Bulrushes, Flowering Rush, Sweet Flag, etc. Many other sweet names will also at once occur to us--Snowdrops, Daffodils and Hearts-ease, Lady's Mantles and Lady's Tresses, Eyebright, Milkwort, Foxgloves, Herb Roberts, Geraniums, and among rarer species, at least in England, Columbines and Lilies. But Nature does not provide delights for the eye only. The other senses are not forgotten. A thousand sounds--many delightful in themselves, and all by association--songs of birds, hum of insects, rustle of leaves, ripple of water, seem to fill the air. Flowers again are sweet, as well as lovely. The scent of pine woods, which is said to be very healthy, is certainly delicious, and the effect of Woodland scenery is good for the mind as well as for the body. "Resting quietly under an ash tree, with the scent of flowers, and the odour of green buds and leaves, a ray of sunlight yonder lighting up the lichen and the moss on the oak trunk, a gentle air stirring in the branches above, giving glimpses of fleecy clouds sailing in the ether, there comes into the mind a feeling of intense joy in the simple fact of living."[24] The wonderful phenomenon of phosphorescence is not a special gift to the animal kingdom. Henry O. Forbes describes a forest in Sumatra: "The stem of every tree blinked with a pale greenish-white light which undulated also across the surface of the ground like moonlight coming and going behind the clouds, from a minute thread-like fungus invisible in the day-time to the unassisted eye; and here and there thick dumpy mushrooms displayed a sharp, clear dome of light, whose intensity never varied or changed till the break of day; long phosphorescent caterpillars and centipedes crawled out of every corner, leaving a trail of light behind them, while fire-flies darted about above like a lower firmament."[25] Woods and Forests were to our ancestors the special scenes of enchantment. The great Ash tree Yggdrasil bound together Heaven, Earth, and Hell. Its top reached to Heaven, its branches covered the Earth, and the roots penetrated into Hell. The three Normas or Fates sat under it, spinning the thread of life. Of all the gods and goddesses of classical mythology or our own folk-lore, none were more fascinating than the Nature Spirits--Elves and Fairies, Neckans and Kelpies, Pixies and Ouphes, Mermaids, Undines, Water Spirits, and all the Elfin world Which have their haunts in dale and piny mountain, Or forests, by slow stream or tingling brook. They come out, as we are told, especially on moonlight nights. But while evening thus clothes many a scene with poetry, forests are fairy land all day long. Almost any wood contains many and many a spot well suited for Fairy feasts; where one might most expect to find Titania, resting, as once we are told, She lay upon a bank, the favourite haunt Of the Spring wind in its first sunshine hour, For the luxuriant strawberry blossoms spread Like a snow shower then, and violets Bowed down their purple vases of perfume About her pillow,--linked in a gay band Floated fantastic shapes; these were her guards, Her lithe and rainbow elves. The fairies have disappeared, and, so far as England is concerned, the larger forest animals have vanished almost as completely. The Elk and Bear, the Boar and Wolf have gone, the Stag has nearly disappeared, and but a scanty remnant of the original wild Cattle linger on at Chillingham. Still the woods teem with life; the Fox and Badger, Stoat and Weasel, Hare and Rabbit, and Hedgehog, The tawny squirrel vaulting through the boughs, Hawk, buzzard, jay, the mavis and the merle,[26] the Owls and Nightjar, the Woodpecker, Nuthatch, Magpie, Doves, and a hundred more. In early spring the woods are bright with the feathery catkins of the Willow, followed by the soft green of the Beech, the white or pink flowers of the Thorn, the pyramids of the Horse-chestnut, festoons of the Laburnum and Acacia, and the Oak slowly wakes from its winter sleep, while the Ash leaves long linger in their black buds. Under foot is a carpet of flowers--Anemones, Cowslips, Primroses, Bluebells, and the golden blossoms of the Broom, which, however, while Gorse and Heather continue in bloom for months, "blazes for a week or two, and is then completely extinguished, like a fire that has burnt itself out."[27] In summer the tints grow darker, the birds are more numerous and full of life; the air teems with insects, with the busy murmur of bees and the idle hum of flies, while the cool of morning and evening, and the heat of the day, are all alike delicious. As the year advances and the flowers wane, we have many beautiful fruits and berries, the red hips and haws of the wild roses, scarlet holly berries, crimson yew cups, the translucent berries of the Guelder Rose, hanging coral beads of the Black Bryony, feathery festoons of the Traveller's Joy, and others less conspicuous, but still exquisite in themselves--acorns, beech nuts, ash keys, and many more. It is really difficult to say which are most beautiful, the tender greens of spring or the rich tints of autumn, which glow so brightly in the sunshine. Tropical fruits are even more striking. No one who has seen it can ever forget a grove of orange trees in full fruit; while the more we examine the more we find to admire; all perfectly and exquisitely finished "usque ad ungues," perfect inside and outside, for Nature Does in the Pomegranate close Jewels more rare than Ormus shows.[28] In winter the woods are comparatively bare and lifeless, even the Brambles and Woodbine, which straggle over the tangle of underwood being almost leafless. Still even then they have a beauty and interest of their own; the mossy boles of the trees; the delicate tracery of the branches which can hardly be appreciated when they are covered with leaves; and under foot the beds of fallen leaves; while the evergreens seem brighter than in summer; the ruddy stems and rich green foliage of the Scotch Pines, and the dark spires of the Firs, seeming to acquire fresh beauty. Again in winter, though no doubt the living tenants of the woods are much less numerous, many of our birds being then far away in the dense African forests, on the other hand those which remain are much more easily visible. We can follow the birds from tree to tree, and the Squirrel from bough to bough. It requires little imagination to regard trees as conscious beings, indeed it is almost an effort not to do so. "The various action of trees rooting themselves in inhospitable rocks, stooping to look into ravines, hiding from the search of glacier winds, reaching forth to the rays of rare sunshine, crowding down together to drink at sweetest streams, climbing hand in hand among the difficult slopes, opening in sudden dances among the mossy knolls, gathering into companies at rest among the fragrant fields, gliding in grave procession over the heavenward ridges--nothing of this can be conceived among the unvexed and unvaried felicities of the lowland forest; while to all these direct sources of greater beauty are added, first the power of redundance, the mere quantity of foliage visible in the folds and on the promontories of a single Alp being greater than that of an entire lowland landscape (unless a view from some Cathedral tower); and to this charm of redundance, that of clearer visibility--tree after tree being constantly shown in successive height, one behind another, instead of the mere tops and flanks of masses as in the plains; and the forms of multitudes of them continually defined against the clear sky, near and above, or against white clouds entangled among their branches, instead of being confused in dimness of distance."[29] There is much that is interesting in the relations of one species to another. Many plants are parasitic upon others. The foliage of the Beech is so thick that scarcely anything will grow under it, except those spring plants, such as the Anemone and the Wood Buttercup or Goldilocks, which flower early before the Beech is in leaf. There are other cases in which the reason for the association of species is less evident. The Larch and the Arolla (Pinus Cembra) are close companions. They grow together in Siberia; they do not occur in Scandinavia or Russia, but both reappear in certain Swiss valleys, especially in the cantons of Lucerne and Valais and the Engadine. Another very remarkable case which has recently been observed is the relation existing between some of our forest trees and certain Fungi, the species of which have not yet been clearly ascertained. The root tips of the trees are as it were enclosed in a thin sheet of closely woven mycelium. It was at first supposed that the fungus was attacking the roots of the tree, but it is now considered that the tree and the fungus mutually benefit one another. The fungus collects nutriment from the soil, which passes into the tree and up to the leaves, where it is elaborated into sap, the greater part being utilized by the tree, but a portion reabsorbed by the fungus. There is reason to think that, in some cases at any rate, the mycelium is that of the Truffle. [Illustration: TROPICAL FOREST. _To face page 179._] The great tropical forests have a totally different character from ours. I reproduce here the plate from Kingsley's _At Last_. The trees strike all travellers by their magnificence, the luxuriance of their vegetation, and their great variety. Our forests contain comparatively few species, whereas in the tropics we are assured that it is far from common to see two of the same species near one another. But while in our forests the species are few, each tree has an independence and individuality of its own. In the tropics, on the contrary, they are interlaced and interwoven, so as to form one mass of vegetation; many of the trunks are almost concealed by an undergrowth of verdure, and intertwined by spiral stems of parasitic plants; from tree to tree hang an inextricable network of lianas, and it is often difficult to tell to which tree the fruits, flowers, and leaves really belong. The trunks run straight up to a great height without a branch, and then form a thick leafy canopy far overhead; a canopy so dense that even the blaze of the cloudless blue sky is subdued, one might almost say into a weird gloom, the effect of which is enhanced by the solemn silence. At first such a forest gives the impression of being more open than an English wood, but a few steps are sufficient to correct this error. There is a thick undergrowth matted together by wiry creepers, and the intermediate space is traversed in all directions by lines and cords. The English traveller misses sadly the sweet songs of our birds, which are replaced by the hoarse chatter of parrots. Now and then a succession of cries even harsher and more discordant tell of a troop of monkeys passing across from tree to tree among the higher branches, or lower sounds indicate to a practised ear the neighbourhood of an ape, a sloth, or some other of the few mammals which inhabit the great forests. Occasionally a large blue bee hums past, a brilliant butterfly flashes across the path, or a humming-bird hangs in the air over a flower like, as St. Pierre says, an emerald set in coral, but "how weak it is to say that that exquisite little being, whirring and fluttering in the air, has a head of ruby, a throat of emerald, and wings of sapphire, as if any triumph of the jeweller's art could ever vie with that sparkling epitome of life and light."[30] Sir Wyville Thomson graphically describes a morning in a Brazilian forest:-- "The night was almost absolutely silent, only now and then a peculiarly shrill cry of some night bird reached us from the woods. As we got into the skirt of the forest the morning broke, but the _réveil_ in a Brazilian forest is wonderfully different from the slow creeping on of the dawn of a summer morning at home, to the music of the thrushes answering one another's full rich notes from neighbouring thorn-trees. Suddenly a yellow light spreads upwards in the east, the stars quickly fade, and the dark fringes of the forest and the tall palms show out black against the yellow sky, and almost before one has time to observe the change the sun has risen straight and fierce, and the whole landscape is bathed in the full light of day. But the morning is yet for another hour cool and fresh, and the scene is indescribably beautiful. The woods, so absolutely silent and still before, break at once into noise and movement. Flocks of toucans flutter and scream on the tops of the highest forest trees hopelessly out of shot, the ear is pierced by the strange wild screeches of a little band of macaws which fly past you like the wrapped-up ghosts of the birds on some gaudy old brocade."[31] Mr. Darwin tells us that nothing can be better than the description of tropical forests given by Bates. "The leafy crowns of the trees, scarcely two of which could be seen together of the same kind, were now far away above us, in another world as it were. We could only see at times, where there was a break above, the tracery of the foliage against the clear blue sky. Sometimes the leaves were palmate, or of the shape of large outstretched hands; at others finely cut or feathery like the leaves of Mimosæ. Below, the tree trunks were everywhere linked together by sipos; the woody flexible stems of climbing and creeping trees, whose foliage is far away above, mingled with that of the taller independent trees. Some were twisted in strands like cables, others had thick stems contorted in every variety of shape, entwining snake-like round the tree trunks or forming gigantic loops and coils among the larger branches; others, again, were of zigzag shape, or indented like the steps of a staircase, sweeping from the ground to a giddy height." The reckless and wanton destruction of forests has ruined some of the richest countries on earth. Syria and Asia Minor, Palestine and the north of Africa were once far more populous than they are at present. They were once lands "flowing with milk and honey," according to the picturesque language of the Bible, but are now in many places reduced to dust and ashes. Why is there this melancholy change? Why have deserts replaced cities? It is mainly owing to the ruthless destruction of the trees, which has involved that of nations. Even nearer home a similar process may be witnessed. Two French departments--the Hautes- and Basses-Alpes--are being gradually reduced to ruin by the destruction of the forests. Cultivation is diminishing, vineyards are being washed away, the towns are threatened, the population is dwindling, and unless something is done the country will be reduced to a desert; until, when it has been released from the destructive presence of man, Nature reproduces a covering of vegetable soil, restores the vegetation, creates the forests anew, and once again fits these regions for the habitation of man. In another part of France we have an illustration of the opposite process. The region of the Landes, which fifty years ago was one of the poorest and most miserable in France, has now been made one of the most prosperous owing to the planting of Pines. The increased value is estimated at no less than 1,000,000,000 francs. Where there were fifty years ago only a few thousand poor and unhealthy shepherds whose flocks pastured on the scanty herbage, there are now sawmills, charcoal kilns, and turpentine works, interspersed with thriving villages and fertile agricultural lands. In our own country, though woodlands are perhaps on the increase, true forest scenery is gradually disappearing. This is, I suppose, unavoidable, but it is a matter of regret. Forests have so many charms of their own. They give a delightful impression of space and of abundance. The extravagance is sublime. Trees, as Jefferies says, "throw away handfuls of flower; and in the meadows the careless, spendthrift ways of grass and flower and all things are not to be expressed. Seeds by the hundred million float with absolute indifference on the air. The oak has a hundred thousand more leaves than necessary, and never hides a single acorn. Nothing utilitarian--everything on a scale of splendid waste. Such noble, broadcast, open-armed waste is delicious to behold. Never was there such a lying proverb as 'Enough is as good as a feast.' Give me the feast; give me squandered millions of seeds, luxurious carpets of petals, green mountains of oak-leaves. The greater the waste the greater the enjoyment--the nearer the approach to real life." It is of course impossible here to give any idea of the complexity of structure of our forest trees. A slice across the stem of a tree shows many different tissues with more or less technical names, bark and cambium, medullary rays, pith, and more or less specialised tissue; air-vessels, punctate vessels, woody fibres, liber fibres, scalariform vessels, and other more or less specialised tissues. Let us take a single leaf. The name is synonymous with anything very thin, so that we might well fancy that a leaf would consist of only one or two layers of cells. Far from it, the leaf is a highly complex structure. On the upper surface are a certain number of scattered hairs, while in the bud these are often numerous, long, silky, and serve to protect the young leaf, but the greater number fall off soon after the leaf expands. The hairs are seated on a layer of flattened cells--the skin or epidermis. Below this are one or more layers of "palisade cells," the function of which seems to be to regulate the quantity of light entering the leaf. Under these again is the "parenchyme," several layers of more or less rounded cells, leaving air spaces and passages between them. From place to place in the parenchyme run "fibro-vascular bundles," forming a sort of skeleton to the leaf, and comprising air-vessels on the upper side, rayed or dotted vessels with woody fibre below, and vessels of various kinds. The under surface of the leaf is formed by another layer of flattened cells, supporting generally more or less hairs, and some of them specially modified so as to leave minute openings or "stomata" leading into the air passages. These stomata are so small that there are millions on a single leaf, and on plants growing in dry countries, such as the Evergreen Oak, Oleander, etc., they are sunk in pits, and further protected by tufts of hair. The cells of the leaf again are themselves complex. They consist of a cell wall perforated by extremely minute orifices, of protoplasm, cell fluid, and numerous granules of "Chlorophyll," which give the leaf its green colour. While these are, stated very briefly, the essential parts of a leaf, the details differ in every species, while in the same species and even in the same plant, the leaves present minor differences according to the situation in which they grow. Since, then, there is so much complex structure in a single leaf, what must it be in a whole plant? There is a giant sea-weed (Macrocystis), which has been known to reach a length of 1000 feet, as also do some of the lianas of tropical forests. These, however, attain no great bulk, and the most gigantic specimens of the vegetable kingdom yet known are the Wellingtonia (Sequoia) gigantea, which grows to a height of 450 feet, and the Blue Gum (Eucalyptus) even to 480. One is apt to look on animal structure as more delicate, and of a higher order, than that of plants. And so no doubt it is. Yet an animal, even man himself, will recover from a wound or an operation more rapidly and more perfectly than a tree.[32] Trees again derive a special interest from the venerable age they attain. In some cases, no doubt, the age is more or less mythical, as, for instance, the Olive of Minerva at Athens, the Oaks mentioned by Pliny, "which were thought coeval with the world itself," the Fig tree, "under which the wolf suckled the founder of Rome and his brother, lasting (as Tacitus calculated) 840 years, putting out new shoots, and presaging the translation of that empire from the Cæsarian line, happening in Nero's reign."[33] But in other cases the estimates rest on a surer foundation, and it cannot be doubted that there are trees still living which were already of considerable size at the time of the Conquest. The Soma Cypress of Lombardy, which is 120 feet high and 23 in circumference, is calculated to go back to forty years before the birth of Christ. Francis the First is said to have driven his sword into it in despair after the battle of Padua, and Napoleon altered his road over the Simplon so as to spare it. Ferdinand and Isabella in 1476 swore to maintain the privileges of the Biscayans under the old Oak of Guernica. In the Ardennes an Oak cut down in 1824 contained a funeral urn and some Samnite coins. A writer at the time drew the conclusion that it must have been already a large tree when Rome was founded, and though the facts do not warrant this conclusion, the tree did, no doubt, go back to Pagan times. The great Yew of Fountains Abbey is said to have sheltered the monks when the abbey was rebuilt in 1133, and is estimated at an age of 1300 years; that at Brabourne in Kent at 3000. De Candolle gives the following as the ages attainable:-- The Ivy 450 years Larch 570 " Plane 750 " Cedar of Lebanon 800 " Lime 1100 " Oak 1500 " Taxodium distichum 4000 to 6000 Baobab 6000 years Nowhere is woodland scenery more beautiful than where it passes gradually into the open country. The separate trees, having more room both for their roots and branches, are finer, and can be better seen, while, when they are close together, "one cannot see the wood for the trees." The vistas which open out are full of mystery and of promise, and tempt us gradually out into the green fields. What pleasant memories these very words recall, games in the hay as children, and sunny summer days throughout life. "Consider," says Ruskin,[34] "what we owe to the meadow grass, to the covering of the dark ground by that glorious enamel, by the companies of those soft countless and peaceful spears. The fields! Follow but forth for a little time the thought of all that we ought to recognise in those words. All spring and summer is in them--the walks by silent scented paths, the rests in noonday heat, the joy of herds and flocks, the power of all shepherd life and meditation, the life of sunlight upon the world, falling in emerald streaks, and soft blue shadows, where else it would have struck on the dark mould or scorching dust, pastures beside the pacing brooks, soft banks and knolls of lowly hills, thymy slopes of down overlooked by the blue line of lifted sea, crisp lawns all dim with early dew, or smooth in evening warmth of barred sunshine, dinted by happy feet, and softening in their fall the sound of loving voices. * * * * * "Go out, in the spring time, among the meadows that slope from the shores of the Swiss lakes to the roots of their lower mountains. There, mingled with the taller gentians and the white narcissus, the grass grows deep and free, and as you follow the winding mountain paths, beneath arching boughs all veiled and dim with blossom,--paths, that for ever droop and rise over the green banks and mounds sweeping down in scented undulation, steep to the blue water, studded here and there with new mown heaps, filling all the air with fainter sweetness,--look up towards the higher hills, where the waves of everlasting green roll silently into their long inlets among the shadows of the pines; and we may, perhaps, at last know the meaning of those quiet words of the 147th Psalm, 'He maketh the grass to grow upon the mountains.'" "On fine days," he tells us again in his _Autobiography_, "when the grass was dry, I used to lie down on it, and draw the blades as they grew, with the ground herbage of buttercup or hawkweed mixed among them, until every square foot of meadow, or mossy bank, became an infinite picture and possession to me, and the grace and adjustment to each other of growing leaves, a subject of more curious interest to me than the composition of any painter's masterpieces." In the passage above quoted, Ruskin alludes especially to Swiss meadows. They are especially remarkable in the beauty and variety of flowers. In our fields the herbage is mainly grass, and if it often happens that they glow with Buttercups or are white with Ox-eye-daisies, these are but unwelcome intruders and add nothing to the value of the hay. Swiss meadows, on the contrary, are sweet and lovely with wild Geraniums, Harebells, Bluebells, Pink Restharrow, Yellow Lady's Bedstraw, Chervil, Eyebright, Red and White Silenes, Geraniums, Gentians, and many other flowers which have no familiar English names; all adding not only to the beauty and sweetness of the meadows, but forming a valuable part of the crop itself.[35] On the other hand "turf" is peculiarly English, and no turf is more delightful than that of our Downs--delightful to ride on, to sit on, or to walk on. The turf indeed feels so springy under our feet that walking on it seems scarcely an exertion: one could almost fancy that the Downs themselves were still rising, even higher, into the air. The herbage of the Downs is close rather than short, hillocks of sweet thyme, tufts of golden Potentilla, of Milkwort--blue, pink, and white--of sweet grass and Harebells: here and there pink with Heather, or golden with Furze or Broom, while over all are the fresh air and sunshine, sweet scents, and the hum of bees. And if the Downs seem full of life and sunshine, their broad shoulders are types of kindly strength, they give also an impression of power and antiquity, while every now and then we come across a tumulus, or a group of great grey stones, the burial place of some ancient hero, or a sacred temple of our pagan forefathers. On the Downs indeed things change slowly, and in parts of Sussex the strong slow oxen still draw the waggons laden with warm hay or golden wheat sheaves, or drag the wooden plough along the slopes of the Downs, just as they did a thousand years ago. I love the open Down most, but without hedges England would not be England. Hedges are everywhere full of beauty and interest, and nowhere more so than at the foot of the Downs, when they are in great part composed of wild Guelder Roses and rich dark Yews, decked with festoons of Traveller's Joy, the wild Bryonies, and garlands of Wild Roses covered with thousands of white or delicate pink flowers, each with a centre of gold. At the foot of the Downs spring clear sparkling streams; rain from heaven purified still further by being filtered through a thousand feet of chalk; fringed with purple Loosestrife and Willowherb, starred with white Water Ranunculuses, or rich Watercress, while every now and then a brown water rat rustles in the grasses at the edge, and splashes into the water, or a pink speckled trout glides out of sight. In many of our midland and northern counties most of the meadows lie in parallel undulations or "rigs." These are generally about a furlong (220 yards) in length, and either one or two poles (5-1/2 or 11 yards) in breadth. They seldom run straight, but tend to curve towards the left. At each end of the field a high bank, locally called a balk, often 3 or 4 feet high, runs at right angles to the rigs. In small fields there are generally eight, but sometimes ten, of these rigs, which make in the one case 4, in the other 5 acres. These curious characters carry us back to the old tenures, and archaic cultivation of land, and to a period when the fields were not in pasture, but were arable. They also explain our curious system of land measurement. The "acre" is the amount which a team of oxen were supposed to plough in a day. It corresponds to the German "morgen" and the French "journée." The furlong or long "furrow" is the distance which a team of oxen can plough conveniently without stopping to rest. Oxen, as we know, were driven not with a whip, but with a goad or pole, the most convenient length for which was 16-1/2 feet, and the ancient ploughman used his "pole" or "perch" by placing it at right angles to his first furrow, thus measuring the amount he had to plough. Hence our "pole" or "perch" of 16-1/2 feet, which at first sight seems a very singular unit to have selected. This width is also convenient both for turning the plough, and also for sowing. Hence the most convenient unit of land for arable purposes was a furlong in length and a perch or pole in width. The team generally consisted of eight oxen. Few peasants, however, possessed a whole team, several generally joining together, and dividing the produce. Hence the number of "rigs," one for each ox. We often, however, find ten instead of eight; one being for the parson's tithe, the other tenth going to the ploughman. When eight oxen were employed the goad would not of course reach the leaders, which were guided by a man who walked on the near side. On arriving at the end of each furrow he turned them round, and as it was easier to pull than to push them, this gradually gave the furrow a turn towards the left, thus accounting for the slight curvature. Lastly, while the oxen rested on arriving at the end of the furrow, the ploughmen scraped off the earth which had accumulated on the coulter and ploughshare, and the accumulation of these scrapings gradually formed the balk. It is fascinating thus to trace indications of old customs and modes of life, but it would carry us away from the present subject. Even though the Swiss meadows may offer a greater variety, our English fields are yet rich in flowers: yellow with Cowslips and Primroses, pink with Cuckoo flowers and purple with Orchis, while, however, unwelcome to the eye of the farmer, the rich Buttercup Its tiny polished urn holds up, Filled with ripe summer to the edge,[36] turning many a meadow into a veritable field of the cloth of gold, and there are few prettier sights in nature than an English hay field on a summer evening, with a copse perhaps at one side and a brook on the other; men with forks tossing the hay in the air to dry; women with wooden rakes arranging it in swathes ready for the great four-horse waggon, or collecting it in cocks for the night; while some way off the mowers are still at work, and we hear from time to time the pleasant sound of the whetting of the scythe. All are working with a will lest rain should come and their labour be thrown away. This too often happens. But though we often complain of our English climate, it is yet, take it all in all, one of the best in the world, being comparatively free from extremes either of heat or cold, drought or deluge. To the happy mixture of sunshine and of rain we owe the greenness of our fields, sparkling with dewdrops Indwelt with little angels of the Sun,[37] lit and warmed by golden sunshine And fed by silver rain, which now and again sprinkles the whole earth with diamonds. FOOTNOTES: [22] _The Spectator._ [23] Milton. [24] Jefferies. [25] Forbes, _A Naturalist's Wanderings in the Eastern Archipelago_. [26] Tennyson. [27] Hamerton. [28] Marvell. [29] Ruskin. [30] Thomson, _Voyage of the Challenger_. [31] Thomson, _Voyage of the Challenger_. [32] Sir J. Paget, _On the Pathology of Plants_. [33] Evelyn's _Sylva_. [34] _Modern Painters._ [35] M. Correvon informs me that the Gruyère cheese is supposed to owe its peculiar flavour to the alpine Alchemilla, which is now on that account often purposely sown elsewhere. [36] J. R. Lowell. [37] Hamerton. CHAPTER VI MOUNTAINS Mountains "seem to have been built for the human race, as at once their schools and cathedrals; full of treasures of illuminated manuscript for the scholar, kindly in simple lessons for the worker, quiet in pale cloisters for the thinker, glorious in holiness for the worshipper. They are great cathedrals of the earth, with their gates of rock, pavements of cloud, choirs of stream and stone, altars of snow, and vaults of purple traversed by the continual stars."--RUSKIN. [Illustration: SUMMIT OF MONT BLANC. _To face page 203._] CHAPTER VI MOUNTAINS The Alps are to many of us an inexhaustible source of joy and peace, of health, and even of life. We have gone to them jaded and worn, feeling, perhaps without any external cause, anxious and out of spirits, and have returned full of health, strength, and energy. Among the mountains Nature herself seems freer and happier, brighter and purer, than elsewhere. The rush of the rivers, and the repose of the lakes, the pure snowfields and majestic glaciers, the fresh air, the mysterious summits of the mountains, the blue haze of the distance, the morning tints and the evening glow, the beauty of the sky and the grandeur of the storm, have all refreshed and delighted us time after time, and their memories can never fade away. Even now as I write comes back to me the bright vision of an Alpine valley--blue sky above, glittering snow, bare grey or rich red rock, dark pines here and there, mixed with bright green larches, then patches of smooth alp, with clumps of birch and beech, and dotted with brown châlets; then below them rock again, and wood, but this time with more deciduous trees; and then the valley itself, with emerald meadows, interspersed with alder copses, threaded together by a silver stream; and I almost fancy I can hear the tinkling of distant cowbells coming down from the alp, and the delicious murmur of the rushing water. The endless variety, the sense of repose and yet of power, the dignity of age, the energy of youth, the play of colour, the beauty of form, the mystery of their origin, all combine to invest mountains with a solemn beauty. I feel with Ruskin that "mountains are the beginning and the end of all natural scenery; in them, and in the forms of inferior landscape that lead to them, my affections are wholly bound up; and though I can look with happy admiration at the lowland flowers, and woods, and open skies, the happiness is tranquil and cold, like that of examining detached flowers in a conservatory, or reading a pleasant book." And of all mountain views which he has seen, the finest he considers is that from the Montanvert: "I have climbed much and wandered much in the heart of the high Alps, but I have never yet seen anything which equalled the view from the cabin of the Montanvert." It is no mere fancy that among mountains the flowers are peculiarly large and brilliant in colour. Not only are there many beautiful species which are peculiar to mountains,--alpine Gentians, yellow, blue, and purple; alpine Rhododendrons, alpine Primroses and Cowslips, alpine Lychnis, Columbine, Monkshood, Anemones, Narcissus, Campanulas, Soldanellas, and a thousand others less familiar to us,--but it is well established that even within the limits of the same species those living up in the mountains have larger and brighter flowers than their sisters elsewhere. Various alpine species belonging to quite distinct families form close moss-like cushions, gemmed with star-like flowers, or covered completely with a carpet of blossom. On the lower mountain slopes and in alpine valleys trees seem to flourish with peculiar luxuriance. Pines and Firs and Larches above; then, as we descend, Beeches and magnificent Chestnuts, which seem to rejoice in the sweet, fresh air and the pure mountain streams. To any one accustomed to the rich bird life of English woods and hedgerows, it must be admitted that Swiss woods and Alps seem rather lonely and deserted. Still the Hawk, or even Eagle, soaring high up in the air, the weird cry of the Marmot, and the knowledge that, even if one cannot see Chamois, they may all the time be looking down on us, give the Alps, from this point of view also, a special interest of their own. Another great charm of mountain districts is the richness of colour. "Consider,[38] first, the difference produced in the whole tone of landscape colour by the introductions of purple, violet, and deep ultra-marine blue which we owe to mountains. In an ordinary lowland landscape we have the blue of the sky; the green of the grass, which I will suppose (and this is an unnecessary concession to the lowlands) entirely fresh and bright; the green of trees; and certain elements of purple, far more rich and beautiful than we generally should think, in their bark and shadows (bare hedges and thickets, or tops of trees, in subdued afternoon sunshine, are nearly perfect purple and of an exquisite tone), as well as in ploughed fields, and dark ground in general. But among mountains, in addition to all this, large unbroken spaces of pure violet and purple are introduced in their distances; and even near, by films of cloud passing over the darkness of ravines or forests, blues are produced of the most subtle tenderness; these azures and purples passing into rose colour of otherwise wholly unattainable delicacy among the upper summits, the blue of the sky being at the same time purer and deeper than in the plains. Nay, in some sense, a person who has never seen the rose colour of the rays of dawn crossing a blue mountain twelve or fifteen miles away can hardly be said to know what tenderness in colour means at all; bright tenderness he may, indeed, see in the sky or in a flower, but this grave tenderness of the far-away hill-purples he cannot conceive." "I do not know," he says elsewhere, "any district possessing a more pure or uninterrupted fulness of mountain character (and that of the highest order), or which appears to have been less disturbed by foreign agencies, than that which borders the course of the Trient between Valorsine and Martigny. The paths which lead to it, out of the valley of the Rhone, rising at first in steep circles among the walnut trees, like winding stairs among the pillars of a Gothic tower, retire over the shoulders of the hills into a valley almost unknown, but thickly inhabited by an industrious and patient population. Along the ridges of the rocks, smoothed by old glaciers, into long, dark, billowy swellings, like the backs of plunging dolphins, the peasant watches the slow colouring of the tufts of moss and roots of herb, which, little by little, gather a feeble soil over the iron substance; then, supporting the narrow strip of clinging ground with a few stones, he subdues it to the spade, and in a year or two a little crest of corn is seen waving upon the rocky casque." Tyndall, speaking of the scene from the summit of the Little Scheideck,[39] says: "The upper air exhibited a commotion which we did not experience; clouds were wildly driven against the flanks of the Eiger, the Jungfrau thundered behind, while in front of us a magnificent rainbow, fixing one of its arms in the valley of Grindelwald, and, throwing the other right over the crown of the Wetterhorn, clasped the mountain in its embrace. Through jagged apertures in the clouds floods of golden light were poured down the sides of the mountain. On the slopes were innumerable châlets, glistening in the sunbeams, herds browsing peacefully and shaking their mellow bells; while the blackness of the pine trees, crowded into woods, or scattered in pleasant clusters over alp and valley, contrasted forcibly with the lively green of the fields." Few men had more experience of mountains than Mr. Whymper, and from him, I will quote one remarkable passage describing the view from the summit of the Matterhorn just before the terrible catastrophe which overshadows the memory of his first ascent. "The day was one of those superlatively calm and clear ones which usually precede bad weather. The atmosphere was perfectly still and free from all clouds or vapours. Mountains fifty, nay, a hundred miles off looked sharp and near. All their details--ridge and crag, snow and glacier--stood out with faultless definition. Pleasant thoughts of happy days in bygone years came up unbidden as we recognised the old familiar forms. All were revealed, not one of the principal peaks of the Alps was hidden. I see them clearly now, the great inner circle of giants, backed by the ranges, chains, and _massifs_.... Ten thousand feet beneath us were the green fields of Zermatt, dotted with châlets, from which blue smoke rose lazily. Eight thousand feet below, on the other side, were the pastures of Breuil. There were black and gloomy forests; bright and cheerful meadows, bounding waterfalls and tranquil lakes, fertile lands and savage wastes, sunny plains and frigid plateaux. There were the most rugged forms and the most graceful outlines, bold perpendicular cliffs and gentle undulating slopes; rocky mountains and snowy mountains, sombre and solemn, or glittering and white, with walls, turrets, pinnacles, pyramids, domes, cones, and spires! There was every combination that the world can give, and every contrast that the heart could desire." These were summer scenes, but the Autumn and Winter again have a grandeur and beauty of their own. "Autumn is dark on the mountains; grey mist rests on the hills. The whirlwind is heard on the heath. Dark rolls the river through the narrow plain. The leaves twirl round with the wind, and strew the grave of the dead."[40] Even bad weather often but enhances the beauty and grandeur of mountains. When the lower parts are hidden, and the peaks stand out above the clouds, they look much loftier than if the whole mountain side is visible. The gloom lends a weirdness and mystery to the scene, while the flying clouds give it additional variety. Rain, moreover, adds vividness to the colouring. The leaves and grass become a brighter green, "every sunburnt rock glows into an agate," and when fine weather returns the new snow gives intense brilliance, and invests the woods especially with the beauty of Fairyland. How often in alpine districts does one long "for the wings of a dove," more thoroughly to enjoy and more completely to explore, the mysteries and recesses of the mountains. The mind, however, can go, even if the body must remain behind. Each hour of the day has a beauty of its own. The mornings and evenings again glow with different and even richer tints. In mountain districts the cloud effects are brighter and more varied than in flatter regions. The morning and evening tints are seen to the greatest advantage, and clouds floating high in the heavens sometimes glitter with the most exquisite iridescent hues that blush and glow Like angels' wings.[41] On low ground one may be in the clouds, but not above them. But as we look down from mountains and see the clouds floating far below us, we almost seem as if we were looking down on earth from one of the heavenly bodies. Not even in the Alps is there anything more beautiful than the "after glow" which lights up the snow and ice with a rosy tint for some time after the sun has set. Long after the lower slopes are already in the shade, the summit of Mont Blanc for instance is transfigured by the light of the setting sun glowing on the snow. It seems almost like a light from another world, and vanishes as suddenly and mysteriously as it came. As we look up from the valleys the mountain peaks seem like separate pinnacles projecting far above the general level. This, however, is a very erroneous impression, and when we examine the view from the top of any of the higher mountains, or even from one of very moderate elevation, if well placed, such say as the well-known Piz Languard, we see that in many cases they must have once formed a dome, or even a table land, out of which the valleys have been carved. Many mountain chains were originally at least twice as high as they are now, and the highest peaks are those which have suffered least from the wear and tear of time. We used to speak of the everlasting hills, and are only beginning to realise the vast and many changes which our earth has undergone. There rolls the deep where grew the tree. O earth, what changes hast thou seen! There where the long street roars, hath been The stillness of the central sea. The hills are shadows, and they flow From form to form, and nothing stands; They melt like mist, the solid lands, Like clouds they shape themselves and go.[42] THE ORIGIN OF MOUNTAINS Geography moreover acquires a new interest when we once realise that mountains are no mere accidents, but that for every mountain chain, for every peak and valley, there is a cause and an explanation. The origin of Mountains is a question of much interest. The building up of Volcanoes is even now going on before our eyes. Some others, the Dolomites for instance, have been regarded by Richthofen and other geologists as ancient coral islands. The long lines of escarpment which often stretch for miles across country, are now ascertained, mainly through the researches of Whitaker, to be due to the differential action of aerial causes. The general origin of mountain chains, however, was at first naturally enough attributed to direct upward pressure from below. To attribute them in any way to subsidence seems almost a paradox, and yet it appears to be now well established that the general cause is lateral compression, due to contraction of the underlying mass. The earth, we know, has been gradually cooling, and as it contracted in doing so, the strata of the crust would necessarily be thrown into folds. When an apple dries and shrivels in winter, the surface becomes covered with ridges. Or again, if we place some sheets of paper between two weights on a table, and then bring the weights nearer together, the paper will be crumpled up. [Illustration: Fig. 17.--Adapted from Ball's paper "On the Formation of Alpine Valleys and Lakes," _Lond. and Ed. Phil. Mag._ 1863, p. 96.] In the same way let us take a section of the earth's surface AB (Fig. 17), and suppose that, by the gradual cooling and consequent contraction of the mass, AB sinks to A'B', then to A''B'', and finally to A'''B'''. Of course if the cooling of the surface and of the deeper portion were the same, then the strata between A and B would themselves contract, and might consequently still form a regular curve between A''' and B'''. As a matter of fact, however, the strata at the surface of our globe have long since approached a constant temperature. Under these circumstances there would be no contraction of the strata between A and B corresponding to that of those in the interior, and consequently they could not lie flat between A''' and B''', but must be thrown into folds, commencing along any line of least resistance. Sometimes indeed the strata are completely inverted, as in Fig. 19, and in other cases they have been squeezed for miles out of their original position. This explanation was first, I believe, suggested by Steno. It has been recently developed by Ball and Suess, and especially by Heim. In this manner it is probable that most mountain chains originated.[43] The structure of mountain districts confirms this theoretical explanation. It is obvious of course that when strata are thrown into folds, they will, if strained too much, give way at the summit of the fold. Before doing so, however, they are stretched and consequently loosened, while on the other hand the strata at the bottom of the fold are compressed: the former, therefore, are rendered more susceptible of disintegration, the latter on the contrary acquire greater powers of resistance. Hence denudation will act with more effect on the upper than on the lower portion of the folds, and if continued long enough, so that, as shown in the above diagram, the dotted portion is removed, we find the original hill tops replaced by valleys, and the original valleys forming the hill tops. Every visitor to Switzerland must have noticed hills where the strata lie as shown in parts of Fig. 18, and where it is obvious that strata corresponding to those in dots must have been originally present. In the Jura, for instance, a glance at any good map of the district will show a succession of ridges running parallel to one another in a slightly curved line from S.W. to N.E. That these ridges are due to folds of the earth's surface is clear from the following figure in Jaccard's work on the Geology of the Jura, showing a section from Brenets due south to Neuchâtel by Le Locle. These folds are comparatively slight and the hills of no great height. Further south, however, the strata are much more violently dislocated and compressed together. The Mont Salève is the remnant of one of these ridges. [Illustration: Fig. 18.--Section across the Jura from Brenets to Neuchâtel.] In the Alps the contortions are much greater than in the Jura. Fig. 19 shows a section after Heim, from the Spitzen across the Brunnialp, and the Maderanerthal. It is obvious that the valleys are due mainly to erosion, that the Maderaner valley has been cut out of the crystalline rocks _s_, and was once covered by the Jurassic strata _j_, which must have formerly passed in a great arch over what is now the valley. However improbable it may seem that so great an amount of rock should have disappeared, evidence is conclusive. Ramsay has shown that in some parts of Wales not less than 29,000 feet have been removed, while there is strong reason for the belief that in Switzerland an amount has been carried away equal to the present height of the mountains; though of course it does not follow that the Alps were once twice as high as they are at present, because elevation and erosion must have gone on contemporaneously. [Illustration: Fig. 19.--_e_, Eocene strata; _j_, Jurassic; _s_, Crystalline rocks.] It has been calculated that the strata between Bâle and the St. Gotthard have been compressed from 202 miles to 130 miles, the Ardennes from 50 to 25 miles, and the Appalachians from 153 miles to 65! Prof. Gumbel has recently expressed the opinion that the main force to which the elevation of the Alps was due acted along the main axis of elevation. Exactly the opposite inference would seem really to follow from the facts. If the centre of force were along the axis of elevation, the result would, as Suess and Heim have pointed out, be to extend, not to compress, the strata; and the folds would remain quite unaccounted for. The suggestion of compression is on the contrary consistent with the main features of Swiss geography. The principal axis follows a curved line from the Maritime Alps towards the north-east by Mont Blanc and Monte Rosa and St. Gotthard to the mountains overlooking the Engadine. The geological strata follow the same direction. North of a line running through Chambery, Yverdun, Neuchâtel, Solothurn, and Olten to Waldshut on the Rhine are Jurassic strata; between that line and a second nearly parallel and running through Annecy, Vevey, Lucerne, Wesen, Appenzell, and Bregenz on the Lake of Constance, is the lowland occupied by later Tertiary strata; between this second line and another passing through Albertville, St. Maurice, Lenk, Meiringen, and Altdorf lies a more or less broken band of older Tertiary strata; south of which are a Cretaceous zone, one of Jurassic age, then a band of crystalline rocks, while the central core, so to say, of the Alps, as for instance at St. Gotthard, consists mainly of gneiss or granite. The sedimentary deposits reappear south of the Alps, and in the opinion of some high authorities, as, for instance, of Bonney and Heim, passed continuously over the intervening regions. The last great upheaval commenced after the Miocene period, and continued through the Pliocene. Miocene strata attain in the Righi a height of 6000 feet. For neither the hills nor the mountains are everlasting, or of the same age. The Welsh mountains are older than the Vosges, the Vosges than the Pyrenees, the Pyrenees than the Alps, and the Alps than the Andes, which indeed are still rising; so that if our English mountains are less imposing so far as mere height is concerned, they are most venerable from their great antiquity. But though the existing Alps are in one sense, and speaking geologically, very recent, there is strong reason for believing that there was a chain of lofty mountains there long previously. "The first indication," says Judd, "of the existence of a line of weakness in this portion of the earth's crust is found towards the close of the Permian period, when a series of volcanic outbursts on the very grandest scale took place" along a line nearly following that of the present Alps, and led to the formation of a range of mountains, which, in his opinion, must have been at least 8000 to 9000 feet high. Ramsay and Bonney have also given strong reasons for believing that the present line of the Alps was, at a still earlier period, occupied by a range of mountains no less lofty than those of to-day. Thus then, though the present Alps are comparatively speaking so recent, there are good grounds for the belief that they were preceded by one or more earlier ranges, once as lofty as they are now, but which were more or less completely levelled by the action of air and water, just as is happening now to the present mountain ranges. Movements of elevation and subsidence are still going on in various parts of the world. Scandinavia is rising in the north, and sinking at the south. South America is rising on the west and sinking in the east, rotating in fact on its axis, like some stupendous pendulum. The crushing and folding of the strata to which mountain chains are due, and of which the Alps afford such marvellous illustrations, necessarily give rise to Earthquakes, and the slight shocks so frequent in parts of Switzerland[44] appear to indicate that the forces which have raised the Alps are not yet entirely spent, and that slow subterranean movements are still in progress along the flanks of the mountains. But if the mountain chains are due to compression, the present valleys are mainly the result of denudation. As soon as a mountain range is once raised, all nature seems to conspire against it. Sun and Frost, Heat and Cold, Air and Water, Ice and Snow, every plant, from the Lichen to the Oak, and every animal, from the Worm to Man himself, combine to attack it. Water, however, is the most powerful agent of all. The autumn rains saturate every pore and cranny; the water as it freezes cracks and splits the hardest rocks; while the spring sun melts the snow and swells the rivers, which in their turn carry off the debris to the plains. Perhaps, however, it would after all be more correct to say that Nature, like some great artist, carves the shapeless block into form, and endows the rude mass with life and beauty. "What more," said Hutton long ago, "is required to explain the configuration of our mountains and valleys? Nothing but time. It is not any part of the process that will be disputed; but, after allowing all the parts, the whole will be denied; and for what? Only because we are not disposed to allow that quantity of time which the absolution of so much wasted mountain might require." The tops of the Swiss mountains stand, and since their elevation have probably always stood, above the range of ice, and hence their bold peaks. In Scotland, on the contrary, and still more in Norway, the sheet of ice which once, as is the case with Greenland now, spread over the whole country, has shorn off the summits and reduced them almost to gigantic bosses; while in Wales the same causes, together with the resistless action of time--for, as already mentioned, the Welsh hills are far older than the mountains of Switzerland--has ground down the once lofty summits and reduced them to mere stumps, such as, if the present forces are left to work out their results, the Swiss mountains will be thousands, or rather tens of thousands, of years hence. The "snow line" in Switzerland is generally given as being between 8500 and 9000 feet. Above this level the snow or _névé_ gradually accumulates until it forms "glaciers," solid rivers of ice which descend more or less far down the valleys. No one who has not seen a glacier can possibly realise what they are like. Fig. 20 represents the glacier of the Blümlis Alp, and the Plate the Mer de Glace. [Illustration: Fig. 20.--Glacier of the Blümlis Alp.] [Illustration: THE MER DE GLACE. _To face page 229._] They are often very beautiful. "Mount Beerenberg," says Lord Dufferin, "in size, colour, and effect far surpassed anything I had anticipated. The glaciers were quite an unexpected element of beauty. Imagine a mighty river, of as great a volume as the Thames, started down the side of a mountain, bursting over every impediment, whirled into a thousand eddies, tumbling and raging on from ledge to ledge in quivering cataracts of foam, then suddenly struck rigid by a power so instantaneous in its action that even the froth and fleeting wreaths of spray have stiffened to the immutability of sculpture. Unless you had seen it, it would be almost impossible to conceive the strangeness of the contrast between the actual tranquillity of these silent crystal rivers and the violent descending energy impressed upon their exterior. You must remember too all this is upon a scale of such prodigious magnitude, that when we succeeded subsequently in approaching the spot--where with a leap like that of Niagara one of these glaciers plunges down into the sea--the eye, no longer able to take in its fluvial character, was content to rest in simple astonishment at what then appeared a lucent precipice of grey-green ice, rising to the height of several hundred feet above the masts of the vessel."[45] The cliffs above glaciers shower down fragments of rock which gradually accumulate at the sides and at the end of the glaciers, forming mounds known as "moraines." Many ancient moraines occur far beyond the present region of glaciers. In considering the condition of alpine valleys we must remember that the glaciers formerly descended much further than they do at present. The glaciers of the Rhone for instance occupied the whole of the Valais, filled the Lake of Geneva--or rather the site now occupied by that lake--and rose 2000 feet up the slopes of the Jura; the Upper Ticino, and contributory valleys, were occupied by another which filled the basin of the Lago Maggiore; a third occupied the valley of the Dora Baltea, and has left a moraine at Ivrea some twenty miles long, and which rises no less than 1500 feet above the present level of the river. The Scotch and Scandinavian valleys were similarly filled by rivers of ice, which indeed at one time covered the whole country with an immense sheet, as Greenland is at present. Enormous blocks of stone, the Pierre à Niton at Geneva and the Pierre à Bot above Neuchâtel, for instance, were carried by these glaciers for miles and miles; and many of the stones in the Norfolk cliffs were brought by ice from Norway (perhaps, however, by Icebergs), across what is now the German Ocean. Again wherever the rocks are hard enough to have withstood the weather, we find them polished and ground, just as, and even more so than, those at the ends and sides of existing glaciers. The most magnificent glacier tracks in the Alps are, in Ruskin's opinion, those on the rocks of the great angle opposite Martigny; the most interesting those above the channel of the Trient between Valorsine and the valley of the Rhone. In Great Britain I know no better illustration of ice action than is to be seen on the road leading down from Glen Quoich to Loch Hourn, one of the most striking examples of desolate and savage scenery in Scotland. Its name in Celtic is said to mean the Lake of Hell. All along the roadside are smoothed and polished hummocks of rock, most of them deeply furrowed with approximately parallel striæ, presenting a gentle slope on the upper end, and a steep side below, clearly showing the direction of the great ice flow. Many of the upper Swiss valleys contain lakes, as, for instance, that of the Upper Rhone, the Lake of Geneva, of the Reuss, the Lake of Lucerne, of the Rhine, that of Constance. These lakes are generally very deep. The colour of the upper rivers, which are white with the diluvium from the glaciers, is itself evidence of the erosive powers which they exercise. This finely-divided matter is, however, precipitated in the lakes, which, as well as the rivers issuing from them, are a beautiful rich blue. "Is it not probable that this action of finely-divided matter may have some influence on the colour of some of the Swiss lakes--as that of Geneva for example? This lake is simply an expansion of the river Rhone, which rushes from the end of the Rhone glacier, as the Arveiron does from the end of the Mer de Glace. Numerous other streams join the Rhone right and left during its downward course; and these feeders, being almost wholly derived from glaciers, join the Rhone charged with the finer matter which these in their motion have ground from the rocks over which they have passed. But the glaciers must grind the mass beneath them to particles of all sizes, and I cannot help thinking that the finest of them must remain suspended in the lake throughout its entire length. Faraday has shown that a precipitate of gold may require months to sink to the bottom of a bottle not more than five inches high, and in all probability it would require ages of calm subsidence to bring all the particles which the Lake of Geneva contains to its bottom. It seems certainly worthy of examination whether such particles suspended in the water contribute to the production of that magnificent blue which has excited the admiration of all who have seen it under favourable circumstances."[46] Among the Swiss mountains themselves each has its special character. Tyndall thus describes a view in the Alps, certainly one of the most beautiful--that, namely, from the summit of the Ægischhorn. "Skies and summits are to-day without a cloud, and no mist or turbidity interferes with the sharpness of the outlines. Jungfrau, Monk, Eiger, Trugberg, cliffy Strahlgrat, stately lady-like Aletschhorn, all grandly pierce the empyrean. Like a Saul of Mountains, the Finsteraarhorn overtops all his neighbours; then we have the Oberaarhorn, with the riven glacier of Viesch rolling from his shoulders. Below is the Mârjelin See, with its crystal precipices and its floating icebergs, snowy white, sailing on a blue green sea. Beyond is the range which divides the Valais from Italy. Sweeping round, the vision meets an aggregate of peaks which look as fledglings to their mother towards the mighty Dom. Then come the repellent crags of Mont Cervin; the ideal of moral savagery, of wild untameable ferocity, mingling involuntarily with our contemplation of the gloomy pile. Next comes an object, scarcely less grand, conveying, it may be, even a deeper impression of majesty and might than the Matterhorn itself--the Weisshorn, perhaps the most splendid object in the Alps. But beauty is associated with its force, and we think of it, not as cruel, but as grand and strong. Further to the right the great Combin lifts up his bare head; other peaks crowd around him; while at the extremity of the curve round which our gaze has swept rises the sovran crown of Mont Blanc. And now, as day sinks, scrolls of pearly clouds draw themselves around the mountain crests, being wafted from them into the distant air. They are without colour of any kind; still, by grace of form, and as the embodiment of lustrous light and most tender shade, their beauty is not to be described."[47] VOLCANOES Volcanoes belong to a totally different series of mountains. It is practically impossible to number the Volcanoes on our earth. Humboldt enumerated 223, which Keith Johnston raised to nearly 300. Some, no doubt, are always active, but in the majority the eruptions are occasional, and though some are undoubtedly now extinct, it is impossible in all cases to distinguish those which are only in repose from those whose day of activity is over. Then, again, the question would arise, which should be regarded as mere subsidiary cones and which are separate volcanoes. The slopes of Etna present more than 700 small cones, and on Hawaii there are several thousands. In fact, most of the very lofty volcanoes present more or less lateral cones. The molten matter, welling up through some fissure, gradually builds itself up into a cone, often of the most beautiful regularity, such as the gigantic peaks of Chimporazo, Cotopaxi (Fig. 21), and Fusiyama, and hence it is that the crater is so often at, or very near, the summit. [Illustration: Fig. 21.--Cotopaxi.] Perhaps no spectacle in Nature is more magnificent than a Volcano in activity. It has been my good fortune to have stood more than once at the edge of the crater of Vesuvius during an eruption, to have watched the lava seething below, while enormous stones were shot up high into the air. Such a spectacle can never be forgotten. The most imposing crater in the world is probably that of Kilauea, at a height of about 4000 feet on the side of Mouna Loa, in the Island of Hawaii. It has a diameter of 2 miles, and is elliptic in outline, with a longer axis of about 3, and a circumference of about 7 miles. The interior is a great lake of lava, the level of which is constantly changing. Generally, it stands about 800 feet below the edge, and the depth is about 1400 feet. The heat is intense, and, especially at night, when the clouds are coloured scarlet by the reflection from the molten lava, the effect is said to be magnificent. Gradually the lava mounts in the crater until it either bursts through the side or runs over the edge, after which the crater remains empty, sometimes for years. A lava stream flows down the slope of the mountain like a burning river, at first rapidly, but as it cools, scoriæ gradually form, and at length the molten matter covers itself completely (Fig. 22), both above and at the sides, with a solid crust, within which, as in a tunnel, it continues to flow slowly as long as it is supplied from the source, here and there breaking through the crust which, as continually, re-forms in front. Thus the terrible, inexorable river of fire slowly descends, destroying everything in its course. [Illustration: Fig. 22.--Lava Stream.] The stream of lava which burst from Mouna Loa in 1885 had a length of 70 miles; that of Skaptar-Jokul in Iceland in 1783 had a length of 50 miles, and a maximum depth of nearly 500 feet. It has been calculated that the mass of lava equalled that of Mont Blanc. The stones, ashes, and mud ejected during eruptions are even more destructive than the rivers of lava. In 1851 Tomboro, a volcano on the Island of Sumbava, cost more lives than fell in the battle of Waterloo. The earthquake of Lisbon in 1755 destroyed 60,000 persons. During the earthquake of Riobamba and the mud eruption of Tunguragua, and again in that of Krakatoa, it is estimated that the number who perished was between 30,000 and 40,000. At the earthquake of Antioch in 526 no less than 200,000 persons are said to have lost their lives. Perhaps the most destructive eruption of modern times has been that on Cosequina. For 25 miles it covered the ground with muddy water 16 feet in depth. The dust and ashes formed a dense cloud, extending over many miles, some of it being carried 20 degrees to the west. The total mass ejected has been estimated at 60 milliards of square yards. Stromboli, in the Mediterranean (Fig. 23), though only 2500 feet in height, is very imposing from its superb regularity, and its roots plunge below the surface to a depth of 4000 feet. It is, moreover, very interesting from the regularity of its action, which has a period of 5 minutes or a little less. On looking down into the crater one sees at a depth of say 300 feet a seething mass of red-hot lava; this gradually rises, and then explodes, throwing up a cloud of vapour and stones, after which it sinks again. So regular is it that the Volcano has been compared to a "flashing" lighthouse, and this wonderful process has been going on for ages. [Illustration: Fig. 23.--Stromboli, viewed from the north-west, April 1874.] Though long extinct, volcanoes once existed in the British Isles; Arthur's Seat, near Edinburgh, for instance, appears to be the funnel of a small volcano, belonging to the Carboniferous period. The summit of a volcanic mountain is sometimes entirely blown away. Between my first two visits to Vesuvius 200 feet of the mountain had thus disappeared. Vesuvius itself stands in a more ancient crater, part of which still remains, and is now known as Somma, the greater portion having disappeared in the great eruption of 79, when the mountain, waking from its long sleep, destroyed Herculaneum and Pompeii. As regards the origin of volcanoes there have been two main theories. Impressed by the magnitude and grandeur of the phenomena, enhanced as they are by their destructive character, many have been disposed to regard the craters of volcanoes as gigantic chimneys, passing right through the solid crust of the globe, and communicating with a central fire. Recent researches, however, have indicated that, grand and imposing as they are, volcanoes must yet be regarded as due mainly to local and superficial causes. A glance at the map shows that volcanoes are almost always situated on, or near, the sea coast. From the interior of continents they are entirely wanting. The number of active volcanoes in the Andes, contrasted with their absence in the Alps and Ourals, the Himalayas, and Central Asian chains, is very striking. Indeed, the Pacific Ocean is encircled, as Ritter has pointed out, by a ring of fire. Beginning with New Zealand, we have the Volcanoes of Tongariro, Whakaii, etc.; thence the circle passes through the Fiji Islands, Solomon Islands, New Guinea, Timor, Flores, Sumbava, Lombock, Java, Sumatra, the Philippines, Japan, the Aleutian Islands, along the Rocky Mountains, Mexico, Peru, and Chili, to Tierra del Fuego, and, in the far south, to the two great Volcanoes of Erebus and Terror on Victoria Land. We know that the contraction of the Earth's surface with the strains and fractures, the compression and folds, which must inevitably result, is still in operation, and must give rise to areas of high temperature, and consequently to volcanoes. We must also remember that the real mountain chains of our earth are the continents, compared to which even the Alps and Andes are mere wrinkles. It is along the lines of the great mountain chains, that is to say, along the main coast lines, rather than in the centres of the continents, which may be regarded as comparatively quiescent, that we should naturally expect to find the districts of greatest heat, and this is perhaps why volcanoes are generally distributed along the coast lines. Another reason for regarding Volcanoes as local phenomena is that many even of those comparatively near one another act quite independently. This is so with Kilauea and Mouna Loa, both on the small island of Hawaii. Again, if volcanoes were in connection with a great central sea of fire, the eruptions must follow the same laws as regulate the tides. This, however, is not the case. There are indeed indications of the existence of slight tides in the molten lake which underlies Vesuvius, and during the eruption of 1865 there was increased activity twice a day, as we should expect to find in any great fluid reservoir, but very different indeed from what must have been the case if the mountain was in connection with a central ocean of molten matter. Indeed, unless the "crust" of our earth was of great thickness we should be subject to perpetual earthquakes. No doubt these are far more frequent than is generally supposed; indeed, with our improved instruments it can be shown that instead of occasional vibrations, with long intermediate periods of rest, we have in reality short intervals of rest with long periods of vibration, or rather perhaps that the crust of the earth is in constant tremor, with more violent oscillation from time to time. It appears, moreover, that earthquakes are not generally deep-seated. The point at which the shock is vertical can be ascertained, and it is also possible in some cases to determine the angle at which it emerges elsewhere. When this has been done it has always been found that the seat of disturbance must have been within 30 geographical miles of the surface. Yet, though we cannot connect volcanic action with the central heat of the earth, but must regard it as a minor and local manifestation of force, volcanoes still remain among the grandest, most awful, and at the same time most magnificent spectacles which the earth can afford. FOOTNOTES: [38] Ruskin. [39] _The Glaciers of the Alps._ [40] Ossian. [41] Bullar, _Azores_. [42] Tennyson. [43] See especially Heim's great work, _Unt. ü. d. Mechanismus der Gebirgsbildung_. [44] In the last 150 years more than 1000 are recorded. [45] _Letters from High Latitudes._ [46] _Glaciers of the Alps._ [47] _Mountaineering in 1861._ CHAPTER VII WATER Of all inorganic substances, acting in their own proper nature, and without assistance or combination, water is the most wonderful. If we think of it as the source of all the changefulness and beauty which we have seen in the clouds; then as the instrument by which the earth we have contemplated was modelled into symmetry, and its crags chiselled into grace; then as, in the form of snow, it robes the mountains it has made, with that transcendent light which we could not have conceived if we had not seen; then as it exists in the foam of the torrent, in the iris which spans it, in the morning mist which rises from it, in the deep crystalline pools which mirror its hanging shore, in the broad lake and glancing river, finally, in that which is to all human minds the best emblem of unwearied, unconquerable power, the wild, various, fantastic, tameless unity of the sea; what shall we compare to this mighty, this universal element, for glory and for beauty? or how shall we follow its eternal cheerfulness of feeling? It is like trying to paint a soul.--RUSKIN. [Illustration: RYDAL WATER. _To face page 251._] CHAPTER VII WATER In the legends of ancient times running water was proof against all sorcery and witchcraft: No spell could stay the living tide Or charm the rushing stream.[48] There was much truth as well as beauty in this idea. Flowing waters, moreover, have not only power to wash out material stains, but they also clear away the cobwebs of the brain--the results of over incessant work--and restore us to health and strength. Snowfields and glaciers, mountain torrents, sparkling brooks, and stately rivers, meres and lakes, and last, not least, the great ocean itself, all alike possess this magic power. "When I would beget content," says Izaak Walton, "and increase confidence in the power and wisdom and providence of Almighty God, I will walk the meadows by some gliding stream, and there contemplate the lilies that take no care, and those very many other little living creatures that are not only created, but fed (man knows not how) by the goodness of the God of Nature, and therefore trust in Him;" and in his quaint old language he craves a special blessing on all those "that are true lovers of virtue, and dare trust in His Providence, and be quiet, and go a angling." At the water's edge flowers are especially varied and luxuriant, so that the banks of a river are a long natural garden of tall and graceful grasses and sedges, the Meadow Sweet, the Flowering Rush, the sweet Flag, the Bull Rush, Purple Loosestrife, Hemp Agrimony, Dewberry, Forget-me-not, and a hundred more, backed by Willows, Alders, Poplars, and other trees. The Animal world, if less conspicuous to the eye, is quite as fascinating to the imagination. Here and there a speckled Trout may be detected (rather by the shadow than the substance) suspended in the clear water, or darting across a shallow; if we are quiet we may see Water Hens or Wild Ducks swimming among the lilies, a Kingfisher sitting on a branch or flashing away like a gleam of light; a solemn Heron stands maybe at the water's edge, or slowly rises flapping his great wings; Water Rats, neat and clean little creatures, very different from their coarse brown namesakes of the land, are abundant everywhere; nor need we even yet quite despair of seeing the Otter himself. Insects of course are gay, lively, and innumerable; but after all the richest fauna is that visible only with a microscope. "To gaze," says Dr. Hudson, "into that wonderful world which lies in a drop of water, crossed by some stems of green weed, to see transparent living mechanism at work, and to gain some idea of its modes of action, to watch a tiny speck that can sail through the prick of a needle's point; to see its crystal armour flashing with ever varying tint, its head glorious with the halo of its quivering cilia; to see it gliding through the emerald stems, hunting for its food, snatching at its prey, fleeing from its enemy, chasing its mate (the fiercest of our passions blazing in an invisible speck); to see it whirling in a mad dance, to the sound of its own music, the music of its happiness, the exquisite happiness of living--can any one, who has once enjoyed this sight, ever turn from it to mere books and drawings, without the sense that he has left all Fairyland behind him?"[49] The study of Natural History has indeed the special advantage of carrying us into the country and the open air. Lakes are even more restful than rivers or the sea. Rivers are always flowing, though it may be but slowly; the sea may rest awhile, now and then, but is generally full of action and energy; while lakes seem to sleep and dream. Lakes in a beautiful country are like silver ornaments on a lovely dress, like liquid gems in a beautiful setting, or bright eyes in a lovely face. Indeed as we gaze down on a lake from some hill or cliff it almost looks solid, like some great blue crystal. [Illustration: WINDERMERE. _To face page 254._] It is not merely for purposes of commerce or convenience that men love to live near rivers. Let me live harmlessly, and near the brink Of Trent or Avon have my dwelling-place; Where I may see my quill, or cork, down sink, With eager bite of pike, or bleak, or dace; And on the world and my Creator think: While some men strive ill-gotten goods t' embrace: And others spend their time in base excess Of wine; or worse, in war, or wantonness. Let them that will, these pastimes still pursue, And on such pleasing fancies feed their fill: So I the fields and meadows green may view And daily by fresh rivers walk at will, Among the daisies and the violets blue, Red hyacinth and yellow daffodil.[50] It is interesting and delightful to trace a river from its source to the sea. "Beginning at the hill-tops," says Geikie, "we first meet with the spring or 'well-eye,' from which the river takes its rise. A patch of bright green, mottling the brown heathy slope, shows where the water comes to the surface, a treacherous covering of verdure often concealing a deep pool beneath. From this source the rivulet trickles along the grass and heath, which it soon cuts through, reaching the black, peaty layer below, and running in it for a short way as in a gutter. Excavating its channel in the peat, it comes down to the soil, often a stony earth bleached white by the peat. Deepening and widening the channel as it gathers force with the increasing slope, the water digs into the coating of drift or loose decomposed rock that covers the hillside. In favourable localities a narrow precipitous gully, twenty or thirty feet deep, may thus be scooped out in the course of a few years." If, however, we trace one of the Swiss rivers to its source we shall generally find that it begins in a snow field or _névé_ nestled in a shoulder of some great mountain. Below the _névé_ lies a glacier, on, in, and under which the water runs in a thousand little streams, eventually emerging at the end, in some cases forming a beautiful blue cavern, though in others the end of the glacier is encumbered and concealed by earth and stones. [Illustration: Fig. 24.--Upper Valley of St. Gotthard.] The uppermost Alpine valleys are perhaps generally, though by no means always, a little desolate and severe, as, for instance, that of St. Gotthard (Fig. 24). The sides are clothed with rough pasture, which is flowery indeed, though of course the flowers are not visible at a distance, interspersed with live rock and fallen masses, while along the bottom rushes a white torrent. The snowy peaks are generally more or less hidden by the shoulders of the hills. The valleys further down widen and become more varied and picturesque. The snowy peaks and slopes are more often visible, the "alps" or pastures to which the cows are taken in summer, are greener and dotted with the huts or châlets of the cow-herds, while the tinkling of the cowbells comes to one from time to time, softened by distance, and suggestive of mountain rambles. Below the alps there is generally a steeper part clothed with Firs or with Larches and Pines, some of which seem as if they were scaling the mountains in regiments, preceded by a certain number of skirmishers. Below the fir woods again are Beeches, Chestnuts, and other deciduous trees, while the central cultivated portion of the valley is partly arable, partly pasture, the latter differing from our meadows in containing a greater variety of flowers--Campanulas, Wild Geraniums, Chervil, Ragged Robin, Narcissus, etc. Here and there is a brown village, while more or less in the centre hurries along, with a delightful rushing sound, the mountain torrent, to which the depth, if not the very existence of the valley, is mainly due. The meadows are often carefully irrigated, and the water power is also used for mills, the streams seeming to rush on, as Ruskin says, "eager for their work at the mill, or their ministry to the meadows." Apart from the action of running water, snow and frost are continually disintegrating the rocks, and at the base of almost any steep cliff may be seen a slope of debris (as in Figs. 25, 26). This stands at a regular angle--the angle of repose--and unless it is continually removed by a stream at the base, gradually creeps up higher and higher, until at last the cliff entirely disappears. [Illustration: Fig. 25.--Section of a river valley. The dotted line shows a slope or talus of debris.] Sometimes the two sides of the valley approach so near that there is not even room for the river and the road: in that case Nature claims the supremacy, and the road has to be carried in a cutting, or perhaps in a tunnel through the rock. In other cases Nature is not at one with herself. In many places the debris from the rocks above would reach right across the valley and dam up the stream. Then arises a struggle between rock and river, but the river is always victorious in the end; even if dammed back for a while, it concentrates its forces, rises up the rampart of rock, rushes over triumphantly, resumes its original course, and gradually carries the enemy away. [Illustration: Fig. 26.--Valley of the Rhone, with the waterfall of Sallenches, showing talus of debris.] Another prominent feature in many valleys is afforded by the old river, or lake, terraces, which were formed at a time when the river ran at a level far above its present bed. Thus many a mountain valley gives some such section as the following. [Illustration: Fig. 27.--_A_, present river valley; _B_, old river terrace.] First, a face of rock, very steep, and in some places almost perpendicular; secondly, a regular talus of fallen rocks, stones, etc., as shown in the view of the Rhone Valley (Fig. 26), which takes what is known as the slope of repose, at an angle which depends on the character of the material. As a rule for loose rock fragments it may be taken roughly to be an angle of about 45°. Then an irregular slope followed in many places by one or more terraces, and lastly the present bed of the river. [Illustration: Fig. 28.--Diagram of an Alpine valley showing a river cone. Front view.] The width or narrowness of the valley in relation to its depth depends greatly on the condition of the rocks, the harder and tougher they are the narrower as a rule being the valley. From time to time a side stream enters the main valley. This is itself composed of many smaller rivulets. If the lateral valleys are steep, the streams bring with them, especially after rains, large quantities of earth and stones. When, however, they reach the main valley, the rapidity of the current being less, their power of transport also diminishes, and they spread out the material which they carry down in a depressed cone (Figs. 28, 29, 31, 32). A side stream with its terminal cone, when seen from the opposite side of the valley, presents the appearance shown in Figs. 28, 31, or, if we are looking down the valley, as in Figs. 29, 32, the river being often driven to one side of the main valley, as, for instance, is the case in the Valais, near Sion, where the Rhone (Fig. 30) is driven out of its course by, and forms a curve round, the cone brought down by the torrent of the Borgne. [Illustration: Fig. 29.--Diagram of an Alpine valley, showing a river cone. Lateral view.] Sometimes two lateral valleys (see Plate) come down nearly opposite one another, so that the cones meet, as, for instance, some little way below Vernayaz, and, indeed, in several other places in the Valais (Fig. 31). Or more permanent lakes may be due to a ridge of rock running across the valley, as, for instance, just below St. Maurice in the Valais. [Illustration: Fig. 30.] [Illustration: VIEW IN THE VALAIS BELOW ST. MAURICE. _To face page 266._] [Illustration: Fig. 31.--View in the Rhone Valley, showing a lateral cone.] Almost all river valleys contain, or have contained, in their course one or more lakes, and where a river falls into a lake a cone like those just described is formed, and projects into the lake. Thus on the Lake of Geneva, between Vevey and Villeneuve (see Fig. 33), there are several such promontories, each marking the place where a stream falls into the lake. [Illustration: Fig. 32.--View in the Rhone Valley, showing the slope of a river cone.] The Rhone itself has not only filled up what was once the upper end of the lake, but has built out a strip of land into the water. [Illustration: Fig. 33.--Shore of the Lake of Geneva, near Vevey.] That the lake formerly extended some distance up the Valais no one can doubt who looks at the flat ground about Villeneuve. The Plate opposite, from a photograph taken above Vevey, shows this clearly. It is quite evident that the lake must formerly have extended further up the valley, and that it has been filled up by material brought down by the Rhone, a process which is still continuing. At the other end of the lake the river rushes out 15 feet deep of "not flowing, but flying water; not water neither--melted glacier matter, one should call it; the force of the ice is in it, and the wreathing of the clouds, the gladness of the sky, and the countenance of time."[51] [Illustration: VIEW UP THE VALAIS FROM THE LAKE OF GENEVA. _To face page 270._] In flat countries the habits of rivers are very different. For instance, in parts of Norfolk there are many small lakes or "broads" in a network of rivers--the Bure, the Yare, the Ant, the Waveney, etc.--which do not rush on with the haste of some rivers, or the stately flow of others which are steadily set to reach the sea, but rather seem like rivers wandering in the meadows on a holiday. They have often no natural banks, but are bounded by dense growths of tall grasses, Bulrushes, Reeds, and Sedges, interspersed with the spires of the purple Loosestrife, Willow Herb, Hemp Agrimony, and other flowers, while the fields are very low and protected by dykes, so that the red cattle appear to be browsing below the level of the water; and as the rivers take most unexpected turns, the sailing boats often seem (Fig. 34) as if they were in the middle of the fields. [Illustration: Fig. 34.--View in the district of the Broads, Norfolk.] At present these rivers are restrained in their courses by banks; when left free they are continually changing their beds. Their courses at first sight seem to follow no rule, but, as it is termed, from a celebrated river of Asia Minor, to "meander" along without aim or object, though in fact they follow very definite laws. Finally, when the river at length reaches the sea, it in many cases spreads out in the form of a fan, forming a very flat cone or "delta," as it is called, from the Greek capital [Greek: Delta], a name first applied to that of the Nile, and afterwards extended to other rivers. This is due to the same cause, and resembles, except in size, the comparatively minute cones of mountain streams. [Illustration: Fig. 35.] Fig. 35 represents the delta of the Po, and it will be observed that Adria, once a great port, and from which the Adriatic was named, is now more than 20 miles from the sea. Perhaps the most remarkable case is that of the Mississippi (Fig. 36), the mouths of which project into the sea like a hand, or like the petals of a flower. For miles the mud is too soft to support trees, but is covered by sedges (Miegea); the banks of mud gradually become too soft and mobile even for them. The pilots who navigate ships up the river live in frail houses resting on planks, and kept in place by anchors. Still further, and the banks of the Mississippi, if banks they can be called, are mere strips of reddish mud, intersected from time to time by transverse streams of water, which gradually separate them into patches. These become more and more liquid, until the land, river, and sea merge imperceptibly into one another. The river is so muddy that it might almost be called land, and the mud so saturated by water that it might well be called sea, so that one can hardly say whether a given spot is on the continent, in the river, or on the open ocean. [Illustration: Fig. 36.] FOOTNOTES: [48] Leyden. [49] Dr. Hudson, Address to the Microscopical Society, 1889. [50] F. Davors. [51] Ruskin. CHAPTER VIII RIVERS AND LAKES ON THE DIRECTIONS OF RIVERS In the last chapter I have alluded to the wanderings of rivers within the limits of their own valleys; we have now to consider the causes which have determined the directions of the valleys themselves. If a tract of country were raised up in the form of a boss or dome, the rain which fell on it would partly sink in, partly run away to the lower ground. The least inequality in the surface would determine the first directions of the streams, which would carry down any loose material, and thus form little channels, which would be gradually deepened and enlarged. It is as difficult for a river as for a man to get out of a groove. In such a case the rivers would tend to radiate with more or less regularity from the centre or axis of the dome, as, for instance, in our English lake district (Fig. 37). Derwent Water, Thirlmere, Coniston Water, and Windermere, run approximately N. and S.; Crummock Water, Loweswater, and Buttermere N.W. by S.E.; Waste Water, Ullswater, and Hawes Water N.E. by S.W.; while Ennerdale Water lies nearly E. by W. Can we account in any way, and if so how, for these varied directions? The mountains of Cumberland and Westmoreland form a more or less oval boss, the axis of which, though not straight, runs practically from E.N.E. to W.S.W., say from Scaw Fell to Shap Fell; and a sketch map shows us almost at a glance that Derwent Water, Thirlmere, Ullswater, Coniston Water, and Windermere run at right angles to this axis; Ennerdale Water is just where the boss ends and the mountains disappear; while Crummock Water and Waste Water lie at the intermediate angles. [Illustration: Fig. 37.--Map of the Lake District.] So much then for the direction. We have still to consider the situation and origin, and it appears that Ullswater, Coniston Water, the River Dudden, Waste Water, and Crummock Water lie along the lines of old faults, which no doubt in the first instance determined the flow of the water. Take another case. In the Jura the valleys are obviously (see Fig. 18) in many cases due to the folding of the strata. It seldom happens, however, that the case is so simple. If the elevation is considerable the strata are often fractured, and fissures are produced. Again if the part elevated contains layers of more than one character, this at once establishes differences. Take, for instance, the Weald of Kent (Figs. 38, 39). Here we have (omitting minor layers) four principal strata concerned, namely, the Chalk, Greensand, Weald Clay, and Hastings Sands. [Illustration: Fig. 38.--_a_, _a_, Upper Cretaceous strata, chiefly Chalk, forming the North and South Downs; _b_, _b_, Escarpment of Lower Greensand, with a valley between it and the Chalk; _c_, _c_, Weald Clay, forming plains; _d_, Hills formed of Hastings Sand and Clay. The Chalk, etc., once spread across the country, as shown in the dotted lines.] The axis of elevation runs (Fig. 39) from Winchester by Petersfield, Horsham, and Winchelsea to Boulogne, and as shown in the following section, taken from Professor Ramsay, we have on each side of the axis two ridges or "escarpments," one that of the Chalk, the other that of the Greensand, while between the Chalk and the Greensand is a valley, and between the Greensand and the ridge of Hastings Sand an undulating plain, in each case with a gentle slope from about where the London and Brighton railway crosses the Weald towards the east. Under these circumstances we might have expected that the streams draining the Weald would have run in the direction of the axis of elevation, and at the bases of the escarpments, as in fact the Rother does for part of its course, into the sea between the North and South Downs, instead of which as a rule they run north and south, cutting in some cases directly through the escarpments; on the north, for instance, the Wye, the Mole, the Darenth, the Medway, and the Stour; and on the south the Arun, the Addur, the Ouse, and the Cuckmere. [Illustration: Fig. 39.--Map of the Weald of Kent.] They do not run in faults or cracks, and it is clear that they could not have excavated their present valleys under circumstances such as now exist. They carry us back indeed to a time when the Greensand and Chalk were continued across the Weald in a great dome, as shown by the dotted lines in Fig. 38. They then ran down the slope of the dome, and as the Chalk and Greensand gradually weathered back, a process still in operation, the rivers deepened and deepened their valleys, and thus were enabled to keep their original course. Other evidence in support of this view is afforded by the presence of gravel beds in some places at the very top of the Chalk escarpment--beds which were doubtless deposited when, what is now the summit of a hill, was part of a continuous slope. The course of the Thames offers us a somewhat similar instance. It rises on the Oolites near Cirencester, and cuts through the escarpment of the Chalk between Wallingford and Reading. The cutting through the Chalk has evidently been effected by the river itself. But this could not have happened under existing conditions. We must remember, however, that the Chalk escarpment is gradually moving eastwards. The Chalk escarpments indeed are everywhere, though of course only slowly, crumbling away. Between Farnham and Guildford the Chalk is reduced to a narrow ridge known as the Hog's Back. In the same way no doubt the area of the Chalk formerly extended much further west than it does at present, and, indeed, there can be little doubt, somewhat further west than the source of the Thames, almost to the valley of the Severn. At that time the Thames took its origin in a Chalk spring. Gradually, however, the Chalk was worn away by the action of weather, and especially of rain. The river maintained its course while gradually excavating, and sinking deeper and deeper into, the Chalk. At present the river meets the Chalk escarpment near Wallingford, but the escarpment itself is still gradually retreating eastward. So, again, the Elbe cuts right across the Erz-Gebirge, the Rhine through the mountains between Bingen and Coblenz, the Potomac, the Susquehannah, and the Delaware through the Alleghanies. The case of the Dranse will be alluded to further on (p. 292). In these cases the rivers preceded the mountains. Indeed as soon as the land rose above the waters, rivers would begin their work, and having done so, unless the rate of elevation of the mountain exceeded the power of erosion of the river, the two would proceed simultaneously, so that the river would not alter its course, but would cut deeper and deeper as the mountain range gradually rose. Rivers then are in many cases older than mountains. Moreover, the mountains are passive, the rivers active. Since it seems to be well established that in Switzerland a mass, more than equal to what remains, has been removed; and that many of the present mountains are not sites which were originally raised highest, but those which have suffered least, it follows that if in some cases the course of the river is due to the direction of the mountain ridges, on the other hand the direction of some of the present ridges is due to that of the rivers. At any rate it is certain that of the original surface not a trace or a fragment remains _in situ_. Many of our own English mountains were once valleys, and many of our present valleys occupy the sites of former mountain ridges. Heim and Rütimeyer point out that of the two factors which have produced the relief of mountain regions, the one, elevation, is temporary and transitory; the other, denudation, is constant, and gains therefore finally the upper hand. We must not, however, expect too great regularity. The degree of hardness, the texture, and the composition of the rocks cause great differences. On the other hand, if the alteration of level was too rapid, the result might be greatly to alter the river courses. Mr. Darwin mentions such a case, which, moreover, is perhaps the more interesting as being evidently very recent. "Mr. Gill," he says, "mentioned to me a most interesting, and as far as I am aware, quite unparalleled case, of a subterranean disturbance having changed the drainage of a country. Travelling from Casma to Huaraz (not very far distant from Lima) he found a plain covered with ruins and marks of ancient cultivation, but now quite barren. Near it was the dry course of a considerable river, whence the water for irrigation had formerly been conducted. There was nothing in the appearance of the water-course to indicate that the river had not flowed there a few years previously; in some parts beds of sand and gravel were spread out; in others, the solid rock had been worn into a broad channel, which in one spot was about 40 yards in breadth and 8 feet deep. It is self-evident that a person following up the course of a stream will always ascend at a greater or less inclination. Mr. Gill therefore, was much astonished when walking up the bed of this ancient river, to find himself suddenly going downhill. He imagined that the downward slope had a fall of about 40 or 50 feet perpendicular. We here have unequivocal evidence that a ridge had been uplifted right across the old bed of a stream. From the moment the river course was thus arched, the water must necessarily have been thrown back, and a new channel formed. From that moment also the neighbouring plain must have lost its fertilising stream, and become a desert."[52] The strata, moreover, often--indeed generally, as we have seen, for instance, in the case of Switzerland--bear evidence of most violent contortions, and even where the convulsions were less extreme, the valleys thus resulting are sometimes complicated by the existence of older valleys formed under previous conditions. In the Alps then the present configuration of the surface is mainly the result of denudation. If we look at a map of Switzerland we can trace but little relation between the river courses and the mountain chains. [Illustration: Fig. 40.--Sketch Map of the Swiss Rivers.] The rivers, as a rule (Fig. 40), run either S.E. by N.W., or, at right angles to this, N.E. and S.W. The Alps themselves follow a somewhat curved line from the Maritime Alps, commencing with the islands of Hyères, by Briancon, Martigny, the Valais, Urseren Thal, Vorder Rhein, Innsbruck, Radstadt, and Rottenmann to the Danube, a little below Vienna,--at first nearly north and south, but gradually curving round until it becomes S.W. by N.E. The central mountains are mainly composed of Gneiss, Granite, and crystalline Schists: the line of junction between these rocks and the secondary and tertiary strata on the north, runs, speaking roughly, from Hyères to Grenoble, and then by Albertville, Sion, Chur, Inns, bruck, Radstadt, and Hieflau, towards Vienna. It is followed (in some part of their course) by the Isère, the Rhone, the Rhine, the Inn, and the Enns. One of the great folds shortly described in the preceding chapter runs up the Isère, along the Chamouni Valley, up the Rhone, through the Urseren Thal, down the Rhine Valley to Chur, along the Inn nearly to Kufstein, and for some distance along the Enns. Thus, then, five great rivers have taken advantage of this main fold, each of them eventually breaking through into a transverse valley. The Pusterthal in the Tyrol offers us an interesting case of what is obviously a single valley, which has, however, been slightly raised in the centre, near Toblach, so that from this point the water flows in opposite directions--the Drau eastward, and the Rienz westward. In this case the elevation is single and slight: in the main valley there are several, and they are much loftier, still we may, I think, regard that of the Isère from Chambery to Albertville, of the Rhone from Martigny to its source, of the Urseren Thal, of the Vorder Rhine from its source to Chur, of the Inn from Landeck to below Innsbruck, even perhaps of the Enns from Radstadt to Hieflau as in one sense a single valley, due to one of these longitudinal folds, but interrupted by bosses of gneiss and granite,--one culminating in Mont Blanc, and another in the St. Gotthard,--which have separated the waters of the Isère, the Rhone, the Vorder Rhine, the Inn, and the Enns. That the valley of Chamouni, the Valais, the Urseren Thal, and that of the Vorder Rhine really form part of one great fold is further shown by the presence of a belt of Jurassic strata nipped in, as it were, between the crystalline rocks. This seems to throw light on the remarkable turns taken by the Rhone at Martigny and the Vorder Rhine at Chur, where they respectively quit the great longitudinal fold, and fall into secondary transverse valleys. The Rhone for the upper part of its course, as far as Martigny, runs in the great longitudinal fold of the Valais; at Martigny it falls into and adopts the transverse valley, which properly belongs to the Dranse; for the Dranse is probably an older river and ran in the present course even before the great fold of the Valais. This would seem to indicate that the Oberland range is not so old as the Pennine, and that its elevation was so gradual that the Dranse was able to wear away a passage as the ridge gradually rose. After leaving the Lake of Geneva the Rhone follows a course curving gradually to the south, until it reaches St. Genix, where it falls into and adopts a transverse valley which properly belongs to the little river Guiers; it subsequently joins the Ain and finally falls into the Saône. If these valleys were attributed to their older occupiers we should therefore confine the name of the Rhone to the portion of its course from the Rhone glacier to Martigny. From Martigny it occupies successively the valleys of the Dranse, Guiers, Ain, and Saône. In fact, the Saône receives the Ain, the Ain the Guiers, the Guiers the Dranse, and the Dranse the Rhone. This is not a mere question of names, but also one of antiquity. The Saône, for instance, flowed past Lyons to the Mediterranean for ages before it was joined by the Rhone. In our nomenclature, however, the Rhone has swallowed up the others. This is the more curious because of the three great rivers which unite to form the lower Rhone, namely, the Saône, the Doubs, and the Rhone itself, the Saône brings for a large part of the year the greatest volume of water, and the Doubs has the longest course. Other similar cases might be mentioned. The Aar, for instance, is a somewhat larger river than the Rhine. [Illustration: Fig. 41.--Diagram in illustration of Mountain structure.] But why should the rivers, after running for a certain distance in the direction of the main axis, so often break away into lateral valleys? If the elevation of a chain of mountains be due to the causes suggested in p. 214, it is evident, though, so far as I am aware, stress has not hitherto been laid upon this, that the compression and consequent folding of the strata (Fig. 41) would not be in the direction _A B_ only, but also at right angles to it, in the direction _A C_, though the amount of folding might be much greater in one direction than in the other. Thus in the case of Switzerland, while the main folds run south-west by north-east, there would be others at right angles to the main axis. The complex structure of the Swiss mountains may be partly due to the coexistence of these two directions of pressure at right angles to one another. The presence of a fold so originating would often divert the river to a course more or less nearly at right angles to its original direction. Switzerland, moreover, slopes northwards from the Alps, so that the lowest part of the great Swiss plain is that along the foot of the Jura. Hence the main drainage runs along the line from Yverdun to Neuchâtel, down the Zihl to Soleure, and then along the Aar to Waldshut: the Upper Aar, the Emmen, the Wiggern, the Suhr, the Wynen, the lower Reuss, the Sihl, and the Limmat, besides several smaller streams, running approximately parallel to one another north-north-east, and at angles to the main axis of elevation, and all joining the Aar from the south, while on the north it does not receive a single contributary of any importance. On the south side of the Alps again we have the Dora Baltea, the Sesia, the Ticino, the Olonna, the Adda, the Adige, etc., all running south-south-east from the axis of elevation to the Po. [Illustration: Fig. 42.] Indeed, the general slope of Switzerland, being from the ridge of the Alps towards the north, it will be observed (Fig. 42) that almost all the large affluents of these rivers running in longitudinal valleys fall in on the south, as, for instance, those of the Isère from Albertville to Grenoble, of the Rhone from its source to Martigny, of the Vorder Rhine from its source to Chur, of the Inn from Landeck to Kufstein, of the Enns from its source to near Admont, of the Danube from its source to Vienna, and as just mentioned, of the Aar from Bern to Waldshut. Hence also, whenever the Swiss rivers running east and west break into a transverse valley, as the larger ones all do, and some more than once, they invariably, whether originally running east or westwards, turn towards the north. But although we thus get a clue to the general structure of Switzerland, the whole question is extremely complex, and the strata have been crumpled and folded in the most complicated manner, sometimes completely reversed, so that older rocks have been folded back on younger strata, and even in some cases these folds again refolded. Moreover, the denudation by aerial action, by glaciers, frosts, and rivers has removed hundreds, or rather thousands, of feet of strata. In fact, the mountain tops are not by any means the spots which have been most elevated, but those which have been least denuded; and hence it is that so many of the peaks stand at about the same altitude. THE CONFLICTS AND ADVENTURES OF RIVERS Our ancestors looked upon rivers as being in some sense alive, and in fact in their "struggle for existence" they not only labour to adapt their channel to their own requirements, but in many cases enter into conflict with one another. In the plain of Bengal, for instance, there are three great rivers, the Brahmapootra coming from the north, the Ganges from the west, and the Megna from the east, each of them with a number of tributary streams. Mr. Fergusson[53] has given us a most interesting and entertaining account of the struggles between these great rivers to occupy the fertile plain of Bengal. The Megna, though much inferior in size to the Brahmapootra, has one great advantage. It depends mainly on the monsoon rains for its supply, while the Brahmapootra not only has a longer course to run, but relies for its floods, to a great extent, on the melting of the snow, so that, arriving later at the scene of the struggle, it finds the country already occupied by the Megna to such an extent that it has been driven nearly 70 miles northwards, and forced to find a new channel. Under these circumstances it has attacked the territory of the Ganges, and being in flood earlier than that river, though later than the Megna, it has in its turn a great advantage. Whatever the ultimate result may be the struggle continues vigorously. At Sooksaghur, says Fergusson, "there was a noble country house, built by Warren Hastings, about a mile from the banks of the Hoogly. When I first knew it in 1830 half the avenue of noble trees, which led from the river to the house, was gone; when I last saw it, some eight years afterwards, the river was close at hand. Since then house, stables, garden, and village are all gone, and the river was on the point of breaking through the narrow neck of high land that remained, and pouring itself into some weak-banded nullahs in the lowlands beyond: and if it had succeeded, the Hoogly would have deserted Calcutta. At this juncture the Eastern Bengal Railway Company intervened. They were carrying their works along the ridge, and they have, for the moment at least, stopped the oscillation in this direction." This has affected many of the other tributaries of the Ganges, so that the survey made by Rennell in 1780-90 is no longer any evidence as to the present course of the rivers. They may now be anywhere else; in some cases all we can say is that they are certainly not now where they were then. The association of the three great European rivers, the Rhine, the Rhone, and the Danube, with the past history of our race, invests them with a singular fascination, and their past history is one of much interest. They all three rise in the group of mountains between the Galenstock and the Bernardino, within a space of a few miles; on the east the waters run into the Black Sea, on the north into the German Ocean, and on the west into the Mediterranean. But it has not always been so. Their head-waters have been at one time interwoven together. At present the waters of the Valais escape from the Lake of Geneva at the western end, and through the remarkable defile of Fort de l'Ecluse and Malpertius, which has a depth of 600 feet, and is at one place not more than 14 feet across. Moreover, at various points round the Lake of Geneva, remains of lake terraces show that the water once stood at a level much higher than the present. One of these is rather more than 250 feet[54] above the lake. A glance at the map will show that between Lausanne and Yverdun there is a low tract of land, and the Venoge, which falls into the Lake of Geneva between Lausanne and Morges, runs within about half a mile of the Nozon, which falls into the Lake of Neuchâtel at Yverdun, the two being connected by the Canal d'Entreroches, and the height of the watershed being only 76 metres (250 feet), corresponding with the above mentioned lake terrace. It is evident, therefore, that when the Lake of Geneva stood at the level of the 250 feet terrace the waters ran out, not as now at Geneva and by Lyons to the Mediterranean, but near Lausanne by Cissonay and Entreroches to Yverdun, and through the Lake of Neuchâtel into the Aar and the Rhine. But this is not the whole of the curious history. At present the Aar makes a sharp turn to the west at Waldshut, where it falls into the Rhine, but there is reason to believe that at a former period, before the Rhine had excavated its present bed, the Aar continued its course eastward to the Lake of Constance, by the valley of the Klettgau, as is indicated by the presence of gravel beds containing pebbles which have been brought, not by the Rhine from the Grisons, but by the Aar from the Bernese Oberland, showing that the river which occupied the valley was not the Rhine but the Aar. It would seem also that at an early period the Lake of Constance stood at a considerably higher level, and that the outlet was, perhaps, from Frederichshaven to Ulm, along what are now the valleys of the Schussen and the Ried, into the Danube. Thus the head-waters of the Rhone appear to have originally run by Lausanne and the Lake of Constance into the Danube, and so to the Black Sea. Then, after the present valley was opened between Waldshut and Basle, they flowed by Basle and the present Rhine, and after joining the Thames, over the plain which now forms the German Sea into the Arctic Ocean between Scotland and Norway. Finally, after the opening of the passage at Fort de l'Ecluse, by Geneva, Lyons, and the Valley of the Saône, to the Mediterranean. It must not, however, be supposed that these changes in river courses are confined to the lower districts. Mountain streams have also their adventures and vicissitudes, their wars and invasions. Take for instance the Upper Rhine, of which we have a very interesting account by Heim. It is formed of three main branches, the Vorder Rhine, Hinter Rhine, and the Albula. The two latter, after meeting near Thusis, unite with the Vorder Rhine at Reichenau, and run by Chur, Mayenfeld, and Sargans into the Lake of Constance at Rheineck. At some former period, however, the drainage of this district was very different, as is shown in Fig. 43. The Vorder and Hinter Rhine united then (Fig. 43) as they do now at Reichenau, but at a much higher level, and ran to Mayenfeld, not by Chur, but by the Kunckel Pass to Sargans, and so on, not to the Lake of Constance, but to that of Zurich. The Landwasser at that time rose in the Schlappina Joch, and after receiving as tributaries the Vereina and the Sardasca, joined the Albula, as it does now at Tiefenkasten; but instead of going round to meet the Hinter Rhine near Thusis, the two together travelled parallel with, but at some distance from, the Hinter Rhine, by Heide to Chur, and so to Mayenfeld. In the meanwhile, however, the Landquart was stealthily creeping up the valley, attacked the ridge which then united the Casanna and the Madrishorn, and gradually forcing the passage, invaded (Fig. 44) the valleys of the Schlappina, Vereina, and Sardasca, absorbed them as tributaries, and, detaching them from their allegiance to the Landwasser, annexed the whole of the upper province which had formerly belonged to that river. [Illustration: Fig. 43.--River system round Chur, as it used to be.] The Schyn also gradually worked its way upwards from Thusis till it succeeded in sapping the Albula, and carried it down the valley to join the Vorder Rhine near Thusis. In what is now the main valley of the Rhine above Chur another stream ate its way back, and eventually tapped the main river at Reichenau, thus diverting it from the Kunckel, and carrying it round by Chur. [Illustration: Fig. 44.--River system round Chur, as it is.] At Sargans a somewhat similar process was repeated, with the addition that the material brought down by the Weisstannen, or perhaps a rockfall, deflected the Rhine, just as we see in Fig. 30 that the Rhone was pushed on one side by the Borgne. The Rhone, however, had no choice, it was obliged to force, and has forced its way over the cone deposited by the Borgne. The Rhine, on the contrary, had the option of running down by Vaduz to Rheinach, and has adopted this course. The watershed between it and the Weisstannen is, however, only about 20 feet in height, and the people of Zurich watch it carefully, lest any slight change should enable the river to return to its old bed. The result of all these changes is that the rivers have changed their courses from those shown in Fig. 43 to their present beds as shown in Fig. 44. Another interesting case is that of the Upper Engadine (Fig. 45), to which attention has been called by Bonney and Heim. The fall of the Val Bregaglia is much steeper than that of the Inn, and the Maira has carried off the head-waters of that river away into Italy. The Col was formerly perhaps as far south as Stampa: the Albegna, the Upper Maira, and the stream from the Forgno Glacier, originally belonged to the Inn, but have been captured by the Lower Maira. Their direction still indicates this; they seem as if they regretted the unwelcome change, and yearned to rejoin their old companions. [Illustration: Fig. 45.--River system of the Maloya.] Moreover, as rivers are continually cutting back their valleys they must of course sometimes meet. In these cases when the valleys are at different levels the lower rivers have drained the upper ones, and left dry, deserted valleys. In other cases, especially in flatter districts, we have bifurcations, as, for instance, at Sargans, and several of the Italian lakes. Every one must have been struck by the peculiar bifurcation of the Lakes of Como and Lugano, while a very slight depression would connect the Lake Varese with the Maggiore, and give it also a double southern end. ON LAKES The problem of the origin of Lakes is by no means identical with that of Valleys. The latter are due, primarily as a rule to geological causes, but so far as their present condition is concerned, mainly to the action of rain and rivers. Flowing water, however, cannot give rise to lakes. It is of course possible to have valleys without lakes, and in fact the latter are, now at least, exceptional. There can be no lakes if the slope of the valley is uniform. To what then are lakes due? Professor Ramsay divides Lakes into three classes:-- 1. Those due to irregular accumulations of drift, and which are generally quite shallow. 2. Those formed by moraines. 3. Those which occupy true basins scooped by glacier ice out of the solid rock. To these must, however, I think be added at least one other great class and several minor ones, namely,-- 4. Those due to inequalities of elevation or depression. 5. Lakes in craters of extinct volcanoes, for instance, Lake Avernus. 6. Those caused by subsidence due to the removal of underlying soluble rocks, such as some of the Cheshire Meres. 7. Loop lakes in deserted river courses, of which there are many along the course of the Rhine. 8. Those due to rockfalls, landslips, or lava currents, damming up the course of a river. 9. Those caused by the advance of a glacier across a lateral valley, such as the Mergelen See, or the ancient lake whose margins form the celebrated "Parallel Roads of Glen Roy." As regards the first class we find here and there on the earth's surface districts sprinkled with innumerable shallow lakes of all sizes, down to mere pools. Such, for instance, occur in the district of Le Doubs between the Rhone and the Saône, that of La Sologne near Orleans, in parts of North America, and in Finland. Such lakes are, as a rule, quite shallow. Some geologists, Geikie, for instance, ascribe them to the fact of these regions having been covered by sheets of ice which strewed the land with irregular masses of clay, gravel, and sand, lying on a stratum impervious to water, either of hard rock such as granite or gneiss, or of clay, so that the rain cannot percolate through it, and without sufficient inclination to throw it off. 2. To Ramsay's second class of Lakes belong those formed by moraines. The materials forming moraines being, however, comparatively loose, are easily cut through by streams. There are in Switzerland many cases of valleys crossed by old moraines, but they have generally been long ago worn through by the rivers. 3. Ramsay and Tyndall attribute most of the great Swiss and Italian lakes to the action of glaciers, and regard them as rock basins. It is of course obvious that rivers cannot make basin-shaped hollows surrounded by rock on all sides. The Lake of Geneva, 1230 feet above the sea, is over 1000 feet deep; the Lake of Brienz is 1850 feet above the sea, and 2000 feet deep, so that its bottom is really below the sea level. The Italian Lakes are even more remarkable. The Lake of Como, 700 feet above the sea, is 1929 feet deep. Lago Maggiore, 685 feet above the sea, is no less than 2625 feet deep. If the mind is at first staggered at the magnitude of the scale, we must remember that the ice which is supposed to have scooped out the valley in which the Lake of Geneva now reposes, was once at least 4000 feet thick; while the moraines were also of gigantic magnitude, that of Ivrea, for instance, being no less than 1500 feet above the river, and several miles long. Indeed it is obvious that a glacier many hundred, or in some cases several thousand, feet in thickness, must exercise great pressure on the bed over which it travels. We see this from the striæ and grooves on the solid rocks, and the fine mud which is carried down by glacial streams. The deposit of glacial rivers, the "loess" of the Rhine itself, is mainly the result of this ice-waste, and that is why it is so fine, so impalpable. That glaciers do deepen their beds seems therefore unquestionable. Moreover, though the depth of some of these lakes is great, the true slope is very slight. Tyndall and Ramsay do not deny that the original direction of valleys, and consequently of lakes, is due to cosmical causes and geological structure, while even those who have most strenuously opposed the theory which attributes lakes to glacial erosion do not altogether deny the action of glaciers. Favre himself admits that "it is impossible to deny that valleys, after their formation, have been swept out and perhaps enlarged by rivers and glaciers." Even Ruskin admits "that a glacier may be considered as a vast instrument of friction, a white sand-paper applied slowly but irresistibly to all the roughness of the hill which it covers." It is obvious that sand-paper applied "irresistibly" and long enough, must gradually wear away and lower the surface. I cannot therefore resist the conclusion that glaciers have taken an important part in the formation of lakes. The question has sometimes been discussed as if the point at issue were whether rivers or glaciers were the most effective as excavators. But this is not so. Those who believe that lakes are in many cases due to glaciers might yet admit that rivers have greater power of erosion. There is, however, an essential difference in the mode of action. Rivers tend to regularise their beds; they drain, rather than form lakes. Their tendency is to cut through any projections so that finally their course assumes some such curve as that below, from the source (_a_) to its entrance into the sea (_b_). [Illustration: Fig. 46.--Final Slope of a River.] Glaciers, however, have in addition a scooping power, so that if similarly _a d b_ in Fig. 47 represent the course of a glacier, starting at _a_ and gradually thinning out to _e_, it may scoop out the rock to a certain extent at _d_; in that case if it subsequently retires say to _c_, there would be a lake lying in the basin thus formed between _c_ and _e_. [Illustration: Fig. 47.] On the other hand I am not disposed to attribute the Swiss lakes altogether to the action of glaciers. In the first place it does not seem clear that they occupy true rock basins. On this point more evidence is required. That some lakes are due to unequal changes of level will hardly be denied. No one, for instance, as Bonney justly observes,[55] would attribute the Dead Sea to glacial erosion. The Alps, as we have seen, are a succession of great folds, and there is reason to regard the central one as the oldest. If then the same process continued, and the outer fold was still further raised, or a new one formed, more quickly than the rivers could cut it back, they would be dammed up, and lakes would result. Moreover, if the formation of a mountain region be due to subsidence, and consequent crumpling, as indicated on p. 217, so that the strata which originally occupied the area A B C D are compressed into A' B' C' D', it is evident, as already mentioned, that while the line of least resistance, and, consequently, the principal folds might be in the direction A' B', there must also be a tendency to the formation of similar folds at right angles, or in the direction A' C'. Thus, in the case of Switzerland, while the main folds run south-west by north-east there would also be others at right angles, though the amount of folding might be much greater in the one direction than in the other. To this cause the bosses, for instance--at Martigny, the Furca, and the Ober Alp,--which intersect the great longitudinal valley of Switzerland, are perhaps due. The great American lakes also are probably due to differences of elevation. Round Lake Ontario, for instance, there is a raised beach which at the western end of the lake is 363 feet above the sea level, but rises towards the East and North until near Fine it reaches an elevation of 972 feet. As this terrace must have been originally horizontal we have here a lake barrier, due to a difference of elevation, amounting to over 600 feet. In the same way we get a clue to the curious cruciform shape of the Lake of Lucerne as contrasted with the simple outline of such lakes as those of Neuchâtel or Zurich. That of Lucerne is a complex lake. Soundings have shown that the bottom of the Urner See is quite flat. It is in fact the old bed of the Reuss, which originally ran, not as now by Lucerne, but by Schwytz and through the Lake of Zug. In the same way the Alpnach See is the old bed of the Aa, which likewise ran through the Lake of Zug. The old river terraces of the Reuss can be traced in places between Brunnen and Goldau. Now these terraces must have originally sloped from the upper part downwards, from Brunnen towards Goldau. But at present the slope is the other way, _i.e._ from Goldau towards Brunnen. From this and other evidence we conclude that in the direction from Lucerne towards Rapperschwyl there has been an elevation of the land, which has dammed up the valleys and thus turned parts of the Aa and the Reuss into lakes--the two branches of the Lake of Lucerne known as the Alpnach See and Urner See. During the earthquakes of 1819 while part of the Runn of Cutch, 2000 square miles in area, sunk several feet, a ridge of land, called by the natives the Ulla-Bund or "the wall of God," thirty miles long, and in parts sixteen miles wide, was raised across an ancient arm of the Indus, and turned it temporarily into a lake. In considering the great Italian lakes, which descend far below the sea level, we must remember that the Valley of the Po is a continuation of the Adriatic, now filled up and converted into land, by the materials brought down from the Alps. Hence we are tempted to ask whether the lakes may not be remains of the ancient sea which once occupied the whole plain. Moreover just as the Seals of Lake Baikal in Siberia carry us back to the time when that great sheet of fresh water was in connection with the Arctic Ocean, so there is in the character of the Fauna of the Italian lakes, and especially the presence of a Crab in the Lake of Garda, some confirmation of such an idea. Further evidence, however, is necessary before these interesting questions can be definitely answered. Lastly, some lakes and inland seas seem to be due to even greater cosmical causes. Thus a line inclined ten degrees to the pole beginning at Gibraltar would pass through a great chain of inland waters--the Mediterranean, Black Sea, Caspian, Aral, Baikal, and back again through the great American lakes. But though many causes have contributed to the original formation and direction of Valleys, their present condition is mainly due to the action of water. When we contemplate such a valley, for example, as that which is called _par excellence_ the "Valais," we can at first hardly bring ourselves to realise this; but we can trace up valleys, from the little water-course made by last night's rains up to the greatest valleys of all. These considerations, however, do not of course apply to such depressions as those of the great oceans. These were probably formed when the surface of the globe began to solidify, and, though with many modifications, have maintained their main features ever since. ON THE CONFIGURATION OF VALLEYS The conditions thus briefly described repeat themselves in river after river, valley after valley, and it adds, I think, very much to the interest with which we regard them if, by studying the general causes to which they are due, we can explain their origin, and thus to some extent understand the story they have to tell us, and the history they record. What, then, has that history been? The same valley may be of a very different character, and due to very different causes, in different parts of its course. Some valleys are due to folds (see Fig. 41) caused by subterranean changes, but by far the greater number are, in their present features, mainly the result of erosion. As soon as any tract of land rose out of the sea, the rain which fell on the surface would trickle downwards in a thousand rills, forming pools here and there (see Fig. 37), and gradually collecting into larger and larger streams. Wherever the slope was sufficient the water would begin cutting into the soil and carrying it off to the sea. This action would be the same in any case, but, of course, would differ in rapidity according to the hardness of the ground. On the other hand, the character of the valley would depend greatly on the character of the strata, being narrow where they were hard and tough; broader, on the contrary, where they were soft, so that they crumbled readily into the stream, or where they were easily split by the weather. Gradually the stream would eat into its bed until it reached a certain slope, the steepness of which would depend on the volume of water. The erosive action would then cease, but the weathering of the sides and consequent widening would continue, and the river would wander from one part of its valley to another, spreading the materials and forming a river plain. At length, as the rapidity still further diminished, it would no longer have sufficient power even to carry off the materials brought down. It would form, therefore, a cone or delta, and instead of meandering, would tend to divide into different branches. These three stages, we may call those of-- 1. Deepening and widening; 2. Widening and levelling; 3. Filling up; and every place in the second stage has passed through the first; every one in the third has passed through the second. A velocity of 6 inches per second will lift fine sand, 8 inches will move sand as coarse as linseed, 12 inches will sweep along fine gravel, 24 inches will roll along rounded pebbles an inch diameter, and it requires 3 feet per second at the bottom to sweep along angular stones of the size of an egg. When a river has so adjusted its slope that it neither deepens its bed in the upper portion of its course, nor deposits materials, it is said to have acquired its "regimen," and in such a case if the character of the soil remains the same, the velocity must also be uniform. The enlargement of the bed of a river is not, however, in proportion to the increase of its waters as it approaches the sea. If, therefore, the slope did not diminish, the regimen would be destroyed, and the river would again commence to eat out its bed. Hence as rivers enlarge, the slope diminishes, and consequently every river tends to assume some such "regimen" as that shown in Fig. 46. Now, suppose that the fall of the river is again increased, either by a fresh elevation, or locally by the removal of a barrier. Then once more the river regains its energy. Again it cuts into its old bed, deepening the valley, and leaving the old plain as a terrace high above its new course. In many valleys several such terraces may be seen, one above the other. In the case of a river running in a transverse valley, that is to say of a valley lying at right angles to the "strike" or direction of the strata (such, for instance, as the Reuss), the water acts more effectively than in longitudinal valleys running along the strike. Hence the lateral valleys have been less deeply excavated than that of the Reuss itself, and the streams from them enter the main valley by rapids or cascades. Again, rivers running in transverse valleys cross rocks which in many cases differ in hardness, and of course they cut down the softer strata more rapidly than the harder ones; each ridge of harder rock will therefore form a dam and give rise to a rapid, or cataract. We often as we ascend a river, after a comparatively flat plain, find ourselves in a narrow defile, down which the water rushes in an impetuous torrent, but at the summit of which, to our surprise, we find another broad flat valley. Another lesson which we learn from the study of river valleys, is that, just as geological structure was shown by Sir C. Lyell to be no evidence of cataclysms, but the result of slow action; so also the excavation of valleys is due mainly to the regular flow of rivers; and floods, though their effects are more sudden and striking, have had, after all, comparatively little part in the result. The mouths of rivers fall into two principal classes. If we look at any map we cannot but be struck by the fact that some rivers terminate in a delta, some in an estuary. The Thames, for instance, ends in a noble estuary, to which London owes much of its wealth and power. It is obvious that the Thames could not have excavated this estuary while the coast was at its present level. But we know that formerly the land stood higher, that the German Ocean was once dry land, and the Thames, after joining the Rhine, ran northwards, and fell eventually into the Arctic Ocean. The estuary of the Thames, then, dates back to a period when the south-east of England stood at a higher level than the present, and even now the ancient course of the river can be traced by soundings under what is now sea. The sites of present deltas, say of the Nile, were also once under water, and have been gradually reclaimed by the deposits of the river. It would indeed be a great mistake to suppose that rivers always tend to deepen their valleys. This is only the case when the slope exceeds a certain angle. When the fall is but slight they tend on the contrary to raise their beds by depositing sand and mud brought down from higher levels. Hence in the lower part of their course many of the most celebrated rivers--the Nile, the Po, the Mississippi, the Thames, etc.--run upon embankments, partly of their own creation. [Illustration: Fig. 48.--Diagrammatic section of a valley (exaggerated) _R R_, rocky basis of valley; _A A_, sedimentary strata; _B_, ordinary level of river; _C_, flood level.] The Reno, the most dangerous of all the Apennine rivers, is in some places as much as 30 feet above the adjoining country. Rivers under such conditions, when not interfered with by Man, sooner or later break through their banks, and leaving their former bed, take a new course along the lowest part of their valley, which again they gradually raise above the rest. Hence, unless they are kept in their own channels by human agency, such rivers are continually changing their course. If we imagine a river running down a regularly inclined plane in a more or less straight line; any inequality or obstruction would produce an oscillation, which when once started would go on increasing until the force of gravity drawing the water in a straight line downwards equals that of the force tending to divert its course. Hence the radius of the curves will follow a regular law depending on the volume of water and the angle of inclination of the bed. If the fall is 10 feet per mile and the soil homogeneous, the curves would be so much extended that the course would appear almost straight. With a fall of 1 foot per mile the length of the curve is, according to Fergusson, about six times the width of the river, so that a river 1000 feet wide would oscillate once in 6000 feet. This is an important consideration, and much labour has been lost in trying to prevent rivers from following their natural law of oscillation. But rivers are very true to their own laws, and a change at any part is continued both upwards and downwards, so that a new oscillation in any place cuts its way through the whole plain of the river both above and below. The curves of the Mississippi are, for instance, for a considerable part of its course so regular that they are said to have been used by the Indians as a measure of distance. If the country is flat a river gradually raises the level on each side, the water which overflows during floods being retarded by reeds, bushes, trees, and a thousand other obstacles, gradually deposits the solid matter which it contains, and thus raising the surface, becomes at length suspended, as it were, above the general level. When this elevation has reached a certain point, the river during some flood bursts its banks, and deserting its old bed takes a new course along the lowest accessible level. This then it gradually fills up, and so on; coming back from time to time if permitted, after a long cycle of years, to its first course. In evidence of the vast quantity of sediment which rivers deposit, I may mention that the river-deposits at Calcutta are more than 400 feet in thickness. In addition to temporary "spates," due to heavy rain, most rivers are fuller at one time of year than another, our rivers, for instance, in winter, those of Switzerland, from the melting of the snow, in summer. The Nile commences to rise towards the beginning of July; from August to October it floods all the low lands, and early in November it sinks again. At its greatest height the volume of water sometimes reaches twenty times that when it is lowest, and yet perhaps not a drop of rain may have fallen. Though we now know that this annual variation is due to the melting of the snow and the fall of rain on the high lands of Central Africa, still when we consider that the phenomenon has been repeated annually for thousands of years it is impossible not to regard it with wonder. In fact Egypt itself may be said to be the bed of the Nile in flood time. Some rivers, on the other hand, offer no such periodical differences. The lower Rhone, for instance, below the junction with the Saône, is nearly equal all through the year, and yet we know that the upper portion is greatly derived from the melting of the Swiss snows. In this case, however, while the Rhone itself is on this account highest in summer and lowest in winter, the Saône, on the contrary, is swollen by the winter's rain, and falls during the fine weather of summer. Hence the two tend to counterbalance one another. Periodical differences are of course comparatively easy to deal with. It is very different with floods due to irregular rainfall. Here also, however, the mere quantity of rain is by no means the only matter to be considered. For instance a heavy rain in the watershed of the Seine, unless very prolonged, causes less difference in the flow of the river, say at Paris, than might at first have been expected, because the height of the flood in the nearer affluents has passed down the river before that from the more distant streams has arrived. The highest level is reached when the rain in the districts drained by the various affluents happens to be so timed that the different floods coincide in their arrival at Paris. FOOTNOTES: [52] Darwin's _Voyage of a Naturalist_. [53] _Geol. Jour._, 1863. [54] Favre, _Rech. Geol. de la Savoie._ [55] _Growth and Structure of the Alps._ CHAPTER IX THE SEA There is a pleasure in the pathless woods, There is a rapture on the lonely shore, There is society, where none intrudes, By the deep Sea, and music in its roar: I love not Man the less, but Nature more, From these our interviews, in which I steal From all I may be, or have been before, To mingle with the Universe, and feel What I can ne'er express, yet cannot all conceal. Roll on, thou deep and dark-blue Ocean--roll! BYRON. [Illustration: THE LAND'S END. _To face page 337._] CHAPTER IX THE SEA When the glorious summer weather comes, when we feel that by a year's honest work we have fairly won the prize of a good holiday, how we turn instinctively to the Sea. We pine for the delicious smell of the sea air, the murmur of the waves, the rushing sound of the pebbles on the sloping shore, the cries of the sea-birds; and long to Linger, where the pebble-paven shore, Under the quick, faint kisses of the Sea, Trembles and sparkles as with ecstasy.[56] How beautiful the sea-coast is! At the foot of a cliff, perhaps of pure white chalk, or rich red sandstone, or stern grey granite, lies the shore of gravel or sand, with a few scattered plants of blue Sea Holly, or yellow-flowered Horned Poppies, Sea-kale, Sea Convolvulus, Saltwort, Artemisia, and Sea-grasses; the waves roll leisurely in one by one, and as they reach the beach, each in turn rises up in an arch of clear, cool, transparent, green water, tipped with white or faintly pinkish foam, and breaks lovingly on the sands; while beyond lies the open Sea sparkling in the sunshine. ... O pleasant Sea Earth hath not a plain So boundless or so beautiful as thine.[57] The Sea is indeed at times overpoweringly beautiful. At morning and evening a sheet of living silver or gold, at mid-day deep blue; even Too deeply blue; too beautiful; too bright; Oh, that the shadow of a cloud might rest Somewhere upon the splendour of thy breast In momentary gloom.[58] There are few prettier sights than the beach at a seaside town on a fine summer's day; the waves sparkling in the sunshine, the water and sky each bluer than the other, while the sea seems as if it had nothing to do but to laugh and play with the children on the sands; the children perseveringly making castles with spades and pails, which the waves then run up to and wash away, over and over and over again, until evening comes and the children go home, when the Sea makes everything smooth and ready for the next day's play. Many are satisfied to admire the Sea from shore, others more ambitious or more free prefer a cruise. They feel with Tennyson's voyager: We left behind the painted buoy That tosses at the harbour-mouth; And madly danced our hearts with joy, As fast we fleeted to the South: How fresh was every sight and sound On open main or winding shore! We knew the merry world was round, And we might sail for evermore. Many appreciate both. The long roll of the Mediterranean on a fine day (and I suppose even more of the Atlantic, which I have never enjoyed), far from land in a good ship, and with kind friends, is a joy never to be forgotten. To the Gulf Stream and the Atlantic Ocean Northern Europe owes its mild climate. The same latitudes on the other side of the Atlantic are much colder. To find the same average temperature in the United States we must go far to the south. Immediately opposite us lies Labrador, with an average temperature the same as that of Greenland; a coast almost destitute of vegetation, a country of snow and ice, whose principal wealth consists in its furs, and a scattered population, mainly composed of Indians and Esquimaux. But the Atlantic would not alone produce so great an effect. We owe our mild and genial climate mainly to the Gulf Stream--a river in the ocean, twenty million times as great as the Rhone--the greatest, and for us the most important, river in the world, which brings to our shores the sunshine of the West Indies. The Sea is outside time. A thousand, ten thousand, or a million years ago it must have looked just as it does now, and as it will ages hence. With the land this is not so. The mountains and hills, rivers and valleys, animals and plants are continually changing: but the Sea is always the same, Steadfast, serene, immovable, the same Year after year. Directly we see the coast, or even a ship, the case is altered. Boats may remain the same for centuries, but ships are continually being changed. The wooden walls of old England are things of the past, and the ironclads of to-day will soon be themselves improved off the face of the ocean. The great characteristic of Lakes is peace, that of the Sea is energy, somewhat restless, perhaps, but still movement without fatigue. The Earth lies quiet like a child asleep, The deep heart of the Heaven is calm and still, Must thou alone a restless vigil keep, And with thy sobbing all the silence fill.[59] A Lake in a storm rather gives us the impression of a beautiful Water Spirit tormented by some Evil Demon; but a storm at Sea is one of the grandest manifestations of Nature. Yet more; the billows and the depths have more; High hearts and brave are gathered to thy breast; They hear not now the booming waters roar, The battle thunders will not break their rest. Keep thy red gold and gems, thou stormy grave; Give back the true and brave.[60] The most vivid description of a storm at sea is, I think, the following passage from Ruskin's _Modern Painters_: "Few people, comparatively, have ever seen the effect on the sea of a powerful gale continued without intermission for three or four days and nights; and to those who have not, I believe it must be unimaginable, not from the mere force or size of the surge, but from the complete annihilation of the limit between sea and air. The water from its prolonged agitation is beaten, not into mere creaming foam, but into masses of accumulated yeast, which hangs in ropes and wreaths from wave to wave, and, where one curls over to break, form a festoon like a drapery from its edge; these are taken up by the wind, not in dissipating dust, but bodily, in writhing, hanging, coiling masses, which make the air white and thick as with snow, only the flakes are a foot or two long each: the surges themselves are full of foam in their very bodies underneath, making them white all through, as the water is under a great cataract; and their masses, being thus half water and half air, are torn to pieces by the wind whenever they rise, and carried away in roaring smoke, which chokes and strangles like actual water. Add to this, that when the air has been exhausted of its moisture by long rain, the spray of the sea is caught by it as described above, and covers its surface not merely with the smoke of finely divided water, but with boiling mist; imagine also the low rain-clouds brought down to the very level of the sea, as I have often seen them, whirling and flying in rags and fragments from wave to wave; and finally, conceive the surges themselves in their utmost pitch of power, velocity, vastness, and madness, lifting themselves in precipices and peaks, furrowed with their whirl of ascent, through all this chaos, and you will understand that there is indeed no distinction left between the sea and air; that no object, nor horizon, nor any landmark or natural evidence of position is left; and the heaven is all spray, and the ocean all cloud, and that you can see no further in any direction than you see through a cataract." SEA LIFE The Sea teems with life. The Great Sea Serpent is, indeed, as much a myth as the Kraken of Pontoppidan, but other monsters, scarcely less marvellous, are actual realities. The Giant Cuttle Fish of Newfoundland, though the body is comparatively small, may measure 60 feet from the tip of one arm to that of another. The Whalebone Whale reaches a length of over 70 feet, but is timid and inoffensive. The Cachalot or Sperm Whale, which almost alone among animals roams over the whole ocean, is as large, and much more formidable. It is armed with powerful teeth, and is said to feed mainly on Cuttle Fish, but sometimes on true fishes, or even Seals. When wounded it often attacks boats, and its companions do not hesitate to come to the rescue. In one case, indeed, an American ship was actually attacked, stove in, and sunk by a gigantic male Cachalot. The Great Roqual is still more formidable, and has been said to attain a length of 120 feet, but this is probably an exaggeration. So far as we know, the largest species of all is Simmond's Whale, which reaches a maximum of 85 to 90 feet. In former times Whales were frequent on our coasts, so that, as Bishop Pontoppidan said, the sea sometimes appeared as if covered with smoking chimneys, but they have been gradually driven further and further north, and are still becoming rarer. As they retreated man followed, and to them we owe much of our progress in geography. Is it not, however, worth considering whether they might not also be allowed a "truce of God," whether some part of the ocean might not be allotted to them where they might be allowed to breed in peace? As a mere mercantile arrangement the maritime nations would probably find this very remunerative. The reckless slaughter of Whales, Sea Elephants, Seals, and other marine animals is a sad blot, not only on the character, but on the common sense, of man. The monsters of the ocean require large quantities of food, but they are supplied abundantly. Scoresby mentions cases in which the sea was for miles tinged of an olive green by a species of Medusa. He calculates that in a cubic mile there must have been 23,888,000,000,000,000, and though no doubt the living mass did not reach to any great depth, still, as he sailed through water thus discoloured for many miles, the number must have been almost incalculable. This is, moreover, no rare or exceptional case. Navigators often sail for leagues through shoals of creatures, which alter the whole colour of the sea, and actually change it, as Reclus says, into "une masse animée." Still, though the whole ocean teems with life, both animals and plants are most abundant near the coast. Air-breathing animals, whether mammals or insects, are naturally not well adapted to live far from dry land. Even Seals, though some of them make remarkable migrations, remain habitually near the shore. Whales alone are specially modified so as to make the wide ocean their home. Of birds the greatest wanderer is the Albatross, which has such powers of flight that it is said even to sleep on the wing. Many Pelagic animals--Jelly-fishes, Molluscs, Cuttle-fishes, Worms, Crustacea, and some true fishes--are remarkable for having become perfectly transparent; their shells, muscles, and even their blood have lost all colour, or even undergone the further modification of having become blue, often with beautiful opalescent reflections. This obviously renders them less visible, and less liable to danger. The sea-shore, wherever a firm hold can be obtained, is covered with Sea-weeds, which fall roughly into two main divisions, olive-green and red, the latter colour having a special relation to light. These Sea-weeds afford food and shelter to innumerable animals. The clear rocky pools left by the retiring tide are richly clothed with green sea-weeds, while against the sides are tufts of beautiful filmy red algæ, interspersed with Sea-anemones,--white, creamy, pink, yellow, purple, with a coronet of blue beads, and of many mixed colours; Sponges, Corallines, Starfish, Limpets, Barnacles, and other shell-fish; feathery Zoophytes and Annelides expand their pink or white disks, while here and there a Crab scuttles across; little Fish or Shrimps timidly come out from crevices in the rocks, or from among the fronds of the sea-weeds, or hastily dart from shelter to shelter; each little pool is, in fact, a miniature ocean in itself, and the longer one looks the more and more one will see. The dark green and brown sea-weeds do not live beyond a few--say about 15--fathoms in depth. Below them occur delicate scarlet species, with Corallines and a different set of shells, Sea-urchins, etc. Down to about 100 fathoms the animals and plants are still numerous and varied. But they gradually diminish in numbers, and are replaced by new forms. To appreciate fully the extreme loveliness of marine animals they must be seen alive. "A tuft of Sertularia, laden with white, or brilliantly tinted Polypites," says Hincks, "like blossoms on some tropical tree, is a perfect marvel of beauty. The unfolding of a mass of Plumularia, taken from amongst the miscellaneous contents of the dredge, and thrown into a bottle of clear sea-water, is a sight which, once seen, no dredger will forget. A tree of Campanularia, when each one of its thousand transparent calycles--itself a study of form--is crowned by a circlet of beaded arms, drooping over its margin like the petals of a flower, offers a rare combination of the elements of beauty. "The rocky wall of some deep tidal pool, thickly studded with the long and slender stems of Tubularia, surmounted by the bright rose-coloured heads, is like the gay parterre of a garden. Equally beautiful is the dense growth of Campanularia, covering (as I have seen it in Plymouth Sound) large tracts of the rock, its delicate shoots swaying to and fro with each movement of the water, like trees in a storm, or the colony of Obelia on the waving frond of the tangle looking almost ethereal in its grace, transparency, and delicacy, as seen against the coarse dark surface that supports it." Few things are more beautiful than to look down from a boat into transparent water. At the bottom wave graceful sea-weeds, brown, green, or rose-coloured, and of most varied forms; on them and on the sands or rocks rest starfishes, mollusca, crustaceans, Sea-anemones, and innumerable other animals of strange forms and varied colours; in the clear water float or dart about endless creatures; true fishes, many of them brilliantly coloured; Cuttle-fishes like bad dreams; Lobsters and Crabs with graceful, transparent Shrimps; Worms swimming about like living ribbons, some with thousands of coloured eyes, and Medusæ like living glass of the richest and softest hues, or glittering in the sunshine with all the colours of the rainbow. And on calm, cool nights how often have I stood on the deck of a ship watching with wonder and awe the stars overhead, and the sea-fire below, especially in the foaming, silvery wake of the vessel, where often suddenly appear globes of soft and lambent light, given out perhaps from the surface of some large Medusa. "A beautiful white cloud of foam," says Coleridge, "at momently intervals coursed by the side of the vessel with a roar, and little stars of flame danced and sparkled and went out in it; and every now and then light detachments of this white cloud-like foam darted off from the vessel's side, each with its own small constellation, over the sea, and scoured out of sight like a Tartar troop over a wilderness." Fish also are sometimes luminous. The Sun-fish has been seen to glow like a white-hot cannon-ball, and in one species of Shark (Squalus fulgens) the whole surface sometimes gives out a greenish lurid light which makes it a most ghastly object, like some great ravenous spectre. THE OCEAN DEPTHS The Land bears a rich harvest of life, but only at the surface. The Ocean, on the contrary, though more richly peopled in its upper layers, which swarm with such innumerable multitudes of living creatures that they are, so to say, almost themselves alive--teems throughout with living beings. The deepest abysses have a fauna of their own, which makes up for the comparative scantiness of its numbers, by the peculiarity and interest of their forms and organisation. The middle waters are the home of various Fishes, Medusæ, and animalcules, while the upper layers swarm with an inexhaustible variety of living creatures. It used to be supposed that the depths of the Ocean were destitute of animal life, but recent researches, and especially those made during our great national expedition in the "Challenger," have shown that this is not the case, but that the Ocean depths have a wonderful and peculiar life of their own. Fish have been dredged up even from a depth of 2750 fathoms. The conditions of life in the Ocean depths are very peculiar. The light of the sun cannot penetrate beyond about two hundred fathoms; deeper than this complete darkness prevails. Hence in many species the eyes have more or less completely disappeared. Sir Wyville Thomson mentions a kind of Crab (Ethusa granulata), which when living near the surface has well developed eyes; in deeper water, 100 to 400 fathoms, eyestalks are present, but the animal is apparently blind, the eyes themselves being absent; while in specimens from a depth of 500-700 fathoms the eyestalks themselves have lost their special character, and have become fixed, their terminations being combined into a strong, pointed beak. In other deep sea creatures, on the contrary, the eyes gradually become more and more developed, so that while in some species the eyes gradually dwindle, in others they become unusually large. Many of the latter species may be said to be a light to themselves, being provided with a larger or smaller number of curious luminous organs. The deep sea fish are either silvery, pink, or in many cases black, sometimes relieved with scarlet, and when the luminous organs flash out must present a very remarkable appearance. We have still much to learn as to the structure and functions of these organs, but there are cases in which their use can be surmised with some probability. The light is evidently under the will of the fish.[61] It is easy to imagine a Photichthys (Light Fish) swimming in the black depths of the Ocean, suddenly flashing out light from its luminous organs, and thus bringing into view any prey which may be near; while, if danger is disclosed, the light is again at once extinguished. It may be observed that the largest of these organs is in this species situated just under the eye, so that the fish is actually provided with a bull's eye lantern. In other cases the light may rather serve as a defence, some having, as, for instance, in the genus Scopelus, a pair of large ones in the tail, so that "a strong ray of light shot forth from the stern-chaser may dazzle and frighten an enemy." In other cases they appear to serve as lures. The "Sea-devil" or "Angler" of our coasts has on its head three long, very flexible, reddish filaments, while all round its head are fringed appendages, closely resembling fronds of sea-weed. The fish conceals itself at the bottom, in the sand or among sea-weed, and dangles the long filaments in front of its mouth. Little fishes, taking these filaments for worms, unsuspectingly approach, and thus fall victims. Several species of the same family live at great depths, and have very similar habits. A mere red filament would be invisible in the dark and therefore useless. They have, however, developed a luminous organ, a living "glow-lamp," at the end of the filament, which doubtless proves a very effective lure. In the great depths, however, fish are comparatively rare. Nor are Molluscs much more abundant. Sea-urchins, Sea Slugs, and Starfish are more numerous, and on one occasion 20,000 specimens of an Echinus were brought up at a single haul. True corals are rare, nor are Hydrozoa frequent, though a giant species, allied to the little Hydra of our ponds but upwards of 6 feet in height, has more than once been met with. Sponges are numerous, and often very beautiful. The now well known Euplectella, "Venus's Flower-basket," resembles an exquisitely delicate fabric woven in spun silk; it is in the form of a gracefully curved tube, expanding slightly upwards and ending in an elegant frill. The wall is formed of parallel bands of glassy siliceous fibres, crossed by others at right angles, so as to form a square meshed net. These sponges are anchored on the fine ooze by wisps of glassy filaments, which often attain a considerable length. Many of these beautiful organisms, moreover, glow when alive with a soft diffused light, flickering and sparkling at every touch. What would one not give to be able to wander a while in these wonderful regions! It is curious that no plants, so far as we know, grow in the depths of the Ocean, or, indeed, as far as our present information goes, at a greater depth than about 100 fathoms. As regards the nature of the bottom itself, it is in the neighbourhood of land mainly composed of materials, brought down by rivers or washed from the shore, coarser near the coast, and tending to become finer and finer as the distance increases and the water deepens. The bed of the Atlantic from 400 to 2000 fathoms is covered with an ooze, or very fine chalky deposit, consisting to a great extent of minute and more or less broken shells, especially those of Globigerina. At still greater depths the carbonate of lime gradually disappears, and the bottom consists of fine red clay, with numerous minute particles, some of volcanic, some of meteoric, origin, fragments of shooting stars, over 100,000,000 of which are said to strike the surface of our earth every year. How slow the process of deposition must be, may be inferred from the fact that the trawl sometimes brings up many teeth of Sharks and ear-bones of Whales (in one case no less than 600 teeth and 100 ear-bones), often semi-fossil, and which from their great density had remained intact for ages, long after all the softer parts had perished and disappeared. The greatest depth of the Ocean appears to coincide roughly with the greatest height of the mountains. There are indeed cases recorded in which it is said that "no bottom" was found even at 39,000 feet. It is, however, by no means easy to sound at such great depths, and it is now generally considered that these earlier observations are untrustworthy. The greatest depth known in the Atlantic is 3875 fathoms--a little to the north of the Virgin Islands, but the soundings as yet made in the deeper parts of the Ocean are few in number, and it is not to be supposed that the greatest depth has yet been ascertained. CORAL ISLANDS In many parts of the world the geography itself has been modified by the enormous development of animal life. Most islands fall into one of three principal categories: Firstly, Those which are in reality a part of the continent near which they lie, being connected by comparatively shallow water, and standing to the continent somewhat in the relation of planets to the sun; as, for instance, the Cape de Verde Islands to Africa, Ceylon to India, or Tasmania to Australia. Secondly, Volcanic islands; and Thirdly, Those which owe their origin to the growth of Coral reefs. [Illustration: Fig. 49.--Whitsunday Island.] Coral islands are especially numerous in the Indian and Pacific Oceans, where there are innumerable islets, in the form of rings, or which together form rings, the rings themselves being sometimes made up of ringlets. These "atolls" contain a circular basin of yellowish green, clear, shallow water, while outside is the dark blue deep water of the Ocean. The islands themselves are quite low, with a beach of white sand rising but a few feet above the level of the water, and bear generally groups of tufted Cocoa Palms. It used to be supposed that these were the summits of submarine volcanoes on which the coral had grown. But as the reef-making coral does not live at greater depths than about twenty-five fathoms, the immense number of these reefs formed an almost insuperable objection to this theory. The Laccadives and Maldives for instance--meaning literally the "lac of or 100,000 islands," and the "thousand islands"--are a series of such atolls, and it was impossible to imagine so great a number of craters, all so nearly of the same altitude. In shallow tracts of sea, coral reefs no doubt tend to assume the well-known circular form, but the difficulty was to account for the numerous atolls which rise to the surface from the abysses of the ocean, while the coral-forming zoophytes can only live near the surface. Darwin showed that so far from the ring of corals resting on a corresponding ridge of rocks, the lagoons, on the contrary, now occupy the place which was once the highest land. He pointed out that some lagoons, as for instance that of Vanikoro, contain an island in the middle; while other islands, such as Tahiti, are surrounded by a margin of smooth water separated from the ocean by a coral reef. Now if we suppose that Tahiti were to sink slowly it would gradually approximate to the condition of Vanikoro; and if Vanikoro gradually sank, the central island would disappear, while on the contrary the growth of the coral might neutralise the subsidence of the reef, so that we should have simply an atoll with its lagoon. The same considerations explain the origin of the "barrier reefs," such as that which runs for nearly a thousand miles, along the north-east coast of Australia. Thus Darwin's theory explains the form and the approximate identity of altitude of these coral islands. But it does more than this, because it shows that there are great areas in process of subsidence, which though slow, is of great importance in physical geography. The lagoon islands have received much attention; which "is not surprising, for every one must be struck with astonishment, when he first beholds one of these vast rings of coral-rock, often many leagues in diameter, here and there surmounted by a low verdant island with dazzling white shores, bathed on the outside by the foaming breakers of the ocean, and on the inside surrounding a calm expanse of water, which, from reflection is generally of a bright but pale green colour. The naturalist will feel this astonishment more deeply after having examined the soft and almost gelatinous bodies of these apparently insignificant coral-polypifers, and when he knows that the solid reef increases only on the outer edge, which day and night is lashed by the breakers of an ocean never at rest. Well did François Pyrard de Laval, in the year 1605 exclaim, 'C'est une merveille de voir chacun de ces atollons, environné d'un grand banc de pierre tout autour, n'y ayant point d'artifice humain.'"[62] Of the enchanting beauty of the coral beds themselves we are assured that language conveys no adequate idea. "There were corals," says Prof. Ball, "which, in their living state, are of many shades of fawn, buff, pink, and blue, while some were tipped with a magenta-like bloom. Sponges which looked as hard as stone spread over wide areas, while sprays of coralline added their graceful forms to the picture. Through the vistas so formed, golden-banded and metallic-blue fish meandered, while on the patches of sand here and there Holothurias and various mollusca and crustaceans might be seen slowly crawling." Abercromby also gives a very graphic description of a Coral reef. "As we approached," he says, "the roaring surf on the outside, fingery lumps of beautiful live coral began to appear of the palest lavender-blue colour; and when at last we were almost within the spray, the whole floor was one mass of living branches of coral. "But it is only when venturing as far as is prudent into the water, over the outward edge of the great sea wall, that the true character of the reef and all the beauties of the ocean can be really seen. After walking over a flat uninteresting tract of nearly bare rock, you look down and see a steep irregular wall, expanding deeper into the ocean than the eye can follow, and broken into lovely grottoes and holes and canals, through which small resplendent fish of the brightest blue or gold flit fitfully between the lumps of coral. The sides of these natural grottoes are entirely covered with endless forms of tender-coloured coral, but all beautiful, and all more or less of the fingery or branching species, known as madrepores. It is really impossible to draw or describe the sight, which must be taken with all its surroundings as adjuncts."[63] The vegetation of these fairy lands is also very lovely; the Coral tree (Erythrina) with light green leaves and bunches of scarlet blossoms, the Cocoa-nut always beautiful, the breadfruit, the graceful tree ferns, the Barringtonia, with large pink and white flowers, several species of Convolvulus, and many others unknown to us even by name. THE SOUTHERN SKIES In considering these exquisite scenes, the beauty of the Southern skies must not be omitted. "From the time we entered the torrid zone," says Humboldt, "we were never wearied with admiring, every night, the beauty of the southern sky, which, as we advanced towards the south, opened new constellations to our view. We feel an indescribable sensation, when, on approaching the equator, and particularly on passing from one hemisphere to the other, we see those stars which we have contemplated from our infancy, progressively sink, and finally disappear. Nothing awakens in the traveller a livelier remembrance of the immense distance by which he is separated from his country, than the aspect of an unknown firmament. The grouping of the stars of the first magnitude, some scattered nebulæ rivalling in splendour the milky way, and tracts of space remarkable for their extreme blackness, give a particular physiognomy to the southern sky. This sight fills with admiration even those, who, uninstructed in the branches of accurate science, feel the same emotions of delight in the contemplation of the heavenly vault, as in the view of a beautiful landscape, or a majestic river. A traveller has no need of being a botanist to recognise the torrid zone on the mere aspect of its vegetation; and, without having acquired any notion of astronomy, he feels he is not in Europe, when he sees the immense constellation of the Ship, or the phosphorescent clouds of Magellan, arise on the horizon. The heaven and the earth, in the equinoctial regions, assume an exotic character." "The sunsets in the Eastern Archipelago," says H. O. Forbes,[64] "were scenes to be remembered for a lifetime. The tall cones of Sibissie and Krakatoa rose dark purple out of an unruffled golden sea, which stretched away to the south-west, where the sun went down; over the horizon gray fleecy clouds lay in banks and streaks, above them pale blue lanes of sky, alternating with orange bands, which higher up gave place to an expanse of red stretching round the whole heavens. Gradually as the sun retreated deeper and deeper, the sky became a marvellous golden curtain, in front of which the gray clouds coiled themselves into weird forms before dissolving into space...." THE POLES The Arctic and Antarctic regions have always exercised a peculiar fascination over the human mind. Until now every attempt to reach the North Pole has failed, and the South has proved even more inaccessible. In the north, Parry all but reached lat. 83; in the south no one has penetrated beyond lat. 71.11. And yet, while no one can say what there may be round the North Pole, and some still imagine that open water might be found there, we can picture to ourselves the extreme South with somewhat more confidence. Whenever ships have sailed southwards, except at a few places where land has been met with, they have come at last to a wall of ice, from fifty to four hundred feet high. In those regions it snows, if not incessantly, at least very frequently, and the snow melts but little. As far as the eye can reach nothing is to be seen but snow. Now this snow must gradually accumulate, and solidify into ice, until it attains such a slope that it will move forward as a glacier. The enormous Icebergs of the Southern Ocean, moreover, show that it does so, and that the snow of the extreme south, after condensing into ice, moves slowly outward and at length forms a wall of ice, from which Icebergs, from time to time, break away. We do not exactly know what, under such circumstances, the slope would be; but Mr. Croll points out that if we take it at only half a degree, and this seems quite a minimum, the Ice cap at the South Pole must be no less than twelve miles in thickness. It is indeed probably even more, for some of the Southern tabular icebergs attain a height of eight hundred, or even a thousand feet above water, indicating a total thickness of the ice sheet even at the edge, of over a mile. Sir James Ross mentions that--"Whilst measuring some angles for the survey near Mount Lubbock an island suddenly appeared, which he was quite sure was not to be seen two or three hours previously. He was much astonished, but it eventually turned out to be a large iceberg, which had turned over, and so exposed a new surface covered with earth and stones." The condition of the Arctic regions is quite different. There is much more land, and no such enormous solid cap of ice. Spitzbergen, the land of "pointed mountains," is said to be very beautiful. Lord Dufferin describes his first view of it as "a forest of thin lilac peaks, so faint, so pale, that had it not been for the gem-like distinctness of their outline one could have deemed them as unsubstantial as the spires of Fairyland." It is, however, very desolate; scarcely any vegetation excepting a dark moss, and even this goes but a little way up the mountain side. Scoresby ascended one of the hills near Horn Sound, and describes the view as "most extensive and grand. A fine sheltered bay was seen to the east of us, an arm of the same on the north-east, and the sea, whose glassy surface was unruffled by a breeze, formed an immense expanse on the west; the glaciers, rearing their proud crests almost to the tops of mountains between which they were lodged, and defying the power of the solar beams, were scattered in various directions about the sea-coast and in the adjoining bays. Beds of snow and ice filling extensive hollows, and giving an enamelled coat to adjoining valleys, one of which, commencing at the foot of the mountain where we stood, extended in a continual line towards the north, as far as the eye could reach--mountain rising above mountain, until by distance they dwindled into insignificance, the whole contrasted by a cloudless canopy of deepest azure, and enlightened by the rays of a blazing sun, and the effect, aided by a feeling of danger, seated as we were on the pinnacle of a rock almost surrounded by tremendous precipices--all united to constitute a picture singularly sublime." One of the glaciers of Spitzbergen is 11 miles in breadth when it reaches the sea-coast, the highest part of the precipitous front adjoining the sea being over 400 feet, and it extends far upwards towards the summit of the mountain. The surface forms an inclined plane of smooth unsullied snow, the beauty and brightness of which render it a conspicuous landmark on that inhospitable shore. From the perpendicular face great masses of ice from time to time break away, Whose blocks of sapphire seem to mortal eye Hewn from cærulean quarries of the sky.[65] Field ice is comparatively flat, though it may be piled up perhaps as much as 50 feet. It is from glaciers that true icebergs, the beauty and brilliance of which Arctic travellers are never tired of describing, take their origin. The attempts to reach the North Pole have cost many valuable lives; Willoughby and Hudson, Behring and Franklin, and many other brave mariners; but yet there are few expeditions more popular than those to "the Arctic," and we cannot but hope that it is still reserved for the British Navy after so many gallant attempts at length to reach the North Pole. FOOTNOTES: [56] Shelley. [57] Campbell. [58] Holmes. [59] Bell. [60] Hemans. [61] Gunther, _History of Fishes_. [62] Darwin, _Coral Reefs_. [63] Abercromby, _Seas and Skies in many Latitudes_. [64] _A Naturalist's Wanderings in the Eastern Archipelago._ [65] Montgomery. CHAPTER X THE STARRY HEAVENS A man can hardly lift up his eyes towards the heavens without wonder and veneration, to see so many millions of radiant lights, and to observe their courses and revolutions, even without any respect to the common good of the Universe.--SENECA. CHAPTER X THE STARRY HEAVENS Many years ago I paid a visit to Naples, and ascended Vesuvius to see the sun rise from the top of the mountain. We went up to the Observatory in the evening and spent the night outside. The sky was clear; at our feet was the sea, and round the bay the lights of Naples formed a lovely semicircle. Far more beautiful, however, were the moon and the stars overhead; the moon throwing a silver path over the water, and the stars shining in that clear atmosphere with a brilliance which I shall never forget. For ages and ages past men have admired the same glorious spectacle, and yet neither the imagination of Man nor the genius of Poetry had risen to the truer and grander conceptions of the Heavens for which we are indebted to astronomical Science. The mechanical contrivances by which it was attempted to explain the movements of the heavenly bodies were clumsy and prosaic when compared with the great discovery of Newton. Ruskin is unjust I think when he says "Science teaches us that the clouds are a sleety mist; Art, that they are a golden throne." I should be the last to disparage the debt we owe to Art, but for our knowledge, and even more, for our appreciation, feeble as even yet it is, of the overwhelming grandeur of the Heavens, we are mainly indebted to Science. There is scarcely a form which the fancy of Man has not sometimes detected in the clouds,--chains of mountains, splendid cities, storms at sea, flights of birds, groups of animals, monsters of all kinds,--and our superstitious ancestors often terrified themselves by fantastic visions of arms and warriors and battles which they regarded as portents of coming calamities. There is hardly a day on which Clouds do not delight and surprise us by their forms and colours. They belong, however, to our Earth, and I must now pass on to the heavenly bodies. [Illustration: THE MOON. _To face page 377._] THE MOON The Moon is the nearest, and being the nearest, appears to us, with the single exception of the Sun, the largest, although it is in reality one of the smallest, of the heavenly bodies. Just as the Earth goes round the Sun, and the period of revolution constitutes a year, so the Moon goes round the Earth approximately in a period of one month. But while we turn on our axis every twenty-four hours, thus causing the alternation of light and darkness--day and night--the Moon takes a month to revolve on hers, so that she always presents the same, or very nearly the same, surface to us. Seeing her as we do, not like the Sun and Stars, by light of her own, but by the reflected light of the Sun, her form appears to change, because the side upon which the Sun shines is not always that which we see. Hence the "phases" of the Moon, which add so much to her beauty and interest. Who is there who has not watched them with admiration? "We first see her as an exquisite crescent of pale light in the western sky after sunset. Night after night she moves further and further to the east, until she becomes full, and rises about the same time that the Sun sets. From the time of full moon the disc of light begins to diminish, until the last quarter is reached. Then it is that the Moon is seen high in the heavens in the morning. As the days pass by, the crescent shape is again assumed. The crescent wanes thinner and thinner as the Moon draws closer to the Sun. Finally, she becomes lost in the overpowering light of the Sun, again to emerge as the new moon, and again to go through the same cycle of changes."[66] But although she is so small the Moon is not only, next to the Sun, by far the most beautiful, but also for us the most important, of the heavenly bodies. Her attraction, aided by that of the Sun, causes the tides, which are of such essential service to navigation. They carry our vessels in and out of port, and, indeed, but for them many of our ports would themselves cease to exist, being silted up by the rivers running into them. The Moon is also of invaluable service to sailors by enabling them to determine where they are, and guiding them over the pathless waters. The geography of the Moon, so far as concerns the side turned towards us, has been carefully mapped and studied, and may almost be said to be as well known as that of our own earth. The scenery is in a high degree weird and rugged; it is a great wilderness of extinct volcanoes, and, seen with even a very moderate telescope, is a most beautiful object. The mountains are of great size. Our loftiest mountain, Mount Everest, is generally stated as about 29,000 feet in height. The mountains of the Moon reach an altitude of over 42,000, but this reckons to the lowest depression, and it must be remembered that we reckon the height of mountains to the sea level only. Several of the craters on the Moon have a diameter of 40 or 50--one of them even as much as 78--miles. Many also have central cones, closely resembling those in our own volcanic regions. In some cases the craters are filled nearly to the brim with lava. The volcanoes seem, however, to be all extinct; and there is not a single case in which we have conclusive evidence of any change in a lunar mountain. [Illustration: Fig. 50.--A group of Lunar Volcanoes.] The Moon, being so much smaller than the earth, cooled, of course, much more rapidly, and it is probable that these mountains are millions of years old--much older than many of our mountain chains. Yet no one can look at a map of the Moon without being struck with the very rugged character of its mountain scenery. This is mainly due to the absence of air and water. To these two mighty agencies, not merely "the cloud-capped towers, the gorgeous palaces, the solemn temples," but the very mountains themselves, are inevitable victims. Not merely storms and hurricanes, but every gentle shower, every fall of snow, tends to soften our scenery and lower the mountain peaks. These agencies are absent from the Moon, and the mountains stand to-day just as they were formed millions of years ago. But though we find on our own globe (see, for instance, Fig. 21) volcanic regions closely resembling those of the Moon, there are other phenomena on the Moon's surface for which our earth presents as yet no explanation. From Tycho, for instance, a crater 17,000 feet high and 50 miles across, a number of rays or streaks diverge, which for hundreds, or in some cases two or three thousand, miles pass straight across plains, craters, and mountains. The true nature of these streaks is not yet understood. THE SUN The Sun is more than 400 times as distant as the Moon; a mighty glowing globe, infinitely hotter than any earthly fiery furnace, 300,000 times as heavy, and 1,000,000 times as large as the earth. Its diameter is 865,000 miles, and it revolves on its axis in between 25 and 26 days. Its distance is 92,500,000 miles. And yet it is only a star, and by no means one of the first magnitude. The surface of the Sun is the seat of violent storms and tempests. From it gigantic flames, consisting mainly of hydrogen, flicker and leap. Professor Young describes one as being, when first observed, 40,000 miles high. Suddenly it became very brilliant, and in half an hour sprang up 40,000 more. For another hour it soared higher and higher, reaching finally an elevation of no less than 350,000 miles, after which it slowly faded away, and in a couple of hours had entirely disappeared. This was no doubt an exceptional case, but a height of 100,000 miles is not unusual, and the velocity frequently reaches 100 miles in a second. The proverbial spots on the Sun in many respects resemble the appearances which would be presented if a comparatively dark central mass was here and there exposed by apertures through the more brilliant outer gases, but their true nature is still a matter of discussion. During total eclipses it is seen that the Sun is surrounded by a "corona," or aureola of light, consisting of radiant filaments, beams, and sheets of light, which radiate in all directions, and the true nature of which is still doubtful. Another stupendous problem connected with the Sun is the fact that, as geology teaches us, it has given off nearly the same quantity of light and heat for millions of years. How has this come to pass? Certainly not by any process of burning such as we are familiar with. Indeed, if the heat of the Sun were due to combustion it would be burnt up in 6000 years. It has been suggested that the meteors, which fall in showers on to the Sun, replace the heat which is emitted. To some slight extent perhaps they do so, but the main cause seems to be the slow condensation of the Sun itself. Mathematicians tell us that a contraction of about 220 feet a year would account for the whole heat emitted, and as the present diameter of the Sun is about 860,000 miles, the potential store of heat is still enormous. To the Sun we owe our light and heat; it is not only the centre of our planetary system, it is the source and ruler of our lives. It draws up water from the ocean, and pours it down in rain to fill the rivers and refresh the plants; it raises the winds, which purify the air and waft our ships over the seas; it draws our carriages and drives our steam-engines, for coal is but the heat of former ages stored up for our use; animals live and move by the Sun's warmth; it inspires the song of birds, paints the flowers, and ripens the fruit. Through it the trees grow. For the beauties of nature, for our food and drink, for our clothing, for our light and life, for the very possibility of our existence, we are indebted to the Sun. What is the Sun made of? Comte mentioned as a problem, which it was impossible that man could ever solve, any attempt to determine the chemical composition of the heavenly bodies. "Nous concevons," he said, "la possibilité de déterminer leurs formes, leurs distances, leurs grandeurs, et leurs mouvements, tandis que nous ne saurions jamais étudier par aucun moyen leur composition chimique ou leur structure minéralogique." To do so might well have seemed hopeless, and yet the possibility has been proved, and a beginning has been made. In the early part of this century Wollaston observed that the bright band of colours thrown by a prism, and known as the spectrum, was traversed by dark lines, which were also discovered, and described more in detail, by Fraunhofer, after whom they are generally called "Fraunhofer's lines." The next step was made by Wheatstone, who showed that the spectrum formed by incandescent vapours was formed of bright lines, which differed for each substance, and might, therefore, be used as a convenient mode of analysis. In fact, by this process several new substances have actually been discovered. These bright lines were found on comparison to coincide with the dark lines in the spectrum, and to Kirchhoff and Bunsen is due the credit of applying this method of research to astronomical science. They arranged their apparatus so that one-half was lighted by the Sun, the other by the incandescent gas they were examining. When the vapour of sodium was treated in this way they found that the bright line in the flame of soda exactly coincided with a line in the Sun's spectrum. The conclusion was obvious; there is sodium in the Sun. It must, indeed, have been a glorious moment when the thought flashed upon them; and the discovery, with its results, is one of the greatest triumphs of human genius. The Sun has thus been proved to contain hydrogen, sodium, barium, magnesium, calcium, aluminium, chromium, iron, nickle, manganese, titanium, cobalt, lead, zinc, copper, cadmium, strontium, cerium, uranium, potassium, etc., in all 36 of our terrestrial elements, while as regards some others the evidence is not conclusive. We cannot as yet say that any of our elements are absent, nor though there are various lines which cannot as yet be certainly referred to any known substance, have we clear proof that the Sun contains any element which does not exist on our earth. On the whole, then, the chemical composition of the Sun appears closely to resemble that of our earth. THE PLANETS The Syrian shepherds watching their flocks by night long ago noticed--and they were probably not the first--that there were five stars which did not follow the regular course of the rest, but, apparently at least, moved about irregularly. These they appropriately named Planets, or wanderers. Further observations have shown that this irregularity of their path is only apparent, and that, like our own Earth, they really revolve round the Sun. To the five first observed--Mercury, Venus, Mars, Jupiter, and Saturn--two large ones, Uranus and Neptune, and a group of minor bodies, have since been added. The following two diagrams give the relative orbits of the Planets. [Illustration: Fig. 51.--Orbits of the inner Planets.] MERCURY It is possible, perhaps probable, that there may be an inner Planet, but, so far as we know for certain, Mercury is the one nearest to the Sun, its average distance being 36,000,000 miles. It is much smaller than the Earth, its weight being only about 1/24th of ours. Mercury is a shy though beautiful object, for being so near the Sun it is not easily visible; it may, however, generally be seen at some time or other during the year as a morning or evening star. [Illustration: Fig. 52.--Relative distances of the Planets from the Sun.] VENUS The true morning or evening star, however, is Venus--the peerless and capricious Venus. Venus, perhaps, "has not been noticed, not been thought of, for many months. It is a beautifully clear evening; the sun has just set. The lover of nature turns to admire the sunset, as every lover of nature will. In the golden glory of the west a beauteous gem is seen to glisten; it is the evening star, the planet Venus. A week or two later another beautiful sunset is seen, and now the planet is no longer a glistening point low down; it has risen high above the horizon, and continues a brilliant object long after the shades of night have descended. Again a little longer and Venus has gained its full brilliancy and splendour. All the heavenly host--even Sirius and Jupiter--must pale before the splendid lustre of Venus, the unrivalled queen of the firmament."[67] Venus is about as large as our Earth, and when at her brightest outshines about fifty times the most brilliant star. Yet, like all the other planets, she glows only with the reflected light of the Sun, and consequently passes through phases like those of the Moon, though we cannot see them with the naked eye. To Venus also owe we mainly the power of determining the distance, and consequently the magnitude, of the Sun. THE EARTH Our own Earth has formed the subject of previous chapters. I will now, therefore, only call attention to her movements, in which, of course, though unconsciously, we participate. In the first place, the Earth revolves on her axis in 24 hours. Her circumference at the tropics is 24,000 miles. Hence a person at the tropics is moving in this respect at the rate of 1000 miles an hour, or over 16 miles a minute. But more than this, astronomers have ascertained that the whole solar system is engaged in a great voyage through space, moving towards a point on the constellation of Hercules at the rate of at least 20,000 miles an hour, or over 300 miles a minute.[68] But even more again, we revolve annually round the Sun in a mighty orbit 580,000,000 miles in circumference. In this respect we are moving at the rate of no less than 60,000 miles an hour, or 1000 miles a minute--a rate far exceeding of course, in fact by some 100 times, that of a cannon ball. How few of us know, how little we any of us realise, that we are rushing through space with such enormous velocity. MARS To the naked eye Mars appears like a ruddy star of the first magnitude. It has two satellites, which have been happily named Phobos and Deimos--Fear and Dismay. It is little more than half as large as the Earth, and, though generally far more distant, it sometimes approaches us within 35,000,000 miles. This has enabled us to study its physical structure. It seems very probable that there is water in Mars, and the two poles are tipped with white, as if capped by ice and snow. It presents also a series of remarkable parallel lines, the true nature of which is not yet understood. THE MINOR PLANETS A glance at Figs. 51 and 52 will show that the distances of the Planets from the Sun follow a certain rule. If we take the numbers 0, 3, 6, 12, 24, 48, 96, each one (after the second) the double of that preceding, and add four, we have the series. 4 7 10 16 28 52 100 Now the distances of the Planets from the Sun are as follow:-- Mercury. Venus. Earth. Mars. Jupiter. Saturn. 3.9 7.2 10 15.2 52.9 95.4 For this sequence, which was first noticed by Bode, and is known as Bode's law, no explanation can yet be given. It was of course at once observed that between Mars and Jupiter one place is vacant, and it has now been ascertained that this is occupied by a zone of Minor Planets, the first of which was discovered by Piazzi on January 1, 1801, a worthy prelude to the succession of scientific discoveries which form the glory of our century. At present over 300 are known, but certainly these are merely the larger among an immense number, some of them doubtless mere dust. JUPITER Beyond the Minor Planets we come to the stupendous Jupiter, containing 300 times the mass, and being 1200 times the size of our Earth--larger indeed than all the other planets put together. It is probably not solid, and from its great size still retains a large portion of the original heat, if we may use such an expression. Jupiter usually shows a number of belts, supposed to be due to clouds floating over the surface, which have a tendency to arrange themselves in belts or bands, owing to the rotation of the planet. Jupiter has four moons or satellites. SATURN [Illustration: Fig. 53.--Saturn.] Next to Jupiter in size, as in position, comes Saturn, which, though far inferior in dimensions, is much superior in beauty. To the naked eye Saturn appears as a brilliant star, but when Galileo first saw it through a telescope it appeared to him to be composed of three bodies in a line, a central globe with a small one on each side. Huyghens in 1655 first showed that in reality Saturn was surrounded by a series of rings (see Fig. 53). Of these there are three, the inner one very faint, and the outer one divided into two by a dark line. These rings are really enormous shoals of minute bodies revolving round the planet, and rendering it perhaps the most marvellous and beautiful of all the heavenly bodies. While we have one Moon, Mars two, and Jupiter four, Saturn has no less than eight satellites. URANUS Saturn was long supposed to be the outermost body belonging to the solar system. In 1781, however, on the 13th March, William Herschel was examining the stars in the constellation of the Twins. One struck him because it presented a distinct disc, while the true fixed stars, however brilliant, are, even with the most powerful telescope, mere points of light. At first he thought it might be a comet, but careful observations showed that it was really a new planet. Though thus discovered by Herschel it had often been seen before, but its true nature was unsuspected. It has a diameter of about 31,700 miles. Four satellites of Uranus have been discovered, and they present the remarkable peculiarity that while all the other planets and their satellites revolve nearly in one plane, the satellites of Uranus are nearly at right angles, indicating the presence of some local and exceptional influence. NEPTUNE The study of Uranus soon showed that it followed a path which could not be accounted for by the influence of the Sun and the other then known planets. It was suspected, therefore, that this was due to some other body not yet discovered. To calculate where such a body must be so as to account for these irregularities was a most complex and difficult, and might have seemed almost a hopeless, task. It was, however, solved almost simultaneously and independently by Adams in this country, and Le Verrier in France. Neptune, so far as we yet know the out-most of our companions, is 35,000 miles in diameter, and its mean distance from the Sun is 2,780,000,000 miles. ORIGIN OF THE PLANETARY SYSTEM The theory of the origin of the Planetary System known as the "Nebular Hypothesis," which was first suggested by Kant, and developed by Herschel and Laplace, may be fairly said to have attained a high degree of probability. The space now occupied by the solar system is supposed to have been filled by a rotating spheroid of extreme tenuity and enormous heat, due perhaps to the collision of two originally separate bodies. The heat, however, having by degrees radiated into space, the gas cooled and contracted towards a centre, destined to become the Sun. Through the action of centrifugal force the gaseous matter also flattened itself at the two poles, taking somewhat the form of a disc. For a certain time the tendency to contract, and the centrifugal force, counterbalanced one another, but at length a time came when the latter prevailed and the outer zone detached itself from the rest of the sphere. One after another similar rings were thrown off, and then breaking up, formed the planets and their satellites. That each planet and satellite did form originally a ring we still have evidence in the wonderful and beautiful rings of Saturn, which, however, in all probability will eventually form spherical satellites like the rest. Thus then our Earth was originally a part of the Sun, to which again it is destined one day to return. M. Plateau has shown experimentally that by rotating a globe of oil in a mixture of water and spirit having the same density this process may be actually repeated in miniature. This brilliant, and yet simple, hypothesis is consistent with, and explains many other circumstances connected with the position, magnitude, and movements of the Planets and their satellites. The Planets, for instance, lie more or less in the same plane, they revolve round the Sun and rotate on their own axis in the same direction--a series of coincidences which cannot be accidental, and for which the theory would account. Again the rate of cooling would of course follow the size; a small body cools more rapidly than a large one. The Moon is cold and rigid; the Earth is solid at the surface, but intensely hot within; Jupiter and Saturn, which are immensely larger, still retain much of their original heat, and have a much lower density than the Earth; and astronomers tell us on other grounds that the Sun itself is still contracting, and that to this the maintenance of its temperature is due. Although, therefore, the Nebular Theory cannot be said to have been absolutely proved, it has certainly been brought to a high state of probability, and is, in its main features, generally accepted by astronomers. The question has often been asked whether any of the heavenly bodies are inhabited, and as yet it is impossible to give any certain answer. It seems _à priori_ probable that the millions of suns which we see as stars must have satellites, and that some at least of them may be inhabited. So far as our own system is concerned the Sun is of course too hot to serve as a dwelling-place for any beings with bodies such as ours. The same may be said of Mercury, which is at times probably ten times as hot as our tropics. The outer planets appear to be still in a state of vapour. The Moon has no air or water. Mars is in a condition which most nearly resembles ours. All, however, that can be said is that, so far as we can see, the existence of living beings on Mars is not impossible. COMETS The Sun, Moon, and Stars, glorious and wonderful as they are, though regarded with great interest, and in some cases worshipped as deities, excited the imagination of our ancestors less than might have been expected, and even now attract comparatively little attention, from the fact that they are always with us. Comets, on the other hand, both as rare and occasional visitors, from their large size and rapid changes, were regarded in ancient times with dread and with amazement. Some Comets revolve round the Sun in ellipses, but many, if not the majority, are visitors indeed, for having once passed round the Sun they pass away again into space, never to return. The appearance which is generally regarded as characteristic of a Comet is that of a head with a central nucleus and a long tail. Many, however, of the smaller ones possess no tail, and in fact Comets present almost innumerable differences. Moreover the same Comet changes rapidly, so that when they return, they are identified not in any way by their appearance, but by the path they pursue. Comets may almost be regarded as the ghosts of heavenly bodies. The heads, in some cases, may consist of separate solid fragments, though on this astronomers are by no means agreed, but the tails at any rate are in fact of almost inconceivable tenuity. We know that a cloud a few hundred feet thick is sufficient to hide, not only the stars, but even the Sun himself. A Comet is thousands of miles in thickness, and yet even extremely minute stars can be seen through it with no appreciable diminution of brightness. This extreme tenuity of comets is moreover shown by their small weight. Enormous as they are I remember Sir G. Airy saying that there was probably more matter in a cricket ball than there is in a comet. No one, however, now doubts that the weight must be measured in tons; but it is so small, in relation to the size, as to be practically inappreciable. If indeed they were comparable in mass even to the planets, we should long ago have perished. The security of our system is due to the fact that the planets revolve round the Sun in one direction, almost in circles, and very nearly in the same plane. Comets, however, enter our system in all directions, and at all angles; they are so numerous that, as Kepler said, there are probably more Comets in the sky than there are fishes in the sea, and but for their extreme tenuity they would long ago have driven us into the Sun. When they first come in sight Comets have generally no tail; it grows as they approach the Sun, from which it always points away. It is no mere optical illusion; but while the Comet as a whole is attracted by the Sun, the tail, how or why we know not, is repelled. When once driven off, moreover, the attraction of the Comet is not sufficient to recall it, and hence perhaps so many Comets have now no tails. Donati's Comet, the great Comet of 1858, was first noticed on the 2d June as a faint nebulous spot. For three months it remained quite inconspicuous, and even at the end of August was scarcely visible to the naked eye. In September it grew rapidly, and by the middle of October the tail extended no less than 40 degrees, after which it gradually disappeared. Faint as is the light emitted by Comets, it is yet their own, and spectrum analysis has detected the presence in them of carbon, hydrogen, nitrogen, sodium, and probably of iron. Comets then remain as wonderful, and almost as mysterious, as ever, but we need no longer regard "a comet as a sign of impending calamity; we may rather look upon it as an interesting and a beautiful visitor, which comes to please us and to instruct us, but never to threaten or to destroy."[69] We are free, therefore, to admire them in peace, and beautiful, indeed, they are. "The most wonderful sight I remember," says Hamerton, "as an effect of calm, was the inversion of Donati's Comet, in the year 1858, during the nights when it was sufficiently near the horizon to approach the rugged outline of Graiganunie, and be reflected beneath it in Loch Awe. In the sky was an enormous aigrette of diamond fire, in the water a second aigrette, scarcely less splendid, with its brilliant point directed upwards, and its broad, shadowy extremity ending indefinitely in the deep. To be out on the lake alone, in a tiny boat, and let it rest motionless on the glassy water, with that incomparable spectacle before one, was an experience to be remembered through a lifetime. I have seen many a glorious sight since that now distant year, but nothing to equal it in the association of solemnity with splendour."[70] SHOOTING STARS On almost any bright night, if we watch a short time some star will suddenly seem to drop from its place, and, after a short plunge, to disappear. This appearance is, however, partly illusory. While true stars are immense bodies at an enormous distance, Shooting Stars are very small, perhaps not larger than a paving stone, and are not visible until they come within the limits of our atmosphere, by the friction with which they are set on fire and dissipated. They are much more numerous on some nights than others. From the 9th to the 11th August we pass through one cluster which is known as the Perseids; and on the 13th and 14th November a still greater group called by astronomers the Leonids. The Leonids revolve round the Sun in a period of 33 years, and in an elliptic orbit, one focus of which is about at the same distance from the Sun as we are, the other at about that of Uranus. The shoal of stars is enormous; its diameter cannot be less than 100,000 miles, and its length many hundreds of thousands. There are, indeed, stragglers scattered over the whole orbit, with some of which we come in contact every year, but we pass through the main body three times in a century--last in 1866--capturing millions on each occasion. One of these has been graphically described by Humboldt: "From half after two in the morning the most extraordinary luminary meteors were seen in the direction of the east. M. Bonpland, who had risen to enjoy the freshness of the air, perceived them first. Thousands of bodies and falling stars succeeded each other during the space of four hours. Their direction was very regular from north to south. They filled a space in the sky extending from due east 30° to north and south. In an amplitude of 60° the meteors were seen to rise above the horizon at east-north-east, and at east, to describe arcs more or less extended, and to fall towards the south, after having followed the direction of the meridian. Some of them attained a height of 40°, and all exceeded 25° or 30°. No trace of clouds was to be seen. M. Bonpland states that, from the first appearance of the phenomenon, there was not in the firmament a space equal in extent to three diameters of the moon which was not filled every instant with bolides and falling stars. The first were fewer in number, but as they were of different sizes it was impossible to fix the limit between these two classes of phenomena. All these meteors left luminous traces from five to ten degrees in length, as often happens in the equinoctial regions. The phosphorescence of these traces, or luminous bands, lasted seven or eight seconds. Many of the falling stars had a very distinct nucleus, as large as the disc of Jupiter, from which darted sparks of vivid light. The bodies seemed to burst as by explosion; but the largest, those from 1° to 1° 15' in diameter, disappeared without scintillation, leaving behind them phosphorescent bands (trabes), exceeding in breadth fifteen or twenty minutes. The light of these meteors was white, and not reddish, which must doubtless be attributed to the absence of vapour and the extreme transparency of the air."[71] The past history of the Leonids, which Le Verrier has traced out with great probability, if not proved, is very interesting. They did not, he considers, approach the Sun until 126 A.D., when, in their career through the heavens, they chanced to come near to Uranus. But for the influence of that planet they would have passed round the Sun, and then departed again for ever. By his attraction, however, their course was altered, and they will now continue to revolve round the Sun. There is a remarkable connection between star showers and comets, which, however, is not yet thoroughly understood. Several star showers follow paths which are also those of comets, and the conclusion appears almost irresistible that these comets are made up of Shooting Stars. We are told, indeed, that 150,000,000 of meteors, including only those visible with a moderate telescope, fall on the earth annually. At any rate, there can be no doubt that every year millions of them are captured by the earth, thus constituting an appreciable, and in the course of ages a constantly increasing, part of the solid substance of the globe. THE STARS We have been dealing in the earlier part of this chapter with figures and distances so enormous that it is quite impossible for us to realise them; and yet we have still others to consider compared with which even the solar system is insignificant. In the first place, the number of the Stars is enormous. When we look at the sky at night they seem, indeed, almost innumerable; so that, like the sands of the sea, the Stars of heaven have ever been used as effective symbols of number. The total number visible to the naked eye is, however, in reality only about 3000, while that shown by the telescope is about 100,000,000. Photography, however, has revealed to us the existence of others which no telescope can show. We cannot by looking long at the heavens see more than at first; in fact, the first glance is the keenest. In photography, on the contrary, no light which falls on the plate, however faint, is lost; it is taken in and stored up. In an hour the effect is 3600 times as great as in a second. By exposing the photographic plate, therefore, for some hours, and even on successive nights, the effect of the light is as it were accumulated, and stars are rendered visible, the light of which is too feeble to be shown by any telescope. The distances and magnitudes of the Stars are as astonishing as their numbers, Sirius, for instance, being about twenty times as heavy as the Sun itself, 50 times as bright, and no less than 1,000,000 times as far away; while, though like other stars it seems to us stationary, it is in reality sweeping through the heavens at the rate of 1000 miles a minute; Maia, Electra, and Alcyone, three of the Pleiades, are considered to be respectively 400, 480, and 1000 times as brilliant as the Sun, Canopus 2500 times, and Arcturus, incredible as it may seem, even 8000 times, so that, in fact, the Sun is by no means one of the largest Stars. Even the minute Stars not separately visible to the naked eye, and the millions which make up the Milky Way, are considered to be on an average fully equal to the Sun in lustre. Arcturus is, so far as we know at present, the swiftest, brightest, and largest of all. Its speed is over 300 miles a second, it is said to be 8000 times as bright as the Sun, and 80 times as large, while its distance is so great that its light takes 200 years in reaching us. The distances of the heavenly bodies are ascertained by what is known as "parallax." Suppose the ellipse (Fig. 54), marked Jan., Apr., July, Oct., represents the course of the Earth round the Sun, and that A B are two stars. If in January we look at the star A, we see it projected against the front of the sky marked 1. Three months later it would appear to be at 2, and thus as we move round our orbit the star itself appears to move in the ellipse 1, 2, 3, 4. The more distant star B also appears to move in a similar, but smaller, ellipse; the difference arising from the greater distance. The size of the ellipse is inversely proportional to the distance, and hence as we know the magnitude of the earth's orbit we can calculate the distance of the star. The difficulty is that the apparent ellipses are so minute that it is in very few cases possible to measure them. [Illustration: Fig. 54.--The Parallactic Ellipse.] The distances of the Fixed Stars thus tested are found to be enormous, and indeed generally incalculable; so great that in most cases, whether we look at them from one end of our orbit or the other--though the difference of our position, corresponding to the points marked January and July in Fig. 54, is 185,000,000 miles--no apparent change of position can be observed. In some, however, the parallax, though very minute, is yet approximately measurable. The first star to which this test was applied with success was that known as 61 Cygni, which is thus shown to be no less than 40 billions of miles away from us--many thousand times as far as we are from the Sun. The nearest of the Stars, so far as we yet know, is [Greek: alpha] Centauri, the distance of which is about 25 billions of miles. The Pleiades are considered to be at a distance of nearly 1500 billions of miles. As regards the chemical composition of the Stars, it is, moreover, obvious that the powerful engine of investigation afforded us by the spectroscope is by no means confined to the substances which form part of our system. The incandescent body can thus be examined, no matter how great its distance, so long only as the light is strong enough. That this method was theoretically applicable to the light of the Stars is indeed obvious, but the practical difficulties are very great. Sirius, the brightest of all, is, in round numbers, a hundred millions of millions of miles from us; and, though as bright as fifty of our suns, his light when it reaches us, after a journey of sixteen years, is at most one two-thousand-millionth part as bright. Nevertheless, as long ago as 1815 Fraunhofer recognised the fixed lines in the light of four of the Stars; in 1863 Miller and Huggins in our own country, and Rutherford in America, succeeded in determining the dark lines in the spectrum of some of the brighter Stars, thus showing that these beautiful and mysterious lights contain many of the material substances with which we are familiar. In Aldebaran, for instance, we may infer the presence of hydrogen, sodium, magnesium, iron, calcium, tellurium, antimony, bismuth, and mercury. As might have been expected, the composition of the Stars is not uniform, and it would appear that they may be arranged in a few well-marked classes, indicating differences of temperature, or perhaps of age. Thus we can make the Stars teach us their own composition with light, which started from its source years ago, in many cases long before we were born. Spectrum analysis has also thrown an unexpected light on the movements of the Stars. Ordinary observation, of course, is powerless to inform us whether they are moving towards or away from us. Spectrum analysis, however, enables us to solve the problem, and we know that some are approaching, some receding. [Illustration: Fig. 55.--Displacement of the hydrogen line in the spectrum of Rigel.] If a star, say for instance Sirius, were motionless, or rather if it retained a constant distance from the earth, Fraunhofer's lines would occupy exactly the same position in the spectrum as they do in that of the Sun. On the contrary, if Sirius were approaching, the lines would be slightly shifted towards the blue, or if it were receding towards the red. Fig. 55 shows the displacement of the hydrogen line in the spectrum of Rigel, due to the fact that it is receding from us at the rate of 39 miles a second. The Sun affords us an excellent test of this theory. As it revolves on its axis one edge is always approaching and the other receding from us at a known rate, and observation shows that the lines given by the light of the two edges differ accordingly. So again as regards the Stars, we obtain a similar test derived from the Earth's movement. As we revolve in our orbit we approach or recede any given star, and our rate of motion being known we thus obtain a second test. The results thus examined have stood their ground satisfactorily, and in Huggins' opinion may be relied on within about an English mile a second. The effect of this movement is, moreover, independent of the distance. A lateral motion, say of 20 miles a second, which in a nearer object would appear to be a stupendous velocity, becomes in the Stars quite imperceptible. A motion of the same rapidity, on the other hand, towards or away from us, displaces the dark lines equally, whatever the distance of the object may be. We may then affirm that Sirius, for instance, is receding from us at the rate of about 20 miles a second. Betelgeux, Rigel, Castor, Regulus, and others are also moving away; while some--Vega, Arcturus, and Pollux, for example--are approaching us. By the same process it is shown that some groups of stars are only apparently in relation to one another. Thus in Charles' Wain some of the stars are approaching, others receding. I have already mentioned that Sirius, though it seems, like other stars, so stationary that we speak of them as "fixed," is really sweeping along at the rate of 1000 miles a minute. Even this enormous velocity is exceeded in other cases. One, which is numbered as 1830 in Groombridge's _Catalogue of the Stars_, and is therefore known as "Groombridge's 1830," moves no less than 12,000 miles a minute, and Arcturus 22,000 miles a minute, or 32,000,000 of miles a day; and yet the distances of the Stars are so great that 1000 years would make hardly any difference in the appearance of the heavens. Changes, however, there certainly would be. Even in the short time during which we have any observations, some are already on record. One of the most interesting is the fading of the 7th Pleiad, due, according to Ovid, to grief at the taking of Troy. Again, the "fiery Dogstar," as it used to be, is now, and has been for centuries, a clear white. The star known as Nova Cygni--the "new star in the Constellation of the Swan"--was first observed on the 24th November 1876 by Dr. Schmidt of Athens, who had examined that part of the heavens only four days before, and is sure that no such star was visible then. At its brightest it was a brilliant star of the third magnitude, but this only lasted for a few days; in a week it had ceased to be a conspicuous object, and in a fortnight became invisible without a telescope. Its sudden splendour was probably due to a collision between two bodies, and was probably little, if at all, less than that of the Sun itself. It is still a mystery how so great a conflagration can have diminished so rapidly. But though we speak of some stars as specially variable, they are no doubt all undergoing slow change. There was a time when they were not, and one will come when they will cease to shine. Each, indeed, has a life-history of its own. Some, doubtless, represent now what others once were, and what many will some day become. For, in addition to the luminous heavenly bodies, we cannot doubt that there are countless others invisible to us, some from their greater distance or smaller size, but others, doubtless, from their feebler light; indeed, we know that there are many dark bodies which now emit no light, or comparatively little. Thus in the case of Procyon the existence of an invisible body is proved by the movement of the visible star. Again, I may refer to the curious phenomena presented by Algol, a bright star in the head of Medusa. The star shines without change for two days and thirteen hours; then in three hours and a half dwindles from a star of the second to one of the fourth magnitude; and then, in another three and a half hours, reassumes its original brilliancy. These changes led astronomers to infer the presence of an opaque body, which intercepts at regular intervals a part of the light emitted by Algol; and Vogel has now shown by the aid of the spectroscope that Algol does in fact revolve round a dark, and therefore invisible, companion. The spectroscope, in fact, makes known to us the presence of many stars which no telescope could reveal. Thus the floor of heaven is not only "thick inlaid with patines of bright gold," but studded also with extinct stars, once probably as brilliant as our own Sun, but now dead and cold, as Helmholtz tells us that our Sun itself will be some seventeen millions of years hence. Such dark bodies cannot of course be seen, and their existence, though we cannot doubt it, is a matter of calculation. In one case, however, the conclusion has received a most interesting confirmation. The movements of Sirius led mathematicians to conclude that it had also a mighty and massive neighbour, the relative position of which they calculated, though no such body had ever been seen. In February 1862, however, the Messrs. Alvan Clark of Cambridgeport were completing their 18-inch glass for the Chicago Observatory. "'Why, father,'" exclaimed the younger Clark, "'the star has a companion.' The father looked, and there was a faint star due east from the bright one, and distant about ten seconds. This was exactly the predicted direction for that time, though the discoverers knew nothing of it. As the news went round the world many observers turned their attention to Sirius; and it was then found that, though it had never before been noticed, the companion was really shown under favourable circumstances by any powerful telescope. It is, in fact, one-half of the size of Sirius, though only 1/10000th of the brightness."[72] Stars are, we know, of different magnitudes and different degrees of glory. They are also of different colours. Most, indeed, are white, but some reddish, some ruddy, some intensely red; others, but fewer, green, blue, or violet. It is possible that the comparative rarity of these colours is due to the fact that our atmosphere especially absorbs green and blue, and it is remarkable that almost all of the green, blue, or violet stars are one of the pairs of a Double Star, and in every case the smaller one of the two, the larger being red, orange, or yellow. One of the most exquisite of these is [Greek: beta] Cygni, a Double Star, the larger one being golden yellow, the smaller light blue. With a telescope the effect is very beautiful, but it must be magnificent if one could only see it from a lesser distance. Double Stars occur in considerable numbers. In some cases indeed the relation may only be apparent, one being really far in front of the other. In very many cases, however, the association is real, and they revolve round one another. In some cases the period may extend to thousands of years; for the distance which separates them is enormous, and, even when with a powerful telescope it is indicated only by a narrow dark line, amounts to hundreds of millions of miles. The Pole Star itself is double. Andromeda is triple, with perhaps a fourth dark and therefore invisible companion. These dark bodies have a special interest, since it is impossible not to ask ourselves whether some at any rate of them may not be inhabited. In [Greek: epsilon] Lyræ there are two, each again being itself double. [Greek: xi] Cancri, and probably also [Greek: theta] Orionis, consist of six stars, and from such a group we pass on to Star Clusters in which the number is very considerable. The cluster in Hercules consists of from 1000 to 4000. A stellar swarm in the Southern Cross contains several hundred stars of various colours, red, green, greenish blue, and blue closely thronged together, so that they have been compared to a "superb piece of fancy jewellery."[73] The cluster in the Sword Handle of Perseus contains innumerable stars, many doubtless as brilliant as our Sun. We ourselves probably form a part of such a cluster. The Milky Way itself, as we know, entirely surrounds us; it is evident, therefore, that the Sun, and of course we ourselves, actually lie in it. It is, therefore, a Star Cluster, one of countless numbers, and containing our Sun as a single unit. It has as yet been found impossible to determine even approximately the distance of these Star Clusters. NEBULÆ From Stars we pass insensibly to Nebulæ, which are so far away that their distance is at present quite immeasurable. All that we can do is to fix a minimum, and this is so great that it is useless to express it in miles. Astronomers, therefore, take the velocity of light as a unit. It travels at the rate of 180,000 miles a second, and even at this enormous velocity it must have taken hundreds of years to reach us, so that we see them not as they now are but as they were hundreds of years ago. It is no wonder, therefore, that in many of these clusters it is impossible to distinguish the separate stars of which they are composed. As, however, our telescopes are improved, more and more clusters are being resolved. Photography also comes to our aid, and, as already mentioned, by long exposure stars can be made visible which are quite imperceptible to the eye, even with aid of the most powerful telescope. Spectrum analysis also seems to show that such a nebula as that in Andromeda, which with our most powerful instruments appears only as a mere cloud, is really a vast cluster of stellar points. This, however, by no means applies to all the nebulæ. The spectrum of a star is a bright band of colour crossed by dark lines; that of a gaseous nebula consists of bright lines. This test has been made use of, and indicates that some of the nebulæ are really immense masses of incandescent and very attenuated gas; very possibly, however, in a condition of which we have no experience, and arranged in discs, bands, rings, chains, wisps, knots, rays, curves, ovals, spirals, loops, wreaths, fans, brushes, sprays, lace, waves, and clouds. Huggins has shown that many of them are really stupendous masses of glowing gas, especially of hydrogen, and perhaps of nitrogen, while the spectrum also shows other lines which perhaps may indicate some of the elements which, so far as our Earth is concerned, appear to be missing between hydrogen and lithium. Many of the nebulæ are exquisitely beautiful, and their colour very varied. In some cases, moreover, nebulæ seem to be gradually condensing into groups of stars, and in many cases it is difficult to say whether we should consider a given group as a cluster of stars surrounded by nebulous matter or a gaseous nebula condensed here and there into stars. "Besides the single Sun," says Proctor, "the universe contains groups and systems and streams of primary suns; there are galaxies of minor orbs; there are clustering stellar aggregations showing every variety of richness, of figure, and of distribution; there are all the various forms of star cloudlets, resolvable and irresolvable, circular, elliptical, and spiral; and lastly, there are irregular masses of luminous gas clinging in fantastic convolutions around stars and star systems. Nor is it unsafe to assert that other forms and varieties of structure will yet be discovered, or that hundreds more exist which we may never hope to recognise." Nor is it only as regards the magnitude and distances of the heavenly bodies that we are lost in amazement and admiration. The lapse of time is a grander element in Astronomy even than in Geology, and dates back long before Geology begins. We must figure to ourselves a time when the solid matter which now composes our Earth was part of a continuous and intensely heated gaseous body, which extended from the centre of the Sun to beyond the orbit of Neptune, and had, therefore, a diameter of more than 6,000,000,000 miles. As this slowly contracted, Neptune was detached, first perhaps as a ring, and then as a spherical body. Ages after this Uranus broke away. Then after another incalculable period Saturn followed suit, and here the tendencies to coherence and disruption were so evenly balanced that to this day a portion circulates as rings round the main body instead of being broken up into satellites. Again after successive intervals Jupiter, Mars, the Asteroids, the Earth, Venus, and Mercury all passed through the same marvellous phases. The time which these changes would have required must have been incalculable, and they all of course preceded, and preceded again by another incalculable period, the very commencement of that geological history which itself indicates a lapse of time greater than human imagination can realise. Thus, then, however far we penetrate in time or in space, we find ourselves surrounded by mystery. Just as in time we can form no idea of a commencement, no anticipation of an end, so space also extends around us, boundless in all directions. Our little Earth revolves round the mighty Sun; the Sun itself and the whole solar system are moving with inconceivable velocity towards a point in the constellation of Hercules; together with all the nearer stars it forms a cluster in the heavens, which appears to our eyes as the Milky Way; while outside our star cluster again are innumerable others, which far transcend, alike in magnitude, in grandeur, and in distance, the feeble powers of our finite imagination. FOOTNOTES: [66] Ball, _Story of the Heavens_. [67] Ball, _Story of the Heavens_. [68] Some authorities estimate it even higher. [69] Ball. [70] Hamerton, _Landscape_. [71] Humboldt, _Travels_. [72] Clarke, _System of the Stars_. [73] Kosmos. 
22302	----	[Illustration: THE TWINS, BLUFF CITY, UTAH The distance from the bottom of the cliff to the top of the erosion columns is 275 feet. _Frontispiece_] THE WESTERN UNITED STATES _A GEOGRAPHICAL READER_ BY HAROLD WELLMAN FAIRBANKS, PH.D. AUTHOR OF "STORIES OF OUR MOTHER EARTH," "HOME GEOGRAPHY," "STORIES OF ROCKS AND MINERALS," "PHYSIOGRAPHY OF CALIFORNIA," ETC. BOSTON, U.S.A. D. C. HEATH & CO., PUBLISHERS 1904 PREFACE In the preparation of this book the author has had in mind the needs of the upper grammar grades. The subject matter has not been selected with the object of covering the field of Western geography in a systematic manner, but instead the attempt has been made to picture as graphically as may be some of its more striking and interesting physical features, and the influence which these features have exerted upon its discovery and settlement. Those subjects have been presented which have more than local interest and are illustrative of world-wide principles. Clear conceptions of the earth and man's relation to it are not gained by general statements as readily as by the comprehensive study of concrete examples. Nowhere outside of the Cordilleran region are to be found so remarkable illustrations of the growth and destruction of physical features, or so clear examples of the control which physical features exercise over the paths of exploration, settlement, and industrial development. The fact that the West furnishes a wealth of material for geography teaching has long been recognized in a general way, although there has been but little attempt to present this material in a form suitable for the use of schools. The illustrations are, with few exceptions, from the author's own photographs, and the descriptions are made up from his personal observations. Since the illustrations are numerous and have been selected with much care, it is hoped that they will add greatly to the value of the text. They should be _used_, and a proper understanding of the pictures made a part of every lesson. CONTENTS THE WORK OF THE COLORADO RIVER A TRIP INTO THE GRAND CAÑON OF THE COLORADO HOW THE COLUMBIA PLATEAU WAS MADE THE CAÑONS OF THE SIERRA NEVADA MOUNTAINS AN OREGON GLACIER SOMETHING ABOUT EARTHQUAKES AND MOUNTAIN BUILDING THE LAST VOLCANIC ERUPTIONS IN THE UNITED STATES THE MUD VOLCANOES OF THE COLORADO DESERT THE HISTORY OF A COAST LINE THE DISCOVERY OF THE COLUMBIA RIVER THE GREAT BASIN AND ITS PECULIAR LAKES FRÉMONT'S ADVENTURES IN THE GREAT BASIN THE STORY OF GREAT SALT LAKE THE SKAGIT RIVER THE STORY OF LAKE CHELAN THE NATIVE INHABITANTS OF THE PACIFIC SLOPE THE STORY OF LEWIS AND CLARK THE RUSSIANS IN CALIFORNIA DEATH VALLEY THE CLIFF DWELLERS AND THEIR DESCENDANTS THE LIFE OF THE DESERT THE PONY EXPRESS HOW CLIMATE AND PHYSICAL FEATURES INFLUENCED THE SETTLEMENT OF THE WEST THE LIFE OF THE PROSPECTOR GOLD AND GOLD-MINING COPPER-MINING COAL AND PETROLEUM THE CLIMATE OF THE PACIFIC SLOPE SOMETHING ABOUT IRRIGATION THE LOCATION OF THE CITIES OF THE PACIFIC SLOPE THE FOREST BELT OF THE SIERRA NEVADA MOUNTAINS THE NATIONAL PARKS AND FOREST RESERVES THE WESTERN UNITED STATES THE WORK OF THE COLORADO RIVER The Colorado River is not old, as we estimate the age of rivers. It was born when the Rocky Mountains were first uplifted to the sky, when their lofty peaks, collecting the moisture of the storms, sent streams dashing down to the plains below. Upon the western slope of the mountains a number of these streams united in one great river, which wound here and there, seeking the easiest route across the plateau to the Gulf of California. At first the banks of the river were low, and its course was easily turned one way or another. From the base of the mountains to the level of the ocean there is a fall of more than a mile, so that the river ran swiftly and was not long in making for itself a definite channel. Many thousands of years passed. America was discovered. The Spaniards conquered Mexico and sent expeditions northward in search of the cities of Cibola, where it was said that gold and silver were abundant. One of these parties is reported to have reached a mighty cañon, into which it was impossible to descend. The cañon was so deep that rocks standing in the bottom, which were in reality higher than the Seville cathedral, appeared no taller than a man. Another party discovered the mouth of the river and called it, because of their safe arrival, The River of Our Lady of Safe Conduct. They went as far up the river as its shallow waters would permit, but failed to find the seven cities of which they were in search, and turned about and went back to Mexico. For years afterward the river remained undisturbed, so far as white men were concerned. A great part of the stream was unknown even to the Indians, for the barren plateaus upon either side offered no inducements to approach. Trappers and explorers in the Rocky Mountains reached the head waters of the river nearly one hundred years ago, and followed the converging branches down as far as they dared toward the dark and forbidding cañons. It was believed that no boat could pass through the cañons, and that once launched upon those turbid waters, the adventurer would never be able to return. The Colorado remained a river of mystery for nearly three centuries after its discovery. When California and New Mexico had become a part of the Union, about the middle of the last century, the cañon of the Colorado was approached at various points by government exploring parties, which brought back more definite reports concerning the rugged gorge through which the river flows. In 1869 Major Powell, at the head of a small party, undertook the dangerous trip through the cañon by boat. After enduring great hardships for a number of weeks, the party succeeded in reaching the lower end of the cañon. Major Powell's exploit has been repeated by only one other company, and some members of this party perished before the dangerous feat was accomplished. [Illustration: FIG. 1.--THE GRAND CAÑON OF THE COLORADO The work of a river] The Colorado is a wonderful stream. It is fed by the perpetual snows of the Rocky Mountains. For some distance the tributary streams flow through fertile valleys, many of them now richly and widely cultivated. But soon the branches unite in one mighty river which, seeming to shun life and sunlight, buries itself so deeply in the great plateau that the traveller through this region may perish in sight of its waters without being able to descend far enough to reach them. After passing through one hundred miles of cañon, the river emerges upon a desert region, where the rainfall is so slight that curious and unusual forms of plants and animals have been developed, forms which are adapted to withstand the almost perpetual sunshine and scorching heat of summer. Below the Grand Cañon the river traverses an open valley, where the bottom lands support a few Indians who raise corn, squashes, and other vegetables. At the Needles the river is hidden for a short time within cañon walls, but beyond Yuma the valley widens, and the stream enters upon vast plains over which it flows to its mouth in the Gulf of California. No portion of the river is well adapted to navigation. Below the cañon the channels are shallow and ever changing. At the mouth, enormous tides sweep with swift currents over the shallows and produce foam-decked waves known as the "bore." Visit the Colorado River whenever you will, at flood time in early summer, or in the fall and winter when the waters are lowest, you will always find it deeply discolored. The name "Colorado" signifies red, and was given to the river by the Spaniards. Watch the current and note how it boils and seethes. It seems to be thick with mud. The bars are almost of the same color as the water and are continually changing. Here a low alluvial bank is being washed away, there a broad flat is forming. With the exception of the Rio Grande in New Mexico, and the Gila, which joins the Colorado at Yuma, no other river is known to be so laden with silt. No other river is so rapidly removing the highlands through which it flows. [Illustration: FIG. 2.--LOOKING DOWN THE COLORADO RIVER FROM ABOVE THE NEEDLES] Over a large portion of the watershed of the Colorado the rainfall is light. This fact might lead one to think that upon its slopes the work of erosion would go on more slowly than where the rainfall is heavy. This would, however, be a wrong conclusion, for in places where there is a great deal of rain the ground becomes covered with a thick growth of vegetation which holds the soil and broken rock fragments and keeps them from being carried away. The surface of the plateaus and lower mountain slopes in the basin of the Colorado are but little protected by vegetation. When the rain does fall in this arid region, it often comes with great violence. The barren mountain sides are quickly covered with trickling streams, which unite in muddy torrents in the gulches, carrying along mud, sand, and even boulders in their rapid course; the torrents in turn deliver a large part of their loads to the river. As the rain passes, the gulches become dry and remain so until another storm visits the region. It is storming somewhere within the basin of the Colorado much of the time, for the river drains two hundred and twenty-three thousand square miles. So it comes about that whether one visits the river in winter or summer one always finds it loaded with mud. But what becomes of all this mud? The river cannot drop it in the narrow cañons. It is not until the river has carried its load of mud down to the region about its mouth, where the current becomes sluggish, that the heavy brown burden can be discharged. Dip up a glassful of the water near the mouth of the river, and let it settle, then carefully remove the clear water and allow the sediment in the bottom to dry. If the water in the glass was six inches deep, there will finally remain in the bottom a mass of hardened mud, which will vary in amount with the time of the year in which the experiment is performed, but will average about one-fiftieth of an inch in thickness. Each cubic foot of the water, then, must contain nearly six cubic inches of solid sediment or silt. It has been estimated that the average flow of the Colorado River at Yuma throughout the year is eighteen thousand cubic feet of water per second. From this fact we can calculate that there would be deposited at the mouth of the river every year, enough sediment to lie one foot deep over sixty-six square miles of territory. Nearly one three-hundredth part of the Colorado River water is silt, while in the case of the Mississippi the silt forms only one part in twenty-nine hundred. [Illustration: FIG. 3.--LOOKING TOWARD THE DELTA OF THE COLORADO FROM YUMA] Now we are prepared to understand the origin of the vast lowlands about the head of the Gulf of California. Long ago this gulf extended one hundred and fifty miles farther north than it does at present, so that it reached nearly to the place where the little town of Indio now stands in the northern end of the Colorado desert. When the Colorado River first began to flow, it emptied its waters into the gulf not far from the spot where Yuma is situated. The water was probably loaded with silt then as it is now. Part of this sediment was dropped at the mouth of the stream, while part was spread by the currents over the bottom of the adjoining portions of the gulf. The rapidly growing delta crept southward and westward into the gulf. As fast as the sediment was built up above the reach of the tide, vegetation appeared, which, retarding the flow of the water at times of flood, aided the deposition of silt and the building up of the delta. As the centuries went by, these lowland plains became more and more extensive, until the gulf was actually divided into two parts by the spreading of the delta across to the western shore. The portion of the gulf thus cut off from the ocean formed a salt lake fully one hundred miles in length. We may suppose that for a long time before the barrier was high and strong, the tidal currents occasionally broke over the delta and supplied the lake with water. As the river meandered here and there over the flat delta, its channels must have undergone many changes at every time of flood. A part of the water without doubt flowed into the salt lake, and another portion into the open gulf. In fact, the basin in which the lake lay, now known as the Colorado desert, continued to receive water from the river, at intervals, until very recently. In 1891 an overflow occurred, through the channel known as New River, which flooded the lower portion of the basin and threatened to cover the railroad. When the ocean had been permanently shut off from the head of the gulf, and the river itself had been largely diverted toward the south, the lake began to dry up. At last, most of the water disappeared and there remained a vast desert basin, at its greatest depth two hundred and fifty feet below the level of the ocean. In the bottom of the basin a bed of salt appeared, for this substance could not be carried away, as the water had been, by the thirsty air. Remarkably perfect beaches still exist around the shores of this old lake, and on them are found the pearly shells of multitudes of fresh-water mollusks. The presence of these shells leads us to believe that after the salt lake dried up, the river again broke in and formed a new lake of comparatively fresh water which also, after a time, dried up. The wonderful fertility of the Colorado delta is just beginning to be appreciated. Canals have been dug to take the water from the river and distribute it over the land. Year by year the cultivated lands are being extended. The change which irrigation is making upon the surface of one of the worst deserts in the country is indeed remarkable. The Colorado River is working on quietly and steadily. We may think, and truly, that it has already done a great at work in excavating the mighty cañons along its course, but, in reality, the work already accomplished is small in comparison with that which remains to be done. In time, if the land is not disturbed by the forces which build mountains, the plateaus through which the river now flows in such deep cañons will be carried away in the form of sand and mud. Broad valleys will replace the cañons, and the Gulf of California will become a fertile plain. As the highlands wear away the process will go on more and more slowly, for there will be less rainfall. The river will become smaller and its basin more arid. All these changes will be brought about through the crumbling of the rocks, and the removal of the waste matter by the running water. A TRIP INTO THE GRAND CAÑON OF THE COLORADO We may read of the Colorado plateau, and of the Grand Cañon with its precipitous walls of variously colored rock, but unless we actually visit this wonderland, it is hard to realize the height and extent of the plateau and the depth of the gashes made in its surface by running water, gashes so deep that they seem to expose the very heart of the earth. Nature has chosen a remote and half-desert region for the location of this, the most picturesque cañon in the world, as if she wished to keep it as long as possible from the eyes of men. Once a traveller could not view the cañon without making a long and weary journey across hundreds of miles of desert; now it is quite different, for one can almost look into its depths from the windows of a palace car. But to appreciate and understand fully the stupendous work that nature has done throughout this region we must leave the cars at a somewhat distant point, and before reaching the cañon become acquainted with the country in which it lies through the old-fashioned ways of travelling on horseback or wagon. Flagstaff was formerly the starting-point for travellers to the cañon, and we will choose it now, for the old stage road offers an interesting ride. The road first winds around that lofty snow-clad peak, the San Francisco Mountain, which can be seen from all northern Arizona. Leaving the mountain behind, we strike out directly across the high plateau. The country is nearly level, and the open park-like forest extends in every direction as far as one can see. It is difficult for us to believe that we are seven thousand feet above the sea, a height greater than that of the highest mountains in the United States east of the Mississippi Valley. It is this elevation, however, which brings the summer showers and makes the air cool and pleasant, for the lowlands of this portion of the United States are barren deserts, upon which the sun beats with almost savage heat. After the rainy season green grass and an abundance of flowers appear in the open meadows scattered through the forest. But, as a rule, the entire absence of water strikes one as being very strange. Where are the springs and running streams which usually abound in mountainous regions? Throughout the whole distance of seventy miles from Flagstaff to the cañon, there are but one or two spots where water is to be found. These places are known as "water-holes"; they are simply hollows in the surface of the ground where the water collects after the showers. There is another strange feature about the plateau over which the road leads; instead of sloping down toward the Colorado River and the Grand Cañon, the surface slowly rises, so that the little streams which are formed after the heavy rains flow away from the river. Our journey draws to an end, but there is nothing to indicate the presence of the cañon until we get glimpses through the trees of an apparently bottomless gulf. The gulf widens upon a closer view, we reach the edge, and all its wonderful proportions burst upon us. Does the Grand Cañon look as you thought it would? Probably not, for it is unlike any other in the world. The cañon is very deep. The river has worn its way for more than a mile down into the plateau, which once stretched unbroken from the cliffs upon which we stand, across to those upon the opposite side, nearly ten miles away. The clear air makes objects upon the opposite side and in the bottom of the cañon seem much nearer than they really are. You may think that it is an easy task to go to the bottom of the cañon and climb back again in a day, but in reality it is so difficult an undertaking that only those who are accustomed to mountain climbing can accomplish it. It is not merely the great width and depth of the cañon that impress us, but also the bright, variegated colors which the different rock layers display as they stretch in horizontal bands along the faces of the cliffs, or sweep around the towers and pinnacles until their detailed outlines are lost in the distant blue haze. Our eyes wander far down, toward the bottom of the cañon, following the alternate lines of precipitous cliffs and slopes covered with rock fragments. The cliffs and slopes succeed each other like the steps in a giant stairway, until at the very bottom the opposite walls meet in a gorge so narrow that in only a few places does the river come into view, glistening like a silver thread. A hotel stands among the trees a short distance from the brink of the cañon. Living here is expensive, for every article of food has to be brought upon the cars and wagons for a distance of hundreds of miles. Even the water has to be brought in wagons from a distant spring. [Illustration: FIG. 4.--A SCENE ON THE TRAIL] In visiting the cañon we have the choice of going on horseback or on foot. While the latter method is much harder, yet one feels safer upon his own feet while moving along the steep and narrow trail. Our start is made in the cool air of the early morning. Leaving the top of the plateau, where among the pines the summer air is seldom sultry, and the winters are cold and snowy, we descend, until, by luncheon time, we are far below the heights and in the midst of an almost tropical climate. This difference in climatic features between the top and bottom of the cañon is equal to the change which the traveller experiences in a trip from the pine forests of the northern United States to the cactus-covered plains of Arizona. As we look down from the top of the trail it does not seem possible to pass the great cliffs below, and yet there must be a way, since others have gone before us. All that we have to do is simply to follow the beaten path. Nature has conveniently left narrow shelves, crevices, and less precipitous slopes here and there, which need only the application of the pick and shovel to be made passable even for pack animals. Where the trail winds into shady recesses, we find stunted fir and pine trees clinging to the crevices and stretching their roots down into the waste rock collected upon projecting ledges. Down, down we go. The belt of the yellow pine and fir is left behind, and we come to the habitat of the piñon pine and juniper. These two will flourish where there is less moisture than is needed by the trees which grow nearer the top. Soon the trees have all disappeared and such plants as the greasewood, cactus, and agave take their place. Here, if it were not for the walls of rock rising on every hand, we might imagine ourselves upon one of the desert plains of Arizona. [Illustration: FIG. 5.--CLIFFS ON THE TRAIL INTO THE GRAND CAÑON] New views open at every turn in the trail, as it winds along the narrow shelves of rock with precipitous walls above and below. Now it zigzags back and forth down a gentle slope, but is soon stopped by another precipice. In one place, to escape a rocky point, the trail has been carried around the face of a cliff on a sort of shelf made of logs. It then passes through a crevice formed by the splitting away of a huge piece of the wall. In many places the grade is so steep that the trail is made practically a stairway, for the steps are necessary to keep animals from slipping. Step by step we descend until the slope becomes more gentle and a sort of terrace is reached, where men are at work developing a copper mine. Everything needed for the mine is carried down packed upon the backs of sure-footed burros. Even the water has to be brought in kegs from a little spring still deeper in the cañon. The trail leaves the mine and winds down past another cliff, until, when more than three thousand feet from the top of the plateau, we find water for the first time. The little springs issue from the sandstone, and their limited supply of water is soon drunk up by the thirsty sands. As far as the water flows it forms a little oasis upon the barren slope. Along the course of the streams are little patches of green grass, flowers, and bushes. Birds flit about, and there are tracks of small animals in the mud. Evidently the water is as great an attraction to them as it is to us. If a well were dug in the plateau above, we can understand now how deep it would have to be in order to reach water. A well three-fourths of a mile deep would be a difficult one to pump. We are now in the bottom of the main cañon, but deeper still is the last and inner gorge, through which the Colorado is flowing. For thousands of centuries the river has been sawing its way down into the earth. The precipitous cliffs which we have passed are formed of hard sandstone or limestone. The more gentle slopes consist of softer shales. Now the river has cut through them all and has reached the very heart of the earth, the solid granite. [Illustration: FIG. 6.--THE INNER GORGE OF THE GRAND CAÑON OF THE COLORADO] This inner gorge has almost vertical walls twelve hundred to fifteen hundred feet high. We can sit upon the brink under a ledge of rock which protects us from the hot sun, and watch the river as we eat our luncheon. Far below, almost directly under us, it rushes along. The roar of the current rises but faintly to our ears. The water is very muddy and not at all like the clear mountain streams, far away upon the continental divide, which unite to form the river. It seems as if the water, ashamed of its soiled appearance, wanted to hide from the sight of men. If so, it has succeeded well, for it can be seen only at rare intervals from the top of the cañon walls, and even at the bottom of the main cañon the river itself is not visible unless one stands upon the very brink of the granite gorge. The work of the river is not yet done. It will go on until the great cliffs have crumbled and have been replaced by gentle slopes. It will not stop until, at some far distant time, a broad valley has been worn out of the rocky strata. The cañon appears much wider when viewed from the bottom than from the top, and the great cliffs far back along the trail seem less precipitous, but only because they are so far away. A weary climb of several miles awaits us. We must rest and take breath frequently or we shall not reach the top. As night approaches and the shadows begin to fall, every turret and pinnacle stands out in bold relief. The bands of yellow and red shade into purple, and everything, save the long winding trail, begins to have a weird and mystical look. HOW THE COLUMBIA PLATEAU WAS MADE Years ago people disputed as to the way in which the earth was made. Those who lived where all the rocks had, like lava, the appearance of having once been melted, believed that fire had done all the work. Those who lived where the rocks appeared to be formed of hardened mud, sand, and lime, substances such as we find accumulating under water, said that water alone had been the means. But in later years the earth's surface has been more widely explored, and now it is known that both opinions were partly right. Water and fire have both been concerned in the making of the earth. In the great valleys fire-formed rocks are rare, but they are more or less abundant in all mountainous regions, for where mountains are, there the crust of the earth is weakest. There are many reasons for believing that the interior of the earth is very hot. We know that the surface is settling in some places and rising in others, and that where the strain of the upheaval is too great the rocks are broken. These convulsions sometimes cause earthquakes and sometimes volcanic eruptions, when enormous quantities of molten rock are poured out over the surface. In all the long history of our earth probably no greater flood of lava than that which made the Columbia plateau was ever spread over the surface of any region. Travel where you will over the plains of southern Idaho, central Washington, or Oregon, and examine the rocks which here and there rise above the soil or are exposed in the cañons, and you will find that they all appear to have been formed by fire. [Illustration: FIG. 7.--SNAKE RIVER AT IDAHO FALLS Just beginning to cut a cañon in the volcanic plateau] These rocks are dark in color and very hard. They are not arranged in regular layers like sandstone and shale; many of them show numerous little cavities which once contained steam. These cavities give to the rock a slag-like appearance. In this kind of rock, which we shall call lava, there are, of course, no remains of shells or bones of animals such as are often found in rocks formed from sand or clay. Do not picture to yourself the Columbia plateau as one continuous stretch of level land, for it is broken by many mountain ranges. Some of these are old mountains which were too tall to be buried by the lava, but most of them have been formed out of the plateau itself. The eruptions which made the plateau extended through a very long time, perhaps hundreds of thousands of years, and the older lava is deeply decayed and covered with soil. Some of the later flows show extremely rough and rugged surfaces and are probably only a few hundred years old. [Illustration: MAP OF THE COLUMBIA PLATEAU] Long ago, before the eruptions began, the geography of the Northwest was very different from what it is now. Instead of a vast plateau there were mountains and valleys. Lowlands occupied most of the region where the Cascade Range now rises with its lofty volcanic peaks. Portions of the basin of the present Columbia River were occupied by lakes which extended southwest into California. Movements of the earth began to affect the region of the present plateau, and at many points the solid rocks were fissured and broken. Then from that mysterious region far beneath the surface came steam and gases, escaping through the fissures with explosive force. In some places cinder cones were built about the openings by the fragments of lava which were hurled out. In other places, during periods of less explosive eruption, molten lava flowed out in vast quantities. The lava was very hot and almost as liquid as water, so that it spread in thin sheets over hundreds of square miles of lowland. One important series of fissures through which eruptions took place marked the line where the Cascade Range was to be built. Other volcanoes appeared over the surface of southern Idaho, central Washington, Oregon, and northeastern California. The eruptions were not continuous over the whole field; now in this place, now in that, there came long periods of quiet. During such periods the earthquakes ceased, the lava became cold, and the clouds of volcanic ashes cleared from the air. Frequently the lava intercepted streams and blocked the valleys so that large lakes were formed. Whenever the periods of quiet were very long, plants spread over the surface and animals of many kinds made their homes about the lakes. In eastern Oregon the John Day River and its branches have eroded cañons through the later lava and have exposed the sands, clays, and gravels which collected at the bottom of one of those ancient lakes. In these beds the skeletons of many strange and interesting animals have been found. Evidently they had once lived about the borders of the lake, and the streams had washed their bones into the water and mingled them with the sediment. [Illustration: FIG. 8.--BLUE LAKES, IDAHO Formed by springs issuing from underneath the lava of the plateau] One of these animals appears to have been an ancestor of the present horse. It was about the size of a sheep, and had three toes instead of one. Another, probably a very dangerous animal, was related to our present hog, but stood nearly seven feet high. Others resembled the rhinoceros, camel, tapir, or peccary. All but the peccary are now extinct upon this continent. Of the carnivorous animals there were wolves and cats of large size. The eruptions continued, filling the valleys little by little, until in places the lava reached a thickness of nearly four thousand feet. The lower mountains were hidden from sight. We know of the existence of these buried mountains because the wearing away of the lava in some places has exposed their summits to view. The lava flood reached farther and farther. In southern Idaho it formed the Snake River plains, which must have been, when first formed, hundreds of miles long, seventy-five miles wide, and almost as even as a floor. If we could have looked on while these things were taking place it would have appeared as if the whole land was about to sink under the fiery mass which flowed out of the earth. The streams and valleys were completely buried. The region of the John Day Lake, with all its animal remains, was covered. The lava, like a sea, crept up against the mountains surrounding the plateau region. Bays of lava extended into the valleys among the mountains, while mountain ridges rose like islands and capes from the surface of the flood. We never tire of looking at the lofty snow-capped peaks of the Cascade Range. A dozen of them rise over ten thousand feet, and two, Mounts Shasta and Ranier, are more than fourteen thousand feet high. All these mountains were formed of material thrown out of the interior of the earth during the building of the Columbia plateau. The process was very similar for each. About some one exceptionally active crater immense quantities of scoriæ[1] and lapilli[2] accumulated. Then came streams of fiery lava, some of which, hardening upon the outer slopes of the crater, added still more to the growth of the mountain. The process was very slow, however. A time of eruption, marked by tremblings of the earth, explosive noises, and a sky filled with dust and clouds, might last for many years. Then came a long period of rest when the falling rains, gathering in dashing torrents, cut deep gullies down the sides of the mountain. [Footnote 1: _scorioe_, cellular, slaggy lava.] [Footnote 2: _lapilli_, volcanic ashes, consisting of small, angular, stony fragments.] [Illustration: FIG. 9.--PITT RIVER CAÑON, NORTHERN CALIFORNIA The plateau is built of layers of lava] The volcanoes at last ceased to grow any higher, for the lava, if the eruptions continued, formed new craters at their bases. It is probable that all these great peaks have been extinct for several thousand years, although some are much older and more worn away than others. One of these volcanoes has completely disappeared, and in its place lies that wonderful sheet of water known as Crater Lake. It is thought that the interior of this mountain was melted away during a period of activity, and that the outer portion fell in, leaving a crater five miles across and nearly a mile deep. The streams of lava, as they flowed here and there building up the plateau, frequently broke up the rivers and turned them into new channels. As time went on the eruptions were less violent, and the rivers became established in the channels which they occupy to-day. The Columbia River, winding about over the plateau, sought the easiest path to the sea. It soon began to dig a channel, and now has hidden itself between dark walls of lava. But other forces besides the streams were now at work in this volcanic region. The lava plateau began slowly to bend upward along the line of the great volcanoes, lifting them upward with it. In this manner the Cascade Range was formed. The Columbia River, instead of seeking another way to the sea, continued cutting its channel deeper and deeper into the growing mountain range, and so has given us that picturesque cañon which forms a most convenient highway from the interior of Washington and Oregon to the coast. Take a sheet of writing paper, lay it upon an even surface, then slowly push the opposite edges toward each other. This simple experiment will aid one in understanding one of the ways in which mountain ranges are made. Besides the upward fold of the plateau which made the Cascade Range, another was formed between the Blue Mountains in eastern Oregon and a spur of the Rocky Mountains in northern Idaho. This fold lay across the path of the Snake River, but its movement was so slow that the river kept its former channel and in this rising land excavated a cañon which to-day is more than a mile deep. The upper twenty-five hundred feet of the cañon are cut into the lava of the plateau, and the lower three thousand into the underlying granite. The cañon is not so picturesque as the Colorado, for it has no rocks with variegated coloring or castellated walls. Its sides are, however, exceedingly precipitous and it is difficult to enter. [Illustration: FIG. 10.--SHOSHONE FALLS, SNAKE RIVER, IDAHO] Along portions of the lower Columbia and Snake rivers, navigation is obstructed by rapids and waterfalls. The presence of these falls teaches us that these streams are still at work cutting their channels deeper. The Snake River in its upper course has as yet cut only a very shallow channel in the hard lava, and the beautiful Shoshone Falls marks a point where its work is slow. These falls, which are the finest in the northwest, owe their existence to the fact that at this particular spot layers of strong resistant lava cover the softer rocks. There are other cañons in the plateau region which are fully as remarkable as those which have been mentioned. That of the Des Chutes River in central Oregon is in places a thousand feet deep, with almost vertical walls of lava. We have already seen how mountains have been formed upon the Columbia plateau, by a bending of the earth upward. Other mountains of the plateau are due to fractures in the solid rocks, often many miles long. Upon one side of these fractures the surface has been depressed, while upon the other it has been raised. The amount of the uplift varies from a few hundred to thousands of feet. The mountains thus formed have a long, gentle slope upon one side and a very steep incline upon the other. They are known as "block mountains," and those upon the Columbia plateau are the most interesting of their kind in the world. With the exception of a few large rivers, the greater portion of the Columbia plateau is remarkable for its lack of surface streams. The water which reaches the borders of the plateau from the surrounding mountains often sinks into the gravel between the layers of lava and forms underground rivers. The deep cañons which have been mentioned intercept some of these underground rivers, so that their waters pour out and down over the sides of the cañons in foaming cascades. The greatest of these cascades is that known as the Thousand Springs in the Snake River cañon. The waters of the Blue Lakes in the cañon of the same river below Shoshone Falls also come from underneath the lava. They are utilized in irrigating the most picturesque fruit ranch in southern Idaho. [Illustration: FIG. 11.--CAÑON OF CROOKED RIVER NEAR THE DES CHUTES RIVER Eroded in the Columbia plateau] The climate of the plateau is dry, and its eastern portion is practically a desert. Toward the west, however, the rainfall is greater, and in central Washington and northern Oregon the plateau becomes one vast grain-field. It is difficult to irrigate the plateau because the streams flow in such deep cañons, but above the point where the cañon of the Snake River begins there is an extensive system of canals and cultivated fields. With a sufficient water supply, the lava makes one of the richest and most productive of soils. Along the Snake and Columbia rivers, wherever there is a bit of bottom land, orchards have been planted. Little steamers ply along these rivers between the rapids, gathering the fruit and delivering it at the nearest railroad point. Mining is carried on only in the mountains which rise above the lava flood, for the mineral veins are for the most part older than the lava of the plateau. We are certain that many very valuable deposits of the precious metals lie buried beneath the lava fields. It is thought that the volcanic history of the Columbia plateau has been completed. Now the streams are at work carrying away the materials of which it is composed and may in time uncover the old buried land surface. THE CAÑONS OF THE SIERRA NEVADA MOUNTAINS The western half of our country contains the deepest and most picturesque cañons in the world. Those of the Colorado and Snake rivers form trenches in a comparatively level but lofty plateau region. The cañons of the Sierra Nevada Range, on the contrary, take their rise and extend for much of their length among rugged snowcapped peaks which include some of the highest mountains in the United States. All these cañons are the work of erosion. The rivers did not find depressions formed ready for them to occupy, but had to excavate their channels by the slow process of grinding away the solid rock. The streams of the Sierra Nevada mountains begin their course in steep-walled alcoves under the shadows of the high peaks, where they are fed by perpetual snow-banks. Soon they bury themselves between granite walls, which at last tower three thousand feet above their roaring waters. After many miles the cañons widen, the walls decrease in height, and the streams come out upon the fertile stretches of the Great Valley of California. Nature works in many ways. Her tools are of different kinds, but the most important one is running water. The forms which she produces are dependent upon the kind of rock upon which she works. Where the surface of the earth is soft the results of her labor are not very interesting, but if the crust is hard the forms which she produces are often so remarkable that they arouse our wonder and admiration. [Illustration: FIG. 12.--SAN JOAQUIN RIVER EMERGING UPON THE PLAIN OF THE GREAT VALLEY] In shaping the Sierra Nevada mountains Nature had a grand opportunity. Here she produced the Yosemite Valley, which has a setting of cliffs and waterfalls that attract people from all over the world. Hetch-Hetchy Valley at the north of the Yosemite, and Tehipite and King's River cañons at the south, are interesting places, but not so majestic and inspiring as the Yosemite. Nature never seems satisfied with her work. After she has created a piece of wonderful scenery she proceeds to destroy it. The great cliffs of the Yosemite will sometime lose their grandeur and be replaced by gentle slopes down which the streams will flow quietly. The mountains of the Laurentian highlands in the northeastern portion of the continent undoubtedly were once lofty and picturesque, but there were no people upon the earth at that time to enjoy this scenery. Now these mountains have become old and are nearly worn down. [Illustration: FIG. 13.--WHERE THE CAÑONS BEGIN UNDER PRECIPITOUS PEAKS The head of the King's River] In one portion of the earth after another, Nature raises great mountain ranges and immediately proceeds to remove them. This continent was discovered and California was settled at the right time for the Sierra Nevadas to be seen in all their grandeur. When the pioneers came in sight of the Sierra Nevada (snowy range), they little dreamed of the cañons hidden among these mountains. Gold, and not scenery, was the object of their search. The great cañons were outside of the gold regions, and so inaccessibly situated that no one except the Indians looked upon them until 1851. In that year a party of soldiers following the trail of some thieving Indians discovered and entered the Yosemite Valley, but it was not explored until 1855. For many years the valley could be reached only by the roughest trails, but as its advantages became more widely known roads were built, and there are now three different wagon routes by which it may be entered. The history of the Yosemite Valley is like that of all the other cañons of the Sierra Nevada mountains. Long ago there were no high mountains in eastern California. If there had been explorers crossing the plains in those days, they would have found no rugged wall shutting them off from the Pacific. There came a time, however, when the surface of the western portion of America was broken by violent earthquake movements, and hundreds of fissures were formed. Some of the earth blocks produced by these fissures were shoved upward, while others were dropped. One enormous block, which was to form the Sierra Nevada, was raised along its eastern edge until it stood several thousand feet above the adjoining country. The movement was like that of a trap-door opened slightly, so that upon one side--in this case the western one--the slope was long and gentle, while upon the east it was very abrupt. [Illustration: FIG. 14.--THE YOSEMITE VALLEY] Nature, the sculptor, took this mountain block in hand, and with the aid of running water began to carve its surface into a most intricate system of cañons and ridges. The streams first flowed over the easiest slopes to the Great Valley of California, but soon they began to cut their way down into the granite, while along the crests of the ridges the more resistant rocks began to stand out as jagged peaks. Thus Nature worked until the mountains promised before long to be well worn down. The cañons had widened to valleys and the rugged slopes had given place to gentle ones. Toward the northern end of the range the work was even farther advanced, for the streams, now choked with gravel and sand, flowed over broad flood plains. In this gravel was buried a part of the wealth of California. The rocks over which the streams flowed contained veins of quartz with little particles of gold scattered through it, and as the surface rock crumbled and was worn away, the gold, being much heavier, slowly accumulated in the gravel at the bottom of the streams. This gold amounted in value to hundreds of millions of dollars. The forces within the earth became active again. Apparently Nature did not intend that the gold should be forever buried, or that the country should always appear so uninteresting. Internal forces raised the mountain block for a second time, tilting it still more to the westward. Volcanoes broke forth along the summit of the range near the line of fracture, and floods of lava and volcanic mud ran down the slopes, completely filling the broad valleys of the northern Sierras and burying a great part of the gold-bearing gravel. The eruptions turned the streams from their channels, but on the steeper slope of the mountains the rivers went energetically to work making new beds. They cut down through the lava and the buried gravel until they finally reached the solid rock underneath. Into this rock, which we call "bed-rock," they have now worn cañons two thousand feet deep. The beds of gravel that lay under the old streams frequently form the tops of the hills between these deep cañons. Here they are easily accessible to the miners, who by tunnels or surface workings have taken out many millions of dollars' worth of gold. The important cañons of the northern Sierras, where the gold is found, have been made by the American and Feather rivers. Farther south are the deeper and more rugged cañons of the Tuolumne, Merced, King's, and Kern rivers, which open to us inviting pathways into the mountains. It might be supposed that the mantle of snow and ice which at that time covered most of the surface of the earth would have protected it from further erosion, but this was not the case. In the basin at the head of each stream the snow accumulated year after year until it was more than a thousand feet deep. Under the influence of the warm days and cold nights the snow slowly turned to ice, and moved by its own weight, crept down into the cañons. The solid rock walls were ground and polished, and even now, so long a time after the glaciers have melted, some of these polished surfaces still glisten in the sunlight. The glaciers deepened and enlarged the cañons, but running water was the most important agent in their making. Upon the disappearance of the glaciers, the streams went to work again deepening their cañons. From their starting-points, under the lofty crags, they first ran through broad upland valleys, then tumbled into the cañons; but until they had reached the lower mountain slopes, to which the glaciers had not extended, they passed through a dreary and desolate region devoid of almost every sign of life. The glaciers had swept away all the loose rock and soil, and it was many long years before the surface again crumbled so that forest trees could spread over it once more. The grandeur and attractiveness of the Yosemite is partly due to the precipitous cliffs enclosing the valley, some of which are nearly four thousand feet in height, partly to the high waterfalls, and partly to the green meadows and forest groves through which the Merced River winds. Although the glaciers had little to do with the making of the Yosemite Valley, yet they added to its attractiveness. The valley is situated where a number of smaller streams join the Merced River. Erosion was more rapid here because the granite was soft, while the vertical seams in the rock gave the growing valley precipitous walls. When the glacier came it pushed out the loose rocks and boulders, and dropping a portion of them at the lower end, made a dam across the Merced River. At first a shallow lake filled the valley, but after a time the silt and gravel which the streams were continually bringing in filled the lake, and formed marshy flats. Finally, grasses and trees spread over these flats and gave the valley the appearance which it has to-day. Besides the meadows, the glaciers gave us two of the waterfalls. Yosemite Creek, which comes down over the walls twenty-seven hundred feet in three successive falls, was turned into its present channel by a dam which a glacier had left across its old course. A glacier also turned the Merced River at its entrance to the main valley so as to form the Nevada Fall. [Illustration: FIG. 15.--THE CAÑON OF BUBB'S CREEK, A BRANCH OF THE KING'S RIVER CAÑON] After the valley had been made and clothed in vegetation, it was discovered by a small tribe of Indians who came here to make their home, secure from all their enemies. There were fish in the streams and animals in the woods. The oaks supplied acorns, and in early summer the meadows were covered with strawberries. Legends were associated with many of the cliffs and waterfalls, for the Indians, like ourselves, are impressed by the wonders of Nature. Hetch-Hetchy Valley, twenty-five miles north of the Yosemite, has been formed upon much the same plan, but a portion of its floor is marshy and there are few waterfalls. King's River Cañon has no green meadows and no high waterfalls, while its great granite walls are not so precipitous as those of the Yosemite. Next to the Yosemite, in the wildness of its scenery, is Tehipite Cañon. This cañon is situated upon the middle fork of King's River, about a hundred miles south. For many miles its walls and domes present ever changing views. A continual struggle is going on between the forces within the earth and the sculptor working upon its surface. First one, then the other, gains the advantage. Where the mountains are steep and high, often the forces within have recently been active. Where they are low and the slopes are gentle, the sculptor has long held sway. She begins by making the surface as rough and picturesque as possible, but after a time she destroys her own handiwork. AN OREGON GLACIER There are records all about us of events which took place upon the earth long before there were any human inhabitants. These records have been preserved in the rocks, in the geographic features of the land and water, and in the distribution of the animals and plants. On every hand appear evidences of changes in the surface of the earth and in the climate. Through all the central and northern United States, if we except some of the mountains of the West, the winter snows entirely disappear long before the coming of summer. But the climate of this region has not always been so pleasant and mild. Lands now densely peopled were once buried under a thick mantle of ice which lasted through many thousands of years. Scattered over the surface of the northern United States are vast numbers of boulders and rock fragments which are not at all like the solid rocks beneath the soil. The history of these materials takes us back to the Glacial period, which can be best understood from a study of some one of the glaciers now existing upon the mountains of the northwestern part of our country. Among the lofty mountain ranges of the Cordilleran region there are many peaks upon which perpetual snow-banks nestle, defying the long summer days. Where the winters are long and cold and the storms are severe, immense drifts of snow collect in the hollows and cañons of the mountain slopes. Each summer all or a part of this snow melts. Upon the northern slopes the melting process is slower, and if there happens to be a large basin upon that side, an extensive field of snow remains until the winter storms come again. Each winter new snow is added to the surface, while the older snow, becoming hard and firm through repeated freezing and thawing, at last turns to ice. This mass of snow and ice does not remain stationary, as might be expected from its apparent solidity. Under the influence of its own weight and of alternations of heat and cold, it flows down the incline like a very thick liquid. During the winter the ice melts but little, and the movement is slow, but in the summer, under the influence of the warm days and cool nights, both the melting and the rate of flow of the ice are increased. A moving body of snow and ice of this sort is called a "glacier." It creeps down the mountain slope and into some cañon, until, in the warmer air of the lower mountains, the rate of advance is exactly balanced by the rate of melting at the lower end of the mass. The glaciers in the United States are at present comparatively small, but once these icy masses stretched over the mountains and lowlands of a large portion of the continent. In the southern Sierra Nevada mountains no permanent snow exists below an elevation of about eleven thousand feet, but as we go north snow-fields are found lower and lower, until in the fiords of Alaska enormous glaciers reach down to the sea. A glacier worthy of our study may be found upon the Three Sisters, a group of lofty and picturesque volcanic mountains rising from the summit of the Cascade Range in central Oregon. There is a deep depression between two of the peaks, which slopes down to the north and is thus particularly well adapted to catch and retain the drifting snows. Consequently the glacier to which it gives rise is of exceptional size, being nearly three miles long and half a mile wide. [Illustration: FIG. 16.--THE THREE SISTERS, FROM THE NORTH Showing snow-fields and glacier. Fields of recent lava appear in the foreground] The easiest path to the Three Sisters is by way of the McKenzie River from Eugene, Oregon. The McKenzie is a noted stream and one of the most beautiful in the state. The river courses through dense forests, and its clear, cold water is filled with trout. So tempestuous is the weather about the Cascade range that July is almost the only month in which one can visit the Three Sisters without danger of being caught in severe storms. The traveller leaves the river a few miles above McKenzie Bridge, where a small tributary known as Lost Creek joins it. Lost Creek flows under the lava from a lake near the Three Sisters, while another stream, coming from the glacier of which we are in search, flows down the same valley upon the surface of the lava and almost directly over the hidden stream. Upon the summit of the Cascade Range the dense forests of the river valley give place to more open woods interspersed with park-like meadows. A few miles away to the south rise the volcanic peaks of the Three Sisters, clear and cold in the mountain air, wrapt about with a mantle of white except where the slopes are too precipitous to hold the snow. An indistinct trail leads through the tamarack forest and over a field of rugged lava to the base of the peaks. Here we come upon a swiftly flowing stream of a strange milky color. This appearance is due to the presence of fine mud, the product of the work of the glacier at the head of the stream as it slowly and with mighty power grinds away the surface of the rocks over which it moves. Wherever one meets a stream of this kind, he will probably be safe in asserting that it is fed by a glacier upon some distant mountain peak. This little stream, the course of which we must follow to reach the glacier, is choked with sand and pebbles brought to it by the moving ice. These are not ordinary stream pebbles, for they have strangely flattened sides which often show scratches, and look as if they had been ground off against a grindstone. They are the tools with which the ice does its work. The ice block takes up the rock fragments which fall upon its surface or which it tears from beneath, and carries them along, grinding every surface which it touches. The fragments are dropped at the end of the glacier, and the smaller pebbles are washed away down the stream that flows from the melting ice. [Illustration: FIG. 17.--GLACIER ON THE THREE SISTERS] We follow up the little glacial creek, past icy snow-banks and through groves of fir trees where the warm sunshine brings out the resinous odors. Upon one side of the cañon there lies a field of black lava which not many hundreds of years ago forced this glacial creek from an earlier channel into its present bed. Now we come upon what appears at first to be a snow-bank lying across the course of the stream, and from beneath which its waters issue. Deep cracks in the outer mass of snow show the clear, pale-green ice below. This is the lower end of the glacier which we have been so long a time in reaching. A short climb up a steep slope brings us to the top of the glacier. It forms a perfectly even plain, extending back with a gentle slope to the head of a deep notch between the two northern Sisters, while above and beyond rise the steeper snow-fields, from which this ice is continually renewed. The glacier does not terminate in the usual manner, with a stream flowing from its centre, for the outlet is at one side, while the middle abuts against a low mound of rock. This mound we find most interesting, for upon reaching its top we look down into a volcanic crater. From this crater flowed the great stream of lava to which we have already referred. The lava ran downward, bending this way and that among the hollows, until it spread nearly to the McKenzie River. During the Glacial period, before the eruption took place, this glacier was much larger. The summit of the Cascade Range was then covered by glaciers. This fact we know from the presence of grooved and polished rocks wherever the surface has not been worn away or covered with newer lava. The Glacial period had passed away and the climate had become much the same as it now is when the volcanic forces broke out at the spot where the crater is situated. The eruption undoubtedly melted the ice in the vicinity, but after it had ceased and the rocks had become cold, the glacier never gained strength enough to push the loose materials of the volcanic cone out of its path. The ice banked up snugly against the obstruction, and as it melted the water found its way out at the side of the lava. Although the surface of the glacier appears at first to offer an easy route to the higher mountain slopes, yet there are numerous hidden crevices into which one may fall. The safest arrangement is to tie a company of people together with a stout rope, so that if one falls into a crevice the rope will save him. Toward the middle of the glacier the ice becomes so badly fissured that it is necessary to turn toward the right margin. There are two sets of these fissures, one parallel to the direction in which the glacier is moving, the other at right angles. They are due to the strain to which the ice is subjected as it moves along at an uneven rate and over a surface composed of hollows and ridges. [Illustration: FIG. 18.--MORAINE AT THE END OF THE GLACIER] Leaving the glacier, we climb upon a long low ridge of gravel and boulders mixed with fragments of ice. The fragments of rock which have fallen upon the surface of the ice or been torn from the rock over which it is moving, have been heaped up along its sides somewhat as a ridge of snow is raised along each side of the course of a snow-plough. Such a ridge of débris along the side of a glacier is known as a marginal moraine. A similar ridge, formed by the accumulation of rock fragments at the lower end of the glacier, is a terminal moraine. These ridges and hollows formed by the ice are found all over the northern portion of the United States. The hollows once filled with ice are now occupied by the beautiful lakes of this portion of our country. As we climb along the moraine at the margin of the glacier, many openings appear in the clear green ice. There is the sound of gurgling waters, and occasionally pieces of ice and rock fall into dimly outlined caverns which are narrow at the top, but far below widen out to the proportion of chambers. After the head of the glacier is attained there is still a hard climb over the snow-fields, which extend upward so far that they seem to have no end. When at last the gap between the peaks is gained we are completely tired out. The summit of the middle Sister rising directly above us is still a thousand feet higher, but there is not time to-day to reach it. A magnificent vista is spread out upon every hand. Extending north and south along the crest of the Cascade Range there is a line of sharp snowy peaks with summer clouds floating about them. How these peaks contrast with the dark blue of the surrounding forests! Opposite us, upon the south, is the third Sister, white with snow from top to bottom, while in the basin between this peak and the ridge on which we are standing lie the remnants of a once mighty glacier. But it is time to return. The cold, foggy clouds are hiding the summits and will soon envelop the spot where we stand. We go down by a different path, but over almost continuous snow-fields, for more than two miles. The return is much easier than the ascent, although if one lost his footing upon some steep slope, it would mean a long slide or tumble. The solid earth is reached without accident. What a relief to have some firm hold for the feet again! Climbing over a field of rough lava is easier than toiling through soft snow. [Illustration: FIG. 19.--A BOULDER LEFT BY A GLACIER] The region about the Three Sisters is just as nature left it, for the home of the nearest settler is many miles away. Although now it has few visitors, this country will become attractive when its wonderful volcanic and glacial phenomena are better known. SOMETHING ABOUT EARTHQUAKES AND MOUNTAIN BUILDING Our everyday experiences lead us to feel that nothing is more permanent than the features of the earth upon which we live. Great cities containing costly buildings are built by the water's edge with the expectation that the ocean will remain where it is. The building of railroads and canals, and the establishment of industries to make the earth more fruitful and better adapted to our use, are based upon the idea that the mountains and valleys with their various, climates will not change. The study of history, however, makes plain the fact that at different times in the past certain portions of the earth have been visited by destructive changes. Cities have been shaken down by earthquakes, and the ocean has swept in over the land, drowning thousands of people. Even the mountains, which stand upon broad and firm foundations, sometimes bring disaster, by means of avalanches and land-slides, to the people who live at their bases. The truth is that the earth's surface is everywhere slowly and quietly changing; but our lives are so short, and the history of even the oldest cities is so brief in comparison with the rate at which most of the changes take place, that we as a rule are aware of only the uncommon and sudden ones. The occurrence of earthquakes establishes the unmistakable fact that there are forces at work from within disturbing the surface, while land-slides, and even little gullies washed out by the rain, show that other forces are working from without. The vibration or trembling of the earth which we call an "earthquake" always arouses alarm, and frequently occasions great destruction and loss of life. Only a few of the various causes that may bring about earthquakes are as yet fully understood. Earthquakes are very interesting, however, because they are often associated with the birth and growth of lofty mountain ranges. Volcanic eruptions, hot springs, and the high temperature which exists toward the bottom of deep mines show us that the interior of the earth is very hot. It is thought that at one time the whole earth glowed with heat, but as ages passed it became cold upon the outside and a solid crust was formed. Every one has observed that fruit becomes wrinkled as the pulp within dries and contracts. The materials of the earth occupy more space when they are hot than when cold, and as the interior portion is still cooling, the outer layer or crust continues to shrink down upon it, forming folds or wrinkles, as in the case of the skin of an apple. There is probably no portion of the surface that is fixed in its present position. The land is either rising or sinking continually. If the area that is pushed upward is large, it becomes a plateau; but if long and narrow like a wrinkle, it forms a mountain range. We should not be aware of these movements in many cases if it were not for the horizontal shelf cut upon the borders of the land by the ocean waves. Along some coasts old wave-cut cliffs stand hundreds of feet above the present ocean level. Other coasts have sunk, so that the water has flooded the adjoining land and made a new shore line. When the movements of the land are sudden, they manifest themselves to us through earthquakes. The crust of the earth is not so flexible as the skin of an apple, and when the strain upon it becomes too great it suddenly breaks. The rock walls usually slide past one another along such a fracture. If the rising wall becomes high enough it will form a mountain range. The great mountain systems border the oceans, for the lines of weakness occur where the land dips steeply down beneath the water. It sometimes happens that the fractures in the rocks where mountains are being made are situated underneath the water, or in some position where water passes down through them in large quantities. What do you think would happen if such an underground stream of water came in contact with hot or molten rocks far below the surface? Note the effect produced by drops of water falling upon a hot stove. Each one, as it strikes, is partly changed to steam with a slight explosive sound. The result is similar when water is turned into the hot and nearly empty boiler of a steam-engine--an explosion is sure to follow. When the pressure of steam suddenly formed within the earth is too great, a volcanic explosion takes place at some point where the overlying rocks are weakest, probably on or near one of the lines of fracture about which we have been speaking. The explosion is accompanied by thundering noises, tremblings of the earth, and the hurling of rock and molten lava into the air. That the rocks of the earth's crust are elastic is shown by the rebounding of a pebble thrown against a large boulder. If a file be drawn across the edge of a sheet of tin upon which sand has been sprinkled, the tin vibrates over its whole extent, as is shown by the jumping of the sand grains. Because of like elasticity in the materials which make up the surface of the earth, the vibrations produced by an explosion are carried through the solid earth for hundreds of miles. [Illustration: FIG. 20.--EARTHQUAKE FISSURES NEAR MONO LAKE, CALIFORNIA] The records of earthquakes show that they are much more violent and occur oftener where the crust of the earth is being disturbed by folding. We have seen that there are two main causes of earthquakes: the slipping of portions of the earth past each other along a fissure, and the contact of water with very hot rocks far below the surface. It is probable that the earthquakes which occur so often in the western portion of the United States are due to the first of these causes. The numerous extinct volcanoes show that at one period this region was frequently shaken by explosive eruptions. [Illustration: FIG. 21.--THE WASATCH RANGE From Salt Lake City] Mono Lake (see Fig. 42, page 99), at the eastern base of the Sierra Nevada Range, has been a centre for explosive eruptions, which were extremely violent at one time. The islands which rise in the lake are shattered, while Black Point, upon the northern shore, has been uplifted by an explosion from beneath, which split the rocks apart and formed deep fissures. It is an interesting fact that in the Cordilleran region the mountains have been increasing in height in very recent years. We might almost say that they are growing to-day. In this region, then, we can actually see how mountains are made; we do not have to depend upon descriptions of the manner in which they are supposed to have been made thousands of years ago. [Illustration: FIG. 22.--BLUFF FORMED BY AN EARTHQUAKE At the foot of the Wasatch Range, Utah] Any good map will show that the mountains of the Cordilleran region have in general a north and south direction. Their direction was determined by fissures formed long ago in the crust of the earth. Movements have continued to take place along many of these fissures up to the present time, and probably will continue for some time to come. In order to become better acquainted with these remarkable mountains, let us examine some of them, taking first the Wasatch Range in eastern Utah. The range has an elevation of nearly eleven thousand feet, rising gradually upon the eastern side, but presenting a bold and picturesque front upon the west, toward the plain of Great Salt Lake. A short drive from Salt Lake City brings us to the foot of the range, at the mouth of Little Cottonwood Cañon. A peculiar bluff which extends for a number of miles along the base of the mountains at once attracts our attention. The steep face of the bluff, which is from fifty to seventy-five feet high, appears to have been formed by a rising of the land upon the side next the mountains, or a dropping upon the valley side. There are reasons for believing that the formation of the bluff was due to the occurrence of an earthquake some time within the last century. The bluff is closely related to the mighty mountains behind it. It was formed by the last of a series of movements in the earth which raised the great block known as the Wasatch Range to an elevation of six thousand feet above the plains at its base. Is it to be wondered at that disturbances of the earth which result in the erection of mountains of such height are frequently so severe as to destroy the strongest buildings? Now let us go westward across the various parallel ranges of the Great Basin to Owens Valley at the eastern base of the Sierra Nevada mountains. This is the highest and longest continuous mountain range in the United States. For a distance of more than one hundred miles its elevation is from twelve thousand to over fourteen thousand feet. [Illustration: FIG. 23.--EASTERN FACE OF THE SIERRA NEVADA MOUNTAINS Formed by a great fracture in the earth's crust] Owens Valley was in 1872 the centre of one of the most severe and extensive earthquakes ever recorded in the United States. The little village of Lone Pine, situated in the valley below Mount Whitney, was utterly demolished, twenty people were killed and many injured. A portion of the valley near the village sank so low that the water flowed in and formed a lake above it. The land was so shaken up that the fields of one man were thrust into those of his neighbor. For a distance of several hundred miles to the north along the base of the mountains the earth was fractured, and bluffs from ten to forty feet high were formed as a result either of the dropping of the surface of the valley upon the eastern side, or of the raising of the mountains upon the west. This slipping of the earth which gave rise to the earthquake bluffs was the most recent of a long series of similar events which have raised the precipitous eastern wall of the Sierra Nevada mountains to a height of two miles above Owens Valley. If you will go out into the centre of the valley and look west toward the mountains, you will see three bluffs or scarps. The first, which is twenty feet high, was made at the time of the last earthquake; the second, known as the Alabama Hills and rising about four hundred feet, was formed at an earlier time; the third, rising back of the others, is that of the main Sierra. Similar cliffs appear at the bases of other ranges of mountains in the Great Basin. Springs abound along these fractures in the earth, for the surface waters have an opportunity to collect wherever the rocks are broken. Numerous fertile valleys mark the line of earthquake movements, for the broken rocks and abundant springs favor rapid erosion. Among the Coast Ranges of California there appears a series of fractures in the earth which form a line nearly four hundred miles long. They extend from a point near San Bernardino in a northwesterly direction to the neighborhood of San Francisco. Severe earthquakes have taken place along this line since the country was settled. The pressure and grinding of the earth upon opposite sides of the fissures has formed long low ridges of earth. Small valleys have been blocked, and the old stage road from Los Angeles to Bakersfield, which followed the course of the fissures for a number of miles, has been almost obliterated. [Illustration: FIG. 24.--ELIZABETH LAKE, CALIFORNIA Occupying a valley primarily due to earthquake movements] Hundreds of cliffs and mountain scarps throughout the West have come into existence as the results of movements such as we have been describing. Where the disturbances have been recent the mountains are bold and picturesque. Those produced in earlier times are in many instances so worn away that it is difficult to tell with certainty how they were made. THE LAST VOLCANIC ERUPTIONS IN THE UNITED STATES There are more volcanoes in our country than is generally supposed. Some are very small and some rank among the greatest of mountain peaks, but all together there are many hundreds, perhaps thousands, of them. At present they are all silent and apparently dead. We are accustomed to speak of them as extinct volcanoes, but of this we must not be too sure. They stand dark and cold, giving no clue to the nature of the forces which made them, except perhaps by the presence of an occasional hot spring and the appearance of the rocks of which they are composed. The slag-like character of these rocks we have learned to associate with intense heat. Some of these volcanoes are very old and have been nearly worn away; others are new and almost as perfect as when they were first made. Where shall we go to find these volcanoes? Are there any upon the Atlantic coast or neighboring highlands? Though you may travel over all that portion of our country, you will find none, although you will discover in places, as for instance in the palisades of the Hudson, lavas which came from very ancient volcanoes, worn down so long ago that their very sites are lost to view. If we search the Mississippi basin we find there even fewer traces of volcanic action than upon the eastern highlands. The greater portion of the vast area embraced by the Mississippi River and its tributaries has had a very uneventful history, although at times earthquakes may have occurred and the sky may have been darkened by ashes from eruptions in distant parts of the earth. [Illustration: FIG. 25.--FISSURE IN THE LAVA, SHADOW MOUNTAIN The groovings in the lava show that it was squeezed out in a half-solid condition] It is in the country west of the Rockies, the region last to be explored and settled, that the objects of our search come to light. Here are volcanoes and lava fields so extensive as almost to bury from sight the older surface of the earth. Some of them appear as if but yesterday they had been glowing with heat. In the Cordilleran region Nature has carried on her work with a master hand. She has lifted the earth's crust to form a great plateau. Portions of the plateau she has broken, projecting the fragments upward to form lofty mountains, while along the fissures thus created she has squeezed out fiery molten matter from the interior of the earth. This molten material has spread out in fields of lava or has piled itself about small openings, forming volcanic cones, which in some cases have overtopped the loftiest mountain ranges of the continent. It is believed that a number of these volcanic eruptions have occurred in the Cordilleran region of the United States since the discovery of America, and that one took place within the lifetime of many persons now living. San Francisco Mountain, in northern Arizona, is the loftiest volcanic peak of a region dotted with volcanoes and lava flows. This great volcano, like most of its neighbors, has long been extinct, although a few miles to the eastward there appears a group of small but very new cones. A ride of fifteen miles from the town of Flagstaff, across the forest-covered plateau, brings us to Shadow Mountain and the fields of lava and volcanic sand lying at its base. The mountain, throughout its height of over one thousand feet, is a conical aggregate of loose lapilli which give way under the feet and make climbing the peak very tiresome. The lapilli and scoriæ are slag-like fragments of lava which have been blown out of the throat of the volcano while in a hot or semi-molten condition. These fragments, as they fall back to the earth, collect about the opening and in time build up the volcano, or cinder cone, as such a mountain is frequently called. The finer particles, which have the appearance of dark sand, fall farther away and form a layer over the surface for some miles upon every side. These products of an explosive volcano are sometimes called cinders and ashes, because of their resemblance to the slag and refuse of furnaces. In the case of the volcano which we are studying, the lapilli are so black that they give the cone the appearance of being darkened by the shadow of a cloud, and on this account the peak is named Shadow Mountain. As the days are usually bright here, the shadow effect is very striking. [Illustration: FIG. 26.--EDGE OF LAVA FIELD, WITH PUMICE IN THE FOREGROUND Near Shadow Mountain] There are several smaller craters, east of the main one, which also threw out volcanic sand and lapilli. The surrounding hills are of volcanic origin, although very much older than Shadow Mountain. These hills are covered with pine forests; but trees or plants have gained only slight hold upon the newer surfaces of the cinder cones, which present a picture of almost complete desolation. There have been two other eruptions since the making of the cinder cones, and these were marked by flows of molten lava. Although the rough and rugged surface of the older flow has not yet begun to crumble and form soil, as it must do in time, yet a few trees are found here and there, reaching their roots down for the scanty nourishment to be drawn from the crevices of the rocks. The last flow of lava, which was very small, ran into a depression in the other flow just described. This lava appears so fresh that we almost expect to find the rocks still warm. What a contrast between the wooded hillside adjoining, with its carpet of soft volcanic sand, and the jagged surface of the lava! Care must be taken in climbing over the lava, for the sharp points and angles are ever ready to tear one's shoes and hands. It cannot be many years since these hard, cold rocks formed a glowing mass of molten matter creeping quietly out of some hidden fissure which reached far down into the earth. The lava hardened as it became cold, just as does molten iron when led from the furnace to make a casting. At one spot in the lava field stand the remains of rude stone houses built into caverns in the lava. About them are scattered pieces of broken pottery. These rude dwellings were probably occupied by some of the prehistoric people whose homes are also found along many of the streams, and in the caves of the plateau region. We can see no reason for their coming to this desolate place, so far from a water supply, unless it was that the rugged lava offered some protection from their enemies. Now let us imagine ourselves transported to northern California. Near Lassen Peak, the southernmost of the great volcanoes of the Cascade Range, there lies another field of recent volcanic activity of even greater interest than the first. The centre of attraction is Cinder Cone, similar to Shadow Mountain in its manner of formation as well as in materials, but more symmetrical in form. Upon one side is a field of black lava several miles in extent, while volcanic sand has been spread over all the adjacent country. [Illustration: FIG. 27.--THE CRATER OF CINDER CONE] As nearly as can be determined, only a little more than two hundred years ago the valley now occupied by Cinder Cone and the lava fields gave no indication of ever becoming a new centre of volcanic action. It has been thousands of years since the ancient volcanic peaks and cinder cones of this mountainous region became extinct. The glaciers had come, and torn and ground away the surface of the lava, and afterward dense forests had hidden all the rocky slopes, while lakes had occupied many of the valleys. Far below, however, the fires had not gone out. In many places there were boiling springs from which the steam, upon cold mornings, rose in dense white clouds. Then, for some reason which we do not understand, the forces beneath the surface increased their activity. The force of the steam and other gases was too great to be restrained, and at a weak spot in the overlying rocks they broke through. Molten lava accompanied them, and a new volcano came into life in the valley where Cinder Cone now raises its dark, symmetrical slopes. The eruptions were violent. With explosive force the molten lava was torn into fragments, and sand, lapilli, and bombs were hurled out into the air. The finer particles were carried by the air currents far over the surrounding country. The lapilli, scoriæ, and bombs fell around the throat of the volcano, finally building up the cone to its present proportions. The great bombs, some of them five feet in diameter, are among the most remarkable products of this eruption. They lie scattered about upon the surface of the ground at the foot of the cone, and, although they are often irregular in shape, they might almost be mistaken for huge cannon-balls. The eruption killed and burned the trees in the near-by forests, burying them under six or seven feet of fine sand or ashes. After the cone had been built and the explosive eruptions had nearly stopped, a stream of molten lava burst from the base of the cone and filled a portion of the valley. Now followed a long period of quiet. Trees began to grow upon the sand and gradually to encroach upon the barren wastes about Cinder Cone. It appeared as if there were to be no more eruptions. But the volcano was only resting. At about the time, perhaps, when the gold seekers began to pour across the continent to California, there was another eruption; but this time it took the form of a lava flow and was so quiet as to create no disturbance in the surrounding country. [Illustration: FIG. 28.--CINDER CONE The trees were killed by the last eruption of volcanic ashes] A stream of thick, viscous lava flowed slowly out of an opening at the southern base of Cinder Cone. As the lava crept down the gentle slopes of the valley, it crusted over, forming a black, slag-like surface. The surface was from time to time broken up and mixed with the softer portions beneath, so that the movement of the flow was still further retarded. At the lower end of the valley the lava occupied a portion of a body of water now known as Lake Bidwell; its rugged front made a dam across the valley above, forming Snag Lake. The stumps of the trees which were killed by the water when the lake was first formed are still standing. [Illustration: FIG. 29.--THE LAST LAVA FLOW IN THE UNITED STATES At Cinder Cone, California. It formed a dam across a valley, thus creating Snag Lake] One's feet sink deep into volcanic sands, and walking is tiresome. The lava field resulting from the last eruption is free from sand, but its rough surface, formed of broken blocks, is difficult to cross. A few charred stumps rise out of the sand, pathetic remnants of the forest trees that were growing at the time of the first eruption. Most of the trees have completely disappeared, leaving shallow pits where they once stood. It is exceedingly difficult to climb the cone, which rises over six hundred feet, for the slopes, composed of loose lapilli, are so steep that one slips back at every step nearly as far as he advances. From the summit a remarkable sight meets the eye. Within the rim of the main crater is a second crater with a rim nearly as high as the first, while the cavity within has a depth of about two hundred and fifty feet. Because of the loose character of the material of which it is built, no streamlets have yet worn channels down the slopes of Cinder Cone, and except for the presence of two small bushes which cling to its side, it is just as bare and perfect in form as when first completed. Little by little the forests are encroaching upon the sand-covered slopes about the cone, and in time these slopes, the black fields of lava, and the cone itself, will be covered with forests like the older lava fields and cinder cones which appear upon every hand. THE MUD VOLCANOES OF THE COLORADO DESERT The Colorado Desert is a strange, weird region. Here is a vast basin at the head of the Gulf of California which was once a part of the gulf, but is now separated from it by the delta of the Colorado River. With the drying up of the water, the centre of the basin was left a salt marsh more than two hundred and fifty feet below the level of the ocean. In summer the air quivers under the blazing sun, and it seems as if no form of life could withstand the scorching heat, but in winter the atmosphere is cool and full of life-giving energy. Around this desert rise the mountains, some old and nearly worn down, their tops barely rising out of the long slopes of sand and gravel; others rugged and steep, lifting their crests far above the burning desert into the cold, clear sky. Curious forms of plants and animals find their homes upon the slopes about the basin, where they adapt themselves to the heat and dryness. But toward the centre the soil is bare clay, for when the water dried up so much alkali and salt were left that nothing could grow. However we do not now intend to study the plants or the animals, interesting though they are, but rather a group of mud volcanoes, which forms almost the only relief in the monotony of the bare plain. These volcanoes are in no way related to real volcanoes except in shape, for water and mud, instead of fire and lava, have been concerned in their building. [Illustration: FIG. 30.--MUD VOLCANOES, COLORADO DESERT] Once it required a long journey in wagons or upon horseback to reach the mud volcanoes, but now the railroad takes us within three miles of the spot. We alight from the train before a section house which stands in the midst of the great desert. Far, far away stretches the barren clay floor of the ancient lake. Here and there are scattered stunted shrubs, the only specimens of plant life which have been able to withstand the alkali in the clay. Seen from the station, the volcanoes appear like dark specks almost upon the horizon, but in reality they are not far away, and an hour's brisk walk will bring us to them. The mud springs, which are scattered over an area of several hundred acres, present many strange and interesting features. There are holes in the earth with bubbling mud at the bottom, cones from the tops of which streams of muddy water issue, and ponds of mud, in some cases as thick as molasses, in others thin and watery. There are little jets of steam, strange odors, and a vista of many mingled colors. Taken altogether, it is a place quite different from any other that we have ever seen. The ground is soft and marshy, and in some places undermined by the water, so that we have to take great care in walking about. Some of the smaller springs occupy round depressions, sometimes three or four feet across, which look as if they had been made by pressing a large pan down into the clay. The bubbling mud in the bottom of the pan, as well as the hot water in many of the springs, makes it easy to imagine that we are standing upon the top of a great cooking stove in which a hot fire is burning. As the gas with which the water is impregnated comes up through the mud, it forms huge bubbles which finally break and settle down, only to rise again. In this way concentric mud rings, perfect in form, are made to cover the entire surface of the pool. Where there is little water, the surface of the mud hardens and leaves a small opening, through which the bubbling gas throws small columns of mud at regular intervals. From the large pools, some of which are forty to fifty feet in diameter, there comes a low murmuring sound like the boiling of many kettles. The water is sputtering and bubbling, and in some places it is hot enough to give off thin clouds of steam. Occasionally we get whiffs of sulphur, while about the borders of some of the ponds pretty crystals of this mineral can be found. More commonly the pools are crusted about with a white deposit of salt, for they all contain more or less of this substance in solution. Around a few of the pools the mud is stained with the red tinge of iron, and red lines mark the paths of the streams as they run off from the pools toward the still lower portions of the desert. [Illustration: FIG. 31.--POT-HOLES] The built-up cones or volcanoes appear in every stage, from the little ones a few inches high to the patriarchs, which in some cases have reached a height of twelve feet. These cones are formed by the hardening and piling up of mud about the openings; but when they have reached the height mentioned, the passages up through their centres, corresponding in each case to the throat of a real volcano, become clogged and new holes are formed in the mud at the base. [Illustration: FIG. 32.--AN EXTINCT MUD VOLCANO With small active one at its side] Many of these mud volcanoes closely resemble true volcanoes in form and structure. The mud which pours out at the top forms streams down the slopes very like those of molten lava. New cones are built upon the sides or at the bases of the old ones in much the same way as are those in the volcanic regions. There are no signs of volcanic action in the vicinity of these mud springs, and it is likely that the water is forced to the surface by large quantities of gas produced by chemical changes taking place deep within the clay beds of the old lake. Similar springs occur farther south, nearer the mouth of the Colorado River, in the Yellowstone Park, and near Lassen Peak, but nowhere in America except in the Colorado desert have they formed such large and interesting mounds. THE HISTORY OF A COAST LINE The story of our Pacific coast reads more like a tale from the "Arabian Nights" than like a plain statement of events which have actually happened. The meeting place of the land and ocean is not really so permanent a line as it appears. The shore has been continually moving back and forth throughout the long history of the earth. That which was dry land at one time was at another time deeply buried beneath the ocean. The Pacific border seems never to have been at rest. It has risen and sunk again repeatedly. It has been squeezed, folded, and broken, shaken by earthquakes, and disturbed by volcanic eruptions. One might be led to think from this statement that it would not be safe to live on the Pacific coast, and that both animals and men would shun the region. The fact is, however, that these changes usually come to pass so very slowly that we are not aware of them. Severe earthquakes and volcanic disturbances take place so rarely in comparison with the length of a man's life, that we may pass our whole lives without experiencing any of these violent disturbances. The Pacific coast region, with its forest-covered mountains, fertile valleys, and beautiful homes, presents so quiet and peaceful an appearance that it is difficult to believe that parts of its history have been so tumultuous. Perhaps you will ask how we can know so much about the past. It is true that no one was here to witness the events which are supposed to have taken place. But Nature has left a record of her doings which we have only to see and understand in order to learn with certainty many things which happened in the far distant past. Too many of us go through life seeing and understanding almost as little of the world about us as if we were blind. Our early ancestors were obliged to understand many things about Nature and to cultivate clear and close observation for the sake of self-preservation. The very life of the savage depends upon the training of his eyes. He must be able to tell the meaning of a distant object or an indistinct trail, for his enemies may have passed that way recently. If we could bring the sharp eyes of the savage to our aid, the world would mean much more to us. In order to learn something of the history of the Pacific shore line, we must see what the waves are doing at the present time. The projecting points of land are being worn away (Fig. 33). The waves form the cliffs against which they beat, and sometimes, as they eat their way slowly into the land, they cut off portions and leave them standing alone as islands. The pebbles and boulders (Fig. 34) were once angular fragments torn from the cliff. They have been washed about and hurled against the solid rock until they have been worn smooth; and the cliff in turn has had a cave ground out at its base. Above the lower cave there is a remnant of a second one, with pebbles upon its floor. This was made when the land stood ten feet lower than at present. As the waves wear away the loose earth and the solid rock below it, moving the cliffs inland, they leave a comparatively smooth surface which is partly exposed at low tide. The fact that this surface is not marked by stream channels, as is the land, helps us to realize the great difference between the irregular surface of the latter and the plain-like character of the ocean floor. [Illustration: FIG. 33.--POINT BUCHON, CALIFORNIA The waves are eating their way into the land] Along the whole coast of California there are many old sea beaches and cliffs which the waves abandoned long ago. The highest of these beaches lies so far up the slopes of the mountains bordering the ocean that it makes us wonder what the geography of California could have been like when the region was so deeply submerged. The lowest and newest terrace is the one shown in Fig. 35, ten feet above the ocean. Each succeeding terrace is less distinct, and the highest, fourteen hundred feet in elevation, can now be distinguished in only a few places. Where the old sea cliffs are best preserved they form a series of broad, flat steps, rising one above the other. Each bench, or terrace as it is commonly called, is a part of an old plain cut out of the land by the waves when the ocean stood at that level. The steeper slope rising at the back is the remnant of the cliff against which the waves used to beat. If we are fortunate, we shall find at its base some water-worn pebbles and possibly a few fragments of sea-shells. The crumbling of the rocks and the erosive action of the rills are fast destroying the old cliffs, so that in many places they have entirely disappeared. [Illustration: FIG. 34.--OCEAN CAVE AT LOW TIDE Pebbles of a former beach are seen above] Upon the seaward face of San Pedro Hill, in southern California, there are eleven terraces, rising to a height of twelve hundred feet. What an interesting record this shows! Long ago the land stood twelve hundred feet lower than at present, and the waves beat about San Pedro Hill, nearly submerging it. Then the land began to rise, but stopped after a time, and the waves cut a terrace. The upward movement was continued, with repeated intervals of rest, until the land stood higher than it does now. [Illustration: FIG. 35.--WAVE-CUT TERRACES Point San Pedro, California] North of San Francisco there stands a terrace fourteen hundred feet above the ocean. Numerous terraces appear along the Oregon coast, but those in Washington are not as high as those in California. It is probable that the land in this region was not so deeply submerged. The ancient shore lines of British Columbia and Alaska are now deeply buried beneath the ocean, as those of California once were. The fiords, so common in these countries, are old river valleys which have been drowned by the sinking of the land. The islands were once portions of the coast mountains, but have been cut off by the same process. Let us picture in our minds the changes in the geography of the Pacific coast of the United States which must have been made by a sinking of the land to a depth of only six hundred feet. We will begin upon the north, at the Strait of Fuca. Puget Sound once opened to the south as well as to the north, so that the Olympic Mountains formed an island. The broad and fertile Willamette Valley was but an arm of the sea, somewhat like Puget Sound to-day. The body of water which once filled this valley has been called Willamette Sound. The ocean overspread the low Oregon coast, and reached far up the valleys of the Umpqua and Rogue rivers. But the boundaries of the Klamath Mountains were not greatly changed, for in many places they rise quite abruptly from the present shore line. All the large valleys of California were flooded, including the San Joaquin-Sacramento valley, which was then a great sound, open to the ocean in the region of the present Strait of Carquinez. The Coast range was broken up into islands and peninsulas. The islands off the coast of southern California are high and therefore were not entirely submerged. The Gulf of California spread over the Colorado Desert, while from the west the water penetrated inland over the plain of Los Angeles to a point beyond San Bernardino, so that at the San Gorgonio pass only a narrow neck of land connected the San Jacinto Mountains and the Peninsula Range with the mainland. If California had been inhabited at this time, the state would not have been noted for orchards and grain-fields, but rather for its mineral wealth. There would have been comparatively little low land fit for cultivation, but the mountains, where almost all the precious metals are found, would have appeared nearly as they do to-day. The surface of the earth may be divided into the ocean basins and the continental masses which rise above them, but we must not make the mistake of thinking that the shore line always corresponds with the border of the continental masses. We have learned that the land is almost always moving slowly up or down, so that the shore is continually changing back and forth. At one time the shore line may be far within the borders of the continent, as we have seen was once the case upon our Pacific coast; at another time, if the land should rise, the shore line might coincide with the real border of the continent. By the real border of the continent we mean the line along which the earth slopes down steeply to the abysmal depths of the ocean. It is an interesting fact that outside the present shore line of California there is a submerged strip of the continent varying from ten to one hundred and fifty miles in width. This strip of land is like a bench upon the side of the continent, and is known as the continental plateau. The water over the plateau is comparatively shallow. Upon one side the land rises, while upon the other there is a rapid descent into the deep Pacific. The surface of the plateau is in general fairly smooth, but in places mountains lift their summits above the water and form islands. There was a time, thousands of years earlier than the period when California was so nearly covered by the waters of the Pacific, when this land stood far higher than it does now. The coast line was then much farther west, near the border of the submarine plateau. The Santa Barbara Islands at that time formed a mountain range upon the edge of the continental land. This fact was established by the discovery upon one of the islands of a large number of bones of an extinct American elephant. These animals could have reached the submerged mountains only at a time when there was dry land between them and the present shore line. We should like to know how it came about that these bones were left where they are. Perhaps the land sank so suddenly that the water cut the elephants off from the mainland and compelled them to spend the remainder of their lives upon these islands. While the land stood so high, some of the larger streams wore deep channels across what is now the submarine plateau. These channels have been discovered by soundings made from the ships of the United States Coast Survey. The largest of the submerged valleys extends through the Bay of Monterey, and runs so close to the shore that it has offered a favorable location for a wharf. Before the buried valleys upon the northern coast of California were all known, the presence of one of them led to the wreck of a ship. The shore was obscured by fog, but the soundings made by the sailors showed deep water and led them to believe they were a long distance from land, when suddenly the ship drifted in upon the rocks. The last significant movement of the land of the Pacific border was a downward one. It flooded the mouths of the streams and formed all the large harbors which are of so great commercial importance. San Francisco Bay occupies a great stretch of lowland at the meeting of several valleys of the Coast Ranges and forms the outlet for the most important drainage system of California. If this region had been settled before the subsidence of the land which let in the ocean through the Golden Gate, how the farmers would have lamented the flooding of their fertile lands! But we can understand how small the loss would have been, compared with the advantages to be gained from the magnificent harbor which now exists here. If the land had not sunk the history of the Pacific coast would have been far different. [Illustration: FIG. 36.--ISLAND ROUNDED BY A GLACIER Near Anacortes, Puget Sound] Puget Sound, another very important arm of the ocean, is also a submerged valley, but it has had an entirely different history from that of San Francisco Bay. The valley was at one time occupied by a great glacier which came down from the Cascade Range and moved northwest through the sound and into the Strait of Juan de Fuca, scouring and polishing the rocks over which it passed. A little island near Anacortes (Fig. 36) has been rounded by the action of the ice into a form like a whale's back. [Illustration: FIG. 37.--AN ABANDONED OCEAN CLIFF Southern California] The sinking of the land flooded the lower Columbia River and the mouth of the Willamette, so that ocean ships may now go up as far as Portland. The currents and waves soon threw up bars across the mouths of the smaller streams, and formed lagoons behind them. Ships frequently have difficulty in entering many of the harbors because of the sand bars which have been built up part way to the surface of the water. It is thought that along some portions of the coast there has recently been a slight upward movement of the land. Figure 37 shows a bit of California coast, near San Juan, where the Santa Fé railroad has laid its tracks for several miles along a strip of abandoned beach, at the base of a cliff against which the waves once beat. [Illustration: FIG. 38.--LIMESTONE CLIFF, QUATSINO SOUND, VANCOUVER ISLAND] At the northern end of Vancouver island there is a deep arm of the ocean called Quatsino Sound. A limestone cliff upon the shore of this sound (Fig. 38) has been undermined by the dissolving of the limestone, but now the water lacks three feet of rising to the notch which it recently formed. THE DISCOVERY OF THE COLUMBIA RIVER The influence exerted by the various features of the land and water upon the settlement of a new region are not always fully appreciated. If the entrance to San Francisco Bay had been broader and more easily discerned by the early navigators who sailed past it, and if the mouth of the Columbia River had not been obscured by lowlands and a line of breakers upon the bar, the history of western America would probably have been very different. In the seventeenth century the prospect seemed to be that Spain would control the Pacific Ocean. She claimed, by right of discovery, all the lands bordering upon this ocean and the exclusive right to navigate its waters. Every vessel found there without license from the court of Spain was, by royal decree, to be confiscated. It is interesting, after all these years and with our present knowledge, to look back and see how unreasonable were the claims of Spain. In the fifteenth century the extent of the Pacific ocean was not known. In fact, men's ideas as to the distribution of land and water over the earth were so indefinite that it was at first supposed that the islands which Columbus discovered belonged to the East Indies. The claims of Spain to the Pacific Ocean were based upon its discovery by Balboa, but she never made any serious efforts to enforce them, for the attempt would have involved her in war with all the maritime nations of Europe. Spain lacked the ability to take advantage of the great discoveries which her navigators and explorers had made, and for that reason she merely looked on, though with jealous eyes, when in the eighteenth century the ships of England, France, Holland, and Russia entered the Pacific Ocean with a view to exploration and conquest. Determined at last to support their claim to the Pacific coast of North America, the Spaniards began to realize the necessity of exploring it more fully and of founding settlements. It was their plan to take possession of the whole region between Mexico upon the south and the Russian trading posts along the shores of Alaska. As exploration by land was impossible because of mountain ranges and deserts, the Spanish adventurers were forced to rely upon the ocean, with all its uncertainties of storm and contrary winds. Between 1774 and 1779 voyages were made as far north as Queen Charlotte's Island, in latitude 54°. A station was established and held for many years at Nootka Sound, upon the west coast of Vancouver Island. The first expedition passed the Strait of Juan de Fuca apparently without seeing it, although there was a rumor to the effect that a broad opening into the land had been discovered by a certain Juan de Fuca in 1592, while he was exploring in the employ of Spain. The latitude of this opening, as he gave it, nearly corresponds to that of the strait which now bears his name. For many years the attempt to discover a passage around the northern part of America engaged the early navigators upon both the Atlantic and Pacific oceans. Their desire to find an easy route to India spurred them to constant effort. For a time it was believed that such an opening actually existed, and mariners went so far as to give it a name, calling it the Straits of Anian. The reputed discoveries of Juan de Fuca materially strengthened the general belief in a passage to the northward of America. Vizcaino, in his voyage of 1603, reached latitude 43° north and thought that he had discovered a great river flowing into the Pacific Ocean. This opening, although south of the point supposed to have been reached by Juan de Fuca, was believed for a time to be the entrance to the long-sought Straits of Anian. During the latter part of the seventeenth century California was represented upon the Spanish maps as an island having Cape Blanco, which Vizcaino discovered and named, as its northern point, and separated from the mainland by an extension of the Gulf of California northward. To return now to the Spanish explorations, in the latter part of the seventeenth century we find that Heceta, following the first expedition, succeeded in getting as far as Vancouver Island, where, having been parted from an accompanying ship by a storm, he turned southward, passing the Strait of Juan de Fuca and keeping close by the shore. In latitude 46° 17' he found an opening in the coast from which a strong current issued. He felt sure that he had discovered the mouth of some large river. Upon the later Spanish maps this was called Heceta's Inlet, or River of San Roque. A glance at the map will show how closely the latitude given corresponds to the mouth of the river which was discovered later by Captain Gray and named, after his ship, the Columbia. A short time before Heceta's discovery, Captain Jonathan Carver of Connecticut set out on an exploring tour, partly for the purpose of determining the width of the continent and the nature of the Indian inhabitants. He mentions four great rivers rising within a few leagues of one another, "The river Bourbon (Red River of the North) which empties itself into Hudson's Bay, the waters of the St. Lawrence, the Mississippi, and the river Oregon, or River of the West, that falls into the Pacific Ocean at the Straits of Anian." Carver's descriptions are fanciful, and it is not likely that he ever saw the river which is now known as the Columbia, although there is a possibility that he heard stories from the Indians of a great river upon the western slope of the Rocky Mountains, and invented for it the name Oregon. In 1787 Meares, an English trader, visited the coast, and sailing southward from the Strait of Juan de Fuca, attempted to find the river San Roque as it was laid down upon the Spanish charts. Reaching the proper latitude, Meares rounded a promontory and found behind it a bay which he was unable to enter because of a continuous line of breakers extending across it. He became satisfied that there was no such river as the San Roque, and named the promontory Cape Disappointment and the bay Deception Bay. If Meares had entered the bay through the breakers, the English would undoubtedly have made good their claim to the discovery of the Columbia River. After the Revolution, American trading ships began to extend their operations into the North Pacific. In 1787 two such vessels left Boston, one of them under command of a Captain Gray. After reaching the Pacific, the ships were parted during a storm, and Captain Gray finally touched the American coast near the forty-sixth degree of north latitude. For nine days he tried to enter an opening which was in all probability the one attempted by Meares. After nearly losing his ship and suffering an Indian attack, he sailed north to Nootka Sound. Captain Gray returned to Boston, but in 1790 started upon another trading expedition in command of the ship _Columbia_. Arriving safely in the North Pacific, he spent the winter of 1791-1792 upon Vancouver Island. Vancouver, whose name has been given to the largest island upon the western coast of North America, and who did so much to make known the intricate coast line of the Puget Sound region, arrived upon the scene in 1792. He was authorized to carry on explorations, and to treat with Spain concerning the abandonment of the Spanish claim to Nootka Sound. Vancouver sailed up the coast, keeping a close lookout for the river San Roque. No opening in the land appeared, although at one spot he sailed through a muddy-colored sea which he judged was affected by the water of some river. Upon reaching the Strait of Fuca, Vancouver expressed the opinion that there was no river between the fortieth and forty-eighth degrees of north latitude, "only brooks insufficient for our vessels to navigate." Shortly after this time, Vancouver met Captain Gray with his ship _Columbia_. The disheartened explorer placed no confidence in Captain Gray's report that, upon his former voyage, he had discovered a large river to the south. Vancouver in his narrative says, "I was thoroughly convinced that we could not possibly have passed any safe navigable opening, harbor, or place of security for shipping on this coast from Cape Mendocino to the promontory of Closset" (Cape Flattery). Captain Gray, however, determined to make further investigations. He sailed southward and entered a port now known as Gray's Harbor, where he spent several days trading with the Indians. From this harbor he ran on south for a few miles past Cape Disappointment, and then sailed through an opening in the breakers into a bay which he supposed formed the mouth of the river of which he was in search. He finally anchored, as he says, "in a large river of fresh water." [Illustration: FIG. 39.--A SCENE ON GRAY'S HARBOR, WASHINGTON Showing sawmills and log booms] Later Captain Gray took the vessel twelve or fifteen miles up the river, and would have gone farther if he had not wandered into the wrong channel. When he left the river he named it the Columbia in honor of his vessel. Thus by the right of actual discovery the United States was at last able to make good its claim to the river. The English claimed that Gray did not enter the river itself, as the tide sets up many miles farther than the point which his ship reached. They insisted that what he saw was simply a bay. But the truth is that Gray was actually in the mouth of the river. The mere fact that the tide enters the lower portion of the river makes no difference. The actual mouth of the Columbia is marked by the north and south coast line. The entrance of the tide water, and the backing of the current for many miles up stream, is the result of a recent sinking of the land. The same features are presented by the Hudson River. If the English had discovered and entered the river first it is probable that this stream would have become the boundary line between the United States and British Columbia, in which case the whole northern portion of the Oregon territory would have been lost to us. As it was, the English laid insistent claim to the northern bank of the river and established trading posts at various points. The lowest of these posts stood upon the site of Fort Vancouver, a little above the mouth of the Willamette River. The famous exploring expedition under Captains Lewis and Clark wintered at the mouth of the Columbia in 1804-1805, in a group of rude log cabins known as Fort Clatsop. The first settlement in the vicinity was made in 1811, when a fur company organized by John Jacob Astor attempted to establish a trading post upon the Columbia. Two parties were sent out from New York. One travelled by water around Cape Horn, while the other, with great difficulty, crossed the continent by the way of the Missouri, Snake, and Columbia rivers. The undertaking proved unsuccessful, for after the War of 1812 began supplies could no longer be sent safely to the post. The Astor company finally surrendered its establishment to an English company, and in this way the control of the river was transferred to England. With the return of peace the post was restored to the United States, and its location is marked now by the city of Astoria. [Illustration: FIG. 40.--TILLAMOOK ROCK Near the mouth of the Columbia River] What small things sometimes determine the trend of great events! A little more care and energy on the part of Vancouver or Meares would have placed the Columbia River in the hands of the English. The existence of an open river mouth without any breaking bar would have brought about the same result. The Spaniards came first to the Pacific slope, claiming the whole coast as far north as the Russian possessions. Later the United States, by treaty with Spain and Russia, acquired a right to all that portion of the Pacific coast of North America which lies between California and the Russian possessions. But because of the greater energy of the English, and the failure upon the part of the United States to realize the value of this vast region, a considerable section was again lost by the terms of the treaty which made the forty-ninth parallel the boundary line. The intelligence and energy of Captain Gray alone preserved to us the rich lands of Washington. [Illustration: FIG. 41.--ASTORIA, OREGON At the mouth of the Columbia River] THE GREAT BASIN AND ITS PECULIAR LAKES As our country was slowly being explored and settled, one region was brought to light which Nature seemed to have left unfinished and in a desolate condition. This barren stretch of country was once marked upon the maps as the Great American Desert, and included a large part of the extensive region lying between the Rocky Mountains upon the east and the Sierra Nevada Mountains upon the west. To the south lay the Grand Cañon of the Colorado, while upon the north the boundary was formed by the cañons of the Snake and Columbia rivers. After a time it was found that this region, covering about two hundred and twenty-five thousand square miles, not only was extremely dry, but had no outlet to the ocean. A rim of higher land all about made of it so perfect a basin that it became known as the Great Basin. None of the water that falls upon the surface of this basin ever reaches the ocean through surface streams. Some of it soaks into the rocks, but the greater part is evaporated into the dry air. We have already learned something about the way in which the ridges and hollows of the earth's surface are made. We have learned of the wrinkling of the crust, of the formation of fissures, and of the erosive work of running water. The interesting features of the Great Basin are mainly the result of two causes: the sinking of a portion of the earth's surface, and the lack of rainfall. Long ago the Wasatch Range of eastern Utah and the Sierra Nevadas of California formed parts of a vast elevated plateau. Then there came a time when the forces holding up the plateau were relaxed, and as the weight of the plateau pressed it down, the solid rocks broke into huge fragments. Some of the blocks thus made sank and formed valleys; others were tilted or pushed up and formed mountains. Thus the north and south mountain ranges and valleys of the Great Basin were born. We must understand, then, that the Great Basin is not a simple depression with higher land all about. The breaking up of the surface produced many basins, large and small. Some of these basins are six thousand feet above the level of the sea, others are much lower, and one has been dropped below the level of the sea, so that if it were not for barriers the water would flow in. Some of the basins are rimmed all about by steep mountains, others are so broad and flat that it is difficult to tell that they really are basins. Many of the valleys are so connected with one another that if a heavy rainfall should ever occur drainage systems would be quickly established. The Great Basin now appears like the skeleton of a dried-up world; but if the climate should change and become like that of the Mississippi Valley, the surface of the desert would undergo a wondrous transformation. The hundreds of basins, if fed by streams from the surrounding mountains, would then become lakes. The highest, overflowing, would empty into a lower, and this in turn into a still lower basin, until the water had accumulated in vast inland seas. These seas, overflowing the rim of the Great Basin at its lowest points, would send rivers hastening away to the ocean. [Illustration: Map of the Great Basin showing the location and extent of the ancient lake beds.] What a region of lakes this would be for a time! Then they would begin to disappear, for lakes are short-lived as compared with mountains. Some would be filled with clay and gravel brought by the streams. Others would be drained by a cutting down of their outlets. Great Salt Lake, which is the only body of water in the Basin that has ever sent a stream to the ocean, was lowered four hundred feet by the washing away of the rock and earth at its outlet. We know that the rainfall never has been heavy in this region since the Great Basin was formed, although at one time it was sufficiently great to form two inland seas, one in northwestern Nevada, the other in Utah. The chief reason for the dryness of the Great Basin is the presence of that lofty barrier, the Sierra Nevada mountain range, between the Basin and the Pacific Ocean. The storms, which usually come from the ocean, are intercepted by this range, and the greater portion of their moisture is taken away. The little moisture that remains falls upon the highlands of the Great Basin, and so relieves its surface from utter barrenness. The adjacent slopes of the Sierra Nevada and Wasatch ranges furnish numerous perennial streams which feed the lakes about the borders of the Basin, such as Great Salt Lake, Pyramid, Walker, Mono, Honey, and Owens lakes. The wet weather streams, flowing down the desert mountains for a short time each year, frequently form broad, shallow lakes which disappear with the coming of the summer sun. The climate of the Great Basin has changed from time to time. During one period it was much drier than it is now, and the lakes were nearly or quite dried up. It must have been a desolate region then, shunned by animals and forbidden to man. During the Glacial period, a few thousand years ago, the climate was moister and cooler than it is now. The mountains were covered with deep snows, and glaciers crept down the slopes of the higher peaks. Great Salt Lake covered all northwestern Utah; to this former body of water the name Bonneville has been given, in honor of a noted trapper. Pyramid, Winnemucca, Carson, Walker, and Honey lakes, now separated from one another by sagebrush deserts, were then united in one great lake, to which the name Lahontan has been given, in honor of an early French explorer. [Illustration: FIG. 42.--MONO LAKE, CALIFORNIA] Lake Lahontan covered a large portion of northwestern Nevada and penetrated into California. It was broken into long winding arms and bays by various mountain ranges. The deepest portion of this ancient lake is now occupied by Pyramid Lake, which is, perhaps, the most picturesque of all the Basin lakes. Fish can live in the waters of this lake, although nearly all the others are so salty or so alkaline that they support none of the ordinary forms of life. [Illustration: FIG. 43.--ROUND HOLE, A SPRING IN THE SMOKE CREEK DESERT Bed of old Lake Lahontan] Upon the Black Rock Desert, in northern Nevada, there are large springs once covered by Lake Lahontan, in which fish are found. It is thought that the ancestors of these fish must have been left there at the time of the drying up of the water. After the Glacial period the present arid climate began to prevail in the land. Hundreds of the shallow lakes which had been scattered over this extensive region disappeared. Others contained water for only a portion of each year. A body of water which is not permanent, but comes and goes with the seasons, we call a playa lake. Many of these playa lakes present in summer a hard, yellow-clay floor of many miles in extent and entirely free from vegetation. The beds of others are covered with a whitish crust, formed of the various salts which were in solution in the lake water. [Illustration: FIG. 44.--ROGERS LAKE, MOHAVE DESERT A playa lake] An important feature of the lakes of the Great Basin is the presence of large quantities of such substances as common salt, soda, borax, and nitre. The ocean is salt because it has no outlet, while the rivers of the globe are continually bringing into it various minerals, dissolved from the rocks over which they flow. Lakes with outlets are not salty, because with a continuous change of the water there is no opportunity for the minerals to accumulate, although they are always present in small quantities. Any lake which does not receive enough running water to cause it to overflow the borders of its basin, will in course of time become rich in various kinds of salt. No two of the lakes of the Great Basin are alike in the composition of their waters. This fact may be due to a difference in the rocks about the lake basin, to the presence of varying mineral springs, or to the drying up of one or more of the lakes at some time so that their former salts were buried under sands and clays when the water again filled the basin. Great Salt Lake contains little besides common salt. In Mono Lake, soda and salt are equally important constituents, while Owens Lake contains an excess of soda. In other basins borax was present in such quantities that when the waters dried up it formed important deposits. The value of these deposits is now fully understood, and many enterprising companies are at work separating and purifying the borax. Owens Lake was once fresh, although now it is so strong with soda that it would destroy the skin if a bather should remain in it very long. The former outlet of this lake was toward the south, through a pass separating the Sierra Nevada from the Coso Mountains. For a distance of thirty miles the old river-bed has been transformed into a wagon road, and it is interesting to ride all day along the bed of this dead river, past bold cliffs against which the waters once surged and foamed. The river emptied far to the south, into a broad, shallow lake whose former bed is now white with soda and borax. The old beach lines stand out distinctly upon the slopes of the enclosing mountains. The lake bed is now the seat of an important industry--the gathering of the borax and its refining. There are extensive buildings at one spot upon its border, and men come and go across the blinding white surface. A twenty-mule team dragging three huge wagons creeps slowly along the base of the distant mountains, but all that can be distinguished is a cloud of dust. [Illustration: FIG. 45.--FREIGHTING BORAX ACROSS THE DESERT] The slow crumbling of the rocks, and the setting free of those constituents which are soluble, the work of the streams in gathering the rock waste into the lakes, the dry air and the heat of the long summer days, have all conspired together to give us these valuable deposits in the dried-up lakes of the Great Basin. No portion of the earth seems to be without value to man. The great bodies of water are convenient highways. The rich valleys and timbered mountains offer useful products. Even the deserts, where living things of every description find the struggle for existence very hard, become indispensable. If the climate in the Great Basin had been moist, the salts would not have been preserved, but would have been carried away to the ocean, from which only common salt could have been recovered in commercial quantities. [Illustration: FIG. 46.--MUSHROOM ROCK, PYRAMID LAKE Formed of calcareous tufa] The crossing of the Great Basin was dreaded by the early emigrants on their way to the Pacific coast. In many cases the locations of the few springs and water-courses were unknown, and the journey over the vast barren stretches was fraught with danger. Stand upon a mountain in the desert some clear day in summer and you will see range after range, with intervening sandy wastes, stretching away to the horizon. The air below is tremulous with heat, and every living thing that can move has sought the shade of some rock or cliff. The plants seem almost dead, for the little springs, hidden at rare intervals in the deep cañons, are of no use to them. What transformations would be wrought upon these desert slopes if it were possible for the soil to receive and retain large quantities of water! Forest-covered mountains, green hillsides, rippling streams, lakes, farms, orchards, and towns would appear as if by magic. FRÉMONT'S ADVENTURES IN THE GREAT BASIN Frémont, "the Pathfinder," did greater service than any other man in making known the geographic features of the Cordilleran region. In the fifth decade of the last century, while California still belonged to Mexico and the pioneers were turning their attention to the Oregon country, Frémont organized and conducted three exploring expeditions under the direction of the government. When in California upon the third expedition he took part in the skirmishes which resulted in the transference of this section to the United States. A fourth expedition, undertaken by Frémont on his own account, resulted disastrously. The explorers foolishly tried to cross the Rocky Mountains in the middle of winter, but had to give up the attempt after many of the party had died from cold and starvation. It is hard for us to realize, now, that only sixty years ago the territory lying between the Rocky Mountains and the Pacific coast was practically unknown. Try to imagine the feelings of emigrants, bound for the gold-fields of California, who have pushed into the Great Basin without knowing where to look for grass or water. They are camped by a spring of alkaline water scarcely fit to drink; their weary animals nibble at the scanty grass about the spring; far ahead stretches the pathless desert which they must cross; upon their choice of a route their very lives will depend. Now it is all changed. The whole region is crossed and recrossed by wagon roads and railways. Many mining towns are scattered through the mountains which dot the seemingly boundless expanse of desert, while in every place where water can be found there are gardens, green fields of alfalfa, and herds of cattle. Before the year 1840 some knowledge had been acquired of the borders of the Great Basin. Trappers and explorers had crossed the Rocky Mountains and had gone down the Columbia River. There were Spanish settlements in New Mexico, Arizona, and along the coast of California. Frémont's first expedition had taken him to the summit of the Rocky Mountains in northwestern Wyoming. In 1843 he started upon the second expedition. He was at that time commissioned to cross the Rockies, descend the Columbia to Fort Vancouver, and return by a route farther to the south, across the unknown region between the Columbia and the Colorado rivers. Let us follow the little band of explorers led by Captain Frémont as day after day they made their way across what was then a trackless waste, and see what troubles they encountered because of the inaccuracy of the maps of that period. Leaving Fort Vancouver, upon the lower Columbia, for the return trip, the party ascended the river to The Dalles and then turned southward along the eastern side of the Cascade Range. They soon entered upon a region never before traversed by white men. At the time when autumn was giving place to winter, without reliable guides or maps, they were to cross the deserts lying between them and the Rocky Mountains. [Illustration: FIG. 47.--MAP OF A PORTION OF WESTERN NORTH AMERICA, MADE IN 1826 Showing the Buenaventura River] They met with no great difficulties until they had gone as far south as Klamath Lake. "From this point," Frémont says, "our course was intended to be about southeast to a reported lake called Mary's, at some days' journey in the Great Basin, and thence, still on southeast to the reputed Buenaventura (good chance) River, which has had a place on so many maps, and countenanced the belief in the existence of a great river flowing from the Rocky Mountains to the Bay of San Francisco." Figure 47 shows one of the maps to which Frémont refers. How interesting it is! Compare it with a good map in your geography and you will readily see that it is very misleading. The Sierra Nevada, one of the greatest mountain ranges in the United States, hardly appears, while traced directly across the map is the great Buenaventura River which Frémont expected to find and follow eastward toward its source near the Rocky Mountains. If this river had really been where it was mapped, it is likely that Frémont would have had no trouble, for if hard pressed he could have followed the stream down to the ocean. But a wall of snow-covered mountains lying in the way made matters very different. Winter was coming on when the party entered what is now northwestern Nevada, looking for the Buenaventura River. For several weeks they toiled on, often through the snow. Concerning this part of the journey Frémont says: "We had reached and run over the position where, according to the best maps in my possession, we should have found Mary's lake or river. We were evidently on the verge of the desert, and the country was so forbidding that we were afraid to enter it." The party then turned south, still hoping that the river might be discovered. After a time they came upon a large lake and travelled for many miles along its eastern shore. One camp was made opposite a tall, pyramid-shaped island, the white surface of which made it conspicuous for a long distance. Frémont was much impressed by the resemblance of the island to the pyramids of Egypt and so named the body of water Pyramid Lake. At the southern end of the lake the travellers found a large stream flowing into it (now known as the Truckee River), and followed along its banks for some distance; but as the river turned toward the west, they left it and struck out across the country. Frémont says again, "With every stream I now expected to see the great Buenaventura, and Carson (Kit Carson, the famous scout) hurried eagerly to search on every one we reached for beaver cuttings, which he always maintained we should find only on waters which ran to the Pacific." [Illustration: FIG. 48.--PYRAMID ISLAND, PYRAMID LAKE, NEVADA] But all the streams flowed in the wrong direction, until at last the explorers grew weary of hunting for the river which had no existence. Although it was the middle of the winter, Frémont determined to cross the lofty Sierras which rose like a white wall to the west. Once over the mountains, he hoped to gain the American settlements in the Sacramento Valley, where already Sutter's Fort had been established. The party ascended Walker River, dragging, with great difficulty, a howitzer which they had brought with them. The snows grew deeper as storm succeeded storm. Feeling that they were really lost, the disheartened men at length abandoned the gun, at a spot which has since been named Lost Cañon. [Illustration: FIG. 49.--LOST CAÑON, EASTERN SLOPE OF THE SIERRA NEVADA MOUNTAINS] When their own provisions were nearly gone, the party obtained some pine nuts and also several rabbits from the Indians. A dog which had been brought along made one good meal for the wayfarers. An Indian who had been persuaded to act as guide pointed out the spot where two white men, one of whom was Walker, a noted frontiersman, had once crossed the mountains; but the guide made them understand that it was impossible to cross at that time of the year, saying, in his own language, "Rock upon rock, snow upon snow." Although they could advance only by breaking paths through the snow, and were reduced to eating mule and horse flesh, yet the Frémont party pushed on. Finally they reached the summit of the mountains and turned down by the head of a stream flowing westward, which proved to be the American River. After three weeks more of terrible suffering they came out of the mountains at Sutter's Fort, where they obtained supplies and had an opportunity to rest and recruit. [Illustration: FIG. 50.--FRÉMONT PEAK, MOHAVE DESERT] Frémont now recognized the incorrectness of the maps which had so nearly caused the destruction of the party. As he says in his notes: "No river from the interior does, or can, cross the Sierra Nevada, itself more lofty than the Rocky Mountains... There is no opening from the Bay of San Francisco into the interior of the continent." When the return journey was begun the party did not recross the high Sierras, but turned southward through the San Joaquin Valley and gained the Mohave Desert by the way of Tehachapai pass. The route now led eastward across the deserts and low mountain ranges of California and southern Nevada, until at last Great Salt Lake was reached. [Illustration: FIG. 51.--SAGE-BRUSH IN THE GREAT BASIN] Among the many geographical discoveries of the expedition was the demonstration of the existence of the Great Basin. In his report, Frémont, while speaking of its vast sterile valleys and of the Indians which inhabit them, says: "That it is peopled we know, but miserably and sparsely ... dispersed in single families ... eating seeds and insects, digging roots (hence their name) [Digger Indians], such is the condition of the greater part. Others are a degree higher and live in communities upon some lake or river from which they repulse the miserable Diggers. "The rabbit is the largest animal known in this desert, its flesh affords a little meat.... The wild sage is their only wood, and here it is of extraordinary size--sometimes a foot in diameter and six or eight feet high. It serves for fuel, for building material, for shelter for the rabbits, and for some sort of covering for the feet and legs in cold weather. But I flatter myself that what is discovered, though not enough to satisfy curiosity, is sufficient to excite it, and that subsequent explorations will complete what has been commenced." THE STORY OF GREAT SALT LAKE The most interesting geographical feature of Utah is the Great Salt Lake. Few tourists now cross the continent without visiting the lake and taking a bath in its briny waters. This strange body of water has, however, been slowly growing smaller for some years, and probably will in time disappear. A study of the history of the lake may throw some light upon the important question of its possible disappearance, and it will certainly bring out many interesting facts. We do not know with certainty who was the first white man to look upon this inland sea, although it is supposed to have been James Bridger, a noted trapper, who in 1825 followed Bear River down to its mouth. He tasted the water and found it salt, a fact which encouraged him in the belief that he had found an arm of the Pacific Ocean. More than two hundred years ago there were vague ideas about a salt lake situated somewhere beyond the Rocky Mountains. In 1689 Baron Lahontan published an account of his travels from Mackinac to the Mississippi River and the region beyond. He states that he ascended a westerly branch of the river for six weeks, until the season became too late for farther progress. He reports meeting savages who said that one hundred and fifty leagues beyond there was a salt lake, "three hundred leagues in circumference--its mouth stretching a great way to the southward." This imaginative story aroused interest in the West. In a book published in 1772, devoted to a description of the province La Louisiane, the possibility of water communication with the South Sea is discussed as follows: "It will be of great convenience to this country, if ever it becomes settled, that there is an easy communication therewith, and the South Sea, which lies between America and China, and that two ways: by the north branch of the great Yellow River, by the natives called the river of the 'Massorites' (Missouri), which hath a course of five hundred miles, navigable to its head, or springs, and which proceeds from a ridge of hills somewhat north of New Mexico, passable by horse, foot, or wagon, in less than half a day. On the other side are rivers which run into a great lake that empties itself by another navigable river into the South Sea. The same may be said of the Meschaouay, up which our people have been, but not so far as the Baron Lahontan, who passed on it above three hundred miles almost due west, and declares it comes from the same ridge of hills above mentioned, and that divers rivers from the other side soon make a large river, which enters into a vast lake, on which inhabit two or three great nations, much more populous and civilized than other Indians; and out of that lake a great river disembogues into the South Sea." In 1776 Father Escalante travelled from Santa Fé far to the north and west. He met Indians who told him of a lake the waters of which produced a burning sensation when placed upon the skin. This was probably Great Salt Lake, but it is not thought that he himself ever saw it. The Escalante Desert, in southern Utah, once covered by the waters of the lake, is named after this explorer. Nothing more seems to have been learned of the lake after its discovery by Bridger until in 1833 Bonneville, a daring leader among the trappers, organized a party for its exploration. Washington Irving, in his history of Captain Bonneville, says of the party, "A desert surrounded them and stretched to the southwest as far as the eye could reach, rivalling the deserts of Asia and Africa in sterility. There was neither tree, nor herbage, nor spring, nor pool, nor running stream, nothing but parched wastes of sand, where horse and rider were in danger of perishing." [Illustration: FIG. 52.--SCENE ON GREAT SALT LAKE] Although decreasing in area so rapidly, Great Salt Lake is still the largest body of water in the western part of the United States, and the largest salt lake within its boundaries. It has a length of seventy miles and a maximum width of nearly fifty miles. Desolate, indeed, must have appeared the surroundings of the lake, with its salt-incrusted borders, as the Mormon emigrants gained the summit of the Wasatch Range and looked out over the vast expanse to the west. But as the slopes at the foot of the mountains seemed capable of producing food for their support, they stopped and made their homes there. Now in this same region, after half a century, one can ride for many miles through as beautiful and highly cultivated a country as the sun ever looked down upon. In the early days the barren plains were broken only by mountains almost as barren, which rose from them like the islands from the surface of the Great Salt Lake. The only pleasing prospect was toward the east, where stood the steep and rugged Wasatch Range, with its snow-capped peaks. From its deep cañons issued large streams of pure, cold water, which flowed undisturbed across the brush-covered slopes, then unbroken by irrigating ditches, and at last were lost in the salt lake. One might think that streams of water apparently so pure would at last freshen the lake, but in reality they are carrying along invisible particles of mineral matter which add to its saltness day by day. The dry air steals away the water from the lake as fast as it runs in, but cannot take the minerals which it holds in solution. Great Salt Lake is still considered very large, but at one time it was ten times its present size, while still longer ago there was no lake at all. Without a basin there can be no lake, and at that far-away time, as we have already learned, the Great Basin did not exist, and the streams, if there were any, ran away to the ocean without hindrance. When the Great Basin was formed by a breaking and bending of the crust of the earth, many a stream lost its connection with the ocean and went to work filling up the smaller basins, thus giving rise to the lakes which have already been described. The largest of these bodies of water, and in some respects the most interesting, is Great Salt Lake. [Illustration: FIG. 53.--OLD SHORE LINE OF LAKE BONNEVILLE Foot of the Wasatch Range] This lake, lying close to the lofty Wasatch Range, received so much water from numerous streams during the Glacial period that it slowly spread over thousands of square miles, overrunning the desert valleys and making islands of the scattered mountain ranges. It extended from north to south across Utah, into southern Idaho and almost to the Arizona line, until this body of water, which arose from so small beginnings, had become a veritable inland sea, three hundred miles long, one hundred miles wide, and one thousand feet deep. By the time the lake had covered an area of twenty thousand square miles the lowest point in the rim of the basin was reached and the overflow began. No map will tell you where the outlet was, for no river exists there now. If you could explore the shore lines of this ancient lake, which has been called Bonneville after the noted trapper, you would find two low spots in the mountains which hem the waters in, one upon the south, facing the Colorado River, the other on the north toward the Snake River. The one on the north happened to be a little lower, so that the break occurred there. First as a little, trickling stream, then as a mighty, surging river, the water poured northward down the valley of a small stream, widening and deepening it until, passing the spot where now the town of Pocatello stands, it joined the Snake River. This old outlet is now known as Red Rock Pass, and it forms an easy route for the Oregon Short Line from Salt Lake City to the plains of southern Idaho. The old river-bed is marked by marshes and fertile farms. With an outlet established, Lake Bonneville could rise no higher, and its waves began the formation of a well-defined terrace or beach, just as waves are sure to do along every shore. The level of the water could not remain permanently at the same height, for the rocks at the outlet were being worn away by the large volume of water which flowed over them. In the course of years the level of the lake was lowered four hundred feet. The sinking was not uniform, but took place by stages, while at each period of rest the waves made a new beach line. The lake during all this time must have been a beautiful sheet of fresh water filled with fish. Its shores, also, must have been much richer in vegetation than they are now. [Illustration: FIG. 54.--RED ROCK PASS, SOUTHERN IDAHO Outlet of Lake Bonneville] The water remained for a long time at the level of four hundred feet below its highest stage. This fact is evident from the width of the wave-cut terrace, which is the most prominent of all those that mark the old levels along the sides of the mountains. Finally, for some reason the climate began to change, the streams supplied less water to the lake, and the evaporation from its surface became greater because the air was drier. As a result the lake was lowered to such an extent that it lost its outlet. The mighty river flowing down through Red Rock Cañon grew smaller and at last dried up altogether. In this manner the lake was again cut off from the ocean, as it had been during its earlier history. The waters still continued to recede, but not at a uniform rate. During periods of greater rain its level remained stationary, so that the waves added new terraces to those already formed. As the lake had no outlet and was decreasing in volume, the water became salty, for the minerals brought by the streams could no longer be carried away. The fish either died or passed up into the purer waters of the inflowing streams. The water of the present lake is so salt that in every four quarts there is one quart of salt, and the preparation of this commodity by a process of evaporating the water in ponds has become an important industry. The water is the strongest kind of brine and it is impossible for a bather to sink in it. One floats about upon it almost as lightly as wood does upon ordinary water. After bathing it is necessary to wash in fresh water to remove the salt from the body. The dry bed of the former Lake Bonneville stretches far to the south and west of the present lake, and forms one of the most barren and arid regions in the United States. It is sometimes called the Great American Desert. Why is the lake receding now? Some people think that the climate is growing still more arid, and that the lake will eventually disappear. Others think that its shrinkage is the result of irrigation, for a large part of the water from the streams which supply it is now taken out and turned upon the land. There is still another reason which may account for the low water. The lake is known to rise and fall during a series of wet and dry years. When first mapped, in the middle of the last century, it was about as low as it is now. Then it gradually rose for a number of years and lately has again been falling. The story of Great Salt Lake has been much more complicated than the statement given above, but this is sufficient for our purpose. Irrigation has made a garden spot of a large part of the old bed of Lake Bonneville, but much of the beauty and attractiveness of this region would be lost if the present lake should give place to a bed of glistening salt. Let us hope that it will remain as it is. THE SKAGIT RIVER The Skagit is not one of the great rivers of the world, for very little of its course lies outside the boundaries of a single state. It is, however, none the less interesting. Few rivers with a length of only one hundred and fifty miles present so great a variety of instructive features. We shall certainly learn more from a study of the Skagit than from many a better known and more pretentious river. Innumerable torrents, fed by the glaciers of the Cascade Range, pour down the rocky slopes and lose themselves in the wooded cañons below. The cañon streams, of much greater size, flow less impetuously over gentler slopes, and are frequently blocked by boulders and logs. These streams unite in one broad, deep river, which moves on quietly to its resting-place in Puget Sound. Its name, Skagit, is of Indian origin and means _wild cat_. By following the Skagit River and a tributary stream, one can go from the bare and snowy summit of the Cascade Range down through dense forests, and come out at last upon a magnificent delta, where a fertile plain is slowly but steadily encroaching upon the waters of the sound. What contrasting scenes are presented along the few short miles of the course of the river! A trip from its source to its mouth will be worth all the trouble it involves, although the trail is often disagreeably wet and sometimes dangerous. There is no grander scenery in the United States than that of the Cascade Range; nor are there more dense forests than those found upon its western slope. The range is hidden in almost perpetual clouds and storms, and they are fortunate who can reach its summit upon a pleasant day. [Illustration: FIG. 55.--SUMMIT OF THE CASCADE RANGE, NEAR THE HEAD OF THE SKAGIT RIVER] The forests of fir and hemlock have gained a foothold nearly to the summit of the range. Upon the little benches and in the protected nooks the trees grow thriftily, and dense groves are found up to an elevation of nearly five thousand feet; but upon the more exposed and rocky slopes stunted trunks show the effect of a constant struggle with the rocks and winds. Upon other slopes, too high for the trees to grow, there are low shrubs and arctic mosses; but above all rise precipitous crags and peaks, utterly bare except for the glaciers nestling among them. Under the shade of the upland forests the moss is damp and the wood wet, so that it is difficult to make a comfortable camp or to build a fire. But these discomforts are not worthy of consideration in view of the inspiration which one gains by the outlook from some commanding point upon the summit of the mountain range. All about are jagged, splintered peaks. Upon every gentle slope there rests, within some alcove, a glistening mass of snow and ice. A score of these glaciers are in sight. They are supplied in winter by the drifting snows, and yield in summer, from their lower extremities, streams of ice-cold water. A multitude of streams raise a gentle murmur, broken occasionally by a dull roar as some glacier, in its slow descent, breaks upon the edge of a precipice and its fragments fall into the cañon below. From a position upon the summit above the point where the Skagit trail crosses the mountains may be seen a little lake, on the surface of which remains some of last winter's ice not yet melted by the August sun. If the climate were a little colder, the basin would be occupied by a glacier instead of a lake. All about the lake there are steep, rocky slopes, more or less completely covered with low arctic plants and stunted, storm-beaten hemlocks. From among the trees at the foot of the lake rises the roof of a miner's log cabin, and a few hundred feet beyond a small, dark opening in the face of a cliff shows where the miner is running a tunnel in his search for gold. Far below, and heading close under the sharp crest of the range, are densely wooded cañons. The fair weather is passing, and it is necessary to find the trail and descend. Clouds are sweeping across the ridges and peaks, and soon the whole summit will be covered by them. From a point a little east of the summit the clouds present a grand sight at the gathering of a storm. Higher and higher they pile upon the ocean face of the mountains. At the bottom they are dark and threatening, but the thunder-heads above can be seen bathed in the bright sunlight. For a time the clouds hang upon the summit as if stopped by some invisible barrier; perhaps they are loath to pass into the drier air of the eastern slope. But finally they move on, and rain or snow soon envelops the whole landscape. The trail descends rapidly for four thousand feet to Cascade River, a tributary of the Skagit. It is a steep and slippery way, and in many places it is not safe to ride the horses. The sub-arctic climate of the summit is left behind, and one is soon surrounded by dense and luxuriant vegetation. Such a change as this, in a short distance, shows how greatly elevation affects climate and plant growth. Upon every hand there is the sound of rushing water. From the cliffs ribbon-like cascades are falling. The rivulets unite in one stream, which roars and tumbles down the cañon over logs and boulders. The trail crosses and recrosses the torrent until the water becomes too deep for fording, and then it leads one to a rude bridge made of two logs with split planks laid across them. As the cañon widens, the trail leads farther from the river and through dense forests. The woods are so silent that they become oppressive, and the air is damp, for the sunlight is almost excluded. The tall trees, fir, hemlock, and spruce, with now and then a cedar, stand close together. Shrubs of many kinds are crowded among them, while mosses and ferns cover the ground. The fallen trunks are wrapped in moss, and young trees are growing upon them, drawing their nourishment from the decaying tissues. In the more open spots grow the salal bushes with their purple berries, the yellow salmon berries, and the blue-black huckleberries. It is difficult to get an idea of the density of a Washington forest, or of the character of the streams, unless one has actually taken a trip through the region. If one wishes to escape the forest by following the streams, he will find the path blocked by fallen trees. It is necessary continually to climb over or under obstructions, and the traveller is fortunate if he does not fall into the cold water. Upon the banks it is even worse; one must struggle through dense prickly bushes and ferns, and be tripped every few rods. Though the forest may appear at first to offer an easier way, it will soon be found that creeping and crawling through the undergrowth of bushes and young trees is exceedingly tiresome, and one will gladly return to the muddy trail, thankful for its guidance. The mountains become less precipitous and the cañon widens to a valley, until at last the trail comes out at a clearing where the Cascade River joins the Skagit. At this point, known as Marble Mountain, there is a ferry, also a store and several other buildings. The cleared fields seem a relief after many miles of dense forest, but such openings are infrequent, for few settlers have yet pushed far into the forests of the Skagit valley. To make a clearing of any size, tear out the stumps, and prepare the land for cultivation, requires many years of hard labor. How silently and yet with what momentum the river sweeps on! The water is clear in summer, but in winter it must be very muddy, for the Skagit is building one of the largest deltas upon Puget Sound. [Illustration: FIG. 56.--SKAGIT RIVER IN ITS MIDDLE COURSE] At Marble Mountain the traveller may, if he wishes, leave his horses, hire an Indian canoe, and float down the river to the nearest railroad station. The ride in the cedar canoe, with an Indian at the stern carefully guiding it past snags and boulders, is one of the pleasantest portions of the trip. The winding river is followed for nearly fifty miles. There is mile after mile of silent forest, the solitude broken only here and there by camps of Indians who are spending the summer by the river, fishing and picking huckleberries. Now and then a call comes from one of these camps, and in spite of the danger of being swamped by the swift current, the canoe is turned toward the shore, but the stop is only for a moment. At last a new railroad grade comes in sight, with gangs of men at work. The valley of the Skagit contains one of the finest bodies of timber in Washington, and the railroad is being built for the purpose of reaching this timber. There is little other inducement for the building of a railroad; for beside a few summer visitors, the only inhabitants are the scattered prospectors and miners. We enter the train at a little town in the woods and are soon speeding down the valley toward the mouth of the river. Clearings appear in the forest, and at last the view opens out over extensive meadows which stretch away, almost as level as a floor, to the waters of the sound. Here and there the meadows are broken by forest trees or irregular groups of farm buildings. Rich lands form the delta of the Skagit River. The value of these natural meadows was quickly recognized by the early settlers, for not only was the land exceedingly fertile, but it did not have to be cleared in order to be transformed into productive grain-fields. For centuries, ever since the melting of the great glaciers which once descended the Cascade Range and crept down the sound, the river has been building this delta. It grew rapidly, for immense accumulations of gravels and clays were left by the retreating glaciers. The delta has already spread westward into the sound, until it has enveloped some of the smaller islands. The forests growing upon these islands, which rise from the surface of the delta plain, are in picturesque contrast to the fields dotted with stacks of grain. The delta is now practically joined to the eastern side of the San Juan Islands. The railroad reaches the islands by means of a trestle across the intervening tidal flats, delivering its load of logs at the mills and leaving the passengers at the town of Anacortes, where they may take one of the many steamers passing up and down the sound. [Illustration: FIG. 57.--THE DELTA OF THE SKAGIT RIVER Enveloping former islands in Puget Sound] Of all the deltas now forming about Puget Sound that of the Skagit is the largest and most interesting. One might think that the forests would so protect the slopes that erosion would not be rapid, but the valleys of all the tributary streams appear deeply filled with rock fragments, which have, for the most part, accumulated from the higher portions of the range, where frost and ice are slowly tearing down the cliffs. At each period of flood some of this material is passed on to the river, which in turn drops it upon the borders of its delta. The Skagit River, from its source to its mouth, takes the traveller through varying climates and life zones, from the barren crest where the miner is the only inhabitant, down through forests where the lumberman is busy, until it leaves him upon the rich meadows of its delta. THE STORY OF LAKE CHELAN Chelan is the largest and most beautiful of our mountain lakes. The lake itself is most attractive, and the basin in which it lies has had an interesting history, so that it is well worth study. Notwithstanding the beauties of this lake, it is not widely known, for it is situated far away from the main lines of travel, in a remote cañon of the Cascade Range. Fortunately the lake and the rugged mountains about it have been included in a forest reserve, so that they will be kept in all their wild natural beauty. The Columbia River, in its crooked course across the state of Washington, follows for some distance the junction of the vast treeless plateau of the central portion and the rugged, forest-clad slopes of the Cascade Range. We have already learned how the plateau grew to its present extent through the outpouring of successive floods of lava which swept around the higher mountains like an ocean. Many cañons furrow the eastern slope of the Cascade Range, and terminate in the greater cañon of the Columbia at the edge of the lava. One of these cañons, deeper and longer than the rest, has been blocked by a dam at its lower end. Beautiful Lake Chelan lies in the basin thus formed. It begins only three miles from the Columbia River, but winds for sixty miles among the rugged and steep-walled mountains, terminating almost in the heart of the range. The lake can be reached either by crossing the mountains from Puget Sound, over a wet and difficult trail, or by ascending the Columbia River from Wenache, the nearest railroad station. The trip can be made from the latter point either upon the stage or river steamer. The wagon road is very picturesque, winding now under lofty cliffs with the river surging below, now along the occasional patches of bottom land where in July the orchards are loaded with fruit. The first sight of Lake Chelan is disappointing, for at the lower end, where the wagon road stops, there is little to suggest the remarkable scenery farther back in the mountains. Rolling hills, covered with grass and scattered pine trees, slope down to the lake, while here and there farmhouses appear. One cannot help asking at the first view what there is about Lake Chelan which has made it, next to Crater Lake, the most noted body of water upon the Pacific slope of the continent. But wait a little. Either hire a rowboat and prepare with blankets and provisions for a camping trip about the shores; or if the time is too short for carrying out that plan, take the little steamer which makes tri-weekly trips to the hotel at the head of the lake. Long before you reach the upper end you will begin to appreciate the grandeur of the lake scenery in its setting of steep-walled mountains. Little of Lake Chelan can be seen at one time, for its course among the mountains to the west is a very crooked one. The noisy steamer leaves the town at the foot of the lake and in the course of ten miles steeper slopes begin to close in upon us. Many little homes are scattered along this portion of the lake, wherever there is a bit of land level enough to raise fruit and vegetables. Now the mountains become more rugged and rise more steeply from the water's edge. The steamer is very slow; it takes all day to make the sixty miles, but no one is sorry. Occasionally the whistle is sounded and the boat heads in toward the land, where some camping party is on the lookout for mail or a supply of provisions. [Illustration: FIG. 58.--LOOKING DOWN ON LAKE CHELAN] The lake averages less than two miles in width, and seems all the narrower for being shut in between gigantic mountains. For some miles we pass under the precipitous cliffs of Goat Mountain, where formerly numerous herds of mountain goats found pasturage. At every bend in the lake the views become more grand and inspiring. Here is a dashing stream, roaring in a mad tumble over the boulders into the quiet lake--a stream which has its source perhaps a mile above, in some snow-bank hidden from sight by the steep, rocky walls. Next a waterfall comes into view, pouring over a vertical cliff into the lake. Occasionally snow-clad peaks appear, but only to disappear again behind the near mountains. What pleasant spots we notice for camping by the ice-cold streams! They are full of brook trout, while larger fish are to be found in the lake. At the head of this body of water there is a little hotel for the accommodation of visitors, and the Stehekin River, which is steadily at work filling up the lake, hurries past its doors. Since the melting of the glacier which once filled the cañon, the river has built a delta fully half a mile out into the water. The lake has the appearance of filling an old river valley or cañon. Perhaps the latter is the better name because the bed is so narrow and deep. This cañon winds among the mountains just like other cañons in which rivers are flowing, but it has no outlet at the present time. In some way a dam has been formed, and the cañon, filling with water to the top of the dam, has become a lake. Soundings have shown that the water is fourteen hundred feet deep; that is, a little more than a quarter of a mile. With the exception of Crater Lake, in Oregon, this is the deepest body of water in the United States. It is also interesting to note that the bottom of the lake is fully three hundred feet below the level of the ocean. How could a river cut a channel for itself so far below the ocean level? Rivers cannot do work of this kind unless they have a swift current; moreover, as they empty into the ocean, their beds must be above sea level. Some people think that the great glacier, which certainly at some time occupied the depression in which the lake lies, dug out the cañon. This glacier was over three thousand feet in thickness, for the rocks are grooved and polished to a height of nearly two thousand feet above the surface of the water. It is, nevertheless, improbable that the glacier did anything more than deepen and widen the cañon somewhat. It was certainly made, as we at first supposed, by a river which flowed through it at some remote period. At that time the land of our Pacific coast must have stood many hundred feet higher than it does now. [Illustration: FIG. 59.--GOAT MOUNTAIN, NORTH SHORE OF LAKE CHELAN] The surface of Lake Chelan is a little more than three hundred feet above the bed of the Columbia River, which flows through a deep cañon only three miles distant. If we could remove the dam of glacial boulders and gravel at the lower end of the lake, the water would be lowered only three hundred feet. The lake would not be drained, for it is very much deeper. Now here is another puzzle for us: the bottom of the lake is more than one thousand feet below the level of the Columbia. We shall have to go still farther back into the past to get a satisfactory explanation this time. Hundreds of thousands of years ago there was no plateau filling central Washington, and no Columbia River crossing it. The Cascade Range stood where we see it to-day, and the region of the plateau was a broad valley, toward which flowed the streams that had already cut cañons upon the eastern side of the range. These streams probably united in a river emptying westward into the Pacific by a course now unknown. The shores of the ocean were farther west than at present, for the land stood higher. The cañon of Lake Chelan was made by a river of this period, which through many long years gradually deepened and enlarged its channel. The river worked just as we see rivers working at the present time, for throughout all the history of the earth rivers have not changed their habits. Then came the long period of volcanic eruptions. Our Northwest was flooded by fiery lava, which built up the Columbia plateau and buried under thousands of feet of rock the old river valley into which the cañon of Chelan emptied. Then streams of water began to flow over the plateau from the higher mountains above the reach of the lava. These streams formed the Columbia River, which sought the easiest way to the sea, and finally excavated a cañon for hundreds of miles. In a portion of its course the river came close to the edge of the Cascade Range. The ancient cañon of Lake Chelan had been dammed up by the lava, and a lake occupied a portion of the former bed of the river. The Columbia could not cut its channel deep enough to drain the lake, and there it remained. [Illustration: FIG. 60.--LOOKING DOWN LAKE CHELAN FROM THE UPPER END] Then another change came: the climate grew cold and heavy snows gathered upon the Cascade Range. The snow did not all melt during the summers, but went on increasing from year to year. The masses of snow moved gradually down the mountain slopes, growing more and more icy until they became true glaciers. In this manner it came about that a river of ice occupied the cañon in which the old lake lay, and, displacing its waters, scraped and ground out the bottom and sides. The moving ice deposited the waste material at the lower end of the cañon, where it joined the Columbia River, the cañon of which was also occupied by a glacier coming from farther north. When the glacier began to retreat up the Chelan cañon, it left a great mass of rock débris, forming a dam between its basin and the Columbia. After the ice had disappeared, water collected in the cañon above the dam, and the narrow, deep lake was formed, enclosed within granite walls. As the snows melted, forests spread over the mountains, the bear, deer, and mountain goats came back again, while the streams, bringing down earth and rocks, began their work of filling up the lake. This task they will succeed in accomplishing some day unless something unforeseen happens to prevent. A valley, composed partly of meadow and partly of boulder-covered slopes, will then have taken the place of the lake. THE NATIVE INHABITANTS OF THE PACIFIC SLOPE The explorers and early settlers found a native race occupying nearly every portion of our continent. These people had many characteristics in common and were all called Indians. It is believed that they came originally from Asia, but their migration and scattering occurred so long ago that they have become divided into many groups, each having its own language and customs. In the western portion of the country, where the surface is broken by numerous barriers, such as mountains and deserts, almost every valley was found to be occupied by a distinct group of Indians called a "tribe." The language of each tribe differed so much from the languages of adjoining tribes that they could with difficulty understand one another. These tribes were almost continually at war. The Indians upon the Pacific slope were generally found to be inferior in most respects to those living in the central and eastern portions of the continent. One might suppose that the tribes possessing the fair and fertile valleys of California would be the most advanced in civilization, but such was not the case. Many of them were among the most degraded upon the continent. They seemed unable to adapt themselves to the white man and his ways, and in the older settled districts they have now nearly disappeared. In the newer portions of the Northwest and along the coast toward Alaska the Indians have not yet come into so direct contact with the white men, and remain more nearly in their primitive condition. When the Indians of central California were first seen, they wore but little clothing, and knew how to construct only the simplest dwellings for protection from the weather. They did not cultivate the soil, nor did they hunt a great deal, although the country abounded with game. Along the larger streams fish was an important article of food, but in other places, acorns, pine nuts, and roots constituted the main supplies. The acorns were ground in stone mortars and made into soup or into a kind of bread. These Indians have often been called Diggers because they depended so largely for their living upon the roots which they dug. It would seem natural that about San Francisco Bay the natives should have used canoes, but, according to early travellers, they had none. When they wished to go out upon the water they built rafts of bundles of rushes or tules tied together. At favorable points along the shore the Indians collected for their feasts, and these spots are now indicated by heaps of shells, in some places forming mounds of considerable size. Many interesting implements have been dug from these mounds, or kitchen middens as they are sometimes called. In the mountains the sites of the villages are marked by chips of obsidian (a volcanic glass used in making arrow-tips) and by holes in the flat surfaces of granitic rocks near some spring or stream. These holes were made for the purpose of grinding acorns or nuts. Many of the Indian tribes developed great skill in the weaving of baskets, which they used for many different purposes. The baskets are still made in some places, and are much sought after because of their beauty. The Indians of northern California in building their homes dug round, shallow holes, over which poles were bent in the form of a half-circle, and then tied together at the top. Bark was laid upon the outside, and earth was thrown over the whole structure. [Illustration: FIG. 61.--HOLES IN ROCK, MADE FOR GRINDING FOOD] "Sweat houses" were built in much the same manner, and were used chiefly during the winter. When an Indian wished to take a sweat, hot stones were placed in one of these houses, and after he had entered and all openings were closed, he poured water upon the stones until the room was filled with steam. After enduring this process as long as he desired, the Indian came out and plunged into the cold water of a near-by stream. As may be imagined, such a bath often resulted disastrously to the weak or sick. The fact that the California Indians could support themselves without any great exertion undoubtedly had the effect of making them indolent, while in the desert regions of the Great Basin the struggle for something to eat was so severe that it kept the natives in a degraded condition. [Illustration: FIG. 62.--CALIFORNIA INDIAN BASKET] The Indians of the Columbia basin built better houses than those farther south. Where wood was abundant their homes were similar in some respects to those of the coast Indians north of the mouth of the Columbia. Fish was their main article of diet. At certain seasons of the year, when salmon were plentiful, each tribe or group of Indians established its camp near one of the many rapids and waterfalls along the Columbia River. Large numbers of the salmon were caught by the use of traps. After being partly dried they were packed in bales for winter use. The fish thus prepared were considered very valuable and formed an article of trade with the tribes living farther from the river. The Indians inhabiting the coast northward from the mouth of the Columbia were different in many respects from those farther south or inland. They built better homes, took more pains with their clothing, were skilled in the making of canoes, and showed marked ability in navigating the stormy waters of the channels and sounds. [Illustration: FIG. 63.--HESQUIAT INDIAN VILLAGE Nootka Sound, Vancouver Island] The Vancouver Island Indians are called Nootkas, from the name of an important tribe upon the west coast. Those of Queen Charlotte Islands, still farther north, are known as Haidas. These two groups are very similar. They live upon the shores of densely wooded, mountainous lands and travel little except by water. Some of the canoes which these tribes construct are over fifty feet long and will easily carry from fifty to one hundred persons. Such a canoe is hewn out of a single cedar log, and presents a very graceful appearance with its upward-curving bow. In these boats the Indians take trips of hundreds of miles. [Illustration: FIG. 64.--FLATHEAD INDIAN WOMAN, VANCOUVER ISLAND] A ride in one of the large canoes is an interesting experience. When a party starts out to visit the neighboring villages, carrying invitations to a festival, the men are gayly dressed, and shout and sing in unison as they ply their paddles. The great canoe jumps up and onward like a living thing at every stroke of the paddles, which are dipped into the water all at once as the rowers keep time to their songs. But this enthusiasm quickly disappears if a head wind comes up, and the party goes ashore to wait for the breeze to turn in a more favorable direction. These Indians, as might be supposed, live largely upon fish. Berries are abundant during the summer and are also much used for food. The clothing of the Indians was originally a sort of blanket made of the woven fibres of cedar bark, or more rarely, of the skins of animals, although among the northern tribes skins were used almost exclusively. Matting made of the cedar bark is still in common use in their houses. [Illustration: FIG. 65.--INDIAN HOUSES, FORT RUPERT, VANCOUVER ISLAND] Among the Vancouver Island Indians, a few have peculiarly flattened foreheads (Fig. 64). This deformity is produced by binding a piece of board upon the forehead in babyhood and leaving it there while the head is growing. The villages are located in some protected spot where the canoes can lie in safety. The buildings are strung along the shore close under the edge of the thick forest and just above the reach of the waves at high tide. They are very solidly constructed, for these Indians do not move about as much as those farther south where the forests are less dense. Figure 65 shows the framework of a partially built house, while another stands at one side completed. Large posts are set in the ground at the corners and ends of the building; cross logs are then placed upon the middle posts, and upon these a huge log is placed for a ridge-pole. This is sometimes two feet in diameter and from sixty to eighty feet long. It must require the united strength of many men to roll such a log into position. Upon the framework thus constructed split cedar boards are fastened, and the building is practically finished. Such a house is usually occupied by a number of families. Upon Queen Charlotte Islands there is a dwelling of this kind large enough to hold seven hundred Indians. The fronts of the houses are ornamented with figures hewn out of wood. These represent men, birds and animals and have a religious significance. Sometimes these figures are mounted upon the tops of tall poles. The "totem pole" is a most interesting affair. Figure 66 represents the pole at Alert Bay, east of Vancouver Island. It is one of the finest upon the north coast. The figures of animals and birds carved upon it represent the mythological ancestors of the family or clan in front of whose abode the pole stands. The Indians often hunt similar animals to-day, but believe that their ancestors had supernatural power which raised them above the ordinary creatures. The Chinook Indians live upon the lower Columbia. The name "chinook" has been given to a warm, dry wind which blows down the eastern slope of the Rocky Mountains and out upon the Great Plains. This wind is so named because it blows from the direction of the Chinook Indians' country. The "Chinook" jargon is a strange sort of mixed language with which nearly all the tribes of the Northwest are familiar. It is formed of words from the Chinook language, together with others from different Indian languages, French-Canadian, and English. Through the influence of the trappers and traders the "Chinook" has come into wide use, so that by means of it conversation can be carried on with tribes speaking different languages. [Illustration: FIG. 66.--TOTEM POLE Alert Bay, British Columbia] Although there are so many different tribes, with great diversities of language, throughout the West, they were probably all derived from the same source. As we go north the similarity between the coast Indians and the inhabitants of eastern Asia becomes more noticeable. It seems almost certain that these American Indians originally came across the narrow strip of water separating Asia from America. We do not know how long the Indians have occupied our country, but it has probably been several thousand years. Some of the main groups have undoubtedly been here longer than others. Unless we protect the Indians and permit them so far as possible to lead their own natural lives, most of them will soon disappear. THE STORY OF LEWIS AND CLARK In the seventeenth century it appeared likely that France would before long control the northern and interior portion of North America. La Salle discovered the Ohio River, traversed the Great Lakes, and descended the Mississippi River to its mouth. In 1742 other French explorers pushed west from the Great Lakes and sighted the Rocky Mountains. But when the English triumphed at Quebec, France gave up to them all of her possessions east of the Mississippi River, and ceded the province of Louisiana to the Spanish. This province was very much larger than the state which now bears the name. Bounded by the Mississippi River upon the east, and the Spanish possessions upon the southwest, it stretched north and west with very indefinite boundaries, although in the latter direction it was supposed to be limited by the Rocky Mountains. At one time Napoleon dreamed of founding a great colony in America, and induced Spain to cede Louisiana back to the French; but being unable to carry out his plans, he made a proposition to the United States to take this territory. His offer was accepted, and in 1803, during the presidency of Thomas Jefferson, the vast province was taken into the Union. It was immediately evident that more definite knowledge should be acquired concerning the great region beyond the Mississippi, particularly the portion about the head of the Missouri River. The unknown region lying between the source of this river and the Pacific should also be explored, for Captain Gray's discovery of the Columbia River gave to the United States a claim upon this part of the continent which must be maintained. If something were not done soon, the territory would be occupied by the English fur companies. Two young men, Captains Lewis and Clark, were chosen to lead an expedition into the Northwest, which proved to be one of the most remarkable in the history of our country. They were the first white men to cross the Rocky Mountains and to traverse the continent from the Atlantic to the Pacific within the present boundaries of the United States. How interesting it must have been to push into the Rocky Mountains, beyond the farthest point previously reached by white men; to see Nature in her wild state, to note the new plants and animals, and to study the Indians before their contact with Europeans had changed their customs! Lewis and Clark were particularly instructed to investigate the sources of the Missouri, to learn how the continental divide could be crossed, and to ascertain the nature of the streams which flowed westward to the Pacific. They were also to study the resources of the country, and to examine into the character and customs of all the Indian tribes that they should meet. The start was made from St. Louis in May, 1804, with two large rowboats and one sail-boat. The latter was to return with news of the party when the farthest outpost upon the Missouri was reached. Through the summer months and late into the fall the boats toiled up the river against the swift current, finally reaching a village of the Mandan Indians in the present state of North Dakota, where the explorers spent the winter. Thus far they were in a region frequently visited by the traders and trappers from St. Louis. [Illustration: FIG. 67.--THE GREAT FALLS OF THE MISSOURI] In the spring they pushed on again in canoes, at length entering an unknown region. The Missouri forked so frequently that it was often difficult to determine which was the main stream. To the surprise of the travellers, the country appeared to be uninhabited, so that they could get no assistance from the Indians. Only a small stock of provisions remained, and as the party numbered about thirty, it was necessary to keep hunters out in advance all the time. As we are carried swiftly through this region to-day in the cars, no signs of wild creatures are to be seen, and it is difficult for us to believe that game was once abundant. The narrative of the expedition abounds with descriptions of various large animals which the explorers met in herds, such as deer, antelope, buffalo, bears, and wolves. The bears, both white and brown, were very numerous and bold. The white bears in particular were so ferocious that the hunters had many serious encounters with them. They would sometimes enter the camp at night, and at one time a herd of buffalo stampeded through it. When undecided at one point which branch of the river to follow, Captain Lewis went some distance in advance and discovered the Great Falls of the Missouri. He was greatly impressed and awed by the magnitude and height of the successive falls, which were twenty-four, forty-seven, and eighty feet high respectively, and were connected by a series of cascades. Many days were spent there in a long and laborious portage, for everything had to be carried a distance of twelve miles before the quiet water above the falls was reached. How the coming of the white man has changed the region about the falls! The game has disappeared; an important city, supported by the enormous water-power, is growing up; while the smoke rising from extensive plants for reducing the gold, silver, and copper ores mined in the Rocky Mountains floats out over the country. Proceeding up the river, the party reached the Gate of the Mountains--a picturesque spot where the stream leaves the mountains through a narrow defile between high and jagged cliffs and enters upon its long course across the Great Plains (Fig. 68). Gradually the river became smaller, and at last the travellers came to the point where it divided into three branches, to which they gave the names of Gallatin, Madison, and Jefferson forks. The party made their way up the latter fork, which flowed from a westerly direction. [Footnote: FIG. 68.--THE GATE OF THE MOUNTAINS The Missouri River at the entrance to the Rocky Mountains] Now they began to look anxiously for the Indians, from whom it would be necessary to get horses to transport their baggage when the river should become too small for the canoes. This region was inhabited by the Shoshones. It may well be asked how it happened that these Indians had horses, since no white people had ever visited them before. Their purchase of horses came about through the processes of trade with the tribes to the south, who in turn came in contact with the Spanish of New Mexico. One or the other of the leaders kept in advance, on the lookout for the Indians. At last Captain Lewis, while crossing the divide at the head of the stream which they had been following, came suddenly upon several Indians. After overcoming their fear by presents, he accompanied them to their camp and induced them to return with horses to assist the party. Upon reaching the Pacific side of the continental divide the explorers were in doubt as to which way to proceed. No man had been before them, and the Indians told stories of fearful deserts to the southwest (probably the Snake River plains), and said that the mountains were too steep for the horses, and the rivers too rapid for canoes. If you will examine a map of the country about the head of the Jefferson fork of the Missouri, you will not wonder that Captains Lewis and Clark were in doubt as to which way they should go in order to reach the Columbia. They first attempted to go down the Salmon River, but soon gave up this project. They turned about and crossed the mountains to the Bitter Root River, which flows north and empties into Lake Pend d'Oreille through Clark's Fork of the Columbia. After going down the Bitter Root for a short distance they turned west again across the Bitter Root Mountains and came out upon the head waters of the Kooskooskie River. Unable to follow its cañons, they wandered to the north among the mountains. At this time their sufferings were intense. Food became so scarce that they were obliged to eat their horses. After many weary days they again reached the stream, but this time at a point where it was navigable. They floated down to its junction with the Lewis or Snake River, where the growing city of Lewiston now stands. At this point they met the Nez Percés Indians, who assisted them in every possible way. [Illustration: FIG. 69.--CELILO FALLS, COLUMBIA RIVER] The party continued down the Snake River in canoes until they finally reached the Columbia. The difficulties of navigation were great, for at intervals of every few miles the river was broken by rapids through which it was dangerous to take the canoes. By treating the Indians kindly, the party succeeded in trading with them for such articles of food as horses and dogs. They also obtained some salmon. The presence of this fish in the streams gave them the first assurance that the Pacific slope had been reached. Along the Columbia River salmon was one of the chief articles of food for the Indians. At Celilo Falls, a short distance above the present city of The Dalles, the travellers found great difficulty in proceeding, as the canoes and loads had to be carried, or "portaged," around the falls. Lewis and Clark called these the Great Falls of the Columbia (Fig. 69). As the canoes floated down through the magnificent cañon by which the Columbia passes the Cascade Range, they encountered another rapid, now known as the Cascades of the Columbia. This rapid is due to a great landslide which has formed a dam across the river. Captain Lewis speaks of the broken trunks of trees rising from the water above the dam, a fact which would lead one to suppose that it had not been very long since the slide occurred. Below the Cascades the party soon began to notice the influence of the tides in the rise and fall of the river, and knew then that the Pacific could not be very far away. Early in November they came in sight of the ocean, and in a few days had the pleasure of standing upon its shores. The long and dangerous trip of four thousand miles had been completed without any serious accident. Continual rains poured upon them, and before winter quarters could be prepared they were in a very uncomfortable position. A permanent camp was selected upon the Oregon side of the Columbia, and log buildings were erected. The camp was called Fort Clatsop. While in their winter quarters the party cultivated friendly relations with the Indians, and made extensive notes upon their habits and characteristics. [Illustration: FIG. 70.--THE CASCADES OF THE COLUMBIA A steamer going up to the locks] In the spring, since no ship had appeared which would carry them back by water, Lewis and Clark determined to return overland. First, however, they left some records with the Indians, with directions that these should be given to the captain of any ship which might happen to visit the mouth of the Columbia. The leaders wished to make sure that if anything happened to the party the knowledge gained by their explorations should not be lost. One can imagine with what pleasure the men turned homeward. Although they had started with flour, rice, corn, and other articles of food, these had given out long before they reached the lower Columbia, and for some months their only diet had been fish and the animals that the hunters had killed. Their stock for trading with the Indians was also nearly gone; all the articles that were left could be put into two pocket handkerchiefs. After ascending the Columbia River to a point above The Dalles, the party left the stream, as they found that it would be impossible to make much headway with the canoes. Obtaining horses from the Indians, they followed the outward route back as far as the Kooskooskie River. Then they turned north and crossed the mountains to the Missoula River. Near the present city of Missoula the party divided, Captain Lewis going up Hell Gate River and crossing the continental divide to examine the country lying north of the Missouri. Captain Clark, with another portion of the company, went up the Bitter Root River and over the mountains to the Jefferson Fork, which the whole party had ascended the year before. He followed this river down to its junction with the Gallatin, and travelled for a distance up the latter stream, then crossed by land to the Yellowstone River. Canoes were constructed upon the Yellowstone, and the party floated down to the junction of this river with the Missouri. There the two bands were fortunately reunited, and together they passed rapidly down the Missouri until they reached the "village" of St. Louis, where the whole population came out to welcome them. As the party had been gone more than two years, it was feared that they would never be heard from again. There can be no doubt that the expedition of Lewis and Clark added greatly to the public interest in the vast region which they traversed, and helped to bring about the final retention of the Oregon country. The Hudson Bay Fur Company soon after established trading posts at various points along the Columbia, and kept up their contention that all the country lying north of the river rightfully belonged to England. It was very remarkable that the Lewis and Clark expedition had made the long journey to the Pacific and back without meeting with serious accident. There were perils to be met on account of the ruggedness of the country, the rapids in the streams, the lack of food, and the danger of attack from the Indians. The successful accomplishment of the plan was without a doubt largely due to the ability of the two brave leaders. THE RUSSIANS IN CALIFORNIA How many of us know that the Russians once established a post upon the coast of California and held it for nearly a third of a century? If the geographic conditions about this post had been different, it is possible that the Russian colonists would hold their position now. The discoveries made upon the North American coast by the Russian navigator, Bering, in 1741, led to fur trading with the Indians; and in 1798 the Russian American company was organized and established its headquarters at Sitka. The Spaniards still claimed the whole Pacific coast of North America as far north as the Strait of Fuca, though they had given up their station at Nootka Sound, Vancouver Island. They had, however, made no settlements north of the port of San Francisco. It was nearly one hundred years ago that Rezanof, a leading Russian official, arrived at Sitka and began to investigate the condition of the settlements of the Russian American Fur Company. He found them in a sorry state; the people were nearly starved and most of them were sick with the scurvy. No grain or vegetables were grown along that northern coast, nor could they be supplied from Asia. Rezanof conceived the idea of establishing trade relations with the people of California. By this means furs might be exchanged for the fresh provisions which were so sorely needed in the north. Rezanof sailed south in 1806 and tried to enter the Columbia River, where the company had planned to establish a settlement, for upon the Russian maps of this time all of the coast as far south as the Columbia was included under Russian jurisdiction. Rezanof was, however, unable to enter the river, probably for the same reason that Meares, the English navigator, had failed to enter. He then proceeded down the coast and finally ran into the port of San Francisco, where he was treated in a fairly polite manner by the Spanish. After the return of the expedition to the north, definite plans were made for the establishment of an agricultural and trading station on the California coast, as a permanent supply depot for the northern settlements. Rezanof hoped in time to secure a portion of this fair southern land from Spain. Several hunting expeditions, chiefly made up of Aleut Indians with Russian officers, were sent south and told to keep a sharp lookout for a suitable place to begin operations. In 1809 one expedition entered Bodega Bay, an inlet of some size about sixty miles northwest of San Francisco. This bay, which had been previously discovered and named by the Spaniards, was thoroughly explored two years later. No good spot for a settlement was found upon this inlet, but in 1812 a location was determined upon, ten miles north of the mouth of the stream we now know as Russian River. There was no good harbor here, simply a little cove, but back of this cove a broad grassy tract formed a gently sloping terrace at the foot of a line of hills. The soil was good and timber was near at hand. The Russians first made friends with the Indians, who ceded to them the territory in the neighborhood for three blankets, three pair of breeches, three hoes, two axes, and some trinkets. In order to protect themselves from possible Indian attacks as well as to be able to hold their position against the Spanish, the Russians constructed a strong stockade. It was made of upright posts set in the ground and pierced with loopholes. At the corners, and a little distance within, were erected two hexagonal blockhouses with openings for cannon. As it happened, however, no occasion ever arose for the use of the ten cannon with which the fort was supplied. The post was given the name Ross, a word which forms the root of the word Russia. The Spanish, of course, claimed the territory by right of discovery, and watched the work of the Russians with jealous eyes. They were not strong enough to drive the Russians away by force, although they protested more than once against the unlawful occupation of the land. Some trading was carried on between the Russians and the Spanish, and occasionally loads of grain and cattle were sent north. The number of people at Fort Ross varied from one hundred and fifty to five hundred. The population consisted of Russians, Aleuts, and other Indians. The Aleuts were the hunters and sealers. They spent their time upon the ocean, sometimes entering San Francisco Bay, but usually hunting in the region of the Farralone Islands, which were originally inhabited by great herds of fur seal. There were also otters, sea-lions, and an infinite number of seabirds. A station was maintained upon the Farralones, where a few men stayed to gather birds' eggs and kill seagulls. Many thousands of gulls were taken each year, and every part of their bodies was utilized for some purpose. [Illustration: FIG. 71.--FORT ROSS FROM THE SEA Schooner loading wood] Kotzebue, a Russian navigator, whose name has been given to a sound upon northern Alaska, visited Fort Ross and also San Francisco Bay. He considered it a great pity that the Russians had not gained possession of this territory before the Spaniards, for the magnificent bay of San Francisco, in the midst of a fertile country, would have been a prize worth working for. Year after year the Russian Fur Company sent expeditions to California to trade and bring back provisions. They tried to extend the area under their jurisdiction, but the geographical conditions of the country were unfavorable. The narrow strip of land next the coast was cut off from the interior valleys by mountain ridges and cañons. If the Sonoma Valley had opened westward instead of toward San Francisco Bay, it would have been easy to extend their territory gradually. As it was, the Spanish, who were in control of the bay, had easy access to all of the fertile valleys of central California. As the sealing industry decreased in importance, and as the maintenance of Fort Ross was expensive, the Russians in 1839 began to consider the question of giving up their post. They finally sold everything at Ross and Bodega, except the land, to Sutter, an American who had acquired a large ranch and established a post or fort at the mouth of the American River. In 1841 the Russians sailed away, never to return. The Spaniards were greatly relieved when this happened, for they had not known how to get rid of their unwelcome neighbors peaceably, and were reluctant to stir up trouble with Russia. The stockade at Fort Ross has entirely disappeared, but two blockhouses, the little chapel, and the officers' quarters remain as the Russians left them. Fort Ross is now-a pleasant, quiet hamlet. A store and a farm-house have been added to the old buildings. Behind the sloping meadows rise the partly wooded hills, while in front lies the little bay where once the boats of the Russian and Aleut seal hunters moved to and fro. Occasionally a small schooner visits the cove for the purpose of loading wood or tan-bark for the San Francisco market. [Illustration: FIG. 72.--RUSSIAN BLOCKHOUSE, FORT ROSS] Fort Ross was never marked by serious strife and seems destined to go on in its quiet way. The blockhouses are rotting and beginning to lean with age, and in time all evidences of the once formidable Russian post will have disappeared. DEATH VALLEY To most of us Death Valley is thought of only as a mysterious region somewhere in the Southwest, a place which we are accustomed to picture to ourselves as being the embodiment of everything that is desolate and lifeless,--a region where there is no water, where there are no living things, simply bare rocks and sand upon which the sun beats pitilessly and over which the scorching winds blow in clouds of dust. The reality is hardly so bad as this, for there are living things in the valley, and water may occasionally be found. Nevertheless it is a fearful spot in summer, and has become the final resting place of many wanderers in these desert regions, who having drunk all their water failed to find more. We have already learned something about the Great Basin: we know that it is made up of vast desert plains or valleys, separated by a few partly isolated mountain ranges. The valleys are peculiar in that they are basins without outlets, and for this reason are known as sinks. Many of the lakes once occupying the valleys are now quite or nearly dry, and the lower portions of their beds are either whitened with deposits of borax and soda, or have been transformed into barren expanses of hardened yellow clay. The long, gentle slopes about the sinks, which have been built up by the waste rock from the mountains, as a result of the occasional cloudbursts are dotted with sage-brush, greasewood, or other low plants, and furnish a home for numerous animals. Back of the gravel slopes rise the mountains, browned under the fierce rays of the summer sun. In some of their deeper cañons little springs and streams are found, but the water usually dries up before leaving the protecting shadows of the cliffs. Toward the mountain tops the desert juniper appears; and if the peaks rise high enough to get more of the moisture of the cooler air, they support groves of the piñon and possibly yellow pine. The valleys are all much alike. In summer the days are unbearably hot, while in winter the air is cool and invigorating. The skies are overcast for only a few days in the year, but in the autumn and spring fierce winds, laden with dust and sand, sweep across the valleys and through the mountain passes. Strange rock forms, of many contrasting colors, worn out by wind and water, mark the desert mountains. The granite wears a brown, sunburned coat, while the masses of black lava show here and there patches of pink, yellow, and red. The air is often so wondrously clear that distant mountains seem much nearer than they really are. During the hot summer days the mirage forms apparent lakes and shady groves, illusions which have lured many a thirsty traveller to his death. Death Valley is the lowest and hottest of the desert basins. Its surface, over four hundred feet below the level of the sea, is the lowest dry land in the United States. The valley is long and narrow and enclosed by mountains. Those upon the east are known as the Funeral Mountains, while upon the west the peaks of the Panamint Range rise to a height of about ten thousand feet. If the rainfall were greater, Death Valley would be occupied by a salt or alkaline lake, but in this dry region lakes cannot exist, and the bottom of the sink, sometimes marshy after exceptional winter rains, is in many places almost snowy white from deposits of salt, soda, or borax. Death Valley, then, differs from scores of other valleys in the Great Basin by being a little lower, a little hotter, and a little more arid. Strange as it may seem, old prospectors say that Death Valley is the best watered of all the desert valleys. Since it is the lowest spot in all the surrounding country, the scanty water supply all flows toward it. But the water runs under the gravels of the old river beds instead of on the top, where it might be utilized. Occasionally, however, the water comes to the surface in the form of springs, which are marked by a few willows or mesquite trees and little patches of salt grass. Long ago, when the rainfall was greater, Death Valley was a saline lake and received a number of streams, two of which were large enough to be called rivers. The Amargoza River, starting from Nevada and pursuing a roundabout way, entered the southern end of the valley. The Mohave River, which rises in the San Bernardino Range, also emptied into the valley at one time, but now its waters, absorbed by the thirsty air and by the sands, disappear in the sink of the Mohave fifty miles to the south. The summer is the dreaded season in Death Valley. A temperature of one hundred and thirty-seven degrees has been reported by the Pacific Coast Borax Company at the mouth of Furnace Creek. This temperature was recorded in the shade, and is the hottest ever experienced in the United States. In the sun it is of course much hotter. Many a person has lost his life in trying to cross the heated valley in the middle of a summer day instead of making the journey at night. [Illustration: FIG. 73.--ENTERING DEATH VALLEY] Dangerous as this region is, even now when we know so much about it, it was of course much more dangerous for the first white men who entered it. Only those who have had some experience upon the desert can realize the difficulties and dangers which beset the first emigrants who attempted to cross the deserts lying between Salt Lake City and the Sierra Nevada mountains. The story of the sufferings and final escape of that party which, by taking the wrong course, was lost in the great sink, is extremely interesting although sad. The valley received its name from the experiences of the members of this party. In the latter part of 1849 many emigrants, who had reached Salt Lake City too late in the season to take the usual route through northern Nevada and over the Sierra Nevada mountains, decided that rather than remain in the town all winter, they would follow the south trail across southern Nevada to San Bernardino and Los Angeles. A party of people finally collected with one hundred and seven wagons and about five hundred horses and cattle. The course led in a southwesterly direction past Sevier Lake and Mountain Meadows in southwestern Utah. In the latter locality the party divided, the larger number leaving the old trail and taking a more westerly direction. They thought in this way to shorten the distance, and hoped, by skirting the southern end of the Sierra Nevada mountains, to-gain the San Joaquin Valley in California. Now trouble began. No one had ever been over the new route, and the location of the springs and the passes through which the wagons could be taken had to be sought out in advance. Soon many of the party turned back to the known trail, but the others continued, though with no knowledge of the nature of the country which they must cross. Day after day and week after week the slow ox-teams crawled across the broad deserts and over the low mountain ranges. From the top of each successive mountain ridge the men looked with longing eyes toward the west, hoping to get a sight of the snowy Sierras. Finally want of water and food began to weaken the cattle and the wagons were lightened as much as possible. As the party approached the eastern boundary of California the mountains grew higher and the deserts more arid. In the clear air the snow-covered peaks of the Panamint Range began to be visible, although one hundred miles away. The weary emigrants believed that these peaks belonged to the Sierra Nevadas, and that beyond them lay the green valleys of California. How great was their mistake! The Panamint Range looks down upon Death Valley with a bold and almost impassable front, while still other broad deserts lie between this range and the real Sierras. Upon reaching the head of the Amargosa River the party began to separate, for by this time many thought only of saving their lives at any cost. Some followed Furnace Creek to its sink in Death Valley; others went over the Funeral range and came down upon the lower portion of the Amargosa River. In many cases the wagons were abandoned and the oxen were killed for food. When they came into the sink we now know as Death Valley, the members of the different parties began to feel that they were really lost. From the records that have come down to us we can see that they had not the slightest idea of the direction which they should take or of their distance from the settlements in California. Fortunately it was the winter season and the heat did not trouble them; moreover, the rains and snows furnished some water. None of the wagons were taken beyond the camp at the western edge of the valley, under the towering peaks of the Panamint Range. This place is now known as Bennett's Wells. Here the wagons were broken up and burned, and the loads, which were now very light, were either taken by the men themselves or placed upon the backs of the few remaining oxen. It was thought that the fair fields of California would be seen from the top of the Panamint Range; but when the travellers reached the summit other desert valleys appeared in the west, and beyond these, in the dim distance, another snowy range was visible. The emigrants now divided into parties. One party reached Owens Lake, and turning south, finally passed over the Sierras by the way of Walkers Pass and went down the valley of the Kern River. Another, the Bennett party, including some women and children, remained at the springs in Death Valley, while two of the men started out alone, in the hope of reaching the settlements and returning with food. These men crossed the Panamint Range and struggled on for days in a southwesterly direction, over desert valleys and mountains. They were frequently on the point of giving up in despair for want of food and water. At last, far to the south, the snowy crest of the San Gabriel Range came into sight. Continuing in a southwesterly direction through the Mohave Desert, the men reached a low pass in the mountains and followed a stream until they came upon a Mexican ranch, where the sight of green meadows, upon which horses and cattle were feeding, delighted their weary eyes. Several animals were secured and loaded with food. Then the men turned back into the desert. They at last reached the desolate valley again, after an absence of about a month, and found most of the party alive, although nearly driven to despair. With the aid of a mule and several oxen, the party came safely to the fertile valleys near the coast. Another party, known as the Jayhawkers, struggled on behind the two men who went for relief, and the most of its members also came safely out of the desert, though not without extreme suffering. In all, fourteen people of this expedition perished. [Illustration: FIG. 74.--SOUTHERN END OF DEATH VALLEY Showing the white deposits of soda] If you ever have an opportunity to travel over this region, you will wonder that any of the people escaped. The seemingly endless succession of deserts and mountains, the lack of food, and the scanty supply of water, often unfit to drink, would lead one to think that strangers to these wilds would be far more likely to perish than to find their way out. THE CLIFF DWELLERS AND THEIR DESCENDANTS The region of the high plateaus of the southwestern United States presents many strange and interesting aspects. Equipped with pack animals for the trails, and conducted by a guide who knows the position of the springs, one might wander for months over this rugged and semi-arid region without becoming weary of the wonderful sights which Nature has prepared. In travelling over the plateau one has to consider that often for long distances the precipitous walls of the cañons cannot be scaled, and that the springs are few and inaccessible. To one not acquainted with the plateau it appears incapable of supporting human life. There is little wild game and scarcely any water to irrigate the dry soil. However, if the country is examined closely, the discovery will be made that it was once inhabited, though by a people very different from the savage Indians who wandered over it when the white men first came. These early people had permanent homes and were much more civilized than the Indians. They lived chiefly by agriculture, cultivating little patches of land wherever water could be obtained. Go in whatever way you will from the meeting point of the four states and territories, Colorado, Utah, Arizona, and New Mexico, and you will find the ruins of houses and forts. Upon the tops of precipitous cliffs, in the caves with which the cañon walls abound, by the streams and springs, there are crumbling stone buildings, many of them of great extent, and once capable of sheltering hundreds of people. Scattered over the surface of the ground and buried in the soil about the ruins are fragments of pottery, stone implements, corn-cobs, and in protected spots the remains of corn and squash stems. The people who once inhabited these ruins have been called Cliff Dwellers, because their homes are so frequently found clinging to the cliffs, like the nests of birds, in the caverns and recesses of the precipitous cañon walls. The Cliff Dwellers have left no written records, but from a study of their buildings and of the materials found in them, and from the traces of irrigating ditches, we are sure that they were a peaceful, agricultural people. The oldest ruins are probably those in the open and less protected valleys. It is evident that after these dwellings had been occupied for an indefinite time the more fierce and warlike Indians began to overrun the plateau region and make attacks upon the primitive inhabitants. These people, peacefully inclined and probably not strong in numbers, could find no protection in the valleys where they irrigated little patches of land and raised corn and squashes; so, retreating to the more inaccessible cañons, they became cliff dwellers. Seeking out the caverns so abundant in these cañons, they went to work with tireless energy to build for themselves impregnable homes and fortresses to which they could retreat when the savage Indians appeared. The cañon of Beaver Creek in central Arizona contains one of the most interesting of these fortresses, known as Montezuma's Castle. Many small buildings nestle along the sides of the cañon upon the ledges and under over-hanging rocks, but Montezuma's Castle is the most magnificent of them all, and must have given protection to a number of families. Halfway up the face of a cliff two hundred feet in height, there is a large cavern with an upward sloping floor and jagged overhanging top. Here with infinite toil the Cliff Dwellers constructed a fortress, the front of which rose forty feet from the foundation and contained five stories. This front was not made straight, but concave, to correspond to the curve of the cliff. What an effort it must have been for these people, who had nothing but their hands to work with, to quarry the stone. To carry their materials from the bottom of the cañon, by means of rude ladders, up the steep and rugged wall to the foot of the cavern, and then to lay the foundation securely upon the sloping floor, must have been a still harder task. The stones were laid in mud, and in most cases were also plastered with it. Here and there little holes were left to let in light, but the rooms, with their low ceilings, would have seemed very dismal and dark to us. Beams were set in the walls to support the different floors. Smaller sticks were laid upon the beams, and then a layer of earth was placed over the top. To pass through the openings between the different rooms the inhabitants had to crawl upon their hands and knees. The places where they built their fires are indicated by the dark stains which the smoke has left upon the walls. Broken pottery and corn-cobs are scattered profusely about the building. How safe these ancient people must have felt in this retreat, where they were protected, both from the storms and from their enemies! [Illustration: FIG. 75.--MONTEZUMA'S CASTLE, BEAVER CREEK CAÑON, ARIZONA] Near some of the ruined dwellings in this region there are remains of buildings which are supposed to have been watch-towers. We can picture to ourselves the sentinels' alarm given to the workers in the fields at the approach of the savage Apaches, and the hasty flight of the Cliff Dwellers to the castle far up the cañon wall,--the pulling up of the ladders and the retreat to the upper rooms from which they could look down in perfect safety. They must have kept water and food stored in the cave houses. As long as these supplies held out no injury need be feared from the attacking party. But apparently there came a time when the Cliff Dwellers either abandoned their gardens and fortresses or were killed. It is possible that the climate of the plateau region became more arid and that many of the springs dried up, for there is no water now within long distances of some of the ruins. It is, perhaps, more probable that the attacks of the savages became so frequent that the Cliff Dwellers were driven from their little farms and were no longer able to procure food. Those who were not killed by enemies or by starvation retreated southward and gathered in a few large villages, or pueblos, where they were still resisting the attacks of their enemies at the time of the coming of the early Spanish explorers. [Illustration: FIG. 76.--PUEBLO OF TAOS, NEW MEXICO] A careful study of the early inhabitants of America reveals the fact that the Pueblo Indians are the descendants of the race of Cliff Dwellers. Their houses, their pottery, and their religious ceremonies are, so far as can be determined, very similar to those of the Cliff Dwellers. If you travel through northwestern New Mexico and northeastern Arizona, you will find the villages situated upon commanding rocks which are often surrounded by almost inaccessible cliffs. To these elevated villages all the food and water has to be carried from the valleys below. The houses are solidly built of stone, and rise, terrace-fashion, several stories in height, each succeeding story standing a little back of the one below. These houses can be entered only by a ladder from the outside. In time of danger the ladders are drawn up so that the walls cannot be easily scaled. There are a number of groups of the Pueblo Indians, but the Zuni and Moki are perhaps as interesting as any of them. [Illustration: FIG. 77.--GRINDING GRAIN, LAGUNA, NEW MEXICO] Wonderful indeed are some of the pueblo villages which were still occupied at the time of the coming of the Spanish, more than three centuries and a half ago. As in the pueblos now occupied, there were no separate family houses. The people of an entire pueblo lived in one great building of many rooms. Some of the pueblos were semi-circular, with a vertical wall upon the outside, while upon the inside the successive stories formed a series of huge steps similar to the tiers of seats in an ancient amphitheatre. [Illustration: FIG. 78.--THE ENCHANTED MESA The summit was once the site of an Indian pueblo] In the pueblo of Pecos were the largest buildings of this kind ever discovered. One had three hundred and seventeen rooms, and another five hundred and eighty-five. Taos is another of the large pueblos, and is especially interesting because it is still inhabited. This great building has from three to six stories with several hundred rooms. In the foreground of the photograph (Fig. 76) appears one of the ovens in which the baking is done. In some of these pueblos the women still grind their corn by hand in stone _matates_, just as their ancestors did for many hundreds and perhaps thousands of years. [Illustration: FIG. 79.--POTTERY OF THE ACOMA INDIANS, NEW MEXICO] In northwestern New Mexico there is a remarkable flat-topped rock known as the Enchanted Mesa, which rises with precipitous walls to a height of four hundred feet above the valley in which it stands. It was long believed that human beings had never been upon this rock, although there were traditions to the effect that a village once existed upon its summit. According to the tradition, the breaking away of a great mass of rock left the summit inaccessible ever afterward. The cliffs were scaled recently by the aid of ropes, and evidences were found in the shape of pottery fragments, to show that the Indians had once inhabited the mesa. Two or three miles away, across the valley, is the large village of Acoma, where a great deal of pottery is made for sale. The pottery of the Pueblo Indians is very attractive, and their religious festivals and peculiar dances draw many visitors. These Indians no longer fear attacks from the savage Apache or Navajo, but they have become so used to their rock fortresses that it is not likely they will soon. leave them. The Navajos now live in peace and raise large herds of sheep and goats; while the more savage Apaches have been gathered upon reservations, never more to go upon the war-path. Most of the Apaches still live in their rude brush habitations. [Illustration: FIG. 80.--NAVAJO WOMAN WEAVING A BLANKET] While the Pueblo Indians make attractive pottery, the Navajos are noted for their blankets. The wool, which is taken from their herds, is dyed different colors, and woven upon their simple looms into the most beautiful and costly blankets. We usually think of the native inhabitants of America as leading a wild and rude life, moving from place to place in search of food, and constantly engaged in warfare with one another. The Pueblo Indians alone are different. Possibly if the white man had never come to America these Indians might in time have become highly civilized. But it is more than likely that in their struggle with Nature in this wild and rugged country, where they were constantly subjected to attacks from their more savage neighbors, they would have sunk lower instead of rising, and would finally have disappeared. The Apaches were dreaded alike by the agricultural Indians and the early Spanish. Issuing from their mountain fastnesses the Apaches would raid the unprotected villages and missions, and then retreat as quickly as they came. For many years after the American occupation prospectors had to be constantly on their guard, and many are the tragedies that have marked this remote corner of our country. THE LIFE OF THE DESERT During the blinding glare of summer the deserts of southwestern Arizona and the adjoining portions of California are forbidding in the extreme. Day after day the pitiless sun pours its heat upon the vast stretches of barren mountain and plain, until the rocks are baked brown and it seems as if every particle of life must have left the seared and motionless plants. Month after month passes without rain. Now and then light clouds float into sight, and occasionally rain can be seen falling from them, but they are so high that the drops all disappear in the dry and thirsty air long before they can reach the ground. Cloud-bursts may take place about the peaks of some of the higher mountains, but they have very little effect upon the life out on the plains. Animals and plants brought to this region from a moister climate must drink continually to make up for the rapid evaporation of moisture from their bodies; a day without water may result in death. And yet the living things that have homes in the desert can resist the dry air for many months without a renewal of their moisture. There are areas where the average rainfall is less than three inches, and sometimes two years may pass without a drop of rain. It will certainly be worth our while to find out something about these desert plants and the way in which Nature enables them to get along with so little water. Go where we will, from the moist heat of the tropics or the dry heat of the deserts to the icy north, we find that everywhere the plants and animals are suited to the climate of the particular place in which they live. Therefore we might conclude that they thrive better in those places than they would anywhere else, but that is not always true. A struggle is going on continually among plants for a footing in the soil and for a share of the sunshine. The weaker plants are generally killed, while those hardy enough to survive have to adapt themselves to new conditions of life, becoming stunted and deformed upon barren slopes; but they have plenty of room there because fewer plants are striving for the same place. It is not likely that the deserts of the southwest have always been as dry as they are now. As the amount of rainfall slowly lessened through thousands of years, the animals could migrate when it became too dry; but the plants, fixed in one place, had either to give up and die, or change their characters and habits to suit the demands of the changing climate. The fact that these extremely dry deserts are filled with plant life to-day is without doubt due to this ability to change. In a moist, warm climate plants are luxuriant; they take up a large amount of water through their roots and evaporate it through the leaves. If placed in a desert, such plants would immediately wither and die. To avoid too rapid evaporation the bodies of the desert plants have become smaller, and their leaves have either shrunk greatly or wholly disappeared. Strong-smelling, resinous juices exude from the remaining leaves and stems, and form a surface varnish through which water passes with difficulty. Some forms of plant life, such as the prickly-pear, are provided with fleshy stems which hold a supply of moisture to be drawn upon during the long dry season. Men and animals are sometimes saved from death by chewing the pulp of the prickly-pear or other cactuses. After a period of exceptional drought, the stems of the prickly-pear lose their bright green color and become shrunken. [Illustration: FIG. 81.--PRICKLY-PEAR, BALL CACTUS, AND SPANISH BAYONET] The development of the underground part of the plant is frequently out of all proportion to the part above the surface. The manzanita, which grows in the semi-arid climate of southern California, is a low shrub with branches that are rarely large enough for fuel. The roots, however, are large and massive, and are extensively used for firewood. The desert plants are armed, not only against the dry air, but against the wandering animals which would bite them and suck their juices. The smell of the sagebrush is such that very few animals will touch it. Other plants are protected by thorns. In fact, the drier the region, the more thorny are its plants. A little shrub called the crucifixion thorn has no leaves at all, nothing but long, sharp spines. Besides the straight thorns there are curved and also barbed ones, for every conceivable form is represented among the plants of these dry lands. As the desert plants are armed against the animals, so the animals are armed against each other. Many of the insects and reptiles are extremely poisonous; the greater the heat of their habitat, the more dangerous are their bites. The horned toad, while not poisonous, is protected by having horny spines upon its head and back. The little rattlesnake known as the "side-winder" is perhaps the most dangerous of all, although the tarantula, centipede, and scorpion are formidable foes. The Gila monster, long believed to be so dangerous, is now considered non-poisonous under ordinary conditions. [Illustration: FIG. 82.--CRUCIFIXION THORN] The desert tortoise is perhaps the most remarkable of all the animals of the desert. It is rare, and little is known of its habits except that it lives in the most arid valleys of southeastern California, far removed from any water. This tortoise has a diameter across its shell of at least eighteen inches. Its flesh is much prized by the Indians and prospectors. A specimen which had been without water for an indefinite period was dissected, and the discovery was made that upon each side there was a membranous sac, containing clear water, perhaps a pint in all. The desert tortoise, then, carries his store of water with him, and is thus enabled to go many months without a new supply. [Illustration: FIG. 83.--THE GILA MONSTER] A trip across the deserts of the lower Colorado in spring, before the bracing air of winter has entirely gone, is one never to be forgotten. The poisonous insects and reptiles are not at this time warmed up to full activity, while many peculiar plants are just coming into bloom. Let us study some of the strange forms growing thickly over the rocky slopes and sandy plains. There are miles of forest, but not such a forest as we are accustomed to see. Tall, fluted columns of the giant cactus (saguaro), with rows of sharp spines, reach upward to a height of from twenty to fifty feet. At one or more nodes, bud-like branches spring from the main trunk and, curving upward, form columns about the parent stem. [Illustration: FIG. 84.--THE PALO VERDE TREE AND SAGUARO] The giant cactus bears near the top a purple flower and a large, edible fruit. This fruit, which has a red pulp, is a favorite food with the Indians, and also with many insects and birds. It is gathered by means of long forked sticks, for if it should drop to the ground it would be broken. The pulp of the stalk yields a little juice or sap which is used by the Indians when hard pressed for water. [Illustration: FIG. 85.--A FOREST ON THE PLAINS OF SOUTHERN ARIZONA Showing cholla and saguaro] Scattered among the huge club-shaped columns of the saguaro is the cholla, the next largest of the cactuses. This species, which is tree-like in its branching and in rare cases grows to a height of twelve feet, bears bright red or yellow flowers. One must approach with care, for its jointed stems are so easily broken that at the slightest touch of the hand or clothing, pieces break off and adhere firmly by means of their sharp curved and barbed spines. Another species of the cholla is small, reaching but a foot or two above the ground, but this and other low forms so cover the ground in places that one has to be constantly on guard to keep from running the spines into his feet. These are not all the plants of this wonderful forest. The ocatilla is a cactus-like form having a group of long slender stems bunched together at the root. In the spring each is tipped with a spike of red flowers, and as the snake-like stalks wave in the breeze they present an appearance scarcely less attractive than the saguaro. [Illustration: FIG. 86.--OCATILLA] Scattered among the vegetation just mentioned is the palo verde (green tree), so named from the yellowish green of its bark. It is remarkable for the small size of the leaves, which afford scarcely any shade for the traveller upon a hot summer day. (Fig. 84.) Along the dry water courses we find the mesquite, a tree which does not grow upon the gravelly plains and rocky slopes, for it needs more moisture than most of the desert vegetation. In the spring it puts out delicate green leaves which form a pleasing contrast with the other plants. Riding through one of these forests in the deepening twilight, one is impressed with a feeling of awe and mystery by the strange, weird shapes outlined against the sky. In the cooler air of evening the animals come from their retreats. The insects and the snakes are then abroad, and if one is on foot the sudden buzz of a rattlesnake is not a pleasant sound to hear. [Illustration: FIG. 87.--MESQUITE TREE, SANTA CRUZ VALLEY, SOUTHERN ARIZONA] The prickly-pear prefers slopes not quite so dry and hot as those of the forest just described. Its broad, spade-like, jointed stems are very interesting. The red fruit clustered upon their extremities is not disagreeable to the taste, but is covered with a soft, prickly down. Associated with the prickly-pear is a species of agave, but this does not grow so large in Arizona as it does farther south in Mexico. The plant is familiar to us as the common century plant of our gardens. The long fleshy leaves with spines at the ends are clustered at the surface of the ground, and from their centre, at blooming time, rises a tall flower stalk. The agave requires many years to mature. When the flower stalk has once started it grows rapidly, but after blossoming the plant dies. The mezcal, or pulque, the national drink of the Mexicans, is made from the sap of the agave. The fibre of the agave, known as sisal hemp, is used in the manufacture of rope, twine, mats, brushes, etc. Other parts of the plant have various uses. [Illustration: FIG. 88.--THE AGAVE] [Illustration: FIG. 89.--SPANISH BAYONET IN BLOOM] There are many kinds of yucca in the more elevated portions of the desert. They range in size from those only two or three feet high, of which the Spanish bayonet is a type, to the giant yucca of the Mohave Desert, which attains the proportions of a tree and forms thick forests over an area of many miles. The Spanish bayonet, with its long stalk of white, waxy blossoms, presents a very beautiful appearance, as do also the young specimens of the tree yucca. At rare intervals, once perhaps in many years, there is an unusual amount of rainfall in the spring, and in a few weeks the desert becomes transformed as if by magic. Seeds germinate, the presence of which one would never have suspected in the drier weather. In an incredibly short time the long gravelly or sandy slopes about the bases of the mountains are covered with a veritable carpet of green, yellow, and red. The sand verbena, the evening primrose, baby blue-eyes, and different kinds of lilies grow so thickly in places that every footstep crushes them. [Illustration: FIG. 90.--YOUNG YUCCAS IN BLOOM] But in a few short days the beauty has disappeared. The seeds mature speedily and drop into the sand. A hot wind withers the stems and leaves and blows them away; drifting sands take the place of the rich carpet. How readily these plants have adapted themselves to the brief period in which life is possible! Thus it is that this vast region about the lower Colorado, although so dry and hot, and at first sight apparently so unfitted for sustaining life, nevertheless supports its share. Many of the plant forms have assumed strange and monstrous shapes in their efforts to withstand the hard conditions in the struggle for existence, while others simply lie in waiting, sleeping during the long dry year, but ready to spring into life when the favorable showers come, as they sometimes do. THE PONY EXPRESS Although it is only a little more than fifty years since the discovery of gold was made and the rapid settlement of the West began, what a change has come over this great region! It was at first supposed to be impossible to connect the growing settlements upon the Pacific with the East by anything more than a wagon road, and those who advocated the building of a railroad were ridiculed. Now the journey across the continent is made upon smooth steel tracks in comfortable coaches, for the skill of the engineer has overcome the difficulties of the desert, the mountain wall, and the cañon. The pioneers who pushed westward from the Mississippi River with their slow ox-teams took all summer to reach the fertile valleys of California and Oregon, and considered themselves fortunate if they arrived at their destination before the coming of the winter storms. The first overland stage line was established by way of New Mexico and Arizona, terminating at Los Angeles. Twenty-two days were required for this part of the tiresome and dangerous trip. The route was longer and more desert-like than that farther north across Nevada, but the winter storms were avoided. The stage-coach proved too slow for the needs of the growing settlements upon the Pacific slope. A telegraph line was planned, but it could not be completed for some time, and even then it was probable that the Indians would destroy the poles and wires. Then came the idea of a relay of fast messengers upon horseback, and the pony express was organized. It is difficult to believe that by this means the journey of two thousand miles between St. Joseph, a point upon the Missouri a little above Kansas City, and Sacramento, California, was once made in about eight days. This is only a little more than twice the time required by the fast trains at present. For two years the trip was regularly made in about nine days, averaging two hundred and twenty miles a day. It can be readily understood that this wonderful feat required many relays of men and horses scattered along the route. The express rider had no well-graded roads to follow, but only the rough trail of the emigrants. This led across broad deserts and over rugged mountains, and throughout most of the journey exposed the rider to the attacks of Indians. Let us take a map and trace the route of the express. It followed closely the main overland trail which the gold-seekers had opened. Now towns and cities are scattered along the old trail, and the railroad crosses and recrosses it. But let us try to picture the country as it appeared in its wild state. Mountains, valleys and plains made up the landscape. Vast herds of buffalo darkened the Great Plains east of the Rocky Mountains, while farther west were numerous bands of antelope. The streams were filled with beaver and other fur-bearing animals. Here and there along the rivers were Indian villages with their curiously shaped tepees. Even the deserts of Nevada were not uninhabited, for the Indians lived there also, gathered in little family groups about the desolate springs. When we speak of the overland trail we do not mean a narrow path for animals, but the wagon road, rude though it was, which the early emigrants had made. They were determined to cross the continent, no matter what the difficulties and dangers. Wagons could be drawn by the oxen over the plains and deserts with little difficulty, although there were some dangerous rivers to be crossed. Mountains and cañons offered the most serious obstructions. In many places the wagons had to be let down over precipices with ropes, or be taken apart and carried piece by piece around the obstructions. It was not the mountains alone which made the trip "across the plains" one long to be remembered. It was often difficult to obtain water and fodder for the animals, and at many points savage Indians, bent upon plunder, were in hiding, waiting for a chance to stampede the cattle or kill the emigrants. The way was marked by abandoned wagons, household goods, bones of cattle, and the graves of human beings. The trail led from the Missouri across the state of Kansas to the Platte River, then followed this long stream to its head at South Pass on the continental divide. From the South Pass the trail led southwest past Fort Bridger, in southwestern Wyoming, through Echo Cañon and over Emigrant pass of the Wasatch Range down to Salt Lake City, which had been founded but a short time before the discovery of gold. West of Salt Lake City the trail skirted the northern shore of the Great Salt Lake, and after passing a low mountain divide in what is now northwestern Utah, reached the head waters of the Humboldt River. Thence the path ran along by this river down to the place where it disappeared in a vast sandy desert known as the sink of the Carson. The Carson River, after the dreary desert was passed, led the emigrants still westward toward a wall of mighty mountains known as the Sierra Nevada. Here Nature seemed to have done her utmost to shut off California, with its fertile valleys and rich gold-fields, from the longing eyes of the emigrants. There are, however, several low places in the range, and through one of these openings, at the head of the Carson River, the travellers gained the western slope of the mountains. Then in good time they reached the mining town of Placerville, and at length Sacramento, the capital of California. [Illustration: FIG. 91.--CHIMNEY ROCK On the old overland trail near the Platte River, western Nebraska] In order that the pony express might make the time required over the two thousand miles, five hundred horses and several hundred men were needed. The stations were placed about ten miles apart and were strongly built so that they might withstand the attacks of the Indians. These stations, nearly two hundred in number, all had to be supplied by means of freight teams, which often hauled hay, grain, and food for the messengers for hundreds of miles. The horses selected for the messengers to ride were the small, sure-footed ponies called mustangs. Through a stretch of ten miles the pony was pushed to its utmost speed, then it was carefully groomed, fed, and rested until the time came to make the return trip. In selecting the riders three things were of great importance: they must be light in weight, must be possessed of great powers of endurance, and also must be brave and resolute. At each station, as the time approached for the express to arrive, the relay horse was saddled and in waiting. As the rider dashed in he jumped from his horse, and with but a moment's rest, threw the saddle-bags containing the letters upon the fresh horse and was off again, riding like the wind. Upon smooth stretches the horses often made twenty miles an hour, but it was quite impossible to maintain this speed over the rocky and rugged portions of the route. Storms and Indian ambuscades often delayed the riders. Sometimes the messenger kept up a running fight with the Indians for miles. The riders were frequently killed, but the mail-bags were rarely lost. If a rider did not come in on time, it was known that something serious had happened, and search was immediately made. The riders were not allowed to stop for any purpose whatsoever; neither storms of the greatest severity nor even the presence of hostile Indians near the trail kept them from their duty. One of the few riders who are still living says that he was never afraid except on dark, cloudy nights. At such times he made no attempt to guide his horse, but trusting to the intelligence of the well-trained animal, gave it rein, and at the same time spurred it to its utmost speed. Think of riding at such speed into the dark night, not knowing what is ahead of you! The rider's only safety lay in the carefulness and sagacity of the horse. Such a ride called for more courage than did a conflict with Indians! [Illustration: FIG. 92.--PALISADES OF THE HUMBOLDT RIVER, NEVADA Near the overland trail] The pony express carried no passengers. It carried no freight, not even the usual express package. The messenger was intrusted with nothing but two bundles of letters carefully stowed away in a pair of saddle-bags. The letters were not like our ordinary letters, for the paper used was the thinnest and lightest possible. Hundreds of the letters weighed only a few pounds. It was very important that there should be no great weight, for if the horses were heavily loaded, they could not make the required time. Only those whose business was of great importance could afford to send letters by this express, for the charge was five dollars upon each letter. In spite of the high charge the pony express is said never to have been profitable, for the expenses were very heavy. It was discontinued in 1860, as by that time a telegraph line had been constructed across the continent. HOW CLIMATE AND PHYSICAL FEATURES INFLUENCED THE SETTLEMENT OF THE WEST The story of the exploration and settlement of the Pacific coast, and of the great region lying between the Pacific slope and the Mississippi Valley, offers a most interesting opportunity to study the control which physical features of the earth exert upon the trend of men's activities. The position of the mountains, the courses of the rivers, and the character of the sea-coast have all helped to shape the history of the West. The presence of gold in the rocks of the Sierra Nevada mountains was the chief incentive which led to the breaking down of the barriers placed by Nature between the Pacific and the Mississippi basin. When an unknown land is accessible by water, the shore line offers the easiest means for the first explorations and settlements. So it came about that nearly all the eastern coast of North America was known before men ventured far into the interior. Then the large rivers, like the St. Lawrence, the Hudson, and the Mississippi, seemed to offer inviting routes into the recesses of the continent, but exploration through the pathless woods and rough mountains was slow. It was soon discovered that the Hudson was a short river and did not lead across the continent as was at first hoped. Because of the absence of other large rivers upon that portion of the coast which the English occupied, their settlements did not spread westward as rapidly as they otherwise would have done. The country was covered with dense forests, and savage Indians disputed the right to occupy it. In time, however, passes were found leading over the Appalachian Mountains to the Ohio River and through the Mohawk Valley to the region of the Great Lakes. The advantages for travel offered by the St. Lawrence River and the chain of lakes above it were utilized at an early day. The route of the French missionary explorers and fur traders was from Montreal up the Ottawa River, then by a short portage and a series of small lakes to Lake Huron. From this point the most remote shores of Lakes Superior and Michigan could be easily reached. By the aid of several small bodies of water west of Lake Superior, Lake Winnipeg and Great Slave Lake were finally discovered; but from this point the waterways into the West were small and could be followed no farther, so that it was a long time before the Rocky Mountains were crossed. By floating down the Illinois River the French arrived at the Mississippi, explored much of its course, and took possession of the country in advance of the English. This fact was directly due to the difficulties which the English explorers experienced in forcing their way over the Appalachian highlands. The Spanish explored the southern shores of the continent, and crossing the Isthmus, were the first to behold the Pacific. The fact that the Pacific coast of North America was so easily reached at this point gave the Spanish a great advantage, and explains why they gained such a hold upon the lands bordering that ocean. It was a comparatively simple matter for them to fit out ships, and sailing north and south, to take possession wherever they desired. However, when they had gone as far as California, their progress was for a long time almost completely blocked by storms and head winds, for the prevailing direction of the wind is down the coast. The Spanish finally reached Vancouver Island, but never succeeded in making settlements north of San Francisco. Even the interior of California was little known to them, for the mountains and deserts discouraged their progress in that direction. From an examination of a map we might suppose that the Colorado River would offer as good a means for penetrating the continent as did the Mississippi River, but as a matter of fact it is navigable for a comparatively short distance. The Spanish made one attempt to ascend this river, but finding themselves surrounded on every hand by a most desolate, barren country, they turned back before reaching the Grand Cañon. In the eager search for gold the Spaniards pushed north from Mexico and planted settlements in Arizona and New Mexico, but upon the northwest their progress was stopped by cañons and deserts. Now we are prepared to understand why it was that the western portion of North America remained for so long a time a mysterious and unknown region. There were no waterways by which it could be explored, while snow-clad mountains and deserts made access to it doubly difficult. By the beginning of the last century the Americans had overcome the natural obstacles in their westward progress, and their settlements reached as far into the wilderness as the Mississippi River. Hunters and traders were soon pushing far beyond, spreading over the Great Plains and up to the very base of the Rocky, or Stony Mountains, as they were then called. The Missouri River became the great highway into the Northwest, for the adventurers took advantage of the streams wherever possible. Many other rivers were discovered flowing from the western mountains, but with the exception of the Platte and Arkansas they were generally too shallow for navigation even with a light canoe. Starting in the early spring from the mouth of the Missouri, the hardy trappers sailed and paddled up the river, taking several months to reach the head of navigation at the Great Falls. In the autumn, when the boats were loaded with furs, it was a comparatively easy matter to drop down the river with the current. It would have been almost impossible to transport the loads of goods on pack-horses across the thousand miles of prairie, where the traders would be subject to attack from hostile Indians. Adventurous men pushed farther and farther west through the passes in the mountains and began trapping upon the waters which flow into the Pacific. It had long been supposed that the Rocky Mountains formed a barrier beyond which our country could not be extended, and that the Pacific slope was made up of mountains and deserts not worth securing. The explorers showed that the Rocky Mountains were not continuous, but consisted of partly detached ranges, and that while their eastern fronts were indeed almost impassable for long distances, there were places so low that it was difficult to locate the exact spot where the waters parted to seek the Pacific Ocean and the Gulf of Mexico. In southwestern Wyoming the continental divide, known as the Great Divide mesa, though more than a mile above the sea, is but a continuation of the long, gentle slope of the Great Plains. The Rocky Mountains decrease in height toward the south, near the line between New Mexico and Colorado. Here is situated Raton Pass, an ancient Indian highway from the valley of the Arkansas to the Rio Grande. In the early half of the last century this trail was much used by the caravans of traders and came to be known as the Santa Fé trail. [Illustration: FIG. 93.--ON THE CONTINENTAL DIVIDE IN SOUTHWESTERN WYOMING] In the early days of the American occupation of California, the Santa Fé trail became an important route to the Pacific. From the Mexican town of Santa Fé it led down the valley of the Rio Grande, following the old road to Mexico, and then turned west across the broad plateau of the continental divide, not far from the present course of the Southern Pacific Railroad. Passing Tucson, the road kept near the course of the Gila River to Fort Yuma, and then led over the Colorado Desert to Los Angeles. This path avoided all the high mountains, but much of it lay across deserts, where the heat and scarcity of water made it an impracticable route for the emigrants. One not acquainted with the physical geography of the West might wonder why the gold-seekers on their way to California did not make use of the Missouri River, which, except for the Great Falls, was navigable for small boats to the very base of the Rocky Mountains. A partial explanation is found in the report of the hardships endured by the Lewis and Clark exploring expedition, and later by the Astor party, which went out to found a fur trading post at the mouth of the Columbia. It had been supposed that after once crossing the continental divide it would be an easy matter to embark upon some stream and float down to the Pacific Ocean. The parties referred to became lost in the defiles of the mountains, and when they finally reached the Snake River it was only to find that rapids and waterfalls continually obstructed navigation. Although there was in most places plenty of water upon this northern route, yet the mountains were impassable for wagons. Because of these conditions the emigrants started out boldly across the plains, following the general course of the Platte River, and crossing the Rocky Mountain divide at the South Pass in western Wyoming, a place famous in its day. At this point those who were going to Oregon turned northwestward to Fort Hall, a trading post of the Hudson Bay Company. From here they crossed southern Idaho, keeping near the course of the Snake River until they reached the point where it enters the grand cañon; there they left the river, and climbing over the Blue Mountains, entered the fertile valleys about the present city of Walla Walla. From this place the emigrants followed the Columbia River to The Dalles, whence they proceeded either by boat or raft until Fort Vancouver and the mouth of the Willamette were finally gained. Wagons were taken through on this route, and it was not dangerous, although accidents sometimes happened at the Cascades, where locks were built at a later day. [Illustration: FIG. 94.--THE OLD SANTA FÉ TRAIL Over this thousands of freight and emigrant wagons have passed] The emigrants for California, who were the most numerous, turned southwest at South Pass, and after crossing the Wasatch Range through Emigration Cañon, came out upon the plain of Great Salt Lake. Then, traversing desert plains, they reached the Humboldt River, which they followed until it sank into the sands. Several routes had been opened across the Sierra Nevada mountains into California, but those through the Carson and Donner passes were most used. Several high ranges of mountains lay between the Willamette Valley of Oregon and the Great Valley of California, so that in the early days there was very little travel between these two territories. The overland trip required so long a time, and involved such dangers and hardships, that many preferred the water route, in spite of the fact that its ships were crowded, and the voyagers must cross the fever-infected Isthmus. It is very interesting to note how widely different the rivers are upon the opposite sides of the Rocky Mountains. Those upon the east, with the exception of the Missouri at the Great Falls, are not marked by waterfalls after leaving the mountains. There are few cañons of importance. The streams generally flow in channels only slightly sunken below the general level of the Great Plains. The streams upon the west, on the contrary, are broken by rapids and waterfalls, and are generally buried in cañons so deep and precipitous that in places a man might die of thirst in sight of water. No other great migration of people over the surface of the earth ever encountered such difficulties as that which pressed westward after the discovery of gold. It was at first thought that railroads could not be constructed through the mountains and deserts, and until the mineral wealth of the West became known, many men believed that the greater portion of the country was not worth taking. It would be interesting to consider each of the main lines of railroad which connect the Mississippi Valley with the Pacific, and study the features of the country through which it runs, determining as far as possible the surveyor's reasons for selecting that particular course. Some of the railroads follow for long distances the routes of the emigrants. The emigrants, in their turn, often made use of the ancient Indian trails. [Illustration: FIG. 95.--THE CARSON PASS, SUMMIT OF SIERRA NEVADA MOUNTAINS One of the main emigrant routes to the Pacific Coast] While Nature seems to have striven to raise impassable barriers to shut off the Pacific slope from the rest of the continent, yet she failed at some points, and through the unguarded passes the wild animals and Indians first found their way. Then came the trappers, prospectors, farmers, and at last the railroad, until the wilderness was over-run. Because of its temperate climate, abundant rainfall, and rich soil, the Mississippi Valley was rapidly settled after the pioneers had once reached it. The plains rising slowly westward toward the base of the Rocky Mountains were found to be more arid the farther they were explored. Consequently there exists a broad strip of plain which is even to-day sparsely settled. The emigrants went on to the fertile valleys nearer the Pacific, where the rainfall is more abundant. The American settlers did not then understand irrigation, although it was practised by the Mexicans to the south. Because the discovery of precious metals was first made in California, the pioneers crossed the intervening mountains without giving a thought to the mineral riches which might be concealed in their depths. Later, mines were opened in the mountains all through the arid regions. The necessity of providing food for the miners brought about the discovery that the desert lands were very productive wherever the waters of the streams could be brought to them. THE LIFE OF THE PROSPECTOR Perhaps some of us who have comfortable homes, sleep upon soft beds, wear neat clothes, and can obtain every variety of food that we wish, think with pity of the men who lead a rough and lonely life among the mountains far from all comforts. Let us learn something more about the life and work of the prospectors, for we may find much that is desirable in their experiences. Not many thousands of years ago our ancestors led what we would now call a wild and savage life. They had no permanent homes, but wandered here and there in search of food, and lived in caves or constructed the rudest kind of shelter from the storms. Perhaps we are right in feeling thankful that we were not born in those primitive times, but are there not really many things to regret about the way in which we have to live at the present day? The utterly free outdoor life is not open to many. We have little or no opportunity to become acquainted with Nature, the guardian of our ancestors. The woods, the rocks, the mountains, and the dashing streams are almost complete strangers to many of us. Many men are now obliged to go every day to their work in office or shop, and spend the hours shut in from the fresh air and bright sunshine. At night they sleep in rooms into which they admit little fresh air for fear of taking cold. To-day each man has to learn to do one thing well to the exclusion of nearly everything else, in order to make a living. For this very reason we are in danger of becoming human machines and of losing the use of some of the powers with which Nature has endowed us. Many things about our present mode of life are not natural to us, but through successive generations we have become somewhat adapted to them. The Indians, if taken from a life in the open air and made to live as we do, often sicken and die. The farmer enjoys much more freedom and more of the sweet fresh air than do the artisans and office workers; but of all the men in civilized countries the trappers and prospectors live most out of doors. To be sure, they have to endure many hardships and dangers, and their beds are not always the softest nor their food the best, but you will seldom find one who is willing to exchange his free life for work in the town or city. The trappers have nearly disappeared. Their occupation will be gone with the passing of the wild animals which were once so abundant. The prospectors are, however, becoming more numerous year by year throughout the mountains of western America. To them we owe a great debt, for had not their searching eyes brought to light the hidden mineral deposits this portion of our country would be far more thinly populated than it is to-day. The discovery of gold in California was accidental. A man named Marshall was building a mill for Sutter in the foot-hills of the Sierra Nevada mountains at the time (1848) when California had just come into the possession of the United States. While at work he noticed some shining grains in the sand of the mill-race. A little testing of the grains led him to the conclusion that they were gold. The news spread rapidly over the world, and since that time a constantly increasing tide of gold-seekers has been pushing out into the unexplored portions of the earth. Comparatively few of these men have become wealthy, but their discoveries have led to the settlement of new regions and to the growth of important industries. In truth, if it were not for the deposits of valuable metals, large areas of the desert and mountainous West would be of small value. [Illustration: FIG. 96.--A PROSPECTOR IN THE DESERT] The prospector needs little capital except health and strength, but he must be willing to lead a rough life. He will be more likely to succeed if he knows something about the different kinds of minerals and rocks, and is able to distinguish the valuable ones from those which are of little or no worth. The prospector may have a pack-horse and a second horse to ride, or he may go afoot with merely two burros to carry blankets, provisions, and tools. A burro costs little and will live upon almost anything. The variety of food that can be carried is not large; such things as bacon, flour, sugar, beans, and coffee are the most important. With the rifle one may frequently add to the supply. This, you may think, is pretty hard fare, but life in the open air will make one hungry enough to relish almost any sort of food. The prospector does not need a road or even a trail. He seeks the least-known portion of some mountain district where he has an idea that gold may be found. Through the cañons he goes, and over the mountains, either on horseback or driving the burros before him. Water and grass are usually abundant, and the little cavalcade stops where night overtakes it. In the desert prospecting is more difficult and often dangerous, because of the scarcity of water. It is necessary to know the location of the few scattered springs, and to make one of the burros useful in carrying water kegs. A spring must be the starting-point in the morning, and a sufficient amount of water must be taken to last until the traveller can get back to the same spring or until he can reach another. A pick, a shovel, and a hammer are among the most important parts of the prospector's outfit. Gold is a heavy substance, and as it washes down the mountain sides and into the gulches from some quartz vein, its weight finally takes it to the bed-rock beneath the sand and gravel. With his pick and shovel the prospector can reach the bed-rock. He takes some of the gravel from its hiding-place close to the rock, places it in a pan filled with water, and then, with a peculiar rotary movement, washes away the lighter materials, leaving the heavier substances and the gold, if there is any, at the bottom of the pan. If there is no trace of gold, the prospector goes on to another creek; but if some of the yellow metal is washed out, he tests the place thoroughly for more. In searching for ledges the prospector spends his time in the smaller gulches and upon the mountain sides. Every piece of detached quartz that meets his eye is examined, and if any specks of gold appear, the search is directed toward the vein or ledge from which the specimen came. With the hammer, pieces of quartz are broken from the veins which here and there rise above the surface of loose and crumbling rock. When the worker finds a piece that is stained with iron and has the appearance of carrying gold, he places it in his bag and keeps it for further examination. At camp, the pieces of quartz are pounded to a powder in a mortar and then washed in a horn spoon. A string of fine grains of gold tells of the discovery of a rich vein. [Illustration: FIG. 97.--A PROSPECTOR'S CABIN IN THE ROCKY MOUNTAINS] It is not usually an easy matter to find home of a piece of stray quartz upon the mountain side. Days and weeks may pass while search is made up the slope, for the fragment must have come from some point above. But the ledge, once discovered, is traced along the surface for the purpose of determining its direction and extent. When a promising bed of gravel or a vein of gold-bearing quartz is found, the prospector posts the proper notices of his right to the claim and has them recorded at the nearest land office. Then he makes a permanent camp by cutting down trees and building a cabin. The interior of the cabin is very simple. Its table and chairs are made of split lumber. One end of the single room is occupied by the bunk, and the other by a large fireplace. There may be no windows, and the roof may be made of earth piled upon logs, or of long split shingles commonly known as shakes. Sometimes, after discovering a very rich quartz ledge, the prospector goes back to a settlement to attempt to interest some one in buying or developing it. Sometimes it happens that he loses the location of the vein and cannot go back to the place where it was discovered. In this way his discovery becomes a "lost mine," and grows in importance in people's minds as the story of its riches spreads from one to another. Although men may spend years looking for such mines, they are not often found again. Frequently two men go prospecting together so that their work will be less dangerous and lonely. If they are not at once successful, they manage in some way to get supplies for a trip each year into the mountains. Often they are "grub-staked," that is, some man who has money furnishes their supplies in return for a share in their findings. If they have enough to eat, the prospectors, in their snug cabin, are comfortable and happy. The cabin is built as near as possible to the mine, so that the men need not be cut off from their work during the stormy weather. The temperature underground is about the same in both winter and summer, so that winter storms and summer heat form no hindrance to the work. [Illustration: FIG. 98.--MOUTH OF A TUNNEL] Years spent in life of this kind lead men to love the mountains. They feel a sympathy with Nature and a companionship in her presence. When they have to visit the town for supplies, they long to get back to their little cabins. They feel lost in the whirl and confusion of the city. Summer is a delightful time at the many little miners' cabins scattered through the mountains. The air is invigorating, the water pure and cold. There is everything in the surroundings to make one happy. In the winter the miner sits by his great fireplace, with the flames roaring up the chimney. He has no stove to make the air close and oppressive. About the fireplace his dishes are arranged--the kettle for beans, the coffee-pot, and the Dutch oven in which the bread is baked. If there are some old paper-covered story-books at hand, it does not matter how fiercely the storms rage without. Ask any old prospector who has spent years in this manner if he would exchange his cabin for a house in the city, and he will most decidedly answer "no." This lonely life in the mountains seems to engender hospitality. The old-time prospector will make you welcome to his cabin and will share his last crust with you. When he asks you in to have some coffee and beans, he does not do it merely for the sake of being polite, and he will feel hurt if you do not accept his hospitality. His dishes may not be as white as those to which you are accustomed, but I will venture to say that you have never tasted better beans than those with which he will fill your plate from his soot-begrimed kettle. We ought all to see more of this wildlife. Even if we do not care to, make our permanent homes among the mountains, it would do us good to go there every summer at least, and so not only become stronger, but cultivate that familiarity with and love for outdoor life which our ancestors enjoyed. GOLD AND GOLD-MINING Gold derives its value partly from its purchasing power, partly from those properties which make it serviceable in the arts, and partly from its beauty. The high esteem in which gold money is held is as much the result of its comparative rarity as of its physical properties. Among nearly all the nations of the world it has been agreed upon as a standard of exchange. Gold has one disadvantage as a medium of exchange; it is rather too soft to wear well. But this difficulty is overcome by alloying the gold with another mineral of nearly the same color,--copper, for instance. In order that we may understand better the position which gold occupies in the arts and trades of the world, let us compare it with other metals, and first with platinum. This mineral is far less abundant and has many properties which make it valuable in the arts. Like gold, platinum is malleable and ductile and does not tarnish in the air, but it differs from gold in not being easily fusible, so that it is used in the laboratory for crucibles. The steel-gray color of platinum is, however, so much less attractive than the yellow of gold, that it is not used for ornamental purposes. An effort was made at one time by Russia, where a comparatively large amount of platinum is found, to coin this metal into money, but its continued use was not found practicable because of its changing price in the markets of the world. If the leading nations would agree upon a fixed value for platinum, it might be used like gold as a medium of exchange. Silver is brighter and more attractive than platinum, but is of little use in the laboratory. It has been found in recent years to be so much more abundant than gold that its value has decreased greatly as a commercial article. In our country when coined it has, like paper money, been given a value equal to gold. The diamond has a value far exceeding that of gold, but this value is dependent almost wholly upon its ornamental properties, although the brilliant stone is also useful as an abrasive and cutting agent. From these facts it is evident that gold, because of its rarity, its physical properties, and its beauty, combines a larger number of desirable characteristics than any other mineral. Gold can be found in very small quantities nearly everywhere. It is present in all the rocks and also in sea-water. The gold that is distributed in this manner is of no value to us, for it would cost many times as much to obtain it as it is worth. Nature has, however, concentrated it for us in some places. In portions of the world where the crust has been folded and broken there are veins of quartz extending in long, narrow, and irregular sheets through the rocks. This quartz is the home of the gold, and it is usually found in hilly or mountainous regions. Do not mistake the yellow iron pyrites for gold. Pyrites is brittle, while gold is malleable. You can hammer a little grain of gold into a thin sheet. Do not make the mistake, either, of thinking that the shining yellow scales of mica which you see in the sand in the bottom of a clear stream are gold. These yellow minerals that look like gold have been called "fools' gold" because people have sometimes been utterly deceived by them. [Illustration: FIG. 99.--A GOLD-SILVER MINE Summit of San Juan Range, Colorado] Upon the Pacific slope minerals are now being deposited in some of the openings of the rocks from which hot springs issue. A study of these springs has led to the opinion that the gold-bearing quartz veins were formed in a similar manner, but at a very remote time in the past. The milky or glassy quartz, which is so hard that you cannot scratch it with the point of your knife, the little grains of pale yellow iron pyrites, and the grains and threads of gold scattered through the quartz, were at one time in solution in water. This water came from some region far down in the earth, farther than we can ever reach with the deepest shafts, and there, where it is very hot and the pressure is great, the water dissolved the little particles of gold and other minerals from the rocks; and then, gathering them up, bore them along toward the surface, depositing them as solid particles again in the form of veins in the fissures through which the stream was passing. [Illustration: FIG. 100.--HYDRAULIC MINING ON THE KLAMATH RIVER, CALIFORNIA] As the rocks upon the surface decay and the crumbling material is carried away by running water, the gold, being very heavy, washes down the hillsides and is at last gathered in the gulches. This fact explains why we find gold both in veins and in the gravel of the streams. Getting gold from the veins is called quartz-mining. Washing it from the gravel is called placer-mining; and if the gravel is deep and a powerful stream of water is required, the work is called hydraulic mining. [Illustration: FIG. 101.--MAY ROCK, A VEIN OF QUARTZ ON THE MOTHER LODE] Everyone has heard of the Mother Lode of California. Every miner wishes that his mine were upon this famous lode, which is made up of a large number of quartz veins extending along the western slope of the Sierra Nevada mountains, and is marked by hundreds of important mines. A line of towns marks the course of the Mother Lode for over a hundred miles. They are almost entirely supported by the gold which the lode supplies. The gold first discovered in California was placer gold. After the miners had worked over the stream gravels and had secured all that they could in that way, they began to search for the home of the gold. It could not always have been in the creek beds, and the miners were correct in thinking that it must have been washed from some other place. Gold was so frequently found in pieces of loose or float quartz that this fact finally turned their attention to the quartz veins which were numerous upon the mountain slopes. Then came the discovery of the series of great quartz veins now known as the Mother Lode. [Illustration: FIG. 102.--AN ARASTRA] When the miners first found the quartz flecked with gold, they used the simplest means for separating the two substances. If the quartz was very rich in gold, it was pounded and ground fine in a hand mortar. Then the lighter quartz was washed away and the gold left. The miners also made use of the Mexican arastra. This is a very crude apparatus, and is employed even now by miners who cannot afford to procure a stamp-mill. To build an arastra, a circular depression ten or twelve feet wide and a foot or more deep is made in the ground. This depression is lined with stone, which forms a hard bottom or floor. Four bars extend outward from an upright post placed in the middle of the floor, and a large flat stone is fastened to the end of each bar by means of a rope. A horse is hitched to one of the bars, which is purposely left longer than the others. The ore is thrown into the arastra, and water is admitted, a little at a time. As the horse is driven around the stones are dragged over the circular depression, crushing the ore and setting free the gold. [Illustration: FIG. 103.--THE STAMPS IN A QUARTZ-MILL] This way of separating the gold was too slow, and in a short time the stamp-mill was invented. It has grown from a very simple affair into the great mill which crushes hundreds of tons of ore in a day. The iron stamps each weigh nearly half a ton. They are raised by powerful machinery and allowed to drop in succession upon the ore, which is gradually fed under them. The stamps crush the ore to a fine sand more easily and rapidly than could be done by any other method. Water is kept running over the ore, and as fast as it is crushed sufficiently fine for the particles to pass through a wire screen, the water with which they are mixed is allowed to flow over large plates of copper which have been coated with quicksilver. The latter mineral has an attraction for gold, and so catches and holds most of the particles, no matter how small they are. The compound of gold and quicksilver is a soft white substance known as amalgam, utterly unlike either metal. When the amalgam is subjected to heat, the quicksilver is driven off in the form of a vapor, and the gold is left pure. The quicksilver vapor is condensed in a cool chamber and is used again. The iron pyrites in the ore contains gold which cannot be separated by the crushing process and a machine called a concentrator has been invented to save this also. After passing over the copper plates the crushed rock and pyrites are washed upon a broad, flat surface, which is moving in such a way that the lighter rock waste is carried away by the water. The pyrites now appears as a dark, heavy sand. This sand is placed in a roasting furnace, where the sulphur is driven off, and the gold and iron are left together. Now the gold is dissolved by means of chlorine gas, with which it unites in a compound called gold chloride. From this compound the metallic gold is easily separated. All this may seem a complicated process, but it is carried through so cheaply that the ore which contains only two or three dollars to the ton can be profitably worked. [Illustration: FIG. 104.--MINING THE GRAVEL OF AN OLD RIVER-BED] Not all quartz veins carry gold. There are many in which not a single speck of the precious metal can be found. Gold usually prefers the society of quartz to that of other substances, for minerals, like people, seem to have their likes and dislikes. Along the Mother Lode, however, gold is sometimes found in little bunches and "stringers" scattered through slate. In such cases the slate is mined and sent to the mill. Some miners devote themselves to pocket mining. They trace the little seams in the rock, and where two seams cross they sometimes find what they call a "pocket." This is a mass of nearly pure gold of irregular shape, varying from a few dollars to thousands of dollars in value. This kind of mining is very uncertain in its results, for a man may make hundreds of dollars in one day, and then not find anything more for months. The western slope of the Sierra Nevada mountains was once covered with the camps of thousands of placer miners. Piles of boulders and gravel are scattered along the creeks where the eager workers took out millions of dollars' worth of gold-dust and nuggets. Now many of the streams and gulches are entirely deserted. But in other places, where the quartz veins outcrop, there are scores of stamp-mills at work, night and day, pounding out the gold. Some of the mines have been sunk more than a half mile into the earth, and the gold is still as abundant as ever. In some portions of the mountains hydraulic mining is more common than quartz-mining. Years ago many of the rivers occupied different channels from their present ones. The gravels of these old channels in the Sierra Nevada mountains, and in other parts of the West where gold-bearing veins occur, are rich in gold. In these channels the gold is so deeply buried that it cannot usually be obtained by means of pick and shovel. In order that the overlying gravel may be removed as cheaply as possible, water is supplied by means of ditches, often many miles long. From some near-by hill the stream is conducted down to the mine in strong iron pipes. It thus acquires a great force, and when directed against a gravel bank rapidly washes it away. Torrents of water bearing boulders, gravel, and sand, together with the particles of gold, are turned into sluice boxes lined at the bottom with quick-silver. This metal catches the gold and forms an amalgam as it does in the quartz-mills. COPPER-MINING There is a city hidden away in a narrow cañon in the extreme southern portion of Arizona which is supported solely by a copper-mine. The cañon lies upon the southern slope of a range of mountains, and from its mouth one can look far off to the south across the desert plains and mountains of Mexico. The city has an elevation of more than a mile above the sea, and the cañon in which it is situated is so narrow and steep-walled that you can almost jump down from one street upon the roofs of the houses along the street below. Stairways, instead of walks, lead up the hillsides from the main street in the bottom of the cañon. You might well wonder at the position of the city, and think that out of all the waste land in this region a better place might have been selected for its location. But cities grow where people gather, and people do not come to live in the desert unless there is important work to be done there. A party of prospectors who were searching carefully over the mountains found several mineral veins with green copper stains crossing this cañon and outcropping in the adjacent hills. Claims were staked out and recorded at the nearest land office. Then shafts and tunnels were opened, and the miners became confident from the rich character of the ore that an important copper-mine might be developed. Supplies were brought across the desert with teams, and cabins were built in the lonely cañon. Then an enterprising man started a store. As the mine was opened farther, its importance was better understood. There was a call for more miners and the town grew larger. The houses clustered about the mine, the centre of all the activities. At last a railroad was built, and the town became a city, with narrow, winding streets occupying the winding cañon, while tier upon tier of houses crept up the sides of the cañon, which formerly had been covered only by growths of cactus and other plants of the desert. If the mine should close, there would be no inducement to keep people in the locality, and the city would become merely a group of deserted buildings. Water is so scarce that only a small amount is allowed to each family, and it is delivered in barrels instead of by pipes. Provisions of all kinds are very expensive, for they have to be brought a long distance. The great mine supports the thousands of inhabitants. The varied industries represented there are dependent upon it alone. As long as it pays to mine the copper, the people are as contented as if they were not tucked away in a cañon in a remote corner of the world. The most interesting things to be seen about the city are the mine and the smelter. In the former the ore is obtained; in the latter the ore goes through various processes until it comes out in the form of shining, metallic copper. The copper ore, we must understand, is not metallic or "native copper," as it is called when found pure, but a combination of copper with other substances which change its appearance entirely. [Illustration: FIG. 105.--COPPER SMELTER AND CITY OF BISBEE, ARIZONA The pipe leading up the hill carries away sulphur fumes from the smelter] The mine is opened by a shaft, that is, a square hole sunk in the ground. The shaft of this mine is a thousand feet deep, and is being continually extended downward. If we wish to go down into the mine, we must put on some old clothes and get the foreman to act as guide. The cage in which we are to descend stands at the mouth of the shaft, suspended by a steel rope. It looks much like the elevators found in city buildings. At different levels horizontal passages, called drifts, extend to the right and left upon the vein of copper ore. We step out of the car at one of these levels and with lighted candles start to walk through a portion of the mine. There are so many miles of tunnels that it would take us days to go through them all. Overhead, under our feet, and upon the sides of the drift, lies the vein of copper are, presenting a different appearance at different places. The various ores sparkle in the light and we gather specimens of each. The common are is chalcopyrite, a copper sulphide; that is, it is composed of copper and sulphur. It has a brass-yellow color, but is often stained with beautiful iridescent tints. In places the chalcopyrite has been changed to the delicate green carbonate of copper called malachite. In other places it has given place to the oxide of copper. The little crimson crystals of this mineral give bright metallic reflections. The deposit of copper ore is apparently inexhaustible, for in places the vein widens so that chambers one hundred feet wide and several hundred feet long and high have been made in taking it out. In going through the mine we have to be very careful not to step into openings in the floor of the passages, or drop rock fragments into them, for far below miners may be working. The places where the men are taking out the ore are called "stopes," and to reach them we have to crawl and creep through all sorts of winding passages, now through a "manhole," and now down a long ladder which descends into black depths. From the stopes the ore, as it is blasted out, is shovelled into chutes running down to some drift where there are men with cars. Each car holds about a ton of ore, and after being filled it is pushed along the drift and upon a cage which raises it to the surface. [Illustration: FIG. 106.--HOMES OF MINERS, BISBEE, ARIZONA] The mine is not wet, for there is so little rain in this region that there are few underground streams. In places, however, it is warm, for when the oxygen of the air reaches the fresh sulphide it begins to oxidize the ore; that is, it begins to burn it, and change it into a different compound, just as fire changes wood or coal. Wherever oxidation is going on, heat is produced. Fresh air is constantly needed in these workings far underground. A supply is forced down in pipes, and then allowed to flow back to the surface. In this way a thorough circulation is kept up. Underground one loses all thought of the changes between night and day, for it is always dark there. Consequently we are surprised on coming up from the mine to find that night has settled over the town. Lights are twinkling everywhere, and miners with their pails of luncheon are coming for the night shift. Another interesting experience now awaits us in the form of a visit to the smelter. Here the bright copper is extracted from the rough-looking ores. How different the two substances appear! They look as if they had scarcely anything in common. The interior of the smelter seems like a bit of the infernal regions set upon the earth. While watching what goes on, we might imagine that we were far down in the earth, where Vulcan, the fire god, was at work. At night the scene is particularly weird and impressive, for the shadows and general indistinctness make everything appear strange. The glowing furnaces, the showers of sparks, the roar of the blast furnaces, the suffocating fumes of sulphur, and the half-naked figures of the Mexican workmen, passing to and fro with cloths over their mouths, form all together a bewildering scene. The ore is first pulverized, and then placed in large revolving cylinders, where it is roasted. A fire is started in the cylinder at first, but after the ore becomes so much heated that the sulphur in it begins to burn, no further artificial aid is necessary. Little by little the ore is added in quantities sufficient to keep the fire going. The object of the roasting is to drive off as much sulphur as possible. After being raked from the roasting furnace, the ore is wheeled in barrows to the huge upright furnaces and is thrown in. Here such materials as limestone and iron are also added to aid in the formation of a perfectly fused or molten mass. These substances are known as fluxes. With the melting of the ore the copper begins to separate from the impurities. The melted ore, in the form of a glowing liquid, gathers at the bottom of the furnace and runs out into a large kettle-like receptacle. When ore of these vessels is full it is tipped up and the molten copper which has collected at the bottom, because it is heavier than the slag, is allowed to run into another large kettle, supported by chains from a rolling truck above. [Illustration: FIG. 107.--SHIPPING COPPER MATTE] The slag is dumped into a car and is carried outside, while the huge dish containing the copper and some slag is swung to the opposite side of the building, where its contents are cast into another furnace. A very strong blast of air is forced up through the molten mass in this furnace, and the remaining portion of slag is blown out at the top in a shower of glowing particles. From the bottom of the furnace the liquid copper is drawn out and allowed to run into moulds where it finally cools. It is then known as copper matte. The copper still contains some impurities, and retains in addition whatever gold and silver may have been present in the ore. Most copper ores carry a small amount of these precious metals. The heavy bars of copper matte are now ready for shipment to some manufacturing point, where they are refined still further and made into the various copper utensils, copper wire, etc. Copper is valuable for many purposes, as it does not rust easily, is highly malleable and ductile, and is a good conductor of electricity. In the great copper-mines upon Lake Superior, copper is found in the native state mixed with the rock, and does not have to be smelted; but in most mines the ore must go through a process very like the one described before metallic copper can be obtained. It does not matter how remote a region may be, how intense the heat or cold, or how desert-like the surrounding country, men will go to it if minerals of value are discovered; and there they will perhaps spend the whole of their lives, mining these substances which are of such importance to the industries of the world. COAL AND PETROLEUM People are beginning to ask where fuel will be obtained when the coal-beds are exhausted and the petroleum is all pumped out of the earth. The cold winters will not cease to come regularly, and we shall continue to need fires for many purposes. This is a question which need not trouble us. So long as the sun lasts in the sky and the oceans cover so much of the earth, and so long as there are mountains upon the land, there must be streams with rapids and waterfalls. The power of these streams, which has for ages gone to waste, is now being turned into electricity for purposes of light and heat. We may be sure that long before the mines cease to produce coal and the wells to supply petroleum, there will be something better ready to take their places. But coal and petroleum are still such important commodities that everyone should know something about the way in which they were made. This earth of ours has had a very long history, much of which has been recorded in the rocks beneath our feet, and the record is more accurate than are many human histories which have been preserved in the printed books. The story of the earth has been divided into different periods, each marked by the predominance of certain kinds of living things. The Carboniferous period has been so named because at that time the climate and features of the earth in many places favored the growth of dense and heavy vegetation. This vegetation accumulated through the long years, so that it formed thick deposits which gradually changed to beds of coal. It would be wrong, however, to think that all the beds of coal were formed at about the same time. Ever since there have been forests and marshes upon the earth there have been opportunities for the forming of coal-beds. Materials are accumulating even now which will in time be transformed to beds of coal. We must be equally careful to gain correct ideas of the making of petroleum, for many wrong notions are current. While coal has come from the accumulation of plant remains, petroleum has been derived from sea organisms, chiefly animals. If coal and petroleum are found near each other, the occurrence is accidental and does not mean that the two substances are in any way related. Our earth is very old, and its surface has gone through many transformations; mountains, plains, and portions of the sea floor have changed places with one another. Wherever there have been marshy lowlands, since plants first began to grow luxuriantly upon the earth, it has been possible for beds of coal to be formed. We all know how rankly plants grow where there is plenty of heat and moisture. Many of us have been in swampy forests and have seen the masses of rotting tree trunks, limbs, and leaves. Now, if we should form a picture in our minds of such a swamp slowly sinking until the water of some lake or ocean had flowed over it and killed the plants, and then washed sand and clay upon the buried forest until it was covered deeply in the earth, we should understand how the coal-beds began. Veins of coal that have been opened by the miners frequently show trunks and stumps of trees, as well as impressions of leaves and ferns. Underneath the coal there is usually a bed of clay, while above sand or sandstone is commonly found. The oldest coal has been changed the most. It is hard and rather difficult to ignite, but when once on fire it gives more heat and burns longer than other coals. This coal, known as anthracite, is not found extensively in the United States outside of Pennsylvania. Coal which is younger and has been less changed by the heat and pressure brought to bear upon it when it was buried deep in the earth, is known as bituminous. This is the kind of coal which is found in the Mississippi and Ohio valleys, in the Rocky Mountains, and upon the Pacific slope. A still younger coal, which is soft and has a brownish color, is called lignite, and is found mostly in the South and West. Still another sort of fuel, known as peat, is found in swamps where considerable vegetation is now accumulating, or has accumulated in recent times. Peat is a mass of plant stems, roots, and moss, partly decayed and pressed together. In countries where wood is scarce peat is cut out, dried, and used for fuel. The larger part of the coal in the eastern United States was formed during the Carboniferous period. That part of our country was then low and swampy; but the West, which is now an elevated area of mountains and plateaus, was at that time largely beneath the ocean. Then, as the surface of the earth continued to change, the ocean retreated from the Rocky Mountain region, and extensive marshy lowlands with lakes of fresh or brackish water came into existence. There were such marshes in the areas that are now covered by New Mexico, Colorado, Wyoming, Dakota, and Montana. Westward for some distance the land was higher, but in the states of Washington, Oregon, and California there were other marshy lowlands covered with heavy vegetation. We know from what we have seen of the manner in which wood decays, that in the dry, open air it does not accumulate, but is in great part carried away by the wind. It is only in swamps and shallow bodies of water that the decaying wood can gather in beds. From these facts we have a right to draw conclusions as to the former nature of the surface where there are no coal-beds. There are extensive beds of limestone in the western United States which are of the same age as the coal-beds in the east. As such beds of limestone could have formed only in the ocean, their presence throws a good deal of light upon the geography of those distant times. Upon the Pacific slope the marshes were not so extensive, nor did they last for so long a period, as those in the East. Nature seems to have confined her strongest efforts at coal-making to the country east of the Rocky Mountains. Perhaps she thought that the people of the West would not need coal if she gave them plenty of gold and silver. In the Appalachian mountains Nature folded the strata and left them in such a position that the coal could be mined easily. In the Mississippi Valley the beds were left flat, almost in their original position, so that shafts had to be sunk to reach the coal. Upon the Pacific slope Nature seems to have had a large amount of trouble in arranging things satisfactorily. She has made and remade the mountains so many times, and folded and broken the crust of the earth so severely where the swamps stood, that now large portions of the coal beds which once existed have crumbled and been washed away by the streams. The scanty supply of coal which now remains is in most places hard to find and difficult to mine. [Illustration: FIG. 108.--SEAMS OF COAL ENCLOSED IN SANDSTONE, CALIFORNIA] The best coal mined near the Pacific comes from Vancouver Island. Large beds of a younger and poorer coal are found southeast of Puget Sound. There are other beds in the Coast ranges of western Oregon, and a few small ones in the Coast ranges of California. The great interior region between the Rocky Mountains and the Coast ranges has very little coal. The people of California have to import large quantities of coal. Some is brought by the railroads from the Rocky Mountain region, but the most comes by ships from various parts of the world, from England, Australia, or British Columbia. The ships bring the coal at low rates and take away grain and lumber. Coal is almost the only important mineral which Nature has bestowed sparingly upon the Pacific slope. In California, however, she has made amends by storing up large quantities of petroleum. In Pennsylvania and Ohio there is petroleum as well as coal. Oil has also been discovered in the Rocky Mountain region and in Texas. [Illustration: FIG. 109.--A SPRING OF WATER AND PETROLEUM The black streak is petroleum] Petroleum is found flowing from the rocks in the form of springs, either by itself or associated with gases and strong-smelling mineral water. The oil is usually obtained by boring wells, but in southern California there is one mountain range which furnishes large quantities through tunnels which have been run into its side. Petroleum is commonly found in porous sandstones or shales, from one or two hundred to three thousand feet below the surface. It was not made in these rocks, but has soaked into them just as water soaks into a brick. The rocks which produced the oil or petroleum are dark, strong-smelling shales or limestone. Heat a piece of such rock, and you will drive out a little oil. [Illustration: FIG. 110.--OIL WELLS IN THE CITY OF LOS ANGELES, CALIFORNIA Pool of oil in foreground] Examine a piece of the shale from one of the oil districts of California, and you will discover that it is a very peculiar rock, for it is made up almost wholly of minute organisms which once inhabited the ocean. Among the forms which you will find are the silicious skeletons of diatoms, the calcareous skeletons of foraminifera, scales of fish, and, rarely, the whole skeleton of a fish. Where now there are mountains and valleys dotted with oil derricks, there was once the water of the open ocean. This water was filled, as the water of the ocean is to-day, with an infinite number of living things. As these creatures died, their bodies sank to the bottom, and while the soft parts dissolved, the hard parts or skeletons remained. Through perhaps hundreds of thousands of years, the skeletons continued to accumulate until beds were formed hundreds or even thousands of feet in thickness. The materials of the beds, at first a soft mass like the ooze which the dredger brings up from the bottom of the present ocean, became packed together in a solid mass. Then disturbances affected this old sea bottom. It was raised, and gravel, clay, and sand from some new shore were washed over the bed of animal remains, burying it deeply. Continued movements of the earth finally folded these rocks, which, as they were, squeezed and broken, became warm. The heat and pressure started chemical action in the decayed animal bodies, and particles of organic matter were driven off in the form of oil and gas. These substances were forced here and there through the fissures in the rocks. Part of the products found a way to the surface and formed springs, while other portions collected to form vast reservoirs in such porous rocks as sandstone. The sulphur and mineral springs which occur in oil regions tell us that this work of oil-making is still going on. The oil as it comes from the ground is usually brownish or greenish in color, and much thicker than the refined product which we use in our lamps. Some of the crude petroleum is thick and tar-like in appearance, and when long exposed to the air turns to a solid black mass called "asphaltum." This, when softened by heat and mixed with sand, makes a valuable material for street pavement. THE CLIMATE OF THE PACIFIC SLOPE The western portion of the United States exhibits very interesting climatic features. In California, for example, there may be found every degree of temperature between tropic heat and arctic cold. In the deserts of the southeastern portion of the state the air is extremely dry, while in the northwest it rains nearly every month in the year. Upon the borders of Puget Sound the thermometer seldom falls below the freezing-point, while southern Newfoundland, in the same latitude, is marked by cold and snowy weather for at least six months of every year. Southern California has the same latitude as central Georgia, but its average temperature near the coast is but little higher than that of Puget Sound, while it is warmer in winter and cooler in summer than Georgia. The deserts of southern California and Arizona are so hot that for four months of the year work in the sun is almost impossible; yet the higher portions of the Sierra Nevada mountains, but a short distance away, have an arctic climate. The whole Pacific coast region has, with the exception of the mountains, a much milder climate than one would expect from a mere knowledge of its latitude. It will be instructive to search out the reasons for the remarkable contrasts in climate presented by different portions of the slope. The imaginary lines passing through points of equal temperature upon the earth are called "isotherms." These lines rarely accord in direction with the parallels of latitude, but curve far to the north or south. The irregular course of the isotherms is due to many causes. Among these are the distribution of the land and water, the direction of the prevailing wind, the position of the mountain ranges, and the elevation above sea-level. [Illustration: WEATHER MAPS Fair weather over central portion of Pacific slope. Storm coming in upon coast of Washington Stormy weather over the western half of the United States] In winter the isotherms curve far to the north over the North Pacific and North Atlantic oceans; but over the intervening land they curve as much to the south. In summer the isotherms are almost reversed in position, at least as far as the land is concerned, for they bend to the north in the heart of the continent. There are important reasons for the slight variation of the isothermal lines upon the western borders of North America and Europe, and their great change of position in the interior from winter to summer, but these reasons are not at all difficult to understand. The temperature of large bodies of water changes but little throughout the year, for water warms and cools slowly. The surface of the land, on the contrary, heats rapidly, and then as quickly loses its heat with the changing season. The air over the ocean is cooler in summer and warmer in winter because of the influence of the water, but over the land, in districts far from a large body of water, the changes in temperature between day and night, summer and winter, are very great. It was formerly thought that the warm Japan current, which flows against the western shore of North America, was responsible for the exceptionally mild climate there, and that the Gulf Stream produced a similar climate upon the coast of western Europe. More careful study, however, has shown that not the warm ocean currents, but rather the winds blowing from the water, are the cause of the mild climate in those lands across which they blow. In temperate latitudes there is a slow movement of the air in an easterly direction, and in consequence the climate of the western coast of North America is not marked by such extremes in winter and summer as are the interior and the eastern sections. It is also surprising to find how nearly alike the average winter and summer temperature is at San Francisco. It is also surprising to note that the average temperature of Seattle differs so little from that of San Diego, although these two places are separated by sixteen degrees of latitude. In some places the climatic conditions which we should naturally expect seem to be reversed. Oranges are grown in the Great Valley of California as far north as Red Bluff, and actually ripen a month sooner than they do near Los Angeles, five hundred miles farther south. The early ripening of fruits in the Great Valley may be explained by the presence of the inclosing mountain ranges: the Sierra Nevada mountains upon the northeast shut off the cold winds of winter, while the Coast ranges upon the west break the cool summer winds which come from off the Pacific. Another interesting fact connected with the climate of the West is the influence exerted by the direction of the mountain ranges. As these ranges usually lie across the path of the prevailing winds, their tempering influence is lost much more quickly than it otherwise would be. West of the Coast ranges the summers are cool and the winters are warm. Upon the eastern side of these mountains the winters are somewhat cooler and the summers very much warmer. In the dry, clear air of the desert valleys, far from the ocean, the daily range in temperature is sometimes as great as fifty degrees, while the winters are cool and the summers unbearably hot. We all know how much cooler a hill-top is than a valley upon a summer day. Where the mountains rise abruptly to a great height, as, for example, does the San Bernardino Range of southern California, one can stand among stunted plants of an arctic climate and look down upon orange orchards where frost rarely forms. Mount Tamalpais, a peak of the Coast Range north of San Francisco, has an elevation of nearly three thousand feet. The summer temperature upon this mountain forms an exception to the general rule, for while the lowlands are buried in chilling fog, the air upon the summit is warm and pleasant. [Illustration: FIG. 111.--ORANGE ORCHARDS CLOSE UNDER SNOW-CAPPED PEAKS Highlands, California] The north and south mountain ranges not only make the interior hotter than it would otherwise be, but rob it of much of the moisture which it should receive. The winter storms coming in from the ocean find the cool mountains lying across their path and quickly part with a large proportion of their moisture. Where the coast mountains are low, as is the case with a great part of California and of Oregon, more of the moisture passes on to the next line of mountains, the Sierra Nevada-Cascade Range, the western slope of which is well watered. In the region of the Columbia the Cascade Range is also low, and the storms, which often follow one another in quick succession, sweep across the Columbia plateau and over the Rocky Mountains. Farther south, not only are the storms fewer in number, but the mountains are very much higher, so that the desert basins of the lower Colorado and Death Valley region are extremely dry. One can in imagination stand upon the summit of the Sierra Nevada mountains, and upon the one hand look down upon barren valleys of vast extent, broken by mountains almost as barren, where nothing can be grown except by means of irrigation; and upon the other side, toward the coast, see a country plentifully visited by rain, and either covered with forests or given over to farming and fruit-raising. The Rocky Mountains form the eastern barrier which the storms encounter. Their summits are very high and are covered with deep snow during the winter. East of these mountains lie the Great Plains, where the precipitation is light until we go far enough toward the Mississippi Valley to reach the influence of the moist air currents from the Gulf of Mexico. Many storms originate over the region of the Gulf of California, particularly in the late summer, and supplement to some extent the light winter storms of Arizona and New Mexico. The storms of which we have been speaking are known as cyclones. This term does not refer to the local storms which occur in the Mississippi Valley and are frequently so destructive, but to great disturbances of the air. Sometimes the column of whirling air is more than a thousand miles in diameter. The air in a cyclone is circling and at the same time rising, so that the motion is spiral. If you will study an eddy in a stream of water, you will get an idea of the nature of the motion, except that in the case of the water eddy the movement is downward. The motion of the particles in the dust-whirls which all have seen moving across the fields near noon on warm summer days illustrate the movement of the air in one of these great storms. The direction of the air in a cyclone is opposite to that of the hands of a clock. When the wind comes up from a southerly point, when high, thin clouds, gradually growing thicken, spread over the sky, and the barometer begins to fall, then it is known that a storm is corning. If one will learn to watch the clouds and the winds carefully he may become able to predict a storm with almost as much certainty as if he had a barometer. This instrument registers the pressure of the air, which is always less within the area of a storm, because then the air is rising. So when the barometer falls we may always know that a storm is approaching. The greater number of the storms which occur in the central and northern United States come in from the Pacific Ocean in the latitude of Washington. Continuing east or southeast they reach the Mississippi Valley, and then turn northeastward toward the St. Lawrence Valley. In the summer months there are few storms, and they very rarely reach as far south as California. As winter approaches the storms become more frequent and severe, and move farther and farther south until the whole land as far as Mexico receives a wetting. Upon the Pacific coast there is often very little warning of the coming of a storm, but in the Middle and Eastern States they may frequently be predicted several days in advance. With the passing of one of these storms the temperature falls rapidly, and this lowering of temperature, together with the fierce wind, gives rise upon the Great Plains to "blizzards" or "northers." These storms endanger the lives of both men and animals. At different times in the year, particularly in winter, spring, and early summer, warm, dry winds occur. Those winds which sweep down from the heights of the Rocky Mountains and quickly melt the snows are known as "chinooks." The hot north and east winds of California often do great damage to growing crops. Now let us sum up briefly the factors which have together produced the climatic features of the Pacific slope. (1) Ordinarily the factor of the greatest importance is latitude. We should expect that Seattle would have a much colder climate than San Diego because it receives the sun's rays more slantingly. (2) The influence of latitude is greatly modified by the temperate winds blowing from the Pacific, so that places far separated in latitude differ but little in average temperature, their summers being cooler and their winters warmer than we should expect them to be. (3) The storms pass over the land with the general easterly movement of the air. The largest number pass east across the northern portion of the United States. The farther south we go the fewer are the storms and the less the rainfall. Along the coast of Washington the annual rainfall is nearly one hundred inches. At San Diego it is only about ten inches. (4) The position of the mountain ranges causes the influence of the ocean on the air to be lost within a short distance toward the interior of the continent, so that the extremes of temperature rapidly become greater. The position of the mountains also affects the rainfall of the interior. Since a large proportion of the moisture is condensed upon their ocean slopes, the climate of each succeeding range toward the interior becomes more dry and desert-like. While in some of the lowlands thus cut off from the ocean the climate is extremely arid, yet the country is relieved from utter barrenness through the presence of mountain peaks and ranges, which often condense considerable moisture. [Illustration: FIG. 112.--SCENE IN FORESTS OF WASHINGTON Showing spruce and cedar] (5) The higher a region is above the sea, the colder the climate. The summit of a high mountain and the valley at its base may be in the same latitude, and yet one may possess an arctic climate while the other has a sub-tropical one. The heavy rainfall in western Washington, Oregon, and northern California results in dense forests. To the south, the rainfall upon the lowlands is not sufficient to produce forests, but as it is greater upon the mountains, trees thrive upon their sides. The elevation at which trees will grow becomes higher and higher as we go into the more desert regions, until in northern Arizona it is found to be above six thousand feet. The high plateaus are generally treeless, but are covered with such shrubs as greasewood and sage-brush. We see now that our climate is the product of many factors. It frequently varies greatly in places only a few miles distant from each other. Consequently there may be a great variety of productions and industries in one small area, while in other regions the climate and productions are almost unchanged for hundreds of miles. SOMETHING ABOUT IRRIGATION Travellers from the Eastern States who visit New Mexico for the first time are attracted by many unusual sights. There are the interesting little donkeys, the low adobe houses of the native Mexicans, and the water ditches winding through the gardens and fields, which are divided into squares by low ridges of earth. If the fields are seen in the winter time, when dry and barren, the meaning of their checkered appearance is not at first clear, but in the spring and summer one is not long in finding out all about them. When the time comes to sow the seed, water is turned into these squares from the ditches which traverse the valleys, and one square at a time is filled until the ground in each is thoroughly soaked. Afterward, when the ground has dried enough to be easily worked, the crop is put in. The seeds soon sprout under the influence of the warm sun, and the land becomes green with growing plants. The same method of moistening the ground is used for the orchards and vineyards. What is the use of all this work? Why not wait for the rains to come and wet the earth, as the farmer does in the eastern United States? The Mexicans, who have tilled these valleys for more than two hundred years, ought certainly to have learned in all that time how to get the best returns. You may be sure that they would not water the ground in this way if it were not necessary. The fact is that over a large portion of the western half of the United States it does not rain enough to enable the farmer to grow his crops. The climate is generally very different from that of the Middle and Eastern States. When the Mexicans moved northward into the valley of the Rio Grande River, into Arizona and California, they found a climate similar in many respects to that at home, and soon learned that it was necessary to water the land artificially in order to make it productive. Though in many places sufficient rain fell, yet the heaviest rainfall came in the late summer or winter, when the plants needed it less, while the spring and summer were long and dry. The Mexicans were not the first to practise watering the land, if we may judge from the ruins of ancient ditches constructed by the primitive Indian inhabitants. It is evident that they too made use of water in this manner for the growing of their corn and squashes. This turning of water upon the land to make it productive is termed "irrigation." The work is performed in different ways, as we shall see later. Irrigation is now carried on through all portions of the United States where the rainfall is light and streams of water are available. To one who has lived in a country where there is plenty of rain, it seems to involve a great deal of work to prepare the land and to conduct water to it. One may feel pity for the farmer who has to support himself in this manner in so barren a country. I am sure, however, that if any such person will stop to think, he will remember times when in his own fertile home the expected rain did not come, and the vegetation wilted and dried up. He may have become discouraged because of a number of "dry years," but probably never thought that he had the means at hand to make up, at least in part, for the shortcomings of Nature, in sending too much rain one year, and another year too little. [Illustration: FIG. 113.--WATER-WHEEL FOR LIFTING WATER FOR IRRIGATION, VIRGIN RIVER, SOUTHERN UTAH] It would doubtless have paid such a farmer many fold to have been prepared at the coming of a dry year to turn the water from a neighboring stream over his lands. This process would have involved a good deal of labor; but how the plants would have rejoiced, and how abundantly they would have repaid him for the extra trouble! The showers come without regard to the time when growing things need them most, but with irrigation the crops are independent of the weather. The farmer may be sure that, if he prepares the ground properly and sows the seed, the returns will be all that he can wish. In many localities several crops may be raised in a year by this method where otherwise only one would grow. Now let us see how the water is taken from the streams and what are the different methods employed to distribute it over the land. Almost every valley is traversed by a stream, great or small. It may be a river, with a large volume of water, or a creek which completely dries up during the long, rainless summers of the West. [Illustration: FIG. 114.--GARDEN IRRIGATION, LAS CRUCES, NEW MEXICO] In rare cases the stream may flow upon a built-up channel which is as high as the valley, but usually it is sunken below the level of the floor of the valley, and enclosed by banks of greater or less height. How is the water to be sent over the land? Where the current is swift you may sometimes see a slowly turning water-wheel, having at the ends of the spokes little cups, which dip up the water as the wheel revolves and pour it into a flume that runs back over the land. At some places engines are used to pump the water from the stream and lift it to the desired height. [Illustration: FIG. 115.--IRRIGATING AN ALFALFA FIELD, ARIZONA] Generally, however, another method is employed: the water is taken out of the stream in an artificial channel dug in the earth. But in order to get the water at a sufficient height to make it flow over the fields, it is necessary to start a ditch or canal at a favorable point some distance up the stream, perhaps miles from the garden. The ditch is made with a slope just sufficient for the water to flow. The slope must be less than that of the river from which the water is taken, so as to carry the stream, at last, high enough to cover the lands to be irrigated. Visit almost any valley in the West where agriculture or fruit-growing is being carried on, and you will at once notice the lines of the ditches, apparently level, as they wind around the hillsides. At convenient distances there are gates to let out the water for the orchards and fields. The ground may be moistened in different ways. The first method is that employed by the Mexicans, who, if we except the Cliff Dwellers, were the first to introduce irrigation into our country. This consists in dividing the land into squares by embankments and allowing the water to flood each in succession. The method is known as irrigation by checks, and can be used conveniently only upon nearly level land. In many orchards a series of shallow furrows is ploughed between the rows of trees, and the water is allowed to flow down these until the soil is thoroughly soaked. In alfalfa fields the water is often turned upon the upper end and permitted to work its way across until it reaches the lower edge, soaking the ground as it goes. The slopes must in every case be so gentle that the current will not be strong enough to carry away the soil. Once in every two to four weeks throughout the spring and summer, the exact period depending upon the rapidity with which the ground dries, the wetting is repeated. If the soil is light the water must be turned on more often and a larger supply is required. It frequently happens that the stream from which the water is taken so nearly dries up in the summer, when the water is most needed, that the cultivated lands suffer severely. During the winter little if any irrigation is necessary, but at that time the streams are so full that they frequently run over their banks and do great damage. How to preserve the water thus going to waste and have it at hand for summer use has been an important problem in regions where every particle of water is valuable. Study of the question has led to the examination of the streams with reference to the building of reservoirs to hold back the flood waters. A reservoir may be formed of a natural lake in the mountains in which the stream rises, by placing a dam across its outlet and so making it hold more water. If this cannot be done, a narrow place in the cañon of the stream is selected, above which there is a broad valley. At such a place the dam which is built across the cañon is held firmly in place by the walls of rock upon each side, and an artificial lake or reservoir is made. Ditches lead away from this reservoir, and by means of gates the water is supplied when and where it is needed. [Illustration: FIG. 116.--SWEETWATER RESERVOIR, NEAR SAN DIEGO, CALIFORNIA] The streams which furnish the water for irrigation in the arid region rise in mountains with steep rocky slopes, and until the water issues from these mountains it is confined to cañons with bottoms of solid rock, so that no water is lost except by evaporation. After the streams emerge from the cañons upon the long, gentle slopes of gravel and soil which lie all about the bases of the mountains, they begin immediately to sink into the porous material. They frequently disappear entirely before they have flowed many miles. Some of this water can be brought to the surface again by digging wells and constructing pumping plants, but the greater part is lost to the thirsty land. To prevent the water from sinking into the gravel, ditches lined with cement are often made to carry it from the cañons to the points where it is needed. Sometimes iron pipes or wooden flumes are used in place of the ditches. What a transformation irrigation makes in the dry and desert-like valleys of the West! Land which under Nature's treatment supports only a scanty growth of sagebrush or greasewood, and over which a few half-starved cattle have roamed, becomes, when irrigated, covered with green fields and neat homes, while sleek, well-fed herds graze upon the rich alfalfa. Ten acres of irrigated land will in many places support a family, where without irrigation a square mile would not have sufficed. One might suppose that the soil of these naturally barren valleys was poor, but such is not the case. The ground did not lack plant food, but merely the water to make this food available. With plenty of water the most luxuriant vegetation is produced. The soil is, indeed, frequently richer than in well-watered regions, for a lavish supply of water carries away a portion of the plant food. In some places, where the land is almost level and the soil is filled with large quantities of soluble materials, such as soda and salt, keeping the ground moist through irrigation brings these substances to the surface in such quantities as to injure and sometimes kill the vegetation. In order that such lands may be successfully cultivated, the salts have to be either neutralized or washed away. [Illustration: FIG. 117.--IRRIGATING DITCH, NEAR PHOENIX, ARIZONA] Many of the rivers of the West carry large quantities of silt in suspension, which fills the ditches and causes a great deal of trouble; but when the silt is deposited over the surface it adds continually to the richness of the land. The full development of irrigation will mean a great increase in the population and wealth of all the Western States. THE LOCATION OF THE CITIES OF THE PACIFIC SLOPE This old earth has to be consulted upon every occasion. It is a silent partner in all our undertakings. We sometimes think that we come and go as we please, but a little thought convinces us that we are not really so free. The traveller must take account of the slopes of the land. It is much easier for him to follow a valley and cross a mountain range through a low spot, although his course be very crooked, than it is to make a "bee line" for his destination. The farmer, in choosing his home and the kind of produce which he will raise, has to consult the soil and climate. He cannot expect to grow grain where the soil is poor and dry, or grow apples where the late spring frosts kill the buds. The miner knows that he cannot expect to find gold veins in the valleys, where the rocks are deeply covered by the soil, and so he turns his steps toward the mountains, where Nature has made his work easy by lifting up the rocks and exposing them to his view. Routes of commerce and trade are governed by geographic, and to a certain extent by climatic, conditions. Shallow streams with rapids and waterfalls obstruct navigation. The absence of harbors along a given coast makes it difficult for ships to take and discharge cargoes. Railroads cannot be constructed unless long and expensive surveys have first been made to determine the route which Nature has made the easiest between two given points. The character of the climate and geographic features of a given country determine whether it shall become noted for agricultural productions, mining industries, manufactures, or commerce. The locations of the cities and towns and the roads connecting them depend upon geographic conditions. There is not an occupation of any importance in which people engage at any particular place that is not dependent in large degree for its success upon the conditions which Nature has imposed upon that place. A city will not grow up at a given point unless the geographic conditions are favorable. There must be some natural reason to induce people to gather in large numbers in one place. At one spot there are facilities for manufacturing, such as water-power and coal, and easy means of communication with other parts of the world. At another, the only reason for the growth of a city is the existence of rich mines. A third place may be conveniently located in the midst of a rich agricultural region, where it is easy to bring in supplies and ship out the products of the soil. A study of the founding and growth of some of the cities of the West, and particularly of the Pacific slope, will bring out many interesting facts. San Francisco is the metropolis of the Pacific; its population will soon reach half a million. If we look back seventy-five years we find San Francisco an unimportant Mexican military post and the seat of one of the smaller missions. Monterey, the capital of the province of California and one of the two leading towns (Los Angeles being the other), apparently had all the advantages in the race for supremacy. In date of discovery (1603) Monterey Bay has the advantage of more than one hundred and fifty years over San Francisco Bay. It is difficult to understand why the different navigators who sailed north along the coast failed to discover California's most magnificent bay. Sir Francis Drake went by it, evidently not seeing the narrow opening between the headlands now known as the Golden Gate. Vizcaino, after discovering Monterey Bay, also passed by and anchored where Drake had stopped, in a little bay now called Drake's Bay, a few miles north of San Francisco Bay. After the founding of San Diego, in 1769, a party started overland for Monterey, but by reason of the peculiar position of the bay they passed it unknowingly, and by accident came upon the body of water which has since been of so great importance to the commercial life of California. Monterey Bay in time lost its importance, partly because it was not thoroughly protected from the storms, and partly from the lack of easy communication with the rest of the state. Immediately after the acquisition of California and the discovery of gold, the advantages of San Francisco Bay began to be appreciated, and the little Mexican town grew rapidly. The narrow entrance to the bay, which had for so long a time delayed its discovery, completely protected it from the storms, while its long arms opened across the coast mountains directly into the important valleys of the interior. Ocean vessels could go up the bay and through the Strait of Carquinez, while river boats could be used for many miles farther. After the discovery of gold, ships from all parts of the world found ample room and shelter in San Francisco Bay; and the incoming miners, going by the water routes to Marysville, Sacramento, and Stockton, easily reached the gold-bearing gravels of the Sierra Nevada streams. With the exception of southern California and a portion of the northern coast, almost all the agricultural and mineral resources of California are directly tributary to San Francisco. This place is naturally the centre of home trade, of foreign commerce, and of population. [Illustration: FIG. 118.--SAN FRANCISCO BAY Formed by the sinking of the land and flooding of a river valley] Nature failed to supply San Francisco with one essential advantage, namely, cheap power for manufacturing. There is no water-power near and but little coal in the state. Since the coal has to be shipped in from distant points, its high price has impeded manufacturing. But now it appears that San Francisco is not so badly off after all, for important deposits of petroleum have been discovered in the central and southern portions of California; and besides, processes have been invented for transforming the unlimited water-power of the mountain streams into electric energy, and transmitting this power to all the cities about the bay. The early Spaniards founded the pueblo of Los Angeles in its present location, because at this point the Los Angeles River carried an abundance of pure water which could be led out in ditches to irrigate the fertile bottom lands in the vicinity. Partly because it became a railroad centre, and partly because it is surrounded by rich valleys, Los Angeles has grown with great rapidity and now stands next to San Francisco in size among California cities. San Diego, which has a harbor next in importance to that of San Francisco, has grown more slowly, because of the greater difficulty in developing water systems for irrigation, and because access is not so easy on account of the enclosing mountains. However, it must in time become the second commercial city of the state. Mountain barriers make travel from one portion of California to another somewhat difficult. Mountains separate San Francisco and the Great Valley of California from all other portions of the continent. Nature seems to have planned here a little empire all by itself. But engineering skill in the construction of railroads has overcome the barrier upon the north which separates California from Oregon. The Sierra Nevada range upon the east has been crossed at Donner Pass, and upon the south an outlet has been found through the Tehachapi Pass. In the state of Oregon, the city of Portland ranks first in importance. Why did not Astoria or Fort Vancouver develop into the metropolis of the Columbia basin? Astoria, which was founded in the early part of the last century, has a spacious and well-protected harbor, but it has no large tributary agricultural valleys. Moreover, the greater number of deep-water ships pass it by, and go as far up the Columbia as possible to take on their loads of grain. Fort Vancouver, on the site of the old Hudson Bay trading post, is practically at the head of deep-water navigation upon the Columbia, but there seems to be no particular reason why trade should centre here, and this town also has been left behind in the march of progress. The earliest settlements in western Oregon were made upon the Willamette River, which drains a large and extremely fertile valley. Near the point at which this river joins the Columbia, the city of Portland sprang up. This town occupies an ideal position. It is accessible for deep sea vessels, and has communication by river boats with the Willamette Valley and the upper Columbia River. In the eighteenth century, when sailors were looking for a passage across the northern portion of the continent, an opening was found extending into the land between Vancouver Island and Cape Flattery. It was at first thought that this was the desired waterway, but various navigators, among them Vancouver, explored the body of water into which the Strait of Fuca opened, only to find that every branch and inlet terminated in the land. Puget Sound is nearly enclosed by water and is so large as really to form an inland sea. Its long arms reach out in three directions among the most heavily timbered valleys and mountain slopes of the United States. The cities of Puget Sound had a later start than most of the other cities of the Pacific coast, for this portion of the old Oregon territory was for a long time claimed by the English, and during that period was peopled only by Indians and trappers. In 1846 the present boundary was established, and Puget Sound passed into the possession of the United States. Because of the dense forests, agriculture could not play an important part in the development of the sound region for some time. Lumbering was naturally the leading occupation. This industry could be carried on all the more advantageously because of the innumerable inlets penetrating the land. The advantages of Puget Sound for foreign commerce began to be evident, but the Cascade Range stood in the way of railroads from the eastward. Although it was a comparatively easy task to build a railroad north from Portland, yet the sound region did not begin to grow rapidly until, after careful surveys, two railroads finally found passes through the Cascade Range so as to reach tide-water. As in other places, when the necessity for overcoming them arose, the obstacles which Nature had interposed were found not to be so troublesome as was at first supposed. Now the once formidable range has been tunnelled and will no longer form a serious barrier between the interior portion of Washington and the coast. Tacoma, Seattle, and Everett have grown up on the sound as important commercial and manufacturing cities, and will, on account of their favorable situation, receive their share of the commerce of the Pacific. The cities of the sound are particularly well situated for intercourse and commerce with Alaska and northeastern Asia. These cities are also well situated for manufacturing, because coal and wood are plentiful and consequently cheap, but they have not in their immediate vicinity so extensive agricultural valleys as the Willamette and the Great Valley of California. The lumberman must be supplanted by the farmer and fruit-grower before the slopes about Puget Sound can be fully developed. The natural outlet for the great wheat-fields of central Washington is by way of the Columbia River to the ocean, but the tunnelling of the Cascades partly diverts their products to the sound region. [Illustration: FIG. 119.--FALLS OF SPOKANE RIVER Location of the city of Spokane] The city of Spokane, in eastern Washington, clearly illustrates the control which physical features exert upon the settlements and industries of men. The Spokane River, soon after issuing from Coeur d'Alene Lake, flows out over the volcanic plains of Washington. In the course of a few miles it descends into a shallow cañon by a series of cascades and waterfalls. The water-power furnished by these falls has determined the position and growth of Spokane. The falls brought sawmills and manufacturing plants, and these in turn brought people and railroads. The city has become a great commercial centre for all the region round about. The extensive and rich mineral district upon the north, extending even into British Columbia, finds its most convenient source of supplies at Spokane. East of the city is the Coeur d'Alene mining region, while south and west are large areas devoted to the cultivation of fruit and grain. [Illustration: FIG. 120.--VIRGINIA CITY, NEVADA Supported entirely by mining] The city of Great Falls, Montana, in the Missouri River basin, is destined to become a great industrial centre, because of the presence of unlimited water-power afforded by the Great Falls of the Missouri River. No other reason would lead to the growth of a settlement at this particular spot, for boundless plains extend about it in every direction. [Illustration: FIG. 121.--BUTTE, MONTANA A city of smelters] The mining cities of the West, such as Butte, Virginia City, and Leadville, illustrate the growth of important centres of population in the vicinity of large deposits of minerals. In the case of these cities, as well as many others, there are no agricultural resources in the surrounding country to support the people gathered together here. Nearly all their food has to be shipped hundreds of miles. Cities supported by mining are less likely to be permanent than those supported by an agricultural community, by commerce, or by manufacturing. THE FOREST BELT OF THE SIERRA NEVADA MOUNTAINS No other coniferous forests in the world can compare with those covering the western slope of the Sierra Nevada and Cascade ranges. They are remarkable both for the number of species and for the size of the trees. The moderate temperature and the moist winds from the Pacific seem to offer the conditions which are best suited to the growth of cone-bearing trees. As we go northward along the coast, or ascend the mountain slopes, we find the climate growing cooler and cooler. With this changing climate the species of conifers change, for each has become accustomed to certain conditions of temperature and moisture, which it must have in order to thrive. The Sierra Nevada is the most continuous lofty range of mountains in North America. From the great valley at its western base to the crest of the range the distance is about sixty miles. Because of the great height of the mountains, there is found within these few miles every variety of climate between the sub-tropical atmosphere of the valley, where oranges ripen to perfection, and the arctic cold of the summits, where little or no vegetation can live. Thus, by climbing a single mountain range, we may experience all kinds of climate, and have an opportunity to observe the different forms of plant life such as we could not otherwise obtain without a journey of several thousand miles. [Illustration: FIG. 122.--FOREST BELT OF THE FOOT-HILLS, SIERRA NEVADA MOUNTAINS] Passing through the groves of valley oak, and beyond the orange orchards at the foot of the mountains, we reach the foot-hills and begin to ascend. Several species of oak are found upon the hillsides and in the valleys, while mingled with them in many places appear such shrubs as the California lilac, chamiso, and manzanita. Where the soil is too poor or the slopes too steep for the trees, these shrubs, commonly called "chaparral," are massed together in almost impenetrable thickets. The first of the coniferous trees which we meet is an odd-looking one known as the digger pine. Instead of having a single straight trunk it divides a short distance above the ground into many branches. The large cones are armed with long hooked spines, so that they must be handled rather carefully, but when opened they are found to be filled with nutritious nuts. These nuts were an important source of food for the Indians who once inhabited the foot-hills. Now the Indians are gone, but the nuts are not wasted, if one may judge by the fragments of the cones with which the squirrels strew the ground. [Illustration: FIG. 123.--THE DIGGER PINE] The road climbs the foot-hills by many turns and windings through cañons and up and down ridges. At an elevation of about two thousand feet specimens of the yellow pine appear. The trees increase in size and grow more closely together as we ascend. We soon find ourselves in the edge of the forest belt which extends unbroken northward to the arctic zone, and upward to the line of almost perpetual snow. The yellow pine, so named from the color of the bark, sometimes attains a diameter of six feet, but does not form so dense forests as we shall find higher on the mountains. The rays of the warm sun, reaching down between the trees to the carpet of needles and "bear clover," draw out their spicy fragrance. The yellow pine, although it does not afford as good a quality of lumber as some of the other pines, is one of our most important trees because of its wide distribution through nearly all mountains of the West. It has a much wider range in elevation than most trees, one variety reaching upward nearly to the timber line. [Illustration: FIG. 124.--A YELLOW PINE FOREST] After getting well into the yellow pine forest, we soon come upon other trees that contend with the pines for a footing upon the slopes and for a bit of the sunshine. Among these the black oaks deserve special mention, for in places they form dense groves upon the ridges. The cedars, with their rich brown bark and flat, drooping branches, are easily recognized. As these trees grow old they become gnarled and knotty and very picturesque. [Illustration: FIG. 125.--SUGAR PINE] We first meet that "king of pines," the sugar pine, upon the more shaded mountain slopes. Although higher up, on barren, rocky ridges, this tree grows to noble size, yet it cannot withstand heat and dryness. Our attention may be first called to the sugar pine by the slender cones, ten to fifteen inches in length, which are scattered over the ground. Then, as we look up to see whence the cones come, our eyes light upon the smooth trunks, often over six feet in diameter and reaching up one hundred and fifty feet before the branches appear. From the ends of the long, drooping branches hang slender green cones. The name of this pine is derived from the fact that a white sugar gathers in little bunches at the spots where the trunk has been injured. This sugar is pleasant to the taste and somewhat medicinal. [Illustration: FIG. 126.--ZONE OF THE FIR FOREST, SIERRA NEVADA MOUNTAINS] The wood of the sugar pine, which is white and fine-grained, is of greater value commercially than that of any of the other pines. This fact leads the shake-maker and lumberman to seek out the noble tree and mark it for destruction. The sugar pine, when once destroyed in a given locality, rarely replaces itself, as it is crowded out by the more vigorous conifers. Scattered through the forests of yellow pine, cedar, and sugar pine is the Douglas spruce, commonly known in the market as the Oregon pine. This is the most important forest tree in Oregon and Washington. It often grows to a height of three hundred feet, and forms dense forests for hundreds of miles along the base and western slope of the Cascade Range. In Washington it is found growing down to the sea-level, but in the Sierra Nevada the requisite moisture for its growth is not found much below an elevation of four thousand feet. As we go upward the pines become fewer and the firs and "Big Trees" take their places. The Big Trees are found in scattered groves, at an elevation of five thousand to eight thousand feet, for a distance of two hundred and fifty miles along the slopes of the Sierra Nevada mountains. The Sequoia, as the genus is called, which also includes the redwood of the Coast ranges, is in many respects the most remarkable of all our coniferous trees. [Illustration: FIG. 127.--THE BIG TREE FOREST IN THE SIERRA NEVADA MOUNTAINS] After travelling through forests made up of other trees of great size it is difficult at first to appreciate the magnitude of the Big Trees. Rising from a swelling base, which is sometimes thirty feet in diameter, the symmetrical trunk reaches up and up, finally terminating in a top three hundred to three hundred and fifty feet above the ground. Their size, their reddish-brown bark, and their small cones, clearly distinguish these trees. Great holes have been burned in many of them, and in the hollows thus formed men have made for themselves comfortable living rooms. In one of the southern groves a fallen hollow tree has been used as a cabin. The Big Trees and redwoods are the last surviving species of a genus which was once widely distributed over the earth. The ancestry of the Sequoia can be traced farther back than that of any of the other living conifers. Impressions of cones and small stems with needles attached belonging to the Sequoia have been found in the oldest rocks of the Coast ranges of California. These cones and stems were washed into some muddy estuary and there buried, millions of years ago. The mud inclosing them was compressed and hardened, and finally changed to slate. This was at last exposed upon the surface through the uplifting of a mountain range and the work of erosion. Some of the groves of the Big Trees have been included in government parks and reservations, but others are being cut as rapidly as possible by the lumbermen. The redwood of the Coast ranges is not easily killed, for it sprouts from the stump, and will in the course of time form forests again; but the Big Trees rarely replace themselves when a grove has been cut down. These trees are so few in number and of such remarkable interest that they should be spared the fate of the common forest tree. It would make you feel sad to visit one of the groves and see, as I did, a fallen giant, fully thirty feet in diameter, lying split open upon the ground. This tree was so large that, in order that it might be handled at all, powder had to be used to blast it in pieces. The tree was knotty, and according to the lumbermen, of little value, and might as well have been left. What excuse is there for the wanton destruction of a noble tree like this one? It must have stood from five thousand to six thousand years. It was a mighty tree at the beginning of the Christian era, and was growing, a strong tree, when our ancestors were the rudest savages in the wilds of Europe. But we must not remain among the Big Trees, for the forests extend much farther up the mountains. The most important tree of the upper forest belt is the fir, which is found growing from five thousand to nearly nine thousand feet above sea-level. It is one of the most graceful of the conifers. Sometimes these trees reach a height of two hundred and fifty feet and form dense forests with little undergrowth. The branches make the soft, fragrant beds which so rest and delight the tired mountain climber. Here and there about the springs and at the heads of the streamlets the firs appear to stand back, making room for green meadows brightened with a profusion of flowers. [Illustration: FIG. 128.--ALPINE HEMLOCKS] The tamarack, or lodge-pole pine, is sometimes found at about the same elevation as the firs, but seems to prefer the moist lands about the meadows and the bottoms of the narrow valleys. This tree is widely distributed at high altitudes all over our Western mountains. Continuing our climb toward the alpine regions, we reach an elevation where the trees begin to show the effects of the winter storms. The fact that life is not so easy as it is farther down the slopes is apparent from the gnarled and stunted trunks. Here are the alpine hemlocks, dwarf pines, and junipers. The juniper somewhat resembles the cedar, but has a short, thick trunk. Near the timber line this tree grows but a few feet high and becomes exceedingly gnarled. It seems to like the most exposed and rocky places, but in truth, like many another form of plant life, it has become accustomed to such locations because it cannot successfully compete with other trees in happier ones. Most weird and picturesque of all are the dwarf white pines, growing upon the extensive mountain shoulders and ridges at a height of ten thousand to eleven thousand five hundred feet above the sea. Since an arctic climate surrounds them for nine months in the year, their growth is very slow. Their short, gnarled trunks and branches are twisted into all sorts of fantastic shapes. When, after struggling with the cold and the storms, the trees at last die, they do not quickly decay and fall, but continue to stand for many years. These trees become smaller and smaller in size until at the extreme timber line they are almost prostrate upon the ground. In many cases they rise only three or four feet, and have the appearance of shrubs rather than trees. Still above them, however, there are rocky slopes and snow-banks reaching to an elevation of over fourteen thousand feet. If we examine these upper slopes carefully we shall find that they are not utterly devoid of life, but that certain plants have been able to obtain a foothold upon them. In sheltered nooks there are little shrubs and lichens. In some places among the rocks, beneath overhanging snow-banks, beautiful flowers spring up at the coming of the late summer, blossom, mature their seeds, and die with the return of the winter cold. [Illustration: FIG. 129.--THE UPPER LIMIT OF THE TIMBER Sierra Nevada Mountains] The magnificent forests through which we have passed in our long climb, if destroyed by the lumberman, cannot be replaced for hundreds of years. They contribute much to the glory of the mountains. They hold back the water so that it does not run off rapidly, and thus aid in giving rise to innumerable clear, cold springs. The springs help feed the streams during the long, dry summers, when the water is so sorely needed in the hot valleys below. THE NATIONAL PARKS AND FOREST RESERVES The people who first pushed into the unknown country west of the Mississippi, in the earlier half of the last century, were chiefly hunters and trappers. They did not intend to make permanent homes in the wilds, but rather to stay only so long as they could secure an abundance of fur-bearing animals. Then came the discovery of the precious metals, and thousands of gold-seekers crossed the plains, and spread out over the mountains of the Cordilleran region. They, too, expected to get rich by making use of the resources of the country, and return to their homes in the East. At the present time the destruction of our forests and serious injury to the water supply has been threatened through the organization of large lumber companies. Those interested in lumbering usually live far removed from the scenes of their operations, and consequently care little about the condition in which the deforested lands are left. The farmers were the first permanent occupants of the West. Unlike the wandering trappers and miners, they established homes and made the land richer instead of poorer. As long as the population was scanty there was not much danger of exterminating the wild animals, and the demands for timber were small. Our forefathers who settled the Eastern states had to contend with the forests. Nearly every acre of ground had to be laboriously cleared before anything could be planted. It was only natural that they should come to regard the forests as a hindrance rather than a blessing. As the settlers spread westward to the prairies and plains they came upon a region almost destitute of forests; but still farther, in the mountains of the continental divide and the Pacific slope, they again found extensive forests. To them it seemed impossible that these forests could ever be exhausted, and therefore little care was taken for their preservation. As the population increased, more and more lumber was needed for building purposes. Before the sawmill came split lumber was used, and the shake-maker did not hesitate to cut down the largest and most valuable pines on the mere possibility that fifteen or twenty feet of the butt would split well enough to make shakes. It made no difference to him that the whole trunk rotted upon the ground. When the sawmills were built and there came a demand from abroad for lumber, the forests were attacked upon a much larger scale. The need of the moment was all that concerned the lumbermen, and they took no care for the preservation of the young trees, which in time would have renewed the supply. The litter of the trunks and branches which they left upon the ground furnished fuel for the fires which frequently swept over these areas and killed the remaining growth. As a result of these fires, the few animals that have escaped the hunters have been killed or driven from their homes, and the forest cover, which would retain much of the moisture and preserve it for the supply of the streams in summer, has been destroyed. The removal of the forest cover leads also to the washing away of the soil, the shoaling of the streams, floods in spring, and low water in summer. In fact, all the people and industries of the region are affected by its loss. It may take hundreds of years for the country to recover; indeed, if the rainfall is light, the forests may never grow again, without artificial aid. [Illustration: FIG. 130.--A BURNED FOREST, CASCADE RANGE, OREGON] The careless stockman, seeking to enlarge his pastures by burning the underbrush, sets fires which often destroy hundreds of square miles of forest. The summer camper and the prospector also frequently go on their way without extinguishing the camp fire, though a great forest fire may be the result. Ours is a fertile and productive earth, capable of supporting a multitude of living things. For ages the lower animals, as well as savage man, lived under the protection of Nature, making the best use of her products of which they were capable; but they never brought about the unnecessary, and often wanton, destruction of which we are guilty,--we, who call ourselves civilized. In killing the wild animals we cannot make the plea of necessity, as can savages who have no other means of support. Likewise, there is no necessity for killing the beautiful singing birds, merely for their plumage. [Illustration: FIG. 131.--EROSION UPON AN UNPROTECTED SLOPE] The forests are cut away without any thought of the retribution which Nature is sure to bring upon us. They are of vast importance to the well-being of the country and are the natural possession of all its people. We ought not to permit them to be destroyed indiscriminately for the benefit of a few. We need lumber for many purposes; but a careful treatment of the forests with an eye to their continuance, the plan of cutting large trees, and preserving the small ones, is a very different thing from our present wasteful methods. Every summer the air is filled with the smoke of burning forests, and the lumbermen are at work harder than ever felling virgin forests upon more and more remote mountain slopes. Books of travel written fifty years ago tell of animal life in such abundance in many portions of the West that we can hardly believe their stories. A description of California written in 1848 mentions elk, antelope, and deer as abundant in the Great Valley. How many of us living at the present time have ever seen one of these animals in its native haunts? There is hope now that this wasteful use of Nature's gifts will soon be stopped. Large areas of the mountainous portions of the public domain are being set aside as parks and forest reserves. The parks contain some of the finest scenery and most wonderful natural curiosities to be found upon the face of the whole earth. This wild scenery, together with the forests and plants of every kind, as well as the animals and birds that inhabit these areas, are to remain just as they were when the first white man looked upon them. The parks form asylums for the wild creatures which have been hard pressed for so many years. In the Yellowstone National Park, where they have been protected the longest, the animals have almost lost their fear of man and act as if they knew that they are safe within its limits. In the Yellowstone you may see great herds of elk feeding in the rich meadows; deer stand by the roadside and watch you pass, while the bears have become so tame about the hotels that they make themselves a nuisance. Sixteen bears at a time have been seen feeding at the garbage pile near the Grand Cañon hotel. The forest reserves differ from the parks in that they are established for utility rather than for pleasure. The forests now existing are to be cared for by the government and to be wisely used when lumber is needed. Fires are to be avoided so far as possible, and burned areas are to be replanted with trees. Another object to be accomplished is the retention of the forests about the heads of the streams so as to preserve the summer water supply. The water runs off more slowly from a slope covered with vegetation than from a barren one, and therefore has more time to soak into the ground. This is a very important matter in all mountainous districts, particularly where the rainfall is light. The Yellowstone National Park is situated upon the continental divide in northwestern Wyoming. It is largely a plateau, with an elevation of seven thousand to eight thousand feet above the level of the sea. The surface of the plateau is covered with forests, meadows, and lakes; but the region is particularly remarkable for the geysers and hot springs, and the Grand Cañon and falls of the Yellowstone River. Springs dot the surface of many parts of the park. The hot water is continually bringing mineral substances, the chief of which is silica, from the depths of the earth and depositing them about the orifices of the springs. In this manner wonderful basins, terraces, and cones have been built up, while the rocks have been either reddened or bleached out and softened into a form of clay. The park region must have been for a long period the seat of volcanic action, for nearly all the rocks are cooled lavas. While the heat has disappeared from the surface, it must still be very great below, if we may judge by the quantities of hot water continually issuing from the springs. In many a subterranean cavern steam accumulates until its pressure becomes too great for the column of water occupying the channel that leads to the surface; then the water is suddenly and forcibly expelled, giving rise to a geyser eruption. When the pressure of the steam has become exhausted, the water sinks back into the earth, leaving the basin of the geyser nearly or quite empty until the steam has again collected. Each geyser has its own period of eruption and is generally very regular. One little geyser, known as the Economic, because it throws out but little water, spouts regularly about every five minutes. Other geysers are active at intervals of several hours, while some take several years to get ready for a new eruption and then spout whole rivers of boiling water. In the Upper Geyser Basin the effect is very impressive, particularly upon a cool morning. The clouds of steam and the throbbing or roaring geysers lend to the region a weird and unearthly aspect. The Yellowstone Lake is a large body of water situated almost upon the continental divide. Before the cañon, or Great Falls, or even the Yellowstone River itself existed, the lake stood about one hundred and fifty feet higher than at present, and its water emptied into the Pacific Ocean instead of the Gulf of Mexico. The drainage was changed by the work of a small stream having its source in the volcanic plateau north of the lake. It deepened its channel and extended its head waters back until they tapped the lake at a point where the rim of the basin was lowest, and so drew away its waters in the opposite direction. The Yellowstone River, with its deep, wondrously colored cañon and grand waterfalls, is the result of this change. [Illustration: FIG. 132.--ECONOMIC GEYSER, YELLOWSTONE PARK] To the south of Yellowstone Park, but included in one of the forest reserves, are Jackson Lake and the Teton range. The Three Tetons, one of which reaches a height of over thirteen thousand feet, were evidently noted landmarks for the hunters and trappers in the early days, for you will find them mentioned in many of the narratives of those times. The precipitous range, with its crown of jagged peaks and the beautiful lake nestling at its base, presents a picture never to be forgotten. Very different from the region which we have been studying is that embracing the Crater Lake, National Park, which is situated upon the summit of the Cascade Range in southern Oregon. Here occurred, not many thousand years ago, one of the strangest catastrophes which, so far as we know, has ever overtaken any portion of our earth. Towering over the present basin of Crater Lake was a great volcano, reaching, probably, nearly three miles toward the sky. During the glacial period it stood there, its slopes white with snow, apparently as strong and firm as Shasta or Hood or Ranier. But for some reason the volcanic forces within this mountain, which has been called Mazama, awoke to renewed action. The interior of the mountain was melted, and the whole mass, unable to stand longer, fell in and was engulfed in the fiery, seething lava. This lava, instead of welling up and filling the crater and perhaps flowing out, was drawn down through the throat of the volcano into the earth, and left an enormous pit or crater where once the mountain stood. After the floor of the crater cooled and hardened, small eruptions occurred within it and a new volcano grew up, but, though nearly three thousand feet high, it does not reach to the top of the encircling walls of the old crater, which are, on an average, nearly four thousand feet high. Then the rains and melting snows formed a body of water in the crater, and the wonderful lake came into existence. No such sight is to be found elsewhere upon the earth. Within a circling rim of cliffs, from eight hundred to two thousand feet high and nearly vertical, lies the lake, rivalling the sky in the depth of its blue coloring. The height of its encircling cliffs and its five-mile expanse of blue water help to make the lake a spectacle grand beyond description. At the present time the volcanic fires appear to be entirely extinct. [Illustration: FIG. 133.--CRATER LAKE From the top of the cliffs two thousand feet above. Upon the right is Wizard Island, a volcanic cone] Forests of fir and tamarack have spread over the once barren slopes of lava and pumice which extend back from the cliffs. In the hollows, after the lingering winter snows have melted, there are grassy meadows dotted with flowers. It is many miles from the lake to any human habitation, and all the region about remains just as Nature left it. It was a happy thought to make another national park here. [Illustration: FIG. 134.--THE PUNCH BOWL, YELLOWSTONE PARK] We have already learned something of the grandeur of the Yosemite Valley and have seen how it came into existence. The valley is owned and cared for as a public park by the state of California, but, with Hetch-Hetchy Valley, it is included in a larger park under the control of the general government. Within the boundaries of this national park, as in the case of the others described, the natural features of the landscape, the forests, and the animals, are to be left forever undisturbed. The Yosemite Valley, although situated in the heart of the rugged Sierras, is reached by several good wagon roads and many more people visit it than go to Crater Lake, although the latter is fully as interesting. [Illustration: FIG. 135.--THE FALLS OF THE YELLOWSTONE, YELLOWSTONE CAÑON] About a hundred miles south of the Yosemite is the General Grant National Park. This park is of comparatively small size, but contains a group of some of the largest and finest Big Trees in the country. Still farther south there is a reserve called the Sequoia Park, which contains the largest remaining groves of the Big Trees. There are also many state parks scattered over different parts of the Union. The establishment of these parks is intended to preserve either the forests or natural scenery. The retention by the state or general government of large tracts of mountain and timber land, and of those areas which are particularly interesting on account of their natural scenery, is of the greatest importance. The timber and water are preserved for the general good instead of being squandered for the enrichment of individuals. The preservation of scenic features in their original wild state is just and right, because such things add to the pleasure of out-of-door life, elevate men's feelings, and cultivate a love for the beautiful. The protection afforded the plant and animal life by these reserves gives a better opportunity for studying them, and tends to foster a general interest in the welfare of living things. ADVERTISEMENTS. THE HEATH READERS A new series, that excels in its 1. Interesting and well graded lessons. 2. Masterpieces of English and American literature. 3. Beautiful and appropriate illustrations. 4. Clear and legible printing. 5. Durable and handsome binding. 6. 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38148	----	Wisconsin Geological and Natural History Survey. E. A. BIRGE, Director. C. R. VAN HISE, Consulting Geologist. BULLETIN NO. V. EDUCATIONAL SERIES NO. 1. THE GEOGRAPHY OF THE REGION ABOUT DEVIL'S LAKE AND THE DALLES OF THE WISCONSIN, With Some Notes on Its Surface Geology. BY ROLLIN D. SALISBURY, A. M., _Professor of Geographic Geology, University of Chicago,_ AND WALLACE W. ATWOOD, B. S., _Assistant in Geology, University of Chicago._ MADISON, WIS. Published by the State. 1900. Wisconsin Geological and Natural History Survey. ------------------------------------------------------------------- BOARD OF COMMISSIONERS. EDWARD SCOFIELD, Governor of the State. L. D. HARVEY, State Superintendent of Public Instruction. CHARLES K. ADAMS, President, President of the University of Wisconsin. EDWIN E. BRYANT, Vice-President, President of the Commissioners of Fisheries. CHARLES S. SLICHTER, Secretary, President of the Wisconsin Academy of Sciences, Arts, and Letters. -------------------------------------------------------------- E. A. BIRGE, Director of the Survey. C. R. VAN HISE, Consulting Geologist. E. R. BUCKLEY, Assistant Geologist. In charge of Economic Geology. S. WEIDMAN, Assistant Geologist. In charge of Geology of Wausau District. L. S. SMITH, in charge of Hydrography. S. V. PEPPEL, Chemist. F. R. DENNISTON, Artist. [Illustration: THE DALLES OF THE WISCONSIN.] CONTENTS. --------------------------------------------------------- PART I. THE TOPOGRAPHY WITH SOME NOTES ON THE SURFACE GEOLOGY. CHAPTER I. GENERAL GEOGRAPHIC FEATURES I. The Plain Surrounding the Quartzite Ridges. Topography Structure Origin of the Sandstone and Limestone Origin of the Topography II. The Quartzite Ridges Topography The Structure and Constitution of the Ridges III. Relations of the Sandstone of the Plain to the Quartzite of the Ridges PART II. HISTORY OF THE TOPOGRAPHY. CHAPTER II. OUTLINE OF THE HISTORY OF THE ROCK FORMATIONS WHICH SHOW THEMSELVES AT THE SURFACE. I. The Pre-Cambrian History of the Quartzite From loose Sand to Quartzite Uplift and Deformation. Dynamic Metamorphism Erosion of the Quartzite Thickness of the Quartzite II. The History of the Paleozoic Strata The Subsidence The Potsdam Sandstone (and Conglomerate) The Lower Magnesian Limestone The St. Peters Sandstone Younger Beds Climatic Conditions Time involved The Uplift CHAPTER III. GENERAL OUTLINE OF RAIN AND RIVER EROSION Elements of Erosion Weathering Corrasion Erosion without Valleys The Beginning of a Valley The Course of a Valley Tributary Valleys How a Valley gets a Stream Limits of a Valley A Cycle of Erosion Effects of unequal Hardness Falls and Rapids Narrows Erosion of folded Strata Base-level Plains and Peneplains Transportation and Deposition Topographic Forms resulting from Stream Deposition Rejuvenation of Streams Underground Water CHAPTER IV. EROSION AND THE DEVELOPMENT OF STRIKING SCENIC FEATURES Establishment of Drainage Striking scenic Features The Baraboo Bluffs The Narrows in the Quartzite Glens Natural Bridge The Dalles of the Wisconsin The Mounds and Castle Rocks CHAPTER V. THE GLACIAL PERIOD. The Drift Snow Fields and ice Sheets The North American ice Sheets The Work of glacier Ice Erosive Work of Ice. Effect on Topography Deposition by the Ice. Effect on Topography Direction of ice Movement Effect of Topography on Movement Glacial Deposits The ground Moraine Constitution Topography Terminal Moraines Topography of terminal Moraines The terminal Moraine about Devil's Lake The Moraine on the main Quartzite Range Constitution of the marginal Ridge The Slope of the upper Surface of the Ice at the Margin Stratified Drift Its Origin Glacial Drainage Stages in the History of an Ice Sheet Deposits made by extraglacial Waters during the maximum Extension of the Ice At the Edge of the Ice, on Land Beyond the Edge of the Ice, on Land Deposits at and beyond the Edge of the Ice in standing Water Deposits made by extraglacial Waters during the Retreat of the Ice Deposits made by extraglacial Waters during the Advance of the Ice Deposits made by subglacial Streams Relations of stratified to unstratified Drift Complexity of Relations Classification of stratified Drift on the Basis of Position Extraglacial Deposits Supermorainic deposits The submorainic (basal) Deposits Intermorainic stratified Drift Changes in Drainage effected by the Ice While the Ice was on Wisconsin Lake Baraboo Lake Devil's Lake in glacial Times After the Ice had disappeared Lakes Existing Lakes Changes in Streams Skillett Creek The Wisconsin The Driftless Area Contrast between glaciated and unglaciated Areas Topography Drainage Mantle Rock LIST OF ILLUSTRATIONS. ------------------------------------------------------------ PLATES. Plate Frontispiece. The Dalles of the Wisconsin I. General map of the Devil's Lake region II. Local map of the Devil's Lake region III. Fig. 1--Ripple marks on a slab of sandstone Fig. 2--Piece of Potsdam conglomerate IV. Lower Narrows of the Baraboo V. Devil's Lake notch VI. East bluff of Devil's Lake VII. East bluff at the Upper Narrows of the Baraboo near Ableman's VIII. Vertical shear zone face of east bluff at Devil's Lake IX. Massive quartzite in situ in road through Upper Narrows near Ableman's X. Brecciated quartzite XI. Northwest wall of the Upper Narrows XII. Steamboat Rock XIII. Fig. 1--A very young valley Fig. 2--A valley at later stage of development Fig. 3--Young valleys XIV. Fig. 1--Same valleys as shown in Pl. XIII, Fig. 3, but at a later stage of development Fig. 2--Same valleys as shown in Fig. 1 in later stage of development XV. Diagram illustrating how a hard inclined layer of rock becomes a ridge in the process of degradation XVI. Skillett Falls XVII. A group of mounds on the plain northwest from Camp Douglas XVIII. Castle Rock near Camp Douglas XIX. Fig. 1--Sketch of a young valley Fig. 2--Same valleys as shown in Fig. 1 in later stage of development XX. Fig. 1--Sketch of a part of a valley at a stage of development corresponding to the cross section shown in Figure 21 Fig. 2--Sketch of a section of the Baraboo valley XXI. Cleopatra's Needle XXII. Turk's Head XXIII. Devil's Doorway XXIV. Talus slope on east bluff of Devil's Lake XXV. Dorward's Glen XXVI. Natural Bridge near Denzer XXVII. The Navy Yard XXVIII. Chimney Rock XXIX. An island in the Lower Dalles XXX. View in Lower Dalles XXXI. Stand Rock XXXII. Petenwell Peak XXXIII. North American ice sheet XXXIV. Owl's Head XXXV. Cut in glacial drift XXXVI. Glaciated stones XXXVII. Topographic map of a small area about Devil's Lake XXXVIII. Distorted laminæ of silt and clay FIGURES IN TEXT. Figure 1. Profile across the Baraboo quartzite ranges through Baraboo 2. Profile across the Baraboo ranges through Merrimac Transcriber's note: There is no figure 3. 4. Diagram showing the structure of the quartzite 5. Diagram showing the relation of the Potsdam sandstone to the Baraboo quartzite 6. Diagram illustrating effect of faulting on outcrop 7. Diagram showing the disposition of sediments about an island 8. The same as 7 after subsidence 9. Diagram showing relation of Potsdam conglomerate to quartzite at Devil's Lake 10. Cross section of a delta 11. The geological formations of southern Wisconsin 12. A typical river system 13. Diagram illustrating the relations of ground water to streams 14. Diagram illustrating the shifting of divides 15. Diagram showing topography at the various stages of an erosion cycle 16. Diagram illustrating the development of rapids and falls 17. Sketch looking northwest from Camp Douglas 18. Diagrammatic cross section of a young valley 19. Diagrammatic profile of a young valley 20. Diagrammatic cross section of a valley in a later stage of development 21. The same at a still later stage 22. Diagram illustrating the topographic effect or rejuvenation of a stream by uplift 23. Normal profile of a valley bottom 24. Profile of a stream rejuvenated by uplift 25. Diagram illustrating monoclinal shifting 26. Diagram showing the relation of the Potsdam sandstone to the quartzite at the Upper Narrows 27. Diagrammatic cross section of a field of ice and snow 28. Shape of an erosion hill before glaciation 29. The same after glaciation 30. Diagram showing the effect of a valley on the movement of ice 31. The same under different conditions 32. Diagram showing the relation of drift to the underlying rock where the drift is thick 33. The same where the drift is relatively thin 34. Diagrammatic representation of the effect of a hill on the edge of the ice 35. The same at a later stage of the ice advance 36. Map showing the relation of the ice lobes during the Wisconsin epoch of the glacial period 37. Sketch of the terminal moraine topography east of Devil's Lake 38. Cut through the terminal moraine east of Kirkland 39. Cross section of the marginal ridge of the moraine on the south slope of the Devil's nose 40. Cross section of the marginal ridge of the moraine on the crest of the quartzite range 41. Morainic outwash plain 42. The same in other relations 43. Skillett Creek and its peculiarities 44. The Wisconsin valley near Kilbourn city 45. Drainage in the driftless area 46. Drainage in the glaciated area 47. Section in the driftless region showing relation of the soil to the solid rock beneath PART I. ------------------------------------------------------------ THE TOPOGRAPHY. WITH SOME NOTES ON THE SURFACE GEOLOGY. GEOGRAPHY AND SURFACE GEOLOGY OF THE DEVIL'S LAKE REGION. CHAPTER I. GENERAL GEOGRAPHIC FEATURES. This report has to do with the physical geography of the area in south central Wisconsin, shown on the accompanying sketch map, Plate I. The region is of especial interest, both because of its striking scenery, and because it illustrates clearly many of the principles involved in the evolution of the geography of land surfaces. Generally speaking, the region is an undulating plain, above which rise a few notable elevations, chief among which are the Baraboo quartzite ranges, marked by diagonal lines on Plates I and II. These elevations have often been described as two ranges. The South or main range lies three miles south of Baraboo, while the North or lesser range, which is far from continuous, lies just north of the city. The main range has a general east-west trend, and rises with bold and sometimes precipitous slopes 500 to 800 feet above its surroundings. A deep gap three or four miles south of Baraboo (Plates II, V, and XXXVII) divides the main range into an eastern and a western portion, known respectively as the _East and West bluffs_ or _ranges_. In the bottom of the gap lies Devil's lake (i, Plate II and Plate XXXVII), perhaps the most striking body of water of its size in the state, if not in the whole northern interior. A general notion of the topography of a small area in the immediate vicinity of the lake may be obtained from Plate XXXVII. The highest point in the range is about four miles east of the lake, and has an elevation of more than 1,600 feet above sea level, more than 1,000 feet above Lake Michigan, and about 800 feet above the Baraboo valley at its northern base. The eastward extension of the west range (Plate XXXVII) lying south of the lake, and popularly known as the _Devil's nose_, reaches an elevation of a little more than 1,500 feet. The lesser or North quartzite range (Plate II) rises 300 feet to 500 feet above its surroundings. It assumes considerable prominence at the Upper and Lower narrows of the Baraboo (b and c, Plate II, c, Plate XXXVII and Plate IV). The North range is not only lower than the South range, but its slopes are generally less steep, and, as Plate II shows, it is also less continuous. The lesser elevation and the gentler slopes make it far less conspicuous. About three miles southwest of Portage (Plate II) the North and South ranges join, and the elevation at the point of union is about 450 feet above the Wisconsin river a few miles to the east. The lower country above which these conspicuous ridges rise, has an average elevation of about 1,000 feet above the sea, and extends far beyond the borders of the area with which this report is concerned. The rock underlying it in the vicinity of Baraboo is chiefly sandstone, but there is much limestone farther east and south, in the area with which the Baraboo region is topographically continuous. Both the sandstone and limestone are much less resistant than the quartzite, and this difference has had much to do with the topography of the region. The distinctness of the quartzite ridges as topographic features is indicated in Plate XXXVII by the closeness of the contour lines on their slopes. The same features are shown in Figs. 1 and 2, which represent profiles along two north-south lines passing through Baraboo and Merrimac respectively. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. I. General map showing the location of the chief points mentioned in this report. The location of the area shown in Plate XXXVII, centering about Baraboo, is indicated.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. II. Map of Area considered in this Report.] [Illustration: Fig. 1.--Profile along a line extending due north and south from Baraboo across the north and south ranges. The dotted continuation northward, represents the extension of the profile beyond the topographic map, Plate XXXVII.] [Illustration: Fig. 2.--Profile north from Merrimac across the quartzite ranges. The dotted continuation northward represents the extension of the profile beyond the topographic map, Plate XXXVII.] I. THE PLAIN SURROUNDING THE QUARTZITE RIDGES. _Topography._--As seen from the top of the quartzite ridges, the surrounding country appears to be an extensive plain, but at closer range it is seen to have considerable relief although there are extensive areas where the surface is nearly flat. The relief of the surface is of two somewhat different types. In some parts of the area, especially in the western part of the tract shown on Plate II, the surface is made up of a succession of ridges and valleys. The ridges may be broken by depressions at frequent intervals, but the valleys are nowhere similarly interrupted. It would rarely be possible to walk along a ridge or "divide" for many miles without descending into valleys; but once in a valley in any part of the area, it may be descended without interruption, until the Baraboo, the Wisconsin, the Mississippi, and finally the gulf is reached. In other words, the depressions are continuous, but the elevations are not. This is the first type of topography. Where this type of topography prevails its relation to drainage is evident at a glance. All the larger depressions are occupied by streams continuously, while the smaller ones contain running water during some part of the year. The relations of streams to the depressions, and the wear which the streams effect, whether they be permanent or temporary, suggest that running water is at least one of the agencies concerned in the making of valleys. An idea of the general arrangement of the valleys, as well as many suggestions concerning the evolution of the topography of the broken plain in which they lie might be gained by entering a valley at its head, and following it wherever it leads. At its head, the valley is relatively narrow, and its slopes descend promptly from either side in such a manner that a cross-section of the valley is V-shaped. In places, as west of Camp Douglas, the deep, steep-sided valleys are found to lead down and out from a tract of land so slightly rolling as to be well adapted to cultivation. Following down the valley, its progressive increase in width and depth is at once evident, and at the same time small tributary valleys come in from right and left. At no great distance from the heads of the valleys, streams are found in their bottoms. As the valleys increase in width and depth, and as the tributaries become more numerous and wider, the topography of which the valleys are a feature, becomes more and more broken. At first the tracts between the streams are in the form of ridges, wide if parallel valleys are distant from one another, and narrow if they are near. The ridges wind with the valleys which separate them. Whatever the width of the inter-stream ridges, it is clear that they must become narrower as the valleys between them become wider, and in following down a valley a point is reached, sooner or later, where the valleys, main and tributary, are of such size and so numerous that their slopes constitute a large part of the surface. Where this is true, and where the valleys are deep, the land is of little industrial value except for timber and grazing. When, in descending a valley system, this sort of topography is reached, the roads often follow either the valleys or the ridges, however indirect and crooked they may be. Where the ridges separating the valleys in such a region have considerable length, they are sometimes spoken of as "hog backs." Still farther down the valley system, tributary valleys of the second and lower orders cross the "hog backs," cutting them into hills. By the time this sort of topography is reached, a series of flats is found bordering the streams. These flats may occur on both sides of the stream, or on but one. The topography and the soil of these flats are such as to encourage agriculture, and the river flats or alluvial plains are among the choicest farming lands. With increasing distance from the heads of the valleys, these river plains are expanded, and may be widened so as to occupy the greater part of the surface. The intervening elevations are there relatively few and small. Their crests, however, often rise to the same level as that of the broader inter-stream areas farther up the valleys. The relations of the valleys and the high lands separating them, is such as to suggest that there are, generally speaking, two sets of flat surfaces, the higher one representing the upland in which the valleys lie, the lower one representing the alluvial plains of the streams. The two sets of flats are at once separated and connected by slopes. At the head of a drainage system, the upland flats predominate; in the lower courses, the river plains; in an intermediate stage, the slopes are more conspicuous than either upper or lower flat. Southwest from Devil's lake and northwest from Sauk City, in the valley of Honey creek, and again in the region southwest from Camp Douglas, the topography just described is well illustrated. In both these localities, as in all others where this type of topography prevails, the intimate relations of topography and drainage cannot fail to suggest that the streams which are today widening and deepening the valleys through which they flow, had much to do with their origin and development. This hypothesis, as applied to the region under consideration, may be tested by the study of the structure of the plain. The second type of topography affecting the plain about the quartzite ranges is found east of a line running from Kilbourn City to a point just north of Prairie du Sac. Though in its larger features the area east of this line resembles that to the west, its minor features are essentially different. Here there are many depressions which have no outlets, and marshes, ponds, and small lakes abound. Not only this, but many of the lesser elevations stand in no definite relation to valleys. The two types of topography make it clear that they were developed in different ways. _Structure._--Examination of the country surrounding the Baraboo ridges shows that its surface is underlaid at no great depth by horizontal or nearly horizontal beds of sandstone and limestone (see Plates XVI, XXVIII, and Frontispiece). These beds are frequently exposed on opposite sides of a valley, and in such positions the beds of one side are found to match those on the other. This is well shown along the narrow valley of Skillett creek just above the "Pewit's nest." Here the swift stream is rapidly deepening its channel, and it is clear that a few years hence, layers of sandstone which are now continuous beneath the bed of the creek will have been cut through, and their edges will appear on opposite sides of the valley just as higher layers do now. Here the most skeptical might be convinced that the layers of rock on either side of the narrow gorge were once continuous across it, and may see, at the same time, the means by which the separation was effected. Between the slight separation, here, where the valley is narrow, and the great separation where the valleys are wide, there are all gradations. The study of progressively wider valleys, commencing with such a gorge as that referred to, leaves no room for doubt that even the wide valleys, as well as the narrow ones, were cut out of the sandstone by running water. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. III. Illustration: FIG. 1. Ripple marks on a slab of Potsdam sandstone. Illustration: FIG. 2. Piece of Potsdam conglomerate. The larger pebbles are about three inches in diameter.] The same conclusion as to the origin of the valleys may be reached in another way. Either the beds of rock were formed with their present topography, or the valleys have been excavated in them since they were formed. Their mode of origin will therefore help to decide between these alternatives. _Origin of the sandstone and limestone._--The sandstone of the region, known as the Potsdam sandstone, consists of medium sized grains of sand, cemented together by siliceous, ferruginous, or calcareous cement. If the cement were removed, the sandstone would be reduced to sand, in all respect similar to that accumulating along the shores of seas and lakes today. The surfaces of the separate layers of sandstone are often distinctly ripple-marked (Fig. 1, Pl. III), and the character of the markings is identical in all essential respects with the ripples which affect the surface of the sand along the shores of Devil's lake, or sandy beaches elsewhere, at the present time. These ripple marks on the surfaces of the sandstone layers must have originated while the sand was movable, and therefore before it was cemented into sandstone. In the beds of sandstone, fossils of marine animals are found. Shells, or casts of shells of various sorts are common, as are also the tracks and burrowings of animals which had no shells. Among these latter signs of life may be mentioned the borings of worms. These borings are not now always hollow, but their fillings are often so unlike the surrounding rock, that they are still clearly marked. These worm borings, like the ripple marks, show that the sand was once loose. The basal beds of the sandstone are often conglomeratic. The conglomeratic layers are made up of water-worn pieces of quartzite, Plate III, Fig. 2, ranging in size from small pebbles to large bowlders. The interstices of the coarse material are filled by sand, and the whole cemented into solid rock. The conglomeratic phase of the sandstone may be seen to advantage at Parfrey's glen (a, Plate XXXVII) and Dorward's glen, (b, same plate) on the East bluff of Devil's lake above the Cliff House, and at the Upper narrows of the Baraboo, near Ablemans. It is also visible at numerous other less accessible and less easily designated places. From these several facts, viz.: the horizontal strata, the ripple-marks on the surfaces of the layers, the fossils, the character of the sand, and the water-worn pebbles and bowlders of the basal conglomerate, positive conclusions concerning the origin of the formation may be drawn. The arrangement in definite layers proves that the formation is sedimentary; that is, that its materials were accumulated in water whither they had been washed from the land which then existed. The ripple-marks show that the water in which the beds of sand were deposited was shallow, for in such water only are ripple-marks made.[1] Once developed on the surface of the sand they may be preserved by burial under new deposits, just as ripple-marks on sandy shores are now being buried and preserved. [1] Ripple marks are often seen on the surface of wind-blown sand, but the other features of this sandstone show that this was not its mode of accumulation. The conglomerate beds of the formation corroborate the conclusions to which the composition and structure of the sandstone point. The water-worn shapes of the pebbles and stones show that they were accumulated in water, while their size shows that the water must have been shallow, for stones of such sizes are handled only by water of such slight depth that waves or strong currents are effective at the bottom. Furthermore, the large bowlders show that the source of supply (quartzite) must have been close at hand, and that therefore land composed of this rock must have existed not far from the places where the conglomerate is found. The fossils likewise are the fossils of aquatic life. Not only this, but they are the fossils of animals which lived in salt water. The presence of salt water, that is, the sea, in this region when the sand of the sandstone was accumulating, makes the wide extent of the formation rational. From the constitution and structure of the sandstone, it is therefore inferred that it accumulated in shallow sea water, and that, in the vicinity of Devil's lake, there were land masses (islands) of quartzite which furnished the pebbles and bowlders found in the conglomerate beds at the base of the formation. This being the origin of the sandstone, it is clear that the layers which now appear on opposite sides of valleys must once have been continuous across the depressions; for the sand accumulated in shallow water is never deposited so as to leave valleys between ridges. It is deposited in beds which are continuous over considerable areas. Within the area under consideration, limestone is much less widely distributed than sandstone. Thin beds of it alternate with layers of sandstone in the upper portion of the Potsdam formation, and more massive beds lie above the sandstone on some of the higher elevations of the plain about the quartzite ridge. This is especially true in the southern and southwestern parts of the region shown on Plate II. The limestone immediately overlying the sandstone is the _Lower Magnesian_ limestone. The beds of limestone, like those of the sandstone beneath, are horizontal or nearly so, and the upper formation lies conformably on the lower. The limestone does not contain water-worn pebbles, and the surfaces of its layers are rarely if ever ripple-marked; yet the arrangement of the rock in distinct layers which carry fossils of marine animals shows that the limestone, like the sandstone beneath, was laid down in the sea. The bearing of this origin of the limestone on the development of the present valleys is the same as that of the sandstone. _Origin of the topography._--The topography of the plain surrounding the quartzite ridges, especially that part lying west of Devil's lake, is then an erosion topography, developed by running water. Its chief characteristic is that every depression leads to a lower one, and that the form of the elevations, hills or ridges, is determined by the valleys. The valleys were made; the hills and ridges left. If the material carried away by the streams could be returned, the valleys would be filled to the level of the ridges which bound them. Were this done, the restored surface would be essentially flat. It is the sculpturing of such a plain, chiefly by running water, which has given rise to the present topography. In the development of this topography the more resistant limestone has served as a capping, tending to preserve the hills and ridges. Thus many of the hills, especially in the southwest portion of the area shown in Plate II, are found to have caps of the Lower Magnesian formation. Such hills usually have flat tops and steep or even precipitous slopes down to the base of the capping limestone, while the sandstone below, weathering more readily, gives the lower portions of the hills a gentler slope. The elevations of the hills and ridges above the axes of the valleys or, in other words, the relief of the plain is, on the average, about 300 feet, only a few of the more prominent hills exceeding that figure. The topography east of the line between Kilbourn City and Prairie du Sac is not of the unmodified erosion type, as is made evident by marshes, ponds and lakes. The departure from the erosion type is due to a mantle of glacial drift which masks the topography of the bedded rock beneath. Its nature, and the topographic modifications which it has produced, will be more fully considered in a later part of this report. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. IV. The Lower Narrows of the Baraboo from a point on the South range.] II. THE QUARTZITE RIDGES. _Topography._--The South or main quartzite range, about 23 miles in length and one to four miles in width, rises 500 feet to 800 feet above the surrounding sandstone plain. Its slopes are generally too steep for cultivation, and are clothed for the most part with a heavy growth of timber, the banks of forest being broken here and there by cultivated fields, or by the purple grey of the rock escarpments too steep for trees to gain a foothold. With the possible exception of the Blue mounds southwest of Madison, this quartzite range is the most obtrusive topographic feature of southern Wisconsin. As approached from the south, one of the striking features of the range is its nearly even crest. Extending for miles in an east-west direction, its summit gives a sky-line of long and gentle curves, in which the highest points are but little above the lowest. Viewed from the north, the evenness of the crest is not less distinct, but from this side it is seen to be interrupted by a notable break or notch at Devil's lake (Plates V and XXXVII). The pass across the range makes a right-angled turn in crossing the range, and for this reason is not seen from the south. The North or lesser quartzite range lying north of Baraboo is both narrower and lower than the south range, and its crest is frequently interrupted by notches or passes, some of which are wide. Near its eastern end occurs the striking gap known as the _Lower narrows_ (Plate IV) through which the Baraboo river escapes to the northward, flowing thence to the Wisconsin. At this narrows the quartzite bluffs rise abruptly 500 feet above the river. At a and b, Plate II, there are similar though smaller breaks in the range, also occupied by streams. The connection between the passes and streams is therefore close. There are many small valleys in the sides of the quartzite ranges (especially the South range) which do not extend back to their crests, and therefore do not occasion passes across them. The narrow valleys at a and b in Plate XXXVII, known as Parfrey's and Dorward's glens, respectively, are singularly beautiful gorges, and merit mention as well from the scenic as from the geologic point of view. Wider valleys, the heads of which do not reach the crest, occur on the flanks of the main range (as at d and e, Plate II) at many points. One such valley occurs east of the north end of the lake (x, Plate XXXVII), another west of the south end (y, Plate XXXVII), another on the north face of the west bluff west of the north end of the lake and between the East and West Sauk roads, and still others at greater distances from the lake in both directions. It is manifest that if the valleys were extended headward in the direction of their axes, they would interrupt the even crest. Many of these valleys, unlike the glens mentioned above, are very wide in proportion to their length. In some of these capacious valleys there are beds of Potsdam sandstone, showing that the valleys existed before the sand of the sandstone was deposited. _The structure and constitution of the ridges._--The quartzite of the ridges is nothing more nor less than altered sandstone. Its origin dates from that part of geological time known to geologists as the Upper Huronian period. The popular local belief that the quartzite is of igneous origin is without the slightest warrant. It appears to have had its basis in the notion that Devil's lake occupies an extinct volcanic crater. Were this the fact, igneous rock should be found about it. Quartzite is sandstone in which the intergranular spaces have been filled with silica (quartz) brought in and deposited by percolating water subsequent to the accumulation of the sand. The conversion of sandstone into quartzite is but a continuation of the process which converts sand into sandstone. The Potsdam or any other sandstone formation might be converted into quartzite by the same process, and it would then be a _metamorphic_ rock. Like the sandstone, the quartzite is in layers. This is perhaps nowhere so distinctly shown on a large scale as in the bluffs at Devil's lake, and at the east end of the Devil's nose. On the East bluff of the lake, the stratification is most distinctly seen from the middle of the lake, from which point the photograph reproduced in Plate VI was taken. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. V. The Notch in the South quartzite range, at Devil's Lake.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. VI. The east bluff of Devil's lake, showing the dip of quartzite (to the left), and talus above and below the level where the beds are shown.] Unlike the sandstone and limestone, the beds of quartzite are not horizontal. The departure from horizontality, technically known as the _dip_, varies from point to point (Fig. 4). In the East bluff of the lake as shown in Plate VI, the dip is about 14° to the north. At the Upper and Lower narrows of the Baraboo (b and c, Plate II) the beds are essentially vertical, that is, they have a dip of about 90°. Between these extremes, many intermediate angles have been noted. Plate VII represents a view near Ablemans, in the Upper narrows, where the nearly vertical beds of quartzite are well exposed. The position of the beds in the quartzite is not always easy of recognition. The difficulty is occasioned by the presence of numerous cleavage planes developed in the rock after its conversion into quartzite. Some of these secondary cleavage planes are so regular and so nearly parallel to one another as to be easily confused with the bedding planes. This is especially liable to make determinations of the dip difficult, since the true bedding was often obscured when the cleavage was developed. In spite of the difficulties, the original stratification can usually be determined where there are good exposures of the rock. At some points the surfaces of the layers carry ripple marks, and where they are present, they serve as a ready means of identifying the bedding planes, even though the strata are now on edge. Layers of small pebbles are sometimes found. They were horizontal when the sands of the quartzite were accumulating, and where they are found they are sufficient to indicate the original position of the beds. Aside from the position of the beds, there is abundant evidence of dynamic action[2] in the quartzite. Along the railway at Devil's lake, half a mile south of the Cliff House, thin zones of schistose rock may be seen parallel to the bedding planes. These zones of schistose rock a few inches in thickness were developed from the quartzite by the slipping of the rock on either side. This slipping presumably occurred during the adjustment of the heavy beds of quartzite to their new positions, at the time of tilting and folding, for no thick series of rock can be folded without more or less slipping of the layers on one another. The slipping (adjustment) takes place along the weaker zones. Such zones of movement are sometimes known as _shear zones_, for the rock on the one side has been sheared (slipped) over that on the other. [2] Irving: "The Baraboo Quartzite Ranges." Vol. II, Geology of Wisconsin, pp. 504-519. Van Hise: "Some Dynamic Phenomena Shown by the Baraboo Quartzite Ranges of Central Wisconsin." Jour. of Geol., Vol. I, pp. 347-355. [Illustration: Fig. 4.--Diagram made by plotting the different dips now at hand along a section from A to B, Plate II, and connecting them so as to show the structure indicated by the known data. The full lines, oblique or vertical, represent the beds of quartzite. The continuous line above them represents the present surface of the quartzite, while the dotted lines suggest the continuation of the beds which completed the great folds of which the present exposures appear to be remnants.] [Illustration: Fig. 5.--A diagrammatic section showing the relation of the sandstone to the quartzite.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. VII. The East Bluff at the Upper Narrows of the Baraboo near Ablemans, showing the vertical position of the beds of quartzite. In the lower right-hand corner, above the bridge, appears some breccia.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. VIII. Vertical shear zone in face of east bluff at Devil's lake.] Near the shear zones parallel to the bedding planes, there is one distinct vertical shear zone (Plate VIII) three to four feet in width. It is exposed to a height of fully twenty-five feet. Along this zone the quartzite has been broken into angular fragments, and at places the crushing of the fragments has produced a "friction clay." Slipping along vertical zones would be no necessary part of folding, though it might accompany it. On the other hand, it might have preceded or followed the folding. Schistose structure probably does not always denote shearing, at least not the shearing which results from folding. Extreme pressure is likely to develop schistosity in rock, the cleavage planes being at right angles to the direction of pressure. It is not always possible to say how far the schistosity of rock at any given point is the result of shear, and how far the result of pressure without shear. Schistose structure which does not appear to have resulted from shear, at least not from the shear involved in folding, is well seen in the isolated quartzite mound about four miles southwest of Baraboo on the West Sauk road (f, Plate II). These quartzite schists are to be looked on as metamorphosed quartzite, just as quartzite is metamorphosed sandstone. At the Upper narrows of the Baraboo also (b, Plate II), evidence of dynamic action is patent. Movement along bedding planes with attendant development of quartz schist has occurred here as at the lake (Plate IX). Besides the schistose belts, a wide zone of quartzite exposed in the bluffs at this locality has been crushed into angular fragments, and afterwards re-cemented by white quartz deposited from solution by percolating waters (Plate X). This quartzite is said to be brecciated. Within this zone there are spots where the fragments of quartzite are so well rounded as to simulate water-worn pebbles. Their forms appear to be the result of the wear of the fragments on one another during the movements which followed the crushing. Conglomerate originating in this way is _friction conglomerate_ or _Reibungsbreccia_. The crushing of the rock in this zone probably took place while the beds were being folded; but the brecciated quartzite formed by the re-cementation of the fragments has itself been fractured and broken in such a manner as to show that the formation has suffered at least one dynamic movement since the development of the breccia. That these movements were separated by a considerable interval of time is shown by the fact that the re-cementation of the fragmental products of the first movement preceded the second. What has been said expresses the belief of geologists as to the origin of quartzite and quartz schists; but because of popular misconception on the point it may here be added that neither the changing of the sandstone into quartzite, nor the subsequent transformation of the quartzite to schist, was due primarily to heat. Heat was doubtless generated in the mechanical action involved in these changes, but it was subordinate in importance, as it was secondary in origin. Igneous rock is associated with the quartzite at a few points. At g and h, Plate II there are considerable masses of porphyry, sustaining such relations to the quartzite as to indicate that they were intruded into the sedimentary beds after the deposition of the latter. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. IX. A mass of quartzite _in situ_, in the road through the Upper Narrows near Ableman's. The bedding, which is nearly vertical, is indicated by the shading, while the secondary cleavage approaches horizontality.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. X. Brecciated quartzite near Ablemans in the Upper Narrows. The darker parts are quartzite, the lighter parts the cementing quartz.] III. RELATIONS OF THE SANDSTONE OF THE PLAIN TO THE QUARTZITE OF THE RIDGES. The horizontal beds of Potsdam sandstone may be traced up to the bases of the quartzite ranges, where they may frequently be seen to abut against the tilted beds of quartzite. Not only this, but isolated patches of sandstone lie on the truncated edges of the dipping beds of quartzite well up on the slopes, and even on the crest of the ridge itself. In the former position they may be seen on the East bluff at Devil's lake, where horizontal beds of conglomerate and sandstone rest on the layers of quartzite which dip 14° to the north. The stratigraphic relations of the two formations are shown in Fig. 5 which represents a diagrammatic section from A to B, Plate II. Plate XI is reproduced from a photograph taken in the Upper narrows of the Baraboo near Ablemans, and shows the relations as they appear in the field. The quartzite layers are here on edge, and on them rest the horizontal beds of sandstone and conglomerate. Similar stratigraphic relations are shown at many other places. This is the relationship of _unconformity_. Such an unconformity as that between the sandstone and the quartzite of this region shows the following sequence of events: (1) the quartzite beds were folded and lifted above the sea in which the sand composing them was originally deposited; (2) a long period of erosion followed, during which the crests of the folds were worn off; (3) the land then sank, allowing the sea to again advance over the region; (4) while the sea was here, sand and gravel derived from the adjacent lands which remained unsubmerged, were deposited on its bottom. These sands became the Potsdam sandstone. This sequence of events means that between the deposition of the quartzite and the sandstone, the older formation was disturbed and eroded. Either of these events would have produced an unconformity; the two make it more pronounced. That the disturbance of the older formation took place before the later sandstone was deposited is evident from the fact that the latter formation was not involved in the movements which disturbed the former. Although the sandstone appears in patches on the quartzite ranges, it is primarily the formation of the surrounding plains, occupying the broad valley between the ranges, and the territory surrounding them. The quartzite, on the other hand, is the formation of the ridges, though it outcrops at a few points in the plain. (Compare Plates II and XXXVII.) The striking topographic contrasts between the plains and the ridges is thus seen to be closely related to the rock formations involved. It is the hard and resistant quartzite which forms the ridges, and the less resistant sandstone which forms the lowlands about them. That quartzite underlies the sandstone of the plain is indicated by the occasional outcrops of the former rock on the plain, and from the fact that borings for deep wells have sometimes reached it where it is not exposed. The sandstone of the plain and the quartzite of the ridges are not everywhere exposed. A deep but variable covering of loose material or _mantle rock (drift)_ is found throughout the eastern part of the area, but it does not extend far west of Baraboo. This mantle rock is so thick and so irregularly disposed that it has given origin to small hills and ridges. These elevations are superimposed on the erosion topography of the underlying rock, showing that the drift came into the region after the sandstone, limestone, and quartzite had their present relations, and essentially their present topography. Further consideration will be given to the drift in a later part of this report. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XI. The northeast wall of the Upper Narrows, north of Ableman's, showing the horizontal Potsdam sandstone and conglomerate lying unconformably on the quartzite, the beds of which are vertical.] PART II. HISTORY OF THE TOPOGRAPHY. CHAPTER II. OUTLINE OF THE HISTORY OF THE ROCK FORMATIONS WHICH SHOW THEMSELVES AT THE SURFACE. I. THE PRE-CAMBRIAN HISTORY OF THE QUARTZITE. _From loose sand to quartzite._--To understand the geography of a region it is necessary to understand the nature of the materials, the sculpture of which has made the geography. It has already been indicated that the Huronian quartzite of which the most prominent elevations of this region are composed, was once loose sand. Even at the risk of repetition, the steps in its history are here recounted. The source of the sand was probably the still older rocks of the land in the northern part of Wisconsin. Brought down to the sea by rivers, or washed from the shores of the land by waves, the sand was deposited in horizontal or nearly horizontal beds at the bottom of the shallow water which then covered central and southern Wisconsin. Later, perhaps while it was still beneath the sea, the sand was converted into sandstone, the change being effected partly by compression which made the mass of sand more compact, but chiefly by the cementation of its constituent grains into a coherent mass. The water contained in the sand while consolidation was in progress, held in solution some slight amount of silica, the same material of which the grains of sand themselves are composed. Little by little this silica in solution was deposited on the surfaces of the sand grains, enlarging them, and at the same time binding them together. Thus the sand became sandstone. Continued deposition of silica between and around the grains finally filled the interstitial spaces, and when this process was completed, the sandstone had been converted into quartzite. While quartzite is a metamorphic sandstone, it is not to be understood that sandstone cannot be metamorphosed in other ways. _Uplift and deformation. Dynamic metamorphism._--After the deposition of the sands which later became the quartzite, the beds were uplifted and deformed, as their present positions and relations show. It is not possible to say how far the process of transformation of sand into quartzite was carried while the formation was still beneath the shallow sea in which it was deposited. The sand may have been changed to sandstone, and the sandstone to quartzite, before the sea bottom was converted into land, while on the other hand, the formation may have been in any stage of change from sand to quartzite, when that event occurred. If the process of change was then incomplete, it may have been continued after the sea retired, by the percolating waters derived from the rainfall of the region. Either when first converted into land, or at some later time, the beds of rock were folded, and suffered such other changes as attend profound dynamic movements. The conversion of the sandstone into quartzite probably preceded the deformation, since many phenomena indicate that the rock was quartzite and not sandstone when the folding took place. For example, the crushing of the quartzite (now re-cemented into brecciated quartzite) at Ablemans probably dates from the orogenic movements which folded the quartzite, and the fractured bits of rock often have corners and edges so sharp as to show that the rock was thoroughly quartzitic when the crushing took place. The uplift and deformation of the beds was probably accomplished slowly, but the vertical and highly tilted strata show that the changes were profound (see Fig. 4). The dynamic metamorphism which accompanied this profound deformation has already been referred to. The folding of the beds involved the slipping of some on others, and this resulted in the development of quartz schist along the lines of severest movement. Changes effected in the texture and structure of the rock under such conditions constitute _dynamic metamorphism_. In general, the metamorphic changes effected by dynamic action are much more profound than those brought about in other ways, and most rocks which have been profoundly metamorphosed, were changed in this way. Dynamic action generates heat, but contrary to the popular notion, the heat involved in profound metamorphism is usually secondary, and the dynamic action fundamental. At the same time that quartz schist was locally developed from the quartzite, crushing probably occurred in other places. This is _demorphism_, rather than metamorphism. _Erosion of the quartzite._--When the Huronian beds were raised to the estate of land, the processes of erosion immediately began to work on them. The heat and the cold, the plants and the animals, the winds, and especially the rain and the water which came from the melting of the snow, produced their appropriate effects. Under the influence of these agencies the surface of the rock was loosened by weathering, valleys were cut in it by running water, and wear and degradation went on at all points. The antagonistic processes of uplift and degradation went on for unnumbered centuries, long enough for even the slow processes involved to effect stupendous results. Degradation was continuous after the region became land, though uplift may not have been. On the whole, elevation exceeded degradation, for some parts of the quartzite finally came to stand high above the level of the sea,--the level to which all degradation tends. Fig. 4 conveys some notion of the amount of rock which was removed from the quartzite folds about Baraboo during this long period of erosion. The south range would seem to represent the stub of one side of a great anticlinal fold, a large part of which (represented by the dotted lines) was carried away, while the north range may be the core of another fold, now exposed by erosion. Some idea of the geography of the quartzite at the close of this period of erosion may be gained by imagining the work of later times undone. The younger beds covering the quartzite of the plains have a thickness varying from zero to several hundred feet, and effectually mask the irregularities of the surface of the subjacent quartzite. Could they be removed, the topography of the quartzite would be disclosed, and found to have much greater relief than the present surface; that is, the vertical distance between the crest of the quartzite ridge, and the surface of the quartzite under the surrounding lowlands, would be greater than that between the same crest and the surface of the sandstone. But even this does not give the full measure of the relief of the quartzite at the close of the long period of erosion which followed its uplift, for allowance must be made for the amount of erosion which the crests of the quartzite ranges have suffered since that time. The present surface therefore does not give an adequate conception of the irregularity of the surface at the close of the period of erosion which followed the uplift and deformation of the quartzite. So high were the crests of the quartzite ranges above their surroundings at that time, that they may well be thought of as mountainous. From this point of view, the quartzite ranges of today are the partially buried mountains of the pre-Potsdam land of south central Wisconsin. When the extreme hardness of the quartzite is remembered and also the extent of the erosion which affected it (Fig. 4) before the next succeeding formation was deposited, it is safe to conclude that the period of erosion was very long. _Thickness of the quartzite._--The thickness of the quartzite is not known, even approximately. The great thickness in the south range suggested by the diagram (Fig. 4) may perhaps be an exaggeration. Faulting which has not been discovered may have occurred, causing repetition of beds at the surface (Fig. 6), and so an exaggerated appearance of thickness. After all allowances have been made, it is still evident that the thickness of the quartzite is very great. II. THE HISTORY OF THE PALEOZOIC STRATA. _The subsidence._--Following the long period of erosion, the irregular and almost mountainous area of central Wisconsin was depressed sufficiently to submerge large areas which had been land. The subsidence was probably slow, and as the sea advanced from the south, it covered first the valleys and lowlands, and later the lower hills and ridges, while the higher hills and ridges of the quartzite stood as islands in the rising sea. Still later, the highest ridges of the region were themselves probably submerged. [Illustration: Fig. 6.--A diagrammatic cross-section, showing how, by faulting, the apparent thickness of the quartzite would be increased.] _The Potsdam sandstone (and conglomerate)._--So soon as the sea began to overspread the region, its bottom became the site of deposition, and the deposition continued as long as the submergence lasted. It is to the sediments deposited during the earlier part of this submergence that the name _Potsdam_ is given. The sources of the sediments are not far to seek. As the former land was depressed beneath the sea, its surface was doubtless covered with the products of rock decay, consisting of earths, sands, small bits and larger masses of quartzite. These materials, or at least the finer parts, were handled by the waves of the shallow waters, for they were at first shallow, and assorted and re-distributed. Thus the residuary products on the submerged surface, were one source of sediments. From the shores also, so long as land areas remained, the waves derived sediments. These were composed in part of the weathered products of the rock, and in part of the undecomposed rock against which the waves beat, after the loose materials had been worn away. These sediments derived from the shore were shifted, and finally mingled with those derived from the submerged surface. So long as any part of the older land remained above the water, its streams brought sediments to the sea. These also were shifted by the waves and shore currents, and finally deposited with the others on the eroded surface of the quartzite. Thus sediments derived in various ways, but inherently essentially similar, entered into the new formation. [Illustration: Fig. 7.--Diagram to illustrate the theoretical disposition of sediments about an island.] [Illustration: Fig. 8.--Same as Fig. 7, except that the land has been depressed.] The first material to be deposited on the surface of the quartzite as it was submerged, was the coarsest part of the sediment. Of the sediment derived by the waves from the coasts, and brought down to the sea by rivers, the coarsest would at each stage be left nearest the shore, while the finer was carried progressively farther and farther from it. Thus at each stage the sand was deposited farther from the shore than the gravel, and the mud farther than the sand, where the water was so deep that the bottom was subject to little agitation by waves. The theoretical distribution of sediments about an island as it was depressed, is illustrated by the following diagrams, Figs. 7 and 8. It will be seen that the surface of the quartzite is immediately overlain by conglomerate, but that the conglomerate near its top is younger than that near its base. In conformity with this natural distribution of sediments, the basal beds of the Potsdam formation are often conglomeratic (Fig. 9, Plate III, Fig. 2, and Plate XXV). This may oftenest be seen near the quartzite ridges, for here only is the base of the formation commonly exposed. The pebbles and larger masses of the conglomerate are quartzite, like that of the subjacent beds, and demonstrate the source of at least some of the material of the younger formation. That the pebbles and bowlders are of quartzite is significant, for it shows that the older formation had been changed from sandstone to quartzite, before the deposition of the Potsdam sediments. The sand associated with the pebbles may well have come from the breaking up of the quartzite, though some of it may have been washed in from other sources by the waters in which the deposition took place. [Illustration: Fig. 9.--Sketch showing relation of basal Potsdam conglomerate and sandstone to the quartzite, on the East bluff at Devil's lake, behind the Cliff house.] The basal conglomerate may be seen at many places, but nowhere about Devil's lake is it so well exposed as at Parfrey's glen (a, Plate XXXVII), where the rounded stones of which it is composed vary from pebbles, the size of a pea, to bowlders more than three feet in diameter. Other localities where the conglomerates may be seen to advantage are Dorward's glen (b, Plate XXXVII), the East bluff at Devil's lake just above the Cliff house, and at the Upper narrows of the Baraboo, above Ablemans. While the base of the Potsdam is conglomeratic in many places, the main body of it is so generally sandstone that the formation as a whole is commonly known as the Potsdam sandstone. The first effect of the sedimentation which followed submergence was to even up the irregular surface of the quartzite, for the depressions in the surface were the first to be submerged, and the first to be filled. As the body of sediment thickened, it buried the lower hills and the lower parts of the higher ones. The extent to which the Potsdam formation buried the main ridge may never be known. It may have buried it completely, for as already stated patches of sandstone are found upon the main range. These patches make it clear that some formation younger than the quartzite once covered essentially all of the higher ridge. Other evidence to be adduced later, confirms this conclusion. It has, however, not been demonstrated that the high-level patches of sandstone are Potsdam. There is abundant evidence that the subsidence which let the Potsdam seas in over the eroded surface of the Huronian quartzite was gradual. One line of evidence is found in the cross-bedding of the sandstone (Plate XII) especially well exhibited in the Dalles of the Wisconsin. The beds of sandstone are essentially horizontal, but within the horizontal beds there are often secondary layers which depart many degrees from horizontality, the maximum being about 24°. Plates XXVII and XII give a better idea of the structure here referred to than verbal description can. The explanation of cross-bedding is to be found in the varying conditions under which sand was deposited. Cross-bedding denotes shallow water, where waves and shore currents were effective at the bottom where deposition is in progress. For a time, beds were deposited off shore at a certain angle, much as in the building of a delta (Fig. 10). Then by subsidence of the bottom, other layers with like structure were deposited over the first. By this sequence of events, the dip of the secondary layers should be toward the open water, and in this region their dip is generally to the south. At any stage of deposition the waves engendered by storms were liable to erode the surface of the deposits already made, and new layers, discordant with those below, were likely to be laid down upon them. The subordinate layers of each deposit might dip in any direction. If this process were repeated many times during the submergence, the existing complexity would be explained. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XII. Steamboat rock,--an island in the Dalles of the Wisconsin.] [Illustration: Fig. 10.--A diagrammatic cross-section of a delta.] The maximum known thickness of the Potsdam sandstone in Wisconsin is about 1,000 feet, but its thickness in this region is much less. Where not capped by some younger formation, its upper surface has suffered extensive erosion, and the present thickness therefore falls short of the original. The figures given above may not be too great for the latter. _The Lower Magnesian limestone._--The conditions of sedimentation finally changed in the area under consideration. When the sand of the sandstone was being deposited, adjacent lands were the source whence the sediments were chiefly derived. The evidence that the region was sinking while the sand was being deposited shows that the land masses which were supplying the sand, were becoming progressively smaller. Ultimately the sand ceased to be washed out to the region here described, either because the water became too deep[3] or because the source of supply was too distant. When these relations were brought about, the conditions were favorable for the deposition of sediments which were to become limestone. These sediments consisted chiefly of the shells of marine life, together with an unknown amount of lime carbonate precipitated from the waters of the sea. The limestone contains no coarse, and but little fine material derived from the land, and the surfaces of its layers are rarely if ever ripple-marked. The materials of which it is made must therefore have been laid down in quiet waters which were essentially free from land-derived sediments. The depth of the water in which it was deposited was not, however, great, for the fossils are not the remains of animals which lived in abysmal depths. [3] A few hundred feet would suffice. The deposition of limestone sediments following the deposition of the Potsdam sands, does not necessarily mean that there was more or different marine life while the younger formation was making, but only that the shells, etc., which before had been mingled with the sand, making fossiliferous sandstone, were now accumulated essentially free from land-derived sediment, and therefore made limestone. Like the sandstone beneath, the limestone formation has a wide distribution outside the area here under discussion, showing that conditions similar to those of central Wisconsin were widely distributed at this time. The beds of limestone are conformable on those of the sandstone, and the conformable relations of the two formations indicate that the deposition of the upper followed that of the lower, without interruption. The thickness of the Lower Magnesian limestone varies from less than 100 to more than 200 feet, but in this region its thickness is nearer the lesser figure than the larger. The limestone is now present only in the eastern and southern parts of the area, though it originally covered the whole area. _The St. Peters sandstone._--Overlying the Lower Magnesian limestone at a few points, are seen remnants of St. Peters sandstone. The constitution of this formation shows that conditions of sedimentation had again changed, so that sand was again deposited where the conditions had been favorable to the deposition of limestone but a short time before. This formation has been recognized at but two places (d and e) within the area shown on Plate XXXVII, but the relations at these two points are such as to lead to the conclusion that the formation may once have covered the entire region. This sandstone formation is very like the sandstone below. Its materials doubtless came from the lands which then existed. The formation is relatively thin, ranging from somewhat below to somewhat above 100 feet. The change from the deposition of limestone sediments to sand may well have resulted from the shoaling of the waters, which allowed the sand to be carried farther from shore. Rise of the land may have accompanied the shoaling of the waters, and the higher lands would have furnished more and coarser sediments to the sea. _Younger beds._--That formations younger than the St. Peters sandstone once overlaid this part of Wisconsin is almost certain, though no remnants of them now exist. Evidence which cannot be here detailed[4] indicates that sedimentation about the quartzite ridges went on not only until the irregularities of surface were evened up, but until even the highest peaks of the quartzite were buried, and that formations as high in the series as the Niagara limestone once overlay their crests. Before this condition was reached, the quartzite ridges had of course ceased to be islands, and at the same time had ceased to be a source of supply of sediments. The aggregate thickness of the Paleozoic beds in the region, as first deposited, was probably not less than 1,500 feet, and it may have been much more. This thickness would have buried the crests of the quartzite ridges under several hundred feet of sediment (see Fig. 11). [4] Jour. of Geol., Vol. III (pp. 655-67). [Illustration: Fig. 11.--The geological formations of southern Wisconsin in the order of their occurrence. Not all of these are found about Devil's lake.] It is by no means certain that south central Wisconsin was continuously submerged while this thick series of beds was being deposited. Indeed, there is good reason to believe that there was at least one period of emergence, followed, after a considerable lapse of time, by re-submergence and renewed deposition, before the Paleozoic series of the region was complete. These movements, however, had little effect on the geography of the region. Finally the long period of submergence, during which several changes in sedimentation had taken place, came to an end, and the area under discussion was again converted into land. _Time involved._--Though it cannot be reduced to numerical terms, the time involved in the deposition of these several formations of the Paleozoic must have been very long. It is probably to be reckoned in millions of years, rather than in denominations of a lower order. _Climatic conditions._--Little is known concerning the climate of this long period of sedimentation. Theoretical considerations have usually been thought to lead to the conclusion that the climate during this part of the earth's history was uniform, moist, and warm; but the conclusion seems not to be so well founded as to command great confidence. _The uplift._--After sedimentation had proceeded to some such extent as indicated, the sea again retired from central Wisconsin. This may have been because the sea bottom of this region rose, or because the sea bottom in other places was depressed, thus drawing off the water. The topography of this new land, like the topography of those portions of the sea bottom which are similarly situated, must have been for the most part level. Low swells and broad undulations may have existed, but no considerable prominences, and no sudden change of slope. The surface was probably so flat that it would have been regarded as a level surface had it been seen. The height to which the uplift carried the new land surface at the outset must ever remain a matter of conjecture. Some estimate may be made of the amount of uplift which the region has suffered since the beginning of this uplift, but it is unknown how much took place at this time, and how much in later periods of geological history. The new land surface at once became the site of new activities. All processes of land erosion at once attacked the new surface, in the effort to carry its materials back to the sea. The sculpturing of this plain, which, with some interruption, has continued to the present day, has given the region the chief elements of its present topography. But before considering the special history of erosion in this region, it may be well to consider briefly the general principles and processes of land degradation. CHAPTER III. GENERAL OUTLINE OF RAIN AND RIVER EROSION. _Elements of erosion._--The general process of subaerial erosion is divisible into the several sub-processes of weathering, transportation, and corrasion.[5] [5] There is an admirable exposition of this subject in Gilbert's "Henry Mountains." _Weathering_ is the term applied to all those processes which disintegrate and disrupt exposed surfaces of rock. It is accomplished chiefly by solution, changes in temperature, the wedge-work of ice and roots, the borings of animals, and such chemical changes as surface water and air effect. The products of weathering are transported by the direct action of gravity, by glaciers, by winds, and by running water. Of these the last is the most important. _Corrasion_ is accomplished chiefly by the mechanical wear of streams, aided by the hard fragments such as sand, gravel and bowlders, which they carry. The solution effected by the waters of a stream may also be regarded as a part of corrasion. Under ordinary circumstances solution by streams is relatively unimportant, but where the rock is relatively soluble, and where conditions are not favorable for abrasion, solution may be more important than mechanical wear. So soon as sea bottom is raised to the estate of land, it is attacked by the several processes of degradation. The processes of weathering at once begin to loosen the material of the surface if it be solid; winds shift the finer particles about, and with the first shower transportation by running water begins. Weathering prepares the material for transportation and transportation leads to corrasion. Since the goal of all material transported by running water is the sea, subaerial erosion means degradation of the surface. _Erosion without valleys._--In the work of degradation the valley becomes the site of greatest activity, and in the following pages especial attention is given to the development of valleys and to the phases of topography to which their development leads. If a new land surface were to come into existence, composed of materials which were perfectly homogeneous, with slopes of absolute uniformity in all directions, and if the rain, the winds and all other surface agencies acted uniformly over the entire area, valleys would not be developed. That portion of the rainfall which was not evaporated and did not sink beneath the surface, would flow off the land in a sheet. The wear which it would effect would be equal in all directions from the center. If the angle of the slope were constant from center to shore, or if it increased shoreward, the wear effected by this sheet of water would be greatest at the shore, because here the sheet of flowing water would be deepest and swiftest, and therefore most effective in corrasion. _The beginning of a valley._--But land masses as we know them do not have equal and uniform slopes to the sea in all directions, nor is the material over any considerable area perfectly homogeneous. Departure from these conditions, even in the smallest degree, would lead to very different results. That the surface of newly emerged land masses would, as a rule, not be rough, is evident from the fact that the bottom of the sea is usually rather smooth. Much of it indeed is so nearly plane that if the water were withdrawn, the eye would scarcely detect any departure from planeness. The topography of a land mass newly exposed either by its own elevation or by the withdrawal of the sea, would ordinarily be similar to that which would exist in the vicinity of Necedah and east of Camp Douglas, if the few lone hills were removed, and the very shallow valleys filled. Though such a surface would seem to be moderately uniform as to its slopes, and homogeneous as to its material, neither the uniformity nor the homogeneity are perfect, and the rain water would not run off in sheets, and the wear would not be equal at all points. Let it be supposed that an area of shallow sea bottom is raised above the sea, and that the elevation proceeds until the land has an altitude of several hundred feet. So soon as it appears above the sea, the rain falling upon it begins to modify its surface. Some of the water evaporates at once, and has little effect on the surface; some of it sinks beneath the surface and finds its way underground to the sea; and some of it runs off over the surface and performs the work characteristic of streams. So far as concerns modifications of the surface, the run-off is the most important part. The run-off of the surface would tend to gather in the depressions of the surface, however slight they may be. This tendency is shown on almost every hillside during and after a considerable shower. The water concentrated in the depressions is in excess of that flowing over other parts of the surface, and therefore flows faster. Flowing faster, it erodes the surface over which it flows more rapidly, and as a result the initial depressions are deepened, and _washes_ or _gullies_ are started. Should the run-off not find irregularities of slope, it would, at the outset, fail of concentration; but should it find the material more easily eroded along certain lines than along others, the lines of easier wear would become the sites of greater erosion. This would lead to the development of gullies, that is, to irregularities of slope. Either inequality of slope or material may therefore determine the location of a gully, and one of these conditions is indispensable. Once started, each wash or gully becomes the cause of its own growth, for the gully developed by the water of one shower, determines greater concentration of water during the next. Greater concentration means faster flow, faster flow means more rapid wear, and this means corresponding enlargement of the depression through which the flow takes place. The enlargement effected by successive showers affects a gully in all dimensions. The water coming in at its head carries the head back into the land (head erosion), thus lengthening the gully; the water coming in at its sides wears back the lateral slopes, thus widening it; and the water flowing along its bottom deepens it. Thus gullies grow to be ravines, and farther enlargement by the same processes converts ravines into valleys. A river valley therefore is often but a gully grown big. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XIII. FIG. 1. A very young valley. Illustration: FIG. 2. A valley in a later stage of development. Illustration: FIG. 3. Young valleys.] _The course of a valley._--In the lengthening of a gully or valley headward, the growth will be in the direction of greatest wear. Thus in Plate XIII, Fig. 1, if the water coming in at the head of the gully effects most wear in the direction a, the head of the gully will advance in that direction; if there be most wear in the direction b or c, the head will advance toward one of these points. The direction of greatest wear will be determined either by the slope of the surface, or by the nature of the surface material. The slope may lead to the concentration of the entering waters along one line, and the surface material may be less resistant in one direction than in another. If these factors favor the same direction of head-growth, the lengthening will be more rapid than if but one is favorable. If there be more rapid growth along two lines, as b and c, Plate XIII, Fig. 1, than between them, two gullies may develop (Plate XIII, Fig. 2). The frequent and tortuous windings common to ravines and valleys are therefore to be explained by the inequalities of slope or material which affected the surface while the valley was developing. _Tributary valleys._--Following out this simple conception of valley growth, we have to inquire how a valley system (a main valley and its tributaries) is developed. The conditions which determine the location and development of gullies in a new land surface, determine the location and development of tributary gullies. In flowing over the lateral slopes of a gully or ravine, the water finds either slope or surface material failing of uniformity. Both conditions lead to the concentration of the water along certain lines, and concentration of flow on the slope of an erosion depression, be it valley or gully, leads to the development of a tributary depression. In its growth, the tributary repeats, in all essential respects, the history of its main. It is lengthened headward by water coming in at its upper end, is widened by side wash, and deepened by the downward cutting of the water which flows along its axis. The factors controlling its development are the same as those which controlled the valley to which it is tributary. There is one peculiarity of the courses of tributaries which deserves mention. Tributaries, as a rule, join their mains with an acute angle up stream. In general, new land surfaces, such as are now under consideration, slope toward the sea. If a tributary gully were to start back from its main at right angles, more water would come in on the side away from the shore, on account of the seaward slope of the land. This would be true of the head of the gully as well as of other portions, and the effect would be to turn the head more and more toward parallelism with the main valley. Local irregularities of surface may, and frequently do, interfere with these normal relations, so that the general course of a tributary is occasionally at right angles to its main. Still more rarely does the general course of a tributary make an acute angle with its main on the down stream side. Local irregularities of surface determine the windings of a tributary, so that their courses for longer or shorter distances may be in violation of the general rule (c, Fig. 43); but on the whole, the valleys of a system whose history has not been interrupted in a region where the surface material is not notably heterogeneous, follow the course indicated above. This is shown by nearly every drainage system on the Atlantic Coastal plain which represents more nearly than any other portion of our continent, the conditions here under consideration. Fig. 12 represents the drainage system of the Mullica river in southern New Jersey and is a type of the Coastal plain river system. _How a valley gets a stream._--Valleys may become somewhat deep and long and wide without possessing permanent streams, though from their inception they have _temporary_ streams, the water for which is furnished by showers or melting snow. Yet sooner or later, valleys come to have permanent streams. How are they acquired? Does the valley find the stream or the stream the valley? For the answer to these questions, a brief digression will be helpful. [Illustration: Fig. 12.--A typical river system of the Coastal plain type.] In cultivated regions, wells are of frequent occurrence. In a flat region of uniform structure, the depth at which well water may be obtained is essentially constant at all points. If holes (wells 1 and 2, Fig. 13) be excavated below this level, water seeps into them, and in a series of wells the water stands at a nearly common level. This means that the sub-structure is full of water up to that level. These relations are illustrated by Fig. 13. The diagram represents a vertical section through a flat region from the surface (s s) down below the bottom of wells. The water stands at the same level in the two cells (1 and 2), and the plane through them, at the surface of the water, is the _ground water level_. If in such a surface a valley were to be cut until its bottom was below the ground water level, the water would seep into it, as it does into the wells; and if the amount were sufficient, a permanent stream would be established. This is illustrated in Fig. 13. The line A A represents the ground water level, and the level at which the water stands in the wells, under ordinary circumstances. The bottom of the valley is below the level of the ground water, and the water seeps into it from either side. Its tendency is to fill the valley to the level A A. But instead of accumulating in the open valley as it does in the enclosed wells, it flows away, and the ground water level on either hand is drawn down. [Illustration: Fig. 13.--Diagram illustrating the relations of ground water to streams.] The level of the ground water fluctuates. It is depressed when the season is dry (A' A'), and raised when precipitation is abundant (A'' A''). When it is raised, the water in the wells rises, and the stream in the valley is swollen. When it falls, the ground water surface is depressed, and the water in the wells becomes lower. If the water surface sinks below the bottom of the wells, the wells "go dry;" if below the bottom of the valley, the valley becomes for the time being, a "dry run." When a well is below the lowest ground-water level its supply of water never fails, and when the valley is sufficiently below the same level, its stream does not cease to flow, even in periods of drought. On account of the free evaporation in the open valley, the valley depression must be somewhat below the level necessary for a well, in order that the flow may be constant. It will be seen that _intermittent_ streams, that is, streams which flow in wet seasons and fail in dry, are intermediate between streams which flow after showers only, and those which flow without interruption. In the figure the stream would become dry if the ground water level sank to A' A'. It is to be noted that a permanent stream does not normally precede its valley, but that the valley, developed through gully-hood and ravine-hood to valley-hood by means of the temporary streams supplied by the run-off of occasional showers, _finds a stream_, just as diggers of wells find water. The case is not altered if the stream be fed by springs, for the valley finds the spring, as truly as the well-digger finds a "vein" of water. _Limits of a valley._--So soon as a valley acquires a permanent stream, its development goes on without the interruption to which it was subject while the stream was intermittent. The permanent stream, like the temporary one which preceded it, tends to deepen and widen its valley, and, under certain conditions, to lengthen it as well. The means by which these enlargements are affected are the same as before. There are limits, however, in length, depth, and width, beyond which a valley may not go. No stream can cut below the level of the water into which it flows, and it can cut to that level only at its outlet. Up stream from that point, a gentle gradient will be established over which the water will flow without cutting. In this condition the stream is _at grade_. Its channel has reached _baselevel_, that is, the level to which the stream can wear its bed. This grade is, however, not necessarily permanent, for what was baselevel for a small stream in an early stage of its development, is not necessarily baselevel for the larger stream which succeeds it at a later time. Weathering, wash, and lateral corrasion of the stream continue to widen the valley after it has reached baselevel. The bluffs of valleys are thus forced to recede, and the valley is widened at the expense of the upland. Two valleys widening on opposite sides of a divide, narrow the divide between them, and may ultimately wear it out. When this is accomplished, the two valleys become one. The limit to which a valley may widen on either side is therefore its neighboring valley, and since, after two valleys have become one by the elimination of the ridge between them, there are still valleys on either hand, the final result of the widening of all valleys must be to reduce all the area which they drain to baselevel. As this process goes forward, the upper flat into which the valleys were cut is being restricted in area, while the lower flats developed by the streams in the valley bottoms are being enlarged. Thus the lower flats grow at the expense of the higher. There are also limits in length which a valley may not exceed. The head of any valley may recede until some other valley is reached. The recession may not stop even there, for if, on opposite sides of a divide, erosion is unequal, as between 1A and 1B, Fig. 14, the divide will be moved toward the side of less rapid erosion, and it will cease to recede only when erosion on the two sides becomes equal (4A and 4B). In homogeneous material this will be when the slopes on the two sides are equal. [Illustration: Fig. 14.--Diagram showing the shifting of a divide. The slopes 1A and 1B are unequal. The steeper slope is worn more rapidly and the divide is shifted from 1 to 4, where the two slopes become equal and the migration of the divide ceases.] It should be noted that the lengthening of a valley headward is not normally the work of the permanent stream, for the permanent stream begins some distance below the head of the valley. At the head, therefore, erosion goes on as at the beginning, even after a permanent stream is acquired. Under certain circumstances, the valley may be lengthened at its debouchure. If the detritus carried by it is deposited at its mouth, or if the sea bottom beyond that point rise, the land may be extended seaward, and over this extension the stream will find its way. Thus at their lower, as well as at their upper ends, both the stream and its valley may be lengthened. _A cycle of erosion._--If, along the borders of a new-born land mass, a series of valleys were developed, essentially parallel to one another, they would constitute depressions separated by elevations, representing the original surface not yet notably affected by erosion (see Plate XIV, Fig. 1). These inter-valley areas might at first be wide or narrow, but in process of time they would necessarily become narrow, for, once, a valley is started, all the water which enters it from either side helps to wear back its slopes, and the wearing back of the slopes means the widening of the valleys on the one hand and the narrowing of the inter-valley ridges on the other. Not only would the water running over the slopes of a valley wear back its walls, but many other processes conspire to the same end. The wetting and drying, the freezing and the thawing, the roots of plants and the borings of animals, all tend to loosen the material on the slopes or walls of the valleys, and gravity helps the loosened material to descend. Once in the valley bottom, the running water is likely to carry it off, landing it finally in the sea. Thus the growth of the valley is not the result of running water alone, though this is the most important single factor in the process. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XIV. FIG. 1. The same valleys as shown in Plate XIII, Fig. 3, in a later stage of development. Illustration: FIG. 2. Same valleys as shown in Fig. 1, in a still later stage of development.] Even if valleys developed no tributaries, they would, in the course of time, widen to such an extent as to nearly obliterate the intervening ridges. The surface, however, would not easily be reduced to perfect flatness. For a long time at least there would remain something of slope from the central axis of the former inter-stream ridge, toward the streams on either hand; but if the process of erosion went on for a sufficiently long period of time, the inter-stream ridge would be brought very low, and the result would be an essentially flat surface between the streams, much below the level of the old one. The first valleys which started on the land surface (see Plate XIII, Fig. 3) would be almost sure to develop numerous tributaries. Into tributary valleys water would flow from their sides and from their heads, and as a result they would widen and deepen and lengthen just as their mains had done before them. By lengthening headward they would work back from their mains some part, or even all of the way across the divides separating the main valleys. By this process, the tributaries cut the divides between the main streams into shorter cross-ridges. With the development of tributary valleys there would be many lines of drainage instead of two, working at the area between two main streams. The result would be that the surface would be brought low much more rapidly, for it is clear that many valleys within the area between the main streams, widening at the same time, would diminish the aggregate area of the upland much more rapidly than two alone could do. The same thing is made clear in another way. It will be seen (Plate XIV, Figs. 1 and 2) that the tributaries would presently dissect an area of uniform surface, tending to cut it into a series of short ridges or hills. In this way the amount of sloping surface is greatly increased, and as a result, every shower would have much more effect in washing loose materials down to lower levels, whence the streams could carry them to the sea. [Illustration: Fig. 15.--Cross-sections showing various stages of erosion in one cycle.] The successive stages in the process of lowering a surface are suggested by Fig. 15, which represents a series of cross-sections of a land mass in process of degradation. The uppermost section represents a level surface crossed by young valleys. The next lower represents the same surface at a later stage, when the valleys have grown larger, while the third and succeeding sections represent still later stages in the process of degradation. Plate XIII, Fig. 3, and Plate XIV, Figs. 1 and 2, represent in another way the successive stages of stream work in the general process of degradation. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XV. Diagram illustrating how a hard inclined layer of rock becomes a ridge in the process of degradation.] In this manner a series of rivers, operating for a sufficiently long period of time, might reduce even a high land mass to a low level, scarcely above the sea. The new level would be developed soonest near the sea, and the areas farthest from it would be the last--other things being equal--to be brought low. The time necessary for the development of such a surface is known as a _cycle of erosion_, and the resulting surface is a _base-level plain_, that is, a plain as near sea level as river erosion can bring it. At a stage shortly preceding the base-level stage the surface would be a _peneplain_. A peneplain, therefore, is a surface which has been brought toward, but not to base-level. Land surfaces are often spoken of as young or old in their erosion history according to the stage of advancement which has been made toward base-leveling. Thus the Colorado canyon, deep and impressive as it is, is, in terms of erosion, a young valley, for the river has done but a small part of the work which must be done in order to bring its basin to baselevel. _Effects of unequal hardness._--The process of erosion thus sketched would ultimately bring the surface of the land down to base-level, and in case the material of the land were homogeneous, the last points to be reduced would be those most remote from the axes of the streams doing the work of leveling. But if the material of the land were of unequal hardness, those parts which were hardest would resist the action of erosion most effectively. The areas of softer rock would be brought low, and the outcrops of hard rock (Plate XV) would constitute ridges during the later stages of an erosion cycle. If there were bodies of hard rock, such as the Baraboo quartzite, surrounded by sandstone, such as the Potsdam, the sandstone on either hand would be worn down much more readily than the quartzite, and in the course of degradation the latter would come to stand out prominently. The region in the vicinity of Devil's lake is in that stage of erosion in which the quartzite ridges are conspicuous (Plate XXXVII). The less resistant sandstone has been removed from about them, and erosion has not advanced so far since the isolation of the quartzite ridges as to greatly lower their crests. The harder strata are at a level where surface water can still work effectively, even though slowly, upon them, and in spite of their great resistance they will ultimately be brought down to the common level. It will be seen that, from the point of view of subaerial erosion, a base-level plain is the only land surface which is in a condition of approximate stability. _Falls and rapids._--If in lowering its channel a stream crosses one layer of rock much harder than the next underlying, the deepening will go on more rapidly on the less resistant bed. Where the stream crosses from the harder to the less hard, the gradient is likely to become steep, and a rapids is formed. These conditions are suggested in Fig. 16 which represents the successive profiles (a b, a c, d e, f e, g e, and h e) of a stream crossing from a harder to a softer formation. Below the point a the stream is flowing over rock which is easily eroded, while above that point its course is over a harder formation. Just below a (profile a b) the gradient has become so steep that there are rapids. Under these conditions, erosion is rapid just beyond the crossing of the hard layer, and the gradient becomes higher and higher. When the steep slope of the rapids approaches verticality, the rapids become a _fall_ (profile a c). [Illustration: Fig. 16.--Diagram to illustrate the development of a rapid and fall. The upper layer is harder than the strata below. The successive profiles of the stream below the hard layer are represented by the lines a b, a c, d e, f e, g e, and h e.] As the water falls over the precipitous face and strikes upon the softer rock below, part of it rebounds against the base of the vertical face (Fig. 16). The result of wear at this point is the undermining of the hard layer above, and sooner or later, portions of it will fall. This will occasion the recession of the fall (profile d e and f e). As the fall recedes, it grows less and less high. When the recession has reached the point i, or, in other words, when the gradient of the stream below the fall crosses the junction of the beds of unequal hardness, as it ultimately must, effective undermining ceases, and the end of the fall is at hand. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XVI. Skillett Falls, in the Potsdam formation, three miles southwest of Baraboo. The several small falls are occasioned by slight inequalities in the hardness of the layers.] When the effective undercutting ceases because the softer bed is no longer accessible, the point of maximum wear is transferred to the top of the hard bed just where the water begins to fall (g, Fig. 16). The wear here is no greater than before, though it is greater relatively. The relatively greater wear at this point destroys the verticality of the face, converting it into a steep slope. When this happens, the fall is a thing of the past, and rapids succeed. With continued flow the bed of the rapids becomes less and less steep, until it is finally reduced to the normal gradient of the stream (h e), when the rapids disappear. When thin layers of rock in a stream's course vary in hardness, softer beds alternating with harder ones, a series of falls such as shown in Plate XVI, may result. As they work up stream, these falls will be obliterated one by one. Thus it is seen that falls and rapids are not permanent features of the landscape. They belong to the younger period of a valley's history, rather than to the older. They are marks of topographic youth. _Narrows._--Where a stream crosses a hard layer or ridge of rock lying between softer ones, the valley will not widen so rapidly in the hard rock as above and below. If the hard beds be vertical, so that their outcrop is not shifted as the degradation of the surface proceeds, a notable constriction of the valley results. Such a constriction is a _narrows_. The Upper and Lower narrows of the Baraboo (Plate IV) are good examples of the effect of hard rock on the widening of a valley. _Erosion of folded strata._--The processes of river erosion would not be essentially different in case the land mass upon which erosion operated were made of tilted and folded strata. The folds would, at the outset, determine the position of the drainage lines, for the main streams would flow in the troughs (synclines) between the folds (anticlines). Once developed, the streams would lower their beds, widen their valleys, and lengthen their courses, and in the long process of time they would bring the area drained nearly to sea-level, just as in the preceding case. It was under such conditions that the general processes of subaerial erosion operated in south central Wisconsin, after the uplift of the quartzite and before the deposition of the Potsdam sandstone. It was then that the principal features of the topography of the quartzite were developed. In regions of folded strata, certain beds are likely to be more resistant than others. Where harder beds alternate with softer, the former finally come to stand out as ridges, while the outcrops of the latter mark the sites of the valleys. Such alternations of beds of unequal resistance give rise to various peculiarities of drainage, particularly in the courses of tributaries. These peculiarities find no illustration in this region and are not here discussed. _Base-level plains and peneplains._--It is important to notice that a plane surface (base-level) developed by streams could only be developed at elevations but slightly above the sea, that is, at levels at which running water ceases to be an effective agent of erosion; for so long as a stream is actively deepening its valley, its tendency is to roughen the area which it drains, not to make it smooth. The Colorado river, flowing through high land, makes a deep gorge. All the streams of the western plateaus have deep valleys, and the manifest result of their action is to roughen the surface; but given time enough, and the streams will have cut their beds to low gradients. Then, though deepening of the valleys will cease, widening will not, and inch by inch and shower by shower the elevated lands between the valleys will be reduced in area, and ultimately the whole will be brought down nearly to the level of the stream beds. This is illustrated by Fig. 15. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XVII. A group of mounds on the plain southwest from Camp Douglas. The base-level surface is well shown, and above it rise the remnants of the higher plain from which the lower was reduced.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XVIII. Castle Rock near Camp Douglas. In this view the relation of the erosion remnant to the extensive base-leveled surface is well shown.] It is important to notice further that if the original surface on which erosion began is level, there is no stage intermediate between the beginning and the end of an erosion cycle, when the surface is again level, or nearly so, though in the stage of a cycle next preceding the last--the peneplain stage (fourth profile, Fig. 15)--the surface approaches flatness. It is also important to notice that when streams have cut a land surface down to the level at which they cease to erode, that surface will still possess some slight slope, and that to seaward. No definite degree of slope can be fixed upon as marking a base-level. The angle of slope which would practically stop erosion in a region of slight rainfall would be great enough to allow of erosion if the precipitation were greater. All that can be said, therefore, is that the angle of slope must be low. The Mississippi has a fall of less than a foot per mile for some hundreds of miles above the gulf. A small stream in a similar situation would have ceased to lower its channel before so low a gradient was reached. The nearest approach to a base-leveled region within the area here under consideration is in the vicinity of Camp Douglas and Necedah (see Plate I). This is indeed one of the best examples of a base-leveled plain known. Here the broad plain, extending in some directions as far as the eye can reach, is as low as it could be reduced by the streams which developed it. The erosion cycle which produced the plain was, however, not completed, for above the plain rise a few conspicuous hills (Plates XVII and XVIII, and Fig. 17), and to the west of it lie the highlands marking the level from which the low plain was reduced. Where a region has been clearly base-leveled, isolated masses or ridges of resistant rock may still stand out conspicuously above it. The quartzite hill at Necedah is an example. Such hills are known as _monadnocks_. This name was taken from Mount Monadnock which owes its origin to the removal of the surrounding less resistant beds. The name has now become generic. Many of the isolated hills on the peneplain east of Camp Douglas are perhaps due to superior resistance, though the rock of which they are composed belongs to the same formation as that which has been removed. [Illustration: Fig. 17.--Sketch, looking northwest from Camp Douglas.] CHARACTERISTICS OF VALLEYS AT VARIOUS STAGES OF DEVELOPMENT. In the early stages of its development a depression made by erosion has steep lateral slopes, the exact character of which is determined by many considerations. Its normal cross-section is usually described as V-shaped (Fig. 18). In the early stages of its development, especially if in unconsolidated material, the slopes are normally convex inward. If cut in solid rock, the cross section may be the same, though many variations are likely to appear, due especially to the structure of the rock and to inequalities of hardness. If a stream be swift enough to carry off not only all the detritus descending from its slopes, but to abrade its bed effectively besides, a steep-sided gorge develops. If it becomes deep, it is a canyon. For the development of a canyon, the material of the walls must be such as is capable of standing at a high angle. A canyon always indicates that the down-cutting of a stream keeps well ahead of the widening. [Illustration: Fig. 18.--Diagrammatic cross-section of a young valley.] Of young valleys in loose material (drift) there are many examples in the eastern portion of the area here described. Shallow canyons or gorges in rock are also found. The gorge of Skillett creek at and above the Pewit's nest about three miles southwest from Baraboo, the gorge of Dell creek two miles south of Kilbourn City, and the Dalles of the Wisconsin at Kilbourn City may serve as illustrations of this type of valley. [Illustration: Fig. 19.--Diagrammatic profile of a young valley.] The profile of a valley at the stage of its development corresponding to the above section is represented diagrammatically by the curve A B in Fig. 19. The sketch (Pl. XIX, Fig. 1) represents a bird's-eye view of a valley in the same stage of development. [Illustration: Fig. 20.--Diagrammatic cross-section of a valley at a stage corresponding with that shown in Plate XIX, Fig. 2.] At a stage of development later than that represented by the V-shaped cross-section, the corresponding section is U-shaped, as shown in Fig. 20. The same form is sketched in Plate XIX, Fig. 2. This represents a stage of development where detritus descending the slopes is not all carried away by the stream, and where the valley is being widened faster than it is deepened. Its slopes are therefore becoming gentler. The profile of the valley at this stage would be much the same as that in the preceding, except that the gradient in the lower portion would be lower. Still later the cross section of the valley assumes the shape shown in Fig. 21, and in perspective the form sketched in Plate XX, Fig. 1. This transformation is effected partly by erosion, and partly by deposition in the valley. When a stream has cut its valley as low as conditions allow, it becomes sluggish. A sluggish stream is easily turned from side to side, and, directed against its banks, it may undercut them, causing them to recede at the point of undercutting. In its meanderings, it undercuts at various points at various times, and the aggregate result is the widening of the valley. By this process alone the stream would develop a flat grade. At the same time all the drainage which comes in at the sides tends to carry the walls of the valley farther from its axis. [Illustration: Fig. 21.--Diagrammatic cross-section of a valley at a stage later than that shown in Fig. 20.] A sluggish stream is also generally a depositing stream. Its deposits tend to aggrade (build up) the flat which its meanderings develop. When a valley bottom is built up, it becomes wider at the same time, for the valley is, as a rule, wider at any given level than at any lower one. Thus the U-shaped valley is finally converted into a valley with a flat bottom, the flat being due in large part to erosion, and in smaller part to deposition. Under exceptional circumstances the relative importance of these two factors may be reversed. It will be seen that the cross-section of a valley affords a clue to its age. A valley without a flat is young, and increasing age is indicated by increasing width. Valleys illustrating all stages of development are to be found in the Devil's lake region. The valley of Honey creek southwest of Devil's lake may be taken as an illustration of a valley at an intermediate stage of development, while examples of old valleys are found in the flat country about Camp Douglas and Necedah. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XIX. FIG. 1. Sketch of a valley at the stage of development corresponding to the cross section shown in Fig. 18. Illustration: FIG. 2. Sketch of a valley at the stage of development corresponding to the cross section shown in Fig. 20.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XX. FIG. 1. Sketch of a part of a valley at the stage of development corresponding to the cross section shown in Fig 21. Illustration: FIG. 2. Sketch of a section of the Baraboo valley.] _Transportation and Deposition._ Sediment is carried by streams in two ways: (1) by being rolled along the bottom, and (2) by being held in suspension. Dissolved mineral matter (which is not sediment) is also carried in the water. By means of that rolled along the bottom and carried in suspension, especially the former, the stream as already stated abrades its bed. The transporting power of a stream of given size varies with its velocity. Increase in the declivity or the volume of a stream increases its velocity and therefore its transportive power. The transportation effected by a stream is influenced (1) by its transporting power, and (2) by the size and amount of material available for carriage. Fine material is carried with a less expenditure of energy than an equal amount of coarse. With the same expenditure of energy therefore a stream can carry a greater amount of the former than of the latter. Since the transportation effected by a stream is dependent on its gradient, its size, and the size and amount of material available, it follows that when these conditions change so as to decrease the carrying power of the river, deposition will follow, if the stream was previously fully loaded. In other words, a stream will deposit when it becomes overloaded. Overloading may come about in the following ways: (1) By decrease in gradient, checking velocity and therefore carrying power; (2) by decrease in amount of water, which may result from evaporation, absorption, etc.; (3) by change in the shape of the channel, so that the friction of flow is increased, and therefore the force available for transportation lessened; (4) by lateral drainage bringing in more sediment than the main stream can carry; (5) by change in the character of the material to which the stream has access; for if it becomes finer, the coarse material previously carried will be dropped, and the fine taken; and (6) by the checking of velocity when a stream flows into a body of standing water. _Topographic forms resulting from stream deposition._--The topographic forms resulting from stream deposition are various. At the bottoms of steep slopes, temporary streams build _alluvial cones_ or _fans_. Along its flood-plain portion, a stream deposits more or less sediment on its flats. The part played by deposition in building a river flat has already been alluded to. A depositing stream often wanders about in an apparently aimless way across its flood plain. At the bends in its course, cutting is often taking place on the outside of a curve while deposition is going on in the inside. The valley of the Baraboo illustrates this process of cutting and building. Fig. 2, Plate XX, is based upon the features of the valley within the city of Baraboo. Besides depositing on its flood-plain, a stream often deposits in its channel. Any obstruction of a channel which checks the current of a loaded stream occasions deposition. In this way "bars" are formed. Once started, the bar increases in size, for it becomes an obstacle to flow, and so the cause of its own growth. It may be built up nearly to the surface of the stream, and in low water, it may become an island by the depression of the surface water. In some parts of its course, as about Merrimac, the Wisconsin river is marked by such islands at low water, and by a much larger number of bars. At their debouchures, streams give up their loads of sediment. Under favorable conditions deltas are built, but delta-building has not entered into the physical history of this region to any notable extent. _Rejuvenation of Streams._ After the development of a base-level plain, its surface would suffer little change (except that effected by underground water) so long as it maintained its position. But if, after its development, a base-level plain were elevated, the old surface in a new position would be subject to a new series of changes identical in kind with those which had gone before. The elevation would give the established streams greater fall, and they would reassume the characteristics of youth. The greater fall would accelerate their velocities; the increased velocities would entail increased erosion; increased erosion would result in the deepening of the valleys, and the deepening of the valleys would lead to the roughening of the surface. But in the course of time, the _rejuvenated_ streams would have cut their valleys as low as the new altitude of the land permitted, that is, to a new base-level. The process of deepening would then stop, and the limit of vertical relief which the streams were capable of developing, would be attained. But the valleys would not stop widening when they stopped deepening, and as they widened, the intervening divides would become narrower, and ultimately lower. In the course of time they would be destroyed, giving rise to a new level surface much below the old one, but developed in the same position which the old one occupied when it originated; that is, a position but little above sea level. If at some intermediate stage in the development of a second base-level plain, say at a time when the streams, rejuvenated by uplift, had brought half the elevated surface down to a new base-level, another uplift were to occur, the half completed cycle would be brought to an end, and a new one begun. The streams would again be quickened, and as a result they would promptly cut new and deeper channels in the bottoms of the great valleys which had already been developed. The topography which would result is suggested by the following diagram (Fig. 22) which illustrates the cross-section which would be found after the following sequence of events: (1) The development of a base-level, A A; (2) uplift, rejuvenation of the streams, and a new cycle of erosion half completed, the new base-level being at B B; (3) a second uplift, bringing the second (incomplete) cycle of erosion to a close, and by rejuvenating the streams, inaugurating the third cycle. As represented in the diagram, the third cycle has not progressed far, being represented only by the narrow valley C. The base-level is now 2-2, and the valley represented in the diagram has not yet reached it. [Illustration: Fig. 22.--Diagram (cross-section), illustrating the topographic effect of rejuvenation by uplift.] [Illustration: Fig. 23.--Normal profile of a valley bottom in a non-mountainous region.] The rejuvenation of a stream shows itself in another way. The normal profile of a valley bottom in a non-mountainous region is a gentle curve, concave upward with gradient increasing from debouchure to source. Such a profile is shown in Fig. 23. Fig. 24, on the other hand, is the profile of a rejuvenated stream. The valley once had a profile similar to that shown in Fig. 23. Below B its former continuation is marked by the dotted line B C. Since rejuvenation the stream has deepened the lower part of its valley, and established there a profile in harmony with the new conditions. The upper end of the new curve has not yet reached beyond B. [Illustration: Fig. 24.--Profile of a stream rejuvenated by uplift.] _Underground Water._ In what has preceded, reference has been made only to the results accomplished by the water which runs off over the surface. The water which sinks beneath it is, however, of no small importance in reducing a land surface. The enormous amount of mineral matter in solution in spring water bears witness to the efficiency of the ground water in dissolving rock, for since the water did not contain the mineral matter when it entered the soil, it must have acquired it below the surface. By this means alone, areas of more soluble rock are lowered below those of less solubility. Furthermore, the water is still active as a solvent agent after a surface has been reduced to so low a gradient that the run-off ceases to erode mechanically. CHAPTER IV. EROSION AND THE DEVELOPMENT OF STRIKING SCENIC FEATURES. The uplift following the period of Paleozoic deposition in south central Wisconsin, inaugurated a period of erosion which, with some interruptions, has continued to the present day. The processes of weathering began as soon as the surface was exposed to the weather, and corrasion by running water began with the first shower which fell upon it. The sediment worn from the land was carried back to the sea, there to be used in the building of still younger formations. The rate of erosion of a land surface depends in large measure upon its height. As a rule, it is eroded rapidly if high, and but slowly if low. It is not known whether the lands of central Wisconsin rose to slight or to great heights at the close of the period of Paleozoic sedimentation. It is therefore not known whether the erosion was at the outset rapid or slow. If the land of southern Wisconsin remained low for a time after the uplift which brought the Paleozoic sedimentation to a close, weathering would have exceeded transportation and corrasion. A large proportion of the rainfall would have sunk beneath the surface, and found its way to the sea by subterranean routes. Loosening of material by alternate wetting and drying, expansion and contraction, freezing and thawing, and by solution, might have gone on steadily, but so long as the land was low, there would have been little run-off, and that little would have flowed over a surface of gentle slopes, and transportation would have been at a minimum. On the whole, the degradation of the land under these conditions could not have advanced rapidly. If, on the other hand, the land was raised promptly to a considerable height, erosion would have been vigorous at the outset. The surface waters would soon have developed valleys which the streams would have widened, deepened and lengthened. Both transportation and corrasion would have been active, and whatever material was prepared for transportation by weathering, and brought into the valleys by side-wash, would have been hurried on its way to the sea, and degradation would have proceeded rapidly. _Establishment of drainage._--Valleys were developed in this new land surface according to the principles already set forth. Between the valleys there were divides, which became higher as the valleys became deeper, and narrower as the valleys widened. Ultimately the ridges were lowered, and many of them finally eliminated in the manner already outlined. The distance below the original surface and that at which the first series of new flats were developed is conjectural, but it would have depended on the height of the land. So far as can now be inferred, the new base-plain toward which the streams cut may have been 400 or 500 feet below the crests of the quartzite ridges. It was at this level that the oldest base-plain of which this immediate region shows evidence, was developed. Had the quartzite ranges not been completely buried by the Paleozoic sediments, they would have appeared as ridges on the new land surface, and would have had a marked influence on the development of the drainage of the newly emerged surface. But as the ranges were probably completely buried, the drainage lines were established regardless of the position of the hard, but buried ridges. When in the process of degradation the quartzite surfaces were reached, the streams encountered a formation far more resistant than the surrounding sandstone and limestone. As the less resistant strata were worn away, the old quartzite ridges, long buried, again became prominent topographic features. In this condition they were "resurrected mountains." If, when erosion on the uplifted surface of Paleozoic rocks began, a valley had been located directly over the buried quartzite ridge, and along its course, it would have been deepened normally until its bottom reached the crest of the hard formation. Then, instead of sinking its valley vertically downward into the quartzite, the stream would have shifted its channel down the slope of the range along the junction of the softer and harder rock (Fig. 25). Such changes occasioned by the nature and position of the rock concerned, are known as _adjustments_. [Illustration: Fig. 25.--Diagram illustrating the hypothetical case of a stream working down the slope of the quartzite range. The successive sections of the valley are suggested by the lines ae, be, ce and de.] Streams which crossed the quartzite ridges on the overlying strata might have held their courses even after their valleys were lowered to the level of the quartzite. Such streams would have developed narrows at the crossing of the quartzite. In so far as there were passes in the quartzite range before the deposition of the Paleozoic beds, they were filled during the long period of sedimentation, to be again cleared out during the subsequent period of erosion. The gap in the South range now occupied by the lake was a narrows in a valley which existed, though perhaps not to its present depth, before the Potsdam sandstone was deposited. It was filled when the sediments of that formation were laid down, to be again opened, and perhaps deepened, in the period of erosion which followed the deposition of the Paleozoic series. During the earliest period of erosion of which there is positive evidence, after the uplift of the Paleozoic beds, the softer formations about the quartzite were worn down to a level 400 or 500 feet below the crests of the South quartzite range. At this lower level, an approximate plain, a peneplain, was developed, the level of which is shown by numerous hills, the summits of which now reach an elevation of from 1,000 to 1,100 feet above the sea. At the time of its development, this peneplain was but little above sea level, for this is the only elevation at which running water can develop such a plain. Above the general level of this plain rose the quartzite ranges as elongate monadnocks, the highest parts of which were fully 500 feet above the plain. A few other points in the vicinity failed to be reduced to the level of the peneplain. The 1,320 foot hill (d, Plate XXXVII), one and one-half miles southeast of the Lower narrows, and Gibraltar Rock (e, same Plate), two miles southeast of Merrimac, rose as prominences above it. It is possible that these crests are remnants of a base-level plain older than that referred to above. If while the quartzite remained much as now, the valleys in the sandstone below 1,000 or 1,100 feet were filled, the result would correspond in a general way to the surface which existed in this region when the first distinctly recognizable cycle of erosion was brought to a close. Above the undulating plain developed in the sandstone and limestone, the main quartzite ridge would have risen as a conspicuous ridge 400 to 500 feet. This cycle had not been completed, that is, the work of base-leveling had not been altogether accomplished, when the peneplain was elevated, and the cycle, though still incomplete, brought to a close. By the uplift, the streams were rejuvenated, and sunk their valleys into the elevated peneplain. Thus a new cycle of erosion was begun, and the uplifted peneplain was dissected by the quickened streams which sank their valleys promptly into the slightly resistant sandstone. At their new base-level, they ultimately developed new flats. This cycle of erosion appears to have advanced no farther than to the development of wide flats along the principal streams, such as the Wisconsin and the Baraboo, and narrow ones along the subordinate water courses, when it was interrupted. Along the main streams the new flats were at a level which is now from 800 to 900 feet above the sea, and 700 to 800 feet below the South quartzite range. It was at this time that the plains about Camp Douglas and Necedah, already referred to, were developed. During this second incomplete cycle, the quartzite ranges, resisting erosion, came to stand up still more prominently than during the first. The interruption of this cycle was caused by the advent of the glacial period which disturbed the normal course of erosion. This period was accompanied and followed by slight changes of level which also had their influence on the streams. The consideration of the effects of glaciation and of subsequent river erosion are postponed, but it may be stated that within the area which was glaciated the post-glacial streams have been largely occupied in removing the drift deposited by the ice from the preglacial valleys, or in cutting new valleys in the drift. The streams outside the area of glaciation were less seriously disturbed. At levels other than those indicated, partial base-levels are suggested, and although less well marked in this region, they might, in the study of a broader area, bring out a much more complicated erosion history. As already suggested, one cycle may have preceded that the remnants of which now stand 1,000-1,100 feet above sea level, and another may have intervened between this and that marked by the 800 to 900 foot level. From the foregoing it is clear that the topography of the region is, on the whole, an erosion topography, save for certain details in its eastern portion. The valleys differ in form and in size, with their age, and with the nature of the material in which they are cut; while the hills and ridges differ with varying relations to the streams, and with the nature of the material of which they are composed. _Striking Scenic Features._ In a region so devoid of striking scenery as the central portion of the Mississippi basin, topographic features which would be passed without special notice in regions of greater relief, become the objects of interest. But in south central Wisconsin there are various features which would attract attention in any region where the scenery is not mountainous. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXI. Cleopatra's Needle. West Bluff of Devil's Lake.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXII. Turk's Head. West Bluff of Devil's Lake.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXIII. Devil's Doorway. East of Devil's Lake.] On the bluffs at Devil's lake there are many minor features which are sure to attract the attention of visitors. Such are "Cleopatra's Needle" (Plate XXI), "Turk's Head" (Plate XXII), and the "Devil's Doorway" (Plate XXIII). These particular forms have resulted from the peculiar weathering of the quartzite. The rock is affected by several systems of vertical or nearly vertical joint planes (cracks), which divide the whole formation into a series of vertical columns. There are also horizontal and oblique planes of cleavage dividing the columns, so that the great quartzite pile may be said to be made up of a series of blocks, which are generally in contact with one another. The isolated pillars and columns which have received special names have been left as they now stand by the falling away of the blocks which once surrounded them. They themselves must soon follow. The great talus slopes at the base of the bluffs, such as those on the west side of the lake and on the East bluff near its southeast corner, Plate XXIV, are silent witnesses of the extent to which this process has already gone. The blocks of rock of which they are composed have been loosened by freezing water, by the roots of trees, and by expansion and contraction due to changing temperature, and have fallen from their former positions to those they now occupy. Their descent, effected by gravity directly, is, it will be noted, the first step in their journey to the sea, the final resting place of all products of land degradation. _The Baraboo bluffs._--Nowhere in southern Wisconsin, or indeed in a large area adjacent to it, are there elevations which so nearly approach mountains as the ranges of quartzite in the vicinity of Baraboo and Devil's lake. So much has already been said of their history that there is need for little further description. Plate IV gives some idea of the appearance of the ranges. The history of the ranges, already outlined, involves the following stages: (1) The deposition of the sands in Huronian time; (2) the change of the sand to sandstone and the sandstone to quartzite; (3) the uplift and deformation of the beds; (4) igneous intrusions, faulting, crushing, and shoaring, with the development of schists accompanying the deformation; (5) a prolonged period of erosion during which the folds of quartzite were largely worn away, though considerable ridges, the Huronian mountains of early Cambrian times, still remained high above their surroundings; (6) the submergence of the region, finally involving even the crests of the ridges of quartzite; (7) a protracted period of deposition during which the Potsdam sandstone and several later Paleozoic formations were laid down about, and finally over, the quartzite, burying the mountainous ridges; (8) the elevation of the Paleozoic sea-bottom, converting it into land; (9) a long period of erosion, during which the upper Paleozoic beds were removed, and the quartzite re-discovered. Being much harder than the Paleozoic rocks, the quartzite ridges again came to stand out as prominent ridges, as the surrounding beds of relatively slight resistance were worn away. They are "resurrected" mountains, though not with the full height which they had in pre-Cambrian time, for they are still partially buried by younger beds. _The narrows in the quartzite._--There are four narrows or passes in the quartzite ridges, all of which are rather striking features. One of them is in the South range, one in the North range near its eastern end, while the others are in an isolated area of quartzite at Ablemans which is really a continuation of the North range. Two of these narrows are occupied by the Baraboo river, one by Narrows creek, and the fourth by Devil's lake. From Ablemans to a point several miles east of Baraboo, the Baraboo river flows through a capacious valley. Where it crosses the North range, six miles or more north of east of Baraboo, the broad valley is abruptly constricted to a narrow pass with precipitous sides, about 500 feet high (c, Plate XXXVII). This constriction is the Lower narrows, conspicuous from many points on the South range, and from the plains to the north. Beyond the quartzite, the valley again opens out into a broad flat. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXIV. Talus slope on the east bluff of Devil's lake.] Seen from a distance, the narrows has the appearance of an abrupt notch in the high ridge (Plate IV). Seen at closer range, the gap is still more impressive. It is in striking contrast with the other narrows in that there are no talus accumulations at the bases of the steep slopes, and in that the slopes are relatively smooth and altogether free from the curious details of sculpture seen in the other gaps where the slopes are equally steep. The Upper narrows of the Baraboo at Ablemans (b, Plate II) is in some ways similar to the Lower, though less conspicuous because less deep. Its slopes are more rugged, and piles of talus lie at their bases as at Devil's lake. This narrows also differs from the Lower in that the quartzite on one side is covered with Potsdam conglomerate, which overlies the truncated edges of the vertical layers of quartzite with unconformable contact. So clear an example of unconformity is not often seen. Potsdam sandstone is also seen to rest against the quartzite on either side of the narrows (Fig. 26), thus emphasizing the unconformity. The beauty and interest of this narrows is enhanced by the quartzite breccia ( which appears on its walls. [Illustration: Fig. 26.--A generalized diagrammatic cross-section at the Upper narrows, to show the relation of the sandstone to the quartzite.] One and one-half miles west of Ablemans (a, Plate II) is the third pass in the north quartzite ridge. This pass is narrower than the others, and is occupied by Narrows creek. Its walls are nearly vertical and possess the same rugged beauty as those at Ablemans. As at the Upper narrows, the beds of quartzite here are essentially vertical. They are indeed the continuation of the beds exposed at that place. The fourth narrows is across the South range (i, Plate II). It is not now occupied by a stream, though like the others it was cut by a stream, which was afterwards shut out from it. Because of its depth, 600 feet, and the ruggedness of its slopes, and because of its occupancy by the lake, this pass is the center of interest for the whole region. So much has already been said concerning it in other portions of this report that further description is here omitted. The manner in which the pass was robbed of its stream will be discussed later. The history of these several narrows, up to the time of the glacial period may now be summarized. Since remnants of Potsdam sandstone are found in some of them, it is clear that they existed in pre-Cambrian time,[6] and there is no reason to doubt that they are the work of the streams of those ancient days, working as streams now work. Following the pre-Cambrian period of erosion during which the notches were cut, came the submergence of the region, and the gaps were filled with sand and gravel, and finally the ridges themselves were buried. Uplift and a second period of erosion followed, during which the quartzite ranges were again exposed by the removal of the beds which overlay them, and the narrows cleaned out and deepened, and again occupied by streams. This condition of things lasted up to the time when the ice invaded the region. [6] It is not here asserted that these notches were as deep as now, in pre-Cambrian time. It is, however, certain that the quartzite was deeply eroded, previous to the deposition of the Potsdam sandstone. _Glens._--No enumeration of the special scenic features of this region would be complete without mention of Parfrey's and Dorward's glens (a and b, Plate XXXVII, and Plate XXV). Attention has already been directed to them as illustrations of young valleys, and as places where the Potsdam conglomerate is well shown, but they are attractive from the scenic point of view. Their frequent mention in earlier parts of this report makes further reference to them at this point unnecessary. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXV. In Dorward's Glen. The basal conglomerate of the Potsdam formation is shown at the lower right-hand corner, and is overlain by sandstone. (Photograph furnished by Mr. Wilfred Dorward).] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXVI. Natural bridge near Denzer.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXVII. Navy Yard. Dalles of the Wisconsin.] Pine Hollow (k, Plate II) is another attractive gorge on the south flank of the greater quartzite range. The rock at this point is especially well exposed. This gorge is beyond the drift-covered portion of the range, and therefore dates from the pre-glacial time. The Pewit's nest, about three miles southwest of Baraboo (m, Plate II), is another point of interest. Above the "nest," Skillett creek flows through a narrow and picturesque gorge in the Potsdam sandstone. The origin of this gorge is explained elsewhere. _Natural Bridge._--About two miles north and a little west of the village of Denzer (Sec. 17, T. 10 N., R. 5 E.), is a small natural bridge, which has resulted from the unequal weathering of the sandstone (see Plate XXVI). The "bridge" is curious, rather than beautiful or impressive. _The Dalles of the Wisconsin._--The _dalles_ is the term applied to a narrow canyon-like stretch of the Wisconsin valley seven miles in length, near Kilbourn City (see frontispiece). The depth of the gorge is from 50 to 100 feet. The part above the bridge at Kilbourn City is the "Upper dalles;" that below, the "Lower dalles." Within this stretch of the valley are perhaps the most picturesque features of the region. The sides of the gorge are nearly vertical much of the way, and at many points are so steep on both sides that landing would be impossible. Between these sandstone walls flows the deep and swift Wisconsin river. Such a rock gorge is in itself a thing of beauty, but in the dalles there are many minor features which enhance the charm of the whole. One of the features which deserves especial mention is the peculiar crenate form of the walls at the banks of the river. This is perhaps best seen in that part of the dalles known as the "Navy Yard." Plate XXVII. The sandstone is affected by a series of vertical cracks or joints. From weathering, the rock along these joints becomes softened, and the running water wears the softened rock at the joint planes more readily than other parts of its bank, and so develops a reëntrant at these points. Rain water descending to the river finds and follows the joint planes, and thus widens the cracks. As a result of stream and rain and weathering, deep reëntrant angles are produced. The projections between are rounded off so that the banks of the stream have assumed the crenate form shown in Plate XXVIII, and Frontispiece. When this process of weathering at the joints is carried sufficiently far, columns of rock become isolated, and stand out on the river bluffs as "chimneys" (Plate XXVIII). At a still later stage of development, decay of the rock along the joint planes may leave a large mass of rock completely isolated. "Steamboat rock" (Plate XII) and "Sugar bowl" (Plate XXIX) are examples of islands thus formed. The walls of sandstone weather in a peculiar manner at some points in the Lower dalles, as shown on Plate XXX. The little ridges stand out because they are harder and resist weathering better than the other parts. This is due in part at least to the presence of iron in the more resistant portions, cementing them more firmly. In the process of segregation, cementing materials are often distributed unequally. The effect of differences in hardness on erosion is also shown on a larger scale and in other ways. Perhaps the most striking illustration is _Stand rock_ (Plate XXXI), but most of the innumerable and picturesque irregularities on the rock walls are to be accounted for by such differences. Minor valleys tributary to the Wisconsin, such as _Witch's gulch_ and _Cold Water canyon_ deserve mention, both because of their beauty, and because they illustrate a type of erosion at an early stage of valley development. In character they are comparable to the larger gorge to which they are tributary. In the downward cutting, which far exceeds the side wear in these tributary canyons, the water has excavated large bowl or jug-like forms. In Witch's gulch such forms are now being excavated. They are developed just below falls, where the water carrying debris, eddies, and the jugs or pot-holes are the result of the wear effected by the eddies. The "Devil's jug" and many similar hollows are thus explained. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXVIII. Chimney Rock. Dalles of the Wisconsin. Cross-bedding well shown in foreground near bottom.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXIX. An Island in the Lower Dalles.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXX. View in lower Dalles showing peculiar honeycomb weathering.] _The mounds and castle rocks._--In the vicinity of Camp Douglas and over a large area to the east, are still other striking topographic forms, which owe their origin to different conditions, though they were fashioned by the same forces. Here there are many "tower" or "castle" rocks, which rise to heights varying from 75 to 190 feet above the surrounding plain. They are remnants of beds which were once continuous over the low lands above which the hills now rise. In Plates XVII and XVIII the general character of these hills is shown. The rock of which they are composed is Potsdam sandstone, the same formation which underlies most of the area about Baraboo. The effect of the vertical joints and of horizontal layers of unequal hardness is well shown. Rains, winds, frosts, and roots are still working to compass the destruction of these picturesque hills, and the talus of sand bordering the "castle" is a reminder of the fate which awaits them. These hills are the more conspicuous and the more instructive since the plain out of which they rise is so flat. It is indeed one of the best examples of a base-level plain to be found on the continent. The crests of these hills reach an elevation of between 1,000 and 1,100 feet. They appear to correspond with the level of the first peneplain recognized in the Devil's lake region. It was in the second cycle of erosion, when their surroundings were brought down to the new base-level, that these hills were left. West of Camp Douglas, there are still higher elevations, which seem to match Gibraltar rock. The Friendship "mounds" north of Kilbourn City, the castellated hills a few miles northwest of the same place, and Petenwell peak on the banks of the Wisconsin (Plate XXXII), are further examples of the same class of hills. All are of Potsdam sandstone. In addition to the "castle" rocks and base-level plain about Camp Douglas, other features should be mentioned. No other portion of the area touched upon in this report affords such fine examples of the different types of erosion topography. In the base-level plain are found "old-age" valleys, broad and shallow, with the stream meandering in a wide flood-plain. Traveling up such a valley, the topography becomes younger and younger, and the various stages mentioned earlier in the text, and suggested in Plate XIX, Figs. 1 and 2, and Plate XX, Fig. 1, are here illustrated. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXI. Stand Rock. Upper end of the Upper Dalles.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXII. Petenwell Peak.] CHAPTER V. THE GLACIAL PERIOD. The eastern part of the area with which this report deals, is covered with a mantle of drift which, as already pointed out, has greatly modified the details of its topography. To the consideration of the drift and its history attention is now turned. _The drift._--The drift consists of a body of clay, sand, gravel and bowlders, spread out as a cover of unequal thickness over the rock formations beneath. These various classes of material may be confusedly commingled, or they may be more or less distinctly separated from one another. When commingled, all may be in approximately equal proportions, or any one may predominate over any or all the others to any extent. It was long since recognized that the materials of the drift did not originate where they now lie, and that, in consequence, they sustain no genetic relationship to the strata on which they rest. Long before the drift received any special attention from geologists, it was well known that it had been transported from some other locality to that where it now occurs. The early conception was that it had been drifted into its present position from some outside source by water. It was this conception of its origin which gave it the name of _drift_. It is now known that the drift was deposited by glacier ice and the waters which arose from its melting, but the old name is still retained. Clearly to understand the origin of the drift, and the method by which it attained its present distribution, it may be well to consider some elementary facts and principles concerning climate and its effects, even at the risk of repeating what is already familiar. _Snow fields and ice sheets._--The temperature and the snowfall of a region may stand in such a relation to each other that the summer's heat may barely suffice to melt the winter's snow. If under these circumstances the annual temperature were to be reduced, or the fall of snow increased, the summer's heat would fail to melt all the winter's snow, and some portion of it would endure through the summer, and through successive summers, constituting a perennial snow-field. Were this process once inaugurated, the depth of the snow would increase from year to year. The area of the snow-field would be extended at the same time, since the snow-field would so far reduce the surrounding temperature as to increase the proportion of the annual precipitation which fell as snow. In the course of time, and under favorable conditions, the area of the snow-field would attain great dimensions, and the depth of the snow would become very great. As in the case of existing snow fields the lower part of the snow mass would eventually be converted into ice. Several factors would conspire to this end. 1. The pressure of the overlying snow would tend to compress the lower portion, and snow rendered sufficiently compact by compression would be regarded as ice. 2. Water arising from the melting of the surface snow by the sun's heat, would percolate through the superficial layers of snow, and, freezing below, take the form of ice. 3. On standing, even without pressure or partial melting, snow appears to undergo changes of crystallization which render it more compact. In these and perhaps other ways, a snow-field becomes an ice-field, the snow being restricted to its surface. Eventually the increase in the depth of the snow and ice in a snow-field will give rise to new phenomena. Let a snow and ice field be assumed in which the depth of snow and ice is greatest at the center, with diminution toward its edges. The field of snow, if resting on a level base, would have some such cross-section as that represented in the diagram, Fig. 27. When the thickness of the ice has become considerable, it is evident that the pressure upon its lower and marginal parts will be great. We are wont to think of ice as a brittle solid. If in its place there were some plastic substance which would yield to pressure, the weight of the ice would cause the marginal parts to extend themselves in all directions by a sort of flowing motion. [Illustration: Fig. 27.--Diagrammatic cross-section of a field of ice and snow (c) resting on a level base A-B.] Under great pressure, many substances which otherwise appear to be solid, exhibit the characteristics of plastic bodies. Among the substances exhibiting this property, ice is perhaps best known. Brittle and resistant as it seems, it may yet be molded into almost any desirable form if subjected to sufficient pressure, steadily applied through long intervals of time. The changes of form thus produced in ice are brought about without visible fracture. Concerning the exact nature of the movement, physicists are not agreed; but the result appears to be essentially such as would be brought about if the ice were capable of flowing, with extreme slowness, under great pressure continuously applied. In the assumed ice-field, there are the conditions for great pressure and for its continuous application. If the ice be capable of moving as a plastic body, the weight of the ice would induce gradual movement outward from the center of the field, so that the area surrounding the region where the snow accumulated would gradually be encroached upon by the spreading of the ice. Observation shows that this is what takes place in every snow-field of sufficient depth. Motion thus brought about is glacier motion, and ice thus moving is glacier ice. Once in motion, two factors would determine the limit to which the ice would extend itself: (1) the rate at which it advances; and (2) the rate at which the advancing edge is wasted. The rate of advance would depend upon several conditions, one of which, in all cases, would be the pressure of the ice which started and which perpetuates the motion. If the pressure be increased the ice will advance more rapidly, and if it advance more rapidly, it will advance farther before it is melted. Other things remaining constant, therefore, increase of pressure will cause the ice-sheet to extend itself farther from the center of motion. Increase of snowfall will increase the pressure of the snow and ice field by increasing its mass. If, therefore, the precipitation over a given snow-field be increased for a period of years, the ice-sheet's marginal motion will be accelerated, and its area enlarged. A decrease of precipitation, taken in connection with unchanged wastage would decrease the pressure of the ice and retard its movement. If, while the rate of advance diminished, the rate of wastage remained constant, the edge of the ice would recede, and the snow and ice field be contracted. The rate at which the edge of the advancing ice is wasted depends largely on the climate. If, while the rate of advance remains constant, the climate becomes warmer, melting will be more rapid, and the ratio between melting and advance will be increased. The edge of the ice will therefore recede. The same result will follow, if, while temperature remains constant, the atmosphere becomes drier, since this will increase wastage by evaporation. Were the climate to become warmer and drier at the same time, the rate of recession of the ice would be greater than if but one of these changes occurred. If, on the other hand, the temperature over and about the ice field be lowered, melting will be diminished, and if the rate of movement be constant, the edge of the ice will advance farther than under the earlier conditions of temperature, since it has more time to advance before it is melted. An increase in the humidity of the atmosphere, while the temperature remains constant, will produce the same result, since increased humidity of the atmosphere diminishes evaporation. A decrease of temperature, decreasing the melting, and an increase of humidity, decreasing the evaporation, would cause the ice to advance farther than either change alone, since both changes decrease the wastage. If, at the same time that conditions so change as to increase the rate of movement of the ice, climatic conditions so change as to reduce the rate of waste, the advance of the ice before it is melted will be greater than where only one set of conditions is altered. If, instead of favoring advance, the two series of conditions conspire to cause the ice to recede, the recession will likewise be greater than when but one set of conditions is favorable thereto. Greenland affords an example of the conditions here described. A large part of the half million or more square miles which this body of land is estimated to contain, is covered by a vast sheet of snow and ice, thousands of feet in thickness. In this field of snow and ice, there is continuous though slow movement. The ice creeps slowly toward the borders of the island, advancing until it reaches a position where the climate is such as to waste (melt and evaporate) it as rapidly as it advances. The edge of the ice does not remain fixed in position. There is reason to believe that it alternately advances and retreats as the ratio between movement and waste increases or decreases. These oscillations in position are doubtless connected with climatic changes. When the ice edge retreats, it may be because the waste is increased, or because the snowfall is decreased, or both. In any case, when the ice edge recedes from the coast, it tends to recede until its edge reaches a position where the melting is less rapid than in its former position, and where the advance is counterbalanced by the waste. This represents a condition of equilibrium so far as the edge of the ice is concerned, and here the edge of the ice would remain so long as the conditions were unchanged. When for a period of years the rate of melting of the ice is diminished, or the snowfall increased, or both, the ice edge advances to a new line where melting is more rapid than at its former edge. The edge of the ice would tend to reach a position where waste and advance balance. Here its advance would cease, and here its edge would remain so long as climatic conditions were unchanged. If the conditions determining melting and flowage be continually changing, the ice edge will not find a position of equilibrium, but will advance when the conditions are favorable for advance, and retreat when the conditions are reversed. Not only the edge of the ice in Greenland, but the ends of existing mountain glaciers as well, are subject to fluctuation, and are delicate indices of variations in the climate of the regions where they occur. _The North American ice sheet._--In an area north of the eastern part of the United States and in another west of Hudson Bay it is believed that ice sheets similar to that which now covers Greenland began to accumulate at the beginning of the glacial period. From these areas as centers, the ice spread in all directions, partly as the result of accumulation, and partly as the result of movement induced by the weight of the ice itself. The ice sheets spreading from these centers came together south of Hudson's bay, and invaded the territory of the United States as a single sheet, which, at the time of its greatest development, covered a large part of our country (Plate XXXIII), its area being known by the extent of the drift which it left behind when it was melted. In the east, it buried the whole of New England, most of New York, and the northern parts of New Jersey and Pennsylvania. Farther west, the southern margin of the ice crossed the Ohio river in the vicinity of Cincinnati, and pushed out over the uplands a few miles south of the river. In Indiana, except at the extreme east, its margin fell considerably short of the Ohio; in Illinois it reached well toward that river, attaining here its most southerly latitude. West of the Mississippi, the line which marks the limit of its advance curves to the northward, and follows, in a general way, the course of the Missouri river. The total area of the North American ice sheet, at the time of its maximum development, has been estimated to have been about 4,000,000 square miles, or about ten times the estimated area of the present ice-field of Greenland. Within the general area covered by the ice, there is an area of several thousand square miles, mainly in southwestern Wisconsin, where there is no drift. The ice, for some reason, failed to cover this _driftless area_ though it overwhelmed the territory on all sides. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXIII. The North American Ice Sheet, at the time of maximum development.] [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXIV. View from the north of the Owl's Head, a hill two miles north of east of Merrimac, which has been shaped by the ice. The side to the left is the stone side.] Plate II shows the limit of ice advance in the area here described. The region may have been affected by the ice of more than one glacial epoch, but the chief results now observable were effected during the last, and the others need not be considered. _The Work of Glacier Ice._ As the edge of an ice sheet, or as the end of a glacier, retreats, the land which it has previously covered is laid bare, and the effects which the passage of the ice produced may be seen. In some cases one may actually go back a short distance beneath the ice now in motion, and see its mode of work and the results it is effecting. The beds of living glaciers, and the beds which glaciers have recently abandoned, are found to present identical features. Because of their greater accessibility, the latter offer the better facilities for determining the effects of glaciation. The conspicuous phenomena of abandoned glacier beds fall into two classes, (1) those which pertain to the bed rock over which the ice moved, and (2) those which pertain to the drift left by the ice. _Erosive work of the ice._--_Effect on topography._--The leading features of the rock bed over which glacier ice has moved, are easily recognized. Its surface is generally smoothed and polished, and frequently marked by lines (striæ) or grooves, parallel to one another. An examination of the bottom of an active glacier discloses the method by which the polishing and scoring are accomplished. The lower surface of the ice is thickly set with a quantity of clay, sand, and stony material of various grades of coarseness. These earthy and stony materials in the base of the ice are the tools with which it works. Thus armed, the glacier ice moves slowly forward, resting down upon the surfaces over which it passes with the whole weight of its mass, and the grinding action between the stony layer at the base of the ice and the rock bed over which it moves, is effective. If the material in the bottom of the ice be fine, like clay, the rock bed is polished. If coarser materials, harder than the bed-rock, be mingled with the fine, the rock bed of the glacier will be scratched as well as polished. If there are bowlders in the bottom of the ice they may cut grooves or gorges in the underlying rock. The grooves may subsequently be polished by the passage over and through them of ice carrying clay or other fine, earthy matter. All these phases of rock wear may be seen about the termini of receding glaciers, on territory which they have but recently abandoned. There can thus be no possible doubt as to the origin of the polishing, planing and scoring. There are other peculiarities, less easily defined, which characterize the surface of glacier beds. The wear effected is not confined to the mere marking of the surface over which it passes. If prominences of rock exist in its path, as is often the case, they oppose the movement of the ice, and receive a corresponding measure of abrasion from it. If they be sufficiently resistant they may force the ice to yield by passing over or around them; but if they be weak, they are likely to be destroyed. As the ice of the North American ice sheet advanced, seemingly more rigid when it encountered yielding bodies, and more yielding when it encountered resistant ones, it denuded the surface of its loose and movable materials, and carried them forward. This accumulation of earthy and stony debris in the bottom of the ice, gave it a rough and grinding lower surface, which enabled it to abrade the land over which it passed much more effectively than ice alone could have done. Every hill and every mound which the ice encountered contested its advance. Every sufficiently resistant elevation compelled the ice to pass around or over it; but even in these cases the ice left its marks upon the surface to which it yielded. The powerful pressure of pure ice, which is relatively soft, upon firm hills of rock, which are relatively hard, would effect little. The hills would wear the ice, but the effect of the ice on the hills would be slight. But where the ice is supplied with earthy and stony material derived from the rock itself, the case is different. Under these conditions, the ice, yielding only under great pressure and as little as may be, rubs its rock-shod base over every opposing surface, and with greatest severity where it meets with greatest resistance. Its action may be compared to that of a huge "flexible-rasp" fitting down snugly over hills and valleys alike, and working under enormous pressure. The abrasion effected by a moving body of ice under such conditions would be great. Every inch of ice advance would be likely to be attended by loss to the surface of any obstacle over or around which it is compelled to move. The sharp summits of the hills, and all the angular rugosities of their surfaces would be filed off, and the hills smoothed down to such forms as will offer progressively less and less resistance. If the process of abrasion be continued long enough, the forms, even of the large hills, may be greatly altered, and their dimensions greatly reduced. Among the results of ice wear, therefore, will be a lowering of the hills, and a smoothing and softening of their contours, while their surfaces will bear the marks of the tools which fashioned them, and will be polished, striated or grooved, according to the nature of the material which the ice pressed down upon them during its passage. Figs. 28 and 29 show the topographic effects which ice is likely to produce by erosion. Plate XXXIV is a hill two miles northeast of Merrimac, which shows how perfectly the wear actually performed corresponds to that which might be inferred. [Illustration: Fig. 28.--A hill before the ice passes over it.] A rock hill was sometimes left without covering of drift after having been severely worn by the ice. Such a hill is known as a _roche moutonnée_. An example of this type of hill occurs three miles north of east of Baraboo at the point marked z on Plate XXXVII. This hill, composed of quartzite, is less symmetrical than those shown in Figs. 28 and 29. Its whole surface, not its stoss side only, has been smoothed and polished by the ice. This hill is the most accessible, the most easily designated, and, on the whole, the best example of a _roche moutonnée_ in the region, though many other hills show something of the same form. [Illustration: Fig. 29.--The same hill after it has been eroded by the ice. A the stoss side. B the lee side.] It was not the hills alone which the moving ice affected. Where it encountered valleys in its course they likewise suffered modification. Where the course of a valley was parallel to the direction of the ice movement, the ice moved through it. The depth of moving ice is one of the determinants of its velocity, and because of the greater depth of ice in valleys, its motion here was more rapid than on the uplands above, and its abrading action more powerful. Under these conditions the valleys were deepened and widened. Where the courses of the valleys were transverse to the direction of ice movement, the case was different. The ice was too viscous to span the valleys, and therefore filled them. In this case it is evident that the greater depth of the ice in the valley will not accelerate its motion, since the ice in the valley-trough and that above it are in a measure opposed. If left to itself, the ice in the valley would tend to flow in the direction of the axis of the valley. But in the case under consideration, the ice which lies above the valley depression is in motion at right angles to the axis of the valley. Under these circumstances three cases might arise: (1) If the movement of the ice sheet over the valley were able to push the valley ice up the farther slope, and out on the opposite highland, this work would retard the movement of the upper ice, since the resistance to movement would be great. In this case, the thickness of the ice is not directly and simply a determinant of its velocity. Under these conditions the bottom of the valley would not suffer great erosion, since ice did not move along it; but that slope of the valley against which the ice movement was projected would suffer great wear (Fig. 30). The valley would therefore be widened, and the slope suffering greatest wear would be reduced to a lower angle. Shallow valleys, and those possessing gentle slopes, favor this phase of ice movement and valley wear. [Illustration: Fig. 30.--Diagram showing effect on valley of ice moving transversely across it.] (2) The ice in the valley might become stationary, in which case it might serve as a bridge for the upper ice to cross on (Fig. 31). In this case also the total thickness of ice will not be a determinant of its velocity, for it is the thickness of the moving ice only, which influences the velocity. In this case the valley would not suffer much wear, so long as this condition of things continued. Valleys which have great depth relative to the thickness of the ice, and valleys whose slopes are steep, favor this phase of movement. (3) In valleys whose courses are transverse to the direction of ice movement, transverse currents of ice may exist, following the direction of the valleys. If the thickness of the ice be much greater than the depth of the valley, if the valley be capacious, and if one end of it be open and much lower than the other, the ice filling it may move along its axis, while the upper ice continues in its original course at right angles to the valley. In this case the valley would be deepened and widened, but this effect would be due to the movement along its course, rather than to that transverse to it. [Illustration: Fig. 31--Diagram to illustrate case where ice fills a valley (C) and the upper ice then moves on over the filling.] If the course of a valley were oblique to the direction of ice movement, its effect on the movement of ice would be intermediate between that of valleys parallel to the direction of movement, and those at right angles to it. It follows from the foregoing that the corrasive effects of ice upon the surface over which it passed, were locally dependent on pre-existent topography, and its relation to the direction of ice movement. In general, the effort was to cut down prominences, thus tending to level the surface. But when it encountered valleys parallel to its movement they were deepened, thus locally increasing relief. Whether the reduction of the hills exceeded the deepening of the valleys, or whether the reverse was true, so far as corrasion alone is concerned, is uncertain. But whatever the effect of the erosive effect of ice action upon the total amount of relief, the effect upon the contours was to make them more gentle. Not only were the sharp hills rounded off, but even the valleys which were deepened were widened as well, and in the process their slopes became more gentle. A river-erosion topography, modified by the wearing (not the depositing) action of the ice, would be notably different from the original, by reason of its gentler slopes and softer contours (Figs. 28 and 29). _Deposition by the ice. Effect on topography._--On melting, glacier ice leaves its bed covered with the debris which it gathered during its movement. Had this debris been equally distributed on and in and beneath the ice during its movement, and had the conditions of deposition been everywhere the same, the drift would constitute a mantle of uniform thickness over the underlying rock. Such a mantle of drift would not greatly alter the topography; it would simply raise the surface by an amount equal to the thickness of the drift, leaving elevations and depressions of the same magnitude as before, and sustaining the same relations to one another. But the drift carried by the ice, in whatever position, was not equally distributed during transportation, and the conditions under which it was deposited were not uniform, so that it produced more or less notable changes in the topography of the surface on which it was deposited. The unequal distribution of the drift is readily understood. The larger part of the drift transported by the ice was carried in its basal portion; but since the surface over which the ice passed was variable, it yielded a variable amount of debris to the ice. Where it was hilly, the friction between it and the ice was greater than where it was plain, and the ice carried away more load. From areas where the surface was overspread by a great depth of loose material favorably disposed for removal, more debris was taken than from areas where material in a condition to be readily transported was meager. Because of the topographic diversity and lithological heterogeneity of the surface of the country over which it passed, some portions of the ice carried much more drift than others, and when the ice finally melted, greater depths of drift were left in some places than in others. Not all of the material transported by the ice was carried forward until the ice melted. Some of it was probably carried but a short distance from its original position before it lodged. Drift was thus accumulating at some points beneath the ice during its onward motion. At such points the surface was being built up; at other points, abrasion was taking place, and the surface was being cut down. The drift mantle of any region does not, therefore, represent simply the material which was on and in and beneath the ice of that place at the time of its melting, but it represents, in addition, all that lodged beneath the ice during its movement. The constant tendency was for the ice to carry a considerable part of its load forward toward its thinned edge, and there to leave it. It follows that if the edge of the ice remained constant in position for any considerable period of time, large quantities of drift would have accumulated under its marginal portion, giving rise to a belt of relatively thick drift. Other things being equal, the longer the time during which the position of the edge was stationary, the greater the accumulation of drift. Certain ridge-like belts where the drift is thicker than on either hand, are confidently believed to mark the position where the edge of the ice-sheet stood for considerable periods of time. Because of the unequal amounts of material carried by different parts of the ice, and because of the unequal and inconstant conditions of deposition under the body of the ice and its edge, the mantle of drift has a very variable thickness; and a mantle of drift of variable thickness cannot fail to modify the topography of the region it covers. The extent of the modification will depend on the extent of the variation. This amounts in the aggregate, to hundreds of feet. The continental ice sheet, therefore, modified the topography of the region it covered, not only by the wear it effected, but also by the deposits it made. In some places it chanced that the greater thicknesses of drift were left in the positions formerly marked by valleys. Locally the body of drift was so great that valleys were completely filled, and therefore completely obliterated as surface features. Less frequently, drift not only filled the valleys but rose even higher over their former positions than on either side. In other places the greater depths of drift, instead of being deposited in the valleys, were left on pre-glacial elevations, building them up to still greater heights. In short, the mantle of drift of unequal thickness was laid down upon the rock surface in such a manner that the thicker parts sometimes rest on hills and ridges, sometimes on slopes, sometimes on plains, and sometimes in valleys. [Illustration: Fig. 32.--Diagrammatic section showing relation of drift to underlying rock, where the drift is thick relative to the relief of the rock. a and b represent the location of post-glacial valleys.] These relations are suggested by Figs. 32 and 33. From them it will be seen that in regions where the thickness of the drift is great, relative to the relief of the underlying rock, the topography may be completely changed. Not only may some of the valleys be obliterated by being filled, but some of the hills may be obliterated by having the lower land between them built up to their level. In regions where the thickness of the drift is slight, relative to the relief of the rock beneath, the hills cannot be buried, and the valleys cannot be completely filled, so that the relative positions of the principal topographic features will remain much the same after the deposition of the drift, as before (Fig. 33). [Illustration: Fig. 33.--Diagrammatic section showing relation of drift to underlying rock where the drift is thin relative to the relief of the underlying rock.] In case the pre-glacial valleys were filled and the hills buried, the new valleys which the surface waters will in time cut in the drift surface will have but little correspondence in position with those which existed before the ice incursion. A new system of valleys, and therefore a new system of ridges and hills, will be developed, in some measure independent of the old. These relations are illustrated by Fig. 32. Inequalities in the thickness of drift lead to a still further modification of the surface. It frequently happened that in a plane or nearly plane region a slight thickness of drift was deposited at one point, while all about it much greater thicknesses were left. The area of thin drift would then constitute a depression, surrounded by a higher surface built up by the thicker deposits. Such depressions would at first have no outlets, and are therefore unlike the depressions shaped by rain and river erosion. The presence of depressions without outlets is one of the marks of a drift-covered (glaciated) country. In these depressions water may collect, forming lakes or ponds, or in some cases only marshes and bogs. DIRECTION OF ICE MOVEMENT. The direction in which glacier ice moved may be determined in various ways, even after the ice has disappeared. The shapes of the rock hills over which the ice passed, the direction from which the materials of the drift came, and the course of the margin of the drift, all show that the ice of south central Wisconsin was moving in a general southwest direction. In the rock hills, this is shown by the greater wear of their northeast ("stoss") sides (Plate XXXIV). From the course of the drift margin, the general direction of movement may be inferred when it is remembered that the tendency of glacier ice on a plane surface is to move at right angles to its margin. For the exact determination of the direction of ice movement, recourse must be had to the striæ on the bed-rock. Were the striated rock surface perfectly plane, and were the striæ even lines, they would only tell that the ice was moving in one of two directions. But the rock surface is not usually perfectly plane, nor the striæ even lines, and between the two directions which lines alone might suggest, it is usually possible to decide. The minor prominences and depressions in the rock surface were shaped according to the same principles that govern the shaping of hills (Fig. 29) and valleys (Fig. 30); that is, the stoss sides of the minor prominences, and the distal sides of small depressions suffered the more wear. With a good compass, the direction of the striæ may be measured to within a fraction of a degree, and thus the direction of ice movement in a particular place be definitely determined. The striæ which have been determined about Baraboo are shown on Plate II. _Effect of topography on movement._--The effect of glaciation on topography has been sketched, but the topography in turn exerted an important influence on the direction of ice movement. The extreme degree of topographic influence is seen in mountain regions like the Alps, where most of the glaciers are confined strictly to the valleys. As an ice sheet invades a region, it advances first and farthest along the lines of least resistance. In a rough country with great relief, tongues or lobes of ice would push forward in the valleys, while the hills or other prominences would tend to hold back or divide the onward moving mass. The edge of an ice sheet in such a region would be irregular. The marginal lobes of ice occupying the valleys would be separated by re-entrant angles marking the sites of hills and ridges. If the ice crossed a plane surface above which rose a notable ridge or hill, the first effect of the hill would be to indent the ice. The ice would move forward on either side, and if its thickness became sufficiently great, the parts moving forward on either side would again unite beyond it. A hill thus surrounded by ice is a nunatak. Later, as the advancing mass of ice became thicker, it might completely cover the hill; but the thickness of ice passing over the hill would be less than that passing on either side by an amount equal to the height of the hill. It follows that as ice encounters an isolated elevation, three stages in its contest with the obstruction may be recognized: (1) the stage when the ridge or hill acts as a wedge, dividing the moving ice into lobes, Fig. 34; (2) the nunatak stage, when the ice has pushed forward and reunited beyond the hill, Fig. 35; (3) the stage when the ice has become sufficiently deep to cover the hill. [Illustration: Fig. 34.--Diagrammatic representation of the effect of a hill on the edge of the ice.] After the ice has disappeared, the influence of the obstruction might be found in the disposition of the drift. If recession began during the first stage, that is, when the ice edge was separated into lobes, the margin of the drift should be lobate, and would loop back around the ridge from its advanced position on either side. If recession began during the second stage, that is, when the lobes had become confluent and completely surrounded the hill, a _driftless area_ would appear in the midst of drift. If recession began during the third stage, that is, after the ice had moved on over the obstruction, the evidence of the sequence might be obliterated; but if the ice moved but a short distance beyond the hill, the thinner ice over the hill would have advanced less far than the thicker ice on either side (Fig. 35), and the margin of the drift would show a re-entrant pointing back toward the hill, though not reaching it. All these conditions are illustrated in the Devil's lake region. [Illustration: Fig. 35.--Same as Fig. 34, when the ice has advanced farther.] _Limit of the Ice._ The region under description is partly covered with drift, and partly free from it. The limit of the ice, at the time of its maximum expansion is well defined at many points, and the nature and position of the drift limit are so unique as to merit attention (see Plates II and XXXVII). They illustrate many of the principles already discussed. The ice which covered the region was the western margin of the Green Bay lobe (Fig. 36) of the last continental ice sheet. Its limit in this region is marked by a ridge-like accumulation of drift, the _terminal moraine_, which here has a general north-south direction. The region may have been affected by the ice of more than one epoch, but since the ice of the last epoch advanced as far to the west in this region as that of any earlier epoch, the moraine is on the border between the glaciated country to the east, and the driftless area to the west (Plates I and II). That part of the moraine which lies west of the Wisconsin river follows a somewhat sinuous course from Kilbourn City to a point a short distance north of Prairie du Sac. The departures from this general course are especially significant of the behavior of glacier ice. [Illustration: Fig. 36.--Map showing relations of lobes of ice during the Wisconsin ice epoch, to the driftless area.] In the great depression between the quartzite ranges, the moraine bends westward, showing that the ice advanced farther on the lowlands than on the ridges. As the moraine of this low area approaches the south range, it curves to the east. At the point southwest of Baraboo where the easterly curve begins to show itself, the moraine lies at the north base of the quartzite range; but as it is traced eastward, it is found to lie higher and higher on the slope of the range, until it reaches the crest nearly seven miles from the point where the eastward course was assumed. At this point it crosses the range, and, once across the crest, it turns promptly to the westward on the lower land to the south. Here the ice advanced up the valley between the East bluff (east of the lake) and the Devil's nose (Plate XXXVII), again illustrating the fact that lowlands favor ice advance. The valley between the Devil's nose and the East bluff is a narrow one, and the ice advanced through it nearly to the present site of the lake. Meanwhile the restraining influence of the "nose" was making itself felt, and the margin of the ice curved back from the bottom of the bluff near Kirkland, to the top of the bluff at the end of the nose. Here the edge of the ice crossed the point of the nose, and after rounding it, turned abruptly to the west. Thence its edge lay along the south slope of the ridge, descending from the crest of the ridge at the nose, to the base of the ridge two miles farther west. Here the ice reached its limit on the lowland, and its edge, as marked by the moraine, turned southward, reaching the Wisconsin river about a mile and a half above Prairie du Sac. The course of the terminal moraine across the ridges is such as the margin of the ice would normally have when it advanced into a region of great relief. The great loop in the moraine with its eastern extremity at k, Plate XXXVII, is explained by the presence of the quartzite ridge which retarded the advancing ice while it moved forward on either side. The minor loop around the Devil's nose is explained in the same way. Both the main loop, and the smaller one on the nose, illustrate the point made earlier in the text. The narrow and curious loop at m, is of a slightly different origin, though in principle the same. It is in the lee of a high point in the quartzite ridge. The ice surmounted this point, and descended its western slope; but the thickness of the ice passing over the summit was so slight that it advanced but a short distance down the slope before its force was exhausted, while the thicker ice on either side advanced farther before it was melted. _Glacial Deposits._ Before especial reference is made to the drift of this particular region, it will be well to consider the character of drift deposits in general. When the ice of the continental glacier began its motion, it carried none of the stony and earthy debris which constitute the drift. These materials were derived from the surface over which the ice moved. From the method by which it was gathered, it is evident that the drift of any locality may contain fragments of rock of every variety which occurs along the route followed by the ice which reached that locality. Where the ice had moved far, and where there were frequent changes in the character of the rock constituting its bed, the variety of materials in the drift is great. The heterogeneity of the drift arising from the diverse nature of the rocks which contributed to it is _lithological heterogeneity_--a term which implies the commingling of materials derived from different rock formations. Thus it is common to find pieces of sandstone, limestone, quartzite, granite, gneiss, schist, etc., intimately commingled in the drift, wherever the ice which produced it passed over formations of these several sorts of rock. Lithological heterogeneity is one of the notable characteristics of glacial formations. Another characteristic of the drift is its _physical heterogeneity_. As first gathered from the bed of moving ice, some of the materials of the drift were fine and some coarse. The tendency of the ice in all cases was to reduce its load to a still finer condition. Some of the softer materials, such as soft shale, were crushed or ground to powder, forming what is known in common parlance as clay. Clayey (fine) material is likewise produced by the grinding action of ice-carried bowlders upon the rock-bed, and upon one another. Other sorts of rock, such as soft sandstone, were reduced to the physical condition of sand, instead of clay, and from sand to bowlders all grades of coarseness and fineness are represented in the glacial drift. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXV. Cut in drift, showing its physical heterogeneity.] Since the ice does not assort the material which it carries, as water does, the clay, sand, gravel and bowlders will not, by the action of the ice, be separated from one another. They are therefore not stratified. As left by the ice, these physically heterogeneous materials are confusedly commingled. The finer parts constitute a matrix in which the coarser are embedded. Physical heterogeneity (Plate XXXV), therefore, is another characteristic of glacial drift. It is not to be understood that the proportions of these various physical elements, clay, sand, gravel, and bowlders, are constant. Locally any one of them may predominate over any or all the others to any extent. Since lithological and physical heterogeneity are characteristics of glacial drift, they together afford a criterion which is often of service in distinguishing glacial drift from other surface formations. It follows that this double heterogeneity constitutes a feature which can be utilized in determining the former extension of existing glaciers, as well as the former existence of glaciers where glaciers do not now exist. Another characteristic of glacial drift, and one which clearly distinguishes it from all other formations with which it might be confounded, is easily understood from its method of formation. If the ice in its motion holds down rock debris upon the rock surface over which it passes with such pressure as to polish and striate the bed-rock, the material carried will itself suffer wear comparable to that which it inflicts. Thus the stones, large and small, of glacial drift, will be smoothed and striated. This sort of wear on the transported blocks of rock, is effected both by the bed-rock reacting on the bowlders transported over it, and by bowlders acting on one another in and under the ice. The wear of bowlders by bowlders is effected wherever adjacent ones are carried along at different rates. Since the rate of motion of the ice is different in different parts of the glacier, the mutual abrasion of transported materials is a process constantly in operation. A large proportion of the transported stone and blocks of rock may thus eventually become striated. From the nature of the wear to which the stones are subjected when carried in the base of the ice, it is easy to understand that their shapes must be different from those of water-worn materials. The latter are rolled over and over, and thus lose all their angles and assume a more or less rounded form. The former, held more or less firmly in the ice, and pressed against the underlying rock or rock debris as they are carried slowly forward, have their faces planed and striated. The planation and striation of a stone need not be confined to its under surface. On either side or above it other stones, moving at different rates, are made to abrade it, so that its top and sides may be planed and scored. If the ice-carried stones shift their positions, as they may under various circumstances, new faces will be worn. The new face thus planed off may meet those developed at an earlier time at sharp angles, altogether unlike anything which water-wear is capable of producing. The stone thus acted upon shows a surface bounded by planes and more or less beveled, instead of a rounded surface such as water wear produces. We find, then, in the shape of the bowlders and smaller stones of the drift, and in the markings upon their surfaces, additional criteria for the identification of glacier drift (Plate XXXVI). The characteristics of glacial drift, so far as concerns its constitution, may then be enumerated as, (1) its lithological, and (2) physical heterogeneity; (3) the shapes, and (4) the markings of the stones of the drift. In structure, the drift which is strictly glacial, is unstratified. In the broadest sense of the term, all deposits made by glacier ice are _moraines_. Those made beneath the ice and back from its edge constitute the _ground moraine_, and are distinguished from the considerable marginal accumulations which, under certain conditions, are accumulated at or near the margin. These marginal accumulations are _terminal moraines_. Associated with the moraines which are the deposits of the ice directly, there are considerable bodies of stratified gravel and sand, the structure of which shows that they were laid down by water. This is to be especially noted, since lack of stratification is popularly supposed to be the especial mark of the formations to which the ice gave rise. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXVI. Glaciated stones, showing both form and striæ. (Matz.)] These deposits of stratified drift lie partly beyond the terminal moraine, and partly within it. They often sustain very complicated relations both to the ground and terminal moraines. The drift as a whole is therefore partly stratified and partly unstratified. Structurally the two types are thoroughly distinct, but their relations are often most complex, both horizontally and vertically. A fuller consideration of these relations will be found on a later page. _The Ground Moraine._ The ground moraine constitutes the great body of the glacial drift. _Bowlder clay_, a term descriptive of its constitution in some places, and _till_, are other terms often applied to the ground moraine. The ground moraine consists of all the drift which lodged beneath the ice during its advance, all that was deposited back from its edge while its margin was farthest south, and most of that which was deposited while the ice was retreating. From this mode of origin it is readily seen that the ground moraine should be essentially as widespread as the ice itself. Locally, however, it failed of deposition. Since it constitutes the larger part of the drift, the characteristics already enumerated as belonging to drift in general are the characteristics of the till. Wherever obstacles to the progress of the ice lay in its path, there was a chance that these obstacles, rising somewhat into the lower part of the ice, would constitute barriers against which debris in the lower part of the ice would lodge. It might happen also that the ice, under a given set of conditions favoring erosion, would gather a greater load of rock-debris than could be transported under the changed conditions into which its advance brought it. In this case, some part of the load would be dropped and over-ridden. Especially near the margin of the ice where its thickness was slight and diminishing, the ice must have found itself unable to carry forward the loads of debris which it had gathered farther back where its action was more vigorous. It will be readily seen that if not earlier deposited, all material gathered by the under surface of the ice would ultimately find itself at the edge of the glacier, for given time enough, ablation will waste all that part of the ice occupying the space between the original position of the debris, and the margin of the ice. Under the thinned margin of the ice, therefore, considerable accumulations of drift must have been taking place while the ice was advancing. While the edge of the ice sheet was advancing into territory before uninvaded, the material accumulated beneath its edge at one time, found itself much farther from the margin at another and later time. Under the more forcible ice action back from the margin, the earlier accumulations, made under the thin edge, were partially or wholly removed by the thicker ice of a later time, and carried down to or toward the new and more advanced margin. Here they were deposited, to be in turn disturbed and transported still farther by the farther advance of the ice. Since in its final retreat the margin of the ice must have stood at all points once covered by it, these submarginal accumulations of drift must have been made over the whole country once covered by the ice. The deposits of drift made beneath the marginal part of the ice during its retreat, would either cover the deposits made under the body of the ice at an earlier time, or be left alongside them. The constitution of the two phases of till, that deposited during the advance of the ice, and that deposited during its retreat, is essentially the same, and there is nothing in their relative positions to sharply differentiate them. They are classed together as _subglacial till_. Subglacial till was under the pressure of the overlying ice. In keeping with these conditions of accumulation, the till often possesses a firmness suggestive of great compression. Where its constitution is clayey it is often remarkably tough. Where this is the case, the quality here referred to has given rise to the suggestive name "hard pan." Where the constitution of the till is sandy, rather than clayey, this firmness and toughness are less developed, or may be altogether wanting, since sand cannot be compressed into coherent masses like clay. _Constitution._--The till is composed of the more or less comminuted materials derived from the land across which the ice passed. The soil and all the loose materials which covered the rock entered into its composition. Where the ice was thick and its action vigorous, it not only carried away the loose material which it found in its path, but, armed with this material, it abraded the underlying rock, wearing down its surface and detaching large and small blocks of rock from it. It follows that the constitution of the till at any point is dependent upon the nature of the soil and rock from which it was derived. If sandstone be the formation which has contributed most largely to the till, the matrix of the till will be sandy. Where limestone instead of sandstone made the leading contribution to it, the till has a more earthy or clayey matrix. Any sort of rock which may be very generally reduced to a fine state of division under the mechanical action of the ice, will give rise to clayey till. The nature and the number of the bowlders in the till, no less than the finer parts, depend on the character of the rock overridden. A hard and resistant rock, such as quartzite, will give rise to more bowlders in proportion to the total amount of material furnished to the ice, than will softer rock. Shale or soft sandstone, possessing relatively slight resistance, will be much more completely crushed. They will, therefore, yield proportionately fewer bowlders than harder formations, and more of the finer constituents of till. The bowlders taken up by the ice as it advanced over one sort of rock and another, possessed different degrees of resistance. The softer ones were worn to smaller dimensions or crushed with relative ease and speed. Bowlders of soft rock are, therefore, not commonly found in any abundance at great distances from their sources. The harder ones yielded less readily to abrasion, and were carried much farther before being destroyed, though even such must have suffered constant reduction in size during their subglacial journey. In general it is true that bowlders in the till, near their parent formations, are larger and less worn than those which have been transported great distances. The ice which covered this region had come a great distance and had passed over rock formations of many kinds. The till therefore contains elements derived from various formations; that is, it is lithologically heterogeneous. This heterogeneity cannot fail to attract the attention of one examining any of the many exposures of drift about Baraboo at road gradings, or in the cuts along the railway. Among the stones in the drift at these exposures are limestone, sandstone, quartzite, diabase, gabbro, gneiss, granite, schist, and porphyry, together with pieces of flint and chert. Such an array may be found at any of the exposures within the immediate vicinity of Devil's lake. To the north, and a few miles to the south of the Baraboo ranges, the quartzite from these bluffs, and the porphyry from the point marked h in Plate II, are wanting, though other varieties of porphyry are present. The ice moved in a general west-southwest direction in this region, and the quartzite in the drift, so far as derived from the local formation, is therefore restricted to a narrow belt. The physical heterogeneity may be seen at all exposures, and is illustrated in Plate XXXV. The larger stones of the drift are usually of some hard variety of rock. Near the Baraboo ranges, the local quartzite often predominates among the bowlders, and since such bowlders have not been carried far, they are often little worn. Away from the ranges, the bowlders are generally of some crystalline rock, such as granite and diabase. Bowlders of these sorts of rock are from a much more distant source, and are usually well worn. In general the till of any locality is made up largely of material derived from the formations close at hand. This fact seems to afford sufficient warrant for the conclusion that a considerable amount of deposition must have gone on beneath the ice during its movement, even back from its margin. To take a concrete illustration, it would seem that the drift of southeastern Wisconsin should have had a larger contribution than it has of material derived from Canadian territory, if material once taken up by the ice was all or chiefly carried down to its thinned edge before deposition. The fact that so little of the drift came from these distant sources would seem to prove that a large part of the material moved by the ice, is moved a relatively short distance only. The ice must be conceived of as continually depositing parts of its load, and parts which it has carried but a short distance, as it takes up new material from the territory newly invaded. In keeping with the character of till in general, that about Devil's lake was derived largely from the sandstone, limestone and quartzite of the immediate vicinity, while a much smaller part of it came from more distant sources. This is especially noticeable in the fine material, which is made up mostly of the comminuted products of the local rock. _Topography._--The topography of the ground moraine is in general the topography already described in considering the modification of preglacial topography effected by ice deposition. As left by the ice, its surface was undulating. The undulations did not take the form of hills and ridges with intervening valleys, but of swells and depressions standing in no orderly relationship to one another. Undrained depressions are found in the ground moraine, but they are, as a rule, broader and shallower than the "kettles" common to terminal moraines. It is in the broad, shallow depressions of the ground moraine that many of the lakes and more of the marshes of southeastern Wisconsin are located. The rolling, undulating topography characteristic of ground moraines is well shown about the City of Baraboo and between that point and the lake, and at many less easily designated points about Merrimac. In thickness the ground moraine reaches at least 160 feet, though its average is much less--too little to obliterate the greater topographic features of the rock beneath. It is, however, responsible for many of the details of the surface. _Terminal Moraines._ The marginal portion of the ice sheet was more heavily loaded--certainly more heavily loaded relative to its thickness--than any other. Toward its margin the thinned ice was constantly losing its transportive power, and at its edge this power was altogether gone. Since the ice was continually bringing drift down to this position and leaving it there, the rate of drift accumulation must have been greater, on the average, beneath the edge of the ice than elsewhere. Whenever, at any stage in its history, the edge of the ice remained essentially constant in position for a long period of time, the corresponding submarginal accumulation of drift was great, and when the ice melted, the former site of the stationary edge would be marked by a broad ridge or belt of drift, thicker than that on either side. Such thickened belts of drift are _terminal moraines_. It will be seen that a terminal moraine does not necessarily mark the terminus of the ice at the time of its greatest advance, but rather its terminus at any time when its edge was stationary or nearly so. From the conditions of their development it will be seen that these submarginal moraines may be made up of materials identical with those which constitute the ground moraine, and such is often the case. But water arising from the melting of the ice, played a much more important role at its margin than farther back beneath it. One result of its greater activity may be seen in the greater coarseness which generally characterizes the material of the terminal moraine as compared with that of the adjacent ground moraine. This is partly because the water carried away such of the finer constituents as it was able to transport, leaving the coarser behind. Further evidence of the great activity of water near the margin of the ice is to be seen in the relatively large amount of assorted and stratified sand and gravel associated with the terminal moraine. Such materials as were carried on the ice were dropped at its edge when the ice which bore them melted from beneath. If the surface of the ice carried many bowlders, many would be dropped along the line of its edge wherever it remained stationary for any considerable period of time. A terminal moraine therefore embraces (1) the thick belt of drift accumulated beneath the edge of the ice while it was stationary, or nearly so; and (2) such debris as was carried on the surface of the ice and dumped at its margin. In general the latter is relatively unimportant. At various stages in its final retreat, the ice made more or less protracted halts. These halting places are marked by marginal moraines of greater or less size, depending on the duration of the stop, and the amount of load carried. A terminal moraine is not the sharp and continuous ridge we are wont to think it. It is a belt of thick drift, rather than a ridge, though it is often somewhat ridge-like. In width, it varies from a fraction of a mile to several miles. In the region under consideration it is rarely more than fifty feet high, and rarely less than a half mile wide, and a ridge of this height and width is not a conspicuous topographic feature in a region where the relief is so great as that of the Devil's lake region. _Topography of terminal moraines._--The most distinctive feature of a terminal moraine is not its ridge-like character, but its peculiar topography. In general, it is marked by depressions without outlets, associated with hillocks and short ridges comparable in dimensions to the depressions. Both elevations and depressions are, as a rule, more abrupt than in the ground moraine. In the depressions there are many marshes, bogs, ponds and small lakes. The shapes and the abundance of round and roundish hills have locally given rise to such names as "The Knobs," "Short Hills," etc. Elsewhere the moraine has been named the "Kettle Range" from the number of kettle-like depressions in its surface. It is to be kept in mind that it is the association of the "knobs" and "kettles," rather than either feature alone, which is the distinctive mark of terminal moraine topography. [Illustration: Fig. 37.--Sketch of terminal moraine topography, on the quartzite ridge east of Devil's lake. (Matz.)] The manner in which the topography of terminal moraines was developed is worthy of note. In the first place, the various parts of the ice margin carried unequal amounts of debris. This alone would have caused the moraine of any region to have been of unequal height and width at different points. In the second place, the margin of the ice, while maintaining the same _general_ position during the making of a moraine, was yet subject to many minor oscillations. It doubtless receded to some slight extent because of increased melting during the summer, to advance again during the winter. In its recession, the ice margin probably did not remain exactly parallel to its former position. If some parts receded more than others, the details of the line of its margin may have been much changed during a temporary retreat. When the ice again advanced, its margin may have again changed its form in some slight measure, so as to be parallel neither with its former advanced position, nor with its position after its temporary retreat. With each successive oscillation of the edge, the details of the margin may have altered, and at each stage the marginal deposits corresponded with the edge. There might even be considerable changes in the edge of the ice without any general recession or advance, as existing glaciers show. It was probably true of the margin of the American ice sheet, as of existing glaciers, that there were periods of years when the edge of the ice receded, followed by like periods when it remained stationary or nearly so, and these in turn followed by periods of advance. During any advance, the deposits made during the period of recession would be overridden and disturbed or destroyed. If the ice were to retreat and advance repeatedly during a considerable period of time, always within narrow limits, and if during this oscillation the details of its margin were frequently changing, the result would be a complex or "tangle" of minor morainic ridges of variable heights and widths. Between and among the minor ridges there would be depressions of various sizes and shapes. Thus, it is conceived, many of the peculiar hillocks and hollows which characterize terminal moraines may have arisen. Some of the depressions probably arose in another way. When the edge of the ice retreated, considerable detached masses of ice might be left beyond the main body. This might be buried by gravel and sand washed out from the moraine. On melting, the former sites of such blocks of ice would be marked by "kettles." In the marginal accumulations of drift as first deposited, considerable quantities of ice were doubtless left. When this melted, the drift settled and the unequal settling may have given rise to some of the topographic irregularities of the drift. _The terminal moraine about Devil's lake._--On the lower lands, the terminal moraine of the Devil's lake region has the features characteristic of terminal moraines in general. It is a belt of thick drift varying in width from half a mile or less to three-quarters of a mile or more. Its surface is marked by numerous hills and short ridges, with intervening depressions or "kettles." Some of the depressions among the hills contain water, making ponds or marshes, though the rather loose texture of the drift of this region is not favorable to the retention of water. The moraine belt, as a whole, is higher than the land on either side. It is therefore somewhat ridge-like, and the small, short hills and ridges which mark its surface, are but constituent parts of the larger, broader ridge. Approached from the west, that is from the driftless side, the moraine on the lower lands is a somewhat prominent topographic feature, often appearing as a ridge thirty, forty or even fifty feet in height. Approached from the opposite direction, that is, from the ground moraine, it is notably less prominent, and its inner limit wherever located, is more or less arbitrary. [Illustration: Fig. 38.--Cut through the terminal moraine just east of Kirkland, partially diagrammatic.] A deep, fresh railway cut in the moraine southeast of Devil's lake illustrates its complexity of structure, a complexity which is probably no greater than that at many other points where exposures are not seen. The section is represented in Fig. 38. The stratified sand to the right retains even the ripple-marks which were developed when it was deposited. To the left, at the same level, there is a body of _till_ (unstratified drift), over which is a bed of stoneless and apparently structureless clay. In a depression just above the clay with till both to the right and left, is a body of loam which possesses the characteristics of normal loess. It also contains calcareous concretions, though no shells have been found. This occurrence of loess is the more noteworthy, since loess is rarely found in association with drift of the last glacial epoch.[7] [7] An account of loess in connection with the drift of the last glacial epoch is given in the _Journal of Geology_, Vol. IV, pp. 929-987. For a general account of loess, see Sixth Annual Report of U.S. Geological Survey. _The moraine on the main quartzite range._--In tracing the moraine over the greater quartzite range, it is found to possess a unique feature in the form of a narrow but sharply defined ridge of drift, formed at the extreme margin of the ice at the time of its maximum advance. For fully eleven miles, with but one decided break, and two short stretches where its development is not strong, this unique marginal ridge separates the drift-covered country on the one hand, from the driftless area on the other. In its course the ridge lies now on slopes, and now on summits, but in both situations preserves its identity. Where it rests on a plain, or nearly plain surface, its width at base varies from six to fifteen rods, and its average height is from twenty to thirty feet. Its crest is narrow, often no more than a single rod. Where it lies on a slope, it is asymmetrical in cross section (see Fig. 39), the shorter slope having a vertical range of ten to thirty-five feet, and its longer a range of forty to one hundred feet. This asymmetrical form persists throughout all that portion of the ridge which lies on an inclined surface, the slope of which does not correspond with the direction of the moraine. Where it lies on a flat surface, or an inclined surface the slope of which corresponds in direction with the course of the ridge itself, its cross section is more nearly symmetrical (see Fig. 40). In all essential characteristics this marginal ridge corresponds with the _End-Moräne_ of the Germans. [Illustration: Fig. 39.--Diagrammatic cross-section of the marginal ridge as it occurs on the south slope of the Devil's Nose. The slope below, though glaciated, is nearly free from drift.] [Illustration: Fig. 40.--Diagrammatic cross-section of the marginal ridge as it appears when its base is not a sloping surface.] For the sake of bringing out some of its especially significant features, the ridge may be traced in detail, commencing on the south side of the west range. Where the moraine leaves the lowlands south of the Devil's nose, and begins the ascent of the prominence, the marginal ridge first appears at about the 940-foot contour (f, Plate XXXVII). Though at first its development is not strong, few rods have been passed before its crest is fifteen to twenty feet above the driftless area immediately to the north (see Fig. 39) and from forty to one hundred feet above its base to the south, down the slope. In general the ridge becomes more distinct with increasing elevation, and except for two or three narrow post-glacial erosion breaks, is continuous to the very summit at the end of the nose (g). The ridge in fact constitutes the uppermost forty or forty-five feet of the crest of the nose, which is the highest point of the west range within the area shown on the map. Throughout the whole of this course the marginal ridge lies on the south slope of the nose, and has the asymmetrical cross section shown in Fig. 39. Above (north of) the ridge at most points not a bowlder of drift occurs. So sharply is its outer (north) margin defined, that at many points it is possible to locate it within the space of less than a yard. At the crest of the nose (g) the marginal ridge, without a break, swings northward, and in less than a quarter of a mile turns again to the west. Bearing to the north it presently reaches (at h) the edge of the precipitous bluff, bordering the great valley at the south end of the lake. Between the two arms of the loop thus formed, the surface of the nose is so nearly level that it could have offered no notable opposition to the progress of the ice, and yet it failed to be covered by it. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXVII. Topographic map (contour interval 100 feet) of a small area about Devil's lake, taken from the Baraboo sheet of the United States Geological Survey. Each contour line connects points of the same elevation, and the figures upon them give the heights above sea level. Where contour lines lie close together, they indicate steep slopes.] In the great valley between the nose and the east bluff, the marginal ridge does not appear. In the bottom of the valley the moraine takes on its normal form, and the slopes of the quartzite ridges on either hand are much too steep to allow any body of drift, or loose material of any sort, to lodge on them. Ascending the east bluff a little east of the point where the drift ridge drops off the west bluff, the ridge is again found (at i) in characteristic development. For some distance it is located at the edge of the precipitous south face of the bluff. Farther on it bears to the north, and soon crosses a col (j) in the ridge, building it up many feet above the level of the bed-rock. From this point eastward for about three miles the marginal ridge is clearly defined, the slopes about equal on either side, and the crest as nearly even as the topography of the underlying surface permits. The topographic relations in this part of the course are shown in Fig. 40. At k, this marginal ridge attains its maximum elevation, 1,620 feet. At this great elevation, the ridge turns sharply to the northwest at an angle of more than 90°. Following this direction for little more than half a mile, it turns to the west. At some points in this vicinity the ridge assumes the normal morainic habit, but this is true for short distances only. Farther west, at l, it turns abruptly to the northeast and is sharply defined. It here loops about a narrow area less than sixty rods wide, and over half a mile in length, the sharpest loop in its whole course. The driftless tract enclosed by the arms of this loop is lower than the drift ridge on either hand. The ice on either side would need to have advanced no more than thirty rods to have covered the whole of it. From the minor loop just mentioned, the marginal ridge is continued westward, being well developed for about a mile and a half. At this point the moraine swings south to the north end of Devil's lake, loses the unique marginal ridge which has characterized its outer edge across the quartzite range for so many miles, and assumes the topography normal to terminal moraines. At no other point in the United States, so far as known to the writers, is there so sharply marked a marginal ridge associated with the terminal moraine, for so long a distance. From Plate II it will be seen that the moraine as a whole makes a great loop to the eastward in crossing the quartzite range. From the detailed description just given of the course of the marginal ridge, it will be seen that it has three distinct loops; one on the Devil's nose (west of g, Plate XXXVII); one on the main ridge (west of k) and a minor one on the north side of the last (southwest of m). The first and third are but minor irregularities on the sides of the great loop, the head of which is at k. The significant fact in connection with these irregularities in the margin of the moraine is that each loop stands in a definite relation to a prominence. The meaning of this relation is at once patent. The great quartzite range was a barrier to the advance of the ice. Acting as a wedge, it caused a re-entrant in the advancing margin of the glacier. The extent and position of the re-entrant is shown by the course of the moraine in Plate II. Thus the great loop in the moraine, the head of which is at k, Plate XXXVII, was caused by the quartzite range itself. The minor loops on the sides of the major are to be explained on the same principle. Northeast of the minor loop on the north side of the larger one (m) there are two considerable hills, reaching an elevation of nearly 1,500 feet. Though the ice advancing from the east-northeast overrode them, they must have acted like a wedge, to divide it into lobes. The ice which reached their summits had spent its energy in so doing, and was unable to move forward down the slope ahead, and the thicker bodies of ice which passed on either side of them, failed to unite in their lee (compare Figs. 34 and 35). The application of the same principle to the loop on the Devil's nose is evident. _Constitution of the marginal ridge._--The material in the marginal ridge, as seen where erosion has exposed it, is till, abnormal, if at all, only in the large percentage of widely transported bowlders which it contains. This is especially true of the surface, where in some places 90 per cent. of the large bowlders are of very distant origin, and that in spite of the fact that the ice which deposited them had just risen up over a steep slope of quartzite, which could easily have yielded abundant bowlders. In other places the proportion of foreign bowlders is small, no more than one in ten. In general, however, bowlders of distant origin predominate over those derived close at hand. _The slope of the upper surface of the ice at the margin._--The marginal ridge on the south slope of Devil's nose leads to an inference of especial interest. Its course lies along the south slope of the nose, from its summit on the east to its base on the west. Throughout this course the ridge marks with exactness the position of the edge of the ice at the time of its maximum advance, and its crest must therefore represent the slope of the upper surface of the ice at its margin. The western end of the ridge (f, Plate XXXVII) has an altitude of 940 feet, and its eastern end (g) is just above the 1,500-foot contour. The distance from the one point to the other is one and three-fourths miles, and the difference in elevation, 560 feet. These figures show that the slope of the ice along the south face of this bluff was about 320 feet per mile. This, so far as known, is the first determination of the slope of the edge of the continental ice sheet _at its extreme margin_. It is to be especially noted that these figures are for the extreme edge of the ice only. The angle of slope back from the edge was doubtless much less. _Stratified Drift._ While it is true that glacier ice does not distinctly stratify the deposits which it makes, it is still true that a very large part of the drift for which the ice of the glacial period was directly or indirectly responsible is stratified. That this should be so is not strange when it is remembered that most of the ice was ultimately converted into running water, just as the glaciers of today are. The relatively small portion which disappeared by evaporation was probably more than counterbalanced, at least near the margin of the ice, by the rain which fell upon it. It cannot be considered an exaggeration, therefore, to say that the total amount of water which operated on the drift, first and last, was hardly less than the total amount of the ice itself. The drift deposited by the marginal part of the ice was affected during its deposition, not only by the water which arose from the melting of the ice which did the depositing, but by much water which arose from the melting of the ice far back from the margin. The general mobility of the water, as contrasted with ice, allowed it to concentrate its activities along those lines which favored its motion, so that different portions of the drift were not affected equally by the water of the melting ice. All in all it will be seen that the water must have been a very important factor in the deposition of the drift, especially near the margin of the ice. But the ice sheet had a marginal belt throughout its whole history, and water must have been active and effective along this belt, not only during the decadence of the ice sheet, but during its growth as well. It is further to be noted that any region of drift stood good chance of being operated upon by the water after the ice had departed from it, so that in regions over which topography directed drainage after the withdrawal of the ice, the water had the last chance at the drift, and modified it in such a way and to such an extent as circumstances permitted. _Its origin._--There are various ways in which stratified drift may arise in connection with glacier deposits. It may come into existence by the operation of water alone; or by the co-operation of ice and water. Where water alone was immediately responsible for the deposition of stratified drift, the water concerned may have owed its origin to the melting ice, or it may have existed independently of the ice in the form of lakes. When the source of the water was the melting ice, the water may have been running, when it was actively concerned in the deposition of stratified drift; or it may have been standing (glacial lakes and ponds), when it was passively concerned. When ice co-operated with water in the development of stratified drift the ice was generally a passive partner. _Glacial drainage._--The body of an ice sheet during any glacial period is probably melting more or less at some horizons all the time, and at all horizons some of the time. Most of the water which is produced at the surface during the summer sinks beneath it. Some of it may congeal before it sinks far, but much of it reaches the bottom of the ice without refreezing. It is probable that melting is much more nearly continuous in the body of a moving ice sheet than at its surface, and that some of the water thus produced sinks to the bottom of the ice without refreezing. At the base of the ice, so long as it is in movement, there is doubtless more or less melting, due both to friction and to the heat received by conduction from the earth below. Thus in the ice and under the ice there must have been more or less water in motion throughout essentially all the history of an ice sheet. If it be safe to base conclusions on the phenomena of existing glaciers, it may be assumed that the waters beneath the ice, and to a less extent the waters in the ice, organized themselves to a greater or less degree into streams. For longer or shorter distances these streams flowed in the ice or beneath it. Ultimately they escaped from its edge. The subglacial streams doubtless flowed, in part, in the valleys which affected the land surface beneath the ice, but they were probably not all in such positions. The courses of well-defined subglacial streams were tunnels. The bases of the tunnels were of rock or drift, while the sides and tops were of ice. It will be seen, therefore, that their courses need not have corresponded with the courses of the valleys beneath the ice. They may sometimes have followed lines more or less independent of topography, much as water may be forced over elevations in closed tubes. It is not to be inferred, however, that the subglacial streams were altogether independent of the sub-ice topography. The tunnels in which the water ran probably had too many leaks to allow the water to be forced up over great elevations. This, at least, must have been the case where the ice was thin or affected by crevasses. Under such circumstances the topography of the land surface must have been the controlling element in determining the course of the subglacial drainage. When the streams issued from beneath the ice the conditions of flow were more or less radically changed, and from their point of issue they followed the usual laws governing river flow. If the streams entered static water as they issued from the ice, and this was true where the ice edge reached the sea or a lake, the static water modified the results which the flowing waters would otherwise have produced. _Stages in the history of an ice sheet._--The history of an ice sheet which no longer exists involves at least two distinct stages. These are (1) the period of growth, and (2) the period of decadence. If the latter does not begin as soon as the former is complete, an intervening stage, representing the period of maximum ice extension, must be recognized. In the case of the ice sheets of the glacial period, each of these stages was probably more or less complex. The general period of growth of each ice sheet is believed to have been marked by temporary, but by more or less extensive intervals of decadence, while during the general period of decadence, it is probable that the ice was subject to temporary, but to more or less extensive intervals of recrudescence. For the sake of simplicity, the effects of these oscillations of the edge of the ice will be neglected at the outset, and the work of the water accompanying the two or three principal stages of an ice sheet's history will be outlined as if interruptions in the advance and in the retreat, respectively, had not occurred. As they now exist, the deposits of stratified drift made at the edge of the ice or beyond it during the period of its maximum extension present the simplest, and at the same time most sharply defined phenomena, and are therefore considered first. _Deposits Made by Extraglacial Waters During the Maximum Extension of the Ice._ The deposits made by the water at the time of the maximum extension of the ice and during its final retreat, were never disturbed by subsequent glacier action. So far as not destroyed by subsequent erosion, they still retain the form and structure which they had at the outset. Such drift deposits, because they lie at the surface, and because they are more or less distinct topographically as well as structurally, are better known than the stratified drift of other stages of an ice sheet's history. Of stratified drift made during the maximum extension of the ice, and during its final retreat, there are several types. _A. At the edge of ice, on land._--If the subglacial streams flowed under "head," the pressure was relieved when they escaped from the ice. With this relief, there was diminution of velocity. With the diminution of velocity, deposition of load would be likely to take place. Since these changes would be likely to occur at the immediate edge of the ice, one class of stratified drift deposits would be made in this position, in immediate contact with the edge of the ice, and their form would be influenced by it. At the stationary margin of an ice sheet, therefore, at the time of its maximum advance, ice and water must have co-operated to bring into existence considerable quantities of stratified drift. The edge of the ice was probably ragged, as the ends of glaciers are today, and as the waters issued from beneath it, they must frequently have left considerable quantities of such debris as they were carrying, against its irregular margin, and in its re-entrant angles and marginal crevasses. When the ice against which this debris was first lodged melted, the marginal accumulations of gravel and sand often assumed the form of kames. A typical kame is a hill, hillock, or less commonly a short ridge of stratified drift; but several or many are often associated, giving rise to groups and areas of _kames_. Kames are often associated with terminal moraines, a relation which emphasizes the fact of their marginal origin. So far as the superficial streams which flowed to the edge of the ice carried debris, this was subject to deposition as the streams descended from the ice. Such drift would tend to increase the body of marginal stratified drift from subglacial sources. Marginal accumulations of stratified drift, made by the co-operation of running water and ice, must have had their most extensive development, other things being equal, where the margin of the ice was longest in one position, and where the streams were heavily loaded. The deposits made by water at the edge of the ice differ from those of the next class--made beyond the edge of the ice--in that they were influenced in their disposition and present topography, by the presence of ice. In the Devil's lake region isolated and well-defined kames are not of common occurrence. There are, however, at many points hills which have something of a kame-like character. There is such a hill a mile southeast of the Court house at Baraboo, at the point marked p, Plate XXXVII. In this hill there are good exposures which show its structure. There are many hillocks of a general kame-like habit associated with the terminal moraine south of the main quartzite range, and north of the Wisconsin river. Many of them occur somewhat within the terminal moraine a few miles northwest of Merrimac. _B. Beyond the edge of the ice, on land._--As the waters escaping from the ice flowed farther, deposits of stratified drift were made quite beyond the edge of the ice. The forms assumed by such deposits are various, and depended on various conditions. Where the waters issuing from the edge of the ice found themselves concentrated in valleys, and where they possessed sufficient load, and not too great velocity, they aggraded the valleys through which they flowed, developing fluvial plains of gravel and sand, which often extended far beyond the ice. Such fluvial plains of gravel and sand constitute the _valley trains_ which extend beyond the unstratified glacial drift in many of the valleys of the United States. They are found especially in the valleys leading out from the stouter terminal moraines of late glacial age. From these moraines, the more extensive valley trains take their origin, thus emphasizing the fact that they are deposits made by water beyond a stationary ice margin. Valley trains have all the characteristics of alluvial plains built by rapid waters carrying heavy loads of detritus. Now and then their surfaces present slight variations from planeness, but they are minor. Like all plains of similar origin they decline gradually, and with diminishing gradient, down stream. They are of coarser material near their sources, and of finer material farther away. Valley trains constitute a distinct topographic as well as genetic type. A perfect example of a valley train does not occur within the region here discussed. There is such a train starting at the moraine where it crosses the Wisconsin river above Prairie du Sac, and extending down that valley to the Mississippi, but at its head this valley train is wide and has the appearance of an overwash plain, rather than a valley train. Farther from the moraine, however, it narrows, and assumes the normal characteristics of a valley train. It is the gravel and sand of this formation which underlies Sauk Prairie, and its topographic continuation to the westward. Where the subglacial streams did not follow subglacial valleys, they did not always find valleys when they issued from the ice. Under such circumstances, each heavily loaded stream coming out from beneath the ice must have tended to develop a plain of stratified material near its point of issue--a sort of alluvial fan. Where several such streams came out from beneath the ice near one another, their several plains, or fans, were likely to become continuous by lateral growth. Such border plains of stratified drift differ from valley trains particularly (1) in being much less elongate in the direction of drainage; (2) in being much more extended parallel to the margin of the ice; and (3) in not being confined to valleys. Such plains stood an especially good chance of development where the edge of the ice remained constant for a considerable period of time, for it was under such conditions that the issuing waters had opportunity to do much work. Thus arose the type of stratified drift variously known as _overwash plains_, _outwash plains_, _morainic plains_, and _morainic aprons_. These plains sometimes skirt the moraine for many miles at a stretch. Overwash plains may sometimes depart from planeness by taking on some measure of undulation, of the sag and swell (kame) type, especially near their moraine edges. The same is often true of the heads of valley trains. The heads of valley trains and the inner edges of overwash plains, it is to be noted, occupy the general position in which kames are likely to be formed, and the undulations which often affect these parts of the trains and plains, respectively, are probably to be attributed to the influence of the ice itself. Valley trains and overwash plains, therefore, at their upper ends and edges respectively, may take on some of the features of kames. Indeed, either may head in a kame area. Good examples of overwash or outwash plains may be seen at various points in the vicinity of Baraboo. The plain west of the moraine just south of the main quartzite ridge has been referred to under valley trains. In Sauk Prairie, however, its characteristics are those of an outwash plain, rather than those of a valley train. [Illustration: Fig. 41.--The morainic or outwash plain bordering the terminal moraine. The figure is diagrammatic, but represents, in cross section, the normal relation as seen south of the quartzite range at the east edge of Sauk Prairie, north of the Baraboo river and at some points between the South range and the Baraboo.] A good example of an outwash plain occurs southwest of Baraboo, flanking the moraine on the west (Fig. 41). Seen from the west, the moraine just north of the south quartzite range stands up as a conspicuous ridge twenty to forty feet above the morainic plain which abuts against it. Traced northward, the edge of the outwash plain, as it abuts against the moraine, becomes higher, and in Section 4, Township 11 N., Range 6 E., the moraine edge of the plain reaches the crest of the moraine (Fig. 42). From this point north to the Baraboo river the moraine scarcely rises above the edge of the outwash beyond. [Illustration: Fig. 42.--The outwash plain is built up to the crest of the moraine. The figure is diagrammatic, but this relation is seen at the point marked W, Plate II.] North of the Baraboo river the moraine is again distinct and the overwash plain to the west well developed much of the way from the Baraboo to Kilbourn City. A portion of it is known as Webster's Prairie. Locally, the outwash plains of this region have been much dissected by erosion since their deposition, and are now affected by many small valleys. In composition these plains are nearly everywhere gravel and sand, the coarser material being nearer the moraine. The loose material is in places covered by a layer of loam several feet deep, which greatly improves the character of the soil. This is especially true of Sauk Prairie, one of the richest agricultural tracts in the state. When the waters issuing from the edge of the ice were sluggish, whether they were in valleys or not, the materials which they carried and deposited were fine instead of coarse, giving rise to deposits of silt, or clay, instead of sand or gravel. At many points near the edge of the ice during its maximum stage of advance, there probably issued small quantities of water not in the form of well-defined streams, bearing small quantities of detritus. These small quantities of water, with their correspondingly small loads, were unable to develop considerable plains of stratified drift, but produced small patches instead. Such patches have received no special designation. In the deposition of stratified drift beyond the edge of the ice, the latter was concerned only in so far as its activity helped to supply the water with the necessary materials. _C. Deposits at and beyond the edge of the ice in standing water._--The waters which issued from the edge of the ice sometimes met a different fate. The ice in its advance often moved up river valleys. When at the time of its maximum extension, it filled the lower part of a valley, leaving the upper part free, drainage through the valley stood good chance of being blocked. Where this happened a marginal valley lake was formed. Such a lake was formed in the valley of the Baraboo when the edge of the ice lay where the moraine now is (Plate II). The waters which were held back by the ice dam, reinforced by the drainage from the ice itself, soon developed a lake above the point of obstruction. This extinct lake may be named Baraboo lake. In this lake deposits of laminated clay were made. They are now exposed in the brick yards west of Baraboo, and in occasional gullies and road cuts in the flat bordering the river. At the point marked s (Plate XXXVII) there was, in glacial times, a small lake having an origin somewhat different from that of Baraboo lake. The former site of the lake is now marked by a notable flat. Excavations in the flat show that it is made up of stratified clay, silt, sand and gravel, to the depth of many feet,--locally more than sixty. These lacustrine deposits are well exposed in the road cuts near the northwest corner of the flat, and in washes at some other points. Plate XXXVIII shows some of the silt and clay, the laminæ of which are much distorted. _Deltas_ must have been formed where well-defined streams entered the lakes, and _subaqueous overwash plains_ where deltas became continuous by lateral growth. The accumulation of stratified drift along the ice-ward shores of such lakes must have been rapid, because of the abundant supply of detritus. These materials were probably shifted about more or less by waves and shore currents, and some of them may have been widely distributed. Out from the borders of such lakes, fine silts and clays must have been in process of deposition, at the same time that the coarse materials were being laid down nearer shore. [Illustration: WISCONSIN GEOL. AND NAT. HIST. SURVEY. BULLETIN NO. V., PL. XXXVIII. Distorted laminae of silt and clay.] Good examples of deltas and subaqueous overwash plains do not appear to exist in the region, although conditions for their development seem to have been present. Thus in the lake which occupied the valley of the Baraboo, conditions would seem to have been ideal for the development of such features; that is, the overwash plains previously described should, theoretically, have been subaqueous overwash plains; but if this be their character, their distinctive marks have been destroyed by subsequent erosion. During the maximum extension of an ice sheet, therefore, there was chance for the development, at its edge or beyond it, of the following types of stratified drift: (1) kames and kame belts, at the edge of the ice; (2) fluvial plains or valley trains, in virtual contact with the ice at their heads; (3) border plains or overwash plains, in virtual contact with the ice at their upper edges; (4) ill-defined patches of stratified drift, coarse or fine near the ice; (5) subaqueous overwash plains and deltas, formed either in the sea or lakes at or near the edge of the ice; (6) lacustrine and marine deposits of other sorts, the materials for which were furnished by the waters arising from the ice. So far as this region is concerned, all the deposits made in standing water were made in lakes. _Deposits Made by Extraglacial Waters During the Retreat of the Ice._ During the retreat of any ice sheet, disregarding oscillations of its edge, its margin withdrew step by step from the position of extreme advance to its center. When the process of dissolution was complete, each portion of the territory once covered by the ice, had at some stage in the dissolution, found itself in a marginal position. At all stages in its retreat the waters issuing from the edge of the ice were working in the manner already outlined in the preceding paragraphs. Two points of difference only need be especially noted. In the first place the deposits made by waters issuing from the retreating ice were laid down on territory which the ice had occupied, and their subjacent stratum was often glacial drift. So far as this was the case, the stratified drift was super-morainic, not extra-morainic. In the second place the edge of the ice in retreat did not give rise to such sharply marked formations as the edge of the ice which was stationary. The processes which had given rise to valley trains, overwash plains, kames, etc., while the ice edge was stationary, were still in operation, but the line or zone of their activity (the edge of the ice) was continually retreating, so that the foregoing types, more or less dependent on a stationary edge, were rarely well developed. As the ice withdrew, therefore, it allowed to be spread over the surface it had earlier occupied, many incipient valley trains, overwash plains, and kames, and a multitude of ill-defined patches of stratified drift, thick and thin, coarse and fine. Wherever the ice halted in its retreat, these various types stood chance of better development. Such deposits did not cover all the surface discovered by the ice in its retreat, since the issuing waters, thanks to their great mobility, concentrated their activities along those lines which favored their motion. Nevertheless the aggregate area of the deposits made by water outside the ice as it retreated, was great. It is to be noted that it was not streams alone which were operative as the ice retreated. As its edge withdrew, lakes and ponds were continually being drained, as their outlets, hitherto choked by the ice, were opened, while others were coming into existence as the depressions in the surface just freed from ice, filled with water. Lacustrine deposits at the edge of the ice during its retreat were in all essential respects identical with those made in similar situations during its maximum extension. Disregarding oscillations of the ice edge at these stages, the deposits made by extraglacial waters during the maximum extension of an ice sheet, and during its retreat, were always left at the surface, so far as the work of that ice sheet was concerned. The stratified drift laid down by extraglacial waters in these stages of the last ice sheet which affected any region of our continent still remain at the surface in much the condition in which they were deposited, except for the erosion they have since suffered. It is because of their position at the surface that the deposits referable to these stages of the last ice sheet of any given region have received most attention and are therefore most familiar. _Deposits Made by Extraglacial Waters During the Advance of the Ice._ During the advance of an ice sheet, if its edge forged steadily forward, the waters issuing from it, and flowing beyond, were effecting similar results. They were starting valley trains, overwash plains, kames, and small ill-defined patches of stratified drift which the ice did not allow them to complete before pushing over them, thus moving forward the zone of activity of extraglacial waters. Unlike the deposits made by the waters of the retreating ice, those made by the waters of the advancing stage were laid down on territory which had not been glaciated, or at least not by the ice sheet concerned in their deposition. If the ice halted in its advance, there was at such time and place opportunity for the better development of extraglacial stratified drift. Lakes as well as streams were concerned in the making of stratified beds of drift, during the advance of the ice. Marginal lakes were obliterated by having their basins filled with the advancing ice, which displaced the water. But new ones were formed, on the whole, as rapidly as their predecessors became extinct, so that lacustrine deposits were making at intervals along the margin of the advancing ice. Deposits made in advance of a growing ice sheet, by waters issuing from it, were subsequently overridden by the ice, to the limit of its advance, and in the process, suffered destruction, modification, or burial, in whole or in part, so that now they rarely appear at the surface. _Deposits Made by Subglacial Streams._ Before their issuance from beneath the ice, subglacial waters were not idle. Their activity was sometimes erosive, and at such times stratified deposits were not made. But where the sub-glacial streams found themselves overloaded, as seems frequently to have been the case, they made deposits along their lines of flow. Where such waters were not confined to definite channels, their deposits probably took on the form of irregular patches of silt, sand, or gravel; but where depositing streams were confined to definite channels, their deposits were correspondingly concentrated. When subglacial streams were confined to definite channels, the same may have been constant in position, or may have shifted more or less from side to side. Where the latter happened there was a tendency to the development of a belt or strip of stratified drift having a width equal to the extent of the lateral migrations of the under-ice stream. Where the channel of the subglacial stream remained fixed in position, the deposition was more concentrated, and the bed was built up. If the stream held its course for a long period of time, the measure of building may have been considerable. In so far as these channel deposits were made near the edge of the ice, during the time of its maximum extension or retreat, they were likely to remain undisturbed during its melting. The aggraded channels then came to stand out as ridges. These ridges of gravel and sand are known as osars or eskers. It is not to be inferred that eskers never originated in other ways, but it seems clear that this is one method, and probably the principal one, by which they came into existence. Eskers early attracted attention, partly because they are relatively rare, and partly because they are often rather striking topographic features. The essential conditions, therefore, for their formations, so far as they are the product of subglacial drainage, are (1) the confining of the subglacial streams to definite channels; and (2) a sufficient supply of detritus. One esker only has been found in the region under consideration. It is located at the point marked j, Plate II, seven and one-half miles northeast of Merrimac and one and one-half miles south of Alloa (g, Plate II). The esker is fully a quarter of a mile long, about thirty feet high, and four rods wide at its base. Subglacial deposits of stratified drift were sometimes made on unstratified drift (till) already deposited by the ice before the location of the stream, and sometimes on the rock surfaces on which no covering of glacier drift had been spread. It is to be kept in mind that subglacial drainage was operative during the advance of an ice sheet, during its maximum extension, and during its retreat, and that during all these stages it was effecting its appropriate results. It will be readily seen, however, that all deposits made by subglacial waters, were subject to modification or destruction or burial, through the agency of the ice, and that those made during the advance of the ice were less likely to escape than those made during its maximum extension or retreat. RELATIONS OF STRATIFIED TO UNSTRATIFIED DRIFT. When it is remembered that extraglacial and subglacial waters were active at all stages of an ice sheet's history, giving rise, or tending to give rise to all the phases of stratified drift enumerated above; when it is remembered that the ice of several epochs affected much of the drift-covered country; and when it is remembered further that the edge of the ice both during advance and retreat was subject to oscillation, and that each advance was likely to bury the stratified drift last deposited, beneath unstratified, it will be seen that the stratified drift and the unstratified had abundant opportunity to be associated in all relationships and in all degrees of intimacy, and that the relations of the one class of drift to the other may come to be very complex. As a result of edge oscillation, it is evident that stratified drift may alternate with unstratified many times in a formation of drift deposited during a single ice epoch, and that two beds of till, separated by a bed of stratified drift, do not necessarily represent two distinct glacial epochs. The extent of individual beds of stratified drift, either beneath the till or inter-bedded with it, may not be great, though their aggregate area and their aggregate volume is very considerable. It is to be borne in mind that the ice, in many places, doubtless destroyed all the stratified drift deposited in advance on the territory which it occupied later, and that in others it may have left only patches of once extensive sheets. This may help to explain why it so frequently happens that a section of drift at one point shows many layers of stratified drift, while another section close by, of equal depth, and in similar relationships, shows no stratified material whatsoever. Such deposits as were made by superglacial streams during the advance of the ice must likewise have been delivered on the land surface, but would have been subsequently destroyed or buried, becoming in the latter case, submorainic. This would be likely to be the fate of all such superglacial gravels as reached the edge of the ice up to the time of its maximum advance. Streams descending from the surface of the ice into crevasses also must have carried down sand and gravel where such materials existed on the ice. These deposits may have been made on the rock which underlies the drift, or they may have been made on stratified or unstratified drift already deposited. In either case they were liable to be covered by till, thus reaching an inter-till or sub-till position. Englacial streams probably do little depositing, but it is altogether conceivable that they might accumulate such trivial pockets of sand and gravel as are found not infrequently in the midst of till. The inter-till position would be the result of subsequent burial after the stratified material reached a resting place. Complexity of relations.--From the foregoing it becomes clear that there are diverse ways by which stratified drift, arising in connection with an ice sheet, may come to be interbedded with till, when due recognition is made of all the halts and oscillations to which the edge of a continental glacier may have been subject during both its advance and retreat. CLASSIFICATION OF STRATIFIED DRIFT ON THE BASIS OF POSITION. In general the conditions and relations which theoretically should prevail are those which are actually found. On the basis of position stratified drift deposits may be classified as follows: 1. Extraglacial deposits, made by the waters of any glacial epoch if they flowed and deposited beyond the farthest limit of the ice. 2. Supermorainic deposits, made chiefly during the final retreat of the ice from the locality where they occur, but sometimes by extraglacial streams or lakes of a much later time. Locally too, stratified deposits of an early stage of a glacial epoch, lying on till, may have failed to be buried by the subsequent passage of the ice over them, and so remain at the surface. In origin, supermorainic deposits were for the most part extraglacial (including marginal), so far as the ice sheet calling them into existence was concerned. Less commonly they were subglacial, and failed to be covered, and less commonly still superglacial. 3. The submorainic (basal) deposits were made chiefly by extraglacial waters in advance of the first ice which affected the region where they occur. They were subsequently overridden by the ice and buried by its deposits. Submorainic deposits, however, may have arisen in other ways. Subglacial waters may have made deposits of stratified drift on surfaces which had been covered by ice, but not by till, and such deposits may have been subsequently buried. The retreat of an ice sheet may have left rock surfaces free from till covering, on which the marginal waters of the ice may have made deposits of stratified drift. These may have been subsequently covered by till during a re-advance of the ice in the same epoch or in a succeeding one. Still again, the till left by one ice sheet may have been exposed to erosion to such an extent as to have been completely worn away before the next ice advance, so that stratified deposits connected with a second or later advance may have been made on a driftless surface, and subsequently buried. 4. Intermorainic stratified drift may have originated at the outset in all the ways in which supermorainic drift may originate. It may have become intermorainic by being buried in any one of the various ways in which the stratified drift may become submorainic. CHANGES IN DRAINAGE EFFECTED BY THE ICE. _While the Ice Was on._ As the continental ice sheet invaded a region, the valleys were filled and drainage was thereby seriously disturbed. Different streams were affected in different ways. Where the entire basin of a stream was covered by ice, the streams of that basin were, for the time being, obliterated. Where the valley of a stream was partially filled with ice, the valley depression was only partially obliterated, and the remaining portion became the scene of various activities. Where the ice covered the lower course of a stream but not the upper, the ice blocked the drainage, giving rise to a lake. Where the ice covered the upper course of a stream, but not its lower, the lower portion was flooded, and though the river held its position, it assumed a new phase of activity. Streams issuing from the ice usually carry great quantities of gravel and sand, and make deposits along their lower courses. Long continued glacial drainage usually results in a large measure of aggradation. This was true of the streams of the glacial period. Where a stream flowed parallel or approximately parallel to the edge of the advancing ice it was sometimes shifted in the direction in which the ice was moving, keeping parallel to the front of the ice. All of these classes of changes took place in this region. _Wisconsin lake._--Reference has already been made to certain lakes which existed in the region when the ice was there. The largest of these lakes was that which resulted from the blocking of the Wisconsin river. The ice crossed its present course at Kilbourn City, and its edge lay to the west of the river from that point to Prairie du Sac (see Plate I). The waters from the area now draining into the Wisconsin must either have found an avenue of escape beneath the ice, or have accumulated in a lake west of the edge of the ice. There is reason to believe that the latter was what happened, and that a great lake covered much of the low land west of the Wisconsin river above and below Kilbourn City. The extensive gravel beds on the north flank of the quartzite bluff at Necedah, and the water-worn pebbles of local origin on the slope of Petenwell peak (Plate XXXII), as well as the gravels at other points, are presumably the work of that lake. The waters in this lake, as in that in the Baraboo valley, probably rose until the lowest point in the rim of the basin was reached, and there they had their outlet. The position of this outlet has not been definitely determined, but it has been thought to be over the divide of the Black river.[8] It is possible, so far as now known, that this lake was connected with that of the Baraboo valley. Until topographic maps of this region are made, the connections will not be easily determined. [8] Chamberlin: Geology of Wisconsin, Vol. 1. Even after the ice had retreated past the Wisconsin, opening up the present line of drainage, the lakes did not disappear at once, for the ice had left considerable deposits of drift in the Wisconsin valley. Thus at F, Plates II and XXXVII, and perhaps at other points, the Wisconsin has made cuts of considerable depth in the drift. Were these cuts filled, as they must have been when the ice melted, the drainage would be ponded, the waters standing at the level of the dam. This drift obstruction at F would therefore have prolonged the history of the lake which had come into existence when the ice blocked the drainage of the Wisconsin. As the drift of the valley was removed the level of the lake sank and finally disappeared. _Baraboo lake._--Another lake which existed in this region when the ice was here, occupied the valley of the Baraboo and its tributaries when the ice blocked the valley at Baraboo. This lake occupied not only the valley of the Baraboo, but extended up the lower course of every tributary, presumably rising until it found the lowest point in the rim of the drainage basin. The location of this point, and therefore the height of the lake when at its maximum, are not certainly known, though meager data on this point have been collected. At a point three miles southeast of Ablemans on the surface of a sandstone slope, water-worn gravel occurs, the pebbles of which were derived from the local rock. On the slope below the gravel, the surface is covered with loam which has a suggestion of stratification, while above it, the soil and subsoil appear to be the product of local rock decomposition. This water-worn gravel of local origin on a steep slope facing the valley, probably represents the work of the waves of this lake, perhaps when it stood at its maximum height. This gravel is about 125 feet (aneroid measurement) above the Baraboo river to the north. Further evidence of a shore line has been found at the point marked T, Plate II. At this place water-worn gravel of the local rock occurs in much the same relationship as that already mentioned, and at the same elevation above the Baraboo river. At a point two and one-half miles southwest of Ablemans there is local water-worn gravel, with which is mingled glacial material (pieces of porphyry and diabase) which could have reached this point only by being carried thither by floating ice from the glacier. The level of this mixed local and glacial material is (according to aneroid measurement) approximately the same as that of the other localities. When the ice melted, an outlet was opened _via_ the Lower narrows, and the water of the lake drained off to the Wisconsin by this route. Had the ice left no drift, the lake would have been promptly drained when the ice melted; but the lake did not entirely disappear immediately after the ice retreated, for the drift which the ice left obstructed drainage to the east. The moraine, however, was not so high as the outlet of the lake while the ice was on, so that, as the ice retreated, the water flowed over the moraine to the east, and drew down the level of the lake to the level of the lowest point in the moraine. The postglacial cut through the moraine is about ninety feet deep. Besides being obstructed where crossed by the terminal moraine, the valley of the Baraboo was clogged to a less extent by drift deposits between the moraine and the Lower narrows. At one or two places near the City of Baraboo, such obstructions, now removed, appear to have existed. Just above the Lower narrows (c, Plate XXXVII) there is positive evidence that the valley was choked with drift. Here in subsequent time, the river has cut through the drift-filling of the preglacial valley, developing a passage about twenty rods wide and thirty-five feet deep. If this passage were filled with drift, reproducing the surface left by the ice, the broad valley above it would be flooded, producing a shallow lake. The retreat of the ice therefore left two well defined drift dams in the valley, one low one just above the Lower narrows, and a higher one, the moraine dam, just west of Baraboo. Disregarding the influence of the ice, and considering the Baraboo valley only, these two dams would have given rise to two lakes, the upper one behind the higher dam being deeper and broader, and covering a much larger area; the lower one behind the lower dam, being both small and shallow. Up to the time that the ice retreated past the Lower narrows, the waters of the upper and lower lakes were united, held up to a common level by the ice which blocked this pass. After the ice retreated past the Lower narrows, the level of the Baraboo lake did not sink promptly, for not until the ice had retreated past the site of the Wisconsin was the present drainage established. Meantime the waters of the Baraboo lake joined those of Wisconsin lake through the Lower narrows. If the lakes had been before connected at some point farther west, this connection through the narrows would not have changed the level of either. If they were not before connected, and if the Wisconsin lake was lower than the Baraboo, this connection would have drawn down the level of the latter. Since the drainage from the Baraboo went to the Wisconsin, the Baraboo lake was not at first lowered below the level of the highest obstruction in the valley of the Wisconsin even after the ice had retreated beyond that stream. As the drift obstructions of the Wisconsin valley were lowered, the levels of all the lakes above were correspondingly brought down. When the level of the waters in these lakes was brought down to the level of the moraine dam above Baraboo, the one Baraboo lake of earlier times became two. The level of the upper of these two lakes was determined by the moraine above Baraboo, that of the lower by the highest obstruction below the moraine in either the Baraboo or Wisconsin valley. The drift obstructions in the Baraboo valley were probably removed about as fast as those in the Wisconsin, and since the obstructions were of drift, and the streams strong, the removal of the dams was probably rapid. Both the upper and lower Baraboo lakes, as well as the Wisconsin, had probably been reduced to small proportions, if not been completely drained, before the glacial period was at an end. _Devil's lake in glacial times._--While the ice edge was stationary in its position of maximum advance, its position on the north side of the main quartzite range was just north of Devil's lake (Plate XXXVII). The high ridge of drift a few rods north of the shore is a well defined moraine, and is here more clearly marked than farther east or west, because it stands between lower lands on either side, instead of being banked against the quartzite ridge. North of the lake it rises about 75 feet above the water. When the ice edge lay in this position on the north side of the range, its front between the East bluff and the Devil's nose lay a half mile or so from the south end of the lake. In this position also there is a well defined moraine. While the ice was at its maximum stand, it rose above these moraine ridges at either end of the lake. Between the ice at these two points there was then a notable basin, comparable to that of the present lake except that the barriers to the north and southeast were higher than now. The melting of the ice supplied abundant water, and the lake rose above its present level. The height which it attained is not known, but it is known to have risen at least 90 feet above its present level. This is indicated by the presence of a few drift bowlders on the West bluff of the lake at this height. They represent the work of a berg or bergs which at some stage floated out into the lake with bowlders attached. Bowlders dropped by bergs might be dropped at any level lower than the highest stand of the lake. _Other lakes._--Another glacial lake on the East quartzite bluff has already been referred to. Like the Devil's lake in glacial time, its basin was an enclosure between the ice on the one hand, and the quartzite ridge on the other. The location of this lake is shown on Plate XXXVII (s). Here the edge of the ice, as shown by the position of the moraine, was affected by a re-entrant curve, the two ends of which rested against the quartzite ridge. Between the ice on the one hand and the quartzite ridge on the other, a small lake was formed. Its position is marked by a notable flat. With the exception of the north side, and a narrow opening at the northwest corner, the flat is surrounded by high lands. When the ice occupied the region, its edge held the position shown by the line marking the limit of its advance, and constituted an ice barrier to the north.[9] The area of the flat was, therefore, almost shut in, the only outlet being a narrow one at t, Plate XXXVII. If the filling of stratified drift which underlies the flat were removed, the bottom of the area would be much lower than at present, and much lower than the outlet at t. It is therefore evident that when the ice had taken its position along the north side of the flat, an enclosed basin must have existed, properly situated for receiving and holding water. Since this lake had but a short life and became extinct before the ice retreated, its history is here given. [9] The moraine line on the map represents the crest of the marginal ridge rather than its outer limit, which is slightly nearer the lake margin. Stratified drift of the nature of overwash also intervenes at points between the moraine and the lake border. At first the lake had no outlet and the water rose to the level of the lowest point (t) in the rim of the basin, and thence overflowed to the west. Meanwhile the sediments borne in by the glacial drainage were being deposited in the lake in the form of a subaqueous overwash plain, the coarser parts being left near the shore, while the finer were carried further out. Continued drainage from the ice continued to bring sediment into the lake, and the subaqueous overwash plain extended its delta-like front farther and farther into the lake, until its basin was completely filled. With the filling of the basin the lake became extinct. The later drainage from the ice followed the line of the outlet, the level of which corresponds with the level of the filled lake basin. This little extinct lake is of interest as an example of a glacial lake which became extinct by having its basin filled during glacial times, by sediments washed out from the ice. Near the northwest corner of this flat, an exposure in the sediments of the old lake bed shows the curiously contorted layers of sand, silt, and clay represented in Plate XXXVIII. The layers shown in the figure are but a few feet below the level of the flat which marks the site of the lake. It will be seen that the contorted layers are between two series of horizontal ones. The material throughout the section is made up of fine-grained sands and clays, well assorted. That these particular layers should have been so much disturbed, while those below and above remained horizontal, is strange enough. The grounding of an iceberg on the surface before the overlying layers were deposited, the action of lake ice, or the effect of expansion and contraction due to freezing and thawing, may have been responsible for the singular phenomenon. Contorted laminæ are rather characteristic of the deposits of stratified drift. _After the Ice Had Disappeared._ As has already been indicated, the irregular deposition of glacial drift gave rise to many depressions without outlets in which surface waters collected after the ice had disappeared, forming ponds or lakes. So abundant are lakes and ponds and marshes in recently glaciated regions and so rare elsewhere, that they constitute one of the more easily recognized characteristics of a glaciated region. After the ice had melted, the mantle of drift which it left was sometimes so disposed as to completely obliterate preglacial valleys. More commonly it filled preglacial valleys at certain points only. In still other cases a valley was not filled completely at any point, though partially at many. In this last case, the partial fillings at various points constituted dams above which drainage was ponded, making lakes. If the dams were not high enough to throw the drainage out of the valley, the lakes would have their outlets over them. The drift dam being unconsolidated would be quickly cut down by the outflowing water, and the lake level lowered. When the dam was removed or cut to its base, the lake disappeared and drainage followed its preglacial course. In case the valley was completely filled, or completely filled at points, the case was very different. The drainage on the drift surface was established with reference to the topography which obtained when the ice departed, and not with reference to the preglacial valleys. Wherever the preglacial valleys were completely filled, the postglacial drainage followed lines which were altogether independent of them. When preglacial valleys were filled by the drift in spots only, the postglacial streams followed them where they were not filled, only to leave them where the blocking occurred. In the former case the present drainage is through valleys which are preglacial in some places, and postglacial in others. Thus the drainage changes effected by the drift after the ice was gone, concerned both lakes and rivers. In this region there are several illustrations of these changes. _Lakes._--The lake basins of drift-covered regions are of various types. Some of them are altogether in drift, some partly in drift and partly in rock, and some wholly in rock. Basins in the drift were likely to be developed whenever heavy deposits surrounded thin ones. They are especially common in the depressions of terminal moraines. Another class of lake basins occurs in valleys, the basins being partly rock and partly drift. If a thick deposit of drift be made at one point in a valley, while above there is little or none, the thick deposit will form a dam, above which waters may accumulate, forming a pond or lake. Again, a ridge of drift may be deposited in the form of a curve with its ends against a rock-ridge, thus giving rise to a basin. In the course of time, the lakes and ponds in the depressions made or occasioned by the drift will be destroyed by drainage. Remembering how valleys develop it is readily understood that the heads of the valleys will sooner or later find the lakes, and drain them if their bottoms be not too low. Drainage is hostile to lakes in another way. Every stream which flows into a lake brings in more or less sediment. In the standing water this sediment is deposited, thus tending to fill the lake basin. Both by filling their basins and by lowering their outlets, rivers tend to the destruction of lakes, and given time enough, they will accomplish this result. In view of this double hostility of streams, it is not too much to say that "rivers are the mortal enemies of lakes." The destruction of lakes by streams is commonly a gradual process, and so it comes about that the abundance and the condition of the undrained areas in a drift-covered region is in some sense an index of the length of time, reckoned in terms of erosion, which has elapsed since the drift was deposited. In this region there were few lakes which lasted long after the ice disappeared. The basins of the Baraboo and Wisconsin lakes were partly of ice, and so soon as the ice disappeared, the basins were so nearly destroyed, and the drift dams that remained so easily eroded, that the lakes had but a brief history,--a history that was glacial, rather than postglacial. The history of the little lake on the East quartzite bluff as already pointed out, came to an end while the ice was still present. The beds of at least two other extinct ponds or small lakes above the level of the Baraboo are known. These are at v and w, Plate XXXVII. They owed their origin to depressions in the drift, but the outflowing waters have lowered their outlets sufficiently to bring them to the condition of marshes. Both were small in area and neither was deep. _Existing lakes._--Relatively few lakes now remain in this immediate region, though they are common in most of the country covered by the ice sheet which overspread this region. Devil's lake only is well known. The lake which stood in this position while the ice was on, has already been referred to. After the ice had melted away, the drift which it had deposited still left an enclosure suitable for holding water. The history of this basin calls for special mention. At the north end of the lake, and again in the capacious valley leading east from its south end, there are massive terminal moraines. Followed southward, this valley though blocked by the moraine a half mile below the lake, leads off towards the Wisconsin river, and is probably the course of a large preglacial stream. Beyond the moraine, this valley is occupied by a small tributary to the Wisconsin which heads at the moraine. To the north of the lake, the head of a tributary of the Baraboo comes within eighty rods of the lake, but again the terminal moraine intervenes. From data derived from wells it is known that the drift both at the north and south ends of the lake extends many feet below the level of its water, and at the north end, the base of the drift is known to be at least fifty feet below the level of the bottom of the lake. The draining of Devil's lake to the Baraboo river is therefore prevented only by the drift dam at its northern end. It is nearly certain also, that, were the moraine dam at the south end of the lake removed, all the water would flow out to the Wisconsin, though the data for the demonstration of this conclusion are not to be had, as already stated. There can be no doubt that the gorge between the East and West bluffs was originally the work of a pre-Cambrian stream, though the depth of the pre-Cambrian valley may not have been so great as that of the present. Later, the valley, so far as then excavated, was filled with the Cambrian (Potsdam) sandstone, and re-excavated in post-Cambrian and preglacial time. Devil's lake then occupies an unfilled portion of an old river valley, isolated by great morainic dams from its surface continuations on either hand. Between the dams, water has accumulated and formed the lake. _Changes in Streams._ In almost every region covered by the ice, the streams which established themselves after its departure follow more or less anomalous courses. This region is no exception. Illustrations of changes which the deposition of the drift effected have already been given in one connection or another in this report. _Skillett creek._--An illustration of the sort of change which drift effects is furnished by Skillett creek, a small stream tributary to the Baraboo, southwest of the city of that name. For some distance from its head (a to b, Fig. 43) its course is through a capacious preglacial valley. The lower part of this valley was filled with the water-laid drift of the overwash plain. On reaching the overwash plain the creek therefore shifted its course so as to follow the border of that plain, and along this route, irrespective of material, it has cut a new channel to the Baraboo. The postglacial portion of the valley (b to c) is everywhere narrow, and especially so where cut in sandstone. The course and relations of this stream suggest the following explanation: Before the ice came into the region, Skillett creek probably flowed in a general northeasterly direction to the Baraboo, through a valley comparable in size to the preglacial part of the present valley. As the ice advanced, the lower part of this valley was occupied by it, and the creek was compelled to seek a new course. The only course open to it was to the north, just west of the advancing ice, and, shifting westward as fast as the ice advanced, it abandoned altogether its former lower course. Drainage from the ice then carried out and deposited beyond the same, great quantities of gravel and sand, making the overwash plain. This forced the stream still farther west, until it finally reached its present position across a sandstone ridge or plain, much higher than its former course. Into this sandstone it has since cut a notable gorge, a good illustration of a postglacial valley. The series of changes shown by this creek is illustrative of the changes undergone by streams in similar situations and relations all along the margin of the ice. [Illustration: Fig. 43.--Skillett Creek, illustrating the points mentioned in the text.] The picturesque glens (Parfrey's and Dorward's) on the south face of the East bluff are the work of post-glacial streams. The preglacial valleys of this slope were obliterated by being filled during the glacial epoch. _The Wisconsin._--The preglacial course of the Wisconsin river is not known in detail, but it was certainly different from the course which the stream now follows. On Plate I the relations of the present stream to the moraine (and former ice-front) may be seen.[10] As the ice approached it from the east, the preglacial valley within the area here under consideration was affected first by the overwash from the moraine, and later by the ice itself, from the latitude of Kilbourn City to Prairie du Sac. [10] The preglacial course was probably east of the present in the vicinity of Kilbourn City. It has already been stated that the ice probably dammed the river, and that a lake was formed above Kilbourn City, reaching east to the ice and west over the lowland tributary to the river, the water rising till it found an outlet, perhaps down to the Black river valley. When the ice retreated, the old valley had been partly filled, and the lowest line of drainage did not everywhere correspond with it. Where the stream follows its old course, it flows through a wide capacious valley, but where it was displaced, it found a new course on the broad flat which bordered its preglacial course. Displacement of the stream occurred in the vicinity of Kilbourn City, and, forced to find a new line of flow west of its former course, the stream has cut a new channel in the sandstone. To this displacement of the river, and its subsequent cutting, we are indebted for the far-famed Dalles of the Wisconsin. But not all the present route of the river through the dalles has been followed throughout the entire postglacial history of the stream. In Fig. 44, the depression A, B, C, was formerly the course of the stream. The present course between D and E is therefore the youngest portion of the valley, and from its lesser width is known as the "narrows." During high water in the spring, the river still sends part of its waters southward by the older and longer route. The preglacial course of the Wisconsin south of the dalles has never been determined with certainty, but rational conjectures as to its position have been made. The great gap in the main quartzite range, a part of which is occupied by Devil's lake, was a narrows in a preglacial valley. The only streams in the region sufficiently large to be thought of as competent to produce such a gorge are the Baraboo and the Wisconsin. If the Baraboo was the stream which flowed through this gorge in preglacial time, the comparable narrows in the north quartzite range--the Lower narrows of the Baraboo--is to be accounted for. The stream which occupied one of these gorges probably occupied the other, for they are in every way comparable except in that one has been modified by glacial action, while the other has not. [Illustration: Fig. 44.--The Wisconsin valley near Kilbourn City.] The Baraboo river flows through a gorge--the Upper narrows--in the north quartzite range at Ablemans, nine miles west of Baraboo. This gorge is much narrower than either the Lower narrows or the Devil's lake gorge, suggesting the work of a lesser stream. It seems on the whole probable, as suggested by Irving,[11] that in preglacial time the Wisconsin river flowed south through what is now the Lower narrows of the Baraboo, thence through the Devil's lake gorge to its present valley to the south. If this be true, the Baraboo must at that time have joined this larger stream at some point east of the city of the same name. [11] Irving. Geology of Wisconsin, Vol. II. _The Driftless Area._ Reference has already been made to the fact that the western part of the area here described is driftless, and the line marking the limit of ice advance has been defined. Beyond this line, gravel and sand, carried beyond the ice by water, extends some distance to the west. But a large area in the southwestern part of the state is essentially free from drift, though it is crossed by two belts of valley drift (valley trains) along the Wisconsin and Mississippi rivers. The "driftless area" includes, besides the southwestern portion of Wisconsin, the adjoining corners of Minnesota, Iowa and Illinois. In the earlier epochs of the glacial period this area was completely surrounded by the ice, but in the last or Wisconsin epoch it was not surrounded, since the lobes did not come together south of it as in earlier times. (Compare Plate XXXIII and Fig. 36.) Various suggestions have been made in the attempt to explain the driftless area. The following is perhaps the most satisfactory:[12] [12] Chamberlin and Irving. Geology of Wisconsin, Vols. I and II. The adjacent highlands of the upper peninsula of Michigan, are bordered on the north by the capacious valley of Lake Superior leading off to the west, while to the east lies the valley of Lake Michigan leading to the south. These lake valleys were presumably not so broad and deep in preglacial times as now, though perhaps even then considerable valleys. When the ice sheet, moving in a general southward direction from the Canadian territory, reached these valleys, they led off two great tongues or lobes of ice, the one to the south through the Lake Michigan depression, the other to the south of west through the Lake Superior trough. (Fig. 36.) The highland between the lake valleys conspired with the valleys to the same end. It acted as a wedge, diverting the ice to either side. It offered such resistance to the ice, that the thin and relatively feeble sheet which succeeded in surmounting it, did not advance far to the south before it was exhausted. On the other hand, the ice following the valleys of Lakes Superior and Michigan respectively, failed to come together south of the highland until the latitude of northern Iowa and Illinois was reached. The driftless area therefore lies south of the highlands, beyond the limit of the ice which surmounted it, and between the Superior and Michigan glacial lobes above their point of union. The great depressions, together with the intervening highland, are therefore believed to be responsible for the absence of glaciation in the driftless area. _Contrast Between Glaciated and Unglaciated Areas._ The glaciated and unglaciated areas differ notably in (1) topography, (2) drainage, and (3) mantle rock. 1. _Topography._--The driftless area has long been exposed to the processes of degradation. It has been cut into valleys and ridges by streams, and the ridges have been dissected into hills. The characteristic features of a topography fashioned by running water are such as to mark it clearly from surfaces fashioned by other agencies. Rivers end at the sea (or in lakes). Generally speaking, every point at the bottom of a river valley is higher than any other point in the bottom of the same valley nearer the sea, and lower than any other point correspondingly situated farther from the sea. This follows from the fact that rivers make their own valleys for the most part, and a river's course is necessarily downward. In a region of erosion topography therefore, tributary valleys lead down to their mains, secondary tributaries lead down to the first, and so on; or, to state the same thing in reverse order, in every region where the surface configuration has been determined by rain and river erosion, every gully and every ravine descends to a valley. The smaller valleys descend to larger and lower ones, which in turn lead to those still larger and lower. The lowest valley of a system ends at the sea, so that the valley which joins the sea is the last member of the series of erosion channels of which the ravines and gullies are the first. It will thus be seen that all depressions in the surface, worn by rivers, lead to lower ones. The surface of a region sculptured by rivers is therefore marked by valleys, with intervening ridges and hills, the slopes of which descend to them. All topographic features are here determined by the water courses. [Illustration: Fig. 45.--Drainage in the driftless area. The absence of ponds and marshes is to be noted.] The relief features of the glaciated area, on the other hand, lack the systematic arrangement of those of the unglaciated territory, and stream valleys are not the controlling elements in the topography. 2. _Drainage._--The surface of the driftless area is well drained. Ponds and lakes are essentially absent, except where streams have been obstructed by human agency. The drainage of the drift-covered area, on the other hand, is usually imperfect. Marshes, ponds and lakes are of common occurrence. These types are shown by the accompanying maps, Figs. 45 and 46, the one from the driftless area, the other from the drift-covered. [Illustration: Fig. 46.--Drainage in a glaciated region. Walworth and Waukesha counties, Wisconsin, showing abundance of marshes and lakes.] 3. _Mantle rock._--The unglaciated surface is overspread to an average depth of several feet by a mantle of soil and earth which has resulted from the decomposition of the underlying rock. This earthy material sometimes contains fragments and even large masses of rock like that beneath. These fragments and masses escaped disintegration because of their greater resistance while the surrounding rock was destroyed. This mantle rock grades from fine material at the surface down through coarser, until the solid rock is reached, the upper surface of the rock being often ill-defined (Fig. 47). The thickness of the mantle is approximately constant in like topographic situations where the underlying rock is uniform. The residual soils are made up chiefly of the insoluble parts of the rock from which they are derived, the soluble parts having been removed in the process of disintegration. [Illustration: Fig. 47.--Section in a driftless area, showing relation of the mantle rock to the solid rock beneath.] With these residuary soils of the driftless area, the mantle rock of glaciated tracts is in sharp contrast. Here, as already pointed out, the material is diverse, having come from various formations and from widely separated sources. It contains the soluble as well as the insoluble parts of the rock from which it was derived. In it there is no suggestion of uniformity in thickness, no regular gradation from fine to coarse from the surface downward. The average thickness of the drift is also much greater than that of the residual earths. Further, the contact between the drift and the underlying rock surface is usually a definite surface. (Compare Figs. 32 and 47.) POSTGLACIAL CHANGES. Since the ice melted from the region, the changes in its geography have been slight. Small lakes and ponds have been drained, the streams whose valleys had been partly filled, have been re-excavating them, and erosion has been going on at all points in the slow way in which it normally proceeds. The most striking example of postglacial erosion is the dalles of the Wisconsin, and even this is but a small gorge for so large a stream. The slight amount of erosion which has been accomplished since the drift was deposited, indicates that the last retreat of the ice, measured in terms of geology and geography, was very recent. It has been estimated at 7,000 to 10,000 years, though too great confidence is not to be placed in this, or any other numerical estimate of post-glacial time. INDEX. -------------------------------------------------- PAGES Ablemans 66,67 Baraboo Lake 130 Baraboo Quartzite ranges 2, 65 Constitution of 14 Dynamic action in 15, 17, 18 Gaps in-- Devil's Lake Gap 3, 13 Lower Narrows 5, 13, 67 Narrows Creek 66 Upper Narrows 5, 10, 17, 19, 67 Igneous rock in 18 Structure of 15 Topography of 5, 13 Base-level 47 Base-level plains 50 Bowlder clay 97 Breccia 18 Castle Rock 71 Cleopatra's Needle 65 Cold Water Canyon 70 Conglomerate 10, 28 Basal (Potsdam) 29 Corrasion 36 Cross-bedding 30 Cycle of erosion 44, 47 Dalles of the Wisconsin 69 Origin of 53 Scenery of 69, 140 Dell Creek 53 Deltas 30, 56, 120 Deposits-- By extra-glacial waters 115-123 By ice 85, 94 By rivers 55, 56 By subglacial streams 124 Of drift classified 127 Devil's Doorway 65 Devil's Lake 132 History of 132 In glacial times 132 Location 3, 9 Origin of 132 Devil's Nose 5, 110 Divides, Shifting of 44 Dorward's Glen 10, 14, 29, 68 Drift 73 Characteristics of 96 Constitution of 94 Deposits classified 127 Effect on topography 85, 88 Relation of stratified to unstratified 125 Stratified 111 Topography of 101, 103 Driftless area 79, 142 Drainage-- Adjustment of 62 Changes in, effected by the ice 128, 142 Establishment of 61 Glacial 113 Of drift-covered area 144 Of driftless area 144 Postglacial changes in 146 Endmoräne 108 Erosion-- By rain, and rivers, general outline of 36-58 Elements of 36 Of folded strata 50 Of rocks of unequal hardness 47 Of the quartzite 25 Preglacial 60 Topography 12 Without valleys 37 Eskers 124 Falls 48 Fossils-- In limestone 12 In sandstone 9, 11 Friendship mounds 71 Geographic features, general 3-20 Glacial drainage 113 Glaciated area 78, 91, 143 Glacier ice-- Deposition by 85 Direction of movement 88 Erosive work of 79-84 Formation of 74 Movement of, affected by topography 89 Glens 68 Green Bay lobe 91 Gibraltar rock 63 Ground Moraine-- Constitution of 99 Location of 97 Topography of 101 Groundwater level 41 Ice sheets-- Formation of 74 History of 114 Movement of 75, 88 North American ice sheet 78 Igneous rock 18 Intermittent streams 42 Kames 115 Lakes-- Wisconsin Lake 129 Baraboo Lake 130 Devil's Lake 3, 9, 132, 137 Limestone, see Lower Magnesian. Lower Magnesian limestone-- Fossils of 12 History of 31-32 Occurrence of 11 Origin of 11 Position of 12 Structure of 8 Lower Narrows 5, 13, 67 Mantle rock 20, 144 Metamorphism 14, 24 Monadnocks 51 Moraines (see terminal moraine and ground moraine). Morainic aprons 119 Narrows 49 In quartzite 66, 67 Natural bridge 69 Navy Yard 69 Niagara limestone 33 North American ice sheet 78 Nunatak 89 Osars (see Eskers). Outwash plains 118, 120 Overwash plains 118, 120 Parfrey's Glen 10, 14, 29, 68 Peneplain 47, 50 Pewit's nest 9, 53, 69 Pine Hollow 69 Postglacial changes 146 Potsdam sandstone-- Fossils of 9, 11 History of 27-31 Origin of 9-11 Relation to quartzite 19 Structure of 8 Quartzite (see also Baraboo quartzite ranges)-- Dynamic Metamorphism of 24 Erosion of 25 Origin of 23 Submergence of 27 Thickness of 26 Uplift of 24 Rapids 48 Rejuvenation of streams 56 Ripple marks 9, 15 Roches moutonnée 81 Sandstone (see Potsdam and St. Peters). Sauk Prarie 117, 118, 119 Skillett Creek 8, 53, 138 Slope of upper surface of ice 111 Snow fields 74 Soil 7, 144, 146 Stand rock 70 Steamboat rock 70 St. Peter's sandstone 32 Stratified drift 111-112, 125 Streams, changes in 138 Subaqueous overwash plains 120 Subglacial till (ground moraines) 99 Sugar Bowl 70 Talus slopes 65 Terminal moraines-- Across the United States 78 Development of 102 In Devil's Lake region 105 Boundaries of 106 Location of 92, 93, 108 On the main quartzite range 107 Width of 106 Topography of 103 Till 97 Topography-- Effect of, on ice movement 89 Erosion topography 12 Of drift-covered country 8, 143 Of driftless area 6, 7, 12, 143 Of plain surrounding quartzite ridge 6 Of quartzite ridges 5 Transportation by streams 55 Tributary valleys 39 Turk's Head 65 Unconformity 19 Underground water 58 Unglaciated areas 79, 142, 143 Unstratified drift 99, 102, 125 Upper Narrows 5, 10, 17, 19, 67 Valley, the-- Beginning of 37 Characteristics of, at various stages 52-54 Course of 39 How a valley gets a stream 40 Limits of 43 Valley trains 116 Waterfalls 48 Weathering 36 Webster's Prarie 119 Wisconsin Lake 129 Wisconsin River 139 Witch's Gulch 70 
38066	----	THE ADVENTURES OF A GRAIN OF DUST _STRANGE ADVENTURES IN NATURE'S WONDERLANDS_ THE ADVENTURES OF A GRAIN OF DUST BY HALLAM HAWKSWORTH AUTHOR OF "THE STRANGE ADVENTURES OF A PEBBLE" CHARLES SCRIBNER'S SONS NEW YORK CHICAGO BOSTON COPYRIGHT, 1922, BY CHARLES SCRIBNER'S SONS Printed in the United States of America C [Illustration] JUST A WORD I don't want you to think that I'm boasting, but I _do_ believe I'm one of the greatest travellers that ever was; and if anybody, living or dead, has ever gone through with more than I have I'd like to hear about it. Not that I've personally been in all the places or taken part in all the things I tell in this book--I don't mean to say that--but I do ask you to remember how long it is possible for a grain of dust to last, and how many other far-travelled and much-adventured dust grains it must meet and mix with in the course of its life. The heart of the most enduring grains of dust is a little particle of sand, the very hardest part of the original rock fragment out of which it was made. That's what makes even the finest mud seem gritty when it dries on your feet. And the longer these sand grains last the harder they get, as you may say; for it is the hardest part that remains, of course, as the grain wears down. Moreover, the smaller it gets the less it wears. If it happens to be spending its time on the seashore, for example, the very same kind of waves that buffet it about so, waves that, farther down the beach hurl huge blocks of stone against the cliffs and crack them to pieces, not only do not wear away the sand grains, to speak of, but actually save them from wear. The water between the grains protects them; like little cushions. And the sand in the finer dust grains carried by the wind is protected by the material that gathers on its surface. Why, if a pebble of the size of a hickory-nut may be ages and ages old--almost in the very form in which you see it,[1] think what the age of this long-enduring part of a grain of dust must be. [1] "The Strange Adventures of a Pebble." Then remember what the ever-changing material on the surface of these immortal grains is made of; the dust particles of plants and animals, of buried Cæsars and still older ancients, such as those early settlers of Chapter II. Finally, if what we call flesh and blood can think and talk, why not a grain of dust? In fact, what is flesh and blood but dust come back to life? Says the poet--and the poets know: "The very dust that blows along the street Once whispered to its love that life is sweet." You see it's as likely a thing as could happen--this whole story. THE GRAIN OF DUST. (Per H. H.) CONTENTS CHAPTER PAGE I. _The Little Old Man of the Rock_ 1 II. _Some Early Settlers and Their Bones_ 19 III. _The Winds and the World's Work_ 37 IV. _The Bottom-Lands_ 55 V. _What the Earth Owes to the Earthworm_ 75 VI. _The Little Farmers with Six Feet_ 92 VII. _Farmers with Four Feet_ 114 VIII. _Water Farmers Who Help Make Land_ 137 IX. _Farmers Who Wear Feathers_ 162 X. _The Busy Fingers of the Roots_ 186 XI. _The Autumn Stores and the Long Winter Night_ 204 XII. _The Brotherhood of the Dust_ 225 _Index_ 247 THE ILLUSTRATIONS The author wishes to make special acknowledgment to the following publishers for their courtesy in supplying illustrations: The Macmillan Company for the pictures from Tarr and Martin's "College Physiography" on page 239; Darwin's "Formation of Vegetable Mould" on page 77. D. Appleton and Company for the pictures from Gilbert and Brigham's "Introduction to Physical Geography" on page 94; "Picturesque America" on page 243. J. B. Lippincott Company for the pictures from Beard's "American Boy's Book of Bugs, Butterflies, and Beetles" on page 229; McCook's "Natural History of the Agricultural Ant of Texas" on pages 206 and 213. _McClure's Magazine_ for the pictures on pages 149 and 157. Scientific American Publishing Company for the picture from "Scientific American Boy at School" on page 227. Harper and Brothers for the pictures from McCook's "Nature's Craftsmen" on pages 98, 105, 109, 207, and 208. _Strand Magazine_ for the pictures on pages 165, 182, and 204. Charles Scribner's Sons for the pictures from Yard's "Top of the Continent" on page 5; "Country Life Reader" on pages 9, 64, 85, 114, 186, and 241; Osborn's "Men of the Old Stone Age" on page 33. Hornaday's "American Natural History" on pages 116, 117, 119, 123, 130, 144, and 225; Seton's "Life Histories of Northern Animals" on pages 123, 129, 147, and 151. Henry Holt and Company for the pictures from Beebe's "The Bird, Its Form and Function" on page 167; Salisbury's "Physiography" on pages 55, 71, and 167. Carnegie Institution of Washington for the pictures on pages 8 and 69. University of Nebraska for the picture on page 37. Columbia University Press for the picture from Wheeler's "Ants and Their Structure" on page 95. Houghton Mifflin Company for the pictures from Sharp's "Year Out of Doors" on page 11; "Riverside Natural History" on page 117; Mill's "In the Beaver World" on pages 152 and 153. Ginn and Company for the pictures from Breasted's "Ancient Times" on page 67; "Agriculture for Beginners" on page 47; Bergen's "Foundation of Botany" on pages 49, 190, and 197; Bergen's "Elements of Botany" on pages 193 and 195; Beal's "Seed Dispersal" on page 51. U. S. Geological Survey for the pictures on pages 21, 22, 23, 30, 31, and 59. New York Zoological Society for the pictures on pages 145, 159, and 216. _School Arts Magazine_ for the picture on page 221. U. S. Department of Agriculture for the pictures on pages 125 and 189. American Museum of Natural History for the pictures on pages 20, 24, 26, 139, and 162. Cassell and Company for the pictures from "Popular History of Animals" on pages 118, 177, 179, and 217; "Popular Science" on page 242. Hutchinson for the pictures from "Marvels of the Universe" on pages 92, 101, 103, 141, 169, and 173; "Marvels of Insect Life" on page 211. The Dunham Company for the picture on page 45. International Harvester Company for the picture on page 199. Northern Pacific Railway for the pictures on pages 235 and 237. THE ADVENTURES OF A GRAIN OF DUST It will be understood, as stated in the preface, that, like "The Strange Adventures of a Pebble," this is an autobiography. In other words, it is the grain of dust itself that tells the story of the life of the soil of which it is a part. THE ADVENTURES OF A GRAIN OF DUST CHAPTER I (JANUARY) In truth you'll find it hard to say How it could ever have been young It looks so old and grey. --_Wordsworth._ THE LITTLE OLD MAN OF THE ROCK Some say it was Leif Ericson, some say it was Columbus, but _I_ say it was The Little Old Man of the Rock. And I go further. I say he not only discovered America but Europe, Asia, and Africa, and the islands of the sea. I'll tell you why. I. HOW LITTLE MR. LICHEN DISCOVERED THE WORLD As everybody knows, we must all eat to live, and how could either Columbus or anybody else--except Mr. Lichen--have done much discovering in a world where there was nothing to eat? When the continents first rose out of the sea[2] there wasn't anything to eat but rock. Rock, to be sure, makes very good eating if you have the stomach for it, as Mr. Lichen has. It contains sulphur, phosphorus, silica, potash, soda, iron, and other things that plants are fond of, but ordinary plants can't get these things out of the rock--let alone human beings and other animals; and that's why Mr. Lichen had the first seat at the table and always does. [2] "The Strange Adventures of a Pebble." On bare granite boulders in the fields, on the rocky ruins at the foot of mountains, and even on the mountain tops themselves, on projecting rocks far above the snow line, you find the lichens. On rock of every kind they settle down and get to work. They never complain of the climate--hot or cold, moist or dry. When the land goes dry they simply knock off, and then when a little moisture is to be had they're busy again. A little goes a long way with members of the family who live in regions where water is scarce. Indeed, most of them get along with hardly any moisture at all. The very hardiest of them are so small that a whole colony looks like a mere stain upon the rock. While lichens are generally gray--they seem to have been _born_ old, these queer little men of the rock--you can find some that are black, others bright yellow or cream-colored. Others are pure white or of various rusty and leaden shades. Some are of the color of little mice. To make out any shapes in these tiny forms, you must look very close; and if you have a hand lens you will be surprised to find that this fairy-land of the lichens isn't so drab as it seems to the naked eye. For there are flower gardens--the tiny spore cups. Some of them are vivid crimson and, standing out on a background of pure white, they're very lovely. Some of the science people believe the colors attract the minute insects that the lens shows wandering around in these fairy flower gardens. But just what the insects can be there for nobody knows, since the lichens are scattered, not by insects, but by the wind. As a rule lichens grow only in open, exposed places, although some are like the violets--they enjoy the shade. Some varieties grow on trees, some on the ground, others on the bleached bones of animals in fields and wastes and on the bones of whales cast up by the sea. Of course the whole country was awfully wild when the continents first came out of the sea, but that just suited Mr. Lichen, for there is one thing he can't stand, and that is city life, with its smoke and bad air. "Why, one can't get one's breath!" he says. WHY THE LICHENS DISLIKE CITY LIFE So, while you will not meet Mr. Lichen in cities--at least, until after the people are all gone; that is to say, on ruins of cities of the past--you will find him beautifying the ancient walls of abbeys, old seats of learning like Oxford, and the tombstones of the cities of the dead. Mr. Lichen always travels light. On the surface of the lichens are what seem to be little grains of dust, and these serve the purpose of seeds. A puff of wind will carry away thousands of them, and so start new colonies in lands remote. You see, the fact that he requires so little baggage must have been a great advantage to Mr. Lichen in those early days, when he had to discover not only America but all the rest of the world map, spread out so wide and far. You can just imagine how the grains of lichen dust, the seed of the race, must have gone whirling across the world with the winds. But if a breath of wind would carry them away so easily, how could they _stay_ on a rock, these tiny lichen travellers? Especially as they have no roots? They have curious rootlike fibres which absorb food by dissolving the rock, and this dissolved rock, hardening, holds them on. The fibres of lichens that grow on granite actually sink into it by dissolving the mica and forcing their way between the other kinds of particles in the rock that they can't eat. Thus they help break it up. As we all know, little people are great eaters in proportion to their size, but it is said the lichens are the heartiest eaters in the world. They eat more mineral matter than any other plant, and all plants are eaters of minerals. Yet, you'd wonder what they do with the food they eat--most of them grow so slowly. A student of lichens watched one of them on the tiled roof of his house in France--one of the kind of lichens that look like plates of gold--and in forty years he couldn't see that it had grown a single bit, although he measured it carefully. HOW MR. LICHEN EATS UP STONES But how could such feeble creatures, as they seem to be, ever eat anything so hard as rock? Well, they couldn't if it wasn't for one thing--they understand chemistry. At least they carry with them, or know how to make, an acid, and it's this acid which enables them to dissolve the rock so that they can absorb it. The acid is in their fibres--what answer for roots. And the dissolved rock not only gives them their daily bread, but, as I said a moment ago, holds them on. This use of acid is their way of eating; chewing their food very fine, and mixing it with saliva, as all of us young people are taught to do. The first and smallest of the lichen family spread and decay into a thin film of soil. This decay makes more acid, just as decaying leaves do to-day--they learned it, no doubt, from the lichens--and this acid of decay also eats into the rock and makes more soil. (You see nature, from the start, has been helping those that help themselves, just as the old proverb has it.) Then, after the first tiny lichens--mere grains of dust that have just begun to feel the stir of life--come somewhat larger lichens which can only live where there is a little soil to begin with. These in turn die, which means a still deeper layer of soil, still more acid of decay, and so on up to larger lichens and later more ambitious plants. Then, on the soil made by these successive generations of lichens, higher types of plants--plants with true roots--get a foothold. Besides making soil themselves, the lichens help accumulate soil by holding grains of rock broken up by their fibres and loosened by the action of the heat and cold of day and night and change of season. These little grains become entangled in the larger lichens and are kept, many of them, from being washed away by the heavy rains. So held, they are in time crumbled into soil by the action of the acids and by mixture with the products of plant decay. To this day, go where you will, over the whole face of the earth, and you'll find the lichens there ahead of you, dressed in their sober suits, some gray as ashes, others brown, but some are as yellow as gold; for even these old people like a little color once in a while. As travellers they beat all. "Their geographical range is more extended than that of any other class of plants." That's how the learned lichenologists put it. For these lichens, these humble little brothers of our dust, that many of us never looked at twice on the stones of the field, or the gray stumps and dead limbs in the wood, are so interesting when you've really met them--been properly introduced--that a whole science has grown up around them called "lichenology." And exciting! You ought to hear the hot discussions that lichenologists get into. You read, for instance, that such and such a theory "was received with a storm of opposition" (as most new theories are, by the way, particularly if they are sound). But the tumults and the strifes of science, of politics, or of wars don't disturb little old Mr. Lichen himself. There on his rock he'll sit, overlooking the scenery and watching life and the seasons come and go for 100, 200, 500 years, and more. For while they grow so slowly the lichens make up for it by living to an extreme age. THE LICHENS AND THE ROMAN EMPIRE Why, do you know that during the lifetime of certain lichens that are still hale and hearty, not only a long line of Cæsars might rise, flourish, die, and, with their clay, stop holes to keep the wind away, as Mr. Shakespere put it, but the vast Roman Empire could and did come into being, move across the stage with its banners and trumpets and glittering pomp and go back to the dust again. Some lichens, growing on the highest mountain ranges of the world, are known to be more than 2,000 years old! [Illustration: THE SEQUOIAS; THE SUNLIGHT AND THE SHADE Wonderful sunlight effect, isn't it? We are here in Sequoia National Park and those big trees are sequoias, members of the pine-tree family.] II. THE MARCH OF THE TREES Of course I don't mean to say it takes any 2,000 years for the average lichen to die and turn to dust. These long-lived lichens are the Methuselahs of their race. Most kinds die much younger, as time goes among the lichens, and in a comparatively few years, a century say, after their first settlement on the rock, the lichens have become soil. All this time the heating of the rock by day and the cooling off at night, the work of frost and the gases of the rain and the air[3] have also helped to make more soil and by and by there is enough for lichens of a larger growth; and mosses begin to get a foothold. These, in turn, die and, in decaying, make acids, as did the little lichens before them, and this acid joins hands with all the other forces to work up the rock into soil. Presently there is enough soil to let certain adventurers of the Weed family drop in. The picking is very thin, to be sure, but some of these Weed people have learned to put up with almost anything. Don't suppose, however, that all weeds are alike in this respect. Oh, dear, no! They come into new plant communities just as the trees do, not haphazard, but according to a certain more or less settled order. Some of them, the adventurer type, will, it is true, settle down and seem contented enough on land so poor that to quote the witty Lady Townshend "you will only find here and there a single blade of grass and two rabbits fighting for that"; while other weeds will have nothing to do with soil that, in their opinion, is not good enough for people of their family connections. [3] All these things put together are called "weathering." [Illustration: EARLY SETTLERS IN THE DESERT Besides earning their own living under hard conditions, these sturdy pioneers of the desert are preparing the way for plants of a higher kind, as the next two pictures will tell you.] It has long been known that the character of soil may be told, to a considerable degree, by the kind of weeds that grow on it. An old English writer pointed this out in his quaint way some 200 years ago: "Ground which, though it bear not any extraordinary abundance of grass yet will load itself with strong and lusty weeds, as Hemlocks, Docks, Nettles and such like, is undoubtedly a most rich and fruitful ground for any grain whatsoever." But, he goes on to say: "When you see the ground covered with Heath, Broom, Bracken, Gorse and such like, they be most apparent signs of infinite great barrenness. And, of these infertile places, you shall understand, that it is the clay ground which for the most part brings forth the Moss, the Broom, the Gorse and such like." Wherever soil is coarse and bouldery the weeds also are of a sturdy breed. In his long, delightful days among the mountains Muir[4] tells us what a brave show the thistles made in this new world of soil; how royal they looked in their purple bloom, standing up head and shoulders above the other plants, like Saul among the people. [4] Muir. "The Mountains of California." [Illustration: WHAT THE DESERT PIONEERS DO FOR FUTURE GENERATIONS Only the sturdiest kinds of shrubs and weeds, such as you see in the desert, can earn their keep in sandy soil, always thirsty, like that on the right. But the desert vegetation, dying and decaying--it is then called "humus"--not only knits the soil together but absorbs moisture and ammonia from the air and so helps grow good crops.] HOW PLANT PEOPLE PAY THEIR TAXES In all these plant republics each citizen must pay something into the common treasury for its board and keep. This fund not only meets "national expenses" during the lifetime of the ones who pay these taxes, but it helps prepare the land for the great citizens of the future--the trees. In another hundred years--making two hundred in all, after the arrival of the very first lichens--low shrubs and bushes often find spots in these new communities where the soil is thick enough for their needs. It is very curious how members of the plant world, growing side by side, seek their food at different depths, and send out their roots accordingly. It reminds one of the rigid class distinctions below stairs in a nobleman's household where the chef has his meals in his own private apartment, the kitchen maids in their quarters, the chauffeurs, footman, under butler, and pantry boys in the servants' hall. [Illustration: THE LEADERS OF THE GRAND MARCH] But most striking, it has always seemed to me, is the settled order in which trees march into the land. Why shouldn't the oaks come before the maples? Or the maples before the beeches? Or the beeches before the pines? Why is it that, with the exception of a straggler here and there, the first trees to climb the stony mountainsides are the pines? Then close behind come such trees as the poplars, and along the streams below, the willows. Still farther down the valley are the beeches; farther still the maples, and last of all the oaks. So it is they advance in a certain regular way, each in its own place in the ranks. At first it seems as strange as the coming of Birnam wood to Dunsinane that gave poor Macbeth such a turn that time. But, after all, the explanation is quite simple and no doubt you have guessed it already. The reason such trees as the pines, poplars, and willows come first is that the seeds are so light they are easily carried by the winds and so reach new soil ahead of other trees with winged seeds like the beeches and the maples; for, although these seeds also travel on the wind, they are much larger than the winged seeds of the pine and they travel much more slowly and for shorter distances. Moreover, at the end of their first journey, having once fallen to the ground, they are apt to stay. Then there is no further advance, so far as these particular seeds are concerned, until trees have sprung from them and they, in turn, bear seeds. In the case of very light seeds, like those of the pines, the wind not only carries them far beyond the comparatively slow and heavy march of the beech and the maple, but if they fall on rock with little or no soil the next wind picks them up and carries them farther, so that they may strike some other spot where there is soil and perhaps a little network of grass and weeds to secure them until they can take root and so hold their own. It is not only a great advantage to the pine seeds to be so small, so far as getting ahead of other trees is concerned, but it is an advantage in another way. Because they are so small they require comparatively little soil to start with, are more easily covered up, and so they soon begin to sprout. The very winds that carry them up among the mountain rocks are quite likely to cover them with enough dust to start on, and I myself have helped raise many a giant of the mountain forests in this way. It is really wonderful how little soil a pine-tree can get along with; if, say, its fortunes are cast on some mass of mountain rock. Somehow it manages to get a living among the cracks and at the same time to hold its own in the bitter struggle with the winds. "The pine trees," says Muir, "march up the sun-warmed moraines in long hopeful files, taking the ground and establishing themselves as soon as it is ready for them." [Illustration: _From the painting by Rousseau in the Metropolitan Museum of Art._ THE EDGE OF THE WOODS Last of all come tramping along the sturdy old oaks.] Last of all come tramping along the sturdy old oaks and the nut-bearing trees. Their seeds are so heavy they get little help from the winds, and then only in the most violent storms. They must advance very slowly indeed, with occasional help from absent-minded squirrels who carry away and bury nuts and acorns and then forget where they put them. [Illustration: HOW SQUIRRELS HELP OAKS TO MARCH Sometimes they bury acorns and forget just where. When frightened they often drop them and run away.] ROUGH CITIZENS AMONG THE PIONEERS The beginnings of a forest are stunted because the soil is thin. Moreover, the company in which the trees find themselves is very miscellaneous, like the population of all pioneer communities--weeds, grasses, briers, shrubs. High up on a mountainside you can find all these types of vegetation. Pines growing clear to the snow line; farther down the mountain, in crannies, sumach and elder bushes with field daisies and goldenrod scattered among them; while on the barren rocks are the lichens and the mosses. Not only do the citizens of the plant world follow a certain fixed order in coming into new regions, but also in giving place to one another. All plants of a higher order can live only on the remains of those of a lower, and it is most interesting to note the process by which each lower form comes, does its work, passes on, and is replaced by a superior type. The shrubs, which can only grow after the weeds and grasses have made enough soil for them, at length shade out these smaller pioneers. Haven't you often noticed, when picnicing in deep woods, that the grasses and flowers are to be found only in the sunny spaces, where there are no trees? But these thickets themselves, after a while, disappear, and pines take their places. I am speaking now of the growth of forests, where the soil-making has so far advanced that forests are possible. The thickets, with their good soil and the shade which keeps it damp, are just the places for the pine seeds brought in by the wind to get a foothold and sprout up. When they grow into big trees they gather with their high branches so much of the sunshine for themselves that little of it gets through to the shrubs below, so these shrubs disappear, surviving only in the sunny open spaces or along the borders of the wood. But now notice what happens to the pines. When the trees become larger, the young pines that spring up beneath their shade can't get enough sunshine, so, as the big trees grow old and die, there are fewer and fewer young pines to take their places. Now comes the turn of the spruces. For spruces require more and better soil than the pines and they don't mind a reasonable amount of shade. So, as the woods grow thicker and shadier, the pines gradually disappear and the spruces take their places. At first, in the reign of the spruces, some of the old residents begin to come back. A spruce forest, not being so dense in the beginning as a pine forest, lets in a good deal of sunlight, and you'll find scattered through its aisles and byways gentians, bluebells, daisies, goldenrod. In course of time, however, the leaves and branches of the spruces become so thick that hardly a sunbeam can get through and you have a forest where noontime looks like twilight; a forest of deep shade and silence with its thick carpet of brown needles, and where all the shrubs and grasses and flowers have disappeared, except in the open spaces. It was in such a forest and in one of these sunny glades, no doubt, that the knight the little girl tells of in Tennyson: "... while he past the dim lit woods Himself beheld three spirits mad with joy Come dashing down on a tall wayside flower That shook beneath them as the thistle shakes When three gray linnets wrangle for the seed." HOW NATURE RESTORES ABANDONED FARMS So it is that new lands pass from barren rock to forest, and deep rich soil, and so it is that worn-out soils, the result of reckless farming are finally restored. Hardly any soil is too poor for some kind of a weed. These weeds springing up, die and make soil that better kinds of weeds can use. Later come a few woody plants. In the course of fifteen or twenty years the soil is deep enough to support trees; and in fifty years there is a young forest. At the end of a century fine timber can be cut, the land cleared, and the old place may be as good as new. But it's a long time to wait! It's a much better plan to take care of the land in the first place. HIDE AND SEEK IN THE LIBRARY One of the strangest things about Mr. Lichen, as you will see by looking up the subject in any botany or encyclopædia, is that he is really _two_ people--two different plants that have grown into partnership; and that one of the partners supplies water for the firm while the other furnishes the food. The part of "him" that supplies the food is green, or blue-green, and that is why it is able to do this. This idea that Mr. Lichen is really two people was one of those that was "received with a storm of opposition," but certain lichenologists actually took two different kinds of plants, put them together and _made_ a lichen themselves, as you will see when you look the matter up. As to just who among these two kinds of plants shall go into partnership--that usually depends on chance and the winds; although in the case of some lichens, the parents determine upon these partnerships, just as they often do in human relations. If you want to continue this interesting study and become Learned Lichenologists, you will be interested to know that there are a lot of things to be learned, including not only no end of delightful names, such as _Endocarpon_, _Collema_, _Pertusaria_, not to speak of _Xanthoria parietina_, and loads of others, but there are still things unknown that _you_ may be able some day to find out. For instance, while they know that the two kinds of vegetation that together make a lichen, feed and water each other, it's not known exactly _how_ they do it; although the "Britannica" article has a picture showing the two partners in the very act of going into partnership. The article in the "Americana" shows some striking forms of lichens, and how nature from these very dawnings of life begins to dream of beauty. You will be surprised at the forms shown in the "Americana," they are either so graceful, symmetrical, or picturesque. One of them looks like a very elaborate helmet decoration, or plume of a knight. This article also tells what an incredible number of species of lichens there are--enough to make quite a good-sized town, if they were all real people. It also tells why the orange and yellow lichens take to the shady side of the rock; and something about how the lichens get those remarkable decorations and sculpturings, and what the weather has to do with it. There you will also get a probable explanation of the fact that the manna which the Israelites found on the ground in the morning appeared so suddenly. In the article in the "International" you will find another picture of how the two partners--the fungus and the alga--make the lichen, and you will learn that Mr. Lichen's name, like Mr. Lichen himself, is centuries old; being the very name given him by the Greeks, and afterward by the Romans. In the "Country Life Reader" there is an article on the soil that has a very close relationship to the subject of the lichens and their work. It tells, among other things, about the value of humus--decayed leaves, grass, etc.--to the soil. It was the lichens, you know, who _started_ the humus-making business. The article in the reader on "Planting Time," by L. H. Bailey, expresses the wonder we must all feel when we stop to think about it, at the magic work of the soil in changing a little speck of a seed into a plant. CHAPTER II (FEBRUARY) Behold a strange monster our wonder engages! If dolphin or lizard your wit may defy. Some thirty feet long, on the shore of Lyme-Regis With a saw for a jaw and a big staring eye. A fish or a lizard? An Ichthyosaurus, With a big goggle-eye and a very small brain, And paddles like mill-wheels in chattering chorus Smiting tremendous the dread-sounding main. --_Professor Blackie._ SOME EARLY SETTLERS AND THEIR BONES But a farm where nothing but plants grow isn't much of a farm. Every good farmer knows that nowadays, and so he stocks his place with horses and cows and chickens and things. Mother Nature understood this principle from the beginning, and the plants and animals on her farm have always got on well together. For one thing the plant and the animal each help the other to get its breath. That is to say, plants, when they take in the air, keep most of the carbon there is in it and give back most of the oxygen, which is just what the animal world wants; while the animals, when they breathe, keep most of the oxygen and give back most of the carbon--just the thing that plants grow on. But the service of the animals to the plants is very important after they have stopped breathing altogether; since their flesh and bones, like the dead bodies of the plants, go back to enrich their common dust. The bones and bodies and shells of members of the animal kingdom, however, are far richer food for soils than is dead vegetation. The shell creatures of the sea to which we owe our wonderfully fertile limestone soils are--many of them--so small that you can only make them out with a microscope; while certain other contributors to our food-supply were so big that one of them, walking down a country road, would almost fill the road from fence to fence. I. MR. DINOSAUR AND HIS NEIGHBORS A STRANGE FACE IN THE MEADOW Now let's take a look at some of these big fellows. How would you like to have such a creature as the one at the right of this page come ambling up to meet you at the meadow gate of an evening when you went to milk the cows? Yet more than likely either this gentle animal, or some of his kin, browsed over the very field where now the cattle pasture, for he, too, was a grass-eater, and with an appetite most hearty. If you kept him in a barn his stall would have to be eighty feet long, and it would be necessary to fill his rack with a ton of fodder every third day. But, assuming there was a market for him in the shape of steaks and roasts, you would be well repaid; for, in prime condition, he weighed twenty tons. [Illustration: IN THE LAND OF HIS FATHERS] These monsters who ate grass, and other monsters who ate them, and still other monsters who lived in the sea, appeared comparatively late in the life of the world. [Illustration: NO WONDER HE NEVER WORRIED! Quite aside from the fact that he had so little brain to worry with, it seems highly improbable that the Stegosaurus ever felt any apprehension about attacks from the rear, in the frequent military operations which distinguished the times in which he lived. In addition to the horny plates down his back he had those horny spines which were swung by a tail some ten feet long.] TONS AND TONS OF ANCIENT BONES It is only about 15,000,000 years ago, for example, that the biggest of them all, the Dinosaurs, lived, while the earth itself is now supposed to be some 100,000,000 years old. Their numbers were enormous, and it is probable there is not an acre of ground from the Atlantic to the Pacific, and from Alaska to the tip end of South America that has not been fertilized by their bones. In fact, of certain species I have found the bones scattered all the way from Oregon to Patagonia; so this must have been their pasture. They were not only all over the land, but in the lakes and in the great sea that once extended right through North America from the Gulf of Mexico to the Arctic Ocean. And they were along the shores of the sea and in the swamps. The bones of the ancestors of the whale were found in such quantities in some of the Southern States that they were used to build fences until it was found they were much more valuable to enrich the fields themselves. [Illustration: THE HEAD OF HESPERORNIS "Then there was a great toothed, diving creature with wings. They've named him the Hesperornis, which means 'western bird,' because the fossils of the best-known species were found in the chalk-beds of Kansas."] In the great American inland sea of those days swam one kind of fierce fish-lizard that took such big bites he had to have a hinge in his jaw. Because of this hinge he could open his mouth wider without putting anything out of place, don't you see? He was called the Mesosaur. But he never bit the Archelon, who was in his crowd, because he couldn't. The Archelon was the king of turtles, and, like all the turtle family, wore heavy armor. He was over twelve feet long. And sharks--no end of them! A shark at his best is bad enough, but the sharks of those days were almost too terrible to think about. Such jaws! And teeth like railroad spikes! Then there was a great toothed diving creature with wings. They've named him the "Hesperornis," which means "western bird." He was given the name because the fossils of the best-known species were found in the chalk-beds of Kansas. [Illustration: GREATEST OF ANCIENT FLYING MACHINES Mr. Pterodactyl, on his way to dinner, looked like this. He was the largest of all flying-machines before the days of the Wright brothers. He would have measured--if there had been anybody to measure him--twenty feet across the wings! Like the Hesperornis, he always dined on fish.] Over the waters flew another bird-like, fish-like, bat-like thing called the Pterodactyl. Look at his picture and you will see how he got his nickname. It means "finger-toe." He was the largest of all flying-machines until the days of the Wright brothers. It was over twenty feet across his wings, from tip to tip; and, like the Hesperornis, he always had fish for dinner. [Illustration: A BIG "LITTLE FINGER" AND WHAT IT WAS FOR Mr. Pterodactyl means "finger toe." What is our little finger was the longest of his five digits. It helped support and operate that big bat-like wing extending from his arms to his toes.] THE EARLIEST RULERS OF THE SEA The first monsters, like the first of almost everything else, including the land itself, were in the sea.[5] For a time giant fish, armor-plated like a man-of-war, and with awful appetites, just about ran everything. Then came the reign of the sharks. Some of them had jaws that opened to the height of a door--six feet or over. Next in succession, as rulers of the sea, were the fish-lizards, of whom that hinge-jawed Mesosaur was one. Of another of these fish-lizards a famous teacher of Edinburgh University, Professor Blackie, wrote that funny verse at the head of this chapter. The bones of this particular specimen were found sticking out of a cliff at Lyme-Regis, a popular watering-place in the English Channel, by a pretty English girl who was strolling along the beach. [5] "The Strange Adventures of a Pebble." [Illustration: A FAMILY PARTY The imagination of the artist enables us to picture this family party--Mrs. Ichthyosaurus and her children out for a stroll in prehistoric waters.] The Ichthyosaurus, as Professor Blackie says in his verse, was some thirty feet long, with a comparatively large head--like an alligator's--set close to his body. Another fish-lizard, well and unfavorably known by his neighbors of the sea, was the Plesiosaurus. Instead of fins he had big paddles resembling those of the seal. He was a kind of side-wheeler, like the Mississippi River steamboats, and he could go like everything! His neck was long and he darted after the smaller creatures he lived on. REIGN OF THE LIZARD FAMILY But these queer fish seem to have just been getting ready to land; for, by being lizards, they after a while managed it. A lizard, you know, belongs to the reptile family, and out of these sea reptiles there grew, in course of time, reptiles which lived, not in the sea but in the swamps along the sea. These reptiles were the Dinosaurs, and they are related to the Minosaurs and the Ichthyosaurus, and the rest of the Saurs, as you can see by the family name; for "saur" means lizard. Dinosaur means "terrible lizard." Don't you think he looks it? Although some of these Dinosaurs were no larger than chickens, others were by far the largest creatures that ever were, on sea or land. Many of the biggest lived on grass, just like an old cow, while the flesh-eating Dinosaurs lived on them. Some of these Dinosaurs went on all fours, while others ran about on their hind legs, and when they stood still, propped themselves up on their big, thick tails as do kangaroos. The Camptosaurus, one of whose favorite resorts was the land that is now Wyoming, was thirty feet long. Another called the Brontosaurus, was sixty feet long. The Atlantosaurus, one of the pioneers of Colorado, measured eighty feet from the end of his nose to the end of his tail, and all of them were built in proportion. The Stegosaurus, also an early settler in Wyoming, had huge bony plates, like ploughshares, sticking out all along his back from the nape of his neck to the end of his tail. He seems to have gone about looking quite ugly and humpbacked, as our old cat does when she has words with the dog. After the swamps dried up and the lizards could no longer make a living, came the reign of the mammals; including the Mastodons and the Mammoths, marching in countless herds, trumpeting through the forests. HOW SOME MONSTERS PLOUGHED THE FIELD But besides what they did in the way of fertilizing the land with their flesh and bones some of the mammals did a good deal of ploughing. Among these early ploughmen were the Mastodons and the Mammoths, and another elephant-like creature with two tusks, that he wore, not after the fashion among elephants to-day, but curving down from his chin, somewhat like Uncle Sam's goatee. He used these tusks, it is supposed, not only for self-defense, but for grubbing up roots which he ate. If so, they must have been about as good ploughs as those crooked sticks that were used by the early farmers among men, and that are still in use among primitive peoples. THE ELEPHANT FAMILY AS PLOUGHMEN What makes it more likely that the creature with the down-curving tusks stirred the soil with them is that his cousins, the elephants of to-day, are themselves great ploughmen. Elephants feed, not only on grass and the tender shoots of trees, but on bulbs buried in the soil, which they hunt out by their fine sense of smell. In digging these bulbs they turn up whole acres of ground. Elephants also do a great deal of ploughing by uprooting trees so as to make it more convenient to get at their tender tops. Sir Samuel Baker, the explorer, says the work done by a herd of elephants in a mimosa forest in this way is very great and that trees over four feet in circumference are uprooted. In the case of the biggest trees several elephants work together, some pulling the tree with their trunks, while others dig under the roots with their tusks. To be sure, the mimosa-trees have no tap roots, but tearing them out of the ground is no small job, nevertheless. It takes strength and it takes engineering. Another early ploughman was a bird, the Moa. The Moa had no wings, but his muscular legs were simply enormous, and so were his feet. New Zealand seems to have been the headquarters of the Moas. There used to be loads of them as shown by the huge deposits of their bones. They are supposed to have been killed in countless numbers during the Ice Ages in the Southern Hemisphere; for there were Ice Ages in the Southern as well as the Northern Hemisphere. In one great morass in New Zealand abounding in warm springs, bones of the Moas were found in such countless numbers, layer upon layer, that it is thought the big birds gathered at these springs to keep warm during those great freezes. THE MILLSTONES OF THE MOAS Besides the work they did with feet and bills you may imagine how much nice fresh stone the Moas must have ground up in their crops during the millions of years they existed. It was a regular mill--the gizzard of a Moa--full of pebbles as big as hickory nuts. Scattered about the springs where their bones are found are little heaps of these pebbles, each the contents of a gizzard. Like miniature tumuli, they mark the spots where the bodies of the Moas returned to dust. Perhaps some of those flesh-eating Dinosaurs did a little ploughing once in a while, too; for one theory is that those ridiculous little arms were used for scratching out a nest for the eggs, just as the crocodiles and the alligators and the turtles dig nests for their eggs to-day. For all these animals, as did the Dinosaurs, belong to the reptile family, and show the family trait of digging out nests for their eggs. [Illustration: A PUZZLE PAGE FROM THE GREAT STONE BOOK Talk about your cut-out puzzles! Here is a specimen of the kind of puzzle Nature and the course of things in the darkest ages of world history have cut out for the paleontologists. It is a find of ancient bones in the asphalt deposits near Los Angeles.] Although the Dinosaurs roamed the swamps and lowlands of all the ancient world, their favorite resort was the territory now occupied by our Western States--judging from the quantities of bones they left--while that old Mediterranean Sea of ours was full of their kin, the sea-lizards. Professor Marsh, of Yale, who was among the first explorers of the graves of these monarchs of the past, says that one day, while riding through a valley in the Rocky Mountains, he saw the bones of no less than seven sea-lizards staring at him from the cliffs. Yet, only here and there by the wearing through of the rocks by flowing streams has nature opened up these vast mausoleums, the mountains and the cliffs. What enormous quantities of bones, then, must still be buried there, what tons and tons must have given their lime and phosphate to the soil. So you see this story of old bones, even from a farming standpoint, is no light matter. [Illustration: HOW THE WISE MEN ANSWER THE PUZZLES By their marvellous skill and their knowledge of the mechanics of monster anatomy the paleontologists fit one bone fragment to another, supply the missing parts in artificial material, and behold! the monsters take their places in the long procession of the ages. There has been nothing equal to it since the vision of the prophet in the Valley of Dry Bones. (Ezekiel 37:1-10.)] II. HOW THE MONSTERS DIED AND RETURNED TO DUST "But you said these monsters lived in the sea and in swamps. Then how, in the name of common sense, did their bones get up into the mountains?" WHEN THE INLAND SEA WENT DRY Well, it's like this: As I said a while back, in the days of the monster fish and the monster lizards, there was a great sea reaching clear from the Gulf of Mexico to the Arctic Ocean, and with swamps along the borders extending far into lands that afterward became the Rocky Mountains. When the land began to rise, due to the shrinking of the earth--a thing that has been going on ever since the earth was born--the sea and the swamps went dry, and far to the west the land wrinkled up into the Rocky Mountains. In these layers of rock that made the mountains were the bones of the monsters that had died when the rocks were still mud, in the swamps and along the borders of the inland sea. Not only did the land under the western portion of the sea slowly rise until the waters were completely closed in on the west, and the sea thus made that much narrower, but the rise of the land on the south cut off connection with the great salt ocean which surrounds the continents to-day. So the salt-water fish, for lack of salt water, died, and with them the monsters like the Ichthyosaurus that lived on the salt-water fish that lived in this salt sea. But it wasn't alone that the seas grew narrower and more shallow because of the elevation of the lands. The mountains rising in the west, cut off the rain-laden winds which blew from the Pacific in those days just as they do now. Thus the seas dried up so much the faster. But first, before the sea went entirely dry, its place was taken by the lakes and swamps into which it shrivelled up. Low, swampy land is just what reptiles like, so this was their Golden Age, just as the previous time of the wide, deep sea was the Golden Age of the big fish and the fish-lizards. Then, as the land still rose and the climate grew dryer, the reptiles passed away, and in came the mammal family, to which the cows and the horses and the cats and the kittens, and all the rest of us, belong. [Illustration: THE TIGER WITH THE SABRE TEETH Tigers like this lived ages ago in both the Old World and the New. They had canine teeth, curved like a sabre, in the upper jaw.] TOO MUCH BRAWN, TOO LITTLE BRAIN Of course, even where they didn't die with their boots on, so to speak, as so many of them did in those lawless days, there came a time for each monster, in the order of nature, when he drew his last breath. But what seems so strange is that all these monsters--the biggest and strongest of them--entirely disappeared and left no descendants![6] The whole of the mystery has not been unravelled yet, even by the wise men of science, but still they have learned a good deal. For one thing, they know that most of the reptiles and the fish-lizards disappeared because so much of the land where they lived went dry. They had to get a new boarding-place, and there wasn't any to get! Another thing was that these big fellows, although they _were_ so big, and got along finely while everything was just so, had so little brain they couldn't change their habits to meet new conditions, as our closer and cleverer cousins, the mammals, did. Why, do you know that one of these monsters, who was twenty-five feet long if he was an inch, and twelve feet high, had a brain no bigger than a man's fist? All the monsters of those days were like that--tons of bone and muscle, but a very small supply of brains. [6] That is to say, no descendants worthy of them. It is now thought some of the modern reptiles may be degenerate descendants of the big reptiles of old. So when things went against them, they just had to give up, and, like a queer dream, they faded away. But their history makes one of the most interesting chapters in the whole wonderful story of the dust. Of all the live stock that have fed on the great world-farm and helped enrich it with their bones, these animals were surely the strangest that ever were seen! HIDE AND SEEK IN THE LIBRARY "But since these monsters passed away many millions of years ago, and all that is usually found is a piece of them here and there, how do the men of science know so much about them--how they looked, and how they ate, and how they treated one another?" That's a good question. It _does_ seem strange. Why, to hear them talk, you'd suppose these men, learned in ancient bones, had actually _met_ the monsters! And, speaking of meeting them, I must tell you a little story. It's a good story and it will answer your question. Baron Cuvier, one of the most famous of the paleontologists, awoke from a deep sleep to see standing by his bed a strange, hairy creature with horns and hoofs. And it said: "Cuvier! Cuvier! I have come to eat you!" But the baron, taking in the form of the monster at a glance, only laughed. "Horns and hoofs? You can't. You're a grain-eater!" See the point? The baron argued that because the monster had horns and hoofs he must be a grain-eater; for all creatures with both horns and hoofs are grain-eaters. This particular creature, to be sure, was an eater of both meat and grain--being one of Cuvier's students who was trying to play a trick on him. But the principle holds good. The scientists, _knowing_ one thing, _infer_ another. Because animals with both horns and hoofs eat no meat Cuvier knew his visitor couldn't eat _him_, even if he'd been real and not just made up. For another instance, take our queer old friend that Professor Blackie wrote the funny rhyme about--the Ichthyosaurus "with a saw for a jaw and a big staring eye." The scientists figure, just from looking into the hollow socket where the eye used to be, that he could see at night like a cat--and right through muddy water, too; that he spent most of his time in shallows near the shore; that it didn't make any difference to him whether a fish was near or far, provided it wasn't too far, of course, for he could see it and catch it, just the same. They also said--these learned men, after peering into the dark hollow where that remarkable eye used to be--that Mr. Ichthyosaurus spent a great deal of time diving and a great deal of time with his homely face just above the surface of the water. Why they could reason all this from a hollow eye socket and some bony, flexible plates around the outer edge of it, you will see by referring to such books as "Animals of the Past," by F. A. Lucas, director of the American Museum of Natural History; "Creatures of Other Days" and "Extinct Monsters," by Hutchinson; "Extinct Animals," by Lankester; "Mighty Animals," by Mix; the chapter "When the World was Young," in Lang's "Red Book of Animal Stories," and "Restoring Prehistoric Monsters" in "Uncle Sam, Wonder Worker," by Du Puy. Here are some more conclusions they draw from certain facts. See how near you can come to reasoning them out for yourself before looking them up in the books that tell. Why it is supposed the Dinosaurs swam like Crocodiles. (Look at the picture of Mr. I., and pay _particular_ attention to his tail.) Why it is they say that the sea-lizards with long necks must have had small heads. Why it is argued that because the Mesosaurus had a hinge in his jaw he must have had a big, loose, baggy throat. "Keeping Up the Soil," in "The Country Life Reader," deals with the subject of the use of fertilizers on the farm--how easy it is to waste them, how easy it is to save them, and how important it is that they should be saved; while the article on "Acid Soils" tells how the lime in the bones of the monsters has helped keep the soil from getting "sour stomach," and also how they unlocked the potash and phosphorus in the soil so that the plants could get at them. [Illustration: FERTILE FIELDS THAT RODE ON THE WIND The winds that now help grow the corn and wheat on these broad fields by carrying the pollen from one plant to another, also brought the soil on which they grew. These are the loess plains of Nebraska. There are 42,000 acres of them.] CHAPTER III (MARCH) ... the busy winds That kept no intervals of rest. --_Wordsworth._ Except wind stands as never it stood 'Tis an ill wind turns none to good. --_Tusser._ THE WINDS AND THE WORLD'S WORK That saying "idle as the winds" must have started in the days when they didn't know; for if ever there was a busy people, it's the Winds. Not only do they help plant the trees of the forest, sow the fields with grass and flowers, and water them with rain, but they make and carry soil all over the world. And, like everything else in Nature, they have a sense of beauty and the picturesque. Rock, for example, weathered away into dust by the help of the winds, as it is, takes on all sorts of picturesque shapes. And, of course, the winds love music; everybody knows that. Before we get through with this chapter we're going to end a happy day outdoors with a grand musical festival in the forest, with light refreshments--spice-laden winds from the sea. There'll be nobody there but the trees and the winds and John Muir and us; all nice people. I. SUCH CLOUDS OF DUST! March leads the procession of the dusty months because the warming up of the land, as the sun advances from the south, brings the colder and heavier winds down from the north. These winds seem to have a wrestling match with the southern winds and with each other, and among them they kick up a tremendous dust, because there's so much of it lying around loose; for the snows have gone, and the rainy season hasn't begun, and the fields are bare. ABOUT THE DUST WE GET IN OUR EYES Most people think these March winds a great nuisance because some of us dust grains are apt to get into their eyes; but dust in the eye is only the right thing in the wrong place. Just think of the amount of dust going about in March that _doesn't_ get into your eye; and how nice and fine it is, and how mixed with all the magic stuff of different kinds of soil, thus brought together from everywhere. An English writer on farming says he thinks the fact that English farms have done their work so well for so many centuries is due, in no small degree, to the March winds that have brought us world-travelled dust grains from other parts of the globe. And the wind is a good friend to the good farmer, but no friend to the poor one; for it carries away dust all nicely ground from the fields of the farmer who doesn't protect his soil and carries it to farmers who have wood lots and good pastures and winter wheat, and leaves it there; for woods and pastures and sown fields hold the soil they have, as well as the fresh, new soil the winds bring to them. Most of the fine prairie soils in our Western States owe not a little of their richness to wind-borne dust. In western Missouri, southwestern Iowa, and southeastern Nebraska are deep deposits of yellowish-brown soil, the gift of the winds. And, my, what apples it raises! It is in this soil that many of the best apple orchards of these States are located. And now, of course, the apple-growers see to it that this soil stays at home. But there's another kind of dust that deserves special mention, and that's the kind of dust that comes from volcanoes. Volcanoes make a very valuable kind of soil material, often called "volcanic ash." It isn't ashes, really. It's the very fine dust made by the explosion of the steam in the rocks thrown out by the volcano. The pores of the rocks, deep-buried in the earth, are filled with water, and when these rocks get into a volcanic explosion, this water turns to steam, and the steam not only blows out through the crater of the volcano, but the rocks themselves are blown to dust. This dust the winds catch and distribute far and wide. Sometimes the dust of a volcanic explosion is carried around the world. In the eruption of Krakatoa, in 1883, its dust was carried around the earth, not once but many times. The progress of this dust was recorded by the brilliant sunsets it caused. It is probable that every place on the earth has dust brought by the wind from every other place. So you see if you happen to be a grain of dust yourself, and keep your eyes and ears open, you can learn a lot, as I did, just from the other little dust people you meet. THE WINDS AND VOLCANOES But that isn't all of this business--this partnership--between the volcanoes and the winds. Did anybody ever tell you how the volcanoes help the winds to help the plants to get their breath? It's curious. And more than that, it's so important--this part of the work--that if it weren't carried on in just the way it is, we'd all of us--all the living world, plants and animals--soon mingle our dust with that of the early settlers we read about in the last chapter. In other words, all the _plant_ world would die for lack of fresh air and all the _animal_ world would die for lack of fresh vegetables. So they say! According to that fine system--the breath exchange between the people of the plant and animal kingdoms--the plants breathe in the carbon gas that the animals breathe out; you remember about that. But the amount of carbon gas in the air is never very large, and if there were no other supply to draw on except the breath of animals and the release of this same gas when the plants themselves decay, we'd very soon run out. Now this needed additional supply comes from the volcanoes. Every time a volcano goes off--and they're always going off somewhere along the world's great firing-line--it throws out great quantities of this gas, and this also the winds distribute widely and mix through the atmosphere. And another thing: This carbon in the air helps crumble up the rocks already made, and it enters into the manufacture of the limestone in the rock mills of the sea. This limestone will make just as rich soil for the farmers of the future as the limestones of other ages have made for the famous Blue-Grass region of Kentucky, for example. All of which only goes to show how first unpleasant impressions about people and things are often wrong. A "dusty March day," you see, isn't just a dusty March day. It's quite an affair! II. THE DUST MILLS OF THE WIND But wind is not alone a carrier for other dust-makers; it has dust mills of its own. The greatest of these mills are away off among the mountains and in desert lands, but after making it in these distant factories the winds carry much of this fresh new soil material to lands of orchard and pasture and growing grain. Not long ago two of the professors at the University of Wisconsin found a good illustration of what an immense amount of soil is distributed in this way, and what long distances it travels. Among the weather freaks of a March day was a fall of colored snow that, it was found, covered an area of 100,000 square miles, probably more. The color on the snow was made by dust blown clear from the dry plains of the Southwestern States, a thousand miles away. The whole of this dust amounted to at least a million tons; and may even have amounted to hundreds of millions of tons, so the professors think. [Illustration: TYPES OF NATURE'S SCREW PROPELLERS You can see for yourself (from the picture on the left) that long before man ever thought of driving his ships through the water with screw propellers or pulling his flying machines through the air by the whirligigs on the end of their noses, some flying seeds, such as those of the ash here, had screw propellers of their own. And do you know that Nature also employs the propeller principle, not only in the operation of the wings of birds but in the wing feathers themselves? The two pictures on the right show the action of the wing and the wing feathers when a bird is in flight.] LITTLE MILLSTONES IN BIG BUSINESS For grinding rocks to get out ore, or for making cement in cement mills, men use big machines, somewhat on the style of a coffee-mill. These machines are called "crushers." The winds, in their enormous business of soil-grinding, however, stick to the idea you see so much in Nature, that of using _little_ things to do _big_ tasks; as in digging canyons and river beds, and spreading out vast alluvial plains by using raindrops made up into rivers; in working the wonders of the Ice Ages with snowflakes; and building the bones and bodies of those big early settlers, and of all animal life, and the giant trees of the forest out of little cells. For, what do you suppose the winds take for millstones in grinding down the mountains into dust? Little grains of sand! And with the help of the sun and Jack Frost it makes these fairy millstones for itself. The outside of a big rock grows bigger under the warm sun, in the daytime, and then when the sun goes down and the rock cools off it shrinks, and this spreading and shrinking movement keeps cracking up and chipping off pieces of rock of various sizes. Up on the mountain tops, among the peaks, the change of temperature between night and day is very great, and even in midsummer you can always hear a rattling of stones at sunrise. The heat of the rising sun warms and expands the rock, and so loosens the pieces that Jack Frost has pried off with his ice wedges during the night. Then also during periods of alternate freezing and thawing in Spring and Fall, the rock is slivered up. These changes in the weather as between one day and another are due to the winds. In January and February, for example, thaws and freezes are common. When the winds blow from the south, the snow melts, water runs into cracks in the rock and fills their pores; then a shift of the winds to the north, a freeze, and the water in the crevices and the pores turns to ice, expands, and breaks off more rock. And what muscles Jack has! Freezing water exerts a pressure of 138 tons to the square foot; so there's no holding out against him once he gets his ice wedges in a good crack. He sends huge blocks tumbling down the mountainside. The larger blocks, striking against one another, break off smaller fragments. The smallest fragments the wind seizes. Others are washed down by the rains. The largest, carried away by mountain torrents, bump together as they thunder along, and so break off more fragments and grind them so small that the wind can pick them up along the banks when the torrents shrink, or in their beds when these sudden streams go dry. RUNNING WATER AND THE WINDS In changing rock into soil, running water and the winds each have an advantage over the other. Water weighs a great deal more than air--over 800 times as much--and so grinds faster with its tools of pebbles and sand. The winds, on the other hand, get over a great deal more territory, and they, like the lichens, understand chemistry. Two of the gases they always carry right with them--carbon dioxide and oxygen--help decay the rocks. As I said, the winds do most work in dry and desert regions, but when you remember that over a fifth of the globe is just that--dry as a bone most of the time--you see this is a great field. It has been so from the beginning, for it is thought probable that there was always about the same proportion of desert lands. Night and day the winds have been busy through all these ages. Dust is carried up by ascending air currents. Then the same force that keeps the earth in its orbit--gravity--pulls down on a grain of dust. But its fall is checked by the friction of the air. You see there's a lot of mechanics involved in moving a grain of dust; and Nature goes about it as if it were the most serious business in the world; handles every grain as if the future of the universe depended on it. In the case of sand or coarse dust, unless the winds are very strong, gravity soon gets the best of it, and down the dust grain comes to the ground again; then up with another current, then down again--carried far by stiff breezes, only a short distance by puffs--a kind of hop, skip, and jump. But fine dust getting a good lift into the upper currents at the start may stay in the air for weeks. [Illustration: _Courtesy of The Dunham Company._ TO KEEP MOISTURE AND SOIL AT HOME In the broad fields of the West, where "dry-farming" is practised, they have these huge machines. They are called "Cultipackers." They are cultivators with big, broad-brimmed wheels that pack the surface of the soil after the blades of the cultivator have stirred it. This not only prevents the moisture in the soil from evaporating as fast as it would otherwise do, but keeps the winds from carrying away the soil itself.] In very wild wind-storms it has been figured out that there may be as much as 126,000 tons of dust per cubic mile; several good farms in the air at once, over every square mile of the earth below! III. THE STORM PLOUGHS OF THE WIND TWO KINDS OF WOODEN PLOUGHS They use wooden ploughs, these winds, just as primitive man did, and as primitive peoples do now; but not quite in the same way, and the ploughing they do is much better. For man's wooden plough is a crooked stick made from the branches of a tree while the winds use the whole tree--roots and all, and both on mountainsides and on level lands the amount of ploughing they do is immense. Almost all forests are liable to occasional hurricanes which lay the trees over thousands of acres in one immense swath. A large number of these trees, owing to their strong trunks, do not break off but uproot, lifting great sheets of earth. Soon, by the action of its own weight and the elements, this soil falls back. The depth to which this natural ploughing is done depends, of course, on the character of the tree, but as it is the older and larger trees that are most likely to be overturned, since they spread more surface to the wind, the ploughing is much deeper than men do with ordinary ploughs. The result is that new unused soil is constantly being brought to the surface; and not only this, but air is introduced into the soil far below the point reached by ordinary ploughing. The soil needs air just as we do; for the air hurries the decay of the soil and its preparation for the uses of the plant. The immediate purpose of ploughing is to loosen the soil so that the roots of the plants can get their food and air more easily. It also helps to keep the fields fertile by exposing the lower soil to more rapid decay. But here's the trouble: While the ordinary plough introduces air into the soil for a few inches from the surface, the subsoil, which is very important to the prosperity of the plant, is practically left out of it, so far as getting needed fresh air is concerned. The long roots of the trees that, among other things opened for it channels to the air, are gone. The burrowing animals that used to loosen up the earth, man has driven away. More than that, the foot of the plough which has to press heavily on the subsoil in order to turn the furrow, smears and compacts the earth into a hard layer, which shuts out the air, and also--to a certain extent--the water from the lower levels. [Illustration: HOW THE SOIL GETS ITS BREATH Plants must have air to breathe, both above and below the soil, and the microscope is showing us here how a sandy loam allows the air to reach the roots.] In mountain regions these "storm ploughs," as we may call them, not only help to renew and prepare the soil in the valleys, but are a part of the machinery of delivery of new soil from mountain to valley. When trees on the mountainside are overturned, they not only bring up the soil, which the mountain rains quickly carry to the valleys, but the roots having penetrated--as they always do--into the crevices of the rocks, bring up stones already partly decayed by the acids of the roots. These stones, as the roots die, decay and so release their hold, and also go tumbling down toward the valley. Consider how much of this storm-ploughing must be done in the forests of the world in a single year, and that this has been going on ever since trees grew big on the face of the earth. In a storm in the woods of California, Muir heard trees falling at the rate of one every two or three minutes. And, as I said, it is precisely the trees that can do the most ploughing--the older and larger trees--that are most apt to go down before the wind. Younger trees will bend while older and stiffer trees hold on to the last. Before a mountain gale, pines, six feet in diameter, will bend like grass. But when the roots, long and strong as they are, can no longer resist the prying of the mighty lever--the trunk with its limbs and branches--swaying in the winds, down go the old giants with crashes that shake the hills. After a violent gale the ground is covered thick with fallen trunks[7] that lie crossed like storm-lodged wheat. [7] Muir: "Mountains of California." There are two trees, however, Muir says, that are never blown down so long as they continue in good health. These are the juniper and dwarf pine of the summit peaks. "Their stout, crooked roots grip the storm-beaten ledges like eagle's claws, while their lithe, cord-like branches bend round completely, offering but slight holds for winds, however violent." AT THE STORM FESTIVAL WITH MR. MUIR Trees were among Muir's best friends, and he spent a large part of his life chumming with them. What do you think that man did once? He was always doing such things. He climbed a tree in a terrific gale so that he could see right into the heart of the storm and watch everything that was going on. Just hear him tell about it: "After cautiously casting about I made choice of the tallest of a group of Douglas spruces that were growing close together like a tuft of grass, no one of which seemed likely to fall unless the rest fell with it. Being accustomed to climb trees in making botanical studies, I experienced no difficulty in reaching the top of this one, and never before did I enjoy so noble an exhilaration of motion." And such odors! These winds had come all the way from the sea, over beds of flowers in the mountain meadows of the Sierras; then across the plains and up the foot-hills and into the piny woods "with all the varied incense gathered by the way." [Illustration: THREE KINDS OF SEED THAT THE WIND SHAKES FREE Here are three kinds of seed adapted for dispersal by the shaking action of the wind.] Though comparatively young, these trees--the one Mr. Muir climbed into and its neighbors--were about 100 feet high, and "their lithe, brushy tops were rocking and swirling in wild ecstasy." In its greatest sweeps the top of Muir's tree described an arc of from twenty to thirty degrees, but he felt sure it wouldn't break, and so he proceeded to take in the great storm show. "Now my eye roved over the piny hills and dales as over fields of waving grain, and felt the light running in ripples across the valleys from ridge to ridge, as the shining foliage was stirred by the waves of air. Oftentimes these waves of reflected light would break up suddenly into a kind of beaten foam and finally disappear on some hillside, like sea waves on a shelving shore." This was his impression of the forest as a whole, a dark green sea of tossing waves. But if we study trees as long and lovingly as Muir did, we can pick out the different members of the family a mile away--even several miles away--by their gestures, their style of grave and graceful dancing in the wind. [Illustration: TYPES OF FLYING MACHINE Here is the type of flying machine that carries men. On the opposite page is the kind that carries the dandelion seeds.] [Illustration: THE DANDELION-SEED FLYING MACHINE The dandelion on the left shows how the seeds are kept in the "hangar" at night and on rainy days, shut up tight to prevent them from getting wet with rain or dew and so made unfit for flying.] Muir especially mentions the sugar-pines as interpreting that storm to him. They seemed to be roused by the wildest bursts of the wind music to a "passionate exhilaration," as if saying "_Oh_, what a glorious day this is!" This was the picture part of it--the glorious moving-picture show. Now listen to some of the music: "The sounds of the storm corresponded gloriously with the wild exuberance of light and motion. The profound bass of the naked branches and boles booming like waterfalls, the quick, tense vibrations of the pine-needles, now rising to a shrill, whistling hiss, now falling to a silky murmur. The rustling of laurel groves in the dells, and the keen metallic click of leaf on leaf--all this was heard in easy analysis when the attention was calmly bent. "Even when the grand anthem had swelled to its highest pitch I could distinctly hear the varying tones of individual trees--spruce, fir, pine, and oak--and even the infinitely gentle rustle of the withered grasses at my feet." When the winds began to fall and the sky to clear, Muir climbed down and made his way back home. "The storm tones died away, and turning toward the east I beheld the countless hosts of the forests hushed and tranquil, towering above one another on the slopes of the hills like a devout audience. The setting sun filled them with amber light, and seemed to say while they listened: "'My peace I give unto you.'" HIDE AND SEEK IN THE LIBRARY Did you know that the ash and maple seeds actually have screw propellers, like a ship, so that they can ride on the wind? Pettigrew's great work, "Design in Nature," makes this very plain, both in word and picture. In what way does the wind help to _produce_ the seed of grasses as well as carry and plant them? (Any encyclopædia or botany will tell you how plants are fertilized.) How could a tempest that blew down a tree help its seeds to get a start? Wallace, in his "World of Life," says that on a full-grown oak or beech there may be 100,000 seeds that are thus given a better chance of life. Speaking of "wind ploughs," what is the object of ploughing anyway? The article on preparing the seed bed in "The Country Life Reader" tells about what ploughing means to the soil and also: Why good soil takes up more room than poor. Why it is a good thing to plough deep, but a bad thing, if you don't do it just right. And farther on there is a most inspiring poem about the history of the plough from the days of early Egypt to the present. It begins like this: "From Egypt behind my oxen, With their stately step and slow, Northward and east and west I went, To the desert and the snow; Down through the centuries, one by one, Turning the clod to the shower, Till there's never a land beneath the sun But has blossomed behind my power." The deserts have helped to make western China fertile. How did they do it? (Look at your geography map and remember that the prevailing winds of the world are westerly.) You'll find many interesting things about the winds and the soil in Keffer's "Nature Studies on the Farm" and Shaler's "Outlines of Earth's History." Shaler's "Man and the Earth" says a single gale may blow away more soil from an unprotected field than could be made in a geological age, and an hour's rain may carry off more than would pass away in a thousand years if the land were in its natural state. He also tells what to do to prevent the best part of ploughed fields from being carried off by the wind. Have you any idea how far seed may be carried by a hurricane? Wallace, in his "Darwinism" deals with this question, and it's very important in the story of the earth. Beal's admirably written and illustrated little book on "Seed Dispersal" tells a world of interesting things about the wind as a sower. For instance: How pigweed seeds are built so that wind can help them toboggan on snow or float on water; How wind and water work together in the distribution of seeds; About seeds that ride in an ice-boat; About the monoplane of the basswood; About the "flail" of the buttonwood, and how the wind helps it to whip out the seeds; and how the seeds then open their parachutes. Dandelions go through quite a remarkable process in preparing for flight. I wonder if you have ever noticed it. Before the seeds get ripe Mother Dandelion blankets them at night and puts a rain-cloak on them on rainy days, and just won't let them get out, as shown on page 51. And do you know how she opens the flowers for the bees on sunshiny days? There is no island, no matter how remote, that isn't supplied with insects. How do you suppose they get there? You may be sure the wind has something to do with it or I wouldn't mention the subject at the end of this chapter. (Wallace: "Darwinism.") [Illustration: THE WEST WINDS AND THE RAINS On the western slopes of this mountain the trees, with the help of the winds and the rain, climb to the very summit, while the other side of the mountain remains only a barren rock. The moisture-laden winds from the west glide up the slope, the air expands as it rises, the expansion cools it and down comes the rain! But the eastern slope gets little or none of it.] CHAPTER IV (APRIL) The higher Nilus swells The more it promises; as it ebbs, the seedsman Upon the slime and ooze scatters his grain, And shortly comes the harvest. --_Shakespere: "Antony and Cleopatra."_ THE BOTTOM-LANDS All that wind was bound to blow up rain. I said so at the time. And, sure enough, here it is; right where we want it, at the beginning of April, a month famous for its rains. The work of the rains is going to make one of the most interesting chapters in the long story of the dust. At least I hope so. But don't think I intend to tell it all. Why, it would make a whole book in itself. But you can believe every single thing I do tell, no matter how it makes you open your eyes; for, if I've helped it rain once I've helped it rain a million times! I. THE MARCH DUST AND THE APRIL RAINS HOW RAIN GOES UP BEFORE IT COMES DOWN It's this way: You remember how you can "see your breath," as we say, on a cold morning? Well, that's because the moisture in your breath is condensed by the cold. Now as the waters of the earth--the seas, lakes, rivers, ponds, and so on--are warmed by the sun, the air above them is filled with moisture, for the heating of the air causes it to expand and draw in moisture from the water like a sponge. Expansion makes it lighter also, and it rises. Rising, it turns cooler, and the moisture condenses and comes down as rain. Mountains usually have clouds around them because moist air striking the mountainside is driven up the slope, cooling as it rises. So rain and snow fall often in mountain regions, and that's why so many rivers rise in mountains. The moist air is also condensed when it meets other and cooler air currents. But right here is where the work of the dust comes in. For to make rain you've got to have clouds, and clouds are due to this moisture collecting around the little particles of dust of which the air is full. When these little motes of matter become cooler than the air that touches them the moisture in the air condenses into a film of water around them. Fairy worlds with fairy oceans floating in the sky! Each of these baby worlds is falling toward the big world below. But very slowly; only a few feet a day, so that even if nothing happened it might be months--yes, years--before it would come to the ground, even in still air. But when air is very thick with moisture the water films on these dust particles grow rapidly, and thus increasing in weight, they fall faster and faster, and finally strike the earth as raindrops. But here's another thing that helps. On the way down two or more raindrops, falling in with each other, will go into partnership--melt into one--and then they hurry down so much the faster. That's why the sky grows darker and darker just before a rain, and why the lower part of a rain-cloud is the darkest: the little raindrops are forming into bigger raindrops as they fall. THE LITTLE ARTISTS THAT SHAPE THE CLOUDS But the shapes of clouds are supposed to be due to another thing, the mysterious force we call electricity, and that other mysterious force we call gravity. Just as the worlds attract each other by gravity so these raindrops--or dust grains growing into raindrops--are drawn toward one another. Here's where Electricity steps in. These rain particles are full of electricity and when two of these electrified particles meet in the air--unless they strike one another in falling, in which case, as I said a moment ago, they blend into one--they get very close together and yet keep dancing around one another without touching! It is this dancing about that makes all those strange and beautiful and ever-changing forms in the vast picture-gallery of the sky. Of course the wind currents help to change these shapes, but I'm talking about the original designs. II. THE RAINDROPS AND THE RIVER MILLS So much for the dust that helps make raindrops; now for the raindrops that help make dust. This the raindrops do in several ways. Falling on big rocks or decaying pebbles, for example, they pound loose with their patter, patter, patter, any little bits of soil and grains of sand that have been made by the other soil makers--the sun, the wind, the lichens, the chemists of the air, and so on. This soil and these sand particles, if there is already any depth of earth there, they carry down into the ground. Some of this soil, with various stops and mixings with other soils on the way, finally reaches the sea, where it helps to make the rich limestone soils for the Kentuckies of millenniums yet to be, by supplying food for sea creatures and lime for their shells. For these shells become limestone when the shell-fish are through with them. Mother Nature, in addition to feeding her big, hungry families of to-day in the plant and animal world, is always laying by something for the future. But before it gets back to the sea, by far the greatest part of the ground-up soil the rivers carry is spread out in the lowlands in those "alluvial plains" your geography tells about and that make a large proportion of the fertile farms of the world. If the raindrops fall on comparatively barren rock--in the mountains, say--they carry some of this fresh soil to the mountain valleys below, and some of it they may spread in bottom-lands a thousand miles away, where the new soil helps feed the plants. The sand grains in it not only help the soil to get its breath by making little air spaces, but these sand grains themselves slowly decay and so make more soil. [Illustration: WHAT IRRIGATION DOES FOR DESERTS It is such land as this, in the arid regions of the West, that irrigation converts from a desert to a garden of abundance. The soil is rich in all the substances that plant life needs.] But it isn't alone that they carry away the soil already made and bury the sand grains. Some of the raindrops soak into cracks in stones and dissolve the material that binds the rock particles together, and so get them ready to give way under the fairy hammers of the next shower that comes along. After Nature finally gets an original waste of barren rock all nicely set with grass and flowers and trees and things, the raindrops help to make soil in still another way. Soaking through the decaying leaves, they pick up acids which are just the thing for eating into rock and crumbling it into soil. To be sure, the water soaking into the soil and coming out of springs carries some plant food away with it; but it takes it to lands farther down the river valleys, and more than makes up for what it carries away by the new soil made by its acids from the rocks, as it soaks into their pores and runs among the cracks. HOW RAINDROPS MANAGE TO GRIND UP THE ROCKS Moreover, raindrops actually grind up rocks. In order to do this a lot of raindrops have to get together, to be sure, and become rivers; but after all it's the raindrops that do it. There'd never be any rivers if it weren't for the rains and, of course, the snows. Well, anyhow, the rivers, besides running other people's mills, have mills of their own; and millstones. Most of these stones originally came from mountains and were brought into the milling business by mountain streams, with the help of Jack Frost. For the frost not only pries stones from the mountains and so sends them tumbling down the slopes, but it keeps edging them along and edging them along, farther down, after they have fallen. You'd hardly think that, would you? Yet it's simple enough. The water in the pores of the rock expands when it freezes and that makes the whole rock expand, for the time being. Then when the frozen water in the rock pores thaws out, the rock contracts, and this spreading out and pulling together, small as it is, causes the rock to keep hitching along down the incline; oh, say a fraction of an inch a year. But still, in the course of the ages, these inches foot up, and after a while this tortoise-like gait lands the stone--lands tens of thousands of such stones--in the beds of the mountain torrents that run along at the bottom of these inclines. There they get ground together and so grind out more soil material, particularly when the floods are on, with the melting of the snows in spring and the falling of the heavy and frequent rains. [Illustration: AN OLD RIVER MILL It used to do a lot of business--this old river mill. Its grist was ground-up rock that helped make fine farming land in the bottoms along the river's course. Such mills, called "pot holes," are found in the rocky floors of rapid streams, where the eddying current or the water of a waterfall wears depressions in the bed. Into these depressions stones are washed, and then by the whirl of the flowing water kept going round and round, grinding themselves away and grinding out the sides and bottom of the mill.] Another curious thing is how the river mills help themselves to new millstones when they need them. If a river hasn't enough for its work, it has a way of drawing on its banks for more. Whenever the stones in its bed get scarce, so that it can make comparatively little new soil--having so few stones to grind together--it proceeds to dig its own bed deeper, since this bed is no longer protected by a rock pavement in the bottom. This, of course, deepens its channel, and so adds to the steepness of the slope of its banks. Then, owing to this increase in the incline of the slope, more rocks tumble in, and the "milling business" picks up again. THE GOVERNOR IN THE RIVER MILL But there may be too much of a good thing; the rocks may come in faster than the river mill can take care of them. Then the river bottom becomes so completely paved over that the channel stops wearing down at all, to speak of, and the river remains at the same level until the rains and the wind and other workers have worn the banks down and lessened the incline. Then, with fewer and fewer fresh stones tumbling in, the river gets a chance to catch up with its work. It is this ground-up rock stuff of the mountain river mills, made by the grinding of the running streams all the way down, that has helped form the rich bottom-lands of the Mississippi Valley. For uncounted ages, the water of the Mississippi and its tributaries have been at work, and by the time you get down into southern Louisiana you come to the delta where this rich soil has been piled up for more than 1,000 feet above the bottom of the old Mediterranean Sea, that used to reach north and south across the country. You remember the lines, don't you: "Little drops of water, little grains of sand Make the mighty ocean and the pleasant land." Well, this is how they do it; all this that I've been telling you. [Illustration: _Courtesy of the Scientific American._ THOUSANDS OF FARMS POURED INTO THE GULF The Father of Waters is a good farmer in some respects but needs training in others. The Mississippi's floods, like those of Father Nile, enrich the bottom lands, but the river is apt to break all bounds and do a lot of damage. Moreover, every year it carries away thousands of acres of good soil and pours it into the Gulf. How to teach the Mississippi to work in harness, as the Nile has been taught to do in recent years, is one of the problems which will require all of Uncle Sam's ingenuity and skill to solve. A good deal of the yearly waste could be prevented, however, by the various means employed by good farmers.] III. HOW THE RIVERS ACT AS BANKERS FOR THE FARMERS AND THE SEA We speak of river banks and the kind of banks that handle those promissory notes our arithmetics tell about as if they were entirely different; and so they are, I suppose, if one just looks at the surface of the thing. But if we dig into the subject a little we shall see that they are much alike in the fact that one of the principal businesses of both kinds of banks is to make loans at interest. Men's banks loan money, to be sure, while the river banks loan pebbles, but if it were not for these pebble loans there would be a mighty sight less money for the banks to loan, or the farmer to borrow; and the way both banks do business ought to be a good lesson to certain farmers I know, who seem to think they can always be cashing checks on their banks--the farm lands--by hauling away the crops without ever putting anything back. [Illustration: WHERE THE RIVERS ACT AS BANKERS Here is a fine piece of bottom land, one of those "banks" where the rivers keep "checking accounts" for the farmers and the sea; using pebbles for currency, as explained in this chapter.] HOW THE RIVERS PLACE PEBBLES ON DEPOSIT The rivers make loans to the soil by depositing pebbles in the broad bottom-lands along their banks, and then draw interest by carrying along to other lands, from time to time, some of the fine rich soil these pebbles help make by their decay. And the river does this in regular banking style, "checking out" the pebbles from time to time, and then depositing other pebbles in their places. Take the banks and bottom-lands of the Mississippi River, for example. It has been estimated that it requires about 40,000 years for a pebble to make the journey to the Gulf from the mountains of a tributary stream where it was first broken from the rock as a sharp fragment. The first part of the journey in the mountains is over steep down grades, and so is comparatively fast, but as the river gets farther from the mountains, the slope of its bed becomes less and less, the onward movement is slower and slower, and more of the pebbles stop to rest. In times of flood they are carried far away from the regular channel and spread over the wide flood-plain of the river. Then, as the flood goes down, they are left buried there under a coating of mud. So buried, they decay and enrich the soil. Then the next flood that comes along sweeps the pebbles with it--checks them out of the bank--but at the same time carries away not only some of the soil richness which these pebbles helped to make but the soil material made by the decay of the vegetation these pebbles thus helped to grow, such as the roots and blades of wheat and corn and stubble and chaff left in the fields. That's the interest on the loan. Then, when the flood subsides, the pebbles are again deposited farther along in the river's course, but meanwhile the same flood has brought fresh deposits of pebbles from up-stream, and these are left in place of those taken away. RIVER BANKING AND HUMAN CIVILIZATION This banking business has been going on for ages and is a very important part of the history of civilization. Here and there along the sides of the older and larger river valleys are found the remains of ancient plains. These plains are now, many of them, quite a distance above the level of the stream. This means that they were at one time the bottom-lands of that same stream, but the stream, as it dug deeper and deeper into its bed, grew narrower, and so abandoned its old flood-plains. As savage man gradually settled down and took to farming, he found these bottom-lands, with their rich, mellow soil, just the thing for his crooked-sticks and stone hoes--the only kinds of ploughs and hoes there were in those days. With such crude farming tools he couldn't have managed to scratch a living on any other kind of soil. When the river floods came along, all these crooked-stick farmers had to do was to keep out of the way until the floods went down, and there were their fields all fertilized for them, as good as new, and they could go on for thousands of years working the same fields without ever bothering their heads as to whether they needed any lime or potash or nitrogen, or anything; for they didn't. The river floods attended to all that. [Illustration: FATHER NILE AND THE MAKING OF EGYPT "Egypt," said Herodotus, "is the gift of the Nile"; and it is true so far as her fertile lands are concerned. The ancients attributed the annual floods to the god of the Nile, as shown in that statue of Father Nile in the Vatican. Below is a threshing scene in Egypt painted by Gerome. The last picture, from a carving in the tomb of an Egyptian noble, shows how they ploughed and sowed in the Pyramid age.] So, in course of time, civilizations such as those of Egypt and India and Persia grew up, and in further course of time these civilizations spread into Europe, and finally to the New World. HOW RIVER BANKS GO BANKRUPT Now all this is very well, this leaving it to Nature to fertilize the fields, where everything is just right for it, as it is along the Nile, but in most lands it won't do it all. The trouble is that, in raising the grain foods, the ground must be kept free of grass and weeds, and well ploughed during the rainy season. But the same rains that water the fields wash more or less good soil into the streams; much more than Nature alone can put back. For instance, down in Italy where, if the old forests were still there, the rains wouldn't wash away more than a foot of soil in 5,000 years, this soil is being carried into the Po, and by the Po emptied into the sea so fast--a foot in less than 1,000 years--that if you visit Italy to-day, say, and then go back in ten years, you'll see bare rocks on many a hillside that is now clothed in green. On such rocks the soil is already thin, and in ten years more it is all gone; all washed away! This thing is going on all around the shores of the Mediterranean. You are constantly coming on sections of country that used to be covered with great forests and prosperous farming communities where the soil has vanished, and many stretches of barren, rocky land where hardly a weed can find a foothold. [Illustration: WHAT HAPPENS TO THE LAND WHEN THE TREES ARE GONE Could anything be more desolate? You can see from this example how vital to our national life is the forest conservation work of our government. Trees, by the network of their roots, keep the soil from washing away, retain moisture by their shade, and absorb the water of the rains and the melting snows so that it reaches the rivers and the creeks gradually. But when the trees are gone the water, unchecked, rushes down the slopes in floods, washing away the precious soil and leaving them as barren as a desert.] "But, what are you going to do about it?" you say. "You can't change the slope of the hills, can you? And the farmer has _got_ to plough his land--you just said so yourself." Yes, he's got to plough his land, to be sure; but so has he got to have pasture for his live stock. If he hasn't any live stock, that just shows what kind of a farmer he is. Every farmer ought to have live stock. Corn always brings a great deal more when it goes to market "on four feet," as the saying is; and, besides, the live stock give back to the fields, in the shape of manure, a large part of what they eat. Now, if you have live stock you must have pasture, and all land with a slope of more than one foot in thirty should be used partly for pasture and partly to grow wood for the kitchen stove, and hickory-nuts and walnuts for winter firesides. Although the land slopes, the mat made by the grass roots will keep it from washing away. "But suppose you lived where there wasn't any land to speak of that didn't tip up; in New England, say--what would you do then?" Leave the upper part of the slopes in the woods. Then the water that carries off the soil will not run entirely away, as it does in ploughed fields, but will creep down slowly, and, charged with the decay of the woods, help fertilize the lower lands and change the rocks beneath them into soil--the acids from the decaying vegetable matter eating into them. "But still," you say, "there are farm lands that must be ploughed even if they do wash away; they're all the land a man has, sometimes. What then?" Plough deep. Then the soil soaks up more of the rain and lets the water pass away in clear springs. This not only saves soil but, as we have just said, helps to decompose the subsoil and the bed rock. Then there's another thing that good farmers do in such cases. They plough ditches along the hillside leading by a gentle slope to the natural watercourses; so the water of the rains, instead of going down the hills with a rush, and going faster the farther it runs--like a boy on a toboggan--is caught and checked in these sloping ditches, and much of the soil it contains deposited before it reaches the streams. [Illustration: HOW THE FRENCH PROTECT THEIR HILLSIDE FARMS This is how the French peasant keeps the mountain torrents from carrying off his precious soil.] The best way of all, of course, is to build terraces, as they do in the thickly settled parts of Europe. But this is only profitable for the more valuable crops and not for ordinary grains. SUCH SPENDTHRIFTS OF GOD'S GOOD SOIL! My, but it's a shame the way we've wasted soil in this country. What spendthrifts! To start with--when the country was first settled--there seemed no end to the fine land, and every one could have a good farm for the asking. All he had to do was to make his wants known to Uncle Sam and then go out and help himself. What happened then? Why, what always happens? Easy come, easy go. These pioneer farmers worked their farms for all there was in them; didn't bother, many of them, even to haul the barn manure into the fields. Then when the old farm was exhausted they moved off to new lands and did the same thing over again. [Illustration: A HOME IN THE DESERT Doesn't look much like a home in the desert, does it? But it is--a lovely home in what the old geographies called "The Great American Desert." In the Sahara oases are few and far between, but modern irrigation engineering makes oases to order--thousands and thousands of acres of them!] They ploughed on steep hillsides; they allowed gulches to form, as they will quickly do on sloping ploughed land, if you don't watch out; they cut away the timber. It's easy in a hill country like the eastern part of the United States to have all the good top-soil washed away in twenty years after the forests have been destroyed; the good soil that it probably took 2,000 years to make. Doctor Shaler[8] estimated that in the States south of the Ohio and the James Rivers more than 8,000 square miles of originally fertile land had, by this shiftless and thoughtless way of doing things, been put into such a state that it wouldn't grow anything; and over 1,500 square miles of this, actually worn down to the subsoil, and even to the bed rock, so that it may never be profitable to farm again--at least not in our time--no matter what they do! [8] "Outlines of Earth's History." I knew a farmer with a small son to whom he intended to leave the farm when he grew up, who did things like that for twenty years. By the time the little boy was old enough to vote, there was no farm to leave; all the good part of it was gone. Serious thing for that little boy, wasn't it? HIDE AND SEEK IN THE LIBRARY What have burrowing animals to do with the drainage system of the land? (Keffer's "Nature Studies on the Farm.") How do angleworms help drain the soil? How do the forests help make good use of the rain that falls, not only for themselves but for the rest of us? How do the rains help to warm the ground in the spring? The heat they carry into the soil is produced in two ways. The book mentioned above tells of one of these ways, and Russell's little book, "The Story of the Soil," tells of another. Beale's "Seed Dispersal" tells how the raindrops (working together, of course) help plant maple, elm, sycamore, willow, and other trees that grow by the waterside, to scatter their seeds. You'd be surprised what a series of adventures the seeds of a bladderwort have before they get planted on some new shore, after having left the parent shrub. First, they float down-stream, as you know, but when autumn comes on, what do you suppose they do? They go to bed. Where? Right in the bottom of the stream. Then how do they ever get up and get planted on the shore? Well, you just look it up in that Beale book and see. Do you know how the rains help to get the mineral food up into the plant? And why swamps are such poor producers? And how the sun acts as a pump for the plant world? You will find answers to all these questions in Shaler's "Outlines of Earth's History" and in your books on botany and agriculture. Russell's book on the soil tells how the ancient Gauls and Britons used to fertilize their land with marl, and how the tides help to fertilize England. It's just the reverse of the way Father Nile looks after Egypt, as you will see. If you want to read an interesting description of the difficulties of farming on wet lands, you will find it in this meaty little book. If you don't know how serious a thing it is to let gullies form in land, look it up in Shaler's "Man and the Earth" and you will see. How do you suppose deserts that get so little rain themselves could _help make it rain_ in other places? For example, the desert of Thibet is the chief cause of the monsoon rains that do so much for India. That part of your geography that explains the circulation of the air will help you figure this out; particularly with a map under your eye that shows the relative location of the desert and the Indian Ocean, over which the monsoon winds blow. [Illustration: AN EXAMPLE OF MAN'S DEBT TO THE EARTHWORM Much of the earth's Maytime bloom and beauty is due to the labor of our humble little brother of the dust, the earthworm; a striking fact which was never recognized until the great Charles Darwin looked into the matter and wrote a book about him. This picture by Millet is called "Springtime" and hangs in the Louvre, in Paris.] CHAPTER V (MAY) It may be doubted whether there are many other animals which have played so important a part in the history of the world as these lowly organized creatures. --_Darwin: "The Formation of Vegetable Mould."_ WHAT THE EARTH OWES TO THE EARTHWORM Suppose father had a hired hand who would plough his fields, fertilize them at his own expense, build his own house, board himself, and for all this ask only the privilege of living on the place, studying Botany, Geology, and Geometry, and enjoying the scenery. "Where can I get a man like that?" I imagine father saying. "You've got him now," you might reply. "He's already working for you--thousands of him, and has been working for you--millions of him--for thousands and millions of years." We have all known him well from boyhood by several names--angleworm, fishworm, earthworm. He also, as you will find in the dictionary, has a nice long Latin title. And it is particularly fitting that his name should be so associated with antiquity, since he belongs to one of the oldest families in the world; a family far older than the Roman Empire itself, which his people long ago helped grind back into the dust from which it came. And, speaking of Romans, every few years Mr. Earthworm does what Julius Cæsar did, captures the whole of England--all the best parts of it--and then, unlike Cæsar, gives it back to the English, made over again, better than it was before, as you will see. I. THE CITIES OF WORMS If you happen to be a high school boy you, of course, know about a certain city of Worms and what great things took place there once upon a time, but there are many cities of worms on any good farm, and each has more inhabitants than the famous city of Worms of history--something like 25,000 to the acre; and, in garden soil, 50,000! [Illustration: ANOTHER "CATHEDRAL OF WORMS" In the story of the Reformation in your history you will read of a certain Cathedral of Worms and what took place there once upon a time. Here is a "cathedral of worms" as interesting to the student of nature as that famous edifice is to the historian and the architect. It is the tower-like casting of a big earthworm and was found in the Botanic Garden at Calcutta. The picture is "life-size."] Did you ever notice how big boulders in a field are frequently sunk into the ground as if dropped from a great height? It is the earthworms that help sink them in the course of their soil-making. They like the moist shelter of the stones and burrow under them. Finally the weight of the stones crushes the burrows, and so the stones sink down. PIONEER LIFE AMONG THE EARTHWORMS Poor soil, as every boy knows, is a poor place to look for fishworms. But you have noticed that the mounds the worm throws up on such soil are larger than those on rich soil. The reason is that the soil, being less nutritious, the worm must eat more of it and, in so doing, pulverizes and fertilizes it. But a menu of earth alone not being to the earthworm's liking, undesirable regions have fewer of these farmers working underground; and this, for the same reason that these regions are sparsely settled on the surface--it is so hard to make a living. So the earthworms may be said to have a decided taste in landscape. They don't care for desert scenery like Gerome's picture of the lion's big front yard,[9] but they are very fond of orchards where the soil is rich and leaves are plenty. The pathways artists are fond of putting in landscapes would also probably attract the eyes of earthworms--if they had any, for the worms prefer soil a little packed, as it is in pathways, because it makes more substantial burrows. And, singularly enough, the worms also like most the very thing that the artist emphasizes to lead the eye into his picture--the border lines that _define_ the path. It is along the edges of a pathway that you find most worms. [9] "The Two Majesties." This painting, by a great French realist, shows a lion getting home rather late, after his night out, stopping for a look at the rising sun; a thing with which, owing to his habits, he is not very familiar. [Illustration: _Painted by F. O. Sylvester._ _Painted by Westman._ THE EARTHWORM'S TASTE IN SCENERY Two features common to both these pictures--the trees and the pathways--appeal to earthworms as well as artists, for reasons you have learned in this chapter.] The earthworm, in addition to working over and fertilizing the soil already made, actually helps make soil out of rock. He does this in two ways: (1) With acids--for, like the Little Old Man of the Rock, he is a chemist; (2) by grinding up rock in a little mill he always carries with him. HOW THE EARTHWORM COOKS HIS MEALS The earthworm's favorite diet is leaves and he has a way of cooking them. It is not quite like our way of cooking beet or dandelion leaves, but it answers the same purpose--it partially digests them. In glands, in his "mouth," he secretes a fluid which, like our saliva, contains an alkali. But the earthworm's alkaline solution is much stronger, and when he covers a fresh green leaf with it--as he is usually obliged to do in Summer when there are so few stale vegetables, the kind he prefers, in his market--the leaf quickly turns brown and becomes as soft as a boiled cabbage. Of course, there are always dead leaves in the woods, and these, which even the cow with her fine digestive outfit cannot handle, are a delight to the earthworm; for he also has a much larger supply of pancreatic juice than the higher animals, and this takes care of the leaves after he has swallowed them. He swallows bit by bit; just like a nice little boy who has been taught not to bolt his food. The acids in the earthworm's "stomach," acting on the leaves, help make other acids which remain in the soil after it has passed through the earthworm's body and help dissolve those fine grains of sand which make your bare feet so gritty when mud dries on them. And, not only that, but this coating of soil lying upon the bed rock hastens its decay; for the earthworm's burrow runs down four to six feet, sometimes farther. Besides the soil he thus grinds up and fertilizes so well with leaf-mould--what your text-book on agriculture calls "humus"--the earthworm does a lot of useful grinding in connection with the building of his house. He begins, as we do, by digging the cellar; but there he stops, for _his_ house is _all_ cellar! He makes it in two ways: (1) By pushing aside the earth as he advances; (2) by swallowing earth and passing it through his body, thus making the little mounds you see on the surface. THE EARTHWORM SYSTEM AT PANAMA A principle similar to his swallowing operations is frequently employed in engineering; as in making the Panama Canal, where dredging machinery dug out swamps and pumped the mud through a tube into other swamps to fill them up and help get rid of the mosquitoes. In pushing the earth away the worm uses the principle of the wedge, stretching out his "nose"--as you have often seen him do when crawling--and poking it into the crevices in the ground; much as the wheat roots poke _their_ little noses through the fertile soil the earthworm makes. And, as in human engineering and the work of the ant, the earthworm doesn't throw the dirt around carelessly. He casts it out, first on one side and then on the other; using his tail to spread it about neatly. THE TILING IN THE EARTHWORM'S HOUSE The walls of the earthworm's house are plastered, too. At first they are made a little larger than his body. Then he coats them with earth, ground very fine, like the clay for making our cups and saucers, and for making the beautiful white tiling on the walls at the stations of a city subway. When this earthworm "porcelain" dries it forms a lining, hard and smooth, which keeps the earthworm's tender body from being scratched as he moves up and down his long hallway. It also enables him to travel faster because it is smooth, and it strengthens the walls. The burrows which run far down into the ground, as all finally do toward Autumn, end in a little chamber. Into this tiny bedroom the worm retires during the hot, dry days of August and there he spends the Winter--usually with several companions, all sound asleep, packed together for warmth. AND RUGS ON THE FLOORS! Sometimes the Summer and Winter residences are quite ambitious, several burrows opening into one large chamber and each tunnel having two, sometimes three, chambers of its own--like a fashionable apartment with its main reception-room, and still more like the central sitting-rooms in Greek and Roman palaces. And the earthworm seems even to have some idea of mosaics, for it is the general practice to pave these chambers with little pebbles about the size of a mustard-seed. This is to help keep the worm's body from the cold ground. In addition to the mosaic floors the earthworms have rugs with lovely leaf patterns like the Oriental rugs that are so highly prized; and, as in the case of genuine Oriental rugs, no two patterns are alike. These rugs are leaves which the earthworm drags into his burrow, not for food but for house furnishing. When used for house furnishing they are placed in the entrance-hall; that is to say, they are used to coat the mouth of the burrow to prevent the worm's body from coming in contact with the ground. The mouth of the burrow, of course, is just where it is coldest at night in the Summer, the time of year when the earthworm spends a great deal of his time in the front of his house. The surface of the earth, you know, cools very rapidly after sunset and the dew on the grass in the morning is so cold it makes your bare feet ache. The worm requires damp earth around him because he breathes through his skin and must keep it moist, but at the same time he is sensitive to cold. And to drafts. Ugh! PEBBLE-FORT DEFENSES AGAINST THE FOE So he is very careful to keep the front door closed. This he does by stopping it up with leaves, leaf stems, and sticks. He also protects the door with little heaps of smooth round pebbles; but these pebbles are of a larger size than those he uses for paving the floor of his chamber. Besides helping to keep out drafts these pebbles serve another purpose. As our ancestors, the cave-builders, barred the door with boulders to keep out bears and other unwelcome callers, so the earthworms are protected by the pebbles, to a certain extent, from one of their enemies--the thousand-legged worm. Because of these little forts, the earthworms can remain with more safety near the doorway and enjoy the warmth of the morning sun. (So we might have reproduced Corot's "Morning" as a kind of landscape the earthworm enjoys!) II. THE MIND OF THE EARTHWORM From all of which you can see the earthworm, for what small schooling he gets, is a very bright boy! If we were as bright, according to our opportunities, we would probably have answered long ago such puzzles as the question whether there is really anybody at home in Mars, how to keep stored eggs from tasting of the shell, and other great scientific problems of our day. WHERE MR. EARTHWORM KEEPS HIS BRAIN Just as we have little brains in the tips of our fingers, the earthworms have brains in the ends of their "noses." They have neither eyes nor ears, but, like that wonderful girl, Helen Keller, they make up for the lack of these senses, to a remarkable degree, by the development of the sense of touch. They acquire quite a little knowledge of Botany, for example. They not only know that leaves are good to eat, but they know which is the "petiole" and which is the "base." They always drag leaves into their burrows by the smallest ends, because this makes it easier to get them through the door. And it is not by mere instinct that they do this. Supply worms with leaves of different form from those which grow in the region where they live, and they will experiment with them until they find just the best way in which to pull them into the burrows. After that they will always take hold of them so, without further experiment. That is the majority of them will do this; for earthworms are like other little people--all of them are not equally ambitious or studious. And the earthworm also knows something about Geometry. Cut paper into little triangles of various shapes and pretend to the worms that they are leaves by scattering them near the mouths of the burrows. Then remove the leaves with which the burrows are stopped. The worms will pull in the slips to close the door and they will--most of them--take hold by the apex of the triangle because that is the narrowest point. THE EARTHWORM'S TASTE IN MUSIC So you see the earthworm is a very cultivated country gentleman with his knowledge of Botany and Geometry, and his taste for landscape. But this is not all. He also has opinions about music. There are certain notes that apparently get on his nerves. Put worms in good soil in a flower-pot, and some evening when they are lying outside their burrows set the pot on the piano and strike the note C in the bass clef. Instantly they will pull themselves into their burrows. They will do the same thing at the sound of G above the line in the treble clef. Although they cannot hear, they are sensitive to vibrations, and these are carried from the sounding-board of the piano into the pot. They are less sensitive when the pot itself is tapped. The music seems to go right through them. WHY THE EARLY BIRD GETS THE WORM Except in rainy weather worms ordinarily come out of their burrows only at night. By early morning they have withdrawn into their holes and lie with their noses close to the surface to get the warmth of the morning sun. Then the early bird gets _them_! The reason a robin cocks his head in such a funny way--like a lord with a monocle--just before he captures a worm, is not because he is _listening_, as many people think; for the worm isn't saying a word and he isn't moving, and wouldn't make a bit of noise if he did move. The robin's eyes are on each side of his head and not in the middle of his face like ours, so he must turn his head in order to bring his eye in line with the hole where he sees the tip of Mr. Earthworm's nose. [Illustration: THREE EARLY BIRDS. FIND THE THIRD Don't they look happy--these two tow-heads? They are evidently going fishing in the early morning. Another early bird--several of him--that we are saying a good deal about in these pages is to be found in the can. Still another, the one at the bottom of the page, is taking advantage of the earthworm's family habit of warming his "nose" in the early sun rays.] [Illustration] And many people also believe that earthworms come down with the rain. Even park policemen believe it. At least, one said to me, in Central Park: "In dhry spells ye won't see wan. But let there come a little shower an' th' walks and the dhrives will be covered wid them; like the fairy stones that fall wid the rain in the ould counthry." DO EARTHWORMS COME DOWN WITH THE RAIN? The reason you see so many worms after a rain is that earthworms like moisture, and the rain seems to make them feel particularly good and breed a spirit of adventure. So out of their holes and away they go! A rain is their shower-bath; and you know how a shower-bath makes you feel. The mornings when the earthworms are apt to be thickest are those following a comparatively light rain in early Spring when the worms have recently awakened from their long Winter nap. With the beginning of the rainy season in the Fall, the worms also do a good deal of travelling into foreign lands, but in both Spring and Fall you will usually find more worms after a light shower than after a long, heavy downpour. If the worms were drowned out it would be the other way around, don't you see? To be sure, you will often find dead worms in shallow pools by the roadside; particularly after Autumn rains. These are sick worms and the chill was too much for them. But it's remarkable how low a temperature a good husky angleworm can stand. A professor in the University of Chicago, near which I live, tells me he has often found the ground in the neighboring park covered with worms after November rains when his hands, and those of the students who were helping him gather them for study, were numb with the cold. And how much work do you suppose these farmers do in grinding up and fertilizing the soil? In many parts of England the whole of the best land--the vegetable mould--passes through their bodies every few years, and they are doing similar work all over the world. They not only fertilize the earth by mixing it with the leaves they eat and those that decay in their burrows, but their castings help to bury fallen leaves and twigs and dead insects, and they also bring up lower soil to the surface, thus increasing its fertility. And by loosening the soil they let in more air. Remember that roots, like people, must have air. III. THE MILL OF THE EARTHWORM For the grinding up of the earth and the leaves, the earthworm has, as I have already said, a little mill that he always carries with him. Do you know what a gold mill is? Well, a gold mill is a mill that grinds up rock and so grinds out the gold. The earthworm's mill, in a manner of speaking, also grinds out gold, for it grinds the little particles of stone in the soil, and this soil grows fields of golden grain. The earthworm's mill is his gizzard. This gizzard is made and works very much like the gizzard of the chicken. And like the chicken the earthworm swallows little stones to help his digestion. So these stones, too, are ground into soil. Like the chicken's gizzard the gizzard of the earthworm is lined with a thick, tough membrane, and it has muscles--such muscles! There are two sets of these muscles and they cross each other somewhat like the warp and woof of the cloth in your clothes. The muscles that run lengthwise are not so very strong, for all they have to do is to help the earthworm swallow, but the muscles that run around the gizzard are wonderfully strong. They are about ten times as thick as the other muscles. One of Mr. Earthworm's French biographers[10] calls these muscles "veritable armatures"; that is, freely translated, "veritable hoops of steel." [10] When you study French, if you want to read this book--like most French works on science it is very interesting--ask for Perrier's "Organization des Lumbricus Terrestris." I said, in the second paragraph above this, that worms swallow grains of sand and stones to help their digestions, as chickens do. But the earthworm saves time, for he takes the stones with his meals; just as some Englishmen, fat old squires, when they get along in years, or for any other reason are a little weak in their digestive regions--keep pepsin on the table with the pepper and salt. And--believe it or not--the earthworm actually makes his _own_ millstones sometimes! The chalk in the chalky fluid of the glands that help him digest his meals frequently hardens into little grains in grinding the food. It's almost as if the saliva in our mouths, in addition to acting directly on the food, also made a new set of teeth for us! Suppose we had a stomach like the earthworm, wouldn't it be fun? We could digest the biggest dinners at Thanksgiving and Christmas and picnics and birthdays. We could even eat apples without waiting for them to get quite ripe. Haven't you done it to your sorrow? And no stomachache and no mince-pie nightmares! WHY THE EARTHWORM NEVER HAS NIGHTMARES By the way, the earthworm, although he has his troubles like the rest of us, never _has_ nightmares. For one thing he has that stomach[11] and--a still better reason, perhaps--he never sleeps at night. Like the moths and the bats and the burglars and members of Parliament, he makes night his busy day. [11] Just listen to this: "Worms," says Mr. Darwin, in that remarkable book of his, "are indifferent to very sharp objects, even rose thorns and small splinters of glass." And, in other ways, while he is so much like the rest of us worms of the dust, his life differs from that of most people. For instance, he not only works by night while we work by day, and works underground while we work on top, but he takes his vacation in the Winter while we take ours in Summer. In that respect Mr. Earthworm is like the millionaires at Palm Beach; for in Winter he, too, goes in the direction we call south on the map--that is to say _down_. But, as you say, it takes all kinds of people to make a world; including earthworms and millionaires! HIDE AND SEEK IN THE LIBRARY Who was that in Mother Goose that went a-fishing "for to catch a whale"? Anyhow, there are fishworms so big that one might suppose they were made for catching whales. How long do you suppose they are, these big fishworms? A foot? Pshaw! We have fishworms of our own a foot long. Two feet? More. Three feet? More. You look it up in the article on the earthworm in the "Britannica." And how many kinds of earthworms do you suppose there are? You will be surprised to learn. Also, you will find that the earthworms have relatives who live in the water all the time. The article in the "International" tells why these modest neighbors of ours don't come to the surface in the daytime. That will be an interesting thing to know. Don't you think so? And did you ever count an earthworm's rings? Other scientists have. (All live boys and girls are scientists; they want to _know_.) Try counting the rings of an earthworm and then compare your figures with those given in the article in the "International." How many hearts do you suppose an earthworm has? You will find in the "International's" article they have a good many of what are sometimes called "hearts," and how different the earthworm's circulation system is from ours. Does our saliva do for us anything like what it does for the earthworm; and our pancreatic juice? Compare the earthworm's method of digging his subway with that of the armadillo. How do they differ in the way of using their noses? Do you know how men dig subways; like those under New York City and Boston, for instance? Books that tell about this phase of human engineering and tell it in a very interesting way are "On the Battle-front of Engineering" ("New York's Culebra Cut") and "Romance of Modern Engineering" ("City Railways"), "Travelers and Traveling" ("How Elevated Roads and Subways Are Built"). Speaking of the earthworm's wedge and how he uses it, do you know that all of man's complicated machinery is the result of only a few simple mechanical principles combined; and that the wedge is one of the most important? Look up "_wedge_," "_machine_," "_simple machine_," etc., in the dictionary or encyclopædia. How does the earthworm's method of pushing his way in the world with the end of his nose compare with the way a root works along in the ground? (See Chapter X.) The earthworm's neat way of disposing of the dirt he casts out reminds me of how the beaver handles dirt when he builds a canal, and the way of the ants in digging their underground homes. (Chapters VI and VIII.) We have little brains in our finger-tips just as the earthworm has on the end of his nose. How much do you know about the little brains scattered through our bodies (_Ganglia_)? You see the simple earthworm is the A, B, C of a lot of things; and even Mr. Darwin's famous book doesn't contain all there is to be learned about him in books and in personal interviews with Mr. Earthworm himself. A farm boy to whom the writer read the story of the earthworm, when asked how he thought the worm could turn in his burrow when it fits him so closely, said, "Why, he turns around in that little room at the end of the hall," thereby solving, as I think, a problem that puzzled Mr. Darwin, and which he left unsolved. [Illustration: SINFUL TACTICS OF A SACRED BEETLE The beetle pushing backward is the owner of the ball and is on his way--as he thinks--to his burrow. The other is altering the direction toward his own burrow. Fabre's book on the Sacred Beetle--the tumblebug of our fields and roadways--tells how the thing came out.] CHAPTER VI (JUNE) Go to the ant, thou sluggard; Consider her ways, and be wise. --_Proverbs_ 6:6. THE LITTLE FARMERS WITH SIX FEET I don't believe I've ever heard anybody say anything against an angleworm; although not many people, even to this day, I'll be bound, realize what a useful citizen the angleworm is. But now we come to a class of farmers that, as a class, are positively disliked; farmers that nobody has a good word for, that nobody wants for neighbors. The charge against them is that, like the man in the Bible, they are always reaping where they have not sown; always helping themselves to other people's crops--bushels of wheat, bushels of rye, tons of cotton, loads of hay and apples and peaches and plums; and nice garden vegetables; and even the trees in the wood lot. It is estimated, for instance, that the chinch-bug helps himself every year to $30,000,000 worth of Uncle Sam's grain; while other insects make away with 10 per cent of his hay crop, 20 per cent of mother's garden vegetables, $10,000,000 worth of father's tobacco; and the Hessian fly sees to it that between 10 and 25 per cent of the farmer's wheat never gets to mill. "Yes, and sometimes it's 50-50 between the farmer and the fly," said the high school boy, who often spends his vacation with a country cousin. Then there are insects that injure and destroy forest trees because they like to eat the leaves or the wood itself; and some 300 kinds of insects that make themselves free with other people's orchards. I. CONSIDERING THE ANT But, as I said a few moments ago, it takes all sorts of people to make a world; and as there are good and bad citizens among men, so there are good and bad among insects. Indeed there are so many useful insects that help make or fertilize the soil by grinding up earth and burying things in it, that even this chapter, which is rather long, as you see, can't begin to tell about all of them. So suppose we give our space to a few by way of example, and then look up others in other books in the library. AMOUNT OF WORK DONE BY ANTS First of all let us consider the ways of the ant (as the Bible tells us to). The ant's work may be said to take up where the earthworm leaves off. Mr. Earthworm, as we have seen, is a little fastidious about the kind of land he tills. Among other things, he is inclined to avoid sandy soil, while the ants will be found piling up their pretty cones of sand or clay as well as of black earth. And in some soils the ants do more important work than the worm that helped make Mr. Darwin famous. In the course of a single year they may bring fresh soil to the surface to the average depth of a quarter of an inch over many square miles. This not only helps to keep the farmer's fields fertile by adding fresh, unused earth, but enriches them by burying the vegetation--such as leaves and twigs and branches broken from dead trees by storms--so that it decays. This burying of vegetation is the very thing the good farmer does when he spreads his fields with manure from the barnyard, or when he ploughs under the stubble. [Illustration: A HEAP OF GRIST FROM AN ANT SOIL MILL Something of an ant-hill, isn't it? It is a foot high and measures nearly three feet across. You will find such ant hills in the Arkansas Valley in Colorado, where the photograph of this one was taken.] Ants are very glad to do this for the farmer because it isn't any extra trouble for them. Their little heaps of fresh earth are thrown out in connection with the building of their homes. The mining ants dig galleries in clay, building pillars to support the work and covering them with thatches of grass. The red and yellow field ants are the masons. They first raise pillars and then construct arches between them, covering these arches with the loose piles of soil which we know as ant-hills. The carpenter-ants bore their cells in the dead limbs of trees, and the wood dust they make from them hurries on the process of returning these dead limbs to the soil. One kind of carpenter-ant covers its walls with a mixture of sawdust, earth, and spiders' webs. An ant in Australia builds its home of leaves fastened together with a kind of saliva. One kind of ant, whose calling card among scientific people is Formica fusca,[12] adds new stories to old houses as the colony grows; much as in the growth of cities and hamlets the buildings grow taller with the growth of the town. Just as men do, such ants first build the side walls and then the ceilings. As if these ants are working under contract and must get their job done by a certain time, two groups are employed on the ceiling at the same time, each group working toward the other from the opposite wall and meeting in the middle. [12] In the world of science, the ant goes by her Latin name, _Formica_, and the whole family is known as the _Formicidæ_. To a Roman boy _Formica_ simply meant "ant." _Fusca_ is also Latin, and means "dark"; so you can see this part of the story is about a species of dark ant. As a matter of fact he is dark brown. [Illustration: THE DESERTED VILLAGE UNDER THE STONE If Oliver Goldsmith had been as much interested in ants as was the French "Homer of the insect," Henri Fabre, he might have written of another kind of "Deserted Village," its "desert walks" and its "mouldering walls." This is a deserted village of ants. The little citizens that built it lived under a stone. When the stone was lifted it took the entire roof off the place.] THE ANT WHO DIDN'T KNOW HIS TRADE As you may suppose, this is real architectural engineering and no place for amateurs. I once saw a foolish worker starting a roof from the top of one of the side walls without paying any attention to the fact that the other wall was much higher. The result was he struck the middle of it, instead of joining it at the top. Another ant passing, possibly the supervising architect, saw what was going to happen. So what does he do but stop and tear down the other's work and build the ceiling over again! "There! _That's_ the way to put in a ceiling," he seemed to say. "For goodness sake, where _did_ you learn your trade?" Huber, the famous student of ants, saw two of these wonderful insects do the very same thing. Sometimes the situation is such that it is necessary to build a very wide ceiling, so wide that it would fall of its own weight unless supported in some way. Then what would you do; that is, if _you_ were an ant? "Why, I'd put up pillars to hold it." That's exactly what the ants do; they put up pillars; but instead of using steel beams, as men do in this day of steel, the ant architects make pillars of clay--build them up with pellets, little clay bricks which they shape with their mandibles--their jaws. But the ants seem to have some of the methods of steel construction, too; the use of girders and things. Ebrard, a French student of ants, tells how, when a certain roof threatened to fall, some Sir Christopher Wren of the ant world used a blade of grass as a girder, just as Sir Christopher in his day put in girders to support the roof of Saint Paul's Cathedral, and as men use steel girders to-day. The ant fastened a little mass of earth on the end of a grass stalk growing near to bend it over; then gnawed it a little at the bottom to make it bend still more, and finally fixed it with mud pellets into the roof. But here's something that will make you smile! You have heard about the lazy man down in Arkansas with the hole in his roof? You remember he never mended it in dry weather because it didn't need it, and when it rained he _couldn't_ mend it on account of the rain! RAINY-DAY WORK IN THE ANT WORLD Well, these _Formica fusca_ folks are as different from that Arkansas man as anything you could imagine. First of all, being ants, they are anything but lazy; secondly, they never put off needed work on their roofs on account of rain. In fact, they _choose_ the first wet day to do it. As soon as the rain begins they build up a thick terrace on the roof of the old dwelling, carrying in their jaws little piles of finely ground earth which they spread out with their hind legs. Then, by hollowing out this roof, they turn it into a new story. Last of all they put on the ceiling. You see the rain helps them in mixing their clay. There are ants that build up vaulted viaducts or covered ways, and they use clay for that.[13] They make the clay by mixing earth with saliva. Some of these viaducts reach out from the house--the ants' house--to their "cow" pasture. [13] The scientific name for this particular kind of ant is _Lasius niger_. [Illustration: AN ANT CARRYING ONE OF HER COWS] You know about how ants keep cows, little bugs called aphids? The aphids feed on plants, and the clay viaducts protect the ants from their enemies and from the sun in going to and from the pasture; for this particular family of ants doesn't like the sun. They make clay sheds for their cattle, too. Here and there along the clay viaduct are large roomy spaces, cow-sheds, so to speak--where the little honey cows gather when they aren't feeding. Another kind of ant builds earth huts around its cow pastures. The large red ants (_F. rufa_), sometimes called "horse ants," build hills as large as small haycocks. II. THE TERMITES AND THEIR TOWERS OF BABEL But speaking of big buildings, did you ever hear of a skyscraper a mile high? Well the home of the six-footed farmer I am going to tell you about now is as much taller than he is as a mile-high skyscraper would be taller than a man. The remarkable little creatures that build these skyscrapers are called "termites." Termites are also known as "white ants." This seems funny when we know that they are neither "ants" nor are they white. The young of the workers are white, to be sure, but the grown-ups are of various colors, and never milky white as they are when young. The termites were first called "white ants" in books of travel because the termites the travellers saw were the young people. HOW TERMITES ARE LIKE THE ANTS The termites are really closer relatives of dragon-flies, cockroaches, and crickets than of the ants, but they do look a great deal like an ant, and they have many of the ways of the ants. As in the case of ants, all the members of one community are the children of one queen. The king lives with the queen in a private apartment. Sometimes--as with human royalties--the king and queen will have separate residences, but the termite royalties always live in the same house with their people; they are very democratic. Some kinds of termites live in rotten trees, which they tunnel into, and that is their contribution to soil-making; while others build great, big solid houses of earth and fibres, mixed. These houses are called "termitariums," and are six, eight, ten, even twenty-five feet high; fully 1,000 times the length of the worker. Think of a man five feet high, and then multiply by 1,000, and you see you have got nearly a mile! [Illustration: SKYSCRAPERS A MILE HIGH "Some kinds of termites build great, solid houses of earth and fibres mixed. These houses are six, eight, ten, even twenty-five feet high, fully one thousand times the length of the worker. Think of a man five feet high and then multiply by one thousand, and you see you have got nearly a mile."] These termite skyscrapers aren't much to look at on the outside, but inside they're just fine; they have everything the most particular ant could want. For instance, the termites are right up-to-date in their ideas about fresh air, their houses being well ventilated through windows left in the walls for that purpose. You can see the importance of this fresh-air system when you know there are thousands of termites under the same roof. They also have a sewage system for carrying off the water of the rains. And a fine piece of mechanical engineering the building of it is, too; for these "water-pipes" are the underground passages hollowed out in getting the clay to build the homes. The termites build their homes with one hand and dig the sewer with the other, so to speak. THE THERMOSTATS FOR THE NURSERIES The termitarium has as many rooms in it as a big hotel--oh, I don't know _how_ many--and they are all built around the chambers of the king and queen. Next to the royal apartments are the pantries, a lot of them, and they are all stored with food. In the upper part of the termitarium are the nurseries--many nurseries--for no one nursery could care for any such numbers of babies as the queen has. Between the nursery and the roof is an air-space, and there are also air-spaces on the sides and beneath. The nursery thus being surrounded by air, the eggs and, when they come along, the babies are protected from changes of temperature. It's the same principle that's employed in making refrigerators and thermos bottles. The rooms in which the eggs are kept are divided by walls made of fragments of wood and gum glued together. This mixture is a bad conductor[14] of heat or cold. And so the eggs are kept at an even temperature. [14] A "bad" conductor is often a _good_ thing, as you'll see by looking it up in the dictionary. While we cannot see any of the termite skyscrapers in the United States, because we have none of the species of termites that build them, we can see a member of the termite family. This is the common white ant that digs into joists of houses. On the outside of these same joists, and up in the attics of old farmhouses, if there happens to be a broken window-pane, or some other hole through which she can get in, you can see the nest of another tiller of the soil, the wasp. The mason-wasps or mud daubers are the most common. You will find their nests on the rafters of the barn when you go to throw down hay, or when you go into the corn-crib. They have all sorts of fancies--these wasps--about their clay homes and where to build them. Some build on the walls and some in the corners of rafters, others prefer outdoor life. Some want to live alone, others like society. What are known as "social" wasps sometimes build their nests in tiny hollows that they dig in the ground; others fasten their nests to the boughs of trees. The work of these wasps, from the farming standpoint, is useful not alone in grinding the soil, but helping to supply it with humus; for their nests are made of wood fibre, which they tear with their mandibles from gateposts, rail fences, and the bark of trees. [Illustration: NESTS OF MASON-WASPS] The carpenter-wasp is both a wood-worker and a clay-worker. He cuts tubular nests in wood and divides them by partitions. We think we're pretty smart, we humans, because we are always picking up ideas, but here's a creature, no bigger than the end of your finger, who has picked up an idea from the carpenter-bee, grafted it on his native trade of clay-worker, and made himself as nice and cosey a country place as you'd want to see! ABOUT THE WASP, THE FOX, AND THE BUMBLEBEE Here's another example of the same thing, this spreading of good ideas among the neighbors. It's about the fox, the digger-wasps, and the bumblebee. The fox can dig his own burrow when he has to, but if he finds somebody else's that he can use, he just helps himself--provided, of course, the owner isn't Brer Bear, or some other big fellow that Brer Fox doesn't care to have any words with. In the same way the digger-wasps make their own little burrows if they are obliged to, but prefer to help themselves to ones they find already made, although they don't drive anybody else out. They simply take possession of holes left by field-mice. The bumblebee does the same thing. The bumblebee digs a hole a foot or more deep, carpets it with leaves, and lines it with wax. Leading up to the home is a long, winding tunnel. As Bumblebeeville grows bigger there may be two or three hundred bees in one nest. As the bumblebee babies keep coming and coming, the burrow has to be dug bigger and bigger, to take care of them. III. THE HOUSE THAT MRS. MASON BUILT But the greatest of bee workers in the soil is the mason-bee. You can get an idea of what a useful citizen the mason-bee is when I tell you that one of the little villages of one species sometimes contains enough clay to make a good load for a team of oxen. Yet for all that, they might have gone on with their work for years and years to come--just as they have for ages in the past--and people wouldn't have thought much about it, if it hadn't been for some boys. One time, in a village in southern France, a school-teacher, who was getting on in years, took his small class of farmer boys outdoors to study surveying--setting up stakes and things, you know, the way George Washington used to do. It's a stony, barren land--this part of France--and the fields are covered with pebbles. The teacher noticed that often when he sent a boy to plant a stake, he would stoop every once in a while, pick up a pebble and _stick a straw into it_! That's what it looked like! Then he would suck the straw. Well, to make a long story short,[15] these pebbles had on them the little clay cells of the mason-bee. Mrs. Mason-Bee fills these cells with honey, lays an egg in the honey, and when the babies come along--don't you see? In other words, Mother Bee not only puts up their lunch for them, but puts them right into the lunch! This makes it convenient all around; for, like almost all insect mothers, Mrs. Mason-Bee is never there after the babies come. [15] The whole story is told in the famous book, "The Mason Bee," by Henri Fabre. He was the teacher. [Illustration: MASON-BEE CELLS AMONG THE ROCKS] There were so many of these pebbles scattered over the plain, and the bees that were building new homes or repairing old ones flew so straight and so fast between the pebbles and a near-by road that "they looked like trails of smoke," as Fabre expresses it. Now, you may well wonder why the bees flew clear over to that road to get dirt to build their nests when there was plenty of loose earth right at their own door-steps; right around the pebbles themselves. Isn't that queer? Well, here's something that sounds stranger still. Mrs. Mason-Bee takes those extra trips because a roadway is so much harder to dig in! It's not because she needs the exercise, goodness knows--this busy Mrs. Mason-Bee--but because the hard earth of the roadway makes the strongest homes; that is, when she finally gets it dug out and worked up. And here's another thing that will seem odd at first; although the soil she thus works over must be dampened before she can plaster it into the walls of her home, she just won't use damp soil to begin with. Nothing will do her but dust, and dust that she herself scrapes from the roadway. The reason of this is that the moisture already in the soil will not answer at all. She has got to knead the soil carefully and thoroughly with saliva, which acts as a kind of mortar. This saliva, of course, she supplies. And the dust she works with must be as fine as powder and as dry as a bone. Then it absorbs the saliva, and when it dries it is almost like stone. In fact it's a kind of cement, like that men use for sidewalks and for buildings and bridges. [Illustration: _Copyright by Brown Brothers._ FABRE STUDYING THE MASON-BEE] But this wonderful old teacher and his boys[16] found that even this isn't all this little house-builder and house-keeper has to think of. She must have dust that is really ground-up stone! So she digs in the roadway where the bits of stone in this stony soil have been ground to powder and then packed hard by the wheels of the farmer's cart and by the hoofs of horses and oxen drawing their heavy loads. But what did Mrs. M. B. do for ground-up stone in the long ages before man came along with his carts? Mr. Earl Reed, who, beside being the distinguished etcher of "The Dunes," is a close observer of nature in general, tells me he has often seen a mason-bee gathering the pulverized stone at the base of cliffs. Evidently the mills of the wind and rain, that we have read of in previous chapters, had Mrs. B's wants in mind too. [16] The boys were a great help. You ought to see what Fabre himself says about them in that famous book of his. BEING A MASON-BEE FOR A LITTLE WHILE Now, just to show you one more thing about Mrs. Mason-Bee as a house-builder--how clever she is--let's try something right here. Let's suppose ourselves--yourself and myself--Mrs. Mason-Bees. We have got a home to build for some baby mason-bees that will be along by and by. Say we already know that we must use this stone dust of the roadway, and that we must make our mortar not with _water_ but with _saliva_. Here's the _next_ problem: Shall the mixing be done where the building is going up over there? That's the way human masons do it. But Mrs. Mason-Bee evidently thinks otherwise, for at the very time she is prying up those atoms of dust with so much energy, you notice she is doing her mixing. She rolls and kneads her mortar until she has it in the shape of a ball as big as she can possibly carry. Then "buz-z-z-z!" Away she goes, straight as an arrow, back home, and the mortar is spread where it is needed. You see, after all, this is the best way. If she didn't turn the dust into mortar before she started, so a good-sized lump of it would stick together, she couldn't carry much of it at a time, and it would be forever and a day before she could get her house built. As it is, the pellets she carries are of the size of small shot; a pretty big load, let me tell you, for a little body no bigger than Mrs. Mason-Bee. And remember, this goes on all day long from sunrise to sunset. Without a moment's rest, she adds her pellets to the growing walls and then back she goes to the precise spot where she has found the building material that best suits her needs. In building a nest, the mason-bee, in going to and fro, day after day, travels, on the average, about 275 miles; half the distance across the widest part of France. All in about five or six weeks, she does this. Then her work is over. She retires to some quiet place under the stones, and dies. As I said, she never sees the babies she has done so much for. [Illustration: SURFACE MOUNDS OF THE MASON-ANT There are mason-ants as well as mason-bees. This illustration shows the works thrown up by some mason-ants that Dr. McCook found in a garden path one morning in May.] And although they are so stoutly built, the houses of the mason-bees, like those "cloud-capped towers and gorgeous palaces" that Shakespere speaks of, finally go back to the dust. But while one of these little mothers is building a new home or repairing an old one left by a mother of the previous year, you would suppose the fate of the world hung on it; as indeed the fate of the world of mason-bees does. Scrape! Scrape! Scrape! With the tips of those little jaws, her mandibles, she makes the stony dust. Rake! Rake! Rake! With her front feet she gathers and mixes it with the saliva from her mouth. How eager and excited she gets, how wrapped up in her work as she digs away in the hard-packed mass in the tracks of the roadway! Passing horses and oxen, and the French peasants with their wooden shoes, are almost on her before she will budge. And even then she only flits aside until the danger has passed. Then down she drops and at it again! But sometimes, the boys and the teacher found, she starts to move too late--so absorbed is she, it would seem, in the thought of that tiny little home over there among the pebbles. Poor little lady! HIDE AND SEEK IN THE LIBRARY Perhaps nothing in nature is more wonderful than an insect; particularly when you consider that he _is_ only an insect! So, of course, whole libraries have been written about insects. Here are a few of the most interesting books dealing with the subject: Beard's "Boy's Book of Bugs, Butterflies and Beetles"; Comstock's "Ways of the Six-Footed"; Crading's "Our Insect Friends and Foes"; Doubleday's "Nature's Garden"; Du Puy's "Trading Bugs with the Nations." This about trading bugs is an article in "Uncle Sam: Wonder Worker," and tells how Uncle Sam "swaps" with other nations to get rid of injurious insects and bring in useful ones. Grant Allen's "Sextons and Scavengers" ("Nature's Work Shop") tells many curious things about the sexton beetles; how, by tasting bad, they keep birds and things from eating them; why you will always find an even number--never an _odd_ number--of sextons at work together; what they use for spades in their digging; why male sextons bury their wives alive, and why there is reason to believe that these weird little insects have a sense of beauty and of music. The same essay tells about the sacred beetle of the Egyptians, the insect that we know as the "tumblebug"; why first the Egyptians and then the Greeks regarded this bug as sacred; and why men and women wear imitation beetles for brooches and watch-charms to-day. But the greatest work on this famous beetle has been written by the famous French observer Fabre, "The Homer of the Insect." You will find this book, "The Sacred Beetle," in any good public library. Among other things Fabre gives a very minute description of the variety of tools used by the beetle; tells how two beetles roll a ball;[17] how they dig their holes; how they "play possum," and then (I'm almost ashamed to tell this) rob their partners! How they wipe the dust out of their eyes; about a tumblebug's wheelbarrow; why their underground burrows sometimes have winding ways; why there are fewer beetles in hard times; about their autumn gaieties; their value as weather-prophets, and how Fabre's little son Paul helped him in writing his great book. [17] You've often noticed them, haven't you? Now read Fabre's wonderful book and see how much you _didn't_ notice. Allen's essay, "The Day of the Canker Worm" in "Nature's Work Shop," tells many interesting things about the Cicada, the locust that only comes once in seventeen years;[18] about Lady Locust's saw (it looks like a cut-out puzzle); about the clay galleries the locusts build when they come up out of the ground; how many times they have to put on new dresses before they finally look like locusts; why, at one stage of the process, they look like ghosts, and how they blow up their wings as you do a bicycle tire. [18] "And that's once too many," as the old farmer said; and we must agree with him when we think only of the damage they do. (Fabre's book on the sacred beetle also deals, incidentally, with the Cicada.) Often one thing is named after another from a merely fanciful resemblance, as, for instance, the "sea horse." But the mole cricket really seems to have been patterned on the mole; either that, or both the four-legged and the six-legged moles were patterned after something _else_. Mole crickets are very useful little people to know. You should see how they protect their nest-eggs from the weather and how and why they move their nests up and down with the change of the seasons. What good to the soil do the insects do that eat up dead-wood? Scott Elliott, in his "Romance of Plant Life," deals with this subject. The mining bees are very interesting, and some of these days, perhaps millions of years hence, they will be still more interesting, for they are learning to work together, although not to the extent that the bees and ants do. Working together seems to develop the brains of insects just as it does human beings. Thomson's "Biology of the Seasons" tells how the mining bees are learning "team-work." The tarantula spider is a relation of the six-footed farmers, you should know, although he is not an insect himself. In "Animal Arts and Crafts" in the "Romance of Science" series you will find how, in his digging, he makes little pellets of earth, wraps them up in silk, and then shoots them away, somewhat as a boy shoots a marble. The same book tells why the trap-door spider usually builds on a slope. It also tells why she puts on the front door soon after beginning her house. (This looks funny, but you wouldn't think it was so funny if _you_ were a trap-door spider and you had a certain party for a neighbor, as you will agree when you look it up.) The door, by the way, has a peculiar edge to make it fit tight. What kind of an edge would _you_ put on a door to make it fit tight? (Look at the stopper in the vinegar-cruet and see if it will give you an idea.) This book also tells about a certain wasp that makes pottery and gets her clay from the very same bank that certain other people depend on for _their_ potter's clay. This wasp sings at her work and has three different songs for different parts of the work. [Illustration: THE FIELD MOUSE AND THE FARMER When we remember how much soil the field mouse worked over, and so made better, long before man's time on earth--to say nothing of what the mice have done since--doesn't it give an added and deeper meaning to the lines of Burns? "I doubt na, whyles, but thou may thieve. What then? Poor beastie, thou maun live." ] CHAPTER VII (JULY) Well said, old mole! Canst work i' the earth so fast? --_Shakespere: "Hamlet."_ FARMERS WITH FOUR FEET Before we start this chapter--it's going to be about the farmers with four feet, you see--I want to say something, and that's this: _Don't let anybody tell you moles eat roots._ They don't! They eat the cutworms that do eat the roots. Haven't I been in mole runs often enough to know! Of course, the moles do cut a root here and there occasionally when it happens to be in the way, as they tunnel along, but what does that amount to? Why, in France they put Mr. Mole in vineyards--on purpose! He's one of the regular hands about the place, just like the hired man. I. MR. MOLE AND HIS RELATIONS Moles do a lot of good work for the farmer. Not only were they ploughing and ploughing and ploughing the soil--over and over again--thousands of centuries before man came along to plant seed in it, but they are all the time eating, among other things, destructive worms and insects in the soil. They work all over the world, that is to say, in the upper half of it--the Northern Hemisphere; and there's where the biggest half of the land is, if I haven't forgotten my geography. WONDERFUL LITTLE MACHINES ON FOUR LEGS Closely related to the moles are the shrews--quaint little mouse-like creatures with long, pointed heads and noses that they can twist about almost any way in hunting their meals and finding out other things in this big world that concern them. On these funny, long noses they have whiskers like a pussy-cat; and that helps, too, when you want to keep posted on what's going on around you. Like the moles the shrews are found all over the Northern Hemisphere. What is known as the "long-tailed shrew," is the very smallest of our relations among the mammalia. Why, they're no bigger than the end of a man's little finger; and the smallest watch _I_ ever heard of was a good deal bigger than that. Yet, inside these wee bodies is as much machinery as it takes to run any other mammal--an elephant, say. [Illustration: THE COMMON AND THE SHORT-TAILED SHREW] The shrews get around very fast, considering their size; and they're on the go all the time. I never saw such busy-bodies; nosing about in the old leaves and dead grass and under logs and boring into loose loam, punky wood, decayed stumps--anywhere you'd be likely to find a worm, a grub, a beetle, or a slug. Hard workers, these shrews, but _so_ quarrelsome! When two Mr. Shrews meet there's pretty sure to be trouble. They're regular little swashbucklers among themselves; and--the queerest thing, until you know why--they don't seem to be afraid even of cats. Fancy telling Cousin Mouse that! But it isn't because the shrews _wouldn't_ be afraid if the cats got after them, but because cats always let shrews alone. They don't taste good! [Illustration: THE CILIATED SHREW] Shrews are so nimble on their tiny feet and so quick of hearing, they are very hard to catch. And please don't try! You simply _can't_ tame them, and in spite of the fact they're so fierce and bold at home--among their own kind--they're easily frightened to death. A shock of fear and that wonderful little heart engine of theirs stops short--never to go again. MR. MOLE'S PAWS AND HOW HE WORKS THEM But while the shrews can get around so much faster above ground the moles are the most remarkable travellers _under_ ground. The mole's paws, you notice, are turned outward, as one's hands are when swimming. In fact he does almost swim through the soft, loose soil--so fast does he move along! His two shovels, with the muscles that work them, weigh as much as all the rest of his body. Why, he has a chest like an athlete! He pierces the soil with his muzzle and then clears it away with his paws. His skull is shaped like a wedge. He has a strong, boring snout and a smooth, round body. This snout, by the way, has a bone near the tip. You see how handy that would come in, don't you? At the same time, although it's so hard--this snout of his--it's very sensitive, like the fingers of the blind; for Mr. Mole must always be feeling his way along in the dark, you know. [Illustration: SECTION OF MR. MOLE'S CASTLE This is a cross-section of a mole-hill, showing the central chamber and the rooms leading into it.] The kind of moles you find in Europe live in what seem to be little earthen fortresses, and the tops, sticking above ground, make hillocks. In each of these little forts there is a central chamber; then outside of this, running all the way around, are two galleries, one above the other. The upper gallery has several openings into the central chamber. The galleries are connected by two straight up-and-down shafts. From the lower galleries several passages, usually from eight to ten, lead away to where the moles go out to feed; and if there is a body of water near by--a pond or a creek, say--there's a special tunnel leading to that. Mr. Mole works hard and he sleeps hard. The big middle room in his home is the bedchamber of Mr. Mole and his family. Usually he sleeps soundly all night, but occasionally, on fine Summer nights, he comes out and enjoys the air. [Illustration: THE COMMON AND THE STAR-NOSED MOLE] You'd think he'd get awfully dirty, wouldn't you, boring his way along in the ground all the time? But he doesn't. His hair is always as spick and span as if he'd just come out of the barber-shop. Do you know why? It's because he wears his hair pompadoured. It grows straight out from the skin. So you see he can go backward and forward--as he is obliged to do constantly in the day's work--without mussing it up at all. If it lay down, like yours or like pussy-cat's, it would get into an _awful_ mess! In France the children call Mr. Mole "The Little Gentleman in the Velvet Coat." II. FOUR-FOOTED FARMERS THAT WEAR ARMOR But, speaking of coats, I want to introduce you to a still more rapid worker in the soil, who wears a coat of mail. He is called the armadillo. There used to be a species of armadillo in western Texas. Whether there are any there still I don't know,[19] but go on down to South America and you'll find all you want. The woods are full of them, and so are those vast prairies--the pampas. The plates in the armadillo's coat of mail are not made of steel, of course, but of bone. These bony plates are each separate from the other on most of his body but made into solid bucklers over the shoulders and the hips. The armadillos have very short, stout legs and very long, strong claws, and how they can dig! They can dig fast in any kind of soil, but in the loose soil of the pampas they dig so fast that if you happen to catch sight of one when out riding and he sees _you_, you'll have to start toward him with your horse on the run if you want to see anything more of him. Before you can get to him and throw yourself from the saddle, he'll have buried himself in the ground. And you can't catch him; not even if you have a spade and dig away with all your might. He'll dig ahead of you, faster--a good deal faster--than you can follow. [19] One of my friends in the faculty of the University of Chicago tells me there are still a good many armadillos in Texas. MR. ARMADILLO'S REMARKABLE NOSE DRILL For all he looks so knightly, so far as his armor is concerned, the armadillo is timid, peaceful, and never looking for trouble with anybody, but once aroused fights fiercely and does much damage with his long hooked claws. His chief diet is ants. These he finds with his nose. He locates them by scent and then bores in after them. You'd think he'd twist it off, that long nose of his; he turns it first one way and then the other, like a gimlet. And so fast! The armadillo dislikes snakes as much as all true knights disliked dragons. That is, he doesn't like them socially; although he's quite fond of them as a variation in diet. He'll leap on a snake, paying not the slightest attention to his attempts to bite through that coat of mail, and tear him into bits and eat him. Another armored knight that eats snakes and that other animals seldom eat--much as they'd like to--is the hedgehog. If you were a fox, instead of a boy or girl, I wouldn't have to tell you about how hard it is to serve hedgehog at the family table. One of the earliest things a little fox learns in countries where there are hedgehogs is to let the hedgehog alone. "Hedgehogs would be very nice--to eat, I mean--if they weren't so ugly about not wanting to be eaten." We can imagine Mamma Fox saying that to the children. Then she goes on: "The whole ten inches of a hedgehog--he's about that long--are covered with short, stiff, sharp, gray spines. He's easy to catch--just ambles along, hardly lifting his short legs from the ground. And he goes about at night--just when we foxes are out marketing. That would be so handy, don't you see; but the trouble is about those nasty spines of his. Try to catch him and he rolls up into a ball with all his spines--they're sharp as needles--sticking out everywhere, and every which way. And--well, you simply can't get at him, that's all. So just don't have anything to do with him. It's only a waste of time." Hedgehogs live in hedges and thickets and in narrow gulches covered with bushes. They do their share of ploughing when nosing about with their pig-like snouts for slugs, snails, and insects, and when they dig places for their home nests. These homes they line with moss, grass, and leaves, and in them spend the long Winter, indifferent to the tempests and the cold. But there's another place to look for hedgehogs, and you never would guess! In people's kitchens. If you ever go to England you'll find them in many country homes, helping with the work. They're great on cockroaches, and they're perfectly safe from the cat and the dog. Both Puss and Towser know all about those spines, just as well as Mrs. Fox does. When they've eaten all the cockroaches, give them some cooked vegetables, porridge, or bread and milk, and they'll be perfectly content. They're easy to tame and get very friendly. In the wild state, besides the insects and things I mentioned, they eat snakes; and poison snakes, too! The poison never seems to bother them at all. Their table manners are interesting, also, when it comes to eating snakes. They always begin at the tail.[20] They'd no more think of eating a snake any other way than one would of picking up the wrong fork at a formal dinner. [20] Isn't that the way a toad swallows an angleworm? Or how _does_ he do it? UNDER THE HEDGEHOG'S WATER-PROOF ROOF That's one of the things about good manners Mamma Hedgehog teaches the babies, I suppose. Of these she has from two to four, and she makes a curious nest especially for them; a nest with a roof on it that sheds rain like any other roof. Just as it is with puppies and kittens, the babies are born blind; and not only that, but they can't hear at first, either. While they are young their spines--I don't mean their back-bones, but their other spines--are soft, but they become hard as the babies grow and open their eyes and ears on the world. The muscles on their backs get very thick and strong, so that when they don't want to have anything to do with anybody--say a fox, or a dog, or a weasel--they just pull the proper muscle strings and tie themselves up into a kind of bag made of their own needle-cushion skins, with the needles all sticking out, point up! III. A VISIT TO SOME FARM VILLAGES TWELVE LITTLE MARMOTS ALL IN ONE BED Next I'd like you to visit with me certain other farmers who remind us of the Middle Ages also; not because they wear armor, like the armadillos and the hedgehogs and the lords of castles, but because they live in farm villages as the farmer peasants used to do around the castles of the lords. Moreover, one reason they live together in this way is for protection--just as it was with the peasants--only among these little democrats there's no overlord business; each one's home is his castle. Another reason for this village arrangement is that it's such a sociable way to live; and they're great society people, these farm villagers. The marmots, for example, the largest and heaviest of the squirrel family, just love company. In their mountain country--they're mountain people, the marmots--they play together, work together, and during the long, cold night of Winter snuggle together in their burrows. Their burrows are close by each other among the rocks. They have both Summer and Winter residences. In Summer they go away up in the mountains, hollow out their burrows and raise their babies. When the snows of late Autumn send them down the mountainsides, twelve or fifteen of them, all working together, pitch in and make a tunnel in the soil among the rocks, enlarging it at the end into a big room. Next they put in a good pile of dry hay, carefully close the front door and lock it up with stones caulked with grass and moss. Then they all cuddle down together, as snug as you please, and stay there until Spring. [Illustration: HIGHWAYS OF GROUND-SQUIRREL TOWN Almost as crooked as the streets of London town, aren't they? And as hard to find one's way about in--unless, of course, one were a ground-squirrel. This is the burrow of a Richardson ground-squirrel sketched by Thompson Seton, near Whitewater, Manitoba.] Another member of the marmot family who is very fond of good company is the prairie-dog. There may be thousands in a prairie-dog town. Each little prairie-dog home has in front of it a mound something like an Eskimo's hut. The prairie-dogs make these mounds in digging out their burrows. They pile the dirt right at the front door. This may not look neat to us, but you'll see it's just the thing--this dirt pile--when you know what the prairie-dog does with it. He uses it as a watch-tower. When, from this watch-tower, he spies certain people he doesn't want to meet, you ought to see how quickly he can make for his front door and into the house! The times are still lawless where the prairie-dog lives, and he has to be on the lookout all the while for coyotes, for foxes, for badgers, for the black-footed ferret and the old gray wolf; to say nothing of hawks and brown owls. SUCH NEAT CHAMBERMAIDS! The prairie-dogs like sandy or gravelly soil for their homes, and in making them they do a lot of ploughing. And besides they supply this same soil with a great deal of humus--the grass that they use for bedding. They're very particular about changing their beds every day; always clearing out the old bedding and putting in new. They do this along about sundown. You can see them do it right in New York City, for there is a flourishing colony of them at the zoo. [Illustration: THIS MUST BE A PLEASANT DAY In nice weather the Prairie Dog's front door stands wide open like this, but before a rain he stuffs it tight with grass because, when it _does_ rain in the arid regions where he lives, it comes down in bucketfuls!] Mr. Prairie-Dog is about a foot long and as fat as butter. The reason he's called a dog isn't because he is a dog or even looks like one, but because he has a sharp little bark like a very much excited puppy. He thinks he sees something suspicious: "Yap! Yap!" Or he spies a neighbor down the street: "Yap! Yap! Hello, neighbor! Looks like another fine day, doesn't it?" "Yap! Yap!" says neighbor. (This "yap" passes for "yes," no doubt--although it isn't quite the way Mr. Webster would say it, perhaps.) Then maybe a neighbor from away over on the avenue, that he hasn't seen for some time, comes calling--as they're always doing, these neighborly little chaps. Then it's: "Yap! Yap! Yap! Yap! Why, how _are_ you? And what have you been doing? And how are the little folks?" And so it goes, all day long. The prairie-dog's native home is on our Western plains, but he has a cousin away off in South America--although he may never have heard of him--called the viscacha. The viscachas live on the great grassy plains of the La Plata in colonies of twenty or more, in villages of deep-chambered burrows with large pit-like entrances grouped close together; so close, in fact, that the whole village makes one large irregular mound, thirty to forty feet in diameter and two to three feet high. These villages being on the level prairie, the viscachas are careful to build them high enough so that floods will not reach them. They make a clear space all around the town. In doing this these little people seem to have two purposes: (1) To make it more difficult for enemies to slip up on them unnoticed, and (2) to furnish a kind of athletic field for the community; for it is in these open spaces that they have their foot-races, wrestling matches, and the like. If you ever happen down their way, the first thing that will strike you is the enormous size of the entrances to the central burrows. You'd think somebody as big as a bear lived in them. The entrance is four to six feet across and deep enough for a tall man to stand in up to the waist. Like our prairie-dogs, the viscachas are very sociable, and little paths, the result of neighborly calls, lead from one village to another. They are neighborly indeed; and in the Bible sense. Of course, they like to get together of an evening and talk things over and gossip and all that, but that isn't the end of it. To take an instance: These South American prairie-dogs, like our prairie-dogs up North, are not popular with the cattlemen; and the cattlemen, to get rid of them, bury whole villages with earth. Then neighbors from distant burrows come--just as soon as the cattlemen go away--and dig them out! [Illustration: MR. P. GOPHER AS THE MASTER PLOUGHMAN Thompson Seton calls the pocket-gopher "the master ploughman of the West," and this is how he illustrates the extent of his labors.] Another ploughman besides the prairie-dog and the viscacha, who isn't popular with farmers--although Thompson Seton calls him "The Master Ploughman of the West"--is the pocket-gopher. He has farmed it from Canada to Texas, all through the fertile Mississippi Valley. The reason he has that queer expression on his face--you couldn't help noticing it--is that each cheek has a big outside pocket in it; and, like the big pockets in a small boy's trousers, they're there for business. On each forefoot he has a set of long claws; and dig, you should see him! He's a regular little steam-shovel. He sinks his burrow below the frost-line and into this, stuffed in his two pockets, he carries food to eat when he wakes up during the following Spring, before earth's harvests are ripe. [Illustration: POCKETS OF THE POCKET-MOUSE] IV. THE HOME OF THE RED FOX Another country gentleman, not as popular with his neighbors, I must say, as he might be, but whose people, in the course of the ages, have done a good deal of ploughing, is Brer Fox. I mean particularly the red fox, for the gray fox usually lives in hollow trees or in ready-made houses among the rocks of the mountainside. THE THREE ROOMS IN THE FOX HOUSE The red fox is the cunningest of his tribe. One of the ways he shows his cunning--and also his lack of conscience, in dealings outside the fox family--is in his way of getting a home. Whenever he can find a burrow of a badger, for example, he drives the badger out and then enlarges the place to suit his own needs. For Mr. Fox's residence is quite an affair. Usually it has three rooms; the front room where either Mr. or Mrs. Fox--depending on which is going marketing--stops and looks about to see if the coast is clear; back of that the storeroom for food, and behind this the family bedroom and nursery. Mr. and Mrs. Fox are among the thriftiest folks I know. They not only provide for to-day, but for to-morrow and the day after. For example, when Mr. Fox visits a poultry-yard, he doesn't simply carry off enough for one meal. He keeps catching and carrying off chickens, ducks, or geese--whatever comes handy--all night; working clear up to daybreak. And the fresh meat he thus gets for the family table he buries--each fowl in a separate place--not so very far away from the poultry-yard. Then later he comes and gets this buried treasure and takes it home to be shared with mother and the babies. Of these babies there are from three to five. Young foxes are very playful and think there's no such sport as chasing each other about in the sunshine, while mother sits in the doorway keeping an eye out for possible danger and watching their antics with a complacent smile, as much as to say: "_Aren't_ they the little dears!" If just one little fox wants to play while his brothers and sisters want to sleep--and that sometimes happens--he goes off by himself and chases his own tail around, just like a kitten. Little foxes are very nice and polite that way. [Illustration: THE KANGAROO RAT AND THE POCKET-MOUSE The kangaroo rat and the pocket-mouse live in the arid regions of the United States. Both have pockets in their cheeks, but the mouse is named for his pockets and the rat for his long kangaroo hind legs.] V. WORK AND PLAY IN CHIPMUNKVILLE It isn't often one gets a chance to see little foxes at play, except occasionally in the big city zoos, for foxes are now so scarce; and, besides, their papas and mammas in the wild state are suspicious of human spectators, but there are certain nimble four-legged babies to be found all over the country that play in much the same way. If, along in July, you should see a certain little body in a lovely striped suit chasing another little body in a striped suit, exactly like it, along the old rail fence or over the boulder wall or across the meadow, ten to one, it will be two baby chipmunks playing tag. When one bites the other's tail--they're always trying to do that in these tag games--it means he's "it," I think. In fact, I'm quite sure, for always, when one little Mr. Chipmunk bites another little Mr. Chipmunk on the tail, little Mr. Chipmunk No. 2 turns right around and chases little Mr. Chipmunk No. 1, and tries to bite _his_ tail. They keep this up on sunshiny days all through July and along into early August. Then the serious business of life begins. They sober down, these chipmunk children--they were only born last May--and learn to make homes for themselves. You never would think the way they love the sunshine that the homes of all the chipmunks are under the ground, and as dark as can be. But they are. You notice the chipmunks have rather large feet, considering what dainty little creatures they are. These feet, like the feet of the mole, are for digging. The chipmunk digs deep under the roots of trees and stone walls, if there happens to be either handy by, but, so far as I've seen, he's quite contented to make his burrows in the open meadows. The round nest at the end of the burrow is lined with fine grass. It has two entrances, one right opposite the other, like front and back doors. Sometimes there are as many as three doors; four, maybe, in case of a chipmunk of a particularly nervous disposition. All chipmunks are easily frightened and dive into their holes, quick as a wink, when there's any danger; and often when there's really nothing to be scared at at all. WHEN THOSE EXTRA DOORS COME HANDY But you can't blame them. There are times when it's no fun being a chipmunk, I tell you. The hawks get after you, and the minks and the foxes and the weasels. Those extra doors into the nest are very useful places to dodge into when you're outside and a savage old hawk swoops down on you, or a fox makes a jump at you. And they're just as handy--these extra doors--to run _out_ of when a mink or a weasel follows you in. They'll do that, if you're a chipmunk; chase you right into your own house! When a pair of grown-up chipmunks start housekeeping for themselves--that is to say when they are about ten weeks old--they first dig a little tunnel, almost straight down for several feet. Then they make a hall that runs along horizontally--like anybody's hall--for a few yards. Then, supposing you're Mr. or Mrs. Chipmunk in your new place, after it's all done--you go up a slant--a flight of stairs, you might say, although, of course, there aren't any stairs--and there you are in the family bedroom, the nest. Not long after the chipmunks stop their outdoor games in the Fall you might think it was because they had the mumps; they go around with their faces all swelled out in such a funny way. The reason is they have their cheeks full of nuts and seeds that they are storing for the Winter. They don't put these stores in the nest--for then where would they sleep, the nest is so small--but in special cellars that they build near the nest, with connecting passages. These cellars, like the nests, are well below frost-line, so that Jack can't get the nuts or nip the noses of the chipmunks while they are asleep. [Illustration: PICTURESQUE HOME OF A CONNECTICUT WOODCHUCK This is the truly artistic residence of a Connecticut woodchuck which I found in a rocky knoll by the wayside during a summer vacation at Kent and reproduced as well as I could with my fountain-pen. Mr. W. as he often does in digging his burrows, had availed himself of the protection of the roots of a tree. Here there were two projecting roots, forming a curious arch over the doorway, which was tastily decorated by a little overhanging vine, on its way up the knoll, along the stones, and up the foot of the tree.] When Winter finally sets in, the chipmunks get very drowsy and go up to bed. And there they stay until Spring--one great long nap, except that they wake up and stir around occasionally on bright days and if it happens to warm up a little. "Such sleepyheads!" you say. "And what about all those nuts? I should think they'd be fine for Winter parties." They would, I dare say. But you know a body doesn't have much of an appetite when he doesn't get any outdoor exercise, and that's why the chipmunks only take a few bites now and then, during the Winter. And, besides, if they ate up everything in the Winter--you know how folks eat at parties--what would they do in the Spring, with no good nuts lying around on the ground, as there are in the Fall; and nothing else to be had that chipmunks care about? So they keep most of the nuts and seeds and things for the great Spring breakfast, and all the other meals, until berries are ripe. The berries they eat until the next nut harvest comes along. Until then, you see, they haven't much of anything to do but play around and sit in the sun and chat. So why shouldn't they? HIDE AND SEEK IN THE LIBRARY You will find some most readable things about foxes in Burrough's "Squirrels and Other Fur Bearers"; Comstock's "Pet Book"; Cram's "Little Beasts of Field and Wood"; Wright's "Four-Footed Americans"; Jordan's "Five Tales of Birds and Beasts"; Long's "Ways of Wood Folk"; and Seton's "Wild Animals I Have Known." Comstock's "Pet Book" also tells about the prairie-dog; and Seton, in his "Wild Animals I Have Known," tells about "The Prairie Dog and His Kin." It's a very common superstition among English country folk that shrews always drop dead if they attempt to cross a road. How do you suppose such a strange idea ever got started? Allen, in his "Nature's Work Shop," reasons it out, and his reasons seem very plausible. It's a fact that their dead bodies are nearly always found in roadways. You'll also find some interesting information about shrews in Johonnott's "Curious Flyers, Creepers and Swimmers" and Wright's "Four-Footed Americans." There's some little dispute about squirrels as tree-planters; that is to say as to just how they do it, for there's no question that they _do_ plant oaks and other trees. Thoreau, in his "Walden," gives the squirrel credit for doing an immense amount of tree-planting, but Ernest Ingersoll, in his article on squirrels in "Wild Neighbors," thinks the squirrel leaves comparatively few acorns or hickory-nuts, and that he doesn't forget where he puts them, as other writers on nature say. "They seem to know precisely the spot," says Mr. Ingersoll, "where each nut is buried, and go directly to it; and I have seen them hundreds of times when the snow was more than a foot deep, wade floundering through it straight to a certain point, dive down, perhaps far out of sight, and in a moment emerge with a nut in their jaws." But _how_ the squirrel knows it's there--that's the mystery! Read what Ingersoll says about it. The whole essay is extremely good reading, and will tell you a number of things to watch out for in squirrels that you perhaps never have noticed. In Pliny's "Natural History" you will find, among other quaint stories, one to the effect that mountain marmots put away hay in the fall by one animal using itself as a hay-rack--lying on his back with his load clasped close while he is pulled home by the tail. "Animal Arts and Crafts" tells what a simple little thing originated this idea. Many of the peasants of the Alps still believe it. Hornaday, in his "Two Years in the Jungle," gives an interesting account of how one of the four-footed knights in armor--the pangolin--does himself up in a ball, and how next to impossible it is to "unlock" him. Ingersoll, in discussing the various uses of tails in "Wild Neighbors," tells how a gerboa kangaroo brings home grass for his nest, done up in a sheaf of which his own little tail is the binder. An interesting four-footed burrower, when he can't rob a prairie-dog of his hole--or some other body smaller than himself--is the coyote. There is a long talk on the coyote and his ways in "Wild Neighbors." This little book also gives pictures of the different kinds of shrews in the United States, and a lot of detail about them and their little paws and their noses and their tails. It's a queer thing how systematic and prompt shrews and moles are in business. You can actually set your watch by them, as you will see in the same book. In the article on the gopher in the "Americana" you will find how the gopher got his name. Can you guess, when I tell you it's from a French word meaning "honeycomb"? CHAPTER VIII (AUGUST) 'Till he came unto a streamlet In the middle of the forest To a streamlet still and tranquil That had overflowed its margin, To a dam made by the beavers, To a pond of quiet water, Where knee-deep the trees were standing, Where the water-lilies floated, Where the rushes waved and whispered. --_Longfellow: "Hiawatha."_ WATER FARMERS WHO HELP MAKE LAND As we all spend more or less time in the water in August I thought it would be a good idea to take as the subject of this chapter the lives of the water farmers. Some of these--the crayfish and the turtle, for example--you know well, and everybody has heard of the beaver family, but they will all bear closer acquaintance. I know, for I've spent a good deal of time among them. I. THE TURTLE PEOPLE Every boy who has tramped along creeks and ponds knows the mud-turtle. We ought to call him a tortoise, perhaps, but the name turtle is more common. I don't know why; perhaps because it's a little easier to say. Strictly speaking, the name "turtle" is applied to the members of the family that have flippers, and spend nearly all their time in the water; while the tortoises are the ones that have feet and put in much of their time on land. (And then, of course, there are the tortoises of fables that run races with hares, and so teach us not to be too confident of ourselves because we think we are cleverer than some other people.) [Illustration: A HAWKSBILL TURTLE] The common box-turtle of the United States you'll meet in the woods in the evening and early morning, wandering about looking for something to eat. He spends practically all his time on land in Summer; and in the Winter, all his time in bed. As soon as cold weather comes on he digs a hole in the ground, or scoops out a place under some brush, and turns in. But the box-turtle--he's really a tortoise--is what some of his relatives would call a "landlubber," no doubt, for many of the tortoises who live in the sea rarely leave it; as if they had half a mind to go back and be only flipper people, as the ancestors of both the turtles and the tortoises must have been; since all life is supposed to have begun in the sea. All the tortoises of temperate regions dig in for the Winter, but one Southern member of the family makes his home in a dugout throughout the year. He's called the "gopher" turtle. The gopher turtles are natives of Florida, and live in pairs in burrows. Other members of the turtle tribe do not pair, but there's one time in their lives when both land and water turtles dig into the soil and that's when they are laying their eggs. The females scoop out hollows with their hind legs, kicking up the dirt, first with one leg and then with the other. But they're as careful of the dirt they dig out as a beaver is when he digs a canal. They scrape it up in a little ridge all around the hole. What for? Just watch. HOW MOTHER TURTLE "TAMPS" HER NEST As soon as she has finished laying her eggs, Mother Turtle carefully scrapes this dirt back over them and tamps it down, much as a foundryman tamps the sand in a mould. You can guess what she uses for a tamper--the under side of her shell, raising and lowering herself on her legs like a Boy Scout taking his morning setting-up exercises in a Summer camp. After that she doesn't pay any more attention to her eggs. She leaves the sun to do her hatching for her. Both land and sea turtles--or, more properly speaking, the tortoises and the turtles--hatch their young in this way. The sea-turtles scramble up out of the water on their flippers, much as a seal does in climbing on a rock, and make their way back from the shore, great crowds of them, at nesting-time, to some stretch of sand, and there lay their eggs. This march of the mother turtles always takes place at night. When the young are hatched they dig their way up through the sand and make for the sea. II. THE CRAB FAMILY Another one of the water people who help make land and one that everybody knows, is the crayfish. Every small boy is afraid Mr. Crayfish will catch his little big toe sooner or later, when he goes swimming; although I never heard of a crayfish that did. But they never worry about _their_ toes--the crayfish don't. When they lose a whole foot even--as they often do--it grows right out again. The science people say this is because they belong to a low order in the animal world, but I think it would come in right handy for any of us--this way of regrowing not toe-nails alone, but toes and all--don't you? The crayfish, as you may know, love to burrow in the mud, for you are always coming across their little mud towers along the margins of the brooks. Related to the crayfish are the crabs. Mother Nature seems to have been very fond of crabs--she has made them after so many different patterns and scattered them all over the world; in the deep sea, along the shallows of its shores, and on land. Those you are most apt to meet must have more or less business on land, for the shape of their legs shows that they are formed for walking rather than swimming. But go far out to sea and you'll find crabs with paddles on all four pairs of legs, like banks of oars; while others, living on the borders of the sea, have paddles only on the last pair. [Illustration: SOUTH SEA ISLAND AND COCOANUT COLUMBUS Here we are on an island of the Southern Seas--the home of a colony of cocoanut crabs. One of the members of the colony is climbing a tree to get a nut. "And who has a better right?" says he. "This tree," he might continue, "is the descendant of a nut that some of my ancestors sailed upon to this island; for a cocoanut, dropping into the water from a tree near some far shore, often carries on it the crab who had started to eat it. Then a current of the sea carries the nut and its passenger to some other island. Later cocoanut Santa Marias and their Columbuses reach the island in the same way, and so it becomes populated with both cocoanuts and crabs--which makes it very nice for the crabs!"] One of the big families of crabs live on land most of the time and make burrows in which they live. These have legs specially fitted for digging. Like most of the crab family, the land-crab earns its living at night and, except in rainy weather, seldom leaves its burrow by day. Like small boys, these crabs seem to love to play in the rain. The fact is they do this to keep their gills wet; for, although they spend most of their time on land, crabs breathe with their gills, like fish; and while some of them--as the mountain crab of the West Indies--live quite a distance back from the sea, they must have some moisture for their gills, and this they get, in part, in their damp cellars--the burrows. But it's queer, isn't it, what different ways people have of looking at things? Take land crabs and turtles, for example. Turtles, when they lay their eggs, think the only thing is to get clear away from the water and put their eggs in an incubator, as we saw them do a few pages back. The land-crabs evidently think just the opposite; for no matter how far they may live away from the sea--one, two, even three miles sometimes--nothing will do but they must go to the water to lay their eggs. In April and May you'll see them swarming down by hundreds and thousands. And they'll climb right over you if you don't get out of their way! "This is my busy day and I can't stop for anything," says Mrs. Crab. Besides the work they do for the soil in grinding and mixing it, the crab people, like all the crustaceans, help a lot by adding lime to it, and that's one of the very best things you can do to soil, you know. They add this lime when they change their clothes; that is, when they moult or cast their shells. The shell they take off as if it were indeed a dress. They "unbutton" it down the back. Sometimes, in trying to get out of the legs of the suit, they leave not only the leg covering but the leg itself. That leg is good for the soil, too, of course, and the loss of a leg doesn't bother a crab so very much. He just grows a new one, that's all! These shells--particularly the shells of the largest species of crabs--not only contain a great deal of lime but carbon and phosphorus, also, and these are splendid soil stuff, too. In the smaller kinds of crabs--of crustaceans, generally--these shells are mostly chitin, the stuff that the coverings of insects is made of. The crustaceans, by the way, are closely related to the insects. You may _suspect_ this by comparing their shapes, but then you'll see there isn't any doubt about it when I tell you that in getting born from the egg, the crabs and their kin don't come out dressed in their final shape, but change after they are born, first into one shape and then into another, just as insects do. Each shape, as it comes along, looks funnier than the rest; that is, it looks funny to us, but not, naturally, to the crabs. It must seem just the thing to them, for they always dress the same way and look as solemn about it as a man does when he wears a monocle. In fact, they do something almost as funny as wearing a monocle. For many of them carry their eyes about, not on the end of a cord, to be sure, but on the end of a stick. These "sticks" are called foot stalks. And they're not a bad idea either--for a crab. By moving them around the crabs can keep much better posted on what is going on about them than they could otherwise; particularly as a crab always moves sidewise or backward. What good a monocle does, though, nobody knows. III. THE STRANGER THAT MADE LONDON LAUGH But if we can hardly look a crab in the eye and keep a straight face, what would we do if we met a duck-billed mole? We'd laugh right out! I'm sure of it, for that's what even the men of science did when they saw the first one that came to England. This strange foreigner--it came to London all the way from Australia--had a body like a mole. But you couldn't call it a mole. For one thing, it had a bill like a duck. Yet no more could you call it a duck; for, besides having a body like a mole, it had a tail like a beaver. Still I'm afraid the beavers wouldn't have owned it--hospitable as they are--even if they could have overlooked that bill. For--can you believe it?--this duck-billed, mole-bodied, beaver-tailed creature lays eggs! [Illustration: THE ANIMAL X FROM THE ANTIPODES A mole's body, a duck's bill, a beaver's tail, this strange citizen of that land of strange animals, Australia, lays eggs like a bird and suckles its young like a pussy-cat! Do you wonder that the wise men of London laughed at the idea that there is any such creature--even when they were looking right at one?] Yet the ducks just couldn't take it into their families either, for what else do you think it does? It suckles its young, like a pussy-cat! Talk about your sensations; it made the hit of the season--this Animal X from the Antipodes. The learned men of London town, they looked him up and they looked him down, and they came to the same conclusion, at first, that the old gentleman did when he saw the dromedary. They said: "They _ain't_ no such animal!" (Only, of course, being learned men, they used good grammar.) They really did say that in effect, and you can't blame them; for, as if to complete the joke, the first member of the duck-billed mole family to move in scientific society came in like a Christmas turkey; in other words, he was a stuffed specimen. So the men of science said he wasn't _real_ at all; that he was just made up of the parts of _other_ animals. But being true men of science, after all, they finally began looking up the stranger's record among his neighbors back in Australia, and they found there actually are living creatures in that land of strange creatures, just like that specimen, and that they live in burrows which they dig in the banks of the streams. [Illustration: COUSIN ECHIDNA The echidna--you can see one in the New York Zoo--is closely related to our duck-billed friend and is also a native of Australia. It uses that long, tapering nose and those claws to burrow for the ants on which it lives.] Still the scientists didn't know what to call this paradox of the animal kingdom; so they named him just that--paradoxicus, _Ornythoryncus paradoxicus_. A little Greek boy, without having to look it up in a dictionary, would have told us that "ornythoryncus" means "bird-billed"; for it's like those Greek picture words that always told their own story to the little Greeks. As for "paradox" if you don't know what that means, look it up in the dictionary and then look at the _Ornythoryncus paradoxicus_, and you'll understand. IV. THE BEAVERS Of course you wouldn't like to be a duck-billed mole--nobody would, but I always thought it would be rather nice to be a beaver. The beaver is, in many ways, the most remarkable of all the water people that help make the lands that give us bread. [Illustration: BEAVERS AT WORK AND AT PLAY Whether he's working because he is more industrious than those beavers in the water or because it's recess time with them, the young beaver gnawing the tree seems to be having quite as good a time practising his profession as the others do in playing about.] But it is not alone for the amount of work he does that I admire Mr. Beaver so much; it is for his intelligent, not to say brilliant, way of doing it. Suppose, for instance, you had to build a house out in the water, the way our great, great-grandparents, the lake-dwellers, did, to protect yourself from enemies and for other reasons. And then suppose you didn't have any _tools_; nothing but a pair of paws and a set of teeth. Could you do it? Another thing: The lake-dwellers had plenty of water to build in; plenty, but not too much. The beavers don't have this advantage. They usually build in the water of flowing streams, and they have to make their _own_ lakes. How would you do it; even if you had tools? But remember, being a beaver, you've got nothing to use but two honest paws and a set of teeth. It was with these Mr. Beaver did it all--with his teeth, his paws, and his head; the inside of his head, I mean--his brain. Take the matter of water arrangements. He gets the water to lie quietly and at just the right depth by building his dam across the stream. This dam not only provides him with water of just the right depth to protect his front door from enemies and to keep rushing torrents from carrying his house away, but the spreading out of the original stream bed into a pond helps in gathering the Fall harvest of trees, since it brings the trees nearer to the water's edge, and water transportation among beavers, as among men, is always cheapest. Although dams are usually built of trees which the beavers cut down themselves, they also use cobblestones where trees are scarce; for Mr. Beaver is a very thrifty soul; he doesn't waste material nor time nor effort. Many books about beavers say they cut the trees so they will fall across the stream, but Mills says, in his book on the beaver, written after many years of patient observation, that beavers don't seem to care how the tree falls, just so it doesn't fall on _them_! Not but what they _could_ cut trees to fall in the water if they thought best; for just watch them build a dam and see how clever they are; cleverer, possibly, than some of us. [Illustration: BEAVERS AT WORK ON A DAM See how many of the features of the building of a beaver dam, as described in our story of these wise little people, you can make out in this picture.] Let's see. Say you've got your trees up to where the dam is to be; now how are you going to set them in building the dam? SEE IF YOU'RE AS CLEVER AS MR. BEAVER "Right across the dam," you would say, wouldn't you? That is what most people have said when I have asked them that question; for that is the way men do it. But remember, if you built the dam as men build dams you would have to drive stakes or do something to keep the logs from washing away. Years ago, when writers used to theorize a great deal on how things were done, instead of getting outdoors and watching patiently to see how they actually _were_ done, it was said that Mr. Beaver in building his dam did really drive stakes and that he did it with that big tail of his. But what Mr. Mills found was that the beaver lays his trees lengthwise of the stream. You see why that is, don't you? When the trees are laid lengthwise, the water, instead of striking them broadside, strikes only the end and so there is less likelihood of their being carried away. Another thing, two things, about the trees in the dam--in fact four: 1. It wouldn't do, you see, to lay the trees broadside to the stream, but what position could we give them that would help still further in keeping the water from carrying them away? 2. Shall we use trees with the branches still on them or trees trimmed down like sticks of cord-wood? (What kind do you see in the picture of the beaver dam?) 3. Or shall we use both trimmed and untrimmed trees? If so, why? And how? 4. If we use untrimmed trees, which end shall we put up-stream? The butt or the tip? [Illustration: SECTION OF A BEAVER DAM You can see that there was a sufficient flow of water in the stream from which this sketch of a section of a beaver dam was taken; otherwise the dam would have been plastered with mud to conserve the supply. The longest slope, of course, was up-stream--a fundamental principle in beaver bridge engineering.] In building his dam the beaver uses, for the most part, slender green poles trimmed and cut in lengths; but mixed with these are small untrimmed trees which he places with the butt end up-stream, and propped with mud and sticks so that the up end will be a foot or so higher than the down end. In this way, you see, the branches are made to resist the push of the waters against the butt end; while, if they were placed the other way, the current would have a pulling purchase on the butt end. The raising of the ends also lessens the pushing force of the water as it doesn't strike the butt of the tree "full on," as it would otherwise do. And the branches not only help to hold the trees in place, but, together, form a kind of foundation on which to pile and intermix the trimmed poles. The timbers, being cut green, become water-soaked. This makes them heavier and so causes them to sink and helps to hold them in place; while the branches and twigs of the untrimmed trees form a kind of basketwork that catches the sediment and drift of the stream, and so the dam lets less and less water through. The upside stream is plastered by the beavers with mud in cases where the flow of water in the stream is meagre. Otherwise it is left unplastered. You see Mr. Beaver's idea is not to make the dam absolutely water-tight, for then it would be running over all the time and so be worn away. What he wants is a dam that will let the water through slowly and at the same time keep a proper level. [Illustration: BEAVER HOME WITHOUT TIME LOCK Here is a beaver home as it looks before the time lock is put on in the Fall.] Mr. Beaver's chief purpose in building these dams seems to be to keep his front-door yard full of water. This may look like a funny idea at first, but in this, as in other things, Mr. Beaver shows he has a very wise head on his shoulders; for one peculiarity of his life is that he is obliged to come and go through the cellar door. As he doesn't want any of his enemies--the wolf, the coyote, and all that class of people--to use this door, he keeps it under water. And in winter-time, when he goes out to the wood-pile to get something to eat, the water must be deep enough so that the pond doesn't freeze solid to the bottom. [Illustration: A BEAVER HOME WITH TIME LOCK Here, as it looks after being made secure against hungry wolves and the Winter winds.] As for those professional highwaymen, the wolves and coyotes, that are so much bigger than he is, Mr. Beaver keeps out of their way in Summer, when they don't bother much about him, anyway, as he sticks so close to the water and is hard to catch. In the Winter, when they get hungry and desperate and would break into his house, if they could, he makes it practically burglar-proof, by putting on a time lock; a lock that just won't open, even to a wolf's sharp claws, until Spring. And in the simplest way. Just before Winter sets in Mr. Beaver plasters the outside of his house with mud, and the mud freezes as hard as a stone. But sometimes, even among the beavers, there are shiftless characters, like that Arkansas man who just _wouldn't_ look after his roof. These careless beavers don't plaster their roofs. But then, just see what happens! Some hungry wolf comes along and breaks through and has a nice fat beaver for supper, maybe. And maybe not; for, even in that case, if Mr. Beaver wakes up in time, he dives down through the cellar door and into the tunnel and out under the ice. "Aha! You got fooled that time, didn't you? You mean old thing!" (Can't you almost hear him say it?) In putting the mud coating on their houses or dams the beavers carry it in their fore paws. Sometimes, in a very steep place, they climb up the roof with three feet and hold the mud with one. When they have delivered the mud they use these same little paws to pat it down--not their trowel-like tails, as one would naturally suppose. THAT MYSTERY ABOUT THE BEAVER'S TAIL Then what _do_ they do with those tails? Well, for one thing, they sometimes use them to carry mud by curling them between their legs and holding the mud against their bodies. Perhaps they resort to this way of carrying mud where they have such a steep climb up the roof they need all four legs to climb with; or it may be just an individual fancy of some beavers. For, being really _thinkers_ and not mere machines, acting entirely on what is called instinct, different beavers have different ways of doing things. The beaver's tail is also very useful in swimming, and Mr. Beaver is a great swimmer. You should see him. He swims mostly with his hind feet and tail, holding his fore paws against his breast as a squirrel does when he's sitting up looking at you. His tail he uses as one uses an oar in sculling, turning it slightly on edge as he works it back and forth. But he has two other important uses for this big tail, as we shall now see; for the beavers of this colony we are watching, having put up their dam and built their big house, are now ready for the Fall harvest that is to provide for the long Winter. The beavers are strict vegetarians. Their diet consists of the tender bark of young trees and roots dug from the bottom and along the banks of the ponds in which they live. "But, for mercy's sake, where are they going to get the tender bark of trees in the dead of Winter, when all the trees are frozen solid and the beavers can't get from under the ice anyhow?" Well, Mr. Beaver has thought out just how to do it and we didn't. That's the beauty of being a beaver. What he does is to cut down small trees, trim them, divide them into lengths, and then heap them up in a great pile at his door, under the water. By the time they are three years old beavers feel grown-up; as, indeed, they are in size, although, like certain other young people I could name, they have a great deal yet to learn. At this age they choose their mates and either settle down in the home colony or go away somewhere else. School takes up with the beavers in September. All through September and October the harvest is gathered and preparations made for the long Winter. The baby beavers of the Spring, who by this time are four or five months old, take part in the harvesting; at least they play at it. They don't do much, but they learn a great deal. Now let's all be little beavers for a few minutes and see what we can learn. We are out in the harvest-field--the woods--with father, and he's going to cut down a tree for the Winter food-pile. Watch him. He picks out a young tree something less than six inches thick. Then he looks up as if he wanted to see what kind of a day it was going to be; although the fact is he never bothers his head about the weather. What he is really looking up for is to see if the top of the tree he is going to chop down is likely to get tangled in the tops of other trees when it falls. (All beavers, I should add, don't take this precaution; only the older and wiser ones.) After this inspection he either cuts the tree in two with his long sharp chisel teeth so that it will fall clear of the tangling branches of other trees, or, if he sees he can't prevent this, he moves away to another tree. Just before the tree is ready to fall he thumps the ground several times with his tail to warn other beavers working near by. They all scamper as fast as their fat bodies and short legs will let them. If they are near water, as they usually are--they "plunk" into it. After the tree falls the limbs are cut off, the trunk gnawed into sections four to six feet long, depending on the size of the trunk, the distance from the water, and the number of beavers that are going to help move it. Although, as a rule, only one beaver works on a tree in cutting it down, they all pitch in and help in getting the sections home; dragging them across the ground and into the pond or into one of their wonderful canals. THE BEAVERS AND THEIR PANAMA CANALS The beavers knew all about digging canals long before the days of Colonel Goethals. They dug them for much the same reason we dug the great Panama Canal, to save time and expense in moving freight and for protection from possible enemies. On land the beaver is easy prey for wolves and such, but once in the water he can laugh at them. These canals not only enable him to haul his wood easily and safely, but are just the things to dive into when somebody is after you. Another purpose of the canals is to fill ponds where water is getting low; or to make a pond where there isn't any at all, as in a dry ravine. Whether you look at them from the standpoint of their intelligence and good habits, or their usefulness, beavers are the most interesting of all our little four-legged brothers of field or wood, and it is pleasing to know that many States have passed laws to protect them. [Illustration: SUN BATH AFTER THE SWIM Boys, after an hour or so in the "ole swimmin' hole," like to take a sun bath. That's what these young beavers are doing on a nice grassy spot by the pond.] And besides he is such a good fellow, Mr. Beaver is; peaceable, industrious, dependable, and with the best heart in the world! Why, do you know what they do--the beavers--when neighbors get burned out by forest-fires or their houses broken into by a mean old wolf or coyote or anything? Take them right in, children and all! If you were a little beaver you'd have from two to four twin brothers and sisters to start with, and then two to four more for each of the remaining two years before you left home to make your own way in the world. You'd be born with your eyes open and not like a puppy or kitten. And, what do you think, _in less than two weeks_ you could go swimming. Mother would be right with you in case anything happened. Then when you were tired swimming you'd climb up on top of the house and rest and doze in the sun; take your afternoon nap just like any other baby. [Illustration: LITTLE BEAVERS IN THEIR HOME] But maybe it wouldn't be your own mamma that would be with you; for lots of sad things happen to beaver people, and when one little beaver's mother dies another mother beaver will take care of him, and all his brothers and sisters besides! Mr. Mills tells in that most interesting book of his about how one day a mother beaver was killed by a hunter who thought he didn't have anything better to do than kill poor little beavers; and the very next evening a lady beaver, who _already_ had four babies of her own, travelled a quarter of a mile with them to the house of her dead neighbor and stayed there and brought all the little orphans up! HIDE AND SEEK IN THE LIBRARY The crayfish is a thing you've got to take seriously if you want to get the most out of it. Huxley says that a thorough study of a crayfish is almost a whole course in zoology. Think of going to school to a crayfish! But you'd enjoy it, I'm sure. For just look--and these are only a few of the interesting things you will find in Huxley's famous book on "The Crayfish": How they swim backward (no doubt you know this already), and how they walk on the bottom of the water. Why they seem to know the points of the compass--for they prefer rivers that run north and south. Why they are most active toward evening. Where they spend the winter. Why they eat their old clothes. How early in the spring you may expect to find them. When they hatch their eggs and how the mother crayfish uses her tail for a nursery. In what respect they resemble moths. How they chew their meals with their feet and work their jaws like a camel from side to side--only more so! How they grow by fits and starts, and what this has to do with the way they change their clothes. How you can tell the age of a crayfish. (You don't do it by looking at its teeth. You couldn't see its teeth anyway, because they are in its stomach.) And all this in less than the first fifty pages of a book, which has more than 350. One of the most famous of the crab family, not only on account of his part in agriculture, but because of his funny ways, is the robber-crab. You should read about the wild life of adventure some of these crabs lead--regular Robinson Crusoes who get wrecked on islands far away from home and build houses there and shift for themselves in many ingenious ways, just as the human Robinson Crusoe did. Kingsley's "Madam How and Lady Why" has some interesting pages about them; and so has Darwin's "Voyage Around the World." Of the many things that have been written about beavers the following are among the most interesting: The story of the beaver in "Stories of Adventure," edited by Edward Everett Hale; "The Forest Engineer," by T. W. Higginson, in Johonnott's "Glimpses of the Animal World"; "How the Beaver Builds His House," in "The Animal Story Book," edited by Lang; "The Builders," in Lang's "Ways of Wood Folks"; and "The House in the Water," by Roberts. The most interesting book of all on beavers, however, is "The Beaver World," by Mills, referred to in this chapter. I have not told you one-half of the remarkable things you will find about them in this book. One of the most curious is about how a beaver sometimes gets his breath in the winter time. He may have to travel quite a distance under the ice, and one good breath has to last him to the end of the journey. "But does he hold his breath all this time? How can he?" He can't. He just uses the same breath over again. See how he does it. The Mills book tells. Look up the muskrat and compare his ways with those of the beaver. In the "Country Life Reader" you will find a graphic description of one of the perils of life for the beavers and their cousins the muskrats; namely in attacks by the great horned owl. [Illustration: CITY LIFE AMONG THE FLAMINGOES We don't have to go to Florida to get this bird's-eye view of a flamingo city. It is one of the habitat groups in the American Museum of Natural History in New York, and reproduces perfectly the architecture and the social life of these interesting people.] CHAPTER IX (SEPTEMBER) On the housetop, one by one Flock the synagogue of swallows Met to vote that Autumn's gone. --_Gautier: "Life."_ FARMERS WHO WEAR FEATHERS Sh! Go easy! Pretend you're a horse or a cow.[21] We've gone south with the swallows--it's September you see--and those queer birds over there are flamingoes. The flamingoes are a shy lot; I don't know why. I can't think it's on account of their looks; for there's the kiwi, the hornbill, and sakes alive--the puffins! _They_ all have funny noses, too, but none of them are particularly shy, and you can walk right up to a Papa Puffin almost. Whatever the reason is, the flamingoes are very easily frightened and they're particularly suspicious of human beings. Yet we've simply got to meet them and have them in this chapter, for they are among the most interesting of the feathered workers of the soil. They just live in mud; build those tower-like nests out of it, walk about in it, and get their meals by scooping up mud and muddy water from the marshes where they live, on the borders of lakes and seas. They strain out the little creatures wiggling about in these scooped-up mouthfuls. [21] Observers find that flamingoes can be successfully approached by putting on the skin of a cow or a horse. I. FEATHERED FARMERS WITH QUEER NOSES "What a funny nose! What happened to it?" I knew you'd say that. Everybody does. But just watch now and see. That flamingo over there, stalking about on his stilt-like legs, sticks his long neck down to the muddy water, turns that funny nose upside down and---- "Why, of all things, is he going to stand on his head?" WHY FLAMINGOES HAVE SUCH FUNNY NOSES No, not that. Don't you see, he's getting his dinner? After that crooked scoop bill--for that's what it really is, a scoop--is filled, the water strains out through ridges along the edge of the bill and what's left is his food. That picture looks as if it had a tremendous lot of flamingoes in it, doesn't it? It has. It's quite a town, Flamingoburg is. Although flamingoes are so wary about meeting two-legged people without feathers--that is, human beings--they're very sociable among themselves and there may be a thousand, even two thousand, pair in a single flamingo city, such as Doctor Chapman studied in the Bahama Islands some years ago. Their nests are cupped-out hollows in little towers of dried mud raised a foot or so to keep high tides from swamping them. They scrape up the mud with that shovel-like bill. After the conical-tower nest is made, the mud piled up and patted into shape with her bill and feet, Mother Flamingo lays one or two eggs--and then she goes to setting. You notice there's just one little chick in the nest in the lower left-hand corner of the picture, and just one egg in the nest near by. With such a low stool to sit on you wonder what the mother bird does with her long legs. In some pictures in children's nature books of not so many years ago you'll find her represented as sitting on the nest with her legs hanging down the sides--but you see that couldn't be; the nest isn't tall enough. What she really does is to fold her legs under her body; just once, of course, at the joint. But they're so long that, even when folded, they reach out beyond her tail. While setting, the lady birds reach around with their long necks shovelling up things to eat and gossiping, more or less, with the neighbors; for the nests, you notice, are very close together. Sometimes two of them will reach across the narrow alley that separates the residence of Mrs. Flamingo Smith from Mrs. Flamingo Jones, take each other playfully by the bill and hold together for a while. Maybe this is their way of saying "Good morning," or "How do you do?" [Illustration: FLAMINGO SOCIETY NOTES FROM THE ZOO THE TOILETTE You'd expect a lady wearing so many nice feathers to be particularly careful about her dress, wouldn't you? A LITTLE NAP Queer notion, sleeping on one leg like that, isn't it? But then flamingoes _are_ queer! A TOUCH OF RHEUMATISM Of course flamingoes don't go around like that even in zoos. This is the artist's joking way of telling that in our northern climate they are subject to rheumatism. And the keepers actually do oil their legs.] You'd hardly think it--with those long legs of theirs--but the flamingoes swim beautifully. With their long necks drawn back--the way swans do it, you know--they are very graceful, and a flock of them floating about is one of the loveliest sights in the world. They look like a big, fleecy, pink cloud resting right on the surface of the water. You can now find only a few flamingoes in Florida, where there used to be so many; but go on south into Central and South America and there are thousands of them. They are still fairly numerous in countries bordering the Mediterranean and the Indian Ocean. In Persia they are called "red geese." And the name isn't so far wrong as you'd think. You notice that, unlike those stilt-walkers, the herons, the flamingoes have webbed feet. Like geese and ducks, also, they have those rows of tooth-like ridges on the edges of their bills. It is these "teeth" that, coming together, act as strainers. But a queer thing about their bills, besides the funny-way they have of crooking down all of a sudden, is that the upper bill is smaller and fits down into the lower. Stranger still, the birds can raise and lower this upper bill like the cover of a coffee-pot. They can move the under bill a little, too, but not to amount to anything; so you see there was even more to the upside-downness of that bill than there seemed to be at first. The whole arrangement looks odd to us, but it works out beautifully for the birds. When they turn their heads upside down they can stir the ooze to various depths, as required, by using the upper bill as a ploughshare and setting it at different angles. Although they've borrowed some ideas from both the goose and the heron families, the flamingoes are so different from either they are put into a family by themselves, the _Phoenicopteridæ_. This family name is from two Greek words meaning "red-winged." If you want to be formal in speaking of or to a goose you must refer to her family as the _Anserinæ_ which is Latin for "geese." [Illustration: WHERE THE FLAMINGO KEEPS ITS TEETH While teeth, like those of the Hesperornis, went out of fashion ages ago, the flamingoes have substitutes for teeth which answer their purposes much better. They have little horny spines on their bills and on their tongues. These spines serve as fences to prevent the escape of the minute creatures which the flamingo scoops up with its bill. You notice the spines on the tongue are pointed backward toward the throat; and that's a help--to the flamingo, I mean, for once on that tongue there's no turning back.] A LATE BIRD, BUT HE GETS THE WORM Another of the long-nosed earth workers, as curious in his make-up as the flamingoes, is the kiwi of New Zealand. Like the flamingo, the kiwi uses his queer bill to get his living out of the soil. You've heard the saying "it's the early bird that gets the worm"; but while this is true of most birds it doesn't apply to the kiwis. Although they live on worms, as does Mr. Early Bird of the proverb, they do their feeding by night. And such a funny thing for a bird to do, the kiwis go about with their noses to the ground like a dog smelling after a rat. The reason they do this is that their nostrils are situated, not next to their heads, as in most birds, but at the end of the bill--and on purpose; for they locate their suppers, the worms in the earth, by the sense of smell, although most birds have a very poor sense of smell. Just after sunset, you'll see the kiwis moving about softly (as if they were afraid of scaring away the worms!), and with the tips of their bills against the ground. "Sniff! Sniff!" (You actually can hear them sniff.) There, he's found one! His bill is not only long, but bends rather easily and that's why, perhaps, he's able to follow up so closely the hints he gets from his nose as to the location of worms, for he usually brings the worm out whole, and not all pulled apart as the robins do it sometimes. He works in soft earth, where most worms are found, and generally drives his bill in up to his forehead. If all goes well he pulls it right out with the worm at the end; but if there is any likelihood of an accident, the kiwi gently moves his head and neck to and fro until he has the soil loosened up and so clears the way. Once the worm is fairly out of the ground, he throws up his head with a jerk and swallows it whole. Because they roam about so much at night, the kiwis sleep much of the day. You'll find them in thickets or in among the forested hills, where they make their homes. Sometimes, however, you'll see one standing, leaning on his long bill, like a street-idler propping himself up with his cane. If you disturb him, he yawns, as if to say: "Oh, these bores! Why can't they let a fellow alone?" But don't you go too far and annoy him or he'll get real peevish and strike at you with his foot. Both Mr. and Mrs. Kiwi drill the earth every day--or rather every night--in their search for worms, but Lady Kiwi does all the excavating when it comes to making the nest. This she does by digging a tunnel, generally under the roots of a tree fern. There she lays two eggs and then her family cares are practically over for the time being, since it is the male kiwi who does most of the setting. [Illustration: MR. HORNBILL LOCKS THE DOOR In Africa, Southern Asia, and the East Indies live the Hornbills. After the nest is built and the eggs laid in the hollow of some big tree like that, Mrs. Hornbill begins to set; and Mr. Hornbill, to protect her from enemies, walls up the nest with mud--all but that hole through which she puts her bill and gets food from the devoted father and husband.] Other long-nosed tunnel diggers you must have seen many a time when you've been fishing, for they are fishers, too--Mr. and Mrs. Kingfisher. Their home is at the end of a tunnel in the banks of the stream where they do their fishing. While we're visiting them and making a study of their household arrangements, it's a good thing for us that we're not kingfishers ourselves; for if there's anything that makes the kingfishers mad it's to have other kingfishers fooling around their place or even coming into their front yard. Each pair of kingfishers lays claim to the part of the creek in the neighborhood of their nest, as their fishing preserve, and woe betide any other kingfisher that trespasses! Human fishermen and hunters give it out sometimes that kingfishers eat big fish that might otherwise be caught with a hook or a seine, but the fact is these birds catch only minnows and little shallow-water fish. In digging the tunnels for their nests the two birds work together, and these tunnels are sometimes fifteen feet long. So you see that with kingfishers scattered around the world as they are--some 200 species in all--they must have done an enormous amount of ploughing in the course of time; to say nothing of what they have done in the way of enriching the soil with fish-bones, one of the very best of all fertilizers. The kingfisher's nest wouldn't be at all attractive to some birds--the swallows, for example, who are so particular about having feather-beds. It has just a hard-earth floor like the cabins of the American pioneers, but the little kingfishers are perfectly contented and happy; for their meals are very plentiful, fairly regular, and the fish are always fresh. FISHING DAYS AND OTHER DAYS But some days even the kingfishers don't have fish for dinner. Instead they serve crayfish and frogs. This is on cloudy days, or when the wind is stiff and the water rough. On such days even the keen eyes of the kingfisher can't see a fish or make out exactly where the fish is when he does see one. But on clear, quiet days, you should see him fish. He often dives from a perch fifty feet or more above the creek and strikes the water so hard you'd think it would knock the breath out of him. But up he comes with his fish, nearly every time! Of course he misses occasionally, but just think of seeing a fish that far away--under the water, mind you; and not a big fish, but a little minnow, only two or three inches long. II. UNDER THE OVEN-BIRD'S FRIENDLY ROOF Another great little farmer is the oven-bird. We can't afford to miss him and his wife for anything; and although we have to go to South America to meet them, we'll do it. So here we are! The oven-birds build a nest of clay mixed with some hair or grass or real fine little roots. This nest, when it's all done--it takes a good while to build it--is so big you'd hardly believe it was the home of so small a bird. It's a dome-shaped affair, like a Dutch oven. In the United States we have what we call an "oven-bird," too--one of the water-thrushes; but as its dome-shaped nest is made of grass and leaves and has no clay in it, we will not include this bird among the feathered farmers. The oven-bird of South America knows how to build its dome of clay without any scaffolding, which isn't easy. OVEN-BIRD DOORS AND THE FRIENDLY ROAD While the big flamingoes are so shy, the little oven-birds don't care who sees them--provided they can see _him_ first. This is possibly because they want to keep an eye on any suspicious movements; for they make it an invariable rule to build so that their front doors will face the road. But really I think they do this, not because they are suspicious, but because they want to be neighborly and arrange their homes so they can sit on their front stoop and watch the crowd go by. They not only have their doors where they can see what's going on, but they nearly always build near the country road or the village street, and in the most conspicuous place they can find, instead of staying off by themselves in those vast, lonesome woods of Brazil where they lived before man came. When a nest is to be built the oven-bird picks up the first likely-looking root fibre, or a horsehair, or a hair from an old cow's tail, carries it to some pond or puddle and, with this binding material, works bits of mud into a little ball about the size of a filbert. Then he flies with this pellet to the place where the nest is going up. With clay balls like this laid down and then worked together, the two birds make the floor of their little house. On the outer edge of the floor they build up the walls. These walls they gradually incline inward, just as the Eskimos build their snow-block huts, until they form a dome with a little hole in it. The last little ball they bring goes to fill that little hole and then the house is done, so far as the walls and roof are concerned. Next, a front door is cut through the wall that faces the road. [Illustration: THE FRIENDLY DOOR THAT FACES THE ROAD Oven-birds make it a rule to build their adobe homes so that the front door will face the road. And they nearly always build near the road or the village street. Neighborly little creatures!] From the front door a partition is built reaching nearly to the back of the house, shutting off the front room from the family bedroom. After the eggs are laid Papa Oven-bird stays in the front room--or thereabouts--while mamma sets in the back room. The object of the little partition seems to be to protect mother and the eggs and, when they come, the babies from wind and rain. When the four or five baby birds arrive both papa and mamma put in most of their time, of course, feeding them. The nests of the oven-birds weigh eight or nine pounds. The work of these little feathered farmers and their wives reminds us in more ways than one of that of Mrs. Mason-Bee,[22] but they evidently have quite different notions about housekeeping; for, although their residences are so big, the oven-birds would evidently rather build than clean house, while with Mrs. Bee it's just the other way. The nests of the oven-birds are so thick and strong they often stand for two or three years in spite of the rains; but the birds build a new nest every year, nevertheless. [22] Chapter VI. III. THE MOUND-BUILDERS Another class of birds that have a fancy for big dome-like nests are the mound-birds. We find them in Australia, the Philippines, and the islands of the South Seas. Their scientific nickname is _Megapoddidae_, the "big-footed." It's with their big feet that they pile immense heaps of leaves, twigs, and rotten wood over their eggs. And what for, do you suppose? To hatch them! This heap of material not only absorbs the heat of the sun, but, in decaying, makes heat of its own. These mounds, of course, contribute tons and tons of fertilizer to the soil, but what interests the birds is that these warm heaps hatch their eggs. It's a kind of an incubator system, you see. As it is with many tens of thousands of our own little chickens, these days, the baby megapodes are born orphans. That heap of dead sticks, leaves, and earth is all the mother they ever know. As soon as the mother birds have laid their eggs in the mounds and covered them up, they go off gossiping with other lady megapodes, and don't bother their heads any more about their babies. WHY LITTLE BIG FOOT NEVER SAYS "MAMMA" But it really doesn't seem to matter. It's more of a question of sentiment than anything else, for the babies get on very well by themselves. When the time comes they not only make their own way out of the shell, as all birds do, but they work their way up through the rubbish-heap and run off at once into the woods to hunt something to eat. It's all right, after all, I suppose; but if _I_ were a little mound-builder's baby, I'd rather have a mamma that would stay around and go places with me, wouldn't you? There's one nice thing about these mamma mound-builders, though; they're so neighborly and sociable. It's like a regular old-fashioned quilting party to see them build a nest. The birds look like turkeys, and one of the species is called the "brush turkey," but they are no bigger than an ordinary chicken--than a rather small chicken, in fact. When I tell you, then, that these mounds of theirs are often six feet high and twelve feet across in the widest part, the middle, you can see it takes good team-work to put them up. [Illustration: BRUSH TURKEYS BUILDING THEIR INCUBATORS It's like an old-fashioned quilting party--the co-operative mound building of the brush turkeys. The text tells you about that back kick of theirs.] So a lot of the lady mound-builders get together in woodsy places, where there's plenty of leaves and twigs lying around and together build a mound. One will run forward a little way, rake up and grasp a handful of sticks and leaves--I mean to say a footful--and kick it backward. The motion is much like that of an old hen scratching. Then another bird gathers a footful; then another, and soon they are all throwing the rubbish toward the same pile; all as busy as a sewing-circle, but--curiously enough--nobody saying a word! Before the mounds are quite done, they all begin laying their eggs in them; as many as forty or fifty, before they are through. Some species frequent scrubby jungles along the sea. These scratch a slanting hole in the sandy soil about three feet deep and lay their eggs on the bottom, loosely covering up the mouth of the hole with a collection of sticks, shells, and seaweed. The natives say these birds, before they leave, go carefully over the footprints leading to this treasure-house, scratch them out and make tracks leading in various directions away from the nest. And all species lay their eggs at night. You see why, don't you? They're just that cautious. SUCH AN EGG FROM SUCH A BIRD But if you should find one of their nests full of brick-red eggs you'd never guess who laid them, they're so big! Away back in 1673, an English missionary to China who had stopped off at the Philippines, on his way, wrote a little book when he got back home about where he had been and what he had seen, and he just couldn't get over the wonder of the mound-builders. Among other things he says, in one place in his book: "There is a very singular bird called Tabon. What I and very many more admired[23] is that being in body no bigger than an ordinary chicken, it lays an egg larger than a goose's." [23] "Admire," in those days, meant "to wonder at." "So," he adds, "the egg is bigger than the bird itself!" IV. THE SWALLOWS To make the acquaintance of either the mound-builders or those dear little oven-birds--_aren't_ they dear?--we must be travellers, of course, for with their short wings neither the mound-builders nor the oven-birds ever could come all the way up here to see us. But another feathered farmer--and, like the oven-bird, a clay-worker and most neighborly--everybody knows; the swallow. Like Kim, the swallow is the little friend of all the world. Swallows of one kind and another are found everywhere--almost everywhere that people can live; usually where people _do_ live. And if all the soil they've helped pulverize and mix--even since the days when the swallows built under the eaves and rafters of the ark--was spread out, it would easily make another Egypt, I do believe! But, speaking of the way swallows take to human society, do you know where our barn-swallows came from? They were originally cliff-dwellers away out West. The early explorers found enormous collections of their nests plastered all over the perpendicular cliffs and along the bluffs. Just as soon, however, as the country settled up and men put up barns these little cliff-dwellers, deserting rocks and bluffs, began building their bottle-shaped nests under the eaves. The swallows live on insects--including squash-bugs, stink-bugs, shield-bugs, and jumping plant-lice; and that's supposed to be one of the reasons for the curious fact that they left their ancient family seats--they found so many more insects about the barns and the farmer's fields and the gardens and the orchards. TINY SOIL MILLS OF THE BABY SWALLOW Haven't you often watched them and listened to them, diving and chattering around the barn in their busy season; that is to say, in the spring and summer time? Then the air is full of insects and is fairly woven with their darting wings. Some keep busy picking up the insects that are always hovering about in a barnyard, while others dash away to some near-by marsh or to the meadow or to the creek. Over the grain-fields they go, over the meadows and back again straight to the nest where downy babies are cheeping for them. The parents feed them, stop and chatter a moment, and then off they go. Follow that one down to the marsh. See how she flies high, round and round in circles, and then swoops for an insect. She missed him! Then she wheels, darts up--darts down--to right--to left. There, she's got him! Then off like an arrow to the nest. The soft-bodied insects are chosen and chewed up for the babies, while the parents eat the tougher ones. And to help digestion they give the babies little bits of gravel, although they don't use it themselves. So, in grinding up this gravel the baby birds help make soil before they are old enough to do any nest-building. [Illustration: THE SAND MARTIN AND HIS HOME IN THE BANK] You've noticed, of course, that all the swallows about a barn don't build under the eaves. Some build under the rafters inside the barn. That isn't just a matter of taste; it's family tradition. The eave-builders are descendants of the cliff-swallows, while the birds known to bird students as "barn" swallows build under the rafters. But they don't take to the fine, new modern barns--all spick and span--the barn-swallows don't. If there's an old gray barn with doors that never shut quite snug, a board off here and there, and several panes in the cob-webbed windows broken out---- "Oh, just the thing!" say Mr. and Mrs. Swallow, and they turn their backs on the new barn and proceed to build their cute little nests of clay among the rafters of that old tumbled-down affair. In their preference for the old gray barns, the swallows are like the artists, the painters that Mr. Dooley told about. He was talking about artists to his friend, Mr. Hennessey: "I don't mane the kind of painther that paints yer fine new barn," said Mr. Dooley. "I mane the kind of painther that makes a pitcher of yer _old_ barn and wants to charge ye more'n the barn itself is worth." WHY ARTISTS AND SWALLOWS PREFER OLD BARNS The reason the artists prefer old barns is that they look better in pictures, but the reason the barn-swallow shows the same taste is that, with windows that have panes in them and doors that shut tight you'd no sooner start to build a nest than, coming back with a pellet of clay, or bringing a feather for the little feather-bed, you'd be liable to find the door shut and you could no more get in until chore time than you could open the time-lock in the First National Bank. And suppose there were babies and you'd just _got_ to get back--you see it wouldn't do at all! But both the barn-swallows and the old gray barns will be seen only in pictures before long, if things keep on; what with these new barns and the cats always trying to catch the few swallows there are left--when you're swooping low to catch a squash-bug, say--and those hateful sparrows that tear your nest to pieces. And for several years swallows were killed by thousands to make ornaments for women's hats until this shameful business was stopped by law! On the Pacific Coast, if you're out there even as early as March, you'll see a purplish-bronze swallow, with bronze-green markings. These swallows make a specialty of orchard insects and that's why, perhaps, they build under the eaves of the farmhouse rather than the barn. But, like the rest of the swallow family, they think nothing quite so nice as a bed of feathers to raise babies in, and they know as well as the cliff-swallows and the barn-swallow that a barnyard is a great place for feathers. And besides, there's a man out there, in one place, that keeps a supply of feathers just to give away when the swallows are nesting. Watch him, over on the hillside. He takes a little bunch of feathers and throws them up into the air from his open hand. A swallow skims by and catches one of these feathers before it touches the ground. But soon the word passes along: "Here's that nice man with the feathers!" And, pretty soon, there are a half-dozen in the game. They flit closer and closer to that generous hand, seizing the feathers almost the moment they are in the air. Then one, bolder than the rest, snatches a feather right from the man's thumb and finger. The little rogue! By the way, do you know who that man is? It's Mr. W. L. Finley, State Ornithologist of Oregon. "Our little brothers of the air," as Olive Thorne Miller calls the birds, are getting to be so much appreciated, not only as the friends of man, but for their beauty and the usefulness of their lives, that both our State and national governments have laws to protect them, and such men as Mr. Finley are employed to look after their interests. Of course, he doesn't _have_ to furnish feather-beds for the baby swallows--he just does! [Illustration: OFF FOR THE SOUTH] HIDE AND SEEK IN THE LIBRARY If you want to get better acquainted with ostriches you should read Olive Thorne Miller's "African Nine Feet High," in "Little Folks in Feathers and Fur." Carpenter deals with the ostrich in his "How the World is Clothed" and in his "Geographic Reader on Africa"; Johonnott's "Neighbors with Wings and Fins" gives a chapter to "Giants of Desert and Plain," among which you may be sure he includes the ostrich. Allen, in writing about "Some Strange Nurseries" ("Nature's Work Shop"), tells why it is Papa Ostrich has most to do with the hatching of the eggs when the sun is not on the job. Lucas, in his "Animals of the Past," speaks of ostriches and crocodiles as the nearest living relatives of--guess what--the dinosaurs! (Yet look at the dinosaur in "The Strange Adventures of a Pebble" and see if you can't make out a good deal of the ostrich and the crocodile in him.) But, speaking of Papa Ostrich's parental duties, did you know that it's _Mr._ Puffin, and not _Mrs._ Puffin, who digs the family burrow? Arabella Buckley's "Morals of Science" tells that and many other interesting things about devoted husbands among the birds, including how Papa Nightingale feeds Mamma Nightingale. In the "Children's Hour," Volume 7, page 310, you will find an interesting article about the puffins of Iceland. "The Romance of Animal Arts and Crafts" tells about one of the feathered clay-workers, the nuthatch of Syria, and why he makes his nest look like a rock. These nuthatches love to build so well that they often make nests that they never use; and they even help put up nests for their neighbors! This book also gives interesting details about the hornbill, and how and why he walls up his mate in her nest in the hollow of a tree. Father Hornbill, of course, gets all the meals for Mother Hornbill, while she's setting. She simply _can't_ get out, and you should see him by the time the babies are old enough to leave the nest. He's worn to a shadow! Rooks, it seems, do a little digging under certain circumstances. Selous tells about it in his "Bird Life Glimpses." In this book you will find a delightful description of martins building. It almost makes you want to _be_ a martin. It also tells about the work of the sand martins. You will hardly believe how fast they work. The house-martin's nest is more elaborate than the swallow's. This book tells why the house-martins begin work so early in the morning, and why they have to delay their nest-building if the weather is either too wet or too dry. White, in his famous "Natural History of Selbourne," tells how worried he was because certain swallows just _would_ build facing southeast and southwest. Birds, besides being workers of the soil, are great sowers of seeds. Darwin tells how he reared eighty seedlings from a single little clod on a bird's foot. What do you suppose he did that for? You just look it up in the index to his "Origin of Species." Doesn't it seem funny that one of the little farmer birds--a burrower--should go into partnership with a lizard? There is one in New Zealand that does that very thing. He is called the titi. What the titi does for the lizard is to provide him with a home in his burrow, but what do you suppose the lizard does in return to pay for his lodging? Read about it in Ingersoll's "Wit of the Wild," in the chapter on "Animal Partnerships." Do you know why the phoebe bird so often uses moss in building her nest? And how the phoebes that make green nests keep them green? And how Mrs. P. puts a stone roof on her house? You will find all about it in "Wit of the Wild." The same chapter, "The Phoebe at Home," tells why the phoebe bird took to building under bridges, and why she builds in a carriage shed instead of a barn, as the barn-swallow does. "Bird Life," by Chapman, is a guide to the study of our common birds. The beauty about this book is that it has seventy-five full-page plates in the natural colors, with brief descriptions, so that all you have to do is to bring the _mind_ picture of the bird you have seen alongside the picture in the book, and there's the answer! Nobody has written more delightful books on birds than Olive Thorne Miller. "Little Brothers of the Air" is one of them. You couldn't keep your hands off a book with a name like that, could you? Then there is her "Children's Book of Birds," "True Bird Stories," illustrated by Louis Agassiz Fuertes, and "Little Folks in Feathers and Fur," which, as you can see, goes outside the bird family. John Burroughs's "Wake Robin" deals not with robins alone, but with birds and bird habits in general. But the greatest book about birds--the wonder of the bird and his relations to the whole animal world--is very properly called "The Bird," by C. William Beebe, who is at the head of the bird department of the great New York Zoo. Among other things it tells: How Nature practised drawing--so to speak--for years before she could finally make a proper bird. (If you have ever tried to draw a bird from memory and realized what a bad job you made out of it, you will sympathize with her.) How they know that the earliest birds Nature made, as well as being very homely, weren't at all smart; not to be mentioned in the same breath with clever Jim Crow, for example. How "a bird's swaddling clothes and his first full-dress are cut from the same piece," the very words of the book. About certain birds that have one set of wings to play in and a new set for flying, like a child wearing jumpers to save his nice clothes! About the world of interesting things you can discover with the bones of a boiled chicken. And so on for nearly five hundred pages, and as many illustrations; the most striking collection of pictures explaining birds that I ever saw. [Illustration: THE END OF A BUSY SEASON "And there's the corn and the pumpkins and the carrots and the turnips and the potatoes in the root cellar and the jelly in the jelly-glasses--we helped make them all."] CHAPTER X (OCTOBER) It is hardly an exaggeration to say that the tip of a root acts like the brain of the lower animals. --_Darwin._ THE BUSY FINGERS OF THE ROOTS This has been a very busy season for Mr. Root and his family. It always is, and you can imagine they're all glad when Fall comes and they can lay by for the Winter. "There's your apple crop, I helped make that," Mr. Root might say. "And there's the corn and the wheat in the granary, and the rye and the oats and the barley; and the hay in the mow; and the pumpkins and the carrots, and the turnips, and the potatoes in the root cellar; and the jelly in the jelly-glasses, and the jam, and the preserves--we helped make them all. "And we've been working for you almost since the world began; almost, but not quite--for the earliest plants, the Lichens, for example--didn't have true roots. "Yes, and--well, I don't want to say anything--Mr. Lichen has been a good neighbor--but he never did amount to much; never could. No plant can amount to much without roots. But with roots and a good start a plant can do almost anything--raise flowers and fruit and nuts, and help grow trees so tall you can hardly see the tops of them. And, it isn't alone what we do for the plants we belong to, but for the soil, for other plants and roots that come after we're dead and gone. For them we even split up rocks, and so start these rocks on their way to becoming soil." I. ALL IN THE DAY'S WORK It's a fact. Roots do split rocks. Hundreds of times I've been in the cracks of rocks that were split in that way. I mean right when the splitting was going on. This happened oftenest where trees grew on the stony flanks of mountains. Seeds of the pines, say, dropped in crevices by the wind, sprout in the soil they find there, and then, as these shoots grow up into trees, the enlarged roots, in their search for more soil, thrust themselves deeper and deeper into the original lodging-place, and so split even big rocks. The tap-roots do the heaviest part of this pioneer work. After the older and larger roots have broken up the rock, the smaller roots and fibres, feeling their way about among the stones, enter the smaller openings and by their growth divide the rock again and again. But it's a lot of hard work for little return, so far as these early settlers are concerned; just a bare living. All these rock fragments, in the course of the years, become soil, but the amount of decay is small in the lifetime of the tree that does the breaking. A root, as you doubtless know, tapers. This enables it to enter a rock crevice like a wedge. As it pushes its way in farther and farther it is growing bigger and bigger, and it is this steady pressure that breaks the rock. Even the tiny root of a bean grows with a force of several pounds, and the power exerted by the growth of big roots is something tremendous. At Amherst Agricultural College, one time, they harnessed up a squash to see how hard it could push by growing. From a force of sixty pounds, when it was a mere baby, what do you suppose its push amounted to when it had reached full squashhood in October? Nearly 5,000 pounds; over two tons! [Illustration: HOW A LITTLE ROOT SPLIT A GRANITE BLOCK The little winged seed from which this pine-tree grew was carried by the wind one day into a tiny crack in that big granite block. As the treelet grew the tap root split the rock, penetrated to the earth below and fed the trunk until it became, as you see, a tree 40 feet high and 18 inches in diameter!] But don't think because roots can and do split rocks, if need be, that they go about looking for such hard work. On the contrary. In travelling through the soil they always choose the easiest route, the softest spots. They use their brains as well as their muscles, and what they do with these brains is almost unbelievable. Yet the roots are such modest, retiring folks, always hiding, that it was a long time before the wise men--the science people--found out what all they do. It took a lot of science people and the wisest--including the great Darwin--to get the story, and they haven't got it all yet, as you will see. It was Darwin who first thought of having Mr. Root write out his autobiography--or part of it--the story of his travels; for he does travel, not only forward--as everybody knows--but around and around. A regular globe-trotter! [Illustration: WHY BABY PLANTS BACK INTO THE WORLD Most plants back into the world out of the seed like that. Why? To protect their tender first leaves. Suppose you were taking some very valuable thing, easily injured--baby brother, say--through a swinging door and you had to use both hands to carry him. You wouldn't open the door by pushing that dear, little tender head of his against it, would you? You'd open it by backing through.] Mr. Darwin was a wonderful hand at that sort of thing--getting nature people to tell their stories. He was an inventor, like Mr. Edison; only, instead of inventing telephones for human beings to talk with, he invented ways of talking for nature people. You saw how he fixed it so that the earthworms could tell what they knew about geometry and botany. Well, in the case of the roots, what did he do one day but take a piece of glass, smoke it all over with lampblack--you'd have thought he was going to look at an eclipse--and then set it so that Mr. Root could use it as a kind of writing-desk. In a hitching, jerky sort of way roots turn round and round as they grow forward. In the ground, to be sure, a root can't move as freely nor as fast as it did out in the open and over this smooth glass, but it does turn, slowly, little by little. The very first change in a growing seed is the putting out of a tiny root, and from the first this root feels its way along, like one trying to find something in a dark room. Thus it searches out the most mellow soil and also any little cracks down which it can pass. [Illustration: CHARLES DARWIN The great naturalist.] "Here's a fine opening for a live young chap," we can imagine one of these roots saying when it comes to an empty earthworm's burrow or a vacancy left by some other little root that has decayed and gone away. Roots always help themselves, when they can, to ready-made openings, and it is this round-and-round motion that enables them to find these openings. But even this isn't all. A root not only moves forward and bends down--so that it may always keep under cover and away from the light--but it has a kind of rocking motion, swinging back and forth, like a winding river between its banks, and for a somewhat similar reason. "It's looking for a soft spot!" says the high school boy, "just as the river does." NO HIT-OR-MISS METHODS FOR MR. ROOT Exactly. But not in the sense that this phrase is used in slang. The root has certain work to do, and it does it in the quickest and best way. It can get food more quickly out of mellow soil than out of hard, and so it constantly hunts it up. I mean just that--_hunts it up_. For it isn't by aimless rocking back and forth that roots just _happen_ upon the mellow places. It's the other way around; it's from a careful feeling along for the mellow places that the rocking motion results. "But how on earth do the roots do this? What makes them do it?" That's what any live boy would ask, wouldn't he? So you may be sure that's what the science people asked, and this is the answer: The roots, like all parts of the plant--like all parts of boys and girls and grown people, for the matter of that--are made up of little cells. Well, these cells, first on one side of the root and then the other, enlarge, and so pump in an extra flow of sap. Now, as we know, the sap contains food for the plant, just as blood contains food for our bodies; and more food means more growth. So the side of the root where the cells first swell out grows fastest and thus pushes the root over on the opposite side. Then the cells on this opposite side swell, and the root is turned in the other direction again. So it goes--right and left, up and down. And when these two motions--the up and down and right and left--are put together, don't you see what you get? The round-and-round motion! Precisely the same thing happened right now when you turned your finger round and round to imitate the motion of the root. (I saw you!) The muscles that did the work swelled up first on one side and then on the other, just as they do when you bend your elbow, when you walk, when you breathe, when you laugh. And more than that: You know how tired you get if you keep using one set of muscles all the time--in sawing fire-wood, for example. Yet you can play ball by the hour and never think of being tired until it's all over; because, for one thing, you are constantly bringing new muscles into action as you go to bat, as you strike, as you run bases. It's the same way with the roots, it seems. For the theory is that after the cells on one side have swelled, they rest; then the cells on the other side get to work. "But what starts the movement?" you may say. "The idea of moving my arms and legs starts in my brain." WHERE MR. ROOT KEEPS HIS BRAINS Just so again. The root has a brain, too, or what answers for a brain. And the root's brain, is in its head; at least in the vicinity of its nose--that is to say, its tip. It's the tip that first finds out which side of the road is best, and passes the word back to the part of the root just behind it to bend this way or that. It's also the tip that feels the pull of gravity and knows that it's the business of roots to keep under cover. And Mr. Root just _will_ have it that way! You can't change his mind. Mr. Darwin tried it and he couldn't; although he finally changed human people's minds a lot. [Illustration: WHERE MR. ROOT WEARS HIS CAP A root wears its cap right where you do--over its brain department; that is to say, the tip. It is called the "root cap" and protects the tip from injury.] This is how he tried it on a root. He took a bean with a little root that had just started out into the world. He cut off the tip and then set the bean so that the root stuck straight up. It continued to grow that way for some little time. Finally, however, a new tip had formed. Then there was a general waking up, as if the tip said to the rest of the root: "Here, here, this will never do! Where are you going? You must bend _down_!" Anyhow that's what the root proceeded to do. One side seemed to stop growing, almost, while the other side grew rapidly and so the bending was done. "Did you ever! But how does the tip send back word?" "Don't ask me!" says the science man; say all the science men, even to this day. "We don't know yet just _how_ it's done. But we're studying these things all the time, and we'll know more about it by and by. Meanwhile, perhaps you'll tell _us_ why you say 'ouch' and pull your finger away when you touch something hot." "Oh," you reply, "I say 'ouch' because it hurts; and teacher and the Physiology say my arm pulls my hand away because my head tells it to." "Yes, but how does the head make the arm do the pulling? What's the connection?" says the science man. Well, I guess we'll have to tell him we don't know, won't we? But all the root's brains aren't in the tip, any more than all _our_ brains are in our heads. Scattered through our bodies, you know, are _little_ brains, the ganglia, that control different parts of the body. So it is with roots. For instance, a root at a short distance from the tip, is sensitive to the touch of hard objects in such a way that it bends toward them instead of turning away, as the tip does. The result is that when a root comes to a pebble, say, under ground, the sides of the root press close up to the sides of the pebble--turn around corners sharply, by the shortest route--and so get over the obstruction as soon as possible and resume their course in the soil. [Illustration: BUT THEY COULDN'T CHANGE ITS MIND Some sprouting seedlings were attached to a disk like that, and when the roots started to grow down, the disk was turned to make them point upwards. But, no Sir! The roots just _wouldn't_ grow upward. They turned downward. Every time!] And different parts of a plant's root system respond in different ways to the pull of gravity, and some don't respond at all. The tap-root, for example, which always grows down, has roots growing out from it horizontally. They just won't grow any other way, and yet this is also supposed to be due to the influence of gravity. Then, from these horizontal roots, grow out a third set, and they don't seem to pay any attention whatever to gravity. They grow out in all directions--every which way--so that if there is a bit to eat anywhere in the neighborhood they are reasonably sure to find it. You see it works out all right. When a plant first begins to peep into the world out of that wonder box we call the seed, it's the root, as we know, that does the peeping; it comes first. And its first business is to get a firm hold in the soil. So a lot of fine hairlike fibres grow right and left and all around and take a firm grip. There is an acid in the root that dissolves whatever the root touches that has any food in it--including pebbles and old bones--and so makes a kind of sticky stuff that hardens. In this way these fibrous roots not only get good meals for themselves and the rest of the plant, but they hold the plant firmly in the soil, against the strain of the winds. They also give the tap-root something to brace its back against, as it were, while it pushes down for water, for the moisture in the damper portion of the soil beneath. As you may have noticed, a seed merely lying loose on the ground is lifted up by its first little root in its effort to poke its nose into the soil. But Nature makes provisions for covering seeds up. They are covered by the castings of the earthworms, the dirt thrown out by burrowing animals and scratching birds. Some seeds fall into cracks where the ground is very dry and others are washed into them by the rains; while these as well as seeds lying on the surface are covered by the washings of the rain. Then come the roots that grip the soil. Always growing just back of the tip, are thousands of root-hairs, as fine as down. These get food from the soil. They soon disappear from the older parts of the root, so that it stops gathering food itself and puts in all its time passing along to the stem and leaves the food gathered by the finer and younger roots. This is why plants are so apt to wilt if you aren't careful when transplanting them; the root-hairs get broken off. For the same reason, corn, after it grows tall, is not ploughed deeply. The fine roots reach out between the rows and the ploughshare would cut them off. II. MR. ROOT'S PRESENCE OF MIND All these things and more the roots do in their daily work--in the ordinary course of business. And it's wonderful enough. Don't you think so? But there are even stranger things to tell; things that would almost make us believe roots have what in human beings we call "presence of mind." That is to say, the faculty of thinking just what to do when something happens that one isn't looking for; when the house takes fire, for example, or the baby upsets the ink. [Illustration: THREE SCHOOLS OF STRATEGY] A ROOT'S WAY OF CROSSING A ROAD Take the case of tree roots crossing a country road for a drink of water. They do it just as you or I would, I'll be bound. Just suppose you and I were roots of a big tree that wanted to reach the moist bank of a stream, and there was a hard road-bed between. We can't go over the top, and the road-bed is so hard we can't go straight through on our natural level so we'll just stoop down and go under, won't we? That's exactly what the roots do. They dip down until they get under the hard-packed soil, and then up they come again on the other side and into the moist bank they started for. The roots of each kind of plant or tree have their natural level; that's one reason, as we know, why so many different kinds of plants--grass, trees, bushes, and things--get on so well together in the fields and woods. The tree roots that we have just seen crossing the road only went down below their natural level because they had to, as if the tip said: "This soil is too hard. We can never get through. Bend down! Bend down!" So the roots bent down until they came to softer soil, then forward, but always working up toward their natural level, and so it was at their natural level they came out on the other side. A ROOT'S STRANGE ADVENTURE WITH A SHOE But here's an example of "presence of mind," that nobody has accounted for. A good-sized root, working along through the soil, like Little Brother Mole, to earn its board and keep, came right up against the sole of somebody's old shoe that had got buried in the soil. In the sole were a lot of holes where the stitches used to be. The root divided into many parts, and many of these smaller roots found their way through the stitch holes. Then, coming out on the other side, these little roots got together and travelled on, side by side! [Illustration: HOW THE RAG BABIES TELL THE FORTUNE OF THE SEED CORN In what is popularly called "the Rag Baby Test" the seed corn is placed on squares marked on cloth with numbers corresponding to the numbered ears. Then they are rolled up in one of those moistened rags until they sprout.] Isn't that a story for you? But there's no accounting for it. As we have seen, the men of science know a little bit about how a root manages to turn round and round and away from the light and so on, but what kind of machinery or process is it that could tell the root if it would split up into little threads it could get through the stitch holes in that old boot? You can't imagine; at least, nobody so far has thought how it was done. But it's all true. We'll find the story and a lot of other things about the ways of roots in one of the books we'll get acquainted with when we come to the "Hide and Seek." [Illustration: © _International Harvester Company_ THIS IS THE ANSWER The seed from Ear No. 12 came out beautifully, didn't it? That from Ear No. 13 looks as if they were superstitious in Corn Land; but of course it was the fault of the seed and not of the number.] Here's another example of the same thing; what we have called "presence of mind," resourcefulness, invention. This example is even more striking, if possible, because, for one thing, it is a case where roots still more completely altered their habits to save a tree struggling for its life on a stony mountain cliff. Maeterlinck tells about it in his picturesque and dramatic style. The subject--the hero, as it were--of this story was a laurel-tree growing on some cliff above a chasm at the bottom of which ran a mountain torrent. "It was easy to see in its twisted and, so to say, writhing trunk, the whole drama of its hard and tenacious life. The young stem had started from a vertical plane, so that its top, instead of rising toward the sky, bent down over the gulf. It was obliged, therefore, notwithstanding the weight of its branches, stubbornly to bend its disconcerted trunk into the form of an elbow close to the rock, and thus, like a swimmer who throws back his head, by means of an incessant will, to hold the heavy leaves straight up into the sky." This bent arm, in course of time, struggling with wind and storm, grew so that it swelled out in knots and cords, like muscles upholding a terrific burden. But the strain finally proved too much. The tree began to crack at the elbow and decay set in. "The leafy dome grew heavier, while a hidden canker gnawed deeper into the tragic arm that supported it in space. Then, obeying I know not what order of instinct, two stout roots, issuing from the trunk at some considerable distance above the elbow, grew out and moored it to the granite wall." As if the roots, naturally so afraid of light, had heard a frantic call for help and, regardless of everything, had come to the rescue. To be sure, certain roots--the prop-roots of corn-stalks, for instance, as you have noticed--habitually reach from above ground down into the soil, and serve to brace the tall stem swaying in the winds, but trees usually have no such roots and no such habits. Yet, here a tree seems suddenly to have learned, somehow, that elsewhere in the land of plants this thing is done. But how did it learn it? Did the brownies or the gnomes tell it; or was it some of the spirits of the wind that go everywhere and see everything? It might have been the same wind sprites that carry the seeds of the laurel and the pine so far up the mountain flanks. Or it might have been the dryads, those beautiful creatures of the wood the Greeks knew so much about. I tell you there are some mighty queer things going on in the plant world, and perhaps Bud was right! "Some peoples thinks they ain't no Fairies _now_, No more yet! But they _is_, I bet!" HIDE AND SEEK IN THE LIBRARY And, what is more, real live fairies have been found right down in the world of roots! The science people call them "Bacteria," but what of that? The thing about a fairy that makes it a fairy is that it is always changing something into something else. Isn't that right? Well, that's exactly what is done by the bacteria on the roots of certain kinds of plants--clover roots, for one; and the roots of beans, peas, peanuts, and alfalfa. These plants belong to the legume family, and if you will look up the word _Legumes_ you will find out all about these fairy factories on the roots. Among other things you'll learn how small these fairies are. Why, 100,000 of the bacteria that live on clover roots, marching single file, wouldn't much more than reach across this typed page.[24] And in their little "villages" on one system of clover roots there are so many that all of them put together would make a city as big as London or New York; if the bacteria were as big as people, I mean. [24] By the way, the funny thing is that, while the bacteria that live on roots of the legumes are plants and not animals, most of them _do_ move about. Of course you have to take a microscope to see them--a very powerful microscope--and even then some kinds of bacteria you can't see until you put colored clothes on them. (Every high school boy who has worked in the "lab" knows how this is done.) And when you finally see them, a strange thing happens. You've hardly got your eye on a little Mr. Bacteria before he's two! "What's this! What's this!" you say. "Am I seeing double?" You look again and he's _four_! But don't be alarmed, you aren't seeing double; it's just the little Mr. Bacterias multiplying by division. How they multiply by division is one of the interesting things you can learn by looking them up. But it's a good thing that the bacteria people in the little nitrogen factories on the clover roots can get more farm-hands in this way, for they have a lot to do, and their work is one of the most interesting things that goes on about the place. The article in the "Country Life Reader" on "The Smallest Plant on the Farm" will tell you how important these nitrogen farmers are. You would hardly believe how great their work is, they're so quiet about it. Do you know what a human nitrogen factory is like? Well, for one thing, it's the _noisiest_ place in the world. Men, as do the bacteria, capture the nitrogen out of the air, but they do it by keeping up continual thunder and rain storms in big barrels. You will find one of these factories described in an article in _St. Nicholas_, Volume 45, page 1137. But what a fuss these human factories make! Why, in growing-time, out in the clover field, where the loudest sound you hear is the drone of the bumblebee among the blossoms, the little bacteria people down among the roots are making nitrogen so much cheaper than the big noisy factories that it only costs the farmer about one-fifth as much as the storm-barrel nitrogen. And yet, of course, it often pays to buy the artificial nitrogen, too. There are many more striking things about the habits of roots than I have had room to tell about here, which you will find in such books as Elliot's "Romance of Plant Life," Coulter's "Plant Studies," Coulter's "First Book of Botany," Allen's "Story of the Plants," Chase's "Buds, Stems and Roots," Atkinson's "First Studies of Plant Life," Darwin's "Power of Movement in Plants," France's "Germs of Mind in Plants," Gray's "How Plants Behave," Carpenter's "Vegetable Physiology," Detmer's "Plant Physiology," and Parsons's "Plants and Their Children." [Illustration: THANKSGIVING DINNER OF THE DORMICE They don't sit at the dinner table like that, to be sure, but along in the Fall and up to nearly the time of our Thanksgiving dinners, the dormice eat unusually heavy meals and put fat on their little bones to help them through the long, cold, and barren months of winter.] CHAPTER XI (NOVEMBER) All-cheering plenty, with her flowing horn Led yellow Autumn, wreathed with nodding corn. --_Burns: "Brigs of Ayr."_ There's silence in the harvest field, And blackness in the mountain glen, And clouds that will not pass away From the hill tops for many a day; And stillness round the homes of men. --_Mary Howitt: "Winter."_ THE AUTUMN STORES AND THE LONG WINTER NIGHT When the caveman was still living from hand to mouth; before he had even got as far as his first crooked stick for a plough, and when Mrs. Cave couldn't have canned a bean or a berry to save her life, even if she had had the cans, a certain little farmer already knew how to get root crops in the Fall and clean them and cut them and put them away in his little barn under the ground for Winter use. Several of these forehanded folk we have already met--the beaver and the chipmunk, among others--but since we are now at the end of the harvest year I thought we might spend this evening--the last but one, I am sorry to say, that we shall be together--in a little chat about these thrifty brothers of the wild, and how some of them are going to spend the long Winter that begins in the Autumn and lasts until Spring. I. LITTLE GRANARIES UNDER THE GROUND I was going to begin by saying that one of the most _fore_-handed of them all has _six_ feet, but as that would be almost as bad as a pun, I decided not to. You would have known, of course, that by people with six feet I meant the insects. ANTS THAT THRESH AND STORE Among the six-legged farmers, you may be sure, there have always been many who took thought for the morrow--the ants, for example. One can believe almost anything of ants. If that sluggard had gone to the ant, as wise King Solomon told him to, and learned all their ways, he would have found, among other things, how one species harvests the seeds of the plant known as the "shepherd's-purse," by twisting off the pods with its hind legs. These members of the ant family store grains of oats, nettle, and other plants. They pick up all the seeds they can find that the Autumn winds have already threshed for them, but they're not the least like that lazy man who wouldn't have the corn that was offered by kind neighbors to keep him from starving, because it wasn't shelled. If they don't find enough seeds on the ground when it comes time to think about the Winter stores they climb up and gather in the seeds themselves. On the shepherd's-purse, for example, the ant climbs up, selects a well-filled pod which is not sufficiently dried to have had its seeds threshed out by the winds, takes the pod in its little jaws and then--watch him--turns round and round on his hind legs until he twists it off! Then with it he carefully moves down the stem, like a baggageman carrying a big trunk from the third apartment; only the baggageman carries the trunk in front of him or on his shoulders, while the ant backs his way down. Sometimes two ants work together, one twisting, the other cutting away the fibres with its teeth. Sometimes they drop the pods to companions waiting below, and these other helpers never run off with it, but carry it to the common granary; for ants always play fair. [Illustration: HOW THE ANTS WORK IN DIGGING OUT THEIR GRANARIES] And they have granaries, these ant farmers--hundreds of them, made just for that, each about the size of father's watch. [Illustration: THE INSIDE OF THE GRANARY Underneath the dome of the ant house you see in the previous picture, are flat chambers like these, connected by galleries, in which the grain is stored. One is prepared not to be surprised at anything about ants, but listen to this: The Agricultural Ants not only gather and store this grain, but they actually plant and cultivate it. They sow it before the wet season in the Fall, keep it weeded, and gather it in June of the following year. Seems incredible, doesn't it? But I'm only telling you what McCook, an ant student, recognized everywhere as a reliable observer, saw these six-footed Texas farmers actually do.] Now here's a thing; you stow away a lot of seeds in a little hill where, of course, there's moisture, and what's going to happen? Those seeds are going to sprout and grow and spoil, and this, of course, destroys their value as food. Then what are you going to do? Of course, a human farmer would put his grains in a dry granary where they couldn't sprout, but you see the ants haven't any granary of that sort; nothing but those little holes in the moist ground. Just what they do to these seeds has not been discovered. They do something that keeps them from either spoiling or sprouting. But, when they get ready for these seeds to grow, they let them grow; not so that they can raise a crop, but for the same reason that the Chinaman lets the barley sprout that he uses in making chop-suey; so that it will be nice and soft to eat. This growing digests the starch in the seeds into sugar. When the sprouts have grown as far as the ants want them to, they gnaw the stalk a little, and cut off the roots with their mandibles. When this sugar-making has gone on long enough the ants bring all the plants out into the sun and let them lie there until they are nice and dry. Then they put them in their barns, and as long as Winter lasts they live on this sweet flour, grinding it in their mouth mills as they go along. Why, it's like living on cookies, almost! Only the ants have been used to this steady diet of sweets for ages, and it doesn't hurt _their_ little stomachs as it would ours. [Illustration: CLEANING UP AFTER THE DAY'S WORK While the Agricultural Ants don't take a bath after the day's work they do the next best thing. They give each other a kind of massage, and they evidently find it very enjoyable. You know how the cat loves to be stroked, dogs and horses to be patted, and little pigs to have their backs scratched. The ants below are giving each other a massage (left, abdomen; right, legs and sides). The lady above who seems to be braiding her back hair, is cleaning her antennæ.] This particular kind of a farming ant is called the Attabara, but there's another kind more wonderful still. If we want to call on them by their scientific names--these remarkable little creatures I'm going to tell about now--we'll have to go to Texas and ask if the _Pogononyrmex barbatus_ family are at home. "Oh, to be sure," says the gentleman who first introduced them to scientific society,[25] "just come with me." [25] Rev. H. S. McCook: "The Agricultural Ant of Texas." So he takes us over into Texas and shows us the ants at work. They destroy every plant on their little farms except that known as ant-rice. Compared to the size of the ants themselves, these grain-fields are giant forests, far bigger than the Sequoia Forests of California. The ants watch for rain at harvest-time as anxiously as a farmer, and on the first sunny day, they do their cutting and hurry the grain into the barn. Then on later sunny days, they bring it out to dry before finally storing it away. "Well," you say, "is there anything left that these farmers _don't_ do?" I can't think of anything except the planting. One observer says that they do actually plant the seeds, and Doctor McCook says, he wouldn't be surprised if they did, but he never saw them do it. [Illustration: THE OLD HOME PLACE This is the farm of some Agricultural Ants in Texas. See the granary and the roads leading to it? They collect and store the seeds of a plant which from this fact is called "ant-rice." It looks like oats and tastes like rice. All plants growing around the nest--which is also called the granary--the ants cut away, so clearing a space for 10 or 12 feet. Roads 5 inches broad near the nest, but narrowing as they recede, are made for hundreds of feet in different directions.] In tropical America there is a species of ant that raises "mushrooms"; at least a kind of fungus that passes for mushrooms with the ants. They don't exactly set the mushrooms out, but they save time by planting both the mushrooms and the leaves that make them as one and the same job. This is how they do it. They climb the trees, cut circular pieces of leaf with their scissor-like jaws and carry them back to low, wide mounds in the neighborhood of which they allow nothing to grow; the purpose being, as it is supposed, to ventilate the galleries of their homes by keeping a clear space about the mound. HOW THE ANTS RAISE MUSHROOMS The leaves are used as a fertilizer on which grow a small species of mushrooms. The leaves are first left out to be dampened by the rain, and are carried into the ants' cellars before they are quite dry. In very dry weather the ants work only during the cool of the day and at night. Occasionally inexperienced ants bring in grass or unsuitable leaves, but these are carried out and thrown away by older members of the family. But you see how valuable all these leaves are to the soil. [Illustration: ANTS CARRYING LEAVES FOR THE MUSHROOM CELLAR You'd never guess what the ants are going to do with those leaves! Read what it says on this page about these six-legged epicures.] MR. HAMSTER'S THRESHING HARVESTER Of course, we always expect the ants to do extraordinary things, but one of those four-legged farmers I mentioned in the beginning of the chapter anticipated the principle of the very latest type of threshing-machine. It's a fact. This remarkable little animal threshing-machine is called the hamster. He is found in Europe east of the Rhine and in certain portions of Asia. He does both his cutting and threshing in his field; something the Gauls did in the days of the Romans in a crude way, but which men of our day have only got to doing in recent years. He pulls down the wheat ear, cuts it off between his teeth, and then threshes it by drawing the heads through his mouth. The grain falls right into sacks as fast as it is threshed; just as it does in those huge, combined reapers and threshers that you see on our big wheat farms. Mr. Hamster's sacks are his cheek-pouches, one on each side. When these are filled, this little threshing-machine turns itself into an auto, a commercial truck, and off it goes with its load of wheat to the little barn hidden in the ground. These cheek-pouches, by the way, reach from the hamster's cheeks clear back to his shoulders, and both of these pouches will together hold something like a thousand grains of wheat. He empties them by holding his paws tight against the side of his face and then pushing forward. Rather a clever unloading device, too; don't you think so? Just as good for Mr. Hamster's purposes as the endless-chain system at the Buffalo grain elevator that Mr. Kipling admired so much. And in the mere matter of the amount of grain handled, the work of the hamster is not to be laughed at. The peasant farmers are very glad to find a hamster granary, which, of course, they promptly take possession of by due process of law: "The good old rule, the simple plan That they shall take who have the power, And they shall hold who can." One of Mr. Hamster's neighbors, the field-rat of Hungary and Asia, stores his grain right in the house--the place where he lives with his family. Mr. Hamster, however, has his barns separate from his home. Sometimes he has one, sometimes two; and the older members of the community may have four or five. II. MR. VOLE AND HIS ROOT CELLAR The farmer I mentioned at the beginning of this chapter, who is so thrifty about his root crops and so neat, belongs to the Vole family. He lives away over in Siberia and his full name is _Arvicola economus_. In gathering his crop of roots, he first digs a little trench around them and lays them bare. Then he cleans them off nicely so as not to fill his storehouse with dirt; cuts them up in sizes convenient for carrying, and then hauls them home and piles them up in little cellars made specially for them. He only takes one piece at a time, walking along backward and pulling it after him with his teeth. He travels long distances in this fashion, going around tufts of grass, stones, and logs that lie in the way. When he gets home, he backs in the front door and into the living-room, and then into the barns which are back of the living-room. There are several of these and they are at the end of a long crooked passage. Some of the Vole family make a specialty of wheat. One species of these wheat harvesters used to be common in Greece. He made such a nuisance of himself--from the Greek farmer's standpoint--that the Greeks had a special god to get after him; Apollo Myoktonos, "Apollo, Destroyer of Mice."[26] For the vole is just a kind of field-mouse. The runs of these wheat-harvesting voles are eight to twelve inches below the ground, and are connected with the surface by vertical holes. The end of the run is enlarged into a big room for the nest, and there are special rooms leading from the main runway that are used for the storing of the grain. These voles do their harvesting in the evening. Standing on their hind legs and holding to the stock with their little paws as a beaver clasps a tree, they cut off the wheat head with their teeth. They work very fast. [26] Strictly speaking, I presume this was the same Apollo who carried the sun about in his chariot, and "Destroyer of Mice" was one of his many nicknames. HOW DID THESE FARMERS LEARN TO STORE? Neither the voles nor any other of these interesting farmers and warehousemen used to get much credit for what they did. The fact that they helped themselves to some of the good things of earth annoyed Man, of course, and then, when it came to the matter of intelligence, conceited Mr. Man said: "Oh, _that's_ just _instinct_." But nowadays when scientists have begun to study to find out what "instinct" really is, it is thought that man's brother animals, although they are born with more knowledge of how to do things--with more of what we call "instinct"--have also learned by experience just as man did. It is argued that the storing habit was forced on animals wherever the climate cut off the food-supply for a time--either because it was too cold or too hot. The idea of putting something by for a rainy day appealed particularly to the burrowers because they are a timid lot. Not being able to defend themselves very well against their enemies they were obliged to pack up what they could and hurry to some hidden eating-place. That is where the cheek-pouches, which many of them have, come in handy. They are also very industrious, and as the seeds and nuts on which they lived began to ripen, they just couldn't resist the impulse to gather and gather and gather more than they could possibly eat at the time. So, as a result of this habit, food piled up in their underground homes. Then, as they were kept indoors by cold weather or by their enemies, they took to eating more and more from the pantry shelf, and thus the members of the family that were the busiest and, therefore, had the most to eat would naturally survive and leave children of a similar disposition, while the less thrifty would die off. III. THE LONG WINTER SLEEP Some of these forehanded people, instead of putting their Winter supply of food in the ground, put it on their bones. That is to say, before turning in for the Winter, they get as fat as can be and then live on this fat until Spring. A great advantage of this system of storage is that it is particularly pleasant work--you eat and eat and enjoy your meals, that's all. Another advantage is that you can't be robbed of your store as easily as the hamster, for example, frequently is. You carry it right with you wherever you go. There are a lot of curious things about this hibernation. Not only will warmth arouse the sleepers but also extreme cold, and after the extreme cold may come another sleep from which the sleepers never awaken; in other words, too much cold kills them. So the object of burying one's self as the ground-hog does, or under the snow as rabbits do, or in hollow caves and trees as Brer Bear does, is to keep from getting too cold. Sometimes two or more "bunk" together, as little pigs do on cold March days. The body of each helps to keep his bedfellows warm. IT'S THE COLD THAT MAKES ONE DROWSY It is the cold itself that seems to make hibernating animals feel sleepy; just as it does human beings. At a moderate temperature, say 45 or 50 degrees, dormice and hedgehogs will wake up, eat something, and then go to sleep again. The dormouse usually wakes in every twenty-four hours, while the hedgehog's Winter naps are two or three days long. Hunger seems to be the cause of their waking, just as it is with babies. The little dormouse, as the air grows colder, gradually dozes off, and his breathing is very deep and slow. As the temperature rises, he begins to take shorter and more rapid breaths and gradually wakes up. Then, if he is in his own little home under the ground, he feeds on the nuts and other foods that he stored in Autumn and drops off again. He sleeps from five to seven months, depending on the weather. Moles and shrews, so far as observation goes, don't hibernate. The moles simply dig deeper, and there they find worms and insects that are buried away from the reach of frost. The shrews hunt spiders and hundred-legged worms and larvæ in holes and crannies of the soil or beneath leaves of ground plants and old logs. [Illustration: LITTLE HEDGEHOG IN MAN'S HAND] A queer thing is that the hedgehog, which belongs to the same family as the shrew and the mole, is dead to the world all Winter. Like all complete hibernators he stops breathing entirely. The reason for this difference between the hedgehog and the mole is that the mole doesn't need to go to sleep, because he digs below the frost-line. As for the shrews, they have little bodies and are very active, and so get themselves food and keep warm, while the hedgehog is so much bigger and slower that, when there is so little to eat and it is so cold, he would either freeze or starve to death if he went about looking for food. He finds it cheaper to turn in and sleep than to work. [Illustration: A HEDGEHOG AND HER BABIES] None of the tree-squirrels seem to take any unusually long naps in the Winter. We often see them around on pleasant days in the parks and in the woods. They run out, get a few nuts from their stores, and then back again to their nests, but the chipmunks and the gophers, who are closely related to the squirrels, stay from late Autumn to Spring in their burrows, where they have plenty of food stowed away, and they sleep most of the time. In the home of four chipmunks was found a pint of wheat, a quart of nuts, a peck of acorns, and two quarts of buckwheat, besides a lot of corn and grass seed; all to feed four fat chipmunks. So, with such plentiful supplies, it is not surprising that after their long Winter sleep the chipmunks are as sleek as can be and as fat as butter, while Mr. Bear comes out in the Spring lean and with his hair all mussed up and as hungry as--well, as hungry as a bear! All the bear family, except the polar bears, retire to caves or some sheltered spot under a ledge of a rock or the roots of a big tree. Among the polar bears the rule seems to be that it's Mamma Bear only who goes to bed for the Winter. She is careful to put on enough fat not only for herself, but so that the babies that come along in the Spring will have plenty of milk. She is buried by snow that drifts on her and her breath melts a funnel up to the fresh air. IV. MR. GROUND-HOG AND HIS SHADOW The woodchuck, like the bear, is a "meat-packer." People talk about him more or less in February. His other name is "ground-hog" and his shadow is quite as famous as he is. But is there anything in that old weather saw? Well, yes and no. You see, it's like this: Mr. Ground-Hog goes to bed very early in the Fall--long before the cold weather sets in--and so he is up very early the next Spring; long before the snow is all gone and, as it is with the other all-Winter sleepers, a little extra warmth may wake him up. Along toward morning, you know, we all begin to stir around in our beds and get half awake. So in addition to the fact that it is nearly daybreak for him--that is to say, Springtime--let there come along a bright, warm day in February--the second is as good as any other--and Mr. Ground-Hog is likely to come out of his hole. And, if he does, of course he will see his shadow, after which there is likely to be quite a lot of cold weather. HOW WEATHER AVERAGES UP Not that his shadow makes any difference, but the point is that if you have much warm weather _early_ in February you are likely to have colder weather _later_ and running on into March. It's just the law of averages, that's all. You see it running through the year--this averaging up of weather; it just sways back and forth like a pendulum. Take it in any storm of rain or snow; first the clear sky, then the clouds, then the downfall, and after that the clear sky again. Take any month as a whole, or a year as a whole, and it's the same way; you get about so much rain, so much sunshine, so much heat and cold. The United States Weather Bureau went to work once and, from the records, classified the storms for the last thirty years, and they found that about fifteen storms each year start over the region of the West Gulf States, twelve begin over the mountains of Colorado, forty cross the country from the North Pacific by way of Washington and Oregon; and so on, just about so many from each region each year. [Illustration: _The Last Snow, by Lippincott_] And records and old diaries, going back a hundred years, show that the longer the period you examine for weather facts, the closer the average. The weather for one ten-year period will be almost as much like any other ten-year period, as the peas in a pea shell are like each other. Coming back to the subject of February weather, we find in the diary of an old resident of Philadelphia in 1779: "The Winter was mild, and particularly the month of February, when trees were in bloom." He doesn't say anything about the ground-hog, but there is this to be said of the sharper changes of February and March, that at this season the earth is getting more and more warmed up and yet the cold winds from the North don't like to go; so there is a constant wrestling-match, and it is the wrestling of the winds one way and another that brings the changes of the weather. So if the South Winds get the best of it early in February, the North Winds, with their cold weather, are likely to win later in the month, and vice versa. Moreover, if you believe in the ground-hog proverb you are apt to _notice_ the warm days (or cold days, as the case may be) for the next six weeks after February 2, and you _won't_ notice so much the weather that doesn't fit your proverb! It's a way we all have; _seeing_ the things that go to prove what we believe and _overlooking_ the things that don't. [Illustration: MR. GROUND-HOG AND HIS SHADOW "But is there anything in the old weather saw? Well, yes and no. Mr. Ground-Hog goes to bed early in the Fall and is up early next Spring. Let there come a bright, warm day in February--the second is as good as any--and Mr. G.-H. is likely to come out and see his shadow. And if you have warm weather early in February you are likely to have colder weather later. It's the law of averages, that's all."] HIDE AND SEEK IN THE LIBRARY I don't care what it says in "Alice in Wonderland," dormice never drink tea; although dormice have been at table with people ever since the days of the Romans. Dormice are still eaten in some parts of Europe, and the Romans used to keep them as part of their live stock. The European dormouse is really a little squirrel. Varro's "Roman Farm Management" (of which you are apt to find a good translation in the public library) tells how the Romans put their dormice in clay jars specially made, "with paths contrived on the side and a hollow to hold their food." Crocodiles and other tropical animals take very long naps during the hottest weather. Hartwig's "Harmonies of Nature" tells about an officer who was asleep in a tent in the tropics, when his bed moved under him, and he found it was because a crocodile, in the earth beneath, was just waking up! Imagine what the dried-up ponds and streams of the llanos of South America must look like when the rainy season comes on, after the dry spell, with crocodiles asleep just under the surface everywhere. Doctor Hartwig's book tells. But the most remarkable case of drying up that ever I heard of was that of the Egyptian snail in the British Museum, that Woodward tells about in his "Manual of the Mollusca." This snail was sent to England, simply as a shell, in 1846. Never dreaming there was anybody at home, they glued him to a piece of cardboard, marked it _Helix Desertorum_, and there he stuck until March 7, 1850, when somebody discovered a certain thing that indicated that there _was_ somebody "at home," and that he was alive. They gave him a warm bath and he opened his four eyes on the world! In his "Animal and Vegetable Hedgehogs" ("Nature's Work Shop") Grant Allen tells why the hedgehog works at night and sleeps in the daytime. How he fastens on his winter overcoat of leaves, using his spines for pins, and how funny it makes him look. How Mother Nature manages to have breakfast ready for him in the Spring just when he is ready for _it_. How hedgehogs use their spines when they want to get down from a high bank or precipice real quickly. How their eyes tell how smart they are; for a hedgehog is smart. You will also find interesting things about hibernation in Gould's "Mother Nature's Children" and Richard's "Four Feet, Two Feet and No Feet." In one of his essays on nature topics--"Seven Year Sleepers"--Grant Allen tells how the toad goes to bed in an earthenware pot, which he makes for himself, and how this habit may have helped start the story that live toads are found inside of stones. Ingersoll, in that delightful book I have already referred to several times, "The Wit of the Wild," calls the pikas "the haymakers of the snow peaks." In his article on these interesting little creatures, he tells why you may often be looking right at one and still not see it; why the pikas gather bouquets and why they always lay them out in the hot sun; why their harvest season only lasts about two weeks, and why, although they usually go to bed at sunset, they work far into the night in harvest time. "The Country Life Reader" has a good story of a woodchuck named "Tommy." Among other things it tells about the variety of residences a woodchuck has; and why animals that work at night, as all woodchucks do, have an unusually keen sense of smell. Can you guess why? The reason is simple enough. Here's a clever bit of verse about the woodchuck by his other name, that I came across in some newspaper: "The festive ground-hog wakes to-day, And with reluctant roll, He waddles up his sinuous way And pops forth from his hole. He rubs his little blinking eyes, So heavy from long sleep, That he may read the tell-tale skies-- Which is it--wake or sleep?" Ingersoll's "Nature's Calendar" tells why Brer Bear stays up all winter when there is plenty of food, but goes to bed if food is scarce; how he uses roots of a fallen tree to help when he is digging his winter house; how he makes his bed and what he uses for the purpose; how the winds help him put on his roof, and how he locks himself in so tight that he can't get out until spring, even if he wants to. [Illustration: "IT MUST BE BRER BEAR!"] CHAPTER XII (DECEMBER) While man exclaims "See all things for my use!" "See man for mine!" replies the pampered goose. --_Pope: "Essay on Man."_ THE BROTHERHOOD OF THE DUST But whether they store it in their little barns, like the chipmunk, or on their bones, like Brer Bear, these farmers deserve more friendly understanding than they usually get from that two-legged farmer, Mr. Man. Just think of the ages upon ages that they have been at work, these humble brothers of ours, and their ancestors--making the soil that gives us food--and yet after all this Mr. Man comes along and says: "Get out of my fields!" I. THE LORD OF CREATION "Oh, but--please Mr. Man--we were here _first_!" Was that the dormouse speaking? Anyhow, whoever it was, I think he was more than half right, don't you? Mr. Man, when he complains of these people, is apt not only to forget what he owes to them but in claiming that what they eat is wasted, to forget what a waster he is himself--wasting the soil and wasting the trees and everything. BRER BEAR GIVES MR. MAN A PIECE OF HIS MIND "Now just don't you overdo this Lord-of-Creation business, Mr. Man," says a deep, growly voice. (It must be Brer Bear!) "Other people have rights as well as you! And if you'd tend to your work half as well as they've attended to theirs, for ages before you were born, this would be a better world to live in; a good deal better, and there'd be a lot more of the good things of life to go around. "And now that you've waked me up I'm going to tell you something else. You human beings are not only a hard lot, but a stupid lot. You think you're mighty smart, don't you, with your bear-traps and your shooting machines that you shoot each other with, as well as shooting the rest of us! But do you know what _I_ think? I think if some of us--the bears or the beavers or the ants, for example--had had half your chance they'd have been twice as smart; and then we bears might have gone around shooting at you, the way Mr. Beard showed once in one of those funny pictures of his." [Illustration: HUNTING THAT DOESN'T HURT Hunting with a gun is great sport. But now you know from my story what good the animals do in the world you may not like so well to kill them. And there is a new kind of hunting that is just as much fun--with a camera. This picture shows a boy in ambush, ready to shoot, by pressing a bulb; for the bird in the tree is exactly in front of the shutter of the camera.] You see, Brer Bear has a good tongue in his head as well as a wise old head on his shoulders, and I must say he's entirely right when he makes the statement that human beings aren't anywhere near as bright, according to the chance they've had, as the bears and the beavers and the ants and the bees, and many others that could be named. Why, do you know that in the whole history of the human race there have been only a few really bright people, like Mr. Shakespere and Mr. Kipling, Mr. Archimedes and Mr. Edison. It was such men as these--not over two thousand or three thousand out of the millions upon millions of human beings who have lived on the earth--that raised the rest up from the Stone Age to where they are to-day. "Into the coarse dough of humanity an infrequent genius has put some enchanted yeast." That's the way a recent English writer puts it. And then he goes on to say that if snakes and beasts of prey had been as clever as the bees and ants and beavers, men would have been exterminated. They could have saved themselves only by getting on with their education, climbing up the grades, a good deal faster than they have done. He says it--this Englishman--almost in the very words of Brer Bear. And we can imagine Brer Bear going on, taking up where the Englishman leaves off. "In other words," says Brer Bear, "it was because the bees and ants and beavers went on minding their own business, neither hurting you nor giving any pointers to the wolves and the lions and the snakes, that you're still here, Mr. Lord Man! That's part of the story of how you got to be lord of creation. Now listen to the rest of it:[27] [27] Here imagine Brer Bear putting on his specs and reading from the book. "'The cave-dwellings of men were stolen from cave-lions and cave-bears; their pit-dwellings were copied from the holes and tunnels burrowed by many animals; and in their lake-dwellings they collected hints from five sources: natural bridges, the platforms built by apes, the habits of waterfowl, the beaver's dam and lodge, and the nests of birds. In the round hut, which was made with branches and wattle-and-daub, stick nests were united to the plaster work of rock martins. Yes, a good workman in the construction of mud walls does no more than rock martins have done in all the ages of their nest-building. "'Suppose primitive man cut down a tree with his flint axe, choosing one that grew aslant over a chasm or across a river; or suppose he piled stepping-stones together in the middle of a waterway, and then used this pier as a support for two tree trunks, whose far ends rested on the bank sides. Neither of these ideas has more mother wit than that which has enabled ants to bore tunnels under running water, and to make bridges by clinging to each other in a suspension chain of their wee, brave bodies.'" HOW MAN HELPED HIMSELF TO OTHER PEOPLE'S IDEAS So you see that isn't just Mr. Bear's way of putting it; there are human beings who think a good deal as he does. Myself, I agree with Brer Bear and Brer Brangyn.[28] For man certainly, take him by and large, doesn't always set a good example to his fellow animals, either in making the best of his _opportunities_ or in giving his humble brothers a square deal. [28] That's the name of the Englishman I've just been quoting. He's a famous artist, but, like most cultivated Englishmen, can also write a good book when he feels like it. [Illustration: _From "Bugs, Butterflies and Beetles," by Dan Beard. By permission of J. B. Lippincott_ IF BEETLES WERE AS BIG AS BOYS Our six-footed brothers are wonderfully strong in proportion to their size, and it would go hard with us if beetles, for example, were as big as boys.] Do you know what I felt like saying, back there in Chapter IX, when we were speaking of kingfishers, and how certain parties had given it out that kingfishers eat big fish that otherwise might be caught with a hook or a seine? This is what I _felt_ like saying: "What if they do? Who's got a better right?" Then they'd say--these men--I suppose: "Why, _we_ have; _we're_ sportsmen!" "Oh, yes," I'd say, "you're the kind of sportsman that's so afraid somebody else will see and kill something before you do; particularly if that somebody is itself a wild creature that has to earn its living that way and only takes what it needs for its family!" And they're so good-natured about it, most of these country cousins of ours, that we walked right in on and ordered out, Cousin Woodchuck, for instance. "The woodchuck can no more see the propriety of fencing off--though he admits that stone walls are fine refuges, in case he has to run for it--a space of the very best fodder than the British peasant can see the right of shutting him out of a grove where there are wild rabbits, or forbidding him to fish in certain streams. So he climbs over, or digs under, or creeps through, the fence, and makes a path or a playground for himself amid the timothy and the clover, and laughs, as he listens from a hole in the wall or under a stump, to hear the farmer using language which is good Saxon but bad morals, and the dog barking himself into a fit."[29] [29] Ingersoll: "Wild Neighbors." II. THE SCHOOL OF THE WOODS AND FIELDS I don't mean to say, mind you, that the farmer hasn't any rights in his own fields, and that he should turn everything over to the woodchuck and the rest, but I do mean to say that our wild kinsmen have rights and that there is a lot more to be got out of them than their flesh or their hides or the pleasure of killing them. For one thing, the ant and the angleworm, the birds and the woodchucks, the little lichens and the big trees, the winds and the rains, are all teachers in the Great School of Out-of-Doors, and in this school you can learn almost everything there is to be learned. It's really a university. Nature study, as you call it in the grades, besides all the facts it teaches you, trains the eye to see, and the ear to listen, and the brain to reason, and the heart to feel. STORY OF THE LONDON BANKER AND HIS ANTS [Illustration: SIR JOHN LUBBOCK The great London banker who carried ants in his pocket.] Once there was a London banker who used to go around with--what do you think--in his pockets? Money? Yes, I suppose so; but what else? You'll never guess--ants! He was a lot more interested in ants than he was in money; and so, while the business world knew him as a big banker, all the scientific world knew him as a great naturalist. He wrote not only nature books but other books, including one on "The Pleasures of Life," and among life's greatest pleasures he placed the "friendship," as he puts it, of things in Nature. He said he never went into the woods but he found himself welcomed by a glad company of friends, every one with something interesting to tell. And, in speaking of the wide-spread growth of interest in Nature in recent years, he said: "The study of natural history indeed, seems destined to replace the loss of what is, not very happily, I think, termed 'sport.'" And isn't it curious, when one comes to think of it, why a man should take pleasure in seeing a beautiful deer fall dead with a bullet in its heart? You'd think there would be so much more pleasure in seeing him run--the very poetry of motion. Or, why should a boy want to kill a little bird? You'd think it would have been so much greater pleasure to study its flight or to listen to the happy notes pour out from that "little breast that will throb with song no more." WHY MAN KILLS AND CALLS IT "SPORT" Among other animals that this banker naturalist studied was man himself; man when he was even more of an animal than he is to-day, and he came to the conclusion that this curious killing instinct is a survival of the long ages when man had to earn his living by the chase. "Deep in the gloom of a fireless cave When the night fell o'er the plain And the moon hung red o'er the river bed, He mumbled the bones of the slain. Loud he howled through the moonlit wastes, Loud answered his kith and kin; From west and east to the crimson feast The clan came trooping in. O'er joint and gristle and padded hoof, They fought and clawed and tore."[30] [30] Adapted from Langdon Smith. Not a very pretty picture, is it? Yet it's true. But, fortunately, so is this one of the happiest hours of the caveman's grandchild. "Oh, for boyhood's painless play, Sleep that wakes in laughing day, Health that mocks the doctor's rules, Knowledge never learned of schools: Of the wild bee's morning chase, Of the wild flower's time and place; Flight of fowl, and habitude Of the tenants of the wood; How the tortoise bears his shell, How the woodchuck digs his cell And the ground-mole sinks his well. Of the black wasp's cunning way, Mason of his walls of clay And the architectural plans Of gray hornet artisans. For, eschewing books and tasks, Nature answers all he asks."[31] [31] Whittier's "Barefoot Boy." Some boy wrote to John Burroughs once, and asked how to become a naturalist. In his reply, Burroughs said: "I have spent seventy-seven years in the world, and they have all been contented and happy years. I am certain that my greatest source of happiness has been my love of nature; my love of the farm, of the birds, the animals, the flowers, and all open-air things. "You can begin to be a naturalist right where you are, in any place, in any season."[32] [32] "Pictured Knowledge." [Illustration: WHOSE AUTOGRAPH IS THIS? If you're a boy scout you will probably recognize this autograph in the snow. If not look it up in the Boy Scout Handbook.] It is the wholesomest, most inspiring reading in all the world, this Book of Nature. And there is simply no end to it. Just see what all we've been led into merely in following out the story of a grain of dust; and even then, I've only dipped into it here and there, as you can see by the hints of things to be looked up in the library. If we had gone into all the highways and byways of the subject--for it's all one continued story, from the making of the planets, circling in the fields of space, to the making of the little dust grains that are whirled along in the winds of March--if we followed the story all through we would have to have learned professors to teach us Astronomy, Geology, Chemistry, Zoology, with its subdivisions of Paleontology, Ornithology, Entomology, and so on; a whole college faculty sitting on a grain of dust! III. THE WORLD BROTHERHOOD An obvious thing in Nature is what is called "the struggle for existence"; animals and plants fighting among themselves and against enemies of their species in the universal struggle for food. What is not so obvious, is how the whole world of things works together toward the common good. HOW THE LICHENS AND THE VOLCANOES WORK TOGETHER For example, working with those quiet little people, the lichens, is one of the biggest and noisiest things in the world--the volcano. The volcanoes not only pour into the air vast quantities of carbon-gas, which is the breath of life to plants, but help the lichens and the rest of the soil-makers with their work in other ways. And as the volcanoes help the lichens get their breath, the lichens forward the world service of the volcanoes by turning their lava into soil; in course of time, hiding the most desolate of these black iron wastes under a rich garment of green. It is thus the dead lava comes to life, and it is the very smallest of the lichen family that starts the process. [Illustration: _Courtesy of the Northern Pacific Railway_ HOW THE DEAD LAVA COMES TO LIFE Lava, after it has been converted into soil, by the agents of decay, makes the richest land in the world. This picture shows a vineyard on the fertile plains overlooked by Mt. Ranier, which is an extinct volcano. In the days when Mt. Rainer was being built these plains were covered with molten lava.] Among the two principal gases of the air there is a working brotherhood; just as there is between the plants and the animals in their great breath exchange. The oxygen in the air makes a specialty of crumbling up rock containing iron. It rusts this iron into dust; while the CO_{2}, as the High School Boy calls what I have called carbon, for short, goes after the rocks that contain lime, potash, and soda. Working with both these gases is the frost that, with its prying fingers, enlarges the cracks in stones, and so allows the gases of the water and the air to reach in farther than they could otherwise do. Every Winter, with its frost and its storing up of moisture in the great snow-fields of the mountains, is a benefit to the lands and their people, but the Ice Age, "The Winter that Lasted All Summer,"[33] not only worked wonders in other ways, but was of far greater benefit to the soil because it was so much more of a Winter. [33] "The Strange Adventures of a Pebble." Mr. Shakespere, in his day, didn't know anything about an Ice Age, but Brer Bear might have quoted certain lines of his, just the same: "Blow, blow, thou winter wind, Thou art not so unkind As man's ingratitude. Freeze, freeze, thou bitter sky, Thou dost not bite so nigh As benefits forgot."[34] [34] "As You Like It." [Illustration: _Courtesy of the Northern Pacific Railway_ ASTER GROWING IN VOLCANIC ASH ON MT. RANIER] THE GREAT PLOUGHS OF THE ICE AGES With all the work the other agencies do in changing the rock into soil, and fertilizing and refreshing it with additions from the subsoil, there still remains an important thing to be done, and that is to mix the soil from different kinds of rock. This is still done constantly by the winds and flowing waters, but every so often, apparently, there needs to be a deeper, wider stirring and mixing. This the great ice ploughs and glacial rivers of the Ice Ages did. And they do it every so often, probably; for there was more than one Ice Age in the past, and, as Nature's processes do not change, it is more than likely there will be more ice ages and more deep ploughing and redistribution of the soil in the future. As you will see, if you take the trouble to look it up in "The Strange Adventures of a Pebble," it is thought we may now be in the springtime of one of those vaster changes which bring Springs lasting for ages, followed by long Summers and Autumns, and by the age-long Winters and the big glaciers and all. [Illustration: HOW THE MOUNTAINS FEED THE PLAINS "The elevations of the earth's surface provide for it a perpetual renovation. The higher mountains suffer their summits to be broken into fragments and to be cast down in sheets of massy rock, full of every substance necessary for the nourishment of plants, and each filtering thread of summer rain is bearing its own appointed burden of earth to be thrown down on the dingles below."] The glaciers, moving over thousands of miles and often meeting and dumping their loads together on vast fields, did the very same thing for everybody that England does for herself to-day in bringing different kinds of fertilizers from all over the world to enrich her farms. I'm very glad to speak of this because the author of the story of the pebble may have left a bad impression of the glaciers--"The Old Men of the Mountain"--as farmers, by what he said about their carrying off the original farm lands of New England, and leaving a lot of pebbles and boulders instead. While these pebbles have not produced what you would call a brilliant performer among soils, they have made a good, steady soil that in New England has helped greatly in growing farm boys into famous men, while the pebbles of Wisconsin have been of immense service to her famous cows. In the counties in Wisconsin where there are plenty of pebbles scattered through the soil, the production of cheese and butter is something like 50 per cent greater than it is in regions where there are comparatively few pebbles.[35] [35] Martin: "Physiography of Wisconsin." [Illustration: _From Tarr and Martin's "College Physiography." By permission of the Macmillan Company_ GOOD CROPS FROM NEW ENGLAND'S STONY FIELDS While the stones, big and little, with which the fields of New England are so richly supplied have not produced what you would call a brilliant performer among soils, they have made a good steady soil that can turn its hand to almost anything, and that has helped greatly in growing farm boys into famous men. In building those stone fences, for example, the boys learned that it always pays to do your work well. A hundred years is merely the tick of a watch in the life of a fence like that!] The soils of New England are like the New Englander himself, they can turn their hands to almost anything; raise any kind of crop suited to the climate, while richer soils are often not so versatile. The reason is that these pebbles were originally gathered by the glaciers from widely separated river-beds, and so contain all varieties of rock with every kind of plant food in them. It takes a long, long time to make soil out of bed-rock, but in the case of soils in which there are a great many pebbles it is different; and you can see why. On a great mass of rock there is comparatively little surface for the air and other pioneer soil-makers to get at, and so decay is slow; while the same amount of rock broken up into pebbles presents a great deal of surface for decay. If you will examine with a glass--an ordinary hand-glass will do--one of these decaying pebbles lying embedded in the grass you can trace on it a number of wrinkly lines--sometimes even a network. These are the marks, the "finger-prints," of little roots. Little roots, as we have seen, are very wise. They always know what they are about, and the fact that they cling to the pebbles in this way means that they are getting food out of them. And that's right where the cows of Wisconsin come in. The rootlets of the grasses get a steady supply of food from the decaying surfaces of these pebbles scattered through the pastures, and then pass it on to the cows. [Illustration: HOW PEBBLES HELP FEED THE COWS You'll think I'm joking at first, but it's the truth: _Pebbles are good for cows._ Otherwise how are you going to account for the fact that in the counties in Wisconsin where there are plenty of pebbles the production of cheese and butter is something like 50 per cent greater than it is in regions where there are comparatively few pebbles? Examine, with a hand-glass, the "finger prints" of the little roots on a decaying pebble, and see if you can't guess why. Then read the explanation in this chapter.] TEAMWORK BETWEEN MOUNTAINS AND PEBBLES But now, going from little things to big things again, notice how the mountains and the pebbles are linked together in this chain of service. The mountains, too, continually feed the plains. Ruskin, in speaking of this great service, says: "The elevations of the earth's surface provide for it a perpetual renovation. The higher mountains suffer their summits to be broken into fragments, and to be cast down in sheets of massy rock, full of every substance necessary for the nourishment of plants. These fallen fragments are again broken by frost and ground by torrents into various conditions of sand and clay--materials which are distributed perpetually by the streams farther and farther from the mountain's base. Every shower which swells the rivulets enables their waters to carry certain portions of earth into new positions, and exposes new banks of ground to be mined in their turn. The turbid foaming of the angry water--the tearing down of bank and rock along the flanks of its fury--these are no disturbances of the kind course of nature; they are beneficent operations of laws necessary to the existence of man, and to the beauty of the earth; ... and each filtering thread of summer rain which trickles through the short turf of the uplands is bearing its own appointed burden of earth to be thrown down on some new natural garden in the dingles below." [Illustration: THE MILL OF THE EARTHWORM AND THE EARTH MILLS OF THE SEA "From the gizzard mills of the earthworm to the great earth mills of the sea, all are--most evidently--parts of one great system." (In the picture on the left an earthworm has been laid open to show its grinding apparatus.)] So we find a wonderful variety of things working together in making and feeding the soil that feeds the world: mountains and pebbles, volcanoes and lichens, the breath of the living and the bones of the dead; the sun, the winds, the sea, the rains; the farmers with four feet, the farmers with six feet; the swallow building her nest under the eaves, the earthworms burrowing under our feet, each bent on its own affairs, to be sure, but at the same time each helping to carry on the great business of the universe. From the little gizzard mills of the earthworm to the great earth mills of the sea, that renew the soil for the ages yet to come, all are--most evidently--parts of one great system; are together helping to work out great purposes in the advance of men and things; purposes which require that "While the earth remaineth, summer and winter, seed-time and harvest, shall not cease." HIDE AND SEEK IN THE LIBRARY As I said, most people not only think that they're smarter than their fellow animals, but when you point out to them how clever some of these other animals are, they say: "Oh, _that's_ just instinct!" As if animals don't think and learn by experience, and all, just as we do! You look up "instinct" in the encyclopædia, and you'll see. Then read Long's "Wood Folk at School." There's really a lot more fun in shooting animals with a camera than with a shotgun or a rifle. Did you ever try it? "Hunting with a Camera" in "The Scientific American Boy at School," by Bond, will tell you how to get the best results. Other good pointers on animal photography will be found in Verrill's "Boy Collector's Hand Book" ("Photographing Wild Things") and in "On the Trail," by A. B. and Lina Beard. And if you ever feel like killing a bird "just for fun," read in the diary of "Opal" about the farmer boy who shot the little girl's pet crow; it was "only a crow," he said, and he wanted to see if he could hit it. That will cure you, I think. The diary of "Opal" reads like a fairy-tale, but it's all true, and although it was written--every word of it--by a little girl of seven, it is one of the most remarkable books that anybody ever wrote. The crow's name, by the way, was "Lars Porsina of Clusium." The little girl used to give her pets names like that. Don't forget what the great naturalist, Agassiz, said about the pencil being "the best eye"; that is to say, you can get a more accurate knowledge of things and come nearer to seeing them as they really are, by drawing them. Drawing, in the best schools, is a part of Nature Study, and when you get so that you can draw fairly well--as everybody can with practice--you will find there is even more of a thrill in thus _creating_ forms--out of nothing, as you might say--than there is in taking photographs. The pencil is a magician's wand! As an example and inspiration for taking your pencil and sketch-book into the fields, get "Eye Spy," by Gibson, and, of course, Seton's animal books. I do believe Seton drew his pictures with those simple, expressive outlines so that young folks could redraw them. The difference between redrawing a drawing and simply looking at it, is a lot like the difference between _reading_ a book and merely glancing at the print. You are sure to be interested in Sir John Lubbock's book on "Ants, Bees and Wasps," and you will find a world of interesting things about the earlier animal days of man in his "Origin of Civilization" and "Pre-Historic Times." And who do you suppose had most to do with teaching men they were really brothers, and so bringing them up to the civilized life we know to-day? Mother! (See Drummond's "Ascent of Man," or Chapter XII of "The Strange Adventures of a Pebble," where the whole marvellous story of evolution is told in simple form.) If Nature Study proves half as delightful and profitable to you as I am sure it will, the following list of books will be very useful in building up your library on the subject, and in selecting books from the public library: "Among the Farmyard People," by Clara D. Pierson, deals with various things you probably never noticed about chickens and pigs, and other domestic animals. "Among the Meadow People," by the same author, tells about birds and insects. You can see what her "Among the Pond People" tells about--tadpoles, frogs, and so on. Really, it's a perfect fairy-land, an old pond is! "Among the Moths and Butterflies," by Julia P. Ballard, is about fairies, too, as the title shows. For children of the seventh to eighth grades, and up, Hornaday's "American Natural History" will be a delight, and it has loads of pictures which, as in all well-illustrated scientific books, are as valuable as the text. You know who Hornaday is, don't you? He is the man at the head of the great Zoo in New York City. Margaret W. Morley's "The Bee People" is worthy of its subject, and that's about the highest praise you could give to a book about bees, I think. Then don't forget, when you are in the library, to look up her "Grasshopper Land." The grasshopper book also treats of the grasshopper's cousins, which include the crickets and the katydids; yes, and the "walking sticks"; and the "praying mantis." (Did you know that whether you spell this weird little creature's first name, "praying," with an "e" or an "a" you'd be correct?) Every boy and girl, of course, is supposed to know about Ernest Thompson Seton's books, but for fear some of them don't, I'll mention a few that it simply wouldn't do to miss. "Animal Heroes" gives the history of a cat, a dog, a pigeon, a lynx, two wolves and a reindeer; "Krag and Johnny Bear" is made up from his larger book, "Lives of the Hunted"; "Lobo, Rag and Vixen" is from his "Wild Animals I Have Known," and "The Trail of the Sandhill Stag." John Burroughs is very different from Seton and Long, but the older you get the better you will like him. His is one of the great names in the study of Nature's pages at first hand and, as literature, ranks with the work of Thoreau. Get his "Birds, Bees and Other Papers," "Squirrels and Other Fur-bearers." Darwin, one of the greatest men in the whole history of science--the man whose name is most prominently identified with the greatest discovery in science, the principle of evolution--how do you suppose he started out? Just by looking around! Read about it in "What Mr. Darwin Saw in His Voyage around the World." INDEX (For numerous practical suggestions as to the use of an index the reader is referred to the preface to the index in the author's "Strange Adventures of a Pebble.") Africa, one country where the Hornbills live, 169 Ants, their interesting habits in relation to the history of the soil, 94; ants that thresh and store, 205, 213; how they clean up after the day's work, 208 Aphids, how they supply the ants with honey, 99 Armadillo, a four-footed farmer who wears armor; how fast he can dig, 120; the funny gimlet nose that helps him travel so fast under the ground, 121 Asia, one of the countries where the Hornbills live, 169; home of a farmer who stores grain for the winter, 212 Australia, home of that animal paradox, the Duck-billed Mole, 144; and of birds that hatch their babies with an incubator, 174 Bears, how they go into winter quarters, 216, 219 Beavers, their work and their wisdom, 148 Bees. (See Mason Bee and Bumblebee.) Beetle, Sacred (Tumble Bug), sinful tactics of, 92 Birds, their ancestors among the ancient monsters, 24; service of the Moas in ploughing and in grinding up rock, 28; other farmers who wear feathers, 162 Bumblebees, their homes under the ground, 104 Caveman, what he learned from his fellow animals, 228 Central America, a good place to look for Flamingoes, 166 Chipmunks, work and play in Chipmunkville, 131; why they have large feet for such little people, 132; inside the Chipmunk's home, 132; why they have several front doors, 133; how they spend the winter, 218 Clouds, how dust helps make them, 56; and shape them, 57 Colorado, once the home of prehistoric monsters, 27 Corn, how the "rag babies" tell the fortune of the seed, 199 Crabs, water farmers who help make land, 140 Crayfish, their habits and their service in helping get land ready for the farmer, 140 Crustaceans, their relation to insects, 143 Cuvier, Baron, the famous paleontologist, and his adventure with a "monster," 34 Dandelions, flying machines of, 51 Darwin, Charles, on the importance of earthworms in the history of human civilization, 75; what he said about the intelligence of roots and why he said it (the whole chapter is about that), 186; how he taught roots to write their autobiographies, 190 Deserts, plant pioneers in, 8; rich in plant food, 59; how irrigation transforms them, 72 Dormice, their Thanksgiving dinners and their long winter naps, 204, 217 Duck-billed Mole, the Animal X that lays eggs like a bird and yet suckles its young like a pussy-cat, 144 Dust, how it helps the rain come down, 56 Earthworms, great importance of their work in pulverizing and fertilizing the soil, 75; their habits and remarkable intelligence, 75; how the great sea and the little earthworms work together, 242 East Indies, home of some of the Hornbills, 169 Electricity, how it helps in the shaping of the clouds, 57 Elephants, their ancestors among the prehistoric monsters, 27; elephants as ploughmen, 28 Fabre, Henri, his study of the Mason Bee and how his schoolboys helped him, 108 Farms, abandoned, how Nature restores them, 16 Fish, monster fish of other days, 23 Flamingoes, habits of some feathered farmers with queer noses, 162 Florida, one place where you may find flamingoes, 166 Fox, home life and habits, 128 Frost, Jack, how he helps convert rock into soil, 43; how he makes stones "walk" and in other ways co-operates with the river mills in making soil, 60 Geese, their relation to the flamingoes, 166 Groundhog. (See Woodchuck.) Hamster, a four-footed farmer who uses a threshing-machine, 210 Hedgehogs, why they are so unpopular as food, 121; their homes and how they do their ploughing, 122; pictures of baby hedgehogs, 216, 217; why they go into winter quarters, 216, 218 Hibernation, "The Autumn Stores and the Long Winter Night," 204 Hornbills, why Mr. Hornbill shuts his wife up in their home in a hollow tree, 169 Hungary, home of the field rat, a farmer who stores grain for the winter, 212 Ice Ages, how the glaciers ploughed and mixed the soil, 237 Insects, their service in pulverizing and fertilizing the soil, 92; damage done by injurious insects, 93; relation of insects to crustaceans, 143 Kangaroo rat, 131 Kingfishers, their tunnel homes in the bank and how their fishing habits help enrich the soil, 171 Kiwi, a late bird that nevertheless gets the worm, 167 Lichens, first of the soil makers--how they helped Columbus discover the world by discovering it first, 1; how the volcanoes and the lichens work together, 235 Lizards, reign of the lizard family in the days of the prehistoric monsters, 25 Lubbock, Sir John, the great London banker who carried ants in his pocket--what he had to say about the pleasures of Nature Study, 231 Maeterlinck, on the presence of mind of a tree and its heroic struggle against adverse circumstances, 200 Marmots, their farm villages, 124 Mason-Bees. The house that Mrs. Mason-Bee built and its relation to the story of the soil, 104 Moles, their work as ploughmen, 115; how they do their tunnelling, 117; Mr. Mole's castle under the ground, 118; how he keeps his hair so sleek, 119; where he spends the winter, 218 Monsters, prehistoric, what they looked like, their habits and how they help the farmers of to-day with their farming, 20 Mosses, as soil makers, 8 Mound-Birds, how they build their incubators; other interesting habits, 174 Mountains, how the trees climb them, 13; why you always hear a rattle of stones in the mountains at sunrise, 43; how the winds help trees to climb the western slopes, 55; how the mountains help the rain to come down and why so many rivers rise in mountains, 56; why the bones of the monsters are found in the mountains, 31; how the mountains helped kill off the monsters, 32; farm villages of the marmots in the mountains, 124; team-work between mountains and pebbles, 240 Nature Study, its great value, 231; how it is taking the place of cruel sport, 232 New England, why its soil is so versatile and dependable, and how it helps grow farm boys into famous men, 239 New Zealand, home of a bird that is a very late riser but nevertheless gets the worm, 167 Oven-Birds, of South America, how they differ from the American oven-birds, 172; their remarkable adobe homes and their friendliness toward man, 172 Pebbles, how they help feed the Wisconsin cows, 239, 240; team-work between mountains and pebbles, 240 Philippines, one of the regions where mound-birds live, 174, 176 Ploughing, Nature's system: work of the squirrels, 14; of the elephants and their ancestors among prehistoric monsters, 27; of the Moas, 28; of the Dinosaurs, 29; storm ploughs of the winds, 46; use of the plough to prevent soil waste, 70; the great ploughs of the Ice Ages, 237 Pocket Gopher, Thompson-Seton's "master ploughman," 128; why he has that queer expression on his face, 128; how he spends the winter, 218 Pocket-Mouse, 130, 131 Pot Holes, soil-grinding mills of the rivers, 61 Prairie-Dog, his watch tower and how it protects him from his enemies, 126; his great sociability, 127 Rains, their work in making and transporting soil, 44, 55 Rivers, work of the river mills in soil making, 60 Roots, how lichens get along without them, 4; how and why they work at different levels, 11; how they make their way about (you won't wonder that Darwin said their actions suggested intelligence!), 186 Sand, how it helps the soil to breathe, 59 Seeds, how they determine the order of march of the trees, 12; use of screw-propellers and other devices, 42, 49, 51; how and why baby plants back into the world, 190; how they tried to change a sprouting seedling's mind but couldn't, 195; how "rag babies" tell the fortune of corn, 199 Shrews, their work as ploughmen, 115; where they spend the winter, 218 Siberia, there you will find the voles and their root cellars, 212 South America, home of the four-footed farmers that wear armor, 120; and of the viscacha, 127; a good place to look for flamingoes, 166; and for oven-birds, 171 South Sea Islands, one of the regions in which you find birds that hatch their babies with an incubator, 174 Squirrels, how they help the trees to march, 14; the winding streets of Ground-Squirrel Town, 123; marmots, the largest of the squirrel family, 124; how the tree-squirrels spend the winter, 218 Swallows, their habits and their service as soil makers, 177 Termites, insects improperly called "white ants"; their habits in relation to the history of the soil, 100 Terracing, how employed to prevent waste of soil, 71 Texas, you can still find armadillos there, 120 Trees, their settled order of march into new lands, 8; how the winds and the rains help trees to climb the western slopes of mountains, 55; how waste of trees causes waste of soil, 69 Turtles, how turtles differ from tortoises; habits of both these water farmers, 137; how turtles differ from crabs in their notions about laying eggs, 142 Viscachas, South American relatives of the prairie-dogs; their villages and their athletic fields, 127; how they rescue their buried comrades, 128 Volcanoes, their contribution to soil making, 39; how they help the plant world to get its breath, 40; team-work between volcanoes and lichens, 235 Voles, four-footed farmers who fill root cellars for the winter, 212 Wasps, their habits in relation to the history of the soil, 102 Weather and the groundhog's shadow, 219 Weeds, as soil makers, 9 Winds, how they helped Mr. Lichen to discover the world, 1; how they help the trees to march, 12; their work in making, mixing, and transporting soil, 37 Winter in the animal world, under the ground, 204 Woodchuck (Groundhog), picturesque home of a Connecticut woodchuck, 134; Mr. Woodchuck's winter quarters and his shadow, 219 Wyoming, one of the homes of the prehistoric monsters, 27 Transcriber's note: In the scanned version of this book, there is apparently a printer error in the acknowledgments for sources of illustrations (page x) where the author refers to an illustration on page 125. There is no illustration on page 125 in the original text. However the closest illustration (caption: This Must Be a Pleasant Day) is located on page 126 in the original text. Another possible printer error occurred on page 52, where the phrase "branches and holes" appears in the original text. In an effort to relate the context of the phrase, this has been changed to "branches and boles" in this text. In some cases illustrations have been moved from the original location in order to avoid breaks in paragraphs, and to place them more closely to the related paragraph. 
18562	----	[Illustration: _Dunes at Ipswich Light, Massachusetts. Note the effect of bushes in arresting the movement of the wind-blown sand._] OUTLINES OF THE EARTH'S HISTORY A POPULAR STUDY IN PHYSIOGRAPHY BY NATHANIEL SOUTHGATE SHALER PROFESSOR OF GEOLOGY IN HARVARD UNIVERSITY DEAN OF LAWRENCE SCIENTIFIC SCHOOL ILLUSTRATED WITH INDEX NEW YORK AND LONDON D. APPLETON AND COMPANY 1898, 1910 PREFACE. The object of this book is to provide the beginner in the study of the earth's history with a general account of those actions which can be readily understood and which will afford him clear understandings as to the nature of the processes which have made this and other celestial spheres. It has been the writer's purpose to select those series of facts which serve to show the continuous operations of energy, so that the reader might be helped to a truer conception of the nature of this sphere than he can obtain from ordinary text-books. In the usual method of presenting the elements of the earth's history the facts are set forth in a manner which leads the student to conceive that history as in a way completed. The natural prepossession to the effect that the visible universe represents something done, rather than something endlessly doing, is thus re-enforced, with the result that one may fail to gain the largest and most educative impression which physical science can afford him in the sense of the swift and unending procession of events. It is well known to all who are acquainted with the history of geology that the static conception of the earth--the idea that its existing condition is the finished product of forces no longer in action--led to prejudices which have long retarded, and indeed still retard, the progress of that science. This fact indicates that at the outset of a student's work in this field he should be guarded against such misconceptions. The only way to attain the end is by bringing to the understanding of the beginner a clear idea of successions of events which are caused by the forces operating in and on this sphere. Of all the chapters of this great story, that which relates to the history of the work done by the heat of the sun is the most interesting and awakening. Therefore an effort has been made to present the great successive steps by which the solar energy acts in the processes of the air and the waters. The interest of the beginner in geology is sure to be aroused when he comes to see how very far the history of the earth has influenced the fate of men. Therefore the aim has been, where possible, to show the ways in which geological processes and results are related to ourselves; how, in a word, this earth has been the well-appointed nursery of our kind. All those who are engaged in teaching elementary science learn the need of limiting the story they have to tell to those truths which can be easily understood by beginners. It is sometimes best, as in stating such difficult matters as those concerning the tides, to give explanations which are far from complete, and which, as to their mode of presentation, would be open to criticism were it not for the fact that any more elaborate statements would most likely be incomprehensible to the novice, thus defeating the teacher's aim. It will be observed that no account is here given of the geological ages or of the successions of organic life. Chapters on these subjects were prepared, but were omitted for the reason that they made the story too long, and also because they carried the reader into a field of much greater difficulty than that which is found in the physical history of the earth. N.S.S. _March, 1898._ CONTENTS. CHAPTER PAGE I.--INTRODUCTION TO THE STUDY OF NATURE 1 II.--WAYS AND MEANS OF STUDYING NATURE 9 III.--THE STELLAR REALM 31 IV.--THE EARTH 81 V.--THE ATMOSPHERE 97 VI.--GLACIERS 207 VII.--THE WORK OF UNDERGROUND WATER 250 VIII.--THE SOIL 313 IX.--THE ROCKS AND THEIR ORDER 349 LIST OF FULL-PAGE ILLUSTRATIONS. FACING PAGE Dunes at Ipswich Light, Massachusetts _Frontispiece_ Seal Rocks near San Francisco, California 33 Lava stream, in Hawaiian Islands, flowing into the sea 72 Waterfall near Gadsden, Alabama 90 South shore, Martha's Vineyard, Massachusetts 121 Pocket Creek, Cape Ann, Massachusetts 163 Muir Glacier, Alaska 207 Front of Muir Glacier 240 Mount Ætna, seen from near Catania 201 Mountain gorge, Himalayas, India 330 OUTLINES OF THE EARTH'S HISTORY. CHAPTER I. AN INTRODUCTION TO THE STUDY OF NATURE. The object of this book is to give the student who is about to enter on the study of natural science some general idea as to the conditions of the natural realm. As this field of inquiry is vast, it will be possible only to give the merest outline of its subject-matter, noting those features alone which are of surpassing interest, which are demanded for a large understanding of man's place in this world, or which pertain to his duties in life. In entering on any field of inquiry, it is most desirable that the student should obtain some idea as to the ways in which men have been led to the knowledge which they possess concerning the world about them. Therefore it will be well briefly to sketch the steps by which natural science has come to be what it is. By so doing we shall perceive how much we owe to the students of other generations; and by noting the difficulties which they encountered, and how they avoided them, we shall more easily find our own way to knowledge. The primitive savages, who were the ancestors of all men, however civilized they may be, were students of Nature. The remnants of these lowly people who were left in different parts of the world show us that man was not long in existence before he began to devise some explanation concerning the course of events in the outer world. Seeing the sun rise and set, the changes of the moon, the alternation of the seasons, the incessant movement of the streams and sea, and the other more or less orderly successions of events, our primitive forefathers were driven to invent some explanation of them. This, independently, and in many different times and places, they did in a simple and natural way by supposing that the world was controlled by a host of intelligent beings, each of which had some part in ordering material things. Sometimes these invisible powers were believed to be the spirits of great chieftains, who were active when on earth, and who after death continued to exercise their power in the larger realms of Nature. Again, and perhaps more commonly, these movements of Nature were supposed to be due to the action of great though invisible beasts, much like those which the savage found about him. Thus among our North American Indians the winds are explained by the supposition that the air is fanned by the wings of a great unseen bird, whose duty it is to set the atmosphere into motion. That no one has ever seen the bird doing the work, or that the task is too great for any conceivable bird, is to the simple, uncultivated man no objection to this view. It is long, indeed, before education brings men to the point where they can criticise their first explanations of Nature. As men in their advance come to see how much nobler are their own natures than those of the lower animals, they gradually put aside the explanation of events by the actions of beasts, and account for the order of the world by the supposition that each and every important detail is controlled by some immortal creature essentially like a man, though much more powerful than those of their own kind. This stage of understanding is perhaps best shown by the mythology of the Greeks, where there was a great god over all, very powerful but not omnipotent; and beneath him, in endless successions of command, subordinate powers, each with a less range of duties and capacities than those of higher estate, until at the bottom of the system there were minor deities and demigods charged with the management of the trees, the flowers, and the springs--creatures differing little from man, except that they were immortal, and generally invisible, though they, like all the other deities, might at their will display themselves to the human beings over whom they watched, and whose path in life they guided. Among only one people do we find that the process of advance led beyond this early and simple method of accounting for the processes of Nature, bringing men to an understanding such as we now possess. This great task was accomplished by the Greeks alone. About twenty-five hundred years ago the philosophers of Greece began to perceive that the early notion as to the guidance of the world by creatures essentially like men could not be accepted, and must be replaced by some other view which would more effectively account for the facts. This end they attained by steps which can not well be related here, but which led them to suppose separate powers behind each of the natural series--powers having no relation to the qualities of mankind, but ever acting to a definite end. Thus Plato, who represents most clearly this advance in the interpretation of facts, imagined that each particular kind of plant or animal had its shape inevitably determined by something which he termed an idea, a shape-giving power which existed before the object was created, and which would remain after it had been destroyed, ever ready again to bring matter to the particular form. From this stage of understanding it was but a short step to the modern view of natural law. This last important advance was made by the great philosopher Aristotle, who, though he died about twenty-two hundred years ago, deserves to be accounted the first and in many ways the greatest of the ancient men of science who were informed with the modern spirit. With Aristotle, as with all his intellectual successors, the operations of Nature were conceived as to be accounted for by the action of forces which we commonly designate as natural laws, of which perhaps the most familiar and universal is that of gravitation, which impels all bodies to move toward each other with a degree of intensity which is measured by their weight and the distance by which they are separated. For many centuries students used the term law in somewhat the same way as the more philosophical believers in polytheism spoke of their gods, or as Plato of the ideas which he conceived to control Nature. We see by this instance how hard it is to get rid of old ways of thinking. Even when the new have been adopted we very often find that something of the ancient and discarded notions cling in our phrases. The more advanced of our modern philosophers are clear in their mind that all we know as to the order of Nature is that, given certain conditions, certain consequences inevitably follow. Although the limitations which modern men of science perceive to be put upon their labours may seem at first sight calculated to confine our understanding within a narrow field of things which can be seen, or in some way distinctly proved to exist, the effect of this limitation has been to make science what it is--a realm of things known as distinct from things which may be imagined. All the difference between ancient science and modern consists in the fact that in modern science inquirers demand a businesslike method in the interpretation of Nature. Among the Greeks the philosopher who taught explanations of any feature in the material world which interested him was content if he could imagine some way which would account for the facts. It is the modern custom now to term the supposition of an explanation a _working hypothesis_, and only to give it the name of theory after a very careful search has shown that all the facts which can be gathered are in accordance with the view. Thus when Newton made his great suggestion concerning the law of gravitation, which was to the effect that all bodies attracted each other in proportion to their masses, and inversely as the square of their distance from each other, he did not rest content, as the old Greeks would have done, with the probable truth of the explanation, but carefully explored the movements of the planets and satellites of the solar system to see if the facts accorded with the hypothesis. Even the perfect correspondence which he found did not entirely content inquirers, and in this century very important experiments have been made which have served to show that a ball suspended in front of a precipice will be attracted toward the steep, and that even a mass of lead some tons in weight will attract toward itself a small body suspended in the manner of a pendulum. It is this incessant revision of the facts, in order to see if they accord with the assumed rule or law, which has given modern science the sound footing that it lacked in earlier days, and which has permitted our learning to go on step by step in a safe way up the heights to which it has climbed. All explanations of Nature begin with the work of the imagination. In common phrase, they all are guesses which have at first but little value, and only attain importance in proportion as they are verified by long-continued criticism, which has for its object to see whether the facts accord with the theory. It is in this effort to secure proof that modern science has gathered the enormous store of well-ascertained facts which constitutes its true wealth, and which distinguishes it from the earlier imaginative and to a great extent unproved views. In the original state of learning, natural science was confounded with political and social tradition, with the precepts of duty which constitute the law of the people, as well as with their religion, the whole being in the possession of the priests or wise men. So long as natural action was supposed to be in the immediate control of numerous gods and demigods, so long, in a word, as the explanation of Nature was what we term polytheistic, this association of science with other forms of learning was not only natural but inevitable. Gradually, however, as the conception of natural law replaced the earlier idea as to the intervention of a spirit, science departed from other forms of lore and came to possess a field to itself. At first it was one body of learning. The naturalists of Aristotle's time, and from his day down to near our own, generally concerned themselves with the whole field of Nature. For a time it was possible for any one able and laborious man to know all which had been ascertained concerning astronomy, chemistry, geology, as well as the facts relating to living beings. The more, however, as observation accumulated, and the store of facts increased, it became difficult for any one man to know the whole. Hence it has come about that in our own time natural learning is divided into many distinct provinces, each of which demands a lifetime of labour from those who would know what has already been done in the field, and what it is now important to do in the way of new inquiries. The large divisions which naturalists have usually made of their tasks rest in the main on the natural partitions which we may readily observe in the phenomenal world. First of all comes astronomy, including the phenomena exhibited in the heavens, beyond the limits of the earth's atmosphere. Second, geology, which takes account of all those actions which in process of time have been developed in our own sphere. Third, physics, which is concerned with the laws of energy, or those conditions which affect the motion of bodies, and the changes which are impressed upon them by the different natural forces. Fourth, chemistry, which seeks to interpret the principles which determine the combination of atoms and the molecules which are built of them under the influence of the chemical affinities. Fifth, biology, or the laws of life, a study which pertains to the forms and structures of animals and plants, and their wonderful successions in the history of the world. Sixth, mathematics, or the science of space and number, that deals with the principles which underlie the order of Nature as expressed at once in the human understanding and in the material universe. By its use men were made able to calculate, as in arithmetic, the problems which concern their ordinary business, as well as to compute the movements of the celestial bodies, and a host of actions which take place on the earth that would be inexplicable except by the aid of this science. Last of all among the primary sciences we may name that of psychology, which takes account of mental operations among man and his lower kindred, the animals. In addition to the seven sciences above mentioned, which rest in a great measure on the natural divisions of phenomena, there are many, indeed, indefinitely numerous, subdivisions which have been made to suit the convenience of students. Thus astronomy is often separated into physical and mathematical divisions, which take account either of the physical phenomena exhibited by the heavenly bodies or of their motions. In geology there are half a dozen divisions relating to particular branches of that subject. In the realm of organic life, in chemistry, and in physics there are many parts of these sciences which have received particular names. It must not be supposed that these sciences have the independence of each other which their separate names would imply. In fact, the student of each, however, far he may succeed in separating his field from that of the other naturalists, as we may fitly term all students of Nature, is compelled from time to time to call in the aid of his brethren who cultivate other branches of learning. The modern astronomer needs to know much of chemistry, or else he can not understand many of his observations on the sun. The geologists have to share their work with the student of animal and vegetable life, with the physicists; they must, moreover, know something of the celestial spheres in order to interpret the history of the earth. In fact, day by day, with the advance of learning, we come more clearly to perceive that all the processes of Nature are in a way related to each other, and that in proportion as we understand any part of the great mechanism, we are forced in a manner to comprehend the whole. In other words, we are coming to understand that these divisions of the field of science depend upon the limitations of our knowledge, and not upon the order of Nature itself. For the purposes of education it is important that every one should know something of the great truths which each science has disclosed. No mortal man can compass the whole realm of this knowledge, but every one can gain some idea of the larger truths which may help him to understand the beauty and grandeur of the sphere in which he dwells, which will enable him the better to meet the ordinary duties of life, that in almost all cases are related to the facts of the world about us. It has been of late the custom to term this body of general knowledge which takes account of the more evident facts and important series of terrestrial actions physiography, or, as the term implies, a description of Nature, with the understanding that the knowledge chosen for the account is that which most intimately concerns the student who seeks information that is at once general and important. Therefore, in this book the effort is made first to give an account as to the ways and means which have led to our understanding of scientific problems, the methods by which each person may make himself an inquirer, and the outline of the knowledge that has been gathered since men first began to observe and criticise the revelations the universe may afford them. CHAPTER II. WAYS AND MEANS OF STUDYING NATURE. It is desirable that the student of Nature keep well in mind the means whereby he is able to perceive what goes on in the world about him. He should understand something as to the nature of his senses, and the extent to which these capacities enable him to discern the operations of Nature. Man, in common with his lower kindred, is, by the mechanism of the body, provided with five somewhat different ways by which he may learn something of the things about him. The simplest of these capacities is that of touch, a faculty that is common to the general surface of the body, and which informs us when the surface is affected by contact with some external object. It also enables us to discern differences of temperature. Next is the sense of taste, which is limited to the mouth and the parts about it. This sense is in a way related to that of touch, for the reason that it depends on the contact of our body with material things. Third is the sense of smell, so closely related to that of taste that it is difficult to draw the line between the two. Yet through the apparatus of the nose we can perceive the microscopically small parts of matter borne to us through the air, which could not be appreciated by the nerves of the mouth. Fourth in order of scope comes the hearing, which gives us an account of those waves of matter that we understand as sound. This power is much more far ranging than those before noted; in some cases, as in that of the volcanic explosions from the island of Krakatoa, in the eruption of 1883, the convulsions were audible at the distance of more than a thousand miles away. The greater cannon of modern days may be heard at the distance of more than a hundred miles, so that while the sense of touch, taste, and smell demand contact with the bodies which we appreciate, hearing gives us information concerning objects at a considerable distance. Last and highest of the senses, vastly the most important in all that relates to our understanding of Nature, is sight, or the capacity which enables us to appreciate the movement of those very small waves of ether which constitute light. The eminent peculiarity of sight is that it may give us information concerning things which are inconceivably far away; it enables us to discern the light of suns probably millions of times as remote from us as is the centre of our own solar system. Although much of the pleasure which the world affords us comes through the other senses, the basis of almost all our accurate knowledge is reported by sight. It is true that what we have observed with our eyes may be set forth in words, and thus find its way to the understanding through the ears; also that in many instances the sense of touch conveys information which extends our perceptions in many important ways; but science rests practically on sight, and on the insight that comes from the training of the mind which the eyes make possible. The early inquirers had no resources except those their bodies afforded; but man is a tool-making creature, and in very early days he began to invent instruments which helped him in inquiry. The earliest deliberate study was of the stars. Science began with astronomy, and the first instruments which men contrived for the purpose of investigation were astronomical. In the beginning of this search the stars were studied in order to measure the length of the year, and also for the reason that they were supposed in some way to control the fate of men. So far as we know, the first pieces of apparatus for this purpose were invented in Egypt, perhaps about four thousand years before the Christian era. These instruments were of a simple nature, for the magnifying glass was not yet contrived, and so the telescope was impossible. They consisted of arrangements of straight edges and divided circles, so that the observers, by sighting along the instruments, could in a rough way determine the changes in distance between certain stars, or the height of the sun above the horizon at the various seasons of the year. It is likely that each of the great pyramids of Egypt was at first used as an observatory, where the priests, who had some knowledge of astronomy, found a station for the apparatus by which they made the observations that served as a basis for casting the horoscope of the king. In the progress of science and of the mechanical invention attending its growth, a great number of inventions have been contrived which vastly increase our vision and add inconceivably to the precision it may attain. In fact, something like as much skill and labour has been given to the development of those inventions which add to our learning as to those which serve an immediate economic end. By far the greatest of these scientific inventions are those which depend upon the lens. By combining shaped bits of glass so as to control the direction in which the light waves move through them, naturalists have been able to create the telescope, which in effect may bring distant objects some thousand times nearer to view than they are to the naked eye; and the microscope, which so enlarges minute objects as to make them visible, as they were not before. The result has been enormously to increase our power of vision when applied to distant or to small objects. In fact, for purposes of learning, it is safe to say that those tools have altogether changed man's relation to the visible universe. The naked eye can see at best in the part of the heavens visible from any one point not more than thirty thousand stars. With the telescope somewhere near a hundred million are brought within the limits of vision. Without the help of the microscope an object a thousandth of an inch in diameter appears as a mere point, the existence of which we can determine only under favourable circumstances. With that instrument the object may reveal an extended and complicated structure which it may require a vast labour for the observer fully to explore. Next in importance to the aid of vision above noted come the scientific tools which are used in weighing and measuring. These balances and gauges have attained such precision that intervals so small as to be quite invisible, and weights as slight as a ten-thousandth of a grain, can be accurately measured. From these instruments have come all those precise examinations on which the accuracy of modern science intimately depends. All these instruments of precision are the inventions of modern days. The simplest telescopes were made only about two hundred and fifty years ago, and the earlier compound microscopes at a yet later date. Accurate balances and other forms of gauges of space, as well as good means of dividing time, such as our accurate astronomical clocks and chronometers, are only about a century old. The instruments have made science accurate, and have immensely extended its powers in nearly all the fields of inquiry. Although the most striking modern discoveries are in the field which was opened to us by the lens in its manifold applications, it is in the chemist's laboratory that we find that branch of science, long cultivated, but rapidly advanced only within the last two centuries, which has done the most for the needs of man. The ancients guessed that the substances which make up the visible world were more complicated in their organization than they appear to our vision. They even suggested the great truth that matter of all kinds is made up of inconceivably small indivisible bits which they and we term atoms. It is likely that in the classic days of Greece men began to make simple experiments of a chemical nature. A century or two after the time of Mohammed, the Arabians of his faith, a people who had acquired Greek science from the libraries which their conquests gave them, conducted extensive experiments, and named a good many familiar chemical products, such as alcohol, which still bears its Arabic name. These chemical studies were continued in Europe by the alchemists, a name also of Arabic origin, a set of inquirers who were to a great extent drawn away from scientific studies by vain though unending efforts to change the baser metals into gold and silver, as well as to find a compound which would make men immortal in the body. By the invention of the accurate balance, and by patient weighing of the matters which they submitted to experiment, by the invention of hypotheses or guesses at truth, which were carefully tested by experiment, the majestic science of modern chemistry has come forth from the confused and mystical studies of the alchemists. We have learned to know that there are seventy or more primitive or apparently unchangeable elements which make up the mass of this world, and probably constitute all the celestial spheres, and that these elements in the form of their separate atoms may group themselves in almost inconceivably varied combinations. In the inanimate realm these associations, composed of the atoms of the different substances, forming what are termed molecules, are generally composed of but few units. Thus carbonic-acid gas, as it is commonly called, is made up of an aggregation of molecules, each composed of one atom of carbon and two of oxygen; water, of two atoms of hydrogen and one of oxygen; ordinary iron oxide, of two atoms of iron and three of oxygen. In the realm of organic life, however, these combinations become vastly more complicated, and with each of them the properties of the substance thus produced differ from all others. A distinguished chemist has estimated that in one group of chemical compounds, that of carbon, it would be possible to make such an array of substances that it would require a library of many thousand ordinary volumes to contain their names alone. It is characteristic of chemical science that it takes account of actions which are almost entirely invisible. No contrivances have been or are likely to be invented which will show the observer what takes place when the atoms of any substance depart from their previous combination and enter on new arrangements. We only know that under certain conditions the old atomic associations break up, and new ones are formed. But though the processes are hidden, the results are manifest in the changes which are brought about upon the masses of material which are subjected to the altering conditions. Gradually the chemists of our day are learning to build up in their laboratories more and more complicated compounds; already they have succeeded in producing many of the materials which of old could only be obtained by extracting them from plants. Thus a number of the perfumes of flowers, and many of the dye-stuffs which a century ago were extracted from vegetables, and were then supposed to be only obtainable in that way, are now readily manufactured. In time it seems likely that important articles of food, for which we now depend upon the seeds of plants, may be directly built up from the mineral kingdom. Thus the result of chemical inquiry has been not only to show us much of the vast realm of actions which go on in the earth, but to give us control of many of these movements so that we may turn them to the needs of man. Animals and plants were at an early day very naturally the subjects of inquiry. The ancients perceived that there were differences of kind among these creatures, and even in Aristotle's time the sciences of zoölogy and botany had attained the point where there were considerable treatises on those subjects. It was not, however, until a little more than a century ago that men began accurately to describe and classify these species of the organic world. Since the time of Linnæus the growth of our knowledge has gone forward with amazing swiftness. Within a century we have come to know perhaps a hundred times as much concerning these creatures as was learned in all the earlier ages. This knowledge is divisible into two main branches: in one the inquirers have taken account of the different species, genera, families, orders, and classes of living forms with such effect that they have shown the existence at the present time of many hundred thousand distinct species, the vast assemblage being arranged in a classification which shows something as to the relationship which the forms bear to each other, and furthermore that the kinds now living have not been long in existence, but that at each stage in the history of the earth another assemblage of species peopled the waters and the lands. At first naturalists concerned themselves only with the external forms of living creatures; but they soon came to perceive that the way in which these organisms worked, their physiology, in a word, afforded matters for extended inquiry. These researches have developed the science of physiology, or the laws of bodily action, on many accounts the most modern and extensive of our new acquisitions of natural learning. Through these studies we have come to know something of the laws or principles by which life is handed on from generation to generation, and by which the gradations of structure have been advanced from the simple creatures which appear like bits of animated jelly to the body and mind of man. The greatest contribution which modern naturalists have made to knowledge concerns the origin of organic species. The students of a century ago believed that all these different kinds had been suddenly created either through natural law or by the immediate will of God. We now know that from the beginning of organic life in the remote past to the present day one kind of animal or plant has been in a natural and essentially gradual way converted into the species which was to be its successor, so that all the vast and complicated assemblage of kinds which now exists has been derived by a process of change from the forms which in earlier ages dwelt upon this planet. The exact manner in which these alterations were produced is not yet determined, but in large part it has evidently been brought about by the method indicated by Mr. Darwin, through the survival of the fittest individuals in the struggle for existence. Until men came to have a clear conception as to the spherical form of the earth, it was impossible for them to begin any intelligent inquiries concerning its structure or history. The Greeks knew the earth to be a sphere, but this knowledge was lost among the early Christian people, and it was not until about four hundred years ago that men again came to see that they dwelt upon a globe. On the basis of this understanding the science of geology, which had in a way been founded by the Greeks, was revived. As this science depends upon the knowledge which we have gained of astronomy, physics, chemistry, and biology, all of which branches of learning have to be used in explaining the history of the earth, the advance which has been made has been relatively slow. Geology as a whole is the least perfectly organized of all the divisions of learning. A special difficulty peculiar to this science has also served to hinder its development. All the other branches of learning deal mainly, if not altogether, with the conditions of Nature as they now exist. In this alone is it necessary at every step to take account of actions which have been performed in the remote past. It is an easy matter for the students of to-day to imagine that the earth has long endured; but to our forefathers, who were educated in the view that it had been brought from nothingness into existence about seven thousand years ago, it was most difficult and for a time impossible to believe in its real antiquity. Endeavouring, as they naturally did, to account for all the wonderful revolutions, the history of which is written in the pages of the great stone book, the early geologists supposed this planet to have been the seat of frequent and violent changes, each of which revolutionized its shape and destroyed its living tenants. It was only very gradually that they became convinced that a hundred million years or more have elapsed since the dawn of life on the earth, and that in this vast period the march of events has been steadfast, the changes taking place at about the same rate in which they are now going on. As yet this conception as to the history of our sphere has not become the general property of the people, but the fact of it is recognised by all those who have attentively studied the matter. It is now as well ascertained as any of the other truths which science has disclosed to us. It is instructive to note the historic outlines of scientific development. The most conspicuous truth which this history discloses is that all science has had its origin and almost all its development among the peoples belonging to the Aryan race. This body of folk appears to have taken on its race characteristics, acquired its original language, its modes of action, and the foundations of its religion in that part of northern Europe which is about the Baltic Sea. Thence the body of this people appear to have wandered toward central Asia, where after ages of pastoral life in the high table lands and mountains of their country it sent forth branches to India, Asia Minor and Greece, to Persia, and to western Europe. It seems ever to have been a characteristic of these Aryan peoples that they had an extreme love for Nature; moreover, they clearly perceived the need of accounting for the things that happened in the world about them. In general they inclined to what is called the pantheistic explanation of the universe. They believed a supreme God in many different forms to be embodied in all the things they saw. Even their own minds and bodies they conceived as manifestations of this supreme power. Among the Aryans who came to dwell in Europe and along the eastern Mediterranean this method of explaining Nature was in time changed to one in which humanlike gods were supposed to control the visible and invisible worlds. In that marvellous centre of culture which was developed among the Greeks this conception of humanlike deities was in time replaced by that of natural law, and in their best days the Greeks were men of science essentially like those of to-day, except that they had not learned by experience how important it was to criticise their theories by patiently comparing them with the facts which they sought to explain. The last of the important Greek men of science, Strabo, who was alive when Christ was born, has left us writings which in quality are essentially like many of the able works of to-day. But for the interruption in the development of Greek learning, natural science would probably have been fifteen hundred years ahead of its present stage. This interruption came in two ways. In one, through the conquest of Greece and the destruction of its intellectual life by the Romans, a people who were singularly incapable of appreciating natural science, and who had no other interest in it except now and then a vacant and unprofitable curiosity as to the processes of the natural world. A second destructive influence came through the fact that Christianity, in its energetic protest against the sins of the pagan civilization, absolutely neglected and in a way despised all forms of science. The early indifference of Christians to natural learning is partly to be explained by the fact that their religion was developed among the Hebrews, a people remarkable for their lack of interest in the scientific aspects of Nature. To them it was a sufficient explanation that one omnipotent God ruled all things at his will, the heavens and the earth alike being held in the hollow of his hand. Finding the centre of its development among the Romans, Christianity came mainly into the control of a people who, as we have before remarked, had no scientific interest in the natural world. This condition prolonged the separation of our faith from science for fifteen hundred years after its beginning. In this time the records of Greek scientific learning mostly disappeared. The writings of Aristotle were preserved in part for the reason that the Church adopted many of his views concerning questions in moral philosophy and in politics. The rest of Greek learning was, so far as Europe was concerned, quite neglected. A large part of Greek science which has come down to us owes its preservation to a very singular incident in the history of learning. In the ninth century, after the Arabs had been converted to Mohammedanism, and on the basis of that faith had swiftly organized a great and cultivated empire, the scholars of that folk became deeply interested in the remnants of Greek learning which had survived in the monastic and other libraries about the eastern Mediterranean. So greatly did they prize these records, which were contemned by the Christians, that it was their frequent custom to weigh the old manuscripts in payment against the coin of their realm. In astronomy, mathematics, chemistry, and geology the Arabian students, building on the ancient foundations, made notable and for a time most important advances. In the tenth century of our era they seemed fairly in the way to do for science what western Europe began five centuries later to accomplish. In the fourteenth century the centre of Mohammedan strength was transferred from the Arabians to the Turks, from a people naturally given to learning to a folk of another race, who despised all such culture. Thenceforth in place of the men who had treasured and deciphered with infinite pains all the records of earlier learning, the followers of Mohammed zealously destroyed all the records of the olden days. Some of these records, however, survived among the Arabs of Spain, and others were preserved by the Christian scholars who dwelt in Byzantium, or Constantinople, and were brought into western Europe when that city was captured by the Turks in the fifteenth century. Already the advance of the fine arts in Italy and the general tendency toward the study of Nature, such as painting and sculpture indicate, had made a beginning, or rather a proper field for a beginning, of scientific inquiry. The result was a new interest in Greek learning in all its branches, and a very rapid awakening of the scientific spirit. At first the Roman Church made no opposition to this new interest which developed among its followers, but in the course of a few years, animated with the fear that science would lead men to doubt many of the dogmas of the Church, it undertook sternly to repress the work of all inquirers. The conflict between those of the Roman faith and the men of science continued for above two hundred years. In general, the part which the Church took was one of remonstrance, but in a few cases the spirit of fanaticism led to the persecution of the men who did not obey its mandates and disavow all belief in the new opinions which were deemed contrary to the teachings of Scripture. The last instance of such oppression occurred in France in the year 1756, when the great Buffon was required to recant certain opinions concerning the antiquity of the earth which he had published in his work on Natural History. This he promptly did, and in almost servile language withdrew all the opinions to which the fathers had objected. A like conflict between the followers of science and the clerical authorities occurred in Protestant countries. Although in no case were the men of science physically tortured or executed for their opinions, they were nevertheless subjected to great religious and social pressure: they were almost as effectively disciplined as were those who fell under the ban of the Roman Church. Some historians have criticised the action of the clerical authorities toward science as if the evil which was done had been performed in our own day. It should be remembered, however, that in the earlier centuries the churches regarded themselves as bound to protect all men from the dangers of heresy. For centuries in the early history of Christianity the defenders of the faith had been engaged in a life-and-death struggle with paganism, the followers of which held all that was known of Nature. Quite naturally the priestly class feared that the revival of scientific inquiry would bring with it the evils from which the world had suffered in pagan times. There is no doubt that these persecutions of science were done under what seemed the obligations of duty. They may properly be explained particularly by men of science as one of the symptoms of development in the day in which they were done. It is well for those who harshly criticise the relations of the Church to science to remember that in our own country, about two centuries ago, among the most enlightened and religious people of the time, Quakers were grievously persecuted, and witches hanged, all in the most dutiful and God-fearing way. In considering these relations of science to our faith, the matter should be dealt with in a philosophical way, and with a sense of the differences between our own and earlier ages. To the student of the relations between Christianity and science it must appear doubtful whether the criticism or the other consequences which the men of science had to meet from the Church was harmful to their work. The early naturalists, like the Greeks whom they followed, were greatly given to speculations concerning the processes of Nature, which, though interesting, were unprofitable. They also showed a curious tendency to mingle their scientific speculations with ancient and base superstitions. They were often given to the absurdity commonly known as the "black art," or witchcraft, and held to the preposterous notions of the astrologists. Even the immortal astronomer Kepler, who lived in the sixteenth century, was a professional astrologer, and still held to the notion that the stars determined the destiny of men. Many other of the famous inquirers in those years which ushered in modern science believed in witchcraft. Thus for a time natural learning was in a way associated with ancient and pernicious beliefs which the Church was seeking to overthrow. One result of the clerical opposition to the advancement of science was that its votaries were driven to prove every step which led to their conclusions. They were forced to abandon the loose speculation of their intellectual guides, the Greeks, and to betake themselves to observation. Thus a part of the laborious fact-gathering habit on which the modern advance of science has absolutely depended was due to the care which men had to exercise in face of the religious authorities. In our own time, in the latter part of the nineteenth century, the conflict between the religious authority and the men of science has practically ceased. Even the Roman Church permits almost everywhere an untrammelled teaching of the established learning to which it was at one time opposed. Men have come to see that all truth is accordant, and that religion has nothing to fear from the faithful and devoted study of Nature. The advance of science in general in modern times has been greatly due to the development of mechanical inventions. Among the ancients, the tools which served in the arts were few in number, and these of exceeding simplicity. So far as we can ascertain, in the five hundred years during which the Greeks were in their intellectual vigour, not more than half a dozen new machines were invented, and these were exceedingly simple. The fact seems to be that a talent for mechanical invention is mainly limited to the peoples of France, Germany, and of the English-speaking folk. The first advances in these contrivances were made in those countries, and all our considerable gains have come from their people. Thus, while the spirit of science in general is clearly limited to the Aryan folk, that particular part of the motive which leads to the invention of tools is restricted to western and northern Europe, to the people to whom we give the name of Teutonic. Mechanical inventions have aided the development of our sciences in several ways. They have furnished inquirers with instruments of precision; they have helped to develop accuracy of observation; best of all, they have served ever to bring before the attention of men a spectacle of the conditions in Nature which we term cause and effect. The influence of these inventions on the development of learning has been particularly great where the machines, such as our wind and water mills, and our steam engine, make use of the forces of Nature, subjugating them to the needs of man. Such instruments give an unending illustration as to the presence in Nature of energy. They have helped men to understand that the machinery of the universe is propelled by the unending application of power. It was, in fact, through such machines that men of science first came to understand that energy, manifested in the natural forces, is something that eternally endures; that we may change its form in our arts as its form is changed in the operations of Nature, but the power endures forever. It is interesting to note that the first observation which led to this most important scientific conclusion that energy is indestructible however much it may change its form, was made by an American, Benjamin Thompson, who left this country at the time of the Revolution, and after a curious life became the executive officer, and in effect king, of Bavaria. While engaged in superintending the manufacture of cannon, he observed that in boring out the barrel of the gun an amount of heat was produced which evaporated a certain amount of water. He therefore concluded that the energy required to do the boring of the metal passed into the state of heat, and thus only changed its state, in no wise disappearing from the earth. Other students pursuing the same line of inquiry have clearly demonstrated what is called the law of the conservation of energy, which more than anything has helped us to understand the large operations of Nature. Through these studies we have come to see that, while the universe is a place of ceaseless change, the quantities of energy and of matter remain unaltered. The foregoing brief sketch, which sets forth some of the important conditions which have affected the development of science, may in a way serve to show the student how he can himself become an interpreter of Nature. The evidence indicates that the people of our race have been in a way chosen among all the varieties of mankind to lead in this great task of comprehending the visible universe. The facts, moreover, show that discovery usually begins with the interest which men feel in the world immediately about them, or which is presented to their senses in a daily spectacle. Thus Benjamin Franklin, in the midst of a busy life, became deeply interested in the phenomena of lightning, and by a very simple experiment proved that this wonder of the air was due to electrical action such as we may arouse by rubbing a stick of sealing-wax or a piece of amber with a cloth. All discoveries, in a word, have had their necessary beginnings in an interest in the facts which daily experience discloses. This desire to know something more than the first sight exhibits concerning the actions in the world about us is native in every human soul--at least, in all those who are born with the heritage of our race. It is commonly strong in childhood; if cultivated by use, it will grow throughout a lifetime, and, like other faculties, becomes the stronger and more effective by the exertions which it inspires. It is therefore most important that every one should obey this instinctive command to inquiry, and organize his life and work so that he may not lose but gain more and more as time goes on of this noble capacity to interrogate and understand the world about him. It is best that all study of Nature should begin not in laboratories, nor with the things which are remote from us, but in the field of Nature which is immediately about us. The student, even if he dwell in the unfavourable conditions of a great city, is surrounded by the world which has yielded immeasurable riches in the way of learning, which he can appropriate by a little study. He can readily come to know something of the movements of the air; the buildings will give him access to a great many different kinds of stone; the smallest park, a little garden, or even a few potted plants and captive animals, may tell him much concerning the forms and actions of living beings. By studying in this way he can come to know something of the differences between things and their relations to each other. He will thus have a standard by which he can measure and make familiar the body of learning concerning Nature which he may find in books. From printed pages alone, however well they be written, he can never hope to catch the spirit that animates the real inquirer, the true lover of Nature. On many accounts the most attractive way of beginning to form the habit of the naturalist is by the study of living animals and plants. To all of us life adds interest, and growth has a charm. Therefore it is well for the student to start on the way of inquiry by watching the actions of birds and insects or by rearing plants. It is fortunate if he can do both these agreeable things. When the habit of taking an account of that most important part of the world which is immediately about him has been developed in the student, he may profitably proceed to acquire the knowledge of the invisible universe which has been gathered by the host of inquirers of his race. However far he journeys, he should return to the home world that lies immediately and familiarly about him, for there alone can he acquire and preserve that personal acquaintance with things which is at once the inspiration and the test of all knowledge. Along with this study of the familiar objects about us the student may well combine some reading which may serve to show him how others have been successful in thus dealing with Nature at first hand. For this purpose there are, unfortunately, but few works which are well calculated to serve the needs of the beginner. Perhaps the best naturalist book, though its form is somewhat ancient, is White's Natural History of Selborne. Hugh Miller's works, particularly his Old Red Sandstone and My Schools and Schoolmasters, show well how a man may become a naturalist under difficulties. Sir John Lubbock's studies on Wasps, and Darwin's work on Animals and Plants under Domestication are also admirable to show how observation should be made. Dr. Asa Gray's little treatise on How Plants Grow will also be useful to the beginner who wishes to approach botany from its most attractive side--that of the development of the creature from the seed to seed. There is another kind of training which every beginner in the art of observing Nature should obtain, and which many naturalists of repute would do well to give themselves--namely, an education in what we may call the art of distance and geographical forms. With the primitive savage the capacity to remember and to picture to the eye the shape of a country which he knows is native and instinctive. Accustomed to range the woods, and to trust to his recollection to guide him through the wilderness to his home, the primitive man develops an important art which among civilized people is generally dormant. In fact, in our well-trodden ways people may go for many generations without ever being called upon to use this natural sense of geography. The easiest way to cultivate the geographic sense is by practising the art of making sketch maps. This the student, however untrained, can readily do by taking first his own dwelling house, on which he should practise until he can readily from memory make a tolerably correct and proportional plan of all its rooms. Then on a smaller scale he should begin to make also from recollection a map showing the distribution of the roads, streams, and hills with which his daily life makes him familiar. From time to time this work from memory should be compared with the facts. At first the record will be found to be very poor, but with a few months of occasional endeavour the observer will find that his mind takes account of geographic features in a way it did not before, and, moreover, that his mind becomes enriched with impressions of the country which are clear and distinct, in place of the shadowy recollections which he at first possessed. When the student has attained the point where, after walking or riding over a country, he can readily recall its physical features of the simpler sort, he will find it profitable to undertake the method of mapping with contour lines--that is, by pencilling in indications to show the exact shape of the elevations and depressions. The principle of contour lines is that each of them represents where water would come against the slope if the area were sunk step by step below the sea level--in other words, each contour line marks the intersection of a horizontal plane with the elevation of the country. Practice on this somewhat difficult task will soon give the student some idea as to the complication of the surface of a region, and afford him the basis for a better understanding of what geography means than all the reading he can do will effect. It is most desirable that training such as has been described should be a part of our ordinary school education. Very few people have clear ideas of distances. Even the men whose trade requires some such knowledge are often without that which a little training could give them. Without some capacity in this direction, the student is always at a disadvantage in his contact with Nature. He can not make a record of what he sees as long as the element of horizontal and vertical distance is not clearly in mind. To attain this end the student should begin by pacing some length of road where the distances are well known. In this way he will learn the length of his step, which with a grown man generally ranges between two and a half and three feet. Learning the average length of his stride by frequent counting, it is easy to repeat the trial until one can almost unconsciously keep the count as he walks. Properly to secure the training of this sort the observer should first attentively look across the distance which is to be determined. He should notice how houses, fences, people, and trees appear at that distance. He will quickly perceive that each hundred feet of additional interval somewhat changes their aspect. In training soldiers to measure with the eye the distances which they have to know in order effectively to use the modern weapons of war, a common device is to take a squad of men, or sometimes a company, under the command of an officer, who halts one man at each hundred yards until the detachment is strung out with that interval as far as the eye can see them. The men then walk to and fro so that the troops who are watching them may note the effects of increased distance on their appearance, whether standing or in motion. At three thousand yards a man appears as a mere dot, which is not readily distinguishable. Schoolboys may find this experiment amusing and instructive. After the student has gained, as he readily may, some sense of the divisions of distance within the range of ordinary vision, he should try to form some notion of greater intervals, as of ten, a hundred, and perhaps a thousand miles. The task becomes more difficult as the length of the line increases, but most persons can with a little address manage to bring before their eyes a tolerably clear image of a hundred miles of distance by looking from some elevation which commands a great landscape. It is doubtful, however, whether the best-trained man can get any clear notion of a thousand miles--that is, can present it to himself in imagination as he may readily do with shorter intervals. The most difficult part of the general education which the student has to give himself is begun when he undertakes to picture long intervals of time. Space we have opportunities to measure, and we come in a way to appreciate it, but the longest lived of men experiences at most a century of life, and this is too small a measure to give any notion as to the duration of such great events as are involved in the history of the earth, where the periods are to be reckoned by the millions of years. The only way in which we can get any aid in picturing to ourselves great lapses of time is by expressing them in units of distance. Let a student walk away on a straight road for the distance of a mile; let him call each step a year; when he has won the first milestone, he may consider that he has gone backward in time to the period of Christ's birth. Two miles more will take him to the station which will represent the age when the oldest pyramids were built. He is still, however, in the later days of man's history on this planet. To attain on the scale the time when man began, he might well have to walk fifty miles away, while a journey which would thus by successive steps describe the years of the earth's history since life appeared upon its surface would probably require him to circle the earth at least four times. We may accept it as impossible for any one to deal with such vast durations save with figures which are never really comprehended. It is well, however, to enlarge our view as to the age of the earth by such efforts as have just been indicated. When we go beyond the earth into the realm of the stars all efforts toward understanding the ranges of space or the durations of time are quite beyond the efforts of man. Even the distance of about two hundred and forty thousand miles which separates us from the moon can not be grasped by even the greater minds. No human intelligence, however cultivated, can conceive the distance of about ninety-five million miles which separates us from the sun. In the celestial realm we can only deal with relations of space and time in a general and comparative way. We can state the distances if we please in millions of miles, or we can reckon the ampler spaces by using the interval which separates the earth from the sun as we do a foot rule in our ordinary work, but the depths of the starry spaces can only be sounded by the winged imagination. Although the student has been advised to begin his studies of Nature on the field whereon he dwells, making that study the basis of his most valuable communications with Nature, it is desirable that he should at the same time gain some idea as to the range and scope of our knowledge concerning the visible universe. As an aid toward this end the following chapters of this book will give a very brief survey of some of the most important truths concerning the heavens and the earth which have rewarded the studies of scientific men. Of remoter things, such as the bodies in the stellar spaces, the account will be brief, for that which is known and important to the general student can be briefly told. So, too, of the earlier ages of the earth's history, although a vast deal is known, the greater part of the knowledge is of interest and value mainly to geologists who cultivate that field. That which is most striking and most important to the mass of mankind is to be found in the existing state of our earth, the conditions which make it a fit abode for our kind, and replete with lessons which he may study with his own eyes without having to travel the difficult paths of the higher sciences. Although physiography necessarily takes some account of the things which have been, even in the remote past, and this for the reason that everything in this day of the world depends on the events of earlier days, the accent of its teaching is on the immediate, visible, as we may say, living world, which is a part of the life of all its inhabitants. CHAPTER III. THE STELLAR REALM. Even before men came to take any careful account of the Nature immediately about them they began to conjecture and in a way to inquire concerning the stars and the other heavenly bodies. It is difficult for us to imagine how hard it was for students to gain any adequate idea of what those lights in the sky really are. At first men imagined the celestial bodies to be, as they seemed, small objects not very far away. Among the Greeks the view grew up that the heavens were formed of crystal spheres in which the lights were placed, much as lanterns may be hung upon a ceiling. These spheres were conceived to be one above the other; the planets were on the lower of them, and the fixed stars on the higher, the several crystal roofs revolving about the earth. So long as the earth was supposed to be a flat and limitless expanse, forming the centre of the universe, it was impossible for the students of the heavens to attain any more rational view as to their plan. The fact that the earth was globular in form was understood by the Greek men of science. They may, indeed, have derived the opinion from the Egyptian philosophers. The discovery rested upon the readily observed fact that on a given day the shadow of objects of a certain height was longer in high latitude than in low. Within the tropics, when the sun was vertical, there would be no shadow, while as far north as Athens it would be of considerable length. The conclusion that the earth was a sphere appears to have been the first large discovery made by our race. It was, indeed, one of the most important intellectual acquisitions of man. Understanding the globular form of the earth, the next and most natural step was to learn that the earth was not the centre of the planetary system, much less of the universe, but that that centre was the sun, around which the earth and the other planets revolved. The Greeks appear to have had some idea that this was the case, and their spirit of inquiry would probably have led them to the whole truth but for the overthrow of their thought by the Roman conquest and the spread of Christianity. It was therefore not until after the revival of learning that astronomers won their way to our modern understanding concerning the relation of the planets to the sun. With Galileo this opinion was affirmed. Although for a time the Church, resting its opposition on the interpretation of certain passages of Scripture, resisted this view, and even punished the men who held it, it steadfastly made its way, and for more than two centuries has been the foundation of all the great discoveries in the stellar realm. Yet long after the fact that the sun was the centre of the solar system was well established no one understood why the planets should move in their ceaseless, orderly procession around the central mass. To Newton we owe the studies on the law of gravitation which brought us to our present large conception as to the origin of this order. Starting with the view that bodies attracted each other in proportion to their weight, and in diminishing proportion as they are removed from each other, Newton proceeded by most laborious studies to criticise this view, and in the end definitely proved it by finding that the motions of the moon about the earth, as well as the paths of the planets, exactly agreed with the supposition. The last great path-breaking discovery which has helped us in our understanding of the stars was made by Fraunhofer and other physicists, who showed us that substances when in a heated, gaseous, or vaporous state produced, in a way which it is not easy to explain in a work such as this, certain dark lines in the spectrum, or streak of divided light which we may make by means of a glass prism, or, as in the rainbow, by drops of water. Carefully studying these very numerous lines, those naturalists found that they could with singular accuracy determine what substances there were in the flame which gave the light. So accurate is this determination that it has been made to serve in certain arts where there is no better means of ascertaining the conditions of a flaming substance except by the lines which its light exhibits under this kind of analysis. Thus, in the manufacture of iron by what is called the Bessemer process, it has been found very convenient to judge as to the state of the molten metal by such an analysis of the flame which comes forth from it. [Illustration: _Seal Rocks near San Francisco, California, showing slight effect of waves where there is no beach._] No sooner was the spectroscope invented than astronomers hastened by its aid to explore the chemical constitution of the sun. These studies have made it plain that the light of our solar centre comes forth from an atmosphere composed of highly heated substances, all of which are known among the materials forming the earth. Although for various reasons we have not been able to recognise in the sun all the elements which are found in our sphere, it is certain that in general the two bodies are alike in composition. An extension of the same method of inquiry to the fixed stars was gradually though with difficulty attained, and we now know that many of the elements common to the sun and earth exist in those distant spheres. Still further, this method of inquiry has shown us, in a way which it is not worth while here to describe, that among these remoter suns there are many aggregations of matter which are not consolidated as are the spheres of our own solar system, but remain in the gaseous state, receiving the name of nebulæ. Along with the growth of observational astronomy which has taken place since the discoveries of Galileo, there has been developed a view concerning the physical history of the stellar world, known as the nebular hypothesis, which, though not yet fully proved, is believed by most astronomers and physicists to give us a tolerably correct notion as to the way in which the heavenly spheres were formed from an earlier condition of matter. This majestic conception was first advanced, in modern times at least, by the German philosopher Immanuel Kant. It was developed by the French astronomer Laplace, and is often known by his name. The essence of this view rests upon the fact previously noted that in the realm of the fixed stars there are many faintly shining aggregations of matter which are evidently not solid after the manner of the bodies in our solar system, but are in the state where their substances are in the condition of dustlike particles, as are the bits of carbon in flame or the elements which compose the atmosphere. The view held by Laplace was to the effect that not only our own solar system, but the centres of all the other similar systems, the fixed stars, were originally in this gaseous state, the material being disseminated throughout all parts of the heavenly realm, or at least in that portion of the universe of which we are permitted to know something. In this ancient state of matter we have to suppose that the particles of it were more separated from each other than are the atoms of the atmospheric gases in the most perfect vacuum which we can produce with the air-pump. Still we have to suppose that each of these particles attract the other in the gravitative way, as in the present state of the universe they inevitably do. Under the influence of the gravitative attraction the materials of this realm of vapour inevitably tended to fall in toward the centre. If the process had been perfectly simple, the result would have been the formation of one vast mass, including all the matter which was in the original body. In some way, no one has yet been able to make a reasonable suggestion of just how, there were developed in the process of concentration a great many separate centres of aggregation, each of which became the beginning of a solar system. The student may form some idea of how readily local centres may be produced in materials disseminated in the vaporous state by watching how fog or the thin, even misty clouds of the sunrise often gather into the separate shapes which make what we term a "mackerel" sky. It is difficult to imagine what makes centres of attraction, but we readily perceive by this instance how they might have occurred. When the materials of each solar system were thus set apart from the original mass of star dust or vapour, they began an independent development which led step by step, in the case of our own solar system at least, and presumably also in the case of the other suns, the fixed stars, to the formation of planets and their moons or satellites, all moving around the central sun. At this stage of the explanation the nebular hypothesis is more difficult to conceive than in the parts of it which have already been described, for we have now to understand how the planets and satellites had their matter separated from each other and from the solar centre, and why they came to revolve around that central body. These problems are best understood by noting some familiar instances connected with the movement of fluids and gases toward a centre. First let us take the case of a basin in which the water is allowed to flow out through a hole in its centre. When we lift the stopper the fluid for a moment falls straight down through the opening. Very quickly, however, all the particles of the water start to move toward the centre, and almost at once the mass begins to whirl round with such speed that, although it is working toward the middle, it is by its movement pushed away from the centre and forms a conical depression. As often as we try the experiment, the effect is always the same. We thus see that there is some principle which makes particles of fluid that tend toward a centre fail directly to attain it, but win their way thereto in a devious, spinning movement. Although the fact is not so readily made visible to the eye, the same principle is illustrated in whirling storms, in which, as we shall hereafter note with more detail, the air next the surface of the earth is moving in toward a kind of chimney by which it escapes to the upper regions of the atmosphere. A study of cyclones and tornadoes, or even of the little air-whirls which in hot weather lift the dust of our streets, shows that the particles of the atmosphere in rushing in toward the centre of upward movement take on the same whirling motion as do the molecules of water in the basin--in fact, the two actions are perfectly comparable in all essential regards, except that the fluid is moving downward, while the air flows upward. Briefly stated, the reason for the movement of fluid and gas in the whirling way is as follows: If every particle on its way to the centre moved on a perfectly straight line toward the point of escape, the flow would be directly converging, and the paths followed would resemble the spokes of a wheel. But when by chance one of the particles sways ever so little to one side of the direct way, a slight lateral motion would necessarily be established. This movement would be due to the fact that the particle which pursued the curved line would press against the particles on the out-curved side of its path--or, in other words, shove them a little in that direction--to the extent that they departed from the direct line they would in turn communicate the shoving to the next beyond. When two particles are thus shoving on one side of their paths, the action which makes for revolution is doubled, and, as we readily see, the whole mass may in this way become quickly affected, the particles driven out of their path, moving in a curve toward the centre. We also see that the action is accumulative: the more curved the path of each particle, the more effectively it shoves; and so, in the case of the basin, we see the whirling rapidly developed before our eyes. In falling in toward the centre the particles of star dust or vapour would no more have been able one and all to pursue a perfectly straight line than the particles of water in the basin. If a man should spend his lifetime in filling and emptying such a vessel, it is safe to say that he would never fail to observe the whirling movement. As the particles of matter in the nebular mass which was to become a solar system are inconceivably greater than those of water in the basin, or those of air in the atmospheric whirl, the chance of the whirling taking place in the heavenly bodies is so great that we may assume that it would inevitably occur. As the vapours in the olden day tended in toward the centre of our solar system, and the mass revolved, there is reason to believe that ringlike separations took place in it. Whirling in the manner indicated, the mass of vapour or dust would flatten into a disk or a body of circular shape, with much the greater diameter in the plane of its whirling. As the process of concentration went on, this disk is supposed to have divided into ringlike masses, some approach to which we can discern in the existing nebulæ, which here and there among the farther fixed stars appear to be undergoing such stages of development toward solar systems. It is reasonably supposed that after these rings had been developed they would break to pieces, the matter in them gathering into a sphere, which in time was to become a planet. The outermost of these rings led to the formation of the planet farthest from the sun, and was probably the first to separate from the parent mass. Then in succession rings were formed inwardly, each leading in turn to the creation of another planet, the sun itself being the remnant, by far the greater part of the whole mass of matter, which did not separate in the manner described, but concentrated on its centre. Each of these planetary aggregations of vapour tended to develop, as it whirled upon its centre, rings of its own, which in turn formed, by breaking and concentrating, the satellites or moons which attend the earth, as they do all the planets which lie farther away from the sun than our sphere. [Illustration: Fig. 1.--Saturn, Jan. 26, 1889 (Antoniadi).] As if to prove that the planets and moons of the solar system were formed somewhat in the manner in which we have described it, one of these spheres, Saturn, retains a ring, or rather a band which appears to be divided obscurely into several rings which lie between its group of satellites and the main sphere. How this ring has been preserved when all the others have disappeared, and what is the exact constitution of the mass, is not yet well ascertained. It seems clear, however, that it can not be composed of solid matter. It is either in the form of dust or of small spheres, which are free to move on each other; otherwise, as computation shows, the strains due to the attraction which Saturn itself and its moons exercise upon it would serve to break it in pieces. Although this ring theory of the formation of the planets and satellites is not completely proved, the occurrence of such a structure as that which girdles Saturn affords presumptive evidence that it is true. Taken in connection with what we know of the nebulæ, the proof of Laplace's nebular hypothesis may fairly be regarded as complete. It should be said that some of the fixed stars are not isolated suns like our own, but are composed of two great spheres revolving about one another; hence they are termed double stars. The motions of these bodies are very peculiar, and their conditions show us that it is not well to suppose that the solar system in which we dwell is the only type of order which prevails in the celestial families; there may, indeed, be other variations as yet undetected. Still, these differences throw no doubt on the essential truth of the theory as to the process of development of the celestial systems. Though there is much room for debate as to the details of the work there, the general truth of the theory is accepted by nearly all the students of the problem. A peculiar advantage of the nebular hypothesis is that it serves to account for the energy which appears as light and heat in the sun and the fixed stars, as well as that which still abides in the mass of our earth, and doubtless also in the other large planets. When the matter of which these spheres were composed was disseminated through the realms of space, it is supposed to have had no positive temperature, and to have been dark, realizing the conception which appears in the first chapter of Genesis, "without form, and void." With each stage of the falling in toward the solar centres what is called the "energy of position" of this original matter became converted into light and heat. To understand how this took place, the reader should consider certain simple yet noble generalizations of physics. We readily recognise the fact that when a hammer falls often on an anvil it heats itself and the metal on which it strikes. Those who have been able to observe the descent of meteoric stones from the heavens have remarked that when they came to the earth they were, on their surfaces at least, exceedingly hot. Any one may observe shining meteors now and then flashing in the sky. These are known commonly to be very small bits of matter, probably not larger than grains of sand, which, rushing into our atmosphere, are so heated by the friction which they encounter that they burn to a gas or vapour before they attain the earth. As we know that these particles come from the starry spaces, where the temperature is somewhere near 500° below 0° Fahr., it is evident that the light and heat are not brought with them into the atmosphere; it can only be explained by the fact that when they enter the air they are moving at an average speed of about twenty miles a second, and that the energy which this motion represents is by the resistance which the body encounters converted into heat. This fact will help us to understand how, as the original star dust fell in toward the centre of attraction, it was able to convert what we have termed the energy of position into temperature. We see clearly that every such particle of dust or larger bit of matter which falls upon the earth brings about the development of heat, even though it does not actually strike upon the solid mass of our sphere. The conception of what took place in the consolidation of the originally disseminated materials of the sun and planets can be somewhat helped by a simple experiment. If we fit a piston closely into a cylinder, and then suddenly drive it down with a heavy blow, the compressed air is so heated that it may be made to communicate fire. If the piston should be slowly moved, the same amount of heat would be generated, or, as we may better say, liberated by the compression, though the effect would not be so striking. A host of experiments show that when a given mass of matter is brought to occupy a less space the effect is in practically all cases to increase the temperature. The energy which kept the particles apart is, when they are driven together, converted into heat. These two classes of actions are somewhat different in their nature; in the case of the meteors, or the equivalent star dust, the coming together of the particles is due to gravitation. In the experiment with the cylinder above described, the compression is due to mechanical energy, a force of another nature. There is reason for believing that all our planets, as well as the sun itself, and also the myriad other orbs of space, have all passed through the stages of a transition in which a continually concentrating vapour, drawn together by gravitation, became progressively hotter and more dense until it assumed the condition of a fluid. This fluid gradually parted with its heat to the cold spaces of the heavens, and became more and more concentrated and of a lower temperature until in the end, as in the case of our earth and of other planets, it ceased to glow on the outside, though it remained intensely heated in the inner parts. It is easy to see that the rate of this cooling would be in some proportion to the size of the sphere. Thus the earth, which is relatively small, has become relatively cold, while the sun itself, because of its vastly greater mass, still retains an exceedingly high temperature. The reason for this can readily be conceived by making a comparison of the rate of cooling which occurs in many of our ordinary experiences. Thus a vial of hot water will quickly come down to the temperature of the air, while a large jug filled with the fluid at the same temperature will retain its heat many times as long. The reason for this rests upon the simple principle that the contents of a sphere increase with its enlargement more rapidly than the surface through which the cooling takes place. The modern studies on the physical history of the sun and other celestial bodies show that their original store of heat is constantly flowing away into the empty realms of space. The rate at which this form of energy goes away from the sun is vast beyond the powers of the imagination to conceive; thus, in the case of our earth, which viewed from the sun would appear no more than a small star, the amount of heat which falls upon it from the great centre is enough each day to melt, if it all could be put to such work, about eight thousand cubic miles of ice. Yet the earth receives only 1/2,170,000,000 part of the solar radiation. The greater part of this solar heat--in fact, we may say nearly all of it--slips by the few and relatively small planets and disappears in the great void. The destiny of all the celestial spheres seems in time to be that they shall become cooled down to a temperature far below anything which is now experienced on this earth. Even the sun, though its heat will doubtless endure for millions of years to come, must in time, so far as we can see, become dark and cold. So far as we know, we can perceive no certain method by which the life of the slowly decaying suns can be restored. It has, however, been suggested that in many cases a planetary system which has attained the lifeless and lightless stage may by collision with some other association of spheres be by the blow restored to its previous state of vapour, the joint mass of the colliding systems once again to resume the process of concentration through which it had gone before. Now and then stars have been seen to flash suddenly into great brilliancy in a way which suggests that possibly their heat had been refreshed by a collision with some great mass which had fallen into them from the celestial spaces. There is room for much speculation in this field, but no certainty appears to be attainable. The ancients believed that light and heat were emanations which were given off from the bodies that yielded them substantially as odours are given forth by many substances. Since the days of Newton inquiry has forced us to the conviction that these effects of temperature are produced by vibrations having the general character of waves, which are sent through the spaces with great celerity. When a ray of light departs from the sun or other luminous body, it does not convey any part of the mass; it transmits only motion. A conception of the action can perhaps best be formed by suspending a number of balls of ivory, stone, or other hard substance each by a cord, the series so arranged that they touch each other. Then striking a blow against one end of the line, we observe that the ball at the farther end of the line is set in motion, swinging a little away from the place it occupied before. The movement of the intermediate balls may be so slight as to escape attention. We thus perceive that energy can be transmitted from one to another of these little spheres. Close observation shows us that under the impulse which the blow gives each separate body is made to sway within itself much in the manner of a bell when it is rung, and that the movement is transmitted to the object with which it is in contact. In passing from the sun to the earth, the light and heat traverse a space which we know to be substantially destitute of any such materials as make up the mass of the earth or the sun. Judged by the standards which we can apply, this space must be essentially empty. Yet because motions go through it, we have to believe that it is occupied by something which has certain of the properties of matter. It has, indeed, one of the most important properties of all substances, in that it can vibrate. This practically unknown thing is called ether. The first important observational work done by the ancients led them to perceive that there was a very characteristic difference between the planets and the fixed stars. They noted the fact that the planets wandered in a ceaseless way across the heavens, while the fixed stars showed little trace of changing position in relation to one another. For a long time it was believed that these, as well as the remoter fixed stars, revolved about the earth. This error, though great, is perfectly comprehensible, for the evident appearance of the movement is substantially what would be brought about if they really coursed around our sphere. It was only when the true nature of the earth and its relations to the sun were understood that men could correct this first view. It was not, indeed, until relatively modern times that the solar system came to be perceived as something independent and widely detached from the fixed stars system; that the spaces which separate the members of our own solar family, inconceivably great as they are, are but trifling as compared with the intervals which part us from the nearer fixed stars. At this stage of our knowledge men came to the noble suggestion that each of the fixed stars was itself a sun, each of the myriad probably attended by planetary bodies such as exist about our own luminary. It will be well for the student to take an imaginary journey from the sun forth into space, along the plane in which extends that vast aggregation of stars which we term the Milky Way. Let him suppose that his journey could be made with something like the speed of light, or, say, at the rate of about two hundred thousand miles a second. It is fit that the imagination, which is free to go through all things, should essay such excursions. On the fancied outgoing, the observer would pass the interval between the sun and the earth in about eight minutes. It would require some hours before he attained to the outer limit of the solar system. On his direct way he would pass the orbits of the several planets. Some would have their courses on one side or the other of his path; we should say above or below, but for the fact that we leave these terms behind in the celestial realm. On the margin of the solar system the sun would appear shrunken to the state where it was hardly greater than the more brilliant of the other fixed stars. The onward path would then lead through a void which it would require years to traverse. Gradually the sun which happened to lie most directly in his path would grow larger; with nearer approach, it would disclose its planets. Supposing that the way led through this solar system, there would doubtless be revealed planets and satellites in their order somewhat resembling those of our own solar family, yet there would doubtless be many surprises in the view. Arriving near the first sun to be visited, though the heavens would have changed their shape, all the existing constellations having altered with the change in the point of view, there would still be one familiar element in that the new-found planets would be near by, and the nearest fixed stars far away in the firmament. With the speed of light a stellar voyage could be taken along the path of the Milky Way, which would endure for thousands of years. Through all the course the journeyer would perceive the same vast girdle of stars, faint because they were far away, which gives the dim light of our galaxy. At no point is it probable that he would find the separate suns much more aggregated or greatly farther apart than they are in that part of the Milky Way which our sun now occupies. Looking forth on either side of the "galactic plane," there would be the same scattering of stars which we now behold when we gaze at right angles to the way we are supposing the spirit to traverse. As the form of the Milky Way is irregular, the mass, indeed, having certain curious divisions and branches, it well might be that the supposed path would occasionally pass on one or the other side of the vast star layer. In such positions the eye would look forth into an empty firmament, except that there might be in the far away, tens of thousands of years perhaps at the rate that light travels away from the observer, other galaxies or Milky Ways essentially like that which he was traversing. At some point the journeyer would attain the margin of our star stratum, whence again he would look forth into the unpeopled heavens, though even there he might discern other remote star groups separated from his own by great void intervals. * * * * * The revelations of the telescope show us certain features in the constitution and movements of the fixed stars which now demand our attention. In the first place, it is plain that not all of these bodies are in the same physical condition. Though the greater part of these distant luminous masses are evidently in the state of aggregation displayed by our own sun, many of them retain more or less of that vaporous, it may be dustlike, character which we suppose to have been the ancient state of all the matter in the universe. Some of these masses appear as faint, almost indistinguishable clouds, which even to the greatest telescope and the best-trained vision show no distinct features of structure. In other cases the nebulous appearance is hardly more than a mist about a tolerably distinct central star. Yet again, and most beautifully in the great nebula of the constellation of Orion, the cloudy mass, though hardly visible to the naked eye, shows a division into many separate parts, the whole appearing as if in process of concentration about many distinct centres. The nebulas are reasonably believed by many astronomers to be examples of the ancient condition of the physical universe, masses of matter which for some reason as yet unknown have not progressed in their consolidation to the point where they have taken on the characteristics of suns and their attendant planets. Many of the fixed stars, the incomplete list of which now amounts to several hundred, are curiously variable in the amount of light which they send out to the earth. Sometimes these variations are apparently irregular, but in the greater number of cases they have fixed periods, the star waxing and waning at intervals varying from a few months to a few years. Although some of the sudden flashings forth of stars from apparent small size to near the greatest brilliancy may be due to catastrophes such as might be brought about by the sudden falling in of masses of matter upon the luminous spheres, it is more likely that the changes which we observe are due to the fact that two suns revolving around a common centre are in different stages of extinction. It may well be that one of these orbs, presumably the smaller, has so far lost temperature that it has ceased to glow. If in its revolution it regularly comes between the earth and its luminous companion, the effect would be to give about such a change in the amount of light as we observe. The supposition that a bright sun and a relatively dark sun might revolve around a common centre of gravity may at first sight seem improbable. The fact is, however, that imperfect as our observations on the stars really are, we know many instances in which this kind of revolution of one star about another takes place. In some cases these stars are of the same brilliancy, but in others one of the lights is much brighter than the other. From this condition to the state where one of the stars is so nearly dark as to be invisible, the transition is but slight. In a word, the evidence goes to show that while we see only the luminous orbs of space, the dark bodies which people the heavens are perhaps as numerous as those which send us light, and therefore appear as stars. Besides the greater spheres of space, there is a vast host of lesser bodies, the meteorites and comets, which appear to be in part members of our solar system, and perhaps of other similar systems, and in part wanderers in the vast realm which intervenes between the solar systems. Of these we will first consider the meteors, of which we know by far the most; though even of them, as we shall see, our knowledge is limited. From time to time on any starry night, and particularly in certain periods of the year, we may behold, at the distance of fifty or more miles above the surface of the earth, what are commonly called "shooting stars." The most of these flashing meteors are evidently very small, probably not larger than tiny sand grains, possibly no greater than the fragments which would be termed dust. They enter the air at a speed of about thirty miles a second. They are so small that they burn to vapour in the very great heat arising from their friction on the air, and do not attain the surface of the earth. These are so numerous that, on the average, some hundreds of thousands probably strike the earth's atmosphere each day. From time to time larger bodies fall--bodies which are of sufficient bulk not to be burned up in the air, but which descend to the ground. These may be from the smallest size which may be observed to masses of many hundred pounds in weight. These are far less numerous than the dust meteorites; it is probable, however, that several hundred fragments each year attain the earth's surface. They come from various directions of space, and there is as yet no means of determining whether they were formed in some manner within our planetary system or whether they wander to us from remoter realms. We know that they are in part composed of metallic iron commingled with nickel and carbon (sometimes as very small diamonds) in a way rarely if ever found on the surface of our sphere, and having a structure substantially unknown in its deposits. In part they are composed of materials which somewhat resemble certain lavas. It is possible that these fragments of iron and stone which constitute the meteorites have been thrown into the planetary spaces by the volcanic eruption of our own and other planets. If hurled forth with a sufficient energy, the fragments would escape from the control of the attraction of the sphere whence they came, and would become independent wanderers in space, moving around the sun in varied orbits until they were again drawn in by some of the greater planets. As they come to us these meteorites often break up in the atmosphere, the bits being scattered sometimes over a wide area of country. Thus, in the case of the Cocke County meteorite of Tennessee, one of the iron species, the fragments, perhaps thousands in number, which came from the explosion of the body were scattered over an area of some thousand square miles. When they reach the surface in their natural form, these meteors always have a curious wasted and indented appearance, which makes it seem likely that they have been subject to frequent collisions in their journeys after they were formed by some violent rending action. In some apparent kinship with the meteorites may be classed the comets. The peculiarity of these bodies is that they appear in most cases to be more or less completely vaporous. Rushing down from the depths of the heavens, these bodies commonly appear as faintly shining, cloudlike masses. As they move in toward the sun long trails of vapour stream back from the somewhat consolidated head. Swinging around that centre, they journey again into the outer realm. As they retreat, their tail-like streamers appear to gather again upon their centres, and when they fade from view they are again consolidated. In some cases it has been suspected that a part at least of the cometary mass was solid. The evidence goes to show, however, that the matter is in a dustlike or vaporous condition, and that the weight of these bodies is relatively very small. [Illustration: Fig. 2.--The Great Comet of 1811, one of the many varied forms of these bodies.] Owing to their strange appearance, comets were to the ancients omens of calamity. Sometimes they were conceived as flaming swords; their forms, indeed, lend themselves to this imagining. They were thought to presage war, famine, and the death of kings. Again, in more modern times, when they were not regarded as portents of calamity, it was feared that these wanderers moving vagariously through our solar system might by chance come in contact with the earth with disastrous results. Such collisions are not impossible, for the reason that the planets would tend to draw these errant bodies toward them if they came near their spheres; yet the chance of such collisions happening to the earth is so small that they may be disregarded. MOTIONS OF THE SPHERES. Although little is known of the motions which occur among the celestial bodies beyond the sphere of our solar family, that which has been ascertained is of great importance, and serves to make it likely that all the suns in space are upon swift journeys which in their speed equal, if they do not exceed, the rate of motion among the planetary spheres, which may, in general, be reckoned at about twenty miles a second. Our whole solar system is journeying away from certain stars, and in the direction of others which are situated in the opposite part of the heavens. The proof of this fact is found in the observations which show that on one side of us the stars are apparently coming closer together, while on the other side they are going farther apart. The phenomenon, in a word, is one of perspective, and may be made real to the understanding by noting what takes place when we travel down a street along which there are lights. We readily note that these lights appear to close in behind us, and widen their intervals in the direction in which we journey. By such evidence astronomers have become convinced that our sphere, along with the sun which controls it, is each second a score of miles away from the point where it was before. There is yet other and most curious evidence which serves to show that certain of the stars are journeying toward our part of the heavens at great speed, while others are moving away from us by their own proper motion. These indications are derived from the study of the lines in the light which the spectrum reveals to us when critically examined. The position of these cross lines is, as we know, affected by the motion of the body whence the light comes, and by close analysis of the facts it has been pretty well determined that the distortion in their positions is due to very swift motions of the several stars. It is not yet certain whether these movements of our sun and of other solar bodies are in straight lines or in great circles. It should be noted that, although the evidence from the spectroscope serves to show that the matter in the stars is akin to that of our own earth, there is reason to believe that those great spheres differ much from each other in magnitude. We have now set forth some of the important facts exhibited by the stellar universe. The body of details concerning that realm is vast, and the conclusions drawn from it important; only a part, however, of the matter with which it deals is of a nature to be apprehended by the student who does not approach it in a somewhat professional way. We shall therefore now turn to a description of the portion of the starry world which is found in the limits of our solar system. There the influences of the several spheres upon our planet are matters of vital importance; they in a way affect, if they do not control, all the operations which go on upon the surface of the earth. THE SOLAR SYSTEM. We have seen that the matter in the visible universe everywhere tends to gather into vast associations which appear to us as stars, and that these orbs are engaged in ceaseless motion in journeys through space. In only one of these aggregations--that which makes our own solar system--are the bodies sufficiently near to our eyes for us, even with the resources of our telescopes and other instruments, to divine something of the details which they exhibit. In studying what we may concerning the family of the sun, the planets, and their satellites, we may reasonably be assured that we are tracing a history which with many differences is in general repeated in the development of each star in the firmament. Therefore the inquiry is one of vast range and import. Following, as we may reasonably do, the nebular hypothesis--a view which, though not wholly proved, is eminently probable--we may regard our solar system as having begun when the matter of which it is composed, then in a finely divided, cloudy state, was separated from the similar material which went to make the neighbouring fixed stars. The period when our solar system began its individual life was remote beyond the possibility of conception. Naturalists are pretty well agreed that living beings began to exist upon the earth at least a hundred million years ago; but the beginnings of our solar system must be placed at a date very many times as remote from the present day.[1] [Footnote 1: Some astronomers, particularly the distinguished Professor Newcomb, hold that the sun can not have been supplying heat as at present for more than about ten million years, and that all geological time must be thus limited. The geologist believes that this reckoning is far too short.] According to the nebular theory, the original vapour of the solar system began to fall in toward its centre and to whirl about that point at a time long before the mass had shrunk to the present limits of the solar system as defined by the path of the outermost planets. At successive stages of the concentration, rings after the manner of those of Saturn separated from the disklike mass, each breaking up and consolidating into a body of nebulous matter which followed in the same path, generally forming rings which became by the same process the moons or satellites of the sphere. In this way the sun produced eight planets which are known, and possibly others of small size on the outer verge of the system which have eluded discovery. According to this view, the planetary masses were born in succession, the farthest away being the oldest. It is, however, held by an able authority that the mass of the solar system would first form a rather flat disk, the several rings forming and breaking into planets at about the same time. The conditions in Saturn, where the inner ring remains parted, favours the view just stated. Before making a brief statement of the several planets, the asteroids, and the satellites, it will be well to consider in a general way the motions of these bodies about their centres and about the sun. The most characteristic and invariable of these movements is that by which each of the planetary spheres, as well as the satellites, describes an orbit around the gravitative centre which has the most influence upon it--the sun. To conceive the nature of this movement, it will be well to imagine a single planet revolving around the sun, each of these bodies being perfect spheres, and the two the only members of the solar system. In this condition the attraction of the two bodies would cause them to circle around a common centre of gravity, which, if the planet were not larger or the sun smaller than is the case in our solar system, would lie within the mass of the sun. In proportion as the two bodies might approach each other in size, the centre of gravity would come the nearer to the middle point in a line connecting the two spheres. In this condition of a sun with a single planet, whatever were the relative size of sun and planet, the orbits which they traverse would be circular. In this state of affairs it should be noted that each of the two bodies would have its plane of rotation permanently in the same position. Even if the spheres were more or less flattened about the poles of their axes, as is the case with all the planets which we have been able carefully to measure, as well as with the sun, provided the axes of rotation were precisely parallel to each other, the mutual attraction of the masses would cause no disturbance of the spheres. The same would be the case if the polar axis of one sphere stood precisely at right angles to that of the other. If, however, the spheres were somewhat flattened at the poles, and the axes inclined to each other, then the pull of one mass on the other would cause the polar axes to keep up a constant movement which is called nutation, or nodding. The reason why this nodding movement of the polar axes would occur when these lines were inclined to each other is not difficult to see if we remember that the attraction of masses upon each other is inversely as the square of the distance; each sphere, pulling on the equatorial bulging of the other, pulls most effectively on the part of it which is nearest, and tends to draw it down toward its centre. The result is that the axes of the attracted spheres are given a wobbling movement, such as we may note in the spinning top, though in the toy the cause of the motion is not that which we are considering. If, now, in that excellent field for the experiment we are essaying, the mind's eye, we add a second planet outside of the single sphere which we have so far supposed to journey about the sun, or rather about the common centre of gravity, we perceive at once that we have introduced an element which leads to a complication of much importance. The new sphere would, of course, pull upon the others in the measure of its gravitative value--i.e., its weight. The centre of gravity of the system would now be determined not by two distinct bodies, but by three. If we conceive the second planet to journey around the sun at such a rate that a straight line always connected the centres of the three orbs, then the only effect on their gravitative centre would be to draw the first-mentioned planet a little farther away from the centre of the sun; but in our own solar system, and probably in all others, this supposition is inadmissible, because the planets have longer journeys to go and also move slower, the farther they are from the sun. Thus Mercury completes the circle of its year in eighty-eight of our days, while the outermost planet requires sixty thousand days (more than one hundred and sixty-four years) for the same task. The result is not only that the centre of gravity of the system is somewhat displaced--itself a matter of no great account--but also that the orbit of the original planet ceases to be circled and becomes elliptical, and this for the evident reason that the sphere will be drawn somewhat away from the sun when the second planet happens to lie in the part of its orbit immediately outside of its position, in which case the pull is away from the solar centre; while, on the other hand, when the new planet was on the other side of the sun, its pull would serve to intensify the attraction which drew the first sphere toward the centre of gravity. As the pulling action of the three bodies upon each other, as well as upon their equatorial protuberances, would vary with every change in their relative position, however slight, the variations in the form of their orbits, even if the spheres were but three in number, would be very important. The consequences of these perturbations will appear in the sequel. In our solar system, though there are but eight great planets, the group of asteroids, and perhaps a score of satellites, the variety of orbital and axial movement which is developed taxes the computing genius of the ablest astronomer. The path which our earth follows around the sun, though it may in general and for convenience be described as a variable ellipse, is, in fact, a line of such complication that if we should essay a diagram of it on the scale of this page it would not be possible to represent any considerable part of its deviations. These, in fact, would elude depiction, even if the draughtsman had a sheet for his drawing as large as the orbit itself, for every particle of matter in space, even if it be lodged beyond the limits of the farthest stars revealed to us by the telescope, exercises a certain attraction, which, however small, is effective on the mass of the earth. Science has to render its conclusions in general terms, and we can safely take them as such; but in this, as in other instances, it is well to qualify our acceptance of the statements by the memory that all things are infinitely more complicated than we can possibly conceive or represent them to be. We have next to consider the rotations of the planetary spheres upon their axes, together with the similar movement, or lack of it, in the case of their satellites. This rotation, according to the nebular hypothesis, may be explained by the movements which would set up in the share of matter which was at first a ring of the solar nebula, and which afterward gathered into the planetary aggregation. The way of it may be briefly set forth as follows: Such a ring doubtless had a diameter of some million miles; we readily perceive that the particles of matter in the outer part of the belt would have a swifter movement around the sun than those on the inside. When by some disturbance, as possibly by the passage of a great meteoric body of a considerable gravitative power, this ring was broken in two, the particles composing it on either side would, because of their mutual attraction, tend to draw away from the breach, widening that gap until the matter of the broken ring was aggregated into a sphere of the star dust or vapour. When the nebulous matter originally in the ring became aggregated into a spherical form, it would, on account of the different rates at which the particles were moving when they came together, be the surer to fall in toward the centre, not in straight lines, but in curves--in other words, the mass would necessarily take on a movement of rotation essentially like that which we have described in setting forth the nebular hypothesis. In the stages of concentration the planetary nebulæ might well repeat those through which the greater solar mass proceeded. If the volume of the material were great, subordinate rings would be formed, which when they broke and concentrated would constitute secondary planets or satellites, such as our moon. For some reason as yet unknown the outer planets--in fact, all those in the solar system except the two inner, Venus and Mercury and the asteroids--formed such attendants. All these satellite-forming rings have broken and concentrated except the inner of Saturn, which remains as an intellectual treasure of the solar system to show the history of its development. To the student who is not seeking the fulness of knowledge which astronomy has to offer, but desires only to acquaint himself with the more critical and important of the heavenly phenomena which help to explain the earth, these features of planetary movement should prove especially interesting for the reason that they shape the history of the spheres. As we shall hereafter see, the machinery of the earth's surface, all the life which it bears, its winds and rains--everything, indeed, save the actions which go on in the depths of the sphere--is determined by the heat and light which come from the sun. The conditions under which this vivifying tide is received have their origin in the planetary motion. If our earth's path around the centre of the system was a perfect circle, and if its polar axis lay at right angles to the plane of its journey, the share of light and heat which would fall upon any one point on the sphere would be perfectly uniform. There would be no variations in the length of day or night; no changes in the seasons; the winds everywhere would blow with exceeding steadiness--in fact, the present atmospheric confusion would be reduced to something like order. From age to age, except so far as the sun itself might vary in the amount of energy which it radiated, or lands rose up into the air or sunk down toward the sea level, the climate of each region would be perfectly stable. In the existing conditions the influences bring about unending variety. First of all, the inclined position of the polar axis causes the sun apparently to move across the heavens, so that it comes in an overhead position once or twice in the year in quite half the area of the lands and seas. This apparent swaying to and fro of the sun, due to the inclination of the axis of rotation, also affects the width of the climatal belts on either side of the equator, so that all parts of the earth receive a considerable share of the sun's influence. If the axis of the earth's rotation were at right angles to the plane of its orbit, there would be a narrow belt of high temperature about the equator, north and south of which the heat would grade off until at about the parallels of fifty degrees we should find a cold so considerable and uniform that life would probably fade away; and from those parallels to the poles the conditions would be those of permanent frost, and of days which would darken into the enduring night or twilight in the realm of the far north and south. Thus the wide habitability of the earth is an effect arising from the inclination of its polar axis. [Illustration: Fig. 3.--Inclination of Planetary Orbits (from Chambers).] As the most valuable impression which the student can receive from his study of Nature is that sense of the order which has made possible all life, including his own, it will be well for him to imagine, as he may readily do, what would be the effect arising from changes in relations of earth and sun. Bringing the earth's axis in imagination into a position at right angles to the plane of the orbit, he will see that the effect would be to intensify the equatorial heat, and to rob the high latitudes of the share which they now have. On moving the axis gradually to positions where it approaches the plane of the orbit, he will note that each stage of the change widens the tropic belt. Bringing the polar axis down to the plane of the orbit, one hemisphere would receive unbroken sunshine, the other remaining in perpetual darkness and cold. In this condition, in place of an equatorial line we should have an equatorial point at the pole nearest the sun; thence the temperatures would grade away to the present equator, beyond which half the earth would be in more refrigerating condition than are the poles at the present day. In considering the movements of our planet, we shall see that no great changes in the position of the polar axis can have taken place. On this account the suggested alterations of the axis should not be taken as other than imaginary changes. It is easy to see that with a circular orbit and with an inclined axis winter and summer would normally come always at the same point in the orbit, and that these seasons would be of perfectly even length. But, as we have before noted, the earth's path around the sun is in its form greatly affected by the attractions which are exercised by the neighbouring planets, principally by those great spheres which lie in the realm without its orbit, Jupiter and Saturn. When these attracting bodies, as is the case from time to time, though at long intervals, are brought together somewhere near to that part of the solar system in which the earth is moving around the sun, they draw our planet toward them, and so make its path very elliptical. When, however, they are so distributed that their pulling actions neutralize each other, the orbit returns more nearly to a circular form. The range in its eccentricity which can be brought about by these alterations is very great. When the path is most nearly circular, the difference in the major and minor axis may amount to as little as about five hundred thousand miles, or about one one hundred and eighty-sixth of its average diameter. When the variation is greatest the difference in these measurements may be as much as near thirteen million miles, or about one seventh of the mean width of the orbit. The first and most evident effect arising from these changes of the orbit comes from the difference in the amount of heat which the earth may receive according as it is nearer or farther from the sun. As in the case of other fires, the nearer a body is to it the larger the share of light and heat which it will receive. In an orbit made elliptical by the planetary attraction the sun necessarily occupies one of the foci of the ellipse. The result is, of course, that the side of the earth which is toward the sun, while it is thus brought the nearer to the luminary, receives more energy in the form of light and heat than come to any part which is exposed when the spheres are farther away from each other in the other part of the orbit. Computations clearly show that the total amount of heat and the attendant light which the earth receives in a year is not affected by these changes in the form of its path. While it is true that it receives heat more rapidly in the half of the ellipse which is nearest the source of the inundation, it obtains less while it is farther away, and these two variations just balance each other. Although the alterations in the eccentricity of its orbit do not vary the annual supply of heat which the earth receives, they are capable of changing the character of the seasons, and this in the way which we will now endeavour to set forth, though we must do it at the cost of considerable attention on the part of the reader, for the facts are somewhat complicated. In the first place, we must note that the ellipticity of the earth's orbit is not developed on fixed lines, but is endlessly varied, as we can readily imagine it would be for the reason that its form depends upon the wandering of the outer planetary spheres which pull the earth about. The longer axis of the ellipse is itself in constant motion in the direction in which the earth travels. This movement is slow, and at an irregular rate. It is easy to see that the effect of this action, which is called the revolution of the apsides, or, as the word means, the movement of the poles of the ellipse, is to bring the earth, when a given hemisphere is turned toward the sun, sometimes in the part of the orbit which is nearest the source of light and heat, and sometimes farther away. It may thus well come about that at one time the summer season of a hemisphere arrives when it is nearest the sun, so that the season, though hot, will be very short, while at another time the same season will arrive when the earth is farthest from the sun, and receives much less heat, which would tend to make a long and relatively cool summer. The reason for the difference in length of the seasons is to be found in the relative swiftness of the earth's revolution when it is nearest the sun, and the slowness when it is farther away. There is a further complication arising from that curious phenomenon called the precession of the equinoxes, which has to be taken into account before we can sufficiently comprehend the effect of the varying eccentricity of the orbit on the earth's seasons. To understand this feature of precession we should first note that it means that each year the change from the winter to the summer--or, as we phrase it, the passage of the equinoctial line--occurs a little sooner than the year before. The cause of this is to be found in the attraction which the heavenly bodies, practically altogether the moon, exercises on the equatorial protuberance of the earth. We know that the diameter of our sphere at the equator is, on the average, something more than twenty-six miles greater than it is through the poles. We know, furthermore, that the position of the moon in relation to the earth is such that it causes the attraction on one half of this protuberance to be greater than it is upon the other. We readily perceive that this action will cause the polar axis to make a certain revolution, or, what comes to the same thing, that the plane of the equator will constantly be altering its position. Now, as the equinoctial points in the orbit depend for their position upon the attitude of the equatorial plane, we can conceive that the effect is a change in position of the place in that orbit where summer and winter begin. The actual result is to bring the seasonal points backward, step by step, through the orbit in a regular measure until in twenty-two thousand five hundred years they return to the place where they were before. This cycle of change was of old called the Annus Magnus, or great year. If the earth's orbit were an ellipse, the major axis of which remained in the same position, we could readily reckon all the effects which arise from the variations of the great year. But this ellipse is ever changing in form, and in the measure of its departure from a circle the effects on the seasons distributed over a great period of time are exceedingly irregular. Now and then, at intervals of hundreds of thousands or millions of years, the orbit becomes very elliptical; then again for long periods it may in form approach a circle. When in the state of extreme ellipticity, the precession of the equinoxes will cause the hemispheres in turn each to have their winter and summer alternately near and far from the sun. It is easily seen that when the summer season comes to a hemisphere in the part of the orbit which is then nearest the sun the period will be very hot. When the summer came farthest from the sun that part of the year would have the temperature mitigated by its removal to a greater distance from the source of heat. A corresponding effect would be produced in the winter season. As long as the orbit remained eccentric the tendency would be to give alternately intense seasons to each hemisphere through periods of about twelve thousand years, the other hemisphere having at the same time a relatively slight variation in the summer and winter. At first sight it may seem to the reader that these studies we have just been making in matters concerning the shape of the orbit and the attendant circumstances which regulate the seasons were of no very great consequence; but, in the opinion of some students of climate, we are to look to these processes for an explanation of certain climatal changes on the earth, including the Glacial periods, accidents which have had the utmost importance in the history of man, as well as of all the other life of the planet. It is now time to give some account as to what is known concerning the general conditions of the solar bodies--the planets and satellites of our own celestial group. For our purpose we need attend only to the general physical state of these orbs so far as it is known to us by the studies of astronomers. The nearest planet to the sun is Mercury. This little sphere, less than half the diameter of our earth, is so close to the sun that even when most favourably placed for observation it is visible for but a few minutes before sunrise and after sunset. Although it may without much difficulty be found by the ordinary eye, very few people have ever seen it. To the telescope when it is in the _full moon_ state it appears as a brilliant disk; it is held by most astronomers that the surface which we see is made up altogether of clouds, but this, as most else that has been stated concerning this planet, is doubtful. The sphere is so near to the sun that if it were possessed of water it would inevitably bear an atmosphere full of vapour. Under any conceivable conditions of a planet placed as Mercury is, provided it had an atmosphere to retain the heat, its temperature would necessarily be very high. Life as we know it could not well exist upon such a sphere. Next beyond Mercury is Venus, a sphere only a little less in diameter than the earth. Of this sphere we know more than we do of Mercury, for the reason that it is farther from the sun and so appears in the darkened sky. Most astronomers hold that the surface of this planet apparently is almost completely and continually hidden from us by what appears to be a dense cloud envelope, through which from time to time certain spots appear of a dark colour. These, it is claimed, retain their place in a permanent way; it is, indeed, by observing them that the rotation period of the planet has, according to some observers, been determined. It therefore seems likely that these spots are the summits of mountains, which, like many of our own earth, rise above the cloud level. Recent observations on Venus made by Mr. Percival Lowell appear to show that the previous determinations of the rotation of that planet, as well as regards its cloud wrap, are in error. According to these observations, the sphere moves about the sun, always keeping the same side turned toward the solar centre, just as the moon does in its motion around the earth. Moreover, Mr. Lowell has failed to discover any traces of clouds upon the surface of the planet. As yet these results have not been verified by the work of other astronomers; resting, however, as they do on studies made with an excellent telescope and in the very translucent and steady air of the Flagstaff Station, they are more likely to be correct than those obtained by other students. If it be true that Venus does not turn upon its axis, such is likely to be the case also with the planet Mercury. Next in the series of the planets is our own earth. As the details of this planet are to occupy us during nearly all the remainder of this work, we shall for the present pass it by. Beyond the earth we pass first to the planet Mars, a sphere which has already revealed to us much concerning its peculiarities of form and physical state, and which is likely in the future to give more information than we shall obtain from any other of our companions in space, except perhaps the moon. Mars is not only nearer to us than any other planet, but it is so placed that it receives the light of the sun under favourable conditions for our vision. Moreover, its sky appears to be generally almost cloudless, so that when in its orbital course the sphere is nearest our earth it is under favourable conditions for telescopic observation. At such times there is revealed to the astronomer a surface which is covered with an amazing number of shadings and markings which as yet have been incompletely interpreted. The faint nature of these indications has led to very contradictory statements as to their form; no two maps which have been drawn agree except in their generalities. There is reason to believe that Mars has an atmosphere; this is shown by the fact that in the appropriate season the region about either pole is covered by a white coating, presumably snow. This covering extends rather less far toward the planet's equator than does the snow sheet on our continents. Taking into account the colour of the coating, and the fact that it disappears when the summer season comes to the hemisphere in which it was formed, we are, in fact, forced to believe that the deposit is frozen water, though it has been suggested that it may be frozen carbonic acid. Taken in connection with what we have shortly to note concerning the apparent seas of this sphere, the presumption is overwhelmingly to the effect that Mars has seasons not unlike our own. The existence of snow on any sphere may safely be taken as evidence that there is an atmosphere. In the case of Mars, this supposition is borne out by the appearance of its surface. The ruddy light which it sends back to us, and the appearance on the margin of the sphere, which is somewhat dim, appears to indicate that its atmosphere is dense. In fact, the existence of an atmosphere much denser than that of our own earth appears to be demanded by the fact that the temperatures are such as to permit the coming and going of snow. It is well known that the temperature of any point on the earth, other things being equal, is proportionate to the depth of atmosphere above its surface. If Mars had no more air over its surface than has an equal area of the earth, it would remain at a temperature so low that such seasonal changes as we have observed could not take place. The planet receives one third less heat than an equal area of the earth, and its likeness to our own temperature, if such exists, is doubtless brought about by the greater density of its atmosphere, that serves to retain the heat which comes upon its surface. The manner in which this is effected will be set forth in the study of the earth's atmosphere. [Illustration: Fig. 4.--Mars, August 27, 1892 (Guiot), the white patch is the supposed Polar Snow Cap.] As is shown by the maps of Mars, the surface is occupied by shadings which seem to indicate the existence of water and lands. Those portions of the area which are taken to be land are very much divided by what appear to be narrow seas. The general geographic conditions differ much from those of our own sphere in that the parts of the planet about the water level are not grouped in great continents, and there are no large oceans. The only likeness to the conditions of our earth which we can perceive is in a general pointing of the somewhat triangular masses of what appears to be land toward one pole. As a whole, the conditions of the Martial lands and seas as regards their form, at least, is more like that of Europe than that of any other part of the earth's surface. Europe in the early Tertiary times had a configuration even more like that of Mars than it exhibits at present, for in that period the land was very much more divided than it now is. If the lands of Mars are framed as are those of our own earth, there should be ridges of mountains constituting what we may term the backbones of the continent. As yet such have not been discerned, which may be due to the fact that they have not been carefully looked for. The only peculiar physical features which have as yet been discerned on the lands of Mars are certain long, straight, rather narrow crevicelike openings, which have received the name of "canals." These features are very indistinct, and are just on the limit of visibility. As yet they have been carefully observed by but few students, so that their features are not yet well recorded; as far as we know them, these fissures have no likeness in the existing conditions of our earth. It is difficult to understand how they are formed or preserved on a surface which is evidently subjected to rainfalls. It will require much more efficient telescopes than we now have before it will be possible to begin any satisfactory study on the geography of this marvellous planet. We can not hope as yet to obtain any indications as to the details of its structure; we can not see closely enough to determine whether rivers exist, or whether there is a coating which we may interpret as vegetation, changing its hues in the different seasons of the year. An advance in our instruments of research during the coming century, if made with the same speed as during the last, will perhaps enable us to interpret the nature of this neighbour, and thereby to extend the conception of planetary histories which we derive from our own earth. [Illustration: Fig. 5.--Comparative Sizes of the Planets (Chambers).] Beyond Mars we find one of the most singular features of our solar system in a group of small planetary bodies, the number of which now known amounts to some two hundred, and the total may be far greater. These bodies are evidently all small; it is doubtful if the largest is three hundred and the smaller more than twenty miles in diameter. So far as it has been determined by the effect of their aggregate mass in attracting the other spheres, they would, if put together, make a sphere far less in diameter than our earth, perhaps not more than five hundred miles through. The forms of these asteroids is as yet unknown; we therefore can not determine whether their shapes are spheroidal, as are those of the other planets, or whether they are angular bits like the meteorites. We are thus not in a position to conjecture whether their independence began when the nebulous matter of the ring to which they belonged was in process of consolidation, or whether, after the aggregation of the sphere was accomplished, and the matter solidified, the mass was broken into bits in some way which we can not yet conceive. It has been conjectured that such a solid sphere might have been driven asunder by a collision with some wandering celestial body; but all we can conceive of such actions leads us to suppose that a blow of this nature would tend to melt or convert materials subjected to it into the state of vapour, rather than to drive them asunder in the manner of an explosion. The four planets which lie beyond the asteroids give us relatively little information concerning their physical condition, though they afford a wide field for the philosophic imagination. From this point of view the reader is advised to consult the writings of the late R.A. Proctor, who has brought to the task of interpreting the planetary conditions the skill of a well-trained astronomer and a remarkable constructive imagination. The planet Jupiter, by far the largest of the children of the sun, appears to be still in a state where its internal heat has not so far escaped that the surface has cooled down in the manner of our earth. What appear to be good observations show that the equatorial part of its area, at least, still glows from its own heat. The sphere is cloud-wrapped, but it is doubtful whether the envelope be of watery vapour; it is, indeed, quite possible that besides such vapour it may contain some part of the many substances which occupy the atmosphere of the sun. If the Jovian sphere were no larger than the earth, it would, on account of its greater age, long ago have parted with its heat; but on account of its great size it has been able, notwithstanding its antiquity, to retain a measure of temperature which has long since passed away from our earth. In the case of Saturn, the cloud bands are somewhat less visible than on Jupiter, but there is reason to suppose in this, as in the last-named planet, that we do not behold the more solid surface of the sphere, but see only a cloud wrap, which is probably due rather to the heat of the sphere itself than to that which comes to it from the sun. At the distance of Saturn from the centre of the solar system a given area of surface receives less than one ninetieth of the sun's heat as compared with the earth; therefore we can not conceive that any density of the atmosphere whatever would suffice to hold in enough temperature to produce ordinary clouds. Moreover, from time to time bright spots appear on the surface of the planet, which must be due to some form of eruptions from its interior. Beyond Saturn the two planets Uranus and Neptune, which occupy the outer part of the solar system, are so remote that even our best telescopes discern little more than their presence, and the fact that they have attendant moons. From the point of view of astronomical science, the outermost planet Neptune, of peculiar interest for the reason that it was, as we may say, discovered by computation. Astronomers had for many years remarked the fact that the next inner planetary sphere exhibited peculiarities in its orbit which could only be accounted for on the supposition that it was subjected to the attraction of another wandering body which had escaped observation. By skilful computation the place in the heavens in which this disturbing element lay was so accurately determined that when the telescope was turned to the given field a brief study revealed the planet. Nothing else in the history of the science of astronomy, unless it be the computation of eclipses, so clearly and popularly shows the accuracy of the methods by which the work of that science may be done. As we shall see hereafter, in the chapters which are devoted to terrestrial phenomena, the physical condition of the sun determines the course of all the more important events which take place on the surface of the earth. It is therefore fit that in this preliminary study of the celestial bodies, which is especially designed to make the earth more interpretable to us, we should give a somewhat special attention to what is known under the title of "Solar Physics." The reader has already been told that the sun is one of many million similar bodies which exist in space, and, furthermore, that these aggregations of matter have been developed from an original nebulous condition. The facts indicate that the natural history of the sun, as well as that of its attendant spheres, exhibits three momentous stages: First, that of vapour; second, that of igneous fluidity; third, that in which the sphere is so far congealed that it becomes dark. Neither of these states is sharply separated from the other; a mass may be partly nebulous and partly fluid; even when it has been converted into fluid, or possibly into the solid state, it may still retain on the exterior some share of its original vaporous condition. In our sun the concentration has long since passed beyond the limits of the nebulous state; the last of the successively developed rings has broken, and has formed itself into the smallest of the planets, which by its distance from the sun seems to indicate that the process of division by rings long ago attained in our solar system its end, the remainder of its nebulous material concentrating on its centre without sign of any remaining tendency to produce these planet-making circles. THE CONSTITUTION OF THE SUN. Before the use of the telescope in astronomical work, which was begun by the illustrious Galileo in 1608, astronomers were unable to approach the problem of the structure of the sun. They could discern no more than can be seen by any one who looks at the great sphere through a bit of smoked glass, as we know this reveals a disklike body of very uniform appearance. The only variation in this simple aspect occurs at the time of a total eclipse, when for a minute or two the moon hides the whole body of the sun. On such occasions even the unaided eye can see that there is about the sphere a broad, rather bright field, of an aspect like a very thin cloud or fog, which rises in streamer like projections at points to a quarter of a million miles or more above the surface of the sphere. The appearance of this shining field, which is called the corona, reminds one of the aurora which glows in the region about either pole of the earth. One of the first results of the invention of the telescope was the revelation of the curious dark objects on the sun's disk, known by the name of spots from the time of their discovery, or, at least, from the time when it was clearly perceived that they were not planets, but really on the solar body. The interest in the constitution of the sphere has increased during the last fifty years. This interest has rapidly grown until at the present time a vast body of learning has been gathered for the solution of the many problems concerning the centre of our system. As yet there is great divergence in the views of astronomers as to the interpretation of their observations, but certain points of great general interest have been tolerably well determined. These may be briefly set forth by an account of what would meet the eye if an observer were able to pass from the surface of the earth to the central part of the sun. [Illustration: _Lava stream, in Hawaiian Islands, flowing into the sea. Note the "ropy" character of the half-frozen rock on the sides of the nearest rivulet of the lava._] In passing from the earth to a point about a quarter of a million miles from the sun's surface--a distance about that of the moon from our sphere--the observer would traverse the uniformly empty spaces of the heavens, where, but for the rare chance of a passing meteorite or comet, there would be nothing that we term matter. Arriving at a point some two or three hundred thousand miles from the body of the sun, he would enter the realm of the corona; here he would find scattered particles of matter, the bits so far apart that there would perhaps be not more than one or two in the cubic mile; yet, as they would glow intensely in the central light, they would be sufficient to give the illumination which is visible in an eclipse. These particles are most likely driven up from the sun by some electrical action, and are constantly in motion, much as are the streamers of the aurora. Below the corona and sharply separated from it the observer finds another body of very dense vapour, which is termed the chromosphere, and which has been regarded as the atmosphere of the sun. This layer is probably several thousand miles thick. From the manner in which it moves, in the way the air of our own planet does in great storms, it is not easy to believe that it is a fluid, yet its sharply defined upper surface leads us to suppose that it can not well be a mere mass of vapour. The spectroscope shows us that this chromosphere contains in the state of vapour a number of metallic substances, such as iron and magnesium. To an observer who could behold this envelope of the sun from the distance at which we see the moon, the spectacle would be more magnificent than the imagination, guided by the sight of all the relatively trifling fractures of our earth, can possibly conceive. From the surface of the fiery sea vast uprushes of heated matter rise to the height of two or three hundred thousand miles, and then fall back upon its surface. These jets of heated matter have the aspect of flames, but they would not be such in fact, for the materials are not burning, but merely kept at a high temperature by the heat of the great sphere beneath. They spring up with such energy that they at times move with a speed of one hundred and fifty miles a second, or at a rate which is attained by no other matter in the visible universe, except that strange, wandering star known to astronomers as "Grombridge, 1830," which is traversing the firmament with a speed of not less than two hundred miles a second. Below the chromosphere is the photosphere, the lower envelope of the sun, if it be not indeed the body of the sphere itself; from this comes the light and heat of the mass. This, too, can not well be a firm-set mass, for the reason that the spots appear to form in and move over it. It may be regarded as an extremely dense mass of gas, so weighed down by the vast attraction of the great sphere below it that it is in effect a fluid. The near-at-hand observer would doubtless find this photosphere, as it appears in the telescope, to be sharply separated from the thinner and more vaporous envelopes--the chromosphere and the corona--which are, indeed, so thin that they are invisible even with the telescope, except when the full blaze of the sun is cut off in a total eclipse. The fact that the photosphere, except when broken by the so-called spots, lies like a great smooth sea, with no parts which lie above the general line, shows that it has a very different structure from the envelope which lies upon it. If they were both vaporous, there would be a gradation between them. On the surface of the photosphere, almost altogether within thirty degrees of the equator of the sun, a field corresponding approximately to the tropical belt of the earth, there appear from time to time the curious disturbances which are termed spots. These appear to be uprushes of matter in the gaseous state, the upward movement being upon the margins of the field and a downward motion taking place in the middle of the irregular opening, which is darkened in its central part, thus giving it, when seen by an ordinary telescope, the aspect of a black patch on the glowing surface. These spots, which are from some hundred to some thousand miles in diameter, may endure for months before they fade away. It is clear that they are most abundant at intervals of about eleven years, the last period of abundance being in 1893. The next to come may thus be expected in 1904. In the times of least spotting more than half the days of a year may pass without the surface of the photosphere being broken, while in periods of plenty no day in the year is likely to fail to show them. [Illustration: Fig. 6.--Ordinary Sun-spot, June 22, 1885.] It is doubtful if the closest seeing would reveal the cause of the solar spots. The studies of the physicists who have devoted the most skill to the matter show little more than that they are tumults in the photosphere, attended by an uprush of vapours, in which iron and other metals exist; but whether these movements are due to outbreaks from the deeper parts of the sun or to some action like the whirling storms of the earth's atmosphere is uncertain. It is also uncertain what effect these convulsions of the sun have on the amount of the heat and light which is poured forth from the orb. The common opinion that the sun-spot years are the hottest is not yet fully verified. Below the photosphere lies the vast unknown mass of the unseen solar realm. It was at one time supposed that the dark colour of the spots was due to the fact that the photosphere was broken through in those spaces, and that we looked down through them upon the surface of the slightly illuminated central part of the sphere. This view is untenable, and in its place we have to assume that for the eight hundred and sixty thousand miles of its diameter the sun is composed of matter such as is found in our earth, but throughout in a state of heat which vastly exceeds that known on or in our planet. Owing to its heat, this matter is possibly not in either the solid or the fluid state, but in that of very compressed gases, which are kept from becoming solid or even fluid by the very high temperature which exists in them. This view is apparently supported by the fact that, while the pressure upon its matter is twenty-seven times greater in the sun than it is in the earth, the weight of the whole mass is less than we should expect under these conditions. As for the temperature of the sun, we only know that it is hot enough to turn the metals into gases in the manner in which this is done in a strong electric arc, but no satisfactory method of reckoning the scale of this heat has been devised. The probabilities are to the effect that the heat is to be counted by the tens of thousands of degrees Fahrenheit, and it may amount to hundreds of thousands; it has, indeed, been reckoned as high as a million degrees. This vast discharge is not due to any kind of burning action--i.e., to the combustion of substances, as in a fire. It must be produced by the gradual falling in of the materials, due to the gravitation of the mass toward its centre, each particle converting its energy of position into heat, as does the meteorite when it comes into the air. It is well to close this very imperfect account of the learning which relates to the sun with a brief tabular statement showing the relative masses of the several bodies of the solar system. It should be understood that by mass is meant not the bulk of the object, but the actual amount of matter in it as determined by the gravitative attraction which it exercises on other celestial bodies. In this test the sun is taken as the measure, and its mass is for convenience reckoned at 1,000,000,000. TABLE OF RELATIVE MASSES OF SUN AND PLANETS.[2] +------------------------------------------------------------+ | The sun 1,000,000,000 | | Mercury 200 | | Venus 2,353 | | Earth 3,060 | | Mars 339 | | Asteroids ? | | Saturn 285,580 | | Jupiter 954,305 | | Uranus 44,250 | | Neptune 51,600 | | Combined mass of the four inner planets 5,952 | | Combined mass of all the planets 1,341,687 | +------------------------------------------------------------+ [Footnote 2: See Newcomb's Popular Astronomy, p. 234. Harper Brothers, New York.] It thus appears that the mass of all the planets is about one seven hundredth that of the sun. Those who wish to make a close study of celestial geography will do well to procure the interesting set of diagrams prepared by the late James Freeman Clarke, in which transparencies placed in a convenient lantern show the grouping of the important stars in each constellation. The advantage of this arrangement is that the little maps can be consulted at night and in the open air in a very convenient manner. After the student has learned the position of a dozen of the constellations visible in the northern hemisphere, he can rapidly advance his knowledge in the admirable method invented by Dr. Clarke. Having learned the constellations, the student may well proceed to find the several planets, and to trace them in their apparent path across the fixed stars. It will be well for him here to gain if he can the conception that their apparent movement is compounded of their motion around the sun and that of our own sphere; that it would be very different if our earth stood still in the heavens. At this stage he may well begin to take in mind the evidence which the planetary motion supplies that the earth really moves round the sun, and not the sun and planets round the earth. This discovery was one of the great feats of the human mind; it baffled the wits of the best men for thousands of years. Therefore the inquirer who works over the evidence is treading one of the famous paths by which his race climbed the steeps of science. The student must not expect to find the evidence that the sun is the centre of the solar system very easy to interpret; and yet any youth of moderate curiosity, and that interest in the world about him which is the foundation of scientific insight, can see through the matter. He will best begin his inquiries by getting a clear notion of the fact that the moon goes round the earth. This is the simplest case of movements of this nature which he can see in the solar system. Noting that the moon occupies a different place at a given hour in the twenty-four, but is evidently at all times at about the same distance from the earth, he readily perceives that it circles about our sphere. This the people knew of old, but they made of it an evidence that the sun also went around our sphere. Here, then, is the critical point. Why does the sun not behave in the same manner as the moon? At this stage of his inquiry the student best notes what takes place in the motions of the planets between the earth and the sun. He observes that those so-called inferior planets Mercury and Venus are never very far away from the central body; that they appear to rise up from it, and then to go back to it, and that they have phases like the moon. Now and then Venus may be observed as a black spot crossing the disk of the sun. A little consideration will show that on the theory that bodies revolve round each other in the solar system these movements of the inner planets can only be explained on the supposition that they at least travel around the great central fire. Now, taking up the outer planets, we observe that they occasionally appear very bright, and that they are then at a place in the heavens where we see that they are far from the solar centre. Gradually they move down toward the sunset and disappear from view. Here, too, the movement, though less clearly so, is best reconcilable with the idea that these bodies travel in orbits, such as those which are traversed by the inner planets. The wonder is that with these simple facts before them, and with ample time to think the matter over, the early astronomers did not learn the great truth about the solar system--namely, that the sun is the centre about which the planets circled. Their difficulty lay mainly in the fact that they did not conceive the earth as a sphere, and even after they attained that conception they believed that our globe was vastly larger than the planets, or even than the sun. This misconception kept even the thoughtful Greeks, who knew that the earth was spherical in form, from a clear notion as to the structure of our system. It was not, indeed, until mathematical astronomy attained a considerable advance, and men began to measure the distances in the solar system, and until the Newtonian theory of gravitation was developed, that the planetary orbits and the relation of the various bodies in the solar system to each other could be perfectly discerned. Care has been taken in the above statements to give the student indices which may assist him in working out for himself the evidence which may properly lead a person, even without mathematical considerations of a formal kind, to construct a theory as to the relation of the planets to the sun. It is not likely that he can go through all the steps of this argument at once, but it will be most useful to him to ponder upon the problem, and gradually win his way to a full understanding of it. With that purpose in mind, he should avoid reading what astronomers have to say on the matter until he is satisfied that he has done as much as he can with the matter on his own account. He should, however, state his observations, and as far as possible draw the results in his note-book in a diagrammatic form. He should endeavour to see if the facts are reconcilable with any other supposition than that the earth and the other planets move around the sun. When he has done his task, he will have passed over one of the most difficult roads which his predecessors had to traverse on their way to an understanding of the heavens. Even if he fail he will have helped himself to some large understandings. The student will find it useful to make a map of the heavens, or rather make several representing their condition at different times in the year. On this plot he should put down only the stars whose places and names he has learned, but he should plot the position of the planets at different times. In this way, though at first his efforts will be very awkward, he will soon come to know the general geography of the heavens. Although the possession or at least the use of a small astronomical telescope is a great advantage to a student after he has made a certain advance in his work, such an instrument is not at all necessary, or, indeed, desirable at the outset of his studies. An ordinary opera-glass, however, will help him in picking out the stars in the constellations, in identifying the planets, and in getting a better idea as to the form of the moon's surface--a matter which will be treated in this work in connection with the structure of the earth. CHAPTER IV. THE EARTH. In beginning the study of the earth it is important that the student should at once form the habit of keeping in mind the spherical form of the planet. Many persons, while they may blindly accept the fact that the earth is a sphere, do not think of it as having that form. Perhaps the simplest way of securing the correct image of the shape is to imagine how the earth would appear as seen from the moon. In its full condition the moon is apt to appear as a disk. When it is new, and also when in its waning stages it is visible in the daytime, the spherical form is very apparent. Imagining himself on the surface of the moon, the student can well perceive how the earth would appear as a vast body in the heavens; its eight thousand miles of diameter, about four times that of the satellite, would give an area sixteen times the size which the moon presents to us. On this scale the continents and oceans would appear very much more plain than do the relatively slight irregularities on the lunar surface. With the terrestrial globe in hand, the student can readily construct an image which will represent, at least in outline, the appearance which the sphere he inhabits would present when seen from a distance of about a quarter of a million miles away. The continent of Europe-Asia would of itself appear larger than all the lunar surface which is visible to us. Every continent and all the greater islands would be clearly indicated. The snow covering which in the winter of the northern hemisphere wraps so much of the land would be seen to come and go in the changes of the seasons; even the permanent ice about either pole, and the greater regions of glaciers, such as those of the Alps and the Himalayas, would appear as brilliant patches of white amid fields of darker hue. Even the changes in the aspect of the vegetation which at one season clothes the wide land with a green mantle, and at another assumes the dun hue of winter, would be, to the unaided eye, very distinct. It is probable that all the greater rivers would be traceable as lines of light across the relatively dark surface of the continents. By such exercises of the constructive imagination--indeed, in no other way--the student can acquire the habit of considering the earth as a vast whole. From time to time as he studies the earth from near by he should endeavour to assemble the phenomena in the general way which we have indicated. The reader has doubtless already learned that the earth is a slightly flattened sphere, having an average diameter of about eight thousand miles, the average section at the equator being about twenty-six miles greater than that from pole to pole. In a body of such large proportions this difference in measurement appears not important; it is, however, most significant, for it throws light upon the history of the earth's mass. Computation shows that the measure of flattening at the poles is just what would occur if the earth were or had been at the time when it assumed its present form in a fluid condition. We readily conceive that a soft body revolving in space, while all its particles by gravitation tended to the centre, would in turning around, as our earth does upon its axis, tend to bulge out in those parts which were remote from the line upon which the turning took place. Thus the flattening of our sphere at the poles corroborates the opinion that its mass was once molten--in a word, that its ancient history was such as the nebular theory suggests. Although we have for convenience termed the earth a flattened spheroid, it is only such in a very general sense. It has an infinite number of minor irregularities which it is the province of the geographer to trace and that of the geologist to account for. In the first place, its surface is occupied by a great array of ridges and hollows. The larger of these, the oceans and continents, first deserve our attention. The difference in altitude of the earth's surface from the height of the continents to the deepest part of the sea is probably between ten and eleven miles, thus amounting to about two fifths of the polar flattening before noted. The average difference between the ocean floor and the summits of the neighbouring continents is probably rather less than four miles. It happens, most fortunately for the history of the earth, that the water upon its surface fills its great concavities on the average to about four fifths of their total depth, leaving only about one fifth of the relief projecting above the ocean level. We have termed this arrangement fortunate, for it insures that rainfall visits almost all the land areas, and thereby makes those realms fit for the uses of life. If the ocean had only half its existing area, the lands would be so wide that only their fringes would be fertile. If it were one fifth greater than it is, the dry areas would be reduced to a few scattered islands. From all points of view the most important feature of the earth's surface arises from its division into land and water areas, and this for the reason that the physical and vital work of our sphere is inevitably determined by this distribution. The shape of the seas and lands is fixed by the positions at which the upper level of the great water comes against the ridges which fret the earth's surface. These elevations are so disposed that about two thirds of the hard mass is at the present time covered with water, and only one third exposed to the atmosphere. This proportion is inconstant. Owing to the endless up-and-down goings of the earth's surface, the place of the shore lines varies from year to year, and in the geological ages great revolutions in the forms and relative area of water and land are brought about. Noting the greater divisions of land and water as they are shown on a globe, we readily perceive that those parts of the continental ridges which rise above the sea level are mainly accumulated in the northern hemisphere--in fact, far more than half the dry realm is in that part of the world. We furthermore perceive that all the continents more or less distinctly point to the southward; they are, in a word, triangles, with their bases to the northward, and their apices, usually rather acute, directed to the southward. This form is very well indicated in three of the great lands, North and South America and Africa; it is more indistinctly shown in Asia and in Australia. As yet we do not clearly understand the reason why the continents are triangular, why they point toward the south pole, or why they are mainly accumulated in the northern hemisphere. As stated in the chapter on astronomy, some trace of the triangular form appears in the land masses of the planet Mars. There, too, these triangles appear to point toward one pole. Besides the greater lands, the seas are fretted by a host of smaller dry areas, termed islands. These, as inquiry has shown, are of two very diverse natures. Near the continents, practically never more than a thousand miles from their shores, we find isles, often of great size, such as Madagascar, which in their structure are essentially like the continents--that is, they are built in part or in whole of non-volcanic rocks, sandstones, limestones, etc. In most cases these islands, to which we may apply the term continental, have at some time been connected with the neighbouring mainland, and afterward separated from it by a depression of the surface which permitted the sea to flow over the lowlands. Geologists have traced many cases where in the past elevations which are now parts of a continent were once islands next its shore. In the deeper seas far removed from the margins of the continents the islands are made up of volcanic ejections of lava, pumice, and dust, which has been thrown up from craters and fallen around their margin or are formed of coral and other organic remains. Next after this general statement as to the division of sea and land we should note the peculiarities which the earth's surface exhibits where it is bathed by the air, and where it is covered by the water. Beginning with the best-known region, that of the dry land, we observe that the surface is normally made up of continuous slopes of varying declivity, which lead down from the high points to the sea. Here and there, though rarely, these slopes centre in a basin which is occupied by a lake or a dead sea. On the deeper ocean floors, so far as we may judge with the defective information which the plumb line gives us, there is no such continuity in the downward sloping of the surface, the area being cast into numerous basins, each of great extent. When we examine in some detail the shape of the land surface, we readily perceive that the continuous down slopes are due to the cutting action of rivers. In the basin of a stream the waters act to wear away the original heights, filling them into the hollows, until the whole area has a continuous down grade to the point where the waters discharge into the ocean or perhaps into a lake. On the bottom of the sea, except near the margin of the continent, where the floor may in recent geological times have been elevated into the air, and thus exposed to river action, there is no such agent working to produce continuous down grades. Looking upon a map of a continent which shows the differences in altitude of the land, we readily perceive that the area is rather clearly divided into two kinds of surface, mountains and plains, each kind being sharply distinguished from the other by many important peculiarities. Mountains are characteristically made up of distinct, more or less parallel ridges and valleys, which are grouped in very elongated belts, which, in the case of the American Cordilleras, extend from the Arctic to the Antarctic Circle. Only in rare instances do we find mountains occupying an area which is not very distinctly elongated, and in such cases the elevations are usually of no great height. Plains, on the other hand, commonly occupy the larger part of the continent, and are distributed around the flanks of the mountain systems. There is no rule as to their shape; they normally grade away from the bases of the mountains toward the sea, and are often prolonged below the level of the water for a considerable distance beyond the shore, forming what is commonly known as the continental shelf or belt of shallows along the coast line. We will now consider some details concerning the form and structure of mountains. In almost any mountain region a glance over the surface of the country will give the reader a clew to the principal factor which has determined the existence of these elevations. Wherever the bed rocks are revealed he will recognise the fact that they have been much disturbed. Almost everywhere the strata are turned at high angles; often their slopes are steeper than those of house roofs, and not infrequently they stand in attitudes where they appear vertical. Under the surface of plains bedded rocks generally retain the nearly horizontal position in which all such deposits are most likely to be found. If the observer will attentively study the details of position of these tilted rocks of mountainous districts, he will in most cases be able to perceive that the beds have been flexed or folded in the manner indicated by the diagram. Sometimes, though rarely, the tops of these foldings or arches have been preserved, so that the nature of the movement can be clearly discerned. More commonly the upper parts of the upward-arching strata have been cut off by the action of the decay-bringing forces--frost, flowing water, or creeping ice in glaciers--so that only the downward pointing folds which were formed in the mountain-making are well preserved, and these are almost invariably hidden within the earth. [Illustration: Fig. 7.--Section of mountains. Rockbridge and Bath counties, Va. (from Dana). The numbers indicate the several formations.] By walking across any considerable mountain chain, as, for instance, that of the Alleghanies, it is generally possible to trace a number of these parallel up-and-down folds of the strata, so that we readily perceive that the original beds had been packed together into a much less space than they at first occupied. In some cases we could prove that the shortening of the line has amounted to a hundred miles or more--in other words, points on the plain lands on either side of the mountain range which now exists may have been brought a hundred miles or so nearer together than they were before the elevations were produced. The reader can make for himself a convenient diagram showing what occurred by pressing a number of leaves of this book so that the sheets of paper are thrown into ridges and furrows. By this experiment he also will see that the easiest way to account for such foldings as we observe in mountains is by the supposition that some force residing in the earth tends to shove the beds into a smaller space than they originally occupied. Not only are the rocks composing the mountains much folded, but they are often broken through after the manner of masonry which has been subjected to earthquake shocks, or of ice which has been strained by the expansion that affects it as it becomes warmed before it is melted. In fact, many of our small lakes in New England and in other countries of a long winter show in a miniature way during times of thawing ice folds which much resemble mountain arches. At first geologists were disposed to attribute all the phenomena of mountain-folding to the progressive cooling of the earth. Although this sphere has already lost a large part of the heat with which it was in the beginning endowed, it is still very hot in its deeper parts, as is shown by the phenomena of volcanoes. This internal heat, which to the present day at the depth of a hundred miles below the surface is probably greater than that of molten iron, is constantly flowing away into space; probably enough of it goes away on the average each day to melt a hundred cubic miles or more of ice, or, in more scientific phrase, the amount of heat rendered latent by melting that volume of frozen water. J.R. Meyer, an eminent physicist, estimated the quantity of heat so escaping each day of the year to be sufficient to melt two hundred and forty cubic miles of ice. The effect of this loss of heat is constantly to shrink the volume of the earth; it has, indeed, been estimated that the sphere on this account contracts on the average to the amount of some inches each thousand years. For the reason that almost all this heat goes from the depths of the earth, the cool outer portion losing no considerable part of it, the contraction that is brought about affects the interior portions of the sphere alone. The inner mass constantly shrinking as it loses heat, the outer, cold part is by its weight forced to settle down, and can only accomplish this result by wrinkling. An analogous action may be seen where an apple or a potato becomes dried; in this case the hard outer rind is forced to wrinkle, because, losing no water, it does not diminish in its extent, and can only accommodate itself to the interior by a wrinkling process. In one case it is water which escapes, in the other heat; but in both contraction of the part which suffers the loss leads to the folding of the outside of the spheroid. Although this loss of heat on the part of the earth accounts in some measure for the development of mountains, it is not of itself sufficient to explain the phenomena, and this for the reason that mountains appear in no case to develop on the floors of the wide sea. The average depth of the ocean is only fifteen thousand feet, while there are hundreds, if not thousands, of mountain crests which exceed that height above the sea. Therefore if mountains grew on the sea floor as they do upon the land, there should be thousands of peaks rising above the plain of the waters, while, in fact, all of the islands except those near the shores of continents are of volcanic origin--that is, are lands of totally different nature. Whenever a considerable mountain chain is formed, although the actual folding of the beds is limited to the usually narrow field occupied by these disturbances, the elevation takes place over a wide belt of country on one or both sides of the range. Thus if we approach the Rocky Mountains from the Mississippi Valley, we begin to mount up an inclined plane from the time we pass westward from the Mississippi River. The beds of rock as well as the surface rises gradually until at the foot of the mountain; though the rocks are still without foldings, they are at a height of four or five thousand feet above the sea. It seems probable--indeed, we may say almost certain--that when the crust is broken, as it is in mountain-building, by extensive folds and faults, the matter which lies a few score miles below the crust creeps in toward those fractures, and so lifts up the country on which they lie. When we examine the forms of any of our continents, we find that these elevated portions of the earth's crust appear to be made up of mountains and the table-lands which fringe those elevations. There is not, as some of our writers suppose, two different kinds of elevation in our great lands--the continents and the mountains which they bear--but one process of elevation by which the foldings and the massive uplifts which constitute the table-lands are simultaneously and by one process formed. Looking upon continents as the result of mountain growth, we may say that here and there on the earth's crust these dislocations have occurred in such association and of such magnitude that great areas have been uplifted above the plain of the sea. In general, we find these groups of elevations so arranged that they produce the triangular form which is characteristic of the great lands. It will be observed, for instance, that the form of North America is in general determined by the position of the Appalachian and Cordilleran systems on its eastern and western margins, though there are a number of smaller chains, such as the Laurentians in Canada and the ice-covered mountains of Greenland, which have a measure of influence in fixing its shore lines. [Illustration: _Waterfall near Gadsden, Alabama. The upper shelf of rock is a hard sandstone, the lower beds are soft shale. The conditions are those of most waterfalls, such as Niagara._] The history of plains, as well as that of mountains, will have further light thrown upon it when in the next chapter we come to consider the effect of rain water on the land. We may here note the fact that the level surfaces which are above the seashores are divisible into two main groups--those which have been recently lifted above the sea level, composed of materials laid down in the shallows next the shore, and which have not yet shared in mountain-building disturbances, and those which have been slightly tilted in the manner before indicated in the case of the plains which border the Rocky Mountains on the east. The great southern plain of eastern and southern United States, extending from near New York to Mexico, is a good specimen of the level lands common on all the continents which have recently emerged from the sea. The table-lands on either side of the Mississippi Valley, sloping from the Alleghanies and the Cordilleras, represent the more ancient type of plain which has already shared in the elevation which mountain-building brings about. In rarer cases plains of small area are formed where mountains formerly existed by the complete moving down of the original ridges. There is a common opinion that the continents are liable in the course of the geologic ages to very great changes of position; that what is now sea may give place to new great lands, and that those already existing may utterly disappear. This opinion was indeed generally held by geologists not more than thirty years ago. Further study of the problem has shown us that while parts of each continent may at any time be depressed beneath the sea, the whole of its surface rarely if ever goes below the water level. Thus, in the case of North America, we can readily note very great changes in its form since the land began to rise above the water. But always, from that ancient day to our own, some portion of the area has been above the level of the sea, thus providing an ark of refuge for the land life when it was disturbed by inundations. The strongest evidence in favour of the opinion that the existing continents have endured for many million years is found in the fact that each of the great lands preserves many distinct groups of animals and plants which have descended from ancient forms dwelling upon the same territory. If at any time the relatively small continent of Australia had gone beneath the sea, all of the curious pouched animals akin to the opossum and kangaroo which abound in that country--creatures belonging in the ancient life of the world--would have been overwhelmed. We have already noted the fact that the uplifting of mountains and of the table-lands about them, which appears to have been the basis of continental growth, has been due to strains in the rocks sufficiently strong to disturb the beds. At each stage of the mountain-building movement these compressive strains have had to contend with the very great weight of the rocks which they had to move. These lands are not to be regarded as firm set or rigid arches, but as highly elastic structures, the shapes of which may be determined by any actions which put on or take off burden. We see a proof of this fact from numerous observations which geologists are now engaged in making. Thus during the last ice epoch, when almost all the northern part of this continent, as well as the northern part of Europe, was covered by an ice sheet several thousand feet thick, the lands sank down under their load, and to an extent roughly proportional to the depth of the icy covering. While the northern regions were thus tilted down by the weight which was upon them, the southern section of this land, the region about the Gulf of Mexico, was elevated much above its present level; it seems likely, indeed, that the peninsula of Florida rose to the height of several hundred feet above its present shore line. After the ice passed away the movements were reversed, the northern region rising and the southern sinking down. These movements are attested by the position of the old shore lines formed during the later stages of the Glacial epoch. Thus around Lake Ontario, as well as the other Great Lakes, the beaches which mark the higher positions of those inland seas during the closing stages of the ice time, and which, of course, were when formed horizontal, now rise to the northward at the rate of from two to five feet for each mile of distance. Recent studies by Mr. G.K. Gilbert show that this movement is still in progress. Other evidence going to show the extent to which the movements of the earth's crust are affected by the weight of materials are found in the fact that wherever along the shores thick deposits of sediments are accumulated the tendency of the region where they lie is gradually to sink downward, so that strata having an aggregate thickness of ten thousand feet or more may be accumulated in a sea which was always shallow. The ocean floor, in general, is the part of the earth's surface where strata are constantly being laid down. In the great reservoir of the waters the _débris_ washed from the land, the dust from volcanoes, and that from the stellar spaces, along with the vast accumulation of organic remains, almost everywhere lead to the steadfast accumulation of sedimentary deposits. On the other hand, the realms of the surface above the ocean level are constantly being worn away by the action of the rivers and glaciers, of the waves which beat against the shores, and of the winds which blow over desert regions. The result is that the lands are wearing down at the geologically rapid average rate of somewhere about one foot in five thousand years. All this heavy matter goes to the sea bottoms. Probably to this cause we owe in part the fact that in the wrinklings of the crust due to the contraction of the interior the lands exhibit a prevailing tendency to uprise, while the ocean floors sink down. In this way the continents are maintained above the level of the sea despite the powerful forces which are constantly wearing their substance away, while the seas remain deep, although they are continually being burdened with imported materials. [Illustration: Fig. 8.--Diagram showing the effect of the position of the fulcrum point in the movement of the land masses. In diagrams I and II, the lines _a b_ represent the land before the movement, and _a' b'_ its position after the movement; _s_, _s_, the position of the shore line; _p_, _p_, the pivotal points; _l_, _s_, the sea line. In diagram III, the curved line designates a shore; the line _a b_, connecting the pivotal points _p_, _p_, is partly under the land and partly under the sea.] It is easy to see that if the sea floors tend to sink downward, while the continental lands uprise, the movements which take place may be compared with those which occur in a lever about a fulcrum point. In this case the sea end of the bar is descending and the land end ascending. Now, it is evident that the fulcrum point may fall to the seaward or to the landward of the shore; only by chance and here and there would it lie exactly at the coast line. By reference to the diagram (Fig. 8), it will be seen that, while the point of rotation is just at the shore, a considerable movement may take place without altering the position of the coast line. Where the point of no movement is inland of the coast, the sea will gain on the continent; where, however, the point is to seaward, beneath the water, the land will gain on the ocean. In this way we can, in part at least, account for the endless changes in the attitude of the land along the coastal belt without having to suppose that the continents cease to rise or the sea floors to sink downward. It is evident that the bar or section of the rocks from the interior of the land to the bottoms of the seas is not rigid; it is also probable that the matter in the depths of the earth, which moves with the motions of this bar, would change the position of the fulcrum point from time to time. Thus it may well come about that our coast lines are swaying up and down in ceaseless variation. In very recent geological times, probably since the beginning of the last Glacial period, the region about the Dismal Swamp in Virginia has swayed up and down through four alternating movements to the extent of from fifty to one hundred feet. The coast of New Jersey is now sinking at the rate of about two feet in a hundred years. The coast of New England, though recently elevated to the extent of a hundred feet or more, at a yet later time sank down, so that at some score of points between New York and Eastport, Me., we find the remains of forests with the roots of their trees still standing below high-tide mark in positions where the trees could not have grown. Along all the marine coasts of the world which have been carefully studied from this point of view there are similar evidences of slight or great modern changes in the level of the lands. At some points, particularly on the coast of Alaska and along the coast of Peru, these uplifts of the land have amounted to a thousand feet or more. In the peninsular district of Scandinavia the swayings, sometimes up and sometimes down, which are now going on have considerably changed the position of the shore lines since the beginning of the historical period. There are other causes which serve to modify the shapes and sizes of the continents which may best be considered in the sequel; for the present we may pass from this subject with the statement that our great lands are relatively permanent features; their forms change from age to age, but they have remained for millions of years habitable to the hosts of animals and plants which have adapted their life to the conditions which these fields afford them. CHAPTER V. THE ATMOSPHERE. The firm-set portion of the earth, composed of materials which became solid when the heat so far disappeared from the sphere that rocky matter could pass from its previous fluid condition to the solid or frozen state, is wrapped about by two great envelopes, the atmosphere and the waters. Of these we shall first consider the lighter and more universal air; in taking account of its peculiarities we shall have to make some mention of the water with which it is greatly involved; afterward we shall consider the structure and functions of that fluid. Atmospheric envelopes appear to be common features about the celestial spheres. In the sun there is, as we have noted, a very deep envelope of this sort which is in part composed of the elements which form our own air; but, owing to the high temperature of the sphere, these are commingled with many substances which in our earth--at least in its outer parts--have entered in the solid state. Some of the planets, so far as we can discern their conditions, seem also to have gaseous wraps; this is certainly the case with the planet Mars, and even the little we know of the other like spheres justifies the supposition that Jupiter and Saturn, at least, have a like constitution. We may regard an atmosphere, in a word, as representing a normal and long-continued state in the development of the heavenly orbs. In only one of these considerable bodies of the solar system, the moon, do we find tolerably clear evidence that there is no atmosphere. The atmosphere of the earth is composed mainly of very volatile elements, known as nitrogen and argon. This is commingled with oxygen, also a volatile element. Into this mass a number of other substances enter in varying but always relatively very small proportions. Of these the most considerable are watery vapour and carbon dioxide; the former of these rarely amounts to one per cent of the weight of the air, considering the atmosphere as a whole, and the latter is never more than a small fraction of one per cent in amount. As a whole, the air envelope of the earth should be regarded as a mass of nitrogen and argon, which only rarely, under the influence of conditions which exist in the soil, enters into combinations with other elements by which it assumes a solid form. The oxygen, though a permanent element in the atmosphere, tends constantly to enter into combinations which fix it temporarily or permanently in the earth, in which it forms, indeed, in its combined state about one half the weight of all the mineral substances we know. The carbon dioxide, or carbonic-acid gas, as it is commonly termed, is a most important substance, as it affords plants all that part of their bodies which disappear on burning. It is constantly returned to the atmosphere by the decay of organic matter, as well as by volcanic action. In addition to the above-noted materials composing the air, all of which are imperatively necessary to the wonderful work accomplished by that envelope, we find a host of other substances which are accidentally, variably, and always in small quantities contained in this realm. Thus near the seashores, and indeed for a considerable distance into the continent, we find the air contains a certain amount of salt so finely divided that it floats in the atmosphere. So, too, we find the air, even on the mountain tops amid eternal snows, charged with small particles of dust, which, though not evident to the unassisted eye, become at once visible when we permit a slender ray of light to enter a dark chamber. It is commonly asserted that the atmosphere does not effectively extend above the height of forty-five miles; we know that it is densest on the surface of the earth, the most so in those depressions which lie below the level of the sea. This is proved to us by the weight which the air imposes upon the mercury at the open end of a barometric tube. If we could deepen these cavities to the extent of a thousand miles, the pressure would become so great that if the pit were kept free from the heat of the earth the gaseous materials would become liquefied. Upward from the earth's surface at the sea level the atoms and molecules of the air become farther apart until, at the height of somewhere between forty and fifty miles, the quantity of them contained in the ether is so small that we can trace little effect from them on the rays of light which at lower levels are somewhat bent by their action. At yet higher levels, however, meteors appear to inflame by friction against the particles of air, and even at the height of eighty miles very faint clouds have at times been discerned, which are possibly composed of volcanic dust floating in the very rarefied medium, such as must exist at this great elevation. The air not only exists in the region where we distinctly recognise it; it also occupies the waters and the under earth. In the waters it occurs as a mechanical mixture which is brought about as the rain forms and falls in the air, as the streams flow to the sea, and as the waves roll over the deep and beat against the shores. In the realm of the waters, as well as on the land, the air is necessary for the maintenance of all animal forms; but for its presence such life would vanish from the earth. Owing to certain peculiarities in its constitution, the atmosphere of our earth, and that doubtless of myriad other spheres, serves as a medium of communication between different regions. It is, as we know, in ceaseless motion at rates which may vary from the speed in the greatest tempests, which may move at the rate of somewhere a hundred and fifty miles an hour, to the very slow movements which occur in caverns, where the transfer is sometimes effected at an almost microscopic rate in the space of a day. The motion of the atmosphere is brought about by the action of heat here and there, and in a trifling way, by the heat from the interior of the earth escaping through hot springs or volcanoes, but almost altogether by the heat of the sun. If we can imagine the earth cut off from the solar radiation, the air would cease to move. We often note how the variable winds fall away in the nighttime. Those who in seeking for the North Pole have spent winters in the long-continued dark of that region have noted that the winds almost cease to blow, the air being disturbed only when a storm originated in the sunlit realm forced its way into the circumpolar darkness. The sun's heat does not directly disturb the atmosphere; if we could take the solid sphere of the world away, leaving the air, the rays would go straight through, and there would be no winds produced. This is due to the fact that the air permits the direct rays of heat, such as come from the sun, to pass through it with very slight resistance. In an aërial globe such as we have imagined, the rays impinging upon its surface would be slightly thrown out of their path as they are in passing through a lens, but they would journey on in space without in any considerable measure warming the mass. Coming, however, upon the solid earth, the heat rays warm the materials on which they are arrested, bringing them to a higher temperature than the air. Then these heated materials radiate the energy into the air; it happens, however, that this radiant heat can not journey back into space as easily as it came in; therefore the particles of air next the surface acquire a relatively high temperature. Thus a thermometer next the ground may rise to over a hundred degrees Fahrenheit, while at the same time the fleecy clouds which we may observe floating at the height of five or six miles above the surface are composed of frozen water. The effect of the heated air which acquires its temperature by radiation from the earth's surface is to produce the winds. This it brings about in a very simple manner, though the details of the process have a certain complication. The best illustration of the mode in which the winds are produced is obtained by watching what takes place about an ordinary fire at the bottom of a chimney. As soon as the fire is lit, we observe that the air about it, so far as it is heated, tends upward, drawing the smoke with it. If the air in the chimney be cold, it may not draw well at first; but in a few minutes the draught is established, or, in other words, the heated lower air breaks its way up the shaft, gradually pushing the cooler matter out at the top. In still air we may observe the column from the flue extending about the chimney-top, sometimes to the height of a hundred feet or more before it is broken to pieces. It is well here to note the fact that the energy of the draught in a chimney is, with a given heat of fire and amount of air which is permitted to enter the shaft, directly proportionate to the height; thus in very tall flues, between two and three hundred feet high, which are sometimes constructed, the uprush is at the speed of a gale. Whenever the air next the surface is so far heated that it may overcome the inertia of the cooler air above, it forces its way up through it in the general manner indicated in the chimney flue. When such a place of uprush is established, the hot air next the surface flows in all directions toward the shaft, joining the expedition to the heights of the atmosphere. Owing to the conditions of the earth's surface, which we shall now proceed to trace, these ascents of heated air belong in two distinct classes--those which move upward through more or less cylindrical chimneys in the atmosphere, shafts which are impermanent, which vary in diameter from a few feet to fifty or perhaps a hundred miles, and which move over the surface of the earth; and another which consists of a broad, beltlike shaft in the equatorial regions, which in a way girdles the earth, remains in about the same place, continually endures, and has a width of hundreds of miles. Of these two classes of uprushes we shall first consider the greatest, which occurs in the central portions of the tropical realm. Under the equator, owing to the fact that the sun for a considerable belt of land and sea maintains the earth at a high temperature, there is a general updraught which began many million years ago, probably before the origin of life, in the age when our atmosphere assumed its present conditions. Into this region the cooler air from the north and south necessarily flows, in part pressed in by the weight of the cold air which overlies it, but aided in its motion by the fact that the particles which ascend leave place for others to occupy. Over the surfaces of the land within the tropical region this draught toward what we may term the equatorial chimney is perturbed by the irregularities of the surface and many local accidents. But on the sea, where the conditions are uniform, the air moving toward the point of ascent is marked in the trade winds, which blow with a steadfast sweep down toward the equator. Many slight actions, such as the movement of the hot and cold currents of the sea, the local air movements from the lands or from detached islands, somewhat perturb the trade winds, but they remain among the most permanent features in this changeable world. It is doubtful if anything on this sphere except the atoms and molecules of matter have varied as little as the trade winds in the centre of the wide ocean. So steadfast and uniform are they that it is said that the helm and sails of a ship may be set near the west coast of South America and be left unchanged for a voyage which will carry the navigator in their belt across the width of the Pacific. Rising up from the earth in the tropical belt, the air attains the height of several thousand feet; it then begins to curve off toward the north and south, and at the height of somewhere about three to five miles above the surface is again moving horizontally toward either pole; attaining a distance on that journey, it gradually settles down to the surface of the earth, and ceases to move toward higher latitudes. If the earth did not revolve upon its axis the course of these winds along the surface toward the equator, and in the upper air back toward the poles, would be made in what we may call a square manner--that is, the particles of air would move toward the point where they begin to rise upward in due north and south lines, according as they came from the southern or northern hemisphere, and the upper currents or counter trades would retrace their paths also parallel with the meridians or longitude lines. But because the earth revolves from west to east, the course of the trade winds is oblique to the equator, those in the northern hemisphere blowing from northeast to southwest, those in the southern from southeast to northwest. The way in which the motion of the earth affects the direction of these currents is not difficult to understand. It is as follows: Let us conceive a particle of air situated immediately over the earth's polar axis. Such an atom would by the rotation of the sphere accomplish no motion except, indeed, that it might turn round on its own centre. It would acquire no velocity whatever by virtue of the earth's movement. Then let us imagine the particle moving toward the equator with the speed of an ordinary wind. At every step of its journey toward lower latitudes it would come into regions having a greater movement than those which it had just left. Owing to its inertia, it would thus tend continually to lag behind the particles of matter about it. It would thus fall off to the westward, and, in place of moving due south, would in the northern hemisphere drift to the southwest, and in the southern hemisphere toward the northwest. A good illustration of this action may be obtained from an ordinary turn-table such as is used about railway stations to reverse the position of a locomotive. If the observer will stand in the centre of such a table while it is being turned round he will perceive that his body is not swayed to the right or left. If he will then try to walk toward the periphery of the rotating disk, he will readily note that it is very difficult, if not impossible, to walk along the radius of the circle; he naturally falls behind in the movement, so that his path is a curved line exactly such as is followed by the winds which move toward the equator in the trades. If now he rests a moment on the periphery of the table, so that his body acquires the velocity of the disk at that point, and then endeavours to walk toward the centre, he will find that again he can not go directly; his path deviates in the opposite direction--in other words, the body continually going to a place having a less rate of movement by virtue of the rotation of the earth, on account of its momentum is ever moving faster than the surface over which it passes. This experiment can readily be tried on any small rotating disk, such as a potter's wheel, or by rolling a marble or a shot from the centre to the circumference and from the circumference to the centre. A little reflection will show the inquirer how these illustrations clearly account for the oblique though opposite sets of the trade winds in the upper and lower parts of the air. The dominating effect of the tropical heat in controlling the movements of the air currents extends, on the ocean surface, in general about as far north and south as the parallels of forty degrees, considerably exceeding the limits of the tropics, those lines where the sun, because of the inclination of the earth's axis, at some time of the year comes just overhead. Between these belts of trade winds there is a strip or belt under the region where the atmosphere is rising from the earth, in which the winds are irregular and have little energy. This region of the "doldrums" or frequent calms is one of much trouble to sailing ships on their voyages from one hemisphere to another. In passing through it their sails are filled only by the airs of local storms, or winds which make their way into that part of the sea from the neighbouring continents. Beyond the trade-wind belt, toward the poles, the movements of the atmosphere are dependent in part on the counter trades which descend to the surface of the earth in latitudes higher than that in which the surface or trade winds flow. Thus along our Atlantic coast, and even in the body of the continent, at times when the air is not controlled by some local storm, the counter trade blows with considerable regularity. The effect of the trade and counter-trade movements of the air on the distribution of temperature over the earth's surface is momentous. In part their influence is due to the direct heat-carrying power of the atmosphere; in larger measure it is brought about by the movement of the ocean waters which they induce. Atmospheric air, when deprived of the water which it ordinarily contains, has very little heat-containing capacity. Practically nearly all the power of conveying heat which it possesses is due to the vapour of water which it contains. By virtue of this moisture the winds do a good deal to transfer heat from the tropical or superheated portion of the earth's surface to the circumpolar or underheated realms. At first, the relatively cool air which journeys toward the equator along the surface of the sea constantly gains in heat, and in that process takes up more and more water, for precisely the same reason that causes anything to dry more rapidly in air which has been warmed next a fire. The result is that before it begins to ascend in the tropical updraught, being much moisture-laden, the atmosphere stores a good deal of heat. As it rises, rarefies, and cools, the moisture descends in the torrential rains which ordinarily fall when the sun is nearly vertical in the tropical belt. Here comes in a very interesting principle which is of importance in understanding the nature of great storms, either the continuous storm of the tropics or the local and irregular whirlings which occur in various parts of the earth. When the moisture-laden air starts on its upward journey from the earth it has, by virtue of the watery vapour which it contains, a store of energy which becomes applied to promoting the updraught. As it rises, the moisture in the air gathers together or condenses, and in so doing parts with the heat which caused it to evaporate from the ocean surface. For a given weight of water, the amount of heat required to effect the evaporation is very great; this we may roughly judge by observing what a continuous fire is required to send a pint of water into the state of steam. This energy, when it is released by the condensation of water into rain or snow, becomes again heat, and tends somewhat, as does the fire in the chimney, to accelerate the upward passage of the air. The result is that the water which ascends in the equatorial updraught becomes what we may term fuel to promote this important element in the earth's aërial circulation. Trades and counter trades would doubtless exist but for the efficiency of this updraught, which is caused by the condensation of watery vapour, but the movement would be much less than it is. WHIRLING STORMS. In the region near the equator, or near the line of highest temperature, which for various reasons does not exactly follow the equator, there is, as we have noticed, a somewhat continuous uprushing current where the air passes upward through an ascending chimney, which in a way girdles the sea-covered part of the earth. In this region the movements of the air are to a great extent under the control of the great continuous updraught. As we go to the north and south we enter realms where the air at the surface of the earth is, by the heat which it acquires from contact with that surface, more or less impelled upward; but there being no permanent updraught for its escape, it from time to time breaks through the roof of cold air which overlies it and makes a temporary channel of passage. Going polarward from the equator, we first encounter these local and temporary upcastings of the air near the margin of the tropical belt. In these districts, at least over the warmer seas, during the time of the year when it is midsummer, and in the regions where the trade winds are not strong enough to sweep the warm and moisture-laden air down to the equatorial belt, the upward tending strain of the atmosphere next the earth often becomes so strong that the overlying air is displaced, forming a channel through which the air swiftly passes. As the moisture condenses in the way before noted, the energy set free serves to accelerate the updraught, and a hurricane is begun. At first the movement is small and of no great speed, but as the amount of air tending upward is likely to be great, as is also the amount of moisture which it contains, the aërial chimney is rapidly enlarged, and the speed of the rising air increased. The atmosphere next the surface of the sea flows in toward the channel of escape; its passage is marked by winds which are blowing toward the centre. On the periphery of the movement the particles move slowly, but as they win their way toward the centre they travel with accelerating velocity. On the principle which determines the whirling movement of the water escaping through a hole in the bottom of a basin, the particles of the air do not move on straight lines toward the centre, but journey in spiral paths, at first along the surface, and then ascending. We have noted the fact that in a basin of water the direction of the whirling is what we may term accidental--that is, dependent on conditions so slight that they elude our observation--but in hurricanes a certain fact determines in an arbitrary way the direction in which the spin shall take place. As soon as such a movement of the air attains any considerable diameter, although in its beginning it may have spun in a direction brought about by local accidents, it will be affected by the diverse rates of travel, by virtue of the earth's rotation, of the air on its equatorial and polar sides. On the equatorial side this air is moving more rapidly than it is on the polar side. By observing the water passing from a basin this principle, with a few experiments, can be made plain. The result is to cause these great whirlwinds of the hurricanes of higher latitudes to whirl round from right to left in the northern hemisphere and in the reverse way in the southern. The general system of the air currents still further affects these, as other whirling storms, by driving their centres or chimneys over the surface of the earth. The principle on which this is done may be readily understood by observing how the air shaft above a chimney, through which we may observe the smoke to rise during a time of calm, is drawn off to one side by the slight current which exists even when we feel no wind; it may also be discerned in the little dust whirls which form in the streets on a summer day when the air is not much disturbed. While they spin they move on in the direction of the air drift. In this way a hurricane originating in the Gulf of Mexico may gradually journey under the influence of the counter trades across the Antilles, or over southern Florida, and thence pursue a devious northerly course, generally near the Atlantic coast and in the path of the Gulf Stream, until it has travelled a thousand miles or more toward the North Atlantic. The farther it goes northward the less effectively it is fed with warm and moisture-laden air, the feebler its movement becomes, until at length it is broken up by the variable winds which it encounters. A very interesting and, from the point of view of the navigator, important peculiarity of these whirls is that at their centre there is a calm, similar in origin and nature to the calm under the equator between the trade-wind belts. Both these areas are in the field where the air is ascending, and therefore at the surface of the earth does not affect the sails of ships, though if men ever come to use flying machines and sail through the tropics at a good height above the sea it will be sensible enough. The difference between the doldrum of the equator and that of the hurricane, besides their relative areas, is that one is a belt and the other a disk. If the seafarer happens to sail on a path which leads him through the hurricane centre, he will first discern, as from the untroubled air and sea he approaches the periphery of the storm, the horizon toward the disturbance beset by troubled clouds, all moving in one direction. Entering beneath this pall, he finds a steadily increasing wind, which in twenty miles of sailing may, and in a hundred miles surely will, compel him to take in all but his storm sails, and is likely to bring his ship into grave peril. The most furious winds the mariner knows are those which he encounters as he approaches the still centre. These trials are made the more appalling by the fact that in the furious part of the whirl the rain, condensing from the ascending air, falls in torrents, and the electricity generated in the condensation gives rise to vivid lightning. If the storm-beset ship can maintain her way, in a score or two of miles of journey toward the centre, generally very quickly, it passes into the calm disk, where the winds, blowing upward, cease to be felt. In this area the ship is not out of danger, for the waves, rolling in from the disturbed areas on either side, make a torment of cross seas, where it is hard to control the movements of a sailing vessel because the impulse of the winds is lost. Passing through this disk of calm, the ship re-encounters in reverse order the furious portion of the whirl, afterward the lessening winds, until it escapes again into the airs which are not involved in the great torment. In the old days, before Dove's studies of storms had shown the laws of hurricane movement, unhappy shipmasters were likely to be caught and retained in hurricanes, and to battle with them for weeks until their vessels were beaten to pieces. Now the "Sailing Directions," which are the mariner's guide, enable him, from the direction of the winds and the known laws of motion of the storm centre, to sail out of the danger, so that in most cases he may escape calamity. It is otherwise with the people who dwell upon the land over which these atmospheric convulsions sweep. Fortunately, where these great whirlwinds trespass on the continent, they quickly die out, because of the relative lack of moisture which serves to stimulate the uprush which creates them. Thus in their more violent forms hurricanes are only felt near the sea, and generally on islands and peninsulas. There the hurricane winds, by the swiftness of their movement, which often attains a speed of a hundred miles or more, apply a great deal of energy to all obstacles in their path. The pressure thus produced is only less destructive than that which is brought about by the tornadoes, which are next to be described. There is another effect from hurricanes which is even more destructive to life than that caused by the direct action of the wind. In these whirlings great differences in atmospheric pressure are brought about in contiguous areas of sea. The result is a sudden elevation in the level of one part of the water. These disturbances, where the shore lands are low and thickly peopled, as is the case along the western coast of the Bay of Bengal, may produce inundations which are terribly destructive to life and property. They are known also in southern Florida and along the islands of the Caribbean, but in that region are not so often damaging to mankind. Fortunately, hurricanes are limited to a very small part of the tropical district. They occur only in those regions, on the eastern faces of tropical lands, where the general westerly set of the winds favours the accumulation of great bodies of very warm, moist air next the surface of the sea. The western portion of the Gulf of Mexico and the Caribbean, the Bay of Bengal, and the southeastern portion of Asia are especially liable to their visitations. They sometimes develop, though with less fury, in other parts of the tropics. On the western coast of South America and Africa, where the oceans are visited by the dry land winds, and where the waters are cooled by currents setting in from high latitudes, they are unknown. Only less in order of magnitude than the hurricanes are the circular storms known as cyclones. These occur on the continents, especially where they afford broad plains little interrupted by mountain ranges. They are particularly well exhibited in that part of North America north of Mexico and south of Hudson Bay. Like the hurricanes, they appear to be due to the inrush of relatively warm air entering an updraught which had been formed in the overlying, cooler portions of the atmosphere. They are, however, much less energetic, and often of greater size than the hurricane whirl. The lack of energy is probably due to the comparative dryness of the air. The greater width of the ascending column may perhaps be accounted for by the fact that, originating at a considerable height above the sea, they have a less thickness of air to break through, and so the upward setting column is readily made broad. The cyclones of North America appear generally to originate in the region of the Rocky Mountains, though it is probable that in some instances, perhaps in many, the upward set of the air which begins the storm originates in the ocean along the Pacific coast. They gather energy as they descend the great sloping plain leading eastward from the Rocky Mountains to the central portion of the great continental valley. Thence they move on across the country to the Atlantic coast. Not infrequently they continue on over the ocean to the European continent. The eastward passage of the storm centre is due to the prevailing eastward movement of the air in its upper part throughout that portion of the northern hemisphere. Commonly they incline somewhat to the northward of east in their journey. In all cases the winds appear to blow spirally into the common storm centre. There is the same doldrum area or calm field in the centre of the storm that we note between the trade winds and in the middle of a hurricane disk, though this area is less defined than in the other instances, and the forward motion of the storm at a considerable speed is in most cases characteristic of the disturbance. On the front of one of these storms in North America the winds commonly begin in the northeast, thence they veer by the east to the southwest. At this stage in the movement the storm centre has passed by, the rainfall commonly ceases, and cold, dry winds setting to the northwestward set in. This is caused by the fact that the ascending air, having attained a height above the earth, settles down behind the storm, forming an anticyclone or mass of dry air, which presses against the retreating side of the great whirlwind. In front of the storm the warm and generally moist relatively warm air, pressing in toward the point of uprise and overlaid by the upper cold air, is brought into a condition where it tends to form small subordinate shafts up through which it whirls on the same principle, but with far greater intensity than the main ascending column. The reason for the violence of this movement is that the difference in temperature of the air next the surface and that at the height of a few thousand feet is great. As might be expected, these local spinnings are most apt to occur in the season when the air next the earth is relatively warm, and they are aptest to take place in the half of the advancing front lying between the east and south, for the reason that there the highest temperatures and the greatest humidity are likely to coexist. In that part of the field, during the time when the storm is advancing from the Rocky Mountains to the Atlantic, a dozen or more of these spinning uprushes may be produced, though few of them are likely to be of large size or of great intensity. The secondary storms of cyclones, such as are above noted, receive the name of tornadoes. They are frequent and terrible visitations of the country from northern Texas, Florida, and Alabama to about the line of the Great Lakes; they are rarely developed in the region west of central Kansas, and only occasionally do they exhibit much energy in the region east of the plain-lands of the Ohio Valley. Although known in other lands, they nowhere, so far as our observations go, exhibit the paroxysmal intensity which they show in the central portion of the North American continent. There the air which they affect acquires a speed of movement and a fury of action unknown in any other atmospheric disturbances, even in those of the hurricanes. The observer who has a chance to note from an advantageous position the development of a tornado observes that in a tolerably still air, or at least an air unaffected by violent winds--generally in what is termed a "sultry" state of the atmosphere--the storm clouds in the distance begin to form a kind of funnel-shaped dependence, which gradually extends until it appears to touch the earth. As the clouds are low, this downward-growing column probably in no case is observed for the height of more than three or four thousand feet. As the funnel descends, the clouds above and about it may be seen to take on a whirling movement around the centre, and under favourable circumstances an uprush of vapours may be noted in the centre of the swaying shaft. As the whirl comes nearer, the roar of the disturbance, which at a distance is often compared to the sound made by a threshing machine or to that of distant musketry, increases in loudness until it becomes overwhelming. When a storm such as this strikes a building, it is not only likely to be razed by the force of the wind, but it may be exploded, as by the action of gunpowder fired within its walls, through the sudden expansion of the air which it contains. In the centre of the column, although it rarely has a diameter of more than a few hundred feet, the uprush is so swift that it makes a partial vacuum. The air, striving to get into the space which it is eager to occupy, is whirling about at such a rate that the centrifugal motion which it thus acquires restrains its entrance. In this way there may be, as the column rapidly moves by, a difference of pressure amounting probably to what the mercury of a barometer would indicate by four or five inches of fall. Unless the structure is small and its walls strong, its roof and sides are apt to be blown apart by this difference of pressure and the consequent expansion of the contained air. In some cases where wooden buildings have withstood this curious action the outer clapboards have been blown off by the expansion of the small amount of air contained in the interspaces between that covering and the lath and plaster within (see Fig. 9). [Illustration: Fig. 9.--Showing effect of expansion of air contained in a hollow wall during the passage of the storm.] The blow of the air due to its rotative whirling has in several cases proved sufficient to throw a heavy locomotive from the track of a well-constructed railway. In all cases where it is intense it will overturn the strongest trees. The ascending wind in the centre of the column may sometimes lift the bodies of men and of animals, as well as the branches and trunks of trees and the timber of houses, to the height of hundreds of feet above the surface. One of the most striking exhibitions of the upsucking action in a tornado is afforded by the effect which it produces when it crosses a small sheet of water. In certain cases where, in the Northwestern States of this country, the path of the storm lay over the pool, the whole of the water from a basin acres in extent has been entirely carried away, leaving the surface, as described by an observer, apparently dry enough to plough. Fortunately for the interests of man, as well as those of the lower organic life, the paths of these storms, or at least the portion of their track where the violence of the air movement makes them very destructive, often does not exceed five hundred feet in width, and is rarely as great as half a mile in diameter. In most cases the length of the journey of an individual tornado does not exceed thirty miles. It rarely if ever amounts to twice that distance. In every regard except their small size and their violence these tornadoes closely resemble hurricanes. There is the same broad disk of air next the surface spirally revolving toward the ascending centre, where its motion is rapidly changed from a horizontal to a vertical direction. The energy of the uprush in both cases is increased by the energy set free through the condensation of the water, which tends further to heat and thus to expand the air. The smaller size of the tornado may be accounted for by the fact that we have in their originating conditions a relatively thin layer of warm, moist air next the earth and a relatively very cold layer immediately overlying it. Thus the tension which serves to start the movement is intense, though the masses involved are not very great. The short life of a tornado may be explained by the fact that, though it apparently tends to grow in width and energy, the central spout is small, and is apt to be broken by the movements of the atmosphere, which in the front of a cyclone are in all cases irregular. On the warmer seas, but often beyond the limits of the tropics, another class of spinning storms, known as waterspouts, may often be observed. In general appearance these air whirls resemble tornadoes, except that they are in all cases smaller than that group of whirlings. As in the tornadoes, the waterspout begins with a funnel, which descends from the sky to the surface of the sea. Up the tube vapours may be seen ascending at great speed, the whole appearing like a gigantic pillar of swiftly revolving smoke. When the whirl reaches the water, it is said that the fluid leaps up into the tube in the form of dense spray, an assertion which, in view of the fact of the action of a tornado on a lake as before described, may well be believed. Like the tornadoes and dust whirls, the life of a waterspout appears to be brief. They rarely endure for more than a few minutes, or journey over the sea for more than two or three miles before the column appears to be broken by some swaying of the atmosphere. As these peculiar storms are likely to damage ships, the old-fashioned sailors were accustomed to fire at them with cannon. It has been claimed that a shot would break the tube and end the little convulsion. This, in view of the fact that they appear to be easily broken up by relatively trifling air currents, may readily be believed. The danger which these disturbances bring to ships is probably not very serious. The special atmospheric conditions which bring about the formation of waterspouts are not well known; they doubtless include, however, warm, moist air next the surface of the sea and cold air above. Just why these storms never attain greater size or endurance is not yet known. These disturbances have been seen for centuries, but as yet they have not been, in the scientific sense, observed. Their picturesqueness attracts all beholders; it is interesting to note the fact that perhaps the earliest description of their phenomena--one which takes account in the scientific spirit of all the features which they present--was written by the poet Camoëns in the Lusiad, in which he strangely mingles fancy and observation in his account of the great voyage of Vasco da Gama. The poet even notes that the water which falls when the spout is broken is not salt, but fresh--a point which clearly proves that not much of the water which the tube contains is derived from the sea. It is, in fact, watery vapour drawn from the air next the surface of the ocean, and condensed in its ascent through the tube. In this and other descriptions of Nature Camoëns shows more of the scientific spirit than any other poet of his time. He was in this regard the first of modern writers to combine a spiritual admiration for Nature with some sense of its scientific meaning. In treating of the atmosphere, meteorologists base their studies largely on changes in the weight of that medium, which they determine by barometric observations. In fact, the science of the air had its beginning in Pascal's admirable observation on the changes in the height of a column of mercury contained in a bent tube as he ascended the volcanic peak known as Puy de Dome, in central France. As before noted, it is to the disturbances in the weight of the air, brought about mainly by variations in temperature, that we owe all its currents, and it is upon these winds that the features we term climate in largest measure depend. Every movement of the winds is not only brought about by changes in the relative weight of the air at certain points, but the winds themselves, owing to the momentum which the air attains by them, serve to bring about alterations in the quantity of air over different parts of the earth, which are marked most distinctly by barometric variations. These changes are exceedingly complicated; a full account of them would demand the space of this volume. A few of the facts, however, should be presented here. In the first place, we note that each day there is normally a range in the pressure which causes the barometer to be at the lowest at about four o'clock in the morning and four o'clock in the afternoon, and highest at about ten o'clock in those divisions of the day. This change is supposed to be due to the fact that the motes of dust in the atmosphere in the night, becoming cooled, condense the water vapour upon their surfaces, thus diminishing the volume of the air. When the sun rises the water evaporated by the heat returns from these little storehouses into the body of the atmosphere. Again in the evening the condensation sets in; at the same time the air tends to drift in from the region to the westward, where the sun is still high, toward the field where the barometer has been thus lowered; the current gradually attains a certain volume, and so brings about the rise of the barometer about ten o'clock at night. In the winter time, particularly on the well-detached continent of North America, we find a prevailing high barometer in the interior of the country and a corresponding low state of pressure on the Atlantic Ocean. In the summer season these conditions are on the whole reversed. Under the tropics, in the doldrum belt, there is a zone of low barometer connected to the ascending currents which take place along that line. This is a continuous manifestation of the same action which gives a large area of a disklike form in the centre or eye of the hurricane and in the middle portion of the tornado's whirl. In general, it may be said that the weight of the air is greatest in the regions from which it is blowing toward the points of upward escape, and least in and about those places where the superincumbent air is rising through a temporary or permanent line of escape. In other words, ascending air means generally a relatively low barometer, while descending air is accompanied by greater pressure in the field upon which it falls. In almost every part of the earth which is affected by a particular physiography we find that the movements of the atmosphere next the surface are qualified by the condition which it encounters. In fact, if a person were possessed of all the knowledge which could be obtained concerning winds, he could probably determine as by a map the place where he might chance to find himself, provided he could extend his observations over a term of years. In other words, the regimen of the winds--at least those of a superficial nature--is almost as characteristic of the field over which they go as is a map of the country. Of these special winds a number of the more important have been noted, only a few of which we can advert to. First among these may well come the land and sea breezes which are remarked about all islands which are not continuously swept by permanent winds. One of the most characteristic instances of these alternate winds is perhaps that afforded on the island of Jamaica. The island of Jamaica is so situated within the basin of the Caribbean that it does not feel the full influence of the trades. It has a range of high mountains through its middle part. In the daytime the surface of the land, which has the sun overhead twice each year, and is always exposed to nearly vertical radiation, becomes intensely hot, so that an upcurrent is formed. The formation of this current is favoured by the mountains, which apply a part of the heat at the height of about a mile above the surface of the sea. This action is parallel to that we notice when, in order to create a draught in the air of a chimney, we put a torch some distance up above the fireplace, thus diminishing the height of the column of air which has to be set in motion. It is further shown by the fact that when miners sought to make an upcurrent in a shaft, in order to lead pure air into the workings through other openings, they found after much experience that it was better to have the fire near the top of the shaft rather than at the bottom. The ascending current being induced up the mountain sides of Jamaica, the air is forced in from the sea to the relatively free space. Before noon the current, aided in its speed by a certain amount of the condensation of the watery vapour before described, attains the proportions of a strong wind. As the sun begins to sink, the earth's surface pours forth its heat; the radiation being assisted by the extended surfaces of the plants, cooling rapidly takes place. Meanwhile the sea, because of the great heat-storing power of water, is very little cooled, the ascent of the air ceases, the temporary chimney with its updraught is replaced by a downward current, and the winds blow from the land until the sun comes again to reverse the current. In many cases these movements of the daily winds flowing into and from islands induce a certain precipitation of moisture in the form of rain. Generally, however, their effect is merely to ameliorate the heat by bringing alternately currents from the relatively cool sea and from the upper atmosphere to lessen the otherwise excessive temperature of the fields which they traverse. Although characteristic sea and land winds are limited to regions where the sun's heat is great, they are traceable even in high latitudes during the periods of long-continued calm attended with clear skies. Thus on the island of Martha's Vineyard, in Massachusetts, the writer has noted, when the atmosphere was in such a state, distinct night and day, or sea and land, breezes coming in their regular alternation. During the night when these alternate winds prevail the central portion of the island, at the distance of three miles from the sea, is remarkably cold, the low temperature being due to the descending air current. To the same physical cause may be attributed the frequent insets of the sea winds toward midday along the continental shores of various countries. Thus along the coast of New England in the summer season a clear, still, hot day is certain to lead to the creation of an ingoing tide of air, which reaches some miles into the interior. This stream from the sea enters as a thin wedge, it often being possible to note next the shore when the movement begins a difference of ten degrees of temperature between the surface of the ground to which the point of the wedge has attained, and a position twenty feet higher in the air. This is a beautiful example to show at once how the relative weight of the atmosphere, even when the differences are slight, may bring about motion, and also how masses of the atmosphere may move by or through the rest of the medium in a way which we do not readily conceive from our observations on the transparent mass. Very few people have any idea how general is the truth that the air, even in continuous winds, tends to move in more or less individualized masses. This, however, is made very evident by watching the gusts of a storm or the wandering patches of wind which disturb the surface of an otherwise smooth sea. [Illustration: _South shore, Martha's Vineyard, Massachusetts, showing a characteristic sand beach with long slope and low dunes. Note the three lines of breakers and the splash flows cutting little bays in the sand._] Among the notable local winds are those which from their likeness to the Föhn of the Swiss valleys receive that name. Föhns are produced where a body of air blowing against the slope of a continuous mountain range is lifted to a considerable height, and, on passing over the crest, falls again to a low position. In its ascent the air is cooled, rarefied, and to a great extent deprived of its moisture. In descending it is recondensed, and by the process by which its atoms are brought together its latent heat is made sensible. There being but little watery vapour in the mass, this heat is not much called for by that heat-storing fluid, and so the air is warmed. So far Föhn winds have only been remarked as conspicuous features in Switzerland and on the eastern face of the Rocky Mountains. In the region about the head waters of the Missouri and to the northward their influence in what are called the Chinook winds is distinctly to ameliorate the severe winter climate of the country. In almost all great desert regions, particularly in the typical Sahara, we find a variety of storm belonging to the whirlwind group, which, owing to the nature of the country, take on special characteristics. These desert storms take up from the verdureless earth great quantities of sand and other fine _débris_, which often so clouds the air as to bring the darkness of night at midday. Their whirlings appear in size to be greater than those which produce tornadoes or waterspouts, but less than hurricanes or cyclones. Little, however, is known about them. They have not been well observed by meteorologists. In some ways they are important, for the reason that they serve to carry the desert sand into regions previously verdure-clad, and thus to extend the bounds of the desolate fields in which they originate. Where they blow off to the seaward, they convey large quantities of dust into the ocean, and thus serve to wear down the surface of the land in regions where there are no rivers to effect that action in the normal way. Notwithstanding its swift motion when impelled by differences in weight, the movements of the air have had but little direct and immediate influence on the surface of the earth. The greater part of the work which it does, as we shall see hereafter, is done through the waters which it impels and bears about. Yet where winds blow over verdureless surfaces the effect of the sand which they sweep before them is often considerable. In regions of arid mountains the winds often drive trains of sand through the valleys, where the sharp particles cut the rocks almost as effectively as torrents of water would, distributing the wearing over the width of the valley. The dust thus blown, from a desert region may, when it attains a country covered with vegetation, gradually accumulate on its surface, forming very thick deposits. Thus in northwestern China there is a wide area where dust accumulations blown from the arid districts of central Asia have gradually heaped up in the course of ages to the depth of thousands of feet, and this although much of the _débris_ is continually being borne away by the action of the rain waters as they journey toward the sea. Such dust accumulations occur in other parts of the world, particularly in the districts about the upper Mississippi and in the valleys of the Rocky Mountains, but nowhere are they so conspicuous as in the region first mentioned. Where prevailing winds from the sea, from great lakes, and even from considerable rivers, blow against sandy shores or cliffs of the same nature, large quantities of sand and dust are often driven inland from the coast line. In most cases these wind-borne materials take on the form of dunes, or heaps of sand, varying from a few feet to several hundred feet in height. It is characteristic of these hills of blown sand that they move across the face of the country. Under favourable conditions they may journey scores of miles from the shore. The marching of a dune is effected through the rolling up of the sand on the windward side of the elevation, when it is impelled by the current of air to the crest where it falls into the lee or shelter which the hill makes to the wind. In this way in the course of a day the centre of the dune, if the wind be blowing furiously, may advance a measurable distance from the place it occupied before. By fits and starts this ongoing may be indefinitely continued. A notable and picturesque instance of the march of a great dune may be had from the case in which one of them overwhelmed in the last century the village of Eccles in southeastern England. The advancing sand gradually crept into the hamlet, and in the course of a decade dispossessed the people by burying their houses. In time the summit of the church spire disappeared from view, and for many years thereafter all trace of the hamlet was lost. Of late years, however, the onward march of the sands has disclosed the church spire, and in the course of another century the place may be revealed on its original site, unchanged except that the marching hill will be on its other side. In the region about the head of the Bay of Biscay the quantity of these marching sands is so great that at one time they jeopardized the agriculture of a large district. The French Government has now succeeded, by carefully planting the surface of the country with grasses and other herbs which will grow in such places, in checking the movement of the wind-blown materials. By so doing they have merely hastened the process by which Nature arrests the march of dunes. As these heaps creep away from the sea, they generally come into regions where a greater variety of plants flourish; moreover, their sand grains become decayed, so that they afford a better soil. Gradually the mat of vegetation binds them down, and in time covers them over so that only the expert eye can recognise their true nature. Only in desert regions can the march of these heaps be maintained for great distances. Characteristic dunes occur from point to point all along the Atlantic coast from the State of Maine to the northern coast of Florida. They also occur along the coasts of our Great Lakes, being particularly well developed at the southern end of Lake Michigan, where they form, perhaps, the most notable accumulations within the limits of the United States. When blown sands invade a forest and the deposit is rapidly accumulated, the trees are often buried in an undecayed condition. In this state, with certain chemical reactions which may take place in the mass, the woody matter is apt to become replaced by silex dissolved from the sand, which penetrates the tissues of the plants. In this way salicified forests are produced, such as are found in the region of the Rocky Mountains, where the trunks of the trees, now very hard stone, so perfectly preserve their original structure that when cut and polished they may be used for decorative purposes. Conspicuous as is this work of the dunes, it is in a geological way much less important than that accomplished by the finer dust which drifts from one region of land to another or into the sea. Because of their weight, the sand grains journey over the surface of the earth, except, indeed, where they are uplifted by whirl storms. They thus can not travel very fast or far. Dust, however, rises into the air, and journeys for indefinite distances. We thus see how slight differences in the weight of substances may profoundly affect the conditions of their deportation. THE SYSTEM OF WATERS. The envelope of air wraps the earth completely about, and, though varying in thickness, is everywhere present over its surface. That of the waters is much less equally distributed. Because of its weight, it is mainly gathered in the depths of the earth, where it lies in the interstices of the rocks and in the great realm of the seas. Only a very small portion of the fluid is in the atmosphere or on the land. Perhaps less than a ten thousandth part of the whole is at any one time on this round from the seas through the air to the land and back to the great reservoir. The great water store of the earth is contained in two distinct realms--in the oceans, where the fluid is concentrated in a quantity which fills something like nine tenths of the hollows formed by the corrugations of the earth's surface; and in the rocks, where it is stored in a finely divided form, partly between the grains of the stony matter and partly in the substance of its crystals, where it exists in a combination, the precise nature of which is not well known, but is called water of crystallization. On the average, it seems likely that the materials of the earth, whether under the sea or on the land, have several per cent of their mass of the fluid. It is not yet known to what depth the water-bearing section of the earth extends; but, as we shall see more particularly hereafter when we come to consider volcanoes, the lavas which they send up to the surface are full of contained water, which passes from them in the form of steam. The very high temperature of these volcanic ejections makes it necessary for us to suppose that they come from a great depth. It is difficult to believe that they originate at less than a hundred miles below the earth's surface. If, then, the rocks contain an average of even five per cent of water to the depth of one hundred miles, the quantity of the fluid stored within the earth is greater than that which is contained in the reservoir of the ocean. The oceans, on the average, are not more than three miles deep; spread evenly over the surface of the whole earth, their depth would be less than two miles, while the water in the rocks, if it could be added to the seas, would make the total depth seven miles or more. As we shall note hereafter, the processes of formation of strata tend to imprison water in the beds, which in time is returned to the earth's surface by the forces which operate within the crust. Although the water in the seas is, as we have seen, probably less than one half of the store which the earth possesses, the part it plays in the economy of the planet is in the highest measure important. The underground water operates solely to promote certain changes which take place in the mineral realm. Its effect, except in volcanic processes, are brought about but slowly, and are limited in their action. The movements of this buried water are exceedingly gradual; the forces which impel it about and which bring it to do its work originate in the earth. In the seas the fluid has an exceeding freedom of motion; it can obey the varied impulses which the solar energy imposes upon it. The rôle of these wonderful actions which we are about to trace includes almost everything which goes on upon the surface of the planet--that which relates to the development of animal and vegetable life, as well as to the vast geological changes which the earth is undergoing. If the surface of the earth were uniformly covered with water to the depth of ten thousand feet or more, every particle of fluid would, in a measure, obey the attraction of the sun, of the moon, and, theoretically, also of all the other bodies in space, on the principle that every particle of matter in the universe exercises a gravitative effect on every other. As it is, owing to the divided condition of the water on the earth's surface, only that which is in the ocean and larger seas exhibits any measurable influence from these distant attractions. In fact, only the tides produced by the moon and sun are of determinable magnitude, and of these the lunar is of greater importance, the reason being the near position of our satellite to our own sphere. The solar tide is four tenths as great as the lunar. The water doubtless obeys in a slight way the attraction of the other celestial bodies, but the motions thus imparted are too small to be discerned; they are lost in the great variety of influences which affect all the matter on the earth. Although the tides are due to the attraction of the solar bodies, mainly to that of the moon, the mode in which the result is brought about is somewhat complicated. It may briefly and somewhat incompletely be stated as follows: Owing to the fact that the attracting power of the earth is about eighty times greater than that of the moon, the centre of gravity of the two bodies lies within the earth. About this centre the spheres revolve, each in a way swinging around the other. At this point there is no centrifugal motion arising from the revolution of the pair of spheres, but on the side of the earth opposite the moon, some six thousand miles away, the centrifugal force is considerable, becoming constantly greater as we pass away from the turning point. At the same time the attraction of the moon on the water becomes less. Thus the tide opposite the satellite is formed. On the side toward the moon the same centrifugal action operates, though less effectively than in the other case, for the reason that the turning point is nearer the surface; but this action is re-enforced by the greater attraction of the moon, due to the fact that the water is much nearer that body. In the existing conditions of the earth, what we may call the normal run of the tides is greatly interrupted. Only in the southern ocean can the waters obey the lunar and solar attraction in anything like a normal way. In that part of the earth two sets of tides are discernible, the one and greater due to the moon, the other, much smaller, to the sun. As these tides travel round at different rates, the movements which they produce are sometimes added to each other and sometimes subtracted--that is, at times they come together, while again the elevation of one falls in the hollow of the other. Once again supposing the earth to be all ocean covered, computation shows that the tides in such a sea would be very broad waves, having, indeed, a diameter of half the earth's circumference. Those produced by the moon would have an altitude of about one foot, and those by the sun of about three inches. The geological effects of these swayings would be very slight; the water would pass over the bottom to and fro twice each day, with a maximum journey of a hundred or two feet each way from a fixed point. This movement would be so slow that it could not stir the fine sediment; its only influence would perhaps be to help feed the animals which were fixed upon the bottom by drawing the nurture-bringing water by their mouths. Although the divided condition of the ocean perturbs the action of the tides, so that except by chance their waves are rarely with their centres where the attracting bodies tend to make them, the influence of these divisions is greatly to increase the geological or change-bringing influences arising from these movements. When from the southern ocean the tides start to the northward up the bays of the Atlantic, the Pacific, or the Indian Ocean, they have, as before noted, a height of perhaps less than two feet. As they pass up the narrowing spaces the waves become compressed--that is, an equal volume of moving water has less horizontal room for its passage, and is forced to rise higher. We see a tolerably good illustration of the same principle when we observe a wind-made wave enter a small recess of the shore, the sides of which converge in the direction of the motion. With the diminished room, the wave gains in height. It thus comes about that the tide throughout the Atlantic basin is much higher than in the southern ocean. On the same principle, when the tide rolls in against the shores every embayment of a distinct kind, whose sides converge toward the head, packs up the tidal wave, often increasing its height in a remarkable way. When these bays are wide-mouthed and of elongate triangular form, with deep bottoms, the tides which on their outer parts have a height of ten or fifteen feet may attain an altitude of forty or fifty feet at the apex of the triangle. We have already noted the fact that the tide, such as runs in the southern ocean, exercises little or no influence upon the bottom of the sea over which it moves. As the height of the confined waters increases, the range of their journey over the bottom as the wave comes and goes rapidly increases. When they have an elevation of ten feet they can probably stir the finer mud on the ocean floor, and in shallow water move yet heavier particles. In the embayments of the land, where a great body of water journeys like an alternating river into extensive basins, the tidal action becomes intense; the current may be able to sweep along large stones quite as effectively as a mountain torrent. Thus near Eastport, Me., where the tides have a maximum rise and fall of over twenty feet, the waters rush in places so swiftly that at certain stages of the movement they are as much troubled as those at the rapids of the St. Lawrence. In such portions of the shore the tides do important work in carving channels into the lands. Along the shores of the continents about the North Atlantic, where the tides act in a vigorous manner, we almost everywhere find an underwater shelf extending from the shore with a declivity of only five to ten feet to the mile toward the centre of the sea, until the depth of about five hundred feet is attained; from this point the bottom descends more steeply into the ocean's depth. It is probable that the larger part of the material composing these continental shelves has been brought to its position by tidal action. Each time the tidal wave sweeps in toward the shore it urges the finer particles of sediment along with it. When it moves out it drags them on the return journey toward the depths of the sea. If this shelf were perfectly horizontal, the two journeys of the sand and mud grains would be of the same length; but as the movement takes place up and down a slope, the bits will travel farther under the impulse which leads them downward than under that which impels them up. The result will be that the particles will travel a little farther out from the shore each time it is swung to and fro in the alternating movement of the tide. The effect of tidal movement in nurturing marine life is very great. It aids the animals fixed on the bottoms of the deep seas to obtain their provision of food and their share of oxygen by drawing the water by their bodies. All regions which are visited by strong tides commonly have in the shallows near the shores a thick growth of seaweed which furnishes an ample provision of food for the fishes and other forms of animal life. A peculiar effect arising from tidal action is believed by students of the phenomena to be found in the slowing of the earth's rotation on its axis. The tides rotate around the earth from east to west, or rather, we should say, the solid mass of the earth rubs against them as it spins from west to east. As they move over the bottom and as they strike against the shores this push of the great waves tends in a slight measure to use up the original spinning impulse which causes the earth's rotation. Computation shows that the amount of this action should be great enough gradually to lengthen the day, or the time occupied by the earth in making a complete revolution on the polar axis. The effect ought to be great enough to be measurable by astronomers in the course of a thousand years. On the other hand, the records of ancient eclipses appear pretty clearly to show that the length of the day has not changed by as much as a second in the course of three thousand years. This evidence does not require us to abandon the supposition that the tides tend to diminish the earth's rate of rotation. It is more likely that the effect of the reduction in the earth's diameter due to the loss of heat which is continually going on counterbalances the influence of the tidal friction. As the diameter of a rotating body diminishes, the tendency is for the mass to spin more rapidly; if it expands, to turn more slowly, provided in each case the amount of the impulse which leads to the turning remains the same. This can be directly observed by whirling a small weight attached to a string in such a manner that the cord winds around the finger with each revolution; it will be noted that as the line shortens the revolution is more quickly accomplished. We can readily conceive that the earth is made up of weights essentially like that used in the experiment, each being drawn toward the centre by the gravitative stress, which is like that applied to the weight by the cord. The fact that the days remain of the same length through vast periods of time is probably due to this balance between the effects of tidal action and those arising from the loss of heat--in other words, we have here one of those delicate arrangements in the way of counterpoise which serve to maintain the balanced conditions of the earth's surface amid the great conflicts of diverse energies which are at work in and upon the sphere. It should be understood that the effects of the attraction which produces tides are much more extensive than they are seen to be in the movements of the sea. So long as the solar and planetary spheres remain fluid, the whole of their masses partake of the movement. It is a consequence of this action, as the computations of Prof. George Darwin has shown, that the moon, once nearer the earth than it is at present, has by a curious action of the tidal force been pushed away from the centre of our sphere, or rather the two bodies have repelled each other. An American student of the problem, Mr. T.J.J. See, has shown that the same action has served to give to the double stars the exceeding eccentricity of their orbits. Although these recent studies of tidal action in the celestial sphere are of the utmost importance to the theory of the universe, for they may lead to changes in the nebular hypotheses, they are as yet too incomplete and are, moreover, too mathematical to be presented in an elementary treatise such as this. * * * * * We now turn to another class of waves which are of even more importance than those of the tides--to the undulations which are produced by the action of the wind on the surface of the water. While the tide waves are limited to the open ocean, and to the seas and bays which afford them free entrance, wind waves are produced everywhere where water is subjected to the friction of air which flows over it. While tidal waves come upon the shores but twice each day, the wind waves of ordinary size which roll in from the ocean deliver their blows at intervals of from three to ten seconds. Although the tidal waves sometimes, by a packing-up process, attain the height of fifty feet, their average altitude where they come in contact with the shore probably does not much exceed four feet; usually they come in gently. It is likely that in a general way the ocean surges which beat against the coast are of greater altitude. Wind waves are produced and perform their work in a manner which we shall now describe. When the air blows over any resisting surface, it tends, in a way which we can hardly afford here to describe, to produce motions. If the particle is free to move under the impulse which it communicates, it bears it along; if it is linked together in the manner of large masses, which the wind can not transport, it tends to set it in motion in an alternating way. The sounds of our musical instruments which act by wind are due to these alternating vibrations, such as all air currents tend to produce. An Æolian harp illustrates the action which we are considering. Moving over matter which has the qualities that we denote by the term fluid, the swayings which the air produces are of a peculiar sort, though they much resemble those of the fiddle string. The surface of the liquid rises and falls in what we term waves, the size of which is determined by the measure of fluidity, and by the energy of the wind. Thus, because fresh water is considerably lighter than salt, a given wind will produce in a given distance for the run of the waves heavier surges in a lake than it will in the sea. For this reason the surges in a great storm which roll on the ocean shore, because of the wide water over which they have gathered their impetus, are in size very much greater than those of the largest lakes, which do not afford room for the development of great undulations. To the eye, a wave in the water appears to indicate that the fluid is borne on before the wind. Examination, however, shows that the amount of motion in the direction in which the wind is blowing is very slight. We may say, indeed, that the essential feature of a wave is found in the transmission of impulse rather than in the movement of the fluid matter. A strip of carpet when shaken sends through its length undulations which are almost exactly like water waves. If we imagine ourselves placed in a particle of water, moving in the swayings of a wave in the open and deep sea, we may conceive ourselves carried around in an ellipse, in each revolution returning through nearly the same orbit. Now and then, when the particle came to the surface, it would experience the slight drift which the continual friction of the wind imposes on the water. If the wave in which the journey was made lay in the trade winds, where the long-continued, steadfast blowing had set the water in motion to great depths, the orbit traversed would be moving forward with some rapidity; where also the wind was strong enough to blow the tops of the waves over, forming white-caps, the advance of the particle very near the surface would be speedy. Notwithstanding these corrections, waves are to be regarded each as a store of energy, urging the water to sway much in the manner of a carpet strip, and by the swaying conveying the energy in the direction of the wave movement. The rate of movement of wind waves increases with their height. Slight undulations go forward at the rate of less than half a mile an hour. The greater surges of the deeps when swept by the strongest winds move with the speed which, though not accurately determined, has been estimated by the present writer as exceeding forty miles an hour. As these surges often have a length transverse to the wind of a mile or more, a width of about an eighth of a mile, and a height of from thirty-five to forty-five feet, the amount of energy which they transmit is very great. If it could be effectively applied to the shores in the manner in which the energy of exploding gunpowder is applied by cannon shot, it is doubtful whether the lands could have maintained their position against the assaults of the sea. But there are reasons stated below why the ocean waves can use only a very small part of their energy in rending the rocks against which they strike on the coast line. In the first place, we should note that wind waves have very little influence on the bottom of the deep sea. If an observer could stand on the sea floor at the depth of a mile below a point over which the greatest waves were rolling, he could not with his unaided senses discern that the water was troubled. He would, indeed, require instruments of some delicacy to find out that it moved at all. Making the same observations at the depth of a thousand feet, it is possible that he would note a slight swaying motion in the water, enough sensibly to affect his body. At five hundred feet in depth the movement would probably be sufficient to disturb fine mud. At two hundred feet, the rasping of the surge on the bottom would doubtless be sufficient to push particles of coarse sand to and fro. At one hundred feet in depth, the passage of the surge would be strong enough to urge considerable pebbles before it. Thence up the slope the driving action would become more and more intense until we attained the point where the wave broke. It should furthermore be noted that, while the movement of the water on the floor of the deep sea as the wave passes overhead would be to and fro, with every advance in the shallowing and consequent increased friction on the bottom, the forward element in the movement would rapidly increase. Near the coast line the effect of the waves is continually to shove the detritus up the slopes of the continental shelf. Here we should note the fact that on this shelf the waves play a part exactly the opposite of that effected by the tides. The tides, as we have noted, tend to drag the particles down the slope, while the waves operate to roll them up the declivity. As the wave in advancing toward the shore ordinarily comes into continually shallowing water, the friction on the bottom is ever-increasing, and serves to diminish the energy the surge contains, and therefore to reduce its proportions. If this action operated alone, the subtraction which the friction makes would cause the surf waves which roll in over a continental shelf to be very low, probably in height less than half that which they now attain. In fact, however, there is an influence at work to increase the height of the waves at the expense of its width. Noting that the friction rapidly increases with the shallowing, it is easy to see that this resistance is greatest on the advancing front of the wave, and least on its seaward side. The result is that the front moves more slowly than the rear, so that the wave is forced to gain in height; but for the fact that the total friction which the wave encounters takes away most of its impetus, we might have combers a hundred feet high rolling upon the shelving shores which almost everywhere face the seas. As the wave shortens its width and gains in relative height, though not in actual elevation, another action is introduced which has momentous consequences. The water in the bottom of the wave is greatly retarded in its ongoing by its friction over the sea floor, while the upper part of the surge is much less affected in this way. The result is that at a certain point in the advance, the place of which is determined by the depth, the size, and the speed of the undulation, the front swiftly steepens until it is vertical, and the top shoots forward to a point where it is no longer supported by underlying water, when it plunges down in what is called the surf or breaker. In this part of the wave's work the application of the energy which it transmits differs strikingly from the work previously done. Before the wave breaks, the only geological task which it accomplishes is effected by forcing materials up the slope, in which movement they are slightly ground over each other until they come within the battering zone of the shore, where they may be further divided by the action of the mill which is there in operation. When the wave breaks on the shore it operates in the following manner: First, the overturning of its crest sends a great mass of water, it may be from the height of ten or more feet, down upon the shore. Thus falling water has not only the force due to its drop from the summit of the wave, but it has a share of the impulse due to the velocity with which the surge moved against the shore. It acts, in a word, like a hammer swung down by a strong arm, where the blow represents not only the force with which the weight would fall of itself, but the impelling power of the man's muscles. Any one who will expose his body to this blow of the surf will recognise how violent it is; he may, if the beach be pebbly, note how it drives the stones about; fragments the size of a man's head may be hurled by the stroke to the distance of twenty feet or more; those as large as the fist may be thrown clear beyond the limits of the wave. So vigorous is this stroke that the sound of it may sometimes be heard ten miles inland from the coast where it is delivered. Moving forward up the slope of a gently inclined beach, the fragments of the wave are likely to be of sufficient volume to permit them to regather into a secondary surge, which, like the first, though much smaller, again rises into a wall, forming another breaker. Under favourable conditions as many as four or five of these successive diminishing surf lines may be seen. The present writer has seen in certain cases as many as a dozen in the great procession, the lowest and innermost only a few inches high, the outer of all with a height of perhaps twenty feet. Along with the direct bearing action of the surf goes a to-and-fro movement, due to the rushing up and down of the water on the beach. This swashing affects not only the broken part of the waves, but all the water between the outer breaker and the shore. These swayings in the surf belt often swing the _débris_ on the inner margin over a range of a hundred feet or more, the movement taking place with great swiftness, affecting the pebbles to the depth of several inches, and grinding the bits together in a violent way. Listening to the turmoil of a storm, we can on a pebbly beach distinctly hear the sound of the downward stroke, a crashing tone, and the roar of the rolling stones. As waves are among the interesting things in the world, partly on account of their living quality and partly because of their immediate and often exceeding interest to man, we may here note one or two peculiar features in their action. In the first place, as the reader who has gained a sense of the changes in form of action may readily perceive, the beating of waves on the shore converts the energy which they possess into heat. This probably warms the water during great storms, so that by the hand we may note the difference in temperature next the coast line and in the open waters. This relative warmth of the surf water is perhaps a matter of some importance in limiting the development of ice along the shore line; it may also favour the protection of the coast life against the severe cold of the winter season. The waves which successively come against the shore in any given time, particularly if a violent wind is blowing on to the coast, are usually of about the same size. When, however, in times of calm an old sea, as it is called, is rolling in, the surges may occasionally undergo very great variations in magnitude. Not infrequently these occasional waves are great enough to overwhelm persons who are upon the rocks next the shore. These greater surges are probably to be accounted for by the fact that in the open sea waves produced by winds blowing in different directions may run on with their diverse courses and varied intervals until they come near the shore. Running in together, it very well happens that two of the surges belonging to different sets may combine their forces, thus doubling the swell. The danger which these conjoined waves bring is obviously greatest on cliff shores, where, on account of the depth of water, the waves do not break until they strike the steep. * * * * * Having considered in a general way the action of waves as they roll in to the shore, bearing with them the solar energy which was contributed to them by the winds, we shall now take up in some detail the work which goes on along the coast line--work which is mainly accomplished by wave action. On most coast lines the observer readily notes that the shore is divided into two different kinds of faces--those where the inner margin of the wave-swept belt comes against rocky steeps, and those bordered by a strand altogether composed of materials which the surges have thrown up. These may be termed for convenience cliff shores and wall-beach shores. We shall begin our inquiry with cliff shores, for in those sections of the coast line the sea is doing its most characteristic and important work of assaulting the land. If the student has an opportunity to approach a set of cliffs of hard rock in time of heavy storm, when the waves have somewhere their maximum height, he should seek some headland which may offer him safe foothold whence he can behold the movements which are taking place. If he is so fortunate as to have in view, as well may be the case, cliffs which extend down into deep water, and others which are bordered by rude and generally steeply sloping beaches covered with large stones, he may perceive that the waves come in against the cliffs which plunge into deep water without taking on the breaker form. In this case the undulation strikes but a moderate blow; the wave is not greatly broken. The part next the rock may shoot up as a thin sheet to a considerable height; it is evident that while the ongoing wave applies a good deal of pressure to the steep, it does not deliver its energy in the effective form of a blow as when the wave overturns, or in the consequent rush of the water up a beach slope. It is easy to perceive that firm-set rock cliffs, with no beaches at their bases, can almost indefinitely withstand the assaults. On the steep and stony beach, because of its relatively great declivity, the breaker or surf forms far in, and even in its first plunge often attains the base of the precipice. The blow of the overfalling as well as that of the inrush moves about stones of great size; those three feet or more in diameter are often hurled by the action against the base of the steep, striking blows, the sharp note of which can often be heard above the general roar which the commotion produces. The needlelike crags forming isles standing at a distance from the shore, such as are often found along hard rock coasts, are singularly protected from the action of effective waves. The surges which strike against them are unarmed with stones, and the water at their bases is so deep that it does not sway with the motion with sufficient energy to move them on the bottom. Where a cliff is in this condition, it may endure until an elevation of the coast line brings its base near the level of the sea, or until the process of decay has detached a sufficient quantity of stone to form a talus or inclined plane reaching near to the water level. As before noted, it is the presence of a sloping beach reaching to about the base of the cliff which makes it possible for the waves to strike at with a hammer instead of with a soft hand. Battering at the base of the cliff, the surges cut a crease along the strip on which they strike, which gradually enters so far that the overhanging rock falls of its own weight. The fragments thus delivered to the sea are in turn broken up and used as battering instruments until they are worn to pieces. We may note that in a few months of heavy weather the stones of such a fall have all been reduced to rudely spherical forms. Observations made on the eastern face of Cape Ann, Mass., where the seas are only moderately heavy, show that the storms of a single winter reduce the fragments thrown into the sea from the granite quarries to spheroidal shapes, more than half of their weight commonly being removed in the form of sand and small pebbles which have been worn from their surfaces. We can best perceive the effect of battering action which the sea applies to the cliffs by noting the points where, owing to some chance features in the structure in the rock, it has proved most effective. Where a joint or a dike, or perhaps a softer layer, if the rocks be bedded, causes the wear to go on more rapidly, the waves soon excavate a recess in which the pebbles are retained, except in stormy weather, in an unmoved condition. When the surges are heavy, these stones are kept in continuous motion, receding as the wave goes back, and rushing forward with its impulse until they strike against the firm-set rock at the end of the chasm. In this way they may drive in a cut having the length of a hundred feet or more from the face of the precipice. In most cases the roofs over these sea caves fall in, so that the structure is known as a chasm. Occasionally these roofs remain, in which case, for the reason that the floor of the cutting inclines upward, an opening is made to the surface at their upper end, forming what is called in New England a "spouting horn"; from the inland end of the tunnel the spray may be thrown far into the air. As long as the cave is closed at this inner end, and is not so high but that it may be buried beneath a heavy wave, the inrushing water compresses the air in the rear parts of the opening. When the wave begins to retreat this air blows out, sending a gust of spray before it, the action resembling the discharge of a great gun from the face of a fortification. It often happens that two chasms converging separate a rock from the cliff. Then a lowering of the coast may bring the mass to the state of a columnar island, such as abound in the Hebrides and along various other shores. If a cliff shore retreats rapidly, it may be driven back into the shore, and its face assumes the curve of a small bay. With every step in this change the bottom is sure to become shallower, so that the waves lose more and more of their energy in friction over the bottom. Moreover, in entering a bay the friction which the waves encounter in running along the sides is greater than that which they meet in coming in upon a headland or a straight shore. The result is, with the inward retreat of the steep it enters on conditions which diminish the effectiveness of the wave stroke. The embayment also is apt to hold detritus, and so forms in time a beach at the foot of the cliff, over which the waves rarely are able to mount with such energy as will enable them to strike the wall in an effective manner. With this sketch of the conditions of a cliff shore, we will now consider the fate of the broken-tip rock which the waves have produced on that section of the coast land. By observation of sea-beaten cliffs the student readily perceives that a great amount of rocky matter has been removed from most cliff-faced shores. Not uncommonly it can be shown that such sea faces have retreated for several miles. The question now arises, What becomes of the matter which has been broken up by the wave action? In some part the rock, when pulverized by the pounding to which it is subjected, has dissolved in the water. Probably ninety per cent of it, however, retains the visible state, and has a fate determined by the size of the fragments of which it is composed. If these be as fine as mud, so that they may float in the water, they are readily borne away by the currents which are always created along a storm-swept shore, particularly by the undertow or bottom outcurrent--the "sea-puss," as it is sometimes called--that sweeps along the bottom from every shore, against which the waves form a surf. If as coarse as sand grains, or even very small pebbles, they are likely to be drawn out, rolling over the bottom to an indefinite distance from the sea margin. The coarser stones, however, either remain at the foot of the cliff until they are beaten to pieces, or are driven along the shore until they find some embayment into which they enter. The journey of such fragments may, when the wind strikes obliquely to the shore, continue for many miles; the waves, running with the wind, drive the fragments in oscillating journeys up and down the beach, sometimes at the rate of a mile or more a day. The effect of this action can often be seen where a vessel loaded with brick or coal is wrecked on the coast. In a month fragments of the materials may be stretched along for the distance of many miles on either side of the point where the cargo came ashore. Entering an embayment deep enough to restrain their further journey, the fragments of rock form a boulder beach, where the bits roll to and fro whenever they are struck by heavy surges. The greater portion of them remain in this mill until they are ground to the state of sand and mud. Now and then one of the fragments is tossed up beyond the reach of the waves, and is contributed to the wall of the beach. In very heavy storms these pebbles which are thrown inland may amount in weight to many tons for each mile of shore. The study of a pebbly beach, drawn from crest to the deep water outside, will give an idea as to the history of its work. On either horn of the crescent by which the pebbles are imported into the pocket we find the largest fragments. If the shore of the bay be long, the innermost part of the recess may show even only very small pebbles, or perhaps only fine sand, the coarser material having been worn out in the journey. On the bottom of the bay, near low tide, we begin to find some sand produced by the grinding action. Yet farther out, below high-tide mark, there is commonly a layer of mud which represents the finer products of the mill. Boulder beaches are so quick in answering to every slight change in the conditions which affect them that they seem almost alive. If by any chance the supply of detritus is increased, they fill in between the horns, diminish the incurve of the bay, and so cause its beach to be more exposed to heavy waves. If, on the other hand, the supply of grist to the mill is diminished, the beach becomes more deeply incurved, and the wave action is proportionately reduced. We may say, in general, that the curve of these beaches represents a balance between the consumption and supply of the pebbles which they grind up. The supply of pebbles brought along the shore by the waves is in many cases greatly added to by a curious action of seaweeds. If the bottom of the water off the coast is covered by these fragments, as is the case along many coast lines within the old glaciated districts, the spores of algæ are prone to take root upon them. Fastening themselves in those positions, and growing upward, the seaweeds may attain considerable size. Being provided with floats, the plant exercises a certain lifting power on the stone, and finally the tugging action of the waves on the fronds may detach the fragments from the bottom, making them free to journey toward the shore. Observing from near at hand the straight wall of the wave in times of heavy storm, the present writer has seen in one view as many as a dozen of these plant-borne stones, sometimes six inches in diameter, hanging in the walls of water as it was about to topple over. As soon as they strike the wave-beaten part of the shore these stones are apt to become separated from the plants, though we can often notice the remains or prints of the attachments adhering to the surface of the rock. Where the pebbles off the shore are plenty, a rocky beach may be produced by this process of importation through the agency of seaweeds without any supply being brought by the waves along the coast line. Returning to sand beaches, we enter the most interesting field of contact between seas and lands. Probably nine tenths of all the coast lines of the open ocean are formed of arenaceous material. In general, sand consists of finely broken crystals of silica or quartz. These bits are commonly distinctly faceted; they rarely have a spherical form. Not only do accumulations of sand border most of the shore line, but they protect the land against the assaults of the sea, and this in the following curious manner: When shore waves beat pebbles against each other, they rapidly wear to bits; we can hear the sound of the wearing action as the wave goes to and fro. We can often see that the water is discoloured by the mud or powdered rock. When, however, the waves tumble on a sandy coast, they make but a muffled sound, and produce no mud. In fact, the particles of sand do not touch each other when they receive the blow. Between them there lies a thin film of water, drawn in by the attraction known as capillarity, which sucks the fluid into a sponge or between plates of glass placed near together. The stroke of the waves slightly compresses this capillary water, but the faces of the grains are kept apart as sheets of glass may be observed to be restrained from contact when water is between them. If the reader would convince himself as to the condition of the sand grains and the water which is between them, he may do so by pressing his foot on the wet beach which the wave has just left. He will observe that it whitens and sinks a little under the pressure, but returns in good part to its original form when the foot is lifted. In the experiment he has pushed a part of the contained water aside, but he has not brought the grains together; they do not make the sound which he will often hear when the sand is dry. The result is that the sand on the seashore may wear more in going the distance of a mile in the dry sand dune than in travelling for hundreds along the wet shore. If the rock matter in the state of sand wore as rapidly under the heating of the waves as it does in the state of pebbles, the continents would doubtless be much smaller than they are. Those coasts which have no other protection than is afforded by a low sand beach are often better guarded against the inroads of the sea than the rock-girt parts of the continents. It is on account of this remarkable endurance of sand of the action of the waves that the stratified rocks which make up the crust of the earth are so thick and are to such an extent composed of sand grains. The tendency of the _débris_-making influences along the coast line is to fill in the irregularities which normally exist there; to batter off the headlands, close up the bays and harbours, and generally to reduce the shores to straight lines. Where the tide has access to these inlets, it is constantly at work in dragging out the detritus which the waves make and thrust into the recesses. These two actions contend with each other, and determine the conditions of the coast line, whether they afford ports for commerce or are sealed in by sand bars, as are many coast lines which are not tide-swept, as that of northern Africa, which faces the Mediterranean, a nearly tideless sea. The same is the case with the fresh-water lakes; even the greater of them are often singularly destitute of shelters which can serve the use of ships, and this because there are no tides to keep the bays and harbours open. THE OCEAN CURRENTS. The system of ocean currents, though it exhibits much complication in detail, is in the main and primarily dependent on the action of the constant air streams known as the trade winds. With the breath from the lips over a basin of water we can readily make an experiment which shows in a general way the method in which the winds operate in producing the circulation of the sea. Blowing upon the surface of the water in the basin, we find that even this slight impulse at once sets the upper part in motion, the movement being of two kinds--pulsating movements or waves are produced, and at the same time the friction of the air on the surface causes its upper part to slide over the under. With little floats we can shortly note that the stream which forms passes to the farther side of the vessel, there divides, and returns to the point of beginning, forming a double circle, or rather two ellipses, the longer sides of which are parallel with the line of the air current. Watching more closely, aiding the sight by the particles which float at various distances below the surface, we note the fact that the motion which was at first imparted to the surface gradually extends downward until it affects the water to the depth of some inches. In the trade-wind belt the ocean waters to the depth of some hundreds of feet acquire a continuous movement in the direction in which they are impelled by those winds. This motion is most rapid at the surface and near the tropics. It diminishes downwardly in the water, and also toward the polar sides of the trade-wind districts. Thus the trades produce in the sea two broad, slow-moving, deep currents, flowing in the northern hemisphere toward the southwest, and in the southern hemisphere toward the northwest. Coming down upon each other obliquely, these broad streams meet about the middle of the tropical belt. Here, as before noted, the air of the trade winds leaves the surface and rises upward. The waters being retained on their level, form a current which moves toward the west. If the earth within the tropics were covered by a universal sea, the result of this movement would be the institution of a current which, flowing under the equator, would girdle the sphere. With a girdling equatorial current, because of the intense heat of the tropics and the extreme cold of the parallels beyond the fortieth degree of latitude, the earth would be essentially uninhabitable to man, and hardly so to any forms of life. Its surface would be visited by fierce winds induced by the very great differences of temperature which would then prevail. Owing, however, to the barriers which the continents interpose to the motions of these windward-setting tropical currents, all the water which they bear, when it strikes the opposing shores, is diverted to the right and left, as was the stream in the experiment with the basin and the breath, the divided currents seeking ways toward high latitudes, conveying their store of heat to the circumpolar lands. So effective is this transfer of temperature that a very large part of the heat which enters the waters in the tropical region is taken out of that division of the earth's surface and distributed over the realms of sea and land which lie beyond the limits of the vertical sun. Thus the Gulf Stream, the northern branch of the Atlantic tropical current, by flowing into the North Atlantic, contributes to the temperature of the region within the Arctic Circle more heat than actually comes to that district by the direct influx from the sun. The above statements as to the climatal effect of the ocean streams show us how important it is to obtain a sufficient conception as to the way in which these currents now move and what we can of their history during the geologic ages. This task can not yet be adequately done. The fields of the sea are yet too imperfectly explored to afford us all the facts required to make out the whole story. Only in the case of our Gulf Stream can we form a full conception as to the journey which the waters undergo and the consequence of their motion. In the case of this current, observations clearly show that it arises from the junction near the equatorial line of the broad stream created by the two trade-wind belts. Uniting at the equator, these produce a westerly setting current, having the width of some hundred miles and a depth of several hundred feet. Its velocity is somewhat greater than a mile an hour. The centre of the current, because of the greater strength of the northern as compared with the southern trades, is considerably south of the equator. When this great slow-moving stream comes against the coast of South America, it encounters the projecting shoulder of that land which terminates at Cape St. Roque. There it divides, as does a current on the bows of an anchored ship, a part--rather more than one half--of the stream turning to the northward, the remainder passing toward the southern pole; this northerly portion becomes what is afterward known as the Gulf Stream, the history of which we shall now briefly follow. Flowing by the northwesterly coast of South America, the northern share of the tropical current, being pressed in against the land by the trade winds, is narrowed, and therefore acquires at once a swifter flow, the increased speed being due to conditions like those which add to the velocity of the water flowing through a hose when it comes to the constriction of the nozzle. Attaining the line of the southeastern or Lesser Antilles, often known as the Windward Islands, a part of this current slips through the interspaces between these isles and enters the Gulf of Mexico. Another portion, failing to find sufficient room through these passages, skirts the Antilles on their eastern and northern sides, passes by and among the Bahama Islands, there to rejoin the part of the stream which entered the Caribbean. This Caribbean portion of the tide spreads widely in that broad sea, is constricted again between Cuba and Yucatan, again expands in the Gulf of Mexico, and is finally poured forth through the Straits of Florida as a stream having the width of forty or fifty miles, a depth of a thousand feet or more, and a speed of from three to five miles an hour, exceeding in its rate of flow the average of the greatest rivers, and conveying more water than do all the land streams of the earth. In this part of its course the deep and swift stream from the Gulf of Mexico, afterward to be named the Gulf Stream, receives the contribution of slower moving and shallower currents which skirted the Antilles on their eastern verge. The conjoined waters then move northward, veering toward the east, at first as a swift river of the sea having a width of less than a hundred miles and of great depth; with each step toward the pole this stream widens, diminishing proportionately in depth; the speed of its current decreases as the original impetus is lost, and the baffling winds set its surface waters to and fro in an irregular way. Where it passes Cape Hatteras it has already lost a large share of its momentum and much of its heat, and is greatly widened. Although the current of the Gulf Stream becomes more languid as we go northward, it for a very long time retains its distinction from the waters of the sea through which it flows. Sailing eastward from the mouth of the Chesapeake, the navigator can often observe the moment when he enters the waters of this current. This is notable not only in the temperature, but in the hue of the sea. North of that line the sharpness of the parting wall becomes less distinct, the stream spreads out broadly over the surface of the Atlantic, yet its thermometric effects are distinctly traceable to Iceland and Nova Zembla, and the tropical driftwood which it carries affords the principal timber supply of the inhabitants of the first-named isle. Attaining this circumpolar realm, and finally losing the impulse which bore it on, the water of the Gulf Stream partly returns to the southward in a relatively slight current which bears the fluid along the coast of Europe until it re-enters the system of tropical winds and the currents which they produce. A larger portion stagnates in the circumpolar region, in time slowly to return to the tropical district in a manner afterward to be described. Although the Gulf Stream in the region north of Cape Hatteras is so indistinct that its presence was not distinctly recognised until the facts were subjected to the keen eye of Benjamin Franklin, its effects in the way of climate are so great that we must attribute the fitness of northern Europe for the uses of civilized man to its action. But for the heat which this stream brings to the realm of the North Atlantic, Great Britain would be as sterile as Labrador, and the Scandinavian region, the cradle-land of our race, as uninhabitable as the bleakest parts of Siberia. It is a noteworthy fact that when the equatorial current divides on the continents against which it flows, the separate streams, although they may follow the shores for a certain distance toward the poles, soon diverge from them, just as the Gulf Stream passes to the seaward from the eastern coast of the United States. The reason for this movement is readily found in the same principle which explains the oblique flow of the trades and counter trades in their passage to and from the equatorial belt. The particle of water under the equator, though it flows to the west, has, by virtue of the earth's rotation, an eastward-setting velocity of a thousand miles an hour. Starting toward the poles, the particle is ever coming into regions of the sea where the fluid has a less easterly movement, due to the earth's rotation on its axis. Consequently the journeying water by its momentum tends to move off in an easterly course. Attaining high latitudes and losing its momentum, it abides in the realm long enough to become cooled. We have already noted the fact that only a portion of the waters sent northward in the Gulf Stream and the other currents which flow from the equator to the poles is returned by the surface flow which sets toward the equator along the eastern side of the basins. The largest share of the tide effects its return journey in other ways. Some portion of this remainder sets equatorward in local cold streams, such as that which pours forth through Davis Strait into Baffin Bay, flowing under the Gulf Stream waters for an unknown distance toward the tropics. There are several of these local as yet little known streams, which doubtless bring about a certain amount of circulation between the polar regions and the tropical districts. Their effect is, however, probably small as compared with that massive drift which we have now to note. The tropical waters when they attain high latitudes are constantly cooled, and are overlaid by the warmer contributions of that tide, and are thus brought lower and lower in the sea. When they start downward they have, as observations show, a temperature not much above the freezing point of salt water. They do not congeal for the reason that the salt of the ocean lowers the point at which the water solidifies to near 28° Fahr. The effect of this action is gradually to press down the surface cold water until it attains the very bottom in all the circumpolar regions. At the same time this descending water drifts along the bottom of the ocean troughs toward the equatorial realm. As this cold water is heavier than that which is of higher temperature and nearer the surface, it has no tendency to rise. Being below the disturbing influences of any current save its own, it does not tend, except in a very small measure, to mingle with the warmer overlying fluid. The result is that it continues its journey until it may come within the tropics without having gained a temperature of more than 35° Fahr., the increase in heat being due in small measure to that which it receives from the earth's interior and that which it acquires from the overlying warmer water. Attaining the region of the tropical current, this drift water from the poles gradually rises, to take the place of that which goes poleward, becomes warm, and again starts on its surface journey toward the arctic and antarctic regions. Nothing is known as to the rate of this bottom drift from the polar districts toward the equator, but, from some computation which he has made, the writer is of the opinion that several centuries is doubtless required for the journey from the Arctic Circle to the tropics. The speed of the movement probably varies; it may at times require some thousand years for its accomplishment. The effect of the bottom drift is to withdraw from seas in high latitudes the very cold water which there forms, and to convey it beneath the seas of middle latitudes to a realm where it is well placed for the reheating process. If all the cold water of circumpolar regions had to journey over the surface to the equator, the perturbing effect of its flow on the climates of various lands would be far greater than it is at present. Where such cold currents exist the effect is to chill the air without adding much to the rainfall; while the currents setting northward not only warm the regions near which they flow, but by so doing send from the water surfaces large quantities of moisture which fall as snow or rain. Thus the Gulf Stream, directly and indirectly, probably contributes more than half the rainfall about the Atlantic basin. The lack of this influence on the northern part of North America and Asia causes those lands to be sterilized by cold, although destitute of permanent ice and snow upon their surfaces. We readily perceive that the effect of the oceanic circulation upon the temperatures of different regions is not only great but widely contrasted. By taking from the equatorial belt a large part of the heat which falls within that realm, it lowers the temperature to the point which makes the district fit for the occupancy of man, perhaps, indeed, tenable to all the higher forms of life. This same heat removed to high latitudes tempers the winter's cold, and thus makes a vast realm inhabitable which otherwise would be locked in almost enduring frosts. Furthermore, this distribution of temperatures tends to reduce the total wind energy by diminishing the trades and counter trades which are due to the variations of heat which are encountered in passing polarward from the equator. Still further, but for this circulation of water in the sea, the oceans about the poles would be frozen to their very bottom, and this vast sheet of ice might be extended southward to within the parallels of fifty degrees north and south latitude, although the waters under the equator might at the same time be unendurably hot and unfit for the occupancy of living beings. A large part of the difficulties which geologists encounter in endeavouring to account for the changes of the past arise from the evidences of great climatal revolutions which the earth has undergone. In some chapters of the great stone book, whose leaves are the strata of the earth, we find it plainly written in the impressions made by fossils that all the lands beyond the equatorial belt have undergone changes which can only be explained by the supposition that the heat and moisture of the countries have been subjected to sudden and remarkable changes. Thus in relatively recent times thick-leaved plants which retained their vegetation in a rather tender state throughout the year have flourished near to the poles, while shortly afterward an ice sheet, such as now covers the greater part of Greenland, extended down to the line of the Ohio River at Cincinnati. Although these changes of climate are, as we shall hereafter note, probably due to entangled causes, we must look upon the modifications of the ocean streams as one of the most important elements in the causation. We can the more readily imagine such changes to be due to the alterations in the course and volume of the ocean current when we note how trifling peculiarities in the geography of the shores--features which are likely to be altered by the endless changes which occur in the form of a continent--affect the run of these currents. Thus the growth of coral reefs in southern Florida, and, in general, the formation of that peninsula, by narrowing the exit of the great current from the Gulf of Mexico, has probably increased its velocity. If Florida should again sink down, that current would go forth into the North Atlantic with the speed of about a mile an hour, and would not have momentum enough to carry its waters over half the vast region which they now traverse. If the lands about the western border of the Caribbean Sea, particularly the Isthmus of Darien, should be depressed to a considerable depth below the ocean level, the tropical current would enter the Pacific Ocean, adding to the temperature of its waters all the precious heat which now vitalizes the North Atlantic region. Such a geographic accident would not only profoundly alter the life conditions of that part of the world, but it would make an end of European civilization. In the chapter on climatal changes further attention will be given to the action of ocean currents from the point of view of their influence on the heat and moisture of different parts of the world. We now have to consider the last important influence of ocean currents--that which they directly exercise on the development of organic life. The most striking effect of this nature which the sea streams bring about is caused by the ceaseless transportation to which they subject the eggs and seeds of animals and plants, as well as the bodies of the mature form which are moved about by the flowing waters. But for the existence of these north and south flowing currents, due to the presence of the continental barriers, the living tenants of the seas would be borne along around the earth, always in the same latitude, and therefore exposed to the same conditions of temperature. In this state of affairs the influences which now make for change in organic species would be far less than they are. Journeying in the great whirlpools which the continental barriers make out of the westward setting tropical currents, these organic species are ever being exposed to alterations in their temperature conditions which we know to be favourable to the creation of those variations on which the advance of organic life so intimately depends. Thus the ocean currents not only help to vary the earth by producing changes in the climate of both sea and land, breaking up the uniformity which would otherwise characterize regions at the same distance from the equator, but they induce, by the consequences of the migrations which they enforce, changes in the organic tenants of the sea. Another immediate effect of ocean streams arises where their currents of warm water come against shores or shallows of the sea. At these points, if the water have a tropical temperature, we invariably find a vast and rapid development of marine animals and plants, of which the coral-making polyps are the most important. In such positions the growth of forms which secrete solid skeletons is so rapid that great walls of their remains accumulate next the shore, the mass being built outwardly by successive growths until the realm of the land may be extended for scores of miles into the deep. In other cases vast mounds of this organic _débris_ may be accumulated in mid ocean until its surface is interspersed with myriads of islands, all of which mark the work due to the combined action of currents and the marine life which they nourish. Probably more than four fifths of all the islands in the tropical belt are due in this way to the life-sustaining action of the currents which the trade winds create. There are many secondary influences of a less important nature which are due to the ocean streams. The reader will find on most wall-maps of the world certain areas in the central part of the oceans which are noted as Sargassum seas, of which that of the North Atlantic, west and south of the Azore Islands, is one of the most conspicuous. In these tracts, which in extent may almost be compared with the continents, we find great quantities of floating seaweed, the entangled fronds of which often form a mass sufficiently dense to slightly restrain the speed of ships. When the men on the caravels of Columbus entered this tangle, they were alarmed lest they should be unable to escape from its toils. It is a curious fact that these weeds of the sea while floating do not reproduce by spores the structures which answer to the seeds of higher plants, but grow only by budding. It seems certain that they could not maintain their place in the ocean but for the action of the currents which convey the bits rent off from the shores where the plant is truly at home. This vast growth of plant life in the Sargassum basins doubtless contributed considerable and important deposits of sediment to the sea floors beneath the waters which it inhabits. Certain ancient strata, known as the Devonian black shale, occupying the Ohio valley and the neighbouring parts of North America to the east and north of that basin, appear to be accumulations which were made beneath an ancient Sargassum sea. The ocean currents have greatly favoured and in many instances determined the migrations not only of marine forms, but of land creatures as well. Floating timber may bear the eggs and seeds of many forms of life to great distances until the rafts are cast ashore in a realm where, if the conditions favour, the creatures may find a new seat for their life. Seeds of plants incased in their often dense envelopes may, because they float, be independently carried great distances. So it comes about that no sooner does a coral or other island rise above the waters of the sea than it becomes occupied by a varied array of plants. The migrations of people, even down to the time of the voyages which discovered America, have in large measure been controlled by the run of the ocean streams. The tropical set of the waters to the westward helped Columbus on his way, and enabled him to make a journey which but for their assistance could hardly have been accomplished. This same current in the northern part of the Gulf Stream opposed the passage of ships from northern Europe to the westward, and to this day affects the speed with which their voyages are made. THE CIRCUIT OF THE RAIN. We have now to consider those movements of the water which depend upon the fact that at ordinary temperatures the sea yields to the air a continued and large supply of vapour, a contribution which is made in lessened proportion by water in all stages of coldness, and even by ice when it is exposed to dry air. This evaporation of the sea water is proportional to the temperature and to the dryness of the air where it rests upon the ocean. It probably amounts on the average to somewhere about three feet per annum; in regions favourably situated for the process, as on the west coast of northern Africa, it may be three or four times as much, while in the cold and humid air about the poles it may be as little as one foot. When contributed to the air, the water enters on the state of vapour, in which state it tends to diffuse itself freely through the atmosphere by virtue of the motion which is developed in particles when in the vaporous or gaseous state. The greater part of the water evaporated from the seas probably finds its way as rain at once back into the deep, yet a considerable portion is borne away horizontally until it encounters the land. The precipitation of the water from the air is primarily due to the cooling to which it is subjected as it rises in the atmosphere. Over the sea the ascent is accomplished by the simple diffusion of the vapour or by the uprise through the aërial shaft, such as that near the equator or over the centres of the whirling storms. It is when the air strikes the slopes of the land that we find it brought into a condition which most decidedly tends to precipitate its moisture. Lifted upward, the air as it ascends the slopes is brought into cooler and more rarefied conditions. Losing temperature and expanding, it parts with its water for the same reason that it does in the ascending current in the equatorial belt or in the chimneys of the whirl storms. A general consequence of this is that wherever moisture-laden winds from the sea impinge upon a continent they lay down a considerable part of the water which they contain. If all the lands were of the same height, the rain would generally come in largest proportion upon their coastal belt, or those portions of the shore-line districts over which the sea winds swept. But as these winds vary in the amount of the watery vapour which they contain, and as the surface of the land is very irregular, the rainfall is the most variable feature in the climatal conditions of our sphere. Near the coasts it ranges from two or three inches in arid regions--such as the western part of the Sahara and portions of the coast regions of Chili and Peru--to eight hundred inches about the head waters of the Brahmapootra River in northern India, where the high mountains are swept over by the moisture-laden airs from the neighbouring sea. Here and there detached mountainous masses produce a singular local increase in the amount of the rainfall. Thus in the lake district in northwestern England the rainfall on the seaward side of mountains, not over four thousand feet high, is very much greater than it is on the other slope, less than a score of miles away. These local variations are common all over the world, though they are but little observed. In general, the central parts of continents are likely to receive much less rainfall than their peripheral portions. Thus the central districts of North America, Asia, and Australia--three out of the five continental masses--have what we may call interior deserts. Africa has one such, though it is north of the centre, and extends to the shores of the Mediterranean and the Atlantic. The only continent without this central nearly rainless field is South America, where the sole characteristic arid district is situated on the western slope of the Cordilleran range. In this case the peculiarity is due to the fact that the strong westerly setting winds which sweep over the country encounter no high mountains until they strike the Andean chain. They journey up a long and rather gradual slope, where the precipitation is gradually induced, the process being completed when they strike the mountain wall. Passing over its summit, they appear as dry winds on the Pacific coast. Even while the winds frequently blow in from the sea, as along the western coast of the Americas, they may come over water which is prevailingly colder than the land. This is characteristically the case on the western faces of the American continent, where the sea is cooled by the currents setting toward the equator from high latitudes. Such cool sea air encountering the warm land has its temperature raised, and therefore does not tend to lay down its burden of moisture, but seeks to take up more. On this account the rainfall in countries placed under such conditions is commonly small. By no means all the moisture which comes upon the earth from the atmosphere descends in the form of rain or snow. A variable, large, though yet undetermined amount falls in the form of dew. Dew is a precipitation of moisture which has not entered the peculiar state which we term fog or cloud, but has remained invisible in the air. It is brought to the earth through the radiation of heat which continually takes place, but which is most effective during the darkened half of the day, when the action is not counterbalanced by the sun's rays. While the sun is high and the air is warm there is a constant absorption of moisture in large part from the ground or from the neighbouring water areas, probably in some part from those suspended stores of water, the clouds, if such there be in the neighbourhood. We can readily notice how clouds drifting in from the sea often melt into the dry air which they encounter. Late in the afternoon, even before the sun has sunk, the radiation of heat from the earth, which has been going on all the while, but has been less considerable than the incurrent of temperature, in a way overtakes that influx. The air next the surface becomes cooled from its contact with the refrigerating earth, and parts with its moisture, forming a coating of water over everything it touches. At the same time the moisture escaping from the warmed under earth likewise drops back upon its cooled surface almost as soon as it has escaped. The thin sheet of water precipitated by this method is quickly returned to the air when it becomes warmed by the morning sunshine, but during the night quantities of it are absorbed by the plants; very often, indeed, with the lowlier vegetation it trickles down the leaves and enters the earth about the base of the stem, so that the roots may appropriate it. Our maize, or Indian corn, affords an excellent example of a plant which, having developed in a land of droughts, is well contrived, through its capacities for gathering dew, to protect itself against arid conditions. In an ordinary dew-making night the leaves of a single stem may gather as much as half a pint of water, which flows down their surfaces to the roots. So efficient is this dew supply, this nocturnal cloudless rain, that on the western coast of South America and elsewhere, where the ordinary supply of moisture is almost wanting, many important plants are able to obtain from it much of the water which they need. The effect is particularly striking along seashores, where the air, although it may not have the humidity necessary for the formation of rain, still contains enough to form dew. It is interesting to note that the quantity of dew which falls upon an area is generally proportioned to the amount of living vegetation which it bears. The surfaces of leaves are very efficient agents of radiation, and the tangle which they make offers an amount of heat-radiating area many times as great as that afforded by a surface of bared earth. Moreover, the ground itself can not well cool down to the point where it will wring the moisture out of the air, while the thin membranes of the plants readily become so cooled. Thus vegetation by its own structure provides itself with means whereby it may be in a measure independent of the accidental rainfall. We should also note the fact that the dewfall is a concomitant of cloudless skies. The quantity which is precipitated in a cloudy night is very small, and this for the reason that when the heavens are covered the heat from the earth can not readily fly off into space. Under these conditions the temperature of the air rarely descends low enough to favour the precipitation of dew. Having noted the process by which in the rain circuit the water leaves the sea and the conditions of distribution when it returns to the earth, we may now trace in more detail the steps in this great round. First, we should take note of the fact that the water after it enters the air may come back to the surface of the earth in either of two ways--directly in the manner of dewfall, or in a longer circuit which leads it through the state of clouds. As yet we are not very well informed as to the law of the cloud-making, but certain features in this picturesque and most important process have been tolerably well ascertained. Rising upward from the sea, the vapour of water commonly remains transparent and invisible until it attains a considerable height above the surface, where the cooling tends to make it assume again the visible state of cloud particles. The formation of these cloud particles is now believed to depend on the fact that the air is full of small dust motes, exceedingly small bits of matter derived from the many actions which tend to bring comminuted solid matter into the air, as, for instance, the combustion of meteoric stones, which are greatly heated by friction in their swift course through the air, the ejections of volcanoes, the smoke of forest and other fires, etc. These tiny bits, floating in the air, because of their solid nature radiate their heat, cool the air which lies against them, and thereby precipitate the water in the manner of dew, exactly as do the leaves and other structures on the surface of the earth. In fact, dew formation is essentially like cloud formation, except that in the one case the water is gathered on fixed bodies, and in the other on floating objects. Each little dust raft with its cargo of condensed water tends, of course, to fall downward toward the earth's surface, and, except for the winds which may blow upward, does so fall, though with exceeding slowness. Its rate of descent may be only a few feet a day. It was falling before it took on the load of water; it will fall a little more rapidly with the added burden, but even in a still air it might be months or years before it would come to the ground. The reason for this slow descent may not at first sight be plain, though a little consideration will make it so. If we take a shot of small size and a feather of the same weight, we readily note that their rate of falling through the air may vary in the proportion of ten to one or more. It is easy to conceive that this difference is due to the very much less friction which the smaller body encounters in its motion by the particles of air. With this point in mind, the student should observe that the surface presented by solid bodies in relation to their solid contents is the greater the smaller the diameter. A rough, though not very satisfactory, instance of this principle may be had by comparing the surface and interior contents of two boxes, one ten feet square and the other one foot square. The larger has six hundred feet of surface to one thousand cubic feet of interior, or about half a square foot of outer surface to the cubic foot of contents; while the smaller box has six feet of surface for the single cubic foot of interior, or about ten times the proportion of exterior to contents. The result is that the smaller particles encounter more friction in moving toward the earth, until, in the case of finely divided matter, such as the particles of carbon in the smoke from an ordinary fire, the rate of down-falling may be so small as to have little effect in the turbulent conditions of atmospheric motion. [Illustration: _Pocket Creek, Cape Ann, Massachusetts. Note the relatively even size of the pebbles, and the splash wave which sets them in motion._] The little drops of water which gather round dust motes, falling but slowly toward the earth, are free to obey the attractions which they exercise upon each other--impulses which are partly gravitative and partly electrical. We have no precise knowledge concerning these movements, further than that they serve to aggregate the myriad little floats into cloud forms, in which the rafts are brought near together, but do not actually touch each other. They are possibly kept apart by electrical repulsion. In this state of association without union the divided water may undergo the curiously modified aggregations which give us the varied forms of clouds. As yet we know little as to the cause of cloud shapes. We remark the fact that in the higher of these agglomerations of condensed vapour, the clouds which float at an elevation of from twenty to thirty thousand feet or more, the masses are generally thin, and arranged more or less in a leaflike form, though even here a tendency to produce spherical clouds is apparent. In this high realm floating water is probably in the frozen state, answering to the form of dew, which we call hoar frost. The lower clouds, gathering in the still air, show very plainly the tendency to agglomerate into spheres, which appears to be characteristic of all vaporous material which is free to move by its own impulses. It is probable that the spherical shape of clouds is more or less due to the same conditions as gathered the stellar matter from the ancient nebular chaos into the celestial spheres. Upon these spherical aggregations of the clouds the winds act in extremely varied ways. The cloud may be rubbed between opposite currents, and so flattened out into a long streamer; it may take the same form by being carried off by a current in the manner of smoke from a fire; the spheres may be kept together, so as to form the patchwork which we call "mackerel" sky; or they may be actually confounded with each other in a vast common cloud-heap. In general, where the process of aggregation of two cloud bodies occurs, changes of temperature are induced in the masses which are mixed together. If the temperature resulting from this association of cloud masses is an average increase, the cloud may become lighter, and in the manner of a balloon move upward. Each of the motes in the cloud with its charge of vapour may be compared with the ballast of the balloon; if they are warmed, they send forth a part of their load of condensed water again to the state of invisible vapour. Rising to a point where it cools, the vapour gathers back on the rafts and tends again to weight the cloud downward. The ballast of an ordinary balloon has to be thrown away from its car; but if some arrangement for condensing the moisture from the air could be contrived, a balloon might be brought into the adjustable state of a cloud, going up or down according as it was heated or cooled. When the formation of the drop of water or snowflake begins, the mass is very small. If in descending it encounters great thickness of cloud, the bit may grow by further condensation until it becomes relatively large. Generally in this way we may account for the diversities in the size of raindrops or snowflakes. It often happens that the particles after taking on the form of snowflakes encounter in their descent air so warm that they melt into raindrops, or, if only partly melted, reach the surface as sleet. Or, starting as raindrops, they may freeze, and in this simple state may reach the earth, or after freezing they may gather other frozen water about them, so that the hailstone has a complicated structure which, from the point of view of classification, is between a raindrop and a snowflake. In the process of condensation--indeed, in the steps which precede the formation of rain and snow--there is often more or less trace of electrical action; in fact, a part of the energy which was involved in the vapourization of water, on its condensation, even on the dust motes appears to be converted into electrical action, which probably operates in part to keep the little aggregates of water asunder. When they coalesce in drops or flakes, this electricity often assumes the form of lightning, which represents the swift passage of the electric store from a region where it is most abundant to one where it is less so. The variations in this process of conveying the electricity are probably great. In general, it probably passes, much as an electric current is conveyed, through a wire from the battery which produces the force. In other cases, where the tension is high, or, in other words, where the discharge has to be hastened, we have the phenomena of lightning in which the current burns its way along its path, as it may traverse a slender wire, vapourizing it as it goes. In general, the lightning flash expends its force on the air conductors, or lines of the moist atmosphere along which it breaks its path, its energy returning into the vapour which it forms or the heat which it produces in the other parts of the air. In some cases, probably not one in the thousand of the flashes, the charge is so heavy that it is not used up in its descent toward the earth, and so electrifies, or, as we say, strikes, some object attached to the earth, through which it passes to the underlying moisture, where it finds a convenient place to take on a quiet form. Almost all these hurried movements of electrical energy which intensely heat and light the air which they traverse fly from one part of a cloud to another, or cross from cloud sphere to cloud sphere; of those which start toward the earth, many are exhausted before they reach its surface, and even those that strike convey but a portion of their original impulse to the ground. The wearing-out effect of lightning in its journey along the air conductors in its flaming passages is well illustrated by what happens when the charge strikes a wire which is not large enough freely to convey it. The wire is heated, generally made white hot, often melted, and perhaps scattered in the form of vapour. In doing this work the electricity may, and often is, utterly dissipated--that is, changed into heat. It has been proposed to take advantage of this principle in protecting buildings from lightning by placing in them many thin wires, along which the current will try to make its way, being exhausted in melting or vaporizing the metal through which it passes. There are certain other forms of lightning, or at least of electrical discharges, which produce light and which may best be described in this connection. It occasionally happens that the earth becomes so charged that the current proceeds from its surface to the clouds. More rarely, and under conditions which we do not understand, the electric energy is gathered into a ball-like form, which may move slowly along the surface until it suddenly explodes. It is a common feature of all these forms of lightning which we have noted that they ordinarily make in their movement considerable noise. This is due to the sudden displacement of the air which they traverse--displacement due to the action of heat in separating the particles. It is in all essential regards similar to the sounds made by projectiles, such as meteors or swift cannon shots, as they fly through the air. It is even more comparable to the sound produced by exploding gunpowder. The first sound effect from the lightning stroke is a single rending note, which endures no longer--indeed, not as long--as the explosion of a cannon. Heard near by, this note is very sharp, reminding one of the sound made by the breaking of glass. The rolling, continuous sound which we commonly hear in thunder is, as in the case of the noise produced by cannon, due to echo from the clouds and the earth. Thunder is ordinarily much more prolonged and impressive in a mountainous country than in a region of plains, because the steeps about the hearer reverberate the original single crash. The distribution of thunderstorms is as yet not well understood, but it appears in many cases that they are attendants on the advancing face of cyclones and hurricanes, the area in front of these great whirlstorms being subjected to the condensation and irregular air movements which lead to the development of much electrical energy. There are, however, certain parts of the earth which are particularly subjected to lightning flashes. They are common in the region near the equator, where the ascending currents bring about heavy rains, which mean a rapid condensation and consequent liberation of electrical energy. They diminish in frequency toward the arctic regions. An observer at the pole would probably fail ever to perceive strong flashes. For the same reason thunderstorms are more frequent in summer, the time when the difference in temperature between the surface and the upper air is greatest, when, therefore, the uprushes of air are likely to be most violent. They appear to be more common in the night than in the daytime, for the reason that condensation is favoured by the cooling which occurs in the dark half of the day. It is rare, indeed, that a thunderstorm occurs near midday, a period when the air is in most cases taking up moisture on account of the swiftly increasing heat. There are other forms of electrical discharges not distinctly connected with the then existing condensation of moisture. What the sailors call St. Elmo's fire--a brush of electric light from the mast tops and other projections of the ship--indicates the passage of electrical energy between the vessel and the atmosphere. Similar lights are said sometimes to be seen rising from the surface of the water. Such phenomena are at present not satisfactorily explained. Perhaps in the same group of actions comes the so-called "Jack-o'-lantern" or "Will-o'-the-wisp" fires flashing from the earth in marshy places, which are often described by the common people, but have never been observed by a naturalist. If this class of illuminations really exists, we have to afford them some other explanation than that they are emanations of self-inflamed phosphoretted hydrogen, a method of accounting for them which illogically finds a place in many treatises on atmospheric phenomena. A gas of any kind would disperse itself in the air; it could not dance about as these lights are said to do, and there is no chemical means known whereby it could be produced in sufficient purity and quantity from the earth to produce the effects which are described.[3] [Footnote 3: The present writer has made an extended and careful study of marsh and swamp phenomena, and is very familiar with the aspect of these fields in the nighttime. He has never been able to see any sign of the Jack-o'-lantern light. Looking fixedly into any darkness, such as is afforded by the depths of a wood, the eye is apt to imagine the appearance of faint lights. Those who have had to do with outpost duty in an army know how the anxious sentry, particularly if he is new to the soldier's trade, will often imagine that he sees lights before him. Sometimes the pickets will be so convinced of the fact that they see lights that they will fire upon the fiction of the imaginations. These facts make it seem probable that the Jack-o'-lantern and his companion, the Will-o'-the-wisp, are stories of the overcredulous.] In the upper air, or perhaps even beyond the limits of the field which deserves the name, in the regions extending from the poles to near the tropics, there occur electric glowings commonly known as the aurora borealis. This phenomenon occurs in both hemispheres. These illuminations, though in some way akin to those of lightning, and though doubtless due to some form of electrical action, are peculiar in that they are often attended by glows as if from clouds, and by pulsations which indicate movements not at electric speed. As yet but little is known as to the precise nature of these curious storms. It has been claimed, however, that they are related to the sun spots; those periods when the solar spots are plenty, at intervals of about eleven years, are the times of auroral discharges. Still further, it seems probable that the magnetic currents of the earth, that circling energy which encompasses the sphere, moving round in a general way parallel to the equator, are intensified during these illuminations of the circumpolar skies. GEOLOGICAL WORK OF WATER. We turn now to the geological work which is performed by falling water. Where the rain or snow returns from the clouds to the sea, the energy of position given to the water by its elevation above the earth through the heat which it acquired from the sun is returned to the air through which it falls or to the ocean surface on which it strikes. In this case the circuit of the rain is short and without geological consequence which it is worth while to consider, except to note that the heat thus returned is likely to be delivered in another realm than that in which the falling water acquired the store, thus in a small way modifying the climate. When, however, the precipitation occurs on the surface of the land, the drops of frozen or fluid water apply a part of their energy in important geological work, the like of which is not done where they return at once to the sea. [Illustration: Fig. 10.--Showing the diverse action of rain on wooded and cleared fields, _a_, wooded area; _b_, tilled ground.] We shall first consider what takes place when the water in the form of drops of rain comes to the surface of the land. Descending as they do with a considerable speed, these raindrops apply a certain amount of energy to the surface on which they fall. Although the beat of a raindrop is proverbially light, the stroke is not ineffective. Observing what happens where the action takes place on the surface of bare rock, we may notice that the grains of sand or small pebbles which generally abound on such surfaces, if they be not too steeply inclined, dance about under the blows which they receive. If we could cover hard plate glass, a much firmer material than ordinary stone, with such bits, we should soon find that its surface would become scratched all over by the friction. Moreover, the raindrops perceptibly urge the small detached bits of stone down the slopes toward the streams. If all the earth's surface were bare rocks, the blow of the raindrops would deserve to be reckoned among the important influences which lead to the wearing of land. As it is, when a country is in a state of Nature, only a small part of its surface is exposed to this kind of wearing. Where there is rain enough to effect any damage, there is sure to be sufficient vegetation to interpose a living and self-renewed covering between the rocks and the rain. Even the lichens which coat what at first sight often seems to be bare rock afford an ample covering for this purpose. It is only where man bares the field by stripping away and overturning this protecting vegetation that the raindrops cut away the earth. The effect of their action can often be noted by observing how on ploughed ground a flat stone or a potsherd comes after a rain to cap a little column. The geologist sometimes finds in soft sandstones that the same action is repeated in a larger way where a thin fragment of hard rock has protected a column many feet in height against the rain work which has shorn down the surrounding rock. When water strikes the moistened surface it at once loses the droplike form which all fluids assume when they fall through the air.[4] [Footnote 4: This principle of the spheroidal form in falling fluids is used in making ordinary bird shot. The melted lead drops through sievelike openings, the resulting spheres of the metal being allowed to fall into water which chills them. Iron shot, used in cutting stone, where they are placed between the saw and the surface of the rock, are also made in the same manner. The descending fluid divides into drops because it is drawn out by the ever-increasing speed of the falling particles, which soon make the stream so thin that it can not hold together.] When the raindrops coalesce on the surface of the earth, the rôle of what we may call land water begins. Thenceforward until the fluid arrives at the surface of the sea it is continually at work in effecting a great range of geological changes, only a few of which can well be traced by the general student. The work of land water is due to three classes of properties--to the energy with which it is endowed by virtue of its height above the sea, a power due to the heat of the sun; to the capacity it has for taking substances into solution; and to its property of giving some part of its own substance to other materials with which it comes in contact. The first of these groups of properties may be called dynamical; the others, chemical. The dynamic value of water when it falls upon the land is the amount of energy it can apply in going down the slope which separates it from the sea. A ton of the fluid, such as may gather in an ordinary rain on a thousand square feet of ground in the highlands of a country--say at an elevation of a thousand feet above the sea--expends before it comes to rest in the great reservoir as much energy as would be required to lift that weight from the ocean's surface to the same height. The ways in which this energy may be expended we shall now proceed in a general way to trace. As soon as the water has been gathered, from its drop to its sheet state--a process which takes place as soon as it falls--the fluid begins its downward journey. On this way it is at once parted into two distinct divisions, the surface water and the ground water: the former courses more or less swiftly, generally at the rate of a mile or more an hour, in the light of day; the latter enters the interstices of the earth, slowly descends therein to a greater or less depth, and finally, journeying perhaps at the rate of a mile a year, rejoins the surface water, escaping through the springs. The proportion of these two classes, the surface and the ground water, varies greatly, and an intermixture of them is continually going on. Thus on the surface of bare rock or frozen earth all the rain may go away without entering the ground. On very sandy fields the heaviest rainfall may be taken up by the porous earth, so that no streams are found. On such surfaces the present writer has observed that a rainfall amounting to six inches in depth in two hours produced no streams whatever. We shall first follow the history of the surface water, afterward considering the work which the underground movements effect. If the student will observe what takes place on a level ploughed field--which, after all, will not be perfectly level, for all fields are more or less undulating--he will note that, though the surface may have been smoothed by a roller until it appears like a floor, the first rain, where the fall takes place rapidly enough to produce surface streams, will create a series of little channels which grow larger as they conjoin, the whole appearing to the eye like a very detailed map, or rather model, of a river system; it is, indeed, such a system in miniature. If he will watch the process by which these streamlet beds are carved, he will obtain a tolerably clear idea as to that most important work which the greater streams do in carving the face of the lands. The water is no sooner gathered into a sheet than, guided by the slightest irregularities which it encounters, it begins to flow. At first the motion is so slow that it does not disturb its bed, but at some points in the bottom of the sheet the movement soon becomes swift enough to drag the grains of sand and clay from their adhesions, bearing them onward. As soon as this beginning of a channel is formed the water moves more swiftly in the clearer way; it therefore cuts more rapidly, deepening and enlarging its channel, and making its motion yet more free. The tiny rills join the greater, all their channels sway to and fro as directed this way and that by chance irregularities, until something like river basins are carved out, those gentle slopes which form broad valleys where the carving has been due to the wanderings of many streams. If the field be large, considerable though temporary brooks may be created, which cut channels perhaps a foot in depth. At the end of this miniature stream system we always find some part of the waste which has been carved out. If the streamlet discharges into a pool, we find the tiny representative of deltas, which form such an important feature on the coast line where large rivers enter seas or lakes. Along the lines of the stream we may observe here and there little benches, which are the equivalent in all save size of the terraces that are generally to be observed along the greater streams. In fact, these accidents of an acre help in a most effective way the student to understand the greater and more complicated processes of continental erosion. A normal river--in fact, all the greater streams of the earth--originates in high country, generally in a region of mountains. Here, because of the elevation of the region, the streams have cut deep gorges or extensive valleys, all of which have slopes leading steeply downward to torrent beds. Down these inclined surfaces the particles worn off from the hard rock by frost and by chemical decay gradually work their way until they attain the bed of the stream. The agents which assist gravitation in bearing this detritus downward are many, but they all work together for the same end. The stroke of the raindrop accomplishes something, though but little; the direct washing action of the brooklets which form during times of heavy rain, but dry out at the close of the storm, do a good deal of the work; thawing and freezing of the water contained in the mass of detritus help the movement, for, although the thrust is in both directions, it is most effective downhill; the wedges of tree roots, which often penetrate between and under the stones, and there expand in their process of growth, likewise assist the downward motion. The result is that on ordinary mountain slopes the layer of fragments constituting the rude soil is often creeping at the rate of from some inches to some feet a year toward the torrent bed. If there be cliffs at the top of the slope, as is often the case, very extensive falls of rock may take place from it, the masses descending with such speed that they directly attain the stream. If the steeps be low and the rock divided into vertical joints, especially where there is a soft layer at the base of the steep, detached masses from the precipice may move slowly and steadfastly down the slope, so little disturbed in their journey that trees growing upon their summits may continue to develop for the thousands of years before the mass enters the stream bed. Although the fall of rocks from precipices does not often take place in a conspicuously large way, all great mountain regions which have long been inhabited by man abound in traditions and histories of such accidents. Within a century or two there have been a dozen or more catastrophes of this nature in the inhabited valleys of the Alps. As these accidents are at once instructive and picturesque, it is well to note certain of them in some detail. At Yvorgne, a little parish on the north shore of the Rhône, just above the lake of Geneva, tradition tells that an ancient village of the name was overwhelmed by the fall of a great cliff. The vast _débris_ forming the steep slope which was thus produced now bears famous vineyards, but the vintners fancy that they from time to time hear deep in the earth the ringing of the bells which belonged to the overwhelmed church. In 1806 the district of Goldau, just north of Lake Lucerne, was buried beneath the ruins of a peak which, resting upon a layer of clay, slipped away like a launching ship on the surface of the soft material. The _débris_ overwhelmed a village and many detached houses, and partly filled a considerable lake. The wind produced by this vast rush of falling rock was so great that people were blown away by it; some, indeed, were killed in this singular manner. The most interesting field of these Swiss mountain falls is a high mountain valley of amphitheatrical form, known as the Diablerets, or the devil's own district. This great circus, which lies at the height of about four thousand feet above the sea, is walled around on its northern side by a precipice, above which rest, or rather once rested, a number of mountain peaks of great bulk. The region has long been valued for the excellent pasturage which the head of the valley affords. Two costly roads, indeed, have been built into it to afford footpaths for the flocks and herds and their keepers in the summer season. Through this human experience with the valley, we have a record of what has gone on in this part of the mountain wilderness. Within the period of history and tradition, three very great mountain falls have occurred in this field, each having made its memory good by widespread disaster which it brought to the people of the _chalets_. The last of these was brought about by the fall of a great peak which spread itself out in a vast field of ruins in the valley below. The belt of destruction was about half a mile wide and three miles long. When the present writer last saw it, a quarter of a century ago, it was still a wilderness of great rocks, but here and there the process of their decay was giving a foothold for herbage, and in a few centuries the field will doubtless be so verdure-clad that its story will not be told on its face. It is likely, however, to be preserved in the memory of the people, and this through a singular and pathetic tradition which has grown up about the place, one which, if not true, comes at least among the legends which we should like to believe. As told the present writer by a native of the district, it happened when, in the nighttime the mountain came down, the herdsmen and their cows gathered in the _chalets_--stout buildings which are prepared to resist avalanches of snow. In one of these, which was protected from crushing by the position of the stones which covered it, a solitary herdsman found himself alive in his unharmed dwelling. With him in the darkness were the cows, a store of food and water, and his provisions for the long summer season. With nothing but hope to animate him, he set to work burrowing upward among the rocks, storing the _débris_ in the room of the _chalet_. He toiled for some months, but finally emerged to the light of day, blanched by his long imprisonment in the darkness, but with the strength to bear him to his home. In place of the expected warm welcome, the unhappy man found himself received as a ghost. He was exorcised by the priest and driven away to the distance. It was only when long afterward his path of escape was discovered that his history became known. Returning to the account of the _débris_ which descends at varied speed into the torrents, we find that when the detritus encounters the action of these vigorous streams it is rapidly ground to pieces while it is pushed down the steep channels to the lower country. Where the stones are of such size that the stream can urge them on, they move rapidly; at least in times when the torrent is raging. They beat over each other and against the firm-set rocks; the more they wear, the smaller they become, and the more readily they are urged forward. Where the masses are too large to be stirred by the violent current, they lie unmoved until the pounding of the rolling stones reduces them to the proportions where they may join the great procession. Ordinarily those who visit mountains behold their torrents only in their shrunken state, when the waters stir no stones, and fail even to bear a charge of mud, all detachable materials having been swept away when the streams course with more vigour. In storm seasons the conditions are quite otherwise; then the swollen torrents, their waters filled with clay and sand, bear with them great quantities of boulders, the collisions of which are audible above the muffled roar of the waters, attesting the very great energy of the action. When the waste on a mountain slope lies at a steep angle, particularly where the accumulation is due to the action of ancient glaciers, it not infrequently happens that when the ground is softened with frost great masses of the material rush down the slope in the manner of landslides. The observer readily notes that in many mountain regions, as, for instance, in the White Mountains of New Hampshire, the steep slopes are often seamed by the paths of these great landslides. Their movement, indeed, is often begun by sliding snow, which gives an impulse to the rocks and earth which it encounters in its descent. At a place known as the Wylie Notch, in the White Mountains, in the early part of this century, a family of that name was buried beneath a mass of glacial waste which had hung on the mountain slope from the ancient days until a heavy rain, following on a period of thaw, impelled the mass down the slope. Although there have been few such catastrophes noted in this country, it is because our mountains have not been much dwelt in. As they become thickly inhabited as the Alps are, men are sure to suffer from these accidents. As the volume of a mountain torrent increases through the junction of many tributaries, the energy of its moving waters becomes sufficient to sweep away the fragments which come to its bed. Before this stage is attained the stream rarely touches the solid under rock of the mountain, the base of the current resting upon the larger loose stones which it was unable to stir. In this pebble-paved section, because the stream could not attack the foundation rock, we find no gorges--in fact, the whole of this upper section of the torrent system is peculiarly conditioned by the fact that the streams are dealing not with bed-rock, but with boulders or smaller loose fragments. If they cut a little channel, the materials from either side slip the faster, and soon repave the bed. But when the streams have by a junction gained strength, and can keep their beds clear, they soon carve down a gorge through which they descend from the upper mountain realm to the larger valleys, where their conjoined waters take on a riverlike aspect. It should be noted here that the cutting power of the water moving in the torrent or in the wave, the capacity it has for abrading rock, resides altogether in the bits of stone or cutting tools with which it is armed. Pure water, because of its fluidity, may move over or against firm-set stones for ages without wearing them; but in proportion as it moves rocky particles of any size, the larger they are, the more effective the work, it wears the rock over which it flows. A capital instance of this may be found where a stream from a hose is used in washing windows. If the water be pure, there is no effect upon the glass; but if it be turbid, containing bits of sand, in a little while the surface will appear cloudy from the multitude of line scratches which the hard bits impelled by the water have inflicted upon it. A somewhat similar case occurs where the wind bears sand against window panes or a bottle which has long lain on the shore. The glass will soon be deeply carved by the action, assuming the appearance which we term "ground." This principle is made use of in the arts. Glass vessels or sheets are prepared for carving by pasting paper cut into figures on their surfaces. The material is then exposed to a jet of air or steam-impelling sand grains; in a short time all the surface which has not been protected by paper has its polish destroyed and is no longer translucent. The passage from the torrent to the river, though not in a geographical way distinct, is indicated to the observant eye by a simple feature--namely, the appearance of alluvial terraces, those more or less level heaps of water-borne _débris_ which accumulate along the banks of rivers, which, indeed, constitute the difference between those streams and torrents. Where the mountain waters move swiftly, they manage to bear onward the waste which they receive. Even where the blocks of stone cling in the bed, it is only a short time before they are again set in motion or ground to pieces. If by chance the detritus accumulates rapidly, the slope is steepened and the work of the torrent made more efficient. As the torrent comes toward the base of the mountains, where it neither finds nor can create steep slopes over which to flow, its speed necessarily diminishes. With each reduction in this feature its carrying power very rapidly diminishes. Thus water flowing at the rate of ten miles an hour can urge stones four times the mass that it can move when its speed is reduced to half that rate. The result is that on the lowlands, with their relatively gentle slopes, the combined torrents, despite the increase in the volume of the stream arising from their confluence, have to lay down a large part of their load of detritus. If we watch where a torrent enters a mountain river, we observe that the main stream in a way sorts over the waste contributed to it, bearing on only those portions which its rate of flow will permit it to carry, leaving the remainder to be built into the bank in the form of a rude terrace. This accumulation may not extend far below the point where the torrent which imported the _débris_ joins the main stream; a little farther down, however, we are sure to find another such junction and a second accumulation of terrace material. As these contributions increase, the terrace accumulations soon become continuous, lying on one side or the other of the river, sometimes bordering both banks of the stream. In general, it can be said that so long as the rate of fall of the torrent exceeds one hundred feet to the mile it does not usually exhibit these shelves of detritus. Below that rate of descent they are apt to be formed. Much, however, depends upon the amount of detritus which the stream bears and the coarseness of it; moreover, where the water goes through a gorge in the manner of a flume with steep rocky sides, it can urge a larger amount before it than when it traverses a wide valley, through which it passes, it may be, in a winding way. At first sight it may seem rather a fine distinction to separate torrents from rivers by the presence or absence of terraces. As we follow down the stream, however, and study its action in relation to these terraces, and the peculiar history of the detritus of which they are composed, we perceive that these latter accumulations are very important features. Beginning at first with small and imperfect alluvial plains, the river, as it descends toward the sea, gaining in store of water and in the amount of _débris_ which comes with that water from the hills, while the rate of fall and consequent speed of the current are diminished, soon comes to a stage where it is engaged in an endless struggle with the terrace materials. In times of flood, the walls of the terraces compel the tide to flow over the tops of these accumulations. Owing to the relative thinness of the water beyond the bed, and to the growth of vegetation there, the current moves more slowly, and therefore lays down a considerable deposit of the silt and sand which it contains. This may result during a single flood in lifting the level of the terrace by some inches in height, still further serving to restrict the channel. Along the banks of the Mississippi and other large rivers the most of this detritus falls near the stream; a little of it penetrates to the farther side of the plains, which often have a width of ten miles or more. The result is that a broad elevation is constructed, a sort of natural mole or levee, in a measure damming the flood waters, which can now only enter the "back swamps" through the channels of the tributary streams. Each of these back swamps normally discharges into the main stream through a little river of its own, along the banks of which the natural levees do not develop. We have now to note a curious swinging movement of rivers which was first well observed by the skilful engineers of British India. This movement can best be illustrated by its effects. If on any river which winds through alluvial plains a jetty is so constructed as to deflect the stream at any point, the course which it follows will be altered during its subsequent flow, it may be, for the distance of hundreds of miles. It will be perceived that in its movements a river normally strikes first against one shore and then against the other. Its water in a general way moves as does a billiard ball when it flies from one cushion to another. It is true that in a torrent we have the same conditions of motion; but there the banks are either of hard rock or, if of detritus, they are continually moving into the stream in the manner before described. In the case of the river, however, its points of collision are often on soft banks, which are readily undermined by the washing action of the stream. In the ordinary course of events, the river beginning, we may imagine, with a straight channel, had its current deflected by some obstacle, it may be even by the slight pressure of a tributary stream, is driven against one bank; thence it rebounds and strikes the other. At each point of impinge it cuts the alluvium away. It can bear on only a small portion of that which it thus obtains; the greater part of the material is deposited on the opposite side of the stream, but a little lower down, where it makes a shallow. On these shallows water-loving plants and even certain trees, such as the willows and poplars, find a foothold. When the stream rises, the sediment settles in this tangle, and soon extends the alluvial plain from the neighbouring bank, or in rarer cases the river comes to flow on either side of an island of its own construction. The natural result of this billiard-ball movement of the waters is that the path of the stream is sinuous. The less its rate of fall and the greater the amount of silt it obtains from its tributaries, the more winding its course becomes. This gain in those parts of the river's curvings where deposition tends to take place may be accelerated by tree-planting. Thus a skilful owner of a tract of land on the south bank of the Ohio River, by assiduously planting willow trees on the front of his property, gained in the course of thirty years more than an acre in the width of his arable land. When told by the present writer that he was robbing his neighbours on the other side of the stream, he claimed that their ignorance of the laws of river motion was sufficient evidence that they did not deserve to own land. In the primitive state of a country the water-loving plants, particularly the trees which flourish in excessively humid conditions, generally make a certain defence against these incursions of the streams. But when a river has gained an opening in the bank it can, during a flood, extend its width often to the distance of hundreds of feet. During the inundations of the Mississippi the river may at times be seen to eat away acres of land in a single day along one of the outcurves of its banks. The undermined forests falling into the flood join the great procession of drift timber, composed of trees which have been similarly uprooted, which occupies the middle part of the stream. This driftwood belt often has a width of three or four hundred feet, the entangled stems and branches making it difficult for a boat to pass from one side of the river to the other. [Illustration: Fig. 11.--Oxbows and cut-off. Showing the changes in the course of a river in its alluvial plain.] When the curves of a river have been developed to a certain point (see Fig. 11), when they have attained what is called the "oxbow" form, it often happens that the stream breaks through the isthmus which connects one of the peninsulas with the mainland. Where, as is not infrequently the case, the bend has a length of ten miles or more, the water just above and below the new-made opening is apt to differ in height by some feet. Plunging down the declivity, the stream, flowing with great velocity, soon enlarges the channel so that its whole tide may take the easier way. When this result is accomplished, the old curve is deserted, sand bars are formed across their mouths, which may gradually grow to broad alluvial plains, so that the long-surviving, crescent-shaped lake, the remnant of the river bed, may be seen far from the present course of the ever-changing stream. Gradually the accumulations of vegetable matter and the silt brought in by floods efface this moat or oxbow cut-off, as it is so commonly termed. As soon as the river breaks through the neck of a peninsula in the manner above described, the current of the stream becomes much swifter for many miles below and above the opening. Slowly, however, the slopes are rearranged throughout its whole course, yet for a time the stream near the seat of the change becomes straighter than before, and this for the reason that its swifter current is better able to dispose of the _débris_ which is supplied to it. The effect of a change in the current produced by such new channels as we have described as forming across the isthmuses of bends is to perturb the course of the stream in all its subsequent downward length. Thus an oxbow cut-off formed near the junction of the Ohio and Mississippi may tend more or less to alter the swings of the Mississippi all the way to the Gulf of Mexico. Although the swayings of the streams to and fro in their alluvial plains will give the reader some idea as to the struggle which the greater rivers have with the _débris_ which is committed to them, the full measure of the work and its consequences can only be appreciated by those who have studied the phenomena on the ground. A river such as the Mississippi is endlessly endeavouring to bear its burden to the sea. If its slope were a uniform inclined plane, the task might readily be accomplished; but in this, as in almost all other large water ways, the slope of the bed is ever diminishing with its onward course. The same water which in the mountain torrent of the Appalachians or Cordilleras rolled along stones several feet in diameter down slopes of a hundred feet or more to the mile can in the lower reaches of the stream move no pebbles which are more than one fourth of an inch in diameter over slopes which descend on the average about half a foot in a mile. Thus at every stage from the torrent to the sea the detritus has from time to time to rest within the alluvial banks, there awaiting the decay which slowly comes, and which may bring it to the state where it may be dissolved in the water, or divided into fragments so small that the stream may bear them on. A computation which the present writer has made shows that, on the average, it requires about forty thousand years for a particle of stone to make its way down the Mississippi to the sea after it has been detached from its original bed. Of course, some bits may make the journey straightforwardly; others may require a far greater time to accomplish the course which the water itself makes at most in a few weeks. This long delay in the journey of the detritus--a delay caused by its frequent rests in the alluvial plain--brings about important consequences which we will now consider. As an alluvial plain is constructed, we generally find at the base pebbly material which fell to the bottom in the current of the main stream as the shores grew outward. Above this level we find the deposits laid down by the flood waters containing no pebbles, and this for the reason that those weightier bits remained in the stream bed when the tide flowed over the plain. As the alluvial deposit is laid down, a good deal of vegetable matter was built into it. Generally this has decayed and disappeared. On the surface of the plain there has always been growing abundant vegetation, the remains of which decayed on the surface in the manner which we may observe at the present day. This decomposing vegetable matter within and upon the porous alluvial material produces large quantities of carbonic acid, a gas which readily enters the rain water, and gives it a peculiar power of breaking up rock matter. Acting on the _débris_, this gas-charged water rapidly brings about a decay of the fragments. Much of the material passes at once into solution in this water, and drains away through the multitudinous springs which border the river. As this matter is completely dissolved, as is sugar in water, it goes straight away to the sea without ever again entering the alluvium. In many, if not most, cases this dissolving work which is going on in alluvial terraces is sufficient to render a large part of the materials which they contain into the state where it disappears in an unseen manner; thus while the annual floods are constantly laying down accumulations on the surface of these plains, the springs are bearing it away from below. In this way, through the decomposition which takes place in them, all those river terraces where much vegetable matter is mingled with the mineral substances, become laboratories in which substances are brought into solution and committed to the seas. We find in the water of the ocean a great array of dissolved mineral substances; it, indeed, seems probable that the sea water contains some share, though usually small, of all the materials which rivers encounter in their journey over and under the lands. As the waters of the sea obtain but little of this dissolved matter along the coast, it seems likely that the greater share of it is brought into the state of solution in the natural laboratories of the alluvial plains. Here and there along the sides of the valleys in which the rivers flow we commonly find the remains of ancient plains lying at more or less considerable heights above the level of the streams. Generally these deposits, which from their form are called terraces, represent the stages of down-wearing by which the stream has carved out its way through the rocks. The greater part of these ancient alluvial plains has been removed through the ceaseless swinging of the stream to and fro in the valley which it has excavated. In all the states of alluvial plains, whether they be the fertile deposits near the level of the streams which built them, or the poorer and ruder surfaced higher terraces, they have a great value to mankind. Men early learned that these lands were of singularly uniform goodness for agricultural use. They are so light that they were easily delved with the ancient pointed sticks or stone hoes, or turned by the olden, wooden plough. They not only give a rich return when first subjugated, but, owing to the depth of the soil and the frequency with which they are visited by fertilizing inundations, they yield rich harvests without fertilizing for thousands of years. It is therefore not surprising that we find the peoples who depended upon tillage for subsistence first developed on the great river plains. There, indeed, were laid the foundations of our higher civilization; there alone could the state which demands of its citizens fixed abodes and continuous labour take rise. In the conditions which these fields of abundance afforded, dense populations were possible, and all the arts which lead toward culture were greatly favoured. Thus it is that the civilization of China, India, Persia, and Egypt, the beginnings of man's higher development, began near the mouths of the great river valleys. These fields were, moreover, most favourably placed for the institution of commerce, in that the arts of navigation, originating in the sheltered reaches of the streams, readily found its way through the estuaries to the open sea. Passing down the reaches of a great river as it approaches the sea, we find that the alluvial plains usually widen and become lower. At length we attain a point where the flood waters cover the surface for so large a part of the year that the ground is swampy and untillable unless it is artificially and at great expense of labour won to agriculture in the manner in which this task has been effected in the lower portion of the Rhine Valley. Still farther toward the sea, the plain gradually dips downward until it passes below the level of the waters. Through this mud-flat section the stream continues to cut channels, but with the ever-progressive slowing of its motion the burden of fine mud which it carries drops to the bottom, and constantly closes the paths through which the water escapes. Every few years they tend to break a new way on one side or the other of their former path. Some of the greatest engineering work done in modern times has been accomplished by the engineers engaged in controlling the exits of large rivers to the sea. The outbreak of the Yellow River in 1887, in which the stream, hindered by its own accumulations, forced a new path across its alluvial plains, destroyed a vast deal of life and property, and made the new exit seventy miles from the path which it abandoned. Below the surface of the open water the alluvial deposits spread out into a broad fan, which slopes gradually to a point where, in the manner of the continental shelf, the bottom descends steeply into deep water. It is the custom of naturalists to divide the lower section of river deposits--that part of the accumulation which is near the sea--from the other alluvial plains, terming the lower portion the delta. The word originally came into use to describe that part of the alluvium accumulated by the Nile near its mouth, which forms a fertile territory shaped somewhat like the fourth letter of the Greek alphabet. Although the definition is good in the Egyptian instance, and has a certain use elsewhere, we best regard all the detritus in a river valley which is in the state of repose along the stream to its utmost branches as forming one great whole. It is, indeed, one of the most united of the large features which the earth exhibits. The student should consider it as a continuous inclined plane of diminishing slope, extending from the base of the torrents to the sea, and of course ramifying into the several branches of the river system. He should further bear in mind the fact that it is a vast laboratory where rock material is brought into the soluble state for delivery to the seas. The diversity in the form of river valleys is exceedingly great. Almost all the variety of the landscape is due to this impress of water action which has operated on the surface in past ages. When first elevated above the sea, the surface of the land is but little varied; at this stage in the development the rivers have but shallow valleys, which generally cut rather straight away over the plain toward the sea. It is when the surface has been uplifted to a considerable height, and especially when, as is usually the case, this uplifting action has been associated with mountain-building, that valleys take on their accented and picturesque form. The reason for this is easily perceived: it lies in the fact that the rocks over which the stream flows are guided in the cutting which they effect by the diversities of hardness in the strata that they encounter. The work which it does is performed by the hard substances that are impelled by the current, principally by the sand and pebbles. These materials, driven along by the stream, become eroding tools of very considerable energy. As will be seen when we shortly come to describe waterfalls, the potholes formed at those points afford excellent evidence as to the capacity of stream-impelled bits of stone to cut away the firmest bed rocks. Naturally the ease with which this carving work is done is proportionate to the energy of the currents, and also to the relative hardness of the moving bits and the rocks over which they are driven. So long as the rocks lie horizontally in their natural construction attitude the course of the stream is not much influenced by the variations in hardness which the bed exhibits. Where the strata are very firm there is likely to be a narrow gorge, the steeps of which rise on either side with but slight alluvial plains; where the beds are soft the valley widens, perhaps again to contract where in the course of its descent it encounters another hard layer. Where, however, the beds have been subjected to mountain-building, and have been thrown into very varied attitudes by folding and faulting, the stream now here and now there encounters beds which either restrain its flow or give it freedom. The stream is then forced to cut its way according to the positions of the various underlying strata. This effect upon its course is not only due to the peculiarities of uplifted rocks, but to manifold accidents of other nature: veins and dikes, which often interlace the beds with harder or softer partitions than the country rock; local hardenings in the materials, due to crystallization and other chemical processes, often create indescribable variations which are more or less completely expressed in the path of the stream. When a land has been newly elevated above the sea there is often--we may say, indeed, generally--a very great difference between the height of its head waters and the ocean level. In this condition of a country the rivers have what we may call a new aspect; their valleys are commonly narrow and rather steep, waterfalls are apt to abound, and the alluvial terraces are relatively small in extent. Stage by stage the torrents cut deeper; the waste which they make embarrasses the course of the lower waters, where no great amount of down-cutting is possible for the reason that the bed of the stream is near sea level. At the same time the alluvial materials, building out to sea, thus diminish the slope of the stream. In the extreme old age of the river system the mountains are eaten down so that the torrent section disappears, and the stream becomes of something like a uniform slope; the higher alluvial plains gradually waste away, until in the end the valley has no salient features. At this stage in the process, or even before it is attained, the valley is likely to be submerged beneath the sea, where it is buried beneath the deposits formed on the floor; or a further uplift of the land may occur with the result that the stream is rejuvenated; or once more endowed with the power to create torrents, build alluvial plains, and do the other interesting work of a normal river. It rarely, if ever, happens that a river valley attains old age before it has sunk beneath the sea or been refreshed by further upliftings. In the unstable conditions of the continents, one or the other of these processes, sometimes in different places both together, is apt to be going on. Thus if we take the case of the Mississippi and its principal tributaries, the Ohio and Missouri, we find that for many geological ages the mountains about their sources have frequently, if not constantly, grown upward, so that their torrent sections, though they have worn down tens of thousands of feet, are still high above the sea level, perhaps on the average as high as they have ever been. At the same time the slight up-and-down swayings of the shore lands, amounting in general to less than five hundred feet, have greatly affected the channels of the main river and its tributaries in their lower parts. Not long ago the Mississippi between Cairo and the Gulf flowed in a rather steep-sided valley probably some hundreds of feet in depth, which had a width of many miles. Then at the close of the last Glacial period the region sank down so that the sea flooded the valley to a point above the present junction of the Ohio River with the main stream. Since then alluvial plains have filled this estuary to even beyond the original mouth. In many other of our Southern rivers, as along the shore from the Mississippi to the Hudson, the streams have not brought in enough detritus to fill their drowned valleys, which have now the name of bays, of which the Delaware and Chesapeake on the Atlantic coast, and Mobile Bay on the Gulf of Mexico, are good examples. The failure of Chesapeake and Delaware Bays to fill with _débris_ in the measure exhibited by the more southern valleys is due to the fact that the streams which flow into them to a great extent drain from a region thickly covered with glacial waste, a mass which holds the flood waters, yielding the supply but slowly to the torrents, which there have but a slight cutting power. In our sketch of river valleys no attention has been given to the phenomena of waterfalls, those accidents of the flow which, as we have noted, are particularly apt to characterize rivers which have not yet cut down to near the sea level. Where the normal uniform descent which is characteristic of a river's bed is interrupted by a sudden steep, the fact always indicates the occurrence of one of a number of geological actions. The commonest cause of waterfalls is due to a sudden change in the character of horizontal or at least nearly level beds over which the stream may flow. Where after coursing for a distance over a hard layer the stream comes to its edge and drops on a soft or easily eroded stratum, it will cut this latter bed away, and create a more or less characteristic waterfall. Tumbling down the face of the hard layer, the stream acquires velocity; the _débris_ which it conveys is hurled against the bottom, and therefore cuts powerfully, while before, being only rubbed over the stone as it moved along, it cut but slightly. Masses of ice have the same effect as stones. Bits dropping from the ledge are often swept round and round by the eddies, so that they excavate an opening which prevents their chance escape. In these confined spaces they work like augers, boring a deep, well-like cavity. As the bits of stone wear out they are replaced by others, which fall in from above. Working in this way, the fragments often develop regular well-like depressions, the cavities of which work back under the cliffs, and by the undermining process deprive the face of the wall of its support, so that it tumbles in ruin to the base, there to supply more material for the potholing action. Waterfalls of the type above described are by far the commonest of those which occur out of the torrent districts of a great river system. That of Niagara is an excellent specimen of the type, which, though rarely manifested in anything like the dignity of the great fall, is plentifully shown throughout the Mississippi Valley and the basin of the Great Lakes. Within a hundred miles of Niagara there are at least a hundred small waterfalls of the same type. Probably three quarters of all the larger accidents of this nature are due to the conditions of a hard bed overlying softer strata. Falls are also produced in very many instances by dikes which cross the stream. So, too, though rarely, only one striking instance being known, an ancient coral reef which has become buried in strata may afford rock of such hardness that when the river comes to cross it it forms a cascade, as at the Falls of the Ohio, at Louisville, Ky. It is a characteristic of all other falls, except those first mentioned, that they rarely plunge with a clean downward leap over the face of a precipice which recedes at its base, but move downward over an irregular sloping surface. In the torrent district of rivers waterfalls are commonly very numerous, and are generally due to the varying hardness in the rocks which the streams encounter. Here, where the cutting action is going on with great rapidity, slight differences in the resistance which the rocks make to the work will lead to great variations in the form of the bed over which they flow, while on the more gently sloping bottoms of the rivers, where the _débris_ moves slowly, such variations would be unimportant in their effect. When the torrents escape into the main river valleys, in regions where the great streams have cut deep gorges, they often descend from a great vertical height, forming wonderful waterfalls, such as those which occur in the famous Lauterbrunnen Valley of Switzerland or in that of the Yosemite in California. This group of cascades is peculiar in that the steep of the fall is made not by the stream itself, but by the action of a greater river or of a glacier which may have some time taken its place. Waterfalls have an economic as well as a picturesque interest in that they afford sources of power which may be a very great advantage to manufacturers. Thus along the Atlantic coast the streams which come from the Appalachian highlands, and which have hardly escaped from their torrent section before they attain the sea, afford numerous cataracts which have been developed so that they afford a vast amount of power. Between the James on the south and the Ste. Croix on the north more than a hundred of these Appalachian rivers have been turned to economic use. The industrial arts of this part of the country depend much upon them for the power which drives their machinery. The whole of the United States, because of the considerable size of its rivers and their relatively rapid fall, is richly endowed with this source of energy, which, originating in the sun's heat and conveyed through the rain, may be made to serve the needs of man. In view of the fact that recent inventions have made it possible to convert this energy of falling water into the form of electricity, which may be conveyed to great distances, it seems likely that our rivers will in the future be a great source of national wealth. We must turn again to river valleys, there to trace certain actions less evident than those already noted, but of great importance in determining these features of the land. First, we have to note that in the valley or region drained by a river there is another degrading or down-wearing action than that which is accomplished by the direct work of the visible stream. All over such a valley the underground waters, soaking through the soil and penetrating through the underlying rock, are constantly removing a portion of the mineral matter which they take into solution and bear away to the sea. In this way, deprived of a part of their substance, the rocks are continually settling down by underwear throughout the whole basin, while they are locally being cut down by the action of the stream. Hence in part it comes about that in a river basin we find two contrasted features--the general and often slight slope of a country toward the main stream and its greater tributaries, and the sharp indentation of the gorge in which the streams flow, these latter caused by the immediate and recent action of the streams. If now the reader will conceive himself standing at any point in a river basin, preferably beyond the realms of the torrents, he may with the guidance of the facts previously noted, with a little use of the imagination, behold the vast perceptive which the history of the river valley may unfold to him. He stands on the surface of the soil, that _débris_ of the rocks which is just entering on its way to the ocean. In the same region ten thousand years ago he would have stood upon a surface from one to ten feet higher than the present soil covering. A million years ago his station would have been perhaps five hundred feet higher than the surface. Ten million years in the past, a period less than the lifetime of certain rivers, such as the French Broad River in North Carolina, the soil was probably five thousand feet or more above its present plane. There are, indeed, cases where river valleys appear to have worked down without interruption from the subsidence of the land beneath the sea to the depth of at least two miles. Looking upward through the space which the rocks once occupied, we can conceive the action of the forces in their harmonious co-operation which have brought the surface slowly downward. We can imagine the ceaseless corrosion due to the ground water, bringing about a constant though slow descent of the whole surface. Again and again the streams, swinging to and fro under the guidance of the underlying rock, or from the obstacles which the _débris_ they carried imposed upon them, have crossed the surface. Now and then perhaps the wearing was intensified by glacial action, for an ice sheet often cuts with a speed many times as great as that which fluid water can accomplish. On the whole, this exercise of the constructive imagination in conceiving the history of a river valley is one of the most enlarging tasks which the geologist can undertake. Where in a river valley there are many lateral streams, and especially where the process of solution carried on by the underground waters is most effective, as compared with erosive work done in the bed of the main river, we commonly find the valley sloping gently toward its centre, the rivers having but slight steeps near their banks. On the other hand, where, as occasionally happens, a considerable stream fed by the rain and snow fall in its torrent section courses for a great distance over high, arid plains, on which the ground water and the tributaries do but little work, the basin may slope with very slight declivity to the river margins, and there descend to great depths, forming very deep gorges, of which the Colorado Cañon is the most perfect type. As instances of these contrasted conditions, we may take, on the one hand, the upper Mississippi, where the grades toward the main stream are gentle and the valley gorge but slightly exhibited; on the other, the above-mentioned Colorado, which bears a great tide of waters drawn from the high and relatively rainy region of the Rocky Mountains across the vast plateau lying in an almost rainless country. In this section nearly all the down-wearing has been brought about in the direct path of the stream, which has worn the elevated plain into a deep gorge during the slow uprising of the table-land to its present height. In this way a defile nearly a mile in depth has been created in a prevailingly rather flat country. This gorge has embranchments where the few great tributaries have done like work, but, on the whole, this river flows in an almost unbroken channel, the excavation of which has been due to its swift, pebble-bearing waters. The tendency of a newly formed river is to cut a more or less distinct cañon. As the basin becomes ancient, this element of the gorge tends to disappear, the reason for this being that, while the river bed is high above the sea, the current is swift and the down-cutting rapid, while the slow subsidence of the country on either side--a process which goes on at a uniform rate--causes the surface of that region to be left behind in the race for the sea level. As the stream bed comes nearer the sea level its rate of descent is diminished, and so the outlying country gradually overtakes it. In regions where the winters are very cold the effect of ice on the development of the stream beds both in the torrent and river sections of the valley is important. This work is accomplished in several diverse ways. In the first place, where the stream is clear and the current does not flow too swiftly, the stones on the bottom radiate their heat through the water, and thus form ice on their surfaces, which may attain considerable thickness. As ice is considerably lighter than water, the effect is often to lift up the stones of the bed if they be not too large; when thus detached from the bottom, they are easily floated down stream until the ice melts away. The ice which forms on the surface of the water likewise imprisons the pebbles along the banks, and during the subsequent thaw may carry them hundreds of miles toward the sea. It seems likely, from certain observations made by the writer, that considerable stones may thus be carried from the Alleghany River to the main Mississippi. Perhaps the most important effect of ice on river channels is accomplished when in a time of flood the ice field which covered the stream, perhaps to the depth of some feet, is broken up into vast floes, which drift downward with the current. When, as on the Ohio, these fields sometimes have the area of several hundred acres, they often collide with the shores, especially where the stream makes a sharp bend. Urged by their momentum, these ice floes pack into the semblance of a dam, which may have a thickness of twenty, thirty, or even fifty feet. Beginning on the shore, where the collision takes place, the dam may swiftly develop clear across the stream, so that in a few minutes the way of the waters is completely blocked. The on-coming ice shoots up upon the accumulation, increases its height, and extends it up stream, so that in an hour the mass completely bars the current. The waters then heap up until they break their way over the obstacle, washing its top away, until the whole is light enough to be forced down the stream, where, by the friction it encounters on the bottom and sides of the channel, it is broken to pieces. It is easy to see that such moving dams of ice may sweep the bed of a river as with a great broom. Sometimes where the gorges do not form a stationary dam large cakes of ice become turned on edge and pack together so that they roll down the stream like great wheels, grinding the bed rock as they go. In high northern countries, as in Siberia, the rivers, even the deepest, often become so far frozen that their channels are entirely obstructed. Where, as in the case of these Siberian rivers, the flow is from south to north, it often happens that the spring thaw sets in before the more northern beds of the main stream are released from their bondage of frost. In this case the inundations have to find new paths on either side of the obstructed way. The result is a type of valleys characterized by very irregular and changeable stream beds, the rivers having no chance to organize themselves into the shapely curves which they ordinarily follow. The supply which finds its way to a river is composed, as has been already incidentally noted, in part of the water which courses underground for a greater or less distance before it emerges to the surface, and in part of that which moves directly over the ground. These two shares of water have somewhat different histories. On the share of these two depends the stability of the flow. Where, as in New England and other glaciated countries, the surface of the earth is covered with a thick layer of sand and gravel, which, except when frozen, readily admits the water; the rainfall is to a very great extent absorbed by the earth, and only yielded slowly to the streams. In these cases floods are rare and of no great destructive power. Again, where also the river basin is covered by a dense mantle of forests, the ground beneath which is coated, as is the case in primeval woods, with a layer of decomposing vegetation a foot or more in depth, this spongy mass retains the water even more effectively than the open-textured glacial deposits above referred to. When the woods, however, are removed from such an area, the rain may descend to the streams almost as speedily as it finds its way to the gutters from the house roofs. It thus comes about that all regions, when reduced to tillage, and where the rainfall is enough to maintain a good agriculture, are, except when they have a coating of glacial waste, exceedingly liable to destructive inundations. Unhappily, the risk of river floods is peculiarly great in all the regions of the United States lying much to the east of the Rocky Mountains, except in the basin of the Great Lakes and in the district of New England, where the prevalence of glacial sands and gravels affords the protection which we have noted. Throughout this region the rainfall is heavy, and the larger part of it is apt to come after the ground has become deeply snow-covered. The result is a succession of devastating floods which already are very damaging to the works of man, and promise to become more destructive as time goes on. More than in any other country, we need the protection which forests can give us against these disastrous outgoings of our streams. LAKES. In considering the journey of water from the hilltops to the sea, we should take some account of those pauses which it makes on its way when for a time it falls into the basin of a lake. These arrests in the downward motion of water, which we term lakes, are exceedingly numerous; their proper discussion would, indeed, require a considerable volume. We shall here note only the more important of their features, those which are of interest to the general student. The first and most noteworthy difference in lakes is that which separates the group of dead seas from the living basins of fresh water. When a stream attains a place where its waters have to expand into the lakelike form, the current moves in a slow manner, and the broad surface exposed to the air permits a large amount of evaporation. If the basin be large in proportion to the amount of the incurrent water, this evaporation may exceed the supply, and produce a sea with no outlet, such as we find in the Dead Sea of Judea, in that at Salt Lake, Utah, and in a host of other less important basins. If the rate of evaporation be yet greater in proportion to the flow, the lake may altogether dry away, and the river be evaporated before it attains the basin where it might accumulate. In that case the river is said to sink, but, in place of sinking into the earth, its waters really rise into the air. Many such sinks occur in the central portion of the Rocky Mountain district. It is important to note that the process of evaporation we are describing takes place in the case of all lakes, though only here and there is the air so dry that the evaporation prevents the basin from overflowing at the lowest point on its rim, forming a river which goes thence to the sea. Even in the case of the Great Lakes of North America a considerable part of the water which flows into them does not go to the St. Lawrence and thence to the sea. As long as the lake finds an outlet to the sea its waters contain but little more dissolved mineral matter than that we find in the rivers. But because all water which has been in contact with the earth has some dissolved mineral substances, while that which goes away by evaporation is pure water, a lake without an outlet gradually becomes so charged with these materials that it can hold no more in solution, but proceeds to lay them down in deposits of that compound substance which from its principal ingredient we name salt. The water of dead seas, because of the additional weight of the substances which it holds, is extraordinarily buoyant. The swimmer notes a difference in this regard in the waters of rivers and fresh-water lakes and those of the sea, due to this same cause. But in those of dead seas, saturated with saline materials, the human body can not sink as it does in the ordinary conditions of immersion. It is easy to understand how the salt deposits which are mined in many parts of the world have generally, if not in all cases, been formed in such dead seas.[5] [Footnote 5: In some relatively rare cases salt deposits are formed in lagoons along the shores of arid lands, where the sea occasionally breaks over the beach into the basin, affording waters which are evaporated, leaving their salt behind them.] It is an interesting fact that almost all the known dead seas have in recent geological times been living lakes--that is, they poured over their brims. In the Cordilleras from the line between Canada and the United States to central Mexico there are several of these basins. All of those which have been studied show by their old shore lines that they were once brimful, and have only shrunk away in modern times. These conditions point to the conclusion that the rainfall in different regions varies greatly in the course of the geologic ages. Further confirmation of this is found in the fact that very great salt deposits exist on the coast of Louisiana and in northern Europe--regions in which the rainfall is now so great in proportion to the evaporation that dead seas are impossible. Turning now to the question of how lake basins are formed, we note a great variety in the conditions which may bring about their construction. The greatest agent, or at least that which operates in the construction of the largest basins, are the irregular movements of the earth, due to the mountain-building forces. Where this work goes on on a large scale, basin-shaped depressions are inevitably formed. If all those which have existed remained, the large part of the lands would be covered by them. In most cases, however, the cutting action of the streams has been sufficient to bring the drainage channels down to the bottom of the trough, while the influx of sediments has served to further the work by filling up the cavities. Thus at the close of the Cretaceous period there was a chain of lakes extending along the eastern base of the Rocky Mountains, constituting fresh-water seas probably as large as the so-called Great Lakes of North America. But the rivers, by cutting down and tilling up, have long since obliterated these water areas. In other cases the tiltings of the continent, which sometimes oppose the flow of the streams, may for a time convert the upper part of a river basin which originally sloped gently toward the sea into a cavity. Several cases of this description occurred in New England in the closing stages of the Glacial period, when the ground rose up to the northward. We have already noted the fact that the basin of a dead sea becomes in course of time the seat of extensive salt deposits. These may, indeed, attain a thickness of many hundred feet. If now in the later history of the country the tract of land with the salt beneath it were traversed by a stream, its underground waters may dissolve out the salt and in a way restore the basin to its original unfilled condition, though in the second state that of a living lake. It seems very probable that a portion at least of the areas of Lakes Ontario, Erie, and Huron may be due to this removal of ancient salt deposits, remains of which lie buried in the earth in the region bordering these basins. By far the commonest cause of lake basins is found in the irregularities of the surface which are produced by the occupation of the country by glaciers. When these great sheets of ice lie over a land, they are in motion down the slopes on which they rest; they wear the bed rocks in a vigorous manner, cutting them down in proportion to their hardness. As these rocks generally vary in the resistance which they oppose to the ice, the result is that when the glacier passes away the surface no longer exhibits the continued down slope which the rivers develop, but is warped in a very complicated way. These depressions afford natural basins in which lakes gather; they may vary in extent from a few square feet to many square miles. When a glacier occupies a country, the melting ice deposits on the surface of the earth a vast quantity of rocky _débris_, which was contained in its mass. This detritus is irregularly accumulated; in part it is disposed in the form of moraines or rude mounds made at the margin of the glacier, in part as an irregular sheet, now thick, now thin, which covers the whole of the field over which the ice lay. The result of this action is the formation of innumerable pools, which continue to exist until the streams have cut channels through which their waters may drain away, or the basins have become filled with detritus imported from the surrounding country or by peat accumulations which the plants form in such places. Doubtless more than nine tenths of all the lake basins, especially those of small size, which exist in the world are due to irregularities of the land surface which are brought about by glacial action. Although the greater part of these small basins have been obliterated since the ice left this country, the number still remaining of sufficient size to be marked on a good map is inconceivably great. In North America alone there are probably over a hundred and fifty thousand of these glacial lakes, although by far the greater part of those which existed when the glacial sheet disappeared have been obliterated. Yet another interesting group of fresh-water lakes, or rather we should call them lakelets from their small size, owes its origin to the curious underground excavations or caverns which are formed in limestone countries. The water enters these caverns through what are termed "sink holes"--basins in the surface which slope gently toward a central opening through which the water flows into the depths below. The cups of the sink holes rarely exceed half a mile in diameter, and are usually much smaller. Their basins have been excavated by the solvent and cutting actions of the rain water which gathers in them to be discharged into the cavern below. It often happens that after a sink hole is formed some slight accident closes the downward-leading shaft, so that the basin holds water; thus in parts of the United States there are thousands of these nearly circular pools, which in certain districts, as in southern Kentucky, serve to vary the landscape in much the same manner as the glacial lakes of more northern countries. Some of the most beautiful lakes in the world, though none more than a few miles in diameter, occupy the craters of extinct volcanoes. When for a time, or permanently, a volcano ceases to do its appointed work of pouring forth steam and molten rock from the depths of the earth, the pit in the centre of the cone gathers the rain water, forming a deep circular lake, which is walled round by the precipitous faces of the crater. If the volcano reawakens, the water which blocks its passage may be blown out in a moment, the discharge spreading in some cases to a great distance from the cone, to be accumulated again when the vent ceases to be open. The most beautiful of these volcanic lakes are to be found in the region to the north and south of Rome. The original seat of the Latin state was on the shores of one of these crater pools, south of the Eternal City. Lago Bolsena, which lies to the northward, and is one of the largest known basins of this nature, having a diameter of about eight miles, is a crater lake. The volcanic cone to which it belongs, though low, is of great size, showing that in its time of activity, which did not endure very long, this crater was the seat of mighty ejections. The noblest specimen of this group of basins is found in Crater Lake, Oregon, now contained in one of the national parks of the United States. Inclosed bodies of water are formed in other ways than those described; the list above given includes all the important classes of action which produce these interesting features. We should now note the fact that, unlike the seas, the lakes are to be regarded as temporary features in the physiography of the land. One and all, they endure for but brief geologic time, for the reason that the streams work to destroy them by filling them with sediment and by carving out channels through which their waters drain away. The nature of this action can well be conceived by considering what will take place in the course of time in the Great Lakes of North America. As Niagara Falls cut back at the average rate of several feet a year, it will be but a brief geologic period before they begin to lower the waters of Lake Erie. It is very probable, indeed, that in twenty thousand years the waters of that basin will be to a great extent drained away. When this occurs, another fall or rapid will be produced in the channel which leads from Lake Huron to Lake Erie. This in turn will go through its process of retreat until the former expanse of waters disappears. The action will then be continued at the outlets of Lakes Michigan and Superior, and in time, but for the interposition of some actions which recreate these basins, their floors will be converted into dry land. It is interesting to note that lakes owe in a manner the preservation of their basins to an action which they bring about on the waters that flow into them. These rivers or torrents commonly convey great quantities of sediment, which serve to rasp their beds and thus to lower their channels. In all but the smaller lakelets these turbid waters lay down all their sediment before they attain the outlet of the basin. Thus they flow away over the rim rock in a perfectly pure state--a state in which, as we have noted before, water has no capacity for abrading firm rock. Thus where the Niagara River passes from Lake Erie its clean water hardly affects the stone over which it flows. It only begins to do cutting work where it plunges down the precipice of the Falls and sets in motion the fragments which are constantly falling from that rocky face. These Falls could not have begun as they did on the margin of Lake Ontario except for the fact that when the Niagara River began to flow, as in relatively modern times, it found an old precipice on the margin of Lake Ontario, formed by the waves of the lake, down which the waters fell, and where they obtained cutting tools with which to undermine the steep which forms the Falls. Many great lakes, particularly those which we have just been considering, have repeatedly changed their outlets, according as the surface of the land on which they lie has swayed up and down in various directions, or as glacial sheets have barred or unbarred the original outlets of the basins. Thus in the Laurentian Lakes above Ontario the geologist finds evidence that the drainage lines have again and again been changed. For a time during the Glacial period, when Lake Ontario and the valley of the St. Lawrence was possessed by the ice, the discharge was southward into the upper Mississippi or the Ohio. At a later stage channels were formed leading from Georgian Bay to the eastern part of Ontario. Yet later, when the last-named lake was bared, an ice dam appears to have remained in the St. Lawrence, which held back the waters to such a height that they discharged through the valley of the Mohawk into the Hudson. Furthermore, at some time before the Glacial period, we do not know just when, there appears to have been an old Niagara River, now filled with drift, which ran from Lake Erie to Ontario, a different channel from that occupied by the present stream. The effects of lakes on the river systems with which they are connected is in many ways most important. Where they are of considerable extent, or where even small they are very numerous, they serve to retain the flood waters, delivering them slowly to the excurrent streams. In rising one foot a lake may store away more water than the river by its consequent rise at the point of outflow will carry away in many months, and this for the simple reason that the lake may be many hundred or even thousand times as wide as the stream. Moreover, as before noted, the sediment gathered by the stream above the level of the lake is deposited in its basin, and does not affect the lower reaches of the river. The result is that great rivers, such as drain from the Laurentian Lakes, flow clear water, are exempt from floods, are essentially without alluvial plains or terraces, and form no delta deposits. In all these features the St. Lawrence River affords a wonderful contrast to the Mississippi. Moreover, owing to the clear waters, though it has flowed for a long time, it has never been able to cut away the slight obstructions which form its rapids, barriers which probably would have been removed if its waters had been charged with sediment. [Illustration: _Muir Glacier, Alaska, showing crevasses and dust layer on surface of ice._] CHAPTER VI. GLACIERS. We have already noted the fact that the water in the clouds is very commonly in the frozen state; a large part of that fluid which is evaporated from the sea attains the solid form before it returns to the earth. Nevertheless, in descending, at least nine tenths of the precipitation returns to the fluid state, and does the kind of work which we have noted in our account of water. Where, however, the water arrives on the earth in the frozen condition, it enters on a rôle totally different from that followed by the fluid material. Beginning its descent to the earth in a snowflake, the little mass falls slowly, so that when it comes against the earth the blow which it strikes is so slight that it does no effective work. In the state of snow, even in the separate flakes, the frozen water contains a relatively large amount of air. It is this air indeed, which, by dividing the ice into many flakes that reflect the light, gives it the white colour. This important point can be demonstrated by breaking transparent ice into small bits, when we perceive that it has the hue of snow. Much the same effect is given where glass is powdered, and for the same reason. As the snowflakes accumulate layer on layer they imbed air between them, so that when the material falls in a feathery shape--say to the depth of a foot--more than nine tenths of the mass is taken up by the air-containing spaces. As these cells are very small, the circulation in them is slight, and so the layer becomes an admirable non-conductor, having this quality for the same reason that feathers have it--i.e., because the cells are small enough to prevent the circulation of the air, so that the heat which passes has to go by conduction, and all gases are very poor conductors. The result is that a snow coating is in effect an admirable blanket. When the sun shines upon it, much of the heat is reflected, and as the temperature does not penetrate it to any depth, only the superficial part is melted. This molten water takes up in the process of melting a great deal of heat, so that when it trickles down into the mass it readily refreezes. On the other hand, the heat going out from the earth, the store accumulated in its superficial parts in the last warm season, together with the small share which flows out from the earth's interior, is held in by this blanket, which it melts but slowly. Thus it comes about that in regions of long-enduring snowfall the ground, though frozen to the depth of a foot or more at the time when the accumulation took place, may be thawed out and so far warmed that the vegetation begins to grow before the protecting envelope of snow has melted away. Certain of the early flowers of high latitudes, indeed, begin to blossom beneath the mantle of finely divided ice. In those parts of the earth which for the most part receive only a temporary coating of snow the effect of this covering is inconsiderable. The snow water is yielded to the earth, from which it has helped to withdraw the frost, so that in the springtime, the growing season of plants, the ground contains an ample store of moisture for their development. Where the snowfall accumulates to a great thickness, especially where it lodges in forests, the influence of the icy covering is somewhat to protract the winter and thus to abbreviate the growing season. Where snow rests upon a steep slope, and gathers to the depth of several feet, it begins to creep slowly down the declivity in a manner which we may often note on house roofs. This motion is favoured by the gradual though incomplete melting of the flakes as the heat penetrates the mass. Making a section through a mass of snow which has accumulated in many successive falls, we note that the top may still have the flaky character, but that as we go down the flakes are replaced by adherent shotlike bodies, which have arisen from the partial melting and gathering to their centres of the original expanded crystalline bits. In this process of change the mass can move particle by particle in the direction in which gravity impels it. The energy of its motion, however, is slight, yet it can urge loose stones and forest waste down hill. Sometimes, as in the cemetery at Augusta, Me., where stone monuments or other structures, such as iron railings, are entangled in the moving mass, it may break them off and convey them a little distance down the slope. So long as the summer sun melts the winter's snow, even if the ground be bare but for a day, the rôle of action accomplished by the snowfall is of little geological consequence. When it happens that a portion of the deposit holds through the summer, the region enters on the glacial state, and its conditions undergo a great revolution, the consequences of which are so momentous that we shall have to trace them in some detail. Fortunately, the considerations which are necessary are not recondite, and all the facts are of an extremely picturesque nature. Taking such a region as New England, where all the earth is life-bearing in the summer season, and where the glacial period of the winter continues but for a short time, we find that here and there on the high mountains the snow endures throughout most of the summer, but that all parts of the surface have a season when life springs into activity. On the top of Mount Washington, in the White Mountains of New Hampshire, in a cleft known as Tuckerman's Ravine, where the deposit accumulates to a great depth, the snow-ice remains until midsummer. It is, indeed, evident that a very slight change in the climatal conditions of this locality would establish a permanent accumulation of frozen water upon the summit of the mountain. If the crest were lifted a thousand feet higher, without any general change in the heat or rainfall of the district, this effect would be produced. If with the same amount of rainfall as now comes to the earth in that region more of it fell as snow, a like condition would be established. Furthermore, with an increase of rainfall to something like double that which now descends the snow bore the same proportion to the precipitation which it does at present, we should almost certainly have the peak above the permanent snow line, that level below which all the winter's fall melts away. These propositions are stated with some care, for the reason that the student should perceive how delicate may be--indeed, commonly is--the balance of forces which make the difference between a seasonal and a perennial snow covering. As soon as the snow outlasts the summer, the region which it occupies is sterilized to life. From the time the snow begins to hold over the warm period until it finally disappears, that field has to be reckoned out of the habitable earth, not only to man, but to the lowliest organisms.[6] [Footnote 6: In certain fields of permanent snow, particularly near their boundaries, some very lowly forms of vegetable life may develop on a frozen surface, drawing their sustenance from the air, and supplied with water by the melting which takes place during the summertime. These forms include the rare phenomenon termed red snow.] If the snow in a glaciated region lay where it fell, the result would be a constant elevation of the deposit year by year in proportion to the annual excess of deposition over the melting or evaporation of the material. But no sooner does the deposit attain any considerable thickness than it begins to move in the directions of least resistance, in accordance with laws which the students of glaciers are just beginning to discern. In small part this motion is accomplished by avalanches or snow slides, phenomena which are in a way important, and therefore merit description. Immediately after a heavy snowfall, in regions where the slopes are steep, it often happens that the deposit which at first clung to the surface on which it lay becomes so heavy that it tends to slide down the slope; a trifling action, the slipping, indeed, of a single flake, may begin the movement, which at first is gradual and only involves a little of the snow. Gathering velocity, and with the materials heaped together from the junction of that already in motion with that about to be moved, the avalanche in sliding a few hundred feet down the slope may become a deep stream of snow-ice, moving with great celerity. At this stage it begins to break off masses of ice from the glaciers over which it may flow, or even to move large stones. Armed with these, it rends the underlying earth. After it has flowed a mile it may have taken up so much earth and material that it appears like a river of mud. Owing to the fact that the energy which bears it downward is through friction converted into heat, a partial melting of the mass may take place, which converts it into what we call slush, or a mixture of snow and water. Finally, the torrent is precipitated into the bottom of a valley, where in time the frozen water melts away, leaving only the stony matter which it bore as a monument to show the termination of its flow. It was the good fortune of the writer to see in the Swiss Oberland one very great avalanche, which came from the high country through a descent of several thousand feet to the surface of the Upper Grindelwald Glacier. The first sign of the action was a vague tremor of the air, like that of a great organ pipe when it begins to vibrate, but before the pulsations come swiftly enough to make an audible note. It was impossible to tell when this tremor came, but the wary guide, noting it before his charge could perceive anything unusual, made haste for the middle of the glacier. The vibration swelled to a roar, but the seat of the sound amid the echoing cliffs was indeterminable. Finally, from a valley high up on the southern face of the glacier, there leaped forth first a great stone, which sprang with successive rebounds to the floor of ice. Then in succession other stones and masses of ice which had outrun the flood came thicker and thicker, until at the end of about thirty seconds the steep front of the avalanche appeared like a swift-moving wall. Attaining the cliffs, it shot forth as a great cataract, which during the continuance of the flow--which lasted for several minutes--heaped a great mound of commingled stones and ice upon the surface of the glacier. The mass thus brought down the steep was estimated at about three thousand cubic yards, of which probably the fiftieth part was rock material. An avalanche of this volume is unusual, and the proportion of stony matter borne down exceptionally great; but by these sudden motions of the frozen water a large part of the snow deposited above the zone of complete melting is taken to the lower valleys, where it may disappear in the summer season, and much of the erosion accomplished in the mountains is brought about by these falls. In all Alpine regions avalanches are among the most dreaded accidents. Their occurrence, however, being dependent upon the shape of the surface, it is generally possible to determine in an accurate way the liability of their happening in any particular field. The Swiss take precaution to protect themselves from their ravages as other folk do to procure immunity from floods. Thus the authorities of many of the mountain hamlets maintain extensive forests on the sides of the villages whence the downfall may be expected, experience having shown that there is no other means so well calculated to break the blow which these great snowfalls can deliver, as thick-set trees which, though they are broken down for some distance, gradually arrest the stream. As long as the region occupied by permanent snow is limited to sharp mountain peaks, relief by the precipitation of large masses to the level below the snow line is easily accomplished, but manifestly this kind of a discharge can only be effective from a very small field. Where the relief is not brought about by these tumbles of snow, another mode of gravitative action accomplishes the result, though in a more roundabout way, through the mechanism of glaciers. We have already noted the fact that the winter's snow upon our hillsides undergoes a movement in the direction of the slope. What we have now to describe in a rather long story concerning glaciers rests upon movements of the same nature, though they are in certain features peculiarly dependent on the continuity of the action from year to year. It is desirable, however, that the student should see that there is at the foundation no more mystery in glacial motion than there is in the gradual descent of the snow after it has lain a week on a hillside. It is only in the scale and continuity of the action that the greatest glacial envelope exceeds those of our temporary winters--in fact, whenever the snow falls the earth it covers enters upon an ice period which differs only in degree from that from which our hemisphere is just escaping. Where the reader is so fortunate as to be able to visit a region of glaciers, he had best begin his study of their majestic phenomena by ascending to those upper realms where the snow accumulates from year to year. He will there find the natural irregularities of the rock surface in a measure evened over by a vast sheet of snow, from which only the summits of the greater mountains rise. He may soon satisfy himself that this sheet is of great depth, for here and there it is intersected by profound crevices. If the visit is made in the season when snow falls, which is commonly during most of the year, he may observe, as before noted in our winter's snow, that the deposit, though at first flaky, attains at a short distance below the surface a somewhat granular character, though the shotlike grains fall apart when disturbed. Yet deeper, ordinarily a few feet below the surface, these granules are more or less cemented together; the mass thus loses the quality of snow, and begins to appear like a whitish ice. Looking down one of the crevices, where the light penetrates to the depth of a hundred feet or more, he may see that the bluish hue somewhat increases with the depth. A trace of this colour is often visible even in the surface snow on the glacier, and sometimes also in our ordinary winter fields. In a hole made with a stick a foot or more in depth a faint cerulean glimmer may generally be discerned; but the increased blueness of the ice as we go down is conspicuous, and readily leads us to the conclusion that the air, to which, as we before noted, the whiteness of the snow is due, is working out of the mass as the process of compaction goes on. In a glacial district this snow mass above the melting line is called the _névé_. Remembering that the excess of snow beyond the melting in a _névé_ district amounts, it may be, to some feet of material each year, we easily come to the conclusion that the mass works down the slope in the manner which it does even where the coating is impermanent. This supposition is easily confirmed: by observing the field we find that the sheet is everywhere drawing away from the cliffs, leaving a deep fissure between the _névé_ and the precipices. This crevice is called by the German-Swiss guides the _Bergschrund_. Passage over it is often one of the most difficult feats to accomplish which the Alpine explorer has to undertake. In fact, the very appearance of the surface, which is that of a river with continuous down slopes, is sufficient evidence that the mass is slowly flowing toward the valleys. Following it down, we almost always come to a place where it passes from the upper valleys to the deeper gorges which pierce the skirts of the mountain. In going over this projection the mass of snow-ice breaks to pieces, forming a crowd of blocks which march down the slope with much more speed than they journeyed when united in the higher-lying fields. In this condition and in this part of the movement the snow-ice forms what are called the _seracs_, or curds, as the word means in the French-Swiss dialect. Slipping and tumbling down the steep slope on which the _seracs_ develop, the ice becomes broken into bits, often of small size. These fragments are quickly reknit into the body of ice, which we shall hereafter term the glacier, and in this process the expulsion of the air goes on more rapidly than before, and the mass assumes a more transparent icelike quality. The action of the ice in the pressures and strains to which it is subjected in joining the main glacier and in the further part of its course demand for their understanding a revision of those notions as to rigidity and plasticity which we derive from our common experience with objects. It is hard to believe that ice can be moulded by pressure into any shape without fracturing, provided the motion is slowly effected, while at the same time it is as brittle as ice to a sudden blow. We see, however, a similar instance of contrasted properties in the confection known as molasses candy, a stick of which may be indefinitely bent if the flexure is slowly made, but will fly to pieces like glass if sharply struck. Ice differs from the sugary substance in many ways; especially we should note that while it may be squeezed into any form, it can not be drawn out, but fractures on the application of a very slight tension. The conditions of its movement we will inquire into further on, when we have seen more of its action. Entering on the lower part of its course, that where it flows into the region below the snow line, the ice stream is now confined between the walls of the valley, a channel which in most cases has been shaped before the ice time, by a mountain torrent, or perhaps by a slower flowing river. In this part of its course the likeness of a glacial stream to one of fluid water is manifest. We see that it twists with the turn of the gorge, widens where the confining walls are far apart, and narrows where the space is constricted. Although the surface is here and there broken by fractures, it is evident that the movement of the frozen current, though slow, is tolerably free. By placing stakes in a row across the axis of a glacier, and observing their movement from day to day, or even from hour to hour if a good theodolite is used for the purpose, we note that the movement of the stream is fastest in the middle parts, as in the case of a river, and that it slows toward either shore, though it often happens, as in a stream of molten water, that the speediest part of the current is near one side. Further observations have indicated that the movement is most rapid on the surface and least at the bottom, in which the stream is also riverlike. It is evident, in a word, that though the ice is not fluid in strict sense, the bits of which it is made up move in substantially the manner of fluids--that is, they freely slip over each other. We will now turn our attention to some important features of a detailed sort which glaciers exhibit. If we visit a glacier during the part of the year when the winter snows are upon it, it may appear to have a very uninterrupted surface. But as the summer heat advances, the mask of the winter coating goes away, and we may then see the structure of the ice. First of all we note in all valley glaciers such as we are observing that the stream is overlaid by a quantity of rocky waste, the greater part of which has come down with the avalanches in the manner before described, though a small part may have been worn from the bed over which the ice flows. In many glaciers, particularly as we approach their termination, this sheet of earth and rock materials often covers the ice so completely that the novice in such regions finds it difficult to believe that the ice is under his feet. If the explorer is minded to take the rough scramble, he can often walk for miles on these masses of stone without seeing, much less setting foot on any frozen water. In some of the Alaskan glaciers this coating may bear a forest growth. In general, this material, which is called moraine, is distributed in bands parallel to the sides of the glaciers, and the strips may amount to a half dozen or more. Those on the sides of the ice have evidently been derived from the precipices which they have passed. Those in the middle have arisen from the union of the moraines formed in two or more tributary valleys. [Illustration: Fig. 12.--Map of glaciers and moraines near Mont Blanc.] Where the avalanches fall most plentifully, the stones lie buried with the snow, and only melt out when the stream attains the region where the annual waste of its surface exceeds the snowfall. In this section we can see how the progressive melting gradually brings the rocky _débris_ into plain view. Here and there we will find a boulder perched on a pedestal of ice, which indicates a recent down-wearing of the field. A frequent sound in these regions arises from the tumble of the stones from their pedestals or the slipping of the masses from the sharp ridge which is formed by the protection given to the ice through the thick coating of detritus on its surface. These movements of the moraines often distribute their waste over the glacier, so that in its lower part we can no longer trace the contributions from the several valleys, the whole area being covered by the _débris_. At the end of the ice stream, where its forward motion is finally overcome by the warmth which it encounters, it leaves in a rude heap, extending often like a wall across the valley, all the coarse fragments which it conveys. This accumulation, composed of all the lateral moraines which have gathered on the ice by the fall of avalanches, is called the terminal moraine. As the ice stream itself shrinks, a portion of the detritus next the boundary wall is apt to be left clinging against those slopes. It is from the presence of these heaps in valleys now abandoned by glaciers that we obtain some information as to the former greater extent of glacial action. The next most noticeable feature is the crevasse. These fractures often exist in very great numbers, and constitute a formidable barrier in the explorer's way. The greater part of these ruptures below the _serac_ zone run from the sides of the stream toward the centre without attaining that region. These are commonly pointed up stream; their formation is due to the fact that, owing to the swifter motion in the central parts of the stream, the ice in that section draws away from the material which is moving more slowly next the shore. As before noted, these ice fractures when drawn out naturally form fissures at right angles to the direction of the strain. In the middle portions of the ice other fissures form, though more rarely, which appear to depend on local strains brought about through the irregularity of the surface over which the ice is flowing. If the observer is fortunate, he may in his journey over the glacier have a chance to see and hear what goes on when crevasses are formed. First he will hear a deep, booming sound beneath his feet, which merges into a more splintering note as the crevice, which begins at the bottom or in the distance, comes upward or toward him. When the sound is over, he may not be able to see a trace of the fracture, which at first is very narrow. But if the break intersect any of the numerous shallow pools which in a warm summer's day are apt to cover a large part of the surface, he may note a line of bubbles rushing up through the water, marking the escape of the air from the glacier, some remnant of that which is imprisoned in the original snow. Even where this indication is wanting, he can sometimes trace the crevice by the hissing sound of the air streams where they issue from the ice. If he will take time to note what goes on, he can usually in an hour or two behold the first invisible crack widen until it may be half an inch across. He may see how the surface water hastens down the opening, a little river system being developed on the surface of the ice as the streams make their way to one or more points of descent. In doing this work they excavate a shaft which often becomes many feet in diameter, down which their waters thunder to the base of the glacier. This well-like opening is called a _moulin_, or mill, a name which, as we shall see, is well deserved from the work which falling waters accomplish. Although the institution of the _moulin_ shaft depends upon the formation of a crevice, it often happens that as the ice moves farther on its journey its walls are again thrust together, soldered in the manner peculiar to ice, so that no trace of the rupture remains except the shaft which it permitted to form. Like everything else in the glacier, the _moulin_ slowly moves down the slope, and remains open as long as it is the seat of descending waters produced by the summer melting. When it ceases to be kept open from the summer, its walls are squeezed together in the fashion that the crevices are closed. Forming here and there, and generally in considerable numbers, the crevices of a glacier entrap a good deal of the morainal _débris_, which falls through them to the bottom of the glacier. Smaller bits are washed into the _moulin_, by the streams arising from the melting ice, which is brought about by the warm sun of the summer, and particularly by the warm rains of that season. On those glaciers where, owing to the irregularity of the bottom over which the ice flows, these fractures are very numerous, it may happen that all the detritus brought upon the surface of the glacier by avalanches finds its way to the floor of the ice. Although it is difficult to learn what is going on at the under surface of the glacier, it is possible directly and indirectly to ascertain much concerning the peculiar and important work which is there done. The intrepid explorer may work his way in through the lateral fissures, and even with care safely descend some of the fissures which penetrate the central parts of a shallow ice stream. There, it may be at the depth of a hundred feet or more, he will find a quantity of stones, some of which may be in size like to a small house held in the body of the ice, but with one side resting upon the bed rock. He may be so fortunate as to see the stone actually in process of cutting a groove in the bed rock as it is urged forward by the motion of the glacier. The cutting is not altogether in the fixed material, for the boulder itself is also worn and scored in the work. Smaller pebbles are caught in the space between the erratic and the motionless rock and ground to bits. If in his explorations the student finds his way to the part of the floor on which the waters of a _moulin_ fall, he may have a chance to observe how the stones set in motion serve to cut the bed rock, forming elongated potholes much as in the case of ordinary waterfalls, or at the base of those shafts which afford the beginnings of limestone caverns. The best way to penetrate beneath the glacier is through the arch of the stream which always flows from the terminal face of the ice river. Even in winter time every large glacier discharges at its end a considerable brook, the waters of which have been melted from the ice in small part by the outflow of the earth's heat; mainly, however, by the warmth produced in the friction of the ice on itself and on its bottom--in other words, by the conversion of that energy of position, of which we have often to speak, into heat. In the summer time this subglacial stream is swollen by the surface waters descending through the crevices and the _moulins_ which come from them, so that the outflow often forms a considerable river, and thus excavates in the ice a large or at least a long cavern, the base of which is the bed rock. In the autumn, when the superficial melting ceases, this gallery can often be penetrated for a considerable distance, and affords an excellent way to the secrets of the under ice. The observer may here see quantities of the rock material held in the grip of the ice, and forced to a rude journey over the bare foundation stones. Now and then he may find the glacial mass in large measure made up of stones, the admixture extending many feet above the bottom of the cavern, perhaps to the very top of the arch. He may perchance find that these stones are crushing each other where they are in contact. The result will be brought about by the difference in the rate of advance of the ice, which moves the faster the higher it is above the surface over which it drags, and thus forces the stones on one level over those below. Where the waters of the subglacial stream have swept the bed rock clean of _débris_ its surface is scored, grooved, and here and there polished in a manner which is accomplished only by ice action, though some likeness to it is afforded where stones have been swept over for ages by blowing sand. Here and there, often in a way which interrupts the cavern journey, the shrunken stream, unable to carry forward the _débris_, deposits the material in the chamber, sometimes filling the arch so completely that the waters are forced to make a detour. This action is particularly interesting, for the reason that in regions whence glaciers have disappeared the deposits formed in the old ice arches often afford singularly perfect moulds of those caverns which were produced by the ancient subglacial streams. These moulds are termed _eskers_. If the observer be attentive, he will note the fact that the waters emerging from beneath the considerable glacier are very much charged with mud. If he will take a glass of the water at the point of escape, he will often find, on permitting it to settle, that the sediment amounts to as much as one twentieth of the volume. While the greater part of this detritus will descend to the bottom of the vessel in the course of a day, a portion of it does not thus fall. He may also note that this mud is not of the yellowish hue which he is accustomed to behold in the materials laid down by ordinary rivers, but has a whitish colour. Further study will reveal the fact that the difference is due to the lack of oxidation in the case of the glacial detritus. River muds forming slowly and during long-continued exposure to the action of the air have their contained iron much oxidized, which gives them a part of their darkened appearance. Moreover, they are somewhat coloured with decayed vegetable matter. The waste from beneath the glacier has been quickly separated from the bed rock, all the faces of the grains are freshly fractured, and there is no admixture of organic matter. The faces of the particles thus reflect light in substantially the same way as powdered glass or pulverized ice, and consequently appear white. A little observation will show the student that this very muddy character of waters emerging from beneath the glacier is essentially peculiar to such streams as we have described. Ascending any of the principal valleys of Switzerland, he may note that some of the streams flow waters which carry little sediment even in times when they are much swollen, while others at all seasons have the whitish colour. A little further exploration, or the use of a good map, will show him that the pellucid streams receive no contributions of glacial water, while those which look as if they were charged with milk come, in part at least, from the ice arches. From some studies which the writer has made in Swiss valleys, it appears that the amount of erosion accomplished on equal areas of similar rock by the descent of the waters in the form of a glacier or in that of ordinary torrents differs greatly. Moving in the form of ice, or in the state of ice-confined streams, the mass of water applies very many times as much of its energy of position to grinding and bearing away the rocks as is accomplished where the water descends in its fluid state. The effect of the intense ice action above noted is rapidly to wear away the rocks of the valley in which the glacier is situated. This work is done not only in a larger measure but in a different way from that accomplished by torrents. In the case of the latter, the stream bed is embarrassed by the rubbish which comes into it; only here and there can it attack the bed rock by forcing the stones over its surface. Only in a few days of heavy rain each year is its work at all effective; the greater part of the energy of position of its waters is expended in the endless twistings and turnings of its stream, which result only in the development of heat which flies away into the atmosphere. In the ice stream, owing to its slow movement and to the detritus which it forces along the bottom, a vastly greater part of the energy which impels it down the slope is applied to rock cutting. None of the boulders, even if they are yards in diameter, obstruct its motion; small and great alike are to it good instruments wherewith to attack the bed rocks. The fragments are never left to waste by atmospheric decay, but are to a very great extent used up in mechanical work, while the most of the detritus which comes to a torrent is left in a coarse state when it is delivered to the stream; the larger part of that which the glacier transports is worn out in its journey. To a great extent it is used up in attacking the bed rock. In most cases the _débris_ in the terminal moraine is evidently but a small part of what entered the ice during its journey from the uplands; the greater part has been worn out in the rude experiences to which it has been subjected. It is evident that even in the regions now most extensively occupied by glaciers the drainage systems have been shaped by the movement of ordinary streams--in other words, ice action is almost everywhere, even in the regions about the poles, an incidental feature in the work of water, coming in only to modify the topography, which is mainly moulded by the action of fluid water. When, owing to climatal changes, a valley such as those of the Alps is occupied by a glacial stream, the new current proceeds at once, according to its evident needs, to modify the shape of its channel. An ordinary torrent, because of the swiftness of its motion, which may, in general, be estimated at from three to five miles an hour, can convey away the precipitation over a very narrow bed. Therefore its channel is usually not a hundredth part as wide as the gorge or valley in which it lies. But when the discharge takes place by a glacier, the speed of which rarely exceeds four or five feet a day, the ice stream because of its slow motion has to fill the trough from side to side, it has to be some thousand times as deep and wide as the torrent. The result is that as soon as the glacial condition arises in a country the ice streams proceed to change the old V-shaped torrent beds into those which have a broad U-like form. The practised eye can in a way judge how long a valley has been subjected to glacial action by the extent to which it has been widened by this process. In the valleys of Switzerland and other mountain districts which have been attentively studied it is evident that glacial action has played a considerable part in determining their forms. But the work has been limited to that part of the basin in which the ice is abundantly provided with cutting tools in the stone which have found their way to the base of the stream. In the region of the _névé_, where the contributions of rocky matter to the surface of the deposit made from the few bare cliffs which rise above the sheet of snow is small, the snow-ice does no cutting of any consequence. Where it passes over the steep at the head of the deep valley into which it drains, and is riven into the _seracs_, such stony matter as it may have gathered is allowed to fall to the bottom, and so comes into a position where it may do effective work. From this _serac_ section downward the now distinct ice river, being in general below the snow line, has everywhere cliffs, on either side from which the contributions of rock material are abundant. Hence this part of the glacier, though it is the wasting portion of its length, does all the cutting work of any consequence which is performed. It is there that the underrunning streams become charged with sediment, which, as we have noted, they bear in surprising quantities, and it is therefore in this section of the valley that the impress of the ice work is the strongest. Its effect is not only to widen the valley and deepen it, but also to advance the deep section farther up the stream and its tributaries. The step in the stream beds which we find at the _seracs_ appears to mark the point in the course of the glacier where, owing to the falling of stones to its base, as well as to its swifter movements and the firmer state of the ice, it does effective wearing. There are many other features connected with glaciers which richly repay the study of those who have a mind to explore in the manner of the physicist interested in ice actions the difficult problems which they afford; but as these matters are not important from the point of view of this work, no mention of them will here be made. We will now turn our attention to that other group of glaciers commonly termed continental, which now exist about either pole, and which at various times in the earth's history have extended far toward the equator, mantling over vast extents of land and shallow sea. The difference between the ice streams of the mountains and those which we term continental depends solely on the areas of the fields and the depth of the accumulation. In an ordinary Alpine region the _névé_ districts, where the snow gathers, are relatively small. Owing to the rather steep slopes, the frozen water is rapidly discharged into the lower valleys, where it melts away. Both in the _névé_ and in the distinct glacier of the lower grounds there are, particularly in the latter, projecting peaks, from which quantities of stone are brought down by avalanches or in ordinary rock falls, so that the ice is abundantly supplied with cutting tools, which work from its surface down to its depths. As the glacial accumulation grows in depth there are fewer peaks emerging from it, and the streams which it feeds rise the higher until they mantle over the divides between the valleys. Thus by imperceptible stages valley glaciers pass to the larger form, usually but incorrectly termed continental. We can, indeed, in going from the mountains in the tropics to the poles, note every step in this transition, until in Greenland we attain the greatest ice mass in the world, unless that about the southern pole be more extensive. In the Greenland glacier the ice sheet covers a vast extent of what is probably a mountain country, which is certainly of this nature in the southern part of the island, where alone we find portions of the earth not completely covered by the deep envelope. Thanks to the labours of certain hardy explorers, among whom Nansen deserves the foremost place, we now know something as to the conditions of this vast ice field, for it has been crossed from shore to shore. The results of these studies are most interesting, for they afford us a clew as to the conditions which prevail over a large part of the earth during the Glacial period from which the planet is just escaping, and in the earlier ages when glaciation was likewise extensive. We shall therefore consider in a somewhat detailed way the features which the Greenland glacier presents. Starting from the eastern shore of that land, if we may thus term a region which presents itself mainly in the form of ice, we find next the shore a coast line not completely covered with ice and snow, but here and there exhibiting peaks which indicate that if the frozen mantle were removed the country would appear deeply intersected with fiords in the manner exhibited in the regions to the south of Greenland or the Scandinavian peninsula. The ice comes down to the sea through the valleys, often facing the ocean for great distances with its frozen cliffs. Entering on this seaward portion of the glacier, the observer finds that for some distance from the coast line the ice is more or less rifted with crevices, the formation of which is doubtless due to irregularities of the rock bottom over which it moves. These ruptures are so frequent that for some miles back it is very difficult to find a safe way. Finally, however, a point is attained where these breaks rather suddenly disappear, and thence inward the ice rises at the rate of upward slope of a few feet to the mile in a broad, nearly smooth incline. In the central portion of the region for a considerable part of the territory the ice has very little slope. Thence it declines toward the other shore, exhibiting the same features as were found on the eastern versant until near the coast, when again the surface is beset with crevices which continue to the margin of the sea. Although the explorations of the central field of Greenland are as yet incomplete, several of these excursions into or across the interior have been made, and the identity of the observations is such that we can safely assume the whole region to be of one type. We can furthermore run no risk in assuming that what we find in Greenland, at least so far as the unbroken nature of the central ice field is concerned, is what must exist in every land where the glacial envelope becomes very deep. In Greenland it seems likely that the depth of the ice is on the average more than half a mile, and in the central part of the realm the sheet may well have a much greater profundity; it may be nearly a mile deep. The most striking feature--that of a vast unbroken expanse, bordered by a region where the ice is ruptured--is traceable wherever very extensive and presumably deep deposits of ice have been examined. As we shall see hereafter, these features teach us much as to the conditions of glacial action--a matter which we shall have to examine after we have completed our general survey as to the changes which occur during glacial periods. In the present state of that wonderful complex of actions which we term climate, glaciers are everywhere, so far as our observations enable us to judge, generally in process of decrease. In Switzerland, although the ancients even in Roman days were in contact with the ice, they were so unobservant that they did not even remark that the ice was in motion. Only during the last two centuries have we any observations of a historic sort which are of value to the geologist. Fortunately, however, the signs written on the rock tell the story, except for its measurement in terms of years, as clearly as any records could give it. From this testimony of the rocks we perceive that in the geological yesterday, though it may have been some tens of thousands of years ago, the Swiss glaciers, vastly thickened, and with their horizontal area immensely expanded, stretched over the Alpine country, so that only here and there did any of the sharper peaks rise above the surface. These vast glaciers, almost continually united on their margins, extended so far that every portion of what is now the Swiss Republic was covered by them. Their front lay on the southern lowlands of Germany, on the Jura district of France; on the south, it stretched across the valley of the Po as far as near Milan. We know this old ice front by the accumulations of rock _débris_ which were brought to it from the interior of the mountain realm. We can recognise the peculiar kinds of stone, and with perfect certainty trace them to the bed rock whence they were riven. Moreover, we can follow back through the same evidence the stages of retreat of the glaciers, until they lost their broad continental character and assumed something like their present valley form. Up the valley of any of the great rivers, as, for instance, that of the Rhône above the lake of Geneva, we note successive terminal moraines which clearly indicate stages in the retreat of the ice when for a time it ceased to go backward, or even made a slight temporary readvance. It is easily seen that on such occasions the stones carried to the ice front would be accumulated in a heap, while during the time when day by day the glacier was retreating the rock waste would be left broadcast over the valley. As we go up from the course of the glacial streams we note that the successive moraines have their materials in a progressively less decayed state. Far away from the heap now forming, and in proportion to the distance, the stones have in a measure rotted, and the heaps which they compose are often covered with soil and occupied by forests. Within a few miles of the ice front the stones still have a fresh aspect. When we arrive within, say, half a mile of the moraine now building, we come to the part of the glacial retreat of which we have some written or traditional account. This is in general to the effect that the wasting of the glaciers is going on in this century as it went on in the past. Occasionally periods of heavy snow would refresh the ice streams, so that for a little time they pushed their fronts farther down the valley. The writer has seen during one of these temporary advances the interesting spectacle of ice destroying and overturning the soil of a small field which had been planted in grain. It should be noted that these temporary advances of the ice are not due to the snowfall of the winter or winters immediately preceding the forward movement. So slow is the journey of the ice from the _névé_ field to the end of a long glacier that it may require centuries for the store accumulated in the uplands to affect the terminal portion of the stream. We know that the bodies of the unhappy men who have been lost in the crevices of the glacier are borne forward at a uniform and tolerably computable rate until they emerge at the front, where the ice melts away. In at least one case the remains have appeared after many years in the _débris_ which is contributed to the moraine. On account of this slow feeding of the glacial stream, we naturally may expect to find, as we do, in fact, that a great snowfall of many years ago, and likewise a period when the winter's contribution has been slight, would influence the position of the terminal point of the ice stream at different times, according to its length. If the length of the flow be five miles, it may require twenty or thirty years for the effect to be evident; while if the stream be ten miles long, the influence may not be noted in less than threescore years. Thus it comes about that at the present time in the same glacial district some streams may be advancing while others are receding, though, on the whole, the ice is generally in process of shrinkage. If the present rate of retreat should be maintained, it seems certain that at the end of three centuries the Swiss glaciers as a whole will not have anything like their present area, and many of the smaller streams will entirely disappear. Following the method of the illustrious Louis Agassiz, who first attentively traced the evidence which shows the geologically recent great extension of glaciers by studying the evidence of the action in fields they no longer occupy, geologists have now inspected a large part of the land areas with a view to finding the proofs of such ice work. So far as these indications are concerned, the indications which they have had to trace are generally of a very unmistakable character. Rarely, indeed, does a skilled student of such phenomena have to search in any region for more than a day before he obtains indubitable evidence which will enable him to determine whether or not the field has recently been occupied by an enduring ice sheet--one which survives the summer season and therefore deserves the name of glacier. The indications which he has to consider consist in the direction and manner in which the surface materials have been carried, the physical conditions of these materials, the shape of the surface of the underlying rock as regards its general contour, and the presence or absence of scratches and groovings on its surface. As these records of ice action are of first importance in dealing with this problem, and as they afford excellent subjects for the study of those who dwell in glaciated regions, we shall note them in some detail. The geologist recognises several ways in which materials may be transported on the surface of the earth. They may be cast forth by volcanoes, making their journey by being shot through the air, or by flowing in lava streams; it is always easy at a glance, save in very rare instances, to determine whether fragments have thus been conveyed. Again, the detritus may be moved by the wind; this action is limited; it only affects dust, sand, and very small pebbles, and is easily discriminated. The carriage may be effected by river or marine currents; here, again, the size of the fragments moved is small, and the order of their arrangement distinctly traceable. The fragments may be conveyed by ice rafts; here, too, the observer can usually limit the probabilities he has to consider by ascertaining, as he can generally do, whether the region which he is observing has been below a sea or lake. In a word, the before-mentioned agents of transportation are of somewhat exceptional influence, and in most cases can, as explanations of rock transportation, be readily excluded. When, therefore, the geologist finds a country abundantly covered with sand, pebbles, and boulders arranged in an irregular way, he has generally only to inquire whether the material has been carried by rivers or by glaciers. This discrimination can be quickly and critically effected. In the first place, he notes that rivers only in their torrent sections can carry large fragments of rock, and that in all cases the fragments move down hill. Further, that where deposits are formed, they have more or less the form of alluvial deposits. If now the observations show that the rock waste occupying the surface of any region has been carried up hill and down, across the valleys, particularly if there are here and there traces of frontal moraines, the geologist is entitled to suppose--he may, indeed, be sure--that the carriage has been effected by a glacial sheet. Important corroborative evidence of ice action is generally to be found by inspecting the bed rock below the detritus, which indicates glacial action. Even if it be somewhat decayed, as is apt to be the case where the ice sheet long since passed away, the bed rock is likely to have a warped surface; it is cast into ridges and furrows of a broad, flowing aspect, such as liquid water never produces, which, indeed, can only be created by an ice sheet moving over the surface, cutting its bed in proportion to the hardness of the material. Furthermore, if the bed rock have a firm texture, and be not too much decayed, we almost always find upon it grooves or scratches, channels carved by the stones embedded in the body of the ice, and drawn by its motion over the fixed material. Thus the proof of glacial extension in the last ice epoch is made so clear that accurate maps can be prepared showing the realm of its action. This task is as yet incomplete, although it is already far advanced. While the study of glaciers began in Europe, inquiries concerning their ancient extension have been carried further and with more accuracy in North America than in any other part of the world. We may therefore well begin our description of the limits of the ice sheets with this continent. Imagining a seafarer to have approached America by the North Atlantic, as did the Scandinavians, and that his voyage came perhaps a hundred thousand years or more before that of Leif Ericsson, he would have found an ice front long before he attained the present shores of the land. This front may have extended from south of Greenland, off the shores of the present Grand Banks of Newfoundland, thence and westward to central or southern New Jersey. This cliff of ice was formed by a sheet which lay on the bottom of the sea. On the New Jersey coast the ice wall left the sea and entered on the body of the continent. We will now suppose that the explorer, animated with the valiant scientific spirit which leads the men of our day to seek the poles, undertook a land journey along the ice front across the continent. From the New Jersey coast the traveller would have passed through central Pennsylvania, where, although there probably detached outlying glaciers lying to the southward as far as central Virginia, the main front extended westward into the Ohio Valley. In southern Ohio a tongue of the ice projected southwardly until it crossed the Ohio River, where Cincinnati now lies, extending a few miles to the southward of the stream. Thence it deflected northwardly, crossing the Mississippi, and again the Missouri, with a tongue or lobe which went far southward in that State. Then again turning to the northwest, it followed in general the northern part of the Missouri basin until it came to within sight of the Rocky Mountains. There the ice front of the main glacier followed the trend of the mountains at some distance from their face for an unknown extent to the northward. In the Cordilleras, as far south as southern Colorado, and probably in the Sierra Nevada to south of San Francisco, the mountain centres developed local glaciers, which in some places were of very great size, perhaps exceeding any of those which now exist in Switzerland. It will thus be seen that nearly one half of the present land area of North America was beneath a glacial covering, though, as before noted, the region about the Gulf of Mexico may have swayed upward when the northern portion of the land was borne down by the vast load of ice which rested upon it. Notwithstanding this possible addition to the land, our imaginary explorer would have found the portion of the continent fit for the occupancy of life not more than half as great as it is at present. In the Eurasian continent there was no such continuous ice sheet as in North America, but the glaciers developed from a number of different centres, each moving out upon the lowlands, or, if its position was southern, being limited to a particular mountain field. One of these centres included Scandinavia, northern Germany, Great Britain about as far south as London, and a large part of Ireland, the ice covering the intermediate seas and extending to the westward, so that the passage of the North Atlantic was greatly restricted between this ice front and that of North America. Another centre, before noted, was formed in the Alps; yet another, of considerable area, in the Pyrenees; other less studied fields existed in the Apennines, in the Caucasus, the Ural, and the other mountains of northern Asia. Curiously enough, however, the great region of plains in Siberia does not appear to have been occupied by a continuous ice sheet, though the similar region in North America was deeply embedded in a glacier. Coincident with this development of ice in the eastern part of the continent, the ice streams of the Himalayan Mountains, some of which are among the greatest of our upland glaciers, appear to have undergone but a moderate extension. Many other of the Eurasian highlands were probably ice-bound during the last Glacial period, but our knowledge concerning these local fields is as yet imperfect. In the southern hemisphere the lands are of less extent and, on the whole, less studied than in the northern realm. Here and there where glaciers exist, as in New Zealand and in the southern part of South America, observant travellers have noticed that these ice fields have recently shrunk away. Whether the time of greatest extension and of retreat coincided with that of the ice sheets in the north is not yet determined; the problem, indeed, is one of some difficulty, and may long remain undecided. It seems, however, probable that the glaciers of the southern hemisphere, like those in the north, are in process of retreat. If this be true, then their time of greatest extension was probably the same as that of the ice sheets about the southern pole. From certain imperfect reports which we have concerning evidences of glaciation in Central America and in the Andean district in the northern part of South America, it seems possible that at one time the upland ice along the Cordilleran chain existed from point to point along that system of elevations, so that the widest interval between the fields of permanent snow with their attendant glaciers did not much exceed a thousand miles. Observing the present gradual retreat of those ice remnants which remain mere shreds and patches of the ancient fields, it seems at first sight likely that the extension and recession of the great glaciers took place with exceeding slowness. Measured in terms of human life, in the manner in which we gauge matters of man's history, this process was doubtless slow. There are reasons, however, to believe that the coming and going were, in a geological sense, swift; they may have, indeed, been for a part of the time of startling rapidity. Going back to the time of geological yesterday, before the ice began its development in the northern hemisphere, all the evidence we can find appears to indicate a temperate climate extending far toward the north pole. The Miocene deposits found within twelve degrees, or a little more than seven hundred miles, of the north pole, and fairly within the realm of lowest temperature which now exists on the earth, show by the plant remains which they contain that the conditions permitted the growth of forests, the plants having a tolerably close resemblance to those which now freely develop in the southern portion of the Mississippi Valley. Among them there are species which had the habit of retaining their broad, rather soft leaves throughout the winter season. The climate appears, in a word, to have been one where the mean annual temperature must have been thirty degrees or more higher than the present average of that realm. Although such conditions near the sea level are not inconsistent with the supposition that glaciers existed in the higher mountains of the north, they clearly deny the possibility of the realm being occupied by continental glaciers. Although the Pliocene deposits formed in high latitudes have to a great extent been swept away by the subsequent glacial wearing, they indicate by their fossils a climatal change in the direction of greater cold. We trace this change, though obscurely, in a progressive manner to a point where the records are interrupted, and the next interpretable indication we have is that the ice sheet had extended to somewhere near the limits which we have noted. We are then driven to seek what we can concerning the sojourn of the ice on the land by the amount of wearing which it has inflicted upon the areas which it occupied. This evidence has a certain, though, as we shall see, a limited value. When the students of glacial action first began the great task of interpreting these records, they were led to suppose that the amount of rock cutting which was done by the ice was very great. Observing what goes on, in the manner we have noted, beneath a valley glacier such as those of Switzerland, they saw that the ice work went on rapidly, and concluded that if the ice remained long at work in a region it must do a vast deal of erosion. They were right in a part of their premises, but, as we shall see, probably in another part wrong. Looking carefully over the field where the ice has operated, we note that, though at first sight the area appears to have lost all trace of its preglacial river topography, this aspect is due mainly to the irregular way in which the glacial waste is laid down. Close study shows us that we may generally trace the old stream valleys down to those which were no larger than brooks. It is true that these channels are generally and in many places almost altogether filled in with rubbish, but a close study of the question has convinced the writer, and this against a previous view, that the amount of erosion in New England and Canada, where the work was probably as great as anywhere, has not on the average exceeded a hundred feet, and probably was much less than that amount. Even in the region north of Lake Ontario, over which the ice was deep and remained for a long time, the amount of erosion is singularly small. Thus north of Kingston the little valleys in the limestone rocks which were cut by the preglacial streams, though somewhat encumbered with drift, remain almost as distinct as they are on similar strata in central Kentucky, well south of the field which the ice occupied. In fact, the ice sheet appears to have done the greatest part of its work and to have affected the surface most in the belt of country a few hundred miles in width around the edges of the sheet. It was to be expected that in a continental glacier, as in those of mountain valleys, the most of the _débris_ should be accumulated about the margin where the materials dropped from the ice. But why the cutting action should be greatest in that marginal field is not at first sight clear. To explain this and other features as best we may, we shall now consider the probable history of the great ice march in advance and retreat, and then take up the conditions which brought about its development and its disappearance. Ice is in many ways the most remarkable substance with which the physicist has to deal, and among its eminent peculiarities is that it expands in freezing, while the rule is that substances contract in passing from the fluid to the solid state. On this account frozen water acts in a unique manner when subjected to pressure. For each additional atmosphere of pressure--a weight amounting to about fifteen pounds to the square inch--the temperature at which the ice will melt is lowered to the amount of sixteen thousandths of a degree centigrade. If we take a piece of ice at the temperature of freezing and put upon it a sufficient weight, we inevitably bring about a small amount of melting. Where we can examine the mass under favourable conditions, we can see the fluid gather along the lines of the crystals or other bits of which the ice is composed. We readily note this action by bringing two pieces of ice together with a slight pressure; when the pressure is removed, they will adhere. The adhesion is brought about not by any stickiness of the materials, for the substance has no such property. It is accomplished by melting along the line of contact, which forms a film of water, that at once refreezes when the pressure is withdrawn. When a firm snowball is made by even pressing snow, innumerable similar adhesions grow up in the manner described. The fact is that, given ice at the temperature at which it ordinarily forms, pressure upon it will necessarily develop melting. The consequences of pressure melting as above described are in glaciers extremely complicated. Because the ice is built into the glacier at a temperature considerably below the freezing point, it requires a great thickness of the mass before the superincumbent weight is sufficient to bring about melting in its lower parts. If we knew the height at which a thermometer would have stood in the surface ice of the ancient glacier which covered the northern part of North America, we could with some accuracy compute how thick it must have been before the effect of pressure alone would have brought about melting; but even then we should have to reckon the temperature derived from the grinding of the ice over the floor and the crushing of rocks there effected, as well as the heat which is constantly though slowly coming forth from the earth's interior. The result is that we can only say that at some depth, probably less than a mile, the slowly accumulating ice would acquire such a temperature that, subjected to the weight above it, the material next the bottom would become molten, or at least converted into a sludgelike state, in which it could not rub against the bottom, or move stones in the manner of ordinary glaciers. As fast as the ice assumed this liquid or softened state, it would be squeezed out toward the region where, because of the thinning of the glacier, it would enter a field where pressure melting did not occur. It would then resume the solid state, and thence journey to the margin of the ice in the ordinary manner. We thus can imagine how such a glacier as occupied the northern part of this continent could have moved from the central parts toward its periphery, as we can not do if we assume that the glacier everywhere lay upon the bed rock. There is no slope from Lake Erie to the Ohio River at Cincinnati. Knowing that the ice moved down this line, there are but two methods of accounting for its motion: either the slope of the upper surface to the northward was so steep that the mass would have been thus urged down, the upper parts dragging the bottom along with them, or the ice sheet for the greater part of its extent rested upon pressure-molten water, or sludge ice, which was easily squeezed out toward the front. The first supposition appears inadmissible, for the reason that the ice would have to be many miles deep at Hudson Bay in order that its upper surface should have slope enough to overcome the rigidity of the material and bring about the movement. We know that any such depth is not supposable. The recent studies in Greenland supply us with strong corroborative evidence for the support of the view which is here urged. The wide central field of that area, where the ice has an exceeding slight declivity, and is unruptured by crevices, can not be explained except on the supposition that it rests on pressure-molten water. The thinner section next the shore, where the glacier is broken up by those irregular movements which its wrestle with the bottom inevitably induces, shows that there it is in contact with the bed rock, for it behaves exactly as do the valley glaciers of like thickness. The view above suggested as to the condition of continental glaciers enables us to explain not only their movements, but the relatively slight amount of wearing which they brought about on the lands they occupied. Beginning to develop in mountain regions, or near the poles on the lowlands, these sheets, as soon as they attained the thickness where the ice at their bottom became molten, would rapidly advance for great distances until they attained districts where the melting exceeded the supply of frozen material. In this excursion only the marginal portion of the glacier would do erosive work. This would evidently be continued for the greatest amount of time near the front or outer rim of the ice field, for there, we may presume, that for the longest time the cutting rim would rest upon the bed rock of the country. As the ice receded, this rim would fall back; thus in the retreat as in the advance the whole of the field would be subjected to a certain amount of erosion. On this supposition we should expect to find that the front of a continental glacier, fed with pressure-molten water from all its interior district, which became converted into ice, would attain much warmer regions than the valley streams, where all the flow took place in the state of ice, and, furthermore, that the speed of the going on the margin would be much more rapid than in the Alpine streams. These suppositions are well borne out by the study of existing continental ice sheets, which move with singular rapidity at their fronts, and by the ancient glaciers, which evidently extended into rather warm fields. Thus, when the ice front lay at the site of Cincinnati, at six hundred feet above the sea, there were no glaciers in the mountains of North Carolina, though those rise more than five thousand feet higher in the air, and are less than two hundred miles farther south. It is therefore evident that the continental glacier at this time pushed southward into a comparatively warm country in a way that no stream moving in the manner of a valley glacier could possibly have done. The continental glaciers manage in many cases to convey detritus from a great distance. Thus, when the ice sheet advanced southwardly from the regions north of the Great Lakes, they conveyed quantities of the _débris_ from that section as far south as the Ohio River. In part this rubbish was dragged forward by the ice as the sheet advanced; in part it was urged onward by the streams of liquid water formed by the ordinary process of ice melting. Such subglacial rivers appear to have been formed along the margins of all the great glaciers. We can sometimes trace their course by the excavation which they have made, but more commonly by the long ridges of stratified sand and gravel which were packed into the caverns excavated by these subglacial rivers, which are known to glacialists as _eskers_, or as serpent kames. In many cases we can trace where these streams flowed up stream in the old river valleys until they discharged over their head waters. Thus in the valley of the Genesee, which now flows from Pennsylvania, where it heads against the tributaries of the Ohio and Susquehanna, to Lake Ontario, there was during the Glacial epoch a considerable river which discharged its waters into those of the Ohio and the Susquehanna over the falls at the head of its course. [Illustration: _Front of Muir Glacier, showing ice entering the sea; also small icebergs._] The effect of widespread glacial action on a country such as North America appears to have been, in the first place, to disturb the attitude of the land by bearing down portions of its surface, a process which led to the uprising of other parts which lay beyond the realm of the ice. Within the field of glaciation, so far as the ice rested bodily on the surface, the rocks were rapidly worn away. A great deal of the _débris_ was ground to fine powder, and went far with the waters of the under-running streams. A large part was entangled in the ice, and moved forward toward the front of the glacier, where it was either dropped at the margin or, during the recession of the glacier, was laid upon the surface as the ice melted away. The result of this erosion and transportation has been to change the conditions of the surface both as regards soil and drainage. As the reader has doubtless perceived, ordinary soil is, outside of the river valleys, derived from the rock beneath where it lies. In glaciated districts the material is commonly brought from a considerable distance, often from miles away. These ice-made soils are rarely very fertile, but they commonly have a great endurance for tillage, and this for the reason that the earth is refreshed by the decay of the pebbles which they contain. Moreover, while the tillable earth of other regions usually has a limited depth, verging downward into the semisoil or subsoil which represent the little changed bed rocks, glacial deposits can generally be ploughed as deeply as may prove desirable. The drainage of a country recently affected by glaciers is always imperfect. Owing to the irregular erosion of the bed rocks, and to the yet more irregular deposition of the detritus, there are very numerous lakes which are only slowly filled up or by erosion provided with drainage channels. Though several thousand years have passed by since the ice disappeared from North America, the greater part of the area of these fresh-water basins remains, the greater number of them, mostly those of small size, have become closed. Where an ice stream descends into the sea or into a large lake, the depth of which is about as great as the ice is thick, the relative lightness of the ice tends to make it float, and it shortly breaks off from the parent mass, forming an iceberg. Where, as is generally the case in those glaciers which enter the ocean, a current sweeps by the place where the berg is formed, it may enter upon a journey which may carry the mass thousands of miles from its origin. The bergs separated from the Greenland glaciers, and from those about the south pole, are often of very great size; sometimes, indeed, they are some thousand feet in thickness, and have a length of several miles. It often happens that these bergs are formed of ice, which contains in its lower part a large amount of rock _débris_. As the submerged portion of the glacier melts in the sea water, these stones are gradually dropped to the bottom, so that the cargo of one berg may be strewed along a line many hundred miles in length. It occasionally happens that the ice mass melts more slowly in those parts which are in the air than in its under-water portions. It thus becomes top-heavy and overturns, in which case such stony matter as remains attains a position where it may be conveyed for a greater distance than if the glacier were not capsized. It is likely, indeed, that now and then fragments of rock from Greenland are dropped on the ocean floor in the part of the Atlantic which is traversed by steamers between our Atlantic ports and Great Britain. Except for the risks which they bring to navigators, icebergs have no considerable importance. It is true they somewhat affect the temperature of sea and air, and they also serve to convey fragments of stone far out to sea in a way that no other agent can effect; but, on the whole, their influence on the conditions of the earth is inconsiderable. Icebergs in certain cases afford interesting indices as to the motion of oceanic currents, which, though moving swiftly at a depth below the surface, do not manifest themselves on the plain of the sea. Thus in the region about Greenland, particularly in Davis Strait, bergs have been seen forcing their way southward at considerable speed through ordinary surface ice, which was either at rest or moving in the opposite direction. The train of these bergs, which moves upward from the south polar continent, west of Patagonia, indicates also in a very emphatic way the existence of a very strong northward-setting current in that part of the ocean. * * * * * We have now to consider the causes which could bring about such great extensions of the ice sheet as occurred in the last Glacial period. Here again we are upon the confines of geological knowledge, and in a field where there are no well-cleared ways for the understanding. In facing this problem, we should first note that those who are of the opinion that a Glacial period means a very cold climate in the regions where the ice attained its extension are probably in error. Natural as it may seem to look for exceeding cold as the cause of glaciation, the facts show us that we can not hold this view. In Siberia and in the parts of North America bordering on the Arctic Sea the average cold is so intense that the ground is permanently frozen--as it is, for instance, in the Klondike district--to the depth of hundreds of feet, only the surface thawing out during the warm summers. All this region is cold enough for glaciers, but there is not sufficient snowfall to maintain them. On the other hand, in Greenland, and in a less though conspicuous degree in Scandinavia, where the waters of the North Atlantic somewhat diminish the rigour of the cold, and at the same time bring about a more abundant snowfall, the two actions being intimately related, we have very extensive glaciers. Such facts, which could be very much extended, make it clear that the climate of glacial periods must have been characterized by a great snowfall, and not by the most intense cold. It is evident that what would be necessary again to envelop the boreal parts of North America with a glacial sheet would not be a considerable decrease of heat, but an increase in the winter's contribution of frozen water. Even if the heat released by this snowfall elevated the average temperature of the winter, as it doubtless would in a considerable measure, it would not melt off the snow. That snowfall tends to warm the air by setting free the heat which was engaged in keeping the water in a state of vapour is familiarly shown by the warming which attends an ordinary snowstorm. Even if the fall begin with a temperature of about 0° Fahr., the air is pretty sure to rise to near the freezing point. It is evident that no great change of temperature is required in order to bring about a very considerable increase in the amount of snowfall. In the ordinary succession of seasons we often note the occurrence of winters during which the precipitation of snow is much above the average, though it can not be explained by a considerable climatal change. We have to account for these departures from the normal weather by supposing that the atmospheric currents bring in more than the usual amount of moisture from the sea during the period when great falls of snow occur. In fact, in explaining variations in the humidity of the land, whether those of a constant nature or those that are to be termed accidental, we have always to look to those features which determine the importation of vapour from the great field of the ocean where it enters the air. We should furthermore note that these peculiarities of climate are dependent upon rather slight geographic accidents. Thus the snowfall of northern Europe, which serves to maintain the glaciation of that region, and, curiously enough, in some measure its general warmth, depends upon the movement of the Gulf Stream from the tropics to high latitudes. If by any geographical change, such as would occur if Central America were lowered so as to make a free passage for its waters to the westward, the glaciers of Greenland and of Scandinavia would disappear, and at the same time the temperature of those would be greatly lowered. Thus the most evident cause of glaciation must be sought in those alterations of the land which affect the movement of the oceanic currents. Applying this principle to the northern hemisphere, we can in a way imagine a change which would probably bring about a return of such an ice period as that from which the boreal realm is now escaping. Let us suppose that the region of not very high land about Bering Strait should sink down so as to afford the Kuro Siwo, or North Pacific equivalent of our Gulf Stream, an opportunity to enter the Arctic Sea with something like the freedom with which the North Atlantic current is allowed to penetrate to high latitudes. It seems likely that this Pacific current, which in volume and warmth is comparable to that of the Atlantic, would so far elevate the temperature of the arctic waters that their wide field would be the seat of a great evaporation. Noting once again the fact that the Greenland glaciers, as well as those of Norway, are supplied from seas warmed by the Gulf Stream, we should expect the result of this change would be to develop similar ice fields on all the lands near that ocean. Applying the data gathered by Dr. Croll for the Gulf Stream, it seems likely that the average annual temperature induced in the Arctic Sea by the free entrance of the Japan current would be between 20° and 30° Fahr. This would convert this wide realm of waters into a field of great evaporation, vastly increasing the annual precipitation. It seems also certain that the greater part of this precipitation would be in the form of snow. It appears to the writer that this cause alone may be sufficient to account for the last Glacial period in the northern hemisphere. As to the probability that the region about Bering Strait may have been lowered in the manner required by this view, it may be said that recent studies on the region about Mount St. Elias show that during or just after the ice epoch the shores in that portion of Alaska were at least four thousand feet lower than at present. As this is but a little way from the land which we should have to suppose to be lowered in order to admit the Japan current, we could fairly conclude that the required change occurred. As for the cause of the land movement, geologists are still in doubt. They know, however, that the attitudes of the land are exceedingly unstable, and that the shores rarely for any considerable time maintain their position. It is probable that these swayings of the earth's surface are due to ever-changing combinations of the weight in different parts of the crust and the strains arising from the contraction of its inner parts. In the larger operations of Nature the effects which we behold, however simple, are rarely the products of a single cause. In fact, there are few actions so limited that they can fairly be referred to one influence. It is therefore proper to state that there are many other actions besides those above noted which probably enter into those complicated equations which determine the climatal conditions of the earth. To have these would carry us into difficult and speculative inquiries. As before remarked, all the regions which have been subjected to glaciation are still each year brought temporarily into the glacial state. This fact serves to show us that the changes necessary to produce great ice sheets are not necessarily of a startling nature, however great the consequences may be. Assuming, then, that relatively slight alterations of climate may cause the ice sheet to come and go, we may say that all the influences which have been suggested by the students of glaciation, and various other slighter causes which can not be here noted, may have co-operated to produce the peculiar result. In this equation geographic change has affected the course of the ocean currents, and has probably been the most influential, or at least the commonest, cause to which we must attribute the extension of ice sheets. Next, alterations of the solar heat may be looked to as a change-bringing action; unfortunately, however, we have no direct evidence that this is an efficient cause. Thirdly, the variations in the eccentricity of the earth's orbit, combined with the precession of the equinoxes and the rotation of the apsides, may be regarded as operative. The last of all, changes in the constitution of the atmosphere, have to be taken into account. To these must be added, as before remarked, many less important actions which influence this marvellously delicate machine, the work of which is expressed in the phenomena assembled under the name of climate. Evidence is slowly accumulating which serves to show that glacial periods of greater or less importance have been of frequent occurrence at all stages in the history of the earth of which we have a distinct record. As these accidents write their history upon the ground alone, and in a way impermanently, it is difficult to trace the ice times of ancient geological periods. The scratches on the bed rocks, and the accumulations of detritus formed as the ice disappeared, have alike been worn away by the agents of decay. Nevertheless, we can trace here and there in the older strata accumulations of pebbly matter often containing large boulders, which clearly were shaped and brought together by glacial action. These are found in some instances far south of the region occupied by the glaciers during the last ice epoch. They occur in rocks of the Cambrian or Silurian age in eastern Tennessee and western North Carolina; they are also found in India beyond the limits to which glaciers have attained in modern times. In closing this inadequate account of glacial action, a story which for its complete telling would require many volumes, it is well for the reader to consider once again how slight are the changes of climate which may alternately withdraw large parts of the land from the uses of life, and again quickly restore the fields to the service of plants and animals. He may well imagine that these changes, by driving living creatures to and fro, profoundly affect the history of their development. This matter will be dealt with in the volume concerning the history of organic beings. When the ice went off from the northern part of this continent, the surface of the country, which had been borne down by the weight of the glacier, still remained depressed to a considerable depth below the level of the sea, the depression varying from somewhere about one hundred feet in southern New England to a thousand feet or more in high latitudes. Over this region, which lay beneath the level of the sea, the glacier, when it became thin enough to float, was doubtless broken up into icebergs, in the manner which we now behold along the coast of Greenland. Where the shore was swept by a strong current, these bergs doubtless drifted away; but along the most of the coast line they appear to have lain thickly grouped next the shores, gradually delivering their loads of stones and finer _débris_ to the bottom. These masses of floating ice in many cases seem to have prevented the sea waves from attaining the shore, and thus hindered the formation of those beaches which in their present elevated condition enable us to interpret the old position of the sea along coast lines which have been recently elevated. Here and there, however, from New Jersey to Greenland, we find bits of these ancient shores which clearly tell the story of that down-sinking of the land beneath the burden of the ice which is such an instructive feature in the history of that period. CHAPTER VII. THE WORK OF UNDERGROUND WATER. We have already noted two means by which water finds its way underground. The simplest and largest method by which this action is effected is by building in the fluid as the grains of the rock are laid down on the floors of seas or lakes. The water thus imprisoned is firmly inclosed in the interstices of the stone, it in time takes up into its mass a certain amount of the mineral materials which are contained in the deep-buried rocks. The other portion of the ground water--that with which we are now to be specially concerned--arises from the rain which descends into the crevices of the earth; it is therefore peculiar to the lands. For convenience we shall term the original embedded fluid _rock water_, and that which originates from the rain _crevice water_, the two forming the mass of the earth water. The crevice water of the earth, although forming at no time more than a very small fraction of the hidden fluid, is an exceedingly potent geological agent, doing work which, though unseen, yet affords the very foundations on which rest the life alike of land and sea. When this water enters the earth, though it is purified of all mineral materials, it has already begun to acquire a share of a gaseous substance, carbonic acid, or, as chemists now term it, carbon dioxide, which enables the fluid to begin its rôle of marvellous activities. In its descent as rain, probably even before it was gathered in drops in the cloud realm, the water absorbs a certain portion of this gas from the atmosphere. Entering the realm of the soil, where the decaying organic matter plentifully gives forth carbon dioxide, a further store of the gas is acquired. At the ordinary pressure of the air, water may take in many times its bulk of the gas. The immediate effect of carbonic acid when it is absorbed by water is greatly to increase the capacity which that fluid has for taking mineral matters into solution. When charged with this gas, in the measure in which it may be in the soil, water is able to dissolve about fifty times as much limestone as it can in its perfectly pure form take up. A familiar instance of this peculiar capacity which the gas gives may often be seen where the water from a soda-water fountain drips upon the marble slab beneath. In a few years this slab will be considerably corroded, though pure water would in the same time have had no effect upon it. The first and by far the most important effect of crevice water is exercised upon the soil, which is at once the product of this action, and the laboratory where the larger part of the work is done. Penetrating between the grains of the detrital covering, held in large quantities in the coating, and continually in slow motion, the gas-charged water takes a host of substances into solution, and brings them into a condition where they may react upon each other in the chemical manner. These materials are constantly being offered to the roots of plants and brought in contact with the underlying rock which has not passed into the state of soil. The changes induced in this stony matter lead to its breaking up, or at least to its softening to the point where the roots can penetrate it and complete its destruction. Thus it comes about that the water which to a great extent divides the rocks into the state of soil, which is continually wearing away the material on the surface, or leaching it out through the springs, is also at work in restoring the layer from beneath. The greater part of the water which enters the soil does not penetrate to any great depth in the underlying rocks, but finds its way to the surface after no long journey in the form of small springs. Generally those superficial springs do not emerge through distinct channels, but move, though slowly, in a massive way down the slopes until they enter a water course. Along the banks of any river, however small, or along the shores of the sea, a pit a few inches deep just above the level of the water will be quickly filled by a flow from this sheet which underlies the earth. At a distance from the stream this sheet spring is in contact with the bed rocks, and may be many feet below the surface, but it comes to the level of the river or the sea near their margins. Here and there the shape of the bed rocks, being like converging house roofs, causes the superficial springs to form small pipelike channels for the escape of their gathered waters, and the flow emerges at a definite point. Almost all these sources of considerable flow are due to the action of the water on the underlying rock, where we shall now follow that portion of the crevice water which penetrates deeply into the earth. Almost all rocks, however firm they may appear to be, are divided by crevices which extend from the soil level it may be to the depths of thousands of feet. These rents are in part due to the strains of mountain-building, which tend to disrupt the firmest stone, leaving open fractures. They are also formed in other ways, as by the imperfectly understood agencies which produce joint planes. It often happens that where rocks are highly tilted water finds its way downward between the layers, which are imperfectly soldered together, or a bed of coarse material, such as sandstone or conglomerate, may afford an easy way by which the water may descend for miles beneath the surface. Passing through rocks which are not readily soluble, the water, already to a great extent supplied with mineral matter by its journey through the soil, may not do much excavating work, and even after a long time may only slightly enlarge the spaces in which it may be stored or the channels by which it discharges to the surface. Hence it comes about that in many countries, even where the waters penetrate deeply, they do not afford large springs. It is otherwise where the crevice waters enter limestones composed of materials which are readily dissolved. In such places we find the rain so readily entering the underlying rock that no part of the fall goes at once to the brooks, but all has a long underground journey. In any limestone district where the beds of the material are thick and tolerably pure--as, for instance, in the cavern district of southern Kentucky--the traveller who enters the region notes at once that the usual small streams which in every region of considerable rainfall he is accustomed to see intersecting the surface of the country are entirely absent. In their place he notes everywhere pitlike depressions of bowl-shaped form, the sink holes to which we have already adverted. Through the openings in the bottom of these the rain waters descend into the depths of the earth. Although the most of these depressions have but small openings in their bottom, now and then one occurs with a vertical shaft sufficiently large to permit the explorer to descend into it, though he needs to be lowered down in the manner of a miner who is entering a shaft. In fact, the journey is nearly always one of some hazard; it should not be undertaken save with many precautions to insure safety. When one is lowered away through an open sink hole, though the descent may at first be somewhat tortuous, the explorer soon finds himself swinging freely in the air, it may be at a point some hundred feet above the base of the bottle-shaped shaft or dome into which he has entered. Commonly the neck of the bottle is formed where the water has worked its way through a rather sandy limestone, a rock which was not readily dissolved by the water. In the pure and therefore easily cut limestone layers the cavity rapidly expands until the light of the lantern may not disclose its walls. Farther down there is apt to be a shelf composed of another impure limestone, which extends off near the middle of the shaft. If the explorer can land upon this shelf, he is sure to find that from this imperfect floor the cavern extends off in one or more horizontal galleries, which he may follow for a great distance until he comes to the point where there is again a well-like opening through the hard layer, with another dome-shaped base beneath. Returning to the main shaft, the explorer may continue his descent until he attains the base of this vertical section of the cave, where he is likely to find himself delivered in a pool of water of no great depth, the bottom of which is occupied by a quantity of small, hard stones of a flinty nature, which have evidently come from the upper parts of the cavern. The close observer will have noted that here and there in the limestone there are flinty bits, such as those which he finds in the pool. From the bottom of the dome a determined inquirer can often make his way along the galleries which lead from that level, though it may be after a journey of miles to the point where he emerges from the cavern on the banks of an open-air river. Although a journey by way of the sink holes through a cavern system is to be commended for the reason that it is the course of the caverning waters, it is, on the whole, best to approach the cave through their exits along the banks of a stream or through the chance openings which are here and there made by the falling in of their roofs. One advantage of this cavity of entrance is that we can thus approach the cavern in times of heavy rain when the processes which lead to their construction are in full activity. Coming in this way to one of the domes formed beneath a sink hole, we may observe in rainy weather that the water falling down the deep shaft strikes the bottom with great force; in many of the Kentucky caves it falls from a greater height than Niagara. At such times the stones in the basin at the bottom of the shaft are vigorously whirled about, and in their motion they cut the rocks in the bottom of the basin--in fact, this cavity is a great pot hole, like those at the base of open-air cascades. It is now easy to interpret the general principles which determine the architecture of the cavern realm. When it first enters the earth all the work which the water does in the initial steps of cavern formation is effected by solution. As the crevice enlarges and deepens, the stream acquires velocity, and begins to use the bits of hard rock in boring. It works downward in this way by the mixed mechanical and chemical action until it encounters a hard layer. Then the water creeps horizontally through the soft stratum, doing most of its work by solution, until it finds a crevice in the floor through which it can excavate farther in the downward direction; so it goes on in the manner of steps until it burrows channels to the open stream. In time the vertical fall under the sink hole will cut through the hard layer, when the water, abandoning the first line of exit, will develop another at a lower level, and so in time it comes about that there may be several stories of the cave, the lowest being the last to be excavated. Of the total work thus done, only a small part is accomplished by the falling of the water, acting through the boring action of its tools, the bits of stone before mentioned; the principal part of the task is done by the solvent action of the carbonated waters on the limestone. In the system of caverns known as the Mammoth Cave, in Kentucky, the writer has estimated that at least nine tenths of the stone was removed in the state of solution. When first excavated, the chambers of a limestone cavern have little beauty to attract the eye. The curves of the walls are sometimes graceful, but the aspect of the chambers, though in a measure grand, is never charming. When, however, the waters have ceased to carve the openings, when they have been drained away by the formation of channels on a lower level, there commonly sets in a process known as stalactitization, which transforms the scene into one of singular beauty. We have already noted the fact that everywhere in ordinary rocks there are crevices through which water, moving under the pressure of the fluid which is above, may find its way slowly downward. In the limestone roofs of caverns, particularly in those of the upper story, this ooze of water passes through myriads of unseen fissures at a rate so slow that it often evaporates in the dry air without dropping to the floor. When it comes out of the rocks the water is charged with various salts of lime; when it evaporates it leaves the material behind on the roof. Where the outflow is so slight that the fluid does not gather into drops, it forms an incrustation of limy matter, which often gathers in beautiful flowerlike forms, or perhaps in the shape of a sheet of alabaster. Where drops are formed, a small, pendent cone grows downward from the ceiling, over which the water flows, and on which it evaporates. This cone grows slowly downward until it may attain the floor of the chamber, which has a height of thirty feet or more. If all the water does not evaporate, that which trickles off the apex of the cone, striking on the floor, is splashed out into a thin sheet, so that it evaporates in a speedy manner, lays down its limestone, and thus builds another and ruder cone, which grows upward toward that which is pendent above it. Finally, they grow together, enlarged by the process which constructed them, until a mighty column may be formed, sculptured as if by the hands of a fantastic architect. [Illustration: Fig. 13.--Stalactites and stalagmites on roof and floor of a cavern. The arrows show the direction of the moving water.] All the while that subterranean streams are cutting the caverns downward the open-air rivers into which they discharge are deepening their beds, and thereby preparing for the construction of yet lower stories of caves. These open-air streams commonly flow in steep-sided, narrow valleys, which themselves were caves until the galleries became so wide that they could no longer support the roof. Thus we often find that for a certain distance the roof over a large stream has fallen in, so that the water flows in the open air. Then it will plunge under an arch and course, it may be, for some miles, before it again arrives at a place where the roof has disappeared, or perhaps attains a field occupied by rocks of another character, in which caverns were not formed. At places these old river caverns are abandoned by the streams, which find other courses. They form natural tunnels, which are not infrequently of considerable length. One such in southwestern Virginia has been made useful for a railway passing from one valley to another, thus sparing the expense of a costly excavation. Where the remnant of the arch is small, it is commonly known as a natural bridge, of which that in Rockbridge County, in Virginia, is a very noble example. Arches of this sort are not uncommon in many cavern countries; five such exist in Carter County, Kentucky, a district in the eastern part of that State which abounds in caverns, though none of them are of conspicuous height or beauty.[7] [Footnote 7: It is reported that one of these natural bridges of Carter County has recently fallen down. This is the natural end of these features. As before remarked, they are but the remnants of much more extensive roofs which the processes of decay have brought to ruin.] At this stage of his studies on cavern work the student will readily conceive that, as the surface of the country overlying the cave is incessantly wearing down, the upper stories of the system are continually disappearing, while new ones are forming at the present drainage level of the country. In fact, the attentive eye can in such a district find here and there evidences of this progressive destruction. Not only do the caves wear out from above, but their roofs are constantly falling to their floors, a process which is greatly aided by the growth of stalactites. Forming in the crevices or joints between the stones, these rock growths sometimes prize off great blocks. In other cases the weight of the pendent stalactite drags the ill-supported masses of the roof to the floor. In this way a gallery originally a hundred feet below the surface may work its way upward to the light of day. The entrance by which the Mammoth Cave is approached appears to have been formed in this manner, and at several points in that system of caverns the effect of this action may be distinctly observed. We must now go a step further on the way of subterranean water, and trace its action in the depths below the plane of ordinary caves, which, as we have noted, do not extend below the level of the main streams of the cavern district. The first group of facts to be attended to is that exhibited by artesian wells. These occur where rocks have been folded down into a basinlike form. It often happens that in such a basin the rocks of which it is composed are some of them porous, and others impervious to water, and that the porous layers outcrop on the high margins of the depression and have water-tight layers over them. These conditions can be well represented by supposing that we have two saucers, one within the other, with an intervening layer of sand which is full of water. If now we bore an opening in the bottom of the uppermost saucer, we readily conceive that the water will flow up through it. In Nature we often find these basins with the equivalent of the sandy layer in the model just described rising hundreds of feet above the valley, so that the artesian well, so named from the village of Artois, near Paris, where the first opening of this nature was made, may yield a stream which will mount upward, especially where piped, to a great height. At many places in the world it is possible by such wells to obtain a large supply of tolerably pure water, but in general it is found to contain too large a supply of dissolved mineral matter or sulphuretted gases to be satisfactory for domestic purposes. It may be well to note the fact that the greater part of the so-called artesian wells, or borings which deliver water to a height above the surface, are not true artesian sources, in that they do not send up the water by the action of gravitation, but under the influence of gaseous pressure. Where, as in the case of upturned porous beds, the crevice water penetrates far below the earth's surface or the open-air streams which drain the water away, the fluid acquires a considerable increase of temperature, on the average about one degree Fahrenheit for each eighty feet of descent. It may, indeed, become so heated that if it were at the earth's surface it would not only burst into steam with a vast explosive energy, but would actually shine in the manner of heated solids. As the temperature of water rises, and as the pressure on it increases, it acquires a solvent power, and takes in rocky matter in a measure unapproached at the earth's surface. At the depth of ten miles water beginning as inert rain would acquire the properties which we are accustomed to associate with strong acids. Passing downward through fissures or porous strata in the manner indicated in the diagram, the water would take up, by virtue of its heat and the gases it contained, a share of many mineral substances which we commonly regard as insoluble. Gold and even platinum--the latter a material which resists all acids at ordinary temperatures--enters into the solution. If now the water thus charged with mineral stores finds in the depths a shorter way to the surface than that which it descended, which may well happen by way of a deep rift in the rocks, it will in its ascent reverse the process which it followed on going down. It will deposit the several minerals in the order of their solubilities--that is, the last to be taken in will be the first to be crystallized on the walls of the fissure through which the upflow is taking place. The result will be the formation of a vein belonging to the variety known as fissure veins. [Illustration: Fig. 14.--Diagram of vein. The different shadings show the variations in the nature of the deposits.] A vein deposit such as we are considering may, though rarely, be composed of a single mineral. Most commonly we find the deposit arranged in a banded form in the manner indicated in the figure (see diagram 14). Sometimes one material will abound in the lower portions of the fissure and another in its higher parts, a feature which is accounted for by the progressive cooling and relinquishment of pressure to which the water is subjected on its way to the surface. With each decrement of those properties some particular substance goes out of the fluid, which may in the end emerge in the form of a warm or hot spring, the water of which contains but little mineral matter. Where, however, the temperature is high, some part of the deposit, even a little gold, may be laid down just about the spring in the deposits known as sinter, which are often formed at such places. In many cases the ore deposits are formed not only in the main channel of the fissure, but in all the crevices on either side of that way. In this manner, much as in the case of the growth of stalactitic matter between the blocks of stone in the roofs of a cavern, large fragments of rock, known as "horses," are often pushed out into the body of the vein. In some instances the growth of the vein appears to enlarge the fissure or place of the deposit as the accumulation goes on, the process being analogous to that by which a growing root widens the crevice into which it has penetrated. In other instances the fissure formed by the force has remained wide open, or at most has been but partly filled by the action of the water. It not infrequently happens that the ascending waters of hot springs entering limestones have excavated extensive caves far below the surface of the earth, these caverns being afterward in part filled by the ores of various metals. We can readily imagine that the water at one temperature would excavate the cavern, and long afterward, when at a lower heat, they might proceed to fill it in. At a yet later stage, when the surface of the country had worn down many thousands of feet below the original level, the mineral stores of the caverns may be brought near the surface of the earth. Some of the most important metalliferous deposits of the Cordilleras are found in this group of hot-water caverns. These caverns are essentially like those produced by cold water, with the exception of the temperature of the fluid which does the work and the opposite direction of the flow. In following crevice water which is free to obey the impulses of gravitation far down into the earth, we enter on a realm where the rock or construction water, that which was built into the stone at the time of its formation, is plentiful. Where these two groups of waters come in contact an admixture occurs, a certain portion of the rock water joining that in the crevices. Near the surface of the ground we commonly find that all the construction water has been washed out by this action. Yet if the rocks be compact, or if they have layers of a soft and clayey nature, we may find the construction water, even in very old deposits, remaining near the surface of the ground. Thus in the ancient Silurian beds of the Ohio Valley a boring carried a hundred feet below the level of the main rivers commonly discovers water which is clearly that laid down in the crevices of the material at the time when the rocks were formed in the sea. In all cases this water contains a certain amount of gases derived from the decomposition of various substances, but principally from the alteration of iron pyrite, which affords sulphuretted hydrogen. Thus the water is forced to the surface with considerable energy, and the well is often named artesian, though it flows by gas pressure on the principle of the soda-water fountain, and not by gravity, as in the case of true artesian wells. The passage between the work done by the deeply penetrating surface water and that due to the fluid intimately blended with the rock built into the mass at the time of its formation is obscure. We are, however, quite sure that at great depths beneath the earth the construction water acts alone not only in making veins, but in bringing about many other momentous changes. At a great depth this water becomes intensely heated, and therefore tends to move in any direction where a chance fissure or other accident may lessen the pressure. Creeping through the rocks, and moving from zones of one temperature to another, these waters bring about in the fine interstices chemical changes which lead to great alterations in the constitution of the rock material. It is probably in part to these slow driftings of rock water that beds originally made up of small, shapeless fragments, such as compose clay slates, sandstones, and limestones, may in time be altered into crystalline rocks, where there is no longer a trace of the original bits, all the matter having been taken to pieces by the process of dissolving, and reformed in the regular crystalline order. In many cases we may note how a crystal after being made has been in part dissolved away and replaced by another mineral. In fact, many of our rocks appear to have been again and again made over by the slow-drifting waters, each particular state in their construction being due to some peculiarity of temperature or of mineral contents which the fluid held. These metamorphic phenomena, though important, are obscure, and their elucidation demands some knowledge of petrographic science, that branch of geology which considers the principles of rock formation. They will therefore not be further considered in this work. VOLCANOES. Of old it was believed that volcanoes represented the outpouring of fluid rock which came forth from the central realm of the earth, a region which was supposed still to retain the liquid state through which the whole mass of our earth has doubtless passed. Recent studies, however, have brought about a change in the views of geologists which is represented by the fact that we shall treat volcanic phenomena in connection with the history of rock water. In endeavouring to understand the phenomena of volcanoes it is very desirable that the student should understand what goes on in a normal eruption. The writer may, therefore, be warranted in describing some observations which he had an opportunity to make at an eruption of Vesuvius in 1883, when it was possible to behold far more than can ordinarily be discerned in such outbreaks--in fact, the opportunity of a like nature has probably not been enjoyed by any other person interested in volcanic action. In the winter of 1882-'83 Vesuvius was subjected to a succession of slight outbreaks. At the time of the observations about to be noted the crater had been reduced to a cup about three hundred feet in diameter and about a hundred feet deep. The vertical shaft at the bottom, through which the outbursts were taking place, was about a hundred feet across. Taking advantage of a heavy gale from the northwest, it was practicable, notwithstanding the explosions, to climb to the edge of the crater wall. Looking down into the throat of the volcano, although the pit was full of whirling vapours and the heat was so great that the protection of a mask was necessary, it was possible to see something of what was going on at the moment of an explosion. The pipe of the volcano was full of white-hot lava. Even in a day of sunshine, which was only partly obscured by the vapours which hung about the opening, the heat of the lava made it very brilliant. This mass of fluid rock was in continuous motion, swaying violently up and down the tube. From four to six times a minute, at the moment of its upswaying, it would burst as by the explosion of a gigantic bubble. The upper portion of the mass was blown upward in fragments, the discharge being like that of shot from a fowling piece; the fragments, varying in size from small, shotlike bits to masses larger than a man's head, were shot up sometimes to the height of fifteen hundred feet above the point of ejection. The wind, blowing at the rate of about forty miles an hour, drove the falling bits of rock to the leeward, so that there was no considerable danger to be apprehended from them. Some seconds after the explosion they could be heard rattling down on the farther slope of the cone. Observations on the interval between the discharge and the fall of the fragments made it easy to compute the height to which they were thrown. At the moment when the lava in the pipe opened for the passage of the vapour which created the explosion the movement, though performed in a fraction of a second, was clearly visible. At first the vapour was colourless; a few score feet up it began to assume a faint, bluish hue; yet higher, when it was more expanded, the tint changed to that of steam, which soon became of the ordinary aspect, and gathered in swift-revolving clouds. The watery nature of the vapour was perfectly evident by its odour. Though commingled with sulphurous-acid gas, it still had the characteristic smell of steam. For a half hour it was possible to watch the successive explosions, and even to make rough sketches of the scene. Occasionally the explosions would come in quick succession, so that the lava was blown out of the tube; again, the pool would merely sway up and down in a manner which could be explained only by supposing that great bubbles of vapour were working their way upward toward the point where they could burst. Each of these bubbles probably filled a large part of the diameter of the pipe. In general, the phenomena recalled the escape of the jet from a geyser, or, to take a familiar instance, that of steam from the pipe of a high-pressure engine. When the heat is great, steam may often be seen at the mouth of the pipe with the same transparent appearance which was observed in the throat of the crater. In the cold air of the mountain the vapour was rapidly condensed, giving a rainbow hue in the clouds when they were viewed at the right angle. The observations were interrupted by the fact that the wind so far died away that large balls of the ejected lava began to fall on the windward side of the cone. These fragments, though cooled and blackened on their outside by their considerable journey up and down through the air, were still so soft that they splashed when they struck the surface of cinders. Watching the cone from a distance, one could note that from time to time the explosions, increasing in frequency, finally attained a point where the action appeared to be continuous. The transition was comparable to that which we may observe in a locomotive which, when it first gets under way, gives forth occasional jets of steam, but, slowly gaining speed, finally pours forth what to eye and ear alike seem to be a continuous outrush. All the evidence that we have concerning volcanic outbreaks corroborates that just cited, and is to the effect that the essence of the action consists in the outbreak of water vapour at a high temperature, and therefore endowed with very great expansive force. Along with this steam there are many other gases, which always appear to be but a very small part of the whole escape of a vaporous nature--in fact, the volcanic steam, so far as its chemical composition has been ascertained, has the composition which we should expect to find in rock water which had been forced out from the rock by the tensions that high temperature creates. Because of its conspicuous nature, the lava which flows from most volcanoes, or is blown out from them in the form of finely divided ash, is commonly regarded as the primary feature in a volcanic outbreak. Such is not really the case. Volcanic explosions may occur with very little output of fluid rock, and that which comes forth may consist altogether of the finely divided bits of rock to which we give the name of ash. In fact, in all very powerful explosions we may expect to find no lava flow, but great quantities of this finely divided rock, which when it started from the depths of the earth was in a fluid state, but was blown to pieces by the contained vapour as it approached the surface. If the student is so fortunate as to behold a flood of lava coming forth from the flanks of a volcano, he will observe that even at the very points of issue, where the material is white-hot and appears to be as fluid as water, the whole surface gives forth steam. On a still day, viewed from a distance, the path of a lava flow is marked by a dense cloud of this vapour which comes forth from it. Even after the lava has cooled so that it is safe to walk upon it, every crevice continues to pour forth steam. Years after the flowing has ceased, and when the rock surface has become cool enough for the growth of certain plants upon it, these crevices still yield steam. It is evident, in a word, that a considerable part of a lava mass, even after it escapes from the volcanic pipes, is water which is intimately commingled with the rock, probably lying between the very finest grains of the heated substance. Yet this lava which has come forth from the volcano has only a portion of the water which it originally contained; a large, perhaps the greater part, has gone forth in the explosive way through the crater. It is reasonably believed that the fluidity of lava is in considerable measure due to the water which it contains, and which serves to give the mass the consistence of paste, the partial fluidity of flour and rock grains being alike brought about in the same manner. So much of the phenomena of volcanoes as has been above noted is intended to show the large part which interstitial water plays in volcanic action. We shall now turn our attention again to the state of the deeply buried rock water, to see how far we may be able by it to account for these strange explosive actions. When sediments are laid down on the sea floor the materials consist of small, irregularly shaped fragments, which lie tumbled together in the manner of a mass of bricks which have been shot out of a cart. Water is buried in the plentiful interspaces between these bits of stone; as before remarked, the amount of this construction water varies. In general, it is at first not far from one tenth part of the materials. Besides the fluid contained in the distinct spaces, there is a share which is held as combined water in the intimate structure of the crystals, if such there be in the mass. When this water is built into the stone it has the ordinary temperature of the sea bottom. As the depositing actions continue to work, other beds are formed on the top of that which we are considering, and in time the layer may be buried to the depth of many thousand feet. There are reasons to believe that on the floors of the oceans this burial of beds containing water may have brought great quantities of fluid to the depth of twenty miles or more below the outer surface of the rocks. [Illustration: Fig. 15.--Flow of lava invading a forest. A tree in the distance is not completely burned, showing that the molten rock had lost much of its original heat.] The effect of deep burial is to increase the heat of strata. This result is accomplished in two different ways. The direct effect arising from the imposition of weight, that derived from the mass of stratified material, is, as we know, to bring about a down-sinking of the earth's crust. In the measure of this falling, heat is engendered precisely as it is by the falling of a trip-hammer on the anvil, with which action, as is well known, we may heat an iron bar to a high temperature. It is true that this down-sinking of the surface under weight is in part due to the compression of the rocks, and in part to the slipping away of the soft underpinning of more or less fluid rock. Yet further it is in some measure brought about by the wrinkling of the crust. But all these actions result in the conversion of energy of position into heat, and so far serve to raise the temperature of the rocks which are concerned in the movements. By far the largest source of heat, however, is that which comes forth from the earth's interior, and which was stored there in the olden day when the matter forming the earth gathered into the mass of our sphere. This, which we may term the original heat, is constantly flowing forth into space, but makes its way slowly, because of the non-conductive, or, as we may phrase it, the "blanketing" effect of the outer rock. The effect of the strata is the same as that exercised by the non-conductive coatings which are put on steam boilers. A more familiar comparison may be had from the blankets used for bedclothing. If on top of the first blanket we put a second, we keep warmer because the temperature of the lower one is elevated by the heat from our body which is held in. In the crust of the earth each layer of rock resists the outflow of heat, and each addition lifts the temperature of all the layers below. When water-bearing strata have been buried to the depth of ten miles, the temperature of the mass may be expected to rise to somewhere between seven hundred and a thousand degrees Fahrenheit. If the depth attained should be fifty miles, it is likely that the temperature will be five times as great. At such a heat the water which the rocks contain tends in a very vigorous way to expand and pass into the state of vapour. This it can not readily do, because of its close imprisonment; we may say, however, that the tendency toward explosion is almost as great as that of ignited gunpowder. Such powder, if held in small spaces in a mass of cast steel, could be fired without rending the metal. The gases would be retained in a highly compressed, possibly in a fluid form. If now it happens that any of the strain in the rocks such as lead to the production of faults produce fissures leading from the surface into this zone of heated water, the tendency of the rocks containing the fluid, impelled by its expansion, will be to move with great energy toward the point of relief or lessened pressure which the crevice affords. Where rocks are in any way softened, pressure alone will force them into a cavity, as is shown by the fact that beds of tolerably hard clay stones in deep coal mines may be forced into the spaces by the pressure of the rocks which overlie them--in fact, the expense of cutting out these in-creeping rocks is in some British mines a serious item in the cost of the product. The expansion of the water contained in the deep-lying heated rocks probably is by far the most efficient agent in urging them toward the plane of escape which the fissure affords. When the motion begins it pervades all parts of the rock at once, so that an actual flow is induced. So far as the movement is due to the superincumbent weight, the tendency is at once to increase the temperature of the moving mass. The result is that it may be urged into the fissure perhaps even hotter than when it started from the original bed place. In proportion as the rocky matter wins its way toward the surface, the pressure upon it diminishes, and the contained vapours are freer to expand. Taking on the vaporous form, the bubbles gather to each other, and when they appear at the throat of the volcano they may, if the explosions be infrequent, assume the character above noted in the little eruption of Vesuvius. Where, however, the lava ascends rapidly through the channel, it often attains the open air with so much vapour in it, and this intimately mingled with the mass, that the explosion rends the materials into an impalpably fine powder, which may float in the air for months before it falls to the earth. With a less violent movement the vapour bubbles expand in the lava, but do not rend it apart, thus forming the porous, spongy rock known as pumice. With a yet slower ascent a large part of the steam may go away, so that we may have a flow of lava welling forth from the vent, still giving forth steam, but with a vapour whose tension is so lowered that the matter is not blown apart, though it may boil violently for a time after it escapes into the air. Although the foregoing relatively simple explanation of volcanic action can not be said as yet to be generally accepted by geologists, the reasons are sufficient which lead us to believe that it accounts for the main features which we observe in this class of explosions--in other words, it is a good working hypothesis. We shall now proceed in the manner which should be followed in all natural inquiry to see if the facts shown in the distribution of volcanoes in space and time confirm or deny the view. The most noteworthy feature in the distribution of volcanoes is that, at the present time at least, all active vents are limited to the sea floors or to the shore lands within the narrow range of three hundred miles from the coast. Wherever we find a coast line destitute of volcanoes, as is the case with the eastern coast of North and South America, it appears that the shore has recently been carried into the land for a considerable distance--in other words, old coast lines are normally volcanic; that is, here and there have vents of this nature. Thus the North Atlantic, the coasts of which appear to have gone inland for a great distance in geologically recent times, is non-volcanic; while the Pacific coast, which for a long time has remained in its present position, has a singularly continuous line of craters near the shore extending from Alaska to Tierra del Fuego. So uninterrupted is this line of volcanoes that if they were all in eruption it would very likely be possible to journey down the coast without ever being out of sight of the columns of vapour which they would send forth. On the floor of the sea volcanic peaks appear to be very widely distributed; only a few of them--those which attain the surface of the water--are really known, but soundings show long lines of elevations which doubtless represent cones distributed along fault lines, none of the peaks of sufficient height to break the surface of the sea. It is likely, indeed, that for one marine volcano which appears as an island there are scores which do not attain the surface. Volcanic islands exist and generally abound in the ocean and greater seas; every now and then we observe a new one forming as a small island, which is apt to be washed away by the sea shortly after the eruption ceases, the disappearance being speedy, for the reason that the volcanic ashes of which these cones are composed drift away like snow before the movement of the waves. If the waters of the ocean and seas were drained away so that we could inspect the portion of the earth's surface which they cover as readily as we do the dry lands, the most conspicuous feature would be the innumerable volcanic eminences which lie hidden in these watery realms. Wherever the observer passed from the centres of the present lands he would note within the limits of those fields only mountains, much modified by river action; hills which the rivers had left in scarfing away the strata; and dales which had been carved out by the flowing waters. Near the shore lines of the vanished seas he would begin to find mountains, hills, and vales occasionally commingled with volcanic peaks, those structures built from the materials ejected from the vents. Passing the coast line to the seaward, the hills and dales would quickly disappear, and before long the mountains would vanish from his way, and he would gradually enter on a region of vast rolling plains beset by volcanic peaks, generally accumulated in long ranges, somewhat after the manner of mountains, but differing from those elevations not only in origin but in aspect, the volcanic set of peaks being altogether made up of conical, cup-topped elevations. A little consideration will show us that the fact of volcanoes being in the limit to the sea floors and to a narrow fringe of shore next certain ocean borders is reconcilable with the view as to their formation which we have adopted. We have already noted the fact that the continents are old, which implies that the parts of the earth which they occupy have long been the seats of tolerably continuous erosion. Now and then they have swung down partly beneath the sea, and during their submersion they received a share of sediments. But, on the whole, all parts of the lands except strips next the coast may be reckoned as having been subjected to an excess of wearing action far exceeding the depositional work. Therefore, as we readily see, underneath such land areas there has been no blanketing process going on which has served to increase the heat in the deep underlying rocks. On the contrary, it would be easy to show, and the reader may see it himself, that the progressive cooling of the earth has probably brought about a lowering of the temperature in all the section from the surface to very great depths, so that not only is the rock water unaffected by increase of heat, but may be actually losing temperature. In other words, the conditions which we assume bring about volcanic action do not exist beneath the old land. Beneath the seas, except in their very greatest depths, and perhaps even there, the process of forming strata is continually going on. Next the shores, sometimes for a hundred or two miles away to seaward, the principal contribution may be the sediment worn from the lands by the waves and the rivers. Farther away it is to a large extent made up of the remains of animals and plants, which when dying give their skeletons to form the strata. Much of the materials laid down--perhaps in all more than half--consist of volcanic dust, ashes, and pumice, which drifts very long times before it finds its way to the bottom. We have as yet no data of a precise kind for determining the average rate of accumulation of sediments upon the sea floor, but from what is known of the wearing of the lands, and the amount of volcanic waste which finds its way to the seas, it is probably not less than about a foot in ten thousand years; it is most likely, indeed, much to exceed this amount. From data afforded by the eruptions in Java and in other fields where the quantity of volcanic dust contributed to the seas can be estimated, the writer is disposed to believe that the average rate of sedimentation on the sea floors is twice as great as the estimate above given. Accumulating at the average rate of one foot in ten thousand years, it would require a million years to produce a hundred feet of sediments; a hundred million to form ten thousand feet, and five hundred million to create the thickness of about ten miles of bed. At the rate of two feet in ten thousand years, the thickness accumulated would be about twenty miles. When we come to consider the duration of the earth's geologic history, we shall find reasons for believing that the formation of sediment may have continued for as much as five hundred million years. The foregoing inquiries concerning the origin of volcanoes show that at the present time they are clearly connected with some process which goes on beneath the sea. An extension of the inquiry indicates that this relation has existed in earlier geological times; for, although the living volcanoes are limited to places within three hundred miles of the sea, we find lava flows, ashes, and other volcanic accumulations far in the interior of the continents, though the energy which brought them forth to the earth's surface has ceased to operate in those parts of the land. In these cases of continental volcanoes it generally, if not always, appears that the cessation of the activity attended the removal of the shore line of the ocean or the disappearance of great inland seas. Thus the volcanoes of the Yellowstone district may have owed their activity to the immense deposits of sediment which were formed in the vast fresh-water lakes which during the later Cretaceous and early Tertiary times stretched along the eastern face of the Rocky Mountains, forming a Mediterranean Sea in North America comparable to that which borders southern Europe. It thus appears that the arrangement of volcanoes with reference to sea basins has held for a considerable period in the past. Still further, when we look backward through the successive formations of the earth's crust we find here and there evidences in old lava flows, in volcanic ashes, and sometimes in the ruins of ancient cones which have been buried in the strata, that igneous activity such as is now displayed in our volcanoes has been, since the earliest days of which we have any record, a characteristic feature of the earth. There is no reason to suppose that this action has in the past been any greater or any less than in modern days. All these facts point to the conclusion that volcanic action is due to the escape of rock water which has been heated to high temperatures, and which drives along with it as it journeys toward a crevice the rock in which it has been confined. We will now notice some other explanations of volcanic action which have obtained a certain credence. First, we may note the view that these ejections from craters are forced out from a supposed liquid interior of the earth. One of the difficulties of this view is that we do not know that the earth's central parts are fluid--in fact, many considerations indicate that such is not the case. Next, we observe that we not infrequently find two craters, each containing fluid lava, with the fluid standing at differences of height of several thousand feet, although the cones are situated very near each other. If these lavas came from a common internal reservoir, the principles which control the action of fluids would cause the lavas to be at the same elevation. Moreover, this view does not provide any explanation of the fact that volcanoes are in some way connected with actions which go on on the floors of great water basins. There is every reason to believe that the fractures in the rocks under the land are as numerous and deep-going as those beneath the sea. If it were a mere question of access to a fluid interior, volcanoes should be equally distributed on land and sea floors. Last of all, this explanation in no wise accounts for the intermixture of water with the fluid rock. We can not well believe that water could have formed a part of the deeper earth in the old days of original igneous fusion. In that time the water must have been all above the earth in the vaporous state. Another supposition somewhat akin to that mentioned is that the water of the seas finds its way down through crevices beneath the floors of the ocean, and, there coming in contact with an internal molten mass, is converted into steam, which, along with the fluid rock, escapes from the volcanic vent. In addition to the objections urged to the preceding view, we may say concerning this that the lava, if it came forth under these circumstances, would emerge by the short way, that by which the water went down, and not by the longer road, by which it may be discharged ten thousand feet or more above the level of the sea. The foregoing general account of volcanic action should properly be followed by some account of what takes place in characteristic eruptions. This history of these matters is so ample that it would require the space of a great encyclopædia to contain them. We shall therefore be able to make only certain selections which may serve to illustrate the more important facts. By far the best-known volcanic cone is that of Vesuvius, which has been subjected to tolerably complete record for about twenty-four hundred years. About 500 B.C. the Greeks, who were ever on the search for places where they might advantageously plant colonies, settled on the island of Ischia, which forms the western of what is now termed the Bay of Naples. This island was well placed for tillage as well as for commerce, but the enterprising colonists were again and again disturbed by violent outbreaks of one or more volcanoes which lie in the interior of this island; at one time it appears that the people were driven away by these explosions. In these pre-Christian days Vesuvius, then known as Monte Somma, was not known to be a volcano, it never having shown any trace of eruption. It appeared as a regularly shaped mountain, somewhat over two thousand feet high, with a central depression about three miles in diameter at the top, and perhaps two miles over at the bottom, which was plainlike in form, with some lakes of bitter water in the centre. The most we know of this central cavity is connected with the insurrection of the slaves led by Spartacus, the army of the revolters having camped for a time on the plain encircled by the crater walls. The outer slopes of the mountain afforded then a remarkably fertile soil; some traces, indeed, of the fertility have withstood the modern eruptions which have desolated its flanks. This wonderful Bay of Naples became the seat of the fairest Roman culture, as well as of a very extended commerce. Toward the close of the first century of our era the region was perhaps richer, more beautifully cultivated, and the seat of a more elaborate luxury than any part of the shore line of Europe at the present day. At the foot of the mountain, on the eastern border of the bay, the city of Pompeii, with a population of about fifty thousand souls, was a considerable port, with an extensive commerce, particularly with Egypt. The charming town was also a place of great resort for rich Egyptians who cared to dwell in Europe. On the flanks of the mountain there was at least one large town, Herculaneum, which appears to have been an association of rich men's residences. On the eastern side of the bay, at a point now known as Baiæ, the Roman Government had a naval station, which in the year 79 was under the command of the celebrated Pliny, a most voluminous though unscientific writer on matters of natural history. With him in that year there was his nephew, commonly known as the younger Pliny, then a student of eighteen years, but afterward himself an author. These facts are stated in some detail, for they are all involved in the great tragedy which we are now to describe. For many years there had been no eruption about the Bay of Naples. The volcanoes on Ischia had been still for a century or more, and the various circular openings on the mainland had been so far quiet that they were not recognised as volcanoes. Even the inquisitive Pliny, with his great learning, was so little of a geologist that he did not know the signs which indicate the seat of volcanic action, though they are among the most conspicuous features which can meet the eye. The Greeks would doubtless have recognised the meaning of these physical signs. In the year 63 the shores of the Bay of Naples were subjected to a distinctive earthquake. Others less severe followed in subsequent years. In an early morning in the year 79, a servant aroused the elder Pliny at Baiæ with the news that there was a wonderful cloud rising from Monte Somma. The younger Pliny states that in form it was like a pine tree, the common species in Italy having a long trunk with a crown of foliage on its summit, shaped like an umbrella. This crown of the column grew until it spread over the whole landscape, darkening the field of view. Shortly after, a despatch boat brought a message to the admiral, who at once set forth for the seat of the disturbance. He invited his nephew to accompany him, but the prudent young man relates in his letters to Tacitus, from whom we know the little concerning the eruption which has come down to us, that he preferred to do some reading which he had to attend to. His uncle, however, went straight forward, intending to land at some point on the shore at the foot of the cone. He found the sea, however, so high that a landing was impossible; moreover, the fall of rock fragments menaced the ship. He therefore cruised along the shore for some distance, landing at a station probably near the present village of Castellamare. At this point the fall of ashes and pumice was very great, but the sturdy old Roman had his dinner and slept after it. There is testimony that he snored loudly, and was aroused only when his servants began to fear that the fall of ashes and stones would block the way out of his bedchamber. When he came forth with his attendants, their heads protected by planks resting on pillows, he set out toward Pompeii, which was probably the place where he sought to land. After going some distance, the brave man fell dead, probably from heart disease; it is said that he was at the time exceedingly asthmatic. No sooner were his servants satisfied that the life had passed from his body than they fled. The remains were recovered after the eruption had ceased. The younger Pliny further relates that after his uncle left, the cloud from the mountain became so dense that in midday the darkness was that of midnight, and the earthquake shocks were so violent that wagons brought to the courtyard of the dwelling to bear the members of the household away were rolled this way and that by the quakings of the earth. Save for the above-mentioned few and unimportant details concerning the eruption, we have no other contemporaneous account. We have, indeed, no more extended story until Dion Cassius, writing long after the event, tells us that Herculaneum and Pompeii were overwhelmed; but he mixes his story with fantastic legends concerning the appearance of gods and demons, as is his fashion in his so-called history. Of all the Roman writers, he is perhaps the most untrustworthy. Fortunately, however, we have in the deposits of ashes which were thrown out at the time of this great eruption some basis for interpreting the events which took place. It is evident that for many hours the Vesuvian crater, which had been dormant for at least five hundred years, blew out with exceeding fury. It poured forth no lava streams; the energy of the uprushing vapours was too great for that. The molten rock in their path was blown into fine bits, and all the hard material cast forth as free dust. In the course of the eruption, which probably did not endure more than two days, possibly not more than twenty-four hours, ash enough was poured forth to form a thick layer which spread far over the neighbouring area of land and sea floor. It covered the cities of Herculaneum and Pompeii to a depth of more than twenty feet, and over a circle having a diameter of twenty miles the average thickness may have been something like this amount. So deep was it that, although almost all the people of these towns survived, it did not seem to them worth while to undertake to excavate their dwelling places. At Pompeii the covering did not overtop the higher of the low houses. An amount of labour which may be estimated at not over one thirtieth of the value, or at least the cost which had been incurred in building the city, would have restored it to a perfectly inhabitable state. The fact that it was utterly abandoned probably indicates a certain superstitious view in connection with the eruption. The fact that the people had time to flee from Herculaneum and Pompeii, bearing with them their more valuable effects, is proved by the excavations at these places which have been made in modern times. The larger part of Pompeii and a considerable portion of Herculaneum have been thus explored; only rarely have human remains been found. Here and there, particularly in the cellars, the labourers engaged in the work of disinterring the cities note that their picks enter a cavity; examining the space, they find they have discovered the remains of a human skeleton. It has recently been learned that by pouring soft plaster of Paris into these openings a mould may be obtained which gives in a surprisingly perfect manner the original form of the body. The explanation of this mould is as follows: Along with the fall of cinders in an eruption there is always a great descent of rain, arising from the condensation of the steam which pours forth from the volcano. This water, mingling with the ashes, forms a pasty mud, which often flows in vast streams, and is sometimes known as mud lava. This material has the qualities of cement--that is, it shortly "sets" in a manner comparable to plaster of Paris or ordinary mortar. During the eruption of 79 this mud penetrated all the low places in Pompeii, covering the bodies of the people, who were suffocated by the fumes of the volcanic emanations. We know that these people were not drowned by the inundation; their attitudes show that they were dead before the flowing matter penetrated to where they lay. It happened that Pompeii lay beyond the influence of the subsequent great eruptions of Vesuvius, so that it afterward received only slight ash showers. Herculaneum, on the other hand, has century by century been more and more deeply buried until at the present time it is covered by many sheets of lava. This is particularly to be regretted, for the reason that, while Pompeii was a seaport town of no great wealth or culture, Herculaneum was the residence place of the gentry, people who possessed libraries, the records of which can be in many cases deciphered, and from which we might hope to obtain some of the lost treasures of antiquity. The papyrus rolls on which the books of that day were written, though charred by heat and time, are still interpretable. After the great explosion of 79, Vesuvius sank again into repose. It was not until 1056 that vigorous eruptions again began. From time to time slight explosions occurred, none of which yielded lava flows; it was not until the date last mentioned that this accompaniment of the eruption began to appear. In 1636, after a repose of nearly a century and a half, there came a very great outbreak, which desolated a wide extent of country on the northwestern side of the cone. At this stage in the history of the crater the volcanic flow began to attain the sea. Washing over the edge of the old original crater of Monte Somma, and thus lowering its elevation, these streams devastated, during the eruption just mentioned and in various other outbreaks, a wide field of cultivated land, overwhelming many villages. The last considerable eruption which yielded large quantities of lava was that of 1872, which sent its tide for a distance of about six miles. Since 1636 the eruptions of Vesuvius have steadily increased in frequency, and, on the whole, diminished in violence. In the early years of its history the great outbreaks were usually separated by intervals of a century or more, and were of such energy that the lava was mostly blown to dust, forming clouds so vast that on two occasions at least they caused a midnight darkness at Constantinople, nearly twelve hundred miles away. This is as if a volcano at Chicago should completely hide the sun in the city of Boston. In the present state of Vesuvius, the cone may be said to be in slight, almost continuous eruption. The old central valley which existed before the eruption of 79, and continued to be distinct for long after that time, has been filled up by a smaller cone, bearing a relatively tiny crater of vent, the original wall being visible only on the eastern and northern parts of its circuit, and here only with much diminished height. On the western face the slope from the base of the mountain to the summit of the new cone is almost continuous, though the trained eye can trace the outline of Monte Somma--its position in a kind of bench, which is traceable on that side of the long slope leading from the summit of the new cone to the sea. The fact that the lavas of Vesuvius have broken out on the southwestern side, while the old wall of the cone has remained unbroken on the eastern versant, has a curious explanation. The prevailing wind of Naples is from the southwest, being the strong counter trades which belong in that latitude. In the old days when the Monte Somma cone was constructed these winds caused the larger part of the ashes to fall on the leeward side of the cone, thus forming a thicker and higher wall around that part of the crater. From the nature of the recent eruptions of Vesuvius it appears likely that the mountain is about to enter on a second period of inaction. The pipes leading through the new cone are small, and the mass of this elevation constitutes a great plug, closing the old crater mouth. To give vent to a large discharge of steam, the whole of this great mass, having a depth of nearly two thousand feet, would have to be blown away. It seems most likely that when the occasion for such a discharge comes, the vapours of the eruption will seek a vent through some other of the many volcanic openings which lie to the westward of this great cone. The history of these lesser volcanoes points to the conclusion that when the path by way of Vesuvius is obstructed they may give relief to the steam which is forcing its course to the surface. Two or three times since the eruption of Pliny, during periods when Vesuvius had long been quiet, outbreaks have taken place on Ischia or in the Phlægræn Fields, a region dotted with small craters which lies to the west of Naples. The last of these occurred in 1552, and led to the formation of the beautiful little cone known as Monte Nuovo. This eruption took place near the town of Puzzuoli, a place which was then the seat of a university, the people of which have left us records of the accident. [Illustration: Fig. 16.--Diagrammatic sections through Mount Vesuvius, showing changes in the form of the cone. (From Phillips.)] The outbreak which formed Monte Nuovo was slight but very characteristic. It occurred in and beside a circular pool known as the Lucrine Lake, itself an ancient crater. At the beginning of the disturbance the ground opened in ragged cavities, from which mud and ashes and great fragments of hard rock were hurled high in the air, some of the stones ascending to a height of several thousand feet. With slight intermissions this outbreak continued for some days, resulting in the formation of a hill about five hundred feet high, with a crater in its top, the bottom of which lay near the level of the sea. Although this volcanic elevation, being made altogether of loose fragments, is rapidly wearing down, while the crater is filling up, it remains a beautiful object in the landscape, and is also noteworthy for the fact that it is the only structure of this nature which we know from its beginning. In the Phlægræn Field there are a number of other craters of small size, with very low cones about them. These appear to have been the product of brief, slight eruptions. That known as the Solfatara, though not in eruption during the historic period, is interesting for the fact that from the crevices of the rocks about it there comes forth a continued efflux of carbonic-acid gas. This substance probably arises from the effect of heat contained in old lavas which are in contact with limestone in the deep under-earth. We know such limestones are covered by the lavas of Vesuvius, for the reason that numerous blocks of the rock are thrown out during eruptions, and are often found embedded in the lava streams. It is an interesting fact that these craters of the Phlægræn Field, lying between the seats of vigorous eruption on Ischia and at Vesuvius, have never been in vigorous eruption. Their slight outbreaks seem to indicate that they have no permanent connection with the sources whence those stronger vents obtain their supply of heated steam. The facts disclosed by the study of the Vesuvian system of volcanoes afford the geologist a basis for many interesting conclusions. In the first place, he notes that the greater part of the cones, all those of small size, are made up of finely divided rock, which may have been more or less cemented by the processes of change which go on within it. It is thus clear that the lava flows are unessential--indeed, we may say accidental--contributions to the mass. In the case of Vesuvius they certainly do not amount to as much as one tenth of the elevation due to the volcanic action. The share of the lava in Vesuvius is probably greater than the average, for during the last six centuries this vent has been remarkably lavigerous.[8] Observation on the volcanoes of other districts show that the Vesuvian group is in this regard not peculiar. Of nearly two hundred cones which the writer has examined, not more than one tenth disclose distinct lavas. [Footnote 8: I venture to use this word in place of the phrase "lava-yielding" for the reason that the term is needed in the description of volcanoes.] An inspection of the old inner wall of Monte Somma in that portion where it is best preserved, on the north side of the Atria del Cavallo, or Horse Gulch--so called for the reason that those who ascended Vesuvius were accustomed to leave their saddle animals there--we perceive that the body of the old cone is to a considerable extent interlaced with dikes or fissures which have been filled with molten lava that has cooled in its place. It is evident that during the throes of an eruption, when the lava stands high in the crater, these rents are frequently formed, to be filled by the fluid rock. In fact, lava discharges, though they may afterward course for long distances in the open air, generally break their way underground through the cindery cone, and first are disclosed at the distance of a mile or more from the inner walls of the crater. Their path is probably formed by riftings in the compacted ashes, such as we trace on the steep sides of the Atria del Cavallo, as before noted. For the further history of these fissures, we shall have to refer to facts which are better exhibited in the cone of Ætna. The amount of rock matter which has been thrown forth from the volcanoes about the Bay of Naples is very great. Only a portion of it remains in the region around these cones; by far the greater part has been washed or blown away. After each considerable eruption a wide field is coated with ashes, so that the tilled grounds appear as if entirely sterilized; but in a short time the matter in good part disappears, a portion of it decays and is leached away, and the most of the remainder washes into the sea. Only the showers, which accumulate a deep layer, are apt to be retained on the surface of the country. A great deal of this powdered rock drifts away in the wind, sometimes in great quantities, as in those cases where it darkened the sky more than a thousand miles from the cone. Moreover, the water of the steam which brought about the discharges and the other gases which accompanied the vapour have left no traces of their presence, except in the deep channels which the rain of the condensing steam have formed on the hillsides. Nevertheless, after all these subtractions are made, the quantity of volcanic matter remaining on the surface about the Bay of Naples would, if evenly distributed, form a layer several hundred feet in thickness--perhaps, indeed, a thousand feet in depth--over the territory in which the vents occur. All this matter has been taken in relatively recent times from the depths of the earth. The surprising fact is that no considerable and, indeed, no permanent subsidence of the surface has attended this excavation. We can not believe that this withdrawal of material from the under-earth has resulted in the formation of open underground spaces. We know full well that any such, if it were of considerable size, would quickly be crushed in by the weight of the overlying rocks. We have, indeed, to suppose that these steam-impelled lavas, which are driven toward the vent whence they are to go forth in the state of dust or fluid, come underground from distances away, probably from beneath the floors of the sea to the westward. Although the shores of the Bay of Naples have remained in general with unchanged elevation for about two thousand years, they have here and there been subjected to slight oscillations which are most likely connected with the movement of volcanic matter toward the vents where it is to find escape. The most interesting evidence of this nature is afforded by the studies which have been made on the ruins of the Temple of Serapis at Puzzuoli. This edifice was constructed in pre-Christian times for the worship of the Egyptian god Serapis, whose intervention was sought by sick people. The fact that this divinity of the Nile found a residence in this region shows how intimate was the relation between Rome and Egypt in this ancient day. The Serapeium was built on the edge of the sea, just above its level. When in modern days it began to be studied, its floor was about on its original level, but the few standing columns of the edifice afford indubitable evidence that this part of the shore has been lowered to the amount of twenty feet or more and then re-elevated. The subsidence is proved by the fact that the upper part of the columns which were not protected by the _débris_ accumulated about them have been bored by certain shellfish, known as _Lithodomi_, which have the habit of excavating shelters in soft stone, such as these marble columns afford. At present the floor on which the ruin stands appears to be gradually sinking, though the rate of movement is very slow. Another evidence that the ejections may travel for a great distance underground on their way to the vent is afforded by the fact that Vesuvius and Ætna, though near three hundred miles apart, appear to exchange activities--that is, their periods of outbreak are not simultaneous. Although these elements of the chronology of the two cones may be accidental, taken with similar facts derived from other fields, they appear to indicate that vents, though far separated from each other, may, so to speak, be fed from a common subterranean source. It is a singular fact in this connection that the volcano of Stromboli, though situated between these two cones, is in a state of almost incessant activity. This probably indicates that the last-named vent derives its vapours from another level in the earth than the greater cones. In this regard volcanoes probably behave like springs, of which, indeed, they may be regarded as a group. The reader is doubtless aware that hot and cold springs often escape very near together, the difference in the temperature being due to the depth from which their waters come forth. As the accidents of volcanic explosion are of a nature to be very damaging to man, as well as to the lower orders of Nature, it is fit that we should note in general the effect of the Neapolitan eruptions on the history of civilization in that region. As stated above, the first Greek settlements in this vicinity--those on the island of Ischia--were much disturbed by volcanic outbreaks, yet the island became the seat of a permanent and prosperous colony. The great eruption of 79 probably cost many hundred lives, and led to the abandonment of two considerable cities, which, however, could at small cost have been recovered to use. Since that day various eruptions have temporarily desolated portions of the territory, but only in very small fields have the ravages been irremediable. Where the ground was covered with dust, it has in most places been again tillable, and so rapid is the decay of the lavas that in a century after their flow has ceased vines can in most cases be planted on their surfaces. The city of Naples, which lies amid the vents, though not immediately in contact with any of them, has steadfastly grown and prospered from the pre-Christian times. It is doubtful if any lives have ever been lost in the city in consequence of an eruption, and no great inconvenience has been experienced from them. Now and then, after a great ash shower, the volcanic dust has to be removed, but the labour is less serious than that imposed on many northern cities by a snowstorm. Through all these convulsions the tillage of the district has been maintained. It has ever been the seat of as rich and profitable a husbandry as is afforded by any part of Italy. In fact, the ash showers, as they import fine divided rock very rich in substances necessary for the growth of plants, have in a measure served to maintain the fertility of the soil, and by this action have in some degree compensated for the injury which they occasionally inflict. Comparing the ravages of the eruptions with those inflicted by war, unnecessary disease, or even bad politics, and we see that these natural accidents have been most merciful to man. Many a tyrant has caused more suffering and death than has been inflicted by these rude operations of Nature. From the point of view of the naturalist, Ætna is vastly more interesting than Vesuvius. The bulk of the cone is more than twenty times as great as that of the Neapolitan volcano, and the magnitude of its explosions, as well as the range of phenomena which they exhibit, incomparably greater. It happens, however, that while human history of the recorded kind has been intimately bound up with the tiny Vesuvian cone, partly because the relatively slight nature of its disturbances permitted men to dwell beside it, the larger Ætna has expelled culture from the field near its vent, and has done the greater part of its work in the vast solitude which it has created.[9] [Footnote 9: In part the excellent record of Vesuvius is due to the fact that since the early Christian centuries the priests of St. Januarius, the patron of Naples, have been accustomed to carry his relics in procession whenever an eruption began. The cessation of the outbreak has been written down to the credit of the saint, and thus we are provided with a long story of the successive outbreaks.] Ætna has been in frequent eruption for a very much longer time than Vesuvius. In the odes of Pindar, in the sixth century before Christ, we find records of eruptions. It is said also that the philosopher Empedocles sought fame and death by casting himself into the fiery crater. There has thus in the case of this mountain been no such long period of repose as occurred in Vesuvius. Though our records of the outbreaks are exceedingly imperfect, they serve to show that the vent has maintained its activity much more continuously than is ordinarily the case with volcanoes. Ætna is characteristically a lava-yielding cone; though the amount of dust put forth is large, the ratio of the fluid rock which flows away from the crater is very much greater than at Vesuvius. Nearly half the cone, indeed, may be composed of this material. Our space does not permit anything like a consecutive story of the Ætnean eruptions since the dawn of history, or even a full account of its majestic cone; we can only note certain features of a particularly instructive nature which have been remarked by the many able men who have studied this structure and the effects of its outbreak. The most important feature exhibited by Ætna is the vast size of its cone. At its apex its height, though variable from the frequent destruction and rebuilding of the crater walls, may be reckoned as about eleven thousand feet. The base on which the volcanic material lies is probably less than a thousand feet above the sea, so that the maximum thickness of the heap of volcanic ejections is probably about two miles. The average depth of this coating is probably about five thousand feet, and, as the cone has an average diameter of about thirty miles, we may conclude that the cone now contains about a thousand cubic miles of volcanic materials. Great as is this mass, it is only a small part of the ejected material which has gone forth from the vent. All the matter which in its vaporous state went forth with the eruption, the other gases and vapours thus discharged, have disappeared. So, too, a large part of the ash and much of the lava has been swept away by the streams which drain the region, and which in times of eruption are greatly swollen by the accompanying torrential rains. The writer has estimated that if all the emanations from the volcano--solid, fluid, and gaseous--could be heaped on the cone, they would form a mass of between two and three thousand cubic miles in contents. Yet notwithstanding this enormous outputting of earthy matter, the earth on which the Ætnean cone has been constructed has not only failed to sink down, but has been in process of continuous, slow uprising, which has lifted the surface more than a thousand feet above the level which it had at the time when volcanic action began in this field. Here, even more clearly than in the case of Vesuvius, we see that the materials driven forth from the crater are derived not from just beneath its foundation, but from a distance, from realms which in the case of this insular volcano are beneath the sea floors. It is certain that here the migration of rock matter, impelled by the expansion of its contained water toward the vent, has so far exceeded that which has been discharged through the crater that an uprising of the surface such as we have observed has been brought about. [Illustration: _Mount Ætna, seen from near Catania. The imperfect cones on the sky line to the left are those of small secondary eruptions._] There are certain peculiarities of Mount Ætna which are due in part to its great size and in part to the climatal conditions of the region in which it lies. The upper part of the mountain in winter is deeply snow-clad; the frozen water often, indeed, forms great drifts in the gorges near the summit. Here it has occasionally happened that a layer of ashes has deeply buried the mass, so that it has been preserved for years, becoming gradually more inclosed by the subsequent eruptions. At one point where this compact snow--which has, indeed, taken on the form of ice--has been revealed to view, it has been quarried and conveyed to the towns upon the seacoast. It is likely that there are many such masses of ice inclosed between the ash layers in the upper part of the mountain, where, owing to the height, the climate is very cold. This curious fact shows how perfect a non-conductor the ash beds of a volcano are to protect the frozen water from the heat of the rocks about the crater. The furious rains which beset the mountain in times of great eruptions excavate deep channels on its sides. The lava outbreaks which attend almost every eruption, and which descend from the base of the cinder cone at the height of from five to eight thousand feet above the sea, naturally find their way into these channels, where they course in the manner of rivers until the lower and less valleyed section of the cone is reached. Such a lava flow naturally begins to freeze on the surface, the lava at first becoming viscid, much in the manner of cream on the surface of milk. Urged along by the more fluid lava underneath, this viscid coating takes a ropy or corrugated form. As the freezing goes deeper, a firm stone roof may be formed across the gorge, which, when the current of lava ceases to flow from the crater, permits the lower part of the stream to drain away, leaving a long cavern or scries of caves extending far up the cone. The nature of this action is exactly comparable to that which we may observe when on a frosty morning after rain we may find the empty channels which were occupied by rills of water roofed over with ice; the ice roofs are temporary, while those of lava may endure for ages. Some of these lava-stream caves have been disclosed, in the manner of ordinary caverns, by the falling of their roofs; but the greater part are naturally hidden beneath the ever-increasing materials of the cone. The lava-stream caves of Ætna are not only interesting because of their peculiarities of form, which we shall not undertake to describe, but also for the reason that they help us to account for a very peculiar feature in the history of the great cone. On the slopes of the volcano, below the upper cindery portion, there are several hundred lesser cones, varying from a few score to seven hundred feet in height. Each of these has its appropriate crater, and has evidently been the seat of one or more eruptions. As the greater part of these cones are ancient, many of them being almost effaced by the rain or buried beneath the ejections which have surrounded their bases since the time they were formed, we are led to believe that many thousands of them have been formed during the history of the volcano. The history of these subsidiary cones appears to be connected with the lava caves noted above. These caverns, owing to the irregularities of their form, contain water. They are, in fact, natural cisterns, where the abundant rainfall of the mountain finds here and there storage. When, during the throes of an eruption, dikes such as we know often to penetrate the mountain, are riven outward from the crater through the mass of the cone, and filled with lava, the heated rock must often come in contact with these masses of buried water. The result of this would inevitably be the local generation of steam at a high temperature, which would force its way out in a brief but vigorous eruption, such as has been observed to take place when these peripheral volcanoes are formed. Sometimes it has happened that after the explosion the lava has found its way in a stream from the fissure thus opened. That this explanation is sufficient is in a measure shown by observations on certain effects of lava flows from Vesuvius. The writer was informed by a very judicious observer, a resident of Naples, who had interested himself in the phenomena of that volcano, that the lava streams when they penetrated a cistern, such as they often encounter in passing over villages or farmsteads, vaporized the water, and gave rise, through the action of the steam, to small temporary cones, which, though generally washed away by the further flow of the liquid rock, are essentially like those which we find on Ætna. Such subsidiary, or, as they are sometimes called, parasitic cones, are known about other volcanoes, but nowhere are they so characteristic as on the flanks of that wonderful volcano. A very conspicuous feature in the Ætnean cone consists of a great valley known as the Val del Bove, or Bull Hollow, which extends from the base of the modern and ever-changeable cinder cone down the flanks of the older structure to near its base. This valley has steep sides, in places a thousand or more feet high, and has evidently been formed by the down-settling of portions of the cone which were left without support by the withdrawal from beneath them of materials cast forth in a time of explosion. In an eruption this remarkable valley was the seat of a vast water flood, the fluid being cast forth from the crater at the beginning of the explosion. In the mouths of this and other volcanoes, after a long period of repose, great quantities of water, gathering from rains or condensed from the steam which slowly escapes from these openings, often pours like a flood down the sides of the mountains. In the great eruption of Galongoon, in Java, such a mass of water, cast forth by a terrific explosion, mingled with ashes, so that the mass formed a thick mud, was shot forth with such energy that it ravaged an area nearly eighty miles in diameter, destroying the forests and their wild inhabitants, as well as the people who dwelt within the range of the amazing disaster. So powerfully was this water driven from the crater that the districts immediately at the base of the cone were in a manner overshot by the vast stream, and escaped with relatively little injury. When it comes forth from the base of the cinder cone, or from one of the small peripheral craters, the lava stream usually appears to be white hot, and to flow with almost the ease of water. It does not really have that measure of fluidity; its condition is rather that of thin paste; but the great weight of the material--near two and a half times that of water--causes the movement down the slope to be speedy. The central portion of the lava stream long retains its high temperature; but the surface, cooling, is first converted into a tough sheet, which, though it may bend, can hardly be said to flow. Further hardening converts these outlying portions of the current into hard, glassy stone, which is broken into fragments in a way resembling the ice on the surface of a river. It thus comes about that the advancing front of the lava stream becomes covered, and its motion hindered by the frozen rock, until the rate of ongoing may not exceed a few feet an hour, and the appearance is that of a heap of stone slowly rolling down a slope. Now and then a crevice is formed, through which a thin stream of liquid lava pours forth, but the material, having already parted with much of its heat, rapidly cools, and in turn becomes covered with the coating of frozen fragments. In this state of the stream the lava flow stands on all sides high above the slope which it is traversing; it is, in fact, walled in by its own solidified parts, though it is urged forward by the contribution which continues to flow in the under arches. In this state of the movement trifling accidents, or even human interference, may direct the current this way or that. Some of the most interesting chapters in the history of Ætna relate to the efforts of the people to turn these slow-moving streams so that their torrents might flow into wilderness places rather than over the fields and towns. In the great flow of 1669, which menaced the city of Catania, a large place on the seashore to the southeast of the cone, a public-spirited citizen, Señor Papallardo, protecting himself and his servants with clothing made of hides, and with large shields, set forth armed with great hooks with the purpose of diverting the course of the lava mass. He succeeded in pulling away the stones on the flank of the stream, so that a flow of the molten rock was turned in another direction. The expedient would probably have been successful if he had been allowed to continue his labours; but the inhabitants of a neighbouring village, which was threatened by the off-shooting current which Papallardo had created, took up arms and drove him and his retainers away. The flow continued until it reached Catania. The people made haste to build the city walls on the side of danger higher than it was before, but the tide mounted over its summit. Although the lavas which come forth from the volcano evidently have a high temperature, their capacity for melting other rocks is relatively small. They scour these rocks, because of their weight, even more energetically than do powerful torrents of water, but they are relatively ineffective in melting stone. On Ætna and elsewhere we may often observe lavas which have flowed through forests. When the tide of molten rock has passed by, the trees may be found charred but not entirely burned away; even stems a few inches in diameter retain strength enough to uphold considerable fringes and clots of the lava which has clung to them. These facts bear out the conclusion that the fluidity of the heated stone depends in considerable measure on the water which is contained, either in its fluid or vaporous state, between the particles of the material. If we consider the Italian volcanoes as a whole, we find that they lie in a long, discontinuous line extending from the northern part of the valley of the Po, within sight of the Alps, to Ætna, and in subterranean cones perhaps to the northern coast of Africa. At the northern end of the line we have a beautiful group of extinct volcanoes, known as the Eugean Mountains. Thence southward to southern Tuscany craters are wanting, but there is evidence of fissures in the earth which give forth thermal waters. From southern Tuscany southward through Rome to Naples there are many extinct craters, none of which have been active in the historic period. From Naples southward the cones of this system, about a dozen in number, are on islands or close to the margin of the sea. It is a noteworthy fact that the greater part of these shore or insular vents have been active since the dawn of history; several of them frequently and furiously so, while none of those occupying an inland position have been the seat of explosions. This is a striking instance going to show the relation of these processes to conditions which are brought about on the sea bottom. Ætna is, as we have noticed, a much more powerful volcano than Vesuvius. Its outbreaks are more vigorous, its emanations vastly greater in volume, and the mass of its constructions many times as great as those accumulated in any other European cone. There are, however, a number of volcanoes in the world which in certain features surpass Ætna as much as that crater does Vesuvius. Of these we shall consider but two--Skaptar Jokul, of Iceland, remarkable for the volume of its lava flow, and Krakatoa, an island volcano between Java and Sumatra, which was the seat of the greatest explosion of which we have any record. The whole of Iceland may be regarded as a volcanic mass composed mainly of lavas and ashes which have been thrown up by a group of volcanoes lying near the northern end of the long igneous axis which extends through the centre of the Atlantic. The island has been the seat of numerous eruptions; in fact, since its settlement by the Northmen in 1070 its sturdy inhabitants have been almost as much distressed by the calamities which have come from the internal heat as they have been by the enduring external cold. They have, indeed, been between frost and fire. The greatest recorded eruption of Iceland occurred in 1783, when the volcano of Skaptar, near the southern border of the island, poured forth, first, a vast discharge of dust and ashes, and afterward in the languid state of eruption inundated a series of valleys with the greatest lava flow of which we have any written record. The dust poured forth into the upper air, being finely divided and in enormous quantity, floated in the air for months, giving a dusky hue to the skies of Europe, which led the common people and many of the learned to fear that the wrath of God was upon them, and that the day of judgment was at hand. Even the poet Cowper, a man of high culture and education, shared in this unreasonable view. The lava flow in this eruption filled one of the considerable valleys of the island, drying up the river, and inundating the plains on either side. Estimates which have been made as to the volume of this flow appear to indicate that it may have amounted to more than the bulk of the Mont Blanc. This great eruption, by the direct effect of the calamity, and by the famine due to the ravaging of the fields and the frightening of the fish from the shores which it induced, destroyed nearly one fifth of the Icelandic people. It is, in fact, to be remembered as one of the three or four most calamitous eruptions of which we have any account, and, from the point of view of lava flow, the greatest in history. Just a hundred years after the great Skaptar eruption, which darkened the skies of Europe, the island of Krakatoa, an isle formed by a small volcano in the straits of Java, was the seat of a vapour explosion which from its intensity is not only unparalleled, but almost unapproached in all accounts of such disturbances. Krakatoa had long been recognised as a volcanic isle; it is doubtful, however, if it had ever been seen in eruption during the three centuries or more since European ships began to sail by it until the month of May of the year above mentioned. Then an outbreak of what may be called ordinary violence took place, which after a few days so far ceased that observers landed and took account of the changes which the convulsion had brought about. For about three months there were no further signs of activity, but on the 29th of August a succession of vast explosions took place, which blew away a great part of the island, forming in its place a submarine crater two or three miles in diameter, creating world-wide disturbances of sea and air. The sounds of the outbreak were heard at a distance of sixteen hundred miles away. The waves of the air attendant on the explosion ran round the earth at least once, as was distinctly indicated by the self-recording barometers; it is possible, indeed, that, crossing each other in their east and west courses, these atmospheric tides twice girdled the sphere. In effect, the air over the crater was heaved up to the height of some tens of thousands of feet, and thence rolled off in great circular waves, such as may be observed in a pan of milk when a sharp blow pushes the bottom upward. The violent stroke delivered to the waters of the sea created a vast wave, which in the region where it originated rolled upon the shores with a surf wall fifty or more feet high. In a few minutes about thirty thousand people were overwhelmed. The wave rolled on beyond its destructive limits much in the manner of the tide; its influence was felt in a sharp rise and fall of the waters as far as the Pacific coast of North America, and was indicated by the tide gauges in the Atlantic as far north as the coast of Europe. Owing to the violence of the eruption, Krakatoa poured forth no lava, but the dust and ashes which ascended into the air--or, in other words, the finely divided lava which escaped into the atmosphere--probably amounted in bulk to more than twenty cubic miles. The coarser part of this material, including much pumice, fell upon the seas in the vicinity, where, owing to its lightness, it was free to drift in the marine currents far and wide throughout the oceanic realm. The finer particles, thrown high into the air, perhaps to the height of nearly a hundred thousand feet--certainly to the elevation of more than half this amount--drifted far and wide in the atmosphere, so that for years the air of all regions was clouded by it, the sunrise and sunset having a peculiar red glow, which the dust particles produce by the light which they reflect. In this period, at all times when the day was clear, the sun appeared to be surrounded by a dusky halo. In time the greater part of this dust was drawn down by gravity, some portion of it probably falling on every square foot of the earth. Since the disappearance of the characteristic phenomena which it produced in the atmosphere, European observers have noted the existence of faint clouds lying in the upper part of the air at the height of a hundred miles or more above the surface. These clouds, which were at first distinctly visible in the earliest stage of dawn and in the latest period of the sunset glow, seemed to be in rapid motion to the eastward, and to be mounting higher above the earth. It has been not unreasonably supposed that these shining clouds represent portions of the finest dust from Krakatoa, which has been thrown so far above the earth's attraction that it is separating itself from the sphere. If this view be correct, it seems likely that we may look to great volcanic explosions as a source whence the dustlike particles which people the celestial spaces may have come. They may, in a word, be due to volcanic explosions occurring on this and other celestial spheres. The question suggested above as to the possibility of volcanic ejections throwing matter from the earth beyond the control of its gravitative energy is one of great scientific interest. Computations (not altogether trustworthy) show that a body leaving the earth's surface under the conditions of a cannon ball fired vertically upward would have to possess a velocity at the start of at least seven miles a second in order to go free into space. It would at first sight seem that we should be able to reckon whether volcanoes can propel earth matter upward with this speed. In fact, however, sufficient data are not obtainable; we only know in a general way that the column of vapour rises to the height of thirty or forty thousand feet, and this in eruptions of no great magnitude. In an accident such as that at Krakatoa, even if an observer were near enough to see clearly what was going on, the chance of his surviving the disturbance would be small. Moreover, the ascending vapours, owing to their expansion of the steam in the column, begin to fly out sideways on its periphery, so that the upper part of the central section in the discharge is not visible from the earth. It is in the central section of the uprushing mass, if anywhere, that the dust might attain the height necessary to put it beyond the earth's attraction, bringing it fairly into the realm of the solar system, or to the position where its own motion and the attraction of the other spheres would give it an independent orbital movement about the sun, or perhaps about the earth. We can only say that observations on the height of volcanic ejections are extremely desirable; they can probably only be made from a balloon. An ascension thus made beyond the cloud disk which the eruption produces might bring the observer where he could discern enough to determine the matter. Although the movements of the rocky particles could not be observed, the colour which they would give to the heavens might tell the story which we wish to know. There is evidence that large masses of stone hurled up by volcanic eruption have fallen seven miles from the base of the cone. Assuming that the masses went straight upward at the beginning of their ascent, and that they were afterward borne outwardly by the expansion of the column, computations which have a general but no absolute value appear to indicate that the masses attained a height of from thirty to fifty miles, and had an initial velocity which, if doubled, might have carried them into space. Last of all, we shall note the conditions which attend the eruptions of submarine volcanoes. Such explosions have been observed in but a few instances, and only in those cases where there is reason to believe that the crater at the time of its explosion had attained to within a few hundred feet of the sea level. In these cases the ejections, never as yet observed in the state of lava, but in the condition of dust and pumice, have occasionally formed a low island, which has shortly been washed away by the waves. Knowing as we do that volcanoes abound on the sea floor, the question why we do not oftener see their explosions disturbing the surface of the waters is very interesting, but not as yet clearly explicable. It is possible, however, that a volcanic discharge taking place at the depth of several thousand feet below the surface of the water would not be able to blow the fluid aside so as to open a pipe to the surface, but would expend its energy in a hidden manner near the ocean floor. The vapours would have to expand gradually, as they do in passing up through the rock pipe of a volcano, and in their slow upward passage might be absorbed by the water. The solid materials thrown forth would in this case necessarily fall close about the vent, and create a very steep cone, such, indeed, as we find indicated by the soundings off certain volcanic islands which appear only recently to have overtopped the level of the waters. As will be seen, though inadequately from the diagrams of Vesuvius, volcanic cones have a regularity and symmetry of form far exceeding that afforded by the outlines of any other of the earth's features. Where, as is generally the case, the shape of the cone is determined by the distribution of the falling cinders or divided lava which constitutes the mass of most cones, the slope is in general that known as a catenary curve--i.e., the line formed by a chain hanging between two points at some distance from the vertical. It is interesting to note that this graceful outline is a reflection or consequence of the curve described by the uprushing vapour. The expansion in the ascending column causes it to enlarge at a somewhat steadfast rate, while the speed of the ascent is ever diminishing. Precisely the same action can be seen in the like rush of steam and other gases and vapours from the cannon's mouth; only in the case of the gun, even of the greatest size, we can not trace the movement for more than a few hundred feet. In this column of ejection the outward movement from the centre carries the bits of lava outwardly from the centre of the shaft, so that when they lose their ascending velocity they are drawn downward upon the flanks of the cone, the amount falling upon each part of that surface being in a general way proportional to the thickness of the vaporous mass from which they descend. The result is, that the thickest part of the ash heap is formed on the upper part of the crater, from which point the deposit fades away in depth in every direction. In a certain measure the concentration toward the centre of the cone is brought about by the draught of air which moves in toward the ascending column. Although, in general, ejections of volcanic matter take place through cones, that being the inevitable form produced by the escaping steam, very extensive outpourings of lava, ejections which in mass probably far exceed those thrown forth through ordinary craters, are occasionally poured out through fissures in the earth's crust. Thus in Oregon, Idaho, and Washington, in eastern Europe, in southern India, and at some other points, vast flows, which apparently took place from fissures, have inundated great realms with lava ejections. The conditions which appear to bring about these fissure eruptions of lava are not yet well understood. A provisional and very probable account of the action can be had in the hypothesis which will now be set forth. Where any region has been for a long time the seat of volcanic action, it is probable that a large amount of rock in a more or less fluid condition exists beneath its surface. Although the outrushing steam ejects much of this molten material, there are reasons to suppose that a yet greater part lies dormant in the underground spaces. Thus in the case of Ætna we have seen that, though some thousands of miles of rock matter have come forth, the base of the cone has been uplifted, probably by the moving to that region of more or less fluid rock. If now a region thus underlaid by what we may call incipient lavas is subjected to the peculiar compressive actions which lead to mountain-building, we should naturally expect that such soft material would be poured forth, possibly in vast quantities through fault fissures, which are so readily formed in all kinds of rock when subject to irregular and powerful strains, such as are necessarily brought about when rocks are moved in mountain-making. The great eruptions which formed the volcanic table-lands on the west coast of North America appear to have owed the extrusion of their materials to mountain-building actions. This seems to have been the case also in some of those smaller areas where fissure flows occur in Europe. It is likely that this action will explain the greater part of these massive eruptions. It need not be supposed that the rock beneath these countries, which when forced out became lava, was necessarily in the state of perfect fluidity before it was forced through the fissures. Situated at great depth in the earth, it was under a pressure so great that its particles may have been so brought together that the material was essentially solid, though free to move under the great strains which affected it, and acquiring temperature along with the fluidity which heat induces as it was forced along by the mountain-building pressure. As an illustration of how materials may become highly heated when forced to move particle on particle, it may be well to cite the case in which the iron stringpiece on top of a wooden dam near Holyoke, Mass., was affected when the barrier went away in a flood. The iron stringer, being very well put together, was, it is said, drawn out by the strain until it became sensibly reddened by the motion of its particles, and finally fell hissing into the waters below. A like heating is observable when metal is drawn out in making wire. Thus a mass of imperfectly fluid rock might in a forced journey of a few miles acquire a decided increase of temperature. Although the most striking volcanic action--all such phenomena, indeed, as commonly receives the name--is exhibited finally on the earth's surface, a great deal of work which belongs in the same group of geological actions is altogether confined to the deep-lying rock, and leads to the formation of dikes which penetrate the strata, but do not rise to the open air. We have already noted the fact that dikes abound in the deeper parts of volcanic cones, though the fissures into which they find their way are seldom riven up to the surface. In the same way beneath the ground in non-volcanic countries we may discover at a great depth in the older, much-changed rock a vast number of these crevices, varying from a few inches to a hundred feet or more in width, which have been filled with lavas, the rock once molten having afterward cooled. In most cases these dikes are disclosed to us through the down-wearing of the earth that has removed the beds into which the dikes did not penetrate, thus disclosing the realm in which the disturbances took place. Where, as is occasionally the case in deep mines, or on some bare rocky cliff of great height, we can trace a dike in its upward course through a long distance, we find that we can never distinctly discover the lower point of its extension. No one has ever seen in a clear way the point of origin of such an injection. We can, however, often follow it upward to the place where there was no longer a rift into which it could enter. In its upward path the molten matter appears generally to have followed some previously existing fracture, a joint plane or a fault, which generally runs through the rocks on those planes. We can observe evidence that the material was in the state of igneous fluidity by the fact that it has baked the country rocks on either side of the fissure, the amount of baking being in proportion to the width of the dike, and thus to the amount of heat which it could give forth. A dike six inches in diameter will sometimes barely sear its walls, while one a hundred feet in width will often alter the strata for a great distance on either side. In some instances, as in the coal beds near Richmond, Va., dikes occasionally cut through beds of bituminous coal. In these cases we find that the coal has been converted into coke for many feet either side of a considerable injection. The fact that the dike material was molten is still further shown by the occurrence in it of fragments which it has taken up from the walls, and which may have been partly melted, and in most cases have clearly been much heated. Where dikes extend up through stratified beds which are separated from each other by distinct layers, along which the rock is not firmly bound together, it now and then happens, as noted by Mr. G.K. Gilbert, of the United States Geological Survey, that the lava has forced its way horizontally between these layers, gradually uplifting the overlying mass, which it did not break through, into a dome-shaped elevation. These side flows from dikes are termed laccolites, a word which signifies the pool-like nature of the stony mass which they form between the strata. In many regions, where the earth has worn down so as to reveal the zone of dikes which was formed at a great depth, the surface of the country is fairly laced with these intrusions. Thus on Cape Ann, a rocky isle on the east coast of Massachusetts, having an area of about twenty square miles, the writer, with the assistance of his colleague, Prof. R.S. Tarr, found about four hundred distinct dikes exhibited on the shore line where the rocks had been swept bare by the waves. If the census of these intrusions could have been extended over the whole island, it would probably have appeared that the total number exceeded five thousand. In other regions square miles can be found where the dikes intercepted by the surface occupy an aggregate area greater than that of the rocks into which they have been intruded. Now and then, but rarely, the student of dikes finds one where the bordering walls, in place of having the clean-cut appearance which they usually exhibit, has its sides greatly worn away and much melted, as if by the long-continued passage of the igneous fluid through the crevice. Such dikes are usually very wide, and are probably the paths through which lavas found their way to the surface of the earth, pouring forth in a volcanic eruption. In some cases we can trace their relation to ancient volcanic cones which have worn down in all their part which were made up of incoherent materials, so that there remains only the central pipe, which has been preserved from decay by the coherent character of the lava which filled it. The hypothesis that dikes are driven upward into strata by the pressure of the beds which overlie materials hot and soft enough to be put in motion when a fissure enters them, and that their movement upward through the crevice is accounted for by this pressure, makes certain features of these intrusions comprehensible. Seeing that very long, slender dikes are found penetrating the rock, which could not have had a high temperature, it becomes difficult to understand how the lava could have maintained its fluidity; but on the supposition that it was impelled forward by a strong pressure, and that the energy thus transmitted through it was converted into heat, we discover a means whereby it could have been retained in the liquid condition, even when forced for long distances through very narrow channels. Moreover, this explanation accounts for the fact which has long remained unexplained that dikes, except those formed about volcanic craters, rarely, if ever, rise to the surface. The materials contained in dikes differ exceedingly in their chemical and mineral character. These variations are due to the differences in Nature of the deposits whence they come, and also in a measure to exchanges which take place between their own substance and that of the rocks between which they are deposited. This process often has importance of an economic kind, for it not infrequently leads to the formation of metalliferous veins or other aggregations of ores, either in the dike itself or in the country rock. The way in which this is brought about may be easily understood by a familiar example. If flesh be placed in water which has the same temperature, no exchange of materials will take place; but if the water be heated, a circulation will be set up, which in time will bring a large part of the soluble matter into the surrounding water. This movement is primarily dependent on differences of temperature, and consequently differences in the quantity of soluble substances which the water seeks to take up. When a dike is injected into cooler rocks, such a slow circulation is induced. The water contained in the interstices of the stone becomes charged with mineral materials, if such exist in positions where it can obtain possession of them, and as cooling goes on, these dissolved materials are deposited in the manner of veins. These veins are generally laid down on the planes of contact between the two kinds of stone, but they may be formed in any other cavities which exist in the neighbourhood. The formation of such veins is often aided by the considerable shrinkage of the lava in the dike, which, when it cools, tends to lose about fifteen per cent of its volume, and is thus likely to leave a crevice next the boundary walls. Ores thus formed afford some of the commonest and often the richest mineral deposits. At Leadville, in Colorado, the great silver-bearing lodes probably were produced in this manner, wherein lavas, either those of dikes or those which flowed in the open air, have come in contact with limestones. The mineral materials originally in the once molten rock or in the limy beds was, we believe, laid down on ancient sea floors in the remains of organic forms, which for their particular uses took the materials from the old sea water. The vein-making action has served to assemble these scattered bits of metal into the aggregation which constitutes a workable deposit. In time, as the rocks wear down, the materials of the veins are again taken into solution and returned to the sea, thence perhaps to tread again the cycle of change. In certain dikes, and sometimes also, perhaps, in lavas known as basalts, which have flowed on the surface, the rock when cooling, from the shrinkage which then occurs, has broken in a very regular way, forming hexagonal columns which are more or less divided on their length by joints. When worn away by the agencies of decay, especially where the material forms steep cliffs, a highly artificial effect is produced, which is often compared, where cut at right angles to the columns, to pavements, or, where the division is parallel to the columns, to the pipes of an organ. What we know of dikes inclines us to the opinion that as a whole they represent movements of softened rock where the motion-compelling agent is not mainly the expansion of the contained water which gives rise to volcanic ejection, but rather in large part due to the weight of superincumbent strata setting in motion materials which were somewhat softened, and which tended to creep, as do the clays in deep coal mines. It is evident, however; it is, moreover, quite natural, that dike work is somewhat mingled with that produced by the volcanic forces; but while the line between the two actions is not sharp, the discrimination is important, and occurs with a distinctness rather unusual on the boundary line between two adjacent fields of phenomena. * * * * * We have now to consider the general effects of the earth's interior heat so far as that body of temperature tends to drive materials from the depths of the earth to the surface. This group of influences is one of the most important which operates on our sphere; as we shall shortly see, without such action the earth would in time become an unfit theatre for the development of organic life. To perceive the effect of these movements, we must first note that in the great rock-constructing realm of the seas organic life is constantly extracting from the water substances, such as lime, potash, soda, and a host of other substances necessary for the maintenance of high-grade organisms, depositing these materials in the growing strata. Into these beds, which are buried as fast as they form, goes not only these earthy materials, but a great store of the sea water as well. The result would be in course of time a complete withdrawal into the depths of the earth of those substances which play a necessary part in organic development. The earth would become more or less completely waterless on its surface, and the rocks exposed to view would be composed mainly of silica, the material which to a great extent resists solution, and therefore avoids the dissolving which overtakes most other kinds of rocks. Here comes in the machinery of the hot springs, the dikes, and the volcanoes. These agents, operating under the influence of the internal heat of the earth, are constantly engaged in bearing the earthy matter, particularly its precious more solvent parts, back to the surface. The hot springs and volcanoes work swiftly and directly, and return the water, the carbon dioxide, and a host of other vaporizable and soluble and fusible substances to the realm of solar activity, to the living surface zone of the earth. The dikes operate less immediately, but in the end to the same effect. They lift their materials miles above the level where they were originally laid, probably from a zone which is rarely if ever exposed to view, placing them near the surface, where the erosive agents can readily find access to them. Of the three agents which serve to export earth materials from its depths, volcanoes are doubtless the most important. They send forth the greater part of the water which is expelled from the rocks. Various computations which the writer has made indicate that an ordinary volcano, such as Ætna, in times of most intense explosion, may send forth in the form of steam one fourth of a cubic mile or more of water during each day of its discharge, and in a single great eruption may pour forth several times this quantity. In its history Ætna has probably returned to the atmosphere some hundred cubic miles of water which but for the process would have remained permanently locked up in its rock prison. The ejection of rock material, though probably on the average less in quantity than the water which escapes, is also of noteworthy importance. The volcanoes of Java and the adjacent isles have, during the last hundred and twenty years, delivered to the seas more earth material than has been carried into those basins by the great rivers. If we could take account of all the volcanic ejections which have occurred in this time, we should doubtless find that the sum of the materials thus cast forth into the oceans was several times as great as that which was delivered from the lands by all the superficial agents which wear them away. Moreover, while the material from the land, except the small part which is in a state of complete solution, all falls close to the shore, the volcanic waste, because of its fine division or because of the blebs of air which its masses contain, may float for many years before it finds its way to the bottom, it may be at the antipodes of the point at which it came from the earth. While thus journeying through the sea the rock matter from the volcanoes is apt to become dissolved in water; it is, indeed, doubtful if any considerable part of that which enters the ocean goes by gravitation to its floor. The greater portion probably enters the state of solution and makes its way thence through the bodies of plants and animals again into the ponderable state. If an observer could view the earth from the surface of the moon, he would probably each day behold one of these storms which the volcanoes send forth. In the fortnight of darkness, even with the naked eye, it would probably be possible to discern at any time several eruptions, some of which would indicate that the earth's surface was ravaged by great catastrophes. The nearer view of these actions shows us that although locally and in small measure they are harmful to the life of the earth, they are in a large way beneficent. CHAPTER VIII. THE SOIL. The frequent mention which it has been necessary to make of soil phenomena in the preceding chapters shows how intimately this feature in the structure of the earth is blended with all the elements of its physical history. It is now necessary for us to take up the phenomena of soils in a consecutive manner. The study of any considerable river basin enables us to trace the more important steps which lead to the destructure and renovation of the earth's detrital coating. In such an interpretation we note that everywhere the rocks which were built on the sea bottom, and more or less made over in the great laboratory of the earth's interior, are at the surface, when exposed to the conditions of the atmosphere, in process of being taken to pieces and returned to the sea. This action goes on everywhere; every drop of rain helps it. It is aided by frost, or even by the changes of expansion and contraction which occur in the rocks from variations of heat. The result is that, except where the slopes are steep, the surface is quickly covered with a layer of fragments, all of which are in the process of decay, and ready to afford some food to plants. Even where the rock appears bare, it is generally covered with lichens, which, adhering to it, obtain a share of nutriment from the decayed material which they help to hold on the slope. When they have retained a thin sheet of the _débris_, mosses and small flowering plants help the work of retaining the detritus. Soon the strong-rooted bushes and trees win a foothold, and by sending their rootlets, which are at first small but rapidly enlarge, into the crevices, they hasten the disruption of the stones. If the construction of soil goes on upon a steep cliff, the quantity retained on the slope may be small, but at the base we find a talus, composed of the fragments not held by the vegetation, which gradually increases as the cliff wears down, until the original precipice may be quite obliterated beneath a soil slope. At first this process is rapid; it becomes gradually slower and slower as the talus mounts up the cliff and as the cliff loses its steepness, until finally a gentle slope takes the place of the steep. From the highest points in any river valley to the sea level the broken-up rock, which we term soil, is in process of continuous motion. Everywhere the rain water, flowing over the surface or soaking through the porous mass, is conveying portions of the material which is taken into solution in a speedy manner to the sea. Everywhere the expansion of the soil in freezing, or the movements imposed on it by the growth of roots, by the overturning of trees, or by the innumerable borings and burrowings which animals make in the mass, is through the action of gravitation slowly working down the slope. Every little disturbance of the grains or fragments of the soil which lifts them up causes them when they fall to descend a little way farther toward the sea level. Working toward the streams, the materials of the soil are in time delivered to those flowing waters, and by them urged speedily, though in most cases interruptedly, toward the ocean. There is another element in the movement of the soils which, though less appreciable, is still of great importance. The agents of decay which produce and remove the detritus, the chemical changes of the bed rock, and the mechanical action which roots apply to them, along with the solutional processes, are constantly lowering the surface of the mass. In this way we can often prove that a soil continuously existing has worked downward through many thousand feet of strata. In this process of downgoing the country on which the layer rests may have greatly changed its form, but the deposit, under favourable conditions, may continue to retain some trace of the materials which it derived from beds which have long since disappeared, their position having been far up in the spaces now occupied by the air. Where the slopes are steep and streams abound, we rarely find detritus which belonged in rock more than a hundred feet above the present surface of the soil. Where, however, as on those isolated table-lands or buttes which abound in certain portions of the Mississippi Valley, as well as in many other countries, we find a patch of soil lying on a nearly level surface, which for geologic ages has not felt the effect of streams, we may discover, commingled in the _débris_, the harder wreckage derived from the decay of a thousand feet or more of vanished strata. When we consider the effect of organic life on the processes which go on in the soil, we first note the large fact that the development of all land vegetation depends upon the existence of this detritus--in a word, on the slow movement of the decaying rocky matter from the point where it is disrupted to its field of rest in the depths of the sea. The plants take their food from the portion of this rocky waste which is brought into solution by the waters which penetrate the mass. On the plants the animals feed, and so this vast assemblage of organisms is maintained. Not only does the land life maintain itself on the soil, and give much to the sea, but it serves in various ways to protect this detrital coating from too rapid destruction, and to improve its quality. To see the nature of this work we should visit a region where primeval forests still lie upon the slopes of a hilly region. In the body of such a wood we find next the surface a coating of decayed vegetable matter, made up of the falling leaves, bark, branches, and trunks which are constantly descending to the earth. Ordinarily, this layer is a foot or more in thickness; at the top it is almost altogether composed of vegetable matter; at the bottom it verges into the true soil. An important effect of this decayed vegetation is to restrain the movement of the surface water. Even in the heaviest rains, provided the mass be not frozen, the water is taken into it and delivered in the manner of springs to the larger streams. We can better note the measure of this effect by observing the difference in the ground covered by this primeval forest and that which we find near by which has been converted into tilled fields. With the same degree of rapidity in the flow, the distinct stream channels on the tilled ground are likely to be from twenty to a hundred times in length what they are on the forest bed. The result is that while the brook which drains the forested area maintains a tolerably constant flow of clean water, the other from the tilled ground courses only in times of heavy rain, and then is heavily charged with mud. In the virgin conditions of the soil the downwear is very slow; in its artificial state this wearing goes on so rapidly that the sloping fields are likely to be worn to below the soil level in a few score years. Not only does the natural coating of vegetation, such as our forests impose upon the country, protect the soil from washing away, but the roots of the larger plants are continually at work in various ways to increase the fertility and depth of the stratum. In the form of slender fibrils these underground branches enter the joints and bed planes of the rock, and there growing they disrupt the materials, giving them a larger surface on which decay may operate. These bits, at first of considerable size, are in turn broken up by the same action. Where the underlying rocks afford nutritious materials, the branches of our tap-rooted trees sometimes find their way ten feet or more below the base of the true soil. Not only do they thus break up the stones, but the nutrition which they obtain in the depths is brought up and deposited in the parts above the ground, as well as in the roots which lie in the true soil, so that when the tree dies it becomes available for other plants. Thus in the forest condition of a country the amount of rock material contributed to the deposit in general so far exceeds that which is taken away to the rivers by the underground water as to insure the deepening of the soil bed to the point where only the strongest roots--those belonging to our tap-rooted trees--can penetrate through it to the bed rocks. Almost all forests are from time to time visited by winds which uproot the trees. When they are thus rent from the earth, the underground branches often form a disk containing a thick tangle of stones and earth, and having a diameter of ten or fifteen feet. The writer has frequently observed a hundred cubic feet of soil matter, some of it taken from the depth of a yard or more, thus uplifted into the air. In the path of a hurricane or tornado we may sometimes find thousands of acres which have been subjected to this rude overturning--a natural ploughing. As the roots rot away, the _débris_ which they held falls outside of the pit, thus forming a little hillock along the side of the cavity. After a time the thrusting action of other roots and the slow motion of the soil down the slope restore the surface from its hillocky character to its original smoothness; but in many cases the naturalist who has learned to discern with his feet may note these irregularities long after it has been recovered with the forest. Great as is the effect of plants on the soil, that influence is almost equalled by the action of the animals which have the habit of entering the earth, finding there a temporary abiding place. The number of these ground forms is surprisingly great. It includes, indeed, a host of creatures which are efficient agents in enriching the earth. The species of earthworms, some of which occupy forested districts as well as the fields, have the habit of passing the soil material through their bodies, extracting from the mass such nutriment as it may contain. In this manner the particles of mineral matter become pulverized, and in a measure affected by chemical changes in the bodies of the creatures, and are thus better fitted to afford plant food. Sometimes the amount of the earth which the creatures take in in moving through their burrows and void upon the surface is sufficient to form annually a layer on the surface of the ground having a depth of one twentieth of an inch or more. It thus may well happen that the soil to the depth of two or three feet is completely overturned in the course of a few hundred years. As the particles which the creatures devour are rather small, the tendency is to accumulate the finer portions of the soil near the surface of the earth, where by solution they may contribute to the needs of the lowly plants. It is probably due to the action of these creatures that small relics of ancient men, such as stone tools, are commonly found buried at a considerable depth beneath the earth, and rarely appear upon the surface except where it has been subjected to deep ploughing or to the action of running streams. Along with the earthworms, the ants labour to overturn the soil; frequently they are the more effective of the two agents. The common species, though they make no permanent hillocks, have been observed by the writer to lay upon the surface each year as much as a quarter of an inch of sand and other fine materials which they have brought up from a considerable depth. In many regions, particularly in those occupied by glacial drift, and pebbly alluvium along the rivers, the effect of this action, like that of earthworms, is to bring to the surface the finer materials, leaving the coarser pebbles in the depths. In this way they have changed the superficial character of the soil over great areas; we may say, indeed, over a large part of the earth, and this in a way which fits it better to serve the needs of the wild plants as well as the uses of the farmer. Many thousand species of insects, particularly the larger beetles, have the habit of passing their larval state in the under earth. Here they generally excavate burrows, and thus in a way delve the soil. As many of them die before reaching maturity, their store of organic matter is contributed to the mass, and serves to nourish the plants. If the student will carefully examine a section of the earth either in its natural or in its tilled state, he will be surprised to find how numerous the grubs are. They may often be found to the number of a score or more of each cubic foot of material. Many of the species which develop underground come from eggs which have carefully been encased in organic matter before their deposition in the earth. Thus some of the carrion beetles are in the habit of laying their eggs in the bodies of dead birds or field mice, which they then bury to the depth of some inches in the earth. In this way nearly all the small birds and mammals of our woods disappear from view in a few hours after they are dead. Other species make balls from the dung of cattle in which they lay their eggs, afterward rolling the little spheres, it may be for hundreds of feet, to the chambers in the soil which they have previously prepared. In this way a great deal of animal matter is introduced into the earth, and contributes to its fertility. Many of our small mammals have the habit of making their dwelling places in the soil. Some of them, such as the moles, normally abide in the subterranean realm for all their lives. Others use the excavations as places of retreat. In any case, these excavations serve to move the particles of the soil about, and the materials which the animals drag into the earth, as well as the excrement of the creatures, act to enrich it. This habit of taking food underground is not limited to the mammals; it is common with the ants, and even the earthworms, as noted by Charles Darwin in his wonderful essay on these creatures, are accustomed to drag into their burrows bits of grass and the slender leaves of pines. It is not known what purpose they attain by these actions, but it is sufficiently common somewhat to affect the conditions of the soil. The result of these complicated works done by animals and plants on the soil is that the material to a considerable depth are constantly being supplied with organic matter, which, along with the mineral material, constitutes that part of the earth which can support vegetation. Experiment will readily show that neither crushed rock nor pure vegetable mould will of itself serve to maintain any but the lowliest vegetation. It requires that the two materials be mixed in order that the earth may yield food for ordinary plants, particularly for those which are of use to man, as crops. On this account all the processes above noted whereby the waste of plant and animal life is carried below the surface are of the utmost importance in the creation and preservation of the soil. It has been found, indeed, in almost all cases, necessary for the farmer to maintain the fertility of his fields to plough-in quantities of such organic waste. By so doing he imitates the work which is effected in virgin soil by natural action. As the process is costly in time and material, it is often neglected or imperfectly done, with the result that the fields rapidly diminish in fertility. The way in which the buried organic matter acts upon the soil is not yet thoroughly understood. In part it accomplishes the results by the materials which on its decay it contributes to the soil in a state in which they may readily be dissolved and taken up by the roots into their sap; in part, however, it is believed that they better the conditions by affording dwelling places for a host of lowly species, such as the forms which are known as bacteria. The organisms probably aid in the decomposition of the mineral matter, and in the conversion of nitrogen, which abounds in the air or the soil, into nitrates of potash and soda--substances which have a very great value as fertilizers. Some effect is produced by the decay of the foreign matter brought into the soil, which as it passes away leaves channels through which the soil water can more readily pass. By far the most general and important effect arising from the decay of organic matter in the earth is to be found in the carbon dioxide which is formed as the oxygen of the air combines with the carbon which all organic material contains. As before noted, water thus charged has its capacity for taking other substances into solution vastly increased, and on this solvent action depends in large part the decay of the bed rocks and the solution of materials which are to be appropriated by the plants. Having now sketched the general conditions which lead to the formation of soils, we must take account of certain important variations in their conditions due to differences in the ways in which they are formed and preserved. These matters are not only of interest to the geologist, but are of the utmost importance to the life of mankind, as well as all the lower creatures which dwell upon the lands. First, we should note that soils are divisible into three great groups, which, though not sharply parted from each other, are sufficiently peculiar for the purposes of classification. Where the earth material has been derived from the rocks which nearly or immediately underlie it, we have a group of soils which may be entitled those of immediate derivation--that is, derived from rocks near by, or from beds which once overlaid the level and have since been decayed away. Next, we have alluvial soils, those composed of materials which have been transported by streams, commonly from a great distance, and laid down on their flood plains. Third, the soils the mineral matters of which have been brought into their position by the action of glaciers; these in a way resemble those formed by rivers, but the materials are generally imperfectly sorted, coarse and fine being mingled together. Last of all, we have the soils due to the accumulation of blown dust or blown sand, which, unlike the others, occupy but a small part of the land surface. It would be possible, indeed, to make yet another division, including those areas which when emerging from the sea were covered with fine, uncemented detritus ready at once to serve the purposes of a soil. Only here and there, and but seldom, do we find soils of this nature. It is characteristic of soils belonging to the group to which we have given the title of immediate derivation that they have accumulated slowly, that they move very gradually down the slopes on which they lie, and that in all cases they represent, with a part of their mass at least, levels of rock which have disappeared from the region which they occupied. The additions made to their mass are from below, and that mass is constantly shrinking, generally at a pretty rapid rate, by the mineral matter which is dissolved and goes away with the spring water. They also are characteristically thin on steep slopes, thickening toward the base of the incline, where the diminished grade permits the soil to move slowly, and therefore to accumulate. In alluvial soils we find accumulations which are characterized by growth on their upper surfaces, and by the distant transportation of the materials of which they are composed. In these deposits the outleaching removes vast amounts of the materials, but so long as the floods from time to time visit their surfaces the growth of the deposits is continued. This growth rarely takes place from the waste of the bed rocks on which the alluvium lies. It is characteristic of alluvial soils that they are generally made up of _débris_ derived from fields where the materials have undergone the change which we have noted in the last paragraph; therefore these latter deposits have throughout the character which renders the mineral materials easily dissolved. Moreover, the mass as it is constructed is commonly mingled with a great deal of organic waste, which serves to promote its fertility. On these accounts alluvial grounds, though they vary considerably in fertility, commonly afford the most fruitful fields of any region. They have, moreover, the signal advantage that they often may be refreshed by allowing the flood waters to visit them, an action which but for the interference of man commonly takes place once each year. Thus in the valley of the Nile there are fields which have been giving rich grain harvests probably for more than four thousand years, without any other effective fertilizing than that derived from the mud of the great river. The group of glaciated soils differs in many ways from either of those mentioned. In it we find the mineral matter to have been broken up, transported, and accumulated without the influence of those conditions which ordinarily serve to mix rock _débris_ with organic matter during the process by which it is broken into bits. When vegetation came to preoccupy the fields made desolate by glacial action, it found in most places more than sufficient material to form soils, but the greater part of the matter was in the condition of pebbles of very hard rock and sand grains, fragments of silex. Fortunately, the broken-up state of this material, by exposing a great surface of the rocky matter to decay, has enabled the plants to convert a portion of the mass into earth fit for the uses of their roots. But as the time which has elapsed since the disappearance of the glaciers is much less than that occupied in the formation of ordinary soil, this decay has in most cases not yet gone very far, so that in a cubic foot of glaciated waste the amount of material available for plants is often only a fraction of that held in the soils of immediate derivation. In the greater portion of the fields occupied by glacial waste the processes which lead to the introduction of organic matter into the earth have not gone far enough to set in effective work the great laboratory which has to operate in order to give fertile soil. The pebbles hinder the penetration of the roots as well as the movement of insects and other animals. There has not been time enough for the overturning of trees to bring about a certain admixture of vegetable matter with the soil--in a word, the process of soil-making, though the first condition, that of broken-up rock, has been accomplished, is as yet very incomplete. It needs, indeed, care in the introduction of organic matter for its completion. It is characteristic of glacial soils that they are indefinitely deep. This often is a disadvantageous feature, for the reason that the soil water may pass so far down into the earth that the roots are often deprived of the moisture which they need, and which in ordinary soils is retained near the surface by the hard underlayer. On the other hand, where the glacial waste is made up of pebbles formed from rocks of varied chemical composition, which contain a considerable share of lime, potash, soda, and other substances which are required by plants, the very large surface which they expose to decay provides the soil with a continuous enrichment. In a cubic foot of pebbly glacial earth we often find that the mass offers several hundred times as much surface to the action of decay as is afforded by the underlying solid bed rock from which a soil of immediate derivation has to win its mineral supply. Where the pebbly glacial waste is provided with a mixture of vegetable matter, the process of decay commonly goes forward with considerable rapidity. If the supply of such matter is large, such as may be produced by ploughing in barnyard manure or green crops, the nutritive value of the earth may be brought to a very high point. It is a familiar experience in regions where glacial soils exist that the earth beneath the swamps when drained is found to be extraordinarily well suited for farming purposes. On inspecting the pebbles from such places, we observe that they are remarkably decayed. Where the masses contain large quantities of feldspar, as is the case in the greater part of our granitic and other crystalline rocks, this material in its decomposition is converted into kaolin or feldspar clay, and gives the stones a peculiar white appearance, which marks the decomposition, and indicates the process by which a great variety of valuable soil ingredients are brought into a state where they may be available for plants. In certain parts of the glacial areas, particularly in the region near the margin of the ice sheet, where the glacier remained in one position for a considerable time, we find extensive deposits of silicious sand, formed of the materials which settled from the under-ice stream, near where they escaped from the glacial cavern. These kames and sand plains, because of the silicious nature of their materials and the very porous nature of the soil which they afford, are commonly sterile, or at most render a profit to the tiller by dint of exceeding care. Thus in Massachusetts, although the first settlers seized upon these grounds, and planted their villages upon them because the forests there were scanty and the ground free from encumbering boulders, were soon driven to betake themselves to those areas where the drift was less silicious, and where the pebbles afforded a share of clay. Very extensive fields of this sandy nature in southeastern New England have never been brought under tillage. Thus on the island of Martha's Vineyard there is a connected area containing about thirty thousand acres which lies in a very favourable position for tillage, but has been found substantially worthless for such use. The farmers have found it more advantageous to clear away the boulders from the coarser drift in order to win soil which would give them fair returns. Those areas which are occupied by soil materials which have been brought into their position by the action of the wind may, as regards their character, be divided into two very distinct groups--the dunes and loess deposits. In the former group, where, as we have noted (see page 123), the coarse sea sands or those from the shores of lakes are driven forward as a marching hillock, the grains of the material are almost always silicious. The fragments in the motion are not taken up into the air, but are blown along the surface. Such dune accumulations afford an earth which is even more sterile than that of the glacial sand plains, where there is generally a certain admixture of pebbles from rocks which by their decomposition may afford some elements of fertility. Fortunately for the interests of man, these wind-borne sands occupy but a small area; in North America, in the aggregate, there probably are not more than one thousand square miles of such deposits. Where the rock material drifted by the winds is so fine that it may rise into the air in the form of dust, the accumulations made of it generally afford a fertile soil, and this for the reason that they are composed of various kinds of rock, and not, as in the case of dunes, of nearly pure silica. In some very rare cases, where the seashore is bordered by coral reefs, as it is in parts of southern Florida, and the strand is made up of limestone bits derived from the hard parts which the polyps secrete, small dunes are made of limy material. Owing, however, in part to the relatively heavy nature of this substance, as well as to the rapid manner in which its grains become cemented together, such limestone dunes never attain great size nor travel any distance from their point of origin. As before noted, dust accumulations form the soil in extended areas which lie to the leeward of great deserts. Thus a considerable part of western China and much of the United States to the west of the Mississippi is covered by these wind-blown earths. Wherever the rainfall is considerable these loess deposits have proved to have a high agricultural value. Where a region has an earth which has recently passed from beneath the sea or a great lake, the surface is commonly covered by incoherent detritus which has escaped consolidation into hard rock by the fact that it has not been buried and thus brought into the laboratory of the earth's crust. When such a region becomes dry land, the materials are immediately ready to enter into the state of soil. They commonly contain a good deal of waste derived from the organic life which dwelt upon the sea bottom and was embedded in the strata as they were formed. Where these accumulations are made in a lake, the land vegetation at once possesses the field, even a single year being sufficient for it to effect its establishment. Where the lands emerge from the sea, it requires a few years for the salt water to drain away so that the earth can be fit for the uses of plants. In a general way these sea-bottom soils resemble those formed in the alluvial plains. They are, however, commonly more sandy, and their substances less penetrated by that decay which goes on very freely in the atmosphere because of the abundant supply of oxygen, and but slowly on the sea floor. Moreover, the marine deposits are generally made up in large part of silicious sand, a material which is produced in large quantities by the disruption of the rocks along the sea coast. The largest single field of these ocean-bottom soils of North America is found in the lowland region of the southern United States, a wide belt of country extending along the coast from the Rio Grande to New York. Although the streams have channelled shallow valleys in the beds of this region, the larger part of its surface still has the peculiar features of form and composition which were impressed upon it when it lay below the surface of the sea. Local variations in the character of the soil covering are exceedingly numerous, and these differences of condition profoundly affect the estate of man. We shall therefore consider some of the more important of these conditions, with special reference to their origin. The most important and distinctly marked variation in the fertility of soils is that which is produced by differences in the rainfall. No parts of the earth are entirely lacking in rain, but over considerable areas the precipitation does not exceed half a foot a year. In such realms the soil is sterile, and the natural coating of vegetation limited to those plants which can subsist on dew or which can take on an occasional growth at such times as moisture may come upon them. With a slight increase in precipitation, the soil rapidly increases in productivity, so that we may say that where as much as about ten inches of water enters the earth during the summer half of the year, it becomes in a considerable measure fit for agriculture. Observations indicate that the conditions of fertility are not satisfied where the rainfall is just sufficient to fill the pores of the soil; there must be enough water entering the earth to bring about a certain amount of outflow in the form of springs. The reason of this need becomes apparent when we study the evident features of those soils which, though from season to season charged with water, do not yield springs, but send the moisture away through the atmosphere. Wherever these conditions occur we observe that the soil in dry seasons becomes coated with a deposit of mineral matter, which, because of its taste, has received the name of alkali. The origin of this coating is as follows: The pores of the soil, charged from year to year with sufficient water to fill them, become stored with a fluid which contains a very large amount of dissolved mineral matter--too much, indeed, to permit the roots of plants, save a few species which have become accustomed to the conditions, to do their appointed work. In fact, this water is much like that of the sea, which the roots of only a few of our higher plants can tolerate. When the dry season comes on, the heat of the sun evaporates the water at the surface, leaving behind a coating composed of the substances which the water contains. The soil below acts in the manner of a lamp-wick to draw up fluid as rapidly as the heat burns it away. When the soil water is as far as possible exhausted, the alkali coating may represent a considerable part of the soluble matter of the soil, and in the next rainy season it may return in whole or in part to the under-earth, again to be drawn in the manner before described to the upper level. It is therefore only when a considerable share of the ground water goes forth to the streams in each year that the alkaline materials are in quantity kept down to the point where the roots of our crop-giving plants can make due use of the soil. Where, in an arid region, the ground can be watered from the enduring streams or from artificial reservoirs, the main advantage arising from the process is commonly found in the control which it gives the farmer in the amount of the soil water. He can add to the rainfall sufficient to take away the excess of mineral matter. When such soils are first brought under tillage it is necessary to use a large amount of water from the canals, in order to wash away the old store of alkali. After that a comparatively small contribution will often keep the soil in excellent condition for agriculture. It has been found, however, in the irrigated lands beside the Nile that where too much saving is practised in the irrigation, the alkaline coating will appear where it has been unknown before, and with it an unfitness of the earth to bear crops. Although the crust of mineral matters formed in the manner above described is characteristic of arid countries, and in general peculiar to them, a similar deposit may under peculiar conditions be formed in regions of great rainfall. Thus on the eastern coast of New England, where the tidal marshes have here and there been diked from the sea and brought under tillage, the dissolved mineral matters of the soil, which are excessive in quantity, are drawn to the surface, forming a coating essentially like that which is so common in arid regions. The writer has observed this crust on such diked lands, having a thickness of an eighth of an inch. In fact, this alkali coating represents merely the extreme operation of a process which is going on in all soils, and which contributes much to their fertility. When rain falls and passes downward into the earth, it conveys the soluble matter to a depth below the surface, often to beyond the point where our ordinary crop plants, such as the small grains, can have access to it, and this for the reason that their roots do not penetrate deeply. When dry weather comes and evaporation takes place from the surface, the fluid is drawn up to the upper soil layer, and there, in process of evaporation, deposits the dissolved materials which it contains. Thus the mineral matter which is fit for plant food is constantly set in motion, and in its movement passes the rootlets of the plants. It is probably on this account--at least in part--that very wet weather is almost as unfavourable to the farmer as exceedingly dry, the normal alternation in the conditions being, as is well known, best suited to his needs. So long as the earth is subjected to conditions in which the rainfall may bring about a variable amount of water in the superficial detrital layer, we find normal fruitful soils, though in their more arid conditions they may be fit for but few species of plants. When, by increasing aridity, we pass to conditions where there is no tolerably permanent store of water in the _débris_, the material ceases to have the qualities of a soil, and becomes mere rock waste. At the other extreme of the scale we pass to conditions where the water is steadfastly maintained in the interstices of the detritus, and there again the characteristic of the soil and its fitness for the uses of land vegetation likewise disappear. In a word, true soil conditions demand the presence of moisture, but that in insufficient quantities, to keep the pores of the earth continually filled; where they are thus filled, we have the condition of swamps. Between these extremes the level at which the water stands in the soil in average seasons is continually varying. In rainy weather it may rise quite to the surface; in a dry season it may sink far down. As this water rises and falls, it not only moves, as before noted, the soluble mineral materials, but it draws the air into and expels it from the earth with each movement. This atmospheric circulation of the soil, as has been proved by experiment, is of great importance in maintaining its fertility; the successive charges of air supply the needs of the microscopic underground creatures which play a large part in enriching the soil, and the direct effect of the oxygen in promoting decay is likewise considerable. A part of the work which is accomplished by overturning the earth in tillage consists in this introduction of the air into the pores of the soil, where it serves to advance the actions which bring mineral matters into solution. [Illustration: _Mountain gorge, Himalayas, India. Note the difference in the slope of the eroded rocks and the effect of erosion upon them; also the talus slopes at the base of the cliffs which the torrent is cutting away. On the left of the foreground there is a little bench showing a recent higher line of the water._] In the original conditions of any country which is the seat of considerable rainfall, and where the river system is not so far developed as to provide channels for the ready exit of the waters, we commonly find very extensive swamps; these conditions of bad drainage almost invariably exist where a region has recently been elevated above the level of the sea, and still retains the form of an irregular rolling plain common to sea floors, and also in regions where the work done by glaciers has confused the drainage which the antecedent streams may have developed. In an old, well-elaborated river system swamps are commonly absent, or, if they occur, are due to local accidents of an unimportant nature. For our purpose swamps may be divided into three groups--climbing bogs, lake bogs, and marine marshes. The first two of these groups depend on the movements of the rain water over the land; the third on the action of the tides. Beginning our account with the first and most exceptional of these groups, we note the following features in their interesting history: Wherever in a humid region, on a gentle slope--say with an inclination not exceeding ten feet to the mile--the soil is possessed by any species of plants whose stems grow closely together, so that from their decayed parts a spongelike mass is produced, we have the conditions which favour the development of climbing bogs. Beginning usually in the shores of a pool, these plants, necessarily of a water-loving species, retain so much moisture in the spongy mass which they form that they gradually extend up the slope. Thus extending the margin of their field, and at the same time thickening the deposit which they form, these plants may build a climbing bog over the surface until steeps are attained where the inclination is so great that the necessary amount of water can not be held in the spongy mass, or where, even if so held, the whole coating will in time slip down in the manner of an avalanche. The greater part of the climbing bogs of the world are limited to the moist and cool regions of high latitudes, where species of moss belonging to the genus _Sphagnum_ plentifully flourish. These plants can only grow where they are continuously supplied with a bath of water about their roots. They develop in lake bogs as far south as Mexico, but in the climbing form they are hardly traceable south of New England, and are nowhere extensively developed within the limits of the United States. In more northern parts of this continent, and in northwestern Europe, particularly in the moist climate of Ireland, climbing bogs occupy great areas, and hold up their lakes of interstitially contained water over the slopes of hills, where the surface rises at the rate of thirty feet or more to the mile. So long as the deposit of decayed vegetable matter which has accumulated in this manner is thin, therefore everywhere penetrated by the fibrous roots of the moss, it may continue to cling to its sloping bed; but when it attains a considerable thickness, and the roots in the lower part decay, the pulpy mass, water-laden in some time of heavy rain, break away in a vast torrent of thick, black mud, which may inundate the lower lands, causing widespread destruction. In more southern countries, other water-loving plants lead to the formation of climbing bogs. Of these, the commonest and most effective are the species of reeds, of which our Indian cane is a familiar example. Brakes of this vegetation, plentifully mingled with other species of aquatic growth, form those remarkable climbing bogs known as the Dismal and other swamps, which numerously occur along the coast line of the United States from southern Maryland to eastern Texas. Climbing bogs are particularly interesting, not only from the fact that they are eminently peculiar effects of plant growth, but because they give us a vivid picture of those ancient morasses in which grew the plants that formed the beds of vegetable matter now appearing in the state of coal. Each such bed of buried swamp material was, with rare exceptions, where the accumulation took place in lakes, gathered in climbing bogs such as we have described. Lake bogs occur in all parts of the world, but in their best development are limited to relatively high latitudes, and this for the reason that the plants which form vegetable matter grow most luxuriantly in cool climates and in regions where the level of the basin is subject to less variation than occurs in the alternating wet and dry seasons which exist in nearly all tropical regions. The fittest conditions are found in glaciated regions, where, as before noted, small lakes are usually very abundant. On the shores of one of these pools, of size not so great that the waves may attain a considerable height, or in the sheltered bay of a larger lake, various aquatic plants, especially the species of pond lilies, take root upon the bottom, and spread their expanded leaves on the surface of the water. These flexible-leaved and elastic-stemmed plants can endure waves which attain no more than a foot or two of height, and by the friction which they afford make the swash on the shore very slight. In the quiet water, rushes take root, and still further protect the strand, so that the very delicate vegetation of the mosses, such as the _Sphagnum_, can fix itself on the shore. As soon as the _Sphagnum_ mat has begun its growth, the strength given by its interlaced fibres enables it to extend off from the shore and float upon the water. In this way it may rapidly enlarge, if not broken up by the waves, so that its front advances into the lake at the rate of several inches each year. While growing outwardly it thickens, so that the bottom of the mass gradually works down toward the floor of the basin. At the same time the lower part of the sheet, decaying, contributes a shower of soft peat mud to the floor of the lake. In this way, growing at its edge, deepening, and contributing to an upgrowth from the bottom, a few centuries may serve entirely to fill a deep basin with peaty accumulation. In general, however, the surface of the bog closes over the lake before the accumulation has completely filled the shoreward portions of the area. In these conditions we have what is familiarly known as a quaking bog, which can be swayed up and down by a person who quickly stoops and rises while standing on the surface. In this state the tough and thick sheet of growing plants is sufficient to uphold a considerable weight, but so elastic that the underlying water can be thrown into waves. Long before the bog has completely filled the lake with the peaty accumulations the growth of trees is apt to take place on its surface, which often reduces the area to the appearance of a very level wet wood. [Illustration: Fig. 17.--Diagram showing beginning of peat bog: A, lake; B, lilies and rushes; C, lake bog; D, climbing bog.] Climbing and lake bogs in the United States occupy a total area of more than fifty thousand square miles. In all North America the total area is probably more than twice as great. Similar deposits are exceedingly common in the Eurasian continent and in southern Patagonia. It is probable that the total amount of these fields in different parts of the world exceeds half a million square miles. These two groups of fresh-water swamps have an interest, for the reason that when reduced to cultivation by drainage and by subsequent removal of the excess of peaty matter, by burning or by natural decay, afford very rich soil. The fairest fields of northern Europe, particularly in Great Britain and Ireland, have been thus won to tillage. In the first centuries of our era a large part of England--perhaps as much as one tenth of the ground now tilled in that country--was occupied by these lands, which retained water in such measure as to make them unfit for tillage, the greater portion of this area being in the condition of thin climbing bog. For many centuries much of the energy of the people was devoted to the reclamation of these valuable lands. This task of winning the swamp lands to agriculture has been more completely accomplished in England than elsewhere, but it has gone far on the continent of Europe, particularly in Germany. In the United States, owing to the fact that lands have been cheap, little of this work of swamp-draining has as yet been accomplished. It is likely that the next great field of improvement to be cultivated by the enterprising people will be found in these excessively humid lands, from which the food-giving resources for the support of many million people can be won. [Illustration: Fig. 18.--Diagram showing development of swamp: A, remains of lake; B, surface growth; c, peat.] The group of marine marshes differs in many important regards from those which are formed in fresh water. Where the tide visits any coast line, and in sheltered positions along that shore, a number of plants, mostly belonging to the group of grasses, species which have become accustomed to having their roots bathed by salt water, begin the formation of a spongy mat, which resembles that composed of _Sphagnum_, only it is much more solid. This mat of the marine marshes soon attains a thickness of a foot or more, the upper or growing surface lying in a position where it is covered for two or three hours at each visit of the tide. Growing rapidly outward from the shore, and having a strength which enables it to resist in a tolerably effective manner waves not more than two or three feet high, this accumulation makes head against the sea. To a certain extent the waves undermine the front of the sheet and break up masses of it, which they distribute over the shallow bottom below the level at which these plants can grow. In this deeper water, also, other marine animals and plants are continually developing, and their remains are added to the accumulations which are ever shallowing the water, thus permitting a further extension of the level, higher-lying marsh. This process continues until the growth has gone as far as the scouring action of the tidal currents will permit. In the end the bay, originally of wide-open water, is only such at high tide. For the greater part of the time it appears as broad savannas, whose brilliant green gives them the aspect of rare fertility. Owing to the conditions of their growth, the deposits formed in marine marshes contain no distinct peat, the nearest approach to that substance being the tangle of wirelike roots which covers the upper foot or so of the accumulation. The greater part of the mass is composed of fine silt, brought in by the streams of land water which discharge into the basin, and by the remains of animals which dwelt upon the bottom or between the stalks of the plants that occupy the surface of the marshes. These interspaces afford admirable shelter to a host of small marine forms. The result is, that the tidal marshes, as well as the lower-lying mud flats, which have been occupied by the mat of vegetation, afford admirable earth for tillage. Unfortunately, however, there are two disadvantages connected with the redemption of such lands. In the first place, it is necessary to exclude the sea from the area, which can only be accomplished by considerable engineering work; in the second place, the exclusion of the tide inevitably results in the silting up of the passage by which the water found its way to the sea. As these openings are often used for harbours, the effect arising from their destruction is often rather serious. Nevertheless, in some parts of the world very extensive and most fertile tracts of land have thus been won from the sea; a large part of Holland and shore-land districts in northern Europe are made up of fields which were originally covered by the tide. Near the mouth of the Rhine, indeed, the people have found these sea-bottom soils so profitable that they have gone beyond the zone of the marshes, and have drained considerable seas which of old were permanently covered, even at the lowest level of the waters. On the coast of North America marine marshes have an extensive development, and vary much in character. In the Bay of Fundy, where the tides have an altitude of fifty feet or more, the energy of their currents is such that the marsh mat rarely forms. Its place, however, is taken by vast and ever-changing mud flats, the materials of which are swept to and fro by the moving waters. The people of this region have learned an art of a peculiar nature, by which they win broad fields of excellent land from the sea. Selecting an area of the flats, the surface of which has been brought to within a few feet of high tide, they inclose it with a stout barrier or dike, which has openings for the free admission of the tidal waters. Entering this basin, the tide, moving with considerable velocity, bears in quantities of sediment. In the basin, the motion being arrested, this sediment falls to the bottom, and serves to raise its level. In a few months the sheet of sediment is brought near the plane of the tidal movement, then the gates are closed at times when the tide has attained half of its height, so that the ground within the dike is not visited by the sea water, and can be cultivated. [Illustration: Fig. 19.--Map of Ipswich marshes, Massachusetts, formed behind a barrier beach.] Along the coast of New England the ordinary marine marshes attain an extensive development in the form of broad-grassed savannas. With this aspect, though with a considerable change in the plants which they bear, the fringe of savannas continues southward along the coast to northern Florida. In the region about the mouth of the Savannah River, so named from the vast extent of the tidal marshes, these fields attain their greatest development. In central and southern Florida, however, where the seacoast is admirably suited for their development, these coastal marshes of the grassy type disappear, their place being taken by the peculiar morasses formed by the growth of the mangrove tree. In the mangrove marshes the tree which gives the areas their name covers all the field which is visited by the tide. This tree grows with its crown supported on stiltlike roots, at a level above high tide. From its horizontal branches there grow off roots, which reach downward into the water, and thence to the bottom. The seeds of the mangrove are admirably devised so as to enable the plant to obtain a foothold on the mud flats, even where they are covered at low tide with a depth of two or three feet of water. They are several inches in length, and arranged with booklets at their lower ends; floating near the bottom, they thus catch upon it, and in a few weeks' growth push the shoot to the level of the water, thus affording a foundation for a new plantation. In this manner, extending the old forests out into the shallow water of the bays, and forming new colonies wherever the water is not too deep, these plants rapidly occupy all the region which elsewhere would appear in the form of savannas. [Illustration: Fig. 20.--Diagram showing mode of growth of mangroves.] The tidal marshes of North America, which may be in time converted to the uses of man, probably occupy an area exceeding twenty thousand square miles. If the work of reclaiming such lands from the sea ever attains the advance in this country that it has done in Holland, the area added to the dry land by engineering devices may amount to as much as fifty thousand square miles--a territory rather greater than the surface of Kentucky, and with a food-yielding power at least five times as great as is afforded by that fertile State. In fact, these conquests from the sea are hereafter to be among the great works which will attract the energies of mankind. In the arid region of the Cordilleras, as well as in many other countries, the soil, though destitute of those qualities which make it fit for the uses of man, because of the absence of water in sufficient amount, is, as regards its structure and depth, as well as its mineral contents, admirably suited to the needs of agriculture. The development of soils in desert regions is in almost all cases to be accounted for by the former existence in the realms they occupy of a much greater rainfall than now exists. Thus in the Rocky Mountain country, when the deep soils of the ample valleys were formed, the lakes, as we have before noted, were no longer dead seas, as is at present so generally the case, but poured forth great streams to the sea. Here, as elsewhere, we find evidence that certain portions of the earth which recently had an abundant rainfall have now become starved for the lack of that supply. All the soils of arid regions where the trial has been made have proved very fertile when subjected to irrigation, which can often be accomplished by storing the waters of the brief rainy season or by diverting those of rivers which enter the deserts from well-watered mountain fields. In fact, the soil of these arid realms yields peculiarly ample returns to the husbandman, because of certain conditions due to the exceeding dryness of the air. This leads to an absence of cloudy weather, so that from the time the seed is planted the growth is stimulated by uninterrupted and intense sunshine. The same dryness of the air leads, as we have seen, to a rapid evaporation from the surface, by which, in a manner before noted, the dissolved mineral matter is brought near the top of the soil, where it can best serve the greater part of our crop plants. On these accounts an acre of irrigated soil can be made to yield a far greater return than can be obtained from land of like chemical composition in humid regions. In many parts of the world, particularly in the northern and western portions of the Mississippi Valley, there are widespread areas, which, though moderately well watered, were in their virgin state almost without forests. In the prairie region the early settlers found the country unwooded, except along the margins of the streams. On the borders of the true prairies, however, they found considerable areas of a prevailingly forested land, with here and there a tract of prairie. There were several of these open fields south of the Ohio, though the country there is in general forested; one of these prairie areas, in the Green River district of Kentucky, was several thousand square miles in extent. At first it was supposed that the absence of trees in the open country of the Mississippi Valley was due to some peculiarity of the soil, but experience shows that plantations luxuriantly develop, and that the timber will spread rapidly in the natural way. In fact, if the seeds of the trees which have been planted since the settlement of the country were allowed to develop as they seek to do, it would only be a few centuries before the region would be forest-clad as far west as the rainfall would permit the plants to develop. Probably the woods would attain to near the hundredth meridian. In the opinion of the writer, the treeless character of the Western plains is mainly to be accounted for by the habit which our Indians had of burning the herbage of a lowly sort each year, so that the large game might obtain better pasturage. It is a well-known fact to all those who have had to deal with cattle on fields which are in the natural state that fire betters the pasturage. Beginning this method of burning in the arid regions to the west of the original forests, the natural action of the fire has been gradually to destroy these woods. Although the older and larger trees, on account of their thick bark and the height of their foliage above the ground, escaped destruction, all the smaller and younger members of the species were constantly swept away. Thus when the old trees died they left no succession, and the country assumed its prairie character. That the prairies were formed in this manner seems to be proved by the testimony which we have concerning the open area before mentioned as having existed in western Kentucky. It is said that around the timberless fields there was a wide fringe of old fire-scarred trees, with no undergrowth beneath their branches, and that as they died no kind of large vegetation took their place. When the Indians who set these fires were driven away, as was the case in the last decade of the last century, the country at once began to resume its timbered condition. From the margin and from every interior point where the trees survived, their seeds spread so that before the open land was all subjugated to the plough it was necessary in many places to clear away a thick growth of the young forest-building trees. The soils which develop on the lavas and ashes about an active volcano afford interesting subjects for study, for the reason that they show how far the development of the layer which supports vegetation may depend upon the character of the rocks from which it is derived. Where the materials ejected from a volcano lie in a rainy district, the process of decay which converts the rock into soil is commonly very rapid, a few years of exposure to the weather being sufficient to bring about the formation of a fertile soil. This is due to the fact that most lavas, as well as the so-called volcanic ashes, which are of the same material as the lavas, only blown to pieces, are composed of varied minerals, the most of which are readily attacked by the agents of decay. Now and then, however, we find the materials ejected from a particular volcano, or even the lavas and ashes of a single eruption, in such a chemical state that soils form upon them with exceeding slowness. * * * * * The foregoing incomplete considerations make it plain that the soil-covering of the earth is the result of very delicate adjustments, which determine the rate at which the broken-down rocks find their path from their original bed places to the sea. The admirable way in which this movement is controlled is indicated by the fact that almost everywhere we find a soil-covering deep enough for the use of a varied vegetation, but rarely averaging more than a dozen feet in depth. Only here and there are the rocks bare or the earth swathed in a profound mass of detritus. This indicates how steadfast and measured is the march of the rock waste from the hills to the sea. Unhappily, man, when by his needs he is forced to till the soil, is compelled to break up this ancient and perfect order. He has to strip the living mantle from the earth, replacing it with growth of those species which serve his needs. Those plants which are most serviceable--which are, indeed, indispensable in the higher civilization, the grains--require for their cultivation that the earth be stripped bare and deeply stirred during the rainy season, and thus subjected to the most destructive effect of the rainfall. The result is, that in almost all grain fields the rate of soil destruction vastly surpasses that at which the accumulation is being made. We may say, indeed, that, except in alluvial plains, where the soil grows by flood-made additions to its upper surface, no field tilled in grain can without exceeding care remain usable for a century. Even though the agriculturist returns to the earth all the chemical substances which he takes away in his crops, the loss of the soil by the washing away of its substance to the stream will inevitably reduce the region to sterility. It is not fanciful to say that the greatest misfortune which in a large way man has had to meet in his agriculture arises from this peculiar stress which grain crops put upon the soil. If these grains grew upon perennial plants, in the manner of our larger fruits, the problem of man's relation to the soil would be much simpler than it is at present. He might then manage to till the earth without bringing upon it the inevitable destruction which he now inflicts. As it is, he should recognise that his needs imperil this ancient and precious element in the earth's structure, and he should endeavour in every possible way to minimize the damage which he brings about. This result he may accomplish in certain simple ways. First, as regards the fertility of the soil, as distinguished from the thickness of the coating, it may be said that modern discoveries enable us to see the ways whereby we may for an indefinite period avoid the debasement of our great heritage, the food-giving earth. We now know in various parts of the world extensive and practically inexhaustible deposits, whence may be obtained the phosphates, potash, soda, etc., which we take from the soil in our crops. We also have learned ways in which the materials contained in our sewage may be kept from the sea and restored to the fields. In fact, the recent developments of agriculture have made it not only easy, but in most cases profitable, to avoid this waste of materials which has reduced so many regions to poverty. We may fairly look forward to the time, not long distant, when the old progressive degradation in the fertility of the soil coating will no longer occur. It is otherwise with the mass of the soil, that body of commingled decayed rock and vegetable matter which must possess a certain thickness in order to serve its needs. As yet no considerable arrest has been made in the processes which lead to the destruction of this earthy mass. In all countries where tillage is general the rivers are flowing charged with all they can bear away of soil material. Thus in the valley of the Po, a region where, if the soil were forest-clad, the down-wearing of the surface would probably be at no greater rate than one foot in five thousand years, the river bears away the soil detritus so rapidly that at the present time the downgoing is at the rate of one foot in eight hundred years, and each decade sees the soil disappear from hillsides which were once fertile, but are now reduced to bare rocks. All about the Mediterranean the traveller notes extensive regions which were once covered with luxuriant forests, and were afterward the seats of prosperous agriculture, where the soil has utterly disappeared, leaving only the bare rocks, which could not recover its natural covering in thousands of years of the enforced fallow. Within the limits of the United States the degradation of the soil, owing to the peculiar conditions of the country, is in many districts going forward with startling rapidity. It has been the habit of our people--a habit favoured by the wide extent of fertile and easily acquired frontier ground--recklessly to till their farms until the fields were exhausted, and then to abandon them for new ground. By shallow ploughing on steep hillsides, by neglect in the beginning of those gulches which form in such places, it is easy in the hill country of the eastern United States to have the soil washed away within twenty years after the protecting forests have been destroyed. The writer has estimated that in the States south of the Ohio and James Rivers more than eight thousand square miles of originally fertile ground have by neglect been brought into a condition where it will no longer bear crops of any kind, and over fifteen hundred miles of the area have been so worn down to the subsoil or the bed rock that it may never be profitable to win it again to agricultural uses. Hitherto, in our American agriculture, our people have been to a great extent pioneers; they have been compelled to win what they could in the cheapest possible way and with the rudest implements, and without much regard to the future of those who were in subsequent generations to occupy the fields which they were conquering from the wilderness and the savages. The danger is now that this reckless tillage, in a way justified of old, may be continued and become habitual with our people. It is, indeed, already a fixed habit in many parts of the country, particularly in the South, where a small farmer expects to wear out two or three plantations in the course of his natural life. Many of them manage to ruin from one to two hundred acres of land in the course of half a century of uninterrupted labour. This system deserves the reprobation of all good citizens; it would be well, indeed, if it were possible to do so, to stamp it out by the law. The same principle which makes it illegal for a man to burn his own dwelling house may fairly be applied in restraining him from destroying the land which he tills. There are a few simple principles which, if properly applied, may serve to correct this misuse of our American soil. The careful tiller should note that all soils whatever which lie on declivities having a slope of more than one foot in thirty inevitably and rapidly waste when subject to plough tillage. This instrument tends to smear and consolidate the layer of earth over which its heel runs, so that at a depth of a few inches below the surface a layer tolerably impervious to water is formed. The result is that the porous portion of the deposit becomes excessively charged with water in times of heavy rain, and moves down the hillside in a rapid manner. All such steep slopes should be left in their wooded state, or, if brought into use, should be retained as pasture lands. Where, as is often the case with the farms in hilly countries, all the fields are steeply inclined, it is an excellent precaution to leave the upper part of the slope with a forest covering. In this condition not only is the excessive flow of surface water diminished, but the moisture which creeps down the slope from the wooded area tends to keep the lower-lying fields in a better state for tillage, and promotes the decay of the underlying rocks, and thus adds to the body and richness of the earth. On those soils which must be tilled, even where they tend to wash away, the aim should be to keep the detritus open to such a depth that it may take in as much as possible of the rainfall, yielding the water to the streams through the springs. This end can generally be accomplished by deep ploughing; it can, in almost all cases, be attained by under-drainage. The effect of allowing the water to penetrate is not only to diminish the superficial wearing, but to maintain the process of subsoil and bed-rock decay by which the detrital covering is naturally renewed. Where, as in many parts of the country, the washing away of the soil can not otherwise be arrested, the progress of the destruction can be delayed by forming with the skilful use of the plough ditches of slight declivity leading along the hillsides to the natural waterways. One of the most satisfactory marks of the improvement which is now taking place in the agriculture of the cotton-yielding States of this country is to be found in the rapid increase in the use of the ditch system here mentioned. This system, combined with ploughing in the manner where the earth is with each overturning thrown uphill, will greatly reduce the destructive effect of rainfall on steep-lying fields. But the only effective protection, however, is accomplished by carefully terracing the slopes, so that the tilled ground lies in level benches. This system is extensively followed in the thickly settled portions of Europe, but it may be a century before it will be much used in this country. The duty of the soil-tiller by the earth with which he deals may be briefly summed up: He should look upon himself as an agent necessarily interfering with the operations which naturally form and preserve the soil. He should see that his work brings two risks; he may impoverish the accumulation of detrital material by taking out the plant food more rapidly than it is prepared for use. This injurious result may be at any time reparable by a proper use of manures. Not so, however, with the other form of destruction, which results in the actual removal of the soil materials. Where neglect has brought about this disaster, it can only be repaired by leaving the area to recover beneath the slowly formed forest coating. This process in almost all cases requires many thousands of years for its accomplishment. The man who has wrought such destruction has harmed the inheritance of life. CHAPTER IX. THE ROCKS AND THEIR ORDER. In the preceding chapters of this book the attention of the student has been directed mainly to the operations of those natural forces which act upon the surface of the earth. Incidentally the consequences arising from the applications of energy to the outer part of the planet have been attended to, but the main aim has been to set forth the work which solar energy, operating in the form of heat, accomplishes upon the lands. We have now to consider one of the great results of these actions, which is exhibited in the successive strata that make up the earth's crust. The most noteworthy effect arising from the action of the solar forces on the earth and their co-operation with those which originate in our sphere is found in the destruction of beds or other deposits of rock, and the removal of the materials to the floors of water basins, where they are again aggregated in strata, and gradually brought once more into a stable condition within the earth. This work is accomplished by water in its various states, the action being directly affected by gravitation. In the form of steam, water which has been built into rocks and volcanically expelled by tensions, due to the heat which it has acquired at great depths below the surface, blows forth great quantities of lava, which is contributed to the formation of strata, either directly in the solid form or indirectly, after having been dissolved in the sea. Acting as waves, water impelled by solar energy transmitted to it by the winds beats against the shores, wearing away great quantities of rock, which is dragged off to the neighbouring sea bottoms, there to resume the bedded form. Moving ice in glaciers, water again applying solar energy given to it by its elevation above the sea, most effectively grinds away the elevated parts of the crust, the _débris_ being delivered to the ocean. In the rain the same work is done, and even in the wind the power of the sun serves to abrade the high-lying rocks, making new strata of their fragments. As gravity enters as an element in all the movements of divided rock, the tendency of the waste worn from the land is to gather on to the bottoms of basins which contain water. Rarely, and only in a small way, this process results in the accumulation of lake deposits; the greater part of the work is done upon the sea floor. When the beds are formed in lake basins, they may be accumulated in either of two very diverse conditions. They may be formed in what are called dead seas, in which case the detrital materials are commonly small in amount, for the reason that the inflowing streams are inconsiderable; in such basins there is normally a large share of saline materials, which are laid down by the evaporation of the water. In ordinary lakes the deposits which are formed are mostly due to the sediment that the rivers import. These materials are usually fine-grained, and the sand or pebbles which they contain are plentifully mingled with clay. Hence lake deposits are usually of an argillaceous nature. As organic life, such as secretes limestone, is rarely developed to any extent in lake basins, limy beds are very rarely formed beneath those areas of water. Where they occur, they are generally due to the fact that rivers charged with limy matter import such quantities of the substance that it is precipitated on the bottom. As lake deposits are normally formed in basins above the level of the sea, and as the drainage channels of the basins are always cutting down, the effect is to leave such strata at a considerable height above the sea level, where the erosive agents may readily attack them. In consequence of this condition, lacustrine beds are rarely found of great antiquity; they generally disappear soon after they are formed. Where preserved, their endurance is generally to be attributed to the fact that the region they occupy has been lowered beneath the sea and covered by marine strata. The great laboratory in which the sedimentary deposits are accumulated, the realm in which at least ninety-nine of the hundred parts of these materials are laid down, is the oceanic part of the earth. On the floors of the seas and oceans we have not only the region where the greater part of the sedimentation is effected, but that in which the work assumes the greatest variety. The sea bottoms, as regards the deposits formed upon them, are naturally divided into two regions--the one in which the _débris_ from the land forms an important part of the sediment, and the other, where the remoteness of the shores deprives the sediment of land waste, or at least of enough of that material in any such share as can affect the character of the deposits. What we may term the littoral or shore zone of the sea occupies a belt of prevailingly shallow water, varying in width from a few score to a few hundred miles. Where the bottom descends steeply from the coast, where there are no strong off-shore setting currents, and where the region is not near the mouth of a large river which bears a great tide of sediment to the sea, the land waste may not affect the bottom for more than a mile or two from the shore. Where these conditions are reversed, the _débris_ from the air-covered region may be found three or four hundred miles from the coast line. It should also be noted that the incessant up-and-down goings of the land result in a constant change in the position of the coast line, and consequently in the extension of the land sediment, in the course of a few geological periods over a far wider field of sea bottom than that to which they would attain if the shores remained steadfast. It is characteristic of the sediments deposited within the influence of the continental detritus that they vary very much in their action, and that this variation takes place not only horizontally along the shores in the same stratum, but vertically, in the succession of the beds. It also may be traced down the slope from the coast line to deep water. Thus where all the _débris_ comes from the action of the waves, the deposits formed from the shore outwardly will consist of coarse materials, such as pebbles near the coast, of sand in the deeper and remoter section, and of finer silt in the part of the deposit which is farthest out. With each change in the level of the coast line the position of these belts will necessarily be altered. Where a great river enters the sea, the changes in the volume of sediment which it from time to time sends forth, together with the alternations in the position of its point of discharge, led to great local complexities in the strata. Moreover, the turbid water sent forth by the stream may, as in the case of the tide from the Amazon, be drifted for hundreds of miles along the coast line or into the open sea. The most important variations which occur in the deposits of the littoral zone are brought about by the formations of rocks more or less composed of limestone. Everywhere the sea is, as compared with lake waters, remarkably rich in organic life. Next the shore, partly because the water is there shallow, but also because of its relative warmth and the extent to which it is in motion, organic life, both that of animals and plants, commonly develops in a very luxuriant way. Only where the bottom is composed of drifting sands, which do not afford a foothold for those species which need to rest upon the shore, do we fail to find that surface thickly tenanted with varied forms. These are arranged according to the depth of the bottom. The species of marine plants which are attached to fixed objects are limited to the depth within which the sunlight effectively penetrates the water; in general, it may be said that they do not extend below a depth of one hundred feet. The animal forms are distributed, according to their kinds, over the floor, but few species having the capacity to endure any great range in the pressure of the sea water. Only a few forms, indeed, extend from low tide to the depth of a thousand feet. The greatest development of organic life, the realm in which the largest number of species occur, and where their growth is most rapid, lies within about a hundred feet of the low-tide level. Here sunlight, warmth, and motion in the water combine to favour organic development. It is in this region that coral reefs and other great accumulations of limestone, formed from the skeletons of polyps and mollusks, most abundantly occur. These deposits of a limy nature depend upon a very delicate adjustment of the conditions which favour the growth of certain creatures; very slight geographic changes, by inducing movements of sand or mud, are apt to interrupt their formation, bringing about a great and immediate alteration in the character of the deposits. Thus it is that where geologists find considerable fields of rock, where limestones are intercalated with sandstones and deposits of clay, they are justified in assuming that the strata were laid down near some ancient shore. In general, these coast deposits become more and more limy as we go toward the tropical realms, and this for the reason that the species which secrete large amounts of lime are in those regions most abundant and attain the most rapid growth. The stony polyps, the most vigorous of the limestone makers, grow in large quantities only in the tropical realm, or near to it, where ocean streams of great warmth may provide the creatures with the conditions of temperature and food which they need. As we pass from the shore to the deeper sea, the share of land detritus rapidly diminishes until, as before remarked, at the distance of five hundred miles from the coast line, very little of that waste, except that from volcanoes, attains the bottom of the sea. By far the larger part of the contributions which go to the formation of these deep-sea strata come from organic remains, which are continually falling upon the sea floor. In part, this waste is derived from creatures which dwell upon the bottom; in considerable measure, however, it is from the dead bodies of those forms which live near the surface of the sea, and which when dying sink slowly through the intermediate realm to the bottom. Owing to the absence of sunlight, the prevailingly cold water of the deeper seas, and the lack of vegetation in those realms, the growth of organic forms on the deep-sea floor is relatively slow. Thus it happens that each shell or other contribution to the sediment lies for some time on the bottom before it is buried. While in this condition it is apt to be devoured by some of the many species which dwell on the bottom and subsist from the remains of animals and plants which they find there. In all cases the fossilization of any form depends upon the accumulation of sediment before the processes of destruction have overtaken them, and among these processes we must give the first place to the creatures which subsist on shells, bones, or other substances of like nature which find their way to the ocean floor. In the absolute darkness, the still water, and the exceeding cold of the deeper seas, animals find difficult conditions for development. Moreover, in this deep realm there is no native vegetation, and, in general, but little material of this nature descends to the bottom from the surface of the sea. The result is, the animals have to subsist on the remains of other animals which at some step in the succession have obtained their provender from the plants which belong on the surface or in the shallow waters of the sea. This limitation of the food supply causes the depths of the sea to be a realm of continual hunger, a region where every particle of organic matter is apt to be seized upon by some needy creature. In consequence of the fact that little organic matter on the deeper sea floors escapes being devoured, the most of the material of this nature which goes into strata enters that state in a finely divided condition. In the group of worms alone--forms which in a great diversity of species inhabit the sea floor--we find creatures which are specially adapted to digesting the _débris_ which gathers on the sea bottom. Wandering over this surface, much in the manner of our ordinary earthworms, these creatures devour the mud, voiding the matter from their bodies in a yet more perfectly divided form. Hence it comes about that the limestone beds, so commonly formed beneath the open seas, are generally composed of materials which show but few and very imperfect fossils. Studying any series of limestone beds, we commonly find that each layer, in greater or less degree, is made up of rather massive materials, which evidently came to their place in the form of a limy mud. Very often this lime has crystallized, and thus has lost all trace of its original organic structure. One of the conspicuous features which may be observed in any succession of limestone beds is the partings or divisions into layers which occur with varied frequency. Sometimes at vertical intervals of not more than one or two inches, again with spacings of a score of feet, we find divisional planes, which indicate a sudden change in the process of rock formation. The lime disappears, and in place of it we have a thin layer of very fine detritus, which takes on the form of a clay. Examining these partings with care, we observe that on the upper surface on the limestone the remains of the animal which dwelt on the ancient sea floor are remarkably well preserved, they having evidently escaped the effect of the process which reduced their ancestors, whose remains constitute the layer, to mud. Furthermore, we note that the shaly layer is not only lacking in lime, but commonly contains no trace of animals such as might have dwelt on the bottom. The fossils it bears are usually of species which swam in the overlying water and came to the bottom after death. Following up through the layer of shale, we note that the ordinary bottom life gradually reappears, and shortly becomes so plentiful that the deposit resumes the character which it had before the interruption began. Often, however, we note that the assemblage of species which dwelt on the given area of sea floor has undergone a considerable change. Forms in existence in the lower layer may be lacking in the upper, their place being taken by new varieties. So far the origin of these divisional planes in marine deposits has received little attention from geologists; they have, indeed, assumed that each of these alterations indicates some sudden disturbance of the life of the sea floors. They have, however, generally assumed that the change was due to alterations in the depth of the sea or in the run of ocean currents. It seems to the writer, however, that while these divisions may in certain cases be due to the above-mentioned and, indeed, to a great variety of causes, they are in general best to be explained by the action of earthquakes. Water being an exceedingly elastic substance, an earthquake passes through it with much greater speed than it traverses the rocks which support the ocean floor. The result is that, when the fluid and solid oscillate in the repeated swingings which a shock causes, they do not move together, but rub over each other, the independent movements having the swing of from a few inches to a foot or two in shocks of considerable energy. When the sea bottom and the overlying water, vibrating under the impulse of an earthquake shock, move past each other, the inevitable result is the formation of muddy water; the very fine silt of the bottom is shaken up into the fluid, which afterward descends as a sheet to its original position. It is a well-known fact that such muddying of water, in which species accustomed to other conditions dwell, inevitably leads to their death by covering their breathing organs and otherwise disturbing the delicately balanced conditions which enable them to exist. We find, in fact, that most of the tenants of the water, particularly the forms which dwell upon the bottom, are provided with an array of contrivances which enable them to clear away from their bodies such small quantities of silt as may inconvenience them. Thus, in the case of our common clam, the breathing organs are covered with vibratory cilia, which, acting like brooms, sweep off any foreign matter which may come upon their surfaces. Moreover, the creature has a long, double, spoutlike organ, which it can elevate some distance above the bottom, through which it draws and discharges the water from which it obtains food and air. Other forms, such as the crinoids, or sea lilies, elevate the breathing parts on top of tall stems of marvellous construction, which brings those vital organs at the level, it may be, of three or four feet above the zone of mud. In consequence of the peculiar method of growth, the crinoids often escape the damage done by the disturbance of the bottom, and thus form limestone beds of remarkable thickness; sometimes, indeed, we find these layers composed mainly of crinoidal remains, which exhibit only slight traces of partings such as we have described, being essentially united for the depth of ten or twenty feet. Where the layers have been mainly accumulated by shellfish, their average thickness is less than half a foot. When we examine the partitions between the layers of limestone, we commonly find that, however thin, they generally extend for an indefinite distance in every direction. The writer has traced some of these for miles; never, indeed, has he been able to find where they disappeared. This fact makes it clear that the destruction which took place at the stage where these partings were formed was widespread; so far as it was due to earthquake shocks, we may fairly believe that in many cases it occurred over areas which were to be measured by tens of thousands of square miles. Indeed, from what we know of earthquake shocks, it seems likely that the devastation may at times have affected millions of square miles. Another class of accidents connected with earthquakes may also suddenly disturb the mud on the sea bottom. When, as elsewhere noted, a shock originates beneath the sea, the effect is suddenly to elevate the water over the seat of the jarring and the regions thereabouts to the height of some feet. This elevation quickly takes the shape of a ringlike wave, which rolls off in every direction from its point of origin. Where the sea is deep, the effect of this wave on the bottom may be but slight; but as the undulation attains shallower water, and in proportion to the shoaling, the front of the surge is retarded in its advance by the friction of the bottom, while the rear part, being in deeper water, crowds upon the advancing line. The action is precisely that which has been described as occurring in wind-made waves as they approach the beach; but in this last-named group of undulations, because of the great width of the swell, the effect of the shallowing is evident in much deeper water. It is likely that at the depth of a thousand feet the passing of one of these vast surges born of earthquakes may so stir the mud of the sea floor as to bring about a widespread destruction of life, and thus give rise to many of the partitions between strata. If we examine with the microscope the fine-grained silts which make up the shaly layers between limestones, we find the materials to be mostly of inorganic origin. It is hard to trace the origin of the mineral matter which it contains; some of the fragments are likely to prove of Volcanic origin; others, bits of dust from meteorites; yet others, dust blown from the land, which may, as we know, be conveyed for any distance across the seas. Mingled with this sediment of an inorganic origin we almost invariably find a share of organic waste, derived not from creatures which dwelt upon the bottom, but from those which inhabited the higher-lying waters. If, now, we take a portion of the limestone layer which lies above or below the shale parting, and carefully dissolve out with acids the limy matter which it contains, we obtain a residuum which in general character, except so far as the particles may have been affected by the acid, is exactly like the material which forms the claylike partition. We are thus readily led to the conclusion that on the floors of the deeper seas there is constantly descending, in the form of a very slow shower, a mass of mineral detritus. Where organic life belonging to the species which secrete hard shells or skeletons is absent, this accumulation, proceeding with exceeding slowness, gradually accumulates layers, which take on a shaly character. Where limestone-making animals abound, they so increase the rate of deposition that the proportion of the mineral material in the growing strata is very much reduced; it may, indeed, become as small as one per cent of the mass. In this case we may say that the deposit of limestone grew a hundred times as fast as the intervening beds of shale. The foregoing considerations make it tolerably clear that the sea floor is in receipt of two diverse classes of sediment--those of a mineral and those of an organic origin. The mineral, or inorganic, materials predominate along the shores. They gradually diminish in quantity toward the open sea, where the supply is mainly dependent on the substances thrown forth from volcanoes, on pumice in its massive or its comminuted form--i.e., volcanic dust, states of lava in which the material, because of the vesicles which it contains, can float for ages before it comes to rest on the sea bottom. Variations in the volcanic waste contributed to the sea floor may somewhat affect the quantity of the inorganic sediments, but, as a whole, the downfalling of these fragments is probably at a singularly uniform rate. It is otherwise with the contributions of sediment arising from organic forms. This varies in a surprising measure. On the coral reefs, such as form in the mid oceans, the proportion of matter which has not come into the accumulation through the bodies of animals and plants may be as small as one tenth of one per cent, or less. In the deeper seas, it is doubtful whether the rate of animal growth is such as to permit the formation of any beds which have less than one half of their mass made up of materials which fell through the water. In certain areas of the open seas the upper part of the water is dwelt in by a host of creatures, mostly foraminifera, which extract limestone from the water, and, on dying, send their shells to the bottom. Thus in the North Atlantic, even where the sea floor is of great depth beneath the surface, there is constantly accumulating a mass of limy matter, which is forming very massive limestone strata, somewhat resembling chalk deposits, such as abundantly occur in Great Britain, in the neighbouring parts of Europe, in Texas, and elsewhere. Accumulations such as this, where the supply is derived from the surface of the water, are not affected by the accidents which divide beds made on the bottom in the manner before described. They may, therefore, have the singularly continuous character which we note in the English chalk, where, for the thickness of hundreds of feet, we may have no evident partitions, except certain divisions, which have evidently originated long after the beds were formed. We have already noted the fact that, while the floors of the deeper seas appear to lack mountainous elevations, those arising from the folding of strata, they are plentifully scattered over with volcanic cones. We may therefore suppose that, in general, the deposits formed on the sea floor are to a great extent affected by the materials which these vents cast forth. Lava streams and showers represent only a part of the contributions from volcanoes, which finally find their way to the bottom. In larger part, the materials thrown forth are probably first dissolved in the water and then taken up by the organic species; only after the death of these creatures does the waste go to the bottom. As hosts of these creatures have no solid skeleton to contribute to the sea floor, such mineral matter as they may obtain is after their death at once restored to the sea. Not only does the contribution of organic sediment diminish in quantity with the depth which is attained, but the deeper parts of the ocean bed appear to be in a condition where no accumulations of this nature are made, and this for the reason that the water dissolves the organic matter more rapidly than it is laid down. Thus in place of limestone, which would otherwise form, we have only a claylike residuum, such as is obtained when we dissolve lime rocks in acids. This process of solution, by which the limy matter deposited on the bottom is taken back into the water, goes on everywhere, but at a rate which increases with the depth. This increase is due in part to the augmentation of pressure, and in part to the larger share of carbonic dioxide which the water at great depths holds. The result is, that explorations with the dredge seem to indicate that on certain parts of the deeper sea floors the rocks are undergoing a process of dissolution comparable to that which takes place in limestone caverns. So considerable is the solvent work that a large part of the inorganic waste appears to be taken up by the waters, so as to leave the bottom essentially without sedimentary accumulations. The sea, in a word, appears to be eating into rocks which it laid down before the depression attained its present great depth. We should here note something of the conditions which determine the supply of food which the marine animals obtain. First of all, we may recur to the point that the ocean waters appear to contain something of all the earth materials which do not readily decompose when they are taken into the state of solution. These mineral substances, including the metals, are obtained in part from the lands, through the action of the rain water and the waves, but perhaps in larger share from the volcanic matter which, in the form of floating lava, pumice, or dust, is plentifully delivered to the sea. Except doubtfully, and at most in a very small way, this chemical store of the sea water can not be directly taken into the structures of animals; it can only be immediately appropriated by the marine plants. These forms can only develop in that superficial realm of the seas which is penetrated by the sunlight, or say within the depth of five hundred feet, mostly within one hundred feet of the surface, about one thirtieth of the average, and about one fiftieth of the maximum ocean depth. On this marine plant life, and in a small measure on the vegetable matter derived from the land, the marine animals primarily depend for their provender. Through the conditions which bring about the formation of _Sargassum_ seas, those areas of the ocean where seaweeds grow afloat, as well as by the water-logging and weighting down of other vegetable matter, some part of the plant remains is carried to the sea floor, even to great depths; but the main dependence of the deep-sea forms of animals is upon other animal forms, which themselves may have obtained their store from yet others. In fact, in any deep-sea form we might find it necessary to trace back the food by thousands of steps before we found the creature which had access to the vegetable matter. It is easy to see how such conditions profoundly limit the development of organic being in the abysm of the ocean. The sedentary animals, or those which are fixed to the sea bottom--a group which includes the larger part of the marine species--have to depend for their sustenance on the movement of the water which passes their station. If the seas were perfectly still, none of these creatures except the most minute could be fed; therefore the currents of the ocean go far by their speed to determine the rate at which life may flourish. At great depths, as we have seen, these movements are practically limited to that which is caused by the slow movement which the tide brings about. The amount of this motion is proportional to the depth of the sea; in the deeper parts, it carries the water to and fro twice each day for the distance of about two hundred and fifty feet. In the shallower water this motion increases in proportion to the shoaling, and in the regions near the shores the currents of the sea which, except the massive drift from the poles, do not usually touch the bottom, begin to have their influence. Where the water is less than a hundred feet in depth, each wave contributes to the movement, which attains its maximum near the shore, where every surge sweeps the water rapidly to and fro. It is in this surge belt, where the waves are broken, that marine animals are best provided with food, and it is here that their growth is most rapid. If the student will obtain a pint of water from the surf, he will find that it is clouded by fragments of organic matter, the quantity in a pound of the fluid often amounting to the fiftieth part of its weight. He will thus perceive that along the shore line, though the provision of victuals is most abundant, the store is made from the animals and plants which are ground up in the mill. In a word, while the coast is a place of rapid growth, it is also a region of rapid destruction; only in the case of the coral animals, which associate their bodies with a number of myriads in large and elaborately organized communities, do we find animals which can make such head against the action of the waves that they can build great deposits in their realm. It should be noted that a part of the advantage which is afforded to organic life by the shore belt is due to the fact that the waters are there subjected to a constant process of aëration by the whipping into foam and spray which occurs where the waves overturn. It will be interesting to the student to note the great number of mechanical contrivances which have been devised to give security to animals and plants which face these difficult conditions arising from successive violent blows of falling water. Among these may be briefly noted those of the limpets--mollusks which dwell in a conical shell, which faces the water with a domelike outside, and which at the moment of the stroke is drawn down upon the rock by the strong muscle which fastens the creature to its foundation. The barnacles, which with their wedge-shaped prows cut the water at the moment of the stroke, but open in the pauses between the waves, so that the creature may with its branching arms grasp at the food which floats about it; the nullipores, forms of seaweed which are framed of limestone and cling firmly to the rock--afford yet other instances of protective adaptations contrived to insure the safety of creatures which dwell in the field of abundant food supply. * * * * * The facts above presented will show the reader that the marine sediments are formed under conditions which permit a great variety in the nature of the materials of which they are composed. As soon as the deposits are built into rocks and covered by later accumulations, their materials enter the laboratory of the under earth, where they are subjected to progressive changes. Even before they have attained a great depth, through the laying down of later deposits upon them, changes begin which serve to alter their structure. The fragments of a soluble kind begin to be dissolved, and are redeposited, so that the mass commonly becomes much more solid, passing from the state of detritus to that of more or less solid rock. When yet more deeply buried, and thereby brought into a realm of greater warmth, or perhaps when penetrated by dikes and thereby heated, these changes go yet further. More of the material is commonly rearranged by solution and redeposition, so that limestone may be converted into crystalline marble, granular sandstones into firm masses, known as quartzites, and clays into the harder form of slate. Where the changes go to the extreme point, rocks originally distinctly bedded probably may be so taken to pieces and made over that all traces of their stratification may be destroyed, all fossils obliterated, and the stone transformed into mica schist, or granite or other crystalline rock. It may be injected into the overlying strata in the form of dikes, or it may be blown forth into the air through volcanoes. Involved in mountain-folding, after being more or less changed in the manner described, the beds may become tangled together like the rumpled leaves of a book, or even with the complexity of snarled thread. All these changes of condition makes it difficult for the geologist to unravel the succession of strata so that he may know the true order of the rocks, and read from them the story of the successive geological periods. This task, though incomplete, has by the labours of many thousand men been so far advanced that we are now able to divide the record into chapters, the divisions of the geologic ages, and to give some account of the succession of events, organic and geographic, which have occurred since life began to write its records. EARTHQUAKES. In ordinary experience we seem to behold the greater part of the earth which meets our eyes as fixed in its position. A better understanding shows us that nothing in this world is immovable. In the realm of the inorganic world the atoms and molecules even in solid bodies have to be conceived as endowed with ceaseless though ordered motions. Even when matter is built into the solid rock, it is doubtful whether any grain of it ever comes really to rest. Under the strains which arise from the contraction of the earth's interior and the chemical changes which the rocks undergo, each bit is subject to ever-changing thrusts, which somewhat affect its position. If we in any way could bring a grain of sand from any stratum under a microscope, so that we could perceive its changes of place, we should probably find that it was endlessly swaying this way and that, with reference to an ideally fixed point, such as the centre of the earth. But even that centre, whether of gravity or of figure, is probably never at rest. Earth movements may be divided into two groups--those which arise from the bodily shifting of matter, which conveys the particles this way or that, or, as we say, change their place, and those which merely produce vibration, in which the particles, after their vibratory movement, return to their original place. For purposes of illustration the first, or translatory motion, may be compared to that which takes place when a bell is carried along upon a locomotive or a ship; and the second, or vibratory movement, to what takes place when the bell is by a blow made to ring. It is with these ringing movements, as we may term them, that we find ourselves concerned when we undertake the study of earthquakes. It is desirable that the reader should preface his study of earthquakes by noting the great and, at the same time, variable elasticity of rocks. In the extreme form this elasticity is very well shown when a toy marble, which is made of a close-textured rock, such as that from which it derives its name, is thrown upon a pavement composed of like dense material. Experiment will show that the little sphere can often be made to bounce to the height of twenty feet without breaking. If, then, with the same energy the marble is thrown upon a brick floor, the rebound will be very much diminished. It is well to consider what happens to produce the rebound. When the sphere strikes the floor it changes its shape, becoming shorter in the axis at right angles to the point which was struck, and at the same instant expanded along the equator of that axis. The flattening remains for only a small fraction of a second; the sphere vibrates so that it stretches along the line on which it previously shortened, and, as this movement takes place with great swiftness, it may be said to propel itself away from the floor. At the same time a similar movement goes on in the rock of the floor, and, where the rate of vibration is the same, the two kicks are coincident, and so the sphere is impelled violently away from the point of contact. Where the marble comes in contact with brick, in part because of the lesser elasticity of that material, due to its rather porous structure, and partly because it does not vibrate at the same rate as the marble, the expelling blow is much less strong. All rocks whatever, even those which appear as incoherent sands, are more or less set into vibratory motion whenever they are struck by a blow. In the crust of the earth various accidents occur which may produce that sudden motion which we term a blow. When we have examined into the origin of these impulses, and the way in which they are transmitted through the rocks, we obtain a basis for understanding earthquake shocks. The commonest cause of the jarrings in the earth is found in the formation of fractures, known as faults. If the reader has ever been upon a frozen lake at a time when the weather was growing colder, and the ice, therefore, was shrinking, he may have noted the rending sound and the slight vibration which comes with the formation of a crack traversing the sheet of ice. At such a time he feels a movement which is an earthquake, and which represents the simpler form of those tremors arising from the sudden rupture of fault planes. If he has a mind to make the experiment, he may hang a bullet by a thread from a small frame which rests upon the ice, and note that as the vibration occurs the little pendulum sways to and fro, thus indicating the oscillations of the ice. The same instrument will move in an identical manner when affected by a quaking in the rocks. Where the rocks are set in vibration by a rent which is formed in them, the phenomena are more complicated, and often on a vastly larger scale than in the simple conditions afforded by a sheet of ice. The rocks on either side of the rupture generally slide over each other, and the opposing masses are rent in their friction upon one another; the result is, not only the first jar formed by the initial fracture, but a great many successive movements from the other breakages which occur. Again, in the deeper parts of the crust, the fault fissures are often at the moment of their formation filled by a violent inrush of liquid rock. This, as it swiftly moves along, tears away masses from the walls, and when it strikes the end of the opening delivers a blow which may be of great violence. The nature of this stroke may be judged by the familiar instance where the relatively slow-flowing stream from a hydrant pipe is suddenly choked by closing the stopcock. Unless the plumber provides a cushion of air to diminish the energy of the blow, it is often strong enough to shake the house. Again, when steam or other gases are by a sudden diminution of pressure enabled to expand, they may deliver a blow which is exactly like that caused by the explosion of gunpowder, which, even when it rushes against the soft cushion of the air, may cause a jarring that may be felt as well as heard to a great distance. Such movements very frequently occur in the eruptions of volcanoes; they cause a quivering of the earth, which may be felt for a great distance from the immediate seat of the disturbance. When by any of the sudden movements which have been above described a jar is applied to the rocks, the wave flies through the more or less elastic mass until the energy involved in it is exhausted. This may not be brought about until the motion has travelled for the distance of hundreds of miles. In the great earthquake of 1755, known as the Lisbon shock, the records make it seem probable that the movement was felt over one eighth part of the earth's surface. Such great disturbances probably bring about a motion of the rocks near the point of origin, which may be expressed in oscillations having an amplitude of one to two feet; but in the greater number of earthquakes the maximum swing probably does not exceed the tenth of that amount. Very sensible shaking, even such as may produce considerable damage to buildings, are caused by shocks in which the earth vibrates with less than an inch of swing. When a shock originates, the wave in the rocks due to the compression which the blow inflicts runs at a speed varying with the elasticity of the substance, but at the rate of about fifteen hundred feet a second. The movements of this wave are at right angles to the seat of the originating disturbance, so that the shock may come to the surface in a line forming any angle between the vertical and the nearly horizontal. Where, as in a volcanic eruption, the shock originates with an explosion, these waves go off in circles. Where, however, as is generally the case, the shock originates in a fault plane, which may have a length and depth of many miles, the movement has an elliptical form. If the earthquake wave ran through a uniform and highly elastic substance, such as glass, it would move everywhere with equal speed, and, in the case of the greater disturbances, the motion might be felt over the whole surface of the earth. But as the motion takes place through rocks of varying elasticity, the rate at which it journeys is very irregular. Moving through materials of one density, and with a rate of vibration determined by those conditions, the impulse is with difficulty communicated to strata which naturally vibrate at another speed. In many cases, as where a shock passing through dense crystalline strata encounters a mass of soft sandstone, the wave, in place of going on, is reflected back toward its point of origin. These earthquake echoes sometimes give rise to very destructive movements. It often happens that before the original tremors of a shock have passed away from a point on the surface the reflex movements rush in, making a very irregular motion, which may be compared to that of the waves in a cross-sea. The foregoing account of earthquake action will serve to prepare the reader for an understanding of those very curious and important effects which these accidents produce in and on the earth. Below the surface the sensible action of earthquake shocks is limited. It has often been observed that people in mines hardly note a swaying which may be very conspicuous to those on the surface, the reason for this being that underground, where the rocks are firmly bound together, all those swingings which are due to the unsupported position of such objects as buildings, columnar rocks, trees, and the waters of the earth, are absent. The effect of the movements which earthquakes impress on the under earth is mainly due to the fact that in almost every part of the crust tensions or strains of other kinds are continually forming. These may for ages prove without effect until the earth is jarred, when motions will suddenly take place which in a moment may alter the conditions of the rocks throughout a wide field. In a word, a great earthquake caused by the formation of an extensive fault is likely to produce any number of slight dislocations, each of which is in turn shock-making, sending its little wave to complicate the great oscillation. Nor does the perturbing effect of these jarring movements cease with the fractures which they set up and the new strains which are in turn developed by the motions which they induce. The alterations of the rocks which are involved in chemical changes are favoured by such motions. It is a familiar experience that a vessel of water, if kept in the state of repose, may have its temperature lowered three or four degrees below the freezing point without becoming frozen. If the side of the vessel is then tapped with the finger, so as to send a slight quake through the mass, it will instantly congeal. Molecular rearrangements are thus favoured by shocks, and the consequences of those which run through the earth are, from a chemical point of view, probably important. The reader may help himself to understand something of the complicated problem of earth tensions, and the corresponding movements of the rocks, by considering certain homely illustrations. He may observe how the soil cracks as it shrinks in times of drought, the openings closing when it rains. In a similar way the frozen earth breaks open, sometimes with a shock which is often counted as an earthquake. Again, the ashes in a sifter or the gravel on a sieve show how each shaking may relieve certain tensions established by gravity, while they create others which are in turn to be released by the next shock. An ordinary dwelling house sways and strains with the alternations of temperature and moisture to which it is subjected in the round of climatal alterations. Now and then we note the movements in a cracking sound, but by far the greater part of them escape observation. With this sketch of the mechanism of earthquake shocks we now turn to consider their effects upon the surface of the earth. From a geological point of view, the most important effect of earthquake shocks is found in the movement of rock masses down steep slopes, which is induced by the shaking. Everywhere on the land the agents of decay and erosion tend to bring heavy masses into position where gravitation naturally leads to their downfall, but where they may remain long suspended, provided they are not disturbed. Thus, wherever there are high and steep cliffs, great falls of rock are likely to occur when the earthquake movements traverse the under earth. In more than one instance observers, so placed that they commanded a view of distant mountains, have noticed the downfall of precipices in the path of the shock before the trembling affected the ground on which they stood. In the famous earthquake of 1783, which devastated southern Italy, the Prince of Scylla persuaded his people to take refuge in their boats, hoping that they might thereby escape the destruction which threatened them on the land. No sooner were the unhappy folk on the water than the fall of neighbouring cliffs near the sea produced a great wave, which overwhelmed the vessels. Where the soil lies upon steep slopes, in positions in which it has accumulated during ages of tranquillity, a great shock is likely to send it down into the valleys in vast landslides. Thus, in the earthquake of 1692, the Blue Mountains of Jamaica were so violently shaken that the soil and the forests which stood on it were precipitated into the river beds, so that many tree-clad summits became fields of bare rock. The effect of this action is immensely to increase the amount of detritus which the streams convey to the sea. After the great Jamaica shock, above noted, the rivers for a while ceased to flow, their waters being stored in the masses of loose material. Then for weeks they poured forth torrents of mud and the _débris_ of vegetation--materials which had to be swept away as the streams formed new channels. In all regions where earthquake movements are frequent, and the shock of considerable violence, the trained observer notes that the surfaces of bare rock are singularly extensive, the fact being that many of these areas, where the slope lies at angles of from ten to thirty degrees, which in an unshaken region would be thickly soil-covered, are deprived of the coating by the downward movement of the waste which the disturbances bring about. A familiar example of this action may be had by watching the workmen engaged in sifting sand, by casting the material on a sloping grating. The work could not be done but for an occasional blow applied to the sifter. An arrangement for such a jarring motion is commonly found in various ore-dressing machines, where the object is to move fragments of matter over a sloping surface. Even where the earth is so level that an earthquake shock does not cause a sliding motion of the materials, such as above described, other consequences of the shaking may readily be noted. As the motion runs through the mass, provided the movement be one of considerable violence, crevices several feet in width, and sometimes having the length of miles, are often formed. In most cases these fissures, opened by one pulsation of the shock, are likely to be closed by the return movement, which occurs the instant thereafter. The consequences of this action are often singular, and in cases constitute the most frightful elements of a shock which the sufferer beholds. In the great earthquake of 1811, which ravaged the section of the Mississippi Valley between the mouth of the Ohio and Vicksburg, these crevices were so numerously formed that the pioneers protected themselves from the danger of being caught in their jaws by felling trees so that they lay at right angles to the direction in which the rents extended, building on these timbers platforms to support their temporary dwelling places. The records of earthquakes supply many instances in which people have been caught in these earth fissures, and in a single case it is recorded that a man who disappeared into the cavity was in a moment cast forth in the rush of waters which in this, as in many other cases, spouts forth as the walls of the opening come together. Sometimes these rents are attended by a dislocation, which brings the earth on one side much higher than on the other. The step thus produced may be many miles in length, and may have a height of twenty feet or more. It needs no argument to show that we have here the top of a fault such as produced the shock, or it may be one of a secondary nature, such as any earthquake is likely to bring about in the strata which it traverses. In certain cases two faults conjoin their action, so that a portion of the surface disappears beneath the earth, entombing whatever may have stood on the vanished site. Thus in the great shock known as that of Lisbon, which occurred in 1755, the stone quay along the harbour, where many thousand people had sought refuge from the falling buildings of the city, suddenly sank down with the multitude, and the waters closed over it; no trace of the people or of the structure was to be found after the shock was over. There is a story to the effect that during the same earthquake an Arab village in northern Africa sank down, the earth on either side closing over it, so that no trace of the habitations remained. In both these instances the catastrophes are best explained by the diagram. [Illustration: Fig. 21.--Diagram showing how a portion of the earth's surface may be sunk by faulting. Fig. A shows the original position; B, the position after faulting; b b' and c c' the planes of the faults; the arrows the direction of the movement.] In the earthquake of 1811 the alluvial plains on either side of the Mississippi at many points sank down so that arable land was converted into lakes; the area of these depressions probably amounted to some hundred square miles. The writer, on examining these sunken lands, found that the subsidences had occurred where the old moats or abandoned channels of the great river had been filled in with a mixture of decaying timber and river silt. When violently shaken, this loose-textured _débris_ naturally settled down, so that it formed a basin occupied by a crescent-shaped lake. The same process of settling plentifully goes on wherever the rocks are still in an uncemented state. The result is often the production of changes which lead to the expulsion of gases. Thus, in the Charleston earthquake of 1883, the surface over an area of many hundred square miles was pitted with small craters, formed by the uprush of water impelled by its contained gases. These little water volcanoes--for such we may call them--sometimes occur to the number of a dozen or more on each acre of ground in the violently shaken district. They indicate one result of the physical and chemical alterations which earthquake shocks bring about. As earthquakes increase in violence their effect upon the soil becomes continually greater, until in the most violent shocks all the loose materials on the surface of the earth may be so shaken about as to destroy even the boundaries of fields. After the famous earthquake of Riobamba, which occurred on the west coast of South America in 1797, the people of the district in which the town of that name was situated were forced to redivide their land, the original boundaries having disappeared. Fortunately, shocks of this description are exceedingly rare. They occur in only a few parts of the world. Certain effects of earthquakes where the shock emerges beneath the sea have been stated in the account of volcanic eruptions (see page 299). We may therefore note here only certain of the more general facts. While passing through the deep seas, this wave may have a height of not more than two or three feet and a width of some score miles. As it rolls in upon the shore the front of the undulation is retarded by the friction of the bottom in such a measure that its speed is diminished, while the following part of the waves, being less checked, crowds up toward this forward part. The result is, that the surge mounts ever higher and higher as it draws near the shore, upon which it may roll as a vast wave having the height of fifty feet or more and a width quite unparalleled by any wave produced from wind action. Waves of this description are most common in the Pacific Ocean. Although but occasional, the damage which they may inflict is very great. As the movement approaches the shore, vessels, however well anchored, are dragged away to seaward by the great back lash of the wave, a phenomenon which may be perceived even in the case of the ordinary surf. Thus forced to seaward, the crews of the ships may find their vessels drawn out for the distance of some miles, until they come near the face of the advancing billow. This, as it approaches the shore, straightens up to the wall-fronted form, and then topples upon the land. Those vessels which are not at once crushed down by the blow are generally hurled far inland by the rush of waters. In the great Jamaica earthquake of 1692 a British man-of-war was borne over the tops of certain warehouses and deposited at a distance from the shore. Owing to the fact that water is a highly elastic material, the shocks transmitted to it from the bottom are sent onward with their energy but little diminished. While the impulse is very violent, these oscillations may prove damaging to shipping. The log-books of mariners abound in stories of how vessels were dismasted or otherwise badly shaken by a sudden blow received in the midst of a quiet sea. The impression commonly conveyed to the sailors is that the craft has struck upon a rock. The explanation is that an earthquake jar, in traversing the water, has delivered its blow to the ship. As the speed of this jarring movement is very much greater than that of any ordinary wave, the blow which it may strike may be most destructive. There seems, indeed, little reason to doubt that a portion of the vessels which are ever disappearing in the wilderness of the ocean are lost by the crushing effect of these quakings which pass through the waters of the deep. We have already spoken of the earthquake shock as an oscillation. It is a quality of all bodies which oscillate under the influence of a blow, such as originates in earthquake shocks, to swing to and fro, after the manner of the metal in a bell or a tuning fork, in a succession of movements, each less than the preceding, until the impulse is worn out, or rather, we should in strict sense say, changed to other forms of energy. The result is, that even in the slightest earthquake shock the earth moves not once to and fro, but very many times. In a considerable shock the successive diminishing swingings amount to dozens before they become so slight as to elude perception. Although the first swaying is the strongest, and generally the most destructive, the quick to-and-fro motions are apt to continue and to complete the devastation which the first brings about. The vibrations due to any one shock take place with great rapidity. They may, indeed, be compared to those movements which we perceive in the margin of a large bell when it has received a heavy blow from the clapper. The reader has perhaps seen that for a moment the rim of the bell vibrates with such rapidity that it has a misty look--that is, the motions elude the sight. It is easy to see that a shaking of this kind is particularly calculated to disrupt any bodies which stand free in the air and are supported only at their base. In what we may call the natural architecture of the earth, the pinnacles and obelisks, such as are formed in many high countries, the effect of these shakings is destructive, and, as we have seen, even the firmer-placed objects, such as the strong-walled cliffs and steep slopes of earth, break down under the assaults. It is therefore no matter of surprise that the buildings which man erects, where they are composed of masonry, suffer greatly from these tremblings. In almost all cases human edifices are constructed without regard to other problems of strength than those which may be measured by their weight and the resistance to fracture from gravitation alone. They are not built with expectation of a quaking, but of a firm-set earth. The damage which earthquakes do to buildings is in most cases due to the fact that they sway their walls out of plumb, so that they are no longer in position to support the weight which they have to bear. The amount of this swaying is naturally very much greater than that which the earth itself experiences in the movement. A building of any height with its walls unsupported by neighbouring structures may find its roof rocked to and fro through an arc which has a length of feet, while its base moves only through a length of inches. The reader may see an example of this nature if he will poise a thin book or a bit of plank a foot long on top of a small table; then jarring the table so that it swings through a distance of say a quarter of an inch, he will see that the columnar object swings at its top through a much greater distance, and is pretty sure to be overturned. Where a building carries a load in its upper parts, such as may be afforded by its heavy roof or the stores which it contains, the effect of an earthquake shock such as carries the earth to and fro becomes much more destructive than it might otherwise be. This weight lags behind when the earth slips forward in the first movement of the oscillation, with the effect that the walls of the building are pretty sure to be thrust so far beyond the perpendicular that they give way and are carried down by the weight which they bore. It has often been remarked in earthquake shocks that tall columns, even where composed of many blocks, survive a shock which overturns lower buildings where thin walls support several floors, on each of which is accumulated a considerable amount of weight. In the case of the column, the strains are even, and the whole structure may rock to and fro without toppling over. As the energy of the undulations diminish, it gradually regains the quiet state without damage. In the ordinary edifice the irregular disposition of the weight does not permit the uniform movement which may insure safety. Thus, if the city of Washington should ever be violently shaken, the great obelisk, notwithstanding that it is five hundred feet high, may survive a disturbance which would wreck the lower and more massive edifices which lie about it. Where, as is fortunately rarely the case, the great shock comes to the earth in a vertical direction, the effect upon all movable objects is in the highest measure disastrous. In such a case buildings are crushed as if by the stroke of a giant's hand. The roofs and floors are at one stroke thrown to the foundations, and all the parts of the walls which are not supported by strong masonry continuous from top to bottom are broken to pieces. In such cases it has been remarked that the bodies of men are often thrown considerable distances. It is asserted, indeed, that in the Riobamba shock they were cast upward to the height of more than ninety feet. It is related that the solo survivor of a congregation which had hastened at the outset of the disturbance into a church was thrown by the greatest and most destructive shock upward and through a window the base of which was at the height of more than twenty feet from the ground. It is readily understood that an earthquake shock may enter a building in any direction between the vertical and the horizontal. As the movement exhausts itself in passing from the place of its origin, the horizontal shocks are usually of least energy. Those which are accurately vertical are only experienced where the edifices are placed immediately over the point where the motion originates. It follows, therefore, that the destructive work of earthquakes is mainly performed in that part of the field where the motion is, as regards its direction, between the vertical and the horizontal--a position in which the edifice is likely to receive at once the destructive effect arising from the sharp upward thrust of the vertical movement and the oscillating action of that which is in a horizontal direction. Against strains of this description, where the movements have an amplitude of more than a few inches, no ordinary masonry edifice can be made perfectly safe; the only tolerable security is attained where the building is of well-framed timber, which by its elasticity permits a good deal of motion without destructive consequences. Even such buildings, however, those of the strongest type, may be ruined by the greater earthquakes. Thus, in the Mississippi Valley earthquake of 1811, the log huts of the frontiersmen, which are about as strong as any buildings can be made, were shaken to pieces by the sharp and reiterated shocks. It is by no means surprising to find that the style of architecture adopted in earthquake countries differs from that which is developed in regions where the earth is firm-set. The people generally learn that where their buildings must meet the trials of earthquakes they have to be low and strong, framed in the manner of fortifications, to withstand the assault of this enemy. We observe that Gothic architecture, where a great weight of masonry is carried upon slender columns and walls divided by tall windows, though it became the dominant style in the relatively stable lands of northern Europe, never gained a firm foothold in those regions about the Mediterranean which are frequently visited by severe convulsions of the earth. There the Grecian or the Romanesque styles, which are of a much more massive type, retain their places and are the fashions to the present day. Even this manner of building, though affording a certain security against slight tremblings, is not safe in the greater shocks. Again and again large areas in southern Italy have been almost swept of their buildings by the destructive movements which occur in that realm. The only people who have systematically adapted their architectural methods to earthquake strains are the Japanese, who in certain districts where such risks are to be encountered construct their dwellings of wood, and place them upon rollers, so that they may readily move to and fro as the shock passes beneath them. In a measure the people of San Francisco have also provided against this danger by avoiding dangerous weights in the upper parts of their buildings, as well as the excessive height to which these structures are lifted in some of our American towns. Earthquakes of sensible energy appear to be limited to particular parts of the earth's crust. The regions, indeed, where within the period of human history shocks of devastating energy have occurred do not include more than one fifteenth part of the earth's surface. There is a common notion that these movements are most apt to happen in volcanic regions. It is, indeed, true that sensible shocks commonly attend the explosions from great craters, but the records clearly show that these movements are very rarely of destructive energy. Thus in the regions about the base of Vesuvius and of Ætna, the two volcanoes of which most is known, the shocks have never been productive of extensive disaster. In fact, the reiterated slight jarrings which attend volcanic action appear to prevent the formation of those great and slowly accumulated strains which in their discharge produce the most violent tremblings of the earth. The greatest and most continuous earthquake disturbances of history--that before noted in the early days of this century, in the Mississippi Valley, where shocks of considerable violence continued for two years--came about in a field very far removed from active volcanoes. So, too, the disturbances beneath the Atlantic floor which originated the shocks that led to the destruction of Lisbon, and many other similar though less violent movements, are developed in a field apparently remote from living volcanoes. Eastern New England, which has been the seat of several considerable earthquakes, is about as far away from active vents as any place on the habitable globe. We may therefore conclude that, while volcanoes necessarily produce shocks resulting from the discharge of their gases and the intrusion of lava into the dikes which are formed about them, the greater part of the important shocks are in no wise connected with volcanic explosions. With the exception of the earthquake in the Mississippi Valley, all the great shocks of which we have a record have occurred in or near regions where the rocks have been extensively disturbed by mountain-building forces, and where the indications lead us to believe that dislocations of strata, such as are competent to rive the beds asunder, may still be in progress. This, taken in connection with the fact that many of these shocks are attended by the formation of fault planes, which appear on the surface, lead us to the conclusion that earthquakes of the stronger kind are generally formed by the riving of fissures, which may or may not be developed upward to the surface. This view is supported by many careful observations on the effect which certain great earthquakes have exercised on the buildings which they have ravaged. The distinguished observer, Mr. Charles Mallet, who visited the seat of the earthquake which, in 1854, occurred in the province of Calabria in Italy, with great labour and skill determined the direction in which the shock moved through some hundreds of edifices on which it left the marks of its passage. Platting these lines of motion, he found that they were all referred to a vertical plane lying at the depth of some miles beneath the surface, and extending for a great distance in a north and south direction. This method of inquiry has been applied to other fields, with the result that in the case of all the instances which have been subjected to this inquiry the seat of the shock has been traced to such a plane, which can best be accounted for by the supposition of a fault. The method pursued by Mr. Mallet in his studies of the origin of earthquakes, and by those who have continued his inquiry, may be briefly indicated as follows: Examining disrupted buildings, it is easy to determine those which have been wrecked by a shock that emerged from the earth in a vertical direction. In these cases, though tall walls may remain standing, the roofs and floors are thrown into the cellars. With a dozen such instances the plane of what is called the seismic vertical is established (_seismos_ is the Greek for earthquake). Then on either side of this plane, which indicates the line but not the depth of the disturbance, other observations may be made which give the clew to the depth. Thus a building may be found where the northwest corner at its upper part has been thrown off. Such a rupture was clearly caused by an upward but oblique movement, which in the first half of the oscillation heaved the structure upwardly into the northwest, and then in the second half, or rebound, drew the mass of the building away from the unsupported corner, allowing that part of the masonry to fly off and fall to the ground. Constructing a line at right angles to the plane of the fracture, it will be found to intersect the plane, the position of which has been in part determined by finding the line where it intersects the earth, or the seismic vertical before noted. Multiplying such observations on either side of the last-mentioned line, the attitude of the underground parts of the plane, as well as the depth to which it attained, can be approximately determined. It is worth while to consider the extent to which earthquake shocks may affect the general quality of the people who dwell in countries where these disturbances occur with such frequency and violence as to influence their lives. There can be no question that wherever earthquakes occur in such a measure as to produce widespread terror, where, recurring from time to time, they develop in men a sense of abiding insecurity, they become potent agents of degradation. All the best which men do in creating a civilization rests upon a sense of confidence that their efforts may be accumulated from year to year, and that even after death the work of each man may remain as a heritage to his kind. It is likely, indeed, that in certain realms, as in southern Italy, a part of the failure of the people to advance in culture is due to their long experience of such calamities, and the natural expectation that they will from time to time recur. In a similar way the Spanish settlements in Central and South America, which lie mostly in lands that are subject to disastrous shocks, may have been retarded by the despair, as well as the loss of property and life, which these accidents have so frequently inflicted upon them. It will not do, however, to attribute too much to such terrestrial influences. By far the most important element in determining the destiny of a people is to be found in their native quality, that which they owe to their ancestors of distant generations. In this connection it is well to consider the history of the Icelandic people, where a small folk has for a thousand years been exposed to a range and severity of trials, such as earthquakes, volcanic explosions, and dearth of harvests may produce, and all these in a measure that few if any other countries experience. Notwithstanding these misfortunes, the Icelanders have developed and maintained a civilization which in all else, except its material results, on the average transcends that which has been won by any other folk in modern times. If a people have the determining spirit which leads to high living, they can successfully face calamities far greater than those which earthquakes inflict. It was long supposed that the regions where earthquakes are not noticeable by the unaided senses were exempt from all such disturbances. The observations which seismologists have made in recent years point to the conclusion that no part of the earth's surface is quite exempt from movements which, though not readily perceived, can be made visible by the use of appropriate instruments. With an apparatus known as the horizontal pendulum it is possible to observe vibrations which do not exceed in amplitude the hundredth part of an inch. This mechanism consists essentially of a slender bar supported near one end by two wires, one from above, the other from below. It may readily be conceived that any measurable movement will cause the longer end of the rod to sway through a considerable arc. Wherever such a pendulum has been carefully observed in any district, it has been found that it indicates the occurrence of slight tremors. Even certain changes of the barometer, which alter the weight of the atmosphere that rests upon the earth to the amount indicated by an inch in the height of the mercury column, appears in all cases to create such tremors. Many of these slight shocks may be due to the effect of more violent quakings, which have run perhaps for thousands of miles from their point of origin, and have thus been reduced in the amplitude of their movement. Others are probably due to the slight motion brought about through the chemical changes of the rocks, which are continuously going on. The ease with which even small motions are carried to a great distance may be judged by the fact that when the ground is frozen the horizontal pendulum will indicate the jarring due to a railway train at the distance of a mile or more from the track. In connection with the earth jarring, it would be well to note the occurrence of another, though physically different, kind of movement, which we may term earth swayings, or massive movements, which slowly dislocate the vertical, and doubtless also the horizontal, position of points upon its surface. It has more than once been remarked that in mountain countries, where accurate sights have been taken, the heights of points between the extremities of a long line appear somewhat to vary in the course of a term of years. Thus at a place in the Apennines, where two buildings separated by some miles of distance are commonly intervisible over the crest of a neighbouring peak, it has happened that a change of level of some one of the points has made it impossible to see the one edifice from the other. Knowing as we do that the line of the seacoast is ever-changing, uprising taking place at some points and down-sinking at others, it seems not unlikely that these irregular swayings are of very common occurrence. Moreover, astronomers are beginning to remark the fact that their observatories appear not to remain permanently in the same position--that is, they do not have exactly the same latitude and longitude. Certain of these changes have recently been explained by the discovery of a new and hitherto unnoted movement of the polar axis. It is not improbable, however, that the irregular swaying of the earth's crust, due to the folding of strata and to the alterations in the volume of rocks which are continually going on, may have some share in bringing about these dislocations. Measured by the destruction which was wrought to the interests of man, earthquakes deserve to be reckoned among the direst calamities of Nature. Since the dawn of history the records show us that the destruction of life which is to be attributed to them is to be counted by the millions. A catalogue of the loss of life in the accidents of this description which have occurred during the Christian era has led the writer to suppose that probably over two million persons have perished from these shocks in the last nineteen centuries. Nevertheless, as compared with other agents of destruction, such as preventable disease, war, or famine, the loss which has been inflicted by earth movements is really trifling, and almost all of it is due to an obstinate carelessness in the construction of buildings without reference to the risks which are known to exist in earthquake-ridden countries. Although all our exact knowledge concerning the distribution of earthquakes is limited to the imperfect records of two or three thousand years, it is commonly possible to measure in a general way the liability to such accidents which may exist in any country by a careful study of the details of its topography. In almost every large area the process of erosion naturally leaves quantities of rock, either in the form of detached columns or as detrital accumulations deposited on steep slopes. These features are of relatively slow formation, and it is often possible to determine that they have been in their positions for a time which is to be measured by thousands of years. Thus, on inspecting a country such as North America, where the historic records cover but a brief time, we may on inquiry determine which portions of its area have long been exempt from powerful shocks. Where natural obelisks and steep taluses abound--features which would have disappeared if the region had been moved by great shocks--we may be sure that the field under inspection has for a great period been exempt from powerful shaking. Judged by this standard, we may safely say that the region occupied by the Appalachian Mountains has been exempt from serious trouble. So, too, the section of the Cordilleras lying to the east of what is commonly called the Great Basin, between the Rocky Mountains and the Sierra Nevada, has also enjoyed a long reign of peace. In glaciated countries the record is naturally less clear than in those parts of the world which have been subjected to long-continued, slow decay of the rocks. Nevertheless, in those fields boulders are often found poised in position which they could not have maintained if subjected to violent shaking. Judged by this evidence, we may say that a large part of the northern section of this continent, particularly the area about the Great Lakes, has been exempt from considerable shocks since the glacier passed away. The shores which are subject to the visitations of the great marine waves, caused by earthquake shocks occurring beneath the bottom of the neighbouring ocean, are so swept by those violent inundations that they lose many features which are often found along coasts that have been exempted from such visitations. Thus wherever we find extensive and delicately moulded dunes, poised stones, or slender pinnacled rocks along a coast, we may be sure that since these features were formed the district has not been swept by these great waves. [Illustration: Fig. 22.--Poised rocks indicating a long exemption from strong earthquakes in the places where such features occur.] Around the northern Atlantic we almost everywhere find the glacial waste here and there accumulated near the margin of the sea in the complicated sculptured outlines which are assumed by kame sands and gravels. From a study of these features just above the level of high tide, the writer has become convinced that the North Atlantic district has long been exempt from the assaults of other waves than those which are produced during heavy storms. At the present time the waves formed by earthquakes appear to be of destructive violence only on the west coast of South America, where they roll in from a region of the Pacific lying to the south of the equator and a few hundred miles from the shore of the continent, which appears to be the seat of exceedingly violent shocks. A similar field occurs in the Atlantic between the Lesser Antilles and the Spanish peninsula, but no great waves have come thence since the time of the Lisbon earthquake. The basin of the Caribbean and the region about Java appear to be also fields where these disturbances may be expected, though in each but one wave of this nature has been recorded. Therefore we may regard these secondary results of a submarine earthquake as seldom phenomena. DURATION OF GEOLOGICAL TIME. Although it is beyond the power of man to conceive any such lapses of time as have taken place in the history of this earth, it is interesting, and in certain ways profitable, to determine as near as possible in the measure of years the duration of the events which are recorded in the rocks. Some astronomers, basing their conclusions on the heat-containing power of matter, and on the rate at which energy in this form flows from the sun, have come to the conclusion that our planet could not have been in independent existence for more than about twenty million years. The geologist, however, resting his conclusions on the records which are the subject of his inquiry, comes on many different lines to an opinion which traverses that entertained by some distinguished astronomers. The ways in which the student of the earth arrives at this opinion will now be set forth. By noting the amount of sediment carried forth to the sea by the rivers, the geologist finds that the lands of the earth--those, at least, which are protected by their natural envelopes of vegetation--are wearing down at a rate which pretty certainly does not exceed one foot in about five thousand years, or two hundred feet in a million years. Discovering at many places on the earth's surface deposits which originally had a thickness of five thousand feet or more, which have been worn down to the depths of thousands of feet in a single rather brief section of geological time, the student readily finds himself prepared to claim that a period of from five to ten million years has often been required for the accomplishment of but a very small part of the changes which he knows to have occurred on this earth. As the geologist follows down through the sections of the stratified rocks, and from the remains of strata determines the erosion which has borne away the greater part of the thick deposits which have been exposed to erosion, he comes upon one of those breaks in the succession, or encounters what is called an unconformity, as when horizontal strata lie against those which are tilted. In many cases he may observe that at this time there was a great interval unrepresented by deposits at the place where his observations are made, yet a great lapse of time is indicated by the fact that a large amount of erosion took place in the interval between the two sets of beds. Putting together the bits of record, and assuming that the rate of erosion accomplished by the agents which operate on the land has always been about the same, the geologist comes to the conclusion that the section of the rocks from the present day to the lowest strata of the Laurentian represents in the time required for their formation not less than a hundred million years; more likely twice that duration. To this argument objection is made by some naturalists that the agents of erosion may have been more active in the past than they are at present. They suggest that the rainfall may have been much greater or the tides higher than they now are. Granting all that can be claimed on this score, we note the fact that the rate of erosion evidently does not increase in anything like a proportionate way with the amount of rainfall. Where a country is protected by its natural coating of vegetation, the rain is delivered to the streams without making any considerable assault upon the surface of the earth, however large the fall may be. Moreover, the tides have little direct cutting power; they can only remove detritus which other agents have brought into a condition to be borne away. The direct cutting power of the tidal movement does not seem to be much greater in the Bay of Fundy, where the maximum height of the waves amounts to fifty feet, than on the southern coast of Massachusetts, where the range is not more than five. So far as the observer can judge, the climatal conditions and the other influences which affect the wear of rocks have not greatly varied in the past from what they are at the present day. Now and then there have been periods of excessive erosion; again, ages in which large fields were in the conditions of exceeding drought. It is, however, a fair presumption that these periods in a way balance each other, and that the average state was much like that which we find at present. If after studying the erosive phenomena exhibited in the structure of the earth the student takes up the study of the accumulations of strata, and endeavours to determine the time required for the laying down of the sediments, he finds similar evidence of the earth's great antiquity. Although the process of deposition, which has given us the rocks visible in the land masses, has been very much interrupted, the section which is made by grouping the observations made in various fields shows that something like a maximum thickness of a hundred and fifty thousand feet of beds has been accumulated in that part of geologic time during which strata were being laid down in the fields that are subjected to our study. Although in these rocks there are many sets of beds which were rapidly formed, the greater part of them have been accumulated with exceeding slowness. Many fine shales, such as those which plentifully occur in the Devonian beds of this country, must have required a thousand years or more for the deposition of the materials that now occupy an inch in depth. In those sections a single foot of the rock may well represent a period of ten thousand years. In many of the limestones the rate of accumulation could hardly have been more speedy. The reckoning has to be rough, but the impression which such studies make upon the mind of the unprejudiced observer is to the effect that the thirty miles or so of sedimentary deposits could not have been formed in less than a hundred million years. In this reckoning it should be noted that no account is taken of those great intervals of unrecorded time, such as elapsed between the close of the Laurentian and the beginning of the Cambrian periods. There is a third way in which we may seek an interpretation of duration from the rocks. In each successive stage of the earth's history, in different measure in the various ages, mountains were formed which in time, during their exposure to the conditions of the land, were worn down to their roots and covered by deposits accumulated during the succeeding ages. A score or more of these successively constructed series of elevations may readily be observed. Of old, it was believed that mountain ranges were suddenly formed, but there is, however, ample evidence to prove that these disturbed portions of the strata were very gradually dislocated, the rate of the mountainous growth having been, in general, no greater in the past than it is at the present day, when, as we know full well, the movements are going on so slowly that they escape observation. Only here and there, as an attendant on earthquake shocks or other related movements of the crust, do we find any trace of the upward march which produces these elevations. Although not a subject for exact measurements, these features of mountain growth indicate a vast lapse of time, during which the elevations were formed and worn away. Yet another and very different method by which we may obtain some gauge of the depths of the past is to be found in the steps which have led organic life from its lowest and earliest known forms to the present state of advancement. Taking the changes of species which have occurred since the beginning of the last ice epoch, we find that the changes which have been made in the organic life have been very small; no naturalist who has obtained a clear idea of the facts will question the statement that they are not a thousandth part of the alterations which have occurred since the Laurentian time. The writer is of the opinion that they do not represent the ten thousandth part of those vast changes. These changes are limited in the main to the disappearance of a few forms, and to slight modifications in those previously in existence which have survived to the present day. So far as we can judge, no considerable step in the organic series has taken place in this last great period of the earth's history, although it has been a period when, as before noted, all the conditions have combined to induce rapid modifications in both animals and plants. If, then, we can determine the duration of this period, we may obtain a gauge of some general value. Although we can not measure in any accurate way the duration of the events which have taken place since the last Glacial period began to wane, a study of the facts seems to show that less than a hundred thousand years can not well be assumed for this interval. Some of the students who have approached the subject are disposed to allow a period of at least twice this length as necessary for the perspective which the train of events exhibits. Reckoning on the lowest estimate, and counting the organic changes which take place during the age as amounting to the thousandth part of the organic changes since the Laurentian age, we find ourselves in face once again of that inconceivable sum which was indicated by the physical record. Here, again, the critics assert that there may have been periods in the history of the earth when the changes of organic life occurred in a far swifter manner than in this last section of the earth's history. This supposition is inadmissible, for it rests on no kind of proof; it is, moreover, contraindicated by the evident fact that the advance in the organic series has been more rapid in recent time than at any stage of the past. In a word, all the facts with which the geologist deals are decidedly against the assumption that terrestrial changes in the organic or the inorganic world ever proceed in a spasmodic manner. Here and there, and from time to time, local revolutions of a violent nature undoubtedly occur, but, so far as we may judge from the aspect of the present or the records of the past, these accidents are strictly local; the earth has gone forward in its changes much as it is now advancing. Its revolutions have been those of order rather than those of accident. The first duty of the naturalist is to take Nature as he finds it. He must avoid supposing any methods of action which are not clearly indicated in the facts that he observes. The history of his own and of all other sciences clearly shows that danger is always incurred where suppositions as to peculiar methods of action are introduced into the interpretation. It required many centuries of labour before the students of the earth came to adopt the principle of explaining the problems with which they had to deal by the evidence that the earth submitted to them. Wherever they trusted to their imaginations for guidance, they fell into error. Those who endeavour to abbreviate our conception of geologic time by supposing that in the olden days the order of events was other than that we now behold are going counter to the best traditions of the science. Although the aspect of the record of life since the beginning of the Cambrian time indicates a period of at least a hundred million years, it must not be supposed that this is the limit of the time required for the development of the organic series. All the important types of animals were already in existence in that ancient period with the exception of the vertebrates, the remains of which have apparently now been traced down to near the Cambrian level. In other words, at the stage where we first find evidence of living beings the series to which they belong had already climbed very far above the level of lifeless matter. Few naturalists will question the statement that half the work of organic advance had been accomplished at the beginning of the Cambrian rocks. The writer is of the opinion that the development which took place before that age must have required a much longer period than has elapsed from that epoch to the present day. We thus come to the conclusion that the measurement of duration afforded by organic life indicates a yet more lengthened claim of events, and demands more time than appears to be required for the formation of the stratified rocks. The index of duration afforded by the organic series is probably more trustworthy than that which is found in the sedimentary strata, and this for the reason that the records of those strata have been subjected to numerous and immeasurable breaks, while the development of organic life has of necessity been perfectly continuous. The one record can at any point be broken without interrupting the sequences; the other does not admit of any breaches in the continuity. THE MOON. Set over against the earth--related to, yet contrasted with it in many ways--the moon offers a most profitable object to the student of geology. He should often turn to it for those lessons which will be briefly noted. In the beginning of their mutual history the materials of earth and moon doubtless formed one vaporous body which had been parted from the concentrating mass of the sun in the manner noted in the sketch of the history of the solar system. After the earth-moon body had gathered into a nebulous sphere, it is most likely that a ring resembling that still existing about Saturn was formed about the earth, which in time consolidated into the satellite. Thenceforth the two bodies were parted, except for the gravitative attraction which impelled them to revolve about their common centre of gravity, and except for the light and heat they might exchange with one another. The first stages after the parting of the spheres of earth and moon appear to have been essentially the same in each body. Concentrating upon their centres, they became in time fluid by heat; further on, they entered the rigid state--in a word, they froze--at least in their outer parts. At this point in their existence their histories utterly diverge; or rather, we may say, the development of the earth continued in a vast unfolding, while that of the moon appears to have been absolutely arrested in ways which we will now describe. With the naked eye we see on the moon a considerable variation in the light of different parts of its surface; we discern that the darker patches appear to be rudely circular, and that they run together on their margins. Seeing this little, the ancients fancied that our satellite had seas and lands like the earth. The first telescopes did not dispel their fancies; even down to the early part of this century there were astronomers who believed the moon to be habitable; indeed, they thought to find evidence that it was the dwelling place of intelligent beings who built cities, and who tried to signal their intellectual kindred of this planet. When, however, strong glasses were applied to the exploration, these pleasing fancies were rudely dispelled. Seen with a telescope of the better sort, the moon reveals itself to be in large part made up of circular depressions, each surrounded by a ringlike wall, with nearly level but rough places between. The largest of these walled areas is some four hundred miles in diameter; thence they grade down to the smallest pits which the glass can disclose, which are probably not over as many feet across. The writer, from a careful study of these pits, has come to the conclusion that the wider are the older and the smaller the last formed. The rude elevations about these pits--some of which rise to the height of ten thousand feet or more--constitute the principal topographic reliefs of the lunar surface. Besides the pits above mentioned, there are numerous fractures in the surface of the plains and ringlike ridges; on the most of these the walls have separated, forming trenches not unlike what we find in the case of some terrestrial breaks such as have been noted about volcanoes and elsewhere. It may be that the so-called canals of Mars are of the same nature. [Illustration: Fig. 23.--Lunar mountains near the Gulf of Iris.] The most curious feature on the moon's surface are the bands of lighter colour, which, radiating from certain of the volcanolike pits--those of lesser size and probably of latest origin--extend in some cases for five hundred miles or more across the surface. These light bands have never been adequately explained. It seems most likely that they are stains along the sides of cracks, such as are sometimes observed about volcanoes. The eminent peculiarity of the moon is that it is destitute of any kind of gaseous or aqueous envelope. That there is no distinct atmosphere is clearly shown by the perfectly sharp and sudden way in which the light of a star disappears when it goes behind the moon and the clear lines of the edge of the satellite in a solar eclipse. The same evidence shows that there is no vapour of water; moreover, a careful search which the writer has made shows that the surface has none of those continuous down grades which mark the work of water flowing over the land. Nearly all of the surface consists of shallow or deep pits, such as could not have been formed by water action. We therefore have not only to conclude that the moon is waterless, but that it has been in this condition ever since the part that is turned toward us was shaped. As the moon, except for the slight movement termed its "libration," always turns the same face to us, so that we see in all only about four sevenths of its surface, it has naturally been conjectured that the unseen side, which is probably some miles lower than that turned toward us, might have a different character from that which we behold. There are reasons why this is improbable. In the first place, we see on the extreme border of the moon, when the libration turns one side the farthest around toward the earth, the edge of a number of the great walled pits such as are so plenty on the visible area; it is fair to assume that these rings are completed in the invisible realm. On this basis we can partly map about a third of the hidden side. Furthermore, there are certain bands of light which, though appearing on the visible side, evidently converge to some points on the other. It is reasonable to suppose that, as all other bands radiate from walled pits, these also start from such topographic features. In this way certain likenesses of the hidden area to that which is visible is established, thus making it probable that the whole surface of the satellite has the same character. Clearly as the greater part of the moon is revealed to us--so clearly, indeed, that it is possible to map any elevation of its surface that attains the height of five hundred feet--the interpretation of its features in the light of geology is a matter of very great difficulty. The main points seem to be tolerably clear; they are as follows: The surface of the moon as we see it is that which was formed when that body, passing from the state of fluidity from heat, formed a solid crust. The pits which we observe on its surface are the depressions which were formed as the mass gradually ceased to boil. The later formed of these openings are the smaller, as would be the case in such a slowing down of a boiling process. As the diameter of the moon is only about one fourth of that of the earth, its bulk is only about one sixteenth of that of its planet; consequently, it must have cooled to the point of solidification ages before the larger sphere attained that state. It is probable that the same changeless face that we see looked down for millions of years on an earth which was still a seething, fiery mass. In a word, all that vast history which is traceable in the rocks beneath our feet--which is in progress in the seas and lands and is to endure for an inconceivable time to come--has been denied our satellite, for the reason that it had no air with which to entrap the solar heat and no water to apply the solar energy to evolutionary processes. The heat which comes upon the moon as large a share for each equal area as it comes upon the earth flies at once away from the airless surface, at most giving it a temporary warmth, but instituting no geological work unless it be a little movement from the expansion and contraction of the rocks. During the ages in which the moon has remained thus lifeless the earth, owing to its air and water, has applied a vast amount of solar energy to geological work in the development and redevelopment of its geological features and to the processes of organic life. We thus see the fundamental importance of the volatile envelopes of our sphere, how absolutely they have determined its history. It would be interesting to consider the causes which led to the absence of air and water on the moon, but this matter is one of the most debatable of all that relates to that sphere; we shall therefore have to content ourselves with the above brief statements as to the vast and far-acting effects which have arisen from the non-existence of those envelopes on our nearest neighbour of the heavens. METHODS IN STUDYING GEOLOGY. So far as possible the preceding pages, by the method adopted in the presentation of facts, will serve to show the student the ways in which he may best undertake to trace the order of events exhibited in the phenomena of the earth. Following the plan pursued, we shall now consider certain special points which need to be noted by those who would adopt the methods of the geologist. At the outset of his studies it may be well for the inquirer to note the fact that familiarity with the world about him leads the man in all cases to a certain neglect and contempt of all the familiar presentations of Nature. We inevitably forget that those points of light in the firmament are vast suns, and we overlook the fact that the soil beneath our feet is not mere dirt, but a marvellous structure, more complicated in its processes than the chemist's laboratory, from which the sustenance of our own and all other lives is drawn. We feel our own bodies as dear but commonplace possessions, though we should understand them as inheritances from the inconceivable past, which have come to us through tens of thousands of different species and hundreds of millions of individual ancestors. We must overlook these things in our common life. If we could take them into account, each soul would carry the universe as an intellectual burden. It is, however, well from time to time to contemplate the truth, and to force ourselves to see that all this apparently simple and ordinary medley of the world about us is a part of a vast procession of events, coming forth from the darkness of the past and moving on beyond the light of the present day. Even in his professional work the naturalist of necessity falls into the commonplace way of regarding the facts with which he deals. If he be an astronomer, he catalogues the stars with little more sense of the immensities than the man who keeps a shop takes account of his wares. Nevertheless, the real profit of all learning is in the largeness of the understanding which it develops in man. The periods of growth in knowledge are those in which the mind, enriched by its store, enlarges its conception while it escapes from commonplace ways of thought. With this brief mention of what is by far the most important principle of guidance which the student can follow, we will turn to the questions of method that the student need follow in his ordinary work. With almost all students a difficulty is encountered which hinders them in acquiring any large views as to the world about them. This is due to the fact that they can not make and retain in memory clear pictures of the things they see. They remember words rather than things--in fact, the training in language, which is so large a part of an education, tends ever to diminish the element of visual memory. The first task of the student who would become a naturalist is to take his knowledge from the thing, and to remember it by the mental picture of the thing. In all education in Nature, whether the student is guided by his own understanding or that of the teacher, a first and very continuous aim should be to enforce the habit of recalling very distinct images of all objects which it is desired to remember. To this end the student should practise himself by looking intently upon a landscape or any other object; then, turning away, he should try to recall what he has beheld. After a moment the impression by the sight should be repeated, and the study of the memory renewed. The writer knows by his own experience that even in middle-aged people, where it is hard to breed new habits, such deliberate training can greatly increase the capacity of the memory for taking in and reproducing images which are deemed of importance. Practice of this kind should form a part of every naturalist's daily routine. After a certain time, it need not be consciously done. The movements of thought and action will, indeed, become as automatic as those which the trained fencer makes with his foil. Along with the habit of visualizing memories, and of storing them without the use of words, the student should undertake to enlarge his powers of conceiving spaces and directions as they exist in the field about him. Among savages and animals below the grade of man, this understanding of spacial relations is very clear and strong. It enables the primitive man to find his way through the trackless forest, and the carrier pigeon to recover his mate and dwelling place from the distance of hundreds of miles away. In civilized men, however, the habit of the home and street and the disuse of the ancient freedom has dulled, and in some instances almost destroyed, all sense of this shape of the external world. The best training to recover this precious capacity will now be set forth. The student should begin by drawing a map on a true scale, however roughly the work may be done, of those features of the earth about him with which he is necessarily most familiar. The task may well be begun with his own dwelling or his schoolroom. Thence it may be extended so as to include the plan of the neighbouring streets or fields. At first, only directions and distances should be platted. After a time to these indications should be added on the map lines indicating in a general way contours or the lines formed by horizontal planes intersecting the area subject to delineation. After attaining certain rude skill in such work, the student may advantageously make excursions to districts which he can see only in a hurried way. As he goes, he should endeavour to note on a sketch map the positions of the hills and streams and the directions of the roads. A year of holiday practice in such work will, if the tasks occupy somewhere about a hundred hours of his time, serve greatly to extend or reawaken what may be called the topographic sense, and enable him to place in terms of space the observations of Nature which he may make. In his more detailed work the student should select some particular field for his inquiry. If he be specially interested in geologic phenomena, he will best begin by noting two classes of facts--those exhibited in the rocks as they actually appear in the state of repose as shown in the outcrops of his neighbourhood, and those shown in the active manifestations of geological work, the decay of the rocks and the transportation of their waste, or, if the conditions favour, the complicated phenomena of the seashores. As soon as the student begins to observe, he should begin to make a record of his studies. To the novice in any science written, and particularly sketched, notes are of the utmost importance. These, whether in words or in drawings, should be made in face of the facts; they should, indeed, be set down at the close of an observation, though not until the observer feels that the object he is studying has yielded to him all which it can at that time give. It is well to remark that where a record is made at the outset of a study the student is apt to feel that he is in some way pledged to shape all he may see to fit that which he has first written. In his early experience as a teacher, the writer was accustomed to have students compare their work of observation and delineation with that done by trained men on the same ground. It now seems to him best for the beginner at first to avoid all such reference of his own work to that of others. So great is the need of developing independent motive that it is better at the outset to make many blunders than to secure accuracy by trust in a leader. The skilful teacher can give fitting words of caution which may help a student to find the true way, but any reference of his undertakings to masterpieces is sure to breed a servile habit. Therefore such comparisons are fitting only after the habit of free work has been well formed. The student who can afford the help of a master, or, better, the assistance of many, such as some of our universities offer, should by all means avail himself of this resource. More than any other science, geology, because of the complexity of the considerations with which it has to deal, depends upon methods of labour which are to a great extent traditional, and which can not, indeed, be well transmitted except in the personal way. In the distinctly limited sciences, such as mathematics, physics, or even those which deal with organic bodies, the methods of work can be so far set forth in printed directions that the student may to a great extent acquire sound ways of work without the help of a teacher. Although there is a vast and important literature concerning geology, the greater part of it is of a very special nature, and will convey to the beginner no substantial information whatever. It is not until he has become familiar with the field with which he is enabled to deal in the actual way that he can transfer experience thus acquired to other grounds. Therefore beyond the pleasing views which he may obtain by reading certain general works on the science, the student should at the outset of his inquiry limit his work as far as possible to his field of practice, using a good text-book, such as Dana's Manual of Geology, as a source of suggestions as to the problems which his field may afford. The main aim of the student in this, as in other branches of inquiry, is to gain practice in following out the natural series of actions. To the primitive man the phenomenal world presents itself as a mere phantasmagoria, a vast show in which the things seen are only related to each other by the fact that they come at once into view. The end of science is to divine the order of this host, and the ways in which it is marshalled in its onward movement and the ends to which its march appears to be directed. So far as the student observes well, and thus gains a clear notion of separated facts, he is in a fair way to gather the data of knowledge which may be useful; but the real value of these discernments is not gained until the observations go together, so as to make something with a perspective. Until the store of separate facts is thus arranged, it is merely crude material for thought; it is not in the true meaning science, any more than a store of stone and mortar is architecture. When the student has developed an appetite for the appreciation of order and sources of energy in phenomena, he has passed his novitiate, and becomes one of that happy body of men who not only see what is perceived by the mass of their fellows, but are enabled to look through those chains of action which, when comprehended, serve to rationalize and ennoble all that the senses of man, aided by the instruments which he has devised, tell us concerning the visible world. INDEX. Ætna, Mount, 381. Agriculture, American, 346; in England, winning swamp lands for, 335; recent developments of, 345. Alaska, changes on the coast of, 96. Ants taking food underground, 319; work of the, on the soil, 318. Apsides, revolution of the, 61, 62. Arabians, chemical experiments of the, 13. Arches, natural, in cavern districts, 258. Artesian wells, 258, 259. Arts, advance of Italian fine, 19. Asteroids, 53; motions of, about their centres and about the sun, 53. Astronomers, the solar system and the early, 79. Astronomy, 31-80; growth of, since the time of Galileo, 33, 34; the first science, 10. Atmosphere, 97-206; along the tropical belt, 102; as a medium of communication between different regions, 99; deprived of water, containing little heat, 105; beginning of the science of the, 117; counter-trade movements of the, 105; envelope of the earth, 98; expansion of, in a hollow wall during the passage of a storm, 114; heat-carrying power of the, 105; heights to which it extends, 99; in water, 99; movements no direct influence on the surface of the earth, 122; movements of the, qualified by the condition which it encounters, 118; of mountains, 98; of the seashore, 98; of the earth, 98; of the sun, 73; snow as an evidence of, 65; supplying needs of underground creatures, 331; uprushes of, 101, 102; upward strain of the, next the earth, 107; weight and motion of the, 120, 121. Atmospheric circulation of the soil, 330, 331; envelopes, 97. Aurora borealis, 168. Avalanches, 210-213; dreaded, in the Alpine regions, 212; great, in the Swiss Oberland, 211, 212; rocky, 175-177. Axis, imaginary changes in the earth's, 59; of the earth's rotation, 58; polar, inclined position of, 58; polar, nodding movement of the axes, 54; rotations of the planetary spheres on their axes, 56. Barometer, causes of changes in the, 117, 118. Basalts, 309. Beaches, 93, 142, 144; boulder, 142, 143; pebbly, 142; sand, 144. Beetles, work of, on the soil, 318, 319. Belief of the early astronomers about the solar system, 79. _Bergschrund_, the, 214. Birds and mammals contributing to the fertility of the soil, 319. "Blanketing," 269. Bogs, climbing, 331-334; lake, 331-333; peat, 334, 335; quaking, 334. Botany, rapid advance in, 14, 15. Boulders, 217, 220. Breakers, 135, 137, 139. Bridges, natural, 257, 258. Canals of Mars, 67. Cañon, newly formed river cutting a, 195. Cataracts, 193. Caves, 253-258, 261; architecture of, 255-258; hot-water, 261; mammoth cave, 258; stalactites and stalagmites on the roof and floor of, 257. Chasms, 140, 141. Chemistry, 6, 12, 14; advance of, 12; modern, evolving from the studies of alchemists, 13, 14. Chromosphere, 73. Civilization of the Icelanders, 384. Cliffs, sea-beaten, 132, 141, 142. Climate, changes of, due to modifications of the ocean streams, 153; effect of the ocean on the, 147; of the Gulf Stream, 149, 150. Clouds, 159; formation of, 162, 163; shape of, 163; water of, usually frozen, 207; cloud-making, laws of, 161, 162. Coast, changes on the Scandinavian, 96; line, effect of tide on the, 145; of Greenland, 226; of New Jersey sinking, 95; marine, changes in, 95. Cold in Siberia, 243. Comets, 47, 50; collisions of, 50; kinship of meteorites and, 48; omens of calamity to the ancients, 50; the great, of 1811, 49, 50. Cones. See under VOLCANOES. Conflict between religion and science, 20, 22; between the Protestant countries and the followers of science, 20. Continental shelves, 125. Continents and oceans, 83; changes in position of, 91; cyclones of the, 111; forms of, 90; proofs that they have endured for many years, 92; shape of, 84, 96. Coral reefs, 153, 353. Corona, realm of the, 73. Craters. See under VOLCANOES. Crevasse, a barrier to the explorer, 218. Crevice water, 250. Curds, 214. Currents, coral reefs in Florida affecting the velocity of, 153; equatorial, 150; of the Gulf Stream, 147-149; hot and cold, of the sea, 102; ocean, 145; oceanic action of trade winds on, 145; effect on migration of, 157; icebergs indicating, 243; surface, history of, 172; uprushing, near the equator, 106. Cyclones, 111; cause of, 111; of North America, 111; secondary storms of, 112. Deltas, 173, 187. Deposits, vein, 260, 261. Deserts, interior, 158. Dew, 159, 160; a concomitant of cloudless skies, 160, and vegetation, 160; formation of, 159-161. Diablerets, 174. Diagram of a vein, 260; showing development of swamp, 335; how a portion of the earth's surface may be sunk by faulting, 374; growth of mangroves, 340; the effect of the position of the fulcrum point in the movement of the land masses, 94. Diameter of our sphere at the equator, 62; of the earth, 82. Dikes, 192, 293; 305-310; abounding in volcanic cones, 305; cutting through coal, 306; driven upward, 307; formation of, 305, 310; material of, 307, 308; representing movements of softened rock, 309; their relation to volcanic cones, 307; variations of the materials of, 307, 308; waterfalls produced by, 192; zone of, 306. Dismal Swamp, 95, 333. Distances, general idea of, 27; good way to study, 27, 28; training soldiers to measure, 28. Doldrums, 104, 109; doldrum of the equator, 109; of the hurricane, 109. Drainage, imperfect, of a country affected by glaciers, 242. Dunes, 123, 124, 325, 326, 387; moulded, 387. Duration of geological time, 389. Dust accumulations from wind, in China, 122. Earth, a flattened sphere, 82; air envelope of the, 98; amount of heat falling from the sun on the, 41; antiquity of the, 391; atmosphere of the, 98; attracting power of the, 127; axis of the rotation of the, 58; composition of the atmosphere of the, 98; crust of the, affected by weight, 93; deviation of the path of the, varied, 61; diameter of the, 82; of the, affected by loss of heat, 131; difference in altitude of the surface of the, 83; discovery that it was globular, 31, 32; effect of imaginary changes in the relations of sun and, 59; effect of the interior heat of the, 309, 310; effect of the sun on the, 60, 61; formerly in a fluid state, 82; imaginary view of the, from the moon, 81; important feature of the surface of the, 83; jarring caused by faults, 367; surface of the, determined by heat and light from the sun, 57; most important feature of the surface of the, 83; motion of the, affecting the direction of trade winds, 103; movements, 366; natural architecture of the, 377; no part of the, exempt from movement, 384; parting of the moon and, 396; path of the, around the sun, 55, 56, 59, 60; revolving from east to west, 103; shrinking of the, from daily escape of heat, 89; soil-covering of the, 343; study of the, 81-96; swaying, 385; tensions, problem of, 371; tremors, caused by chemical changes in the rocks, 385; tropical belt of the, 74; viewed from the surface of the moon, 311, 312; water store of the, 125. Earthquakes, 277, 278, 280, 356, 358, 370-384, 388-390; accidents of, 358; action of, 356; agents of degradation, 383, 384; basis of, 367; certain limitations to, 380, 381; Charleston, of 1883, 374, 375; countries, architecture in, 381; echoes, 369, 370; damages of, 377, 390; effect of, on the soil, 375; the surface of the earth, 371; formed by riving of fissures, 382; great, occurring where rocks have been disturbed by mountain-building, 381, 382; Herculaneum and Pompeii destroyed by an, 277, 280; Italian, in 1783, 371, 372; important, not connected with volcanic explosions, 381; Jamaica, in 1692, 372, 376; Lisbon, in 1755, 368, 369, 373, 374, 381; maximum swing of, 369; measuring the liability to, 386, 387; mechanism of, 370, 371; method of the study of, followed by Mr. Charles Mallet, 382, 383; Mississippi, in 1811, 373, 374, 380, 381; movement of the earth during, 377; originating from a fault plane, 367, 369, 370; originating from the seas, 358, 375; oscillation of, 376; poised rocks indicating a long exemption from strong, 388; Riobamba, in 1797, 375; shocks of, and their effect upon people, 383; the direct calamities of Nature, 386; waves of, 389. Earthworms, 317-319; taking food underground, 319. Eclipses, record of ancient, 130. Electrical action in the formation of rain and snow, 164. Elevations of seas and lands, 83. Energy indestructible, 23. Envelope, lower, of the sun, 74. Equator, diameter of our sphere at the, 62; doldrum of the, 109; updraught under the, 102; uprushing current near the, 106. Equinoxes, precession of the, 61, 62. _Eskers_, 221. Expansion of air contained in a hollow wall during the passage of the storm, 114. Experiment, illustrating consolidation of disseminated materials of the sun and planets, 40. Falls. See WATERFALLS. Fault planes, 382. Feldspar, 324. Floods, 180, 197; rarity of, in New England, 121; river, frequent east of Rocky Mountains, 198. Föhns, 121. Forests, salicified, 124. Fossilization, 354-356. Fulcrum point, 95. Galactic plane, 45. Galongoon, eruption of, 294. Geological work of water, 168-206. Glacial action in the valleys of Switzerland, 224; periods, 63, 243, 246; in the northern hemisphere, 246; waste, 324. Glaciation, effect of, in North America, 241; in Central America, 234; South America, 234. Glaciers, 207-249; action of ice in forming, 230-232; Alaskan, 216; continental, 225, 239, 240; discharge of, 220; exploring, 220; extensive, in Greenland and Scandinavia, 244; former, of North America, 232, 234; map of, and moraines near Mont Blanc, 217; motions of, 213; retreat of the, 228, 230, 235; secrets of the under ice of, 221; speed of a, 224; study of, in the Swiss valleys, 222; testimony of the rocks regarding, 228; when covered with winter snows, 216; valley, 216. Gombridge, 1830, 74. Gravitation, law of, 4. Greeks' idea of the heavens, 31; not mechanically inventive, 22. Gulf Stream, current of the, 147. Heat, amount of, daily escaping from the earth, 89; amount of, falling from the sun on the earth, 41; belief of the ancients regarding, 42; dominating effect on air currents of tropical, 104; energy with which it leaves the sun, 41; internal, of the earth, 88, 89; of the earth's interior, 309, 310; sun, effect on the atmosphere of the, 100; Prof. Newcomb's belief regarding the, of the sun, 52; radiation of the earth's, causing winds, 101; solar, 41; tropical, and air currents, 104. Hills, sand, 123. Horizontal pendulum, 384. Horse latitudes, 104. "Horses," 261. Hurricanes, 107, 110, 317; commencement of, 107; doldrum of, 109; felt near the sea, 110; in the tropics, 110. Hypothesis, nebular, 34, 35, 39, 52, 56; working, 4, 5. Ice action, effect of intense, 222, 223; in forming glaciers, 230, 232; recent studies in Greenland of, 239; depth of, in Greenland, 227; effect of, on river channels, 196; effect of, on stream beds, 196; expanding when freezing, 237; epoch, 92, 93, 246; floating, 242; made soils rarely fertile, 241; mass, greatest, in Greenland, 226, 227; moulded by pressure, 215; streams, continental, 225, 226; of the mountains, 225; of the Himalayan Mountains, 234. Icebergs, 242, 243; indicating oceanic currents, 243. Iceland, volcanic eruptions in, 297, 298. Instruments, first, astronomical, 10, 11. Inventions, mechanical, aiding science, 22. Islands, 84, 272; continental, 84; in the deeper seas made up of volcanic ejections, 272; volcanic, 272. Jack-o'-lantern, 167. Jupiter, gaseous wraps of, 97; path of the earth affected by, 59, 60; the largest planet of the sun, 69. Kames, 325. Kant, Immanuel, and nebular hypothesis, 34. Kaolin, 324. Klondike district, cold in, 243, 244. Krakatoa, eruption of, 298-300; effect of, on the sea, 299; effect of, on the sun, 300. Lacolites, 306. Lacustrine beds, 351. Lagoons, salt deposits found in, 200. Lake basins, formation of, 200, 201; bogs, 331, 333, 334; deposits, 350, 351. Lakes, 199-206; effect of, on the river system, 205; fresh-water, 145; formed from caverns, 202; great, changing their outlets, 205; of extinct volcanoes, 203; temporary features of the land, 203; volcanic, 203. Lands, great, relatively unchangeable, 96; table, 91; movements resulting in change of coast line, 351, 352; shape of the seas and, 83, 84; accounting for the changes in the attitude of the, 95; and water, divisions of, 84; dry, surface of, 85; general statement as to the division of the, 83, 84; surface, shape of the, 85; triangular forms of great, 90. Latitudes, horse, troublesome to mariners, 104. Laplace and nebular hypothesis, 34. Lava, 266-268, 270, 271, 292, 293, 295, 296, 303, 304; flow of, invading a forest, 268; from Vesuvius, 293; of 1669, 295, 296; temperature of, 295, 296; incipient, 304; outbreaks of, 292, 303; stream eaves, 292, 293. Law, natural, Aristotle and, 3; of gravitation, 4; of the conservation of energy, 23. Leaves, radiation of, 160. Length of days affected by tidal action, 131. Level surfaces, 91. Life, organic, evolution of, 15, 16. Light, belief of the ancients regarding, 42. Lightning, 24, 164-168; noise from, 166; proceeding from the earth to the clouds, 165; protection of buildings from, 165; stroke, wearing-out effect of, 165. Limestones, 353, 357, 358, 360, 364; formation of, 357, 360. Lisbon, earthquake of, 1755, 368, 369. Lowell, Mr. Percival, observations on Venus, 64. Lunar mountains near the Gulf of Iris, 397. Mackerel sky, 35. Mallet, Mr. Charles, and the study of earthquakes, 382, 383. Man as an inventor of tools, 10. Mangroves, 340; diagram showing mode of growth, 340; marshes of, 339. Map of glaciers and moraines near Mont Blanc, 217; of Ipswich marshes, 338. Mapping with contour lines, 27. Maps, desirable, for the study of celestial geography, 77; geographic sketch, 26, 27. Marching sands jeopardizing agriculture, 123. Marine animals, sustenance of, 361-363; deposits, 325-327, 349, 356; marshes, 336-340; waves caused by earthquakes, 387. Mars, 65-67, 84, 97; belief that it has an atmosphere, 65; canals of, 67; gaseous wraps of, 97; more efficient telescopes required for the study of, 67; nearer to the earth than other planets, 65. Marshes, mangrove, 339; map of Ipswich, 338; marine, 336-340; deposits found in, 336; of North America, 337; on the coast of New England, 339; phenomena of, 167, 168; tidal, good earth for tillage, 337; tidal, of North America, 340. Mercury, 55, 63, 78; nearest to the sun, 63; time in which it completes the circle of its year, 55. Meteorites, 47, 48; kinship of comets and, 48. Meteors, 47; falling, 47; composition of, 48; flashing, 39, 40, 47; speed of, 47; inflamed by friction with air, 99. Methods in studying geology, 400. Milky Way, 45; voyage along the path of the, 44, 45. Mineral crusts, 328, 329; deposits, 308. Moon, 38, 395-400; absence of air and water on the, 399; attended by satellites, 57; attraction which it exercises on the earth, 62; curious feature of the, 397; destitute of gaseous or aqueous envelope, 397; diameter of the, 399; imaginary view of the earth from the, 81; "libration" of the, 398; made up of circular depressions, 396, 397; movements of the, 78; no atmosphere in the, 97; parting of the earth and, 396; position of the, in relation to the earth, 62; tidal action and the, 131; tides of the, 126, 127; why does the sun not act in the same manner as the, 78. Moraines, 216, 218, 229, 230; map of glaciers and, near Mont Blanc, 217; movements of the, 216-218; terminal, 228. _Moulin_, 219. Mount Ætna, 288-310; lava yielding, 290, 293, 294; lava stream caves of, 292, 293; more powerful than Vesuvius, 297; peculiarities of, 291, 292; size of, 289-291; turning of the torrents of, 295. Mountain-building, 90-93, 304; folding, 86, 87, 90, 365; attributed to cooling of the earth, 88; growth, 392; Swiss falls, 174; torrents, energy of, 177. Mountains, 85, 86, 89, 90-93; 174-178; form and structure of, 86; partly caused by escape of heat from the earth, 89; sections of, 87. Mount Nuova, formation of, 284. Mount Vesuvius, 263-285, 288, 289, 293, 302, 381; description of the eruption of, in A.D. 79, 277-280; diagrammatic sections through, showing changes in the form of the cone, 283; eruption of, in 1056, 281; in 1882-'83, 264, 266; eruption of, in 1872, 282; eruptions of, increased since 1636, 282; flow of lava from, 285; likely to enter on a period of inaction, 282, 283; outbreak of, in 1882-'83, 264, 266. Naples, prosperity of the city, 289. Nebular hypothesis, 34, 35, 39, 52. Neptune, 70. _Névé_, the, 214; no ice-cutting in the region of the, 224. Newcomb's (Prof.) belief regarding the heat of the sun, 52. Niagara Falls, 191, 192, 204; cutting back of, 204. North America, changes in the form of, 91, 92; triangular form of, 90. Ocean, average depth of the, 89; climatal effect of the, 147; currents, 145; effect of, on migration, 156; effect of, on organic life, 154; floor, 85, 93; hot and cold currents of the, 102; sinking of the, 93, 94; the laboratory of sedimentary deposits, 351; depth of the, 89, 126. Oceanic circulation, effect of, on the temperature, 152. Oceans and continents, 83. Orbit, alterations of the, and the seasons, 60, 61; changing of the, 59-63; shape of the, 61-63. Organic life, 315, 317, 321, 352, 353, 363; action of, on the soil, 317, 321; advantages of the shore belt to, 363; development of in the sea, 352, 353; effect of ocean currents on, 154; processes of, in the soil, 315; decay of, in the earth, 321. Orion, 46. Oscillations of the shores of the Bay of Naples, 287. Oxbow of a river, 182, 183. Oxbows and cut-off, 182. Pebbles, action of seaweeds on, 143; action of the waves on, 142, 144. Photosphere, 74. Plains, 86; alluvial, 91, 179, 182, 184-186, 325; history of, 91; sand, 325. Planets, 38; attended by satellites, 57; comparative sizes of the, 68; experiments illustrating consolidation of disseminated materials of the sun and, 40; gaseous wraps of, 97; important observations by the ancients of fixed stars and planets, 43; movements of, 57-61; outer, 78; table of relative masses of sun and, 77. Plant life in the Sargassum basins, 156. Plants and animals, protection of, by mechanical contrivances, 364; and trees, work of the roots of, on the soil, 316, 317; water-loving, 181; forming climbing bogs, 332. Polar axes, nodding movement of, 54. Polar snow cap, 66. Polyps, 155, 353. Pools, circular, 203. Prairies, 340, 342. Radiation of heat, 159. Rain, 152, 156, 164, 168, 170, 328, 330; circuit of the, 156-168; drops, force of, 169, 170; spheroidal form of, 170; electrical action in the formation of snow and, 164; work of the, 171. Realm, unseen solar, 75. Reeds, 332. Religion, conflict between science and, 20, 22; struggle between paganism and, 21. Rivers and _débris_, 183; changes in the course of, in alluvial plain, 182; deposition of, accelerated by tree-planting, 181; great, always clear, 205; inundation of the Mississippi, eating away land, 182; muds, 222; newly formed, cutting a cañon, 195; of snow-ice, 211; origin of a normal, 173; oxbow of a, 182,183; sinking of, 199; swinging movement of, 179-181; river-valleys, 193, 194; diversity in the form of 188-191. Rocks, 145; accidents from falling, 174; cut away by sandstones, 188; divided by crevices, 252; duration of events recorded in, 389, 390, ejection of, material, 311; falling of, 174-176; formation of, 262, 263; from the present day to the strata of the Laurentian, 390; migration of, 291; poised, indicating a long exemption from strong earthquakes, 388; rents in, 252, 253; stratification of, 349, 350, 352, 365, 390; testimony of the, in regard to glaciers, 228; under volcanoes, 303; variable elasticity of, 366; vibration of, 367, 368; rock-waste, march of the, 343; water, 250, 267. Rotation of the earth affected by tides, 130; of the planetary spheres on their axes, 56. Salicified forests, 124. Salt deposits formed in lagoons, 200; found in lakes, 199-200. Sand bars, 183; endurance of, against the waves, 145; hills, travelling of, 123; marching, 123; silicious stones cutting away rooks, 188. Satellites, 53, 54; motions of, about their centres and about the sun, 53, 54. Saturn, 38, 53, 57, 396; cloud bands of, 70; gaseous wraps of, 97; path of the earth affected by, 59, 60. Savages, primitive, students of Nature, 1. Scandinavia, changes on the coasts of, 96. Science, advance of, due to mechanical inventions, 22; astronomy beginning with, 10; chemical, characteristics of, 14; conflict between religion and, 20, 22; conflict between the Roman faith and, 20; mechanical inventions as aids to, 22, 23; modern and ancient, 4; natural, 5, 6; of botany in Aristotle's time, 14; of physiology, 15; of zoölogy in Aristotle's time, 14; resting practically on sight, 10. Scientific development, historic outlines of, 17; tools used in measuring and weighing, as an aid to vision, 12. Sea, battering action of the, 140; coast ever changing, 385, 386; effect of volcanic eruptions on the, 299; floor deposits of the, affected by volcanoes, 360, 361; in receipt of organic and mineral matter, 359; hot and cold currents of the, 102; littoral zone of the, 351, 352; puss, 142; rich in organic life, 352, 353; solvent action of the, 361; strata, formation of, 354; water, minerals in, 185; weeds, 155, 156. Seas, dead, originally living lakes, 200; water of, buoyant, 199; eventually the seat of salt deposits, 199-201; general statement as to division of, 83, 84; shape of the, 83, 84. Seashore, air of the, 98. Seasons, changing the character of the, 61, 62. Sense of hearing, 9,10; of sight, 10; of smell, 9, 10; of taste, 9, 10; of touch, 9, 10. _Seracs_, 214. Shocks, earthquake. See under EARTHQUAKES. Shore lines, variation of, 83, 84. Shores, cliff, 138-142. Sink holes, 202; in limestone districts, 253, 254. Skaptar, eruption of, 297, 298; lava from the eruption of, 298. Sky, mackerel, 35. Snow, 207-225, 244; as an evidence of atmosphere, 65; blankets, early flowers beginning to blossom under, 208; covering, difference between an annual and perennial, 210; effect of, on plants, 208; electrical action in the formation of rain and, 164; flakes, formation of, 164; red, 210; slides, 210; slides, phenomena of, 210, 211. Soil, alluvial, 321, 322; atmospheric circulation of, 330, 331; conditions leading to formation of, 313, 331; continuous motion of the, 314; covering of the earth, 343; decay of the, 314, 315; degradation of the, 344-348; means for correcting, 346-348; destruction in grain fields greater than the accumulation, 344; developing on lava and ashes an interesting study, 343; development of, in desert regions, 340; effect of animals and plants on the, 317-320; effect of earthquakes on the, 375; fertility of the, distinguished from the coating, 344, 345; fertility of, affected by rain, 327; formation of, 314-321; glacial, characteristics of, 324; glaciated, 323, 324; irrigation of the, 328-330; local variation of, 327; mineral, 321; of arid regions fertile when subjected to irrigation, 341; of dust or blown sand, 321; of immediate derivation, 321, 322; phenomena, 313; processes of organic life in the, 315; variation in, 321-331; vegetation protecting the, 316, 317; washing away of the, 346, 347; winning, from the sea, 337; work of ants on the, 318; tiller, duty of the, 348. Solar bodies, general conditions of the, 63-71; forces, action of, on the earth, 349; system, 52, 56; independent from the fixed stars system, 43; original vapour of, 52, 53; singular features of our, 68; tide, 127. Spheres, difference in magnitude of, 51; motions of the, 50, 51; planetary, rotation of, on their axes, 56. Spots, sun, 72. Spouting horn, 141. Springs, formation of small, 252. Stalactitization, 256. Stalagmites and stalactites on the roof and floor of a cavern, 257. Stars as dark bodies in the heavens, 47; discovery of Fraunhofer and others on, 23, 38; double, 39; and tidal action, 131; earliest study of, 10; fixed, important observations by the ancients of planets and, 43; not isolated suns, 38, 39; variation in the light of, 46; limit of, seen by the naked eye, 11; revolution of one star about another, 46, 47; shooting, 47; speed of certain, 51; study of, 31-80; sudden flashing forth of, due to catastrophe, 46; voyage through the, 44, 45; star, wandering, 74. Stellar realm, 31-80. Storms, circular, 111; desert, 121, 122; expansion of air contained in a hollow wall during the passage of, 114; great principle of, 105, 106; in the Sahara, 121; lightning, more frequent in summer, 167; paths of, 115; secondary, of cyclones, 112; spinning, 115; thunder, 165-167; whirling, 106, 124; whirling peculiarity of, 108, 109. Strabo, writings of, 18. Sun, atmosphere of the, 73; constitution of the, 72; distance of the earth from the, 29; effect from changes in the, and earth, 59; envelope of the, 73, 74, 97; experiments illustrating consolidation of disseminated materials of planets and, 40; finally, dark and cold, 42; formation of the eight planets of the, 53; heat leaving the, 41; heat of the, 76; imaginary journey from the, into space, 44; mass of the, 76, 77; path of the earth around the, 55; physical condition of the, 71; Prof. Newcomb's belief regarding the heat of the, 52; spots, 75; abundant at certain intervals, 72; difficulty in revealing cause of, 75; structure of the, a problem before the use of the telescope, 72; table of relative masses of, and planets, 77; three stages in the history of the, 71; tides, 126; why does it not act in the same manner as the moon? 78. Surfaces, level, 90. Surf belt, swayings of the, 137. Swamps, diagram showing remains of, 335; Dismal Swamp, 95, 333; drainage of, 334, 335; fresh-water, 334, 335; phenomena of, 167, 168. Table-lands, 91. Table of relative masses of sun and planets, 77. Telescopes, 11, 12, 45; first results of, 72; power of, 11; revelations of, 45. Temperature, effects of, produced by vibration, 42; in the doldrum belt, 118; of North America, 118; of the Atlantic Ocean, 118. Tempests, rate of, 99, 100. Thunder, 166; more pronounced in the mountains, 166. Thunderstorms, 165, 166; distribution of, 166, 167. Tidal action, recent studies of, 131, 132; marshes of North America, 340. Tides, carving channels, 129; effecting the earth's rotation, 130; effect of, on marine life, 130; height of, 128, 129; moon and sun, 126, 127; normal run of the, 127; production of, 131; of the trade winds, 150; solar, 127; travelling of, 127, 128. Tillage introducing air into the pores of the soil, 331. Tornadoes, 112, 113, 317; development of, 113; effect of, on buildings, 113; fiercest in North America, 113; length of, 115; resemblance of, to hurricanes, 115; upsucking action of, 114, 115. Torrents, 177-179, 204. Trade winds. See under WINDS. Training in language, diminishing visual memory, 401; soldiers to measure distances, 28; to measure intervals of time, 28; for a naturalist, 25-29. Tunnels, natural, 257. Uranus, 70. Valley of Val del Bove formed from disturbances of Mount Ætna, 294. Valleys, diversity in the form of river, 188-191; river, 193. Vapour, 156, 157, 159, 163; gravitative attraction of, 34, 35; nebular theory of, 52, 53; original, of the solar system, 52, 53. Vegetation, and dew, 160; in a measure, independent of rain, 160; protecting the soil, 316, 317. Vein, diagram of a, 260. Venus, 64, 78; recent observations of, by Mr. Percival Lowell, 64. Vesuvian system, study of the, 285. Vesuvius. See MOUNT VESUVIUS. Visualizing memories, 402, 403. Volcanic action, 268-276. Volcanic eruption of A.D. 79, 288; important facts concerning, 276-279; islands, 272; lava a primary feature in, 266; observations of, made from a balloon, 301; peaks along the floor of the sea, 272, 273; possibility of throwing matter beyond control of gravitative energy, 300. Volcanoes, 125, 203, 263; abounding on the sea floor, 302; accidents from eruptions of, 288; along the Pacific coast, 271; ash showers of, maintaining fertility of the soil, 289; distribution of, 271; eruption of, 286-294, 368; explosions from, coming from a supposed liquid interior of the earth, 275; exporting earth material, 310; little water, 375; Italian, considered collectively, 296, 297; Neapolitan eruptions of and the history of civilization, 288; subsidence of the earth after eruption of, 287, 291; origin of, 263-274; phenomena of, 263-267; submarine, 301; travelling of ejections from, 287, 288. Waters, crevice, 250; of the earth, 250, 251; cutting action of, 117, 192; drift, from the poles, 151; journey of, from the Arctic Circle to the tropics, 151, 152; dynamic value of, 171; expansion of, in rocks, 270; geological work of, 168-206; in air, 99; of the clouds usually frozen, 207; pure, no power for cutting rocks, 204; rock, 250, 263; sea, minerals in, 185; store of the earth, 125; system of, 125, 156; tropical, 151; velocity of the, under the equator, 150; wearing away rocks, 178, 179; underground, carrying mineral matter to the sea, 193; chemical changes of, leading to changes in rock material, 262, 263; effect of carbonic-acid gas on, 251; operations of the, 126; wearing away rocks, 178, 179; work of, 250. Waterfalls, 189-193; cause of, 191; the Yosemite, 192; Niagara, 191, 192; numerous in the torrent district of rivers, 192; produced by dikes, 192; valuable to manufactures, 192, 193. Waterspouts, 115, 116; atmospheric cause of, 116; firing at, 116; life of a, 116; picturesqueness of, 116; the water of fresh, 117. Waves, 128, 129, 132, 145; action of friction on, 135, 136; break of the, 136; endurance of sand against the, 145; force of, 133, 136, 139; marine, caused by earthquakes, 387; of earthquakes, 389; peculiar features in the action of, 137; size of, 137, 138; stroke of the, 144; surf, 135; tidal height of, 132; undulations of, 132; wind, 132; wind influence of, on the sea, 134, 135; wind-made, 128. Ways and means of studying Nature, 9. Weeds of the sea, 155. Well, artesian, 258, 259. Whirling of fluids and gas, 36, 37. Whirlwinds in Sahara, 121. Will-o'-the-wisp, 167. Winds, 101, 110, 122, 317; effect of sand, 122; hurricane, 110; illustration of how they are produced, 101; in Martha's Vineyard, 120; of the forests, work of the, 317; of tornadoes, effect of, 113; on the island of Jamaica, 119, 120; regimen of the, 119; variable falling away in the nighttime, 100; trade, 102-105; 145, 146, 150; action of, on ocean currents, 145: affected by motion of the earth, 103; belt, motion of the ocean in, 146; flow and counter-flow of the, 150; tide of the, 150; uniform condition of the, 102; waves, work of, 132, 134, 135. Witchcraft, belief of, in the early ages, 21. Zoölogy, rapid advance in, 14, 15. 
47119	----	Transcriber's Note Text emphasis is displayed as _Italics_ and =Bold= respectively. Superscript characters are denoted with the carat character (i.e., 8^e). Whole and fractional parts are displayed as 5-1/2. FRAGMENTS OF EARTH LORE [Illustration: PLATE I OROGRAPHIC MAP OF SCOTLAND] FRAGMENTS OF EARTH LORE SKETCHES & ADDRESSES Geological and Geographical BY JAMES GEIKIE, D.C.L., LL.D., F.R.S., &c. MURCHISON-PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF EDINBURGH FORMERLY OF H.M. GEOLOGICAL SURVEY OF SCOTLAND WITH MAPS AND ILLUSTRATIONS EDINBURGH JOHN BARTHOLOMEW & CO. LONDON: SIMPKIN, MARSHALL, HAMILTON, KENT & Co., Ltd. 1893 PREFACE. The articles in this volume deal chiefly with the history of Glacial times and the origin of surface-features. As they were not written with any view to their subsequent appearance in a collected form, each is so far independent and complete in itself. Under these circumstances some repetition was unavoidable, if the articles were not to be recast, and I did not think it advisable to make such radical alteration. With the exception of verbal changes and some excisions, therefore, the papers remain substantially in their original state. Here and there a footnote has been added to indicate where the views expressed in the text have since been modified; but I have not been careful to insert such notes throughout. Geologists, like other folk, live and learn, and the reader will probably discover that the opinions set forth in some of the later articles are occasionally in advance of those maintained in the writer's earlier days. I have to thank the Publishers of _Good Words_ for allowing me to republish the articles on the Cheviot Hills and the Outer Hebrides. My acknowledgments are also due to Mr. Bartholomew for the excellent maps with which the volume is so well illustrated. Edinburgh, _April 5th, 1893_. LIST OF MAPS. Plate I. PHYSICAL FEATURES OF SCOTLAND _Frontispiece_ " II. STRUCTURE OF MOUNTAINS 60 " III. PAST AND PRESENT GLACIATION OF THE WORLD 193 " IV. ICE AGE IN NORTHERN EUROPE 324 " V. THE GEOGRAPHICAL EVOLUTION OF CONTINENTS 348 " VI. BATHY-HYPSOMETRICAL MAP, ILLUSTRATING DEVELOPMENT OF COAST-LINES 428 CONTENTS. CHAP. PAGE I. GEOGRAPHY AND GEOLOGY 1 II. THE PHYSICAL FEATURES OF SCOTLAND 14 III. MOUNTAINS: THEIR ORIGIN, GROWTH, AND DECAY 36 IV. THE CHEVIOT HILLS 62 V. THE LONG ISLAND, OR OUTER HEBRIDES 125 VI. THE ICE AGE IN EUROPE AND NORTH AMERICA 160 VII. THE INTERCROSSING OF ERRATICS IN GLACIAL DEPOSITS 194 VIII. RECENT RESEARCHES IN THE GLACIAL GEOLOGY OF THE CONTINENT 220 IX. THE GLACIAL PERIOD AND THE EARTH-MOVEMENT HYPOTHESIS 248 X. THE GLACIAL SUCCESSION IN EUROPE 288 XI. THE GEOGRAPHICAL EVOLUTION OF EUROPE 326 XII. THE EVOLUTION OF CLIMATE 349 XIII. THE SCIENTIFIC RESULTS OF DR. NANSSEN'S EXPEDITION 382 XIV. THE GEOGRAPHICAL DEVELOPMENT OF COAST-LINES 393 I. Geography and Geology.[A] [A] Portion of a lecture given in 1886 to the Class of Geology in the University of Edinburgh. The teaching of Geography naturally occupies a prominent place in every school curriculum. It is rightly considered essential that we should from an early age begin to know something of our own and other countries. I am not sure, however, that Geography is always taught in the most interesting and effective manner. Indeed, according to some geographers, who are well qualified to express an opinion, the manner in which their subject is presented in many of our schools leaves much to be desired. But a decided advance has been made in recent years, and with the multiplication of excellent text-books, maps, and other appliances, I have no doubt that this improvement will continue. When I attended school the text-books used by my teachers were about as repellent as they could be. Our most important lesson was to commit to memory a multitude of place-names, and the maps which were supposed to illustrate the text-books were, if possible, less interesting and instructive. Nowadays, however, teachers have a number of more or less excellent manuals at their service, and the educational maps issued by our cartographers show in many cases a very great advance on the bald and misleading caricatures which did duty in my young days as pictures of the earth's surface. During the progress of some war we often remark that the task of following the military operations compels us to brush up our Geography. I am uncharitable enough to suspect that it would frequently be truer to say that, before these campaigns commenced, we had no such knowledge to brush up. The countries involved in the commotion were probably mere names to many of us. We had no immediate interest in them or their inhabitants, and had we been asked, before the outbreak of hostilities, to indicate the precise positions of the places upon a map, some of us perhaps might have been sorely puzzled to do so. Nor is such ignorance always discreditable. One cannot know everything; the land-surface of the globe contains upwards of 50 millions of square miles, and one may surely be excused for not having a detailed knowledge of this vast area. I have referred to the subject simply because I think it gives us a hint as to how the teaching of Political Geography might be made most instructive and interesting. Historical narrative might often be interwoven with the subject in such a way as to fix geographical features indelibly on the memory. Striking and picturesque incidents, eventful wars, the rise and progress of particular trades, the routes followed by commerce, the immigration and emigration of races, the gradual development of the existing political divisions of the Old World, the story of Columbus and the early voyagers, the geographical discoveries of later times--all these, and such as these, might be introduced into our lessons in Political Geography. The wanderings of a Mungo Park, a Bruce, a Livingstone, a Stanley, traced on a good map, could not fail to arrest the attention of the youthful student of African geography. In like manner, the campaigns of the great Napoleon might be made to do good service in illustrating the geographical features of large portions of our own continent. Then, as regards Britain, what a world of poetry and romantic story clings to every portion of its surface--why, the very place-names themselves might suggest to any intelligent teacher themes and incidents, the deft treatment of which would make the acquisition of Geography a delightful task to the dullest boy or girl. The intimate relation that obtains between Political Geography and History has indeed long been recognised, and is in fact self-evident. And we are all well aware that in our school manuals of Geography it has been usual for very many years to note the scenes of remarkable events. Such notes, however, are of necessity extremely brief; and it need hardly be said that to fully incorporate history in a text-book of general Geography would be quite impracticable. It might be done to a certain extent for our own and a few of the more important countries; but similar detail need not be attempted in regard to regions which are of less consequence from the political point of view. Indeed, I should be inclined to leave the proper application of historical knowledge in the teaching of Geography very much to the teacher himself, who would naturally select such themes and incidents as seemed best adapted to attract the attention of his pupils. Be that, however, as it may, it is enough for my present purpose if I insist upon the fact that the proper study of Political Geography involves the acquisition of some historical knowledge. One can hardly conceive the possibility of an intelligent student taking pains to become acquainted with the political geography of a country without at the same time endeavouring to learn something of its history--otherwise, his geographical attainments would hardly surpass those of a commercial traveller, whose geographical studies have been confined to the maps and tables of his Bradshaw. But if it be impossible to ignore History in the teaching of Political Geography, it is just as impossible to exclude from our attention great physical features and characteristics. Surface-configuration, climate, and natural products all claim our attention. It is obvious, in fact, that the proper study of Political Geography must give us at least a general notion of the configuration, the river-systems, and climatic conditions of many different lands. For has not the political development of races depended most largely on the physical conditions and natural resources of the countries occupied by them? So far, then, as these have sensibly influenced the progress of peoples, they come naturally under the consideration of Political Geography. Thus, if Political Geography be closely connected and interwoven, as it were, with History, not less intimate are its relations to Physical Geography. It does not embrace all Physical Geography, but it introduces us to many facts and phenomena, the causes and mutual relations of which we cannot understand without first mastering the teachings of Physical Geography. In the study of this latter science we come more closely into contact with Nature; we cease to think of the surface of the earth as parcelled out into so many lots by its human occupants--we no longer contemplate that surface from the limited point of view of the political geographer--we are now not merely members of one particular community, but have become true citizens of the world. To us north and south, east and west are of equal interest and importance. Our desire now is to understand, if haply we may, the complex system of which we ourselves form a part. The distribution of land and water--the configuration of continental areas and oceanic basins--the circulation of oceanic and terrestrial waters--earth-movements and volcanoes--ice-formations--the atmosphere--climatology--the geographical distribution of plants and animals--in a word, _the world as one organic whole_ now forms the subject of our contemplation. Such being the scope of Physical Geography, it is satisfactory to know that its importance as a subject of study in our schools has been fully recognised. This being admitted, I shall now proceed to show that Physical Geography, although, like Political Geography, it is a separate and distinct subject, yet, just as the study of the latter involves some knowledge of History, so the prosecution of Physical Geography compels us to make a certain acquaintance with Geology. We cannot, in fact, learn much about the atmosphere, about rain and rivers, glaciers and icebergs, earthquakes and volcanoes, and the causes of climate, without at the same time becoming more or less familiar with the groundwork on which geological investigations are based. And just as a knowledge of history enables us better to understand the facts of Political Geography, so some acquaintance with the results of geological inquiry are necessary before we can hope to comprehend many of the phenomena of which Physical Geography treats. Let me try to make this plain. The physical geographer, we shall suppose, is considering the subject of terrestrial waters. He tells us what is meant by the drainage-system of a country, points out how the various minor water-courses or brooks and streams unite to form a river, describes for us the shape of the valley through which a typical river makes its way--how the valley-slope diminishes from the mountains onwards to the sea-coast--how, at first, in its upper or mountain-track, the flow of the river is torrential--how, as the slope of the valley decreases, the river begins to wind about more freely, until it reaches the head of its plain-track or delta, when, no longer receiving affluents, it begins to divide, and enters the sea at last by many mouths. He tells us further what proportion of the rainfall of the country passes seawards in our river, and he can measure for us the quantity of water which is actually discharged. All this is purely Physical Geography; but when we come to ask why some rivers flow in deep cañons, like those of the Colorado--why valleys should widen out in one part and contract, as it were, elsewhere--why the courses of some rivers are interrupted by waterfalls and rapids, and many other similar questions, the physical geographer must know something of Geology before he can give an answer. He can describe the actual existing conditions; without the aid of Geology, he can tell us nothing of their origin and cause. So the political geographer can map out for us the present limits of the various countries of Europe, but History must be invoked if we would know how those boundaries came to be determined. The moment, therefore, the physical geographer begins to inquire into the origin of any particular physical feature, he enters upon the domains of the geologist. And as he cannot possibly avoid doing so, it is quite common now to find a good deal of the subject-matter of Geology treated of in text-books of Physical Geography. I state this merely to show how very closely the two sciences are interlocked. Take, for example, the configuration of river valleys just referred to. The physical geographer recognises the fact that a river performs work; by means of the sediment which it carries in suspension and rolls along its course, it erodes its bed in many places, and undermines its banks, and thus its channel is deepened and widened. He can measure the amount of sediment which it carries down to the sea, and the quantity of saline matters which its waters hold in solution: and knowing that all these substances have been abstracted from the land, he is able to estimate approximately the amount of material which is annually transferred from the surface of the drainage-area involved. He discovers this to be so relatively enormous that he has no difficulty in believing that the valleys in which rivers flow might have been hollowed out by the rivers themselves. But, without trespassing further into the geologist's domains, he cannot go beyond this: and you will at once perceive that something more is required to prove that any particular valley owes its origin to the erosive action of running water. Suppose someone were to suggest to him that his river-valley might be a minor wrinkle in the earth's crust caused by earth-movements, or that it might indicate the line of a fissure or dislocation, due to some comparatively recent convulsion--how could his computation of the amount of material at present carried seawards by the river prove such suggestions to be erroneous? And what light could it throw upon the origin of the varied configuration of the river-valley--how would it explain the presence or absence of cascades and rapids, of narrow gorges and open expanses? None of these phenomena can be interpreted and accounted for without the aid of the geologist: without some knowledge of rocks and rock-structures, the origin of the earth's surface-features is quite inexplicable. To give an adequate explanation of all the surface-features of a country in detail would of course require a profound study of Geology; but a general acquaintance only with its elementary facts is quite sufficient to enable us to form a reasonable and intelligent view of the cause and origin of the main features of the land as a whole. Thus a few lessons in elementary Geology would make clear to any child how rivers have excavated valleys, why cataracts and gorges occur here, and open valleys with gently-flowing waters elsewhere. Let me select yet another example to show how dependent Physical Geography is upon Geology. The physical geographer, in describing the features of the land, tells us how the great continental areas are traversed in various directions by what he calls mountain-chains. Thus, in speaking of America, he tells us that it may be taken as a type of the continental structure--namely a vast expanse of land, low or basin-like in the interior, and flanked along the maritime regions by elevated mountain borders--the highest border facing the deepest ocean. He points out further that the great continental areas are crossed from west to east by well-marked depressions, to a large extent occupied by water. Thus Europe is separated from Africa by the Mediterranean, a depression which is continued eastward through the Black Sea into the Aralo-Caspian area. South America is all but cut away from North America, while Australia is separated from Asia by the East India Seas. We find, in fact, all over the world that well-marked natural features are constantly being repeated. Not only do the great land-masses of the globe bear certain resemblances to each other, but even in their detailed structure similar parallelisms recur. The physical geographer notes all these remarkable phenomena, but he can give us no clue to their meaning. He may describe with admirable skill the characteristic features of plains and plateaux, of volcanic mountains and mountain-chains, but he cannot tell us why plains should occur here and mountains there; nor can he explain why some mountains, such as those of Scotland or Norway, differ so much in configuration from the Alps and the Pyrenees. The answer to all these questions can only be given by Geology. It is from this science we learn how continental areas and oceanic basins have been evolved. The patient study of the rocks has revealed the origin of the present configuration of the land. There is not a hill or valley, not a plateau or mountain-region, which does not reveal its own history. The geologist can tell you why continents are bordered by coast-ranges, and why their interiors are generally comparatively low and basin-shaped. The oceanic basins and continental areas, we learn, are primeval wrinkles in the earth's crust, caused by its irregular subsidence upon the gradually cooling and contracting nucleus. The continents are immense plateau-like areas rising more or less abruptly above those stupendous depressions of the earth's crust which are occupied by the ocean. While those depressions are in progress the maritime borders of the land-areas are subjected to enormous squeezing and crushing, and coast-ranges are the result--the elevation of those ranges necessarily holding some relation to the depth of the contiguous ocean. For, the deeper the ocean the greater has been the depression under the sea, and, consequently, the more intense the upheaval along the continental borders. It is for the same reason that destructive earthquakes are most likely to occur in the vicinity of coast-ranges which are of comparatively recent geological age. These, and indeed all, mountains of elevation are lines of weakness along which earth-movements may continue from time to time to take place. But all mountains are not mountains of elevation; many elevated regions owe their mountainous character simply to the erosive action of sub-aërial agents, such as rain, frost, ice, and running water, the forms assumed by the mountains being due to their petrological character and geological structure. There are, for example, no true mountains of elevation in Scotland; hence to write of the _chain of the Grampians_ or the _range of the Lowthers_ is incorrect and actually misleading. Without the aid of Geology the geographer cannot, in fact, discriminate between mountains of elevation and mountains of denudation; hence geographical terms so constantly in use as _mountain-range_ and _mountain-chain_ are very often applied by writers, ignorant of geological structure, to elevated regions which have no claim to be described either as _chains_ or _ranges_. Some knowledge of Geology, therefore, is essential to us if we would have correct views of many of the grandest features of the globe. But it will be said that, after all, the physical geographer deals with the earth as we now find it; he does not need to trouble himself with the origin of the phenomena he describes. Well, as I have just shown, he cannot, even if he would, escape trenching on Geology; and if he could, his subject would be shorn of much of its interest. He recognises that the world he studies has in it the elements of change--the forces of Nature are everywhere modifying the earth's surface--considerable changes are sometimes brought about even in one's lifetime, while within the course of historical ages still greater mutations have taken place--he becomes conscious, in short, that the existing state of things is but the latest phase of an interminable series of changes stretching back into the illimitable past, and destined to be prolonged into the indefinite future. Thus he gladly welcomes the labours of the geologist, whose researches into the past have thrown such a flood of light upon the present. In fact, he can no more divorce his attention from the results of geological inquiry than the political geographer can shut his eyes to the facts of History. Let me, in conclusion, give one further illustration of the close inter-dependence of the two sciences of which I am speaking. One of the subjects treated of by Physical Geography is the present geographical distribution of plants and animals. The land-surface of the globe has been mapped out into so many biological regions, each of which is characterised by its special fauna and flora. The greatest changes in the flora and fauna of a continent are met with as we pass from south to north, or _vice versa_. Proceeding in the direction of the latitude, the changes encountered are much less striking. Now, these facts are readily explained by the physical geographer, who points out that the distribution is due chiefly to climatic conditions--a conclusion which is obvious enough. But when we go into details we find that mere latitude will not account for all the phenomena. Take, for example, the case of the Scandinavian flora of our own Continent. It is true that this flora is largely confined to northern latitudes; but isolated colonies occur in our own mountains and in the mountains of middle and southern Europe. How are these to be accounted for? The physical geographer says that the plants grow there simply because they obtain at high levels in low latitudes the favourable climatic conditions underneath which they flourish at low levels in high latitudes. He therefore concludes that the distribution of life-forms is due to varying climatic and physical conditions. But if we ask him how those curious colonies of foreigners come to be planted on our mountains, he cannot tell. To get our answer we must come to the geologist; and he will explain that they are, as it were, living fossils--monuments of former great physical and climatic changes. He will prove to us that the climate of Europe was at a recent geological period so cold that the Scandinavian flora spread south into middle Europe, where it occupied the low grounds. When the climate became milder, then the northern invaders gradually retired--the main body migrating back to the north--while some stragglers, retreating before the stronger Germanic flora, took shelter in the mountains, whither the latter could not or would not follow, and so there our Scandinavians remain, the silent witnesses of a stupendous climatic revolution. Now, all the world over, plants and animals have similar wonderful tales to tell of former geographical changes. The flora and fauna of our country, for example, prove that the British Islands formed part of the Continent at a very recent geological period; and so, from similar evidence, we know that not long ago Europe was joined on to Africa. On the other hand, the facts connected with the present distribution of life demonstrate that some areas, such as Australia, have been separated from the nearest continental land for vastly prolonged periods of time. It would be a very easy matter to adduce many further illustrations to show how close is the connection between the studies of the physical geographer and the geologist. I do not indeed exaggerate when I say that no one can hope to become a geologist who is not well versed in Physical Geography; nor, on the other hand, can the physical geographer possibly dispense with the aid of Geology. The two subjects are as closely related and interwoven, the one with the other, as History is with Political Geography. I do not see therefore how educationists who have admitted the great importance of Physical Geography as a branch of general education, can logically exclude Geology as a subject of instruction in schools. Already, indeed, it has been introduced by many teachers, and I am confident that ere long it will be as generally taught as Physical Geography. I would not, however, present the subject to young people as a lesson to be learned from books. A good teacher should be able to dispense with these helps, or rather hindrances--for such they really are to a young beginner. His pupils ought to have previously studied the subject of Physical Geography, and if they have been well taught they ought to have already acquired no mean store of geological knowledge. They ought, in fact, to have learned a good deal about the great forces which are continually modifying the surface of the globe, and what they have now to do is to study more particularly the results which have followed from the constant operation of those forces. We shall suppose, for example, that the teacher has described how rivers erode their channels, and waves tend to cut back a coast-line, and how the products of erosion, consisting of gravel, sand, and mud, are distributed along river-valleys and accumulated in lakes and seas. He now exhibits to his class good-sized fragments of conglomerate, sandstone, and shale, and points out how each of these rocks is of essentially the same character, and must therefore have had the same origin, as modern sedimentary accumulations. His pupils should be encouraged to examine the rocks of their own neighbourhood, whether exhibited in natural sections or artificial exposures, and to compare these with the products of modern geological action. One hour's instruction in the field is, in fact, worth twenty hours of reading or listening to lectures. Knowledge at first hand is what is wanted. There are many excellent popular or elementary treatises dealing with Historical Geology, and these have their uses, and may be read with profit as well as pleasure. But the mere reading of such books, it is needless to say, will never make us geologists. They help no doubt to store the mind with interesting and entertaining knowledge, but they do not cultivate the faculties of observation and reasoning. And unless geology is so taught as to accomplish this result, I do not see why it should enter into any school curriculum. Further, I would remark that, however interesting a geological treatise may be, it cannot possibly stimulate the imagination as the practical study of the science is bound to do. One may put into the hands of a youth a clear and well-written description of some particular fossiliferous limestone, and he may by dint of slavish toil be able to repeat verbatim all that he has read. That is how a good deal of book-knowledge of science is acquired. Only think, however, of the drudgery it involves--the absolute waste of time and energy. But let us illustrate our lesson by means of a lump of the limestone itself; let us show him the character of the rock and the nature of its fossil contents, and his difficulties disappear. Better still--let us take him, if we can, into a limestone quarry, and he will be a dull boy indeed if he fails fully to understand what limestone is, or to realise the fact that the rock he is looking at accumulated slowly, like existing oceanic formations, at the bottom of a sea that teemed with animal life. It is unnecessary, however, that I should illustrate this subject further. I would only repeat that the beginner should be taught from the very first to use his own eyes, and to draw logical conclusions from the facts which he observes. Trained after this manner, he would acquire, not only a precise and definite knowledge of what geological data really are, but he would learn also how to interpret those data. He would become familiar, in fact, with the guiding principles of geological inquiry. How much or how little of Historical Geology should be given in schools will depend upon circumstances. Great care, however, should be taken to avoid wearying the youthful student with strings of mere names. What good is gained by learning to repeat the names of fifty or a hundred fossils, if you cannot recognise any one of these when it is put into your hand? With young beginners I should not attempt anything of that kind. If the neighbourhood chanced to be rich in fossils, I should take my pupils out on Saturday to the sections where they were found, and let them ply their hammers and collect specimens for themselves. I should describe no fossils which they had not seen and handled. Of the more remarkable forms of extinct animals and plants, which are often represented by only fragmentary remains, I should exhibit drawings showing the creatures as they have been restored by the labours of comparative anatomists. Such restorations and ideal views of geological scenes like those given by Heer, Dana, Saporta, and others, convey far more vivid impressions of the life of a geological period than the most elaborate description. In fine, the story of our earth should be told much in the same manner as Scott wrote the history of Scotland for his grandson. There is no more reason for requiring the juvenile student to drudge through minute geological data before introducing him to the grand results of geological investigation, than there is for compelling him to study the manuscripts in our Record Offices before allowing him to read the history which has been drawn from these and similar sources of information. It is enough if at the beginning of his studies he has already learned the general nature of geological evidence and the method of its interpretation. Provided with such a stock of geological knowledge as I have indicated, our youth would leave school with some intelligent appreciation of existing physical conditions, and a not inadequate conception of world-history. II. The Physical Features of Scotland.[B] [B] _Scottish Geographical Magazine_, vol. i., 1885. Scotland, like "all Gaul," is divided into three parts, namely, the Highlands, the Central Lowlands, and the Southern Uplands. These, as a correctly drawn map will show, are natural divisions, for they are in accordance not only with the actual configuration of the surface, but with the geological structure of the country. The boundaries of these principal districts are well defined. Thus, an approximately straight or gently undulating line taken from Stonehaven, in a south-west direction, along the northern outskirts of Strathmore to Glen Artney, and thence through the lower reaches of Loch Lomond to the Firth of Clyde at Kilcreggan, marks out with precision the southern limits of the Highland area and the northern boundary of the Central Lowlands. The line that separates the Central Lowlands from the Southern Uplands is hardly so prominently marked throughout its entire course, but it follows precisely the same north-east and south-west trend, and may be traced from Dunbar along the base of the Lammermoor and Moorfoot Hills, the Lowthers, and the hills of Galloway and Carrick, to Girvan. In each of the two mountain-tracts--the Highlands and the Southern Uplands--areas of low-lying land occur, while in the intermediate Central Lowlands isolated prominences and certain well-defined belts of hilly ground make their appearance. The statement, so frequently repeated in class-books and manuals of geography, that the mountains of Scotland consist of three (some writers say five) "ranges" is erroneous and misleading. The original author of this strange statement probably derived his ignorance of the physical features of the country from a study of those antiquated maps upon which the mountains of poor Scotland are represented as sprawling and wriggling about like so many inebriated centipedes and convulsed caterpillars. Properly speaking, there is not a true mountain-range in the country. If we take this term, which has been very loosely used, to signify a linear belt of mountains--that is, an elevated ridge notched by cols or "passes" and traversed by transverse valleys--then in place of "three" or "five" such ranges we might just as well enumerate fifty or sixty, or more, in the Highlands and Southern Uplands. Or, should any number of such dominant ridges be included under the term "mountain-range," there seems no reason why all the mountains of the country should not be massed under one head and styled the "Scottish Range." A mountain-range, properly so called, is a belt of high ground which has been ridged up by earth-movements. It is a fold, pucker, or wrinkle in the earth's crust, and its general external form coincides more or less closely with the structure or arrangement of the rock-masses of which it is composed. A mountain-range of this characteristic type, however, seldom occurs singly, but is usually associated with other parallel ranges of the same kind--the whole forming together what is called a "mountain-chain," of which the Alps may be taken as an example. That chain consists of a vast succession of various kinds of rocks, which at one time were disposed in horizontal layers or strata. But during subsequent earth-movements those horizontal beds were compressed laterally, squeezed, crumpled, contorted, and thrown, as it were, into gigantic undulations and sharper folds and plications. And, notwithstanding the enormous erosion or denudation to which the long parallel ridges or ranges have been subjected, we can yet see that the general contour of these corresponds in large measure to the plications or foldings of the strata. This is well shown in the Jura, the parallel ranges and intermediate hollows of which are formed by undulations of the folded strata--the tops of the long hills coinciding more or less closely with the arches, and the intervening hollows with the troughs. Now folded, crumpled, and contorted rock-masses are common enough in the mountainous parts of Scotland, but the configuration of the surface rarely or never coincides with the inclination of the underlying strata. The mountain-crests, so far from being formed by the tops of great folds of the strata, frequently show precisely the opposite kind of structure. In other words, the rocks, instead of being inclined away from the hill-tops like the roof of a house from its central ridge, often dip into the mountains. When they do so on opposite sides the strata of which the mountains are built up seem arranged like a pile of saucers, one within another. There is yet another feature which brings out clearly the fact that the slopes of the surface have not been determined by the inclination of the strata. The main water-parting that separates the drainage-system of the west from that of the east of Scotland does not coincide with any axis of elevation. It is not formed by an anticlinal fold or "saddleback." In point of fact it traverses the strata at all angles to their inclination. But this would not have been the case had the Scottish mountains consisted of a chain of true mountain-ranges. Our mountains, therefore, are merely monuments of denudation, they are the relics of elevated plateaux which have been deeply furrowed and trenched by running water and other agents of erosion. A short sketch of the leading features presented by the three divisions of the country will serve to make this plain. * * * * * The Highlands.--The southern boundary of this, the most extensive of the three divisions, has already been defined. The straightness of that boundary is due to the fact that it coincides with a great line of fracture of the earth's crust--on the north or Highland side of which occur slates, schists, and various other hard and tough rocks, while on the south side the prevailing strata are sandstones, etc., which are not of so durable a character. The latter, in consequence of the comparative ease with which they yield to the attacks of the eroding agents--rain and rivers, frost and ice--have been worn away to a greater extent than the former, and hence the Highlands, along their southern margin, abut more or less abruptly upon the Lowlands. Looking across Strathmore from the Sidlaws or the Ochils, the mountains seem to spring suddenly from the low grounds at their base, and to extend north-east and south-west, as a great wall-like rampart. The whole area north and west of this line may be said to be mountainous, its average elevation being probably not less than 1500 feet above the sea. A glance at the contoured or the shaded sheets of the Ordnance Survey's map of Scotland will show better than any verbal description the manner in which our Highland mountains are grouped. It will be at once seen that to apply the term "range" to any particular area of those high grounds is simply a misuse of terms. Not only are the mountains not formed by plications and folds, but they do not even trend in linear directions. It is true that a well-trained eye can detect certain differences in the form and often in the colouring of the mountains when these are traversed from south-east to north-west. Such differences correspond to changes in the composition and structure of the rock-masses, which are disposed or arranged in a series of broad belts and narrower bands, running from south-west to north-east across the whole breadth of the Highlands. Each particular kind of rock gives rise to a special configuration, or to certain characteristic features. Thus, the mountains that occur within a belt of slate, often show a sharply cut outline, with more or less pointed peaks and somewhat serrated ridges--the Aberuchill Hills, near Comrie, are an example. In regions of gneiss and granite the mountains are usually rounded and lumpy in form. Amongst the schists, again, the outlines are generally more angular. Quartz-rock often shows peaked and jagged outlines; while each variety of rock has its own particular colour, and this in certain states of the atmosphere is very marked. The mode in which the various rocks yield to the "weather"--the forms of their cliffs and corries--these and many other features strike a geologist at once; and therefore, if we are to subdivide the Highland mountains into "ranges," a geological classification seems the only natural arrangement that can be followed. Unfortunately, however, our geological lines, separating one belt or "range" from another, often run across the very heart of great mountain-masses. Our "ranges" are distinguished from each other simply by superficial differences of feature and structure. No long parallel hollows separate a "range" of schist-mountains from the succeeding "ranges" of quartz-rock, gneiss, or granite. And no degree of careful contouring could succeed in expressing the niceties of configuration just referred to, unless the maps were on a very large scale indeed. A geological classification or grouping of the mountains into linear belts cannot therefore be shown upon any ordinary orographical map. Such a map can present only the relative heights and disposition of the mountain-masses, and these last, in the case of the Highlands, as we have seen, cannot be called "ranges" without straining the use of that term. Any wide tract of the Highlands, when viewed from a commanding position, looks like a tumbled ocean in which the waves appear to be moving in all directions. One is also impressed with the fact that the undulations of the surface, however interrupted they may be, are broad--the mountains, however they may vary in detail according to the character of the rocks, are massive, and generally round-shouldered and often somewhat flat-topped, while there is no great disparity of height amongst the dominant points of any individual group. Let us take, for example, the knot of mountains between Loch Maree and Loch Torridon. There we have a cluster of eight pyramidal mountain-masses, the summits of which do not differ much in elevation. Thus in Liathach two points reach 3358 feet and 3486 feet; in Beinn Alligin there are also two points reaching 3021 feet and 3232 feet respectively; in Beinn Dearg we have a height of 2995 feet; in Beinn Eighe are three dominant points--3188 feet, 3217 feet, and 3309 feet. The four pyramids to the north are somewhat lower--their elevations being 2860 feet, 2801 feet, 2370 feet, and 2892 feet. The mountains of Lochaber and the Monadhliath Mountains exhibit similar relationships; and the same holds good with all the mountain-masses of the Highlands. No geologist can doubt that such relationship is the result of denudation. The mountains are monuments of erosion--they are the wreck of an old table-land--the upper surface and original inclination of which are approximately indicated by the summits of the various mountain-masses and the direction of the principal water-flows. If we in imagination fill up the valleys with the rock-material which formerly occupied their place, we shall in some measure restore the general aspect of the Highland area before its mountains began to be shaped out by Nature's saws and chisels. It will be observed that while streams descend from the various mountains to every point in the compass, their courses having often been determined by geological structure, etc., their waters yet tend eventually to collect and flow as large rivers in certain definite directions. These large rivers flow in the direction of the average slope of the ancient table-land, while the main water-partings that separate the more extensive drainage-areas of the country mark out, in like manner, the dominant portions of the same old land-surface. The water-parting of the North-west Highlands runs nearly north and south, keeping quite close to the western shore, so that nearly all the drainage of that region flows inland. The general inclination of the North-west Highlands is therefore easterly towards Glenmore and the Moray Firth. In the region lying east of Glenmore the average slopes of the land are indicated by the directions of the rivers Spey, Don, and Tay. These two regions--the North-west and South-east Highlands--are clearly separated by the remarkable depression of Glenmore, which extends through Loch Linnhe, Loch Lochy, and Loch Ness, and the further extension of which towards the north-east is indicated by the straight coast-line of the Moray Firth as far as Tarbat Ness. Now, this long depression marks a line of fracture and displacement of very great geological antiquity. The old plateau of the Highlands was fissured and split in two--that portion which lay to the north-west sinking along the line of fissure to a great but at present unascertained depth. Thus the waters that flowed down the slopes of the north-west portion of the broken plateau were dammed by the long wall of rock on the "up-cast," or south-east side of the fissure, and compelled to flow off to north-east and south-west along the line of breakage. The erosion thus induced sufficed in the course of time to hollow out Glenmore and all the mountain-valleys that open upon it from the west. The inclination of that portion of the fissured plateau which lay to the south-east is indicated, as already remarked, by the trend of the principal rivers. It was north-east in the Spey district, nearly due east in the area drained by the Don, east and south-east in that traversed by the Tay and its affluents, westerly and south-westerly in the district lying east of Loch Linnhe.[C] Thus, a line drawn from Ben Nevis through the Cairngorm and Ben Muich Dhui Mountains to Kinnaird Point passes through the highest land in the South-east Highlands, and probably indicates approximately the dominant portion of the ancient plateau. North of that line the drainage is towards the Moray Firth; east of it the rivers discharge to the North Sea; while an irregular winding line, drawn from Ben Nevis eastward through the Moor of Rannoch and southward to Ben Lomond, forms the water-parting between the North Sea and the Atlantic, and doubtless marks another dominant area of the old table-land. [C] The geological reader hardly requires to be reminded that many of the minor streams would have their courses determined, or greatly modified, by the geological structure of the ground. Thus, such streams often flow along the "strike" and other "lines of weakness," and similar causes, doubtless, influenced the main rivers during the gradual excavation of their valleys. That the valleys which discharge their water-flow north and east to the Moray Firth and the North Sea have been excavated by rivers and the allied agents of erosion, is sufficiently evident. All the large rivers of that wide region are typical. They show the orthodox three courses--namely, a torrential or mountain-track, a middle or valley-track, and a lower or plain-track. The same is the case with some of the rivers that flow east from the great north-and-south water-parting of the North-west Highlands, as, for example, those that enter the heads of Beauly Firth, Cromarty Firth, and Dornoch Firth. Those, however, which descend to Loch Lochy and Loch Linnhe, and the sea-lochs of Argyllshire, have no lower or plain-track. When we cross the north-and-south water-parting of the North-west Highlands, we find that many of the streams are destitute of even a middle or valley-track. The majority are mere mountain-torrents when they reach the sea. Again, on the eastern watershed of the same region, a large number of the valleys contain lakes in their upper and middle reaches, and this is the case also with not a few of the valleys that open upon the Atlantic. More frequently, however, the waters flowing west pass through no lakes, but enter the sea at the heads of long sea-lochs or fiords. This striking contrast between the east and west is not due to any difference in the origin of the valleys. The western valleys are as much the result of erosion as those of the east. The present contrast, in fact, is more apparent than real, and arises from the fact that the land area on the Atlantic side has been greatly reduced in extent by subsidence. The western fiords are merely submerged land-valleys. Formerly the Inner and Outer Hebrides were united to themselves and the mainland, the country of which they formed a part stretching west into the Atlantic, as far probably as the present 100 fathoms line. Were that drowned land to be re-elevated, each of the great sea-lochs would appear as a deep mountain-valley containing one or more lake-basins of precisely the same character as those that occur in so many valleys on the eastern watershed. Thus we must consider all the islands lying off the west coast of the Highlands, including the major portions of Arran and Bute, as forming part and parcel of the Highland division of Scotland. The presence of the sea is a mere accident; the old lands now submerged were above its level during a very recent geological period--a period well within the lifetime of the existing fauna and flora. The old table-land of which the Highlands and Islands are the denuded and unsubmerged relics, is of vast geological antiquity. It was certainly in existence, and had even undergone very considerable erosion, before the Old Red Sandstone period, as is proved by the fact that large tracts of the Old Red Sandstone formation are found occupying hollows in its surface. Glenmore had already been excavated when the conglomerates of the Old Red Sandstone began to be laid down. Some of the low-lying maritime tracts of the Highland area in Caithness, and the borders of the Moray Firth, are covered with the sandstones of that age; and there is evidence to show that these strata formerly extended over wide regions, from which they have since been removed by erosion. The fact that the Old Red Sandstone deposits still occupy such extensive areas in the north-east of the mainland, and in Orkney, shows that the old table-land shelved away gradually to north and east, and the same conclusion may be drawn, as we have seen, from the direction followed by the main lines of the existing drainage-system. We see, in short, in the table-land of the Highlands, one of the oldest elevated regions of Europe--a region which has been again and again submerged either in whole or in part, and covered with the deposits of ancient seas and lakes, only to be re-elevated, time after time, and thus to have those deposits in large measure swept away from its surface by the long-continued action of running water and other agents of denudation. * * * * * The Central Lowlands.--The belt of low-lying ground that separates the Highlands from the Southern Uplands is, as we have seen, very well defined. In many places the Uplands rise along its southern margin as abruptly as the Highlands in the north. The southern margin coincides, in fact, for a considerable distance (from Girvan to the base of the Moorfoots) with a great fracture that runs in the same direction as the bounding fracture or fault of the Highlands. The Central Lowlands may be described, in a word, as a broad depression between two table-lands. A glance at the map will show that the principal features of the Lowlands have a north-easterly trend--the same trend, in fact, as the bounding lines of the division. To this arrangement there are some exceptions, the principal being the belt of hilly ground that extends from the neighbourhood of Paisley, south-east through the borders of Renfrewshire and Ayrshire, to the vicinity of Muirkirk. The major part of the Lowlands is under 500 feet in height, but some considerable portions exceed an elevation of 1000 feet, while here and there the hills approach a height of 2000 feet--the two highest points (2352 and 2335 feet) being attained in Ben Cleugh, one of the Ochils, and in Tinto. Probably the average elevation of the Lowland division does not exceed 350 or 400 feet. Speaking generally, the belts of hilly ground, and the more or less isolated prominences, are formed of more durable rocks than are met with in the adjacent lower-lying tracts. Thus the Sidlaws, the Ochil Hills, and the heights in Renfrewshire and Ayrshire, are composed chiefly of more or less hard and tough volcanic rocks; and when sandstones enter into the formation of a line of hills, as in the Sidlaws, they generally owe their preservation to the presence of the volcanic rocks with which they are associated. This is well illustrated by the Lomond Hills in Fifeshire, the basal and larger portion of which consists chiefly of somewhat soft sandstones, which have been protected from erosion by an overlying sheet of hard basalt-rock. All the isolated hills in the basin of the Forth are formed of knobs, bosses, and sheets of various kinds of igneous rock, which are more durable than the sandstones, shales, and other sedimentary strata by which they are surrounded. Hence it is very evident that the configuration of the Lowland tracts of Central Scotland is due to denudation. The softer and more readily disintegrated rocks have been worn away to a greater extent than the harder and less yielding masses. Only in a few cases do the slopes of the hill-belts coincide with folds of the strata. Thus, the northern flanks of the Sidlaws and the Ochils slope towards the north-west, and this also is the general inclination of the old lavas and other rocks of which those hills are composed. The southern flanks of the same hill-belt slope in Fifeshire towards the south-east--this being also the dip or inclination of the rocks. The crest of the Ochils coincides, therefore, more or less closely, with an anticlinal arch or fold of the strata. But when we follow the axis of this arch towards the north-east into the Sidlaws, we find it broken through by the Tay valley--the axial line running down through the Carse of Gowrie to the north of Dundee. From the fact that many similar anticlinal axes occur throughout the Lowlands, which yet give rise to no corresponding features at the surface, we may conclude that the partial preservation of the anticline of the Ochils and Sidlaws is simply owing to the greater durability of the materials of which those hills consist. Had the arch been composed of sandstones and shales it would most probably have given rise to no such prominent features as are now visible. Another hilly belt, which at first sight appears to correspond roughly to an anticlinal axis, is that broad tract of igneous rocks which separates the Kilmarnock coal-field from the coal-fields of the Clyde basin. But although the old lavas of that hilly tract slope north-east and south-west, with the same general inclination as the surface, yet examination shows that the hills do not form a true anticline. They are built up of a great variety of ancient lavas and fragmental tuffs or "ashes," which are inclined in many different directions. In short, we have in those hills the degraded and sorely denuded fragments of an ancient volcanic bank, formed by eruptions that began upon the bottom of a shallow sea in early Carboniferous times, and subsequently became sub-aërial. And there is evidence to show that after the eruptions ceased the volcanic bank was slowly submerged, and eventually buried beneath the accumulating sediments of later Carboniferous times. The exposure of the ancient volcanic bank at the surface has been accomplished by the denudation of the stratified masses which formerly covered it, and its existence as a dominant elevation at the present day is solely due to the fact that it is built up of more resistant materials than occur in the adjacent low-lying areas. The Ochils and the Sidlaws are of greater antiquity, but have a somewhat similar history. Into this, however, it is not necessary to go. The principal hills of the Lowlands form two interrupted belts, extending north-east and south-west, one of them, which we may call the Northern Heights, facing the Highlands, and the other, which may in like manner be termed the Southern Heights, flanking the great Uplands of the south. The former of these two belts is represented by the Garvock Hills, lying between Stonehaven and the valley of the North Esk; the Sidlaws, extending from the neighbourhood of Montrose to the valley of the Tay at Perth; the Ochil Hills, stretching along the south side of the Firth of Tay to the valley of the Forth at Bridge-of-Allan; the Lennox Hills, ranging from the neighbourhood of Stirling to Dumbarton; the Kilbarchan Hills, lying between Greenock and Ardrossan; the Cumbrae Islands and the southern half of Arran; and the same line of heights reappears in the south end of Kintyre. A well-marked hollow, trough, or undulating plain of variable width, separates these Northern Heights from the Highlands, and may be followed all the way from near Stonehaven, through Strathmore, to Crieff and Auchterarder. Between the valleys of the Earn and Teith this plain attains an abnormal height (the Braes of Doune); but from the Teith, south-west by Flanders Moss and the lower end of Loch Lomond to the Clyde at Helensburgh, it resumes its characteristic features. It will be observed also that a hollow separates the southern portion of Arran from the much loftier northern or Highland area. The tract known as the Braes of Doune, extending from Glen Artney south-east to Strath Allan, although abutting upon the Highlands, is clearly marked off from that great division by geological composition and structure, by elevation and configuration. It is simply a less deeply eroded portion of the long trough or hollow. Passing now to the Southern Heights of the Lowlands, we find that these form a still more interrupted belt than the Northern Heights, and that they are less clearly separated by an intermediate depression from the great Uplands which they flank. They begin in the north-east with the isolated Garleton Hills, between which and the Lammermoors a narrow low-lying trough or hollow appears. A considerable width of low ground now intervenes before we reach the Pentland Hills, which are in like manner separated from the Southern Uplands by a broad low-lying tract. At their southern extremity, however, the Pentlands merge more or less gradually into a somewhat broken and interrupted group of hills which abut abruptly on the Southern Uplands, in the same manner as the Braes of Doune abut upon the slate hills of the Highland borders. In this region the greatest heights reached are in Tinto (2335 feet), and Cairntable (1844 feet), and, at the same time, the hills broaden out towards north-west, where they are continued by the belt of volcanic rocks already described as extending between the coal-fields of the Clyde and Kilmarnock. Although the Southern Heights abut so closely upon the Uplands lying to the south, there is no difficulty in drawing a firm line of demarcation between the two areas--geologically and physically they are readily distinguished. No one with any eye for form, no matter how ignorant he may be of geology, can fail to see how strongly contrasted are such hills as Tinto and Cairntable with those of the Uplands, which they face. The Southern Heights are again interrupted towards the south-east by the valleys of the Ayr and the Doon, but they reappear in the hills that extend from the Heads of Ayr to the valley of the Girvan. Betwixt the Northern and Southern Heights spread the broad Lowland tracts that drain towards the Forth, together with the lower reaches of the Clyde valley, and the wide moors that form the water-parting between that river and the estuary of the Forth. The hills that occur within this inner region of the Central Lowlands are usually more or less isolated, and are invariably formed by outcrops of igneous rock. Their outline and general aspect vary according to the geological character of the rocks of which they are composed--some forming more or less prominent escarpments like those of the Bathgate Hills and the heights behind Burntisland and Kinghorn, others showing a soft rounded contour like the Saline Hills in the west of Fifeshire. Of the same general character as this inner Lowland region is the similar tract watered by the Irvine, the Ayr, and the Doon. This tract, as we have seen, is separated from the larger inner region lying to the east by the volcanic hills that extend from the Southern Heights north-west into Renfrewshire. The largest rivers that traverse the Central Lowlands take their rise, as might be expected, in the mountainous table-lands to the north and south. Of these the principal are the North and South Esks, the Tay and the Isla, the Earn, and the Forth, all of which, with numerous tributaries, descend from the Highlands. And it will be observed that they have breached the line of the Northern Heights in three places--namely, in the neighbourhood of Montrose, Perth, and Stirling. The only streams of importance coming north from the Southern Uplands are the Clyde and the Doon, both of which in like manner have broken through the Southern Heights. Now, just as the main water-flows of the Highlands indicate the average slope of the ancient land-surface before it was trenched and furrowed by the innumerable valleys that now intersect it, so the direction followed by the greater rivers that traverse the Lowlands mark out the primeval slopes of that area. One sees at a glance, then, that the present configuration of this latter division has been brought about by the erosive action of the principal rivers and their countless affluents, aided by the sub-aërial agents generally--rain, frost, ice, etc. The hills rise above the average level of the ground, not because they have been ridged up from below, but simply owing to the more durable nature of their component rocks. That the Northern and Southern Heights are breached only shows that the low grounds, now separating those heights from the adjacent Highlands and Southern Uplands, formerly stood at a higher level, and so allowed the rivers to make their way more or less directly to the sea. Thus, for example, the long trough of Strathmore has been excavated out of sandstones, the upper surface of which once reached a much greater height, and sloped outwards from the Highlands across what is now the ridge of the Sidlaw Hills. Here then, in the Central Lowlands, as in the Highlands, true mountain- or hill-ranges are absent. But if we are permitted to term any well-marked line or belt of high ground a "range," then the Northern and Southern Heights of the Lowlands are better entitled to be so designated than any series of mountains in the Highlands. * * * * * The Southern Uplands.--The northern margin of this wide division having already been defined, we may now proceed to examine the distribution of its mountain-masses. Before doing so, however, it may be as well to point out that considerable tracts in Tweeddale, Teviotdale, and Liddesdale, together with the Cheviot Hills, do not properly belong to the Southern Uplands. In fact, the Cheviots bear the same relation to those Uplands as the Northern Heights do to the Highlands. Like them they are separated by a broad hollow from the Uplands, which they face--a hollow that reaches its greatest extent in Tweeddale, and rapidly wedges out to south-west, where the Cheviots abut abruptly on the Uplands. Even where this abrupt contact takes place, however, the different configuration of the two regions would enable any geologist to separate the one set of mountains from the other. But for geographical purposes we may conveniently disregard these geological contrasts, and include within the Southern Uplands all the area lying between the Central Lowlands and the English Border. If there are no mountains in the Highlands so grouped and arranged as to be properly termed "ranges," this is not less true of the Southern Uplands. Perhaps it is the appearance which those Uplands present when viewed from the Central Lowlands that first suggested the notion that they were ranges. They seem to rise like a wall out of the low grounds at their base, and extend far as eye can reach in an approximately straight line. It seems more probable, however, that our earlier cartographers merely meant, by their conventional hill-shading, to mark out definitely the water-partings. But to do so in this manner now, when the large contour maps of the Ordnance Survey may be in any one's hands, is inexcusable. A study of those maps, or, better still, a visit to the tops of a few of the dominant points in the area under review, will effectually dispel the idea that the Southern Uplands consist of a series of ridges zigzagging across the country. Like the Highlands, the area of the Southern Uplands is simply an old table-land, furrowed into ravine and valley by the operation of the various agents of erosion. Beginning our survey of these Uplands in the east, we encounter first the Lammermoor Hills--a broad undulating plateau--the highest elevations of which do not reach 2000 feet. West of this come the Moorfoot Hills and the high grounds lying between the Gala and the Tweed--a tract which averages a somewhat higher elevation--two points exceeding 2000 feet in height. The next group of mountains we meet is that of the Moffat Hills, in which head a number of important rivers--the Tweed, the Yarrow, the Ettrick, and the Annan. Many points in this region exceed 2000 feet, others approach 2500 feet; and some reach nearly 3000 feet, such as Broad Law (2754 feet), and Dollar Law (2680 feet). In the south-west comes the group of the Lowthers, with dominant elevations of more than 2000 feet. Then follow the mountain-masses in which the Nith, the Ken, the Cree, the Doon, and the Girvan take their rise, many of the heights exceeding 2000 feet, and a number reaching and even passing 2500 feet, the dominant point being reached in the noble mountain-mass of the Merrick (2764 feet). In the extreme south-west the Uplands terminate in a broad undulating plateau, of which the highest point is but little over 1000 feet. All the mountain-groups now referred to are massed along the northern borders of the Southern Uplands. In the south-west the general surface falls more or less gradually away towards the Solway--the 500 feet contour line being reached at fifteen miles, upon an average, from the sea-coast. In the extreme north-east the high grounds descend in like manner into the rich low grounds of the Merse. Between these low grounds and Annandale, however, the Uplands merge, as it were, into the broad elevated moory tract that extends south-east, to unite with the Cheviots--a belt of hills rising along the English Border to heights of 1964 feet (Peel Fell), and 2676 feet (the Cheviot). The general configuration of the main mass of the Southern Uplands--that is to say, the mountain-groups extending along the northern portion of the area under review, from Loch Ryan to the coast between Dunbar and St. Abb's Head--is somewhat tame and monotonous. The mountains are flat-topped elevations, with broad, rounded shoulders and smooth grassy slopes. Standing on the summits of the Higher hills, one seems to be in the midst of a wide, gently undulating plain, the surface of which is not broken by the appearance of any isolated peaks or eminences. Struggling across the bogs and peat-mosses that cover so many of those flat-topped mountains, the wanderer ever and anon suddenly finds himself on the brink of a deep green dale. He discovers, in short, that he is traversing an elevated undulating table-land, intersected by narrow and broad trench-like valleys that radiate outwards in all directions from the dominant bosses and swellings of the plateau. The mountains, therefore, are merely broad ridges and banks separating contiguous valleys; in a word, they are, like the mountains of the Highlands, monuments of erosion, which do not run in linear directions, but form irregular groups and masses. The rocks that enter into the formation of this portion of the Southern Uplands have much the same character throughout. Consequently there is less variety of contour and colour than in the Highlands. The hills are not only flatter atop, but are much smoother in outline, there being a general absence of those beetling crags and precipices which are so common in the Highland regions. Now and again, however, the mountains assume a rougher aspect. This is especially the case with those of Carrick and Galloway, amongst which we encounter a wildness and grandeur which are in striking contrast to the gentle pastoral character of the Lowthers and similar tracts extending along the northern and higher parts of the Southern Uplands. Descending to details, the geologist can observe also modifications of contour even among those monotonous rounded hills. Such modifications are due to differences in the character of the component rocks, but they are rarely so striking as the modifications that arise from the same cause in the Highlands. To the trained eye, however, they are sufficiently manifest, and upon a geologically coloured map, which shows the various belts of rock that traverse the Uplands from south-west to north-east, it will be found that the mountains occurring within each of those separate belts have certain distinctive features. Such features, however, cannot be depicted upon a small orographical map. The separation of those mountains into distinct ranges, by reference to their physical aspect, is even less possible here than in the Highlands. Now and again, bands of certain rocks, which are of a more durable character than the other strata in their neighbourhood, give rise to pronounced ridges and banks, while hollows and valleys occasionally coincide more or less closely with the outcrops of the more readily eroded strata; but such features are mere minor details in the general configuration of the country. The courses of brooks and streams may have been frequently determined by the nature and arrangement of the rocks, but the general slope of the Uplands and the direction of the main lines of water-flow are at right angles to the trend of the strata, and cannot therefore have been determined in that way. The strata generally are inclined at high angles--they occur, in short, as a series of great anticlinal arches and synclinal curves, but the tops of the grand folds have been planed off, and the axes of the synclinal troughs, so far from coinciding with valleys, very often run along the tops of the highest hills. The foldings and plications do not, in a word, produce any corresponding undulations of the surface. Mention has been made of the elevated moory tracts that serve to connect the Cheviots with the loftier Uplands lying to north-west. The configuration of these moors is tamer even than that of the regions just described, but the same general form prevails from the neighbourhood of the Moffat Hills to the head-waters of the Teviot. There, however, other varieties of rock appear, and produce corresponding changes in the aspect of the high grounds. Not a few of the hills in this district stand out prominently. They are more or less pyramidal and conical in shape, being built up of sandstones often crowned atop with a capping of some crystalline igneous rock, such as basalt. The Maiden Paps, Leap Hill, Needs Law, and others are examples. The heights draining towards Liddesdale and lower reaches of Eskdale, composed chiefly of sandstones, with here and there intercalated sheets of harder igneous rock, frequently show escarpments and terraced outlines, but have a general undulating contour; and similar features are characteristic of the sandstone mountains that form the south-west portion of the Cheviots. Towards the north-east, however, the sandstones give place to various igneous rocks, so that the hills in the north-east section of the Cheviots differ very much in aspect and configuration from those at the other extremity of the belt. They have a more varied and broken outline, closely resembling many parts of the Ochils and other portions of the Northern and Southern Heights of the Central Lowlands. The low-lying tracts of Roxburghshire and the Merse, in like manner, present features which are common to the inner region of the Central Lowlands. Occasional ridges of hills rise above the general level of the land, as at Smailholm and Stitchell to the north of Kelso, while isolated knolls and prominences--some bald and abrupt, others smooth and rounded--help to diversify the surface. Bonchester Hill, Rubers Law, the Dunian, Penielheugh, Minto Hills, and the Eildons may be mentioned as examples. All of these are of igneous origin, some being mere caps of basalt resting upon a foundation of sandstone, while others are the stumps of isolated volcanoes. In the maritime tracts of Galloway the low grounds repeat, on a smaller scale, the configuration of the lofty Uplands behind, for they are composed of the same kinds of rock. Their most remarkable feature is the heavy mountain-mass of Criffel, rising near the mouth of the Nith to a height of 1800 feet. Everywhere, therefore, throughout the region of the Southern Uplands, in hilly and low-lying tracts alike, we see that the land has been modelled and contoured by the agents of erosion. We are dealing, as in the Highlands, with an old table-land, in which valleys have been excavated by running water and its helpmates. Nowhere do we encounter any linear banks, ridges, or ranges as we find described in the class-books, and represented upon many general maps of the country. In one of those manuals we read that in the southern district "the principal range of mountains is that known as the Lowther Hills, which springs off from the Cheviots, and, running in a zigzag direction to the south-west, terminates on the west coast near Loch Ryan." This is quite true, according to many common maps, but unfortunately the "range" exists upon those maps and nowhere else. The zigzag line described is not a range of mountains, but a water-parting, which is quite another matter. The table-land of the Southern Uplands, like that of the Highlands, is of immense antiquity. Long before the Old Red Sandstone period, it had been furrowed and trenched by running water. Of the original contour of its surface, all we can say is that it formed an undulating plateau, the general slope of which was towards south-east. This is shown by the trend of the more important rivers, such as the Nith and the Annan, the Gala and the Leader; and by the distribution of the various strata pertaining to the Old Red Sandstone and later geological periods. Thus, strata of Old Red Sandstone and Carboniferous age occupy the Merse and the lower reaches of Teviotdale, and extend up the valleys of the Whiteadder and the Leader into the heart of the Silurian Uplands. In like manner Permian sandstones are well developed in the ancient hollows of Annandale and Nithsdale. Along the northern borders of the Southern Uplands we meet with similar evidence to show that even as early as Old Red Sandstone times the old plateau, along what is now its northern margin, was penetrated by valleys that drained towards the north. The main drainage, however, then as now, was directed towards south-east. Many geological facts conspire to show that the Silurian table-land of these Uplands has been submerged, like the Highlands, in whole or in part. This happened at various periods, and each time the land went down it received a covering of newer accumulations--patches of which still remain to testify to the former extent of the submergences. From the higher portions of the Uplands those accumulations have been almost wholly swept away, but they have not been entirely cleared out of the ancient valleys. They still mantle the borders of the Silurian area, particularly in the north-east, where they attain a great thickness in the moors of Liddesdale and the Cheviot Hills. The details of the evolution of the whole area of the Southern Uplands form an interesting study, but this pertains rather to Geology than to Physical Geography. It is enough, from our present point of view, to be assured that the main features of the country were chalked out, as it were, at a very distant geological period, and that all the infinite variety in the relief of our land has been brought about directly, not by titanic convulsions and earth-movements, but by the long-continued working of rain and rivers--of frost and snow and ice, supplemented from time to time by the action of the sea. The physical features more particularly referred to in this paper are of course only the bolder and more prominent contours--those namely which can be expressed with sufficient accuracy upon sheets of such a size as the accompanying orographical map of Scotland (Plate I.). With larger maps considerably more detail can be added, and many characteristic and distinguishing features will appear according to the care with which such maps are drawn. In the case of the Ordnance Survey map, on the scale of 1 inch to a mile, the varying forms of the surface are so faithfully delineated as frequently to indicate to a trained observer the nature of the rocks and the geological structure of the ground. The artists who sketched the hills must indeed have had good eyes for form. So carefully has their work been done, that it is often not difficult to distinguish upon their maps hills formed of such rocks as sandstone from those that are composed of more durable kinds. The individual characteristics of mountains of schist, of granite, of quartz-rock, of slate, are often well depicted: nay, even the varieties of igneous rock which enter into the formation of the numerous hills and knolls of the Lowlands can frequently be detected by the features which the artists have so intelligently caught. Another set of features which their maps display are those due to glaciation. These are admirably brought out, even down to the smallest details. A glance at such maps as those of Teviotdale and the Merse, for example, shows at once the direction taken by the old _mer de glace_. The long parallel flutings of the hill-slopes, _roches moutonnées_, projecting knolls and hills with their "tails," the great series of banks and ridges of stony clay which trend down the valley of the Tweed--these, and many more details of interest to specialists, are shown upon the maps. All over Scotland similar phenomena are common, and have been reproduced with marvellous skill on the shaded sheets issued by the Ordnance Survey. And yet the artists were not geologists. The present writer is glad of this opportunity of recording his obligations to those gentlemen. Their faithful delineations of physical features have given him many valuable suggestions, and have led up to certain observations which might otherwise not have been made. III. Mountains: Their Origin, Growth, and Decay.[D] [D] _Scottish Geographical Magazine_, vol. ii., 1886. Mountains have long had a fascination for lovers of nature. Time was, however, when most civilised folk looked upon them with feelings akin to horror; and good people, indeed, have written books to show that they are the cursed places of the earth--the ruin and desolation of their gorges and defiles affording indubitable proof of the evils which befell the world when man lapsed from his primitive state of innocence and purity. All this has changed. It is the fashion now to offer a kind of worship to mountains; and every year their solitudes are invaded by devotees--some, according to worthy Meg Dods, "rinning up hill and down dale, knapping the chuckie-stanes to pieces wi' hammers, like sae mony roadmakers run daft--to see, as they say, how the warld was made"--others trying to transfer some of the beauty around them to paper or canvas--yet others, and these perhaps not the least wise, content, as old Sir Thomas Browne has it, "to stare about with a gross rusticity," and humbly thankful that they are beyond the reach of telegrams, and see nothing to remind them of the _fumun et opes strepitumque Romæ_. But if the sentiment with which mountains are regarded has greatly changed, so likewise have the views of scientific men as to their origin and history. Years ago no one doubted that all mountains were simply the result of titanic convulsions. The crust of the earth had been pushed up from below, tossed into great billows, shivered and shattered--the mountains corresponding to the crests of huge earth-waves, the valleys to the intervening depressions, or to gaping fractures and dislocations. This view of the origin of mountains has always appeared reasonable to those who do not know what is meant by geological structure, and in some cases it is pretty near the truth. A true mountain-chain, like that of the Alps, does indeed owe its origin to gigantic disturbances of the earth's crust, and in such a region the larger features of the surface often correspond more or less closely with the inclination of the underlying rocks. But in many elevated tracts, composed of highly disturbed and convoluted strata, no such coincidence of surface-features and underground structure can be traced. The mountains do not correspond to great swellings of the crust--the valleys neither lie in trough-shaped strata, nor do they coincide with gaping fractures. Again, many considerable mountains are built up of rocks which have not been convoluted at all, but occur in approximately horizontal beds. Evidently, therefore, some force other than subterranean action must be called upon to explain the origin of many of the most striking surface-features of the land. Every geologist admits--it is one of the truisms of his science--that corrugations and plications are the result of subterranean action. Nor does any one deny that when a true mountain-chain was first upheaved the greater undulations of the folded strata probably gave rise to similar undulations at the surface. Some of the larger fractures and dislocations might also have appeared at the surface and produced mural precipices. So long a time, however, has elapsed since the elevation of even the youngest mountain-chains of the globe that the sub-aërial agents of erosion--rain, frost, rivers, glaciers, etc.--have been enabled greatly to modify their primeval features. For these mountains, therefore, it is only partially true that their present slopes coincide with those of the underlying strata. Such being the case with so young a chain as the Alps, we need not be surprised to meet with modifications on a still grander scale in mountain-regions of much greater antiquity. In many such tracts the primeval configuration due to subterranean action has been entirely remodelled, so that hills now stand where deep hollows formerly existed, while valleys frequently have replaced mountains. And this newer configuration is the direct result of erosion, guided by the mineralogical composition and structural peculiarities of the rocks. It is difficult, or even impossible, for one who is ignorant of geological structure to realise that the apparently insignificant agents of erosion have played so important a _rôle_ in the evolution of notable earth-features. It may be well, therefore, to illustrate the matter by reference to one or two regions where the geological structure is too simple to be misunderstood. The first examples I shall give are from tracts of horizontal strata. Many readers are doubtless aware of the fact that our rock-masses consist for the most part of the more or less indurated and compacted sediments of former rivers, lakes, and seas. Frequently those ancient water-formed rocks have been very much altered, so as even sometimes to acquire a crystalline character. But it is enough for us now to remember that the crust of the globe, so far as that is accessible to observation, is built up mostly of rocks which were originally accumulated as aqueous sediments. Such being the case, it is obvious that our strata of sandstone, conglomerate, shale, limestone, etc., must at first have been spread out in approximately horizontal or gently inclined sheets or layers. We judge so from what we know of sediments which are accumulating at present. The wide flats of our river valleys, the broad plains that occupy the sites of silted-up lakes, the extensive deltas of such rivers as the Nile and the Po, the narrow and wide belts of low-lying land which within a recent period have been gained from the sea, are all made up of various kinds of sediment arranged in approximately horizontal layers. Now, over wide regions of the earth's surface the sedimentary strata still lie horizontally, and we can often tell at what geological period they became converted into dry land. Thus, for example, we know that the elevated plateau through which the river Colorado flows is built up of a great series of nearly horizontal beds of various sedimentary deposits, which reach a thickness of many thousand feet. It is self-evident that the youngest strata must be those which occur at the surface of the plateau, and they, as we know, are of lacustrine origin and belong to the Tertiary period. Now, American geologists have shown that since that period several thousands of feet of rock-materials have been removed from the surface of that plateau--the thickness of rock so carried away amounting in some places to nearly 10,000 feet. Yet all that prodigious erosion has been effected since early Tertiary times. Indeed, it can be proved that the excavation of the Grand Cañon of the Colorado, probably the most remarkable river-trench in the world, has been accomplished since the close of the Tertiary period, and is therefore a work of more recent date than the last great upheaval of the Swiss Alps. The origin of the cañon is self-evident--it is a magnificent example of river-erosion, and the mere statement of its dimensions gives one a forcible impression of the potency of sub-aërial denudation. The river-cutting is about 300 miles long, 11 or 12 miles broad, and varies from 3000 to 6000 feet in depth. Take another example of what denuding agents have done within a recent geological period. The Faröe Islands, some twenty in number, extend over an area measuring about 70 miles from south to north, and nearly 50 miles from west to east. These islands are composed of volcanic rocks--beds of basalt with intervening layers of fine fragmental materials, and are obviously the relics of what formerly was one continuous plateau, deeply trenched by valleys running in various directions. Subsequent depression of the land introduced the sea to these valleys, and the plateau was then converted into a group of islands, separated from each other by narrow sounds and fiords. Were the great plateau through which the Colorado flows to be partially submerged, it would reproduce on a larger scale the general phenomena presented by this lonely island-group of the North Atlantic. The flat-topped "buttes" and "mesas," and the pyramidal mountains of the Colorado district would form islands comparable to those of the Faröes. Most of the latter attain a considerable elevation above the sea--heights of 1700, 2000, 2500, and 2850 feet being met with in several of the islands. Indeed, the average elevation of the land in this northern archipelago can hardly be less than 900 feet. The deep trench-like valleys are evidently only the upper reaches of valleys which began to be excavated when the islands formed part and parcel of one and the same plateau--the lower reaches being now occupied by fiords and sounds. It is quite certain that all these valleys are the work of erosion. One can trace the beds of basalt continuously across the bottoms, and be quite sure that the valleys are not gaping cracks or fractures. Now, as the strata are approximately horizontal, it is obvious that the hollows of the surface have nothing whatever to do with undulations produced by earth-movements. The sub-aërial erosion of the islands has resulted in the development of massive flat-topped and pyramidal mountains. These stand up as eminences simply because the rock-material which once surrounded them has been gradually broken up and carried away. Nothing can well be more impressive to the student of physical geology than the aspect presented by these relics of an ancient plateau (Plate II. Fig. 1). Standing on some commanding elevation, such as Nakkin in Suderöe, one sees rising before him great truncated pyramids--built up of horizontal beds of basalt rising tier above tier--the mountains being separated from each other by wide and profound hollows, across which the basalt-beds were once continuous. Owing to the parallel and undisturbed position of the strata, it is not hard to form an estimate of the amount of material which has been removed during the gradual excavation of the valleys. In order to do so we have simply to measure the width, depth, and length of the valleys. Thus in Suderöe, which is 19 miles long and 6 miles broad, the bottoms of the valleys are 1000 feet at least below the tops of the mountains, and some of the hollows in question are a mile in width. Now, the amount of rock worn away from this one little island by sub-aërial erosion cannot be less than that of a mass measuring 10 miles in length by 6 miles in breadth, and 800 feet in thickness. And yet the Faröe Islands are composed of rocks which had no existence when the soft clays, etc., of the London Basin were being accumulated. All the erosion referred to has taken place since the great upheaval of the Eocene strata of the Swiss Alps. But if the evidence of erosion be so conspicuous in regions composed of horizontal strata, it is not less so in countries where the rocks are inclined at various angles to the horizon. Indeed, the very fact that inclined strata crop out at the surface is sufficient evidence of erosion. For it is obvious that these outcrops are merely the truncated ends of beds which must formerly have had a wider extension. But while the effects produced by the erosion of horizontal strata are readily perceived by the least-informed observer, it requires some knowledge of geological structure to appreciate the denudation of curved or undulating strata. And yet there is really no mystery in the matter. All we have to do is by careful observation to ascertain the mode of arrangement of the rocks--this accomplished, we have no difficulty in estimating the minimum erosion which any set of strata may have experienced. An illustration may serve to make this plain. Here, for example, is a section across a region of undulating strata (Fig. 2). Let the line _A B_ represent the surface of the ground, and _C D_ be any datum line--say, the sea-level. An observer at _A_, who should walk in the direction of _B_, would cross successively eight outcrops of coal; and, were he incapable of reading the geological structure of the ground, he might imagine that he had come upon eight separate coal-seams. A glance at the section, however, shows that in reality he had met with only two coals, and that the deceptive appearances, which might be misread by an incautious observer, are simply the result of denudation. In this case the tops of a series of curved or arched beds have been removed (as at _E_), and, by protracting the lines of the truncated beds until they meet, we can estimate the minimum amount of erosion they have sustained. Thus, if the strata between _o_ and _p_ be 300 feet thick, it is self-evident that a somewhat greater thickness of rock must have been removed from the top of the anticlinal arch or "saddleback" at _E_. Again, let us draw a section across strata which have been fractured and dislocated, and we shall see how such fractures likewise enable us to estimate the minimum amount of erosion which certain regions have experienced. In Fig. 3 we have a series of strata containing a bed of limestone _L_, and a coal-seam _a_. The present surface of the ground is represented by the line _A B_. At _F_ the strata are traversed by a fault or dislocation--the beds being thrown down for say 500 feet on the low side of the fault--so that the coal at _a^2_ occurs now at a depth of 500 feet below its continuation at _a^1_. At the surface of the ground there is no inequality of level--the beds overlying the coal (_a²_) having been removed by denudation. Were the missing rocks to be replaced, they would occupy the space contained within the dotted lines above the present surface _A B_. Such dislocations are of common occurrence in our coal-fields, and it is not often that they give rise to any features at the surface. We may thus traverse many level or gently-undulating tracts, and be quite unconscious of the fact that geologically we have frequently leaped up or dropped down for hundreds of feet in a single step. Nay, some Scottish streams and rivers flow across dislocations by which the strata have been shifted up or down for thousands of feet, and in some places one can have the satisfaction of sitting upon rocks which are geologically 3000 yards below or above those on which he rests his feet. In other words, thousands of feet of strata have been removed by denudation from the high sides of faults. These, as I have said, often give rise to no feature at the surface; but, occasionally, when "soft" rocks have been shifted by dislocations, and brought against "hard" rocks, the latter, by better resisting denudation than the former, cause a more or less well-marked feature at the surface, and thus betray the presence of a fault to the geologist. The phenomena presented by faults, therefore, are just as eloquent of denudation as is the truncated appearance of our strata; and only after we have carefully examined the present extension and mutual relations of our rock-masses, their varied inclination, and the size of the dislocations by which they are traversed, can we properly appreciate the degree of erosion which they have sustained. Before we are entitled to express any opinion as to the origin of the surface-features of a country, we must first know its geological structure. Until we have attained such knowledge, all our views as to the origin of mountains are of less value than the paper they are written upon. I have spoken of the evidence of denudation which we find in our truncated and dislocated rock-masses; there is yet another line of evidence which I may very shortly point out. As every one knows, there exist in this and many other countries enormous masses of igneous rocks, which have certainly been extruded from below. Now, some of these rocks, such as granite, belong to what is called the _plutonic_ class of rocks; they are of deep-seated origin--that is to say, they never were erupted at the surface, but cooled and consolidated at great depths in the earth's crust. I need not go into any detail to show that this is the case--it is a conclusion based upon incontrovertible facts, and accepted by every practical geologist. When, therefore, we encounter at the actual surface of the earth great mountain-masses of granite, we know that in such regions enormous denudation has taken place. The granite appears at the surface simply because the thick rock-masses under which it solidified have been gradually removed by erosion. The facts which I have now briefly passed in review must convince us that erosion is one of the most potent factors with which the geologist has to deal. We have seen what it has been able to effect in certain tracts composed of strata which date back to a recent geological period, such as the plateau of the Colorado and the pyramidal mountains of the Faröe Islands. If in regions built up of strata so young as the rocks of those tracts the amount of erosion be so great, we may well expect to meet with evidence of much more extensive denudation in regions which have been subjected for enormously longer periods to the action of the eroding agents. The study of geological structure, or the architecture of the earth's crust, has enabled us to group all mountains under these three principal heads:-- 1. _Mountains of Accumulation._ 2. _Mountains of Elevation._ 3. _Mountains of Circumdenudation._ 1. Mountains of Accumulation.--Volcanoes may be taken as the type of this class of mountains. These are, of course, formed by the accumulation of igneous materials around the focus or foci of eruption, and their mode of origin is so generally understood, and, indeed, so obvious, that I need do no more than mention them. Of course, they are all subject to erosion, and many long-extinct volcanoes are highly denuded. Some very ancient ones, as those of our own country, have been so demolished that frequently all that remains are the now plugged-up pipes or flues through which the heated materials found a passage to the surface--all those materials, consisting of lavas and ashes, having in many cases entirely disappeared. In former times volcanic eruptions often took place along the line of an extensive fissure--the lava, instead of being extruded at one or more points, welled-up and overflowed along the whole length of the fissure, so as to flood the surrounding regions. And this happening again and again, vast plateaux of igneous rock came to be built up, such as those of the Rocky Mountains, Iceland, the Faröes, Antrim and Mull, Abyssinia and the Deccan. These are called _plateaux of accumulation_ (see Fig. 1), and all of them are more or less highly denuded, so that in many cases the plateaux have quite a mountainous appearance. Of course, plateaux of accumulation are not always formed of igneous rocks. Any area of approximately horizontal strata of aqueous origin, rising to a height of a thousand feet or more above the sea, would come under this class of plateau--the plateau of the Colorado being a good example. Although that plateau is of recent origin, yet its surface, as we have seen, has been profoundly modified by superficial erosion; and this is true to a greater extent of plateaux which have been much longer exposed to denudation. It is obvious that even mountains and plateaux of accumulation often owe many of their present features to the action of the surface-agents of change. 2. Mountains of Elevation.--We have seen that the strata which enter most largely into the composition of the earth's crust, so far as that is open to observation, consist of rocks which must originally have been disposed in horizontal or approximately horizontal layers. But, as every one knows, the stratified rocks are not always horizontally arranged. In Scotland they rarely are so. On the contrary, they are inclined at all angles from the horizon, and not infrequently they even stand on end. Moreover, they are often traversed by dislocations, large and small. No one doubts that these tilted and disturbed rocks are evidence of wide-spread earth-movements. And it has been long known to geologists that such movements have happened again and again in this and many other countries where similar disturbed strata occur. Some of these movements, resulting in the upheaval of enormous mountain-masses, have taken place within comparatively recent geological times. Others again date back to periods inconceivably remote. The Pyrenees, the Alps, the Caucasus, the Himalaya, which form the back-bone of Eurasia, are among the youngest mountains of the globe. The Highlands of Scotland and Scandinavia are immeasurably more ancient; they are, in point of fact, the oldest high grounds in Europe, nor are there any mountain-masses elsewhere which can be shown to be older. But while the Alps and other recent mountains of elevation still retain much of their original configuration, not a vestige of the primeval configuration of our own Highlands has been preserved; their present surface-features have no direct connection with those which must have distinguished them in late Silurian times. Our existing mountains are not, like those of the Alps, mountains of elevation. The structure of a true mountain-chain is frequently very complicated, but the general phenomena can be readily expressed in a simple diagram. Let Fig. 5 be a section taken across a mountain-chain, _i.e._ at right angles to its trend or direction. The dominant point of the chain is shown at _B_, while _A_ and _C_ represent the low grounds. Now, an observer at _A_, advancing towards _B_, would note that the strata, at first horizontal, would gradually become undulating as he proceeded on his way--the undulations getting always more and more pronounced. He would observe, moreover, that the undulations, at first symmetrical, as at _a_, would become less so as he advanced--one limb of an arch or _anticline_, as it is termed, being inclined at a greater angle than the other, as at _b_. Approaching still nearer to =B=, the arches or anticlines would be seen eventually to bend over upon each other, so as to produce a general dip or inclination of the strata towards the central axis of the chain. Crossing that axis (_B_), and walking in the direction of the low grounds (_C_), the observer would again encounter the same structural arrangement, but of course in reverse order. Thus, in its simplest expression, a true mountain-chain consists of strata arranged in a series of parallel undulations--the greater mountain ridges and intervening hollows corresponding more or less closely to the larger undulations and folds of the strata. Now, could these plicated strata be pulled out, could the folds and reduplications be smoothed away, so as to cause the strata to assume their original horizontal position, it is obvious that the rocks would occupy a greater superficial area. We see, then, that such a mountain-chain must owe its origin to a process of tangential or lateral thrusting and crushing. The originally horizontal strata have been squeezed laterally, and have yielded to the force acting upon them by folding and doubling up. It seems most probable that the larger contortions and foldings which are visible in all true mountain-chains, owe their origin to the sinking down of the earth's crust upon the cooling and contracting nucleus. During such depressions of the crust the strata are necessarily subjected to enormous lateral compression; they are forced to occupy less space at the surface, and this they can only do by folding and doubling-back upon themselves. If the strata are equally unyielding throughout a wide area, then general undulation may ensue; but should they yield unequally, then folding and contortion will take place along one or more lines of weakness. In other words, the pressure will be relieved by the formation of true mountain-chains. Thus, paradoxical as it may seem, the loftiest mountains of the globe bear witness to profound depression or subsidence of the crust. The Andes, for example, appear to owe their origin to the sinking down of the earth's crust under the Pacific; and so in like manner the Alps would seem to have been ridged up by depression of the crust in the area of the Mediterranean. Mountain-chains, therefore, are true wrinkles in the crust of the earth; they are lines of weakness along which the strata have yielded to enormous lateral pressure. A glance at the geological structure of the Alps and the Jura shows us that these mountains are a typical example of such a chain; they are mountains of elevation. In the Jura the mountains form a series of long parallel ridges separated by intervening hollows; and the form or shape of the ground coincides in a striking manner with the foldings of the strata. In these mountains we see a succession of symmetrical flexures, the beds dipping in opposite directions at the same angle from the axis of each individual anticline. There each mountain-ridge corresponds to an _anticline_, and each valley to a _syncline_, or trough-shaped arrangement of strata. But as we approach the Alps the flexures become less and less symmetrical, until in the Alps themselves the most extraordinary convolutions and intricate plications appear, the strata being often reversed or turned completely upside down. Though it is true that the slopes of this great mountain-chain not infrequently correspond more or less closely to the slope or inclination of the underlying rocks, it must not be supposed that this correspondence is often complete. Sometimes, indeed, we find that the mountains, so far from coinciding with anticlines, are in reality built up of synclinal or basin-shaped strata; while in other cases deep and broad valleys run along the lines of anticlinal axes (Fig. 6). All this speaks to enormous erosion. A study of the geological structure of the Alps demonstrates that thousands of feet of rock have been removed from those mountains since the time of their elevation. A section drawn across any part of the chain would show that the strata have been eroded to such an extent, and the whole configuration so profoundly modified, that it is often difficult, or even impossible, to tell what may have been the original form of the surface when the chain was upheaved. And yet the Alps, it must be remembered, are of comparatively recent age, some of their highly-confused and contorted rocks consisting of marine strata which are of no greater antiquity than the incoherent clays and sands of the London Tertiary basin. Now, when we reflect upon the fact that, in the case of so young a mountain-chain, the configuration due to undulations of the strata has been so greatly modified, and even in many places obliterated, it is not hard to believe that after sufficient time has elapsed--after the Alps have existed for as long a period, say, as the mountains of middle Germany--every mountain formed of anticlinal strata shall have disappeared, and those synclines which now coincide with valleys shall have developed into hills. The reader who may have paid little or no attention to geological structure and its influence upon the form of the ground, will probably think this a strange and extravagant statement; yet I hope to show presently that it is supported by all that we know of regions of folded strata which have been for long periods of time subjected to denudation. * * * * * 3. Mountains of Circumdenudation.--In countries composed of undulating and folded strata which have been for long ages exposed to the action of eroding agents, the ultimate form assumed by the ground is directly dependent on the character of the rocks, and the mode of their arrangement. The various rock-masses which occur in such a neighbourhood as Edinburgh, for example, differ considerably in their power of resisting denudation. Hence the less readily eroded rocks have come in time to form hills of less or greater prominence. Such is the case with the Castle Rock, Corstorphine Hill, the Braids, the Pentlands, etc. These hills owe their existence, as such, to the fact that they are composed of more enduring kinds of rock than the softer sandstones and shales by which they are surrounded, and underneath which they were formerly buried to great depths. Some hills, again, which are for the most part built up of rocks having the same character as the strata that occur in the adjacent low grounds, stand up as prominences simply because they have been preserved by overlying caps or coverings of harder rocks--rocks which have offered a stronger resistance to the action of the denuding agents. The Lomond Hills are good examples. Those hills consist chiefly of sandstones which have been preserved from demolition by an overlying sheet of basalt-rock. But the mode in which rocks are arranged is a not less important factor in determining the shape which the ground assumes under the action of the agents of erosion. Thus, as we have already seen, flat-topped, pyramidal mountains, and more or less steep-sided or trench-like valleys, are characteristic features in regions of horizontal strata. When strata dip or incline in one general direction, then we have a succession of escarpments or dip-slopes, corresponding to the outcrops of harder or less readily eroded beds, and separated from each other by long valleys, hollows, or undulating plains, which have the same trend as the escarpments (Fig. 7). This kind of configuration is well exemplified over a large part of England. The general dip or inclination of the Mesozoic or Secondary strata throughout that country, between the shores of the North Sea and the English Channel, is easterly and south-easterly--so that the outcrops of the more durable strata form well-defined escarpments that face the west and north-west, and can be followed almost continuously from north to south. Passing from the Malvern Hills in a south-easterly direction, we traverse two great escarpments--the first coinciding with the outcrop of the Oolite, and forming the Cotswold Hills; and the second corresponding to the outcrop of the Chalk, and forming the Chiltern Hills. The plains and low undulating tracts that separate these escarpments mark the outcrops of more yielding strata--the low grounds that intervene between the Cotswolds and the Malvern Hills being composed of Liassic and Triassic clays and sandstones. In Scotland similar escarpments occur, but owing to sudden changes of the dip, and various interruptions of the strata, the Scottish escarpments are not so continuous as those of the sister-country. Many of the belts of hilly ground in the Scottish Lowlands, however, exemplify the phenomena of escarpment and dip-slope. Thus, the Sidlaws in Forfarshire consist of a series of hard igneous rocks and interbedded sandstones and flags--the outcrops of which form a succession of escarpments with intervening hollows. The same appearances recur again and again all over the Lowlands. Wherever, indeed, any considerable bed of hard rock occurs in a series of less enduring strata--the outcrop of the harder rock invariably forms a well-marked feature or escarpment. As examples, I may refer to Salisbury Crags, Craiglockhart Hill, Dalmahoy Crags, the Bathgate Hills, King Alexander's Crag, etc. All these are conspicuous examples of the work of denudation--for it can be demonstrated that each of these rock-masses was at one time deeply buried under sandstones and shales, and they now crop out at the surface, and form prominent features simply because the beds which formerly covered and surrounded them have been gradually removed. From what has now been said it will be readily understood that in regions composed of strata the inclination or dip of which is not constant but continually changing in direction, the surface-features must be more or less irregular. If the strata dip east the outcrops of the harder beds will form escarpments facing the west, and the direction of the escarpments will obviously change with the direction of the dip. Undulating strata of variable composition will, in short, give rise to an undulating surface, but the superficial undulations will not coincide with those of the strata. On the contrary, in regions consisting of undulating strata of diverse consistency the hills generally correspond with synclinal troughs--or, in other words, trough-shaped strata tend to form hills; while, on the other hand, arch-shaped or anticlinal strata most usually give rise to hollows (see Fig. 2). This remarkable fact is one of the first to arrest the attention of every student of physical geology, and its explanation is simple enough. An anticlinal arrangement of strata is a weak structure--it readily succumbs to the attacks of the denuding agents; a synclinal arrangement on the contrary, is a strong structure, which is much less readily broken up. Hence it is that in all regions which have been exposed for prolonged periods to sub-aërial denudation synclinal strata naturally come to form hills, and anticlinal strata valleys or low grounds. In the case of a mountain-chain so recently elevated as that of the Alps, the mountain-ridges, as we have seen, often coincide roughly with the greater folds of the strata. Such anticlinal mountains are weakly built, and consequently rock-falls and landslips are of common occurrence among them--far more common, and on a much larger scale, than among the immeasurably older mountains of Scandinavia and Scotland. The valleys of the Pyrenees, the Alps, and the Apennines, are cumbered with enormous chaotic heaps of fallen rock-masses. From time to time peaks and whole mountain-sides give way, and slide into the valleys, burying hamlets and villages, and covering wide tracts of cultivated land. Hundreds of such disastrous rock-falls have occurred in the Alps within historical ages, and must continue to take place until every weakly-formed mountain has been demolished. The hills and mountains of Scotland have long since passed through this phase of unstable equilibrium. After countless ages of erosion our higher grounds have acquired a configuration essentially different from that of a true mountain-chain. Enormous landslips like that of the Rossberg are here impossible, for all such weakly-constructed mountains have disappeared. A little consideration will serve to show how such modifications and changes have come about. When strata are crumpled up they naturally crack across, for they are not elastic. During the great movements which have originated all mountains of elevation, it is evident that the strata forming the actual surface of the ground would often be greatly fissured and shattered along the crests of the sharper anticlinal ridges. In the synclinal troughs, however, although much fissuring would take place, yet the strata would be compelled by the pressure to keep together. Now, when we study the structure of such a region as the Alps, we find that the tops of the anticlines have almost invariably been removed, so as to expose the truncated ends of the strata--the ruptured and shattered rock-masses having in the course of time been carried away by the agents of erosion. Such mountains are pre-eminently weak structures. Let us suppose that the mountains represented in the diagram (Fig. 8) consist of a succession of strata, some of which are more or less permeable by water, while others are practically impermeable. It is obvious that water soaking down from the surface will find its way through the porous strata (_p_), and come out on the slopes of the mountains along the joints and cracks (_c_) by which all strata are traversed. Under the influence of such springs and the action of frost, the rock at the surface will eventually be broken up, and ever and anon larger and smaller portions will slide downwards over the surface of the underlying impermeable stratum. The undermining action of rivers will greatly intensify this disintegrating and disrupting process. As the river deepens and widens its valley (_v_), it is apparent that in doing so it must truncate the strata that are inclined towards it. The beds will then crop out upon the slopes of the valley (as at _b_, _b_), and so the conditions most favourable for a landslip will arise. Underground water, percolating through the porous beds (p), and over the surface of the underlying impermeable beds (_i_, _i_, _i_), must eventually bring about a collapse. The rocks forming the surface-slopes of the mountain will from time to time give and slide into the valley, or the whole thickness of the truncated strata may break away and rush downwards; and this process must continue so long as any portion of the anticlinal arch remains above the level of the adjacent synclinal troughs. Thus it will be seen that an anticlinal arch is a weak structure--a mountain so constructed falls a ready prey to the denuding agents; and hence in regions which have been exposed to denudation for as long a period as the Scottish or Scandinavian uplands, a mountain formed of anticlinally arranged strata is of very exceptional occurrence. When it does appear, it is only because the rocks of which it is composed happen to be of a more enduring character than those of the adjacent tracts. The Ochil Hills exemplify this point. These hills consist of a great series of hard igneous rocks, which are arranged in the form of a depressed anticlinal arch--the low grounds lying to the north and south being composed chiefly of sandstones and shales. Here it is owing to the more enduring character of the igneous rocks that the anticlinal arch has not been entirely removed. We know, however, that these igneous rocks were formerly buried under a great thickness of strata, and that their present appearance at the surface is simply the result of denudation. If an anticlinal arch be a weak structure, a synclinal arrangement of strata is quite the opposite. In the case of the former each bed has a tendency to slip or slide away from the axis, while in a syncline it is just the reverse--the strata being inclined towards and not away from the axis. Underground water, springs, and frost are enabled to play havoc with anticlinal strata, for the structure is entirely in their favour. But in synclinal beds the action of these powerful agents is opposed by the structure of the rocks--and great rock-falls and landslips cannot take place. Synclinal strata therefore endure, while anticlinal strata are worn more readily away. Even in a true mountain-range so young as the Alps, denudation has already demolished many weakly-built anticlinal mountains, and opened up valleys along their axes; while, on the other hand, synclinal troughs have been converted into mountains. And if this be true of the Alps, it is still more so of much older mountain-regions, in which the original contours due to convolutions of the strata have entirely disappeared (see Fig. 9). The mountains of such regions, having been carved out and modelled by denuding agents, are rightly termed _mountains of circumdenudation_, for they are just as much the work of erosion as the flat-topped and pyramidal mountains which have been carved out of horizontal strata. The Scottish Highlands afford us an admirable example of a mountainous region of undulating and often highly-flexed strata, in which the present surface-features are the result of long-continued erosion. As already remarked, this region is one of the oldest land-surfaces in the world. In comparison with it, the Pyrenees, the Alps, and the Himalayas are creations of yesterday. The original surface or configuration assumed by the rocks composing our Highland area at the time when these were first crushed and folded into anticlines and synclines had already been demolished at a period inconceivably more remote than the latest grand upheaval of the Alps. Even before the commencement of Old Red Sandstone times, our Archæan, Cambrian, and Silurian rocks had been planed down for thousands of feet, so that the bottom beds of the Old Red Sandstone were deposited upon a gently undulating surface, which cuts across anticlines and synclines alike. In late Silurian and early post-Silurian times the North-west Highlands probably existed as a true mountain-chain, consisting of a series of parallel ranges formed by the folding and reduplication of the strata. The recent observations of my friends, Professor Lapworth and Messrs. Peach and Horne, in Sutherland, have brought to light the evidence of gigantic earth-movements, by which enormous masses of strata have been convoluted and pushed for miles out of place. We see in that region part of a dissected mountain-chain. The mountain-masses which are there exposed to view are the basal or lower portions of enormous sheets of disrupted rock, the upper parts of which have been removed by denudation. In a word, the mountains of Sutherland are mountains of circumdenudation--they have been carved out of elevated masses by the long-continued action of erosion. To prove this, one has only to draw an accurate section across the North-west Highlands, when it becomes apparent that the form or shape of the ground does not correspond or coincide with the convolutions of the strata, and that a thickness of thousands of feet of rock has been denuded away since those strata were folded and fractured. All over the Highlands we meet with similar evidence of enormous denudation. The great masses of granite which appear at the surface in many places are eloquent of the result produced by erosion continued for immeasurable periods of time. Every geologist knows that granite is a rock which could only have been formed and consolidated at great depths. When, therefore, such a rock occurs at the surface, it is evidence beyond all doubt of prodigious erosion. The granite has been laid bare by the removal of the thick rock-masses underneath which it cooled and consolidated. A glance at any map of Scotland will show that many river-valleys, and not a few lakes, of the Highlands have a north-east and south-west trend. This trend corresponds to what geologists call the _strike_ of the strata. The rocks of the Highlands have been compressed into a series of folds or anticlines and synclines, which have the direction just stated--namely, north-east and south-west. A careless observer might therefore rashly conclude that these surface-features resembled those of the Jura--in other words, that the long parallel hollows were synclinal troughs, and that the intervening ridges and high grounds were anticlinal arches or saddle-backs. Nothing could be further from the truth. A geological examination of the ground would show that the features in question were everywhere the result of denudation, guided by the petrological character and geological structure of the rocks. Several of the most marked hollows run along the backs of anticlinal axes, while some of the most conspicuous mountains are built up of synclinal or trough-shaped strata. Ben Lawers, and the depression occupied by Loch Tay, are excellent examples; and since that district has recently been mapped in detail by Mr. J. Grant Wilson, of the Geological Survey, I shall give a section (Fig. 10) to show the relation between the form of the ground and the geological structure of the rocks. This section speaks for itself. Here evidently is a case where "valleys have been exalted and mountains made low." A well-marked syncline, it will be observed, passes through Ben Lawers, while Loch Tay occupies a depression scooped out of an equally well-defined anticline--a structure which is just the opposite of that which we should expect to find in a true mountain-chain. It will be also noted that Glen-Lyon coincides neither with a syncline nor a fault; it has been eroded along the outcrops of the strata. Many of the north-east and south-west hollows of the Highlands indeed run along the base of what are really great escarpments--a feature which, as we have seen, is constantly met with in every region where the strata "strike" more or less steadily in one direction. In the Highlands the strata are most frequently inclined at considerable angles, so that the escarpments succeed each other more rapidly than would be the case if the strata were less steeply inclined. In no case does any north-east and south-west hollow coincide with a structural cavity. Loch Awe has been cited as an example of a superficial depression formed by the inward dip of the strata on either side. But, as was shown many years ago by my brother, A. Geikie,[E] this lake winds across the _strike_ of the strata. Moreover, if it owed its existence to a great synclinal fold, why, he asks, does it not run along the same line as far as the same structure continues? It does not do so: it is not continuous with the synclinal fold, while vertical strata appear in the middle of the lake, where, as my brother remarks, they have clearly no business to be if the sides of the lake are formed by the inward dip of the schists. [E] _Trans. Edin. Geol. Soc._ vol. ii. p. 267. The Great Glen, as I mentioned in the preceding article, coincides with a fracture or dislocation--a line of weakness along which the denuding agents had worked for many ages before the beginning of Old Red Sandstone times; and it is possible that smaller dislocations may yet be detected in other valleys. But in each and every case the valleys as we now see them are valleys of erosion; in each and every case the mountains are mountains of circumdenudation; they project as eminences because the rock-masses which formerly surrounded them have been gradually removed. We have only to protract the outcrops of the denuded strata--to restore their continuations--to form some faint idea of the enormous masses of rock which have been carried away from the surface of the Highland area since the strata were folded and fractured. All this erosion speaks to the lapse of long ages. The mountains of elevation which doubtless at one time existed within the Highland area had already, as we have seen, suffered extreme erosion before the beginning of Old Red Sandstone times, much of the area having been converted into an undulating plateau or plain, which, becoming submerged in part, was gradually overspread by the sedimentary deposits of the succeeding Old Red Sandstone period. Those sediments were doubtless derived in large measure from the denudation of the older rocks of the Highlands, and since they attain in places a thickness of 20,000 feet, and cover many square miles, they help us to realise in some measure the vast erosion the Highland area had sustained before the commencement of the Carboniferous period. Nor must we forget that the Old Red Sandstone formation which borders the Highlands has itself experienced excessive denudation: it formerly had a much greater extension, and doubtless at one time overspread large tracts of the Highlands. Again, we have to remember that during the Carboniferous and Permian periods, and the later Mesozoic and Cainozoic eras, the Highlands probably remained more or less continuously in the condition of land. Bearing this in mind, we need not be surprised that not a vestige of the primeval configuration brought about by the great earth-movements of late Silurian times has been preserved. Indeed, had the Highland area, after the disappearance of the Old Red Sandstone inland seas, remained undisturbed by any movement of elevation or depression, it must long ago have been reduced by sub-aërial erosion to the condition of a low-lying undulating plain. But elevation en masse from time to time took place, and so running water and its numerous allies have been enabled to carry on the work of denudation. Thus in the geological history of the Scottish Highlands we may trace the successive phases through which many other elevated tracts have passed. The Scandinavian plateau, and many of the mountains of middle Germany--such, for example, as the Harz, the Erzgebirge, the Thüringer-Wald, etc.--show by their structure that they have undergone similar changes. First we have an epoch of mountain-elevation, when the strata are squeezed and crushed laterally, fractured and shattered--the result being the production of a series of more or less parallel anticlines and synclines, or, in other words, a true mountain-chain. Next we have a prolonged period of erosion, during which running water flows through synclinal troughs, works along the backs of broken and shattered anticlines, and makes its way by joints, gaping cracks, and dislocations, to the low grounds. As time goes on, the varying character of the rocks and the mode of their arrangement begin to tell: the weaker structures are broken up; rock-falls and landslips ever and anon take place; anticlinal ridges are gradually demolished, while synclines tend to endure, and thus grow, as it were, into hills, by the gradual removal of the more weakly-constructed rock-masses that surround them. Valleys continue to be deepened and widened, while the intervening mountains, eaten into by the rivers and their countless feeders, and shattered and pulverised by springs and frosts, are gradually narrowed, interrupted, and reduced, until eventually what was formerly a great mountain-chain becomes converted into a low-lying undulating plain. Should the region now experience a movement of depression, and sink under the sea, new sedimentary deposits will gather over its surface to a depth, it may be, of many hundreds or even thousands of feet. Should this sunken area be once more elevated en masse--pushed up bodily until it attains a height of several thousand feet--it will form a plateau, composed of a series of horizontal strata resting on the contorted and convoluted rocks of the ancient denuded mountain-chain. The surface of the plateau will now be traversed by streams and rivers, and in course of time it must become deeply cleft and furrowed, the ground between the various valleys rising into mountain-masses. Should the land remain stationary, its former fate shall again overtake it; it will inevitably be degraded and worn down by the sub-aërial agents of erosion, until once more it assumes the character of a low-lying undulating plain. Through such phases our Highlands have certainly passed. At a very early epoch the Archæan rocks of the north-west were ridged up into great mountain-masses, but before the beginning of the pre-Cambrian period wide areas of those highly-contorted rocks had already been planed across, so that when subsidence ensued the pre-Cambrian sandstones were deposited upon a gently undulating surface of highly convoluted strata. Another great epoch of mountain-making took place after Lower Silurian times, and true mountain-ranges once more appeared in the Highland area. We cannot tell how high those mountains may have been, but they might well have rivalled the Alps. After their elevation a prolonged period of erosion ensued, and the lofty mountain-land was reduced in large measure to the condition of a plain, wide areas of which were subsequently overflowed by the inland seas of Old Red Sandstone times--so that the sediments of those seas or lakes now rest with a violent unconformity on the upturned and denuded edges of the folded and contorted Silurian strata. At a later geological period the whole Highland area was elevated _en masse_, forming an undulating plateau, traversed by countless streams and rivers, some of which flowed in hollows that had existed before the beginning of Old Red Sandstone times. Since that epoch of elevation the Highland area, although subject to occasional oscillations of level, would appear to have remained more or less continuously in the condition of dry land. The result is, that the ancient plateau of erosion has been deeply incised--the denuding agents have carved it into mountain and glen--the forms and directions of which have been determined partly by the original surface-slopes of the plateau, and partly by the petrological character of the rocks and the geological structure of the ground. [Illustration: PLATE II. INFLUENCE OF ROCK STRUCTURE ON THE FORM OF THE GROUND. FIG. 1. PLATEAU OF ACCUMULATION: HORIZONTAL STRATA, DENUDED. FIG. 2. SYNCLINAL (S.O.) AND ANTICLINAL (E.) STRATA, DENUDED. FIG. 3. FAULTED STRATA, SHOWING DENUDATION. FIG. 4. MOUNTAIN OF ACCUMULATION,--VOLCANO. FIG. 5. DIAGRAMMATIC SECTION OF A TYPICAL MOUNTAIN CHAIN, OR MOUNTAINS OF UPHEAVAL. FIG. 6. TYPES OF ROCK STRUCTURE IN THE ALPS (AFTER PROF. HEIM) _The dotted lines show portions of strata, denuded._ FIG. 7. ESCARPMENTS (e) AND DIP SLOPES (d). FIG. 8. EROSION OF ANTICLINAL MOUNTAINS. FIG. 9. PLATEAU OF EROSION, SHOWING MOUNTAINS OF CIRCUMDENUDATION (aa). FIG 10. SECTION ACROSS BEN LAWERS AND LOCH TAY, SHOWING MOUNTAINS OF CIRCUMDENUDATION. The Edinburgh Geographical Institute J. G. Bartholomew F.R.G.S. ] Thus, in the evolution of the surface-features of the earth, the working of two great classes of geological agents is conspicuous--the subterranean and the sub-aërial. The sinking down of the crust upon the cooling nucleus would appear to have given rise to the great oceanic depressions and continental ridges, just as the minor depressions within our continental areas have originated many mountain-chains. In the area undergoing depression the strata are subjected to intense lateral pressure, to which they yield along certain lines by folding up. The strata forming the Alps, which are 130 miles broad, originally occupied a width of 200 miles; and similar evidence of enormous compression is conspicuous in the structure of all mountains of elevation. Great elevation, however, may take place with little or no disturbance of stratification: wide continental areas have been slowly upheaved _en masse_, and sea-bottoms and low-lying plains have in this way been converted into lofty plateaux.[F] Many of the most conspicuous features of the earth's surface, therefore, are due directly to subterranean action. All those features, however, become modified by denudation, and eventually the primeval configuration may be entirely destroyed, and replaced by contours which bear no direct relation to the form of the original surface. (See Fig. 9.) In the newer mountain-chains of the globe the surface-features are still largely those due directly to upheaval; so in some recently elevated plateaux the ground has not yet been cut up and converted into irregular mountain-masses. Many of the more ancient mountain-chains and ranges, however, have been exposed so long to the abrading action of the denuding agents that all trace of their original contour has vanished. And in like manner plateaux of great age have been so highly denuded, so cut and carved by the tools of erosion, that their plateau character has become obscured. They have been converted into undulating mountainous and hilly regions. Everywhere throughout the world we read the same tale of subsidence and accumulation, of upheaval and denudation. The ancient sedimentary deposits which form the major portion of our land-surfaces, are the waste materials derived from the demolition of plains, plateaux, and mountains of elevation. In some mountain-regions we read the evidence of successive epochs of uplift, separated by long intervening periods of erosion, followed by depression and accumulation of newer sediments over the denuded surface. Thus the Alps began to be elevated towards the close of Palæozoic times. Erosion followed, and subsequently the land became depressed, and a vast succession of deposits accumulated over its surface during the long-continued Mesozoic era into early Cainozoic times. Again, a great upheaval ensued, and the Mesozoic and Eocene strata were violently contorted and folded along the flanks of the chain. Then succeeded another period of erosion and depression, which was again interrupted by one or more extensive upheavals. Away from those lines of weakness which we call mountain-chains, we constantly encounter evidence of widespread movements of elevation, during which broad areas of sea-bottom have been upheaved to the light of day, and, after suffering extensive denudation have subsided, to be again overspread with the spoils of adjacent lands, and then upheaved once more. And such oscillations of level have occurred again and again. Looking back through the long vista of the past, we see each continental area in a state of flux--land alternating with sea, and sea with land--mountains and plateaux appearing and disappearing--a constant succession of modifications, brought about by the antagonistic subterranean and sub-aërial agents. The hills are shadows, and they flow From form to form, and nothing stands; They melt like mists, the solid lands, Like clouds they shape themselves and go. [F] This is the generally accepted view of modern geologists. It is very difficult, however, to understand how a wide continental area can be vertically upheaved. It seems more probable that the upheaval of the land is only apparent. The land seems to rise because the sea retreats as the result of the subsidence of the crust within the great oceanic basins. See Article xiv. (1892.) IV. The Cheviot Hills.[G] [G] From _Good Words_ for 1876. I. The ridge of high ground that separates England from Scotland is not, like many other hilly districts, the beloved of tourists. No guide-book expatiates upon the attractiveness of the Cheviots; no cunningly-worded hotel-puffs lure the unwary vagrant in search of health, or sport, or the picturesque, to the quiet dells and pastoral uplands of the Borders. Since the biographer of Dandie Dinmont, of joyous memory, joined the shades, no magic sentences, either in verse or prose, have turned any appreciable portion of the annual stream of tourists in the direction of the Cheviots. The scenery is not of a nature to satisfy the desires of those who look for something piquant--something "sensational," as it were. It is therefore highly improbable that the primeval repose of these Border uplands will ever be disturbed by inroads of the "travelling public," even should some second Burns arise to render the names of hills and streams as familiar as household words. And yet those who can spare the time to make themselves well acquainted with that region should do so; they will have no reason to regret their visit, but very much the reverse. For the scenery is of a kind which grows upon one. It shows no clamant beauties--you cannot have its charms photographed--the passing stranger may see nothing in it to detain him; but only tarry for a while amongst these green uplands, and you shall find a strange attraction in their soft outlines, in their utter quiet and restfulness. For those who are wearied with the crush and din of life, I cannot think of a better retreat. One may wander at will amongst the breezy hills, and inhale the most invigorating air; springs of the coolest and clearest water abound, and there are few of the brooks in their upper reaches which will not furnish natural shower-baths. Did the reader ever indulge in such a mountain-bath? If not, then let him on a summer day seek out some rocky pool, sheltered from the sun, if possible, by birch and mountain-ash, and, creeping in below the stream where it leaps from the ledges above, allow the cool water to break upon his head, and he will confess to having discovered a new aqueous luxury. Then from the slopes and tops of the hills you have some of the finest panoramic views to be seen in this island. Nor are there wanting picturesque nooks, and striking rock scenery amongst the hills themselves: the sides of the Cheviot are seamed with some wild, rugged chasms, which are just as weird in their way as many of the rocky ravines that eat into the heart of our Highland mountains. The beauty of the lower reaches of some of the streams that issue from the Cheviots is well known; and few tourists who enter the vale of the Teviot neglect to make the acquaintance of the sylvan Jed. But other streams, such as the Bowmont, the Kale, the Oxnam, and the Rule will also well repay a visit. In addition to all these natural charms, the Cheviot district abounds in other attractions. Those who are fond of Border lore, who love to seek out the sites of old forays, and battles, and romantic incidents, will find much to engage them; for every stream, and almost every hill, is noted in tale and ballad. Or if the visitor have antiquarian tastes, he may rival old Monkbarns, and do his best to explain the history of the endless camps, ramparts, ditches, and terraces which abound everywhere, especially towards the heads of the valleys. To the geologist the district is not less interesting, as I hope to be able, in the course of these papers, to show. The geological history of the Cheviots might be shortly summed up, and given in a narrative form, but it will perhaps be more interesting, and, at the same time more instructive, if we shall, instead, go a little into detail, and show first what the nature of the evidence is, and, second, how that evidence may be pieced together so as to tell its own story. I may just premise that my descriptions refer almost exclusively to the Scottish side of the Cheviots--which is not only the most picturesque, but also the most interesting, both from an antiquarian and geological point of view. The Cheviots extend from the head of the Tyne in Northumberland, and of the Liddel in Roxburghshire, to Yeavering Bell and the heights in its neighbourhood (near Wooler), a distance of upwards of thirty miles. Some will have it that the range goes westward so as to include the heights about the source of the Teviot, but this is certainly a mistake, for after leaving Peel Fell and crossing to the heights on the other side of the Liddel Water, we enter a region which, both in its physical aspect and its geological structure, differs considerably from the hilly district that lies between Peel Fell and the high-grounds that roll down to the wide plains watered by the Glen and the Till. The highest point in the range is that which gives its name to the hills--namely, the Cheviot--a massive broad-topped hill, which reaches an elevation of 2767 feet above the sea, and from which a wonderful panorama can be scanned on a clear day. The top of the hill is coated with peat, fifteen to twenty feet thick, in some places. A number of deep ravines trench its slopes, the most noted of which are Hen Hole and the Bizzle. Peel Fell, at the other extremity of the range, is only 1964 feet high, while the dominant points between Peel Fell and the Cheviot are still lower--ranging from 1500 feet to 1800 feet. The general character of the hills is that of smooth rounded masses, with long flowing outlines. There are no peaks, nor serrated ridges, such as are occasionally met with in the northern Highlands; and the valleys as a rule show no precipitous crags and rocky precipices, the most conspicuous exceptions being the deep clefts mentioned as occurring in the Cheviot. The hills fall away with a long gentle slope into England, while on the Scottish side the descent is somewhat abrupt; so that upon the whole the northern or Scottish portion of the Cheviots has more of the picturesque to commend it than the corresponding districts in England. Indeed, the opposite slopes of the range show some rather striking contrasts. The long, flat-topped elevations on the English side, that sweep south and south-west from Carter Fell and Harden Edge, and which are drained by the Tyne, the Rede Water, and the Coquet, are covered for the most part with peat. Sometimes, however, when the slope is too great to admit of its growth, the peat gives place to rough scanty grass and scrubby heath, which barely suffice to hide the underlying barren sandstone rocks. One coming from the Scottish side is hardly prepared, indeed, for the dreary aspect of this region as viewed from the dominant ridge of the Cheviots. If in their physical aspect the English slopes of these hills are for the most part less attractive than the Scottish, it is true also that they offer less variety of interest to the geologist. Those who have journeyed in stagecoaching times from England into Scotland by Carter Fell, will remember the relief they felt when, having surmounted the hill above Whitelee, and escaped from the dreary barrens of the English border, they suddenly caught a sight of the green slopes of the Scottish hills, and the well-wooded vales of Edgerston Burn and Jed Water. On a clear day the view from this point is very charming. Away to the west stretch in seemingly endless undulations the swelling hills that circle round the upper reaches of Teviotdale. To east and north-east the eye glances along the bright-green Cheviots of the Scottish border, and marks how they plunge, for the most part somewhat suddenly, into the low grounds, save here and there, where they sink in gentler slopes, or throw out a few scattered outposts--abrupt verdant hills that somehow look as if they had broken away from the main mass of the range. From the same standpoint one traces the valleys of the Rule and the Jed--sweetest of border streams--stretching north into the well-clothed vale of the Teviot. Indeed, nearly the whole of that highly-cultivated and often richly-wooded country that extends from the base of the Cheviots to the foot of the Lammermuirs, lies stretched before one. Here and there abrupt isolated hills rise up amid the undulating low grounds, to hide the country behind them. Of these the most picturesque are dark Rubers Law, overlooking the Rule Water; Minto Crags, and Penielheugh with its ugly excrescence of a monument, both on the north side of the Teviot; and the Eildon Hills, which, as all the world knows, are near Melrose. After he has sated himself with the rare beauty of this landscape (and still finer panoramic views are to be had from the top of Blackhall Hill, Hownam Law, the Cheviot, as also from various points on the line of the Roman Road and other paths across the hills into England), the observer will hardly fail to be struck by the great variety of outlines exhibited. Some of the hills, especially those to the west and north-west, are grouped in heavy masses, and present for the most part a soft, rounded contour, the hills being broad atop and flowing into each other with long, smooth slopes. Other elevations, such as those to the east and north-east of Carter Fell, while showing similar long gentle slopes, yet are somewhat more irregular in form and broken in outline, the hills having frequently a lumpy contour. Very noteworthy objects in the landscape also are the little isolated hills of the low grounds, such as Rubers Law, and the Dunian, above Jedburgh. They rise, as I have said, quite suddenly out of that low gently undulating country that sinks softly into the vales of the Teviot and the Tweed. This variety arises from the geological structure of the district. The hills vary in outline partly because they are made up of different kinds of rock, and partly owing to the mode in which these rocks have been arranged. But notwithstanding all this variety of outline, one may notice a certain sameness too. Flowing outlines are more or less conspicuous all over the landscape. Many of the hills, especially as we descend into Teviotdale, seem to have been smoothed or rounded off, as it were, so as to present their steepest faces as a rule towards the south-west. And if we take the compass-bearing of the hill-ridges of the same district, we shall find that these generally trend from south-west to north-east So much, then, at present for the surface configuration of the Cheviot region. When we come to treat of the various rock-masses, and to describe the superficial accumulations underneath which these are often concealed, we shall be in a better position to give an intelligible account of the peculiar form of the ground, and the causes to which that configuration must be ascribed. The solid rocks which enter into the composition of the Cheviots consist mainly of (1) hard grey and blue rocks, called _greywacké_ by geologists, with which are associated blue and grey shale; (2) various old igneous rocks; and (3) sandstones, red and white, interbedded with which occur occasional dark shales. Now, before we can make any endeavour towards reconstructing in outline the physical geography of the Cheviot Hills during past ages, it is necessary that we should discover the order in which the rock-masses just referred to have been amassed. I shall first describe, therefore, some sections where the members of the different series are found in juxtaposition, for the purpose of pointing out which is the lowest-lying, and consequently the oldest, and which occupy the uppermost and intermediate positions. [Illustration: FIG 1.--Conglomerate and Red Sandstone, etc., _c_, resting on Greywacké and Shale, _g_.] The first section to which reference may be made is exposed in the course of the River Jed, at Allars Mill, a little above Jedburgh. This section is famous in its way as having been described and figured by Dr. Hutton, who may be said to have founded the present system of physical geology. In the bed of the stream are seen certain confused ridges of a greyish blue rock running right across the river course--that is, in a direction a little north of east and south of west. These ridges are the exposed edges of beds of greywacké and shale, which are here standing on end. The beds are somewhat irregular, being inclined from the vertical, now in one direction and now in another, or, as a geologist would say, the "dip" changes rapidly, sometimes being up the valley and sometimes down. The same beds continue up the steep bank of the river for a yard or two, and are there capped by another set of rocks altogether, namely, by soft red sandy beds which at the bottom become _conglomeratic_--that is to say, they are charged with water-worn stones. The annexed diagram (Fig. 1) will show the general appearances presented: _g_ represents the vertical greywacké and shale, and _c_ the overlying deposits of conglomerate and red sandy beds. Now let us see what this section means. What, in the first place, is greywacké? The term itself has really no meaning, being a name given by the miners in the Harz Mountains to the unproductive rocks associated with the vein-stones which they work. When we break the rock we may observe that it is a granular mixture of small particles of quartz, to which sometimes felspar and other minerals are added. The grains are bound together in a hardened matrix of argillaceous or clayey and silicious matter, blue, or grey, or green, or brown and yellow, as the case may be. At Allars Mill, and generally throughout the Cheviot district, the prevailing colour is a pale greyish blue or bluish grey; but shades of green and brown often occur. The component particles of the rock are usually rounded or water-worn. Again, we notice that the ridges and bands of rock that traverse the course of the Jed at Allars Mill are merely the outcrops of successive _strata_ or beds. It is clear then that greywacké and the grey shales that accompany it are _aqueous_ rocks--that is to say, they consist of hardened sediment, which has undoubtedly been deposited in successive layers of variable thickness by water in motion. But since the sediments of rivers and currents are laid down in approximately horizontal planes, it is evident that if the greywacké and shale be sedimentary deposits they have suffered considerable disturbance since the time of their formation; for, as we have seen, the beds, instead of being horizontal or only gently inclined, actually approach the vertical. The fact is, that the outcrops which we see are only the truncated portions of what were formerly rapid undulations or folds of the strata, the tops of the folds or arches having been cut away by geological agencies, to which I shall refer by-and-by. What were at one time horizontal strata have been crumpled up into great folds, the folds being squeezed tightly together, and their upper portions planed away before the overlying red sandy beds were laid down. The accompanying diagram (Fig. 2) may serve to make all this clearer. Let A A represent the present surface of the ground, and B B a depth of say fifty feet or a hundred feet from the surface. The continuous lines between A and B represent the greywacké beds as we now see them in section; the dotted lines above A A indicate the former extension of the strata, and the dotted lines below B B their continuation below that datum line. Hence it is obvious that in a succession of vertical or highly inclined beds, we may have the same strata repeated many times, the same beds coming again and again to the surface. Thus the stratum at S is evidently the same bed as that at W, X, Y, and Z. [Illustration: Fig 2.] Such great foldings or redoublings of strata are most probably originated during subsidence of a portion of the earth's crust. While the ground is slowly sinking down, the strata underneath are perforce compelled to occupy less space laterally, and this they can only do by yielding amongst themselves. All folding or contortion on the large scale--that, namely, which has affected areas of strata extending over whole countries--seems to have taken place under great pressure; in other words, to have been produced at considerable depths from the earth's surface. We can conceive, therefore, of a wide tract of land sinking down for hundreds of feet, and producing at the surface comparatively little change. But a depression of a few hundred feet at the surface implies a considerably greater depression at a depth of several thousand feet from the surface, and it is at great depths, therefore, that the most violent folding must take place. Consequently considerable contortion, and much folding, and lateral crushing and reduplication of strata may occur, and yet no trace of this be observable at the surface, save only a gentle depression. For example, in Greenland, a movement of subsidence has been going on for many years--the land has been slowly sinking down. The rocks at the surface are of course quite undisturbed by this widely-extended movement, but the strata at great depths may be undergoing much compression and contortion. It follows from such considerations, that if we now get highly contorted strata covering wide areas at the surface, we suspect that very considerable _denudation_ has taken place. That is to say, large masses of rock have been removed by the geological agents of change, so as to expose the once deeply-buried tops of the arched or curved and folded strata. We may therefore infer from a study of the phenomena in the Jed at Allars Mill, first, that the red sandy beds are younger than the greywacké and shale, seeing that they rest upon them; and, second, that a very long period of time must have elapsed between the deposition of the older and the accumulation of the younger set of strata; for it is obvious that considerable time was required for the consolidation and folding of the greywacké, and an incalculable lapse of ages was also necessary to allow of the gradual wearing away by rain, frost, and running water of the great thickness of rocks underneath which the greywacké was crumpled. And all this took place before the horizontally-bedded red sandstone and conglomerate gathered over the upturned ends of the underlying strata. The succession of rocks at Allars Mill is seen in many other places in the Cheviot district, but enough has been said to prove that the greywacké beds are the older of the two sets of strata. There is another class of rocks, the relative position of which we must now ascertain, for no one shall wander much or far among the Cheviots without becoming aware of the existence of other kinds of rock than greywacké and sandstone. Many of the hills east of Oxnam and Jed Waters, for example, are composed of igneous masses--of rocks which have had a volcanic origin. As we shall afterwards see, the whole north-eastern section of the Cheviots is built up of such rocks. At present, however, we are only concerned with the relation which these bear to the greywacké and the red sandy beds. Now at various localities--for example, in Edgerston Burn, on the hill-face south of Plenderleith, and again along the steep front of Hindhope and Blackball Hills, which are on the crest of the Cheviots--we find that the igneous rocks rest upon the greywacké and shale (see Fig. 3) precisely in the same way as do the red sandy beds. They therefore belong to a later date than the greywacké. In other places, again, we meet with the conglomerates and red sandstones (_c_, Fig. 4) resting upon and wrapping round the igneous rocks, _i_, and thus it becomes quite obvious that the latter occupy an intermediate position between the greywacké and shale on the one hand, and the conglomerate and red sandstone upon the other. [Illustration: Fig. 3.--Igneous rocks (_i_, _a_) resting on Greywacké and Shale, _g_.] [Illustration: Fig. 4.--_c_, Conglomerate and Sandstones, resting on Igneous rocks, _i_.] We have now cleared the way so far, preparatory to an attempt to trace the geological history of the Cheviots. The three sets of rocks, whose mutual relations we have been studying, are those of which the district is chiefly composed; but, as we shall see in the sequel, there are others, not certainly of much extent, but nevertheless having an interesting story to tell us. Nor shall we omit to notice the superficial accumulations of clay, gravel, sand, silt, alluvium, and peat; monuments as they are of certain great changes, climatic and geographical, which have characterised not the Cheviots only, but a much wider area. II. If we draw a somewhat straight line from Girvan, on the coast of Ayrshire, in a north-east direction to the shores of the North Sea, near Dunbar, we shall find that south of that line, up to the English border, nearly the whole country is composed of various kinds of greywacké and shale like the basement beds of the Cheviot district. Here and there, however, especially in certain of the valleys and some of the low-lying portions of this southern section of Scotland, one comes upon small isolated patches and occasional wider areas of younger strata, which rest upon and conceal the greywackés and shales. Such is the case in Teviotdale, the Cheviot district, and the country watered by the lower reaches of the Tweed, in which regions the bottom beds are hidden for several hundreds of square miles underneath younger rocks. Indeed, the greywacké and shale form but a very small portion of the surface in the Cheviots, appearing upon a coloured geological map like so many islands or fragments, as it were, which have somehow been detached from the main masses of greywacké of which the Lammermuirs and the uplands of Dumfries and Selkirk shires are composed. Although the bottom rocks of the Cheviot Hills are thus apparently separated from the great greywacké area, there can be no doubt that they are really connected with it, the connection being obscured by the overlying younger strata. For if we could only strip off these latter, if we could only lift aside the great masses of igneous rock and sandstone that are piled up in the Cheviot Hills and the adjoining districts, we should find that the bottom upon which these rest is everywhere greywacké and shale. In part proof of this it may be mentioned that at various places in those districts which are entirely occupied by sandstone and igneous rock, the streams have cut right down through the younger rocks so as to expose the bottom beds, as in Jed Water at Allars Mill. Again, when we trace out the boundaries of any detached areas of greywacké we invariably find these bottom beds disappearing on all sides underneath the younger strata by which they are surrounded. One such isolated area occurs in the basin of the Oxnam Water, between Littletonleys and Bloodylaws, a section across which would exhibit the general appearance shown in the accompanying diagram (Fig. 5). Another similarly isolated patch is intersected by Edgerston Burn and the Jed Water between Paton Haugh and Dovesford. But the largest of these detached portions appears, forming the crest of the Cheviots, at the head of the River Coquet. There the basement beds occupy the watershed, extending westward, some three or four miles, as far as the sandstones of Hungry Law, while to the north and east they plunge under the igneous rocks of Brownhart Law and the Hindhope Hills. Now it is evident that all those detached and isolated areas of greywacké and shale are really connected underground, and not only so, but they also piece on in the same way to the great belt of similar strata that stretches from sea to sea across the whole breadth of Scotland. Indeed, we may observe in the Cheviot district how long and massive promontories of greywacké jut out from that great belt, and extend often for miles into the areas that are covered with younger strata, as, for example, in the Brockilaw and Wolfelee Hills. A generalised section across the greywacké regions of the Cheviot Hills would therefore present the appearances shown in the annexed diagram (Fig. 6), in which G represents the basement beds, I the igneous rocks, and C the red sandstones, etc. [Illustration: Fig. 5.--Section across Greywacké area of Oxnam Water; G, Greywacké and Shale; C, Sandstone, etc.] [Illustration: Fig. 6.--Diagram section across Greywacké districts of Cheviot Hills.] Throughout the whole of the district under review the bottom beds are observed to dip at a high angle--the strata in many places being actually vertical--and the edges or crops of the strata run somewhat persistently in one direction, namely, from south by west to north by east; or, as a geologist would express it, the beds have an approximately south-west and north-east "strike." Now as the dip is sometimes to north-west and sometimes to south-east, it is evident that the rocks have been folded up in a series of rapid convolutions, and that some of the beds must be often repeated. From the character of the fossils which the bottom beds have yielded we learn that the strata belong to that division of past time which is known as the Silurian age. These fossils appear to be of infrequent occurrence, and the creatures of which they are the relics occupied rather a humble place in the scale of being. They are called _graptolites_ (from their resemblance to pens), an extinct group of hydroid zoophytes, apparently resembling the sertularians of our own seas. The general appearance of the Silurian strata of the Cheviots is indicative of deposition in comparatively quiet water, but how deep that water was one cannot say. Upon the whole, the beds look not unlike the sediments that gather in calm reaches of the sea, such as estuaries, betokening the presence of some not distant land from which fine mud and sand were washed down. Another proof that some of the strata at all events were accumulated not far from a shore-line, is found in certain coarse bands of grit and pebbles, which are not likely to have been formed in deep water. This evidence, however, cannot be considered decisive, and in the present state of our knowledge all that we can assert with anything like confidence is simply this:--That during the deposition of the Silurian strata the whole of the Cheviot area lay under water--existed, in short, as a muddy sea-bottom, in the slime of which flourished here and there, in favourable spots, those minute hydroid animals called _graptolites_. Between the deposition of the Silurian and the formation of the rocks that come next in order a long interval elapsed, during which the mud, sand, and grit that gathered on the floor of the ancient sea were hardened into solid masses, and eventually squeezed together into great folds and undulations. It has already been pointed out that these changes could hardly have been effected save under extreme pressure, and this consideration leads us to infer that a great thickness of strata has been removed entirely from the Cheviot district, so as to leave no trace of its former existence. Long before the deposition of the younger strata that now rest upon and conceal the Silurian rocks, the action of the denuding forces--the sea, frosts, rain, and rivers--had succeeded in not only sweeping gradually away the strata underneath which the bottom beds were folded, but in deeply scarping and carving these bottom beds themselves. Can we form any reasonable conjecture as to the geological age of the strata underneath which the bottom beds of the Cheviots were folded, and which, as we have seen, had entirely disappeared before the younger rocks of the district were accumulated? Well, it is obvious that the missing strata must have been of later formation than the bottom beds, and it is equally evident that they must have been of much more ancient date than the igneous rocks of the Cheviot Hills. Now, as we shall afterwards see, these igneous rocks belong to the Old Red Sandstone age, that is to say, to the age that succeeded the Silurian. How is it then, if the bottom beds be really of Silurian and the igneous rocks of Old Red Sandstone age, that a gap is said to exist between them? The explanation of this apparent contradiction is not far to seek. When we compare the fossils that occur in the Silurian strata of the Cheviot Hills and the districts to the west, with the organic remains disinterred from similar strata elsewhere, as in Wales for example, we find that the bottom beds of the Cheviots were in all probability accumulated at approximately the same time as certain strata that occur in the middle division of the Upper Silurian. In Wales and in Cumberland the strata that approximate in age to the Silurian of the Cheviots are covered by younger strata belonging to the same formation which reach a thickness of several thousand feet. It may quite well be, therefore, that the succession of Silurian strata in the Cheviots was at one time more complete than it is now. The upper portions of the formation which are so well developed in Wales and Cumberland, and which are likewise represented to a small extent in Scotland, had in all probability their equivalents in what are our border districts. In other words, there are good grounds for believing that the existing Silurian rocks of the Cheviots were in times preceding the Old Red Sandstone age covered with younger strata belonging to the same great system. The missing Silurian strata of the Cheviots may have attained a thickness of several thousand feet, and underneath such a mass of solid rock the lower-lying strata might well have been consolidated and subsequently squeezed into folds. We now pass on to consider the next chapter in the geological history of the Cheviot Hills. As we proceed in our investigations it will be noticed that the evidence becomes more abundant, and we are thus enabled to build up the story of the past with more confidence, and with fuller details. For it is with geological history as with human records--the further back we go in time the scantier do the facts become. The rocks upon which Nature writes her own history are palimpsests, on which the later writing is ever the most easily deciphered. Nay, she cannot compile her newer records without first destroying some of those compiled in earlier times. The sediments accumulating in modern lake and sea are but the materials derived from the degradation of the rocks we see around us, just as these in like manner have originated from the demolition of yet older strata. Thus the further we trace back the history of our earth, the more fragmentary must we expect the evidence to be; and conversely, the nearer we approach to the present condition of things the more abundant and satisfactory must the records become. Accordingly, we find that the igneous rocks of the Cheviot Hills tell us considerably more than the ancient Silurian deposits upon which they rest. The surface of the latter appears to be somewhat irregular underneath the igneous rocks, showing that hills and valleys, or an undulating table-land, existed in the Cheviot district prior to the appearance of the younger formation. But before we attempt to summarise the history of that formation, it is necessary to give some description, however short, of the rocks that compose it. These consist chiefly of numerous varieties of a rock called porphyrite by geologists, piled in more or less irregular beds, one on top of another, in a somewhat confused manner. The colour of the freshly fractured rocks is very variable, being usually some shade of blue or purple; but pink, red, brown, greenish, and dark grey or almost black varieties also occur. Some of the rocks are finely crystalline; others, again, are much coarser, while many are compact, or nearly so, a lens being required to detect a crystalline texture. The mineral called felspar is usually scattered more or less abundantly through the matrix or base, which itself is composed principally of felspathic materials. Besides distinct scattered crystals of felspar, other minerals often occur in a similar manner; mica and hornblende being the commonest. Occasionally the rocks contain numerous circular, oval, or flattened cavities, which are sometimes so abundant as to give the appearance of a kind of coarse slag to the porphyrite. These little cavities, however, are usually filled up with mineral matter--such as calcspar, calcedony, jasper, quartz, etc. Sometimes also cracks, crannies, and crevices of some size have been sealed up with similar minerals. Now nearly all these appearances are specially characteristic of rocks which have at one time been in a state of igneous fusion; nor can there be any doubt that the Cheviot porphyrites are merely solidified lava-beds, which have been poured out from the bowels of the earth. In modern lavas we may notice not only a crystalline texture, but frequently also we observe those in our porphyrites. Such cavities are due to the expansive force of the vapours imprisoned in the molten mass at the time of eruption. They form chiefly towards the upper surface of a lava stream, and are often drawn out or flattened in the direction in which the lava flows. Thus a stream of lava, as it creeps on its way, becomes slaggy and scoriaceous or cindery above and in front, and as the molten mass within continues to flow, the slags and cinders that cover its face tumble down before it, and form the pavement upon which the stream advances. In this way slags and cinders become incorporated with the bottom of the lava, and hence it is that so many volcanic rocks are scoriaceous, as well below as above. The vapours which produce the cavities usually contain minerals in solution, and these, as the lava cools, are frequently deposited, partially filling up the vesicles, so as to form what are called geodes. But many of the cavities have been filled in another way--by the subsequent infiltration of water carrying mineral matter in solution. And since we know that all rocks are so permeated by water, it is clear that the cavities may have received their contents during many successive periods, after the solidification of the rock in which they occur. It is in this manner that the jaspers, calcedony, and beautiful agates of commerce have been formed. Rocks abundantly charged with cavities are said to be _vesicular_, and when the vesicles are filled with mineral matter, then the mass becomes, in geological language, _amygdaloidal_, from the almond-like shape assumed by the flattened vesicles. Now all the appearances described above, and many others hardly less characteristic of true lavas, are to be met with amongst those porphyrites which, as I have said, form the major portion of the Cheviot Hills. From the valley of the Oxnam, east by Cessford, Morebattle, and Hoselaw, and south by Edgerston, Letham, Browndeanlaws, and Hindhope, the porphyrites extend over the whole area, sweeping north-east across the border on to the heights above the Rivers Glen and Till. In the hills at Hindhope we notice a good display of the oldest beds of the series. At the base occurs a very peculiar rock resting upon the Silurian, and thus forming the foundation of the porphyrites. It varies in colour, being pink, grey, green, red, brown, or variously mottled. Sometimes it is fine-grained and gritty, like a soft, coarse-grained sandstone; at other times it is not unlike a granular porphyrite; but when most typically developed it consists of a kind of coarse angular gravel embedded in a gritty matrix. The stones sometimes show distinct traces of arrangement into layers; but they are often heaped rudely together with little or no stratification at all. They consist chiefly of fragments of porphyrites; but bits of Silurian rocks also occur amongst them. This peculiar deposit unquestionably answers to the heaps of dust, sand, stones, and bombs which are shot out of modern volcanoes; it is a true tuff--that is, a collection of loose volcanic ejectamenta. Upon what kind of surface did it fall? Long before the eruptions began, the Silurian rocks had been sculptured into hills and valleys by the action chiefly of the sub-aërial forces, and it was upon these hills and in these valleys that the igneous materials accumulated. It is difficult to say, however, whether at this period the Cheviot district was above or under water. The traces of bedding in the tuff would seem to indicate the assorting power of water; but the evidence is too slight to found upon, because we know that in modern eruptions, loose ejectamenta frequently assume a kind of irregular bedded arrangement. For aught we can say to the contrary, therefore, dry land may have extended across what is now southern Scotland and northern England when the first rumblings of volcanic disturbance shook the Cheviot area. Be that as it may, we know that the volcanic outbursts began in those old times, as they almost invariably commence now, by a discharge of sand, small stones, blocks, and cinders. These, we may infer, covered a wide area round the centre of dispersion--the chief focus of eruption being probably in the vicinity of the big Cheviot, where a mass of granite seems to occupy the core or deep-seated portion of the old volcanic centre. The locality where the tuff occurs is some nine miles or so distant from this point, and the intervening ground could hardly have escaped being more or less thickly sprinkled with the same materials. The whole of that intervening ground, however, now lies deeply buried under the massive streams of once-molten rock that followed in succession after the first dispersion of stones and débris. Although, as I have said, it may be doubted whether at the beginning of their activity the Cheviot volcanoes were sub-aqueous, yet there are not a few facts that lead to the inference that the eruption of the porphyrites took place for the most part, if not exclusively, under water. The beds are occasionally separated by layers of sandstone, grit, and conglomerate; but such beds are rare, and true tuffs are rarer still. If the outbursts had been sub-aërial, we ought surely to have met with these latter in greater abundance, while we should hardly have expected to find such evidently water-arranged strata as do occur here and there. The porphyrites themselves present certain appearances which lead to the same conclusion. Thus we may observe how the bottoms of the beds frequently contain baked or hardened sand and mud, showing that the molten rock had been poured out over some muddy or sandy bottom, and had caught up and enclosed the soft, sedimentary materials, which now bear all the marks of having been subjected to the action of intense heat. Sometimes, indeed, the old lava-streams seem to have licked up beds of unconsolidated gravel, the water-worn stones being now scattered through their under portions. As no fossils occur in any of the beds associated with the porphyrites, one cannot say whether the latter flowed into the sea or into great freshwater lakes. Neither can we be certain that towards their close the eruptions were not sub-aërial. They may quite well have been so. The porphyrites attain a thickness of probably not less than fifteen hundred or two thousand feet, and the beds which we now see are only the basal, and therefore the older portions of the old volcanoes. The upper parts have long since disappeared, the waste of the igneous masses having been so great that only the very oldest portions now remain, and these, again, are hewn and carved into hill and valley. Any loose accumulation of stones and débris, therefore, which may have been thrown out in the later stages of the eruptions, must long ere this have utterly disappeared. We can point to the beds which mark the beginning of volcanic activity in the Cheviots; we can prove that volcanoes continued in action there for long ages, great streams of lava being poured out--the eruptions of which were preceded and sometimes succeeded by showers of stones and débris; we can show, also, that periods of quiescence, more or less prolonged, occasionally intervened, at which times water assorted the sand and mud, and rounded the stones, spreading them out in layers. But whether this water action took place in the sea or in a lake we cannot tell. Indeed, for aught one can say, some of the masses of rounded stones I refer to may point to the action of mountain torrents, and thus be part evidence that the volcanoes were sub-aërial. If we are thus in doubt as to some of the physical conditions that obtained in the Cheviot district during the accumulation of the porphyrites and their associated beds, we are left entirely to conjecture when we seek to inquire into the conditions that prevailed towards the close of the volcanic period. For just as we have proof that before this period began the Silurian strata had been subjected to the most intense denudation--had, in short, been worn into hill and valley--so do we learn from abundant evidence that the rocks representing the old volcanoes of the Cheviots are merely the wrecks of formerly extensive masses. Not only have the upper portions of these volcanoes been swept away, but their lower portions, likewise, have been deeply incised, and thousands of feet of solid rock have been carried off by the denuding forces. And by much the greater part of all this waste took place before the accumulation of those sandstones which now rest upon the worn outskirts of the old volcanic region. III. Some reference has already been made (see p. 64) to the general appearance presented by the valleys of the Cheviots. In their upper reaches they are often rough and craggy; narrow dells, in fact, flanked with steep shingle-covered slopes, and occasionally overlooked by beetling cliffs, or fringed with lofty scaurs of decomposing rocks. As we follow down the valleys they gradually widen out; the hill-slopes becoming less steep, and retiring from the stream so as to leave a narrow strip of meadow-land through which the clear waters canter gaily on to the low grounds of the Teviot. In their middle reaches these upland dales are not infrequently well cultivated to a considerable height, as in the districts between Hownam and Morebattle, and between Belford and Yetholm--the former in the valley of the Kale, and the latter in that of the Bowmont. It is noticeable that all the narrower and steeper reaches lie among Silurian strata and Old Red Sandstone porphyrites. No sooner do we leave the regions occupied by these tough and hard rock-masses than the whole aspect of the scenery changes. The surrounding hills immediately lose in height and fall away into a softly undulating country, through which the streams and rivers have dug for themselves deep romantic channels. Nevertheless, it is a fact, as we shall see by-and-by, that south-west of the region occupied by the igneous rocks of the Cheviot Hills, all the higher portions of the range (Hungry Law, Carter Fell, Peel Fell, etc.) are built up of sandstones. For the present, however, I confine attention to those valleys whose upper reaches lie either wholly or in part among igneous rocks or Silurian strata. A typical and certainly the most beautiful example is furnished us by the vale of the River Jed. This stream rises among the sandstone heights which have just been mentioned as composing the south-west portion of the Cheviot range. The first seven or eight miles of its course lead us through a broad open valley, which has been hollowed out almost exclusively in sandstones and shales; by-and-by, however, we are led into a Silurian tract, and thereupon the valley contracts and the hill-slopes descend more steeply to the stream. But we soon leave the grassy glades of this Silurian tract and enter all at once upon what may be termed the lower reaches of the Jed. No longer cooped up in the rocky gully, painfully worn for itself in the hard greywacké and shales, the stream now winds through a much deeper and broader channel which has evidently been excavated with greater ease. Precipitous banks and scaurs here overlook the river at every bend, the banks becoming higher and higher and retiring further and further from each other, as the water glides on its way, until at last they fairly open upon the broad vale of the Teviot. Sometimes the river flows along one side of its valley for a considerable distance, and whenever this is the case, it gives us a line of bold cliffs which are usually flanked on the opposite side by sloping ground. This is the general character of all valleys of erosion, and especially of the lower reaches of the Jed. A glance at the cliffs and scaurs of the Jed shows that they consist of horizontal or gently undulating strata of soft earthy, friable, shaly sandstone, arranged in thin beds and bands, which alternate rapidly with crumbling, sandy, and earthy shales; the whole forming a loose and unconsolidated mass that readily becomes a prey to the action of the weather, rain, frost, and running water. The prevailing colour is a dull red, but pale yellow, white, green, and purple discolorations are visible when the strata are closely scanned. The finest sections occur between Glen Douglas and Inchbonnie, and at Mossburnford, but the cliffs throughout present the same general appearance, and are picturesque in the highest degree. Everywhere the banks are thickly wooded, and even the steep red scaurs are dashed and flecked with greenery, which droops and springs from every ledge and crevice in which a root can fix itself. How vivid and striking is the contrast between the fresh delicate green of early summer and the rich warm tint of these rocks, which when lit up by the setting sun seem almost to glow and burn! Well may the good folk of Jedburgh be proud of the lovely valley in which their lot is cast. In no similar district in Scotland will the artist meet with a greater number of such "delicious bits," in which all the charms of wood and water, of meadow and rock are so harmoniously combined. It is not with the scenic beauties of the Jed, however, that we have at present to do. I wish the reader to examine with me certain appearances visible at the base of the red beds, where these rest upon those older rocks which have formed the subject of the preceding papers. In the bed of the river at Jedburgh, we see the junction between the red beds and the Silurian strata, and may observe how the bottom portions of the former, which repose immediately upon the greywackés, are abundantly charged with well-rounded and water-worn stones. Many of these stones consist of greywacké, hardened grit, and other kinds of rock, and most of them undoubtedly have been derived from Silurian strata. In other districts where the old igneous rocks of the Cheviots form the pavement upon which the red beds repose, the stones in the lower portions of the latter are made up chiefly of rounded fragments of the underlying porphyrites. All which clearly shows that the red beds have been built out of the ruins of the older strata of the district. This is unquestionably the origin not only of the conglomerates, but of all the red beds through which the River Jed cuts its way from the base of the hills to the Teviot. When we trace out the boundary of these beds, we find that this leads us along the base of the hills, close to the hill-foot; and not only so, but it frequently takes us into the hill-valleys also. And this shows that the Cheviots had already been deeply excavated by streams before any portion of the red beds was deposited. I have said that the red beds are approximately horizontal; sometimes, however, they have a decided _dip_ or inclination, and when this is continuous, it is invariably in a direction away from the hills. Thus as we traverse the ground from the hill-foot to the Teviot, we pass over the outcrops of the red beds and slowly rise from a lower to a higher geological position. The strata, however, are generally so flat that their dip is often not greater than the average slope or inclination of the ground. Hence when we ascend the valley-slopes from the stream, we soon reach the higher beds of the series, as, for example, in the undulating heights that overlook the Jed in the neighbourhood of Jedburgh. In that district a number of quarries have been opened, in which the upper beds of the red series are well exposed, as at Ferniehirst, Tudhope, etc. These consist of thick beds of greyish white, yellowish, and reddish sandstones, which, unlike the crumbling earthy deposits below, are quite suitable for building purposes. Scales of fish and plant remains are often met with in the thick sandstones, but the underlying earthy, friable red beds appear to be quite destitute of any organic remains. Let us now briefly recapitulate the main facts we have just ascertained. They are these:--1. All the low grounds that abut upon the hills are composed of horizontal or nearly horizontal strata, which consist chiefly of red earthy beds, passing down into conglomerates, and up into whitish and reddish sandstones. 2. The conglomeratic portion forms the boundary of the series, fringing the outskirts of the hills, and resting sometimes upon Silurian strata and sometimes upon Old Red Sandstone igneous rocks. 3. Fossils occur in the white and red sandstones, but seem to be wanting in the underlying red earthy beds. [Illustration: Fig. 7.--S, Silurian strata; _i_, Old Red Sandstone Igneous Rocks; _a^1_, Conglomerate; _a^2_, Red earthy beds; _a^3_, White and Red Sandstones.] The accompanying diagram (Fig. 7) gives a generalised view of the relation borne by the red beds to the older rocks of the Cheviots. It will be seen that the former rest _unconformably_ upon the Old Red Sandstone igneous rocks, and also, of course, upon the Silurian strata. The section shows that the red beds lie upon a worn and denuded surface. Now this speaks to the lapse of a long period of time. It may be remembered that we had some grounds for believing that the latest eruptions of the Cheviot volcanoes were sub-aërial. The evidence now enables us to advance further, and to state that after the close of the volcanic period, the whole Cheviot district existed as an elevated tract of dry land, from which streams flowed north and south. And for so long a time did these conditions endure, that the rivulets and streams were enabled to scoop out many channels and broad valleys before any of the outlying red beds had come into existence. Before the conglomerate beds were laid down, the ancient volcanic bank of the Cheviots had thus suffered great erosion. This is what "unconformability" means. It points to the prolonged continuance of a land-surface, subject as that must always be to the wearing action of the sub-aërial forces. Rain and frost disintegrate the rocks, and running water rolls the débris from higher to lower levels, and piles it up in the form of gravel, sand, and mud in lakes and the sea. While the old volcanic country of the Cheviots was being thus denuded, it would appear that a wide extent of land existed in the Northern Highlands and Southern Uplands of Scotland, and also in what are now the lake districts of England and the hilly tracts of Wales. And in all these regions valleys were formed, which at a subsequent time were more or less filled up with newer deposits. The presence of the red beds that sweep round the base of the Cheviot Hills shows unmistakably that a period of submergence followed these land conditions. All the low grounds of Southern Scotland disappeared beneath a wide sheet of water, which stretched from the foot of the Lammermuirs up to the base of the Cheviots, and here and there entered the valleys, and so extended into the hills. This water, however, does not seem to have been that of an open sea; rather was it portion of a great freshwater lake, brackish lagoon, or inland sea. The lowest beds of the red series are merely hardened layers and masses of gravel and rolled shingle, which would seem at first sight to indicate the former action of waves along a sea-beach. There are certain appearances, however, which lead one to suspect that these ancient shingle beds may have had quite another origin. In some places the stones exactly resemble those which are found so abundantly in glacial deposits. They are sub-angular and blunted, and, like glaciated stones, occasionally show striæ or scratches. This, however, is very rarely the case. Most of the stones appear subsequently to have been rolled about in water, and in this process they must have lost any ice-markings they may have had, and become smoothed and rounded like ordinary gravel stones. The same appearances may be noted in the glacier valleys of Norway and Switzerland, where at the present day the glaciated stones which are pushed out at the lower ends of the glaciers are rolled about in the streams, and soon lose all trace of ice-work. It is impossible, however, to enter here into all the details of the evidence which lead one to suspect that glaciers may have existed at this early period among the Cheviot and Lammermuir Hills. In the latter district, the conglomerates occur in such masses and so exactly resemble the morainic débris and ice-rubbish of modern glacial regions, that the late Sir A. C. Ramsay long ago suggested their ice-origin. Let us conceive, then, that when the ancient lake or inland sea of which I have spoken reached the base of the Cheviots, glaciers may have nestled in the valleys. Streams issuing from the lower ends of these would sweep great quantities of gravel down the valleys to the margin of the lake, and it is quite possible that there might be enough wave-action to spread the gravel out along the shores. It is evident, however, that the main heaps of shingle would gather opposite what were at that time the mouths of glacier valleys; and it is just in such positions that we now meet with the thickest masses of conglomerate. Ere long, however, the supposed glaciers would seem to have melted away, and only fine sand and mud, with here and there small rounded stones and grit, accumulated round the shores of the ancient lake. Of course, during all this time fine-grained sediment gathered over the deeper parts of the lake-bottom. We have no evidence to show what kind of creatures, if any, inhabited the land at this time; nor do any fossils occur in the red earthy beds to throw light upon the conditions of life that may have obtained in the lake. If glaciers really existed and sent down ice-cold water, the conditions would hardly be favourable to life of any kind; for glacial lakes are generally barren. But the absence of fossils may be due to other causes than this. It is a remarkable fact, that red strata are, as a rule, unfossiliferous, and the few fossils which they do sometimes yield are generally indicative rather of lacustrine and brackish-water, than marine conditions. The paucity or absence of organic remains seems to have been often due to the presence in the water of a superabundance of salts. Now this excessive salinity may have arisen in either of two ways. First, we may suppose some wide reach of the sea to have been cut off from communication with the open ocean by an elevation of a portion of its bed; and in this case we should have a lagoon of saltwater, which evaporation would tend to concentrate to such a degree, that by-and-by nothing would be able to live in its waters. Or, again, we may have a lake so poisoned by the influx of springs and streams, carrying various salts in solution, as to render it uninhabitable by life of any kind, either animal or vegetable. Many red sandstone deposits, as Sir A. C. Ramsay has pointed out, are evidently lagoon-formations, which is proved by the presence of associated beds of rock-salt, gypsum, and magnesian limestone. They have slowly accumulated in great inland seas or lakes having no outlet, whose waters were subject to evaporation and concentration, although now and then they seem to have communicated more or less freely with the ocean. The red earthy beds of the Jed, however, though unfossiliferous, yet contain no trace of rock-salt or magnesian limestone. The only character they have in common with the salt-bearing strata of the New Red Sandstone of England is their colour, due to the presence of peroxide of iron, which we can hardly conceive could have been deposited in the mud of a sea communicating freely with the ocean. But a quiet lake, fed by rivulets and streams that drained an old volcanic district, is precisely the kind of water-basin in which highly ferruginous mud and sand might be expected to accumulate. Such a lake, tainted with the various salts, etc., carried into it by streams and springs (some of which may have been thermal; for, as we shall see presently, the volcanic forces, although quiescent, were yet not extinct), might well be unfitted for either animal or plant, and probably this is one reason why the red earthy beds of the Jed are so unfossiliferous. After some time, the physical conditions in the regions under review experienced some further modification. Considerable depression of the land supervened, and the waters of our inland sea or lake rose high on the slopes of the Cheviots. Mark now how the character of the sediment changes. The prevailing red colour has disappeared, and white, yellow, and pale greenish or grey sand begins to be poured over the bed of the lake. Even yet, however, ferruginous matter exists in sufficient quantity to tint the sediment red in some places. With the appearance of these lighter-coloured sandy deposits, the conditions seem to have become better fitted to sustain life. Fish of peculiar forms, which, like the gar-pike of North American lakes, were provided with a strong scaly armour of tough bone, began to abound, weeds grew in the water, and the neighbouring land supported a vegetation now very meagrely represented by the few remains of plants which have been preserved. In some places fish-scales are found in considerable abundance. They belong to several genera and species which are more or less characteristic of the Old Red Sandstone formation. The most remarkable form was the _Pterichthys_, or wing-finned fish. Its blunt-shaped head and the anterior portion of its body were sheathed in a solid case of bone, formed by the union of numerous bony scales or plates. Two curious curved spine-like arms occupied the place of pectoral fins, and may have been used by the creature in paddling along the bottom of the sea or lake in which it lived. The posterior part of the body was covered with bony scales, but these were not suturally united. Other kinds of fish were the _Holoptychius_ and _Coccosteus_, both of which were, like the Pterichthys, furnished with bony scales. The scales of the former overlapped, and had a curious wrinkled surface. The head of the Coccosteus was protected by a large bony shield or buckler, and a similar bony armour covered the ventral region. The organic remains of these fish-bearing strata are too scanty, however, to enable us to form any idea of the kind of climate which characterised the district at this long-past period; but if we rely upon the fossils which have been met with in strata of the same or approximately the same age elsewhere, we may be pretty sure the climate was genial, and nourished on the land an abundant vegetation, consisting of ferns, great reeds, and club-mosses, which attained the dimensions of large trees, conifers, and other strange trees which have no living analogues. It seems most likely that when the land sank down in the Cheviot district, so as to allow the old lake to reach as it were a higher level, some communication with the outlying ocean was effected. Red ferruginous mud would then cease to accumulate, or gather only now and then; the deposits would for the most part be white or yellow, or pale green; and fish would be able to come in from the sea. The communication with the ocean, however, was probably never very free, but liable to frequent interruption. Here, then, ends the third great period of time represented by the rocks of the Cheviot district. The first period, as we have seen, closed with the deposition of the Silurian strata. Thereafter supervened a vast lapse of time, not recorded in the Cheviots by the presence of any rocks, but represented in other regions by younger members of the Silurian system. During this unrecorded portion of past time, the Silurian strata of the Cheviots were hardened, compressed, folded, upheaved to the light of day, and worn into hills and valleys by the action of the sub-aërial forces. Then began the second period of rock-forming in our district. Volcanoes poured out successive beds of molten matter and showers of stones and ashes, and so built up the rock-masses of the highest parts of the Cheviot Hills. These eruptions belong to the Old Red Sandstone age, and form a portion of what we term the Lower Old Red Sandstone. After the extinction of the volcanoes, another prolonged period elapsed, which is not accounted for in the Cheviots by the presence of any rocks. Then it was, as we know, that the great volcanic bank was denuded and worn into a system of hills and valleys. Now, since it is evident that the red beds of the Jed and other places are also of Old Red Sandstone age, it follows that they must belong to a higher place in the Old Red Sandstone formation than the much-denuded igneous rocks upon which they rest unconformably. The reasonable conclusion seems to be that the denudation or wearing away of the Lower Old Red Sandstone igneous rocks of the Cheviots was effected during that period which is represented in other districts of Scotland by what is called the Middle Old Red Sandstone, so that the Jed beds will thus rank as Upper Old Red Sandstone. [Illustration: Fig. 8.--_s_, Silurian strata; _i_, Cheviot Igneous Rocks (Lower Old Red Sandstone); _r_, Upper Old Red Sandstone series; _c_, Kelso Igneous Rocks (Lower Carboniferous); _d_, Lower Carboniferous Sandstones, Shales, etc.] I come now to speak of certain rocks which, although they are developed chiefly beyond the limits of our district, yet require a little consideration before we can complete our account of the geological history of the Cheviots. The rocks referred to consist chiefly of old lava-beds, which very closely resemble those of the Lower Old Red Sandstone. They appear on the south side of the Tweed valley below Kelso, whence they extend south-west and west, crossing the river at Makerstoun, and sweeping north to form the hills about Smailholm, Stichill, and Hume (Fig. 8). All to the east of these rocks, the valley of the Tweed is occupied by a great thickness of grey sandstones, and grey and blue shales and clays, with which are associated thin cement-stone bands, and occasional coarse sandy limestones called cornstone. These strata rest upon the outskirts of the Kelso igneous rocks, and are clearly of later date than these, since in their lower beds, which are often conglomeratic, we find numerous rounded fragments of the igneous rocks upon which the sandstones and shales abut. The latter have yielded a number of fossils, both animals and plants, to which I shall refer presently. In the bed of the Teviot near Roxburgh, and elsewhere, the Kelso igneous rocks are found reposing upon whitish and reddish sandstones, which are evidently the upper members of the red beds of the Jed Water and other localities. Strata closely resembling the grey sandstones and shales of the Tweed valley appear among the Cheviot Hills at the head of the Jed Water, where they are marked by the presence of thick massive sandstones, which form all the tops of the hills between Hungry Law and the heights that overlook the sources of the Liddel Water--the greatest height reached being at Carter Fell, which is 1815 feet above the sea-level. The strata at this place contain some impure limestone and thin seams of coal, while beds of lava and tuff appear intercalated in the series. [Illustration: Fig. 9.--Section across old volcanic neck. The dotted line above suggests the original form of the volcano; _b_, plug of igneous rock which rose in a molten state and cooled in the vent.] Now let us rapidly sum up what seem to be the inferences suggested by these briefly-stated facts. We have seen that the Upper Old Red Sandstone began to be deposited in a lake which, as time wore on, probably communicated with the sea, while the land was undergoing a process of depression, so that the area of deposition was thus widely increased, and sediment gradually accumulated in places and at levels which had existed as land when the ancient lake first appeared in the Cheviot district. The old lava-beds of Kelso show that the volcanic forces, which had long been quiescent, again became active. Great floods of molten matter issued from the bowels of the earth, and poured over the bottom of the inland sea. But all the larger volcanoes of this period were confined to the centre of the Tweed valley. Not a few little isolated volcanoes, however, seem to have dotted the sea-bottom beyond the limits of the Kelso area. From these, showers of stones were ejected, and sometimes also they poured out molten matter. Their sites are now represented by rounded hills which stand up, more or less abruptly, above the level of the undulating tracts in which they occur (Fig. 9). Among the most marked are Rubers Law, Black Law, the Dunian, and Lanton Hill. Of course it is only the plugged-up vents or necks that now remain; all the loose ejectamenta by which these must at one time have been surrounded have long since been worn and washed away. At last the Kelso volcanoes became extinct, and the little ones also probably died out at the same time. Another long period now ensued, during which the inland sea disappeared, and its dried-up bed was subjected to the denuding action of the sub-aërial forces. The volcanic rocks of the Kelso district suffered considerable erosion, while the softer sandy strata amongst which they were erupted no doubt experienced still greater waste. Ere long, however, the scene again changes; and what is now the vale of Tweed becomes a wide estuary, the shores of which are formed at first by the Kelso igneous rocks. Into this estuary, rivers and streams carry the spoil of the Southern Uplands, and strew its bed with sand and mud. Occasionally ferns and large coniferous trees are floated down, and, getting water-logged, sink to the bottom, where they become entombed in the slowly accumulating sediment. The character of these buried plants shows that the climate must have been genial. They belong to species which are characteristic of the Carboniferous system, and we look upon them with interest as the forerunners of that vast plant-growth which by-and-by was to cover wide areas in Britain, and to give rise to our coal-seams, the source of so much national wealth. In the waters of the estuary, minute crustaceous creatures called _cyprides_ abounded, and with these was associated a number of small molluscs, chiefly univalves. Here and there considerable quantities of calcareous mud and sand gathered on the bed of the estuary, and formed in time beds of cement-stone, and impure limestone or cornstone. How long that condition of things obtained in the Tweed valley we cannot tell; but we know that after a very considerable thickness of sediment had accumulated, estuarine conditions prevailed over the south-west end of what is now the Cheviot range. This points to a considerable depression of the land. In this same region volcanic action appeared, and streams of lava and showers of fragmental materials were ejected--the remains of which are seen in Hungry Law, Catcleugh Shin, and the head-waters of the Jed. Genial climatic conditions continued; and here and there, along what were either low islets or the flat muddy shores of the estuary, plants grew in sufficient quantity to form masses of vegetation which, subsequently buried under mud and sand, were compressed and mineralised, and so became coal. The only place where these are now met with is on the crest of the Cheviots at Carter Fell. The process of depression still continuing, thick sand gradually spread over the site of the submerged forests. To trace the physical history immediately after this, we must go out of the Cheviot district; and it may suffice if I merely state that these estuarine or lacustrine conditions, which prevailed for a long time not only over the Tweed and Cheviot areas but in various other parts of Scotland, at last gave place to the sea. In this sea, corals, sea-lilies, and numerous molluscs and fishes abounded--all pointing to the prevalence of genial climatic conditions. The organic remains and the geological position of the estuarine beds of the Tweed and the Cheviots--resting as they do upon the Upper Old Red Sandstone--prove them to belong to the Lower series of the great Carboniferous system. It was some time during the Carboniferous period that wide sheets of melted matter were forcibly intruded among the Old Red Sandstone and the Lower Carboniferous strata of the Cheviot district; but although these are now visible at the surface, as at Southdean, Bonchester, etc., they never actually reached that surface at the time of their irruption. They cooled in the crust of the earth amongst the strata between which they were intruded, and have only been exposed to view by the action of the denuding forces which have worn away the sedimentary beds by which they were formerly covered. A very wide blank next occurs in the geological history of the Cheviots. We have no trace of the many great systems, comprising vast series of strata and representing long eras of time, which we know, from the evidence supplied by other regions, followed after the deposition of the Lower Carboniferous strata. The Middle and Upper Carboniferous groups are totally wanting, so likewise is the Permian system; and all the great series of "Secondary" systems, of which the major portion of England is composed, are equally absent. Nay, even Tertiary accumulations are wanting. There is one very remarkable relic, however, of Tertiary times, and that is a long dyke or vertical wall of basalt-rock which traverses the country from east to west, crossing the crest of the Cheviots near Brownhart Law, and striking west by north through Belling Hill, by the Rule Water at Hallrule Mill, on towards Hawick. This is one of a series of such dykes, common enough in some parts of Scotland, which become more numerous as we approach the west coast, where they are found associated with certain volcanic rocks of Tertiary age, in such a way as to lead to the belief that they all belong to the same period. The melted rock seems to have risen and cooled in great cracks or fissures, and seldom to have overflowed at the surface. Indeed it is highly probable that many or even most of the dykes never reached the surface at all, but have been exposed by subsequent denudation of the rocks that once overlaid them. Such would appear to have been the case with the great dyke of the Cheviot district. We can only conjecture what the condition of this part of southern Scotland was in the long ages that elapsed between the termination of the Lower Carboniferous period and the close of the Tertiary ages. It is more than likely that it shared in some of the submergences that ensued during the deposition of the upper group of the Carboniferous system; but after that it may have remained, for aught we can tell, in the condition of dry land all through those prolonged periods which are unrecorded in the rocks of the Cheviot Hills, but have left behind them such noteworthy remains in England and other countries. Of one thing we may be sure, that during a large part of those unrecorded ages the Cheviot district could not have been an area of deposition. Rather must it have existed for untold eras as dry land; and this explains and accounts for the enormous denudation which the whole country has experienced; for there can be little doubt that the Lower Carboniferous strata of Carter Fell were at one time continuous with the similar strata of the lower reaches of the Tweed valley. Yet hardly a trace of the missing beds remains in any part of the country between the ridge of the hills at the head of the Jed Water and the Tweed at Kelso. Only little patches are found capping the high ground opposite Jedburgh, as at Hunthill, etc. Thus more than a thousand feet of Lower Carboniferous strata, and probably not less than five hundred or six hundred feet of Old Red Sandstone rocks, have been slowly carried away, grain by grain, from the face of the Cheviot district since the close of the Lower Carboniferous period. IV. In the first of these papers some reference was made to the configuration of the ground in the Cheviot district. We have seen that the outlines assumed by the country have been determined in large measure by the nature of the rocks. Thus where igneous masses abound, the hills present a more or less irregular, and broken or lumpy contour, while the valleys are frequently narrow and deep. In the tracts occupied by Silurian strata, we have, as a rule, broad-topped hill-masses with a smoothly-rounded outline, whose slopes generally fall away with a long gentle sweep into soft green valleys, along the bottoms of which the streams often flow in deep gullies and ravines. Where the country is formed of sandstones, and other associated strata, the hills are generally broad and well-rounded, but the outline is not infrequently interrupted by lines of cliff and escarpment. These strata, however, are confined chiefly to the low-grounds, where they form a gently-undulating country, broken here and there, as in Dunian Hill, Bonchester Hill, Rubers Law, etc., by abrupt cones and knobs of igneous rock. It is evident, then, that the diversified character of the Cheviot Hills and the adjoining low-grounds depends on the character of the rocks and also, as we shall see presently, upon geological structure. Each kind of rock has its own peculiar mode of weathering. All do not crumble away under the action of rain, frost, and running water in precisely the same manner. Some which yield equally and uniformly give rise to smooth outlines, others of more irregular composition, such as many igneous rocks, break up and crumble unequally in a capricious and eccentric way, and these in the course of time present a hummocky, lumpy, and rough irregular configuration. And as soft and readily-weathered rocks must wear away more rapidly than indurated and durable masses, it follows that the former will now be found most abundantly at low levels, while the latter will enter most extensively into the composition of the hills. But the contour of a country depends not only upon the relative durability of the rocks, but also upon the mode of their occurrence in the crust of the earth. Strata, as we have seen, do not all lie in one way; some are horizontal, others are inclined to the horizon, while yet others are vertical. Again, many rocks are amorphous; that is to say, they occur in somewhat thick masses which show no trace of a bedded arrangement. Such differences of structure and arrangement influence in no small degree the weathering and denudation of rocks, and cannot be left out of account when we are seeking to discover the origin of the present configuration of our hills and valleys. Thus, escarpments and the terraced aspect of many hill-slopes are due to inequalities in the strata of which such hills are built up. The softer strata crumble away more rapidly under the touch of the atmospheric forces than the harder beds which rest upon them, and hence the latter are undermined, and their exposed ends or crops, losing support, fall away and roll down the slopes. The igneous rocks of the Cheviots are arranged in beds; but so massive are these, that frequently a hill proves to be composed from base to summit of one and the same sheet of old lava. Hence there is a general absence of that terraced aspect which is so conspicuous in hills that are built up of bedded rock-masses. Here and there, however, the beds are not so massive, several cropping out upon a hill-side; and whenever this is the case (as near Yetholm) we find the hill-slopes presenting the usual terraced appearance--a series of cliffs and escarpments, separated by intervening slopes, rising one above the other. In the Silurian districts no such terraces or escarpments exist, the general high dip of the strata, which often approaches the vertical, precluding any such contour. In a region composed of highly-inclined greywacké and shale, however, we should expect to find that where the strata are of unequal durability, the harder beds will stand up in long narrow ridges, separated by intervening hollows, which have been worn out along the outcrops of the softer and more easily-denuded beds. And such appearances do show themselves in some parts of the Silurian area. As a rule, however, the Silurian strata are not thick-bedded, and harder and softer bands alternate so rapidly that they yield on the whole a smooth surface under the action of the atmospheric forces. In the low-lying districts, which, as I have said, are mostly occupied by sandstones and shaly beds, all the abrupt isolated hills are formed of igneous rocks, which are much harder and tougher than the strata that surround them. It is quite evident that these hills owe their present appearance to the durable nature of their constituent rocks, which now project above the general level of the surface, simply because they have been better able to resist the denuding agents than the softer rocks that once covered and concealed them. We see, then, that each kind of rock has its own particular mode of weathering, and that the configuration of a country depends primarily upon this and upon geological structure. Indeed, so close is the connection between the geology and the surface-outline of a country, that to a practised observer the latter acts as an unfailing index to the general nature of the underlying rocks, and tells him at a glance whether these are igneous like basalt and porphyrite, aqueous like sandstone and shale, or hardened and altered strata like greywacké. But while one cannot help noticing how in the Cheviot district the character of the scenery depends largely upon the nature and structure of the rocks, he shall, nevertheless, hardly fail to observe that flowing outlines are more or less conspicuous over all the region. And as he descends into the main valleys, he shall be struck with the fact that the hill-slopes seem to be smoothed off in a direction that coincides with the trend of these valleys. In short, he cannot help noticing that the varied configuration that results from the weathering of different rock-masses has been subsequently modified by some agent which seems to have acted universally over the whole country. In the upper reaches of the Cheviot valleys, the rocks have evidently been rounded off by some force pressing upon them in a direction coinciding with that of the valleys; but soon after entering upon their lower reaches, we notice that the denuding or moulding force must have turned gradually away to the north-east--the northern spurs of the Cheviots, and the low-grounds that abut upon these being smoothed off in a direction that corresponds exactly with the trend of that great strath through which flow the Teviot and the Tweed, from Melrose downwards. Throughout this broad strath, which extends from the base of the Lammermuirs to the foot of the Cheviots, and includes the whole of Teviotdale, the ground presents a remarkable closely-wrinkled surface, the ridges and intervening hollows all coinciding in direction with the general trend of the great strath, which is south-west and north-east; but turning gradually round to east, as we approach the lower reaches of the Tweed. Passing round the north-eastern extremity of the Cheviot range into Northumberland, we observe that the same series of ridges and hollows continues to follow an easterly direction until we near the sea-board, when the trend gradually swings round to the south-east, as in the neighbourhood of Belford and Bamborough, where the ridges run parallel with the coast-line. The ridges and hollows are most conspicuous in the low-grounds of Roxburghshire and Berwickshire, especially in the regions between Kelso and Smailholm, and between Duns and Coldstream. The dwellers along the banks of the Tweed are quite familiar with the fact that the roads which run parallel with the river are smooth and level, for they coincide with the trend of the ridges and hollows; whilst those that cross the country at right angles to this direction must of course traverse ridge after ridge, and are therefore exceedingly uneven. In this low-lying district most of the ridges are composed of superficial deposits of stony and gravelly clay and sand, and the same is the case with those that sweep round the north-eastern spurs of the Cheviots by Coldstream and Ancroft. Some ridges, however, consist either of solid rock alone, as near Stichill, or of rock and overlying masses of clay and stones. In the hilly regions, again, nearly all the ridges are of rock alone, especially in the districts lying between Melrose and Selkirk and between Selkirk and Hawick. Indeed, the hills drained by the upper reaches of the Teviot and its tributaries are more or less fluted and channelled, as it were--many long parallel narrow hollows having been driven out along their slopes and even frequently across their broad tops. This scolloped and ridged aspect of the hills, however, disappears as we approach the upper reaches of the hill-valleys. From Skelfhill Pen (1745 feet) by Windburgh Hill (1662 feet), on through the ridge of the Cheviot watershed, none of the hills shows any appearance of a uniformly-wrinkled surface. [Illustration: Fig. 10.--Rounded Rocks, with superficial deposits, _t_ _t_ _t_, heaped up against steep faces. The arrows indicate direction followed by the smoothing agent.] A close inspection of the rock-ridges satisfies one that they have been smoothed off by some agent pressing upon them in a direction that coincides with their own trend; and not only so, but the smoothing agent, it is clearly seen, must have come from the watersheds and then pressed outwards to the low-grounds which are now watered by the Teviot and the Tweed. This is shown by the manner in which the rocks have been smoothed off, for their smooth faces look towards the dominant watersheds, while their rough and unpolished sides point away in the opposite direction. Sometimes, however, we find that more or less steeply projecting rocks _face_ the dominant watersheds. When such is the case, there is usually a long sloping "tail" behind the crag--a "tail" which is composed chiefly of superficial deposits. The hills between Hume and Stichill afford some good examples. The two kinds of appearances are exhibited in the accompanying diagram (Figs. 10, 11.) The appearance shown in Fig. 10 is of most common occurrence in the upland parts of the country, while "crag and tail" (as shown in Fig. 11) is seen to greatest advantage in the open low-grounds. In both cases it will be observed that superficial deposits (_t_) nestle behind a more or less steep face of rock. [Illustration: Fig. 11.--"Crag and Tail"; boss of hard rock, _c_; intersecting sandstones, _s_; superficial deposits heaped up in rear of crag, _t_. The arrow indicates direction followed by smoothing agent.] When the rocks have not been much exposed to the action of the weather, they often show a polished surface covered with long parallel grooves and striæ or scratches. Such polished and scratched surfaces are best seen when the superficial deposits have been only recently removed. Often, too, when we tear away the thick turf that mantles the hill-slopes, we find the same phenomena. Indeed, wherever the rocks have not been much acted upon by the weather, and thus broken up and decomposed, we may expect to meet with more or less well-marked grooves and stride. Now the remarkable circumstance about these scratches is this--they agree in direction with the trend of the rock-ridges and the hollows described above. Nor can we doubt that the superficial markings have all been produced by one and the same agent. In the upper valleys of the Cheviots, the scratches coincide in direction with the valleys, which is, speaking generally, from south to north, but as we approach the low-grounds they begin to turn more to the east (just, as we have seen, is the case with the ridges and hollows), until we enter England to the east of Coldstream, where the striæ point first nearly due east, but eventually swing round to the south-east, as is well seen upon the limestone rocks between Lowick and Belford. In Teviotdale the general trend of the striæ is from south-west to north-east, a direction which continues to hold good until the lower reaches of the Tweed are approached, when, as we have just mentioned, they begin to turn more and more to the east. Thus it becomes evident that the denuding agent, whatever it was, that gave rise to these ridges and scratched rock-surfaces must have pressed outwards from all the dominant watersheds, and, sweeping down through the great undulating strath that lies between the Cheviots and the Lammermuirs, must have gradually turned away to the east and south as it rounded the northern spurs of the former range, so as to pass south-east over the contiguous maritime districts of Northumberland. A few words now as to the character of the superficial deposits which enter so largely into the composition of the long parallel banks and ridges in the low-grounds of Roxburghshire, Berwickshire, and the northern part of Northumberland. The most conspicuous and noteworthy deposit is a hard tough tenacious clay, which is always more or less well-charged with blunted and sub-angular stones and boulders, scattered pell-mell through the mass. This clay is as a rule quite unstratified--it shows no lines of bedding, and although here and there it contains irregular patches and beds of gravel and sand, yet it evidently does not owe its origin to the action of water. Its colour in the upper part of Teviotdale and the Cheviots is generally a drab-brown, or pale grey and sometimes yellow, while here and there, as in the upper reaches of the Jed valley, it is a dark dingy bluish grey. In the lower parts of Teviotdale and in the Tweed district it is generally red or reddish brown. The stones in the clay have all been derived from the rocks of the region in which it occurs. Thus in Teviotdale we find that in the higher reaches of the dale which are Silurian the stones and boulders consist of various kinds of greywacké, etc. In the lower reaches, however, when we pass into the Red Sandstone area, we note that the clay begins to contain fragments of red sandstone, while the clay itself takes on a reddish tinge, until we get down to the vale of the Tweed, where not only is the clay very decidedly red, but its sandstone boulders also are very numerous. The same appearances present themselves in passing outwards from the Cheviots. At first the clay contains only stones that have been derived from the upper parts of the hills, but by-and-by, as we near the low-grounds, other kinds begin to make their appearance, so that by the time we reach the Tweed we may obtain from the clay specimens of every kind of rock that occurs within the drainage-area of the Teviot and the lower reaches of the River Tweed. Look at the stones, and you shall observe that all the harder and finer-grained specimens are well-smoothed and covered with striæ or scratches, the best marked of which run parallel with the longer axis of each stone and boulder. These scratches are evidently very similar to those markings that cover the surface of the underlying solid rock, and we may feel sure, therefore, that the denuding agent which smoothed and scratched the solid rocks had also something to do with the stones and boulders of the clay. Underneath the stony clay, or _Till_, as it is called, we find here and there certain old river gravels. We know that these gravels are river-formations, because not only do they lie at the bottom of the river-valleys, but the stones, we can see, have been arranged by water running in one constant direction, and that direction is always _down_ the valley in which the gravels chance to occur. Frequently, however, there is no trace of such underlying gravels, but the till rests directly upon the solid rocks. Now what do all these appearances mean? It is clear that there is no natural agent in this country engaged in rounding and scratching the rocks, or in accumulating a stony clay like till. In alpine regions, however, we know that glaciers, as they slowly creep down their valleys, grind and polish and scratch the rocks over which they pass, and that underneath the moving ice one may detect smoothed and striated stones precisely resembling those that occur in till. Frost in such alpine regions splits up the rocks of the cliffs and mountain-slopes that overlook a glacier, and immense masses of angular stones and débris, thus loosened, roll down and accumulate along the flanks of the ice-streams. Eventually such accumulations are borne slowly down the valley upon the back of the glacier, and are dropped at last over the terminal front of the ice, where they become intermingled with the stones and rubbish, which are pushed or washed out from underneath the ice. These heaps and masses of angular débris and stones are called "moraines," and one can see that in Switzerland the glaciers must at some time have been much larger, for ancient moraines occur far down in the low-grounds of that country--the glaciers being now confined to the uppermost reaches of the deep mountain-valleys. Moreover, we may note how the mountain-slopes overlooking the present puny glaciers have been rubbed by ice up to a height of sometimes a thousand feet and more above the level of the existing ice-streams. Now since the aspect presented by the glaciated rock-surfaces of Switzerland is exactly paralleled by the rounded and smoothed rocks of Scotland, there can be no doubt that the latter have had a similar origin. Again, we find throughout the low-grounds of Switzerland a deposit of till precisely resembling that which is so well developed in Teviotdale and the valley of the Tweed. And as there can be no doubt that the Swiss till has been produced by the action of glacier ice, we are compelled to believe the same of the till in Scotland. Let us further note that in the deep mountain-valleys of Switzerland the glacial deposits consist for the most part of coarse morainic débris--of such materials, in short, as the terminal moraines of existing glaciers are mainly composed. Not infrequently this morainic débris has been more or less acted upon by the rivers that escape from the glaciers, and the angular stones have been rounded and arranged in bedded masses. It is only when we get out of the mountain-valleys and approach the low-grounds that the till, or stony clay, begins to appear abundantly. The same phenomena characterise the Cheviot district. In the upper reaches of the mountain-valleys at the heads of the Teviot, the Kale, the Bowmont, etc., either till does not occur or it is thin and often concealed below masses of rude morainic débris and gravel. Out in the low-grounds, however, till, as we have already remarked, is the most conspicuous of all the superficial deposits. From these facts it may be inferred that till indicates the former presence of great confluent glaciers, while morainic débris in hill-valleys points to the action of comparatively small local and isolated glaciers. What, then, are the general conclusions which may be derived from a study of the rock-ridges, flutings, and striæ, and the till of the Cheviot district? Clearly this: that the whole country has at one time been deeply buried under glacier ice. The evidence shows us that the broad strath stretching between the Lammermuirs and the Cheviots must have been filled to overflowing with a great mass of ice that descended from the uplands of Peebles and Selkirk and the broad-topped heights that overlook the sources of the Teviot. The Cheviots appear to have been quite buried underneath this wide sea of ice, and so likewise were the Lammermuirs. At the same time, as we know, all Scotland was similarly enveloped in a vast sheet of snow and ice, which streamed out from the main watersheds of the country, and followed the lines of the chief straths--that is to say, the general slope of the ground. The track of the ice in the Cheviot district is very distinctly marked. In Teviotdale it followed the trend of the valley, and, grinding along the outcrop of the Silurian strata, deepened old hollows and scooped out new ones in the soft shaly beds, while the intervening harder strata, which offered greater resistance to the denuding action of the ice, did not wear so easily, and so were rounded off, and formed a series of ridges running parallel to the eroded hollows. The stones and rubbish, dragged along underneath the ice, necessarily increased as the glacier mass crept on its way. The rocks were scratched and grooved by the stones that were forced over them, and the polishing was completed by the finer sand and clay which resulted from the grinding process. Wherever a rock projected there would be a tendency for the stones and clay and sand to gather behind it. One may notice the same kind of action upon the bed of a stream, where the sediment tends to collect in the rear of prominent stones and boulders. And we can hardly fail to have observed further that the sediment of a river often arranges itself under the action of the current in long banks, which run parallel to the course of the water. Underneath the ice-sheet the stones, sand, and clay behaved in the same way. Behind projecting rocks in sheltered nooks and hollows, they accumulated, while in places exposed to the full sweep of the ice-stream they were piled up and drawn out into long parallel banks and ridges, the trend of which coincided with that of the ice-flow. The presence of confused and irregular patches and lenticular beds of sand, clay, and gravel in the till is not difficult to understand when we know that there is always more or less water flowing on underneath a glacier. Such streams must assort the débris, and roll angular fragments into rounded stones and pebbles; but the materials thus assorted in layers will ever and anon be crushed up so as to be either partially or wholly obliterated by the slowly moving glacier. As the stones and clay were derived from the underlying rocks, it is no wonder that the colour of the till should vary. In the Silurian tracts it is pale yellowish, or bluish grey, and the stones consist chiefly of fragments of Silurian rocks, all blunted and smoothed, and often beautifully polished and striated. When we get into the Red Sandstone region of the low-grounds the colour of the clay begins by-and-by to change, and fragments of red sandstone become commingled with the Silurian stones, until ere long the colour of the deposit is decidedly red, and sandstone fragments abound. Everywhere the stones show that they have been carried persistently in one direction, and that is _out from the watershed, and down the main valleys_. The direction of the ice-marks upon the solid rocks, and the trend of the "drums," as the parallel ridges of till are termed, show that the ice-sheet of Teviotdale and Tweed gradually turned away to the east and south-east as it swept round the north-eastern spurs of the Cheviots. Now we may well ask why the ice did not go right out into the North Sea, which is apparently the course it ought to have followed. The same curious deflection affected the great ice-stream that occupied the basin of the Forth. When it got past North Berwick, that stream, instead of flowing directly east into the North Sea, turned away to the south-east and overflowed the northern spurs of the Lammermuirs, bringing with it into the valley of the Tweed stones and boulders which had travelled all the way from the Highlands. It is obvious there must have been some impediment to the flow of the Scottish ice into the basin of the North Sea. What could have blocked its passage in that direction? At the very time that Scotland lay concealed beneath its ice-sheet, Norway and Sweden were likewise smothered in ice which attained a thickness of not less than five or six thousand feet. The whole basin of the Baltic was occupied by a vast glacier which flowed south into Northern Germany, and this sheet was continuous with glacier-ice that crossed over Denmark. When we consider how shallow the North Sea is (it does not average more than forty fathoms between Scotland and the Continent), we cannot doubt that the immense masses of ice descending from Norway could not possibly have floated off, but must actually have crept across the bottom of that sea until they abutted upon and coalesced with the Scottish ice, so as to form one vast _mer de glace_. Thus it was that the Scandinavian ice blocked up the path of the Scottish glaciers into the basin of the North Sea, and compelled them to flow south-east into England.[H] Had there been no such obstruction to the passage of the Scottish glaciers, it is impossible to believe that snow and ice could ever have accumulated to such a depth in Scotland. The Scottish ice reached a thickness of some three thousand feet in its deeper parts. It is evident, however, that had there been a free course for the glaciers, they would have moved off before they could have attained this thickness. And we can hardly doubt, therefore, that it was the damming-up of their outlet by the great Scandinavian ice-sheet that enabled them to deepen to such an extent in the valleys and low-grounds of Scotland. [H] In the extreme north of Scotland we find that the Scottish ice was, in like manner, compelled to turn aside and overflow Caithness from south-east to north-west. When the ice-sheet was at its thickest, the Cheviots were completely covered, nevertheless they served to divide the ice-flow between Scotland and England, although here and there one finds that the ice passed over some of the lower summits, carrying with it boulders and stones. This is by no means an uncommon circumstance in Scotland and other glaciated countries. Thus we note that Highland boulders have been brought into the vale of the Tweed across the Lammermuirs; and in the same way boulders from the heights overlooking Eskdale have been carried over some of the lower hill-tops into the vale of the Teviot. In like manner the Swedish ice occasionally overflowed the lower mountain-tops of the dividing ridge or watershed into Norway. What wonder now that the Cheviot area should exhibit so many flowing outlines, that the hills should be so smoothed and rounded and fluted, that the low-grounds should be cumbered with such heaps of clay and striated stones? Long before the great glaciers appeared, the rocks were weathered and worn by the action of the usual atmospheric forces, and each had assumed its own peculiar outline; but how greatly has this been modified by the grinding action of the ice-sheet! To what an extent have projecting rocks been rubbed, and how great is the destruction that has befallen the loose accumulations of river gravel, sand, and clay that gathered in the valleys before the advent of the Ice Age! All that now remains of these are a few patches preserved here and their underneath the till. The Cheviots can tell us nothing of the kinds of plants and animals that clothed and peopled the country in pre-glacial times. All we learn is that streams and rivers flowed as they flow now, and that by-and-by everything was changed, and the land disappeared underneath a vast covering of snow and ice. In my concluding paper I will show how this ice period passed away, and how the present condition of things succeeded. V. I have described the condition of the Cheviot district during the climax of the Ice Age as one of intense arctic cold, the whole ridge of hills being then completely smothered in snow and ice. This excessive climate, however, did not last continuously throughout the so-called glacial period, but was interrupted by more than one mild interglacial epoch. We have evidence in Scotland, as in other countries, to show that the great confluent ice-masses melted away so as to uncover all the low-grounds and permit the reappearance of plants and animals. Rivers again watered the land, and numerous lakes diversified the face of the country. Willows, hazels, and alders grew in the sheltered valleys, oak-trees flourished in the low-grounds, and Scots firs clustered upon the hill-slopes. A strong, grassy vegetation covered wide areas, and sedges and rushes luxuriated in marshy places and encroached upon the margins of the lakes. The mammoth, or woolly-coated elephant, roamed over the land, and among its congeners were the extinct ox, the horse, the Irish elk, and the reindeer. After such a temperate condition of things had continued for some time--perhaps for thousands of years--the land, during the last interglacial epoch, became gradually submerged to a depth of several hundred feet, and a cold, ungenial sea, in which flourished species of northern and arctic shells, covered the low-grounds of Scotland. The cold continuing to increase, our glaciers descended for the last time from the mountains and encroached upon the bed of the sea, until they became confluent, fairly usurping the floor of the German Ocean, and pushing back the western seas as far as, and even beyond, the islands of the Outer Hebrides. There is good reason to believe that such great changes of climate occurred several times during the glacial period, which thus seems to have consisted of an alternation of cold and genial epochs. But as the last phase in this extraordinary series of changes was a cold one, during which great glaciers scoured the face of the country, we now obtain only a few scattered traces of the genial conditions that characterised the preceding mild interglacial epochs. Vegetable accumulations, lake and river deposits with mammalian remains, marine beds and their shelly contents, were all ploughed up by the ice, and to a very large extent demolished. Here and there, however, we find in the till or boulder-clay that marks the last cold epoch, wasted fragments of trees, tusks of mammoths, and broken sea-shells; while underneath the till we occasionally come upon old lake deposits with vegetable and mammalian remains, or, as the case may be, beds of marine origin well stocked with sea-shells of arctic species. And these freshwater and marine beds repose, in many cases, upon an older accumulation of till, which belongs to an earlier cold epoch of the glacial period. In the Cheviot district proper, the traces of mild, interglacial conditions are very slight, but in the immediate neighbourhood we find them more strongly marked. Thus, in the valley of the Slitrig, near Hawick, we notice freshwater beds with peaty matter lying between a lower and an upper till or boulder-clay; and interglacial freshwater beds also appear in the neighbouring county of Peebles, particularly in the valley of the Leithan Water. Again, in the valley of the Tweed near Carham, there occur interglacial beds in which I detected numerous bones of water-rats and frogs. These interglacial remains acquire a peculiar interest when we come to view the "superficial deposits" of Scotland in connection with those of England and the Continent; for, as I have endeavoured to show elsewhere,[I] it is most likely that the ancient gravels of England, which contain the earliest traces of man, belong for the most part to interglacial times; and the extraordinary changes of climate described above may therefore have been actually witnessed by human eyes. Indeed, I believe it was the advent of the last cold epoch of the Ice Age that drove out the old tribes who used the rude flint implements that are now found in the gravel deposits and caves of England, and who occupied the British area along with hippopotami, rhinoceroses, elephants, lions, hyænas, and other animals. The men who entered Britain after the final disappearance of arctic conditions, were more advanced in civilisation, and were accompanied by a very different assemblage of animals--by a group represented by oxen, sheep, dogs, and other creatures, most of which are still indigenous to Britain. [I] _Great Ice Age._ But to return to the Cheviots. When the final cold epoch had reached its climax, and the ice-sheet began to melt away for the last time, the tops of the hills then once more became uncovered, and large blocks, detached by the action of the frost, fell upon the surface of the glaciers, and were borne down the valleys, some of them to become stranded here and there on hill-slopes, others to be carried far away from the Cheviot area and dropped at last over Northumberland and Durham, or even further south. As the melting of the ice continued, and the glacier of the Tweed ceased to reach the sea, great accumulations of gravel and sand were formed. Underneath the ice, sub-glacial streams ploughed out the till, and paved their hidden courses with gravel and sand. In summer-time, the whole surface of the Tweed glacier was abundantly washed with water, which, pouring down by clefts and holes in the ice, swelled all the sub-glacial streams and rivers. At the same time, floods descending from the Lammermuirs and the Cheviots, pushed with them vast quantities of shingle, gravel, and sand, part of which was swept upon the surface of the Tweed glacier, while much seems to have gathered along its flanks, forming banks and ridges running parallel with the course of the valley. At last the time came when the ice had fairly vanished from the lower reaches of the Tweed, and we now walk over its bed and mark the long ridges and banks of shingle and gravel that were formed by the sub-glacial streams and rivers, and the somewhat similar accumulations that gathered along the sides of the glacier at the foot of the Lammermuir Hills. Here and there, also, we note the heaps (_i.e._ moraines) of shingle, earth, clay, and débris, with large erratics which travelled on the surface of the ice, and were dropped upon the ground as that ice melted away. All the loose erratics that lie at the surface in the lower reaches of the Tweed valley have come from the west. Some of them rest upon hard rock, others upon till, and yet others crown the tops and slopes of gravel and sand hillocks, or appear in low mounds of morainic origin. In the valleys of the Cheviot Hills one traces the footsteps of the retiring glaciers in mounds and hummocks of rude earthy débris, blocks, and rock-rubbish. These are terminal moraines, and they indicate certain pauses in the recession of the ice. The most remarkable examples occur in the valley of the Kale Water at Blinkbonny, a mile or so above the village of Eckford. At that place a bank of morainic matter at one time blocked up the valley of the Kale, and thus formed a wide and extensive lake that stretched up to and beyond Morebattle. Numerous curious hillocks of gravel and sand are banked against the moraine, and point to the action of the flood-waters that escaped from the melting glacier. Other gravelly moraine mounds occur higher up the same valley, as near Grubbit Mill. These last tell us of a time when the Kale glacier had retreated still further, so as to have its terminal front near where Morebattle now is. Wreaths and hummocks of gravel and sand, extending from Grubbit to the north-east, along the hollow in the hills that leads to Yetholm Loch, indicate the course taken by a portion of the torrents that escaped from the ice in summer-time. In other hill-valleys, similar indications of ancient local glaciers may be seen. Some of the most conspicuous of these appear upon the slopes and in the high valleys within the drainage-areas of the Jed and the Kale. They consist chiefly of mounds and hillocks, made up of coarse earthy débris and rock-rubbish; sometimes these are solitary and rest in the throat of a valley, at other times they are scattered all over the hill-slopes and valley-bottom. One can have no doubt as to what they mean: they indicate clearly the presence of insignificant glaciers that were soon to vanish away. The larger and better-defined mounds are true terminal moraines, while the scattered heaps of rubbish point out for us the beds in which the glaciers lay. Thus, from the sea-coast up to the highest ridge of this border country, we follow the spoor of the melting ice; passing from massive and wide-spread deposits of till, gravel, and sand, and angular débris in the low-grounds, up to insignificant heaps and scatterings of rock-rubbish and angular boulders at the higher levels of the country. Several more or less extensive flats in the hill-valleys indicate the former presence of lakes which have become obliterated by the action of the streams. But by far the most conspicuous example of such silted-up lakes is that of the Kale valley, to which reference has already been made. In the later stages of the Ice Age that river-valley must have existed as a lake from Marlfield up to and beyond Morebattle. Indeed, there is evidence to show that even within historical times a considerable lake overspread the flat grounds in this neighbourhood. The name _Morebattle_ is supposed to mean the "village by the lake," and, up to a few years ago, there was a sheet of water called Linton Loch a little to the east of Morebattle. But this has been drained by the proprietor, and is now represented by only two insignificant pools. The present course of the Kale between Marlfield and Kalemouth is of post-glacial age--the old pre-glacial and interglacial course being filled up with drifted materials. As the appearances at this place are somewhat typical of many of the valleys of the Cheviot district, I may briefly summarise the history of the Morebattle lake. Before the advent of the last great age of ice the Kale would seem to have flowed from Marlfield, close to the line now followed by the turnpike road as far as Easter Wooden, after which it passed near the present sites of Blinkbonny and Mosstower, and so on to the Teviot, which it joined some little distance above Kalemouth. During the Ice Age many of the old river-courses were completely choked up with clay, stones, and gravel, so that when the ice melted away the rivers did not always or even often regain their old channels. Thus, in the case of the Kale, we find that the present course of the river below Marlfield is of recent or post-glacial age, having been excavated by the river since the close of the glacial epoch. The old or pre-glacial course lies completely choked up and concealed under the rubbish shot into it at a time when glacier-ice filled all the valley of the Kale down to Marlfield. At this latter place the Kale glacier seems to have made a considerable pause--it ceased for some time to retreat--and thus a heavy bank of gravel, sand, shingle, earth, blocks, and angular rubbish gathered in front of it, and obliterated the old river-course into which they were dropped. When the glacier at last disappeared, a lake was formed above the morainic dam that closed the valley below Marlfield, and the outflow of the lake took place at a point lying some little distance to the north of the old or pre-glacial course of the Kale. By slow degrees the river excavated a new channel for itself in the Old Red Sandstone rocks, and in doing so gradually lowered the level of the waters. This and the silting action of the Kale and its feeders slowly converted the lake-hollow into a broad alluvial flat through which the river now winds its way. Another extensive lake seems to have occupied the vale of the Teviot between Jedfoot and Eckford, and similar old lake-beds occur in several of the hill-valleys. One good example is seen in the valley of the Oxnam Water, where the flat tract that extends from the old village of Oxnam up to the foot of the Row Hill indicates the former presence of a lake which has been drained by the stream cutting for itself a gorge in Silurian greywackés and shales. In many other valleys it is easy to see that the streams do not always occupy their pre-glacial courses, and some of the old forsaken courses are still patent enough. Thus, a glance at the hollow that extends from Mossburnford on the Jed to Hardenpeel on the Oxnam is enough to convince one that in pre-glacial, and probably in early post-glacial times also, a considerable stream has flowed from what is now the vale of the Jed into the valley of the Oxnam. In all the valleys we meet with striking evidence to show that the streams and rivers must formerly have been larger than they are now. Certain banks and ridges of gravel fringe the valley-slopes at considerable heights, and indicate the action of deeper and broader currents than now make their way towards the sea. It is probable that these high-level gravel terraces date their existence back to the close of the Ice Age, when local glaciers still lingered in some of the mountain-valleys, and when in summer-time great floods and torrents descended from the hills. An extremely humid climate seems to have characterised Scotland even in post-glacial times, as may be gathered from the phenomena of her peat-mosses. Very little peat occurs on the Scottish side of the Cheviots, and it is conspicuous chiefly on the very crest of the hills, where it attains a thickness that varies from a foot or two up to five or six yards. Here and there we detect the remains of birch under the peat, but the peat itself is composed chiefly of bog-moss and heather. The evidence so abundantly supplied by the peat-mosses in other parts of Scotland shows that after the Ice Age had passed away the Scottish area became clothed with luxuriant forests of oak, pine, and other trees. At that time the British Islands appear to have been joined to themselves and the Continent across the upraised beds of the Irish Sea and the German Ocean. Races of men who used polished stone implements and sailed in canoes that were hollowed out of single oaks inhabited the country, together with certain species of oxen (now either extinct or domesticated), the elk, the beaver, the wolf, and other animals, such as the dog and the sheep, which are still indigenous. The climate was more excessive then than it is now--the summers being warmer and the winters colder. By-and-by, however, submergence ensued, the great wooded plain that seems once to have extended between Britain and the Continent disappeared below the waves, and the climate of this country became more humid. The old forests began to decay and the peat-mosses to increase, until by-and-by large areas in the low-grounds passed into the condition of dreary moor and morass, and even the brushwood and stunted trees of the hills died down and became enveloped in a mantle of bog-moss. A study of the present condition of the Scottish peat-mosses leads one to believe that the rate of increase is now much exceeded by the rate of decay, and that the eventual disappearance of the peat that clothes hill-tops and valley-bottoms is only a question of time. Draining and other agricultural operations have no doubt influenced to some extent this general decay of the peat-mosses; but there is reason to suspect that the change of climate, to which the decay of the peat is due, may really be owing to some cosmical cause. Quite recently an accomplished Norwegian botanist has come to similar conclusions regarding the peat-mosses of the Scandinavian peninsula. We have now traced the geological history of the Cheviot district down to the "Recent Period." From this point the story of the past must be continued by the archæologist, and into his province I will not trespass further than to indicate some of the more remarkable traces which the early human occupants of the upland valleys left behind them. Before doing so, however, I may briefly recapitulate the general results we have obtained from our rapid review of the glacial and post-glacial deposits. A study of these has taught us that the Cheviot Hills and the adjoining low-grounds participated in those arctic conditions under the influence of which all Scotland and a large portion of England were buried beneath a wide-spread _mer de glace_. The Cheviots themselves were completely smothered under a mass of glacier-ice which extended across the vale of the Tweed, and was continuous over the Lammermuirs with the vast sheet that filled all the great lowlands of central Scotland. But although the Cheviots were thus overwhelmed, they yet served to divide the ice-flow, for we find that the gelid masses moved outwards from the hills towards the valley of the Tweed, turning gradually away to east and south-east to creep over the north part of England. How far south the ice-sheet reached has not yet been determined, but its _moraine profonde_ or till may be traced to the edge of the Thames valley; and I have picked up in Norfolk ice-worn fragments of igneous rock, which have been derived from the Cheviots themselves, showing that Scottish ice actually invaded the low-grounds south of the Wash. Such severe glacial conditions, after continuing for a long time, were interrupted more than once by intervening periods characterised by a milder and more genial climate. The great _mer de glace_ then melted out of the valleys, and for aught that we can say the snow and ice may even have vanished from the hills themselves. Vegetation now covered the country, and herds of the mammoth, the old extinct ox, the Irish elk, the reindeer, the horse, and probably other creatures, roamed over the now deserted beds of the glaciers. It was probably at this time that Palæolithic man lived in Britain. He was contemporaneous with lions, elephants, rhinoceroses, hippopotami, mammoths, reindeer, and other animals of southern and northern habitats, the former living in England when the climate was genial, but being replaced by the northern species when the temperature began again to fall, and snow and glaciers once more reappeared and crept downwards and outwards from the hills. Towards the close of the interglacial period the land became submerged to a considerable extent, and species of arctic shells lived over the sites of the drowned land where the mammoth and its congeners had flourished. By-and-by the cold so far increased that another great ice-sheet filled up the shallow sea, and as it slowly ground over the face of the land and the sea-bottom, it scoured out and demolished to a large extent all loose fluviatile, lacustrine, and marine accumulations. When at last the ice melted away, it left the ground cumbered with stony clay, and with much gravel and sand and morainic débris. It is underneath these deposits that we yet obtain now and again fragments of the life of that interglacial epoch. But in all the regions visited by the last great incursion of the _mer de glace_, such relics are comparatively rare; it is only when we get beyond the districts that were overwhelmed that the ancient interglacial remains are well preserved. Beyond the southern extremity reached by the latest general ice-sheet--that is to say, in the regions south of the Humber, we find the country often sprinkled with tumultuous heaps and wide-spread sheets of gravel and brick-earth, which seem to owe their origin to the floods and torrents that escaped from the melting ice. These waters, sweeping over the land, carried along with them such relics of man and beast as lay at the surface, washing away interglacial river-deposits, and scattering the materials far and wide over the undulating low-grounds of central and eastern England. Mr. S. B. J. Skertchly, of the Geological Survey of England, has shown that such is the origin of the so-called "river-gravels" with ancient flint implements and mammalian remains in the districts watered by the Little Ouse, the Waveney, and other rivers in that part of England. These gravels could not possibly have been deposited by the present rivers, for they are found capping the hills at a height of more than eighty feet above the sources of the streams. The whole aspect of the gravels, indeed, betokens the action of rapid floods and torrents, such as must have been discharged abundantly in summer-time from the melting ice-sheet that lay at no great distance to the north. When the ice-sheet vanished away, it left the ground covered thickly in many places with its various deposits. Rivers and streams were thus often debarred from their old channels, and were forced to cut out for themselves new courses, partly in drifted materials, and partly in solid rock. A number of lakes then existed which have since been silted up. So long as glaciers lingered in the hill-valleys, the rivers seem to have flowed in greater volume than they now do. By-and-by the bare and treeless country became clothed with a luxuriant forest-growth, and was tenanted by animals, many of which are still indigenous to our country, while others have become locally extinct, such as wolf, beaver, and wild boar. In certain of the old lake-beds of the Cheviot district numerous remains of red-deer and other animals have been turned out in the search for marl, and in land drainage and reclamation operations--the red-deer antlers being sometimes of noble dimensions. It seems probable that in early post-glacial times our country was joined to the Continent and shared in a continental climate, the summers being then warmer and the winters colder than now. The men who lived in Britain after the final disappearance of the great glaciers used stone implements, which were often polished and highly finished, and they sailed in canoes, being probably a race of active hunters and fishers. They belong to the archæologist's "Neolithic" or new-stone period--the "Palæolithic" or old-stone period being of much older date, and separated, as I believe, from Neolithic times by the intervention of the last cold epoch of the Ice Age. To the forest epoch succeeded a time when the climate became very humid, a result which may have been due in large part to the separation of Britain from the Continent. It was then that the ancient forests began to decay, and peat-mosses to increase. How long such humid conditions of climate characterised the country we can hardly say, but we know that nowadays our peat-mosses do not grow so rapidly as they once did, and indeed almost everywhere the rate of decay is greater than the rate of increase. This points to a further change of climate, and brings us at once face to face with the present. And now a few words, in conclusion, as to the old camps and other remains that occur so abundantly in the valleys of the Cheviot Hills. In many of the hill-valleys, especially towards their upper reaches, as in the valleys of the Kale and the Bowmont, almost every hill is marked by the presence of one or more circular or oval camps or forts. They are generally placed in the most defensible positions, on the very tops of the hills or on projecting spurs and ridges. Most of them are of inconsiderable dimensions, and could not have afforded protection to any large number of men, for many hardly exceed one hundred feet in diameter. Not a few consist of only a single circular or oval rampart with an external ditch--the rampart being composed of the rude débris which was dug out to form the ditch. Others, however, are not only much larger (five to six hundred feet in diameter), but surrounded, in whole or in part, with two or more ramparts separated by intervening ditches; and I have noticed that as a rule the side which must have been most easily assailable was protected by several ramparts rising one above the other. From the extraordinary number of these hill-forts one has the impression that the upper valleys of the Cheviots must at one time have been thickly peopled, probably in pre-Roman times. It is easy to see that the camps or forts overlooking a valley often bear a certain relation to each other, as if the one had been raised to support the other, and not infrequently we can trace well-marked intrenchments extending across a hill-ridge, or along a hill-slope for a distance of not much short of a mile, and evidently having some strategic connection with the forts or camps in their vicinity. I found no trace of any "dwellings," either near the forts or in the vicinity of the terraces. The only indications of what may have been the walls of such appear within a fortified camp, called the Moat Hill, at Buchtrig. This is an isolated knoll of rock, which has been strongly fortified--large slabs and blocks of the porphyrite of which it is composed having been wedged out with infinite pains to form circular ramparts. The "walls" are of course nearly level with the ground and grassed over, but they indicate little square enclosures, which may very possibly have been huts closely huddled together. This fort is oval, and measures five hundred feet by two hundred and seventy. In the same neighbourhood we also meet with plentiful marks of ancient cultivation and with places of sepulture--all of which may without much doubt be referred to the same period as the camps and forts. The slopes of the hills are often marked with broad horizontal terraces, that remind one strongly of the "lazy-beds" of the Hebrides. They are evidently the "cultivated grounds" of the hill-men, and doubtless the hill-slopes were selected for various reasons, chief among which would be their retired and somewhat inaccessible position. The ease with which they could be drained and irrigated would be another of their recommendations; and we must bear in mind that at this early date the low-grounds were covered with forests and morasses, and therefore not so easily cultivated as the hill-slopes. Here and there we notice also little conical hillocks or tumuli. They were formerly much more numerous, and by-and-by they will doubtless all disappear. Numbers, even within recent years, have been pulled down, partly to clear the ground, and partly for the sake of the stones of which they are composed. This is much to be regretted; for their destruction simply means the obliteration of historical records, the loss of which can never be made good. I asked a farmer what had become of the tumuli which at one time, according to the Ordnance Survey map, were dotted over the hill behind his house. "If it's the wee knowes (knolls) you mean, I pu'd them down, for they were jist in the way. There was naething o' importance below the stanes, only a wheen worthless bits o' pottery!" And the worthy pointed to a heap of stones behind a neighbouring "dyke," where I afterwards found some fragments of the pottery which had been so ruthlessly demolished. These tumuli are no doubt old burial-places, and much information concerning the habits of our ancient predecessors might often be obtained by a careful examination of the mounds, when it is deemed essential to remove them. But, surely, after all, they might be spared, for they can seldom be so very much "in the way"; and, at all events, if they must be removed, might it not be well to communicate the fact of their approaching demolition to some local archæological society, or to any member of the Berwickshire Naturalists' Club, who for the sake of science would, I feel certain, do what was possible to preserve an accurate account of their contents? "Standing-stones" are met with now and again, either singly or in groups, and sometimes they form circles. It is most likely that they were raised by the same people who made the forts and tilled the horizontal "lazy-beds." One can only conjecture that they may have been designed as memorial stones, to mark the place where a chief or person of consequence was slain in battle. They may also mark burial-places, or indicate the site of some deed of prowess or other action or circumstance worthy of being remembered. Antiquarians at one time considered that all these stones were relics of druidical worship; but it is needless to say that this view has long been abandoned. That the ancient inhabitants of the Cheviots may have had some kind of religion is exceedingly probable, but it must have been of a very primitive kind, not more advanced than that of the North American Indians. Such are some of the more notable relics of the people who lived in the valleys of the Cheviot Hills in pre-Roman times. These valleys, as I have said, seem to have supported a numerous population, who tilled the slopes and probably hunted in the forests of the adjoining low-grounds. That they lived in fear of foes is sufficiently evident from the number of their intrenchments and fortified camps, to which they would betake themselves whenever their enemies appeared. What effect the Roman occupation had on the dwellers among these hills we cannot tell. The great "Watling Street" passes across the Cheviots, and there are some old circular forts and camps quite close to that wonderful road, along which many a battalion of Roman soldiers must have marched; and these forts, if of pre-Roman age, were not at all likely to have been held by the natives after Watling Street was made. In the remoter fastnesses of the hills, however, the old tribes may have continued to crop their "lazy-beds," to hunt, and tend their herds, during the Roman occupation, and the old forts may have been in requisition long after the last Roman had disappeared over the borders. But I have already, I fear, delayed too long over the old history of the Cheviot Hills, and must now draw my meagre sketches to a close. In my first paper I said that these hills were a _terra incognita_ to the tourist. Those who visit the district must not therefore expect to meet with hotel accommodation. But "knowing" pedestrians will not be much disturbed with this information, and will probably find, after they have concluded their wanderings, that the hospitality and general heartiness for which our stalwart Borderers were famous in other days are still as noteworthy characteristics as they used to be. V. The Long Island, or Outer Hebrides.[J] [J] _Good Words_, 1879. I. That long range of islands and islets which, extending from latitude 56° 47' N. to latitude 58° 32' N., acts as a great natural breakwater to protect the north-west coast of Scotland from the rude assaults of the Atlantic billows is not much visited by the ordinary tourist. During "the season" the steamers now and again, it is true, deposit a few wanderers at Tarbert and Stornoway, some of whom may linger for a shorter or longer time to try a cast for salmon in Loch Laxdail, while others, on similar piscatorial deeds intent, may venture inland as far as Gearaidh nah Aimhne (Garrynahine). Others, again, who are curious in the matter of antiquities, may visit the weird standing-stones of Callernish, or even brave the jolting of a "trap" along the somewhat rough road that leads from Tarbert to Rodel, in order to inspect the picturesque little chapel there, and take rubbings of its quaint tombstones with their recumbent effigies of knights, and Crusaders' swords, and somewhat incomprehensible Latinity. Occasionally a few bolder spirits may be tempted by the guide-books to visit Barra Head, with its ruddy cliffs and clouds of noisy sea-birds, or even to run north to the extremity of the Long Island to view the wonders of the Butt of Lewis. But, as a rule, the few summer visitants who are landed at Stornoway content themselves with a general inspection of the grounds about Sir James Mathieson's residence, while those who are dropped at Tarbert on Saturday are usually quite ready to depart on Monday with the steamer that brought them. The fact is that hotel accommodation in the Outer Hebrides is rather limited, and the means of locomotion through the islands is on the same slender scale. Those, therefore, who are not able and willing to rough it had better not venture far beyond Tarbert and Stornoway. When the islands are first approached they present, it must be confessed, a somewhat forbidding aspect. Bare, bleak rocks, with a monotonous rounded outline, crowd along the shore, and seem to form all but the very highest portions of the land that meet our view, while such areas of low-ground as we can catch a glimpse of appear to be everywhere covered with a dusky mantle of heath and peat. But, although the general character of the scenery is thus tame and sombre, yet there are certain districts which in their wild picturesqueness are hardly surpassed by many places in the northern Highlands, while one may search the coast-line of the mainland in vain for cliffs to compare with those gaunt walls of rock, against which the great rollers of the Atlantic continually surge and thunder. It is wonderful, too, how, under the influence of a light-blue sky, flecked with shining silvery clouds, the sombre peat-lands lighten up and glow with regal purple and ruddy brown. With such a sky above him, and with a lively breeze fresh from the Atlantic and laden with the sweetness of clover and meadow-hay and heather-bloom sweeping gaily past him, what wanderer in the Outer Hebrides need be pitied? And such days are by no means so rare in these islands as many a jaundiced Lowlander has maintained. It is true that heavy mists and drizzling rain are often provokingly prevalent, and I cannot forget the experience of a sad-hearted exile, who had resided continuously for a year in Lewis, and who, upon being asked what kind of climate that island enjoyed, replied: "Sir, it has no climate. There are nine months of winter, and three months of very bad weather." For myself, I can say that my experience of the climate in June, July, and early August of several years has been decidedly favourable. During those months I found comparatively few days in which a very fair amount of walking and climbing could not be accomplished with ease and pleasure, and that is a good deal more than one could venture to say of Skye and many parts of the west coast of the mainland. The greatest drawback to one's comfort are the midges, which in these islands are beyond measure bloodthirsty, and quite as obnoxious as the most carnivorous mosquitoes. Smoking, and all the other arts and devices by which the designs of these tiny pests are usually circumvented, have no effect upon the Hebridean vampires. In the low-grounds especially they make life a burden. But those who have already become acquainted with the Ross-shire midges, and yet have preserved their equanimity, may feel justified in braving the ferocity of the Hebridean hosts. And if they do so I believe they will be well repaid for their courage. To the hardy pedestrian, especially, who likes to escape from the beaten track laid down in guide-books, it will be a pleasure in itself to roam over a region which has not yet come entirely under the dominion of Mr. Cook. If he be simply a lover of the picturesque he will yet not be disappointed, and possibly he may pick up a few hints in these notes as to those districts which are most likely to repay him for his toil in reaching them. But if to his love of the picturesque he joins a taste for archæological pursuits, then I can assure him there is a rich and by no means exhausted field of study in the antiquities of the Long Island. Interesting, however, as are the relics of prehistoric and later times which one meets with, yet it is the geologist, perhaps, who will be most rewarded by a visit to these islands. The physical features of the Outer Hebrides are, as already stated, somewhat monotonous, but this is quite consistent with considerable variety of scenic effect. All the islands are not equally attractive, although the configuration of hills and low-grounds remains persistently the same from the Butt of Lewis to Barra Head. The most considerable island is that of which Lewis and Harris form the northern and southern portions respectively. By far the larger part of the former is undulating moorland, the only really mountainous district being that which adjoins Harris in the south. A good general idea of the moorlands is obtained by crossing the island from Stornoway to Garrynahine. What appeared at first to be only one vast extended peat-bog is then seen to be a gently-undulating country, coated, it is true, with much peat in the hollows, but clad for the most part with heath, through which ever and anon peer bare rocks and rocky débris. Now and again, indeed, especially towards the centre of the island, the ground rises into rough round-topped hills, sprinkled sparingly with vegetation. One of the most striking features of the low-grounds, however, is the enormous number of freshwater lakes, which are so abundant as to form no small proportion of the surface. They are, as a rule, most irregular in outline, but have a tendency to arrange themselves in two directions--one set trending from south-east to north-west, while another series is drawn out, as it were, from south-west to north-east. I am sure that I am within the mark in estimating the freshwater lakes in the low-grounds of Lewis to be at least five hundred in number. In the mountain-district the lakes are, of course, confined to the valleys, and vary in direction accordingly. Harris and the southern part of Lewis are wholly mountainous, and show hardly a single acre of level ground. The mountains are often bold and picturesque, especially those which are over 1600 feet in height. They are also exceedingly bare and desolate, the vegetation on their slopes being poor and scanty in the extreme. Some of the hills, indeed, are absolutely barren. In North Harris we find the highest peaks of the Outer Hebrides: these are the Clisham, 2622 feet, and the Langa, 2438 feet. The glens in this elevated district are often wild and rugged, such as the Bealach-Miavag and the Bealach-na-Ciste, both of which open on West Loch Tarbert. But amid all this ruggedness and wild disorder of broken crag and beetling precipice, even a very non-observant eye can hardly fail to notice that the general contour or configuration of the hills is smooth, rounded, and flowing, up to a rather well-marked level, above which the outline becomes broken and interrupted, and all the rounded and smoothed appearance vanishes. The contrast between the smoothly-flowing contour of the lower elevations and the shattered and riven aspect of the harsh ridges, sharp peaks, and craggy tors above, is particularly striking. The mammillated and dome-shaped masses have a pale, ghastly grey hue, their broad bare surfaces reflecting the light freely, while at higher elevations the abundant irregularities of the rocks throw many shadows, and impart a darker aspect to the mountain-tops. The appearances now described are very well seen along the shores of West Loch Tarbert. All the hills that abut upon that loch show smoothed and rounded faces, and this character prevails up to a height of 1600 feet, or thereabout, when all at once it gives way, and a broken, interrupted contour succeeds. Thus the top of the Tarcall ridge in South Harris is dark, rough, and irregular, while the slopes below are grey, smooth, and flowing. The same is conspicuously the case with the mountains in North Harris, the ruinous and sombre-looking summits of the Langa and the Clisham soaring for several hundred feet above the pale grey mammillated hills that sweep downwards to the sea. After having familiarised themselves with the aspect of the hills as seen from below, the lover of the picturesque, not less than the geologist, will do well to ascend some dominant point from which an extensive bird's-eye view can be obtained. For such purpose I can recommend the Tarcall and Roneval in South Harris, the Clisham and the Langa in North Harris, and Suainabhal in Lewis. The view from these hills is wonderfully extensive and very impressive. From Suainabhal one commands nearly all Lewis; and what a weird picture of desolation it is! An endless succession of bare, grey, round-backed rocks and hills, with countless lakes and lakelets nestling in their hollows, undulates outwards over the districts of Uig and Pairc. Away to the north spread the great moorlands with their lochans, while immediately to the south one catches a fine panoramic view of the mountains of Harris. And then those long straggling arms of the sea, reaching into the very heart of the island--how blue, and bright, and fresh they look! I suppose the natives of the Lewis must have been fishermen from the very earliest times. It seems hardly possible otherwise to believe that the bare rocks and peat-bogs, which form the major portion of its surface, could ever have supported a large population; and yet there is every evidence to show that this part of the Long Island was tolerably well populated in very early days. The great standing-stones of Callernish and the many other monoliths, both solitary and in groups, that are scattered along the west coast of Lewis, surely betoken as much. And those curious round towers, or places of refuge and defence, which are so well represented in the same district, although they may be much younger in date than the monoliths of Callernish, tell the same tale. From the summits of the Clisham and the Langa the view is finer than that obtained from Suainabhal. The former overlook all the high-grounds of Harris and Lewis, and the monotonous moors with their countless straggling lakes and peaty tarns. Indeed, they dominate nearly the whole of the Long Island, the hills of distant Barra being quite distinguishable. Of course, the lofty island of Rum, and Skye with its Coolins, are both clearly visible, the whole view being framed in to eastward by the mountains of Ross and Sutherland. On a clear day, which, unfortunately, I did not get, one should be quite able to see St. Kilda. Hardly less extensive is the view obtained from Roneval (1506 feet) in the south of Harris. Far away to the west lie St. Kilda and its little sister islet of Borerey. Southwards stretch the various islands of the Outer Hebrides--North Uist, Benbecula, South Uist, and Barra. How plainly visible they all are--a screen of high mountains facing the Minch, and extending, apparently, along their whole eastern margin--with broad lake-dappled plains sweeping out from the foot-hills to the Atlantic. In the east, Skye with its spiky Coolins spreads before one, and north of Skye we easily distinguish Ben Slioch and the mountains of Loch Maree and Loch Torridon. South Harris lies, of course, under our feet, and it is hard to give one who has not seen it an adequate notion of its sterile desolation. Round-backed hills and rocks innumerable, scraped bare of any soil, and supporting hardly a vestige of vegetation; heavy mountain-masses with a similar rounded contour, and equally naked and desolate; blue lakelets scattered in hundreds among the hollows and depressions of the land: such is the general appearance of the rocky wilderness that stretches inland from the shores of the Minch. Then all around lies the great blue sea, shining like sapphire in the sun, and flecked with tiny sails, where the fishermen are busy at their calling. From what has now been said, it will readily be understood that there is not much cultivable land in Harris and the hilly parts of Lewis. What little there is occurs chiefly along the west coast, a character which we shall find is common to most of the islands of the Outer Hebrides. In the neighbourhood of Stornoway, and over considerable areas along the whole west coast of Lewis, the moorlands have been broken in upon by spade and plough, with more or less success. But natural meadow-lands, such as are frequently met with on the west side of many of the islands both of the Outer and Inner Hebrides, are not very common in Lewis. One of the most notable features of the hillier parts of the Long Island are the enormous numbers of loose stones and boulders which are everywhere scattered about on hill-top, hill-side, and valley-bottom. Harris is literally peppered with them, and they are hardly less abundant in the other islands. They are of all shapes and sizes--round, sub-angular, and angular. One great block in Barra I estimated to weigh seven hundred and seventy tons. Many measure over three or four yards across, while myriads are much smaller. These boulders are sometimes utilised in a singular way. In Harris, there being only one burial-place, the poor people have often to carry their dead a long distance, and this of course necessitates resting on the journey. To mark the spot where they have rested, the mourners are wont to erect little cairns by the road-side, many of which are neatly built in the form of cones and pyramids, while others are mere shapeless heaps of stones thrown loosely together. Instead of raising cairns, however, they occasionally select some boulder, and make it serve the purpose by canting it up and inserting one or more stones underneath. Occasionally I have seen in various parts of the mainland great boulders cocked up at one end in the same way. Some of these may be in their natural position, but as they often occupy conspicuous and commanding situations, I am inclined to think that the cromlech-builders may have tampered with them for memorial purposes. The present custom of the Harris men may therefore be a survival from that far-distant period when Callernish was in its glory. North Uist is truly a land of desolation and dreariness. Bare, rocky hills, which are remarkable for their sterile nakedness even in the Long Island, form the eastern margin, and from the foot of these the low, undulating rocky and peaty land stretches for some ten or twelve miles to the Atlantic. The land is everywhere intersected by long, straggling inlets of sea-water, and sprinkled with lakes and peaty tarns innumerable. Along the flat Atlantic coast, which is overlooked by some sparsely-clad hills, are dreary stretches of yellow sand blown up into dunes. Near these are a few huts and a kirk and manse. Not a tree, not even a bush higher than heather, is to be seen. Peat, and water, and rock; rock, and water, and peat--that is North Uist. The neighbourhood of Lochmaddy, which is the residence of a sheriff-substitute, and rejoices besides in the possession of a jail, is depressing in the extreme. It is made up of irregular bits of flat land all jumbled about in a shallow sea, so that to get to a place one mile in direct distance you may have to walk five or six miles, or even more. I could not but agree with the natives of the more coherent parts of the Long Island, who are wont to declare that Lochmaddy is only "the clippings of creation"--the odds and ends and scraps left over after the better lands were finished. North Uist, however, boasts of some interesting antiquities--Picts' houses, and a great cairn called the Barp, inside of which, according to tradition, rest the remains of a wicked prince of the "good old days." Notwithstanding these, there are probably few visitors who will not pronounce North Uist to be a dreary island. Benbecula is precisely like North Uist, but it lacks the bare mountains of the latter. There is only one hill, indeed, in Benbecula; all the rest is morass, peat, and water. Massive mountains fringe all the eastern shores of South Uist, and send westward numerous spurs and foot-hills that encroach upon the "machars," or good lands, so as to reduce then to a mere narrow strip, bordering on the Atlantic. Save the summits of Beinn Mhor (2033 feet) and Hecla (1988 feet), which are peaked and rugged, all the hills show the characteristic flowing outline which has already been described in connection with the physical features of Harris. The low-grounds are, as usual, thickly studded with lakes, and large loose boulders are scattered about in all directions. Barra is wholly mountainous, and, except that it is somewhat less sterile, closely resembles Harris in its physical features, the hills being smoothed, rounded, and bare, especially on the side of the island that faces the Minch. Of the smaller islands that lie to the south, such as Papey, Miuley, and Bearnarey, the most noteworthy features are the lofty cliffs which they present to the Atlantic. For the rest, they show precisely the same appearances as the hillier and barer portions of the larger islands--rounded rocks with an undulating outline, dotted over with loose stones and boulders, and now and again half-smothered in yellow sand, which the strong winds blow in upon them. There is thus, as I have said, considerable uniformity and even monotony throughout the whole range of the Outer Hebrides. I speak, however, chiefly as a geologist. An artist, no doubt, will find infinite variety, and as he wends his way by moorland, or mountain-glen, or sea-shore, scenes are constantly coming into view which he will be fain to transfer to his sketch-book. The colour-effects, too, are often surprisingly beautiful. When the rich meadow-lands of the west coast are in all their glory, they show many dazzling tints and shades, the deep tender green being dashed and flushed with yellow, and purple, and scarlet, and blue, over which the delighted eye wanders to a belt of bright sand upon the shore, and the vast azure expanse of the Atlantic beyond. Inland are the heath-clad moors, sprinkled with grey boulders and masses of barren rock, and interspersed with lakes, some of which are starred with clusters of lovely water-lilies. Behind the moorlands, again, rise the grim, bald mountains, seamed and scarred with gullies, and in their very general nakedness and sterility offering the strongest contrast to the variegated border of russet moor, and green meadow, and yellow beach that fringe the Atlantic coast. All through the islands, indeed, the artist will come upon interesting subjects. A most impressive scene may sometimes be witnessed on crossing the North Ford, between North Uist and Benbecula. At low-water, the channel or sound between these two islands, which is five miles in breadth, disappears and leaves exposed a wide expanse of wet sand and silt, dotted with black rocks and low tangle-covered reefs and skerries. On the morning I passed over, ragged sheets of mist hung low down on the near horizon, half-obscuring and half-revealing the stony islets, and crags, and hills that lay between the ford and the Minch. Seen through such a medium, the rocks assumed the most surprising forms, sometimes towering into great peaks and cliffs, at other times breaking up, as it were, into low reefs and shoals, and anon dissolving in grey mist and vapour. At other times the thin cloud-curtain would lift, and then one fancied one saw some vast city with ponderous walls and battlements, and lofty towers and steeples, rising into the mist-wreaths that hung above it, while from many points on the Benbecula coast, where kelp was being prepared, clouds of smoke curled slowly upwards, as if from the camp-fires of some besieging army. The track of the ford winds round and about innumerable rocks, upon which a number of "natives," each stooping solitary and silent to his or her work, were reaping the luxuriant seaweed for kelp-making. Their silence was quite in keeping with the general stillness, which would have been unbroken but for the harsh scream of the sea-birds, as they ever and anon rose scared from their favourite feeding-grounds while we plodded and plashed on our way. The artist who could successfully cope with such a scene would paint a singularly weird and suggestive picture. But, to return to the physical features of the Long Island, what, we may ask, is the cause of that general monotony of outline to which reference has so frequently been made? At first we seem to get an answer to our question when we are told that the islands of the Outer Hebrides are composed chiefly of one and the same kind of rock. Everyone nowadays has some knowledge of the fact that the peculiar features of any given district are greatly due to the character and arrangement of the rock-masses. For example, who is not familiar with the outline of a chalk country, as distinguished from the contour of a region the rocks of which are composed, let us say, of alternating beds of limestone and sandstone and masses of old volcanic material? The chalk country, owing to the homogeneousness of its component strata, has been moulded by the action of weather and running water into an undulating region with a softly-flowing outline, while the district of composite formation has yielded unequally to the action of Time's workers--rains, and frosts, and rivers--and so is diversified with ridge, and escarpment, and knolls, and crags. When, therefore, we learn that the Outer Hebrides are composed for the most part of the rock called _gneiss_ and its varieties, we seem to have at once found the meaning of the uniformity and monotony. It is true that although pink and grey gneiss and schistose rocks prevail from the Butt of Lewis to Barra Head, yet there are some other varieties occasionally met with--thus soft red sandstone and conglomerate rest upon the gneissic rocks near Stornoway, but they occur nowhere else throughout the Long Island. Now and again, however, the gneiss gives place to granite, as on the west coast of Lewis near Carloway; and here and there the strata are pierced by vertical dykes and curious twisted and reticulated veins of basalt-rock. All these, however, hold but a minor and unimportant place as constituents of the islands. Gneiss is beyond question the most prevalent rock, and we seem justified in assigning the peculiar monotony of the Outer Hebridean scenery to that fact. But when we come to examine the matter more attentively, we find that there is still some important factor wanting. We have not got quite to the solution of the question. When we study the manner in which the gneiss and gneissic rocks disintegrate and break up at the sea-coast or along the flanks of some rugged mountain-glen, we see they give rise to an irregular uneven surface. They do not naturally decompose and exfoliate into rounded dome-shaped masses, such as are so commonly met with all through the islands, but rather tend to assume the aspect of rugged tors, and peaks, and ridges. The reason for this will be more readily understood when it is learned that the gneissic rocks of the Outer Hebrides are for the most part arranged in strata, which, notwithstanding their immense antiquity--(they are the oldest rocks in Europe)--and the many changes they have undergone, are yet, as a rule, quite distinguishable. The strata are seldom or never horizontal, but are usually inclined at a high angle, either to north-east or south-west, although sometimes, as in the vicinity of Stornoway, the "dip" or inclination of the beds is to south-east. Throughout the major portion of the Long Island, however, the outcrop of the strata runs transversely across the land from south-east to north-west. Now we know that when this is the case strata of variable composition and character give rise to long escarpments and intervening hollows--the escarpments marking the outcrops of the harder and more durable beds, and the hollows those strata that are softer and more easily eroded by the action of the denuding forces, water and frost. When the dip of the strata is north-east we expect the escarpments to face the south-west, and the reverse will be the case when the strata incline in the opposite direction. Seeing then that the Outer Hebrides are composed chiefly of gneissic rocks and schists which yield unequally to the weather, and which, in the course of time, would naturally give rise to lines of sharp-edged escarpments or ridges and intervening hollows, with now and again massive hills and mountains showing great cliffs and a generally broken and irregular outline, why is it that such rugged features are so seldom present at low levels, and are only conspicuous at the very highest elevations? The rocks of the Outer Hebrides are of immense antiquity, and there has therefore been time enough for them to assume the irregular contour which we might have expected. But in place of sharp-rimmed escarpments, and tors, and broken shattered ridges, we see everywhere a rounded and smoothly-flowing configuration which prevails up to a height of 1600 feet or thereabout, above which the rocks take on the rugged appearance which is natural to them. By what magic have the strata at the lower levels escaped in such large measure from the action of rain and frost, which have furrowed and shattered the higher mountain-tops? I have said that long lines of escarpment and ridges, corresponding to the outcrops of the harder and more durable strata, are not apparent in these islands. A trained eye, however, is not long in discovering that such features, although masked and obscured, are yet really present. The round-backed rocks are drawn out, as it were, in one persistent direction, which always agrees with the _strike_ or outcrop of the strata; and in many districts one notices also that long hollows traverse the land from south-east to north-west in the same way. Such alternating hollows and rounded ridges are very conspicuous in Barra and the smaller islands to the south, and they may likewise be noted in most of the larger islands also. Looking at these and other features, the geologist has no hesitation in concluding that the whole of the islands have been subjected to some powerful abrading force, which has succeeded to a large extent in obliterating the primary configuration of the land. The rough ridges have been rounded off, the sharp escarpments have been bevelled, the abrupt tors and peaks have been smoothed down. Here and there, it is true, the dome-shaped rock-masses are beginning again to break up under the action of the weather so as to resume their original irregular configuration. And, doubtless, after the lapse of many ages, rain and frost will gradually succeed in destroying the present characteristic flowing outlines, and the islands will then revert to their former condition, and rugged escarpments, sharp peaks, and rough broken hummocks and tors will again become the rule. But for a long time to come these grey Western Islands will continue to present us with some of the most instructive examples of rounded and mammillated rock-masses to be met with in Europe. From Barra Head in Bearnarey to the Butt of Lewis we are constantly confronted by proofs of the former presence of that mysterious abrading power, which has accommodated itself to all the sinuosities of the ground, so that from the sea-level up to a height of 1600 feet at least, the eye rests almost everywhere upon bare round-backed rocks and smoothed surfaces. II. In the preceding article I have described the peculiar configuration of the Long Island--rounded and flowing for the most part--and have pointed out how that softened outline is not such as the rocks would naturally assume under the influence of the ordinary agents of erosion with which we are familiar in this country. The present contour has superseded an older set of features, which, although highly modified or disguised, and often well-nigh obliterated, are yet capable of being traced, and are, no doubt, the conformation assumed by the rocks under the long-continued action of rain and frost and running water. We have now to inquire what it was that removed or softened down the primal configuration I refer to, and gave to the islands their present monotonous, undulating contour. Any one fresh from the glacier-valleys of Switzerland or Norway could have little doubt as to the cause of the transformation. The smoothed and rounded masses of the Outer Hebrides are so exactly paralleled by the ice-worn, dome-shaped rocks over which a glacier has flowed, that our visitor would have small hesitation in ascribing to them a similar origin; and the presence of the countless perched blocks and boulders which are scattered broadcast over the islands would tend to confirm him in his belief. A closer inspection of the phenomena would soon banish all doubt from his mind; for, on the less-weathered surfaces, he would detect those long parallel scratches and furrows which are the sure signs of glacial action, while, in the hollows and over the low-grounds, he would be confronted with that peculiar deposit of clay and sand and glaciated stones and boulders which are dragged on underneath flowing ice. Having satisfied ourselves that the rounded outline of the ground is the result of former glacial action, our next step is to discover, if we can, in what direction the abrading agent moved. Did the ice, as we might have supposed, come out of the mountain-valleys and overflow the low country? If that had been the case, then we should expect to find the glacial markings radiating outwards in all directions from the higher elevations. Thus the low-grounds of Uig, in Lewis, should give evidence of having been overflowed by ice coming from the Forest of Harris; the undulating, rocky, and lake-dappled region that extends between Loch Roag and Loch Erisort should be abraded and striated from south-west to north-east. Instead of this, however, the movement has clearly been from south-east to north-west. All the prominent rock-faces that look towards the Minch have been smoothed off and rounded, while in their rear the marks of rubbing and abrading are much less conspicuous. It is evident that the south-east exposure has borne the full brunt of the ice-grinding--the surfaces that are turned in the opposite direction, or towards the Atlantic, having been in a measure protected or sheltered by their position. The striations or scratches that are seen upon the less-weathered surfaces point invariably towards the north-west, and from their character and the mode in which they have been graved upon the rock, we are left in no doubt as to the trend of the old ice-plough--which was clearly from south-east to north-west. Nor is it only the low-grounds that are marked in this direction. Ascend Suaina (1300 feet), and you shall find it showing evident signs of having been abraded all over, from base to summit. The same, indeed, is the case with all the hills that stretch from sea to sea between Uig and Loch Seaforth. Beinn Mheadonach, Ceann Resort, Griosamul, and Liuthaid, are all strongly glaciated from south-east to north-west. North and South Harris yield unequivocal evidence of having been overflowed by ice which did not stream out of the mountain-valleys, but crossed the island from the Minch to the Atlantic. A number of mountain-glens, coming down from the Forest of Harris, open out upon West Loch Tarbert, and these we see have been crossed at right angles by the ice--the mountains between them being strongly abraded from south-east to north-west. It is the same all over South Harris, which affords the geologist every evidence of having been literally smothered in ice, which has moved in the same persistent direction. The rock-faces that look towards the Minch are all excessively naked; they have been terribly ground down and scraped, and the same holds good with every part of the island exposed to the south-east. Now, the mode in which the rocks have been so ground, scraped, rounded, and smoothed betokens very clearly the action of land-ice, and not of floating-ice or icebergs. The abrading agent has accommodated itself to all the sinuosities of the ground, sliding into hollows and creeping out of them, moulding itself over projecting rocks, so as eventually to grind away all their asperities, and convert rugged tors and peaks into round-backed, dome-shaped masses. It has carried away the sharp edges of escarpments and ridges, and has deepened the intervening hollows in a somewhat irregular way, so that now these catch the drainage of the land and form lakes. Steep rocks facing the Minch have been bevelled off and rounded atop, while in their rear the ice-plough, not being able to act with effect, has not succeeded in removing the primeval ruggedness of the weathered strata. I have said that the movement of the ice was from south-east to north-west. But a close examination of the ice-markings will show that the flow was very frequently influenced by the form of the ground. Minor features it was able to disregard, but some prominent projecting rock-masses succeeded in deflecting the ice that flowed against them. For example, if we study the rocks in North Harris, we shall find that the Langa and the Clisham have served as a wedge to divide the ice, part of which flowed away into Lewis, while the other current or stream crept out to sea by West Loch Tarbert. The Langa and the Clisham, indeed, raised their heads above the glacier mass--they were islets in a sea of ice. It is for this reason that they and the Tarcull ridge in South Harris have not been smoothed and abraded, but still preserve their weathered outline. All surfaces below a height of 1600 feet which are exposed to the south-east, and which have not been in recent times broken up by the action of rain and frost, exhibit strongly-marked glaciation. But above that level no signs of ancient ice-work can be recognised. We see now why it is that the hill-slopes opposite the Minch should, as a rule, be so much more sterile than those which slope down to the Atlantic. The full force of the ice was exerted upon the south-east front, in the rear of which there would necessarily be comparatively "quiet" ice. For the same reason we should expect to find much of the rock débris which the ice swept off the south-east front sheltering on the opposite side. Neither clay nor sand nor stones would gather under the ice upon the steep rocks that face the Minch. The movement there was too severe to permit of any such accumulation. But stones and clay and sand were carried over and swept round the hills, and gradually accumulated in the rear of the ice-worn rocks, just in the same way as gravel and sand are heaped up behind projecting stones and boulders in the bed of a stream. Hence it is that the western margin of Harris is so much less bleak than the opposite side. Considerable taluses of "till," as the sub-glacial débris is called, gather behind the steeper crags, and ragged sheets of the same material extend over the low-grounds. All the low-grounds of Lewis are in like manner sprinkled with till. Over that region the ice met with but few obstacles to its course, and consequently the débris it forced along underneath was spread out somewhat equally. But wherever hills and peaks and hummocks of rock broke the regularity of the surface, there great abrasion took place and no till was accumulated. Thus the position and distribution of this sub-glacial débris or bottom-moraine tell the same tale as the abraded rocks and glacial striæ, and clearly indicate an ice-flow from the south-east. This is still further proved by the manner in which the upturned ends of the strata are frequently bent over underneath the till in a north-westerly direction, while the fragments dislodged from them and enclosed in the sub-glacial débris stream away as it were to the same point of the compass. Not only so, but in the west of Lewis, where no red sandstone occurs, we find boulders of red sandstone enclosed in the till, which could not have been derived from any place nearer than Stornoway. In other words, these boulders have travelled across the island from the shores of the Minch to the Atlantic sea-board. Having said so much about the glaciation of Lewis and Harris, I need not do more than indicate very briefly some of the more interesting features of the islands further south. I spent some time cruising up and down the Sound of Harris, and found that all the islets there had been ground and scraped by ice flowing in the normal north-west direction, and sub-glacial débris occurs on at least one of the little islands--Harmetrey. But all the phenomena of glaciation are met with in most abundance in the dreary island of North Uist. The ridge of mountains that guards its east coast has been battered, and ground down, and scraped bare in the most wonderful manner, while the melancholy moorlands are everywhere sprinkled with till, full of glaciated stones, many of which have travelled west from the coast range. Benbecula shows in like manner a considerable sprinkling of till, and the trend of the glacial striæ is the same there as in North Uist, namely, a little north of west. There are no hills of any consequence in Benbecula, but the highly-abraded and barren-looking mountains that fringe the eastern margin of North Uist are continued south in the islands of Roney and Fuiey, either of which it would be hard to surpass as examples of the prodigious effect of land-ice in scouring, scraping, and grinding the surface over which it moves. South Uist presents the same general configuration as North Uist, its east coast being formed of a long range of intensely glaciated mountains, in the rear of which ragged sheets and heaps of sub-glacial débris are thrown and scattered over the low, undulating tract that borders the Atlantic. No part of either Benbecula or North Uist has escaped the action of ice, but in South Uist that knot of high-ground which is dominated by the fine mountains of Beinn Mhor and Hecla towered above the level of the glacier-mass, and have thus been the cause of considerable deflection of the ice-flow. The ice-stream divided, as it were, part flowing round the north flank of Hecla, and part streaming past the southern slopes of Beinn Mhor. But the ice-flow thus divided speedily reunited in the rear of the mountains, the southern stream creeping in from the south-east, and the northern stream stealing round Hecla towards the south-west. The track of this remarkable deflection and reunion is clearly marked out by numerous striæ all over the low-grounds that slope outwards to the Atlantic coast. The till, it need hardly be added, affords the same kind of evidence as the sub-glacial deposits of the other islands, and points unmistakably to a general ice-movement across South Uist from the Minch to the Atlantic. The influence which an irregular surface has in causing local deflections of an ice-flow is also well seen in Barra, where the striæ sometimes point some 5° or 10°, and sometimes 25° and even 35° north of west--these variations being entirely due to the configuration of the ground. This island is extremely bare in many places, more especially over all the region that slopes to the Minch. The Atlantic border is somewhat better covered with soil, as is the case with South Uist and the other islands already described. Vatersey, Saundry, Papey, Miuley, and Bearnarey, are all equally well glaciated; but as they show little or no low-ground with gentle slopes, they have preserved few traces of sub-glacial débris. In this respect they resemble the rockier and hillier parts of the large islands to the north. Till, however, is occasionally met with, as for example on the low shores of Vatersey Bay, and on the southern margin of Miuley. Doubtless, if it were carefully looked for it would be found sheltering in patches in many nooks and hollows, protected from the grind of the ice that advanced from the south-east. I saw it in several such places in the islet of Bearnarey, where the striæ indicated an ice-flow as usual towards the north-west. We have now seen that the whole of the Long Island has been ground, and rubbed, and scraped by land- or glacier-ice which has traversed the ground in a prevalent south-east and north-west direction. We have seen also that this ice attained so great a thickness that it was able to overflow all the hills up to a height of 1600 feet above the sea. It is needless to say that such a mass could not have been nurtured on the islands themselves. They have no gathering grounds of sufficient extent, and if they had, the ice would not have taken the peculiar direction it did. Instead of flowing across the islands it would have radiated outwards from the mountain-valleys. Where, then, did the ice come from? Looking across the Minch we see Skye and the mountains of the north-west Highlands, and those regions, as we know, have also been subjected to extreme glaciation. From the appearances presented by the mountains of Ross-shire we are compelled to believe that all that region was buried in ice up to a height of not less than 3000 feet--the ice-sheet was probably even as much as 3500 feet in thickness. The evidence shows that the under portion of this vast ice-sheet flowed slowly off the country into the Minch by way of the great sea-lochs. Thus we know that an enormous mass crept down Loch Carron and united with another great stream stealing out from the mountains of Skye, to flow north through the hollows of Raasay Sound and the Inner Sound into the Minch. So deep was the ice that it completely smothered the island of Raasay (1272 feet high) and overflowed all the lofty trappean table-lands of Skye. From the Coolins, as a centre-point, another movement of the ice-sheet was towards the south-west, against the islands of Rum, Cannay, and Eigg. Further north similar vast masses of ice streamed out into the Minch, from Loch Torridon, Gairloch, Loch Ewe, and Loch Broom. The direction of the glaciation in the north of Skye, which is towards north-west, shows that the glacier-mass which overflowed that area must eventually have reached the shores of the Long Island. In short, there cannot be a reasonable doubt that the immense sheet of ice that streamed off the north-west Highlands must have filled up entirely the basin of the Minch, and thereafter streamed across the Outer Hebrides. But it may be objected that if the Outer Hebrides were overflowed by ice that streamed from the mainland across the north end of Skye, we ought to get many fragments of Skye rocks and Ross-shire rocks too in the sub-glacial débris or till of Lewis and Harris, and the north end of North Uist. But all such fragments are apparently wanting. True, there are bits of stone like the igneous rocks of Skye often met with in the Hebridean till, but as veins or dykes of precisely the same kind of rock occur in the Long Island itself, we cannot say that the stones referred to are other than native. A little reflection will show us, however, that it is extremely improbable indeed that stones derived from Skye and the mainland should ever have been dragged on under the ice, and deposited amongst the till of the Long Island. There is only one part of the whole Outer Hebrides where we might have anticipated that fragments from the mainland should occur; and there, sure enough, they put in an appearance. But before I attempt to explain the non-occurrence of Skye rocks in the till of the Outer Hebrides, let me show in a few words what the glaciation of the Long Island, Skye, and the north-west Highlands teaches us as to the general aspect presented by the ice-sheet. The height reached by the surface of the ice in Ross-shire and the Long Island respectively indicates of course that the main movement was from the mainland. We must conceive of an immense sheet of solid ice filling up all the inequalities of the land, obliterating the glens, and sweeping across the hill-tops; and not only so, but occupying the wide basin of the Minch to the entire exclusion of the sea, the surface of the ice rising so high that it overtopped the whole of the Outer Hebrides, and left only the tips of a few of the higher mountains uncovered. The slope of the surface was persistently outwards from the mainland, and the striation of the Long Island indicates clearly that the dip or inclination of that surface was towards the north-west. Nay, more than this, we are now enabled for the first time to say with some approach to certainty what was the precise angle of that inclination. If we take the upper surface of the ice in Ross-shire to have been 3000 feet (and it was not less), then the slope between the mainland and the Outer Hebrides was only 25 feet in the mile, or about 1 in 210. It is quite possible, however, and even probable, that the actual height attained by the ice-sheet in the north-west Highlands was more than 3000 feet. I think it may yet turn out to have been 3500 feet, and if this were so it would give an inclination for the surface of the ice of about 35 feet in the mile. In either case the slope was so very gentle that to the eye it would have appeared like a level plain. Over the surface of this plain would be scattered here and there a solitary big erratic or two, while in other places long trains of large and small angular boulders would stream outwards. All these would be derived from such mountain in Skye and the mainland as were able to keep their heads above the level of the ice-flow; while a few also might be dislodged by the frost and rolled down upon the glacier from the tips of the Clisham and the Langa in Harris, and Hecla and Beinn Mhor in South Uist. Every such block, it is evident, would be carried across the buried Hebrides, out into the Atlantic in the direction indicated by the glaciation of the Long Island--that is, towards the north-west. But while the upper strata of the ice doubtless followed that particular course, it is obvious that this could not be the case with the under portion of the great sheet, the path of which would be controlled in large measure by the form of the ground over which the ice moved. The upper strata that overflowed the Outer Hebrides, as we have seen, were locally deflected again and again by important obstacles, and it is quite certain that the same would take place with the deeper portions of the ice-flow. It is well known that the sea along the inner margin of the Long Island is very deep. In many places it reaches a depth of 600 feet, and occasionally the sounding-lead plunges down for upwards of 700 feet. It would seem, however, that these great depths did not exist before the advent of the ice-sheet, but that the bottom of the Minch along the eastern borders of the Long Island was then some 250 or 300 feet shallower than now, the floor of the sea having since been excavated in the manner I shall presently describe. It is quite apparent, therefore, that the long ridge of the Outer Hebrides must have offered an insuperable obstacle to the direct passage of the bottom-ice out to the Atlantic. Here was a great wall of rock shooting up from the floor of the Minch, at a high angle, to a height ranging in elevation from 400 feet to upwards of 3000 feet. It is simply impossible that the lower strata of the ice that occupied the bed of the Minch could climb that precipitous barricade. They were necessarily deflected, one portion creeping to north-east and another to south-west, but both hugging the great wall of rock all the way. We see precisely the same result taking place in the bed of every stream. Let us stand upon an almost submerged boulder, and note how the water is deflected to right and left, and we shall observe at the same time that the boulder, by obstructing the current, forces the water downwards upon the bed of the stream, the result being that a hollow is dug out in front. Now, in a similar manner, the ice, squeezed and pressed against the Hebridean ridge by the steady flow of the great current that crossed the Minch, necessarily acted with intense erosive force upon its bed. Hence in the course of time it scooped out a series of broad deep trenches along the whole inner margin of the Long Island, the amount of the excavation reaching from 200 to 300 feet. Similar excavated basins occur in like positions opposite all the precipitous islands of the Inner Hebrides. Wherever, indeed, the ice-sheet met with any great obstruction to its flow, there excessive erosion took place, and a more or less deep hollow was dug out in front of the opposing cliff, or crag, or precipitous mountain. While, therefore, the upper strata of the ice-sheet overflowed the Outer Hebrides from south-east to north-west, the under portions of the same great ice-flow were compelled by the contour of the ground to creep away to north-east and south-west, until they could steal round the ridge and so escape outwards to the Atlantic. This being the case, we have a very simple and obvious explanation of the absence of Skye rocks in the till of the Long Island. One sees readily enough that the sub-glacial débris dragged across the Minch would naturally be carried away to south-west and north-east by the "under-tow" or deflected ice. It is quite impossible that any Skye fragments or bits of rock from the mainland could travel over the bed of the Minch, and then be pushed up the precipitous rock wall of the Long Island. There is only one place in all the Outer Hebrides where we might expect to meet with extraneous boulders in the till, and that is in the north of Lewis, where the land shelves gently into the sea, and the great rocky ridge terminates. Here the under-strata of the ice would begin to steal up upon the land, favoured by its gentle inclination, and in that very place accordingly we meet with a deposit of till in which are found many boulders of a hard red sandstone, and some of various porphyries which are quite alien to the Long Island. Moreover, the till itself in that locality is much more of a clay than the usual sub-glacial débris in other parts of Lewis, and contains numerous fragments of sea-shells. All this is quite in keeping with the other evidence. The extreme north end of Lewis was overflowed by the under-current that crept up the bed of the Minch, hugging the Hebridean ridge, and dragging along with it a muddy mass interspersed with the shells and other marine exuviæ that lay in its path, and numerous stones, some of which may have come from Skye, while others were derived from the mainland. I have already said enough, perhaps, about the abrasion of the Hebrides, but I may add a few words upon the origin of the freshwater lakes. Many of these rest in complete rock-basins; others, again, seem to lie partly upon solid rock and partly upon till; while yet others appear to occupy mere shallow depressions in the surface of the till. All of them thus owe their origin to the action of the ice-sheet. As one might have expected, the great majority lie along the outcrop of the gneissic strata, which, as a rule, corresponds pretty closely to the flow of the ice. Hence the general trend of the lakes is from south-east to north-west. In many cases in fashioning these rock-basins the ice has merely deepened in an irregular manner previously existing hollows, which are now, of course, filled with water. In not a few places, however, the lakes are drawn out in other directions--this being due usually to changes in the strike or outcrop of the strata. For example, over a considerable district in the south of Lewis many lake-hollows extend from south-west to north-east, or at right angles to the direction of the ice-flow. Such lakes are usually dammed up at one or both extremities by glacial débris. Thus most of the features characteristic of the Outer Hebrides owe their origin directly or indirectly to the action of that great sheet of ice which swept over the islands during what is called the Glacial Period. And there is no region in northern Europe where the immensity of the abrading agent can be more vividly realised. From a study of the phenomena there exhibited we for the first time obtain a definite idea of the surface-slope, and are able to plumb the old ice-sheet, and ascertain with some approach to accuracy its exact thickness. In the deeper parts of the area, between the mainland and the Long Island, its thickness was not less than 3800 feet. Of course this great depth of ice could not have been derived exclusively from the snow that fell on the mountains of the north-west Highlands. Doubtless the precipitation took place over its whole surface, just as is the case in Greenland and over the Antarctic continent. The winter cold must have been excessive, but the precipitation necessary to sustain such a mass of ice implies great evaporation; in other words, the direct heat of the sun _per diem_ in summer-time was probably considerably in excess of what it is now in these latitudes. The west and south-west winds must have been laden with moisture, the greater portion of which would necessarily fall in the form of snow. We see something analogous to this taking place in the Antarctic regions at the present day. That quarter of the globe has its summer in perihelion, and, therefore, must be receiving then more heat _per diem_ than our hemisphere does in its summer season, which, as every one knows, happens when the earth is furthest removed from the sun. But, notwithstanding this, the summer of the Antarctic continent is cold and ungenial--the presence of the great ice-sheet there cooling the air and causing most of the moisture to fall as snow. Paradoxical as it may seem, therefore great summer heat is almost, if not quite, as necessary as excessive winter cold for the production and maintenance of a wide continental glacier. III. When we last took a peep at the Outer Hebrides we found those luckless islands all but obliterated under an immense sheet of ice extending from the mainland out into the Atlantic. How far west the great glacier spread itself we cannot as yet positively say; but if the known slope of its surface between the north-west Highlands and the Long Island continued, as there is every reason to believe it would, then it is extremely probable that the ice flowed out to the edge of the great Scottish submarine plateau. Here the sudden deepening of the Atlantic would arrest its progress and cause it to break up into icebergs. In those old times, therefore, a steep wall of ice would extend all along the line of what is now the edge of the 100-fathoms plateau. From this wall large tabular masses would ever and anon break away and float off into the Atlantic--a condition of things which is closely paralleled at present along the borders of the ice-drowned Antarctic continent. By-and-by, however, a great change took place, and the big ice-sheet melted off the Long Island and vanished from the Minch. We read the evidence for this change of climate in certain interesting deposits which occur in considerable bulk at the northern extremity of Lewis, and in smaller patches in the Eye peninsula of the same island. In those districts the old sub-glacial débris or till is covered with beds of clay and sand in which many marine exuviæ are found--shells of molluscs, entomostraca, foraminifera, etc. They clearly prove, then, that after the ice-sheet had vanished Lewis was submerged in the sea to a depth of not less than 200 feet, and they also prove that the temperature of the sea was much the same then as now, for the shells all belong to species that are still living in these northern waters. It is very remarkable that the marine deposits in question seem to occur nowhere else in any part of the Long Island. We cannot believe that the submergence was restricted to the very limited areas where the shell-beds are met with: it must, on the contrary, have affected a very large portion, if not the whole, of the Outer Hebrides. Why, then, do not we meet with shelly sands and clays, with raised beaches and other relics of the former occupation of these islands by the sea, covering wide areas in the low-grounds? How can we explain the absence of such relics from all those districts which, being much under the level of 200 feet, must necessarily have at one time formed part of the sea-floor? The explanation is not difficult to discover. Resting upon the surface of the shell-beds at Ness and Garabost we find an upper or overlying accumulation of sub-glacial débris or till. At Ness this upper till closely resembles, in general appearance, the lower deposit that rests directly upon the rocks. It is a pell-mell accumulation of silty clay, crammed with glaciated stones, amongst which are many fragments of red sandstone and some extra-Hebridean rocks, and interspersed through it occur also broken fragments of sea-shells. The marine deposits lying below are usually much confused and contorted, and here and there they are even violently commingled with the upper till. They show, generally, a most irregular surface under that accumulation, and are evidently only the wreck of what they must at one time have been. Now the presence of this upper till proves beyond doubt that the intense arctic conditions of climate once more supervened. A big ice-sheet again filled up the basin of the Minch and flowed over the Long Island--its under-tow creeping along the inner margin of the lofty rock-barrier as before, and eventually stealing over the low-ground at the Butt, where its bottom-moraine or till was dragged over the marine deposits, and confusedly commingled with them. The upper strata of the ice that streamed across the islands renewed the work of abrasion, and succeeded in scraping away all traces of the late occupation by the sea. If any such now exist they must lie buried under the till that cloaks the low-ground on the western margins of the islands. Hence it is that we find not a vestige of shelly beds in any part of the Long Island which was exposed to the full brunt of the ice-flow. At Garabost they have been ploughed through in the most wonderful manner, and only little patches remain. At Ness, however, they are more continuous. This is owing to the circumstance that the ground in that neighbourhood is low-lying and offered no obstacle to the passage of the ice out to sea. Hence the shell-beds were not subjected to such excessive erosion as overtook them along the whole eastern border of the Long Island. Eventually, however, this later advance of the ice-sheet ceased. The climate grew less arctic, and the great glacier began to melt away, until the time came that its upper strata ceased to overflow the islands. They then passed away to north and south, along the hollow now occupied by the Minch, following the same path as the bottom-ice. Considerable snow-fields, however, still covered the Outer Hebrides, and large local glaciers occupied all the mountain-valleys, and, descending to low levels, piled up their terminal moraines. Some of these local glaciers appear to have gone right out into the Minch, as in South Uist, and may have coalesced with the great glacier that still filled that basin. It was during this condition of things that most of the great perched blocks that are scattered so profusely over the islands began to be dropt into their present positions. During the climax of glacial cold, when the upper strata of the ice-sheet streamed across the Hebrides, large fragments of rock would certainly be wrenched off and carried on underneath the ice; but as only a few of the Hebridean mountain-tops were then exposed, there would be a general absence of such enormous erratics as are detached by frost and rolled down upon the surface of a glacier, and any such superficially-borne erratics would be transported, of course, far beyond the Long Island into the Atlantic. When the ice had ceased to overflow the islands, boulders derived from Skye and the mainland would no longer be carried so directly out to the Atlantic, but would travel thither by the more circuitous route, which the now diminished ice-sheet was compelled to follow. As the snow and ice melted off the Hebrides, the rocks would begin to be exposed to the action of intense frost, and many fragments, becoming dislodged and falling upon _névé_, small local ice-sheets, and glaciers, would be stranded on hill-slopes and sprinkled over the low-grounds, along with much broken débris and rock-rubbish. Eventually all the lower-grounds would be deserted by the ice, glaciers would die out of the less elevated valleys, and linger in only a few of the glens that drain the higher mountain-masses. Such local glaciers have flowed often at right angles to the direction followed by the great ice-sheet. Thus, the ice-markings in the glens that come down from the Forest of Harris to West Loch Tarbert, run from north to south, while the trend of the older glaciation on the intervening high-grounds is from south-east to north-west. The morainic rubbish and erratics of this latest phase in the glacial history of the Long Island may be traced down almost to the water's edge, showing plainly that there has been no great submergence of that region since the disappearance of glacial conditions. This is somewhat remarkable, because along the shores of central and southern Scotland we have indisputable evidence to show that the land was drowned to the depth of at least fifty feet in post-glacial times. In the Outer Hebrides, however, there are no traces of any post-glacial submergence exceeding a dozen feet or so; that is to say, there is no proof that the Outer Hebrides have been of much less extent than they are now. On the contrary, we have many reasons for believing that they were within comparatively recent times of considerably larger size, and were even in all probability united to the mainland. The abundance of large trees in the peat-mosses, and the fact that these ancient peat-covered forests extend out to sea, are alone sufficient to convince one that the Outer Hebrides have been much reduced in area since the close of the glacial period. These now bleak islands at one time supported extensive forests, although nowadays a tree will hardly grow unless it be carefully looked after. That old forest period coincided in all probability with the latest continental condition of the British Islands--when the broad plains which are now drowned under the German Ocean formed part of a great forest-land, that included all the British Islands, and extended west for some distance into tracts over which now roll the waves of the Atlantic. The palmy days of the great British forests, however, passed away when the German Ocean came into existence. The climatic conditions were then not so favourable for the growth of large trees; and in the uplands of our country, and what are now our maritime districts, the forests decayed, and were gradually overgrown by and buried under peat-mosses. The submergence of the land continued after that, until central and southern Scotland were reduced to a considerably smaller size than now, and then by-and-by the process was reversed, and the sea once more retreated, leaving behind it a number of old raised beaches to mark the levels at which it formerly stood. The greatest submergence that overtook central and southern Scotland in times posterior to the latest continental condition of Britain did not exceed fifty feet, or thereabout; and the extreme limits reached by the sea in the period that supervened between the close of the glacial epoch and the "age of forests" was not more than one hundred feet. The Outer Hebrides, however, were certainly not smaller in post-glacial times than they are now, and we have no evidence to show that after the "age of forests" had passed away the sea rose higher than a dozen feet or so above its present level. Now there are only two ways in which all this can be accounted for. Either the Hebrides remained stationary, or stood at a level higher than now, while the central and southern parts of Scotland were being submerged; or else there has been a very recent depression within the Hebridean area, which has carried down below the sea all traces of late glacial and post-glacial raised beaches. All we know for certain is, that the only raised beaches in the Long Island are met with in low maritime regions at only a few feet above the present high-water mark. My own impression is that the whole district has been submerged within comparatively recent times; for if the present coast-line had endured since the close of the glacial period, or even since the last continental condition of Britain, I should have expected the sea to have done more than it has in the way of excavation and erosion. In a former article I have spoken of the sand-dunes and sandy flats of the west coast of the Long Island. These receive their greatest development in North Uist, Benbecula, and South Uist. Along the whole western margin of these islands stretch wide shoals and banks of yellow sand and silt, and similar shoals and banks cover the bed of the shallow sounds or channels. In the middle of the Sound of Harris one may often touch the bottom with an oar, and even run one's boat aground. It is the same in the Sound of Barra, while, as I have already mentioned, one may walk at low-water from Benbecula into the adjacent islands of North and South Uist. Where does all this sand come from? Certainly not from the degradation of the islands by the sea, for the sounds appear to be silting up, and the general appearance of the sandy flats along the west coast indicates that the land is upon the whole gaining rather than losing. I have no doubt at all that this sand and silt are merely the old sub-glacial débris which the ice-sheet spread over the low shelving plateau that extends west under the Atlantic to the 100-fathoms line. That plateau must have been thickly covered with till, and with heaps and sheets of gravel and sand and silt, and it is these deposits, sifted and winnowed by the sea, which the tides and waves sweep up along the Atlantic margin of the islands. There are many other points of interest to that I might touch upon, but I have said enough perhaps to indicate to any intelligent observer the kind of country he may be led to expect in the Long Island. Of course the history of the glacial period is very well illustrated in many parts of the mainland, which are much easier of access than the Outer Hebrides. But these islands contain, at least, one bit of evidence which does not occur anywhere else in Britain. In them we obtain, for the first time, data for measuring the actual slope of the ice-sheet. It does not follow, however, that the inclination of the surface towards the Atlantic was the same all over the area covered by the ice-sheet. The slope of the sheet that flowed east into the basin of the German Ocean, for example, may have been, and probably was, less than that of the Hebridean ice-flow. But apart altogether from this particular point, I think there is no part of the British Islands where the evidence for the former action of a great ice-sheet is more abundant and more easily read, or where one may realise with such vividness the conditions that obtained during that period of extraordinary climatic vicissitudes, which geologists call the Glacial Epoch. Leaving these old arctic scenes, and coming down to the actual present, no one, I think, can wander much about the Outer Hebrides without pondering over the fate of the islanders themselves. Many writers have asserted that the Celt of these rather out-of-the-way places is a lazy, worthless creature, whom we Saxons should do our best to weed out. One cannot help feeling that this assertion is unfair and cruel. The fact is, we judge him by a wrong standard. He is by nature and long-inherited habits a fisherman, and has been wont to cultivate only so much land as should suffice for the sustenance of himself and those immediately dependent upon him. In old times he was often enough called upon to fight, wrongly or rightly, and thus acquired that proud bearing which it has taken so many long years of misery to crush out. He is, as a rule, totally unfit for the close confinement and hard work which are the lot of the great mass of our mechanics--does not see the beauty of that, and has rather a kind of contempt for the monotonous drudgery of large manufacturing towns. One of the few situations in town that he cares to fill is that of police-constable. Give him a life in the open air, however trying it may be, and he will be quite content if he can make enough to feed himself and family. If the fishing chance to be very profitable he does not, as a rule, think of saving the surplus he has made, but looks forward rather to a spell of idleness, when he can smoke his pipe and talk interminable long talks with his neighbours. No doubt this, judged by our own standard, is all very shocking. Why doesn't he put his money in the savings-bank, and by-and-by die and leave it to those who come after him? Simply because he is a Celt, and not a Saxon. Of course one knows how it will all end. Ere long the unadulterated Celt will be driven or improved out of these islands, and will retire to other lands, where, mingling and intermarrying with Teutons, he will eventually disappear, but not without leavening the races amongst which he is destined to vanish. And who will take his place in the Long Island? Probably a few farmers, a few shepherds, and a sprinkling of gamekeepers; and it is just possible that a few fishermen also may be allowed to settle down here and there upon the coast. One may see the process going on at present. Large tracts that once supported many villages are now quite depopulated. The time will come when somebody in Parliament will move for the reduction of the Civil Service estimates by the amount of the sheriff-substitute's salary, and when the jail at Lochmaddy will have nothing higher in the scale of being to imprison than some refractory ram. One may be pardoned for wishing that he could foretell for the islands another fate than this. It is sad to think that a fine race of people is thus surely passing away from amongst us, for, despite all that can be urged against them, they are what I say. The fishermen of Lewis and Barra are bold, stalwart fellows, whom it would be difficult to peer amongst any similar class of men on the mainland. And all through the island one meets with equally excellent specimens of our kind. Many a brave soldier who fought our battles in the great French wars hailed from these outer islands. Pity it is that no feasible plan to prevent the threatened scattering of the race has yet been brought forward. Some day we may regret this, and come to think that though mutton and wool in the Long Island are desirable, yet islanders would have been better. [Postscript.--On pages 153.4 I have described the second general ice-sheet that overflowed the Outer Hebrides as having eventually become resolved into a series of local ice-sheets and glaciers. Subsequent research, however, has since led me to believe that the district ice-sheets and local glaciers referred to were not the direct descendants of the last great ice-sheet. They appear to have come into existence long after that ice-sheet had entirely disappeared. _See_ Article X.] VI. The Ice Age in Europe and North America.[K] [K] Address to the Geological Society of Edinburgh, 1884. In casting about for a subject upon which to address you this evening, I thought I could hardly do better than give you the result of a comparison which I have recently been able to make between the glacial phenomena of Europe and North America. The subject of glaciation seems to be now somewhat worn; but I gather from the fact that writers can still be found who see in our superficial deposits strong evidence of the Deluge, that a short outline of what we really do know may not be unacceptable. In the short time at our disposal, it is obvious that I cannot enter into much detail, and that many interesting questions must remain untouched. It will be as well, therefore, that I should at the outset define the limits of the present inquiry, and state clearly what are the chief points to which I wish to direct your attention. My main object, then, will be to bring into prominence such evidence as seems to betoken in a special manner the uniformity of conditions that obtained in the northern hemisphere during the Ice Age. In other words, I shall confine myself to a description of certain characteristic and representative phenomena which are common to Europe and North America, with the view of showing that the physical conditions of the glacial period were practically the same in both continents. The phenomena which might be considered under this head embrace nearly all the facts with which glacialists are familiar, but I purpose restricting myself to three questions only, viz.:-- 1st. _The extent of glaciation._ 2nd. _Changes of climate during the Ice Age._ 3rd. _The results of fluvio-glacial action._ The consideration of these questions, even if it were exhaustive (which it cannot be on this occasion), would still leave the general subject very incomplete, for we must forego the discussion of all such interesting topics as the "connection between glaciation and submergence," "the formation of rock-basins," and the "origin of the geographical distribution of our faunas and floras." Confining my inquiry within the limits just specified, I shall begin by sketching broadly the general results obtained by glacialists in Europe, and thereafter I shall proceed to give an outline of the corresponding conclusions arrived at by American observers. I. _The Extent of Glaciation in Europe._ To what extent, then, let us ask, has Europe been glaciated? What areas have been covered with perennial snow and ice? Owing to the fulness and clearness of the evidence, we are able to give a very definite answer to this question. It is hardly too much to say that we are as well acquainted with the distribution of glacier-ice in Europe during the Ice Age as we are with that of existing snow-fields and glaciers. The nature of the evidence upon which our knowledge is based is doubtless familiar to many whom I have the pleasure of now addressing, but for the sake of those who have not such familiarity with the subject I may be allowed to indicate very briefly its general character. A rock-surface over which ice has flowed for any considerable time exhibits either an abraded, worn, and smoothed appearance, or the rocks are disrupted and broken, and larger or smaller fragments are found to have been removed and carried forward in the direction followed by the ice. Now, ice-worn and shattered rock-surfaces of this description, such as can be seen underneath existing glaciers, occur more or less abundantly over vast regions in Europe. They are met with from the North Cape south as far as Leipzig, and from the Outer Hebrides east to the valley of the Petchora and the foot-slopes of the Ural Mountains. Nor are they confined to northern Europe. They appear again and again in France and Spain and Italy, and in the low-grounds of middle Europe, where they occupy positions now far removed from the influence of glacial action. Such ice-worn and disrupted rock-surfaces not only prove that glacier-ice formerly covered large portions of our Continent, but they also indicate for us the directions in which that enveloping ice moved. The smoother surfaces in question are very frequently marked with coarse and fine parallel scratches and grooves of precisely the same nature and origin as the scratches and grooves which characterise the rocky bed of a modern glacier. And these markings, having been produced by the sand, grit, and stones which are pushed and dragged over the rocks by flowing ice, necessarily discover for us the path of glacial movement. But all rocks subjected to glacial action are not necessarily smoothed and polished. Sometimes, owing to structural peculiarities, and for various other reasons, rocks cannot resist the pressure of the ice, but are crushed and broken, and the resulting fragments are rolled and dragged forward in the direction of ice-flow. In this manner the path of a glacier becomes strewed with débris which has from time to time been forced from its rocky bed. There is really no mystery, therefore in tracking the spoor of extinct glaciers; for we have two sets of facts to aid us, either of which might suffice to indicate the extent and direction of glaciation. Consider, however, for a moment, what one observes in connection with rock-striation. We have, in the first place, the rounding and smoothing, and the parallel ruts and striæ. Not only so, but we frequently find that one side of prominent projecting knolls and hills is more highly worn and abraded than the other. Often, indeed, one side may show no trace whatsoever of abrasion. Here, again, we have clear evidence of the direction of ice-flow. Who can doubt that the worn and abraded rocks look towards the point whence the ice came, and that the non-glaciated rocks in the rear have been sheltered by the rocks in front? It is for this reason that in the mountainous regions of northern Europe the striated and smoothed rock-surfaces invariably look up the valleys, while the broken and unworn rock-ledges face in the opposite direction. Once more, note the manner in which the sub-glacial rock-rubbish, consisting of clay, sand, grit, stones, and boulders, has been amassed. In places where the ice must have moved more or less rapidly, as on considerable slopes, no accumulation took place, while in the rear of projecting crags and knobs of rock, sub-glacial materials often gathered deeply. Again, over low-lying tracts, where the motion of the ice would necessarily be retarded, clay, sand, and stones tended to collect. And this particularly appears to have been the case in those regions where the slow-creeping and gradually thinning ice-sheet approached its terminal line. Hence it is that we encounter such thick and wide-spread sheets of sub-glacial detritus upon the undulating low-grounds and plains of southern Sweden, Denmark, Schleswig-Holstein, Holland, northern Germany, Poland, and Russia. The sub-glacial débris to which I specially refer is known as _Till_ or _Boulder-clay_ in this country, as _Krosstenslera_ in Sweden, as _Geschiebelehm_ or _Geschiebemergel_ in Germany, and as _Grundmoräne_ or _Moraine profonde_ in Switzerland. Its general characters are too well known to require more than the briefest summary. In general this peculiar accumulation is an unstratified clay, containing, scattered higgledy-piggledy through it, stones and boulders of all shapes and sizes. Many of these rock-fragments are smoothed and striated, and even the smallest particles, when viewed under the microscope, often show delicate scratches. Frequently, too, the clay is excessively hard and tough, and in many places it shows a kind of pseudo-lamination, which is generally more or less crumpled, and often highly involved. These appearances prove that the clay has not only been subjected to intense pressure, but has actually been rolled over upon itself. I need only refer to the plentiful occurrence of "slickensides" in such clays--the joints by which the clay is often traversed showing such polishing clearly on their faces. These, and many other facts which time forbids me to mention, have received an explanation which has now been generally adopted by European glacialists. The boulder-clay or till is considered by them to represent the ground- or bottom-moraine of glacier-ice. There used to be a notion prevalent amongst geologists in our country that this clay was almost peculiar to these islands. It occurs, however, in most countries of Europe. Vast regions in the north are more or less continuously covered by it, and we meet with it abundantly also upon the low-grounds of Switzerland, from which it may be followed far down the great valley of the Rhone into the sunny plains of France. The lower valleys of the Pyrenees and other Spanish ranges show it well, and it is conspicuous likewise in northern Italy, especially over the low tracts at the mouths of the great lake-valleys. In all those places one can see boulder-clay of as pronounced a character as any to be met with in Scotland. Danish, Dutch, German, and Russian geologists have of late years devoted much attention to the study of this clay, which is so remarkably developed in their respective countries. It has been long well known that a large proportion of the stones and boulders contained in the till are of northern derivation, but it is only of recent years that we have ascertained the particular routes by which those wanderers or erratics have travelled. The rock-fragments in question have been tracked back, as it were, to their parent masses, and thus, partly in this way, and partly by the evidence of ice-worn surfaces, we have been enabled to follow the spoor of the great northern ice-sheet in a most satisfactory manner. Let one or two examples suffice. Boulders derived from Lapland and Finland occur in the till at St. Petersburg, and have been traced south-east to Moscow. Again, fragments carried from Gottland, in the Baltic, are met with in the boulder-clay of east Prussia, and have been followed south to beyond Berlin. In like manner boulders of well-known Scanian rocks appear in the boulder-clay of Leipzig. So also Swedish and Norwegian rock-fragments are seen in the boulder-clay of Denmark, Hanover, and Holland. Very wide areas in northern Germany are covered with an almost continuous sheet of glacial detritus, so that it is only occasionally that the underlying rocks crop out at the surface. Striated rock-surfaces are therefore by no means so commonly exposed as in regions like the Lowlands of Scotland. They are not wanting, however, and their evidence is very striking. Thus, in the neighbourhood of Leipzig and Dresden, we find glacial striæ impressed upon certain highly-abraded and ice-worn hillocks of porphyry, the striæ being the work of ice which flowed into Saxony from the north. Similar striæ;, having a general southerly trend, occur at Rüdersdorf, near Berlin, at Gommern, near Magdeburg, at Velpke in Brunswick, at Osnabrück in Hanover, and at other places. Again, we encounter remarkable evidence of the powerful pressure exerted by the ice in the displacement and removal of huge blocks of strata. In Saxony, for example, the Tertiary strata are turned up, pushed out of place, and involved in boulder-clay to such an extent that the brown coals have often been mined for in this strange position. Witness also the extensive displacements and dislocations of the Cretaceous formation in the Danish islands of the Baltic. So great are the contortions and displacements of the Chalk in Moen, that these disturbances were formerly attributed to subterranean action. Along the north-east coast of that island, cliffs 400 feet in height exhibit the Cretaceous beds thrown upon end, twisted, bent, and even inverted, boulder-clay being squeezed into and between the disjointed and ruptured rock-masses. From a study of these and similar phenomena, it has been demonstrated that during the climax of the Ice Age a very large part of northern Europe was buried under a thick covering of glacier-ice. And it has been conclusively shown that this ice-sheet streamed outwards in all directions from the high-grounds of Scandinavia, for which reason it is often spoken of as the Scandinavian ice-sheet. But as it was fed, not from the snow-fields of Scandinavia alone, but from the precipitation of snow over its whole surface, it is better, I think, to speak of it as the northern ice-sheet. In the extreme north of Scandinavia the ice flowed northward into the Arctic Ocean, while south of the dominant watershed of Lapland and Sweden its course in those high latitudes was east and south-east. It filled up the depressions of the White Sea, the Gulf of Bothnia, and the Baltic, extending east to the valley of the Petchora and the base of the Ural Mountains, and south-east to Kazan, some 200 miles east of Nijnii-Novgorod. From this point its terminal front trended a little west of south, until it reached the fiftieth parallel of latitude. Undulating a few miles south and north of this parallel, it swept directly west through Russia into Galicia, till it touched the foot-hills of the Carpathian range. After this we follow it along the northern base of the Riesen Gebirge, the Erz Gebirge, and the Harz, and thence westward through Hanover, and into the Low Countries, as far south at least as the mouth of the Rhine. Throughout the vast regions lying west and north of this terminal line, the track followed by the ice has been well ascertained. It was east and south-east in Russia, southerly in east Prussia, south-westerly in Denmark, Hanover, and Holland. The action of a mass of glacier-ice, reaching a thickness of several thousand feet, must necessarily have resulted in extensive erosion of the rocks over which it passed. Everywhere, therefore, throughout the vast area just indicated, we meet with evidence of severe erosion. But, as one should expect, such erosion is most marked in the hilly regions--in those areas where steep slopes induced more rapid motion of the ice, and where projecting crags and hills opposed the advance of the eroding agent. All such prominent obstructions were energetically assailed--abraded, rounded, worn, and smoothed, or crushed, shattered, dislocated, and displaced. The high-grounds of Scandinavia and Finland, formed for the most part of tough, crystalline rocks, or of more or less durable strata, show everywhere _roches moutonnées_--smoothed and rounded rocks--while innumerable rock-basins have been scooped out in front of prominent crags and hills. In Denmark and other countries, where less durable rocks prevail, the strata have often been broken and disrupted, and pushed out of place. But as regions formed of such rocks are generally gently-undulating, and seldom show abrupt crags and hills, they oppose few obstructions to the advance of an ice-sheet. When the northern ice-sheet flowed into Russia and Germany, it crept over a low-lying and, for the most part, gently-undulating surface; and although here and there the form of the ground favoured glacial erosion and disruption, and extensive displacements of rock-masses took place, yet, upon the whole the low-lying regions referred to became areas of accumulation. The sub-glacial detritus--ground out or wrenched away from the rough Scandinavian plateau and the uplands of Finland--was dragged on underneath the ice, and spread over the great plains lying to the south-east and south, as the gradually attenuated ice-sheet crawled to its terminal line. My friend Dr. Amund Helland, the well-known Norwegian geologist, has made an estimate of the amount of rock-débris derived from Scandinavia and Finland which lies scattered over the low-grounds of northern Europe. According to him, the area in Denmark, Holland, Germany, and Russia (exclusive of Finland), over which northern detritus is scattered, contains about 2,100,000 square kilometres, and the average thickness of the deposits is about 150 feet, of which, however, only two-thirds, or 100 feet, are of northern origin, the remaining third consisting of local materials. Taking, then, 100 feet as fairly representing the average thickness of the rock-rubbish derived from Finland and Scandinavia, the area of which is given as 800,000 square kilometres, there is enough of this material to raise the general surface of those lands by 255 feet. The same amount of material would suffice to fill up all the numerous lakes of Finland and Sweden sixteen or seventeen times over. Or, if tumbled into the Baltic, it would fill the basin of that sea one and a half times. In short, enough northern rock-débris lies upon the low-grounds of northern Europe, which, were it restored to the countries from which it has been taken, would obliterate all the lake-hollows of Finland and Sweden, raise the level of those lands by 80 feet, and fill up the entire basin of the Baltic, with all its bays. And yet this estimate leaves out of account all the material which the ice-sheet carried away from Norway and the British Islands. Of the glaciation of our own land I need say very little. The configuration of our country necessarily made it a centre of dispersion during the Ice Age, and the ice which covered Ireland, Scotland, and the major portion of England radiated outwards from the dominant elevations of the land. But as the ice creeping outwards from those centres became confluent, the directions which it followed were often considerably modified, especially upon the low-grounds. We know that the British ice-sheet not only covered the land up to near the tops of our higher mountains, but filled up all our seas and extended into the Atlantic beyond the coasts of Ireland and the Outer Hebrides--these latter islands having been glaciated from the east by the ice that flowed outwards from the mainland. Another point upon which we are now well assured is the fact that the British and Scandinavian ice-sheets coalesced, so that the basin of the North Sea completely brimmed over with glacier-ice. Finally, then, in contemplating the physical conditions that obtained in northern Europe at the climax of the Ice Age, we have to picture to ourselves the almost total obliteration under a vast ice-sheet of all the land-features of the British Islands, Scandinavia, and Finland, and the adjacent low-lying tracts of Denmark, Holland, Germany, Poland, and Russia. If at that distant date a prehistoric man could have stood on the summit of Snaehatten, he would have seen an apparently interminable plain of snow and ice, bounded only by the visible horizon. Could he have followed the plain southwards in hopes of escaping from it, he would have descended its gently-sloping surface by imperceptible gradations for a distance of 700 miles, before he reached its termination at the foot of the mountains of middle Germany. Or, could he have set out upon an easterly course, he would have crossed the Gulf of Bothnia, buried several thousand feet beneath him, and touched the foot-slopes of the Ural Mountains before he gained the terminal front of the ice-cap, a distance of 1600 miles. On the other hand, had he walked south-west in the direction of Ireland, he would have traversed the area of the North Sea at a height of several thousand feet above its bed, and, crossing the British area, would only have reached the ice-front at a point some 50 miles beyond the coast of Ireland. Here he would have seen the ice-sheet presenting a steep face to the assaults of the Atlantic, and breaking away in massive tabular bergs, like those which are calved by the ice-cap of the Antarctic regions. I must now pass rapidly in review the facts relating to the glaciation of the mountainous regions which lay outside of the area covered by the northern ice-sheet. The glaciers of the Alps of Switzerland, about which so much has been written, and the study of which first gave Venetz, Charpentier, and Agassiz the clue to the meaning of striated rocks, boulder-clay, and erratics, are, as is well known, the puny descendants of former gigantic ice-flows. At the culmination of the Ice Age all the mountain-valleys of Switzerland and northern Italy were choked with glaciers that streamed out upon the low-grounds. Along the northern slopes of the Alps, as in Bavaria and Würtemberg, these glaciers coalesced to form a considerable ice-sheet, and so likewise did the glaciers that descended from Switzerland, Savoy, and Dauphiny, into the great valley of the Rhone. Even in north Italy the same was the case with the glaciers that occupied the valleys in which now lie Lakes Orta, Maggiore, Varese, Lugano, and Como--the united ice-flows of those valleys forming a glacier which deployed upon the plains of the Po, with a frontage of not less than 40 miles. To the north of the Alps, the Vosges Mountains and the Black Forest, the Harz, the Erz Gebirge, the Riesen Gebirge, and the Böhmer-Wald--all had their perennial ice and glaciers, although none of those elevated tracts now reaches the snow-line. It was the same with the Carpathians and the Urals, amongst which we meet with relics of much larger ice-streams than any that now exist in the Alps. Considerably further south were the glaciers of the Despoto Dagh of Roumelia. Great glaciers also in former times descended from the Caucasus, and in many hilly regions of Asia Minor indubitable traces of similar large ice-flows have been detected. The high-grounds of central France, and the mountains of Beaujolais and Lyonnais supported considerable glaciers, while from the Pyrenees numerous glaciers of the first class flowed out upon the low-grounds of France, and considerable ice-streams occupied the mountain-valleys on the Spanish side. Other Peninsular chains--the Serra da Estrella, the Sierra Guadarama, and the Sierra Nevada--had likewise their snow-fields and ice-streams. The same was the case with the Apennines and the Apuan Alps of Italy, the traces of former glacial action being conspicuous over a considerable part of Tuscany. Even in Corsica we encounter the same evidence of glaciation--striated rock-surfaces and moraines--which point to the former descent of considerable glaciers from Monte Rotondo. But rock-striæ and moraines are not the only proofs of former cold and humid conditions having prevailed over middle and southern Europe at the climax of the glacial period. The limestone-breccias of Gibraltar have been described by Professor Ramsay and myself, and we have shown that these could only have been formed under the influence of excessive frost and melting snows. The limestone of the Rock has been broken up along the ridge, and its fragments showered down the slopes, at a time when these were more or less thickly covered with snow. Resting upon and imbedded in this snow, the rock-rubbish would be carried downward and outward during the gradual melting that took place in summer. And in this way immense accumulations of débris were borne forwards over the low-grounds that extended from the base of the Rock into regions which are now partially submerged. Breccias which have probably had a similar origin occur also in Corsica, Malta, and Cyprus, and doubtless they will yet be recognised in many other places. Again, over wide areas in northern France and the south of England, we meet with extensive sheets of earthy clay and rock-rubbish, which have certainly been heaped up under very different conditions of climate than obtain now. This stony earth has evidently travelled down the gentle slopes of the land, under the influence of frost and melting snow, in much the same way as ice-driven rock-rubbish and soil move slowly down the slopes of such dreary regions as Patagonia and certain low-lying tracts within the Arctic Circle. II. _Changes of Climate in Europe during the Ice Age._ We come next to the very interesting question of alternations of climate during the Ice Age. The evidence under this head has accumulated to such an extent within recent years as to convince most students of Pleistocene geology that very extensive changes of climate characterised the glacial period. How many such changes took place we are not yet in a position to say, but we know that the intensely arctic condition of things which has just been described was interrupted more than once by what have been termed "interglacial epochs," during which a mild and genial climate prevailed over middle and northern Europe. For some time it was believed that such "interglacial epochs" had only a local significance, that they bespoke mere transitory retreats of the ice-fields, such as are known to have taken place within historical times in the glacier-valleys of the Alps. But increased observation and reflection have shown that this explanation of the phenomena of "interglacial beds" will not suffice. It is impossible to enter here upon details, but I may briefly state that the evidence in question is two-fold. _First_, we have the stratigraphical evidence. We have ascertained the existence, over wide areas in this and other glaciated countries, of several successive sheets of boulder-clay, which are often separated from each other by fossiliferous aqueous strata. It has been demonstrated that each of these sheets of sub-glacial detritus is the accumulation of a separate and distinct ice-flow. _Second_, we have the evidence of fossil organic remains. We find, for example, that the flora which covered the low-grounds of middle and temperate Europe during a certain stage of the glacial or Pleistocene period, consisted of plants which are now restricted to the tops of our mountains and to northern Scandinavia. The characteristic fauna associated with that flora embraced the reindeer, glutton, mammoth, woolly rhinoceros, Arctic fox lemming, chamois, and so forth. We know, indeed, that man hunted the reindeer and the mammoth in the south of France. Similar testimony to the coldness and humidity of the climate is borne by the land- and freshwater shells which occur in certain Pleistocene deposits in Italy, Corsica, southern France, Switzerland, Germany, etc. That this flora and fauna were contemporaneous with the great glaciation of our Continent has been as well ascertained as the fact of the Roman occupation of Britain. But if the evidence of organic remains strongly confirms and supports that supplied by the distribution of glacial deposits in Europe, no less forcibly does it corroborate the physical evidence as to the former existence of a warm and genial interglacial climate. During interglacial times a most abundant mammalian fauna roamed over all temperate Europe--a fauna comprising such animals as Irish deer, urus, bison, horse, stag, saiga, brown bear, grisly bear, several species of elephant, rhinoceros, and hippopotamus, hyæna, lion, leopard, etc. A like tale of genial conditions is told by the land- and freshwater shells, which occur in some of the Pleistocene deposits of England, France, Belgium, Germany, Switzerland, and Italy. The testimony of the associated flora is just as striking. How genial and equable must have been the climate which permitted plants like the Canary laurel, the Judas-tree, the fig-tree, and others to flourish side by side in the north of France, with such forms as the hazel, willow, ash, and sycamore! The most noteworthy additions to our knowledge of interglacial conditions which have recently been made are the results obtained by M. Gaudry in the valley of the Seine, and by Dr. Penck in Bavarian Tyrol, the latter of whom has shown that there have been at least three great advances of the Alpine glaciers, separated by long-continued mild conditions, during which the glaciers receded far into the mountains. It is interesting to observe that we have, especially in our own islands, good evidence to show that during the glacial period considerable oscillations of the relative level of land and sea took place. Thus, it has been ascertained, that just before the latest epoch of extensive glaciation, the British Islands were largely submerged in the sea. To what depth this remarkable submergence was carried we do not know, because any marine deposits which may have been accumulated at that time over the drowned country were for the most part obliterated by the action of the ice-sheet which subsequently covered and reglaciated our lands.[L] But the few fragments of such marine deposits as have been preserved show us that the depression reached more than 500 feet in Scotland (_i.e._, measured from the present sea-level), and exceeding 1000 feet in Wales and Ireland. We note, then, in passing, that the only great Pleistocene submergence of these lands of which geologists have any knowledge took place before the appearance of the last general ice-sheet that overflowed our low-grounds. The submergences of a later date were of inconsiderable importance, hardly exceeding 100 feet or thereabouts below the present sea-level. The latest occupant of our islands and of northern Europe was not the sea, but ice. The "Palæocrystic Sea," which we have been recently assured would account for our glacial phenomena, is of "the stuff that dreams are made of." There is not a jot or tittle of evidence for the former existence of such a sea over any part of Britain or the continent of Europe. [L] I no longer believe in this "great submergence." The marine shells in the high-level drift-deposits of our islands are "erratics," carried by the ice-sheet which occupied the basin of the Irish Sea. That the low-grounds were submerged but the amount of the submergence has not been ascertained; probably it did not exceed a few hundred feet. It is not necessary for my present purpose to enter further into the evidence of interglacial conditions. The latest northern ice-sheet was preceded by a long epoch of mild and genial conditions, during which elephants and hippopotami ranged north as far at least as Yorkshire; while middle Germany, as we know from the testimony of its interglacial deposits, enjoyed a similar delightful climate. And yet the immediately preceding glacial epoch had seen all those fertile regions covered with an ice-sheet that extended south as far as the fiftieth parallel of latitude. Now the question with which I am at present concerned is the extent of the latest general glaciation. Did the last great ice-sheet reach as far south as its predecessor? It certainly did not. Its bottom-moraine has now been mapped out and distinguished from that of the older ice-sheet, and we know that it does not extend so far south as the latter. It is entirely absent over all the region to the west of the River Elbe, from near Dresden to Hamburg and the coast of Holland.[M] So that western Germany and Holland, which were covered by ice during the epoch of greatest glaciation, were not invaded by the ice-sheet underneath which the upper boulder-clay was accumulated. This latest ice-sheet, however, overwhelmed all Mecklenburg and Mark Brandenburg, and streamed south nearly as far as Saxony; its southern margin extended east through Silesia, by Liegnitz and Breslau, into Poland and Russia. But the precise line it followed in the latter country has yet to be ascertained. We may surmise, however, that it nowhere reached so far south or east as the ice-flow of the earlier epoch. I may add that the southern termination of the latest ice-sheet is in many places marked out by heaps, mounds, and ridges of earthy sand, gravel, rolled stones, and erratics; in short, by terminal moraines. These, however, are frequently highly degraded and washed down. [M] Klockmann, _Jahrb. der k. preuss. geol. Landesanstalt für 1883_, p. 330. Of the extension of glacier-ice in the British Islands at the epoch in question I shall only say that the glaciation of Scotland was hardly, if at all, less extensive than during the climax of the Ice Age. Ireland, too, appears to have been almost as thickly mantled; but the ice-sheet that covered England and Wales did not extend so far south as that of the penultimate glacial epoch, a considerable area in East Anglia and the midland counties remaining apparently free from invasion. The Scandinavian and British ice-sheets, however, again coalesced upon the floor of the North Sea. III. _The Results of Fluvio-glacial Action in Europe._ The third question which I now proceed to consider is the result produced by the rivers and torrents of the Ice Age. This, I am aware, is a wide subject, and one upon which much has been written. But there are a few points which may be advantageously discussed for the purpose of bringing into prominent view the conditions which obtained in the river-valleys of Europe during the last great extension of glacier-ice. A little consideration will serve to convince one that the intense glacial conditions that obtained in our Continent during the cold epochs of the glacial period were due to a low temperature, combined with excessive snow-fall. The winters, we can have no doubt, must have been prolonged and severe. But mere low temperature will not account for the enormous precipitation of snow. For this, great evaporation was required. And we are therefore forced to admit that the direct heat of the sun in summer must have been greater than it is in the same regions at the present day. Now, if this were really the case (and I do not see how otherwise the facts can be explained), then we ought to meet with evidence of swollen rivers, torrents, and widespread inundations everywhere outside of the glaciated areas. And this is precisely what we do find. Immense accumulations of coarse gravels are widely spread over all the valleys that head in regions which were formerly the sites of snow-fields and glaciers. These gravels are of such a character and are so distributed as to make it certain that they could not have been transported to and deposited in their present positions by rivers like those which now wind their way down the valleys of middle Europe. Still more remarkable are the enormous sheets of loam which are spread over much wider areas and reach to more considerable heights than the gravels. The origin of the gravels is sufficiently evident; they are simply the coarser detritus, swept along by the enormously flooded rivers of the glacial period, and meet with their analogues in the torrential gravels of modern glacier-valleys in the Alps and other elevated regions. The more widely-spread loams, according to the opinion of most glacialists, represent the finer mud and silt deposited from the muddy waters of the same period. But the height to which such gravels and loams ascend is so great that those who hold them to be of fluvio-glacial origin have found it difficult to maintain this view. Some writers, indeed, who have not sufficiently considered the weight of the evidence in its favour, have set it aside, and boldly suggested all kinds of wonderful hypotheses in its place. One imaginative author, for example, believes the wide-spread loams to be of volcanic origin, while another finds in the same deposits strong evidence of the Deluge. By a well-known and experienced observer, the famous löss of middle Europe is considered to be an Æolian accumulation--that is to say, a wind-blown deposit--the result of long-continued or frequently-repeated dust-storms. This is the opinion of Baron Richthofen, whose great work on China is so justly esteemed. He infers that at the time of the formation of our löss central Europe was a dry desiccated region, just as wide areas in central Asia are in our own day. He does not attempt to show us, however, how such climatic conditions could ever obtain in Europe. In point of fact, the geographical conditions of our Continent have not changed materially since Pleistocene times, and the presence of the wide Atlantic Ocean, that laves all our western shores, is of itself sufficient to preclude the possibility of such a climate having obtained in middle Europe. Richthofen's theory likewise fails to account for the geographical distribution of the löss, and for many facts relating to its geology. Only one of these last shall I mention. The löss is intimately associated with accumulations, the glacial and fluvio-glacial origin of which cannot be doubted. It belongs, in fact, to the glacial series, and was laid down at a time when vast snow-fields and ice-sheets existed, and when it is quite impossible that a dry climate could have characterised any part of our Continent. In common with most geologists, I believe that the löss is simply an inundation-mud, deposited in temporary lakes and over flooded areas during the summer meltings of the snow- and ice-fields; and I shall now try to show how the occurrence at high levels of gravels and such loams as the löss may be accounted for without having recourse to volcanic action or to winds, or even to the Deluge. I shall invoke no agencies other than those which we are perfectly well assured were in full operation during the Ice Age. Now, I ask you, in the first place, to bear in mind that while a glacial epoch continued, extreme conditions could not have been restricted to the areas undergoing glaciation. There is abundant evidence, indeed, to show that heavy, snows occasionally covered other regions, and that in such places severe frosts acted upon the rocks and soils even of the low-grounds. Need we wonder if at a time when the northern ice-sheet approached the fiftieth parallel of latitude in middle Europe, when almost every mountain-group of central and southern Europe had its snow-fields and glaciers--need we wonder if at such a time the climate of wide areas outside of the glaciated tracts was extremely ungenial? The more closely the superficial accumulations of such areas are studied, the more clearly do we perceive in them the evidence of cold and humid conditions. Try, then, to picture to yourselves the probable aspect of those regions during a glacial epoch. Immediately south of the northern ice-sheet deep snows must have buried large tracts of country, and such snows may have endured often for long years, notwithstanding the great melting that took place in summer. Even much further south, as in Spain and Italy, deep snows would cover the lesser hills and hill-ranges, while frost would act energetically in many a district where such action is now either inconsiderable or unknown. Such being the general conditions that must have obtained in the non-glaciated areas, let us very briefly consider what the results of such conditions must necessarily have been. Every one has noticed, during the more or less rapid melting of snow in winter and early spring, that our streams and rivers are then much muddier than when in summer and autumn they are swollen by heavy rains. This of course is due to the action of frost, by means of which rocks are disintegrated and soils are broken up and pulverised, so that when thaw supervenes, the superficial covering becomes soaked with moisture like a sponge. To such an extent does this take place, that one may often see the saturated soil creeping, slipping, and even flowing down the slopes. The effect of mere thaw is of course much intensified when the water derived from melting snows is present. Rills and tiny brooks then become converted into dark muddy torrents, and enormous quantities of fine-grained detritus are eventually swept into the rivers. The rivers rise in flood and inundate their plains, over the surface of which considerable deposits of loam and silt often accumulate. We cannot doubt that similar but much more intense action must have taken place over very wide regions in Europe during a glacial epoch. Such having necessarily been the case, we are not required to suppose that the löss and similar loams have been deposited entirely by rivers flowing from glaciers. It is doubtless true that most of the rivers headed in those days in glacier regions, and must in consequence have been highly discoloured with glacial mud, and probably a very large proportion of the loams in question consists of the fine flour of rocks--the result of glacial grinding. But the action of frost and thaw and melting snow upon the low-grounds, such as I have described, cannot be ignored, and seems to have played a more important _rôle_ than has yet been recognised. I think it helps us better to explain the well-known fact that land-shells are more or less commonly distributed through the löss. One can readily understand, at all events, how snail-shells might be swept down the slopes of the land at the time of the spring thaws, and how large numbers might find their way eventually into the swollen glacial rivers. I have often observed, during the melting of snow and the thawing of soils, quantities of snail-shells in the very act of being swept into our brooks and rills. And we are all familiar with the fact that, after a spring-flood has subsided, snail-shells, along with vegetable débris, are often plentifully stranded upon the valley-slopes and flood-plains of our rivers. Admitting, then, that the löss and similar accumulations are simply inundation-loams formed at a time when glaciers were discharging immense volumes of muddy water, and when the low-grounds were liable every summer to the denuding action of melting snows, and so forth, I have yet to account for the fact that these supposed inundation-loams sometimes occur at a height of 100 feet, or even of 300 feet, above the present levels of the rivers. Two theories have been advanced in explanation, each of which seems to me to contain an element of truth. It has, in the first place, been maintained, as by Prestwich, that the löss at the higher levels was probably deposited long before the rivers had excavated their channels to their present depths. Thus, during flood, they would be enabled to overflow tracts which they could not possibly have reached when they had deepened their valleys to a much greater degree. But while we must fully admit that the erosion effected by the rivers of the Pleistocene or Glacial period was excessive, yet we find it difficult or impossible to believe that great valleys, several miles in width, and two or three hundred feet in depth, were excavated in hard Devonian and other equally durable rocks by the swollen and active rivers of the Ice Age. And although it is extremely probable that the löss at the highest levels is older than the similar deposit at the lowest levels of such a valley as the Rhine, yet this does not get us out of our difficulty. The other view to which I have alluded takes little or no account of river-erosion, but maintains that the floods of the Ice Age were sufficiently great to reach the highest levels at which river-gravels and loams occur. It is likely enough that, under present conditions, we can form but a very inadequate idea of the vast bodies of freshwater which formerly swept down our valleys, but we may be pardoned if we express our inability to conceive of our European rivers flowing with a breadth of many miles, and a depth of two or three hundred feet. A few years before his death, Mr. Darwin made a suggestion to me, which I think gives us the true solution of the problem. He thought that during an Ice Age great beds of frozen snow might have accumulated over the low-grounds outside of the glaciated areas (in the manner I have already described), and that many valleys might have been filled to a considerable depth during a large part of the year with blown snow, afterwards congealed. In autumn, when the running water failed, the lines of drainage might in many cases be more or less choked, and it would be a mere chance whether the drainage, together with gravel, sand, and mud, would follow precisely the same lines during the next summer. Such action being repeated year after year, it might well happen that many river-valleys might become largely filled with rudely alternating layers of frozen snow and fluviatile detritus. And if this were so, the flooded rivers in summer would be enabled to overflow much wider and more elevated tracts than they could otherwise have reached. As the climate became less excessive, we can conceive of the frozen snows gradually melting, and of river-detritus being deposited at lower and lower levels in the valleys. The probability of such frozen masses having choked up valleys and impeded the drainage during the Ice Age is not a mere plausible conjecture. In the far north of Alaska--in a region which was certainly not overflowed by the North American ice-cap--extensive sheets of ice occur, more or less deeply buried under thick soil. Nor can there be much doubt that these ice-masses date back to the Glacial period itself, seeing that in the soils which overlie them we meet with remains of the mammoth and other contemporaneous mammalian forms. Here, then, we have direct proof of the fact of frozen snow and ice having accumulated in the hollows of the land outside of the glaciated areas.[N] [N] I have given Mr. Darwin's views, and discussed the origin of the Pleistocene fluvio-glacial deposits at some length in _Prehistoric Europe_, chaps, viii. and ix. To this work I refer for detailed geological evidence in support of the view advocated above. Now, if such conditions existed in the valleys of middle Europe, the widespread loss of those regions is readily accounted for. The occurrence of irregular sheets and shreds of gravel and loam at heights of more than a hundred feet above a valley-bottom offers no difficulty--it is in fact precisely the kind of phenomenon we might have expected. We are therefore not required to go out of our way to dream about impossible volcanic action, or to call upon the winds of heaven to help us, or upon the waters of the Deluge to float us out of our difficulties. But while I believe the views I have now advocated sufficiently account for the appearances presented by the ancient valley-gravels and loams of central Europe, there are two very considerable areas of löss which require some further explanation. The first of these is that broad belt of löss which extends from west to east across the plains of northern Germany, and the northern boundary of which coincides with the limits reached by the last great ice-sheet, from which it spreads south to the foot-hills of the Harz, and other mountains of middle Europe. Here we have a sheet of löss which bears no apparent relation to the valley-systems of the region in which it occurs. But the fact of its northern boundary being coincident with the terminal front of the last great northern ice-sheet at once suggests its origin. It is evident that this ice-sheet must have blocked the rivers flowing north, and dammed back their waters.[O] A wide sheet of muddy water must therefore have extended east and west over the very area which is now covered by the belt of löss in question. This temporary lake would doubtless be subject to great alternations of level--a portion draining away perhaps under the ice-sheet--but the water would for the most part make its way westward, and eventually escape into the English Channel. From the waters of this great lake, fed by many large glacial rivers, abundant precipitation of loam and silt must have taken place. [O] The late Mr. Belt, as is well known, was of opinion that all the rivers flowing north in Europe and Asia were dammed back by a great Polar glacier, and that all the low-tracts in the northern portions of the two continents were thus covered by wide inland seas of freshwater. As I do not believe that such a Polar ice-cap existed during the Glacial period, I cannot agree with Mr. Belt that the alluvial plains of northern Siberia mark the sites of ice-dammed lakes. The second and by far the most extensive sheet of löss in Europe is the so-called "black earth," or "tchernozem," with which such enormous tracts in southern Russia are covered. This widespread löss--for such it really is--I have elsewhere tried to show consists of the flood-loam and inundation-muds laid down by the water escaping along the margin of the northern ice-sheet, which discharged its drainage in the direction of the Black Sea, its black colour being due to the grinding down and pulverising of the black Jurassic shales which extend over such wide regions in middle Russia. IV. _The Extent of Glaciation in North America._ The various phenomena of glaciation which go to prove that a great ice-sheet formerly covered a wide region in northern Europe are developed on a still more extensive scale in North America. Smoothed and striated rock-surfaces, crushed and dislocated rock-masses, and enormous accumulations of morainic débris and fluvio-glacial detritus, all combine to tell the same tale. The morainic accumulations of North America have been distributed upon the same principles as the similar deposits of our own Continent. Boulder-clay of precisely the same character as that of Scotland and Scandinavia, of Switzerland and north Italy, covers vast tracts in the low-grounds of the British Possessions and the northern States of the Union, where it forms enormous sheets, varying in thickness from 30 or 50 up to 100 feet or more. In the rough Laurentian high-lands, however, it is more sparingly developed, and the same is the case in the hilly regions of New England. In short, it thickens out upon the low-grounds, and thins off upon the steeper slopes, while it attains its greatest thickness and forms the most continuous sheets in the country that lies south of the great lakes. The southern limits of this deposit form a kind of rude semi-circle. From New York the boundary-line has been followed north-west through New Jersey and Pennsylvania to beyond the forty-second parallel, after which it turns to the south-west, passing down through Ohio to Cincinnati (39°); then, striking west and south-west through Indiana, it traverses the southern portion of Illinois. Its course after it reaches the valley of the Missouri has been only approximately determined, but it turns at last rather abruptly to the north-west, sweeping away in that direction through Kansas, Nebraska, Dakota, and Montana. The general course followed by the ice-sheet underneath which this boulder-clay was formed has been well ascertained, partly by the evidence of the clay and its contents, and partly by that of _roches moutonnées_ and striated rocks. The observations of geologists in Canada and the States leave it in no doubt that an enormous sheet of ice flowed south over all the tracts which are now covered with boulder-clay. During a recent visit to Canada and the States, I had opportunities of examining the glacial deposits at various points over a somewhat extensive area, and everywhere I found the exact counterparts of our own accumulations. In Minnesota, Wisconsin, Iowa, Illinois, Indiana, and Ohio, and again in New York, Connecticut, and Massachusetts, and the low-grounds of Canada, I recognised boulder-clay of precisely the same character as that with which we are familiar at home. The glacial phenomena of the Hudson valley and of the lower part of the Connecticut River were especially interesting. In those regions the evidence of a southward flow of the ice is most conspicuous, and the phenomena, down to the smallest details, exactly recalled those of many parts of Europe. Professor Dana, under whose guidance I visited the Connecticut valley, showed me, at a considerable height upon the valley-slope, an ancient water-course, charged with gravel and shingle, which could not possibly have been laid down under present conditions. It was, in fact, a sub-glacial water-course, and resembled the similar water-courses which are associated with boulder-clay in our own country. If I met with only familiar glacial phenomena in the low-lying tracts traversed by me, I certainly saw nothing strange or abnormal in the hillier tracts. In passing over the dreary regions between the valley of the Red River and Lake Superior I was constantly reminded of the bleak tracts of Archæan gneiss in the north-west of Scotland, and of the similar rough broken uplands in many parts of Scandinavia and Finland. The whole of that wild land is _moutonnée_. Rough tors and crags are smoothed off, while boulder-clay nestles on the lee-side. In the hollows between the _roches moutonnées_ are straggling lakes and pools and bogs innumerable. Frequently, too, one comes upon rounded cones and smooth banks of morainic gravel and sand, and heaps of coarse shingle and boulders, while erratics in thousands are scattered over the whole district. If you wish to have a fair notion of the geological aspect of the region I refer to, you will find samples of it in many parts of the Outer Hebrides and western Ross-shire and Sutherland. Cover those latter districts with scraggy pines, and their resemblance to the uplands of Canada will be complete. From descriptions given by travellers it would appear that morainic detritus--mounds and sheets of stony clay, gravel and sand, shingle, boulders, and erratics--are more or less plentifully sprinkled over all the British Possessions and the islands of the Arctic Archipelago; so that we have every reason to believe that the ice-sheet which left its moraines at New York and Cincinnati extended northwards to the Arctic Ocean. Nor can there be much doubt that this same _mer de glace_ became confluent in the west with the great glaciers that streamed outwards from the Rocky Mountains; while we know for a certainty that the southern portion of Alaska, together with British Columbia and Vancouver Island, were buried in ice that flowed outwards into the Pacific. Along the eastern sea-board north of New York city there is no tract which has not been overflowed by ice. The islands in Boston Harbour are made up for the most part of tough boulder-clay; and boulder-clay and striated rocks occur also in Maine, New Brunswick, Nova Scotia, and Newfoundland. Thus we may say that the ice-covered region of North America was bounded on the north by the Arctic, on the west by the Pacific, and on the east by the Atlantic Oceans. The Rocky Mountains, however, divided the great _mer de glace_ that overflowed Canada and the States from the ice that streamed outwards to the Pacific. Measured from the base of the Rockies to the Atlantic, the _mer de glace_ of Canada and the States must have exceeded 2500 miles in width, and it stretched from north to south over 40 degrees of latitude. Outside of this vast region and the great mountain-ranges of the far west, there are few hilly areas in the States which reach any considerable elevation. South of the _mers de glace_ of the north and west, no such mountain-groups as those of middle and southern Europe occur, and consequently we do not expect to meet with many traces of local glaciation. Nevertheless, these have been recognised in the Alleghany Mountains, West Virginia, and in the Unaka Mountains, between Tennessee and North Carolina. But the glaciers of those minor hill-ranges were of course mere pigmies in comparison with the enormous ice-streams that flowed down the valleys of the Rocky Mountains and the Sierra Nevada. Even as far south as the Sierra Madre of Mexico glaciers seem formerly to have existed; and Mr. Belt has described the occurrence of what he considered to be boulder-clays at a height of 2000 to 3000 feet in Nicaragua. I have mentioned the fact that in Europe we have, outside of the glaciated areas, certain accumulations (such as the Gibraltar breccias) which could only have been formed under the influence of extreme cold. Similar accumulations occur in North Carolina, where they have been carefully studied by Mr. W. C. Kerr. According to Mr. Kerr, these deposits have crept down the declivities of the ground under the influence of successive freezings and thawings; and now that attention has been called to such phenomena, our American friends will doubtless detect similar appearances in many other places. The facts which I have now briefly indicated suffice to show that during the climax of glaciation North America must have presented very much the same appearance as Europe. Each continent had its great northern ice-sheet, south of which local glaciers existed in hilly districts, many of which are now far below the limits of perennial snow. We may note, also, that in each continent the _mers de glace_ attained their greatest development over those regions which at the present day have the largest rainfall. Following the southern limits of glaciation in Europe, we are led at first directly east, until we reach central Russia, when the line we follow trends rapidly away to the north-east. The like is the case with North America. Trace the southern boundary of the ice-sheet west of New York, and you find, when you reach the valley of the Missouri, that it bends away to the north-west. Now we can hardly doubt that one principal reason for the non-appearance of the _mer de glace_ in the far east of Europe and the far west of America was simply a diminishing snow-fall. Those non-glaciated regions which lay north of the latitudes reached by the ice-sheets were dry regions in glacial times for the same reasons that they are dry still. The only differences between glacial Europe and America were differences due to geographical position and physical features. The glaciation of the Urals was comparatively unimportant, because those mountains, being flanked on either side by vast land-areas, could have had only a limited snow-fall; while the mountain-ranges of western North America, on the other hand, being situated near the Pacific, could not fail to be copiously supplied. For obvious reasons, also, the North American ice-sheet greatly exceeded that of Europe. In all other respects the conditions were similar in both continents. V. _Changes of Climate in North America during the Ice Age._ American geologists are now pretty well agreed that their "interglacial deposits"--the existence of which is not disputed--have precisely the same meaning as the similar deposits which occur in Europe. They tell of great climatic changes. At present, however, there is no certain evidence in the American deposits of more than one interglacial epoch; but the proofs of such an epoch having obtained are overwhelming. The occurrence again and again of fossiliferous beds intercalated between two separate and distinct sheets of boulder-clay and morainic accumulations, leaves us in no doubt that we are dealing with precisely the same phenomena which confront us in Europe. No mere partial recession and re-advance of the _mer de glace_ will account for the facts. We have seen that during the culmination of the Glacial period the American ice-sheet overflowed Ohio, Indiana, and Illinois. Now interglacial deposits occur as far north as the Canadian shores of Lakes Ontario and Superior, so that all the country to the south must have been uncovered by ice before those interglacial deposits were laid down. But the evidence entitles us to say much more than this. The interglacial beds of Ohio, Indiana, Illinois, and other States, afford abundant evidence of a great forest-growth having covered the regions vacated by the ice of the penultimate glacial epoch. The trees of this forest-land included sycamore, beech, hickory, red-cedar, and others; and amongst the plants were grape vines of enormous growth, which, according to Professor Cox, "indicate perhaps the luxuriance of a warmer climate." At all events, the climate that nourished such a forest-growth could not have been less genial than the present. And such being the case, we may reasonably infer that the vast regions to the north of the lakes were no more inhospitable then than they are now. To this genial interglacial epoch succeeded the last glacial epoch, when a great ice-sheet once more enveloped a wide area. In the extreme east this latest _mer de glace_ appears to have reached as far south as that of the earlier epoch; but as we follow its terminal moraines westward they lead us further and further away from the southern limits attained by the preceding ice-sheet. These great terminal moraines form an interesting study, and the general results obtained by American observers have been very carefully put together by Professor Chamberlin. I traversed wide regions of those moraines in Indiana, Illinois, Wisconsin, and Minnesota, and, so far as my observations went, I could only confirm the conclusions arrived at by Professor Chamberlin and others. The mounds, banks, cones, and ridges are unquestionably moraines--of enormous dimensions, no doubt, but in all their phenomena strictly analogous to similar gravelly moraines in our own country and the Continent. Many of the American moraines consist almost entirely of water-worn material--sand, gravel, shingle, and boulders, together with large angular and sub-angular erratics. These deposits are generally stratified, and frequently show diagonal or false-bedding. In this and other respects they exactly reproduce--but of course on a much larger scale--our Scottish kames, and the similar accumulations of north Germany and Finland, and the low-grounds of Italy opposite the mouths of the great Alpine lakes. The kames of Wisconsin again and again reminded me of the gravelly moraines that cover the ground for many miles round the lower end of Lake Garda. It is this gravelly and sandy aspect of the American moraines that is most conspicuous, water-assorted materials seeming everywhere to form their upper and outer portions. Now and again, however, a deep cutting discloses underneath and behind such water-worn detritus a mass of confused materials, consisting of clay, sand, gravel, shingle, and boulders, which are angular and sub-angular, often smoothed and striated, and of all shapes and sizes. According to Mr. Chamberlin, this unstratified material "is indistinguishable from true till, and is doubtless to be regarded as till pushed up into corrugations by the mechanical action of the ice." This grand series of moraines stretches from the peninsula of Cape Cod across the northern States, and passes in a north-westerly direction into the British Possessions, over which it has been followed for some 400 miles. The disposition of the moraines, forming as they do a series of great loops, shows that the ice-sheet terminated in a number of lobes or gigantic tongue-like processes. Nothing seen by me suggested any marine action; on the contrary, every appearance, as I have said, betokened the morainic origin of the mounds; and Mr. Chamberlin assured me that their peculiar distribution was everywhere suggestive of this origin. No one who has traversed the regions I refer to is at all likely to agree with Sir W. Dawson's view, that the American mounds, etc., are the shore-accumulations of an ice-laden sea. The morainic origin of these accumulations having been demonstrated by American geologists, we are now able to draw another parallel between the European and American glacial deposits. We have seen that in Europe the ice-sheet of the latest glacial epoch was by no means so extensive as that of the preceding glacial epoch. The same was the case in North America. Moreover, in America, just as in Europe, the latest occupant of the land was not the sea, but glacier-ice. In Scotland and Scandinavia the gradual disappearance of the latest ice-sheets was marked by a partial submergence, which in the former country did not greatly exceed 100 feet, and in the latter 700 feet. In America, in like manner, we find traces of a similar partial submergence. In Connecticut this did not exceed 40 or 50 feet, but increased to some 500 feet in the St. Lawrence, and to over 1000 feet in the Arctic regions. If there ever was during the Glacial period a greater submergence than this in North America it must have taken place in earlier glacial or interglacial times, but of such a submergence no trace has yet been recognised. In this respect the American record differs somewhat from our own, for in Britain we have evidence of a submergence of over 1000 feet, which supervened in times immediately preceding the latest great extension of continental ice.[P] But nowhere in middle Europe, and nowhere in North America, in the region south and west of the great lakes, is there any trace of a general marine submergence. The "Palæocrystic Sea" is as idle a dream for the northern States of America as it is for any part of Europe. [P] See footnote, p. 173. VI. _The Results of Fluvio-glacial Action in North America._ The close analogies which obtain between the glacial and interglacial deposits of Europe and North America are equally characteristic of the fluvio-glacial accumulations of the two continents. As in Europe, so in America we meet with considerable sheets of gravel and shingle, sand, fine clay, and loam, which are evidently of freshwater origin. In the gently-undulating tracts of the northern States those deposits often spread continuously over wide regions; in the hillier districts, however, they are most characteristic of the valleys. They are very well represented, for example, in the Connecticut valley, where they have been carefully studied by Professor Dana. Like the similar deposits of our own Continent, they have been laid down by the torrents and swollen rivers of the Glacial period. The great range of moraines which marks the extreme limits reached by the latest ice-sheet is generally associated with sheets of gravel and sand, which one can see at a glance are of contemporaneous origin, having been spread out by the water escaping from the melting ice. Nor can one doubt that the vast sheets of löss in the Missouri and Mississippi valleys are strictly analogous in origin, as they are in structure and disposition, to the löss of Europe. I have spoken of the probable existence of a glacial lake formed by the damming back of the Rhine and other rivers by the European ice-sheet. Now, in North America we meet with evidence of the same phenomenon. When the last ice-sheet of that continent attained its maximum development, all the water escaping from its margin in the north States necessarily flowed south into the Mississippi and Missouri rivers. But in course of time the ice melted away beyond the drainage-area of those rivers, and disappeared from the valley of the Red River of the north, which, it will be remembered, empties itself northward into Lake Winnipeg. When the ice-front had retired so far it naturally impeded the drainage of the Red River basin, and thus formed a vast glacial lake, the limits of which have been approximately mapped out by Mr. Upham, by whom the ancient lake has been designated Lake Agassiz. The deposits laid down in this lake consist of finely laminated clays, etc., which resemble in every particular the similar unfossiliferous clays so frequently found associated with glacial accumulations in Europe. Had the drainage of the Red River valley been south instead of north, the clays and loams of the far north-west would not have been arrested and spread out where they now are, and Manitoba would have been covered for the most part with loose shingle, gravel, and sand. Thus the final disappearance of the American ice-sheet was marked by the formation not only of moraines, but of flood-gravels and torrential- and inundation-deposits of the same character as those with which we are familiar at home. Wherever similar geographical conditions prevailed, there similar geological results followed. VII. _Conclusion._ There are many other points of resemblance between the glacial and fluvio-glacial accumulations of the two continents, but to these time forbids any reference. Indeed, I cannot recall any signal difference. Such differences as do occur are due simply to the varying conditions of the two continental areas. The glacial phenomena of North America are a repetition of those of Europe, but upon a much grander scale. The boulder-clays of the former continent, in their composition, structure, and distribution, exactly recall our own. Interglacial beds occur under similar circumstances in both continents; and the same is the case with the gravelly moraines and fluvio-glacial accumulations. We are driven, then, to the conclusion that the physical conditions of the Glacial period were practically the same in Europe and North America. What those conditions were I have already indicated, and have shown that the results arrived at by geologists are not vague dreams and speculations, but a logical induction from well-ascertained facts. Before we can believe that volcanic eruptions, a general deluge, or a Palæocrystic Sea have produced the many varied phenomena of our glacial formations, either in whole or in part, we must first shut our eyes and then erase from our minds all knowledge of the facts which have been so laboriously gathered by a long succession of competent observers. [Illustration: PLATE III DISTRIBUTION OF ICE PAST AND PRESENT. POLAR VIEW OF THE WORLD ON LAMBERTS EQUAL AREA PROJECTION ] VII. The Intercrossing of Erratics in Glacial Deposits.[Q] [Q] _The Scottish Naturalist_, 1881. Among the many phenomena connected with the glacial deposits of this country which have puzzled geologists there is none more remarkable than the "intercrossing of erratics." The fact that such wandered blocks have apparently crossed each other's tracks in their journeys appears at first sight inexplicable on the assumption that their transport has been effected by land-ice. The phenomena in question, therefore, have always been appealed to by those who uphold the iceberg origin of our boulder-clays, etc., as evidence decisively in favour of their views. No one can deny that any degree and amount of intercrossing might take place in the case of icebergs. We can readily conceive how floating ice, detached from a long line of coast, might be compelled by shifting winds and changing currents to tack about again and again, so as to pursue the most devious course, and scatter their stony burdens in the most erratic manner over the sea-bottom; while, on the other hand, it is quite impossible to understand how a similar irregular distribution of erratics could take place under one and the same glacier flowing in a determinate direction. It is little wonder, then, that the curious phenomena of the intercrossing of erratics should have had much importance attached to it by the upholders of the iceberg theory, seeing that all the other proofs which have been adduced in favour of this theory have only served to demonstrate its insufficiency. Upon the facts connected with the intercrossing of erratics, the supporters of this time-honoured theory are now making what I must believe is their last stand. I purpose therefore, in this paper, to give a short outline of those facts, with the view of showing that so far from being antagonistic to the land-ice theory, they are in complete harmony with it; and indeed must be considered as affording an additional demonstration of its truth. Some years ago I called attention to the fact that in the middle districts of Scotland the boulder-clay not infrequently contains a curious commingling of northern and southern erratics.[R] I showed that this was the case throughout a belt of country extending from the sea-coast near Ayr, north-east to the valley of the Irvine, and thence across the watershed into the Avon, and east to Lesmahagow, then down the valley of the Clyde to Carluke, stretching away to the east by Wilsontown, and thereafter continuing along the crest of the Pentlands and the northern slopes of the Lammermuir Hills, by Reston and Ayton, to the sea. "All along this line," I remarked, "we have a 'debatable ground' of variable breadth, throughout which we find a commingling in the till of stones which have come from north and from south. South of it, characteristic Highland stones do not occur, and north of it stones derived from the south are similarly absent." The explanation of these facts is obvious. The belt of ground referred to was evidently the meeting-place of the Highland and southern _mers de glace_. Here the two opposing ice-flows coalesced and became deflected by their mutual pressure to right and left--one great current going east and another west. It is evident that the line of junction between the two _mers de glace_ could not be rigorously maintained in one and the same position during a period of glaciation, but would tend to oscillate backwards and forwards, according as one or the other ice-sheet prevailed. Sometimes the southern ice-sheet would be enabled to push back the northern _mer de glace_, while at other times the converse would take place. Nor is it necessary to suppose that the advance of one ice-sheet was general along the whole line. On the contrary, it is most likely that the movement was quite irregular--an ice-sheet advancing in some places, while at other points its line of junction with the opposing ice-sheet remained stationary, or even retrograded. Such movements would obviously give rise to oscillations in the sub-glacial débris of clay and stones; and thus we have a simple and natural explanation of those intercrossings of erratics which are so characteristic of that region which I have termed the "debatable ground." And this conclusion is borne out by the fact that the glacial striæ of the same "debatable ground" afford like evidence of oscillation in the trend of the ice-flow. [R] _Great Ice Age_, 2nd edit., p. 609. Along the base of the Highland mountains in Forfarshire, etc., we meet with similar intercrossings of erratics. Thus we occasionally encounter in the boulder-clays overlying the Silurian regions erratics of Old Red Sandstone rocks which have come from the east or south-east; while the abundant presence of erratics of Silurian origin, on the other hand, bespeak an ice-flow from the west towards the low-grounds. In some places within the Silurian area we encounter a greyish-blue boulder-clay containing Silurian fragments only, while in other places within the same area the boulder-clay becomes reddish, and is charged with many boulders of Old Red Sandstone rocks. Now the greyish-blue till could only have been laid down by glacier-ice descending from the Silurian high-grounds to Strathmore, while the red boulder-clay points to a partial invasion of the Silurian regions by land-ice, which had previously traversed the lower-lying Old Red Sandstone areas. These apparently contradictory movements are readily accounted for by the former presence in the area of the North Sea of the great Scandinavian _mer de glace_. Dr. James Croll was the first to point out that the glacial phenomena of Caithness and the Shetlands could only be accounted for by the advance of the Scandinavian ice-sheet towards our coasts, where it encountered and deflected the Scottish ice-sheet out of its normal course--a sagacious induction, which the admirable and exhaustive researches of my colleagues, Messrs. B. N. Peach and J. Horne, have now firmly established. The lower blue boulder-clay was evidently accumulated at a time when the Scottish ice was able to flow more or less directly east or south-east towards what is now the coast-line; while the overlying red boulder-clay points to a subsequent period when the presence of the Scandinavian _mer de glace_ was sufficiently great to compel the Scottish ice out of its normal course, and cause it to flow in a north-easterly direction. In doing so it now and again passed from tracts of Old Red Sandstone to invade the Silurian area, and thus an overlying red boulder-clay was here and there accumulated upon the surface of a greyish-blue till in which not a single fragment of any Old Red Sandstone rock occurs. Recently Messrs. B. N. Peach and J. Horne, in a most instructive paper on the "Glaciation of Caithness,"[S] have described some remarkable comminglings of material which occur in a region where the glacial striæ afford equally striking evidence of conflicting ice-movements. These phenomena are developed here and there along a line which indicates the meeting-place of two rival ice-streams, on each side of which the boulder-clay presents different characteristics--the one boulder-clay being the _moraine profonde_ of the ice that flowed ENE. and NNE. towards the Caithness plain, while the other is an accumulation formed underneath the ice that streamed across that plain from SE. to NW. These phenomena are thus, as my colleagues remark, quite analogous to those met with in the middle districts of Scotland, as described by me, and referred to in a preceding paragraph. Now it is obvious that while these examples of "intercrossings" of erratics and "cross-hatching" of striæ all go strongly to support the land-ice theory of the glacial phenomena, they at the same time negative the notion of floating-ice having had anything to do with the production of the phenomena under review. [S] _Proceedings Royal Physical Society_, Edinburgh, 1881. Before considering the evidence adduced by Mr. Mackintosh and others as to the intercrossings of erratics in the drift-deposits of England, I shall mention some of the more remarkable examples of the same phenomena which have been noticed by continental geologists. The first cases I shall cite are those which have been observed in the glacial accumulations of the Rhone valley in eastern France. The land-ice origin of these accumulations has never been called in question, and as the intercrossings of erratics in that region are not only more common, but much more striking and apparently inexplicable than any which have been noticed elsewhere, it will be admitted that they of themselves afford a strong presumption that the conflicting courses followed by the erratics in certain regions of our own country are the result rather of oscillations in the flow of land-ice than of the random and eccentric action of icebergs. The researches of Swiss and French glacialists have proved that during the climax of the Glacial period an enormous area in the low-grounds of eastern France was covered with a huge _mer de glace_, formed by the union of the great Rhone glacier with the glaciers descending from the mountains of Savoy and Dauphiny. A line drawn from Bourg by way of Chatillon, Villeneuve, Trévoux, and Lyons to Vienne, and thence south-east by Beaurepaire to the valley of the Isère, a few miles above St. Marcellin, indicates roughly the furthest limits reached by the _mer de glace_. Over all the low-grounds between that terminal line and the mountains are found widespread sheets of boulder-clay and sand and gravel, together with loose erratics. Now and again, too, well-marked terminal moraines make their appearance, while the rock-surfaces, when these are visible and capable of bearing and retaining glacial markings, present the usual aspect of _roches moutonnées_. The same kinds of morainic materials and ice-markings may of course be followed up into the valleys not only of the Alps properly so-called, but also into those of the hills of Bugey and the secondary mountain-chain of Savoy and Dauphiny. It has indeed long been known that local glaciers formerly occupied the mountain-valleys of Bugey. For example, a number of small glaciers have descended from the slopes of the mountains west of Belley (such as Bois de la Morgue, Bois de Lind, etc.) to the Rhone, and again from Mont du Chat to the north-west. These glaciers were quite independent of the greater ice-streams of the neighbouring Alps of Savoy, and the same was the case with the glaciers of that mountainous tract which extends from Nantua south to Culoz, between the valleys of the Ain and the Rhone. From this elevated region many local glaciers descended, such as that of the Valromey, which flowed for a distance of some twenty miles from north to south. Again, similar local glaciers have left abundant traces of their former presence throughout the mountainous belt of land that stretches between Chambery and Grenoble to the west of the valley of the Isère. The moraines of all those local glaciers, charged as they are with the débris of the neighbouring heights, clearly indicate that the local glaciers flowed each down its own particular valley. There are certain other appearances, however, which seem at first sight to contradict this view. Sometimes, for example, we encounter in the same valleys erratics which do not belong to the drainage-system within which they occur, but have without doubt been derived from the higher Alps of Switzerland and Savoy. And the course followed by these foreign erratics has crossed at all angles that which the local glaciers have certainly pursued--occasionally, indeed, the one set of erratics has travelled in a direction exactly opposed to the trend taken by the others. As examples, I may cite the case of the erratics which occur in Petit Bugey. In this district we encounter many locally-derived erratics which have come from Mont du Chat to the west of the Lac du Bourget--that is to say, they have travelled in a north-westerly direction. But in the same neighbourhood are found many erratics of Alpine origin which have been carried from north-east to south-west, or at right angles to the course followed by the local erratics. Again, in the valley of the Seran we have evidence in erratics and terminal moraines of a local glacier which flowed south as far as the Lyons and Geneva Railway, in the neighbourhood of which, a few miles to the west of Culoz, its terminal moraines may be observed. This is the extinct Glacier du Valromey of MM. Falsan and Chantre. Now it is especially worthy of note that in the same valley we have distinct evidence of an ice-flow from south to north--_i.e._, _up_ the valley. Erratics and morainic materials which are unquestionably of Alpine origin have been followed a long way up the Seran valley--for two-thirds of its length at least. Before they could have entered that valley and approached the slopes of Romey, they must have travelled down the valley of the Rhone from the higher Alps of Savoy in a _south-west_ and _south_ direction until they rounded the Montagne du Grand Colombier. It was only after they had rounded this massive mountain-ridge that they could pursue their course up the valley of the Seran, in a direction precisely opposite to that which they had previously followed. These and many similar and even more remarkable examples of the "intercrossings" of streams of erratics are described by MM. Falsan and Chantre, and graphically portrayed in their beautiful and instructive work on the "Ancient Glaciers and Erratic Deposits of the Basin of the Rhone"; and the explanation of the phenomena given by them is extremely simple and convincing. The local erratics and moraines pertain partly to the commencement and partly to the closing stage of the Glacial period. Long before the south branch of the great glacier of the Rhone had united with the glacier of the Arve, and this last with the glaciers of Annecy and Beaufurt, and before these had become confluent with the glacier of the Isère, etc., the secondary mountain-ranges of Savoy and Dauphiny and the hills of Bugey were covered with very considerable snow-fields, from which local glaciers descended all the valleys to the low-ground. But when the vast ice-flows of Switzerland, Upper Savoy, etc., at last became confluent, they completely overflowed many of the hilly districts which had formerly supported independent snow-fields and glaciers, and deposited their bottom-moraines over the morainic débris of the local glaciers. In other cases, where the secondary hill-ranges were too lofty to be completely drowned in the great _mer de glace_, long tongues of ice dilated into the valleys, and compelled the local ice out of its course; sometimes, as in the case of the Valromey, forcing it backward up the valleys down which it formerly flowed. But when once more the mighty _mer de glace_ was on the wane, then the local glaciers came again into existence, and reoccupied their old courses. And thus it is that in the hilly regions at the base of the higher Alps, and even out upon the low-grounds and plains, we encounter that remarkable commingling of erratics which has been described above. Not infrequently, indeed, we find one set of moraines superposed upon another, just as in the low-grounds of northern Germany, etc., we may observe one boulder-clay overlying another, the erratics in which give evidence of transport in different directions. The observations recorded by MM. Falsan and Chantre, and their colleagues, thus demonstrate that "intercrossings" of erratics of the most pronounced character have been brought about solely by the action of glaciers. In the case of the erratics and morainic accumulations of the basin of the Rhone, the action of icebergs is entirely precluded. I may now mention some of the more remarkable examples of intercrossings of erratics which have been recorded from the glacial accumulations of north Germany, etc. An examination of the glacial striæ, _roches moutonnées_, and boulder-clays of Saxony leads to the conviction, according to Credner, Penck, Torell, Helland, and others, that the whole of that region has been invaded by the great Scandinavian _mer de glace_ which flowed into Saxony from NNE. to SSW. Erratics from southern Sweden and Gothland occur in the boulder-clay, and the presence of these, taken in connection with the direction of the glaciation, leaves us no alternative but to agree with the conclusions arrived at by the Saxon geologists. But, apparently in direct contradiction of this conclusion, we have evidence to show that boulders of the same kinds of rock occur in Denmark and Holland, pointing to a former ice-flow from north-east to south-west and west. Thus boulders derived from Gothland occur at Gröningen in Holland, while fragments from the island of Öland are met with in Faxö; and erratics from the borders of the Gulf of Finland are encountered at Hamburg. Indeed, when geologists come to examine the erratics in north Germany and Poland generally, they find evidence of apparently two ice-flows--one of which went south-south-west, south, and south-east--spreading out, as it were, in a fan-shape towards the southern limits reached by the great "Northern Drift,"--while the other seems to have followed the course of the Baltic depression, overflowing the low-grounds of northern Prussia, Holland, etc., in a south-west and west direction. Now, it is quite evident that no one _mer de glace_ could have followed these various directions at one and the same time. The explanation of the apparent anomaly, however, is not far to seek. It is reasonable to infer that long before the _mer de glace_ had attained its maximum dimensions, when as yet it was confined to the basin of the Baltic and was only able to overflow the northern regions of Prussia, etc., its course would be determined by the contour of the pavement upon which it advanced. It would, therefore, be compelled to follow the Baltic depression, and for a long time it would carry erratics from Finland, the Baltic islands, and eastern Sweden in a south-west and west-south-west direction. And this would continue to be the direction even after a considerable portion of the low-grounds of Prussia, etc., had been overflowed. But when the ice-sheet was enabled to advance south into Saxony, Poland, and Lithuania, erratics from Finland, the Baltic islands, etc., would necessarily cease to travel towards the west, and hold on a south-south-east, south, and south-south-west course. Again, when the _mer de glace_ was on the decline, a time would return when the ice, as before, would be controlled in its flow by the Baltic depression, and this would give rise to a further distribution of erratics in a prevalent west-by-south direction.[T] [T] For a fuller discussion of the distribution of erratics on the Continent, I may refer to Appendix, Note B, in _Prehistoric Europe_, where the reader will find references to the literature of this interesting subject. [Continental geologists now recognise a distinct stage of the Ice Age, during which their "Upper Diluvium" was deposited by a great glacier that occupied the basin of the Baltic. This "Great Baltic Glacier" appears to have been contemporaneous with the local ice-sheets and valley-glaciers of the Highlands and other mountain-tracts of our island. See Article X. 1892.] No one of late years has been more assiduous in the collection of facts relating to the intercrossing of erratics in the drift-deposits of England than Mr. D. Mackintosh.[U] He has written many instructive and interesting descriptions of the phenomena in question, which he justly thinks are of prime importance from a theoretical point of view. In a recent paper[V] he presents us with the results of a systematic survey of the direction and limits of dispersion of the erratics of the west of England and east of Wales, which he evidently is of opinion afford strong support to the iceberg theory, while at the same time they are directly opposed to the theory of transport by land-ice. I have attentively considered all the arguments advanced by Mr. Mackintosh in favour of his views--the one upon which he apparently lays most stress being that of the intercrossings of erratics observed by him--and I shall now proceed to point out how the phenomena described by him are most satisfactorily explained by the land-ice theory. They seem to me, indeed, to lend additional support to that theory, in the same manner as the intercrossings of boulders observed in Scotland, northern Germany, etc., and sub-alpine regions of France. Mr. Mackintosh calls attention to the fact that erratics of the well-known Criffel granite are found scattered over a large part of the plain of Cumberland, from which they extend south along the coast to near the mouth of the estuary of the Duddon. They reappear on the coast in the neighbourhood of Blackpool and Liverpool, and again at intervals on the coasts of north Wales from Flint to Colwyn Bay, and thence to Penmaenmawr and the neighbourhood of Beaumaris. They are dispersed over the peninsula of Wirral and the Cheshire plain, etc., and they have been followed south-east as far as the neighbourhood of Cardington, near Church Stretton, Burton, Wolverhampton, Stafford, Hare Castle, Macclesfield, and Manchester. This great stream of boulders, therefore, spreads out to south-east, south, and south-west: the erratics, to quote Mr. Mackintosh, "have radiated from an area much smaller than their terminal breadth." The same is the case, I may remark in passing, with erratics in the boulder-clays of Scotland, Scandinavia, north Germany, etc., as also with those in the drift-deposits of the great Rhone glacier and other ancient glaciers both on the north and south side of the Alps. Now, the course followed by the Criffel erratics is crossed at an acute angle by the path pursued by many boulders of Eskdale granite, and various felspathic rocks derived from the Cumberland mountains. For example, Cumberland erratics of the kinds mentioned occur near St. Asaph and Moel-y-Tryfane and in Anglesey, and they have been followed over a wide district in Cheshire, etc., extending as far south as Church Stretton and Wolverhampton, and as far east as Rochdale. More than this, we find that numerous erratics of felstone, derived from the mountain of Great Arenig, in north Wales, have gone to north-east as far as Halkin Mountain, in Flintshire, Eryrys, near Llanarmon, and Chirk, from which last-named place they have been traced in a south-easterly direction to Birmingham, Bromsgrove, etc. A glance at the map of England will show that this south-easterly drift of erratics crosses at an acute angle the paths followed by the Criffel granite boulders and the erratics derived from Cumberland, so that we have now several intercrossings to account for. How can this be done by the land-ice theory? [U] This enthusiastic geologist died in 1891. [V] _Quart. Journ. Geol. Soc._, vol. xxxv. p. 425 The explanation seems to me obvious, for the phenomena are, after all, less striking than similar appearances which have been observed in Scotland, especially by my colleagues, Messrs. Peach and Horne, in Caithness and the Orkney and Shetland Islands; and they are certainly less intricate than the facts recorded by MM. Falsan and Chantre concerning the intercrossing, interosculation, and direct opposition of erratic paths in Savoy and Dauphiny. We have only to reflect that the great _mer de glace_--to which, as I believe, all the English phenomena are due--did not come into existence and attain its maximum dimensions in the twinkling of an eye, nor could it afterwards have disappeared in the same sudden manner. On the contrary, a period of local glaciation must have preceded the appearance of the great ice-sheet. At first, and for a long time, permanent snow would be confined to the higher elevations of the land, and glaciers would be limited to mountain-valleys; but as the temperature fell the snow-line would gradually descend, until at last, probably after a prolonged period, it reached what is now the sea-level. Thus the formation of _névé_ and glacier-ice would eventually take place over what are now our low-grounds, and other tracts also, which are now submerged. It is quite impossible that the vast sheets of ice which can be demonstrated to have covered Scotland, a large part of England, Ireland, Scandinavia, and north Germany, and even the limited area of the Faröe Islands, could possibly have been fed by the snow-fields of mountain-heights only. The precipitation and accumulation of snow, and the formation of _névé_ and glacier-ice, must have taken place over enormous regions in what are now the temperate latitudes of Europe. It is obvious that the direction of ice-flow in the basin of the Irish Sea opposite the south of Scotland and the west of England, while preserving a general southerly trend, would vary at different periods. Before the _mer de glace_ in that basin had attained its climax there must have been a time when the ice, streaming outwards from the high-grounds of Cumberland, was enabled to push its way far westward out into the basin of the Irish Sea. At that time it was still able to hold its own against the pressure exerted by the Scottish ice. But as the general _mer de glace_ increased in thickness, the course of the Cumberland ice would be diverted ever further and further to the south-east, until, eventually, the Scottish ice came to hug the coast of Cumberland, and to overflow Lancashire in its progress towards the south-east. So gorged with ice did the basin of the Irish Sea become, that a portion of the Scottish ice was forced over the plain of Cumberland and up the valley of the Eden, where it coalesced with the ice coming north from the Shap district, and thereafter flowed in an easterly direction to join the great _mer de glace_ of the North Sea basin. Thus the intercrossings of the Criffel and Cumberland erratics described by Mr. Mackintosh receive a ready explanation by the land-ice theory. Nor do the intercrossings of the Welsh erratics with those derived from Scotland and Cumberland offer any difficulty. The ice coming from the Welsh mountains would naturally be deflected towards south-east by the _mer de glace_ that streamed in that direction, and might quite well have carried its characteristic boulders as far as Birmingham before the general _mer de glace_ had attained its greatest dimensions. But when that period of maximum glaciation arrived, the Welsh boulders would be unable to travel so far towards the east, and the Scottish and Cumberland boulders would then cross the path formerly followed by the felstone erratics from Great Arenig. Again, it is evident that when the _mer de glace_ was gradually decreasing similar oscillations of the ice-flow would take place, but in reverse order, and thus would give rise to a second series of intercrossings. Moreover, we must remember that the Glacial period was characterised by several great changes of climate. It was not one continuous and prolonged period of cold conditions, but consisted rather of a succession of arctic and genial climates; so that the same countries were overrun at different epochs by successive _mers de glace_, each of which would rework, denude, and redistribute to a large extent the morainic materials of its predecessor, and thus might well cause even greater complexity in the dispersion of erratics than has yet been recognised anywhere in these islands. Mr. Mackintosh refers to the occurrence of chalk-flints and Lias fossils associated with northern erratics in the drift-deposits of the west of England, the presence of which, he thinks, is fatal to the theory of transport by land-ice. Thus, he says, chalk-flints, etc., have been met with at Lillieshall (east of Wellington), at Strethill (near Ironbridge), at Seisdon (between Wolverhampton and Bridgenorth), at Wolverhampton, near Stafford, and near Bushbury. Chalk-flints have also been found as far west as Malvern and Hatfield Camp, south of Ledbury. All these erratics have crossed England from the east, according to Mr. Mackintosh and other observers. Not only so, but, as Mr. Mackintosh remarks, those found at Wolverhampton, Birmingham, etc., "must have _crossed the course_ of the northern boulders near its southerly termination." And since both northern and eastern erratics are found associated in the same drift-deposit, it seems to him "impossible to explain the intercrossing by land-ice or glaciers." Now, on the contrary, those eastern erratics are scattered over the very districts where I should have expected to find them. The observations of geologists in East Anglia have shown that that region has been invaded by the _mer de glace_ of the North Sea basin.[W] This remarkable glacial invasion is proved not only by the direction followed by stones of local derivation, and by boulders which have come south from Scotland and the northern counties, but by the occurrence in the boulder-clay at Carnelian Bay and Holderness of erratics of certain well-known Norwegian rocks, which have been recognised by Mr. Amund Helland. The occurrence of chalk-flints and fragments of Oolitic rocks in the neighbourhoods mentioned by Mr. Mackintosh thus only affords additional evidence in favour of the land-ice origin of the drift-deposits described by him. The _mer de glace_ that flowed down the east coast of England seems to have encroached more and more upon the land, until eventually it swept over the low-lying Midlands in a south-westerly direction, and coalesced with the _mer de glace_ that streamed inland from the basin of the Irish Sea, and the ice that flowed outwards from the high-grounds of Wales. The united ice-stream would thereafter continue on its south-westerly course down the Severn valley to the Bristol Channel. I have no doubt that Mr. Mackintosh will yet chronicle the occurrence of chalk-flints and other eastern erratics from localities much further to the south than Ledbury. [W] See Mr. Skertchly's description of East Anglian deposits in _Great Ice Age_, 2nd edit., p. 358. Again, considerable stress has been laid by Mr. Mackintosh upon the occurrence of chalk-flints in the drift-deposits of Blackpool, Dawpool, Parkgate, Halkin Mountain, Wrexham, the peninsula of Wirral, Runcorn, Delamere, Crewe, Leylands, Piethorne (near Rochdale), and other places. "All these flints," Mr. Mackintosh remarks, "belong to the basin of the Irish Sea, and have almost certainly crossed the general course of the northern boulders on their way from Ireland." Here, unfortunately, the Irish Sea intervenes to conceal the evidence that is needed to enable us to track the exact path followed by the erratics in question. I am not so certain as Mr. Mackintosh that the chalk-flints he refers to came from the north of Ireland. Chalk-flints occur pretty numerously in the drift-deposits in the maritime districts of north-eastern Scotland, which we have every reason to believe have been derived from an area of Cretaceous rocks covering the bottom of the adjacent sea; and for aught one can say to the contrary, patches of chalk-with-flints may occur in like manner in the bed of the Irish Sea. I cannot at present remember whether any boulders of the basalt-rocks, which are associated with the Chalk in the north of Ireland, have been recognised in the drifts of the west of England; but if the chalk-flints really came from Antrim, it is more than probable that they would be accompanied by fragments of the hard igneous rocks which overlie the Cretaceous strata of north Ireland. Chalk and chalk-flints occur in the boulder-clay of the Isle of Man, where they are associated, Mr. Horne tells us, with Criffel granite and fragments of a dark trap-rock.[X] Possibly these last are basalt-rocks from Antrim. It seems reasonable, therefore, to believe that erratics of Irish origin have found their way to the Isle of Man; and if this be so, it may be permissible to assume that the chalk-flints of Blackpool, etc. (and perhaps also some of the basalt-rocks), have come from the same quarter. Mr. Horne has no doubt that the Irish erratics were brought to the Isle of Man by land-ice. Referring to the conclusion arrived at by Mr. Close that the Irish _mer de glace_ "was probably not less than 3000 feet in depth," he remarks: "It is highly probable that this great mass of Irish ice succeeded, after a hard battle (_i.e._, with the Scottish ice-sheet), in reaching the Manx coast-line. It is not to be supposed that the normal momentum of the respective ice-sheets remained constant. The moving force must have varied with changing conditions. On the other hand, it is quite possible that there may have been an 'under-tow' of the ice from the north-east coast of Ireland, which would easily account for Antrim chalk and chalk-flints in the Manx till." I would go further, and state my conviction that before the united ice-sheets had attained their maximum development, it is almost certain that the ice flowing into the Irish Sea basin by the North Channel would for a long time exceed in mass the coalescent glaciers that descended from the Southern Uplands of Scotland, and would therefore be enabled to extend much further to the east than it could at a later date, when the general _mer de glace_ had reached its climax. It might thus have advanced as far as and even beyond the Isle of Man. This inference is based upon the simple fact that the area drained by the _mer de glace_ of the North Channel was very much greater than the area extending from the watershed of the Southern Uplands of Scotland to the Isle of Man. Erratics from the north of Ireland would thus travel down the bed of the North Channel, and eventually be distributed over a wide area up to and possibly even some distance beyond the Isle of Man. But as the Scottish and Cumbrian ice-flows gradually increased in importance, the _mer de glace_ coming from the North Channel would be forced further and further to the west, until the ice-flow issuing from the high-grounds of Kirkcudbright at last succeeded in reaching the middle of the Irish Sea basin. This gradual modification of the general ice-flow in that basin would of course give rise to a redistribution of the ground-moraine, and the Irish erratics would then travel onwards underneath the Scottish ice, and eventually reach the low-grounds of Lancashire and Cheshire, along with erratics from Criffel and the Cumbrian mountains. It is, therefore, quite unnecessary to suppose that the _mer de glace_ of the North Channel actually crossed the whole breadth of the basin of the Irish Sea to invade Lancashire, Cheshire, and north Wales. Had this been the case, chalk-flints, chalk, and many other kinds of rock derived from the north of Ireland, and even from Arran and Argyll, would have abounded in the drifts of the west of England. Erratics coming from Ireland could not possibly have travelled underneath Irish ice further east than the Isle of Man. There or thereabouts, as I have said, the _mer de glace_ of the North Channel would begin to encounter the ice streaming down from the uplands of Galloway and the mountains of Cumberland: and as the ice from these quarters increased in thickness, it would gradually override what had formerly been the bottom-moraine or till of the North Channel _mer de glace_. Thus Irish erratics would become commingled with erratics from Criffel, etc., and be carried forward in a southerly and south-easterly direction. The chalk-flints in the drifts of Lancashire, Cheshire, etc., are probably therefore _remaniés_--the relics of the bottom-moraine of the North Channel _mer de glace_ rearranged and redistributed. And this is why they and other Irish rocks are so comparatively rare in the glacial accumulations of the west of England. [X] _Trans. Edin. Geol. Soc._, vol. ii., 1874. Thus all the instances of intercrossings adduced by Mr. Mackintosh as favouring the iceberg theory, and condemning its rival, I would cite as proving exactly the opposite. So far from presenting any real difficulty to an upholder of the land-ice theory, they, in point of fact, as I have already remarked, lend that view additional support. It is not my purpose to criticise all the arguments and reasons advanced by Mr. Mackintosh in favour of his special views, but I may be allowed a few remarks on the somewhat extraordinary character of the agents which, according to him, were mainly instrumental in producing the drift-phenomena of western England. Before doing so, however, I may point out that, in ascribing the transport of erratics in that region (and, by implication, the formation of the boulder-clays, etc., with which most of these erratics are associated) to floating-ice and sea-currents, Mr. Mackintosh has failed to furnish us with any "fossil evidence" to show that western England was under water at the time the boulder-clays and erratics were being accumulated. He speaks of cold and warm currents, but where do we find any traces of the marine organisms which must have abounded in those waters? Where are the raised sea-beaches which must have marked the retreat of the sea? Where do we encounter any organic relics that might help us to map out the zones of shallow and deep water? The sea-shells, etc., which occur in the boulder-clays are undeniably _remaniés_; they are erratics just as much as the rock-fragments with which they are associated. Similar assemblages of organic remains are met with in the till of Caithness, where shallow-water and deep-sea shells, and shells indicative of genial and again of cold conditions, are all confusedly distributed throughout one and the same deposit. The same or analogous facts are encountered in the _Blocklehm_ of some parts of Prussia, marine and freshwater shells occurring commingled in the boulder-clay. Nay, even in the _moraine profonde_ of the ancient Rhone glacier, broken and well-preserved shells of Miocene and Pliocene species appear enclosed in the tumultuous accumulation of clay, sand, and erratics. And precisely similar phenomena confront us in the glacial deposits of the neighbourhood of Lago Lugano. Mr. Mackintosh refers to the so-called "stratification" of the boulder-clay, as if that were a proof of accumulation in water. But a rude kind of bedding, generally marked by differences of colour, and sometimes by lines of stones, was the inevitable result of the sub-glacial formation of the boulder-clay. The "lines of bedding" are due to the shearing of the clay under great pressure, and may be studied in the boulder-clay of Switzerland and Italy, and in the till not only of the Lowlands but of the Highlands of Scotland. Occasionally the "lines" are so close that the clay sometimes presents the appearance of rude and often wavy and irregular lamination--a section of such a boulder-clay reminding one sometimes of that of a gnarled gneiss or crumpled schist. And these appearances may be noted in boulder-clays which occupy positions that preclude the possibility of their being marine--as in certain valleys of the Highlands, such as Strathbraan, and in the neighbourhood of Como, in Italy. This "lamination" is merely indicative of the intense pressure to which the till was subjected during its gradual accumulation under the ice. It is assuredly not the result of aqueous action. Aqueous lamination is due to sifting and winnowing--the coarser or heavier and finer or lighter particles being separated in obedience to their different specific gravity, and arranged in layers of more or less regularity according to circumstances. There is nothing of this kind of arrangement, however, in the so-called stratified boulder-clay. If the clay of an individual lamina be washed and carefully sifted, it will be found to be composed of grains of all shapes, sizes, and weights, down to the finest and most impalpable flour. It is impossible to believe that such a heterogeneous assemblage of grains could have been dropt into water without the particles being separated and sifted in their progress to the bottom. Of course, every one knows that patches and beds of laminated clay and sand of veritable aqueous origin occur now and again in boulder-clay. I suppose there is no boulder-clay without them. I have seen them in the till of Italy and Switzerland, where they show precisely the same features as the similar laminated clays in the till of our own islands. But these included patches and beds point merely to the action of sub-glacial waters, such as we know circulate under the glaciers of the Alps, of Norway, and of Greenland. Again, I would remark that Mr. Mackintosh has ignored all the evidence which has been brought forward from time to time to demonstrate the sub-glacial origin of boulder-clay, and to prove the utter insufficiency of floating-ice to account for the phenomena. And he adduces no new facts in support of the now discredited iceberg theory, unless it be his statement that _flat_ striated rock-surfaces (such as those near Birkenhead) have been caused by floating-ice--the dome-shaped _roches moutonnées_ being, on the other hand the work of land-ice. As a matter of personal observation, I can assure Mr. Mackintosh that _flat_ striated surfaces are by no means uncommonly associated in one and the same region with _roches moutonnées_. What are _roches moutonnées_ but the rounded relics of what were formerly rough uneven tors, projecting bosses, and prominent rocks? The general tendency of glacial action is to reduce the asperities of a land-surface; hence projecting points are rounded off, while flat surfaces are simply, as a rule, planed smoother. Mr. Mackintosh might traverse acres of such smoothed rock-surfaces in regions where the strata are comparatively horizontal--for example, in the case of the basaltic plateaux of the Faröes and of Iceland, which have certainly been glaciated by land-ice. Similar flat glaciated surfaces are met with again and again both in the Highlands and Lowlands of Scotland, occupying positions and associated with _roches moutonnées_ and till of such a character as to prove beyond any doubt that they no less certainly are the result of the action of land-ice. But it is needless to discuss the probability or possibility of glaciation of any kind being due to floating-ice. We know that glaciers can and do polish and striate rock-surfaces; no one, however, can say the same of icebergs: and until some one can prove to us that icebergs have performed this feat, or can furnish us with well-considered reasons for believing them to be capable of it, glacialists will continue sceptical. But leaving these and other points which serve to show the weakness of the cause which Mr. Mackintosh supports with such keen enthusiasm, I may, in conclusion, draw attention to certain very remarkable theoretical views of his which seem to me to be not only self-contradictory, but opposed to well-known natural laws. Briefly stated, his general view is that the erratics of the west of England have been distributed by floating-ice during a period of submergence--the scattering of erratics and the accumulation of the associated glacial deposits having commenced at or about the time when the land began to sink, and continued until the submergence reached some 2000 feet below the present sea-level. In applying this hypothesis to explain the phenomena, Mr. Mackintosh makes rather free use of sea-currents and winds. For example, he holds that a current coming from Criffel carried with it boulder-laden ice which flowed south-west to the Isle of Man, south to north Wales, and south-east in the direction of Blackpool and Manchester, Liverpool and Wolverhampton, Dawpool and Church Stretton. Now, in the first place, it is very strange that there is not a vestige or trace of any such submergence, either in the neighbourhood of Criffel itself or in the region to the north of it. The whole of that region has been striated and rubbed by land-ice coming down from the watershed of the Galloway mountains, to the north of which the striæ, _roches moutonnées_, and tracks followed by erratics, indicate an ice-flow _towards_ the north-west, north, and north-east. It is, therefore, absolutely certain that at the time the granite erratics are supposed to have sailed away from Criffel on floating-ice, the whole of the Southern Uplands of Scotland were covered with a great ice-field extending from Wigtown to Berwickshire; so that, according to Mr. Mackintosh's hypothesis, we should be forced to believe that an ocean-current originated in Criffel itself! But waiving this and other insuperable objections which will occur to any geologist who is familiar with the glacial phenomena of the south of Scotland, and confining myself to the evidence supplied by the English drifts, I would remark that Mr. Mackintosh's hypothesis is not consistent with itself. A current flowing in the direction supposed could not possibly have permitted floating-ice to sail from Cumbria to the Isle of Man, to Moel-y-Tryfane and Colwyn Bay. Mr. Mackintosh admits this himself, but infers that the transport of the Cumbrian erratics may have taken place at a different time. But how could this be, seeing that the Criffel and Cumbrian erratics occur side by side in one and the same deposit? Again, the hypothesis of an ocean-current coming from Criffel is inconsistent with the presence of the Irish chalk-flints in the drifts of the west of England. Did these also come at a different time? And what about the dispersion of erratics from Great Arenig, which have gone north-east and north-north-east, almost exactly in the face of the supposed Criffel current? Here an ocean-current is obviously out of the question; and accordingly we are told that this dispersion of Welsh boulders was probably the result of wind. But why should this wind have propelled the floating-ice so far and no further in an easterly direction? Surely if floating-ice was swept outwards from Great Arenig as far as Eryrys, bergs must have been carried now and again much further to the east. And if they did not sail eastwards, what became of them? Did they all melt away immediately when they came into the ice-laden current that flowed towards the south-east?[Y] A still greater difficulty remains. The Criffel and Cumbrian erratics suddenly cease when they are followed to the south, great quantities of them being accumulated over a belt of country extending from beyond Wolverhampton to Bridgenorth. What was it that defined the southern limits of these northern boulders? It is clear that it could not have been high-ground, for the Severn valley, not to speak of low-lying regions further to the north-east, must have been submerged according to Mr. Mackintosh's hypothesis. There was therefore plenty of sea-room for the floating-ice to escape southwards. And yet, notwithstanding this, vast multitudes of bergs and floes, as soon as they arrived at certain points, suddenly melted away and dropt their burdens! In what region under the sun does anything like that happen at the present day? Mr. Mackintosh thinks that the more or less sharply-defined boundary-line reached by the erratics "could only have resulted from close proximity to a persistent current of water (or air?) sufficiently warm to melt the boulder-laden ice." He does not tell us, however, where this warm current of water or air came from, or in what direction it travelled. He forgets some of his own facts connected with the appearance of erratics of eastern derivation, and which, according to him, point to an ocean-current that flowed across from Lincolnshire into the very sea in which the Criffel granite and Cumbrian boulders were being dropt. The supposed warm ocean-current, then, if such it was rather than air, could hardly have come from the east. Neither is it at all likely that it could have come from the west, sheltered as the region of the Severn valley must have been by the ice-laden mountains of Wales. Again, the south is shut to us; for there are no erratics in the south of England from which to infer a submergence of that district. If it be true that all the northern erratics which are scattered over the low-grounds of England, Denmark, Holland, Germany, Poland, and Russia, owe their origin to boulder-laden ice carried by ocean-currents, no such warm water as Mr. Mackintosh desiderates could possibly have come from the east or south-east. We are left, then, to infer that the supposed warm current[Z] must have flowed up the Severn valley directly in the face of the Criffel current, underneath which it suddenly plunged at a high temperature, the line of junction between it and the cold water being sharply defined, and retaining its position unchanged for a long period of time! However absurd this conclusion may be, it is forced upon us if we admit the hypothesis at present under review. For we must remember that the floating-ice is supposed to have melted whenever it came into contact with the warm current. The erratics occur up to a certain boundary-line, where they are concentrated in enormous numbers, and south of which they do not appear. Here, then, large and small floes alike must have vanished at once! Certainly a very extraordinary case of dissolution. [Y] Mr. Mackintosh says nothing about the "carry" or direction of the erratics in west and south Wales. Were the paths of these erratics delineated upon a map, we should find it necessary to suppose that the wind- or sea-current by which the floating-ice was propelled had flowed outwards in all directions from the dominant heights! [Z] It must have likewise flowed in more or less direct opposition to the current which, in accordance with the iceberg hypothesis, transported boulders southwards from the high-grounds of south Wales! If we dismiss the notion of a warm ocean-current for that of a warm wind, we do not improve our position a whit. Where did the warm wind come from? Not, certainly, from the ice-laden seas to the east. Are we to suppose, then, that it flowed in from the south or south-west? If so, we might well ask how it came to pass that in the immediate proximity of such a very warm wind as the hypothesis demands, great snow-fields and glaciers were allowed to exist in Wales? Passing that objection, we have still to ask how this wind succeeded in melting large and small masses of floating-ice with such rapidity that it prevented any of them ever trespassing south of a certain line? It is obvious that it must have been an exceedingly hot wind; and that, just as the hypothetical warm ocean-current must have suddenly dived under the cold water coming from the north, so the hot wind, after passing over the surface of the sea until it reached a certain more or less well-defined line, must have risen all at once and flowed vertically upwards into the cold regions above. Thus, in seeking to escape from what he doubtless considers the erroneous and extravagant views of "land-glacialists," Mr. Mackintosh adopts a hypothesis which lands him in self-contradictions and a perfect "sea of troubles"--a kind of chaos, in fact. In attempting to explain the drifts of western England and east Wales he has ignored the conditions that must have obtained in contiguous regions--thus forgetting that "nothing in the world is single," and that one ought not to infer physical conditions for one limited area without stopping to inquire whether these are in consonance with what is known of adjacent districts, or in harmony with the existing phenomena of nature. I have so strongly opposed Mr. Mackintosh's explanation of the sudden termination of the northern erratics in the neighbourhood of Wolverhampton and elsewhere, that perhaps I ought to offer an explanation of my own, that it may, in its turn, undergo examination. I labour under the disadvantage, however, of not having studied the drifts in and around Wolverhampton, etc., and the suggestion which I shall throw out must therefore be taken for what it is worth. It seems to me, then, that the concentration of boulders in the neighbourhood of Wolverhampton, and the limits reached by the northern erratics generally, mark out, in all probability, the line of junction between the _mer de glace_ coming from the basin of the Irish Sea and that flowing across the country from the vast _mer de glace_ that occupied the basin of the German Ocean. Along this line the southerly transport of the northern boulders would cease, and here they would therefore tend to become concentrated. But it is most likely that now and again they would get underneath the ice-flow that set down the Severn valley, and I should anticipate that they will yet be detected, along with erratics of eastern origin, as far south even as the Bristol Channel. If it be objected to this view that erratics from Great Arenig have been met with south of Wolverhampton, at Birmingham and Bromsgrove, I would reply that these erratics were probably carried south either before or after the general _mer de glace_ had attained its climax--at a period when the Welsh ice was able to creep out further to the east than it could when the invasion of the North Sea ice was at its height. I cannot conclude this paper without expressing my admiration for the long-continued and successful labours of the well-known geologist whose views I have been controverting. Although I have entered my protest against his iceberg hypothesis, and have freely criticised his theoretical opinions, I most willingly admit that the practical results of his unwearied devotion to the study of those interesting phenomena with which he is so familiar have laid all his fellow-workers under a debt of gratitude. VIII. Recent Researches in the Glacial Geology of the Continent.[AA] [AA] Presidential Address to the Geological Section of the British Association, Newcastle, 1889. THE President of this section must often have some difficulty in selecting a subject for his address. It is no longer possible to give an interesting and instructive summary of the work done by the devotees of our science during even one year. So numerous have the students of geological science become--so fertile are the fields they cultivate--so abundant the harvests they reap, that one in my present position may well despair of being able to take stock of the numerous additions to our knowledge which have accumulated within the last twelve months. Neither is there any burning question which at this time your President need feel called upon to discuss. True, there are controversies that are likely to remain unsettled for years to come--there are still not a few matters upon which we must agree to differ--we do not yet see eye to eye in all things geological. But experience has shown that as years advance truth is gradually evolved, and old controversies die out, and so doubtless it will continue to be. The day when controversies shall cease, however, is yet, I hope, far in the future; for should that dull and unhappy time ever arrive, it is quite certain that mineralogists, petrologists, palæontologists, and geologists shall have died out of the world. Following the example of many of my predecessors, I shall confine my remarks to certain questions in which I have been specially interested; and in doing so I shall endeavour to steer clear, as far as I can, of controversial matters. My purpose, then, is to give an outline of some of the results obtained during the last few years by Continental workers in the domain of glacial geology. Those who are not geologists will probably smile when they hear one declare that wielders of the hammer are extremely conservative--that they are slow to accept novel views, and very tenacious of opinions which have once found favour in their eyes. Nevertheless, such is the case, and well for us that it is so. However captivating, however imposing, however strongly supported by evidence a new view may appear to be, we do well to criticise, to sift the evidence, and to call for more facts and experiments, if such are possible, until the proofs become so strong as to approach as near a demonstration as geologists can in most cases expect such proofs to go. The history of our science, and indeed of most sciences, affords abundant illustration of what I say. How many long years were the views of sub-aërial erosion, as taught by Hutton and Playfair, canvassed and controverted before they became accepted! And even after their general soundness had been established, how often have we heard nominal disciples of these fathers of physical geology refuse to go so far as to admit that the river-valleys of our islands have been excavated by epigene agents! If, as a rule, it takes some time for a novel view to gain acceptance, it is equally true that views which have long been held are only with difficulty discarded. Between the new and the old there is a constant struggle for existence, and if the latter should happen to survive, it is only in a modified form. I have often thought that a history of the evolution of geological theories would make a very entertaining and instructive work. We should learn from it, amongst other things, that the advance of our science has not always been continuous--now and again, indeed, it has almost seemed as if the movement had been retrograde. Knowledge has not come in like an overwhelming flood--as a broad majestic river--but rather like a gently-flowing tide, now advancing, now retiring, but ever, upon the whole, steadily gaining ground. The history I speak of would also teach us that many of the general views and hypotheses which have been from time to time abandoned as unworkable, are hardly deserving of the reproach and ridicule which we in these latter days may be inclined to cast upon them. As the Scots proverb says: "It is easy to be wise behindhand." It could be readily shown that not a few discarded notions and opinions have frequently worked for good, and have rather stimulated than checked inquiry. Such reflections should be encouraging to every investigator, whether he be a defender of the old or an advocate of the new. Time tries all, and each worker may claim a share in the final establishment of the truth. Perhaps there is no department of geological inquiry that has given rise to more controversy than that which I have selected for the subject of this address. Hardly a single step in advance has been taken without vehement opposition. But the din of contending sides is not so loud now--the dust of the conflict has to some extent cleared away, and the positions which have been lost or maintained, as the case may be, can be readily discerned. The glacialist who can look back over the last twenty-five years of wordy conflict has every reason to be jubilant and hopeful. Many of those who formerly opposed him have come over to his side. It is true he has not had everything his own way. Some extreme views have been abandoned in the struggle; that of a great Polar ice-sheet, for example, as conceived of by Agassiz. I am not aware, however, that many serious students of glacial geology ever adopted that view. But it was quite an excusable hypothesis, and has been abundantly suggestive. Had Agassiz lived to see the detailed work of these later days, he would doubtless have modified his notion and come to accept the view of large continental glaciers which has taken its place. The results obtained by geologists who have been studying the peripheral areas of the drift-covered regions of our Continent, are such as to satisfy us that the drifts of those regions are not iceberg-droppings, as we used to suppose, but true morainic matter and fluvio-glacial detritus. Geologists have not jumped to this conclusion--they have only accepted it after laborious investigation of the evidence. Since Dr. Otto Torell, in 1875, first stated his belief that the Diluvium of north Germany was of glacial origin a great literature on the subject has sprung up, a perusal of which will show that with our German friends glacial geology has passed through much the same succession of controversial phases as with us. At first icebergs are appealed to as explaining everything--next we meet with sundry ingenious attempts at a compromise between floating-ice and a continuous ice-sheet. As observations multiply, however, the element of floating-ice is gradually eliminated, and all the phenomena are explained by means of land-ice and "Schmelz-wasser" alone. It is a remarkable fact that the iceberg hypothesis has always been most strenuously upheld by geologists whose labours have been largely confined to the peripheral areas of drift-covered countries. In the upland and mountainous tracts, on the other hand, that hypothesis has never been able to survive a moderate amount of accurate observation. Even in Switzerland--the land of glaciers--geologists at one time were of opinion that the boulder-clays of the low-grounds had a different origin from those which occur in the mountain-valleys. Thus, it was supposed that at the close of the Pleistocene period the Alps were surrounded by great lakes or by gulfs of some inland sea, into which the glaciers of the high valleys flowed and calved their icebergs--these latter scattering erratics and earthy débris over the drowned areas. Sartorius von Waltershausen[AB] set forth this view in an elaborate and well-illustrated paper. Unfortunately for his hypothesis no trace of the supposed great lakes or the inland sea has ever been detected: on the contrary, the character of the morainic accumulations, and the symmetrical grouping and radiation of the erratics and perched blocks over the foot-hills and low-grounds, show that these last have been invaded and overflowed by the glaciers themselves. Even the most strenuous upholders of the efficacy of icebergs as originators of some boulder-clays, admit that the boulder-clay or till, of what we may call the inner or central region of a glaciated tract is the product of land-ice. Under this category comes the boulder-clay of Norway, Sweden, and Finland, and of the Alpine Lands of central Europe, not to speak of the hilly parts of our own islands. [AB] "Untersuchungen über die Klimate der Gegenwart und der Vorwelt," etc.--_Natuurkundige Verhandelingen v. d. Holland. Maatsch. d. Wetensch. te Haarlem_, 1865. When we come to study the drifts of the peripheral areas, it is not difficult to see why these should be considered to have had a different origin. They present certain features which, although not absent from the glacial deposits of the inner region, are not nearly so characteristic of such upland tracts. I refer especially to the frequent interstratification of boulder-clays with well-bedded deposits of clay, sand, and gravel; and to the fact that these boulder-clays are often less compressed than those of the inner region, and have even occasionally a silt-like character. Such appearances do seem at first to be readily explained on the assumption that the deposits have been accumulated in water opposite the margin of a continental glacier or ice-sheet--and this was the view which several able investigators in Germany were for some time inclined to adopt. But when the phenomena came to be studied in greater detail, and over a wider area, this preliminary hypothesis did not prove satisfactory. It was discovered, for example, that "giants' kettles"[AC] were more or less commonly distributed under the glacial deposits, and such "kettles" could only have originated at the bottom of a glacier. Again, it was found that pre-glacial accumulations were plentifully developed in certain places below the drift, and were often involved with the latter in a remarkable way. The "brown-coal formation" in like manner was violently disturbed and displaced, to such a degree that frequently the boulder-clay is found to underlie it. Similar phenomena were encountered in regions where the drift overlies the Chalk--the latter presenting the appearance of having been smashed and shattered--the fragments having often been dragged some distance, so as to form a kind of friction-breccia underlying the drift, while large masses are often included in the clay itself. All the facts pointed to the conclusion that these disturbances were due to tangential thrusting or crushing, and were not the result of vertical displacements, such as are produced by normal faulting, for the disturbances in question die out from above downwards. Evidence of similar thrusting or crushing is seen in the remarkable faults and contortions that so often characterise the clays and sands that occur in the boulder-clay itself. The only agent that could produce the appearances, now briefly referred to, is land-ice, and we must therefore agree with German geologists that glacier-ice has overflowed all the drift-covered regions of the peripheral area. No evidence of marine action in the formation of the stony clays is forthcoming--not a trace of any sea-beach has been detected. And yet, if these clays had been laid down in the sea during the retreat of the ice-sheet from Germany, surely such evidence as I have indicated ought to be met with. To the best of my knowledge the only particular facts which have been appealed to, as proofs of marine action, are the appearance of bedded deposits in the boulder-clays, and the occasional occurrence in the clays themselves of a sea-shell. But other organic remains are also met with now and again in similar positions, such as mammalian bones and freshwater shells. All these, however, have been shown to be derivative in their origin--they are just as much erratics as the stones and boulders with which they are associated. The only phenomena, therefore, that the glacialist has to account for are the bedded deposits which occur so frequently in the boulder-clays of the peripheral regions, and the occasional silty and uncompressed character of the clays themselves. [AC] These appear to have been first detected by Professor Berendt and Professor E. Geinitz. The intercalated beds are, after all, not hard to explain. If we consider for a moment the geographical distribution of the boulder-clays, and their associated aqueous deposits, we shall find a clue to their origin. Speaking in general terms, the stony clays thicken out as they are followed from the mountainous and high-lying tracts to the low-grounds. Thus they are of inconsiderable thickness in Norway, the higher parts of Sweden, and in Finland, just as we find is the case in Scotland, northern England, Wales, and the hilly parts of Ireland. Traced south from the uplands of Scandinavia and Finland, they gradually thicken out as the low-grounds are approached. Thus in southern Sweden they reach a thickness of 43 metres or thereabout, and of 80 metres in the northern parts of Prussia, while over the wide low-lying regions to the south they attain a much greater thickness--reaching in Holstein, Mecklenburg, Pomerania, and west Prussia, a depth of 120 to 140 metres, and still greater depths in Hanover, Mark Brandenburg, and Saxony. In those regions, however, a considerable portion of the diluvium consists, as we shall see presently, of water-formed beds. The geographical distribution of the aqueous deposits, which are associated with the stony clays, is somewhat similar. They are very sparingly developed in districts where the boulder-clays are thin. Thus they are either wanting, or only occur sporadically in thin irregular beds, in the high-grounds of northern Europe generally. Further south, however, they gradually acquire more importance, until in the peripheral regions of the drift-covered tracts they come to equal and eventually to surpass the boulder-clays in prominence. These latter, in fact, at last cease to appear, and the whole bulk of the diluvium, along the southern margin of the drift area, appears to consist of aqueous accumulations alone. The explanations of these facts advanced by German geologists are quite in accordance with the views which have long been held by glacialists elsewhere, and have been tersely summed up by Dr. Jentzsch.[AD] The northern regions, he says, were the feeding-grounds of the inland-ice. In those regions melting was at a minimum, while the grinding action of the ice was most effective. Here, therefore, erosion reached its maximum--ground-moraine or boulder-clay being unable to accumulate to any thickness. Further south melting greatly increased, while ground-moraine at the same time tended to accumulate--the conjoint action of glacier-ice and sub-glacial water resulting in the complex drifts of the peripheral area. In the disposition and appearance of the aqueous deposits of the diluvium we have evidence of an extensive sub-glacial water-circulation--glacier-mills that gave rise to "giants' kettles"--chains of sub-glacial lakes in which fine clays gathered--streams and rivers that flowed in tunnels under the ice, and whose courses were paved with sand and gravel. Nowhere do German geologists find any evidence of marine action. On the contrary, the dovetailing and interosculation of boulder-clay with aqueous deposits are explained by the relation of the ice to the surface over which it flowed. Throughout the peripheral area it did not rest so continuously upon the ground as was the case in the inner region of maximum erosion. In many places it was tunnelled by rapid streams and rivers, and here and there it arched over sub-glacial lakes, so that accumulation of ground-moraine proceeded side by side with the formation of aqueous sediments. Much of that ground-moraine is of the usual tough and hard-pressed character, but here and there it is somewhat less coherent and even silt-like. Now a study of the ground-moraines of modern glaciers affords us a reasonable explanation of such differences. Dr. Brückner[AE] has shown that in many places the ground-moraine of the Alpine glaciers is included in the bottom of the ice itself. The ground-moraine, he says, frequently appears as an ice-stratum abundantly impregnated with silt and rock-fragments--it is like a conglomerate or breccia which has ice for its binding material. When this ground-moraine melts out of the ice--no running water being present--it forms a layer of unstratified silt or clay, with stones scattered irregularly through it. Such being the case in modern glaciers, we can hardly doubt that over the peripheral areas occupied by the old northern ice-sheet boulder-clay must frequently have been accumulated in the same way. Nay, when the ground-moraine melted out and dropt here and there into quietly-flowing water it might even acquire in part a bedded character. [AD] _Jahrb. d. königl. preuss. geologischen Landesanstalt für 1884_, p. 438. [AE] "Die Vergletscherung des Salzachgebietes, etc.": _Geographische Abhandlungen herausgegeben v. A. Penck_, Band i. Heft 1. The limits reached by the inland-ice during its greatest extension are becoming more and more clearly defined, although its southern margin will probably never be so accurately determined as that of the latest epoch of general glaciation. The reasons for this are obvious. When the inland-ice flowed south to the Harz and the hills of Saxony it formed no great terminal moraines. Doubtless many erratics and much rock-rubbish were showered upon the surface of the ice from the higher mountains of Scandinavia, but owing to the fanning-out of the ice on its southward march, such superficial débris was necessarily spread over a constantly-widening area. It may well be doubted, therefore, whether it ever reached the terminal front of the ice-sheet in sufficient bulk to form conspicuous moraines. It seems most probable that the terminal moraines of the great inland-ice would consist of low banks of boulder-clay and aqueous materials-the latter, perhaps, strongly predominating, and containing here and there larger and smaller angular erratics which had travelled on the surface of the ice. However that may be, it is certain that the whole region in question has been considerably modified by subsequent denudation, and to a large extent is now concealed under deposits belonging to later stages of the Pleistocene period. The extreme limits reached by the ice are determined rather by the occasional presence of rock-striæ and _roches moutonnées_, of boulder-clay and northern erratics, than by recognisable terminal moraines. The southern limits reached by the old inland-ice appear in this way to have been tolerably well ascertained over a considerable portion of central Europe. Some years ago I published a small sketch-map[AF] showing the extent of surface formerly covered by ice. On this map I did not venture to draw the southern margin of the ice-sheet in Belgium further south than Antwerp, where northern erratics were known to occur, but the more recent researches of Belgian geologists show that the ice probably flowed south for some little distance beyond Brussels.[AG] Here and there in other parts of the Continent the southern limits reached by the northern drift have also been more accurately determined, but, so far as I know, none of these later observations involves any serious modification of the sketch-map referred to. [AF] _Prehistoric Europe_, 1881. [AG] See a paper by M. E. Delvaux: _Ann. de la. Soc. géol. de Belg._, t. xiii. p. 158. I have now said enough, however, to show that the notion of a general ice-sheet having covered so large a part of Europe, which a few years ago was looked upon as a wild dream, has been amply justified by the labours of those who are so assiduously investigating the peripheral areas of the "great northern drift." And perhaps I may be allowed to express my own belief that the drifts of middle and southern England, which exhibit the same complexity as the Lower Diluvium of the Continent, will eventually be generally acknowledged to have had a similar origin. I have often thought that whilst politically we are happy in having the sea all round us, geologically we should have gained perhaps by its greater distance. At all events we should have been less ready to invoke its assistance to explain every puzzling appearance presented by our glacial accumulations. I now pass on to review some of the general results obtained by continental geologists as to the extent of area occupied by inland-ice during the last great extension of glacier-ice in Europe. It is well known that this latest ice-sheet did not overflow nearly so wide a region as that underneath which the lowest boulder-clay was accumulated. This is shown not only by the geographical distribution of the youngest boulder-clay, but by the direction of rock-striæ, the trend of erratics, and the position of well-marked terminal moraines. Gerard de Geer has given a summary[AH] of the general results obtained by himself and his fellow-workers in Sweden and Norway; and these have been supplemented by the labours of Berendt, E. Geinitz, Hauchecorne, Keilhack, Klockmann, Schröder, Wahnschaffe, and others in Germany, and by Sederholm in Finland.[AI] From them we learn that the end-moraines of the ice circle round the southern coasts of Norway, from whence they sweep south-east by east across the province of Gottland in Sweden, passing through the lower ends of Lakes Wener and Wetter, while similar moraines mark out for us the terminal front of the inland-ice in Finland--at least two parallel frontal moraines passing inland from Hango Head on the Gulf of Finland through the southern part of that province to the north of Lake Ladoga. Further north-east than this they have not been traced; but, from some observations by Helmersen, Sederholm thinks it probable that the terminal ice-front extended north-east by the north of Lake Onega to the eastern shores of the White Sea. Between Sweden and Finland lies the basin of the Baltic, which at the period in question was filled with ice, forming a great Baltic glacier which overflowed the Öland Islands, Gottland, and Öland, and which, fanning-out as it passed towards the south-west, invaded, on the south side, the Baltic provinces of Germany, while, on the north, it crossed the southern part of Scania in Sweden and the Danish islands to enter Jutland. [AH] _Zeitschrift d. deutsch. geolog. Ges._, Bd. xxxvii., p. 177. [AI] For papers by Berendt and his associates see especially the _Jahrbuch d. k. preuss. geol. Landesanstalt_, and the _Zaitschr. d. deutsch. geol. Ges._ for the past few years. Geinitz: _Forsch. z. d. Lands- u. Volkskunde_, i. 5; _Leopoldina_, xxii., p. 37; I. _Beitrag z. Geologie Mecklenburgs_, 1880, pp. 46, 56. Sederholm: _Fennia_, I. No. 7. The upper boulder-clay of those regions is now recognised as the ground-moraine of this latest ice-sheet. In many places it is separated from the older boulder-clay by interglacial deposits--some of which are marine, while others are of freshwater and terrestrial origin. During interglacial times the sea that overflowed a considerable portion of north Germany was evidently continuous with the North Sea, as is shown not only by the geographical distribution of the interglacial marine deposits, but by their North Sea fauna. German geologists generally group all the interglacial deposits together, as if they belonged to one and the same interglacial epoch. This perhaps we must look upon as only a provisional arrangement. Certain it is that the freshwater and terrestrial beds which frequently occur on the same or a lower level, and at no great distance from the marine deposits, cannot in all cases be contemporaneous with the latter. Possibly, however, such discordances may be accounted for by oscillations in the level of the interglacial sea--land and water having alternately prevailed over the same area. Two boulder-clays, as we have seen, have been recognised over a wide region in the north of Germany. In some places, however, three or more such boulder-clays have been observed overlying one another throughout considerable areas, and these clays are described as being distinctly separate and distinguishable the one from the other.[AJ] Whether they, with their intercalated aqueous deposits, indicate great oscillations of one and the same ice-sheet--now advancing, now retreating--or whether the stony clays may not be the ground-moraines of so many different ice-sheets, separated the one from the other by true interglacial conditions, future investigations must be left to decide. [AJ] H. Schröder: _Jahrb. d. k. preuss. geol. Landesanstalt für 1887_ , p. 360. The general conclusions arrived at by those who are at present investigating the glacial accumulations of northern Europe may be summarised as follows:-- 1. Before the invasion of northern Germany by the inland-ice the low-grounds bordering on the Baltic were overflowed by a sea which contained a boreal and arctic fauna. These marine conditions are indicated by the presence under the lower boulder-clay of more or less well-bedded fossiliferous deposits. On the same horizon occur also beds of sand, containing freshwater shells, and now and again mammalian remains, some of which imply cold and others temperate climatic conditions. Obviously all these deposits may pertain to one and the same period, or more properly to different stages of the same period--some dating back to a time when the climate was still temperate, while others clearly indicate the prevalence of cold conditions, and are therefore probably somewhat younger. 2. The next geological horizon in ascending order is that which is marked by the Lower Diluvium--the glacial and fluvio-glacial detritus of the great ice-sheet which flowed south to the foot of the Harz Mountains. The boulder-clay on this horizon now and again contains marine, freshwater, and terrestrial organic remains--derived undoubtedly from the so-called pre-glacial beds already referred to. These latter, it would appear, were ploughed up and largely incorporated with the old ground-moraine. 3. The interglacial beds which next succeed contain remains of a well-marked temperate fauna and flora, which point to something more than a mere partial or local retreat of the inland-ice. The geographical distribution of the beds, and the presence in these of such forms as _Elephas antiquus_, _Cervus elephas_, _C. megaceros_, and a flora comparable to that now existing in northern Germany, justify geologists in concluding that the interglacial epoch was one of long duration, and characterised in Germany by climatic conditions apparently not less temperate than those that now obtain. One of the phases of that interglacial epoch, as we have seen, was the overflowing of the Baltic provinces by the waters of the North Sea. 4. To this well-marked interglacial epoch succeeded another epoch of arctic conditions, when the Scandinavian inland-ice once more invaded Germany, ploughing through the interglacial deposits, and working these up in its ground-moraine. So far as I can learn, the prevalent belief among geologists in north Germany is that there was only one interglacial epoch; but, as already stated, doubt has been expressed whether all the facts can be thus accounted for. There must always be great difficulty in the correlation of widely-separated interglacial deposits, and the time does not seem to me to have yet come when we can definitely assert that all those interglacial beds belong to one and the same geological horizon. I have dwelt upon the recent work of geologists in the peripheral areas of the drift-covered regions of northern Europe, because I think the results obtained are of great interest to glacialists in this country. And for the same reason I wish next to call attention to what has been done of late years in elucidating the glacial geology of the Alpine Lands of central Europe--and more particularly of the low-grounds that stretch out from the foot of the mountains. Any observations that tend to throw light upon the history of the complex drifts of our own peripheral areas cannot but be of service. It is quite impossible to do justice in this brief sketch to the labours of the many enthusiastic geologists who within recent years have increased our knowledge of the glaciation of the Alpine Lands. At present, however, I am not so much concerned with the proofs of general glaciation as with the evidence that goes to show how the Alpine ground-moraines have been formed, and with the facts which have led certain observers to conclude that the Alps have endured several distinct glaciations within Pleistocene times. Swiss geologists are agreed that the ground-moraines which clothe the bottoms of the great Alpine valleys, and extend outwards sometimes for many miles upon the low-grounds beyond, are of true glacial origin. Now these ground-moraines are closely similar to the boulder-clays of this country and northern Europe--like them, they are frequently tough and hard-pressed, but now and again somewhat looser, and less firmly coherent. Frequently also they contain lenticular beds, and more or less thick sheets of aqueous deposits--in some places the stony clays even exhibiting a kind of stratification--and ever and anon such water-assorted materials are commingled with stony clay in the most complex manner. These latter appearances are, however, upon the whole best developed upon the low-grounds that sweep out from the base of the Alps. The only question concerning the ground-moraines that has recently given rise to much discussion is the origin of the materials themselves. It is obvious that there are only three possible modes in which those materials could have been introduced to the ground-moraine: either they consist of superficial morainic débris which has found its way down to the bottom of the old glaciers by crevasses; or they may be made up of the rock-rubbish, shingle, gravel, etc., which doubtless strewed the valleys before these were occupied by ice; or, lastly, they may have been derived in chief measure from the underlying rocks themselves by the action of the ice that overflowed them. The investigations of Penck, Blaas, Böhm, and Brückner appear to me to have demonstrated that the ground-moraines are composed mostly of materials which have been detached from the underlying rocks by the erosive action of the glaciers themselves. Their observations show that the regions studied by them in great detail were almost completely buried under ice--so that the accumulation of superficial moraines was for the most part impossible; and they advance a number of facts which prove positively that the ground-moraines were formed and accumulated under ice. I cannot here recapitulate the evidence, but must content myself by a reference to the papers in which this is fully discussed.[AK] These geologists do not deny that some of the material may occasionally have come from above, nor do they doubt that pre-existing masses of rock-rubbish and alluvial accumulations may also have been incorporated with the ground-moraines; but the enormous extent of the latter, and the direction of transport and distribution of the erratics which they contain cannot be thus accounted for, while all the facts are readily explained by the action of the ice itself, which used its sub-glacial débris as tools with which to carry on the work of erosion. [AK] Penck: _Die Vergletscherung der deutschen Alpen._ Blaas: _Zeitschrift d. Ferdinandeums_, 1885. Böhm: _Jahrb. d. k. k. geol. Reichsanstalt_, 1885, Bd. xxxv., Heft 3. Brückner: _Die Vergletscherung d. Salzachgebietes, etc._, 1886. Professor Heim and others have frequently asserted that glaciers have little or no eroding power, since at the lower ends of existing glaciers we find no evidence of such erosion being in operation. But the chief work of a glacier cannot be carried on at its lower end, where motion is reduced to a minimum, and where the ice is perforated by sub-glacial tunnels and arches, underneath which no glacial erosion can possibly take place; and yet it is upon observations made in just such places that the principal arguments against the erosive action of glaciers have been based. If all that we could ever know of glacial action were confined to what we can learn from peering into the grottoes at the terminal fronts of existing glaciers, we should indeed come to the conclusion that glaciers do not erode their rocky beds to any appreciable extent. But as we do not look for the strongest evidence of fluviatile erosion at the mouth of a river, but in its valley--and mountain-tracks, so if we wish to learn what glacier-ice can accomplish, we must study in detail some wide region from which the ice has completely disappeared. When this plan has been followed, it has happened that some of the strongest opponents of glacial erosion have been compelled by the force of the evidence to go over to the other camp. Dr. Blaas, for example, has been led by his observations on the glacial formations of the Inn valley to recant his former views, and to become a formidable advocate of the very theory which he formerly opposed. To his work and the memoirs by Penck, Brückner, and Böhm already cited, and especially to the admirable chapter on glacier-erosion by the last-named author, I would refer those who may be anxious to know the last word on this much-debated question. The evidence of interglacial conditions within the Alpine lands continues to increase. These are represented by alluvial deposits of silt, sand, gravel, conglomerate, breccia, and lignites. Penck, Böhm, and Brückner find evidence of two interglacial epochs, and maintain that there have been three distinct and separate epochs of glaciation in the Alps. No mere temporary retreat and re-advance of the glaciers, according to them, will account for the various phenomena presented by the interglacial deposits and associated morainic accumulations. During interglacial times the glaciers disappeared from the lower valleys of the Alps--the climate was temperate, and probably the snow-fields and glaciers approximated in extent to those of the present day. All the evidence conspires to show that an interglacial epoch was of prolonged duration. Dr. Brückner has observed that the moraines of the last glacial epoch rest here and there upon löss, and he confirms Penck's observations in south Bavaria that this remarkable formation never overlies the morainic accumulations of the latest glacial epoch. According to Penck and Brückner, therefore, the löss is of interglacial age. There can be little doubt, however, that löss does not belong to any one particular horizon. Wahnschaffe[AL] and others have shown that throughout wide areas in north Germany it is the equivalent in age of the Upper Diluvium, while Schumacher[AM] points out that in the Rhine valley it occurs on two separate and distinct horizons. Professor Andreæ has likewise shown[AN] that there is an upper and lower löss in Alsace--each characterised by its own special fauna. [AL] _Abhandl. z. geol. Specialkarte v. Preussen_, etc., Bd. vii. Heft 1; _Zeitschr. d. Zeutsch. geol. Ges._, 1885, p. 904; 1886, p. 367. [AM] _Hygienische Topographie von Strassburg i. E._, 1885. [AN] _Abhandl. z. geol. Specialkarte a. Elsass-Lothringen_, Bd. iv. Heft 2. There is still considerable difference of opinion as to the mode of formation of this remarkable accumulation. By many it is considered to be an aqueous deposit; others, following Richthofen, are of opinion that it is a wind-blown accumulation; while some incline to the belief that it is partly the one and partly the other. Nor do the upholders of these various hypotheses agree amongst themselves as to the precise manner in which water or wind has worked to produce the observed results. Thus, amongst the supporters of the aqueous origin of the löss, we find this attributed to the action of heavy rains washing over and rearranging the material of the boulder-clays.[AO] Many, again, have held it probable that löss is simply the finest loam distributed over the low-grounds by the flood-waters that escaped from the northern inland-ice and the _mers de glace_ of the Alpine lands of central Europe. Another suggestion is that much of the material of the löss may have been derived from the denudation of the boulder-clays by flood-water, during the closing stages of the last cold period. It is pointed out that in some regions, at least, the löss is underlaid by a layer of erratics, which are believed to be the residue of the denuded boulder-clay. We are reminded by Klockmann[AP] and Wahnschaffe[AQ] that the inland-ice must have acted as a great dam, and that wide areas in Germany, etc., would be flooded, partly by water derived from the melting inland-ice, and partly by waters flowing north from the hilly tracts of middle Germany. In the great basins thus formed there would be a commingling of fine silt material derived from north and south, which would necessarily come to form a deposit having much the same character throughout. [AO] Laspeyres: _Erläuterungen z. geol Specialkaret v Preussen_, etc., _Blatt. Gröbzig, Zörbig, und Petersberg_. [AP] Klockmann: _Jahrb. d. k. preuss. geol. Landesanstalt für 1883_, p. 262. [AQ] Wahnschaffe: _Op. cit._, and _Zeitschr. d. deutsch. geol. Ges._, 1886, p. 367. From what I have myself seen of the löss in various parts of Germany, and from all that I have gathered from reading and in conversation with those who have worked over löss-covered regions, I incline to the opinion that löss is for the most part of aqueous origin. In many cases this can be demonstrated, as by the occurrence of bedding and the intercalation of layers of stones, sand, gravel, etc., in the deposit; again, by the not infrequent appearance of freshwater shells; but, perhaps, chiefly by the remarkable uniformity of character which the löss itself displays. It seems to me reasonable also to believe that the flood-waters of glacial times must needs have been highly charged with finely-divided sediment, and that such sediment would be spread over wide regions in the low-grounds--in the slackwaters of the great rivers and in the innumerable temporary lakes which occupied, or partly occupied, many of the valleys and depressions of the land. There are different kinds of löss or löss-like deposits, however, and all need not have been formed in the same way. Probably some may have been derived, as Wahnschaffe has suggested, from denudation of boulder-clay. Possibly also, some löss may owe its origin to the action of rain on the stony clays, producing what we in this country would call "rain-wash." There are other accumulations, however, which no aqueous theory will satisfactorily explain. Under this category comes much of the so-called _Berglöss_, with its abundant land-shells, and its generally unstratified character. It seems likely that such löss is simply the result of sub-aërial action, and owes its origin to rain, frost, and wind acting upon the superficial formations, and rearranging their finer-grained constituents. And it is quite possible that the upper portion of much of the löss of the lower-grounds may have been re-worked in the same way. But I confess I cannot yet find in the facts adduced by German geologists any evidence of a dry-as-dust epoch having obtained in Europe during any stage of the Pleistocene period. The geographical position of our Continent seems to me to forbid the possibility of such climatic conditions, while all the positive evidence we have points to humidity rather than dryness as the prevalent feature of Pleistocene climates. It is obvious, however, that after the flood-waters had disappeared from the low-grounds of the Continent, sub-aërial action would come into play over the wide regions covered by the glacial and fluvio-glacial deposits. Thus, in the course of time, these deposits would become modified,--just as similar accumulations in these islands have been top-dressed, as it were, and to some extent even rearranged. I am strengthened in these views by the conclusions arrived at by M. Falsan--the eminent French glacialist. Covering the plateaux of the Dombes, and widely spread throughout the valleys of the Rhone, the Ain, the Isère, etc., in France there is a deposit of löss, he says, which has been derived from the washing of the ancient moraines. At the foot of the Alps, where black schists are largely developed, the löss is dark grey, but west of the secondary chain the same deposit is yellowish, and composed almost entirely of silicious materials, with only a very little carbonate of lime. This _limon_ or löss, however, is very generally modified towards the top by the chemical action of rain--the yellow löss acquiring a red colour. Sometimes it is crowded with calcareous concretions, but at other times it has been deprived of its calcareous element and converted into a kind of pulverulent silica or quartz. This, the true löss, is distinguished from another _lehm_, which Falsan recognises as the product of atmospheric action--formed, in fact, _in situ_, from the disintegration and decomposition of the subjacent rocks. Even this lehm has been modified by running water--dispersed or accumulated locally, as the case may be.[AR] [AR] Falsan: _La Période glaciaire_, p. 81. All that we know of the löss and its fossils compels us to include this accumulation as a product of the Pleistocene period. It is not of post-glacial age--even much of what one may call the "remodified löss" being of late Glacial or Pleistocene age. I cannot attempt to give here a summary of what has been learned within recent years as to the fauna of the löss. The researches of Nehring and Liebe have familiarised us with the fact that, at some particular stage in the Pleistocene period, a fauna like that of the alpine steppe-lands of western Asia was indigenous to middle Europe, and the recent investigations by Woldrich have increased our knowledge of this fauna. At what horizon, then, does this steppe-fauna make its appearance? At Thiede Dr. Nehring discovered in so-called löss three successive horizons, each characterised by a special fauna. The lowest of these faunas was decidedly arctic in type; above that came a steppe-fauna, which last was succeeded by a fauna comprising such forms as mammoth, woolly rhinoceros, _Bos_, _Cervus_, horse, hyæna, and lion. Now, if we compare this last fauna with the forms which have been obtained from true post-glacial deposits--those deposits, namely, which overlie the younger boulder-clays and flood-accumulations of the latest glacial epoch, we find little in common. The lion, the mammoth, and the rhinoceros are conspicuous by their absence from the post-glacial beds of Europe. In place of them we meet with a more or less arctic fauna, and a high-alpine and arctic flora, which as we all know eventually gave place to the flora and fauna with which Neolithic man was contemporaneous. As this is the case throughout north-western and central Europe, we seem justified in assigning the Thiede beds to the Pleistocene period, and to that interglacial stage which preceded and gradually merged into the last glacial epoch. That the steppe-fauna indicates relatively drier conditions of climate than obtained when perennial snow and ice covered wide areas of the low-ground goes without saying, but I am unable to agree with those who maintain that it implies a dry-as-dust climate, like that of some of the steppe-regions of our own day. The remarkable commingling of arctic- and steppe-faunas discovered in the Böhmer-Wald[AS] by Woldrich shows, I think, that the jerboas, marmots, and hamster-rats were not incapable of living in the same regions contemporaneously with lemmings, arctic hares, Siberian social voles, etc. But when a cold epoch was passing away the steppe-forms probably gradually replaced their arctic congeners, as these migrated northwards during the continuous amelioration of the climate. [AS] Woldrich: _Sitzungsb. d. kais. Akad. d. W. math. nat. Cl._, 1880, p. 7; 1881, p. 177; 1883, p. 978. If the student of the Pleistocene faunas has certain advantages in the fact that he has to deal with forms many of which are still living, he labours at the same time under disadvantages which are unknown to his colleagues who are engaged in the study of the life of far older periods. The Pleistocene period was distinguished above all things by its great oscillations of climate--the successive changes being repeated and producing correlative migrations of floras and faunas. We know that arctic and temperate faunas and floras flourished during interglacial times, and a like succession of life-forms followed the final disappearance of glacial conditions. A study of the organic remains met with in any particular deposit will not necessarily, therefore, enable us to assign these to their proper horizon. The geographical position of the deposit, and its relation to Pleistocene accumulations elsewhere, must clearly be taken into account. Already, however, much has been done in this direction, and it is probable that ere long we shall be able to arrive at a fair knowledge of the various modifications which the Pleistocene floras and faunas experienced during that protracted period of climatic changes of which I have been speaking. We shall even possibly learn how often the arctic, steppe-, prairie-, and forest-faunas, as they have been defined by Woldrich, replaced each other. Even now some approximation to this better knowledge has been made. Dr. Pohlig,[AT] for example, has compared the remains of the Pleistocene faunas obtained at many different places in Europe, and has presented us with a classification which, although confessedly incomplete, yet serves to show the direction in which we must look for further advances in this department of inquiry. [AT] Pohlig: _Sitzungsb. d. niederrheinischen Gesellschaft zu Bonn_, 1884; _Zeitschr. d. deutsch. geolog. Ges._, 1887, p. 798. For a very full account of the diluvial European and northern Asiatic mammalian faunas by Woldrich, see _Mém. de l'Acad. des Sciences de St. Pétersbourg_, vii^e sér., t. xxxv., 1887. During the last twenty years the evidence of interglacial conditions both in Europe and America has so increased that geologists generally no longer doubt that the Pleistocene period was characterised by great changes of climate. The occurrence at many different localities on the Continent of beds of lignite and freshwater alluvia, containing remains of Pleistocene mammalia, intercalated between separate and distinct boulder-clays has left us no other alternative. The interglacial beds of the Alpine Lands of central Europe are paralleled by similar deposits in Britain, Scandinavia, Germany, and France. But opinions differ as to the number of glacial and interglacial epochs--many holding that we have evidence of only two cold stages and one general interglacial stage. This, as I have said, is the view entertained by most geologists who are at work on the glacial accumulations of Scandinavia and north Germany. On the other hand, Dr. Penck and others, from a study of drifts of the German Alpine Lands, believe that they have met with evidence of three distinct epochs of glaciation, and two epochs of interglacial conditions. In France, while some observers are of opinion that there have been only two epochs of general glaciation, others, as, for example, M. Tardy, find what they consider to be evidence of several such epochs. Others again, as M. Falsan, do not believe in the existence of any interglacial stages, although they readily admit that there were great advances and retreats of the ice during the Glacial period. M. Falsan, in short, believes in oscillations, but is of opinion that these were not so extensive as others have maintained. It is, therefore, simply a question of degree, and whether we speak of oscillations or of epochs, we must needs admit the fact that throughout all the glaciated tracts of Europe, fossiliferous deposits occur intercalated among glacial accumulations. The successive advance and retreat of the ice, therefore, was not a local phenomenon, but characterised all the glaciated areas. And the evidence shows that the oscillations referred to were on a gigantic scale. The relation borne to the glacial accumulations by the old river alluvia which contain relics of palæolithic man early attracted attention. From the fact that these alluvia in some places overlie glacial deposits, the general opinion (still held by some) was that palæolithic man must needs be of post-glacial age. But since we have learned that all boulder-clay does not belong to one and the same geological horizon--that, in short, there have been at least two, and probably more, epochs of glaciation--it is obvious that the mere occurrence of glacial deposits underneath palæolithic gravels does not prove these latter to be post-glacial. All that we are entitled in such a case to say is simply that the implement-bearing beds are younger than the glacial accumulations upon which they rest. Their horizon must be determined by first ascertaining the relative position in the glacial series of the underlying deposits. Now, it is a remarkable fact that the boulder-clays which underlie such old alluvia belong, without exception, to the earlier stages of the Glacial period. This has been proved again and again, not only for this country but for Europe generally. I am sorry to reflect that some twenty years have now elapsed since I was led to suspect that the palæolithic deposits were not of post-glacial but of glacial and interglacial age. In 1871-72 I published a series of papers in the _Geological Magazine_ in which were set forth the views I had come to form upon this interesting question. In these papers it was maintained that the alluvia and cave-deposits could not be of post-glacial age, but must be assigned to pre-glacial and interglacial times, and in chief measure to the latter. Evidence was led to show that the latest great development of glacier-ice in Europe took place after the southern pachyderms and palæolithic man had vacated England--that during this last stage of the Glacial period man lived contemporaneously with a northern and alpine fauna in such regions as southern France--and lastly, that palæolithic man and the southern mammalia never revisited north-western Europe after extreme glacial conditions had disappeared. These conclusions were arrived at after a somewhat detailed examination of all the evidence then available--the remarkable distribution of the palæolithic and ossiferous alluvia having, as I have said, particularly impressed me. I coloured a map to show at once the areas covered by the glacial and fluvio-glacial deposits of the last glacial epoch, and the regions in which the implement-bearing and ossiferous alluvia had been met with, when it became apparent that the latter never occurred at the surface within the regions occupied by the former. If ossiferous alluvia did here and there appear within the recently glaciated areas it was always either in caves, or as infra- or interglacial deposits. Since the date of these researches our knowledge of the geographical distribution of Pleistocene deposits has greatly increased, and implements and other relics of palæolithic man have been recorded from many new localities throughout Europe. But none of this fresh evidence contradicts the conclusions I had previously arrived at; on the contrary, it has greatly strengthened my general argument. Professor Penck was, I think, the first on the Continent to adopt the views referred to. He was among the earliest to recognise the evidence of interglacial conditions in the drift-covered regions of northern Germany, and it was the reflections which those remarkable interglacial beds were so well calculated to suggest that led him into the same path as myself. Dr. Penck has published a map[AU] showing the areas covered by the earlier and later glacial deposits in northern Europe and the Alpine Lands, and indicating at the same time the various localities where palæolithic finds have occurred, and in not a single case do any of the latter appear within the areas covered by the accumulations of the last glacial epoch. [AU] _Archiv für Anthropologie_, Bd. xv. Heft 3, 1884. A glance at the papers which have been published in Germany within the last few years will show how greatly students of the Pleistocene ossiferous beds have been influenced by what is now known of the interglacial deposits and their organic remains. Professors Rothpletz[AV] and Andreæ,[AW] Dr. Pohlig[AX] and others, do not now hesitate to correlate with those beds the old ossiferous and implement-bearing alluvia which lie altogether outside of glaciated regions. [AV] Rothpletz: _Denkschrift d. schweizer. Ges. für d. gesammt. Nat._, Bd. xxviii. 1881. [AW] Andreæ: _Abhandl. z. geolog. Specialkarte v. Elsass-Lothringen_, Bd. iv. Heft 2, 1884. [AX] Pohlig: _op. cit._ The relation of the Pleistocene alluvia of France to the glacial deposits of that and other countries has been especially canvassed. Rothpletz, in the paper I have cited, includes these alluvia amongst the interglacial deposits, and in the present year (1889) we have an interesting essay on the same subject by the accomplished secretary of the Anthropological and Archæological Congress which met recently in Paris. M. Boule[AY] correlates the palæolithic cave- and river-deposits of France with those of other countries, and shows that they must be of interglacial age. His classification, I am gratified to find, does not materially differ from that given by myself a number of years ago. He is satisfied that in France there is evidence of three glacial epochs and two well-marked interglacial horizons. The oldest of the palæolithic stages of Mortillet (Chelléenne) culminated according to Boule during the last interglacial epoch, while the more recent palæolithic stages (Moustérienne, Solutréenne, and Magdalénienne) coincided with the last great development of glacier-ice. The Palæolithic age, so far as Europe is concerned, came to a close during this last cold phase of the Glacial period. [AY] Boule: _Revue d'Anthropologie_, 1889, t. 1. There are many other points relating to glacial geology which have of late years been canvassed by Continental workers, but these I cannot discuss here. I have purposely indeed restricted my remarks to such parts of a wide subject as I thought might have interest for glacialists in this country, some of whom may not have had their attention directed to the results which have recently been attained by their fellow-labourers in other lands. Had time permitted I should gladly have dwelt upon the noteworthy advances made by our American brethren in the same department of inquiry. Especially should I have wished to direct attention to the remarkable evidence adduced in favour of the periodicity of glacial action. Thus Messrs. Chamberlin and Salisbury, after a general review of that evidence, maintain that the Ice Age was interrupted by one chief interglacial epoch and also by three interglacial sub-epochs or episodes of deglaciation. These authors discuss at some length the origin of the löss, and come to the general conclusion that while deposits of this character may have been formed at different stages of the Glacial period, and under different conditions, yet upon the whole they are best explained by aqueous action. Indeed a perusal of the recent geological literature of America shows a close accord between the theoretical opinions of many Transatlantic and European geologists. Thus as years advance the picture of Pleistocene times becomes more and more clearly developed. The conditions under which our old palæolithic predecessors lived--the climatic and geographical changes of which they were the witnesses--are gradually being revealed with a precision that only a few years ago might well have seemed impossible. This of itself is extremely interesting, but I feel sure that I speak the conviction of many workers in this field of labour when I say that the clearing up of the history of Pleistocene times is not the only end which they have in view. One can hardly doubt that when the conditions of that period and the causes which gave rise to these have been more fully and definitely ascertained we shall have advanced some way towards the better understanding of the climatic conditions of still earlier periods. For it cannot be denied that our knowledge of Palæozoic, Mesozoic, and even early Cainozoic climates is unsatisfactory. But we may look forward to the time when much of this uncertainty will disappear. Meteorologists are every day acquiring a clearer conception of the distribution of atmospheric pressure and temperature and the causes by which that distribution is determined, and the day is approaching when we shall be better able than we are now to apply this extended meteorological knowledge to the explanation of the climates of former periods in the world's history. One of the chief factors in the present distribution of atmospheric temperature and pressure is doubtless the relative position of the great land- and water-areas; and if this be true of the present, it must be true also of the past. It would almost seem, then, as if all one had to do to ascertain the climatic conditions of any particular period, was to prepare a map depicting with some approach to accuracy the former relative position of land and sea. With such a map could our meteorologists infer what the climatic conditions must have been? Yes, provided we could assure them that in other respects the physical conditions did not differ from the present. Now there is no period in the past history of our globe the geographical conditions of which are better known than the Pleistocene. And yet, when we have indicated these upon a map, we find that they do not give the results which we might have expected. The climatic conditions which they seem to imply are not such as we know did actually obtain. It is obvious, therefore, that some additional and perhaps exceptional factor was at work to produce the recognised results. What was this disturbing element, and have we any evidence of its interference with the operation of the normal agents of climatic change in earlier periods of the world's history? We all know that various answers have been given to such questions. Whether amongst these the correct solution of the enigma is to be found, time will show. Meanwhile, as all hypothesis and theory must starve without facts to feed on, it behoves us as working geologists to do our best to add to the supply. The success with which other problems have been attacked by geologists forbids us to doubt that ere long we shall have done much to dispel some of the mystery which still envelopes the question of geological climates. IX. The Glacial Period and the Earth-Movement Hypothesis.[AZ] [AZ] This article contains the substance of two papers, one read before the Victoria Institute, in 1892; the other an address delivered to the Geological Society of Edinburgh, in 1891. Perhaps no portion of the geological record has been more assiduously studied during the last quarter of a century than its closing chapters. We are now in possession of manifold data concerning the interpretation of which there seems to be general agreement. But while that is the case, there remain, nevertheless, certain facts or groups of facts which are variously accounted for. Nor have all the phenomena of the Pleistocene period received equal attention from those who have recently speculated and generalised on the subject of Pleistocene climate and geography. Yet, we may be sure, geologists are not likely to arrive at any safe conclusions as to the conditions that obtained in Pleistocene times, unless the evidence be candidly considered in all its bearings. No interpretation of that evidence which does not recognise every outstanding group of facts can be expected to endure. It may be possible to frame a plausible theory to account for some particular conspicuous phenomena, but should that theory leave unexplained a residuum of less conspicuous but nevertheless well-proved facts, then, however strongly it may be fortified, it must assuredly fall. As already remarked, there are many phenomena in the interpretation of which geologists are generally agreed. It is, for example, no longer disputed that in Pleistocene times vast sheets of ice--continental _mers de glace_--covered broad areas in Europe and North America, and that extensive snow-fields and large local glaciers existed in many mountain-regions where snow-fields and glaciers are now unknown, or only meagrely developed. It is quite unnecessary, however, that I should give even the slightest sketch of the aspect presented by the glaciated tracts of our hemisphere at the climax of the Ice Age. The geographical distribution and extent of the old snow-fields, glaciers, and ice-sheets is matter now of common knowledge. It will be well, however, to understand clearly the nature of the conditions which obtained at the climax of glacial cold--at that stage, namely, when the Alpine glaciers reached their greatest development, and when so much of Europe was cased in snow and ice. This we shall best do by comparing the present with the past. Now in our day the limits of perennial snow are attained at heights that necessarily vary with the latitude. This is shown as follows:-- _Region._ _N. Lat._ _Height of Snow-Line._ Iceland, 65° 3,070 feet. Norway, 61° 5,180-5,570 " N. Urals, 59° 30' 4,790 " Alps, 46° 8,884 or 9,000 " Caucasus, 43° 10,600-11,000 " Apennines, 42° 30' 9,520 " Etna, 37° 30' 9,530 " Sierra Nevada, 37° 11,187 " Thus in traversing Europe from north to south the snow-line may be said to rise from 3000 feet to 11,000 feet in round numbers. It is possible from such data to draw across the map a series of isochional lines, or lines of equal perennial snow, and this has been done by my friend, Professor Penck of Vienna.[BA] It will be understood that each isochional line traverses those regions above which the line of névé is estimated to occur at the same height. Thus the isochional line of 1000 metres (3280 feet) runs from the north of Norway down to lat. 64° on the west coast, whence it must pass west to the south of Iceland. The line of 1500 metres (4920 ft.) is traced from the north end of the Urals in a westerly direction. It then follows the back-bone of the Scandinavian peninsula, passes over to Scotland, and thence strikes west along lat. 55°. For each of these lines good data are obtainable. The line of 2000 metres (6560 ft.) is, however, hypothetical. It is estimated to extend from the Ural Mountains, about the lat. of 57°, over the mountains of middle Germany and above the north of France. The line of 2500 metres (8200 ft.) passes from the southern termination of the Urals, in lat. 51°, to the east Carpathians, thence along the north face of the Alps, thereafter south-west across the Cevennes to the north-west end of the Pyrenees; and thence above the Cantabrian and the Portuguese Highlands to the coast in lat. 39°. The line of 3000 metres (9840 ft.) is estimated to occur above the Caspian Sea, near lat. 44°, and extends west through the north end of the Caucasus to the Balkans. Thence it is traced north-west to the Alps, south-west to the Pyrenees, which range it follows to the west, and thereafter sweeps south above the coast at Cadiz. The line of 3500 metres (11,480 ft.) runs from the Caucasus south-west across Asia Minor to the Lebanon Mountains; thence it follows the direction of the Mediterranean, and traverses Morocco above the north face of the Atlas range. Finally the line of 4000 metres (13,120 feet) is estimated to trend in the same general direction as the last-mentioned line, but, of course, further to the south. Although these isochional lines are to some extent conjectural, yet the data upon which they are based are sufficiently numerous and well-known to prevent any great error, and we may admit that the lines represent with tolerable accuracy the general position of the snow-line over our Continent. So greatly has our knowledge of the glaciation of Europe increased during recent years, that the height of the snow-line of the Glacial period has been determined by MM. Simony, Partsch, Penck, and Höfer. Their method is simple enough. They first ascertain the lowest parts of a glaciated region from which independent glaciers have flowed. This gives the maximum height of the old snow-line. Next they determine the lowest point reached by such glaciers. It is obvious that the snow-line would occur higher up than that, but at a lower level than the actual source of the glaciers; and thus the minimum height of the former snow-line is approximately ascertained. The lowest level from which independent glaciers formerly flowed, and the terminal point reached by the highest-lying glaciers having been duly ascertained, it is possible to determine with sufficient accuracy the mean height of the old snow-line. The required data are best obtained, as one might have expected, in the Pyrenees and amongst the mountains of middle and southern Europe. In those regions the snow-line would seem to have been some 3000 feet or so lower than now. From such data Professor Penck has constructed a map showing the isochional lines of the Glacial period. These lines are, I need hardly say, only approximations, but they are sufficiently near the truth to bring out the contrast between the Ice Age and the present. Thus the isochional of 1000 metres, which at present lies above northern Scandinavia, was pushed south to the latitude of southern France and north Italy; while the isochional of 2000 metres (now overlying the extreme north of France and north Germany) passed in glacial times over the northern part of the Mediterranean.[BB] [BA] "Geographische Wirkungen der Eiszeit," _Verhandl. d. vierten deutschen Geographentages zu München_, 1884. [BB] It is interesting to note that while in the Tatra (north Carpathians) the snow-line was depressed in glacial times to the extent of 2700 feet only, in the Alps it descended some 4000 feet or more below its present level. With the snow-line of that great chain at such an elevation it is obvious that only a few of the higher points of the Apennines could rise into the region of _névé_. This is the reason why moraines are met with in only the higher valleys of that range. Isochional lines are not isotherms. Their height and direction are determined not only by temperature, but by the amount and distribution of the snow-fall. Nevertheless, the position of the snow-line in Europe during the Ice Age enables us to form a rough estimate of the temperature. At present in middle Europe the temperature falls 1° F. for every 300 feet of ascent. Hence if we take the average depression of the snow-line in glacial times at 3000 feet, that would correspond approximately to a lowering of the temperature by 10°.[BC] This may not appear to be much, but, as Penck points out, were the mean annual temperature to be lowered to that extent it would bring the climate of northern Norway down to southern Germany, and the climate of Sweden to Austria and Moravia, while that of the Alps would be met with over the basin of the Mediterranean. [BC] Professor Brückner thinks the general lowering of temperature may not have exceeded 5-1/2° to 7° F. _Verhandlungen der 73 Jahresversammlung der schweizerischen Naturforschenden Gesellschaft in Davos_, 1890. Let it be noted further that this lowering of the temperature--this displacement of climatic zones, was experienced over the whole continent--extending on the one hand south into Africa, and on the other east into Asia. But while the conditions in northern and central Europe were markedly glacial, further south only more or less isolated snow-capped mountains and local glaciers appeared--such, for example, as those of the Sierra Nevada, the Apennines, Corsica, the Atlas, the Lebanon, etc. In connection with these facts we may note also that the Azores were reached by floating ice; and I need only refer in a word to the evidence of cold wet conditions as furnished by the plant and animal remains of the Pleistocene tufas, alluvia, and peat of southern Europe. Again in north Africa and Syria we find, in desiccated regions, widespread fluviatile accumulations, which, in the opinion of a number of competent observers, are indicative of rainy conditions contemporaneous with the Glacial period of Europe. When we compare the conditions of the Ice Age with those of the present we are struck with the fact that the former were only an exaggeration of the latter. The development of glaciation was in strict accordance with existing conditions. Thus in Pleistocene times North America was more extensively glaciated than northern Europe, just as to-day Greenland shows more snow and ice than Scandinavia. No traces of glaciation have been observed as yet in northern Asia or in northern Alaska, and to-day the only glaciers and ice-sheets that exist in northern regions are confined to the formerly glaciated areas. Again, in Pleistocene Europe glacial phenomena were more strongly developed in the west than in the east. Large glaciers, for example, existed in central France, and a considerable ice-flow poured into the basin of the Douro. But in the same latitudes of eastern Europe we meet with few or no traces of ice-action. Again, the Vosges appear to have been more severely glaciated than the mountains of middle Germany; and so likewise the old glaciers of the western Alps were on a much more extensive scale than those towards the east end of the chain. Similar contrasts may be noted at the present day. Thus we find glaciers in Norway under lat. 60°, while in the Ural Mountains in the same latitude there is none. The glaciers of the western Alps, again, are larger than those in the eastern part of the chain. The Caucasus region, it is true, has considerable glaciers, but then the mountains are higher. Now turn for a moment to North America. The eastern area was covered by one immense ice-sheet, while in the mountainous region of the west gigantic glaciers existed. In our own day we see a similar contrast. In the north-east lies Greenland well-nigh drowned in ice, while the north-west region on the other hand, although considerably higher and occurring in the same latitude, holds only local glaciers. We may further note that at the present day very dry regions, even when these are relatively lofty and in high latitudes, such as the uplands of Siberia, contain no glaciers. And the same was the case in the Glacial period. These facts are sufficient to show that the conditions of glacial times bore an intimate relation to those that now obtain. Could the requisite increase of precipitation and lowering of temperature take place, we cannot doubt that ice-sheets and glaciers would reappear in precisely the same regions where they were formerly so extensively developed. No change in the relative elevation of the land would be required--increased precipitation accompanied by a general lowering of the snow-line for 3000 or 3500 feet would suffice to reintroduce the Ice Age. From the foregoing considerations we may conclude:--(1) That the cold of the Glacial period was a general phenomenon, due to some widely-acting cause--a cause sufficient to influence contemporaneously the climate of Europe and North America; (2) that glaciation in our continent increased in intensity from east to west, and from south to north; (3) that where now we have the greatest rainfall, in glacial times the greatest snow-fall took place, and the snow tended most to accumulate; (4) that in the extreme south of Europe, and in north Africa and west Asia, increased rain precipitation accompanied lowering of temperature, from which it may be inferred that precipitation in glacial times was greater generally than it is now. Having considered the climatic conditions that obtained at the climax of the Glacial period, I have next to recapitulate what is known as to the climatic changes of Pleistocene times. It is generally admitted that the glacial conditions of which I have been speaking were repeated twice, some say three times, during the Pleistocene period; while others maintain that even a larger number of glacial episodes may have occurred. Two glacial epochs, at all events, have been recognised generally both in Europe and North America. These were separated by an interglacial stage of more genial conditions, the evidence for which is steadily increasing. No one now calls in question the existence of interglacial deposits, but, as their occurrence is rather a stumbling-block in the way of certain recently resuscitated hypotheses, some attempt has been made to minimise their importance--to explain them away, in fact. It has been suggested, for example--(and the suggestion is by no means new)--that the deposits in question only show that there were local oscillations during the advance and retreat of the old ice-sheets and glaciers. This, however, is not the view of those who have observed and described interglacial beds--who know the nature of the organic remains which they have yielded, and the conditions under which the beds must have been accumulated. I need not refer to the interglacial deposits of our own country further than to remark that they certainly cannot be explained away in that summary fashion. The peat and freshwater beds that lie between the lower and upper tills in the neighbourhood of Edinburgh, for example, are of themselves sufficient to prove a marked and decided change of climate. No mere temporary retreat and re-advance of the ice-sheet will account for their occurrence. The lower till is unquestionably the bottom-moraine of an ice-sheet which, in that region, flowed towards the east. When the geographical position of the deposits in question is considered it becomes clear that an easterly flow of ice in Mid-Lothian proves beyond gainsaying that during the accumulation of the lower till all Scotland was drowned in ice. But when water once more flowed over the land-surface--when a temperate flora, composed of hazels and other plants, again appeared, it is obvious that the ice-sheet had already vanished from central Scotland. This is not the case of a mere temporary recession of the ice-front. It is impossible to believe that a temperate or even cold-temperate flora could have flourished in central Scotland at a period when thick glacier-ice mantled any portion of our Lowlands. Again, in the upper till we read the evidence of a recurrence of extreme glacial conditions--when central Scotland was once more overwhelmed by confluent ice-streams coming from the Highlands and the southern Uplands. Similar evidence of recurrent glacial conditions, I need hardly remind you, has been detected in other parts of the country. We are justified, then, in maintaining that our interglacial beds point to distinct oscillations of climate--oscillations which imply a long lapse of time. Continental observers are equally convinced that the interglacial epoch, of which so many interesting relics have been preserved over a wide region, was marked at its climax by a temperate climate and endured for a long period. The interglacial beds of northern and central Europe form everywhere marked horizons in the glacial series. Geologists sometimes forget that in every region where glacial accumulations are well developed, good observers had recognised an upper and lower series of "drift-deposits" long before the idea of two separate glacial epochs had presented itself. Thus, in north Germany, so clearly is the Upper differentiated from the Lower Diluvium that the two series had been noted and mapped as separate accumulations for years before geologists had formulated the theory of successive ice-epochs.[BD] The division of the German Diluvium into an upper and a lower series is as firmly established as any other well-marked division in historical geology. The stratigraphical evidence has been much strengthened, however, by the discovery between upper and lower boulder-clays of true interglacial beds, containing lignite, peat, diatomaceous earth, and marine, brackish, and freshwater molluscs, fish, etc., and now and again bones of Pleistocene mammals.[BE] A similar strongly-marked division characterises the glacial accumulations of Sweden, as has been clearly shown by De Geer,[BF] who thinks that the older and younger epochs of glaciation were separated by a protracted period of interglacial conditions. In short, evidence of a break in the glacial succession has been traced at intervals across the whole width of the Continent, from the borders of the North Sea to central Russia. M. Krischtafowitsch has recently detected in the neighbourhood of Moscow[BG] certain fossiliferous interglacial beds, the flora and fauna of which indicate a warmer and moister climate than the present. The interglacial stage, he says, must have been of long duration, and separated in Russia as in western Europe two distinct epochs of glaciation. [BD] Wahnschaffe: _Forschungen zur deutschen Landes- und Volkskunde von Dr. A. Kirchhoff_, Bd. vi., Heft 1. [BE] For interglacial beds of north Germany see Helland: _Zeitschr. d. deutsch. geol._ Ges., xxxi., 879; Penck: _Ibid._, xxxi., 157; _Länderkunde von Europa_ (Das deutsche Reich), 1887, 512; Dames: _Samml. gemeinverständl. wissensch. Vorträge, von Virchow u. Holtzendorff:_ xx. Ser., 479 Heft; Schröder: _Jahrb. d. k. geol. Landensanst. f._ 1885, p. 219. For further references see Wahnschaffe, _op. cit._ I have not thought it worth while in this paper to refer to the interglacial deposits of our own islands. A general account of them will be found in my _Great Ice Age_, and _Prehistoric Europe_. The interglacial phenomena of the Continent seem to be less known here than they ought to be. [BF] _Zeitschrift d. deutsch. geolog. Gesellschaft_, Bd. xxxvii, p. 197. [BG] _Anzeichen einer interglaziären Epoche in Central-Russland_, Moskau, 1891. No mere temporary retreat and re-advance of the ice-front can account for these phenomena. The occurrence of remains of the great pachyderms at Rixdorf, near Berlin, and the character of the flora met with in the interglacial beds of north Germany and Russia are incompatible with glacial conditions in the low-grounds of northern Europe. The interglacial beds, described by Dr. C. Weber[BH] as occurring near Grünenthal, in Holstein, are among the more recent discoveries of this kind. These deposits rest upon boulder-clay, and are overlaid by another sheet of the same character, and belong, according to Weber, to "that great interglacial period which preceded the last ice-sheet of northern Europe." The section shows 8 feet of peat resting on freshwater clay, 2 feet thick, which is underlaid by some 10 feet of "coral sand," with bryozoa. The flora and fauna have a distinctly temperate facies. It is no wonder, then, that Continental geologists are generally inclined to admit that north Germany and the contiguous countries have been invaded at least twice by the ice-sheets of two separate and distinct glacial epochs. This is not all, however. While every observer acknowledges that the Diluvium is properly divided into an upper and a lower series, there are some geologists who have described the occurrence of three, and even more boulder-clays--the one clearly differentiated from the other, and traceable over wide areas. Is each of these to be considered the product of an independent ice-sheet, or do they only indicate more or less extensive oscillations of the ice-front? The boulder-clays are parted from each other by thick beds of sand and clay, in some of which fossils have occasionally been detected. It is quite possible that such stratified beds were deposited during a temporary retreat of the ice-front, which when it re-advanced covered them up with its bottom-moraine. On the other hand, the phenomena are equally explicable on the assumption that each boulder-clay represents a separate epoch of glaciation. Until the stratified beds have yielded more abundant traces of the life of the period, our judgment as to the conditions implied by them must be suspended. It is worthy of note in this connection, however, that in North America the existence of one prolonged interglacial epoch has been well established, while distinct evidence is forthcoming of what Chamberlin discriminates as "stages of deglaciation and re-advancing ice."[BI] [BH] _Neues Jahrbuch f. Mineralogie, Geologie, u. Palæontologie_, 1891, Bd. ii., pp. 62, 228; 1892, Bd. i., p. 114. [BI] _Sixth Annual Report, U. S. Geol. Survey_, 1884-5, P. 315. When we turn to the Alpine Lands, we find that there also the occurrence of former interglacial conditions has been recognised. The interglacial deposits, as described by Heer and others, are well known. These form as definite a geological horizon as the similar fossiliferous zone in the Diluvium of northern Germany. The lignites, as Heer pointed out, represent a long period of time, and this is still further illustrated by the fact that considerable fluviatile erosion supervened between the close of the first and the advent of the later glacial epoch. No mere temporary retreat and re-advance of the ice will account for the phenomena. Let us for a moment consider the conditions under which the accumulations in question were laid down. The glacial deposits underlying the lignite beds contain, amongst other erratics, boulders which have come from the upper valley of the Rhine. This means, of course, that the ancient glacier of the Rhine succeeded in reaching the Lake of Zurich; and it is well known that it extended at the same time to Lake Constance. That glacier, therefore exceeded sixty miles in length. One cannot doubt that the climatic conditions implied by this great extension were excessive, and quite incompatible with the appearance in the low-grounds of Switzerland of such a flora as that of the lignites. The organic remains of the lignite beds indicate a climate certainly not less temperate than that which at present characterises the district round the Lake of Zurich. We may safely infer, therefore, that during interglacial times the glaciers of the Alps were not more extensively developed than at present. Again, as the lignites are overlaid by glacial deposits, it is obvious that the Rhine glacier once more reached Lake Zurich--in other words, there was a return of the excessive climate that induced the first great advance of that and other Swiss glaciers. That these advances were really due to extreme climatic conditions is shown by the fact that it was only under such conditions that the Scandinavian flora could have invaded the low-grounds of Europe, and entered Switzerland. It is impossible, therefore, that the interglacial flora could have flourished in Switzerland while the immigration of these northern plants was taking place. Lignites of the same age as those of Dürnten and Utznach occur in many places both on the north and south sides of the Alpine chain. At Imberg, near Sonthofen, in Bavaria, for example, they are described by Penck[BJ] as being underlaid and overlaid by thick glacial accumulations. The deposits in question form a terrace along the flanks of the hills, at a height of 700 feet above the Iller. The flora of the lignite has not yet been fully studied, but it is composed chiefly of conifers, which must have grown near where their remains now occur--that is at 3000 feet, or thereabout, above the sea. It is incredible that coniferous forests could have flourished at that elevation during a glacial epoch. A lowering of the mean annual temperature by 3° C. only would render the growth of trees at that height almost impossible, and certainly would be insufficient to cause the glaciers of Algau to descend to the foot of the mountains, as we know they did--a distance of at least twenty-four miles. The Imberg lignites, therefore, are evidence of a climate not less temperate than the present. More than this, there is clear proof that the interglacial stage was long continued, for during that epoch the Iller had time to effect very considerable erosion. The succession of changes shown by the sections near Sonthofen are as follows. 1. The Iller Valley is filled with glacier-ice which flows out upon the low-grounds at the base of the Alps. 2. The glacier retreats, and great sheets of shingle and gravel are spread over the valley. 3. Coniferous forests now grow over the surface of the gravels; and as the lignite formed of their remains attains a thickness of ten feet in all, it obviously points to the lapse of some considerable time. 4. Eventually the forests decay, and their débris is buried under new accumulations of shingle and gravel. 5. The Iller cuts its way down through all the deposits to depths of 680 to 720 feet. 6. A glacier again descends and fills the valley, but does not flow so far as that of the earlier glacial stage. [BJ] _Die Vergletscherung der deutschen Alpen_, 1882, p. 256. In this section, as in those at Dürnten and Utznach, we have conclusive evidence of two glacial epochs, sharply marked off the one from the other. Nor does that evidence stand alone, for at various points between Lake Geneva and the lower valley of the Inn similar interglacial deposits occur. Sometimes these appear at the foot of the mountains, as at Mörschweil on Lake Constance; sometimes just within the mountain area, as at Imberg; sometimes far in the heart of the Alpine Lands, as at Innsbruck. Professor Penck has further shown, and his observations have been confirmed by Brückner, Blaas, and Böhm, that massive sheets of fluviatile gravel are frequently met with throughout the valleys of the Alps, occupying interglacial positions. These gravels are exactly comparable to the interglacial gravels of the Sonthofen sections. And it has been demonstrated that they occur on two horizons, separated the one from the other by characteristic ground-moraine, or boulder-clay. The lower gravels rest on ground-moraine, and the upper gravels are overlaid by sheets of the same kind of glacial detritus. In short, three separate and distinct ground-moraines are recognised. The gravels, one cannot doubt, are simply the torrential and fluviatile deposits laid down before advancing and retreating glaciers; and it is especially to be noted that each sheet of gravel, after its accumulation, was much denuded and cut through by river-action. In a word, as Penck and others have shown, the valleys of Upper Bavaria have been occupied by glaciers at three successive epochs--each separated from the other by a period during which much river-gravel was deposited and great erosion of the valley-bottoms was effected. On the Italian side of the Alps, similar evidence of climatic changes is forthcoming. The lignites and lacustrine strata of Val Gandino, and of Val Borlezza, as I have elsewhere shown,[BK] are clearly of interglacial age. From these deposits many organic remains have been obtained--amongst the animals being _Rhinoceros hemitoechus_ and _R. leptorhinus_. According to Sordelli, the plants indicate a climate as genial as that of the plains of Lombardy and Venetia, and warmer therefore than that of the upland valleys in which the interglacial beds occur. Professor Penck informs me that some time ago he detected evidence in the district of Lake Garda of three successive glacial epochs--the evidence being of the same character as that recognised in the valleys of the Bavarian Alps. [BK] _Prehistoric Europe_, p. 303. In the glaciated districts of France similar phenomena are met with. Thus in Cantal, according to M. Rames,[BL] the glacial deposits belong to two separate epochs. The older morainic accumulations are scattered over the surface of the plateau of Archæan schistose rocks, and extend up the slopes of the great volcanic cone of that region to heights of 2300 to 3300 feet. One of the features of these accumulations are the innumerable gigantic erratics, known to the country folk as _cimetière des enragés_. Sheets of fluvio-glacial gravel are also associated with the moraines, and it is worthy of note that both have the aspect of considerable age--they have evidently been subjected to much denudation. In the valleys of the same region occurs a younger series of glacial deposits, consisting of conspicuous lateral and terminal moraines, which, unlike the older accumulations, have a very fresh and well-preserved appearance. With them, as with the older moraines, fluvio-glacial gravels are associated. M. Rames shows that the interval that supervened between the formation of the two series of glacial deposits must have been prolonged, for the valleys during that interval were in some places eroded to a depth of 900 feet. Not only was the volcanic _massif_ deeply incised, but even the old plateau of crystalline rocks on which the volcanic cone reposes suffered extensive denudation in interglacial times. M. Rames further recognises that the second glacial epoch was marked by two advances of the valley-glaciers, separated by a marked episode of fusion, the evidence for which is conspicuous in the valley of the Cère. [BL] _Bull. Soc. Géol. de France_, 1884. The glacial and interglacial phenomena of Auvergne are quite analogous to those of Cantal. Dr. Julien has described the morainic accumulations of a large glacier that flowed from Mont Dore. After that glacier had retreated a prolonged period of erosion followed, when the morainic deposits were deeply trenched, and the underlying rocks cut into. In the valleys and hollows thus excavated freshwater beds occur, containing the relics of an abundant flora, together with the remains of elephant (_E. meridionalis_), rhinoceros (_R. leptorhinus_), hippopotamus, horse, cave-bear, hyæna, etc.--a fauna comparable to that of the Italian interglacial deposits. After the deposition of the freshwater beds, glaciers again descended the Auvergne valleys and covered the beds in question with their moraines.[BM] [BM] _Des Phénomènes glaciaires dans le Plateau central de France, etc._ According to the researches of Martins, Collomb, Garrigou, Piette, and Penck, there is clear evidence in the Pyrenees of two periods of glaciation, separated by an interval of much erosion and valley-excavation. Penck, indeed, has shown that the valleys of the Pyrenees have been occupied at three successive epochs by glaciers--each epoch being represented by its series of moraines and by terraces of fluvio-glacial detritus, which occur at successively lower levels. I have referred in some detail to these discoveries of interglacial phenomena because they so strongly corroborate the conclusions arrived at a number of years ago by glacialists in our own country. Many additional examples might be cited from other parts of Europe, but those already given may serve to show that at least one epoch of interglacial conditions supervened during the Pleistocene period. Before leaving this part of my subject, however, I may point out the significant circumstance that long before much was known of glaciation, and certainly before the periodicity of ice-epochs had been recognised, Collomb had detected in the Vosges conspicuous evidence of two successive glaciations.[BN] [BN] _Preuves de l'existence d'anciens glaciers dans les vallées des Vosges_, 1847, p. 141. Having shown that alike in the regions formerly occupied by the great northern ice-sheet, and in the Alpine Lands of central and southern Europe, alternations of cold and genial conditions characterised the so-called Glacial period, we may now glance at the evidence supplied by those Pleistocene deposits that lie outside of the glaciated areas. Of these we have a typical example in the river-accumulations of the Rhine Valley between Bâle and Bingen. Here and there these deposits have yielded remains of extinct and no longer indigenous mammals and relics of Palæolithic man--one of the most interesting deposits from which mammalian remains have been obtained being the Sands of Mosbach, between Wiesbaden and Mayence. The fauna in question is characteristically Pleistocene, nor can it be doubted that the Mosbach Sands belong to the same geological horizon as the similar fluviatile deposits of the Seine, the Thames, and other river-valleys in western Europe. Dr. Kinkelin has shown,[BO] and with him Dr. Schumacher agrees,[BP] that the Mosbach deposits are of interglacial age; while Dr. Pohlig has no hesitation in assigning them to the same horizon.[BQ] It is true there are no glacial accumulations in the region where they occur, but they rest upon a series of unfossiliferous gravels which are recognised as the equivalents of the fluvio-glacial and glacial deposits of the Vosges, the Black Forest, the Alps, etc. These gravels are traced at intervals up to considerable heights above the Rhine, and contain numerous erratics, some of which are several feet in diameter, while a large proportion are not at all water-worn, but roughly and sharply angular. The blocks have unquestionably been transported by river-ice, and imply therefore cold climatic conditions. The overlying Mosbach Sands have yielded not only _Elephas antiquus_ and _Hippopotamus major_, but the reindeer, the mammoth, and the marmot--two strongly contrasted faunas, betokening climatic changes similar to those that marked the accumulation of the river-deposits of the Thames, the Seine, etc. Of younger date than the Mosbach Sands is another series of unfossiliferous gravels, which, like the older series, are charged with ice-floated erratics. The beds at Mosbach are thus shown to be of interglacial age: they occupy the same geological horizon as the interglacial beds of Switzerland and other glaciated tracts in central and northern Europe. [BO] Kinkelin: _Bericht über die Senckenberg. naturf. Ges. in Frankfurt a. M._, 1889. [BP] Schumacher: _Mittheilungen d. Commission für d. geolog. Landes-Untersuch. v. Elsass-Lothringen_, Bd. ii., 1890, p. 184. [BQ] _Zeitschr. d. deutsch. geolog. Ges._, 1887, p. 806. To this position must likewise be assigned the Pleistocene river-alluvia of other districts. There is no other horizon, indeed, on which these can be placed. That they are not of post-glacial age is shown by the fact that in many places the angular gravels and flood-loams of the Glacial period overlie them. And that they cannot all belong to pre-glacial times is proved by the frequent occurrence underneath them of glacial or fluvio-glacial accumulations. It is quite possible, of course, that here and there in the valleys of western and southern Europe some of the Pleistocene alluvia may be of pre-glacial age. But in the main these alluvia must be regarded as the equivalents of the glacial and interglacial deposits of northern and Alpine districts. This will appear a reasonable conclusion when we bear in mind that long before the Pliocene period came to a close the climate of Europe had begun to deteriorate. In England, as we know, glacial conditions supervened almost at the advent of the Pleistocene period. And the same was the case in the Alpine Lands of the south. Again, in the glaciated areas of north and south alike, the closing stage of the Pleistocene was characterised by cold climatic conditions. And thus in those regions the glacial and interglacial epochs were co-extensive with that period. It follows, therefore, that the Pleistocene deposits of extra-glacial areas must be the equivalents of the glacial and interglacial accumulations elsewhere. If we refused to admit this we should be puzzled indeed to tell what the rivers of western and southern Europe were doing throughout the long-continued Glacial period. There is no escape from the conclusion that the Pleistocene river-alluvia and cave-accumulations must be assigned to the same general horizon as the glacial and interglacial deposits. This is now admitted by Continental palæontologists who find in the character of Pleistocene organic remains abundant proof that the old river-alluvia and cave-accumulations were laid down under changing climatic conditions. Did neither glacial nor interglacial deposits exist, the relics of the Pleistocene flora and fauna met with in extra-glacial regions would yet lead us to the conclusion that after the close of the Pliocene period, extremely cold and very genial climates alternated up to the dawn of the present. Thus during one stage of the Pleistocene "clement winters and cool summers permitted the wide diffusion and intimate association of plants which have now a very different range. Temperate and southern species like the ash, the poplar, the sycamore, the fig-tree, the judas-tree, etc., overspread all the low-grounds of France as far north at least as Paris. It was under such conditions that the elephants, rhinoceroses, hippopotamuses, and the vast herds of temperate cervine and bovine species ranged over Europe, from the shores of the Mediterranean up to the latitude of Yorkshire, and probably even further north still, and from the borders of Asia to the western ocean. Despite the presence of numerous fierce carnivora--lions, hyænas, tigers, and others--Europe at that time, with its shady forests, its laurel-margined streams, its broad and deep-flowing rivers--a country in every way suited to the needs of a race of hunters and fishers--must have been no unpleasant habitation for Palæolithic man." But during another stage of the Pleistocene period, the climate of our continent presented the strongest contrast to those genial conditions. At that time "the dwarf birch of the Scottish Highlands, and the Arctic willow, with their northern congeners, grew upon the low-grounds of middle Europe. Arctic animals, such as the musk-sheep and the reindeer, lived then, all the year round, in the south of France; the mammoth ranged into Spain and Italy; the glutton descended to the shores of the Mediterranean; the marmot came down to the low-grounds at the foot of the Apennines; and the lagomys inhabitated the low-lying maritime districts of Corsica and Sardinia. The land and freshwater molluscs of many Pleistocene deposits tell a similar tale: high alpine, boreal, and hyperborean forms are characteristic of those deposits in central Europe; even in the southern regions of our continent the shells testify to a former colder and wetter climate. It was during the climax of these conditions that the caves of Aquitaine were occupied by those artistic men who appear to have delighted in carving and engraving."[BR] Such, in brief, is the testimony of the Pleistocene flora and fauna of extra-glacial regions. It is from the deposits in these regions, therefore, that we derive our fullest knowledge of the life of the period. But a comparison of their organic remains with those that occur in the glacial and interglacial deposits of alpine and northern lands shows us that the Pleistocene accumulations of glacial and extra-glacial countries are contemporaneous--for there is not a single life-form obtained from interglacial beds which does not also occur in the deposits of extra-glacial regions. The converse is not true--nor is that to be wondered at, for interglacial deposits have only been sparingly preserved. In regions liable to glaciation such superficial accumulations must frequently have been ploughed up and incorporated with ground-moraine. It was only in the extra-glacial tracts that alluvia of interglacial age were at all likely to be preserved in any abundance. To appreciate fully the climatic conditions of the Pleistocene period, therefore, it is necessary to combine the evidence derived from the glaciated areas with that obtained from the lands that lay beyond the reach of the ice-plough. The one is the complement of the other, and this being so, it is obvious that any attempted explanation of the origin of the Glacial period which does not fully realise the importance of the interglacial phase of that period cannot be accepted. [BR] _Prehistoric Europe_, p. 67. But if the climatic changes of Pleistocene times are the most important phenomena which the geologist who essays to trace the history of that period is called upon to consider, he cannot ignore the evidence of contemporaneous geographical mutations. These are so generally admitted, however, that it is only necessary here to state the well-known fact that everywhere throughout the maritime tracts of the glaciated lands of Europe and North America frequent changes in the relative level of land and sea took place during Pleistocene and post-glacial times. I must now very briefly review the evidence bearing on the climatic conditions of post-glacial times. And first, let it be noted that the closing stage of the Pleistocene period was one of cold conditions, accompanied in north-western Europe by partial depression of the land below its present level. This is shown by the late-glacial marine deposits of central Scotland and the coast-lands of Scandinavia. The historical records of the succeeding post-glacial period are furnished chiefly by raised beaches, river- and lake-alluvia, calcareous tufas, and peat-bogs. An examination of these has shown that the climate, at first cold, gradually became less ungenial, so that the Arctic-alpine flora and northern fauna were eventually supplanted in our latitude by those temperate forms which, as a group, still occupy this region. The amelioration of the climate was accompanied by striking geographical changes, the British Islands becoming united with themselves and the opposite coasts of the continent. The genial character of the climate at this time is shown by the great development of forests, the remains of which occur under our oldest peat-bogs. Not only did trees then grow at greater altitudes in these regions than is at present the case, but forests ranged much further north, and flourished in lands where they cannot now exist. In Orkney and Shetland, in the far north of Norway, and even in the Faröe Islands and in Iceland relics of this old forest-epoch are met with. In connection with these facts reference may be made to the evidence obtained from certain raised beaches on both sides of the N. Atlantic, and from recent dredgings in the intervening sea. The occurrence of isolated colonies of southern molluscs in our northern seas, and the appearance in raised beaches of many forms which are now confined to the waters of more southern latitudes, seem to show that in early post-glacial times the seas of these northern latitudes were warmer than now. And it is quite certain that the southern forms referred to are not the relics of any pre-glacial or interglacial immigration. They could only have entered our northern seas after the close of the Glacial period, and their evidence taken in connection with that furnished by the buried trees of our peat-bogs, leads to the conclusion that a genial climate supervened after the cold of the last glacial epoch and of earliest post-glacial times had passed away. To this genial stage succeeded an epoch of cold humid conditions, accompanied by geographical changes which resulted in the insulation of Britain and Ireland--the sea encroaching to some extent on what are now our maritime regions. The climate was less favourable to the growth of forests, which began to decay and to become buried under widespread accumulations of growing peat. At this time glaciers reappeared in the glens of the Scottish Highlands, and here and there descended to the sea. The evidence for these is quite conspicuous, for the moraines are found resting on the surface of post-glacial beaches. Thus my friend Mr. L. Hinxman, of the Geological Survey, tells us that at the foot of Glen Thraill well-formed moraines are seen in section reposing on beach-deposits at the distance of about three-quarters of a mile above the head of Loch Torridon.[BS] The evidence of this recrudescence of glacial conditions in post-glacial times is not confined to Scotland. I believe it will yet be recognised in many other mountain-regions; but already Prof. Penck has detected it in the valleys of the Pyrenees.[BT] Dr. Kerner von Marilaun has also described similar phenomena in the higher valleys of Tyrol, while Professor Brückner has obtained like evidence in the Salzach region.[BU] [BS] For Scottish post-glacial glaciers see J. Geikie: _Scottish Naturalist_, Jan., 1880; _Prehistoric Europe_, pp. 386,407; Penck: _Deutsche geographische Blätter_, Bd. vi., p. 323; _Verhand. d. Ges. f. Erdkunde, Berlin_, 1884, Heft 1; Hinxman: _Trans. Edin. Geol. Soc._, vol. vi., p. 249. [BT] "Die Eiszeit in den Pyrenäen": _Mitth. d. Vereins. f. Erdkunde_, Leipzig, 1883. [BU] Kerner: _Mitth. k. k. geograph. Ges. Wien_, 1890, p. 307; _Sitzungsb. d. kais. Akad. d. Wissensch. in Wien_, Bd. c., Abth. i., 1891; Brückner: _X. Jahresbericht d. geograph. Ges. v. Bern_, 1891. I have elsewhere traced the history of the succeeding stages of the post-glacial period, and brought forward evidence of similar but less strongly-marked climatic changes having followed upon those just referred to, and my conclusions, I may add, have been supported by the independent researches of Professor Blytt in Norway. But these later changes need not be considered here, and I shall leave them out of account in the discussion that follows. It is sufficient for my present purpose to confine attention to the well-proved conclusion that in early post-glacial times genial climatic conditions obtained, and that these were followed by cold and humid conditions, during the prevalence of which considerable local glaciers reappeared in certain mountain-valleys.[BV] [BV] For a full statement of the evidence see _Prehistoric Europe_, chaps. xvi., xvii. We speak of Pleistocene or Glacial and of Post-glacial periods as if the one were more or less sharply marked off from the other. Of course, that is not the case, and in point of fact it would be for many reasons preferable to include them under some general term. Taken together they form one tolerably well-defined cycle of time, characterised above all by its remarkable climatic changes--by alternations of cold and genial conditions, which were most strongly contrasted in the earlier stages of the period. It is further worthy of note that various oscillations of the sea-level appear to have taken place again and again both in the earlier and later stages of the cycle. We may now proceed to inquire whether the phenomena we have been considering can be accounted for by movements of the earth's crust--a view which has recently received considerable support, more especially in America. I need hardly say that the view in question is no novelty. Many years ago, while our knowledge of the Pleistocene phenomena was somewhat rudimentary, it was usual to infer that glaciation had been induced by elevation of the land. This did not seem an unreasonable conclusion, for above our heads, at a less or greater elevation, according to latitude, an Arctic climate prevails. One could not doubt, therefore, that if a land-surface were only sufficiently uplifted it would reach the snow-line, and become more or less extensively glaciated. But with the increase of our knowledge of Pleistocene and post-glacial conditions, such a ready interpretation failed to satisfy, although not a few geologists have continued to defend the "earth-movement hypothesis," as accounting fairly well for the phenomena of the Glacial period. By these staunch believers in the adequacy of that view, it has been pointed out that elevation might not only lift lands into the region of eternal snow, but, by converting large areas of the sea-bed into land, would greatly modify the direction of ocean-currents, and thus influence the climate. What might not be expected to happen were the Gulf Stream to be excluded from northern regions? What would be the fate of the temperate latitudes of North America and Europe were that genial ocean-river to be deflected into the Pacific across a submerged Isthmus of Panama? The possibility of such changes having supervened in Pleistocene times has often been present to my mind, but I long ago came to the conclusion that they could not account for the facts. Moreover, I have never been able to meet with any evidence in favour of the postulated "earth-movements." Having carefully studied all that has been advanced of late years in support of the hypothesis in question I find myself more than ever constrained to oppose it, not only because it is grounded on no basis of fact, but because it altogether fails to explain the conditions that obtained in Pleistocene and post-glacial times. There are various forms in which the hypothesis has appeared, and these I shall now consider seriatim, and with such brevity as may be. It has been maintained, for example, that at the advent of the Glacial period vast areas of northern and north-western Europe, together with enormous regions in the corresponding latitudes of North America, stood several thousand feet higher than at present. But when we ask what evidence can be adduced to prove this we get no satisfactory reply. We are simply informed that a glacial climate must have resulted from great elevation, and that the latter, therefore, must have taken place at the beginning of the Glacial period. Some writers, however, have ventured to give reasons for their faith. Thus Mr. W. Upham, pointing to the evidence of the fiords of North America, and to the fact that drowned river-valleys have been traced outwards across the 100-fathoms line of the marginal plateau to depths of over 3500 feet, maintains that the whole continent north of the Gulf of Mexico stood at the commencement of the Glacial period some 3000 feet at least higher than now. Of course he cites the fiords of Europe as evidence of a similar great upheaval for the northern and north-western regions of our Continent. Mr. Upham even favours the notion that during glacial times a land-connection probably existed between North America and Europe, by way of the British Islands, Iceland, and Greenland. When "this uplifting attained its maximum, and brought on the Glacial period," he says, "North America and north-western Europe stood 2500 to 3000 feet above their present height."[BW] [BW] _American Geologist_, vi., p. 327. That fiords are simply submerged land-valleys has long been recognised: that they have been formed mainly by the action of running water--just in the same way as the mountain-valleys of Norway and Scotland--has been the belief for many years of most students of physical geology. But it is hard to understand why they should have been cited by Mr. Upham in support of his contention, seeing that their evidence seems to militate strongly against the very hypothesis he strives to maintain. No one acquainted with the physical features and geological structure of Scotland and Norway can doubt that the valleys which terminate in fiords are of great geological antiquity. Their excavation by fluviatile action certainly dates back to a period long anterior to the advent of the Ice Age. And a like tale is told by the fiords and drowned valley-troughs of North America, which cannot be referred to so recent a period as post-Tertiary times. Those who are convinced that our continental areas have persisted throughout long æons of geological time, and that rivers frequently have survived great geological revolutions--cutting their way across mountain-elevations as fast as these were uplifted--will readily believe that some of the submarine river-troughs of North America, such as that of the Hudson, may belong even to Secondary times.[BX] It would be hard to say at what particular date the excavation of the Scottish Highland valleys commenced--but it was probably during the later part of the Palæozoic era. The process has doubtless been retarded and accelerated frequently enough, during successive movements of depression and elevation, but it was practically completed before the beginning of Pleistocene times, and that is all that we may trouble about here. Precisely the same conclusion holds good for Norway: and such being the case it is obvious that the question of the origin and age of the fiords has no bearing on the problem of the glacial climate and its cause. In point of fact the evidence, as already remarked, tells against the "earth-movement hypothesis," for it shows us that, during a period when Europe and North America stood several thousand feet higher, and extended much further seawards, rivers, and not glaciers, were the occupants of our mountain-valleys. It was not until all those valleys had come to assume much the appearance they now present that general glaciation supervened. [BX] Professor Dana inclines to date the erosion of the Hudson trough so far back as the Jura-Trias period.--_American Journ. Science_, xl., p. 435. We are not without direct evidence, however, as to the geographical conditions that obtained in the ages that immediately preceded the Pleistocene period. The distribution of the Pliocene marine beds of Britain entitles us to assume that at the time of their accumulation our lands did not extend quite so far to the south and east as now. The absence of similar deposits from the coast-lands of North America is supposed to support the view of great continental elevation in pre-glacial times. All it seems to prove, however, is that in Pliocene times the North American continent was not less extensive than it is at present. It is even quite possible that in glacial times pre-existing Pliocene beds may have been ploughed out by the ice, just as seems to have been the case in the north-east of Scotland. But without going so far back as Pliocene times, we meet with evidence almost everywhere throughout the maritime regions of the glaciated areas of Europe and North America, to show that immediately before those tracts became swathed in ice the geographical conditions were much the same as at present. The shelly boulder-clays in various parts of our islands, and the similar occurrence of marine and brackish-water shells in and underneath the Diluvium of north Germany, etc., prove clearly enough that just before the coming-on of glacial conditions neither Britain nor the present maritime lands of the Continent were far removed from the sea. It is true that the buried river-channels of Scotland indicate a pre-glacial elevation of some 200 or 300 feet above the existing sea-level, but it is quite certain that the Minch, St. George's Channel, the Irish Sea, the North Sea, and the Baltic were all in existence at the commencement of the Glacial period. And we are led to similar conclusions with regard to the geographical conditions of North America at that time, from the occurrence of marine shells in the boulder-clays of Canada and New England. We note indeed that there is abundant evidence of land-submergence during glacial times. Indeed, we may say that the Pleistocene marine deposits of northern latitudes are almost invariably indicative of colder conditions than now obtain. If it be true that cold climatic conditions were contemporaneous in our latitude with submergence, it is equally true that an extensive land-surface in north-west Europe has, sometimes at least, co-existed with markedly genial conditions. In Tertiary times, for example, as the Oligocene deposits of Scotland, the Faröe Islands, Iceland, and Greenland testify, a land-connection existed between Europe and the North American continent. Again, it has been shown that during the interglacial phase of the Pleistocene period Britain was continental, and enjoyed at the time a peculiarly genial climate. And somewhat similar geographical and climatic conditions again supervened in post-glacial times. In other words, when the land was more elevated and extensive than now, it enjoyed a warmer climate. Nor can we escape the conclusion that the excavation of the fiord-valleys of northern latitudes, which is a very old story (far older than the Pleistocene), was the work not of glaciers but of running water, at a time when north-western Europe and the corresponding regions of America were much more elevated than they are now. Thus there appears to be no evidence either direct or indirect in favour of the view that glacial conditions were superinduced by great continental elevation. But it may be argued that even although no evidence can be cited in proof of such elevation, still, if the glacial phenomena can be well explained by its means, we may be justified in admitting it as a working hypothesis. Movements of elevation and depression have frequently taken place--the Pleistocene marine deposits themselves testify to oscillations of the sea-level--and there can be no objection, therefore, to such postulations as are made by the hypothesis under review. All this is readily granted, but I deny that the conditions that obtained in Pleistocene times can be accounted for by elevation and depression. Let us see how the desiderated elevation of northern lands would work. Were north-western Europe and the corresponding latitudes of North America to be upheaved for 3000 feet, and a land-passage to obtain between the two continents by way of the Faröe Islands, Iceland, and Greenland, how would the climate be affected? It is obvious that under such changed conditions the elevated lands in higher latitudes might well be subjected to more or less extensive glaciation. Norway would become uninhabitable and glaciers might well appear in the mountain-valleys of Scotland. But it may be doubted whether the climate of France and Spain, or the corresponding latitudes of North America, would be much affected. For were a land-passage to appear between Britain and Greenland no Arctic current would flow into the North Atlantic, while no portion of the Gulf Stream would be lost in Arctic seas. The North Atlantic would then form a great gulf round which a warm ocean-current would circulate. The temperature of that sea, therefore, would be raised and the prevailing westerly and south-westerly winds of Europe would be warmer than now. However much such warm moist winds might increase the snow-fall in North Britain and Scandinavia, we cannot suppose they could have much influence in central and southern Europe, and in North Africa; and still less could they affect the climate of Asia Minor and the mountainous regions of the far east, in most of which evidence of extensive glaciation occurs. And how, we may ask, could the postulated geographical changes bring about the glaciation of the mountainous tracts on the Pacific sea-board? In fine, we may conclude that however much the geographical changes referred to might affect north-western Europe and north-eastern America, they are wholly insufficient to account for the glacial phenomena of other regions. The continuous research of recent years has shown that the lowering of temperature of glacial times was not limited to the lands which would be affected by any such elevation as that we are considering. A marked and general displacement of climatic zones took place over the whole continent of Europe; and similar changes supervened in North America and Asia. Are we then to suppose that all the lands within the Northern Hemisphere were extensively and contemporaneously upheaved? We may now consider another form of the "earth-movement hypothesis." It has frequently been suggested that our glacial phenomena may have been caused by the submergence of the Isthmus of Panama, and the deflection of the Equatorial Current into the Pacific. But it may be doubted whether a submergence of that isthmus, unless very extensive indeed, would result in more than a partial escape of Atlantic water into the Pacific basin. The Counter Current of the Pacific which now strikes against the isthmus might even sweep into the Caribbean Sea, and join the Equatorial on its way to the Gulf of Mexico. But putting that consideration aside, what evidence have we that the Isthmus of Panama was submerged during the glacial epoch? None whatsoever, it may be replied. It is only a pious opinion. Considerable movements of elevation and depression of the islands in the Caribbean Sea would seem to have taken place at a comparatively recent date, but those movements may quite well belong to Pliocene times. Whether they be of Pliocene or Pleistocene age, however, no one has yet proved that the Isthmus of Panama was sufficiently submerged, either at the one time or the other, to permit the escape of the Atlantic Equatorial into the Pacific basin. But let it be supposed that the isthmus has become so deeply submerged that the Equatorial Current is wholly deflected, and that no Gulf Stream issues through the Straits of Florida to temper the climate of higher latitudes. What would result from such an unhappy change? Can any one conversant with the geographical distribution of the glacial phenomena imagine that the conditions of the Glacial period could be thus reproduced? Norway might indeed become a second south Greenland, and perennial snow and ice might appear in the mountainous tracts of the British Islands. The climate of Hudson's Bay and the surrounding lands might be experienced in the Baltic and its neighbourhood, and what are now the temperate latitudes of Europe, north of the 50th parallel, would possibly approach Siberia in character. But surely these changes are not comparable to the conditions of the Glacial period. The absence of a Gulf Stream would not sensibly affect the climate of south-eastern Europe and Asia, and could not have the smallest influence on that of the Pacific coast-lands of North America. Yes, but if we conceive the submergence of the Isthmus of Panama to coincide with great elevation of northern lands, would not such geographical conditions bring about a glacial epoch comparable to that of Pleistocene times? It is hard to see how they could. No doubt the climate of all those regions that would be affected by the withdrawal of the Gulf Stream alone would become still more deteriorated if they stood some 3000 feet higher than now. A vast area in the north-west of Europe would certainly be uninhabitable, but it is for the advocates of the "earth-movement hypothesis" to explain why those inhospitable regions should necessarily be covered with an ice-sheet. For the production of great snow-fields and continental ice-sheets, considerable precipitation, no less than a low temperature, is requisite. Under the conditions we have been imagining, however, precipitation would probably be much less than it is at present. But to whatever extent north-west Europe might be glaciated, it is obvious that the geographical revolutions referred to could have little influence on the climate of south-eastern Europe, not to mention central and eastern Asia. Nor could they possibly influence the climate of the Pacific coast-lands of North America. And yet, as is well known, the climate of all those regions was more or less profoundly affected during the Glacial period. To account for the widespread evidences of glaciation by means of elevation it would therefore seem necessary to infer that all the affected areas were in Pleistocene times uplifted _en masse_ into the Arctic zone that stretches above our heads. Now it seems easier to believe that the snow-line was lowered by several thousand feet than that the continents were elevated to the same extent. Glaciation, as we have seen, was developed in the same directions and over the same areas as we should expect it to be were the snow-line to be generally depressed. To put it in another way, were the snow-line by some means or other to be lowered over Europe, Asia, and North America, then, with sufficient precipitation, great ice-fields and glaciers would reappear in the very regions which they visited during Pleistocene times. Neither elevation nor depression of the land would be required to bring about such a result. Certain advocates of the "earth-movement hypothesis," however, do not maintain that all the glaciated areas were uplifted at one and the same time. The glaciation of the Alps, they think, may have taken place earlier or later than that of north-western Europe, while the ice-period of the Rocky Mountains may not have coincided with that of eastern North America. It is not impossible, they suppose, that the glaciation of the Himalayas may have been caused by an uplifting of that great chain, quite independent of similar earth-movements in other places. It can be demonstrated, however, that the glaciation of the Alps and of northern Europe were contemporaneous, and the facts go far to prove that the glaciers of the Rocky Mountains and the inland-ice of north-east America likewise co-existed. At all events all the old glacial accumulations of our hemisphere are of Pleistocene age, and it is for the advocates of the hypothesis under review to prove that they are not contemporaneous. Their doubts on the subject probably arise from the simple fact that they are well aware how highly improbable or even impossible it is that all those glaciated lands could have been pushed up within the snow-line at one and the same time. Let me, however, advance to another objection. We know that the Glacial period was interrupted by at least one interglacial epoch of temperate and even genial conditions. Two glacial epochs with one protracted interglacial epoch are now generally admitted. How do the supporters of the "earth-movement hypothesis" explain this remarkable succession of climatic changes? Their views as to the cause of glacial conditions we have considered. If we can believe that the glacial phenomena were due to elevation of the land, then we need have no difficulty in understanding how glacial conditions would disappear when the continents again subsided to a lower level. Not only did North America and Europe lose all their early glacial elevation, but by a lucky coincidence the Isthmus of Panama reappeared, and the Gulf Stream resumed its beneficent course into the North Atlantic. This we are to suppose was the cause of the interglacial epoch. But I would point out that the geographical conditions which are thus inferred to have brought about the disappearance of the glacial climate, and to have ushered in the interglacial epoch, are precisely those that now obtain--and, nevertheless, we are not yet in the enjoyment of a climate like that of interglacial times. The strangely equable conditions that permitted the development of the remarkable Pleistocene flora and fauna are not experienced in the Europe of our day. And what about the second glacial epoch? Are we to suppose that once more the lands were greatly uplifted, and that convenient Isthmus of Panama was again depressed? Did the Alps, the Pyrenees, and the plateau of central France--in all of which we have distinct evidence of at least two glacial epochs--did these heights, one may ask, rise up to bring about their earlier glaciation, sink down again to induce interglacial conditions, and once more become uplifted at the succeeding cold epoch, to subside eventually in order to cause a final retreat of their glaciers? But the climatic changes to be accounted for were in all probability more numerous and complex than those just referred to. Competent observers have adduced unmistakable evidence of three epochs of glaciation in the Alpine Lands of Europe. And we are not without distinct hints that similar changes have taken place in northern and western Europe. Nor in this connection can we ignore the evidence of several interglacial episodes which Mr. Chamberlin and others have detected in the glaciated tracts of North America. Even this is not all, for the upholders of the "earth-movement hypothesis" have still further to account for the climatic oscillations of post-glacial times. If it be hard enough to allow the possibility of one great movement of elevation having affected so enormous an area of our hemisphere, if we find it extremely difficult to believe either that one such widespread movement, or that a multitude of local movements, each more or less independent of the other, could have lifted the glaciated regions successively within reach of the snow-line--we shall yet find it impossible to admit that such remarkable upheavals could be repeated again and again. We seem driven to conclude, therefore, that the "earth-movement hypothesis" fails to explain the phenomena of Pleistocene times. One cannot deny, indeed, that glaciation might be induced locally by elevation of the land. It is quite conceivable that mountains now below the limits of perennial snow might come to be ridged up to such an extent as to be capable of sustaining snow-fields and glaciers. And such local movements may possibly have happened here and there during the long-continued Pleistocene period. But the glacial phenomena of that period are on much too grand a scale and far too widely distributed to be accounted for in that way. And if the occurrence of even one glacial epoch cannot be thus explained, we may leave the supporters of the "earth-movement hypothesis" to show us what light is thrown by their urim and thummim on the origin of succeeding interglacial and glacial climates. There is yet another physical condition of the Pleistocene and post-glacial periods which any adequate explanation must embrace. I refer to the oscillation of sea-level, of which so many proofs are forthcoming. It is very remarkable that almost everywhere throughout the maritime regions of formerly glaciated areas we find evidence of submergence. So commonly is this the case, that geologists have long suspected that the connection between glaciation and submergence might be one of cause and effect. The possible influence of great ice-sheets in disturbing the relative level of land and sea is a question, therefore, of very great importance. It is one, however, which must be solved by physicists. Croll and others have advocated the view that the great accumulations of ice of the Glacial period may have displaced the earth's centre of gravity, and thus caused the sea to rise upon the glaciated hemisphere. The various results arrived at by physicists are hardly comparable, because each has used different data, but it seems probable that we have in this view a _vera causa_ of oscillations of the sea-level. Another hypothesis would explain the rise of the sea as due to the attractive influence of the great ice-masses, but Dr. Drygalski's and Mr. Woodward's elaborate investigations would seem to have demonstrated that this notion does not account for the facts. Yet another speculation has been advanced. Mr. Jamieson has suggested that the mere weight of the ice-sheets would suffice to press down the earth's crust into a supposed liquid substratum, and this explanation has met with much acceptance. Unfortunately our knowledge of the condition of the earth's interior is so very limited that we cannot be certain as to how the crust would be affected by the weight of an ice-sheet. No doubt Mr. Jamieson's hypothesis gives a specious explanation of certain geological phenomena, but if there be no liquid substratum underlying a thin crust it cannot be true. At present the prevalent view of physicists appears to be that the earth is substantially solid. Professor George Darwin has shown that the prominent inequalities of the earth's surface could not be sustained unless the crust be as rigid as granite for a depth of 1000 miles. "If the earth be solid throughout," he remarks, "then at 1000 miles from the surface the material must be as strong as granite. If it be fluid or gaseous inside, and the crust 1000 miles thick, that crust must be stronger than granite, and if only 200 or 300 miles in thickness, much stronger than granite." This conclusion is obviously strongly confirmatory of Sir William Thomson's view, that the earth is solid throughout. But many geologists find it hard to account for the convolutions of strata and other structural phenomena on the supposition that the earth is entirely solid, and they are inclined, therefore, to adopt the hypothesis of a sub-crust layer of liquid matter. Whether this be actually the condition or not physicists must be left to determine. All that we need note is, that if there be any force in Professor Darwin's argument, it is obvious that the crust is possessed of great rigidity, and could not be readily deformed by the mere weight of an ice-sheet. According to Dr. Drygalski, however, the presence of an ice-sheet, by reducing the temperature of the underlying crust, would bring about contraction, and in this way cause the surface to sink. When the ice-sheet had disappeared, then free radiation of earth-heat would be resumed, the depressed isogeotherms would rise, and a general warming of the upper portion of the lithosphere would take place. But the space occupied by the depressed section, owing to the spheroidal form of the earth, would be smaller than that which it occupied before sinking had commenced, and consequently when the ice vanished expansion of the crust would follow, and the land-surface would then rise again. The whole question is one for physicists to decide upon, but I may point out that if Drygalski's explanation be well founded, then it is obvious that it throws no light upon the origin and subsequent disappearance of an ice-sheet. Somehow or other this ice-sheet comes into existence, and the cooling and contracting crust sinks below it; and that depressed condition of the glaciated area must continue so long as the ice-sheet remains unmelted. Re-elevation can only take place when, owing to some other cause or causes, the climate changes and the ice-sheet vanishes. Those who advocate the "earth-movement hypothesis" as an explanation of the origin of extensive glaciation have welcomed Mr. Jamieson's view as harmonising well with their conclusions. They contend, as we have seen, that glacial conditions were induced by an extensive upheaval of the crust in northern latitudes, accompanied by a depression of the Isthmus of Panama. They then proceed to point out that the ice-sheets brought about their own dissolution by pressing down the crust, and introducing with submergence a disappearance of glacial conditions. See now how much they take for granted. In the first place, they assume an amount of pre-glacial or early glacial elevation of northern regions for which not a scrap of evidence can be adduced, while they can give no proof of contemporaneous depression of the Isthmus of Panama. Next, relying on Mr. Jamieson's hypothesis, they take for granted that the ice-sheets, called into existence by their postulated earth-movements, succeeded in depressing the earth's surface even below its present level. That is to say, the land, which, according to them, was in glacial times some 3000 feet higher than now, sank down under the weight of its glacial covering for, say, 3600 feet in north-western Europe. In North America, in like manner, all the pre-glacial elevation was lost--the land sinking below its present level for some 200 feet in New England, for 520 feet at Montreal, for 1000 to 1500 feet in Labrador, and for 1000 to 2000 feet in the Arctic regions. Now, even if we concede the reasonableness of Mr. Jamieson's hypothesis, and admit that a certain degree of deformation may take place under the mere weight of an ice-sheet, it is difficult to believe that the crust can be so readily deformed as the supporters of the "earth-movement hypothesis" seem to imply. If it could yield so readily to pressure, one is at a loss to understand how a great ice-sheet could accumulate--the ice would simply float off as the land subsided. Take the case of north-western Europe. The ice-sheet that covered Scotland did not attain, on the average, 3000 feet in thickness, and yet we are to suppose that it was able to depress the land for some 600 feet below its present level--that is to say, for 3600 feet below its assumed pre-glacial elevation. Either the ice depressed the crust to that remarkable extent, or the land upon which the ice accumulated was not nearly so high as the advocates of the "earth-movement hypothesis" have supposed. But the average I have taken for the thickness of the Scottish ice-sheet is excessive, for it was only in the low-grounds that the _mer de glace_ attained such a depth. A large part of our country, however, is mountainous, and the mountain-tops were, of course, not nearly so thickly mantled with ice as the valleys. And the same to even a larger extent holds good for the Scandinavian peninsula. If we take the thickness of the Scandinavian ice-sheet that coalesced with that of Scotland as 4000 feet, we shall be over the mark. Now, I ask, is it possible to believe that a sheet of ice of that thickness actually pressed down the crust of the earth for not less than 3600 feet? But if we accept the "earth-movement hypothesis," as it has been recently advocated, that is what we must believe. If we cannot do so, then we cannot accept the assumption of great elevation of the land in pre-glacial and glacial times. Let me put the case shortly: if the glacial marine beds and raised beaches of the Atlantic borders of Europe and North America owe their origin to depression induced by the weight of an ice-sheet, then it is quite certain that at the advent of glacial conditions the land could not have been so highly elevated as the advocates of the "earth-movement hypothesis" suppose. But if we are to accept the notion of great elevation of the land, then we must conclude that the submergence to which the raised beaches testify cannot have been caused by the pressure of ice-sheets. It is hardly necessary to pursue this particular subject further, but before leaving it, attention may be drawn for a moment to the curious conclusion that the ice-sheets were self-destructive. One is left to guess at what particular stage the sinking process began, but if the earth's crust were as readily deformed as the extreme views I have been examining would compel one to imply, then depression must have commenced almost immediately with the accumulation of snow and ice. The several ice-sheets must soon have attained their maximum thickness, and their disappearance must have been correspondingly rapid. And yet all the evidence goes to show that a glacial epoch endured for a comparatively long time--for a time sufficient to account for a prodigious amount of rock-erosion, and for the accumulation of vast sheets of glacial débris and fluvio-glacial detritus.[BY] [BY] It must not be inferred from the above remarks that I deny the possibility of deformation of the crust having been induced by the old ice-sheets. The geological evidence is certainly suggestive of such having been the case. But I much doubt whether the sinking of the surface was brought about by the mere weight of the ice pressing the crust down into a subjacent liquid layer. Dr. Drygalski's explanation would better account for the geological phenomena, but, according to Rev. Osmond Fisher, it cannot be maintained. If it be difficult to understand how the "earth-movement hypothesis" can account for the origin of one glacial epoch, the difficulty is not lessened when we remember that there are two or more such epochs to account for. And until the advocates of that hypothesis can furnish us with some reliable evidence, they can hardly expect us to believe in their mysterious upheavals and depressions of northern and temperate regions, and in the no less wonderfully rhythmic movements of the Isthmus of Panama. In fine, the views which I have been controverting seem to me to be untenable, inasmuch as they are founded on mere assumptions, and do not even give a reasonable and intelligible explanation of the phenomena of glaciated regions, while they practically ignore or leave unsolved the problem of interglacial conditions. Some five-and-twenty years have now elapsed since my lamented friend and colleague, James Croll, published his well-known physical theory of the Glacial period. That theory, as you all know, has been frequently criticised by physicists and others, to whose objections Croll made a final reply in his _Climate and Cosmology_. In that work he has successfully defended his views, and even added considerably to the strength of his general argument. I am not aware that since then any serious objections to Croll's theory have appeared. The only one indeed that seems to have attracted attention is that which has been urged especially by certain American geologists. Their belief is that the close of the Glacial period must have taken place at a much more recent date than Croll has inferred. And this belief of theirs is based upon various estimates which have been made as to the time required for the erosion of valleys and the accumulation of alluvial deposits since the Glacial period. Thus, according to Mr. Gilbert, the post-glacial gorge of Niagara, at the present rate of erosion, must have been excavated within 7000 years; while Mr. Winchell, from similar measurements of the post-glacial erosion of the Falls of St. Anthony, concludes that 8000 years have elapsed since the close of the Ice Age. I might cite a number of similar estimates that tend to show that since the close of the Glacial period only 7000 or 10,000 years have elapsed. What will archæologists say to this conclusion? We know that Egypt was already occupied by a civilised people nearly 6000 years ago, and their marvellously advanced civilisation at that time presupposes, according to Egyptologists, many thousands of years of development. Are we, then, prepared to admit that the close of the Ice Age coincided with the dawn of Egyptian civilisation? But all American observers are not so parsimonious with regard to post-glacial time. Thus Professor Spencer has given the age of the Falls of Niagara as 24,000 years, and he informed me recently that this does not represent half of the time since the formation of the third great series of glacial deposits of the Canadian uplands. In our own Continent similar estimates have been based on the rate of erosion of river-valleys, the rate of accumulation of alluvial deposits, of peat-bogs, of stalagmite in caves, and what not, with results that, to say the least, are rather discordant. The fact is that all such measurements and estimates, however carefully conducted and cautiously made, are in the nature of things unreliable. We are insufficiently acquainted with all the factors of the problem to be solved, and I cannot therefore agree with those who attribute much weight to conclusions based on such uncertain data. Dr. Croll's theory may eventually be modified, but I feel sure that it will not be overturned by the inconclusive and unsatisfactory estimates to which I have referred. Moreover, opponents of that theory may be reminded that its truth does not rest on the accuracy of its author's conclusion as to the date of the last Ice Age. That periods of high eccentricity of the earth's orbit have occurred is beyond all doubt, but whether the formulæ employed by Croll in calculating the date of the last great cycle can be relied upon for that purpose is quite another question. At present, so far as I understand the facts, the glacial and the interglacial phenomena are explained by the astronomical theory, and by no other. It gives a simple, coherent, and consistent interpretation of the climatic vicissitudes of the Pleistocene and post-glacial periods, and in especial it is the only theory that throws any light on the very remarkable climates of interglacial times. X. The Glacial Succession in Europe.[BZ] [BZ] _Trans. Royal Soc. Edinburgh_, vol. xxxvii. (1892). For many years geologists have recognised the occurrence of at least two boulder-clays in the British Islands and the corresponding latitudes of the Continent. It is no longer doubted that these are the products of two separate and distinct glacial epochs. This has been demonstrated by the appearance of intercalated deposits of terrestrial, freshwater, or, as the case may be, marine origin. Such interglacial accumulations have been met with again and again in Britain, and they have likewise been detected at many places on the Continent, between the border of the North Sea and the heart of Russia. Their organic contents indicate in some cases cold climatic conditions; in others, they imply a climate not less temperate or even more genial than that which now obtains in the regions where they occur. Nor are such interglacial beds confined to northern and north-western Europe. In the Alpine Lands of the central and southern regions of our Continent they are equally well developed. Impressed by the growing strength of the evidence, it is no wonder that geologists, after a season of doubt, should at last agree in the conclusion that the glacial conditions of the Pleistocene period were interrupted by at least one protracted interglacial epoch. Not a few observers go further, and maintain that the evidence indicates more than this. They hold that three or even more glacial epochs supervened in Pleistocene times. This is the conclusion I reached many years ago, and I now purpose reviewing the evidence which has accumulated since then, in order to show how far it goes to support that conclusion. In our islands we have, as already remarked, two boulder-clays, of which the lower or older has the wider extension southwards, for it has been traced as far as the valley of the Thames. The upper boulder-clay, on the other hand, does not extend south of the midlands of England. In the north of England, and throughout Scotland and the major portion of Ireland, it is this upper boulder-clay which usually shows at the surface. The two clays, however, frequently occur together, and are exposed again and again in deep artificial and natural sections, as in pits, railway-cuttings, quarries, river-banks, and sea-cliffs. Sometimes the upper clay rests directly upon the lower; at other times they are separated by alluvial and peaty accumulations or by marine deposits. The wider distribution of the lower till, the direction of transport of its included erratics, and the trend of the underlying _roches moutonnées_ and rock-striæ, clearly show that the earlier _mer de glace_ covered a wider area than its successor, and was confluent on the floor of the North Sea with the Scandinavian ice-sheet. It was during the formation of the lower till, in short, that glaciation in these islands attained its maximum development. The interglacial beds, which in many places separate the lower from the upper till, show that after the retreat of the earlier _mer de glace_ the climate became progressively more temperate, until eventually the country was clothed with a flora essentially the same as the present. Wild oxen, the great Irish deer, and the horse, elephant, rhinoceros, and other mammals then lived in Britain. From the presence of such a flora and fauna we may reasonably infer that the climate during the climax of interglacial times was as genial as now. The occurrence of marine deposits associated with some of the interglacial peaty beds shows that eventually submergence ensued; and as the shells in some of the marine beds are boreal and arctic forms, they prove that cold climatic conditions accompanied the depression of the land. To what extent the land sank under water we cannot tell. It may have been 500 feet or not so much, for the evidence is somewhat unsatisfactory. The upper boulder-clay of our islands is the product of another _mer de glace_, which in Scotland would seem to have been hardly less thick and extensive than its predecessor. Like the latter, it covered the whole country, overflowed the Outer Hebrides, and became confluent with the Scandinavian inland-ice on the bed of the North Sea. But it did not flow so far to the south as the earlier ice-sheet. It is well known that this later _mer de glace_ was succeeded in our mountain-regions by a series of large local glaciers, which geologists generally believe were its direct descendants. It is supposed, in short, that the inland-ice, after retreating from the low-grounds, persisted for a time in the form of local glaciers in mountain-valleys. This view I also formerly held, although there were certain appearances which seemed to indicate that, after the ice-sheet had melted away from the Lowlands and shrunk far into the mountains, a general advance of great valley-glaciers had taken place. I had observed, for example, that the upper boulder-clay is often well developed in the lower reaches of our mountain-valleys--that, in fact, it may be met with more or less abundantly up to the point at which large terminal moraines are encountered. More than this, I had noticed that upland valleys, in which no local or terminal moraines occur, are usually clothed and paved with boulder-clay throughout. Again, the aspect of valleys which have been occupied by large local glaciers is very suggestive. Above the point at which terminal moraines occur only meagre patches of till are met with on the bottoms of the valleys. The adjacent hill-slopes up to a certain line may show bare rock, sprinkled perchance with erratics and superficial morainic detritus; but above this line, if the acclivity be not too great, boulder-clay often comes on again. These appearances are most conspicuously displayed in the southern Uplands of Scotland, particularly in south Ayrshire and Galloway, and long ago they led me to suspect that the local glaciers into which our latest _mer de glace_ was resolved, after retreating continuously towards the heads of their valleys, so as to leave the boulder-clay in a comparatively unmodified condition, had again advanced and ploughed this out, down to the point at which they dropped their terminal moraines. Subsequent observations in the Highlands and the Inner and Outer Hebrides confirmed me in my suspicion, for in all those regions we meet with phenomena of precisely the same kind. My friends and colleagues, Messrs. Peach and Horne, had independently come to a similar conclusion; and the more recent work of the Geological Survey in the north-west Highlands, as they inform me, has demonstrated that after the dissolution of the general ice-sheet underneath which the upper boulder-clay was accumulated, a strong recrudescence of glacial conditions supervened, and a general advance of great valley-glaciers took place--the glaciers in many places coalescing upon the low-grounds to form united _mers de glace_ of considerable extent. The development of these large glaciers, therefore, forms a distinct stage in the history of the Glacial period. They were of sufficient extent to occupy all the fiords of the northern and western Highlands, at the mouths of which they calved their icebergs, and they descended the valleys on the eastern slopes of the land into the region of the great lakes, at the lower ends of which we encounter their outermost terminal moraines. The Shetland and Orkney Islands and the Inner and Outer Hebrides at the same time nourished local glaciers, not a few of which flowed into the sea. Such, for example, was the case in Skye, Harris, South Uist, and Arran. The broad Uplands of the south were likewise clothed with snow-fields that fed numerous glaciers. These were especially conspicuous in the wilds of Galloway, but they appeared likewise in the Peeblesshire hills; and even in less elevated tracts they have left more or less well-marked traces of their former presence. It is to this third epoch of glaciation that I would assign the final scooping out of our lake-basins and the completion of the deep depressions in the beds of our Highland fiords. All the evidence, indeed, leads to the conviction that the epoch was one of long duration. It goes without saying that what holds good for Scotland must, within certain limits, hold good also for Ireland and England. In Wales and the Cumberland lake district, and in the mountain-regions of the sister island, we meet with evidence of similar conditions. Each of those areas has obviously experienced intense local glaciation subsequent to the disappearance of the last big ice-sheet. Attention must now be directed to another series of facts which help us to realise the general conditions that obtained during the epoch of local glaciation. In the basin of the estuary of the Clyde, and at various other places both on the west and east coasts of Scotland, occur certain clays and sands, which overlie the upper boulder-clay, and in some places are found wrapping round the kames and osar of the last great ice-sheet. These beds are charged with the relics of a boreal and arctic fauna, and indicate a submergence of rather more than 100 feet. In the lower reaches of the rivers Clyde, Forth, and Tay the clays and sands form a well-marked terrace, and a raised sea-beach, containing similar organisms, occurs here and there on the sea-coast, as between Dundee and Arbroath, on the southern shores of the Moray Firth, and elsewhere. When the terraces are traced inland they are found to pass into high-level fluviatile gravels, which may be followed into the mountain-valleys, until eventually they shade off into fluvio-glacial detritus associated with the terminal moraines of the great local glaciers. It is obvious, in short, that the epoch of local ice-sheets and large valley-glaciers was one also of partial submergence. This is further shown by the fact that in some places the glaciers that reached the sea threw down their moraines on the 100-feet beach. It must have been an epoch of much floating ice, as the marine deposits contain now and again many erratics, large and small, and are, moreover, frequently disturbed and contorted as if from the grounding of pack-ice. The phenomena which I have thus briefly sketched suffice to show that the epoch of local glaciation is to be clearly distinguished from that of the latest general _mer de glace_. I have long suspected, indeed, that the two may have been separated by as wide an interval of time as that which divided the earlier from the later epoch of general glaciation. Again and again I have searched underneath the terminal moraines, in the faint hope of detecting interglacial accumulations. My failure to discover these, however, did not weaken my conviction, for it was only by the merest chance that interglacial beds could ever have been preserved in such places. I feel sure, however, that they must occur among the older alluvia of our Lowlands. Indeed, as I shall point out in the sequel, it is highly probable that they are already known, and that we have hitherto failed to recognise their true position in the glacial series. Although we have no direct evidence to prove that a long interglacial epoch of mild conditions immediately preceded the advent of our local ice-sheets and large valley-glaciers, yet the indirect evidence is so strong that we seem driven to admit that such must have been the case. To show this I must briefly recapitulate what is now known as to the glacial succession on the Continent. It has been ascertained, then, that the Scandinavian ice has invaded the low-grounds of Germany on two separate occasions, which are spoken of by Continental geologists as the "first" and "second" glacial epochs. The earlier of these was the epoch of maximum glaciation, when the inland ice flowed south into Saxony, and overspread a vast area between the borders of the North Sea and the base of the Ural Mountains. This ice-sheet unquestionably coalesced with the _mer de glace_ of the British Islands. Its bottom-moraine and the associated fluvio-glacial detritus are known in Germany as "Lower Diluvium," and the various phenomena connected with it clearly show that the inland-ice radiated outwards from the high-grounds of Scandinavia. The terminal front of that vast _mer de glace_ is roughly indicated by a line drawn from the south coast of Belgium round the north base of the Harz, and by Leipzig and Dresden to Krakow, thence north-east to Nijnii Novgorod, and further north to the head-waters of the Dvina and the shores of the Arctic Sea near the Tcheskaia Gulf. The lower diluvium is covered in certain places by interglacial deposits and an overlying upper diluvium--a succession clearly indicative of climatic changes. In the interglacial beds occur remains of _Elephas antiquus_ and other Pleistocene mammals, and a flora which denotes a genial temperate climate. One of the latest discoveries of interglacial remains is that of two peat-beds lying between the lower and upper diluvium near Grünenthal in Holstein.[CA] Among the abundant plant-relics are pines and firs (no longer indigenous to Schleswig-Holstein), aspen, willow, white birch, hazel, hornbeam, oak, and juniper. Associated with these are _Ilex_ and _Trapa natans_, the presence of which, as Dr. Weber remarks, betokens a climate like that of western middle Germany. Amongst the plants is a water-lily, which occurs also in the interglacial beds of Switzerland, but is not now found in Europe. The evidence furnished by this and other interglacial deposits in north Germany shows that, after the ice-sheet of the lower diluvium had melted away, the climate became as temperate as that now experienced in Europe. Another recent find of the same kind[CB] is the "diluvial" peat, etc., of Klinge, in Brandenburg, described by Professor Nehring. These beds have yielded remains of elk (_Cervus alces_), rhinoceros (species not determined), a small fox (?), and Megaceros. This latter is not the typical great Irish deer, but a variety (_C. megaceros_, var. _Ruffii_, Nehring). The plant-remains include pine, fir (_Picea excelsa_), hornbeam, warty birch (_Betula verrucosa_), various willows (_Salix repens_, _S. aurita_, _S. caprea_ [?], _S. cinerea_), hazel, poplar (?), common holly, etc. It is worthy of note that here also the interglacial water-lily (_Cratopleura_) of Schleswig-Holstein and Switzerland makes its appearance. Dr. Weber writes me that the facies of this flora implies a well-marked temperate insular climate (Seeklima). The occurrence of holly in the heart of the Continent, where it no longer grows wild, is particularly noteworthy. The evidence furnished by such a flora leads one to conclude that at the climax of the genial interglacial epoch, the Scandinavian snow-fields and glaciers were not more extensive than they are at present. [CA] _Neues Jahrbuch f. Min. Geol. u. Palæont._, 1891, ii., pp. 62, 228; _Ibid._, 1892, i., p. 114. [CB] _Naturwissenschaftliche Wochenschrift_, Bd. vii. (1892), No. 4, p. 31. The plants were determined by Dr. Weber, Professor Wittmack, and Herr Warnstorf. [More recent investigations have considerably increased our knowledge of this flora. See _Naturwissenschaftliche Wochenschrift_, Bd. vii. (1892), Nr. 24, 25. _Ausland_, 1892, Nr. 20; _Neues Jahrb. f. Min., etc._, 1893, Bd. i., p. 95.] The presence of the upper diluvium, however, proves that such genial conditions eventually passed away, and that an ice-sheet again invaded north Germany. But this later invasion was not on the same scale as that of the preceding one. The geographical distribution of the upper diluvium and the position of large terminal moraines put this quite beyond doubt. The boulder-clay in question spreads over the Baltic provinces of Germany, extending south as far as Berlin,[CC] and west into Schleswig-Holstein and Denmark. At the climax of this later cold epoch glaciers occupied all the fiords of Norway, but did not advance beyond the general coast-line. Norway at that time must have greatly resembled Greenland--the inland-ice covering the interior of the country, and sending seawards large glaciers that calved their icebergs at the mouths of the great fiords. In the extreme south, however, the glaciers did not quite reach the sea, but piled up large terminal moraines on the coast-lands, which may be followed thence into Sweden in an easterly direction by the lower end of Lake Wener and through Lake Wetter. A similar belt of moraines marks out the southern termination of the ice-sheet in Finland. Between Sweden and Finland lies the basin of the Baltic, which, at the epoch in question was filled with ice, forming a great Baltic glacier. This glacier overflowed the Öland Islands, Gottland, and Öland, fanning out as it passed towards the south-west and west, so as to invade on the south the Baltic provinces of Germany, while in the north it traversed the southern part of Scania, and overwhelmed the Danish islands as it spread into Jutland and Schleswig-Holstein. The course of this second ice-sheet is indicated by the direction of transport of erratics, etc., and by the trend of rock-striæ and _roches moutonnées_, as well as by the position of its terminal and lateral moraines. [CC] Not quite so far south. There is no reason to believe that the ice-sheet of the so-called Great Baltic Glacier advanced beyond the Baltic ridge. The upper boulder-clay south of that ridge is the ground-moraine of an earlier glaciation--the equivalent of our upper boulder-clay. See note, page 324. Nov. 1, 1892. Such, then, is the glacial succession which has been established by geologists in Scandinavia, north Germany, and Finland. The occurrence of two glacial epochs, separated by a long interval of temperate conditions, has been proved. The evidence, however, does not show that there may not have been more than two glacial epochs. There are certain phenomena, indeed, connected with the glacial accumulations of the regions in question which strongly suggest that the succession of changes was more complex than is generally understood. Several years ago Dr. A. G. Nathorst adduced evidence to show that a great Baltic glacier, similar to that underneath which the upper diluvium was amassed, existed before the advent of the vast _mer de glace_ of the so-called "first glacial epoch,"[CD] and his observations have been confirmed and extended by H. Lundbohm.[CE] The facts set forth by them prove beyond doubt that this early Baltic glacier smoothed and glaciated the rocks in southern Sweden in a direction from south-east to north-west, and accumulated a bottom-moraine whose included erratics are equally cogent evidence as to the trend of glaciation. That old moraine is overlaid by the lower diluvium--_i.e._, the boulder-clay, etc., of the succeeding vast _mer de glace_ that flowed south to the foot of the Harz--the transport of the stones in the superjacent clay indicating a movement from NNE. to SSW., or nearly at right angles to the trend of the earlier Baltic glacier. It is difficult to avoid the conclusion that we have here to do with the products of two distinct ice-epochs. But hitherto no interglacial deposits have been detected between the boulder-clays in question. It might, therefore, be held that the early Baltic glacier was separated by no long interval of time from the succeeding great _mer de glace_, but may have been merely a stage in the development of the latter. It is at all events conceivable that before the great _mer de glace_ attained its maximum extension, it might have existed for a time as a large Baltic glacier. I would point out, however, that if no interglacial beds had been recognised between the lower and the upper diluvium, geologists would probably have considered that the last great Baltic glacier was simply the attenuated successor of the preceding continental _mer de glace_. But we know this was not so; the two were actually separated by a long epoch of genial temperate conditions. [CD] "Beskrifning. till geol. Kartbl. Trolleholm": _Sveriges Geologiska Undersökning_, Ser. Aa., Nr. 87. [CE] "Om de äldre baltiska isströmmen i södra Sverige": _Geolog. Förening. i Stockholm Förhandl._, Bd. x., p. 157. There are certain other facts that may lead us to doubt whether in the glacial phenomena of the Baltic coast-lands we have not the evidence of more than two glacial epochs. Three, and even four, boulder-clays have been observed in east and west Prussia. They are separated, the one from the other, by extensive aqueous deposits, which are sometimes fossiliferous. Moreover, the boulder-clays in question have been followed continuously over considerable areas. It is quite possible, of course, that all those boulder-clays may be the product of one epoch, laid down during more or less considerable oscillations of an ice-sheet. In this view of the case the intercalated aqueous deposits would indicate temporary retreats, while the boulder-clays would represent successive re-advances of one and the same _mer de glace_. On the other hand, it is equally possible, if not more probable, that the boulder-clays and intercalated beds are evidence of so many separate glacial and interglacial epochs. We cannot yet say which is the true explanation of the facts. But these being as they are, we may doubt if German glacialists are justified in so confidently maintaining that their lower and upper diluvial accumulations are the products of the "first" and "second" glacial epochs. Indeed, as I shall show presently, the upper diluvium of north Germany and Finland cannot represent the second glacial epoch of other parts of Europe. For a long time it has been supposed that the glacial deposits of the central regions of Russia were accumulated during the advance and retreat of one and the same ice-sheet. In 1888, however, Professor Pavlow brought forward evidence to show that the province of Nijnii Novgorod had been twice invaded by a general _mer de glace_. During the first epoch of glaciation the ice-sheet overflowed the whole province, while only the northern half of the same region was covered by the _mer de glace_ of the second invasion. Again, Professor Armachevsky has pointed out that in the province of Tchernigow two types of glacial deposits appear, so unlike in character and so differently distributed that they can hardly be the products of one and the same ice-sheet. But until recently no interglacial deposits had been detected, and the observations just referred to failed, therefore, to make much impression. The missing link in the material evidence has now happily been supplied by M. Krischtafowitsch.[CF] At Troïzkoje, in the neighbourhood of Moscow, occur certain lacustrine formations which have been long known to Russian geologists. These have been variously assigned to Tertiary, lower glacial, post-glacial, and pre-glacial horizons. They are now proved, however, to be of interglacial age, for they rest upon and are covered by glacial accumulations. Amongst their organic remains are oak (_Quercus pedunculata_), alder (_Alnus glutinosa_, _A. incana_), white birch, hazel, Norway maple (_Acer platanoides_), Scots fir, willow, water-lilies (_Nuphar_, _Nymphæa_), mammoth, pike, perch, _Anadonta_, wing-cases of beetles, etc. The character of the plants shows that the climate of central Russia was milder and more humid than it is to-day. [CF] _Bull. de la Soc. Impér. des Naturalistes de Moskau_, No. 4, 1890. It is obvious that the upper and lower glacial deposits of central Russia cannot be the equivalents of the upper and lower diluvium of the Baltic coast-lands. The upper diluvium of those regions is the bottom-moraine of the so-called great Baltic glacier. At the time that glacier invaded north Germany, Finland was likewise covered with an ice-sheet, which flowed towards the south-east, but did not advance quite so far as the northern shores of Lake Ladoga. A double line of terminal moraines, traced from Hango Head on the Gulf of Finland, north-east to beyond Joensuu, puts this beyond doubt.[CG] The morainic deposits that overlie the interglacial beds of central Russia cannot, therefore, belong to the epoch of the great Baltic glacier. They are necessarily older. In short, it is obvious that the upper and lower glacial accumulations near Moscow must be on the horizon of the lower diluvium of north Germany. And if this be so, then it is clear that the latter cannot be entirely the product of one and the same _mer de glace_. When the several boulder-clays described by Schröder and others as occurring in the Baltic provinces of Germany are reinvestigated, they may prove to be the bottom-moraines of as many distinct and separate glacial epochs. [CG] Sederholm, _Fennia_, i., No. 7; Frosterus, _ibid._, iii., No. 8; Ramsay, _ibid._, iv., No. 2. It may be contended that the glacial and interglacial deposits of central Russia are perhaps only local developments--that their evidence may be accounted for by the oscillations of one single _mer de glace_. This explanation, as already pointed out, has been applied to the boulder-clays and intercalated aqueous beds of the lower diluvium of north Germany, and the prevalent character of the associated organic remains makes it appear plausible. It is quite inapplicable, however, to the similar accumulations in central Russia. During the formation of the freshwater beds of Troïzkoje, no part of Russia could have been occupied by an ice-sheet; the climate was more genial and less "continental" than the present. Yet that mild interglacial epoch was preceded and succeeded by extremely arctic conditions. It is impossible that such excessive changes could have been confined to central Russia. Germany, and indeed all northern and north-western Europe, must have participated in the climatic revolutions. So far, then, as the evidence has been considered, we may conclude that three glacial and two interglacial epochs at least have been established for northern Europe. If this be the case, then a similar succession ought to occur in our own islands; and a little consideration of the evidence already adduced will suffice to show that it does. It will be remembered that the lower and upper boulder-clays of the British Islands are the bottom-moraines of two separate and distinct ice-sheets, each of which in its time coalesced on the floor of the North Sea with the inland-ice of Scandinavia. It is obvious, therefore, that our upper boulder-clay cannot be the equivalent of the upper diluvium of the Baltic coast-lands, of Sweden, Denmark, and Schleswig-Holstein. De Geer and others have shown that while the great Baltic glacier was accumulating the upper diluvium of North Germany, etc., the inland-ice of Norway calved its icebergs at the mouths of the great fiords. Thus, during the so-called "second" glacial epoch of Scandinavian and German geologists, the Norwegian inland-ice did not coalesce with any British _mer de glace_. The true equivalent in this country of the upper diluvium is not our upper boulder-clay, but the great valley-moraines of our mountain-regions. It is our epoch of large valley-glaciers which corresponds to that of the great Baltic ice-flow. Our upper and lower boulder-clays are on the horizon of the lower diluvium of Germany and the glacial deposits of central Russia. It will now be seen that the evidence in Britain is fully borne out by what is known of the glacial succession in the corresponding latitudes of the Continent. I had inferred that our epoch of large valley-glaciers formed a distinct stage by itself, and was probably separated from that of the preceding ice-sheet by a prolonged interval of interglacial conditions. One link in the chain of evidence, however, was wanting: I could not point to the occurrence of interglacial deposits underneath the great valley-moraines. But these, as we have seen, form a well-marked horizon on the Continent, and we cannot doubt that a similar interglacial stage obtained in these islands. We may feel confident, in fact, that genial climatic conditions supervened on the dissolution of the last great _mer de glace_ in Britain, and that the subsequent development of extensive snow-fields and glaciers in our mountain-regions was contemporaneous with the appearance of the last great Baltic glacier. We need not be surprised that interglacial beds should be well developed underneath the bottom-moraine of that great glacier, while they have not yet been recognised below the corresponding morainic accumulations of our Highlands and Uplands. The conditions in the low-grounds of the Baltic coast-lands favoured their preservation, for the ice in those regions formed a broad _mer de glace_, under the peripheral areas of which sub-glacial erosion was necessarily at a minimum and the accumulation at a maximum. In our Scottish mountain-valleys, however, the very opposite was the case. The conditions obtaining there were not at all comparable to those that characterised the low-grounds of northern Germany, etc., but were quite analogous to those of Norway, where, as in our own mountain-regions, interglacial beds are similarly wanting. It is quite possible, however, that patches of such deposits may yet be met with underneath our younger moraines, and they ought certainly to be looked for. But whether they occur or not in our mountain-valleys, it is certain that some of the older alluvia of our Lowlands must belong to this horizon. Hitherto all alluvial beds that overlie our upper boulder-clay have been classified as post-glacial; but since we have ascertained that our latest _mer de glace_ was succeeded by genial interglacial conditions, we may be sure that records of that temperate epoch will yet be recognised in such Lowland tracts as were never reached by the glaciers of the succeeding cold epoch. Hence, I believe that some of our so-called "post-glacial" alluvia will eventually be assigned to an interglacial horizon. Amongst these may be cited the old peat and freshwater beds that rest upon the upper boulder-clay at Hailes Quarry, near Edinburgh. To the same horizon, in all probability, belong the clays, with Megaceros, etc., which occur so frequently underneath the peat-bogs of Ireland. An interesting account of these was given some years ago by Mr. Williams,[CH] who, as a collector of Megaceros remains, had the best opportunity of ascertaining the nature of the deposits in which these occur. He gives a section of Ballybetagh Bog, nine miles south-east of Dublin, which is as follows:-- 1. Boulder-clay. 2. Fine tenacious clay, without stones. 3. Yellowish clay, largely composed of vegetable matter. 4. Brownish clay, with remains of Megaceros. 5. Greyish clay. 6. Peat. [CH] _Geol. Mag._, 1881, p. 354. The beds overlying the boulder-clay are evidently of lacustrine origin. The fine clay (No. 2), according to Mr. Williams, is simply reconstructed boulder-clay. After the disappearance of the _mer de glace_ the land would for some time be practically destitute of any vegetable covering, and rain would thus be enabled to wash down the finer ingredients of the boulder-clay that covered the adjacent slopes, and sweep them into the lake. The clay formed in this way is described as attaining a considerable thickness near the centre of the old lake, but it thins off towards the sides. The succeeding bed (No. 3) consists so largely of vegetable débris that it can hardly be called a clay. Mr. Williams describes it as a "bed of pure vegetable remains that has been ages under pressure." He notes that there is a total absence in this bed of any tenacious clay like that of the underlying stratum, and infers, therefore, that the rainfall during the growth of the lacustrine vegetation was not so great as when the subjacent clay was being accumulated. The remains of Megaceros occur resting on the surface of the plant-bed and at various levels in the overlying brownish clay, which attains a thickness of three to four feet. The latter is a true lacustrine sediment, containing a considerable proportion of vegetable matter, interstratified with seams of clay and fine quartz-sand. According to Mr. Williams, it was accumulated under genial or temperate climatic conditions like the present. Between this bed and the overlying greyish clay (from 30 inches to 3 feet thick) there is always in all the bog deposits examined by Mr. Williams a strongly-marked line of separation. The greyish clay consists exclusively of mineral matter, and has evidently been derived from the disintegration of the adjacent granitic hills. Mr. Williams is of opinion that this clay is of aqueo-glacial formation. This he infers from its nature and texture, and from its abundance. "Why," he asks, "did not this mineral matter come down in like quantity all the time of the deposit of the brown clay which underlies it? Simply because, during the genial conditions which then existed, the hills were everywhere covered with vegetation; when the rain fell it soaked into the soil, and the clay being bound together by the roots of the grasses, was not washed down, just as at the present time, when there is hardly any degradation of these hills taking place." He mentions, further, that in the grey clay he obtained the antler of a reindeer, and that in one case the antlers of a Megaceros, found embedded in the upper surface of the brown clay, immediately under the grey clay, were scored like a striated boulder, while the under side showed no markings. Mr. Williams also emphasises the fact that the antlers of Megaceros frequently occur in a broken state--those near the surface of the brown clay being most broken, while those at greater depths are much less so. He shows that this could not be the result of tumultuous river-action--the elevation of the valley precluding the possibility of its receiving a river capable of producing such effects. Moreover, the remains show no trace of having been water-worn, the edges of the teeth of the great deer being as sharp as if the animal had died but yesterday. Mr. Williams thinks that the broken state of the antlers is due to the "pressure of great masses of ice on the surface of the clay in which they were embedded, the wide expanse of the palms of the antlers exposing them to pressure and liability to breakage; and even, in many instances, when there was 12 or 14 inches in circumference of solid bone almost as hard and sound as ivory, it was snapped across." It is remarkable that in this one small bog nearly one hundred heads of Megaceros have been dug up. Mr. Williams' observations show us that the Megaceros-beds are certainly older than the peat-bogs with their buried timber. When he first informed me of the result of his researches (1880), I did not believe the Megaceros-beds could be older than the latest cold phase of the Ice Age. I thought that they were later in date than our last general _mer de glace_, and I think so still, for they obviously rest upon its ground-moraine. But since I now recognise that our upper boulder-clay is not the product of the last glacial epoch, it seems to me highly probable that the Megaceros-beds are of interglacial age--that, in short, they occupy the horizon of the interglacial deposits of north Germany, etc. The appearances described by Mr. Williams in connection with the "grey clay" seem strongly suggestive of ice-action. Ballybetagh Bog occurs at an elevation of 800 feet above the sea, in the neighbourhood of the Three Rock Mountain (1479 feet), and during the epoch of great valley-glaciers the climatic conditions of that region must have been severe. But without having visited the locality in question I should hesitate to say that the phenomena necessarily point to local glaciation. Probably frost, lake-ice, and thick accumulations of snow and _névé_ might suffice to account for the various facts cited by Mr. Williams. I have called special attention to these Irish lacustrine beds, because it is highly probable that the post-glacial age of similar alluvia occurring in many other places in these islands has hitherto been assumed and not proved. Now that we know, however, that a long interglacial stage succeeded the disappearance of the last general _mer de glace_, we may feel sure that the older alluvia of our Lowland districts cannot belong exclusively to post-glacial times. The local ice-sheets and great glaciers of our "third" glacial epoch were confined to our mountain-regions; and in the Lowlands, therefore, which were not invaded, we ought to have the lacustrine and fluviatile accumulations of the preceding interglacial stage. A fresh interest now attaches to our older alluvia, which must be carefully re-examined in the new light thus thrown upon them. Turning next to the Alpine Lands of central Europe, we find that geologists there have for many years recognised two glacial epochs. Hence, like their _confrères_ in northern Europe, they speak of "first" and "second" glacial epochs.[CI] Within recent years, however, Professor Penck has shown that the Alps have experienced at least three separate periods of glaciation. He describes three distinct ground-moraines, with associated river-terraces and interglacial deposits in the valleys of the Bavarian Alps, and his observations have been confirmed by Professor Brückner and Dr. Böhm.[CJ] The same glacialists, I understand, have nearly completed an elaborate survey of the eastern Alps, of which they intend shortly to publish an extended account. The results obtained by them are very interesting, and fully bear out the conclusions already arrived at from their exploration of the Bavarian Alps.[CK] A similar succession of glacial epochs has quite recently been determined by Dr. Du Pasquier in north Switzerland.[CL] Nor is this kind of evidence confined to the north side of the Alps. On the shores of Lake Garda, between Salò and Brescia, three ground-moraines, separated by interglacial accumulations, are seen in section. The interglacial deposits consist chiefly of loams--the result of sub-aërial weathering--and attain a considerable thickness. From this Penck infers that the time which has elapsed since the latest glaciation is less than that required for the accumulation of either of the two interglacial series--a conclusion which, he says, is borne out by similar observations in other parts of the Alpine region.[CM] [CI] Morlot: _Bulletin de la Soc. Vaud. d. Sciences nat._, 1854, 1858, 1860. Deicke: _Bericht. d. St. Gall. naturf. ges._, 1858. Heer: _Urwelt der Schweiz._ Mühlberg: _Festschrift d. aarg. naturf. Ges. z. Feier ihrer 500 Sitz._, 1869. Rothpletz: _Denkschr. d. schweizer. Ges. f. d. ges. Naturwissensch._, Bd. xxviii., 1881. Wettstein: _Geologie v. Zurich u. Umgebung_, 1885. Baltzer: _Mitteil. d. naturf. Ges. Bern_, 1887. Renevier: _Bull. de la Soc. helvèt. d. Sciences nat._, 1887. [CJ] Penck: _Die Vergletscherung d. deutschen Alpen_, 1882. Brückner: "Die Vergletscherung des Salzachgebietes," _Geogr. Abhandl. Wien_, Bd. i. Böhm: _Jahrb. der k. k. geol. Reichsanst._, 1884, 1885. See also O. Fraas, _Neues Jahrb. f. Min. Geol. u. Palæont._, 1880, Bd. i. p. 218; E. Fugger and C. Kastner, _Verhandl. d. k. k. geol. Reichsanst._, 1883, p. 136. [CK] _Mittheil. des deutsch. u. oesterreich. Alpenvereins_, 1890, No. 20 u. 23. [CL] _Beiträge z. geolog. Karte der Schweiz_, 31 Lief., 1891; _Archiv. d. Sciences phys. et nat._, 1891, p. 44. [CM] "Die grosse Eiszeit," _Himmel u. Erde_. Although the occurrence of such sub-äerial products intercalated between separate morainic accumulations is evidence of climatic changes, still it does not tell us how far the glaciers retreated during an interglacial stage. Fortunately, however, lignite beds and other deposits charged with plant remains are met with occupying a similar position, and from these we gather that during interglacial times the glaciers sometimes retired to the very heads of the mountain-valleys, and must have been smaller than their present representatives. Of such interglacial plant-beds, which have been met with in some twenty localities, the most interesting, perhaps, is the breccia of Hötting, in the neighbourhood of Innsbruck.[CN] This breccia rests upon old morainic accumulations, and is again overlaid by the later moraines of the great Inn glacier. From the fact that the breccia yielded a number of supposed extinct species of plants, palæontologists were inclined to assign it to the Pliocene. Professor Penck, however, prefers to include it in the Pleistocene system, along with all the glacial and interglacial deposits of the Alpine Lands. According to Dr. von Wettstein, the flora in question is not Alpine but Pontic. At the time of the formation of the breccia the large-leaved _Rhododendron ponticum_ flourished in the Inn Valley at a height of 1200 metres above the sea; the whole character of the flora, in short, indicates a warmer climate than is now experienced in the neighbourhood of Innsbruck. It is obvious, therefore, that in interglacial times the glaciers must have shrunk back, as Professor Penck remarks, to the highest ridges of the mountains. [CN] Penck: _Die Vergletscherung der deutschen Alpen_, p. 228. _Verhandl. d. k. k. geol. Reichsanst._, 1887, No. 5; _Himmel und Erde_, 1891. Böhm: _Jahrb. d. k. k. geol. Reichsanst._, 1884, p. 147. Blaas: _Ferdinandeums Zeitschr._, iv. Folge; _Bericht. d. naturwissensch. Vereins_, 1889, p. 97. We may now glance at the glacial succession which has been established for central France. More than twenty years ago Dr. Julien brought forward evidence to show that the region of the Puy de Dôme had witnessed two glacial epochs.[CO] During the first of these epochs a large glacier flowed from Mont Dore. After its retreat a prolonged interglacial epoch followed, during which the old morainic deposits and the rocks they rest upon were much eroded. In the valleys and hollows thus excavated freshwater beds occur which have yielded relics of an abundant flora, together with the remains of _Elephas meridionalis_, _Rhinoceros leptorhinus_, etc. After the deposition of these freshwater alluvia, glaciers again descended the valleys and covered the interglacial beds with their moraines. Similar results have been obtained by M. Rames from a study of the glacial phenomenon of Cantal, which he shows belong to two separate epochs.[CP] The interval between the formation of the two series of glacial accumulations must have been prolonged, for the valleys during that interval were in some places eroded to a depth of 900 feet. M. Rames further recognises that the second glacial epoch was distinguished by two advances of valley-glaciers, separated by a marked episode of fusion. Dr. Julien has likewise noted the evidence for two episodes of fusion during the first extension of the glaciers of the Puy de Dôme. [CO] _Des Phénomènes glaciaires dans le Plateau central de la France_, &c.; Paris, 1869. [CP] Bull. _Soc. géol. de France_, 1884; see also M. Boule, _Bull. de la Soc. philomath. de Paris_, 8^e sér. i., p. 87. Two glacial epochs have similarly been admitted for the Pyrenees;[CQ] but Dr. Penck some years ago brought forward evidence to show that these mountains, like the Alps, have experienced three separate and distinct periods of glaciation.[CR] [CQ] Garrigou: _Bull. Soc. géol. de France_, 2^e sér. xxiv., p. 577. Jeanbernat: _Bull. de Soc. d'Hist. nat. de Toulouse_, iv., pp. 114, 138. Piette: _Bull. Soc. géol. de France_, 3^e sér. ii., pp. 503, 507. [CR] _Mitteilungen d. Vereins f. Erdkunde zu Leipzig_, 1883. We may now return to Scotland, and consider briefly the changes that followed upon the disappearance of the local ice-sheets and large valley-glaciers of our mountain-regions. The evidence is fortunately clear and complete. In the valley of the Tay, for example, at and below Perth, we encounter the following succession of deposits:-- 6. Recent alluvia. 5. Carse-deposits, 45 feet above sea-level. 4. Peat and forest bed. 3. Old alluvia. 2. Clays, etc., of 100-feet beach. 1. Boulder-clay. The old alluvia (3) are obviously of fluviatile origin, and show us that after the deposition of the clays, etc., of the 100-feet beach the sea retreated, and allowed the Tay and its tributaries to plough their way down through the marine and estuarine deposits of the "third" glacial epoch. These deposits would appear to have extended at first as a broad and approximately level plain over all the lower reaches of the valleys. Through this plain the Tay and the Earn cut their way to a depth of more than 100 feet, and gradually removed all the material over a course which can hardly be less than 2 miles in breadth below the Bridge of Earn, and considerably exceeds that in the Carse of Gowrie. No organic remains occur in the "old alluvia," but the deposits consist principally of gravel and sand, and show not a trace of ice-action. Immediately overlying them comes the well-known peat-bed (4). This is a mass of vegetable matter, varying in thickness from a few inches up to 3 or 4 feet. In some places it seems to be made up chiefly of reed-like plants and sedges and occasional mosses, commingled with which are abundant fragments of birch, alder, willow, hazel, and pine. In other places it contains trunks and stools of oak and hazel, with hazel-nuts--the trees being rooted in the subjacent deposits. It is generally highly compressed and readily splits into laminæ, upon the surface of which many small reeds, and now and again wing-cases of beetles, may be detected. A large proportion of the woody débris--twigs, branches, and trunks--appears to have been drifted. A "dug-out" canoe of pine was found, along with trunks of the same tree, in the peat at Perth. The Carse-deposits (5), consisting principally of clay and silt, rest upon the peat-bed. The occurrence in these deposits of _Scrobicularia piperata_ and oyster-shells leaves us in no doubt as to their marine origin. They vary in thickness from 10 up to fully 40 feet.[CS] [CS] For a particular account of the Tay-valley Succession, see _Prehistoric Europe_, p. 385. A similar succession of deposits is met with in the valley of the Forth,[CT] and we cannot doubt that these tell precisely the same tale. I have elsewhere[CU] adduced evidence to show that the peat-bed, with drifted vegetable débris, which underlies the Carse accumulations of the Forth and Tay is on the same horizon as the "lower buried forest" of our oldest peat-bogs, and the similar bogs that occur in Norway, Sweden, Denmark, Schleswig-Holstein, Holland, etc. Underneath the "lower buried forest" of those regions occur now and again freshwater clays, charged with the relics of an arctic-alpine flora; and quite recently similar plant remains have been detected in old alluvia at Corstorphine, near Edinburgh. When the beds below our older peat-bogs are more carefully examined, traces of that old arctic flora will doubtless be met with in many other parts of these islands. It was this flora that clothed north-western Europe during the decay of the last district ice-sheets of Britain and the disappearance of the great Baltic glacier. [CT] _Proc. Roy. Soc. Edin._ 1883-84, p. 745; _Mem. Geol. Survey, Scotland_, Explanation of Sheet 31. [CU] _Prehistoric Europe_, chaps. xvi., xvii. The dissolution of the large valley-glaciers of this country was accompanied by a general retreat of the sea--all the evidence leading to the conviction that our islands eventually became united to the Continent. The climatic conditions, as evidenced by the flora of the "lower buried forest," were decidedly temperate--probably even more genial than they are now, for the forests attained at that time a much greater horizontal and vertical range. This epoch of mild climate and continental connection was eventually succeeded by one of submergence, accompanied by colder conditions. Britain was again insulated--the sea-level in Scotland reaching a height of 45-50 feet above present high-water. To this epoch pertain the Carse-clays of the Forth and Tay. A few erratics occur in these deposits, probably betokening the action of floating ice, but the beds more closely resemble the modern alluvial silts of our estuaries than the tenacious clays of the 100-feet terrace. When the Carse-clays are followed inland, however, they pass into coarse river-gravel and shingle, forming a well-marked high-level alluvial terrace of much the same character as the yet higher-level fluviatile terrace which is associated in like manner with the marine deposits of the 100-feet beach. Of contemporaneous age with the Carse-clays, with which indeed they are continuous, are the raised beaches at 45-50 feet. These beaches occur at many places along the Scottish coasts, but they are seldom seen at the heads of our sea-lochs. When the sea stood at this level, glaciers of considerable size occupied many of our mountain-valleys. In the west they came down in places to the sea-coast, and dropped their terminal moraines upon the beach-deposits accumulating there. Thus, in Arran[CV] and in Sutherland,[CW] these moraines are seen reposing on the raised beaches of that epoch. And I think it is probable that the absence of such beaches at the heads of many of the sea-lochs of the Highland area is to be explained by the presence there of large glaciers, which prevented their formation. [CV] _British Association Reports_ (1854): Trans. of Sections, p. 78. [CW] L. Hinxman: Paper read before Edin. Geol. Soc., April 1892. Thus, there is clear evidence to show that after the genial epoch represented by the "lower buried forest," a recrudescence of glacial conditions supervened in Scotland. Many of the small moraines that occur at the heads of our mountain-valleys, both in the Highlands and Southern Uplands, belong in all probability to this epoch. They are characterised by their very fresh and well-preserved appearance.[CX] It is not at all likely that these later climatic changes could have been confined to Scotland. Other regions must have been similarly affected. But the evidence will probably be harder to read than it is with us. Had it not been for the existence of our "lower buried forest," with the overlying Carse-deposits, we could hardly have been able to distinguish so readily between the moraines of our "third" glacial epoch and those of the later epoch to which I now refer. The latter, we might have supposed, simply marked a stage in the final retreat of the antecedent great valley-glaciers. [CX] _Prehistoric Europe_ (chaps. xvi., xvii.) gives a fuller statement of the evidence. I have elsewhere traced the history of the succeeding stages of the Pleistocene period, and adduced evidence of similar, but less strongly-marked, climatic changes having followed upon those just referred to, and my conclusions have been supported by the independent researches of Professor Blytt in Norway. But these later changes need not be considered here. It is sufficient for my general purpose to confine attention to the well-proved conclusion that after the decay of the last district ice-sheets and great glaciers of our "third" glacial epoch genial conditions obtained, and that these were followed by cold and humid conditions, during the prevalence of which glaciers reappeared in many mountain-valleys. We have thus, as it seems to me, clear evidence in Europe of four glacial epochs, separated the one from the other by protracted intervals of genial temperate conditions. So far, one's conclusions are based on data which cannot be gainsaid, but there are certain considerations which lead to the suspicion that the whole of the complex tale has not yet been unravelled, and that the climatic changes were even more numerous than those that I have indicated. Let it be noted that glacial conditions attained their maximum during the earliest of our recognised glacial epochs. With each recurring cold period the ice-sheets and glaciers successively diminished in importance. That is one of the outstanding facts with which we have to deal. Whatever may have been the cause or causes of glacial and interglacial conditions, it is obvious that those causes, after attaining a maximum influence, gradually became less effective in their operation. Such having been the case, one can hardly help suspecting that our epoch of greatest glaciation may have been preceded by an alternation of cold and genial stages analogous to those that followed it. If three cold epochs of progressively diminished severity succeeded the epoch of maximum glaciation, the latter may have been preceded by one or more epochs of progressively increased severity. That something of the kind may have taken place is suggested by the occurrence of the old moraine of that great Baltic glacier that preceded the appearance of the most extensive _mer de glace_ of northern Europe. The old moraine in question, it will be remembered, underlies the lower diluvium. Unfortunately, the very conditions that attended the glaciation of Europe render it improbable that any conspicuous traces of glacial epochs that may have occurred prior to the period of maximum glaciation could have been preserved within the regions covered by the great inland-ice. Their absence, therefore, cannot be held as proving that the lower boulder-clays of Britain and northern Europe are the representatives of the earliest glacial epoch. The lowest boulder-clay, I believe, has yet to be discovered. It is in the Alpine Lands that we encounter the most striking evidence of glacial conditions anterior to the epoch of maximum glaciation. The famous breccia of Hötting has already been referred to as of interglacial age. From the character of its flora, Ettinghausen considered this accumulation to be of Tertiary age. The assemblage of plants is certainly not comparable to the well-known interglacial flora of Dürnten. According to the researches of Dr. R. von Wettstein,[CY] the Hötting flora has most affinity with that of the Pontic Mountains, the Caucasus, and southern Spain, and implies a considerably warmer climate than is now experienced in the Inn Valley. This remarkable deposit, as Dr. Penck pointed out some ten years ago, is clearly of interglacial age. His conclusions were at once challenged, on the ground that the flora had a Tertiary and not a Pleistocene facies; consequently, it was urged that, as all glacial deposits were of Pleistocene age, this particular breccia could not be interglacial. But in this, as in similar cases, the palæontologist's contention has not been sustained by the stratigraphical evidence, and Dr. Penck's observations have been confirmed by several highly-competent geologists, as by MM. Böhm and Du Pasquier. The breccia is seen in several well-exposed sections resting upon the moraine of a local glacier which formerly descended the northern flanks of the Inn Valley, opposite Innsbruck, where the mountain-slopes under existing conditions are free from snow and ice. Nor is this all, for certain erratics appear in the breccia, which could only have been derived from pre-existing glacial accumulations, and their occurrence in this accumulation at a height of 1150 metres shows that before the advent of the Hötting flora the whole Inn Valley must have been filled with ice. The plant-bearing beds are in their turn covered by the ground-moraine of a later and more extensive glaciation. To bring about the glacial conditions that obtained before the formation of the breccia, the snow-line, according to Penck, must have been at least 1000 metres lower than now; while, to induce the succeeding glaciation, the depression of the snow-line could not have been less than 1200 metres. These observations have been extended to many other parts of the Alps, and the conclusion arrived at by Professor Penck and his colleagues, Professor Brückner and Dr. Böhm, is briefly this--that the maximum glaciation of those regions did not fall in the "first" but in the "second" Alpine glacial epoch. [CY] _Sitzungsberichte d. Kais. Acad. d. Wissensch. in Wien, mathem.-naturw. Classe_, Bd. xcvii. Abth. i., 1888. The glacial phenomena of northern and central Europe are so similar--the climatic oscillations which appear to have taken place had so much in common, and were on so grand a scale--that we cannot doubt they were synchronous. We may feel sure, therefore, that the epoch of maximum glaciation in the Alps was contemporaneous with the similar epoch in the north. And if this be so, then in the oldest ground-moraines of the Alps we have the records of an earlier glacial epoch than that which is represented by the lower boulder-clays of Britain and the corresponding latitudes of the Continent. In other words, the Hötting flora belongs to an older stage of the Glacial period than any of the acknowledged interglacial accumulations of northern Europe. The character of the plants is in keeping with this conclusion. The flora has evidently much less connection with the present flora of the Alps than the interglacial floras of Britain and northern Europe have with those that now occupy their place. The Hötting flora, moreover, implies a considerably warmer climate than now obtains in the Alpine regions, while that of our interglacial beds indicates a temperate insular climate, apparently much like the present. The high probability that oscillations of climate preceded the advent of the so-called "first" _mer de glace_ of northern Europe must lead to a re-examination of our Pliocene deposits, with a view to see whether these yield conclusive evidence against such climatic changes having obtained immediately before Pleistocene times. By drawing the line of separation between the Pleistocene and the Pliocene at the base of our glacial series, the two systems in Britain are strongly marked off the one from the other. There is, in short, a distinct "break in the succession." From the Cromer Forest-bed, with its abundant mammalian fauna and temperate flora, we pass at once to the overlying arctic freshwater bed and the superjacent boulder-clay that marks the epoch of maximum glaciation.[CZ] Amongst the mammalian fauna of the Forest-bed are elephants (_Elephas meridionalis_, _E. antiquus_), hippopotamus, rhinoceros, (_R. etruscus_), horses, bison, boar, and many kinds of deer, together with such carnivores as bears, _Machærodus_, spotted hyæna, etc. The freshwater and estuarine beds which contain this extensive fauna rest immediately upon marine deposits (Weybourn Crag), the organic remains of which have a decidedly arctic facies. Here, then, we have what at first sight would seem to be another break in the succession. The Forest-bed, one might suppose, indicated an interglacial epoch, separating two cold epochs. But Mr. Clement Reid, who has worked out the geology of the Pliocene with admirable skill,[DA] has another explanation of the phenomena. It has long been known that the organic remains of the marine Pliocene of Britain denote a progressive lowering of temperature. The lower member of the system is crowded with southern forms, which indicate warm-temperate conditions. But when we leave the Older and pass upwards into the Newer Pliocene those southern forms progressively disappear, while at the same time immigrants from the north increase in numbers, until eventually, in the beds immediately underlying the Forest-bed, the fauna presents a thoroughly arctic facies. During the formation of the Older Pliocene with its southern fauna our area was considerably submerged, so that the German Ocean had then a much wider communication with the seas of lower latitudes. At the beginning of Newer Pliocene times, however, the land emerged to some extent, and all connection between the German Ocean and more southern seas was cut off. When at last the "Forest-bed series" began to be accumulated, the southern half of the North Sea basin had become dry land, and was traversed by the Rhine in its course towards the north, the Forest-bed representing the alluvial and estuarine deposits of that river. [CZ] In some places, however, certain marine deposits (_Leda myalis_ bed) immediately overlie the Forest-bed. [DA] _Mem. of Geol. Survey_, "Pliocene Deposits of Britain." _See postea_, footnote, p. 317. Mr. Reid, in referring to the progressive change indicated by the Pliocene marine fauna, is inclined to agree with Professor Prestwich that this was not altogether the result of a general climatic change. He thinks the successive dying out of southern forms and the continuous arrival of boreal species was principally due to the North Sea remaining fully open to the north, while all connection with southern seas was cut off. Under such conditions, he says, "there was a constant supply of arctic species brought by every tide or storm, while at the same time the southern forms had to hold their own without any aid from without; and if one was exterminated it could not be replaced." Doubtless the isolation of the North Sea must have hastened the extermination of the southern forms, but the change could not have been wholly due to such local causes. Similar, if less strongly-marked, changes characterise the marine Pliocene of the Mediterranean area, while the freshwater alluvia of France, etc., furnish evidence in the same direction. The Cromer Forest-bed overlies the Weybourn Crag, the marine fauna of which has a distinctly Arctic facies. The two cannot, therefore, be exactly contemporaneous: the marine equivalents of the Forest-bed are not represented. But Mr. Reid points out that several arctic marine shells of the Weybourn Crag occur also in the Forest-bed, while certain southern freshwater and terrestrial shells common in the latter are met with likewise in the former, commingled with the prevailing arctic marine species. He thinks, therefore, that we may fairly conclude that the two faunas occupied adjacent areas. One can hardly accept this conclusion without reserve. It is difficult to believe that a temperate flora and mammalian fauna like those of the Forest-bed clothed and peopled eastern England when the adjacent sea was occupied by arctic molluscs, etc. Surely the occurrence of a few forms, which are common to the Forest-bed and the underlying Crag, does not necessarily prove that the two faunas occupied adjacent districts. Mr. Reid, indeed, admits that some of the marine shells in the Forest-bed series may have been derived from the underlying Crag. Were the marine equivalents of the Forest-bed forthcoming we might well expect them to contain many Crag forms, but the facies of the fauna would most probably resemble that of the existing North Sea fauna. Again, the appearance in the Weybourn Crag of a few southern shells common to the Forest-bed does not seem to prove more than that such shells were contemporaneous somewhere with an arctic marine fauna. But it is quite possible that they might have been carried for a long distance from the south; and, even if they actually existed in the near neighbourhood of an arctic marine fauna, we may easily attach too much importance to their evidence.[DB] I cannot think, therefore, that Mr. Reid's conclusion is entirely satisfactory. After all, the Cromer Forest-bed rests upon the Weybourn Crag, and the evidence as it stands is explicable in another way. It is quite possible, for example, that the Forest-bed really indicates an epoch of genial or temperate conditions, preceded, as it certainly was eventually succeeded, by colder conditions. [DB] The inference that the Forest-bed occupies an interglacial position is strengthened by the evidence of certain marine deposits which immediately overlie it. These (known collectively as the _Leda myalis_ bed) occur in irregular patches, which, from the character of their organic remains, cannot all be precisely of the same age. In one place, for example, they are abundantly charged with oysters, having valves united, and with these are associated other species of molluscs that still live in British seas. At another place no oysters occur, but the beds yield two arctic shells, _Leda myalis_ and _Astarte borealis_, and some other forms which have no special significance. Professor Otto Torell pointed out to Mr. Reid that these separate deposits could not be of the same age, for the oyster is sensitive to cold and does not inhabit the seas where _Leda myalis_ and _Astarte borealis_ flourish. From a consideration of this and other evidence Mr. Reid concludes that it is possible that the deposits indicate a period of considerable length, during which the depth of water varied and the climate changed. Two additional facts may be noted: _Leda myalis_ does not occur in any of the underlying Pliocene beds, while the oyster is not found in the Weybourn and Chillesford Crag, though common lower down in the Pliocene series. These facts seem to me to have a strong bearing on the climatic conditions of the Forest-bed epoch. They show us that the oyster flourished in the North Sea before the period of the Weybourn Crag--that it did not live side by side with the arctic forms of that period--and that it reappeared in our seas when favourable conditions returned. When the climate again became cold an arctic fauna (including a new-comer, _Leda myalis_) once more occupied the North Sea. If it be objected that this would include as interglacial what has hitherto been regarded by most as a Pliocene mammalian fauna,[DC] I would reply that the interglacial age of that fauna has already been proved in central France. The interglacial beds of Auvergne, with _Elephas meridionalis_, rest upon and are covered by moraines,[DD] and with these have been correlated the deposits of Saint-Prest. Again, in northern Italy the lignites of Leffe and Pianico, which, as I showed a number of years ago,[DE] occupy an interglacial position, have likewise yielded _Elephas meridionalis_ and other associated mammalian forms. [DC] _Elephas meridionalis_ is usually regarded as a type-form of the Newer Pliocene, but long ago Dr. Fuchs pointed out that in Hungary this species is of quaternary age: _Verhandl. d. k. k. geolog. Reichsanstalt_, 1879, pp. 49, 270. It matters little whether we relegate to the top of the Pliocene or to the base of the Pleistocene the beds in which this species occurs. That it is met with upon an interglacial horizon is certain; and if we are to make the Pleistocene co-extensive with the glacial and interglacial series we shall be compelled to include in that system some portion of the Newer Pliocene. [DD] Julien: _Des Phènoménes glaciaires dans le Plateau central_, etc., 1869. Boule: _Revue d'Anthropologie_, 1879. [DE] _Prehistoric Europe_, p. 306. Professor Penck writes me that he and the Swiss glacialist, Dr. Du Pasquier, have recently examined these deposits, and are able to confirm my conclusion as to their interglacial position. There can be no doubt, then--indeed it is generally admitted--that the cold conditions that culminated in our Glacial period began to manifest themselves in Pliocene times. Moreover, as it can be shown that _Elephas meridionalis_ and its congeners lived in central Europe after an epoch of extensive glaciation, it is highly probable that the Forest-bed, which contains the relics of the same mammalian fauna, is equivalent in age to the early interglacial beds of France and the Alpine Lands. We seem, therefore, justified in concluding that the alternation of genial and cold climates that succeeded the disappearance of the greatest of our ice-sheets was preceded by analogous climatic changes in late Pliocene times. I shall now briefly summarise what seems to have been the glacial succession in Europe:-- {1. Weybourn Crag; ground-moraine of great Baltic { glacier underlying lower diluvium; the oldest { recognised ground-moraines of central Europe. { Glacial { These accumulations represent the earliest { glacial epoch of which any trace has been { discovered. It would appear to have been one of { considerable severity, but not so severe as the { cold period that followed. {2. Forest-bed of Cromer; Hötting breccia; lignites { of Leffe and Pianico; interglacial beds of Interglacial { central France. { { Earliest recognised interglacial epoch; climate { very genial. {3. Lower boulder-clays of Britain; lower diluvium { of Scandinavia and north Germany (in part); { lower glacial deposits of south Germany and { central Russia; ground-moraines and high-level { gravel-terraces of Alpine Lands, etc.; Glacial { terminal moraines of outer zone. { { The epoch of maximum glaciation; the { British and Scandinavian ice-sheets confluent; { the Alpine glaciers attain their greatest development. {4. Interglacial freshwater alluvia, peat, lignite, etc., { with mammalian remains (Britain, Germany, { etc., central Russia, Alpine Lands, etc.); and { marine deposits (Britain, Baltic coast-lands). Interglacial { { Continental condition of British area; climate { at first cold, but eventually temperate. Submergence { ensued towards close of the period, { with conditions passing from temperate to { arctic. {5. Upper boulder-clay of Britain; lower diluvium { of Scandinavia, Germany, etc., in part; upper { glacial series in central Russia; ground-moraines { and gravel-terraces in Alpine Lands. { { Scandinavian and British ice-sheets again Glacial { confluent, but _mer de glace_ does not extend { quite so far as that of the preceding cold epoch. { Conditions, however, much more severe than { those of the next succeeding cold epoch. { Alpine glaciers deposit the moraines of the { inner zone. {6. Freshwater alluvia, lignite, peat, etc. (some of the { so-called post-glacial alluvia of Britain; { interglacial beds of north Germany, etc.; Alpine { Lands(?); marine deposits of Britain and Baltic { coast-lands). Interglacial { { Britain probably again continental; climate at { first temperate and somewhat insular; submergence { ensues with cold climatic conditions--Scotland { depressed for 100 feet; Baltic provinces { of Germany, etc., invaded by the waters of { the North Sea. {7. Ground-moraines, terminal moraines, etc., of the { mountain regions of Britain; upper diluvium { of Scandinavia, Finland, north Germany, etc.; { great terminal moraines of same regions; terminal { moraines in the large longitudinal valleys { of the Alps (Penck). { { Major portion of Scottish Highlands covered Glacial { by ice-sheet; local ice-sheets in Southern Uplands { of Scotland and mountain districts in { other parts of Britain; great valley-glaciers { sometimes coalesce on low-grounds; icebergs { calved at mouths of Highland sea-lochs; terminal { moraines dropped upon marine deposits { then forming (100-feet beach). Scandinavia { shrouded in a great ice-sheet, which broke { away in icebergs along the whole west coast of { Norway. Epoch of the last great Baltic glacier. {8. Freshwater alluvia (with arctic plants); "lower { buried forest and peat" (Britain and north-west { Europe generally). Carse-clays and raised { beaches of 45 to 50-feet level in Scotland. Interglacial { { Britain again continental; climate at first { cold, subsequently becoming temperate: great { forests. Eventual insulation of Britain; climate { humid, and probably colder than now. {9. Local moraines in mountain-valleys of Britain, { here and there resting on 45 to 50-feet beach; { so-called "post-glacial" moraines in the upper { valleys of the Alps. { { Probably final appearance of glaciers in our Glacial { islands. Some of these glaciers attained a { considerable size, reaching the sea and shedding { icebergs. It may be noted here that the decay { of these latest glaciers was again followed by { emergence of the land and a recrudescence of { forest-growth ("upper buried forest"). A word of reference may now be made to that remarkable association of evidence of submergence, with proofs of glacial conditions, which has so frequently been noted by geologists. Take, for example, the succession in Scotland, and observe how each glacial epoch was preceded and apparently accompanied by partial submergence of the land:-- 1. _Epoch of Greatest Mer de Glace_ (lower boulder-clay); British and Scandinavian ice-sheets coalescent. Followed by wide land-surface = Continental Britain, with genial climate. Submergence of land--to what extent is uncertain, but apparently to 500 feet or so. 2. _Epoch of Lesser Mer de Glace_ (upper boulder-clay); British and Scandinavian ice-sheets coalescent. Followed by wide land-surface = Continental Britain, with genial climate. Submergence of land for 100 feet or thereabout. 3. _Epoch of Local Ice-sheets in Mountain Districts;_ glaciers here and there coalesce on the low-grounds; icebergs calved at mouths of Highland sea-lochs (moraines on 100-feet beach). Followed by wide land-surface = Continental Britain, with genial climate. Submergence of land for 50 feet or thereabout. 4. _Epoch of Small Local Glaciers_, here and there descending to sea (moraines on 50-feet beach). These oscillations of the sea-level did not terminate with the emergence of the land after the formation of the 50-feet beach. There is evidence to show that subsequent to the retreat of the small local glaciers (4) and the emergence of the land, our shores extended seawards beyond their present limits, but how far we cannot tell. With this epoch of re-emergence the climate again became more genial, our forests once more attaining a greater vertical and horizontal range. Submergence then followed (the 25 to 30-feet beach), accompanied by colder and more humid conditions, which, while unfavourable to forest-growth, tended greatly to increase the spread of peat-bogs. We have no evidence, however, to show that small local glaciers again appeared. Finally the sea retired, and the present conditions ensued. It will be seen that the submergence which preceded and probably accompanied the advent of the lesser _mer de glace_ (2) was greater than that which heralded the appearance of the local ice-sheets (3), as that in turn exceeded the depression that accompanied the latest local glaciers (4). There would seem, therefore, to be some causal connection between cold climatic conditions and submergence. This is shown by the fact that not only did depression immediately precede and accompany the appearance of ice-sheets and glaciers, but the degree of submergence bore a remarkable relation to the extent of glaciation. Many speculations have been indulged in as to the cause of this curious connection between glaciation and depression; these, however, I will not consider here. None of the explanations hitherto advanced is satisfactory, but the question is one well deserving the attention of physicists, and its solution would be of great service to geology. A still larger question which the history of these times suggests is the cause of climatic oscillations. I have maintained that the well-known theory advanced by James Croll is the only one that seems to throw any light upon the subject, and the observations which have been made since I discussed the question at length, some fifteen years ago, have added strength to that conviction. As Sir Robert Ball has remarked, the astronomical theory is really much stronger than Croll made it out to be. In his recently-published work, _The Cause of an Ice Age_, Sir Robert says that the theory is so thoroughly well based that there is no longer any ground for doubting its truth. "We have even shown," he continues, "that the astronomical conditions are so definite that astronomers are entitled to direct that vigorous search be instituted on this globe to discover the traces of those vast climatic changes through which astronomy declares that our earth must have passed." In concluding this paper, therefore, I may shortly indicate how far the geological evidence seems to answer the requirements of the theory. Following Croll, we find that the last period of great eccentricity of the earth's orbit extended over 160,000 years--the eccentricity reaching its highest value in the earlier stages of the cycle. It is obvious that during this long cycle the precession of the equinox must have completed seven revolutions. We might therefore expect to meet with geological evidence of recurrent cold or glacial and genial or interglacial epochs; and not only so, but the records ought to show that the earlier glacial epoch or epochs were colder than those that followed. Now we find that the epoch of maximum glaciation supervened in early Pleistocene times, and that three separate and distinct glacial epochs of diminished severity followed. Of these three, the first would appear to have been almost as severe as that which preceded it, and it certainly much surpassed in severity the cold epochs of the later stages. But the epoch of maximum glaciation, or the first of the Pleistocene series, was not the earliest glacial epoch. It seems to have been preceded by one of somewhat less severity than itself, but which nevertheless, as we gather from the observations of Penck and his collaborators, was about as important as that which came after the epoch of maximum glaciation. Hence it would appear that the correspondence of the geological evidence with the requirements of the astronomical theory is as close as we could expect it to be. Four glacial with intervening genial epochs appear to have fallen within Pleistocene times; while towards the close of the Pliocene, or at the beginning of the Pleistocene period, according as we choose to classify the deposits, an earlier glacial epoch followed by genial interglacial conditions, supervened. In this outline of a large subject it has not been possible to do more than indicate very briefly the general nature of the evidence upon which the chief conclusions are based. I hope, however, to have an opportunity ere long of dealing with the whole question in detail. [Note.--Since the original publication of this Essay, renewed investigation and study have led me to conclude that the correlation of the British and Continental glacial series is even more simple than I had supposed. I believe the use of the terms "Lower" and "Upper" in connection with the "Diluvial" deposits of the Continent has hitherto blinded us to the obvious succession of the boulder-clays. In Britain we have, as shown above, a "lower boulder-clay," an "upper boulder-clay," and the still younger boulder-clays (ground-moraines), and terminal moraines of our district ice-sheets and valley-glaciers. In the low-grounds of the Continent the succession is precisely similar. Thus the lower boulder-clay that sweeps south into Saxony represents the lower boulder-clay of Britain. In like manner, the upper boulder-clay of western and middle Germany, of Poland, and western and north-western Russia, is the equivalent of our own upper boulder-clay. Lastly, the so-called "upper diluvium" and the great terminal moraines of the Baltic coast-lands are on the horizon of the younger boulder-clays and terminal moraines of the mountainous areas of the British Islands. The so-called "lower diluvium" of the Baltic coast-lands thus represents not the _lower_ but the _upper_ diluvium of western and middle Germany, Poland, etc. German geologists are of opinion that the upper boulder-clays of the Baltic coast-lands and of the valley of the Elbe are the ground-moraines of one and the same ice-sheet, which, on its retreat, piled up the terminal moraines of the Baltic Ridge. I believe the two boulder-clays in question are quite distinct, and that the terminal moraines referred to mark the furthest advance of the last great Baltic glacier. The contemporaneity of the two boulder-clays has been taken for granted simply because they are each underlaid by a lower boulder-clay. But, as we have seen, the upper boulder-clay of the Baltic coast-lands is underlaid not by one only, but by two, and in some places even by three other boulder-clays--phenomena which never present themselves in the regions not invaded by the last great Baltic glacier. Three or four boulder-clays occur in the coast-lands of the Baltic because those regions were overflowed successively by three or four separate ice-sheets. Only two boulder-clays are met with south and east of the Baltic Ridge, because the tracts lying south and south-east of that ridge were traversed by only two _mers de glace_--namely, by that of the epoch of maximum glaciation and by the less extensive ice-sheet of the next succeeding cold period. In the region between the Elbe and the mountains of middle Germany only one boulder-clay appears, because that region has never been invaded by more than one ice-sheet. The succession thus indicated may be tabulated as follows:-- 1. _Epoch of Earliest Baltic Glacier._ Lowest boulder-clay of southern Sweden; lowest boulder-clay of Baltic provinces of Prussia; horizon of the Weybourn Crag. 2. _Epoch of Greatest Mer de Glace._ Lower boulder-clays of middle and southern Germany, central Russia, British Islands; second boulder-clay of Baltic provinces of Prussia. 3. _Epoch of Lesser Mer de Glace._ Upper boulder-clay of western and middle Germany, Poland, and west central Russia; upper boulder-clay of Britain; third boulder-clay of Baltic provinces of Prussia. 4. _Epoch of Last Great Baltic Glacier._ Upper boulder-clay and terminal moraines of Baltic coast-lands; district and valley-moraines of Highlands and Uplands of British Islands. 5. _Epoch of Small Local Glaciers._ Valley-moraines in mountainous regions of Britain, etc. The evidence on which these conclusions are based is set forth at some length in a forthcoming re-issue of my _Great Ice Age_.--Nov. 1, 1892.] [Illustration: PLATE IV SKETCH MAP OF NORTHERN EUROPE SHOWING AREAS COVERED BY ICE DURING THE EPOCH OF MAXIMUM GLACIATION, AND BY THE GREAT BALTIC GLACIER AND THE LOCAL ICE-SHEETS OF BRITAIN AT A LATER DATE. The Edinburgh Geographical Institute J. G. Bartholomew F.R.G.S ] * * * * * Explanation of Plate IV. Map of Europe showing the areas occupied by ice during the Epoch of Maximum Glaciation (Second Glacial Epoch), and the extent of glaciation in Scandinavia, Finland, Baltic coast-lands, etc., and the British Islands during the Fourth Glacial Epoch. For the limits of the greater glaciation on the Continent, Habenicht, Penck, Nikitin, and Nathorst have been followed. The Great Baltic Glacier is chiefly after De Geer. XI. The Geographical Evolution of Europe.[DF] [DF] _The Scottish Geographical Magazine_, vol. ii., 1886. It is one of the commonplaces of geology that the Present is built up out of the ruins of the Past. Every rock beneath our feet has its story of change to tell us. Mountains, valleys, and plains, continents and islands, have passed through vicissitudes innumerable, and bear within them the evidence of a gradual development or evolution. Looking back through the vista of the past one sees the dry lands gradually separating from the ocean, and gathering together into continental masses according to a definite plan. It is this slow growth, this august evolution, carried on through countless æons, which most impresses the student of physical geology. The earth seems for the time as if endowed with life, and like a plant or animal to pass through its successive stages of development until it culminates in the present beautiful world. This conception is one of comparatively recent growth in the history of geological science. Hutton, the father of physical geology, had indeed clearly perceived that the dry lands of the globe were largely composed of the débris of former land-surfaces--that there had been alternate elevations and depressions of the earth's crust, causing now sea and now land to predominate over given areas. But the facts known in this day could not possibly have suggested those modern ideas of geographical evolution, which are the outcome of the multifarious observation and research of later years. It is to Professor Dana, the eminent American geologist, that we are indebted for the first clear enunciation of the views which I am now about to illustrate. According to him the great oceanic basins and continental ridges are of primeval antiquity--their origin is older than that of our oldest sedimentary formations. It is not maintained that the present lands have always continued above the level of the sea. On the contrary, it can be proved that many oscillations of level have taken place within each continental area, by which the extent and outline of the land have been modified again and again. Notwithstanding such changes, however, the great continental ridges would appear to have persisted from the earliest geological times as dominant elevations of the earth's crust. Some portions of these, as Dana remarks, may have been submerged for thousands of feet, but the continents have never changed places with the oceans. I shall presently indicate the nature of the evidence by which it is sought to prove the vast age of our continental masses, but before doing so it will be well to give an outline of the facts which go to show that the oceanic depressions of the globe are likewise of primeval antiquity. The memorable voyage of the _Challenger_ has done much to increase our knowledge of the deep seas and the accumulations forming therein. The researches of the scientific staff of the expedition, and more particularly those of Mr. Murray, have indeed given a new impulse to the study of the larger questions of physical geology, and have lent strong support to the doctrine of the permanence of the oceanic basins and continental ridges. One of the most important facts brought before our attention by Mr. Murray is the absence of any land-derived materials from the sediments now gathering in the deeper abysses of the ocean. The coasts of continents and continental islands are strewn, as every one knows, with the wreck of the land--with gravel, sand, and mud, derived from the demolition of our rocks and soils. The coarser débris accumulates upon beaches and in shallow littoral waters, while the finer materials are swept further out to sea by tidal and other currents--the sediment being gradually sifted as it is borne outwards into deeper water, until only the finest mud and silt remain to be swept forward. As the floor of the ocean shelves down to greater depths the transporting power of currents gradually lessens, and finally land-derived sediment ceases to appear. Such terrigenous materials may be said to extend from the littoral zone down to depths of 2000 feet and more, and to a distance of 60 to 300 miles from shore. They are confined, therefore, to a comparatively narrow belt round the margins of continents and islands. And thus there are vast regions of the oceanic depressions over which no terrigenous or land-derived materials are accumulating. Instead of these we meet with a remarkable red clay and various kinds of ooze, made up largely of the shells of foraminifera, pelagic mollusca, and radiolarians, and the frustules of diatoms. The red clay is the most widely distributed of abysmal deposits. Indeed, it seems to form a certain proportion of all the deep-sea organic oozes, and may be said, therefore, to exist everywhere in the abysmal regions of the oceanic basins. It is extremely fine-grained, and owes its deep brown or red colour to the presence of the oxides of manganese and iron. Scattered through the deposit occur particles of various minerals of volcanic origin, together with lapilli and fragments of pumice, _i.e._, volcanic _ejectamenta_. Such materials may have been thrown out from terrestrial volcanoes and carried by the winds or floated by currents until they became water-logged and sank; or they may to some extent be the relics of submarine eruptions. Whatever may have been their immediate source, they are unquestionably of volcanic origin, and are not associated with any truly terrigenous sediment. The red clay is evidently the result of the chemical action of sea-water on volcanic products; and many facts conspire to show that its formation is an extremely slow process. Thus, remains of vertebrates, consisting of the ear-bones of whales, beaks of ziphius, and teeth of sharks, are often plentifully present, and there is no reason to suppose, as MM. Murray and Renard point out, that the parts of the ocean where these remains occur are more frequented by whales and sharks than other regions where similar relics are rarely or never dredged up. Of these remains some have all the appearance of having lain upon the sea-bottom for a very long time, for they belong to extinct species, and are either partially coated or entirely surrounded with thick layers of manganese-iron. In the same red clay occur small metallic spherules which are of cosmic origin--in other words, meteoric dust. The accumulation of all these substances in such relatively great abundance shows us that the oceanic basins have remained unchanged for a vast period of time, and assures us that the formation of the abysmal red clay is extremely slow. When we come to examine the rocks which enter into the framework of our continents, we find that they may be roughly classed under these heads:-- 1st, Terrestrial and Aqueous Rocks. 2d, Igneous Rocks. 3d, Crystalline Schists. By far the largest areas of land are composed of rocks belonging to the first class. These consist chiefly of the more or less indurated sediments of ancient rivers, lakes, and seas--namely, conglomerate, sandstone, shale, limestone, etc. And now and again, interstratified with such aqueous beds, we meet with rocks of terrestrial origin, such as lignite, coal, and the débris of former glacial action. Now, most of our aqueous rocks have been accumulated in the sea, and thus we arrive at the conclusion that the present continental areas have from time to time been largely submerged--that the sea has frequently covered what are now the dry lands of the globe. But one remarkable fact stands out, and it is this: Nowhere amongst the sedimentary rocks of the earth's crust do we meet with any ancient sediments which can be likened to the red clay now slowly accumulating in the deeper abysses of the ocean. There are no rocks of abysmal origin. Many of our limestones have undoubtedly formed in deep, clear water, but none of these is abysmal. Portions of Europe may now and again have been submerged for several thousand feet, but no part of this or any other continent, so far as we yet know, has within geological time been depressed to depths comparable to those of the present oceanic basins. Nay, by far the larger portions of our marine formations have accumulated in comparatively shallow water--sandstones and shales (sand and mud) being by far the most common kinds of rock that we encounter. In short, aqueous strata have, as a rule, been deposited at no great depth and at no great distance from dry land; the rocks are built up mostly of terrigenous material; and even the purer limestones and chalks, which we may suppose accumulated in seas of moderate depth, not infrequently contain some terrestrial relic which has been drifted out to sea, and afford other evidence to show that the nearest land was never very far away. Followed along their outcrop such rocks sooner or later become mixed and interbedded with ordinary sedimentary matter. Thus, for example, the thick carboniferous limestone of Wales and the Midlands of England must have accumulated in the clear water of a moderately deep sea. But when this limestone is traced north into Northumberland it begins to receive intercalations of sandstone and shale, which become more and more important, until in Scotland they form by much the larger portion of the series--the enormous thick limestones of the south being represented by only a few inconsiderable beds, included, along with seams of ironstone and coal, in a thick succession of sandstones and shales. Of the igneous rocks and the crystalline schists I need not speak at present, but I shall have something to say about them before I have done. Having learned that no truly abysmal rocks enter into the composition of our continents, of what kind of rocks, we may ask, are the islands composed? Well, some of those islands are built up of precisely the same materials as we find in the continents. This is the case with most islands which are not separated from continental areas by profoundly deep seas. Thus our own islands with their numerous satellites are geologically one with the adjacent continent. Their present separation is a mere accident. Were the European area, with the adjacent sea-bed, to be elevated for a few hundred feet we should find that Britain and Ireland form geologically part and parcel of the continent. And the same is the case with Nova Zembla and Spitzbergen in the north, and with the Mediterranean islands in the south. There is another large class of islands, however, which are characterised by the total absence of any of those sedimentary rocks of which, as I have just said, our continents and continental islands are chiefly built up. The islands referred to are scattered over the bosom of the great ocean, and are surrounded by profoundly deep water. Some are apparently composed entirely of coral, others are of volcanic origin, and yet others are formed partly of volcanic rock and partly of coral. Thus we have two distinct kinds of island:-- 1st, Islands which have at one time evidently been connected with adjacent continents, and which are therefore termed _continental islands_; and 2d, _Oceanic islands_, which rise, as it were, from profound depths in the sea, and which have never formed part of the continents. The fauna and flora of the former class agree with those of the neighbouring continents, although some modifications are met with, especially when the insulation has been of long standing. When such has been the case the species of plants and animals may be almost entirely distinct. Nevertheless, such ancient continental islands agree with those which have been separated in more recent geological times in containing both indigenous amphibians and mammals. Oceanic islands, on the other hand, contain no indigenous mammals or amphibians, their life consisting chiefly of insects and birds, and usually some reptiles--just such a fauna as might have been introduced by the influence of winds and of oceanic currents carrying driftwood. Such facts, as have now been briefly summarised, point clearly to the conclusion that the oceanic basins and continental areas are of primeval antiquity. All the geological facts go to prove that abysmal waters have never prevailed over the regions now occupied by dry land; nor is there any evidence to show that continental land-masses ever existed in what are now the deepest portions of the ocean. The islets dotted over the surface of the Pacific and the other great seas are not the relics of a vast submerged continent. They are either the tops of submarine volcanic mountains, or they are coral structures founded upon the shoulders of degraded volcanoes and mountain-chains, and built up to the surface by the indefatigable labours of the humble polyp. We come then to the general conclusion that oceanic basins and intervening continental ridges are great primeval wrinkles in the earth's crust--that they are due to the sinking down of that crust upon the cooling and contracting nucleus. These vast wrinkles had come into existence long before the formation of our oldest geological strata. All our rocks may, in short, be looked upon as forming a mere superficial skin covering and concealing the crystalline materials which no doubt formed the original surface of the earth's crust. Having premised so much, let me now turn to consider the geological history of our own Continent, and endeavour to trace out the various stages in its evolution. Of course I can only do so in a very brief and general manner; it is impossible to go into details. We shall find, however, that the history of the evolution of Europe, even when sketched in outline, is one full of instruction for students of physical geography, and that it amply bears out the view of the permanency of the greater features of the earth's surface. The oldest rocks that we know of are the crystalline schists and gneiss, belonging to what is called the Archæan system. The origin of these rocks is still a matter of controversy--some holding them to be part of the primeval crust of the globe, or the chemical precipitates of a primeval ocean, others maintaining that they are altered or metamorphosed rocks of diverse origin, a large proportion having consisted originally of aqueous or sedimentary rocks, such as sandstone and shale; while not a few are supposed to have been originally eruptive igneous rocks. According to some geologists, therefore, the Archæan rocks represent the earliest sediments deposited over the continental ridges. It is supposed that here and there those ridges rose above the surface of what may have been a boiling or highly-heated ocean, from whose waters copious chemical precipitations took place, while gravel and shingle gathered around the shores of the primeval lands. According to other writers, however, the Archæan rocks were probably accumulated under normal conditions. They consist, it is contended, partly of sediment washed down from some ancient land-surface, and distributed over the floor of an old sea (just as sediments are being transported and deposited in our own day), and partly of ancient igneous rocks. Their present character is attributed to subsequent changes, superinduced by heat and pressure, at a time when the masses in question were deeply buried under later formations, which have since been washed away. In a word, we are still quite uncertain as to the true origin of the Archæan rocks. Not infrequently they show a bedded structure, and in that respect they simulate the appearance of strata of sedimentary origin. It is very doubtful, however, whether this "bedded structure" is any evidence of an original aqueous arrangement. We know now that an appearance of bedding has been induced in originally amorphous rocks during great earth-movements. Granite masses, for example, have been so crushed and squeezed as to assume a bedded aspect, and a similar structure has been developed in many other kinds of rock subjected to enormous pressure. Whatever may have been the origin of the bedded structure of the Archæan rocks, it is certain that the masses have been tilted up and convoluted in the most remarkable manner. Hitherto they have yielded no unequivocal trace of organic remains--the famous _Eozoon_ being now generally considered as of purely mineral origin. The physical conditions under which the Archæan gneiss and schist came into existence are thus quite undetermined, but geologists are agreed that the earliest land-surfaces, of the former existence of which we can be quite certain, were composed of rocks. And this brings us to the beginning of reliable geological history. All subsequent geological time--that, namely, of which we have any record preserved in the fossiliferous strata--is divided into four great eras, namely the Palæozoic, the Mesozoic, the Cainozoic, and the Post-Tertiary eras, each of which embraces various periods, as follows:-- Post-Tertiary {Recent. {Pleistocene. {Pliocene. Tertiary or {Miocene. Cainozoic {Oligocene. {Eocene. {Cretaceous. Secondary or {Jurassic. Mesozoic {Triassic. {Permian. {Carboniferous. Primary or {Devonian and Old Red Sandstone. Palæozoic {Silurian. {Cambrian. Archæan, Fundamental Gneiss. Leaving the Archæan, we find that the next oldest strata are those which were accumulated during the Cambrian period, to which succeeded the Silurian, the Devonian and Old Red Sandstone, the Carboniferous, and the Permian periods--all represented by great thicknesses of strata, which overspread wide regions. Now, at the beginning of the Cambrian period, we have evidence to show that the primeval continental ridge was still largely under water, the dry land being massed chiefly in the north. At that distant date a broad land-surface extended from the Outer Hebrides north-eastwards through Scandinavia, Finland, and northern Russia. How much further north and north-west of the present limits of Europe that ancient land may have extended we cannot tell, but it probably occupied wide regions which are now submerged in the shallow waters of the Arctic Ocean. In the north of Scotland a large inland sea or lake existed in Cambrian times,[DG] and there is some evidence to suggest that similar lacustrine conditions may have obtained in the Welsh area at the beginning of the period. South of the northern land lay a shallow sea covering all middle and southern Europe. That sea, however, was dotted here and there with a few islands of Archæan rocks, occupying the site of what are now some of the hills of middle Germany, such as the Riesen Gebirge, the Erz Gebirge, the Fichtel Gebirge, etc., and possibly some of the Archæan districts of France and the Iberian peninsula. [DG] The Red Sandstones of the north-west Highlands are now believed to be of pre-Cambrian age. The succeeding period was one of eminently marine conditions, the wide distribution of Silurian strata showing that during the accumulation of these, enormous tracts of our Continent were overflowed by the sea. None of these deposits, however, is of truly oceanic origin. They appear for the most part to have been laid down in shallow seas, which here and there may have been moderately deep. During the formation of the Lower Silurian the whole of the British area, with the exception perhaps of some of the Archæan tracts of the north-west, seems to have been under water. The submergence had commenced in Cambrian times, and was continued up to the close of the Lower Silurian period. During this long-continued period of submergence volcanic activity manifested itself at various points--our country being represented at that time by groups of volcanic islands, scattered over the site of what is now Wales, and extending westward into the Irish region, and northwards into the districts of Cumberland and south Ayrshire. Towards the close of the Lower Silurian period considerable earth-movements took place, which had the effect of increasing the amount of dry land, the most continuous mass or masses of which still occupied the northern and north-western part of our Continent. In the beginning of Upper Silurian times a broad sea covered the major portion of middle and probably all southern Europe. Numerous islands, however, would seem to have existed in such regions as Wales, and the various tracts of older Palæozoic and Archæan rocks of middle Germany. Many of these islands, however, were partially and some entirely submerged before the close of Silurian times. The next great period--that, namely, which witnessed the accumulation of the Devonian and Old Red Sandstone strata--was in some respects strongly contrasted to the preceding period. The Silurian rocks, as I have said, are eminently marine. The Old Red Sandstones, on the other hand, appear to have been accumulated chiefly in great lakes or inland seas, and they betoken therefore the former existence of extensive lands, while the contemporaneous Devonian strata are of marine origin. Towards the close of the Upper Silurian period, then, we know that considerable upheavals ensued in western and north-western Europe, and wide stretches of the Silurian sea-bottom were converted into dry land. The geographical distribution of the Devonian in Europe, and the relation of that system to the Silurian, show that the Devonian sea did not cover so broad an expanse as that of the Upper Silurian. The sea had shallowed, and the area of dry land had increased when the Devonian strata began to accumulate. In trying to realise the conditions that obtained during the formation of the Devonian and the Old Red Sandstone, we may picture to ourselves a time when the Atlantic Ocean extended eastwards over the south of England and the north-east of France, and occupied the major portion of central Europe, sweeping north-east into Russia, and how much further we cannot tell. North of that sea stretched a wide land-surface, in the hollows of which lay great lakes or inland seas, which seem now and again to have had communication with the open ocean. It was in these lakes that the Old Red Sandstone was accumulated, while the Devonian or marine rocks were formed in the wide waters lying to the south. Submarine volcanoes were active at that time in Germany; and similarly in Scotland numerous volcanoes existed, such as those of the Sidlaw Hills and the Cheviots. The Carboniferous system contains the record of a long and complex series of geographical changes, but the chief points of importance in the present rapid review may be very briefly summed up. In the earlier part of the period marine conditions prevailed. Thus we find evidence to show that the sea extended further north than it did during the preceding Devonian period. During the formation of the mountain-limestone, a deep sea covered the major portion of Ireland and England, but shallowed off as it entered the Scottish area. A few rocky islets were all that represented Ireland and England at that time. Passing eastwards, the Carboniferous sea appears to have covered the low-grounds of middle Europe and enormous tracts in Russia. The deepest part of the sea lay over the Anglo-Hibernian and Franco-Belgian areas; towards the east it became shallower. Probably the same sea swept over all southern Europe, but many islands may have diversified its surface, as in Brittany and central France, in Spain and Portugal, and in the various areas of older Palæozoic and Archæan rocks in central and south-west Europe. In the latter stages of the Carboniferous period, the limits of the sea were much circumscribed, and wide continental conditions supervened. Enormous marshes, jungles, and forests now overspread the newly-formed lands. Another feature of the Carboniferous was the great number of volcanoes--submarine and sub-aërial--which were particularly abundant in Scotland, especially during the earlier stages of the period. The rocks of the Permian period seem to have been deposited chiefly in closed basins. When, owing to the movement of elevation or upheaval which took place in late Carboniferous times, the carboniferous limestone sea had been drained away from extensive areas in central Europe, wide stretches of sea still covered certain considerable tracts. These, however, as time went on, were cut off from the main ocean and converted into great salt lakes. Such inland seas overspread much of the low-lying tracts of Britain and middle Germany, and they also extended over a broad space in the north-east of Russia. It was in these seas that the Permian strata were accumulated. The period, it may be added, was marked by the appearance of volcanic action in Scotland and Germany. So far, then, as our present knowledge goes, that part of the European continent which was the earliest to be evolved lay towards the north-west and north. All through the Palæozoic era a land-surface would seem to have endured in that direction--a land-surface from the denudation or wearing down of which the marine sedimentary formations of the bordering regions were derived. But when we reflect on the great thickness and horizontal extent of those sediments, we can hardly doubt that the primeval land must have had a much wider range towards the north and north-west than is the case with modern Europe. The lands, from which the older Palæozoic marine sediments of the British Islands and Scandinavia were obtained, must, for the most part, be now submerged. In later Palæozoic times land began to extend in the Spanish peninsula, northern France, and middle Europe, the denudation of which doubtless furnished materials for the elaboration of the contemporaneous strata of those regions. Southern Europe is so largely composed of Mesozoic and Cainozoic rocks that we can say very little as to the condition of that area in Palæozoic times, but the probabilities are that it continued for the most part under marine conditions. In few words, then, we may conclude that while after Archæan times dry land prevailed in the north and north-west, marine conditions predominated further south. Ever and anon, however, the sea vanished from wide regions in central Europe, and was replaced by terrestrial and lacustrine conditions. Further, as none of the Palæozoic marine strata indicates a deep ocean, but all consist for the most part of accumulations formed at moderate depths, it follows that there must have been a general subsidence of our area to allow of their successive deposition--a subsidence, however, which was frequently interrupted by long pauses, and sometimes by movements in the opposite direction. The first period of the Mesozoic era, namely, the Triassic, was characterised by much the same kind of conditions as obtained towards the close of Palæozoic times. A large inland sea then covered a considerable portion of England, and seems to have extended north into the south of Scotland, and across the area of the Irish Sea into the north-east of Ireland. Another inland sea extended westward from the Thüringer-Wald across the Vosges into France, and stretched northwards from the confines of Switzerland over what are now the low-grounds of Holland and northern Germany. In this ancient sea the Harz Mountains formed a rocky island. While terrestrial and lacustrine conditions thus obtained in central and northern Europe, an open sea existed in the more southerly regions of the continent. Towards the close of the period submergence ensued in the English and German areas, and the salt lakes became connected with the open sea. During the Jurassic period the regions now occupied in Britain and Ireland by the older rocks appear to have been chiefly dry land. Scotland and Ireland, for the most part, stood above the sea-level, while nearly all England was under water--the hills of Cumberland and Westmoreland, the Pennine chain, Wales, the heights of Devon and Cornwall, and a ridge of Palæozoic rocks which underlies London, being the chief lands in south Britain. The same sea overflowed an extensive portion of what is now the Continent. The older rocks in the north-west and north-east of France, and the central plateau of the same country, formed dry land; all the rest of that country was submerged. In like manner the sea covered much of eastern Spain. In middle Europe it overflowed nearly all the low-grounds of north Germany, and extended far east into the heart of Russia. It occupied the site of the Jura Mountains, and passed eastward into Bohemia, while on the south side of the Alps it spread over a large part of Italy, extending eastward so as to submerge a broad area in Austria-Hungary and the Turkish provinces. Thus the northern latitudes of Europe continued to be the site of the chief land-masses, what are now the central and southern portions of the Continent being a great archipelago with numerous islands, large and small. The Jurassic rocks, attaining as they do a thickness of several thousand feet, point to very considerable subsidence. The movement, however, was not continuous, but ever and anon was interrupted by pauses. Taken as a whole, the strata appear to have accumulated in a comparatively shallow sea, which, however, was sufficiently deep in places to allow of the growth, in clear water, of coral-reefs. Towards the close of the Jurassic period a movement of elevation ensued, which caused the sea to retreat from wide areas, and thus when the Cretaceous period began the British region was chiefly dry land. Middle Europe would seem also to have participated in this upward movement. Eventually, however, subsidence again ensued. Most of what are now the low-grounds of Britain were submerged, the sea stretching eastwards over a vast region in middle Europe, as far as the slopes of the Urals. The deepest part of this sea, however, was in the west, and lay over England and northern France. Further east, in what are now Saxony and Bohemia, the waters were shallow, and gradually became silted up. In the Mediterranean basin a wide open sea existed, covering large sections of eastern Spain and southern France, overflowing the site of the Jura Mountains, drowning most of the Alpine Lands, the Italian peninsula, the eastern borders of the Adriatic, and Greece. In short, there are good grounds for believing that the Cretaceous Mediterranean was not only much broader than the present sea, but that it extended into Asia, overwhelming vast regions there, and communicated with the Indian Ocean. Summing up what we know of the principal geographical changes that took place during the Mesozoic era, we are impressed with the fact that, all through those changes, a wide land-surface persisted in the north and north-west of the European area, just as was the case in Palæozoic times. The highest grounds were the Urals and the uplands of Scandinavia and Britain. In middle Europe the Pyrenees and the Alps were as yet inconsiderable heights, the loftiest lands being those of the Harz, the Riesen Gebirge, and other regions of Palæozoic and Archæan rocks. The lower parts of England and the great plains of central Europe were sometimes submerged in the waters of a more or less continuous sea; but ever and anon elevation ensued, and the sea was divided, as it were, into a series of great lakes. In the south of Europe a Mediterranean Sea would appear to have endured all through the Mesozoic era--a Mediterranean of considerably greater extent, however, than the present. Thus we see the main features of our Continent were already clearly outlined before the close of the Cretaceous period. The continental area then, as now, consisted of a wide belt of high-ground in the north, extending roughly from south-west to north-east; south of this a vast stretch of low-grounds, sweeping from west to east up to the foot of the Urals, and bounded on the south by an irregular zone of elevated land having approximately the same trend; still further south, the maritime tracts of the Mediterranean basin. During periods of depression the low-grounds of central Europe were invaded by the sea, and the Mediterranean at the same time extended north over many regions which are now dry land. It is in these two low-lying tracts, therefore, and the country immediately adjoining them, that the Mesozoic strata of Europe are chiefly developed. A general movement of upheaval[DH] supervened at the close of the Cretaceous period, and the sea which, during that period, overflowed so much of middle Europe had largely disappeared before the beginning of Eocene times. The southern portions of the continent, however, were still mostly under water, while great bays and arms of the sea extended northwards now and again into central Europe. On to the close of the Miocene period, indeed, southern and south-eastern Europe consisted of a series of irregular straggling islands and peninsulas washed by the waters of a genial sea. Towards the close of early Cainozoic times, the Alps, which had hitherto been of small importance, were greatly upheaved, as were also the Pyrenees and the Carpathians. The floor of the Eocene sea in the Alpine region was ridged up for many thousands of feet, its deposits being folded, twisted, inverted, and metamorphosed. Another great elevation of the same area was effected after the Miocene period, the accumulations of that period now forming considerable mountains along the northern flanks of the Alpine chain. Notwithstanding these gigantic elevations in south-central Europe--perhaps in consequence of them--the low-lying tracts of what is now southern Europe continued to be largely submerged, and even the middle regions of the continent were now and again occupied by broad lakes which sometimes communicated with the sea. In Miocene times, for example, an arm of the Mediterranean extended up the Rhone valley, and stretched across the north of Switzerland to the basin of the Danube. After the elevation of the Miocene strata these inland stretches of sea disappeared, but the Mediterranean still overflowed wider areas in southern Europe than it does in our day. Eventually, however, in late Pliocene times, the bed of that sea experienced considerable elevation, newer Pliocene strata occurring in Sicily up to a height of 3000 feet at least. It was probably at or about that period that the Black Sea and the Sea of Asov retreated from the wide low-grounds of southern Russia, and that the inland seas and lakes of Austria-Hungary finally vanished. [DH] I now doubt whether any vertical upheaval of a wide continental area is possible. The so-called "continental uplifts" are probably in most cases rather negative than positive elevations. In other words, the land seems to rise simply because the sea retreats owing perhaps to the sinking of the crust within the great oceanic basins. See on this subject, Article XIII. The Cainozoic era is distinguished in Europe for its volcanic phenomena. The grandest eruptions were those of Oligocene times. To that date belong the basalts of Antrim, Mull, Skye, the Faröe Islands, and the older series of volcanic rocks in Iceland. These basalts speak to us of prodigious fissure eruptions, when molten rock welled up along the lines of great cracks in the earth's crust, flooding wide regions, and building up enormous plateaux, of which we now behold the merest fragments. The ancient volcanoes of central France, those of the Eifel country and many other places in Germany, and the volcanic rocks of Hungary, are all of Cainozoic age; while, in the south of Europe, Etna, Vesuvius, and other Italian volcanoes date their origin to the later stages of the same great era. Thus before the beginning of Pleistocene times all the main features of Europe had come into existence. Since the close of the Pliocene period there have been many great revolutions of climate; several very considerable oscillations of the sea-level have taken place, and the land has been subjected to powerful and long-continued erosion. But the greater contours of the surface which began to appear in Palæozoic times, and which in Mesozoic times were more strongly pronounced, had been fully evolved by the close of the Pliocene period. The most remarkable geographical changes which have taken place since then have been successive elevations and depressions, in consequence of which the area of our Continent has been alternately increased and diminished. At a time well within the human period our own islands have been united to themselves and the Continent, and the dry land has extended north-west and north, so as to include Spitzbergen, the Faröe Islands, and perhaps Iceland. On the other hand, our islands have been within a recent period largely submerged. The general conclusion, then, to which we are led by a review of the greater geographical changes through which the European continent has passed is simply this--that the substructure upon which all our sedimentary strata repose is of primeval antiquity. Our dry lands are built up of rocks which have been accumulated over the surface of a great wrinkle of the earth's crust. There have been endless movements of elevation and depression, causing minor deformations, as it were, of that wrinkle, and inducing constant changes in the distribution of land and water; but no part of the continental ridge has ever been depressed to an abysmal depth. The ridge has endured through all geological time. We can see also that the land has been evolved according to a definite plan. Certain marked features begin to appear very early in Palæozoic times, and become more and more pronounced as the ages roll on. All the countless oscillations of level, all the myriad changes in the distribution of land and water, all the earthquake disturbances and volcanic eruptions--in a word, all the complex mutations to which the geological record bears witness--have had for their end the completion of one grand design. A study of the geological structure of Europe--an examination of the manner in which the highly folded and disturbed strata are developed--throws no small light upon the origin of the larger or dominant features of our Continent. The most highly convoluted rocks are those of Archæan and Palæozoic age, and these are developed chiefly in the north-western and western parts of the Continent. Highly contorted strata likewise appear in all the mountain-chains of central Europe--some of the rocks being of Palæozoic, while others are of Mesozoic and of Cainozoic age. Leaving these mountains for the moment out of account, we find that it is along the western and north-western sea-board where we encounter the widest regions of highly-disturbed rocks. The Highlands of Scandinavia and Britain are composed, for the most part, of highly-flexed and convoluted rocks, which speak to titanic movements of the crust; and similar much-crushed and tilted rock-masses occur in north-west France, in Portugal, and in western Spain. But when we follow the highly-folded Palæozoic strata of Scandinavia into the low-grounds of the great plains, they gradually flatten out, until in Russia they occur in undisturbed horizontal positions. Over thousands of square miles in that country the Palæozoic rocks are just as little altered and disturbed as strata pertaining to Mesozoic and Cainozoic times. These facts can have but one meaning. Could we smooth out all the puckerings, creases, foldings, and flexures which characterise the Archæan and Palæozoic rocks of western and north-western Europe, it is certain that these strata would stretch for many miles out into the Atlantic. Obviously they have been compressed and crumpled up by some force acting upon them from the west. Now, if it be true that the basin of the Atlantic is of primeval origin, then it is obvious that the sinking down of the crust within that area would exert enormous pressure upon the borders of our continental area. As cooling and contracting of the nucleus continued, subsidence would go on under the oceanic basin, depression taking place either slowly and gradually, during protracted periods, or now and again more or less suddenly. But whether gradually or suddenly effected, the result of the subsidence would be the same upon the borders of our Continent; the strata along the whole western and north-western margins of the European ridge would necessarily be flexed and disturbed. Away to the east, however, the strata, not being subject to the like pressure, would be left in their original horizontal positions. Now it can be shown that the mountains of Scandinavia and the British Islands are much older than the Alps, the Pyrenees, and many other conspicuous ranges in central and southern Europe. Our mountains and those of Scandinavia are the mere wrecks of their former selves. Originally they may have rivaled--they probably exceeded--the Alps in height and extent. It is most likely, indeed, that the areas of Palæozoic rocks in France, Portugal, and Spain also attained mountainous elevations. But the principal upheaval of the western margins of our Continent was practically completed before the close of the Palæozoic period, and since that time those elevated regions have been subjected to prodigious erosion, the later formations being in large measure composed of their débris. I do not, of course, wish it to be understood that there has been no upheaval affecting the west of Europe since Palæozoic times. The tilted position of many of our Mesozoic strata clearly proves the contrary. But undoubtedly the main disturbances which produced the folding, fracturing, and contortion of the Palæozoic strata of western Europe took place before the close of the Palæozoic period. The mountains of Britain and Scandinavia are amongst the oldest in Europe. When we come to inquire into the origin of the mountains of central Europe we have little difficulty in detecting the chief factors in their formation. An examination of the Pyrenees, the Alps, and other hill-ranges having the same general trend shows us that they consist of flexed and convoluted rocks. They are, in short, mountains of elevation, ridged up by tangential thrusts. Of this we need not have the slightest doubt. If, for example, we approach the Alps from the low-grounds of France, we observe the strata as we come towards the Jura beginning to undulate--the undulations becoming more and more marked, and passing into sharp folds and plications, until, in the Alps, the beds become twisted, convoluted, and bent back upon themselves in the wildest confusion. Now, speaking in general terms, we may say that similar facts confront us in connection with every true mountain-range in central Europe. Let it be noted, further, that all those ranges have the same trend, which we may take to be approximately east and west, or nearly at right angles to the trend of the Palæozoic high-grounds of western and north-western Europe. Looked at broadly, our continental ridge may be said to be traversed from west to east by two wide depressions or troughs, separated by the intervening belt of higher grounds just referred to. The former of these troughs corresponds to the great central plain, which passes through the south of England, north-east France, the Low Countries, and Denmark, whence it sweeps east through Germany, and expands into the wide low-grounds of Russia. The southern trough or depression embraces the maritime tracts of the Mediterranean and the regions which that sea covers. Such, then, are the dominant features of our Continent, to which all others are of subordinate importance. Now it cannot be doubted that the two great troughs are belts of subsidence in the continental ridge itself. And their existence explains the origin of the mountain-ranges which separate them. We know that the northern trough is of extreme antiquity; it is older, at all events, than the Silurian period. Even at that distant date its southern limits were marked out by ridges of Archæan rocks, which seem to have formed islands in what is now middle Germany, and probably also in Switzerland and central France. The appearance of those Archæan rocks in central Europe was doubtless due to a ridging up of the crust induced by those parallel movements of subsidence which produced the northern and southern troughs. The northern trough was probably always the shallower depression of the two, for we have evidence to show that, again and again in Mesozoic and later times, the seas which overflowed what are now the central plains of Europe were of less considerable depth than that which occupied the Mediterranean trough. As time rolled on, therefore, the northern trough eventually became silted up; but so low even now is the level of that trough that a relatively slight depression would cause the sea to inundate most extensive regions in middle Europe. In Cainozoic times, as we have seen, the last great elevation of the Alps was effected--an elevation which can hardly have been due to any other cause than the more or less abrupt depression of the earth's crust under the Mediterranean basin. The area of that sea is now much less considerable than it was in Tertiary times--a change due in part to silting up, but chiefly perhaps to the sinking down of its bed to profounder depths. Thus we may conclude that from a very early period--a period ante-dating the formation of our oldest fossiliferous strata--the physical structure of our Continent had already been planned. The dominant features of the primeval continental ridge are those which have endured through all geological time. They are the lines along which the beautiful lands in which we dwell have been constructed. Tilted and convoluted, broken and crushed by myriad earth-movements--scarred, furrowed, worn and degraded by the frosts, the rains, the rivers, and the seas of countless ages--the rocks of our Continent are yet eloquent of design. Where the ignorant sees nothing save confusion and discord, the thoughtful student beholds everywhere the evidence of a well-ordered evolution. Such is the conclusion to which we are led by all geological research. [Illustration: SKETCH-MAPS ILLUSTRATING THE GEOGRAPHICAL EVOLUTION OF CONTINENTAL AREAS By PROFESSOR JAMES GEIKIE, LL.D., D.C.L., F.R.S. PLATE V +-----------------------------+------------------------------+ | MAP SHOWING THE | MAP SHOWING THE | | AREA OF CONTINENTAL PLATEAU | AREA OF CONTINENTAL PLATEAU | | OCCUPIED BY SEA IN | OCCUPIED BY SEA IN | | PALÆOZOIC TIMES. | TERTIARY TIMES. | +-----------------------------+------------------------------+ | MAP SHOWING THE | MAP SHOWING THE | | AREA OF CONTINENTAL PLATEAU | AREAS OF DOMINANT DEPRESSION | | OCCUPIED BY SEA IN | AND ELEVATION. | | MESOZOIC TIMES. | (Below & Above the 1000 | | | fathom Contour Line) | +-----------------------------+------------------------------+ The Edinburgh Geographic Institute J. G. Bartholomew, F.R.G.S. ] XII. The Evolution of Climate.[DI] [DI] Address delivered before the Royal Physical Society at the opening of the Session 1889-90. One of the most interesting questions with which geological science has to deal is that of the evolution of climate. Although there is no general agreement as to how former climatic fluctuations came about, yet the prevalent opinion is that in the past, just as in the present, the character of the climate must have depended mainly on latitude and the relative position of the great land- and water-areas. This was the doctrine taught by Lyell, and its cogency none will venture to dispute. It is true he postulated a total redistribution of oceans and continents--a view which the progress of science has shown to be untenable. We can no longer speculate with him on the possibility of all the great land-areas having been grouped at one time round the equator, and at some other period about the poles. On the contrary, the evidence goes to show that the continents have never changed places with the ocean--that the dominant features of the earth's crust are of primeval antiquity, and ante-date the oldest of the fossiliferous formations. The whole question of climatic changes, therefore, must be reconsidered from the point of view of the modern doctrine of the permanency of continental and oceanic areas. But before proceeding to this discussion, it may be well to glance for a moment at the evidence from which it has been inferred that the climate of the world has varied. Among the chief proofs of climatic fluctuations are the character and the distribution of former floras and faunas. It is true, fossils are, for the most part, relics of extinct forms, and we cannot assert of any one of these that its environment must have been the same as that of some analogous living type. But, although we can base no argument on individual extinct forms, it does not follow that we are precluded from judging of the conditions under which a whole suite of extinct organisms may have lived. Doubtless, we can only reason from the analogy of the present; but, when we take into account all the forms met with in some particular geological system, we seem justified in drawing certain conclusions as to the conditions under which they flourished. Thus, should we encounter in some great series of strata many reef-building corals, associated with large cephalopods and the remains of tree-ferns and cycads, which last from their perfect state of preservation could not have drifted far before they became buried in sediment, we should surely be entitled to conclude that the strata in question had been deposited in the waters of a genial sea, and that the neighbouring land likewise enjoyed a warm climate. Again should a certain system, characterised by the presence of some particular and well-marked flora and fauna, be encountered not only in sub-tropical and temperate latitudes but also far within the Arctic Circle, we should infer that such a flora and fauna lived under climatic conditions of a very different kind from any that now exist. The very presence, in the far north, of fossils having such a geographical distribution would show that the temperature of polar seas and lands could not have been less than temperate. When such broad methods of interpretation are applied to the problems suggested by former floras and faunas, we seem compelled to conclude that the conditions which determined the distribution of life in bygone ages must have been, upon the whole, more uniform and equable than they are now. It is unnecessary that I should go into detailed proof; but I may refer, by way of illustration, to what is known of the Silurian and Carboniferous fossils of the arctic regions. Most of these occur also in the temperate latitudes of Europe and North America, while many are recognised as distinctive types of the same strata nearly all the world over. As showing how strongly the former broad distribution of life-forms is contrasted with their present restricted range, Professor Heilprin has cited the Brachiopoda. Taking existing species and varieties as being 135 in number, he remarks that "there is scarcely a single species which can be said to be strictly cosmopolitan in its range, although not a few are very widely distributed; and, if we except boreal and hyperboreal forms, but a very limited number whose range embraces opposite sides of the same ocean. On the other hand, if we accept the data furnished by Richthofen concerning the Chinese Brachiopoda we find that out of a total of thirteen Silurian and twenty-four Devonian species, no less than ten of the former and sixteen of the latter recur in the equivalent deposits of western Europe: and, further, that the Devonian species furnish eleven, or nearly 50 per cent. of the entire number, which are cosmopolitan or nearly so. Again, of the twenty-five Carboniferous species, North America holds fully fifteen, or 60 per cent., and a very nearly equal number are cosmopolitan." The same palæontologist reminds us that by far the greater number of fossils which occur in the Palæozoic strata of Australia are present also in regions lying well within the limits of the north temperate zone. "In fact," he continues, "the relationship between this southern fauna and the faunas of Europe and North America is so great as to practically amount to identity." But, side by side with such evidence of broad distribution, we are confronted with facts which go to show that, even at the dawn of Palæozoic times, the oceanic areas at all events had their more or less distinct life-provinces. While many of the old forms were cosmopolitan, others were apparently restricted in their range. It would be strange, indeed, had it been otherwise; for, however uniform the climatic conditions may have been, still that uniformity was only comparative. An absolutely uniform world-climate is well-nigh inconceivable. All we can maintain is that the conditions during certain prolonged periods were so equable as to allow of the general diffusion of species over vastly greater areas than now; and that such conditions extended from low latitudes up to polar regions. Now, among the chief factors which in our day determine the limitation of faunas and floras, we must reckon latitude and the geographical position of land and water. What, then, it may be asked, were the causes which allowed of the much broader distribution of species in former ages? It is obvious that before a completely satisfactory answer to that question can be given, our knowledge of past geographical conditions must be considerably increased. If we could prepare approximately correct maps and charts to indicate the position of land and sea during the formation of the several fossiliferous systems, we should be able to reason with some confidence on the subject of climate. But, unfortunately, the preparation of such correct maps and charts is impossible. The data for compilations of the kind required are still inadequate, and it may well be doubted whether, in the case of the older systems, we shall ever be able to arrive at any detailed knowledge of their geographical conditions. Nevertheless, the geological structure of the earth's crust has been so far unravelled as to allow us to form certain general conceptions of the conditions that must have attended the evolution of our continents. And it is with such general conceptions only that I have at present to deal. I said a little ago that the question of geological climates must now be considered from the point of view of the permanency of the great dominant features of the earth's crust. I need not recapitulate the evidence upon which Dana and his followers have based this doctrine of the primeval antiquity of our continental and oceanic areas. It is enough if I remind you that by continental areas we simply mean certain extensive regions in which elevation has, upon the whole, been in excess of depression; by oceanic area, on the other hand, is meant that vast region throughout which depression has exceeded elevation. Thus, while the area of permanent or preponderating depression has, from earliest geological times, been occupied by the ocean, the continental areas have been again and again invaded by the sea--and even now extensive portions are under water. It is not only the continental dry land, therefore, but all the bordering belt of sea-floor which does not exceed 1000 fathoms or so in depth, that must be included in the region of dominant elevation. Were the whole of this region to be raised above the level of the sea, the present continents would become connected so as to form one vast land-mass, or continental plateau. (D, Plate IV.) All the sedimentary strata with which we are acquainted have been accumulated over the surface of that great plateau, and consequently are of comparatively shallow-water origin. They show us, in fact, that at no time in geological history has that plateau ever been drowned in depths at all comparable to those of the deeper portions of our oceanic troughs. The stratified rocks teach us, moreover, that the present land-areas have been gradually evolved, and that, notwithstanding many oscillations of level, these areas have continued to increase in extent--so that there is probably more land-surface now than at any previous era in the history of our globe. To give even a meagre outline of the evidence bearing upon this interesting subject is here impossible. All that I can do is to indicate very briefly some of the general results to which that evidence seems to lead. The oldest rocks with which we are acquainted are the so-called Archæan schists[DJ] But these have hitherto yielded no unequivocal traces of organic life, and as their origin is still doubtful, it would obviously be futile to speculate upon the geographical conditions of the earth's surface at the time of their formation. Reliable geological history only begins with the fossiliferous strata of the Palæozoic era. From these we learn that in the European area the Archæan rocks of Britain, Scandinavia, and Finland formed, at that time, the most extensive tract of dry land in our part of the world. How far beyond the present limits of Europe that ancient northern land extended we cannot tell; but it probably occupied considerable regions which are now submerged in the waters of the Arctic Ocean. Further south, the continental plateau appears to have been, for the most part, overflowed by a shallow sea, the surface of which was dotted by a few islands of Archæan rocks, occupying the sites of what are now some of the hills of middle Germany and the Archæan districts of France and the Iberian Peninsula. Archæan rocks occur likewise in Corsica and Sardinia, and again in Turkey: they also form the nuclei of most of the great European mountain-chains, as the Pyrenees, the Alps, the Carpathians, and the Urals. These areas of crystalline schists may not, it is true, have existed as islands at the beginning of Palæozoic times, for they were doubtless ridged up by successive elevations at later dates; but their very presence as mountain-nuclei is sufficient to show that at a very early geological period, the continental plateau could not have been covered by any great depth of sea. We can go further than this--for all the evidence points to the conclusion that, even so far back as Cambrian times, the dominant features of the present European continent had been, as it were, sketched out. Looked at broadly, that part of the great continental plateau upon which our European lands have been gradually built up may be said to be traversed from west to east by two wide depressions, separated by an intervening elevated tract. The former of these depressions corresponds to the great Central Plain which passes through the south of England, north-east of France, and the Low Countries, whence it sweeps through Germany, to expand into the extensive low-grounds of central and northern Russia. The southern depression embraces the maritime tracts of the Mediterranean, and the regions which that sea covers. To these dominant features all the others are of subordinate importance. The two great troughs are belts of depression in the continental plateau itself. The northern one is of extreme antiquity--it is older, at all events, than the Cambro-Silurian period. Even at that distant date its southern limits were marked out by ridges of Archæan rock, which, as I have said, seem to have formed islands in what is now central Europe. It was probably always the shallower depression of the two, for we have evidence to show that again and again, in Mesozoic and later times, the sea that overflowed what are now the central lowlands of Europe was of less considerable depth than that which occupied the Mediterranean trough. [DJ] I need hardly remind geologists that some of the so-called "Archæan schists" may really be the highly altered accumulations of later geological periods. If we turn to North America, we find similar reason to conclude, with Professor Dana, that the general topography of that region had likewise been foreshadowed as far back as the beginning of the Palæozoic era. Dana tells us that even then the formation of its chief mountain-chains had been commenced, and its great intermediate basins were already defined. The oldest lands of North America were built up, as in Europe, of azoic rocks, and were grouped chiefly in the north. Archæan masses extend over an enormous region, from the shores of the Arctic Ocean down to the great lake country, and they are seen likewise in Greenland and many of the Arctic islands. They appear also in the long mountain-chains that run parallel with the coast-lines of the Continent. In a word, the present distribution of the Archæan rocks, and their relation to overlying strata, lead to the belief that in North America, just as in Europe, they form the foundation-stones of that continent, and stretch continuously throughout its whole extent. We know comparatively little of the geology of the other great land-masses of the globe, but from such evidence as we have there is reason to believe that these in their general structure have much the same story to tell as Europe and North America. In South America, Archæan rocks extend over vast areas in the east and north-east, and reappear in the lofty mountain-chains of the Pacific border. They have been recognised also in various parts of Africa, alike in the north and east, in the interior, and in the west and south. In Asia, again, they occupy wide areas in the Indian Peninsula; they are well developed in the Himalaya, while in China and the mountains and plateaux of central Asia, azoic rocks, which are probably of Archæan age, are well developed. The crystalline schists, which cover extensive tracts in Australia and in the northern island of New Zealand, have also been referred to the same age. Thus, all the world over, Archæan rocks seem to form the surface of the ancient continental plateau upon which all other sedimentary strata have been accumulated. And in every region where Palæozoic rocks occur, we have evidence to prove that at the time these last were formed vast areas of the old continental plateau were under water. The geological structure of the Palæozoic tracts of Europe and America has shown us that, during the protracted period of their accumulation, and notwithstanding many oscillations of level, the land-surface continued to increase. The same growth of dry land characterised Mesozoic and Cainozoic times--the primeval depressions that traverse the continental plateau became more and more silted up, and the sea eventually disappeared from extensive regions which it had overflowed in Palæozoic ages. This land-growth, of course, was not everywhere continuous. Again and again, throughout wide tracts, depression was in excess of sedimentation and elevation. Even at the present time, broad tracts of what was once dry land are submerged. But the simple fact that the younger fossiliferous strata do not extend over such wide areas as the older systems, is sufficient proof that our land-masses have all along tended to grow, and to become more and more consolidated. Reference has already been made to the remarkable fact that no abysmal accumulations have yet been detected amongst the stratified rocks of the earth's crust. Ordinary clastic rocks, such as shale, sandstone, and conglomerate--altered or unaltered, as the case may be--form by far the largest proportion of our aqueous strata, and speak to us only of shallow waters. It is true that some of our limestones must have accumulated in moderately deep clear seas, yet none of these limestones is of abysmal origin. They prove that portions of the continental plateau have now and again been submerged for several thousand feet, but afford no evidence of depths comparable to those of the present oceanic basins. The enormous thickness obtained by the sedimentary strata can only be explained on the supposition that deposition took place over a gradually sinking area. And thus it can be shown that, within the continental plateau, movements of depression have been carried on more or less continuously during vast periods of time--and yet so gradually, that sedimentation was able to keep pace with them. Take, for example, the Cambrian strata of Wales and Shropshire--all, apparently, shallow-water deposits--which attain a thickness of 30,000 feet, or thereabout; or the Silurian strata of the same regions, which are not much less than 20,000 feet thick; and similar great depths of sedimentary rocks might be cited from North America. Passing on to later periods, we find like evidence of long-continued depression in the thick sediments of the younger Palæozoic systems. It is noteworthy, however, that when we come down to still later ages, the movements of depression, as measured by the depths of the strata, appear to have become less and less extensive and profound. Each such movement of depression was eventually brought to a close by one or more movements of upheaval--slowly or more rapidly effected, as the case may have been. Here, then, we are confronted with the striking fact that the continental plateau has, from time to time, sunk down over wide areas to depths exceeding those of existing oceans, and yet at so slow a rate, that sedimentation prevented the depressed regions from becoming abysmal. It is obvious, then, that such areas are now dry land simply because, in the long-run, sedimentation and upheaval have been in excess of depression. And yet, notwithstanding the numerous upheavals which have taken place over the continental plateau, these have succeeded in doing little more than drain away the sea more or less completely from the great primeval depressions by which that plateau is traversed. If it be true, therefore, that the continental plateau owes its existence to the sinking down of the earth's crust within the oceanic basins--if the continents have been squeezed up by the tangential thrusts exerted by the sinking areas that surround them--then it follows that while lands have been gradually extending over the continental plateau, the bed of the ocean has been sinking to greater and greater depths. If this general conclusion holds good, it is obvious that the oceanic troughs of early geological times could not have been so deep as they are now. During the Palæozoic period, the most continuous areas of dry land, as we have seen, were distributed over the northern parts of our hemisphere, while, further south, groups of islands indicated the continuation of the continental plateau. Doubtless South America, Africa, Asia, and Australia were, at that distant date, represented by similar detached areas of dry land. In a word, the primeval continental plateau was still largely under water. Judging from the character and broad distribution of the Palæozoic marine faunas the temperature of the sea was wonderfully uniform. There is certainly nothing to indicate the existence of such climatic zones as those of the present. We know very little of the terrestrial life of early Palæozoic times--the Cambro-Silurian strata are essentially marine. Land-plants, however, become more numerous in the Old Red Sandstone, and, as every one knows, they abound in the succeeding Carboniferous and Permian systems. And the testimony of these floras points to the same conclusion as that furnished by the marine faunas. The Carboniferous floras of the arctic regions, and of temperate Europe and America, not only have the same _facies_, but a considerable number of the species is common to both areas; while many European species occur in the Carboniferous strata of Australia and other distant lands. This common _facies_, and the presence of numerous cosmopolitan forms, surely indicate the former prevalence of remarkably uniform climatic conditions. The conditions, of course, need not--indeed, could not--have been absolutely uniform. At present the various climates which our globe experiences depend upon the amount of heat received directly and indirectly from the sun--oceanic and aërial currents everywhere modifying the results that are due to latitude. It cannot have been otherwise in former times. In all ages the tropics must have received more direct sun-heat than temperate and polar regions; and however much the climatic conditions of the Palæozoic era may have differed from the present--however uniformly temperature may have been distributed--still, as I have said, absolute uniformity was impossible. It was doubtless owing to the fact that the dry lands of Palæozoic times were not only much less extensive than now, but more interrupted, straggling, and insular, that the climate of the globe was so equable. Under such geographical conditions, great oceanic currents would have a much freer course than is now possible, and warm water would find its way readily across wide regions of the submerged continental plateau into the highest latitudes. The winds blowing athwart the land would everywhere be moist and warm, and no such marked differences of temperature, such as now obtain, would distinguish the arctic seas from those of much lower latitudes. At the same time, the comparatively shallow water overlying the submerged areas of the continental plateau would favour the distribution of species, and thus bring about that wide distribution of cosmopolitan forms and general similarity of _facies_, which are such marked features of the Palæozoic faunas. It is even quite possible that migration may have taken place here and there across the great oceanic depression itself; for it may well be doubted whether, at so early a period, the depression had sunk down to its present depth below the level of the continental plateau. Yet, notwithstanding such facilities for migration, and the consequent similarity of _facies_ I have referred to, the Palæozoic faunas of different regions have usually certain distinctive characters. Even at the very dawn of the era the marine faunas were already grouped into provinces, sometimes widely separated from one another, at other times closely adjacent, so that it is evident that barriers to migration here and there existed. It could hardly have been otherwise; for local and more widely-spread movements of elevation and depression took place again and again during Palæozoic times. While the younger Palæozoic systems were being accumulated, excess of upheaval over depression resulted in the gradual increase of the land.[DK] The continental plateau came more and more to the surface, in spite of many oscillations of level. It is quite possible, nay, even probable that this persistent growth of land, and consequent modification of oceanic currents may have rendered the climatic conditions of later Palæozoic times less uniform: but, if so, such diminished uniformity has left no recognisable impress on either faunas or floras; for fossils characteristic of the Devonian and Carboniferous strata of temperate latitudes occur far within the Arctic Circle. [DK] See footnote p. 341. Descending to the Mesozoic era, we find that the character and distribution of marine faunas are still indicative of uniformity. There could have been little difference of temperature at that time between arctic seas and those of our own latitude. Cosmopolitan species abounded in the Jurassic waters, but were relatively less numerous in those of the Cretaceous period. Professor Neumayr maintains that already, in the Jurassic period, the climate had become differentiated into zones. This, he thinks, is indicated by the fact that coral reefs abound in the Jurassic strata of central Europe, while they are wanting in the contemporaneous deposits of boreal regions. Dr. Heilprin, on the other hand, is of opinion that this and certain other distinctive features of separate Jurassic life-provinces may not have been due to differences of temperature, but rather to varying physical conditions, such as character of the sea-bottom, depth of water, and so forth. Perhaps the safest conclusion we can come to, in the present state of the evidence, is that the climatic conditions of the Mesozoic era were, upon the whole, less obviously uniform than those of earlier ages, but that marked zones of climate like the present had not as yet been evolved. At the same time, when we consider how many great geographical revolutions took place during the period in question, we must be prepared to admit that these could hardly fail to influence the climate, and thus to have induced modifications in the distribution of faunas and floras. And probably evidence of such modifications will yet be recognised, if indeed the phenomena referred to by Neumayr be not a case in point. It may be noted, further, that while, according to many botanists, the plants of the Palæozoic periods bespeak not only uniform climatic conditions but the absence of marked seasonal changes, those of late Mesozoic times are indicative of less uniformity. The Cretaceous conifers, for example, show regular rings of growth, and betoken the existence of seasons, which were less marked, however, than is now the case. The geographical changes of Mesozoic times were notable in many respects. The dominant features of Europe, already foreshadowed in early Palæozoic times, had become more clearly outlined before the close of the Cretaceous period. Notwithstanding many movements of depression, the chief land-areas continued to show themselves in the north and north-west. The highest grounds were the Urals, and the uplands of Scandinavia and Britain. In middle Europe the Pyrenees and the Alps were as yet inconsiderable heights, the loftiest lands in that region being those of the Harz, the Riesen Gebirge, and other tracts of Archæan and Palæozoic rocks. The lower parts of England and the great lowland plains of central Europe were sometimes submerged in the waters of a wide, shallow sea, but ever and anon elevation ensued, new lands appeared, and these waters became divided into a series of large inland seas and lakes. In the south, a deep Mediterranean sea would appear to have persisted all through the Mesozoic era--a sea of considerably greater extent, however, than the present. While in Europe the dominant features of the continental plateau run approximately east and west, in North America they follow nearly the opposite direction. In early Mesozoic times, vast tracts of dry land extended across the northern and eastern sections of the latter area. Over the Rocky Mountain region, low lands and saline lakes appear to have stretched, while further west the area of the Great Plateau and the Pacific slope were covered by the sea. Towards the end of the Mesozoic era, the land in the far west became more continuous--a broad belt extending in the direction of the Pacific coast-line from Mexico up to high northern latitudes. In short, before the Cretaceous period closed, the major portion of North America had been evolved. A considerable tract of what is now the western margin of the continent, however, was still under water, while from the Gulf of Mexico (then much wider than now) a broad Mediterranean sea swept north and north-west through Texas and the Rocky Mountain region to communicate with the Arctic Ocean. All to the east of this inland sea was then, as it is now, dry land. Thus, up to the close of the Cretaceous period, in America and Europe alike, oceanic currents coming from the south had ready access across the primeval continental plateau to the higher latitudes. Southern Europe indeed, during Mesozoic times, was simply a great archipelago, having free communication on the one hand across the low-grounds of central and northern Russia with the arctic seas, and, on the other, across vast regions in Asia with the Indian Ocean. Of the other great land-masses of the globe our knowledge is too limited to allow us to trace their geographical evolution with any confidence. But from the very wide distribution of Mesozoic strata in South America, Africa, Asia, and Australia, there can be no doubt that, at the time of their accumulation, enormous tracts in those regions were then under water. The land-masses, in short, were not so continuous and compact as they are at present. And although we must infer that considerable areas of Mesozoic land are now submerged, yet these cannot but bear a very small proportion to the wide regions which have been raised above the sea-level since Mesozoic times. In short, from what we do know of the geological structure of the continents in question, we can hardly doubt that they have passed through geographical revolutions of a like kind with those of Europe and North America. Everywhere over the great continental plateau elevation appears, in the long-run, to have been in excess of depression, so that, in spite of many subsidences, the tendency of the land throughout the world has been to extend its margins, and to become more and more consolidated. The Mesozoic lands were larger than those of the preceding Palæozoic era, but they were still penetrated in many places by the sea, and warm currents could make their way over wide tracts that are now raised above the sea-level. Under such circumstances approximately uniform conditions of climate could not but obtain. Great geographical changes supervened upon the close of the Cretaceous period. North America then acquired nearly its present outline. Its Mediterranean sea had vanished, but the Gulf of Mexico still overflowed a considerably wider region than now, while a narrow margin of the Pacific border of the continent continued submerged. In Europe elevation ensued, and the sea which had overspread so much of the central and eastern portions of our Continent disappeared. Southern Europe, however, was still largely under water, while bays and inlets extended northwards into what are now the central regions of the Continent. On to the close of the Miocene period, indeed, the southern and south-eastern tracts of Europe were represented by straggling islands. In middle Cainozoic times the Alps, which had hitherto been of small importance, were considerably upheaved, as were also the Pyrenees and the Carpathians; and a subsequent great elevation of the Alpine area was effected after the Miocene period. Notwithstanding these gigantic movements, the low-lying tracts of what is now southern Europe continued to be largely submerged, and even the central regions of the Continent were now and again occupied by broad lakes, which sometimes communicated with the sea. After the elevation of the Miocene strata, these inland seas disappeared, but the Mediterranean still overflowed wider areas than it does to-day. Eventually, however, in late Pliocene times, the bed of that sea experienced considerable elevation; and it was probably at or about this stage that the Black Sea and the Sea of Asov retreated from the broad low-grounds of southern Russia, and that the inland seas and lakes of Austria-Hungary finally vanished. The movements of upheaval, which caused the Cretaceous seas to disappear from such broad areas of the continental plateau, induced many changes in the floras and faunas of the globe. A notable break in the succession occurs between the Cretaceous and the Eocene, hardly one species of higher grade than the protozoa passing from one system to the other. In the Cainozoic deposits we are no longer confronted with numerous cosmopolitan species--the range of marine forms has become much more restricted. Nevertheless, the faunas and floras continue to be indicative of much warmer climates for arctic and temperate latitudes than now obtain. But, at the same time, differentiation of climate into zones is distinctly marked. In the early Cainozoic period, our present temperate latitudes supported a flora of decidedly tropical affinities, while the fauna of the adjacent seas had a similar character. Later on the climate of the same latitudes appears to have passed successively through sub-tropical and temperate stages. In short, a gradual lowering of the temperature is evinced by the character and distribution both of floras and faunas. The differentiation of the climate during one stage of the Cainozoic era is well illustrated by the Miocene flora. Thus, at a time when Italy was clothed with a tropical vegetation, in which palm-trees predominated, middle Europe had its extensive forests of evergreens and conifers, while in the region of the Baltic conifers and deciduous trees were the prevalent forms. When one takes into consideration the fact that, notwithstanding many oscillations of level, the land during Cainozoic times was gradually extending, and the sea disappearing from wide regions which it had formerly covered, one can hardly doubt that the seemingly gradual change from tropical to temperate conditions was due, in large measure, to that persistent continental growth. I confess, however, that it is difficult to account for the very genial climate which continued to prevail over the arctic regions. So far as one can gather from the evidence at present available, some of the marine approaches to those latitudes had been cut off by the movements of elevation which brought the Cainozoic era to a close, while the arctic lands were perhaps more extensive than they are now. The Cretaceous Mediterranean Sea of North America had vanished, and we cannot prove that the Tertiary Sea of southern Europe communicated across the low-grounds of Russia with the Arctic Ocean. We know, however, that the archipelago of southern Europe was in direct connection with the Indian Ocean, and it is most probable that a wide arm of the same sea stretched north from the Aralo-Caspain area through Siberia. Indeed, much of what are now the lowlands of western and northern Asia was probably sea in Tertiary times. It seems likely, therefore, that, even at this late period, marine currents continued to reach the Arctic Zone across the continental plateau. When the warm waters of the Indian Ocean eventually ceased to invade Europe, and the Mediterranean became much restricted in area, the climate of the whole Continent could not fail to be profoundly affected. There is yet another line of evidence to which brief reference may be made. I have spoken of the remarkable uniformity of climatic conditions which obtained in Palæozoic times, and of the gradual modification of these conditions which subsequently supervened. Now, it is worthy of note that in their lithological characters the oldest sedimentary strata themselves likewise exhibit a prevalent uniformity which in later systems becomes less and less conspicuous. The Cambro-Silurian mechanical sediments, for example, maintain much the same character all the world over; and the like is true, although in a less degree, of the marine accumulations of the Devonian period. The corresponding mechanical deposits of later Palæozoic ages continue to show more and more diversity, but at the same time they preserve a similarity of character over much more extensive areas than is found to be the case with the analogous sediments of the Mesozoic era. Finally, these last are more or less strongly contrasted with the marine mechanical accumulations of Cainozoic times, which are altogether more local in character. This increasing differentiation is quite in keeping with what we know of the evolution of our land-areas. In early Palæozoic ages, when insular conditions prevailed and the major portion of the primeval continental plateau was covered by shallow seas, it is obvious that mechanical sediments would be swept by tidal and other currents over enormous areas, and that these sediments would necessarily assume a more or less uniform character. Indeed, I suspect that much of the sediment of those early seas may have been the result of tidal scour, and that marine erosion was more generally effective then than it is now. With the gradual growth of the land and the consequent deflection and limitation of currents, marine mechanical sediments would tend to become more and more local in character. Thus the increasing differentiation which we observe in passing from the earlier to the later geological systems is just what might have been expected. Summing up, now, the results of this rapid review of the evidence, we seem justified in coming to the following conclusions:-- (1.) In Palæozoic times, Europe and North America were represented by considerable areas of dry land, massed chiefly in the higher latitudes, while further south groups of smaller islands were scattered over the submerged surface of the primeval continental plateau. The other continents appear, in like manner, to have been represented by islands--some of which may have reached continental dimensions. A very remarkable uniformity of climate accompanied these peculiar geographical conditions. (2.) In Mesozoic times, the primeval continental plateau came more and more to the surface, but the land-areas were still much interrupted, so that currents from tropical regions continued to have ready access to high latitudes. The climate of the whole globe, therefore, was still uniform, but apparently not so markedly as in the preceding era. (3.) In Cainozoic times, the land-masses continued to extend, and the sea to retreat from hitherto submerged areas of the continental plateau; and this persistent land-growth was accompanied by a gradual lowering of the temperature of northern and temperate latitudes, and a more and more marked differentiation of climate into zones. Having thus very briefly sketched the geographical evolution of the land during Palæozoic, Mesozoic, and Tertiary times, and come to the general conclusion that climate has varied according to the relative position of land and sea, I have next to consider the geographical and climatic conditions of the Quaternary period. These, however, are now so well known, that I need to no more than remind you that, so far as the chief features of our lands are considered, all these had come into existence before the dawn of the Ice Age. The greater contours of the surface, which were foreshadowed in Palæozoic times, and which in Mesozoic times were more clearly indicated, had been fully evolved by the close of the Pliocene period. The connection between the Mediterranean and the Indian Ocean probably ceased in late Pliocene times. The most remarkable geographical changes which have taken place since then within European regions have been successive elevations and depressions, in consequence of which the area of our Continent has been alternately increased and diminished. At a time well within the human period, our own islands have been united to themselves and the Continent, and the dry land has extended north-west and north, so as to include Spitzbergen, the Faröe Islands, and perhaps Iceland. On the other hand, our islands have been within a recent period largely submerged. Similarly, in North America, we are furnished with many proofs of like oscillations of level having taken place in Quaternary times. Is it possible, then, to explain the climatic vicissitudes of the Pleistocene period by means of such oscillations? Many geologists have tried to do so, but all these attempts have failed. It is quite true that a general elevation of the land in high latitudes would greatly increase the ice-fields of arctic regions, and might even give rise to perennial snow and glaciers in the mountain-districts of our islands. But it is inconceivable that any such geographical change could have brought about that general lowering of temperature over the whole northern hemisphere which took place in Pleistocene times. For we have to account not only for the excessive glaciation of northern and north-western Europe, and of the northern parts of North America, but for the appearance of snow-fields and glaciers in much more southern latitudes, and in many parts of Asia where no perennial snow now exists. Moreover, we have to remember that arctic conditions of climate obtained in north-western Europe even when the land was relatively much lower than it is at present. The arctic shell-beds of our own and other temperate regions sufficiently prove that geographical conditions were not the only factor concerned in bringing about the peculiar climate of the Pleistocene period. Then, again, we must not forget that at certain stages of the same period genial conditions of climate were coincident with a much wider land-surface in north-western Europe than now exists. The very fact that interglacial deposits occur in every glaciated region is enough of itself to show that the arctic conditions of the Pleistocene could not have resulted entirely from a mere elevation of land in the northern parts of our hemisphere. The only explanation of the peculiar climatic vicissitudes in question which seems to meet the facts, so far as these have been ascertained, is the well-known theory advanced by Dr. Croll. After carefully considering all the objections which have been urged against that theory, there is only one, as it seems to me, that is deserving of serious attention. This objection is not based on any facts connected with the Pleistocene deposits themselves, but on evidence of quite another kind. It is admitted that were the Pleistocene deposits alone considered, Croll's theory would fully account for the phenomena. But, it is argued, we cannot take the Pleistocene by itself, for if that theory be true, then climatic conditions similar to those of the Pleistocene must have supervened again and again during the past. Where, then, we are asked, is there any evidence in Palæozoic, Mesozoic, or Cainozoic strata of former widespread glacial conditions? If continental ice-sheets, comparable to those of the Pleistocene, ever existed in the earlier ages, surely we ought to find more or less unmistakable traces of them. Now, at first sight, this looks a very plausible objection, but it has always seemed to me to be based upon an assumption that is not warranted by our knowledge of geographical evolution. Dr. Croll always admitted implicitly that high eccentricity of the earth's orbit might have happened again and again without inducing glacial conditions like those of the Pleistocene. The objection takes no account of the fact that the excessive climate of the Glacial period was only possible because of special geographical conditions--conditions that do not appear to have been fully evolved before Pliocene times. No one has seen this more clearly than Mr. Wallace,[DL] with the general drift of whose argument I am quite at one. In earlier ages, the warm water of the tropics overflowed wide areas of our present continents--most of the dry land was more or less insular, and the seas within the Arctic Circle were certainly not cold as at present, but temperate and even genial. If we go back to Cambro-Silurian times, we find only the nuclei, as it were, of our existing continents appearing above the surface of widespread shallow seas. It is quite impossible, therefore, that under such geographical conditions, great continuous ice-sheets, like those of the Pleistocene, could have existed--no matter how high the eccentricity of the earth's orbit may have been. The most that could have happened during such a period of eccentricity would be the accumulation of snow-fields on mountains and plateaux of sufficient height, the formation here and there of local glaciers, and the descent of these in some places to the sea. And what evidence of such local glaciation might we now expect to find? No old land-surface of that far-distant period has come down to us: we look in vain for Cambro-Silurian _roches moutonnées_ and boulder-clay or moraines. The only evidence we could expect is just that which actually occurs, namely, erratics (some of them measuring five feet and more in diameter) embedded in marine deposits. It may be said that a few erratics are hardly sufficient to prove that a true Glacial period supervened in Cambro-Silurian times, and I do not insist that they are. But I certainly maintain that if any lowering of the temperature were induced by high eccentricity of the earth's orbit during Cambro-Silurian times, then ice-floated erratics are the only evidence of refrigeration that we need ever hope to find. The geographical conditions of early Palæozoic times forbade the formation of enormous ice-sheets like those of the Pleistocene period. Extreme climatic changes were then impossible, and periods of high eccentricity might have come and gone without inducing any modifications of flora and fauna which we could now recognise. We are ignorant of the terrestrial life of the globe at that distant period, and our knowledge of the marine fauna is not sufficient to enable us to deny the possibility of moderate fluctuations in the temperature of the seas of early Palæozoic times. Moreover, we must not forget there were then no such barriers to migration as now exist. If the conditions became temporarily unsuitable, marine organisms were free to migrate into more genial waters, and to return to their former habitats when the unfavourable conditions had passed away. [DL] See _Island Life_. The uniform climate so characteristic of the Cambro-Silurian period appears to have prevailed likewise during the later stages of the Palæozoic era. This we gather from a general consideration of the floras and faunas, and their geographical distribution. The dry land, as we have seen, continued to increase in extent; but vast areas of the primeval continental plateau of the globe still continued under water, and currents from southern latitudes flowed unrestricted into polar regions. During the protracted lapse of time required for the formation of the later Palæozoic systems several periods of high eccentricity must have occurred. But, so far as one can judge, the disposition of the larger land-areas was never such as to induce a true Ice Age. Nevertheless we are not without evidence of ice-action in Old Red Sandstone, Carboniferous, and Permian strata. And it seems to me probable that the erratic accumulations referred to may really indicate local action, of more or less intensity, brought about by such lowering of the temperature as would supervene during a period of high eccentricity. It is true we may explain the phenomena by inferring the existence of mountains of sufficient elevation--and this, indeed, is the usual explanation. But it is doubtful whether those who adopt that view have fully considered what it involves. Take, for example, the case of the breccias and conglomerates of the Lammermuir Hills, which have all the appearance of being glacial and fluvio-glacial detritus. These deposits overlie the highly-denuded Silurian greywackés of Haddingtonshire in the north and of Berwickshire in the south, and have evidently been derived from the intervening high-grounds--the width of which between the Old Red Sandstone accumulations in question does not exceed eight or nine miles. The breccias reach a height of 1300 feet, while the dominating point of the intervening uplands is 1700 feet. Under present geographical conditions it is doubtful whether perennial snow and glaciers of any size at all could exist in the region of the Lammermuirs at a less altitude than 7000 feet or more. But between the breccias of Haddingtonshire and the equivalent deposits in Berwickshire there is no space for any intermediate range of mountains of circumdenudation of such a height. Moreover, we must remember that under the extremely uniform conditions which obtained in Palæozoic times the snow-line could not possibly have been attained even at that elevation. When the Devonian coral-reefs described by Dupont were growing in the sea that overflowed western Europe, to what height must the southern uplands of Scotland have been elevated in order to reach the snow-line! We may make what allowance we choose for the denudation which the Silurian rocks of the Lammermuirs must have experienced since the deposition of the Old Red Sandstone, but it is simply a physical impossibility that mountains of circumdenudation of the desiderated height could ever have existed in the Lammermuir region at the time the coarse breccias were being accumulated.[DM] It seems to me, then, that these breccias are in every way better accounted for by a lowering of temperature due to increased eccentricity of the orbit. This view frees us from the necessity of postulating excessive upheavals over very restricted areas, and of creating Alps where no Alps could have existed. [DM] It may be objected that the conglomerates were probably not marine, but deposited in lakes, the beds of which may have been much above sea-level. But from all that we know of the Old Red Sandstone of Scotland it would appear that the lakes of the period now and again communicated with the sea, and were probably never much above its level. When we consider the enormous thickness of the strata that constitute any of our larger coal-fields, we can hardly doubt that one or more periods of high eccentricity must have occurred during their accumulation. It does not follow, however, that we should be able to detect in these strata any evidence of alternating cold and warm epochs. So long as ocean-currents from the tropics found ready entrance to polar regions across vast tracts of what is now dry land, extreme and widespread glacial conditions were impossible. Any lowering of temperature due to cosmical causes might indeed induce new snow-fields and glaciers to appear, or existing ones to extend themselves in northern regions and the most elevated lands of lower latitudes; but such local glaciation need not have seriously affected any of the areas in which coal-seams were being formed. For nothing appears more certain than this--that our coal-seams as a rule were formed over broad, low-lying alluvial lands, and in swamps and marshes, along the margins of estuaries or shallow bays of the sea. Some seams, it is true, are evidently formed of drifted vegetable débris, but the majority point to growth _in situ_. The strata with which they are associated are shallow-water sediments which could only have been deposited at some considerable distance from any mountain-regions in which glaciers were likely to exist. It is idle, therefore, to ask for evidence of glacial action amongst strata formed under such conditions. The only evidence of ice-work we are likely to get is that of erratics. And these are not wanting, although it is probable that most of those which are found embedded in coals have been transported by rafts of vegetable matter or in the roots of trees. The same explanation, however, will not account for the boulders which Sir William Dawson has recorded from the coal-fields of Nova Scotia. He describes them as occurring on the outside of a gigantic esker of Carboniferous age, and thinks they were probably dropped there by floating-ice at a time when coal-plants were flourishing in the swamps on the other side of the gravel embankment. If the disposition of the land-areas in Carboniferous times rendered such an ice-age as that of the Pleistocene impossible--in other words, if the effects flowing from high eccentricity of the orbit must to a large extent have been neutralised--the flora and fauna of the period can hardly be expected to yield any recognisable evidence of fluctuating climatic conditions. When our winter happened in aphelion new snow-fields might have appeared, or already existing glaciers might have increased in size; while, with the winter in perihelion, the temperature in northern latitudes would doubtless be raised. But the general result would simply be an alternation of warm and somewhat cooler conditions. And such fluctuations of climate might readily have taken place without materially modifying; the life of the period. The breccias of the Permian system have been described by Ramsay as of glacial origin. Some geologists agree with him, while others do not--and many have been the ingenious suggestions which these last have advanced in explanation of the phenomena. Some have tried to show how the stones and blocks in the breccias may have been striated without having recourse to the agency of glacier-ice, but they cannot explain away the fact that many of the stones (which vary in size from a few inches to three or four feet in diameter) have travelled distances of thirty or forty miles from the parent rocks. Similar erratic accumulations, which may belong to the same system or to the Carboniferous, occur in India and Australia. According to Dr. Blanford, the Indian boulder-beds are clearly indicative of ice-action, and he does not think that they can be explained by an assumed former elevation of the Himalaya. On the contrary, he is of opinion that the facts are best accounted for by a general lowering of the temperature, due probably to the action of cosmical causes. Daintree, Wilkinson, R. Oldham, and others who have studied the Australian erratic beds have likewise stated their belief that these are of true glacial origin. I may pass rapidly over the Mesozoic systems, taking note, however, of the fact that in them we encounter evidence of ice-action of much the same kind as that met with in Palæozoic strata. While, on the one hand, the Mesozoic floras and faunas bespeak climatic conditions similar to those of earlier ages, but probably not quite so uniform; on the other, the occurrence of erratics in various marine accumulations is sufficient to show that now and again ice floated across seas, the floors of which were tenanted by reef-building corals. The geographical conditions continued unfavourable to the formation of extensive ice-sheets in temperate latitudes, no matter how high the eccentricity of the orbit might have been. The erratics which occur in certain Jurassic and Cretaceous deposits are admitted by most geologists to have been ice-borne. Now, it is highly improbable that the transporting agent could have been coast-ice, for it is hardly possible to conceive of ice forming on the surface of a sea in which flourished an abundant Mesozoic fauna. The erratics, therefore, seem to imply the existence in Mesozoic times of local glaciers, which here and there descended to the sea, as in the north-east of Scotland. The erratics in the Scottish Jurassic are evidently of native origin, and it is most improbable that those which have been met with in the Chalk of England and France could have floated from any very great distance. How, then, can we explain the appearance of local glaciers in these latitudes during Mesozoic times? The geographical conditions of the period could not have favoured the formation of perennial snow and ice in our area, unless our lands were at that time much more elevated than now. And this is the usual explanation. It is supposed that mountains much higher than any we now possess probably existed in such regions as the Scottish Highlands. It is easy to imagine the former existence of such mountains. So long a time has elapsed since the Jurassic period, that the Archæan and Palæozoic areas cannot but have suffered prodigious denudation in the interval. But, when one considers how very lofty, indeed, those mountains must have been, in order to reach the snow-line of Jurassic times, one may be excused for expressing a doubt as to whether the suggested explanation is reasonable. At all events, the phenomena are, to say the least, as readily explicable on the supposition that the snow-line was temporarily lowered by cosmical causes. Even with eccentricity at a high value, no great ice-sheets, indeed, could have existed, but local snow-fields and glaciers might have appeared in such mountain-regions as were of sufficient height. And this might have happened without producing any great difference in the temperature of the sea, or any marked modification in the distribution of life. In short, we should simply have, as before, an alternation of warm and somewhat cooler climates, but nothing approaching to the glacial and interglacial epochs of the Pleistocene. These conclusions seem to me to be strongly supported by the evidence of ice-action during Tertiary times. The gigantic erratics of the Alpine Eocene do not appear to have been derived from the Alps, but rather from the Archæan area of southern Bohemia. The strata in which they occur are, for the most part, unfossiliferous; they contain only fucoidal remains, and are presumably marine. How is it possible to account for the appearance of these erratics in marine deposits in central Europe at a time when, as evidenced by the Eocene flora and fauna the climate was warm? Are we to infer the former existence of an extremely lofty range of Bohemian Alps which has since vanished? Is it not more probable that here, too, we have evidence of a lowering of the snow-line, induced by cosmical causes, which brought about the appearance of snow-fields and glaciers in a mountain-tract of much less elevation than would have been required in the absence of high eccentricity of the orbit? If it be objected that such cosmical causes must have had some effect upon the distribution of life, I reply that very probably they had, although not to any extreme extent. The researches of Mr. Starkie Gardner have shown that the flora of the English Eocene affords distinct evidence of climatic changes. But as the geographical conditions of that period precluded the possibility of extensive glaciation, and could only, at the most, have induced local glaciers to appear in elevated mountain-regions, it seems idle to cite the non-occurrence of erratics and morainic accumulations in the Eocene of England and France as an argument against the application of Croll's theory to the case of the erratics of the Flysch. I repeat, then, that under the geographical conditions of the Eocene, all the more obvious effects likely to have resulted from the passage of a period of high eccentricity would be the appearance of a few local glaciers, the existence of which could have had no more influence on the climate of adjacent lowlands than is notable in similar circumstances in our own day. It is absurd, therefore, to expect to find evidence in Eocene strata of as strongly contrasted climates as those of the glacial and interglacial deposits of the Pleistocene. There must, doubtless, have been alternations of climate in our hemisphere; but these would consist simply of passages from warm to somewhat cooler conditions--just such changes, in fact, as are suggested by the plants of the English Eocene. The evidence of ice-action in the Miocene strata is even more striking than that of which I have just been speaking. The often-cited case of the erratics of the Superga near Turin I need do little more than mention. These erratics were undoubtedly carried by icebergs, calved from Alpine glaciers at a time when northern Italy was largely submerged. The erratic deposits are unfossiliferous, and are underlaid and overlaid by fossiliferous strata, in none of which are any erratics to be found. What is the meaning of these intercalated glacial accumulations? Can we believe it possible that the Miocene glaciers were enabled to reach the sea in consequence of a sudden movement of elevation, which must have been confined to the Alps themselves? Then, if this be so, we must go a step further, and suppose that, after some little time, the Alps were again suddenly depressed, so that the glaciers at once ceased to reach the sea-coast. For, as Dr. Croll has remarked, "had the lowering of the Alps been effected by the slow process of denudation, it must have taken a long course of ages to have lowered them to the extent of bringing the glacial state to a close." And we should, in such a case, find a succession of beds indicating a more or less protracted continuance of glacial conditions, and not one set of erratic accumulations intercalated amongst strata, the organic remains in which are clearly suggestive of a warm climate. The occurrence of erratics in the Miocene of Italy is all the more interesting from the fact that in the Miocene of France and Spain similar evidence of ice-action is forthcoming. Opponents of Dr. Croll's theory have made much of Baron Nordenskiöld's statement that he could find no trace of former glacial action in any of the fossiliferous formations within the Arctic regions. He is convinced that "an examination of the geognostic condition, and an investigation of the fossil flora and fauna of the polar lands, show no signs of a glacial era having existed in those parts before the termination of the Miocene period." Well, as we have seen, there is no reason to believe that the geographical conditions in our hemisphere, at any time previous to the close of the Pliocene period, could have induced glacial conditions comparable to those of the Pleistocene Ice Age. The strata referred to by Nordenskiöld, are, for the most part, of marine origin, and their faunas are sufficient to show us that the Arctic seas were formerly temperate and genial. If any ice existed then, it could only have been in the form of glaciers on elevated lands. And it is quite possible that these, during periods of high eccentricity, may have descended to the sea and calved their icebergs; and, if so, erratics may yet be found embedded here and there in the Arctic fossiliferous formations, although Nordenskiöld failed to see them. One might sail all round the Palæozoic coast-lines of Scotland without being able to observe erratics in the strata, and yet, as we know, these have been encountered in the interior of the country. The wholesale scattering of erratics at any time previous to the Pleistocene, must have been exceptional even in arctic regions, and consequently one is not surprised that they do not everywhere stare the observer in the face. The general conclusion, then, to which I think we may reasonably come, is simply this:--That geological climate has been determined chiefly by geographical conditions. So long as the lands of the globe were discontinuous and of relatively small extent, warm ocean-currents reaching polar regions produced a general uniformity of temperature--the climate of the terrestrial areas being more or less markedly insular in character. Under these conditions, the sea would nowhere be frozen. But when the land-masses became more and more consolidated, when owing to the growth of the continents the warm ocean-currents found less ready access to arctic regions, then the temperature of those regions was gradually lowered, until eventually the seas became frost-bound, and the lands were covered with snow and ice. But while the chief determining cause of climate has been the relative distribution of land and water, it is impossible to doubt that during periods of high eccentricity of the orbit, the climate must have been modified to a greater or less extent. In our own day the geographical conditions are such that, were eccentricity to attain a high value, the climate of the Pleistocene would be reproduced, and our hemisphere would experience a succession of alternating cold and genial epochs. But in earlier stages of the world's history, the geographical conditions were not of a kind to favour the accumulation of vast ice-fields. During a period of extreme eccentricity, there would probably be fluctuations of temperature in high latitudes; but nothing like the glacial and interglacial epochs of the Pleistocene could have occurred. At most, there would be a general lowering of the temperature, sufficient to render the climate of arctic seas and lands somewhat cooler, and probably to induce the appearance in suitable places of local glaciers; and, owing to precession of the equinox, these cooler conditions would be followed by a general elevation of the temperature above the normal for the geographical conditions of the period. In Palæozoic and Mesozoic times, the effects of high eccentricity of the orbit appear to have been, in a great measure, neutralised by the geographical conditions, with a possible exception in the Permian period. But in Tertiary times, when the land-masses had become more continuous, the cosmical causes of change referred to must have had greater influence. And I cannot help agreeing with Dr. Croll that the warm climates of the Arctic regions during that era were, to some extent, the result of high eccentricity. In concluding this discussion, I readily admit that our knowledge of geographical evolution is as yet in its infancy. We have still very much to learn, and no one will venture to dogmatise upon the subject. But I hope I have made it clear that the evidence, so far as it goes, does not justify the confident assertions of Dr. Croll's opponents, that his theory is contradicted by what we know of the climatic conditions of Palæozoic, Mesozoic, and Cainozoic times. On the contrary, it seems to me to gain additional support from the very evidence to which Nordenskiöld and others have appealed. Note.--The accompanying sketch-maps (Plate IV.) require a few words of explanation. The geology of the world is still so imperfectly known that any attempt at graphic representation of former geographical conditions cannot but be unsatisfactory. The approximate positions of the chief areas of predominant elevation and depression during stated periods of the past may have been ascertained in a general way; but when we try to indicate these upon a map, such provisional reconstructions are apt to suggest a more precise and definite knowledge than is at present attainable. For it must be confessed that there is hardly a line upon the small maps (A, B, C) which might not have been drawn differently. This, of course, is more especially true of South America, Africa, Asia--of large areas of which the geological structure is unknown. But although the boundaries of the land-masses shown upon the maps referred to are thus confessedly provisional, the maps nevertheless bring out the main fact of a gradual growth and consolidation of the land-areas--a passage from insular to continental conditions. I need hardly say this is no novel idea. It was clearly set forth by Professor Dana upwards of forty years ago (_Silliman's Journal_, 1846, p. 352; 1847, pp. 176, 381), and it received some years later further illustration from Professor Guyot, who insisted upon the insular character of the climate during Palæozoic times (_The Earth and Man_, 1850). It must be understood that the maps (A, B, C) are not meant to exhibit the geographical conditions of the world at any one point of time. In Map A, for example, the area coloured blue was not necessarily covered by sea at any particular stage in the Palæozoic era. It simply represents approximately the regions tended. But, as already stated, numerous oscillations of level occurred in Palæozoic times, so that many changes in the distribution of land and water must have taken place down to the close of the Permian period. The land-areas shown upon the map are simply those which appear to have been more or less persistent through all the geographical changes referred to. Similar remarks apply to the other maps representing the more or less persistent land-areas of Mesozoic and Tertiary times. Thus, for example, there are reasons for believing that Madagascar was joined to the mainland of Africa at some stage of the Mesozoic era, but was subsequently insulated before Tertiary times. Again, as Mesozoic era a land-connection obtained between New Zealand and Australia. The same naturalist also points out that a chain of islands, now represented by numerous islets and shoals, served in Tertiary times to link Madagascar to India. Map D shows the areas of predominant elevation and depression. The area coloured brown represents the great continental plateau, which extends downwards to 1000 fathoms or so below the present sea-level. The area tinted blue is the oceanic depression. From the present distribution of plants and animals, we infer that considerable tracts which are now submerged have formerly been dry land--some of these changes having taken place in very recent geological times. And the same conclusions are frequently suggested by geological evidence. There can be little doubt that Europe in Tertiary times extended further into the Northern Ocean than it does now. And it is quite possible that in the Mesozoic and Palæozoic eras considerable land-areas may likewise have appeared here and there in those northern regions which are at present under water. There is, indeed, hardly any portion of the continental plateau which is now submerged that may not have been land at some time or other. But after making all allowance for such possibilities, the geological evidence, as far as it goes, nevertheless leads to the conclusion that upon the whole a wider expense of primeval continental plateau has come to the surface since Tertiary times than was ever exposed during any former period of the world's history. [Mr. Marcou states (_American Geologist_, 1890, p. 229) that the idea of a gradual growth of land-areas originated with Elie de Beaumont, who was in the habit of showing such maps, and used them in his lectures at Paris as early as 1836. Professor Beudant published three of these same maps for the Jurassic, Cretaceous, and Tertiary seas in his _Cours élémentaire de Géologie_ (1841); and Professor Carl Vogt in his _Lehrbuch der Geologie und Petrefactenkunde_ (1845), which was confessedly based on Elie de Beaumont's lectures during 1844-46, gives four maps of the Carboniferous, Jurassic, Cretaceous, and Tertiary seas.] XIII. The Scientific Results of Dr. Nansen's Expedition.[DN] [DN] From _The Scottish Geographical Magazine_, 1891. In the Appendix to his most interesting and instructive work, _The First Crossing of Greenland_, Dr. Nansen treats of the scientific results of his remarkable journey. The detailed enumeration of these results, he tells us, would have been out of place in a general account of his expedition, but will appear in due time elsewhere. Hence he confines attention in his present work to such questions as are of most obvious interest, such as the extent, outward form, and elevation of the inland-ice of Greenland. By way of introduction his readers are presented with some account of the geological history of the country, which, although it contains nothing that was not already familiar to geologists, will doubtless prove interesting to others. After indicating that Greenland would appear to be composed almost exclusively of Archæan schists and granitoid eruptive rocks, the author glances at the evidence which the Mesozoic and Cainozoic strata of the west coast have supplied as to the former prevalence of genial climatic conditions. Heer is cited to show that during the formation of the Cretaceous beds the mean temperature of north Greenland was probably between 70° and 72° F., while in later Cainozoic times it could not have been less than 55° F., in 70° N.L. These conclusions are based on the character of the fossil floras. Now the mean annual temperature on the west coast of Greenland, where the relics of these old floras occur, is about 15° F., from which it is inferred that there has been a decrease of 40° since Cainozoic times. In those times, says Dr. Nansen, "the country must have rejoiced in a climate similar to that of Naples, while in the earlier Cretaceous period it must have resembled that of Egypt." He then refers to the well-known fact that, long after the deposition of the Cainozoic beds of Greenland, intensely arctic conditions supervened, when the inland-ice of that country extended much beyond its present limits. This was the Glacial period of geologists, during which all the northern regions of America and Europe, down to what are now temperate latitudes were likewise swathed in ice. Various hypotheses have been advanced in explanation of these strange climatic vicissitudes, and some of them are very briefly discussed by Dr. Nansen. None of the suggested solutions of the problem quite satisfies him; but he appears to look with most favour on the view that great climatic revolutions in what are now polar regions may have resulted from movements of the earth's axis. He admits, however, that there are certain strong objections to this hypothesis, and concludes that we have not yet got any satisfactory explanation to cover all the facts of the case. In discussing the question of a possible wandering of the pole, the author cites certain astronomical observations to show that the position of the axis is even now slowly changing, the movement amounting to half a second in six months. This is not much; but if the change, as he remarks, were to continue at the same rate for 3600 years, the shift would amount to one degree. Thus in a period of no more than 72,000 to 108,000 years Greenland might be brought into the latitude required for the growth of such floras as those of Cainozoic and Mesozoic times. Geologists will readily concede these or longer periods if they be required, but they will have graver doubts than Dr. Nansen as to whether any such great changes in the axis are possible. The astronomical observations referred to, even if they were fully confirmed, do not show that the movement is constant in one direction. They indicated, as he mentions, a slight increase of latitude during the first quarter of 1889, followed in the second quarter of the same year by a decrease, which continued to January, 1890. Since the publication of Professor George Darwin's masterly paper on the influence of geological changes on the earth's axis of rotation, geologists have felt assured that the great climatic revolutions to which the stratified rocks bear witness must be otherwise explained than by a wandering of the pole. Indeed, the geological evidence alone is enough to show that profound climatic changes have taken place while the pole has occupied its present position. Thus, there is no reasonable grounds for doubting that during the Glacial period the pole was just where we find it to-day. For, under existing geographical conditions, could a sufficient lowering of temperature be brought about, snow-fields and ice-sheets would gather and increase over the very same areas as we know were glaciated in Pleistocene times. Still further, we have only to recall the fact that several extreme revolutions of climate supervened during the so-called Glacial period, to see how impossible it is to account for the phenomena by movements of the earth's axis. If it be true that the great climatic changes of the Pleistocene period did not result from a wandering to and fro of the pole, then it is not at all likely that the Mesozoic and Cainozoic climates of Greenland were induced by any such movement. But does the geological evidence justify us in believing that the climates in Greenland during Cretaceous and Tertiary times really resembled those of Egypt and southern Italy? It may be strongly doubted if it does. Palæontologists, like other mortals, find it hard to escape the influence of environment. They are apt to project the actual present into the past, without, perhaps, fully considering how far they are justified in doing so. Because there occur in Cretaceous and Tertiary strata, within Arctic regions, certain assemblages of plants which find their nearest representatives in southern Italy and Egypt, surely it is rather rash to conclude that Greenland has experienced climates like those now characteristic of Mediterranean lands. All that the evidence really entitles us to assume is simply that the _winter temperature_ of Greenland was formerly much higher than it is now. That great caution is required in comparing past with present climatological conditions may be seen by glancing for a moment at the character of the flora which lived in Europe during the interglacial phase of the Pleistocene period. The plants of that period are for the most part living species, so that while dealing with these we are on safer ground than when we are treating of the floras of periods so far removed from us as those of Tertiary and Cretaceous times. Now, in the Pleistocene flora of Europe we find a strange commingling of species, such as we nowhere see to-day over any equally wide area of the earth's surface. During Pleistocene times many plants which are still indigenous to southern France flourished side by side in that area with species which are no longer seen in the same region; some of these last having retreated because unable to support the cold of winter, while others have retired to the mountains to escape the dryness of the summer. Similar evidence is forthcoming from the Pleistocene accumulations of Italy, northern France, and Germany. In a word, clement winters and relatively cool and humid summers permitted the wide diffusion and intimate association of plants which have now a very different distribution, temperate and southern species formerly flourishing together over vast areas of southern and central Europe. And similarly we find that during the same period the regions in question were tenanted by southern and temperate forms of animal life--elephants, rhinoceroses, and hippopotamuses, together with cervine, bovine, and other forms, not a few of which are still indigenous to our Continent--that ranged from the shores of the Mediterranean up to our own latitudes. We cannot doubt, indeed, that the present geographical distribution of plants and animals differs markedly from anything that has yet been disclosed by the researches of geologists. The climatic conditions of our day are exceptional as compared with those of earlier times, and the occurrence in Greenland of southern types of plants, therefore, does not justify us in concluding that climates like those of southern Italy and Egypt were ever characteristic of arctic regions. It is a low winter temperature rather than a want of great summer heat that restricts the range northward of southern floras. If Greenland could be divested of its inland-ice--if its winter temperature never fell below that of our own island--it would doubtless become clothed in time with an abundant temperate flora. Judging from what is known of the various floras and faunas that have successively clothed and peopled the world, from Palæozoic down to the close of Cainozoic times, the general climatic conditions of the globe, prior to the Glacial period, would seem to have been prevalently insular rather than continental as they are now. The lands appear to have been formerly much less continuous, and ocean currents from southern latitudes had consequently freer access to high northern regions than is at present possible. In no other way can we account for the facts connected with the geographical distribution and extent of the fossiliferous formations. But are we to infer, from the occurrence of similar assemblages of marine organic remains in arctic, temperate, and tropical latitudes, that the shores of primeval Greenland were washed by waters as warm as those of the tropics? Surely not: an absence of very cold water in the far north is all that we seem justified in assuming. And so, in like manner, the presence in Greenland of fossil floras having the same general facies as those that occur in the corresponding strata of more southern latitudes, does not compel us to believe that conditions at all similar to what are now met with in warm-temperate and sub-tropical lands ever obtained in arctic regions. A relatively high winter temperature alone would permit the range northward of many tribes of plants which are now restricted to southern latitudes. Yet, under the most uniform insular climatic conditions that we can conceive of, there must always have been differences due to latitude--although such differences were never apparently so marked as they are now. In order to appreciate the character of the climate which must have prevailed when the lands of the globe were much more interrupted and insular than at present, we have only to consider how greatly isothermal lines, even under existing continental conditions, are deflected by ocean-currents. In the North Atlantic, for example, the winter isotherm of 32° F. is deflected northward from the parallel of New York to that of Hammerfest--a displacement of at least 30° of latitude. The Arctic Sea now occupies a partially closed basin, into which only one considerable current enters from the south. But in earlier ages the case was otherwise, and there was often communication across what are now our continental areas. Instead of being girdled, as at present, by an almost continuous land-mass, the Arctic Sea seems to have formed with the circumjacent ocean one great archipelago. Thus freely open to the influx of southern currents, it is not difficult to believe that the seas of the far north might never be frozen, and that an "inland-ice" like that of Greenland would be impossible. The present cold summers of that country, as the late Dr. Croll has insisted, are due not so much to high latitude as to the presence of snow and ice. Could these be removed, the summers would be as warm at least as those of England. Now the occurrence in arctic regions of Palæozoic and Mesozoic marine faunas is strongly suggestive of the former presence there of genial waters having free communication with lower latitudes; and it is to the presence of these warm currents, flowing uninterruptedly through polar regions, that we would attribute the high winter temperature and uniform climate to which the fossil floras and faunas of Greenland bear testimony. If these views be at all reasonable, it seems unnecessary to call to our aid hypothetical changes in the position of the earth's axis. It may be admitted, however, that the climate of the Arctic regions must have been from time to time more or less affected by those cosmical causes to which Croll has appealed. So long, however, as insular conditions prevailed, the changes induced by a great increase in the eccentricity of the earth's orbit would not necessarily be strongly marked. Dr. Nansen objects to Croll's well-known theory that "it cannot account for the recurrence of conditions so favourable as to explain the existence in Greenland of a climate comparable to what we now find in tropical regions." No doubt it cannot, but, as we maintain, there is no good reason for supposing that tropical or sub-tropical climates ever characterised any area within the Arctic Circle. The remarkable association in Europe, during so recent a period as the Pleistocene, of southern and temperate species of plants and animals, ought to warn us against taking the present distribution of life-forms as an exact type of the kind of distribution which characterised earlier ages. It is safe to say that were our present continental areas to become broken up into groups of larger and smaller islands, so as to allow of a much less impeded oceanic circulation, the resulting climatic conditions would offer the strongest contrast to the present. And as the lands of the globe were apparently in former times more insular than they are now, it is hazardous to compare the climates of the present with those of the past. It is reasonable to infer, from the occurrence in Greenland of fossil floras which find their nearest representatives in southern Europe and north Africa, that the winters of the far north were formerly mild and clement. But we cannot conclude, from the same evidence, that the Arctic summers were ever as hot as those of our present warm-temperate and sub-tropical zones. But if the recent expedition has thrown no new light on the disputed question as to the cause of the high temperature which formerly prevailed in Greenland, it is needless to say that it has added considerably to our knowledge of the present physical conditions of that country. The view held by many that Greenland must be wrapped in ice has been amply justified, and we can now no longer doubt that the inland-ice covers the whole country from the 75th parallel southwards. A section of Greenland in the latitude at which it was crossed by Nansen and his comrades "gives an almost exact mathematical curve, approximating very closely to the arc of a circle described with a radius of about 6500 miles. The whole way across the surface coincides tolerably accurately with this arc, though it falls away somewhat abruptly at the coasts, and a little more abruptly on the east side than the west." Taking the observations of other Arctic travellers with his own, Nansen is led to the conclusion that "the surface of the inland-ice forms part of a remarkably regular cylinder, the radius of which nevertheless varies not a little at different latitudes, increasing markedly from the south, and consequently making the arc of the surface flatter and flatter as it advances northwards." He points out that this remarkable configuration must to a certain extent be independent of the form of the underlying land-surface, which, to judge from the character of the wild and mountainous coast-lands, probably resembles Norway in its general configuration--if, indeed it be not a group of mountainous islands. The buried interior of Greenland must in fact be a region of high mountains and deep valleys, all of which have totally disappeared under the enveloping _mer de glace_. It is obvious, as Dr. Nansen remarks, that the minor irregularities of the land "have had no influence whatever upon the form of the upper surface of the ice-sheet." That surface-form has simply been determined by the force of pressure--the quasi-viscous mass attaining its maximum thickness towards the central line of the country, where resistance to the movement due to pressure must necessarily have been greatest. Thus although the larger features of the ice-drowned land may have had some influence in determining the position of the ice-shed, it is not by any means certain that this central line coincides with the dominant ridge or watershed of the land itself. For, as Nansen reminds us, the ice-shed of the Scandinavian inland-ice of glacial times certainly lay about 100 miles to the east of the main water-parting of Norway and Sweden. Similar facts, we may add, have been noticed in connection with the old ice-sheets of Scotland and Ireland. The greatest elevation attained by the expedition was 9000 feet. How deeply buried the dominating parts of the land-surface may be at that elevation one cannot tell. It is obvious, however, that the _mer de glace_ must be very unequal in thickness. According to Dr. Nansen the average elevation of the valleys in the interior cannot much exceed 2300 or 3300 feet, so that the ice lying above such depressions must have a thickness of 5700 to 6700 feet. It cannot, of course, lie so deeply over mountain-ridges. The eroding power of such a glacier-mass must be enormous, and Dr. Nansen does not doubt that the buried valleys of Greenland are being widened and deepened by the grinding of the great ice-streams that are ever advancing towards the sea. The expedition met with no streams of surface-water on the inland-ice; indeed, the amount of superficial melting in the interior was quite insignificant. And yet, as is well known, many considerable streams and rivers flow out from underneath the inland-ice all the year round. It is obvious, therefore, that this water-supply does not come from superficial sources, as, according to Dr. Nansen, it is usually supposed to do. But surely it has long been recognised that such rivers as the Mary Minturn must be derived from sub-glacial melting. And the various causes to which our author attributes this melting have already frequently been pointed out. Earth-heat--the influence of pressure in lowering the melting-point of ice--and the friction induced by the movement of the ice itself have all long ago been recognised as factors tending to produce the sub-glacial water-drainage of an ice-sheet. Dr. Nansen's speculations on the origin of the "drumlins" and "kames" of formerly glaciated areas will interest geologists, but are not so novel as he supposes. His description of what are known as "drumlins" is not quite correct. These long lenticular banks cannot be said to lie upon boulder-clay, but are merely a structural form of that accumulation. And it is hardly the case that geologists have "performed the most acrobatic feats" in trying to explain the origin of the banks in question. The usual explanation is that they have been formed underneath the ice as ground-moraine--the upper surface of which varies in configuration--being sometimes approximately even, as in broad mountain-valleys; at other times ridged and corrugated, as in open lowlands. And these modifications of surface are supposed to have resulted from the varying movement and pressure of the overlying ice-sheet. The drumlins, in fact, would appear to be analogous to the banks that accumulate in the beds of rivers. Many drumlins, indeed, are composed partly of solid rock and partly of boulder-clay, which would seem to have accumulated in the lee of the projecting rock, much in the same way as gravel and sand gather behind any large boulder in a stream-course. Dr. Nansen, apparently, to some extent confounds drumlins with "kames" and "åsar," of which certainly many strange and conflicting explanations have been hazarded. These, however, differ essentially from drumlins, for they consist exclusively, or almost exclusively, of water-worn and more or less water-assorted materials. And one widely-accepted view of their origin is that they have accumulated in tunnels underneath an ice-sheet. This is practically the same view as Dr. Nansen's. He thinks that when an ice-sheet has its under-surface furrowed by running water, the ground-moraine will tend to be pressed up into the river-channels. The water will, in this way, be compelled to hollow out the roof of its tunnel to a greater degree, and as the stream continues to work upwards the moraine will follow it, so as to partially fill the tunnel and form a ridge along the back of which the sub-glacial stream will run. The material forming the upper portion of the ridge will thus come to be composed mainly of water-worn and stratified detritus, derived from the erosion of the ground-moraine. This is an ingenious suggestion which may be of good service in some cases, but it is certainly inapplicable to most kames and åsar. If it were a complete explanation we ought to find these ridges consisting of an upper water-assorted portion and a lower unmodified morainic portion (boulder-clay). But this is not the case, for most kames consist entirely, from top to bottom, of water-assorted materials. They are found running across an even or gently-undulating surface of boulder-clay, and sometimes they rest not on boulder-clay but solid rock. Dr. Nansen considers another geological question which has given rise to much controversy, and is still far from being settled--namely, whether the oscillations of level which have left such conspicuous traces in northern regions are in any way connected with the appearance and disappearance of great ice-sheets. Can a big ice-sheet push down the earth's crust by its weight? and does the crust rise again as the ice melts away? Could a thick ice-sheet exercise sufficient attraction upon the sea to cause it to rise upon the land, and thus explain the origin of some of the so-called raised beaches of this and other formerly glaciated lands? Can the weight of a great ice-sheet shift the earth's centre of gravity, and, if so, to what extent? Each of these questions has been answered in the affirmative and the negative by controversialists, and, until the geological evidence has been completely sifted, each, doubtless, will continue to be alternately affirmed and denied. All that need be pointed out here is that some of the movements which occurred during the Pleistocene period were on much too large a scale to be explicable by any of the hypotheses referred to. XIV. The Geographical Development of Coast-lines.[DO] [DO] Presidential Address to the Geographical Section of the British Association, Edinburgh, 1892. Amongst the many questions upon which of late years light has been thrown by deep-sea exploration and geological research, not the least interesting is that of the geographical development of coast-lines. How is the existing distribution of land and water to be accounted for? Are the revolutions in the relative position of land and sea, to which the geological record bears witness, due to movements of the earth's crust or of the hydrosphere? Why are coast-lines in some regions extremely regular, while elsewhere they are much indented? About 150 years ago the prevalent belief was that ancient sea-margins indicated a formerly higher ocean-level. Such was the view held by Celsius, who, from an examination of the coast-lands of Sweden, attributed the retreat of the sea to a gradual drying up of the latter. But this desiccation hypothesis was not accepted by Playfair, who thought it much more likely that the land had risen. It was not, however, until after Von Buch had visited Sweden (1806-1808), and published the results of his observations, that Playfair's suggestion received much consideration. Von Buch concluded that the apparent retreat of the sea was not due to a general depression of the ocean-level, but to elevation of the land--a conclusion which subsequently obtained the strong support of Lyell. The authority of these celebrated men gained for the elevation theory more or less complete assent, and for many years it has been the orthodox belief of geologists that the ancient sea-margins of Sweden and other lands have resulted from vertical movements of the crust. It has long been admitted, however, that highly-flexed and disturbed strata require some other explanation. Obviously such structures are the result of lateral compression and crumpling. Hence geologists have maintained that the mysterious subterranean forces have affected the crust in different ways. Mountain-ranges, they conceive, are ridged up by tangential thrusts and compression, while vast continental areas slowly rise and fall, with little or no disturbance of the strata. From this point of view it is the lithosphere that is unstable, all changes in the relative level of land and sea being due to crustal movements. Of late years, however, Trautschold and others have begun to doubt whether this theory is wholly true, and to maintain that the sea-level may have changed without reference to movements of the lithosphere. Thus Hilber has suggested that sinking of the sea-level may be due, in part at least, to absorption, while Schmick believes that the apparent elevation and depression of continental areas are really the results of grand secular movements of the ocean. The sea, according to him, periodically attains a high level in each hemisphere alternately, the waters being at present heaped up in the southern hemisphere. Professor Suess, again, believing that in equatorial regions the sea is, on the whole, gaining on the land, while in other latitudes the reverse would appear to be the case, points out this is in harmony with his view of a periodical flux and reflux of the ocean between the equator and the poles. He thinks we have no evidence of any vertical elevation affecting wide areas, and that the only movements of elevation that take place are those by which mountains are upheaved. The broad invasions and transgressions of the continental areas by the sea, which we know have occurred again and again, are attributed by him to secular movements of the hydrosphere itself. Apart from all hypothesis and theory, we learn that the surface of the sea is not exactly spheroidal. It reaches a higher level on the borders of the continents than in mid-ocean, and it varies likewise in height at different places on the same coast. The attraction of the Himalaya, for example, suffices to cause a difference of 300 feet between the level of the sea at the delta of the Indus and on the coast of Ceylon. The recognition of such facts has led Penck to suggest that the submergence of the maritime regions of north-west Europe and the opposite coasts of North America, which took place at a recent geological date, and from which the lands in question have only partially recovered, may have been brought about by the attraction exerted by the vast ice-sheets of the Glacial period. But, as Drygalski, Woodward, and others have shown, the heights at which recent marine deposits occur in the regions referred to are much too great to be accounted for by any possible distortion of the hydrosphere. The late James Croll had previously endeavoured to show that the accumulation of ice over northern lands during glacial times would suffice to displace the earth's centre of gravity, and thus cause the sea to rise upon the glaciated tracts. More recently other views have been advanced to explain the apparently causal connection between glaciation and submergence, but these need not be considered here. Whatever degree of importance may attach to the various hypotheses of secular movements of the sea, it is obvious that the general trends of the world's coast-lines are determined in the first place by the position of the dominant wrinkles of the lithosphere. Even if we concede that all "raised beaches," so-called, are not necessarily the result of earth-movements, and that the frequent transgressions of the continental areas by oceanic waters in geological times may possibly have been due to independent movements of the sea, still we must admit that the solid crust of the globe has always been subject to distortion. And this being so, we cannot doubt that the general trends of the world's coast-lines must have been modified from time to time by movements of the lithosphere. As geographers we are not immediately concerned with the mode of origin of those vast wrinkles, nor need we speculate on the causes which may have determined their direction. It seems, however, to be the general opinion that the configuration of the lithosphere is due simply to the sinking-in and doubling-up of the crust on the cooling and contracting nucleus. But it must be admitted that neither physicists nor geologists are prepared with a satisfactory hypothesis to account for the prominent trends of the great world-ridges and troughs. According to the late Professor Alexander Winchell, these trends may have been the result of primitive tidal action. He was of opinion that the transmeridional progress of the tidal swell in early incrustive times on our planet would give the forming crust structural characteristics and aptitudes trending from north to south. The earliest wrinkles to come into existence, therefore, would be meridional or submeridional, and such, certainly, is the prevalent direction of the most conspicuous earth-features. There are many terrestrial trends, however, as Professor Winchell knew, which do not conform to the requirements of his hypothesis; but such transmeridional features, he thought, could generally be shown to be of later origin than the others. This is the only speculation, so far as I know, which attempts, perhaps not altogether unsuccessfully, to explain the origin of the main trends of terrestrial features. According to other authorities, however, the area of the earth's crust occupied by the ocean is denser than that over which the continental regions are spread. The depressed denser part balances the lighter elevated portion. But why these regions of different densities should be so distributed no one has yet told us. Neither does Le Conte's view, that the continental areas and the oceanic depressions owe their origin to unequal radial contraction of the earth in its secular cooling, help us to understand why the larger features of the globe should be disposed as they are. Geographers must for the present be content to take the world as they find it. What we do know is that our lands are distributed over the surface of a great continental plateau of irregular form, the bounding slopes of which plunge down more or less steeply into a vast oceanic depression. So far as geological research has gone, there is reason to believe that these elevated and depressed areas are of primeval antiquity--that they ante-date the very oldest of the sedimentary formations. There is abundant evidence, however, to show that the relatively elevated or continental area has been again and again irregularly submerged under tolerably deep and wide seas. But all historical geology seems to assure us that the continental plateau and the oceanic hollows have never changed places, although from time to time portions of the latter have been ridged up and added to the margins of the former, while ever and anon marginal portions of the plateau have sunk to very considerable depths. We may thus speak of the great world-ridges as regions of dominant elevation, and of the profound oceanic troughs as areas of more or less persistent depression. From one point of view, it is true, no part of the earth's surface can be looked upon as a region of dominant elevation. Our globe is a cooling and contracting body, and depression must always be the prevailing movement of the lithosphere. The elevation of the continental plateau is thus only relative. Could we conceive the crust throughout the deeper portions of the oceanic depression to subside to still greater depths, while at the same time the continental plateau remained stationary, or subsided more slowly, the sea would necessarily retreat from the land, and the latter would then appear to rise. It is improbable, however, that any extensive subsidence of the crust under the ocean could take place without accompanying disturbance of the continental plateau; and in this case the latter might experience in places not only negative but positive elevation. During the evolution of our continents, crustal movements have again and again disturbed the relative level of land and sea; but since the general result has been to increase the land-surface and to contract the area occupied by the sea, it is convenient to speak of the former as the region of dominant elevation, and of the latter as that of prevalent depression. Properly speaking, both are sinking regions, the rate of subsidence within the oceanic trough being in excess of that experienced over the continental plateau. The question of the geographical development of coast-lines is therefore only that of the dry lands themselves. The greater land-masses are all situated upon, but are nowhere co-extensive with, the area of dominant elevation, for very considerable portions of the continental plateau are still covered by the sea. Opinions may differ as to which fathoms-line we should take as marking approximately the boundary between that region and the oceanic depression; and it is obvious, indeed, that any line selected must be arbitrary and more or less misleading, for it is quite certain that the true boundary of the continental plateau cannot lie parallel to the surface of the ocean. In some regions it approaches within a few hundreds of fathoms of the sea-level; in other places it sinks for considerably more than 1000 fathoms below that level. Thus, while a very moderate elevation would in certain latitudes cause the land to extend to the edge of the plateau, an elevation of at least 10,000 feet would be required in some other places to bring about a similar result. Although it is true that the land-surface is nowhere co-extensive with the great plateau, yet the existing coast-lines may be said to trend in the same general direction as its margins. So abruptly does the continental plateau rise from the oceanic trough, that a depression of the sea-level, or an elevation of the plateau, for 10,000 feet, would add only a narrow belt to the Pacific coast between Alaska and Cape Horn, while the gain of land on the Atlantic slope of America between 30° N.L. and 40° S.L. would not be much greater. In the higher latitudes of the northern hemisphere, however, very considerable geographical changes would be accomplished by a much less amount of elevation of the plateau. Were the continental plateau to be upheaved for 3000 feet, the major portion of the Arctic Sea would become land. Thus, in general terms, we may say that the coast-lines of arctic and temperate North America and Eurasia are further withdrawn from the edge of the continental plateau than those of lower latitudes. In regions where existing coast-lines approach the margin of the plateau, they are apt to run for long distances in one determinate direction, and, whether the coastal area be high or not, to show a gentle sinuosity. Their course is seldom interrupted by bold projecting headlands or peninsulas, or by intruding inlets, while fringing or marginal islands rarely occur. To these appearances the northern regions, as every one knows, offer the strongest contrast. Not only do they trend irregularly, but their continuity is constantly interrupted by promontories and peninsulas, by inlets and fiords, while fringing islands abound. But an elevation of some 400 or 500 fathoms only would revolutionise the geography of those regions, and confer upon the northern coast-lines of the world the regularity which at present characterises those of western Africa. It is obvious, therefore, that the coast-lines of such lands as Africa owe their regularity primarily to their approximate coincidence with the steep boundary-slopes of the continental plateau, while the irregularities characteristic of the coast-line of north-western Europe and the corresponding latitudes of North America are determined by the superficial configuration of the same plateau, which in those regions is relatively more depressed. I have spoken of the general contrast between high and low northern latitudes; but it is needless to say that in southern regions the coast-lines exhibit similar contrasts. The regular coast-lines of Africa and South America have already been referred to; but we cannot fail to recognise in the much-indented sea-board and the numerous coastal islands of southern Chile a complete analogy to the fiord regions of high northern latitudes. Both are areas of comparatively recent depression. Again, the manifold irregularities of the coasts of south-eastern Asia, and the multitudes of islands that serve to link that continent to Australia and New Zealand, are all evidence that the surface of the continental plateau in those regions is extensively invaded by the sea. A word or two now as to the configuration of the oceanic trough. There can be no doubt that this differs very considerably from that of the land-surface. It is, upon the whole, flat or gently-undulating. Here and there it swells gently upwards into broad elevated banks, some of which have been traced for great distances. In other places narrower ridges and abrupt mountain-like elevations diversify its surface, and project again and again above the level of the sea, to form the numerous islets of Oceania. Once more, the sounding-line has made us acquainted with the notable fact that numerous deep depressions--some long and narrow, others relatively short and broad--stud the floor of the great trough. I shall have occasion to refer again to these remarkable depressions, and need at present only call attention to the fact that they are especially well-developed in the region of the western Pacific, where the floor of the sea, at the base of the bounding slopes of the continental plateau, sinks in places to depths of three and even of five miles below the existing coast-lines. One may further note the fact that the deepest areas of the Atlantic are met with in like manner close to the walls of the plateau--a long ridge, which rises midway between the continents and runs in the same general direction as their coast-lines, serving to divide the trough of the Atlantic into two parallel hollows. But, to return to our coast-lines and the question of their development, it is obvious that their general trends have been determined by crustal movements. Their regularity is in direct proportion to the closeness of their approach to the margin of the continental plateau. The more nearly they coincide with the edge of that plateau, the fewer irregularities do they present; the further they recede from it, the more highly are they indented. Various other factors, it is true, have played a more or less important part in their development, but their dominant trends were undoubtedly determined at a very early period in the world's history--their determination necessarily dates back, in short, to the time when the great world-ridges and oceanic troughs came into existence. So far as we can read the story told by the rocks, however, it would seem that in the earliest ages of which geology can speak with any confidence, the coast-lines of the world must have been infinitely more irregular than now. In Palæozoic times, relatively small areas of the continental plateau appeared above the level of the sea. Insular conditions everywhere prevailed. But as ages rolled on, wider and wider tracts of the plateau were exposed, and this notwithstanding many oscillations of level. So that one may say there has been, upon the whole, a general advance from insular to continental conditions. In other words, the sea has continued to retreat from the surface of the continental plateau. To account for this change, we must suppose that depression of the crust has been in excess within the oceanic area, and that now and again positive elevation of the continental plateau has taken place, more especially along its margins. That movements of elevation, positive or negative, have again and again affected our land-areas can be demonstrated, and it seems highly probable, therefore, that similar movements may have been experienced within the oceanic trough. Two kinds of crustal movement, as we have seen, are recognised by geologists. Sometimes the crust appears to rise, or, as the case may be, to sink over wide regions, without much disturbance or tilting of strata, although these are now and again more or less extensively fractured and displaced. It may conduce to clearness if we speak of these movements as regional. The other kind of crustal disturbance takes place more markedly in linear directions, and is always accompanied by abrupt folding and mashing together of strata, along with more or less fracturing and displacement. The plateau of the Colorado has often been cited as a good example of regional elevation, where we have a wide area of approximately horizontal strata apparently uplifted without much rock-disturbance, while the Alps or any other chain of highly-flexed and convoluted strata will serve as an example of what we may term axial or linear uplifts. It must be understood that both regional and axial movements result from the same cause--the adjustment of the solid crust to the contracting nucleus--and that the term _elevation_, therefore, is only relative. Sometimes the sinking crust gets relief from the enormous lateral pressure to which it is subjected by crumpling up along lines of weakness, and then mountains of elevation are formed; at other times, the pressure is relieved by the formation of broader swellings, when wide areas become uplifted relatively to surrounding regions. Geologists, however, are beginning to doubt whether upheaval of the latter kind can affect a broad continental area. Probably, in most cases, the apparent elevation of continental regions is only negative. The land appears to have risen because the floor of the oceanic basin has become depressed. Even the smaller plateau-like elevations which occur within some continental regions may in a similar way owe their dominance to the sinking of contiguous regions. In the geographical development of our land, movements of elevation and depression have played an important part. But we cannot ignore the work done by other agents of change. If the orographical features of the land everywhere attest the potency of plutonic agents, they no less forcibly assure us that the inequalities of surface resulting from such movements are universally modified by denudation and sedimentation. Elevated plains and mountains are gradually demolished, and the hollows and depressions of the great continental plateau become slowly filled with their detritus. Thus inland-seas tend to vanish, inlets and estuaries are silted up, and the land in places advances seaward. The energies of the sea, again, come in to aid those of rain and rivers, so that under the combined action of all the superficial agents of change, the irregularities of coast-lines become reduced, and, were no crustal movement to intervene, would eventually disappear. The work accomplished by those agents upon a coast-line is most conspicuous in regions where the surface of the continental plateau is occupied by comparatively shallow seas. Here full play is given to sedimentation and marine erosion, while the latter alone comes into prominence upon shores that are washed by deeper waters. When the coast-lines advance to the edge of the continental plateau, they naturally trend, as we have seen, for great distances in some particular direction. Should they preserve that position, undisturbed by crustal oscillation, for a prolonged period of time, they will eventually be cut back by the sea. In this way a shelf or terrace will be formed, narrow in some places, broader in others, according to the resistance offered by the varying character of the rocks. But no long inlets or fiords can result from such action. At most the harder and less readily demolished rocks will form headlands, while shallow bays will be scooped out of the more yielding masses. In short, between the narrower and broader parts of the eroded shelf or terrace a certain proportion will tend to be preserved. As the shelf is widened, sedimentation will become more and more effective, and in places may come to protect the land from further marine erosion. This action is especially conspicuous in tropical and sub-tropical regions, which are characterised by well-marked rainy seasons. In such regions immense quantities of sediment are washed down from the land to the sea, and tend to accumulate along shore, forming low alluvial flats. All long-established coast-lines thus acquire a characteristically sinuous form, and perhaps no better examples could be cited than those of western Africa. To sum up, then, we may say that the chief agents concerned in the development of coast-lines are crustal movements, sedimentation, and marine erosion. All the main trends are the result of elevation and depression. Considerable geographical changes, however, have been brought about by the silting up of those shallow and sheltered seas which, in certain regions, overflow wide areas of the continental plateau. Throughout all the ages, indeed, epigene agents have striven to reduce the superficial inequalities of that plateau, by levelling heights and filling up depressions, and thus, as it were, flattening out the land-surface and causing it to extend. The erosive action of the sea, from our present point of view, is of comparatively little importance. It merely adds a few finishing touches to the work performed by the other agents of change. A glance at the geographical evolution of our own Continent will render this sufficiently evident. Viewed in detail, the structure of Europe is exceedingly complicated, but there are certain leading features in its architecture which no profound analysis is required to detect. We note, in the first place, that highly-disturbed rocks of Archæan and Palæozoic age reach their greatest development along the north-western and western borders of our Continent, as in Scandinavia, the British Islands, north-west France, and the Iberian peninsula. Another belt of similarly disturbed strata of like age traverses central Europe from west to east, and is seen in the south of Ireland, Cornwall, north-west France, the Ardennes, the Thüringer-Wald, the Erz Gebirge, the Riesen Gebirge, the Böhmer-Wald, and other heights of middle and southern Germany. Strata of Mesozoic and Cainozoic age rest upon the older systems in such a way as to show that the latter had been much folded, fractured, and denuded before they came to be covered with younger formations. North and north-east of the central belt of ancient rocks just referred to, the sedimentary strata that extend to the shores of the Baltic and over a vast region in Russia, range in age from Palæozoic down to Cainozoic times, and are disposed for the most part in gentle undulations--they are either approximately horizontal or slightly inclined. Unlike the disturbed rocks of the maritime regions and of central Europe, they have obviously been subjected to comparatively little folding since the time of their deposition. To the south of the primitive back-bone of central Europe succeeds a region composed superficially of Mesozoic and Cainozoic strata for the most part, which, along with underlying Palæozoic and Archæan rocks, are often highly-flexed and ridged up, as in the chains of the Jura, the Alps, the Carpathians, etc. One may say, in general terms, that throughout the whole Mediterranean area Archæan and Palæozoic rocks appear at the surface only when they form the nuclei of mountains of elevation, into the composition of which rocks of younger age largely enter. From this bald and meagre outline of the general geological structure of Europe, we may gather that the leading orographical features of our Continent began to be developed at a very early period. Unquestionably the oldest land-areas are represented by the disturbed Archæan and Palæozoic rocks of the Atlantic sea-board and central Europe. Examination of those tracts shows that they have experienced excessive denudation. The Archæan and Palæozoic masses, distributed along the margin of the Atlantic, are the mere wrecks of what, in earlier ages, must have been lofty regions, the mountain-chains of which may well have rivalled or even exceeded in height the Alps of to-day. They, together with the old disturbed rocks of central Europe, formed for a long time the only land in our area. Between the ancient Scandinavian tract in the north and a narrow interrupted belt in central Europe, stretched a shallow sea, which covered all the regions that now form our Great Plain; while immediately south of the central belt lay the wide depression of the Mediterranean--for as yet the Pyrenees, the Alps, and the Carpathians were not. Both the Mediterranean and the Russo-Germanic sea communicated with the Atlantic. As time went on land continued to be developed along the same lines, a result due partly to crustal movements, partly to sedimentation. Thus the relatively shallow Russo-Germanic sea became silted up, while the Mediterranean shore-line advanced southwards. It is interesting to note that the latter sea, down to the close of Tertiary times, seems always to have communicated freely with the Atlantic, and to have been relatively deep. The Russo-Germanic sea, on the contrary, while now and again opening widely into the Atlantic, and attaining considerable depths in its western reaches, remained on the whole shallow, and ever and anon vanished from wide areas to contract into a series of inland-seas and large salt lakes. Reduced to its simplest elements, therefore, the structure of Europe shows two primitive ridges--one extending with some interruptions along the Atlantic sea-board, the other traversing central Europe from west to east, and separating the area of the Great Plain from the Mediterranean basin. The excessive denudation which the more ancient lands have undergone, and the great uplifts of Mesozoic and of Cainozoic times, together with the comparatively recent submergence of broad tracts in the north and north-west, have not succeeded in obscuring the dominant features in the architecture of our Continent. I now proceed to trace, as rapidly as I can, the geographical development of the coast-lines of the Atlantic as a whole, and to point out the chief contrasts between them and the coast-lines of the Pacific. The extreme irregularity of the Arctic and Atlantic shores of Europe at once suggests to a geologist a partially-drowned land, the superficial inequalities of which are accountable for the vagaries of the coast-lines. The fiords of Norway and Scotland occupy what were at no distant date land-valleys, and the numerous marginal islands of those regions are merely the projecting portions of a recently-sunken area. The continental plateau extends up to and a little beyond the one hundred fathoms line, and there are many indications that the land formerly reached as far. Thus the sunken area is traversed by valley-like depressions, which widen as they pass outwards to the edge of the plateau, and have all the appearance of being hollows of sub-aërial erosion. I have already mentioned the fact that the Scandinavian uplands and the Scottish Highlands are the relics of what were at one time true mountains of elevation, corresponding in the mode of their formation to those of Switzerland, and, like these, attaining a great elevation. During subsequent stages of Palæozoic time, that highly-elevated region was subjected to long-continued and profound erosion--the mountain-country was planed down over wide regions to sea-level, and broad stretches of the reduced land-surface became submerged. Younger Palæozoic formations then accumulated upon the drowned land, until eventually renewed crustal disturbance supervened, and the marginal areas of the continental plateau again appeared as dry land, but not, as before, in the form of mountains of elevation. Lofty table-lands now took the place of abrupt and serrated ranges and chains--table-lands which, in their turn, were destined in the course of long ages to be deeply sculptured and furrowed by sub-aërial agents. During this process the European coast-line would seem to have coincided more or less closely with the edge of the continental plateau. Finally, after many subsequent movements of the crust in these latitudes, the land became partially submerged--a condition from which north-western and northern Europe would appear in recent times to be slowly recovering. Thus the highly-indented coast-line of those regions does not coincide with the edge of the plateau, but with those irregularities of its upper surface which are the result of antecedent sub-aërial erosion. Mention has been made of the Russo-Germanic plain and the Mediterranean as representing original depressions in the continental plateau, and of the high-grounds that extend between them as regions of dominant elevation, which, throughout all the manifold revolutions of the past, would appear to have persisted as a more or less well-marked boundary, separating the northern from the southern basin. During certain periods it was no doubt in some degree submerged, but never apparently to the same extent as the depressed areas it served to separate. From time to time uplifts continued to take place along this central belt, which thus increased in breadth, the younger formations, which were accumulated along the margins of the two basins, being successively ridged up against nuclei of older rocks. The latest great crustal movements in our Continent, resulting in the uplift of the Alps and other east and west ranges of similar age, have still further widened that ancient belt of dominant elevation which in our day forms the most marked orographical feature of Europe. The Russo-Germanic basin is now for the most part land, the Baltic and the North Sea representing its still submerged portions. This basin, as already remarked, was probably never so deep as that of the Mediterranean. We gather as much from the fact that, while mechanical sediments of comparatively shallow-water origin predominate in the former area, limestones are the characteristic features of the southern region. Its relative shallowness helps us to understand why the northern depression should have been silted up more completely than the Mediterranean. We must remember also that for long ages it received the drainage of a much more extensive land-surface than the latter--the land that sloped towards the Mediterranean in Palæozoic and Mesozoic times being of relatively little importance. Thus the crustal movements which ever and anon depressed the Russo-Germanic area were, in the long-run, counterbalanced by sedimentation. The uplift of the Alps, the Atlas, and other east and west ranges, has greatly contracted the area of the Mediterranean, and sedimentation has also acted in the same direction, but it is highly probable that that sea is now as deep as, or even deeper than, it has ever been. It occupies a primitive depression in which the rate of subsidence has exceeded that of sedimentation. In many respects, indeed, this remarkable transmeridional hollow--continued eastward in the Red Sea, the Black Sea, and the Aralo-Caspian depression--is analogous, as we shall see, to the great oceanic trough itself. In the earlier geological periods linear or axial uplifts and volcanic action again and again marked the growth of land on the Atlantic sea-board. But after Palæozoic times, no great mountains of elevation came into existence in that region, while volcanic action almost ceased. In Tertiary times, it is true, there was a remarkable recrudescence of volcanic activity, but the massive eruptions of Antrim and western Scotland, of the Faröe Islands and Iceland, must be considered apart from the general geology of our Continent. From Mesozoic times onwards it was along the borders of the Mediterranean depression that great mountain uplifts and volcanoes chiefly presented themselves; and as the land-surface extended southwards from central Europe, and the area of the Mediterranean was contracted, volcanic action followed the advancing shore-lines. The occurrence of numerous extinct and of still existing volcanoes along the borders of this inland-sea, the evidence of recent crustal movements so commonly met with upon its margins, the great irregularities of its depths, the proximity of vast axial uplifts of late geological age, and the frequency of earthquake phenomena, all indicate instability, and remind us strongly of similarly constructed and disturbed regions within the area of the vast Pacific. Let us now look at the Arctic and Atlantic coast-lines of North America. From the extreme north down to the latitude of New York the shores are obviously those of a partially-submerged region. They are of the same type as the coasts of north-western Europe. We have every reason to believe also that the depression of Greenland and north-east America, from which these lands have only partially recovered, dates back to a comparatively recent period. The fiords and inlets, like those of Europe, are merely half-drowned land-valleys, and the continental shelf is crossed by deep hollows which are evidently only the seaward continuations of well-marked terrestrial features. Such, for example, is the case with the valleys of the Hudson and the St. Lawrence, the submerged portions of which can be followed out to the edge of the continental plateau, which is notched by them at depths of 474 and 622 fathoms respectively. There is, in short, a broad resemblance between the coasts of the entire Arctic and North Atlantic regions down to the latitudes already mentioned. Everywhere they are irregular and fringed with islands in less or greater abundance--highly-denuded and deeply-incised plateaux being penetrated by fiords, while low-lying and undulating lands that shelve gently seaward are invaded by shallow bays and inlets. Comparing the American with the opposite European coasts one cannot help being struck with certain other resemblances. Thus Hudson Bay at once suggests the Baltic, and the Gulf of Mexico, with the Caribbean Sea, recalls the Mediterranean. But the geological structure of the coast-lands of Greenland and North America betrays a much closer resemblance between these and the opposite shores of Europe than appears on a glance at the map. There is something more than a mere superficial similarity. In eastern North America and Greenland, just as in western Europe, no grand mountain uplifts have taken place for a prodigious time. The latest great upheavals, which were accompanied by much folding and flexing of strata, are those of the Appalachian chain and of the coastal ranges extending through New England, Nova Scotia, and Newfoundland, all of which are of Palæozoic age. Considerable crustal movements affected the American coast-lines in Mesozoic times, and during these uplifts the strata suffered fracture and displacement, but were subjected to comparatively little folding. Again, along the maritime borders of north-east America, as in the corresponding coast-lines of Europe, igneous action, more or less abundant in Palæozoic and early Mesozoic times, has since been quiescent. From the mouth of the Hudson to the Straits of Florida the coast-lines are composed of Tertiary and Quaternary deposits. This shows that the land has continued down to recent times to gain upon the sea--a result brought about partly by quiet crustal movements, but to a large extent by sedimentation, aided, on the coasts of Florida, by the action of reef-building corals. Although volcanic action has long ceased on the American sea-board, we note that in Greenland, as in the west of Scotland and north of Ireland, there is abundant evidence of volcanic activity at so late a period as the Tertiary. It would appear that the great plateau-basalts of those regions, and of Iceland and the Faröe Islands, were contemporaneous, and were possibly connected with an important crustal movement. It has long been suggested that at a very early geological period Europe and North America may have been united. The great thickness attained by the Palæozoic rocks in the eastern areas of the latter implies the existence of a wide land-surface from which ancient sediments were derived. That old land must have extended beyond the existing coast-line, but how far we cannot tell. Similarly in north-west Europe, during early Palæozoic times, the land probably stretched further into the Atlantic than at present. But whether, as some think, an actual land-connection subsisted between the two continents it is impossible to say. Some such connection was formerly supposed necessary to account for life common to the Palæozoic strata of both continents, and which, as they were probably denizens of comparatively shallow water, could only have crossed from one area to another along a shore-line. It is obvious, indeed, that if the oceanic troughs in those early days were of an abysmal character, a belt of shallow water would be required to explain the geographical distribution of cosmopolitan marine life-forms. But if it be true that subsidence of the crust has been going on through all geological time, and that the land-areas have nothwithstanding continued to extend over the continental plateau, then it follows that the oceanic trough must be deeper now than it was in Palæozoic times. There are, moreover, certain geological facts which seem hardly explicable on the assumption that the seas of past ages attained abysmal depths over any extensive areas. The Palæozoic strata which enter so largely into the framework of our lands have much the same appearance all the world over, and were accumulated for the most part in comparatively shallow water. A petrographical description of the Palæozoic mechanical sediments of Europe would serve almost equally well for those of America, of Asia, or of Australia. Take in connection with this the fact that Palæozoic faunas had a very much wider range than those of Mesozoic and later ages, and were characterised above all by the presence of many cosmopolitan species, and we can hardly resist the conclusion that it was the comparative shallowness of the ancient seas that favoured that wide dispersal of species, and enabled currents to distribute sediments the same in kind over such vast regions. As the oceanic area deepened and contracted, and the land-surface increased, marine faunas were gradually restricted in their range, and the cosmopolitan marine forms diminished in numbers, while sediments, gathering in separate regions, became more and more differentiated. For these and other reasons which need not be entered upon here, I see no necessity for supposing that a Palæozoic Atlantis connected Europe with North America. The broad ridge upon which the Faröe Islands and Iceland are founded seems to pertain as truly to the oceanic depression as the long Dolphin Ridge of the South Atlantic. The trend of the continental plateau in high latitudes is shown, as I think, by the general direction of the coast-lines of north-western Europe and east Greenland, the continental shelf being submerged in those regions for a few hundred fathoms only. How the Icelandic ridge came into existence, and what its age may be, we can only conjecture. It may be a wrinkle as old as the oceanic trough which it traverses, or its origin may date back to a much more recent period. We may conceive it to be an area which has subsided more slowly than the floor of the ocean to the north and south; or, on the other hand, it may be a belt of positive elevation. Perhaps the latter is the more probable supposition, for it seems very unlikely that crustal disturbances, resulting in axial and regional uplifts, should have been confined to the continental plateau only. Be that as it may, there is little doubt that land-connection did obtain between Greenland and Europe in the Cainozoic times along this Icelandic ridge, for relics of the same Tertiary flora are found in Scotland, the Faröe Islands, Iceland, and Greenland. The deposits in which these plant-remains occur are associated with great sheets of volcanic rocks, which in the Faröe Islands and Iceland reach a thickness of many thousand feet. Of the same age are the massive basalts of Jan Mayen, Spitzbergen, Franz-Joseph Land, and Greenland. These lavas seem seldom to have issued from isolated foci in the manner of modern eruptions, but rather to have welled up along the lines of rectilineal fissures. From the analogy of similar phenomena in other parts of the world it might be inferred that the volcanic action of these northern regions may have been connected with a movement of elevation, and that the Icelandic ridge, if it did not come into existence during the Tertiary period, was at all events greatly upheaved at that time. It would seem most likely, in short, that the volcanic action in question was connected mainly with crustal movements in the oceanic trough. Similar phenomena, as is well known, are met with further south in the trough of the Atlantic. Thus the volcanic Azores rise like Iceland from the surface of a broad ridge which is separated from the continental plateau by wide and deep depressions. And so again, from the back of the great Dolphin Ridge, spring the volcanic islets of St. Paul's, Ascension, and Tristan d'Acunha. I have treated of the Icelandic bank at some length for the purpose of showing that its volcanic phenomena do not really form an exception to the rule that such eruptions ceased after Palæozoic or early Mesozoic times to disturb the Atlantic coast-lines of Europe and North America. As the bank in question extends between Greenland and the British Islands, it was only natural that both those regions should be affected by its movements. But its history pertains essentially to that of the Atlantic trough; and it seems to show us how transmeridional movements of the crust, accompanied by vast discharges of igneous rock, may come in time to form land-connections between what are now widely-separated areas. Let us next turn our attention to the coast-lines of the Gulf of Mexico and the Caribbean Sea. These enclosed seas have frequently been compared to the Mediterranean, and the resemblance is self-evident. Indeed, it is so close that one may say the Mexican-Caribbean Sea and the Mediterranean are rather homologous than simply analogous. The latter, as we have seen, occupies a primitive depression, and formerly covered a much wider area. It extended at one time over much of southern Europe and northern Africa, and appears to have had full communication across Asia Minor with the Indian Ocean, and with the Arctic Ocean athwart the low-lying tracts of north-western Asia. Similarly, it would seem, the Mexican-Caribbean Sea is the remaining portion of an ancient inland-sea which formerly stretched north through the heart of North America to the Arctic Ocean. Like its European parallel, it has been diminished by sedimentation and crustal movements. It resembles the latter also in the greatness and irregularity of its depths, and in the evidence which its islands supply of volcanic action as well as of very considerable crustal movements within recent geological times. Along the whole northern borders of the Gulf of Mexico the coast-lands, like those on the Atlantic sea-board of the Southern States, are composed of Tertiary and recent accumulations, and the same is the case with Yucatan; while similar young formations are met with on the borders of the Caribbean Sea and in the Antilles. The Bahamas and the Windward Islands mark out for us the margin of the continental plateau, which here falls away abruptly to profound depths. One feels assured that this portion of the plateau has been ridged up to its present level at no distant geological date. But notwithstanding all the evidence of recent extensive crustal movements in this region, it is obvious that the Mexican-Caribbean depression, however much it may have been subsequently modified, is of primitive origin.[DP] [DP] Professor Suess thinks it is probable that the Caribbean Sea and the Mediterranean are portions of one and the same primitive depression which traversed the Atlantic area in early Cretaceous times. He further suggests that it may have been through the gradual widening of the central Mediterranean that the Atlantic in later times came into existence. Before we leave the coast-lands of North America, I would again point out their leading geological features. In a word, then, they are composed for the most part of Archæan and Palæozoic rocks; no great linear or axial uplifts marked by much flexure of strata have taken place in those regions since Palæozoic times; while igneous action virtually ceased about the close of the Palæozoic or the commencement of the Mesozoic period. It is not before we reach the shores of the Southern States and the coast-lands of the Mexican-Caribbean Sea that we encounter notable accumulations of Mesozoic, Tertiary, and younger age. These occur in approximately horizontal positions round the Gulf of Mexico; but in the Sierra Nevada of northern Colombia and the Cordilleras of Venezuela the Tertiary strata enter into the formation of true mountains of elevation. Thus the Mexican-Caribbean depression, like that of the Mediterranean, is characterised not only by its irregular depths and its volcanic phenomena, but by the propinquity of recent mountains of upheaval, which bear the same relation to the Caribbean Sea as the mountains of north Africa do to the Mediterranean. We may now compare the Atlantic coasts of South America with those of Africa. The former coincide in general direction with the edge of the continental plateau, to which they closely approach between Cape St. Roque and Cape Frio. In the north-east, between Cape Paria, opposite Trinidad, and Cape St. Roque, the continental shelf attains a considerably greater breadth, while south of Cape Frio it gradually widens until, in the extreme south, it runs out towards the east in the form of a narrow ridge, upon the top of which rise the Falkland Islands and south Georgia. Excluding from consideration for the present all recent alluvial and Tertiary deposits, we may say that the coast-lands from Venezuela down to the south of Brazil are composed principally of Archæan rocks; the eastern borders of the continent further south being formed of Quaternary and Tertiary accumulations. So far as we know, igneous rocks are of rare occurrence on the Atlantic sea-board. Palæozoic strata approach the coast-lands at various points between the mouths of the Amazons and La Plata, and these, with the underlying and surrounding Archæan rocks, are more or less folded and disturbed, while the younger strata of Mesozoic and Cainozoic age (occupying wide regions in the basin of the Amazons, and here and there fringing the sea-coast) occur in approximately horizontal positions. It would appear, therefore, that no great axial uplifts have taken place in those regions since Palæozoic times. The crustal movements of later ages were regional rather than axial; the younger rocks are not flexed and mashed together, and their elevation (negative or positive) does not seem to have been accompanied by conspicuous volcanic action. The varying width of the continental shelf is due to several causes. The Orinoco, the Amazons, and other rivers descending to the north-east coast, carry enormous quantities of sediment, much of which comes to rest on the submerged slopes of the continental plateau, so that the continental shelf tends to extend seawards. The same process takes place on the south-east coast, where the Rio de la Plata discharges its muddy waters. South of latitude 40° S., however, another cause has come into play. From the mouth of the Rio Negro to the terminal point of the continent the whole character of the coast betokens a geologically recent emergence, accompanied and followed by considerable marine erosion. So that in this region the continental shelf increases in width by the retreat of the coast-line, while in the north-east it gains by advancing seawards. It is to be noted, however, that even there, in places where the shores are formed of alluvia, the sea tends to encroach upon the land. The Atlantic coast of Africa resembles that of South America in certain respects, but it also offers some important contrasts. As the northern coasts of Venezuela and Colombia must be considered in relation rather to the Caribbean depression than to the Atlantic, so the African sea-board between Cape Spartel and Cape Nun pertains structurally to the Mediterranean region. From the southern limits of Morocco to Cape Colony the coastal heights are composed chiefly of Archæan and Palæozoic rocks, the low shore-lands showing here and there strata of Mesozoic and Tertiary age together with still more recent deposits. The existing coast-lines everywhere advance close to the edge of the continental plateau, so that the submarine shelf is relatively narrower than that of eastern South America. The African coast is still further distinguished from that of South America by the presence of several groups of volcanic islands--Fernando Po and others in the Gulf of Guinea, and Cape Verde and Canary Islands. The last-named group, however, notwithstanding its geographical position, is probably related rather to the Mediterranean depression than to the Atlantic trough. The geological structure of the African coast-lands shows that the earliest to come into existence were those that extend between Cape Nun and the Cape of Good Hope. The coastal ranges of that section are much denuded, for they are of very great antiquity, having been ridged up in Palæozoic times. The later uplifts (negative or positive) of the same region were not attended by tilting and folding of strata, for the Mesozoic and Tertiary deposits, like those of South America, lie in comparatively horizontal positions. Between Cape Nun and Cape Spartel the rocks of the maritime tracts range in age from Palæozoic to Cainozoic, and have been traced across Morocco into Algeria and Tunis. They all belong to the Mediterranean region, and were deposited at a time when the southern shores of that inland sea extended from a point opposite the Canary Islands along what is now the southern margin of Morocco, Algeria, and Tunis. Towards the close of the Tertiary period the final upheaval of the Atlas took place, and the Mediterranean, retreating northwards, became an almost land-locked sea. I need hardly stop to point out how the African coast-lines have been modified by marine erosion and the accumulation of sediment upon the continental shelf. The extreme regularity of the coasts is due partly to the fact that the land is nearly co-extensive with the continental plateau, but it also results in large measure from the extreme antiquity of the land itself. This has allowed of the cutting-back of headlands and the rilling up of bays and inlets, a process which has been going on between Morocco and Cape Colony with probably little interruption for a very prolonged period of time. We may note also the effect of the heavy rains of the equatorial region in washing down detritus to the shores, and in this way protecting the land to some extent from the erosive action of the sea. What now, let us ask, are the outstanding features of the coast-lines of the Atlantic Ocean? We have seen that along the margins of each of the bordering continents the last series of great mountain-uplifts took place in Palæozoic times. This is true alike for North and South America, for Europe and Africa. Later movements which have added to the extent of land were not marked by the extreme folding of strata which attended the early upheavals. The Mesozoic and Cainozoic rocks, which now and again form the shore-lands, occur in more or less undisturbed condition. The only great linear uplifts or true mountains of elevation which have come into existence in western Europe and northern Africa since the Palæozoic period trend approximately at right angles to the direction of the Atlantic trough, and are obviously related to the primitive depression of the Mediterranean. The Pyrenees and the Atlas, therefore, although their latest elevation took place in Tertiary times, form no exceptions to the rule that the extreme flexing and folding of strata which is so conspicuous a feature in the geological structure of the Atlantic sea-board dates back to the Palæozoic era. And the same holds true of North and South America. There all the coastal ranges of highly flexed and folded strata are of Palæozoic age. The Cordilleras of Venezuela are no doubt a Tertiary uplift, but they are as obviously related to the Caribbean depression as the Atlas ranges are to that of the Mediterranean. Again, we note that volcanic activity along the borders of the Atlantic was much less pronounced during the Mesozoic period than it appears to have been in the earlier ages. Indeed, if we except the great Tertiary basalt-flows of the Icelandic ridge and the Arctic regions, we may say that volcanic action almost ceased after the Palæozoic era to manifest itself upon the Atlantic coast-lands of North America and Europe. But while volcanic action has died out upon the Atlantic margins of both continents, it has continued during a prolonged geological period within the area of the Mediterranean depression. And in like manner the corresponding depression between North and South America has been the scene of volcanic disturbances from Mesozoic down to recent times. Along the African coasts the only displays of recent volcanic action that appertain to the continental margin are those of the Gulf of Guinea and the Cape de Verde Islands. The Canary Islands and Madeira may come under the same category, but, as we have seen, they appear to stand in relationship to the Mediterranean depression and the Tertiary uplift of North Africa. Of Iceland and the Azores I have already spoken, and of Ascension and the other volcanic islets of the South Atlantic it is needless to say that they are related to wrinkles in the trough of the ocean, and therefore have no immediate connection with the continental plateau. Thus in the geographical development of the Atlantic coast-lines we may note the following stages:--_First_, in Palæozoic times the formation of great mountain-uplifts, frequently accompanied by volcanic action. _Second_, a prolonged stage of comparative coastal tranquillity, during which the maritime ranges referred to were subject to such excessive erosion that they were planed down to low levels, and in certain areas even submerged. _Third_, renewed elevation (negative or positive) whereby considerable portions of the much-denuded Archæan and Palæozoic rocks, now largely covered by younger deposits, were converted into high-lands. During this stage not much rock-folding took place, nor were any true mountains of elevation formed parallel to the Atlantic margins. It was otherwise, however, in the Mediterranean and Caribbean depressions, where coastal movements resulted in the formation of enormous linear uplifts. Moreover, volcanic action is now and has for a long time been more characteristic of these depressions than of the Atlantic coast-lands. I must now ask you to take a comprehensive glance at the coast-lines of the Pacific Ocean. In some important respects these offer a striking contrast to those we have been considering. Time will not allow me to enter into detailed description, and I must therefore confine attention to certain salient features. Examining first the shores of the Americas, we find that there are two well-marked regions of fiords and fringing islands--namely, the coasts of Alaska and British Columbia, and of South America from 40° S.L. to Cape Horn. Although these regions may be now extending seawards in places, it is obvious that they have recently been subject to submergence. When the fiords of Alaska and British Columbia existed as land-valleys it is probable that a broad land-connection obtained between North America and Asia. The whole Pacific coast is margined by mountain-ranges, which in elevation and boldness far exceed those of the Atlantic sea-board. The rocks entering into their formation range in age from Archæan and Palæozoic down to Cainozoic, and they are almost everywhere highly disturbed and flexed. It is not necessary, even if it were possible, to consider the geological history of all those uplifted masses. It is enough for my purpose to note the fact that the coastal ranges of North America and the principal chain of the Andes were all elevated in Tertiary times. It may be remarked further that, from the Mesozoic period down to the present, the Pacific borders of America have been the scene of volcanic activity far in excess of what has been experienced on the Atlantic sea-board. Geographically the Asiatic coasts of the Pacific offer a strong contrast to those of the American borders. The latter, as we have seen, are for the most part not far removed from the edge of the continental plateau. The coasts of the mainland of Asia, on the other hand, retire to a great distance, the true margin of the plateau being marked out by that great chain of islands which extends from Kamchatka south to the Philippines and New Guinea. The seas lying between those islands and the mainland occupy depressions in the continental plateau. Were that plateau to be lifted up for 6000 or 7000 feet the seas referred to would be enclosed by continuous land, and all the principal islands of the East Indian Archipelago--Sumatra, Java, Celebes, and New Guinea, would become united to themselves as well as to Australia and New Zealand. In short, it is the relatively depressed condition of the continental plateau along the western borders of the Pacific basin that causes the Asiatic coast-lines to differ so strikingly from those of America. From a geological point of view the differences are less striking than the resemblances. It is true that we have as yet a very imperfect knowledge of the geological structure of eastern Asia, but we know enough to justify the conclusion that in its main features that region does not differ essentially from western North America. During Mesozoic and Cainozoic times the sea appears to have overflowed vast tracts of Manchooria and China, and even to have penetrated into what is now the great Desert of Gobi. Subsequent crustal movements revolutionised the geography of all those regions. Great ranges of linear uplifts came into existence, and in these the younger formations, together with the foundations on which they rested, were squeezed into folds and ridged up against the nuclei of Palæozoic and Archæan rocks which had hitherto formed the only dry land. The latest of these grand upheavals are of Tertiary age, and, like those of the Pacific slope of America, they were accompanied by excessive volcanic action. The long chains of islands that flank the shores of Asia we must look upon as a series of partially submerged or partially emerged mountain-ranges, analogous geographically to the coast-ranges of North and Central America, and to the youngest Cordilleras of South America. The presence of numerous active and recently extinct volcanoes, taken in connection with the occurrence of many great depressions which furrow the floor of the sea in the East Indian Archipelago, and the profound depths attained by the Pacific trough along the borders of Japan and the Kurile and Aleutian Islands--all indicate conditions of very considerable instability of the lithosphere. We are not surprised, therefore, to meet with much apparently conflicting evidence of elevation and depression in the coast-lands of eastern Asia, where in some places the sea would seem to be encroaching, while in other regions it is retreating. In all earthquake-ridden and volcanic areas such irregular coastal changes may be looked for. So extreme are the irregularities of the sea-floor in the area lying between Australia, the Solomon Islands, the New Hebrides, and New Zealand, and so great are the depths attained by many of the depressions, that the margins of the continental plateau are harder to trace here than anywhere else in the world. The bottom of the oceanic trough throughout a large portion of the southern and western Pacific is, in fact, traversed by many great mountain-ridges, the summits of which approach the surface again and again to form the numerous islets of Polynesia. But notwithstanding the considerable depths that separate Australia from New Zealand there is geological evidence to show that a land-connection formerly linked both to Asia. The continental plateau, therefore, must be held to include New Caledonia and New Zealand. Hence the volcanic islets of the Solomon and New Hebrides groups are related to Australia in the same way as the Liu-kiu, Japanese, and Kurile Islands are to Asia. Having rapidly sketched the more prominent features of the Pacific coast-lines, we are in a position to realise the remarkable contrast they present to the coast-lines of the Atlantic. The highly-folded strata of the Atlantic sea-board are the relics of great mountains of upheaval, the origin of which cannot be assigned to a more recent date than Palæozoic times. During subsequent crustal movements no mountains of corrugated strata were uplifted along the Atlantic margins, the Mesozoic and Cainozoic strata of the coastal regions showing little or no disturbance. It is quite in keeping with all this that volcanic action appears to have been most strongly manifested in Palæozoic times. So many long ages have passed since the upheaval of the Archæan and Palæozoic mountains of the Atlantic sea-board that these heights have everywhere lost the character of true mountains of elevation. Planed down to low levels, partially submerged and covered to some extent by newer formations, they have in many places been again converted into dry lands, forming plateaux--now sorely denuded and cut up into mountains and valleys of erosion. Why the later movements along the borders of the Atlantic basin should not have resulted in the wholesale plication of the younger sedimentary rocks is a question for geologists. It would seem as if the Atlantic margins had reached a stage of comparative stability long before the grand Tertiary uplifts of the Pacific borders had taken place; for, as we have seen, the Mesozoic and the Cainozoic strata of the Atlantic coast-lands show little or no trace of having been subjected to tangential thrusting and crushing. Hence one cannot help suspecting that the retreat of the sea during Mesozoic and Cainozoic ages may have been due rather to subsidence of the oceanic trough and to sedimentation within the continental area than to positive elevation of the land. Over the Pacific trough, likewise, depression has probably been in progress more or less continuously since Palæozoic times, and this movement alone must have tended to withdraw the sea from the surface of the continental plateau in Asia and America. But by far the most important coastal changes in those regions have been brought about by the crumpling-up of the plateau, and the formation of gigantic mountains of upheaval along its margins. From remotest geological periods down almost to the present, the land-area has been increased from time to time by the doubling-up and consequent elevation of coastal accumulations, and by the eruption of vast masses of volcanic materials. It is this long-continued activity of the plutonic forces within the Pacific area which has caused the coast-lands of that basin to contrast so strongly with those of the Atlantic. The latter are incomparably older than the former--the heights of the Atlantic borders being mountains of denudation of vast geological antiquity, while the coastal ranges of the Pacific slope are creations but of yesterday as it were. It may well be that those Cordilleras and mountain-chains reach a greater height than was ever attained by any Palæozoic uplifts of the Atlantic borders. But the marked disparity in elevation between the coast-lands of the Pacific and the Atlantic is due chiefly to a profound difference in age. Had the Pacific coast-lands existed for as long a period and suffered as much erosion as the ancient rocks of the Atlantic sea-board, they would now have little elevation to boast of. The coast-lines of the Indian Ocean are not, upon the whole, far removed from the margin of the continental plateau. The elevation of East Africa for 6000 feet would add only a narrow belt to the land. This would still leave Madagascar an island, but there are geological reasons for concluding that this island was at a far distant period united to Africa, and it must therefore be considered as forming a portion of the continental plateau. The great depths which now separate it from the mainland are probably due to local subsidence, connected with volcanic action in Madagascar itself and in the Comoro Islands. The southern coasts of Asia, like those of East Africa, approach the edge of the continental plateau, so that an elevation of 6000 feet would make little addition to the land-area. With the same amount of upheaval, however, the Malay Peninsula, Sumatra, Java, and West Australia would become united, but without extending much further seawards. Land-connection, as we know, existed in Mesozoic times between Asia, Australia, and New Zealand, but the coast-lines of that distant period must have differed considerably from those that would appear were the regions in question to experience now a general elevation. The Archæan and the Palæozoic rocks of the Malay Peninsula and Sumatra are flanked on the side of the Indian Ocean by great volcanic ridges, and by uplifts of Tertiary strata, which continue along the line of the Nicobar and the Andaman Islands into Burma. Thus the coast-lines of that section of the Indian Ocean exhibit a geographical development similar to that of the Pacific sea-board. Elsewhere, as in Hindustan, Arabia, and East Africa, the coast-lines appear to have been determined chiefly by regional elevations of the land or subsidence of the oceanic trough in Mesozoic and Cainozoic times, accompanied by the out-welling of enormous floods of lava. Seeing, then, that the Pacific and the Indian Oceans are pre-eminently regions which, down to a recent date, have been subject to great crustal movements and to excessive volcanic action, we may infer that in the development of their coast-lines the sea played a very subordinate part. The shores, indeed, are largely protected from marine erosion by partially emerged volcanic ridges and by coral islands and reefs, and to a considerable extent also by the sediment which in tropical regions especially is swept down to the coast in great abundance by rains and rivers. Moreover, as the geological structure of these regions assures us, the land would appear seldom to have remained sufficiently long at one level to permit of much destruction by waves and tidal currents. In fine, then, we arrive at the general conclusion that the coast-lines of the globe are of very unequal age. Those of the Atlantic were determined as far back as Palæozoic times by great mountain-up lifts along the margin of the continental plateau. Since the close of that period many crustal oscillations have taken place, but no grand mountain-ranges have again been ridged up on the Atlantic sea-board. Meanwhile the Palæozoic mountain-chains, as we have seen, have suffered extensive denudation, have been planed down to sea-level, and even submerged. Subsequently converted into land, wholly or partially as the case may have been, they now present the appearance of plains and plateaux of erosion, often deeply indented by the sea. No true mountains of elevation are met with anywhere in the coast-lands of the Atlantic, while volcanic action has well-nigh ceased. In short, the Atlantic margins have reached a stage of comparative stability. The trough itself, however, is traversed by at least two well-marked banks of upheaval--the great meridional Dolphin Ridge, and the approximately transmeridional Faröe-Icelandic belt--both of them bearing volcanic islands. But while all the coast-lands of the Atlantic proper attained relative stability at an early period, those of the Mediterranean and Caribbean depressions have up to recent times been the scenes of great crustal disturbance. Gigantic mountain-chains were uplifted along their margins at so late a period as the Tertiary, and their shores still witness volcanic activity. It is upon the margins and within the trough of the Pacific Ocean, however, that subterranean action is now most remarkably developed. The coast-lines of that great basin are everywhere formed of grand uplifts and volcanic ranges, which, broadly speaking, are comparable in age to those of the Mediterranean and Caribbean depressions. Along the north-eastern margin of the Indian Ocean the coast-lines resemble those of the Pacific, being of like recent age, and similarly marked by the presence of numerous volcanoes. The northern and western shores, however (as in Hindustan, Arabia, and East Africa), have been determined rather by regional elevation or by subsidence of the ocean-floor than by axial uplifts--the chief crustal disturbances dating back to an earlier period than those of the East Indian Archipelago. It is in keeping with this greater age of the western and northern coast-lands of the Indian Ocean that volcanic action is now less strongly manifested in their vicinity. I have spoken of the comparative stability of the earth's crust within the Atlantic area as being evidenced by the greater age of its coastal ranges and the declining importance of its volcanic phenomena. This relative stability is further shown by the fact that the Atlantic sea-board is not much disturbed by earthquakes. This, of course, is what might have been expected, for earthquakes are most characteristic of volcanic regions and of those areas in which mountain-uplifts of recent geological age occur. Hence the coast-lands of the Pacific and the East Indies, the borders of the Caribbean Sea, the volcanic ridges of the Atlantic basin, the lands of the Mediterranean, the Black Sea, and the Aralo-Caspian depressions, the shores of the Red Sea, and vast tracts of southern Asia, are the chief earthquake regions of the globe. It may be noted, further, that shocks are not only most frequent but most intense in the neighbourhood of the sea. They appear to originate sometimes in the volcanic ridges and coastal ranges, sometimes under the floor of the sea itself. Now earthquakes, volcanoes, and uplifts are all expressions of the one great fundamental fact that the earth is a cooling and contracting body, and they indicate the lines of weakness along which the enormous pressures and strains induced by the subsidence of the crust upon its nucleus find relief. We cannot tell why the coast-lands of the Atlantic should have attained at so early a period a stage of relative stability--why no axial uplifts should have been developed along their margins since Palæozoic times. It may be that relief has been found in the wrinkling-up of the floor of the oceanic trough, and consequent formation of the Dolphin Ridge and other great submarine foldings of the crust; and it is possible that the growth of similar great ridges and wrinkles upon the bed of the Pacific may in like manner relieve the coast-lands of that vast ocean, and prevent the formation of younger uplifts along their borders. I have already remarked that two kinds of elevatory movements of the crust are recognised by geologists--namely, axial and regional uplifts. Some, however, are beginning to doubt, with Professor Suess, whether any vast regional uplifts are possible. Yet the view that would attribute all such apparent elevations of the land to subsidence of the crust under the great oceanic troughs is not without its difficulties. Former sea-margins of very recent geological age occur in all latitudes, and if we are to explain these by sub-oceanic depression, this will compel us to admit, as Suess has remarked, a general lowering of the sea-level of upwards of 1000 feet. But it is difficult to believe that the sea-floor could have subsided to such an extent in recent times. Suess thinks it is much more probable that the high-level beaches of tropical regions are not contemporaneous with those of higher latitudes, and that the phenomena are best explained by his hypothesis of a secular movement of the ocean--the water being, as he contends, alternately heaped up at the equator and the poles. The strand-lines in high latitudes, however, are certainly connected with glaciation in some way not yet understood; and if it cannot be confidently affirmed that they indicate regional movements of the land, the evidence, nevertheless, seems to point in that direction. In concluding this imperfect outline-sketch of a large subject, I ought perhaps to apologise for having trespassed so much upon the domains of geology. But in doing so I have only followed the example of geologists themselves, whose divagations in territories adjoining their own are naturally not infrequent. From much that I have said, it will be gathered that with regard to the causes of many coastal changes we are still groping in the dark. It seems not unlikely, however, that as light increases we may be compelled to modify the view that all oscillations of the sea-level are due to movements of the lithosphere alone. That is a very heretical suggestion; but that a great deal can be said for it any one will admit after a candid perusal of Suess's monumental work, _Das Antlitz der Erde_. [Illustration: PLATE VI BATHY-HYPSOMETRICAL MAP OF THE WORLD NOTE _The map is coloured to show the surface relief of the Globe without water in the Ocean Basins._ EXPLANATION OF COLOURING _The Colouring is graded from the Darkest Tint at the Highest Level to the Lightest Tint on the Lowest._ The Edinburgh Geographical Institute J. G. Bartholomew F.R.G.S. ] EDINBURGH PRINTED BY ST GILES' PRINTING COMPANY, 32 YORK PLACE. THE END. Other Works by Professor James Geikie. +-----------------------------------------------------------------+ | =The Great Ice Age.= (New Edition in Preparation.) | | Medium 8vo. Maps and Illustrations. Price, 24s. | | | | =Prehistoric Europe=: A Geological Sketch. | | Demy 8vo. Maps and Illustrations. Price, 25s. | | | | =Outlines of Geology=: For Junior Students and General Readers. | | Post 8vo. Illustrations. Price, 12s. | | | | =Songs and Lyrics, by Heinrich Heine and other | | German Poets=; done into English Verse. Price, 4s. | +-----------------------------------------------------------------+ * * * * * Transcriber's Note Hyphenation was not standardized. The section labeled "Explanation of Plate III." (p. 325) in the original printed version appears to describe Plate IV and changed accordingly. Paragraphs split by illustrations were rejoined. Some plates were moved to end of the chapter. 
14565	----	This material taken from pages i-ii, iv and v, and 3-12 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p i COSMOS VOLUME I [p ii is blank] [p iii - not copied; pertains to reprint series] p iv [portrait] p v COSMOS A SKETCH OR A PHYSICAL DESCRIPTION OF THE UNIVERSE BY ALEXANDER VON HUMBOLDT TRANSLATED FROM THE GERMAN BY E. C. OTTE Naturae vero rerum vis atque majestas in omnibus momentis fides caret, si quis modo partes ejus ac non totam complectatur animo. -- Plin., 'Hist. Nat.', lib. vii, c. 1. VOLUME I WITH AN INTRODUCTION BY NICOLAAS A. RUPKE THE JOHNS HOPKINS UNIVERSITY PRESS Baltimore and London [page vi and Introduction to the 1997 edition not copied] p 1 COSMOS VOLUME I [p 2 is blank] p 3 TRANSLATOR'S PREFACE. ----------------------- I CAN not more appropriately introduce the Cosmos than by presenting a brief sketch of the life of its illustrious author.* While the name of Alexander von Humboldt is familiar to every one, few, perhaps, are aware of the peculiar circumstances of his scientific career and of the extent of his labors in almost every department of physical knowledge. He was born on the 14th of September, 1769, and is, therefore, now in his 80th year. After going through the ordinary course of education at Gottingen, and having made a rapid tour through Holland, England, and France, he became a pupil of Werner at the mining school of Freyburg, and in his 21st year published an "Essay on the Basalts of the Rhine." Though he soon became officially connected with the mining corps, he was enabled to continue his excursions in foreign countries, for, during the six or seven years succeeding the publication of his first essay, he seems to have visited Austria, Switzerland, Italy, and France. His attention to mining did not, however, prevent him from devoting his attention to other scientific pursuits, among which botany and the then recent discovery of galvanism may be especially noticed. Botany, indeed, we know from his own authority, occupied him almost exclusively for some years; but even at this time he was practicing the use of those astronomical and physical instruments which he afterward turned to so singularly excellent an account. [footnote] *For the following remarks I am mainly indebted to the articles on the Cosmos in the two leading Quarterly Reviews. The political disturbances of the civilized world at the close p 4 of the last century prevented our author from carrying out various plans of foreign travel which he had contemplated, and detained him an unwilling prisoner in Europe. In the year 1799 he went to Spain, with the hope of entering Africa from Cadiz, but the unexpected patronage which he received at the court of Madrid led to a great alteration in his plans, and decided him to proceed directly to the Spanish possessions in America, "and there gratify the longings for foreign adventure, and the scenery of the tropics, which had haunted him from boyhood, but had all along been turned in the diametrically opposite direction of Asia." After encountering various risks of capture, he succeeded in reaching America, and from 1799 to 1804 prosecuted there extensive researches in the physical geography of the New World, which has indelibly stamped his name in the undying records of science. Excepting an excursion to Naples with Gay-Lussac and Von Buch in 1805 (the year after his return from America), the succeeding twenty years of his life were spent in Paris, and were almost exclusively employed in editing the results of his American journey. In order to bring these results before the world in a manner worthy of their importance, he commenced a series of gigantic publications in almost every branch of science on which he had instituted observations. In 1817, after twelve years of incessant toil, four fifths were completed, and an ordinary copy of the part then in print cost considerably more than one hundred pounds sterling. Since that time the publication has gone on more slowly, and even now after the lapse of nearly half a century, it remains, and probably ever will remain, incomplete. In the year 1828, when the greatest portion of his literary labor had been accomplished, he undertook a scientific journey to Siberia, under the special protection of the Russian government. In this journey -- a journey for which he had prepared himself by a course of study unparalleled in the history of travel -- he was accompanied by two companions hardly less distinguished than himself, Ehrenberg and Gustav Rose, and p 5 the results obtained during their expedition are recorded by our author in his 'Fragments Asiatiques', and in his 'Asie Centrale', and by Rose in his 'Reise nach dem Oural'. If the 'Asie Centrale' had been his only work, constituting, as it does, an epitome of all the knowledge acquired by himself and by former travelers on the physical geography of Northern and Central Asia, that work alone would have sufficed to form a reputation of the highest order. I proceed to offer a few remarks on the work of which I now present a new translation to the English public, a work intended by its author "to embrace a summary of physical knowledge, as connected with a delineation of the material universe." The idea of such a physical description of the universe had, it appears, been present to his mind from a very early epoch. It was a work which he felt he must accomplish, and he devoted almost a lifetime to the accumulation of materials for it. For almost half a century it had occupied his thoughts; and at length, in the evening of life, he felt himself rich enough in the accumulation of thought, travel, reading, and experimental research, to reduce into form and reality the undefined vision that has so long floated before him. The work, when completed, will form three volumes. The 'first' volume comprises a sketch of all that is at present known of the physical phenomena of the universe; the 'second' comprehends two distinct parts, the first of which treats of the incitements to the study of nature, afforded in descriptive poetry, landscape painting, and the cultivation of exotic plants; while the second and larger part enters into the consideration of the different epochs in the progress of discovery and of the corresponding stages of advance in human civilization. The 'third' volume, the publication of which, as M. Humboldt himself informs me in a letter addressed to my learned friend and publisher, Mr. H. G. Bohn, "has been somewhat delayed, owing to the present state of public affairs, will comprise the special and scientific development of the great Picture of Nature p 6 Each of the three parts of the 'Cosmos' is therefore, to a certain extent, distinct in its object, and may be considered complete in itself. We can not better terminate this brief notice than in the words of one of the most eminent philosophers of our own country, that, "should the conclusion correspond (as we doubt not) with these beginnings, a work will have been accomplished every way worthy of the author's fame, and a crowning laurel added to that wreath with which Europe will always delight to surround the name of Alexander von Humboldt." In venturing to appear before the English public as the interpreter of "the great work of our age,"* I have been encouraged by the assistance of many kind literary and scientific friends, and I gladly avail myself of this opportunity of expressing my deep obligations to Mr. Brooke, Dr. Day, Professor Edward Forbes, Mr. Hind, Mr. Glaisher, Dr. Percy, and Mr. Ronalds, for the valuable aid they have afforded me. [footnote] *The expression applied to the Cosmos by the learned Bunsen, in his late Report on Ethnology, in the 'Report of the British Association for' 1847, p. 265. It would be scarcely right to conclude these remarks without a reference to the translations that have preceded mine. The translation executed by Mrs. Sabine is singularly accurate and elegant. The other translation is remarkable for the opposite qualities, and may therefore be passed over in silence. The present volumes differ from those of Mrs. Sabine in having all the foreign measures converted into corresponding English terms, in being published at considerably less than one third of the price, and in being a translation of the entire work, for I have not conceived myself justified in omitting passages, sometimes amounting to pages, simply because they might be deemed slightly obnoxious to our national prejudices. p 7 AUTHOR'S PREFACE. ------------------- In the late evening of an active life I offer to the German public a work, whose undefined image has floated before my mind for almost half a century. I have frequently looked upon its completion as impracticable, but as often as I have been disposed to relinquish the undertaking, I have again -- although perhaps imprudently -- resumed the task. This work I now present to my contemporaries with a diffidence inspired by a just mistrust of my own powers, while I would willingly forget that writings long expected are usually received with less indulgence. Although the outward relations of life, and an irresistible impulse toward knowledge of various kinds, have led me to occupy myself for many years -- and apparently exclusively -- with separate branches of science, as, for instance, with descriptive botany, geognosy, chemistry, astronomical determinations of position, and terrestrial magnetism, in order that I might the better prepare myself for the extensive travels in which I was desirous of engaging, the actual object of my studies has nevertheless been of a higher character. The principal impulse by which I was directed was the earnest endeavor to comprehend the phenomena of physical objects in their general connection, and to represent nature as one great whole, moved and animated by internal forces. My intercourse with highly-gifted men early led me to discover that, without an earnest striving to attain to a knowledge of special branches of study, all attempts to give a grand and general view of the universe would be nothing more than a vain illusion. These special departments in the great domain of natural p 8 science are, moreover, capable of being reciprocally fructified by means of the appropriative forces by which they are endowed. Descriptive botany, no longer confined to the narrow circle of the determination of genera and species, leads the observer who traverses distant lands and lofty mountains to the study of the geographical distribution of plants of the earth's surface, according to distance from the equator and vertical elevation above the sea. It is further necessary to investigate the laws which regulate the differences of temperature and climate, and the meteorological processes of the atmosphere, before we can hope to explain the involved causes of vegetable distribution; and it is thus that the observer who earnestly pursues the path of knowledge is led from one class of phenomena to another, by means of the mutual dependence and connection existing between them. I have enjoyed an advantage which few scientific travelers have shared to an equal extent, viz., that of having seen not only littoral districts, such as are alone visited by the majority of those who take part in voyages of circumnavigation, but also those portions of the interior of two vast continents which present the most striking contrasts manifested in the Alpine tropical landscapes of South America, and the dreary wastes of the steppes in Northern Asia. Travels, undertaken in districts such as these, could not fail to encourage the natural tendency of my mind toward a generalization of views, and to encourage me to attempt, in a special work, to treat of the knowledge which we at present possess, regarding the sidereal and terrestrial phenomena of the Cosmos in their empirical relations. The hitherto undefined idea of a physical geography has thus, by an extended and perhaps too boldly imagined a plan, been comprehended under the idea of a physical description of the universe, embracing all created things in the regions of space and in the earth. The very abundance of the materials which are presented to the mind for arrangement and definition, necessarily impart no inconsiderable difficulties in the choice of the form under p 9 which such a work must be presented, if it would aspire to the honor of being regarded as a literary composition. Descriptions of nature ought not to be deficient in a tone of life-like truthfulness, while the mere enumeration of a series of general results is productive of a no less wearying impression than the elaborate accumulation of the individual data of observation. I scarcely venture to hope that I have succeeded in satisfying these various requirements of composition, or that I have myself avoided the shoals and breakers which I have known how to indicate to others. My faint hope of success rests upon the special indulgence which the German public have bestowed upon a small work bearing the title of 'Ansichten der Natur', which I published soon after my return from Mexico. This work treats, under general points of view, of separate branches of physical geography (such as the forms of vegetation, grassy plains, and deserts). The effect produced by this small volume has doubtlessly been more powerfully manifested in the influence it has exercised on the sensitive minds of the young, whose imaginative faculties are so strongly manifested, than by means of any thing which it could itself impart. In the work on the Cosmos on which I am now engaged, I have endeavored to show, as in that entitled 'Ansichten der Natur', that a certain degree of scientific completeness in the treatment of individual facts is not wholly incompatible with a picturesque animation of style. Since public lectures seemed to me to present an easy and efficient means of testing the more or less successful manner of connecting together the detached branches of any one science, I undertook, for many months consecutively, first in the French language, at Paris, and afterward in my own native German, at Berlin (almost simultaneously at two different places of assembly), to deliver a course of lectures on the physical description of the universe, according to my conception of the science. My lectures were given extemporaneously, both in French and German, and without the aid of written notes, nor have I, in any way, made use, in the present work, p 10 of those portions of my discourses which have been preserved by the industry of certain attentive auditors. With the exception of the first forty pages, the whole of the present work was written, for the first time, in the years 1843 and 1844. A character of unity, freshness, and animation must, I think, be derived from an association with some definite epoch, where the object of the writer is to delineate the present condition of knowledge and opinions. Since the additions constantly made to the latter give rise to fundamental changes in pre-existing views, my lectures and the Cosmos have nothing in common beyond the succession in which the various facts are treated. The first portion of my work contains introductory considerations regarding the diversity in the degrees of enjoyment to be derived from nature, and the knowledge of the laws by which the universe is governed; it also considers the limitation and scientific mode of treating a physical description of the universe, and gives a general picture of nature which contains a view of all the phenomena comprised in the Cosmos. This general picture of nature, which embraces within its wide scope the remotest nebulous spots, and the revolving double stars in the regions of space, no less than the telluric phenomena included under the department of the geography of organic forms (such as plants, animals, and races of men), comprises all that I deem most specially important with regard to the connection existing between generalities and specialities, while it moreover exemplifies, by the form and style of the composition, the mode of treatment pursued in the selection of the results obtained from experimental knowledge. The two succeeding volumes will contain a consideration of the particular means of incitement toward the study of nature (consisting in animated delineations, landscape painting, and the arrangement and cultivation of exotic vegetable forms), of the history of the contemplation of the universe, or the gradual development of the reciprocal action of natural forces constituting one natural whole; and lastly, of the special p 11 branches of the several departments of science, whose mutual connection is indicated in the beginning of the work. Wherever it has been possible to do so, I have adduced the authorities from whence I derived my facts, with a view of affording testimony both to the accuracy of my statements and to the value of the observations to which reference was made. In those instances where I have quoted from my own writings (the facts contained in which being, from their very nature, scattered through different portions of my works), I have always referred to the original editions, owing to the importance of accuracy with regard to numerical relations, and to my own distrust of the care and correctness of translators. In the few cases where I have extracted short passages from the works of my friends, I have indicated them by marks of quotation; and, in imitation of the practice of the ancients, I have invariably preferred the repetition of the same words to any arbitrary substitution of my own paraphrases. The much-contested question of priority of claim to a first discovery, which it is so dangerous to treat of in a work of this uncontroversial kind, has rarely been touched upon. Where I have occasionally referred to classical antiquity, and to that happy period of transition which has rendered the sixteenth and seventeenth centuries so celebrated, owing to the great geographical discoveries by which the age was characterized, I have been simply led to adopt this mode of treatment, from the desire we experience from time to time, when considering the general views of nature, to escape from the circle of more strictly dogmatical modern opinions, and enter the free and fanciful domain of earlier presentiments. It has frequently been regarded as a subject of discouraging consideration, that while purely literary products of intellectual activity are rooted in the depths of feeling, and interwoven with the creative force of imagination, all works treating of empirical knowledge, and of the connection of natural phenomena and physical laws, are subject to the most marked modifications of form in the lapse of short periods of time, both p 12 by the improvement in the instruments used, and by the consequent expansion of the field of view opened to rational observation, and that those scientific works which have, to use a common expression, become 'antiquated' by the acquisition of new funds of knowledge, are thus continually being consigned to oblivion as unreadable. However discouraging such a prospect must be, no one who is animated by a genuine love of nature, and by a sense of the dignity attached to its study, can view with regret any thing which promises future additions and a greater degree of perfection to general knowledge. Many important branches of knowledge have been based upon a solid foundation which will not easily be shaken, both as regards the phenomena in the regions of space and on the earth; while there are other portions of science in which general views will undoubtedly take the place of merely special; where new forces will be discovered and new substances will be made known, and where those which are now considered as simple will be decomposed. I would, therefore, venture to hope that an attempt to delineate nature in all its vivid animation and exalted grandeur, and to trace the 'stable' amid the vacillating, ever-recurring alternation of physical metamorphoses, will not be wholly disregarded even at a future age. 'Potsdam, Nov.', 1844. This material taken from pages 13-22 NB - The page numbers will be properly aligned in Courier 12 font. COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 13 CONTENTS OF VOL. I. ---------------------- Page The Translator's Preface . . . . . . . . . . . . . . . . . . . . . .3 The Author's Preface . . . . . . . . . . . . . . . . . . . . . . . .7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 INTRODUCTION. The Results of the Study of Physical Phenomena . . . . . . . . . . 23 The different Epochs of the Contemplation of the external World . .24 The different Degrees of Enjoyment presented by the Contemplation of Nature . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Instances of this Species of Enjoyment . . . . . . . . . . . . . . 26 Means by which it is induced . . . . . . . . . . . . . . . . . . . 26 The Elevations and climatic Relations of many of the most celebrated Mountains in the World, considered with Reference to the Effect produced on the Mind of the Observer . . . . . . . . . . . . . . . . . . . . . . . . . .27-33 The Impressions awakened by the Aspect of tropical Regions . . . . 34 The more accurate Knowledge of the Physical Forces of the Universe, acquired by the Inhabitants of a small Section of the temperate Zone . . . . . . . . . . . . . . . . . . . . .36 The earliest Dawn of the Science of the Cosmos . . . . . . . . . . 36 The Difficulties that opposed the Progress of Inquiry . . . . . . . 37 Consideration of the Effect produced on the Mind by the Observation of Nature, and the Fear entertained by some of its injurious Influence . . . . . . . . . . . . . . . . . . . 40 Illustrations of the Manner in which many recent Discoveries have tended to Remove the groundless Fears entertained regarding the Agency of certain Natural Phenomena . . . . . . 43 The Amount of Scientific Knowledge required to enter on the Consideration of Physical Phenomena . . . . . . . . . . . . . 47 The Object held in View by the present Work . . . . . . . . . . . . 49 The Nature of the Study of the Cosmos . . . . . . . . . . . . . . . 50 The special Requirements of the present Age . . . . . . . . . . . . 53 Limits and Method of Exposition of the Physical Description of the Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 Considerations on the terms Physiology and Physics . . . . . . . . .58 Physical Geography . . . . . . . . . . . . . . . . . . . . . . . . 59 Celestial Phenomena . . . . . . . . . . . . . . . . . . . . . . . . 63 The Natural Philosophy of the Ancients directed more to Celestial than to Terrestrial Phenomena . . . . . . . . . . . . . . . . .65 The able Treatises of Varenius and Carl Ritter . . . . . . . . .66, 67 Signification of the Word Cosmos . . . . . . . . . . . . . . . . 68-70 The Domain embraced by Cosmography . . . . . . . . . . . . . . . . 71 Empiricism and Experiments . . . . . . . . . . . . . . . . . . . . 74 The Process of Reason and Induction . . . . . . . . . . . . . . . .77 p 14 GENERAL REVIEW OF NATURAL PHENOMENA. Connection between the Material and the Ideal World . . . . . . . . 80 Delineation of Nature . . . . . . . . . . . . . . . . . . . . . . . 82 Celestial Phenomena . . . . . . . . . . . . . . . . . . . . . . . . 83 Sidereal Systems . . . . . . . . . . . . . . . . . . . . . . . . . 89 Planetary Systems . . . . . . . . . . . . . . . . . . . . . . . . .90 Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Aerolites . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111 Zodiacal Light . . . . . . . . . . . . . . . . . . . . . . . . . . 137 Translatory Motion of the Solar System . . . . . . . . . . . . . . 145 The Milky Way . . . . . . . . . . . . . . . . . . . . . . . . . . .150 Starless Openings . . . . . . . . . . . . . . . . . . . . . . . 152 Terrestrial Phenomena . . . . . . . . . . . . . . . . . . . . . . .154 Geographical Distribution . . . . . . . . . . . . . . . . . . . . .161 Figure of the Earth . . . . . . . . . . . . . . . . . . . . . . . .163 Density of the Earth . . . . . . . . . . . . . . . . . . . . . . . 169 Internal Heat of the Earth . . . . . . . . . . . . . . . . . . . . 172 Mean Temperature of the Earth . . . . . . . . . . . . . . . . . . .175 Terrestrial Magnetism . . . . . . . . . . . . . . . . . . . . . . 177 Magnetism . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183 Aurora Borealis . . . . . . . . . . . . . . . . . . . .. . . . . .193 Geognostic Phenomena . . . . . . . . . . . . . . . . . . . . . . . 202 Earthquakes . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 Gaseous Emanations . . . . . . . . . . . . . . . . . . . . . . . . 207 Hot Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . .221 Salses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224 Volcanoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227 Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247 Palaeontology . . . . . . . . . . . . . . . . . . . . . . . . . . .270 Geognostic Periods . . . . . . . . . . . . . . . . . . . . . . . . 286 Physical Geography . . . . . . . . . . . . . . . . . . . . . . . . 287 Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . .311 Atmospheric Pressure . . . . . . . . . . . . . . . . . . . . . . . 315 Climatology . . . . . . . . . . . . . . . . . . . . . . . . . . . .317 The Snow-line . . . . . . . . . . . . . . . . . . . . . . . . . . .329 Hygrometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332 Atmospheric Electricity . . . . . . . . . . . . . . . . . . . . . .335 Organic Life . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Motion in Plants . . . . . . . . . . . . . . . . . . . . . . . . . 341 Universality of Animal Life . . . . . . . . . . . . . . . . . . . .342 Geography of Plants and Animals . . . . . . . . . . . . . . . . . .346 Floras of different Countries . . . . . . . . . . . . . . . . . . .350 Man . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352 Races . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .353 Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357 Conclusion of the Subject . . . . . . . . . . . . . . . . . . . . .359 p 15 SUMMARY. ----------- Translator's Preface. Author's Preface. Vol I. GENERAL SUMMARY OF THE CONTENTS. Introduction. -- Reflections on the different Degrees of Enjoyment presented to us by the Aspect of Nature and the scientific Exposition of the Laws of the Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 23-78 Insight into the connection of phenomena as the aim of all natural investigation. Nature presents itself to meditative contemplation as a unity in diversity. Differences in the grades of enjoyment yielded by nature. Effect of contact with free nature; enjoyment derived from nature independently of a knowledge of the action of natural forces, or of the physiognomy and configuration of the surface, or of the character of vegetation. Reminiscences of the woody valleys of the Cordilleras and of the Peak of Teneriffe. Advantages of the mountainous region near the equator, where the multiplicity of natural impressions attains its maximum within the most circumscribed limits, and where it is permitted to man simultaneously to behold all the stars of the firmament and all the forms of vegetation -- p. 23-33. Tendency toward the investigation of the causes of physical phenomena. Erroneous views of the character of natural forces arising from an imperfect mode of observation or of induction. The crude accumulation of physical dogmas transmitted from one country to another. Their diffusion among the higher classes. Scientific physics are associated with another and a deep-rooted system of untried and misunderstood experimental positions. Investigation of natural laws. Apprehension that nature may lose a portion of its secret charm by an inquiry into the internal character of its forces, and that the enjoyment of nature must necessarily be weakened by a study of its domain. Advantages of general views which impart an exalted and solemn character to natural science. The possibility of separating generalities from specialties. Examples drawn from astronomy, recent optical discoveries, physical geognosy, and the geography of plants. Practicability of the study of physical cosmography -- p. 33-54. Misunderstood popular knowledge, confounding cosmography with a mere encyclopedic enumeration of natural sciences. Necessity for a simultaneous regard for all branches of natural science. Influence of this study on national prosperity and the welfare of nations; its more earnest and characteristic aim is an inner one, arising from exalted mental activity. Mode of treatment with regard to the object and presentation; reciprocal connection existing between thought and speech -- p. 54-56. The notes to p. 28-33. Comparative hypsometrical data of the elevations of the Dhawalagiri, Jawahir, Chimborazo, Aetna (according to the measurement of Sir John Herschel), the Swiss Alps, etc. -- p. 28. Rarity p 16 of palms and ferns in the Himalaya Mountains -- p. 29. European vegetable forms in the Indian Mountains -- p. 30. Northern and southern limits of perpetual snow on the Himalaya; influence of the elevated plateau of Thibet -- p. 30-33. Fishes of an earlier world -- p. 46. Limits and Method of Exposition of the Physical Description of the Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . Page 56-78 Subjects embraced by the study of the Cosmos or of physical cosmography. Separation of other kindred studies -- p. 56-62. The uranological portion of the Cosmos is more simple than the telluric; the impossibility of ascertaining the diversity of matter simplifies the study of the mechanism of the heavens. Origin of the word 'Cosmos', its signification of adornment and order of the universe. The 'existing' can not be absolutely separated in our contemplation of nature from the 'future'. History of the world and description of the world -- p. 26-73. Attempts to embrace the multiplicity of the phenomena of the Cosmos in the unity of thought and under the form of a purely rational combination. Natural philosophy, which preceded all exact observation in antiquity, is a natural, but not unfrequently ill-directed, effort of reason. Two forms of abstraction rule in the whole mass of knowledge, viz.: the 'quantitative', relative determinations according to number and magnitude, and 'qualitative', material characters. Means of submitting phenomena to calculation. Atoms, mechanical methods of construction. Figurative representations; mythical conception of imponderable matters, and the peculiar vital forces in every organism. That which is attained by observation and experiment (calling forth phenomena) leads, by analogy and induction, to a knowledge of 'empirical laws'; their gradual simplification and generalization. Arrangement of the facts discovered in accordance with leading ideas. The treasure of empirical contemplation, collected through ages, is in no danger of experiencing any hostile agency from philosophy -- p. 73-78. [In the notes appended to p. 66-70 are considerations of the general and comparative geography of Varenius. Philological investigation into the meaning of the words [Greek word] and 'mundus'.] Delineation of Nature. General Review of Natural Phenomena. . . . . p. 79-359 Introduction -- p. 79-83. A descriptive delineation of the world embraces the whole universe ([Greek words]) in the celestial and terrestrial spheres. Form and course of the representation. It begins with the laws of gravitation, and with the region of the remotest nebulous spots and double stars, and then, gradually descending through the starry stratum to which our solar system belongs, it contemplates this terrestrial spheroid, surrounded by air and water, and finally, proceeds to the consideration of the form of our planet, its temperature and magnetic tension, and the fullness of organic vitality which is unfolded on its surface under the action of light. Partial insight into the relative dependence existing among all phenomena. Amid all the mobile and unstable elements in space, 'mean numerical values' are the ultimate aim of investigation, being the expression of the physical laws, or forces of the Cosmos. The delineation of the universe does not begin with the earth, from which a merely subjective point of view might have led us to start, but rather with the objects comprised in the regions of space. Distribution of matter, which is partially conglomerated into rotating p 17 and circling heavenly bodies of very different density and magnitude, and partly scattered as self-luminous vapor. Review of the separate portions of the picture of nature, for the purpose of explaining the reciprocal connection of all phenomena. I. Celestial Portion of the Cosmos . . . . . . . . . . . . . . . . .Page 83-154 II. Terrestrial Portion of the Cosmos . . . . . . . . . . . . . . . .p. 154-359 a. Form of the earth, its mean density, quantity of heat, electro-magnetic activity, process of light -- p. 154-202. b. Vital activity of the earth toward its external surface. Reaction of the interior of a planet on its crust and surface. Subterranean noise without waves of concussion. Earthquakes dynamic phenomena -- p. 202-217. c. Material products which frequently accompany earthquakes. Gaseous and aqueous springs. Salses and mud volcanoes. Upheavals of the soil by elastic forces -- p. 217-228. d. Fire-emitting mountains. Craters of elevation. Distribution of volcanoes on the earth -- p. 228-247. e. Volcanic forces form new kinds of rock, and metamorphose those already existing. Geognostical classification of rocks into four groups. Phenomena of contact. Fossiliferous strata; their vertical arrangement. The faunas and floras of an earlier world. Distribution of masses of rock -- p. 247-384. f. Geognostical epochs, which are indicated by the mineralogical difference of rocks, have determined the distribution of solids and fluids into continents and seas. Individual configuration of solids into horizontal expansion and vertical elevation. Relations of area. Articulation. Probability of the continued elevation of the earth's crust in ridges -- p. 284-301. g. Liquid and aeriform envelopes of the solid surface of our planet. Distribution of heat in both. The sea. The tides. Currents and their effects -- p. 301-311. h. The atmosphere. Its chemical composition. Fluctuations in its density. Law of the direction of the winds. Mean temperature. Enumeration of the causes which tend to raise and lower the temperature. Continental and insular climates. East and west coasts. Cause of the curvature of the isothermal lines. Limits of perpetual snow. Quantity of vapor. Electricity in the atmosphere. Forms of the clouds -- p. 311-339. i. Separation of inorganic terrestrial life from the geography of vital organisms; the geography of vegetables and animals. Physical gradations of the human race -- p. 339-359. Special Analysis of the Delineation of Nature, including References to the Subjects treated of in the Notes. I. Celestial Portion of the Cosmos . . . . . . . . . . . . . . . . . p. 83-154 The universe and all that it comprises -- multiform nebulous spots, planetary vapor, and nebulous stars. The picturesque charm of a southern sky -- note, p. 85. Conjectures on the position in space of the world. Our stellar masses. A cosmical island. Gauging stars. Double stars revolving round a common center. Distance of the star 61 Cygni -- p. 88 and note. Our solar system more complicated than was conjectured at the close of the last century. Primary planets with Neptune, Astrea, Hebe, Iris, and Flora, now constitute 16; secondary planets 18; myriad of comets of which many of the inner ones are inclosed p 18 in the orbits of the planets; a rotating ring (the zodiacal light) and meteoric stones, probably to be regarded as small cosmical bodies. The telescopic planets, Vesta, Juno, Ceres, Pallas, Astrea, Hebe, Iris and Flora, with their frequently intersecting, strongly inclined, and more eccentric orbits, constitute a central group of separation between the inner planetary group (Mercury, Venus, the Earth, and Mars) and the outer group (Jupiter, Saturn, Uranus, and Neptune). Contrasts of these planetary groups. Relations of distance from one central body. Differences of absolute magnitude, density, period of revolution, eccentricity, and inclination of the orbits. The so-called law of the distances of the planets from their central sun. The planets which have the largest number of moons -- p. 96 and note. Relations in space, both absolute and relative, of the secondary planets. Largest and smallest of the moons. Greatest approximation to a primary planet. Retrogressive movement of the moons of Uranus. Libration of the Earth's satellite -- p. 98 and note. Comets; the nucleus and tail; various forms and directions of the emanations in conoidal envelopes, with more or less dense walls. Several tails inclined toward the sun; change of form of fixed stars by the nuclei of comets. Eccentricity of their orbits and periods of revolution. Greatest distance and greatest approximation of comets. Passage through the system of Jupiter's satellites. Comets of short periods of revolution, more correctly termed inner comets (Encke, Biela, Faye) -- p. 107 and note. Revolving aerolites (meteoric stones, fire-balls, falling stars). Their planetary velocity, magnitude, form, observed height. Periodic return in streams; the November stream and the stream of St. Lawrence. Chemical composition of meteoric asteroids -- p. 130 and notes. Ring of zodiacal light. Limitation of the present solar atmosphere -- p. 141 and note. Translatory motion of the whole solar system -- p. 145-149 and note. The existence of the law of gravitation beyond our solar system. The milky way of stars and its conjectured breaking up. Milky way of nebulous spots, at right angles with that of the stars. Periods of revolutions of bi-colored double stars. Canopy of stars; openings in the stellar stratum. Events in the universe; the apparition of new stars. Propagation of light, the aspect of the starry vault of the heavens conveys to the mind an idea of inequality of time -- p. 149-154 and notes. II. Terrestrial Portion of the Cosmos . . . . . . . . . . . . . . Page 154-359 a. Figure of the earth. Density, quantity of heat, electro-magnetic tension, and terrestrial light -- p. 154-202 and note. Knowledge of the compression and curvature of the earth's surface acquired by measurements of degrees, pendulum oscillations, and certain inequalities in the moon's orbit. Mean density of the earth. The earth's crust, and the depth to which we are able to penetrate -- p. 159, 160, note. Threefold movement of the heat of the earth; its thermic condition. Law of the increase of heat with the increase of depth -- p. 160, 161 and note. Magnetism electricity in motion. Periodical variation of terrestrial magnetism. Disturbance of the regular course of the magnetic needle. Magnetic storms; extension of their action. Manifestations of magnetic force on the earth's surface presented under three classes of phenomena, namely, lines of equal force (isodynamic), equal inclination (isoclinic), and equal deviation (isogonic). Position of the magnetic pole. Its probable connection with the poles of cold. Change of all the magnetic phenomena of the earth. Erection of magnetic observatories p 19 since 1828; a far-extending net-work of magnetic stations -- p. 190 and note. Development of light at the magnetic poles; terrestrial light as a consequence of the electro-magnetic activity of our planet. Elevation of polar light. Whether magnetic storms are accompanied by noise. Connection of polar light (an electro-magnetic development of light) with the formation of cirrus clouds. Other examples of the generation of terrestrial light -- p. 202 and note. b. The vital activity of a planet manifested from within outward, the principal source of geognostic phenomena. Connection between merely dynamic concussions or the upheaval of whole portions of the earth's crust, accompanied by the effusion of matter, and the generation of gaseous and liquid fluids, of hot mud and fused earths, which solidify into rocks. Volcanic action, in the most general conception of the idea, is the reaction of the interior of a planet on its outer surface. Earthquakes. Extent of the circles of commotion and their gradual increase. Whether there exists any connection between the changes in terrestrial magnetism and the processes of the atmosphere. Noises, subterranean thunder without any perceptible concussion. The rocks which modify the propagation of the waves of concussion. Upheavals; eruption of water, hot steam, mud mofettes, smoke, and flame during an earthquake -- p. 202-218 and notes. c. Closer consideration of material products as a consequence of internal planetary activity. There rise from the depths of the earth, through fissures and cones of eruption, various gases, liquid fluids (pure or acidulated), mud, and molten earths. Volcanoes are a species of intermittent spring. Temperature of thermal springs; their constancy and change. Depth of the foci -- p. 219-224 and notes. Salses, mud volcanoes. While fire-emitting mountains, being sources of molten earths, produce volcanic rocks, spring water forms, by precipitation, strata of limestone. Continued generation of sedimentary rocks -- p. 228 and note. d. Diversity of volcanic elevations. Dome-like closed trachytic mountains. Actual volcanoes which are formed from craters of elevations or among the detritus of their original structure. Permanent connection of the interior of our earth with the atmosphere. Relation to certain rocks. Influence of the relations of height on the frequency of the eruptions. Heights of the cone of cinders. Characteristics of those volcanoes which rise above the snow-line. Columns of ashes and fire. Volcanic storm during the eruption. Mineral composition of lavas -- p. 236 and notes. Distribution of volcanoes on the earth's surface; central and linear volcanoes; insular and littoral volcanoes. Distance of volcanoes from the sea-coast. Extinction of volcanic forces -- p. 246 and notes. e. Relation of volcanoes to the character of rocks. Volcanic forces form new rocks, and metamorphose the more ancient ones. The study of these relations leads, by a double course, to the mineral portion of geognosy (the study of the textures and of the position of the earth's strata), and to the configuration of continents and insular groups elevated above the level of the sea (the study of the geographical form and outlines of the different parts of the earth. Classification of rocks according to the scale of the phenomena of structure and metamorphosis, which are still passing before our eyes. Rocks of eruption, sedimentary rocks, changed (metamorphosed) rocks, conglomerates -- compound rocks are definite associations of cryctognostically simple fossils. There are four phases in the formative condition; rocks of eruption, p 20 endogenous (granite, sienite, porphyry, greenstone, hyperathene, rock, euphotide, melaphyre, basalt, and phonolithe); sedimentary rocks (silurian schist, coal measures, limestone, travertino, infusorial deposit); metamorphosed rock, which contains also, together with the detritus mica schist, and more ancient metamorphic masses. Aggregate and sandstone formations. The phenomenon of contact explained by the artificial imitation of minerals. Effects of pressure and the various rapidity of cooling. Origin of granular or saccharoidal marble, silicification of schist into ribbon jasper. Metamorphosis of calcareous marl into micaceous schist through granite. Conversion of dolomite and granite into argillaceous schist, by contact with basaltic and doleritic rocks. Filling up of the veins from below. Processes of cementation in agglomerate structures. Friction conglomerates -- p. 269 and note. Relative age of rocks, chronometry of the earth's crust. Fossiliferous strata. Relative age of organisms. Simplicity of the first vital forms. Dependence of physiological gradations on the age of the formations. Geognostic horizon, whose careful investigation may yield certain data regarding the identity or the relative age of formations, the periodic recurrence of certain strata, their parallelism, or their total suppression. Types of the sedimentary structures considered in their most simple and general characters; silurian and devonian formations (formerly known as rocks of transition); the lower trias (mountain limestone, coal measures, together with 'todilegende' and zechstein); the upper trias (butter sandstone, muschelkalk, and keuper); Jura limestone (lias and oolite); freestone, lower and upper chalk, as the last of the flotz strata, which begin with mountain limestone; tertiary formations in three divisions, which are designated by granular limestone, lignite, and south Apennine gravel -- p. 269-278. The faunas and floras of an earlier world, and their relations to existing organisms. Colossal bones of antediluvian mammalia in the upper alluvium. Vegetation of an earlier world; monuments of the history of its vegetation. The points at which certain vegetable groups attain their maximum; cycadeae in the keuper and lias, and coniferae in the butter sandstone. Lignite and coal measures (amber-tree). Deposition of large masses of rock; doubts regarding their origin -- p. 285 and note. f. The knowledge of geognostic epochs -- of the upheaval of mountain chains and elevated plateaux, by which lands are both formed and destroyed, leads, by an internal causal connection, to the distribution into solids and fluids, and to the peculiarities in the natural configuration of the earth's surface. Existing areal relations of the solid to the fluid differ considerably from those presented by the maps of the physical portion of a more ancient geography. Importance of the eruption of quartzose, porphyry with reference to the then existing configuration of continental masses. Individual conformation in horizontal extension (relations of articulation) and in vertical elevation (hypsometrical views). Influence of the relations of the area of land and sea on the temperature, direction of the winds, abundance or scarcity of organic products, and on all meteorological processes collectively. Direction of the major axes of continental masses. Articulation and pyramidal termination toward the south. Series of peninsulas. Valley-like formation of the Atlantic Ocean. Forms which frequently recur -- p. 285-293 and notes. Ramifications and systems of mountain chains, and the means of determining their relative ages. Attempts to determine the centre of gravity of the volume of the lands upheaved above the level p 21 of the sea. The elevation of continents is still progressing slowly, and is being compensated for at some definite points by a perceptible sinking. All geognostic phenomena indicate a periodical alteration of activity in the interior of our planet. Probability of new elevations of ridges -- p. 293-301 and notes. g. The solid surface of the earth has two envelopes, one liquid, and the other aeriform. Contrasts and analogies which these envelopes -- the sea and the atmosphere -- present in their conditions of aggregation and electricity, and in their relations of currents and temperature. Depths of the ocean and of the atmosphere, the shoals of which constitute our highlands and mountain chains. The degree of heat at the surface of the sea in different latitudes and in the lower strata. Tendency of the sea to maintain the temperature of the surface in the strata nearest to the atmosphere, in consequence of the mobility of its particles and the alteration in its density. Maximum of the density of salt water. Position of the zones of the hottest water, and of those having the greatest saline contents. Thermic influence of the lower polar current and the counter currents in the straits of the sea -- p. 302-304 and notes. General level of the sea, and permanent local disturbances of equilibrium; the periodic disturbances manifested as tides. Oceanic currents; the equatorial or rotation current, the Atlantic warm Gulf Stream, and the further impulse which it receives; the cold Peruvian stream in the eastern portion of the Pacific Ocean of the southern zone. Temperature of shoals. The universal diffusion of life in the ocean. Influence of the small submarine sylvan region at the bottom of beds of rooted algae, or on far-extending floating layers of fucus -- p. 302-311 and notes. h. The gaseous envelope of our planet, the atmosphere. Chemical composition of the atmosphere, its transparency, its polarization, pressure, temperature, humidity, and electric tension. Relation of oxygen to nitrogen; amount of carbonic acid; carbureted hydrogen; ammoniacal vapors. Miamata. Regular (horary) changes in the pressure of the atmosphere. Mean barometrical height at the level of the sea in different zones of the earth. Isobarometrical curves. Barometrical windroses. Law of rotation of the winds, and its importance with reference to the knowledge of many meteorological processes. Land and sea winds, trade winds and monsoons -- p. 311-317. Climatic distribution of heat in the atmosphere, as the effect of the relative position of transparent and opaque masses (fluid and solid superficial area), and of the hypsometrical configuration of continents. Curvature of the isothermal lines in a horizontal and vertical direction, on the earth's surface and in the superimposed strata of air. Convexity and concavity of the isothermal lines. Mean heat of the year, seasons, months, and days. Enumeration of the causes which produce disturbances in the form of isothermal lines, i.e., their deviation from the position of the geographical parallels. Isochimenal and isotheral lines are the lines of equal winter and summer heat. Causes which raise or lower the temperature. Radiation of the earth's surface, according to its inclination, color, density, dryness, and chemical composition. The form of the cloud which announces what is passing in the upper strata of the atmosphere is the image of the strongly radiating ground projected on a hot summer sky. Contrast between an insular or littoral climate, such as is experienced by all deeply-articulated continents, and the climate of the interior of large tracts of land. East and west coasts. Difference between the southern and northern hemispheres. Thermal scales of p 22 cultivated plants, going down from the vanilla, cacoa, and musaceae, by citrous and olives, and to vines yielding potable wines. The influence which these scales exercise on the geographical distribution of cultivated plants. The favorable ripening and the immaturity of fruits are essentially influenced by the difference in the action of direct or scattered light in a clear sky or in one overcast with mist. General summary of the causes which yield a more genial climate to the greater portion of Europe considered as the western peninsula of Asia -- p. 326. Determination of the changes in the mean annual and summer temperature, which correspond to one degree of geographical latitude. Equality of the mean temperature of a mountain station, and of the polar distance of any point lying at the level of the sea. Decrease of temperature with the decrease in elevation. Limits of perpetual snow, and the fluctuations in these limits. Causes of disturbance in the regularity of the phenomenon. Northern and southern chains of the Himalaya; habitability of the elevated plateaux of Thibet -- p. 331. Quantity of moisture in the atmosphere, according to the hours of the day, the seasons of the year, degrees of latitude, and elevation. Greatest dryness of the atmosphere observed in Northern Asia, between the river districts of the Irtysch and the Obi. Dew, a consequence of radiation. Quantity of rain -- p. 335. Electricity of the atmosphere, and disturbance of the electric tension. Geographical distribution of storms. Predettermination of atmospheric changes. The most important climatic disturbances can not be traced, at the place of observation, to any local cause, but are rather the consequence of some occurrence by which the equilibrium in the atmospheric currents has been destroyed at some considerable distance -- p. 335-339. i. Physical geography is not limited to elementary inorganic terrestrial life, but, elevated to a higher point of view, it embraces the sphere of organic life, and the numerous gradations of its typical development. Animal and vegetable life. General diffusion of life in the sea and on the land; microscopic vital forms discovered in the polar ice no less than in the depths of the ocean within the tropics. Extension imparted to the horizon of life by Ehrenberg's discoveries. Estimation of the mass (volume) of animal and vegetable organisms -- p. 339-346. Geography of plants and animals. Migrations of organisms in the ovum, or by means of organs capable of spontaneous motion. Spheres of distribution depending on climatic relations. Regions of vegetation, and classification of the genera of animals. Isolated and social living plants and animals. The character of flora and fauna is not determined so much by the predominance of separate families, in certain parallels of latitude, as by the highly complicated relations of the association of many families, and the relative numerical value of their species. The forms of natural families which increase or decrease from the equator to the poles. Investigations into the numerical relation existing in different districts of the earth between each one of the large families to the whole mass of phanerogamia -- p. 346-351. The human race considered according to its physical gradations, and the geographical distribution of its simultaneously occurring types. Races and varieties. All races of men are forms of one single species. Unity of the human race. Languages considered as the intellectual creations of mankind, or as portions of the history of mental activity, manifest a character of nationality, although certain historical occurrences have been the means of diffusing idioms of the same family of languages among nations of wholly different descent -- p. 351-359. In This material taken from pages 23 to 56 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 23 INTRODUCTION. ---------------- REFLECTIONS ON THE DIFFERENT DEGREES OF ENJOYMENT PRESENTED TO US BY THE ASPECT OF NATURE AND THE STUDY OF HER LAWS. In attempting, after a long absence from my native country, to develop the physical phenomena of the globe, and the simultaneous action of the forces that pervade the regions of space, I experience a two-fold cause of anxiety. The subject before me is so inexhaustible and so varied, that I fear either to fall into the superficiality of the encyclopedist, or to weary the mind of my reader by aphorisms consisting of mere generalities clothed in dry and dogmatical forms. Undue conciseness often checks the flow of expression, while diffuseness is alike detrimental to a clear and precise exposition of our ideas. Nature is a free domain, and the profound conceptions and enjoyments she awakens within us can only be vividly delineated by thought clothed in exalted forms of speech, worthy of bearing witness to the majesty and greatness of the creation. In considering the study of physical phenomena, not merely in its bearings on the material wants of life, but in its general influence on the intellectual advancement of mankind, we find its noblest and most important result to be a knowledge of the chain of connection, by which all natural forces are linked together, and made mutually dependent upon each other; and it is the perception of these relations that exalts our views and ennobles our enjoyments. Such a result can, however, only be reaped as the fruit of observation and intellect, combined with the spirit of the age, in which are reflected all the varied phases of thought. He who can trace, through by-gone times, the stream of our knowledge to its primitive source, will learn from history how, for thousands of years, man has labored, amid the ever-recurring changes of form, to recognize the invariability of natural laws, and has thus, by the force of mind, gradually subdued a great portion of the physical world to his dominion. In interrogating the history of the past, we trace the mysterious course of ideas yielding the first glimmering perception of the same image of p 24 a Cosmos, or harmoniously ordered whole, which, dimly shadowed forth to the human mind in the primitive ages of the world, is now fully revealed to the maturer intellect of mankind as the result of long and laborious observation. Each of these epochs of the contemplation of the external world -- the earliest dawn of thought and the advanced stage of civilization -- has its own source of enjoyment. In the former, this enjoyment, in accordance with the simplicity of the primitive ages, flowed from an intuitive feeling of the order that was proclaimed by the invariable and successive reappearance of the heavenly bodies, and by the progressive development of organized beings; while in the latter, this sense of enjoyment springs from a definite knowledge of the phenomena of nature. When man began to interrogate nature, and, not content with observing, learned to evoke phenomena under definite conditions; when once he sought to collect and record facts, in order that the fruit of his labors might aid investigation after his own brief existence had passed away, the 'philosophy of Nature' cast aside the vague and poetic garb in which she had been enveloped from her origin, and, having assumed a severer aspect, she now weighs the value of observations, and substitutes induction and reasoning for conjecture and assumption. The dogmas of former ages survive now only in the superstitions of the people and the prejudices of the ignorant, or are perpetuated in a few systems, which, conscious of their weakness, shroud themselves in a vail of mystery. We may also trace the same primitive intuitions in languages exuberant in figurative expressions; and a few of the best chosen symbols engendered by the happy inspiration of the earliest ages, having by degrees lost their vagueness through a better mode of interpretation, are still preserved among our scientific terms. Nature considered 'rationally', that is to say, submitted to the process of thought, is a unity in diversity of phenomena; a harmony blending together all created things, however dissimilar in form and attributes; one great whole ([Greek words]) animated by the breath of life. The most important result of a rational inquiry into nature is, therefore, to establish the unity and harmony of this stupendous mass of force and matter, to determine with impartial justice what is due to the discoveries of the past and to those of the present, and to analyze the individual parts of natural phenomena without succumbing beneath the weight of the whole. Thus, and thus alone, is it permitted to man, while mindful of the high destiny p 25 of his race, to comprehend nature, to lift the vail that shrouds her phenomena, and as it were, submit the results of observation to the test of reason and of intellect. In reflecting upon the different degrees of enjoyment presented to us in the contemplation of nature, we find that the first place must be assigned to a sensation, which is wholly independent of an intimate acquaintance with the physical phenomena presented to our view, or of the peculiar character of the region surrounding us. In the uniform plain bounded only by a distant horizon, where the lowly heather, the cistus, or waving grasses, deck the soil; on the ocean shore, where the waves, softly rippling over the beach, leave a track, green with the weeds of the sea; every where, the mind is penetrated by the same sense of the grandeur and vast expanse of nature, revealing to the soul, by a mysterious inspiration, the existence of laws that regulate the forces of the universe. Mere communion with nature, mere contact with the free air, exercise a soothing yet strengthening influence on the wearied spirit, calm the storm of passion, and soften the heart when shaken by sorrow to its inmost depths. Every where, in every region of the globe, in every stage of intellectual culture, the same sources of enjoyment are alike vouchsafed to man. The earnest and solemn thoughts awakened by a communion with nature intuitively arise from a presentiment of the order and harmony pervading the whole universe, and from the contrast we draw between the narrow limits of our own existence and the image of infinity revealed on every side, whether we look upward to the starry vault of heaven, scan the far-stretching plain before us, or seek to trace the dim horizon across the vast expanse of ocean. The contemplation of the individual characteristics of the landscape, and of the conformation of the land in any definite region of the earth, gives rise to a different source of enjoyment, awakening impressions that are more vivid, better defined, and more congenial to certain phases of the mind, than those of which we have already spoken. At one time the heart is stirred by a sense of the grandeur of the face of nature, by the strife of the elements, or, as in Northern Asia by the aspect of the dreary barrenness of the far-stretching steppes; at another time, softer emotions are excited by the contemplation of rich harvests wrested by the hand of man from the wild fertility of nature, or by the sight of human habitations raised beside some wild and foaming torrent. Here I regard less the degree of intensity than the difference existing in the p 26 various sensations that derive their charm and permanence from the peculiar character of the scene. If I might be allowed to abandon myself to the recollections of my own distant travels, I would instance, among the most striking scenes of nature, the calm sublimity of a tropical night, when the stars, not sparkling, as in our northern skies, shed their soft and planetary light over the gently-heaving ocean; or I would recall the deep valleys of the Cordilleras, where the tall and slender palms pierce the leafy vail around them, and waving on high their feathery and arrow-like branches for, as it were, "a forest above a forest;"* or I would describe the summit of the Peak of Teneriffe, when a horizontal layer of clouds, dazzling in whiteness, has separated the cone of cinders from the plain below, and suddenly the ascending current pierces the cloudy vail, so that the eye of the traveler may range from the brink of the crater, along the vine-clad slopes of Orotava, to the orange gardens and banana groves that skirt the shore. In scenes like these, it is not the peaceful charm uniformly spread over the face of nature that moves the heart, but rather the peculiar physiognomy and conformation of the land, the features of the landscape, the ever varying outline of the clouds, and their blending with the horizon of the sea, whether it lies spread before us like a smooth and shining mirror, or is dimly seen through the morning mist. All that the senses can but imperfectly comprehend, all that is most awful in such romantic scenes of nature, may become a source of enjoyment to man, by opening a wide field to the creative powers of his imagination. Impressions change with the varying movements of the mind, and we are led by a happy illusion to believe that we receive from the external world that with which we have ourselves invested it. [footnote] *This expression is taken from a beautiful description of tropical forest scenery in 'Paul and Virginia', by Bernardia de Saint Pierre. When far from our native country, after a long voyage, we tread for the first time the soil of a tropical land, we experience a certain feeling of surprise and gratification in recognizing, in the rocks that surround us, the same inclined schistose strata, and the same columnar basalt covered with cellular amygdaloids, that we had left in Europe, and whose identity of character, in latitudes so widely different, reminds us that the solidification of the earth's crust is altogether independent of climatic influences. But these rocky masses of schist and of basalt are covered with vegetation of a character with which we are unacquainted, and of a physiognomy wholly p 27 unknown to us; and it is then, amid the colossal and majestic forms of an exotic flora, that we feel how wonderfully the flexibility of our nature fits us to receive new impressions, linked together by a certain secret analogy. We so readily perceive the affinity existing among all the forms of organic life, that although the sight of a vegetation similar to that of our native country might at first be most welcome to the eye, as the sweet familiar sounds of our mother tongue are to the ear, we nevertheless, by degrees, and almost imperceptibly, become familiarized with a new home and a new climate. As a true citizen of the world, man every where habituates himself to that which surrounds him; yet fearful, as it were, of breaking the links of association that bind him to the home of his childhood, the colonist applies to some few plants in a far-distant clime the names he had been familiar with in his native land; and by the mysterious relations existing among all types of organization, the forms of exotic vegetation present themselves to his mind as nobler and more perfect developments of those he had loved in earlier days. Thus do the spontaneous impressions of the untutored mind lead, like the laborious deductions of cultivated intellect, to the same intimate persuasion, that one sole and indissoluble chain binds together all nature. It may seem a rash attempt to endeavor to separate, into its different elements, the magic power exercised upon our minds by the physical world, since the character of the landscape, and of every imposing scene in nature, depends so materially upon the mutual relation of the ideas and sentiments simultaneously excited in the mind of the observer. The powerful effect exercised by nature springs, as it were, from the connection and unity of the impressions and emotions produced; and we can only trace their different sources by analyzing the individuality of objects and the diversity of forces. The richest and most varied elements for pursuing an analysis of this nature present themselves to the eyes of the traveler in the scenery of Southern Asia, in the Great Indian Archipelago, and more especially, too, in the New Continent, where the summits of the lofty Cordilleras penetrate the confines of the aerial ocean surrounding our globe, and where the same subterranean forces that once raised these mountain chains still shake them to their foundation and threaten their downfall. Graphic delineations of nature, arranged according to systematic views, are not only suited to please the imagination, p 28 but may also, when properly considered, indicate the grades of the impressions of which I have spoken, from the uniformity of the sea-shore, or the barren steppes of Siberia, to the inexhaustible fertility of the torrid zone. If we were even to picture to ourselves Mount Pilatus placed on the Schreckhorn,* or the Schneekoppe of Silesia on Mont Blanc, we should p 29 not have attained to the height of that great Colossus of the Andes, the Chimborazo, whose height is twice that of Mont Aetna; and we must pile the Righi, or Mount Athos, on the summit of the Chimborazo, in order to form a just estimate of the elevation of the Dhawalagiri, the highest point of the Himalaya. [footnote] *These comparisons are only approximative. The several elevations above the level of the sea are, in accurate numbers, as follows: The Schneekoppe or Riesenkoppe, in Silesia about 5270 feet, according to Hallaschka. The Righi, 5902 feet, taking the height of the Lake of Lucerne at 1426 feet, according to Eschman. (See 'Compte Rendu des Mesures Trigonometriques en Suisse', 1840, p. 230.) Mount Athos, 6775 feet, according to Captain Gaultier; Mount Pilatus, 7546 feet; Mount Aetna, 10,871 feet, according to Captain Smyth; or 10,874 feet, according to the barometrical measurement made by Sir John Herschel, and communicated to me in writing in 1825, and 10,899 feet, according to angles of altitude taken by Cacciatore at Palermo (calculated by assuming the terrestrial refraction to be 0.076); the Schreckhorn, 12,383 feet; the Jungfrau, 13,720 feet, according to Tralles; Mount Blanc, 15,775 feet, according to the different measurements considered by Roger ('Bibl. Univ.', May, 1828, 0. 24-53), 15,733 feet, according to the measurements taken from Mount Columbier by Carlini in 1821, and 15,748 feet, as measured by the Austrian engineers from Trelod and the Glacier d'Ambin. [footnote continued] The actual height of the Swiss mountains fluctuates, according to Eschman's observations, as much as 25 English feet, owing to the varying thickness of the stratum of snow that covers the summits. Chimborazo is, according to my trigonometrical measurements, 21,421 feet (see Humboldt, 'Recueil d'Obs. Astr.', tome i., p. 73), and Dhawalagiri, 28,074 feet. As there is a difference of 445 feet between the determinations of Blake and Webb, the elevation assigned to the Dhawalagiri (or white mountain, from the Sanscrit 'dhawala', white, and 'giri', mountain) can not be received with the same confidence as that of the Jawahir, 25,749 feet, since the latter rests on a complete trigonomietrical measurement (see Herbert and Hodgson in the 'Asiat. Res.', vol. xiv., p. 189, and Suppl. to 'Encycl. Brit.', vol. iv., p. 643). I have shown elsewhere ('Ann. des Sciences Naturelles', Mars, 1825) that the height of the Dhawalagiri (28,074 feet) depends on several elements that have not been ascertained with certainty, as azimuths and latitudes (Humboldt, 'Asie Centrale', t. iii., p. 282). It has been believed, but without foundation, that in the Tartaric chain, north of Thibet, opposite to the chain of Kuen-lun, there are several snowy summits, whose elevation is about 30,000 English feet (almost twice that of Mont Blanc), or, at any rate, 29,000 feet (see Captain Alexander Gerard's and John Gerard's 'Journey to the Boorendo Pass', 1840, vol. i., p. 143 and 311). Chimborazo is spoken of in the text only as 'one' of the highest summits of the chain of the Andes; for in the year 1827, the learned and highly-gifted traveler, Pentland, in his memorable expedition to Upper Peru (Bolivia), measured the elevation of two mountains situated to the east of Lake Titicaca, viz., the Sorata, 25,200 feet, and the Illimani, 24,000 feet, both greatly exceeding the height of Chimborazo, which is only 21,421 feet, and being nearly equal in elevation to the Jawahir, which is the highest mountain in the Himalaya that has as yet been accurately measured. Thus Mont Blanc is 5646 feet below Chimborazo; Chimborazo, 3779 feet below the Sorata; the Sorata, 549 feet below the Jawahir, and probably about 2880 feet below the Dhawalagiri. According to a new measurement of the Illimani, by Pentland, in 1838, the elevation of this mountain is given at 23,868 feet, varying only 133 feet from the measurement taken in 1827. The elevations have been given in this note with minute exactness, as erroneous numbers have been introduced into many maps and tables recently published, owing to incorrect reductions of the measurements. [In the preceding note, taken from those appended to the Introduction in the French translation, rewritten by Humboldt himself, the measurements are given in meters, but these have been converted into English feet, for the greater convenience of the general reader.] -- 'Tr.' But although the mountains of India greatly surpass the Cordilleras of South America by their astonishing elevation (which, after being long contested, has at last been confirmed by accurate measurements), they can not, from their geographical position, present the same inexhaustible variety of phenomena by which the latter are characterized. The impression produced by the grander aspects of nature dies not depend exclusively on height. The chain of the Himalaya is placed far beyond the limits of the torrid zone, and scarcely is a solitary palm-tree to be found in the beautiful valleys of Kumaoun and Garhwal.* [Footnote] *The absence of palms and tree-ferns on the temperate slopes of the Himalaya is shown in Don's 'Flora Nepalensis', 1825, and in the remarkable series of lithographs of Wallich's 'Flora Indica', whose catalogue contains the enormous number of 7683 Himalaya species, almost all phanerogamic plants, which have as yet been but imperfectly classified. In Nepaul (lat. 26 1/2 degrees to 27 1/4 degrees) there has hitherto been observed only one species of palm, Chamaerops martiana, Wall. ('Plantae Asiat.', lib. iii., p. 5,211), which is found at the height of 5250 English feet above the level of the sea, in the shady valley of Bunipa. The magnificent tree-fern, Alsophila brunoniana, Wall. (of which a stem 48 feet long has been in the possession of the British Museum since 1831), does not grow in Nepaul, but is found on the mountains of Silhet, to the northwest of Calcutta, in lat. 24 degrees 50 minutes. The Nepaul fern, Paranema cyathoides, Don, formerly known as Sphaeroptera barbata, Wall. ('Plantae Asiat.', lib. i., p. 42, 48), is indeed, nearly related to Cyathea, a species of which I have seen in the South American Missions of Caripe, measuring 33 feet in height; this is not, however, properly speaking a tree. On the southern slope of the ancient Paropamisus, in the latitudes of 28 degrees and 34 degrees, nature no longer displays the same abundance of tree-ferns and arborescent grasses, heliconias and orchideous plants, which in tropical p 30 regions are to be found even on the highest plateaux of the mountains. On the slope of the Himalaya, under the shade of the Deodora and the broad-leaved oak, peculiar to these Indian Alps, the rocks of granite and of mica schist are covered with vegetable forms almost similar to those which characterize Europe and Northern Asia. The species are not identical, but closely analogous in aspect and physiognomy, as, marsh parnassia, and the prickly species of Ribes.* The chain of the Himalaya is also wanting in the imposing phenomena of volcanoes, which in the Andes and in the Indian Archipelago often reveal to the inhabitants, under the most terrific forms, the existence of the forces pervading the interior of our planet. [footnote] *Ribes nubicola, R. glaciale, R. grossularia. The species which compose the vegetation of the Himalaya are four pines, notwithstanding the assertion of the ancients regarding Eastern Asia (Strabo, lib. 11, p. 510, Cas.), twenty-five oaks, four birches, two chestnuts, seven maples, twelve willows, fourteen roses, three species of strawberry, seven species of Alpine roses ('rhododendra'), one of which attains a height of 20 feet, and many other northern genera. Large white apes, having black faces, inhabit the wild chestnut-tree of Kashmir, which grows to a height of 100 feet, in lat. 33 degrees (see Carl von Hugel's 'Kaschmir', 1840, 2d pt. 249). Among the Coniferae, we find the Pinus deodwara, or deodara (in Sanscrit, 'dewa-daru', the timber of the gods), which is nearly allied to Pinus cedrus. Near the limit of perpetual snow flourish the large and showy flowers of the Gentiana venusta, G. Moorcroftiana, Swertia purpurescens, S. speciosa, Parnassia armata, P. nubicola, Poenia Emode, Tulipa stellata; and besides varieties of European genera peculiar to these Indian mountains, true European species as Leontodon taraxacum, Prunella vulgaris, Galium aparine, and Thlaspi arvense. The heath mentioned by Saunders, in Turner's 'Travels', and which had been confounded with Calluna vulgaris, is an Andromeda, a fact of the greatest importance in the geography of Asiatic plants. If I have made use, in this work, of the unphilosophical expressions of European genera, 'European' special, 'growing wild in Asia', etc., it has been in consequence of the old botanical language, which, instead of the idea of a large dissemination, or, rather, of the coexistence of organic productions, has dogmatically substituted the false hypothesis of a migration, which, from predilection for Europe, is further assumed to have been from west to east. Moreover, on the southern declivity of the Himalaya, where the ascending current deposits the exhalations rising from a vigorous Indian vegetation, the region of perpetual snow begins at an elevation of 11,000 or 12,000 feet above the level of the sea,* thus setting a limit to the development of organic p 31 life in a zone that is nearly 3000 feet lower than that to which it attains in the equinoctial region of the Cordilleras. [footnote] *On the southern declivity of the Himalaya, the limit of perpetual snow is 12,978 feet above the level of the sea; on the northern declivity, or, rather, on the peaks which rise above the Thibet, or Tartarian plateau, this limit is at 16,625 feet from 30 1/2 degrees to 32 degrees of latitude, while at the equator, in the Andes of Quito, it is 15,790 feet. Such is the result I have deduced from the combination of numerous data furnished by Webb, Gerard, Herbert, and Moorcroft. (See my two memoirs on the mountains of India, in 1816 and 1820, in the 'Ann. de Chimie et de Physique', t. iii., p. 303; t. xiv., p. 6, 22, 50.) The greater elevation to which the limit of perpetual snow recedes on the Tartarian declivity is owing to the radiation of heat from the neighboring elevated plains, to the purity of the atmosphere, and to the infrequent formation of snow in an air which is both very cold and very dry. (Humboldt, 'Asie Centrale', t. iii., p. 281-326.) My opinion on the difference of height of the snow-line on the two sides of the Himalaya has the high authority of Colebrooke in its favor. He wrote to me in June, 1824, as follows: "I also find, from the data in my possession, that the elevation of the line of perpetual snow is 13,000 feet. On the southern declivity, and at latitude 31 degrees, Webb's measurements give me 13,500 feet, consequently 500 feet more than the height deduced from Captain Hodgson's observations. Gerard's measurements fully confirm your opinion that the line of snow is higher on the northern than on the southern side." It was not until the present year (1840) that we obtained the complete and collected journal of the brothers Gerard, published under the supervision of Mr. Lloyd. ('Narrative of a Journey from Cawnpoor to the Boorendo Pass, in the Himalaya, by Captain Alexander Gerard and John Gerard, edited by George Lloyd', vol. i., p. 292, 311, 320, 327 and 341.) Many interesting details regarding some localities may be found in the narrative of 'A Visit to the Shatool, for the Purpose of determining the Line of Perpetual Snow on the southern face of the Himalaya, in August', 1822. Unfortunately, however, these travelers always confound the elevation at which sporadic snow falls with the maximum of the height that the snow-line attains on the Thibetian plateau. Captain Gerard distinguishes between the summits that rise in the middle of the plateau, where he states the elevation of the snow-line to be between 18,000 and 19,000 feet, and the northern slopes of the chain of the Himalaya, which border on the defile of the Sutledge, and can radiate but little heat, owing to the deep ravines with which they are intersected. The elevation of the village of Tangno is given at only 9300 feet, while that of the plateau surrounding the sacred lake of Maqasa is 17,000 feet. Captain Gerard finds the snow-line 500 feet lower on the northern slopes, where the chain of the Himalaya is broken through, than toward the southern declivities facing Hindostan, and he there estimates the line of perpetual snow at 15,000 feet. The most striking differences are presented between the vegetation on the Thibetian plateau and that characteristic of the southern slopes of the Himalaya. On the latter the cultivation of grain is arrested at 9974 feet and even there the corn has often to be cut when the blades are still green. The extreme limit of forests of tall oaks and deodars is 11,960 feet; that of dwarf birches, 12,983 feet. On the plains, Captain Gerard found pastures up to the height of 17,000 feet; the cereals will grow at 14,100 feet, or even at 18,540 feet; birches with tall stems at 14,100 feet, and copse or brush wood applicable for fuel is found at an elevation of upward of 17,000 feet, that is to say, 1280 feet and above the lower limits of the snow-line at the equator, in the province of Quito. It is very desirable that the 'mean' elevation of the Thibetian plateau, which I have estimated at only about 8200 feet between the Himalaya and the Kuen-lun, and the difference in the height of the line of perpetual snow on the southern and on the northern slopes of the Himalaya, should be again investigated by travelers who are accustomed to judge of the general conformation of the land. Hitherto simple calculations have too often been confounded with actual measurements, and the elevations of isolated summits with that of the surrounding plateau. (Compare Carl Zimmerman's excellent Hypsometrical Remarks in his 'Geographischen Analyse der Karte von Inner Asien', 1841, s. 98.) Lord draws attention to the difference presented by the two faces of the Himalaya and those of the Alpine chain of Hindoo-Coosh, with respect to the limits of the snow-line. "The latter chain," he says, "has the table-land to the south, in consequence of which the snow-line is higher on the southern side, contrary to what we find to be the case with respect to the Himalaya, which is bounded on the south by sheltered plains, as Hindoo-Coosh is on the north." It must, however, be admitted that the hypsometrical data on which these statements are based require a critical revision with regard to several of their details; but still they suffice to establish the main fact, that the remarkable configuration of the land in Central Asia affords man all that is essential to the maintenance of life, as habitation, food, and fuel, at an elevation above the level of the sea which in almost all other parts of the globe is covered with perpetual ice. We must except the very dry districts of Bolivia, where snow is so rarely met with, and where Pentland (in 1838) fixed the snow-line at 15,667 feet, between 16 degrees and 17 3/4 degrees south latitude. The opinion that I had advanced regarding the difference in the snow-line on the two faces of the Himalaya has been most fully confirmed by the barometrical observations of Victor Jacquemont, who fell an early sacrifice to his noble and unwearied ardor. (See his 'Correspondance pendant son Voyage dans l'Inde', 1828 'a' 1832, liv. 23, p. 290, 296, 299.) "Perpetual snow," says Jacquemont, "descends lower on the southern than on the northern slopes of the Himalaya, and the limit constantly rises as we advance to the north of the chain bordering on India. On the Kionbrong, about 18,317 feet in elevation, according to Captain Gerard, I was still considerably below the limit of perpetual snow which I believe to be 19,690 feet in this part of Hindostan." (This estimate I consider much too high.) [Footnote continues] The same traveler says, "To whatever height we rise on the southern declivity of the Himalaya, the climate retains the same character, and the same division of the seasons as in the plains of India; the summer solstice being every year marked by the same prevalence of rain which continues to fall without intermission until the autumnal equinox. But a new, a totally different climate begins at Kashmir, whose elevation I estimate to be 5350 feet, nearly equal to that of the cities of Mexico and Popayan" ('Correspond. de Jacquemont', t. ii., p. 58 et 74). The warm and humid air of the sea, as Leopold von Buch well observes, is carried by the monsoons across the plains of India to the skirts of the Himalaya which arrest its course, and hinder it from diverging to the Thibetian districts of Ladak and Lassa. Carl von Hugel estimates the elevation of the Valley of Kashmir above the level of the sea at 5818 feet, and bases his observation on the determination of the boiling point of water (see theil 11, s. 155, and 'Journal of Geog. Soc.', vol. vi., p. 215). In this valley, where the atmosphere is scarcely ever agitated by storms, and in 34 degrees 7 minutes lat., snow is found, several feet in thickness, from December to March. p 32 But the countries bordering on the equator possess another advantage, to which sufficient attention has not hitherto been p 33 directed. This portion of the surface of the globe affords in the smallest space the greatest possible variety of impressions from the contemplation of nature. Among the colossal mountains of Cundinamarea, of Quito, and of Peru, furrowed by deep ravines, man is enabled to contemplate alike all the families of plants, and all the stars of the firmament. There, at a single glance, the eye surveys majestic palms, humid forests of bambusa, and the varied species of Musaceae, while above these forms of tropical vegetation appear oaks, medlars, the sweet-brier, and umbelliferous plants, as in our European homes. There as the traveler turns his eyes to the vault of heaven, a single glance embraces the constellation of the Southern Cross, the Magellanic clouds, and the guiding stars of the constellation of the Bear, as they circle round the arctic pole. There the depths of the earth and the vaults of heaven display all the richness of their forms and the variety of their phenomena. There the different climates are ranged the one above the other, stage by stage, like the vegetable zones, whose succession they limit; and there the observer may readily trace the laws that regulate the diminution of heat, as they stand indelibly inscribed on the rocky walls and abrupt declivities of the Cordilleras. Not to weary the reader with the details of the phenomena which I long since endeavored graphically to represent,* I will here limit myself to the consideration of a few of the general results whose combination constitutes the 'physical delineation of the torrid zone.' That which, in the vagueness of our p 34 impressions, loses all distinctness of form, like some distant mountain shrouded from view by a vail of mist, is clearly revealed by the light of mind, which, by its scrutiny into the causes of phenomena, learns to resolve and analyze their different elements, assigning to each its individual character. Thus, in the sphere of natural investigation, as in poetry and painting, the delineation of that which appeals most strongly to the imagination, derives its collective interest from the vivid truthfulness with which the individual features are portrayed. [footnote] *See, generally my 'Essai sur la Geographie des Plantes, et le Tableau physique des Regions Equinoxiales', 1807, p. 80-88. On the diurnal and nocturnal variations of temperature, see Plate 9 of my 'Atlas Geogr. et Phys. du Nouveau Continent'; and the Tables in my work, entitled 'De distributione Geographica Plantarum, secundum coeli tempriem, et altitudinem Montium', 1817, p. 90-116; the meteorological portion of my 'Asie Centrale', t. iii., p. 212, 224; and, finally, the more recent and far more exact exposition of the variations of temperature experienced in correspondence with the increase of altitude on the chain of the Andes, given in Boussingault's Memoir, 'Sur la profondeur a laquelle on trouve, sous les Tropiques, la couche de Temperature Invariable.' (Ann. de Chimie et de Physique, 1833, t. liii., p. 225-247.) This treatise contains the elevations of 128 points, included between the level of the sea and the declivity of the Antisana (17,900 feet), as well as the mean temperature of the atmosphere, which varies with the height between 81 degrees and 35 degrees F. The regions of the torrid zone not only give rise to the most powerful impressions by their organic richness and their abundant fertility, but they likewise afford the inestimable advantage of revealing to man, by the uniformity of the variations of the atmosphere and the development of vital forces, and by the contrasts of climate and vegetation exhibited at the different elevations, the invariability of the laws that regulate the course of the heavenly bodies, reflected, as it were, in terrestrial phenomena. Let us dwell, then, for a few moments, on the proofs of this regularity, which is such that it may be submitted to numerical calculation and computation. In the burning plains that rise but little above the level of the sea, reign the families of the banana, the cycas, and the palm, of which the number of species comprised in the flora of tropical regions has been so wonderfully increased in the present day by the zeal of botanical travelers. To these groups succeed, in the Alpine valleys, and the humid and shaded clefts on the slopes of the Cordilleras, the tree-ferns, whose thick cylindrical trunks and delicate lace-like foliage stand out in bold relief against the azure of the sky, and the cinchona, from which we derive the febrifuge bark. The medicinal strength of this bark is said to increase in proportion to the degree of moisture imparted to the foliage of the tree by the light mists which form the upper surface of the clouds resting over the plains. Every where around, the confines of the forest are encircled by broad bands of social plants, as the delicate aralia, the thibaudia, and the myrtle-leaved Andromeda, while the Alpine rose, the magnificent befaria, weaves a purple girdle round the spiry peaks. In the cold regions of the Paramos, which is continually exposed to the fury of storms and winds, we find that flowering shrubs and herbaceous plants, bearing large and variegated blossoms, have given place to monocotyledons, whose slender spikes constitute the sole covering of the soil. This is the zone of the p 35 grasses, one vast savannah extending over the immense mountain plateaux, and reflecting a yellow, almost golden tinge, to the slopes of the Cordilleras, on which graze the lama and the cattle domesticated by the European colonist. Where the naked trachyte rock pierces the grassy turf, and penetrates into those higher strata of air which are supposed to be less charged with carbonic acid, we meet only with plants of an inferior organization, as lichens, lecideas, and the brightly-colored, dust-like lepraria, scattered around in circular patches. Islets of fresh-fallen snow, varying in form and extent, arrest the last feeble traces of vegetable development, and to these succeeds the region of perpetual snow, whose elevation undergoes but little change, and may be easily determined. It is but rarely that the elastic forces at work within the interior of our globe have succeeded in breaking through the spiral domes, which, resplendent in the brightness of eternal snow, crown the summits of the Cordilleras; and even where these subterranean forces have opened a permanent communication with the atmosphere, through circular craters or long fissures, they rarely send forth currents of lava, but merely eject ignited scoriae, steam, sulphureted hydrogen gas, and jets of carbonic acid. In the earliest stages of civilization, the grand and imposing spectacle presented to the minds of the inhabitants of the tropics could only awaken feelings of astonishment and awe. It might, perhaps, be supposed, as we have already said, that the periodical return of the same phenomena, and the uniform manner in which they arrange themselves in successive groups, would have enabled man more readily to attain to a knowledge of the laws of nature; but, as far as tradition and history guide us, we do not find that any application was made of the advantages presented by these favored regions. Recent researches have rendered it very doubtful whether the primitive seat of Hindoo civilization -- one of the most remarkable phases in the progress of mankind -- was actually within the tropics. Airyana Vaedjo, the ancient cradle of the Zend, was situated to the northwest of the upper Indus, and after the great religious schism, that is to say, after the separation of the Iranians from the Brahminical institution, the language that had previously been common to them and to the Hindoos assumed among the latter people (together with the literature, habits, and conditions of society) an individual form in the Magodha of Madhya Desa,* a district that is bounded by the great chain p 36 of Himalaya and the smaller range of the Vindhya. [footnote] *See, on the Madhjadeca, properly so called, Lassen's excellent work, entitled 'Indische Alterthumskunde', bd. i., s. 92. The Chinese give the name of Mo-kie-thi to the southern Bahar, situated to the south of the Ganges (see 'Foe-Koue-Ki' by, 'Chy-Fa-Hian', 1836, p. 256). Djambu-dwipa is the name given to the whole of India; but the words also indicate one of the four Buddhist continents. In less ancient times the Sanscrit language and civilization advanced toward the southeast, penetrating further within the torrid zone, as my brother Wilhelm von Humboldt has shown in his great work on the Kavi and other languages of analogous structure.* [Footnote] *'Ueber die Kawi Sprache auf der Insel Java, nebst einer Einleitung uber die Verschiedenheit des menschlichen Sprachbaues und ihren Ein fluss auf die geistige Entwickelung des Menschengrshlecht's' von Wilhelm v. Humboldt, 1836, bd. i., s. 50519. Notwithstanding the obstacles opposed in northern latitudes to the discovery of the laws of nature, owing to the excessive complication of phenomena, and the perpetual local variations and the distribution of organic forms, it is to the inhabitants of a small section of the temperate zone that the rest of mankind owe the earliest revelation of an intimate and rational acquaintance with the forces governing the physical world. Moreover, it is from the same zone (which is apparently more favorable to the progress of reason, the softening of manners, and the security of public liberty) that the germs of civilization have been carried to the regions of the tropics, as much by the migratory movement of races as by the establishment of colonies, differing widely in their institution from those of the Phoenicians or Greeks. In speaking of the influence exercised by the succession of phenomena on the greater or lesser facility of recognizing the causes producing them, I have touched upon that important stage of our communion with the external world, when the enjoyment arising from a knowledge of the laws, and the mutual connection of phenomena, associates itself with the charm of a simple contemplation of nature. That which for a long time remains merely an object of vague intuition, by degrees acquires the certainty of positive truth; and man, as an immortal poet has said, in our own tongue -- Amid ceaseless change seeks the unchanging pole.* [Footnote] *This verse occurs in a poem of Schiller, entitled 'Der Spaziergang' which first appeared in 1795, in the 'Horen.' In order to trace to its primitive source the enjoyment derived from the exercise of thought, it is sufficient to cast a rapid glance on the earliest dawnings of the philosophy of nature, or of the ancient doctrine of the 'Cosmos.' We find even p 37 among the most savage nations (as my own travels enable me to attest) a certain vague, terror-stricken sense of the all-powerful unity of natural forces, and of the existence of an invisible, spiritual essence manifested in these forces, whether in unfolding the flower and maturing the fruit of the nutrient tree, in upheaving the soil of the forest, or in rending the clouds with the might of the storm. We may here trace the revelation of a bond of union, linking together the visible world and that higher spiritual world which escapes the grasp of the senses. The two become unconsciously blended together, developing in the mind of man, as a simple product of ideal conception and independently of the aid of observation, the first germ of a 'Philosophy of Nature.' Among nations least advanced in civilization, the imagination revels in strange and fantastic creations, and, by its predilection for symbols, alike influences ideas and language. Instead of examining, men are led to conjecture, dogmatize, and interpret supposed facts that have never been observed. The inner world of thought and of feeling does not reflect the image of the external world in its primitive purity. That which in some regions of the earth manifested itself as the rudiments of natural philosophy, only to a small number of persons endowed with superior intelligence, appears in other regions, and among entire races of men, to be the result of mystic tendencies and instinctive intuitions. An intimate communion with nature, and the vivid and deep emotions thus awakened, are likewise the source from which have sprung the first impulses toward the worship and deification of the destroying and preserving forces of the universe. But by degrees, as man, after having passed through the different gradations of intellectual development, arrives at the free enjoyment of the regulating power of reflection, and learns by gradual progress, as it were, to separate the world of ideas from that of sensations, he no longer rests satisfied merely with a vague presentiment of the harmonious unity of natural forces; thought begins to fulfill its noble mission; and observation, aided by reason, endeavors to trace phenomena to the causes from which they spring. The history of science teaches us the difficulties that have opposed the progress of this active spirit of inquiry. Inaccurate and imperfect observations have led, by false inductions, to the great number of physical views that have been perpetuated as popular prejudices among all classes of society. Thus by the side of a solid and scientific knowledge of natural phenomena there has been preserved a system of the pretended p 38 results of observation, which is so much the more difficult to shake, as it denies the validity of the facts by which it may be refuted. This empiricism, the melancholy heritage transmitted to us from former times, invariably contends for the truth of its axioms with the arrogance of a narrow-minded spirit. Physical philosophy, on the other hand, when based upon science, doubts because it seeks to investigate, distinguishes between that which is certain and that which is merely probable, and strives incessantly to perfect theory by extending the circle of observation. This assemblage of imperfect dogmas, bequeathed by one age to another -- this physical philosophy, which is composed of popular prejudices -- is not only injurious because it perpetuates error with the obstinacy engendered by the evidence of ill-observed facts, but also because it hinders the mind from attaining to higher views of nature. Instead of seeking to discover the 'mean' or 'medium' point, around which oscillate, in apparent independence of forces, all the phenomena of the external world, this system delights in multiplying exceptions to the law, and seeks, amid phenomena and in organic forms for something beyond the marvel of a regular succession, and an internal and progressive development. Ever inclined to believe that the order of nature is disturbed, it refuses to recognize in the present any analogy with the past, and guided by its own varying hypotheses, seeks at hazard, either in the interior of the globe or in the regions of space, for the cause of these pretended perturbations. It is the special object of the present work to combat those errors which derive their source from a vicious empiricism and from imperfect inductions. The higher enjoyments yielded by the study of nature depend upon the correctness and the depth of our views, and upon the extent of the subjects that may be comprehended in a single glance. Increased mental cultivation has given rise, in all classes of society, to an increased desire of embellishing life by augmenting the mass of ideas, and by multiplying means for their generalization; and this sentiment fully refutes the vague accusations advanced against the age in which we live, showing that other interests, besides the material wants of life, occupy the minds of men. It is almost with reluctance that I am about to speak of a sentiment, which appears to arise from narrow-minded views, or from a certain weak and morbid sentimentality -- I allude to the 'fear' entertained by some persons, that nature may by degrees lose a portion of the charm and magic of her power, p 39 as we learn more and more how to unvail her secrets, comprehend the mechanism of the movements of the heavenly bodies, and estimate numerically the intensity of natural forces. It is true that, properly speaking, the forces of nature can only exercise a magical power over us as long as their action is shrouded in mystery and darkness, and does not admit of being classed among the conditions with which experience has made us acquainted. The effect of such a power is, therefore, to excite the imagination, but that, assuredly, is not the faculty of mind we would evoke to preside over the laborious and elaborate observations by which we strive to attain to a knowledge of the greatness and excellence of the laws of the universe. The astronomer who, by the aid of the heliometer or a double-refracting prism,* determines the diameter of planetary bodies; who measures patiently year after year, the meridian altitude and the relative distances of stars, or who seeks a telescopic comet in a group of nebulae, does not feel his imagination more excited -- and this is the very guarantee of the precision of his labors -- than the botanist who counts the divisions of the calyx, or the number of stamens in a flower, or examines the connected or the separate teeth of the peristoma surrounding the capsule of a moss. Yet the multiplied angular measurements on the one hand, and the detail of organic relations on the other, alike aid in preparing the way for the attainment of higher views of the laws of the universe. [Footnote] *Arago's ocular micrometer, a happy improvement upon Rochon's prismatic or double-refraction micrometer. See M. Mathieu's note in Delambre's 'Histoire de l'Astronomie au dix-huitieme Siecle', 1827. We must not confound the disposition of mind in the observer at the time he is pursuing his labors, with the ulterior greatness of the views resulting from investigation and the exercise of thought. The physical philosopher measures with admirable sagacity the waves of light of unequal length which by interference mutually strengthen or destroy each other, even with respect to their chemical actions; the astronomer, armed with powerful telescopes, penetrates the regions of space, contemplates, on the extremest confines of our solar system, the satellites of Uranus, or decomposes faintly sparkling points into double stars differing in color. The botanist discovers the constancy of the gyratory motion of the chara in the greater number of vegetable cells, and recognizes in the genera and natural families of plants the intimate relations or organic forms. The vault of heaven, studded with nebulae p 40 and stars, and the rich vegetable mantle that covers the soil in the climate of palms, can not surely fail to produce on the minds of these laborious observers of nature an impression more imposing and more worthy of the majesty of creation than on those who are unaccustomed to investigate the great mutual relations of phenomena. I can not, therefore, agree with Burke when he says, "it is our ignorance of natural things that causes all our admiration and chiefly excites our passions." While the illusion of the senses would make the stars stationary in the vault of heaven, Astronomy, by her aspiring labors, has assigned indefinite bounds to space; and if she have set limits to the great nebula to which our solar system belongs, it has only been to show us in those remote regions of our optic powers, islet on islet of scattered nebulae. The feeling of the sublime, so far as it arises from a contemplation of the distance of the stars, of their greatness and physical extent, reflects itself in the feeling of the infinite, which belongs to another sphere of ideas included in the domain of mind. The solemn and imposing impressions excited by this sentiment are owing to the combination of which we have spoken, and to the analogous character of the enjoyment and emotions awakened in us, whether we float on the surface of the great deep, stand on some lonely mountain summit enveloped in the half-transparent vapory vail of the atmosphere, or by the aid of powerful optical instruments scan the regions of space, and see the remote nebulous mass resolve itself into worlds of stars. The mere accumulation of unconnected observations of details, devoid of generalization of ideas, may doubtlessly have tended to create and foster the deeply-rooted prejudice, that the study of the exact sciences must necessarily chill the feelings, and diminish the nobler enjoyments attendant upon a contemplation of nature. Those who still cherish such erroneous views in the present age, and amid the progress of public opinion, and the advancement of all branches of knowledge, fail in duly appreciating the value of every enlargement of the sphere of intellect, and the importance of the detail of isolated facts in leading us on to general results. The fear of sacrificing the free enjoyment of nature, under the influence of scientific reasoning, is often associated with an apprehension that every mind may not be capable of grasping the truths of the philosophy of nature. It is certainly true that in the midst of the universal fluctuation of phenomena and vital p 41 forces -- in that inextricable net-work of organisms by turns developed and destroyed -- each step that we make in the more intimate knowledge of nature leads us to the entrance of new labyrinths; but the excitement produced by a presentiment of discovery, the vague intuition of the mysteries to be unfolded, and the multiplicity of the paths before us, all tend to stimulate the exercise of thought in every stage of knowledge. The discovery of each separate law of nature leads to the establishment of some other more general law, or at least indicates to the intelligent observer its existence. Nature, as a celebrated physiologist* has defined it, and as the word was interpreted by the Greeks and Romans, is "that which is ever growing and ever unfolding itself in new forms." [Footnote] *Carus, 'Von den Urtheilen des Knochen und Schalen Gerustes', 1828 6. The series of organic types becomes extended or perfected in proportion as hitherto unknown regions are laid open to our view by the labors and researches of travelers and observers; as living organisms are compared with those which have disappeared in the great revolutions of our planet; and as microscopes are made more perfect, and are more extensively and efficiently employed. In the midst of this immense variety, and this periodic transformation of animal and vegetable productions, we see incessantly revealed the primordial mystery of all organic development, that same great problem of 'metamorphosis' which G��the has treated with more than common sagacity, and to the solution of which man is urged by his desire of reducing vital forms to the smallest number of fundamental types. As men contemplate the riches of nature, and see the mass of observations incessantly increasing before them, they become impressed with the intimate conviction that the surface and the interior of the earth, the depths of the ocean, and the regions of air will still, when thousands and thousands of years have passed away, open to the scientific observer untrodden paths of discovery. The regret of Alexander can not be applied to the progress of observation and intelligence.* [footnote] * Plut., in 'Vita Alex. Magni', cap. 7 General considerations, whether they treat of the agglomeration of matter in the heavenly bodies, or of the geographical distribution of terrestrial organisms, are not only in themselves more attractive than special studies, but they also afford superior advantages to those who are unable to devote much time to occupations of this nature. The different branches of the study of natural history are only accessible in certain positions of social life, and do not, at every season p 42 and in every climate, present like enjoyments. Thus, in the dreary regions of the north, man is deprived for a long period of the year of the spectacle presented by the activity of the productive forces of organic nature; and if the mind be directed to one sole class of objects, the most animated narratives of voyages in distant lands will fail to interest and attract us, if they do not touch upon the subjects to which we are most partial. As the history of nations -- if it were always able to trace events to their true causes -- might solve the ever-recurring enigma of the oscillations experienced by the alternately progressive and retrograde movement of human society, so might also the physical description of the world, the science of the 'Cosmos', if it were grasped by a powerful intellect, and based upon a knowledge of all the results of discovery up to a given period, succeed in dispelling a portion of the contradictions which, at first sight, appear to arise from the complication or phenomena and the multitude of the perturbations simultaneously manifested. The knowledge of the laws of nature, whether we can trace them in the alternate ebb and flow of the ocean, in the measured path of comets, or in the mutual attractions of multiple stars, alike increases our sense of the calm of nature, while the chimera so long cherished by the human mind in its early and intuitive contemplations, the belief in a "discord of the elements," seems gradually to vanish in proportion as science extends her empire. General views lead us habitually to consider each organism as a part of the entire creation, and to recognize in the plant or the animal not merely an isolated species, but a form linked in the chain of being to other forms either living or extinct. They aid us in comprehending the relations that exist between the most recent discoveries and those which have prepared the way for them. Although fixed to one point of space, we eagerly grasp at a knowledge of that which has been observed in different and far-distant regions. We delight in tracking the course of the bold mariner through seas of polar ice, or in following him to the summit of that volcano of the antarctic pole, whose fires may be seen from afar, even at mid-day. It is by an acquaintance with the results of distant voyages that we may learn to comprehend some of the marvels of terrestrial magnetism, and be thus led to appreciate the importance of the establishments of the numerous observatories which in the present day cover both hemispheres, and are designed to note p 43 the simultaneous occurrence of perturbations, and the frequency and duration of 'magnetic storms.' Let me be permitted here to touch upon a few points connected with discoveries, whose importance can only be estimated by those who have devoted themselves to the study of the physical sciences generally. Examples chosen from among the phenomena to which special attention has been directed in recent times, will throw additional light upon the preceding considerations. Without a preliminary knowledge of the orbits of comets, we should be unable duly to appreciate the importance attached to the discovery of one of these bodies, whose elliptical orbit is included in the narrow limits of our solar system, and which has revealed the existence of an ethereal fluid, tending to diminish its centrifugal force and the period of its revolution. The superficial half-knowledge, so characteristic of the present day, which leads to the introduction of vaguely comprehended scientific views into general conversation, also gives rise, under various forms, to the expression of alarm at the supposed danger of a collision between the celestial bodies, or of disturbance in the climatic relations of our globe. These phantoms of the imagination are so much the more injurious as they derive their source from dogmatic pretensions to true science. The history of the atmosphere, and of the annual variations of its temperature, extends already sufficiently far back to show the recurrence of slight disturbances in the mean temperature of any given place, and thus affords sufficient guarantee against the exaggerated apprehension of a general and progressive deterioration of the climates of Europe. Encke's comet, which is one of the three 'interior comets', completes its course in 1200 days, but from the form and position of its orbit it is as little dangerous to the earth as Halley's great comet, whose revolution is not completed in less than seventy-six years (and which appeared less brilliant in 1835 than it had done in 1759): the interior comet of Biela intersects the earth's orbit, it is true, but it can only approach our globe when its proximity to the sun coincides with our winter solstice. The quantity of heat received by a planet, and whose unequal distribution determines the meteorological variations of its atmosphere, depends alike upon the light-engendering force of the sun; that is to say, upon the condition of its gaseous coverings, and upon the relative position of the planet and the central body. p 44 There are variations, it is true, which, in obedience to the laws of universal gravitation, affect the form of the earth's orbit and the inclination of the ecliptic, that is, the angle which the axis of the earth makes with the plane of its orbit; but these periodical variations are so slow, and are restricted within such narrow limits, that their thermic effects would hardly be appreciable by our instruments in many thousands of years. The astronomical causes of a refrigeration of our globe, and of the diminution of moisture at its surface, and the nature and frequency of certain epidemics -- phenomena which are often discussed in the present day according to the benighted views of the Middle Ages -- ought to be considered as beyond the range of our experience in physics and chemistry. Physical astronomy presents us with other phenomena, which can not be fully comprehended in all their vastness without a previous acquirement of general views regarding the forces that govern the universe. Such, for instance, are the innumerable double stars, or rather suns, which revolve round one common center of gravity, and thus reveal in distant worlds the existence of the Newtonian law; the larger or smaller number of spots upon the sun, that is to say, the openings formed through the luminous and opaque atmosphere surrounding the solid nucleus; and the regular appearance about the 13th of November and the 11th of August, of shooting stars, which probably form part of a belt of asteroids, intersecting the earth's orbit, and moving with planetary velocity. Descending from the celestial regions to the earth, we would fain inquire into the relations that exist between the oscillations of the pendulum in air (the theory of which has been perfected by Bessel) and the density of our planet; and how the pendulum, acting the part of a plummet, can, to a certain extent, throw light upon the geological constitution of strata at great depths? By means of this instrument we are enabled to trace the striking analogy which exists between the formation of the granular rocks composing the lava currents ejected from active volcanoes, and those endogenous masses of granite, porphyry, and serpentine, which, issuing from the interior of the earth, have broken, as eruptive rocks, through the secondary strata, and modified them by contact, either in rendering them harder by the introduction of silex, or reducing them into dolomite, or, finally, by inducing within them the formation of crystals of the most varied composition. The elevation of sporadic islands, of p 45 domes of trachyte, and cones of basalt, by the elastic forces emanating from the fluid interior of our globe, has led one of the first geologists of the age, Leopold von Buch, to the theory of the elevation of continents, and of mountain chains generally. This action of subterranean forces in breaking through and elevating strata of sedimentary rocks, of which the coast of Chili, in consequence of a great earthquake, furnished a recent example, leads to the assumption that the pelagic shells found by M. Bonpland and myself on the ridge of the Andes, at an elevation of more than 15,000 English feet, may have been conveyed to so extraordinary a position, not by a rising of the ocean, but by the agency of volcanic forces capable of elevating into ridges the softened crust of the earth. I apply the term 'volcanic', in the widest sense of the word, to every action exercised by the interior of a planet on its external crust. The surface of our globe, and that of the moon, manifest traces of this action, which in the former, at least, has varied during the course of ages. Those who are ignorant of the fact that the internal heat of the earth increases so rapidly with the increase of depth that granite is in a state of fusion about twenty or thirty geographical miles below the surface,* can not have a clear conception of the causes, and the simultaneous occurrence of volcanic eruptions at places widely removed from one another, or of the extent and intersection of 'circles of commotion' in earthquakes, or of the uniformity of temperature, and equality of chemical composition observed in thermal springs during a long course of years. [Footnote] * The determinations usually given of the point of fusion are in general much too high for refracting substances. According to the very accurate researches of Mitscherlich, the melting point of granite can hardly exceed 2372 degrees F. [Dr. Mantell states in 'The Wonders of Geology', 1848, vol. i., p. 34, that this increase of temperature amounts to 1 degree of Fahrenheit for every fifty-four feet of vertical depth.] -- Tr. The quantity of heat peculiar to a planet is, however, a matter of such importance -- being the result of its primitive condensation, and varying according to the nature and duration of the radiation -- that the study of this subject may throw some degree of light on the history of the atmosphere, and the distribution of the organic bodies imbedded in the solid crust of the earth. This study enables us to understand how a tropical temperature, independent of latitude (that is, of the distance from the poles), may have been produced by deep fissures remaining open, and exhaling heat from the interior p 46 of the globe, at a period when the earth's crust was still furrowed and rent, and only in a state of semi-solidification; and a primordial condition is thus revealed to us, in which the temperature of the atmosphere, and climates generally, were owing rather to a liberation of caloric and of different gaseous emanations (that is to say, rather to the energetic reaction of the interior on the exterior) than to the position of the earth with respect to the central body, the sun. The cold regions of the earth contain, deposited in sedimentary strata, the products of tropical climates; thus, in the coal formations, we find the trunks of palms standing upright amid coniferae, tree ferns, goniatites, and fishes having rhomboidal osseous scales;* in the Jura limestone, colossal skeletons of crocodiles, plesiosauri, planulites, and stems of the cycadeae; in the chalk formations, small polythalmia and bryozoa, whose species still exist in our seas; in tripoli, or polishing slate, in the semi-opal and the farina-like opal or mountain meal, agglomerations of siliceous infusoria, which have been brought to light by the powerful microscope of Ehrenberg;** and, lastly, in transported soils, and in certain caves, the bones of elephants, hyenas, and lions. [Footnote] *See the classical work on the fishes of the Old World by Agassiz, 'Rech. sur les Poissons Fossiles', 1834, vol. i., p. 38; vol. ii., p. 3, 28, 34, App., p. 6. The whole genus of Amblypterus, Ag., nearly allied to Palaeoniscus (called also Palaeothrissum), lies buried beneath the Jura formations in the old carboniferous strata. Scales which, in some fishes, as in the family of Lepidoides (order of Ganoides), are formed like teeth, and covered in certain parts with enamel, belong, after the Placoides, to the oldest forms of fossil fishes; their living representatives are still found in two genera, the 'Bichir' of the Nile and Senegal, and the 'Lepidosteus' of the Ohio. [Footnote] **[The 'polishing slate' of Bilin is stated by M. Ehrenberg to form a 'series' of strata fourteen feet in thickness, entirely made up of the siliceous shells of 'Gaillonellae', of such extreme minuteness that a cubic inch of the stone contains forty-one thousand millions! The 'Bergmehl' ('mountain meal' or 'fossil farina') of San Fiora, in Tuscany, is one mass of animalculites. See the interesting work of G. A. Mantell, 'On the Medals of Creation', vol. i., p. 233.] -- Tr. An intimate acquaintance with the physical phenomena of the universe leads us to regard the products of warm latitudes that are thus found in a fossil condition in northern regions not merely as incentives to barren curiosity, but as subjects awakening deep reflection, and opening new sources of study. The number and the variety of the objects I have alluded to give rise to the question whether general considerations of physical phenomena can be made sufficiently clear to persons who have not acquired a detailed and special knowledge of p 47 descriptive natural history, geology, or mathematical astronomy? I think we ought to distinguish here between him whose task it is to collect the individual details of various observations, and study the mutual relations existing among them, and him to whom these relations are to be revealed, under the form of general results. The former should be acquainted with the specialities of phenomena, that he may arrive at a generalization of ideas as the result, at least in part, of his own observations, experiments, and calculations. It can not be denied, that where there is an absence of positive knowledge of physical phenomena, the general results which impart so great a charm to the study of nature can not all be made equally clear and intelligible to the reader, but still I venture to hope, that in the work which I am now preparing on the physical laws of the universe, the greater part of the facts advanced can be made manifest without the necessity of appealing to fundamental views and principles. The picture of nature thus drawn, notwithstanding the want of distinctness of some of its outlines, will not be the less able to enrich the intellect, enlarge the sphere of ideas, and nourish and vivify the imagination. There is, perhaps, some truth in the accusation advanced against many German scientific works, that they lessen the value of general views by an accumulation of detail, and do not sufficiently distinguish between those great results which form, as it were, the beacon lights of science, and the long series of means by which they have been attained. This method of treating scientific subjects led the most illustrious of our poets* to exclaim with impatience, "The Germans have the art of making science inaccessible." An edifice can not produce a striking effect until the scaffolding is removed, that had of necessity been used during its erection. [Footnote] *Gothe, in 'Die Aphorismen uber Naturwissenschaft', bd. I., s. 155 ('Werke kleine Ausgabe','von' 1833.) Thus the uniformity of figure observed in the distribution of continental masses, which all terminate toward the south in a pyramidal form, and expand toward the north (a law that determines the nature of climates, the direction of currents in the ocean and the atmosphere, and the transition of certain types of tropical vegetation toward the southern temperate zone), may be clearly apprehended without any knowledge of the geodesical and astronomical operations by means of which these pyramidal forms of continents have been determined. In like manner, physical geography teaches us by how many leagues p 48 the equatorial axis exceeds the polar axis of the globe, and shows us the mean equality of the flattening of the two hemispheres, without entailing on us the necessity of giving the detail of the measurement of the degrees in the meridian, or the observations on the pendulum, which have led us to know that the true figure of our globe is not exactly that of a regular ellipsoid of revolution, and that this irregularity is reflected in the corresponding irregularity of the movements of the moon. The views of comparative geography have been specially enlarged by that admirable work, 'Erdkunde im Verh��ltniss zur Natur und sur Geschichte', in which Carl Ritter so ably delineates the physiognomy of our globe, and shows the influence of its external configuration on the physical phenomena on its surface, on the migrations, laws, and manners of nations, and on all the principal historical events enacted upon the face of the earth. France possesses an immortal work, 'L'Exposition du Syst��me du Monde', in which the author has combined the results of the highest astronomical and mathematical labors, and presented them to his readers free from all processes of demonstration. The structure of the heavens is here reduced to the simple solution of a great problem in mechanics; yet Laplace's work has never yet been accused of incompleteness and want of profundity. The distinction between dissimilar subjects, and the separation of the general from the special, are not only conducive to the attainment of perspicuity in the composition of a physical history of the universe, but are also the means by which a character of greater elevation may be imparted to the study of nature. By the suppression of all unnecessary detail, the great masses are better seen, and the reasoning faculty is enabled to grasp all that might otherwise escape the limited range of the senses. The exposition of general results has, it must be owned, been singularly facilitated by the happy revolution experienced since the close of the last century, in the condition of all the special sciences, more particularly of geology, chemistry, and descriptive natural history. In proportion as laws admit of more general application, and as sciences mutually enrich each other, and by their extension become connected together in more numerous and more intimate relations, the development of general truths may be given with conciseness devoid of superficiality. On being first examined, all phenomena appear to be p 49 isolated, and it is only by the result of a multiplicity of observations, combined by reason, that we are able to trace the mutual relations existing between them. If, however, in the present age, which is so strongly characterized by a brilliant course of scientific discoveries, we perceive a want of connection in the phenomena of certain sciences, we may anticipate the revelation of new facts, whose importance will probably be commensurate with the attention directed to these branches of study. Expectations of this nature may be entertained with regard to meteorology, several parts of optics, and to radiating heat, and electro-magnetism, since the admirable discoveries of Melloni and Faraday. A fertile field is here opened to discovery, although the voltaic pile has already taught us the intimate connection existing between electric, magnetic, and chemical phenomena. Who will venture to affirm that we have any precise knowledge, in the present day, of that part of the atmosphere which is not oxygen, or that thousands of gaseous substances affecting our organs may not be mixed with the nitrogen, or, finally, that we have even discovered the whole number of the forces which pervade the universe? It is not the purpose of this essay on the physical history of the world to reduce all sensible phenomena to a small number of abstract principles, based on reason only. The physical history of the universe, whose exposition I attempt to develop, does not pretend to rise to the perilous abstractions of a purely rational science of nature, and is simply a 'physical geography, combined with a description of the regions of space and the bodies occupying them.' Devoid of the profoundness of a purely speculative philosophy, my essay on the 'Cosmos' treats of the contemplation of the universe, and is based upon a rational empiricism, that is to say, upon the results of the facts registered by science, and tested by the operations of the intellect. It is within these limits alone that the work, which I now venture to undertake, appertains to the sphere of labor to which I have devoted myself throughout the course of my long scientific career. The path of inquiry is not unknown to me, although it may be pursued by others with greater success. The unity which I seek to attain in the development of the great phenomena of the universe, is analogous to that which historical composition is capable of acquiring. All points relating to the accidental individualities, and the essential variations of the actual, whether in the form and arrangement of natural objects in the struggle of man against the elements, or of nations against nations, do not admit of being p 50 based only on a 'rational foundation' -- that is to say, of being deduced from ideas alone. It seems to me that a like degree of empiricism attaches to the Description of the Universe and to Civil History; but in reflecting upon physical phenomena and events, and tracing their causes by the process of reason, we become more and more convinced of the truth of the ancient doctrine, that the forces inherent in matter, and those which govern the moral necessity, and in accordance with movements occurring periodically after longer or shorter intervals. It is this necessity, this occult but permanent connection, this periodical recurrence in the progressive development of forms, phenomena, and events, which constitute 'nature', obedient to the first impulse imparted to it. Physics, as the term signifies, is limited to the explanation of the phenomena of the material world by the properties of matter. The ultimate object of the experimental sciences is, therefore, to discover laws, and to trace their progressive generalization. All that exceeds this goes beyond the province of the physical description of the universe, and appertains to a range of higher speculative views. Emmanuel Kant, one of the few philosophers who have escaped the imputation of impiety, has defined with rare sagacity the limits of physical explanations, in his celebrated essay 'On the Theory and Structure of the Heavens', published at Konigsberg in 1755. The study of a science that promises to lead us through the vast range of creation may be compared to a journey in a far-distant land. Before we set forth, we consider, and often with distrust, our own strength, and that of the guide we have chosen. But the apprehensions which have originated in the abundance and the difficulties attached to the subjects we would embrace, recede from view as we remember that with the increase of observations in the present day there has also arisen a more intimate knowledge of the connection existing among all phenomena. It has not unfrequently happened, that the researches made at remote distances have often and unexpectedly thrown light upon subjects which had long resisted the attempts made to explain them within the narrow limits of our own sphere of observation. Organic forms that had long remained isolated, both in the animal and vegetable kingdom, have been connected by the discovery of intermediate links or stages of transition. The geography of beings endowed p 51 with life attains completeness as we see the species, genera, and entire families belonging to one hemisphere, reflected as it were, in analogous animal and vegetable forms in the opposite hemisphere. There are, so to speak, the 'equivalents' which mutually personate and replace one another in the great series of organisms. These connecting links and stages of transition may be traced, alternately, in a deficiency or an excess of development of certain parts, in the mode of junction of distinct organs, in the differences in the balance of forces, or in a resemblance to intermediate forms which are not permanent, but merely characteristic of certain phases of normal development. Passing from the consideration of beings endowed with life to that of inorganic bodies, we find many striking illustrations of the high state of advancement to which modern geology has attained. We thus see, according to the grand views of Elie de Beaumont, how chains of mountains dividing different climates and floras and different races of men, reveal to us their 'relative age', both by the character of the sedimentary strata they have uplifted, and by the directions which they follow over the long fissures and which the earth's crust is furrowed. Relations of superposition of trachyte and of syenitic porphyry, of diorite and of serpentine, which remain in the rich platinum districts of the Oural, and on the south-western declivity of the Siberian Alti, are elucidated by the observations that have been made on the plateaux of Mexico and Antioquia, and in the unhealthy ravines of Choco. The most important facts on which the physical history of the world has been based in modern times, have not been accumulated by chance. It has at length been fully acknowledged, and the conviction is characteristic of the age, that the narratives of distant travels, too long occupied in the mere recital of hazardous adventures, can only be made a source of instruction where the traveler is acquainted with the condition of the science he would enlarge, and is guided by reason in his researches. It is by this tendency to generalization, which is only dangerous in its abuse, that a great portion of the physical knowledge already acquired may be made the common property of all classes of society; but, in order to render the instruction impaired by these means commensurate with the importance of the subject, it is desirable to deviate as widely as possible from the imperfect compilations designated, till the close of the eighteenth century, by the inappropriate term of 'popular p 52 knowledge.' I take pleasure in persuading myself that scientific subjects may be treated of in language at once dignified, grave, and animated, and that those who are restricted within the circumscribed limits of ordinary life, and have long remained strangers to an intimate communion with nature, may thus have opened to them one of the richest sources of enjoyment, by which the mind is invigorated by the acquisition of new ideas. Communion with nature awakens within us perceptive faculties that had long lain dormant; and we thus comprehend at a single glance the influence exercised by physical discoveries on the enlargement of the sphere of intellect, and perceive how a judicious application of mechanics, chemistry, and other sciences may be made conducive to national prosperity. A more accurate knowledge of the connection of physical phenomena will also tend to remove the prevalent error that all branches of natural science are not equally important in relation to general cultivation and industrial progress. An arbitrary distinction is frequently made between the various degrees of importance appertaining to mathematical sciences, to the study of organized beings, the knowledge of electro-magnetism, and investigations of the general properties of matter in its different conditions of molecular aggregation; and it is not uncommon presumptuously to affix a supposed stigma upon researches of this nature, by terming them "purely theoretical," forgetting , although the fact has been long attested, that in the observation of a phenomenon, which at first sight appears to be wholly isolated, may be concealed the germ of a great discovery. When Aloysio Galvani first stimulated the nervous fiber by the accidental contact of two heterogeneous metals, his contemporaries could never have anticipated that the action of the voltaic pile would discover to us, in the alkalies, metals of a silvery luster, so light as to swim on water, and eminently inflammable; or that it would become a powerful instrument of chemical analysis, and at the same time a thermoscope and a magnet. When Hygens first observed, in 1678, the phenomenon of the polarization of light, exhibited in the difference between the two rays into which a pencil of light divides itself in passing through a doubly refracting crystal, it could not have been foreseen that, a century and a half later, the great philosopher Arago would, by his discovery of 'chromatic polarization', be led to discern, by means of a small fragment of Iceland spar, whether solar light emanates from a solid body or a gaseous covering, or p 53 whether comets transmit light directly or merely by reflection.* [Footnote] *Arago's Discoveries in the year 1811. -- Delambro's 'Histoire de l'Ast.', p. 652. (Passage already quoted.) An equal appreciation of all branches of the mathematical, physical, and natural sciences is a special requirement of the present age, in which the material wealth and the growing prosperity of nations are principally based upon a more enlightened employment of the products and forces of nature. The most superficial glance at the present condition of Europe shows that a diminution, or even a total annihilation of national prosperity, must be the award of those states who shrink with slothful indifference from the great struggle of rival nations in the career of the industrial arts. It is with nations as with nature, which, according to a happy expression of G��the,* "knows no pause in progress and development, and attaches her curse on all inaction." [Footnote] *Gothe, in 'Die Aphorismen uber Naturwissenschaft.' -- 'Werke', bd. 1., s. 4 The propagation of an earnest and sound knowledge of science can therefore alone avert the dangers of which I have spoken. Man can not act upon nature, or appropriate her forces to his own use, without comprehending their full extent, and having an intimate acquaintance with the laws of the physical world. Bacon has said that, in human societies, knowledge is power. Both must rise and sink together. But the knowledge that results from the free action of thought is at once the delight and the indestructible prerogative of man; and in forming part of the wealth of mankind, it not unfrequently serves as a substitute for the natural riches, which are but sparingly scattered over the earth. Those states which take no active part in the general industrial movement, in the choice and preparation of natural substances, or in the application of mechanics and chemistry, and among whom this activity is not appreciated by all classes of society, will infallibly see their prosperity diminish in proportion as neighboring countries become strengthened and invigorated under the genial influence of arts and sciences. As in nobler spheres of thought and sentiment, in philosophy, poetry, and the fine arts, the object at which we aim ought to be an inward one -- an ennoblement of the intellect -- so ought we likewise in our pursuit of science, to strive after a knowledge of the laws and the principles of unity that pervade the vital forces of the universe; and it is by such a course that p 54 physical studies may be made subservient to the progress of industry, which is a conquest of mind over matter. By a happy connection of causes and effects, we often see the useful linked to the beautiful and the exalted. The improvement of agriculture in the hands of freemen, and on properties of a moderate extent -- the flourishing state of the mechanical arts freed from the trammels of municipal restrictions -- the increased impetus imparted to commerce by the multiplied means of the intellectual progress of mankind, and of the amelioration of political institutions, in which this progress is reflected. The picture presented by modern history ought to convince those who are tardy in awakening to the truth of the lesson it teaches. Nor let it be feared that the marked predilection for the study of nature, and for industrial progress, which is so characteristic of the present age, should necessarily have a tendency to retard the noble exertions of the intellect in the domains of philosophy, classical history, and antiquity, or to deprive the arts by which life is embellished of the vivifying breath of imagination. Where all the germs of civilization are developed beneath the aegis of free institutions and wise legislation, there is no cause for apprehending that any one branch of knowledge should be cultivated to the prejudice of others. All afford the state precious fruits, whether they yield nourishment to man and constitute his physical wealth, or whether, more permanent in their nature, they transmit in the works of mind the glory of nations to remotest posterity. The Spartans, notwithstanding their Doric austerity, prayed the gods to grant them "the beautiful with the good."* [Footnote] *Pseudo-Plato, -- 'Alcib.', xi., p. 184, ed. Steph.; Plut., 'Instituta Laconica', p. 253, ed. Hatten. I will no longer dwell upon the considerations of the influence exercised by the mathematical and physical sciences on all that appertains to the material wants of social life, for the vast extent of the course on which I am entering forbids me to insist further upon the utility of these applications. Accustomed to distant excursions, I may, perhaps, have erred in describing the path before us as more smooth and pleasant than it really is, for such is wont to be the practice of those who delight in guiding others to the summits of lofty mountains: they praise the view even when great part of the distant plains lie hidden by clouds, knowing that this half-transparent vapory vail imparts to the scene a certain charm from p 55 the power exercised by the imagination over the domain of the senses. In like manner, from the height occupied by the physical history of the world, all parts of the horizon will not appear equally clear and well defined. This indistinctness will not, however, be wholly owing to the present imperfect state of some of the sciences, but in part, likewise, to the unskillfulness of the guide who has imprudently ventured to ascend these lofty summits. The object of this introductory notice is not, however, solely to draw attention to the importance and greatness of the physical history of the universe, for in the present day these are too well understood to be contested, but likewise to prove how, without detriment to the stability of special studies, we may be enabled to generalize our ideas by concentrating them in one common focus, and thus arrive at a point of view from which all the organisms and forces of nature may be seen as one living active whole, animated by one sole impulse. "Nature," as Schelling remarks in his poetic discourse on art, "is not an inert mass; and to him who can comprehend her vast sublimity, she reveals herself as the creative force of the universe -- before all time, eternal, ever active, she calls to life all things, whether perishable or imperishable." By uniting, under one point of view, both the phenomena of our own globe and those presented in the regions of space, we embrace the limits of the science of the 'Cosmos', and convert the physical history of the globe into the physical history of the universe, the one term being modeled upon that of the other. This science of the Cosmos is not, however, to be regarded as a mere encyclopedic aggregation of the most important and general results that have been collected together from special branches of knowledge. These results are nothing more than the materials for a vast edifice, and their combination can not constitute the physical history of the world, whose exalted part it is to show the simultaneous action and the connecting links of the forces which pervade the universe. The distribution of organic types in different climates and at different elevations -- that is to say, the geography of plants and animals -- differs as widely from botany and descriptive zoology as geology does from mineralogy, properly so called. The physical history of the universe must not, therefore, be confounded with the 'Encyclopedias of the Natural Sciences', as they have hitherto been compiled, and whose title is as vague as their limits are ill defined. In the work before us, partial facts will be considered only in relation to the whole. p 56 The higher the point of view, the greater is the necessity for a systematic mode of treating the subject in language at once animated and picturesque. But thought and language have ever been most intimately allied. If language, by its originality of structure and its native richness, can, in its delineations, interpret thought with grace and clearness, and if, by its happy flexibility, it can paint with vivid truthfulness the objects of the external world, it reacts at the same time upon thought, and animates it, as it were, with the breath of life. It is this mutual reaction which makes words more than mere signs and forms of thought; and the beneficent influence of a language is most strikingly manifested on its native soil, where it has sprung spontaneously from the minds of the people, whose character it embodies. Proud of a country that seeks to concentrate her strength in intellectual unity, the writer recalls with delight the advantages he has enjoyed in being permitted to express his thoughts in his native language; and truly happy is he who, in attempting to give a lucid exposition of the great phenomena of the universe, is able to draw from the depths of a language, which, through the free exercise of thought, and by the effusions of creative fancy, has for centuries past exercised so powerful an influence over the destinies of man. This material taken from pages 56 to 78 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 56 LIMITS AND METHOD OF EXPOSITION OF THE PHYSICAL DESCRIPTION OF THE UNIVERSE. I HAVE endeavored, in the preceding part of my work, to explain and illustrate, by various examples, how the enjoyments presented by the aspect of nature, varying as they do in the sources from when they flow, may be multiplied and ennobled by an acquaintance with the connection of phenomena and the laws by which they are regulated. It remains, then, for me to examine the spirit of the method in which the exposition of the 'physical description of the universe' should be conducted, and to indicate the limits of this science in accordance with the views I have acquired in the course of my studies and travels in various parts of the earth. I trust I may flatter myself with a hope that a treatise of this nature will justify the title I have ventured to adopt for my work, and exonerate me from the reproach of a presumption that would be doubly reprehensible in a scientific discussion. Before entering upon the delineation of the partial phenomena p 57 which are found to be distributed in various groups, I would consider a few general questions intimately connected together, and bearing upon the nature of our knowledge of the external world and its different relations, in all epochs of history and in all phases of intellectual advancement. Under this head will be comprised the following considerations: 1. The precise limits of the physical description of the universe, considered as a distinct science. 2. A brief enumeration of the totality of natural phenomena, presented under the form of a 'general delineation of nature.' 3. The influence of the external world on the imagination and feelings, which has acted in modern times as a powerful impulse toward the study of natural science, by giving animation to the description of distant regions and to the delineation of natural scenery, as far as it is characterized by vegetable physiognomy and by the cultivation of exotic plants, and their arrangement in well-contrasted groups. 4. The history of the contemplation of nature, or the progressive development of the idea of the Cosmos, considered with reference to the historical and geographical facts that have led to the discovery of the connection of phenomena. The higher the point of view from which natural phenomena may be considered, the more necessary it is to circumscribe the science within its just limits, and to distinguish it from all other analogous or auxiliary studies. Physical cosmography is founded on the contemplation of all created things -- all that exists in space, whether as substances or forces -- that is, all the material beings that constitute the universe. The science which I would attempt to define presents itself, therefore, to man, as the inhabitant of the earth, under a two-fold form -- as the earth itself and the regions of space. It is with a view of showing the actual character and the independence of the study of physical cosmography, and at the same time indicating the nature of its relations to 'general physics, descriptive natural history, geology, and comparative geography', that I will pause for a few moments to consider that portion of the science of the Cosmos which concerns the earth. As the history of philosophy does not consist of a mere material enumeration of the philosophical views entertained in different ages, neither should the physical description of the universe be a simple encyclopedic compilation of the sciences we have enumerated. The difficulty of defining the limits of intimately-connected studies has been increased, because for centuries it has been customary to designate various branches p 58 of empirical knowledge by terms which admit either of too wide or too limited a definition of the ideas which they were intended to convey, and are, besides, objectionable from having had a different signification in those classical languages of antiquity from thish chey have been borrowed. The terms physiology, physics, natural history, geology and geography arose, and were commonly used, long before clear ideas were entertained of the diversity of objects embraced by these sciences, and consequently of their reciprocal limitation. Such is the influence of long habit upon language, that by one of the nations of Europe most advanced in civilization the word "physic" is applied to medicine, while in a society of justly deserved universal reputation, technical chemistry, geology and astronomy (purely experimental sciences) are comprised under the head of "Philosophical Transactions." An attempt has often been made, and almost always in vain, to substitute new and more appropriate terms for these ancient designations, which, notwithstanding their undoubted vagueness, are now generally understood. These changes have been proposed, for the most part, by those who have occupied themselves with the general classification of the various branches of knowledge, from the first appearance of the great encyclopedia ('Margarita Philosophica') of Gregory Reisch,* prior of the Chartreuse at Freiburg, toward the close of the fifteenth century, to Lord Bacon, and from Bacon to D'Alembert; and in recent times to an eminent physicist, Andre Marie Ampere.** [footnote] *The 'Margarita Philosophica' of Gregory Reisch, prior of the Chartreuse at Freiburg, first appeared under the following title: Aepitome omnis Philosophi�¾, alias Margarita Philosophica, tractans de omni generi scibili. The Heidelberg edition (1486), and that of Strasburg (1504), both bear this title, but the first part was suppressed in the Freiburg edition of the same year, as well as in the twelve subsequent editions, which succeeded one another, at short intervals, till 1535. This work exercised a great influence on the diffusion of mathematical and physical sciences toward the beginning of the sixteenth century, and Crasles, the learned author of 'L'Aper��u Historique des Methodes en G��ometrica' (1837) has shown the great importance of Reisch's 'Encyclopedia' in the history of mathematics in the Middle Ages. I have had recourse to a passage in the 'Margarita Philosophica', found only in the edition of 1513, to elucidate the important question of the relations between the statements of the geographer of Saint-Die, Hylacomilus (Martin Waldseemuller), the first who gave the name of America to the New Continent, and those of Amerigo Vespucci, Rene, King of Jerusalem and Duke of Lorraine, as also those contained in the celebrated editions of Ptolemy of 1513 and 1522. See my 'Examen Critique de la Gegraphie du Nouveau Continent, et des Progres de l'Astronomie Nautique aux 15e et 16e Siecles', t. iv., p. 99-125. [footnote] II Amp��re, 'Essai sur la Phil. des Sciences', 1834, p. 25. Whewell, 'Philosophy of the Inductive Sciences', vol. ii., p. 277. Park, 'Pantology', p. 87. p 59 The selection of an inappropriate Greek nomenclature has perhaps been even more prejudicial to the last of these attempts than the injudicious use of binary divisions and the excessive multiplication of groups. The physical description of the world, considering the universe as an object of the external senses, does undoubtedly require the aid of general physics and of descriptive natural history, but thecontemplation of all created things, which are linked together, and form one 'whole', animated by internal forces, given to the science we are considering a peculiar character. Phyical science considers only the general properties of bodies; it is the product of abstraction -- a generalization of perceptible phenomena; and even in the work in which were laid the first foundations of general physics, in the eight books on physics of Aristotle,* all the phenomena of nature are considered as depending upon the primitive and vital action of one sole force, from which emaate all the movements of the universe. [footnote] * All changes in the physical world may be reduced to motion. Aristot., 'Phys. Ausc.', iii., 1 and 4, p. 200, 201. Bekker, viii., 1, 8, and 9, p. 250, 262, 265. 'De Genere et Corr.', ii., 10, p. 336. Pseudo-Aristot., 'De Mundo.' cap. vi., p. 398. The terrestrial portion of physical cosmography, for which I would willingly retain the expressive designation of 'physical geography', treats of the distribution of magnetism in our planet with relation to its intensity and direction, but does not enter into a consideration of the laws of attraction or repulsion of the poles, or the means of eliciting either permanent or transitory electro-magnetic currents. Physical geography depicts in broad outlines the even or irregular configuration of continents, the relations of superficial area, and the distribution of continental masses in the two hemispheres, a distribution which exercises a powerful influence on the diversity of climate and the meteorological modifications of the atmosphere; this science defines the character of mountain chains, which, having been elevated at different epochs, constitute distinct systems, whether they run in parallel lines or intersect one another; determines the mean height of continents above the level of the sea, the position of the center of gravity of their volume, and the relation of the highest summits of mountain chains to the mean elevation of their crests, or to their proximity with the sea-shore. It depicts the eruptive rocks as principles of movement, acting upon the sedimentary rocks by traversing, uplifting, and inclining them at various angles; it p 60 considers volcanoes either as isolated, or ranged in single or in double series, and extending their sphere of action to various distances, either by raising long and narrow lines of rocks, or by means of circles of commotion, which expand or diminish in diameter in the course of ages. This terrestrial portion of the science of the Cosmos describes the strife of the liquid element with the solid land; it indicates the features possessed in common by all great rivers in the upper and lower portion of their course, and in their mode of bifurcation when their basins are unclosed; and shows us rivers breaking through the highest mountain chains, or following for a long time a course parallel to them, either at their base, or at a considerable distance, where the elevation of the strata of the mountain system and the direction of their inclination correspond to the configuration of the table-land. It is only the general results of comparative orography and hydrography that belong to the science whose true limits I am desirous of determining, and not the special enumeration of the greatest elevations of our globe, of active volcanoes, of rivers, and the number of their tributaries, these details falliing rather within the domain of geography, properly so called. We would here only consider phenomena in their mutual connection, and in their relations to different zones of our planet, and to its physical constitution generally. The specialties both of inorganic and organized matter, classed according to analogy of form and composition, undoubtedly constitute a most interesting branch of study, but they appertain to a sphere of ideas having no affinity with the subject of this work. The description of different countries certainly furnishes us with the most important materials for the composition of a physical geography; but the combination of these different descriptions, ranged in series, would as little give us a true image of the general conformation of the irregular surface of our globe, as a succession of all the floras of different regions would constitute that which I designate as a 'Geography of Plants.' It is by subjecting isolated observations to the process of thought, and by combining and comparing them, that we are enabled to discover the relations existing in common between the climatic distribution of beings and the individuality of organic forms (in the morphology or descriptive natural history of plants and animals); and it is by induction that we are led to comprehend numerical laws, the proportion of natural families to the whole number of species, and to designate the latitude or geographical position of the zones in whose p 61 plains each organic form attains the maximum of its development. Considerations of this nature, by their tendency to generalization, impress a nobler character on the physical description of the globe, and enable us to understand how the aspect of the scenery, that is to say, the impression produced upon the mind by the physiognomy of the vegetation, depends upon the local distribution, the number, and the luxuriance of growth of the vegetable forms predominating in the general mass. The catalogues of organized beings to which was formerly given the pompous title of 'Systems of Nature', present us with an admirably connected arrangement by analogies of structure, either in the perfected development of these beings, or in the different phases which, in accordance with the views of a spiral evolution, affect in vegetables the leaves, bracts, calyx, corolla and fructifying organs; and in animals, with more or less symmetrical regularity, the cellular and fibrous tissues, and their perfect or but obscurely developed articulations. But these pretended systems of nature, however ingenious their mode of classification may be, do not show us organic beings as they are distributed in groups throughout our planet, according to their different relations of latitude and elevation above the level of the sea, and to climatic influences, which are owing to general and often very remote causes. The ultimate aim of physical geography is, however, as we have already said, to recognise unity in the vast diversity of phenomena, and by the exercise of thought and the combination of observations, to discern the constancy of phenomena in the midst of apparent changes. In the exposition of the terrestrial portion of the Cosmos, it will occasionally be necessary to descend to very special facts; but this will only be in order to recall the connection existing between the actual distribution of organic beings over the globe, and the laws of the ideal classification by natural families, analogy of internal organization and progressive evolution. It follows from these discussions on the limits of the various sciences, and more particularly from the distinction which must necessarily be made between descriptive botany (morphology of vegetables) and the geography of plants, that in the physical history of the globe, the innumerable multitude of organized bodies which embellish creation are considered rather according to 'zones of habitation' or 'stations', and to differently inflected 'isothermal bands', than with reference to the principles of gradation in the development of internal organism. Notwithstanding this, botany and zoology, which constitute p 62 the descriptive natural history of all organized beings, are the fruitful sources whence we draw the materials necessary to give a solid basis to the study of the mutual relations and connection of phenomena. We will here subjoin one important observation by way of elucidating the connection of which we have spoken. The first general glance over the vegetation of a vast extent of a continent shows us forms the most dissimilar -- Graminae and Orchideae, Coniferae and oaks, in local approximation to one another; while natural families and genera, instead of being locally associated, are dispersed as if by chance. This dispersion is, however, only apparent. The physical description of the globe teaches us that vegetation every where presents numerically constant relations in the development of its forms and types; that in the same climates, the species which are wanting in one country are replaced in a neighboring one by other species of the same family; and that this 'law of substitution', which seems to depend upon some inherent mysteries of the organism, considered with reference to its origin, maintains in contiguous regions a numerical relation between the species of various great families and the general mass of the phanerogamic plants constituting the two floras. We thus revealed in the multiplicity of the distinct organizations by which these regions are occupied; and we also discover in each zone, and diversified according to the families of plants, a slow but continuous action on the aerial ocean, depending upon the influence of light -- the primary condition of all organic vitality -- on the solid and liquid surface of our planet. It might be said, in accordance with a beautiful expression of Lavoisier, that the ancient marvel of the myth of Prometheus was incessantly renewed before our eyes. If we extend the course which we have proposed, following in the exposition of the physical description of the earth to the sidereal part of the science of the Cosmos, the delineation of the regions of space and the bodies by which they are occupied, we shall find our task simplified in no common degree. If, according to ancient but unphilosophical forms of nomenclature, we would distinguish between 'physics', that is to say, general considerations on the essence of matter, and the forces by which it is actuated, and 'chemistry', which treats of the nature of substances, their elementary composition, and those attractions that are not determined solely by the relations of mass, we must admit that the description of the earth comprises at p 63 once 'physical' and 'chemical' actions. In addition to gravitation, which must be considered as a primitive force in nature, we observe that attractions of another kind are at work around us, both in the interior of our planet and on its surface. These forces, to which we apply the term 'chemical affinity', act upon molecules in contact, or at infinitely minute distances from one another,* and which, being differently modified by electricity, heat, condensation in porous bodies, or by the contact of an intermediate substance, animate equally the inorganic world and animal and vegetable tissues. [footnote] * On the question already discussed by Newton, regarding the difference existing between the attraction of masses and molecular attraction, see Laplace, 'Exposition du Systeme du Monde', p. 384, and supplement to book x. of the 'Mecanique Celeste', p. 3, 4; Kant, 'Metaph. Anfangegrunde der Naturwissenschaft, S��m. Werke', 1839, bd. v., s. 309 (Metaphysical Principles of the Natural Sciences); Pectet, 'Physique', 1838, vol. i., p. 59-63. If we except the small asteroids, which appear to us under the forms of aerolites and shooting stars, the regions of space have hitherto presented to our direct observation physical phenomena alone; and in the case of these, we know only with certainty the effects depending upon the quantitative relations of matter of the distribution of masses. The phenomena of the regions of space may consequently be considered as influenced by simple dynamical laws -- the laws of motion. The effects that may arise from the specific difference and the hererogeneous nature of matter have not hitherto entered into our calculations of the mechanism of the heavens. The only means by which the inhabitants of our planet can enter into relation with the matter contained within the regions of space, whether existing in scattered forms or united into large spheroids, is by the phenomena of light, the propagation of the force of gravitation or the attraction of masses. The existence of a periodical action of the sun and moon on the variations of terrestrial magnetism is even at the present day extremely problematical. We have no direct experimental knowledge regarding the properties and specific qualities of the masses circulating in space, or of the matter of which they are probably composed, if we except what may be derived from the fall of aerolites or meteoric stones, which, as we have already observed, enter within the limits of our terrestrial sphere. It will be sufficient here to remark, that the direction and the excessive velocity of projection (a velocity wholly planetary) manifested by these masses, render it more than probable that p 64 they are small celestial bodies, which, being attracted by our planet, are made to deviate from their original course, and thus reach the earth enveloped in vapors, and in a high state of actual incandescence. The familiar aspect of these asteroids, and the analogies which they present with the minerals composing the earth's crust, undoubtedly afford ample grounds for surprise,* but, in my opinion, the only conclusion to be drawn from these facts is that, in general, planets and other sidereal masses, which by the influence of a central body, have been agglomerated into rings of vapor, and subsequently into spheroids, being integrant parts of the same system, and having one common origin, may likewise be composed of substances chemically identical. [footnote] I[The analysis of an aerolite which fell a few years since in Maryland, United States, and was examined by Professor Silliman, of New Haven, Connecticut, gave the following results: Oxyd of iron, 24; oxyd of nickel, 1.25; silica, with earthy matter, 3.46; sulphur, a trace - 28.71. Dr. Mantell's 'Wonders of Geology', 1848, vol. i., p. 51.] -- 'Tr.' Again, experiments with the pendulum, particularly those prosecuted with such rare precision by Bessel, confirm the Newtonian axiom, that bodies the most heterogeneous in their nature (as water, gold, quartz, granular limestone, and different masses of aerolites) experience a perfectly similar degree of acceleration from the attraction of the earth. To the experiments of the pendulum may be added the proofs furnished by purely astronomical observations. The almost perfect identity of the mass of Jupiter, deduced from the influence exercised by this stupendous planet on its own satellites, on Enck's comet of short period, and on the small planets Vesta, Juno, Ceres, and Pallas, indicates with equal certainty that within the limits of actual observation attraction is determined solely by the quantity of matter.* [footnote] *Poisson, 'Connaissances des Temps pour l'Anne' 1836, p. 64-66. Bessel, Poggendorf's 'Annalen', bd. xxv., s. 417. Encke, 'Abhandlungen der Berliner Academie' (Trans. of the Berlin Academy), 1826, s. 257. Mitscherlich, 'Lehrbuch der Chemie' (Manual of Chemistry), 1837 bd. i. s. 352. This absence of any perceptible difference in the nature of matter, alike proved by direct observation and theoretical deductions, imparts a high degree of simplicity to the mechanism of the heavens. The immeasurable extent of the regions of space being subjected to laws of motion alone, the sidereal portion of the science of the Cosmos is based on the pure and abundant source of mathematical astronomy, as is the terrestrial portion on physics, chemistry, and organic morphology; but the domain of these three last-named sciences embraces p 65 the consideration of phenomena which are so complicated and have, up to the present time, been found so little susceptible of the application of rigorous method, that the physical science of the earth can not boast of the same certainty and simplicity in the exposition of facts and their mutual connection which characterize the celestial portion of the Cosmos. It is not improbable that the difference to which we allude may furnish an explanation of the cause which, in the earliest ages of intellectual culture among the Greeks, directed the natural philosophy of the Pythagoreans with more ardor to the heavenly bodies and the regions of space than to the earth and its productions, and how through Philolaus, and subsequently through the analogous views of Aristarchus of Samos, and of Seleucus of Erythrea, this science has been made more conducive to the attainment of a knowledge of the true system of the world than the natural philosophy of the Ionian school could ever be to the physical history of the earth. Giving but little attention to the properties and specific differences of matter filling space, the great Italian school, in its Doric gravity, turned by preference toward all that relates to measure, to the form of bodies, and to the number and distances of the planets,* while the Ionian physicists directed their attention to the qualities of matter, its true or supposed metamorphoses, and to relations of origin. [footnote] *Compare Otfried Muller's 'Dorien', bd. i., s. 365. It was reserved for the powerful genius of Aristotle, alike profoundly speculative and practical to sound with equal success the depths of abstraction and the inexhaustible resources of vital activity pervading the material world. Several highly distinguished treatises on physical geography are prefaced by an introduction, whose purely astronomical sections are directed to the consideration of the earth in its planetary dependence, and as constituting a part of that great system which is animated by one central body, the sun. This course is diametrically opposed to the one which I propose following. In order adequately to estimate the dignity of the Cosmos, it is requisite that the sidereal portion, termed by Kant the 'natural history of the heavens', should not be made subordinate to the terrestrial. In the science of the Cosmos, according to the expression of Aristarchus of Samos, the pioneer of the Copernican system, the sun, with its satellites, was nothing more than one of the innumerable stars by which space is occupied. The physical history of the world must, therefore, begin with the description of the heavenly bodies, p 66 and with a geographical sketch of the universe, or, I would rather say, a true 'map of th world', such as was traced by the bold hand of the elder Herschel. If, notwithstanding the smallness of our planet, the most considerable space and the most attentive consideration be here afforded to that which exclusively concerns it, this arises solely from the disproportion in the extent of our knowledge of that which is accessible and of that which is closed to our observation. This subordination of the celestial to the terrestrial portion is met with in the great work of Bernard Varenius,* which appeared in the middle of the seventeenth century. [Footnote] *'Geographia Generalis in qua affectiones generales telluris explicantur.' The oldest Elzevir edition bears date 1650, the second 1672, and the third 1681; these were published at Cambridge, under Newton's supervision. This excellent work by Varenius is, in the true sense of the words, a physical description of the earth. Since the work 'Historia Natural de las Indias', 1590, in which the Jesuit Joseph de Acosta sketched in so masterly a manner the delineation of the New Continent, questions relating to the physical history of the earth have never been considered with such admirable generality. Acosta is richer in original observations, while Varenius embraces a wider circle of ideas, since his sojourn in Holland, which was at that period the center of vast commercial relations, had brought him in contact with a great number of well-iinformed travelers. 'Generalis sive Universalis Geographia dictur quae tellurem in genere considerat atque affectiones explicat, non habita particularium regionum ratione.' The general description of the earth by Varenius ('Pars Absoluta', cap. i.-xxii.) may be considered as a treatise of comparative geography, if we adopt the term used by the author himself ('Geographia Comparativa', cap. xxxiii.-xl.), although this must be understood in a limited acceptation. We may cite the following among the most remarkable passages of this book: the enumeration of the systems of mountains; the examination of the relations existing between their directions and the general form of continents (p. 66, 76, ed. Cantab., 1681); a list of extinct volcanoes, and such as were still in a state of activity; the discussion of facts relative to the general distribution of islands and archipelagoes (p. 220); the depth of the ocean relatively to the height of neighboring coasts (p. 103); the uniformity of level observed in all open seas (p. 97); the dependence of currents on the prevailing winds; the unequal saltness of the sea; the configuration of shores (p. 139); the direction of the winds as the result of differences of temperature, etc. We may further instance the remarkable considerations of Varenius regarding the equinoctial current from east to west, to which he attributes the origin of the Gulf Stream, beginning at Cape St. Augustin, and issuing forth between Cuba and Florida (p. 140). Nothing can be more accurate than his description of the current which skirts the western coast of Africa, between Cape Verde and the island of Fernando Po in the Gulf of Guinea. Varenius explains the formation of sporadic islands by supposing them to be "the raised bottom of the sea:" 'magna spirituum inclusorum vi, sicut aliquando montes e terra protusos esse quidam scribunt' (p. 225). The edition published by Newton in 1681 ('auctior et emendatior' unfortunately contains no additions from this great authority; and there is not even mention made of the polar compression of the globe, although the experiments on the pendulum by Richer had been made nine years prior to the appearance of the Cambridge edition. Newton's 'Principia Mathematica Philosophie Naturalis' were not communicated in manuscript to the Royal Society until April, 1686. Much uncertainty seems to prevail regarding the birth-place of Varenius. Jaecher says it was England, while, according to 'La Biographie Universelle' (b.xlvii., p. 495), he is stated to have been born at Amsterdam; but it would appear, from the dedicatory address to the burgomaster of that city (see his 'Geographia Comparativa', that both suppositions are false. Varenius expressly says that he had sought refuge in Amsterdam, "because his native city had been burned and completely destroyed during a long war," words which appear to apply to the north of Germany, and to the devastations of the Thirty Years' War. In his dedication of another work, 'Descriptio regni Japoniae' (Amst., 1649), to the Senate of Hamburgh, Varenius says that he prosecuted his elementary mathematical studies in the gymnasium of that city. There is, therefore, every reason to believe that this admirable geographer was a native of Germany, and was probably born at Luneburg ('Witten. Mem. Theol.', 1685, p. 2142; Zedler, 'Universal Lexicon', vol. xlvi., 1745, p. 187). p 67 He was the first to distinguish between 'general and special geography', the former of which he subdivides into an 'absolute', or, properly speaking, 'terrestrial' part, and a 'relative or planetary' portion, according to the mode of considering our planet either with reference to its surface in its different zones, or to its relations to the sun and moon. It redounds to the glory of Varenius that his work on 'General and Comparative Geography' should in so high a degree have arrested the attention of Newton. The imperfect state of many of the auxiliary sciences from which this writer was obliged to draw his materials prevented his work from corresponding to the greatness of the design, and it was reserved for the present age, and for my own country, to see the delineation of comparative geography, drawn in its full extent, and in all its relations with the history of man, by the skillful hand of Carl Ritter.* [Footnote] *Carl Ritter's 'Erdkunde im Verh��ltniss zur Natur und zur Geschichte des Menschen, oder allgemeine vergleichende Geographie' (Geography in relation to Nature and the History of Man, or general Comparative Geography). The enumeration of the most important results of the astronomical and physical sciences which in the history of the Cosmos radiate toward one common focus, may perhaps, to a certain degree, justify the designation I have given to my work, and, considered within the circumscribed limits I have proposed to myself, the undertaking may be esteemed less adventurous than the title. The introduction of new terms, especially with reference to the general results of a science which p 68 ought to be accessible to all, has always been greatly in opposition to my own practice; and whenever I have enlarged upon the established nomenclature, it has only been in the specialities of descriptive botany and zoology, where the introduction of hitherto unknown objects rendered new names necessary. The denominations of physical descriptions of the universe, or physical cosmography, which I use indiscriminantely, have been modeled upon those of 'physical descriptions of the earth', that is to say, 'physical geography', terms that have long been in common use. Descartes, whose genius was one of the most powerful manifested in any age, has left us a few fragments of a great work, which he intended publishing under the title of 'Monde', and for which he had prepared hiimself by special studies, including even that of human anatomy. The uncommon, but definite expression of the 'science of the Cosmos' recalls to the mind of the inhabitant of the earth that we are treating of a more widely-extended horizon -- of the assemblage of all things with which space is filled, from the remotest nebulae to the climatic distribution of those delicate tissues of vegetable matter which spread a variegated covering over the surface of our rocks. The influence of narrow-minded views peculiar to the earlier ages of civilization led in all languages to a confusion of ideas in the synonymic use of the words 'earth' and 'world', while the common expressions 'voyages round the world', 'map of the world', and 'new world', afford further illustrations of the same confusion. The more noble and precisely-defined expressions of 'system of the world', 'the planetary world', and 'creation and age of the world', relate either to the totality of the substances by which space is filled, or to the origin of the whole universe. It was natural that, in the midst of the extreme variability of phenomena presented by the surface of our globe, and the aerial ocean by which it is surrounded, man should have been impressed by the aspect of the vault of heaven, and the uniform and regular movements of the sun and planets. Thus the word Cosmos, which primitively, in the Homeric ages, indicated an idea of order and harmony, was subsequently adopted in scientific language, where it was gradually applied to the order observed in the movements of the heavenly bodies, to the whole universe, and then finally to the world in which this harmony was reflected to us. According to the assertion of Philolaus, whose fragmentary works have been so ably commented upon by B��ckh, and conformably to the general testimony p 69 of antiquity, Pythagoras was the first who used the word Cosmos to designate the order that reigns in the universe, or entire world.* [footnote] *[Greek word], in the most ancient, and at the same time most precise, definition of the word, signified 'ornament' (as an adornment for a man, a woman, or a horse); taken figuratively for [Greek word], it implied the order or adornment of a discourse. According to the testimony of all the ancients, it was Pythagoras who first used the word to designate the order in the universe, and the universe itself. Pythagoras left no writings; but ancient attestation to the truth of this assertion is to be found in several passages of the fragmentary works of Philolaus (Stob., 'Eclog.', p. 360 and 460, Heeren), p. 62, 90, in Bockh's German edition. I do not, according to the example of Nake, cite Timof Locris, since his authenticity is doubtful. Plutarch ('De plac. Phil.', ii., I) says, in the most express manner, that Pythatoras gave the name of Cosmos to the universe on account of the order which reigned throughout it; so likewise does Galen ('Hist. Phil.', p. 429). This word, together with its novel signification, passed from the schools of philosophy into the language of poets and prose writers. Plato designates the heavenly bodies by the name of 'Uranos', but the order pervading the regions of space he too terms the Cosmos, and in his 'Timus' (p. 30 a.) he says 'that the world is an animal endowed with a soul' [Greek words]. Compare Anaxag. Claz., ed. Schaubach, p. III, and Plut. ('De plac. Phil.', in Aristotle ('De Caelo', I, 9), 'Cosmos' signifies "the universe and the order pervading it," but it is likewise considered as divided in space into two parts -- the sublunary world, and the world above the moon. ('Meteor.', I., w, 1, and I., 3, 13, p. 339, 'a', and 340, 'b', Bekk.) The definition of Cosmos, which I have already cited is taken from Pseudo-Aristoteles 'de Mundo', cap. ii. (p. 391); the passage referred to is as follows: [Greek words]. Most of the passages occurring in Greek writers on the word 'Cosmos' may be found collected together in the controversy between Richard Bentley and Charles Boyle ('Opuscula Philologica', 1781, p. 347, 445; 'Dissertation upon the Epistles of Phalaris', 1817, p. 254); on the historical existence of Zaleucus, legislator of Leucris, in Nake's excellent work, 'Sched. Crit.', 1812, p. 9, 15; and, finally in Theophilus Schmidt, 'ad Cleom. Cycl. Theor.', met. I., 1, p. ix., 1 and 99. Taken in a more limited sense, the word Cosmos is also used in the plural (Plut., 1, 5), either to designate the stars (Stob., 1, p. 514; Plut., 11, 13) or the innumerable systems scattered like islands through the immensity of space, and each composed of a sun and a moon. (Anax. Claz., 'Fragm.', p. 89, 93, 120; Brandis, 'Gesch. der Griechisch-R��mischen Philosophie', b. i., s. 252 (History of the Greco-Roman Philosophy). Each of these groups forming thus a 'Cosmos', the universe, [Greek words], the word must be understood in a wider sense (Plut., ii., 1). It was not until long after the time of the Ptolemies that the word was applied to the earth. Bockh has made known inscriptions in praise of Trajan and Adrian ('Corpus Inscr. Graec.', I, n. 334 and 1036), in which [Greek word] occurs for [Greek word] in the same manner as we still use the term 'world' to signify the earth alone. We have already mentioned the singular division of the regions of space p 70 [Footnote continues] into three parts, the 'Olympus, Cosmos' and 'Ouranos' (Stob., i., p. 488; Philolaus, p. 95, 303); this division applies to the different regions surrounding that mysterious focus of the universe, the [Greek words] of the Pythagoreans. In the fragmentary passage in which this division is found, the term [Greek word] designates the innermost region, situated between the moon and earth; this is the domain of changing things. The middle region, where the planets circulate in an invariable and harmonious order, is, in accordance with the special conceptions entertained of the universe, exclusively termed 'Cosmos', while the word 'Olympus' is used to express the exterior or igneous region. Bopp, the profound philologist, has remarked that we may deduce, as Pott has done, 'Etymol. Forschungen', th.i., s. 39 and 252 ('Etymol. Researches'), the word [Greek word] from the Sanscrit root 'sud', 'purificari', by assuming two conditions; first that the Greek letter 'kappa' in [Greek word] comes from the palatial 'epsilon', which Bopp represents by 's' and Pott by '��' (in the same manner as [Greek word], 'decem, taihun' in Gothic, comes from the Indian word 'dasan'), and, next, that the Indian 'd'' corresponds, as a general rule, with the Greek 'theta' ('Vergleichende Grammatik' 99 -- Comparative Grammar), which shows the relation of [Greek word] (for [Greek word]) with the Sanscrit root 'sud', whence is also derived [Greek word]. Another Indian term for the world is 'gagat' (pronounced 'dschagat'), which is, properly speaking the present participle of the verb 'gagami' (I go), the root of which is 'ga.' In restricting ourselves to the circle of Hellenic etymologies, we find ('Etymol. M.', p. 532, 12) that [Greek word] is intimately associated with [Greek word] or rather with [Greek word], whence we have [Greek word] or [Greek word] Welcker ('Eine Kretische Col in Theben', s. 23 -- A Cretan Colony in Thebes) combines with this the name [Greek word] , as in Hesychius [Greek word] signifies a Cretan suit of arms. When the scientific language of Greece was introduced among the Romans, the word 'mundus', which at first had only the primary meaning of [Greek word] (female ornament), was applied to designate the entire universe. Ennius seems to have been the first who ventured upon this innovation. In one of the fragments of this poet, preserved by Macrobius, on the occasion of his quarrel with Virgil, we find the word used in its novel mode of acceptation: "Mundus caeli vastus constitit silentio" (Sat., vi., 2). Cicero also says, "Quem nos lucentem mundum vocamus" (Tim�¾us, 'S.de univer.', cap. x.) The Sanscrit root 'mand' from which Pott derives the Latin 'mundus' ('Etym. Forsch.', th. i., s. 240), combines the double signification of shining and adorning. 'Loka' designates in Sanscrit the world and people in general, in the same manner as the French word 'monde', and is derived according to Bopp, from 'lok' (to see and shine); it is the same with the Slavonic root 'swjet', which means both 'light' and 'world.' (Grimm, 'Deutsche Gramm.', b. iii., s. 394 -- German Grammar.) The word 'welt', which the Germans make use of at the present day, and which was 'weralt' in old German, 'worold' in old Saxon, and 'weruld' in Anglo-Saxon, was, according to James Grimm's interpretation, a period of time, an age ('saeculum') rather than a term used for the world in space. The Etruscans figured to themselves 'mundus' as an inverted dome, symmetrically opposed to the celestial vault (Otfried Muller's 'Etrusken', th. ii., s. 96, etc.). Taken in a still more limited sense, the word appears to have signified among the Goths the terrestrial surface girded by seas ('marei, meri',) the 'merigard', literally, 'garden of seas.' From the Italian school of philosophy, the expression passed, in this signification, into the language of those early poets p 71 of nature, Parmenides and Empedocles, and from thence into the works of prose writers. We will not here enter into a discussion of the manner in which, according to the Pythagorean views, Philolaus distinguishes between Olympus, Uranus, or the heavens, and Cosmos, or how the same word, used in a plural sense, could be applied to certain heavenly bodies (the planets) revolving round one central focus of the world, or to groups of stars. In this work I use the word Cosmos in conformity with the Hellenic usage of the term subsequently to the time of Pythagorus, and in accordance with the precise definition given of it in the treatise entitled 'De Mundo', which was long erroneously attributed to Aristotle. It is the assemblage of all things in heaven and earth, the universality of created things constituting the perceptible world. If scientific terms had not long been diverted from their true verbal signification, the present work ought rather to have borne the title of 'Cosmography', divided into 'Uranography' and 'Geography.' The Romans, in their feeble essays on philosophy, imitated the Greeks by applying to the universe the term 'mundus', which, in its primary meaning, indicated nothing more than ornament, and did not even imply order or regularity in the disposition of parts. It is probable that the introduction into the language of Latium of this technical term as an equivalent for Cosmos, in its double signification, is due to Ennius,* who was a follower of the Italian school, and the translator of the writings of Epicharmus and some of his pupils on the Pythagorean philosophy. [footnote] *See, on Ennius, the ingenious researches of Leopold Krahner, in his 'Grundlinien zur Geschichte des Verfalls der Romischen Staats-Reigion', 1837, s. 41-45 (Outlines of the History of the Decay of the Established Religion among the Romans). In all probability, Ennius did not quote from writings of Epicharmus himself, but from poems composed in the name of that philosopher, and in accordance with his views. We would first distinguish between the physical 'history' and the physical 'description' of the world. The former, conceived in the most general sense of the word, ought, if materials for writing it existed, to trace the variations experienced by the universe in the course of ages from the new stars which have suddenly appeared and disappeared in the vault of heaven, from nebul�¾ dissolving or condensing -- to the first stratum of cryptogamic vegetation on the still imperfectly cooled surface of the earth, or on a reef of coral uplifted from the depths of ocean. 'The physical description of the world' presents a picture of all that exists in space -- of the siimultaneous action of p 72 natural forces, together with the phenomena which they produce. But if we would correctly comprehend nature, we must not entirely or absolutely separate the consideration of the present state of things from that of the successive phases through which they have passed. We can not form a just conception of their nature without looking back on the mode of their formation. It is not organic matter alone that is continually undergoing change, and being dissolved to form new combinations. The globe itself reveals at every phase of its existence the mystery of its former conditions. We can not survey the crust of our planet without recognizing the traces of the prior existence and destruction of an organic world. The sedimentary rocks present a succession of organic forms, associated in groups, which have successively displaced and succeeded each other. The different super-imposed strata thus display to us the faunas and floras of different epochs. In this sense the description of nature is intimately connected with its history; and the geologist, who is guided by the connection existing among the facts observed, can not form a conception of the present without pursuing, through countless ages, the history of the past. In tracing the physical delineation of the globe, we behold the present and the past reciprocally incorporated, as it were, with one another; for the domain of nature is like that of languages, in which etymological research reveals a successive development, by showing us the primary condition of an idiom reflected in the forms of speech in use at the present day. The study of the material world renders this reflection of the past peculiarly manifest, by displaying in the process of formation rocks of eruption and sedimentary strata similar to those of former ages. If I may be allowed to borrow a striking illustration from the geological relations by which the physiognomy of a country is determined, I would say that domes of trachyte, cones of basalt, lava streams ('coules')of amygdaloid with elongated and parallel pores, and white deposits of pumice, intermixed with black scoriae, animate the scenery by the associations of the past which they awaken, acting upon the imagination of the enlightened observer like traditional records of an earlier world. Their form is their history. The sense in which the Greeks and Romans originally employed the word 'history' proves that they too were intimately convinced that, to form a complete idea of the present state of the universe, it was necessary to consider it in its successive p 73 phases. It is not, however, in the definition given by Valerius Flaccus,* but in the zoological writings of Aristotle, that the word 'history' presents itself as an exposition of the results of experience and observation. [Footnote] *Aul. Gell., 'Nect. Att.', v., 18. The physical description of the word by Pliny the elder bears the title of 'Natural History', while in the letters of his nephew it is designated by the nobler term of 'History of Nature.' The earlier Greek historians did not separate the description of countries from the narrative of events of which they had been the theater. With these writers, physical geography and history were long intimately associated, and remained simply but elegantly blended until the period of the development of political interests, when the agitation in which the lives of men were passed caused the geographical portion to be banished from the history of nations, and raised into an independent science. It remains to be considered whether by the operation of thought, we may hope to reduce the immense diversity of phenomena comprised by the Cosmos to the unity of a principle, and the evidence afforded by rational truths. In the present state of empirical knowledge, we can scarcely flatter ourselves with such a hope. Experimental sciences, based on the observation of the external world, can not aspire to completeness; the nature of things, and the imperfection of our organs, are alike opposed to it. We shall never succeed in exhausting the immeasurable riches of nature; and no generation of men will ever have cause to boast of having comprehended the total aggregation of phenomena. It is only by distributing them into groups that we have been able, in the case of a few, to discover the empire of certain natural laws, grand and simple as nature itself. The extent of this empire will no doubt increase in proportion as physical sciences are more perfectly developed. Striking proofs of this advancement have been made manifest in our own day, in the phenomena of electro-magnetism, the propagation of luminous waves and radiating heat. In the same manner, the fruitful doctrine of evolution shows us how, in organic development, all that is formed is sketched out beforehand, and how the tissues of vegetable and animal matter uniformly arise from the multiplication and transformation of cells. The generalization of laws, which, being at first bounded by narrow limits, had been applied solely to isolated groups of phenomena, acquires in time more marked gradations, and gains in extent and certainty as long as the process of reasoning p 74 is applied strictly to analogous phenomena; but as soon as dynamical views prove insufficient where the specific properties and heterogeneous nature of matter come into play; it is to be feared that, by persisting in the pursuit of laws, we may find our course suddenly arrested by an impassible chasm. The principle of unity is lost sight of, and the guiding clew is rent asunder whenever any specific and peculiar kind of action manifests itself amid the active forces of nature. The law of equivalents and the numerical proportions of composition, so happily recognized by modern chemists, and proclaimed under the ancient form of atomic symbols, still remains isolated and independent of mathematicl laws of motion and gravitation. Those productions of nature which are objects of direct observation may be logically distributed in classes, orders, and families. This form of distribution undoubtedly sheds some light on descriptive natural history, but the study of organized bodies, considered in their linear connection, although it may impart a greater degree of unity and simplicity to the distribution of groups, can not rise to the height of a classification based on one sole principle of composition and internal organization. As different gradations are presented by the laws of nature according to the extent of the horizon, or the limits of the phenomena to be considered, so there are likewise differently graduated phases in the investigation of the external world. Empiricism originates in isolated views, which are subsequently grouped according to their analogy or dissimilarity. To direct observation succeeds, although long afterward, the wish to prosecute experiments; that is to say, to evoke phenomena under different determined conditions. The rational experimentalist does not proceed at hazard, but acts under the guidance of hypotheses, founded on a half indistinct and more or less just intuition of the connection existing among natural objects or forces. That which has been conquered by observation or by means of experiments, leads, by analysis and induction, to the discovery of empirical laws. These are the phases in human intellect that have marked the different epochs in the life of nations, and by means of which that great mass of facts has been accumulated which constitutes at the present day the solid basis of the natural sciences. Two forms of abstraction conjointly regulate our knowledge, namely, relations of 'quantity', comprising ideas of number and size, and relations of 'quality', embracing the consideration of the specific properties and the heterogeneous nature p 75 of matter. The former, as being more accessible to the exercise of thought, appertains to mathematics; the latter, from the apparent mysteries and greater difficulties, falls under the domain of the chemical sciences. In order to submit phenomena to calculation, recourse is had to a hypothetical construction of matter by a combination of molecules and atoms, whose number, form, position, and polarity determine, modify, or vary phenomena. The mythical ideas long entertained of the imponderable substances and vital forces peculiar to each mode of organization, have complicated our views generally, and shed an uncertain light on the path we ought to pursue. The most various forms of intuition have thus, age after age, aided in augmenting the prodigious mass of empirical knowledge, which, in our own day has been enlarged with ever-increasing rapidity. The investigating spirit of man strives from time to time, with varying success, to break through those ancient forms and symbols invented, to subject rebellious matter to rules of mechanical construction. We are still very far from the time when it will be possible for us to reduce, by the operation of thought, all that we perceive by the senses, to the unity of a rational principle. It may even be doubted if such a victory could ever be achieved in the field of natural philosophy. The complication of phenomena, and of the vast extent of the Cosmos, would seem to oppose such a result; but even a partial solution of the problem -- the tendency toward a comprehension of the phenomena of the universe -- will not the less remain the eternal and sublime aim of every investigation of nature. In conformity with the character of my former writings, as well as with the labors in which I have been engaged during my scientific career, in measurements, experiments, and the investigation of facts, I limit myself to the domain of empirical ideas. The exposition of mutually connected facts does not exclude the classification of phenomena according to their rational connection, the generalization of many specialities in the great mass of observations, or the attempt to discover laws. Conceptions of the universe solely based upon reason, and the principles of speculative philosophy, would no doubt assign a still more exalted aim to the science of the Cosmos. I am far from blaming the efforts of others solely because their success has hitherto remained very doubtful. Contrary to the wishes and counsel of of those profound and powerful thinkers who p 76 have given new life to speculations which were already familiar to the ancients, systems of natural philosophy have in our own country for some time past turned aside the minds of men from the graver study of mathematical and physical sciences. The abuse of better powers, which has led many of our noble but ill-judging youth into the saturnalia of a purely ideal science of nature, has been signalized by the intoxication of pretended conquests, by a novel and fantastically symbolical phraseology, and by a predilection for the formulae of a scholastic rationalism, more contracted in its views than any known to the Middle Ages. I use the expression "abuse of better powers," because superior intellects devoted to philosophical pursuits and experimental sciences have remained strangers to these saturnalia. The results yielded by an earnest investigation in the path of experiment can not be at variance with a true philosophy of nature. If there be any contradiction, the fault must lie either in the unsoundness of speculation, or in the exaggerated pretensions of empiricism, which thinks that more is proved by experiment than is actually derivable from it. External nature may be opposed to the intellectual world, as if the latter were not comprised within the limits of the former, or nature may be opposed to art when the latter is defined as a manifestation of the intellectual power of man; but these contrasts, which we find reflected in the most cultivated languages, must not lead us to separate the sphere of nature from that of mind, since such a separation would reduce the physical science of the world to a mere aggregation of empirical specialities. Science does not present itself to man until mind conquers matter in striving to subject the result of experimental investigation to rational combinations. Science is the labor of mind applied to nature, but the external world has no real existence for us beyond the image reflected within ourselves through the medium of the senses. As intelligence and forms of speech, thought and its verbal symbols, are united by secret and indissoluble links, so does the external world blend almost unconsciously to ourselves with our ideas and feelings. "External phenomena," says Hegel, in his 'Philosophy of History', "are in some degree translated in our inner representations." The objective world, conceived and reflected within us by thought, is subjected to the eternal and necessary conditions of our intellectual being. The activity of the mind exercises itself on the elements furnished to it by the perceptions of the senses. Thus, in the p 77 early ages of mankind, there manifests itself in the simple intuition of natural facts, and in the efforts made to comprehend them, the germ of the philosophy of nature. These ideal tendencies vary, and are more or less powerful, according to the individual characteristics and moral dispositions of nations, and to the degrees of their mental culture, whether attained amid scenes of nature that excite or chill the imagination. History has preserved the record of the numerous attempts that have been made to form a rational conception of the whole world of phenomena, and to recognize in the universe the action of one sole active force by which matter is penetrated, transformed, and animated. These attempts are traced in classical antiquity in those treatises on the principles of things which emanated from the Ionian school, and in which all the phenomena of nature were subjected to hazardous speculations, based upon a small number of observations. By degrees, as the influence of great historical events has favored the development of every branch of science supported by observation, that ardor has cooled which formerly led men to seek the essential nature and connection of things by ideal construction and in purely rational principles. In recent times, the mathematical portion of natural philosophy has been most remarkably and admirably enlarged. The method and the instrument (analysis) have been simultaneously perfected. That which has been acquired by means so different -- by the ingenious application of atomic suppositions, by the more general and intimate study of phenomena, and by the improved construction of new apparatus -- is the common property of mankind, and shouldnot, in our opinion, now, more than in ancient times, be withdrawn from the free exercise of speculative thought. It can not be denied that in this process of thought, the results of experience have had to contend with many disadvantages; we must not, therefore, be surprised if, in the perpetual vicissitude of theoretical views, as is ingeniously expressed by the author of 'Giordano Bruno', "most men see nothing in philosophy but a succession of passing meteors, while even the grander forms in which she has revealed herself share the fate of comets, bodies that do not rank in popular opinion among the eternal and permanent works of nature, p 78 but are regarded as mere fugitive apparitions of igncor vapor." [Footnote] *Schelling's Bruno, 'eber das Gottliche und Naturaliche Princip. der Dinge', 181 (Bruno, on the 'Divine and Natural Principle of Things') We would here remark that the abuse of thought, and the false track it too often pursues, ought not to sanction an opinion derogatory to the intellect, which would imply that the domain of mind is essentially a world of vague fantastic illusions, and that the treasures accumulated by laborious observations in philosophy are powers hostile to its own empire. It does not become the spirit which characterizes the present age distrustfully to reject every generalization of views and every attempt to examine into the nature of things by the process of reason and induction. It would be a denial of the dignity of human nature and the relative importance of the faculties with which we are endowed, were we to condemn at one time austere reason engaged in investigating causes and their natural connections, and at another that exercise of the imagination which prompts and excites discoveries by its creative powers. This material taken from pages 79 to 111 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 79 COSMOS. ------------------------- DELINEATION OF NATURE. GENERAL REVIEW OF NATURAL PHENOMENA. WHEN the human mind first attempts to subject to its control the world of physical phenomena, and strives by meditative contemplation to penetrate the rich luxuriance of living nature, and the mingled web of free and restricted natural forces, man feels himself raised to a height from whence, as he embraces the vast horizon, individual things blend together in varied groups, and appear as if shrouded in a vapory vail. These figurative expressions are used in order to illustrate the point of view from whence we would consider the universe both in its celestial and terrestrial sphere. I am not insensible of the boldness of such an undertaking. Among all the forms of exposition to which these pages are devoted, there is none more difficult than the general delineation of nature, which we purpose sketching, since we must not allow ourselves to be overpowered by a sense of the stupendous richness and variety of the forms presented to us, but must dwell only on the consideration of masses either possessing actual magnitude, or borrowing its semblance from the associations awakened within the subjective sphere of ideas. It is by a separation and classification of phenomena by an intuitive insight into the play of obscure forces, and by animated expressions, in which the perceptible spectacle is reflected with vivid truthfulness, that we may hope to comprehend and describe the 'universal all' [Greek words] in a manner worthy of the dignity of the word 'Cosmos' in its signification of 'universe, order of the world', and 'adornment' of this universal order. May the immeasurable diversity of phenomena which crowd into the picture of nature in no way detract from that harmonious impression of rest and unity which is the ultimate object of every literary or purely artistical composition. Beginning with the depths of space and the regions of remotest nebulae, we will gradually descend through the starry zone to which our solar system belongs, to our own terrestrial spheroid, circled by air and ocean, there to direct our attention p 80 to its form, temperature, and magnetic tension, and to consider the fullness of organic life unfolding itself upon its surface beneath the vivifying influence of light. In this manner a picture of the world may, with a few strokes, be made to include the realms of infinity no less than the minute microscopic animal and vegetable organisms which exist in standing waters and on the weather-beaten surface of our rocks. All that can be perceived by the senses, and all that has been accumulated up to the present day by an attentive and variously directed study of nature, constitute the materials from which this representation is to be drawn, whose character is an evidence of its fidelity and truth. But the descriptive picture of nature which we purpose drawing must not enter too fully into detail, since a minute enumeration of all vital forms, natural objects, and processes is not requisite to the completeness of the undertaking. The delineator of nature must resist the tendency toward endless division, in order to avoid the dangers presented by the very abundance of our empirical knowledge. A considerable portion of the qualitative properties of matter -- or, to speak more in accordance with the language of natural philosophy, of the qualitative expression of forces -- is doubtlessly still unknown to us, and the attempt perfectly to represent unity in diversity must therefore necessarily prove unsuccessful. Thus, besides the pleasure derived and tinged with a shade of sadness, an unsatisfied longing for something beyond the present -- a striving toward regions yet unknown and unopened. Such a sense of longing binds still faster the links which, in accordance with the supreme laws of our being, connect the material with the ideal world, and animates the mysterious relation existing between that which the mind receives from without, and that which it reflects from its own depths to the external world. If, then, nature (understanding by the term all natural objects and phenomena) be illimitable in extent and contents, it likewise presents itself to the human intellect as a problem which can not be grasped, and whose solution is impossible, since it requires a knowledge of the combined action of all natural forces. Such an acknowledgement is due where the actual state and prospective development of phenomena constitute the sole objects of direct investigation, which does not venture to depart from the strict rules of induction. But, although the incessant effort to embrace nature in its universality may remain unsatisfied, the history of the contemplation of the universe (which p 81 will be considered in another part of this work) will teach us how, in the course of ages, mankind has gradually attained to a partial insight into the relative dependence of phenomena. My duty is to depict the results of our knowledge in all their bearings with reference to the present. In all that is subject to motion and change in space, the ultimate aim, the very expression of physical laws, depend upon 'mean numerical values', which show us the constant amid change, and the stable amid apparent fluctuations of phenomena. Thus the progress of modern physical science is especially characterized by the attainment and the rectification of the mean values of certain quantities by means of the processes of weighing and measuring; and it may be said, that the only remaining and widely-diffused hieroglyphic characters still in our writing -- 'numbers' -- appear to us again, as powers of the Cosmos, although in a wider sense than that applied to them by the Italian School. The earnest investigator delights in the simplicity of numerical relations, indicating the dimensions of the celestial regions, the magnitudes and periodical disturbances of the heavenly bodies, the triple elements of terrestrial magnetism, the mean pressure of the atmosphere, and the quantity of heat which the sun imparts in each year, and in every season of the year, to all points of the solid and liquid surface of our planet. These sources of enjoyment do not, however, satisfy the poet of Nature, or the mind of the inquiring many. To both of these the present state of science appears as a blank, now that she answers doubtingly, or wholly rejects as unanswerable, questions to which former ages deemed they could furnish satisfactory replies. In her severer aspect, and clothed with less luxuriance, she shows herself deprived of that seductive charm with which a dogmatizing and symbolizing physical philosophy knew how to deceive the understanding and give the rein to imagination. Long before the discovery of the New World, it was believed that new lands in the Far West might be seen from the shores of the Canaries and the Azores. These illusive images were owing, not to any extraordinary refraction of the rays of light, but produced by an eager longing for the distant and the unattained. The philosophy of the Greeks, the physical views of the Middle Ages, and even those of a more recent period, have been eminently imbued with the charm springing from similar illusive phantoms of the imagination. At the limits of circumscribed knowledge, as from some lofty island shore, the eye delights to penetrate p 82 to distant regions. The belief in the uncommon and the wonderful lends a definite outline to every manifestation of ideal creation; and the realm of fancy -- a fairy-land of cosmological, geognostical, and magnetic visions -- becomes thus involuntarily blended with the domain of reality. Nature, in the manifold signification of the word -- whether considered as the universality of all that is and ever will be -- as the inner moving force of all phenomena, or as their mysterious prototype -- reveals itself to the simple mind and feelings of man as something earthly, and closely allied to himself. It is only within the animated circles of organic structure that we feel ourselves peculiarly at home. Thus, wherever the earth unfolds her fruits and flowers, and gives food to countless tribes of animals, there the image of nature impresses itself most vividly upon our senses. The impression thus produced upon our minds limits itself almost exclusively to the reflection of the earthly. The starry vault and the wide expanse of the heavens belong to a picture of the universe, in which the magnitude of masses, the number of congregated suns and faintly glimmering nebulae, although they excite our wonder and astonishment, manifest themselves to us in apparent isolation, and as utterly devoid of all evidence of their being the scenes of organic life. Thus, even in the earliest physical views of mankind, heaven and earth have been separated and opposed to one another as an upper and lower portion of space. If, then, a picture of nature were to correspond to the requirements of contemplation by the senses, it ought to begin with a delineation of our native earth. It should depict, first, the terrestrial planet as to its size and form; its increasing density and heat at increasing depths in its superimposed solid and liquid strate; the separation of sea and land, and the vital forms animating both, developed in the cellular tissues of plants and animals; the atmospheric ocean, with its waves and currents, through which pierce the forest-crowned summits of our mountain chains. After this delineation of purely telluric relations, the eye would rise to the celestial regions, and the Earth would then, as the well-known seat of organic development, be considered as a planet, occupying a place in the series of those heavenly bodies which circle round one of the innumerable host of self-luminous stars. This succession of ideas indicates the course pursued in the earliest stages of perceptive contemplation, and reminds us of the ancient conception of the "sea-girt disk of earth," supporting the vault of heaven. It begins to exercise in action p 83 at the spot where it originated, and passes from the consideration of the known to the unknown, of the near to the distant. It corresponds with the method pursued in our elementary works on astronomy (and which is so admirable in a mathematical point of view), of proceeding from the apparent to the real movements of the heavenly bodies. Another course of ideas must, however, be pursued in a work which proposes merely to give an exposition of what is known -- of what may in the present state of our knowledge be regarded as certain, or as merely probable in a greater or lesser degree -- and does not enter into a consideration of the proofs on which such results have been based. Here, therefore, we do not proceed from the subjective point of view of human interests. The terrestrial must be treated only as grand and free, uninfluenced by motives of proximity, social sympathy, or relative utility. A physical cosmography -- a picture of the universe -- does not begin, therefore, with the picture of the universe -- does not begin, therefore, with the terrestrial, but with that which fills the regions of space. But as the sphere of contemplation contracts in dimension our perception of the richness of individual parts, the fullness of physical phenomena, and of the heterogeneous properties of matter becomes enlarged. From the regions in which we recognize ony the dominion of the laws of attraction, we descend to our own planet, and to the intricate play of terrestrial forces. The method here described for the delineation of nature is opposed to that which mst be pursued in establishing conclusive results. The one enumerates what the other demonstrates. Man learns to know the external world through the organs of the senses. Phenomena of light proclaim the existence of matter in remotest space, and the eye is thus made the medium through which we may contemplate the universe. The discovery of telescopic vision more than two centuries ago, has transmitted to latest generations a power whose limits are as yet unattained. The first and most general consideration of the Cosmos is that of the 'contents of space' -- the distribution of matter, or of creation, as we are wont to designate the assemblage of all that is and ever will be developed. We see matter either agglomerated into rotating, revolving spheres of different density and size, or scattered through space in the form of self-luminous vapor. If we consider first the cosmical vapor dispersed in definite nebulous spots, its state of aggregation will p 84 appear constantly to vary, sometimes appearing separated into round or elliptical disks, single or in pairs, occasionally connected by a thread of light; while, at another time, these nebulae occur in forms of larger dimensions, and are either elongated, or variously branched or fan-shaped or appear like well-defined rings, including a dark interior. It is conjectured that these bodies are undergoing variously developed formative processes, as the cosmical vapor becomes condensed in conformity with the laws of attraction, either round one or more of the nuclei. Between two and three thousand of such unresolvable nebulae, in which the most powerful telescopes have hitherto been unable to distinguish the presence of stars, have been counted, and their positions determined. The genetic evolution -- that perpetual state of development which seems to affect this portion of the regions of space -- has led philosophical observers to the discovery of the analogy existing among organic phenomena. As in our forests we see the same kind of tree in all the various stages of its growth, and are thus enabled to form an idea of progressive, vital development, so do we also in the great garden of the universe, recognise the most different phases of sidereal formation. The process of condensation, which formed a part of the doctrines of Anaximenes and of the Ionian School, appears to be going on before our eyes. This subject of investigation and conjecture is especially attractive to the imagination, for in the study of the animated circles of nature, and of the action of all the moving forces of the universe, the charm that exercises the most powerful influence on the mind is derived less from a knowledge of that which 'is' than from a perception of that which 'will be', even though the latter be nothing more than a new condition of a known material existence; for of actual creation, of origin, the beginning of existence from non-existence, we have no experience, and can therefore form no conception. A comparison of the various causes influencing the development manifested by the greater or less degree of condensation in the interior of nebulae, no less than a successive course of direct observations, have led to the belief that changes of form have been recognized first in Andromeda, next in the constallation Argo, and in the isolated filamentous portion of the nebula in Orion. But want of uniformity in the power of the instruments employed, different conditions of our atmosphere, and other optical relations, render a part of the results invalid as historical evidence. p 85 'Nebulous stars' must not be confounded either with irregularly-shaped nebulous spots, properly so called, whose separate parts have an unequal degree of brightness (and which may, perhaps, become concentrated into stars as their circumference contracts), nor with the so-called planetary nebulae, whose circular or slightly oval disks manifest in all their parts a perfectly uniform degree of faint light. 'Nebulous stars' are not merely accidental bodies projected upon a nebulous ground, but are a part of the nebulous matter constituting one mass with the body which it surrounds. The not unfrequently considerable magnitude of their apparent diameter, and the remote distance from which they are revealed to us, show that both the planetary nebulae and the nebulous stars must be of enormous dimensions. New and ingenious considerations of the different influence exercised by distance* on the intensity of light of a disk of appreciable diameter, and of a single self-luminous point, render it not improbable that the planetary nebulae are very remote nebulous stars, in which the difference between the central body and the surrounding nebulous covering can no longer be detected by our telescopic instruments. [footnote] * The optical considerations relative to the difference presented by a single luminous point, and by a disk subtending an appreciable angle, in which the intensity of light is constant at every distance, are explained in Arago's 'Analyse des Travaux de Sir William Herschel' ('Annuaire du Bureau des Long.', 1842, p. 410-412, and 441). The magnificent zones of the southern heavens, between 50 degrees and 80 degrees, are especially rich in nebulous stars, and in compressed unresolvable nebua e. The larger of the two Magellanic clouds, which circle round the starless, desert pole of the south, appears, according to the most recent researches,* as "a collection of clusters of stars, composed of globular clusters and nebulae of different magnitude, and of large nebulous spots p 86 not resolvable, which, producing a general brightness in the field of view, form, as it were, the back-ground of the picture." [footnote] *The two Magellanic clouds, Nubecula major and Nubecula minor, are very remarkable objects. The larger of the two is an accumulated mass of stars, and consists of clusters of stars of irregular form, either conical masses or nebulae of different magnitudes and degrees of condensation. This is interspersed with nebulous spots, not resolvable into stars, but which are probably 'star dust', appearing only as a general radiance upon the telescopic field of a twenty-feet reflector, and forming a luminous ground on which other objects of striking and indescribable form are scattered. In no other portion of the heavens are so many nebulous and stellar masses thronged together in an equally small space. Nubecula minor is much less beautiful, has more unresolvable nebulous light, while the stellar masses are fewer and fainter in intensity. -- (From a letter of Sir John Herschel, Feldhuysen, Cape of Good Hope, 13th June, 1836.) The appearance of these clouds, of the brightly-beaming constellation Argo, of the Milky Way between Scorpio, the Centaur, and the Southern Cross, the picturesque beauty, if one may so speak, of the whole expanse of the southern celestial hemisphere, has left upon my mind an ineffaceable impression. The zodiacal light, which rises in a pyramidal form, and constantly contributes, by its mild radiance, to the external beauty of the tropical nights, is either a vast nebulous ring, rotating between the Earth and Mars, or, less probably, the exterior stratum of the solar atmosphere. Besides these luminous clouds and nebulae of definite form, exact and corresponding observations indicate the existence and the general distribution of an apparently non-luminous, infinitely-divided matter, which posssesses a force of resistance and manifests its presence in Encke's, and perhaps also in Biela's comet, by diminishing their eccentricity and shortening their period of revolution. Of this impending, ethereal, and cosmical matter, it may be supposed that it is in motion; that it gravitates, notwithstanding its original tenuity; that it is condensed in the vicinity of the great mass of the Sun; and, finally, that it may, for myriads of ages, have been augmented by the vapor emanating from the tails of comets. If we now pass from the consideration of the vaporous matter of the immeasurable regions of space [(Greek)*] -- whether scattered without definite form and limits, it exists as a cosmical other, or is condensed into nebulous spots, and becomes comprised among the solid agglomerated bodies of the universe -- we approach a class of phenomena exclusively designated by the form of stars, or as the sidereal world. [footnote] *I should have made use, in the place of garden of the universe, of the beautiful expression [Greek], borrowed by Hesychius from an unknown poet, if [Greek] had not rather signified in general an inclosed space. The connection with the German 'garten' and the English 'garden', 'gards' in Gothic (derived according to Jacob Grimm, from 'gairdan', 'to gird'), is, however, evident, as is likewise the affinity with the Slavonic 'grad', 'gorod', and as Pott remarks, in his 'Etymol. Forschungen', th. i., s. 144 (Etymol. Researches), with the Latin 'chors', whence we have the Spanish 'corte', the French 'cour', and the English word 'court', together with the Ossetic 'khart'. To these may be further added the Scandinavian 'gard',** 'gard', a place inclosed, as a court, or a country seat, and the Persian 'gerd', 'gird', a district, a circle, a princely country seat, a castle or city, as we find the term applied to the names of places in Firdusi's Schahnameh, as 'Siyawakschgird', 'Darabgird', etc. ** (This word is written 'gaard' in the Danish) -- Tr. p 87 Here, too, we find differences existing in the solidity or density of the spheroidally agglomerated matter. Our own solar system presents all stages of 'mean' density (or of the relation of 'volume' to 'mass'.) On comparing the planets from Mercury to Mars with the Sun and with Jupiter, and these two last named with the yet inferior density of Saturn, we arrive, by a descending scale -- to draw our illustration from the terrestrial substances -- at the respective densities of antimony, honey, water, and pine wood. In comets, which actually constitute the most considerable portion of our solar system with respect to the number of individual forms, the concentrated part, usually termed the 'head', or 'nucleus', transmits sidereal light unimpaired. The mass of a comet probably in no case equals the five thousandth part of that of the earth, so dissimilar are the formative processes manifested in the original and perhaps still progressive agglomerations of matter. In proceeding from general to special considerations, it was particularly desirable to draw attention to this diversity, not merely as a possible, but as an actually proved fact. The purely speculative conclusions arrived at by Wright, Kant, and Lambert, concerning the general structural arrangement of the universe, and of the distribution of matter in space, have been confirmed by Sir William Herschel, on the more certain path of observation and measurement. That great and enthusiastic, although cautious observer, was the first to sound the depths of heaven in order to determine the limits and form of the starry stratum which we inhabit, and he, too, was the first who ventured to throw the light of investigation upon the relations existing between the position and distance of remote nebulae and our own portion of the sidereal universe. William Herschel, as is well expressed in the elegant inscription on his monument at Upton, broke through the inclosures of heaven ('caelorum perrupit claustra'), and, like another Columbus, penetrated into an unknown ocean, from which he beheld coasts and groups of islands, whose true position it remains for future ages to determine. Considerations regarding the different intensity of light in stars, and their relative number, that is to say, their numerical frequency on telescopic fields of equal magnitude, have led to the assumption of unequal distances and distribution in space in the strata which they compose. Such assumptions, in as far as they may lead us to draw the limits of the individual portions of the universe, can not offer the same degree of mathematical certainty as that which may be attained in all that p 88 relates to our solar system, whether we consider the rotation of double stars with unequal velocity round one common center of gravity, or the apparent or true movements of all the heavenly bodies. If we take up the physical description of the universe from the remotest nebulae, we may be inclined to compare it with the mythical portions of history. The one begins in the obscurity of antiquity, the other in that of inaccessible space; and at the point where reality seems to flee before us, imagination becomes doubly incited to draw from its own fullness, and give definite outline and permanence to the changing forms of objects. If we compare the regions of the universe with one of the island-studded seas of our own planet, we may imagine matter to be distributed in groups, either as unresolvable nebulae of different ages, condensed around one or more nuclei, or as already agglomerated into clusters of stars, or isolated spheroidal bodies. The cluster of stars, to which our cosmical island belongs, forms a lens-shaped, flattened stratum, detached on every side, whose major axis is estimated at seven or eight hundred, and its minor one at a hundred and fifty times the distance of Sirius. It would appear, on the supposition that the parallax of Sirius is not greater than that accurately determined for the brightest star in the Centaur (0".9128), that light traverses one distance of Sirius in three years, while it also follows, from Bessel's earlier excellent Memoir* on the parallax of the remarkable star 61 Cygni (0".3483), (whose considerable motion might lead to the inference of great proximity), that a period of nine years and a quarter is required for the transmission of light from this star to our planet. [footnote] *See Maclear's "Results from 1839 to 1840," in the 'Trans. of the Astronomical Soc.', vol. xii., p. 370, on 'a' Centauri, the probable mean error being 0".0649. For 61 Cygni, see Bessel, in Schumacher's 'Jahrbuch', 1839, s. 47, and Schumacher's 'Astron. Nachr.', bd. xviii., s. 401, 402, probable mean error, 0".0141. With reference to the relative distances of stars of different magnitudes, how those of the third magnitude may probably be three times more remote, and the manner in which we represent to ourselves the material arrangement of the starry strata, I have found the following remarkable passage in Kepler's 'Epitome Astronomiae Copernicanae', 1618, t. i., lib. 1, p. 34-39: "Sol hic noster nil aliud est quam una ex fixis, nobis major et clarior visa, quia propior quam fixa. Pone terram stare ad latus, una semi-diametro via e lactea e, tunc ha ec via lactea apparebit circulus parvus, vel ellipsis parva, tota declinans ad latus alterum; eritque simul uno intuitu conspicua, quae nunc no potest nisi dimidia conspici quovis momento. Itaque fix arum spha era non tantum orbe stellarum, sed etiam circulo lactis versus not deorsum est terminata." Our starry stratum is a disk of inconsiderable thickness, divided a p 89 third of its length into two branches; it is supposed that we are near this division, and nearer to the region of Sirius than to the constellation Aquila, almost in the middle of the stratum in the line of its thickness or minor axis. This position of our solar system, and the form of the whole discoidal stratum, have been inferred from sidereal scales, that is to say, from that method of counting the stars to which I have already alluded, and which is based upon the equidistant subdivision of the telescopic field of view. The relative depth of the stratum in all directions is measured by the greater or smaller number of stars appearing in each division. These divisions give the length of the ray of vision in the same manner as we measure the depth to which the plummet has been thrown, before it reaches the bottom, although in the case of a starry stratum there can not, correctly speaking, be any idea of depth, but merely of outer limits. In the direction of the longer axis, where the stars lie behind one another, the more remote ones appear closely crowded together, united, as it were, by a milky-white radiance or luminous vapor, and are perspectively grouped, encircling as in a zone, the visible vault of heaven. This narrow and branched girdle, studded with a radiant light, and here and there interrupted by dark spots, deviates only by a few degrees from forming a perfect large circle round the concave sphere of heaven, owing to our being near the center of the large starry cluster, and almost on the plane of the Milky Way. If our planetary system were far 'outside' this cluster, the Milky Way would appear to telescopic vision as a ring, and at a still greater distance as a resolvable discoidal nebula. Among the many self-luminous moving suns, erroneously called 'fixed stars', which constitute our cosmical island, our own sun is the only one known by direct observation to be a 'central body' in its relations to spherical agglomerations of matter directly depending upon and revolving round it, either in the form of planets, comets, or aerolite asteroids. As far as we have hitherto been able to investigate 'multiple' stars (double stars or suns), these bodies are not subject, with respect to relative motion and illumination, to the same planetary dependence that characterizes our own solar system. Two or more self-luminous bodies, whose planets and moon, if such exist, have hitherto escaped our telescopic powers of vision, certainly revolve around one common center of gravity; but this is in a portion of space which is probably occupied merely by unagglomerated matter or cosmical vapor, while in our system p 90 the center of gravity is often comprised within the innermost limits of a 'visible' central body. If, therefore, we regard the Sun and the Earth, or the Earth and the Moon, as double-stars, and the whole of our planetary solar system as a multiple cluster of stars, the analogy thus suggested must be limited to the universality of the laws of attraction in different systems, being alike applicable to the independent processes of light and to the method of illumination. For the generalization of cosmical views, corresponding with the plan we have proposed to follow in giving a delineation of nature or of the universe, the solar system to which the Earth belongs may be considered in a two-fold relation: first, with respect to the different classes of individually agglomerated matter, and the relative size, conformation, density, and distance of the heavenly bodies of this system; and secondly, with reference to other portions of our starry cluster, and of the changes of position of its central body, the Sun. The solar system, that is to say, the variously-formed matter circling round the Sun, consists, according to the present state of our knowledge of 'eleven primary planets',* eighteen satellites p 91 or secondary planets, and myriads of comets, three of which, known as the "planetary comets," do not pass beyond the narrow limits of the orbits described by the principal planets. [footnote] * (Since the publication of Baron Humboldt's work in 1845, several other planets have been discovered, making the number of those belonging to our planetary system 'sixteen' instead of 'eleven'. Of these, Astrea, Hebe, Flora, and Iris are members of the remarkable group of asteroids between Mars and Jupiter. Astrea and Hebe were discovered by Hencke at Driesen, the one in 1846 and the other in 1847; Flora and Iris were both discovered in 1847 by Mr. Hind, at the South Villa Observatory, Regent's Park. It would appear from the latest determinations of their elements, that the small planets have the following order with respect to mean distance from the Sun: Flora, Iris, Vesta, Hebe, Astrea, Juno, Ceres, Pallas. Of these, Flora has the shortest period (about 3 1/4 years). The planet Neptune, which, after having been predicted by several astronomers, was actually observed on the 25th of September, 1846, is situated on the confines of our planetary system beyond Uranus. The discovery of this planet is not only highly interesting from the importance attached to it as a question of science, but also from the evidence it affords of the care and unremitting labor evinced by modern astronomers in the investigation and comparison of the older calculations, and the ingenious application of the results thus obtained to the observation of new facts. The merit of having paved the way for the discovery of the planet Neptune is due to M. Bouvard, who, in his persevering and assiduous efforts to deduce the entire orbit of Uranus from observations made during the forty years that succeeded the discovery of that planet in 1781, found the results yielded by theory to be at variance with fact, in a degree that had no parallel in the history of astronomy. This startling discrepancy, which seemed only to gain additional weight from every attempt made by M. Bouvard to correct his calculations, led Leverrier, after a careful modification of the tables of Bouvard, to establish the proposition that there was "a formal incompatibility between the observed motions of Uranus and the hypothesis that he was acted on 'only' by the Sun and known planets, according to the law of universal gravitation." Pursuing this idea, Leverrier arrived at the conclusion that the disturbing cause must be a 'planet', and finally, after an amount of labor that seems perfectly overwhelming, he, on the 31st of August, 1846, laid before the French Institute a paper, in which he indicated the exact spot in the heavens where this new planetary body would be found, giving the following data for its various elements: mean distance from the Sun, 36.154 times that of the Earth; period of revolution, 217.387 years; mean long., Jan. 1st, 1847, 318 degrees 47'; mass, 1/9300th; heliocentric long., Jan 1st1847, 326 degrees 32'. Essential difficulties still intervened, however, and as the remoteness of the planet rendered it improbable that its disk would be discernible by any telescopic instrument, no other means remained for detecting the suspected body but its planetary motion, which could only be ascertained by mapping, after every observation, the quarter of the heavens scanned, and by a comparison of the various maps. Fortunately for the verification of Leverrier's predictions, Dr. Bremiker had just completed a map of the precise region in which it was expected the new planet would apper, this being one of a series of maps made for the Academy of Berlin, of the small stars along the entire zodiac. By means of this valuable assistance, Dr. Galle, of the Berlin Observatory, was led, on the 25th of September, 1846, by the discovery of a star of the eighth magnitude, not recorded in Dr. Bremiker's map, to make the first observation of the planet predicted by Leverrier. By a singular coincidence, Mr. Adams, of Cambridge, had predicted the appearance of the planet simultaneously with M. Leverrier; but by the concurrence of several circumstances much to be regretted, the world at large were not made acquainted with Mr. Adams's valuable discovery until subsequently to the period at which Leverrier published his observations. As the data of Leverrier and Adams stand at present, there is a discrepancy between the predicted and the true distance, and in some other elements of the planet; it remains therefore, for these or future astronomers to reconcile theory with fact, or perhaps, as in the case of Uranus, to make the new planet the means of leading to yet greater discoveries. It would appear from the most recent observations, that the mass of Neptune, instead of being, as at first stated, 1/9300th, is only about 1/23000th that of the Sun, while its periodic time is now given with a greater probability at 166 years, and its mean distance from the Sun nearly 30. The planet appears to have a ring, but as yet no accurate observations have been made regarding its system of satellites. See 'Trans. Astron. Soc.', and 'The Planet Neptune', 1848, by J. P. Nicholl.) -- Tr. We may, with no incondsiderable degree of probability, include within the domain of our Sun, in the immediate sphere of its central force, a rotating ring of vaporous matter, lying probably between the orbits of Venus and Mars, but certainly beyond that of the Earth,* which appears to us in p 92 a pyramidal form, and is known as the 'Zodiacal Light'; and a host of very small asteroids, whose orbits either intersect, or very nearly approach, that of our earth, and which present us with the phenomena of aerolites and falling or shooting stars. [footnote] * "If there should be molecules in the zones diffused by the atmosphere of the Sun of too volatile a nature either to combine with one another or with the planets, we must suppose that they would, in circling round that luminary, present all the appearances of zodiacal light, without opposing any appreciable resistance to the different bodies composing the planetary system, either owing to their extreme rarity, or to the similarity existing between their motion and that of the planets with which they come in contact." -- Laplace, 'Expos. du Syst. du Monde' (ed. 5), p. 415. When we consider the complication of variously-formed bodies which revolve round the Sun in orbits of such dissimilar eccentricity--although we may not be disposed, with the immortal author of the 'Mecanique Celeste', to regard the largr number of comets as nebulous stars, passing from one central system to another,* we yet can not fail to acknowledge that the planetary system, especially so called (that is, the group of heavenly bodies which, together with their satellites, revolve with but slightly eccentric orbits round the Sun), constitutes but a small portion of the whole system with respect to individual numbers, if not to mass. [footnote] *Laplace, 'Exp. du Syst. du Monde', p. 396, 414. It has been proposed to consider the telescopic planets, Vesta, Juno, Ceres, and Pallas, with their more closely intersecting, inclined, and eccentric orbits, as a zone of separation, or as a middle group in space; and if this view be adopted, we shall discover that the interior planetary group (consisting of Mercury, Venus, the Earth, and Mars) presents several very striking contrasts* when compared with the exterior group, comprising Jupiter, Saturn, and Uranus. [footnote] *Littrow, 'Astronomie', 1825, bd.xi., 107. M��dler, 'Astron.', 1841, �¤ 212. Laplace, 'Exp. du Syst. du Monde', p. 210. The planets nearest the Sun, and consequently included in the inner group, are of more moderate size, denser, rotate more slowly and with nearly equal velocity (their periods of revolution being almost all about 24 hours), are less compressed at the poles, and with the exception of one, are without satellites. The exterior planets, which are further removed from the Sun, are very considerably larger, have a density five times less, more than twice as great a velocity in the period of their rotation round their axes, are more compressed at the poles, and if six satellites may be ascribed to Uranus, have a quantitative preponderance in the number of their attendant moons, which is as seventeen to one. p 93 Such general considerations regarding certain characteristic properties appertaining to whole groups, can not, however, be applied with equal justice to the individual planets of every group, nor to the relations between the distances of the revolving planets from the central body, and their absolute size, density, period or rotation, eccentricity, and the inclination of their orbits and the axes. We know as yet of no inherent necessity, no mechanical natural law, similar to the one which teaches us that the squares of the periodic times are proportional to the cubes of the major axes, by which the above-named six elements of the planetary bodies and the form of their orbit are made dependent either on one another, or on their mean distance from the Sun. Mars is smaller than the Earth and Venus, although further removed from the Sun than these last-named planets, approaching most nearly in size to Mercury, the nearest planet to the Sun. Saturn is smaller than Jupiter, and yet much larger than Uranus. The zone of the telescopic planets, which have so inconsiderable a volume, immediately procede Jupiter (the greatest in size of any of the planetary bodies), if we consider them with regard to distance from the Sun; and yet the disks of these small asteroids, which scarcely admit of measurement, have an areal surface not much more than half that of France, Madagascar, or Borneo. However striking may be the extremely small density of all the colossal planets, which are furthest removed from the Sun, we are yet unable in this respect to recognize any regular succession.* [footnote] *See Kepler, on the increasing density and volume of the planets in proportion with their increase of distance from the Sun, which is described as the densest of all the heavenly bodies; in the 'Epitome Astran. Copern. in' vii. 'libros digesta', 1618-1622, p. 420. Leibnitz also inclined to the opinions of Kepler and Otto von Guericke, that the planets increase in volume in proportion to their increase of distance from the Sun. See his letter to the Magdeburg Burgomaster (Mayence, 1671), in Leibnitz, 'Deutschen Schriften, herausg. von Guhrauer', th. i., 264. Uranus appears to be denser than Saturn, even if we adopt the smaller mass, 1/24605, assumed by Lamont; and, notwithstanding the inconsiderable difference of density observed in the innermost planetary group,* we find both Venus and Mars less dense than the Earth, which lies between them. [footnote] *On the arrangement of masses, see Encke, in Schum., 'Astr. Nachr', 1843 Nr. 488, 114. The time of rotation certainly diminishes with increasing solar distance, but yet it is greater in Mars than in the Earth, and in Saturn than in Jupiter. The elliptic p 94 orbits of Juno, Pallas, and Mercury have the greatest degree of eccentricity, and Mars and Venus, which immediately follow each other, have the least. Mercury and Venus exhibit the same contrasts that may be observed in the four smaller planets, or asteroids, whose paths are so closely interwoven. The eccentriciities of Juno and Pallas are very nearly identical, and reach three times as great as those of Ceres and Vesta. The same may be said of the inclination of the orbits of the planets toward the plane of projection of the ecliptic, or in the position of their axes of rotation with relation to their orbits, a position on which the relations of climate, seasons of the year, and length of the days depend more than on eccentricity. Those planets that have the most elongated elliptic orbits, as Juno, Pallas, and Mercury, have also, although not to the same degree their orbits most strongly inclined toward the ecliptic. Pallas has a comet-like inclination nearly twenty-six times greater than that of Jupiter, while in the little planet Vesta, which is so near Pallas, the angle of inclination scarcely by six times exceeds that of Jupiter. An equally irregular succession is observed in the position of the axes of the few planets (four or five) whose planes of rotation we know with any degree of certainty. It would appear from the position of the satellites of Uranus, two of which, the second and fourth, have been recently observed with certainty, that the axis of this, the outermost of all the planets is scarcely inclined as much as 11 degrees toward the plane of its orbit, while Saturn is placed between this planet, whose axis almost coincides with the plane of its orbit, and Jupiter, whose axis of rotation is nearly perpendicular to it. In this enumeration of the forms which compose the world in space, we have delineated them as possessing an actual existence, and not as objects of intellectual contemplation, or as mere links of a mental and causal chain of connection. The planetary system, in its relations of absolute size and relative position of the axes, density, time of rotation, and different degrees of eccentricity of the orbits, does not appear to offer to our apprehension any stronger evidence of a natural necessity than the proportion observed in the distribution of land and water on the Earth, the configuration of continents, or the height of mountain chains. In these respects we can discover no common law in the regions of space or in the inequalities of the earth's crust. They are 'facts' in nature that have arisen from the conflict of manifold forces acting under unknown p 95 conditions, although man considers as 'accidental' whatever he is unable to explain in the planetary formation on purely genetic principles. If the planets have been formed out of separate rings of vaporous matter revolving round the Sun, we may conjecture that the different thickness, unequal density, temperature, and electro-magnetic tension of these rings may have given occasion to the most various agglomerations of matter, in the same manner as the amount of tangential velocity and small variations in its direction have produced so great a differencein the forms and inclinations of the elliptic orbits. Attractions of mass and laws of gravitation have no doubt exercised an influence here, no less than in the geognostic relations of the elevations of continents; but we are unable from the present forms to draw any conclusions regarding the series of conditions through which they have passed. Even the so-called law of the distances of the planets from the Sun, the law of progression (which led Kepler to conjecture the existence of a planet supplying the link that was wanting in the chain of connection between Mars and Jupiter), has been found numerically inexact for the distances between Mercury, Venus, and the Earth, and a variance with the conception of a series, owing to the necessity for a supposition in the case of the first member. The hitherto disscovered principal planets that revolve round our Sun are attended certainly by fourteen, and probably by eighteen secondary planets (moons or satellites). The principal planets are, therefore, themselves the central bodies of subordinate systems. We seem to recognize in the fabric of the universe the same process of arrangement so frequently exhibited in the development of organic life, where we find in the manifold combinations of groups of plants or animals the same typical form repeated in the 'subordinate classes'. The secondary planets or satellites are more frequent in the external region of the planetary system, lying beyond the intersecting orbits of the smaller planets or asteroids; in the inner region none of the planets are attended by satellites, with the exception of the Earth, whose moon is relatively of great magnitude, since its diameter is equal to a fourth of that of the Earth, while the diameter of the largest of all known secondary planets -- the sixth satellite of Saturn -- is probably about one seventeenth, and the largest of Jupiter's moons, the third, only about one twenty-sixth part that of the primary planet or central body. The planets which are attended by the largest number of satellites are most remote from the Sun, p 96 and are at the same time the largest, most compressed at the poles, and the least dense. According to the most recent measurements of M��dler, Uranus has a greater planetary compression than any other of the planets, viz., 1/9.92d. In our Earth and her moon, whose mean distance from one another amounts to 207,200 miles, we find that the differences of mass* and diameter between the two are much less considerable than are usually observed to exist between the principal planets and their attendant satellites, or between bodies of different orders in the solar system. [footnote] *If, according to Burckhardt's determination, the Moon's radius be 0.2725 and its volume 1/49.00th, its density will be 0.5596, or nearly five ninths. Compare, also, Wilh. Beer and H. Madler, 'der Mond', 2, 10, and Madler, 'Ast.', 157. The material contents of the Moon are, according to Hansen, nearly 1/34th (and ��dler 1/40.6th) that of the Earth, and its mass equal to 1/87.73d that of the Earth. In the largest of Jupiter's moons, the third, the relations of volume to the central body are 1/15370th, and of mass 1/11300th. On the polar flattening of Uranus, see Schum, 'Astron. Nachr.', 1844, No. 493. While the density of the Moon is five ninths less than that of the Earth, it would appear, if we may sufficiently depend upon the determinations of their magnitudes and masses, that the second of Jupiter's moons is actually denser than that great planet itself. Among the fourteen satellites that have been investigated with any degree of certainty, the system of the seven satellites of Saturn presents an instance of the greatest possible contrast, both in absolute magnitude and in distance from the central body. The sixth of these satellites is probably not much smaller than Mars, while our moon has a diameter which does not amount to more than half that of the latter planet. With respect to volume, the two outer, the sixth and seventh of Saturn's satellites, approach the nearest to the third and brightest of Jupiter's moons. The two innermost of these satellites belong perhaps, together with the remote moons of Uranus to the smallest cosmical bodies of our solar system, being only made visible under favorable circumstances by the most powerful instruments. They were first discovered by the forty-foot telescope of William Herschel in 1789, and were seen again by John Herschel at the Cape of Good Hope, by Vico at Rome, and by Lamont at Munich. Determinations of the 'true' diameter of satellites, made by the measurement of the apparent size of their small disks, are subjected to many optical difficulties; but numerical astronomy, whose task it is to predetermine by calculation the motions of the heavenly bodies as they will appear when viewed from the Earth, is directed almost p 97 exclusively to motion and mass, and but little to volume. The absolute distance of a satellite from its central body is greatest in the case of the outermost or seventh satellite of Saturn, its distance from the body round which it revolves amounting to more than two millions of miles, or ten times as great a distance as that of our moon from the Earth. In the case of Jupiter we find that the outermost or fourth attendant moon is only 1,040,000 miles from that planet, while the distance between Uranus and its sixth satellite (if the latter really exist) amounts to as much as 1,360,000 miles. If we compare, in each of these subordinate systems, the volume of the satellite, we discover the existence of entirely new numerical relations. The distances of the outermost satellites of Uranus, Saturn, and Jupiter are when expressed in semi-diameters of the main planets, as 91, 64, and 27. The outermost satellite of Saturn appears, therefore, to be removed only about one fifteenth further from the center of that planet than our moon is from the Earth. The first or innermost of Saturn's satellites is nearer to its central body than any other of the secondary planets, and presents, moreover, the only instance of a period of revolution of less than twenty-four hours. Its distance from the center of Saturn may, according to M��dler and Wilhelm Beer, be expressed as 2.47 semi-diameters of that planet, or as 80,088 miles. Its distance from the surface of the main planet is therefore 47,480 miles, and from the outer-most edge of the ring only 4916 miles. The traveler may form to himself an estimate of the smallness of this amount by remembering the statement of an enterprising navigator, Captain Beechey, that he had in three years passed over 72,800 miles. If, instead of absolute distances, we take the semi-diameters of the principal planets, we shall find that even the first or nearest of the moons of Jupiter (which is 26,000 miles further removed from the center of that planet than our moon is from that of the Earth) is only six semi-diameters of Jupiter from its center, while our moon is removed from us fully 60 1/3d semi-diameters of the Earth. In the subordinate systems of satellites, we find that the same laws of gravitation which regulate the revolutions of the principal planets round the Sun likewise govern the mutual relations existing between these planets among one another and with reference to their attendant satellites. The twelve moons of Saturn, Jupiter, and the Earth all most like the primary planets from west to east, and in elliptic orbits, deviating p 98 but little from circles. It is only in the case of one moon, and perhaps in that of the first and innermost of the satellites of Saturn (0.068), that we discover an eccentricity greater than that of Jupiter; according to the very exact observations of Bessel, the eccentricity of the sixth of Saturn's satellites (0.029) exceeds that of the Earth. On the extremest limits of the planetary system, where, at a distance nineteen times greater than that of our Earth, the centripetal force of the Sun is greatly diminished, the satellites of Uranus (which most striking contrasts from the facts observed with regard to other secondary planets. Instead, as in all other satellites, of having their orbits but slightly inclined toward the ecliptic and (not excepting even Saturn's ring, which may be regarded as a fusion of agglomerated satellites) moving from west to east, the satellites of Uranus are almost perpendicular to the ecliptic, and move retrogressively from east to west, as Sir John Herschel has proved by observations continued during many years. If the primary and secondary planets have been formed by the condensation of rotating rings of solar and planetary atmospheric vapor, there must have existed singular causes of retardation or impediment in the vaporous rings revolving round Uranus, by which, under the relations with which we are unacquainted, the revolution of the second and fourth of its satellites was made to assume a direction opposite to that of the rotation of the central planet. It seems highly probable that the period of rotation of 'all' secondary planets is equal to that of their revolution round the main planet, and therefore that they always present to the latter the same side. Inequalities, occasioned by sight variations in the revolution, give rise to fluctuations of from 6 degrees to 8 degrees, or to an apparent libration in longitude as well as in latitude. Thus, in the case of our moon, we sometimes observe more than the half of its surface, the eastern and northern edges being more visible at one time, and the western or southern at another. By means of this libration* we are enabled to see the annular mountain Malapert (which occasionally conceals the Moon's south pole), the arctic landscape round the crater of Gioja, and the large gray plane near Endymion which exceeds in superficial extent the 'Mare Vaporum'. [footnote] *Beer and Madler, op. cit., 185, s.208, and �¤ 347, s. 332; and ix their 'Phys. Kenntniss der himml. Korper', s. 4 und 69, Tab. 1 (Physical History of the Heavenly Bodies). Three sevenths of the Moon's surface are entirely p 99 concealed from our observation, and must always remain so, unless new and unexpected disturbing causes come into play. These cosmical relations involuntarily remind us of nearly similar conditions in the intellectual world, where, in the domain of deep research into the mysteries and the primeval creative forces of nature, there are regions similarly turned away from us, and apparently unattainable, of which only a narrow margin has revealed itself, for thousands of years, to the human mind, appearing, from time to time, either glimmering in true or delusive light. We have hitherto considered the primary planets, their satellites, and the concentric rings which belong to one, at least, of the outermost planets, as products of tangential force, and as closely connected together by mutual attraction; it therefore now only remains for us to speak of the unnumbered host of 'comets' which constitute a portion of the cosmical bodies revolving in independent orbits round the Sun. If we assume an equable distribution of their orbits, and the limits of their perihelia, or greatest proximities to the Sun, and the possibility of their remaining invisible to the inhabitants of the Earth, and base our estimates on the rules of the calculus of probabilities, we shall obtain as the result an amount of myriads perfectly astonishing. Kepler, with his usual animation of expression, said that there were more comets in the regions of space than fishes in the depths of the ocean. As yet, however, there are scarcely one hundred and fifty whose paths have been calculated, if we may assume at six or seven hundred the number of comets whose appearance and passage through known constellations have been ascertained by more or less precise observations. While the so-called classical nations of the West, the Greeks and Romans, although they may occasionally have indicated the position in which a comet first appeared, never afford any information regarding its apparent path, the copious literature of the Chinese (who observed nature carefully, and recorded with accuracy what they saw) contains circumstantial notices of the constellations through which each comet was observed to pass. These notices go back to more than five hundred years before the Christian era, and many of them are still found to be of value in astronomical observations.* [footnote] *The first comets of whose orbits we have any knowledge, and which were calculated from Chinese observations, are those of 240 (under Gordian II.), 539 (under Justinian), 565, 568, 574, 837, 1337, and 1385. See John Russell Hind, in Schum., 'Astron. Nachr.', 1843, No. 498. While the comet of 837 (which, according to Du Sejour, continued during twenty-four hours within a distance of 2,000,000 miles from the Earth) terrified Louis I. of France to that degree that he busied himself in building churches and founding monastic establishments, in the hope of appeasing the evils threatened by its appearance, the Chinese astronomers made observations on the path of this cosmical body, whose tail extended over a space of 60 degrees, appearing sometimes single and sometimes multiple. The first comet that has been calculated solely from European observations was that of 1456, known as Halley's comet, from the belief long, but erroneously, entertained that the period when it was first observed by that astronomer was its first and only well-attested appearance. See Arago, in the 'Annuaire', 1836, p. 204, and Langier, 'Comptes Rendus des Seances de l'Acad.', 1843, t. xvi., 1006. p 100 Although comets have a smaller mass than any other cosmical bodies -- being, according to our present knowledge, probably not equal to 1/5000th part of the Earth's mass -- yet they occupy the largest space, as their tails in several instances extend over many millions of miles. The cone of luminous vapor which radiates from them has been found, in some cases (as in 1680 and 1811), to equal the length of the Earth's distance from the Sun, forming a line that intersects both the orbits of Venus and Mercury. It is even probable that the vapor of the tails of comets mingled with our atmosphere in the years 1819 and 1823. Comets exhibit such diversities of form, which appear rather to appertain to the individual than the class, that a description of one of these "wandering light-clouds," as they were already called by Xenophanes and Theon of Alexandria, contemporaries of Pappus, can only be applied with caution to another. The faintest telescopic comets are generally devoid of visible tails, and resemble Herschel's nebulous stars. They appear like circular nebulae of faintly-glimmering vapor, with the light concentrted toward the middle. This is the most simple type; but it can not, however, be regarded as rudimentary, since it might equally be the type of an older cosmical body, exhausted by exhalation. In the larger comets we may distinguish both the so-called "head" or "nucleus," and the single or multiple tail, which is characteristically denominated by the Chinese astronomers "the brush" ('sui'). The nucleus generally presents no definite outline, although, in a few rare cases, it appears like a star of the first or second magnitude, and has even been seen in bright sunshine;* as, p 101 for instance, in the large comets of 1402, 1532, 1577, 1744, and 1843. [footnote] *Arago, 'Annuaire', 1832, p. 209, 211. The phenomenon of the tail of a comet being visible in bright sunshine, which is recorded of the comet of 1402, occurred again in the case of the large comet of 1843, whose nucleus and tail were seen in North America on the 28th of February (according to the testimony of J. G. Clarke, of Portland, state of Maine), between 1 and 3 o'clock in the afternoon.(a) The distance of the very dense nucleus from the sun's light admitted of being measured with much exactness. The nucleus and tail appeared like a very pure white cloud, a darker space intervening between the tail and the nucleus. ('Amer. Journ. of Science', vol. xiv., No. 1, p. 229.) [footnote] (a) [The translator was at New Bedford, Massachusetts, U.S., on the 28th February, 1843, and distinctly saw the comet, between 1 and 2 in the afternoon. The sky at the time was intensely blue, and the sun shining with a dazzling brightness unknown in European climates.] -- Tr This latter circumstance indicates, in particular individuals, a denser mass, capable of reflecting light with greater intensity. Even in Herschel's large telescope, only two comets, that discovered in Sicily in 1807, and the splendid one of 1811, exhibited well-defined disks;* the one at an angle of 1 second, and the other at 0.77 seconds, whence the true diameters are assumed to be 536 and 428 miles. [footnote] *'Phil. Trans.' for 1808, Part ii., p. 155, and for 1812, Part i., p. 118. The diameters found by Herschel for the nuclei were 538 and 428 English miles. For the magnitudes of the comets of 1798 and 1805, see Arago, 'Annuaire', 1832, p. 203. The diameters of the less well-defined nuclei of the comets of 1798 and 1805 did not appear to exceed 24 or 28 miles. In several comets that have been investigated with great care, especially in the above-named one of 1811, which continued visible for so long a period, the nucleus and its nebulous envelope were entirely separated from the tail by a darker space. The intensity of light in the nucleus of comets does not augment toward the center in any uniform degree, brightly shining zones being in many cases separated by concentric nebulous envelopes. The tails sometimes appear single, sometimes, although more rarely, double; and in the comets of 1807 and 1843 the branches were of different lengths; in one instance (1744) the tail had six branches, the whole forming an angle of 60 degrees. The tails have been sometimes straight, sometimes curved, either toward both sides, or toward the side appearing to us as the exterior (as in 1811), or convex toward the direction in which the comet is moving (as in that of 1618); and sometimes the tail has even appeared like a flame in motion. The tails are always turned away from the sun, so that their line of prolongation passes through its center; a fact which, according to Edward Biot, was noticed by the Chinese astronomers as early as 837, but was first generally made known in Europe by Fracastoro and Peter Apian in the sixteenth century. These emanations may be regarded as conoidal envelopes of greater of less thickness, p 102 and, considered in this manner, they furnish a simple explanation of many of the remarkable optical phenomena already spoken of. Comets are not only characteristically different in form, some being entirely without a visible tail, while others have a tail of immense length (as in the instance of the comet of 1618, whose tail measured 104 degrees), but we also see the same comets undergoing successive and rapidly-changing processes of configuration. These variations of form have been most accurately and admirably described in the comet of 1744, by Hensius, at St. Petersburg, and in Halley's comet, on its last reappearance in 1835, by Bessel, at Konigsberg. A more or less well-defined tuft of rays emanated from that part of the nucleus which was turned toward the Sun; and the rays being bent backward, formed a part of the tail. The nucleus of Halley's comet; with its emanations, presented the appearance of a burning rocket, the end of which was turned sideways by the force of the wind. The rays issuing from the head were seen by Arago and myself, at the Observatory at Paris, to assume very different forms on successive nights.* [footnote] *Arago, 'Des Changements physiques de la Comete de Halley du 15-23 Oct., 1835. 'Annuaire', 1836, p. 218, 221. The ordinary direction of the emanations was noticed even in Nero's time. "Comae radios solis effugiunt." -- Seneca, 'Nat. Quaest.', vii., 20. The great Konigsberg astronomer concluded from many measurements, and from theoretical considerations, "that the cone of light issuing from the comet deviated considerably both to the right and the left of the true direction of the Sun, but that it always returned to that direction, and passed over to the opposite side, so that both the cone of light and the body of the comet from whence it emanated experienced a rotatory, or, rather, a vibratory motion in the plane of the orbit." He finds that "the attractive force exercised by the Sun on heavy bodies is inadequate to explain such vibrations, and is of opinion that they indicate a polar force, which turns one semi-diameter of the comet toward the Sun, and strives to turn the opposite side away from that luminary. The magnetic polarity possessed by the Earth may present some analogy to this, and, should the Sun have an opposite polarity, an influence might be manifested, resulting in the precession of the equinoxes." This is not the place to enter more fully upon the grounds on which explanations of this subject have been based; but observations so remarkable,* and views of so exalted p 103 a character, regarding the most wonderful class of the cosmical bodies belonging to our solar system, ought not to be entirely passed over in this sketch of a general picture of nature. [footnote] *Bessel, in Schumacher, 'Astr. Nachr.', 1836, No. 300-302, s. 188, 192, 197, 200, 202, und 230. Also in Schumacher, 'Jahrb.', 1837, s. 149, 168. William Herschel, in his observations on the beautiful comet of 1811, believed that he had discovered evidences of the rotation of the nucleus and tail ('Phil. Trans.' for 1812, Part i., p. 140). Dunlop, at Paramatta thought the same with reference to the third comet of 1825. Although, as a rule, the tails of comets increase in magnitude and brilliancy in the vicinity of the sun, and are directed away from that central body, yet the comet of 1823 offered the remarkable example of two tails, one of which was turned toward the sun, and the other away from it, forming with each other an angle of 160 degrees. Modifications of polarity and the unequal manner of its distribution, and of the direction in which it is conducted, may in this rare instance have occasioned a double, unchecked, continuous emanation of nebulous matter.* [footnote] *Bessel, in 'Astr. Nachr.', 1836, No. 302, s. 231. Schum, 'Jahrb.', 1837 s. 175. See, also Lehmann, 'Ueber Cometenschweife' (On the Tails of Comets), in Bode, 'Astron. Jahrb. fur' 1826, s. 168. Aristotle, in his 'Natural Philosophy', makes these emanations the means of bringing the phenomena of comets into a singular connection with the existence of the Milky Way. According to his views, the innumerable quantity of stars which compose this starry zone give out a self-luminous, incandescent matter. The nebulous belt which separates the different portions of the vault of heaven was therefore regarded by the Stagirite as a large comet, the substance of which was incessantly being renewed.* [footnote] *Aristot., 'Meteor.', i., 8, 11-14, und 19-21 (ed. Ideler, t. i., p. 32-34). Biese, 'Phil. des Aristoteles', bd. ii., s. 86. Since Aristotle exercised so great an influence throughout the whole of the Middle Ages, it is very much to be regretted that he was so averse to those grander views of the elder Pythagoreans, which inculcated ideas so nearly approximating to truth respecting the structure of the universe. He asserts that comets are transitory meteors belonging to our atmosphere in the very book in which he cites the opinion of the Pythagorean school, according to which these cosmical bodies are supposed to be planets having long periods of revolution. (Aristot., i., 6, 2.) This Pythagorean doctrine, which, according to the testimony of Apollonius Myndius, was still more ancient, having originated with the Chaldeans, passed over to the Romans, who in this instance, as was their usual practice, were merely the copiers of others. The Myndian philosopher describes the path of comets as directed toward the upper and remote regions of heaven. Hence Seneca says, in his 'Nat. Quaest.', vii., 17: "Cometes non est species falsa, sed proprium sidus sicut solis et lunae: altiora mundi secat et tunc demum apparet quum in imum cursum sui venit;" and again (at vii., 27), "Cometes aternos esse et sortis ejusdem, cujus caetera (sidera), etiamsi faciem illis non habent similem." Pliny (ii., 25) also refers to Apollonius Myndius, when he says, "Sunt qui et haec sidera perpetua esse credant suoque ambitu ire, sed non nisi relicta a sole cerni." p 104 The occulation of the fixed stars by the nucleus of a comet, or by its innermost vaporous envelopes, might throw some light on the physical character of these wonderful bodies; but we are unfortunately deficient in observations by which we may be assured* that the occulation was perfectly central; for, as it has already been observed, the parts of the envelope contiguous to the nucleus are alternately composed of layers of dense or very attenuated vapor. [footnote] *Olbers, in 'Astr. Nachr.', 1828, s. 157, 184. Arago, 'De la Constitution physique des Cometes; Annuaire de' 1832, p. 203, 208. The ancients were struck by the phenomenon that it was possible to see through comets as through a flame. The earliest evidence to be met with of stars having been seen through comets is that of Democritus (Aristot., 'Meteor.', i., 6, 11), and the statement leads Aristotle to make the not unimportant remark, that he himself had observed the occulation of one of the stars of Gemini by Jupiter. Seneca only speaks decidedly of the transparence of the tail of comets. "We may see," says he, "stars through a comet as through a cloud ('Nat. Quaest.', vii., 18); but we can ony see through the rays of the tail, and not through the body of the comet itself: 'non in ea parte qua sidus ipsum est spissi et solidi ignis, sed qua rarus splendor occurrit et in crines dispergitur. Per intervalla ignium, non er ipsos, vides" (vii., 26). The last remark is unnecessary, since, as Galileo observed in the 'Saggiatore (Lettera a Monsignor Cesarini', 1619), we can certainly see through a flame when it is not of too great a thickness'. On the other hand the carefully conducted measurements of Bessel prove, beyond all doubt, that on the 29th of September, 1835, the light of a star of the tenth magnitude, which was then at a distance of 7".78 from the central point of the head of Halley's comet, passed through very dense nebulous matter, without experiencing any deflection during its passage.* [footnote] *Bessel, in the 'Astron. Nachr.', 1836, No. 301, s. 204, 206. Struve, in 'Recueil des Mem. de l'Acad. de St. Peterab.', 1836, p. 140, 143, and 'Astr. Nachr.', 1836, No. 303, s. 238, writes as follows: "At Dorpat the star was in conjunction only 2".2 from the brightest point of the comet. The star remained continually visible, and its light was not perceptibly diminished, while the nucleus of the comet seemed to be almost extinguished before the radiance of the small star of the ninth or tenth magnitude." If such an absence of refracting power must be ascribed to the nucleus of a comet, we can scarcely regard the matter composing comets as a gaseous fluid. The question here arises whether this absence of refracting power may not be owing to the extreme tenuity of the fluid; or does the comet consist of separated particles, constituting a cosmical stratum of clouds, which, like the clouds of our atmosphere, that exercise no influence on the p 105 zenith distance of the stars, does not affect the ray of light passing through it? In the passage of a comet over a star, a more or less considerable diminution of light has often been observed; but this has been justly ascribed to the brightness of the ground from which the star seems to stand forth during the passage of the comet. The most important and decisive observations that we possess on the nature and the light of comets are due to Arago's polarization experiments. His polariscope instructs us regarding the physical constitution of the Sun and comets, indicating whether a ray that reaches us from a distance of many millions of miles transmits light directly or by reflection; and if the former, whther the source of light is a solid, a liquid, or a gaseous body. His apparatus was used at the Paris Observatory in examining the light of Capella and that of the great comet of 1819. The latter showed polarized, and therefore reflected light, while the fixed star, as was to be expected, appeared to be a self-luminous sun.* [footnote] *On the 3d of July, 1819, Arago made the first attempt to analyze the light of comets by polarization, on the evening of the sudden appearance of the great comet. I was present at the Paris Observatory, and was fully convinced, as were also Matthieu and the late Bouvard of the dissimilarity in the intensity of the light seen in the polariscope, when the instrument received cometary light. When it received light from Capella, which was near the comet, and at an equal altitude, the images were of equal intensity. On the reappearance of Halley's comet in 1835, the instrument was altered so as to give, according to Arago's chromatic polarization, two images of complementary colors (green and red). ('Annales de Chimie', t. xiii., p. 108; 'Annuaire', 1832, p. 216.) "We must conclude from these observations," says Arago, "that the cometary light was not entirely composed of rays having the properties of direct light, there being light which was reflected specularly or polarized, that is, coming from the sun. It can not be stated with absolute certainty that comets shine only with borrowed light, for bodies, in becoming self-luminous, do not, on that account, lose the power of reflecting foreign light." The existance of polarized cometary light announced itself not only by the inequality of the images, but was proved with greater certainty on the reappearance of Halley's comet, in the year 1835, by the more striking contrast of the complementary colors, deduced from the laws of chromatic polarization discovered by Arago in 1811. These beautiful experiments still leave it undecided whether, in addition to this reflected solar light, comets may not have light of their own. Even in the case of the planets, as, for instance, in Venus, an evolution of independent light seems very probable. The variable intensity of light in comets can not always be p 106 explained by the position of their orbits and their distance from the Sun. It would seem to indicate, in some individuals, the existence of an inherent process of condensation, and an increased or diminished capacity of reflecting borrowed light. In the comet of 1618, and in that which has a period of three years, it was observed first by Hevelius that the nucleus of the comet diminished at its perihelion and enlarged at its aphelion, a fact which, after remaining long unheeded, was again noticed by the talented astronomer Valz at Nismes. The regularity of the change of volume, according to the different degrees of distance from the Sun, appears very striking. The physical explanation of the phenomenon can not, however, be sought in the condensed layers of cosmical vapor occurring in the vicinity of the Sun, since it is difficult to imagine the nebulous envelope of the nucleus of the comet to be vesicular and impervious to the other.* [footnote] *Arago, in the 'Annuaire', 1832, p. 217-220. Sir John Herschel, 'Astron.', 488. The dissimilar eccentricity of the orbits of comets has, in recent times (1819), in the most brilliant manner enriched our knowledge of the solar system. Encke has discovered the existence of a comet of so short a period of revolution that it remains entirely within the limits of our planetary system, attaining its aphelion between the orbits of the smaller planets and that of Jupiter. Its eccentricity must be assumed at 0.845, that of Juno (which has the greatest eccentricity of any of the planets) being 0.255. Encke's comet has several times, although with difficulty, been observed by the naked eye, as in Europe in 1819, and according to Rumker, in New Holland in 1822. Its period of revolution is about 3 1/3d years; but, from a careful comparison of the epochs of its return to its perihelion, the remarkable fact has been discovered that these periods have diminished in the most regular manner between the years 1786 and 1838, the diminution amounting, in the course of 52 years, to about 1 3/10th days. The attempt to bring into unison the results of observation and calculation in the investigation of all the planetary disturbances, with the view of explaining this phenomenon, has led to the adoption of the very probable hypothesis that there exists dispersed in space a vaporous substance capable of acting as a resisting medium. This matter diminished the tangential force, and with it the major axis of the comet's orbit. The value of the constant of the resistance appears to be somewhat different before and after the perihelion; and this may, perhaps, be ascribed p 107 to the altered form of the small nebulous star in the vicinity of the Sun, and to the action of the unequal density of the strata of cosmical ether.* [footnote] *Encke, in the 'Astronomiche Nachrichten', 1843, No. 489, s. 130-132. These facts, and the investigations to which they have led, belong to the most interesting results of modern astronomy. Encke's comet has been the means of leading astronomers to a more exact investigation of Jupiter's mass (a most important point with reference to the calculation of perturbations); and, more recently, the course of this comet has obtained for us the first determination, although only an approximative one, of a smaller mass for Mercury. The discovery of Encke's comet, which had a period of only 3 1/3d years, was speedily followed, in 1826, by that of another, Biela's comet, whose period of revolution is 6 3/4th years, and which is likewise planetary, having its aphelion beyond the orbit of Jupiter, but within that of Saturn. It has a fainter light than Encke's comet, and, like the latter, its motion is direct, while Halley's comet moves in a course opposite to that pursued by the planets. Biela's comet presents the first certain example of the orbit of a comet intersecting that of the Earth. This position, with reference to our planet, may therefore be productive of danger, if we can associate an idea of danger with so extraordinary a natural phenomenon, whose history presents no parallel, and the results of which we are consequently unable correctly to estimate. Small masses endowed with enormous velocity may certainly exercise a considerable power; but Laplace has shown that the mass of the comet of 1770 is probably not equal to 1/5000th that of the Earth, or about 1/2000th that of the Moon.* [footnote] *Laplace, 'Expos. du Syst. du Monde', p. 216, 237. We must not confound the passage of Biela's comet through the Earth's orbit with its proximity to, or collision with our globe. When this passage took place, on the 29th of October, 1832, it required a full month before the Earth would reach the point of intersection of the two orbits. These two comets of short periods of revolution also intersect each other, and it has been justly observed,* that amid the many perturbations experienced by such small bodies from the largr planets, there is a 'possibility' -- supposing a meeting of these comets to occur in October -- that the inhabitants of the Earth may witness the extraordinary spectacle of an encounter between two cosmical bodies, and possibly of their reciprocal penetration and amalgamation, or of their destruction by means of exhausting emanations. [footnote] *Littrow, 'Beschreibende Astron.', 1835, s. 274. On the inner comet recently discovered by M. Faye, at the Observatory of Paris, and whose eccentricity is 0.551, its distance at its perihelion 1.690, and its distance at its aphelion 5.832, see Schumacher, 'Astron. Nachr.', 1844, No. 495. Regarding the supposed identity of the comet of 1766 with the third comet of 1819, see 'Astr. Nachr.', 1833, No. 239; and on the identity of the comet of 1743 and the fourth comet of 1819, see No. 237 or the last mentioned work. Events of this nature, resulting either from deflection occasioned by disturbing masses or primevally intersecting orbits, must have been of frequent occurrence in the course of millions of years in the immeasurable regions of ethereal space; but they must be regarded as isolated occurrences, exercising no more general or alternative effects on cosmical relations than the breaking forth or extinction of a volcano within the limited sphere of our Earth. A third interior comet, having likewise a short period of revolution was discovered by Faye on the 22d of November, 1843, at the Observatory at Paris. Its elliptic path, which approaches much more nearly to a circle than that of any other known comet, is included within the orbits of Mars and Saturn. This comet, therefore, which, according to Goldschmidt, passes beyond the orbit of Jupiter, is one of the few whose perihelia are beyond Mars. Its period of revolution is 7 29/100 years, and it is not improbable that the form of its present orbit may be owing to its great approximation to Jupiter at the close of the year 1839. If we consider the comets in their inclosed elliptic orbits as members of our solar system, and with respect to the length of their major axes, the amount of their eccentricity, and their periods of revolution, we shall probably find that the three planetary comets of Encke, Biela, and Faye are most nearly approached in these respects, first, by the comet discovered in 1766 by Messier, and which is regarded by Clausen as identical with the third comet of 1819; and next, by the fourth comet of the last-mentioned year, discovered by Blaupain, but considered by Clausen as identical with that of the year 1743, and whose orbit appears, like that of Lexell's comet, to have suffered great variations from the proximity and attraction of Jupiter. The two last-named comets would likewise seem to have a period of revolution not exceeding five or six years, and their aphelia are in the vicinity of Jupiter's orbit. Among the comets that have a period of revolution of from seventy to p 109 seventy-six years, the first in point of importance with respect to theoretical and physical astronomy is Halley's comet, whose last appearance, in 1835, was much less brilliant than was to be expected from preceding ones; next we would notice Olbers's comet, discovered on the 6th of March, 1815; and, lastly, the comet discovered by Pons in the year 1812, and whose elliptic orbit has been determined by Encke. The two latter comets were invisible to the naked eye. We now know with certainty of nine returns of Halley's large comet, it having recently been proved by Laugier's calculations*, that in the Chinese table of comets, first made known to us by Edward Biot, the comet of 1378 is identical with Halley's; its periods of revolution have varied in the interval between 1378 and 1835 from 74.91 to 77.58 years, the mean being 76.1. [footnote] *Laugier, in the 'Comptes Rendus des Seances de l'Academie', 1843, t. xvi., p. 1006. A host of other comets may be contrasted with the cosmical bodies of which we have spoken, requiring several thousand years to perform their orbits, which it is difficult to determine with any degree of certainty. The beautiful comet of 1811 requires, according to Argelander, a period of 3065 years for its revolution, and the colossal one of 1680 as much as 8800 years, according to Encke's calculation. These bodies respectively recede, therefore, 21 and 44 times further than Uranus from the Sun, that is to say, 33,600 and 70,400 millions of miles. At this enormous distance the attractive force of the Sun is still manifested; but while the velocity of the comet of 1680 at its perihelion is 212 miles in a second, that is, thirteen times greater than that of the Earth, it scarcely moves ten feet in the second when at its aphelion. This velocity is only three times greater than that of water in our most sluggish European rivers, and equal only to half that which I have observed in the Cassiquiare, a branch of the Orinoco. It is highly probable that, among the innumerable host of uncalculated or undiscovered comets, there are many whose major axes greatly exceed that of the comet of 1680. In order to form some idea by numbers, I do not say of the sphere of attraction, but of the distance in space of a fixed star, or other sun, from the aphelion of the comet of 1680 (the furthest receding cosmical body with which we are acquainted in our solar system), it must be remembered that, according to the most recent determinations of parallaxes, the nearest fixed star is full 250 times further removed from our sun than the comet in its aphelion. The comet's distance is only 44 p 110 times that of Uranus, while 'a' Centauri is 11,000 and 61 Cygni 31,000 times that of Uranus, according to Bessel's determinations. Having considered the greatest distances of comets from the central body, it now remains for us to notice instances of the greatest proximity hitherto measured. Lexell and Burckhardt's comet of 1770, so celebrated on account of the disturbances it experienced from Jupiter, has approached the Earth within a smaller distance than any other comet. On the 28th of June, 1770, its distance from the Earth was ony six times than of the Moon. The same comet passed twice, viz., in 1769 and 1779, through the system of Jupiter's four satellites without producing the slightest notable change in the well-known orbits of these bodies. The great comet of 1680 approached at its perihelion eight or nine times nearer to the surface of the Sun than Lexell's comet did to that of our Earth, being on the 17th of December a sixth part of the Sun's diameter, or seven tenths of the distance of the Moon from that luminary. Perihelia occurring beyond the orbit of Mars can seldom be observed by the inhabitants of the Earth, owing to the faintness of the light of distant comets; and among those already calculated the comet of 1729 is the only one which has its perihelion between the orbits of Pallas and Jupiter; it was even observed beyond the latter. Since scientific knowledge, although frequently blended with vague and superficial views, has been more extensively diffused through wider circles of social life, apprehensions of the possible evils threatened by comets have acquired more weight as their direction has become more definite. The certainty that there are within the known planetary orbits comets which revisit our regions of space at short intervals -- that great disturbances have been produced by Jupiter and Saturn in their orbits, by which such as were apparently harmless have been converted into dangerous bodies -- the intersection of the Earth's orbit by Biela's comet -- the cosmical vapor, which, acting as a resisting and impeding medium, tends to contract all orbits -- the individual difference of comets, which would seem to indicate considerable decreasing gradations in the quantity of the mass of the nucleus, are all considerations more than equivalent, both as to number and variety, to the vague fears entertained in early ages of the general conflagration of the world by 'flaming swords', and stars with 'fiery streaming hair'. As the consolatory considerations which may be derived from the calculus of probabilities address themselves to reason and to p 111 meditative understanding only, and not to the imagination or to a desponding condition of mind, modern science has been accused, and not entirely without reason, of not attempting to allay apprehensions which it has been the very means of exciting. It is an inherent attribute of the human mind to experience fear, and not hope or joy, at the aspect of that which is unexpected and extraordinary.* [footnote] *Fries, 'Vorlesungen uber die Sternkunde', 1833, s. 262-267 (Lectures on the Science of Astronomy). An infelicitously chosen instance of the good omen of a comet may be found in Seneca, 'Nat. Quest.', vii., 17 and 21. The philosopher thus writes of the comet: "Quem nos Neronis principatu latissimo vidimus et qui cometis detraxit infamiam." The strange form of a large comet, its faint nebulous light, and its sudden appearance in the vault of heaven, have in all regions been almost invariably regarded by the people at large as some new and formidable agent inimical to the existing state of things. The sudden occurrence and short duration of the phenomenon lead to the belief of some equally rapid reflection of its agency in terrestrial matters, whose varied nature renders it easy to find events that may be regarded as the fulfillment of the evil foretold by the appearance of these mysterious cosmical bodies. In our own day, however, the public mind has taken another and more cheerful, although singular, turn with regard to comets; and in the German vineyards in the beautiful valleys of the Rhine and Moselle, a belief has arisen, ascribing to these once ill-omened bodies a beneficial influence on the ripening of the vine. The evidence yielded by experience, of which there is no lack in these days, when comets may so frequently be observed, has not been able to shake the common belief in the meteorological myth of the existence of wandering stars capable of radiating heat. This material taken from pages 111- 147 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- From comets I would pass to the consideration of a far more enigmatical class of agglomerated matter -- the smallest of all asteroids, to which we apply the name 'a��rolites', or 'meteoric stones',* when they reach our atmosphere in a fragmentary condition. [footnote] * (Much valuable information may be obtained regarding the origin and composition of a��rolites or meteoric stones in Memoirs on the subject, by Baumbeer and other writers, in the numbers of Poggendorf's 'Annalen', from 1845 to the present time.) -- Tr. If I should seem to dwell on the specific enumeration of these bodies, and of comets, longer than the general nature of this work might warrant, I have not done so undesignedly. The diversity existing in the individual characteristics of comets has already been noticed. The imperfect knowledge we possess of their physical character renders it p 112 diifficult in a work like the present, to give the proper degree of circumstantiality to the phenomena, which, although of frequent recurrence, have been observed with such various degrees of accuracy, or to separate the necessary from the accidental. It is only with respect to measurements and computations that the astronomy of comets has made any marked advancement, and, consequently, a scientific consideration of these bodies must be limited to a specification of the differences of physiognomy and conformation in the nucleus and tail, the instances of great approximation to other cosmical bodies, and of the extremes in the length of their orbits and in their periods of revolution. A faithful delineation of these phenomena, as well as of those which we proceed to consider, can only be given by sketching individual features with the animated circumstantiality of reality. Shooting stars, fire-balls, and meteoric stones are, with great probability, regarded as small bodies moving with planetary velocity, and revolving in obedience to the laws of general gravity in conic sections round the Sun. When these masses meet the Earth in their course, and are attracted by it, they enter within the limits of our atmosphere in a luminous condition, and frequently let fall more or less strongly heated stony fragments, covered with a shining black crust. When we enter into a careful investigation of the facts observed at those epochs when showers of shooting stars fell periodically in Cumana in 1799, and in North America during the years 1833 and 1834, we shall find that 'fire-balls' can not be considered separately from shooting stars. Both these phenomena are frequently not only simultaneous and blended together, but they likewise are often found to merge into one another, the one phenomenon gradually assuming the character of the other alike with respect to the size of their disks, the emanation of sparks, and the velocities of their motion. Although exploding smoking luminous fire-balls are sometimes seen, even in the brightness of tropical daylight,* equaling in size the apparent p 113 diameter of the Moon, innumerable quantities of shooting stars have, on the other hand, been observed to fall in forms of such extremely small dimensions that they appear only as moving points or 'phosphorescent lines.'** [footnote] *A friend of mine, much accustomed to exact trigonometrical measurements, was in the year 1788 at Popayan, a city which is 2 degrees 26' north latitude, lying at an elevation of 5583 feet above the level of the sea, and at noon, when the sun was shining brightly in a cloudless sky, saw his room lighted up by a fire-ball. He had his back to the window at the time, and on turning round, perceived that great part of the path traversed by the fire-ball was still illuminated by the brightest radiance. Different nations have had the most various terms to express these phenomena: The Germans use the word 'Sternschnuppe', literally 'star snuff' -- an expression well suited to the physical views of the vulgar in former times, according to which, the lights in the firmament were said to undergo a process of 'snuffing' or cleaning; and other nations generally adopt a term expressive of a 'shot' or 'fall' of stars, as the Swedish 'stjernifall', the Italian 'stella cadente', and the English 'star shoot.' In the woody district of the Orinoco, on the dreary banks of the Cassiquiare, I heard the natives in the Mission of Vasiva use terms still more inelegant than the German 'star snuff.' ('Relation Historique du Voy. aux R��gions Equinox.', t. ii., p. 513.) These same tribes term the pearly drops of dew which cover the beautiful leaves of the heliconia 'star spit.' In the Lithuanian mythology, the imagination of the people has embodied its ideas of the nature and signification of falling stars under nobler and more graceful symbols. The Parc�¾, 'Werpeja', weave in heaven for the new-born child its thread of fate, attaching each separate thread to a star. When death approaches the person, the thread is rent, and the star wanes and sinks to the earth. Jacob Grimm, 'Deutsche Mythologie', 1843, s. 685. [footnote] ** According to the testimony of Professor Denison Olmsted, of Yale College, New Haven, Connecticut. (See Poggend., 'Annalen der Physik', bd. xxx., s. 194.) Kepler, who excluded fire-balls and shooting stars from the domain of astronomy, because they were, according to his views, "meteors arising from the exhalations of the earth, and blending with the higher ether," expresses himself, however, generally with much caution. He says: "Stell�¾ cadentes sunt materia viscida inflammata. Earum aliqu�¾ inter cadendum absumuntur, aliqu�¾ ver�� in terram cadunt, pondere suo tract�¾. Nec est dissimile vero, quasdam conglobatas esse ex materia f�¾culent��, in ipsam auram �¾theream immixta: exque a��theris regione, tractu rectilineo, per a��rem trajicere, ceu minutos competas, occult�� causa motus utrorumque." -- Kepler, 'Epit. Astron. Copernican�¾', t. i., p. 80. It still remains undertermined whether the many luminous bodies that shoot across the sky may not vary in their nature. On my return from the equinoctial zones, I was impressed with an idea that in the torrid regions of the tropics I had more frequently than in our colder latitudes seen shooting stars fall as if from a height of twelve or fifteen thousand feet; that they were of brighter colors, and left a more brilliant line of light in their track; but this impression was no doubt owing to the greater transparency of the tropical atmosphere*, which enables the eye to penetrate further into distance. [footnote] *'Relation Historique', t. i., p. 80, 213, 527. If in falling stars, as in comets, we distinguish between the head or nucleus and the tail, we shall find that the greater transparency of the atmosphere in tropical climates is evinced in the greater length and brilliancy of the tail which may be observed in those latitudes. The phenomenon is therefore not necessarily more frequent there, because it is oftener seen and continues longer visible. The influence exercised on shooting stars by the character of the atmosphere is shown occasionally even in our temperate zone, and at very small distances apart. Wartmann relates that on the occasion of a November phenomenon at two places lying very near each other, Geneva and Aux Planchettes, the number of the meteors counted were as 1 to 7. (Wartmann, 'M��m. sur les Etoiles filantes', p. 17.) The tail of a shooting star (or its 'train'), on the subject of which Brandes has made so many exact and delicate observations, is in no way to be ascribed to the continuance of the impression produced by light on the retina. It sometimes continues visible a whole minute, and in some rare instances longer than the light of the nucleus of the shooting star; in which case the luminous track remains motionless. (Gilb., 'Ann.', bd. xiv., s. 251.) This circumstance further indicates the analogy between large shooting stars and fire-balls. Admiral Krusenstern saw, in his voyage round the world, the train of a fire-ball shine for an hour after the lluminous body itself had disappeared, and scarcely move throughout the whole time. ('Reise', th. i., s. 58.) Sir Alexander Burnes gives a charming description of the transparency of the clear atmosphere of Bokhara, which was once so favorable to the pursuit of astronomical observations. Bokhara is situated in 39 degrees 48' north latitude, and at an elevation of 1280 feet above the level of the sea. "There is a constant serenity in its atmosphere, and an admirable clearness in the sky. At night, the stars have uncommon luster, and the Milky Way shines gloriously in the firmament. There is also a never-ceasing display of the most brilliant meteors, which dart like rockets in the sky; ten or twelve of them are sometimes seen in an hour, assuming every color -- fiery red, blue, pale, and faint. It is a noble country for astronomical science, and great must have been the advantage enjoyed by the famed observatory of Samarkand." (Burnes, 'Travels into Bokhara', vol. ii. (1834), p. 158.) A mere traveler must not be reproached for calling ten or twelve shooting stars in an hour "many," since it is only recently that we have learned, from careful observations on this subject in Europe, that eight is the mean number which may be seen in an hour in the field of vision of one individual (Quetelet, 'Corresp. Math��m.', Novem., 1837, p. 447); this number is, however, limited to five or six by that diligent observer, Olbers. (Schum., 'Jahrb.', 1838, s. 325.) p 114 Sir Alexander Burnes likewise extols as a consequence of the purity of the atmosphere in Bokhara the enchanting and constantly-recurring spectacle of variously-colored shooting stars. The connection of meteoric stones with the grander phenomenon of fire-balls -- the former being known to be projected from the latter with such force as to penetrate from ten to fifteen feet into the earth -- has been proved, among many other instances, in the falls of azzzuerolites at Barbotan, in the Department des Landes (24th July, 1790), at Siena (16th June, 1794), at Weston, in Connecticut, U. S. (14th December, 1807), and at Juvenas in the Department of Ard��che (14th June, 1821). Meteoric stones are in some instances thrown from dark clouds suddenly formed in a clear sky, and fall with a noise resembling thunder. Whole districts have thus occasionally been covered with thousands of fragmentary masses, of uniform character but unequal magnitudes, that p 115 have been hurled from one of these moving clouds. In less frequent cases, as in that which occurred on the 16th of September, 1843, at Kleinwenden, near M��hilhausen, a large a��rolite fell with a thundering crash while the sky was clear and cloudless. The intimate affinity between fire-balls and shooting stars is further proved by the fact that fire-balls, from which meteoric stones have been thrown have occasionally been found, as at Angers, on the 9th of June, 1822, having a diameter scarcely equal to that of the small fire-works called Roman candles. The formative power, and the nature of the physical and chemical processes involved in these phenomena are questions all equally shrouded in mystery, and we are as yet ignorant whether the particles composing the dense mass of meteoric stones are originally, as in comets, separated from one another when they become luminous to our sight, or whether in the case of smaller shooting stars, any compace substance actually falls, or, finally, whether a meteor is composed only of a smoke-like dust, containing iron and nickel; while we are wholly ignorant of what takes place within the dark cloud from which a noise like thunder is often heard for many minutes before the stones fall.* [footnote] *On 'm��teoric dust', see Arago, in the 'Annuaire' for 1832, p. 254. I haave very recently endeavored to show, in another work ('Asie Centrale', t. i., p. 408). how the Scythian saga of the sacred gold, which fell burning from heaven, and remained in the possession of the Golden Horde of the Paralat�¾ (Herod., iv., 5-7), probably originated in the vague recollection of the fall of an a��rolite. The ancients had also some strange fictions (Dio Cassius, lxxv., 1259) or silver which had fallen from heaven, and with which it had been attempted, under the Emperor Severus, to cover bronze coins; metallic iron was however, known to exist in meteoric stones. (Plin., ii., 56.) The frequently-recurring expression 'lapidibus pluit' must not always be understood to refer to falls of a��rolites. In Liv., xxv., 7, it probably refers to pumice ('rapilli') ejected from the volcano, Mount Albanus (Monte Cavo), which was not wholly extinguished at the time. (See Heyne, 'Opuscula Acad.', t. iii., p. 261; and my 'Relation Hist.', t. i., p. 394.) The contest of Hercules with the Ligyans, on the road from the Caucasus to the Hesperides, belongs to a different sphere of ideas, being an attempt to explain mythically the origin of the round quartz blocks in the Ligyan field of stones at the mouth of the Rhone, which Aristotle supposes to have been ejected from a fissure during an earthquake, and Posidonius to have been caused by the force of the waves of an inland piece of water. In the fragments that we still possess of the play of �®schylus, the 'Prometheus Delivered', every thing proceeds, however, in part of the narration, as in a fall of a��rolites, for Jupiter draws together a cloud, and causes the "district around to be covered by a shower of round stones". Posidonius even ventured to deride the geognostic myth of the blocks and stones. The Lygian field of stones was, however, very naturally and well described by the ancients. The district is now known as 'La Crau.' (See Guerin, 'Mesures Barom��triques dans les Alpes, et M��t��orologie d'Avignon', 1829, chap. xii., p. 115.) p 116 We can ascertain by measurement the enormous, wonderful, and wholly planetary velocity of shooting stars, fire-valls and meteoric stones, and we can gain a knowledge of what is the general and uniform character of the phenomenon, but not of the genetically cosmical process and the results of the metamorphoses. If meteoric stones while revolving in space are already consolidated into dense masses,* less dense, however, p 117 than the mean density of the earth, they must be very small nuclei, which surrounded by inflammable vapor or gas, form the innermost part of fire-balls, from the height and apparent diameter of which we may, in the case of the largest, estimate that the actual diameter varies from 500 to about 2800 feet. [footnote] *The specific weight of a��rolites varies from 1.9 (Alais) to 4.3 (Tabor). Their general density may be set down as 3, water being 1. As to what has been said in the text of the actual diameters of fire-balls, we must remark, that the numbers have been taken from the few measurements that can be relied upon as correct. These give for the fire-ball of Weston, Connecticut (14th December, 1807), only 500; for that observed by Le Roi (10th July, 1771) about 1000 and for that estimated by Sir Charles Blagden (18th January, 1783) 2600 feet in diameter. Brandes ('Unterhaltungen' bd.i., s. 42) ascribes a diameter varying from 80 to 120 feet to shooting stars, and a luminous train extending from 12 to 16 miles. There are, however, ample optical causes for supposing that the apparent diameter of fire-balls and shooting stars has been very much overrated. The volume of the largest fire-ball yet observed can not be compared with that of Ceres, estimating generally so exact and admirable treatise, 'On the Connection of the Physical Sciences', 1835, p. 411.) With the view of elucidating what has been stated in the text regarding the large z��rolite that fell into the bed of the River Narni, but has not again been found, I will give the passage made known by Pertz, from the 'Chronicon Benedicti, Monachi Sancti Andre�¾ in Mont Soracte', a MS. belonging to the tenth century, and preserved in the Chigi Library at Rome. The Barbarous Latin of that age has been left unchanged. "Anno 921, temporibus domini Johannis Decimi pape, in anno pontificatus illius 7 visa sunt signa. Nam juxta urben Romam lapides plurimi de c�¾lo cadere visi sunt. In civilate qu�¾ vocatur Narnia tam diri ac tetri, ut nihil aliud credatur, quam de infernalibus locis deducti essent. Nam ita ex illis lapidibus unus omnium maximum est, ut decidens in flumen Narnus, ad mensuram unius cubiti super aquas fluminus usque hodie videretur. Nam et ignit�¾ita ut pene terra contingeret. AliAnno 921, temporibus domini Johannis Decimi pape, in anno pontificatus illius 7 visa sunt signa. Nam juxta urben Romam lapides plurimi de c�¾lo cadere visi sunt. In civilate qu�¾ vocatur Narnia tam diri ac tetri, ut nihil aliud credatur, quam de infernalibus locis deducti essent. Nam ita ex illis lapidibus unus omnium maximum est, ut decidens in flumen Narnus, ad mensuram unius cubiti super aquas fluminus usque hodie videretur. Nam et ignit�¾ ita ut pene terra contingeret. Ali cadentes," etc. (Pertz, 'Monum. Germ. Hist. Scriptores', t. iii., p. 715.) On the a��rolites of gos Potamus, which fell, according to the Parian Chroniccle, in the 78 1 Olympiad, see B��ckh, 'Corp. Inscr. Graec', t. ii., p. 302, 320, 340; also Aristot., 'Meteor.', i., 7 (Ideler's 'Comm.', t. i., p. 404-407); Stob., 'Eel. Phys.', i., 25, p. 508 (Heeren); Plut., 'Lys.', c. 12; Diog. Laert., ii., 10; and see, also, subsequent notes in this work. According to a Mongolisn tradition, a black fragment of a rock, forty feet in height, fell from heaven on a plain near the source of the Great Yellow River in Western China. (Abel R��musat, in Lam��therie, 'Jour. de Phys.', 1819, Mai p. 264.) The largest meteoric masses as yet known are those of Otumpa, in Chaco, and of Bahia, in Brazil, described by Rubi de Celis as being from 7 to 7 1/2 feet in length. The meteoric stone of gos Potamos, celebrated in antiquity, and even mentioned in the Chronicle of the Parian Marbles, which fell about the year in which Socrates was born, has been described as of the size of two mill-stones, and equal in weight to a full wagon load. Notwithstanding the failure that has attended the efforts of the African traveler, Brown, I do not wholly relinquish the hope that, even after the lapse of 2312 years, this Thracian meteoric mass, which it would be so difficult to destroy, may be found, since the region in which it fell is now bcome so easy of access to European travelers. The huge a��rolite which in the beginning of the tenth century fell into the river at Narni, projected between three and four feet above the surface of the water, as we learn from a document lately discovered by Pertz. It must be remarked that these meteoric bodies, whether in ancient or modern times can only be regarded as the principal fragments of masses that have been broken up by the explosion either of a fire-ball of a dark cloud. On considering the enormous velocity with which, as has been mathematically proved, meteoric stones reach the earth from the extremest confines of the atmosphere, and the lengthened course traversed by fire-balls through the denser strata of the air, it seems more than improbable that these metalliferous stony masses, containing perfectly-formed crystals of olivine, labradorite, and pyroxene, should in so short a period of time has been converted from a vaporous condition to a solid nucleus. Moreover, that which falls from meteoric masses, even where the internal composition is chemically different, exhibits almost always the peculiar character of a fragment, being of a prismatic or truncated pyramidal form, with broad, somewhat curved faces, and rounded angles. But whence comes this form, which was first recognized by Schreiber as characteristic of the 'severed' part of a rotating planetary body? Here, as in the sphere of organic life, all that appertains to the history of development remains hidden in obscurity. Meteoric masses become luminous and kindle at heights which p 118 must be regarded as almost devoid of air, of occupied by an atmosphere that does not even contain 1/100000th part of oxygen. The recent investigations of Biot on the important phenomenon of twilight* have considerably lowered the lines which had, perhaps with some degree of temerity, been usually termed the boundaries of the atmosphere; but processes of light may be evolved independently of the presence of oxygen, and Poisson conjectured that a��roliteswere ignited far beyond the range of our atmosphere. Numerical calculation and geometrical measurement are the only means by which as in the case of the larger bodies of our solar system, we are enabled to impart a firm and safe basis to our investigations of meteoric stones. [footnote] *Biot, 'Trait�� d'Astronomie Physique' (3��me ��d.), 1841, t. i., p. 149, 177, 238, 312. My lamented friend Poisson endeavored, in a singular manner, to solve the difficulty attending an assumption of the spontaneous ignition of meteoric stones at an elevation where the density of the atmosphere is almost null. These are his words: "It is difficult to attribute, as is uaually done, the incandescence of a��rolites to friction against the molecules of the atmosphere at an elevation above the earth where the density of the air is almost null. May we not suppose that the electric fluid, in a neutral condition, forms a kind of atmosphere, extending far beyond the mass of our atmosphere, yet subject to terrestrial attraction, although physically imponderable, and consequently following our globe in its motion? According to this hypothesis, the bodies of which we have been speaking would, on entering this imponderable atmosphere, decompose the neutral fluid by their unequal action on the two electricities, and they would thus be heated, and in a state of incandescence, by becoming electrified." (Poisson, 'Rech. sur la Probabilit�� des Jugements', 1837, p. 6.) Although Halley pronounced the great fire-ball of 1686, whose motion was opposite to that of the earth in its orbit,* to be a cosmical body, Chadni, in 1794, first recognized, with ready acuteness of mind, the connection between fire-balls and the stones projected from the atmosphere, and the motions of the former bodies in space.** [footnote] *'Philos. Transact.', vol. xxix., p. 161-163. [footnote] **The first edition of Chlandni's important treatise, 'Ueber den Ursprung der von Pallas gefundenen und anderen Eisenmassen' (On the Origin of the masses of Iron found by Pallas, and other similar masses), appeared two months prior to the shower of stones at Siena, and two years before Lichtenberg stated, in the 'G��ttingen Taschenbuch', that "stones reach our atmosphere from the remoter regions of space.' Comp., also, Olbers's letter to Benzenberg, 18th Nov., 1837, in Benzenberg's 'Treatise on Shooting Stars', p. 186. A brilliant confirmation of the cosmical origin of these phenomena has been afforded by Denison Olmsted, at New Haven, Connecticut, who has shown on the concurrent authority of all eye-witnesses, that during the celebrated fall of shooting stars on the night between the 12th p 119 and 13th of November, 1833, the fire-balls and shooting stars all emerged from one and the same quarter of the heavens, namely, in the vicinity of the star 'gamma' in the constellation Leo, and did not deviate from this point, although the star changed its apparent height and azimuth during the time of the observation. Such an independence of the Earth's rotation shows that the luminous body must have reached our atmosphere from 'without.' According to Encke's computation* of the whole p 120 number of observations made in the United States of North America, between the thirty-fifth and the forty-second degrees of latitude, it would appear that all these meteors came from the same point of space in the direction in which the Earth was moving at the time. [footnote] *Encke, in Poggend., 'Annalen', bd. xxxiii. (1834), s. 213. Arago, in the 'Annuaire' for 1836, p. 291. Two letters which I wrote to Benzenberg, May 19 and October 22, 1837, on the conjectural precession of the nodes in the orbit of periodical falls of shooting stars. (Benzenberg's 'Sternsch.', s. 207 and 209.) Olbers subsequently adopted this opinion of the gradual retardation of the November phenomenon. ('Astron. Nachr.', 1838, No. 372, s. 180.) If I may venture to combine two of the falls of shooting stars mentioned by the Arabian writers with the epochs found by Boguslawski for the fourteenth century, I obtain the following more or less accordant elements of the movements of the nodes: In Oct., 902, on the night in which King Ibrahim ben Ahmed died, there fell a heavy shower of shooting stars, "like a fiery rain;" and this year was, therefore, called the year of stars. (Conde, 'Hist. de la Domin.' de los Arabes', p. 346.) On the 19th of Oct., 1202, the stars were in motion all night. "They fell like locusts." ('Comptes Rendus', 1837, t. i., p. 294; and Fr�¾hn, in the 'Bull. de l'Acad��mie de St. P��tersbourg', t. iii., p. 308.) On the 21st Oct., O.S., 1366, "'die sequente post festum XI. millia Virginum ab hora matutina usque ad horam primam vis�¾ sunt quasi stell�¾ de c�¾lo cadere continuo, et in tanta multitudine, quod nemo narrare suf ficit.'" This remarkable notice, of which we shall speak more fully in the subsequent part of this work, was found by the younger Von Boguslawski, in Benesse (de Horowic) de Weitmil or Weithm��l, 'Chronicon Ecclesi�¾ Pragensis', p. 389. This chronicle may also be found in the second part of 'Scriptores rerum Bohemicarum', by Pelzel and Dobrowsky, 1784. (Schum., 'Astr. Nachr.', Dec., 1839.) On the night between the 9th and 10th of November, 1787, many falling stars were observed at Manheim, Southern Germany, by Hemmer (K��mtz, 'Meteor.', th. iii., s. 237.) After midnight, on the 12th of November, 1799, occurred the extraordinary fall of stars at Cumana, which Bonpland and myself have described, and which was observed over a great part of the earth. ('Relat. Hist.', t. i., p. 519-527.) Between the 12th and 13th of November, 1822, shooting stars, intermingled with fire-balls, were seen in large numbers by Kloden, at Potsdam. (Gilbert's 'Ann.', bd. lxxii., s. 291.) On the 13th of November, 1831, at 4 o'clock in the morning, a great shower of falling stars was seen by Captain B��rard, on the Spanish coast, near Carthagena del Levante. ('Annuaire', 1836, p. 297.) In the night between the 12th and 13th of November, 1833, occurred the phenomenon so admirably described by Professor Olmsted, in North America. In the night of the 13-14th of November, 1834, a similar fall of shooting stars was seen in North America, although the numbers were not quite so considerable. (Poggend., 'Annalen', bd. xxxiv., s. 129.) On the 13th of November, 1835, a barn was set on fire by the fall of a sporadic fire-ball, at Belley, in the Department de l'Ain. ('Annuaire', 1836, p. 296.) In the year 1838, the stream showed itself most decidedly on the night of the 13-14th of November. ('Astron. Nachr.', 1838, No. 372.) On the recurrence of falls of shooting stars in North America, in the month of November of the years 1834 and 1837, and in the analogous falls observed at Bremen in 1838, a like general parallelism of the orbits, and the same direction of the meteors from the constellation Leo, were again noticed. It has been supposed that a greater parallelism was observable in the direction of periodic falls of shooting stars than in those of sporadic occurrence; and it has further been remarked, that in the periodically-recurring falls in the month of August, as, for instance, in the year 1839, the meteors came principally from one point between Perseus and Taurus, toward the latter of which constellations in the Earth was then moving. This peculiarity of the phenomenon, manifested in the retrograde direction of the orbits in November and August, should be thoroughly investigated by accurate observations, in order that it may either be fully confirmed or refuted. The heights of shooting stars, that is to say, the heights of the points at which they begin and cease to be visible, vary exceedingly, fluctuating between 16 and 140 miles. This important result, and the enormous velocity of these problematical asteroids, were first ascertained by Benzenberg and Brandes, by simultaneous observations and determinations of parallax at the extremities of a base line of 49,020 feet in length.* [footnote] *I am well aware that, among the 62 shooting stars simultaneously observed in Silesia, in 1823, at the suggestion of Professor Brandes some appeared to have an elevation of 183 to 240, or even 400 miles. (Brandes, 'Unterhaltungen f��r Freunde der Astronomie und Physik', heft i., s. 48. Instructive Narratives for the Lovers of Astronomy and Physics.) But Olbers considered that all determinations for elevations beyond 120 miles must be doubtful, owing to the smallness of the parallax. The relative velocity of motion is from 18 to 36 miles in a second, and consequently equal to planetary velocity. This planetary velocity,* as well as the direction of the orbits p 121 of fire-balls and shooting stars, which has frequently been observed to be opposite to that of the Earth, may be considered as conclusive arguments against the hypothesis that a��rolites derive their origin from the so-called active 'lunar volcanoes.' [footnote] *The planetary velocity of translation, the movement in the orbit, is in Mercury 26.4, in Venus 19.2, and in the Earth 16.4 miles in a second. Numerical views regarding a greater or lesser volcanic force on a small cosmical body, not surrounded by any atmosphere, must, from their nature, be wholly arbitrary. We may imagine the reaction of the interior of a planet on its crust ten or even a hundred times greater than that of our present terrestrial volcanoes; the direction of masses projected from a satellite revolving from west to east might appear retrogressive, owing to the Earth in its orbit subsequently reaching that point of space at which these bodies fall. If we examine the whole sphere of relations which I have touched upon in this work, in order to escape the charge of having made unproved assertions, we shall find that the hypothesis of the selenic origin of meteoric stones* depends upon a number of conditions p 122 whose accidental coincidence could alone convert a possible into an actual fact. [footnote] *Chladni states that an Italian physicist, Paolo Maria Terzago, on the occasion of the fall of an a��rolite at Milan in 1660, by which a Franciscan monk was killed, was the first who surmised that a��rolites were of selenic origin. He says, in a memoir entitled 'Mus�¾um Septalianum, Manfredi Septal�¾, Patricii Mediolanensis, industrioso labore constructum' (Tortona, 1664, p. 44), "Labant philosophorum mentes sub horum lapidum ponderibus; ni dicire velimus, lunan terram alteram, sine mundum esse, ex cujus montibus divisa frustra in inferiorem nostrum hunc orben dela bantur." Without any previous knowledge of this conjecture, Olbers was led, in the year 1795 (after the celebrated fall at Siena on the 16th of June, 1794), into an investigation of the amount of the initial tangential force that would be requisite to bring to the Earth masses projected from the Moon. This ballistic problem occupied, during ten or twelve years, the attention of the geometricians Laplace, Biot, Brandes, and Poisson. The opinion which was then so prevalent, but which has since been abandoned, of the existence of active volcanoes in the Moon, where air and water are absent, led to a confusion in the minds of the generality of persons between mathematical possibilities and physical probabilities. Olbers, Brandes, and Chladni thought "that the velocity of 16 to 32 miles, with which fire-balls and shooting stars entered our atmosphere," furnished a refutation to the view of their selenic origin. According to Olbers, it would require to reach the Earth, setting aside the resistance of the air, an initial velocity of 8292 feet in the second; according to Laplace, 7862; to Biot, 8282; and to Poisson, 7595. Laplace states that this velocity is only five or six times as great as that of a cannon ball; but Olbers has shown "that, with such an initial velocity as 7500 or 8000 feet in a second, meteoric stones would arrive at the surface of our earth with a velocity of only 35,000 feet (or 1.53 German geographical mile). But the measured velocity of meteoric stones averages five such miles, or upward of 114,000 feet to a second; and, consequently, the original velocity of projection from the Moon must be almost 110,000 feet, and therefore fourteen times greater than Laplace asserted." (Olbers, in Schum, 'Jahrb.', 1837, p. 52-58; and in Gehler, 'Neues Physik.' 'W��rterbuche', bd. vi., abth.3, s. 2199-2136.) If we could assume volcanic forces to be still active on the Moon's surface, the absence of atmospheric resistance would certainly give to their projectile force an advantage over that of our terrestrial volcanoes; but even in respect to the measure of the latter force (the projectile force of our own volcanoes), we have no observations on which any reliance can be placed, and it has probably been exceedingly overrated. Dr. Peters, who accurately observed and measured the phenomena presented by �®tna, found that the greatest velocity of any of the stones projected from the crater was only 1250 feet to a second. Observations on the Peak of Teneriffe, in 1798, gave 3000 feet. Although Laplace, at the end of his work ('Expos. du Syst. du Monde', ed. de 1824, p. 399), cautiously observes, regarding a��rolites, "that in all probability they come from the depths of space," yet we see from another passage (chap. vi., p. 233) 6that, being probably unacquainted with the extraordinary planetary velocity of meteoric stones, he inclines to the hypothesis of their lunar origin, always, however, assuming that the stones projjected from the Moon "become satellites of our Earth, describing around it more or less eccentric orbits, and thus not reaching its atmosphere until several or even many revolutions have been accomplished." As an Italian at Tortona had the fancy that a��rolites came from the Moon, so some of the Greek philosophers thought they came from the Sun. This was the opinion of Diogenes Laertius (ii., 9) regarding the origin of the mass that fell at "gos Potamos (see note, p. 116). Pliny, whose labors in recording the opinions and statements of preceding writers are astonishing, repeats the theory, and derides it the more freely, because he, with earlier writers (Diog. Laert., 3 and 5, p. 99, H��bner), accuses Anaxagoras of having predicted the fall of a��rolites from the Sun: "Celebrant Gr�¾ci Anaxagoram Clazomenium Olympiadis septuagesim�¾ octav�¾ secundo anno pr�¾dixisse c�¾lestium litterarum scientia quibus diebus saxum casurum esse e sole, idque factum interdia in Thraci�¾ parte ad gos flumen. Quod si quis pr�¾dictum credat, simul fateatur necesse est, majoris miraculi divinitatem Anaxagor�¾ fuisse, solvique rerum natur�¾ intellectum, et confundi omnia, si aut ipse Sol lapis esse aut unquam lapidem in eo fuisse credatur; decidere tamen crebro non erit dubium." The fall of a moderate-sized stone, which is preserved in the Gymnasium at Abydos, is also reported to have been foretold by Anaxagoras. The fall of a��rolites in bright sunshine, and when the Moon's disk was invisible, probably led to the idea of sun-stones. Moreover, according to one of the physical dogmas of Anaxagoras, which brought on him the persecution of the theologians (even as they have attacked the geologists of our own times), the Sun was regarded as "a molten fiery mass" ([Greed words]). In accordance with these views of Anaxagoras, we find Euripides, in 'Pha��ton', terming the Sun "a golden mass;" that is to say, a fire-colored, brightly-shining matter, but not leading to the inference that a��rolites are golden sun-stones. (See note to page 115.) Compare Valckenaer, 'Diatribe in Eurip. perd. Dram. Reliquias', 1767, p. 30. Diog. Laert., ii., 40. Hence, among the Greek philosophers, we find four hypotheses regarding the origin of falling stars: a telluric origin from ascending exhalations; masses of stone raised by hurricane (see Aristot., 'Meteor., lib. i., cap. iv., 2-13, and cap. vii., 9); a solar origin; and, lastly, an origin in the regions of space, as heavenly bodies which had long remained invisible. Respecting this last opinion, which is that of Diogenes of Apollonia, and entirely accords with that of the present day, see pages 124 and 125. It is worthy of remark, that in Syria, as I have been assured by a learned Orientalist, now resident at Smyrna, Andrea de Nericat, who instructed me in Persian, there is a popular belief that a��rolites chiefly fall on clear moonlight nights. The ancients, on the contrary, especially looked for their fall during lunar eclipses. (See Pliny, xxxvii., 10, p. 164. Solinus, c. 37. Salm., 'Exere.', p. 531; and the passages collected by Ukert, in his 'Geogr. der Griechen und R��mer', th. ii., 1, s. 131, note 14.) On the improbability that meteoric masses are formed from metal-dissolving gases, which, according to Fusinieri, may exist in the highest strata of our atmosphere, and previously diffused through an almost boundless space, may suddenly assume a solid condition, and on the penetration and misceability of gases, see my ' Relat. Hist.', t. i., p. 525. p 122 The view of the original existence of p 123 small planetary masses in space is simpler, and at the same time, more analogous with those entertained concerning the formation of other portions of the solar system. It is very probable that a large number of these cosmical bodies traverse space undestroyed by the vicinity of our atmosphere, and revolve round the Sun without experiencing any alteration but a slight increase in the eccentricity of their orbits, occasioned by the attraction of the Earth's mass. We may, consequently, suppose the possibility of these bodied remaining invisible to us during many years and frequent revolutions. The supposed phenomenon of ascending shooting stars and fire-balls, which Chladni has unsuccessfully endeavored to explain on the hypothesis of the 'reflection' of strongly compressed air, appears at first sight as the consequence of some unknown tngential force propelling bodies from the earth; but Bessel has shown by theoretical deductions, confirmed by Feldt's carefully-conducted calculations, that, owing to the absence of any proofs of the simultaneous occurrence of the observed disappearances, the assumptiopn of an ascent of shooting stars was rendered wholly improbable, and inadmissible as a result of observation.* [footnote] *Bessel, in Schum., 'Astr. Nachr.', 1839, No 389 und 381, s. 222 und 346. At the conclusion of the Memoir there is a comparison of the Sun's longitudes with the epochs of the November phenomenon, from the period of the first observations in Cumana in 1799, The opinion advanced by Olbers that the explosion of shooting stars and ignited fire-balls not moving in straight lines may impel meteors upward in the manner of rockets, and influence the direction of their orbits, must be made the subject of future researches. Shooting stars fall either seprately and in inconsiderable numbers, that is, sporadically, or in swarms of many thousands. p 124 The latter, which are compared by Arabian authors to swarms of locusts, are periodic in their occurrence, and move in streams, generally in a parallel direction. Among periodic falls, the most celebrated are that known as the November phenomenon, occurring from about the 12th to the 14th of November, and that of the festival of St. Lawrence (the 10th of August), whose "fiery tears" were noticed in former times in a church calendar of England, no less than in old traditionary legends, as a meteorological event of constant recurrence.* [footnote] *Dr. Thomas Forster ('The Pocket Encyclopedia of Natural Phenomena' 1827, p. 17) states that a manuscript is preserved in the library of Christ's College, Cambridge,** written in the tenth century by a monk, and entitled 'Ephemerides Rerum Naturalium', in which the natural phenomena for each day of the year are inscribed as, for instance, the first flowering of plants, the arrival of birds, etc.; the 10th of August is distinguished by the word "meteorodes." It was this indication, and the tradition of the fiery tears of St. Lawrence, that chiefly induced Dr. Forster to undertake his extremely zealous investigation of the August phenomena. (Quetelet, 'Correspond. Math��m.', S��rie III., t. i., 1837, p. 433.) [further footnote] **[No such manuscript is at present known to exist in the library of that college. For this information I am indebted to the inquiries of Mr. Cory, of Pembroke College, the learned editor of 'Hieroglyphics of Horapollo Nilous', Greek and English, 1840.] -- Tr. Notwithstanding the great quantity of shooting stars and fire-balls of the most various dimensions, which, according to Kl��den, were seen to fall at Potsdam on the night between the 12th and 13th of November, 1822, and on the same night of the year in 1832 throughout the whole of Europe, from Portsmouth to Orenburg on the Ural River, and even in the southern hemisphere, as in the Isle of France, no attention was directed to the 'periodicity' of the phenomenon, and no idea seems to have been entertained of the connection existing between the fall of shooting stars and the recurrence of certain days, until the prodigious swarm of shooting stars which occurred in North America between the 12th and 13th of November, 1833, and was observed by Olmsted and Palmer. The stars fell on this occasion, like flakes of snow, and it was calculated that at least 240,000 had fallen during a period of nine hours. Palmer, of New Haven, Connecticut, was led, in consequence of this splendid phenomenon, to the recollection of the fall of meteoric stones in 1799, first described by Ellicot and myself,* and which, by p 125 a comparison of the facts I had adduced, showed that the phenomenon had been simultaneously seen in the New Continent, from the equator to New Herrnhut in Greenland (65 degrees 14' north latitude), and between 46 degrees and 82 degrees longitude. [footnote] *Humb., 'Rel. Hist.', t. i., p. 519-527. Ellicot in the 'Transactions of the American Society', 1804, vol. vi., . 29. Arago makes the following observations in reference to the November phenomena: "We thus become more and more confirmed in the belief that there exists a zone composed of millions of small bodies, whose orbits cut the plane of the ecliptic at about the point which out Earth annually occupies between the 11th and 13th of November. It is a new planetary world beginning to be revealed to us." ('Annuaire', 1836, p. 296.) The identity of the epochs was recognized with astonishment. The stream which had been seen from Jamaica to Boston (40 degrees 21' north latitude) to traverse the whole vault of heaven on the 12th and 13th of November, 1833, was again observed in the United States in 1834, on the night between the 13th and 14th of November, although on this latter occasion it showed itself with somewhat less intensity. In Europe the periodicity of the phenomenon has since been manifested with great regularity. Another and a like regularly recurring phenomenon is that noticed in the month of August, the meteoric stream of St. Lawrence, appearing between the 9th and 14th of August. Muschenbrock,* as early as in the middle of the last century, drew attention to the frequency of meteors in the month of August' but their certain periodic return about the time of St. Lawrence's day was first shown by Quetelet, Olbers, and Benzenberg. [footnote] *Compare Muschenbroek, 'Introd. ad Phil. Nat.', 1762, t. ii., p. 1061; Howard, 'On the Climate of London', vol. ii., p. 23, observations of the year 1806; seven years, therefore aftr the earliest observations of Brandes (Benzenberg, '��ber Sternschnuppen', s. 240-244); the August observations of Thomas Forster, in Quetelet, op. cit., p. 438-453; those of Adolph Erman, Boguslawski, and Kreil, in Schum., 'Jahrb.', 1838, s. 317-330. Regarding the point of origin in Perseus, on the 10th of August, 1839, see the accurate measurements of Bessel and Erman (Schum., 'Astr. Nachr.', No. 385 und 428); but on the 10th of August, 1837, the path does not apper to have been retrograde; see Arago in 'Comptes Rendus', 1837, t. ii., p. 183. We shall, no doubt, in time, discover other periodically appearing streams,* probably about the 22d to the p. 126 25th of April, between the 6th and 12th of December, and, to judge by the number of true falls of a��rolites enumerated by Capocci, also between the 27th and 29th of November, of about the 17th of July. [footnote] *On the 25th of April, 1095, "innumerable eyes in France saw stars falling from heaven as thickly as hail" ('ut grando, nisi lucerent, pro densitate putaretur'; Baldr., p. 88), and this occurrence was regarded by the Council of Clermont as indicative of the great movement in Christendom. (Wilken, 'Gesch. der Kreuzz��ge', bd. i., s. 75.) On the 25th of April, 1800, a great fall of stars was observed in Virginia and Massachusetts; it was "a fire of rockets that lasted two hours." Arago was the first to call attention to the "train��e d'astero��des," as a recurring phenomenon. ('Annuaire', 1836, p. 297.) The falls of a��rolites in the beginning of the month of December are also deserving of notice. In reference to their periodic recurrence as a meteoric stream, we may mention the early observation of Brandes on the night of the 6th and 7th of December, 1798 (when he counted 2000 falling stars), and very probably the enormous fall of a��rolites that occurred at the Rio Assu, near the village of Macao, in the Brazils, on the 11th of December, 1836. (Brandes, 'Unterhalt. f��r Freunde der Physik', 1825, heft i., s. 65, and 'Comptes Rendus', t. v., p. 211.) Capocci, in the interval between 1809 and 1839, a space of thirty years, has discovered twelve authenticated cases of a��rolites occurring between the 27th and 29th of November, besides others on the 13th of November, the 10th of August, and the 17th of July. ('Comptes Rendus', t. xi., p. 357.) It is singular that in the portion of the Earth's path corresponding with the months of January and February, and probably also with March, no 'periodic' streams of falling stars of a��rolites have as yet been noticed; although when in the South Sea in the year 1803, I observed on the 15th of March a remarkably large number of falling stars, and they were seen to fall as in a swarm in the city of Quito, shortly before the terrible earthquake of Riobamba on the 4th of February, 1797. From the phenomena hitherto observed, the following epochs seem especially worthy of remark: 22d to the 25th of April. 17th of July (17th to the 26th of July?). (Quet., 'Corr.', 1837, p. 435.) 10th of August. 12th to the 14th of November. 27th to the 29th of November. 6th to the 12th of December. When we consider that the regions of space must be occupied by myriads of comets, we are led by analogy, notwithstanding the differences existing between isolated comets and rings filled with asteroids, to regard the frequency of these meteoric streams with less astonishment than the first consideration of the phenomenon would be likely to excite. Although the phenomena hitherto observed appear to have been independent of the distance from the pole, the temperature of the air, and other climatic relations, there is, however, one perhaps accidentally coincident phenomenon which must not be wholly disregarded. The Northern Light, the Aurora Borealis, was unusually brilliant on the occurrence of the Borealis, was unusually brilliant on the occurrence of the splendid fall of meteors of the 12th and 13th November, 1833, described by Olmsted. It was also observed at Bremen in 1838, where the periodic meteoric fall was, however, less remarkable than at Richmond, near London. I have mentioned in another work the singular fact observed by Admiral Wrangel, and frequently confirmed to me by himself,* that when he p 127 was on the Siberian coast of the Polar Sea, he observed, during an Aurora Borealis, certain portions of the vault of heaven which were not illuminated, light up and continue luminous whenever a shooting star passed over them. [footnote] *Ferd. v. Wrangle, 'Reise l��ngs der Nordk��ste von Sibirien in den Jahren', 1820-1824, th. ii., s. 259. Regarding the recurrence of the denser swarm of the November stream after an interval of thirty-three years, see Olbers, in 'Jahrb.', 1837, s. 280. I was informed in Cumana that shortly before the fearful earthquake of 1766, and consequently thirty-three years (the same interval) before the great fall of stars on the 11th and 12th of November, 1799, a similar fiery manifestation had been observed in the heavens. But it was on the 21st of October, 1766, and not in the beginning of November, that the earthquake occurred. Possibly some traveler in Quito may yet be able to ascertain the day on which the volcano of Cayambe, which is situated there, was for the space of an hour enveloped in falling stars, so that the inhabitants endeavored to appease heaven by religious processions. ('Relat. Hist.', t. i., chap. iv., p 307; chap. x., p. 520 and 527.) The different meteoric streams, each of which is composed of myriads of small cosmical bodies, probably intersect our Earth's orbit in the same manner as Biela's comet. According to this hypothesis, we may represent to ourselves these asteroid-meteors as composing a closed ring or zone, within which they all pursue one common orbit. The s aller planets between Mars and Jupiter present us if we except Pallas with an analogous relation in their constantly intersecting orbits. As yet, however, we have no certain knowledge as to whether changes in the periods at which the stream becomes visible, or the 'retardations' of the phenomena of which I have already spoken, indicate a regular precession of oscillation of the nodes -- that is to say, of the points of intersection of the Earth's orbit and of that of the ring; or whether this ring or zone attains so considerable a degree of breadth from the irregular grouping and distances apart of the small bodies, that it requires several days for the Earth to traverse it. The system of Saturn's satellites shows us likewise a group of immense width, composed of most intimately-connected cosmical bodies. In this system, the orbit of the outermost (the seventh) satellite has such a vast diameter, that the Earth, in her revolution round the Sun, requires three days to traverse an extent of space equal to this diameter. If, therefore, in one of these rings, which we regard as the orbit of a periodical stream, the asteroids should be so irregularly distributed as to consist of but few groups sufficiently dense to give rise to these phenomena, we may easily understand why we so seldom witness such glorious spectacles as those exhibited in the November months of 1799 and 1833. The acute mind of Olbers led him almost to predict that the next appearance of the phenomenon of shooting stars and fire-balls intermixed, falling like flakes of snow, would not recur until between the 12th and 14th of November, 1867. p 128 The stream of the November asteroids has occasionally only been visible in a small section of the Earth. Thus, for instance, a very splendid 'meteoric shower' was seen in England in the year 1837, while a most attentive and skillful observer at Braunsberg, in Prussia only saw on the same night, which was there uninterruptedly clear, a few sporadic shooting stars fall between seven o'clock in the evening and sunrise the next morning. Bessel* concluded from this "that a dense group of the bodies composing the great ring may have reached that part of the Earth in which England is situated, while the more eastern districts of the Earth might be passing at the time through a part of the meteoric ring proportionally less densely studded with bodies." [footnote] *From a letter to myself, dated Jan. 24th, 1838. The enormous swarm of falling stars in November, 1799, was almost exclusively seen in America, where it was witnessed from New Herrnhut in Greenland to the equator. The swarms of 1831 and 1832 were visible only in Europe, and those of 1833 and 1834 only in the United States of North America. If the hypothesis of a regular progression or oscillation of the nodes should acquire greater weight, special interest will be attached to the investigation of older observations. The Chinese annals, in which great falls of shooting stars, as well as the phenomena of comets, are recorded, go back beyond the age of Tyrt�¾s, or the second Messenian war. They give a description of two streams in the month of March, one of which is 687 years anterior to the Christian era. Edward Biot has observed that among the fifty-two phenomena which he has collected from the Chinese annals, those that were of most frequent recurrence are recorded at periods nearly corresponding with the 20th and 22d of July, O.S., and might consequently be identical with the stream of St. Lawrence's day, taking into account that it has advanced since the epochs* indicated. [footnote] *Lettre de M. Edouard Biot �� M. Quetelet, sur les anciennes apparitions d'Etoiles Filantes en Chine, in the 'Bull. de l'Acad��mie de Bruxelles', 1843, t. x., No. 7, p. 8. On the notice from the 'Chronicon Ecclesi�¾ Pragensis', see the younger Boguslawski, in Poggend., 'Annalen', bd. xlviii., s. 612. If the fall of shooting stars of the 21st of October, 1366, O.S. (a notice of which was found by the younger Von Boguslawski, in Benessius de Horowic's 'Chronicon Ecclesi�¾ Pragensis'), be identical with our November phenomenon, although the occurrence in the fourteenth century was seen in broad daylight, we find by the precession in 477 years that this system of meteors, or, rather, its common center of gravity, must describe p 129 a retrograde orbit round the Sun. It also follows, from the views thus developed, that the non-appearance, during certain years, in any portion of the Earth, of the two streams hitherto observed in November and about the time of St. Lawrence's day, must be ascribed either to an interruption in the meteoric ring, that is to say, to intervals occurring between the asteroid groups, or, according to Poisson to the action of the larger planets* on the form and position of this annulus. [footnote] *"It appears that an apparently inexhaustible number of bodies, too small to be observed, are moving in the regions of space, either around the Sun or the planets, or perhaps even around their satellites. It is supposed that when these bodies come in contact with our atmosphere, the difference between their velocity and that of our planet is so great, that the friction which they experience from their contact with the air heats them to incandescence, and sometimes causes their explosion. If the group of falling stars form an annulus around the Sun, its velocity of circulation may be very different from that of our Earth; and the displacements it may experience in space, in consequence of the actions of the various planets, may render the phenomenon of its intersecting the planes of the ecliptic possible at some epochs, and altogether impossible at others." -- Poisson, 'Recherches sur la Probabilit�� des Jugements', p. 306, 307. The solid masses which are observed by night to fall to the earth from fire-balls, and by day generally when the sky is clear, from a cark small cloud, are accompanied by much candescence. They undeniably exhibit a great degree of general identity with respect to their external form, the character of their crust, and the chemical composition of their principal constituents. These characteristics of identity have been observed at all the different epochs and in the most various parts of the earth in which these meteoric stones have been found. This striking and early-observed analogy of physiognomy in the denser meteoric masses is, however, met by many exceptions regarding individual points. What differences, for instance, do we not find between the malleable masses of for instance, do we not find between the malleable masses of iron of Hradeschina in the district of Agram, those from the shores of the Sisim in the government of Jeniseisk, rendered so celebrated by Pallas, or those which I brought from Mexico,* all of which contain 96 per cent. of iron, from the a��rolites of Siena, in which the iron scarcely amounts to 2 per cent., or the earthy a��rolite of Alais (in the Department du Gard), which broke up in water, or, lastly, from those of Jonzac and Javenas, which contained no metallic iron, but presented a p 130 mixture of oryctognostically distinct crystalline compoonents! [footnote] *Humboldt, 'Essai Politique sur la Nouv. Espagne' (2de ��dit.), t. iii. p. 310. These differences have led mineralogists to separate these cosmical masses into two classes, namely, those containing nickelliferous meteoric iron, and those consisting of fine or coarsely-granular meteoric dust. The crust or rind of a��rolites is peculiarly characteristic of these bodies, being only a few tenths of a line in thickness, often glossy and pitch-like, and occasionally veined.* [footnote] *The peculiar color of their crust was observed even as early as in the time of Pliny (ii., 56 and 58): "colore adusto." The phrase "lateribus pluisse" seems also to refer to the burned outer surface of a��rolites. There is only one instance on record, as far as I am aware (the a��rolite of Chantonnay, in La Vend��e), in which the rind was absent, and this meteor, like that of Juvenas, presented likewise the peculiarity of having pores and vesicular cavities. In all other cases the black crust is divided from the inner light-gray mass by as sharply-defined a line of separation as is the black leaden-colored investment of the white granit blocks* which I brought from the cataracts of the Orinoco, and which are also associated with many other cataracts, as, for instance, those of the Nile and of the Congo River. [footnote] * Humb., 'Rel. Hist.', t. ii., chap xx., p. 299-302. The greatest heat employed in our porcelain ovens would be insufficient to produce any thing similar to the crust of meteoric stones, whose interior remains wholly unchanged. Here and there, facts have been observed which would seem to indicate a fusion together of the meteoric fragments; but, in general, the character of the aggregate mass, the absence of compression by the fall, and the inconsiderable degree of heat possessed by these bodies when they reach the earth, are all opposed to the hypothesis of the interior being in a state of fusion during their short passage from the boundary of the atmosphere to our Earth. The chemical elements of which these meteoric masses consist, and on which Berzelius has thrown so much light, are the same as those distributed throughout the earth's crust, and are fifteen in number, namely, iron, nickel, cobalt, manganese, chromium, copper, arsenic, zinc, potash, soda, sulphur, phosphorus, and carbon, constituting altogether nearly one third of all the known simple bodies. Notwithstanding this similarity with the primary elements into which inorganic bodies are chemically reducible, the aspect of a��rolites, owing to the mode in which their constituent parts are compounded, presents, generally, some features foreign to our telluric rocks and minerals. The pure native iron, which is almost always p 131 found incorporated with a��rolites, imparts to them a peculiar, but not consequently, a 'selenic' character; for in other regions of space, and in other cosmical bodies besides our Moon, water may be wholly absent, and processes of oxydation of rare occurence. Cosmical gelatinous vesicles, similar to the organic 'nostoc' (masses which have been supposed since the Middle Ages to be connected with shooting stars), and those pyrites of Sterlitamak, west of the Uralian Mountains, which are said to have constituted the interior of hailstones,* must both be classed among the mythical fables of meteorology. [footnote] *Gustav Rose, 'Reise nach dem Ural', bd. II., s. 202. Some few a��rolites, as those composed of a finely granular tissue of olivine, augite, and labradorite blended together* (as the meteoric stone found at Juvenas, in the Department de l'Ard��che, which resembled dolorite), are the only ones, as Gustav Rose has remarked, which have a more familiar aspect. [footnote] *Gustav Rose, in Poggend., 'Ann.', 1825, bd. iv., x. 173-192. Rammelsberg, 'Erstes Suppl. zum chem. Handw��rterbuche der Mineralogie', 1843, s. 102. "It is," says the clear-minded observer Olbers, "a remarkable but hitherto unregarded fact, that while shells are found in secondary and tertiary formations, no 'fossil meteoric stones' have as yet been discovered. May we conclude from this circumstance that previous to the present and last modification of the earth's surface no meteoric stones fell on it, although at the present time it appears probable, from the researches of Schreibers, that 700 fall annually?" (Olbers, in Schum., 'Jahrb.', 1838, s. 329.) Problematical nickelliferous masses of native iron have been found in Northern Asia (at the gold-washing establishment at Petropawlowsk, eighty miles southeast of Kusnezk), imbedded thirty-one feet in the ground, and more recently in the Western Carpathians (the mountain chain of Magura, at Szlanicz), both of which are remarkably like meteoric stones. Compart Erman, 'Archiv f��r wissenschaftliche Kunde von Russland', bd. i., s. 315, and Haidinger, 'Bericht ��ber Szlaniczer Sch��rfe in Ungarn.' These bodiescontain, for instance, crystalline substances, perfectly similar to those of our earth's crust; and in the Siberian mass of meteoric iron investigated by Pallas, the olivine only differs from common olivine by the absence of nickel, which is replaced by the oxyd of tin.* [footnote] *Berzelius, 'Jahresber.', bd. xv., s. 217 und 231. Rammelsberg, 'Handw��rterb., abth. ii., s. 25-28. As meteoric olivine, like our basalt, contains from 47 to 49 per cent. of magnesia, constituting, according to Berzelius, almost the half of the earthy components of meteoric stones, we can not be surprised at the great quantity of silicate of magnesia found in these cosmical bodies. If the z��rolite of Juvenas contain separable crystals of augite and labradorite, the numerical relation of the constituents p 132 render it at least probable that the meteoric masses of Chateau-Renard may be a compound of diorite, consisting of hornblende and albite, and those of Blansko and Chantonnay compounds of hornblende and labradorite. The proofs of the telluric and atmospheric origin of aUerolites, which it is attempted to base upon the oryctognostic analogies presented by these bodies, do not appear to me to possess any great weight. Recalling to mind the remarkable interview between Newton and Conduit at Kensington,* I would ask why the elementary substances that compose one group of cosmical bodies, or one planetary system, may not, in a great measure, be identical? [footnote] * "Sir Isaac Newton said he took all the planets to be composed of the same matter with the Earth, viz., earth, water, and stone, but variously connected." -- Turner, 'Collections for the History of Grantham, containing authentic Memoirs of Sir Isaac Newton', p. 172. Why should we not adopt this view, since we may conjecture that these planetary bodies, like all the larger or smaller agglomerated masses revolving round the sun, have been thrown off from the once far more expanded solar atmosphere, and been formed from vaporous rintgs describing their orbits round the central body? We are not, it appears to me, more justified in applying the term telluric to the nickel and iron, the olivine and pyroxene (augite), found in meteoric stones, than in indicating the German plants which I found beyond the Obi as European species of the flora of Northern Asia. If the elementary substances composing a group of cosmical bodies of different magnitudes be identical, why should they not likewise, in obeying the laws of mutual attraction, blend together under definite relations of mixture, composing the white glittring snow and ice in the polar zones of the planet Mars, or constituting in the smaller cosmical masses mineral bodies inclosing crystals of olivine, augite, and labradorite? Even in the domain of pure conjecture we should not suffer ourselves to be led away by unphilosophical and arbitrary views devoid of the support of inductive reasoning. Remarkable obscurations of the sun's disk, during which the stars have been seen at mid-day (as, for instance, in the obscuration of 1547, which continued for three days, and occurred about the time of the eventful battle of M��hlberg), can not be explained as arising from volcanic ashes or mists, and were regarded by Kepler as owing either to a 'materia cometica', or to a black cloud formed by the sooty exhalations of the solar body. The shorter obscurations of 1090 and 1203, which continued, the one only three, and the other six p 133 hours, were supposed by Chladni and Schnurrer to be occasioned by the passage of meteoric masses before the sun's disk. Since the period that streams of meteoric shooting stars were first considered with reference to the direction of their orbit as a closed ring, the epochs of these mysterious celestial phenomena have been observed to present a remarkable connection with the regular recurrence of swarms of shooting stars Adolph Erman has evinced great acuteness of mind in his accurate investigation of the facts hitherto observed on this subject, and his researches have enabled him to discover the connection of the sun's conjunction with the August asteroids on the 7th of February, and with the November asteroids on the 12th of May, the latter period corresponding with the days of St. Mamert (May 11th), St. Pancras (May 12th), and St. Servatius (May 13th), which according to popular belief, were accounted "cold days."* [footnote] Adolph Erman, in Poggend., 'Annalen', 1839, bd. xlviii., s. 582-601. Biot had previously thrown doubt regarding the probability of the November stream reappearing in the beginning of May ('Comptes Rendus', 1836, t. ii., p. 670). M��dler has examined the mean depression of temperature on the three ill-named days of May by Berlin observations for eighty-six years ('Verhandl. des Vereins zur Bedf��rd, des Gartenbaues', 1834, s. 377), and found a retrogression of temperature amounting to 2.2 degrees Fahr. from the 11th to the 13th of May, a period at which nearly the most rapid advance of heat takes place. It is much to be desired that this phenomenon of depressed temperature, which some have felt inclined to attribute to the melting of the ice in the northeast of Europe, should be also investigated in very remote spots, as in America, or in the southern hemisphere. (Comp. 'Bull. de l'Acad. Imp. de St. P��tersbourg', 1843, t. i., No. 4.) The Greek natural philosophers, who were but little disposed to pursue observations, but evinced inexhaustible fergility of imagination in giving the most various interpretation of half-perceived facts, have, however, left some hypotheses regarding shooting stars and meteoric stones which strikingly accord with the views now almost universally admitted of the cosmical process of these phenomena. "Falling stars," says Plutarch, in his life of Lysander,* are, according to the opinion of some physicists, not eruptions of the ethereal fire extinguished in the air immediately after its ignition, nor yet an inflammatory combustion of the air, which is dissolved in large quantities in the upper regions of space, but these meteors are rather a fall of celestial bodies, which, in consequence of a certain intermission in the rotatory force, and by the impulse of some irregular movements, have been hurled down not only to the inhabited portions of the Earth, but also beyond it into the great ocean, where we can not find them." [footnote] *Plut., 'Vit�¾ par, in Lysandro', cap. 22. The statement of Damachos (Da��machos), that for seventy days continuously there was a fiery cloud seen in the sky, emitting sparks like falling stars, and which then, sinking nearer to the earth, let fall the stone of �®gos Potamos, "which, however, was only a small part of it," is extremely improbable, since the direction and velocity of the fire-cloud would in that case of necessity have to remain for so many days the same as those of the earth; and this, in the fire-ball of the 19th of July, 1686, described by Halley ('Trans.', vol. xxix., p. 163), lasted only a few minutes. It is not altogether certain whether Da��machos, the writer, [Greek words], was the same person as Da��machos of Plat�¾a, who was sent by Selencus to India to the son of Androcottos, and who ws charged by Strabo with being "a speaker of lies" (p. 70, Casaub.). From another passage of Plutarch ('Compar. Solonis c. Cop.', cap. 5) we should almost believe that he was. At all events, we have here only the evidence of a very late author, who wrote a century and a half after the fall of a��rolites occurred in Thrace, and whose authenticity is also doubted by Plutarch. Diogenes of Apollonia* expresses himself still more explicitly. [footnote] *Stob., ed. Heeren, i., 25, p. 508; Plut., 'de plac. Philos.', ii., 13. According to his views, "Stars that are 'invisible', and, consequently, have no name, move in space together with those that are visible. These invisible stars frequently fall burning at �®gos Potamos." The Apollonian, who held all other stellar bodies, when luminous, to be of a pumice-like nature, probably grounded his opinions regarding shooting stars and meteoric masses on the doctrine of Anaxagoras the Clazomenian, who regarded all the bodies in the universe "as fragments of rocks, which the fiery ether, in the force of its gyratory motion, had torn from the Earth and converted into stars." In the Ionian school, therefore, according to the testimony transmitted to us in the views of Diogenes of Apollonia, a��rolites and stars were ranged in one and the same class; both, when considered with reference to their primary origin, being equally telluric, this being understood only so far as the Earth was then regarded as a central body,* p 135 forming all things around it in the same manner was we, according to our present views, suppose the planets of our system to have originated in the expanded atmosphere of another central body, the Sun. [footnote] *The remarkable passage in Plut., 'de plac. Philos.', ii., 13, runs thus: "Anaxagoras teaches that the surrounding ether is a fiety substance, which, by the power of its rotation, tears rocks from the earth, inflames them, and converts them into stars." Applying an ancient fable to illustrate a physical dogma, the Clazomenian appears to have ascribed the fall of the Nem�¾an Lion to the Peloponnesus from the Moon to such a rotatory or centrifugal force. (�®lian., xii., 7; Plut., 'de Facie in Orge Lun�¾' c. 24; Schol. ex Cod. Paris., in 'Apoll. Argon.', lib. i., p. 498, ed. Schaef., t. ii., p. 40; Meineke, 'Annal. Alex.', 1843, p. 85.) Here, instead of stones from the Moon, we have an animal from the Moon! According to an acute remark of B��ckh, the ancient mythology of the Nem�¾an lunar lion has an astronomical origin, and is symbolically connected in chronology with the cycle of intercalation of the lunar year, with the moon-worship at Nem�¾a, and the games by which it was accompanied. These views must not, therefore, be confounded with what is commonly termed the telluric or atmospheric origin of meteoric stones, nor yet with the singular opinion of Aristotle, which supposed the enormous mass of �®gos Potamos to have been raised by a hurricane. That rrogant spirit of incredulity, which rejects facts without attempting to investigate them, is in some cases almost more injurious than an unquestioning credulity. Both are alike detrimental to the force of investigation. Notwithstanding that for more than two thousand years the annals of different nations had recorded falls of meteoric stones, many of which had been attested beyond all doubt by the evidence of irreproachable eye-witnesses -- notwithstanding the important part enacted by the B�¾tylia in the meteor-worship of the ancients -- notwithstanding the fact of the companions of Cortez having see an a��rolite at Cholula which had fallen on the neighboring pyramid -- notwithstanding that califs and Mongolian chiefs had caused swords to be forged from recently-fallen meteoric stones -- nay, notwithstanding that several persons had been struck dead by stones falling from heaven, as for instance, a monk at Crema on the 4th of September, 1511, another monk at Milan in 1650, and two Swedish sailors on board ship in 1674, yet this great cosmical phenomenon remained almost wholly unheeded, and its intimate connection drawn to the subject by Chladni, who had already gained immortal renown by his discovery of the sound-figures. He who is penetrated with a sense of this mysterious connection, and whose mind is open to deep impressions of nature, will feel himself moved by the deepest and most solemn emotion at the sight of every star that shoots across the vault of heaven, no less than at the glorious spectacle of meteoric swarms in the November phenomenon or on St. Lawrence's day. Here motion is suddenly revealed in the midst of nocturnal rest. The still radiance of the vault of heaven is for a moment animated with life and movement. In the mild radiance left on the track of the shooting star, imagination pictures the lengthened path of the meteor through the vault of heaven, p 136 while, every where around, the luminous asteroids proclaim the existence of one common material universe. If we compare the volume of the innermost of Saturn's satellites, or that of Ceres, with the immense volume of the Sun, all relations of magnitude vanish from our minds. The extinction of suddenly resplendent stars in Cassiopeia, Cygnus, and Serpentarius have already led to the assumption of other and non-luminous cosmical bodies. We now know that the meteoric asteroids, spherically agglomerated into small masses, revolve round the Sun, intersect, like comets, the orbits of the luminous larger planets, and become ignited either in the vicinity of our atmosphere or in its upper strata. The only media by which we are brought in connection with other planetary bodies, and with all portions of the universe beyond our atmosphere, are light and heat (the latter of which can scarcely be separated from the former),* and those mysterious powers of attraction exercised by remote masses, according to the quantity of their constituents, upon our globe, the ocean, and the strata of our atmosphere. [footnote' *The following remarkable passage on the radiation of heat from the fixed stars, and on their low combustion and vitality -- one of Kepler's many aspirations -- occurs in the 'Paralipom. in Vitell. Astron. parsOpticqa', 1604, Propos. xxxii., p. 25: "Luciis proprium est calor, sydera omnia calefaciunt. De syderum luce claritatis ratio testatur, calorem universorum in minori esse proportione ad calorem unius solis, quam ut ab homine, cujus est certa caloris mensura, utrque simul percipi et judicari possit. De cincindularum lucula tenuissima negare non potes, quin cum calore sit. Vivunt enim et moventur, hoc auten non sine calefactione perficitur. Sic neque putrescentium lignorum lux sui calore destituitur; nam ipsa puetredo quidam lentus ignis est. Inest et stirpibus suus calor." (Compare Kepler, 'Epit. Astron. Copernican�¾', 1618, t. i., lib. i., p. 35.) Another and different kind of cosmical, or, rather, material mode of contact is, however, opened to us, if we admit falling stars and meteoric stones to be planetary asteroids. They not only act upon us merely from a distance by the excitement of luminous or calorific vibrations, or in obedience to the laws of mutual attraction, but they acquire an actual material existence for us, reaching our atmosphere from the remoter regions of universal space, and remaining on the earth itself. Meteoric stones are the only means by which we can be brought in possible contact with that which is foreign to our own planet. Accustomed to gain our knowledge of what is not telluric solely through measurement, calculations, and the deductions of reason, we experience a sentiment of astonishment at finding that we may examine, weigh, and analyze bodies that appertain p 137 to the outer world. This awakens, by the power of the imagination, a meditative, spiritual train of thought, where the untutored mind perceives only scintillations of light in the firmament, and sees in the blackened stone that falls from the exploded cloud nothing beyond the rough product of a powerful natural force. Although the asteroid-swarms, on which we have been led, from special predilection, to dwell somewhat at length, approximate to a certain degree, in their inconsiderable mass and the diversity of their orbits, to comets, they present this essential difference from the latter bodies, that our knowledge of their existence is almost entirely limited to the moment of their destruction, that is, to the period when, drawn within the sphere of the Earth's attraction they become luminous and ignite. In order to complete our view of all that we have learned to consider as appertaining to our solar system, which now, since the discovery of the small planets, of the interior comets of short revolutions, and of the meteoric asteroids, is so rich and complicated in its form, it remains for us to speak of the ring of Zodiacal light, to which we have already alluded. Those who have lived for many years in the zone of palms must retain a pleasing impression of the mild radiance with which the zodiacal light, shooting pyramidally upward, illumines a part of the uniform length of tropical nights. I have seen it shine with an intensity of light equal to the milky way in Sagittarius, and that not only in the rare and dry atmosphere of the summits of the Andes, at an elevation of from thirteen to fifteen thousand feet, but even on the boundless grassy plains, the Illanos of Venezuela, and on the sea-shore, beneath the ever-clear sky of Cumana. This phenomenon was often rendered especially beautiful by the passage of light, fleecy clouds, which stood out in picturesque and bold relief from the luminous back-ground. A notice of this a��rial spectacle is contained in a passage in my journal, while I was on the voyage from Lima to the western coasts of Mexico: "For three or four nights (between 10�¼degrees and 14�¼degrees north latitude) the zodiacal light has appeared in greater splendor than I have ever observed it. The transparency of the atmosphere must be remarkably great in this part of the Southern Ocean, to judge by the radiance of the stars and nebulous spots. From the 14th to the 19th of March a regular interval of three quarters of an hour occurred between the disappearance of the sun's disk in the ocean and the first manifestation of the zodiacal p 138 light, although the night was already perfectly dark. an hour after sunset it was seen in great briliancy between Aldebaran and the Pleiades; and on the 18th of March it attained an altitude of 39�¼degrees5'minutes. Narrow elongated clouds are scattered over the beautiful deep azure of the distant horizon, flitting past the zodiacal light as before a golden curtain. Above these, other clouds are from time to time reflecting the most brightly variegated colors. It seems a second sunset. On this side of the vault of heaven the lightness of the night appears to increase almost as much as at the first quarter of the moon. Toward 10 o'clock the zodiacal light generally becomes very faint in this part of the Southern Ocean, and at midnight I have scarcely been able to trace a vestige of it. On the 16th of March, when most strongly luminous a faint reflection was visible in the east." In our gloomy so-called "temperate" northern zone, the zodiacal light is only distinctly visible in the beginning of Spring, after the evening twilight, in the western part of the sky, and at the close of Autumn, before the dawn of day, above the eastern horizon. It is difficult to understand how so striking a natural phenomenon should have failed to attract the attention of physicists and astronomers until the middle of the seventeenth century, or how it could have escaped the observation of the Atabian natural philosophers in ancient Bactria, on the euphrates, and in the south of Spain. Almost equal surprise is excited by the tardiness of observation of the nebulous spots in Andromeda and Orion, first described by Simon Marius and Huygens. The earliest explicit descriptions of the zodiacal light occurs in Childrey's 'Britannia Baconica',* in the year 1661. p 139 [footnote] *"There is another thing which I recommend to the observation of mathematical men, which is that in February, and for a little before and a little after that month (as I have observed several years together), about six in the evening, when the twilight hath almost deserted the horizon, you shall see a plainly discernible way of the twilight striking up toward the Pleiades, and seeming almost to touch them. It is so observed any clear night, but it is best illac nocte. There is no such way to be observed at any other time of the year (that I can perceive), nor any other way at that time to be perceived darting up elsewhere; and I believe it hath been, and will be constantly visible at that time of the year; but what the cause of it in nature should be, I can not yet imagine, but leave it to future inquiry." (Childrey, 'Britannia Baconica', 1661, p. 183.) This is the first view and a simple description of the phenomenon. (Cassini, 'D��couverte de la Lumi dfd ��leste qui paro��t dans le Zodiaque', in the 'M��m. de l'Acad.', t. viii., 1730, p 276. Mairan, 'Trait��Phys de l'Aurore Bor��ale', 1754, 0. 16.) In this remarkable work by Childrey there are to be found (p. 91) very clear accounts of the epochs of maxima and minima diurnal and annual temperatures, and of the retardation of the extremes of the effects in meteorological processes. It is, however, to be regretted that our Baconian-philosophy-loving author, who was Lord Henry Somerset's chaplain, fell into the same error as Bernardin de St. Pierre, and regarded the Earth as elongated at the poles (see p. 148). At the first he believes that the Earth was spherical, but supposes that the uninterrupted and increasing addition of layers of ice at both poles has changed its figure; and that as the ice is formed from water, the quantity of that liquid is every where diminishing. The first observation of the phenomenon may have been made two or three years prior to this period; but, notwithstanding, the merit of having (in the spring of 1683) been the first to investigate the phenomenon in all its relations in space is incontestably due to Dominicus Cassini. The light which he saw at Bologna in 1668, and which was observed at the same time in Persia by the celebrated traveler Chardin (the court astrologers of Ispahan called this light, which had never before been observed, 'nyzek', a small lance), was not the zodiacal light, as has often been asserted,* but the p 140 enormous tail of a comet, whose head was concealed in the vapory mist of the horizon, and which, from its length and appearance, presented much similarity to the great comet of 1843. [footnote] *Dominicus Cassini ('M��m. de l'Acad.', t. viii., 1730, p. 188), and Mairan ('Aurore Bor.', p. 16), have even maintained that the phenomenon observed in Persia in 1668 was the zodiacal light. Delambre ('Hist. de l'Astron. Moderne', t. ii., p. 742), in very decided trms ascribes the discovery of this light to the celebrated traveler Chardin; but in the 'Couronnement de Soliman', and in several passages of the narrative of his travels (��d. de Langl��s. t. iv., p. 326; t. x., p. 97), he only applies the term niazouk (nyzek), or "petite lance," to "the great and famous comet which appeared over nearly the whole world in 1668, and whose head was so hidden in the wewst that it could not be perceived in the horizon of Ispahan" ('Atlas du Voyage de Chardin', Tab. iv.; from the observations at Schiraz). The head or nucleus of the comet was, however, visible in the Brazils and in India (Pingr��, 'Com��togr.', t. ii., p. 22). Regarding the conjectured identity of the last great comet of March, 1843, with this, which Cassini mistook for the zodiacal light, see Schum., 'Astr. Nachr.', 1843, No. 476 and 480. In Persian, the term "nizehi ��tesch��n"(fiery spears or lances) is also applied to the rays of the rising or setting sun, in the same way as "nay��zik," according to Freytag's Arabic Lexicon, signifies "stell�¾ cadentes." The comparison of comets to lances and swords was, however, in the Middle Ages, very common in all languages. The great comet of 1500, which was visible from April to June, was always termed by the Italian writers of that time 'il Signor Astone' (see my 'Examen Critique de l'Hist. de la G��ographie', t. v., p. 80). All the hypotheses that have been advanced to show that Descartes (Cassini, p. 230; Mairan, p. 16), and even Kepler (Delambre, t. i., p. 601), were acquainted with the zodiacal light, appear to me altogether untenable. Descartes ('Principes', iii., art. 136, 137) is very obscure in his remarks on comets, observing that their tails are formed "by oblique rays, which, falling on different parts of the planetary orbs, strike the eye laterally by extraordinary refraction," and that they might be seen morning and evening, "like a long beam," when the Sun is between the comet and the Earth. This passage no more refers to the zodiacal light than those in which Kepler ('Epit. Astron. Copernican�¾', t. i., p. 57, and t. ii., p. 893) speaks of the existence of a solar atmosphere (limbus circa solem, coma lucida), which, in eclipses of the Sun, prevents it "from being quite night:" and even more uncertain, or indeed erroneous, is the assumption that the "trabes quas [Greek word] vocant" (Plin., ii., 26 and 27) had reference to the tongue-shaped rising zodiacal light, as Cassini (p. 231, art. xxxi.) and Mairan (p. 15) have maintained. Every where among the ancients the trabes are associated with the bolides (ardores et faces) and other fiery meteors, and even with long-barbed comets. (Regarding [Greek words] . see Sch��fer, 'Schol. Par. ad Apoll. Rhod.', 1813, t. ii., p. 206; Pseudo-Aristot., 'de Mundo, 2, 9; 'Comment. Alex. Joh. Philop. et Olymp. in Aristot. Meteor.', lib. i., cap. vii., 3, p. 195, Ideler; Seneca, 'Nat. Qu�¾st.', i., 1.) We may conjecture, with much probability, that the remarkable light on the elevated plains of Mexico, seen for forty nights consecutively i8n 1509, and observed in the eastern horizon rising pyramidally from the earth, was the zodiacal light. I found a notice of this phenomenon in an ancient Aztec MS., the 'CodexTelleriano-Remensis',* preserved in the Royal Library at Paris. [footnote] *Humboldt, 'Monumens des Peuples Indig��nes de l'Am��rique', t. ii., p. 301. The rare manuscript which belonged to the Archbishop of Rheims, Le Tellier, contains various kinds of extracts from an Aztec ritual, an astrological calendar, and historical annals, extending from 1197 to 1549, and embracing a notice of different natural phenomena, epochs of earthquakes and comets (as, for instance, those of 1490 and 1529), and of (which are important in relation to Mexican chronology) solar eclipses. In Camargo's manuscript 'Historia de Tlascala', the light rising in the east almost to the zenith is, singularly enough, described as "sparkling, and as if sown with stars." The description of this phenomenon, which lasted forty days, can not in any way apply to volcanic eruptions of Popcatepetl, which lies very near, in the southeastery direction. (Prescott, 'History of the Conquest of Mesico', vol. i., p. 284.) Later commentators have confounded this phenomenon, which Montezuma regarded as a warning of his misfortunes, with the "estrella que humeava" (literally, 'which spring forth'; Mexican 'choloa, to leap or spring forth'). With respect to the connection of this vapor with the star Citlal Choloha (Venus) and with "the mountain of the star" (Citialtepetl, the volcano of Orizaba), see my 'Monumens', t. ii., p. 303. This phenomenon, whose primordial antiquity can scarcely be doubted, and which was first noticed in Europe by Childrey and Dominicus Cassini, is not the luminous solar atmosphere itself, since this can not, in accordance with mechanical laws, be more compressed than in the relation of 2 to 3, and consequently can not be diffused beyond 9/20ths of Mercury's heliocentric distance. These same laws teach us that the altitude of the extreme boundaries of the atmosphere of a cosmical p 141 body above its equator, that is to say, the point at which gravity and centrifugal force are in equilibrium, must be the same as the altitude at which a satellite would rotate round the central body simultaneously with the diurnal revolution of the latter.* [footnote] *Laplace, 'Expos. du Syst. du Monde', p. 270; 'M��canique C��leste', t. ii., p. 169 and 171; Schubert, 'Astr.', bd. iii., �¤ 206. This limitation of the solar atmosphere in its present concentrated condition is especially remarkable when we compare the central body of our system with the nucleus of other nebulous stars. Herschel has discovered several, in which the radius of the nebulous matter surrounding the star appeared at an angle of 150". On the assumption that the parallax is not fully equal to 1", we find that the outermost nebulous layer of such a star must be 150 times further from the central body than our Earth is from the Sun. If, therefore, the nebulous star were to occupy the place of our Sun, its atmosphere would not only include the orbit of Uranus, but even extend eight times beyond it.�¥ [footnote] *Arago, in the 'Annuaire', 1842, p. 408. Compare Sir John Herschel's considerations on the volume and faintness of light of planetary nebul�¾, in Mary Somerville's 'Connection of the Physical Sciences', 1835, p. 108. The opinion that the Sun is a nebulous star, whose atmosphere presents the phenomenon of zodiacal light, did not originate with Dominicus Cassini, but was first promulgated by Mairan in 1730 ('Trait�� de l'Aurore Bor.', p. 47 and 263; Arago, in the 'Annuaire', 1842, p. 412). It is a renewal of Kepler's views. Considering the narrow limitation of the Sun's atmosphere, which we have just described, we may with much probability regard the existence of a very compressed annulus of nebulous matter,* revolving freely in space between the orbits of Venus and Mars, as the material cause of the zodiacal light. [footnote] *Cominicus Cassini was the first to assume, as did subsequently Laplace, Schubert, and Poisson, the hypothesis of a separate ring to explain the form of the zodiacal light. He says distinctly, "If the orbits of Mercury and Venus were visible (throughout their whole extent), we should invariably observe them with the same figure and in the same position with regard to the Sun, and at the same time of the year with the zodiacal light." ('M��m. de l'Acad.', t. viii., 1730, p. 218, and Biot, in the 'Comptes Rendus', 1836, t. iii., p. 666.) Cassini believed that the nebulous ring of zodiacal light consisted of innumerable small planetary bodies revolving round the Sun. He even went so far as to believe that the fall of fire-balls might be connected with the passage of the Earth through the zodiacal nebulous ring. Olmsted, and especially Biot (op. cit., p. 673), have attempted to establish its connection with the November phenomenon -- a connection which Olbers doubts. (Schum., 'Jahrb.', 1837, s. 281.) Regarding the question whether the place of the zodiacal light perfectly coincides with that of the Sun's equator, see Houzeau, in Schum., 'Astr. Nachr.', 1843, No. 492, s. 190. As p 142 yet we certainly know nothing definite regarding its actual material dimensions; its augmentation* by emanations from the tails of myriads of comets that come within the Sun's vicinity; the singular changes affecting its expansion, since it sometimes does not apper to extend beyond our Earth's orbit; or, lastly, regarding its conjectural intimate connection with the more condensed cosmical vapor in the vicinity of the Sun. [footnote] *Sir John Herschel, 'Astron.', �¤ 487. The nebulous particles composing this ring, and revolving round the sun in accordance with planetary laws, may either be self-luminous or receive light from that luminary. Even in the case of a terrestrial mist (and this fact is very remarkable), which occurred at the time of the new moon at midnight in 1743, the phosphorescence was so intense that objects could be distinctly recognized at a distance of more than 600 feet. I have occasionally been astonished in the tropical climates of south america, to observe the variable intensity of the zodiacal light. As i passed the nights, during many months, in the open air, on the shores of rivers and on ilanos, i enjoyed ample opportunities of carefully examining this phenomenon. When the zodiacal light had been most intense, i have observed that it would be perceptibly weakened for a few minutes, until it again suddenly shone forth in full brilliancy. In some few instances i have thought that i could perceive -- not exactly a reddish coloration, nor the lower portion darkened in an arc-like form, nor even a scintillation, as mairan affirms he has observed -- but a kind of flickering and wavering of the light.* [footnote] *Arago, in the 'Annuaire', 1832, p. 246. Several physical facts appear to indicate that, in a mechanical separation of matter into its smallest particles, if the mass be very small in relation to the surface, the electrical tension may increase sufficiently for the production of light and heat. Experiments with a large concave mirror have not hitherto given any positive evidence of the presence of radiant heat in the zodiacal light. (Lettre de M. Matthiessen �� M. Arago, in the 'Comptes Rendus', t. xvi., 1843, Avril, p. 687.) Must we suppose that changes are actually in progress in the nebulous ring? or is it not more probable that, although I could not, by my meteorological instruments, detect any change of heat or moisture near the ground, and small stars of the fifth and sixth magnitudes appeared to shine with equally undiminished intensity of light, processes of condensation may be going on in the uppermost strata of the air, by means of which the transparency, or rather, the reflection of light, may be modified in some peculiar and unknown manner? p 143 An assumption of the existence of such meteorological causes on the confines of our atmosphere is strengthened by the "sudden flash and pulsation of light," which, according to the acute observations of Olbers, vibrated for several seconds through the tail of a comet, which appeared during the continuance of the pulsations of light to be lengthened by several degrees, and then again contracted.* [footnote] *"What you tell me of the changes of light in the zodiacal light, and of the causes to which you ascribe such changes within the tropics, is of the greatr interest to me, since I have been for a long time past particularly attentive, every spring, to this phenomenon in our northern latitudes. I, too, have always believed that the zodiacal light rotated; but I assumed (contrary to Poisson's opinion, which you have communicated to me) that it completely extended to the Sun, with considerably augmenting brightness. The light circle which, in total solar eclipses, is seen surrounding the darkened Sun, I have regarded as the brightest portion of the zodiacal light. I have convinced my self that this light is very different in different years, often for several successive years being very bright and diffused, while in othr years it is scarcely perceptible. I tyhink that I find the first trace of an allusion to the zodiacal light in a letter from Rothmann to Tycho, in which he mentions that in the spring he has observed the twilight did not close until the sun was 24�¼degrees below the horizon. Rothmann must certainly have confounded the disappearance of the setting zodiacal light in the vapors of the western horizon with the actual cessation of twilight. I have failed to observe the pulsations of the light, probably on account of the faintness with which it appears in these countries. You are, however, certainly right in ascribing those rapid variations in the light of the heavenly bodies, which you have perceived in tropical climates, to our own atmosphere, and especially to its higher regions. This is especially in the clearest weather, that these tails exhibit pulsations, commencing from the head, as being the lowest part, and vibrating in one or two seconds through the entire tail, which thus appears rapidly to become some degrees longer, but again as rapidly contracts. That these undulations, which were formerly noticed with attention by Robert Hooke, and in more recent times by Schr��ter and Chladni, 'do not actually occur in the tails of the comets', but are produced by our atmosphere, is obvious when we recollect that the individual parts of those tails (which are many millions of miles in length) lie 'at very different distances' from us, and that the light from their extreme points can only reach us at intervals of time which differ several minutes from one another. Whether what you saw on the Orinoco, not at intervals of seconds, but of minutes, were actual coruscations of the zodiacal light, or whether they belonged exclusively to the upper strata of our atmosphere, I will not attempt to decide; neither can I explain the remarkable 'lightness of whole nights', nor the anomalous augmentation and prolongation of the twilight in the year 1831, particularly if, as has been remarked, the lightest part of these singular twilights did not coincide with the Sun's place below the horizon." (From a lettr written by Dr. Olbers to myself, and dated Bremen, Marth 26th, 1833.) As, however, the separate particles of a comet's tail, measuring millions of miles, p 144 are very unequally distant from earth, it is not possible, according to the laws of the velocity and transmission of light, that we should be able, in so short a period of time, to perceive any actual changes in a cosmical body of such vast extent. There considerations in no way exclude the realith of the changes that have been observed in the emanations from the more condensed envelopes around the nucleus of a comet, nor that of the sudden irradiation of the zodiacal light, from internal molecular motion, nor of the increased or diminished reflection of light in the cosmical vapor of the luminous ring, but should simply be the means of drawing our attention to the differences existing between that which appertains to the air of heaven (the realms of universal space) and that which belongs to the strata of our terrestrial atmosphere. It is not possible, as well-attested facts prove, perfectly to explain the operations at work in the much-contested upper boundaries of our atmosphere. The extraordinary lightness of whole nights in the year 1831, during which small print might be read at midnight in the latitudes of Italy and the north of Germany is a fact directly at variance with all that we know, according to the most recent and acute researches on the crepuscular theory, and of the height of the atmosphere.* [footnote] *Biot, 'Trait�� d'Astron. Physique', 3��me ��d., 1841, t. i., p. 171, 238 and 312. The phenomena of light depend upon conditions still less understood, and their variability at twilight, as well as in the zodiacal light, excite our astonishment. We have hitherto considered that which belongs to our solare system -- that world of material forms governed by the Sun -- which includes the primary and secondary planets, comets of short and long periods of revolution, meteoric asteroids, which move thronged together in streams, either sporadically or in closed rings, and finally a luminous nebulous ring, that revolves round the Sun in the vicinity of the Earth, and for which, owing to its position, we may retain the name of zodiacal light. Every where the law of periodicity governs the motions of these bodies, however different may be the amount of tangential velocity, or the quantity of their agglomerated material parts; the meteoric asteroids which enter our atmosphere from the external regions of universal space are alone arrested in the course of their planetary revolution, and retained within the sphere of a larger planet. In the solar system, whose boundaries determine the attractive force of the central body, comets are made to revolve in their elliptical p 145 orbits at a distance 44 times greater than that of Uranus; may, in those comets whose nucleus appears to us, from its inconsiderable mass, like a mere passing cosmical cloud, the Sun exercises its attractive force on the outermost parts of the emanations radiating from the tail over a space of many millions of miles. Central forces, therefore, at once constitute and maintain the system. Our Sun may be considered as at rest when compared to all the large and small, dense and almost vaporous cosmical bodies tht appertain to and revolve around it; but it actually rotates around the common center of gravity of the whole system, which occasionally falls within itself, that is to say, remains within the material circumference of the Sun, whatever changes may be assumed by the position of the planets. A very different phenomenon is that presented by the translatory motion of the Sun, that is, the progressive motion of the center of gravity of the whole solar system in universal space. Its velocity is such* that, according to Bessel, the relative motion of the Sun, and that of 61 Cygni, is not less in one day than 3,336,000 geographical miles. [footnote] *Bessel, in Schum., 'Jahrb. f��r' 1839, s. 51; probably four millions of miles daily, in a relative velocity of at the least 3,336,000 miles, or more than couble the velocity of revolution of the Earth in her orbit round the Sun. This change of the entire solar system would remain unknown to us, if the admirable exactness of our astronomical instruments of measurement, and the advancement recently made in the art of observing, did not cause our advance toward remote stars to be perceptible, like an approximation to the objects of a distant shore in apparent motion. The proper motion of the star 61 Cygni, for instance, is so considerable, that it has amounted to a whole degree in the course of 700 years. The amount or quantity of these alterations in the fixed stars (that is to say, the changes in the relative position of self-luminous stars toward each other), can be determined with a greater degree of certainty than we are able to attach to the genetic explanation of the phenomenon. After taking into consideration what is due to the precession of the equinoxes, and the nutation of the earth's axis produced by the action of the Sun and Moon on the spheroidal figure of our globe, and what may be ascribed to the transmission of light, that is to say, to its aberration, and to the parallax formed by the diametrically opposite position of the Earth in its course round the Sun, we still find that there is a residual portion p 146 of the annual motion of the fixed stars due to the translation of the whole solar system in universal space, and to the true proper motion of the stars. The difficult problem of numerically separating these two elements, the true and the apparent motion, has been effected by the careful study of the direction of the motion of certain individual stars, and by the consideration of the fact that, if all the stars were in a state of absolute rest, they would appear perspectively to recede from the point in space toward which the Sun was directing its course. But the ultimate result of this investigation, confirmed by the calculus of probabilities, is, that our solar system and the stars both change their places in space. According to the admirable researches of d'Argelander at Abo, who has extended and more perfectly developed the work begun by William Herschel and Prevost, the Sun moves in the direction of the constellation Hercules, and probably, from the combination of the observations made of 537 stars, toward a point lying (at the equinox of 1792.5) at 257�¼degrees 49.'7 R.A., and 28�¼degrees 49.'7 N.D. It is extremely difficult, in investigations of this nature, to separate the absolute from the relative motion, and to determine what is aloone owing to the solar system.* [footnote] *Regarding the motion of the solar system, according to Bradley, Tobias Mayer, Lambert, Lalande, and William Herschel, see Arago in the 'Annuaire', 1842, p. 388-399' Argelander, in Schum., 'Astron. Nachr ., No. 363, 364, 398, and in the treatise 'Von der eigenen Bewegung des Sonnensystems' (On the proper Motion of the Solar System), 1837, s. 43, respecting Perseus as the central body of the whole stellar stratum, likewise Otho Struve, in the 'Bull. de l'Acad. de St. P��tersb.', 1842, t. x., No. 9, p. 137-139. The last-named astronomer has found, by a mo4re recent combination, 261�¼degrees 23' R.A.+37�¼degrees 36' Decl. for the direction of the Sun's motion; and, taking the mean of his own results with that of Argelander, we have, by a combination of 797 stars, the formula 259�¼degrees 9' R.A.+34�¼degrees 36' Decl. If we consider the proper, and not the perspective motions of the stars, we shall find many that appear to be distributed in groups, having an opposite direction; and facts hitherto observed do not, at any rate, render it a necessary assumption that all parts of our starry stratum, or the whole of the stellar islands filling space, should move round one large unknown luminous or non-luminous central body. The tendency of the human mind to investigate ultimate and highest causes certainly inclines the intellectual activity, no less than the imagination of mankind, to adopt such an hypothesis. Even the Stagirite proclaimed that "every thing which is moved must be referable to a motor, and that there would be no end to p 147 the concatenation of causes if there were not one primordial immovable morot."* [footnote] *Aristot., 'de C�¾lo', iii., 2, p. 301, Bekker: 'Phys.', viii., t, p. 256. This material taken from pages 147-203 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- The manifold translatory changes of the stars, not those produced by the parallaxes at which they are seen from the changing position of the spectator, but the true changes constantly going on in the regions of space, afford us incontrovertible evidence of the 'dominion of the laws of attraction' in the remotest regions of space, beyond the limits of our solar system. The existence of these laws is revealed to us by many phenomena, as, for instance, by the motion of double stars, and by the amount of retarded or accelerated motion in different parts of their elliptic orbits. Human inquiry need no longer pursue this subject in the domain of vague conjecture, or amid the undefined analogies of the ideal world; for even here the progress made in the method of astronomical observations and calculations has enabled astronomy to take up its position on a firm basis. It is not only the discovery of the astounding numbers of double and multiple stars revolving round a center of gravity lying 'without' their system (2800 such systems having been discovered up to 1837), but rather the extension of our knowledge regarding the fundamental forces of the whole material world, and the proofs we have obtained of the universal empire of the laws of attraction, that must be ranked among the most brilliant discoveries of the age. The periods of revolution of colored stars present the greatest differences; thus, in some instances, the period extends to 43 years, as in �¹pi of Corona, and in others to several thousands,, as in 66 of Cetus, 38 of Gemini, and 100 of Pisces. Since Herschel's measurements in 1782, the satellite of the nearest star in the triple system of [Greek letter] of Cancer has completed more than one entire revolution. By a skillful combination of the altered distances and angles of position,* the elements of these orbits may be found, conclusions drawn regarding the absolute distance of the double stars from the Earth, and comparisons made between their mass and that of the Sun. [footnote] *Savary, in the 'Connaissance des Tems', 1830, p. 56 and 163. Encke, 'Berl. Jahrb.', 1832, s. 253, etc. Arago, in the 'Annuaire' 1834, p. 260, 295. John Herschel, in the 'Memoirs of the Astronom. Soc.', vol. v., p. 171. Whether, however, here and in our solar system, quantity of matter is the only standard of the amount of attractive force, or whether 'specific' forces of attraction proportionate to the mass may not at the same time come into operation, as Bessel was the first to conjecture, are questions p 148 whose practical solution must be left to future ages.* [footnote] * Bessel, 'Untersuchung. des Theils der planetarischen Storungen, welche aus der Bewegung der Sonne entstchen' (An Investigation of the portion of the Planetary Disturbances depending on the motion of the Sun) in 'Abh. der Berl. Akad. der Wissensch.', 1824 (Mathem. Classe), s. 2-6. The question has been raised by John Tobias Mayer, in 'Comment. Soc. Reg. Gotting.', 1804-1808, vol. xvi., p. 31-68. When we compare our Sun with the other fixed stars, that is, with other self-luminous Suns in the lenticular starry stratum of which our system forms a part, we find, at least in the case of some, that channels are opened to us, which may lead, at all events, to an 'approximate' and limited knowledge of their relative distances, volumes, and masses, and of the velocities of their translatory motion. If we assume the distance of Uranus from the Sun to be nineteen times that of the Earth, that is to say, nineteen times as great as that of the Sun from the Earth, the central body of our planetary system will be 11,900 times the distance of Uranus from the star 'a' in the constellation Centaur, almost 31,300 from 61 Cygni, and 41,600 from Vega in the constellation Lyra. The comparison of the volume of the Sun with that of the fixed stars of the first magnitude is dependent upon the apparent diameter of the latter bodies -- an extremely undertain optical element. If even we assume, with Herschel, that the apparent diameter of Arcturus is only a tenth part of a second, it still follows that the true diameter of this star is eleven times greater than that of the Sun.* [footnote] *'Philos. Trans.' for 1803, p. 225. Arago, in the 'Annuaire', 1842, p. 375. In order to obtain a clearer idea of the distances ascribed in a rather earlier part of the text to the fixed stars, let us assume that the Earth is a distance of one foot from the Sun; Uranus is then 19 feet, and Vega Lyrae is 158 geographical miles from it. The distance of the star 61 Cygni, made known by Bessel, has led approximately to a knowledge of the quantity of matter contained in this body as a double star. Notwithstanding that, since Bradley's observations, the portion of the apparent orbit traversed by this star is not sufficiently great to admit of our arriving with perfect exactness at the true orbit nd the major axis of this star, it has been conjectured with much probability by the great Konigsberg astronomer,* "that the mass of this double star can not be very considerably larger or smaller than half of the mass of the Sun." [footnote] *Bessel, in Schum., 'Jahrb.', 1839, s. 53. This result is from actual measurement. The analogies deduced from the relatively larger mass of those planets in our solar system that are attended by satellites, and from the fact that Struve has discovered six times more double stars among p 194 the brighter than among the telescopic fixed stars, have led other astronomers to conjecture that the average mass of the larger number of the binary stars exceeds the mass of the Sun.* [footnote] *M��dler, 'Astron.', s. 476; also in Schum, 'Jahrb.', 1839, s. 95. We are, however, far from having arrived at general results regarding this subject. Our Sun, according to Argenlander, belongs, with reference to proper motion in space, to the class of rapidly-moving fixed stars. The aspect of the starry heavens, the relative position of stars and nebullae, the distribution of their luminous masses, the picturesque beauty, if I may so express myself, of the whole firmament, depend in the course of ages conjointly upon the proper motion of the stars and nebulae, the translation of our solar system in space, the appearance of new stars, and the disappearance or sudden diminution in the intensity of the light of others, and lastly and specially, on the changes which the Earth's axis experiences from the attraction of the Sun and Moon. The beautiful stars in the constellation of the Centaur and the Southern Cross will at some future time be visible in our northern latitudes, while other stars, as Sirius and the stars in the Belt of Orion, will in their turn disappear below the horizon. The places of the North Pole will successively be indicated by the stars �§ beta and a alpha Cephei, and �¶ delta Cygni, until after a period of 12,000 years, Vega in Lyra will shine forth as the brightest of all possible pole stars. These data give us some idea of the extent of the motions which, divided into infinitely small portions of time, proceed without intermission in the great chronometer of the universe. If for a moment we could yield to the power of fancy, and imagine the acuteness of our visual organs to be made equal with the extremest bounds of telescopic vision, and bring together that which is now divided by long periods of time, the apparent rest that reigns in space would suddenly disappear. We should see the countless host of fixed stars moving in thronged groups in different directions; nebulae wandering through space, and becoming condensed and dissolved like cosmical clouds; the vail of the Milky Way separated and broken up in many parts, and 'motion' ruling supreme in every portion of the vault of heave, even as on the Earth's surface, where we see it unfolded in the germ, the leaf, and the blossom, the organisms of the vegetable world. The celebrated Spanish botanist Cavanilles was the first who entertained the idea of "seeing grass grow," and he directed the horizontal micrometer threads of a powerfully magnifying glass at one time to p 150 the apex of the shoot of a bambusa, and at another on the rapidly-growing stem of an American aloe ('Agave Americana', precisely as the astronomer places his cross of net-work against a culminating star. In the collective life of physical nature, in the organic as in the sidereal world, all things that have been, that are, and will be, are alike dependent on motion. The breaking up of the Milky Way, of which I have just spoken, requires special notice. William Herschel, our safe and admirable guide to this portion of the regions of space, has discovered by his star-guagings that the telescopic breadth of the Milky Way extends from six to seven degrees beyond what is indicated by our astronomical maps and by the extent of the sidereal radiance visible to the naked eye.* [footnote] *Sir William Herschel, in the 'Philos. Transact.' for 1817, Part ii p. 438. The two brilliant nodes in which the branches of the zone unite, in the region of Cepheus and Cassiopeia, and in the vicinity of Scorpio and Sagittarius, appear to exercise a powerful attraction on the contiguous stars; in the most brilliant part, however between beta and [Greek symbol] Cygni, one half of the 330,000 stars that have been discovered in a breadth of 5 degrees are directed toward one side, and the remainder to the other. It is in this part that Herschel supposes the layer to be broken up.* [footnote] *Arago, in the 'Annuaire', 1842, p. 569 The number of telescopic stars in the Milky Way uninterrupted by any nebulae is estimated at 18 millions. In order, I will not say, to realize the greatness of this number, but, at any rate, to compare it with something analogous, I will call attention to the fact that there are not in the whole heavens more than about 8000 stars between the first and the sixth magnitudes, visible to the naked eye. The barren astonishment excited by numbers and dimensions in space, when not considered with reference to applications engaging the mental and perceptive powers of man, is awakened in both extremes of the universe, in the celestial bodies as in the minutest animalcules.* [footnote] *Sir John Herschel, in a letter from Feldhuysen, dated Jan. 13th, 1836. Nicholl, 'Architecture of the Heavens', 1838, p. 22. (See, also, some separate notices by Sir William Herschel on the starless space which separates us by a great distance from the Milky Way, in the 'Philos. Transact.' for 1817, Part ii., p. 328.) A cubic inch of the polishing slate of Bilin contains, according to Ehrenberg, 40,000 millions of the silicious shells of Galionellae. The stellar Milky Way, in the region of which, according to Argelander's admirable observations, the brightest stars of the firmament appear to be congregated, is almost at right angles p 151 with another Milky Way, composed of nebulae. The former constitutes, according to Sir John Herschel's views, an annulus, that is to say, an independent zone, somewhat remote from our lenticular-shaped starry stratum, and similar to Saturn's ring. Our planetary system lies in an eccentric direction, nearer to the region of the Cross than to the diametrically opposite point, Cassiopeia.* [footnote] *Sir John Herschel, 'Astronom.', 624; likewise in his 'Observations on Nebulae and Clusters of Stars' ('Phil. Transact.', 1833, Part ii., p. 479, fig. 25): "We have here a brother system, bearing a real physical resemblance and strong analogy of structure to our own." An imperfectly seen nebulous spot, discovered by Messier in 1774, appeared to present a remarkable similarity to the form of our starry stratum and the divided ring of our Milky Way.* [footnote] *Sir William Herschel, in the 'Phil. Trans.' for 1785, Part i., p. 257. Sir John Herschel, 'Astron.', 616. ("The 'nebulous' region of the heavens forms 'a nebulous Milky Way', composed of distinct nebulae, as the other of stars." The same observation was made in a letter he addressed to me in March, 1829.) The Milky Way composed of nebulae does not belong to our starry stratum, but surrounds it at a great distance without being physically connected with it, passing almost in the form of a large cross through the dense nebulae of Virgo, especially in the northern wing, through Comae Berenicis, Ursa Major, Andromeda's girdle, and Pisces Boreales. It probably intersects the stellar Milky Way in Cassiopeia, and connects its dreary poles (rendered starless from the attractive forces by which stellar bodies are made to agglomerate into groups) in the least dense portion of the starry stratum. We see from these considerations that our starry cluster, which bears traces in its projecting branches of having been subject in the course of time to various metamorphoses, and evinces a tendency to dissolve and separate, owing to secondary centers of attraction -- is surrounded by two rings, one of which, the nebulous zone, is very remote, while the other is nearer, and composed of stars alone. The latter, which we generally term the Milky Way, is composed of nebulous stars, averaging from the tenth to the eleventh degree of magnitude,* but appearing, when considered individually, of very different magnitudes, while isolated starry clusters (starry swarms) almost always exhibit throughout a character of great uniformity in magnitude and brilliancy. [footnote] *Sir John Herschel, 'Astron.', 585. In whatever part the vault of heaven has been pierced by powerful and far-penetrating telescopic instruments, stars or luminous nebulae are every where discoverable, the former, in p 152 some cases, not exceeding the twentieth or twenty-fourth degree of telescopic magnitude. A portion of the nebulous vapor would probably be found resolvable into stars by more powerful optical instruments. As the retina retains a less vivid impression of separate than of infinitely near luminous points, less strongly marked photometric relations are excited in the latter case, as Arago has recently shown.* [footnote] *Arago, in the 'Annuaire', 1842, p. 282-285, 409-411, and 439-442. The definite or amorphous cosmical vapor so universally diffused, and which generates heat through condensation, probably modifies the transparency of the universal atmosphere, and diminishes that uniform intensity of light which, according to Halley and Olbers, should arise, if every point throughout the depths of space were filled by an infinite series of stars.* [footnote] *Olbers, on the transparency of celestial space, in Bode's 'Jahrb.', 1826, s. 110-121. The assumption of such a distribution in space is, however, at variance with observation, which shows us large starless regions of space, 'openings' in the heavens, as William Herschel terms them -- one, four degrees in width, in Scorpio, and another in Serpentarius. In the vicinity of both, near their margin, we find unresolvable nebulae, of which that on the western edge of the opening Scorpio is one of the most richly thronged of the clusters of small stars by which the firmament is adorned. Herschel ascribes these openings or starless regions to the attractive and agglomerative forcesof the marginal groups.* [footnote] *"An opening in the heavens," William Herschel, in the 'Phil. Trans.' for 1785, vol. lxxv., Part i., p. 256. Le Francais Lalande, in the 'Connaiss. des Tems pour l'An.' VIII., p. 383. Arago, in the 'Annuaire', 1842, p. 425. "They are parts of our starry stratum," says he, with his usual graceful animation of style, "that have experienced great devastation from time." If we picture to ourselves the telescopic stars lying behind one another as a starry canopy spread over the vault of heaven, these starless regions in Scorpio and Serpentarius may, I think, be regarded as tubes through which we may look into the remotest depths of space. Other stars may certainly lie in those parts where the strata forming the canopy are interrupted, but these are unattainable by our instruments. The aspect of fiery meteors had led the ancients likewise to the idea of clefts or openings ('chasmata') in the vault of heaven. These openings were, however, only regarded as transient, while the reason of their being luminous and fiery, instead of obscure, was supposed to be owing to the p 153 translucent illuminated ether which lay beyond them.* [footnote] *Aristot., 'Meteor.', ii.,, 5, 1. Seneca, 'Natur. Quaest.', i., 14, 2. "Coelum discessisse," in Cic., 'de Divin.', i., 43. Derham, and even Huygens, did not appear disinclined to explain in a similar manner the mild radiance of the nebulae.* [footnote] *Arago, in the 'Annuaire', 1842, p. 429. When we compare the stars of the first magnitude, which, on an average, are certainly the nearest to us, with the non-nebulous telescopic stars, and further, when we compare the nebulous stars with unresolvable nebulae, for instance, with the nebula in Andromeda, or even with the so-called planetary nebulous vapor, a fact is made manifest to us by the consideration of the varying distances and the boundlessness of space, which shows the world of phenomena, and that which constitutes its causal reality, to be dependent upon the 'propagation of light'. The velocity of this propagation is according to Struve's most recent investigations, 166,072 geographical miles in a second, consequently almost a million of times greater than the velocity of sound. According to the measurements of Maclear, Bessel, and Struve, of the parallaxes and distances of three fixed stars of very unequal magnitudes ('a' Centauri, 16 Cygni, and 'a' Lyrae), a ray of light requires respectively 3, 9 1/4, and 12 years to reach us from these three bodies. In the short but memorable period between 1572 and 1604, from the time of Cornelius Gemma and Tycho Brahe to that of Kepler, three new stars suddenly appeared in Cassiopeia and Cygnus, and in the foot of Serpentarius. A similar phenomenon exhibited itself at intervals in 1670, in the constellation Vulpis. In recent times, even since 1837, Sir John Herschel has observed, at the Cape of Good Hope, the brilliant star [Greek symbol] in Argo increase in splendor from the second to the first magnitude.* [footnote] *In December, 1837, Sir John Herschel saw the star [Greek symbol] Argo, which till that time appeared as of the second magnitude, and liable to no change, rapidly increase till it became of the first magnitude. In January, 1838, the intensity of its light was equal to that of 'a' Centauri. According to our latest information, Maclear in March, 1843, found it as bright as Canopus; and even 'a' Crucis looked faint by [Greek symbol] Argo. These events in the universe belong, however, with reference to their historical reality, to other periods of time than those in which the phenomena of light are first revealed to the inhabitants of the Earth: they reach us like the voices of the past. It has been truly said, that with our large and powerful telescopic instruments we penetrate alike through the boundaries of time and space: we measure the former through the latter, for in the course of an p 154 hour a ray of light traverses over a space of 592 millions of miles. While according to the theogony of Hesiod, the dimensions of the universe were supposed to be expressed by the time occupied by bodies in falling to the ground ("the brazen anvil was not more than nine days and nine nights in falling from heaven to earth"), the elder Herschel was of opinion* that light required almost two millions of years to pass to the Earth from the remotest luminous vapor reached by his forty-foot reflector. [footnote] *"Hence it follows that the rays of light of the remotest nebulae must have been almost two millions of years on their way, and that consequently, so many years ago, this object must already have had an existence in the sidereal heaven, in order to send out those rays by which we now perceive it." William Herschel, in the 'Phil. Trans.' for 1802, p. 498. John Herschel, 'Astron.', 590. Arago, in the 'Annuaire', 1842, p. 334, 359, and 382-385. Much, therefore, has vanished long before it is rendered visible to us -- much that we see was once differently arranged from what it now appears. The aspect of the starry heavens presents us with the spectacle of that which is only apparently simultaneous, and however much we may endeavor, by the aid of optical instruments, to bring the mildly-radiant vapor of nebulous masses or the faintly-glimmering starry clusters nearer, and diminish the thousands of years interposed between us and them, that serve as a criterion of their distance, it still remains more than probable, from the knowledge we possess of the velocity of the transmission of luminous rays, that the light of remote heavenly bodies presents us with the most ancient perceptible evidence of the existence of matter. It is thus that the reflective mind of man is led from simple premises to rise to those exalted heights of nature, where in the light-illumined realms of space, "myriads of worlds are bursting into life like the grass of the night."* [fotnote] *From my brother's beautiful sonnet "Freiheit und Gesetz." (Wilhelm von Humboldt, 'Gesammelte Werke', bd. iv., s. 358, No. 25.) From the regions of celestial forms, the domain of Uranus, we will now descend to the more contracted sphere of terrestrial forces -- to the interior of the Earth itself. A mysterious chain links together both classes of phenomena. According to the ancient signification of the Titanic myth,* the powers of organic life, that is to say, the great order of nature, depend upon the combined action of heaven and earth. [footnote] *Otfried Muller, 'Prolegomena', s. 373. If we suppose that the Earth, like all the other planets, primordially belonged, according to its origin, to the central body, the Sun, and to the solar atmosphere that has been separated into nebulous p 155 rings, the same connection with this continguous Sun, as well as with all the remote suns that shine in the firmament, is still revealed through the phenomena of light and radiating heat. The difference in the degree of these actions must not lead the physicist, in his delineation of nature, to forget the connection and the common empire of similar forces in the universe. A small fraction of telluric heat is derived from the regions of universal space in which our planetary system is moving, whose temperature (which according to Fourier, is almost equal to our mean icy polar heat) is the result of the combined radiation of all the stars. The causes that more powerfully excite the light of the Sun in the atmosphere and in the upper strata of our air, that give rise to heat-engendering electric and magnetic currents, and awaken and genially vivify the vital spark in organic structures on the earth's surface, must be reserved for the subject of our future consideration. As we purpose for the present to confine ourselves exclusively within the telluric sphere of nature, it will be expedient to cast a preliminary glance over the relations in space of solids and fluids, the form of the Earth, its mean density, and the partial distribution of this density in the interior of our planet, its temperature and its electro-magnetic tension. From the consideration of these relations in space, and of the forces inherent in matter, we shall pass to the reaction of the interior on the exterior of our globe; and to the special consideration of a universally distributed natural power -- subterranean heat; to the phenomena of earthquakes, exhibited in unequally expanded circles of commotion, which are not referable to the action of dynamic laws alone; to the springing forth of hot wells; and, lastly, to the more powerful actions of volcanic processes. The crust of the Earth, which may scarcely have been perceptibly elevated by the sudden and repeated, or almost uninterrupted shocks by which it has been moved from below, undergoes, nevertheless, great changes in the course of centuries in the relations of the elevation of solid portions, when compared with the surface of the liquid parts, and even in the form of the bottom of the sea. In this manner simultaneous temporary or permanent fissures are opened, by which the interior of the Earth is brought in contact with the external atmosphere. Molten masses, rising from an unknown depth, flow in narrow streams along the declivity of mountains, rushing impetuously onward, or moving slowly and gently, until the fiery source is quenched in the midst of exhalations, and the lava becomes incrusted, as it were, by p 156 the solidification of its outer surface. New masses of rocks are thus formed before our eyes, while the older ones are in their turn converted into other forms by the greater or lesser agency of Platonic forces. Even where no disruption takes place the crystalline moleculres are displaced, combining to form bodies of denser texture. The water presents structures of a totally different nature, as, for instance, concretions of animal and vegetable remains, of earthy, calcareous, or aluminous precipitates, agglomerations of finely-pulverized mineral bodies, covered with layers of the silicious shields of infusoria, and with transported soils containing the bones of fossil animal forms of a more ancient world. The study of the strata which are so differently formed and arranged before our eyes, and of all that has been so variously dislocated, conforted, and upheaved, by mutual compression and volcanic force, leads the reflective observer, by simple analogies, to draw a comparison between the present and an age that has long passed. It is by a combination of actual phenomena, by an ideal enlargement of relations in space, and of the amount of active forces, that we are able to advance into the long sought and indefinitely anticipated domain of geognosy, which has only within the last half century been based on the solid foundation of scientific deduction. It has been acutely remarked, "that notwithstanding our continual employment of large telescopes, we are less acquainted with the exterior than with the interior of other planets, excepting, perhaps, our own satellite." They have been weighed, and their volume measured; and their mass and density are becoming known with constantly-increasing exactness; thanks to the progress made in astronomical observation and calculation. Their physical character is, however, hidden in obscurity, for it is only in our own globe that we can be brought in immediate contact with all the elements of organic and inorganic creation. The diversity of the most heterogenous substances, their admixtures and metamorphoses, and the ever-changing play of the forces called into action, afford to the human mind both nourishment and enjoyment, and open an immeasurable field of observation, from which the intellectual activity of man derives a great portion of its grandeur and power. The world of perceptive phenomena is reflected in the depths of the ideal world, and the richness of nature and the mass of all that admits of classification gradually become the objects of inductive reasoning. I would here allude to the advantage, of which I have already p 157 spoken, possessed by that portion of physical science whose origin is familiar to us, and is connected with our earthly existence. The physical description of celestial bodies from the remotely-glimmering nebulae with their suns, to the central body of our own system, is limited, as we have seen, to general conceptions of the volume and quantity of matter. No manifestation of vital activity is there presented to our senses. It is only from analogies, frequently from purely ideal combinations, that we hazard conjectures on the specific elements of matter, or on their various modifications in the different planetary bodies. But the physical knowledge of the heterogeneous nature of matter, its chemical differences, the regular forms in which its molecules combine together, whether in crystals or granules; its relations to the deflected or decomposed waves of light by which it is penetrated; to radiating, transmitted, or polarized heat; and to the brilliant or invisible, but not, on that account, less active phenomena of electro-magnetism -- all this inexhaustible treasure, by which the enjoyment of the contemplation of nature is so much heightened, is dependent on the surface of the planet which we inhabit, and more on its solid than on its liquid parts. I have already remarked how greatly the study of natural objects and forces, and the infinite diversity of the sources they open for our consideration, strengthen the mental activity, and call into action every manifestation of intellectual progress. These relations require, however, as little comment as that concatenation of causes by which particular nations are permitted to enjoy a superiority over others in the exercise of a material power derived from their command of a portion of these elementary forces of nature. If, on the one hand, it were necessary to indicate the difference existing between the nature of our knowledge of the Earth and of that of the celestial regions and their contents, I am no less desirous, on the other hand, to draw attention to the limited boundaries of that portion of spacefrom which we derive all our knowledge of the heterogeneous character of matter. This has been somewhat inappropriately termed the Earth's crust; it includes the strata most contiguous to the upper surface of our planet, and which have been laid open before us by deep fissure-like valleys, or by the labors of man, in the bores and shafts formed by miners. These labors* do not extend beyond a vertical depth of somewhat more than 2000 feet (about one third of a geographical mile) below the p 159 level of the sea, and consequently only about 1/9800th of the Earth's radius. [footnote] *In speaking of the greatest depths within the Earth reached by human labor, we must recollect that there is a difference between the 'absolute depth' (that is to say, the depth below the Earth's surface at that point) and the 'relative depth' (or that beneath the level of the sea). The greatest relative depth that man has hitherto reached is probably the bore at the new salt-works at Minden, in Prussia: in June, 1814, it was exactly 1993 feet, the absolute depth being 2231 feet. The temperature of the water at the bottom was 98 degrees F., which assuming the mean temperature of the air at 49.3 degrees gives an augmentation of temperature of 1 degree for every 54 feet. The absolute depth of the Artesian well of Grenelle, near Paris, is only 1795 feet. According to the account of the missionary Imbert, the fire-springs, "Ho-tsing." of the Chinese, which are sunk to obtain [carbureted] hydrogen gas for salt-boiling, far exceed our Artesian springs in depth. In the Chinese province of Szu-tschuan these fire-springs are very commonly of the depth of more than 2000 feet; indeed, at Tseu-lieu-tsing (the place of continual flow) there is a Ho-tsing which, in the year 1812, was found to be 3197 feet deep. (Humboldt, 'Asie Centrale', t. ii., p. 521 and 525. 'Annales de l'Association de la Propagation de la Foi', 1829, No. 16, p. 369.) [footnote continues] The relative depth reached at Mount Massi, in Tuscany, south of Volterra, amounts, according to Matteuci, to only 1253 feet. The boring at the new salt-works near Minden is probably of about the same relative depth as the coal-mine at Apendale, near Newcastle-under-Lyme, in Staffordshire, where men work 725 yards below the surface of the earth. (Thomas Smith, 'Miner's Guide', 1836, p. 160.) Unfortunately, I do not know the exact height of its mouth above the level of the sea. The relative depth of the Monk-wearmouth mine, near Newcastle, is only 1496 feet. (Phillips, in the 'Philos. Mag.', vol. v., 1834, p. 446.) That of the Liege coal-mine, 'l'Esperance' at Seraing, is, according to M. Gernaert, Ingenieur des Mines, 1223 feet in depth. The works of greatest absolute depth that have ever been formed are for the most part situated in such elevated plains or valleys that they either do not descend so low as the level of the sea, or at most reach very little below it. Thus the Eselchacht, at Kuttenberg, in Bohemia, a mine which can not now be worked, had the enormous absolute depth of 3778 feet. (Fr. A. Schmidt, 'Berggestze der oter Mon.', abth. i., bd. i., s. xxxii.) Also, at St. Daniel and at Geish, on the Rorerbubel, in the 'Landgericht' (or provincial district) of Kitzbuhl, there were, in the sixteenth century, excavations of 3107 feet. The plans of the works of the Rorerbubel are still preserved. (See Joseph von Sperges, 'Tyroler Bergwerksgeschichte', s. 121. Compare, also, Humboldt, 'Gutachten uber �ºerantreibung des Meissner Stollens in die Freiberger Erzrevier', printed in Herder, 'uber Herantreibung des Meissner Stollens in die Freiberger Erzrevier', printed in Herder, 'uber den jetz begonnenen Erbstollen', 1838, s. cxxiv.) We may presume that the knowledge of the extraordinary depth of the Rorerbuhel reached England at an early period, for I find it remarked in Gilbert, 'de Magnete', that men have penetrated 2400 or even 3000 feet into the crust of the Earth. ("Exigua videtur terrae portio, quae unquam hominibus spectanda emerget aut eruitur; cum profundinus in ejus viscera, ultra efflorescentis extremitatis corruptelam, aut propter aquas in magnis fodin, tanquam per venas scaturientesaut propter seris salubrioris ad vitam operariorum sustinendam necessarii defectum, aut propter ingentex sumptus ad tantos labores exantlandos, multasque difficultates, ad profundiores terrz' partes penetrre non possumus; adeo ut quadrigentas aut [quod rarissime] quingentas orgyas in quibusdam metallis descendisse, stupendus omnibus videatur connatus." -- Guilielmi Gilberti, Colcestrensis, 'de Magnete Physiologia nova'. Lond., 1600, p. 40.) [footnote continues] The absolute depth of the mines in the Saxon Erzgebirge, near Freiburg, are: in the Thurmhofer mines, 1944 feet; in the Honenbirker mines, 1827 feet; the relative depths are only 677 and 277 feet, if, in order to calculate the elevation of the mine's mouth above the level of the sea, we regard the elevation of Freiburg as determined by Reich's recent observations to be 1269 feet. The absolute depth of the celebrated mine of Joachimsthal, in Bohemia (Verkreuzung des Jung Hauer Zechen-und Andreasganges), is full 2120 feet; so that, as Von Dechen's measurements show that its surface is about 2388 feet above the level of the sea, it follows that the excavations have not as yet reached that point. In the Harz, the Samson mine at Andreasberg has an absolute depth of 2197 feet. In what was formerly Spanish America, I know of no mine deeper than the Valenciana, near Guanaxuato (Mexico), where I found the absolute depth of the Planes de San Bernardo to be 1686 feet; but these planes are 5960 feet above the level of the sea. If we compare the depth of the old Kuttenberger mine (a depth greater than the height of our Brocken, and only 200 feet less than that of Vesuvius) with the loftiest structures that the hands of man have erected (with the Pyramid of Cheops and with the Cathedral of Strasburg), we find that they stand in the ratio of eight to one. In this note I have collected all the certain information I could find regarding the greatest absolute and relative depths of mines and borings. In descending eastward from Jerusalem toward the Dead Sea, a view presents itself to the eye, which, according to our present hypsometrical knowledge of the surface of our planet, is unrivaled in any country; as we approach the open ravine through which the Jordan takes its course, we tread, with the open sky above us, on rocks which, according to the barometric measurements of Berton and Russegger are 1385 feet below the level of the Mediterranean. (Humboldt, 'Asie Centrale', th. ii., p. 323.) The crystalline masses that have been erupted from active volcanoes, and are generally similar to the rocks on the upper surface, have come from depths which, although not accurately determined, must certainly be sixty times greater than those to which human labor has been enabled to penetrate. We are able to give in numbers the depth of the shaft where the strata of coal, after penetrating a certain way, rise again at a distance that admits of being accurately defined by measurements. These dips show that the carboniferous strata, together with the fossil organic remains which they contain, must lie, as, for instance, in Belgium, more than five or six thousand feet* below the present level p 160 of the sea, and that the calcareous and the curved strata of the Devonian basin penetrate twice that depth. [footnote] *Basin-shaped curved strata, which dip and reappear at measureable distances, although their deepest portions are beyond the reach of the miner, afford sensible evidence of the nature of the earth's crust at great depths below its surface. Testimony of this kind possesses, consequently, a great geognostic interest. I am indebted to that excellent geognosist, Von Dechen, for the following observations. "The depth of the coal basin of Liege, at Mont St. Gilles, which I, in conjunction with our friend Von Oeynhausen, have ascertained to be 3890 feet below the surface, extends 3464 feet below the surface of the sea, for the absolute height of Mont St. Gilles certainly does not much exceed 400 feet; the coal basin of Mons is fully 1865 feet deeper. But all these depths are trifling compared with those which are presented by the coal strata of Saar-Revier (Saarbrucken). I have found after repeated examinations, that the lowest coal stratum which is known in the neighborhood of Duttweiler, near Bettingen, northeast of Saarlouis, must descend to depths of 20,682 and 22,015 feet (or 3.6 geographical miles) below the level of the sea." This result exceeds, by more than 8000 feet, the assumption made in the text regarding the basin of the Devonian strata. This coal-field is therefore sunk as far below the surface of the sea as Chimborazo is elevated above it -- at a depth at which the Earth's temperature must be as high as 435�¼degrees F. Hence, from the highest pinnacles of the Himalaya to the lowest basins containing the vegetation of an earlier world, there is a vertical distance of about 48,000 feet, or of the 435th part of the Earth's radius. If we compare these subterranean basins with the summits of montains that have hitherto been considered as the most elevated portions of the raised crust of the Earth, we obtain a distance of 37,000 feet (about seven miles), that is, about the 1/524th of the Earth's radius. These, therefore, would be the limits of vertical depth and of the superposition of mineral strata to which geognostical inquiry could penetrate, even if the general elevation of the upper surface of the earth were equal to the height of the Dhawalagigi in the Himalaya, or of the Sorata in Bolivia. All that lies at a greater depth below the level of the sea than the shafts or the basins of which I have spoken, the limits to which man's labors have penetrated, or than the depths to which the sea has in some few instances been sounded (Sir James Ross was unable to find bottom with 27,600 feet of line), is as much unknown to us as the interior of the other planets of our solar system. We only know the mass of the whole Earth and its mean density by comparing it with the open strata, which alone are accessible to us. In the interior of the Earth, where all knowledge of its chemical and mineralogical character fails, we are again limited to as pure conjecture, as in the remotest bodies that revolve round the Sun. We can determine nothing with certainty regarding the depth at which the geological strata must be supposed to be in state of softening or of liquid fusion, of the cavities occupied by elastic vapor, of the condition of fluids when heated under an enormous pressure, or of the law of the increase p 161 of density from the upper surface to the center of the Earth. The consideration of the increase of heat with the increase of depth toward the interior of our planet, and of the reaction of the interior on the external crust, leads us to the long series of volcanic phenomena. These elastic forces are manifested in earthquakes, eruptions of gas, hot wells, mud volcanoes and lava currents from craters of eruption and even in producing alterations in the level of the sea.* [footnote] * [See Daubeney 'On Volcanoes', 2d edit., 3848, p. 539, etc., on the so called 'mud volcanoes', and the reasons advanced in favor of adopting the term "salses" to designate these phenomena.] -- Tr. Large plains and variously indented continents are raised or sunk, lands are separated from seas, and the ocean itself, which is permeated by hot and cold currents, coagulates at both poles, converting water into dense masses of rock, which are either stratified and fixed, or broken up into floating banks. The boundaries of sea and land, of fluids and solids, are thus variously and frequently changed. Plains have undergone oscillatory movements, being alternately elevated and depressed. After the elevation of continents, mountain chains were raised upon long fissures, mostly parallel, and in that case, probably cotemporaneous; and salt lakes and inland seas, long inhabited by the same creatures, were forcibly separated, the fossil remains of shells and zoophytes still giving evidence of their original connection. Thus, in following phenomena in their mutual dependence, we are led from the consideration of the forces acting in the interior of the Earth to those which cause eruptions on its surface, and by the pressure of elastic vapors give rise to burning streams of lava that flow from open fissures. The same powers that raised the chains of the Andes and the Hiimalaya to the regions of perpetual snow, have occasioned new compositions and new textures in the rocky masses, and have altered the strata which had been previously deposited from fluids impregnated with organic substances. We here trace the series of formations, divided and superposed according to their age, and depending upon the changes of configuration of the surface, the dynamic relations of upheaving forces, and the chemical action of vapors issuing from the fissures. The form and distribution of continents, that is to say, of that solid portion of the Earth's surface which is suited to the luxurious development of vegetable life, are associated by intimate connection and reciprocal action with the encircling p 162 sea in which organic life is almost entirely limited to the animal world. The liquid element is again covered by the atmosphere, an a��rial ocean in which the mountain chains and high plains of the dry land rise like shoals, occasioning a variety of currents and changes of temperature, collecting vapor from the region of clouds, and distributing life and motion by the action of the streams of water which flow from their declivities. While the geography of plants and animals depends on these intricate relations of the distribution of sea and land, the configuration of the surface, and the direction of isothermal lines (or zones of equal mean annual heat), we find that the case is totally different when we consider the human race -- the last and noblest subject in a physical description of the globe. The characteristic differences in races, and their relative numerical distribution over the Earth's surface, are conditions affected not by natural relations alone, but at the same time and specially, by the progress of civilization, and by moral and intellectual cultivation on which depends the political superiority that distinguishes national progress. Some few races, clinging, as it were, to the soil, are supplanted and ruined by the dangerous vicinity of others more civilized than themselves, until scarce a trace of their existence remains. Other races, again, not the strongest in numbers, traverse the liquid element, and thus become the first to acquire, although late, a geographical knowledge of at least the maritime lands of the whole surface of our globe, from pole to pole. I have thus, before we enter on the individual characters of that portion of the delineation of nature which includes the sphere of telluric phenomena, shown generally in what manner the consideration of the form of the Earth and the incessant action of electro-magnetism and subterranean heat may enable us to embrace in one view the relations of horizontal expansion and elevation on the Earth's surface, the geognostic type of formations, the domain of the ocean (of the liquid portions of the Earth), the atmosphere with its meteorological processes, the geographical distribution of plants and animals, and, finally, the physical gradations of the human race, which is, exclusively and every where, susceptible of intellectual culture. This unity of contemplation presupposes a connection of phenomena according to their internal combination. A mere tabular arrangement of these facts would not fulfill the object I have proposed to myself, and would not satisfy that requirement for cosmical presentation awakened in me by the p 163 aspect of nature in my journeyings by sea and land, by the careful study of forms and forces, and by a vivid impression of the unity of nature in the midst of the most varied portions of the Earth. In the rapid advance of all branches of physical science, much that is deficient in this attempt will, perhaps, at no remote period, be corrected and rendered more perfect, for it belongs to the history of the development of knowledge that portions which have long stood isolated become gradually connected, and subject to higher laws. I only indicate the empirical path in which I and many others of similar pursuits with myself are advancing, full of expectation that, as Plato tells us Socrates once desired, "Nature may be interpreted by reason alone."* [footnote] *Plato, 'Phaedo', p. 97. (Arist., 'Metaph.', p. 985.) compare Hegel, 'Philosophie der Geschichte', 1840, s. 16. The delineation of the principal characteristics of telluric phenomena must begin with the form of our planet and its relations in space. Here too, we may say that it is not only the mineralogical character of rocks, whether they are crystalline, granular, or densely fossiliferous, but the geometrical form of the Earth itself, which indicates the mode of its origin, and is, in fact, its history. An elliptical spheroid of revolution gives evidence of having once been a soft or fluid mass. Thus the Earth's compression constitutes one of the most ancient geognostic events, as every attentive reader of the book of nature can easily discern; and an analogous fact is presented in the case of the Moon, the perpetual direction of whose axes toward the Earth, that is to say, the increased accumulation of matter on that half of the Moon which is turned toward us, determines the relations of the periods of rotation and revolution, and is probably contemporaneous with the earliest epoch in the formative history of this satellite. The mathematical figure of the Earth is that which it would have were its surface covered entirely by water in a state of rest; and it is this assumed form to which all geodesical measurements of degrees refer. This mathematical surface is different from that true physical surface which is affected by all the accidents and inequalities of the solid parts.* [footnote] *Bessel, 'Allgemeine Betrachtungen uber Gradmessungen nach astronomisch-geod��tischen Arbeiten', at the conclusion of Bessel and Baeyer, 'Gradmessung in Ostpreussen', s. 427. Regarding the accumulation of matter on the side of the Moon turned toward us (a subject noticed in an earlier part of the text), see Laplace, 'Expos. du Syst. du Monde', p. 308. The whole figure of the Earth is determined when we know the amount of the p 164 compression at the poles and the equatorial diameter; in order, however, to obtain a perfect representation of its form it is necessary to have measurements in two directions, perpendicular to one another. Eleven measurements of degrees (or determinations of the curvature of the Earth's surface in different parts), of which nine only belong to the present century, have made us acquainted with the size of our globe, which Pliny names "a point in the immeasurable universe."* [footnote] *Plin., ii., 68. Seneca, 'Nat. Quaest., Praef., c. ii. "El mundo espoco" (the Earth is small and narrow), writes Columbus from Jamaica to Queen Isabella on the 7th of July, 1503: not because he entertained the philosophic views of the aforesaid Romans, but because it appeared advantageous to him to maintain that the journey from Spain was not long, if, as he observes, "we seek the east from the west." Compare my 'Examen Crit. de l'Hist. de la Geogr. du 15 me Siecle', t.i., p. 83, and t. ii., p. 327, where I have shown that the opinion maintained by Delisle, Freret, and Gosselin, that the excessive differences in the statements regarding the Earth's circumference, found in the writings of the Greeks, are only apparent, and dependent on different values being attached to the stadia, was put forward as early as 1495 by Jaime Ferrer, in a proposition regarding the determination of the line of demarkation of the papal dominions. If these measurements do not always accord in the curvatures of different meridians under the same degree of latitude, this very circumstance speaks in favor of the exactness of the instruments and the methods employed, and of the accuracy and the fidelity to nature of these partial results. The conclusion to be drawn from the increase of forces of attraction (in the direction from the equator to the poles) with respect to the figure of a planet is dependent on the distribution of density in its interior. Newton, from theoretical principles, and perhaps likewise prompted by Cassini's discovery, previously to 1666, of the compression of Jupiter,* determined, in his immortal work, 'Philosophiae Naturalis Principia', that the compression of the Earth, as a homogeneous mass, was 1/230th. [footnote] *Brewster, 'Life of Sir Isaac Newton', 1831, p. 162. "The discovery of the spheroidal form of Jupiter by Cassini had probably directed the attention of Newton to the determination of its cause, and consequently, to the investigation of the true figure of the Earth." Although Cassini did not announce the amount of the compression of Jupiter (1/15th) till 1691 ('Anciens Memoires de l'Acad. des Sciences', t. ii., p. 108), yet we know from Lalande ('Astron.', 3me ed., t. iii., p. 335) that Moraldi possessed some printed sheets of a Latin work, "On the Spots of the Planets," commenced by Cassini, from which it was obvious that he was aware of the compression of Jupiter before the year 1666, and therefore at least twenty-one years before the publication of Newton's 'Principia'. Actual mesurements, p 165 made by the aid of new and more perfect analysis, have, however, shown that the compression of the poles of the terrestrial spheroid, when the density of the strata is regarded as increasing toward the center, is very nearly 1/300th. Three methods have been employed to investigate the curvature of the Earth's surface, viz., measurements of degrees, oscillations of the pendulum, and observations of the inequalities in the Moon's orbit. The first is a direct geometrical and astronomical method, while in the other two we determine from accurately observed movements the amount of the forces which occasion those movements, and from these forces we arrive at the cause from whence they have originated, viz., the compression of our terrestrial spheroid. In this part of my delineation of nature, contrary to my usual practice, I have instanced methods because their accuracy affords a striking illustration of the intimate connection existing among the forms and forces of natural phenomena, and also because their application has given occasion to improvements in the exactness of instruments (as those employed in the measurements of space) in optical and chronological observations; to greater perfection in the fundamental branches of astronomy and mechanics in respect to lunar motion and to the resistance experienced by the oscillations of the pendulum; and to the discovery of new and hitherto untrodden paths of analysis. With the exception of the investigations of the parallax of stars, which led to the discovery of aberration and nutation, the history of science presents no problem in which the object attained -- the knowledge of the compression and of the irregular form of our planet -- is so far exceeded in importance by the incidental gain which has accrued, through a long and weary course of investigation, in the general furtherance and improvement of the mathematical and astronomical sciences. The comparison of eleven measurements of degrees (in which are included three extra-European, namely, the old Peruvian and two East Indian) gives, according to the most strictly theoretical requirements allowed for by Bessel,* a compression p 166 of 1/299th. [footnote] *According to Bessel's examination of ten measurements of degrees, in which the error discovered by Poissant in the calculation of the French measurements is taken into consideration (Schumacher, 'Astron. Nachr.', 1841, No. 438, s. 116), the semi-axis major of the elliptical spheroid of revolution to which the irregular figure of the Earth most closely approximates is 3,272,077.14 toises, or 20,924,774 feet; the semi-axis minor, 3,261,159,83 toises, or 20,854,821 feet; and the amount of compression or eccentricity 1/299.152d; the length of a mean degree of the meridian, 57,013.109 toises, or 364,596 feet, with an error of + 2.8403 toises, or 18.16 feet, whence the length of a geographical mile is 3807.23 toises, or 6086.7 feet. Previous combinations of measurements of degrees varied between 1/302d and 1/297th; thus Walbeck ('De Forma of Magnitudine telluris in demensis arcubus Meridiani definiendis', 1819) gives 1/30278th: Ed. Schmidt ('Lehrbuch der Mathem. und Phys. Geographie', 1829, s. 5) gives 1/20742d, as the mean of seven measures. Respecting the influence of great differences of longitude on the polar compression, see 'Bibliotheque Universelle', t. xxxiii., p. 181, and t. xxxv., p. 50: likewise 'Connaissance des Tems', 1829, p. 290. From the lunar inequalities alone, Laplace ('Exposition du Syst. du Monde', p. 229) found it, by the older tables of Burg, to be 1/3245th; and subsequently, from the lunar observations of Burckhardt and Bouvard, he fixed it at 1/299.1th ('Mecanique Celeste', t. v., p. 13 and 43). In accordance with this, the polar radius is 10,938 toises (69,944 feet), or about 11 1/2 miles, shorter than the equatorial radius of our terrestrial spheroid. The excess at the equator in consequence of the curvature of the upper surface of the globe amounts, consequently, in the direction of gravitation, to somewhat more than 4 3/7th times the height of Mont Blanc, or only 2 1/2 times the probable height of the summit of the Chawalagiri, in the Himalaya chain. The lunar inequalities (perturbation in the moon's latitude and longitude) give according to the last investigations of Laplace, almost the same result for the ellipticity as the measurements of degrees, viz., 1/299th. The results yielded by the oscillation of the pendulum give, on the whole, a much greater amount of compression, viz., 1/288th.* [footnote] *The oscillations of the pendulum give 1/288.7th as the general result of Sabine's great expedition (1822 and 1823, from the equator to 80 degrees north latitude); according to Freycinet, 1/286.2d, exclusive of the experiments instituted at the Isle of France, Guam, and Mowi (Mawi); according to Forster, 1/289.5th; according to Duperrey, 1/266.4th; and according to Lutke ('Partie Nautique', 1836, p. 232), 1/270th, calculated from eleven stations. On the other hand, Mathieu ('Connais. des Temps', 1816, p. 330) fixed the amount at 1/298.2d, from observations made between Formentera and Dunkirk; and Biot, at 1/304th, from observations between Formentera and the island of Ust. Compare Baily, 'Report on Pendulum Experiments', in the 'Memoirs of the Royal Astronomical Society', vol. vii., p. 96; also Borenius, in the 'Bulletin de l'Acad. de St. Petersbourg', 1843, t. i., p. 25. The first proposal to apply the length of the pendulum as a standard of measure, and to establish the third part of the seconds pendulum (then supposed to be every where of equal length) as a 'pes horarius', or general measure, that might be recovered at any age and by all nations, is to be found in Huygens's 'Horologium Oscillatorium', 1673, Prop. 25. A similar wish was afterward publicly expressed, in 1742, on a monument erected at the equator by Bouguer, La Condamine, and Godin. On the beautiful marble tablet which exists, as yet uninjured, in the old Jesuits' College at Quito, I have myself read the inscription, 'Penduli simplicis aequinoctialis unius minuti secundi archetypus, mensurae naturalis exemplar, utinam universalis!' From an observation made by La Condamine, in his 'Journal du Voyage a l'Equateur', 1751, p. 163, regarding parts of the inscription that were not filled up, and a slight difference between Bonguer and himself respecting the numbers, I was led to expect that I should find considerable discrepancies between the marble tablet and the inscription as it had been described in Paris; but, after a careful comparison, I merely found two "ex arca graduum plusquam trium," and the date of 1745 instead of 1742. The latter circumstance is singular, because La Condamine returned to Europe in November, 1744, Bouguer in June of the same year, and Godin had left South America in July, 1744. The most necessary and useful amendment to the numbers on this inscription would have been the astronomical longitude of Quito. (Humboldt, 'Recueil d'Observ. Astron.', t. ii., p. 319-354.) Nouet's latitudes, engraved on Egyptian monuments, offer a more recent example of the danger presented by the grave perpetuation of false or careless results. Galileo, who first observed when a boy (having, probably, suffered his thoughts to wander from the service) that the height of the vaulted roof of a church might be measured by the time of the vibration of the chandeliers suspended at different altitudes, could hardly have anticipated that the pendulum would one day be carried from pole to pole, in order to determine the form of the Earth, or, rather, that the unequal density of the strata of the Earth affects the length of the seconds pendulum by means of intricate forces of local attraction, which are, however, almost regular in large tracts of land. These geognostic relations of an instrument intended for the measurement of time -- this property of the pendulum, by which, like a sounding line, it searches unknown depths, and reveals in volcanic islands,* or in the declivity of elevated continental mountain chains,** dense masses of basalt and melaphyre instead of cavities, render it difficult, notwithstanding the admirable simplicity of the method, to arrive at any great result regarding the figure of the Earth from observation of the oscillations of the pendulum. [footnote] *Respecting the augmented intensity of the attraction of gravitation in volcanic islands (St. Helena, Ualan, Fernando de Noronha, Isle of France, Guam, Mowe, and Galapagos), Rawak (Lutke, p. 240) being an exception, probably in consequence of its proximity to the highland of New Guinea, see Mathieu, in Delambre, 'Hist. de l'Astronomie, au 18me Siecle', p. 701. [footnote] **Numerous observations also show great irregularities in the length of the pendulum in the midst of continents, and which are ascribed to local attractions. (Delambre, 'Mesure de la Meridienne', t. iii., p. 548; Biot, in the 'Mem. de l'Academie des Sciences', t. viii., 1829, p. 18 and 23.) In passing over the South of France and Lombardy from west to east, we find the minimum intensity of gravitation at Bordeaux; from thence it increases rapidly as we advance eastward, through Figeac, Clermont-Ferrand, Milan, and Padua; and in the last town we find that the intensity has attained its maximum. The influence of the southern declivities of the Alps is not merely t on the general size of their mass, but (much more), in the opinion of Elie de Beaumont ('Rech. sur les Revol. de la Surface du Globe', 1830, p. 729), on the rocks of melaphyre and serpentine, which have elevated the chain. On the declivity of Ararat, which with Caucasus may be said to lie in the center of gravity of the old continent formed by Europe, Asia, and Africa, the very exact pendulum experiments of Fedorow give indications, not of subterranean cavities, but of dense volcanic masses. (Parrot, 'Reise zum Ararat', bd. ii., s. 143.) In the geodesic operations of Carlini and Plana, in Lombardy, differences ranging from 20" to 47".8 have been found between direct observations of latitude and the results of these operations. (See the instances of Andrate and Mondovi, and those of Milan and Padua, in the 'Operations Geodes. et Astron. pour la Mesure d'un Arc du Parallele Moyen', t. ii., p. 347; 'Effemeridi Astron. di Milano', 1842, p. 57.) The latitude of Milan, deduced from that of Berne, according to the , is 45�¼degrees 27' 52", while, according to direct astronomical observations, it is 45 degrees 27' 35". As the perturbations extend in the plain of Lombardy to Parma, which is far south of the Po (Plana, 'Operat. Geod.', t. ii., p. 847), it is probable that there are deflecting causes 'concealed beneath the soil of the plain itself'. Struve has made similar experiments [with corresponding results] in the most level parts of eastern Europe. (Schumacher, 'Astron. Nachrichten', 1830, No. 164, s. 399.) Regarding the influence of dense masses supposed to lie at a small depth, equal to the mean height of the Alps, see the analytical expressions given by Hossard and Rozet, in the 'Comptes Rendus', t. xviii., 1844, p. 292, and compare them with Poisson, 'Traite de Mecanique' (2me ed., t. i., p. 482. The earliest observations on the influence which different kinds of rocks exercise on the vibration of the pendulum are those of Thomas Young, in the 'Philos. Transactions' for 1819, p. 70-96. In drawing conclusions regarding the Earth's curvature from the length of the pendulum, we ought not to overlook the possibility that its crust may have undergone a process of hardening previously to metallic and dense basaltic masses having penetrated from great depths, through open clefts, and approached near the surface. In the astronomical part of the determination of degrees of latitude, mountain chains, or the denser strata of the Earth, likewise exercise, although in a less degree, an unfavorable influence on the measurement. As the form of the Earth exerts a powerful influence on the motions of other cosmical bodies, and especially on that of its own neighboring satellite, a more perfect knowledge of the motion of the latter will enable us reciprocally to draw an inference regarding the figure of the Earth. Thus, as Laplace ably remarks,* "An astronomer, without leaving his observatory, may, by a comparison of lunar theory with true observations, not only be enabled to determine the form and size of the Earth, but also its distance from the Sun and Moon -- results that otherwise could only be arrived at by long and arduous expeditions to the most remote parts of both hemispheres." [footnote] *Laplace, 'Expos. du Syst. du Monde', p. 231. p 169 The compression which may be inferred from lunar inequalities affords an advantage not yielded by individual measurements of degrees or experiments with the pendulum, since it gives a mean amount which is referable to the whole planet. The comparison of the Earth's compression with the velocity of rotation shows, further, the increase of density from the strata from the surface toward the center -- an increase which a comparison of the ratios of the axes of Jupiter and Saturn with their times of rotation likewise shows to exist in these two large planets. Thus the knowledge of the external form of planetary bodies leads us to draw conclusions regarding their internal character. The northern and southern hemispheres appear to present nearly the same curvature under equal degrees of latitude, but, as has already been observed, pendulum experiments and measurements of degrees yield such different results for individual portions of the Earth's surface that no regular figure can be given which would reconcile all the results hitherto obtained by this method. the true figure of the Earth is to a regular figure as the uneven surfaces of water in motion are on the even surface of water at rest. When the Earth had been measured, it still had to be weighed. The oscillations of the pendulum* and the plummet have here likewise served to determine the mean density of the Earth, either in connection with astronomical and geodetic operations, with the view of finding the deflection of the plummet from a vertical line in the vicinity of a mountain, or by a comparison of the length of the pendulum in a plain and on the summit of an elevation, or, finally, by the employment of a torsion balance, which may be considered as a horizontally vibrating pendulum for the measurement of the relative density of neighbouring strata. [footnote] *La Caille's pendulum measurements at the Cape of Good Hope, which have been calculated with much care by Mathieu (Delambre, 'Hist. de l'Astron. au 18me Siecle', p. 479), give a compression of 1/284.4th; but, from several comparisons of observations made in equal latitudes in the two hemispheres (New Holland and the Malouines (Falkland Islands), compared with Barcelona, New York, and Dunkirk), there is as yet no reason for supposing that the mean compression of the southern hemisphere is greater than that of the northern. (Biot, in the 'Mem. de l'Acad. des Sciences', t. viii., 1829, p. 39-41.) Of these three methods* the p 170 last is the most certain, since it is independent of the difficult determination of the density of the mineral masses of which the spherical segment of the mountain consists near which the observations are made. [footnote] *The three methods of observation give the following results: (1.) by the deflection of the plumb-line in the proximity of the Shehallien Mountain (Gaelic, Thichallin) in Perthshire, r.713, as determined by Maskelyne, Hutton, and Playfair (1774-1776 and 1810), according to a method that had been proposed by Newton; (2.) by pendulum vibrations on mountains, 4.837 (Carlini's observations on Mount Cenis compared with Biot's observations at Bordeaux, 'Effemer. Astron. di Milano', 1824, p. 184); (3.) by the torsion balance used by Cavendish, with an apparatus originally devised by Mitchell, 5.48 (according to Hutton's revision of the calculation, 5.32, and according to that of Eduard Schmidt, 5.52; 'Lehrbuch der Math. Geographie', bd. i., s. 487); by the torsion balance, according to Reich, 5.44. In the calculation of these experiments of Professor Reich, which have been made with masterly accuracy, the original mean result was 5.43 (with a probable error of only 0.0233), a result which, being increased by the quantity by which the Earth's centrifugal force diminishes the force of gravity for the latitude of Freiberg (50 degrees 55'), becomes changed to 5.44. The employment of cast iron instead of lead has not presented any sensible difference, or none exceeding the limits of errors of observation, hence disclosing no traces of magnetic influences. (Reich, 'Vrsuche uber die mittlere Dichtigheit der Erde', 1838, s. 60, 62, and 66.) By the assumption of too slight a degree of ellipticity of the Earth, and by the uncertainty of the estimations regarding the density of rocks on its surface, the mean density of the Earth, as deduced from experiments on and near mountains, was found about one sixth smaller than it really is, namely, 4.761 (Laplace, 'Mecan. Celeste', t. v., p. 46), or 4.785. (Eduard Schmidt, 'Lehrb. der Math. Geogr.', bd. i., 387 und 418.) On Halley's hypothesis of the Earth being a hollow sphere (noticed in page 171), which was the germ of Franklin's ideas concerning earthquakes, see 'Philos. Trans.' for the year 1693, vol. xvii., p. 563 ('On the Structure of the Internal Parts of the Earth, and the concave habited 'Arch of the Shell'). Halley regarded it as more worthy of the Creator "that the Earth, like a house of several stories, should be inhabited both without and within. For light in the hollow sphere (p. 576) provision might in some manner be contrived." According to the most recent experiments of Reich, the result obtained is 5.44; that is to say, the mean density of the whole Earth is 5.44 times greater than tht of pure water. As according to the nature of the mineralogical strata constituting the dry continental part of the Earth's surface, the mean density of this portion scarcely amounts to 2.7, and the density of the dry and liquid surface conjointly to scarcely 1.6, it follows that the elliptical unequally compressed layers of the interior must greatly increase in density toward the center, either through pressure or owing to the heterogeneous nature of the substances. Here again we see that the vertical, as well as the horizontally vibrating pendulum, may justly be termed a geognostical instrument. The results obtained by the employment of an instrument of this kind have led celebrated physicists, according to the difference of the hypothesis from which they started, to adopt p 171 entirely opposite views regarding the nature of the interior of the globe. It has been computed at what depths liquid or even gaseous substances would, from the pressure of their own superimposed strata, attain a density exceeding that of platinum or even iridium; and in order that the compression which has been detrmined within such narrow limits might be brought into harmony with the assumption of simple and infinitely compressible matter, Leslie has ingeniously conceived the nucleus of the world to be a hollow sphere, filled with an assumed "imponderable matter, having an enormous force of expansion." These venturesome and arbitrary conjectures have given rise, in wholly unscientific circles, to still more fantastic notions. The hollow sphere has by degrees been peopled with plants and animals, and two small subterranean revolving planets -- Pluto and Proserpine -- were imaginatively supposed to shed over it their mild light; as, however, it was further imagined that an ever-uniform temperature reigned in these internal regions, the air, which was made self-luminous by compression, might well render the planets of this lower world unnecessary. Near the north pole, at 80 degrees latitude, whence the polar light emanates, was an enormous opening, through which a descent might be made into the hollow sphere, and Sir Humphrey Davy and myself were even publicly and frequently invited by Captain Symmes to enter upon this subterranean expedition: so powerful is the morbid inclination of men to fill unknown spaces with shapes of wonder, totally unmindful of the counter evidence furnished by well-attested facts and universally acknowledged natural laws. Even the celebrated Halley, at the end of the seventeenth century, hollowed out the Earth in his magnetic speculations. Men were invited to believe that a subterranean freely-rotating nucleus occasions by its position the diurnal and annual changes of magnetic declination. It has thus been attempted in our own day, with tedious solemnity, to clothe in a scientific garb the quaintly-devised fiction of the humorous Holbert.* [footnote] *[The work referred to, one of the wittiest productions of the learned Norwegian satirist and dramatist Holberg, was written in Latin, and first appeared under the following title: 'Nicolai Klimii iter subterraneum novam telluris theoriam ac historiam quintae monarchi Nicolai Klimii iter subterraneum novam telluris theoriam ac historiam quintae monarchi ad huc nobis incognitae exhibens e bibliotheca b. Abelini. Hafniae et Lipsiae sunt. Jac. Preuss', 1741. An admirable Danish translation of this learned but severe satire on the institutions, morals, and manners of the inhabitants of the upper Earth, appeared at Copenhagen in 1789, and was entitled 'Niels Klim's underjordiske reise ocd Ludwig Holberg, oversal after den Latinske original of Jens Baggesen'. Holberg, who studied for a time at Oxford, was born at Bergen in 1685, and died in 1754 as Rector of the University of Copenhagen.] -- Tr. p 172 The figure of the Earth and the amount of solidification (density) which it has acquired are intimately connected with the forces by which it is animated, in so far, at least, as they have been excited or awakened from without, through its planetry position with reference to a luminous central body. Compression, when considered as a consequence of centrifugal force acting on a rotating mass, explains the earlier condition of fluidity of our planet. During the solidification of this fluid, which is commonly conjectured to have been gaseous and primordially heated to a very high temperature, an enormous quantity of latent heat must have been liberated. If the process of solidification began as Fourier conjectures, by radiation from the cooling surface exposed to the atmosphere, the particles near the center would have continued fluid and hot. As, after long emanation of heat from the center toward the exterior, a stable condition of the temperature of the Earth would at length be established, it has been assumed that with increasing depth the subterranean heat likewise uninterruptedly increases. The heat of the water which flows from deep borings (Artesian wells), direct experiments regarding the temperature of rocks in mines, but, above all, the volcanic activity of the Earth, shown by the flow of molten masses from open fissures, afford unquestionable evidence of this increase for very considerable depths from the upper strata. According to conclusions based certainly upon mere analogies, this increase is probably much greater toward the center. That which has been learned by an ingenious analytic calculation, expressly perfected for this class of investigations,* p 173 regarding the motion of heat in homogeneous metallic spheroids, must be applied with much caution to the actual character of our planet, considering our present imperfect knowledge of the substances of which the Earth is composed, the difference in the capacity of heat and in the conducting power of different superimposed masses, and the chemical changes experienced by solid and liquid masses from any enormous compression. [footnote] *Here we must notice the admirable analytical labors of Fourier, Biot, Laplace, Poisson, Duhamel, and Lame. In his 'Theorie Mathematique de la Chaleur', 1835, p. 3, 428-430, 436, and 521-524 (see, also, De la Rive's abstract in the 'Bibliotheque Universelle de Geneve', Poisson has developed an hypothesis totally different from Fourier's view ('Theorie Analytique de la Chaleur'.) He denies the present fluid state of the Earth's center; he believes that "in cooling by radiation to the medium surrounding the Earth, the parts which were first solidified sunk, and that by a double descending and ascending current, the great inequality was lessened which would have taken place in a solid body cooling from the surface." It seems more probable to this great geometer that the solidification began in the parts lying nearest to the center: "the phenomenon of the increase of heat with the depth does not extend to the whole mass of the Earth, and is merely a consequence of the motion of our planetary system in space, of which some parts are of a very different temperature from others, in consequence of stellar heat (chaleur stellaire)." Thus, according to Poisson, the warmth of the water of our Artesian wells is merely that which has penetrated into the Earth from without; and the Earth itself "might be regarded as in the same circumstances as a mass of rock conveyed from the equator to the pole in so short a time as not to have entirely cooled. The increase of temperature in such a block would not extend to the central strata." The physical doubts which have reasonably been entertained against this extraordinary cosmical view (which attributes to the regions of space that which probably is more dependent on the first transition of matter condensing from the gaseo-fluid into the solid state) will be found collected in Poggendorf's 'Annalen', bd. xxxix., s 93-100. It is with the greatest difficulty that our powers of comprehension can conceive the boundary line which divides the fluid mass of the interior from the hardened mineral masses of the external surface, or the gradual increase of the solid strata, and the condition of semi-fluidity of the earthy substances, these being conditions to which known laws of hydraulics can only apply under considerable modifications. The Sun and Moon, which cause the sea to ebb and flow, most probably also affect these subterranean depths. We may suppose that the periodic elevations and depressions of the molten mass under the already solidified strata must have caused inequalities in the vaulted surface from the force of pressure. The amount and action of such oscillations must, however, be small; and if the relative position of the attracting cosmical bodies may here also excite "spring tides," it is certainly not to these, but to more powerful internal forces, that we must ascribe the movements that shake the Earth's surface. There are groups of phenomena to whose existence it is necessary to draw attention, in order to indicate the universality of the influence of the attraction of the Sun and Moon on the external and internal conditions of the Earth, however little we may be able to determine the quantity of this influence. According to tolerably accordant experiments in Artesian wells, it has been shown that the heat increases on an average about 1 degree for every 54.5 feet. If this increase can be reduced p 174 to arithmetical relations, it will follow, as I have already observed,* that a stratum of granite would be in a state of fusion at a depth of nearly twenty-one geographical miles, or between four and five times the elevation of the highest summit of the Hinalaya. [footnote] *See the Introduction. This increase of temperature has been found in the Puits de Grenelle, at Paris, at 58.3 feet; in the boring at the new salt-works at Minden, almost 53.6; at Pregny, near Geneva, according to Auguste de la Rive and Marcet, notwithstanding that the mouth of the boring is 1609 feet above the level of the sea, it is also 53.6 feet. This coincidence between the results of a method first proposed by Arago in the year 1821 ('Annuaire du Bureau des Longitudes', 1835, p. 234), for three different mines, of the absolute depths of 1794, 2231, and 725 feet respectively, is remarkable. The two points on the Earth, lying at a small vertical distance from each other, whose annual mean temperatures are most accurately known, are probably at the spot on which the Paris Observatory stands, and the Caves de l'Observatoire beneath it; the mean temperature of the former is 51.5�¼degrees, and of the latter 53.3�¼degrees, the difference being 1.8�¼degrees for 92 feet, or 1 degree for 51.77 feet. (Poisson, 'Theorie Math. de la Chaleur', p. 415 and 462.) In the course of the last seventeen years, from causes not yet perfectly understood, but probably not connected with the actual temperature of the caves, the thermometer standing there has risen very nearly 0.4 degrees. Although in Artesian wells there are sometimes slight errors from the lateral permeation of water, these errors are less injurious to the accuracy of conclusions than those resulting from currents of cold air, which are almost always present in mines. The general result of Reich's great work on the temperature of the mines in the Saxony mining districts gives a somewhat slower increase of the terrestrial heat, or 1 degree to 76.3 feet. (Reich, 'Beob. uber die Temperatur des Gesteins in verschielen en Tiefen', 1834, s. 134.) Phillips, however, found (Pogg., 'Annalen', bd. xxxiv., s. 191), in a shaft of the coal-mine of Monk-wearmouth, near Newcastle, in which, as I have already remarked, excavations are going on at a depth of about 1500 feet below the level of the sea, an increase of 1 degree to 59.06 feet, a result almost identical with that found by Arago in the Puits de Grenell. We must distinguish in our globe three different modes for the transmission of heat. The first is periodic, and affects the temperature of the terrestrial strata according as the heat penetrates from above downward or from below upward, being influenced by the different positions of the Sun and the seasons of the year. The second is likewise an effect of the Sun, although extremely slow: a portion of the heat that has penetrated into the equatorial regions moves in the interior of the globe toward the poles, where it escapes into the atmosphere and the remoter regions of space. The third mode of transmission is the slowest of all, and is derived from the secular cooling of the globe, and from the small portion of the primitive heat which is still being disengaged from the surface. p 175 This loss experienced by the central heat must have been very considerable in the earliest epochs of the Earth's revolutions, but within historical periods it has hardly been appreciable by our instruments. The surface of the Earth is therefore situated between the glowing heat of the inferior strata and the universal regions of space, whose temperature is probably below the freezing-point of mercury. The periodic changes of temperature which have been occasioned on the Earth's surface by the Sun's position and by meteorological processes, are continued in its interior, although to a very inconsiderable depth. The slow conducting power of the ground diminishes this loss of heat in the winter, and is very favorable to deep-rooted trees. Points that lie at very different depths on the same vertical line attain the maximum and minimum of the imparted temperature at very different periods of time. The further they are removed from the surface, the smaller is this difference between the extremes. In the latitudes of our temperate zone (between 48 degrees and 52 degrees), the stratum of invariable temperature is at a depth of from 59 to 64 feet, and at half that depth the oscillations of the thermometer, from the influence of the seasons, scarcely amount to half a degree. In tropical climates this invariable stratum is only one foot below the surface, and this fact has been ingeniously made use of by Boussingault to obtain a convenient, and as he believes, certain determination of the mean temperature of the air of different places.* [footnote] *Boussingault, 'Sur la Profondeus a laquelle se trouve la Couche de Temperature invariable, entre les Tropiques', in the 'Annales de Chimie et de Physique', t. liii., 1833, p. 225-247. This mean temperature of the air at a fixed point, or at a group of contiguous points on the surface, is to a certain degree the fundamental element of the climate and agricultural relations of a district; but the mean temperature of the whole surface is very different from that of the globe itself. The questions so often agitated, whether the mean temperature has experienced any considerable differences in the course of centuries, whether the climate of a country has deteriorated, and whether the winters have not become milder and the summers cooler, can only be answered by means of the thermometer; this instrument has, however, scarcely been invented more than two centuries and a half, and its scientific application hardly dates back 120 years. The nature and novelty of the means interpose, therefore, very narrow limits to our investigation regarding the temperature p 176 of the air. It is quite otherwise, however, with the solution of the great problem of the internal heat of the whole Earth. As we may judge of uniformity of temperature from the unaltered time of vibration of a pendulum, so we may also learn, from the unaltered rotatory velocity of the Earth, the amount of stability in the mean temperature of our globe. This insight into the relations between the 'length of the day' and the 'heat of the Earth' is the result of one of the most brilliant applications of the knowledge we had long possessed of the planet. The rotatory velocity of the Earth depends on its volume; and since, by the gradual cooling of the mass by radiation, the axis of rotation would become shorter, the rotatory velocity would necessarily increase, and the length of the day diminish, with a decrease of the temperature. From the comparison of the secular inequalities in the motions of the Moon with the eclipses observed in ancient times, it follows that, since the time of Hipparchus, that is, for full 2000 years, the length of the day has certainly not diminished by the hundredth part of a second. The decrease of the mean heat of the globe during a period of 2000 years has not, therefore, taking the extremest limits, diminished as much as 1/306th of a degree of Fahrenheit.* [footnote] *Laplace, 'Exp. du Syst. du Monde', p. 229 and 263; 'Mecanique Celeste', t. v., p. 18 and 72. It should be remarked that the fraction 1/306th of a degree of Fahrenheit of the mercurial thermometer, given in the text as the limit of the stability of the Earth's temperature since the days of Hipparchus, rests on the assumption that the dilation of the substances of which the Earth is composed is equal to that of glass, that is to say, 1/18,000th for 1 degree. Regarding this hypothesis, see Arago in the 'Annuaire' for 1834, p. 177-190. This invariability of form presupposes also a great invariability in the distribution of relations of density in the interior of the globe. The translatory movements, which occasion the eruptions of our present volcanoes and of ferruginous lava, and the filling up of previously empty fissures and cavities with dense masses of stone, are consequently only to be regarded as slight superficial phenomena affecting merely one portion of the Earth's crust, which, from their smallness when compared to the Earth's radius, become wholly insignificant. I have described the internal heat of our planet, both with reference to its cause and distribution, almost solely from the results of Fourier's admirable investigations. Poisson doubts the fact of the uninterrupted increase of the Earth's heat p 177 from the surface to the center, and is of opinion that all heat has penetrated from without inward, and that the temperature of the globe depends upon the very high or very low temperature of the regions of space through which the solar temperature of the regions of space, through which the solar system has moved. This hypothesis, imagined by one of the most acute mathematicians of our time, has not satisfied physicists or geologists, or scarcely indeed any one besides its author. But, whatever may be the cause of the internal heat of our planet, and of its limited or unlimited increase in deep strata, it leads us, in this general sketch of nature, through the intimate connection of all primitive phenomena of matter, and through the common bond by which molecular forces are united, into the mysterious domain of magnetism. Changes of temperature call forth magnetic and electric currents. Terrestrial magnetism, whose main character, expressed in the three-fold manifestation of its forces, is incessant periodic variability, is ascribed either to the heated mass of the Earth itself,* or to those galvanic currents which we consider as electricity in motion, that is, electricity moving in a closed circuit.** [footnote] *William Gilbert, of Colchester, whom Galileo pronounced "great to a degree that might be envied," said "magnus magnes ipse est globus terrestris." He ridicules the magnetic mountains of Frascatori, the great contemporary of Columbus, as being magnetic poles: "rejicienda est vulgaris opinio de montibus magneticis, aut rupe aliqua magnetica, aut polo phantastico a polo mundi distante." He assumes the declination of the magnetic needle at any give point on the surface of the Earth to be invariable (variatio uniuscujusque loci constans est), and refers the curvatures of the isogonic lines to the configuration of continents and the relative positions of sea basins, which possess a weaker magnetic force than the solid masses rising above the ocean. (Gilbert, 'de Magnete', ed. 1633, p. 42, 98, 152 and 155.) [footnote] ** Gauss, 'Allgemcine Theorie des Erdmagnetismus', in the 'Resultate aux den Beob. des Magnet. Vereins', 1838, s. 41, p. 56. The mysterious course of the magnetic needle is equally affected by time and space, by the sun's course, and by changes of place on the Earth's surface. Between the tropics, the hour of the day may be known by the direction of the needle as well as by the oscillations of the barometer. It is affected instantly, but only transiently, by the distant northern light as it shoots from the pole, flashing in beams of colored light across the heavens. When the uniform horary motion of the needle is disturbed by a magnetic storm, the perturbation manifests itself 'simultaneously', in the strictest sense of the word, over hundreds and thousands of miles of sea and land, or propagates itself by degrees, in short intervals of time, in p 178 every direction over the Earth's surface.* [footnote] *There are also perturbations which are of a local character, and do not extend themselves far, and are probably less deep-seated. Some years ago I described a rare instance of this kind, in which an extraordinary disturbance was felt in the mines at Freiberg, but was not perceptible at Berlin. ('Lettre de M. de Humboldt a Son Altesse Royale le Duc de Sussex sur les moyens propres a perfectionner la Connaissance du Magnetisme Terrestre', in Becquerel's 'Traite Experimental de l'Electricite' t. vii., p. 442.) Magnetic storms which were simultaneously felt from Sicily to Upsala, did not extend from Upsala to Alten. (Gauss and Weber, 'Resultate des Magnet. Vereins', 1839, 128; Lloyd, in the 'Comptes Rendus de l'Acad. des Sciences', t. xii., 1843, Sem. ii., p. 725 and 827.) Among the numerous examples that have been recently observed, of perturbations occurring simultaneously and extending over wide portions of the Earth's surface, and which are collected in Sabine's important work ('Observ. on Days of unusual Magnetic Disturbance', 1843), one of the most remarkable is that of the 25th of September, 1841, which was observed at Toronto in Canada, at the Cape of Good Hope, at Prague, and partially in Van Diemen's Land. The English Sunday, on which it is deemed sinful, after midnight on Saturday, to register an observation, and to follow out the great phenomena of creation in their perfect development, interrupted the observations in Van Diemen's Land, where in consequence of the difference of the longitude, the magnetic storm fell on the Sunday. ('Observ.', p. xiv., 78, 85, and 87.) In the former case, the simultaneous manifestation of the storm may serve, within certain limitations, like Jupiter's satellites, fire-signals, and well-observed falls of shooting stars, for the geographical determination of degrees of longitude. We here recognize with astonishment that the perturbations of two small magnetic needles, even if suspended at great depths below the surface, can measure the distances apart at which they are placed, teaching us, for instance, how far Kasan is situated east of Gottingen or of the banks of the Seine. There are also districts in the earth where the mariner, who has been enveloped for many days in mist, without seeing either the sun or stars, and deprived of all means of determining the time, may know with certainty, from the variations in the inclination of the magnetic needle, whether he is at the north or the south of the port he is desirous of entering.* [footnote] *I have described, in Lametherie's 'Journal de Physique', 1804, t. lix., p. 449, the application (alluded to in the text) of the magnetic inclination to the determination of latitude along a coast running north and south, and which, like that of Chili and Peru, is for a part of the year enveloped in mist ('garua'). In the locality I have just mentioned, this application is of the greater importance, because, in consequence of the strong current running northward as far as to Cape Parena, navigators incur a great loss of time if they approach the coast to the north of the haven they are seeking. In the South Sea, from Callao de Lima harbor to Truxillo, which differ from each other in latitude by 3 degrees 57' I have observed a variation of the magnetic inclination amounting to 9 degrees (centesimal division); and from Callao to Guayaquil, which differ in latitude by 9 degrees 50', a variation of 23.5 degrees. (See my 'Relat. Hist.', t. iii., p. 622.) At Guarmey (10 degrees 4' south lat.), Huaura (11 degrees 3' south lat.), and Chancay (11 degrees 4' south lat.), Huaura (11 degrees 3' south lat.), and Chancay (11 degrees 32' south lat.), the inclinations are 6.80 degrees, 9 degrees, and 10.35 degrees of the centesimal division. The determination of position by means of the magnetic inclination has this remarkable feature connected with it, that where the ship's course cuts the isoclinalline almost perpendicularly, it is the only one that is independent of all determination of time, and consequently, of observations of the sun or stars. It is only lately that I discovered, for the first time, that as early as at the close of the sixteenth century, and consequently hardly twenty years after Robert Norman had invented the inclinatorium, William Gilbert, in his great work, 'De Magnete', proposed to determine the latitude by the inclination of the magnetic needle. Gilbert ('Physiologia Nova de Magnete', lib. v., cap. 8, p. 200) commends the method as applicable "a��re caliginoso." Edward Wright, in the introduction which he added to his master's great work, describes this proposal as "worth much gold." As he fell into the same error with Gilbert, of presuming that the isoclinal lines coincided with the geographical parallel circles, and that the magnetic and geographical equators were identical, he did not perceive that the proposed method had only a local and very limited application. p 179 When the needle, by its sudden disturbance in its horary course, indicates the presence of a magnetic storm, we are still unfortunately ignorant whether the seat of the disturbing cause is to be sought in the Earth itself or in the upper regions of the atmosphere. If we regard the Earth as a true magnet, we are obliged, according to the views entertained by Friedrich Gauss (the acute propounder of a generaltheory of terrestrial magnetism), to ascribe to every portion of the globe measuring one eighth of a cubic meter (or 3 7/10ths of a French cubic foot) in volume, an average amount of magnetism equal to that contained in a magnetic rod of 1 lb. weight.* [footnote[ *Gauss and Weber, 'Resultate des Magnet. Vereins', 1838, 31, s. 146. If iron and nickel, and probably, also, cobalt (but not chrome, as has long been believed),* are the only substances which become permanently magnetic, and retain polarity from a certain coerceive force, the phenomena of Arago's magnetism of rotation and of Faraday's induced currents show, on the other hand, that all telluric substances may possibly be made transitorily magnetic. According to Faraday ('London and Edinburgh Philosophical Magazine', 1836, vol. viii., p. 178), pure cobalt is totally devoid of magnetic power. I know, however, that other celebrated chemists (Heinrich Rose and Wohler) do not admit this as absolutely certain. If out of two carefully-purified masses of cobalt totally free from nickel, one appears altogether non-magnetic (in a state of equilibrium), I think it probable that the other owes its magnetic property to a want of purity; and this opinion coincides with Faraday's view. According to the experiments of the p 180 first-mentioned of these great physicists, water, ice, glass, and carbon affect the vibrations of the needle entirely in the same manner as mercury in the rotation experiments.* [footnote] *Arago, in the 'Annales de Chimie', t. xxxii., p. 214; Brewster, 'Treaties on Magnetism', 1837, p. 111; Baumgartner, in the 'Zeitschrift fur Phys. und Mathem.', bd. ii., s. 419. Almost all substances show themselves to be, in a certain degree, magnetic when they are conductors, that is to say, when a current of electricity is passing through them. Although the knowledge of the attracting power of native iron magnets or loadstones appears to be of very ancient date among the nations of the West, there is strong historical evidence in proof of the striking fact that the knowledge of the directive power of a magnetic needle and of its relation to terrestrial magnetism was peculiar to the Chinese, a people living in the extremest eastern portions of Asia. More than a thousand years before our era, in the obscure age of Codrus, and about the time of the return of the Heraclidae to the Peloponnesus, the Chinese had already magnetic carriages, on which the movable arm of the figure of a man continually pointed to the south, as a guide by which to find the way across the boundless grass plains of Tartary; nay, even in the third century of our era, therefore at least 700 years before the use of the mariner's compass in European seas, Chinese vessels navigated the Indian Ocean* under the direction of magnetic needles pointing to the south. [footnote] *Humboldt, 'Examen Critique de l'Hist. de la Geographie', t. iii., p. 36. I have shown, in another work, what advantages this means of topographical direction, and the early knowledge and application of the magnetic needle gave the Chinese geographers over the Greeks and Romans, to whom, for instance, even the true direction of the Apennines and Pyrenees always remained unknown.* [footnote] *'Asie Centrale', t. i., Introduction, p. xxxviii-xlii. The Western nations, the Greeks and the Romans, knew that magnetism could be communicated to iron, 'and that that metal would retain it for a length of time'. ("Sola haec materia ferri vires, a maguete lapide accipit, 'retinetque longo tempore." Plin., xxxiv., 14.) The great discovery of the terrestrial directive force depended, therefore, alone on this, that no one in the West had happened to observe an elongated fragment of magnetic iron stone, or a magnetic iron rod, floating, by the aid of a piece of wood, in water, or suspended in the air by a thread, in such a position as to admit of free motion. The magnetic power of our globe is manifested on the terrestrial surface in three classes of phenomena, one of which exhibits itself in the varying intensity of the force, and the two others in the varying direction of the inclination, and in p 181 the horizontal deviation from the terrestrial meridian of the spot. Their combined action may therefore be graphically represented by three systems of lines, the 'isodynamic, isoclinic', and 'isogonic' (or those of equal force, equal inclination, and equal declination). The distances apart, and the relative positions of these moving, oscillating, and advancing curves, do not always remain the same. The total deviation (variation or declination of the magnetic needle) has not at all changed, or, at any rate, not in any appreciable degree, during a whole century, at any particular point on the Earth's surface,* as, for instance, the western part of the Antilles, or Spitzbergen. [footnote] *A very slow secular progression, or a local invariability of the magnetic declination, prevents the confusion which might arise from terrestrial influences in the boundaries of land, when, with an utter disregard for the correction of declination, estates are, after long intervals, measured by the mere application of the compass. "The whole mass of the bottomless pit of endless litigation by the invariability of the magnetic declination in Jamica and the surrounding Archipelago during the whole of the last century, all surveys of property there having been conducted solely by the compass." See Robertson in the 'Philosophical Transactions' for 1806, Part ii., p. 348, 'On the Permanency of the Compass in Jamaica since 1660'. In the mother country (England) the magnetic declination has varied by fully 14 degrees during the period. In like manner, we observe that the isogonic curves, when they pass in their secular motion from the surface of the sea to a continent or an island of considerable extent, continue for a long time in the same position, and become inflected as they advance. These gradual changes in the forms assumed by the lines in their translatory motions, and which so unequally modify the amount of eastern and western declination, in the course of time render it difficult to trace the transitions and analogies of forms in the graphic representations belonging to different centuries. Each branch of a curve has its history, but this history does not reach further back among the nations of the West than the memorable epoch of the 13th of September, 1492, when the re-discoverer of the New World found a line of no variation 3 degrees west of the meridian of the island of Flores, one of the Azores.* [footnote] *I have elsewhere shown that, from the documents which have come down to us regarding the voyages of Columbus, we can, with much certainty, fix upon three places 'in the Atlantic line of no declination' for the 13th of September, 1492, the 21st of May, 1496, and the 16th of August, 1498. The Atlantic line of no declination at that period ran from northeast to southwest. It then touched the South American continent a little east of Cape Codera, while it is not observed to reach that continent on the northern coast of the Brazils. (Humboldt, 'Examen Critique de l'Hist. de la Geogr.', t. iii., p. 44-48.) From Gilbert's 'Physiologia Nova de Magnete', we see plainly (and the fact is very remarkable) that in 1600 the declination was still null in the region of the Azores, just as it had been in the time of Columbus (lib. 4, cap. 1). I believe that in my 'Examen Critique' (t. iii., p. 54) I have proved from documents that the celebrated line of demarkation by which Pope Alexander VI. divided the Western hemisphere between Portugal and Spain was not drawn through the most western point of the Azores, because Columbus wished to convert a physical into a political division. He attached great importance to the zone (raya) "in which the compass shows no variation, where air and ocean, the later covered with pastures of sea-weed, exhibit a peculiar constitution, where cooling winds begin to blow, and where [as erroneous observations of the polar star led him to imagine] the form (sphericity) of the Earth is no longer the same." The whole of Europe, excepting a small p 182 part of Russia, has now a western declination, while at the close of the seventeenth century the needle first pointed due north, in London in 1657, and in Paris in 1669, there being thus a difference of twelve years, notwithstanding the small distance between these two places. In Eastern Russia, to the east of the mouth of the Volga, of Saratow, Nischni-Nowgorod, and Archangel, the easterly declination of Asia is advancing toward us. Two admirable observers, Hansteen and Adolphus Erman, have made us acquainted with the remarkable double curvature of the lines of declination in the vast region of Northern Asia; these being concave toward the pole between Obdorsk, on the Oby, and Turuchansk, and convex between the Lake of Baikal and the Gulf of Ochotsk. In this portion of the earth, in northern Asia, between the mountains of Werchojansk, Jakutsk, and the northern Korea, the isogonic lines form a remarkable closed system. This oval configuration* recurs regularly and over a great extent of the South Sea, almost as far as the meridian of Pitcairn and the group of the Marquesas Islands, between 20 degrees north and 45 degrees p 183 south lat. [footnote] *To determine whether the two oval systems of isogonic lines, so singularly included each within itself, will continue to advance for centuries in the same inclosed form, or will unfold and expand themselves, is a question of the highest interest in the problem of the physical causes of terrestrial magnetism. In the Eastern Asiatic nodes the declination increases from without inward, while in the node or oval system of the South Sea the opposite holds good; in fact, at the present time, in the whole South Sea to the east of the meridian of Kamt-schatka, there is no line where the declination is null, or, indeed, in which it is less than 2 degrees (Erman, in Pogg., 'Annal.', bd. xxxi, 129). Yet Cornelius Schouten, on Easter Sunday, 1616, appears to have found the declination null somewhere to the southeast of Nukahiva, in 15 degrees south lat. and 132 degrees west long., and consequently in the middle of the present closed isogonal system. (Hansteen, 'Magnet. der Erde', 1819 �¤ 28.) It must not be forgotten, in the midst of all these considerations, that we can only follow the direction of the magnetic lines in their progress as they are projected upon the surface of the Earth. One would almost be inclined to regard this singular configuration of closed, almost concentric, lines of declination as the effect of a local character of that portion of the globe; but if, in the course of centuries, these apparently isolated systems should also advance, we must suppose, as in the case of all great natural forces, that the phenomenon arises from some general cause. The horary variations of the declination, which, although dependent upon true time, are apparently governed by the Sun, as long as it remains above the horizon, diminish in angular value with the magnetic latitude of place. Near the equator, for instance, in the island of Rawak, they scarcely amount to three or four minutes, while they are from thirteen to fourteen minutes in the middle of Europe. As in the whole northern hemisphere the north point of the needle moves from east to west on an average from 8 1/2 in the morning until 1 1/2 at mid-day, while in the southern hemisphere the same north point moves from west to east,* attention has recently been drawn, with much justice, to the fact that there must be a region of the Earth between the terrestrial and the magnetic equator where no horary deviations in the declination are to be observed. [footnote] *Arago, in the 'Annuaire', 1836, p. 284, and 1840, p. 330-338. This fourth curve, which might be called the 'curve of no motion', or, rather, 'the line of no variation of horary declination', has not yet been discovered. The term 'magnetic poles' has been applied to those points of the Earth's surface where the horizontal power disappears, and more importance has been attached to these points than properly appertains to them;* and in like manner, the curve, where the inclination of the needle is null, has been termed the 'magnetic equator'. [footnote] *Gauss, 'Allg. Theorie des Erdmagnet.', 31. The position of this line and its secular change of configuration have been made an object of careful investigation in modern times. According to the admirable work of Duperrey,* who crossed the magnetic equator six times between 1822 and 1825, the nodes of the two equators, that is to say, the two points at which the line without inclination intersects the terrestrial equator, and consequently passes from one henisphere into the other, are so unequally placed, that in 1825 the node near the island of St. Thomas, on the western p 184 coast of Africa, was 188 1/2 degrees distant from the node in the South Sea, close to the little islands of Gilbert, nearly in the meridian of the Viti group. [footnote] *Duperrey, 'De la Configuration de l'Equateur Magnetique', in the 'Annales de Chimie', t. xlv., p. 371 and 379. (See also, Morlet, in the 'Memoires presentes par divers Savans a l'Acad. Roy. des Sciences', t. iii., p. 132. In the beginning of the present century, at an elevation of 11,936 feet above the level of the sea, I made an astronomical determination of the point (7 degrees 1' south lat., 48 degrees 40' west long. from Paris), where, in the interior of the New Continent, the chain of the Andes is intersected by the magnetic equator between Quito and Lima. To the west of this point, the magnetic equator continues to traverse the South Sea in the southern hemisphere, at the same time slowly drawing near the terrestrial equator. It first passes into the northern hemisphere a little before it approaches the Indian Archipelago, just touches the southern points of Asia, and enters the African continent to the west of Socotora, almost in the Straits of Bab-el-Mandeb, where it is most distant from the terrestrial equator. After intersecting the unknown regions of the interior of Africa in a southwest direction, the magnetic equator re-enters the south tropical zone in the Gulf of Guinea, and retreats so far from the terrestrial equator that it touches the Brazilian coast near Os Ilheos, north of Porto Seguro, in 15 degrees south lat. From thence to the elevated plateaux of the Cordilleras, between the silver mines of micuipampa and Caxamarca, the ancient seat of the Incas, where I observed the inclination, the line traverses the whole of South America, which in these latitudes is as much a magnetic 'terra incognita' as the interior of Africa. The recent observations of Sabine* have shown that the node near the island of St. Thomas has moved 4 degrees from east to west between 1825 and 1837. [footnote] *See the remarkable chart of isoclinic lines in the Atlantic Ocean for the years 1825 and 1837, in Sabine's 'Contributions to Terrestrial Magnetism', 1840, p. 134. It would be extremely important to know whether the opposite pole, near the Gilbert Islands, in the South Sea, has aproached the meridian of the Carolinas in a westerly direction. These general remarks will be sufficient to connect the different systems of isoclinic non-parallel lines with the great phenomenon of equilibrium which is manifested in the magnetic equator. It is no small advantage, in the exposition of the laws of terrestrial magnetism, that the magnetic equator (whose oscillatory change of form and whose nodal motion exercise an influence on the inclination of the needle in the remotest districts of the world, in consequence of the altered magnetic latitudes)* should traverse the p 185 ocean throughout its whole course, excepting about one fifth, and consequently be made so much more accessible, owing to the remarkable relations in space between the sea and land, and to the means of which we are now possessed for determining with much exactness both the declination and the inclination at sea. [footnote] *Humboldt, 'Ueber die secul��re Ver��nderung der Magnetischen Inclination' (On the secular Change in the Magnetic Inclination), in Pogg. 'Annal.', bd. sv., s. 322. We have described the distribution of magnetism on the surface of our planet according to the two forms of 'declination' and 'inclination'; it now, therefore, remains for us to speak of the 'intensity of the force' which is graphically expressed by isodynamic curves (or lines of equal intensity). The investigation and measurement of this force by the oscillations of a vertical or horizontal needle have only excited a general and lively interest in its telluric relations since the beginning of the nineteenth century. The application of delicate optical and chronometrical instruments has rendered the measurement of this horizontal power susceptible of a degree of accuracy far surpassing that attained in any other magnetic determinations. The isogonic lines are the more important in their immediate application to navigation, while we find from the most recent views that isodynamic lines, especially those which indicate the horizontal force, are the most valuable elements in the theory of terrestrial magnetism.* [footnote] *Gauss, 'Resultate der Beob. des Magn. Vereins', 1838, 21; Sabine, 'Report on the Variations of the Magnetic Intensity', p. 63. One of the earliest facts yielded by observation is, that the intensity of the total force increases from the equator toward the pole.* [footnote] *The following is the history of the discovery of the law that the intensity of the force increases (in general) with the magnetic latitude. When I was anxious to attach myself, in 1798, to the expedition of Captain Bandin, who intended to circumnavigate the globe, I was requested by Borda, who took a warm interest in the success of my project, to examine the oscillations of a vertical needle in the magnetic meridian in different latitudes in each hemisphere, in order to determine whether the intensity of the force was the same, or whether it varied in different places. During my travels in the tropical regions of America, I paid much attention to this subject. I observed that the same needle, which in the space of ten minutes made 245 oscillations in Paris, 246 in the Havana, and 242 in Mexico, performed only 216 oscillations during the same period at St. Carlos del Rio Negro (1 degree 53' north lat. and 80 degrees 40' west long. from Paris), on the magnetic equator, i.e., the line in which the inclination =0; in Peru (7 degrees 1' south lat. and 80 degrees 40' west long. from Paris) only 211;while at Lima (12 degrees 2' south lat.) the number rose to 219. I found, in the years intervening between 1799 and 1803, that the whole force, if we assume it at 1.0000 on the magnetic equator in the Peruvian Andes, between Micuipampa and Caxamarca, may be expressed at Paris by 1.3482, in Mexico by 1.3155, in San Carlos del Rio Negro by 1.0480, and in Lima by 1.0773. When I developed this law of the variable intensity of terrestrial magnetic force, and supported it by the numerical value of observations instituted in 104 different places, in a Memoir read before the Paris Institute on the 26th Frimaire, An. XIII. (of which the mathematical portion was contributed by M. Biot), the facts were regarded as altogether new. It was only after the reading of the paper, as Biot expressly states (Lametherie, 'Journal de Physique', t. lix., p. 446, note 2) and as I have repeated in 'the Relation Historique', t. i., p. 262, note 1, that M. de Rossel communicated to Biot his oscillation experiments made six years earlier (between 1791 and 1794) in Van Diemen's Land, in Java, and in Amboyna. These experiments gave evidence of the same law of decreasing force in the Indian Archipelago. It must, I think be supposed, that this excellent man, when he wrote his work, was not aware of the regularity of the augmentation and diminution of the intensity as before the reading of my paper he never mentioned this (certainly not unimportant) physical law to any of our mutual friends, La Place, Delambre, Prony, or Biot. It was not till 1808, four years after my return from America that the observations made by M. de Rossel were published in the 'Voyage de l'Entrecasteaux', t. ii., p. 287 , 291, 321, 480, and 644. Up to the present day it is still usual, in all the tables of magnetic intensity which have been published in Germany (Hausteen, 'Magnet. der Erde', 1819, s. 71; Gauss, 'Beob. des Magnet. Vereins', 1838, s. 36-39; Erman, 'Physikal. Beob.', 1841, s. 529-579), in England (Sabine, 'Report on Magnet. Intensity', 1838, p. 43-62; 'Contributions to Terrestrial Magnetism', 1843), and in France (Becquerel, 'Traite de Electr. et de Magnet.', t. vii., p. 354-367), to reduce the oscillations observed in any part of the Earth to the standard of force which I found on the magnetic equator in Northern Peru, so that, according to the unit thus arbitrarily assumed, the intensity of the magnetic force at Paris is put down as 1.348. The observations made by Lamanon in the unfortunate expedition of La Perouse, during the stay at Teneriffe (1785), and on the voyage to Macao (1787), are still older than those of Admiral Rossel. They were sent to the Academy of Sciences, and it is known that they were in the possession of Condorcet in the July of 1787 (Becquerel, t. vii., p. 320); but, notwithstanding the most careful search, they are not now to be found. From a copy of a very important letter of Lamanon, now in the possession of Captain Duperrey, which was addressed to the then perpetual secretary of the Academy of Sciences, but was omitted in the narrative of the 'Voyage de La Perouse', it is stated "that the attractive force of the magnet is less in the tropics than when we approach the poles, and that the magnetic intensity deduced from the number of oscillations of the needle of the inclination-compass varies and increases with the latitude." If the Academicians, while they continued to expect the return of the unfortunate La Perouse, had felt themselves justified, in the course of 1787, in publishing a truth which had been independently discovered by no less than three different travelers, the theory of terrestrial magnetism would have been extended by the knowledge of a new class of observations, dating eighteen years earlier than they now do. This simple statement of facts may probably justify the observations contained in the third volume of my 'Relation Historique' p. 615): "The observations on the variation of terrestrial magnetism, to which I have devoted myself for thirty-two years, by means of instruments which admit of comparison with one another, in America, Europe, and Asia, embrace an area extending over 188 degrees of longitude, from the frontier of Chinese Dzoungarie to the west of the South Sea bathing the coasts of Mexico and Peru, and reaching from 60 degrees north lat. to 12 degrees south lat. I regard the discovery of the law of the decrement of magnetic force from the pole to the equator as the most important result of my American voyage." Although not absolutely certain, it is very probable that Condorcet read Lamanon's letter of July, 1787, at a meeting of the Paris Academy of Sciences; and such a simple reading I regard as a sufficient act of publication. ('Annuaire du Bureau des Longitudes', 1842, p. 463.) The first recognition of the law belongs, therefore, beyond all question, to the comparison of La Perouse; but, long disregarded or forgotten, the knowledge of the law that the intensity of the magnetic force of the Earth varied with the latitude, did not, I conceive, acquire an existence in science until the publication of my observations from 1798 to 1804. The object and the length of this note will not be indifferent to those who are familiar with the connection with it, and who, from their own experience, are aware that we are apt to attach some value to that which has cost us the uninterrupted labor of five years, under the pressure of a tropical climate, and of perilous mountain expeditions. p 186 The knowledge which we possess of the quantity of this increase, and of all the numerical relations of the law of intensity p 187 affecting the whole Earth, is especially due, since 1819, to the unwearied activity of Edward Sabine, who, after having observed the oscillations of the same needles at the American north pole, in Greenland, at Spitzbergen, and on the coasts of Guinea and Brazil, has continued to collect and arrange all the facts capable of explaining the direction of the isodynamic system in zones for a small part of South America. These lines are not parallel to lines of equal inclination (isoclinic line), and the intensity of the force is not at its minimum at the magnetic equator, as has been supposed, nor is it even equal at all parts of it. If we compare Erman's observations in the southern part of the Atlantic Ocean, where a faint zone (0.706) extends from Angola over the island of St. Helena to the Brazilian coast, with the most recent investigations of the celebrated navigator James Clark Ross, we shall find that on the surface of our planet the force increases almost in the relation of 1:3 toward the magnetic south pole, where Victoria Land extends from Cape Crozier toward the volcano Erebus, which has been raised to an elevation of 12,600 feet above the ice.* [footnote] *From the observations hitherto collected, it appears that the maximum of intensity for the whole surface of the Earth is 2.052, and the minimum 0.706. Both phenomena occur in the southern hemisphere; the former in 73 degrees 47' S. lat., and 169 degrees 30'E. long. from Paris, near Mount Crozier, west-northwest of the south magnetic pole, at a place where Captain James Ross found the inclination of the needle to be 87 degrees 11' (Sabine, 'Contributions to Terrestrial Magnetism', 1843, No. 5, p. 231); the latter, observed by Erman at 19 degrees 59' S. lat., and 37 degrees 24' W. long. from Paris, 320 miles eastward from the Brazilian coast of Espiritu Santo (Erman, 'Phys. Beob.', 1841, s. 570), at a point where the inclination is only 7 degrees 55'. The actual ratio of the two intensities is therefore as 1 to 2.906. It was long believed that the greatest intensity of the magnetic force was only two and a half times as great as the weakest exhibited on the Earth's surface. (Sabine, 'Report on Magnetic Intensity', p. 82.) If the intensity near the magnetic south pole p 188 be expressed by 2.052 (the unit still employed being the intensity which I discovered on the magnetic equator in Northern Peru), Sabine found it was only 1.624 at the magnetic north pole near Melville Island (70 degrees 27' north lat.), while it is 1.803 at New York, in the United States, which has almost the same latitude as Naples. The brilliant discoveries of Oersted, Arago, and Faraday have established a more intimate connection between the electric tension of the atmosphere and the magnetic tension of our terrestrial globe. While Oestred has discovered that electricity excites magnetism in the neighborhood of the conducting body, Faraday's experiments have elicited electric currents from the liberated magnetism. Magnetism is one of the manifold forms under which electricity reveals itself. The ancient vague presentiment of the identity of electric and magnetic attraction has been verified in our own times. "When electrum (amber)," says Pliny, in the spirit of the Ionic natural philosophy of Thales,* is 'animated' by friction and heat, it will attract bark and dry leaves precisely as the loadstone attracts iron." [footnote] *Of amber (succinum, glessum) Pliny observes (xxxvii., 3), "Genera ejus plura. Attritu digitorum accepta caloris anima trahunt in se paleas ac folia arida quae levia sunt, ac ut magnes lapis ferri ramenta quoque." (Plato, 'in Timaeo', p. 80. Martin, 'Etude sur le Timee', t. ii., p. 343-346. Strabo, xv., p. 703, Casaub,; Clemens Alex., 'Strom.', ii., p. 370, where, singularly enough, a difference is made between [Greek words]) When Thales, in Aristot., 'de Anima', 1, 2, and Hippias, in Diog. Laert., i., 24, describe the magnet and amber as possessing a soul, they refer only to a moving principle. The same words may be found in the literature of an Asiatic nation, and occur in a eulogium on the loadstone by the Chinese physicist Kuopho.* [footnote] *"The magnet attracts iron as amber does the smallest grain of mustard seed. It is like a breath of wind which mysteriously penetrates through both, and communicates itself with the rapidity of an arrow." These are the words of Kuopho, a Chinese panegyrist on the magnet, who wrote in the beginning of the fourth century. (Klaproth, 'Lettre a M. A. de Humboldt, sur l'Invention de la Boussole', 1834, p. 125.) I observed with astonishment, p 189 on the woody banks of the Orinoco, in the sports of the natives, that the excitement of electricity by friction was known to these savage races, who occupy the very lowest place in the scale of humanity. Children may be seen to rub the dry, flat, and shining seeds or husks of a trailing plant (probably a 'Negretia') until they are able to attract threads of cotton and pieces of bamboo cane. That which thus delights the naked copper-colored Indian is calculated to awaken in our minds a deep and earnest impression. What a chasm divides the electric pastime of these savages from the discovery of a metallic conductor discharging its electric shocks, or a pile composed of many chemically-decomposing substances, or a light-engendering magnetic apparatus! In such a chasm lie buried thousands of years that compost the history of the intellectual development of mankind! The incessant change or oscillatory motion which we discover in all magnetic phenomena, whether in those of the inclincation, declination, and intensity of these forces, according to the hours of the day and the night, and the seasons and the course of the whole year, leads us to conjecture the existence of very various and partial systems of electric currents on the surface of the Earth. Are these currents, as in Seebeck's experiments, thermo-magnetic, and excited directly from unequal distribution of heat? or should we not rather regard them as induced by the position of the Sun and by solar heat?* [footnote] *"The phenomena of periodical variations depend manifestly on the action of solar heat, operating probably through the medium of thermo-electric currents induced on the Earth's surface. Beyond this rude guess, however, nothing is as yet known of their physical cause. It is even still a matter of speculation whether the solar influence be a principal or only a subordinate cause in the phenomena of terrestrial magnetism." ('Observations to be made in the Antarctic Expedition', 1840, p. 35.) Have the rotation of the planets, and the different degrees of velocity which the individual zones acquire, according to their respective distances from the equator, any influence on the distribution of magnetism? Must we seek the seat of these currents, that is to say, of the disturbed electricity, in the atmosphere, in the regions of planetary space, or in the polarity of the Sun and Moon? Galileo, in his celebrated 'Dialogo', was inclined to ascribe the parallel direction of the axis of the Earth to a magnetic point of attraction seated in universal space. If we represent to ourselves the interior of the Earth as fused and undergoing an enormous pressure, and at a degree of temperature the amount of which we are unable to assign, p 190 we must renounce all idea of a magnetic nucleus of the Earth. All magnetism is certainly not lost until we arrive at a white heat,* and it is manifested when iron is at a dark red heat, however different, therefore, the modifications may be which are excited in substances in their molecular state, and in the coercive force depending upon that condition in experiments of this nature, there will still remain a considerable thickness of the terrestrial stratum, which might be assumed to be the seat of magnetic currents. [footnote] *Barlow, in the 'Philos. Trans.' for 1822, Pt. i., p. 117; Sir David Brewster, 'Treatise on Magnetism', p. 129. Long before the times of Gilbert and Hooke, it was taught in the Chinese work 'Ow-thea-tsou' that heat diminished the directive force of the magnetic needle. (Klaproth, 'Lettre a M. A. de Humboldt, sur l'Invention de la Boussole', p. 96.) The old explanation of the horary variations of declination by the progressive warming of the Earth in the apparent revolution of the Sun from east to west must be limited to the uppermost surface, since thermometers sunk into the Earth, which are now being accurately observed at so many different places, show how slowly the solar heat penetrates even to the inconsiderable depth of a few feet. Moreover, the thermic condition of the surface of water, by which two thirds of our planet is covered, is not favorable to such modes of explanation, when we have reference to an immediate action and not to an effect of induction in the a��rial and aqueous investment of our terrestrial globe. In the present condition of our knowledge, it is impossible to afford a satisfactory reply to all questions regarding the ultimate physical causes of these phenomena. It is only with reference to that which presents itself in the triple manifestations of the terrestrial force, as a measurable relation of space and time, and as a stable element in the midst of change, that science has recently made such brilliant advances by the aid of the determination of mean numerical values. From Toronto in Upper Canada to the Cape of Good Hope and Van Diemen's Land, from Paris to Pekin, the Earth has been covered, since 1828, with magnetic observatories,* in which every regular p 191 or irregular manifestation of the terrestrial force is detected by uninterrupted and simultaneous observations. A variation p 192 of 1/40000th of the magnetic intensity is measured, and at certain epochs, observations are made at intervals of 2 1/2 minutes, and continued for twenty-four hours consecutively. [footnote] *As the first demand for the establishment of these observatories (a net-work of stations, provided with similar instruments) proceeded from me, I did not dare to cherish the hope that I should live long enough to see the time when both hemispheres should be uniformly covered with magnetic houses under the associated activity of able physicists and astronomers. This has, however, been accomplished, and chiefly through the liberal and continued support of the Russian and British governments. [footnote continues] In the years 1806 and 1807, I and my friend and fellow-laborer, Herr Oltmanns, while at Berlin, observed the movements of the needle, especially at the times of the solstices and equinoxes, from hour to hour, and often from half hour to half hour, for five or six days and nights uninterruptedly. I had persuaded myself that continuous and uninterrupted observations of several days and nights (observatio perpetua) were preferable to the single observations of many months. The apparatus, a Prony's magnetic telescope, suspended in a glass case by a thread devoid of torsion, allowed angles of seven or eight seconds to be read off on a finely-divided scale, placed at a proper distance, and lighted at night by lamps. Magnetic perturbations (storms), which occasionally recurred at the same hour on several successive nights, led me even then to desire extremely that similar apparatus should be used to the east and west of Berlin, in order to distinguish general terrestrial phenomena from those which are mere local disturbances, depending on the inequality of heat in different parts of the Earth, or on the cloudiness of the atmosphere. My departure to Paris, and the long period of political disturbance that involved the whole of the west of Europe, prevented my wish from being then accomplished. (OErsted's great discovery (1820) of the intimate connection between electricity and magnetism again excited a general interest (which had long flagged) in the periodical variations of the electro-magnetic tension of the Earth. Arago, who many years previously had commenced in the Observatory at Paris, with a new and excellent declination instrument by Gambey, the longest uninterrupted series of horary observations which we possess in Europe, showed by a comparison with simultaneous observations of perturbation made at Kasan, what advantages might be obtained from corresponding measurements of declination. When I returned to Berlin, after an eighteen years' residence in France, I had a small magnetic house erected in the autumn of 1828, not only with the view of carrying on the work commenced in 1806, but more with the object that simultaneous observations at hours previously determined might be made at Berlin, Paris, and Freiburg, at a depth of 35 fathoms below the surface. The simultaneous occurrence of the perturbations, and the parallelism of the movements for October and December, 1829, were then graphically represented. (Pogg., 'Annalen', bd. xix., s. 357, taf. i.-iii.) An expedition into Northern Asia, undertaken in 1829, by command of the Emperor of Russia, soon gave me an opportunity of working out my plan on a larger scale. The plan was laid before a select committee of one of the Imperial Academies of Science, and, under the protection of the Director of the Mining Department, Count von Cancrin, and the excellent superintendence of Professor Kupffer, magnetic stations were appointed over the whole of Northern Asia, from Nicolajeff, in the line through Catharinenburg, Barnaul, and Nertschinsk, to Pekin. [footnote continues] The year 1832 ('Gottinger gelehrte Anzeigen', st. 206) is distinguished as the great epoch in which the profound author of a general theory of terrestrial magnetism, Friedrich Gauss, erected apparatus, constructed on a new principle, in the Gottingen Observatory. The magnetic observatory was finished in 1834, and in the same year Gauss distributed new instruments, with instructions for their use, in which the celebrated physicist, Wilhelm Weber, took extreme interest, over a large portion of Germany and Sweden, and the whole of Italy. ('Resultate der Beob. des Magnetischen Verceins in Jahr' 1338, s. 135, and Poggend., 'Annalen.' bd. xxxiii., s. 426.) In the magnetic association that was now formed with Gottingen for its center, simultaneous observations have been undertaken four times a year since 1836, and continued uninterruptedly for twenty-four hours. The periods, however, do not coincide with those of the equinoxes and solstices, which I had proposed and followed out in 1830. Up to this period, Great Britain, in possession of the most extensive commerce and the largest navy in the world, had taken no part in the movement which since 1828 had begun to yield important results for the more fixed ground-work of terrestrial magnetism. I had the good fortune, by a public appeal from Berlin which I sent in April 1836, to the Duke of Sussex, at that time President of the Royal Society (Lettre de M. de Humboldt a S. A. R. le Duc de Sussex, sur les moyens propres a perfectionner la connaissance du magnetisme terrestre par l'establissement des stations magnetiques et d'observations correspondantes), to excite a friendly interest in the undertaking which it had so long been the chief object of my wish to carry out. In my letter to the Duke of Sussex I urged the establishment of permanent stations in Canada, St. Helena, the Cape of Good Hope, the Isle of France, Ceylon, and New Holland, which five years previously I had advanced as good positions. The Royal Society appointed a joint physical and meteorological committee, which not only proposed to the government the establishment of fixed magnetic observatories in both hemispheres, but also the equipment of a naval expedition for magnetic observations in the Antarctic Seas. It is needless to proclaim the obligations of science to the great activity of Sir John Herschel, Sabine, Airy, and Lloyd, as well as the powerful support that was afforded by the British Association for the Advancement of Science at their meeting held at Newcastle in 1838. In June, 1839, the Antarctic magnetic expedition, under the command of Captain James Clark Ross, was fully arranged; and now, since its successful return, we reap the double fruits of the highly important geographical discoveries around the south pole, and a series of simultaneous observations at eight or ten magnetic stations. A great English astronomer and physicist has calculated* that the mass of observations which are in progress will accumulate in the course of three years to 1,958,000. [footnote] *See the article on 'Terrestrial Magnetism', in the 'Quarterly Review' 1840, vol. lxvi., p. 271-312. Never before has so noble and cheerful a spirit presided over the inquiry into the 'quantitative' relations of the laws of the phenomena of nature. We are, therefore, justified in hoping that these laws, when compared with those which govern the atmosphere and the remoter regions of space, may, by degrees, lead us to a more intimate acquaintance with the genetic conditions of magnetic phenomena. As yet we can only boast of having opened a greater number of paths which may possibly lead to an explanation of this subject. In the physical science of terrestrial p 193 magnetism, which must not be confounded with the purely mathematical branch of the study, those persons only will obtain perfect satisfaction who, as in the science of the meteorological processes of the atmosphere conveniently turn aside the practical bearing of all phenomena that can not be explained according to their own views. Terrestrial magnetism, and the electro-dynamic forces computed by the intellectual Ampere,* stand in simultaneous and intimate connection with the terrestrial or polar light, as well as with the internal and external heat of our planet, whose magnetic poles may be considered as the poles of cold.** [footnote] *Instead of ascribing the internal heat of the Earth to the transition of matter from a vapor-like fluid to a solid condition, which accompanies the formation of the planets, Ampere has propounded the idea, which I regard as highly improbable, that the Earth's temperature may be the consequence of the continuous chemical action of a nucleus of the metals of the earths and alkalies on the oxydizing external crust. "It can not be doubted," he observes in his masterly 'Theorie des Phenomenes Electro-dynamiques', 1826, p. 199, "that electro-magnetic currents exist in the interior of the globe, and that these currents are the cause of its temperature. They arise from the action of a central metallic nucleus, composed of the metals discovered by Sir Humphrey Davy, acting on the surrounding oxydized layer." [footnote] **The remarkable connection between the curvature of the magnetic lines and that of my isothermal lines was first detected by Sir David Brewster. See the 'Transactions of the Royal Society of Edinburgh', vol. ix., 1821, p. 318, and 'Treatise on Magnetism', 1837, p. 42, 44, 47, and 268. This distinguished physicist admist two cold poles (poles of maximum cold) in the northern hemisphere, an American one near Cape Walker (73 degrees lat., 100 degrees W. long.), and an Asiatic one (73 degrees lat., 80 degrees E. long.); whence arise, according to him, two hot and two cold meridians, i.e., meridians of greatest heat and cold. Even in the sixteenth century, Acosts ('Historia Natural de las Indias', 1589, lib. i., cap. 17), grounding his opinion on the observations of a very experienced Portuguese pilot, taught that there were four lines without declination. It would seem from the controversy of Henry Bond (the author of 'The Longitude Found', 1676) with Beckborrow, that this view in some measure influenced Halley in his theory of four magnetic poles. See my 'Examen Critique de l'Hist. de la Geographie', t. iii., p. 60. The bold conjecture hazarded one hundred and twenty-eight years since by Halley,* that the Aurora Borealis was a magnetic phenomenon, has acquired empirical certainty from Faraday's brilliant discovery of the evolution of light by magnetic forces. [footnote] *Halley, in the 'Philosophical Transactions', vol. xxix. (for 1714-1716), No. 341. The northern light is preceded by premonitory signs. Thus, in the morning before the occurrence of the phenomenon, the irregular horary course of the magnetic needle generally indicates a disturbance of the equilibrium in the distribution of p 194 terrestrial magnetism.* [footnote] *[The Aurora Borealis of October 24th, 1847, which was one of the most brilliant ever known in this country, was preceded by great magnetic disturbance. On the 22d of October the maximum of the west declination was 23 degrees 10'; on the 23d the position of the magnet was continually changing, and the extreme west declinations were between 22 degrees 44' and 23 degrees 37';on the night between the 23d and 24th of October, the changes of position were very large and very frequent, the magnet at times moving across the field so rapidly that a difficulty was experienced in following it. During the day of the 24th of October there was a constant change of position, but after midnight, when the Aurora began perceptibly to decline in brightness, the disturbance entirely ceased. The changes of position of the horizontal-force magnet were as large and as frequent as those of the declination magnet, but the vertical-force magnet was at no time so much affected as the other two instruments. See 'On the Aurora Borealis, as it was seen on Sunday evening, October 24th, 1847, at Blackheath,' by James Glaisher, Esq., of the Royal Observatory, Greenwich, in the 'London, Edinburgh, and Dublin Philos. Mag and Journal of Science for Nov.', 1847, by John H. Morgan, Esq. We must not omit to mention that magnetic disturbance is now registered by a 'photographic' process: the self-registering photographic apparatus used for this purpose in the Observatory at Greenwich was designed by Mr. Brooke, and another ingenious instrument of this kind has been invented by Mr. F. Ronalds, of the Richmond Observatory.] -- Tr. When this disturbance attains a great degree of intensity, the equilibrium of the distribution is restored by a discharge attended by a development of light "The Aurora* itself is, therefore, not to be regarded as an externally manifested cause of this disturbance, but rather as a result of telluric activity, manifested on the one side by the appearance of the light, and on the other by the vibrations of the magnetic needle." [footnote] *Dove, in Poggend., 'Annalen', bd. xx., s. 341; bd. xix., s. 388. "The declination needle acts in very nearly the same way as an atmospheric electrometer, whose divergence in like manner shows the increased tension of the electricity before this has become so great as to yield a spark." See also, the excellent observations of Professor K��wmtz, in his 'Lehrbuch der Meteorologie', bd. iii., s. 511-519, and Sir David Brewster, in his 'Treatise on Magnetism', p. 280. Regarding the magnetic properties of the galvanic flame, or luminous arch from a Bunsen's carbon and zinc battery, see Casselmann's 'Beobachtungen' (Marburg, 1844), s. 56-62. The splendid appearance of colored polar light is the act of discharge, the termination of a magnetic storm, as in an electrical storm a development of light -- the flash of lightning -- indicates the restoration of the disturbed equilibrium in the distribution of the electricity. An electric storm is generally confined to a small space beyond the limits of which the condition of the atmospheric electricity remains unchanged. A magnetic storm, on the other hand, p 193 shows its influence on the course of the needle over large portions of continents, and, as Arago first discovered far from the spot where the evolution of light was visible. It is not improbable that, as heavily-charged threatening clouds, owing to frequent transitions of the atmospheric electricity to an opposite condition, are not always discharged, accompanied by lightning, so likewise magnetic storms may occasion far-extending disturbances in the horary course of the needle, without there being any positive necessity that the equilibrium of the distribution should be restored by explosion, or by the passage of luminous effusions from one of the poles to the equator, or from pole to pole. In collecting all the individual features of the phenomenon in one general picture, we must not omit to describe the origin and course of a perfectly developed Aurora Borealis. Low down in the distant horizon, about the part of the heavens which is intersected by the magnetic meridian, the sky which was previously clear is at once overcast. A dense wall of bank of cloud seems to rise gradually higher and higher, until it attains an elevation of 8 or 10 degrees. The color of the dark segment passes into brown or violet; and stars are visible through the cloudy stratum, as when a dense smoke darkens the sky. A broad, brightly-luminous arch, first white, then yellow, encircles the dark segment; but as the brilliant arch appears subsequently to the smoky gray segment, we can not agree with Argelander in ascribing the latter to the effect of mere contrast with the bright luminous margin.* [footnote] *Argelander, in the important observations on the northern light embodied in the 'Vortr��gen gehalten in der physikalish-okonomischen Gessellschaft zu Konigsberg', bd. i., 1834, s. 257-264. The highest point of the arch of light is, according to accurate observations made on the subject,* not generally in the magnetic meridian itself, but from 5 degrees to 18 degrees toward the direction of the magnetic declination of the place.** [footnote] *For an account of the results of the observations of Lottin, Bravais, and Siljerstrom, who spent a winter at Bosekop, on the coast of Lapland (70 degrees N. lat.), and in 210 nights saw the northern lights 160 times, see the 'Comptes Rendus de l'Acad. des Sciences', t. x., p. 289, and Martins's 'Meteorologie', 1843, p. 453. See also, Argelander in the 'Vortragen geh. in der Konigsberg Gessellschaft', bd. i., s. 259. [footnote] **[Professor Challis of Cambridge, states that in the Aurora of October 24th, 1847, the streamers all converged toward a single point of the heavens, situated in or very near a vertical circle passing through the magnetic pole. Around this point a corona was formed, the rays of which diverged in all directions from the center, leaving a space free from light: its azimuth was 18 degrees 41' from south to east, and its altitude 69 degrees 54'. See Professor Challis, in the 'Athenaeum', Oct. 31, 1847.] -- Tr. In the northern latitudes, p 196 in the immediate vicinity of the magnetic pole, the smoke-like conical segment appears less dark, and sometimes is not even seen. Where the horizontal force is the weakest, the middle of the luminous arch deviates the most from the magnetic meridian. The luminous arch remains sometimes for hours together flashing and kindling in ever-varying undulations, before rays and streamers emanate from it, and shoot up to the zenith. The more intense the discharges of the northern light, the more bright is the play of colors, through all the varying gradations from violet and bluish white to green and crimson. Even in ordinary electricity excited by friction, the sparks are only colored in cases where the explosion is very violent after great tension. The magnetic columns of flame rise eithr singly from the luminous arch, blended with black rays similar to thick smoke, or simultaneously in many opposite points of the horizon, uniting together to torm a flickering sea of flame, whose brilliant beauty admits of no adequate description, as the luminous waves are every moment assuming new and varying forms. The intensity of this light is at times so great, that Lowenorn (on the 29th of June, 1786) recognized the coruscation of the polar light n bright sunshine. Motion renders the phenomenon more visible. Round the point in the vault of heaven which corresponds to the direction of the inclination of the needle, the beams unite together to form the so-called corona, the crown of the northern light, which encircles the summit of the heavenly canopy with a milder radiance and unflickering emanations of light. It is only in rare instances that a perfect crown or circle is formed, but on its completion the phenomenon has invariably reached its maximum, and the radiations become less frequent, shorter, and more colorless. The crown and the luminous arches break up, and the whole vault of heaven becomes covered with irregularly-scattered, broad, faint, almost ashy-gray luminous immovable patches, which in their turn disappear, leaving nothing but a trace of the dark, smoke-like segment on the horizon. There often remains nothing of the whole spectacle but a white, delicate cloud with feathery edges, or divided at equal distances into small roundish groups like cirio-cumuli. This connection of the polar light with the most delicate cirrous clouds deserves special attention, because it shows that the electro-magnetic evolution of light is a part of a meteorological process. Terrestrial magnetism here manifests its influence p 197 on the atmosphere and on the condensation of aqueous vapor. The fleecy clouds seen in Iceland by Thienemann, and which he considered to be the northern light, have been seen in recent times by Franklin and Richardson near the American north pole, and by Admiral Wrangel on the Siberian coast of the Polar Sea. All remarked "that the Aurora flashed forth in the most vivid beams when masses of cirrous strata were hovering in the upper regions of the air, and when these were so thin that their presence could only be recognized by the formation of a halo round the moon." These clouds sometimes range themselves, even by day in a similar manner to the beams of the Aurora, and then disturb the course of the magnetic needle in the same manner as the latter. On the morning after every distinct nocturnal Aurora, the same superimposed strata of clouds have still been observed that had previously been luminous.* [footnote] *John Franklin, 'Narrative of a Journey to the Shores of the Polar Sea, in the Years 1819-1822', p. 552 and 597; Thienemann in the 'Edinburgh Philosophical Journal', vol. xx., p. 336; Farquharson, in vol. vi., p. 392, of the same journal; Wrangel, 'Phys. Beob.', s. 59. Parry even saw the great arch of the northern light continue throughout the day. ('Journal of the Royal Institution of Great Britain', 1828, Jan., p. 429.) The apparently converging polar zones (streaks of clouds in the direction of the magnetic meridian), which constantly occupied my attention during my journeys on the elevated plateaux of Mexico and in Northern Asia, belong probably to the same group of ciurnal phenomena.* [footnote] *On my return from my American travels, I described the delicate cirro-cumulus cloud, which appears uniformly divided, as if by the action of repulsive forces, under the name of polar bands ('bandes polaires'), because their perspective point of convergence is mostly at first in the magnetic pole, so that the parallel rows of fleecy clouds follow the magnetic meridian. One peculiarity of this mysterious phenomenon is the oscillation, or occasionally the gradually progressive motion, of the point of convergence. It is usually observed that the bands are only fully developed in one region of the heavens, and they are seen to move first from south to north, and then gradually from east to west. I could not trace any connection between the advancing motion of the bands and alterations of the currents of air in the higher regions of the atmosphere. They occur when the air is extremely calm and the heavens are quite serene, and are much more common under the tropics than in the temperate and frigid zones. I have seen this phenomenon on the Andes, almost under the equator, at an elevation of 15,920 feet, and in Northern Asia, in the plains of Krasnojarski, south of Buchtarminsk, so similarly developed, that we must regard the influences producing it as very widely distributed, and as depending on general natural forces. See the important observations of Kamtz ('Vorlesungen uber Meteorologie', 1840, s. 146), and the more recent ones of Martins and Bravais ('Meteorologie', 1843, p. 117). In south polar bands, composed of very delicate clouds, observed by Arqago at Paris on the 23d of June, 1844, dark rays shot upward from an arch running east and west. We have already made mention of black rays, resembling dark smoke, as occurring in brilliant nocturnal northern lights. p 198 Southern lights have often been seen in England by the intelligent and indefatigable observer Dalton and northern lights have been observed in the southern hemisphere as far as 45 degrees latitude (as on the 14th of January, 1831). On occasions that are by no means of rare occurrence, the equilibrium at both poles has been simultaneously disturbed. I have discovered with certainty that northern polar lights have been seen within the tropics in Mexico and Peru. We must distinguish between the sphere of simultaneous visibility of the phenomenon and the zones of the Earth where it is seen almost nightly. Every observer no doubt sees a separate Aurora of his own, as he sees a separate rainbow. A great portion of the Earth simultaneously engenders these phenomena of emanations of light. Many nights may be instanced in which the phenomenon has been simultaneously observed in England and in Pennsylvania, in Rome and in Pekin. When it is stated that Auroras diminish with the decrease of latitude, the latitude must be understood to be magnetic, and as measured by its distance from the magnetic pole. In Iceland, in Greenland, Newfoundland, on the shores of the Slave Lake, and at Fort Enterprise in Northern Canada, these lights appear almost every night at certain seasons of the year, celebrating with their flashing beams, according to the mode of expression common to the inhabitants of the Shetland Isles, "a merry dance in heaven."* [footnote] *The northrn lights are called by the Shetland Islanders "the merry dancers." (Kendal, in the 'Quarterly Journal of Science', new series, vol. iv., p. 395.) While the Aurora is a phenomenon of rare occurrence in Italy, it is frequently seen in the latitude of Philadelphia (39 degrees 57'), owing to the southern position of the American nagnetic pole. In the districts which are remarkable, in the New Continent and the Siberian coasts, for the frequent occurrence of this phenomenon, there are special regions or zones of longitude in which the polar light is particularly bright and brilliant.* [footnote] *See Muncke's excellent work in the new edition of Gehler's 'Physik Worterbuch', bd. vii., i., s 113-268, and especially s. 158. The existence p 199 of local influences can not, therefore, be denied in these cases. Wrangel saw the brilliancy diminish as he left the shores of the Polar Sea, about Mischne-Kolymsk. The observations made in the North Polar expedition appear to prove that in the immediate vicinity of the magnetic pole the development of light is not in the least degree more intense or frequent than at some distance from it. The knowledge which we at present possess of the altitude of the polar light is based on measurements which from their nature, the constant oscillation of the phenomenon of light, and the consequent uncertainty of the angle of parallax, are not deserving of much confidence. The results obtained, setting aside the older data, fluctuate between several miles and an elevation of 3000 or 4000 feet; and, in all probability, the northern lights at different times occur at very different elevations.* [footnote] *Farquharson in the 'Edinburgh Philos. Journal', vol. xvi., p. 304; 'Philos. Transact.' for 1829, p. 113. [The height of the bow of light of the Aurora seen at the Cambridge Observatory, March 19, 1847, was determined by Professors Challis, of Cambridge, and Chevallier, of Durham, to be 177 miles above the surface of the Earth. See the notice of this meteor in 'An Account of the Aurora Borealis of Oct. 24, 1847', by John H. Morgan, Esq., 1848.] -- Tr.] The most recent observers are disposed to place the phenomenon in the region of clouds, and not on the confines of the atmosphere; and they even believe that the rays of the Aurora may be affected by winds and currents of air, if the phenomenon of light, by which alone the existence of an electro-magnetic current is appreciable, be actually connected with matrial groups of vesicles of vapor in motion, or, more correctly speaking, if light penetrate them, passing from one vesicle to another. Franklin saw near Great Bear Lake a beaming northern light, the lower side of which he thought illuminated a stratum of clouds, while, at a distance of only eighteen geographical miles, Kendal, who was on watch throughout the whole night, and never lost sight of the sky, perceived no phenomenon of light. The assertion, so frequently maintained of late, that the rays of the Aurora have been seen to shoot down to the ground between the spectator and some neighboring hill, is open to the charge of optical delusion, as in the cases of strokes of lightning or of the fall of fire-balls. Whether the magnetic storms, whose local character we have illustrated by such remarkable examples, share noise as well as light in common with electric storms, is a question p 200 that has become difficult to answer, since implicit confidence is no longr yielded to the relations of Greenland whale-fishers and Siberian fox-hunters. Northern lights appear to have become less noisy since their occurrences have been more accurately recorded. Parry, Franklin, and Richardson, near the north pole; Thienemann in Iceland; Gieseke in Greenland; Lotur, and Bravais, near the North Cape; Wrangel and Anjou, on the coast of the Polar Sea, have together seen the Aurora thousands of times, but never heard any sound attending the phenomenon. If this negative testimony should not be deemed equivalent to the positive counter-evidence of Hearne on the mouth of the Copper River and of Henderson in Iceland, it must be remembered that, although Hood heard a noise as of quickly-moved musket-balls and a slight cracking sound during an Aurora, he also noticed the same noise on the following day, when there was no northern light to be seen; and it must not be forgotten that Wrangel and Gieseke were fully convinced that the sound they had heard was to be ascribed to the contraction of the ice and the crust of the snow on the sudden cooling of the atmosphere. The belief in a crackling sound has arisen, not among the people generally, but rather among learned travelers, because in earlier times the northern light was declared to be an effect of atmospheric electricity, on account of the luminous manifestation of the electricity in rarefied space, and the observers found it easy to hear what they wished to hear. Recent experiments with very sensitive electrometers have hitherto, contrary to the expectation generally entertained, yielded only negative results. The condition of the electricity in the atmosphere* p 291 is not found to be changed during the most intense Aurora; but, on the other hand, the three expressions of the power of terrestrial magnetism, declination, inclination and intensity, are all affected by polar light, so that in the same night, and at different periods of the magnetic development, the same end of the needle is both attracted and repelled. [footnote] *[Mr. James Glaisher, of the Royal Observatory, Greenwich, in his interesting 'Remarks on the Weather during the Quarter ending December 31st, 1847', says, "It is a fact well worthy of notice, that from the beginning of this quarter till the 29th of December, the electricity of the atmosphere was almost always in a neutral state, so that no signs of electricity were shown for several days together by any of the electrical instruments." During this period there were 'eight' exhibitions of the Aurora Borealis, of which one was the peculiarly bright display of the Aurora Borealis, of which one was the peculiarly bright display of the meteor on the 24th of October. These frequent exhibitions of brilliant Aurorae seem to depend upon many remarkable meteorological relations, for we find, according to Mr. Glaisher's statement in the paper to which we have already alluded, that the previous fifty years afford no parallel season to the closing one of 1847. The mean temperature of evaporation and of the dew point, the mean elastic force of vapor, the mean reading of the barometer, and the mean daily range of the readings of the thermometers in air, were all greater at Greenwich during that season of 1847 than the average range of many preceding years.] -- Tr. The assertion made by Parry, on the strength of the data yielded by his observations in the neighborhood of the magnetic pole at Melville Island, that the Aurora did not disturb, but rather exercised a calming influence on the magnetic needle, has been satisfactorily refuted by Parry's own more exact researches,* detailed in his journal, and by the admirable observations of Richardson, Hood, and Franklin in Northern Canada, and lastly by Bravais and Lottin in Lapland. [footnote] *Kamtz, 'Lehrbuch der Meteorologie', bd. iii., s. 498 and 501. The process of the Aurora is, as has already been observed, the restoration of a disturbed condition of equilibrium. The effect on the needle is different according to the degree of intensity of the explosion. It was only unappreciable at the gloomy winter station of Bosekop when the phenomenon of light was very faint and aptly compared to the flame which rises in the closed circuit of a voltaic pile between two points of carbon at a considerable distance apart, or, according to Fizeau, to the flame rising between a silver and a carbon point, and attracted or repelled by the magnet. This analogy certainly sets aside the necessity of assuming the existence of metallic vapors in the atmosphere, which some celebrated physicists have regarded as the substratum of the northern light. When we apply the indefinite term 'polar light' to the luminous phenomenon which we ascribe to a galvanic current, that is to say, to the motion of electricity in a closed circuit, we merely indicate the local direction in which the evolution of light is most frequently, although by no means invariably, seen. This phenomenon derives the greater part of its importance from the fact that the Earth becomes 'self-luminous', and that as a planet, besides the light which it receives from the central body, the Sun, it shows itself capable in itself of developing light. The intensity of the terrestrial light, or, rather the luminosity which is diffused, exceeds, in cases of the brightest colored radiation toward the zenith, the light of the Moon in its first quarter. Occasionally, as on the 7th of January, 1831, printed characters could be read without difficulty. This almost uninterrupted development of light p 202 in the Earth leads us by analogy to the remarkable process exhibited in Venus. The portion of this planet which is not illumined by the Sun often shines with a phosphorescent light of its own. It is not improbable that the Moon, Jupiter, and the comets shine with an independent light, besides the reflected solar light visible through the polariscope. Without speaking of the problematical but yet ordinary mode in which the sky is illuminated, when a low cloud may be seen to shine with an uninterrupted flickering light for many minutes together, we still meet with other instances of terrestrial development of light in our atmosphere. In this category we may reckon the celebrated luminous mists seen in 1783 and 1831; the steady luminous appearance exhibited without any flickeriing in great clouds observed by Rozier and Beccaria; and lastly, as Arago* well remarks, the faint diffused light which guides the steps of the traveler in cloudy, starless, and moonless nights in autumn and winter, even when there is no snow on the ground. [footnote] *Arago, on the dry fogs of 1783 and 1831, which illuminated the night, in the 'Annuaire du Bureau des Longitudes', 1832, p. 246 and 250; and, regarding extraordinary luminous appearances in clouds without storms, see 'Notices sur la Tonnerre', in the 'Annuaire pour l'an. 1838', p. 279-285. As in polar light or the electro-magnetic storm, a current of brilliant and often colored light streams through the atmosphere in high latitudes, so also in the torrid zones between the tropics, the ocean simultaneously develops light over a space of many thousand square miles. Here the magical effect of light is owing to the forces of organic nature. Foaming with light, the eddying waves flash in phosphorescent sparks over the wide expanse of waters, where every scintillation is the vital manifestation of an invisible animal world. So varied are the sources of terrestrial light! Must we still suppose this light to be latent, and combined in vapors, in order to explain 'Moser's images produced at a distance' -- a discovery in which reality has hitherto manifested itself like a mere phantom of the imagination. As the internal heat of our planet is connected on the one hand with the generation of electro-magnetic currents and the process of terrestrial light (a consequence of the magnetic storm), it, on the other hand, discloses to us the chief source of geognostic phenomena. We shall consider these in their connection with and their transition from merely dynamic disturbances, from the elevation of whole continents and mountain chains to the development and effusion of gaseous and p 203 liquid fluids, of hot mud, and of those heated and molten earths which become solidified into crystalline mineral masses. Modern geognosy, the mineral portion of terrestrial physics, has made no slight advance in having investigated this connection of phenomena. This investigation has led us away from the delusive hypothesis, by which it was customary formerly to endeavor to explain, individually every expression of force in the terrestrial globe: it shows us the connection of the occurrence of heterogeneous substances with that which only appertains to changes in space (disturbances or elevations), and groups together phenomena which at first sight appeared most heterogeneous, as thermal springs, effusion of carbonic acid and sulphurous vapor, innocuous salses (mud eruptions), and the dreadful devastation of volcanic mountains.* [footnote] *[See Mantell's 'Wonders of Geology', 1848, vol. i., p. 34, 36, 105; also Lyell's 'Principles of Geology', vol. ii., and Daubeney 'On Volcanoes', 2d ed., 1848, Part ii., ch. xxxii., xxxiii.] -- Tr. In a general view of nature, all these phenomena are fused together in one sole idea of the reaction of the interior of a planet on its external surface. We thus recognize in the depths of the earth, and in the increase of temperature with the increase of depth from the surface, not only the germ of disturbing movements, but also of the gradual elevation of whole continents (as mountain chains on long fissures), of volcanic eruptions, and of the manifold production of mountains and mineral masses. The influence of this reaction of the interior on the exterior is not, however, limited to inorganic nature alone. It is highly probable that, in an earlier world, more powerful emanations of carbonic acid gas, blended with the atmosphere, must have increased the assimilation of carbon in vegetables, and that an inexhaustible supply of combustible matter (lignites and carboniferous formations) must have been thus buried in the upper strata of the earth by the revolutions attending the destruction of vast tracts of forest. We likewise perceive that the destiny of mankind is in part dependent on the formation of the external surface of the earth, the direction of mountain tracts and high lands, and on the distribution of elevated continents. It is thus granted to the inquiring mind to pass from link to link along the chain of phenomena until it reaches the period when, in the solidifying process of our planet, and in its first transition from the gaseous form to the agglomeration of matter, that portion of the inner heat of the Earth was developed, which does not belong to the action of the Sun. This material taken from pages 204-248 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 204 In order to give a general delineation of the causal connection of geognostical phenomena, we will begin with those whose chief characteristic is dynamic, consisting in motion and in change in space. Earthquakes manifest themselves by quick and successive vertical, or horizontal, or rotatory vibrations.* [footnote] *[See Daubeney 'On Volcanoes', 2d ed., 1848, p. 509.] -- Tr. In the very considerable number of earthquakes which I have experienced in both hemispheres, alike on land and at sea, the two first-named kinds of motion have often appeared to me to occur simultaneously. The mine-like explosiion -- the vertical action from below upward -- was most strikingly manifested in the overthrow of the town of Riobamba in 1797, when the bodies of many of the inhabitants were found to have been hurled to Cullea, a hill several hundred feet in neight, and on the opposite side of the River Lican. The propagation is most generally effected by undulations in a linear direction,* with a velocity of from twenty to twenty-eight miles in a minute, but partly in circles of commotion or large ellipses, in which the vibrations are propagated with decreasing intensity from a center toward the circumference. [footnote] *[On the linear direction of earthquakes, see Daubeney 'On Volcanoes', p. 515.] -- Tr. There are districts exposed to the action of two intersecting circles of commotion. In Northern Asia, where the Father of History,* and subsequently Theophylactus Simocatta,** described the districts of Scythia as free from earthquakes, I have observed the metalliferous portion of the Altai Mountains under the influence of a two-fold focus of commotion, the Lake of Baikal, and the volcano of the Celestial Mountain (Thianschan).*** [footnote] *Herod, iv., 28. The prostration of the colossal statue of Memnon, which has been again restored (Letronne, 'La Statue Vocale de Memnon', 1835, p. 25, 26), presents a fact in opposition to the ancient prejudice that Egypt is free from earthquakes (Pliny, ii., 80); but the valley of the Nile does lie external to the circle of commotion of Byzantium, the Archipelago, and Syria (Ideler ad Aristot., 'Meteor.', p. 584). [footnote] **Saint-Martin, in the learned notes to Lebeau, 'Hist. du Bas Empire', t. ix., p. 401. [footnote] ***Humboldt, 'Asie Centrale', t. ii., p. 110-118. In regard to the difference between agitation of the surface and of the strata lying beneath it, see Gay-Lussac, in the 'Annales de Chimie et de Physique', t. xxii., p. 429. When the circles of commotion intersect one another -- when, for instance, an elevated plain lies between two volcanoes simultaneously in a state of eruption, several wave-systems may exist together, as in fluids, and not mutually disturb one another. We may even suppose 'interference' p 205 to exist here, as in the intersecting waves of sound. The extent of the propagated waves of commotion will be increased on the upper surface of the earth, according to the general law of mechanics, by which, on the transmission of motion in elastic bodies, the stratum lying free on the one side endeavors to separate itself from the other strata. Waves of commotion have been investigated by means of the pendulum and the seismometer* with tolerable accuracy in respect to their direction and total intensity, but by no means with reference to the internal nature of their alternations and their periodic intumescence. [footnote] *[This instrument, in its simplest form, consists merely of a basin filled with some viscid liquid, which, on the occurrence of a shock of an earthquake of sufficient force to disturb the equilibrium of the building in which it is placed, is tilted on one side, and the liquid made to rise in the same direction, thus showing by its height the degree of the disturbance. Professor J. Forbes has invented an instrument of this nature, although on a greatly improved plan. It consists of a vertical metal rod, having a ball of lead movable upon it. It is supported upon a cylindrical steel wire, which may be compressed at pleasure by means of a screw. A lateral movement, such as that of an earthquake, which carries forward the base of the instrument, can only act upon the ball through the medium of the elasticity of the wire, and the direction of the displacement will be indicated by the plane of vibration of the pendulum. A self-registering apparatus is attached to the machine. See Professor J. Forbes's account of his invention in 'Edinb. Phil. Trans.', vol. xv., Part i.] -- Tr. In the city of Quito, which lies at the foot of a still active volcano (the Rucu Pichincha), and at an elevation of 9540 feet above the level of the sea, which has beautiful cupolas, high vaulted churches, and massive edifices of several stories, I have often been astonished that the violence of the nocturnal earthquakes so seldom causes fissures in the walls, while in the Peruvian plains oscillations apparently much less intense injure low reed cottages. The natives, who have experienced many hundred earthquakes, believe that the difference depends less upon the length or shortness of the waves, and the slowness or rapidity of the horizontal vibrations.* than on the uniformity of the motion in opposite directions. [footnote] * "Tutissimum est cum vibrat crispante Aedificiorum crepitu; et cum intumescit assurgens alternoque motu residet, innoxium et cum concurrentia tecta contrario ictu arietant; quoniam alter motus alteri renititur. Undantis inclinatio et fluctus more quaedam volutatio investa est, aut cum in unam partem totus se motus impellitae -- Plin., ii., 82. The circling rotatory commotions are the most uncommon, but, at the same time, the most dangerous. Walls were observed to be twisted, but not thrown down; rows of trees turned from their previous parallel direction; p 206 and fields covered with different kinds of plants found to be displaced in the great earthquake of Riobamba, in the province of Quito, on the 4th of February, 1797, and in that of Calabria, between the 5th of February and the 28th of March, 1782. The phenomenon of the inversion or displacement of fields and pieces of land, by which one is made to occupy the place of another, is connected with a translatory motion or penetration of separate terrestrial strata. When I made the plan of the ruined town of Riobamba, one particular spot was pointed out to me, where all the furniture of one house had been found under the ruins of another. The loose earth had evidently moved like a fluid in currents, which must be assumed to have been directed first downward, then horizontally, and lastly upward. It was found necessary to appeal to the 'Audiencia', or Council of Justice, to decide upon the contentions that arose regarding the proprietorship of objects that had been removed to a distance of many hundred roises. In countries where earthquakes are comparatively of much less frequent occurrence (as for instance, in Southern Europe), a very general belief prevails, although unsupported by the authority of inductive reasoning,* that a calm, an oppressive p 207 heat and a misty horizon, are always the forerunners of this phenomenon. [footnote] *Even in Italy they have begun to observe that earthquakes are unconnected with the state of the weather, that is to say, with the appearance of the heavens immediately before the shock. The numerical results of Friedrich Hoffmann ('Hinterlassene Werke', bd. ii., 366-376) exactly correspond with the experience of the Abbate Scina of Palermo. I have myself several times observed reddish clouds on the day of an earthquake, and shortly before it on the 4th of November, 1799, I experienced two sharp shocks at the moment of a loud clap of thunder. ('Relat. Hist.', liv. iv., chap. 10.) The Turin physicist, Vassalli Eaudi, observed Volta's electrometer to be strongly agitated during the protracted earthquake of Pignerol, which lasted from the 2d of April to the 17th of May, 1808; 'Journal de Physique', t. lxvii., p. 291. But these indications presented by clouds, by modifications of atmospheric electricity, or by calms, can not be regarded as 'generally' or 'necessarily' connected with earthquakes, since in Quito, Peru, and Chili, as well as in Canada and Italy, many earthquakes are observed along with the purest and clearest skies, and with the freshest land and sea breezes. But if no meteorological phenomenon indicates the coming earthquake either on the morning of the shock or a few days previously, the influence of certain periods of the year (the vernal and autumnal equinoxes), the commencement of the rainy season in the tropics after long drought, and the change of the monsoons (according to general belief), can not be overlooked, even though the genetic connection of meteorological processes with those going on in the interior of our globe is still enveloped in obscurity. Numerical inquiries on the distribution of earthquakes throughout the course of the year, such as those of Von Hoff, Peter Merian, and Friedrich Hoffmann, bear testimony to their frequency at the periods of equinoxes. It is singular that Pliny, at the end of his fanciful theory of earthquakes, names the entire frightful phenomenon a subterranean storm; not so much in consequence of the rolling sound which frequently accompanies the shock, as because the elastic forces, concussive by their tension, accumulate in the interior of the earth when they are absent in the atmosphere! "Ventos in causa esse non dubium reor. Neque enim unquam intemiscunt terre, nisi sopito mari, coeloque adeo tranquillo, ut volatus avium non pendeant, subtracto omni spiritu qui vehit; nec unquam nisi post ventos conditos, scilicet in venas et cavernas ejus occulto afflatu. Neque aliad est in terra tremor, quam in nube toonitruum; nec hiatus aliud quam cum fulmen erumpit, incluso spiritu luctante et ad libertatem exire nitente." (Plin., ii., 79.) The germs of almost every thing that has been observed of imagined on the causes of earthquakes, up to the present day, may be found in Seneca, 'Nat. Quaest.', vi., 4-31. The fallacy of this popular opinion is not only refuted by my own experience, but likewise by the observations of all those who have lived many years in districts where, as in Cumana, Quito, Peru, and Chili, the earth is frequently and violently agitated. I have felt earthquakes in clear air and a fresh east wind, as well as in rain and thunder storms. The regularity of the horary changes in the declination of the magnetic needle and in the atmospheric pressure remained undisturbed between the tropics on the days when earthquakes occurred.* [footnote] *I have given proof that the course of the horary variations of the barometer is not affected before or after earthquakes, in my 'Relat. Hist.', t. i., p. 311 and 513. These facts agree with the observations made by Adolph Erman (in the temperate zone, on the 8th of March, 1829) on the occasion of an earthquake at Irkutsk, near the Lake of Baikal. During the violent earthquake of Cumana, on the 4th of November, 1799, I found the declination and the intensity of the magnetic force alike unchanged, but, to my surprise, the inclination of the needle was diminished about 48 degrees.* [footnonte] *Humboldt, 'Relat. Hist.', t. i., p. 515-517. There was no ground to suspect an error in the calculation, and yet, in the many other earthquakes which I have experienced on the elevated plateaux of Quito and Lima, the inclination as well as the other elements of terrestrial magnetism remained always unchanged. Although, in general, the processes at work within the interior of the earth may not be announced by any meteorological phenomena or any special appearance of the sky, it is, on the contrary, not improbable, as we shall soon see, that in cases of violent earthquakes some effect may be imparted to the atmosphere, in consequence of which they can not always act in a purely dynamic manner. p 208 During the long-continued trembling of the ground in the Piedmontese valleys of Pelis and Clusson, the greatest changes in the electric tension of the atmosphere were observed while the sky was cloudless. The intensity of the hollow noise which generally accompanies an earthquake does not increase in the same degree as the force of the oscillations. I have ascertained with certainty that the great shock of the earthquake of Riobamba (4th Feb., 1797) -- one of the most fearful phenomena recorded in the physical history of our planet -- was not accompanied by any noise whatever. The tremendous noise ('el gram ruido') which was heard below the soil of the cities of Quito and Ibarra, but not at Tacunga and Hambato, nearer the center of the motion, occurred between eighteen and twenty minutes 'after' the actual catastrophe. In the celebrated earthquake of Lima and Callao (28th of October, 1746), a noise resembling a subterranean thunder-clap was heard at Truxillo a quarter of an hour after the shock, and unaccompanied by any trembling of the ground. In like manner, long after the great earthquake in New Granada, on the 16th of November, 1827, described by Boussingault, subterranean detonations were heard in the whole valley of Cauca during twenty or thirty seconds, unattended by motion. The nature of the noise varies also very much, being either rolling, or rustling, or clanking like chains when moved, or like near thunder, as, for instance, in the city of Quito; or, lastly, clear and ringing, as if obsidian or some other vitrified masses were struck in subterranean cavities. As solid bodies are excellent conductors of sound, which is propagated in burned clay, for instance, ten or twelve times quicker than in the air, the subterranean noise may be heard at a great distance from the place where it has originated. In Caracas, in the grassy plains of Calabozo, and on the banks of the Rio Apure, which falls into the Orinoco, a tremendously loud noise, resembling thunder, was heard, unaccompanied by an earthquake, over a district of land 9200 square miles in extent, on the 30th of April, 1812, while at a distance of 632 miles to the north-east, the volcano of St. Vincent, in the small Antilles, poured forth a copious stream of lava. With respect to distance, this was as if an eruption of Vesuvius had been heard in the north of France. In the year 1744, on the great eruption of the volcano of Cotopaxi, subterranean noises, resembling the discharge of cannon, were heard in Honda, on the Magdalena River. The crater of Cotopaxi lies not only 18,000 feet higher than Honda, but these two points are separated by the colossal p 209 mountain chain of Quito, Pasto, and Popayan, no less than by numerous valleys and clefts, and they are 436 miles apart. The sound was certainly not propagated through the air, but through the earth, and at a great depth. During the violent earthquake of New Granada, in February, 1835, subterranean thunder was heard simultaneously at Popayan, Bogota, Santa Marta, and Caracas (where it continued for seven hours without any movement of the ground), in Haiti, Jamaica, and on the Lake of Nicaragua. These phenomena of sound, when unattended by any perceptible shocks, produce a peculiarly deep impression even on persons who have lived in countries where the earth has been frequently exposed to shocks. A striking and unparalleled instance of uninterrupted subterranean noise, unaccompanied by any trace of an earthquake, is the phenomenon known in the Mexican elevated plateaux by the name of the "roaring and the subterranean thunder) ('bramidos y truenos subterraneos') of Guanaxuato.* [footnote] *On the 'bramidos' of Guanaxuato, see my 'Essai Polit. sur la Nouv. Espagne', t. i., p. 303. The subterranean noise, unaccompanied with any appreciable shock, in the deep mines and on the surface (the town of Guanaxuata lies 6830 feet above the level of the sea), was not heard in the neighboring elevated plains, but only in the mountainous parts of the Sierra, from the Cuesta de los Aguilares, near Marfil, to the north of Santa Rosa. There were individual parts of the Sierra 24-28 miles northwest of Guanaxuata, to the other side of Chichimequillo, near the boiling spring of San Jose de Comgngillas, to which the waves of sound did not extend. Extremely stringent measures were adopted by the magistrates of the large mountain towns on the 14th of January 1784, when the terror produced by these subterranean thunders was at its height. "The flight of a wealthy family shall be punished with a fine of 1000 piasters, and that of a poor family with two months' imprisonment. The militia shall bring back the fugitives." One of the most remarkable points about the whole affair is the opinion which the magistrates (el cabildo) cherished of their own superior knowledge. In one of their 'proclamas', I find the expression, "The magistrates, in their wisdom (en su sabiduria), will at once know when there is actual danger, and will give orders for flight; for the present, let processions be instituted." The terror excited by the tremor gave rise to a famine, since it prevented the importation of corn from the table-lands, where it abounded. The ancients were also aware that noises sometimes existed without earthquakes. -- Aristot., 'Meteor.', ii., p. 802; Plin., ii., 80. The singular noise that was heard from March, 1822, to September, 1824, in the Dalmatian island Meleda (sixteen miles from Ragusa) and on which Partsch has thrown much light, was occasionally accompanied by shocks. This celebrated and rich mountain city lies far removed from any active volcano. The noise began about midnight on the 9th of January, 1784, and continued for a month. I have been enabled to give a circumstantial p 210 description of it from the report of many witnesses, and from the documents of the municipality, of which I was allowed to make use. From the 13th to the 16th of January, it seemed to the inhabitants as if heavy clouds lay beneath their feet, from which issued alternate slow rolliing sounds and short, quick claps of thunder. The noise abated as gradually as it had begun. It was limited to a small space, and was not heard in a basaltic district at the distance of a few miles. Almost all the inhabitants, in terror, left the city, in which large masses of silver ingots were stored; but the most courageous, and those more accustomed to subterranean thunder, soon returned, in order to drive off the bands of robbers who had attempted to possess themselves of the treasures of the city. Neither on the surface of the earth, nor in mines 1600 feet in depth, was the slightest shock to be perceived. No similar noise had ever before been heard on the elevated tableland of Mexico, nor has this terrific phenomenon since occurred there. Thus clefts are opened or closed in the interior of the earth, by which waves of sound penetrate to us or are impeded in their propagation. The activity of an igneous mountain, however terrific and picturesque the spectacle may be which it presents to our contemplation, is always limited to a very small space. It is far otherwise with earthquakes, which although scarcely perceptible to the eye, nevertheless simultaneously propagate their waves to a distance of many thousand miles. The great earthquake which destroyed the city of Lisbon on the 1st of November, 1755, and whose effects were so admirably investigated by the distinguished philosopher Emmanuel Kant, was felt in the Alps, on the coast of Sweden, in the Antilles, Antigua, Barbadoes, and Martinique; in the great Canadian Lakes, in Thuringia, in the flat country of Northern Germany, and in the small inland lakes on the shores of the Baltic.* [footnote] *[It has been computed that the shock of this earthquake pervaded an area of 700,000 miles, or the twelfth part of the circumference of the globe. This dreadful shock lasted only five minutes: it happened about nine o'clock in the morning of the Feast of all Saints, whien almost the whole population was within the churches, owing to which circumstance no less than 30,000 persons perished by the fall of these edifices. See Daubeney 'On Volcanoes', p. 514-517.] -- Tr. Remote springs were interrupted in their flow, a phenomenon attending earthquakes which had been noticed among the ancients by Demetrius the Callatian. The hot springs of Toplitz dried up, and returned, inundating every thing around, and having their waters colored with iron ocher. In Cadiz p 211 the sea rose to an elevation of sixty-four feet, while in the Antilles, where the tide usually rises only from twenty-six to twenty-eight inches, it suddenly rose above twenty feet, the water being of an inky blackness. It has been computed that on the 1st of November, 1755, a portion of the Earth's surface four times greater than that of Europe, was simultaneously shaken. As yet there is no manifestation of force known to us, including even the murderous inventions of our own race, by which a greater number of people have been killed in the short space of a few minutes: sixty thousand were destroyed in Sicily in 1693, from thirty to forty thousand in the earthquake of Riobamba in 1797, and probably five times as many in Asia Minor and Syria, under Tiberius and Justinian the elder, about the years 19 and 526. There are instances in which the earth has been shaken for many successive days in the chain of the Andes in South America, but I am only acquainted with the following cases in which shocks that have been felt almost every hour for months together have occurred far from any volcano, as, for instance, on the eastern declivity of the Alpine chain of Mount Cenis, at Fenestrelles and Pignerol, from April, 1808; between New Madrid and Little Prairie,* north of Cincinnati in the United States of America, in December, 1811, as well as through the whole winter of 1812; and in the Pachalik of Aleppo, in the months of August and September, 1822. [footnote] *Drake, 'Nat. and Statist. View of Cincinnati', p. 232-238; Mitchell, in the 'Transactions of the Lit. and Philos. Soc. of New York', vol. i., p. 281-308. In the Piedmonese county of Pignerol, glasses of water, filled to the very brim, exhibited for hours a continuous motion. As the mass of the people are seldom able to rise to general views, and are consequently always disposed to ascribe great phenomena to local telluric and atmospheric processes, wherever the shaking of the earth is continued for a long time, fears of the eruption of a new volcano are awakened. In some few cases, this apprehension has certainly proved to be well grounded, as, for instance, in the sudden elevation of volcanic islands, and as we see in the elevation of the volcano of Jorullo, a mountain elevated 1684 feet above the ancient level of the neighboring plain, on the 29th of September 1759, after ninety days of earthquake and subterranean thunder. If we could obtain information regarding the daily condition of all the earth's surface, we should probably discover that the earth is almost always undergoing shocks at some point of its superficies, and is continually influenced by the reaction p 212 of the interior on the exterior. The frequency and general prevalence of a phenomenon which is probably dependent on the raised temperature of the deepest molten strata explain its independence of the nature of the mineral masses in which it manifests itself. Earthquakes have even been felt in the loose alluvial strata of Holland, as in the neighborhood of Middleburg and vliessingen on the 23d of February, 1828. Granite and mica slate are shaken as well as limestone and sandstone, or as trachyte and amygdaloid. It is not, therefore, the chemical nature of the constituents, but rather the mechanical structure of the rocks, which modifies the propagation of the motion, the wave of commotion. Where this wave proceeds along a coast, or at the foot and in the direction of a mountain chain, interruptions at certain points have sometimes been remarked, which manifested themselves during the course of many centuries. The undulation advances in the depths below, but is never felt at the same points on the surface. The Peruvians* say of these unmoved upper strata that "they form a bridge." [footnote] *In Spanish they say, 'rocas que hacen puente'. With this phenomenon of non-propagation through superior strata is connected the remarkable fact that in the beginning of this century shocks were felt in the deep silver mines at Marienberg, in the Saxony mining district, while not the slightest trace was perceptible at the surface. The miners ascended in a state of alarm. Conversely, the workmen in the mines of Falun and Persberg felt nothing of the shocks which in November, 1823, spread dismay among the inhabitants above ground. As the mountain chains appear to be raised on fissures, the walls of the cavities may perhaps favor the direction of undulations parallel to them; occasionally, however, the waves of commotion intersect several chains almost perpenducularly. Thus we see them simultaneously breaking through the littoral chain of Venezuela and the Sierra Parime. In Asia, shocks of earthquakes have been propagated from Lahore and from the foot of the Himalaya (22d of January, 1832) transversely across the chain of the Hindoo Chou to Badakschan, the upper Oxus, and even to Bokhara.* [footnote] *Sir Alex. Burnes, 'Travels in Bokhara', vol. i., p. 18; and Wathen, 'Mem. on the Usbek State', in the 'Journal of the Asiatic Society of Bengal', vol. iii., p. 337. The circles of commotion unfortunately expand occasionally in consequence of a single and usually violent earthquake. It is only since the destruction of Cumana, on the 14th of December, 1797, that shocks on the southern coast have been felt in the mica slate rocks of the peninsula of Maniquarez, situated opposite to the chalk hills of the main land. The advance p 213 from south to north was very striking in the almost uninterrupted undulations of the soil in the alluvial valleys of the Mississippi, the Arkansas, and the Ohio, from 1811 to 1813. It seemed here as if subterranean obstacles were gradually overcome, and that the way being once opened, the undulatory movement could be freely propagated. Although earthquakes appear at first sight to be simply dynamic phenomena of motion, we yet discover, from well-attested facts, that they are not only able to elevate a whole district above its ancient level (as for instance, the Ulla Bund, Delta of the Indus, or the coast of Chili, in November, 1822), but we also find that various substances have been ejected during the earthquake, as hot water at Catania in 1818; hot steam at New Madrid, in the Valley of the Mississippi, in 1812; irrespirable gases, 'Mofettes', which injured the flocks grazing in the chain of the Andes; mud, black smoke, and even flames, at Messina in 1781, and at Cumana on the 14th of November, 1797. During the great earthquake of Lisbon, on the 1st of November, 1755, flames and columns of smoke were seen to rise from a newly-formed fissure in the rock of Alvidras, near the city. The smoke in this case became more dense as the subterranean noise increased in intensity.* [footnote] * 'Philos. Transaci.', vol. xlix. p. 414. At the destruction of Riobamba, in the year 1797, when the shocks were not attended by any outbreak of the neighboring volcano, a singular mass called the 'Moya' was uplifted from the earth in numerous continuous conical elevations, the whole being composed of carbon, crystals of augite, and the silicious shields of infusoria. The eruption of carbonic acid gas from fissures in the Valley of the Magdalene, during the earthquake of New Granada, on the 16th of November, 1827, suffocated many snakes, rats, and other animals. Sudden changes of weather, as the occurrence of the rainy season in the tropics, at an unusual period of the year, have sometimes succeeded violent earthquakes in Quito and Peru. Do gaseous fluids rise from the interior of the earth, and mix with the atmosphere? or are these meteorological processes the action of atmospheric electricity disturbed by the earthquake? In the tropical regions of America, where sometimes not a drop of rain falls for ten months together, the natives consider the repeated shocks of earthquakes, which do not endanger the low reed huts, as auspicious harbingers of fruitfulness and abundant rain. p 214 The intimate connection of the phenomena which we have considered is still hidden in obscurity. Elastic fluids are doublessly the cause of the slight and perfectly harmless trembling of the earth's surface, which has often continued several days (as in 1816, at Scaccia, in Sicily, before the volcanic elevation of the island of Julia), as well as of the terrific explosions accompanied by loud noise. The focus of this destructive agent, the seat of the moving force, lies far below the earth's surface; but we know as little of the extent of this depth as we know of the chemical nature of these vapors that are so highly compressed. At the edges of two craters, Vesuvius, and the towering rock which projects beyond the great abyss of Pichincha, near Quito, I have felt periodic and very regular shocks of earthquakes, on each occasion from 20 to 30 seconds before the burning scoriae or gases were erupted. The intensity of the shocks was increased in proportion to the time intervening between them, and, consequently, to the length of time in which the vapors were accumulating. This simple fact, which has been attested by the evidence of so many travelers, furnishes us with a general solution of the phenomenon, in showing that active volcanoes are to be considered as safety-valves for the immediate neighborhood. The danger of earthquakes increases when the openings of the volcano are closed, and deprived of free communication with the atmosphere; but the destruction of Lisbon, of Caraccas, of Lima, of Cashmir in 1554,* and of so many cities of Calabria, Syria, and Asia Minor, shows us, on the whole, that the force of the shock is not the greatest in the neighborhood of active volcanoes. [footnote] *On the frequency of earthquakes in Cashmir, see Troyer's German translation of the ancient 'Radjataringini', vol. ii., p. 297, and Carl Hugel, 'Reisen', bd. ii., s. 184. As the impeded activity of the volcano acts upon the shocks of the earth's surface, so do the latter react on the volcanic phenomena. Openings of fissures favor the rising of cones of eruption, and the processes which take place in these cones, by forming a free communication with the atmosphere. A column of smoke, which had been observed to rise for months together from the volcano of Pasto, in South America, suddenly disappeared, when on the 4th of February, 1797, the province of Quito, situated at a distance of 192 miles to the south, suffered from the great earthquake of Riobamba. After the earth had continued to tremble for some time through out the whole of Syria, in the Cyclades, and in Euboea, the shocks suddenly ceased on the eruption of a stream of hot mud p 215 on the Lelantine plains near Chalcia.* [footnote] * Strabo, lib. i., p. 100, Casaub. That the expression [Greek words] does not mean erupted mud, but lava, is obvious from a passage in Strabo, lib. vi., p. 412. Compare Walter, in his 'Abnahme der Vulkanischen Thatigkeit in Historischen Zeiten' (On the Decrease of Volcanic Activity during Historical Times), 1844, s. 25. The intelligent geographer of Amasea, to whom we are indebted for the notice of this circumstance, further remarks: "Since the craters of Aetna have been opened, which yield a passage to the escape of fire, and since burning masses and water have been ejected, the country near the sea-shore has not been so much shaken as at the time previous to the separation of Sicily from Lower Italy, when all communications with the external surface were closed." We thus recognize in earthquakes the existence of a volcanic force, which, although every where manifested, and as generally diffused as the internal heat of our planet, attains but rarely, and then only at separate points, sufficient intensity to exhibit the phenomenon of eruptions. The formation of veins, that is to say, the filling up of fissures with crystalline masses bursting forth from the interior (as basalt, melaphyre, and greenstone), gradually disturbs the free intercommunication of elastic vapors. This tension acts in three different ways, either in causing disruptions, or sudden and retroversed elevations, or, finally, as was first observed in a great part of Sweden, in producing changes in the relative level of the sea and land, which, although continuous, are only appreciable at intervals of long period. Before we leave the important phenomena which we have considered not so much in their individual characteristics as in their general physical and geognostical relations, I would advert to the deep and peculiar impression left on the mind by the first earthquake which we experience, eeven where it is not attended by any subterranean noise.* [footnote] *[Dr. Tschudi, in his interesting work, 'Travels in Peru', translated from the German by Thomasina Ross, p. 170, 1847, describes strikingly the effect of an earthquake upon the native and upon the stranger. "No familiarity with the phenomenon can blunt this feeling. The inhabitant of Lima, who from childhood has frequently witnessed these convulsions of nature, is roused from his sleep by the shock, and rushes from his apartment with the cry of 'Misericordia!' The foreigner from the north of Europe, who knows nothing of earthquakes but by description, waits with impatience to feel the movement of the earth, and longs to hear with his own ear the subterranean sounds which he has hitherto considered fabulous. With levity he treats the apprehension of a coming convulsion, and laughs at the fears of the natives: but, as soon as his wish is gratified, he is terror-stricken, and is involuntarily prompted to seek safety in flight."] -- Tr. This impression is not, p 216 in my opinion, the result of a recollection of those fearful pictures of devastation presented to our imaginations by the historical narratives of the past, but is rather due to the sudden revelation of the delusive nature of the inherent faith by which we had clung to a belief in the immobility of the solid parts of the earth. We are accustomed from early childhood to draw a contrast between the mobility of water and the immobility of the soil on which we tread; and this feeling is confirmed by the evidence of our senses. When, therefore, we suddenly feel the ground move beneath us, a mysterious and natural force, with which we are previously unacquainted, is revealed to us as an active disturbance of stability. A moment destroys the illusion of a whole life; our deceptive faith in the repose of nature vanishes, and we feel transported, as it were, into a realm of unknown destructive forces. Every sound -- the faintest motion in the air -- arrests our attention, and we no longer trust the ground on which we stand. Animals, especially dogs and swine, participate in the same anxious disquietude; and even the crocodiles of the Orinoco, which are at other times as dumb as our little lizards, leave the trembling bed of the river, and run with loud cries into the adjacent forests. To man the earthquake conveys an idea of some universal and unlimited danger. We may flee from the crater of a volcano in active eruption, or from the dwelling whose destruction is threatened by the approach of the lava stream; but in an earthquake, direct our flight whithersoever we will, we still feel as if we trod upon the very focus of destruction. This condition of the mind is not of long duration, although it takes its origin in the deepest recesses of our nature; and when a series of faint shocks succeed one another, the inhabitants of the country soon lose every trace of fear. On the coasts of Peru, where rain and hail are unknown, no less than the rolling thunder and the flashing lightning, these luminous explosions of the atmosphere are replaced by the subterranean noises which accompany earthquakes.* [footnote] *["Along the whole coast of Peru the atmosphere is almost uniformly in a state of repose. It is not illuminated by the lightning's flash, or disturbed by the roar of the thunder; no deluges of rain, no fierce hurricanes, destroy the fruits of the fields, and with them the hopes of the husbandman. But the mildness of the elements above ground is frightfully counterbalanced by their subterranean fury. Lima is frequently visited by earthquakes, and several times the city has been reduced to a mass of ruins. At an average, forty-five shocks may be counted on in the year. Most of them occur in the later part of October, in November, December, January, May, and June. Experience gives reason to expect the visitation of two desolating earthquakes in a century. The period between the two is from forty to sixty years. The most considerable catastrophes experienced in Lima since Europeans have visited the west coast of South America happened in the years 1586, 1630, 1687, 1713, 1746, 1806. There is reason to fear that in the course of a few years this city may be the prey of another such visitation."] --Tr. Long habit, and the very p 217 prevalent opinion that dangerous shocks are only to be apprehended two or three times in the course of a century, cause faint oscillations of the soil to be regarded in Lima with scarcely more attention than a hail storm in the temperate zone. Having thus taken a general view of the activity -- the inner life, as it were -- of the Earth, in respect to its internal heat, its electro-magnetic tension, its emanation of light at the poles, and its irregularly-recurring phenomena of motion, we will now proceed to the consideration of the material products, the chemical changes in the earth's surface, and the composition of the atmosphere, which are all dependent on planetary vital activity. We see issue from the ground steam and gaseous carbonic acid, almost always free from the admixture of nitrogen;* carbureted hydrogen gas, which has been used in the Chinese province Sse-tschuan** for several thousand years, and recently in the village of Fredonia, in the State of New York, United States, in cooking and for illumination; sulphureted hydrogen gas and sulphurous vapors; and, more rarely,*** sulphurous and hydrochloric acids.**** [footnote] * Bischof's comprehensive work, 'Warmelchere des inneren Erdkorpers'. [footnote] **On the Artesian fire-springs (Ho-tsing) in China, and the ancient use of portable gas (in bamboo canes) in the city of Khiung-tsheu, see Klaproth, in my 'Asie Centrale', t. iii., p. 519-530. [footnote] *** Boussingault ('Annales de Chimie', t. lii., p. 181) observed no evolution of hydrochloric acid from the volcanoes of New Granada, while Monticelli found it in enormous quantity in the eruption of Vesuvius in 1813. [footnote] ****[Of the gaseous compounds of sulphur, one, sulphurous acid, appears to predominate chiefly in volcanoes possessing a certain degree of activity, while the other, sulphureted hydrogen, has been most frequently perceived among those in a dormant condition. The occurrence of abundant exhalations of sulphuric acid, which have been hitherto noticed chiefly in extinct volcanoes, as for instance, in a stream issuing from that of Purace, between Bogota and Quito, from extinct volcanoes in Java, is satisfactorily explained in a recent paper by M. Dumas, 'Annales de Chimie', Dec., 1846. He shows that when sulphureted hydrogen, at a temperature above 100 degrees Fahr., and still better when near 190 degrees, comes in contact with certain porous bodies, a catalytic action is set up, by which water, sulphuric acid, and sulphur are produced. Hence probably the vast deposits of sulphur, associated with sulphates of lime and strontian, which are met with in the western parts of Sicily.] -- Tr. Such effusions p 218 from the fissures of the earth not only occur in the districts of still burning or long-extinguished volcanoes, but they may likewise be observed occasionally in districts where neither trachyte nor any other volcanic rocks are exposed on the earth's surface. In the chain of Quindiu I have seen sulphur deposited in mica slate from warm sulphurous vapor at an elevation of 6832 feet* above the level of the sea, while the same species of rock, which was formerly regarded as primitive, contains, in the Cerro Cuello, near Tiscan, south of Quito, an immense deposit of sulphur imbedded in pure quartz. [footnote] * Humboldt, 'Recucil d'Observ. Astronomiques', t. i., p. 311 ('Nivellement Barometrique de la Cordillere des Andes', No. 206). Exhalations of carbonic acid ('mofettes') are even in our days to be considered as the most important of all gaseous emanations, with respect to their number and the amount of their effusion. We see in Germany, in the deep valleys of the Eifel, in the neighborhood of the Lake of Laach,* in the crater-like valley of the Wehr and in Western Bohemia, exhalations of carbonic acid gas manifest themselves as the last efforts of volcanic activity in or near the foci of an earlier world. [footnote] *[The Lake of Laach, in the district of the Eifel, is an expanse of water two miles in circumference. The thickness of the vegetation on the sides of its crater-like basin renders it difficult to discover the nature of the subjacent rock, but it is probably composed of black cellular augitic lava. The sides of the crater present numerous loose masses, which appear to have been ejected, and consist of glassy feldspar, ice-spar, sodalite, hauyne, spinellane, and leucite. The resemblance between these products and the masses formerly ejected from Vesuvius is most remarkable. (Daubeney 'On Volcanoes', p. 81.) Dr. Hibbert regards the Lake of Laach as formed in the first instance by a crack caused by the cooling of the crust of the earth, which was widened afterward into a circular cavity by the expansive force of elastic vapors. See 'History of the Extinct Volcanoes of the Basin of Neuwied', 1832.] -- Tr. In those earlier periods, when a higher terrestrial temperature existed, and when a great number of fissures still remained unfilled, the processes we have described acted more powerfully, and carbonic acid and hot steam were mixed in larger quantities in the atmosphere, from whence it follows, as Adolph Bronguiart has ingeniously shown,* that the primitive vegetable world must have exhibited almost every where, and independently of geographical position, the most luxurious abundance and the fullest development of organism. [footnote] *Adolph Bronguiart, in the 'Annales des Sciences Naturelles', t. xv., p. 225. In these constantly warm and damp atmospheric strata, saturated with p 219 carbonic acid, vegetation must have attained a degree of vital activity, and derived the superabundance of nutrition necessary to furnish materials for the formation of the beds of lignite (coal) constituting the inexhaustible means on which are based the physical power and prosperity of nations. Such masses are distributed in basins over certain parts of Europe, occurring in large quantities in the British Islands, in Belgium, in France, in the provinces of the Lower Rhine, and in Upper Silesia. At the same primitive period of universal volcanic activity, those enormous quantities of carbon must also have escaped from the earth which are contained in limestone rocks, and which, if seprated from oxygen and reduced to a solid form, would constitute about the eighth part of the absolute bulk of these mountain masses.* [footnote] * Bischof, op. cit., s. 324, Anm. 2. That portion of the carbon which was not taken up by alkaline earths, but remained mixed with the atmosphere, as carbonic acid, was gradually consumed by the vegetation of the earlier stages of processes of vegetable life, only retained the small quantity which it now possesses, and which is not injurious to the sulphurous vapor have occasioned the destruction of the species of mollusca and fish which inhabited the inland waters of the earlier world, and have given rise to the formation of the contorted beds of gypsum, which have doubtless been frequently affected by shocks of earthquakes. Gaseous and liquid fluids, mud, and molten earths, ejected from the craters of volcanoes, which are themselves only a kind of "intermittent springs," rise from the earth under precisely analogous physical relations.* [footnote] *Humboldt, 'Asie Centrale', t. i., p. 43. All these substances owe their temperature and their chemical character to the place of their origin. The 'mean' temperature of aqueous springs is less than that of the air at the point whence they emerge, if the water flow from a height; but their heat increases with the depth of the strata with which they are in contact at their origin. We have already spoken of the numerical law regulating this increase. The blending of waters that have come from the height of a mountain with those that have sprung from the depths of the earth, render it difficult to determine the position of the 'isogeothermal lines'* (lines of equal internal p 220 terrestrial temperature, when this determination is to be made from the temperature of flowing springs. [footnote] *On the theory of isogeothermal (chthonisothermal) lines, consult the ingenious labors of Kupffer, in Pogg, 'Annalen', bd xv., s. 184, and bd xxxii., s. 270, in the 'Voyage dans l'Oural', p. 382-298, and in the 'Edinburgh Journal of Science', New Series, vol. iv., p. 355. See, also, Kamtz, 'Lehrb. der Meteor.', bd. ii., s. 217; and, on the ascent of the chthonisothermal lines in mountainous districts, Bischof, s. 174-198. Such at any rate, is the result I have arrived at from my own observations and those of my fellow-travelers in Northern Asia. The temperature of springs, which has become the subject of such continuous physical investigation during the last half century, depends, like the elevation of the line of perpetual snow, on very many simultaneous and deeply-involved causes. It is a function of the temperature of the stratum in which they take their rise, of the specific heat of the soil, and of the quantity and temperature of the meteoric water,* which is itself different from the temperature of the lower strata of the atmosphere, according to the different modes of its origin in rain, snow, or hail.** [footnote] *Leop. v. Buch, in Pogg., 'Annalen', bd. xii., s. 405. [footnote] ** On the temperature of the drops, of rain in Cumana, which fell to 72 degrees, when the temperature of the air shortly before had been 86 degrees and 88 degrees, and during the rain sank to 74 degrees, see my 'Relat. Hist.', t. ii., p. 22. The rain-drops, while falling, change the normal temperature they originally possessed, which depends on the height of the clouds from which they fell, and their heating on their upper surface by the solar rays. The rain-drops, on their first production, have a higher temperature than the surrounding medium in the superior strata of our atmosphere, in consequence of the liberation of their latent heat; and they continue to rise in temperature, since, in falling through lower and warmer strata, vapor is precipitated on them, and they thus increase in size (Bischof, 'Warmelehre des inneren Erdkorpers' s. 73); but this additional heating is compensated for by evaporation. The cooling of the air by rain (putting out of the question what probably belongs to the electric process in storms) is effected by the drops, which are themselves of lower temperature, in consequence of the cold situation in which they were formed, and bring down with them a portion of the higher colder air, and which finally, by moistening the ground, give rise to evaporation. The cooling of the air by rain (putting out of the question what probably belongs to the electric process in storms) is effected by the drops, which are themselves of lower temperature, in consequence of the cold situation in which they were formed, and bringi down with them a portion of the higher colder air, and which finally, by moistening the ground, give rise to evaporation. These are the ordinary relations of the phenomenon. When, as occasionally happens, the rain-drops are warmer than the lower strata of the atmosphere (Humboldt, 'Rel. Hist.', t. iii., p. 513), the cause must probably be sought in higher warmer currents, or in a higher temperature of widely-extended and not very thick clouds, from the action of the sun's rays. How, moreover, the phenomenon of supplementary rainbows, which are explained by the interference of light, is connected with the original and increasing size of the falling drops, and how an optical phenomenon, if we know how to observe it accurately, may enlighten us regarding a meteorological process, according to diversity of zone, has been shown, with much talent and ingenuity, by Arago, in the 'Annuaire' for 1836, p. 300. Cold springs can only indicate the mean atmospheric temperature p 221 when they are unmixed with the waters rising from great depths, or descending from considerable mountain elevations, and when they have passed through a long course at a depth from the surface of the earth which is equal in our latitudes to 40 or 60 feet, and according to Boussingault, to about one foot in the equinoctial regions,* these being the depths at which the invariability of the temperature begins in the temperate and torrid zones, that is to say, the depths at which horary, diurnal, and monthly changes of heat in the atmosphere cease to be perceived. [footnote] * The profound investigations of Boussingault fully convince me, that in the tropics, the temperature of the ground, at a very slight depth, exactly corresponds with the mean temperature of the air. The following instances are sufficient to illustrate this fact: ________________________________________________________ Stations Temperature at Mean Height, in within 1 French foot Temperature English Tropic [1.006 of the of the feet, above Zones. English foot] air. the level below the of the sea. earth's surface. ________________________________________________________ Guayaquil 78.8 78.1 0 Anserma Nuevo 74.6 74.8 3444 Zupia 70.7 70.7 4018 Popayan 64.7 65.6 5929 Quito 59.9 59.9 9559 ________________________________________________________ The doubts about the temperature of the earth within the tropics, of which I am probably, in some degree, the cause, by my observations on the Cave of Caripe (Cueva del Guacharo), 'Rel. Hist.', t. iii., p. 191-196), are resolved by the consideration that I compared the presumed mean temperature of the air of the convent of Caripe, 65.3 degrees, not with the temperature of the air of the cave, 65.6 degrees, but with the temperature of the subterranean stream, 62.3degrees, although I observed ('Rel. Hist.', t. iii., p. 146 and 195) that mountain water from a great height might probably be mixed with the water of the cave. Hot springs issue from the most various kinds of rocks. The hottest permanent springs that have hitherto been observed are, as my own researches confirm, at a distance from all volcanoes. I will here advert to a notice in my journal of the Aguas Calientes de las Trincheras', in South America, between Porto Cabello and Nueva Valencia, and the 'Aguas de Comangillas', in the Mexican territory, near Guanaxuato; the former of these, which issued from granite, had a temperature of 194.5 degrees; the latter, issuing from basalt, 205.5degrees. The depth of the source from whence the water flowed with this temperature, judging from what we know of the law of the increase of heat in the interior of the earth, was probably 7140 feet, or above two miles. If the universally-diffused terrestrial heat be the cause of thermal springs, as of active volcanoes, the rocks can only exert an influence by the different capacities p 222 for heat and by their conducting powers. The hottest of all permanent springs (between 203 degrees and 209 degrees) are likewise, in a most remarkable degree, the purest, and such as hold in solution the smallest quantity of mineral substances. Their temperature appears, on the whole, to be less constant than that of springs between 122 degrees and 165 degrees, which in Europe, at least, have maintained, in a most remarkable manner, their 'invariability of heat and mineral contents' during the last fifty or sixty years, a period in which thermometrical measurements and chemical analyses have been applied with increasing exactness. Boussingault found in 1823 that the thermal springs of Las Tricheras had risen 12 degrees during the twenty-three years that had intervened since my travels in 1800.* [footnote] *Boussingault, in the 'Annales de chimie', t. lii., p. 181. The spring of Chaudes Aigues, in Auvergne, is only 176degrees. It is also to be observed, that while the Aguas Calientes de las Trincheras, south of Porto Cabello (Venezuela), springing from granite cleft in regular beds, and far from all volcanoes, have a temperature of fully 206.6 degrees, all the springs which rise in the vicinity of still active volcanoes (Pasto, Cotopaxi, and Tunguragua) have a temperature of only 97 - 130 degrees. This calmly-flowing spring is therefore now nearly 12 degrees hotter than the intermittent fountains of the Geyser and the Strokr, whose temperature has recently been most carefully determined by Krug of Nidda. A very striking proof of the origin of hot springs by the sinking of cold meteoric water into the earth, and by its contact with a volcanic focus, is afforded by the volcano of Jorulla in Mexico, which was unknown before my American journey. When, in September, 1759, Jorullo was suddenly elevated into a mountain 1183 feet above the level of the surrounding plain, two small rivers, the 'Rio de Cuitimba' and 'Rio de San Pedro', disappeared, and some time afterward burst forth again, during violent shocks of an earthquake, as hot springs, whose temperature I found in 1803 to be 186.4 degrees. The springs in Greece still evidently flow at the same places as in the times of Hellenic antiquity. The spring of Erasinos, two hours' journey to the south of Argos, on the declivity of Chaon, is mentioned by Herodotus. At Delphi we still see Cassotis (now the springs of St. Nicholas) rising south of the Lesche, and flowing beneath the Temple of Apollo; Castalia, at the foot of Phaedriadae; Pirene, near Acro-Corinth; and the hot baths of Aedipsus, in Euboea, in which Sulla bathed during the Mithridatic war.* [footnote] *Cassotis (the spring of St. Nicholas) and Castalia, at the Phaedriadae, mentioned in Pausanias, x., 24, 25, and x., 8, 9; Pirene (Acro-Corinth), in Strabo, p. 379; the spring of Erasinos, at Mount Chaon, south of Argos, in Herod., vi., 67, and Pausanias, ii., 24, 7; the springs of Aedipsus in Euboea, some of which have a temperature of 88 degrees, while in others it ranges between 144) qne 167 degrees, in Strabo, p. 60 and 447, and Athenaeus, ii., 3, 73; the hot springs of Thermopylae, at the foot of Oeta, with a temperature of 149 degrees. All from manuscript notes by Professor Curtius, the learned companion of Otfried Muller. I advert with pleasure to these p 223 facts, as they show us that, even in a country subject to frequent and violent shocks of earthquakes, the interior of our planet has retained for upward of 2000 years its ancient configuration in reference to the course of the open fissures that yield a passage to these waters. The 'Fontaine jaillissante' of Lillers, in the Department des Pas de Calais, which was bored as early as the year 1126, still rises to the same height and yields the same quantity of water; and, as another instance, I may mention that the admirable geographer of the Caramanian coast, Captain Beaufort, saw in the district of Phaselis the same flame fed by emissions of inflammable gas which was described by Pliny as the flame of the Lycian Chimera.* [footnnote] (Pliny, ii., 106; Seneca, 'Epist.' 79, 3, ed. Ruhkopf (Beaufort, 'Survey of the Coast of Karamania', 1820, art. Yanar, near Delktasch, the ancient Phaselis, p. 24). See also Ctesias, 'Fragm.', cap. 10 p. 250, ed. Bahr; Strabo, lib. xiv., p. 666, Casaub. ["Not far from the Deliktash, on the side of a mountain, is the perpetual fire described by Captain Beaufort. The travelers found it as brilliant as ever, and even somewhat increased; for, besides the large flame in the corner of the ruins described by Beaufort, there were small jets issuing from crevices in the side of the crater-like cavity five or six feet deep. At the bottom was a shallow pool of sulphureous and turbid water, regarded by the Turks as a sovereign remedy for all skin complaints. The soot deposited from the flames was regarded as efficacious for sore eyelids, and valued as a dye for the eyebrows." See the highly interesting and accurate work, 'Travels in Lycia', by Lieut. Spratt and Professor E. Forbes.] -- Tr. The observation made by Arago in 1821, that the deepest Artesian wells are the warmest,* threw great light on the origin of thermal springs, and on the establishment of the law that terrestrial heat increases with increasing depth. [footnote] *Arago, in the 'Annuaire pour' 1835, p. 234. It is a remarkable fact, which has but recently been noticed, that at the close of the third century, St. Patricus,* probably Bishop of Pertusa, was led to adopt very correct views regarding the phenomenon of the hot springs at Carthage. [footnote] *'Acta S. Patricii', p. 555, ed. Ruinart, t. ii., p. 385, Mazochi. Dureau de la Malle was the first to draw attention to this remarkable passage in the 'Recherches sur la Topographie de Carthage', 1835, p. 276. (See, also, Seneca, 'Nat. Quaest.', iii., 24.) On being asked what was the cause of boiling water bursting from the earth, he replied, "Fire is nourished in the clouds and in the interior p 224 of the earth, as Aetna and other mountains near Naples may teach you. The subterranean waters rise as if through siphons. The cause of hot springs is this: waters which are more remote from the subterranean fire are colder, while those which rise nearer the fire are heated by it, and bring with them to the surface which we inhabit an insupportable degree of heat." As earthquakes are often accompanied by eruptions of water and vapors, we recognize in the 'Salses',* of small mud volcanoes, a transition from the changing phenomena presented by these eruptions of vapor and thermal springs to the more powerful and awful activity of the streams of lava that flow from volcanic mountains. [footnote] *[True volcanoes, as we have seen, generate sulphureted hydrogen and muriatic acid, upheave tracts of land, and omit streams of melted feldspathic materials; salses, on the contrary, disengage little else but carbureted hydrogen, together with bitumen and other products of the distillation of coal, and pour forth no other torrents except of mud, or argillaceous materials mixed up with water. Daubeney, op cit., p. 540.] -- Tr. If we consider these mountains as springs of molten earths producing volcanic rocks, we must remember that thermal water, when impregnated with carbonic acid and sulphurous gases, are continually forming horizontally ranged strata of limestone (travertine) or conical elevations, as in Northern Africa (in Alberia), and in the Banos of Caxamarca, on the western declivity of the Peruvian Cordilleras. The travertine of Van Diemen's Land (near Hobart Town) contains, according to Charles Darwin, remains of a vegetation that no longer exists. Lava and travertine, which are constantly forming before our eyes, present us with the two extremes of geognostic relations. 'Salses' deserve more attention than they have hitherto received from geognosists. Their grandeur has been overlooked because of the two conditions to which they are subject; it is only the more peaceful state, in which they may continue for centuries, which has generally been described: their origin is, however, accompanied by earthquakes, subterranean thunder, the elevation of a whole district, and lofty emissions of flame of short duration. When the mud volcano of Jokmali began to form on the 27th of November, 1827, in the peninsula of Abscheron, on the Caspian Sea, east of Baku, the flames flashed up to an extraordinary height for three hours, while during the next twenty hours they scarcely rose three feet above the crater, from which mud was ejected. Near the village of Baklichli, west of Baku, the flames rose so high that p 225 they could be seen at a distance of twenty-four miles. Enormous masses of rock were torn up and scattered around. Similar masses may be seen round the now inactive mud volcano of Monte Ziblo, near Sassuolo, in Northern Italy. The secondary condition of repose has been maintained for upward of fifteen centuries in the mud volcanoes of Girgenti, the 'Macalubi', in Sicily, which have been described by the ancients. These salses consist of many contitiguous conical hills, from eight to ten, or even thirty feet in height, subject to variations of elevation as well as of form. Streams of argillaceous mud, attended by a periodic development of gas, flow from the small basins at the summits, which are filled with water; the mud, although usualy cold is sometimes at a high temperature, as at Damak, in the province of Samarang, in the island of Java. The gases that are developed with loud noise differ in their nature consisting for instance, of hydrogen mixed with naphtha, or of carbonic acid, or, as Parrot and myself have shown (in the peninsula of Taman, and in the 'Volcancitos de Turbaco', in South America), of almost pure nitrogen.* [footnote] *Humboldt, 'Rel. Hist.', t. iii., p. 562-567; 'Asie Centrale', t. i., p. 43; t. ii., p. 505-515; 'Vues des Cordilleres', pl. xli. Regarding the 'Macalubi', the 'overthrown' or 'inverted', from the word 'Khalaba'), and on "the Earth ejecting fluid earth," see Solinus, cap. 5: "idem ager Agrigentinus eructat limosas scaturigenes, et ut venae fontium sufficiunt rivis subjinistrandis, ita in hac Sicilae parte solo munquam deficiente, Aeterna rejectatione terram terra evomit." Mud volcanoes, after the first violent explosion of fire, which is not, perhaps, in an equal degree common to all, present to the spectator an image of the uninterrupted but weak activity of the interior of our planet. The communication with the deep strata in which a high temperature prevails is soon closed, and the coldness of the mud emissions of the salses seems to indicate that the seat of the phenomenon can not be far removed from the surface during their ordinary condition. The reaction of the interior of the earth on its external surface is exhibited with totally different force in true volcanoes or igneous mountains, at points of the earth in which a permanent, or, at least, continually-renewed connection with the volcanic force is manifested. We must here carefully distinguish between the more or less intensely developed volcanic phenomena, as for instance, between earthquakes, thermal, aqueous, and gaseous springs, mud volcanoes, and the appearance of bell-formed or dome-shaped trachytic rocks without openings; the opening of these rocks, or of the elevated beds of basalt, as p 226 craters of elevation; and, lastly, the elevation of a permanent volcano in the crater of elevation, or among the 'debris' of its earlier formation. At different periods, and in different degrees of activity and force, the permanent volcanoes emit steam acids, luminous scoriae, or, when the resistance can be overcome, narrow, band-like streams of molten earths. Elastic vapors sometimes elevate either separate portions of the earth's crust into dome-shaped unopened masses of feldspathic trachyte and dolerite (as in Puy de Dome and Chimborazo), in consequence of some great or local manifestation of force in the interior of our planet, or the upheaved strata are broken through and curved in such a manner as to form a steep rocky ledge on the opposite inner side, which then constitutes the inclosure of a crater of elevation. If this rocky ledge has been uplifted from the bottom of the sea, which is by no means always the case, it determines the whole physiognomy and form of the island. In this manner has arisen the circular form of Palma, which has been described with such admirable accuracy by Leopold von Buch, and that of Nisyros,* in the Aegean sea. [footnote] *See the interesting little map of the island of Nisyros, in Roise's 'Reisen auf den Griechischen Inseln', bd. ii., 1843, s. 69. Sometimes half of the annular ledge has been destroyed, and in the bay formed by the encroachment of the sea corallines have built their cellular habitations. Even on continents craters of elevation are often filled with water, and embellish in a peculiar manner the character of the landscape. Their origin is not connected with any determined species of rock: they break out in basalt, trachyte, leucitic porphyry (somma), or in doleritic mixtures of augite and labradorite; and hence arise the different nature and external conformation of these inclosures of craters. No phenomena of eruption are manifested in such craters, as they open no permanent channel of communication with the interior, and it is but seldom that we meet with traces of volcanic activity either in the neighborhood or in the interior of these craters. The force which was able to produce so important an action must have been long accumulating in the interior before it could overpower the resistance of the mass pressing upon it; it sometimes, for instance, on the origin of new islands, will raise granular rocks and conglomerated masses (strata of tufa filled with marine plants) above the surface of the sea. The compressed vapors escape through the crater of elevation, but a large mass soon falls back and closes the opening, which had been only formed by these manifestations of force. No volcano can, therefore, p be produced.* [footnote] *Leopold von Buch, 'Phys. Beschreibung der Canarischen Inseln', s. 326; and his Memoir 'uber Erhebungscratere und Vulcane', in Poggend., 'Annal.', bd. xxxvii., s. 169. In his remarks on the separation of Sicily from Calabria, Strbo gives an excellend description of the two modes in which islands are formed: "Some islands," he observes (lib. vi., p. 258, ed. Casaub.), "are fragments of the continent, others have arisen from the sea, as even at the present time is known to happen; for the islands of the great ocean, lying far from the main land, have probably been raised from its depths, while, on the other hand, those near promontories appear (according to reason) to have been separated from the continent." A volcano, properly so called, exists only where a permanent connection is established between the interior of the earth and the atmosphere, and the reaction of the interior on the surface then continues during long periods of time. It may be interrupted for centuries, as in the case of Vesuvius Fisove,* and then manifest itself with renewed activity. [footnote] *Ocre Fisove (Mons Vesuvius) in the Umbrian language. (Lassen 'Deutung der Eugubinischen Tafeln in Rhein. Museum', 1832, s. 387.) The word 'ochre' is very probaby genuine Umbrian, and means, according to Festus, 'mountain'. Aetna would be a burning and shining mountain, if Voss is correct in stating that [Greek work] is an Hellenic sound, and is connected with [Greed word] and [Greek word]; but the intelligent writer Parthey doubts this Hellenic origin on etymological grounds, and also because etna was by no means regarded as a luminous beacon for ships or wanderers, in the same manner as the ever-travailing Stromboli (Strongyle), to which Homer seems to refer in the Odyssey (xii., 68, 202, and 219), and its geographical position was not so well determined. I suspect that tna would be found to be a Sicilian word, if we had any fragmentary materials to refer to. According to Diodorus (v., 6), the Sicani, or aborigines preceding the Sicilians, were compelled to fly to the western part of the island, in the consequence of successive eruptions extending over many years. The most ancient eruption of Mount Aetna on record is that mentioned by Pindar and Schylus, as occurring under Hiero, in the second year of the 75th Olympiad. It is probable that Hesiod was aware of the devastating eruptions of Aetna before the period of Greek immigration. There is, however, some doubt regarding the work [Greek word] in the text of Hesiod, a subject into whci I have entered at some length in another place. (Humboldt, 'Examen Crit. de le Geogr.', t. i., p. 168.) In the time of Nero, men were disposed to rank Aetna among the volcanic mountains which were graduallybecoming extinct,* and subsequently Aelian** even maintained that mariners could no longer see the sinking summit of the mountain from so great a distance at sea. [footnote] *Seaeca. 'Epist.', 79. [footnote] ** Aelian, 'Var. Hist.', viii., 11. Where these evidences -- these old scaffoldings of eruption, I might almost say -- still exist, the volcano rises from a crater of elevation, while a high rocky wall surrounds, like an amphitheater, the isolated conical mount, and forms around it a kind of easing of highly elevated p 228 strata. Occasionally not a trace of this inclosure is visible, and the volcano, which is not always conical rises immediately from the neighboring plateau in an elongated form, as in the case of Pichincha,* at the foot of which lies the city of Quito. [footnote] *[This mountain contains two funnel-shaped craters, apparently resulting from two set of eruptions: the western nearly circular, and having in its center a cone of eruption, from the summit and sides of which are no less than seventy vents, some in activity and others extinct. It is probable that the larger number of the vents were produced at periods anterior to history. Caubney, op. cit., p. 488.] -- Tr. As the nature of rocks, or the mixture (grouping) of simple minerals into granite, gneiss, and mica slate, or into trachyte, basalt, and dolorite, is independent of existing climates, and is the same under the most varied latitudes of the earth, so also we find every where in inorganic nature that the same laws of configuration regulate the reciprocal superposition of the strata of the earth's crust, cause them to penetrate one another in the form of veins, and elevate them by the agency of elastic forces. This constant recurrence of the same phenomena is most strikingly manifested in volcanoes. When the mariner, amid the islands of some distant archipelago, is no longer guided by the light of the same stars with which he had been familiar in his native latitude, and sees himself surrounded by palms and other forms of an exotic vegetation, he still can trace, reflected in the individual characteristics of the landscape, the forms of Vesuvius, of the come-shaped summits of Auvergne, the craters of elevation in the Canaries and Azores, or the fissures of eruption in Iceland. A glance at the satellite of our planet will impart a wider generalization to this analogy of configuration. by means of the charts that have been drawn in accordance with the observations made with large telescopes, we may recognize in the moon, where water and air are both absent, vast craters of elevation surrounding or supporting conical mountains, thus affording incontrovertible evidence of the effects produced by the reaction of the interior on the surface, favored by the influence of a feebler force of gravitation. Although vocanoes are justy termed in many languages "fire-emitting mountains," mountains of this kind are not formed by the gradual accumulation of ejected currents of lava, but their origin seems rather to be a general consequence of the sudden elevation of soft masses of trachyte or labradoritic augite. The amount of the elevating force is manifested p 229 by the elevation of the volcano, which varies from the inconsiderable height of a hill (as the volcano of Cosima, one of the Japanese Kurile islands) to that of a cone above 19,000 feet in height. It has appeared to me that relations of height have a great influence on the occurrence of eruptions, which are more frequent in low than in elevated volcanoes. I might instance the series presented by the following mountains: Stromboli, 2318 feet; Guacamayo, in the province of Quixos, from which detonations are heard almost daily (I myself often heard them at Chillo, near Quito, a distance of eighty-eight miles); Vesuvius, 3876 feet; Aetna, 10871 feet; the Peak of Teneriffe, 12,175 feet; and Cotopaxi, 19,069 feet. If the focus of these volcanoes be at an equal depth below the surface, a greater force must be required where the fused masses have to be raised to an elevation six or eight times greater than that of the lower eminences. While the volcano Stromboli (Strongyle) has been incessantly active since the Homeric ages, and has served as a beacon-light to guide the mariner in the Tyrrhenian Sea, loftier volcanoes have been characterized by loong intervals of quiet. Thus we see that a whole century often intervenes between the eruptions of most of the colossi which crown the summits of the Cordilleras of the Andes. Where we meet with exceptions to this law, to which I long since drew attention, they must depend upon the circumstance that the connections between the volcanic foci and the crater of eruption can not be considered as equaly permanent in the case of all volcanoes. The channel of communication may be closed for a time in the case of the lower ones, so that they less frequently come to a state of eruption, although they do not, on that account, approach more nearly to their final extinction. These relations between the absolute height and the frequency of volcanic eruptions, as far as they are externally perceptible, are intimately connected with the consideration of the local conditions under which lava currents are erupted. Eruptions from the crater are very unusual in many mountains, generally occurring from lateral fissures (as was observed in the case of Aetna, in the sixteenth century, by the celebrated historian Bembo, when a youth*), whenever the sides p 230 of the upheaved mountain were least able, from their configuration and position, to offer any resistance. [footnote] *Petri Bembi Opuscula ('Aetna Dialogus'), Basil, 1556, p. 63: "Quicquid in Aetnae matris utero coulescit, nunquam exit ex cratere superiore, quod vel eo inscondere gravis materia non queat, vel, quia inferius alia spiramenta sunt, non fit opus. Despumant flammis urgentibus ignei rivi pigro fluxu totas delambentes plagas, et in lapidem indurescunt." Cones of eruption are sometimes uplifted on these fissures; the larger ones, which are erroneously termed 'new volcanoes', are ranged together in line marking the direction of a fissure, which is soon reclosed, while the smaller ones are grouped together covering a whole district with their dome-like or hive-shaped forms. To the latter belong the 'hornitos de Jorullo',I the cone of Vesuvius erupted in October, 1822, that of Awatscha, according to Postels, and those of the lava-field mentioned by Erman, near the Baidar Mountains, in the peninsula of Kamtschatka. [footnote] See my drawing of the volcano of Jorullo, of its 'hornitos', and of the uplifted 'malpays', in my 'Vues de Cordilleres', pl. xliii., p. 239. [Burckhardt states that during the twenty-four years that have intervened since Baron Humboldt's visit to Jorullo, the 'hornitos' have either wholly disappeared or completely changed their forms. See 'Aufenthalt und Reisen in Mexico in 1825 und 1834'.] -- Tr. When volcanoes are not isolated in a plain, but surrounded, as in the double chain of the Andes of Quito, by a table-land having an elevation from nine to thirteen thousand feet, this circumstance may probably explain the cause why no lava streams are formed* during the most dreadful eruption of ignited scoriae accompanied by detonations heard at a distance of more than a hundred miles. [footnote] * Humboldt, 'Essaii sur la Geogr. des Plantes et Tableau Phys. des Regions Equinoxiales', 1807, p. 130, and 'Essai Geogn. sur le Gisement des Roches', p. 321. Most of the volcanoes in Java demonstrate that the cause of the perfect absence of lava streams in volcanoes of incessant activity is not alone to be sought for in their form, position, and height. Leop. von Buch, 'Descr. Phys. des Iles Canaries', p. 419; Reinwardt and Hoffmann, in Poggened., 'Annalen.', bd. xii., s. 607. Such are the volcanoes of Popayan, those of the elevated plateau of Los Pastos and of the Andes of Quito, with the exception, perhaps, in the case of the latter, of the volcano of Antisana. The height of the cone of cinders, and the size and form of the crater, are elements of configuration which yield an especial and individual character to volcanoes, although the cone of cinders and the crater are both wholly independent of the dimensions of the mountain. Vesuvius is more than three times lower than the Peak of Teneriffe; its cone of cinders rises to one third of the height of the whole mountain, while the cone of cinders of the Peak is only 1/22d of its altitude. [footnote] * [It may be remarked in general, although the rule is liable to exceptions, that the dimensions of a crater are in an inverse ratio to the elevation of the mountain. Daubeney, op. Cit., p. 444.] -- Tr. In a much higher volcano than that of Teneriffe, the Rueu Pichincha, other relations occur p 231 which approach more nearly to that of Vesuvius. Among all the volcanoes that I have seen in the two hemispheres, the conical form of Cotopaxi is the most beautifully regular. A sudden fusion of the snow at its cone of cinders announces the proximity of the eruption. Before the smoke is visible in the rarefied strata of air surrounding the summit and the opening of the crater, the walls of the cone of cinders are sometimes in a state of glowing heat, when the whole mountain presents an appearance of the most fearful and portentous blackness. The crater, which, with very few exceptions, occupies the summit of the volcano, forms a deep, caldron-like valley, which is often accessible, and whose bottom is subject to constant alterations. The great or lesser depth of the crater is in many volcanoes likewise a sign of the near or distant occurrence of an eruption. Long, narrow fissures, from which vapors issue forth, or small rounding hollows filled with molten masses, alternately open and close in the caldron-like valley; the bottom rises and sinks, eminences of scoriae and cones of eruption are formed, rising sometimes far over the walls of the crater, and continuing for years together to impart to the volcano a peculiar character, and then suddenly fall together and disappear during a new eruption. The openings of these cones of eruption, which rise from the bottom of the crater, must not, as is too often done, be confounded with the crater which incloses them. If this be inaccessible from extreme depth and from the perpendicular descent, as in the case of the volcano of Rucu Pichincha, which is 15,920 feet in height, the traveler may look from the edge on the summit of the mountains which rise in the sulphurous atmosphere of the valley at his feet; and I have never beheld a grander or more remarkable picture than that presented by this volcano. In the interval between two eruptions, a crater may either present no luminous appearance, showing merely open fissures and ascending vapors, or the scarcely heated soil may be covered by eminences of scoriae, that admit of being approached without danger, and thus present to the geologist the spectacle of the eruption of burning and fused masses, which fall back on the ledge of the cone of scoriae, and whose appearance is regularly announced by small wholly local earthquakes. Lava sometimes streams forth from the open fissures and small hollows, without breaking through or escaping beyond the sides of the crater. If, however, it does break through, the newly-opened terrestrial stream generally flows in such a quiet and well-defined course, that the deep valley, which we term the crater, remains accessible p 232 even during periods of eruption. It is impossible, without an exact representation of the configuration -- the normal type, as it were, of fire-emitting mountains, to form a just idea of those phenomena which, owing to fantastic descriptions and an undefined phraseology, have long been comprised under the head of 'craters, cones of eruption', and 'volcanoes'. The marginal ledges of craters vary much less than one would be led to suppose. A comparison of Saussure's measurements with my own yields the remarkable result, for instance, that in the course of forty-nine years (from 1773 to 1822), the elevation of the northwestern margin of Mount Vesuvius ('Rocca del Palo') may be considered to have remained unchanged.* [footnote] *See the ground-work of my measurements compared with those of Saussure and Lord Minto, in the 'Abhandlungen der Akademie der Wiss. zu Berlin' for the years 1822 and 1823. Volcanoes which, like the chain of the Andes, lift their summits high above the boundaries of the region of perpetual snow, present peculiar phenomena. The masses of snow, by their sudden fusion during eruptions, occasion not only the most fearful inundations and torrents of water, in which smoking scoriae are borne along on thick masses of ice, but they likewise exercise a constant action, while the volcano is in a state of perfect repose, by infiltration into the fissures of the trachytic rock. Cavities which are either on the declivity or at the foot of the mountain are gradually converted into subterranean resevoirs of water, which communicate by numerous narrow openings with mountain streams, as we see exemplified in the highlands of Quito. the fishes of these rivulets multiply, especially in the obscurity of the hollows; and when the shocks of earthquakes, which precede all eruptions in the andes, have violently shaken the whole mass of the volcano, these subterranean caverns are suddenly opened, and water, fishes, and tufaceous mud are all ejected together. It is through this singular phenomenon* that the inhabitants of the highlands of Quito became acquainted with the existence of the little cyclopic fishes, termed by them the prenadilla. [footnote] *Pimelodes cyclopum. See Humboldt, 'Recueil d'Observations de Zoologie et d'Anatomie Comparee', t. i., p. 21-25. On the night between the 19th and 20th of June, 1698, when the summit of Carguairazo, a mountain 19,720 feet in height, fell in, leaving only two huge masses of rock remaining of the ledge of the crater, a space of nearly thirty-two square miles was overflowed and devastated by streams of liquid tufa and argillaceous mud ('lodazales'), containing large quantities of dead fish. p 233 In like manner, the putrid fever, which raged seven years previously in the mountain town of Ibarra, north of Quito, was ascribed to the ejection of fish from the volcano of Imbaburu.* [footnote] *[It would appear, as there is no doubt that these fishes proceed from the mountain itself, that there must be large lakes in the interior, which in ordinary season are out of the immediate influence of the volcanic action. See Daubeney, op. cit., p. 488, 497.] -- Tr. Water and mud, which flow not from the crater itself, but from the hollows in the trachytic mass of the mountain, can not, strictly speaking, be classed among volcanic phenomena. They are only indirectly connected with the volcanic activity of the mountain, resembling, in that respect, the singular meteorological process which I have designated in my earlier writings by the term of 'volcanic storm'. The hot stream which rises from the crater during the eruption and spreads itself in the atmosphere, condenses into a cloud, and surrounds the column of fire and cinders which rises to an altitude of many thousand feet. The sudden condensation of the vapors, and, as Gay-Lussac has shown, the formation of a cloud of enormous extent, increase the electric tension. Forked lightning flashes from the column of cinders, and it is then easy to distinguish (as at the close of the eruption of Mount Vesuvius, in the latter end of October, 1822) the rolling thunder of the volcanic storm from the detonations in the interior of the mountain. the flashes of lightning that darted from the volcanic cloud of steam, as we learn from Olafsen's report, killed eleven horses and two men, on the eruption of the volcano of Katlagia, in Iceland, on the 17th of October, 1755. Having thus delineated the structure and dynamic activity of volcanoes, it now remains for us to throw a glance at the differences existing in their material products. The subterranean forces sever old combinations of matter in order to produce new ones, and they also continue to act upon matter as long as it is in a state of liquefaction from heat, and capable of being displaced. The greater or less pressure under which merely softened or wholly liquid fluids are solidified, appears to constitute the main difference in the formation of Plutonic and volcanic rocks. The mineral mass which flows in narrow, elongated streams from a volcanic opening (an earth-spring), is called lava. where many such currents meet and are arrested in their course, they expand in width, filling large basins, in which they become solidified in superimposed strata. These few sentences describe the general character of the products of volcanic activity. p 234 Rocks which are merely broken through by the volcanic action are often inclosed in the igneous products. Thus i have found angular fragments of feldspathic syenite imbedded in the black augitic lava of the volcano of Jorullo, in Mexico; but the masses of dolomite and granular limestone, which contain magnificent clusters of crystalling fossils (vesuvian and garnets, covered with mejonite, nepheline, and sodalite), are not the ejected products of Vesuvius, these belonging rather to very generally distributed formations, viz., strata of tufa, which are more ancient than the elevation of the Somma and of Vesuvius, and are probably the products of a deep-seated and concealed submarine volcanic action.* [footnote] *Leop. von Buch, in Poggend., 'Annalen', bd. xxxvii., s. 179. We find five metals among the products of existing volcanoes, iron, copper, lead, arsenic, and selenium, discovered by Stromeyer in the crater of Volcano.* [footnote] *[The little island of Volcano is separated from Lipari by a narrow channel. It appears to have exhibited strong signs of volcanic activity long before the Christian era, and still emits gaseous exhalations. Stromeyer detected the presence of selenium in a mixture of sal ammoniac and sulphur. Another product, supposed to be peculiar to this volcano, is boracic acid, which lines the sides of the cavities in beautiful white silky crystals. Daubeney, op. cit., p. 257.] -- Tr. The vapors that rise from the 'fumarolles' cause the sublimation of the chlorids of iron, copper, lead, and ammonium; iron glanceI and chlorid of sodium (the latter often in large quantities) fill the cavities of recent lava streams and the fissures of the margin of the crater. [footnote] *Regarding the chemical origin of iron glance in volcanic masses, see Mitscherlich, in Poggend., 'Annalen', bd. xv., s. 630; and on the liberation of hydrochloric acid in the crater, see Gay-Lussac, in the 'Annals de Chimique et de Physique', t. xxii., p. 423. The mineral composition of lava differs according to the nature of the crystalline rock of which the volcano is formed, the height of the point where the eruption occurs, whether at the foot of the mountain or in the neighborhood of the crater, and the condition of temperature of the interior. Vitreous volcanic formations, obsidian, pearl-stone, and pumice, are entirely wanting in some volcanoes, while in the case of others they only proceed from the crater, or, at any rate, from very considerable heights. These important and involved relations can only be explained by very accurate crystallographic and chemical investigations. My fellow-traveler in Siberia, Gustav Rose, and subsequently Hermann Abich, have already been able, by their fortunate and ingenious researches, to throw much light on the structural relations of the various kinds of volcanic rocks. p 235 The greater part of the ascending vapor is mere steam. When condensed, this forms springs, as in Pantellaria,Iwhere they are used by the goatherds of the island. [footnote] *[Steam issues from many parts of this insular mountain, and several hot springs gush forth from it, which form together a lake 6000 feet in circumference. Daubeney, op. cit.] -- Tr. On the morning of the 26th of October, 1822, a current was seen to flow from a lateral fissure of the crater of Vesuvius, and was loong supposed to have been boiling water; it was, however, shown, by Monticelli's accurate investigations, to consist of dry ashes, which fell like sand, and of lava pulverized by friction. The ashes, which sometimes darken the air for hours and days together, and produce great injury to the vineyards and olive groves by adhering to the leaves, indicate by their columnar ascent, impelled by vapors, the termination of every great eqrthquake. This is the magnificent phenomenon which Pliny the younger, in his celebrated letter to Cornelius Tacitus, compares, in the case of Vesuvius, to the form of a lofty and thickly-branched and foliaceous pine. That which is described as flames in the eruption of scoriae, and the radiance of the glowing red clouds that hover over the crater, can not be ascribed to the effect of hydrogen gas in a state of combustion. They are rather reflections of light which issue from molten masses, projected high in the air, and also reflections from the burning depths, whence the glowing vapors ascend. We will not, however, attempt to decide the nature of the flames, which are occasionally seen now, as in the time of Strabo, to rise from the deep sea during the activity of littoral volcanoes, or shortly before the elevation of a volcanic island. When the questions are asked, what is it that burns in the volcano? what excites the heat, fuses together earths and metals, and imparts to lava currents of thick layers a degree of heat that lasts for many years? it is necessarily implied that volcanoes must be connected with the existence of substances capable of maintaining combustion, like the beds of coal in subterranean fires. [footnote] *See the beautiful experiments on the cooling of masses of rock, in Bischof's 'Warmelehre', s. 384, 443, 500-512. According to the different phases of chemical science, bitumen, pyrites, the moist admixture of finely-pulverized sulphur and iron, pyrophoric substances, and the metals of the alkalies and earths, have in turn been designated as the cause of intensely active volcanic phenomena. The great chemist, Sir Humphrey Davy, to whom we are indebted for the knowledge of the most combustible metallic p 236 substances, has himself renounced his bold chemical hypothesis in his last work ('Consolation in Travel, and last Days of a Philosopher') -- a work which can not fail to excite in the reader a feeling of the deepest melancholy. the great mean density of the earth (5.44), when compared with the specific weight of potassium (0.865), of sodium (-.972), or of the metals of the earths (1.2), and the absence of hydrogen gas in the gaseous emanations from the fissures of craters, and from still warm streams of lava, besides many chemical considerations, stand in opposition with the earlier conjectures of Davy and Ampere.* [footnote] *See Berzelius and Wohler, in Poggend., 'Annalen', bd. i., s. 221, and bd. xi., s. 146; Gay-Lussac, in the 'Annals de Chimie', t. x., xii., p. 422; and Bischof's 'Reasons against the Chemical Theory of Volcanoes', in the English edition of his 'Warmelehre', p. 297-309. If hydrogen were evolved from erupted lava, how great must be the quantity of the gas disengaged, when, the seat of the volcanic activity being very low, as in the case of the remarkable eruption at the foot of the Skaptar Jokul in Iceland (from the 11th of June to the 3d of August, 1783, described by Mackenzie and Soemund Magnussen), a space of many square miles was covered by streams of lava, accumulated to the thickness of several hundred feet! Similar difficulties are opposed to the assumption of the penetration of the atmospheric air into the crater, or, as it is figuratively expressed, the 'inhalation of the earth', when we have regard to the small quantity of nitrogen emitted. So general, deep-seated, and far-propagated an activity as that of volcanoes, can not assuredly have its source in chemical affinity, or in the mere contact of individual or merely locally distributed substances. Modern geognosy* rather seeks the cause of this activity in the increased temperature with the increase of depth at all degrees of latitude, in that powerful internal heat which our planet owes to its first solidification, its formation in the regions of space, and to the spherical contraction of p 237 matter revolving elliptically in a gaseous condition. [footnote] *[On the various theories that have been advanced in explanation of volcanic action, see Daubeney 'On Volcanoes', a work to which we have made continual reference during the preceding pages, as it constitutes the most recent and perfect compendium of all the important facts relating to this subject, and is peculiarly adapted to serve as a source of reference to the 'Cosmos', since the learned author in many instances enters into a full exposition of the views advanced by Baron Humboldt. The appendix contains several valuable notes with reference to the most recent works that have appeared on the Continent, on subjects relating to volcanoes; among others, an interesting notice of Professor Bischof's views "on the origin of the carbonic acid discharged from volcanoes," as enounced in his recently published work, 'Lehrbuch der Chemischen und Physikalischen Geologie'.] -- Tr. We have thus mere conjecture and supposition side by side with certain knowledge. A philosophical study of nature strives ever to elevate itself above the narrow requirements of mere natural description, and does not consist, as we have already remarked, in the mere accumulation of isolated facts. The inquiring and active spirit of man must be suffered to pass from the present to the past, to conjecture all that can not yet be known with certainty, and still to dwell with pleasure on the ancient myths of geognosy which are presented to us under so many various forms. If we consider volcanoes as irregular intermittent springs, emitting a fluid mixture of oxydized metals, alkalies, and earths, flowing gently and calmy wherever then find a passage, or being upheaved by the powerful expansive force of vapors, we are involuntarily led to remember the geognostic visions of Plato, according to which hot springs, as well as all volcanic igneous streams, were eruptions that might be traced back to one generally distributed subterranean cause, 'Pyriphlegethon'.* [footnote] *According to Plato's geognostic views, as developed in the 'Phaedo', Pyriphlegethon plays much the same part in relation to the activity of volcanoes that we now ascribe to the augmentation of heat as we descend from the earth's surface, and to the fused condition of its internal strata. ('Phaedo', ed. Ast, p. 603 and 607; Annot., p. 308 and 817.) "Within the earth, and all around it, are larger and smaller caverns. Water flows there in abundance; also much fire and large streams of fire, and streams of moist mud (some purer and others more filthy), like those in Sicily, consisting of mud and fire, preceding the great eruption. These streams fill all places that fall in the way of their course. Pyriphlegethon flows forth into an extensive district burning with a fierce fire, where it forms a lake larger than our sea, boiling with water and mud. From thence it moves in circles round the earth, turbid and muddy." This stream of molten earth and mud is so much the general cause of volcanic phenomena, that Plato expressly adds, "thus is Pyriphlegethon constituted, from which also the streams of fire ([Greek words]), wherever they reach the earth ([Greek words]), inflate such parts (detached fragments)." Volcanic scoriae and lava streams are therefore portions of Pyriphlegethon itself, portions of the subterranean molten and ever-undulating mass. That {Greek words] are lava streams, and not, as Schneider, Passow, and Schleiermacher will have it, "fire-vomiting mountains," is clear enough from many passages, some of which have been collected by Ukert ('Geogr. der Griechen und Romer', th. ii., s. 200): [Greek word] is the volcanic phenomenon in reference to its most striking characteristic, the lava stream. Hence the expression, the [Greek word] of Aetna. Aristot. 'Mirab. Ausc.', t. ii., p. 833; sect. 38, Bekker; Thucyd., iii., 116; Theophrast., 'De Lap'., 22, p. 427, Schneider; Diod., v., 6, and xiv., 59, where are the remarkable words, "Many places near the sea, in the neighborhood of Aetna, were leveled to the ground, [Greek words];" Strabo, vi., p. 269; xiii., p. 268, and where there is a notice of the celebrated burning mud of the Lelantine plains, in Euboea, i., p. 58, Casaub.; and Appian, 'De Bello Civili', v., 114. The blame which Aristotle throws on the geognostical fantasies of the Phaedo ('Meteor.', ii., 2, 19) is especially applied to the sources of the rivers flowing over the earth's surface. The distinct statement of Plato, that "in Sicily eruptions of wet mud precede the glowing (lava) stream," is very remarkable. Observations on Aetna could not have led to such a statement, unless pumice and ashes, formed into a mud-like mass by admixture with melted snow and water, during the volcano-electric storm in the crater of eruption, were mistaken for ejected mud. It is more probable that Plato's streams of moist mud ([Greek words]) originated in a faint recollection of the salses (mud volcanoes) of Agrigentum, which, as I have already mentioned, eject argillaceous mud with a loud noise. It is much to be regretted, in reference to this subject, that the work of Theophrastus [Greek words] 'On the Volcanic Stream in Sicily', to which Diog. Laert., v., 49, refers, has not come down to us. p 238 The different volcanoes over the earth's surface, when they are considered independently of all climatic differences, are acutely and characteristically classified as central and linear volcanoes. Under the first name are comprised those which constitute the central point of many active mouths of eruption, distributed almost regularly in all directions; under the second, those lying at some little distance from one another, forming, as it were, chimneys or vents along an extended fissure. Linear volcanoes again admit of further subdivision, namely, those which rise like separate conical islands from the bottom of the sea, being generally parallel with a chain of primitive mountains, whose foot they appear to indicate, and those volcanic chains which are elevated on the highest ridges of these mountain chains, of which they form the summits.* [footnote] *Leopold von Buch, 'Physikal. Beschreib. der Canarischen Inseln', s. 326-407. I doubt if we can agree with the ingenious Charles Darwin ('Geological Observations on Volcanic Islands', 1844, p. 127) in regarding central volcanoes in general as volcanic chains of small extent on parallel fissures. Friedrich Hoffman believes that in the group of the Lipari Islands, which he has so admirably described, and in which two eruption fissures intersect near Panaria, he has found an intermediate link between the two principal modes in which volcanoes appear, namely, the central volcanoes and volcanic chains of Von Buch (Poggendorf, 'Annalen der Physik', bd. xxvi., s. 81-88). The Peak of Teneriffe, for instance, is a central volcano, being the central point of the volcanic group to which the eruption of Palma and Landerote may be referred. The long, rampart-like chain of the Andes, which is sometimes single, and sometimes divided into two or three parallel branches, connected by various transverse ridges, presents, from the south of Chili to the northwest coast of America, one of the grandest instances of a continental volcanic chain. The proxiimity of p 239 active volcanoes is always manifested in the chain of the Andes by the appearance of certain rocks (as dolerite, melaphyre, trachyte, andesite, and dioritic porphyry), which divide the so-called primitive rocks, the transition slates and sandstones, and the stratified formations. the constant recurrence of this phenomenon convinced me long since that these sporadic rocks were the seat of volcanic phenomena, and were connected with volcanic eruptions. At the foot of the grand Tunguragua, near Penipe, on the banks of the Rio Puela, I first distinctly observed mica slate resting on granite, broken through by a volcanic rock. In the volcanic chain of the New Continent, the separate volcanoes are occasionally, when near together in mutual dependence upon one another; and it is even seen that the volcanic activity for centuries together has moved on in one and the same direction, as for instance, from north to south in the province of Quito.* [footnote] (Humboldt, 'Geognost. Beobach, uber die Vulkane des Hochlandes von Quito', in Poggend., 'Annal. der Physik', bd. xliv., s. 194. The focus of the volcanic action lies below the whole of the highlands of this province; the only channels of communication with the atmosphere are, however, those mountains which we designate by special names, as the mountains of Pichincha, Cotopaxi, and Tunguragua, and which, from their grouping, elevation, and form, constitute the grandest and most picturesque spectacle to be found in any volcanic district of an equally limited extent. Experience shows us, in many instances, that the extremities of such groups of volcanic chains are connected together by subterranean communications; and this fact reminds us of the ancient and true expression made use of by Seneca,* that the igneous mountain is only the issue of the more deeply-seated volcanic forces. [footnote] *Seneca, while he speaks very clearly regarding the problematical sinking of Aetna, says in his 79th letter, "Though this might happen, not because the mountain's height is lowered, but because the fires are weakened, and do not blaze out with their former vehemence; and for which reason it is that such vast clouds of smoke are not seen in the day-time. Yet neither of these seem incredible, for the mountain may possibly be consumed by being daily devoured, and the fire not be so large as formerly, since it is not self-generated here, but is kindled in the distant bowels of the earth, and there rages, being fed with continual fuel, not with that of the mountain, through which it only makes its passage." The subterranean communication, "by galleries," between the volcanoes of Sicily, Lipari, Pithecusa (Ischia), and Vesuvius, "of the last of which we may conjecture that it formerly burned and presented a fiery circle," seems fully understood by Strabl (lib. i., p. 247 and 248). He terms the whole district "sub-igneous." In the Mexican highlands a mutual dependence is p 240 also observed to exist among the volcanic mountains Orizaba, Popocatepel, Jorullo, and Colima; and I have shown* that they all lie in one direction between 18 degrees 59' and 19 degrees 12' north latitude, and are situated in a transverse fissure running from sea to sea. [footnote] *Humboldt, 'Essai Politique sur la Nouv. Espagne', t. ii., p. 173-175. The volcano of Jorullo broke forth on the 29th of September, 1759, exactly in this direction, and over the same transverse fissure, being elevated to a height of 1604 feet above the level of the surrounding plain. The mountain only once emitted an eruption of lava, in the same manner as is recorded of Mount Epomeo in Ischia, in the year 1302. But although Jorullo, which is eighty miles from any active volcano, is in the strict sense of the word a new mountain, it must not be compared with Monte Nuovo, near Puzzuolo, which first appeared on the 19th of September, 1538, and is rather to be classed among craters of elevation. I believe that I have furnished a more natural explanation of the eruption of the Mexican volcano, in comparing its appearance to the elevation of the Hill of Methone, now Methana, in the peninsula of Troezene. The description given by Strabo and Pausanias of this elevation, led one of the Roman poets, most celebrated for his richness of fancy, to develop views which agree in a remarkable manner with the theory of modern geognosy. "Near Troezene is a tumulus, steep and devoid of trees, once a plain, now a mountain. The vapors inclosed in dark caverns in vain seek a passage by which they may escape. The heavier earth, inflated by the force of the compressed vapors, expands like a bladder filled with air, or like a goat-skin. The ground has remained thus inflated, and the high projecting eminence has been solidified by time into a naked rock." Thus picturesquely, and, as analogous phenomena justify us in believing, thus truly has Ovid described that great natural phenomenon which occurred 282 years before our era, and consequently, 45 years bfore the volcanic separation of Thera (Santorino) and Therasia, between Troezene and Epidaurus, on the same spot where Russegger has found veins of trachyte.* [footnote] *Ovid's description of the eruption of Methone ('Metam.', xv., p. 226-306): "Near Troezene stands a hill, exposed in air To winter winds, of leafy shadows bare: This once was level ground; but (strange to tell) Th' included vapors, that in caverns dwell, Laboring with colic pangs, and close confined, In vain sought issue for the rumbling wind: Yet still they heaved for vent, and heaving still, Enlarged the concave and shot up the hill, As breath extends a bladder, or the skins Of goats are blown t'inclose the hoarded wines; The mountain yet retains a mountain's face, And gathered rubbish heads the hollow space." 'Dryden's Translation'. [footnote continues] This description of a dome-shaped elevation on the continent is of great importance in a geognostical point of view, and coincides to a remarkable degree with Aristotle's account ('Meteor.', ii., 89, 17-19) of the upheaval of islands of eruption: "The heaving of the earth does not cease till the wind [(Greek word)] which occasions the shocks has made its escape into the crust of the earth. It is not long ago since this actually happened at Heraclea in Pontus, and a similar event formerly occurred at Hiera, one of the Aeolian Islands. A portion of the earth swelled up, and with loud noise rose into the form of a hill, till the mighty urging blast [(Greek word)] found an outlet, and ejected sparks and ashes which covered the neighborhood of Lipari, and even extended to several Italian cities." In this description, the vesicular distension of the earth's crust (a stage at which many trachytic mountains have remained) is very well distinguished from the eruption itself. Strabo, lib. i., p. 59 (Casaubon), likewise describes the phenomenon as it occurred at Methone: near the town, in the Bay of Hermione, there arose a flaming eruption; a fiery mountain, seven (?) stadia in height, was then thrown up, which during the day was inaccessible from its heat and sulphureous stench, but at night evolved an agreeable odor (?) , and was so hot that the sea boiled for a distance of five stadia, and was turbid for full twenty stadia, and also was filled with detached masses of rock. Regarding the present mineralogical character of the peninsula of Methana, see Fiedler, 'Reise durch Griechenland', th. i., s. 257-263. p 241 Santorino is the most important of all the 'islands of eruption' belonging to volcanic chains.* [footnote] *[I am indebted to the kindness of Professor E. Forbes for the following interesting account of the island of Santorino, and the adjacent islands of Neokaimeni and Microkaimeni. "The aspect of the bay is that of a great crater filled with water, Thera and Therasia forming its walls, and the other islands being after-productions in its center. We sounded with 250 fathoms of line in the middle of the bay, between Therasia and the main islands, but got no bottom. Both these islands appear to be similarly formed of successive strata of volcanic ashes, which, being of the most vivid and variegated colors, present a striking contrast to the black and cindery aspect of the central isles. Neokaimeni, the last-formed island, is a great heap of obsidian and scoriae. So, also, is the greater mass, Microkaimeni, which rises up in a conical form, and has a cavity or crater. On one side of this island, however, a section is exposed, and cliffs of fine pumiceous ash appear stratified in the greater islands. In the main island, the volcanic strata abut against the limestone mass of Mount St. Elias in such a way as to lead to the inference that they were deposited in a sea bottom in which the present mountain rose as a submarine mass of rock. The people at Santorino assured us that subterranean noises are not unfrequently heard, especially during calms and south winds, when they say the water of parts of the bay becomes the color of sulphur. My own impression is, that this group of islands, constitutes a crater of elevation, of which the outer ones are the remains of the walls, while the central group are of later origin, and consist partly of upheaved sea bottoms and partly of erupted matter -- erupted, however, beneath the surface of the water."] -- Tr. It combines within itself p 242 the history of all islands of elevation. For upward of 2000 years, as far as history and tradition certify, it would appear as if nature were striving to form a volcano in the midst of the crater of elevation."* [footnote] *Leop. von Buch, 'Physik. Beschr. der Canar. Inseln', s. 356-358, and particularly the French translation of this excellent work, p. 402; and his memoir in Poggendorf's 'Annalen', bd. xxxviii., s. 183. A submarine island has quite recently made its appearance within the crater of Santorino. In 1810 it was still fifteen fathoms below the surface of the sea, but in 1830 it had risen to within three or four. It rises steeply like a great cone, from the bottom of the sea, and the continuous activity of the submarine crater is obvious from the circumstance that sulphurous acid vapors are mixed with the sea water, in the eastern bay of Neokaimeni, in the same manner as at Vromolimni, near Methana. Coppered ships lie at anchor in the bay in order to get their bottoms cleaned and polished by this natural (volcanic) process. (Virlet, in the 'Bulletin de la Societe Geologique de France', t. iii., p. 109, and Fiedler 'Reise durch Griechenland', th. ii., s. 469 and 584.) Similar insular elevations, and almost always at regular intervals of 80 or 90 years,* have been manifested in the island of St. Michael, in the Azores; but in this case the bottom of the sea has not been elevated at exactly the same parts.** [footnote] *Appearance of a new island near St. Miguel, one of the Azores, 11th of June, 1638, 31st of December, 1719, 13th of June, 1811. [footnote] **[My esteemed friend, Dr. Webster, professor of Chemistry and Mineralogy at Harvard College, Cambridge, Massachusetts, U. S., in his 'Description of the Island of St. Michael, etc.', Boston, 1822, gives an interesting account of the sudden appearance of the island named Sabrina which was about a mile in circumference, and two or three hundred feet above the level of the ocean. After continuing for some weeks, it sank into the sea. Dr. Webster describes the whole of the island of St. Michael as volcanic, and containing a number of conical hills of trachyte, several of which have craters, and appear at some former time to have been the openings of volcanoes. The hot springs which abound in the island are impregnated with sulphureted hydrogen and carbonic acid gases, appearing to attest the existence of volcanic action.] -- Tr. The island which Captain Tillard named 'Sabrina', appeared unfortunately at a time (the 30th of January, 1811) when the political relations of the maritime nations of Western Europe prevented that attention being bestowed upon the subject by scientific institutions which was afterward directed to the sudden appearance (the 2d of July, 1831), and the speedy destruction of the igneous island of Ferdinandea in the Sicilian Sea, between the limestone shores of Sciacca and the purely volcanic island of Pantellaria.* [footnote] *Prevost, in the Bulletin de la Societe Geologique, t. iii., p. 34; Friedrich Hoffman, 'Hinterlassene Werke.' bd. ii., s. 451-456. p 243 The geographical distribution of the volcanoes which have been in a state of activity during historical times, the great number of insular and littoral volcanic mountains, and the occasional, although ephemeral, eruptions in the bottom of the sea, early led to the belief that volcanic activity was connected with the neighborhood of the sea, and was dependent upon it for its continuance. "For many hundred years," says Justinian, or rather Trogus Pompeius, whom he follows,* "Aetna and the Aeolian Islands have been burning, and how could this have continued so long if the fire had not been fed by the p 244 neighboring sea?"** [footnote] *"Accedunt vicini et perpetui Aetnae montis ignes et insularum Aeolidum, veluti ipsis undis alatur incendium; neque enim aliter durare tot seculis tantus ignis potuisset, nisi humoris nutrimentis aleretur." (Justin, 'Hist. Philipp.', iv., i.) The volcanic theory with which the physical description of Sicily here begins is extremely intricate. Deep fissured; violent motion of the waves of the sea, which, as they strike together, draw down the air (the wind) for the maintenance of the fire: such are the elements of the theory of Trogus. Since he seems from Pliny (xi., 52) to have been a physiognomist, we may presume that his numerous lost works were not confined to history alone. The opinion that air is forced into the interior of the earth, there to act on the vocanic furnaces, was connected by the ancients with the supposed influence of winds from different quarters on the intensity of the fires burning in tna, Hiera, and Stromboli. (See the remarkable passage in Strabo, liv. vi., Aetna.) The mountain island of Stromboli (Strongyle) was regarded therefore, as the dwelling-place of Aeolus, "the regulator of the winds," in consequence of the sailors foretelling the weather from the activity of the volcanic eruptions of this island. The connection between the eruption of a small volcano with the state of the barometer and the direction of the wind is still generally recognized (Leop. von Buch, 'Descr. Phys. des Iles Canaries', p. 334; Hoffmann, in Poggend., 'Annalen', bd. xxvi., s. viii), although our present knowledge of volcanic phenomena, and the slight changes of atmospheric pressure accompanying our winds, do not enable us to offer any satisfactory explanation of the fact. Bembo, who during his youth was brought up in Sicily by Greek refugees, gave an agreeable narrative of his wanderings, and in his 'Aetna Dialogus' (written in the middle of the sixteenth century) advances the theory of the penetration of sea water to the very center of the volcanic action, and of the necessity of the proximity of the sea to active volcanoes. In ascending Aetna the following question was proposed: "Explaina potius nobis quae petimus, ea incendia unde oriantur et orta quomodo perdurent. In omni tellure nuspiam majores fistulae aut meatus ampliores sunt quam in locis, quae vel mari vicina sunt, vel a mari protinus alluntur: mare erodit illa facillime pergitque in viscera terrae. Itaque cum in aliena regna sibi viam faciat, ventis etiam facit; ex quo fit, ut loca quaeque maritima maxime terrae motibus subjecta sint, parum mediterranea. Habes quum in sulfuris venas venti furentes inciderint, unde incendia oriantur tn tuae. Vides, quae mare in radicibus habeat, quae sulfurea sit, quae cavernosa, quae a mari aliquando perforata ventos admiscrit Aestuantes, per quos idonea flammae materies incenderetur." [footnote] **[Although extinct volcanoes seem by no means confined to the neighborhood of the present seas, being often scattered over the most inland portions of our existing continents, yet it will appear that, at the time at which they were in an active state, the greater part were in the neighborhood either of the sea, or of the extensive salt or fresh water lakes, which existed at that period over much of what is now dry land. This may be seen either by referring to Dr. Boue's map of Europe, or to that published by Mr. Lyell in the recent edition of his 'Principles of Geology' (1847), from both of which it will become apparent that, at a comparatively recent epoch, those parts of France, of Germany, of Hungary, and of Italy, which afford evidences of volcanic action now extinct, were covered by the ocean. Daubeney 'On Volcanoes', p. 605.] -- Tr. In order to explain the necessity of the vicinity of the sea, recourse has been had, even in modern times, to the hypothesis of the penetration of sea water into the foci of volcanic agency, that is to say, into deep-seated terrestrial strata. When I collect together all the facts that may be derived from my own observation and the laborious researches of others, it appears to me that every thing in this great quantity of aqueous vapors, which are unquestionably exhaled from volcanoes even when in a state of rest, be derived from sea water impregnated with salt, or rather, perhaps with fresh meteoric water; or whether the expansive force of the vapors (which, at a depth of nearly 94,000 feet, is equal to 2800 atmospheres) would be able at different depths to counterbalance the hydrostatic pressure of the sea, and thus afford them, under certain conditions, a free access to the focus;* or whether the formation of metallic chlorids, the presence of chlorid of sodium in the fissures of the crater, and the frequent mixture of hydrochloric acid with the aqueous vapors, necessarily imply access of sea water; or, finally, whether the repose of volcanoes (either when temporary, or permanent and complete) depends upon the closure of the channels by which the sea or meteoric water was conveyed, or whether the absence of flames and of exhalations of hydrogen (and sulphureted hydrogen gas seems more characteristic of solfataras than of active volcanoes) is not directly at variance p 245 with the hypothesis of the decomposition of great masses of water?** [footnote] * Compare Gay-Lussac, 'Sur les Volcans', in the 'Annales de Chimie', t. xxii., p. 427, and Bischof, 'Warmelehre', s. 272. The eruptions of smoke and steam which have at different periods been seen in Lancerote, Iceland, and the Kurile Islands, during the eruption of the neighboring volcanoes, afford indications of the reaction of volcanic foci through tense columns of water; that is to say, these phenomena occur when the expansive force of the vapor exceeds the hydrostatic pressure. [footnote] ** [See Daubeney 'On Volcanoes', Part iii., ch. xxxvi., xxxviii., xxxix.] -- Tr. The discussion of these important physical questions does not come within the scope of a work of this nature; but, while we are considering these phenomena, we would enter somewhat more into the question of the geographical distribution of still active volcanoes. We find, for instance, that in the New World, three, viz., Jorullo, Popocatepetl, and the volcano of De la Fragua, are situated at the respective distances of 80, 132, and 196 miles from the sea-coast, while in Central Asia, as Abel Remusat* first made known to geognosists, the Thianschan (Celestial Mountains), in which are situated the lava-emitting mountain of Pe-schan, the solfatara of Urumtsi, and the still active igneous mountain (Ho-tscheu) of Turfan, lie at an almost equal distance (1480 to 1528 miles) from the shores of the Polar Sea and those of the Indian Ocean. [footnote] *Abel Remusat, 'Lettre a M. Cordier', in the 'Annales de Chimie', t. v., p. 137. Pe-schan is also fully 1360 miles distant from the Caspian Sea,* and 172 and 218 miles from the seas of Issikul and Balkasch. [footnote] *Humboldt, 'Asie Centrale', t. ii., p. 30-33, 38-52, 70-80, and 426-428. The existence of active volcanoes in Kordofan, 540 miles from the Red Sea, has been recently contradicted by Ruppell, 'Reisen in Nubien', 1829, s. 151. It is a fact worthy of notice, that among the four great parallel mountain chains which traverse the Asiatic continent from east to west, the Altai, the Thianschan, the Kuen-lun, and the Himalaya, it is not the latter chain, which is nearest to Kuen-lun, at the distance of 1600 and 720 miles from the sea, which have fire-emitting mountains like Aetna and Vesuvius, and generate ammonia like the volcano of Guatimala. Chinese writers undoubtedly speak of lava streams when they describe the emissions of smoke and flame, which, issuing from Pe-schan, devastated a space measuring ten li* in the first and seventh centuries of our era. [footnote] *[A 'li' is a Chinese measurement, equal to about one thirtieth of a mile.] -- Tr. Burning masses of stone flowed, according to their description "like thin melted fat." The facts that have been enumerated, and to which sufficient attention has not been bestowed, render it probable that the vicinity of the sea, and the penetration of sea water to the foci of volcanoes, are not absolutely necessary to the eruption of p 246 subterranean fire, and that littoral situations only favor the eruption by forming the margin of a deep sea basin, which, covered by strata of water, and lying many thousand feet lower than the interior continent, can offer but an inconsiderable degree of resistance. The present active volcanoes, which communicate by permanent craters simultaneously with the interior of the earth and with the atmosphere, must have been formed at a subsequent period, when the upper chalk strta and all the tertiary formations were already present: this is shown to be the fact by the trachytic and basaltic eruptions which frequently form the walls of the crater of elevation. Melaphyres extend to the middle tertiary formations, but are found already in the Jura limestone, where they break through the variegated sandstone.* [footnote] *Dufrenoy et Elie de Beaumont, 'Explication de la Carte Geologique de la France', t. i., p. 89. We must not confound the earlier outpourings of granite, quartzose porphyry, and euphotide from temporary fissures in the old transition rocks with the present active volcanic craters. The extinction of volcanic activity is either only partial -- in which case the subterranean fire seeks another passage of escape in the same mountain chain -- or it is total, as in Auvergne. More recent examples are recorded in historical times, of the total extinction of the volcano of Mosychlos,* on the island sacred to Hephaestos (Vulcan), whose "high whirling flames" were known to Sophocles; and of the volcano of Medina, which according to Burckhardt, still continued to pour out a stream of lava on the 2d of November, 1276. [footnote] *Sophocl., 'Philoct.', v. 971 and 972. On the supposed epoch of the extinction of the Lemnian fire in the time of Alexander, compare Buttmann, in the 'Museum der Alterhumswissenschaft', bd. i., 1807, s. 295; Dureau de la Malle, in Malte-Brun, 'Annales des Voyages', t. ix., 1809, p. 5; Ukert in Bertuch, 'Geogr. Ephemeriden', bd. xxxix., 1812, s. 361; Rhode, 'Res Lemnicae', 1829, p. 8; and Walter, 'Ueber Abnahame der Vulken. Thatigkeit in Historischen Zeiten', 1844, s. 24. The chart of Lemmos, constructed by Choiseul, makes it extremely probable that the extinct crater of Mosychlos, and the island of Chryse, the desert habitation of Philoctetes (Otfried Muller, 'Minyer', s. 300), have been long swallowed up by the sea. Reefs and shoals, to the northeast of Lemnos, still indicate the spot where the Aegean Sea once possessed an active volcano like Aetna, Vesuvius, Stromboli, and Volcano (in the Lipari Isles). Every stage of volcanic activity, from its first origin to its extinction, is characterized by peculiar products; first by ignited scoriae, streams of lava consisting of trachyte, pyroxene, and obsidian, and by rapilli and tufaceous ashes, accompanied by the development p 247 of large quantities of pure aqueous vapor; subsequently, when the volcano becomes a solfatara, by aqueous vapors mixed with sulphureted hydrogen and carbonic acid gases; and, finally, when it is completely cooled, by exhalations of carbonic acid alone. There is a remarkable class of igneous mountains which do not eject lava, but merely devastating streams of hot water,* impregnated with burning sulphur and rocks reduced to a state of dust (as, for instance, the Galungung in Java); but whether these mountains present a normal condition, or only a certain transitory modification of the volcanic process, must remain undecided until they are visited by geologists possessed of a knowledge of chemistry in its present condition. [footnote] *Compare Reinwardt and Hoffmann, in Poggendorf's 'Annalen', bd. xii., s. 607; Leop. von Buch, 'Descr. des Iles Canaries', p. 424-426. The eruptions of argillaceous mud at Carguairazo, when that volcano was destroyed in 1698, the Lodazales of Igualata, and the Moya of Pelileo -- all on the table-land of Quito -- are volcanic phenomena of a similar nature. I have endeavored in the above remarks to furnish a general description of volcanoes -- comprising one of the most important sections of the history of terrestrial activity -- and I have based my statements partly on my own observations, but more in their general bearing on the results yielded by the labors of my old friend, Leopold von Buch, the greatest geognosist of our own age, and the first who recognized the intimate connection of volcanic phenomena, and their mutual dependence upon one another, considered with reference to their relations in space. Volcanic action, or the reaction of the interior of a planet on its external crust and surface, was long regarded only as an isolated phenomenon, and was considered solely with respect to the disturbing action of the subterranean force; and it is only in recent times that -- greatly to the advantage of geognostical views based on physical analogies -- volcanic forces have been regarded as 'forming new rocks, and transforming those that already existed'. We here arrive at the point to which I have already alluded, at which a well-grounded study of the activity of volcanoes, whether igneous or merely such as emit gaseous exhalations, leads us, on the one hand, to the mineralogical branch of geognosy (the science of the texture and the succession of terrestrial strata), and, on the other, to the science of geographical forms and outlines -- the configuration of continents and insular groups elevated above the level p 248 of the sea. This extended insight into the connection of natural phenomena is the result of the philosophical direction which has been so generally assumed by the more earnest study of geognosy. Increased cultivation of science and enlargement of political views alike tend to unite elements that had long been divided. This material taken from pages 248- COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 248 If, instead of classifying rocks according to their varieties of form and superposition into stratified and unstratified, schistose and compact, normal and abnormal, we investigate those phenomena of formation and transformation which are still going on before our eyes, we shall find that rocks admit of being arranged according to four modes of origin. 'Rocks of eruption', which have issued from the interior of the earth either in a state of fusion from volcanic action, or in a more or less soft, viscous condition, from Plutonic action. 'Sedimentary rocks', which have been precipitated and deposited on the earth's surface from a fluid, in which the most minute particles were either dissolved or held in suspension constituting the greater part of the secondary (or flotz) and tertiary groups. 'Transformed or metamorphic rocks',* in which the internal texture and the mode of stratification have been changed, either p 249 by contact or proximity with a Plutonic or volcanic endogenous rock of eruption,** or, what is more frequently the case, by a gaseous sublimation of substances*** which accompany certain masses erupted in a hot, fluid condition. [footnote] *[As the doctrine of mineral metamorphism is now exciting very general attention, we subjoin a few explanatory observations by the 'New Philos. Journ.', Jan., 1848: "In its widest sense, mineral metamorphism means every change of aggregation, structure, or chemical condition which rocks have undergone subsequently to their deposition and stratification, or the effects which have been produced by other forces than gravity and cohesion. There fall under this definition, the discoloration of the surface of black limestone by the loss of carbon; the formation of brownish-red crusts on rocks of limestone, sandstone, many slate structures, serpentine, granite, etc., by the decomposition of iton pyrites, or magnetic iron, finely disseminated in the mass of the rock; the conversion of anhydrite into gypsum, in consequence of the absorption of water; the crumbling of many granites and porphyries into gravel, occasioned by the decomposition of the mica and feldspar. In its more limited sense, the term metamorphic is confined to those changes of the rock which are produced, not by the effect of the atmosphere or of water on the exposed surfaces, but which are produced, directly or indirectly, by agencies seated in the interior of the earth. In many cases the mode of change may be explained by our physical or chemical theories, and may be viewed as the effect of temperature or of electro-chemical actions. Adjoining rocks, or connecting communications with the interior of the earth, also distinctly point out the seat from which the change proceeds. In many other cases the metamorphic process itself remains a mystery, and from the nature of the products alone do we conclude that such a metamorphic action has taken place.] -- Tr. [footnote] ** In a plan of the neighborhood of Tezcuco, Totonilco, and Moran ('Atlas Geographique et Physique', pl. vii.), which I originally (1803) intended for a work which I never published, entitled 'Pasigrafia Geognostica destinada al uso de los Jovenes del Colegio de Mineria de Mexico', I names (in 1832) the Plutonic and volcanic eruptive rocks 'endogenous' (generated in the interior), and the sedimentary and flotz rocks 'exogenous' (or generated externally on the surface of the earth). Pasiward, [upward arrow] and the latter by the same symbol directed downward [downward arrow]. These signs have at least some advantage over the ascending lines, which in the older systems represent arbitrarily and ungracefully the horizontally ranged sedimentary strata, and their penetration through masses of basalt, porphyry, and syenite. The names proposed in the pasigraphico-geognostic plan were borrowed from De Candolle's nomenclature, in which 'endogenous' is synonymous with monocotyledonous, and 'exogenous' with dicotyledonous plants. Mohl's more accurate examination of vegetable tissues has, however, shown that the growth of monocotyledons from within, and dicotyledons from without, is not strictly and generally true for vegetable organisms (Link, 'Elementa Philosophiae Botanicae', t. i., 1837, p. 287; Endlicher and Unger, 'Grundzugeder Botanik', 1843, s. 89; and Jussieu, 'Traite de Botanique', t. i., p. 85). The rocks which I have termed endogenous are characteristically distinguished by Lyell, in his 'Principles of Geology', 1833, vol. iii., p. 374, as "nether-formed" or "hypogene rocks." [footnote] *** Compare Leop. von Buch, 'Ueber Dolomit als Gebirgsart', 1823, s. 36; and his remarks on the degree of fluidity to be ascribed to Plutonic rocks at the period of their eruption, as well as on the formation of gneiss from schist, through the action of granite and of the substances upheaved with it, to be found in the 'Abhandl. der Akad. der Wissensch. zu Berlin' for the year 1842, s. 58 und 63, and in the 'Jahrbuch fur Wissenschaftliche Kritik', 1840, s. 195. 'Conglomerates'; coarse or finely granular sandstones, or breccias composed of mechanically-divided masses of the three previous species. These four modes of formation -- by the emission of volcanic masses, as narrow lava streams; by the action of these masses on rocks previously hardened; by mechanical separation or chemical precipitation from liquids impregnated with carbonic acid; and, finally, by the cementation of disintegrated rocks of heterogeneous nature -- are phenomena and formative processes which must merely be regarded as a faint reflection of that more energetic activity which must have characterized the chaotic condition of the earlier world under wholly different conditions of pressure and at a higher temperature, not only in the whole crust of the earth, but likewise in the more p 250 extended atmosphere, overloaded with vapors. The vast fissures which were formerly open in the solid crust of the earth have since been filled up or closed by the protrusion of elevated mountain chains, or by the penetration of veins of rocks of eruption (granite, porphyry, basalt, and melaphyre); and while, scarcely more than four volcanoes remaining through which fire and stones are erupted, the thinner, more fissured, and unstable crust of the earth was anciently almost every where covered by channels of communication between the fused interior and the external atmosphere. Gaseous emanations rising from very unequal depths, and therefore conveying substances differing in their chemical nature, imparted greater activity to the Plutonic processes of formation and transformation. The sedimentary formations, the deposits of liquid fluids from cold and hot springs, which we daily see producing the travertine strata near Rome, and near Hobart Town in Van Diemen's Land, afford but a faint idea of the flotz formation. In our seas, small banks of limestone, almost equal in hardness at some parts to Carrara marble,* are in the course of formation, by gradual precipitation, accumulation, and cementation -- processes whose mode of action has not been sufficiently well investigated. [footnote] Darwin, 'Volcanic Islands', 1844, p. 49 and 154. The Sicilian coast, the island of Ascension, and King George's Sound in Australia, are instances of this mode of formation. On the coasts of the Antilles, these formations of the present ocean contain articles of pottery, and other objects of human industry, and in Guadaloupe even human skeletons of the Carib tribes.* [footnote] *[In most instances the bones are dispersed; but a large slab of rock, in which considerable portion of the skeleton of a female is embedded, is preserved in the British Museum. The presence of these bones has been explained by the circumstance of a battle, and the massacre of a tribe of Gallibis by the Caribs, which took place near the spot in which they are found, about 120 years ago; for, as the bodies of the slain were interred on the sea-shore, their skeletons may have been subsequently covered by sand-drift, which has since consolidated into limestone. Dr. Moultrie, of the Medical College, Charleston, South Carolina, U.S., is, however, of opinion that these bones did not belong to individuals of the Carib tribe, but of the Peruvian race, or of a tribe possessing a similar craniological development.] --Tr. The negroes of the French colonies designate these formations by the name of 'Maconne-bon-Dieu'.* Moreau de Jonnes, 'Hist. Phys. des Antilles', t. i., p. 136, 138, and 543; Humboldt, 'Relation Historique', t. iii., p. 367. A small colitic bed, formed in Lancerote, one of the Canary Islands, and which, notwithstanding p 251 its recent formation, bears a resemblance to Jura Limestone, has been recognized as a product of the sea and of tempests.* [footnote] *Near Teguiza. Leop. von Buch, 'Canarische Inseln', s. 301. Composite rocks are definite associations of certain crytonostic, simple minerals, as feldspar, mica, solid silex, augite, and nepheline. Rocks very similar to these consisting of the same elements, but grouped differently, are still formed by volcanic processes, as in the earlier periods of the world. The character of rocks, as we have already remarked is so independent of geographical relations of space,* that the geologist recognizes with surprise, alike to the north or the south of the equator, in the remotest and most dissimilar zones, the familiar aspect, and the repetition of even the most minute characteristics in the periodic stratification of the silurian strata, and in the effects of contact with augitic masses of eruption. [footnote] *Leop. von Buch, op. cit., p. 9. We will now enter more fully into the consideration of the four modes in which rocks are formed -- the four phases of their formative processes manifested in the stratified and unstratified portions of the earth's surface; thus, in the 'endogenous' or 'erupted rocks', designated by modern geognosists as compact and abnormal rocks, we may enumerate the following principal groups as immediate products of terrestrial activity: 1. 'Granite and syenite' of very different respective ages; the granite is frequently the more recent,* traversing the syenite in veins, and being, in that case, the active upheaving agent. "Where the granite occurs in large, insulated masses of a faintly-arched, ellipsoidal form, it is covered by a crust of shell cleft into blocks, instances of which are met with alike in the Hartz district, in Mysore, and in Lower Peru. [footnote] *Bernhard Cotta, 'Geognosie', 1839, s. 273. This surface of the granite, owing to the great expansion that accompanied its first upheaval."* [footnote] *Leop. von Buch, 'Ueber Granit and Gneiss', in the 'Abhandl. der Berl. Akad.' for the year 1842, s. 60. Both in Northern Asia,* on the charming and romantic shores of the Lake of Kolivan, on the northwest declivity of p. 252 the Altai Mountains, and at Las Trincheras, on the slop of the littoral chain of Caraccas,** I have seen granite divided into ledges, owing probably to a similar contraction, although the divisions appeared to penetrate far into the interior. [footnote] * In the projecting mural masses of granite of Lake Kolivan, divided into narrow parallel beds, there are numerous crystals of feldspar and albite, and a few of titanium (Humboldt, 'Asie Centrale', t. i., p. 295, Gustav Rose, 'Reise mach dem Ural', bd. i., s. 524). [footnote] *Humboldt, 'Relation Historique', t. ii., p. 99 Further to the south of Lake Kolivan, toward the boundaries of the Chinese province Ili (between Buchtarminsk and the River Narym), the formation of the erupted rock, in which there is no gneiss, is more remarkable than I ever observed in any other part of the earth. The granite, which is always covered with scales and characterized by tabular divisions, rises in the steppes, either in small hemispherical eminences, scarcely six or eight feet in height, or like basalt, in mounds, terminating on either side of their bases in narrow streams.* [footnote] ** See the sketch of Biri-tau, which I took from the south side, where the Kirghis tents stood, and which is given in Rose's 'Reise', bd. i., s. 584. On spheres of granite scaling off concentrically, see my 'Relat. Hist.', t. ii., p. 497, and 'Essai Geogn. sur les Gisement des Roches', p. 78. At the cataracts of the Orinoco, as well as in the district of the Fichtelgebirge (Seissen), in Galicia, and between the Pacific and the highlands of Mexico (on the Papagallo), I have seen granite in large, flattened spherical masses, which could be divided, like basalt, into concentric layers. In the valley of Irtysch, between Buchtarminsk and Ustkamenogorsk, granite covers transition slate for a space of four miles,* penetrating into it from above in narrow, variously ramified, wedge-like veins. [footnote] *Humboldt, 'Asie Centrale', t. i., p. 299-311, and the drawings in Rose's 'Reise', bd. i., s. 611, in which we see the curvature in the layers of granite which Leop. von Buch has pointed out as chracteristic. I have only instanced these peculiarities in order to designate the individual character of one of the most generally diffused erupted-rocks. As granite is superposed on slate in Siberia and in the Departement de Finisterre (Isle de Mihau), so it covers the Jura limestone in the mountains of Oisons (Fermonts), and syenite, and indirectly also chalk, in Saxony, near Weinbohla.* [footnote] *This remarkable superposition was first described by Weiss in Krsten's 'Archiv fur Bergbau und H�¬ttenwesen', bd. xvi., 1827, s. 5. Near Mursinsk, in the Uralian district, granite is of a drusous character, and here the pores, like the fissures and cavities of recent volcanic products, inclose many kinds of magnificent crystals, especially beryls and topazes. 2. 'Quartzose porphyry' is often found in the relation of veins to other rocks. The base is generally a finely granular mixture of the same elements which occur in the larger imbedded p 253 crystals. In granitic porphyry that is very poor in quartz, the feldspathic base is almost granular and laminated.* [footnote] *Dufrenoy et Elie de Beaumont, 'Geologie de la France', t. i., p. 130. 3. 'Greenstones, Diorite', are granular mixtures of white albite and blackish-green hornblende, forming dioritic porphyry when the crystals are deposited in a base of denser tissue. The greenstones, either pure, or inclosing laminae of diallage (as in the Fichtelgebirge), and passing into serpentine, have sometimes penetrated, in the form of strata, into the old stratified fissures of green argillaceous slate, but they more frequently traverse the rocks in veins, or appear as globular masses of greenstone, similar to domes of basalt and porphyry.* [footnote] *These intercalated beds of diorite play an important part in the mountain district of Nailau, near Steben, where I was engaged in mining operations in the last century, and with which the happiest associations of my early life are connected. Compare Hoffmann, in Poggendorf's 'Annalen', bd. xvi., s. 558. 'Hypersthene rock' is a granular mixture of labradorite and hypersthene. 'Euphotide' and serpentine, containing sometimes crystald of augite and uralite instead of diallage, are thus nearly allied to another more frequent, and I might almost say, more 'energetic' eruptive rock -- augitic porphyry.* [footnote] *In the southern and Bashkirian portion of the Ural. Rose, 'Reise', bd. ii., s. 171. 'Melaphyre', augitic, uralitic, and oligoklastic porphyries. To the last-named species belongs the genuine 'verd-antique', so celebrated in the arts. 'Basalt', containing olivine and constituents which gelatinize in acids; phonolithe (porphyritic slate), trachyte, and colerite; the first of these rocks is only paartially, and the second always, divided into thin laminae, which give them an appearance of stratification when extended over a large space. Mesotype and nepheline constitute, according to Girard, an important part in the composition and internal texture of basalt. The nepheline contained in basalt reminds the geognosist both of the miascite of the Ilmen Mountains in the Ural,* which has been confounded with granite, and sometimes contains zirconium, and of the pyroxenic nepheline discovered by Gumprecht near Lobau and Chemnitz. [footnote] *G. Rose, 'Reise nach dem Ural', bd. ii., s. 47-52. Respecting the identity of eleolite and uepheline (the latter containing rather the more lime), see Scheerer, in Poggend., 'Annalen', bd. xlix., s. 359-381. To the second or sedimentary rocks belong the greater part of the formations which have been comprised under the old p 254 systematic, but not very correct designation of 'transition, flot' or 'secondary', and 'tertiary formations'. If the erupted rocks had not exercised an elevating, and, owing to the simultaneous shock of the earth, a disturbing influence on these sedimentary formations, the surface of our planet would have consisted of strata arranged in a uniformly horizontal direction above one another. Deprived of mountain chains, on whose declivities the gradations of vegetable forms and the scale of the diminishing heat of the atmosphere appear to be picturesquely reflected -- furrowed ony here and there by valleys of erosion, formed by the force of fresh water moving on in gentle undulations, or by the accumulation of detritus, resulting from the action of currents of water -- continents would have presented no other appearance from pole to pole than the dreary uniformity of the llanos of South America or the steppes of Northern Asia. The vault of heaven would everywhere have appeared to rest on vast plains, and the stars to rise as if they emerged from the depths of ocean. Such a condition of things could not, however, have generally prevailed for any length of time in the earlier periods of the world, since subterranean forces must have striven in all epochs to exert a counteracting influence. Sedimentary strta have been either precipitated or deposited from liquids, according as the materials entering into their composition are supposed, whether as limestone or argillaceous slate, to be either chemically dissolved or suspended and commingled. But earth, when dissolved in fluids impregnated with carbonic acid, must be regarded as undergoing a mechanical process while they are being precipitated, deposited, and accumulated into strata. This view is of some importance with respect to the envelopment of organic bodies in petrifying calcareous beds. The most ancient sediments of the transition and secondary formations have probably been formed from water at a more or less high temperature, and at a time when the heat of the upper surface of the earth was still very considerable. Considered in this point of view, a Plutonic action seems to a certain extent also to have taken place in the sedimentary strata, especially the more ancient; but these strata appear to have been hardened into a schistose structure, and under great pressure, and not to have been solidified by cooling, like the rocks that have issued from the interior, as, for instance, granite, porphyry, and basalt. By degrees, as the waters lost their temperature, and were able to absorb a copious supply of the carbonic acid gas with which p 255 the atmosphere was overcharged, they became fitted to hold in solution a larger quantity of lime. 'The sedimentary strata', setting aside all other exogenous, purely mechanical deposits of sand or detritus, are as follows: 'Schist', of the lower and upper transition rock, compositing the silurian and devonian formations; from the lower silurian strata, which were once termed cambrian, to the upper strata of the old red sandstone or devonian formation, immediately in contact with the mountain limestone. 'Carboniferous deposits': 'Limestones' imbedded in the transition and carboniferous formations; zechstein, muschelkalk, Jura formation and chalk, also that portion of the tertiary formation which is not included in sandstone and conflomerate. 'Travertine', fresh-water limestone, and silicious concretions of hot springs, formations which have not been produced under the pressure of a large body of sea water, but almost in immediate contact with the atmosphere, as in shallow marshes and streams. 'Infusorial deposits': geognostical phenomena, whose great importance in proving the influence of organic activity in the formation of the solid part of the earth's crust was first discovered at a recent period by my highly-gifted friend and fellow-traveler, Ehrenberg. If, in this short and superficial view of the mineral constituents of the earth's crust, I do not place immediately after the simple sedimentary rocks the conglomerates and sandstone formations which have also been deposited as sedimentary strata from liquids, and which have been imbedded alternately with schist and limestone, it is only because they contain, together with the detritus of eruptive and sedimentary rocks, also the detritus of gneiss, mica slate, and other metamorphic masses. The obscure process of this metamorphism, and the action if produces, must therefore compose the third class of the fundamental forms of rock. Endogenous or erupted rocks (granite, porphyry, and melaphyre) produce, as I have already frequently remarked, not only cynamical, shaking, upheaving actions, either vertically or laterally displacing the strata, but they also occasion changes in their chemical composition as well as in the nature of their internal structure; new rocks being thus formed, as gneiss, mica slate, and granular limestone (Carrara and Parian marble). The old silurian or devonian transition schists, the belemnitic limestone of Tarantaise, and the dull gray calcareous p 256 sandstone ('Macigno'), which contains alggae found in the northern Apennines, often assume a new and more brilliant appearance after their metamorphosis, which renders it difficult to recognize them. The theory of metamorphism was not established until the individual phases of the change were followed step by step, and direct chemical experiments on the difference in the fusion point, in the pressure and time of cooling, were brought in aid of mere inductive conclusions. Where the study of chemical combinations is regulated by leading ideas,* it may be the means of throwing a clear light on the wide field of geognosy, and over the vast laboratory of nature in which rocks are continually being formed and modified by the agency of subterranean forces. [footnote] *See the admirable researches of Mitscherlich, in the 'Abhandl. der Berl. Akad.' for the years 1822 and 1823, s. 25-41; and in Poggend., 'Annalen', bd. x., s. 137-152; bd. xi., s. 323-332; bd. sli., s. 213-216 (Gustav Rose, 'Ueber Gildung des Kalkspaths und Aragonits', in Poggend., 'Annalen', bd. xli., s, 353-366; Haidinger, in the 'Transactions of the Royal Society of Edinburgh', 1827, p. 148.) The philosopohical inquirer will escape the deception of apparent analogies, and the danger of being led astray by a narrow view of natural phenomena, if he constantly bear in view the complicated conditions which may, by the intensity of their force, have modified the counteracting effect of those individual substances whose nature is better known to us. Simple bodies have, no doubt, at all periods, obeyed the same laws of attraction, and, wherever apparent contradictions present themselves, I am confident that chemistry will in most cases be able to trace the cause to some corresponding error in the experiment. Observations made with extreme accuracy over large tracts of land, show that erupted rocks have not been produced in an irregular and unsystematic manner. In parts of the globe most remote from one another, we often find that granite, basalt, and diorite have exercised a regular and uniform metamorphic action, even in the minutest details, on the strata of argillaceous slate, dense limestone, and the grains of quartz in sandstones. As the same endogenous rock manifests almost every where the same degree of activity, so on the contrary, different rocks belonging to the same class, whether to the endogenous or the erupted, exhibit great differences in their character. Intense heat has undoubtedly influenced all these phenomena, but the degree of fluidity (the more or less perfect mobility of the particles -- their more viscous composition) has varied very considerably from the granite to the basalt, while at different geological p 257 periods (or metamorphic phases of the earth's crust) other substances dissolved in vapors have issued from the interior of the earth simultaneously with the eruption of granite, basalt, greenstone porphyry, and serpentine. This seems a fitting place again to draw attention to the fact that, according to the admirable views of modern geognosy, the metamorphism of rocks is not a mere phenomenon of contact, limited to the effect produced by the apposition of two rocks, since it comprehends all the generic phenomena that have accompanied the appearance of a particular erupted mass. Even where there is no immediate contact, the proximity of such a mass gives rise to modifications of solidification, cohesion, granulation, and crystallization. All eruptive rocks penetrate, as ramifying veins either into the sedimentary strata, or into other equally endogenous masses; but there is a special importance to be attached to the difference manifested between 'Plutonic' rocks* (granite, porphyry, and serpentine) and those termed 'volcanic' in the strict sense of the word (as trachyte, basalt, and lava). [footnote] ([Lyell, 'Principales of Geology', vol. i.i., p. 353 and 359.] -- Tr. The rocks produced by the activity of our present volcanoes appear as band-like streams, but by the confluence of several of them they may form an extended basin. Wherever it has been possible to trace basaltic eruptions, they have generally been found to terminate in slender threads. Examples of these narrow openings may be found in three places in Germany: in the 'Pflaster-kaute', at Marksuhl, eight miles from Eisenach; in the blue 'Kuppe', near Eschwege, on the banks of the Werra; and in the Druidical stone on the Hollert road (Siegen), where the basalt has broken through the variegated sandstone and graywacke slate, and has spread itself into cup-like fungoid enlargements, which are either grouped together like rows of columns, or are sometimes stratified in thin laminae. The case is otherwise with granite, syenite, quartzose porphyry, serpentine, and the whole series of unstratified compact rocks, to which, from a predilection for a mythological nomenclature, the term Plutonic has been applied. These, with the exception of occasional veins, were probably not erupted in a state of fusion, but merely in a softened condition; not from narrow fissures, but from long and widely-extending gorges. They have been protruded, but have not flowed forth, and are found not in streams like lava, but in extended masses.* [footnote] *The description here given of the relation of position under which granite occurs, expresses the general or leading character of the whole formation. But its aspect at some places leads to the belief that it was occasionally more fluid at the period of its eruption. The description given by Rose, in his 'Reise nach dem Ural', bd. i., s. 599, of part of the Narym chain, near the frontiers of the Chinese territories, as well as the evidence afforded by trachyte, as described by Dufrenoy and Elie de Beaumont, in their 'Description Geologique de la France', t. i., p. 70. Having already spoken in the text of the narrow apertures through which the basalts have sometimes been effused, I will here notice the large fissures, which have acted as conducting passages for melaphyres, which must not be confounded with basalts. See Murchison's interesting account ('The Silurian System', p. 126) of a fissure 480 feet wide, through which melaphyre has been ejected, at the coal-mine at Cornbrook, Hoar Edge. Some groups of dolerite and trachyte indicate p 258 a certain degree of basaltic fluidity; others, which have been expanded into vast craterless domes, appear to have been only in a softened condition at the time of their elevation. Other trachytes, like those of the Andes, in which I have frequently perceived a striking analogy with the greenstones and syenitic porphyries (which are argentiferous, and without quartz), are deposited in the same manner as granite and quartzose porphyry. Experiments on the changes which the texture and chemical constitution of rocks experience from the action of heat, have shown that volcanic masses* (diorite, augitic porphyry, basalt, and the lava of AEtna) yield different products, according to the difference of the pressure under which they have been fused, and the length of time occupied during their cooling; thus, where the cooling was rapid, they form a black glass, having a homogeneous fracture, and where the cooling was slow, a stony mass of granular crystalline structure. [footnote] *Sir James Hall, in the 'Edin. Trans.', vol. v., p. 43, and vol. vi., p. 71; Gregory Watt, in the 'Phil. Trans. of the Roy. Soc. of London for' 1804, Part ii., p. 279; Dartigues and Fleurieu de Bellevue, in the 'Journal de Physique', t. lx., p. 456; Bischof, 'Warmelchre', s. 313 und 443. In the latter case, the crystals are formed partly in cavities and partly inclosed in the matrix. The same materials yield the most dissimilar products, a fact that is of the greatest importance in reference to the study of the nature of erupted rocks, and of the metamorphic action which they occasion. Carbonate of lime, when fused under great pressure, does not lose its carbonic acid, but becomes, when cooled, granular limestone; when the crystallization has been effected by the dry method, saccharoidal marble; while by the humid method, calcareous spar and aragonite and produced, the former under a lesser degree of temperature than the latter.* [footnote] *Gustav Rose, in Poggend., 'Annalen.' bd. xliii., s 364. Differences of temperature p 259 likewise modify the direction in which the different particles arrange themselves in the act of crystallization, and also affect the form of the crystal.* [footnote] *On the dimorphism of sulphur, see Mitscherlich, 'Lehrbuch der Chemie', 55-63. Even when a body is not in a fluid condition, the smallest particles may undergo certain relations in their various modes of arrangement, which are manifested by the different action on light.* [footnote] *On gypsum as a uniaxal crystal, and on the sulphate of magnesia, and the oxyds of zinc and nickel, see Mitscherlich, in Poggend., 'Annalen.' bd. xi., s. 328. The phenomena presented by devitrification, and by the formation of steel by cementation and casting -- the transition of the fibrous in the granular tissue of the iron, from the action of heat* and probably, also, by regular and long-continued concussions -- likewise throw a considerable degree of light on the geological process of metamorphism. [footnote] *Coste, 'Versuche am Creusot uber das bruchig werden des Stabeisens.' Elie de Beaumont, 'Mem. Geol.', t. ii., p. 411. Heat may even simultaneously induce opposite actions in crystalline bodies; for the admirable experiments of Mitscherlich have established the fact* that calcareous spar, without altering its condition of aggregation, expands in the direction of one of its axes and contracts in the other. [footnote] * Mitscherlich, 'Ueber die Ausdehnung der Krystallisirten Korper durch die Warmelehre', in Poggend., 'Annalen', bd. x., s. 151. If we pass from these general considerations to individual examples, we find that schist is converted, by the vicinity of Plutonic erupted rocks, into a bluish-black, glistening roofing slate. Here the planes of stratification are intersected by another system of divisional stratification, almost at right angles with the former,* and thus indicating an action subsequent to the alteration. [footnote] * On the double system of divisional planes, see Elie de Beaumont, 'Geologie de la France', p. 41; Credner, 'Geognosie Thuringens und des Harzes', s. 40; and Romer, 'Das Rheinische Uebergangsgebirge', 1844. s. 5 und 9. The penetration of silica causes the argillaceous schist to be traversed by quartz, transforming it, in part, into whetstone and silicious schist; the latter sometimes containing carbon, and being then capable of producing galvanic effects on the nerves. The highest degree of silicifaction of schist is that observed in ribbon jasper, a material highly valuable in the arts,* and which is produced in the Oural Mountains p 260 by the contact and eruption of augitic porphyry (at Orsk), of dioritic porphyry (at Aufschkul), or of a mass of hypersthenic rock conglomerated into spherical masses (at Bogoslowsk). At Monte Serrato, in the island of Elba, according to Frederic Hoffman, and in Tuscany, according to Alexander Brongniart, it is formed by contact with euphotide and serpentine. [footnote] *The silica is not merely colored by peroxyd of iron, but is accompanied by clay, lime, and potash. Rose, 'Reise', bd. ii., s. 187. On the formation of jasper by the action of dioritic porphyry, augite, and by persthene rock, see Rose, bd. ii., s. 169, 187, und 192. See, also, bd. i., s. 427, where there is a drawing of the porphyry spheres between which jasper occurs, in the calcareous graywacke of Bogoslowsk, being produced by the Plutonic influence of the augitic rock; bd. ii., s. 545; and likewise Humboldt, 'Asie Centrale', t. i., p. 486. The contact and Plutonic action of granite have sometimes made argillaceous schist granular, as was observed by Gustav Rose and myself in the Altai Mountains (within the fortress of Buchtarminsk),* and have transformed it into a mass resembling granite, consisting of a mixture of feldspar and mica, in which larger laminae of the latter were again imbedded.** [footnote] *Rose, 'Reise nach dem Ural', bd. i., s. 586-588. [footnote] **In respect to the volcanic origin of mica, it is important to notice that crystals of mica are found in the basalt of the Bohemian Mittelgebirge, in the lava that in 1822 was ejected from Vesuvius (Monticelli, 'Storia del Vesuvio negli Anni 1821 e 1822', 99), and in fragments of agrillaceous alte imbedded in scoriaceous basalt at Hohenfels, not far from Gerolstein, in the Eifel (see Mitscherlich, in Leonhard, 'Basalt-Gebilde', s. 244). On the formation of feldspar in argillaceous schist, through contact with porphyry, occurring between Urval and Po��et (Forez), see Dufrenoy, in 'Geol. de la France', t. i., p. 137. It is probably to a similar contact that certain schists near Paimpol, in Brittany, with whose appearance I was much struck, while making a geological pedestrian tour through that interesting country with Professor Kunth, owe their amygdaloid and cellular character, t. i., p. 234. Most geognosists adhere, with Leopold von Buch, to the well-known hypothesis "that all the gneiss in the silurian strata of the transition formation, between the Icy Sea and the Gulf of Finland, has been produced by the metamorphic action of granite.* [footnote] * Leopold von Buch, in the 'Abhandlungen der Akad. der Wissenschaft zu Berlin, aus dem Jahr' 1842, s. 63, and in the 'Jahrbuchern fur Wissenschaftliche Kritik Jahrg.' 1840, s. 196. In the Alps, at St. Gothard, calcareous marl is likewise changed from granite into mica slate, and then transformed into gneiss." Similar phenomena of the formation of gneiss and mica slate through granite present themselves in the oolitic group of the Tarantaise,* in which belemnites are p 261 found in rocks, which have some claim to be considered as mica slate, and in the schistose group in the western part of the island of Elba, near the promontory of Calamita, and the Fichtelgebirge in Baireuth, between Loomitz and Markleiten.** [footnote] * Elie de Beaumont, in the 'Annales des Sciences Naturelles', t. xv., p. 362-372. "In approaching the primitive masses of Mont Rosa, and the mountains situated to the west of Coni, we perceive that the secondary strata gradually lose the characters inherent in their mode of deposition. Frequently assuming a character apparently arising from a perfectly distinct cause, but not losing their stratification, they somewhat resemble in their physical structure a brand of half-consumed wood, in which we can follow the traces of the ligneous fibers beyond the spots which continue to present the natural characters of wood." (See, also, the 'Annales des Sciences Naturelles', t. xiv., p. 118-122, and von Dechen, 'Geognosie', s. 553.) Among the most striking proofs of the transformation of rocks by Plutonic action, we must place the belemites in the schists of Nuffenen (in the Alpine valley of Eginen and in the Gries-glaciers), and the belemnites found by M. Charpentier in the so-called primitive limestone on the western descent of the Col de la Seigne, between the Enclove de Monjovet and the 'chalet' of La Lanchette, and which he showed to me at Bex in the autumn of 1822 ('Annales de Chimie', t. xxiii., p. 262). [footnote] ** Hoffmann, in Poggend., 'Annalen', bd. xvi., s. 552, "Strate of transition argillaceous schist in the Fichtelgebirge, which can be traced for a length of 16 miles, are transformed into gneiss only at the two extremities, where they come in contact with granite. We can there follow the gradual formation of the gneiss, and the development of the mica and of the feldspathic amygdaloids, in the interior of the argillaceous schist, which indeed contains in itself almost all the elements of these substances." Jasper, which,* as I have already remarked, is a production formed by the volcanic action of augitic porphyry, could only be obtained in small quantities by the ancients, while another material, very generally and efficiently used by them in the arts, was granular or saccharoidal marble, which is likewise to be regarded solely as a sedimentary stratum altered by terrestrial heat and by proximity with erupted rocks. [footnote] * Among the works of art which have come down to us from the ancient Greeks and Romans, we observe that none of any size -- as columns or large vases -- are formed from jasper; and even at the present day, this substance, in large masses, is only obtained from the Ural Mountains. The material worked as jasper from the Rhubarb Mountain (Raveniaga Sopka), in Altai, is a beautiful ribboned porphyry. The word 'jasper' is derived from the Semitic languages; and from the confused description of Theophrastus ('De Lapidibus', 23 and 27) and Pliny (xxxvii., 8 and 9), who rank jasper among the "opaque gems," the name appears to have been given to fragments of 'jaspachat', and to a substance which the ancients termed 'jasponyx', which we now know as 'opal-jasper'. Pliny considers a piece of jasper eleven inches in length so rare as to require his mentioning that he had actually seen such a specimen: "Magnitudinem jaspidis undecim unciarum vidimus, formatamque inde effigem Neronis thoracatam." According to Theophrastus, the stone which he calls emerald, and from which large obelists were cut, must have been an imperfect jasper. This opinion is corroborated by the accurate observations on the phenomena of contact, by the remarkable experiments on fusion p 262 made by Sir James Hall more than half a century ago, and by the attentive study of granitic veins, which has contributed so largely to the establishment of modern geognosy. Sometimes the erupted rock has not transformed the compact into granular limestone to any great depth from the point of contact. Thus, for instance, we meet with a slight transformation -- a penumbra -- as at Belfast, in Ireland, where the basaltic veins traverse the chalk, and, as in the compact calcareous beds, which have been partially inflected by the contact of syenitic granite, at the Bridge of Boscampo and the Cascade of Conzocoli, in the Tyrol (rendered celebrated by the mention made of it by Count Mazari Peucati).* [footnote[ *Humboldt, 'Lettre a M. Brochant de Villiers', in the 'Annales de Chimie et de Physique', t. xxiii., p. 261; Leop. von Buch, 'Geog. Briefe uber das sudliche Tyrol', s. 101, 105, und 273. Another mode of transformation occurs where all the strata of the compact limestone have been changed into granular limestone by the action of granite, and syenitic or dioritic porphyry.* [footnote] *On the transformation of compact into granular limestone by the action of granite, in the Pyrenees at the 'Montagnes de Rancie', see Dufrenoy, in the 'Memoires Geologiques', t. ii., p. 440; and on similar changes in the 'Montagnes de l'Oisans', see Elie de Beaumont, in the 'Mem. Geolog.', t. ii., p. 379-415; on a similar effect produced by the action of dioritic and pyroxenic porphyry (the 'ophite' described by Elie de Beaumont, in the 'Geologie de la France', t. i., p. 72), between Tolosa and St. Sebastian, see Dufrenoy, in the 'Mem. Geolog.', t. ii., p. 130; and by syenite in the Isle of Skye, where the fossils in the altered limestone may still be distinguished, see Von Dechen, in his 'Geognosie', p. 573. In the transformation of chalk by contact with basalt, the transposition of the most minute particles in the processes of crystallization and granulation is the more remarkable, because the excellent microscopic investigations of Ehrenberg have shown that the particles of chalk previously existed in the form of closed rings. See Poggend., 'Annalen der Physic', bd. xxxix., s. 105; and on the rings of aragonite deposited from solution, see Gustav Rose in vol. xlii., p. 354, of the same journal. I would here wish to make special mention of Parian and Carrara marbles, which have acquired such celebrity from the noble works of art into which they have been converted, and which have too long been considered in our geognostic collections as the main types of primitive limestone. The action of granite has been manifested sometimes by immediate contact, as in the Pyrenees,* and sometimes, as in the main land of Greece, and in the insular groups in the gean Sea, through the intermediate layers of gneiss or mica slate. [footnote] *Beds of granular limestone in the granite at Port d'Oo and in the Mont de Labourd. See Charpentier, 'Constitution Geologique des Pyrenes', p. 144, 146. Both cases presuppose a simultaneous but heterogeneous process of transformation. p 263 In Attica, in the island of Euboea, and in the Peloponnesus, it has been remarked, "that the limestone, when superposed on mica slate, is beautiful and crystalline in proportion to the purity of the latter substance and to the smallness of its argillaceous contents; and, as is well known, this rock, together with beds of gneiss, appears at many points, at a considerable depth below the surface, in the islands of Paros and Antiparos."* [footnote] *Leop. von Buch, 'Descr. des Canaries', p. 394; Fiedler, 'Reise durch das Konigreich Griechenland', th. ii., s., 181, 190, und 516. We may here infer the existence of an imperfectly metamorphosed flotz formation, if faith can be yielded to the testimony of Origen, according to whom, the ancient Eleatic, Xenophanes of Colophon* (who supposed the whole earth's crust to have been once covered by the sea), declared that marine fossils had been found in the quarries of Syracuse, and the impression of a fish (a sardine) in the deepest rocks of Paros. [footnote] *I have previously alluded to the remarkable passage in Origen's 'Philosophumena', cap. 14 ('Opera', ed. Delarue, t. i., p. 893). From the whole context, it seems very improbable that Xenophanes meant an impression of a laurel ([Greek words]) instead of an impression of a fish ([Greek words]). Delarue is wrong in blaming the correction of Jacob Gronovius in changing the laurel into a sardel. The petrifaction of a fish is also much more probable than the natural picture of Silenus, which, according to Pliny (lib. xxxvi., 5), the quarry-men are stated to have met with in Parian marble from Mount Marpessos. 'Servius ad Virg., AEn.', vi., 471. The Carrara or Luna marble quarries, which constituted the principal source from which statuary marble was derived even prior to the time of Augustus, and which will probably continue to do so until the quarries of Paros shall be reopened, are beds of calcareous sandstone -- macigno -- altered by Plutonic action, and occurring in the insulated mountain of Apuana, between gneiss-like mica and talcose schist.* [footnote] *On the geognostic relations of Carrara ('The City of the Moon', Strabo, lib. v., p. 222), see Savi 'Osservazioni sui terreni antichi Toscani', in the 'Nuova Giornale de' Letterati di Pisa', and Hoffmann, in Karsten's 'Archiv fur Mineralogie', bd. vi., s. 258-263, as well as in his 'Geogn. Reise durch Italien', s. 244-265. Whether at some points granular limestone may not have been formed in the interior of the earth, and been raised by gneiss and syenite to the surface, where it forms vein-like fissures,* is a question on which I can not hazard an opinion, owing to my own want of personal knowledge of the subject. [footnote] *According to the assumption of an excellent and very experienced observer, Karl von Leonhard. See his 'Jahrbuch fur Mineralogie', 1834 s. 329, and Bernhard Cotta, 'Geognosie', s. 310. p 264 According to the admirable observations of Leopold von Buch, the masses of dolomite found in Southern Tyrol, and on the Italian side of the Alps, present the most remarkable instance of metamorphism produced by massive eruptive rocks on compact calcareous beds. The formation of the limestone seems to have proceeded from the fissures which traverse it in all directions. The cavities are every where covered with rhomboidal crystals of magnesian bitter spar, and the whole formation, without any trace of strtification, or of the fossil remains which it once contained, consists only of a granular aggregation of crystals of dolomite. Talc laminae lie scattered here and there in the newly-formed rock, traversed by masses of serpentine. In the valley of the Fassa, dolomite rises perpendicularly in smooth walls of dazzling whiteness to a height of many thousand feet. It forms sharply-pointed conical mountains, clustered together in large numbers, but yet not in contact with each other. The contour of their forms recalls to mind the beautiful landscape with which the rich imagination of Leonardi da Vinci has embellished the back-ground of the portrait of Mona Lisa. The geognostic phenomena which we are now describing, and which excite the imagination as well as the powers of the intellect, are the result of the action of augite porphyry manifested in its elevating, destroying, and transforming force.* [footnote] *Leop. von Buch, 'Geognostische Briefe an Alex. von Humboldt', 1824, s. 86 and 82; also in the 'Annalen de Chemie', t. xxiii., p. 276, and in the 'Abhandl. der Berliner Akad. aus der Jahren 1822 'und' 1823, s. 83-136; Von Dechen, 'Geognosie.' s. 574-576. The process by which limestone is converted into dolomite is not regarded by the illustrious investigator who first drew attention to the phenomenon as the consequence of the tale being derived from the black porphyry, but rather as a transformatiion simultaneous with the appearance of this erupted stone through wide fissures filled with vapors. It remains for future inquirers to determine how transformation can have been effected without contact with the endogenous stone, where strata of dolomite are found to be interspersed in imestone. Where, in this case, are we to seek the concealed channels by which the Plutonic action is conveyed? Even here it may not, however, be necessary, in conformity with the old Roman adage, to believe "that much that is alike in nature may have been formed in wholly different ways." When we find, over widely extended parts of the earth, that two phenomena are always associated together, as, for instance, the occurrence of melaphyre p 265 and the transformation of compact limestone into a crystaline mass differing in its chemical character, we are, to a certain degree, justified in believing, where the second phenomenon is manifested unattended by the appearance of the first, that this apparent contradiction is owing to the absence, in certain cases, of some of the conditions attendant upon the exciting causes. Who would call in question the volcanic nature and igneous fluidity of basalt merely because there are some rare instances in which basaltic veins, traversing beds of coal or strata of sandstone and chalk, have not materially deprived the coal of its carbon, nor broken and slacked the sandstone, not converted the chalk into granular marble? Wherever we have obtained even a faint light to guide us in the obscure domain of mineral formation, we ought not ungratefully to disregard it, because there may be much that is still unexplained in the history of the relations of the transitions, or in the isolated interposition of beds of unaltered strata. After having spoken of the alteration of compact carbonate of lime into granular limestone and dolomite, it still remains for us to mention a third mode of transformation of the same mineral, which is ascribed to the emission, in the ancient periods of the world, of the vapors of sulphuric acid. This transformation of limestone into gypsum is analogous to the penetration of rock salt and sulphur, the latter being deposited from sulphureted aqueous vapor. In the lofty Cordilleras of Quindin, far from all volcanoes, I have observed deposits of sulphur in fissures in gneiss, while in Sicily (at Cattolica, near Girgenti), sulphur, gypsum, and rock salt belong to the most recent secondary strata, the chalk formations.* [footnote] *Horrman, 'Geogn. Reise', edited by Von Dechen, s. 113-119, and 380-386; Poggend., 'Annalen der Physik', bd. xxvi., s. 41. I have also seen on the edge of the crater of Vesuvius, fissures filled with rock salt, which occurred in such considerable masses as occasionally to lead to its being disposed of by contraband trade. On both declivities of the Pyrenees, the connection of diorite and pyroxene, and colomite, gypsum, and rock salt, can not be questioned;* and here, as in the other phenomena which we have been considering, every thing bears evidence of the action of subterranean forces on the sedimentary strata of the ancient sea. [footnote] *Dufrenoy, in the 'Memoires Geologiques', t. ii., p. 145 and 179. There is much difficulty in explaining the origin of the beds of pure quartz, which occur in such large quantities in South America, and impart so peculiar a character to the chain of p 266 the Andes.* [footnote] *Humboldt, 'Essai Geogn. sur le Gisement des Roches', p. 93; 'Asie Centrale', t. iii., p. 532. In descending toward the South Sea, from Caxamarca toward Guangamarca, I have observed vast masses of quartz, from 7000 to 8000 feet in height, superposed sometimes on porphyry devoid of quartz, and sometimes on diorite. Can these beds have been transformed from sandstone, as Elie de Beaumont conjectures in the case of the quartz strata on the Col de la Poissonniere, east of Brian��on?* [footnote] *Elie de Beaumont, in the 'Annales des Sciences Naturelles', t. xv., p. 362; Murchison, 'Silurian System', p. 286. In the Brazils, in the diamond district of Minas Geraes and St. Paul, which has recently been so accurately investigated by Clausen, Plutonic action has developed in dioritic veins sometimes ordinary mica, and sometimes specular iron in quartzose itacolumite. The diamonds of Grammagoa are imbedded in strata of solid silica, and are occasionally enveloped in laminae of mica, like the garnets found in mica slate. The diamonds that occur furthest to the north, as those discovered in 1829 at 58 degrees lat., on the European slope of the Uralian Mountains, bear a geognostic relation to the black carboniferous dolomite of Adolffskoi* and to augitic porphyry, although more accurate observations are required in order fully to elucidate this subject. [footnote] *Rose, 'Reise nach dem Ural', bd. i., s. 364 und 367. Among the most remarkable phenomena of contact, we must, finally, enumerate the formation of garnets in argillaceous schist in contact with basalt and dolerite (as in Northumberland and the island of Anglesea), and the occurrence of a vast number of beautiful and most various crystals, as garnets, vesuvian, augite, and ceylanite, on the surfaces of contact between the erupted and sedimentary rock, as, for instance, on the junction of the syenite of Monzon with dolomite and compact limestone. [footnote] *Leop. von Buch, 'Briefe', s. 109-129. See also, Elie de Beaumont 'On the Contact of Granite with the Beds of the Jura', in the 'Mem. Geol.' t. ii., p. 408. In the island of Elba, masses of serpentine, which perhaps nowhere more clearly indicate the character of erupted rocks, have occasioned the sublimation of iron glance and red oxyd of iron in fissures of calcareous sandstone. [footnote] *Hoffman, 'Reise', s. 30 und 37. We still daily find the same iron glance formed by sublimation from the vapors and the walls of the fissures of open veins on the margin of the crater, and in the fresh lava currents of the volcanoes of Stromboli, Vesuvius, and AEtna.* [footnote] *On the chemical process in the formation of specular iron, see Gay Lussac, in the 'Annales de Chimie', t. xxii., p. 415, and Mitscherlich, in Poggend., 'Annalen', bd. xv., s. 630. Moreover, crystals of olivine have been formed (probaby by sublimation) in the cavities of the obsidian of Cerro del Jacal, which I brought from Mexico (Gustav Rose, in Poggend., 'Annalen', bd. x., s. 323). Hence olivine occurs in basalt, lava, obsidian, artificial scoriae in meteoric stones, in the syenite of Elfdale, and (as hyalosiderite) in the wacke of the Kaiserstuhl. The veins that p 267 are thus formed beneath our eyes by volcanic forces, where the contiguous rock has already attained a certain degree of solidification, show us how, in a similar manner, mineral and metallic veins may have been every where formed in the more ancient periods of the world, where the solid but thinner crust of our planet, shaken by earthquakes, and rent and fissured by the change of volume to which it was subjected in cooling, may have presented many communications with the interior, and many passages for the escape of vapors impregnated with earthy and metallic substances. The arrangement of the particles in layers parallel with the margins of the beins, the regular recurrence of analogous layers on the opposite sides of the veins (on their different walls), and, finally, the elongated cellular cavities in the middle, frequently afford direct evidence of the Plutonic process of sublimation in metalliferous veins. As the traversing rocks must be of more recent origin than the traversed, we learn from the relations of stratification existing between the porphyry and the argentiferous ores in the Saxon mines (the richest and most important in Germany), that these formations are at any rate more recent than the vegetable remains found in carboniferous strata and in the red sandstone.* [footnote] *Constantin von Veust, 'Ueber die Porphyrgebilde', 1835, s. 89-96; also his 'Belenchtung der Werner'schen Gangtheorie', 1840, s. 6; and C. von Wissenbach, 'Abbildungen merkwurdiger Gangverhaltnisse', 1836, fig. 12. The ribbon-like structure of the veins is, however, no more to be regarded of general occurrence than the periodic order of the different members of these masses. All the facts connected with our geological hypotheses on the formation of the earth's crust and the metamorphism of rocks have been unexpectedly elucidated by the ingenious idea which led to a comparison of the slags or scoriae of our smelting furnaces with natural minerals, and to the attempt of reproducing the latter from their elements.* [footnote] *Mitscherlich, 'Ueber die kunstliche Darstellung der Mineralien', in the 'Abhandl. der Akademie der Wiss. zu Berlin', 1822-3, s. 25-41. In all these operations, the same affinities manifest themselves which determine chemical combinations both in our laboratories and in the interior of the earth. The most considerable part of p 268 the simple minerals which characterize the more generally diffused Plutonic and erupted rocks, as well as those on which they have exercised a metamorphic action, have been produced in a crystalline state, and with perfect identify, in artificial mineral products. We must, however, distinguish here between the scoriae accidentally formed, and those which have been designedly produced by chemists. To the former belong feldspar, mica, augite, olivine, hornblende, crystallized oxyd of iron, magnetic iron in octahedral crystals, and metallis titanium;* to the latter, garnets, idocrase, rubies (equal in hardness to those found in the East), olivine, and augite.** [footnote] *In scoriae crystals of feldspar have been discovered by Heine in the refuse of a furnace for copper fusing, near Sangerhausen, and analyzed by Kersten (Poggend., 'Annalen', bd. xxxiii., s. 337); crystals of augite in scoriae at Sahle (Mitscherlich, in the 'Abhandl. der Akad. zu Berlin', 1822-23, s. 40); of oliving by Seifstrom (Leonhard, 'Basalt-Gebilde', bd. ii., s. 495); of mica in old scoriae of Schloss Garpenberg (Mitscherlich, in Leonhard, op. cit., s. 506); of magnetic iron in the scoriae of Chatillon sur Seine (Leonhard, s. 441); and of micaceous iron in potter's clay (Mitscherlich, in Leohnard, op. cit., s. 234). [See Ebelmer's papers in 'Ann. de Chimie et de Physique', 1847; also 'Report on the Crystalline Slags', by John Percy, M.D., F.R.S., and William Hallows Miller, M.A., 1847. Dr. Percy, in a communication with which he has kindly favored me, says that the minerals which he has found artificially produced and proved by analysis are Humboldtilite, gehlenite, olivine, and magnetic oxyd of iron, in octahedral crystals. He suggests that the circumstance of the production of gehlenite at a high temperature in an iron furnace may possibly be made available by geologists in explaining the formation of the rocks in which the natural mineral occurs, as in Fassathal in the Tyrol.] -- Tr. [footnote] **Of minerals purposely produced, we may mention idocrase and garnet (Mitscherlich, in Poggend., 'Annalen der Physik', bd. xxxii., s. 340); ruby (Gaudin, in the 'Comptes Rendus de l'Academie de Science', t. iv., Part i., p. 999); olivine and augite (Mitscherlich and Berthier, in the 'Annales de Chimie et de Physique', t. xxiv., p. 376). Notwithstanding the greatest possible similarity in crystalline form, and perfect identity in chemical composition, existing, according to Gustav Rose, between augite and hornblende, hornblende has never been found accompanying augite in scoriae, nor have chemists ever succeeded in artificially producing either hornblende or feldspar (Mitscherlich in Poggend., 'Annalen', bd. xxxiii., s. 340, and Rose, 'Reise nach dem Ural', bd. ii., s. 358 und 363). See also, Beaudant, in the 'Mem. de l'Acad. des Sciences', t. viii., p. 221, and Becquerel's ingenious experiments in his 'Trait de l'Electricite,' t. i., p. 334; t. iii., p. 218; and t. v., p. 148 and 185. These minerals constitute the main constituents of granite, gneiss, and mica schist, of basalt, dolerite, and many porphyries. The artificial production of feldspar and mica is of most especial geognostic importance with reference to the theory of the formation of gneiss by the metamorphic agency of argillaceous schist, which contains all the constituents of granite, p 269 potash not excepted.* [footnote] *D'Aubuisson, in the 'Journal de Physique', t. lxviii., p. 128. It would not be very surprising, therefore, as is well observed by the distinguished geognosist, Von Dechen, if we were to meet with a fragment of gneiss formed on the walls of a smelting furnace which was built of argillaceous slate and graywacke. After having taken this general view of the three classes of erupted, sedimentary, and metamorphic rocks of the earth's crust, it still remains for us to consider the fourth class, comprising 'conglomerates', or 'rocks of detrius'. The very term recalls the destruction which the earth's crust has suffered, and likewise, perhaps reminds us of the process of cementation, which has connected together, by means of oxyd of iron, or of some argillaceous and calcareous substances, the sometimes rounded and sometimes angular portions of fragments. Conglomerates and rocks of detritus, when considered in the widest sense of the term, manifest characters of a double origin. The substances which enter into their mechanical composition have not been alone accumulated by the action of the waves of the sea or currents of fresh water, for there are some of these rocks the formation of which can not be attributed to the action of water. "When basaltic islands and trachytic rocks rise on fissures, friction of the elevated rock against the walls of the fissures causes the elevated rock to be inclosed by conglomerates composed of its own matter. The granules composing the sandstones of many formations have been separated rather by friction against the erupted volcanic or Plutonic rock than destroyed by the erosive force of a neighboring sea. The existence of these friction 'conglomerates', which are met with in enormous masses in both hemispheres, testifies the intensity of the force with which the erupted rocks have been propelled from the interior through the earth's crust. This detritus has subsequently been taken up by the waters, which have then deposited it in the strata which it still covers."* [footnote] *Leop. von Buck, 'Geognost. Briefe', s. 75-82, where it is also shown why the new red sandstone (the 'Todtliegende' of the Thuringian flotz formation) and the coal measures must be regarded as produced by erupted porphyry. Sandstone formations are found imbedded in all strata, from the lower silurian transition stone to the beds of the tertiary formations, superposed on the chalk. They are found on the margin of the boundless plains of the New Continent, both within and without the tropics, extending like breast-works along the ancient shore, against which the sea once broke its foaming waves. p 270 If we cast a glance on the geographical distribution of rocks, and their relations in space, in that portion of the earth's crust which is accessible to us, we shall find that the most universally distributed chemical substance is 'silicic acid', generally in a variously-colored and opaque form. Next to solid silicic acid we must reckon carbonate of lime, and then the combinations of silicic acid with alumina, potash, and soda, with lime, magnesia, and oxyd of iron. The substances which we designate as 'rocks' are determinate associations of a small number of minerals, in which some combine parasitically, as it were, with others, but only under definite relations; thus, for instance, although quartz (silica), feldspar, and mica are the principal constituents of granite, these minerals also occur, either individually or collectively, in many other formations. By way of illustrating how the quantitative relations of one feldspathic rock differ from another, richer in mica than the former, I would mention that, according to Mitscherlich, three times more alumina and one third more silica than that ossessed by feldspar, give the constituents that enter into the composition of mica. Potash is contained in both -- a substance whose existence in many kinds of rocks is probably antecedent to the dawn of vegetation on the earth's surface. The order of succession, and the relative age of the different formations, may be recognized by the superposition of the sedimentary, metamorphic, and conglomerate strata; by the nature of the formations traversed by the erupted masses, and -- with the greatest certainty -- by the presence of organic remains and the differences of their structure. The application of botanical and zoological evidence to determine the relative age of rocks -- this chronometry of the earth's surface, which was already present to the lofty mind of Hooke -- indicates one of the most glorious epochs of modern geognosy, which has finally, on the Continent at least, been emancipated from the sway of Semitic doctrines. Palaeontological investigations have imparted a vivifying breath of grace and diversity to the science of the solid structure of the earth. The fossiliferous strata contain, entombed within them, the floras and faunas of by-gone ages. We ascend the stream of time, as in our study of the relations of superposition we descend deeper and deeper through the different strata, in which lies revealed before us a past world of animal and vegetable life. Far-extending disturbances, the elevation of great mountain chains, whose relative ages we are able to define, attest the p 271 destruction of ancient and the manifestation of recent organisms. A few of these older structures have remained in the midst of more recent species. Owing to the limited nature of our knowledge of existence, and from the figurative terms by which we seek to hide our ignorance, we apply the appellation 'recent structure' to the historical henomena of transition manifested in the organisms as well as in the forms of primitive seas and of elevated lands. In some cases these organized structures have been preserved perfect in the minutest details of tissues, integument, and articulated parts, while in others, the animal, passing over soft argillaceous mud, has left nothing but the traces of its course,* or the remains of its undigested food, as in the coprolites.** [footnote] *[In certain localities of the new red sandstone, in the Valley of the Connecticut, numerous tridactyl markings have been occasionally observed on the surface of the slabs of stone when split asunder, in like manner as the ripple-marks appear on the successive layers of sandstone in Tilgate Forest. Some remarkably distinct impressions of this kind, at Turner's Falls (Massachusetts), happening to attract the attention of Dr. James Deane, of Greenfield, that sagacious observer was struck with their resemblance to the foot-marks left on the mud-banks of the adjacent river by the aquatic birds which had recenty frequented the spot. The specimens collected were submitted to Professor G. Hitchcock, who followed up the inquiry with a zeal and success that have led to the most interesting results. No reasonable doubt now exists that the imprints in question have been produced by the tracks of bipeds impressed on the stone when in a soft state. The announcement of this extraordinary phenomenon was first made by Professor Hitchcock, in the 'American Journal of Science' (January, 1836), and that eminent geologist has since published full descriptions of the different species of imprints which he has detected, in his splendid work on the geology of Massachusetts. -- Mantell's 'Medals of Creation', vol. ii., p. 310. In the work of Dr. Mantell above referred to, there is, in vol. ii., p. 815, an admirable diagram of a slab from Turner's Falls, covered with numerous foot-marks of birds, indicating the track of ten or twelve individuals of different sizes.] -- Tr. [footnote] **[From the examination of the fossils spoken of by geologists under the name of 'Coprolites', it is easy to determine the nature of the food of the animals, and some other points; and when, as happened occasionally, the animal was killed while the process of digestion was going on, the stomach and intestines being partly filled with half-digested food, and exhibiting the coprolites actually 'in situ', we can make out with certainty not only the true nature of the food, but the proportionate size of the stomach, and the length and nature of the intestinal canal. Within the cavity of the rib of an extinct animal, the palaeontologist thus finds recorded, in indelible characters, some of those hieroglyphics upon which he founds his history. -- 'The Ancient World', by D. T. Ansted, 1847, p. 173.] -- Tr. In the lower Jura formations (the lias of Lyme Regis), the ink bag of the sepia has been so wonderfully preserved, that the material, which myriads p 272 of years ago might have served the animal to conceal itself from its enemies, still yields the color with which its image may be drawn.* [footnote] *A discovery made by Miss Mary Anning, who was likewise the discoverer of the coprolites of fish. These coprolites, and the excrements of the Ichthyosauri, have been found in such abundance in England (as, for instance, near Lyme Regis), that, according to Buckland's expression, they lie like potatoes scattered in the ground. See Buckland, 'Geology considered with reference to Natural Theology', vol. i., p. 188-202 and 305. With respect to the hope expressed by Hooke "to raise a chronology" from the mere study of broken and fossilized shells "and to state the interval of time wherein such or such castrophes and mutations have happened," see his 'Posthumous Works, Lecture', Feb. 29, 1688. [Still more wonderful is the preservation of the substance of the animal of certain Cephalopodes in the Oxford clay. In some specimens recently obtained, and described by Professor Owen, not only the ink bag, but the muscular mantle, the head, and its crown of arms, are all preserved in connection with the belemnite shell, while one specimen exhibits the large eyes and the funnel of the animal, and the remains of two fins, in addition to the shell and the ink bag. See Ansted's 'Ancient World', p. 147.] -- Tr. In other strata, again, nothing remains but the faint impression of a muscle shell; but even this, if it belong to a main dividion of mollusca,* may serve to show the traveler, in some distant land, the nature of the rock in which it is found, and the organic remains with which it is associated. [footnote] *Leop. von Buch, in the 'Abhandlungen der Akad. der Wiss. zu Berlin in dem Jahr' 1837, s. 64. Its discovery gives the history of the country in which it occurs. The analytic study of primitive animal and vegetable life has taken a double direction: the one is purely morphological, and embraces, especially, the natural history and physiology of organisms, filling up the chasms in the series of still living species by the fossil structures of the primitive world. The second is more specially geognostic, considering fossil remains in their relations to the superposition and relative age of the sedimentary formations. The former has long predominated over the latter, and an imperfect and superficial comparison of fossil remains with existing species has led to errors, which may still be traced in the extraordinary names applied to certain natural bodies. It was sought to identify all fossil species with those still extant in the same manner as, in the sixteenth century, men were led by false analogies to compare the animals of the New Continent with those of the Old. Peter Camper, Sommering, and Blumenbach had the merit of being the first, by the scientific application of a more accurate p 273 comparative anatomy, to throw light on the osteological branch of palaeontology -- the archaeology of organic life; but the actual geognostic views of the doctrine of fossil remains, the felicitous combination of the zoological character with the order of succession, and the relative ages of strata, are due to the labors of George Cuvier and Alexander Brongniart. The ancient sedimentary formations and those of transition rocks exhibit, in the organic remains contained within them, a mixture of structures very variously situated on the scale of progressively-developed organisms. These strata contain but few plants, as, for instance, some species of Fuci, Lycopodiaceae which were probably arborescent, Equisetaceae, and tropical ferns; they present, however, a singular association of animal forms, consisting of Crustacea (trilobites with reticulated eyes, and Calymene), Brachiopoda ('Spirifer, Orthis'), elegant Sphaeronites, nearly allied to the Crinoidea,* Orthoceraitites, of the family of the Cephalopoda, corals, and, blended with these low organisms, fishes of the most singular forms, imbedded in the upper silurian formations. [footnote] *Leop. von Buch, 'Gebirgsformationen von Russland', 1840, s. 24-50. The family of the Cephalaspides, whose fragments of the species 'Pterichtys' were long held to be trilobites, belongs exclusively to the devonian period (the old red), manifesting, according to Agassiz, as peculiar a type among fishes as do the Ichthyosauri and Plesiosauri among reptiles.* [footnote] *Agassiz, 'Monographie des Poissons Fossiles du vieux Gres Rouge', p. vi. and 4. The Goniatites, of the tribe of Ammonites,* a are manifested in the transition chalk, in the graywacke of the devonian periods, and even in the latest silurian formations. [footnote] *Leop. von Buch, in the 'Abhandl. der Berl. Akad.', 1838, s. 149-168; Beyrich, 'Beitr. zur Kenntniss des Rheinischen Uebergangagebirges', 1837, s. 45. The dependence of physiological gradation upon the age of the formations, which has not hitherto been shown with perfect certainty in the case of invertebrata,* is most regularly manifested in vertebrated animals. [footnote] *Agassiz, 'Recherches sur les Poissons Fossiles', t. i., 'Introd.', p. xviii.; Davy, 'Consolation in Travel', dial. iii. The most ancient of these, as we have already seen, are fishes; next in the order of succession of formation, passing from the lower to the upper, come reptiles and mammalia. The first reptile (a Saurian, the Monitor of Cuvier), which excited the attention of Leibnitz,* is found in cuperiferous schist of the Zechstein of Thuringa; the Palaeosaurus and Thecodontosaurus of Bristol are, according to Murchison, of the same age. [footnote] *A Protosaurus, according to Hermann von Meyer. The rib of a Saurian asserted to have been found in the mountain limestone (carbonate of lime) of Northumberland (Herm. von Meyer, 'Palaeologica', s. 299), is regarded by Lyell ('Geology', 1832, vol. i., p. 148) as very doubtful. The discoverer himself referred it to the alluvial strata which cover the mountain limestone. The Saurians are found in large numbers in the muschelkalk,* in the keuper, and in the oolitic formations, where they are the most numerous. [footnote] *F. von Alberti, 'Monographie des Bunten Sandsteins, Muschelkalks und Keupers', 1834, s. 119 und 314. At the period of these formations there existed Pleiosauri, having long, swan-like necks consisting of thirty vertebrae; Megalosauri, monsters resembling the crocodile, forty-five feet in length, and having feet whose bones were like those of terrestrial mammalia, eight species of large-eyed Ichthyosauri, the Geosaurus or 'Lacerta gigantea', of Sommering, and finally, seven remarkable species of Pterodactyles,* of Saurians furnished with membranous wings. [footnote] *See Hermann von Meyer's ingenious considertions regarding the organization of the flying Saurians, in his 'Palaeologica', s. 228-252. In the fossil specimen of the Pterodactylus crassirostris, which, as well as the loonger known P. longirostris (Ornithocephalus of Sommering), was found at Solenhofen, in the lithographic slate of the upper Jura formation, Professor Goldfuss has even discovered traces of the membranous wing, "with the impressions of curling tufts of hair, in some places a full inch in length." In the chalk the number of the crocodilial Saurians diminishes, although this epoch is characterized by the so-called crocodile of Maestricht (the Mososaurus of Conybeare), and the colossal, probably graminivorous Iguandon. Cuvier has found animals belonging to the existing families of the crocodile in the tertiary formation, and Scheuchzer's 'antediluvian man' ('homo diluvii testis'), a large salamander allied to the Axolotl, which I brought with me from the large Mexican lakes, belongs to the most recent fresh-water formations of Oeningen.* [footnote] *[Ansted's 'Ancient World', p. 56.] -- Tr. The determination of the relative ages of organisms by the superposition of the strata has led to important results regarding the relations which have been discovered between extinct families and species (the latter being but few in number) and those which still exist. Ancient and modern observations concur in showing that the fossil floras and faunas differ more from the present vegetable and animal forms in proportion as they belong to lower, that is, more ancient sedimentary formations. The numerical relations first deduced by Cuvier p 275 from the great phenomena of the metamorphism of organic life,* have led, through the admirable labors of Deshayes and Lyell, to the most marked results, especially with reference to the different groups of the tertiary formations, which contain a considerable number of accurately investigated structures. [footnote] *Cuvier, 'Recherches sur les Ossemens Fossiles', t. i., p. 52-57. See, also, the geological scale of epochs in Phillips's 'Geology', 1837, p. 166-185. Agassiz, who has examined 1700 species of fossil fishes, and who estimates the number of living species which have either been described or are preserved in museums at 8000, expressly says, in his masterly work, that, "with the exception of a few small fossil fishes peculiar to the argillaceous geodes of Greenland, he has not found any animal of this class in all the transition, secondary or tertiary formations, which is specifically identical with any still extant fish." He subjoins the important observation "that in the lower tertiary formations, for instance, in the coarse granular calcareous beds, and in the London clay,* one third of the fossil fishes belong to wholly extinct families. [footnote] *[See 'Wonders of Geology', vol. i., p. 230.] -- Tr. Not a single species of a still extant family is to be found under the chalk, while the remarkable family of the 'Sauroidi' (fishes with enameled scales), almost allied to reptiles, and which are found from the coal beds -- in which the larger species lie -- to the chalk, where they occur individually, bear the same relation to the two families (the Lepidosteus and Polypterus) which inhabit the American rivers and the Nile, as our present elephants and tapirs do to the Mastodon and Anaplotheriun of the primitive world."* [footnote] *Agassiz, 'Poissons Fossiles', t. i., p. 30, and t. iii., p. 1-52; Buckland, 'Geology', vol. i., p. 273-277. The beds of chalk which contain two of these sauroid fishes and gigantic reptiles, and a whole extinct world of corals and muscles, have been proved by Ehrenberg's beautiful discoveries to consist of microscopic Polythalamia, many of which still exist in our seas, and in the middle latitudes of the North Sea and Baltic. The first group of tertiary formations above the chalk, which has been designated as belonging to the 'Eocene Period', does not, therefore, merit that designation, since "the 'dawn of the world' in which we live extends much further back in the history of the past than we have hitherto supposed."* [footnote] *Ehrenberg, 'Ueber noch jetzt lebende Thierarten der Kreidelnldung', in the 'Abhandl. der Berliner Akad.', 1839, s. 164. As we have already seen, fishes, which are the most ancient of all vertebrata, are found in the silurian transition strata, p 276 and then uninterruptedly on through all formations to the strata of the tertiary period, while Saurians begin with the zechstone. In like manner, we find the first mammalia ('Thylacotherium Prevostii', and 'T. Bucklandii', which are nearly allied according to Valenciennes,* with marsupial animals) in the oolitic formations (Stonesfield schist), and the first birds in the most ancient cretaceous strata.** [footnote] *Valenciennes, in the 'Comptes Rendus de l'Academie des Sciences', t. vii., 1838, Part ii., p. 580. [footnote] **In the Weald clay; Bendant, 'Geologie', p. 173. The ornitholites increase in number in the gypsum of the tertiary formations. Cuvier, 'Ossemens Fossiles', t. ii., p. 302-328. Such are, according to the present state of our knowledge, the lowest* limits of fishes, Saurians, mammalia, and birds. [footnote] *[Recent collections from the southern hemisphere show that this distribution was not so universal during the earlier epochs as has generally been supposed. See papers by Darwin, Sharpe, Morris, and McCoy, in the 'Geological Journal'.] -- Tr'. Although corals and Serpulidae occur in the most ancient formations simultaneously with highly-developed Cephalopodes and Crustaceans, thus exhibiting the most various orders grouped together, we yet discover very determinate laws in the case of many individual groups of one and the same orders. A single species of fossil, as Goniatites, Trilobites, or Nummulites, sometimes constitutes whole mountains. Where different families are blended together, a determinate succession of organisms has not only been observed with reference to the superposition of the formations, but the association of certain families and species has also been noticed in the lower strata of the same formation. By his acute discovery of the arrangement of the lobes of their chamber-sutures, Leopold von Buch has been enabled to divide the innumerable quantity of Ammonites into well-characterized families, and to show that Ceratites appertain to the muschelkalk, Arietes to the lias, and Goniatites to transition limestone and graywacke.* [footnote] *Leop. von Buch, in the 'Abhandl. der Berl. Akad.', 1830, s. 135-187. The lower limits of Belemnites are, in the keuper, covered by Jura limestone, and their upper limits in the chalk formations.* [footnote] *Quenstedt, 'Flotzgebirge Wurtembergs', 1843, s. 135. It appears, from what we now know of this subject, that the waters must have been inhabited at the same epoch, and in the most widely-remote districts of the world, by shell-fish, which were at any rate, in part, identical with the fossil remains found in England. Leopold von Buch has discovered exogyra and trigonia in the southern hemisphere (volcano of p 277 Maypo in Chili), and D'Orbigny has described Ammonites and Gryphites from the Himalaya and the Indian plains of Cutch, these remains being identical with those found in the old Jurassic sea of Germany and France. The strata which are distinguished by definite kinds of petrifacations, or by the fragments contained within them, form a geognostic horizon, by which the inquirer may guide his steps, and arrive at certain conclusions regarding the identity or relative age of the formations, the periodic recurrence of certain strata, their parallelism, or their total suppression. If certain strata, their parallelism, or their total suppression. If we classify the type of the sedimentary structures in the simplest mode of generalization, we arrive at the following series in proceeding from below upward: 1. The so-called 'transition rocks', in the two divisions of upper and lower graywacke (silurian and devonian systems), the latter being formerly designated as old red sandstone. 2. The 'lower trias',* comprising mountain limestone, coal-measures, together with the lower new red sandstone (Todtliegende and Zechstein).** 3. The 'upper trias', including variegated sandstone,** muschelkalk, and keuper. 4. 'Jura limestone' (lias and oolite). 5. 'Green sandstone', the quader sanstein, upper and lower chalk, terminating the secondary formations, which begin with limestone. 6. 'Tertiary formations' in three divisions, distinguished as granular limestone, the lignites, and the sub-Apennine gravel of Italy. [footnote] *Quenstedt, 'Flotzgebirge Wurtembergs', 1843, s. 13. [footnote] ** Murchison makes two divisions of the 'bunter sandstone', the upper being the same as the 'trias' of Alberti, while the lower division, to which the 'Vosges sandstone' of Elie de Beaumont belongs -- the 'zeckstein' and the 'todtliegende' -- he forms his 'Permian' system. He makes the secondary formations commence with the 'upper trias', that is to say, with the upper division of our (German) bunter sandstone, while the Permian system, the carboniferous or mountain limestone, and the devonian and silurian strata, constitute his 'palaeozoic formatiions'. According to these views, the chalk and Jura constitute the upper, and the keuper, the muschelkalk, and the bunter sandstone the lower secondary formations, while the Permian system and the carboniferous limestone are the upper, and the devonian and silurian strata are the lower palaeooic formation. The fundamental principles of this general classification are developed in the great work in which this indefatigable British geologist purposes to describe the geology of a large part of Eastern Europe. Then follow, in the alluvial beds, the colossal bones of the mammalia of the primitive world, as the mastodon, dinothrium p 278 missurium, and the megatherides, among which is Owen's sloth-like mylodon, eleven feet in the length.* [footnote] *[See Mantell's 'Wonders of Geology', vol. i., p. 168.] -- Tr. Besides these extinct families, we find the fossil remains of still extant animals, as the elephant, rhinoceros, ox, horse, and stag. The field near Bogota, called the 'Campo de Gigantes', which is filled with the bones of mastodons, and in which I caused excavations to be made, lies 8740 feet above the level of the sea, while the osseous remains, found in the elevated plateaux of Mexico, belong to true elephants of extinct species.* [footnote] *Cuvier, 'Ossemens Fossiles', 1821, t. i., p. 157, 261, and 264. See, also, Humboldt, 'Ueber die Hochebene von Bogota', in the 'Deutschen Vierteljahrs-schrift', 1839, bd. i., s. 117. The projecting spurs of the Himalaya, the Sewalik Hills, which have been so zealously investigated by Captain Cantley* and Dr. Falconer, and the Cordilleras, whose elevations are probably, of very different epochs, contain, besides numerous mastodons, the sivatherium, and the gigantic land tortoise of the primitive world ('Colossochelys'), which is twelve feet in length and six in height, and several extant families, as elephants, rhinoceroses, and giraffes; and it is a remarkable fact, that these remains are found in a zone which still enjoys the same tropical climate which must be supposed to have prevailed at the period of the mastodons.** [footnote] *[The fossil fauna of the Sewalik range of hills, skirting the southern base of the Himalaya, has proved more abundant in genera and species of mammalia than that of any other region yet explored. As a general expression of the leading features, it may be stated, that it appears to have been composed of representative forms of all ages, from the 'oldest of the tertiary period down to the modern', and of 'all the geographical' divisions of the Old Continent grouped together into one comprehensive fauna. 'Fauna Antiqua Sivaliensis', by Hugh Falconer, M.D., and Major P. T. Cautley.] -- Tr. Having thus passed in review both the inorganic formations of the earth's crust and the animal remains which are contained within it, another branch of the history of the organic life still remains for our consideration, viz., the epoch of vegetation, and the successive floras that have occurred simultaneously with the increasing extent of the dry land and the modifications of the atmosphere. The oldest transition strata, as we have already observed, contain merely cellular marine plants, and it is only in the devonian system that a few cryptogamic forms of vascular plants (Calamites and Lycopodiaceae) have been observed.* [footnote] *Beyrich, in Karsteu's 'Archiv fur Mineralogie', 1844, bd. xviii., s. 218. Nothing appears to corroborate p 279 the theoretical views that have been started regarding the simplicity of primitive forms of organic life, ow that vegetable preceded animal life, and that the former was necessarily dependent upon the latter. The existence of races of men inhabiting the icy regions of the North Polar lands, and whose nutriment is solely derived from fish and cetaceans, shows the possibility of maintaining life independently of vegetable substances. After the devonian system and the mountain limestone, we come to a formation, the botanical analysis of which has made such brilliant advances in modern times.* [footnote] *By the important labors of Count Sternberg, Adolphe Brongniart, Goppert, and Lindley. The coal measures contain not only fern-like cryptogamic plants and phanerogamic monocotyledons (grasses, yucc-like Liliaceae and palms), but also gymnospermic dicotyledons (Coniferae and Cycadeae), amounting in all to nearly 400 species, as characteristic of the coal formations. Of these we will only enumerate arborescent Calamites and Lycopodiaceae, scaly Lepidodendra, Sigillariae, which attain a height of sixty feet, and are sometimes found standing upright, being distinguished by a double system of vascular bundles, cactus-like Stigmariae, a great number of ferns, in some cases the stems, and in others the fronds alone being found, indicating by their abundance the insular form of the dry land,* Cycadeae** especially palms, although fewer in number.*** [footnote] *See Robert Brown's 'Botany of Congo', p. 42, and the Memoir of the unfortunate E'Urville, 'De la Distribution des Fougeres sur la Surface du Globe Terrestre'. [footnote] **Such are the Cycadeae discovered by Count Sternberg in the old carboniferous formation at Radnitz, in Bohemia, and described by Corda (two species of Cycatides and Zamites Cordai. See Goppert, 'Fossile Cycadeen in den Arbeiten der Schles. Gesellschaft, fur waterl. Cultur im Jahr' 1843, s. 33, 37, 40 and 50). A Cycadea (Pterophyllum gonorchachis, Gopp.) has also been found in the carboniferous formations in Upper Silesia, at Konigshutte. [footnote] ***Lindley, 'Fossil Flora', No. xv., p. 163. Asterophyllites, having whorl-like leaves, and allied to the Naiades, with araucaria-like Coniferae',* which exhibit faint traces of annual rings. [footnote] *'Fossil Coniferae', in Buckland's 'Geology', p. 483-490. Witham has the great merit of having first recognized the existence of Coniferae in the early vegetation of the old carboniferous formation. Almost all the trunks of trees found in this formation were previously regarded as palms. The species of the genus 'Araucaria' are, however, not peculiar to the coal formations of the British Islands; they likewise occur in Upper Silesia. This difference of character from our present vegtation, minifested in the vegetative forms which were so luxuriously developed on the drier p 280 and more elevated portions of the old red sandstone, was maintained through all the subsequent epochs to the most recent chalk formations; amid the peculiar characteristics exhibited in the vegetable forms contained in the coal measures, there is, however, a strikingly-marked prevalence of the same families, if not of the same species,* in all parts of the earth as it then existed, as in New Holland, Canada, Greenland, and Melville Island. [footnote[ *Adolphe Brongniart, 'Prodrome d'une Hist. des Vegetaux Fossiles', p. 179; buckland, 'Geology', p. 479; Endlicher and Unger, 'Grundzuge der Botanik', 1843, s. 455. The vegetation of the primitive period exhibits forms which, from their simultaneous affinity with several families of the present world, testify that many intermediate links must have become extinct in the scale of organic development. Thus, for example, to mention only two instances, we would notice the Lepidodendra, which, according to Lindley, occupy a place between the Coniferae and the Lycopodiaceae*, and the Araucariae and pines, which exhibit some peculiarities in the union of their vascular bundles. [footnote] *"By means of Lepidodendron, a better passage is established from flowering to flowerless plants than by either Equisetum or Cycas, or any other known genus." -- Lindley and Hutton, 'Fossil Flora', vol. ii., p. 53. Even if we limit our consideration to the present world alone, we must regard as highly important the discovery of Cycadeae and Coniferae side by side with Sagenariae and Lepidodendra in the ancient coal measures. The Coniferae are not ony allied to Cupuliferae and Betulinae, with which we find them associated in lignite formations, but also with Lycopodiaceae. The family of the sago-like Cycadeae approaches most nearly to palms in its external appearance, while these plants are specially allied to Coniferae in respect to the structure of their blossoms and seed.* [footnote] *Kunth, 'Anordnung der Pflanzenfamilien', in his 'Handb. der Botanik', s. 307 und 314. Where many beds of coal are superposed over one another, the families and species are not always blended, being most frequently grouped together in separate genera; Lycopodiaceae and certain ferns being alone found in one bed, and Stigmariae and Sigillariae in another. In order to give some idea of the luxuriance of the vegetation of the primitive world, and of the immense masses of vegetable matter which was doubtlessly accumulated in currents and converted in a moist condition into coal,* I would instance the Saarbrucker coal measures, p 281 where 120 beds are superposed on one another, exclusive of a great many which are less than a foot in thickness; the coal beds at Johnstone, in Scotland, and those in the Creuzot, in Burgundy, are some of them, respectively, thirty and fifty feet in thickness,** while in the forests of our temperate zones, the carbon contained in the trees growing over a certain area would hardly suffice, in the space of a hundred years, to cover it with more than a stratum of seven French lines in thickness.*** [footnote] That coal has not been formed from vegetable fibers charred by fire, but that it has more probably been produced in the moist way by the action of sulphuric acid, is strikingly demonstrated by the excellent observation made by Goppert (Karsten, 'Archiv fu Mineralogie', bd. xviii., s. 530), on the conversion of a fragment of amber-tree into black coal. The coal and the unaltered amber lay side by side. Regarding the part which the lower forms of vegetation may have had in the formation of coal beds, see Link, in the 'Abhandl. der Berliner Akademie der Wissenschaften', 1838, s. 38. [footnote] **[The actual total thickness of the different beds in England varies considerably in different districts, but appears to amount in the Lancashire coal field to as much as 150 feet. -- Ansted's 'Ancient World', p. 78. For an enumeration of the thickness of coal measures in America and the Old Continent, see Mantell's 'Wonders of Geology', vol. ii., p. 60.] -- Tr. [footnote] ***See the accurate labors of Chevandier, in the 'Comptes Rendus de l'Academie des Sciences', 1844, t. xviii., Part i., p. 285. In comparing this bed of carbon, seven lines in thickness, with beds of coal, we must not omit to consider the enormous pressure to which the latter have been subjected from superimposed rock, and which manifests itself in the flattened form of the stems of the trees found in these subterranean regions. "The so-called 'wood-hills' discovered in 1806 by Sirowatskoi, on the south coast of the island of New Siberia, consist, according to Hedenstrom, of horizontal strata of sandstone, aolternating with bituminous trunks of trees, forming a mound thirty fathoms in neight; at the summit the stems were in a vertical position. The bed of driftwood is visible at five wersts' distance." -- See Wrangel, 'Reise Iangs der Nordkuste von Siberien, in den Jahren' 1820-24, th. i., s. 102. Near the mouth of the Mississippi, and in the "wood hills" of the Siberian Polar Sea, described by Admiral Wrangel, the vast number of trunks of trees accumulated by river and sea water currents affords a striking instance of theenormous quantities of drift-wood which must have favored the formation of carboniferous deposition in the island waters and insular bays. There can be no doubt that these beds owe a considerable portion of the substances of which they consist to grasses, small branching shrubs, and cryptogamic plants. The association of palms and Coniferae, which we have indicated as being characteristic of the coal formations, is discoverable throughout almost all formations to the tertiary period. In the present condition of the world, these genera p 282 appear to exhibit no tendency whatever to occur associated together. We have so accustomed ourselves, although erroneously, to regard Coniferae as a northern form, that I experienced a feeling of surprise when, in ascending from the shores of the South Pacific toward Chilpansingo and the elevated valleys of Mexico, between the 'Venta de la Moxonera' and the 'Alto de los Caxones', 4000 feet above the level of the sea, I rode a whole day through a dense wood of Pinus occidentalis, where I observed that these trees, which are so similar to the Weymouth pine, were associated with fan palms* ('Corypha dulcis'), swarming with brightly-colored parrots. [[footnote] *This corypha is the 'soyate' (in Aztec, zoyatl), or the 'Palma dulce' of the natives. See Humboldt and Bonplaud, 'Synopsis Plant. AEquinoct. Orbis Novi', t. i., p. 302. Professor Buschmann, who is profoundly acquainted with the American languages, remarks, that the 'Palma soyate' is so named in Yepe's 'Vocabulario de la Lengua Othomi', and that the Aztec word zoyatl (Molina, 'Vocabulario en Lengua Mexicana y Castellana', p. 25) recurs in names of places, such as Zoyatitlan and Zoyapanco, near Chiapa. South America has oaks, but not a single species of pine; and the first time that I again saw the familiar form of a fir-tree, it was thus associated with the strange appearance of the fan palm.* [footnote] *Near Baracoa and Cayos de Moya. See the Admiral's journal of the 25th and 27th of November, 1492, and Humboldt, 'Examen Critique de l'Hist. de la Geographie du Nouveau Continent', t. ii., p. 252, and 5. iii., p. 23. Columbus, who invariably paid the most remarkable attention to all natural objects, was the first to observe the difference between 'Podocarpus' and 'Pinus'. "I find," said he, "en la tierra aspera del Cibao pinos que no Ilevan pinas (fir cones), pero portal orden compuestos por naturaleza, que (los frutos) parecen azeytunas del Axarafe de Sevilla." The great botanist, Richard, when he published his excellent Memoir on Cycadeae and Coniferae, little imagined that before the time of L'Heritier, and even before the end of the fifteenth century, a navigator had separated 'Podocarpus' from the Abietineae. Christopher Columbus, in his first voyage of discovery, saw Coniferae and palms growing together on the northeastern extremity of the island of Cuba, likewise within the tropics, and scarcely above the level of the sea. This acute observer, whom nothing escaped, mentions the fact in his journal as a remarkable circumstance, and his friend Anghiera, the secretary of Frdinand the Catholic, remarks with astonishment "that 'palmeta' and 'pineta' are found associated together in the newly-discovered land." It is a matter of much importance to geology to compare the present distribution of plants over the earth's surface with that exhibited in the fossil floras of the primitive world. The temperate zone of the southern hemisphere, which is so rich in seas and islands, and where p 283 tropical forms blend so remarkably with those of colder parts of the earth, presents according to Darwin's beautiful and animated descriptions,* the most instructive materials for the study of the present and the past geography of plants. [footnote] *Charles Darwin, 'Journal of the Voyages of the Adventure and Beagle', 1839, p. 271. The history of the primordial ages is, in the strict sense of the word, a part of the history of plants. Cycadeae, which, from the number of their fossil species, must have occupied a far more important part in the extinct than in the present vegetable world, are associated with the nearly allied Coniferae from the coal formations upward. They are almost wholly absent in the epoch of the variegated sandstone which contains Coniferae of rare and luxuriant structure ('Voltizia, Haidingera, Albertia'); the Cycadeae, however, occur most frequently in the keuper and lias strata, in which more than twenty different forms appear. In the chalk, marine plants and naiades predominate. The forests of Cycadeae of the Jura formations had, therefore, long disappeared, and even in the more ancient tertiary formations they are quite subordinate to the Coniferae and palms.* [footnote] *Goppert describes three other Cycadeae (species of Cycadites and Pterophyllum), found in the brown carboniferous schistose clay of Alt-sattel and Commotau, in Bohemia. They very probably belong to the Eocene Period. Goppert, 'Fossile Cycadeen', s. 61. The lignites, or beds of brown coal* which are present in all divisions of the tertiary period, present, among the most ancient cryptogamic land plants, some few palms, many Coniferae having distinct annual rings, and foliaceous shrubs of a more or less tropical character. [footnote] *['Medals of Creation', vol. i., ch. v., etc. 'Wonders of Geology', vol. i., p. 278, 392.] -- Tr. In the middle tertiary period we again find palms and Cycadeae fully established, and finally a great similarity with our existing flora, manifested in the sudden and abundant occurrence of our pines and firs, Cupuliferae, maples, and poplars. The dicotyledonous stems found in lignite are occasionally distinguished by colossal size and great age. In the trunk of a tree found at Bonn, Noggerath counted 792 annual rings.* [footnote] *Buckland, 'Geology', p. 509. In the north of France, at Yseux, near Abbeville, oaks have been discovered in the turf moors of the Somme which measured fourteen feet in diameter, a thickness which is very remarkable in the Old Continent and without the tropics. According to Goppert's excellent investigations, which, it is hoped, may soon be illustrated by plates, it would appear that "all the amber of the Baltic comes from p 284 a coniferous tree, which, to judge by the still extant remains of wood and the bark at different ages, approaches very nearly to our white and red pines, although forming a distinct species. The amber-tree of the ancient world ('Pinites succifer') abounded in resin to a degree far surpassing that manifested by any extant coniferous tree; for not only were large masses of amber deposited in and upon the bark, but also in the wood itself, following the course of the medullary rays, which, together with ligneous cells, are still discernible under the microscope, and peripherally between the rings, being some times both yellow and white." "Among the vegetable forms inclosed in amber are male and femald blossoms of our native needle-wood trees and Cupuliferae, while fragments which are recognized as belonging to thuia, cupressus, ephedera, and castania vesca, blended with those of junipers and firs, indicate a vegetation different from that of the coasts and plains of the Baltic."* [footnote] *{The forests of amber-pines, 'Pinites succifer', were in the southeastern part of what is now the bed of the Baltic, in about 55 degrees N. lat., and 37 degrees E. long. The different colors of amber are derived from local chemical admixture. The amber contains fragments of vegetable matter, and from these it has been ascertained tht the amber-pine forests contained four other species of pine (besides the 'Pinites succier'), several cypresses, yews, and junipers, with oaks, poplars, beeches, etc. -- altogether forty-eight species of trees and shrubs, constituting a flora of North American chracter. There are also some ferns, mosses, fungi, and liverworts. See Professor Goppert, 'Geol. Trans.', 1845. Insects, spiders, small crustaceans, leaves, and fragments of vegetable tissue, are imbedded in some of the masses. Upward of 800 species of insects have been observed; most of them belong to species, and even genera, that appear to be distinct from any now known, but others are nearly related to indigenous species, and some are identical with existing forms, that inhabit more southern climes. -- 'Wonders of Geology', vol. i., p. 242, etc.] -- Tr. We have now passed through the whole series of formations comprised in the geological portion of the present work, proceeding from the oldest erupted rock and the most ancient sedimentary formations to the alluvial land on which are scattered those large masses of rock, the causes of whose general distribution have been so long and variously discussed, and which are, in my opinion, to be ascribed rather to the penetration and violent outpouring of pent-up waters by the elevation of mountain chains than to the motion of floating blocks of ice.* [footnote] *Leopold von Buch, in the 'Abhandl. der Akad. der Wissensch. zu Berlin', 1814-15, s. 161; and in Poggend., 'Annalen', bd. ix., s. 575; Elie de Beaumont, in the 'Annales des Sciences Naturelles', t. xix., p. 60. The most ancient structures of the transition formation p 285 with which we are acquainted are slate and graywacke, which contain some remains of sea weeds from the silurian or cambrian sea. On what did these so-called 'most ancient' formations rest, if gneiss and mica schist must be regarded as changed sedimentary strata? Dare we hazard a conjecture on that which can not be an object of actual geognostic observation? According to an ancient Indian myth, the earth is borne up by an elephant, who in his turn is supported by a gigantic tortoise, in order that he may not fall; but it is not permitted to the credulous Brahmins to inquire on what the tortoise rests. We venture here upon a somewhat similar problem, and are prepared to meet with opposition in our endeavors to arrive at its soluion. In the first formation of the planets, as we stated in the astronomical portion of this work, it is probable that nebulous rings revolving round the sun were agglomerated into spheroids, and consolidated by a gradual condensation proceeding from the exterior toward the center. What we term the ancient silurian strata are thus only the upper portions of the solid crust of the earth. The erupted rocks which have broken through and upheaved these strata have been elevated from depths that are wholly inaccessible to our research; they must, therefore, have existed under the silurian strata, and been composed of the same association of minerals which we term granite, augite, and quartzose porphyry, when they are made known to us by eruption through the surface. Basing our inquiries on analogy, we may assume that the substances which fill up deep fissures and traverse the sedimentary strata are merely the ramifications of a lower deposit. The foci of active volcanoes are situated at enormous depths, and judging from the remarkable fragments which I have found in various parts of the earth incrusted in lava currents, I should deem it more than probable tht a primordial granite rock forms the substratum of the whole stratified edifice of fossil remains.* [footnote] *See Elie de Beaumont, 'Descr. Geol. de la France', t. i., p. 65; Beaudant, 'Geologie', 1844, p. 269. Basalt containing olivine first shows itself in the period of the chalk trachyte still later, while eruptions of granite belong, as we learn from the products of their metamorphic action to the epoch of the oldest sedimentary strata of the transition formation. Where knowledge can not be attained from immediate perceptive evidence, we may be allowed from induction, no less than from a careful comparison of facts, to hazard a conjecture by which granite would be restored p 286 to a portion of its contested right and title to be considered as a 'primordial' rock. The recent progress of geognosy, that is to say, the more extended knowledge of the geognostic epochs characterized by differences of mineral formations, by the peculiarities and succession of the organisms contained within them, and by the position of the strata, whether uplifted or inclined horizontally, leads us, by means of the causal connection existing among all natural phenomena, to the distribution of solids and fluids into the continents and seas which constitute the upper crust of our planet. We here touch upon a point of contact between geological and geographical geognosy which would constitute the complete history of the form and extent of continents. The limitation of the solid by the fluid parts of the earth's surface and their mutual relations of area, have varied very considerably in the long series of geognostic epochs. They were very different, for instance, when carboniferous strata were horizontally deposited on the inclined beds of the mountain limestone and old red sandstone; when lias and oolite lay on a substratum of keuper and muschelkalk, and the chalk rested on the slopes of green sandstone and Jura limestone. If, with Elie de Beaumont, we term the waters in which the Jura limestone and chalk formed a soft deposit the 'Jurassic or oolitic', and the 'cretaceous seas', the outlines of these formations will indicate, for the two corresponding epochs, the boundaries between the already dried land and the ocean in which these rocks were forming. An ingenious attempt has been made to craw maps of this physical portion of primitive geography and we may consider such diagrams as more correct than those of the wanderings of Io or the Homeric geography, since the latter are merely graphic representations of mythical images, while the former are based upon positive facts deduced from the science of geology. The results of the investigations made regarding the areal relations of the solid portions of our planet are as follows: in the most ancient times, during the silurian and devonian transition epochs, and in the secondary formations, including the trias, the continental portions of the earth were limited to insular groups covered with vegetation; these islands at a subsequent period became united, giving rise to numerous lakes and deeply-indented bays; and finally, when the chains of the Pyrenees, Apennines, and Carpathian Mountains were elevated about the period of the more ancient tertiary formations, large continents appeared, having almost their present p 287 size.* [footnote] *[These movements, described in so few words, were doubtless going on for many thousands and tens of thousands of revolutions of our planet. They were accompanied, also, by vast but slow changes of other kinds. The expansive force employed in lifting up, by mighty movements, the northern portion of the continent of Asia, found partial vent; and from partial subsqueous fissures there were poured out the tabular masses of basalt occurring in Central India, while an extensive area of depression in the Indian Ocean, marked by the coral islands of the Laccadives, the Maldives, the great Chagos Bank, and some others, were in the course of depression by a counteracting movement. -- Ansted's 'Ancient World', p. 346, etc.] -- Tr. In the silurian epoch, as well as in that in which the Cycadeae flourished in such abundance, and gigantic saurians were living, the dry land, from pole to pole, was probably less than it now is in the South Pacific and the Indian Ocean. We shall see, in a subsequent part of this work, how this preponderating quantity of water, combined with other causes, must have contributed to raise the temperature and induce a greater uniformity of climate. Here we would only remark in considering the gradual extension of the dry land, that, shortly before the 'disturbances' which at longer or shorter intervals caused the sudden destruction of so great a number of colossal vertebrata in the 'diluvial period', some parts of the present continental masses must have been completely separated from one another. There is a great similarity in South America and Australia between still living and extinct species of animals. In New Holland, fossil remains of the kangaroo have been found, and in New Zealand the semi-foxxilized bones of an enormous bird, resembling the ostrich, the dinornis of Owen,* which is nearly allied to the present spteryx, and but little so to the recently extinct dronte (dodo) of the island of Rodriguez. [[footnote] *[See 'American Journal of Science', vol. xiv., p. 187; and 'Medals of Creation', vol. ii., p. 817; 'Trans. Zoolog. Society of London', vol. ii; 'Wonders of Geology', vol. i., p. 129.] -- Tr. The form of the continental portions of the earth may, perhaps, in a great measure, owe their elevation above the surrounding level of the water to the eruption of quartzose porphyry, which overthrew with violence the first great vegetation from which the matrial of our present coal measures was formed. The portions of the earth's surface which we term plains are nothing more than the broad summits of hills and mountains whose bases rest on the bottom of the ocean. Every plain is, therefore, when considered according to its submarine relations, an 'elevated plateau', whose inequalities have been covered over by horizontal deposition of new sedimentary formations and by the accumulation of alluvium. p 288 Among the general subjects of contemplation appertaining to a work of this nature, a prominent place must be given, first, in the consideration of the 'quantity' of the land raised above the level of the sea, and next, to the individual configuration of each part, either in relation to horizontal extension (relations of form) or to vertical elevation (hypsometrical relations of mountain-chains). Our planet has two envelopes, of which one, which is general -- the atmosphere -- is composed of an elastic fluid, and the other -- the sea -- is only locally distributed, surrounding, and therefore modifying, the form of the land. These two envelopes of air and sea constitute a natural whole, on which depend the difference of climate on the earth's surface, according to the relative extension of the aqueous and solid parts, the form and aspect of the land, and the direction and elevation of mountain chains. A knowledge of the reciprocal action of air, sea, and land teaches us that great meteorological phenomena can not be comprehended when considered independently of geognostic relations. Meteorology, as well as the geography of plants and animals, has only begun to make actual progress since the mutual dependence of the phenomena to be investigated has been fully recognized. The word climate has certainly special reference to the character of the atmosphere, but this character is itself dependent on the perpetually concurrent influences of the ocean, which is universally and deeply agitated by currents having a totally opposite temperature, and of radiation from the dry land, which varies greatly in form, elevation, color, and fertility, whether we consider its bare, rocky portions, or those that are covered with arborescent or herbaceous vegetation. In the present condition of the surface of our planet, the area of the solid is to that of the fluid parts as 1:2 4/5ths (according to Rigaud, as 100:270).* [footnote] *See 'Transactions of the Cambridge Philosophical Society', vcl. vi., Part ii., 1837, p. 297. Other writers have given the ratio as 100:284. The islands form scarcely 1/22d of the continental masses, which are so unequally divided that they consist of three times more land in the northern than in the southern hemisphere; the latter being, therefore, pre-eminently oceanic. From 40 degrees south latitude to the Antarctic pole the earth is almost entirely covered with water. The fluid element predominates in like manner between the eastern shores of the Old and the western shores of the New Continent, being only interspersed with some few insular groups. The learned hydrographer Fleurieu has very justly named this p 289 vast oceanic basis, which, under the tropics, extends over 145�¼degrees of longitude, the 'Great Ocean', in contradistinction to all other seas. The southern and western hemispheres (reckoning the latter from the meridian of Teneriffe) are therefore more rich in water than in any other region of the whole earth. These are the main points involved in the consideration of the relative quantity of land and sea, a relation which exercises so important an influence on the distribution of temperature, the variations in atmospheric pressure, the direction of the winds, and the quantity of moisture contained in the air, with which the development of vegetation is so essentially connected. When we consider that nearly three fourths of the upper surface of our planet are covered with water,* we shall be less surprised at the imperfect condition of meteorology before the beginning of the present century, since it is only during the subsequent period that numerous accurate observations on the temperature of the sea at different latitudes and at different seasons have been made and numerically compared together. [footnote] *In the Middle Ages, the opinion prevailed that the sea covered one seventh of the surface of the globe, an opinion which Cardinal d'Ailly ('Imago Mundi', cap. 8) founded on the fourth apocryphal book of Esdras. Columbus, who derived a great portion of his cosmographical knowledge from the cardinal's work, was much interested in upholding this idea of the smallness of the sea, to which the misunderstood expression of "the ocean stream" contributed not a little. See Humboldt, 'Examen Critique de l'Hist. de la Geographie', t. i., p. 186. The horizontal configuration of continents in their general relations of extension was already made a subject of intellectual contemplation by the ancient Greeks. Conjectures were advanced regarding the maximum of the extension from west to east, and Dicaearchus placed it, according to the testimony of Agathemerus, in the latitude of Rhodes, in the direction of a line passing from the Pillars of Hercules to Thine. This line, which has been termed 'the parallel of the diaphragm of Dicaearchus', is laid down with an astronomical accuracy of position, which, as I have stated in another work, is well worthy of exciting surprise and admiration.* [footnote] *Agathemerus, in Hudson, 'Geographi Minores', t. ii., p. 4. See Humboldt, 'Asie Centr.', t. i., p. 120-125. Strabo, who was probably influenced by Eratosthenes, appears to have been so firmly convinced that this parallel of 36 degrees was the maximum of the extension of the then existing world, that he supposed it had some intimate connection with the form of the earth, and therefore places under this line the continent whose existence p 290 he divined in the northern hemisphere, between Theria and the coasts of Thine.* [footnote] *Strabo, lib. i., p. 65, Casaub. See Humboldt, 'Examen Crit.', t. i., p. 152. As we have already remarked, one hemisphere of the earth (whether we divide the sphere through the equator or through the meridian of Teneriffe) has a much greater expansion of elevated land than the opposite one: these two vast ocean-girt tracts of land, which we term the eastern and western, or the Old and New Continents, present, however, conjointly with the most striking contrasts of configuration and position of their axes, some similarities of form, especially with reference to the mutual relations of their opposite coasts. In the eastern continent, the predominating direction -- the position of the major axis -- inclines from east to west (or, more correctly speaking, from southwest to northeast), while in the western continent it inclines from south to north (or, rather, from south-southeast to north-northwest). Both terminate to the north at a parallel coinciding nearly with that of 70�¼degrees, while they extend to the south in pyramidal points, having submarine prolongations of islands and shoals. Such, for instance, are the Archipelago of Tierra del Fuego, the Lagullas Bank south of the Cape of Good Hope, and Van Diemen's Land, separated from New Holland by Bass's Straits. Northern Asia extends to the above parallel at Cape Taimura, which, according to Krusenstern, is 78 degrees 16', while it falls below it from the mouth of the Great Tschukotsehja River eastward to Behring's Straits, in the eastern extremity of Asia -- Cook's East Cape -- which, according to Beechey, is only 66 degrees E.* [footnote] *On the mean latitude of the Northern Asiatic shores, and the true name of Cape Taimura (Cape Siewere-Wostotschnoi), and Cape Northeast (Schalagskoi Mys), see Humboldt, 'Asie Centrale', t. iii., p. 35, 37. The northern shore of the New Continent follows with tolerable exactness the parallel of 70 degrees, since the lands to the north and south of Barrow's Strait, from Boothia Felix and Victoria Land, are merely detached islands. The pyramidal configuration of all the southern extremities of continents belongs to the 'similtudines physicae in configuratione mundi', to which Bacon already called attention in his 'Novum Organon', and with which Reinhold Foster, one of Cook's companions in his second voyage of circumnavigation, connected some ingenious considerations. On looking eastward from the meridian of Teneriffe, we perceive that the southern extremities of the three continents, viz., Africa as the extreme p 291 of the Old World, Australia, and South America, successively approach nearer toward the south pole. New Zealand, whose length extends fully 12 degrees of latitude, forms an intermediate link between Australia and South America, likewise terminating in an island, New Leinster. It is also a remarkable circumstance that the greatest extension toward the south falls in the Old Continent, under the same meridian in which the extremest projection toward the north pole is manifested. This will be perceived on comparing the Cape of Good Hope and the Lagullas Bank with the North Cape of Europe, and the peninsula of Malacca with Cape Taimura in Siberia.* [footnote] *Humboldt, 'Asie Centrale', t. i., p. 198-200. The southern point of America, and the Archipelago which we call Terra del Fuego, lie in the meridian of the northwestern part of Baffin's Bay, and of the great polar land, whose limits have not as yet been ascertained, and which, perhaps, belongs to West Greenland. We know not whether the poles of the earth are surrounded by land or by a sea of ice. Toward the north pole the parallel of 82 degrees 55' has been reached, but toward the south pole only that of 78 degrees 10'. The pyramidal terminations of the great continents are variously repeated on a smaller scale, not only in the Indian Ocean and in the peninsulas of Arabia, Hindostan, and Malacca, but also, as was remarked by Eratosthenes and Polybius, in the Mediterranean, where these writers had ingeniously compared together the forms of the Iberian, Italian, and Hellenic peninsulas.* [footnote] *Strabo, lib. ii., p. 92, 108, Cassaub. Europe, whose area is five times smaller than that of Asia, may almost be regarded as a multifariously articulated western peninsula of the more compact mass of the ontinent of Asia, the climatic relations of the former being to those of the latter as the peninsula of Brittany is to the rest of France. [footnote] *Humboldt, 'Asie Centrale', t. iii., p. 25. As early as the year 1817, in my work 'De distributione Geographica Plantarum, secundum caels temperiem et altitudinem Montium', I directed attention to the important influence of compact and of deeply-articulated continents on climate and human civilization, "Regiones vel per sinus lunatos in longa cornua porrectae, angulois littorum recessibus quasi membratim discerptae, vel spatia patentia in immensum, quorum littora nullis incisa angulis ambit sine aufractu oceanus" (p. 81, 182). On the relations of the extent of coast to the area of a continent (considered in some degree as a measure of the accessibility of the interior), see the inquiries in Berghaus, 'Annalen der Erdkunde', bd. xii., 1835, s. 490, and 'Physikal. Atlas', 1839, No. iii., s. 69. The influence exercised by the articulation and higher development of the form of a continent on the moral and intellectual condition of nations was remarked by Strabo,* who extols p 292 the varied form of our small continent as a special advantage. [footnote] *Strabo, lib. ii., p. 92, 198. Casaub. Africa* and South America, which manifest so great a resemblence in their configuration, are also the two continents that exhibit the simplest littoral outlines. [footnote] *Of Africa, Pliny says (v. 1), "Nec alia pars terrarum paudiores recipit sinus." The small Indian peninsula on this side the Ganges present, in its triangular outline, a third analogous form. In ancient Greece there prevailed an opinion of the regular configuration of the dry land. There were four gulfs or bays, among which the Persian Gulf was placed in opposition to the Hyrcanian or Caspian Sea (Arrian, vii., 16; Plut., 'in vita Alexandri', cap. 44; Dionys. Perieg., v. 48 and 630, p. 11, 38, Bernh.). These four bays and the isthmuses were, according to the optical fancies of Agesianax, supposed to be reflected in the moon (Plut., 'de Facie in Orbem Lunae', p. 921, 19). Respecting the 'terra quadrifida', or four divisions of the dry land, of which two lay north and two south of the equator, see Macrobius, 'Comm. in Somnium Scipionis', ii., 9. I have submitted this portion of the geography of the ancients, regarding which great confusion prevails, to a new and careful examination, in my 'Examen Crit. de l'Hist. de la Geogr.', t. i., p. 119, 145, 180-185, as also in 'Asie Centr.', t. ii., p. 172-178. It is only the eastern shores of Asia, which, broken as it were by the force of the currents of the ocean* ('fractas ex aequore terra'), exhibit a richly-variegated configuration, peninsulas and contiguous islands alternating from the equator to 60 degrees north latitude. [footnote] *Fleurieu, in 'Voyage de Marchand autour du Monde', t. iv., p. 38-42. Our Atlantic Ocean presents all the indications of a valley. It is as if a flow of eddying waters had been directed first toward the northeast, then toward the northwest, and back again to the northeast. The parallelism of the coasts north of 10 degrees south latitude, the projecting and receding angles, the convexity of Brazil opposite to the Gulf of Guinea, that of Africa under the same parallel, with the Gulf of the Antilles, all favor this apparently speculative view.* [footnote] *Humboldt, in the 'Journal de Physique', liii., 1799, p. 33; and 'Rel. Hist.', t. ii., p. 19; t. iii., p. 189, 198. In this Atlantic valley, as is almost every where the case in the configuration of large continental masses, coasts deeply indented, and rich in islands, are situated opposite to those possessing a different character. I long since drew attention to the geognostic importance of entering into a comparison of the western coast of Africa and of South America within the tropics. The deeply curved indentation of the African continent at Fernando Po, 4 degrees 30' north latitude, is repeated on the coast of the Pacific at 18 degrees 15' south latitude, between the Valley of Arica and the Morro de Juan Diaz, where the Peruvian coast suddenly changes the direction from wouth to north which it had previously followed, and inclines to the northwest. This change p 293 of direction extends in like manner to the chain of the Andes, which is divided into two parallel branches affecting not only the littoral portions,* but even the eastern Cordilleras. [footnote] *Humboldt, in Poggendorf's 'Annalen der Physik', bd. xl., s. 171. On the remarkable fiord formation at the southeast end of America, see Darwin's Journal ('Narrative of the Voyages of the Adventure and Beagle', vol. iii.), 1839, p. 266. The parallelism of the two mountain chains is maintained from 5 degrees north latitude. The change in the direction of the coast at Arica appears to be in consequence of the altered course of the fissure, above which the Cordillera of the Andes has been upheaved. In the latter, civilization had its earliest seat in the South American plateaux where the small Alpine lake of Titicaca bathes the feet of the colossal mountains of Sorata and Illimani. Further to the south, from Valdiva and Chilo�� (40 degrees to 42 degrees south latitude), through the Archipelago 'de los Chonos' to 'Terra del Fuego', we find repeated that singular configuration of 'fiords' (a blending of narrow and deeply-indented bays), which in the Northern hemisphere characterizes the western shores of Norway and Scotland. These are the most general considerations suggested by the study of the upper surface of our planet with reference to the form of continents, and their expansion in a horizontal direction. We have collected facts and brought forward some analogies of configuration in distant parts of the earth, but we do not venture to regard them as fixed laws of form. When the traveler on the declivity of an active volcano, as, for instance, of Vesuvius, examines the frequent partial elevations by which portions of the soil are often permanently upheaved several feet above their former level, either immediately precediing or during the continuance of an eruption, thus forming roof-like or flattened summits, he is taught how accidental conditions in the expression of the force of subterranean vapors, and in the resistance to be overcome, may modify the feeble perturbations in the equilibrium of the internal elastic forces of our planet may have inclined them more to its norther than to its southern direction, and caused the continent in the eastern part of the globe to present a broad mass, whose major axis is almost parallel with the equator, while in the western and more oceanic part the southern extremity is extremely narrow. Very little can be empirically determined regarding the causal connection of the phenomena of the formation of continents, or of the analogies and contrasts presented by their p 294 configuration. All that we know regarding this subject resolves itself into this one point, that the active cause is subterranean; that continents did not arise at once in the form they now present, but were, as we have already observed, increased by degrees by means of numerous oscillatory elevations and depressions of the soil, or were formed by the fusion of separate smaller continental masses. Their present form is, therefore, the result of two causes, which have exercised a consecutive action the one on the other; the first is the expression of subterranean force, whose direction we term accidental, owing to our inability to defint it, from its removal from within the sphere of our comprehension, while the second is derived from forces acting on the surface, among which volcanic eruptions, the elevation of mountains, and currents of sea water play the principal parts. How totally different would be the condition of the temperature of the earth, and consequently, of the state of vegetation, husbandry, and human society, if the major axis of the New Continent had the same direction as that of the Old Continent; if, for instance, the Cordilleras, instead of having a southern direction, inclined from east to west; if there had been no radiating tropical continent, like Africa, to the south of Europe; and if the Mediterranean, which was once connected with the Caspian and Red Seas, and which has become so powerful a means of furthering the intercommunication of nations, had never existed, or if it had been elevated like the plains of Lombardy and Cyrene? The changes of the reciprocal relations of height between the fluid and solid portions of the earth's surface (changes which, at the same time, determine the outlines of continents, and the greater or lesser submersion of low lands) are to be ascribed to numerous unequally working causes. The most powerful have incontestably been the force of elastic vapors inclosed in the interior of the earth, the sudden change of temperature of certain dense strata,* the unequal secular loss of p 295 heat experienced by the crust and nucleus of the earth, occasioning ridges in the solid surface, local modifications of gravitation,** and, as a consequence of these alterations, in the curvature of a portion of the liquid element. [footnote] *De la Beche, 'Sections and Views illustrative of Geological Phenomena', 1830, tab. 40; Charles Babbage, 'Observations on the Temple of Serapis at Pozzuoli, near Naples, and on certain Causes which may produce Geological Cycles of great Extent', 1834. "If a stratum of sandstone five miles in thickness should have its temperature raised about 100 degrees, its surface would rise twenty-five feet. Heated beds of clay would, on the contrary, occasion a sinking of the ground by their contraction." See Bischof, 'Wurmelehre des Innern unseres Erdkorpers', s. 303, concerning the calculations for the secular elevation of Sweden, on the supposition of a rise by so small a quantity as 7 degrees in a stratum of about 155,000 feet in thickness, and heated to a state of fusion. [footnote] **The opinion so implicitly entertained regarding the invariability of the force of gravity at any given point of the earth's surface, has in some degree been controverted by the gradual rise of large portions of the earth's surface. See Bessel, 'Ueber Maas und Gewicht', in Schumacher's 'Jahrbuch fur' 1840, s. 134. According to the views generally adopted by geognosists in the present day and which are supported by the observation of a series of well-attested facts, no less than by analogy with the most important volcanic phenomena, it would appear that the elevation of continents is actual, and not merely apparent or owing to the configuration of the upper surface of the sea. The merit of having advanced this view beloongs to Leopold von Buch, the narrative of his memorable 'Travels through Norway and Sweden' in 1806 and 1807.* [footnnote] *Th. ii. (1810), s. 389. See Hallstrom, in 'Kongl. Vetenskaps-Academiens Handlingar' (Stockh.), 1823, p. 30; Lyell in the 'Philos. Trans.' for 1835; Blom (Amtmann in Budskerud), 'Stat. Beschr. von Norwegen',1843, s. 89-116. If not before Von Buch's travels through Scandinavia, at any rate before their publication, Playfair, in 1802, in his illustrations of the Huttonian theory, �¤ 393, and according to Keilhau ('Om Landjardens Stigning in Norge', in the 'Nyt Magazine fur Naturvidenskaberne'), and the Dane Jessen, even before the time of Playfair, had expressed the opinion that it was not the sea which was sinking, but the solid land of Sweden which was rising. Their ideas, however, were wholly unknown to our great geologist, and exerted no influence on 'Norge fremstillet efter dets naturlige og borgerlige Tilstand', Kjobenh., 1763, sought to explain the causes of the changes in the relative levels of the land and sea, basing his views on the early calculations of Celsius, Kalm, and Dalin. He broaches some confused ideas regarding the possibility of an internal growth of rocks, but finally declares himself in favor of an upheaval of the land by earthquakes, "although," he observes, "no such rising was apparent immediately after the earthquake of Egersund, yet the earthquake may have opened the way for other causes producing such an effect." While the whole coast of Sweden and Finland, from Solvitzborg, on the limits of Northern Scania, past Gefle to Tornea, and from Tornea to Abo, experiences a gradual rise of four feet in a century, the southern part of Sweden is, according to Neilson, undergoing a simultaneous depression.* [footnote] *See Berzelius, 'Jahrsbericht uber die Fortschritte der Physichen Wiss.', No. 18, s. 686. The islands of Saltholm, opposite to Copenhagen, and Bjornholm, however, rise but very little -- Bjornholm scarcely one foot in a century. See Forchhammer, in 'Philos. Magazine', 3d Series, vol. ii., p. 309. The maximum of this elevating p 296 force appears to be in the north of Lapland, and to diminish gradually to the south toward Calmar and Solvitzborg. Lines marking the ancient level of the sea in pre-historic times are indicated throughout the whole of Norway,* from Cape Lindesnaes to the extremity of the North Cape, by banks of shells identical with those of the present seas, and which have lately been most accurately examined by Bravais during his long winter sojourn at Bosekop. [footnote] *Keilhan, in 'Nyt Mag. fur Naturvid.', 1832, bd. i., p. 105-254; bd. ii., p. 57; Bravais, 'Surles Lignes d'ancien Niveau de la Mer', 1843, p. 15-40. See, also, Darwin, "on the Parallel Roads of Glen-Roy and Lochaber," in 'Philos. Trans. for' 1839, p. 60. These banks lie nearly 650 feet above the present mean level of the sea, and reappear, according to Keilhau and Eugene Robert, in a north-northwest direction on the coasts of Spitzbergen, opposite the North Cape. Leopold von Buch, who was the first to draw attention to the high banks of shells at Tromsoe (latitude 69 degrees 40'), has, however, shown that the more ancient elevations on the North Sea appertain to a different class of phenomena, from the regular and gradual retrogressive elevations of the Swedish shores in the Gulf of Bothnia. This latter phenomenon, which is well attested by historical evidence, must not be confounded with the changes in the level of the soil occasioned by earthquakes, as on the shores of Chili and of Cutch, and which have recently given occasion to similar observations in other countries. It has been found that a perceptible sinking resulting from a disturbance of the strata of the upper surface sometimes occurs, corresponding with an elevation elsewhere, as, for instance, in West Greenland, according to Pingel and Graah, in Dalmatia and in Scania. Since it is highly probable that the oscillatory movements of the soil, and the rising and sinking of the upper surface, were more strongly marked in the early periods of our planet than at present, we shall be less surprised to find in the interior of continents some few portions of the earth's surface lying below the general level of existing seas. Instances of this kind occur in the soda lakes described by General Andreossy, the small bitter lakes in the narrow Isthmus of Suez, the Caspian Sea, the Sea of Tiberias, and especially the Dead Sea.* [footnote] *Humboldt, 'Asie Centrale', t. ii., p. 319-324; t. iii., p. 549-551. The depression of the Dead Sea has been successively determined by the barometrical measurements of Count Berton, by the more careful ones of Russegger, and by the trigonometrical survey of Lieutenant Symond, of the Royal Navy, who states that the difference of level between the surface of the Dead Sea and the highest houses of Jaffa is about 1605 feet. Mr. Alderson, who communicated this result to the Geographical Society of London in a letter, of the contents of which I was informed by my friend, Captain Washington, was of opinion (Nov. 28, 1841) that the Dead Sea lay about 1400 feet under the level of the Mediterranean. A more recent communication of Lieutenant Symond (Jameson's 'Edinburgh New Philosophical Journal', vol. xxxiv., 1843, p. 178) gives 1312 feet as the final result of two very accordant trigonometrical operations. The level of the water in the two last-named seas is p 297 666 and 1312 feet below the level of the Mediterranean. If we could suddenly remove the alluvial soil which covers the rocky strata in many parts of the earth's surface, we should discover how great a portion of the rocky crust of the earth was then below the present level of the sea. The periodic, although irregularly alternating rise and fall of the water of the Caspian Sea, of which I have myself observed evident traces in the northern portions of its basin, appears to prove,* as do also the observations of Darwin on the coral seas,** that without earthquakes, properly so- called, the surface of the earth is capable of the same gentle and progressive oscillations as those which must have prevailed so generally in the earliest ages, when the surface of the hardening crust of the earth was less compact than at present. [footnote] *'Sur la Mobilite du fond de la Mer Caspienne', in my 'Asie Centr.', t. ii., p. 283-294. The Imperial Academy of Sciences of St. Petersburgh in 1830, at my request, charged the learned physicist Lenz to place marks indicating the mean level of the sea, for definite epochs, in different places near Baku, in the peninsula of Abscheron. In the same manner, in an appendix to the instructions given to Captain (now Sir James C.) Ross for his Antarctic expedition, I urged the necessity of causing marks to be cut in the rocks of the southern hemisphere, as had already been done in Sweden and on the shores of the Caspian Sea. Had this measure been adopted in the early voyages of Bougainville and Cook, we should now know whether the secular relative changes in the level of the seas and land are to be considered as a general, or merely a local natural phenomenon, and whether a law of direction can be recognized in the points which have simultaneous elevation or depression. [footnote] **On the elevation and depression of the bottom of the South Sea, and the diffrent areas of alternate movements, see Darwin's 'Journal', p. 557, 561-566. The phenomena to which we would here direct attention remind us of the instability of the present order of things, and of the changes to which the outlines and configuration of continents are probably still subject at long intervals of time. That which may scarcely be perceptible in one generation, accumulates during periods of time, whose duration is revealed to us by the movement of remote heavenly bodies. The eastern coast of the Scandinavian peninsula has probably risen p 298 about 320 feet in the space of 8000 years; and in 12,000 years, if the movement be regular, parts of the bottom of the sea which lie nearest the shores, and are in the present day covered by nearly fifty fathoms of water, will come to the surface and constitute dry land. But what are such intervals of time compared to the length of the geognostic periods revealed to us in the stratified series of formations, and in the world of extinct and varying organisms! We have hitherto only considered the phenomena of elevation; but the analogies of observed facts lead us with equal justice to assume the possibility of the depression of whole tracts of land. The mean elevation of the non-mountainous parts of France amounts to less than 480 feet. It would not, therefore, require any long period of time, compared with the old geognostic periods, in which such great changes were brought about in the interior of the earth, to effect the permanent submersion of the northwestern part of Europe, and induce essential alterations in its littoral relations. The depression and elevation of the solid or fluid parts of the earth -- phenomena which are so opposite in their action that the effect of elevation in one part is to produce an apparent depression in another -- are the causes of all the changes which occur in the configuration of continents. In a work of this general character, and in an impartial exposition of the phenomena of nature, we must not overlook the 'possibility' of a diminution of the quantity of water, and a constant depression of the level of seas. Thgere can scarcely be a doubt that, at the period when the temperature of the surface of the earth was higher, when the waters were inclosed in larger and deeper fissures, and when the atmosphere possessed a totally different character from what it does at present, great changes must have occurred in the level of seas, depending upon the increase and decrease of the liquid parts of the earth's surface. But in the actual condition of our planet, there is no direct evidence of a real continuous increase or decrease of the sea, and we have no proof of any gradual change in its level at certain definite points of observation, as indicated by the mean range of the barometer. According to experiments made by Daussy and Antonio Nobile, an increase in the height of the barometer would in itself be attended by a depression in the level of the sea. But as the mean pressure of the atmosphere at the level of the sea is not the same at all latitudes, owing to meteorological causes depending upon the direction of the wind and varying degrees of moisture, the p 299 barometer alone can not afford a certain evidence of the general change of level in the ocean. The remarkable fact that some of the ports in the Mediterranean were repeatedly left dry during several hours at the beginning of this century, appears to show that currents may by changes occurring in their direction and force, occasion a 'local'' retreat of the sea, and a permanent drying of a small portion of the shore, without being followed by any actual diminution of water, or any permanent depression of the ocean. We must, however, be very cautious in applying the knowledge which we have lately arrived at, regarding these involved phenomena, since we might otherwise be led to ascribe to water as the elder element, what ought to be referred to the two other elements, earth and air. As the 'external' configuration of continents, which we have already described in their horizontal expansion, exercises, by their variously indented littoral outlines, a favorable influence on climate, trade, and the progress of civilization, so likewise does their internal articulation, or the vertical elevation of the soil (chains of mountains and elevated plateaux), give rise to equally important results. Whatever produces a polymorphic diversity of forms on the surface of our planetary habitation -- such as mountains, lakes, grassy savannas, or even deserts encircled by a band of forests -- impresses some peculiar character on the social condition of the inhabitants. Ridges of high land covered by snow impede intercourse; but a blending of low, discontinued mountain chains* and tracts of valleys, as we see so happily presented in the west and south of Europe, tends to the multiplication of meteorological processes and the products of vegetation, and, from the variety manifested in different kinds of cultivation in each district, even under the same degree of latitude, gives rise to wants that stimulate the activity of the inhabitants. [footnote] *Humboldt, 'Rel. Hist.', t. iii., p. 232-234. See also, the able remarks on the configuration of the earth, and the position of its lines of elevation in Albrechts von Roon, 'Grundzugen der Erd Volker und Staatenkunde', Abth. i., 1837, s. 158, 270, 276. Thus the awful revolutions, during which, by the action of the interior on the crust of the earth, great mountain chains have been elevated by the sudden upheaval of a portion of the oxydized exterior of our planet, have served, after the establishment of repose, and on the revival of organic life, to furnish a richer and more beautiful variety of individual forms, and in a great measure to remove from the earth that aspect of dreary p 300 uniformity which exercises so impoverishing an influence on the physical and intellectual powers of mankind. According to the grand views of Elie de Beaumont, we must ascribe a relative age to each system of mountain chains* on the supposition that their elevation must necessarily have occurred between the period of the deposition of the vertically elevated strata and that of the horizontally inclined strata running at the base of the mountains. [footnnote] *Leop. von Buch, 'Ueber die Geognostischen Systeme von Deutschland', in his 'Geogn. Briefen an Alexander von Humboldt', 1824, s. 265-271; Elie de Beaumont, 'Recherches sur les Revolutions de la Surface du Globe', 1829, p. 297-307. The ridges of the Earth's crust -- elevations of strata which are of the same geognostic age -- appear, moreover, to follow one common direction. The line of strike of the horizontal strata is not always parallel with the axis of the chain, but intersects it, so that, according to my views,* the phenomenon of elevation of the strata, which is even found to be repeated in the neighboring plains, must be more ancient than the elevation of the chain. [footnote] *Humboldt, 'Asie Centrale', t. i., p. 277-283. See, also my 'Essai sur le Gisement des Roches', 1822, p. 57, and 'Relat. Hist.', t. iii., p. 244-250. The main direction of the whole continent of Europe (from southwest to northeast) is opposite to that of the great fissures which pass from northwest to southeast, from the mouths of the Rhine and Elbe, through the Adriatic and Red Seas, and through the mountain system of Putschi-Koh in Luristan, toward the Persian Gulf and the Indian Ocean. This almost rectangular intersection of geodesic lines exercises an important influence on the commercial relations of Europe, Asia, and the northwest of Africa, and on the progress of civilization on the formerly more flourishing shores of the Mediterranean.* [footnote] *'Asie Centrale', t. i., p. 284, 286. The Adriatic Sea likewise follows a direction from S.E. to N.W. Since grand and lofty mountain chains so strongly excite our imagination by the evidence they afford of great terrestrial revolutions, and when considered as the boundaries of climates, as lines of separation for waters, or as the site of a different form of vegetation, it is the more necessary to demonstrate, by a correct numerical estimation of their volume, how small is the quantity of their elevated mass when compared with the area of the adjacent continnents. The mass of the Pyrenees, for instance, the mean elevation of whose summits, and the real quantity of whose base have been ascertained by accurate measurements, would if scattered over p 301 the surface of France, only raise its mean level about 115 feet. The mass of the eastern and western Alps would in like manner only increase the height of Europe about 21 1/2 feet above its present level. I have found by a laborious investigation,* which from its nature, can only give a maximum limit, that the center of gravity of the volume of the land raised above the present level of the sea in Europe and North America is respectively situated at an elevation of 671 and 748 feet, while it is at 1132 and 1152 feet in Asia and South America. [footnote] *'De la hauteur Moyenne des Continents', in my 'Asie Centrale', t. i., p. 82-90, 165-189. The results which I have obtained are to be regarded as the extreme value ('nombres-limites'). Laplace's estimate of the mean height of continents at 3280 feet is at least three times too high. The immortal author of the 'Mecanique Celeste' (t. v., p. 14) was led to this conclusion by hypothetical views as to the mean depth of the sea. I have shown ('Asie Centr.', t. i., p. 93) that the old Alexandrian mathematicians, on the testimony of Plutarch ('in Aemilio Paulo', cap. 15), believed this depth to depend on the height of the mountains. The height of the center of gravity of the volume of the continental masses is probably subject to slight variations in the course of many centuries. These numbers show the low level of norther regions. In Asia the vast steppes of Siberia are compensated for by the great elevations of the land (between the Himalaya, the North Thibetian chain of Kuen-lun, and the Celestial Mountains), from 28 degrees 30' to 40 degrees north latitude. We may, to a certain extent, trace in these numbers the portions of the Earth in which the Plutonic forces were most intensely manifested in the interior by the upheaval of continental masses. There are no reasons why these Plutonic forces may not, in future ages, add new mountain systems to those which Elie de Beaumont has shown to be of such different ages, and inclined in such different directions. Why should the crust of the Earth have lost its property of being elevated in the ridges? The recently-elevated mountain systems of the Alps and the Cordilleras exhibit in Mont Blanc and Monte Rosa, in Sorata, Illimani, and Chimborazo, colossal elevations which do not favor the assumption of a decrease in the intensity of the subterranean forces. All geognostic phenomena indicate the periodic alternation of activity and repose;* but the quiet we now enjoy is only apparent. [footnote] *'Zweiter Geologischer Brief von Elie de Beaumont an Alexander von Humboldt', in Poggendorf's 'Annalen', bd. xxv., s. 1-58. The tremblings which still agitate the surface under all latitudes, and in every species of rock, the elevation of Sweden, the appearance of new islands of eruption, are all conclusive as to the unquiet condition of our planet. p 302 The two envelopes of the solid surface of our planet -- the liquid and the aeriform -- exhibit, owing to the mobility of their particles, their currents, and their atmospheric relations, many analogies combined with the contrasts which arise from the great difference in the condition of their aggregation and elasticity. The depths of ocean and of air are alike unknown to us. At some few places under the tropics no bottom has been found with soundings of 276,000 (or more than four miles), while in the air, if, according to Wollaston, we may assume that it has a limit from which waves of sound may be reverberated, the phenomenon of twilight would incline us to assume a height at least nine times as great.* [footnote] *[See Wilson's Paper, 'On Wollaston's Argument from the Limitation of the Atmosphere as to the finite Divisibility of Matter.' -- 'Trans. of the Royal Society of Edinb.', vol. xvi., p. 1, 1845.] -- Tr. The a��rial ocean rests partly on the solid earth, whose mountain chains and elevated plateaux rise, as we have already seen, like green wooded shoals, and partly on the sea, whose surface forms a moving base, on which rest the lower, denser, and more saturated strata of air. Proceeding upward and downward from the common limit of the a��rial and liquid oceans, we find that the strata of air and water are subject to determinate laws of decrease of temperature. This decrease is much less rapid in the air than in the sea, which has a tendency under all latitudes to maintain its temperature in the strata of water most contiguous to the atmosphere, owing to the sinking of the heavier and more cooled particles. A large series of the most carefully conducted observations on temperature shows us that in the ordinary and mean condition of its surface, the ocean from the equator to the forty-eighth degree of north and south latitude is somewhat warmer than the adjacent strata of air.* [footnnote[ *Hamboldt, 'Relation Hist.', t. iii., chap. xxix., p. 514-530. Owing to this decrease of temperature at increasing depths, fishes and other inhabitants of the sea, the nature of whose digestive and respiratory organs fits them for living in deep water, may even, under the tropics, find the low degree of temperature and the coolness of climate characteristic of more temperate and more northern latitudes. This circumstance, which is analogous to the prevalence of a mild and even cold air on the elevated plains of the torrid zone, exercises a special influence on the migration and geographical distribution of many marine animals. Moreover, the depths at which fishes live, modify, by the increase of pressure, their cutaneous respiration, and the p 303 oxygenous and nitrogenous contents of the swimming bladders. As fresh and salt water do not attain the maximum of their density at the same degree of temperature, and as the saltness of the sea lowers the thermometrical degree corresponding to this point, we can understand how the water drawn from breat depths of the sea during the voyages of the Kotzebue and Dupetit-Thouars could have been found to have only the temperature of 37 degrees and 36.5 degrees. This icy temperatureof sea water, which is likewise manifested at the depths of tropical seas, first led to a study of the lower polar currents, which move from both poles toward the equator. Without these submarine currents, the tropical seas at those depths could only have a temperature equal to the local maximum of cold possessed by the falling particles of water at the radiating and cooled surface of the tropical sea. In the Mediterranean, the cause of the absence of such a refrigeration of the lower strata is ingeniously explained by Arago, on the assumption that the entrance of the deeper polar currents into the Straits of Gibraltar, where the water at the surface flows in from the Atlantic Ocean from west to east, is hindered by the submariine counter-currents which move from east to west, from the Mediterranean into the Atlantic. The ocean, which acts as a general equalizer and moderator of climates, exhibits a most remarkable uniformity and constancy of temperature, especially between 10 degrees north and 10 degrees south latitude,* over spaces of many thousands of square miles, at a distance from land where it is not penetrated by currents of cold and heated water. [footnote] *See the series of observations made by me in the South Sea, from 8 degrees 5' to 13 degrees 16' N. lat., in my 'Asie Centrale', t. iii., p. 234. It has therefore, been justly observed, that an exact and long-continued investigation of these thermic relations of the tropical seas might most easily afford a solution to the great and much-contested problem of the permanence of climates and terrestrial temperatures.* [footnote] *We might (by means of the temperature of the ocean under the tropics) enter into the consideration of a question which has hitherto remained unanswered, namely, that of the constancy of terrestrial temperatures, without taking into account the very circumscribed local influences arising from the diminution of wood in the plains and on mountains, and the drying up of lakes and marshes. Each age might easily transmit to the succeeding one some few data, which would perhaps furnish the most simple, exact, and direct means of deciding whether the sun, which is almost the sole and exclusive source of the heat of our planet, changes its physical constitution and splendor, like the greater number of the stars, or whether, on the contrary, that luminary has attained to a permanent condition." -- Arago, in the 'Comptes Rendus des Seances de l'Acad. des Sciences', t. ii., p. 321, 327. Great changes in the luminous disk of the sun would, p 304 if they were of long duration, be reflected with more certainty in the mean temperature of the sea than in that of the solid land. The zones at which occur the maxima of the oceanic temperature and of the density (the saline contents) of its waters, do not correspond with the equator. The two maxima are separated from one another, and the waters of the highest temperature appear to form two nearly parallel lines north and south of the geographical equator. Lenz, in his voyage of circumnavigation, found in the Pacific the maxima of density in 22 degrees north and 17 degrees south latitude, while its minimum was situated a few degrees to the south of the equator. In the region of calms the solar heat can exercise but little influence on evaporation, because the stratum of air impregnated with saline aqueous vapor, which rests on the surface of the sea, remains still and unchanged. The surface of all connected seas must be considered as having a general perfectly equal level with respect to their mean elevation. Local causes (probably prevailing winds and currents) may, however, produce permanent, although trifling changes in the level of some deeply indented bays, as for instance, the Red Sea. The highest level of the water at the Isthmus of Suez is at different hours of the day from 24 to 30 feet above that of the Mediterranean. The form of the Straits of Bab-el-Mandeb, through which the waters appear to find an easier ingress than egress, seems to contribute to this remarkable phenomenon, which was known to the ancients.* [[footnote] *Humboldt, 'Asie Centrale', t. ii., p. 321, 327. The admirable geodetic operations of Coraboeuf and Delcrois show that no perceptible difference of level exists between the upper surfaces of the Atlantic and the Mediterranean, along the chain of the Pyrenees, or between the coasts of northern Holland and Marseilles.* [footnote] *See the numerical results in p. 328-333 of the volume just named. From the geodesical levelings which, at my request, my friend General Bolivar caused to be taken by Lloyd and Falmare, in the years 1828 and 1829, it was ascertained that the level of the Pacific is at the utmost 3 1/2 feet higher than that of the Caribbean Sea; and even that at different hours of the day each of the seas is in turn the higher, according to their respective hours of flood and ebb. If we reflect that in a distance of 64 miles, comprising 933 stations of observation, an error of three feet would be very apt to occur, we may say that in these new operations we have further confirmation of the equilibrium of the waters which communicate round Cape Horn. (Arago, in the 'Annuaire du Bureau des Longitudes pour' 1831, p. 319.) I had inferred from barometrical observations instituted in 1799 and 1804, that if there were any difference between the level of the Pacific and the Atlantic (Carribean Sea), it could not exceed three meters (nine feet three inches). See my 'Relat. Hist.', t. iii., p. 555-557, and 'Annales de Chimie', t. i., p. 55-64. The measurements, which appear to establish an excess of height for the waters of the Gulf of Mexico, and for those of the northern part of the Adriatic Sea, obtained by combining the trigonometrical operations of Delcrois and Choppin with those of the Swiss and Austrian engineers, are open to many doubts. Notwithstanding the form of the Adriatic, it is improbable that the level of its waters in its northern portion should be 28 feet higher than that of the Mediterranean at Marseilles, and 25 feet higher than the level of the Atlantic Ocean. See my 'Asie Centrale', t. ii., p. 332. p 305 Disturbances of equilibrium and consequent movements of the waters are partly irregular and transitory, dependent upon winds, and producing waves which sometimes, at a distance from the shore and during a storm, rise to a height of more than 35 feet; partly regular and periodic, occasioned by the position and attraction of the sun and moon, as the ebb and flow of the tides; and partly permanent, although less intense, occurring as oceanic currents. The phenomena of tides, which prevail in all seas (with the exception of the smaller ones that are completely closed in, and where the ebbing and flowing waves are scarcely or not at all perceptible), have been perfectly explained by the Newtonian doctrine, and thus brought "within the domain of necessary facts." Each of these periodically-recurring oscillations of the waters of the sea has a duration of somewhat more than half a day. Although in the open sea they scarcely attain an elevation of a few feet, they often rise considerably higher where the waves are opposed by the configuration of the shores, as for instance, at St. Malo and in Nova Scotia, where they reach the respective elevation of 50 feet, and of 65 to 70 feet. "It has been shown by the analysis of the great geometrician Laplace, that, supposing the depth to be wholly inconsiderable when compared with the radius of the earth, the stability of the equilibrium of the sea requires that the density of its fluid should be less than that of the earth; and, as we have already seen, the earth's density is in fact five times greater than that of water. The elevated parts of the land can not therefore be overflowed, nor can the remains of marine animals found on the summits of mountains have been conveyed to those localities by any previous high tides.* [footnote] *Bessel, 'Ueber Fluth und Ebbe', in Schumacher's 'ahrbuch', 1838, s. 225. It is no slight This material taken from pages 305-362 COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 305 [balance of p 305 is in file "09 Humboldt"] It is no slight p 306 evidence of the importance of analysis, which is too often regarded with contempt among the unscientific, that Laplace's perfect theory of tides has enabled us, in our astronomical ephemerides, to predict the height of spring-tides at the periods of new and full moon, and thus put the inhabitants of the sea-shore on their guard against the increased danger attending these lunar revolutions. Oceanic currents, which exercise so important an influence on the intercourse of nations and on the climatic relations of adjacent coasts, depend conjointly upon various causes, differing alike in nature and importance. Among these we may reckon the periods at which tides occur in their progress round the earth; the duration and intensity of prevailing winds; the modifications of density and specific gravity which the particles of water undergo in consequence of differences in the temperature and in the relative quantity of saline contents at different latitudes and depths;* and, lastly, the horary variations of the atmospheric pressure, successively propagated from east to west, and occurring with such regularity in the tropics. [footnote] *The relative density of the particles of water depends simultaneously on the temperature and on the amount of the saline contents -- a circumstance that is not sufficiently borne in mind in considering the cause of currents. The submarine current, which brings the cold polar water to the equatorial regions, would follow an exactly opposite course, that is to say, from the equator toward the poles, if the difference in saline contents were alone concerned. In this view, the geographical distribution of temperature and of density in the water of the ocean, under the different zones of latitude and longitude, is of great importance. The numerous observations of Lenz (Poggendorf's 'Annalen', bd. xx., 1830, s. 129), and those of Captain Beechey, collected in his 'Voyage to the Pacific', vol. ii., p. 727, deserve particular attention. See Humboldt, 'Relat. Hist.', t. i., p. 74, and 'Asie Centrale', t. iii., p. 346. These currents present a remarkable spectacle; like rivers of uniform breadth, they cross the sea in different directions, while the adjacent strata of water, which remain undisturbed, form, as it were, the banks of these moving streams. This diffrence between the moving waters and those at rest is most strikingly manifested where long lines of sea-weed, borne onward by the current, enable us to estimate its velocity. In the lower strata of the atmosphere, we may sometimes, during a storm, observe similar phenomena in the limited aerial current, which is indicated by a narrow line of trees, which are often found to be overthrown in the midst of a dense wood. The general movement of the sea from east to west between p 307 the tropics (termed the equatorial or rotation currnt) is considered to be owing to the propagation of tides and to the trade winds. Its direction is changed by the resistance it experiences from the prominent eastern shores of continents. The results recently obtained by Daussy regarding the velocity of this current, estimated from observations made on the distances traversed by bottles that had purposely been thrown into the sea, agree within one eighteenth with the velocity of motion (10 French nautical miles, 952 toises each, in 24 hours) which I had found from a comparison with earlier experiments.* [footnote] *Humboldt, 'Relat. Hist.', t. i., p. 67; 'Nouvelles Annales des Voyages', 1839, p. 255. Christopher Columbus, during his third voyage, when he was seeking to enter the tropics in the meridian of Teneriffe, wrote in his journal as follows:* "I regard it as proved that the waters of the sea move from east to west, as do the heavens ('las aguas van con los cielos'), that is to say, like the apparent motion of the sun, moon, and stars." [footnote] *Humboldt, 'Examen Crit. de l'Hist. de la Geogr.', t. iii., p. 100. Columbus adds shortly after (Navarrete, 'Coleccion de los Viages y Descubrimientos de los Espanoles', t. i., p. 260), that the movement is strongest in the Caribbean Sea. In fact, Rennell terms this region, "not a current, but a sea in motion". ('Investigation of Currents', p. 23). 66-74. The narrow currents, or true oceanic rivers which traverse the sea, bring warm water into higher and cold water into lower latitudes. To the first class belongs the celebrated Gulf Stream,* which was known to Anghiera, and more especially to Sir Humphrey Gilbert in the sixteenth century. [footnote] *Humboldt, 'Examen Critique', t. ii., p. 250; 'Relat. Hist.', t. i., p. 66-74. [footnote] *Petrus Martyr de Anghiera, 'De Rebus Oceanicis et Orbe Novo', Bas., 1523, Dec. iii., lib. vi., p. 57. See Humboldt, 'Examen Critique', t. ii., p. 254-257, and t. iii., p. 108. Its first impulse and origin is to be sought to the south of the Cape of Good Hope; after a long circuit it pours itself from the Caribbean Sea and the Mexican Gulf through the Straits of the Bahamas, and, following a course from south-southwest to north-northeast, continues to recede from the shores of the United States, until, further deflected to the eastward by the Banks of Newfoundland, it approaches the European coasts, frequently throwing a quantity of tropical seeds ('Mimosa scandens, Guilandina bonduc, Dolichos urens') on the shores of Ireland, the Hebrides, and Norway. The northeastern prolongation tends to mitigate the cold of the ocean, and to ameliorate the climate on the most northern extremity of Scandinavia. At the point where the Gulf Stream p 308 is deflected from the Banks of Newfoundland toward the east, it sends off branches to the south near the Azores.* [footnote] *Humboldt, 'Examen Crit.', t. iii., p. 64-109 This is the situation of the Sargasso Sea, or that great bank of weeds which so vividly occupied the imagination of Christopher Columbus, and which Oviedo calls the sea-weed meadows ('Praderias de yerva'). A host of small marine animals inhabits these tently-moved and evergreen masses of 'Fucus natans', one of the most generally distributed of the social plants of the sea. The counterpart of this current (which in the Atlantic Ocean, between Africa, America, and Europe, belongs almost exclusively to the northern hemisphere) is to be found in the South Pacific, where a current prevails, the effect of whose low temperature on the climate of the adjacent shores I had an opportunity of observing in the autumn of 1802. It brings the cold waters of the high southern latitudes to the coast of Chili, follows the shores of this continent and of Peru, first from south to north, and is then deflected from the Bay of Arica onward from south-southeast to north-northwest. At certain seasons of the year the temperature of this cold oceanic current is, in the tropics, only 60 degrees, while the undisturbed adjacent water exhibits a temperature of 81.5 degrees and 83.7 degrees. On that part of the shore of South America south of Payta, which inclines furthest westward, the current is suddenly deflected in the same direction from the shore, turning so sharply to the west that a ship sailing northward passes suddenly from cold into warm water. It is not known to what depth cold and warm oceanic currents propagate their motion; but the deflection experienced by the South African current, from the Lagullas Bank, which is fully from 70 to 80 fathoms deep, would seem to imply the existence of a far-extending propagation. Sand banks and shoals lying beyond the line of these currents may, as was first discovered by the admirable Benjamin Franklin, be recognized by the coldness of the water over them. This depression of the temperature appears to me to depend upon the fact that, by the propagation of the motion of the sea, deep waters rise to the margin of the banks and mix with the upper strata. My lamented friend, Sir Humphrey Davy, ascribed this phenomenon (the knowledge of which is often of great practical utility in securing the safety of the navigator) to the descent of the particles of water that had been cooled by nocturnal radiation p 309 and which remain nearer to the surface, owing to the hinderance placed in the way of their greater descent by the intervention of sand-banks. By his observations Franklin may be said to have converted the thermometer into a sounding line. Mists are frequently found to rest over these depths, owing to the condensation of the vapor of the atmosphere by the cooled waters. I have seen such mists in the south of Jamaica, and also in the Pacific, defining with sharpness and clearness the form of the shoals below them, appearing to the eye as the aerial reflection of the bottom of the sea. A still more striking effect of the cooling produced by shoals is manifested in the higher strata of air, in a somewhat analogous manner to that observed in the case of flat coral reefs, or sand islands. In the open sea, far from the land, and when the air is calm, clouds are often observed to rest over the spots where shoals are situated, and their bearing may then be taken by the compass in the same manner as that of a high mountain or isolated peak. Although the surface of the ocean is less rich in living forms than that of continents, it is not improbable that, on a further investigation of its depths, its interior may be found to possess a greater richness of organic life than any other portion of our planet. Charles Darwin, in the agreeable narrative of his extensive voyages, justly remarks that our forests do not conceal so many animals as the low woody regions of the ocean, where the sea-weed rooted to the bottom of the shoals, and the severed branches of fuci, loosened by the force of the waves and currents, and swimming free, unfold their delicate foliage, upborne by air-cells.* [footnote] *[See 'Structure and Distribution of Coral Reefs', by Charles Darwin, London, 1842. Also, 'Narrative of the Surveying Voyage of H.M.S. "Fly" in the Eastern Archipelago, during the Years ' 1842-1846, by J. B. Jukes, Naturalist to the expedition, 1847.] -- Tr. The application of the microscope increases, in the most striking manner, our impression of the rich luxuriance of animal life in the ocean, and reveals to the astonished senses a consciousness of the universality of life. In the oceanic depths, far exceeding the height of our loftiest mountain chains, every stratum of water is animated with polygastric sea-worms, Cyclidiae and Ophrydinae. The waters swarm with countless hosts of small luminiferous animalcules, Mammaria (of the order of Acalephae), Crustacea, Peridinea, and circling Nereides, which when attracted to the surface by peculiar meteorological conditions, convert every wave into a foaming band of flashing light. p 310 The abundance of those marine animalcules, and the animal matter yielded by their rapid decomposition are so vast that the sea water itself becomes a nutrient fluid to many of the larger animals. However much this richness in animated forms, and this multitude of the most various and highly-developed microscopic organisms may agreeably excite the fancy, the imagination is even more seriously, and, I might say, more solemnly moved by the impression of boundlessness and immeasureability, which are presented to the mind by every sea voyage. All who possess an ordinary degree of mental activity, and delight to create to themselves an inner world of thought, must be penetrated with the sublime image of the infinite, when gazing around them on the vast and boundless sea, when involuntarily the glance is attracted to the distant horizon, where air and water blend together, and the stars continually rise and set before the eyes of the mariner. This contemplation of the eternal play of the elements is clouded, like every human joy, by a touch of sadness and of longing. A peculiar predilection for the sea, and a grateful remenbrance of the impression which it has excited in my mind, when I have seen it in the tropics in the calm of nocturnal rest, or in the fury of the tempest, have alone induced me to speak of the individual enjoyment afforded by its aspect before I entered upon the consideration of the favorable influence which the proximity of the ocean has incontrovertibly exercised on the cultivation of the intellect and character of many nations, by the multiplication of those bands which ought to encircle the whole of humanity, by affording additional means of arriving at a knowledge of the configuration of the earth, and furthering the advancement of astronomy, and of all other mathematical and physical sciences. A portion of this influence was at first limited to the Mediterranean and the shores of southwestern Africa, but from the sixteenth century it has widely spread, extending to nations who live at a distance from the sea, in the interior of continents. Since Columbus was sent to "unchain the ocean"* (as the unknown voice whispered to him in a dream when he lay on a sick-bed near p 311 the River Belem), man has ever boldly ventured onward toward the discovery of unknown regions. [footnote] *The voice addressed him in these words, "Maravillosamente Dios hizo sonar tu nombre en la tierra; de los atamientos de la mar Oceana, que estaban cerrados con cadenas tan fuertes, te di�� las llaves" -- "God will cause thy name to be wonderfully resounded through the earth, and give thee the keys of the gates of the ocean, which are closed with strong chains." The dream of Columbus is related in the letter to the Catholic monarchs of July the 7th, 1503. (Humboldt, 'Examen Critique', t. iii., p. 234.) The second external and general covering of our planet, the aerial ocean, in the lower strata, and on the shoals of which we live, presents six classes of natural phenomena, which manifest the most intimate connection with one another. They are dependent on the chemical composition of the atmosphere, the variations in its transparency, polarization, and color, its density or pressure, its temperature and humidity, and its electricity. The air contains in oxygen the first element of physical animal life, and besides this benefit, it possesses another, which may be said to be of a nearly equally high character, namely, that of conveying sound; a faculty by which it likewise becomes the conveying sound; a faculty by which it likewise becomes the conveyer of speech and the means of communicating thought, and consequently of maintaining social intercourse. If the Earth were deprived of an atmosphere, as we suppose our moon to be, it would present itself to our imagination as a soundless desert. The relative quantities of the substances composing the strata of air accessible to us have, since the beginning of the nineteenth century, become the object of investigations, in which Gay-Lussac and myself have taken an active part; it is however, only very recently that the admirable labors of Dumas and Boussingault have, by new and more accurate methods, brought the chemical analysis of the atmosphere to a high degree of perfection. According to this analysis, a volume of dry air contains 20.8 of oxygen, and 79.2 of nitrogen, besides from two to five thousandth parts of carbonic acid gas, a still smaller quantity of carbureted hydrogen gas,* and, according to the important experiments of Saussure and Liebig, traces of ammoniacal vapors,** from which plants derive their nitrogenous contents. [footnote] *Boussingault, 'Recherches sur la Composition de l'Atmosphere', in the 'Annales de Chimie et de Physique', t. lvii., 1834, p. 171-173; and lxxi. 1839, p. 116. According to Boussingault and Lewy, the proportion of carbonic acid in the atmosphere at Audilly, at a distance, therefore, from the exhalations of a city, varied only between 0.00028 and 0.00031 in volume. [footnote] **Liebig, in his important work, entitles 'Die Organische Chemie in ihrer Anwendung auf Agricultur und Physiologie', 1840, s. 62-72. On the influence of atmospheric electricity in the production of nitrate of ammonia, which, coming into contact with carbonate of lime, is changed into carbonate of ammonia, see Boussingault's 'Economie Rurale consideree dans ses Rapports avec la Chimie et la Meteorologie', 1844, t. ii., p. 247, 267, and t. i., p. 84. Some observations of Lewy render it probable that the quantity of oxygen varies perceptibly p 312 but slightly, over the sea and in the interior of continents, according to local conditions or to the seasons of the year. We may easily conceive that changes in the oxygen held in solution in the sea, produced by microscopic animal organisms, may be attended by alterations in the strata of air in immediate contact with it.* [footnote] *Lewy, in the 'Comptes Rendus de l'Acad. des Sciences', t. xvii., Part ii., p. 235-248. The air which Martins collected at Faulhorn at an elevation of 8767 feet, contained as much oxygen as the air at Paris.* [footnote] *Dumas, in the 'Annales de Chimie, 3e Serie', t. iii., 1841, p. 257. The admixture of carbonate of ammonia in the atmosphere may probably be considered as older than the existence of organic beings on the surface of the earth. The sources from which carbonic acid* may be yielded to the atmosphere are most numerous. [footnote] *In this enumeration, the exhalation of carbonic acid by plants during the night, while they inhale oxygen, is not taken into account, because the increase of carbonic acid from this source is amply counter-balanced by the respiratory process of plants during the day. See Boussingault's 'Econ. Rurale', t. i., p. 53-68, and Liebig's 'Organische Chemie', s. 16, 21. In the first place we would mention the respiration of animals, who receive the carbon which they inhale from vegetable food, while vegetables receive it from the atmosphere; in the next place, carbon is supplied from the interior of the earth in the vicinity of exhausted volcanoes and thermal springs, from the decomposition of a small quantity of carbureted hydrogen gas in the atmosphere, and from the electric discharges of clouds, which are of such frequent occurrence within the tropics. Besides these substances, which we have considered as appertaining to the atmosphere at all heights that are accessible to us, there are others accidentally mixed with them, especially near the ground, which sometimes, in the form of miasmatic and gaseous contagia, exercise a noxious influence on animal organization. Their chemical nature has not yet been ascertained by direct analysis; but, from the consideration of the processes of decay which are perpetually going on in the animal and vegetable substances with which the surface of our planet is covered, and judging from analogies deduced from the comain of pathology, we are led to infer the existence of such noxious local admixtures. Ammoniacal and other nitrogenous vapors, sulphureted hydrogen gas, and compounds analogous to the polybasic ternary and quaternary compounds analogous to the polybasic ternary and quaternary combinations of the vegetable kingdom, may produce miasmata,* p 313 which, under various forms, may generate ague and typhus fever (not by any means exclusively on wet, marshy ground, or on coasts covered by putrescent mollusca, and low bushes of 'Rhizophora mangle' and Avicennia). [footnote] *Gay-Lussac, in 'Annales de Chimie', t. liii., p. 120; Payen, Mem. sur la Composition Chimique des Vegetaux, p. 36, 42; Liebig, 'Org. Chemie', s. 229-345; Boussingault, 'Econ. Rurale', t. i., p. 142-153. Fogs which have a peculiar smell at some seasons of the year, remind us of these accidental admixtures in the lower strata of the atmosphere. Winds and currents of air caused by the heating of the ground even carry up to a considerable elevation solid substances reduced to a fine powder. The dust which darkens the air for an extended area, and falls on the Cape Verd Islands, to which Darwin has drawn attention, contains, according to Ehrenberg's discovery, a host of silicious-shelled infusoria. As principal features of a general descriptive picture of the atmosphere, we may enumerate: 1. 'Variations of atmospheric pressure': to which belong the horary oscillations, occurring with such regularity in the tropics, where they produce a kind of ebb and flow in the atmosphere, which can not be ascribed to the attraction of the moon,* and which differs so considerably according to geographical latitude, the seasons of the year, and the elevation above the level of the sea. [footnote] *Bouvard, by the application of the formulae, in 1827, which Laplace had deposited with the Board of Longitude shortly before his death, found that the portion of the horary oscillations of the pressure of the atmosphere, which depends on the attraction of the moon, can not raise the mercury in the barometer at Paris more than the 0.018 of a millimeter, while eleven years' observations at the same place show the mean barometric oscillation, from 9 A.M. to 3 P.M., to be 0.756 millim., and from 3 P.M. to 9 P.M., 0.373 millim. See 'Memoires de l'Acad. des Sciences', t. vii., 1827, p. 267. 2. 'Climatic distribution of heat', which depends on the relative position of the transparent and opaque masses (the fluid and solid parts of the surface of the earth), and on the hypsometrical configuration of continents; relations which determine the geographical position and curvature of the isothermal lines (or curves of equal mean annual temperature) both in a horizontal and vertical direction, or on a uniform plane, or in different superposed strata of air. 3. 'The distribution of the humidity of the atmosphere'. The quantitative relations of the humitidy depend on the differences in the solid and oceanic surfaces; on the distance from the equator and the level of the sea; on the form in which the p 314 aqueous vapor is precipitated, and on the connection existing between these deposits and the changes of temperature, and the direction and succession of winds. 4. 'The electric condition of the atmosphere'. the primary cause of this condition, when the heavens are serene, is still much contested. Under this head we must consider the relation of ascending vapors to the electric charge and the form of the clouds, according to the different periods of the day and year; the difference between the cold and warm zones of the earth, or low and high lands; the frequency or rarity of thunder storms, their periodicity and formation in summer and winter; the causal connection of electricity, with the infrequent occurrence of hail in the night, and with the phenomena of water and sand spouts, so ably investigated by Peltier. The horary oscillations of the barometer, which in the tropics present two maxima (viz., at 9 or 9 1/4 P.M., and 4 A.M., occurring, therefore, in almost the hottest and coldest hours), have long been the object of my most careful diurnal and nocturnal observations.* [footnote] *'Observations faites pour constater la Marche des Variations Horaires du Barometre sous les Tropiques', in my 'Relation Historique du Voyage aux Regions Equinoxiales', t. iii., p. 270-313. Their regularity is so great, that, in the daytime especially, the hour may be ascertained from the height of the mercurial column without an error, on the average, of more than fifteen or seventeen minutes. In the torrid zones of the New Continent, on the coasts as well as at elevations of nearly 13,000 feet above the level of the sea, where the mean temperature falls to 44.6 degrees, I have found the regularity of the ebb and flow of the aerial ocean undisturbed by storms, hurricanes, rain, and earthquakes. The amount of the daily oscillations diminishes from 1.32 to 0.18 French lines from the equator to 70 degrees north latitude, where Bravais made very accurate observations at Bosekop.* [footnote] *Bravais, in Daemtz and Martins, 'Meteorologie', p. 263. At Halle (51 degrees 29' N. lat.), the oscillation still amounts to 0.28 lines. It would seem that a great many observations will be required in order to obtain results that can be trusted in regard to the hours of the maximum and minimum on mountains in the temperate zone. See the observations of horary variations, collected on the Faulhorn in 1832, 1841, and 1842 (Martins, 'Meteorologie', p. 254.) The supposition that, much nearer the pole, the height of the barometer is really less at 10 A.M. than at 4 P.M., and consequently, that the maximum and minimum influences of these hours p 315 are inverted, is not confirmed by Parry's observations at Port Bowen (73 degrees 14'). The mean height of the barometer is somewhat less under the equator and in the tropics, owing to the effect of the rising current,* than in the temperate zones, and it appears to attain its maximum in Western Europe between the parallels of 40 degrees and 45 degrees. [footnote] *Humboldt, 'Essai sur la Geographie des Plantes', 1807, p. 90; and in 'Rel. Hist.', t. iii., p. 313; and on the diminuation of atmospheric pressure in the tropical portions of the Atlantic, in Poggend., 'Annalen der Physik', bd. xxxvii., s. 245-258, and s. 463-486. If with K��mtz we connect together by 'isobarometric' lines those places which present the same mean difference between the monthly extremes of the barometer, we shall have curves whose geographical position and inflections yield important conclusions regarding the influence exercised by the form of the land and the distribution of seas on the oscillations of the atmosphere. Hindostan with its high mountain chains and triangular peninsulas, and the eastern coasts of the New Continent, where the warm Gulf Stream turns to the east at the Newfoundland Banks, exhibit greater isobarometric oscillations than do the group of the Antilles and Western Europe. The prevailing winds exercise a principal influence on the diminution of the pressure of the atmosphere, and this, as we have already mentioned, is accompanied, according to Daussey, by an elevation of the mean level of the sea.�¥ [footnote] *Dausay, in the 'Comptes Rendus', t. iii., p. 136. As the most important fluctuations of the pressure of the atmosphere, whether occurring with horary or annual regularity, or accidentally, and then often attended by violence and danger,* are like all the other phenomena of the weather, mainly owing to the heating force of the sun's rays, it has long been suggested (partly according to the idea of Lambert) that the direction of the wind should be compared with the height of the barometer, alternations of temperature, and the increase and decrease of humidity. [footnote] *Dove, 'Ueber die Sturme', in Poggend., 'Annalen', bd. lii., s. 1. Tables of atmospheric pressure during different winds, termed 'barometric windroses', afford a deeper insight into the connection of meteorological phenomena.* [footnote] *Leopold von Buch, 'Barometrische Windrose', in 'Abhandl. der Akad. der Wiss. zu Berlin aus den Jahren', 1818-1819, s. 187. Dove has, with admirable sagacity, recognized, in the "law of rotation" in both hemispheres, which he himself established, the cause of many important processes in the aerial ocean.* [footnote] *See Dove, 'Meteorologishe Untersuchungen', 1837, s. 99-313; and the excellent observations of K��mtz on the descent of the west wind of the upper current in high latitudes, and the general phenomena of the direction of the wind, in his 'Vorlesungen uber �µeterologie', 1840, s. 58-66, 196-200, 327-336, 353-364; and in Schumacher's 'Jahrbuch fur' 1838, s. 291-302. A very satisfactory and vivid representation of meteorological phenomena is given by Dove, in his small work entitled 'Witterungsverh��ltnisse von Berlin', 1842. On the knowledge of the earlier navigators of the rotation of the wind, see Churruca, 'Viage at Magellanes', 1793, p. 15; and on a remarkable expression of Columbus, which his son Don Fernando Colon has presented to us in his 'Vida del Almirante', cap. 55, see Humboldt, 'Examen Critique de l'Hist. de Geographie', t. iv., p. 253. The difference of temperature between the p 315 equatorial and polar regions engenders two opposite currents in the upper strata of the atmosphere and on the Earth's surface. Owing to the difference between the rotatory velocity at the poles and at the equator, the polar current is deflected eastward, and the equatorial current westward. The great phenomena of atmospheric pressure, the warming and cooling of the strata of air, the aqueous deposits, and even, as Dove has correctly represented, the formation and appearance of clouds, alike depend on the opposition of these two currents, on the place where the upper one descends, and on the displacement of the one by the other. Thus the figures of the clouds, which form an animated part of the charms of a landscape, announce the processes at work in the upper regions of the atmosphere, and, when the air is calm, the clouds will often present, on a bright summer sky, the "projected image" of the radiating soil below. Where this influence of radiation is modified by the relative position of large continental and oceanic surfaces, as between the eastern shore of Africa and the western part of the Indian peninsula, its effects are manifested in the Indian monsoons, which change with the periodic variations in the sun's declination,* and which were known to the Greek navigators under the name of 'Hippalos'. [footnote] *'Monsun' (Malayan 'musim', the 'hippalos' of the Greeks) is derived from the Arabic word 'mausim', a set time or season of the year, the time of the assemblage of pilgrims at Mecca. The word has been applied to the seasons at which certain winds prevail, which are, besides, named from places lying in the direction from whence they come; thus, for instance, there is the 'mausim' of Aden, of Guzerat, Malabar, etc. (Lassen, 'Indische Alterthumskunde', bd. i., 1843, s. 211). On the contrasts between the solid or fluid substrata of the atmosphere, see Dove, in 'Der Abhandl. der Akad. der Wiss. zu Berlin aus dem Jahr' 1842, s. 239. In the knowledge of the monsoons, which undoubtedly dates back thousands of years among the inhabitants of Hindostan and China, of the eastern parts of the Arabian Gulf and of the western shores of the Malayan p 317 Sea, and in the still more ancient and more general acquaintance with land and sea winds, lies concealed, as it were, the germ of that meteorological sciences which is now making such rapid progress. The long chain of 'magnetic stations' extending from Moscow to Pekin, across the whole of Northern Asia, will prove of immense importance in determining the 'law of the winds', since these stations have also for their object the investigation of general meteorological relations. The comparison of observations made at places lying so many hundred miles apart, will decide, for instance, whether the same east wind blows from the elevated desert of Gobi to the interior of Russia, or whether the direction of the Aerial current first began in the middle of the series of the stations, by the descent of the air from the higher regions. By means of such observations, we may learn, in the strictest sense, 'whence' the wind cometh. If we only take the results on which we may depend from those places in which the observations on the direction of the winds have been continued more than twenty years, we shall find (from the most recent and careful calculations of Wilhelm Mahlmann) that in the middle latitudes of the temperate zone, in both continents, the prevailing aerial current has a west-southwest direction. Our insight into the 'distribution of heat' in the atmosphere has been rendered more clear since the attempt has been made to connect together by lines those places where the mean annual summer and winter temperatures have been ascertain by correct observations. The system of 'isothermal, osotheral' and 'isochimenal' lines, which I first brought into use in 1817, may, perhaps, if it be gradually perfected by the united efforts of investigators, serve as one of the main foundations of 'comparative climatology'. Terrestrial magnetism did not acquire a right to be regarded as a science until partial results were graphically connected in a system of lines of 'equal declination, equal inclinatiion', and 'equal intensity'. The term 'climate', taken in its most general sense, indicated all the changes in the atmosphere which sensibly affect our organs, as temperature, humidity, variations in the barometrical pressure, the calm state of the air or the action of opposite winds, the amount of electric tension, the purity of the atmosphere or its admixture with more or less noxious gaseous exhalations, and, finally, the degree of ordinary transparency and clearness of the sky, which is not only important with respect to the increased radiation from the Earth, the organic development of plants, and the ripening of fruits, but p 318 also with reference to its influence on the feelings and mental condition of men. If the surface of the Earth consisted of one and the same homogeneous fluid mass, or of strata of rock having the same color, density, smoothness, and power of absorbing heat from the solar rays, and of radiating it in a similar manner through the atmosphere, the isothermal, isotheral, and isochimenal lines would all be parallel to the equator. In this hypothetical condition of the Earth's surface, the power of absorbing and emitting light and heat would every where be the same under the same latitudes. The mathematical consideration of climate, which does not exclude the supposition of the existence of currents of heat in the interior, or in the external crust of the earth, nor of the propagation of heat by atmospheric currents, proceeds from this mean, and, as it were, primitive condition. Whatever alters the capacity for absorption and radiation, at places lying under the same parallel of latitude, gives rise to inflections in the isothermal lines. The nature of these inflections, the angles at which the isothermal, isotheral, or isochimenal lines intersect the parallels of latitude, their convexity or concavity with respect to the pole of the same hemisphere, are dependent on causes which more or less modify the temperature under different degrees of longitude. The progress of 'Climatology' has been remarkably favored by the extension of European civilization to two opposite coasts, by its transmission from our western shores to a continent which is bounded on the east by the Atlantic Ocean. When, after the ephemeral colonization from Iceland and Greenland, the British laid the foundation of the first permanent settlements on the shores of the United States of America, the emigrants (whose numbers were rapidly increased in consequence either of religious persecution, fanaticism, or love of freedom, and who soon spread over the vast extent of territory lying between the Carolinas, Virginia, and the St. Lawrence) were astonished to find themselves exposed to an intensity of winter cold far exceeding that which prevailed in Italy, France, and Scotland, situated in corresponding parallels of latitude. But, however much a consideration of these climatic relations may have awakened attention, it was not attended by any practical results until it could be based on the numerical data of 'mean annual temperature'. If, between 58 degrees and 30 degrees north latitude, we compair Nain, on the coast of Labrador, with Gottenburg; Halifax with Bordeaus; New p 319 York with Naples; St. Augustine, in Florida, with Cairo, we find that, under the same degrees of latitude, the differences of the mean annual temperature between Eastern America and Western Europe, proceeding from north to south, are successively 20.7 degrees, 13.9 degrees, 6.8 degrees, and almost 0 degrees. The gradual decrease of the differences in this series extending over 28 degrees of latitude is very striking. Further to the south, under the tropics, the isothermal lines are every where parallel to the equator in both hemispheres. We see, from the above examples, that the questions often asked in society, how many degrees America (without distinguishing between the eastern and western shores) is colder than Europe? and how much the mean annual temperature of Canada and the United States is lower than that of corresponding latitudes in Europe? are, when thus 'generally expressed', devoid of meaning. There is a separate difference for each parallel of latitude, and without a special comparison of the winter and summer temperatures of the opposite coasts, it will be impossible to arrive at a correct idea of climatic relations, in their influence on agriculture and other industrial pursuits, or on the individual comfort or discomfort of manking in general. In enumerating the causes which produce disturbances in the form of the isothermal lines, I would distinguish between those which 'raise' and those which 'lower' the temperature. To the first class belong the proximity of a western coast in the temperate zone; the divided configuration of a continent into peninsulas, with deeply-indented bays and inland seas; the aspect of the position of a portion of the land with reference either to a sea of ice spreading far into the polar circle, or to a mass of continental land of considerable extent, lying in the same meridian, either under the equator, or, at least, within a portion of the tropical zone; the prevalence of southerly or westerly winds on the western shore of a continent in the temperate northern zone; chains of mountains acting as protecting salls against the winds coming from colder regions; the infrequency of swamps, which, in the spring and beginning of summer, long remain covered with ice, and the absence of woods in a dry, sandy soil; finally the constant serenity of the sky in the summer months, and the vicinity of an oceanic current, bringing water which is of a higher temperature than that of the surrounding sea. Among the causes which tend to 'lower' the mean annual temperature I include the following: elevation above the level of the sea, when not forming part of an extended plain; the p 320 vicinity of an eastern coast in high and middle latitudes; the compact configuration of a continent having no littoral curvatures or bays; the extension of land toward the poles into the region of perpetual ice, without the intervention of a sea remaining open in the winter; a geographical position, in which the equatorial and tropical regions are occupied by the sea, and consequently, the absence, under the same meridian, of a continental tropical land having a strong capacity for the absorption and radiation of heat; mountain chains, whose mural form and direction impede the access of warm winds, the vicinity of isolated peaks, occasioning the descent of cold currents of air down their declivities; extensive woods, which hinder the isolation of the soil by the vital activity of their foliage, which produces great evaporation, owing to the extension of these organs, and increases the surface that is cooled by radiation, acting consequently in a three-fold manner, by shade, evaporation, and radiation; the frequency of swamps or marshes, which in the north form a kind of subterranean glacier in the plains, lasting till the middle of the summer; a cloudy summer sky, which weakens the action of the solar rays; and, finally, a very clear winter sky, favoring the radiation of heat.* [footnote] *Humboldt, 'Recherches sur les Causes des Inflexions des Lignes Isothermes', in 'Asie Centr.', t. iii., p. 103-114, 118, 122, 188. The simultaneous action of these disturbing causes, whether productive of an increase or decrease of heat, determines, as the total effect, the inflection of the isothermal lines, especially with relation to the expansion and configuration of solid continental masses, as compared with the liquid oceanic. These perturbations give rise to convex and concave summits of the isothermal curves. There are, however, different orders of disturbing causes, and each one must, therefore, be considered separately, in order that their total effect may afterward be investigated with reference to the motion (direction, local curvature) of the isothermal lines, and the actions by which they are connected together, modified, destroyed, or increased in intensity, as manifested in the contact and intersection of small oscillatory movements. Such is the method by which, I hope, it may some day be possible to connect together, by empirical and numerically expressed laws, vast series of apparently isolated facts, and to exhibit the mutual dependence which must necessarily exist among them. The trade winds -- easterly winds blowing within the tropics -- give rise, in both temperate zones, to the west, or west-southwest p 321 sinds which prevail in those regions, and which are land winds to eastern coasts, and sea winds to western coasts, estending over a space which, from the great mass and the sinking of its cooled particles, is not capable of any considerable degree of cooling, and hence it follows that the east winds of the Continent must be cooler than the west winds, where their temperature is not affected by the occurrence of oceanic currents near the shore. Cook's young companion on his second voyage of circumnavigation, the intelligent George Forster, to whom I am indebted for the lively interest which prompted me to undertake distant travels, was the first who drew attention, in a definite manner, to the climatic differences of temperature existing in the eastern and western coasts of both continents, and to the similarity of temperature of the western coast of North America in the middle latitudes, with that of Western Europe.* [footnote] *George Forster, 'Klein Schriften', th. iii., 1794, s. 87; Dove, in Schumacher's 'Jahrbuch fur', s. 289; K��mtz, 'Meteorologie', bd. ii., s. 41, 43, 67, and 96; Arago, in the 'Comptes Rendus', t. i., p. 268. Even in northern latitudes exact observations show a striking difference between the 'mean annual temperature' of the east and west coasts of America. The mean annual temperature of Nain, in (lat. 57 degrees 10'), is fully 6.8 degrees 'below' the freezing point, while on the northwest coast, at New Archangel, in Russian America (lat. 57 degrees 3'), it is 12.4 degrees 'above' this point. At the first-named place, the mean summer temperature hardly amounts to 43 degrees, while at the latter place it is 57 degrees. Pekin (39 degrees 54'), on the eastern coast of Asia, has a mean annual tempeerature of 52.8 degrees, which is 9 degrees below that of Naples, situated somewhat further to the north. The mean winter temperature of Pekin is at least 5.4 degrees below the freezing point, while in Western Europe, even at Paris (48 degrees 50'), it is nearly 6 degrees above the freezing point. Pekin has also a mean winter cold which is 4.5 degrees lower than that of Copenhagen, lying 17 degrees further to the north. We have already seen the slowness with which the great mass of the ocean follows the variations of temperature in the atmosphere, and how the sea acts in equalizing temperatures, moderating simultaneously the severity of winter and the heat of summer. Hence arises a second more important contrast -- that, namely, between insular and littoral climates enjoyed by all articulated continents having deeply indented bays and peninsulas, and between the climate of the interior of great masses of solid land. This remarkable contrast has been fully p 322 developed by Leopold von Buch in all its various phenomena, both with respect to its influence on vegetation and agriculrure, on the transparency of the atmosphere, the radiation of the soil, and the elevation of the line of perpetual snow. In the interior of the Asiatic Continent, Tobolsk, Barnaul on the Oby, and Irkutsk, have the same mean summer heat as Berlin, Munster, and Cherbourg in Normandy, the thermometer sometimes remaining for weeks together at 86 degrees or 88 degrees, while the mean winter temperature is, during the coldest month, as low as -0.4 degrees to -4 degrees. These continental climates have therefore justly been termed 'excessive' by the great mathematician and physicist Buffon; and the inhabitants who live in countries having such 'excessive' climates seem almost condemned, as Dante expresses himself, "A sofferir tormenti caldi e geli."* [fiitbite] *Dante, 'Divina Commedia, Purgatorio', canto iii. In no portion of the earth, neither in the Canary Islands, in Spain, nor in the south of France, have I ever seen more luxuriant fruit, especially grapes, than in Astrachan, near the shores of the Caspian Sea (46 degrees 21'). Although the mean annual temperature is about 48�¼degrees, the mean summer heat rises to 70�¼degrees, as at Bordeaux, while not only there, but also further to the south, as at Kislar on the mouth of the Terek (in the latitude of Avignon and Rimini), the thermometer sinks in the winter to -13 degrees or -22 degrees. Ireland, Guernsey, and Jersey, the peninsula of Brittany, the coasts of Normandy, and of the south of England, present, by the mildness of their winters, and by the low temperature and clouded sky of their summers, the most striking contrast to the continental climate of the interior of Eastern Europe. In the northeast of Ireland (54 degrees 56'), lying under the same parallel of latitude as Konigsberg in Prussia, the myrtle blooms as luxuriantly as in Portugal. The mean temperature of the month of August, which in Hungary rises to 70 degrees, scarcely reaches 61 degrees at Dublin, which is situated on the same isothermal line of 49 degrees; the mean winter temperature, which falls to about 28 degrees at Pesth, is 40 degrees at Dublin (whose mean annual temperature is not more than 49 degrees); 3.6 degrees higher than that of Milan, Pavia, Padua, and the whole of Lombardy, where the mean annual temperature is upward of 55�¼degrees. At Stromness, in the Orkneys, scarcely half a degree further south than Stockholm, the winter temperature is 39 degrees, and consequently higher than that of Paris, and neary as high as that of London. p 323 Even in the Faroe Islands, at 62 degrees latitude, the inland waters never freeze, owing to the favoring influence of the west winds and of the sea. On the charming coasts of Devonshire, near Salcombe Bay, which has been termed, on account of the mildness of its climate, the 'Montpellier of the North', the Agave Mexicana has been seen to blossoom in the open air, while orange-trees trained against espaliers, and only slightly protected by matting, are found to bear fruit. There, as well as at Penzance and Gosport, and at Cherbourg on the coast of Normandy, the mean winter temperature exceeds 42 degrees, falling short by only 2.4 degrees of the mean winter temperature of Montpellier and Florence.* [footnote] *Humboldt, 'Sur les Lignes Isothermes', in the 'Memoires de Physique et de Chimie de la Societe d'Arcueil', t. iii., Paris, 1817, p. 143-165; Knight, in the 'Transactions of the Horticultural Society of London', vol. i, p. 32; Watson, 'Remarks on the Geographical Distribution of British Plants', 1835, p. 60; Trevelyan, in Jemieson's 'Edinburgh New Phil. Journal', No. 18, p. 154; Mahlmann in his admirable German translation of my 'Asie Centrale', th. ii., s. 60. These observations will suffice to show the important influence exercised on vegetation and agriculture, on the cultivation of fruit, and on the comfort of mankind, by differences in the distribution of the same mean annual temperature, through the different seasons of the year. The lines which I have termed 'Isochimenal' and 'isotheral' (lines of equal winter and equal summer temperature) are by no means parallel with the 'isothermal' lines (lines of equal annual temperature). If, for instance, in countries where myrtles grow wild, and the earth does not remain covered with snow in the winter, the temperature of the summer and autumn is barely sufficient to bring apples to perfect ripeness, and if, again, we observe that the grape rarely attains the ripeness necessary to convert it into wine, either in islands or in the vicinity of the sea, even when cultivated on a western coast, the reason must not be sought only in the low degree of summer heat, indicated, in littoral situations, by the thermometer when suspended in the shade, but likewise in another cause that has not hitherto been sufficiently considered, although it exercises an active influence on many other phenomena (as, for instance, in the inflammation of a mixture of chlorine and hydrogen), namely the difference between direct and diffused light, or that which prevails when the sky is clear and when it is overcast by mist. I long since endeavored to attract the attention of physicists and physiologists* to this p 324 difference, and to the 'unmeasured' heat which is locally developed in the living vegetable cell by the action of direct light. [footnote] *"Haec de temperie aeris, qui terram late circumfundit, ac in quo, longe a solo, instrumenta nostra meteorologica suspensa habemus. Sed alia est caloris vis, quem radii solis nullis nubibus velati, in foliis ipsia et fructibus maturescentibus, magis minusve coloratis, gignunt, quemque, ut egregia demonstrant experimenta amicissimorum Gay-Lussacii et Thenardi de combustione chlori et hydrogenis, ope thermometri metiri nequis. Etenim locis planis et montanis, vento libe spirante, circumfusi aeris temperies cadem esse potest coelo sudo vel nebuloso; ideoque ex observationibus solis thermometricis, nullo adhibito Photometro, haud cognosces, quam ob causam Galliae septentrionalis tractur Armoricanus et Nervicus, versus littora, coe temperato sed sole raro utentia, Vitem fere non tolerant. Egent enim stirpes non solum caloris stimulo, sed et lucis, quae magis intensa locis excelsis quam planis, duplici modo plantas movet, vi sua tum propria, tum calorem in superficie earum excitante." -- Humboldt, 'De Distributione Geographica Plantarum', 1817, p. 163-164. If, in forming a thermic scale of different kinds of cultivation,* we begin with those plants which require the hottest climate, as the vanilla, the cacao, banana, and cocoa-nut, and proceed to the pine-apples, the sugar-cane, coffee, fruit-bearing date-trees, the cotton-tree, citrons, olives, edible chestnuts, and fines producing potable wine, an exact geographical consideration of the limits of cultivation, both on plains and on the declivities of mountains, will teach us that other climatic relations besides those of mean annual temperature are involved in these phenomena. [footnote] *Humboldt, op. cit., p. 156-161; Meyen, in his 'Grundriss der Pflanzengeographie', 1836 s. 379-467; Boussingault, 'Economie Rurale', t. ii., p. 675. Taking an example, for instance, from the cultivation of the vine, we find that, in order to procure 'potable' wine,* it is requisite that the mean annual heat should exceed 49 degrees, that the winter temperature upward of 64 degrees. [footnote] *the following table illustrates the cultivation of the vine in Europe, and also the depreciation of its produce according to climatic relations. See my 'Asie Centrale', t. iii., p. 159. The examples quoted in the text for Bordeaux and Potsdam are, in respect of numerical relation, alike applicable to the countries of the Rhine and Maine (48 degrees 35' to 40 degrees 7' N. lat.). Cherbourg in Normandy, and Ireland, show in th most remarkable manner how, with thermal relations very nearly similar to those prevailing in the interior of the Continent (as estimated by the thermometer in the shade), the results are nevertheless extremely different as regards the ripeness or the unripeness of the fruit of the vine, this difference undoubtedly depending on the circumstance whether the vegetation of the plant proceeds under a bright sunny sky, or under a sky that is habitually obscured by clouds: [NB Table will line up in Courier 10 point] _____________________________________________________________________ Places. Lat- Ele- Mean Win- Spring. Sum- Aut- Number of the it- va- of the ter. mer. umn. years of the tude tion. Year. observation _____________________________________________________________________ deg ' Eng.ft. Fahr. Bordeaux 44 50 25.6 57.0 43.0 56.0 71.0 58.0 10 Stras- 48 35 479.0 49.6 34.5 50.0 64.6 50.0 35 bourg Heid- 49 24 333.5 59.5 34.0 50.0 64.3 49.7 20 elberg Manheim 49 29 300.5 50.6 34.6 50.8 67.1 49.5 12 Wurzburg 49 48 562.5 50.2 35.5 50.5 65.7 49.4 27 Frank- fort on Maine 50 7 388.5 49.5 33.3 50.0 64.4 49.4 19 Berlin 52 31 102.3 47.5 31.0 46.6 63.6 47.5 23 Cher- bourg (no wine) 49 39 .... 52.1 41.5 50.8 61.7 54.2 3 Dublin (ditto) 53 23 .... 49.1 40.2 47.1 59.6 49.7 13 ___________________________________________________________________ The great accordance in the distribution of the annual temperature through the different seasons, as presented by the results obtained for the valleys of the Rhine and Maine, tends to confirm the accuracy of these meteorological observations. The months of December, January, and February are reckoned as winter months. When the different qualities of the wines produced in Franconia, and in the countries around the Baltic, are compared with the mean summer and autumn temperature of Wurzburg and Berlin, we are almost surprised to find a difference of only about two degrees. The difference in the spring is about four degrees. The influence of late May frosts on the flowering season, and after a correspondingly cold winter, is almost as important an element as the time of the subsequent ripening of the grape. The difference alluded to in the text between the true temperature of the surface of the ground and the indications of a thermometer suspended in the shade and protected from extraneous influences, is inferred by Dove from a consideration of the results of fifteen years' observations made at the Chiswick Gardens. See Dove, in 'Bericht uber die Verhandl. der Berl. Akad. der Wiss.', August, 1844, s. 285. At Bordeaux, in the valley of the Garonne (44 degrees 50' lat.), the mean annual winter, summer, and autumn temperatures are respectively 57 degrees, 43 degrees, 71 degrees, and 58 degrees. In the plains near the p 325 Baltic (52 degrees 30' lat.), where a wine is produced that can scarcely be considered potable, these numbers are as follows: 47.5 degrees, 30 degrees, 63.7 degrees, and 47.5 degrees. If it should appear strange that the great differences indicated by the influence of climate on the production of wine should not be more clearly manifested by our thermometers, the circumstance will appear less singular when we remember that a thermometer standing in the shade, and protected from the effect of direct insolation and nocturnal radiation can not, at all seasong of the year, and during all periodic changes of heat, indicate the true superficial temperature of the ground exposed to the whole effect of the sun's rays. The same relations which exist between the equable littoral climate of the peninsula of Brittany, and the lower winter and p 326 higher summer temperature of the remainder of the continent of France, are likewise manifested in some degree, between Europe and the great continent of Asia, of which the former may be considered to constitute the western peninsula. Europe owes its milder climate, in the first place, to its position with respect to Africa, whose wide extent of tropical land is favorable to the ascending current, while the equatorial region to the south of Asia is almost wholly oceanic; and next to its deeply-articulated configuration, to the vicinity of the ocean on its western shores; and, lastly, to the existence of an open sea, which bounds its northern confines. Europe would therefore become colder* if Africa were to be overflowed by the ocean; of if the mythical Atlantis were to arise and connect Europe with North America; or if the Gulf Stream were no longer to diffuse the warming influence of its waters into the North Sea; or if, finally, another mass of solid land should be upheaved by volcanic action, and interposed between the Scandinavian peninsula and Spitzbergen. [footnote] *See my memoir, 'Ueber die Haupt-Ursachen der Temperaturverschiedenheit auf der Erdoberfl��che', in the 'Abhandl. der Akad. der Wissensch. zu Berlin von dem Jahr' 1827, s. 311. If we observe that in Europe the mean annual temperature falls as we proceed, from west to east, under the same parallel of latitude, from the Atlantic shores of France through Germany, Poland, and Russia, toward the Uralian Mountains, the main cause of this phenomenon of increasing cold must be sought in the form of the continent (which becomes less indented, and wider, and more compact as we advance), in the increasing distance from seas, and in the diminished influence of westerly winds. Beyond the Uralian Mountains these winds are converted into cool land-winds, blowing over extended tracts covered with ice and show. The cold of western Siberia is to be ascribed to these relations of configuration and atmospheric currents, and not -- as Hippocrates and Trogus Pompeius, and even celebrated travelers of the eighteenth century conjectures -- to the great elevation of the soil above the level of the sea.* [footnote] *The general level of Siberia, from Tobolsk, Tomsk, and Barnaul, from the Altai Mountains to the Polar Sea, is not so high as that of Mauheim and Dresden; indeed, Irkutsk, far to the east of the Jenisei, is only 1330 feet above the level of the sea, or about one third lower than Munich. If we pass from the differences of temperature manifested in the plains to the inequalities of the polyhedric form of the surface of our planet, we shall have to consider mountains either in relation to their influence on the climate of neighboring p 327 valleys, or according to the effects of the hyposometrical relations on their own summits, which often spread into elevated plateaux. The division of mountains into chains separates the earth's surface into different basins, which are often narrow and walled in, forming caldron-like valleys, and (as in Greece and in part of Asia Minor) constitute an individual local climate with respect to heat, moisture, transparancy of atmosphere, and frequency of winds and storms. These circumstances have at all times exercised a powerful influence on the character and cultivation of natural products, and on the manners and institutions of neighboring nations, and even on the feelings with which they regard one another. This character of 'geographical individuality' attains its maximum, if we may be allowed so to speak, in countries where the differences in the configuration of the soil are the greatest possible, either in a vertical or horizontal direction, both in relief and in the articulation of the continent. The greatest contrast to these varieties in the relations of the surface of the earth are manifested in the Steppes of Northern Asia, the grassy plains (savannahs, llanos, and pampas) of the New Continent, the heath ('Ericeta') of Europe, and the sandy and stony deserts of Africa. The law of the decrease of heat with the increase of elevation at different latitudes is one of the most important subjects involved in the study of meteorological processes, of the geography of plants, of the theory of terrestrial refraction, and of the various hypotheses that relate to the determination of the height of the atmosphere. In the many mountain journeys which I have undertaken, both within and without the tropics, the investigation of this law has always formed a special object of my researches.* [footnote] *Humboldt, 'Recueil d'Observations Astronomiques', t. i., p. 126-140; 'Relation Historique', t. i., p. 119, 141, 227; Biot, in 'Connaissance des Temps pour l'an' 1841, p. 90-109. Since we have acquired a more accurate knowledge of the true relations of the distribution of heat on the surface of the earth, that is to say, of the inflections of isothermal and isotheral lines, and their unequal distance apart in the different eastern and western systems of temperature in Asia, Central Europe, and North America, we can no longer ask the general question, what fraction of the mean annual or summer temperature corresponds to the difference of one degree of geographical latitude, taken in the same meridian? In each system of 'isothermal' lines of equal curvature there reigns a p 328 close and necessary connection between three elements, namely, the decrease of heat in a vertical direction from below upward, the difference of temperature for every one degree of geographical latitude, and the uniformity in the mean temperature of a mountain station, and the latitude of a point situated at the level of the sea. In the system of Eastern America, the mean annual temperature from the coast of Labrador to Boston changes 1.6�¼degrees for every degree of latitude; from Boston to Charleston about 1.7 degrees; from Charleston to the tropic of Cancer, in Cuba, the variation is less rapid, being only 1.2 degrees. In the tropics this diminution is so much greater, that from the Havana to Cumana the variation is less than 0.4 degrees for every degree of latitude. The case is quite different in the isothermal system of Central Europe. Between the parallels of 38 degrees and 71 degrees I found that the decrease of temperature was very regularly 0.9degrees for every degree of latitude. But as, on the other hand, in Central Europe the decrease of heat is 1.8 degrees for about every 534 feet of vertical elevation, it follows that a difference of elevation of about 267 feet corresponds to the difference of one degree of latitude. The same mean annual temperature as that occurring at the Convent of St. Bernard, at an elevation of 8173 feet, in lat. 45 degrees 50' should therefore be met with at the level of the sea in lat. 75 degrees 50'. In that part of the Cordilleras which falls within the tropics, the observations I made at various heights, at an elevation of upward of 19,000 feet, gave a decrease of 1 degree for every 341 feet; and my friend Boussingault found, thirty years afterward, as a mean result, 319 feet. By a comparison of places in the Cordilleras, lying at an equal elevation above the level of the sea, either on the declivities of the mountains or even on extensive elevated plateaux, I observed that in the latter there was an increase in the annual temperature varying from 2.7 degrees to 4.1 degrees. This difference would be still greater if it were not for the cooling effect of nocturnal radiation. As the different climates are arranged in successive strata, the one above the other, from the cacao woods of the valleys to the region of perpetual snow, and as the temperature in the tropics varies but little throughout the year, we may form to ourselves a tolerably correct representation of the climatic relations to which the inhabitants of the large cities in the Andes are subjected, by comparing these climates with the temperatures of particular months in the plains of France and Italy. While p 329 the heat which prevails daily on the woody shores of the Orinoco exceeds by 7.2 degrees that of the month of August at Palermo, we find, on ascending the chain of the Andes, at Popayan, at an elevation of 3826 feet, the temperature of the three summer months of Marseilles; at Quito, at an elevation of 9541 feet, that of the close of May at Paris; and on the Paramos, at a height of 11,510 feet, where only stunted Alpine shrubs grow, though flowers still bloom in abundance, that of the beginning of April at Paris. The intelligent observer, Peter Martyr de Aughiera, one of the friends of Christopher Columbus, seems to have been the first who recognized (in the expedition undertaken by Rodrigo Enrique Colmenares, in October, 1510) that the limit of perpetual snow continues to ascend as we approach the equator. We read, in the fine work 'De Rebus Oceanicis',* "the River Gaira comes from a mountain in the Sierra Nevada de Santa Maria, which, according to the testimony of the companions of Colmenares, is higher than any other mountain hitherto discovered. [footnote] *Anglerius, 'De Rebus Oceanicis', Dec. xi., lib. ii., p. 140 (ed. Col., 1574). In the Sierra de Santa Marta, the highest point of which appears to exceed 19,000 feet (see my 'Relat. Hist.', t. ii., p. 214), there is a peak that is still called Pico de Gaira. It must undoubtedly be so if 'it retain snow perpetually' in a zone which is not more than 10 degrees from the equinoctial line." The lower limit of perpetual snow, in a given latitude, is the lowest line at which snow continues during summer, or, in other words, it is the maximum of height to which the snow-line recedes in the course of the year. But this elevation must be distinguished from three other phenomena, namely, the annual fluctuation of the snow-line, the occurrence of sporadic falls of snow, and the existence of glaciers, which appear to be peculiar to the temperate and cold zones. This last phenomenon, since Saussure's immortal work on the Alps, has received much light, in recent times, from the labors of Venetz, Charpentier, and the intrepid and persevering observer Agassiz. We know only the 'lower', and not the 'upper' limit of perpetual snow; for the mountains of the earth do not attain to those ethereal regions of the rarefied and dry strata of air, in which we may suppose, with Bouguer, that the vesicles of aqueous vapor are converted into crystals of ice, and thus rendered perceptible to our organs of sight. The lower limit of snow is not, however, a mere function of geographical latitude or of mean annual temperature; nor is it at the equator, or p 330 even, in the region of the tropics, that this limit attains its greatest elevation above the level of the sea. The phenomenon of which we are treating is extremely complicated, depending on the general relations of temperature and humidity, and on the form of the mountains. On submitting these relations to the test of special analysis, as we may be permitted to do from the number of determinations that have recently been made,* we shall find that the controlling causes are the differences in the temperature of different seasons of the year; the direction of the prevailing winds and their relations to this land and sea; the degree of dryness or humitidy in the upper strata of the air; the absolute thickness of the accumulated masses of fallen snow; the relation of the s-line to the total height of the mountain; the relative position of the latter in the chain to which it belongs, and the steepness of its declivity; the vicinity of either summits likewise perpetually covered with show; the expansion, position, and elevation of the plains from which the snow mountain rises as an isolated peak or as a portion of a chain; whether this plain be part of the sea-coast, or of the interior of a continent; whether it be covered with wood or waving grass; and whether, finally, it consist of a dry and rocky soil, or of a wet and marshy bottom. [footnote] *See my table of the height of the line of perpetual snow, in both hemispheres, from 71 degrees 15' north lat. to 53 degrees 54' south lat., in my 'Asie Centrale', t. iii., p. 360. The snow-line which, under the equator in South America, attains an elevation equal to that of the summit of Mont Blanc in the Alps, and descends, according to recent measurements, about 1023 feet lower toward the northern tropic in the elevated plateaux of Mexico (in 19 degrees north latitude), rises, according to Pentland, in the southern tropical zone (14 degrees 30' to 18 degrees south latitude), being more than 2665 feet higher in the maritime and western branch of the Cordilleras of Chili than under the equator near Quito on Chimborazo, Cotopaxi, and Antisana. Dr. Gilles even asserts that much further to the south, on the declivity of the volcano of Peuquenes (latitude 33 degrees), he found the snow-line at an elevation of between 14,520 and 15,030 feet. The evaporation of the snow in the extremely dry air of the summer, and under a cloudless sky, is so powerful, that the volcano of Aconcagua, northeast of Valparaiso (latitude 32 degrees 30'), which was found in the expedition of the Beagle to be more than 1400 feet higher than Chimborazo, was on one occasion seen free from snow.�¥ [footnote] *Darwin, 'Journal of the Voyages of the Adventure and Beagle', p. 297. As the volcano of Aconcagua was not at that time in a state of eruption, we must not ascribe the remarkable phenomenon of this absence of snow to the internal heat of the mountain (to the escape of heated air through fissures), as is sometimes the case with Cotopaxi. Gilles, in the 'Journal of Natural Science', 1830, p. 316. In p 331 an almost equal northern latitude (from 30 degrees 45' to 31 degrees), the snow'line on the southern declivity of the Himalaya lies at an elevation of 12,982 feet, which is about the same as the height which we might have assigned to it from a comparison with other mountain chains; on the northern declivity, however, under the influence of the high lands of Thibet (whose mean elevation appears to be about 11,510 feet), the snow-line is situated at a height of 16,630 feet. This phenomenon, which has long been contested both in Europe and in India, and whose causes I have attempted to develop in various works, published since 1820,* possesses other grounds of interest than p 332 those of a purely physical nature, since it exercises no inconsiderable degree of influence on the mode of life of numerous tribes -- the meteorological processes of the atmosphere being the controlling causes on which depend the agricultural or pastoral pursuits of the inhabitants of extensive tracts of continents. [footnote] *See my 'Second Memoire sur les Montagnes de Inde', in the 'Annales de Chemie et de Physique', t. xiv., p. 5-55; and 'Asie Centrale', t. iii., p. 281-327. While the most learned and experienced travelers in India, Colebrooke, Webb, and Hodgson, Victor Jacquemont, Fobes Royle, Carl von Hugel, and Vigne, who have all personally examined the Himalaya range, are agreed, regarding the greater elevation of the snow-line on the Thibeta=ian side, the accuracy of this statement is called in question by John Gerard, by the geognoist MacClelland, the editor of the 'Calcutta Journal', and by Captain Thomas Hutton, assistant surveyor of the Agra Division. The appearance of my work on Central Asia gave rise to a rediscussion of this question. A recent number (vol. iv., January, 1844) of MacClelland and Griffith's 'Calcutta Journal of Natural History' contains, however, a very remarkable and decisive notice of the determination of the snow-line in the Himalaya. Mr. Batten, of the Bengal service, writes as follows from Camp Semulka, on the Cosillah River, Kumaon: "In the July, 1843, No. 14 of your valuable Journal of Natural History, which I have only lately had the opportunity of seeing, I read Captain Hutton's paper on the snow of the Himalayas, and as I differed almost entirely from the conclusions so confidently drawn by that gentleman, I thought it right, for the interest of scientific truth, to prepare some kind of answer; as however, on a more attentive perusal, I find that you yourself appear implicitly to adopt Captain Hutton's views, and actually use these words, 'We have long been conscious of the error here so well ppointed out by Captain Hutton, 'in common with every one who has visited the Himalayas,' I feel more inclined to address you, in the first instance, and to ask whether you will publish a short reply which I meditate; and whether your not to Captain Hutton's paper was written after your own full and careful examination of the subject, or merely on a general kind of acquiscence with the fact and opinions of your able contributor, who is so well known and esteemed as a collector of scientific data? Now I am one who have visited the Himalaya on the western side; I have crossed the Borendo or Booria Pass into the Buspa Valley, in Lower Kanawar, returning into the Rewaien Mountains of Ghurwal by the Koopin Pass; I have visited the source of the Jumna at Jumnootree; and, moving eastward, the sources of the Kalee or Mundaknee branch of the Ganges at Kadarnath; of the Bishnoo Gunga, or Aluknunda, at Buddrinath and Mana; of the Pindur at the foot of the Great Peak Nundidavi; of the Dhoulee branch of the Ganges, beyond Neetee, crossing and recrossing the pass of that name into Thibet; of the Goree or great branch of the Sardah, or Kalee, near Oonta Dhoora, beyond Melum. I have also, in my official capacity made the settlement of the Bhote Mehals of this province. My residence of more than six years in the hills has thrown me constantly in the way of European and native travelers, nor have I neglected to acquire information from the recorded labors of others. Yet, with all this experience, I am prepared to affirm that 'the perpetual snow-line is at a higher elevation' on the northern slope of 'the Himalaya' than on the southern slope. "The facts mentioned by Captain Hutton appear to me only to refer to the northern sides of all mountains in these regions, and not to affect, in any way the reports of Captain Webb and others, on which Humboldt formed his theory. Indeed how can any facts of one observer in one place falsify the facts of another observer in another place? I willingly allow that the north side of a hill retains the snow longer and deeper than the south side, and this observation applies equally to heights in Bhote; but Humboldt's theory is on the question of the perpetual snow-line, and Captain Hutton's reference to Simla and Mussooree, and other mountain sites, are out of place in this question, or else he fights against a shadow, or an objectioon of his own creation. In no part of his paper does he quote accurately the dictum which he wishes to oppose." If the mean altitude of the thibetian highlands be 11,510 feet, they admit of comparison with the lovely and fruitful plateau of Caxamarca in Peru. But at this estimate they would still be 1300 feet lower than the plateau of Bolivia at the Lake of Titicaca, and the causeway of the town of Potosi. Ladak, as appears from Vigne's measurement, by determining the boiling-point, is 9994 feet high. This is probably also the altitude of H'Lassa (Yul-sung), a monastic city, which Chinese writers describe as the 'realm of pleasure', and which is surrounded by vineyards. Must not these lie in deep valleys? As the quantity of moisture in the atmosphere increases with the temperature, this element, which is so important for the whole organic creation, must vary with the hours of the day, the seasons of the year, and the differences in latitude and elevation. Our knowledge of the hygrometric relations of the Earth's surface has been very materially augmented of late years by the general application of August's psychrometer, framed in accordance with the views of Dalton and Daniell, for determining the relative quantity of vapor, or the p 333 condition of moisture of the atmosphere, by means of the difference of the 'dew point' and of the temperature of the air. Temperature, atmospheric pressure, and the direction of the wind, are all intimately connected with the vivifying action of atmospheric moisture. This influence is not, however, so much a consequence of the quantity of moisture held in solution in different zones, as of the nature and frequency of the precipitation which moistens the ground, whether in the form of dew, mist, rain, or snow. According to the exposition made by Dove of the law of rotation, and to the general views of this distinguished physicist,* it would appear that, in our northern zone, "the elastic force of the vapor is greatest with a southwest, and least with a northeast wind. On the western side of the windrose this elasticity diminishes, while it increases on the eastern side; on the former side, for instance, the cold, dense, and dry current of air repels the warmer, lighter current containing an abundance of aqueous vapor, while on the eastern side it is the former current which is repulsed by the latter. [footnote] *See Dove, 'Meteorologische Vergleichung von Nordamerika und Europa', in Schumacher's 'Jahrbuch fur' 1841, s. 311; and his 'Meteorologische Untersuchungen', s. 140. The agreeable and fresh verdure which is observed in many trees in districts within the tropics, where, for five or seven months of the yeqar, not a cloud is seen on the vault of heaven, and where no perceptible dew or rain falls, proves that the leaves are capable of extyracting water from the atmosphere by a peculiar vital process of their own, which perhaps is not alone that of producing cold by radiation. The absence of rain in the arid plains of Cumana, Coro, and Ceara in North Brazil, forms a striking contrast to the quanitity of rain which falls in some tropical regions, as, for instance, in the Havana, where it would appear, from the average of six years' observation by Ramong de la Sagra, the mean annual quantity of rain is 109 inches, equal to four or five times that which falls at Paris or at Geneva.* [footnote] *The mean annual quantity of rain that fell in Paris between 1805 and 1822 was found by Arago to be 20 inches; in London, between 1812 and 1827, it was determined by Howard at 25 inches; while at Geneva the mean of thirty-two years' observation was 30.5 inches. In Hindostan, near the coast, the quantity of rain is from 115 to 128 inches; and in the island of Cuba, fully 142 inches fell in the year 1821. With regard to the distribution of the quantity of rain in Central Europe, at different periods of the year, see the admirable researches of Gasparin, Schuow, and Bravais, in the 'Bibliotheque Universelle', t. xxxvviii., p. 54 and 264; 'Tableau du Climat de l'Italie', p. 76; and Martins's notes to his excellent French translation of K��mtz's 'Vorlesungen uber Meteorologie', p. 142. On the declivity of the Cordilleras, p 334 the quantity of rain, as well as the temperature, diminishes with the increase in the elevation.* [footnote] *According to Boussingault ('Economie Rurale', t. ii., p. 693), the mean quantity of rain that fell at Marmato (latitude 5 degrees 27', altitude 4675 feet, and mean temperature 69 degrees) in the years 1833 and 1834 was 64 inches, while at Santa Fe de Bogota (latitude 4 degrees 36', altitude 8685 feet, and mean temperature 58 degrees) it only amounted to 39 1/2 inches. My South American fellow-traveler, Caldas, found that, at Santa Fe de Bogota, at an elevation of almost 8700 feet, it did not exceed 37 inches, being consequently little more than on some parts of the western shore of Europe. Boussingault occasionally observed at Quito that Saussure's hygrometer receded to 26 degrees with a temperature of from 53.6 degrees to 55.4 degrees. Gay-Lussac saw the same hygrometer standing at 25.3 degrees in his great aerostatic ascent in a stratum of air 7034 feet high, and with a temperature of 39.2 degrees. The greatest dryness that has yet been observed on the surface of the globe in the low lands is probably that which Gustav Rose, Ehrenberg, and myself found in Northern Asia, between the valleys of the Irtisch and the Oby. In the Steppe of Platowskaja, after southwest winds had blown for a long time from the interior of the Continent, with a temperature of 74.7 degrees, we found the dew point at 24 degrees. The air contained only 16/100ths of aqueous vapor.* [footnote] *For the particulars of this observation, see my 'Asie Centrale', t. iii., p. 85-89 and 467; and regarding the amount of vapor in the atmosphere in the lowlands of tropical South America, consult my 'Relat. Hist.', t. i., p. 242-248; t. ii., p. 45, 164. The accurate observers K��mtz, Bravais, and Martins have raised doubts during the last few years regarding the greater dryness of the mountain air, which appeared to be proved by the hygrometric measurements made by Saussure and myself in the higher regions of the Alps and the Cordilleras. The strata of air at Zurich and on the Faulhorn, which can not be considered as an elevated mountain when compared with non-European elevations, furnished the data employed in the comparisons made by these observers.* [footnote] *K��mtz, 'Vorlesungen uber Meteorologie', s. 117. In the tropical region of the Paramos (near the region where snow begins to fall, at an elevation of between 12,000 and 14,000 feet), some species of large flowering myrtle-leaved alpine shrubs are almost constantly bathed in moisture; but this fqact does not actually prove the existence of any great and absolute quantity of aqueous vapor at such an elevation, merely affording p 335 an evidence of the frequency of aqueous precipitation, in like manner as do the frequent mists with which the lovely plateau of Bogota is covered. Mists arise and disappear several times in the course of an hour in such elevations as these, and with a calm state of the atmosphere. These rapid alternations characterize the Paramos and the elevated plains of the chain of the Andes. 'The electricity of the atmosphere', whether considered in the lower or in the upper strata of the clouds, in its silent problematical diurnal course, or in the explosion of the lightning and thunder of the tempest, appears to stand in a manifold relation to all phenomena of the distribution of heat, of the pressure of the atmosphere and its disturbances, of hydrometeoric exhibitions, and probably, also, of the magnetism of the external crust of the earth. It exercises a powerful influence on the whole animal and vegetable world; not merely by meteorological processes, as precipitations of aqueous vapor, and of the acids and ammoniacal compounds to which it gives rise, but also directly as an electric force acting on the nerves, and promoting the circulation of the organic juices. This is not a place in which to renew the discussion that has been started regarding the actual source of atmospheric eletricity when the sky is clear, a phenomenon that has alternately been ascribed to the evaporation of impure fluids impregnated with earths and salts,* to the growth of plants,** or to some other chemical decompositions on the surface of the earth, to the unequal distribution of heat in the strata of the air,*** and, finally, according to Peltier's intelligent researches,**** to the agency of a constant charge of negative electricity in the terrestrial globe. [footnote] *Regarding the conditions of electricity from evaporation at high temperatures, see Peltier, in the 'Annales de Chimie', t. lxxv., p. 330. [footnote] **Pouillet, in the 'Annales de Chimie', t. xxxv., p. 405. [footnote] ***De la Rive, in his admirable 'Essai Historique sur l'Electricite', p. 140. [footnote] ****Peltier, in the 'Comptes Rendus de l'Acad. des Sciences', t. xii., p. 307; Becquerel, 'Traite de l'Electricite et du Magnetisme', t. iv., p. 107. Limiting itself to results yielded by electrometric observations, such, for instance, as are furnished by the ingenious electro-magnetic apparatus first proposed by Colladon, the physical description of the universe should merely notice the incontestable increase of intensity in the general positive electricity of the atmosphere,* accompanying an increase of altitude and and the absence of trees, its daily variations (which, according to Clark's experiments at Dublin, p 336 take place at more complicated periods than those found by Saussure and myself), and its variations in the different seasons of the year, at different distances from the equator, and in the different relations of continental or oceanic surface. [footnote] *Duprez, 'Sur l'Electricite de l'Air' (Bruxelles, 1844), p. 56-61. The electric equilibrium is less frequently disturbed where the aerial ocean rests on a liquid base than where it impends over the land; and it is very striking to observe how, in extensive seas, small insular groups affect the condition of the atmosphere, and occasion the formation of storms. In fogs, and in the commencement of falls of snow, I have seen, in a long series of observations, the previously permanent positive electricity rapidly pass into the negative condition, both on the plains of the colder zones, and in the Paramos of the Cordilleras, at elevations varying from 11,000 to 15,000 feet. The alternate transition was precisly similar to that indicated by the electrometer shortly before and during a storm.* [footnote] *Humboldt, 'Relation Historique', t. iii., p. 318. I here only refer to those of my experiiments in which the three-foot metallic conductor of Saussure's electrometer was neither moved upward nor downward, nor, according to Volta's proposal, armed with burning sponge. Those of my readers who are well acquainted with the 'quaestiones vexatae' of atmospheric electricity will understand the grounds for this limitation. Respecting the formation of storms in the tropics, see my 'Rel. Hist.', t. ii., p. 45 and 202-209. When the vesicles of vapor have become condensed into clouds, having definite outlines, the electric tension of the external surface will be increased in proportion to the amount of electricity which passes over to it from the separate vesicles of vapor.* [footnote] *Gay-Lussac, in the 'Annales de Chimie et de Physique', t. viii., p. 167. In consequence of the discordant views of Lame, Becquerel, and Peltier, it is difficult to come to a conclusion regarding the cause of the specific distribution of electricity in clouds, some of which have a positive, and others a negative tension. The negative electricity of the air, which near high water-falls is caused by a disintegration of the drops of water -- a fact originally noticed by Tralles, and confirmed by myself in various latitudes -- is very remarkable, and is sufficiently intense to produce an appreciable effect on a delicate electrometer at a distance of 300 or 400 feet. Slate-gray clouds are charged, according to Peltier's experiments at Paris, with negative, and white, red, and orange-colored clouds with positive electricity. Thunder clouds not only envelop the highest summits of the chain of the Andes (I have myself seen the electric effect of lightning on one of the rocky pinnacles which project upward of 15,000 feet above the crater of the volcano of Toluca), but they have also been observed at a vertical height of 26,650 feet over the low p 337 lands in the temperate zone.* [footnote] *Arago, in the 'Annuaire du Bureau des Longitudes pour' 1838, p. 246. Sometimes, however, the stratum of cloud from which the thunder proceeds sinks to a distance of 5000, or, indeed, only 3000 feet above the plain. According to Arago's investigations -- the most comprehensive that we possess on this difficult branch of meteorology -- the evolution of light (lightning) is of three kinds -- zigzag, and sharply defined at the edges; in sheets of light, illuminating a whole cloud, which seems to open and refeal the light within it; and in the form of fire-balls.* [footnote] *Arago, op. cit., p. 249-266. (See also, p. 268-279.) The duration of the two first kinds scarcely continues the thousandth part of a second; but the globular lightning moves much more slowly remaining visible for several seconds. Occasionally (as is proved by the recent observations, which have confirmed the description given by Nicholson and Beccaria of this phenomenon), isolated clouds, standing high above the horizon, continue uninterruptedly for some time to emit a luminous radiance from their interior and from their margins, although there is no thunder to be heard, and no indication of a storm; in some cases even hail-stones, drops of rain, and flakes of snow have been seen to fall in a luminous condition, when the phenomenon was not preceded by thunder. In the geographical distribution of storms, the Peruvian coast, which is not visited by thunder or lightning, presents the most striking contrast to the rest of the tropical zone, in which, at certain seasons of the year, thunder-storms occur almost daily, about four or five hours after the sun has reached the meridian. According to the abundant evidence collected by Arago* from the testiimony of navigators (Scoresby, Parry, Ross, and Franklin), there can be no doubt that, in general, electric explosions are extremely rare in high northern regions (between 70 degrees and 75 degrees latitude). [footnote] *Arago, op. cit., p. 388-391. The learned academician Von Baer, who has done so much for the meteorology of Northern Asia, has not taken into consideration the extreme rarity of storms in Iceland and Greenland; he has only remarked ('Bulletin de l'Academie de St. Petersbourg', 1839, Mai) that in Nova Zembla and Spitzbergen it is sometimes heard to thunder. 'The meteorological portion' of the descriptive history of nature which we are now concluding shows that the processes of the absorption of light, the liberation of heat, and the variations in the elastic and electric tension, and in the hygrometric condition of the vast aerial ocean, are all so intimately connected together, that each individual meteorological process is modified by the action of all the others. The complicated p 338 nature of these disturbing causes (which involuntarily remind us of those which the near and especially the smallest cosmical bodies, the satellites, comets, and shooting stars, are subjected to in their course) increases the difficulty of giving a full explanation of these involved meteorological phenomena, and likewise limits, or wholly precludes, the possibility of that predetermination of atmospheric changes which would be so important for horticulture, agriculture, and navigation, no less than for the comfort and enjoyment of life. Those who place the value of meteorology in this problematic species of prediction rather than in the knowledge of the phenomena themselves, are firmly convinced that this branch of science, on account of which so many expeditions to distant mountainous regions have been undertaken, has not made any very considerable progress for centuries past. The confidence which they refuse to the physicist they yield to changes of the moon, and to certain days marked in the calendar by the superstition of a by-gone age. "Great local deviations from the distribution of the mean temperature are of rare occurrence, the variations being in general uniformly distributed over extensive tracts of land. the deviation, after attaining its maximum at a certain point, gradually decreases to its limits; when these are passed, however, decided deviations are observed in the 'opposite direction'. Similar relations of weather extend more frequently from south to north than from west to east. At the close of the year 1829 (when I had just completed my Siberian journey), the maximum of cold was at Berlin, while North America enjoyed an unusually high temperature. It is an entirely arbitrary assumption to believe that a hot summer succeeds a severe winter, and that a cool summer is preceded by a mild winter." Opposite relations of weather in contiguous countries, or in two corn-growing continents, give rise to a beneficient equalization in the prices of the products of the vine, and of agricultural and horticultural cultivation. It has been justy remarked, that it is the barometer alone which indicates to us the changes that occur in the pressure of the air throughout all the aerial strata from the place of observation to the extremest confines of the atmosphere, while* the thermometer and psychrometer only acquaint us with all the variations occurring in the local heat and moisture of the lower strata of p 339 air in contact with the ground. [footnote] *K��mtz, in Schumacher's 'Jahrbuch fur' 1838, s. 285. Regarding the opposite distribution of heat in the east and the west of Europe and North America, see Dove, 'Repertorium der Physik', bd. iii., s. 392-395. The simultaneous thermic and hygrometric modifications of the upper regions of the air can only be learned (when direct observations on mountain stations or aerostatic ascents are impracticable) from hypothetical combinations, by making the barometer serve both as a thermometer and an hygrometer. Important changes of weather are not owing to merely local causes, situated at the place of observation, but are the consequence of a disturbance in the equilibrium of the aerial currents at a great distance from the surface of the Earth, in the higher strata of the atmosphere, bringing cold or warm, dry or moist air, rendering the sky cloudy or serene, and converting the accumulated masses of clouds into light feathery 'cirri'. As, therefore, the inaccessibility of the phenomenon is added to the manifold nature and complication of the disturbances, it has always appeared to me that meteorology must first seek its foundation and progress in the torrid zone, where the variations of the atmospheric pressure, the course of hydro-meteors, and the phenomena of electric explosion, are all of periodic occurrence. As we have now passed in review the whole sphere of inorganic terrestrial life, and have briefly considered our planet with reference to its form, its internal heat, its electro-magnetic tension, its phenomena of polar light, the volcanic reaction of its interior on its variously composed solid crust, and, lastly, the phenomena of its two-fold envelopes -- the aerial and liquid ocean -- we might, in accordance with the older method of treating physical geography, consider that we had completed our descriptive history of the globe. But the nobler aim I have proposed to myself, of raising the contemplation of nature to a more elevated point of view, would be defeated, and this delineation of nature would appear to lose its most attractive charm, if it did not also include the sphere of organic life in the many stages of its typical development. The idea of vitality is so intimatey associated with the idea of the existence of the active, ever-blending natural forces which animate the terrestrial sphere, that the creation of plants and animals is ascribed in the most ancient mythical representations of many nations to these forces, while the condition of the surface of our planet, before it was animated by vital forms, is regarded as coeval with the epoch of a chaotic conflict of the struggling elements. But the empirical domain of objective contemplation, and the delineation of our planet in its present condition, do not include a consideration p 340 of the mysterious and insoluble problems of origin and existence. A cosmical history of the universe, resting upon facts as its basis, has, from the nature and limitations of its sphere, necessarily no connection with the obscure domain embraced by a 'history of organisms',* if we understand the word 'history' in its broadest sense. [footnote] *The 'history of plants', which Endlicher and Unger have described in a most masterly manner ('Grundzuge der Botanik', 1843, s. 449-468), I myself separated from the 'geography of plants' half a century ago. In the aphorisms appended to my 'Subterranean Flora', the following passage occurs: "Geognosia naturam animantem et inanimam vel, ut vocabulo minus apto, ex antiquitate saltem haud petito, utar, corpora vitur capita: Geographia oryctologica quam simpliciter Geognosiam vel Geologiam dicunt, virque acutissimus Wernerus egregie digessit; Geographia zoologica, cujus doctrinae fundamenta Zimmermannus et Treviranus jecerunt; et Geographic plantarum quam aequales nostri diu intactam reliquerunt. Geographia plantarum vincula et cognationem tradit, quibus omnia vegetabilia inter se connexa sint, terraetractur quos teneant, in aerem atmosphaericum quae sit eorum vis ostendit, saxa atque rupes quibus potissimum algarum primordiis radicibusque destruantur docet, et quo pacto in telluris superficie humus nascatur, commemorat. Est itaque quod differat inter Geognosiam et Physiographiam, 'historia naturalis' perperam nuncupatam quum Zoognosia, Phytognosia, et Oryctognosia, quae quidem omnes in naturae investigatione versantur, non nisi singulorum animalium, plantarum, rerum metallicarum vel (venia sit verbo) fossilium formas, anatomen, vires scrutautur. Historia Telluris, Geognosiae magis quam Physiographiae affinis, nemini adhuc tenata, plantarum animaliumque genera orbem inhabitantia primaevum, migrationes eorum compluriumque interitum, ortum quem montes, valles, saxorum strata et vemae metalliferae ducunt, aerem, mutatis temporum vicibus, modo purum, modo vitiatum, terrae superficiem humo plantisque paulatim obtectam, fluminum inundantium impetu denuo nudatam, iterumque siccatam et gramine vestitam commemorat. Igitur Historia zoolopgica, Historia plantarum et Historia oryctologica, quae non nisi pristinum orbis terrae statum indicant, a Geognosia probe distinguendae." -- Humboldt, 'Flora Friburgensis Subterranea, cui accedunt Aphorismi ex Physiologia Chemica Plantarum', 1793, p. ix.-x. Respecting the "spontaneous motion." which is referred to in a subsequent part of the text, see the remarkable passage in Aristotle, 'De Coelo,' ii., 2, p. 284, Bekker, where the distinction between animate and inanimate bodies is made to depend on the internal or external position of the seat of the determining motion. "No movement," says the Stagirite, "proceeds from the vegetable spirit, because plants are buried in a still sleep, from which nothing can arouse them" (Aristotle, 'De Generat. Animal.', v. i., p. 778, Bekker); and again, "because plants have no desires which incite them to spontaneous motion." (Arist., 'De Somno et Vigil'., cap. i., p. 455, Bekker.) It must, however, be remembered, that the inorganic crust of the Earth contains within it the same elements that enter into the structure of animal and vegetable organs. A physical cosmography would therefore be incomplete p 341 if it were to omit a consideration of these forces, and of the substances which enter into solid and fluid combinations in organic tissues, under conditiions which, from our ignorance of their actual nature, we designate by the vague term of 'vital forces', and group into various systems in accordance with more or less perfectly conceived analogies. The natural tendency of the human mind involuntarily prompts us to follow the physical phenomena of the Earth, through all their varied series, until we reach the final stage of the morphological evolution of vegetable forms, and the self-determining powers of motion in animal organisms. And it is by these links that 'the geography of organic beings -- of plants and animals' -- is connected with the delineation of the inorganic phenomena of our terrestrial globe. Without entering on the difficult question of 'spontaneous motion', or, in other words, on the difference between vegetable and animal life, we would remark, that if nature had endowed us with microscopic powers of vision, and the integuments of plants had been rendered perfectly transparent to our eyes, the vegetable world would present a very different aspect from the apparent immobility and repose in which it is now manifested to our senses. The interior portion of the cellular structure of their organs is incessantly animated by the most varied currents, either rotating, ascending and descending, remifying, and ever changing their direction, as manifested in the motion of the granular mucus of marine plants (Naiades, Characeae, Hydrocharidae), and in the hairs of phanerogamic land plants; in the molecular motion first discovered by the illustrious botanist Robert Brown, and which may be traced in the ultimate portions of every molecule of matter, even when separated from the organ; in the gyratory currents of the globules of cambium ('cyclosis') circulating in their peculiar vessels; and, finally, in the singularly articulated self-unrolling filamentous vessels in the antheridia of the chara, and in the reproductive organs of liverworts and algae, in the structural conditions of which Meyen, unhappily too early lost to science, believed that he recognized an analogy with the spermatozoa of the animal kingdom.* [footnote] *["In certain parts, probably, of all plants, are found peculiar spiral filaments, having a striking resemblance to the spermatozoa of animals. They have been long known in the organs called the antheridia of mosses, Hepaticcae, and Characeae, and have more recently been discovered in peculiar cells on the germinal frond of ferns, and on the very young leaves of the buds of Phanerogamia. They are found in peculiar cells, and when these are placed in water they are torn by the filament, which commences an active spiral motion. The signification of these organs is at present quite unknown; they appear, from the researches of N��geli, to resemble the cell mucilage, or proto-plasma, in composition, and are developed from it. Schleiden regards them as mere mucilaginous deposits, similar to those connected with the circulation in cells, and he contends that the movement of these bodies in water is analogous to the molecular motion of small particles of organic and inorganic substances, and depends on mechanical causes." -- 'Outlines of Structural and Physiological Botany', by A. Henfrey, F.L.S., etc., 1846, p. 23.] -- Tr. If to these p 342 manifold currents and gyratory movements we add the phenomena of endosmosis, nutrition, and growth, we shall have some idea of those forces which are ever active amid the apparent repose of vegetable life. Since I attempted in a former work, 'Ansichten der Natur' (Views of Nature), to delineate the universal diffusion of life over the whole surface of the Earth, in the distribution of organic forms, both with respect to elevation and depth, our knowledge of this branch of science has been most remarkably increased by Ehrenberg's brilliant discovery "on microscopic life in the ocean, and in the ice of the polar regions" -- a discovery based, not on deductive conclusions, but on direct observation. The sphere of vitality, we might almost say, the horizon of life, has been expanded before our eyes. "Not only in the polar regions is there an uninterrupted development of active microscopic life, where larger animals can no longer exist, but we find that the microscopic animals collected in the Antarctic expedition of Captain James Ross exhibit a remarkable abundance of unknown and often most beautiful forms. Even in the residuum obtained from the melted ice, swimming about in round fragments in the latitude of 70 degrees 10', there were found upward of fifty species of silicious-shelled Polygastria and Coscinodiscae with their green ovaries, and therefore living and able to resist the extreme severity of the cold. In the Gulf of Erebus, sixty-eight silicious-shelled Polygastria and Phytolitharia, and only one calcareous-shelled Polythalamia, were brought up by lead sunk to a depth of from 1242 to 1620 feet." The greater number of the oceanic microscopic forms hitherto discovered have been silicious-shelled, although the analysis of sea water does not yield silica as the main constituent, and it can only be imagined to exist in it in a state of suspension. It is not only at particular points in inland seas, or in the vicinity of the land, that the ocean is densely inhabited by living atoms, invisible to the naked eye, but samples of p 343 water taken up by Schayer on his return from Van Diemen's Land (south of the Cape of Good Hope, in 57 degrees latitude, and under the tropics in the Atlantic) show that the ocean in its ordinary condition, without any apparent discoloration, contains numerous microscopic moving organisms, which bear no resemblance to the swimming fragmentary silicious filaments of the genus Chaetoceros, similar to the Oscillatoriae so common in our fresh waters. Some few Polygastria, which have been found mixed with sand and excrements of penguins in Cockburn Island, appear to be spread over the whole earth, while others seem to be peculiar to the polar regions.* [footnote] *See Ehrenberg's treatise 'Ueber das kleinste Leben im Ocean', read before the Academy of Science at Berlin on the 9th of May, 1844. [Dr. J. Hooker found Diatomaceae in countless numbers between the parallels of 70 degrees and 80 degrees south, where they gave a color to the sea, and also the icebergs floating in it. The death of these bodies in the South Arctic Ocean is producing a submarine deposit, consisting entirely of the silicious particles of which the skeletons of these vegetables are composed. This deposit exists on the shores of Victoria Land and at the base of the volcanic mountain Erebus. Dr. Hooker accounted for the fact that the skeletons of Diatomaceae had been found in the lava of volcanic mountains, by referring to these deposits at Mount Erebus, which lie in such a position as to render it quite possible that the skeletons of these vegetables should pass into the lower fissures of the mountain, and then passing into the stream of lava, be thrown out, unacted upon by the heat to which they have been exposed. See Dr. Hooker's Paper, read before the British Association at Oxford, July, 1847.] -- Tr. We thus find from the most recent observations that animal life predominates amid the eternal night of the depths of ocean, while vegetable life, which is so dependent on the periodic action of the solar rays, is most prevalent on continents. The mass of vegetation on the Earth very far exceeds that of animal organisms; for what is the volume of all the large living Cetacea and Pachydermata when compared with the thickly-crosded colossal trunks of trees, of from eight to twelve feet in diameter, which fill the vast forests covering the tropical region of South America, between the Orinoco, the Amazon, and the Rio de Madeira? And although the character of different portions of the earth depends on the combination of external phenomena, as the outlines of mountains -- the physiognomy of plants and animals -- the azure of the sky -- the forms of the clouds -- and the transparency of the atmosphere -- it must still be admitted that the vegetable mantle with which the earth is decked constitutes the main feature of the picture. Animal forms are inferior in mass, and their powers of motion often withdraw them from our sight. The p 344 vegetable kingdom, on the contrary, acts upon our imagination by its continued presence and by the magnitude of its forms; for the size of a tree indicates its age, and here alone age is associated with the expression of a constantly renewed vigor.* [footnote] *Humboldt, 'Ansichten der Natur' (2te Ausgabe, 1826), bd. ii. s. 21. In the animal kingdom (and this knowledge is also the result of Ehrenberg's discoveries), the form which we term microscopic occupy the largest space, in consequence of their rapid propagation.* [footnote] *On multiplication by spontaneous division of the mother-corpuscle and intercalation of new substance, see Ehrenberg 'Van den jetzt lebenden Thierarten der Kreidebildung', in the 'Abhandl. der Berliner Akad. der Wiss.', 1839, s. 94. The most powerful productive faculty in nature is that manifested in the Vorticellae. Estimations of the greatest possible development of masses will be found in Chrenberg's great work 'Die Infusionsthierchen als volkommne Organismen', 1838, s. xiii., xix., and 244. "The Milky Way of these organisms comprises the genera Monas, Vibrio, Bacterium, and Bodo." The universality of life is so profusely distributed throughout the whole of nature, that the smaller Infusoria live as parasites on the larger, and are themselves inhabited by others, s. 194, 211, and 512. The minutest of the Infusoria, the Monadidae, have a diameter which does not exceed 1/3000th of a line, and yet these silicious-shelled organisms form in humid districts subterranean strata of many fathoms in depth. The strong and beneficial influence exercised on the feelings of mankind by the consideration of the diffusion of life, throughout the realms of nature is common to every zone, but the impression thus produced is most powerful in the equatorial regions, in the land of palms, bamboos, and arborescent ferns, where the ground rises from the shore of seas rich in mollusca and corals to the limits of perpetual snow. The local distribution of plants embraces almost all heights and all depths. Organic forms not only descend into the interior of the earth, where the industry of the miner has laid open extensive excavations and sprung deep shafts, but I have also found snow-white stalactiitic columns encircled by the delicate web of an Usnea, in caves where meteoric water could alone penetrate through fissures. Podurellae penetrate into the icy crevices of the glaciers on Mount Rosa, the Grindelwald, and the Upper Aar; the Chionaea nivalis (formerly known as Protococcus), exist in the polar snow as well as in that of our high mountains. The redness assumed by the snow after lying on the ground for soome time was known to Aristotle, and was probably observed by him on the mountains of Macedonia.* [footnote] *Aristot., 'Hist. Animal.', v. xix., p. 552, Bekk. p 345 While, on the loftiest summits of the Alps, only Lecideae, Parmeliae, and Umbilicariae cast their colored but scanty covering over the rocks, exposed by the melted snow, beautiful phanerogamic plants, as the Culcitium rufescens, Sida pinchinchensis, and Saxifraga Boussingaulti, are still found to flourish in the tropical region of the chain of the Andes, at an elevation of more than 15,000 feet. Thermal springs contain small insects (Hydroporus thermalis), Gallionellae, Oscillatoria and Confervae, while their waters bathe the root-fibers of phanerogamic plants. As air and water are aniimated at different temperatures by the presence of vital organisms, so likewise is the interior of the different portions of animal bodies. Animalcules have been found in the blood of the frog and the salmon; according to Nordmann, the fluids in the eyes of fishes are often filled with a worm that lives by suction (Diplostomum), while in the gills of the bleak the same observer has discovered a remarkable double aniimalcule (Diplozoon paradoxum), having a cross-shaped form with two heads and two caudal extremities. Although the existence of meteoric Infusoria is more than doubtful, it can not be denied that, in the same manner as the pollen of the flowers of the pine is observed every year to fall from the atmosphere, minute infusorial animalcules may likewise be retained for a time in the strata of the air, after having been passively borne up by currents of aqueous vapor.* [footnote] *Ehrenberg, op. cit., s. xiv., p. 122 and 403. The rapid multiplication of microscopic organisms is, in the case of some (as, for instance, in wheat-eels, wheel-animals, and water-bears or tardigrade animalcules), accompanied by a remarkable tenacity of life. They have been seen to come to life from a state of apparent death after being dried for twenty-eight days in a vacuum with chloride of line and sulphuric acid, and after being exposed to a heat of 248 degrees. See the beautiful experiments of Doyere, in 'Mem. sur les Tardigrades et sur leur propriete de revenir a la vie', 1842, p. 119, 129, 131, 133. Compare, also, Ehrenberg, s. 492-496, on the revival of animalcules that had been dried during a space of many years. This circumstance merits serious attention in reconsidering the old discussion respecting 'spontaneous generation',* and the p 346 more so, as Ehrenberg, as I have already remarked, has discovered that the nebulous dust or sand which mariners often encounter in the vicinity of the Cape Verd Islands, and even at a distance of 380 geographical miles from the African shore, contains the remains of eighteen species of silicious-shelled polygastric animalcules. [footnote] *On the supposed "primitive transformation" of organized or unorganized matter into plants and animals, see Ehrenberg, in Poggendorf's 'Annalen der Physik', bd. xxiv., s. 1-48, and also his 'Infusionsthierchen', s. 121, 525, and Joh. Muller, 'Physiologie des Menschen' (4te Aufl., 1844), bd. i., s. 8-17. It appears to me worthy of notice that one of the early fathers of the Church, St. Augustine, in treating of the question how islands may have been covered with new animals and plants after the flood, shows himself in no way disinclined to adope the view of the so-called "spontaneous generation" ('generatio aequivoca, spontanea aut primaria'). "If," says he, "animals have not been brought to remote islands by angels, or perhaps by inhabitants of continents addicted to the chase, they must have been spontaneously produced upon the earth; although here the question certainly arises, to what purpose, then, were animals of all kinds assembled in the ark?" "Si e terra exort" sunt (bestiae) secundum originem primam, quando dixit Deus" 'Producat terra animam vivam!' multo clarius apparet, non tam reparandorum animalium causa, quam figurandarum variarum gentium (?) propter ecclesiae sacramentumin arca fuisse omnia genera, si in insulis quo transire non possent, multa animalia terra produxit." Augustinus, 'De Civitate Dei', lib. xvi., cap. 7: 'Opera, ed. Monach. Ordinis S. Benedicti', t. vii., Venet., 1732, p. 422. Two centuries before the tiime of the Bishop of Hippo, we find, by extracts from Trogus Pompeius, that the 'generatio primaria' was brought forward in connection with the earliest drying up of the ancient world, and of the high table-land of Asia, precisely in the same manner as the terraces of Paradise, in the theory of the great Linnaeus, and in the visionary hypotheses entertained in the eighteenth century regarding the fabled Atlantis: "Quod si omnes quondam terrae submersae profundo fuerunt, profecto editissilimam quamque partem decurrentibus aquis primum detectam; humillimo autem solo eandem aquam diutissime immoratam, et quanto prior quaeque pars terrarum siccata sit, tanto prius animalia generare coepisse. Porro Scythiam adeo editiorem omnibus terris esse ut cuncta flumina ibi nata in Maeotium, tum deinde in Ponticum et Aegyptium mare decurrant." -- Justinus, lib. ii., cap. 1. The erroneous supposition that the land of Scythia is an elevated table-land, is so ancient that we meet with it most clearly expressed in Hippocrates, 'De Aere et Aquis', cap. 6, 96, Coray. "Scythia," says he, "coonsists of high and naked plains, which, without being crowned with mountains, ascend higher and higher toward the north." Vital organisms, whose relations in space are comprised under the head of the geography of plants and animals, may be considered either according to the difference and relative numbers of the types (their arrangement into genera and species), or according to the number of individuals of each species on a given area. In the mode of life of plants as in that of animals, an important difference is noticed; they either exist in an isolated state, or live in a social condition. Those species of plants which I have termed 'social'* uniformly cover vast extents of land. [footnote] *Humboldt, 'Aphorismi ex Physiologia Chemica Plantarum', in the 'Flora Fribergensis Subterranea', 1793, p. 178. Among these we may reckon many of the marine Algae -- Cladoniae and mosses, which extend over the desert steppes of Northern Asia -- grasses, and cacti growing p 347 together like the pipes of an organ -- Avicennim and mangroves in the tropics -- and forests of Coniferae and of birches in the plains of the Baltic and in Siberia. This mode of geographical distribution determines, together with the individual form of the vegetable world, the size and type of leaves and flowers, in fact, the principal physiognomy of the district,* its characteracter being but little, if at all, influenced by the ever-moving forms of animal life, which, by their beauty and diversity, so powerfully affect the feelings of man, whether by exciting the sensations of admiration or horror. [footnote] *On the physiognomy of plants, see Humboldt, 'Anischten der Natur', bd. ii., s. 1-125. Agricultural nations increase artificially the predominance of social plants, and thus augment, in many parts of the temperate and northern zones, the natural aspect of uniformity; and while their labors tend to the extirpation of some wild plants, they likewise lead to the cultivation of others, which follow the colonist in his most distant migration. The luxuriant zone of the tropics offers the strongest resistance to these changes in the natural distribution of vegetable forms. Observers who in short periods of time have passed over vast tracts of land, and ascended lofty mountains, in which climates were ranged, as it were in strata one above another, must have been early impressed by the regularity with which vegetable forms are distributed. The results yielded by their observations furnished the rough materials for a science, to which no name had as yet been given. The same zones of regions of vegetation which, in the sixteenth century, Cardinal Bembo, when a youth,*described on the declivity of Aetna, were observed on Mount Ararat by Tournefort. [footnote] *Aetna Dialogus.' 'Opuscula', Basil., 1556, p. 53, 54. A very beautiful geography of the plants of Mount AEtna has recently been published by Philippi. See 'Linnaea', 1832, s. 733. He ingeniously compared the Alpine flora with the flora of plains situated in different latitudes, and was the first to observe the influence exercised in mountainous regions, on the distribution of plants by the elevation of the ground above the level of the sea, and by the distance from the poles in flat countries. Menzel, in an inedited work on the flora of Japan, accidentally made use of the term 'geography of plants'; and the same expression occurs in the fanciful but graceful work of Bernardin de St. Pierre, 'Etudes de la Nature'. A scientific treatment of the subject began, however, only when the geography of plants was intimately associated with the study of the distribution p 348 of heat over the surface of the earth, and when the arrangement of vegetable forms in natural families admitted of a numerical estimate being made of the different forms which increase of decrease as we recede from the equator toward the poles, and of the relations in which, in diffrent parts of the earth, each family stood with reference to the whole mass of phanerogamic indigenous plants of the same region. I consider it a happy circumstance that, at the time during which I devoted my attention almost exclusively to botanical pursuits, I was led by the aspect of the grand and strongly characterized features of tropical scenery to direct my investigations toward these subjects. The study of the geographical distribution of animals, regarding which Buffon first advanced general, and, in most instances, very correct views, has been considerably aided in its advance by the progress made in modern times in the geography of plants. The curves of the isothermal lines, and more especially those of the isochimenal lines, correspond with the limits which are seldom passed by certain species of plants, and of animals which do not wander far from their fixed habitation either with respect to elevation or latitude.* [footnote] *[The following valuable remarks by Professor Forbes, on the correspondence existing between the distribution of existing faunas and floras of the British Islands, and the geological changes that have affected their area, will be read with much interest; they have been copied, by the author's permission, from the 'Survey Report', p. 16: "If the view I have put forward respecting the origin of the flora of the British mountains be true -- and every geological and botanical probability, so far as the are is concerned, favors it -- then must we endeavour to find some more plausible cause than any yet shown for the presence of numerous species of plants, and of some animals, on the higher parts of Alpine ranges in Europe and Asia, specifically identical with animals and plants indigenous in the regions very far north, and not found in the intermediate lowlands. Tournefort first remarked and Humboldt, the great organizer of the science of natural history geography, demonstrated, that zones of elevation on mountains correspond to parallels of latitude, the higher with the more northern or southern, as the case might be. It is well known that this correspondence is recognized in the general 'facies' of the flora and fauna, dependent on generic identities. But when announcing and illustrating the law that climatal zones of animal and vegetable life are mutually repeated or represented by elevation and latitude, naturalists have not hitherto sufficiently (if at all) distinguished between the evidence of that law, as exhibited by 'representative species' and by 'identical'. In reality, the former essentially depend on the law, the latter being an 'accident' not necessarily dependent upon it, and which has hitherto not been accounted for. In the case of the Alpine flora of Britain, the evidence of the activity of the law, and the influence of the accident, are inseparable, the law being maintained by a transported flora, for the transmission of which I have shown we can not account by an appeal to unquestionable geological events. In the case of the Alps and Carpathians, and some other mountain ranges, we find the law maintained partly by a representative flora, special in its region, i.e., by specific centers of their own, and partly by an assemblage more or less limited in the several ranges of identical species, these latter in several cases so numerous that ordinary modes of transportation now in action can no more account for their presence than they can for the presence of a Norwegian flora on the British mountains. Now I am prepared to maintain that the same means which introduced a sub-Arctic (now mmountain) flora into Britain, acting at the same epoch, originated the identity, as far as it goes, of the Alpine floras of middle Europe and Central Asia; for, now that we know the vast area swept by the glacial sea, including almost the whole of Central and Northern Europe, and belted by land, since greatly uplifted, which then presented to the water's edge those climatal lconditions for which a sub-Arctic flora -- destined to become Alpine -- was specially organized, the difficulty of deriving such a flora from its paarent north, and of diffusing it over the snowy hills bounding this glacial ocean, vanishes, and the presence of identical species at such distant pooints remain no longer a mystery. Moreover, when we consider that conditions during the epoch referred to, the undoubted evidences of Continental observers, on the boounds of Asia by Sir Roderick Murchison, in America by Mr. Lyell, Mr. Logan, Captain Bayfield, and others, and that the botanical (and zoological as well) region, essentially northern and Alpine, designated by Professor Schouw that 'of saxifrages and mosses,' and first in his classification, exists now only on the flanks of the great area which suffered such conditions; and that, though similar conditions reappear, the relationship of Alpine and Arctic vegetation in the southern hemisphere, with that in the northern, is entirely maintained by 'representative', and not by identical species (the general truth of my explanation of Alpine floras, including identical species, becomes so strong, that the view proposed acquires fair claims to be ranked as a theory, and not considered merely a convenient or bold hypothesis."] -- Tr. The p 349 elk, for instance, lives in the Scandinavian peninsula, almost ten degrees further north than in the interior of Siberia, where the line of equal winter temperature is so remarkably concave. Plants migrate in the germ; and, in the case of many species, the seeds are furnished with organs adapting them to be conveyed to a distace through the air. When once they have taken root, they become dependent on the soil and on the strata of air surrounding them. Animals, on the contrary, can at pleasure migrate from the equator toward the poles; and this they can more especially doo where the isothermal lines are much inflected, and where hot summers succeed a great degree of winter cold. The royal tiger, which in no respect differs from the Bengal species, penetrates every summer into p 350 the north of Asia as far as the latitudes of Berlin and Hamburg, a fact of which Ehrenberg and myself have spoken in other works.* [footnote] *Ehrenberg, in the 'Annales des Sciences Naturelles', t. xxi., p. 387, 412; Humboldt, 'Asie Centrale', t. i., p. 339-342, and t. iii., p. 96-101. The grouping or association of diffrent vegetable species, to which we are accustomed to apply the term 'Floras', do not appear to me, from what I have observed in different portions of the earth's surface, to manifest such a predominance of individual families as to justify us in marking the geographical distinctions between the regions of the Umbellatae, of the Solidaginae, of the Labiatae, or the Scitamineae. With reference to this subject, my views differ from those of several of my friends, who rank among the most distinguished of the botanists of Germany. The character of the floras of the elevated plateaux of Mexico, New Granada, and Quito, of European Russia, and of Northern Asia, consists, in my opinion, not so much in the relatively larger number of the species presented by one or two natural families, as in the more complicated relations of the coexistence of many families, and in the relative numerical value of their species. The Gramineae and the Cyperaceae undoubtedly predominate in meadow lands and stppes, as do Coniferae, Cupuliferae, and Betulineae in our northern woods; but this predominance of certain forms is only apparent, and owing to the aspect imparted by the social plants. The north of Europe, and that portion of Siberia which is situated to the north of the Altai Mountains, have no greater right to the appellation of a region of Gramineae and Coniferae than have the boundless llanos between the Orinoco and the mountain chain of Caraccas, or the pine forests of Mexico. It is the coexistence of forms which may partially replace each other, and their relative numbers and association, which give rise either to the general impression of luxuriance and diversity, or of poverty and uniformity in the contemplation of the vegetable world. In this fragmentary sketch of the phenomena of organization, I have ascended from the simplest cellI -- the first manifestation of life -- progressively to higher structures. "The p 351 association of mucous granules constitutes a definitely-formed cytoblase, around which a vesicular membrane forms ia closed well," this cell being either produced from another pre-existing cell,** or being due to a cellular formation, which, as in the case of the fermentation-fungus, is concealed in the obscurity of some unknown chemical process.*** [footnote] *Schleiden, 'Ueber die Entwicklungsweise der Pflanzenzellen', in Muller's 'Archiv fur Anatomie und Physiologie', 1838, s. 137-176; also his 'Grundzuge der wissenschaftlichen Botanik', th. i., s. 191, and th. ii., s 11. Schwann, 'Mikroscopische Untersucungen uber die Uebereinstimmung in der Struktur und dem Wachsthum der Thiere und Pflanzen', 1839, s. 45, 220. Compare also, on similar propagation, Joh. Muller 'Physiologie des Menschen', 1840, th. ii., s. 614. [footnote] **Schleiden, 'Grundzuge der wissenschaftlichen Botanik', 1842, th. i., s. 192-197. [footnote] ***[On cellular formation, see Henfrey's 'Outlines of Structural and Physiological Botany', op. cit., p. 16-22.] -- Tr. But in a work like the present we can venture on no more than an allusion to the mysteries that involve the question of modes of origin; the geography of animal and vegetable organisms must limit itself to the consideration of germs already developed, of their haabitation and transplantation, either by voluntary or involuntary migrations, their numerical relation, and their distribution over the surface of the earth. The general picture of nature which I have endeavored to delineate would be incomplete if I did not venture to trace a few of the most marked features of the human race, considered with reference to physical gradations -- to the geographical distribution of contemporaneous types -- to the influence exercised upon man by the forces of nature, and the reciprocal, although weaker action which he in his turn exercises on these natural forces. Dependent, although in a lesser degree than plants and animals, on the soil, and on the meteorological processes of the atmosphere with which he is surroounded -- escaping more readily from the control of natural forces, by activity of mind and the advance of intellectual cultivation, no less than by his wonderful capacity of adapting himself to all climates -- man every where becomes most essentially associated with terrestrial life. It is by these relations that the obscure and much-contested problem of the possibility of one common descent enters into the sphere embraced by a general physical cosmography. The investigation of this problem will impart a nobler, and, if I may so express myself, more purely human interest to the closing pages of this section of my work. The vast domain of language, in whose varied structure we see mysteriously reflected the destinies of nations, is most intimately associated with the affinity of races; and what even slight differences of races may effect is strikingly manifested in the history of the Hellenic nations in the zenith of their intellectual cultivation. The most important questions of the civilization of mankind are connected with the ideas of races, p 352 community of language, and adherence to one original direction of the intellectual and moral faculties. As long as attention was directed solely to the extremes in varieties of color and of form, and to the vividness of the first impression of the senses, the observer was naturally disposed to regard races rather as originally different species than as mere varieties. The permanence of certain types* in the midst of the most hostile influences, especially of climate, appeared to favor such a view, notwithstanding the shortness of the interval of time from which the historical evidence was derived. [footnote] *Tacitus, in his speculations on the inhabitants of Britain ('Agricola', cap. ii.), distinguishes with much judgment between that which may be owing to the local climatic relations, and that which, in the immigrating races, may be owing to the unchangeable influence of a hereditary and transmitted type. "Britanniam qui mortales initio coluerunt, indigenae an advecti, ut inter barbaros, parum coompertum. Habitus corporis varii, alque ex eo argumenta; namque rutilae Caledoniam habitantium comae, magni artus Germanicam originem adseverant. Silu ram colorati vultus et torti plerumque crines, et posita contra Hispania, Iberos veteres trajecisse, easque cedes occupasse fidem faciunt: proximi Gallis, et similes sunt: seu durante originis vi; seu procurrentibus in diversa terris, positio coeli corporibus habitum dedit." Regarding the persistency of types of conformation in the hot and cold regions of the earth, and in the mountainous districts of the New Continent, see my 'Relation Historique', t. i., p. 498, 503, and t. ii., p. 572, 574. In my opinion, however, more powerful reasons can be advanced in support of the theory of the unity of the human race, as, for instance, in the many intermediate gradations* in the color of the skin and in the form of the skull, which have been made known to us in recent times by the rapid progress of geographical knowledge -- the analogies presented by the varieties in the species of many wild and domesticated animals -- and the more correct observations collected regarding the limits of fecundity in hybrids.** [footnote] On the American races generally, see the magnificent work of Samuel George Morton, entitled 'Crania Americana', 1839, p. 62, 86; and on the skulls brought by Pentland from the highlands ot titicaca, see the 'Dublin Journal of Medical and Chemical Science', vol. v., 1834, p. 475; also Alcide d'Orbigny, 'L'homme Americain considere sous ses rapports Physiol. et Mor.', 1839, p. 221; and the work by Prince Maximilian of Wied, which is well worthy of notice for the admirable ethnographical remarks in which it abounds, entitled 'Reise in das Innere von Nordamerika' (1839). [footnote] ** Rudolph Wagner, 'Ueber Blendlinge und Bastarderzeugung', in his notes to the German translation of Prichard's 'Physical History of Mankind', vol. i., p. 138-150. The greater number of the contrasts which were formerly supposed to exist, have disappeared before the laborious researches of Tiedemann on the brain of negroes and of Europeans, and the anatomical investigations p 353 of Vrolik and Weber on the form of the pelvis. On comparing the dark-colored African nations, on whose physical history the admirable work of Prichard has thrown so much light, with the races inhabiting the islands of the South-Indian and West-Australian archipelago, and with the Papuas and Alfourous (Haroforas, Endamenes), we see that a black skin, woolly hair, and a negro-like cast of countenance are not necessarily connected together.* [footnote] *Prichard, op. cit., vol. ii., p. 324. So long as only a small portion of the earth was known to the Western nations, partial views necessarily predominated, and tropical heat and a black skin consequently appeared inseparable. "The Ethiopians," said the ancient tragic poet Theodectes of Phaselis,* "are colored by the near sun-god in his course with a sooty luster, and their hair is dried and crisped with the heat of his rays." [footnote] *Onesicritus, in Strabo, xv., p. 690, 695, Casaub. Welcker, 'Griechische Tragodien', abth. iii., s. 1078, conjectures that the verses of Theodectes, cited by Strabo, are taken from a list tragedy, which probably bore the title of "Memnon." The campaigns of Alexander, which gave rise to so many new ideas regarding physical geography, likewise first excited a discussion on the problematical influence of climate on races. "Families of animals and plants," writes one of the greatest anatomists of the day, Johannes Muller, in his noble and comprehensive work, 'Physiologie des Menschen', "undergo, within certain limitations peculiar to the different races and species, various modifications in their distribution over the surface of the earth, propagating these variations as organic types of species.* [footnote] *[In illustration of this, the conclusions of Professor Edward Forbes respecting the origin and diffusion of the British flora may be cited. See the 'Survey Memoir' already quoted, 'On the Connection between the Distribution of the existing Fauna and Flora of the British Islands, etc.', p. 64. "1. The flora and fauna, terrestrial and marine, of the British islands and seas, have originated, so far as that area is concerned, since the melocene epoch. 2. The assemblages of animals and plants compositing that fauna and flora did not appear in the area they now inhabit simultaneously, but at several distinct points in time. 3. Both the fauna and flora of the British islands and seas are composed partly of species which, either permanently or for a time, appeared in that area before the glacial epoch; partly of such as inhabited it during that epoch; and in great part of those which did not appear there until afterward, and whose appearance on the earth was coeval with the elevation of the bed of the glacial sea and the consequent climatal changes. 4. The greater part of the terrestrial animals and flowering plants now inhabiting the British islands are members of specific centers beyond their area, and have migrated to it over continuous land before, during, or after the glacial epoch. 5. The climatal conditions of the area under discussion, and north, east, and west of it, were severer during the glacial epoch, when a great part of the space now occupied by the British isles was under water, than they are now or were before; but there is good reason to believe that, so far from those conditions having continued severe, or having gradually diminished in severity southward of Britain, the cold region of the glacial epoch came directly into contact with a region of more southern and thermal character than that in which the most southern beds of glacial drift are now to be met with. 6. This state of things did not materially differ from that now existing, under corresponding latitudes, in the North American, Atlantic, and Arctic seas, and on their bounding shores. 7. The Alpine floras of Europe and Asia, so far as they are identical with the flora of the Arctic and sub-Arctic zones of the Old World, are fragments of a flora which was diffused from the north, either by means of transport not now in action on the temperate coasts of Europe, or over continuous land which no longer exists. The deep sea fauna is in like manner a fragment of the general glacial fauna. 8. The floras of the islands of the Atlantic region, between the Gulf-weed Bank and the Old World, are fragments of the Great Mediterranean flora, anciently diffused over a land consistuted out of the upheaval and never again subjerged bed of the (shallow) Meiocene Sea. This great flora, in the epoch anterior to, and probably, in part, during the glacial period, had a greater extension northward than it now presents. 9. The termination of the glacial epoch in Europe was marked by a recession of an Arctic fauna and flora northward, and of a fauna and flora of the Mediterranean type southward; and in the interspace thus produced there appeared on land the Germanic fauna and flora, and in the sea that fauna termed Celtic. 10. The causes which thus preceded the appearance of a new assemblage of organized beings were the destruction of many species of animals, and probably also of plants, either forms of extremely local distribution, or such as were not capable of enduring many changes of conditions -- species, in short, with very limited capacity for horizontal or vertical diffusion. 11. All the changes before, during, and after the glacial epoch appear to have been gradual, and not sudden, so that no marked line of demarkation can be drawn between the creatures inhabiting the same element and the same locality during two proximate periods."] -- Tr. The different races of mankind are forms of one sole species, by the union of two of whose members descendants are propagated. They are not different species of a genus, since in that case their hybrid descendants would remain unfruitful. But whether the human races have descended from several primitive races of men, or from one alone, is a question that can not be determined from experience."* [footnote] *Joh. Muller, 'Physiologie des Menschen', bd. ii., s. 768. Geographical investigations regarding the ancient 'seat', the so-called 'cradle of the human race', are not devoid of a mythical p 355 character. "We do not know," says Wilhelm von Humboldt, in an unpublished work 'On the Varieties of Languages and Nations', "either from history or from authentic tradition, any period of time in which the human race has not been divided into social groups. Whether the gregarious condition was original, or of subsequent occurrence, we have no historic evidence to show. The separate mythical relations found to exist independently of one another in different parts of the earth, appear to refute the first hypothesis, and concur in ascribing the generation of the whole human race to the union of one pair. The general prevalence of this myth has cause it to be regarded as a traditionary record transmitted from the primitive man to his descendants. But this very circumstance seems rather to prove that it has no historical foundation, but has simply arisen from an identity in the mode of intellectual conception, which has every where led man to adopt the same conclusion regarding identical phenomena; in the same manner as many myths have doubtlessly arisen, not from any historical connection existing between them, but rather from an identity in human thought and imagination. Another evidence in favor of the purely mythical nature of this belief is afforded by the fact that the first origin of mankind -- a phenomenon which is wholly beyond the sphere of experience -- is explained in perfect conformity with existing views, being considered on the principle of the colonization of some desert island or remote mountainous valley at a period when mankind had already existed for thousands of years. It is in vain that we direct our thoughts to the solution of the great problem of the first origin, since man is too intimately associated with his own race and with the relations of time to conceive of the existence of an individual independently of a preceding generation and age. A solution of those difficult questions, which can not be determined by inductive reasoning or by experience -- whether the belief in this presumed traditional condition be actually based on historical evidence, or whether mankind inhabited the earth in gregarious associations from the origin of the race -- can not, therefore, be determined from philological data, and yet its elucidation ought not to be sought from other sources." The distribution of mankind is therefore only a distribution into 'varieties', which are commonly designated by the somewhat indefinite term 'races'. As in the vegetable kingdom, and in the natural history of birds and fishes, a classification into many small families is based on a surer foundation than p 356 where large sections are separated into a few but large divisions; so it also appears to me, that in the determination of races a preference should be given to the establishment of small families of nations. Whether we adopt the old classification of my master, Blumenbach, and admit 'five' races (the Caucasian, Mongolian, American, Ethiopian, and Malayan), or that of Prichard, into 'seven races'* (the Iranian, Turanian, American, Hottentots and Bushmen, Negroes, Papuas, and Alfourons), we fail to recognize any typical sharpness of definition, or any general or well-established principle in the division of these groups. [footnote] *Prichard, op. cit., vol. i., p. 247. The extremes of form and color are certainly separated, but without regard to the races, which can not be included in any of these classes, and which have been alternately termed Scythian and Allophyllic. Iranian is certainly a less objectionable term for the European nations than Caucasian; but it may be maintained generally that geographical denominations are very vague when used to express the points of departure of races, more especially where the country which has given its name to the race, as, for instance, Turan (Mawerannahr), has been inhabited at different periods* by Indo-Germanic and Finnish, and not by Mongolian tribes. [footnote] *The late arrival of the Turkish and Mongolian tribes on the Oxus and on the Kirghis Steppes is opposed to the hypothesis of Niebuhr, according to which the Scythians of Herodotus and Hippocrates were Mongolians. It seems far more probable that the Scythians (Scoloti) should be referred to the Indo-Germanic Massagetae (Alani). The Mongolian, true Tartars (the latter term was afterward falsely given to purely Turkish tribes in Russia and Siberia), were settled, at that period, far in the eastern part of Asia. See my 'Asie Centrale', t. i., p. 239, 400; 'Examen Critique de l'Histoire de la Geogr.', th. ii., p. 320. A distinguished philologist, Professor Buschmann, calls attention to the circumstance that the poet Firdousi, in his half-mythical prefatory remarks in the 'Schahnameh', mentions "a fortress of the Alani" on the sea-shore, in which Selm took refuge, this prince being the eldest son of the King Feridun, who in all probability lived two hundred years before Cyrus. The Kirghis of the Scythian steppe were originally a Finnish tribe; their three hordes probably constitute in the present day the most numerous nomadic nation, and their tribe dwelt, in the sixteenth century, in the same steppe in which I have myself seen them. The Byzantine Menander (p. 380-382, ed. Nieb.) expressly states that the Chacan of the Turks (Thu-Khiu), in 569, made a present of a Kirghis slave to Zemarchus, the embassador of ustinish II.; he terms her a [Greek word]; and we find in Abulgasi ('Historia Mongolorum et Tatarorum') that the Kirghis are called Kirkiz. Similarity of manners, where the nature of the country determines the principal characteristics, is a very uncertain evidence of identity of race. The life of the steppes produces among the Turks (Ti Tukiu), the Baschkirs (Fins), the Kirghis, the Torgodi and Dsungari (Mongolians), the same habits of nomadic life, and the same use of felt tents, carried on wagons and pitched among herds of cattle. p 357 Languages, as intellectual creations of man, and as closely interwoven with the development of mind, are, independently of the 'national' form which they exhibit, of the greatest importance in the recognition of similarities or differences in races. This importance is especially owing to the clew which a community of descent affords in treading that mysterious labyrinth in which the connection of physical powers and intellectual forces manifests itself in a thousand different forms. The brilliant progress made within the last half century, in Germany, in philosophical philology, has greatly facilitated our investigations into the 'national' character* of languages and the influence exercised by descent. [footnote] *Wilhelm von Humboldt, 'Ueber die Verschiedenheit der menschlichen Sprachbaues', in his great work 'Ueber die Kawi-Sprache auf der Insel Java', bd. i., s. xxi., xlviii., and ccxiv. But here, as in all domains of ideal speculation, the dangers of deception are closely linked to the rich and certain profit to be derived. Positive ethnographical studies, based on a thorough knowledge of history, teach us that much caution should be applied in entering into these comparisons of nations, and of the languages employed by them at certain epochs. Subjection, long association, the influence of a foreign religion, the blending of races, even when only including a small number of the more influential and cultivated of the immigrating tribes, have produced, in both continents, similarly recurring phenomena; as, for instance, in introducing totally different families of languages among one and the same race, and idioms, having one common root, among nations of the most different origin. Great Asiatic conquerors have exercised the most powerful influence on phenomena of this kind. But language is a part and parcel of the history of the development of mind; and however happily the human intellect, under the most dissimilar physical conditions, may unfettered pursue a self-chosen track, and strive to free itself from the dominion of terrestrial influences, this emancipation is never perfect. There ever remains, in the natural capacities of the mind, a trace of something that has been derived from the influences of race or of climate, whether they be associated with a land gladdened by cloudless azure skies, or with the vapory atmosphere of an insular region. As, therefore, richness and grace of language are unfolded from the most luxuriant p 358 depths of thought, we have been unwilling wholly to disregard the bond which so closely links together the physical world with the sphere of intellect and of the feelings by depriving this general picture of nature of those brighter lights and tints which may be borrowed from considerations, however slightly indicated, of the relations existing between races and languages. While we maintain the unity of the human species, we at the same time repel the depressing assumption of superior and inferior races of men.* [footnote] *The very cheerless, and, in recent times, too often discussed doctrine of the unequal rights of men to freedom, and of slavery as an institution in conformity with nature, is unhappily found most systematically developed in Aristotle's 'Politica', i., 3, 5, 6. There are nations more susceptible of cultivation, more highly civilized, more enobled by mental cultivation than others, but none in themselves nobler than others. All are in like degree designed for freedom; a freedom which, in the ruder conditions of society, belongs only to the individual, but which, in social states enjoying political institutions, appertains as a right to the whole body of the community. "If we would indicate an idea which, throughout the whole course of history, has ever more and more widely extended its empire, or which, more than any other, testifies to the much-contested and still more decidedly misunderstood perfectibility of the whole human race, it is that of establishing our common humanity -- of striving to remove the barriers which prejudice and limited views of every kind have erected among men, and to treat all mankind, without reference to religion, nation, or color, as one fraternity, one great community, fitted for the attainment of one object, the unrestrained development of the physical powers. This is the ultimate and highest aim of society, identical with the direction implanted by nature in the mind of man toward the indefinite extension of his existence. He regards the earth in all its limits, and the heavens as far as his eye can scan their bright and starry depths, as inwardly his own, given to him as the objects of his contemplation, and as a field for the development of his energies. Even the child longs to pass the hills or the seas which inclose his narrow home; yet, when his eager steps have borne him beyond those limits, he pines, like the plant, for his native soil; and it is by this touching and beautiful attribute of man -- this longing for that which is unknown, and this fond remembrance of that which is lost -- that he is spared from an exclusive attachment to the present. p 359 Thus deeply rooted in the innermost nature of man, and even enjoined upon him by his highest tendencies, the recognition of the bond of humanity becomes one of the noblest leading principles in the history of mankind."* [footnote] *Wilhelm von Humboldt, 'Ueber die Kawi-Sprache', bd. iii., s. 426. I subjoin the following extract from this work: "The impetuous conquests of Alexander, the more politic and premeditated extension of territory made by the Romans, the wild and cruel incursions of the Mexicans, and the despotic acquisitions of the incas, have in both hemispheres contributed to put an end to the separate existence of many tribes as independent nations, and tended at the same time to establish more extended international amalgamation. Men of great and strong minds, as well as whole nations, acted under the influence of one idea, the purity of which was, however, utterly unknown to them. It was Christianity which first promulgated the truth of its exalted charity, although the seed sown yielded but a slow and scanty harvest. Before the religion of Christ manifested its form, its existence was only revealed by a faint foreshadowing presentiment. In recent times, the idea of civilization has acquired additional intensity, and has given rise to a desire of extending more widely the relations of national intercourse and of intellectual cultivation; even selfishness begins to learn that by such a course its interests will be better served than by violent and forced isolation. Language more than any other attribute of mankind, binds together the whole human race. By its idiomatic properties it certainly seems to separate nations, but the reciprocal understanding of foreign languages connects men together on the other hand without injuring individual national characteristics." With these words, which draw their charm from the depths of feeling, let a brother be permitted to close this general description of the natural phenomena of the universe. From the remotest nebulae and from the revolving double stars, we have descended to the minutest organisms of animal creation, whether manifested in the depths of ocean or on the surface of our globe, and to the delicate vegetable germs which clothe the naked declivity of the ice-crowned mountain summit; and here we have been able to arrange these phenomena according to partially known laws; but other laws of a more mysterious nature rule the higher spheres of the organic world, in which is comprised the human species in all its varied conformation, its creative intellectual power, and the languages to which it has given existence. A physical delineation of nature terminates at the point where the sphere of intellect begins, and a new world of mind is opened to our view. It marks the limit, but does not pass it. p 360 is blank p 361 ADDITIONAL NOTES TO THE PRESENT EDITION. MARCH, 1849. __________ GIGANTIC BIRDS OF NEW ZEALAND. -- Vol. i., p. 287. An extensive and highly interesting collection of bones, referrible to several species of the 'Moa' (Dinornis of Owen), and to three or four other genera of birds, formed by Mr. Walter Mantell, of Wellington, New Zealand, has recently arrived in England, and is now deposited in the British Museum. This series consists of between 700 and 800 speciments, belonging to different parts of the skeletons of many individuals of various sizes and ages. Some of the largest vertebrae, tibiae, and femora equal in magnitude the most gigantic previously known, while others are not larger than the corresponding bones of the living apteryx. Among these relics are the 'skulls' and 'mandibles' of two genera, the 'Dinornis' and 'Palapteryx'; and of an extinct genus, 'Notornis', allied to the 'Rallidae'; and the mandibles of a species of 'Nestor', a genus of nocturnal owl-like parrots, of which only two living species are known.* [footnote] *See Professor Owen's Memoir on these fossil remains, in 'Zoological Transactions', 1848. These osseous remains are in a very different state of preservation from any previously received from New Zealand; they are light and porous, and of a light fawn-color; the most delicate processes are entire, and the articulating surfaces smooth and uninjured; 'fragments of egg-shells', and even the bony rings of the trachea and air tubes, are preserved'. The bones were dug up by Mr. Walter Mantell from a bed of marly sand, containing magnetic iron, crystals of hornblende and augite, and the detritus of augitic rocks and earthy volcanic tuff. The sand had filled up all the cavities and cancelli, but was in no instance consolidated or aggregated together; it was, therefore, easily removed by a soft brush, and the bones perfectly cleared without injury. The spot whence these precious relics of the colossal birds that once inhabited the islands of New Zealand were obtained, is a flat tract of land, near the embouchure of a river, named Waingongoro, not far from Wanganui, which has its rise in the volcanic regions of Mount Egmont. The natives affirm that this level tract was one of the places first dwelt upon by their remote ancestors; and this tradition is corroborated by the existence of numerous heaps and pits of ashes and charred bones indicating ancient fires, long burning on the same spot. In these fire-heaps Mr. Mantell found burned bones of 'men, moas', and 'dogs'. The fragments of egg-shells, imbedded in the ossiferous deposits, had escaped the notice of all previous naturalists. They are, unfortunately, very small portions, the largest being only four inches long, but they afford a chord by which to estimate the size of the original. Mr. Mantell observes that the egg of the Moa must have been so large that a hat would form a good egg-cup for it. These relics evidently belong to two or more species, perhaps genera. In some examples the external p 362 surface is smooth; in others it is marked with short intercepted linear grooves, resembling the eggs of some of the Struthiouidae, but distinct from all known recent types. In this valuable collection only one bone of a mammal has been detected, namely, 'the femur of a dog'. An interesting memoir on the probable geological position and age of the ornithic bone deposits of New Zealand, by Dr. Mantell, based on the observations of his enterprising son, it published in the Quarterly Journal of the Geological Society of London (1848). It appears that in many instances the bones are imbedded in sand and clay, which lie beneath a thick deposit of volcanic detritus, and rest on an argillaceous stratum abounding in marine shells. The specimens found in the rivers and streams have been washed out of their banks by the currents which now flow through channels from ten to thirty feet deep, formed in the more ancient alluvial soil. Dr. Mantell concludes that the islands of New Zealand were densely peopled at a period geologically recent, though historically remote, by tribes of gigantic brevi-pennate birds allied to the ostrich tribe, all, or almost all, of species and genera now extinct; and that, subsequently to the formation of the most ancient ornithic deposit, the sea-coast has been elevated from fifty to one hundred feet above its original level; hence the terraces of shingle and loam which now skirt the maritime districts. The existing rivers and mountain torrents flow in deep gulleys which they have eroded in the course of centuries in these pleistocene strata, in like manner as the river courses of Auvergne, in Central France, are excavated in the mammiferous tertiary deposits of that country. The last of the gigantic birds were probably exterminated, like the dodo, by human agency: some small species allied to the apteryx may possibly be met with in the unexplored parts of the middle island. THE DODO. -- A most valuable and highly interesting history of the dodo and its kindred* has recently appeared in which the history, affinities, and osteology of the 'Dodo, Solitaire', and other extinct birds of the islands Mauritius, Rodriguez, and Bourbon are admirably elucidated by H. G. Strickland (of Oxford), and Dr. G. A. Melville. [footnote] *'The Dodo and its Kindred'. By Messrs. Strickland and Melville. 1 vol. 4to. with numerous plates. Reeves, London, 1848. The historical part is by the former, the osteological and physiological portion by the latter eminent anatomist. We would earnestly recommend the reader interested in the most perfect history that has ever appeared, of the extinction of a race of large animals, of which thousands existed but three centuries ago, to refer to the original work. We have only space enough to state that the authors have proved, upon the most incontrovertible evidence, that the dodo was neither a vulture, ostrich, nor galline, as previously anatomists supposed, but a 'frugiverous pigeon'. This section from pp 363-379 of: COSMOS: A Sketch of the Physical Description of the Universe, Vol. 1 by Alexander von Humboldt Translated by E C Otte from the 1858 Harper & Brothers edition of Cosmos, volume 1 -------------------------------------------------- p 363 INDEX TO VOL. I. ------------------- ABICH, Hermana, structural relations of volcanic rocks, 234. Acosta, Joseph de, Historia Natural de las Indias, 66, 193. Adams, Mr., planet Neptune. See note by Translator, 90, 91. Aegos Potamos, on the aerolite of, 117, 122. Aelian on Mount Aetna, 227. Aerolites (shooting stars, meteors, meteoric stones, fire-balls, etc), general description of, 111-137; physical character, 112-123; dates of remarkable falls, 114, 115; their planetary velocity, 116-120; ideas of the ancients on, 115, 116; November and August periodic falls of shooting stars, 118-120, 124-126; their direction from one point in the heavens, 120; altitude, 120; orbit, 127; Chinese notices of, 128; media of communication with other planetary bodies, 136; their essential difference from comets, 137; specific weights, 116, 117; large meteoric stones on record, 117; chemical elements, 117, 129-131; crust, 129, 130; deaths occasioned by, 135. Aeschylus, "Prometheus Delivered," 115. Aetna, Mount, its elevation, 28, 229; supposed extinction by the ancients, 227; its eruptions from lateral fissures, 229; similarity of its zones of vegetation to those of Ararat, 347. Agassiz, Researches on Fossil Fishes, 46, 273-277. Alexander, influence of his campaigns on physical science, 353. Alps, the, elevation of, 28, 29. Amber, researches on its vegetable origin, 284; Goppert on the amber-tree of the ancient world (Pinites succifer), 283. Ampere, Andre Marie, 58, 193, 236. Anaxagoras on aerolites, 122; on the surrounding ether, 134. Andes, the, their altitude, etc. See Cordilleras. Anghiera, Peter Martyr de, remarked that the palmeta and pineta were found associated together, 282, 283; first recognized (1510) that the limit of perpetual snow continues to ascend as we approach the equator, 329. Animal life, its universality, 342-345; as viewed with microscopic powers of vision, 341-346; rapid propagation and tenacity of life in animalcules, 344-346; geography of, 341-346. Anning, Miss Mary, discovery of the ink bag of the sepia, and of coprolites of fish, in the lias of Lyme Regis, 271, 272. Austed's, D. R., "Ancient World." See notes by Translator, 271, 272, 274, 281, 287. Aplan, Peter, on comets, 101. Apollonius Myndius, described the paths of comets, 103. Arago, his ocular micrometer, 39; chromatic polarization, 52; optical considerations, 85; on comets, 99-106; polarization experiments on the light of comets, 105; aerolites, 114; on the November fall of meteors, 124; zodiacal light, 143; motion of the solar system, 146, 147; on the increase of heat at increasing depths, 173, 174; magnetism of rotation, 179, 180; horary observations of declination at Paris compared with simultaneous perturbations at Kasan, 191; discovery of the influence of magnetic storms on the course of the needle, 194, 195; on south polar bands, 198; on terrestrial light, 202; phenomenon of supplementary rainbows, 220; observed the deepest Artesian wells to be the warmest, 223; explanation of the absence of a refrigeration of temperature in the lower strata of the Mediterranean, 303; observations on the mean annual quantity of rain in Paris, 333; his investigations on the evolution of lightning, 337. Argelander on the comet of 1811, 109; on the motion of the solar system, 146, 149; on the light of the Aurora, 195, 196. Aristarchus of Samos, the pioneer of the Copernican system, 65. Aristotle, 65; his definition of Cosmos, 69; use of the term history, 75; on comets, 103, 104; on the Ligyan field of stones, 115; aerolites, 122; on the stone of Aegos Potamos, 135; aware that noises sometimes existed without earthquakes, 209; his account of the upheavals of islands of eruption, 241; "spontaneous motion," 341; noticed the redness assumed by long fallen snow, 344. Artesian wells, temperature of, 174, 223. Astronomy, results of, 38-40; phenomena of physical astronomy, 43, 44. Atmosphere, the general description of, 311, 316; its composition and admixture, 312; variation of pressure, 313-317; climatic distribution of heat, 313, 317-328; distribution of humidity, 313, 328, 334; electric condition, 314, 335-338. p 363 August, his psychometer, 332. Augustine, St., his views on spontaneous generation, 345, 346. Aurora Borealis, general description of 193-202; origin and course, 195, 196; altitude, 199; brilliancy coincident with the fall of shooting stars, 126, 127; whether attended with crackling sound, 199, 200; intensity of the light, 201. Bacon, Lord, 53, 58; Novum Organon, 290. Baer, Von, 337. Barometer, the increase of its height attended by a depression of the level of the sea, 298; horary oscillations of, 314, 315 Batten, Mr., letter on the snow-line of the two sides of the Himalayas, 331, 332. Beaufort, Capt., observed the emissions of inflammable gas on the Caramanian coast, as described by Pliny, 223. See also, note by Translator, 223. Beaumont, Elie de, on the uplifting of mountain chains, 51, 300; influence of the rocks of melaphyre and serpentine, on pendulum experiments, 167; conjectures on the quartz strata of the Col de la Poissoniere, 266. Baccaria, observation of steady luminous appearance in the clouds, 202; of lightning clouds, unaccompanied by thunder or indication of storm, 337. Beechey, Capt., 97; observations on the temperature and density of the water of the ocean under different zones of longitude and latitude, 306. Bembo, Cardinal, his observations on the eruptions of Mount Aetna, 229; theory of the necessity of the proximity of volcanoes to the sea, 243; vegetation on the declivity of Aetna, 347. Berard, Capt., shooting stars, 119. Berton, Count, his barometrical measurements of the Dead Sea, 296. Berzelins on the chemical elements of aerolites, 130, 131. Benzenberg on meteors and shooting stars, 119, 120; their periodic return in Autgust, 125. Bessel's theory on the oscillations of the pendulum, 44; pendulum experiments, 64; on the parallax of 61 Cygni, 88; on Halley's comet, 102, 103, 104; on the ascent of shooting stars, 123; on their partial visibility, 128; velocity of the sun's translatory motion, 145; mass of the star 61 Cygni, 148; parallaxes and distances of fixed stars, 153; comparison of measurements of degrees, 165, 166. Biot on the phenomenon of twilight, 118; on the zodical light, 141; pendulum experiments at Bordeaux, 170. Biot, Edward, Chinese observations of comets, 101, 109; of aerolites, 128. Bischof on the interior heat of the globe, 217, 219, 235, 244, 294. Blumenbach, his classification of the races of men, 356. Bockh, origin of the ancient myth of the Nemean lunar lion, 134, 135. Boguslawski, falls of shooting stars, 119, 128. Bonpland, M., and Humboldt, on the pelagic shells found on the ridge of the Andes, 45. Boussingault, on the depth at which is found the mean annual temperature within the tropics, 175; on the volcanoes of New Granada, 217; on the temperature of the earth in the tropics, 220, 221; temperature of the thermal springs of Las Trincheras, 222; his investigations on the chemical analysis of the atmosphere, 311, 312; on the mean annual quantity of rain in different parts of South America, 333, 334. Bouvard, M., 105; his observations on that portion of the horary oscillations of the pressure of the atmosphere, which depends on the attraction of the moon 313. Bramidos y truenos of Guanaxuato, 209, 210. Brandes, falls of shooting stars, 114, 116; height and velocity of shooting stars, 120; their periodic falls, 125, 126. Bravais, on the Aurora, 201; on the daily oscillations of the barometer in 70 degrees north latitude, 314; distribution of the quantity of rain in Central Europe, 334; doubts on the greater dryness of mountain air, 334. Brewster, Sir David, first detected the connection between the curvature of magnetic lines and my isothermal lines, 193. Brongniart, Adolphe, luxuriance of the primitive vegetable world, 218; fossil flora contained in coal measures, 280. Brongniart, Alexander, formation of ribbon jasper, 259; one of the founders of the archaeology of organic life, 273. Brown, Robert, first discoverer of molecular motion, 341. Buch's, Leopold von, theory on the elevation of continents and mountain chains, 45; on the craters and circular form of the island of Palma, 226; on volcanoes, 234, 238, 242, 243, 247; on metamorphic rocks, 249-252, 260, 263, 264; on the origin of various conglomerates and rocks of detritus, 269; classification of ammonites, 276, 277; physical causes of the elevation of continents, 295; on the changes in height of the Swedish coasts, 295. Buckland, 272; on the fossil flora of the coal measures, 279. Buffon, his views on the geographical distribution of animals, 348. Burckhardt, on the volcano of Medina, 246; on the hornitos de Jerullo, see note by Translator, 230. Burnes, Sir Alexander, on the purity of the atmosphere in Bokhara, 114; propagation of shocks of earthquakes, 212. p 365 Caile, La, pendulum measurements at the Cape of Good Hope, 169. Caldas, quantity of rain at Santa Fe de Bogota, 334. Camargo's MS. 'Historia de Tiascala', 140. Capocci, his observations on periodic falls of aerolites, 126. Carlini, geodesic experiments in Lombardy, 168; Mount Cenis, 170. Carrara marble, 262, 263. Carus, his definition of "Nature," 41. Caspian Sea, its periodic rise and fall, 297. Cassini, Dominicus, on the zodiacal light, 139, 140; hypothesis on 141; his discovery of the spheroidal form of Jupiter, 164. Cautley, Capt, and Dr. Falconer, discovery of gigantic fossils in the Himalayas. Cavanilles, first entertained the idea of seeing grass grow, 149. Cavendish, use of the torsion balance to determine the mean density of the Earth, 170. Challis, Professor, on the Aurora, March 19 and Oct. 24th, 1847, see note by Translator, 195, 199. Chardin, noticed in Persia the famous comet of 1608, called "nyzek" or "petite lance," 139. Charpentier, M., belemnites found in the primitive limestone of the Col de la Seigne, 261; glaciers, 329. Chemistry as distinguished from physics, 62; chemical affinity, 63. Chevandier, calculations on the carbon contained in the trees of the forests of our temperate zones, 281. Childrey first described the zodical light in his Britannia Baconica, 138. Chinese accounts of comets, 99, 100, 101; shooting stars, 128: "fire springs," 158; knowledge of the magnetic needle, 180; electro-magnetism, 188, 189. Chladni on meteoric stones, etc., 118, 135; on the selenic origin of aerolites, 121; on the supposed phenomenon of ascending shooting stars, 122; on the obscuration of the Sun's disk, 133; sound-figures, 135; pulsations in the tails of comets, 143. Choiseul, his chart of Lemnos, 246. Chromatic polarization. See Polarization. Cirro-cumulus cloud. See Clouds. Cirrous Strata. See Clouds. Clark, his experiments on the variations of atmospheric electricity, 335, 336. Clarke, J. G., of Maine, U.S., on the comet of 1843, 100. Climatic distribution of heat, 313, 317-328; of humidity, 328, 333, 334. Climatology, 317-329; climate, general sense of, 317, 318. Clouds, their electric tension, color, and height, 236, 337; connection of cirrous strata with the Aurora Borealis, 196; cirro-cumulus cloud, phenomena of, 197; luminous, 202; Dove on their formation and appearance, 315, 316; often present on a bright summer sky the "projected image" of the soil below, 316; volcanic, 233. Coal formations, ancient vegetable remains in, 280, 281. Coal mines, depth of, 158-160. Colebrooke on the snow-line of the two sides of the Himalayas, 31. Colladon, electro-magnetic apparatus, 335. Columbus, his remark that "the Earth is small and narrow," 164; found the compass showed no variation in the Azores, 181, 182; of lava streams, 245; noticed conifers and palms growing together in Cuba, 282; remarks in his journal on the equatorial currents, 307; of the Sargasso Sea, 308; his dream, 310, 311. Comets, general description of, 99-112; Biela's 43, 86, 107, 108; Blaupain's 108; Clausen's 108; Encke's, 43, 64, 86, 107-108; Faye's 107, 108; Halley's, 43, 100, 102-109; Lexell's and Burchardt's 108, 110; Messier's 108; Olbera's, 109; Pons's 109; famous one of 1608, seen in Persia, called "nyzek," or "petit lance," 189; comet of 1843, 101; their nucleus and tail, 87, 100; small mass, 100; diversity of form, 100-103; light, 104-106; velocity, 109; comets of short period, 107-109; long period, 109-110; number, 99; Chinese observations on, 99-101; value of a knowledge of their orbits, 43; possibility of collision of Blela's and Encke's comets, 107, 108; hypothesis of a resisting medium conjectured from the diminishing period of the revolution of Encke's comet, 106; apprehensions of their collision with the Earth, 108, 110, 111; their popular supposed influence on the vintage, 111. Compass, early use of by the Chinese, 180; permanency in the West Indies, 181. Condamine, La, inscription on a marble tablet at the Jesuit's College, Quito on the use of the pendulum as a measure of seconds, 166, 167. Conde, notice of a heavy shower of shooting stars, Oct., 902, 119. Coraboeuf and Delcrois, geodetic operations, 304. Cordilleras, scenery of, 26, 29, 33; vegetation, 34, 35; intensity of the zodiacal light, 137. Cosmography, physical, its object and ultimate aims, 57-60; materials, 60. Cosmos, the author's object, 38, 78; primitive signification and precise definition of the word, 69; how employed by Greek and Roman writers, 69, 60; derivation, 70. Craters. See Volcanoes. Curtius, Professor, his notes on the temperature of various springs in Greece, 222, 223. Cuvier, one of the founders of the archaeology of organic life, 273; discovery of fossil crocodiles in the tertiary formations, 274. Dainachos on the phenomena attending the fall of the stone of Aegos Potamos, 133, 134. Dalman on the existence of Chionaea araneoides in polar snow, 344. Dalton, observed the southern lights in England, 198. Dante, quotation from, 322. Darwin, Charles, fossil vegetation in the travertine of Van Diemen's Land, 224; central volcanoes regarded as volcanic chains of small extent on parallel fissures, 238; instructive materials in the temperate zones of the southern hemisphere for the study of the present and past geography of plants, 282, 283; on the fiord formation at the southeast end of America, 293; on the elevation and depression of the bottom of the South Sea, 297; rich luxuriance of animal life in the ocean, 309, 310; on the volcano of Aconcagua, 330. Daubeney on volcanos. See Translator's notes, 161, 203, 204, 210, 218, 224, 228, 230, 233, 234, 235, 236, 244, 245. Daussy, his barometric expriments, 208; observations on the velocity of the equatorial current, 307. Davy, Sir Humphrey, hypothesis on active volcanic phenomena, 235; on the low temperature of water on shoals, 309. Dead Sea, its depression below the level of the Mediterranean, 296, 297. Dechen, Von, on the depth of the coal-basin of Liege, 160. Delcrois. See Coraboeuf. Descartes, his fragments of a contemplated work, entitled "Monde," 68; on comets, 139. Deshayes and Lyell, their investigations on the numerical relations of extinct and existing organic life, 275. Dicaearchus, his "parallel of the diaphragm," 289. Diogenes Laertius, on the aerolite of Aegos Potamos, 116, 122, 134. D'Orbigny, fossil remains from the Himalaya and the Indian plains of Cutch, 277. Dove on the similar action of the declination needle to the atmospheric electrometer, 194; "law of rotation," 315; on the formation and appearance of clouds, 316; on the difference between the true temperature of the surface of the ground and the indications of a thermometer suspended in the shade, 325; hygrometric windrose, 333. Doyere, his beautiful experiments on the tenacity of life in animalcules, 345. Drake, shaking of the earth for successive days in the United States (1811-12), 211. Dufrenoy et Elie de Beaumont, Geologie de la France, 253, 258, 259, 260, 262, 266. Dumas, results of his chemical analysis of the atmosphere, 311. Dunlop on the comet of 1825, 103. Duperrey on the configuration of the magnetic equator, 183; pendulum oscillations, 166. Duprez, influence of trees on the intensity of electricity in the atmosphere, 335. Eandi, Vassalli, electric perturbation during the protracted earthquake of Pignorol, 206. Earth, survey of its crust, 72; relative magnitude, etc., in the solar system, 95-97; general description of terrestrial phenomena, 154-360; geographical distribution, 161, 162; its mean density, 169-172; internal heat and temperature, 172-176; electro-magnetic activity, 177-193; conjectures on its early high temperature, 172; interior increase of heat with increasing depth, 161; greatest depths reached by human labor, 157-159; methods employed to investigate the curvature of its surface, 165-168; reaction of the interior on the external crust, 161, 202-247; general delineation of its reaction, 204-206; fantastic views on its interior, 171. Earthquakes, general account of, 204-218; their manifestations, 204-206; of Riobamba, 204, 206, 208, 212, 214; Lisbon, 210, 211, 213, 214; Calabria, 206; their propagation, 204, 212, 213; waves of commotion, 205, 206, 212; action on gaseous and aqueous springs, 210, 222, 224; salses and mud volcanoes, 224-228; erroneous popular belief on, 206-208; noise accompanying earthquakes, 208-210; their vast destruction of life, 210, 211; volcanic force, 214, 215; deep and peculiar impression produced on men and animals, 215, 216. Ehrenberg, his discovery of infusoria in the polishing slate of Bilin, 150; infusorial deposits, 255, 262; brilliant discovery of microscopic life in the ocean and in the ice of the polar regions, 342; rapid propogation of animalcules and their tenacity of life, 343-345; transformation of chalk, 262. Electricity, magnetic, 188-202; conjectured electric currents, 189, 190; electric storms, 194; atmospheric 335, 337. Elevations, comparative, of mountains in the two hemispheres, 28, 29. Encke, 106; his computation that the showers of meteors, in 1833, proceeded from the same point of space in the direction in which the earth was moving at the time, 119, 120. Ennius, 71. Epicharmus, writings of, 71. Equator, advantages of the countries bordering on, 33, 34; their organic richness and fertility, 34, 35; magnetic equator, 183-185. Erman, Adolph, on the three cold days of May (11th-13th), 133; lines of declination in Northern Asia, 182; in the southern parts of the Atlantic, 187; observations during the earthquake of Irkutsk, on the non-disturbance of the horary changes of the magnetic needle, 207. Eruptions and exhalations (volcanic), lava, gaseous and liquid fluids, hot mud, mud mofettes, etc., 161, [other page numbers obscured in paper copy] p 367 Ethnographical studies, their importance and teaching, 357, 358. Euripides, his Phaeton, 122. Falconer, Dr., fossil researches in the Himalayas, 278. Faraday, radiating heat, electro-magnetism etc., 49, 179, 188; brilliant discovery of the evolution of light by magnetic forces, 193. Farquharson on the connection of cirrous clouds with the Aurora, 197; its altitude, 199. Federow, his pendulum experiments, 168. Feldt on the ascent of shooting stars, 123. Ferdinandes, igneous island of, 242. Floras, geographical distribution of, 350. Forbes, Professor E., reference to his Travels in Lycia, 223; account of the island of Santorino, 241, 242. Forbes, Professor J., his improved selsmometer, 205; on the correspondence existing between the distribution of existing floras in the British Islands, 348, 349; on the origin and diffusion of the British flora, 353, 354. Forster, George, remarked the climatic difference of temperature of the eastern and western coasts of both continents, 321. Forster, Dr. Thomas, monkish notice of "Meteorodes," 123. Fossil remains of tropical plants and animals found in northern regions, 46, 270-284; of extinct vegetation in the travertine of Van Diemen's Land, 224; fossil human remains, 250. Foster, Reinhold, pyramidal configuration of the southern extremities of continents, 290, 291. Fourier, temperature of our planetary system, 155, 172, 176. Fracastoro on the direction of the tails of comets from the sun, 101. Fraehn, fall of stars, 119. Franklin, Benjamin, existence of sandbanks indicated by the coldness of the water over them, 308. Franklin, Capt., on the Aurora, 197, 199, 200, 201; rarity of electric explosions in high northern regions, 337. Freycinet, pendulum oscillations, 166. Fusinieri on meteoric masses, 123. Galileo, 104, 167. Galle, Dr., 91. Galvant, Aloysio, accidental discovery of galvanism, 52. Gaseous emanations, fluids, mud, and molten earth, 217, 220. Gasparin, distribution of the quantity of rain in Central Europe, 333. Gauss, Friedrich, on terrestrial magnetism, 179; his erection. in 1832, of a magnetic observatory on a new principle, 191, 192. Gay-Lussac, 204, 233, 234, 266, 267, 311, 312, 334, 336. Geognostic or geological description of the earth's surface, 202-286. Geognosy (the study of the textures and position of the earth's surface), its progress, 203. Geography, physical, 288-311; of animal life, 341-346; of plants, 346-351. Geographics, Ritter's (Carl), "Geography in relation to Nature and the History of Man," 48, 67; Varenius (Bernhard), General and Comparative Geography, 66, 67. Gerard, Capts. A. G. and J. G., on the snow-line and vegetation of the Himalayas, 31, 32, 331, 332. German scientific works, their defects, 47. Geyser, intermittent fountains of, 222. Gieseke on the Aurora, 200. Gilbert, Sir Humphrey, Gulf Stream, 307. Gilbert, William, of Colchester, terrestrial magnetism, 158, 159, 177, 179, 182. Gillies, Dr., on the snow-line of South America, 330, 331. Gioja, crater of, 98. Girard, composition and texture of basalt, 253. Glaisher, James, on the Aurora Borealis of Oct. 24, 1847. See Translator's notes, 194, 200. Goldfuss, Professor, examination of fossil specimens of the flying saurians, 274. Goppert on the conversion of a fragment of amber-tree into black coal, 281; eyeadeae, 283; on the amber-tree of the Baltic, 283, 284. Gothe, 41, 47, 53. Greek philosophers, their use of the term Cosmos, 69, 70; hypotheses on aerolites, 122, 123, 134. Grimm, Jacob, graceful symbolism attached to falling stars in the Lithuanian mythology, 112, 113. Gulf Stream, its origin and course, 307. Gumprecht, pyroxenic nepheline, 253. Guanaxuato, striking subterranean noise at, 209. Hall, Sir James, his experiments on mineral fusion, 262. Halley, comet, 43, 100, 102-109; on the meteor of 1686, 118, 133; on the light of stars, 152; hypothesis of the earth being a hollow sphere, 171; his bold conjecture that the Aurora Borealis was a magnetic phenomenon, 193. Hansteen on magnetic lines of declination in Northern Asia, 182. Hausen on the material contents of the moon, 96. Hedenstrom on the so-called "Wood Hills" of New Siberia, 281. Hegel, quotation from his "Philosophy of History," 76. Heine, discovery of crystals of feldspar in scoriae, 268. Hemmer, falling stars, 119. Hencke, planets discovered by. See note by Translator, 90, 91. Henfrey, A., extract from his Outlines of Structural and Physiological Botany. See notes by Translator, 341, 342, 351. p 368 Hensius on the variations of form in the comet of 1744, 102. Herodotus, described Scythia as free from earthquakes, 204; Scythian saga of the sacred gold, which fell burning from heaven, 115. Herschel, Sir William, map of the world, 66; inscription on his monument at Upton, 87; satellites of Saturn, 96; diameters of comets, 101; on the comet of 1811, 103; star guagings, 150; starless space, 150, 152; time required for light to pass to the earth from the remotest luminous vapor, 154. Herschel, Sir John, letter on Magellanic clouds, 85; satellites of Saturn, 98; diameter of nebulous stars, 141; stellar Milky Way, 150, 151; light of isolated starry clusters, 151; observed at the Cape, the star pi in Argo increase in splendor, 153; invariability of the magnetic declination in the West Indes, 181. Hesiod, dimensions of the universe, 154. Hevellus on the comet of 1618, 106. Hibbert, Dr., on the Lake of Laach. See note by Translator, 218. Himalayas, the, their altitude, 28; scenery and vegetation, 29, 30; temperature, 30, 31; variations of the snow-line on their northern and southern declivities, 30-33, 331. Hind, Mr., planets discovered by. See Translator's note, 90, 91. Hindoo civilization, its primitive seat, 35, 36. Hippalos, or monsoons, 316. Hippocrates, his erroneous supposition that the land of Scythia is an elevated table-land, 346. Hoff, numerical inquiries on the distribution of earthquakes throughout the year, 207. Hoffman, Friedrich, observations on earthquakes, 206-207; on eruption fissures in the Lipari Islands, 238. Holberg, his Satire, "Travels of Nic. Klimius, in the world under ground." See Translator's note, 171, 172. Hood on the Aurora, 200, 201. Hooke, Robert, pulsations in the tails of comets, 143; his anticipation of the application of botannical and zoological evidence to determine the relative age of rocks, 270-272. Ho-tsings, Chinese fire-springs, their depth, 158; chemical composition, 217. Howard on the climate of London, 125; mean annual quantity of rain in London, 333. Hugel, Carl von, on the elevation of the valley of Kashmir, 32, 33; on the snow-line of the Himalayas, 331. Humboldt, Alexander von, works by referred to in various notes: Annales de Chimie et de Physique, 31, 305. Annales des Science Naturelles, 28. Ansichten der Natur, 342, 344, 347. Asie Centrale, 28, 31, 33, 115, 158, 159, 160, 204, 217, 219, 225, 245, 251, 252, 260, 289, 290, 291, 292, 296, 300, 301, 303-306, 320, 323, 324, 330, 331, 334, 350, 356. Atlas Geographique et Physique du Nouveau Continent, 33, 249. De distributione Geographica Plantrum, secundum coeli temperiem, et altitudinem Montium, 33, 291, 324. Examen Critique de l'Histoire de la Geographie, 58, 180, 181, 227, 289, 292, 307, 308, 310, 316, 356. Essai Geognostique sur le Gisement des Roches, 230, 252, 266, 300. Essai Politique sur la Nouvelle Espagne, 129, 240. Essai sur la Geographie des Plantes, 33, 230, 315. Flora Friburgensis Subterranea, 340, 346. Journal de Physique, 178, 292. Lettre au Duc de Sussex, sur les Moyens propres a perfectionner la connaissance du Magnetisme Terrestre, 178, 192. Monumens des Peuples Indigenes de l'Amerique, 140. Nouvelles Annales des Voyages, 307. Recueil d'Observations Astronomiques, 28, 167, 218, 327. Recueil d'Observations de Zoologi et d'Anatomie Comparee, 232. Relation Historique du Voyage aux Regions Equinoxiales, 113, 119, 123, 127, 130, 186, 206, 207, 220, 221, 225, 252, 292, 299, 300, 302, 305-307, 314, 315, 327, 329, 334, 336. Tableau Physique des Regions Equinoxiales, 33, 230. Vues des Cordilleres, 225, 230. Humboldt, Wilhelm von, on the primitive seat of Hindoo civilization, 36; sonnet, extract from, 154; on the gradual recognition by the human race of the bond of humanity, 358, 359. Humidity, 313, 332-335. Hutton, Capt. Thomas, his paper on the snow-line of the Himalayas, 331, 332. Huygens, polarization of light, 52; nebulous spots, 138. Hygrometry, 332, 333; hygrometric wind-rose, 333. Imagination, abuse of, by half-civilized nations, 37. Imbert, his account of Chinese "fire-springs," 158. Ionian school of natural philosophy, 65, 77, 84, 134. Isogenic, isoclinical, isodynamic, etc. See Lines. Jacquemont, Victor, his barometrical observations on the snow-line of the Himalayas, 32, 231. Jasper, its formation, 259-261. Jessen on the gradual rise of the coast of Sweden, 295. Jorullo, hornitos de, 230. p 369 Justinian, conjectures on the physical causes of volcanic eruptions, 243. Kamtz, isobarometric lines, 315; doubts on the greater dryness of mountain air, 334. Kant, Emmanuel, "on the theory and structure of the heavens," 50, 65; earthquake at Lisbon, 210. Kelihau on the ancient sea-line of the coast of Spitzbergen, 296. Kepler on the distances of stars, 88; on the density of the planets, 93; law of progression, 95; on the number of comets, 99; shooting stars, 113; on the obscuration of the sun's disk, 132; on the radiations of heat from the fixed stars, 136; on a solar atmosphere, 139. Kloden, shooting stars, 119, 124. Knowledge, superficial, evils of, 43. Krug of Nidda, temperature of the Geyser and the Strokr intermittent fountains, 222. Krusenstern, Admiral, on the train of a fire-ball, 114. Kuopho, a Chinese physicist on the attraction of the magnet, and of amber, 168. Kupffer, magnetic stations in Northern Asia, 191. Lamanon, 187. Lambert, suggestion that the direction of the wind be compared with the height of the barometer, alterations of temperature, humidity, etc., 315. Lamont, mass of Uranus, 93; satellites of Saturn, 96. Language and thought, their mutual alliance, 56; author's praise of his native language, 56. Languages, importance of their study, 357, 359. Laplace, his "Systeme du Monde," 48, 62, 92, 141; mass of the comet of 1770, 107; on the required velocity of masses projected from the Moon, 121, 122; on the altitude of the boundaries of the atmosphere of cosmical bodies, 141; zodiacal light, 141; lunar inequalities, 166; the Earth's form and size inferred from lunar inequalities, 168, 169; his estimate of the mean height of mountains, 301; density of the ocean required to be less than the earth's for the stability of its equilibrium, 305; results of his perfect theory of tides, 306. Latin writers, their use of the term "Mundus," 70, 71. Latitudes, Northern, obstacles they present to a discovery of the laws of Nature, 36; earliest acquaintance with the governing forces of the physical world, there displayed, 36; spread from thence of the germs of civilization, 36. Latitudes, tropical, their advantages for the contemplation of nature, 33; powerful impressions, from their organic richness and fertility, 34; facilities they present for a knowledge of the laws of nature, 35; brilliant display of shooting stars, 113. Laugier, his calculations to prove Halley's comet identical with the comet of 1378, described in Chinese tables, 109. Lava, its mineral composition, 234. Lavoisier, 62. Lawrence (St.), fiery tears, 124; meteoric stream, 125. Leibnitz, his conjecture that the planets increase in volume in proportion to their increase of distance from the Sun, 93. Lenz, observations on the mean level of the Caspian Sea, 297; maxims of density of the oceanic temperature, 304; temperature and density of the ocean under different zones of latitude and longitude, 306. Leonhard, Karl von, assumption on formations of granular limestone, 263. Leverrier, planet Neptune. See Translator's note, 90, 91. Lewy, observations on the varying quantity of oxygen in the atmosphere, according to local conditions, or the seasons, 311, 312. Lichtenberg, on meteoric stones, 118. Liebig on traces of ammonical vapors in the atmosphere, 311. Light, chromatic polarization of, 52; transmission, 88; of comets, 104-106; of fixed stars, 105; extraordinary lightness, instances of, 142-144; propagation of 153; speed of transit, 153, 154. See Aurora, Zodiacal Light, etc. Lignites or beds of brown coal, 283, 284. Lines, isogonic (magnetic equal deviation), 177, 181-185; isoclinal (magnetis equal inclination), 178, 179, 181-185; isodynamic (or magnetic equal force), 181, 185-194; isogeothermal (chthonisothermal), 219; isobarometric, 315; isothermal, isotheral, and isochimenal, 317, 327, 328, 358. Line of no variation of horary declination, 183; lower limit of perpetual snow, 329-332; phosphorescent, 113. Lisbon, earthquake of, 210, 211, 213, 214. Lord on the limits of the snow-line on the Himalayas, 32. Lottin, his observations of the Aurora, with Bravais and Siljerstrom, on the coast of Lapland, 195, 200, 201. Lowenorn, recognized the coruscation of the polar light in bright sunshine, 196. Lyell, Charles, investigations on the numerical relations of extinct and organic life, 274, 275; nether-formed or hypogene rocks, 249; uniformity of the production of erupted rocks, 257. See notes by Translator, 203, 244, 257. Mackenzie, description of a remarkable eruption in Iceland, 236. Maclear on a Centauri, 88; parallaxes and distances of fixed stars, 153; increase in brightness of 'pi' Argo, 153. Madler, planetary compression of Uranus, 96; distance of the innermost satellite of Saturn from the centre of that planet, 97; material contents of the Moon, 96; its libration, 98; mean depression of temperature on the three cold days of May (11th-13th), 133; conjecture that the average mass of the larger number of binary stars exceeds the mass of the Sun, 149. Magellanic clouds, 85. Magnetic attraction, 188; declination, 181-183; horary motion, 177-180; horary variations 183, 190; magnetic storms, 177, 179, 195, 199; their intimate connection with the Aurora, 193-201; represented by three systems of lines, see Lines; movement of oval systems, 182; magnetic equator, 183-185; magnetic poles, 183, 184; observatories, 190-192; magnetic stations, 190, 191, 317. Magnetism, terrestrial, 177-193, 201; electro, 177-191. Magnussen, Soemund, description of remarkable eruption in Iceland, 236. Mahlmann, Wilhelm, south west direction of the a��rial current in the middle latitudes of the temperate zone, 317. Mairan on the zodiacal light, 138, 139, 142; his opinion that the Sun is a nebulous star, 141. Malapert, annular mountain, 98. Malle, Dureau de la, 223. Man, general view of, 351-359; proofs of the flexibility of his nature, 27; results of his intellectual progress, 53, 54; geographical distribution of races, 351-356; on the assumption of superior and inferior races, 351-358; his gradual recognition of the bond of humanity, 358, 359. Mantell, Dr., his "Wonders of Geology," see notes by Translator, 45, 64, 203, 274, 278, 281, 283, 284, 287; "Medals of Creation," 46, 271, 283, 287. Margarita Philosophica by Gregory Reisch, 58. Marius, Simon, first described the nebulous spots in Andromeda and Orion, 138. Martins, observations on polar bands, 198; found that air collected at Faulhorn contained as much oxygen as the air of Paris, 312; on the distribution of the quantity of rain in Central Europe, 333; doubts on the greater dryness of mountain air, 334. Matthessen, letter to Arago on the zodiacal light, 142. Mathieu on the augmented intensity of the attraction of gravitation in volcanic islands, 167. Mayer, Tobias, on the motion of the solar system, 146, 148. Mean numerical values, their necessity in modern physical science, 81. Melloni, his discoveries on radiating heat and electro-magnetism, 49. Menzel, unedited work by, on the flora of Japan, 347. Messier, comet, 108; nebulous spot resembling our starry stratum, 151. Metamorphic Rocks. See Rocks. Meteorology, 311-339. Meteors, see A��rolites; meteoric infusoria, 345, 346. Methone, Hill of, 240. Meyen on forming a thermal scale of cultivation, 324; on the reproductive organs of liverworts and algae, 341. Meyer, Hermann von, on the organization of flying saurians, 274. Milky Way, its figure, 89; views of Aristotle on, 103; vast telescopic breadth, 150; Milky Way of nebulous spots at right angles with that of the stars, 151. Minerals, artificially formed, 268, 269. Mines, greatest depth of, 157, 159; temperature, 158. Mist, phosphorescent, 142. Mitchell, protracted earthquake shocks in North America, 211. Mitscherlich on the chemical origin of iron glance in volcanic masses, 234; chemical combinations, a means of throwing a clear light on geognosy, 256; on gypsum, as a uniaxal crystal, 259; experiments on the simultaneously opposite actions of heat on crystalline bodies, 259; formation of crystals of mica, 260; on artificial mineral products, 268, 271. Mofettes (exhalations of carbonic acid gas), 215-219. Monsoons (Indian), 316, 317. Monticelli on the current of hydrochloric acid from the crater of Vesuvius, 235; crystals of mica found in the lava of Vesuvius, 260. Moon, the, its relative magnitude, 96; density, 96; distance from the earth, 97; its libration, 98, 163; its light compared with that of the Aurora, 201, 202; volcanic action in, 228. Moons or satellites, their diameter, distances, rotation, etc., 95-99. Morgan, John H. "on the Aurora Borealis of Oct. 24, 1847." See Translator's notes, 194, 199. Morton, Samuel George, his magnificent work on the American Races, 362. Moser's images, 202. Mountains, in Asia, America, and Europe, their altitude, scenery, and vegetation, 27-30, 238, 347; their influence on climate, natural productions, and on the human race, its trade, civilization, and social condition, 291, 292, 299, 300, 327; zones of vegetation on the declivities of 29, 30, 327-329; snow-line of, 30-33, 330, 331. Mud volcanoes. See Salses and Volcanoes. Muller, Johannes, on the modifications of plants and aniimals within certain limitations, 353. Muncke on the appearance of Auroras in certain districts, 198. Murchison, Sir R., account of a large fissure through which melaphyre had been ejected, 258; classification of fossiliferous strata, 277; on the age of the Palaeosaurus and Thecodontosaurus of Bristol, 274. Muschenbroek on the frequency of meteors in August, 125. Myndius, Apollonius, on the Pythagorean doctrine of comets, 103, 104. Nature, result of a rational inquiry into, 25; emotions excited by her contemplation, 25; striking scenes, 26; their sources of enjoyment, 26, 27; magnificence of the tropical scenery, 33, 34, 35, 344; religious impulses from a communion with nature, 37; obstacles to an active spirit of inquiry, 37; mischief of inaccurate observations, 38; higher enjoyments of her study, 38; narrow-minded views of nature, 38; lofty impressions produced on the minds of laborious observers, 40; nature defined, 41; her studies inexhaustible, 41; general observations, their great advantages, 42; how to be correctly comprehended, 72; her most vivid impressions earthly, 82. Nature, philosophy of, 24, 37; physical description of, 66, 67, 73. Nebulae, 84-86; nebulous Milky Way at right angles with that of the stars, 150-153; nebulous spots, conjectures on, 83-86; nebulous stars and planetary nebulae, 85, 151, 152; nebulous vapor, 83-86, 87, 152; their supposed condensation in conformity with the laws of attraction, 84. Neilson, gradual depression of the southern part of Sweden, 295. Nericat, Andrea de, popular belief in Syria on the fall of aerolites, 123. Newton, discussed the question on the difference between the attraction of masses and molecular attraction, 63; Newtonian axiom confirmed by Bessel, 64; his edition of the Geography of Varenius, 66; Principia Mathematica, 67; considered the planets to be composed of the same matter with the Earth, 132; compression of the Earth, 165. Nicholl, J. P., note from his account of the planet Neptune, 90, 91. Nicholson, observations of lighting clouds, unaccompanied by thunder or indications of storm, 337. Nobile, Antonio, experiments of the height of the barometer, and its influence on the level of the sea, 298. Noggerath counted 792 annual rings in the trunk of a tree at Bonn, 283. Nordmann on the existence of animalcules in the fluids of the eyes of fishes, 345. Norman, Robert, invented the inclinatorium, 179. Observations, scientific, mischief of inaccurate, 38; tendency of unconnected, 40. Ocean, general view of, 292-311; its extent as compared with the dry land, 288, 289; its depth, 160, 302; tides, 304, 305; decreasing temperature at increased depths, 302; uniformity and constancy of temperature in the same spaces, 303; its currents and their various causes, 306-309; its phosphorescence in the torrid zone, 202; its action on climate, 303, 319-320; influence on the mental and social condition of the human race, 162, 291, 292, 294, 310; richness of its organic life, 300, 310; oceanic microscopic forms, 342, 343; sentiments excited by its contemplation, 310. Oersted, electro-magnetic discoveries, 188, 191. Olbers, comets, 104, 109; aerolites, 114, 118; on their planetary velocity, 121; on the supposed phenomena of ascending shooting stars, 123; their periodic return in August, 125; November stream, 126; prediction of a brilliant fall of shooting stars in Nov., 1867, 127; absence of fossil meteoric stones in secondary and tertiary formations, 131; zodiacal light, its vibration through the tails of comets, 143; on the transparency of celestial space, 152. Olmsted, Denison of New Haven, Connecticut, observations of aerolites, 113, 118, 119, 124. Oltmanns, Herr, observed continuously with Humboldt, at Berlin, the movements of the declination needle, 190, 191. Ovid, his description of the volcanic Hill of Methone, 240. Oviedo describes the weed of the Gulf Stream as Praderias de yerva (sea weed meadows), 308. Palaeontology, 270-284. Pallas, meteoric iron, 131. Palmer, New Haven, Connecticut, on the prodigious swarm of shooting stars, Nov. 12 and 13, 1833, 124; on the non-appearance in certain years of the August and November fall of aerolites, 129. Parallaxes of fixed stars, 88, 89; of the solar system, 145, 146. Perry, Capt., on Auroras, their connection with magnetic perturbations, 197, 201; whether attended with any sound, 200; seen to continue throughout the day, 197; barometric observation at Port Bowen, 314, 315; rarity of electric explosions in northern regions, 337. Patricius, St., his accurate conjectures on the hot springs of Carthage, 223, 224. Peltier on the actual source of atmospheric electricity, 335, 336. Pendulum, its scientific uses, 44; experiments with, 64, 166, 169, 170; employed to investigate the curvature of the earth's surface, 165; local attraction, its influence on the pendulum, and geognostic knowledge deduced from, 44, 45, 167, 168; experiments of Bessel, 64. Pentland, his measurements of the Andes, 28. Percy, Dr., on minerals artifically produced. See note by Translator, 268. Permian system of Murchison, 277. Perouse, La, expedition of, 186. Persia, great comet seen in (1608), 139, 140. Pertz on the large aerolite that fell in the bed of the River Narni, 116. Peters, Dr., velocity of stones projected from Aetna, 122. Peucati, Count Mazari, partial infection of calcareous beds by the contact of syenitic granite in the Tyrol, 262. Phillips on the temperature of a coalmine at increasing depths, 174. Philolaus, his astronomical studies, 65; his fragmentary writings, 68-71. Philosophy of nature, first germ, 37. Phosphorescence of the sea in the torrid zones, 202. Physics, their limits, 50; influence of physical science on the wealth and prosperity of nations, 53; province of physical science, 59; distinction betweeen the physical 'history' and physical 'description' of the world, 71, 72; physical science, characteristics of its modern progress, 81. Pindar, 227. Plans, geodesic experiments in Lombardy, 168. Planets, 89-99; present number discovered, 90. (See note by Translator on the most recent discoveries, 90, 91); Sir Isaac Newton on their composition, 132; limited physical knowledge of, 156, 157; Ceres, 64-92; Earth, 88-99; Juno, 64, 92-97, 106; Jupiter, 64, 87, 92-98, 202; Mars, 87, 91-94, 132; Mercury, 87, 92-94; Pallas, 64, 92; Saturn, 87, 92-94; Venus, 91-94, 202; Uranus, 90-94; planets which have the largest number of moons, 95, 96. Plants, geographical distribution of, 346-350. Plato on the heavenly bodies, etc., 69; interpretation of nature, 163; his geognostic views on hot springs, and volcanic igneous streams, 237, 238. Pliny the elder, his Natural History, 73; on comets, 104; aerolites, 122, 123, 130; magnetism, 180; attraction of amber, 188; on earthquakes, 205, 207; on the flame of inflammable gas, in the district of Phasells, 223; rarity of jasper, 261; on the configuration of Africa, 292. Pliny the younger, his description of the great eruption of Mount Vesuvius, and the phenomenon of volcanic ashes, 235. Plutarch, truth of his conjecture that falling stars are celestial bodies, 133, 134. Poisson on the planet Jupiter, 64; conjecture on the spontaneous ignition of meteoric stones, 118; zodiacal light, 141; theory on the earth's temperature, 172, 173, 174, 176, 177. Polarization, chromatic, results of its discovery, 52; experiments on the light of comets, 105, 106. Polybius, 291. Posidonius on the Ligyran field of stones, 115, 116. Pouilet on the actual source of atmospheric electricity, 335. Prejudices against science, how originated, 38; against the study of the exact sciences, why fallacious, 40-52. Prichard, his physical history of Mankind, 352. Pseudo-Plato, 54. Psychrometer, 332, 338. Pythagoras, first employed the word Cosmos in its modern sense, 69. Pythagoreans, their study of the heavenly bodies, 65; doctrine on comets, 103. Quarterly Review, article on Terrestrial Magnetism, 192. Quetelet on aerolites, 114; their periodic return in August, 125. Races, human, their geographical distribution, and unity, 351, 359. Rain drops, temperature of, 220; mean annual quantity in the two hemispheres, 333, 334. Reich, mean density of the earth, as ascertained by the torsion balance, 170; temperature of the mines in Saxony, 174. Reisch, Gregory, his "Margarita Philosophica," 58. Remusat, Abel, Mongolian tradition on the fall of an aerolite, 116; active volcanoes in Central Asia, at great distances from the sea, 245. Richardson, magnetic phenomena attending the Aurora, 197; whether accompanied by sound 200; influence on the magnetic needle of the Aurora, 201. Riohamba, earthquake at, 204, 205, 208, 213, 214. Ritter, Carl, on his "Geography in relation to Nature and the History of Man," 48, 67. Robert, Eugene, on the ancient sea-line on the coast of Spitzbergen, 296. Robertson on the permanency of the compass in Jamaica, 181. Rocks, their nature and configuration, 228; geognostical classification into four groups, 248-251; i. rocks of eruption, 248, 251-253; ii. sedimentary rocks, 248, 254, 255; iii. transformed, or metamorphic rocks, 248, 259, 255, 256-269; iv. conglomerates, or rocks of detritus, 269, 270; their changes from the action of heat, 258, 259; phenomena of contact, 258-269; effects of pressure and the rapidity of cooling, 258, 267. Rose, Gustav, on the chemical elements, etc., of various aerolites, 131; on the structural relations of volcanic rocks, 254; on crystals of feldspar and albite found in granite, 251; relations of position in which granite occurs, 252-269; chemical process in the formation of various minerals, 265-269. Ross, Sir James, his soundings with 27,000 feet of line, 160; magnetic observations at the South Pole, 187; important results of the Antarctic magnetic expedition in 1839, 192; rarity of electric explosions in high northern regions, 337. Rossell, M. de, his magnetic oscillation experiments, and their date of publication, 186, 187. Rothmann, confounded the setting zodiscal light with the cessation of twilight, 143. Rozier, observation of a steady luminous appearance in the clouds, 202. Rumker, Encke's comet, 106. Ruppell denies the existence of active volcanoes in Kordofan, 245. Sabine, Edward, observations on days of unusual magnetic disturbances, 178; recent magnetic observations, 184, 185, 187, 188. Sagra, Ramon de la, observations on the mean annual quantity of rain in the Havana, 333. Saint Pierre, Bernardin de, Paul and Virginia, 26; Studies of Nature, 347. Salses or mud volcanoes, 224-228; striking phenomena attending their origin, 224, 225. Salt works, depth of 158, 159; temperature, 174. Santorino, the most important of the islands of eruption, 241, 242; description of. See note by Translator, 241. Sargasso Sea, its situation, 308. Satellites revolving round the primary planets, their diameter, distance, rotation, etc., 94, 99; Saturn's 96-98, 127' Earth's see Moon, Jupiter's, 96, 97; Uranus, 96-98. Saurians, flying, fossil remains of, 274, 275. Saussure, measurements of the marginal ledge of the crater of Mount Vesuvius, 232; traces of ammoniacal vapors in the atmosphere, 311; hygrometric measurements with Humboldt, 334-336. Schayer, microscopic organisms in the ocean, 342, 343. Scheerer on the identity of eleolite and nepheline, 253. Schelling on nature, 55; quotation from his Giordino Bruino, 77. Scheuchzner's fossil salamander, conjectured to be an antediluvian man, 274. Schiller, quotation from, 36. Schnurrer on the obscuration of the sun's disk, 133. Schouten, Cornelius, in 1616 found the declination null in the Pacific, 182. Schouw, distribution of the quantity of rain in Central Europe, 333. Schrieber on the fragmentary character of meteoric stones, 117. Scientific researches, their frequent result, 50; scientific knowledge a requirement of the present age, 53, 54; scientific terms, their vagueness and misapplication, 58, 68. Scina, Abbate, earthquakes unconnected with the state of the weather, 206, 207. Scoresby, rarity of electric explosions in high northern regions, 337. Sea. See Ocean. Seismometer, the, 205. Seleucus of Erythrea, his astronomical studies, 65. Seneca, noticed the direction of the tails of comets, 102; his views on the nature and paths of comets, 103, 104; omens drawn from their sudden appearance, 111; the germs of later observations on earthquakes found in his writings, 207; problematical extinction and sinking of Mount Aetna, 227, 240. Shoals, atmospheric indications of their vicinity, 309. Sidereal systems, 89, 90. Siljerstrom, his observations on the Aurora, with Lottin and Bravais, on the coast of Lapland, 195. Sirowatskoi, "Wood Hills" in New Siberia, 281. Snow-line of the Himalayas, 30-33, 331, 334; of the Andes, 330; redness of long-fallen snow, 344. Solar system, general description, 90-154; its position in space, 89; its transistory motion, 145-150. Solinus on mud volcanoes, 225. Sommering on the fossil remains of the large vertebrata, 274. Somerville, Mrs., on the volume of fire-balls and shooting stars, 116; faintness of light of planetary nebulae, 141. Southern celestial hemisphere, its picturesque beauty, 85, 86. Spontaneous generation, 345, 346. Springs, hot and cold, 219-225; intermittent, 219; causes of their temperature, 220-222; thermal, 222, 345; deepest Artesian wells the warmest, observed by Arago, 223; salses, 224-226; influence of earthquake shocks on hot springs, 210, 222-224. Stars, general account of, 85-90; fixed 89, 90, 104; double and multiple, 89, 147; nebulous, 85, 86, 151, 152; their translatory motion, 147-150; parallaxes and distances, 147-149; computations of Bessel and Herschel on their diameter and volume, 148; immense number in the Milky Way, 150, 151; star dust, 85; star gaugings, 150; starless spaces, 150, 152; telescopic stars, 152; velocity of the propagation of light of, 153, 154; apparition of new stars, 153. Storms, magnetic and volcanic. See Magnetism, Volcanoes. Strabo, observed the cessation of shocks of erthquake on the eruption of lava, 215; on the mode in which islands are formed, 227; description of the Hill of Methone, 240; volcanic theory, 243; divined the existence of a continent in the northern hemisphere between Theria and Thine, 289; extolled the varied form of our small continent as favorable to the moral and intellectual development of its people, 291, 292. Struve, Otho, on the proper motion of the solar system, 146; investigations on the propagation of light, 153; parallaxes and distances of fixed stars, 153; observations on Halley's comet, 105. Studer, Professor, on mineral metamorphism. See note by Translator, 248. Sun, magnitude of its volume compared with that of the fixed stars, 136; obscuration of its disk, 132; rotation round the center of gravity of the whole solar system, 145; velocity of its translatory motion, 145; narrow limitations of its atmosphere as compared with the nucleus of other nebulous stars, 141; "sun stones" of the ancients, 122; views of the Greek philosophers on the sun, 122. Symond, Lieut., his trigonometrical survey of the Dead Sea, 296, 297. Tacitus, distinguished local climatic relations from those of race, 352. Temperature of the globe, see Earth and Ocean; remarkable uniformity over the same spaces of the surface of the ocean, 303; zones at which occur the maxima of the oceanic temperature, 319; causes which lower the temperature, 319, 320; temperature of various places, annual, and in the different seasons, 322, 323-328; thermic scale of temperature, 324, 325; of continental climates as compared with insular and littoral climates, 321, 322; law of decrease with increase of elevation, 327; depression of, by shoals, 309; refrigeration of the lower strata of the ocean, 303. Teneriffe, Peak of its striking scenery, 26. Theodectes of Phaselis on the color of the Ethiopians, 353. Theon of Alexandria described comets as "wandering light clouds," 100. Theophylactus described Scythia as free from earthquakes, 204. Thermal scales of cultivated plants, 324, 325. Thermal springs, their temperature, constancy, and change, 221-224; animal and vegetable life in, 345. Thermometer, 338. Thibet, habitability of its elevated plateaux, 331, 332. Thienemann on the Aurora, 197, 200. Thought, results of its free action, 53, 54; union with language, 56. Tiberias, Sea of, its depression below the level of the Mediterranean, 296. Tides of the ocean, their phenomena, 305, 306. Tillard, Capt., on the sudden appearance of the island of Sabrina, 242. Tournefort, zones of vegetation on Mount Ararat, 347. Tralles, his notice of the negative electricity of the air near high waterfalls, 336. Translator, notes by, 29; on the increase of the earth's internal heat with increase of depth, 45; silicious infusoria and animalculites, 46; chemical analysis of an aerolite, 64; on the recent discoveries of planets, 90, 91; observed the comet of 1843, at New Bedford, Massachusetts, in bright sunshine, 101; on meteoric stones, 111; on a MS., said to be in the library of Christ's College, Cambridge, 124; on the term "salses," 161; on Holberg's satire, "Travels in the World under Ground," 171; on the Aurora Borealis of Oct. 24, 1847, 194, 195, 199; on the electricity of the atmosphere during the Aurora, 200; on volcanic phenomena, 203, 204; description of the seismometer, 205; on the great earthquake of Lisbon, 210; impression made on the natives and foreigners by earthquakes in Peru, 215; earthquakes at Lima, 216, 217; on the gaseous compounds of sulphur, 217, 218; on the Lake of Lasch, its craters, 218; on the emissions of inflammable gas in the district of Phasells, 233; on true volcanoes as distinguished from salses, 224; on the volcano of Pichincha, 228; on the hornitos de Jorullo, as seen by Humboldt, 230; general rule on the dimensions of craters, 230; on the ejection of fish from the volcano of Imbaburn, 223; on the little isle of Volcano, 234; volcanic steam of Pantellaria, 235; on Daubeney's work "On Volcanoes," 236; account of the island of Santorino, 241; on the vicinity of extinct volcanoes to the sea, 244; meaning of the Chinese term "li," 245; on mineral metamorphism, 248; on fossil human remains found in Guadaloupe, 250; on minerals artifically produced 267, 268; fossil organic structures, 271, 272; on Coprolites, 271; geognostic distribution of fossils, 276; fossil fauna of the Sewalik Hills, 278; thickness of coal measures, 281; on the amber pine forests of the Baltic, 283, 284; elevation of mountain chains, 286, 287; the dinornis of Owen, 287; depth of the atmosphere, 302; richness of organic life in the ocean, 309; on filaments of plants resembling the spermatozoa of animals, 341; on the Diatomaceae in the South Arctic Ocean, 343; on the distribution of the floras and faunas of the British Isles, 348, 349; on the origin and diffusion of the British flora, 353, 354. Translatory motion of the solar system, 145-150. Trogus, Pompeius, on the supposed necessity that volcanoes were dependent on their vicinity to the sea for their continuance, 243, 244; views of the ancients on spontaneous generation, 346. Tropical latitudes, their advantages for the contemplation of nature, 33; powerful impressions from their organic richness and fertility, 34; facilities they present for a knowledge of the laws of nature 35; transparency of the atmosphere, 114; phosphorescence of the sea, 202. Tschudi, Dr., extract from his "Travels in Peru." See Translator's note, 215, 216, 217. Turner, note on Sir Isaac Newton, 132. Universality of animated life, 342, 343. Valz on the comet of 1618, 106. Varenius, Bernhard, his excellent general and comparative Geography, 66, 67; edited by Newton, 66. Vegetable world, as viewed with microscopic powers of vision, 341; its predominance over animal life, 343. Vegetation, its varied distribution on the earth's surface, 29-31, 62; richness and fertility in the tropics, 33-35; zones of vegetation on the declivities of mountains, 29-32, 346-350. See Aetna, Cordilleras, Himalayas, Mountains. Vico, satellites of Saturn, 96. Vigne, measurement of Ladak, 322. Vine, thermal scale of its cultivation, 324. Volcanoes, 28, 30, 35, 159, 161, 214, 215, 224-248; author's application of the term volcanic, 45; active volcanoes, safety-valves for their immediate neighborhood, 214; volcanic eruptions, 161, 210-270; mud volcanoes or salses, 224-228; traces of volcanic action on the surface of the earth and moon, 228; influence of relations of height on the occurrence of eruptions, 228-233; volcanic storm, 233; volcanic ashes, 233; classification of volcanoes into central and linear, 238; theory of the necessity of their proximity to the sea, 243-246; geographical distribution of still active volcanoes, 245-247; metamorphic action on rocks, 247-249. Vrolik, his anatomical investigations on the form of the pelvis, 352, 353. Wagner, Rudolph, notes on the races of Africa, 352. Walter on the decrease of volcanic activity, 215. Wartmann, meteors, 113, 114. Weber, his anatomical investigations on the form of the pelvis, 353. Webster, Dr. (of Harvard College, U.S.), account of the island named Sabrina. See note by Translator, 242. Winds, 315-321; monsoons, 316, 317; trade winds, 32-, 321; law of rotation, importance of its knowledge, 315-317. Wine on the temperature required for its cultivation, 324; thermic table of mean annual heat, 325. Wolleston on the limitation of the atmosphere, 302. Wrangel, Admiral, on the brilliancy of the Aurora Borealis, coincident with the fall of shooting stars, 126, 127; observations of the Aurora, 197, 200; wood hills of the Siberian Polar Sea, 281. Xenophanes of Colophon, described comets as wandering light clouds, 100; marine fossils found in marble quarries, 263. Young, Thomas, earliest observer of the influence different kinds of rocks exercise on the vibrations of the pendulum, 168. Yul-sung, described by Chinese writers as "the realm of pleasure," 332. Zimmerman, Carl, hypsometrical remarks on the elevation of the Himalayas, 32. Zodiacal light, conjectures on, 86-92; general account of, 137-144; beautiful appearance, 137, 138; first described in Childrey's Britannia Baconica, 138; probable causes, 141; intensity in tropical climates, 142. Zones, of vegetation, on the declivities of mountains, 29-33; of latitude, their diversified vegetation, 62; of the southern heavens, their magnificence, 85, 86; polar, 197, 198. END OF VOL. I. 
37957	----	MAN AND NATURE; OR, PHYSICAL GEOGRAPHY AS MODIFIED BY HUMAN ACTION. BY GEORGE P. MARSH. "Not all the winds, and storms, and earthquakes, and seas, and seasons of the world, have done so much to revolutionize the earth as MAN, the power of an endless life, has done since the day he came forth upon it, and received dominion over it."--H. BUSHNELL, _Sermon on the Power of an Endless Life_. NEW YORK: CHARLES SCRIBNER & CO., No. 654 BROADWAY. 1867. ENTERED, according to Act of Congress, in the year 1864, by CHARLES SCRIBNER, In the Clerk's Office of the District Court of the United States for the Southern District of New York. JOHN F. TROW & CO. PRINTER, STEREOTYPER, AND ELECTROTYPER, 46, 48, & 50 Greene St., New York. PREFACE. The object of the present volume is: to indicate the character and, approximately, the extent of the changes produced by human action in the physical conditions of the globe we inhabit; to point out the dangers of imprudence and the necessity of caution in all operations which, on a large scale, interfere with the spontaneous arrangements of the organic or the inorganic world; to suggest the possibility and the importance of the restoration of disturbed harmonies and the material improvement of waste and exhausted regions; and, incidentally, to illustrate the doctrine, that man is, in both kind and degree, a power of a higher order than any of the other forms of animated life, which, like him, are nourished at the table of bounteous nature. In the rudest stages of life, man depends upon spontaneous animal and vegetable growth for food and clothing, and his consumption of such products consequently diminishes the numerical abundance of the species which serve his uses. At more advanced periods, he protects and propagates certain esculent vegetables and certain fowls and quadrupeds, and, at the same time, wars upon rival organisms which prey upon these objects of his care or obstruct the increase of their numbers. Hence the action of man upon the organic world tends to subvert the original balance of its species, and while it reduces the numbers of some of them, or even extirpates them altogether, it multiplies other forms of animal and vegetable life. The extension of agricultural and pastoral industry involves an enlargement of the sphere of man's domain, by encroachment upon the forests which once covered the greater part of the earth's surface otherwise adapted to his occupation. The felling of the woods has been attended with momentous consequences to the drainage of the soil, to the external configuration of its surface, and probably, also, to local climate; and the importance of human life as a transforming power is, perhaps, more clearly demonstrable in the influence man has thus exerted upon superficial geography than in any other result of his material effort. Lands won from the woods must be both drained and irrigated; river banks and maritime coasts must be secured by means of artificial bulwarks against inundation by inland and by ocean floods; and the needs of commerce require the improvement of natural, and the construction of artificial channels of navigation. Thus man is compelled to extend over the unstable waters the empire he had already founded upon the solid land. The upheaval of the bed of seas and the movements of water and of wind expose vast deposits of sand, which occupy space required for the convenience of man, and often, by the drifting of their particles, overwhelm the fields of human industry with invasions as disastrous as the incursions of the ocean. On the other hand, on many coasts, sand hills both protect the shores from erosion by the waves and currents, and shelter valuable grounds from blasting sea winds. Man, therefore, must sometimes resist, sometimes promote, the formation and growth of dunes, and subject the barren and flying sands to the same obedience to his will to which he has reduced other forms of terrestrial surface. Besides these old and comparatively familiar methods of material improvement, modern ambition aspires to yet grander achievements in the conquest of physical nature, and projects are meditated which quite eclipse the boldest enterprises hitherto undertaken for the modification of geographical surface. The natural character of the various fields where human industry has effected revolutions so important, and where the multiplying population and the impoverished resources of the globe demand new triumphs of mind over matter, suggests a corresponding division of the general subject, and I have conformed the distribution of the several topics to the chronological succession in which man must be supposed to have extended his sway over the different provinces of his material kingdom. I have, then, in the Introductory chapter, stated, in a comprehensive way, the general effects and the prospective consequences of human action upon the earth's surface and the life which peoples it. This chapter is followed by four others in which I have traced the history of man's industry as exerted upon Animal and Vegetable Life, upon the Woods, upon the Waters, and upon the Sands; and to these I have added a concluding chapter upon Probable and Possible Geographical Revolutions yet to be effected by the art of man. I have only to add what, indeed, sufficiently appears upon every page of the volume, that I address myself not to professed physicists, but to the general intelligence of educated, observing, and thinking men; and that my purpose is rather to make practical suggestions than to indulge in theoretical speculations properly suited to a different class from that to which those for whom I write belong. GEORGE P. MARSH. _December 1, 1863._ BIBLIOGRAPHICAL LIST OF WORKS CONSULTED IN THE PREPARATION OF THIS VOLUME. _Amersfoordt, J. P._ Het Haarlemmermeer, Oorsprong, Geschiedenis, Droogmaking. Haarlem, 1857. 8vo. _Andresen, C. 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London, 1863. 8vo. Principles of Geology. New York, 1862. 8vo. _Mardigny, M. de._ Mémoire sur les Inondations des Rivières de l'Ardèche. Paris, 1860. 8vo. _Marschand, A._ Ueber die Entwaldung der Gebirge. Bern, 1849. 12mo. _pamphlet_. _Martineau._ Endeavors after the Christian Life. Boston, 1858. _Martins._ Revue des Deux Mondes, Avril, 1863. _Maury, M. F._ The Physical Geography of the Sea. Tenth edition. London, 1861. 8vo. _Medlicott, Dr._ Observations of, quoted from London Athenæum, 1863. _Meguscher, Francesco._ Memorie sulla migliore maniera per rimettere i Boschi della Lombardia, etc. Milano, 1859. 8vo. _Mejdell, Th._ Om Foranstaltninger til Behandling af Norges Skove. Christiania, 1858. 8vo. _Mella._ Delle Inondazioni del Mella nella notto del 14 al 15 Agosto, 1850. Brescia, 1851. 8vo. _Meyer, J._ Physik der Schweiz. Leipzig, 1854. 8vo. _Michelet, J._ L'Insecte, 4me edition. Paris, 1860. 12mo. ---- L'Oiseau, 7me edition. Paris, 1861. 12mo. _Monestier-Savignat, A._ Étude sur les Phénomènes, l'Aménagement et la Législation des Eaux au point de vue des Inondations. Paris, 1858. 8vo. _Montluisant._ Note sur les Desséchements, les Endiguements et les Irrigations; in Annales des Ponts et Chaussées, 1833, 2me sémestre, pp. 281-294. _Morozzi, Ferdinando._ Dello Stato Antico e Moderno del Fiume Arno. Firenze, 1762. 4to. _Müller, K._ Das Buch der Pflanzenwelt. Leipzig, 1857. 2 vols. 12mo. _Nangis, Guillaume de._ Extracts from, in Nouvelle Collection des Mémoires pour servir par Michaud et Poujoulat. Vol. i. Paris, 1836. _Nanquette, Henri._ Cours d'Aménagement des Forêts. Paris et Nancy, 1860. 8vo. _Newberry, Dr._ Report in Pacific Railroad Report, vol. vi. Niebelunge-Lied, Der. Abdruck der Handschrift von Joseph von Lassberg. Leipzig, 1840. Folio. _Niel._ L'Agriculture des États Sardes. Turin, 1857. 8vo. Pacific Railroad Report. Reports of Explorations and Surveys for a Railroad Route to the Pacific. Washington, various years. 12 vols. 4to. _Palissy, Bernard._ [OE]uvres Complètes, avec des Notes, etc., par Paul-Antoine Cap. Paris, 1844. 12mo. _Parade, A._ See _Lorentz_. _Paramelle, Abbé._ Quellenkunde, Lehre von der Bildung und Auffindung der Quellen; mit einem Vorwort von B. Cotta. Leipzig, 1856. 12mo. _Parish, Dr._ Life of Dr. Eleazer Wheelock. 8vo. _Parry, C. C._ Report in United States and Mexican Boundary Survey, vol. i. _Parthey, G._ Wanderungen durch Sicilien und die Levante. Berlin, 1834. 2 vols. 12mo. _Piper, R. U._ The Trees of America. Boston, 1858, Nos. i-iv. 4to. _Plinii, Historia Naturalis_, ed. Hardouin. Paris, 1723. 3 vols. folio. _Ponz, Antonio._ Viage de España. Madrid, 1788, etc. 18 vols. 12mo. _Quatrefages, A. de._ Souvenirs d'un Naturaliste. Paris, 1854. 2 vols. 12mo. _Reclus, Elisée._ Le Littoral de la France; Revue des Deux Mondes, 15 Decembre, 1862. _Rentzsch, Hermann._ Der Wald im Haushalt der Natur und der Volkswirthschaft. Leipzig, 1862. 8vo. _Ribbe, Charles de_. La Provence au point de vue des Bois, des Torrents et des Inondations. Paris, 1857. 8vo. _Ridolfi, Cosimo._ Lezioni Orali. Firenze, 1862. 2 vols. 8vo. _Ritter, Carl._ Einleitung zur allgemeinen vergleichenden Geographie. Berlin, 1852. 8vo. ---- Die Erdkunde im Verhältniss zur Natur und zur Geschichte des Menschen. Berlin, various years. 19 vols. 8vo. _Rosa, G._ Le Condizioni de' boschi, de' fiumi e de' torrenti nella provincia di Bergamo. Politecnico, Dicembre, 1861, pp. 606, 621. ---- Studii sui Boschi. Politecnico, Maggio, 1862, pp. 232, 238. _Rossmässler, C. A._ Der Wald. Leipzig und Heidelberg, 1863. 8vo. _Roth, J._ Der Vesuv und die Umgebung von Neapel. Berlin, 1857. 8vo. _Rozet, M._ Moyens de forcer les Torrents des Montagnes de rendre une partie du sol qu'ils ravagent. Paris, 1856. 8vo. _pamphlet_. _Salvagnoli-Marchetti, Antonio._ Memorie Economico-Statistiche sulle Maremme Toscane. Firenze, 1846. 8vo. ---- Raccolta di Documenti sul Bonificamento delle Maremmo Toscane. Firenze, 1861. 8vo. ---- Rapporto sul Bonificamento delle Maremmo Toscane. Firenze, 1859. 8vo. ---- Rapporto sulle Operazioni Idrauliche ed Economiche eseguite nel 1859-'60 nelle Maremmo Toscane. Firenze, 1860. 8vo. _Sandys, George._ A Relation of a Journey begun An. Dom. 1610. London, 1627. Folio. _Schacht, H._ Les Arbres, Études sur leur Structure et leur Végétation, traduit par E. Morren. Bruxelles et Leipzig, 1862. 8vo. _Schleiden, M. J._ Die Landenge von Suês. Leipzig, 1858. 8vo. ---- Die Pflanze und ihr Leben. Leipzig, 1848. 8vo. _Schubert, W. von._ Resa genom Sverige, Norrige, Lappland, etc. Stockholm, 1823. 3 vols. 8vo. _Seneca, L. A._ Opera Omnia quæ supersunt, ex rec. Ruhkopf. Aug. Taurinorum, 1831. 6 vols. 8vo. _Simonde, J. E. L._ Tableau de l'Agriculture Toscane. Genève, 1801. 8vo. _Smith, Dr. William._ A Dictionary of the Bible. London, 1860. 3 vols. 8vo. ---- A Dictionary of Greek and Roman Geography. London, 1854, 1857. 2 vols. 8vo. _Smith, John._ Historie of Virginia. London, 1624. Folio. _Somerville, Mary._ Physical Geography. Fifth edition. London, 1862. 12mo. _Springer, John S._ Forest-Life and Forest-Trees. New York, 1851. 12mo. _Stanley, Dr._ Lectures on the History of the Jewish Church. London, 1863. 8vo. _Staring, W. H._ De Bodem van Nederland. Haarlem, 1856. 2 vols. 8vo. ---- Voormaals en Thans. Haarlem, 1858. 8vo. _Stevens, Gov._ Report in Pacific Railroad Report, vol. xii. _Strain, Lieut. I. C._ Darien Exploring Expedition, by J. T. Headley, in Harper's Magazine. New York, March, April, and May, 1855. _Streffleur, V._ Ueber die Natur und die Wirkungen der Wildbäche. Sitz. Ber. der M. N. W. Classe der Kaiserl. Akad. der Wis. February, 1852, viii, p. 248. _Ström, Isr._ Om Skogarnas Vård och Skötsel. Upsala, 1853. _Pamphlet._ _Surell, Alexandre._ Étude sur les Torrents des Hautes Alpes. Paris, 1844. 4to. _Tartini, Ferdinando._ Memorie sul Bonificamento delle Maremme Toscane. Firenze, 1838. Folio. _Thomas and Baldwin._ Gazetteer. Philadelphia, 1855. 1 vol. 8vo. _Thompson, Z._ History of Vermont, Natural, Civil, and Statistical. Burlington, 1842. 8vo. ---- Appendix to History of Vermont. Burlington, 1853. 8vo. _Titcomb, Timothy._ Lessons in Life. New York, 1861. 12mo. _Treadwell, Dr._ Observations of, quoted from Report of Commissioner of Patents. _Troy, Paul._ Étude sur le Reboisement des Montagnes. Paris et Toulouse, 1861. 8vo. _pamphlet_. _Tschudi, Friedrich von._ Ueber die Landwirthschaftliche Bedeutung der Vögel. St. Gallen, 1854. 12mo. _Tschudi, J. J. von._ Travels in Peru. New York, 1848. 8vo. _Vallès, M. F._ Études sur les Inondations, leurs causes et leurs effets. Paris, 1857. 8vo. _Valvasor, Johann Weichard._ Die Ehre des Herzogthums Crain. Laybach, 1689. 4 vols. folio. _Van Lennep._ Extracts from Journal of, in the Missionary Herald. _Vaupell, Chr._ Bögens Indvandring i de Danske Skove. Kjöbenhavn, 1857. 8vo. ---- De Nordsjællandske Skovmoser. Kjöbenhavn, 1851. 4to. _pamphlet_. _Venema, G. A._ Over het Dalen van de Noordelijke Kuststreken van ons Land. Groningen, 1854. 8vo. _Villa, Antonio Giovanni Batt._ Necessità dei Boschi nella Lombardia. Milano, 1850. 4to. _Viollet, J. B._ Théorie des Puits Artésiens. Paris, 1840. 8vo. _Walterhausen, W. Sartorius von._ Ueber den Sicilianischen Ackerbau. Göttingen, 1863. _Webster, Noah._ A Collection of Papers on Political, Literary, and Moral Subjects. New York, 1843. 8vo. _Wessely, Joseph._ Die Oesterreichischen Alpenländer und ihre Forste. Wien, 1853. 2 vols. 8vo. _Wetzstein, J. G._ Reisebericht über Hauran und die Trachonen. Berlin, 1860. 8vo. _Wild, Albert._ Die Niederlande. Leipzig, 1862. 2 vols. 8vo. _Wilhelm, Gustav._ Der Boden und das Wasser. Wien, 1861. 8vo. _Williams, Dr._ History of Vermont. 2 vols. 8vo. _Wittwer, W. C._ Die Physikalische Geographie. Leipzig, 1855. 8vo. _Young, Arthur._ Voyages en France, pendant les années 1787, 1788, 1789, précédée d'une introduction par Lavergne. Paris, 1860. 2 vols. 12mo. ---- Voyages en Italie et en Espagne, pendant les années 1787, 1789. Paris, 1860. 1 vol. 12mo. TABLE OF CONTENTS. CHAPTER I. INTRODUCTORY. Natural Advantages of the Territory of the Roman Empire--Physical Decay of that Territory and of other parts of the Old World-- Causes of the Decay--New School of Geographers--Reaction of Man upon Nature--Observation of Nature--Cosmical and Geological Influences--Geographical Influence of Man--Uncertainty of our Meteorological Knowledge--Mechanical Effects produced by Man on the surface of the Earth--Importance and Possibility of Physical Restoration--Stability of Nature--Restoration of Disturbed Harmonies--Destructiveness of Man--Physical Improvement--Human and Brute Action Compared--Forms and Formations most liable to Physical Degradation--Physical Decay of New Countries--Corrupt Influence of Private Corporations, _Note_, 1 CHAPTER II. TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES. Modern Geography embraces Organic Life--Transfer of Vegetable Life--Foreign Plants grown in the United States--American Plants grown in Europe--Modes of Introduction of Foreign Plants--Vegetables, how affected by transfer to Foreign Soils--Extirpation of Vegetables--Origin of Domestic Plants-- Organic Life as a Geological and Geographical Agency--Origin and Transfer of Domestic Animals--Extirpation of Animals-- Numbers of Birds in the United States--Birds as Sowers and Consumers of Seeds, and as Destroyers of Insects--Diminution and Extirpation of Birds--Introduction of Birds--Utility of Insects and Worms--Introduction of Insects--Destruction of Insects--Reptiles--Destruction of Fish--Introduction and Breeding of Fish--Extirpation of Aquatic Animals--Minute Organisms, 57 CHAPTER III. THE WOODS. The Habitable Earth originally Wooded--The Forest does not furnish Food for Man--First Removal of the Woods--Effects of Fire on Forest Soil--Effects of the Destruction of the Forest--Electrical Influence of Trees--Chemical Influence of the Forest. Influence of the Forest, considered as Inorganic Matter, on Temperature: _a_, Absorbing and Emitting Surface; _b_, Trees as Conductors of Heat; _c_, Trees in Summer and in Winter; _d_, Dead Products of Tree; _e_, Trees as a Shelter to Grounds to the leeward of them; _f_, Trees as a Protection against Malaria--The Forest, as Inorganic Matter, tends to mitigate extremes. Trees as Organisms: Specific Temperature--Total Influence of the Forest on Temperature. Influence of Forests on the Humidity of the Air and the Earth: _a_, as Inorganic Matter; _b_, as Organic--Wood Mosses and Fungi--Flow of Sap--Absorption and Exhalation of Moisture by Trees--Balance of Conflicting Influences--Influence of the Forest on Temperature and Precipitation--Influence of the Forest on the Humidity of the Soil--Its Influence on the Flow of Springs--General Consequences of the Destruction of the Woods--Literature and Condition of the Forest in different Countries--The Influence of the Forest on Inundations-- Destructive Action of Torrents--The Po and its Deposits-- Mountain Slides--Protection against the Fall of Rocks and Avalanches by Trees--Principal Causes of the Destruction of the Forest--American Forest Trees--Special Causes of the Destruction of European Woods--Royal Forests and Game Laws-- Small Forest Plants, Vitality of Seeds--Utility of the Forest--The Forests of Europe--Forests of the United States and Canada--The Economy of the Forest--European and American Trees Compared--Sylviculture--Instability of American Life, 128 CHAPTER IV. THE WATERS. Land artificially won from the Waters: _a_, Exclusion of the Sea by Diking; _b_, Draining of Lakes and Marshes; _c_, Geographical Influence of such Operations--Lowering of Lakes--Mountain Lakes-- Climatic Effects of Draining Lakes and Marshes. Geographical and Climatic Effects of Aqueducts, Reservoirs, and Canals--Surface and Underdraining, and their Climatic and Geographical Effects--Irrigation and its Climatic and Geographical Effects. Inundations and Torrents: _a_, River Embankments; _b_, Floods of the Ardèche; _c_, Crushing Force of Torrents; _d_, Inundations of 1856 in France; _e_, Remedies against Inundations--Consequences if the Nile had been confined by Lateral Dikes. Improvements in the Val di Chiana--Improvements in the Tuscan Maremme--Obstruction of River Mouths--Subterranean Waters-- Artesian Wells--Artificial Springs--Economizing Precipitation, 330 CHAPTER V. THE SANDS. Origin of Sand--Sand now carried down to the Sea--The Sands of Egypt and the adjacent Desert--The Suez Canal--The Sands of Egypt--Coast Dunes and Sand Plains--Sand Banks--Dunes on Coast of America--Dunes of Western Europe--Formation of Dunes--Character of Dune Sand--Interior Structure of Dunes--Form of Dunes--Geological Importance of Dunes--Inland Dunes--Age, Character, and Permanence of Dunes--Use of Dunes as Barrier against the Sea--Encroachments of the Sea--The Lümfjord--Encroachments of the Sea--Drifting of Dune Sands--Dunes of Gascony--Dunes of Denmark--Dunes of Prussia--Artificial Formation of Dunes--Trees suitable for Dune Plantations--Extent of Dunes in Europe--Dune Vineyards of Cape Breton--Removal of Dunes--Inland Sand Plains--The Landes of Gascony--The Belgian Campine--Sands and Steppes of Eastern Europe--Advantages of Reclaiming Dunes--Government Works of Improvement, 451 CHAPTER VI. PROJECTED OR POSSIBLE GEOGRAPHICAL CHANGES BY MAN. Cutting of Marine Isthmuses--The Suez Canal--Canal across Isthmus of Darien--Canals to the Dead Sea--Maritime Canals in Greece-- Canal of Saros--Cape Cod Canal--Diversion of the Nile--Changes in the Caspian--Improvements in North American Hydrography-- Diversion of the Rhine--Draining of the Zuiderzee--Waters of the Karst--Subterranean Waters of Greece--Soil below Rock-- Covering Rocks with Earth--Wadies of Arabia Petræa--Incidental Effects of Human Action--Resistance to great Natural Forces-- Effects of Mining--Espy's Theories--River Sediment--Nothing small in Nature, 517 CHAPTER I. INTRODUCTORY. NATURAL ADVANTAGES OF THE TERRITORY OF THE ROMAN EMPIRE--PHYSICAL DECAY OF THAT TERRITORY AND OF OTHER PARTS OF THE OLD WORLD--CAUSES OF THE DECAY--NEW SCHOOL OF GEOGRAPHERS--REACTION OF MAN UPON NATURE-- OBSERVATION OF NATURE--COSMICAL AND GEOLOGICAL INFLUENCES--GEOGRAPHICAL INFLUENCE OF MAN--UNCERTAINTY OF OUR METEOROLOGICAL KNOWLEDGE-- MECHANICAL EFFECTS PRODUCED BY MAN ON THE SURFACE OF THE EARTH-- IMPORTANCE AND POSSIBILITY OF PHYSICAL RESTORATION--STABILITY OF NATURE--RESTORATION OF DISTURBED HARMONIES--DESTRUCTIVENESS OF MAN-- PHYSICAL IMPROVEMENT--HUMAN AND BRUTE ACTION COMPARED--FORMS AND FORMATIONS MOST LIABLE TO PHYSICAL DEGRADATION--PHYSICAL DECAY OF NEW COUNTRIES--CORRUPT INFLUENCE OF PRIVATE CORPORATIONS, _note_. _Natural Advantages of the Territory of the Roman Empire._ The Roman Empire, at the period of its greatest expansion, comprised the regions of the earth most distinguished by a happy combination of physical advantages. The provinces bordering on the principal and the secondary basins of the Mediterranean enjoyed a healthfulness and an equability of climate, a fertility of soil, a variety of vegetable and mineral products, and natural facilities for the transportation and distribution of exchangeable commodities, which have not been possessed in an equal degree by any territory of like extent in the Old World or the New. The abundance of the land and of the waters adequately supplied every material want, ministered liberally to every sensuous enjoyment. Gold and silver, indeed, were not found in the profusion which has proved so baneful to the industry of lands richer in veins of the precious metals; but mines and river beds yielded them in the spare measure most favorable to stability of value in the medium of exchange, and, consequently, to the regularity of commercial transactions. The ornaments of the barbaric pride of the East, the pearl, the ruby, the sapphire, and the diamond--though not unknown to the luxury of a people whose conquests and whose wealth commanded whatever the habitable world could contribute to augment the material splendor of their social life--were scarcely native to the territory of the empire; but the comparative rarity of these gems in Europe, at somewhat earlier periods, was, perhaps, the very circumstance that led the cunning artists of classic antiquity to enrich softer stones with engravings, which invest the common onyx and carnelian with a worth surpassing, in cultivated eyes, the lustre of the most brilliant oriental jewels. Of these manifold blessings the temperature of the air, the distribution of the rains, the relative disposition of land and water, the plenty of the sea, the composition of the soil, and the raw material of some of the arts, were wholly gratuitous gifts. Yet the spontaneous nature of Europe, of Western Asia, of Libya, neither fed nor clothed the civilized inhabitants of those provinces. Every loaf was eaten in the sweat of the brow. All must be earned by toil. But toil was nowhere else rewarded by so generous wages; for nowhere would a given amount of intelligent labor produce so abundant, and, at the same time, so varied returns of the good things of material existence. The luxuriant harvests of cereals that waved on every field from the shores of the Rhine to the banks of the Nile, the vines that festooned the hillsides of Syria, of Italy, and of Greece, the olives of Spain, the fruits of the gardens of the Hesperides, the domestic quadrupeds and fowls known in ancient rural husbandry--all these were original products of foreign climes, naturalized in new homes, and gradually ennobled by the art of man, while centuries of persevering labor were expelling the wild vegetation, and fitting the earth for the production of more generous growths. Only for the sense of landscape beauty did unaided nature make provision. Indeed, the very commonness of this source of refined enjoyment seems to have deprived it of half its value; and it was only in the infancy of lands where all the earth was fair, that Greek and Roman humanity had sympathy enough with the inanimate world to be alive to the charms of rural and of mountain scenery. In later generations, when the glories of the landscape had been heightened by plantation, and decorative architecture, and other forms of picturesque improvement, the poets of Greece and Rome were blinded by excess of light, and became, at last, almost insensible to beauties that now, even in their degraded state, enchant every eye, except, too often, those which a lifelong familiarity has dulled to their attractions. _Physical Decay of the Territory of the Roman Empire, and of other parts of the Old World._ If we compare the present physical condition of the countries of which I am speaking, with the descriptions that ancient historians and geographers have given of their fertility and general capability of ministering to human uses, we shall find that more than one half of their whole extent--including the provinces most celebrated for the profusion and variety of their spontaneous and their cultivated products, and for the wealth and social advancement of their inhabitants--is either deserted by civilized man and surrendered to hopeless desolation, or at least greatly reduced in both productiveness and population. Vast forests have disappeared from mountain spurs and ridges; the vegetable earth accumulated beneath the trees by the decay of leaves and fallen trunks, the soil of the alpine pastures which skirted and indented the woods, and the mould of the upland fields, are washed away; meadows, once fertilized by irrigation, are waste and unproductive, because the cisterns and reservoirs that supplied the ancient canals are broken, or the springs that fed them dried up; rivers famous in history and song have shrunk to humble brooklets; the willows that ornamented and protected the banks of the lesser watercourses are gone, and the rivulets have ceased to exist as perennial currents, because the little water that finds its way into their old channels is evaporated by the droughts of summer, or absorbed by the parched earth, before it reaches the lowlands; the beds of the brooks have widened into broad expanses of pebbles and gravel, over which, though in the hot season passed dryshod, in winter sealike torrents thunder; the entrances of navigable streams are obstructed by sandbars, and harbors, once marts of an extensive commerce, are shoaled by the deposits of the rivers at whose mouths they lie; the elevation of the beds of estuaries, and the consequently diminished velocity of the streams which flow into them, have converted thousands of leagues of shallow sea and fertile lowland into unproductive and miasmatic morasses. Besides the direct testimony of history to the ancient fertility of the regions to which I refer--Northern Africa, the greater Arabian peninsula, Syria, Mesopotamia, Armenia and many other provinces of Asia Minor, Greece, Sicily, and parts of even Italy and Spain--the multitude and extent of yet remaining architectural ruins, and of decayed works of internal improvement, show that at former epochs a dense population inhabited those now lonely districts. Such a population could have been sustained only by a productiveness of soil of which we at present discover but slender traces; and the abundance derived from that fertility serves to explain how large armies, like those of the ancient Persians, and of the Crusaders and the Tartars in later ages, could, without an organized commissariat, secure adequate supplies in long marches through territories which, in our times, would scarcely afford forage for a single regiment. It appears, then, that the fairest and fruitfulest provinces of the Roman Empire, precisely that portion of terrestrial surface, in short, which, about the commencement of the Christian era, was endowed with the greatest superiority of soil, climate, and position, which had been carried to the highest pitch of physical improvement, and which thus combined the natural and artificial conditions best fitting it for the habitation and enjoyment of a dense and highly refined and cultivated population, is now completely exhausted of its fertility, or so diminished in productiveness, as, with the exception of a few favored oases that have escaped the general ruin, to be no longer capable of affording sustenance to civilized man. If to this realm of desolation we add the now wasted and solitary soils of Persia and the remoter East, that once fed their millions with milk and honey, we shall see that a territory larger than all Europe, the abundance of which sustained in bygone centuries a population scarcely inferior to that of the whole Christian world at the present day, has been entirely withdrawn from human use, or, at best, is thinly inhabited by tribes too few in numbers, too poor in superfluous products, and too little advanced in culture and the social arts, to contribute anything to the general moral or material interests of the great commonwealth of man. _Causes of this Decay._ The decay of these once flourishing countries is partly due, no doubt, to that class of geological causes, whose action we can neither resist nor guide, and partly also to the direct violence of hostile human force; but it is, in a far greater proportion, either the result of man's ignorant disregard of the laws of nature, or an incidental consequence of war, and of civil and ecclesiastical tyranny and misrule. Next to ignorance of these laws, the primitive source, the _causa causarum_, of the acts and neglects which have blasted with sterility and physical decrepitude the noblest half of the empire of the Cæsars, is, first, the brutal and exhausting despotism which Rome herself exercised over her conquered kingdoms, and even over her Italian territory; then, the host of temporal and spiritual tyrannies which she left as her dying curse to all her wide dominion, and which, in some form of violence or of fraud, still brood over almost every soil subdued by the Roman legions.[1] Man cannot struggle at once against crushing oppression and the destructive forces of inorganic nature. When both are combined against him, he succumbs after a shorter or a longer struggle, and the fields he has won from the primeval wood relapse into their original state of wild and luxuriant, but unprofitable forest growth, or fall into that of a dry and barren wilderness. Rome imposed on the products of agricultural labor in the rural districts taxes which the sale of the entire harvest would scarcely discharge; she drained them of their population by military conscription; she impoverished the peasantry by forced and unpaid labor on public works; she hampered industry and internal commerce by absurd restrictions and unwise regulations. Hence, large tracts of land were left uncultivated, or altogether deserted, and exposed to all the destructive forces which act with such energy on the surface of the earth when it is deprived of those protections by which nature originally guarded it, and for which, in well-ordered husbandry, human ingenuity has contrived more or less efficient substitutes.[2] Similar abuses have tended to perpetuate and extend these evils in later ages, and it is but recently that, even in the most populous parts of Europe, public attention has been half awakened to the necessity of restoring the disturbed harmonies of nature, whose well-balanced influences are so propitious to all her organic offspring, of repaying to our great mother the debt which the prodigality and the thriftlessness of former generations have imposed upon their successors--thus fulfilling the command of religion and of practical wisdom, to use this world as not abusing it. _New School of Geographers._ The labors of Humboldt, of Ritter, of Guyot and their followers, have given to the science of geography a more philosophical, and, at the same time, a more imaginative character than it had received from the hands of their predecessors. Perhaps the most interesting field of speculation, thrown open by the new school to the cultivators of this attractive study, is the inquiry: how far external physical conditions, and especially the configuration of the earth's surface, and the distribution, outline, and relative position of land and water, have influenced the social life and social progress of man. _Reaction of Man on Nature._ But, as we have seen, man has reacted upon organized and inorganic nature, and thereby modified, if not determined, the material structure of his earthly home. The measure of that reaction manifestly constitutes a very important element in the appreciation of the relations between mind and matter, as well as in the discussion of many purely physical problems. But though the subject has been incidentally touched upon by many geographers, and treated with much fulness of detail in regard to certain limited fields of human effort, and to certain specific effects of human action, it has not, as a whole, so far as I know, been made matter of special observation, or of historical research by any scientific inquirer.[3] Indeed, until the influence of physical geography upon human life was recognized as a distinct branch of philosophical investigation, there was no motive for the pursuit of such speculations; and it was desirable to inquire whether we have or can become the architects of our own abiding place, only when it was known how the mode of our physical, moral, and intellectual being is affected by the character of the home which Providence has appointed, and we have fashioned, for our material habitation.[4] It is still too early to attempt scientific method in discussing this problem, nor is our present store of the necessary facts by any means complete enough to warrant me in promising any approach to fulness of statement respecting them. Systematic observation in relation to this subject has hardly yet begun,[5] and the scattered data which have chanced to be recorded have never been collected. It has now no place in the general scheme of physical science, and is matter of suggestion and speculation only, not of established and positive conclusion. At present, then, all that I can hope is to excite an interest in a topic of much economical importance, by pointing out the directions and illustrating the modes in which human action has been or may be most injurious or most beneficial in its influence upon the physical conditions of the earth we inhabit. _Observation of Nature._ In these pages, as in all I have ever written or propose to write, it is my aim to stimulate, not to satisfy, curiosity, and it is no part of my object to save my readers the labor of observation or of thought. For labor is life, and Death lives where power lives unused.[6] Self is the schoolmaster whose lessons are best worth his wages; and since the subject I am considering has not yet become a branch of formal instruction, those whom it may interest can, fortunately, have no pedagogue but themselves. To the natural philosopher, the descriptive poet, the painter, and the sculptor, as well as to the common observer, the power most important to cultivate, and, at the same time, hardest to acquire, is that of seeing what is before him. Sight is a faculty; seeing, an art. The eye is a physical, but not a self-acting apparatus, and in general it sees only what it seeks. Like a mirror, it reflects objects presented to it; but it may be as insensible as a mirror, and it does not necessarily perceive what it reflects.[7] It is disputed whether the purely material sensibility of the eye is capable of improvement and cultivation. It has been maintained by high authority, that the natural acuteness of none of our sensuous faculties can be heightened by use, and hence that the minutest details of the image formed on the retina are as perfect in the most untrained, as in the most thoroughly disciplined organ. This may well be doubted, and it is agreed on all hands that the power of multifarious perception and rapid discrimination may be immensely increased by well-directed practice.[8] This exercise of the eye I desire to promote, and, next to moral and religious doctrine, I know no more important practical lessons in this earthly life of ours--which, to the wise man, is a school from the cradle to the grave--than those relating to the employment of the sense of vision in the study of nature. The pursuit of physical geography, embracing actual observation of terrestrial surface, affords to the eye the best general training that is accessible to all. The majority of even cultivated men have not the time and means of acquiring anything beyond a very superficial acquaintance with any branch of physical knowledge. Natural science has become so vastly extended, its recorded facts and its unanswered questions so immensely multiplied, that every strictly scientific man must be a specialist, and confine the researches of a whole life within a comparatively narrow circle. The study I am recommending, in the view I propose to take of it, is yet in that imperfectly developed state which allows its votaries to occupy themselves with such broad and general views as are attainable by every person of culture, and it does not now require a knowledge of special details which only years of application can master. It may be profitably pursued by all; and every traveller, every lover of rural scenery, every agriculturist, who will wisely use the gift of sight, may add valuable contributions to the common stock of knowledge on a subject which, as I hope to convince my readers, though long neglected, and now inartificially presented, is not only a very important, but a very interesting field of inquiry. _Cosmical and Geological Influences._ The revolutions of the seasons, with their alternations of temperature and of length of day and night, the climates of different zones, and the general condition and movements of the atmosphere and the seas, depend upon causes for the most part cosmical, and, of course, wholly beyond our control. The elevation, configuration, and composition of the great masses of terrestrial surface, and the relative extent and distribution of land and water, are determined by geological influences equally remote from our jurisdiction. It would hence seem that the physical adaptation of different portions of the earth to the use and enjoyment of man is a matter so strictly belonging to mightier than human powers, that we can only accept geographical nature as we find her, and be content with such soils and such skies as she spontaneously offers. _Geographical Influence of Man._ But it is certain that man has done much to mould the form of the earth's surface, though we cannot always distinguish between the results of his action and the effects of purely geological causes; that the destruction of the forests, the drainage of lakes and marshes, and the operations of rural husbandry and industrial art have tended to produce great changes in the hygrometric, thermometric, electric, and chemical condition of the atmosphere, though we are not yet able to measure the force of the different elements of disturbance, or to say how far they have been compensated by each other, or by still obscurer influences; and, finally, that the myriad forms of animal and vegetable life, which covered the earth when man first entered upon the theatre of a nature whose harmonies he was destined to derange, have been, through his action, greatly changed in numerical proportion, sometimes much modified in form and product, and sometimes entirely extirpated. The physical revolutions thus wrought by man have not all been destructive to human interests. Soils to which no nutritious vegetable was indigenous, countries which once brought forth but the fewest products suited for the sustenance and comfort of man--while the severity of their climates created and stimulated the greatest number and the most imperious urgency of physical wants--surfaces the most rugged and intractable, and least blessed with natural facilities of communication, have been made in modern times to yield and distribute all that supplies the material necessities, all that contributes to the sensuous enjoyments and conveniences of civilized life. The Scythia, the Thule, the Britain, the Germany, and the Gaul which the Roman writers describe in such forbidding terms, have been brought almost to rival the native luxuriance and easily won plenty of Southern Italy; and, while the fountains of oil and wine that refreshed old Greece and Syria and Northern Africa have almost ceased to flow, and the soils of those fair lands are turned to thirsty and inhospitable deserts, the hyperborean regions of Europe have conquered, or rather compensated, the rigors of climate, and attained to a material wealth and variety of product that, with all their natural advantages, the granaries of the ancient world can hardly be said to have enjoyed. These changes for evil and for good have not been caused by great natural revolutions of the globe, nor are they by any means attributable wholly to the moral and physical action or inaction of the peoples, or, in all cases, even of the races that now inhabit these respective regions. They are products of a complication of conflicting or coincident forces, acting through a long series of generations; here, improvidence, wastefulness, and wanton violence; there, foresight and wisely guided persevering industry. So far as they are purely the calculated and desired results of those simple and familiar operations of agriculture and of social life which are as universal as civilization--the removal of the forests which covered the soil required for the cultivation of edible fruits, the drying of here and there a few acres too moist for profitable husbandry, by draining off the surface waters, the substitution of domesticated and nutritious for wild and unprofitable vegetable growths, the construction of roads and canals and artificial harbors--they belong to the sphere of rural, commercial, and political economy more properly than to geography, and hence are but incidentally embraced within the range of our present inquiries, which concern physical, not financial balances. I propose to examine only the greater, more permanent, and more comprehensive mutations which man has produced, and is producing, in earth, sea, and sky, sometimes, indeed, with conscious purpose, but for the most part, as unforeseen though natural consequences of acts performed for narrower and more immediate ends. The exact measurement of the geographical changes hitherto thus effected is, as I have hinted, impracticable, and we possess, in relation to them, the means of only qualitative, not quantitative analysis. The fact of such revolutions is established partly by historical evidence, partly by analogical deduction from effects produced in our own time by operations similar in character to those which must have taken place in more or less remote ages of human action. Both sources of information are alike defective in precision; the latter, for general reasons too obvious to require specification; the former, because the facts to which it bears testimony occurred before the habit or the means of rigorously scientific observation upon any branch of physical research, and especially upon climatic changes, existed. _Uncertainty of our Meteorological Knowledge._ The invention of measures of heat, and of atmospheric moisture, pressure, and precipitation, is extremely recent. Hence, ancient physicists have left us no thermometric or barometric records, no tables of the fall, evaporation, and flow of waters, and even no accurate maps of coast lines and the course of rivers. Their notices of these phenomena are almost wholly confined to excessive and exceptional instances of high or of low temperatures, extraordinary falls of rain and snow, and unusual floods or droughts. Our knowledge of the meteorological condition of the earth, at any period more than two centuries before our own time, is derived from these imperfect details, from the vague statements of ancient historians and geographers in regard to the volume of rivers and the relative extent of forest and cultivated land, from the indications furnished by the history of the agriculture and rural economy of past generations, and from other almost purely casual sources of information. Among these latter we must rank certain newly laid open fields of investigation, from which facts bearing on the point now under consideration have been gathered. I allude to the discovery of artificial objects in geological formations older than any hitherto recognized as exhibiting traces of the existence of man; to the ancient lacustrine habitations of Switzerland, containing the implements of the occupants, remains of their food, and other relics of human life; to the curious revelations of the Kjökkenmöddinger, or heaps of kitchen refuse, in Denmark, and of the peat mosses in the same and other northern countries; to the dwellings and other evidences of the industry of man in remote ages sometimes laid bare by the movement of sand dunes on the coasts of France and of the North Sea; and to the facts disclosed on the shores of the latter, by excavations in inhabited mounds which were, perhaps, raised before the period of the Roman Empire. These remains are memorials of races which have left no written records, because they perished before the historical period of the countries they occupied began. The plants and animals that furnished the relics found in the deposits were certainly contemporaneous with man; for they are associated with his works, and have evidently served his uses. In some cases, the animals belonged to species well ascertained to be now altogether extinct; in some others, both the animals and the vegetables, though extant elsewhere, have ceased to inhabit the regions where their remains are discovered. From the character of the artificial objects, as compared with others belonging to known dates, or at least to known periods of civilization, ingenious inferences have been drawn as to their age; and from the vegetation, remains of which accompany them, as to the climates of Central and Northern Europe at the time of their production. There are, however, sources of error which have not always been sufficiently guarded against in making these estimates. When a boat, composed of several pieces of wood fastened together by pins of the same material, is dug out of a bog, it is inferred that the vessel, and the skeletons and implements found with it, belong to an age when the use of iron was not known to the builders. But this conclusion is not warranted by the simple fact that metals were not employed in its construction; for the Nubians at this day build boats large enough to carry half a dozen persons across the Nile, out of small pieces of acacia wood pinned together entirely with wooden bolts. Nor is the occurrence of flint arrow heads and knives, in conjunction with other evidences of human life, conclusive proof as to the antiquity of the latter. Lyell informs us that some Oriental tribes still continue to use the same stone implements as their ancestors, "after that mighty empires, where the use of metals in the arts was well known, had flourished for three thousand years in their neighborhood;"[9] and the North American Indians now manufacture and use weapons of stone, and even of glass, chipping them in the latter case out of the bottoms of thick bottles, with great facility.[10] We may also be misled by our ignorance of the commercial relations existing between savage tribes. Extremely rude nations, in spite of their jealousies and their perpetual wars, sometimes contrive to exchange the products of provinces very widely separated from each other. The mounds of Ohio contain pearls, thought to be marine, which must have come from the Gulf of Mexico, or perhaps even from California, and the knives and pipes found in the same graves are often formed of far-fetched material, that was naturally paid for by some home product exported to the locality whence the material was derived. The art of preserving fish, flesh, and fowl by drying and smoking is widely diffused, and of great antiquity. The Indians of Long Island Sound are said to have carried on a trade in dried shell fish with tribes residing very far inland. From the earliest ages, the inhabitants of the Faroe and Orkney Islands, and of the opposite mainland coasts, have smoked wild fowl and other flesh. Hence it is possible that the animal and the vegetable food, the remains of which are found in the ancient deposits I am speaking of, may sometimes have been brought from climates remote from that where it was consumed. The most important, as well as the most trustworthy conclusions with respect to the climate of ancient Europe and Asia, are those drawn from the accounts given by the classical writers of the growth of cultivated plants; but these are by no means free from uncertainty, because we can seldom be sure of an identity of species, almost never of an identity of race or variety, between vegetables known to the agriculturists of Greece and Rome and those of modern times which are thought most nearly to resemble them. Besides this, there is always room for doubt whether the habits of plants long grown in different countries may not have been so changed by domestication that the conditions of temperature and humidity which they required twenty centuries ago were different from those at present demanded for their advantageous cultivation.[11] Even if we suppose an identity of species, of race, and of habit to be established between a given ancient and modern plant, the negative fact that the latter will not grow now where it flourished two thousand years ago does not in all cases prove a change of climate. The same result might follow from the exhaustion of the soil,[12] or from a change in the quantity of moisture it habitually contains. After a district of country has been completely or even partially cleared of its forest growth, and brought under cultivation, the drying of the soil, under favorable circumstances, goes on for generations, perhaps for ages.[13] In other cases, from injudicious husbandry, or the diversion or choking up of natural watercourses, it may become more highly charged with humidity. An increase or diminution of the moisture of a soil almost necessarily supposes an elevation or a depression of its winter or its summer heat, and of its extreme, if not of its mean annual temperature, though such elevation or depression may be so slight as not sensibly to raise or lower the mercury in a thermometer exposed to the open air. Any of these causes, more or less humidity, or more or less warmth of soil, would affect the growth both of wild and of cultivated vegetation, and consequently, without any appreciable change in atmospheric temperature, precipitation, or evaporation, plants of a particular species might cease to be advantageously cultivated where they had once been easily reared.[14] We are very imperfectly acquainted with the present mean and extreme temperature, or the precipitation and the evaporation of any extensive region, even in countries most densely peopled and best supplied with instruments and observers. The progress of science is constantly detecting errors of method in older observations, and many laboriously constructed tables of meteorological phenomena are now thrown aside as fallacious, and therefore worse than useless, because some condition necessary to secure accuracy of result was neglected, in obtaining the data on which they were founded. To take a familiar instance: it is but recently that attention has been drawn to the great influence of slight changes of station upon the results of observations of temperature and precipitation. A thermometer removed but a few hundred yards from its first position differs not unfrequently five, sometimes even ten degrees in its readings; and when we are told that the annual fall of rain on the roof of the observatory at Paris is two inches less than on the ground by the side of it, we may see that the level of the rain-gauge is a point of much consequence in making estimates from its measurements. The data from which results have been deduced with respect to the hygrometrical and thermometrical conditions, the climate in short, of different countries, have very often been derived from observations at single points in cities or districts separated by considerable distances. The tendency of errors and accidents to balance each other authorizes us, indeed, to entertain greater confidence than we could otherwise feel in the conclusions drawn from such tables; but it is in the highest degree probable that they would be much modified by more numerous series of observations, at different stations within narrow limits.[15] There is one branch of research which is of the utmost importance in reference to these questions, but which, from the great difficulty of direct observation upon it, has been less successfully studied than almost any other problem of physical science. I refer to the proportions between precipitation, superficial drainage, absorption, and evaporation. Precise actual measurement of these quantities upon even a single acre of ground is impossible; and in all cabinet experiments on the subject, the conditions of the surface observed are so different from those which occur in nature, that we cannot safely reason from one case to the other. In nature, the inclination of the ground, the degree of freedom or obstruction of the surface, the composition and density of the soil, upon which its permeability by water and its power of absorbing and retaining or transmitting moisture depend, its temperature, the dryness or saturation of the subsoil, vary at comparatively short distances; and though the precipitation upon and the superficial flow from very small geographical basins may be estimated with an approach to precision, yet even here we have no present means of knowing how much of the water absorbed by the earth is restored to the atmosphere by evaporation, and how much carried off by infiltration or other modes of underground discharge. When, therefore, we attempt to use the phenomena observed on a few square or cubic yards of earth, as a basis of reasoning upon the meteorology of a province, it is evident that our data must be insufficient to warrant positive general conclusions. In discussing the climatology of whole countries, or even of comparatively small local divisions, we may safely say that none can tell what percentage of the water they receive from the atmosphere is evaporated; what absorbed by the ground and conveyed off by subterranean conduits; what carried down to the sea by superficial channels; what drawn from the earth or the air by a given extent of forest, of short pasture vegetation, or of tall meadow-grass; what given out again by surfaces so covered, or by bare ground of various textures and composition, under different conditions of atmospheric temperature, pressure, and humidity; or what is the amount of evaporation from water, ice, or snow, under the varying exposures to which, in actual nature, they are constantly subjected. If, then, we are so ignorant of all these climatic phenomena in the best-known regions inhabited by man, it is evident that we can rely little upon theoretical deductions applied to the former more natural state of the same regions--less still to such as are adopted with respect to distant, strange, and primitive countries. _Mechanical Effects produced by Man on the Surface of the Earth more easily ascertainable._ In investigating the mechanical effects of human action on superficial geography, we are treading on safer ground, and dealing with much less subtile phenomena, less intractable elements. Great physical changes can, in some cases, be positively shown, in some almost certainly inferred, to have been produced by the operations of rural industry, and by the labors of man in other spheres of material effort; and hence, in this most important part of our subject, we can arrive at many positive generalizations, and obtain practical results of no small economical value. _Importance and Possibility of Physical Restoration._ Many circumstances conspire to invest with great present interest the questions: how far man can permanently modify and ameliorate those physical conditions of terrestrial surface and climate on which his material welfare depends; how far he can compensate, arrest, or retard the deterioration which many of his agricultural and industrial processes tend to produce; and how far he can restore fertility and salubrity to soils which his follies or his crimes have made barren or pestilential. Among these circumstances, the most prominent, perhaps, is the necessity of providing new homes for a European population which is increasing more rapidly than its means of subsistence, new physical comforts for classes of the people that have now become too much enlightened and have imbibed too much culture to submit to a longer deprivation of a share in the material enjoyments which the privileged ranks have hitherto monopolized. To supply new hives for the emigrant swarms, there are, first, the vast unoccupied prairies and forests of America, of Australia, and of many other great oceanic islands, the sparsely inhabited and still unexhausted soils of Southern and even Central Africa, and, finally, the impoverished and half-depopulated shores of the Mediterranean, and the interior of Asia Minor and the farther East. To furnish to those who shall remain after emigration shall have conveniently reduced the too dense population of many European states, those means of sensuous and of intellectual well-being which are styled "artificial wants" when demanded by the humble and the poor, but are admitted to be "necessaries" when claimed by the noble and the rich, the soil must be stimulated to its highest powers of production, and man's utmost ingenuity and energy must be tasked to renovate a nature drained, by his improvidence, of fountains which a wise economy would have made plenteous and perennial sources of beauty, health, and wealth. In those yet virgin lands which the progress of modern discovery in both hemispheres has brought and is still bringing to the knowledge and control of civilized man, not much improvement of great physical conditions is to be looked for. The proportion of forest is indeed to be considerably reduced, superfluous waters to be drawn off, and routes of internal communication to be constructed; but the primitive geographical and climatic features of these countries ought to be, as far as possible, retained. _Stability of Nature._ Nature, left undisturbed, so fashions her territory as to give it almost unchanging permanence of form, outline, and proportion, except when shattered by geologic convulsions; and in these comparatively rare cases of derangement, she sets herself at once to repair the superficial damage, and to restore, as nearly as practicable, the former aspect of her dominion. In new countries, the natural inclination of the ground, the self-formed slopes and levels, are generally such as best secure the stability of the soil. They have been graded and lowered or elevated by frost and chemical forces and gravitation and the flow of water and vegetable deposit and the action of the winds, until, by a general compensation of conflicting forces, a condition of equilibrium has been reached which, without the action of man, would remain, with little fluctuation, for countless ages. We need not go far back to reach a period when, in all that portion of the North American continent which has been occupied by British colonization, the geographical elements very nearly balanced and compensated each other. At the commencement of the seventeenth century, the soil, with insignificant exceptions, was covered with forests;[16] and whenever the Indian, in consequence of war or the exhaustion of the beasts of the chase, abandoned the narrow fields he had planted and the woods he had burned over, they speedily returned, by a succession of herbaceous, arborescent, and arboreal growths, to their original state. Even a single generation sufficed to restore them almost to their primitive luxuriance of forest vegetation.[17] The unbroken forests had attained to their maximum density and strength of growth, and, as the older trees decayed and fell, they were succeeded by new shoots or seedlings, so that from century to century no perceptible change seems to have occurred in the wood, except the slow, spontaneous succession of crops. This succession involved no interruption of growth, and but little break in the "boundless contiguity of shade;" for, in the husbandry of nature, there are no fallows. Trees fall singly, not by square roods, and the tall pine is hardly prostrate, before the light and heat, admitted to the ground by the removal of the dense crown of foliage which had shut them out, stimulate the germination of the seeds of broad-leaved trees that had lain, waiting this kindly influence, perhaps for centuries. Two natural causes, destructive in character, were, indeed, in operation in the primitive American forests, though, in the Northern colonies, at least, there were sufficient compensations; for we do not discover that any considerable permanent change was produced by them. I refer to the action of beavers and of fallen trees in producing bogs,[18] and of smaller animals, insects, and birds, in destroying the woods. Bogs are less numerous and extensive in the Northern States of the American union, because the natural inclination of the surface favors drainage; but they are more frequent, and cover more ground, in the Southern States, for the opposite reason.[19] They generally originate in the checking of watercourses by the falling of timber, or of earth and rocks, across their channels. If the impediment thus created is sufficient to retain a permanent accumulation of water behind it, the trees whose roots are overflowed soon perish, and then by their fall increase the obstruction, and, of course, occasion a still wider spread of the stagnating stream. This process goes on until the water finds a new outlet, at a higher level, not liable to similar interruption. The fallen trees not completely covered by water are soon overgrown with mosses; aquatic and semi-aquatic plants propagate themselves, and spread until they more or less completely fill up the space occupied by the water, and the surface is gradually converted from a pond to a quaking morass.[20] The morass is slowly solidified by vegetable production and deposit, then very often restored to the forest condition by the growth of black ashes, cedars, or, in southern latitudes, cypresses, and other trees suited to such a soil, and thus the interrupted harmony of nature is at last reëstablished. I am disposed to think that more bogs in the Northern States owe their origin to beavers than to accidental obstructions of rivulets by wind-fallen or naturally decayed trees; for there are few swamps in those States, at the outlets of which we may not, by careful search, find the remains of a beaver dam. The beaver sometimes inhabits natural lakelets, but he prefers to owe his pond to his own ingenuity and toil. The reservoir once constructed, its inhabitants rapidly multiply, and as its harvests of pond lilies, and other aquatic plants on which this quadruped feeds in winter, become too small for the growing population, the beaver metropolis sends out expeditions of discovery and colonization. The pond gradually fills up, by the operation of the same causes as when it owes its existence to an accidental obstruction, and when, at last, the original settlement is converted into a bog by the usual processes of vegetable life, the remaining inhabitants abandon it and build on some virgin brooklet a new city of the waters. In countries somewhat further advanced in civilization than those occupied by the North American Indians, as in mediæval Ireland, the formation of bogs may be commenced by the neglect of man to remove, from the natural channels of superficial drainage, the tops and branches of trees felled for the various purposes to which wood is applicable in his rude industry; and, when the flow of the water is thus checked, nature goes on with the processes I have already described. In such half-civilized regions, too, windfalls are more frequent than in those where the forest is unbroken, because, when openings have been made in it, for agricultural or other purposes, the entrance thus afforded to the wind occasions the sudden overthrow of hundreds of trees which might otherwise have stood for generations, and thus have fallen to the ground, only one by one, as natural decay brought them down.[21] Besides this, the flocks bred by man in the pastoral state, keep down the incipient growth of trees on the half-dried bogs, and prevent them from recovering their primitive condition. Young trees in the native forest are sometimes girdled and killed by the smaller rodent quadrupeds, and their growth is checked by birds which feed on the terminal bud; but these animals, as we shall see, are generally found on the skirts of the wood only, not in its deeper recesses, and hence the mischief they do is not extensive. The insects which damage primitive forests by feeding upon products of trees essential to their growth, are not numerous, nor is their appearance, in destructive numbers, frequent; and those which perforate the stems and branches, to deposit and hatch their eggs, more commonly select dead trees for that purpose, though, unhappily, there are important exceptions to this latter remark.[22] I do not know that we have any evidence of the destruction or serious injury of American forests by insects, before or even soon after the period of colonization; but since the white man has laid bare a vast proportion of the earth's surface, and thereby produced changes favorable, perhaps, to the multiplication of these pests, they have greatly increased in numbers, and, apparently, in voracity also. Not many years ago, the pines on thousands of acres of land in North Carolina, were destroyed by insects not known to have ever done serious injury to that tree before. In such cases as this and others of the like sort, there is good reason to believe that man is the indirect cause of an evil for which he pays so heavy a penalty. Insects increase whenever the birds which feed upon them disappear. Hence, in the wanton destruction of the robin and other insectivorous birds, the _bipes implumis_, the featherless biped, man, is not only exchanging the vocal orchestra which greets the rising sun for the drowsy beetle's evening drone, and depriving his groves and his fields of their fairest ornament, but he is waging a treacherous warfare on his natural allies.[23] In fine, in countries untrodden by man, the proportions and relative positions of land and water, the atmospheric precipitation and evaporation, the thermometric mean, and the distribution of vegetable and animal life, are subject to change only from geological influences so slow in their operation that the geographical conditions may be regarded as constant and immutable. These arrangements of nature it is, in most cases, highly desirable substantially to maintain, when such regions become the seat of organized commonwealths. It is, therefore, a matter of the first importance, that, in commencing the process of fitting them for permanent civilized occupation, the transforming operations should be so conducted as not unnecessarily to derange and destroy what, in too many cases, it is beyond the power of man to rectify or restore. _Restoration of Disturbed Harmonies._ In reclaiming and reoccupying lands laid waste by human improvidence or malice, and abandoned by man, or occupied only by a nomade or thinly scattered population, the task of the pioneer settler is of a very different character. He is to become a co-worker with nature in the reconstruction of the damaged fabric which the negligence or the wantonness of former lodgers has rendered untenantable. He must aid her in reclothing the mountain slopes with forests and vegetable mould, thereby restoring the fountains which she provided to water them; in checking the devastating fury of torrents, and bringing back the surface drainage to its primitive narrow channels; and in drying deadly morasses by opening the natural sluices which have been choked up, and cutting new canals for drawing off their stagnant waters. He must thus, on the one hand, create new reservoirs, and, on the other, remove mischievous accumulations of moisture, thereby equalizing and regulating the sources of atmospheric humidity and of flowing water, both which are so essential to all vegetable growth, and, of course, to human and lower animal life. _Destructiveness of Man._ Man has too long forgotten that the earth was given to him for usufruct alone, not for consumption, still less for profligate waste. Nature has provided against the absolute destruction of any of her elementary matter, the raw material of her works; the thunderbolt and the tornado, the most convulsive throes of even the volcano and the earthquake, being only phenomena of decomposition and recomposition. But she has left it within the power of man irreparably to derange the combinations of inorganic matter and of organic life, which through the night of æons she had been proportioning and balancing, to prepare the earth for his habitation, when, in the fulness of time, his Creator should call him forth to enter into its possession. Apart from the hostile influence of man, the organic and the inorganic world are, as I have remarked, bound together by such mutual relations and adaptations as secure, if not the absolute permanence and equilibrium of both, a long continuance of the established conditions of each at any given time and place, or at least, a very slow and gradual succession of changes in those conditions. But man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords. The proportions and accommodations which insured the stability of existing arrangements are overthrown. Indigenous vegetable and animal species are extirpated, and supplanted by others of foreign origin, spontaneous production is forbidden or restricted, and the face of the earth is either laid bare or covered with a new and reluctant growth of vegetable forms, and with alien tribes of animal life. These intentional changes and substitutions constitute, indeed, great revolutions; but vast as is their magnitude and importance, they are, as we shall see, insignificant in comparison with the contingent and unsought results which have flowed from them. The fact that, of all organic beings, man alone is to be regarded as essentially a destructive power, and that he wields energies to resist which, nature--that Nature whom all material life and all inorganic substance obey--is wholly impotent, tends to prove that, though living in physical nature, he is not of her, that he is of more exalted parentage, and belongs to a higher order of existences than those born of her womb and submissive to her dictates. There are, indeed, brute destroyers, beasts and birds and insects of prey--all animal life feeds upon, and, of course, destroys other life,--but this destruction is balanced by compensations. It is, in fact, the very means by which the existence of one tribe of animals or of vegetables is secured against being smothered by the encroachments of another; and the reproductive powers of species, which serve as the food of others, are always proportioned to the demand they are destined to supply. Man pursues his victims with reckless destructiveness; and, while the sacrifice of life by the lower animals is limited by the cravings of appetite, he unsparingly persecutes, even to extirpation, thousands of organic forms which he cannot consume.[24] The earth was not, in its natural condition, completely adapted to the use of man, but only to the sustenance of wild animals and wild vegetation. These live, multiply their kind in just proportion, and attain their perfect measure of strength and beauty, without producing or requiring any change in the natural arrangements of surface, or in each other's spontaneous tendencies, except such mutual repression of excessive increase as may prevent the extirpation of one species by the encroachments of another. In short, without man, lower animal and spontaneous vegetable life would have been constant in type, distribution, and proportion, and the physical geography of the earth would have remained undisturbed for indefinite periods, and been subject to revolution only from possible, unknown cosmical causes, or from geological action. But man, the domestic animals that serve him, the field and garden plants the products of which supply him with food and clothing, cannot subsist and rise to the full development of their higher properties, unless brute and unconscious nature be effectually combated, and, in a great degree, vanquished by human art. Hence, a certain measure of transformation of terrestrial surface, of suppression of natural, and stimulation of artificially modified productivity becomes necessary. This measure man has unfortunately exceeded. He has felled the forests whose network of fibrous roots bound the mould to the rocky skeleton of the earth; but had he allowed here and there a belt of woodland to reproduce itself by spontaneous propagation, most of the mischiefs which his reckless destruction of the natural protection of the soil has occasioned would have been averted. He has broken up the mountain reservoirs, the percolation of whose waters through unseen channels supplied the fountains that refreshed his cattle and fertilized his fields; but he has neglected to maintain the cisterns and the canals of irrigation which a wise antiquity had constructed to neutralize the consequences of its own imprudence. While he has torn the thin glebe which confined the light earth of extensive plains, and has destroyed the fringe of semi-aquatic plants which skirted the coast and checked the drifting of the sea sand, he has failed to prevent the spreading of the dunes by clothing them with artificially propagated vegetation. He has ruthlessly warred on all the tribes of animated nature whose spoil he could convert to his own uses, and he has not protected the birds which prey on the insects most destructive to his own harvests. Purely untutored humanity, it is true, interferes comparatively little with the arrangements of nature,[25] and the destructive agency of man becomes more and more energetic and unsparing as he advances in civilization, until the impoverishment, with which his exhaustion of the natural resources of the soil is threatening him, at last awakens him to the necessity of preserving what is left, if not of restoring what has been wantonly wasted. The wandering savage grows no cultivated vegetable, fells no forest, and extirpates no useful plant, no noxious weed. If his skill in the chase enables him to entrap numbers of the animals on which he feeds, he compensates this loss by destroying also the lion, the tiger, the wolf, the otter, the seal, and the eagle, thus indirectly protecting the feebler quadrupeds and fish and fowls, which would otherwise become the booty of beasts and birds of prey. But with stationary life, or rather with the pastoral state, man at once commences an almost indiscriminate warfare upon all the forms of animal and vegetable existence around him, and as he advances in civilization, he gradually eradicates or transforms every spontaneous product of the soil he occupies.[26] _Human and Brute Action Compared._ It has been maintained by authorities as high as any known to modern science, that the action of man upon nature, though greater in _degree_, does not differ in _kind_, from that of wild animals. It appears to me to differ in essential character, because, though it is often followed by unforeseen and undesired results, yet it is nevertheless guided by a self-conscious and intelligent will aiming as often at secondary and remote as at immediate objects. The wild animal, on the other hand, acts instinctively, and, so far as we are able to perceive, always with a view to single and direct purposes. The backwoodsman and the beaver alike fell trees; the man that he may convert the forest into an olive grove that will mature its fruit only for a succeeding generation, the beaver that he may feed upon their bark or use them in the construction of his habitation. Human differs from brute action, too, in its influence upon the material world, because it is not controlled by natural compensations and balances. Natural arrangements, once disturbed by man, are not restored until he retires from the field, and leaves free scope to spontaneous recuperative energies; the wounds he inflicts upon the material creation are not healed until he withdraws the arm that gave the blow. On the other hand, I am not aware of any evidence that wild animals have ever destroyed the smallest forest, extirpated any organic species or modified its natural character, occasioned any permanent change of terrestrial surface, or produced any disturbance of physical conditions which nature has not, of herself, repaired without the expulsion of the animal that had caused it.[27] The form of geographical surface, and very probably the climate of a given country, depend much on the character of the vegetable life belonging to it. Man has, by domestication, greatly changed the habits and properties of the plants he rears; he has, by voluntary selection, immensely modified the forms and qualities of the animated creatures that serve him; and he has, at the same time, completely rooted out many forms of animal if not of vegetable being.[28] What is there, in the influence of brute life, that corresponds to this? We have no reason to believe that in that portion of the American continent which, though peopled by many tribes of quadruped and fowl, remained uninhabited by man, or only thinly occupied by purely savage tribes, any sensible geographical change had occurred within twenty centuries before the epoch of discovery and colonization, while, during the same period, man had changed millions of square miles, in the fairest and most fertile regions of the Old World, into the barrenest deserts. The ravages committed by man subvert the relations and destroy the balance which nature had established between her organized and her inorganic creations; and she avenges herself upon the intruder, by letting loose upon her defaced provinces destructive energies hitherto kept in check by organic forces destined to be his best auxiliaries, but which he has unwisely dispersed and driven from the field of action. When the forest is gone, the great reservoir of moisture stored up in its vegetable mould is evaporated, and returns only in deluges of rain to wash away the parched dust into which that mould has been converted. The well-wooded and humid hills are turned to ridges of dry rock, which encumbers the low grounds and chokes the watercourses with its debris, and--except in countries favored with an equable distribution of rain through the seasons, and a moderate and regular inclination of surface--the whole earth, unless rescued by human art from the physical degradation to which it tends, becomes an assemblage of bald mountains, of barren, turfless hills, and of swampy and malarious plains. There are parts of Asia Minor, of Northern Africa, of Greece, and even of Alpine Europe, where the operation of causes set in action by man has brought the face of the earth to a desolation almost as complete as that of the moon; and though, within that brief space of time which we call "the historical period," they are known to have been covered with luxuriant woods, verdant pastures, and fertile meadows, they are now too far deteriorated to be reclaimable by man, nor can they become again fitted for human use, except through great geological changes, or other mysterious influences or agencies of which we have no present knowledge, and over which we have no prospective control. The earth is fast becoming an unfit home for its noblest inhabitant, and another era of equal human crime and human improvidence, and of like duration with that through which traces of that crime and that improvidence extend, would reduce it to such a condition of impoverished productiveness, of shattered surface, of climatic excess, as to threaten the depravation, barbarism, and perhaps even extinction of the species.[29] _Physical Improvement._ True, there is a partial reverse to this picture. On narrow theatres, new forests have been planted; inundations of flowing streams restrained by heavy walls of masonry and other constructions; torrents compelled to aid, by depositing the slime with which they are charged, in filling up lowlands, and raising the level of morasses which their own overflows had created; ground submerged by the encroachments of the ocean, or exposed to be covered by its tides, has been rescued from its dominion by diking;[30] swamps and even lakes have been drained, and their beds brought within the domain of agricultural industry; drifting coast dunes have been checked and made productive by plantation; seas and inland waters have been repeopled with fish, and even the sands of the Sahara have been fertilized by artesian fountains. These achievements are more glorious than the proudest triumphs of war, but, thus far, they give but faint hope that we shall yet make full atonement for our spendthrift waste of the bounties of nature. It is, on the one hand, rash and unphilosophical to attempt to set limits to the ultimate power of man over inorganic nature, and it is unprofitable, on the other, to speculate on what may be accomplished by the discovery of now unknown and unimagined natural forces, or even by the invention of new arts and new processes. But since we have seen aerostation, the motive power of elastic vapors, the wonders of modern telegraphy, the destructive explosiveness of gunpowder, and even of a substance so harmless, unresisting, and inert as cotton, nothing in the way of mechanical achievement seems impossible, and it is hard to restrain the imagination from wandering forward a couple of generations to an epoch when our descendants shall have advanced as far beyond us in physical conquest, as we have marched beyond the trophies erected by our grandfathers. I must therefore be understood to mean only, that no agencies now known to man and directed by him seem adequate to the reducing of great Alpine precipices to such slopes as would enable them to support a vegetable clothing, or to the covering of large extents of denuded rock with earth, and planting upon them a forest growth. But among the mysteries which science is yet to reveal, there may be still undiscovered methods of accomplishing even grander wonders than these. Mechanical philosophers have suggested the possibility of accumulating and treasuring up for human use some of the greater natural forces, which the action of the elements puts forth with such astonishing energy. Could we gather, and bind, and make subservient to our control, the power which a West Indian hurricane exerts through a small area in one continuous blast, or the momentum expended by the waves, in a tempestuous winter, upon the breakwater at Cherbourg,[31] or the lifting power of the tide, for a month, at the head of the Bay of Fundy, or the pressure of a square mile of sea water at the depth of five thousand fathoms, or a moment of the might of an earthquake or a volcano, our age--which moves no mountains and casts them into the sea by faith alone--might hope to scarp the rugged walls of the Alps and Pyrenees and Mount Taurus, robe them once more in a vegetation as rich as that of their pristine woods, and turn their wasting torrents into refreshing streams.[32] Could this old world, which man has overthrown, be rebuilded, could human cunning rescue its wasted hillsides and its deserted plains from solitude or mere nomade occupation, from barrenness, from nakedness, and from insalubrity, and restore the ancient fertility and healthfulness of the Etruscan sea coast, the Campagna and the Pontine marshes, of Calabria, of Sicily, of the Peloponnesus and insular and continental Greece, of Asia Minor, of the slopes of Lebanon and Hermon, of Palestine, of the Syrian desert, of Mesopotamia and the delta of the Euphrates, of the Cyrenaica, of Africa proper, Numidia, and Mauritania, the thronging millions of Europe might still find room on the Eastern continent, and the main current of emigration be turned toward the rising instead of the setting sun. But changes like these must await great political and moral revolutions in the governments and peoples by whom those regions are now possessed, a command of pecuniary and of mechanical means not at present enjoyed by those nations, and a more advanced and generally diffused knowledge of the processes by which the amelioration of soil and climate is possible, than now anywhere exists. Until such circumstances shall conspire to favor the work of geographical regeneration, the countries I have mentioned, with here and there a local exception, will continue to sink into yet deeper desolation, and in the mean time, the American continent, Southern Africa, Australia, and the smaller oceanic islands, will be almost the only theatres where man is engaged, on a great scale, in transforming the face of nature. _Arrest of Physical Decay of New Countries._ Comparatively short as is the period through which the colonization of foreign lands by European emigrants extends, great, and, it is to be feared, sometimes irreparable, injury has been already done in the various processes by which man seeks to subjugate the virgin earth; and many provinces, first trodden by the _homo sapiens Europæ_ within the last two centuries, begin to show signs of that melancholy dilapidation which is now driving so many of the peasantry of Europe from their native hearths. It is evidently a matter of great moment, not only to the population of the states where these symptoms are manifesting themselves, but to the general interests of humanity, that this decay should be arrested, and that the future operations of rural husbandry and of forest industry, in districts yet remaining substantially in their native condition, should be so conducted as to prevent the widespread mischiefs which have been elsewhere produced by thoughtless or wanton destruction of the natural safeguards of the soil. This can be done only by the diffusion of knowledge on this subject among the classes that, in earlier days, subdued and tilled ground in which they had no vested rights, but who, in our time, own their woods, their pastures, and their ploughlands as a perpetual possession for them and theirs, and have, therefore, a strong interest in the protection of their domain against deterioration. _Forms and Formations most liable to Physical Degradation._ The character and extent of the evils under consideration depend very much on climate and the natural forms and constitution of surface. If the precipitation, whether great or small in amount, be equally distributed through the seasons, so that there are neither torrential rains nor parching droughts, and if, further, the general inclination of ground be moderate, so that the superficial waters are carried off without destructive rapidity of flow, and without sudden accumulation in the channels of natural drainage, there is little danger of the degradation of the soil in consequence of the removal of forest or other vegetable covering, and the natural face of the earth may be considered as substantially permanent. These conditions are well exemplified in Ireland, in a great part of England, in extensive districts in Germany and France, and, fortunately, in an immense proportion of the valley of the Mississippi and the basin of the great American lakes, as well as in many parts of the continents of South America and of Africa. Destructive changes are most frequent in countries of irregular and mountainous surface, and in climates where the precipitation is confined chiefly to a single season, and where the year is divided into a wet and a dry period, as is the case throughout a great part of the Ottoman empire, and, more or less strictly, the whole Mediterranean basin. It is partly, though by no means entirely, owing to topographical and climatic causes that the blight, which has smitten the fairest and most fertile provinces of Imperial Rome, has spared Britannia, Germania, Pannonia, and M[oe]sia, the comparatively inhospitable homes of barbarous races, who, in the days of the Cæsars, were too little advanced in civilized life to possess either the power or the will to wage that war against the order of nature which seems, hitherto, an almost inseparable condition precedent of high social culture, and of great progress in fine and mechanical art.[33] In mountainous countries, on the other hand, various causes combine to expose the soil to constant dangers. The rain and snow usually fall in greater quantity, and with much inequality of distribution; the snow on the summits accumulates for many months in succession, and then is not unfrequently almost wholly dissolved in a single thaw, so that the entire precipitation of months is in a few hours hurried down the flanks of the mountains, and through the ravines that furrow them; the natural inclination of the surface promotes the swiftness of the gathering currents of diluvial rain and of melting snow, which soon acquire an almost irresistible force, and power of removal and transportation; the soil itself is less compact and tenacious than that of the plains, and if the sheltering forest has been destroyed, it is confined by few of the threads and ligaments by which nature had bound it together, and attached it to the rocky groundwork. Hence every considerable shower lays bare its roods of rock, and the torrents sent down by the thaws of spring, and by occasional heavy discharges of the summer and autumnal rains, are seas of mud and rolling stones that sometimes lay waste, and bury beneath them acres, and even miles, of pasture and field and vineyard.[34] _Physical Decay of New Countries._ I have remarked that the effects of human action on the forms of the earth's surface could not always be distinguished from those resulting from geological causes, and there is also much uncertainty in respect to the precise influence of the clearing and cultivating of the ground, and of other rural operations, upon climate. It is disputed whether either the mean or the extremes of temperature, the periods of the seasons, or the amount or distribution of precipitation and of evaporation, in any country whose annals are known, have undergone any change during the historical period. It is, indeed, impossible to doubt that many of the operations of the pioneer settler tend to produce great modifications in atmospheric humidity, temperature, and electricity; but we are at present unable to determine how far one set of effects is neutralized by another, or compensated by unknown agencies. This question scientific research is inadequate to solve, for want of the necessary data; but well conducted observation, in regions now first brought under the occupation of man, combined with such historical evidence as still exists, may be expected at no distant period to throw much light on this subject. Australia is, perhaps, the country from which we have a right to expect the fullest elucidation of these difficult and disputable problems. Its colonization did not commence until the physical sciences had become matter of almost universal attention, and is, indeed, so recent that the memory of living men embraces the principal epochs of its history; the peculiarities of its fauna, its flora, and its geology are such as to have excited for it the liveliest interest of the votaries of natural science; its mines have given its people the necessary wealth for procuring the means of instrumental observation, and the leisure required for the pursuit of scientific research; and large tracts of virgin forest and natural meadow are rapidly passing under the control of civilized man. Here, then, exist greater facilities and stronger motives for the careful study of the topics in question than have ever been found combined in any other theatre of European colonization. In North America, the change from the natural to the artificial condition of terrestrial surface began about the period when the most important instruments of meteorological observation were invented. The first settlers in the territory now constituting the United States and the British American provinces had other things to do than to tabulate barometrical and thermometrical readings, but there remain some interesting physical records from the early days of the colonies,[35] and there is still an immense extent of North American soil where the industry and the folly of man have as yet produced little appreciable change. Here, too, with the present increased facilities for scientific observation, the future effects, direct and contingent, of man's labors, can be measured, and such precautions taken in those rural processes which we call improvements, as to mitigate evils, perhaps, in some degree, inseparable from every attempt to control the action of natural laws. In order to arrive at safe conclusions, we must first obtain a more exact knowledge of the topography, and of the present superficial and climatic condition of countries where the natural surface is as yet more or less unbroken. This can only be accomplished by accurate surveys, and by a great multiplication of the points of meteorological registry,[36] already so numerous; and as, moreover, considerable changes in the proportion of forest and of cultivated land, or of dry and wholly or partially submerged surface, will often take place within brief periods, it is highly desirable that the attention of observers, in whose neighborhood the clearing of the soil, or the drainage of lakes and swamps, or other great works of rural improvement, are going on or meditated, should be especially drawn not only to revolutions in atmospheric temperature and precipitation, but to the more easily ascertained and perhaps more important local changes produced by these operations in the temperature and the hygrometric state of the superficial strata of the earth, and in its spontaneous vegetable and animal products. The rapid extension of railroads, which now everywhere keeps pace with, and sometimes even precedes, the occupation of new soil for agricultural purposes, furnishes great facilities for enlarging our knowledge of the topography of the territory they traverse, because their cuttings reveal the composition and general structure of surface, and the inclination and elevation of their lines constitute known hypsometrical sections, which give numerous points of departure for the measurement of higher and lower stations, and of course for determining the relief and depression of surface, the slope of the beds of watercourses, and many other not less important questions.[37] The geological, hydrographical, and topographical surveys, which almost every general and even local government of the civilized world is carrying on, are making yet more important contributions to our stock of geographical and general physical knowledge, and, within a comparatively short space, there will be an accumulation of well established constant and historical facts, from which we can safely reason upon all the relations of action and reaction between man and external nature. But we are, even now, breaking up the floor and wainscoting and doors and window frames of our dwelling, for fuel to warm our bodies and seethe our pottage, and the world cannot afford to wait till the slow and sure progress of exact science has taught it a better economy. Many practical lessons have been learned by the common observation of unschooled men; and the teachings of simple experience, on topics where natural philosophy has scarcely yet spoken, are not to be despised. In these humble pages, which do not in the least aspire to rank among scientific expositions of the laws of nature, I shall attempt to give the most important practical conclusions suggested by the history of man's efforts to replenish the earth and subdue it; and I shall aim to support those conclusions by such facts and illustrations only as address themselves to the understanding of every intelligent reader, and as are to be found recorded in works capable of profitable perusal, or at least consultation, by persons who have not enjoyed a special scientific training. CHAPTER II. TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES. MODERN GEOGRAPHY EMBRACES ORGANIC LIFE--TRANSFER OF VEGETABLE LIFE-- FOREIGN PLANTS GROWN IN THE UNITED STATES--AMERICAN PLANTS GROWS IN EUROPE--MODES OF INTRODUCTION OF FOREIGN PLANTS--VEGETABLES, HOW AFFECTED BY TRANSFER TO FOREIGN SOILS--EXTIRPATION OF VEGETABLES-- ORIGIN OF DOMESTIC PLANTS--ORGANIC LIFE AS A GEOLOGICAL AND GEOGRAPHICAL AGENCY--ORIGIN AND TRANSFER OF DOMESTIC ANIMALS--EXTIRPATION OF ANIMALS--NUMBERS OF BIRDS IN THE UNITED STATES--BIRDS AS SOWERS AND CONSUMERS OF SEEDS, AND AS DESTROYERS OF INSECTS--DIMINUTION AND EXTIRPATION OF BIRDS--INTRODUCTION OF BIRDS--UTILITY OF INSECTS AND WORMS--INTRODUCTION OF INSECTS--DESTRUCTION OF INSECTS--REPTILES-- DESTRUCTION OF FISH--INTRODUCTION AND BREEDING OF FISH--EXTIRPATION OF AQUATIC ANIMALS--MINUTE ORGANISMS. _Modern Geography embraces Organic Life._ It was a narrow view of geography which confined that science to delineation of terrestrial surface and outline, and to description of the relative position and magnitude of land and water. In its improved form, it embraces not only the globe itself, but the living things which vegetate or move upon it, the varied influences they exert upon each other, the reciprocal action and reaction between them and the earth they inhabit. Even if the end of geographical studies were only to obtain a knowledge of the external forms of the mineral and fluid masses which constitute the globe, it would still be necessary to take into account the element of life; for every plant, every animal, is a geographical agency, man a destructive, vegetables, and even wild beasts, restorative powers. The rushing waters sweep down earth from the uplands; in the first moment of repose, vegetation seeks to reëstablish itself on the bared surface, and, by the slow deposit of its decaying products, to raise again the soil which the torrent had lowered. So important an element of reconstruction is this, that it has been seriously questioned whether, upon the whole, vegetation does not contribute as much to elevate, as the waters to depress, the level of the surface. Whenever man has transported a plant from its native habitat to a new soil, he has introduced a new geographical force to act upon it, and this generally at the expense of some indigenous growth which the foreign vegetable has supplanted. The new and the old plants are rarely the equivalents of each other, and the substitution of an exotic for a native tree, shrub, or grass, increases or diminishes the relative importance of the vegetable element in the geography of the country to which it is removed. Further, man sows that he may reap. The products of agricultural industry are not suffered to rot upon the ground, and thus raise it by an annual stratum of new mould. They are gathered, transported to greater or less distances, and after they have served their uses in human economy, they enter, on the final decomposition of their elements, into new combinations, and are only in small proportion returned to the soil on which they grew. The roots of the grasses, and of many other cultivated plants, however, usually remain and decay in the earth, and contribute to raise its surface, though certainly not in the same degree as the forest. The vegetables, which have taken the place of trees, unquestionably perform many of the same functions. They radiate heat, they condense the humidity of the atmosphere, they act upon the chemical constitution of the air, their roots penetrate the earth to greater depths than is commonly supposed, and form an inextricable labyrinth of filaments which bind the soil together and prevent its erosion by water. The broad-leaved annuals and perennials, too, shade the ground, and prevent the evaporation of moisture from its surface by wind and sun.[38] At a certain stage of growth, grass land is probably a more energetic radiator and condenser than even the forest, but this powerful action is exerted, in its full intensity, for a few days only, while trees continue such functions, with unabated vigor, for many months in succession. Upon the whole, it seems quite certain, that no cultivated ground is as efficient in tempering climatic extremes, or in conservation of geographical surface and outline, as is the soil which nature herself has planted. _Transfer of Vegetable Life._ It belongs to vegetable and animal geography, which are almost sciences of themselves, to point out in detail what man has done to change the distribution of plants and of animated life and to revolutionize the aspect of organic nature; but some of the more important facts bearing on this subject may pertinently be introduced here. Most of the fruit trees grown in Europe and the United States are believed, and--if the testimony of Pliny and other ancient naturalists is to be depended upon--many of them are historically known, to have originated in the temperate climates of Asia. The wine grape has been thought to be truly indigenous only in the regions bordering on the eastern end of the Black Sea, where it now, particularly on the banks of the Rion, the ancient Phasis, propagates itself spontaneously, and grows with unexampled luxuriance.[39] But, some species of the vine seem native to Europe, and many varieties of grape have been too long known as common to every part of the United States to admit of the supposition that they were all introduced by European colonists.[40] It is an interesting fact that the commerce--or at least the maritime carrying trade--and the agricultural and mechanical industry of the world are, in very large proportion, dependent on vegetable and animal products little or not at all known to ancient Greek, Roman, and Jewish civilization. In many instances, the chief supply of these articles comes from countries to which they are probably indigenous, and where they are still almost exclusively grown; but in many others, the plants or animals from which they are derived have been introduced by man into the regions now remarkable for their most successful cultivation, and that, too, in comparatively recent times, or, in other words, within two or three centuries. _Foreign Plants grown in the United States._ According to Bigelow, the United States had, on the first of June, 1860, in round numbers, 163,000,000 acres of improved land, the quantity having been increased by 50,000,000 acres within the ten years next preceding.[41] Not to mention less important crops, this land produced, in the year ending on the day last mentioned, in round numbers, 171,000,000 bushels of wheat, 21,000,000 bushels of rye, 172,000,000 bushels of oats, 15,000,000 bushels of pease and beans, 16,000,000 bushels of barley, orchard fruits to the value of $20,000,000, 900,000 bushels of cloverseed, 900,000 bushels of other grass seed, 104,000 tons of hemp, 4,000,000 pounds of flax, and 600,000 pounds of flaxseed. These vegetable growths were familiar to ancient European agriculture, but they were all introduced into North America after the close of the sixteenth century. Of the fruits of agricultural industry unknown to the Greeks and Romans, or too little employed by them to be of any commercial importance, the United States produced, in the same year, 187,000,000 pounds of rice, 18,000,000 bushels of buckwheat, 2,075,000,000 pounds of ginned cotton,[42] 302,000,000 pounds of cane sugar, 16,000,000 gallons of cane molasses, 7,000,000 gallons of sorghum molasses, all yielded by vegetables introduced into that country within two hundred years, and--with the exception of buckwheat, the origin of which is uncertain, and of cotton--all, directly or indirectly, from the East Indies; besides, from indigenous plants unknown to ancient agriculture, 830,000,000 bushels of Indian corn or maize, 429,000,000 pounds of tobacco, 110,000,000 bushels of potatoes, 42,000,000 bushels of sweet potatoes, 39,000,000 pounds of maple sugar, and 2,000,000 gallons of maple molasses. To all this we are to add 19,000,000 tons of hay, produced partly by new, partly by long known, partly by exotic, partly by native herbs and grasses, an incalculable quantity of garden vegetables, chiefly of European or Asiatic origin, and many minor agricultural products. The weight of this harvest of a year would be not less than 60,000,000 tons--which is eleven times the tonnage of all the shipping of the United States at the close of the year 1861--and, with the exception of the maple sugar, the maple molasses, and the products of the Western prairie lands and some small Indian clearings, it was all grown upon lands wrested from the forest by the European race within little more than two hundred years. The wants of Europe have introduced into the colonies of tropical America the sugar cane, the coffee plant, the orange and the lemon,[43] all of Oriental origin, have immensely stimulated the cultivation of the former two in the countries of which they are natives, and, of course, promoted agricultural operations which must have affected the geography of those regions to an extent proportionate to the scale on which they have been pursued. _American Plants grown in Europe._ America has partially repaid her debt to the Eastern continent. Maize and the potato are very valuable additions to the field agriculture of Europe and the East, and the tomato is no mean gift to the kitchen gardens of the Old World, though certainly not an adequate return for the multitude of esculent roots and leguminous plants which the European colonists carried with them.[44] I wish I could believe, with some, that America is not alone responsible for the introduction of the filthy weed, tobacco, the use of which is the most vulgar and pernicious habit engrafted by the semi-barbarism of modern civilization upon the less multifarious sensualism of ancient life;[45] but the alleged occurrence of pipe-like objects in Sclavonic, and, it has been said, in Hungarian sepulchres, is hardly sufficient evidence to convict those races of complicity in this grave offence against the temperance and the refinement of modern society. _Modes of Introduction of Foreign Plants._ Besides the vegetables I have mentioned, we know that many plants of smaller economical value have been the subjects of international exchange in very recent times. Busbequius, Austrian ambassador at Constantinople about the middle of the sixteenth century--whose letters contain one of the best accounts of Turkish life which have appeared down to the present day--brought home from the Ottoman capital the lilac and the tulip. The Belgian Clusius about the same time introduced from the East the horse chestnut, which has since wandered to America. The weeping willows of Europe and the United States are said to have sprung from a slip received from Smyrna by the poet Pope, and planted by him in an English garden; and the Portuguese declare that the progenitor of all the European and American oranges was an Oriental tree transplanted to Lisbon, and still living in the last generation.[46] The present favorite flowers of the parterres of Europe have been imported from America, Japan and other remote Oriental countries, within a century and a half, and, in fine, there are few vegetables of any agricultural importance, few ornamental trees or decorative plants, which are not now common to the three civilized continents. The statistics of vegetable emigration exhibit numerical results quite surprising to those not familiar with the subject. The lonely island of St. Helena is described as producing, at the time of its discovery in the year 1501, about sixty vegetable species, including some three or four known to grow elsewhere also. At the present time its flora numbers seven hundred and fifty species. Humboldt and Bonpland found, among the unquestionably indigenous plants of tropical America, monocotyledons only, all the dicotyledons of those extensive regions having been probably introduced after the colonization of the New World by Spain. The faculty of spontaneous reproduction and perpetuation necessarily supposes a greater power of accommodation, within a certain range, than we find in most domesticated plants, for it would rarely happen that the seed of a wild plant would fall into ground as nearly similar, in composition and condition, to that where its parent grew, as the soils of different fields artificially prepared for growing a particular vegetable are to each other. Accordingly, though every wild species affects a habitat of a particular character, it is found that, if accidentally or designedly sown elsewhere, it will grow under conditions extremely unlike those of its birthplace.[47] Cooper says: "We cannot say positively that _any_ plant is _uncultivable_ anywhere until it has been tried;" and this seems to be even more true of wild than of domesticated vegetation. The seven hundred new species which have found their way to St. Helena within three centuries and a half, were certainly not all, or even in the largest proportion, designedly planted there by human art, and if we were well acquainted with vegetable emigration, we should probably be able to show that man has intentionally transferred fewer plants than he has accidentally introduced into countries foreign to them. After the wheat, follow the tares that infest it. The weeds that grow among the cereal grains, the pests of the kitchen garden, are the same in America as in Europe.[48] The overturning of a wagon, or any of the thousand accidents which befall the emigrant in his journey across the Western plains, may scatter upon the ground the seeds he designed for his garden, and the herbs which fill so important a place in the rustic materia medica of the Eastern States, spring up along the prairie paths but just opened by the caravan of the settler.[49] The hortus siccus of a botanist may accidentally sow seeds from the foot of the Himalayas on the plains that skirt the Alps; and it is a fact of very familiar observation, that exotics, transplanted to foreign climates suited to their growth, often escape from the flower garden and naturalize themselves among the spontaneous vegetation of the pastures. When the cases containing the artistic treasures of Thorvaldsen were opened in the court of the museum where they are deposited, the straw and grass employed in packing them were scattered upon the ground, and the next season there sprang up from the seeds no less than twenty-five species of plants belonging to the Roman campagna, some of which were preserved and cultivated as a new tribute to the memory of the great Scandinavian sculptor, and at least four are said to have spontaneously naturalized themselves about Copenhagen.[50] In the campaign of 1814, the Russian troops brought, in the stuffing of their saddles and by other accidental means, seeds from the banks of the Dnieper to the valley of the Rhine, and even introduced the plants of the steppes into the environs of Paris. The Turkish armies, in their incursions into Europe, brought Eastern vegetables in their train, and left the seeds of Oriental wall plants to grow upon the ramparts of Buda and Vienna.[51] The Canada thistle, _Erigeron Canadense_, is said to have sprung up in Europe, two hundred years ago, from a seed which dropped out of the stuffed skin of a bird.[52] _Vegetables, how affected by Transfer to Foreign Soils._ Vegetables, naturalized abroad either by accident or design, sometimes exhibit a greatly increased luxuriance of growth. The European cardoon, an esculent thistle, has broken out from the gardens of the Spanish colonies on the La Plata, acquired a gigantic stature, and propagated itself, in impenetrable thickets, over hundreds of leagues of the Pampas; and the _Anacharis alsinastrum_, a water plant not much inclined to spread in its native American habitat, has found its way into English rivers, and extended itself to such a degree as to form a serious obstruction to the flow of the current, and even to navigation. Not only do many wild plants exhibit a remarkable facility of accommodation, but their seeds usually possess great tenacity of life, and their germinating power resists very severe trials. Hence, while the seeds of very many cultivated vegetables lose their vitality in two or three years, and can be transported safely to distant countries only with great precautions, the weeds that infest those vegetables, though not cared for by man, continue to accompany him in his migrations, and find a new home on every soil he colonizes. Nature fights in defence of her free children, but wars upon them when they have deserted her banners and tamely submitted to the dominion of man.[53] Not only is the wild plant much hardier than the domesticated vegetable, but the same law prevails in animated brute and even human life. The beasts of the chase are more capable of endurance and privation and more tenacious of life, than the domesticated animals which most nearly resemble them. The savage fights on, after he has received half a dozen mortal wounds, the least of which would have instantly paralyzed the strength of his civilized enemy, and, like the wild boar,[54] he has been known to press forward along the shaft of the spear which was transpiercing his vitals, and to deal a deathblow on the soldier who wielded it. True, domesticated plants can be gradually acclimatized to bear a degree of heat or of cold, which, in their wild state, they would not have supported; the trained English racer outstrips the swiftest horse of the pampas or prairies, perhaps even the less systematically educated courser of the Arab; the strength of the European, as tested by the dynamometer, is greater than that of the New Zealander. But all these are instances of excessive development of particular capacities and faculties at the expense of general vital power. Expose untamed and domesticated forms of life, together, to an entire set of physical conditions equally alien to the former habits of both, so that every power of resistance and accommodation shall be called into action, and the wild plant or animal will live, while the domesticated will perish. The saline atmosphere of the sea is specially injurious both to seeds and to very many young plants, and it is only recently that the transportation of some very important vegetables across the ocean has been made practicable, through the invention of Ward's airtight glass cases. It is by this means that large numbers of the trees which produce the Jesuit's bark have been successfully transplanted from America to the British possessions in the East, where it is hoped they will become fully naturalized. _Extirpation of Vegetables._ Lamentable as are the evils produced by the too general felling of the woods in the Old World, I believe it does not satisfactorily appear that any species of native forest tree has yet been extirpated by man on the Eastern continent. The roots, stumps, trunks, and foliage found in bogs are recognized as belonging to still extant species. Except in some few cases where there is historical evidence that foreign material was employed, the timber of the oldest European buildings, and even of the lacustrine habitations of Switzerland, is evidently the product of trees still common in or near the countries where such architectural remains are found; nor have the Egyptian catacombs themselves revealed to us the former existence of any woods not now familiar to us as the growth of still living trees.[55] It is, however, said that the yew tree, _Taxus baccata_, formerly very common in England, Germany, and--as we are authorized to infer from Theophrastus--in Greece, has almost wholly disappeared from the latter country, and seems to be dying out in Germany. The wood of the yew surpasses that of any other European tree in closeness and fineness of grain, and it is well known for the elasticity which of old made it so great a favorite with the English archer. It is much in request among wood carvers and turners, and the demand for it explains, in part, its increasing scarcity. It is also worth remarking that no insect depends upon it for food or shelter, or aids in its fructification, no bird feeds upon its berries--the latter a circumstance of some importance, because the tree hence wants one means of propagation or diffusion common to so many other plants. But it is alleged that the reproductive power of the yew is exhausted, and that it can no longer be readily propagated by the natural sowing of its seeds, or by artificial methods. If further investigation and careful experiment should establish this fact, it will go far to show that a climatic change, of a character unfavorable to the growth of the yew, has really taken place in Germany, though not yet proved by instrumental observation, and the most probable cause of such change would be found in the diminution of the area covered by the forests. The industry of man is said to have been so successful in the local extirpation of noxious or useless vegetables in China, that, with the exception of a few water plants in the rice grounds, it is sometimes impossible to find a single weed in an extensive district; and the late eminent agriculturist, Mr. Coke, is reported to have offered in vain a considerable reward for the detection of a weed in a large wheatfield on his estate in England. In these cases, however, there is no reason to suppose that diligent husbandry has done more than to eradicate the pests of agriculture within a comparatively limited area, and the cockle and the darnel will probably remain to plague the slovenly cultivator as long as the cereal grains continue to bless him.[56] _Origin of Domestic Plants._ One of the most important, and, at the same time, most difficult questions connected with our subject is: how far we are to regard our cereal grains, our esculent bulbs and roots, and the multiplied tree fruits of our gardens, as artificially modified and improved forms of wild, self-propagating vegetation. The narratives of botanical travellers have often announced the discovery of the original form and habitat of domesticated plants, and scientific journals have described the experiments by which the identity of particular wild and cultivated vegetables has been thought to be established. It is confidently affirmed that maize and the potato--which we must suppose to have been first cultivated at a much later period than the breadstuffs and most other esculent vegetables of Europe and the East--are found wild and self-propagating in Spanish America, though in forms not recognizable by the common observer as identical with the familiar corn and tuber of modern agriculture. It was lately asserted, upon what seemed very strong evidence, that the _Ægilops ovata_, a plant growing wild in Southern France, had been actually converted into common wheat; but, upon a repetition of the experiments, later observers have declared that the apparent change was only a case of temporary hybridation or fecundation by the pollen of true wheat, and that the grass alleged to be transformed into wheat could not be perpetuated as such from its own seed. The very great modifications which cultivated plants are constantly undergoing under our eyes, and the numerous varieties and races which spring up among them, certainly countenance the doctrine, that every domesticated vegetable, however dependent upon human care for growth and propagation in its present form, may have been really derived, by a long succession of changes, from some wild plant not now much resembling it. But it is, in every case, a question of evidence. The only satisfactory proof that a given wild plant is identical with a given garden or field vegetable, is the test of experiment, the actual growing of the one from the seed of the other, or the conversion of the one into the other by transplantation and change of conditions. It is hardly contended that any of the cereals or other plants important as human aliment, or as objects of agricultural industry, exist and propagate themselves uncultivated in the same form and with the same properties as when sown and reared by human art.[57] In fact, the cases are rare where the identity of a wild with a domesticated plant is considered by the best authorities as conclusively established, and we are warranted in affirming of but few of the latter, as a historically known or experimentally proved fact, that they ever did exist, or could exist, independently of man.[58] _Organic Life as a Geological and Geographical Agency._ The quantitative value of organic life, as a geological agency, seems to be inversely as the volume of the individual organism; for nature supplies by numbers what is wanting in the bulk of the plant or animal out of whose remains or structures she forms strata covering whole provinces, and builds up from the depths of the sea large islands, if not continents. There are, it is true, near the mouths of the great Siberian rivers which empty themselves into the Polar Sea, drift islands composed, in an incredibly large proportion, of the bones and tusks of elephants, mastodons, and other huge pachyderms, and many extensive caves in various parts of the world are half filled with the skeletons of quadrupeds, sometimes lying loose in the earth, sometimes cemented together into an osseous breccia by a calcareous deposit or other binding material. These remains of large animals, though found in comparatively late formations, generally belong to extinct species, and their modern congeners or representatives do not exist in sufficient numbers to be of sensible importance in geology or in geography by the mere mass of their skeletons.[59] But the vegetable products found with them, and, in rare cases, in the stomachs of some of them, are those of yet extant plants; and besides this evidence, the recent discovery of works of human art, deposited in juxtaposition with fossil bones, and evidently at the same time and by the same agency which buried these latter--not to speak of alleged human bones found in the same strata--proves that the animals whose former existence they testify were contemporaneous with man, and possibly even extirpated by him.[60] I do not propose to enter upon the thorny question, whether the existing races of man are genealogically connected with these ancient types of humanity, and I advert to these facts only for the sake of the suggestion that man, in his earliest known stages of existence, was probably a destructive power upon the earth, though perhaps not so emphatically as his present representatives. The larger wild animals are not now numerous enough in any one region to form extensive deposits by their remains; but they have, nevertheless, a certain geographical importance. If the myriads of large browsing and grazing quadrupeds which wander over the plains of Southern Africa--and the slaughter of which by thousands is the source of a ferocious pleasure and a brutal triumph to professedly civilized hunters--if the herds of the American bison, which are numbered by hundreds of thousands, do not produce visible changes in the forms of terrestrial surface, they have at least an immense influence on the growth and distribution of vegetable life, and, of course, indirectly upon all the physical conditions of soil and climate between which and vegetation a mutual interdependence exists. The influence of wild quadrupeds upon vegetable life has been little studied, and not many facts bearing upon it have been recorded, but, so far as it is known, it appears to be conservative rather than pernicious.[61] Few if any of them depend for their subsistence on vegetable products obtainable only by the destruction of the plant, and they seem to confine their consumption almost exclusively to the annual harvest of leaf or twig, or at least of parts of the vegetable easily reproduced. If there are exceptions to this rule, they are in cases where the numbers of the animal are so proportioned to the abundance of the vegetable, that there is no danger of the extermination of the plant from the voracity of the quadruped, or of the extinction of the quadruped from the scarcity of the plant. In diet and natural wants the bison resembles the ox, the ibex and the chamois assimilate themselves to the goat and the sheep; but while the wild animal does not appear to be a destructive agency in the garden of nature, his domestic congeners are eminently so. This is partly from the change of habits resulting from domestication and association with man, partly from the fact that the number of reclaimed animals is not determined by the natural relation of demand and spontaneous supply which regulates the multiplication of wild creatures, but by the convenience of man, who is, in comparatively few things, amenable to the control of the merely physical arrangements of nature. When the domesticated animal escapes from human jurisdiction, as in the case of the ox, the horse, the goat, and perhaps the ass--which, so far as I know, are the only well-authenticated instances of the complete emancipation of household quadrupeds--he becomes again an unresisting subject of nature, and all his economy is governed by the same laws as that of his fellows which have never been enslaved by man; but, so long as he obeys a human lord, he is an auxiliary in the warfare his master is ever waging against all existences except those which he can tame to a willing servitude. _Number of Quadrupeds in the United States._ Civilization is so intimately associated with, if not dependent upon, certain inferior forms of animal life, that cultivated man has never failed to accompany himself, in all his migrations, with some of these humble attendants. The ox, the horse, the sheep, and even the comparatively useless dog and cat, as well as several species of poultry, are voluntarily transported by every emigrant colony, and they soon multiply to numbers very far exceeding those of the wild genera most nearly corresponding to them.[62] According to the census of the United States for 1860,[63] the total number of horses in all the States of the American Union, was, in round numbers, 7,300,000; of asses and mules, 1,300,000; of the ox tribe, 29,000,000;[64] of sheep, 25,000,000; and of swine, 39,000,000. The only North American quadruped sufficiently gregarious in habits, and sufficiently multiplied in numbers, to form really large herds, is the bison, or, as he is commonly called in America, the buffalo; and this animal is confined to the prairie region of the Mississippi basin and Northern Mexico. The engineers sent out to survey railroad routes to the Pacific estimated the number of a single herd of bisons seen within the last ten years on the great plains near the Upper Missouri, at not less than 200,000, and yet the range occupied by this animal is now very much smaller in area than it was when the whites first established themselves on the prairies.[65] But it must be remarked that the American buffalo is a migratory animal, and that, at the season of his annual journeys, the whole stock of a vast extent of pasture ground is collected into a single army, which is seen at or very near any one point only for a few days during the entire season. Hence there is risk of great error in estimating the numbers of the bison in a given district from the magnitude of the herds seen at or about the same time at a single place of observation; and, upon the whole, it is neither proved nor probable that the bison was ever, at any one time, as numerous in North America as the domestic bovine species is at present. The elk, the moose, the musk ox, the caribou, and the smaller quadrupeds popularly embraced under the general name of deer,[66] though sufficient for the wants of a sparse savage population, were never numerically very abundant, and the carnivora which fed upon them were still less so. It is almost needless to add that the Rocky Mountain sheep and goat must always have been very rare. Summing up the whole, then, it is evident that the wild quadrupeds of North America, even when most numerous, were few compared with their domestic successors, that they required a much less supply of vegetable food, and consequently were far less important as geographical elements than the many millions of hoofed and horned cattle now fed by civilized man on the same continent. _Origin and Transfer of Domestic Quadrupeds._ Of the origin of our domestic animals, we know historically nothing, because their domestication belongs to the ages which preceded written history; but though they cannot all be specifically identified with now extant wild animals, it is presumable that they have been reclaimed from an originally wild state. Ancient annalists have preserved to us fewer data respecting the introduction of domestic animals into new countries than respecting the transplantation of domestic vegetables. Ritter, in his learned essay on the camel, has shown that this animal was not employed by the Egyptians until a comparatively late period in their history; that he was unknown to the Carthaginians until after the downfall of their commonwealth; and that his first appearance in Western Africa is more recent still. The Bactrian camel was certainly brought from Asia Minor to the Northern shores of the Black Sea, by the Goths, in the third or fourth century.[67] The Arabian single-humped camel, or dromedary, has been carried to the Canary Islands, partially introduced into Australia, Greece, Spain, and even Tuscany, experimented upon to little purpose in Venezuela, and finally imported by the American Government into Texas and New Mexico, where it finds the climate and the vegetable products best suited to its wants, and promises to become a very useful agent in the promotion of the special civilization for which those regions are adapted. America had no domestic quadruped but a species of dog, the lama tribe, and, to a certain extent, the bison or buffalo.[68] Of course, it owes the horse, the ass, the ox, the sheep, the goat, and the swine, as does also Australia, to European colonization. Modern Europe has, thus far, not accomplished much in the way of importation of new animals, though some interesting essays have been made. The reindeer was successfully introduced into Iceland about a century ago, while similar attempts failed, about the same time, in Scotland. The Cashmere or Thibet goat was brought to France a generation since, and succeeds well. The same or an allied species and the Asiatic buffalo were carried to South Carolina about the year 1850, and the former, at least, is thought likely to prove of permanent value in the United States. The yak, or Tartary ox, seems to thrive in France, and success has attended the recent efforts to introduce the South American alpaca into Europe. _Extirpation of Quadrupeds._ Although man never fails greatly to diminish, and is perhaps destined ultimately to exterminate, such of the larger wild quadrupeds as he cannot profitably domesticate, yet their numbers often fluctuate, and even after they seem almost extinct, they sometimes suddenly increase, without any intentional steps to promote such a result on his part. During the wars which followed the French Revolution, the wolf multiplied in many parts of Europe, partly because the hunters were withdrawn from the woods to chase a nobler game, and partly because the bodies of slain men and horses supplied this voracious quadruped with more abundant food. The same animal became again more numerous in Poland after the general disarming of the rural population by the Russian Government. On the other hand, when the hunters pursue the wolf, the graminivorous wild quadrupeds increase, and thus in turn promote the multiplication of their great four-footed destroyer by augmenting the supply of his nourishment. So long as the fur of the beaver was extensively employed as a material for fine hats, it bore a very high price, and the chase of this quadruped was so keen that naturalists feared its speedy extinction. When a Parisian manufacturer invented the silk hat, which soon came into almost universal use, the demand for beavers' fur fell off, and this animal--whose habits, as we have seen, are an important agency in the formation of bogs and other modifications of forest nature--immediately began to increase, reappeared in haunts which he had long abandoned, and can no longer be regarded as rare enough to be in immediate danger of extirpation. Thus the convenience or the caprice of Parisian fashion has unconsciously exercised an influence which may sensibly affect the physical geography of a distant continent. Since the invention of gunpowder, some quadrupeds have completely disappeared from many European and Asiatic countries where they were formerly numerous. The last wolf was killed in Great Britain two hundred years ago, and the bear was extirpated from that island still earlier. The British wild ox exists only in a few English and Scottish parks, while in Irish bogs, of no great apparent antiquity, are found antlers which testify to the former existence of a stag much larger than any extant European species. The lion is believed to have inhabited Asia Minor and Syria, and probably Greece and Sicily also, long after the commencement of the historical period, and he is even said to have been not yet extinct in the first-named two of these countries at the time of the first Crusades.[69] Two large graminivorous or browsing quadrupeds, the ur and the schelk, once common in Germany, are utterly extinct, the eland and the auerochs nearly so. The Nibelungen-Lied, which, in the oldest form preserved to us, dates from about the year 1,200, though its original composition no doubt belongs to an earlier period, thus sings: Then slowe the dowghtie Sigfrid a wisent and an elk, He smote four stoute uroxen and a grim and sturdie schelk.[70] Modern naturalists identify the elk with the eland, the wisent with the auerochs. The period when the ur and the schelk became extinct is not known. The auerochs survived in Prussia until the middle of the last century, but unless it is identical with a similar quadruped said to be found on the Caucasus, it now exists only in the Russian imperial forest of Bialowitz, where about a thousand are still preserved, and in some great menageries, as for example that at Schönbrunn, near Vienna, which, in 1852, had four specimens. The eland, which is closely allied to the American wapiti, if not specifically the same animal, is still kept in the royal preserves of Prussia, to the number of four or five hundred individuals. The chamois is becoming rare, and the ibex or steinbock, once common in all the high Alps, is now believed to be confined to the Cogne mountains in Piedmont, between the valleys of the Dora Baltea and the Orco. _Number of Birds in the United States._ The tame fowls play a much less conspicuous part in rural life than the quadrupeds, and, in their relations to the economy of nature, they are of very much less moment than four-footed animals, or than the undomesticated birds. The domestic turkey[71] is probably more numerous in the territory of the United States than the wild bird of the same species ever was, and the grouse cannot, at the period of their greatest abundance, have counted as many as we now number of the common hen. The dove, however, must fall greatly short of the wild pigeon in multitude, and it is hardly probable that the flocks of domestic geese and ducks are as numerous as once were those of their wild congeners. The pigeon, indeed, seems to have multiplied immensely, for some years after the first clearings in the woods, because the settlers warred unsparingly upon the hawk, while the crops of grain and other vegetable growths increased the supply of food within the reach of the young birds, at the age when their power of flight is not yet great enough to enable them to seek it over a wide area.[72] The pigeon is not described by the earliest white inhabitants of the American States as filling the air with such clouds of winged life as astonish naturalists in the descriptions of Audubon, and, at the present day, the net and the gun have so reduced its abundance, that its appearance in large numbers is recorded only at long intervals, and it is never seen in the great flocks remembered by many still living observers as formerly very common. _Birds as Sowers and Consumers of Seeds, and as Destroyers of Insects._ Wild birds form of themselves a very conspicuous and interesting feature in the _staffage_, as painters call it, of the natural landscape, and they are important elements in the view we are taking of geography, whether we consider their immediate or their incidental influence. Birds affect vegetation directly by sowing seeds and by consuming them; they affect it indirectly by destroying insects injurious, or, in some cases, beneficial to vegetable life. Hence, when we kill a seed-sowing bird, we check the dissemination of a plant; when we kill a bird which digests the seed it swallows, we promote the increase of a vegetable. Nature protects the seeds of wild, much more effectually than those of domesticated plants. The cereal grains are completely digested when consumed by birds, but the germ of the smaller stone fruits and of very many other wild vegetables is uninjured, perhaps even stimulated to more vigorous growth, by the natural chemistry of the bird's stomach. The power of flight and the restless habits of the bird enable it to transport heavy seeds to far greater distances than they could be carried by the wind. A swift-winged bird may drop cherry stones a thousand miles from the tree they grow on; a hawk, in tearing a pigeon, may scatter from its crop the still fresh rice it had swallowed at a distance of ten degrees of latitude,[73] and thus the occurrence of isolated plants in situations where their presence cannot otherwise well be explained, is easily accounted for. There is a large class of seeds apparently specially fitted by nature for dissemination by animals. I refer to those which attach themselves, by means of hooks, or by viscous juices, to the coats of quadrupeds and the feathers of birds, and are thus transported wherever their living vehicles may chance to wander. Some birds, too, deliberately bury seeds, not indeed with a foresight aiming directly at the propagation of the plant, but from apparently purposeless secretiveness, or as a mode of preserving food for future use. An unfortunate popular error greatly magnifies the injury done to the crops of grain and leguminous vegetables by wild birds. Very many of those generally supposed to consume large quantities of the seeds of cultivated plants really feed almost exclusively upon insects, and frequent the wheatfields, not for the sake of the grain, but for the eggs, larvæ, and fly of the multiplied tribes of insect life which are so destructive to the harvests. This fact has been so well established by the examination of the stomachs of great numbers of birds in Europe and New England, at different seasons of the year, that it is no longer open to doubt, and it appears highly probable that even the species which consume more or less grain generally make amends, by destroying insects whose ravages would have been still more injurious.[74] On this subject, we have much other evidence besides that derived from dissection. Direct observation has shown, in many instances, that the destruction of wild birds has been followed by a great multiplication of noxious insects, and, on the other hand, that these latter have been much reduced in numbers by the protection and increase of the birds that devour them. Many interesting facts of this nature have been collected by professed naturalists, but I shall content myself with a few taken from familiar and generally accessible sources. The following extract is from Michelet, _L'Oiseau_ pp. 169, 170: "The _stingy_ farmer--an epithet justly and feelingly bestowed by Virgil. Avaricious, blind, indeed, who proscribes the birds--those destroyers of insects, those defenders of his harvests. Not a grain for the creature which, during the rains of winter, hunts the future insect, finds out the nests of the larvæ, examines, turns over every leaf, and destroys, every day, thousands of incipient caterpillars. But sacks of corn for the mature insect, whole fields for the grasshoppers, which the bird would have made war upon. With eyes fixed upon his furrow, upon the present moment only, without seeing and without foreseeing, blind to the great harmony which is never broken with impunity, he has everywhere demanded or approved laws for the extermination of that necessary ally of his toil--the insectivorous bird. And the insect has well avenged the bird. It has become necessary to revoke in haste the proscription. In the Isle of Bourbon, for instance, a price was set on the head of the martin; it disappeared, and the grasshoppers took possession of the island, devouring, withering, scorching with a biting drought all that they did not consume. In North America it has been the same with the starling, the protector of Indian corn.[75] Even the sparrow, which really does attack grain, but which protects it still more, the pilferer, the outlaw, loaded with abuse and smitten with curses--it has been found in Hungary that they were likely to perish without him, that he alone could sustain the mighty war against the beetles and the thousand winged enemies that swarm in the lowlands; they have revoked the decree of banishment, recalled in haste this valiant militia, which, though deficient in discipline, is nevertheless the salvation of the country.[76] "Not long since, in the neighborhood of Rouen and in the valley of Monville, the blackbird was for some time proscribed. The beetles profited well by this proscription; their larvæ, infinitely multiplied, carried on their subterranean labors with such success, that a meadow was shown me, the surface of which was completely dried up, every herbaceous root was consumed, and the whole grassy mantle, easily loosened, might have been rolled up and carried away like a carpet." _Diminution and Extirpation of Birds._ The general hostility of the European populace to the smaller birds is, in part, the remote effect of the reaction created by the game laws. When the restrictions imposed upon the chase by those laws were suddenly removed in France, the whole people at once commenced a destructive campaign against every species of wild animal. Arthur Young, writing in Provence, on the 30th of August, 1789, soon after the National Assembly had declared the chase free, thus complains of the annoyance he experienced from the use made by the peasantry of their newly won liberty. "One would think that every rusty firelock in all Provence was at work in the indiscriminate destruction of all the birds. The wadding buzzed by my ears, or fell into my carriage, five or six times in the course of the day." * * "The declaration of the Assembly that every man is free to hunt on his own land * * has filled all France with an intolerable cloud of sportsmen. * * The declaration speaks of compensations and indemnities [to the _seigneurs_], but the ungovernable populace takes advantage of the abolition of the game laws and laughs at the obligation imposed by the decree." The French Revolution removed similar restrictions, with similar results, in other countries. The habits then formed have become hereditary on the Continent, and though game laws still exist in England, there is little doubt that the blind prejudices of the ignorant and half-educated classes in that country against birds are, in some degree, at least, due to a legislation, which, by restricting the chase of all game worth killing, drives the unprivileged sportsman to indemnify himself by slaughtering all wild life which is not reserved for the amusement of his betters. Hence the lord of the manor buys his partridges and his hares by sacrificing the bread of his tenants, and so long as the farmers of Crawley are forbidden to follow higher game, they will suicidally revenge themselves by destroying the sparrows which protect their wheatfields. On the Continent, and especially in Italy, the comparative scarcity and dearness of animal food combine with the feeling I have just mentioned to stimulate still further the destructive passions of the fowler. In the Tuscan province of Grosseto, containing less than 2,000 square miles, nearly 300,000 thrushes and other small birds are annually brought to market.[77] Birds are less hardy in constitution, they possess less facility of accommodation,[78] and they are more severely affected by climatic excess than quadrupeds. Besides, they generally want the means of shelter against the inclemency of the weather and against pursuit by their enemies, which holes and dens afford to burrowing animals and to some larger beasts of prey. The egg is exposed to many dangers before hatching, and the young bird is especially tender, defenceless, and helpless. Every cold rain, every violent wind, every hailstorm during the breeding season, destroys hundreds of nestlings, and the parent often perishes with her progeny while brooding over it in the vain effort to protect it.[79] The great proportional numbers of birds, their migratory habits, and the ease with which they may escape most dangers that beset them, would seem to secure them from extirpation, and even from very great numerical reduction. But experience shows that when not protected by law, by popular favor or superstition, or by other special circumstances, they yield very readily to the hostile influences of civilization, and, though the first operations of the settler are favorable to the increase of many species, the great extension of rural and of mechanical industry is, in a variety of ways, destructive even to tribes not directly warred upon by man.[80] Nature sets bounds to the disproportionate increase of birds, while at the same time, by the multitude of their resources, she secures them from extinction through her own spontaneous agencies. Man both preys upon them and wantonly destroys them. The delicious flavor of game birds, and the skill implied in the various arts of the sportsman who devotes himself to fowling, make them favorite objects of the chase, while the beauty of their plumage, as a military and feminine decoration, threatens to involve the sacrifice of the last survivor of many once numerous species. Thus far, but few birds described by ancient or modern naturalists are known to have become absolutely extinct, though there are some cases in which they are ascertained to have utterly disappeared from the face of the earth in very recent times. The most familiar instances are those of the dodo, a large bird peculiar to the Mauritius or Isle of France, exterminated about the year 1690, and now known only by two or three fragments of skeletons, and the solitary, which inhabited the islands of Bourbon and Rodriguez, but has not been seen for more than a century. A parrot and some other birds of the Norfolk Island group are said to have lately become extinct. The wingless auk, _Alca impennis_, a bird remarkable for its excessive fatness, was very abundant two or three hundred years ago in the Faroe Islands, and on the whole Scandinavian seaboard. The early voyagers found either the same or a closely allied species, in immense numbers, on all the coasts and islands of Newfoundland. The value of its flesh and its oil made it one of the most important resources of the inhabitants of those sterile regions, and it was naturally an object of keen pursuit. It is supposed to be now completely extinct, and few museums can show even its skeleton. There seems to be strong reason to believe that our boasted modern civilization is guiltless of one or two sins of extermination which have been committed in recent ages. New Zealand formerly possessed three species of dinornis, one of which, called _moa_ by the islanders, was much larger than the ostrich. The condition in which the bones of these birds have been found and the traditions of the natives concur to prove that, though the aborigines had probably extirpated them before the discovery of New Zealand by the whites, they still existed at a comparatively late period. The same remarks apply to a winged giant the eggs of which have been brought from Madagascar. This bird must have much exceeded the dimensions of the moa, at least so far as we can judge from the egg, which is eight times as large as the average size of the ostrich egg, or about one hundred and fifty times that of the hen. But though we have no evidence that man has exterminated many species of birds, we know that his persecutions have caused their disappearance from many localities where they once were common, and greatly diminished their numbers in others. The cappercailzie, _Tetrao urogallus_, the finest of the grouse family, formerly abundant in Scotland, had become extinct in Great Britain, but has been reintroduced from Sweden.[81] The ostrich is mentioned by all the old travellers, as common on the Isthmus of Suez down to the middle of the seventeenth century. It appears to have frequented Syria and even Asia Minor at earlier periods, but is now found only in the seclusion of remoter deserts. The modern increased facilities of transportation have brought distant markets within reach of the professional hunter, and thereby given a new impulse to his destructive propensities. Not only do all Great Britain and Ireland contribute to the supply of game for the British capital, but the canvas-back duck of the Potomac, and even the prairie hen from the basin of the Mississippi, may be found at the stalls of the London poulterer. Kohl[82] informs us that on the coasts of the North Sea, twenty thousand wild ducks are usually taken in the course of the season in a single decoy, and sent to the large maritime towns for sale. The statistics of the great European cities show a prodigious consumption of game birds, but the official returns fall far below the truth, because they do not include the rural districts, and because neither the poacher nor his customers report the number of his victims. Reproduction, in cultivated countries, cannot keep pace with this excessive destruction, and there is no doubt that all the wild birds which are chased for their flesh or their plumage are diminishing with a rapidity which justifies the fear that the last of them will soon follow the dodo and the wingless auk. Fortunately the larger birds which are pursued for their flesh or for their feathers, and those the eggs of which are used as food, are, so far as we know the functions appointed to them by nature, not otherwise specially useful to man, and, therefore, their wholesale destruction is an economical evil only in the same sense in which all waste of productive capital is an evil. If it were possible to confine the consumption of game fowl to a number equal to the annual increase, the world would be a gainer, but not to the same extent as it would be by checking the wanton sacrifice of millions of the smaller birds, which are of no real value as food, but which, as we have seen, render a most important service by battling, in our behalf, as well as in their own, against the countless legions of humming and of creeping things, with which the prolific powers of insect life would otherwise cover the earth. _Introduction of Birds._ Man has undesignedly introduced into new districts perhaps fewer species of birds than of quadrupeds; but the distribution of birds is very much influenced by the character of his industry, and the transplantation of every object of agricultural production is, at a longer or shorter interval, followed by that of the birds which feed upon its seeds, or more frequently upon the insects it harbors. The vulture, the crow, and other winged scavengers, follow the march of armies as regularly as the wolf. Birds accompany ships on long voyages, for the sake of the offal which is thrown overboard, and, in such cases, it might often happen that they would breed and become naturalized in countries where they had been unknown before.[83] There is a familiar story of an English bird which built its nest in an unused block in the rigging of a ship, and made one or two short voyages with the vessel while hatching its eggs. Had the young become fledged while lying in a foreign harbor, they would of course have claimed the rights of citizenship in the country where they first took to the wing.[84] Some enthusiastic entomologist will, perhaps, by and by discover that insects and worms are as essential as the larger organisms to the proper working of the great terraqueous machine, and we shall have as eloquent pleas in defence of the mosquito, and perhaps even of the tzetze fly, as Toussenel and Michelet have framed in behalf of the bird.[85] The silkworm and the bee need no apologist; a gallnut produced by the puncture of an insect on a Syrian oak is a necessary ingredient in the ink I am writing with, and from my windows I recognize the grain of the kermes and the cochineal in the gay habiliments of the holiday groups beneath them. But agriculture, too, is indebted to the insect and the worm. The ancients, according to Pliny, were accustomed to hang branches of the wild fig upon the domestic tree, in order that the insects which frequented the former might hasten the ripening of the cultivated fig by their punctures--or, as others suppose, might fructify it by transporting to it the pollen of the wild fruit--and this process, called caprification, is not yet entirely obsolete. The earthworms long ago made good their title to the respect and gratitude of the farmer as well as of the angler. The utility of the earthworms has been pointed out in many scientific as well as in many agricultural treatises. The following extract, cut from a newspaper, will answer my present purpose: "Mr. Josiah Parkes, the consulting engineer of the Royal Agricultural Society of England, says that worms are great assistants to the drainer, and valuable aids to the farmer in keeping up the fertility of the soil. He says they love moist, but not wet soils; they will bore down to, but not into water; they multiply rapidly on land after drainage, and prefer a deeply dried soil. On examining with Mr. Thomas Hammond, of Penhurst, Kent, part of a field which he had deeply drained, after long-previous shallow drainage, he found that the worms had greatly increased in number, and that their bores descended quite to the level of the pipes. Many worm bores were large enough to receive the little finger. Mr. Henry Handley had informed him of a piece of land near the sea in Lincolnshire, over which the sea had broken and killed all the worms--the field remained sterile until the worms again inhabited it. He also showed him a piece of pasture land near to his house, in which worms were in such numbers that he thought their casts interfered too much with its produce, which induced him to have it rolled at night in order to destroy the worms. The result was, that the fertility of the field greatly declined, nor was it restored until they had recruited their numbers, which was aided by collecting and transporting multitudes of worms from the fields. "The great depth into which worms will bore, and from which they push up fine fertile soil, and cast it on the surface, has been admirably traced by Mr. C. Darwin, of Down, Kent, who has shown that in a few years they have actually elevated the surface of fields by a large layer of rich mould, several inches thick--thus affording nourishment to the roots of grasses, and increasing the productiveness of the soil." It should be added that the writer quoted, and others who have discussed the subject, have overlooked one very important element in the fertilization produced by earthworms. I refer to the enrichment of the soil by their excreta during life, and by the decomposition of their remains when they die. The manure thus furnished is as valuable as the like amount of similar animal products derived from higher organisms, and when we consider the prodigious numbers of these worms found on a single square yard of some soils, we may easily see that they furnish no insignificant contribution to the nutritive material required for the growth of plants.[86] The perforations of the earthworm mechanically affect the texture of the soil and its permeability by water, and they therefore have a certain influence on the form and character of surface. But the geographical importance of insects proper, as well as of worms, depends principally on their connection with vegetable life as agents of its fecundation, and of its destruction.[87] I am acquainted with no single fact so strikingly illustrative of this importance, as the following statement which I take from a notice of Darwin's volume, On Various Contrivances by which British and Foreign Orchids are Fertilized by Insects, in the _Saturday Review_, of October 18, 1862: "The net result is, that some six thousand species of orchids are absolutely dependent upon the agency of insects for their fertilization. That is to say, were those plants unvisited by insects, they would all rapidly disappear." What is true of the orchids is more or less true of many other vegetable families. We do not know the limits of this agency, and many of the insects habitually regarded as unqualified pests, may directly or indirectly perform functions as important to the most valuable plants as the services rendered by certain tribes to the orchids. I say directly or indirectly, because, besides the other arrangements of nature for checking the undue multiplication of particular species, she has established a police among insects themselves, by which some of them keep down or promote the increase of others; for there are insects, as well as birds and beasts, of prey. The existence of an insect which fertilizes a useful vegetable may depend on that of another, which constitutes his food in some stage of his life, and this other again may be as injurious to some plant as his destroyer is beneficial to another. The equation of animal and vegetable life is too complicated a problem for human intelligence to solve, and we can never know how wide a circle of disturbance we produce in the harmonies of nature when we throw the smallest pebble into the ocean of organic life. This much, however, we seem authorized to conclude: as often as we destroy the balance by deranging the original proportions between different orders of spontaneous life, the law of self-preservation requires us to restore the equilibrium, by either directly returning the weight abstracted from one scale, or removing a corresponding quantity from the other. In other words, destruction must be either repaired by reproduction, or compensated by new destruction in an opposite quarter. The parlor aquarium has taught even those to whom it is but an amusing toy, that the balance of animal and vegetable life must be preserved, and that the excess of either is fatal to the other, in the artificial tank as well as in natural waters. A few years ago, the water of the Cochituate aqueduct at Boston became so offensive in smell and taste as to be quite unfit for use. Scientific investigation found the cause in the too scrupulous care with which aquatic vegetation had been excluded from the reservoir, and the consequent death and decay of the animalculæ which could not be shut out, nor live in the water without the vegetable element.[88] _Introduction of Insects._ The general tendency of man's encroachments upon spontaneous nature has been to increase insect life at the expense of vegetation and of the smaller quadrupeds and birds. Doubtless there are insects in all woods, but in temperate climates they are comparatively few and harmless, and the most numerous tribes which breed in the forest, or rather in its waters, and indeed in all solitudes, are those which little injure vegetation, such as mosquitoes, gnats, and the like. With the cultivated plants of man come the myriad tribes which feed or breed upon them, and agriculture not only introduces new species, but so multiplies the number of individuals as to defy calculation. Newly introduced vegetables frequently escape for years the insect plagues which had infested them in their native habitat; but the importation of other varieties of the plant, the exchange of seed, or some mere accident, is sure in the long run to carry the egg, the larva, or the chrysalis to the most distant shores where the plant assigned to it by nature as its possession has preceded it. For many years after the colonization of the United States, few or none of the insects which attack wheat in its different stages of growth, were known in America. During the Revolutionary war, the Hessian fly, _Cecidomyia destructor_, made its appearance, and it was so called because it was first observed in the year when the Hessian troops were brought over, and was popularly supposed to have been accidentally imported by those unwelcome strangers. Other destroyers of cereal grains have since found their way across the Atlantic, and a noxious European aphis has first attacked the American wheatfields within the last four or five years. Unhappily, in these cases of migration, the natural corrective of excessive multiplication, the parasitic or voracious enemy of the noxious insect, does not always accompany the wanderings of its prey, and the bane long precedes the antidote. Hence, in the United States, the ravages of imported insects injurious to cultivated crops, not being checked by the counteracting influences which nature had provided to limit their devastations in the Old World, are much more destructive than in Europe. It is not known that the wheat midge is preyed upon in America by any other insect, and in seasons favorable to it, it multiplies to a degree which would prove almost fatal to the entire harvest, were it not that, in the great territorial extent of the United States, there is room for such differences of soil and climate as, in a given year, to present in one State all the conditions favorable to the increase of a particular insect, while in another, the natural influences are hostile to it. The only apparent remedy for this evil is, to balance the disproportionate development of noxious foreign species by bringing from their native country the tribes which prey upon them. This, it seems, has been attempted. The United States' Census Report for 1860, p. 82, states that the New York Agricultural Society "has introduced into this country from abroad certain parasites which Providence has created to counteract the destructive powers of some of these depredators." This is, however, not the only purpose for which man has designedly introduced foreign forms of insect life. The eggs of the silkworm are known to have been brought from the farther East to Europe in the sixth century, and new silk spinners which feed on the castor oil bean and the ailanthus, have recently been reared in France and in South America with promising success. The cochineal, long regularly bred in aboriginal America, has been transplanted to Spain, and both the kermes insect and the cantharides have been transferred to other climates than their own. The honey bee must be ranked next to the silkworm in economical importance.[89] This useful creature was carried to the United States by European colonists, in the latter part of the seventeenth century; it did not cross the Mississippi till the close of the eighteenth, and it is only within the last five or six years that it has been transported to California, where it was previously unknown. The Italian stingless bee has very lately been introduced into the United States. The insects and worms intentionally transplanted by man bear but a small proportion to those accidentally introduced by him. Plants and animals often carry their parasites with them, and the traffic of commercial countries, which exchange their products with every zone and every stage of social existence, cannot fail to transfer in both directions the minute organisms that are, in one way or another, associated with almost every object important to the material interests of man.[90] The tenacity of life possessed by many insects, their prodigious fecundity, the length of time they often remain in the different phases of their existence,[91] the security of the retreats into which their small dimensions enable them to retire, are all circumstances very favorable not only to the perpetuity of their species, but to their transportation to distant climates and their multiplication in their new homes. The teredo, so destructive to shipping, has been carried by the vessels whose wooden walls it mines to almost every part of the globe. The termite, or white ant, is said to have been brought to Rochefort by the commerce of that port a hundred years ago.[92] This creature is more injurious to wooden structures and implements than any other known insect. It eats out almost the entire substance of the wood, leaving only thin partitions between the galleries it excavates in it; but as it never gnaws through the surface to the air, a stick of timber may be almost wholly consumed without showing any external sign of the damage it has sustained. The termite is found also in other parts of France, and particularly at Rochelle, where, thus far, its ravages are confined to a single quarter of the city. A borer, of similar habits, is not uncommon in Italy, and you may see in that country, handsome chairs and other furniture which have been reduced by this insect to a framework of powder of post, covered, and apparently held together, by nothing but the varnish. The carnivorous, and often the herbivorous insects render an important service to man by consuming dead and decaying animal and vegetable matter, the decomposition of which would otherwise fill the air with effluvia noxious to health. Some of them, the grave-digger beetle, for instance, bury the small animals in which they lay their eggs, and thereby prevent the escape of the gases disengaged by putrefaction. The prodigious rapidity of development in insect life, the great numbers of the individuals in many species, and the voracity of most of them while in the larva state, justify the appellation of nature's scavengers which has been bestowed upon them, and there is very little doubt that, in warm countries, they consume a much larger quantity of putrescent organic material than the quadrupeds and the birds which feed upon such aliment. _Destruction of Insects._ It is well known to naturalists, but less familiarly to common observers, that the aquatic larvæ of some insects constitute, at certain seasons, a large part of the food of fresh-water fish, while other larvæ, in their turn, prey upon the spawn and even the young of their persecutors.[93] The larvæ of the mosquito and the gnat are the favorite food of the trout in the wooded regions where those insects abound.[94] Earlier in the year the trout feeds on the larvæ of the May fly, which is itself very destructive to the spawn of the salmon, and hence, by a sort of house-that-Jack-built, the destruction of the mosquito, that feeds the trout that preys on the May fly that destroys the eggs that hatch the salmon that pampers the epicure, may occasion a scarcity of this latter fish in waters where he would otherwise be abundant. Thus all nature is linked together by invisible bonds, and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life with which the Creator has peopled the earth. I have said that man has promoted the increase of the insect and the worm, by destroying the bird and the fish which feed upon them. Many insects, in the four different stages of their growth, inhabit in succession the earth, the water, and the air. In each of these elements they have their special enemies, and, deep and dark as are the minute recesses in which they hide themselves, they are pursued to the remotest, obscurest corners by the executioners that nature has appointed to punish their delinquencies, and furnished with cunning contrivances for ferreting out the offenders and dragging them into the light of day. One tribe of birds, the woodpeckers, seems to depend for subsistence almost wholly on those insects which breed in dead or dying trees, and it is, perhaps, needless to say that the injury these birds do the forest is imaginary. They do not cut holes in the trunk of the tree to prepare a lodgment for a future colony of boring larvæ, but to extract the worm which has already begun his mining labors. Hence these birds are not found where the forester removes trees as fast as they become fit habitations for such insects. In clearing new lands in the United States, dead trees, especially of the spike-leaved kinds, too much decayed to serve for timber, and which, in that state, are worth little for fuel, are often allowed to stand until they fall of themselves. Such _stubs_, as they are popularly called, are filled with borers, and often deeply cut by the woodpeckers, whose strong bills enable them to penetrate to the very heart of the tree and drag out the lurking larvæ. After a few years, the stubs fall, or, as wood becomes valuable, are cut and carried off for firewood, and, at the same time, the farmer selects for felling, in the forest he has reserved as a permanent source of supply of fuel and timber, the decaying trees which, like the dead stems in the fields, serve as a home for both the worm and his pursuer. We thus gradually extirpate this tribe of insects, and, with them, the species of birds which subsist principally upon them. Thus the fine, large, red-headed woodpecker, _Picus erythrocephalus_, formerly very common in New England, has almost entirely disappeared from those States, since the dead trees are gone, and the apples, his favorite vegetable food, are less abundant. There are even large quadrupeds which feed almost exclusively upon insects. The ant bear is strong enough to pull down the clay houses built by the species of termites that constitute his ordinary diet, and the curious ai-ai, a climbing quadruped of Madagascar--of which I believe only a single specimen, secured by Mr. Sandwith, has yet reached Europe--is provided with a very slender, hook-nailed finger, long enough to reach far into a hole in the trunk of a tree, and extract the worm which bored it. _Reptiles._ But perhaps the most formidable foes of the insect, and even of the small rodents, are the reptiles. The chameleon approaches the insect perched upon the twig of a tree, with an almost imperceptible slowness of motion, until, at the distance of a foot, he shoots out his long, slimy tongue, and rarely fails to secure the victim. Even the slow toad catches the swift and wary housefly in the same manner; and in the warm countries of Europe, the numerous lizards contribute very essentially to the reduction of the insect population, which they both surprise in the winged state upon walls and trees, and consume as egg, worm, and chrysalis, in their earlier metamorphoses. The serpents feed much upon insects, as well as upon mice, moles, and small reptiles, including also other snakes. The disgust and fear with which the serpent is so universally regarded expose him to constant persecution by man, and perhaps no other animal is so relentlessly sacrificed by him. In temperate climates, snakes are consumed by scarcely any beast or bird of prey except the stork, and they have few dangerous enemies but man, though in the tropics other animals prey upon them.[95] It is doubtful whether any species of serpent has been exterminated within the human period, and even the dense population of China has not been able completely to rid itself of the viper. They have, however, almost entirely disappeared from particular localities. The rattlesnake is now wholly unknown in many large districts where it was extremely common half a century ago, and Palestine has long been, if not absolutely free from venomous serpents, at least very nearly so.[96] _Destruction of Fish._ The inhabitants of the waters seem comparatively secure from human pursuit or interference by the inaccessibility of their retreats, and by our ignorance of their habits--a natural result of the difficulty of observing the ways of creatures living in a medium in which we cannot exist. Human agency has, nevertheless, both directly and incidentally, produced great changes in the population of the sea, the lakes, and the rivers, and if the effects of such revolutions in aquatic life are apparently of small importance in general geography, they are still not wholly inappreciable. The great diminution in the abundance of the larger fish employed for food or pursued for products useful in the arts is familiar, and when we consider how the vegetable and animal life on which they feed must be affected by the reduction of their numbers, it is easy to see that their destruction may involve considerable modifications in many of the material arrangements of nature. The whale does not appear to have been an object of pursuit by the ancients, for any purpose, nor do we know when the whale fishery first commenced.[97] It was, however, very actively prosecuted in the Middle Ages, and the Biscayans seem to have been particularly successful in this as indeed in other branches of nautical industry.[98] Five hundred years ago, whales abounded in every sea. They long since became so rare in the Mediterranean as not to afford encouragement for the fishery as a regular occupation; and the great demand for oil and whalebone for mechanical and manufacturing purposes, in the present century, has stimulated the pursuit of the "hugest of living creatures" to such activity, that he has now almost wholly disappeared from many favorite fishing grounds, and in others is greatly diminished in numbers. What special functions, besides his uses to man, are assigned to the whale in the economy of nature, we do not know; but some considerations, suggested by the character of the food upon which certain species subsist, deserve to be specially noticed. None of the great mammals grouped under the general name of whale are rapacious. They all live upon small organisms, and the most numerous species feed almost wholly upon the soft gelatinous mollusks in which the sea abounds in all latitudes. We cannot calculate even approximately the number of the whales, or the quantity of organic nutriment consumed by an individual, and of course we can form no estimate of the total amount of animal matter withdrawn by them, in a given period, from the waters of the sea. It is certain, however, that it must have been enormous when they were more abundant, and that it is still very considerable. A very few years since, the United States had more than six hundred whaling ships constantly employed in the Pacific, and the product of the American whale fishery for the year ending June 1st, 1860, was seven millions and a half of dollars.[99] The mere bulk of the whales destroyed in a single year by the American and the European vessels engaged in this fishery would form an island of no inconsiderable dimensions, and each one of those taken must have consumed, in the course of his growth, many times his own weight of mollusks. The destruction of the whales must have been followed by a proportional increase of the organisms they feed upon, and if we had the means of comparing the statistics of these humble forms of life, for even so short a period as that between the years 1760 and 1860, we should find a difference sufficient, possibly, to suggest an explanation of some phenomena at present unaccounted for. For instance, as I have observed in another work,[100] the phosphorescence of the sea was unknown to ancient writers, or at least scarcely noticed by them, and even Homer--who, blind as tradition makes him when he composed his epics, had seen, and marked, in earlier life, all that the glorious nature of the Mediterranean and its coasts discloses to unscientific observation--nowhere alludes to this most beautiful and striking of maritime wonders. In the passage just referred to, I have endeavored to explain the silence of ancient writers with respect to this as well as other remarkable phenomena on psychological grounds; but is it not possible that, in modern times, the animalculæ which produce it may have immensely multiplied, from the destruction of their natural enemies by man, and hence that the gleam shot forth by their decomposition, or by their living processes, is both more frequent and more brilliant than in the days of classic antiquity? Although the whale does not prey upon smaller creatures resembling himself in form and habits, yet true fishes are extremely voracious, and almost every tribe devours unsparingly the feebler species, and even the spawn and young of its own. The enormous destruction of the pike, the trout family, and other ravenous fish, as well as of the fishing birds, the seal, and the otter, by man, would naturally have occasioned a great increase in the weaker and more defenceless fish on which they feed, had he not been as hostile to them also as to their persecutors. We have little evidence that any fish employed as human food has naturally multiplied in modern times, while all the more valuable tribes have been immensely reduced in numbers.[101] This reduction must have affected the more voracious species not used as food by man, and accordingly the shark, and other fish of similar habits, though not objects of systematic pursuit, are now comparatively rare in many waters where they formerly abounded. The result is, that man has greatly reduced the numbers of all larger marine animals, and consequently indirectly favored the multiplication of the smaller aquatic organisms which entered into their nutriment. This change in the relations of the organic and inorganic matter of the sea must have exercised an influence on the latter. What that influence has been, we cannot say, still less can we predict what it will be hereafter; but its action is not for that reason the less certain. _Introduction and Breeding of Fish._ The introduction and successful breeding of fish of foreign species appears to have been long practised in China and was not unknown to the Greeks and Romans. This art has been revived in modern times, but thus far without any important results, economical or physical, though there seems to be good reason to believe it may be employed with advantage on an extended scale. As in the case of plants, man has sometimes undesignedly introduced new species of aquatic animals into countries distant from their birthplace. The accidental escape of the Chinese goldfish from ponds where they were bred as a garden ornament, has peopled some European, and it is said American streams with this species. Canals of navigation and irrigation interchange the fish of lakes and rivers widely separated by natural barriers, as well as the plants which drop their seeds into the waters. The Erie Canal, as measured by its own channel, has a length of about three hundred and sixty miles, and it has ascending and descending locks in both directions. By this route, the fresh-water fish of the Hudson and the Upper Lakes, and some of the indigenous vegetables of these respective basins, have intermixed, and the fauna and flora of the two regions have now more species common to both than before the canal was opened. Some accidental attraction not unfrequently induces fish to follow a vessel for days in succession, and they may thus be enticed into zones very distant from their native habitat. Several years ago, I was told at Constantinople, upon good authority, that a couple of fish, of a species wholly unknown to the natives, had just been taken in the Bosphorus. They were alleged to have followed an English ship from the Thames, and to have been frequently observed by the crew during the passage, but I was unable to learn their specific character. Many of the fish which pass the greater part of the year in salt water spawn in fresh, and some fresh-water species, the common brook trout of New England for instance, which, under ordinary circumstances, never visit the sea, will, if transferred to brooks emptying directly into the ocean, go down into the salt water after spawning time, and return again the next season. Sea fish, the smelt among others, are said to have been naturalized in fresh water, and some naturalists have argued from the character of the fish of Lake Baikal, and especially from the existence of the seal in that locality, that all its inhabitants were originally marine species, and have changed their habits with the gradual conversion of the saline waters of the lake--once, as is assumed, a maritime bay--into fresh.[102] The presence of the seal is hardly conclusive on this point, for it is sometimes seen in Lake Champlain at the distance of some hundreds of miles from even brackish water. One of these animals was killed on the ice in that lake in February, 1810, another in February, 1846,[103] and remains of the seal have been found at other times in the same waters. The remains of the higher orders of aquatic animals are generally so perishable that, even where most abundant, they do not appear to be now forming permanent deposits of any considerable magnitude; but it is quite otherwise with shell fish, and, as we shall see hereafter, with many of the minute limeworkers of the sea. There are, on the southern coast of the United States, beds of shells so extensive that they were formerly supposed to have been naturally accumulated, and were appealed to as proofs of an elevation of the coast by geological causes; but they are now ascertained to have been derived from oysters, consumed in the course of long ages by the inhabitants of Indian towns. The planting of a bed of oysters in a new locality might, very probably, lead, in time, to the formation of a bank, which, in connection with other deposits, might perceptibly affect the line of a coast, or, by changing the course of marine currents, or the outlet of a river, produce geographical changes of no small importance. The transplantation of oysters to artificial ponds has long been common, and it appears to have recently succeeded well on a large scale in the open sea on the French coast. A great extension of this fishery is hoped for, and it is now proposed to introduce upon the same coast the American soft clam, which is so abundant in the tide-washed beach sands of Long Island Sound as to form an important article in the diet of the neighboring population. The intentional naturalization of foreign fish, as I have said, has not thus far yielded important fruits; but though this particular branch of what is called, not very happily, _pisciculture_, has not yet established its claims to the attention of the physical geographer or the political economist, the artificial breeding of domestic fish has already produced very valuable results, and is apparently destined to occupy an extremely conspicuous place in the history of man's efforts to compensate his prodigal waste of the gifts of nature. The restoration of the primitive abundance of salt and fresh water fish, is one of the greatest material benefits that, with our present physical resources, governments can hope to confer upon their subjects. The rivers, lakes, and seacoasts once restocked, and protected by law from exhaustion by taking fish at improper seasons, by destructive methods, and in extravagant quantities, would continue indefinitely to furnish a very large supply of most healthful food, which, unlike all domestic and agricultural products, would spontaneously renew itself and cost nothing but the taking. There are many sterile or wornout soils in Europe so situated that they might, at no very formidable cost, be converted into permanent lakes, which would serve not only as reservoirs to retain the water of winter rains and snow, and give it out in the dry season for irrigation, but as breeding ponds for fish, and would thus, without further cost, yield a larger supply of human food than can at present be obtained from them even at a great expenditure of capital and labor in agricultural operations. The additions which might be made to the nutriment of the civilized world by a judicious administration of the resources of the waters, would allow some restriction of the amount of soil at present employed for agricultural purposes, and a corresponding extension of the area of the forest, and would thus facilitate a return to primitive geographical arrangements which it is important partially to restore. _Extirpation of Aquatic Animals._ It does not seem probable that man, with all his rapacity and all his enginery, will succeed in totally extirpating any salt-water fish, but he has already exterminated at least one marine warm-blooded animal--Steller's sea cow--and the walrus, the sea lion, and other large amphibia, as well as the principal fishing quadrupeds, are in imminent danger of extinction. Steller's sea cow, _Rhytina Stelleri_, was first seen by Europeans in the year 1741, on Bering's Island. It was a huge amphibious mammal, weighing not less than eight thousand pounds, and appears to have been confined exclusively to the islands and coasts in the neighborhood of Bering's Strait. Its flesh was very palatable, and the localities it frequented were easily accessible from the Russian establishments in Kamtschatka. As soon as its existence and character, and the abundance of fur animals in the same waters, were made known to the occupants of those posts by the return of the survivors of Bering's expedition, so active a chase was commenced against the amphibia of that region, that, in the course of twenty-seven years, the sea cow, described by Steller as extremely numerous in 1741, is believed to have been completely extirpated, not a single individual having been seen since the year 1768. The various tribes of seals in the Northern and Southern Pacific, the walrus and the sea otter, are already so reduced in numbers that they seem destined soon to follow the sea cow, unless protected by legislation stringent enough, and a police energetic enough, to repress the ardent cupidity of their pursuers. The seals, the otter tribe, and many other amphibia which feed almost exclusively upon fish, are extremely voracious, and of course their destruction or numerical reduction must have favored the multiplication of the species of fish principally preyed upon by them. I have been assured by the keeper of several tamed seals that, if supplied at frequent intervals, each seal would devour not less than fourteen pounds of fish, or about a quarter of his own weight, in a day.[104] A very intelligent and observing hunter, who has passed a great part of his life in the forest, after carefully watching the habits of the fresh-water otter of the Northern American States, estimates their consumption of fish at about four pounds per day. Man has promoted the multiplication of fish by making war on their brute enemies, but he has by no means thereby compensated his own greater destructiveness.[105] The bird and beast of prey, whether on land or in the water, hunt only as long as they feel the stimulus of hunger, their ravages are limited by the demands of present appetite, and they do not wastefully destroy what they cannot consume. Man, on the contrary, angles to-day that he may dine to-morrow; he takes and dries millions of fish on the banks of Newfoundland, that the fervent Catholic of the shores of the Mediterranean may have wherewithal to satisfy the cravings of the stomach during next year's Lent, without imperilling his soul by violating the discipline of the papal church; and all the arrangements of his fisheries are so organized as to involve the destruction of many more fish than are secured for human use, and the loss of a large proportion of the annual harvest of the sea in the process of curing, or in transportation to the places of its consumption.[106] Fish are more affected than quadrupeds by slight and even imperceptible differences in their breeding places and feeding grounds. Every river, every brook, every lake stamps a special character upon its salmon, its shad, and its trout, which is at once recognized by those who deal in or consume them. No skill can give the fish fattened by food selected and prepared by man the flavor of those which are nourished at the table of nature, and the trout of the artificial ponds in Germany and Switzerland are so inferior to the brook fish of the same species and climate, that it is hard to believe them identical. The superior sapidity of the American trout to the European species, which is familiar to every one acquainted with both continents, is probably due less to specific difference than to the fact that, even in the parts of the New World which have been longest cultivated, wild nature is not yet tamed down to the character it has assumed in the Old, and which it will acquire in America also when her civilization shall be as ancient as is now that of Europe. Man has hitherto hardly anywhere produced such climatic or other changes as would suffice of themselves totally to banish the wild inhabitants of the dry land, and the disappearance of the native birds and quadrupeds from particular localities is to be ascribed quite as much to his direct persecutions as to the want of forest shelter, of appropriate food, or of other conditions indispensable to their existence. But almost all the processes of agriculture, and of mechanical and chemical industry, are fatally destructive to aquatic animals within reach of their influence. When, in consequence of clearing the woods, the changes already described as thereby produced in the beds and currents of rivers, are in progress, the spawning grounds of fish are exposed from year to year to a succession of mechanical disturbances; the temperature of the water is higher in summer, colder in winter, than when it was shaded and protected by wood; the smaller organisms, which formed the sustenance of the young fry, disappear or are reduced in numbers, and new enemies are added to the old foes that preyed upon them; the increased turbidness of the water in the annual inundations chokes the fish; and, finally, the quickened velocity of its current sweeps them down into the larger rivers or into the sea, before they are yet strong enough to support so great a change of circumstances.[107] Industrial operations are not less destructive to fish which live or spawn in fresh water. Milldams impede their migrations, if they do not absolutely prevent them, the sawdust from lumber mills clogs their gills, and the thousand deleterious mineral substances, discharged into rivers from metallurgical, chemical, and manufacturing establishments, poison them by shoals. _Minute Organisms._ Besides the larger creatures of the land and of the sea, the quadrupeds, the reptiles, the birds, the amphibia, the crustacea, the fish, the insects, and the worms, there are other countless forms of vital being. Earth, water, the ducts and fluids of vegetable and of animal life, the very air we breathe, are peopled by minute organisms which perform most important functions in both the living and the inanimate kingdoms of nature. Of the offices assigned to these creatures, the most familiar to common observation is the extraction of lime, and more rarely, of silex, from the waters inhabited by them, and the deposit of these minerals in a solid form, either as the material of their habitations or as the exuviæ of their bodies. The microscope and other means of scientific observation assure us that the chalk beds of England and of France, the coral reefs of marine waters in warm climates, vast calcareous and silicious deposits in the sea and in many fresh-water ponds, the common polishing earths and slates, and many species of apparently dense and solid rock, are the work of the humble organisms of which I speak, often, indeed, of animalculæ so small as to become visible only by the aid of lenses magnifying a hundred times the linear measures. It is popularly supposed that animalculæ, or what are commonly embraced under the vague name of infusoria, inhabit the water alone, but the atmospheric dust transported by every wind and deposited by every calm is full of microscopic life or of its relics. The soil on which the city of Berlin stands, contains at the depth of ten or fifteen feet below the surface, living elaborators of silex;[108] and a microscopic examination of a handful of earth connected with the material evidences of guilt has enabled the naturalist to point out the very spot where a crime was committed. It has been computed that one sixth part of the solid matter let fall by great rivers at their outlets consists of still recognizable infusory shells and shields, and, as the friction of rolling water must reduce much of these fragile structures to a state of comminution which even the microscope cannot resolve into distinct particles and identify as relics of animal or of vegetable life, we must conclude that a considerably larger proportion of river deposits is really the product of animalcules.[109] It is evident that the chemical, and in many cases the mechanical character of a great number of the objects important in the material economy of human life, must be affected by the presence of so large an organic element in their substance, and it is equally obvious that all agricultural and all industrial operations tend to disturb the natural arrangements of this element, to increase or to diminish the special adaptation of every medium in which it lives to the particular orders of being inhabited by it. The conversion of woodland into pasturage, of pasture into plough land, of swamp or of shallow sea into dry ground, the rotations of cultivated crops, must prove fatal to millions of living things upon every rood of surface thus deranged by man, and must, at the same time, more or less fully compensate this destruction of life by promoting the growth and multiplication of other tribes equally minute in dimensions. I do not know that man has yet endeavored to avail himself, by artificial contrivances, of the agency of these wonderful architects and manufacturers. We are hardly well enough acquainted with their natural economy to devise means to turn their industry to profitable account, and they are in very many cases too slow in producing visible results for an age so impatient as ours. The over-civilization of the nineteenth century cannot wait for wealth to be amassed by infinitesimal gains, and we are in haste to _speculate_ upon the powers of nature, as we do upon objects of bargain and sale in our trafficking one with another. But there are still some cases where the little we know of a life, whose workings are invisible to the naked eye, suggests the possibility of advantageously directing the efforts of troops of artisans that we cannot see. Upon coasts occupied by the corallines, the reef-building animalcule does not work near the mouth of rivers. Hence the change of the outlet of a stream, often a very easy matter, may promote the construction of a barrier to coast navigation at one point, and check the formation of a reef at another, by diverting a current of fresh water from the former and pouring it into the sea at the latter. Cases may probably be found in tropical seas, where rivers have prevented the working of the coral animalcules in straits separating islands from each other or from the mainland. The diversion of such streams might remove this obstacle, and reefs consequently be formed which should convert an archipelago into a single large island, and finally join that to the neighboring continent. Quatrefages proposed to destroy the teredo in harbors by impregnating the water with a mineral solution fatal to them. Perhaps the labors of the coralline animals might be arrested over a considerable extent of sea coast by similar means. The reef builders are leisurely architects, but the precious coral is formed so rapidly that the beds may be refished advantageously as often as once in ten years.[110] It does not seem impossible that this coral might be transplanted to the American coast, where the Gulf stream would furnish a suitable temperature beyond the climatic limits that otherwise confine its growth; and thus a new source of profit might perhaps be added to the scanty returns of the hardy fisherman. In certain geological formations, the diatomaceæ deposit, at the bottom of fresh-water ponds, beds of silicious shields, valuable as a material for a species of very light firebrick, in the manufacture of water glass and of hydraulic cement, and ultimately, doubtless, in many yet undiscovered industrial processes. An attentive study of the conditions favorable to the propagation of the diatomaceæ might perhaps help us to profit directly by the productivity of this organism, and, at the same time, disclose secrets of nature capable of being turned to valuable account in dealing with silicious rocks, and the metal which is the base of them. Our acquaintance with the obscure and infinitesimal life of which I have now been treating is very recent, and still very imperfect. We know that it is of vast importance in the economy of nature, but we are so ambitious to grasp the great, so little accustomed to occupy ourselves with the minute, that we are not yet prepared to enter seriously upon the question how far we can control and direct the operations, not of unembodied physical forces, but of beings, in popular apprehension, almost as immaterial as they. Nature has no unit of magnitude by which she measures her works. Man takes his standards of dimension from himself. The hair's breadth was his minimum until the microscope told him that there are animated creatures to which one of the hairs of his head is a larger cylinder than is the trunk of the giant California redwood to him. He borrows his inch from the breadth of his thumb, his palm and span from the width of his hand and the spread of his fingers, his foot from the length of the organ so named; his cubit is the distance from the tip of his middle finger to his elbow, and his fathom is the space he can measure with his outstretched arms. To a being who instinctively finds the standard of all magnitudes in his own material frame, all objects exceeding his own dimensions are absolutely great, all falling short of them absolutely small. Hence we habitually regard the whale and the elephant as essentially large and therefore important creatures, the animalcule as an essentially small and therefore unimportant organism. But no geological formation owes its origin to the labors or the remains of the huge mammal, while the animalcule composes, or has furnished, the substance of strata thousands of feet in thickness, and extending, in unbroken beds, over many degrees of terrestrial surface. If man is destined to inhabit the earth much longer, and to advance in natural knowledge with the rapidity which has marked his progress in physical science for the last two or three centuries, he will learn to put a wiser estimate on the works of creation, and will derive not only great instruction from studying the ways of nature in her obscurest, humblest walks, but great material advantage from stimulating her productive energies in provinces of her empire hitherto regarded as forever inaccessible, utterly barren.[111] CHAPTER III. THE WOODS. THE HABITABLE EARTH ORIGINALLY WOODED--THE FOREST DOES NOT FURNISH FOOD FOR MAN--FIRST REMOVAL OF THE WOODS--EFFECTS OF FIRE ON FOREST SOIL--EFFECTS OF THE DESTRUCTION OF THE FOREST--ELECTRICAL INFLUENCE OF TREES--CHEMICAL INFLUENCE OF THE FOREST. INFLUENCE OF THE FOREST, CONSIDERED AS INORGANIC MATTER, ON TEMPERATURE: _a_, ABSORBING AND EMITTING SURFACE; _b_, TREES AS CONDUCTORS OF HEAT; _c_, TREES IN SUMMER AND IN WINTER; _d_, DEAD PRODUCTS OF TREES; _e_, TREES AS A SHELTER TO GROUNDS TO THE LEEWARD OF THEM; _f_, TREES AS A PROTECTION AGAINST MALARIA--THE FOREST, AS INORGANIC MATTER, TENDS TO MITIGATE EXTREMES. TREES AS ORGANISMS: SPECIFIC TEMPERATURE--TOTAL INFLUENCE OF THE FOREST ON TEMPERATURE. INFLUENCE OF FORESTS ON THE HUMIDITY OF THE AIR AND THE EARTH: _a_, AS INORGANIC MATTER; _b_, AS ORGANIC--WOOD MOSSES AND FUNGI-- FLOW OF SAP--ABSORPTION AND EXHALATION OF MOISTURE BY TREES--BALANCE OF CONFLICTING INFLUENCES--INFLUENCE OF THE FOREST ON TEMPERATURE AND PRECIPITATION--INFLUENCE OF THE FOREST ON THE HUMIDITY OF THE SOIL-- ITS INFLUENCE ON THE FLOW OF SPRINGS--GENERAL CONSEQUENCES OF THE DESTRUCTION OF THE WOODS--LITERATURE AND CONDITION OF THE FOREST IN DIFFERENT COUNTRIES--THE INFLUENCE OF THE FOREST ON INUNDATIONS-- DESTRUCTIVE ACTION OF TORRENTS--THE PO AND ITS DEPOSITS--MOUNTAIN SLIDES--PROTECTION AGAINST THE FALL OF ROCKS AND AVALANCHES BY TREES--PRINCIPAL CAUSES OF THE DESTRUCTION OF THE FOREST--AMERICAN FOREST TREES--SPECIAL CAUSES OF THE DESTRUCTION OF EUROPEAN WOODS-- ROYAL FORESTS AND GAME LAWS--SMALL FOREST PLANTS, VITALITY OF SEEDS-- UTILITY OF THE FOREST--THE FORESTS OF EUROPE--FORESTS OF THE UNITED STATES AND CANADA--THE ECONOMY OF THE FOREST--EUROPEAN AND AMERICAN TREES COMPARED--SYLVICULTURE--INSTABILITY OF AMERICAN LIFE. _The Habitable Earth Originally Wooded._ There is good reason to believe that the surface of the habitable earth, in all the climates and regions which have been the abodes of dense and civilized populations, was, with few exceptions, already covered with a forest growth when it first became the home of man. This we infer from the extensive vegetable remains--trunks, branches, roots, fruits, seeds, and leaves of trees--so often found in conjunction with works of primitive art, in the boggy soil of districts where no forests appear to have existed within the eras through which written annals reach; from ancient historical records, which prove that large provinces, where the earth has long been wholly bare of trees, were clothed with vast and almost unbroken woods when first made known to Greek and Roman civilization;[112] and from the state of much of North and of South America when they were discovered and colonized by the European race.[113] These evidences are strengthened by observation of the natural economy of our own time; for, whenever a tract of country, once inhabited and cultivated by man, is abandoned by him and by domestic animals,[114] and surrendered to the undisturbed influences of spontaneous nature, its soil sooner or later clothes itself with herbaceous and arborescent plants, and at no long interval, with a dense forest growth. Indeed, upon surfaces of a certain stability, and not absolutely precipitous inclination, the special conditions required for the spontaneous propagation of trees may all be negatively expressed and reduced to these three: exemption from defect or excess of moisture, from perpetual frost, and from the depredations of man and browsing quadrupeds. Where these requisites are secured, the hardest rock is as certain to be overgrown with wood as the most fertile plain, though, for obvious reasons, the process is slower in the former than in the latter case. Lichens and mosses first prepare the way for a more highly organized vegetation. They retain the moisture of rains and dews, and bring it to act, in combination with the gases evolved by their organic processes, in decomposing the surface of the rocks they cover; they arrest and confine the dust which the wind scatters over them, and their final decay adds new material to the soil already half formed beneath and upon them. A very thin stratum of mould is sufficient for the germination of seeds of the hardy evergreens and birches, the roots of which are often found in immediate contact with the rock, supplying their trees with nourishment from a soil derived from the decomposition of their own foliage, or sending out long rootlets into the surrounding earth in search of juices to feed them. The eruptive matter of volcanoes, forbidding as is its aspect, does not refuse nutriment to the woods. The refractory lava of Etna, it is true, remains long barren, and that of the great eruption of 1669 is still almost wholly devoid of vegetation.[115] But the cactus is making inroads even here, while the volcanic sand and molten rock thrown out by Vesuvius soon becomes productive. George Sandys, who visited this latter mountain in 1611, after it had reposed for several centuries, found the throat of the volcano at the bottom of the crater "almost choked with broken rocks and _trees_ that are falne therein." "Next to this," he continues, "the matter thrown up is ruddy, light, and soft: more removed, blacke and ponderous: the uttermost brow, that declineth like the seates in a theater, flourishing with trees and excellent pasturage. The midst of the hill is shaded with chestnut trees, and others bearing sundry fruits."[116] I am convinced that forests would soon cover many parts of the Arabian and African deserts, if man and domestic animals, especially the goat and the camel, were banished from them. The hard palate and tongue and strong teeth and jaws of this latter quadruped enable him to break off and masticate tough and thorny branches as large as the finger. He is particularly fond of the smaller twigs, leaves, and seedpods of the _sont_ and other acacias, which, like the American Robinia, thrive well on dry and sandy soils, and he spares no tree the branches of which are within his reach, except, if I remember right, the tamarisk that produces manna. Young trees sprout plentifully around the springs and along the winter watercourses of the desert, and these are just the halting stations of the caravans and their routes of travel. In the shade of these trees, annual grasses and perennial shrubs shoot up, but are mown down by the hungry cattle of the Bedouin, as fast as they grow. A few years of undisturbed vegetation would suffice to cover such points with groves, and these would gradually extend themselves over soils where now scarcely any green thing but the bitter colocynth and the poisonous foxglove is ever seen. _The Forest does not Furnish Food for Man._ In a region absolutely covered with trees, human life could not long be sustained, for want of animal and vegetable food. The depths of the forest seldom furnish either bulb or fruit suited to the nourishment of man; and the fowls and beasts on which he feeds are scarcely seen except upon the margin of the wood, for here only grow the shrubs and grasses, and here only are found the seeds and insects, which form the sustenance of the non-carnivorous birds and quadrupeds.[117] _First Removal of the Forest._ As soon as multiplying man had filled the open grounds along the margin of the rivers, the lakes, and the sea, and sufficiently peopled the natural meadows and savannas of the interior, where such existed,[118] he could find room for expansion and further growth, only by the removal of a portion of the forest that hemmed him in. The destruction of the woods, then, was man's first geographical conquest, his first violation of the harmonies of inanimate nature. Primitive man had little occasion to fell trees for fuel, or, for the construction of dwellings, boats, and the implements of his rude agriculture and handicrafts. Windfalls would furnish a thin population with a sufficient supply of such material, and if occasionally a growing tree was cut, the injury to the forest would be too insignificant to be at all appreciable. The accidental escape and spread of fire, or, possibly, the combustion of forests by lightning, must have first suggested the advantages to be derived from the removal of too abundant and extensive woods, and, at the same time, have pointed out a means by which a large tract of surface could readily be cleared of much of this natural incumbrance. As soon as agriculture had commenced at all, it would be observed that the growth of cultivated plants, as well as of many species of wild vegetation, was particularly rapid and luxuriant on soils which had been burned over, and thus a new stimulus would be given to the practice of destroying the woods by fire, as a means of both extending the open grounds, and making the acquisition of a yet more productive soil. After a few harvests had exhausted the first rank fertility of the virgin mould, or when weeds and briers and the sprouting roots of the trees had begun to choke the crops of the half-subdued soil, the ground would be abandoned for new fields won from the forest by the same means, and the deserted plain or hillock would soon clothe itself anew with shrubs and trees, to be again subjected to the same destructive process, and again surrendered to the restorative powers of vegetable nature.[119] This rude economy would be continued for generations, and wasteful as it is, is still largely pursued in Northern Sweden, Swedish Lapland, and sometimes even in France and the United States.[120] _Effects of Fire on Forest Soil._ Aside from the mechanical and chemical effects of the disturbance of the soil by agricultural operations, and of the freer admission of sun, rain, and air to the ground, the fire of itself exerts an important influence on its texture and condition. It consumes a portion of the half-decayed vegetable mould which served to hold its mineral particles together and to retain the water of precipitation, and thus loosens, pulverizes, and dries the earth; it destroys reptiles, insects, and worms, with their eggs, and the seeds of trees and of smaller plants; it supplies, in the ashes which it deposits on the surface, important elements for the growth of a new forest clothing, as well as of the usual objects of agricultural industry; and by the changes thus produced, it fits the ground for the reception of a vegetation different in character from that which had spontaneously covered it. These new conditions help to explain the natural succession of forest crops, so generally observed in all woods cleared by fire and then abandoned. There is no doubt, however, that other influences contribute to the same result, because effects more or less analogous follow when the trees are destroyed by other causes, as by high winds, by the woodman's axe, and even by natural decay.[121] _Effects of Destruction of the Forest._ The physico-geographical effects of the destruction of the forests may be divided into two great classes, each having an important influence on vegetable and on animal life in all their manifestations, as well as on every branch of rural economy and productive industry, and, therefore, on all the material interests of man. The first respects the meteorology of the countries exposed to the action of these influences; the second, their superficial geography, or, in other words, configuration, consistence, and clothing of surface. For reasons assigned in the first chapter, the meteorological or climatic branch of the subject is the most obscure, and the conclusions of physicists respecting it are, in a great degree, inferential only, not founded on experiment or direct observation. They are, as might be expected, somewhat discordant, though certain general results are almost universally accepted, and seem indeed too well supported to admit of serious question. _Electrical Influence of Trees._ The properties of trees, singly and in groups, as exciters or conductors of electricity, and their consequent influence upon the electrical state of the atmosphere, do not appear to have been much investigated; and the conditions of the forest itself are so variable and so complicated, that the solution of any general problem respecting its electrical influence would be a matter of extreme difficulty. It is, indeed, impossible to suppose that a dense cloud, a sea of vapor, can pass over miles of surface bristling with good conductors, without undergoing some change of electrical condition. Hypothetical cases may be put in which the character of the change could be deduced from the known laws of electrical action. But in actual nature, the elements are too numerous for us to seize. The true electrical condition of neither cloud nor forest could be known, and it could seldom be predicted whether the vapors would be dissolved as they floated over the wood, or discharged upon it in a deluge of rain. With regard to possible electrical influences of the forest, wider still in their range of action, the uncertainty is even greater. The data which alone could lead to certain, or even probable, conclusions are wanting, and we should, therefore, only embarrass our argument by any attempt to discuss this meteorological element, important as it may be, in its relations of cause and effect to more familiar and better understood meteoric phenomena. It may, however, be observed that hail storms--which were once generally supposed, and are still held by many, to be produced by a specific electrical action, and which, at least, are always accompanied by electrical disturbances--are believed, in all countries particularly exposed to that scourge, to have become more frequent and destructive in proportion as the forests have been cleared. Caimi observes: "When the chains of the Alps and the Apennines had not yet been stripped of their magnificent crown of woods, the May hail, which now desolates the fertile plains of Lombardy, was much less frequent; but since the general prostration of the forest, these tempests are laying waste even the mountain soils whose older inhabitants scarcely knew this plague.[122] The _paragrandini_,[123] which the learned curate of Rivolta advised to erect, with sheaves of straw set up vertically, over a great extent of cultivated country, are but a Liliputian image of the vast paragrandini, pines, larches, firs, which nature had planted by millions on the crests and ridges of the Alps and the Apennines."[124] "Electrical action being diminished," says Meguscher, "and the rapid congelation of vapors by the abstraction of heat being impeded by the influence of the woods, it is rare that hail or waterspouts are produced, within the precincts of a large forest when it is assailed by the tempest."[125] Arthur Young was told that since the forests which covered the mountains between the Riviera and the county of Montferrat had disappeared, hail had become more destructive in the district of Acqui,[126] and it appears upon good authority, that a similar increase in the frequency and violence of hail storms in the neighborhood of Saluzzo and Mondovì, the lower part of the Valtelline, and the territory of Verona and Vicenza, is probably to be ascribed to a similar cause.[127] _Chemical Influence of the Forest._ We know that the air in a close apartment is appreciably affected through the inspiration and expiration of gases by plants growing in it. The same operations are performed on a gigantic scale by the forest, and it has even been supposed that the absorption of carbon, by the rank vegetation of earlier geological periods, occasioned a permanent change in the constitution of the terrestrial atmosphere.[128] To the effects thus produced, are to be added those of the ultimate gaseous decomposition of the vast vegetable mass annually shed by trees, and of their trunks and branches when they fall a prey to time. But the quantity of gases thus abstracted from and restored to the atmosphere is inconsiderable--infinitesimal, one might almost say--in comparison with the ocean of air from which they are drawn and to which they return; and though the exhalations from bogs, and other low grounds covered with decaying vegetable matter, are highly deleterious to human health, yet, in general, the air of the forest is hardly chemically distinguishable from that of the sand plains, and we can as little trace the influence of the woods in the analysis of the atmosphere, as we can prove that the mineral ingredients of land springs sensibly affect the chemistry of the sea. I may, then, properly dismiss the chemical, as I have done the electrical influences of the forest, and treat them both alike, if not as unimportant agencies, at least as quantities of unknown value in our meteorological equation.[129] Our inquiries upon this branch of the subject will accordingly be limited to the thermometrical and hygrometrical influences of the woods. _Influence of the Forest, considered as Inorganic Matter, on Temperature._ The evaporation of fluids, and the condensation and expansion of vapors and gases, are attended with changes of temperature; and the quantity of moisture which the air is capable of containing, and, of course, the evaporation, rise and fall with the thermometer. The hygroscopical and the thermoscopical conditions of the atmosphere are, therefore, inseparably connected as reciprocally dependent quantities, and neither can be fully discussed without taking notice of the other. But the forest, regarded purely as inorganic matter, and without reference to its living processes of absorption and exhalation of water and gases, has, as an absorbent, a radiator and a conductor of heat, and as a mere covering of the ground, an influence on the temperature of the air and the earth, which may be considered by itself. a. _Absorbing and Emitting Surface._ A given area of ground, as estimated by the every-day rule of measurement in yards or acres, presents always the same apparent quantity of absorbing, radiating, and reflecting surface; but the real extent of that surface is very variable, depending, as it does, upon its configuration, and the bulk and form of the adventitious objects it bears upon it; and, besides, the true superficies remaining the same, its power of absorption, radiation, reflection, and conduction of heat will be much affected by its consistence, its greater or less humidity, and its color, as well as by its inclination of plane and exposure.[130] An acre of chalk, rolled hard and smooth, would have great reflecting power, but its radiation would be much increased by breaking it up into clods, because the actually exposed surface would be greater, though the outline of the field remained the same. The area of a triangle being equal to its base multiplied by half the length of a perpendicular let fall from its apex, it follows that the entire superficies of the triangular faces of a quadrangular pyramid, the perpendicular of whose sides should be twice the length of the base, would be four times the area of the ground it covered, and would add to the field on which it stood so much surface capable of receiving and emitting heat, though, in consequence of obliquity and direction of plane, its actual absorption and emission of heat might not be so great as that of an additional quantity of level ground containing four times the area of its base. The lesser inequalities which always occur in the surface of ordinary earth affect in the same way its quantity of superficies acting upon the temperature of the atmosphere, and acted on by it, though the amount of this action and reaction is not susceptible of measurement. Analogous effects are produced by other objects, of whatever form or character, standing or lying upon the earth, and no solid can be placed upon a flat piece of ground, without itself exposing a greater surface than it covers. This applies, of course, to forest trees and their leaves, and indeed to all vegetables, as well as to other prominent bodies. If we suppose forty trees to be planted on an acre, one being situated in the centre of every square of two rods the side, and to grow until their branches and leaves everywhere meet, it is evident that, when in full foliage, the trunks, branches, and leaves would present an amount of thermoscopic surface much greater than that of an acre of bare earth; and besides this, the fallen leaves lying scattered on the ground, would somewhat augment the sum total.[131] On the other hand, the growing leaves of trees generally form a succession of stages, or, loosely speaking, layers, corresponding to the animal growth of the branches, and more or less overlying each other. This disposition of the foliage interferes with that free communication between sun and sky above, and leaf surface below, on which the amount of radiation and absorption of heat depends. From all these considerations, it appears that though the effective thermoscopic surface of a forest in full leaf does not exceed that of bare ground in the same proportion as does its measured superficies, yet the actual quantity of area capable of receiving and emitting heat must be greater in the former than in the latter case.[132] It must further be remembered that the form and texture of a given surface are important elements in determining its thermoscopic character. Leaves are porous, and admit air and light more or less freely into their substance; they are generally smooth and even glazed on one surface; they are usually covered on one or both sides with spiculæ, and they very commonly present one or more acuminated points in their outline--all circumstances which tend to augment their power of emitting heat by reflection or radiation. Direct experiment on growing trees is very difficult, nor is it in any case practicable to distinguish how far a reduction of temperature produced by vegetation is due to radiation, and how far to exhalation of the fluids of the plant in a gaseous form; for both processes usually go on together. But the frigorific effect of leafy structure is well observed in the deposit of dew and the occurrence of hoarfrost on the foliage of grasses and other small vegetables, and on other objects of similar form and consistence, when the temperature of the air a few yards above has not been brought down to the dew point, still less to 32°, the degree of cold required to congeal dew to frost.[133] b. _Trees as Conductors of Heat._ We are also to take into account the action of the forest as a conductor of heat between the atmosphere and the earth. In the most important countries of America and Europe, and especially in those which have suffered most from the destruction of the woods, the superficial strata of the earth are colder in winter, and warmer in summer than those a few inches lower, and their shifting temperature approximates to the atmospheric mean of the respective seasons. The roots of large trees penetrate beneath the superficial strata, and reach earth of a nearly constant temperature, corresponding to the mean for the entire year. As conductors, they convey the heat of the atmosphere to the earth when the earth is colder than the air, and transmit it in the contrary direction when the temperature of the earth is higher than that of the atmosphere. Of course, then, as conductors, they tend to equalize the temperature of the earth and the air. c. _Trees in Summer and Winter._ In countries where the questions I am considering have the greatest practical importance, a very large proportion, if not a majority, of the trees are of deciduous foliage, and their radiating as well as their shading surface is very much greater in summer than in winter. In the latter season, they little obstruct the reception of heat by the ground or the radiation from it; whereas, in the former, they often interpose a complete canopy between the ground and the sky, and materially interfere with both processes. d. _Dead Products of Trees._ Besides this various action of standing trees considered as inorganic matter, the forest exercises, by the annual moulting of its foliage, still another influence on the temperature of the earth, and, consequently, of the atmosphere which rests upon it. If you examine the constitution of the superficial soil in a primitive or an old and undisturbed artificially planted wood, you find, first, a deposit of undecayed leaves, twigs, and seeds, lying in loose layers on the surface; then, more compact beds of the same materials in incipient, and, as you descend, more and more advanced stages of decomposition; then, a mass of black mould, in which traces of organic structure are hardly discoverable except by microscopic examination; then, a stratum of mineral soil, more or less mixed with vegetable matter carried down into it by water, or resulting from the decay of roots; and, finally, the inorganic earth or rock itself. Without this deposit of the dead products of trees, this latter would be the superficial stratum, and as its powers of absorption, radiation, and conduction of heat would differ essentially from those of the layers with which it has been covered by the droppings of the forest, it would act upon the temperature of the atmosphere, and be acted on by it, in a very different way from the leaves and mould which rest upon it. Leaves, still entire, or partially decayed, are very indifferent conductors of heat, and, therefore, though they diminish the warming influence of the summer sun on the soil below them, they, on the other hand, prevent the escape of heat from that soil in winter, and, consequently, in cold climates, even when the ground is not covered by a protecting mantle of snow, the earth does not freeze to as great a depth in the wood as in the open field. e. _Trees as a Shelter to Ground to the Leeward._ The action of the forest, considered merely as a mechanical shelter to grounds lying to the leeward of it, would seem to be an influence of too restricted a character to deserve much notice; but many facts concur to show that it is an important element in local climate, and that it is often a valuable means of defence against the spread of miasmatic effluvia, though, in this last case, it may exercise a chemical as well as a mechanical agency. In the report of a committee appointed in 1836 to examine an article of the forest code of France, Arago observes: "If a curtain of forest on the coasts of Normandy and of Brittany were destroyed, these two provinces would become accessible to the winds from the west, to the mild breezes of the sea. Hence a decrease of the cold of winter. If a similar forest were to be cleared on the eastern border of France, the glacial east wind would prevail with greater strength, and the winters would become more severe. Thus the removal of a belt of wood would produce opposite effects in the two regions."[134] This opinion receives confirmation from an observation of Dr. Dwight, who remarks, in reference to the woods of New England: "Another effect of removing the forest will be the free passage of the winds, and among them of the southern winds, over the surface. This, I think, has been an increasing fact within my own remembrance. As the cultivation of the country has extended farther to the north, the winds from the south have reached distances more remote from the ocean, and imparted their warmth frequently, and in such degrees as, forty years since, were in the same places very little known. This fact, also, contributes to lengthen the summer, and to shorten the winter-half of the year."[135] It is thought in Italy that the clearing of the Apennines has very materially affected the climate of the valley of the Po. It is asserted in Le Alpi che cingono l'Italia that: "In consequence of the felling of the woods on the Apennines, the sirocco prevails greatly on the right bank of the Po, in the Parmesan territory, and in a part of Lombardy; it injures the harvests and the vineyards, and sometimes ruins the crops of the season. To the same cause many ascribe the meteorological changes in the precincts of Modena and of Reggio. In the communes of these districts, where formerly straw roofs resisted the force of the winds, tiles are now hardly sufficient; in others, where tiles answered for roofs, large slabs of stone are now ineffectual; and in many neighboring communes the grapes and the grain are swept off by the blasts of the south and southwest winds." On the other hand, according to the same authority, the pinery of Porto, near Ravenna--which is 33 kilometres long, and is one of the oldest pine woods in Italy--having been replanted with resinous trees after it was unfortunately cut, has relieved the city from the sirocco to which it had become exposed, and in a great degree restored its ancient climate.[136] The felling of the woods on the Atlantic coast of Jutland has exposed the soil not only to drifting sands, but to sharp sea winds, that have exerted a sensible deteriorating effect on the climate of that peninsula, which has no mountains to serve at once as a barrier to the force of the winds, and as a storehouse of moisture received by precipitation or condensed from atmospheric vapors.[137] It is evident that the effect of the forest, as a mechanical impediment to the passage of the wind, would extend to a very considerable distance above its own height, and hence protect while standing, or lay open when felled, a much larger surface than might at first thought be supposed. The atmosphere, movable as are its particles, and light and elastic as are its masses, is nevertheless held together as a continuous whole by the gravitation of its atoms and their consequent pressure on each other, if not by attraction between them, and, therefore, an obstruction which mechanically impedes the movement of a given stratum of air, will retard the passage of the strata above and below it. To this effect may often be added that of an ascending current from the forest itself, which must always exist when the atmosphere within the wood is warmer than the stratum of air above it, and must be of almost constant occurrence in the case of cold winds, from whatever quarter, because the still air in the forest is slow in taking up the temperature of the moving columns and currents around and above it. Experience, in fact, has shown that mere rows of trees, and even much lower obstructions, are of essential service in defending vegetation against the action of the wind. Hardy proposes planting, in Algeria, belts of trees at the distance of one hundred mètres from each other, as a shelter which experience had proved to be useful in France.[138] "In the valley of the Rhone," says Becquerel, "a simple hedge, two mètres in height, is a sufficient protection for a distance of twenty-two mètres."[139] The mechanical shelter acts, no doubt, chiefly as a defence against the mechanical force of the wind, but its uses are by no means limited to this effect. If the current of air which it resists moves horizontally, it would prevent the access of cold or parching blasts to the ground for a great distance; and did the wind even descend at a large angle with the surface, still a considerable extent of ground would be protected by a forest to the windward of it. If we suppose the trees of a wood to have a mean height of only twenty yards, they would often beneficially affect the temperature or the moisture of a belt of land two or three hundred yards in width, and thus perhaps rescue valuable crops from destruction.[140] The local retardation of spring so much complained of in Italy, France, and Switzerland, and the increased frequency of late frosts at that season, appear to be ascribable to the admission of cold blasts to the surface, by the felling of the forests which formerly both screened it as by a wall, and communicated the warmth of their soil to the air and earth to the leeward. Caimi states that since the cutting down of the woods of the Apennines, the cold winds destroy or stunt the vegetation, and that, in consequence of "the usurpation of winter on the domain of spring," the district of Mugello has lost all its mulberries, except the few which find in the lee of buildings a protection like that once furnished by the forest.[141] "It is proved," says Clavé, "Études," p. 44, "that the department of Ardèche, which now contains not a single considerable wood, has experienced within thirty years a climatic disturbance, of which the late frosts, formerly unknown in the country, are one of the most melancholy effects. Similar results have been observed in the plain of Alsace, in consequence of the denudation of several of the crests of the Vosges." Dussard, as quoted by Ribbe,[142] maintains that even the _mistral_, or northwest wind, whose chilling blasts are so fatal to tender vegetation in the spring, "is the child of man, the result of his devastations." "Under the reign of Augustus," continues he, "the forests which protected the Cévennes were felled, or destroyed by fire, in mass. A vast country, before covered with impenetrable woods--powerful obstacles to the movement and even to the formation of hurricanes--was suddenly denuded, swept bare, stripped, and soon after, a scourge hitherto unknown struck terror over the land from Avignon to the Bouches du Rhone, thence to Marseilles, and then extended its ravages, diminished indeed by a long career which had partially exhausted its force, over the whole maritime frontier. The people thought this wind a curse sent of God. They raised altars to it and offered sacrifices to appease its rage." It seems, however, that this plague was less destructive than at present, until the close of the sixteenth century, when further clearings had removed most of the remaining barriers to its course. Up to that time, the northwest wind appears not to have attained to the maximum of specific effect which now characterizes it as a local phenomenon. Extensive districts, from which the rigor of the seasons has now banished valuable crops, were not then exposed to the loss of their harvests by tempests, cold, or drought. The deterioration was rapid in its progress. Under the Consulate, the clearings had exerted so injurious an effect upon the climate, that the cultivation of the olive had retreated several leagues, and since the winters and springs of 1820 and 1836, this branch of rural industry has been abandoned in a great number of localities where it was advantageously pursued before. The orange now flourishes only at a few sheltered points of the coast, and it is threatened even at Ilyères, where the clearing of the hills near the town has proved very prejudicial to this valuable tree. Marchand informs us that, since the felling of the woods, late spring frosts are more frequent in many localities north of the Alps; that fruit trees thrive well no longer, and that it is difficult to raise young trees.[143] f. _Trees as a Protection against Malaria._ The influence of forests in preventing the diffusion of miasmatic vapors is a matter of less familiar observation, and perhaps does not come strictly within the sphere of the present inquiry, but its importance will justify me in devoting some space to the subject. "It has been observed" (I quote again from Becquerel) "that humid air, charged with miasmata, is deprived of them in passing through the forest. Rigaud de Lille observed localities in Italy where the interposition of a screen of trees preserved everything beyond it, while the unprotected grounds were subject to fevers."[144] Few European countries present better opportunities for observation on this point than Italy, because in that kingdom the localities exposed to miasmatic exhalations are numerous, and belts of trees, if not forests, are of so frequent occurrence that their efficacy in this respect can be easily tested. The belief that rows of trees afford an important protection against malarious influences is very general among Italians best qualified by intelligence and professional experience to judge upon the subject. The commissioners appointed to report on the measures to be adopted for the improvement of the Tuscan Maremme advised the planting of three or four rows of poplars, _Populus alba_, in such directions as to obstruct the currents of air from malarious localities, and thus intercept a great proportion of the pernicious exhalations."[145] Lieutenant Maury even believed that a few rows of sunflowers, planted between the Washington Observatory and the marshy banks of the Potomac, had saved the inmates of that establishment from the intermittent fevers to which they had been formerly liable. Maury's experiments have been repeated in Italy. Large plantations of sunflowers have been made upon the alluvial deposits of the Oglio, above its entrance into the Lake of Iseo near Pisogne, and it is said with favorable results to the health of the neighborhood.[146] In fact, the generally beneficial effects of a forest wall or other vegetable screen, as a protection against noxious exhalations from marshes or other sources of disease situated to the windward of them, are very commonly admitted. It is argued that, in these cases, the foliage of trees and of other vegetables exercises a chemical as well as a mechanical effect upon the atmosphere, and some, who allow that forests may intercept the circulation of the miasmatic effluvia of swampy soils, or even render them harmless by decomposing them, contend, nevertheless, that they are themselves active causes of the production of malaria. The subject has been a good deal discussed in Italy, and there is some reason to think that under special circumstances the influence of the forest in this respect may be prejudicial rather than salutary, though this does not appear to be generally the case.[147] It is, at all events, well known that the great swamps of Virginia and the Carolinas, in climates nearly similar to that of Italy, are healthy even to the white man, so long as the forests in and around them remain, but become very insalubrious when the woods are felled.[148] _The Forest, as Inorganic Matter, tends to mitigate Extremes._ The surface which trees and leaves present augments the general superficies of the earth exposed to the absorption of heat, and increases the radiating and reflecting area in the same proportion. It is impossible to measure the relative value of these two elements--increase of absorbing and increase of emitting surface--as thermometrical influences, because they exert themselves under infinitely varied conditions; and it is equally impossible to make a quantitative estimate of any partial, still more of the total effect of the forest, considered as dead matter, on the temperature of the atmosphere, and of the portion of the earth's surface acted on by it. But it seems probable that its greatest influence in this respect is due to its character of a screen, or mechanical obstacle to the transmission of heat between the earth and the air; and this is equally true of the standing tree and of the dead foliage which it deposits in successive layers at its foot. The complicated action of trees and their products, as dead absorbents, radiators, reflectors, and conductors of heat, and as interceptors of its transmission, is so intimately connected with their effects upon the humidity of the air and the earth, and with all their living processes, that it is difficult to separate the former from the latter class of influences; but upon the whole, the forest must thus far be regarded as tending to mitigate extremes, and, therefore, as an equalizer of temperature. TREES AS ORGANISMS. _Specific Heat._ Trees, considered as organisms, produce in themselves, or in the air, a certain amount of heat, by absorbing and condensing atmospheric vapor, and they exert an opposite influence by absorbing water and exhaling it in the form of vapor; but there is still another mode by which their living processes may warm the air around them, independently of the thermometric effects of condensation and evaporation. The vital heat of a dozen persons raises the temperature of a room. If trees possess a specific temperature of their own, an organic power of generating heat, like that with which the warm-blooded animals are gifted, though by a different process, a certain amount of weight is to be ascribed to this element, in estimating the action of the forest upon atmospheric temperature. "Observation shows," says Meguscher, "that the wood of a living tree maintains a temperature of +12° or 13° Cent. [= 54°, 56° Fahr.] when the temperature of the air stands at 3°, 7°, and 8° [=37°, 46°, 47° F.] above zero, and that the internal warmth of the tree does not rise and fall in proportion to that of the atmosphere. So long as the latter is below 18° [= 67° Fahr.], that of the tree is always the highest; but if the temperature of the air rises to 18°, that of the vegetable growth is the lowest. Since, then, trees maintain at all seasons a constant mean temperature of 12° [= 54° Fahr.], it is easy to see why the air in contact with the forest must be warmer in winter, cooler in summer, than in situations where it is deprived of that influence."[149] Boussingault remarks: "In many flowers there has been observed a very considerable evolution of heat, at the approach of fecundation. In certain _arums_ the temperature rises to 40° or 50° Cent. [= 104° or 122° Fahr.]. It is very probable that this phenomenon is general, and varies only in the intensity with which it is manifested."[150] If we suppose the fecundation of the flowers of forest trees to be attended with a tenth only of this calorific power, they could not fail to exert an important influence on the warmth of the atmospheric strata in contact with them. In a paper on Meteorology by Professor Henry, published in the United States Patent Office Report for 1857, p. 504, that distinguished physicist observes: "As a general deduction from chemical and mechanical principles, we think no change of temperature is ever produced where the actions belonging to one or both of these principles are not present. Hence, in midwinter, when all vegetable functions are dormant, we do not believe that any heat is developed by a tree, or that its interior differs in temperature from its exterior further than it is protected from the external air. The experiments which have been made on this point, we think, have been directed by a false analogy. During the active circulation of the sap and the production of new tissue, variations of temperature belonging exclusively to the plant may be observed; but it is inconsistent with general principles that heat should be generated where no change is taking place." There can be no doubt that moisture is given out by trees and evaporated in extremely cold winter-weather, and unless new fluid were supplied from the roots, the tree would be exhausted of its juices before winter was over. But this is not observed to be the fact, and, though the point is disputed, respectable authorities declare that "wood felled in the depth of winter is the heaviest and fullest of sap."[151] Warm weather in winter, of too short continuance to affect the temperature of the ground sensibly, stimulates a free flow of sap in the maple. Thus, in the last week of December, 1862, and the first week of January, 1863, sugar was made from that tree, in various parts of New England. "A single branch of a tree, admitted into a warm room in winter through an aperture in a window, opened its buds and developed its leaves while the rest of the tree in the external air remained in its winter sleep."[152] The roots of forest trees in temperate climates, remain, for the most part, in a moist soil, of a temperature not much below the annual mean, through the whole winter; and we cannot account for the uninterrupted moisture of the tree, unless we suppose that the roots furnish a constant supply of water. Atkinson describes a ravine in a valley in Siberia, which was filled with ice to the depth of twenty-five feet. Poplars were growing in this ice, which was thawed to the distance of some inches from the stem. But the surface of the soil beneath it must have remained still frozen, for the holes around the trees were full of water resulting from its melting, and this would have escaped below if the ground had been thawed. In this case, although the roots had not thawed the thick covering of earth above them, the trunks must have melted the ice in contact with them. The trees, when observed by Atkinson, were in full leaf, but it does not appear at what period the ice around their stems had melted. From these facts, and others of the like sort, it would seem that "all vegetable functions are" not absolutely "dormant" in winter, and, therefore, that trees may give out _some_ heat at that season. But, however this may be, the "circulation of the sap" commences at a very early period in the spring, and the temperature of the air in contact with trees may then be sufficiently affected by heat evolved in the vital processes of vegetation, to raise the thermometric mean of wooded countries for that season, and, of course, for the year.[153] _Total Influence of the Forest on Temperature._ It has not yet been found practicable to measure, sum up, and equate the total influence of the forest, its processes and its products, dead and living, upon temperature, and investigators differ much in their conclusions on this subject. It seems probable that in every particular case the result is, if not determined, at least so much modified by local conditions which are infinitely varied, that no general formula is applicable to the question. In the report to which I referred on page 149, Gay-Lussac says: "In my opinion we have not yet any positive proof that the forest has, in itself, any real influence on the climate of a great country, or of a particular locality. By closely examining the effects of clearing off the woods, we should perhaps find that, far from being an evil, it is an advantage; but these questions are so complicated when they are examined in a climatological point of view, that the solution of them is very difficult, not to say impossible." Becquerel, on the other hand, considers it certain that in tropical climates, the destruction of the forests is accompanied with an elevation of the mean temperature, and he thinks it highly probable that it has the same effect in the temperate zones. The following is the substance of his remarks on this subject:-- "Forests act as frigorific causes in three ways: "1. They shelter the ground against solar irradiation and maintain a greater humidity. "2. They produce a cutaneous transpiration by the leaves. "3. They multiply, by the expansion of their branches, the surfaces which are cooled by radiation. "These three causes acting with greater or less force, we must, in the study of the climatology of a country, take into account the proportion between the area of the forests and the surface which is bared of trees and covered with herbs and grasses. "We should be inclined to believe _à priori_, according to the foregoing considerations, that the clearing of the woods, by raising the temperature and increasing the dryness of the air, ought to react on climate. There is no doubt that, if the vast desert of the Sahara were to become wooded in the course of ages, the sands would cease to be heated as much as at the present epoch, when the mean temperature is twenty-nine degrees [centigrade, = 85° Fahr.]. In that case, the ascending currents of warm air would cease, or be less warm, and would not contribute, by descending in our latitudes, to soften the climate of Western Europe. Thus the clearing of a great country may react on the climates of regions more or less remote from it. "The observations by Boussingault leave no doubt on this point. This writer determined the mean temperature of wooded and of cleared points, under the same latitude, and at the same elevation above the sea, in localities comprised between the eleventh degree of north and the fifth degree of south latitude, that is to say, in the portion of the tropics nearest to the equator, and where radiation tends powerfully during the night to lower the temperature under a sky without clouds."[154] The result of these observations, which has been pretty generally adopted by physicists, is that the mean temperature of cleared land in the tropics appears to be about one degree centigrade, or a little less than two degrees of Fahrenheit, above that of the forest. On page 147 of the volume just cited, Becquerel argues that, inasmuch as the same and sometimes a greater difference is found in favor of the open ground, at points within the tropics so elevated as to have a temperate or even a polar climate, we must conclude that the forests in Northern America exert a refrigerating influence equally powerful. But the conditions of the soil are so different in the two regions compared, that I think we cannot, with entire confidence, reason from the one to the other, and it is much to be desired that observations be made on the summer and winter temperature of both the air and the ground in the depths of the North American forests, before it is too late.[155] INFLUENCE OF FORESTS ON THE HUMIDITY OF THE AIR AND THE EARTH. a. _As Inorganic Matter._ The most important influence of the forest on climate is, no doubt, that which it exercises on the humidity of the air and the earth, and this climatic action it exerts partly as dead, partly as living matter. By its interposition as a curtain between the sky and the ground, it intercepts a large proportion of the dew and the lighter showers, which would otherwise moisten the surface of the soil, and restores it to the atmosphere by evaporation; while in heavier rains, the large drops which fall upon the leaves and branches are broken into smaller ones, and consequently strike the ground with less mechanical force, or are perhaps even dispersed into vapor without reaching it.[156] As a screen, it prevents the access of the sun's rays to the earth, and, of course, an elevation of temperature which would occasion a great increase of evaporation. As a mechanical obstruction, it impedes the passage of air currents over the ground, which, as is well known, is one of the most efficient agents in promoting evaporation and the refrigeration resulting from it.[157] In the forest, the air is almost quiescent, and moves only as local changes of temperature affect the specific gravity of its particles. Hence there is often a dead calm in the woods when a furious blast is raging in the open country at a few yards' distance. The denser the forest--as for example, where it consists of spike-leaved trees, or is thickly intermixed with them--the more obvious is its effect, and no one can have passed from the field to the wood in cold, windy weather, without having remarked it.[158] The vegetable mould, resulting from the decomposition of leaves and of wood, carpets the ground with a spongy covering which obstructs the evaporation from the mineral earth below, drinks up the rains and melting snows that would otherwise flow rapidly over the surface and perhaps be conveyed to the distant sea, and then slowly gives out, by evaporation, infiltration, and percolation, the moisture thus imbibed. The roots, too, penetrate far below the superficial soil, conduct the water along their surface to the lower depths to which they reach, and thus serve to drain the superior strata and remove the moisture out of the reach of evaporation. b. _The Forest as Organic._ These are the principal modes in which the humidity of the atmosphere is affected by the forest regarded as lifeless matter. Let us inquire how its organic processes act upon this meteorological element. The commonest observation shows that the wood and bark of living trees are always more or less pervaded with watery and other fluids, one of which, the sap, is very abundant in trees of deciduous foliage when the buds begin to swell and the leaves to develop themselves in the spring. The outer bark of most trees is of a corky character, not admitting the absorption of much moisture from the atmosphere through its pores, and we can hardly suppose that the buds are able to extract from the air a much larger supply. The obvious conclusion as to the source from which the extraordinary quantity of sap at this season is derived, is that to which scientific investigation leads us, namely, that it is absorbed from the earth by the roots, and thence distributed to all parts of the plant. Popular opinion, indeed, supposes that all the vegetable fluids, during the entire period of growth, are thus drawn from the bosom of the earth, and that the wood and other products of the tree are wholly formed from matter held in solution in the water abstracted by the roots from the ground. This is an error, for, not only is the solid matter of the tree, in a certain proportion not important to our present inquiry, received from the atmosphere in a gaseous form, through the pores of the leaves and of the young shoots, but water in the state of vapor is absorbed and contributed to the circulation, by the same organs.[159] The amount of water taken up by the roots, however, is vastly greater than that imbibed through the leaves, especially at the season when the juices are most abundant, and when, as we have seen, the leaves are yet in embryo. The quantity of water thus received from the air and the earth, in a single year, by a wood of even a hundred acres, is very great, though experiments are wanting to furnish the data for even an approximate estimate of its measure; for only the vaguest conclusions can be drawn from the observations which have been made on the imbibition and exhalation of water by trees and other plants reared in artificial conditions diverse from those of the natural forest.[160] _Wood Mosses and Fungi._ Besides the water drawn by the roots from the earth and the vapor absorbed by the leaves from the air, the wood mosses and fungi, which abound in all dense forests, take up a great quantity of moisture from the atmosphere when it is charged with humidity, and exhale it again when the air is dry. These humble organizations, which play a more important part in regulating the humidity of the air than writers on the forest have usually assigned to them, perish with the trees they grow on; but, in many situations, nature provides a compensation for the tree mosses in ground species, which, on cold soils, especially those with a northern exposure, spring up abundantly both before the woods are felled, and when the land is cleared and employed for pasturage, or deserted. These mosses discharge a portion of the functions appropriated to the wood, and while they render the soil of improved lands much less fit for agricultural use, they, at the same time, prepare it for the growth of a new harvest of trees, when the infertility they produce shall have driven man to abandon it and suffer it to relapse into the hands of nature.[161] _Flow of Sap._ The amount of sap which can be withdrawn from living trees furnishes, not indeed a measure of the quantity of water sucked up by their roots from the ground--for we cannot extract from a tree its whole moisture--but numerical data which may aid the imagination to form a general notion of the powerful action of the forest as an absorbent of humidity from the earth. The only forest tree known to Europe and North America, the sap of which is largely enough applied to economical uses to have made the amount of its flow a matter of practical importance and popular observation, is the sugar maple, _Acer saccharinum_, of the Anglo-American Provinces and States. In the course of a single "sugar season," which lasts ordinarily from twenty-five to thirty days, a sugar maple two feet in diameter will yield not less than twenty gallons of sap, and sometimes much more.[162] This, however, is but a trifling proportion of the water abstracted from the earth by the roots during this season, when the yet undeveloped leaves can hardly absorb an appreciable quantity of vapor from the atmosphere;[163] for all this fluid runs from two or three incisions or auger holes, so narrow as to intercept the current of comparatively few sap vessels, and besides, experience shows that large as is the quantity withdrawn from the circulation, it is relatively too small to affect very sensibly the growth of the tree.[164] The number of large maple trees on an acre is frequently not less than fifty,[165] and of course the quantity of moisture abstracted from the soil by this tree alone is measured by thousands of gallons to the acre. The sugar orchards, as they are called, contain also many young maples too small for tapping, and numerous other trees--two of which, at least, the black birch, _Betula lenta_, and yellow birch, _Betula excelsa_, both very common in the same climate, are far more abundant in sap than the maple[166]--are scattered among the sugar trees; for the North American native forests are remarkable for the mixture of their crops. The sap of the maple, and of other trees with deciduous leaves which grow in the same climate, flows most freely in the early spring, and especially in clear weather, when the nights are frosty and the days warm; for it is then that the melting snows supply the earth with moisture in the justest proportion, and that the absorbent power of the roots is stimulated to its highest activity.[167] When the buds are ready to burst, and the green leaves begin to show themselves beneath their scaly covering, the ground has become drier, the thirst of the roots is quenched, and the flow of sap from them to the stem is greatly diminished.[168] _Absorption and Exhalation of Moisture._ The leaves now commence the process of absorption, and imbibe both uncombined gases and an unascertained but perhaps considerable quantity of watery vapor from the humid atmosphere of spring which bathes them. The organic action of the tree, as thus far described, tends to the desiccation of air and earth; but when we consider what volumes of water are daily absorbed by a large tree, and how small a proportion of the weight of this fluid consists of matter which enters into new combinations, and becomes a part of the solid framework of the vegetable, or a component of its deciduous products, it is evident that the superfluous moisture must somehow be carried off almost as rapidly as it flows into the tree.[169] At the very commencement of vegetation in spring, some of this fluid certainly escapes through the buds, the nascent foliage, and the pores of the barb, and vegetable physiology tells us that there is a current of sap toward the roots as well as from them.[170] I do not know that the exudation of water into the earth, through the bark or at the extremities of these latter organs, has been directly proved, but the other known modes of carrying off the surplus do not seem adequate to dispose of it at the almost leafless period when it is most abundantly received, and it is therefore difficult to believe that the roots do not, to some extent, drain as well as flood the watercourses of their stem. Later in the season the roots absorb less, and the now developed leaves exhale a vastly increased quantity of moisture into the air. In any event, all the water derived by the growing tree from the atmosphere and the ground is returned again by transpiration or exudation, after having surrendered to the plant the small proportion of matter required for vegetable growth which it held in solution or suspension.[171] The hygrometrical equilibrium is then restored, so far as this: the tree yields up again the moisture it had drawn from the earth and the air, though it does not return it each to each; for the vapor carried off by transpiration greatly exceeds the quantity of water absorbed by the foliage from the atmosphere, and the amount, if any, carried back to the ground by the roots. The evaporation of the juices of the plant, by whatever process effected, takes up atmospheric heat and produces refrigeration. This effect is not less real, though much less sensible, in the forest than in meadow or pasture land, and it cannot be doubted that the local temperature is considerably affected by it. But the evaporation that cools the air diffuses through it, at the same time, a medium which powerfully resists the escape of heat from the earth by radiation. Visible vapors or clouds, it is well known, prevent frosts by obstructing radiation, or rather by reflecting back again the heat radiated by the earth, just as any mechanical screen would do. On the other hand, clouds intercept the rays of the sun also, and hinder its heat from reaching the earth. The invisible vapors given out by leaves impede the passage of heat reflected and radiated by the earth and by all terrestrial objects, but oppose much less resistance to the transmission of direct solar heat, and indeed the beams of the sun seem more scorching when received through clear air charged with uncondensed moisture than after passing through a dry atmosphere. Hence the reduction of temperature by the evaporation of moisture from vegetation, though sensible, is less than it would be if water in the gaseous state were as impervious to heat given out by the sun as to that emitted by terrestrial objects. The hygroscopicity of vegetable mould is much greater than that of any mineral earth, and therefore the soil of the forest absorbs more atmospheric moisture than the open ground. The condensation of the vapor by absorption disengages heat, and consequently raises the temperature of the soil which absorbs it. Von Babo found the temperature of sandy earth thus elevated from 20° to 27° centigrade, making a difference of nearly thirteen degrees of Fahrenheit, and that of soil rich in humus from 20° to 31° centigrade, a difference of almost twenty degrees of Fahrenheit.[172] _Balance of Conflicting Influences._ We have shown that the forest, considered as dead matter, tends to diminish the moisture of the air, by preventing the sun's rays from reaching the ground and evaporating the water that falls upon the surface, and also by spreading over the earth a spongy mantle which sucks up and retains the humidity it receives from the atmosphere, while, at the same time, this covering acts in the contrary direction by accumulating, in a reservoir not wholly inaccessible to vaporizing influences, the water of precipitation which might otherwise suddenly sink deep into the bowels of the earth, or flow by superficial channels to other climatic regions. We now see that, as a living organism, it tends, on the one hand, to diminish the humidity of the air by absorbing moisture from it, and, on the other, to increase that humidity by pouring out into the atmosphere, in a vaporous form, the water it draws up through its roots. This last operation, at the same time, lowers the temperature of the air in contact with or proximity to the wood, by the same law as in other cases of the conversion of water into vapor. As I have repeatedly said, we cannot measure the value of any one of these elements of climatic disturbance, raising or lowering of temperature, increase or diminution of humidity, nor can we say that in any one season, any one year, or any one fixed cycle, however long or short, they balance and compensate each other. They are sometimes, but certainly not always, contemporaneous in their action, whether their tendency is in the same or in opposite directions, and, therefore, their influence is sometimes cumulative, sometimes conflicting; but, upon the whole, their general effect seems to be to mitigate extremes of atmospheric heat and cold, moisture and drought. They serve as equalizers of temperature and humidity, and it is highly probable that, in analogy with most other works and workings of nature, they, at certain or uncertain periods, restore the equilibrium which, whether as lifeless masses or as living organisms, they may have temporarily disturbed. When, therefore, man destroyed these natural harmonizers of climatic discords, he sacrificed an important conservative power, though it is far from certain that he has thereby affected the mean, however much he may have exaggerated the extremes of atmospheric temperature and humidity, or, in other words, may have increased the range and lengthened the scale of thermometric and hygrometric variation. _Influence of the Forest on Temperature and Precipitation._ Aside from the question of compensation, it does not seem probable that the forests sensibly affect the total quantity of precipitation, or the general mean of atmospheric temperature of the globe, or even that they had this influence when their extent was vastly greater than at present. The waters cover about three fourths of the face of the earth,[173] and if we deduct the frozen zones, the peaks and crests of lofty mountains and their craggy slopes, the Sahara and other great African and Asiatic deserts, and all such other portions of the solid surface as are permanently unfit for the growth of wood, we shall find that probably not one tenth of the total superficies of our planet was ever, at any one time in the present geological epoch, covered with forests. Besides this, the distribution of forest land, of desert, and of water, is such as to reduce the possible influence of the former to a low expression; for the forests are, in large proportion, situated in cold or temperate climates, where the action of the sun is comparatively feeble both in elevating temperature and in promoting evaporation; while, in the torrid zone, the desert and the sea--the latter of which always presents an evaporable surface--enormously preponderate. It is, upon the whole, not probable that so small an extent of forest, so situated, could produce an appreciable influence on the _general_ climate of the globe, though it might appreciably affect the local action of all climatic elements. The total annual amount of solar heat absorbed and radiated by the earth, and the sum of terrestrial evaporation and atmospheric precipitation must be supposed constant; but the distribution of heat and of humidity is exposed to disturbance in both time and place, by a multitude of local causes, among which the presence or absence of the forest is doubtless one. So far as we are able to sum up the general results, it would appear that, in countries in the temperate zone still chiefly covered with wood, the summers would be cooler, moister, shorter, the winters milder, drier, longer, than in the same regions after the removal of the forest. The slender historical evidence we possess seems to point to the same conclusion, though there is some conflict of testimony and of opinion on this point, and some apparently well-established exceptions to particular branches of what appears to be the general law. One of these occurs both in climates where the cold of winter is severe enough to freeze the ground to a considerable depth, as in Sweden and the Northern States of the American Union, and in milder zones, where the face of the earth is exposed to cold mountain winds, as in some parts of Italy and of France; for there, as we have seen, the winter is believed to extend itself into the months which belong to the spring, later than at periods when the forest covered the greater part of the ground.[174] More causes than one doubtless contribute to this result; but in the case of Sweden and the United States, the most obvious explanation of the fact is to be found in the loss of the shelter afforded to the ground by the thick coating of leaves which the forest sheds upon it, and the snow which the woods protect from blowing away, or from melting in the brief thaws of winter. I have already remarked that bare ground freezes much deeper than that which is covered by beds of leaves, and when the earth is thickly coated with snow, the strata frozen before it fell begin to thaw. It is not uncommon to find the ground in the woods, where the snow lies two or three feet deep, entirely free from frost, when the atmospheric temperature has been for several weeks below the freezing point, and for some days even below the zero of Fahrenheit. When the ground is cleared and brought under cultivation, the leaves are ploughed into the soil and decomposed, and the snow, especially upon knolls and eminences, is blown off, or perhaps half thawed, several times during the winter. The water from the melting snow runs into the depressions, and when, after a day or two of warm sunshine or tepid rain, the cold returns, it is consolidated to ice, and the bared ridges and swells of earth are deeply frozen.[175] It requires many days of mild weather to raise the temperature of soil in this condition, and of the air in contact with it, to that of the earth in the forests of the same climatic region. Flora is already plaiting her sylvan wreath before the corn flowers which are to deck the garland of Ceres have waked from their winter's sleep; and it is not a popular error to believe that, where man has substituted his artificial crops for the spontaneous harvest of nature, spring delays her coming. In many cases, the apparent change in the period of the seasons is a purely local phenomenon, which is probably compensated by a higher temperature in other months, without any real disturbance of the average thermometrical equilibrium. We may easily suppose that there are analogous partial deviations from the general law of precipitation; and, without insisting that the removal of the forest has diminished the sum total of snow and rain, we may well admit that it has lessened the quantity which annually falls within particular limits. Various theoretical considerations make this probable, the most obvious argument, perhaps, being that drawn from the generally admitted fact, that the summer and even the mean temperature of the forest is below that of the open country in the same latitude. If the air in a wood is cooler than that around it, it must reduce the temperature of the atmospheric stratum immediately above it, and, of course, whenever a saturated current sweeps over it, it must produce precipitation which would fall upon or near it. But the subject is so exceedingly complex and difficult, that it is safer to regard it as a historical problem, or at least as what lawyers call a mixed question of law and fact, than to attempt to decide it upon _à priori_ grounds. Unfortunately the evidence is conflicting in tendency, and sometimes equivocal in interpretation, but I believe that a majority of the foresters and physicists who have studied the question are of opinion that in many, if not in all cases, the destruction of the woods has been followed by a diminution in the annual quantity of rain and dew. Indeed, it has long been a popularly settled belief that vegetation and the condensation and fall of atmospheric moisture are reciprocally necessary to each other, and even the poets sing of Afric's barren sand, Where nought can grow, because it raineth not, And where no rain can fall to bless the land, Because nought grows there.[176] Before stating the evidence on the general question and citing the judgments of the learned upon it, however, it is well to remark that the comparative variety or frequency of inundations in earlier and later centuries is not necessarily, in most cases not probably, entitled to any weight whatever, as a proof that more or less rain fell formerly than now; because the accumulation of water in the channel of a river depends far less upon the quantity of precipitation in its valley, than upon the rapidity with which it is conducted, on or under the surface of the ground, to the central artery that drains the basin. But this point will be more fully discussed in a subsequent chapter. There is another important observation which may properly be introduced here. It is not universally, or even generally true, that the atmosphere returns its humidity to the local source from which it receives it. The air is constantly in motion, ----howling tempests scour amain From sea to land, from land to sea;[177] and, therefore, it is always probable that the evaporation drawn up by the atmosphere from a given river, or sea, or forest, or meadow, will be discharged by precipitation, not at or near the point where it rose, but at a distance of miles, leagues, or even degrees. The currents of the upper air are invisible, and they leave behind them no landmark to record their track. We know not whence they come, or whither they go. We have a certain rapidly increasing acquaintance with the laws of general atmospheric motion, but of the origin and limits, the beginning and end of that motion, as it manifests itself at any particular time and place, we know nothing. We cannot say where or when the vapor, exhaled to-day from the lake on which we float, will be condensed and fall; whether it will waste itself on a barren desert, refresh upland pastures, descend in snow on Alpine heights, or contribute to swell a distant torrent which shall lay waste square miles of fertile corn land; nor do we know whether the rain which feeds our brooklets is due to the transpiration from a neighboring forest, or to the evaporation from a far-off sea. If, therefore, it were proved that the annual quantity of rain and dew is now as great on the plains of Castile, for example, as it was when they were covered with the native forest, it would by no means follow that those woods did not augment the amount of precipitation elsewhere. But I return to the question. Beginning with the latest authorities, I cite a passage from Clavé.[178] After arguing that we cannot reason from the climatic effects of the forest in tropical and sub-tropical countries as to its influence in temperate latitudes, the author proceeds: "The action of the forests on rain, a consequence of that which they exercise on temperature, is difficult to estimate in our climate, but is very pronounced in hot countries, and is established by numerous examples. M. Boussingault states that in the region comprised between the Bay of Cupica and the Gulf of Guayaquil, which is covered with immense forests, the rains are almost continual, and that the mean temperature of this humid country rises hardly to twenty-six degrees (= 80° Fahr.). M. Blanqui, in his 'Travels in Bulgaria,' informs us that at Malta rain has become so rare, since the woods were cleared to make room for the growth of cotton, that at the time of his visit in October, 1841, not a drop of rain had fallen for three years.[179] The terrible droughts which desolate the Cape Verd Islands must also be attributed to the destruction of the forests. In the Island of St. Helena, where the wooded surface has considerably extended within a few years, it has been observed that the rain has increased in the same proportion. It is now in quantity double what it was during the residence of Napoleon. In Egypt, recent plantations have caused rains, which hitherto were almost unknown." Schacht[180] observes: "In wooded countries, the atmosphere is generally humid, and rain and dew fertilize the soil. As the lightning rod abstracts the electric fluid from the stormy sky, so the forest attracts to itself the rain from the clouds, which, in falling, refreshes not it alone, but extends its benefits to the neighboring fields. * * The forest, presenting a considerable surface for evaporation, gives to its own soil and to all the adjacent ground an abundant and enlivening dew. There falls, it is true, less dew on a tall and thick wood than on the surrounding meadows, which, being more highly heated during the day by the influence of insolation, cool with greater rapidity by radiation. But it must be remarked, that this increased deposition of dew on the neighboring fields is partly due to the forests themselves; for the dense, saturated strata of air which hover over the woods descend in cool, calm evenings, like clouds, to the valley, and in the morning, beads of dew sparkle on the leaves of the grass and the flowers of the field. Forests, in a word, exert, in the interior of continents, an influence like that of the sea on the climate of islands and of coasts: both water the soil and thereby insure its fertility." In a note upon this passage, quoting as authority the _Historia de la Conquista de las siete islas de Gran Canaria, de Juan de Abreu Galindo_, 1632, p. 47, he adds: "Old historians relate that a celebrated laurel in Ferro formerly furnished drinkable water to the inhabitants of the island. The water flowed from its foliage, uninterruptedly, drop by drop, and was collected in cisterns. Every morning the sea breeze drove a cloud toward the wonderful tree, which attracted it to its huge top," where it was condensed to a liquid form. In a number of the _Missionary Herald_, published at Boston, the date of which I have mislaid, the Rev. Mr. Van Lennep, well known as a competent observer, gives the following remarkable account of a similar fact witnessed by him in an excursion to the east of Tocat in Asia Minor: "In this region, some 3,000 feet above the sea, the trees are mostly oak, and attain a large size. I noticed an illustration of the influence of trees in general in collecting moisture. Despite the fog, of a week's duration, the ground was everywhere perfectly dry. The dry oak leaves, however, had gathered the water, and the branches and trunks of the trees were more or less wet. In many cases the water had run down the trunk and moistened the soil around the roots of the tree. In two places, several trees had each furnished a small stream of water, and these, uniting, had run upon the road, so that travellers had to pass through the mud; although, as I said, everywhere else the ground was perfectly dry. Moreover, the collected moisture was not sufficient to drop directly from the leaves, but in every case it ran down the branches and trunk to the ground. Farther on we found a grove, and at the foot of each tree, on the north side, was a lump of ice, the water having frozen as it reached the ground. This is a most striking illustration of the acknowledged influence of trees in collecting moisture; and one cannot for a moment doubt, that the parched regions which commence at Sivas, and extend in one direction to the Persian Gulf, and in another to the Red Sea, were once a fertile garden, teeming with a prosperous population, before the forests which covered the hillsides were cut down--before the cedar and the fir tree were rooted up from the sides of Lebanon. "As we now descended the northern side of the watershed, we passed through the grove of walnut, oak, and black mulberry trees, which shade the village of Oktab, whose houses, cattle, and ruddy children were indicative of prosperity." Coultas thus argues: "The ocean, winds, and woods may be regarded as the several parts of a grand distillatory apparatus. The sea is the boiler in which vapor is raised by the solar heat, the winds are the guiding tubes which carry the vapor with them to the forests where a lower temperature prevails. This naturally condenses the vapor, and showers of rain are thus distilled from the cloud masses which float in the atmosphere, by the woods beneath them."[181] Sir John F. W. Herschel enumerates among "the influences unfavorable to rain," "absence of vegetation in warm climates, and especially of trees. This is, no doubt," continues he, "one of the reasons of the extreme aridity of Spain. The hatred of a Spaniard toward a tree is proverbial. Many districts in France have been materially injured by denudation (Earl of Lovelace on Climate, etc.), and, on the other hand, rain has become more frequent in Egypt since the more vigorous cultivation of the palm tree." Hohenstein remarks: "With respect to the temperature in the forest, I have already observed that, at certain times of the day and of the year, it is less than in the open field. Hence the woods may, in the daytime, in summer and toward the end of winter, tend to increase the fall of rain; but it is otherwise in summer nights and at the beginning of winter, when there is a higher temperature in the forest, which is not favorable to that effect. * * * The wood is, further, like the mountain, a mechanical obstruction to the motion of rain clouds, and, as it checks them in their course, it gives them occasion to deposit their water. These considerations render it probable that the forest increases the quantity of rain; but they do not establish the certainty of this conclusion, because we have no positive numerical data to produce on the depression of temperature, and the humidity of the air in the woods."[182] Barth presents the following view of the subject: "The ground in the forest, as well as the atmospheric stratum over it, continues humid after the woodless districts have lost their moisture; and the air, charged with the humidity drawn from them, is usually carried away by the winds before it has deposited itself in a condensed form on the earth. Trees constantly transpire through their leaves a great quantity of moisture, which they partly absorb again by the same organs, while the greatest part of their supply is pumped up through their widely ramifying roots from considerable depths in the ground. Thus a constant evaporation is produced, which keeps the forest atmosphere moist even in long droughts, when all other sources of humidity in the forest itself are dried up. * * * Little is required to compel the stratum of air resting upon a wood to give up its moisture, which thus, as rain, fog, or dew, is returned to the forest. * * * The warm, moist currents of air which come from other regions are cooled as they approach the wood by its less heated atmosphere, and obliged to let fall the humidity with which they are charged. The woods contribute to the same effect by mechanically impeding the motion of fog and rain cloud, whose particles are thus accumulated and condensed to rain. The forest thus has a greater power than the open ground to retain within its own limits already existing humidity, and to preserve it, and it attracts and collects that which the wind brings it from elsewhere, and forces it to deposit itself as rain or other precipitation. * * * In consequence of these relations of the forest to humidity, it follows that wooded districts have both more frequent and more abundant rain, and in general are more humid, than woodless regions; for what is true of the woods themselves, in this respect, is true also of their treeless neighborhood, which, in consequence of the ready mobility of the air and its constant changes, receives a share of the characteristics of the forest atmosphere, coolness and moisture. * * * When the districts stripped of trees have long been deprived of rain and dew, * * * and the grass and the fruits of the field are ready to wither, the grounds which are surrounded by woods are green and flourishing. By night they are refreshed with dew, which is never wanting in the moist air of the forest, and in due season they are watered by a beneficent shower, or a mist which rolls slowly over them."[183] Asbjörnsen, after adducing the familiar theoretical arguments on this point, adds: "The rainless territories in Peru and North Africa establish this conclusion, and numerous other examples show that woods exert an influence in producing rain, and that rain fails where they are wanting; for many countries have, by the destruction of the forests, been deprived of rain, moisture, springs, and watercourses, which are necessary for vegetable growth. * * * The narratives of travellers show the deplorable consequences of felling the woods in the Island of Trinidad, Martinique, San Domingo, and indeed, in almost the entire West Indian group. * * * In Palestine and many other parts of Asia and Northern Africa, which in ancient times were the granaries of Europe, fertile and populous, similar consequences have been experienced. These lands are now deserts, and it is the destruction of the forests alone which has produced this desolation. * * * In Southern France, many districts have, from the same cause, become barren wastes of stone, and the cultivation of the vine and the olive has suffered severely since the baring of the neighboring mountains. Since the extensive clearings between the Spree and the Oder, the inhabitants complain that the clover crop is much less productive than before. On the other hand, examples of the beneficial influence of planting and restoring the woods are not wanting. In Scotland, where many miles square have been planted with trees, this effect has been manifest, and similar observations have been made in several places in Southern France. In Lower Egypt, both at Cairo and near Alexandria, rain rarely fell in considerable quantity--for example, during the French occupation of Egypt, about 1798, it did not rain for sixteen months--but since Mehemet Aali and Ibrahim Pacha executed their vast plantations (the former alone having planted more than twenty millions of olive and fig trees, cottonwood, oranges, acacias, planes, &c.), there now falls a good deal of rain, especially along the coast, in the months of November, December, and January; and even at Cairo it rains both oftener and more abundantly, so that real showers are no rarity."[184] Babinet, in one of his lectures,[185] cites the supposed fact of the increase of rain in Egypt in consequence of the planting of trees, and thus remarks upon it: "A few years ago it never rained in Lower Egypt. The constant north winds, which almost exclusively prevail there, passed without obstruction over a surface bare of vegetation. Grain was kept on the roofs in Alexandria, without being covered or otherwise protected from injury by the atmosphere; but since the making of plantations, an obstacle has been created which retards the current of air from the north. The air thus checked, accumulates, dilates, cools, and yields rain.[186] The forests of the Vosges and Ardennes produce the same effects in the north east of France, and send us a great river, the Meuse, which is as remarkable for its volume as for the small extent of its basin. With respect to the retardation of the atmospheric currents, and the effects of that retardation, one of my illustrious colleagues, M. Mignet, who is not less a profound thinker than an eloquent writer, suggested to me that, to produce rain, a forest was as good as a mountain, and this is literally true." Monestier-Savignat arrives at this conclusion: "Forests on the one hand diminish evaporation; on the other, they act on the atmosphere as refrigerating causes. The second scale of the balance predominates over the other, for it is established that in wooded countries it rains oftener, and that, the quantity of rain being equal, they are more humid."[187] Boussingault--whose observations on the drying up of lakes and springs, from the destruction of the woods, in tropical America, have often been cited as a conclusive proof that the quantity of rain was thereby diminished--after examining the question with much care, remarks: "In my judgment it is settled that very large clearings must diminish the annual fall of rain in a country;" and on a subsequent page, he concludes that, "arguing from meteorological facts collected in the equinoctial regions, there is reason to presume that clearings diminish the annual fall of rain."[188] The same eminent author proposes series of observations on the level of natural lakes, especially on those without outlet, as a means of determining the increase or diminution of precipitation in their basins, and, of course, of measuring the effect of clearing when such operations take place within those basins. But it must be observed that lakes without a visible outlet are of very rare occurrence, and besides, where no superficial conduit for the discharge of lacustrine waters exists, we can seldom or never be sure that nature has not provided subterranean channels for their escape. Indeed, when we consider that most earths, and even some rocks under great hydrostatic pressure, are freely permeable by water, and that fissures are frequent in almost all rocky strata, it is evident that we cannot know in what proportion the depression of the level of a lake is to be ascribed to infiltration, to percolation, or to evaporation.[189] Further, we are, in general, as little able to affirm that a given lake derives all its water from the fall of rain within its geographical basin, or that it receives all the water that falls in that basin except what evaporates from the ground, as we are to show that all its superfluous water is carried off by visible channels and by evaporation. Suppose the strata of the mountains on two sides of a lake, east and west, to be tilted in the same direction, and that those of the hill on the east side incline toward the lake, those of that on the west side from it. In this case a large proportion of the rain which falls on the eastern slope of the eastern hill may find its way between the strata to the lake, and an equally large proportion of the precipitation upon the eastern slope of the western ridge may escape out of the basin by similar channels. In such case the clearing of the _outer_ slopes of either or both mountains, while the forests of the _inner_ declivities remained intact, might affect the quantity of water received by the lake, and it would always be impossible to know to what territorial extent influences thus affecting the level of a lake might reach. Boussingault admits that extensive clearing _below_ an alpine lake, even at a considerable distance, might affect the level of its waters. How it would produce this influence he does not inform us, but, as he says nothing of the natural subterranean drainage of surface waters, it is to be presumed that he refers to the supposed diminution of the quantity of rain from the removal of the forest, which might manifest itself at a point more elevated than the cause which occasioned it. The elevation or depression of the level of natural lakes, then, cannot be relied upon as a proof, still less as a measure of an increase or diminution in the fall of rain within their geographical basins, resulting from the felling of the woods which covered them; though such phenomena afford very strong presumptive evidence that the supply of water is somehow augmented or lessened. The supply is, in most cases, derived much less from the precipitation which falls directly upon the surface of lakes, than from waters which flow above or under the ground around them, and which, in the latter case, often come from districts not comprised within what superficial geography would regard as belonging to the lake basins. It is, upon the whole, evident that the question can hardly be determined except by the comparison of pluviometrical observations made at a given station before and after the destruction of the woods. Such observations, unhappily, are scarcely to be found, and the opportunity for making them is rapidly passing away, except so far as a converse series might be collected in countries--France, for example--where forest plantation is now going on upon a large scale. The Smithsonian Institution at Washington is well situated for directing the attention of observers in the newer territory of the United States to this subject, and it is to be hoped that it will not fail to avail itself of its facilities for this purpose. Numerous other authorities might be cited in support of the proposition that forests tend, at least in certain latitudes and at certain seasons, to produce rain; but though the arguments of the advocates of this doctrine are very plausible, not to say convincing, their opinions are rather _à priori_ conclusions from general meteorological laws, than deductions from facts of observation, and it is remarkable that there is so little direct evidence on the subject. On the other hand, Foissac expresses the opinion that forests have no influence on precipitation, beyond that of promoting the deposit of dew in their vicinity, and he states, as a fact of experience, that the planting of large vegetables, and especially of trees, is a very efficient means of drying morasses, because the plants draw from the earth a quantity of water larger than the average annual fall of rain.[190] Klöden, admitting that the rivers Oder and Elbe have diminished in quantity of water, the former since 1778, the latter since 1828, denies that the diminution of volume is to be ascribed to a decrease of precipitation in consequence of the felling of the forests, and states, what other physicists confirm, that, during the same period, meteorological records in various parts of Europe show rather an augmentation than a reduction of rain.[191] The observations of Belgrand tend to show, contrary to the general opinion, that less rain falls in wooded than in denuded districts. He compared the precipitation for the year 1852, at Vezelay in the valley of the Bouchat, and at Avallon in the valley of the Grenetière. At the first of these places it was 881 millimètres, at the latter 581 millimètres. The two cities are not more than eight miles apart. They are at the same altitude, and it is stated that the only difference in their geographical conditions consists in the different proportions of forest and cultivated country around them, the basin of the Bouchat being entirely bare, while that of the Grenetière is well wooded.[192] Observations in the same valleys, considered with reference to the seasons, show the following pluviometric results: FOR LA GRENETIÈRE. February, 1852, 42.2 millimètres precipitation. November, " 23.8 " " January, 1853, 35.4 " " ----- Total, 106.4 in three cold months. September, 1851, 27.1 millimètres precipitation. May, 1852, 20.9 " " June, " 56.3 " " July, " 22.8 " " September, " 22.8 " " ----- Total, 149.9 in five warm months. FOR LE BOUCHAT. February, 1852, 51.3 millimètres precipitation. November, " 36.6 " " January, 1853, 92.0 " " ----- Total, 179.9 in three cold months. September, 1851, 43.8 millimètres precipitation. May, 1852, 13.2 " " June, " 55.5 " " July, " 19.5 " " September, " 26.5 " " ----- Total, 158.5 in five warm months. These observations, so far as they go, seem to show that more rain falls in cleared than in wooded countries, but this result is so contrary to what has been generally accepted as a theoretical conclusion, that further experiment is required to determine the question. Becquerel--whose treatise on the climatic effects of the destruction of the forest is the fullest general discussion of that subject known to me--does not examine this particular point, and as, in the summary of the results of his investigations, he does not ascribe to the forest any influence upon precipitation, the presumption is that he rejects the doctrine of its importance as an agent in producing the fall of rain. The effect of the forest on precipitation, then, is not entirely free from doubt, and we cannot positively affirm that the total annual quantity of rain is diminished or increased by the destruction of the woods, though both theoretical considerations and the balance of testimony strongly favor the opinion that more rain falls in wooded than in open countries. One important conclusion, at least, upon the meteorological influence of forests is certain and undisputed: the proposition, namely, that, within their own limits, and near their own borders, they maintain a more uniform degree of humidity in the atmosphere than is observed in cleared grounds. Scarcely less can it be questioned that they promote the frequency of showers, and, if they do not augment the amount of precipitation, they equalize its distribution through the different seasons. _Influence of the Forest on the Humidity of the Soil._ I have hitherto confined myself to the influence of the forest on meteorological conditions, a subject, as has been seen, full of difficulty and uncertainty. Its comparative effects on the temperature, the humidity, the texture and consistence, the configuration and distribution of the mould or arable soil, and, very often, of the mineral strata below, and on the permanence and regularity of springs and greater superficial watercourses, are much less disputable as well as more easily estimated, and much more important, than its possible value as a cause of strictly climatic equilibrium or disturbance. The action of the forest on the earth is chiefly mechanical, but the organic process of abstraction of water by its roots affects the quantity of that fluid contained in the vegetable mould, and in the mineral strata near the surface, and, consequently, the consistency of the soil. In treating of the effects of trees on the moisture of the atmosphere, I have said that the forest, by interposing a canopy between the sky and the ground, and by covering the surface with a thick mantle of fallen leaves, at once obstructed insolation and prevented the radiation of heat from the earth. These influences go far to balance each other; but familiar observation shows that, in summer, the forest soil is not raised to so high a temperature as open grounds exposed to irradiation. For this reason, and in consequence of the mechanical resistance opposed by the bed of dead leaves to the escape of moisture, we should expect that, except after recent rains, the superficial strata of woodland soil would be more humid than that of cleared land. This agrees with experience. The soil of the forest is always moist, except in the extremest droughts, and it is exceedingly rare that a primitive wood suffers from want of humidity. How far this accumulation of water affects the condition of neighboring grounds by lateral infiltration, we do not know, but we shall see, in a subsequent chapter, that water is conveyed to great distances by this process, and we may hence infer that the influence in question is an important one. _Influence of the Forest on the Flow of Springs._ It is well established that the protection afforded by the forest against the escape of moisture from its soil, insures the permanence and regularity of natural springs, not only within the limits of the wood, but at some distance beyond its borders, and thus contributes to the supply of an element essential to both vegetable and animal life. As the forests are destroyed, the springs which flowed from the woods, and, consequently, the greater watercourses fed by them, diminish both in number and in volume. This fact is so familiar throughout the American States and the British Provinces, that there are few old residents of the interior of those districts who are not able to testify to its truth as a matter of personal observation. My own recollection suggests to me many instances of this sort, and I remember one case where a small mountain spring, which disappeared soon after the clearing of the ground where it rose, was recovered about ten or twelve years ago, by simply allowing the bushes and young trees to grow up on a rocky knoll, not more than half an acre in extent, immediately above it, and has since continued to flow uninterruptedly. The uplands in the Atlantic States formerly abounded in sources and rills, but in many parts of those States which have been cleared for above a generation or two, the hill pastures now suffer severely from drought, and in dry seasons no longer afford either water or herbage for cattle. Foissac, indeed, quotes from the elder Pliny (_Nat. Hist._, xxxi, c. 30) a passage affirming that the felling of the woods gives rise to springs which did not exist before because the water of the soil was absorbed by the trees; and the same meteorologist declares, as I observed in treating of the effect of the forest on atmospheric humidity, that the planting of trees tends to drain marshy ground, because the roots absorb more water than falls from the air. But Pliny's statement rests on very doubtful authority, and Foissac cites no evidence in support of his own proposition.[193] In the American States, it is always observed that clearing the ground not only causes running springs to disappear, but dries up the stagnant pools and the spongy soils of the low grounds. The first roads in those States ran along the ridges, when practicable, because there only was the earth dry enough to allow of their construction, and, for the same reason, the cabins of the first settlers were perched upon the hills. As the forests have been from time to time removed, and the face of the earth laid open to the air and sun, the moisture has been evaporated, and the removal of the highways and of human habitations from the bleak hills to the sheltered valleys, is one of the most agreeable among the many improvements which later generations have witnessed in the interior of New England and the other Northern States. Almost every treatise on the economy of the forest adduces numerous facts in support of the doctrine that the clearing of the woods tends to diminish the flow of springs and the humidity of the soil, and it might seem unnecessary to bring forward further evidence on this point.[194] But the subject is of too much practical importance and of too great philosophical interest to be summarily disposed of; and it ought particularly to be noticed that there is at least one case--that of some loose soils which, when bared of wood, very rapidly absorb and transmit to lower strata the water they receive from the atmosphere, as argued by Vallès[195]--where the removal of the forest may increase the flow of springs at levels below it, by exposing to the rain and melted snow a surface more bibulous, and at the same time less retentive, than its original covering. Under such circumstances, the water of precipitation, which had formerly flowed off without penetrating through the superficial layers of leaves upon the ground--as, in very heavy showers, it sometimes does--or been absorbed by the vegetable mould and retained until it was evaporated, might descend through porous earth until it meets an impermeable stratum, and then be conducted along it, until, finally, at the outcropping of this stratum, it bursts from a hillside as a running spring. But such instances are doubtless too rare to form a frequent or an important exception to the general law, because it is only under very uncommon circumstances that rain water runs off over the surface of forest ground instead of sinking into it, and very rarely the case that such a soil as has just been supposed is covered by a layer of vegetable earth thick enough to retain, until it is evaporated, all the rain that falls upon it, without imparting any water to the strata below it. If we look at the point under discussion as purely a question of fact, to be determined by positive evidence and not by argument, the observations of Boussingault are, both in the circumstances they detail, and in the weight of authority to be attached to the testimony, among the most important yet recorded. They are embodied in the fourth section of the twentieth chapter of that writer's _Économie Rurale_, and I have already referred to them on page 191 for another purpose. The interest of the question will justify me in giving, in Boussingault's own words, the facts and some of the remarks with which he accompanies the details of them: "In many localities," he observes,[196] "it has been thought that, within a certain number of years, a sensible diminution has been perceived in the volume of water of streams utilized as a motive power; at other points, there are grounds for believing that rivers have become shallower, and the increasing breadth of the belt of pebbles along their banks seems to prove the loss of a part of their water; and, finally, abundant springs have almost dried up. These observations have been principally made in valleys bounded by high mountains, and it is thought to have been noticed that this diminution of the waters has immediately followed the epoch when the inhabitants have begun to destroy, unsparingly, the woods which were spread over the face of the land. "These facts would indicate that, where clearings have been made, it rains less than formerly, and this is the generally received opinion. * * * But while the facts I have stated have been established, it has been observed, at the same time, that, since the clearing of the mountains, the rivers and the torrents, which seemed to have lost a part of their water, sometimes suddenly swell, and that, occasionally, to a degree which causes great disasters. Besides, after violent storms, springs which had become almost exhausted have been observed to burst out with impetuosity, and soon after to dry up again. These latter observations, it will be easily conceived, warn us not to admit hastily the common opinion that the felling of the woods lessens the quantity of rain; for not only is it very possible that the quantity of rain has not changed, but the mean volume of running water may have remained the same, in spite of the appearance of drought presented by the rivers and springs, at certain periods of the year. Perhaps the only difference would be that the flow of the same quantity of water becomes more irregular in consequence of clearing. For instance: if the low water of the Rhone during one part of the year were exactly compensated by a sufficient number of floods, it would follow that this river would convey to the Mediterranean the same volume of water which it carried to that sea in ancient times, before the period when the countries near its source were stripped of their woods, and when, probably, its mean depth was not subject to so great variations as in our days. If this were so, the forests would have this value--that of regulating, of economizing in a certain sort, the drainage of the rain water. "If running streams really become rarer in proportion as clearing is extended, it follows either that the rain is less abundant, or that evaporation is greatly favored by a surface which is no longer protected by trees against the rays of the sun and the wind. These two causes, acting in the same direction, must often be cumulative in their effects, and before we attempt to fix the value of each, it is proper to inquire whether it is an established fact that running waters diminish on the surface of a country in which extensive clearing is going on; in a word, to examine whether an apparent fact has not been mistaken for a real one. And here lies the practical point of the question; for if it is once established that clearing diminishes the volume of streams, it is less important to know to what special cause this effect is due. * * * I shall attach no value except to facts which have taken place under the eye of man, as it is the influence of his labors on the meteorological condition of the atmosphere which I propose to estimate. What I am about to detail has been observed particularly in America, but I shall endeavor to establish, that what I believe to be true of America would be equally so for any other continent. "One of the most interesting parts of Venezuela is, no doubt, the valley of Aragua. Situated at a short distance from the coast, and endowed, from its elevation, with various climates and a soil of unexampled fertility, its agriculture embraces at once the crops suited to tropical regions and to Europe. Wheat succeeds well on the heights of Victoria. Bounded on the north by the coast chain, on the south by a system of mountains connected with the Llanos, the valley is shut in on the east and the west by lines of hills which completely close it. In consequence of this singular configuration, the rivers which rise within it, having no outlet to the ocean, form, by their union, the beautiful Lake of Tacarigua or Valencia. This lake, according to Humboldt, is larger than that of Neufchâtel; it is at an elevation of 439 mètres [= 1,460 English feet] above the sea, and its greatest length does not exceed two leagues and a half [= seven English miles]. "At the time of Humboldt's visit to the valley of Aragua, the inhabitants were struck by the gradual diminution which the lake had been undergoing for thirty years. In fact, by comparing the descriptions given by historians with its actual condition, even making large allowance for exaggeration, it was easy to see that the level was considerably depressed. The facts spoke for themselves. Oviedo, who, toward the close of the sixteenth century, had often traversed the valley of Aragua, says positively that New Valencia was founded, in 1555, at half a league from the Lake of Tacarigua; in 1800, Humboldt found this city 5,260 mètres [= 3-1/3 English miles] from the shore. "The aspect of the soil furnished new proofs. Many hillocks on the plain retain the name of islands, which they more justly bore when they were surrounded by water. The ground laid bare by the retreat of the lake was converted into admirable plantations of cotton, bananas, and sugar cane; and buildings erected near the lake showed the sinking of the water from year to year. In 1796, new islands made their appearance. An important military point, a fortress built in 1740 on the island of Cabrera, was now on a peninsula; and, finally, on two granitic islands, those of Cura and Cabo Blanco, Humboldt observed among the shrubs, some mètres above the water, fine sand filled with helicites. "These clear and positive facts suggested numerous explanations, all assuming a subterranean outlet, which permitted the discharge of the water to the ocean. Humboldt disposed of these hypotheses, and, after a careful examination of the locality, the distinguished traveller did not hesitate to ascribe the diminution of the waters of the lake to the numerous clearings which had been made in the valley of Aragua within half a century. * * * "In 1800, the valley of Aragua possessed a population as dense as that of any of the best-peopled parts of France. * * * Such was the prosperous condition of this fine country when Humboldt occupied the Hacienda de Cura. "Twenty-two years later, I explored the valley of Aragua, fixing my residence in the little town of Maracay. For some years previous, the inhabitants had observed that the waters of the lake were no longer retiring, but, on the contrary, were sensibly rising. Grounds, not long before occupied by plantations, were submerged. The islands of Nuevas Aparecidas, which appeared above the surface in 1796, had again become shoals dangerous to navigation. Cabrera, a tongue of land on the north side of the valley, was so narrow that the least rise of the water completely inundated it. A protracted north wind sufficed to flood the road between Maracay and New Valencia. The fears which the inhabitants of the shores had so long entertained were reversed. * * * Those who had explained the diminution of the lake by the supposition of subterranean channels were suspected of blocking them up, to prove themselves in the right. "During the twenty-two years which had elapsed, important political events had occurred. Venezuela no longer belonged to Spain. The peaceful valley of Aragua had been the theatre of bloody struggles, and a war of extermination had desolated these smiling lands and decimated their population. At the first cry of independence a great number of slaves found their liberty by enlisting under the banners of the new republic; the great plantations were abandoned, and the forest, which in the tropics so rapidly encroaches, had soon recovered a large proportion of the soil which man had wrested from it by more than a century of constant and painful labor. "At the time of the growing prosperity of the valley of Aragua, the principal affluents of the lake were diverted, to serve for irrigation, and the rivers were dry for more than six months of the year. At the period of my visit, their waters, no longer employed, flowed freely." Boussingault proceeds to state that two lakes near Ubate in New Granada, at an elevation of 2,562 mètres (= 8,500 English feet), where there is a constant temperature of 14° to 16° centigrade [= 57°, 61° Fahrenheit], had formed but one, a century before his visit; that the waters were gradually retiring, and the plantations extending over the abandoned bed; that, by inquiry of old hunters and by examination of parish records, he found that extensive clearings had been made and were still going on. He found, also, that the length of the Lake of Fuquené, in the same valley, had, within two centuries, been reduced from ten leagues to one and a half, its breadth from three leagues to one. At the former period, timber was abundant, and the neighboring mountains were covered, to a certain height, with American oaks, laurels, and other trees of indigenous species; but at the time of his visit the mountains had been almost entirely stripped of their wood, chiefly to furnish fuel for salt-works. Our author adds that other cases, similar to those already detailed, might be cited, and he proceeds to show, by several examples, that the waters of other lakes in the same regions, where the valleys had always been bare of wood, or where the forests had not been disturbed, had undergone no change of level. Boussingault further maintains that the lakes of Switzerland have sustained a depression of level since the too prevalent destruction of the woods, and arrives at the general conclusion, that, "in countries where great clearings have been made, there has most probably been a diminution in the living waters which flow upon the surface of the ground." This conclusion he further supports by two examples: one, where a fine spring, at the foot of a wooded mountain in the Island of Ascension, dried up when the mountain was cleared, but reappeared when the wood was replanted; the other at Marmato, in the province of Popayan, where the streams employed to drive machinery were much diminished in volume, within two years after the clearing of the heights from which they derived their supplies. This latter is an interesting case, because, although the rain gauges, established as soon as the decrease of water began to excite alarm, showed a greater fall of rain for the second year of observation than the first, yet there was no appreciable increase in the flow of the mill streams. From these cases, the distinguished physicist infers that very restricted local clearings may diminish and even suppress springs and brooks, without any reduction in the total quantity of rain. It will have been noticed that these observations, with the exception of the last two cases, do not bear directly upon the question of the diminution of springs by clearings, but they logically infer it from the subsidence of the natural reservoirs which springs once filled. There is, however, no want of positive evidence on this subject. Marschand cites the following instances: "Before the felling of the woods, within the last few years, in the valley of the Soulce, the Combe-ès-Mounin and the Little Valley, the Sorne furnished a regular and sufficient supply of water for the iron works of Unterwyl, which was almost unaffected by drought or by heavy rains. The Sorne has now become a torrent, every shower occasions a flood, and after a few days of fine weather, the current falls so low that it has been necessary to change the water wheels, because those of the old construction are no longer able to drive the machinery, and at last to introduce a steam engine to prevent the stoppage of the works for want of water. "When the factory of St. Ursanne was established, the river that furnished its power was abundant, long known and tried, and had, from time immemorial, sufficed for the machinery of a previous factory. Afterward, the woods near its sources were cut. The supply of water fell off in consequence, the factory wanted water for half the year, and was at last obliged to stop altogether. "The spring of Combefoulat, in the commune of Seleate, was well known as one of the best in the country; it was remarkably abundant and sufficient, in spite of the severest droughts, to supply all the fountains of the town; but, as soon as considerable forests were felled in Combe-de-pré Martin and in the valley of Combefoulat, the famous spring which lies below these woods has become a mere thread of water, and disappears altogether in times of drought. "The spring of Varieux, which formerly supplied the castle of Pruntrut, lost more than half its water after the clearing of Varieux and Rongeoles. These woods have been replanted, the young trees are growing well, and with the woods, the waters of the spring are increasing. "The Dog Spring between Pruntrut and Bressancourt has entirely vanished since the surrounding forests grounds were brought under cultivation. "The Wolf Spring, in the commune of Soubey, furnishes a remarkable example of the influence of the woods upon fountains. A few years ago this spring did not exist. At the place where it now rises, a small thread of water was observed after very long rains, but the stream disappeared with the rain. The spot is in the middle of a very steep pasture inclining to the south. Eighty years ago, the owner of the land, perceiving that young firs were shooting up in the upper part of it, determined to let them grow, and they soon formed a flourishing grove. As soon as they were well grown, a fine spring appeared in place of the occasional rill, and furnished abundant water in the longest droughts. For forty or fifty years, this spring was considered the best in the Clos du Doubs. A few years since, the grove was felled, and the ground turned again to a pasture. The spring disappeared with the wood, and is now as dry as it was ninety years ago."[197] "The influence of the forest on springs," says Hummel, "is strikingly shown by an instance at Heilbronn. The woods on the hills surrounding the town are cut in regular succession every twentieth year. As the annual cuttings approach a certain point, the springs yield less water, some of them none at all; but as the young growth shoots up, they now more and more freely, and at length bubble up again in all their original abundance."[198] Piper states the following case: "Within about half a mile of my residence there is a pond upon which mills have been standing for a long time, dating back, I believe, to the first settlement of the town. These have been kept in constant operation until within some twenty or thirty years, when the supply of water began to fail. The pond owes its existence to a stream which has its source in the hills which stretch some miles to the south. Within the time mentioned, these hills, which were clothed with a dense forest, have been almost entirely stripped of trees; and to the wonder and loss of the mill owners, the water in the pond has failed, except in the season of freshets; and, what was never heard of before, the stream itself has been entirely dry. Within the last ten years a new growth of wood has sprung up on most of the land formerly occupied by the old forest; and now the water runs through the year, notwithstanding the great droughts of the last few years, going back from 1856." Dr. Piper quotes from a letter of William C. Bryant the following remarks: "It is a common observation that our summers are become drier, and our streams smaller. Take the Cuyahoga as an illustration. Fifty years ago large barges loaded with goods went up and down that river, and one of the vessels engaged in the battle of Lake Erie, in which the gallant Perry was victorious, was built at Old Portage, six miles north of Albion, and floated down to the lake. Now, in an ordinary stage of the water, a canoe or skiff can hardly pass down the stream. Many a boat of fifty tons burden has been built and loaded in the Tuscarawas, at New Portage, and sailed to New Orleans without breaking bulk. Now, the river hardly affords a supply of water at New Portage for the canal. The same may be said of other streams--they are drying up. And from the same cause--the destruction of our forests--our summers are growing drier, and our winters colder."[199] No observer has more carefully studied the influence of the forest upon the flow of the waters, or reasoned more ably on the ascertained phenomena than Cantegril. The facts presented in the following case, communicated by him to the _Ami des Sciences_ for December, 1859, are as nearly conclusive as any single instance well can be: "In the territory of the commune of Labruguière, there is a forest of 1,834 hectares [4,530 acres], known by the name of the Forest of Montaut, and belonging to that commune. It extends along the northern slope of the Black Mountains. The soil is granitic, the maximum altitude 1,243 mètres [4,140 feet], and the inclination ranges between 15 and 60 to 100. "A small current of water, the brook of Caunan, takes its rise in this forest, and receives the waters of two thirds of its surface. At the lower extremity of the wood and on the stream are several fulleries, each requiring a force of eight horse-power to drive the water wheels which work the stampers. The commune of Labruguière had been for a long time famous for its opposition to forest laws. Trespasses and abuses of the right of pasturage had converted the wood into an immense waste, so that this vast property now scarcely sufficed to pay the expense of protecting it, and to furnish the inhabitants with a meagre supply of fuel. While the forest was thus ruined, and the soil thus bared, the water, after every abundant rain, made an eruption into the valley, brought down a great quantity of pebbles which still clog the current of the Caunan. The violence of the floods was sometimes such that they were obliged to stop the machinery for some time. During the summer another inconvenience was felt. If the dry weather continued a little longer than usual, the delivery of water became insignificant. Each fullery could for the most part only employ a single set of stampers, and it was not unusual to see the work entirely suspended. "After 1840, the municipal authority succeeded in enlightening the population as to their true interests. Protected by a more watchful supervision, aided by well-managed replantation, the forest has continued to improve to the present day. In proportion to the restoration of the forest, the condition of the manufactories has become less and less precarious, and the action of the water is completely modified. For example, there are, no longer, sudden and violent floods which make it necessary to stop the machinery. There is no increase in the delivery until six or eight hours after the beginning of the rain; the floods follow a regular progression till they reach their maximum, and decrease in the same manner. Finally, the fulleries are no longer forced to suspend work in summer; the water is always sufficiently abundant to allow the employment of two sets of stampers at least, and often even of three. "This example is remarkable in this respect, that, all other circumstances having remained the same, the changes in the action of the stream can be attributed only to the restoration of the forest--changes which may be thus summed up: diminution of flood water during rains--increase of delivery at other seasons." _The Forest in Winter._ To estimate rightly the importance of the forest as a natural apparatus for accumulating the water that falls upon the surface and transmitting it to the subjacent strata, we must compare the condition and properties of its soil with those of cleared and cultivated earth, and examine the consequently different action of these soils at different seasons of the year. The disparity between them is greatest in climates where, as in the Northern American States and in the North of Europe, the open ground freezes and remains impervious to water during a considerable part of the winter; though, even in climates where the earth does not freeze at all, the woods have still an important influence of the same character. The difference is yet greater in countries which have regular wet and dry seasons, rain being very frequent in the former period, while, in the latter, it scarcely occurs at all. These countries lie chiefly in or near the tropics, but they are not wanting in higher latitudes; for a large part of Asiatic and even of European Turkey is almost wholly deprived of summer rains. In the principal regions occupied by European cultivation, and where alone the questions discussed in this volume are recognized as having, at present, any practical importance, rain falls at all seasons, and it is to these regions that, on this point as well as others, I chiefly confine my attention. The influence of the forest upon the waters of the earth has been more studied in France than in any other part of the civilized world, because that country has, in recent times, suffered most severely from the destruction of the woods. But in the southern provinces of that empire, where the evils resulting from this cause are most sensibly felt, the winters are not attended with much frost, while, in Northern Europe, where the winters are rigorous enough to freeze the ground to the depth of some inches, or even feet, a humid atmosphere and frequent summer rains prevent the drying up of the springs observed in southern latitudes when the woods are gone. For these reasons, the specific character of the forest, as a winter reservoir of moisture in countries with a cold and dry atmosphere, has not attracted so much attention in France and Northern Europe as it deserves in the United States, where an excessive climate renders that function of the woods more important. In New England, irregular as the climate is, the first autumnal snows usually fall before the ground is frozen at all, or when the frost extends at most to the depth of only a few inches. In the woods, especially those situated upon the elevated ridges which supply the natural irrigation of the soil and feed the perennial fountains and streams, the ground remains covered with snow during the winter; for the trees protect the snow from blowing from the general surface into the depressions, and new accessions are received before the covering deposited by the first fall is melted. Snow is of a color unfavorable for radiation, but, even when it is of considerable thickness, it is not wholly impervious to the rays of the sun, and for this reason, as well as from the warmth of lower strata, the frozen crust, if one has been formed, is soon thawed, and does not again fall below the freezing point during the winter. The snow in contact with the earth now begins to melt, with greater or less rapidity, according to the relative temperature of the earth and the air, while the water resulting from its dissolution is imbibed by the vegetable mould, and carried off by infiltration so fast that both the snow and the layers of leaves in contact with it often seem comparatively dry, when, in fact, the under surface of the former is in a state of perpetual thaw. No doubt a certain proportion of the snow is returned to the atmosphere by direct evaporation, but in the woods it is partially protected from the action of the sun, and as very little water runs off in the winter by superficial watercourses, except in rare cases of sudden thaw, there can be no question that much the greater part of the snow deposited in the forest is slowly melted and absorbed by the earth. The quantity of snow that falls in extensive forests, far from the open country, has seldom been ascertained by direct observation, because there are few meteorological stations in such situations. In the Northeastern border States of the American Union, the ground in the deep woods is covered with snow four or five months, and the proportion of water which falls in snow does not exceed one fifth of the total precipitation for the year.[200] Although, in the open grounds, snow and ice are evaporated with great rapidity in clear weather, even when the thermometer stands far below the freezing point, the surface of the snow in the woods does not indicate much loss in this way. Very small deposits of snowflakes remain unevaporated in the forest, for many days after snow let fall at the same time in the cleared field has disappeared without either a thaw to melt it or a wind powerful enough to drift it away. Even when bared of their leaves, the trees of a wood obstruct, in an important degree, both the direct action of the sun's rays on the snow, and the movement of drying and thawing winds. Dr. Piper records the following observations: "A body of snow, one foot in depth, and sixteen feet square, was protected from the wind by a tight board fence about five feet high, while another body of snow, much more sheltered from the sun than the first, six feet in depth, and about sixteen feet square, was fully exposed to the wind. When the thaw came on, which lasted about a fortnight, the larger body of snow was entirely dissolved in less than a week, while the smaller body was not wholly gone at the end of the second week. "Equal quantities of snow were placed in vessels of the same kind and capacity, the temperature of the air being seventy degrees. In the one case, a constant current of air was kept passing over the open vessel, while the other was protected by a cover. The snow in the first was dissolved in sixteen minutes, while the latter had a small unthawed proportion remaining at the end of eighty-five minutes."[201] The snow in the woods is protected in the same way, though not literally to the same extent as by the fence in one of these cases and the cover in the other. Little of the winter precipitation, therefore, is lost by evaporation, and as it slowly melts at bottom it is absorbed by the earth, and but a very small quantity of water runs off from the surface. The immense importance of the forest, as a reservoir of this stock of moisture, becomes apparent, when we consider that a large proportion of the summer rain either flows into the valleys and the rivers, because it falls faster than the ground can imbibe it; or, if absorbed by the warm superficial strata, is evaporated from them without sinking deep enough to reach wells and springs, which, of course, depend very much on winter rains and snows for their entire supply. This observation, though specially true of cleared and cultivated grounds, is not wholly inapplicable to the forest, particularly when, as is too often the case in Europe, the underwood and the decaying leaves are removed. The general effect of the forest in cold climates is to assimilate the winter state of the ground to that of wooded regions under softer skies; and it is a circumstance well worth noting, that in Southern Europe, where nature has denied to the earth a warm winter-garment of flocculent snow, she has, by one of those compensations in which her empire is so rich, clothed the hillsides with umbrella pines, ilexes, cork oaks, and other trees of persistent foliage, whose evergreen leaves afford to the soil a protection analogous to that which it derives from snow in more northern climates. The water imbibed by the soil in winter sinks until it meets a more or less impermeable, or a saturated stratum, and then, by unseen conduits, slowly finds its way to the channels of springs, or oozes out of the ground in drops which unite in rills, and so all is conveyed to the larger streams, and by them finally to the sea. The water, in percolating through the vegetable and mineral layers, acquires their temperature, and is chemically affected by their action, but it carries very little matter in mechanical suspension. The process I have described is a slow one, and the supply of moisture derived from the snow, augmented by the rains of the following seasons, keeps the forest ground, where the surface is level or but moderately inclined, in a state of saturation through almost the whole year. The rivers fed by springs and shaded by woods are comparatively uniform in volume, in temperature, and in chemical composition. Their banks are little abraded, nor are their courses much obstructed by fallen timber, or by earth and gravel washed down from the highlands. Their channels are subject only to slow and gradual changes, and they carry down to the lakes and the sea no accumulation of sand or silt to fill up their outlets, and, by raising their beds, to force them to spread over the low grounds near their mouth.[202] In this state of things, destructive tendencies of all sorts are arrested or compensated, and tree, bird, beast, and fish, alike, find a constant uniformity of condition most favorable to the regular and harmonious coexistence of them all. _General Consequences of the Destruction of the Forest._ With the disappearance of the forest, all is changed. At one season, the earth parts with its warmth by radiation to an open sky--receives, at another, an immoderate heat from the unobstructed rays of the sun. Hence the climate becomes excessive, and the soil is alternately parched by the fervors of summer, and seared by the rigors of winter. Bleak winds sweep unresisted over its surface, drift away the snow that sheltered it from the frost, and dry up its scanty moisture. The precipitation becomes as regular as the temperature; the melting snows and vernal rains, no longer absorbed by a loose and bibulous vegetable mould, rush over the frozen surface, and pour down the valleys seaward, instead of filling a retentive bed of absorbent earth, and storing up a supply of moisture to feed perennial springs. The soil is bared of its covering of leaves, broken and loosened by the plough, deprived of the fibrous rootlets which held it together, dried and pulverized by sun and wind, and at last exhausted by new combinations. The face of the earth is no longer a sponge, but a dust heap, and the floods which the waters of the sky pour over it hurry swiftly along its slopes, carrying in suspension vast quantities of earthy particles which increase the abrading power and mechanical force of the current, and, augmented by the sand and gravel of falling banks, fill the beds of the streams, divert them into new channels and obstruct their outlets. The rivulets, wanting their former regularity of supply and deprived of the protecting shade of the woods, are heated, evaporated, and thus reduced in their summer currents, but swollen to raging torrents in autumn and in spring. From these causes, there is a constant degradation of the uplands, and a consequent elevation of the beds of watercourses and of lakes by the deposition of the mineral and vegetable matter carried down by the waters. The channels of great rivers become unnavigable, their estuaries are choked up, and harbors which once sheltered large navies are shoaled by dangerous sandbars. The earth, stripped of its vegetable glebe, grows less and less productive, and, consequently, less able to protect itself by weaving a new network of roots to bind its particles together, a new carpeting of turf to shield it from wind and sun and scouring rain. Gradually it becomes altogether barren. The washing of the soil from the mountains leaves bare ridges of sterile rock, and the rich organic mould which covered them, now swept down into the dank low grounds, promotes a luxuriance of aquatic vegetation that breeds fever, and more insidious forms of mortal disease, by its decay, and thus the earth is rendered no longer fit for the habitation of man.[203] To the general truth of this sad picture there are many exceptions, even in countries of excessive climates. Some of these are due to favorable conditions of surface, of geological structure, and of the distribution of rain; in many others, the evil consequences of man's improvidence have not yet been experienced, only because a sufficient time has not elapsed, since the felling of the forest, to allow them to develop themselves. But the vengeance of nature for the violation of her harmonies, though slow, is sure, and the gradual deterioration of soil and climate in such exceptional regions is as certain to result from the destruction of the woods as is any natural effect to follow its cause. In the vast farrago of crudities which the elder Pliny's ambition of encyclopædic attainment and his ready credulity have gathered together, we meet some judicious observations. Among these we must reckon the remark with which he accompanies his extraordinary statement respecting the prevention of springs by the growth of forest trees, though, as is usual with him, his philosophy is wrong. "Destructive torrents are generally formed when hills are stripped of the trees which formerly confined and absorbed the rains." The absorption here referred to is not that of the soil, but of the roots, which, Pliny supposed, drank up the water to feed the growth of the trees. Although this particular evil effect of too extensive clearing was so early noticed, the lesson seems to have been soon forgotten. The legislation of the Middle Ages in Europe is full of absurd provisions concerning the forests, which sovereigns sometimes destroyed because they furnished a retreat for rebels and robbers, sometimes protected because they were necessary to breed stags and boars for the chase, and sometimes spared with the more enlightened view of securing a supply of timber and of fuel to future generations.[204] It was reserved to later ages to appreciate their geographical importance, and it is only in very recent times, only in a few European countries, that the too general felling of the woods has been recognized as the most destructive among the many causes of the physical deterioration of the earth. _Condition of the Forest, and its Literature in different Countries._ The literature of the forest, which in England and America has not yet become sufficiently extensive to be known as a special branch of authorship, counts its thousands of volumes in Germany, Italy, and France. It is in the latter country, perhaps, that the relations of the woods to the regular drainage of the soil, and especially to the permanence of the natural configuration of terrestrial surface, have been most thoroughly investigated. On the other hand, the purely economical aspects of sylviculture have been most satisfactorily expounded, and that art has been most philosophically discussed, and most skilfully and successfully practised, in Germany. The eminence of Italian theoretical hydrographers and the great ability of Italian hydraulic engineers are well known, but the specific geographical importance of the woods has not been so clearly recognized in Italy as in the states bordering it on the north and west. It is true that the face of nature has been as completely revolutionized by man, and that the action of torrents has created as wide and as hopeless devastation in that country as in France; but in the French Empire the desolation produced by clearing the forests is more recent,[205] has been more suddenly effected, and, therefore, excites a livelier and more general interest than in Italy, where public opinion does not so readily connect the effect with its true cause. Italy, too, from ancient habit, employs little wood in architectural construction; for generations she has maintained no military or commercial marine large enough to require exhaustive quantities of timber,[206] and the mildness of her climate makes small demands on the woods for fuel. Besides these circumstances, it must be remembered that the sciences of observation did not become knowledges of practical application till after the mischief was already mainly done and even forgotten in Alpine Italy, while its evils were just beginning to be sensibly felt in France when the claims of natural philosophy as a liberal study were first acknowledged in modern Europe. The former political condition of the Italian Peninsula would have effectually prevented the adoption of a general system of forest economy, however clearly the importance of a wise administration of this great public interest might have been understood. The woods which controlled and regulated the flow of the river sources were very often in one jurisdiction, the plains to be irrigated, or to be inundated by floods and desolated by torrents, in another. Concert of action on such a subject between a multitude of jealous petty sovereignties was obviously impossible, and nothing but the union of all the Italian states under a single government can render practicable the establishment of such arrangements for the conservation and restoration of the forests and the regulation of the flow of the waters as are necessary for the full development of the yet unexhausted resources of that fairest of lands, and even for the permanent maintenance of the present condition of its physical geography. The denudation of the Central and Southern Apennines and of the Italian declivity of the Western Alps began at a period of unknown antiquity, but it does not seem to have been carried to a very dangerous length until the foreign conquests and extended commerce of Rome created a greatly increased demand for wood for the construction of ships and for military material. The Eastern Alps, the Western Apennines, and the Maritime Alps retained their forests much later; but even here the want of wood, and the injury to the plains and the navigation of the rivers by sediment brought down by the torrents, led to some legislation for the protection of the forests, by the Republic of Venice in the fifteenth century, by that of Genoa as early at least as the seventeenth; and Marschand states that the latter Government passed laws requiring the proprietors of mountain lands to replant the woods. These, however, do not seem to have been effectually enforced. It is very common in Italy to ascribe to the French occupation under the first Empire all the improvements, and all the abuses of recent times, according to the political sympathies of the individual; and the French are often said to have prostrated every forest which has disappeared within a century.[207] But, however this may be, no energetic system of repression or restoration was adopted by any of the Italian states after the downfall of the Empire, and the taxes on forest property in some of them were so burdensome that rural municipalities sometimes proposed to cede their common woods to the Government, without any other compensation than the remission of the taxes imposed on forest lands.[208] Under such circumstances, woodlands would soon become disafforested, and where facilities of transportation and a good demand for timber have increased the inducements to fell it, as upon the borders of the Mediterranean, the destruction of the forest and all the evils which attend it have gone on at a seriously alarming rate. It has even been calculated that four tenths of the area of the Ligurian provinces have been washed away or rendered incapable of cultivation by the felling of the woods.[209] The damp and cold climate of England requires the maintenance of household fires through a large part of the year. Contrivances for economizing fuel were of later introduction in that country than on the Continent. The soil, like the sky, was, in general, charged with humidity; its natural condition was unfavorable for common roads, and the transportation of so heavy a material as coal, by land, from the remote counties where alone it was mined in the Middle Ages, was costly and difficult. For all these reasons, the consumption of wood was large, and apprehensions of the exhaustion of the forests were excited at an early period. Legislation there, as elsewhere, proved ineffectual to protect them, and many authors of the sixteenth century express fears of serious evils from the wasteful economy of the people in this respect. Harrison, in his curious chapter "Of Woods and Marishes" in Holinshed's compilation, complains of the rapid decrease of the forests, and adds: "Howbeit thus much I dare affirme, that if woods go so fast to decaie in the next hundred yeere of Grace, as they haue doone and are like to doo in this, * * * it is to be feared that the fennie bote, broome, turfe, gall, heath, firze, brakes, whinnes, ling, dies, hassacks, flags, straw, sedge, réed, rush, and also _seacole_, will be good merchandize euen in the citie of London, whereunto some of them euen now haue gotten readie passage, and taken vp their innes in the greatest merchants' parlours. * * * I would wish that I might liue no longer than to sée foure things in this land reformed, that is: the want of discipline in the church: the couetous dealing of most of our merchants in the preferment of the commodities of other countries, and hinderance of their owne: the holding of faires and markets vpon the sundaie to be abolished and referred to the wednesdaies: and that euerie man, in whatsoeuer part of the champaine soile enioieth fortie acres of land, and vpwards, after that rate, either by frée deed, copie hold, or fee farme, might plant one acre of wood, or sowe the same with oke mast, hasell, béech, and sufficient prouision be made that it may be cherished and kept. But I feare me that I should then liue too long, and so long, that I should either be wearie of the world, or the world of me."[210] Evelyn's "Silva," the first edition of which appeared in 1664, rendered an extremely important service to the cause of the woods, and there is no doubt that the ornamental plantations in which England far surpasses all other countries, are, in some measure, the fruit of Evelyn's enthusiasm. In England, however, arboriculture, the planting and nursing of single trees, has, until recently, been better understood than sylviculture, the sowing and training of the forest. But this latter branch of rural improvement is now pursued on a very considerable scale, though, so far as I know, not by the National Government. _The Influence of the Forest on Inundations._ Besides the climatic question, which I have already sufficiently discussed, and the obvious inconveniences of a scanty supply of charcoal, of fuel, and of timber for architectural and naval construction and for the thousand other uses to which wood is applied in rural and domestic economy, and in the various industrial processes of civilized life, the attention of French foresters and public economists has been specially drawn to three points, namely: the influence of the forests on the permanence and regular flow of springs or natural fountains; on inundations by the overflow of rivers; and on the abrasion of soil and the transportation of earth, gravel, pebbles, and even of considerable masses of rock, from higher to lower levels, by torrents. There are, however, connected with this general subject, several other topics of minor or strictly local interest, or of more uncertain character, which I shall have occasion more fully to speak of hereafter. The first of these three principal subjects--the influence of the woods on springs and other living waters--has been already considered; and if the facts stated in that discussion are well established, and the conclusions I have drawn from them are logically sound, it would seem to follow, as a necessary corollary, that the action of the forest is as important in diminishing the frequency and violence of river floods, as in securing the permanence and equability of natural fountains; for any cause which promotes the absorption and accumulation of the water of precipitation by the superficial strata of the soil, to be slowly given out by infiltration and percolation, must, by preventing the rapid flow of surface water into the natural channels of drainage, tend to check the sudden rise of rivers, and, consequently, the overflow of their banks, which constitutes what is called inundation. The mechanical resistance, too, offered by the trunks of trees and of undergrowth to the flow of water over the surface, tends sensibly to retard the rapidity of its descent down declivities, and to divert and divide streams which may have already accumulated from smaller threads of water.[211] Inundations are produced by the insufficiency of the natural channels of rivers to carry off the waters of their basins as fast as those waters flow into them. In accordance with the usual economy of nature, we should presume that she had everywhere provided the means of discharging, without disturbance of her general arrangements or abnormal destruction of her products, the precipitation which she sheds upon the face of the earth. Observation confirms this presumption, at least in the countries to which I confine my inquiries; for, so far as we know the primitive conditions of the regions brought under human occupation within the historical period, it appears that the overflow of river banks was much less frequent and destructive than at the present day, or, at least, that rivers rose and fell less suddenly before man had removed the natural checks to the too rapid drainage of the basins in which their tributaries originate. The banks of the rivers and smaller streams in the North American colonies were formerly little abraded by the currents. Even now the trees come down almost to the water's edge along the rivers, in the larger forests of the United States, and the surface of the streams seems liable to no great change in level or in rapidity of current. A circumstance almost conclusive as to the regularity of flow in forest rivers, is that they do not form large sedimentary deposits, at their points of discharge into lakes or larger streams, such accumulations beginning, or at least advancing far more rapidly, after the valleys are cleared. In the Northern United States, although inundations are sometimes produced in the height of summer by heavy rains, it will be found generally true that the most rapid rise of the waters, and, of course, the most destructive "freshets," as they are called in America, are produced by the sudden dissolution of the snow before the open ground is thawed in the spring. It frequently happens that a powerful thaw sets in after a long period of frost, and the snow which had been months in accumulating is dissolved and carried off in a few hours. When the snow is deep, it, to use a popular expression, "takes the frost out of the ground" in the woods, and, if it lies long enough, in the fields also. But the heaviest snows usually fall after midwinter, and are succeeded by warm rains or sunshine, which dissolve the snow on the cleared land before it has had time to act upon the frost-bound soil beneath it. In this case, the snow in the woods is absorbed as fast as it melts, by the soil it has protected from freezing, and does not materially contribute to swell the current of the rivers. If the mild weather, in which great snowstorms usually occur, does not continue and become a regular thaw, it is almost sure to be followed by drifting winds, and the inequality with which they distribute the snow leaves the ridges comparatively bare, while the depressions are often filled with drifts to the height of many feet. The knolls become frozen to a great depth; succeeding partial thaws melt the surface snow, and the water runs down into the furrows of ploughed fields, and other artificial and natural hollows, and then often freezes to solid ice. In this state of things, almost the entire surface of the cleared land is impervious to water, and from the absence of trees and the general smoothness of the ground, it offers little mechanical resistance to superficial currents. If, under these circumstances, warm weather accompanied by rain occurs, the rain and melted snow are swiftly hurried to the bottom of the valleys and gathered to raging torrents. It ought further to be considered that, though the lighter ploughed soils readily imbibe a great deal of water, yet the grass lands, and all the heavy and tenacious earths, absorb it in much smaller quantities, and less rapidly than the vegetable mould of the forest. Pasture, meadow, and clayey soils, taken together, greatly predominate over the sandy ploughed fields, in all large agricultural districts, and hence, even if, in the case we are supposing, the open ground chance to have been thawed before the melting of the snow which covers it, it is already saturated with moisture, or very soon becomes so, and, of course, cannot relieve the pressure by absorbing more water. The consequence is that the face of the country is suddenly flooded with a quantity of melted snow and rain equivalent to a fall of six or eight inches of the latter, or even more. This runs unobstructed to rivers often still bound with thick ice, and thus inundations of a fearfully devastating character are produced. The ice bursts, from the hydrostatic pressure from below, or is violently torn up by the current, and is swept by the impetuous stream, in large masses and with resistless fury, against banks, bridges, dams, and mills erected near them. The bark of the trees along the rivers is often abraded, at a height of many feet above the ordinary water level, by cakes of floating ice, which are at last stranded by the receding flood on meadow or ploughland, to delay, by their chilling influence, the advent of the tardy spring. The surface of a forest, in its natural condition, can never pour forth such deluges of water as flow from cultivated soil. Humus, or vegetable mould, is capable of absorbing almost twice its own weight of water. The soil in a forest of deciduous foliage is composed of humus, more or less unmixed, to the depth of several inches, sometimes even of feet, and this stratum is usually able to imbibe all the water possibly resulting from the snow which at any one time covers it. But the vegetable mould does not cease to absorb water when it becomes saturated, for it then gives off a portion of its moisture to the mineral earth below, and thus is ready to receive a new supply; and, besides, the bed of leaves not yet converted to mould takes up and retains a very considerable proportion of snow water, as well as of rain. In the warm climates of Southern Europe, as I have already said, the functions of the forest, so far as the disposal of the water of precipitation is concerned, are essentially the same at all seasons, and are analogous to those which it performs in the Northern United States in summer. Hence, in the former countries, the winter floods have not the characteristics which mark them in the latter, nor is the conservative influence of the woods in winter relatively so important, though it is equally unquestionable. If the summer floods in the United States are attended with less pecuniary damage than those of the Loire and other rivers of France, the Po and its tributaries in Italy, the Emme and her sister torrents which devastate the valleys of Switzerland, it is partly because the banks of American rivers are not yet lined with towns, their shores and the bottoms which skirt them not yet covered with improvements whose cost is counted by millions, and, consequently, a smaller amount of property is exposed to injury by inundation. But the comparative exemption of the American people from the terrible calamities which the overflow of rivers has brought on some of the fairest portions of the Old World, is, in a still greater degree, to be ascribed to the fact that, with all our thoughtless improvidence, we have not yet bared all the sources of our streams, not yet overthrown all the barriers which nature has erected to restrain her own destructive energies. Let us be wise in time, and profit by the errors of our older brethren! The influence of the forest in preventing inundations has been very generally recognized, both as a theoretical inference and as a fact of observation; but Belgrand and his commentator Vallès have deduced an opposite result from various facts of experience and from scientific considerations. They contend that the superficial drainage is more regular from cleared than from wooded ground, and that clearing diminishes rather than augments the intensity of inundations. Neither of these conclusions is warranted by their data or their reasoning, and they rest partly upon facts, which, truly interpreted, are not inconsistent with the received opinions on these subjects, partly upon assumptions which are contradicted by experience. Two of these latter are, first, that the fallen leaves in the forest constitute an impermeable covering of the soil over, not through, which the water of rains and of melting snows flows off, and secondly, that the roots of trees penetrate and choke up the fissures in the rocks, so as to impede the passage of water through channels which nature has provided for its descent to lower strata. As to the first of these, we may appeal to familiar facts within the personal knowledge of every man acquainted with the operations of sylvan nature. I have before me a letter from an acute and experienced observer, containing this paragraph: "I think that rain water does not ever, except in very trifling quantities, flow over the leaves in the woods in summer or autumn. Water runs over them only in the spring, when they are pressed down smoothly and compactly, a state in which they remain only until they are dry, when shrinkage and the action of the wind soon roughen the surface so as effectually to stop, by absorption, all flow of water." I have observed that when a sudden frost succeeds a thaw at the close of the winter after the snow has principally disappeared, the water in and between the layers of leaves sometimes freezes into a solid crust, which allows the flow of water over it. But this occurs only in depressions and on a very small scale; and the ice thus formed is so soon dissolved that no sensible effect is produced on the escape of water from the general surface. As to the influence of roots upon drainage, I believe there is no doubt that they, independently of their action as absorbents, mechanically promote it. Not only does the water of the soil follow them downward,[212] but their swelling growth powerfully tends to enlarge the crevices of rock into which they enter; and as the fissures in rocks are longitudinal, not mere circular orifices, every line of additional width gained by the growth of roots within them increases the area of the crevice in proportion to its length. Consequently, the widening of a fissure to the extent of one inch might give an additional drainage equal to a square foot of open tubing. The observations and reasonings of Belgrand and Vallès, though their conclusions have not been accepted by many, are very important in one point of view. These writers insist much on the necessity of taking into account, in estimating the relations between precipitation and evaporation, the abstraction of water from the surface and surface currents, by absorption and infiltration--an element unquestionably of great value, but hitherto much neglected by meteorological inquirers, who have very often reasoned as if the surface earth were either impermeable to water, or already saturated with it; whereas, in fact, it is a sponge, always imbibing humidity and always giving it off, not by evaporation only, but by infiltration and percolation. The destructive effects of inundations considered simply as a mechanical power by which life is endangered, crops destroyed, and the artificial constructions of man overthrown, are very terrible. Thus far, however, the flood is a temporary and by no means an irreparable evil, for if its ravages end here, the prolific powers of nature and the industry of man soon restore what had been lost, and the face of the earth no longer shows traces of the deluge that had overwhelmed it. Inundations have even their compensations. The structures they destroy are replaced by better and more secure erections, and if they sweep off a crop of corn, they not unfrequently leave behind them, as they subside, a fertilizing deposit which enriches the exhausted field for a succession of seasons.[213] If, then, the too rapid flow of the surface waters occasioned no other evil than to produce, once in ten years upon the average, an inundation which should destroy the harvest of the low grounds along the rivers, the damage would be too inconsiderable, and of too transitory a character, to warrant the inconveniences and the expense involved in the measures which the most competent judges in many parts of Europe believe the respective governments ought to take to obviate it. _Destructive Action of Torrents._ But the great, the irreparable, the appalling mischiefs which have already resulted, and threaten to ensue on a still more extensive scale hereafter, from too rapid superficial drainage, are of a properly geographical character, and consist primarily in erosion, displacement, and transportation of the superficial strata, vegetable and mineral--of the integuments, so to speak, with which nature has clothed the skeleton framework of the globe. It is difficult to convey by description an idea of the desolation of the regions most exposed to the ravages of torrent and of flood; and the thousands, who, in these days of travel, are whirled by steam near or even through the theatres of these calamities, have but rare and imperfect opportunities of observing the destructive causes in action. Still more rarely can they compare the past with the actual condition of the provinces in question, and trace the progress of their conversion from forest-crowned hills, luxuriant pasture grounds, and abundant cornfields and vineyards well watered by springs and fertilizing rivulets, to bald mountain ridges, rocky declivities, and steep earth banks furrowed by deep ravines with beds now dry, now filled by torrents of fluid mud and gravel hurrying down to spread themselves over the plain, and dooming to everlasting barrenness the once productive fields. In traversing such scenes, it is difficult to resist the impression that nature pronounced the curse of perpetual sterility and desolation upon these sublime but fearful wastes, difficult to believe that they were once, and but for the folly of man might still be, blessed with all the natural advantages which Providence has bestowed upon the most favored climes. But the historical evidence is conclusive as to the destructive changes occasioned by the agency of man upon the flanks of the Alps, the Apennines, the Pyrenees, and other mountain ranges in Central and Southern Europe, and the progress of physical deterioration has been so rapid that, in some localities, a single generation has witnessed the beginning and the end of the melancholy revolution. It is certain that a desolation, like that which has overwhelmed many once beautiful and fertile regions of Europe, awaits an important part of the territory of the United States, and of other comparatively new countries over which European civilization is now extending its sway, unless prompt measures are taken to check the action of destructive causes already in operation. It is vain to expect that legislation can do anything effectual to arrest the progress of the evil in those countries, except so far as the state is still the proprietor of extensive forests. Woodlands which have passed into private hands will everywhere be managed, in spite of legal restrictions, upon the same economical principles as other possessions, and every proprietor will, as a general rule, fell his woods, unless he believes that it will be for his pecuniary interest to preserve them. Few of the new provinces which the last three centuries have brought under the control of the European race, would tolerate any interference by the law-making power with what they regard as the most sacred of civil rights--the right, namely, of every man to do what he will with his own. In the Old World, even in France, whose people, of all European nations, love best to be governed and are least annoyed by bureaucratic supervision, law has been found impotent to prevent the destruction, or wasteful economy, of private forests; and in many of the mountainous departments of that country, man is at this moment so fast laying waste the face of the earth, that the most serious fears are entertained, not only of the depopulation of those districts, but of enormous mischiefs to the provinces contiguous to them.[214] The only legal provisions from which anything is to be hoped, are such as shall make it a matter of private advantage to the landholder to spare the trees upon his grounds, and promote the growth of the young wood. Something may be done by exempting standing forests from taxation, and by imposing taxes on wood felled for fuel or for timber, something by premiums or honorary distinctions for judicious management of the woods. It would be difficult to induce governments, general or local, to make the necessary appropriations for such purposes, but there can be no doubt that it would be sound economy in the end. In countries where there exist municipalities endowed with an intelligent public spirit, the purchase and control of forests by such corporations would often prove advantageous; and in some of the provinces of Northern Lombardy, experience has shown that such operations may be conducted with great benefit to all the interests connected with the proper management of the woods. In Switzerland, on the other hand, except in some few cases where woods have been preserved as a defence against avalanches, the forests of the communes have been productive of little advantage to the public interests, and have very generally gone to decay. The rights of pasturage, everywhere destructive to trees, combined with toleration of trespasses, have so reduced their value, that there is, too often, nothing left that is worth protecting. In the canton of Ticino, the peasants have very frequently voted to sell the town woods and divide the proceeds among the corporators. The sometimes considerable sums thus received are squandered in wild revelry, and the sacrifice of the forests brings not even a momentary benefit to the proprietors.[215] It is evidently a matter of the utmost importance that the public, and especially land owners, be roused to a sense of the dangers to which the indiscriminate clearing of the woods may expose not only future generations, but the very soil itself. Fortunately, some of the American States, as well as the governments of many European colonies, still retain the ownership of great tracts of primitive woodland. The State of New York, for example, has, in its northeastern counties, a vast extent of territory in which the lumberman has only here and there established his camp, and where the forest, though interspersed with permanent settlements, robbed of some of its finest pine groves, and often ravaged by devastating fires, still covers far the largest proportion of the surface. Through this territory, the soil is generally poor, and even the new clearings have little of the luxuriance of harvest which distinguishes them elsewhere. The value of the land for agricultural uses is therefore very small, and few purchases are made for any other purpose than to strip the soil of its timber. It has been often proposed that the State should declare the remaining forest the inalienable property of the commonwealth, but I believe the motive of the suggestion has originated rather in poetical than in economical views of the subject. Both these classes of considerations have a real worth. It is desirable that some large and easily accessible region of American soil should remain, as far as possible, in its primitive condition, at once a museum for the instruction of the student, a garden for the recreation of the lover of nature, and an asylum where indigenous tree, and humble plant that loves the shade, and fish and fowl and four-footed beast, may dwell and perpetuate their kind, in the enjoyment of such imperfect protection as the laws of a people jealous of restraint can afford them. The immediate loss to the public treasury from the adoption of this policy would be inconsiderable, for these lands are sold at low rates. The forest alone, economically managed, would, without injury, and even with benefit to its permanence and growth, soon yield a regular income larger than the present value of the fee. The collateral advantages of the preservation of these forests would be far greater. Nature threw up those mountains and clothed them with lofty woods, that they might serve as a reservoir to supply with perennial waters the thousand rivers and rills that are fed by the rains and snows of the Adirondacks, and as a screen for the fertile plains of the central counties against the chilling blasts of the north wind, which meet no other barrier in their sweep from the Arctic pole. The climate of Northern New York even now presents greater extremes of temperature than that of Southern France. The long continued cold of winter is far more intense, the short heats of summer not less fierce than in Provence, and hence the preservation of every influence that tends to maintain an equilibrium of temperature and humidity is of cardinal importance. The felling of the Adirondack woods would ultimately involve for Northern and Central New York consequences similar to those which have resulted from the laying bare of the southern and western declivities of the French Alps and the spurs, ridges, and detached peaks in front of them. It is true that the evils to be apprehended from the clearing of the mountains of New York may be less in degree than those which a similar cause has produced in Southern France, where the intensity of its action has been increased by the inclination of the mountain declivities, and by the peculiar geological constitution of the earth. The degradation of the soil is, perhaps, not equally promoted by a combination of the same circumstances, in any of the American Atlantic States, but still they have rapid slopes and loose and friable soils enough to render widespread desolation certain, if the further destruction of the woods is not soon arrested. The effects of clearing are already perceptible in the comparatively unviolated region of which I am speaking. The rivers which rise in it flow with diminished currents in dry seasons, and with augmented volumes of water after heavy rains. They bring down much larger quantities of sediment, and the increasing obstructions to the navigation of the Hudson, which are extending themselves down the channel in proportion as the fields are encroaching upon the forest, give good grounds for the fear of serious injury to the commerce of the important towns on the upper waters of that river, unless measures are taken to prevent the expansion of "improvements" which have already been carried beyond the demands of a wise economy. I have stated, in a general way, the nature of the evils in question, and of the processes by which they are produced; but I shall make their precise character and magnitude better understood by presenting some descriptive and statistical details of facts of actual occurrence. I select for this purpose the southeastern portion of France, not because that territory has suffered more severely than some others, but because its deterioration is comparatively recent, and has been watched and described by very competent and trustworthy observers, whose reports are more easily accessible than those published in other countries.[216] The provinces of Dauphiny, Avignon, and Provence comprise a territory of fourteen or fifteen thousand square miles, bounded northwest by the Isere, northeast and east by the Alps, south by the Mediterranean, west by the Rhone, and extending from 42° to about 45° of north latitude. The surface is generally hilly and even mountainous, and several of the peaks in Dauphiny rise above the limit of perpetual snow. The climate, as compared with that of the United States in the same latitude, is extremely mild. Little snow falls, except upon the higher mountain ranges, the frosts are light, and the summers long, as might, indeed, be inferred from the vegetation; for in the cultivated districts, the vine and the fig everywhere flourish, the olive thrives as far north as 43½°, and upon the coast, grow the orange, the lemon, and the date palm. The forest trees, too, are of southern type, umbrella pines, various species of evergreen oaks, and many other trees and shrubs of persistent broad-leaved foliage, characterizing the landscape. The rapid slope of the mountains naturally exposed these provinces to damage by torrents, and the Romans diminished their injurious effects by erecting, in the beds of ravines, barriers of rocks loosely piled up, which permitted a slow escape of the water, but compelled it to deposit above the dikes the earth and gravel with which it was charged.[217] At a later period the Crusaders brought home from Palestine, with much other knowledge gathered from the wiser Moslems, the art of securing the hillsides and making them productive by terracing and irrigation. The forests which covered the mountains secured an abundant flow of springs, and the process of clearing the soil went on so slowly that, for centuries, neither the want of timber and fuel, nor the other evils about to be depicted, were seriously felt. Indeed, throughout the Middle Ages, these provinces were well wooded, and famous for the fertility and abundance, not only of the low grounds, but of the hills. Such was the state of things at the close of the fifteenth century. The statistics of the seventeenth show that while there had been an increase of prosperity and population in Lower Provence, as well as in the correspondingly situated parts of the other two provinces I have mentioned, there was an alarming decrease both in the wealth and in the population of Upper Provence and Dauphiny, although, by the clearing of the forests, a great extent of plough land and pasturage had been added to the soil before reduced to cultivation. It was found, in fact, that the augmented violence of the torrents had swept away, or buried in sand and gravel, more land than had been reclaimed by clearing; and the taxes computed by fires or habitations underwent several successive reductions in consequence of the gradual abandonment of the wasted soil by its starving occupants. The growth of the large towns on and near the Rhone and the coast, their advance in commerce and industry, and the consequently enlarged demand for agricultural products, ought naturally to have increased the rural population and the value of their lands; but the physical decay of the uplands was such that considerable tracts were deserted altogether, and in Upper Provence, the fires which in 1471 counted 897, were reduced to 747 in 1699, to 728 in 1733, and to 635 in 1776. These facts I take from the _La Provence au point de vue des Bois, des Torrents et des Inondations_, of Charles de Ribbe, one of the highest authorities, and I add further details from the same source. "Commune of Barles, 1707: Two hills have become connected by land slides, and have formed a lake which covers the best part of the soil. 1746: New slides buried twenty houses composing a village, no trace of which is left; more than one third of the land had disappeared. "Monans, 1724: Deserted by its inhabitants and no longer cultivated. "Gueydan, 1760: It appears by records that the best grounds have been swept off since 1756, and that ravines occupy their place. "Digne, 1762: The river Bléone has destroyed the most valuable part of the territory. "Malmaison, 1768: The inhabitants have emigrated, all their fields having been lost." In the case of the commune of St. Laurent du Var, it appears that, after clearings in the Alps, succeeded by others in the common woods of the town, the floods of the torrent Var became more formidable, and had already carried off much land as early as 1708. "The clearing continued, and more soil was swept away in 1761. In 1762, after another destructive inundation, many of the inhabitants emigrated, and in 1765, one half of the territory had been laid waste. "In 1766, the assessor Serraire said to the Assembly: 'As to the damage caused by brooks and torrents, it is impossible to deny its extent. Upper Provence is in danger of total destruction, and the waters which lay it waste threaten also the ruin of the most valuable grounds on the plain below. Villages have been almost submerged by torrents which formerly had not even names, and large towns are on the point of destruction from the same cause.'" In 1776, Viscount Puget thus reported: "The mere aspect of Upper Provence is calculated to appal the patriotic magistrate. One sees only lofty mountains, deep valleys with precipitous sides, rivers with broad beds and little water, impetuous torrents, which in floods lay waste the cultivated land upon their banks and roll huge rocks along their channels; steep and parched hillsides, the melancholy consequences of indiscriminate clearing; villages whose inhabitants, finding no longer the means of subsistence, are emigrating day by day; houses dilapidated to huts, and but a miserable remnant of population." "In a document of the year 1771, the ravages of the torrents were compared to the effects of an earthquake, half the soil in many communes seeming to have been swallowed up. "Our mountains," said the administrators of the province of the Lower Alps in 1792, "present nothing but a surface of stony tufa; clearing is still going on, and the little rivulets are becoming torrents. Many communes have lost their harvests, their flocks, and their houses by floods. The washing down of the mountains is to be ascribed to the clearings and the practice of burning them over." These complaints, it will be seen, all date before the Revolution, but the desolation they describe has since advanced with still swifter steps. Surell--whose valuable work, _Étude sur les Torrents des Hautes Alpes_, published in 1841, presents the most appalling picture of the desolations of the torrent, and, at the same time, the most careful studies of the history and essential character of this great evil--in speaking of the valley of Dévoluy, on page 152, says: "Everything concurs to show that it was anciently wooded. In its peat bogs are found buried trunks of trees, monuments of its former vegetation. In the framework of old houses, one sees enormous timber, which is no longer to be found in the district. Many localities, now completely bare, still retain the name of 'wood,' and one of them is called, in old deeds, _Comba nigra_ [Black forest or dell], on account of its dense woods. These and many other proofs confirm the local traditions which are unanimous on this point. "There, as everywhere in the Upper Alps, the clearings began on the flanks of the mountains, and were gradually extended into the valleys and then to the highest accessible peaks. Then followed the Revolution, and caused the destruction of the remainder of the trees which had thus far escaped the woodman's axe." In a note to this passage, the writer says: "Several persons have told me that they had lost flocks of sheep, by straying, in the forests of Mont Auroux, which covered the flanks of the mountain from La Cluse to Agnères. These declivities are now as bare as the palm of the hand." The ground upon the steep mountains being once bared of trees, and the underwood killed by the grazing of horned cattle, sheep, and goats, every depression becomes a watercourse. "Every storm," says Surell, page 153, "gives rise to a new torrent. Examples of such are shown, which, though not yet three years old, have laid waste the finest fields of their valleys, and whole villages have narrowly escaped being swept into ravines formed in the course of a few hours. Sometimes the flood pours in a sheet over the surface, without ravine or even bed, and ruins extensive grounds, which are abandoned forever." I cannot follow Surell in his description and classification of torrents, and I must refer the reader to his instructive work for a full exposition of the theory of the subject. In order, however, to show what a concentration of destructive energies may be effected by felling the woods that clothe and support the sides of mountain abysses, I cite his description of a valley descending from the Col Isoard, which he calls "a complete type of a basin of reception," that is, a gorge which serves as a common point of accumulation and discharge for the waters of several lateral torrents. "The aspect of the monstrous channel," says he, "is frightful. Within a distance of less than three kilomètres [= one mile and seven eighths English], more than sixty torrents hurl into the depths of the gorge the debris torn from its two flanks. The smallest of these secondary torrents, if transferred to a fertile valley, would be enough to ruin it." The eminent political economist Blanqui, in a memoir read before the Academy of Moral and Political Science on the 25th of November, 1843, thus expresses himself: "Important as are the causes of impoverishment already described, they are not to be compared to the consequences which have followed from the two inveterate evils of the Alpine provinces of France, the extension of clearing and the ravages of torrents. * * The most important result of this destruction is this: that the agricultural capital, or rather the ground itself--which, in a rapidly increasing degree, is daily swept away by the waters--is totally lost. Signs of unparalleled destitution are visible in all the mountain zone, and the solitudes of those districts are assuming an indescribable character of sterility and desolation. The gradual destruction of the woods has, in a thousand localities, annihilated at once the springs and the fuel. Between Grenoble and Briançon in the valley of the Romanche, many villages are so destitute of wood that they are reduced to the necessity of baking their bread with sun-dried cowdung, and even this they can afford to do but once a year. This bread becomes so hard that it can be cut only with an axe, and I have myself seen a loaf of bread in September, at the kneading of which I was present the January previous. "Whoever has visited the valley of Barcelonette, those of Embrun, and of Verdun, and that Arabia Petræa of the department of the Upper Alps, called Dévoluy, knows that there is no time to lose, that in fifty years from this date France will be separated from Savoy, as Egypt from Syria, by a desert."[218] It deserves to be specially noticed that the district here referred to, though now among the most hopelessly waste in France, was very productive even down to so late a period as the commencement of the French Revolution. Arthur Young, writing in 1789, says: "About Barcelonette and in the highest parts of the mountains, the hill pastures feed a million of sheep, besides large herds of other cattle;" and he adds: "With such a soil, and in such a climate we are not to suppose a country barren because it is mountainous. The valleys I have visited are, in general, beautiful."[219] He ascribes the same character to the provinces of Dauphiny, Provence, and Auvergne, and, though he visited, with the eye of an attentive and practised observer, many of the scenes since blasted with the wild desolation described by Blanqui, the Durance and a part of the course of the Loire are the only streams he mentions as inflicting serious injury by their floods. The ravages of the torrents had, indeed, as we have seen, commenced earlier in some other localities, but we are authorized to infer that they were, in Young's time, too limited in range, and relatively too insignificant, to require notice in a general view of the provinces where they have now ruined so large a proportion of the soil. But I resume my citations. "I do not exaggerate," says Blanqui. "When I shall have finished my excursion and designated localities by their names, there will rise, I am sure, more than one voice from the spots themselves, to attest the rigorous exactness of this picture of their wretchedness. I have never seen its equal even in the Kabyle villages of the province of Constantine; for there you can travel on horseback, and you find grass in the spring, whereas in more than fifty communes in the Alps there is absolutely nothing. "The clear, brilliant, Alpine sky of Embrun, of Gap, of Barcelonette, and of Digne, which for months is without a cloud, produces droughts interrupted only by diluvial rains like those of the tropics. The abuse of the right of pasturage and the felling of the woods have stripped the soil of all its grass and all its trees, and the scorching sun bakes it to the consistence of porphyry. When moistened by the rain, as it has neither support nor cohesion, it rolls down to the valleys, sometimes in floods resembling black, yellow, or reddish lava, sometimes in streams of pebbles, and even huge blocks of stone, which pour down with a frightful roar, and in their swift course exhibit the most convulsive movements. If you overlook from an eminence one of these landscapes furrowed with so many ravines, it presents only images of desolation and of death. Vast deposits of flinty pebbles, many feet in thickness, which have rolled down and spread far over the plain, surround large trees, bury even their tops, and rise above them, leaving to the husbandman no longer a ray of hope. One can imagine no sadder spectacle than the deep fissures in the flanks of the mountains, which seem to have burst forth in eruption to cover the plains with their ruins. These gorges, under the influence of the sun which cracks and shivers to fragments the very rocks, and of the rain which sweeps them down, penetrate deeper and deeper into the heart of the mountain, while the beds of the torrents issuing from them are sometimes raised several feet, in a single year, by the debris, so that they reach the level of the bridges, which, of course, are then carried off. The torrent beds are recognized at a great distance, as they issue from the mountains, and they spread themselves over the low grounds, in fan-shaped expansions, like a mantle of stone, sometimes ten thousand feet wide, rising high at the centre, and curving toward the circumference till their lower edges meet the plain. "Such is their aspect in dry weather. But no tongue can give an adequate description of their devastations in one of those sudden floods which resemble, in almost none of their phenomena, the action of ordinary river water. They are now no longer overflowing brooks, but real seas, tumbling down in cataracts, and rolling before them blocks of stone, which are hurled forward by the shock of the waves like balls shot out by the explosion of gunpowder. Sometimes ridges of pebbles are driven down when the transporting torrent does not rise high enough to show itself, and then the movement is accompanied with a roar louder than the crash of thunder. A furious wind precedes the rushing water and announces its approach. Then comes a violent eruption, followed by a flow of muddy waves, and after a few hours all returns to the dreary silence which at periods of rest marks these abodes of desolation. "This is but an imperfect sketch of this scourge of the Alps. Its devastations are increasing with the progress of clearing, and are every day turning a portion of our frontier departments into barren wastes. "The unfortunate passion for clearing manifested itself at the beginning of the French Revolution, and has much increased under the pressure of immediate want. It has now reached an extreme point, and must be speedily checked, or the last inhabitant will be compelled to retreat when the last tree falls. "The elements of destruction are increasing in violence. Rivers might be mentioned whose beds have been raised ten feet in a single year. The devastation advances in geometrical progression as the higher slopes are bared of their wood, and 'the ruin from above,' to use the words of a peasant, 'helps to hasten the desolation below.' "The Alps of Provence present a terrible aspect. In the more equable climate of Northern France, one can form no conception of those parched mountain gorges where not even a bush can be found to shelter a bird, where, at most, the wanderer sees in summer here and there a withered lavender, where all the springs are dried up, and where a dead silence, hardly broken by even the hum of an insect, prevails. But if a storm bursts forth, masses of water suddenly shoot from the mountain heights into the shattered gulfs, waste without irrigating, deluge without refreshing the soil they overflow in their swift descent, and leave it even more seared than it was from want of moisture. Man at last retires from the fearful desert, and I have, the present season, found not a living soul in districts where I remember to have enjoyed hospitality thirty years ago." In 1853, ten years after the date of Blanqui's memoir, M. de Bonville, prefect of the Lower Alps, addressed to the Government a report in which the following passages occur: "It is certain that the productive mould of the Alps, swept off by the increasing violence of that curse of the mountains, the torrents, is daily diminishing with fearful rapidity. All our Alps are wholly, or in large proportion, bared of wood. Their soil, scorched by the sun of Provence, cut up by the hoofs of the sheep, which, not finding on the surface the grass they require for their sustenance, scratch the ground in search of roots to satisfy their hunger, is periodically washed and carried off by melting snows and summer storms. "I will not dwell on the effects of the torrents. For sixty years they have been too often depicted to require to be further discussed, but it is important to show that their ravages are daily extending the range of devastation. The bed of the Durance, which now in some places exceeds 2,000 mètres [about 6,600 feet, or a mile and a quarter] in width, and, at ordinary times, has a current of water less than 10 mètres [about 33 feet] wide, shows something of the extent of the damage.[220] Where, ten years ago, there were still woods and cultivated grounds to be seen, there is now but a vast torrent: there is not one of our mountains which has not at least one torrent, and new ones are daily forming. "An indirect proof of the diminution of the soil is to be found in the depopulation of the country. In 1852, I reported to the General Council that, according to the census of that year, the population of the department of the Lower Alps had fallen off no less than 5,000 souls in the five years between 1846 and 1851. "Unless prompt and energetic measures are taken, it is easy to fix the epoch when the French Alps will be but a desert. The interval between 1851 and 1856 will show a further decrease of population. In 1862, the ministry will announce a continued and progressive reduction in the number of acres devoted to agriculture; every year will aggravate the evil, and, in a half century, France will count more ruins, and a department the less." Time has verified the predictions of De Bonville. The later census returns show a progressive diminution in the population of the departments of the Lower Alps, the Isère, the Drome, Ariège, the Upper and the Lower Pyrenees, the Lozère, the Ardennes, the Doubs, the Vosges, and, in short, in all the provinces formerly remarkable for their forests. This diminution is not to be ascribed to a passion for foreign emigration, as in Ireland, and in parts of Germany and of Italy; it is simply a transfer of population from one part of the empire to another, from soils which human folly has rendered uninhabitable, by ruthlessly depriving them of their natural advantages and securities, to provinces where the face of the earth was so formed by nature as to need no such safeguards, and where, consequently, she preserves her outlines in spite of the wasteful improvidence of man.[221] Highly colored as these pictures seem, they are not exaggerated, although the hasty tourist through Southern France and Northern Italy, finding little in his high road experiences to justify them, might suppose them so. The lines of communication by locomotive train and diligence lead generally over safer ground, and it is only when they ascend the Alpine passes and traverse the mountain chains, that scenes somewhat resembling those just described fall under the eye of the ordinary traveller. But the extension of the sphere of devastation, by the degradation of the mountains and the transportation of their debris, is producing analogous effects upon the lower ridges of the Alps and the plains which skirt them; and even now one needs but an hour's departure from some great thoroughfares to reach sites where the genius of destruction revels as wildly as in the most frightful of the abysses which Blanqui has painted.[222] There is one effect of the action of torrents which few travellers on the Continent are heedless enough to pass without notice. I refer to the elevation of the beds of mountain streams in consequence of the deposit of the debris with which they are charged. To prevent the spread of sand and gravel over the fields and the deluging overflow of the raging waters, the streams are confined by walls and embankments, which are gradually built higher and higher as the bed of the torrent is raised, so that, to reach a river, you ascend from the fields beside it; and sometimes the ordinary level of the stream is above the streets and even the roofs of the towns through which it passes.[223] The traveller who visits the depths of an Alpine ravine, observes the length and width of the gorge and the great height and apparent solidity of the precipitous walls which bound it, and calculates the mass of rock required to fill the vacancy, can hardly believe that the humble brooklet which purls at his feet has been the principal agent in accomplishing this tremendous erosion. Closer observation will often teach him, that the seemingly unbroken rock which overhangs the valley is full of cracks and fissures, and really in such a state of disintegration that every frost must bring down tons of it. If he compute the area of the basin which finds here its only discharge, he will perceive that a sudden thaw of the winter's deposit of snow, or one of those terrible discharges of rain so common in the Alps, must send forth a deluge mighty enough to sweep down the largest masses of gravel and of rock.[224] The simple measurement of the cubical contents of the semi-circular hillock which he climbed before he entered the gorge, the structure and composition of which conclusively show that it must have been washed out of this latter by torrential action, will often account satisfactorily for the disposal of most of the matter which once filled the ravine. It must further be remembered, that every inch of the violent movement of the rocks is accompanied with crushing concussion, or, at least, with great abrasion, and, as you follow the deposit along the course of the waters which transport it, you find the stones gradually rounding off in form, and diminishing in size until they pass successively into gravel, sand, impalpable slime. I do not mean to assert that all the rocky valleys of the Alps have been produced by the action of torrents resulting from the destruction of the forests. All the greater, and many of the smaller channels, by which that chain is drained, owe their origin to higher causes. They are primitive fissures, ascribable to disruption in upheaval or other geological convulsion, widened and scarped, and often even polished, so to speak, by the action of glaciers during the ice period, and but little changed in form by running water in later eras.[225] In these valleys of ancient formation, which extend into the very heart of the mountains, the streams, though rapid, have lost the true torrential character, if, indeed, they ever possessed it. Their beds have become approximately constant, and their walls no longer crumble and fall into the waters that wash their bases. The torrent-worn ravines, of which I have spoken, are of later date, and belong more properly to what may be called the crust of the Alps, consisting of loose rocks, of gravel, and of earth, strewed along the surface of the great declivities of the central ridge, and accumulated thickly between their solid buttresses. But it is on this crust that the mountaineer dwells. Here are his forests, here his pastures, and the ravages of the torrent both destroy his world, and convert it into a source of overwhelming desolation to the plains below. _Transporting Power of Rivers._ An instance that fell under my own observation in 1857, will serve to show something of the eroding and transporting power of streams which, in these respects, fall incalculably below the torrents of the Alps. In a flood of the Ottaquechee, a small river which flows through Woodstock, Vermont, a milldam on that stream burst, and the sediment with which the pond was filled, estimated after careful measurement at 13,000 cubic yards, was carried down by the current. Between this dam and the slack water of another, four miles below, the bed of the stream, which is composed of pebbles interspersed in a few places with larger stones, is about sixty-five feet wide, though, at low water, the breadth of the current is considerably less. The sand and fine gravel were smoothly and evenly distributed over the bed to a width of fifty-five or sixty feet, and for a distance of about two miles, except at two or three intervening rapids, filled up all the interstices between the stones, covering them to the depth of nine or ten inches, so as to present a regularly formed concave channel, lined with sand, and reducing the depth of water, in some places, from five or six feet to fifteen or eighteen inches. Observing this deposit after the river had subsided and become so clear that the bottom could be seen, I supposed that the next flood would produce an extraordinary erosion of the banks and some permanent changes in the channel of the stream, in consequence of the elevation of the bed and the filling up of the spaces between the stones through which formerly much water had flowed; but no such result followed. The spring freshet of the next year entirely washed out the sand its predecessor had deposited, carried it to ponds and still-water reaches below, and left the bed of the river almost precisely in its former condition, though, of course, with the slight displacement of the pebbles which every flood produces in the channels of such streams. The pond, though often previously discharged by the breakage of the dam, had then been undisturbed for about twenty-five years, and its contents consisted almost entirely of sand, the rapidity of the current in floods being such that it would let fall little lighter sediment, even above an obstruction like a dam. The quantity I have mentioned evidently bears a very inconsiderable proportion to the total erosion of the stream during that period, because the wash of the banks consists chiefly of fine earth rather than of sand, and after the pond was once filled, or nearly so, even this material could no longer be deposited in it. The fact of the complete removal of the deposit I have described between the two dams in a single freshet, shows that, in spite of considerable obstruction from roughness of bed, large quantities of sand may be taken up and carried off by streams of no great rapidity of inclination; for the whole descent of the bed of the river between the two dams--a distance of four miles--is but sixty feet, or fifteen feet to the mile. _The Po and its Deposits._ The current of the river Po, for a considerable distance after its volume of water is otherwise sufficient for continuous navigation, is too rapid for that purpose until near Piacenza, where its velocity becomes too much reduced to transport great quantities of mineral matter, except in a state of minute division. Its southern affluents bring down from the Apennines a large quantity of fine earth from various geological formations, while its Alpine tributaries west of the Ticino are charged chiefly with rock ground down to sand or gravel.[226] The bed of the river has been somewhat elevated by the deposits in its channel, though not by any means above the level of the adjacent plains as has been so often represented. The dikes, which confine the current at high water, at the same time augment its velocity and compel it to carry most of its sediment to the Adriatic. It has, therefore, raised neither its own channel nor its alluvial shores, as it would have done if it had remained unconfined. But, as the surface of the water in floods is from six to fifteen feet above the general level of its banks, the Po can, at that period, receive no contributions of earth from the washing of the fields of Lombardy, and there is no doubt that a large proportion of the sediment it now deposits at its mouth descended from the Alps in the form of rock, though reduced by the grinding action of the waters, in its passage seaward, to the condition of fine sand, and often of silt.[227] We know little of the history of the Po, or of the geography of the coast near the point where it enters the Adriatic, at any period more than twenty centuries before our own. Still less can we say how much of the plains of Lombardy had been formed by its action, combined with other causes, before man accelerated its levelling operations by felling the first woods on the mountains whence its waters are derived. But we know that since the Roman conquest of Northern Italy, its deposits have amounted to a quantity which, if recemented into rock, recombined into gravel, common earth, and vegetable mould, and restored to the situations where eruption or upheaval originally placed, or vegetation deposited it, would fill up hundreds of deep ravines in the Alps and Apennines, change the plan and profile of their chains, and give their southern and northern faces respectively a geographical aspect very different from that they now present. Ravenna, forty miles south of the principal mouth of the Po, was built like Venice, in a lagoon, and the Adriatic still washed its walls at the commencement of the Christian era. The mud of the Po has filled up the lagoon, and Ravenna is now four miles from the sea. The town of Adria, which lies between the Po and the Adige, at the distance of some four or five miles from each, was once a harbor famous enough to have given its name to the Adriatic sea, and it was still a seaport in the time of Augustus. The combined action of the two rivers has so advanced the coast line that Adria is now about fourteen miles inland, and, in other places, the deposits made within the same period by these and other neighboring streams have a width of twenty miles. What proportion of the earth with which they are charged these rivers have borne out into deep water, during the last two thousand years, we do not know, but as they still transport enormous quantities, as the North Adriatic appears to have shoaled rapidly, and as long islands, composed in great part of fluviatile deposits, have formed opposite their mouths, it must evidently have been very great. The floods of the Po occur but once, or sometimes twice in a year.[228] At other times, its waters are comparatively limpid and seem to hold no great amount of mud or fine sand in mechanical suspension; but at high water it contains a large proportion of solid matter, and according to Lombardini, it annually transports to the shores of the Adriatic not less than 42,760,000 cubic mètres, or very nearly 55,000,000 cubic yards, which carries the coast line out into the sea at the rate of more than 200 feet in a year.[229] The depth of the annual deposit is stated at eighteen centimètres, or rather more than seven inches, and it would cover an area of not much less than ninety square miles with a layer of that thickness. The Adige, also, brings every year to the Adriatic many million cubic yards of Alpine detritus, and the contributions of the Brenta from the same source are far from inconsiderable. The Adriatic, however, receives but a small proportion of the soil and rock washed away from the Italian slope of the Alps and the northern declivity of the Apennines by torrents. Nearly the whole of the debris thus removed from the southern face of the Alps between Monte Rosa and the sources of the Adda--a length of watershed not less than one hundred and fifty miles--is arrested by the still waters of the Lakes Maggiore and Como, and some smaller lacustrine reservoirs, and never reaches the sea. The Po is not continuously embanked except for the lower half of its course. Above Piacenza, therefore, it spreads and deposits sediment over a wide surface, and the water withdrawn from it for irrigation at lower points, as well as its inundations in the occasional ruptures of its banks, carry over the adjacent soil a large amount of slime. If we add to the estimated annual deposits of the Po at its mouth, the earth and sand transported to the sea by the Adige, the Brenta, and other less important streams, the prodigious mass of detritus swept into Lago Maggiore by the Tosa, the Maggia, and the Ticino, into the lake of Como by the Maira and the Adda, into the lake of Garda by its affluents, and the yet vaster heaps of pebbles, gravel, and earth permanently deposited by the torrents near their points of eruption from mountain gorges, or spread over the wide plains at lower levels, we may safely assume that we have an aggregate of not less than four times the quantity carried to the Adriatic by the Po, or 220,000,000 cubic yards of solid matter, abstracted every year from the Italian Alps and the Apennines, and removed out of their domain by the force of running water.[230] The present rate of deposit at the mouth of the Po has continued since the year 1600, the previous advance of the coast, after the year 1200, having been only one third as rapid. The great increase of erosion and transport is ascribed by Lombardini chiefly to the destruction of the forests in the basin of that river and the valleys, of its tributaries, since the beginning of the seventeenth century.[231] We have no data to show the rate of deposit in any given century before the year 1200, and it doubtless varied according to the progress of population and the consequent extension of clearing and cultivation. The transporting power of torrents is greatest soon after their formation, because at that time their points of delivery are lower, and, of course, their general slope and velocity more rapid, than after years of erosion above, and deposit below, have depressed the beds of their mountain valleys, and elevated the channels of their lower course. Their eroding action also is most powerful at the same period, both because their mechanical force is then greatest, and because the loose earth and stones of freshly cleared forest ground are most easily removed. Many of the Alpine valleys west of the Ticino--that of the Dora Baltea for instance--were nearly stripped of their forests in the days of the Roman empire, others in the Middle Ages, and, of course, there must have been, at different periods before the year 1200, epochs when the erosion and transportation of solid matter from the Alps and the Apennines were as great as since the year 1600. Upon the whole, we shall not greatly err if we assume that, for a period of not less than two thousand years, the walls of the basin of the Po--the Italian slope of the Alps, and the northern and northeastern declivities of the Apennines--have annually sent down into the Adriatic, the lakes, and the plains, not less than 150,000,000 cubic yards of earth and disintegrated rock. We have, then, an aggregate of 300,000,000,000 cubic yards of such material, which, allowing to the mountain surface in question an area of 50,000,000,000 square yards, would cover the whole to the depth of six yards.[232] There are very large portions of this area, where, as we know from ancient remains--roads, bridges, and the like--from other direct testimony, and from geological considerations, very little degradation has taken place within twenty centuries, and hence the quantity to be assigned to localities where the destructive causes have been most active is increased in proportion. If this vast mass of pulverized rock and earth were restored to the localities from which it was derived, it certainly would not obliterate valleys and gorges hollowed out by great geological causes, but it would reduce the length and diminish the depth of ravines of later formation, modify the inclination of their walls, reclothe with earth many bare mountain ridges, essentially change the line of junction between plain and mountain, and carry back a long reach of the Adriatic coast many miles to the west.[233] It is, indeed, not to be supposed that all the degradation of the mountains is due to the destruction of the forests--that the flanks of every Alpine valley in Central Europe below the snow line were once covered with earth and green with woods, but there are not many particular cases, in which we can, with certainty, or even with strong probability, affirm the contrary. We cannot measure the share which human action has had in augmenting the intensity of causes of mountain degradation, but we know that the clearing of the woods has, in some cases, produced within two or three generations, effects as blasting as those generally ascribed to geological convulsions, and has laid waste the face of the earth more hopelessly than if it had been buried by a current of lava or a shower of volcanic sand. Now torrents are forming every year in the Alps. Tradition, written records, and analogy concur to establish the belief that the ruin of most of the now desolate valleys in those mountains is to be ascribed to the same cause, and authentic descriptions of the irresistible force of the torrent show that, aided by frost and heat, it is adequate to level Mont Blanc and Monte Rosa themselves, unless new upheavals shall maintain their elevation. It has been contended that all rivers which take their rise in mountains originated in torrents. These, it is said, have lowered the summits by gradual erosion, and, with the material thus derived, have formed shoals in the sea which once beat against the cliffs; then, by successive deposits, gradually raised them above the surface, and finally expanded them into broad plains traversed by gently flowing streams. If we could go back to earlier geological periods, we should find this theory often verified, and we cannot fail to see that the torrents go on at the present hour, depressing still lower the ridges of the Alps and the Apennines, raising still higher the plains of Lombardy and Provence, extending the coast still farther into the Adriatic and the Mediterranean, reducing the inclination of their own beds and the rapidity of their flow, and thus tending to become river-like in character. There are cases where torrents cease their ravages of themselves, in consequence of some change in the condition of the basin where they originate, or of the face of the mountain at a higher level, while the plain or the sea below remains in substantially the same state as before. If a torrent rises in a small valley containing no great amount of earth and of disintegrated or loose rock, it may, in the course of a certain period, wash out all the transportable material, and if the valley is then left with solid walls, it will cease to furnish debris to be carried down by floods. If, in this state of things, a new channel be formed at an elevation above the head of the valley, it may divert a part, or even the whole of the rain water and melted snow which would otherwise have flowed into it, and the once furious torrent now sinks to the rank of a humble and harmless brooklet. "In traversing this department," says Surell, "one often sees, at the outlet of a gorge, a flattened hillock, with a fan-shaped outline and regular slopes; it is the bed of dejection of an ancient torrent. It sometimes requires long and careful study to detect the primitive form, masked as it is by groves of trees, by cultivated fields, and often by houses, but, when examined closely, and from different points of view, its characteristic figure manifestly appears, and its true history cannot be mistaken. Along the hillock flows a streamlet, issuing from the ravine, and quietly watering the fields. This was originally a torrent, and in the background may be discovered its mountain basin. Such _extinguished_ torrents, if I may use the expression, are numerous."[234] But for the intervention of man and domestic animals, these latter beneficent revolutions would occur more frequently, proceed more rapidly. The new scarped mountains, the hillocks of debris, the plains elevated by sand and gravel spread over them, the shores freshly formed by fluviatile deposits, would clothe themselves with shrubs and trees, the intensity of the causes of degradation would be diminished, and nature would thus regain her ancient equilibrium. But these processes, under ordinary circumstances, demand, not years, generations, but centuries;[235] and man, who even now finds scarce breathing room on this vast globe, cannot retire from the Old World to some yet undiscovered continent, and wait for the slow action of such causes to replace, by a new creation, the Eden he has wasted. _Mountain Slides._ I have said that the mountainous regions of the Atlantic States of the American Union are exposed to similar ravages, and I may add that there is, in some cases, reason to apprehend from the same cause even more appalling calamities than those which I have yet described. The slide in the Notch of the White Mountains, by which the Willey family lost their lives, is an instance of the sort I refer to, though I am not able to say that in this particular case, the slip of the earth and rock was produced by the denudation of the surface. It may have been occasioned by this cause, or by the construction of the road through the Notch, the excavations for which, perhaps, cut through the buttresses that supported the sloping strata above. Not to speak of the fall of earth when the roots which held it together, and the bed of leaves and mould which sheltered it both from disintegrating frost and from sudden drenching and dissolution by heavy showers, are gone, it is easy to see that, in a climate with severe winters, the removal of the forest, and, consequently, of the soil it had contributed to form, might cause the displacement and descent of great masses of rock. The woods, the vegetable mould, and the soil beneath, protect the rocks they cover from the direct action of heat and cold, and from the expansion and contraction which accompany them. Most rocks, while covered with earth, contain a considerable quantity of water.[236] A fragment of rock pervaded with moisture cracks and splits, if thrown into a furnace, and sometimes with a loud detonation; and it is a familiar observation that the fire, in burning over newly cleared lands, breaks up and sometimes almost pulverizes the stones. This effect is due partly to the unequal expansion of the stone, partly to the action of heat on the water it contains in its pores. The sun, suddenly let in upon rock which had been covered with moist earth for centuries, produces more or less disintegration in the same way, and the stone is also exposed to chemical influences from which it was sheltered before. But in the climate of the United States as well as of the Alps, frost is a still more powerful agent in breaking up mountain masses. The soil that protects the lime and sand stone, the slate and the granite from the influence of the sun, also prevents the water which filters into their crevices and between their strata from freezing in the hardest winters, and the moisture descends, in a liquid form, until it escapes in springs, or passes off by deep subterranean channels. But when the ridges are laid bare, the water of the autumnal rains fills the minutest pores and veins and fissures and lines of separation of the rocks, then suddenly freezes, and bursts asunder huge, and apparently solid blocks of adamantine stone.[237] Where the strata are inclined at a considerable angle, the freezing of a thin film of water over a large interstratal area might occasion a slide that should cover miles with its ruins; and similar results might be produced by the simple hydrostatic pressure of a column of water, admitted by the removal of the covering of earth to flow into a crevice faster than it could escape through orifices below. Earth or rather mountain slides, compared to which the catastrophe that buried the Willey family in New Hampshire was but a pinch of dust, have often occurred in the Swiss Italian, and French Alps. The land slip, which overwhelmed and covered to the depth of seventy feet, the town of Plurs in the valley of the Maira, on the night of the 4th of September, 1618, sparing not a soul of a population of 2,430 inhabitants, is one of the most memorable of these catastrophes, and the fall of the Rossberg or Rufiberg, which destroyed the little town of Goldau in Switzerland, and 450 of its people, on the 2d of September, 1806, is almost equally celebrated. In 1771, according to Wessely, the mountain peak Piz, near Alleghe in the province of Belluno, slipped into the bed of the Cordevole, a tributary of the Piave, destroying in its fall three hamlets and sixty lives. The rubbish filled the valley for a distance of nearly two miles, and, by damming up the waters of the Cordevole, formed a lake about three miles long, and a hundred and fifty feet deep, which still subsists, though reduced to half its original length by the wearing down of its outlet.[238] On the 14th of February, 1855, the hill of Belmonte, a little below the parish of San Stefano, in Tuscany, slid into the valley of the Tiber, which consequently flooded the village to the depth of fifty feet, and was finally drained off by a tunnel. The mass of debris is stated to have been about 3,500 feet long, 1,000 wide, and not less than 600 high.[239] Such displacements of earth and rocky strata rise to the magnitude of geological convulsions, but they are of so rare occurrence in countries still covered by the primitive forest, so common where the mountains have been stripped of their native covering, and, in many cases, so easily explicable by the drenching of incohesive earth from rain, or the free admission of water between the strata of rocks--both of which a coating of vegetation would have prevented--that we are justified in ascribing them for the most part to the same cause as that to which the destructive effects of mountain torrents are chiefly due--the felling of the woods. In nearly every case of this sort the circumstances of which are known, the immediate cause of the slip has been, either an earthquake, the imbibition of water in large quantities by bare earth, or its introduction between or beneath solid strata. If water insinuates itself between the strata, it creates a sliding surface, or it may, by its expansion in freezing, separate beds of rock, which had been nearly continuous before, widely enough to allow the gravitation of the superincumbent mass to overcome the resistance afforded by inequalities of face and by friction; if it finds its way beneath hard earth or rock reposing on clay or other bedding of similar properties, it converts the supporting layer into a semi-fluid mud, which opposes no obstacle to the sliding of the strata above. The upper part of the mountain which buried Goldau was composed of a hard but brittle conglomerate, called _nagelflue_, resting on an unctuous clay, and inclining rapidly toward the village. Much earth remained upon the rock, in irregular masses, but the woods had been felled, and the water had free access to the surface, and to the crevices which sun and frost had already produced in the rock, and of course, to the slimy stratum beneath. The whole summer of 1806 had been very wet, and an almost incessant deluge of rain had fallen the day preceding the catastrophe, as well as on that of its occurrence. All conditions then, were favorable to the sliding of the rock, and, in obedience to the laws of gravitation, it precipitated itself into the valley as soon as its adhesion to the earth beneath it was destroyed by the conversion of the latter into a viscous paste. The mass that fell measured between two and a half and three miles in length by one thousand feet in width, and its average thickness is thought to have been about a hundred feet. The highest portion of the mountain was more than three thousand feet above the village, and the momentum acquired by the rocks and earth in their descent carried huge blocks of stone far up the opposite slope of the Rigi. The Piz, which fell into the Cordevole, rested on a steeply inclined stratum of limestone, with a thin layer of calcareous marl intervening, which, by long exposure to frost and the infiltration of water, had lost its original consistence, and become a loose and slippery mass instead of a cohesive and tenacious bed. _Protection against fall of Rocks and Avalanches by Trees._ Forests often subserve a valuable purpose in preventing the fall of rocks, by mere mechanical resistance. Trees, as well as herbaceous vegetation, grow in the Alps upon declivities of surprising steepness of inclination, and the traveller sees both luxuriant grass and flourishing woods on slopes at which the soil, in the dry air of lower regions, would crumble and fall by the weight of its own particles. When loose rocks lie scattered on the face of these declivities, they are held in place by the trunks of the trees, and it is very common to observe a stone that weighs hundreds of pounds, perhaps even tons, resting against a tree which has stopped its progress just as it was beginning to slide down to a lower level. When a forest in such a position is cut, these blocks lose their support, and a single wet season is enough not only to bare the face of a considerable extent of rock, but to cover with earth and stone many acres of fertile soil below.[240] In Switzerland and other snowy and mountainous countries, forests render a most important service by preventing the formation and fall of destructive avalanches, and in many parts of the Alps exposed to this catastrophe, the woods are protected, though too often ineffectually, by law. No forest, indeed, could arrest a large avalanche once in motion, but the mechanical resistance afforded by the trees prevents their formation, both by obstructing the wind, which gives to the dry snow of the _Staub-Lawine_, or dust avalanche, its first impulse, and by checking the disposition of moist snow to gather itself into what is called the _Rutsch-Lawine_, or sliding avalanche. Marschand states that, the very first winter after the felling of the trees on the higher part of a declivity between Saanen and Gsteig where the snow had never been known to slide, an avalanche formed itself in the clearing, thundered down the mountain, and overthrew and carried with it a hitherto unviolated forest to the amount of nearly a million cubic feet of timber.[241] The path once opened down the flanks of the mountain, the evil is almost beyond remedy. The snow sometimes carries off the earth from the face of the rock, or, if the soil is left, fresh slides every winter destroy the young plantations, and the restoration of the wood becomes impossible. The track widens with every new avalanche. Dwellings and their occupants are buried in the snow, or swept away by the rushing mass, or by the furious blasts it occasions through the displacement of the air; roads and bridges are destroyed; rivers blocked up, which swell till they overflow the valley above, and then, bursting their snowy barrier, flood the fields below with all the horrors of a winter inundation.[242] _Principal Causes of the Destruction of the Forest._ The needs of agriculture are the most familiar cause of the destruction of the forest in new countries; for not only does an increasing population demand additional acres to grow the vegetables which feed it and its domestic animals, but the slovenly husbandry of the border settler soon exhausts the luxuriance of his first fields, and compels him to remove his household gods to a fresher soil. With growing numbers, too, come the many arts for which wood is the material. The demands of the near and the distant market for this product excite the cupidity of the hardy forester, and a few years of that wild industry of which Springer's "Forest Life and Forest Trees" so vividly depicts the dangers and the triumphs, suffice to rob the most inaccessible glens of their fairest ornaments. The value of timber increases with its dimensions in almost geometrical proportion, and the tallest, most vigorous, and most symmetrical trees fall the first sacrifice. This is a fortunate circumstance for the remainder of the wood; for the impatient lumberman contents himself with felling a few of the best trees, and then hurries on to take his tithe of still virgin groves. The unparalleled facilities for internal navigation, afforded by the numerous rivers of the present and former British colonial possessions in North America, have proved very fatal to the forests of that continent. Quebec has become a centre for a lumber trade, which, in the bulk of its material, and, consequently, in the tonnage required for its transportation, rivals the commerce of the greatest European cities. Immense rafts are collected at Quebec from the great Lakes, from the Ottawa, and from all the other tributaries which unite to swell the current of the St. Lawrence and help it to struggle against its mighty tides.[243] Ships, of burden formerly undreamed of, have been built to convey the timber to the markets of Europe, and during the summer months the St. Lawrence is almost as crowded with vessels as the Thames.[244] Of late, Chicago, in Illinois, has been one of the greatest lumber as well as grain depots of the United States, and it receives and distributes contributions from all the forests in the States washed by Lake Michigan, as well as from some more distant points. The operations of the lumberman involve other dangers to the woods besides the loss of the trees felled by him. The narrow clearings around his _shanties_[245] form openings which let in the wind, and thus sometimes occasion the overthrow of thousands of trees, the fall of which dams up small streams, and creates bogs by the spreading of the waters, while the decaying trunks facilitate the multiplication of the insects which breed in dead wood, and are, some of them, injurious to living trees. The escape and spread of camp fires, however, is the most devastating of all the causes of destruction that find their origin in the operations of the lumberman. The proportion of trees fit for industrial uses is small in all primitive woods. Only these fall before the forester's axe, but the fire destroys, indiscriminately, every age and every species of tree.[246] While, then, without much injury to the younger growths, the native forest will bear several "cuttings over" in a generation--for the increasing value of lumber brings into use, every four or five years, a quality of timber which had been before rejected as unmarketable--a fire may render the declivity of a mountain unproductive for a century.[247] _American Forest Trees._ The remaining forests of the Northern States and of Canada no longer boast the mighty pines which almost rivalled the gigantic Sequoia of California; and the growth of the larger forest trees is so slow, after they have attained to a certain size, that if every pine and oak were spared for two centuries, the largest now standing would not reach the stature of hundreds recorded to have been cut within two or three generations.[248] Dr. Williams, who wrote about sixty years ago, states the following as the dimensions of "such trees as are esteemed large ones of their kind in that part of America" [Vermont], qualifying his account with the remark that his measurements "do not denote the greatest which nature has produced of their particular species, but the greatest which are to be found in most of our towns." Diameter. Height. Pine, 6 feet, 247 feet. Maple, 5 " 9 inches, } Buttonwood, 5 " 6 " } Elm, 5 " } Hemlock, 4 " 9 " } Oak, 4 " } From 100 to 200 feet. Basswood, 4 " } Ash, 4 " } Birch, 4 " } He adds a note saying that a white pine was cut in Dunstable, New Hampshire, in the year 1736, the diameter of which was seven feet and eight inches. Dr. Dwight says that a fallen pine in Connecticut was found to measure two hundred and forty-seven feet in height, and adds: "A few years since, such trees were in great numbers along the northern parts of Connecticut River." In another letter, he speaks of the white pine as "frequently six feet in diameter, and two hundred and fifty feet in height," and states that a pine had been cut in Lancaster, New Hampshire, which measured two hundred and sixty-four feet. Emerson wrote in 1846: "Fifty years ago, several trees growing on rather dry land in Blandford, Massachusetts, measured, after they were felled, two hundred and twenty-three feet. All these trees are surpassed by a pine felled at Hanover, New Hampshire, about a hundred years ago, and described as measuring two hundred and seventy-four feet.[249] These descriptions, it will be noticed, apply to trees cut from sixty to one hundred years since. Persons, whom observation has rendered familiar with the present character of the American forest, will be struck with the smallness of the diameter which Dr. Williams and Dr. Dwight ascribe to trees of such extraordinary height. Individuals of the several species mentioned in Dr. Williams's table, are now hardly to be found in the same climate, exceeding one half or at most two thirds of the height which he assigns to them; but, except in the case of the oak and the pine, the diameter stated by him would not be thought very extraordinary in trees of far less height, now standing. Even in the species I have excepted, those diameters, with half the heights of Dr. Williams, might perhaps be paralleled at the present time; and many elms, transplanted, at a diameter of six inches, within the memory of persons still living, measure six, and sometimes even seven feet through. For this change in the growth of forest trees there are two reasons: the one is, that the great commercial value of the pine and the oak have caused the destruction of all the best--that is, the tallest and straightest--specimens of both; the other, that the thinning of the woods by the axe of the lumberman has allowed the access of light and heat and air to trees of humbler worth and lower stature, which have survived their more towering brethren. These, consequently, have been able to expand their crowns and swell their stems to a degree not possible so long as they were overshadowed and stifled by the lordly oak and pine. While, therefore, the New England forester must search long before he finds a pine fit to be the mast Of some great ammiral, beeches and elms and birches, as sturdy as the mightiest of their progenitors, are still no rarity.[250] Another evil, sometimes of serious magnitude, which attends the operations of the lumberman, is the injury to the banks of rivers from the practice of floating. I do not here allude to rafts, which, being under the control of those who navigate them, may be so guided as to avoid damage to the shore, but to masts, logs, and other pieces of timber singly intrusted to the streams, to be conveyed by their currents to sawmill ponds, or to convenient places for collecting them into rafts. The lumbermen usually haul the timber to the banks of the rivers in the winter, and when the spring floods swell the streams and break up the ice, they roll the logs into the water, leaving them to float down to their destination. If the transporting stream is too small to furnish a sufficient channel for this rude navigation, it is sometimes dammed up, and the timber collected in the pond thus formed above the dam. When the pond is full, a sluice is opened, or the dam is blown up or otherwise suddenly broken, and the whole mass of lumber above it is hurried down with the rolling flood. Both of these modes of proceeding expose the banks of the rivers employed as channels of flotation to abrasion,[251] and in some of the American States it has been found necessary to protect, by special legislation, the lands through which they flow from the serious injury sometimes received through the practices I have described.[252] _Special Causes of the Destruction of European Woods._ The causes of forest waste thus far enumerated are more or less common to both continents; but in Europe extensive woods have, at different periods, been deliberately destroyed by fire or the axe, because they afforded a retreat to enemies, robbers, and outlaws, and this practice is said to have been resorted to in the Mediterranean provinces of France as recently as the time of Napoleon I.[253] The severe and even sanguinary legislation, by which some of the governments of mediæval Europe, as well as of earlier ages, protected the woods, was dictated by a love of the chase, or the fear of a scarcity of fuel and timber. The laws of almost every European state more or less adequately secure the permanence of the forest; and I believe Spain is the only European land which has not made some public provision for the protection and restoration of the woods--the only country whose people systematically war upon the garden of God.[254] _Royal Forests and Game Laws._ The French authors I have quoted, as well as many other writers of the same nation, refer to the French Revolution as having given a new impulse to destructive causes which were already threatening the total extermination of the woods.[255] The general crusade against the forests, which accompanied that important event, is to be ascribed, in a considerable degree, to political resentments. The forest codes of the mediæval kings, and the local "coutumes" of feudalism contained many severe and even inhuman provisions, adopted rather for the preservation of game than from any enlightened views of the more important functions of the woods. Ordericus Vitalis informs us that William the Conqueror destroyed sixty parishes, and drove out their inhabitants, in order that he might turn their lands into a forest,[256] to be reserved as a hunting ground for himself and his posterity, and he punished with death the killing of a deer, wild boar, or even a hare. His successor, William Rufus, according to the _Histoire des Ducs de Normandie et des Rois d'Angleterre_, p. 67, "was hunting one day in a new forest, which he had caused to be made out of eighteen parishes that he had destroyed, when, by mischance, he was killed by an arrow wherewith Tyreus de Rois [Sir Walter Tyrell] thought to slay a beast, but missed the beast, and slew the king, who was beyond it. And in this very same forest, his brother Richard ran so hard against a tree that he died of it. And men commonly said that these things were because they had so laid waste and taken the said parishes." These barbarous acts, as Bonnemère observes,[257] were simply the transfer of the customs of the French kings, of their vassals, and even of inferior gentlemen, to conquered England. "The death of a hare," says our author, "was a hanging matter, the murder of a plover a capital crime. Death was inflicted on those who spread nets for pigeons; wretches who had drawn a bow upon a stag were to be tied to the animal alive; and among the seigniors it was a standing excuse for having killed game on forbidden ground, that they aimed at a serf." The feudal lords enforced these codes with unrelenting rigor, and not unfrequently took the law into their own hands. In the time of Louis IX, according to William of Nangis, "three noble children, born in Flanders, who were sojourning at the abbey of St. Nicholas in the Wood, to learn the speech of France, went out into the forest of the abbey, with their bows and iron-headed arrows, to disport them in shooting hares, chased the game, which they had started in the wood of the abbey, into the forest of Enguerrand, lord of Coucy, and were taken by the sergeants which kept the wood. When the fell and pitiless Sir Enguerrand knew this, he had the children straightway hanged without any manner of trial."[258] The matter being brought to the notice of good King Louis, Sir Enguerrand was summoned to appear, and, finally, after many feudal shifts and dilatory pleas, brought to trial before Louis himself and a special council. Notwithstanding the opposition of the other seigniors, who, it is needless to say, spared no efforts to save a peer, probably not a greater criminal than themselves, the king was much inclined to inflict the punishment of death on the proud baron. "If he believed," said he, "that our Lord would be as well content with hanging as with pardoning, he would hang Sir Enguerrand in spite of all his barons;" but noble and clerical interests unfortunately prevailed. The king was persuaded to inflict a milder retribution, and the murderer was condemned to pay ten thousand livres in coin, and to "build for the souls of the three children two chapels wherein mass should be said every day."[259] The hope of shortening the purgatorial term of the young persons, by the religious rites to be celebrated in the chapels, was doubtless the consideration which operated most powerfully on the mind of the king; and Europe lost a great example for the sake of a mass. The desolation and depopulation, resulting from the extension of the forest and the enforcement of the game laws, induced several of the French kings to consent to some relaxation of the severity of these latter. Francis I, however, revived their barbarous provisions, and, according to Bonnemère, even so good a monarch as Henry IV reënacted them, and "signed the sentence of death upon peasants guilty of having defended their fields against devastation by wild beasts." "A fine of twenty livres," he continues, "was imposed on every one shooting at pigeons, which, at that time, swooped down by thousands upon the new-sown fields and devoured the seed. But let us count even this a progress, for we have seen that the murder of a pigeon had been a capital crime."[260] Not only were the slightest trespasses on the forest domain--the cutting of an oxgoad, for instance--severely punished, but game animals were still sacred when they had wandered from their native precincts and were ravaging the fields of the peasantry. A herd of deer or of wild boars often consumed or trod down a harvest of grain, the sole hope of the year for a whole family; and the simple driving out of such animals from this costly pasturage brought dire vengeance on the head of the rustic, who had endeavored to save his children's bread from their voracity. "At all times," says Paul Louis Courier, speaking in the name of the peasants of Chambord, in the "Simple Discours," "the game has made war upon us. Paris was blockaded eight hundred years by the deer, and its environs, now so rich, so fertile, did not yield bread enough to support the gamekeepers."[261] In the popular mind, the forest was associated with all the abuses of feudalism, and the evils the peasantry had suffered from the legislation which protected both it and the game it sheltered, blinded them to the still greater physical mischiefs which its destruction was to entail upon them. No longer protected by law, the crown forests and those of the great lords were attacked with relentless fury, unscrupulously plundered and wantonly laid waste, and even the rights of property in small private woods were no longer respected.[262] Various absurd theories, some of which are not even yet exploded, were propagated with regard to the economical advantages of converting the forest into pasture and ploughland, its injurious effects upon climate, health, facility of internal communication, and the like. Thus resentful memory of the wrongs associated with the forest, popular ignorance, and the cupidity of speculators cunning enough to turn these circumstances to profitable account, combined to hasten the sacrifice of the remaining woods, and a waste was produced which hundreds of years and millions of treasure will hardly repair. _Small Forest Plants, and Vitality of Seed._ Another function of the woods to which I have barely alluded deserves a fuller notice than can be bestowed upon it in a treatise the scope of which is purely economical. The forest is the native habitat of a large number of humbler plants, to the growth and perpetuation of which its shade, its humidity, and its vegetable mould appear to be indispensable necessities.[263] We cannot positively say that the felling of the woods in a given vegetable province would involve the final extinction of the smaller plants which are found only within their precincts. Some of these, though not naturally propagating themselves in the open ground, may perhaps germinate and grow under artificial stimulation and protection, and finally become hardy enough to maintain an independent existence in very different circumstances from those which at present seem essential to their life. Besides this, although the accounts of the growth of seeds, which have lain for ages in the ashy dryness of Egyptian catacombs, are to be received with great caution, or, more probably, to be rejected altogether, yet their vitality seems almost imperishable while they remain in the situations in which nature deposits them. When a forest old enough to have witnessed the mysteries of the Druids is felled, trees of other species spring up in its place; and when they, in their turn, fall before the axe, sometimes even as soon as they have spread their protecting shade over the surface, the germs which their predecessors had shed years, perhaps centuries before, sprout up, and in due time, if not choked by other trees belonging to a later stage in the order of natural succession, restore again the original wood. In these cases, the seeds of the new crop may often have been brought by the wind, by birds, by quadrupeds, or by other causes; but, in many instances, this explanation is not probable. When newly cleared ground is burnt over in the United States, the ashes are hardly cold before they are covered with a crop of fire weed, a tall herbaceous plant, very seldom seen growing under other circumstances, and often not to be found for a distance of many miles from the clearing. Its seeds, whether the fruit of an ancient vegetation or newly sown by winds or birds, require either a quickening by a heat which raises to a certain high point the temperature of the stratum where they lie buried, or a special pabulum furnished only by the combustion of the vegetable remains that cover the ground in the woods. Earth brought up from wells or other excavations soon produces a harvest of plants often very unlike those of the local flora. Moritz Wagner, as quoted by Wittwer,[264] remarks in his description of Mount Ararat: "A singular phenomenon to which my guide drew my attention is the appearance of several plants on the earth-heaps left by the last catastrophe [an earthquake], which grow nowhere else on the mountain, and had never been observed in this region before. The seeds of these plants were probably brought by birds, and found in the loose, clayey soil remaining from the streams of mud, the conditions of growth which the other soil of the mountain refused them." This is probable enough, but it is hardly less so that the flowing mud brought them up to the influence of air and sun, from depths where a previous convulsion had buried them ages before. Seeds of small sylvan plants, too deeply buried by successive layers of forest foliage and the mould resulting from its decomposition to be reached by the plough when the trees are gone and the ground brought under cultivation, may, if a wiser posterity replants the wood which sheltered their parent stems, germinate and grow, after lying for generations in a state of suspended animation. Darwin says: "In Staffordshire, on the estate of a relation, where I had ample means of investigation, there was a large and extremely barren heath, which had never been touched by the hand of man, but several hundred acres of exactly the same nature had been enclosed twenty-five years previously and planted with Scotch fir. The change in the native vegetation of the planted part of the heath was most remarkable--more than is generally seen in passing from one quite different soil to another; not only the proportional numbers of the heath plants were wholly changed, but _twelve species_ of plants (not counting grasses and sedges) flourished in the plantation which could not be found on the heath."[265] Had the author informed us that these twelve plants belonged to a species whose seeds enter into the nutriment of the birds which appeared with the young wood, we could easily account for their presence in the soil; but he says distinctly that the birds were of insectivorous species, and it therefore seems more probable that the seeds had been deposited when an ancient forest protected the growth of the plants which bore them, and that they sprang up to new life when a return of favorable conditions awaked them from a sleep of centuries. Darwin indeed says that the heath "had never been touched by the hand of man." Perhaps not, after it became a heath; but what evidence is there to control the general presumption that this heath was preceded by a forest, in whose shade the vegetables which dropped the seeds in question might have grown?[266] Although, therefore, the destruction of a wood and the reclaiming of the soil to agricultural uses suppose the death of its smaller dependent flora, these revolutions do not exclude the possibility of its resurrection. In a practical view of the subject, however, we must admit that when the woodman fells a tree he sacrifices the colony of humbler growths which had vegetated under its protection. Some wood plants are known to possess valuable medicinal properties, and experiment may show that the number of these is greater than we now suppose. Few of them, however, have any other economical value than that of furnishing a slender pasturage to cattle allowed to roam in the woods; and even this small advantage is far more than compensated by the mischief done to the young trees by browsing animals. Upon the whole, the importance of this class of vegetables, as physic or as food, is not such as to furnish a very telling popular argument for the conservation of the forest as a necessary means of their perpetuation. More potent remedial agents may supply their place in the _materia medica_, and an acre of grass land yields more nutriment for cattle than a range of a hundred acres of forest. But he whose sympathies with nature have taught him to feel that there is a fellowship between all God's creatures; to love the brilliant ore better than the dull ingot, iodic silver and crystallized red copper better than the shillings and the pennies forged from them by the coiner's cunning; a venerable oak tree than the brandy cask whose staves are split out from its heart wood; a bed of anemones, hepaticas, or wood violets than the leeks and onions which he may grow on the soil they have enriched and in the air they made fragrant--he who has enjoyed that special training of the heart and intellect which can be acquired only in the unviolated sanctuaries of nature, "where man is distant, but God is near"--will not rashly assert his right to extirpate a tribe of harmless vegetables, barely because their products neither tickle his palate nor fill his pocket; and his regret at the dwindling area of the forest solitude will be augmented by the reflection that the nurselings of the woodland perish with the pines, the oaks, and the beeches that sheltered them.[267] Although, as I have said, birds do not frequent the deeper recesses of the wood,[268] yet a very large proportion of them build their nests in trees, and find in their foliage and branches a secure retreat from the inclemencies of the seasons and the pursuit of the reptiles and quadrupeds which prey upon them. The borders of the forests are vocal with song; and when the gray morning calls the creeping things of the earth out of their night cells, it summons from the neighboring wood legions of their winged enemies, which swoop down upon the fields to save man's harvests by devouring the destroying worm, and surprising the lagging beetle in his tardy retreat to the dark cover where he lurks through the hours of daylight. The insects most injurious to rural industry do not multiply in or near the woods. The locust, which ravages the East with its voracious armies, is bred in vast open plains which admit the full heat of the sun to hasten the hatching of the eggs, gather no moisture to destroy them, and harbor no bird to feed upon the larvæ.[269] It is only since the felling of the forests of Asia Minor and Cyrene that the locust has become so fearfully destructive in those countries; and the grasshopper, which now threatens to be almost as great a pest to the agriculture of some North American soils, breeds in seriously injurious numbers only where a wide extent of surface is bare of woods. _Utility of the Forest._ In most parts of Europe, the woods are already so nearly extirpated that the mere protection of those which now exist is by no means an adequate remedy for the evils resulting from the want of them; and besides, as I have already said, abundant experience has shown that no legislation can secure the permanence of the forest in private hands. Enlightened individuals in most European states, governments in others, have made very extensive plantations,[270] and France has now set herself energetically at work to restore the woods in the southern provinces, and thereby to prevent the utter depopulation and waste with which that once fertile soil and delicious climate are threatened. The objects of the restoration of the forest are as multifarious as the motives that have led to its destruction, and as the evils which that destruction has occasioned. It is hoped that the planting of the mountains will diminish the frequency and violence of river inundations, prevent the formation of torrents, mitigate the extremes of atmospheric temperature, humidity, and precipitation, restore dried-up springs, rivulets, and sources of irrigation, shelter the fields from chilling and from parching winds, prevent the spread of miasmatic effluvia, and, finally, furnish an inexhaustible and self-renewing supply of a material indispensable to so many purposes of domestic comfort, to the successful exercise of every art of peace, every destructive energy of war.[271] But our enumeration of the uses of trees is not yet complete. Besides the influence of the forest, in mountain ranges, as a means of preventing the scooping out of ravines and the accumulations of water which fill them, trees subserve a valuable purpose, in lower positions, as barriers against the spread of floods and of the material they transport with them; but this will be more appropriately considered in the chapter on the waters; and another very important use of trees, that of fixing movable sand-dunes, and reclaiming them to profitable cultivation, will be pointed out in the chapter on the sands. The vast extension of railroads, of manufactures and the mechanical arts, of military armaments, and especially of the commercial fleets and navies of Christendom within the present century, has greatly augmented the demand for wood,[272] and, but for improvements in metallurgy which have facilitated the substitution of iron for that material, the last twenty-five years would almost have stripped Europe of her only remaining trees fit for such uses.[273] The walnut trees alone felled in Europe within two years to furnish the armies of America with gunstocks, would form a forest of no inconsiderable extent.[274] _The Forests of Europe._ Mirabeau estimated the forests of France in 1750 at seventeen millions of hectares [42,000,000 acres]; in 1860 they were reduced to eight millions [19,769,000 acres]. This would be at the rate of 82,000 hectares [202,600 acres] per year. Troy, from whose valuable pamphlet, _Étude sur le Reboisement des Montagnes_, I take these statistical details, supposes that Mirabeau's statement may have been an extravagant one, but it still remains certain that the waste has been enormous; for it is known that, in some departments, that of Ariège, for instance, clearing has gone on during the last half century at the rate of three thousand acres a year,[275] and in all parts of the empire trees have been felled faster than they have grown. The total area of France, excluding Savoy, is about one hundred and thirty-one millions of acres. The extent of forest supposed by Mirabeau would be about thirty-two per cent. of the whole territory.[276] In a country and a climate where the conservative influences of the forest are so necessary as in France, trees must cover a large surface and be grouped in large masses, in order to discharge to the best advantage the various functions assigned to them by nature. The consumption of wood is rapidly increasing in that empire, and a large part of its territory is mountainous, sterile, and otherwise such in character or situation that it can be more profitably devoted to the growth of wood than to any agricultural use. Hence it is evident that the proportion of forest in 1750, taking even Mirabeau's large estimate, was not very much too great for permanent maintenance, though doubtless the distribution was so unequal that it would have been sound policy to fell the woods and clear land in some provinces, while large forests should have been planted in others.[277] During the period in question, France neither exported manufactured wood or rough timber, nor derived important collateral advantages of any sort from the destruction of her forests. She is consequently impoverished and crippled to the extent of the difference between what she actually possesses of wooded surface and what she ought to have retained. Italy and Spain are bared of trees in a greater degree than France, and even Russia, which we habitually consider as substantially a forest country, is beginning to suffer seriously for want of wood. Jourdier, as quoted by Clavé, observes: "Instead of a vast territory with immense forests, which we expect to meet, one sees only scattered groves thinned by the wind or by the axe of the _moujik_, grounds cut over and more or less recently cleared for cultivation. There is probably not a single district in Russia which has not to deplore the ravages of man or of fire, those two great enemies of Muscovite sylviculture. This is so true, that clear-sighted men already foresee a crisis which will become terrible, unless the discovery of great deposits of some new combustible, as pit coal or anthracite, shall diminish its evils."[278] Germany, from character of surface and climate, and from the attention which has long been paid in all the German States to sylviculture, is, taken as a whole, in a far better condition in this respect than its more southern neighbors; but in the Alpine provinces of Bavaria and Austria, the same improvidence which marks the rural economy of the corresponding districts of Switzerland, Italy, and France, is producing effects hardly less disastrous. As an instance of the scarcity of fuel in some parts of the territory of Bavaria, where, not long since, wood abounded, I may mention the fact that the water of salt springs is, in some instances, conveyed to the distance of sixty miles, in iron pipes, to reach a supply of fuel for boiling it down.[279] _Forests of the United States and Canada._ The vast forests of the United States and Canada cannot long resist the improvident habits of the backwoodsman and the increased demand for lumber. According to the census of the former country for 1860, which gives returns of the "sawed and planed lumber" alone, timber for framing and for a vast variety of mechanical purposes being omitted altogether, the value of the former material prepared for market in the United States was, in 1850, $58,521,976; in 1860, $95,912,286. The quantity of unsawed lumber is not likely to have increased in the same proportion, because comparatively little is exported in that condition, and because masonry is fast taking the place of carpentry in building, and stone, brick, and iron are used instead of timber more largely than they were ten years ago. Still a much greater quantity of unsawed lumber must have been marketed in 1860 than in 1850. It must further be admitted that the price of lumber rose considerably between those dates, and consequently that the increase in quantity is not to be measured by the increase in pecuniary value. Perhaps this rise of prices may even be sufficient to make the entire difference between the value of "sawed and planed lumber" produced in the ten years in question by the six New England States (21 per cent.), and the six Middle States (15 per cent.); but the amount produced by the Western and by the Southern States had doubled, and that returned from the Pacific States and Territories had trebled in value in the same interval, so that there was certainly, in those States, a large increase in the actual quantity prepared for sale. I greatly doubt whether any one of the American States, except, perhaps, Oregon, has, at this moment, more woodland than it ought permanently to preserve, though, no doubt, a different distribution of the forests in all of them might be highly advantageous. It is a great misfortune to the American Union that the State Governments have so generally disposed of their original domain to private citizens. It is true that public property is not sufficiently respected in the United States; and it is also true that, within the memory of almost every man of mature age, timber was of so little value in that country, that the owners of private woodlands submitted, almost without complaint, to what would be regarded elsewhere as very aggravated trespasses upon them.[280] Under such circumstances, it is difficult to protect the forest, whether it belong to the state or to individuals. Property of this kind would be subject to much plunder, as well as to frequent damage by fire. The destruction from these causes would, indeed, considerably lessen, but would not wholly annihilate the climatic and geographical influences of the forest, or ruinously diminish its value as a regular source of supply of fuel and timber. For prevention of the evils upon which I have so long dwelt, the American people must look to the diffusion of general intelligence on this subject, and to the enlightened self interest, for which they are remarkable, not to the action of their local or general legislatures. Even in France, government has moved with too slow and hesitating a pace, and preventive measures do not yet compensate destructive causes. The judicious remarks of Troy on this point may well be applied to other countries than France, other measures of public policy than the preservation of the woods. "To move softly," says he, "is to commit the most dangerous, the most unpardonable of imprudences; it diminishes the prestige of authority; it furnishes a triumph to the sneerer and the incredulous; it strengthens opposition and encourages resistance; it ruins the administration in the opinion of the people, weakens its power and depresses its courage."[281] _The Economy of the Forest._ The legislation of European states upon sylviculture, and the practice of that art, divide themselves into two great branches--the preservation of existing forests, and the creation of new. From the long operation of causes already set forth, what is understood in America and other new countries by the "primitive forest," no longer exists in the territories which were the seats of ancient civilization and empire, except upon a small scale, and in remote and almost inaccessible glens quite out of the reach of ordinary observation. The oldest European woods, indeed, are native, that is, sprung from self-sown seed, or from the roots of trees which have been felled for human purposes; but their growth has been controlled, in a variety of ways, by man and by domestic animals, and they always present more or less of an artificial character and arrangement. Both they and planted forests, which, though certainly not few, are of recent date in Europe, demand, as well for protection as for promotion of growth, a treatment different in some respects from that which would be suited to the character and wants of the virgin wood. On this latter branch of the subject, experience and observation have not yet collected a sufficient stock of facts to serve for the construction of a complete system of sylviculture; but the management of the forest as it exists in France--the different zones and climates of which country present many points of analogy with those of the United States and some of the British colonies--has been carefully studied, and several manuals of practice have been prepared for the foresters of that empire. I believe the best of these is the _Cours Élémentaire de Culture des Bois créé à l'École Forestière de Nancy, par M. Lorentz, complété, et publié par A. Parade_, with a supplement under the title of _Cours d'Aménagement des Forêts, par Henri Nanquette_. The _Études sur l'Économie Forestière, par Jules Clavé_, which I have often quoted, presents a great number of interesting views on this subject, and well deserves to be translated for the use of the English and American reader; but it is not designed as a practical guide, and it does not profess to be sufficiently specific in its details to serve that purpose. Notwithstanding the difference of conditions between the aboriginal and the trained forest, the judicious observer who aims at the preservation of the former will reap much instruction from the treatises I have cited, and I believe he will be convinced that the sooner a natural wood is brought into the state of an artificially regulated one, the better it is for all the multiplied interests which depend on the wise administration of this branch of public economy.[282] One consideration bearing on this subject has received less attention than it merits, because most persons interested in such questions have not opportunities for the comparison I refer to. I mean the great general superiority of cultivated timber to that of strictly spontaneous growth. I say _general_ superiority, because there are exceptions to the rule. The white pine, _Pinus strobus_, for instance, and other trees of similar character and uses, require, for their perfect growth, a density of forest vegetation around them, which protects them from too much agitation by wind, and from the persistence of the lateral branches which fill the wood with knots. A pine which has grown under those conditions possesses a tall, straight stem, admirably fitted for masts and spars, and, at the same time, its wood is almost wholly free from knots, is regular in annular structure, soft and uniform in texture, and, consequently, superior to almost all other timber for joinery. If, while a large pine is spared, the broad-leaved or other smaller trees around it are felled, the swaying of the tree from the action of the wind mechanically produces separations between the layers of annual growth, and greatly diminishes the value of the timber. The same defect is often observed in pines which, from some accident of growth, have much overtopped their fellows in the virgin forest. The white pine, growing in the fields, or in open glades in the woods, is totally different from the true forest tree, both in general aspect and in quality of wood. Its stem is much shorter, its top less tapering, its foliage denser and more inclined to gather into tufts, its branches more numerous and of larger diameter, its wood shows much more distinctly the divisions of annual growth, is of coarser grain, harder and more difficult to work into mitre joints. Intermixed with the most valuable pines in the American forests, are met many trees of the character I have just described. The lumbermen call them "saplings," and generally regard them as different in species from the true white pine, but botanists are unable to establish a distinction between them, and as they agree in almost all respects with trees grown in the open grounds from known white-pine seedlings, I believe their peculiar character is due to unfavorable circumstances in their early growth. The pine, then, is an exception to the general rule as to the inferiority of the forest to the open-ground tree. The pasture oak and pasture beech, on the contrary, are well known to produce far better timber than those grown in the woods, and there are few trees to which the remark is not equally applicable.[283] Another advantage of the artificially regulated forest is, that it admits of such grading of the ground as to favor the retention or discharge of water at will, while the facilities it affords for selecting and duly proportioning, as well as properly spacing, the trees which compose it, are too obvious to require to be more than hinted at. In conducting these operations, we must have a diligent eye to the requirements of nature, and must remember that a wood is not an arbitrary assemblage of trees to be selected and disposed according to the caprice of its owner. "A forest," says Clavé, "is not, as is often supposed, a simple collection of trees succeeding each other in long perspective, without bond of union, and capable of isolation from each other; it is, on the contrary, a whole, the different parts of which are interdependent upon each other, and it constitutes, so to speak, a true individuality. Every forest has a special character, determined by the form of the surface it grows upon, the kinds of trees that compose it, and the manner in which they are grouped."[284] _European and American Trees compared._ The woods of North America are strikingly distinguished from those of Europe by the vastly greater variety of species they contain. According to Clavé, there are in "France and in most parts of Europe" only about twenty forest trees, five or six of which are spike-leaved and resinous, the remainder broad-leaved."[285] Our author, however, doubtless means genera, though he uses the word _espèces_. Rossmässler enumerates fifty-seven species of forest trees as found in Germany, but some of these are mere shrubs, some are fruit and properly garden trees, and some others are only varieties of familiar species. The valuable manual of Parade describes about the same number, including, however, two of American origin--the locust, _Robinia pseudacacia_, and the Weymouth or white pine, _Pinus strobus_--and the cedar of Lebanon from Asia, though it is indigenous in Algeria also. We may then safely say that Europe does not possess above forty or fifty trees of such economical value as to be worth the special care of the forester, while the oak alone numbers not less than thirty species in the United States,[286] and some other North American genera are almost equally diversified.[287] Few European trees, except those bearing edible fruit, have been naturalized in the United States, while the American forest flora has made large contributions to that of Europe. It is a very poor taste which has led to the substitution of the less picturesque European for the graceful and majestic American elm, in some public grounds in the United States. On the other hand, the European mountain ash--which in beauty and healthfulness of growth is superior to our own--the horse chestnut, and the abele, or silver poplar, are valuable additions to the ornamental trees of North America. The Swiss arve or zirbelkiefer, _Pinus cembra_, which yields a well-flavored edible seed and furnishes excellent wood for carving, the umbrella pine which also bears a seed agreeable to the taste, and which, from the color of its foliage and the beautiful form of its dome-like crown, is among the most elegant of trees, the white birch of Central Europe, with its pendulous branches almost rivalling those of the weeping willow in length, flexibility, and gracefulness of fall, and, especially, the "cypresse funerall," might be introduced into the United States with great advantage to the landscape. The European beech and chestnut furnish timber of far better quality than that of their American congeners. The fruit of the European chestnut, though inferior to the American in flavor, is larger, and is an important article of diet among the French and Italian peasantry. The walnut of Europe, though not equal to some of the American species in beauty of growth or of wood, or to others in strength and elasticity of fibre, is valuable for its timber and its oil.[288] The maritime pine, which has proved of such immense use in fixing drifting sands in France, may perhaps be better adapted to this purpose than any of the pines of the New World, and it is of great importance for its turpentine, resin, and tar. The épicéa, or common fir, _Abies picea_, _Abies excelsa_, _Picea excelsa_, abundant in the mountains of France and the contiguous country, is known for its product, Burgundy pitch, and, as it flourishes in a greater variety of soil and climate than almost any other spike-leaved tree, it might be well worth transplantation.[289] The cork oak has been introduced into the United States, I believe, and would undoubtedly thrive in the Southern section of the Union.[290] In the walnut, the chestnut, the cork oak, the mulberry, the olive, the orange, the lemon, the fig, and the multitude of other trees which, by their fruit, or by other products, yield an annual revenue, nature has provided Southern Europe with a partial compensation for the loss of the native forest. It is true that these trees, planted as most of them are at such distances as to admit of cultivation, or of the growth of grass among them, are but an inadequate substitute for the thick and shady wood; but they perform to a certain extent the same offices of absorption and transpiration, they shade the surface of the ground, they serve to break the force of the wind, and on many a steep declivity, many a bleak and barren hillside, the chestnut binds the soil together with its roots, and prevents tons of earth and gravel from washing down upon the fields and the gardens. Fruit trees are not wanting, certainly, north of the Alps. The apple, the pear, and the prune are important in the economy both of man and of nature, but they are far less numerous in Switzerland and Northern France than are the trees I have mentioned in Southern Europe, both because they are in general less remunerative, and because the climate, in higher latitudes, does not permit the free introduction of shade trees into grounds occupied for agricultural purposes.[291] The multitude of species, intermixed as they are in their spontaneous growth, gives the American forest landscape a variety of aspect not often seen in the woods of Europe, and the gorgeous tints, which nature repeats from the dying dolphin to paint the falling leaf of the American maples, oaks, and ash trees, clothe the hillsides and fringe the watercourses with a rainbow splendor of foliage, unsurpassed by the brightest groupings of the tropical flora. It must be admitted, however, that both the northern and the southern declivities of the Alps exhibit a nearer approximation to this rich and multifarious coloring of autumnal vegetation than most American travellers in Europe are willing to allow; and, besides, the small deciduous shrubs which often carpet the forest glades of these mountains are dyed with a ruddy and orange glow, which, in the distant landscape, is no mean substitute for the scarlet and crimson and gold and amber of the transatlantic woodland. No American evergreen known to me resembles the umbrella pine sufficiently to be a fair object of comparison with it.[292] A cedar, very common above the Highlands on the Hudson, is extremely like the cypress, straight, slender, with erect, compressed ramification, and feathered to the ground, but its foliage is neither so dark nor so dense, the tree does not attain the majestic height of the cypress, nor has it the lithe flexibility of that tree. In mere shape, the Lombardy poplar nearly resembles this latter, but it is almost a profanation to compare the two, especially when they are agitated by the wind; for under such circumstances, the one is the most majestic, the other the most ungraceful, or--if I may apply such an expression to anything but human affectation of movement--the most awkward of trees. The poplar trembles before the blast, flutters, struggles wildly, dishevels its foliage, gropes around with its feeble branches, and hisses as in impotent passion. The cypress gathers its limbs still more closely to its stem, bows a gracious salute rather than an humble obeisance to the tempest, bends to the wind with an elasticity that assures you of its prompt return to its regal attitude, and sends from its thick leaflets a murmur like the roar of the far-off ocean. The cypress and the umbrella pine are not merely conventional types of the Italian landscape. They are essential elements in a field of rural beauty which can be seen in perfection only in the basin of the Mediterranean, and they are as characteristic of this class of scenery as the date palm is of the oases of the desert. There is, however, this difference: a single cypress or pine is often enough to shed beauty over a wide area; the palm is a social tree, and its beauty is not so much that of the individual as of the group. The frequency of the cypress and the pine--combined with the fact that the other trees of Southern Europe which most interest a stranger from the north, the orange and the lemon, the cork oak, the ilex, the myrtle, and the laurel, are evergreens--goes far to explain the beauty of the winter scenery of Italy. Indeed it is only in the winter that a tourist who confines himself to wheel carriages and high roads can acquire any notion of the face of the earth, and form any proper geographical image of that country. At other seasons, not high walls only, but equally impervious hedges, and now, unhappily, acacias thickly planted along the railway routes, confine the view so completely, that the arch of a tunnel, or a night cap over the traveller's eyes, is scarcely a more effectual obstacle to the gratification of his curiosity.[293] _Sylviculture._ The art, or, as the Continental foresters call it, the science of sylviculture has been so little pursued in England and America, that its nomenclature has not been introduced into the English vocabulary, and I shall not be able to describe its processes with technical propriety of language, without occasionally borrowing a word from the forest literature of France and Germany. A full discussion of the methods of sylviculture would, indeed, be out of place in a work like the present, but the almost total want of conveniently accessible means of information on the subject, in English-speaking countries, will justify me in presenting it with somewhat more of detail than would otherwise be pertinent. The two best known methods are those distinguished as the _taillis_, copse or coppice treatment,[294] and the _futaie_, for which I find no English equivalent, but which may not inappropriately be called the _full-growth_ system. A _taillis_, copse, or coppice, is a wood composed of shoots from the roots of trees previously cut for fuel and timber. The shoots are thinned out from time to time, and finally cut, either after a fixed number of years, or after the young trees have attained to certain dimensions, their roots being then left to send out a new progeny as before. This is the cheapest method of management, and therefore the best wherever the price of labor and of capital bears a high proportion to that of land and of timber; but it is essentially a wasteful economy. If the woodland is, in the first place, completely cut over, as is found most convenient in practice, the young shoots have neither the shade nor the protection from wind so important to forest growth, and their progress is comparatively slow, while, at the same time, the thick clumps they form choke the seedlings that may have sprouted near them. If domestic animals of any species are allowed to roam in the wood, they browse upon the terminal buds and the tender branches, thereby stunting, if they do not kill, the young trees, and depriving them of all beauty and vigor of growth. The evergreens, once cut, do not shoot up again,[295] and the mixed character of the forest--in many respects an important advantage, if not an indispensable condition of growth--is lost;[296] and besides this, large wood of any species cannot be grown in this method, because trees which shoot from decaying stumps and their dying roots, become hollow or otherwise unsound before they acquire their full dimensions. A more fatal objection still, is, that the roots of trees will not bear more than two or three, or at most four cuttings of their shoots before their vitality is exhausted, and the wood can then be restored only by replanting entirely. The period of cutting coppices varies in Europe from fifteen to forty years, according to soil, species, and rapidity of growth. In the _futaie_, or full-growth system, the trees are allowed to stand as long as they continue in healthy and vigorous growth. This is a shorter period than would be at first supposed, when we consider the advanced age and great dimensions to which, under favorable circumstances, many forest trees attain in temperate climates. But, as every observing person familiar with the natural forest is aware, these are exceptional cases, just as are instances of great longevity or of gigantic stature among men. Able vegetable physiologists have maintained that the tree, like most reptiles, has no natural limit of life or of growth, and that the only reason why our oaks and our pines do not reach the age of twenty centuries and the height of a hundred fathoms, is, that in the multitude of accidents to which they are exposed, the chances of their attaining to such a length of years and to such dimensions of growth are a million to one against them. But another explanation of this fact is possible. In trees affected by no discoverable external cause of death, decay begins at the topmost branches, which seem to wither and die for want of nutriment. The mysterious force by which the sap is carried from the roots to the utmost twigs, cannot be conceived to be unlimited in power, and it is probable that it differs in different species, so that while it may suffice to raise the fluid to the height of five hundred feet in the sequoia, it may not be able to carry it beyond one hundred and fifty in the oak. The limit may be different, too, in different trees of the same species, not from defective organization in those of inferior growth, but from more or less favorable conditions of soil, nourishment, and exposure. Whenever a tree attains to the limit beyond which its circulating fluids cannot rise, we may suppose that decay begins, and death follows, from the same causes which bring about the same results in animals of limited size--such, for example, as the interruption of functions essential to life, in consequence of the clogging up of ducts by matter assimilable in the stage of growth, but no longer so when increment has ceased. In the natural woods, we observe that, though, among the myriads of trees which grow upon a square mile, there are several vegetable giants, yet the great majority of them begin to decay long before they have attained their maximum of stature, and this seems to be still more emphatically true of the artificial forest. In France, according to Clavé, "oaks, in a suitable soil, may stand, without exhibiting any sign of decay, for two or three hundred years; the pines hardly exceed one hundred and twenty, and the soft or white woods [_bois blancs_], in wet soils, languish and die before reaching the fiftieth year."[297] These ages are certainly below the average of those of American forest trees, and are greatly exceeded in very numerous well-attested instances of isolated trees in Europe. The former mode of treating the futaie, called the garden system, was to cut the trees individually as they arrived at maturity, but, in the best regulated forests, this practice has been abandoned for the German method, which embraces not only the securing of the largest immediate profit, but the replanting of the forest, and the care of the young growth. This is effected in the case of a forest, whether natural or artificial, which is to be subjected to regular management, by three operations. The first of these consists in felling about one third of the wood, in such way as to leave convenient spaces for the growth of young trees. The remaining two-thirds are relied upon to replant the vacancies, by natural sowing, which they seldom or never fail to do. The seedlings are watched, are thinned out when too dense, the ill formed and sickly, as well as those of inferior value, and the shrubs and thorns which might otherwise choke or too closely shade them, are pulled up. When they have attained sufficient strength and development of foliage to bear or to require more light and air, the second step is taken, by removing a suitable proportion of the old trees which had been spared at the first cutting; and when, finally, they are hardened enough to bear frost and sun without other protection than that which they mutually give to each other, the remainder of the original forest is felled, and the wood now consists wholly of young and vigorous trees. This result is obtained after about twenty years. At convenient periods afterward, the unhealthy stocks and those injured by wind or other accidents are removed, and in some instances the growth of the remainder is promoted by irrigation or by fertilizing applications.[298] When the forest is approaching to maturity, the original processes already described are repeated; and as, in different parts of an extensive forest, they would take place in different zones, it would afford indefinitely an annual crop of firewood and timber. The duties of the forester do not end here. It sometimes happens that the glades left by felling the older trees are not sufficiently seeded, or that the species, or _essences_, as the French oddly call them, are not duly proportioned in the new crop. In this case, seed must be artificially sown, or young trees planted in the vacancies. One of the most important rules in the administration of the forest is the absolute exclusion of domestic quadrupeds from every wood which is not destined to be cleared. No growth of young trees is possible where cattle are admitted to pasture at any season of the year, though they are undoubtedly most destructive while trees are in leaf.[299] It is often necessary to take measures for the protection of young trees against the rabbit, the mole, and other rodent quadrupeds, and of older ones against the damage done by the larvæ of insects hatched upon the surface or in the tissues of the bark, or even in the wood itself. The much greater liability of the artificial than of the natural forest to injury from this cause is perhaps the only point in which the superiority of the former to the latter is not as marked as that of any domesticated vegetable to its wild representative. But the better quality of the wood and the much more rapid growth of the trained and regulated forest are abundant compensations for the loss thus occasioned, and the progress of entomological science will, perhaps, suggest new methods of preventing the ravages of insects. Thus far, however, the collection and destruction of the eggs, by simple but expensive means, has proved the only effectual remedy.[300] It is common in Europe to permit the removal of the fallen leaves and fragments of bark and branches with which the forest soil is covered, and sometimes the cutting of the lower twigs of evergreens. The leaves and twigs are principally used as litter for cattle, and finally as manure, the bark and wind-fallen branches as fuel. By long usage, sometimes by express grant, this privilege has become a vested right of the population in the neighborhood of many public, and even large private forests; but it is generally regarded as a serious evil. To remove the leaves and fallen twigs is to withdraw much of the pabulum upon which the tree was destined to feed. The small branches and leaves are the parts of the tree which yield the largest proportion of ashes on combustion, and of course they supply a great amount of nutriment for the young shoots. "A cubic foot of twigs," says Vaupell, "yields four times as much ashes as a cubic foot of stem wood. * * For every hundred weight of dried leaves carried off from a beech forest, we sacrifice a hundred and sixty cubic feet of wood. The leaves and the mosses are a substitute, not only for manure, but for ploughing. The carbonic acid given out by decaying leaves, when taken up by water, serves to dissolve the mineral constituents of the soil, and is particularly active in disintegrating feldspar and the clay derived from its decomposition. * * * The leaves belong to the soil. Without them it cannot preserve its fertility, and cannot furnish nutriment to the beech. The trees languish, produce seed incapable of germination, and the spontaneous self-sowing, which is an indispensable element in the best systems of sylviculture, fails altogether in the bared and impoverished soil."[301] Besides these evils, the removal of the leaves deprives the soil of that spongy character which gives it such immense value as a reservoir of moisture and a regulator of the flow of springs; and, finally, it exposes the surface roots to the drying influence of sun and wind, to accidental mechanical injury from the tread of animals or men, and, in cold climates, to the destructive effects of frost. The annual lopping and trimming of trees for fuel, so common in Europe, is fatal to the higher uses of the forest, but where small groves are made, or rows of trees planted, for no other purpose than to secure a supply of firewood, or to serve as supports for the vine, it is often very advantageous. The willows, and many other trees, bear polling for a long series of years without apparent diminution of growth of branches, and though certainly a polled, or, to use an old English word, a doddered tree, is in general a melancholy object, yet it must be admitted that the aspect of some species--the American locust, _Robinia pseudacacia_, for instance--when young, is improved by this process.[302] I have spoken of the needs of agriculture as a principal cause of the destruction of the forest, and of domestic cattle as particularly injurious to the growth of young trees. But these animals affect the forest, indirectly, in a still more important way, because the extent of cleared ground required for agricultural use depends very much on the number and kinds of the cattle bred. We have seen, in a former chapter, that, in the United States, the domestic quadrupeds amount to more than a hundred millions, or three times the number of the human population of the Union. In many of the Western States, the swine subsist more or less on acorns, nuts, and other products of the woods, and the prairies, or natural meadows of the Mississippi valley, yield a large amount of food for beast, as well as for man. With these exceptions, all this vast army of quadrupeds is fed wholly on grass, grain, pulse, and roots grown on soil reclaimed from the forest by European settlers. It is true that the flesh of domestic quadrupeds enters very largely into the aliment of the American people, and greatly reduces the quantity of vegetable nutriment which they would otherwise consume, so that a smaller amount of agricultural product is required for immediate human food, and, of course, a smaller extent of cleared land is needed for the growth of that product, than if no domestic animals existed. But the flesh of the horse, the ass, and the mule is not consumed by man, and the sheep is reared rather for its fleece than for food. Besides this, the ground required to produce the grass and grain consumed in rearing and fattening a grazing quadruped, would yield a far larger amount of nutriment, if devoted to the growing of breadstuffs, than is furnished by his flesh; and, upon the whole, whatever advantages may be reaped from the breeding of domestic cattle, it is plain that the cleared land devoted to their sustenance in the originally wooded part of the United States, after deducting a quantity sufficient to produce an amount of aliment equal to their flesh, still greatly exceeds that cultivated for vegetables, directly consumed by the people of the same regions; or, to express a nearly equivalent idea in other words, the meadow and the pasture, taken together, much exceed the plough land.[303] In fertile countries, like the United States, the foreign demand for animal and vegetable aliment, for cotton, and for tobacco, much enlarges the sphere of agricultural operations, and, of course, prompts further encroachments upon the forest. The commerce in these articles, therefore, constitutes in America a special cause of the destruction of the woods, which does not exist in the numerous states of the Old World that derive the raw material of their mechanical industry from distant lands, and import many articles of vegetable food or luxury which their own climates cannot advantageously produce. The growth of arboreal vegetation is so slow that, though he who buries an acorn may hope to see it shoot up to a miniature resemblance of the majestic tree which shall shade his remote descendants, yet the longest life hardly embraces the seedtime and the harvest of a forest. The planter of a wood must be actuated by higher motives than those of an investment the profits of which consist in direct pecuniary gain to himself or even to his posterity; for if, in rare cases, an artificial forest may, in two or three generations, more than repay its original cost, still, in general, the value of its timber will not return the capital expended and the interest accrued.[304] But when we consider the immense collateral advantages derived from the presence, the terrible evils necessarily resulting from the destruction of the forest, both the preservation of existing woods, and the far more costly extension of them where they have been unduly reduced, are among the most obvious of the duties which this age owes to those that are to come after it. Especially is this obligation incumbent upon Americans. No civilized people profits so largely from the toils and sacrifices of its immediate predecessors as they; no generations have ever sown so liberally, and, in their own persons, reaped so scanty a return, as the pioneers of Anglo-American social life. We can repay our debt to our noble forefathers only by a like magnanimity, by a like self-forgetting care for the moral and material interests of our own posterity. _Instability of American Life._ All human institutions, associate arrangements, modes of life, have their characteristic imperfections. The natural, perhaps the necessary defect of ours, is their instability, their want of fixedness, not in form only, but even in spirit. The face of physical nature in the United States shares this incessant fluctuation, and the landscape is as variable as the habits of the population. It is time for some abatement in the restless love of change which characterizes us, and makes us almost a nomade rather than a sedentary people.[305] We have now felled forest enough everywhere, in many districts far too much. Let us restore this one element of material life to its normal proportions, and devise means for maintaining the permanence of its relations to the fields, the meadows, and the pastures, to the rain and the dews of heaven, to the springs and rivulets with which it waters the earth. The establishment of an approximately fixed ratio between the two most broadly characterized distinctions of rural surface--woodland and plough land--would involve a certain persistence of character in all the branches of industry, all the occupations and habits of life, which depend upon or are immediately connected with either, without implying a rigidity that should exclude flexibility of accommodation to the many changes of external circumstance which human wisdom can neither prevent nor foresee, and would thus help us to become, more emphatically, a well-ordered and stable commonwealth, and, not less conspicuously, a people of progress. NOTE on word _watershed_, omitted on p. 257.--Sir John F. W. Herschel (_Physical Geography_, 137, and elsewhere) spells this word _water-sched_, because he considers it a translation, or rather an adoption of the German "Wasser-scheide, separation of the waters, not water-_shed_, the slope _down which_ the waters run," As a point of historical etymology, it is probable that the word in question was suggested to those who first used it by the German _Wasserscheide_; but the spelling _water-sched_, proposed by Herschel, is objectionable, both because _sch_ is a combination of letters wholly unknown to modern English orthography and properly representing no sound recognized in English orthoepy, and for the still better reason that _watershed_, in the sense of _division-of-the-waters_, has a legitimate English etymology. The Anglo-Saxon _sceadan_ meant both to separate or divide, and to shade or shelter. It is the root of the English verbs _to shed_ and _to shade_, and in the former meaning is the A. S. equivalent of the German verb _scheiden_. _Shed_ in Old English had the meaning _to separate_ or _distinguish_. It is so used in the _Owl and the Nightingale_, v. 197. Palsgrave (_Lesclarcissement, etc._, p. 717) defines _I shede_, I departe thinges asonder; and the word still means _to divide_ in several English local dialects. Hence, _watershed_, the division or separation of the waters, is good English both in sense and spelling. CHAPTER IV. THE WATERS. LAND ARTIFICIALLY WON FROM THE WATERS: _a_, EXCLUSION OF THE SEA BY DIKING; _b_, DRAINING OF LAKES AND MARSHES; _c_, GEOGRAPHICAL INFLUENCE OF SUCH OPERATIONS--LOWERING OF LAKES--MOUNTAIN LAKES--CLIMATIC EFFECTS OF DRAINING LAKES AND MARSHES--GEOGRAPHICAL AND CLIMATIC EFFECTS OF AQUEDUCTS, RESERVOIRS, AND CANALS--SURFACE AND UNDERDRAINING, AND THEIR CLIMATIC AND GEOGRAPHICAL EFFECTS--IRRIGATION AND ITS CLIMATIC AND GEOGRAPHICAL EFFECTS. INUNDATIONS AND TORRENTS: _a_, RIVER EMBANKMENTS; _b_, FLOODS OF THE ARDÈCHE; _c_, CRUSHING FORCE OF TORRENTS; _d_, INUNDATIONS OF 1856 IN FRANCE; _e_, REMEDIES AGAINST INUNDATIONS--CONSEQUENCES IF THE NILE HAD BEEN CONFINED BY LATERAL DIKES. IMPROVEMENTS IN THE VAL DI CHIANA--IMPROVEMENTS IN THE TUSCAN MAREMME--OBSTRUCTION OF RIVER MOUTHS--SUBTERRANEAN WATERS--ARTESIAN WELLS--ARTIFICIAL SPRINGS--ECONOMIZING PRECIPITATION. _Land artificially won from the Waters._ Man, as we have seen, has done much to revolutionize the solid surface of the globe, and to change the distribution and proportions, if not the essential character, of the organisms which inhabit the land and even the waters. Besides the influence thus exerted upon the life which peoples the sea, his action upon the land has involved a certain amount of indirect encroachment upon the territorial jurisdiction of the ocean. So far as he has increased the erosion of running waters by the destruction of the forest, he has promoted the deposit of solid matter in the sea, thus reducing its depth, advancing the coast line, and diminishing the area covered by the waters. He has gone beyond this, and invaded the realm of the ocean by constructing within its borders wharves, piers, lighthouses, breakwaters, fortresses, and other facilities for his commercial and military operations; and in some countries he has permanently rescued from tidal overflow, and even from the very bed of the deep, tracts of ground extensive enough to constitute valuable additions to his agricultural domain. The quantity of soil gained from the sea by these different modes of acquisition is, indeed, too inconsiderable to form an appreciable element in the comparison of the general proportion between the two great forms of terrestrial surface, land and water; but the results of such operations, considered in their physical and their moral bearings, are sufficiently important to entitle them to special notice in every comprehensive view of the relations between man and nature. There are cases, as on the western shores of the Baltic, where, in consequence of the secular elevation of the coast, the sea appears to be retiring; others, where, from the slow sinking of the land, it seems to be advancing. These movements depend upon geological causes wholly out of our reach, and man can neither advance nor retard them. There are also cases where similar apparent effects are produced by local oceanic currents, by river deposit or erosion, by tidal action, or by the influence of the wind upon the waves and the sands of the sea beach. A regular current may drift suspended earth and seaweed along a coast until they are caught by an eddy and finally deposited out of the reach of further disturbance, or it may scoop out the bed of the sea and undermine promontories and headlands; a powerful river, as the wind changes the direction of its flow at its outlet, may wash away shores and sandbanks at one point to deposit their material at another; the tide or waves, stirred to unusual depths by the wind, may gradually wear down the line of coast, or they may form shoals and coast dunes by depositing the sand they have rolled up from the bottom of the ocean. These latter modes of action are slow in producing effects sufficiently important to be noticed in general geography, or even to be visible in the representations of coast line laid down in ordinary maps; but they nevertheless form conspicuous features in local topography, and they are attended with consequences of great moment to the material and the moral interests of men. The forces which produce these results are all in a considerable degree subject to control, or rather to direction and resistance, by human power, and it is in guiding and combating them that man has achieved some of his most remarkable and honorable conquests over nature. The triumphs in question, or what we generally call harbor and coast improvements, whether we estimate their value by the money and labor expended upon them, or by their bearing upon the interests of commerce and the arts of civilization, must take a very high rank among the great works of man, and they are fast assuming a magnitude greatly exceeding their former relative importance. The extension of commerce and of the military marine, and especially the introduction of vessels of increased burden and deeper draught of water, have imposed upon engineers tasks of a character which a century ago would have been pronounced, and, in fact, would have been impracticable; but necessity has stimulated an ingenuity which has contrived means of executing them, and which gives promise of yet greater performance in time to come. Men have ceased to admire the power which heaped up the great pyramid to gratify the pride of a despot with a giant sepulchre; for many great harbors, many important lines of internal communication, in the civilized world, now exhibit works which surpass the vastest remains of ancient architectural art in mass and weight of matter, demand the exercise of far greater constructive skill, and involve a much heavier pecuniary expenditure than would now be required for the building of the tomb of Cheops. It is computed that the great pyramid, the solid contents of which when complete were about 3,000,000 cubic yards, could be erected for a million of pounds sterling. The breakwater at Cherbourg, founded in rough water sixty feet, deep, at an average distance of more than two miles from the shore, contains double the mass of the pyramid, and many a comparatively unimportant railroad has been constructed at twice the cost which would now build that stupendous monument. Indeed, although man, detached from the solid earth, is almost powerless to struggle against the sea, he is fast becoming invincible by it so long as his foot is planted on the shore, or even on the bottom of the rolling ocean; and though on some battle fields between the waters and the land, he is obliged slowly to yield his ground, yet he retreats still facing the foe, and will finally be able to say to the sea: "Thus far shalt thou come and no farther, and here shall thy proud waves be stayed!" The description of works of harbor and coast improvement which have only an economical value, not a true geographical importance, does not come within the plan of the present volume, and in treating this branch of my subject, I shall confine myself to such as are designed either to gain new soil by excluding the waters from grounds which they had permanently or occasionally covered, or to resist new encroachments of the sea upon the land. a. _Exclusion of the Sea by Diking._ The draining of the Lincolnshire fens in England, which converted about 400,000 acres of marsh, pool, and tide-washed flat into plough land and pasturage, is a work, or rather series of works, of great magnitude, and it possesses much economical, and, indeed, no trifling geographical importance. Its plans and methods were, at least in part, borrowed from the example of like improvements in Holland, and it is, in difficulty and extent, inferior to works executed for the same purpose on the opposite coast of the North Sea, by Dutch, Frisic, and Low German engineers. The space I can devote to such operations will be better employed in describing the latter, and I content myself with the simple statement I have already made of the quantity of worthless and even pestilential land which has been rendered both productive and salubrious in Lincolnshire, by diking out the sea, and the rivers which traverse the fens of that country. The almost continued prevalence of west winds upon both coasts of the German Ocean occasions a constant set of the currents of that sea to the east, and both for this reason and on account of the greater violence of storms from the former quarter, the English shores are much less exposed to invasion by the waves than those of the Netherlands and the provinces contiguous to them on the north. The old Netherlandish chronicles are filled with the most startling accounts of the damage done by the irruptions of the ocean, from west winds or extraordinarily high tides, at times long before any considerable extent of seacoast was diked. Several hundreds of these terrible inundations are recorded, and in very many of them the loss of human lives is estimated as high as one hundred thousand. It is impossible to doubt that there must be enormous exaggeration in these numbers; for, with all the reckless hardihood shown by men in braving the dangers and privations attached by nature to their birthplace, it is inconceivable that so dense a population as such wholesale destruction of life supposes could find the means of subsistence, or content itself to dwell, on a territory liable, a dozen times in a century, to such fearful devastation. There can be no doubt, however, that the low continental shores of the German Ocean very frequently suffered immense injury from inundation by the sea, and it is natural, therefore, that the various arts of resistance to the encroachments of the ocean, and, finally, of aggressive warfare upon its domain, and of permanent conquest of its territory, should have been earlier studied and carried to higher perfection in the latter countries, than in England, which had much less to lose or to gain by the incursions or the retreat of the waters. Indeed, although the confinement of swelling rivers by artificial embankments is of great antiquity, I do not know that the defence or acquisition of land from the sea by diking was ever practised on a large scale until systematically undertaken by the Netherlanders, a few centuries after the commencement of the Christian era. The silence of the Roman historians affords a strong presumption that this art was unknown to the inhabitants of the Netherlands at the time of the Roman invasion, and the elder Pliny's description of the mode of life along the coast which has now been long diked in, applies precisely to the habits of the people who live on the low islands and mainland flats lying outside of the chain of dikes, and wholly unprotected by embankments of any sort. It has been conjectured, and not without probability, that the causeways built by the Romans across the marshes of the Low Countries, in their campaigns against the Germanic tribes, gave the natives the first hint of the utility which might be derived from similar constructions applied to a different purpose.[306] If this is so, it is one of the most interesting among the many instances in which the arts and enginery of war have been so modified as to be eminently promotive of the blessings of peace, thereby in some measure compensating the wrongs and sufferings they have inflicted on humanity.[307] The Lowlanders are believed to have secured some coast and bay islands by ring dikes, and to have embanked some fresh water channels, as early as the eighth or ninth century; but it does not appear that sea dikes, important enough to be noticed in historical records, were constructed on the mainland before the thirteenth century. The practice of draining inland accumulation of water, whether fresh or salt, for the purpose of bringing under cultivation the ground they cover, is of later origin, and is said not to have been adopted until after the middle of the fifteenth century.[308] The total amount of surface gained to the agriculture of the Netherlands by diking out the sea and by draining shallow bays and lakes, is estimated by Staring at three hundred and fifty-five thousand _bunder_ or hectares, equal to eight hundred and seventy-seven thousand two hundred and forty acres, which is one tenth of the area of the kingdom.[309] In very many instances, the dikes have been partially, in some particularly exposed localities totally destroyed by the violence of the sea, and the drained lands again flooded. In some cases, the soil thus painfully won from the ocean has been entirely lost; in others it has been recovered by repairing or rebuilding the dikes and pumping out the water. Besides this, the weight of the dikes gradually sinks them into the soft soil beneath, and this loss of elevation must be compensated by raising the surface, while the increased burden thus added tends to sink them still lower. "Tetens declares," says Kohl, "that in some places the dikes have gradually sunk to the depth of sixty or even a hundred feet."[310] For these reasons, the processes of dike building have been almost everywhere again and again repeated, and thus the total expenditure of money and of labor upon the works in question is much greater than would appear from an estimate of the actual cost of diking-in a given extent of coast land and draining a given area of water surface.[311] On the other hand, by erosion of the coast line, the drifting of sand dunes into the interior, and the drowning of fens and morasses by incursions of the sea--all caused, or at least greatly aggravated, by human improvidence--the Netherlands have lost a far larger area of land since the commencement of the Christian era than they have gained by diking and draining. Staring despairs of the possibility of calculating the loss from the first-mentioned two causes of destruction, but he estimates that not less than six hundred and forty thousand bunder, or one million five hundred and eighty-one thousand acres, of fen and marsh have been washed away, or rather deprived of their vegetable surface and covered by water, and thirty-seven thousand bunder, or ninety-one thousand four hundred acres of recovered land, have been lost by the destruction of the dikes which protected them.[312] The average value of land gained from the sea is estimated at about nineteen pounds sterling, or ninety dollars, per acre; while the lost fen and morass was not worth more than one twenty-fifth part of the same price. The ground buried by the drifting of the dunes appears to have been almost entirely of this latter character, and, upon the whole, there is no doubt that the soil added by human industry to the territory of the Netherlands, within the historical period, greatly exceeds in pecuniary value that which has fallen a prey to the waves during the same era. Upon most low and shelving coasts, like those of the Netherlands, the maritime currents are constantly changing, in consequence of the variability of the winds, and the shifting of the sandbanks, which the currents themselves now form and now displace. While, therefore, at one point the sea is advancing landward, and requiring great effort to prevent the undermining and washing away of the dikes, it is shoaling at another by its own deposits, and exposing, at low water, a gradually widening belt of sands and ooze. The coast lands selected for diking-in are always at points where the sea is depositing productive soil. The Eider, the Elbe, the Weser, the Ems, the Rhine, the Maas, and the Schelde bring down large quantities of fine earth. The prevalence of west winds prevents the waters from carrying this material far out from the coast, and it is at last deposited northward or southward from the mouth of the rivers which contribute it, according to the varying drift of the currents. The process of natural deposit which prepares the coast for diking-in is thus described by Staring: "All sea-deposited soil is composed of the same constituents. First comes a stratum of sand, with marine shells, or the shells of mollusks living in brackish water. If there be tides, and, of course, flowing and ebbing currents, mud is let fall upon the sand only after the latter has been raised above low-water mark; for then only, at the change from flood to ebb, is the water still enough to form a deposit of so light a material. Where mud is found at greater depths, as, for example, in a large proportion of the Ij, it is a proof that at this point there was never any considerable tidal flow or other current. * * * The powerful tidal currents, flowing and ebbing twice a day, drift sand with them. They scoop out the bottom at one point, raise it at another, and the sandbanks in the current are continually shifting. As soon as a bank raises itself above low-water mark, flags and reeds establish themselves upon it. The mechanical resistance of these plants checks the retreat of the high water and favors the deposit of the earth suspended in it, and the formation of land goes on with surprising rapidity. When it has risen to high-water level, it is soon covered with grasses, and becomes what is called _schor_ in Zeeland, _kwelder_ in Friesland. Such grounds are the foundation or starting point of the process of diking. When they are once elevated to the flood-tide level, no more mud is deposited upon them except by extraordinary high tides. Their further rise is, accordingly, very slow, and it is seldom advantageous to delay longer the operation of diking."[313] The formation of new banks by the sea is constantly going on at points favorable for the deposit of sand and earth, and hence opportunity is continually afforded for enclosure of new land outside of that already diked in, the coast is fast advancing seaward, and every new embankment increases the security of former enclosures. The province of Zeeland consists of islands washed by the sea on their western coasts, and separated by the many channels through which the Schelde and some other rivers find their way to the ocean. In the twelfth century these islands were much smaller and more numerous than at present. They have been gradually enlarged, and, in several instances, at last connected by the extension of their system of dikes. Walcheren is formed of ten islets united into one about the end of the fourteenth century. At the middle of the fifteenth century, Goeree and Overflakkee consisted of separate islands, containing altogether about ten thousand acres; by means of above sixty successive advances of the dikes, they have been brought to compose a single island, whose area is not less than sixty thousand acres.[314] In the Netherlands--which the first Napoleon characterized as a deposit of the Rhine, and as, therefore, by natural law, rightfully the property of him who controlled the sources of that great river--and on the adjacent Frisic, Low German and Danish shores and islands, sea and river dikes have been constructed on a grander and more imposing scale than in any other country. The whole economy of the art has been there most thoroughly studied, and the literature of the subject is very extensive. For my present aim, which is concerned with results rather than with processes, it is not worth while to refer to professional treatises, and I shall content myself with presenting such information as can be gathered from works of a more popular character.[315] The superior strata of the lowlands upon and near the coast are, as we have seen, principally composed of soil brought down by the great rivers I have mentioned, and either directly deposited by them upon the sands of the bottom, or carried out to sea by their currents, and then, after a shorter or longer exposure to the chemical and mechanical action of salt water and marine currents, restored again to the land by tidal overflow and subsidence from the waters in which it was suspended. At a very remote period, the coast flats were, at many points, raised so high by successive alluvious or tidal deposits as to be above ordinary high water level, but they were still liable to occasional inundation from river floods, and from the sea water also, when heavy or long-continued west winds drove it landward. The extraordinary fertility of this soil and its security as a retreat from hostile violence attracted to it a considerable population, while its want of protection against inundation exposed it to the devastations of which the chroniclers of the Middle Ages have left such highly colored pictures. The first permanent dwellings on the coast flats were erected upon artificial mounds, and many similar precarious habitations still exist on the unwalled islands and shores beyond the chain of dikes. River embankments, which, as is familiarly known, have from the earliest antiquity been employed in many countries where sea dikes are unknown, were probably the first works of this character constructed in the Low Countries, and when two neighboring streams of fresh water had been embanked, the next step in the process would naturally be to connect the river walls together by a transverse dike or raised causeway, which would serve to secure the intermediate ground both against the backwater of river floods and against overflow by the sea. The oldest true sea dikes described in historical records, however, are those enclosing islands in the estuaries of the great rivers, and it is not impossible that the double character they possess as a security against maritime floods and as a military rampart, led to their adoption upon those islands before similar constructions had been attempted upon the mainland. At some points of the coast, various contrivances, such as piers, piles, and, in fact, obstructions of all sorts to the ebb of the current, are employed to facilitate the deposit of slime, before a regular enclosure is commenced. Usually, however, the first step is to build low and cheap embankments, extending from an older dike, or from high ground, around the parcel of flat intended to be secured. These are called summer dikes (_sommer-deich_, pl. _sommer-deiche_, German; _zomerkaai_, _zomerkade_, pl. _zomerkaaie_, _zomerkaden_, Dutch). They are erected when a sufficient extent of ground to repay the cost has been elevated enough to be covered with coarse vegetation fit for pasturage. They serve both to secure the ground from overflow by the ordinary flood tides of mild weather, and to retain the slime deposited by very high water, which would otherwise be partly carried off by the retreating ebb. The elevation of the soil goes on slowly after this; but when it has at last been sufficiently enriched, and raised high enough to justify the necessary outlay, permanent dikes are constructed by which the water is excluded at all seasons. These embankments are constructed of sand from the coast dunes or from sandbanks, and of earth from the mainland or from flats outside the dikes, bound and strengthened by fascines, and provided with sluices, which are generally founded on piles and of very expensive construction, for drainage at low water. The outward slope of the sea dikes is gentle, experience having shown that this form is least exposed to injury both from the waves and from floating ice, and the most modern dikes are even more moderate in the inclination of the seaward scarp than the older ones.[316] The crown of the dike, however, for the last three or four feet of its height, is much steeper, being intended rather as a protection against the spray than against the waves, and the inner slope is always comparatively abrupt. The height and thickness of dikes varies according to the elevation of the ground they enclose, the rise of the tides, the direction of the prevailing winds, and other special causes of exposure, but it may be said that they are, in general, raised from fifteen to twenty feet above ordinary high-water mark. The water slopes of river dikes are protected by plantations of willows or strong semi-aquatic shrubs or grasses, but as these will not grow upon banks exposed to salt water, sea dikes must be faced with stone, fascines, or some other _revêtement_.[317] Upon the coast of Schleswig and Holstein, where the people have less capital at their command, they defend their embankments against ice and the waves by a coating of twisted straw or reeds, which must be renewed as often as once, sometimes twice a year. The inhabitants of these coasts call the chain of dikes "the golden border," a name it well deserves, whether we suppose it to refer to its enormous cost, or, as is more probable, to its immense value as a protection to their fields and their firesides. When outlying flats are enclosed by building new embankments, the old interior dikes are suffered to remain, both as an additional security against the waves, and because the removal of them would be expensive. They serve, also, as roads or causeways, a purpose for which the embankments nearest the sea are seldom employed, because the whole structure might be endangered from the breaking of the turf by wheels and the hoofs of horses. Where successive rows of dikes have been thus constructed, it is observed that the ground defended by the more ancient embankments is lower than that embraced within the newer enclosures, and this depression of level has been ascribed to a general subsidence of the coast from geological causes; but the better opinion seems to be that it is, in most cases, due merely to the consolidation and settling of the earth from being more effectually dried, from the weight of the dikes, from the tread of men and cattle, and from the movement of the heavy wagons which carry off the crops.[318] Notwithstanding this slow sinking, most of the land enclosed by dikes is still above low-water mark, and can, therefore, be wholly or partially freed from rain water, and from that received by infiltration from higher ground, by sluices opened at the ebb of the tide. For this purpose, the land is carefully ditched, and advantage is taken of every favorable occasion for discharging the water through the sluices. But the ground cannot be effectually drained by this means, unless it is elevated four or five feet, at least, above the level of the ebb tide, because the ditches would not otherwise have a sufficient descent to carry the water off in the short interval between ebb and flow, and because the moisture of the saturated subsoil is always rising by capillary attraction. Whenever, therefore, the soil has sunk below the level I have mentioned, and in cases where its surface has never been raised above it, pumps, worked by wind or some other mechanical power, must be very frequently employed to keep the land dry enough for pasturage and cultivation.[319] b. _Draining of Lakes and Marshes._ The substitution of steam engines for the feeble and uncertain action of windmills, in driving pumps, has much facilitated the removal of water from the polders and the draining of lakes, marshes, and shallow bays, and thus given such an impulse to these enterprises, that not less than one hundred and ten thousand acres were reclaimed from the waters, and added to the agricultural domain of the Netherlands, between 1815 and 1858. The most important of these undertakings was the draining of the Lake of Haarlem, and for this purpose some of the most powerful hydraulic engines ever constructed were designed and executed.[320] The origin of this lake is unknown. It is supposed by some geographers to be a part of an ancient bed of the Rhine, the channel of which, as there is good reason to believe, has undergone great changes since the Roman invasion of the Netherlands; by others it is thought to have once formed an inland marine channel, separated from the sea by a chain of low islands, which the sand washed up by the tides has since connected with the mainland and converted into a continuous line of coast. The best authorities, however, find geological evidence that the surface occupied by the lake was originally a marshy tract containing within its limits little solid ground, but many ponds and inlets, and much floating as well as fixed fen. In consequence of the cutting of turf for fuel, and the destruction of the few trees and shrubs which held the loose soil together with their roots, the ponds are supposed to have gradually extended themselves, until the action of the wind upon their enlarged surface gave their waves sufficient force to overcome the resistance of the feeble barriers which separated them, and to unite them all into a single lake. Popular tradition, it is true, ascribes the formation of the Lake of Haarlem to a single irruption of the sea, at a remote period, and connects it with one or another of the destructive inundations of which the Netherland chronicles describe so many; but on a map of the year 1531, a chain of four smaller waters occupies nearly the ground afterward covered by the Lake of Haarlem, and they have more probably been united by gradual encroachments resulting from the improvident practices above referred to, though no doubt the consummation may have been hastened by floods, and by the neglect to maintain dikes, or the intentional destruction of them, in the long wars of the sixteenth century. The Lake of Haarlem was a body of water not far from fifteen miles in length, by seven in greatest width, lying between the cities of Amsterdam and Leyden, running parallel with the coast of Holland at the distance of about five miles from the sea, and covering an area of about 45,000 acres. By means of the Ij, it communicated with the Zuiderzee, the Mediterranean of the Netherlands, and its surface was little above the mean elevation of that of the sea. Whenever, therefore, the waters of the Zuiderzee were acted upon by strong northwest winds, those of the Lake of Haarlem were raised proportionally and driven southward, while winds from the south tended to create a flow in the opposite direction. The shores of the lake were everywhere low, and though in the course of the eighty years between 1767 and 1848 more than £350,000 or $1,700,000 had been expended in checking its encroachments, it often burst its barriers, and produced destructive inundations. On the 29th of November, 1836, a south wind brought its waters to the very gates of Amsterdam, and on the 26th of December of the same year, in a northwest gale, they overflowed twenty thousand acres of land at the southern extremity of the lake, and flooded a part of the city of Leyden. The depth of water did not, in general, exceed fourteen feet, but the bottom was a semi-fluid ooze or slime, which partook of the agitation of the waves, and added considerably to their mechanical force. Serious fears were entertained that the lake would form a junction with the inland waters of the Legmeer and Mijdrecht, swallow up a vast extent of valuable soil, and finally endanger the security of a large proportion of the land which the industry of Holland had gained in the course of centuries from the ocean. For this reason, and for the sake of the large addition the bottom of the lake would make to the cultivable soil of the state, it was resolved to drain it, and the preliminary steps for that purpose were commenced in the year 1840. The first operation was to surround the entire lake with a ring canal and dike, in order to cut off the communication with the Ij, and to exclude the water of the streams and morasses which discharged themselves into it from the land side. The dike was composed of different materials, according to the means of supply at different points, such as sand from the coast dunes, earth and turf excavated from the line of the ring canal, and floating turf,[321] fascines being everywhere used to bind and compact the mass together. This operation was completed in 1848, and three steam pumps were then employed for five years in discharging the water. The whole enterprise was conducted at the expense of the state, and in 1853 the recovered lands were offered for sale for its benefit. Up to 1858, forty-two thousand acres had been sold at not far from sixteen pounds sterling or seventy-seven dollars an acre, amounting altogether to £661,000 sterling or $3,200,000. The unsold lands were valued at more than £6,000 or nearly $30,000, and as the total cost was £764,500 or about $3,700,000, the direct loss to the state, exclusive of interest on the capital expended, may be stated at £100,000 or something less than $500,000. In a country like the United States, of almost boundless extent of sparsely inhabited territory, such an expenditure for such an object would be poor economy. But Holland has a narrow domain, great pecuniary resources, an excessively crowded population, and a consequent need of enlarged room and opportunity for the exercise of industry. Under such circumstances, and especially with an exposure to dangers so formidable, there is no question of the wisdom of the measure. It has already provided homes and occupation for more than five thousand citizens, and furnished a profitable investment for a capital of not less than £400,000 sterling or $2,000,000, which has been expended in improvements over and above the purchase money of the soil; and the greater part of this sum, as well as of the cost of drainage, has been paid as a compensation for labor. The excess of governmental expenditure over the receipts, if employed in constructing ships of war or fortifications, would have added little to the military strength of the kingdom; but the increase of territory, the multiplication of homes and firesides which the people have an interest in defending, and the augmentation of agricultural resources, constitute a stronger bulwark against foreign invasion than a ship of the line or a fortress armed with a hundred cannon. The bearing of the works I have noticed, and of others similar in character, upon the social and moral, as well as the purely economical interests of the people of the Netherlands, has induced me to describe them more in detail than the general purpose of this volume may be thought to justify; but if we consider them simply from a geographical point of view, we shall find that they are possessed of no small importance as modifications of the natural condition of terrestrial surface. There is good reason to believe that before the establishment of a partially civilized race upon the territory now occupied by Dutch, Frisic, and Low German communities, the grounds not exposed to inundation were overgrown with dense woods, that the lowlands between these forests and the sea coasts were marshes, covered and partially solidified by a thick matting of peat plants and shrubs interspersed with trees, and that even the sand dunes of the shore were protected by a vegetable growth which, in a great measure, prevented the drifting and translocation of them. The present causes of river and coast erosion existed, indeed, at the period in question; but some of them must have acted with less intensity, there were strong natural safeguards against the influence of marine and fresh-water currents, and the conflicting tendencies had arrived at a condition of approximate equilibrium, which permitted but slow and gradual changes in the face of nature. The destruction of the forests around the sources and along the valleys of the rivers by man gave them a more torrential character. The felling of the trees, and the extirpation of the shrubbery upon the fens by domestic cattle, deprived the surface of cohesion and consistence, and the cutting of peat for fuel opened cavities in it, which, filling at once with water, rapidly extended themselves by abrasion of their borders, and finally enlarged to pools, lakes, and gulfs, like the Lake of Haarlem and the northern part of the Zuiderzee. The cutting of the wood and the depasturing of the grasses upon the sand dunes converted them from solid bulwarks against the ocean to loose accumulations of dust, which every sea breeze drove farther landward, burying, perhaps, fertile soil and choking up watercourses on one side, and exposing the coast to erosion by the sea upon the other. c. _Geographical Influence of such Operations._ The changes which human action has produced within twenty centuries in the Netherlands and the neighboring provinces, are certainly of no small geographical importance, considered simply as a direct question of loss and gain of territory. They have also undoubtedly been attended with some climatic consequences, they have exercised a great influence on the spontaneous animal and vegetable life of this region, and they cannot have failed to produce effects upon tidal and other oceanic currents, the range of which may be very extensive. The force of the tidal wave, the height to which it rises, the direction of its currents, and, in fact, all the phenomena which characterize it, as well as all the effects it produces, depend as much upon the configuration of the coast it washes, and the depth of water, and form of bottom near the shore, as upon the attraction which occasions it. Every one of the terrestrial conditions which affect the character of tidal and other marine currents has been very sensibly modified by the operations I have described, and on this coast, at least, man has acted almost as powerfully on the physical geography of the sea as on that of the land. _Lowering of Lakes._ The hydraulic works of the Netherlands and of the neighboring states are of such magnitude, that they quite throw into the shade all other known artificial arrangements for defending the land against the encroachments of the rivers and the sea, and for reclaiming to the domain of agriculture and civilization soil long covered by the waters. But although the recovery and protection of lands flooded by the sea seems to be an art wholly of Netherlandish origin, we have abundant evidence, that in ancient as well as in comparatively modern times, great enterprises more or less analogous in character have been successfully undertaken, both in inland Europe and in the less familiar countries of the East. One of the best known of these is the tunnel which serves to discharge the surplus waters of the Lake of Albano, about fourteen miles from Rome. This lake, about six miles in circuit, occupies one of the craters of an extinct volcanic range, and the surface of its waters is about nine hundred feet above the sea. It is fed by rivulets and subterranean springs originating in the Alban Mount, or Monte Cavo, the most elevated peak of the volcanic group just mentioned, which rises to the height of about three thousand feet. At present the lake has no discoverable natural outlet, but it is not known that the water ever stood at such a height as to flow regularly over the lip of the crater. It seems that at the earliest period of which we have any authentic memorials, its level was usually kept by evaporation, or by discharge through subterranean channels, considerably below the rim of the basin which encompassed it, but in the year 397 B. C., the water, either from the obstruction of such channels, or in consequence of increased supplies from unknown sources, rose to such a height as to flow over the edge of the crater, and threaten inundation to the country below by bursting through its walls. To obviate this danger, a tunnel for carrying off the water was pierced at a level much below the height to which it had risen. This gallery, cut entirely with the chisel through the rock for a distance of six thousand feet, or nearly a mile and one seventh, is still in so good condition as to serve its original purpose. The fact that this work was contemporaneous with the siege of Veii, has given to ancient annalists occasion to connect the two events, but modern critics are inclined to reject Livy's account of the matter, as one of the many improbable fables which disfigure the pages of that historian. It is, however, repeated by Cicero and by Dionysins of Halicarnassus, and it is by no means impossible that, in an age when priests and soothsayers monopolized both the arts of natural magic and the little which yet existed of physical science, the Government of Rome, by their aid, availed itself at once of the superstition and of the military ardor of its citizens to obtain their sanction to an enterprise which sounder arguments might not have induced them to approve. Still more remarkable is the tunnel cut by the Emperor Claudius to drain the Lake Fucinus, now Lago di Celano, in the Neapolitan territory, about fifty miles eastward of Rome. This lake, as far as its history is known, has varied very considerably in its dimensions at different periods, according to the character of the seasons. It has no visible outlet, but was originally either drained by natural subterranean conduits, or kept within certain extreme limits by evaporation. In years of uncommon moisture, it spread over the adjacent soil and destroyed the crops; in dry seasons, it retreated, and produced epidemic disease by poisonous exhalations from the decay of vegetable and animal matter upon its exposed bed. Julius Cæsar had proposed the construction of a tunnel to drain the lake, but the enterprise was not actually undertaken until the reign of Claudius, when--after a temporary failure, from errors in levelling by the engineers, as was pretended at the time, or, as now appears certain, in consequence of frauds by the contractors in the execution of the work--it was at least partially completed. From this imperfect construction, it soon got out of repair, but was restored by Hadrian, and seems to have answered its design for some centuries. In the barbarism which followed the downfall of the empire, it again fell into decay, and though numerous attempts were made to repair it during the Middle Ages, no tolerable success seems to have attended any of these efforts, until the present generation. Works have now been some years in progress for restoring, or rather enlarging and rebuilding this ancient tunnel, upon a scale of grandeur which does infinite honor to the liberality and public spirit of the projectors, and with an ingenuity of design and a constructive skill which reflect the highest credit upon the professional ability of the engineers who have planned the works and directed their execution. The length of this tunnel is 18,634 feet, or rather more than three miles and a half. Of course, it is one of the longest subterranean galleries yet executed in Europe, and it offers many curious particulars in its original design which cannot here be described. The difference between the highest and the lowest known levels of the surface of the lake amounts to at least forty feet, and the difference of area covered at these respective stages is not much less than eight thousand acres. The tunnel will reduce the water to a much lower point, and it is computed that, including the lands occasionally overflowed, not less than forty thousand acres of as fertile soil as any in Italy will be recovered from the lake and permanently secured from inundation by its waters. Many similar enterprises have been conceived and executed in modern times, both for the purpose of reclaiming land covered by water and for sanitary reasons.[322] They are sometimes attended with wholly unexpected evils, as, for example, in the case of Barton Pond, in Vermont, and in that of the Lake Storsjö, in Sweden, already mentioned on a former page. Another still less obvious consequence of the withdrawal of the waters has occasionally been observed in these operations. The hydrostatic force with which the water, in virtue of its specific gravity, presses against the banks that confine it, has a tendency to sustain them whenever their composition and texture are not such as to expose them to softening and dissolution by the infiltration of the water. If then, the slope of the banks is considerable, or if the earth of which they are composed rests on a smooth and slippery stratum inclining toward the bed of the lake, they are liable to fall or slide forward when the mechanical support of the water is removed, and this sometimes happens on a considerable scale. A few years ago, the surface of the Lake of Lungern, in the Canton of Unterwalden, in Switzerland, was lowered by driving a tunnel about a quarter of a mile long through the narrow ridge, called the Kaiserstuhl, which forms a barrier at the north end of the basin. When the water was drawn off, the banks, which are steep, cracked and burst, several acres of ground slid down as low as the water receded, and even the whole village of Lungern was thought to be in no small danger. Other inconveniences of a very serious character have often resulted from the natural wearing down, or, much more frequently, the imprudent destruction, of the barriers which confine mountain lakes. In their natural condition, such basins serve both to receive and retain the rocks and other detritus brought down by the torrents which empty into them, and to check the impetus of the rushing waters by bringing them to a temporary pause; but if the outlets are lowered so as to drain the reservoirs, the torrents continue their rapid flow through the ancient bed of the basins, and carry down with them the sand and gravel with which they are charged, instead of depositing their burden as before in the still waters of the lakes. _Mountain Lakes._ It is a common opinion in America that the river meadows, bottoms, or _intervales_, as they are popularly called, are generally the beds of ancient lakes which have burst their barriers and left running currents in their place. It was shown by Dr. Dwight, many years ago, that this is very far from being universally true; but there is no doubt that mountain lakes were of much more frequent occurrence in primitive than in modern geography, and there are many chains of such still existing in regions where man has yet little disturbed the original features of the earth. In the long valleys of the Adirondack range in Northern New York, and in the mountainous parts of Maine, eight, ten, and even more lakes and lakelets are sometimes found in succession, each emptying into the next lower pool, and so all at last into some considerable river. When the mountain slopes which supply these basins shall be stripped of their woods, the augmented swelling of the lakes will break down their barriers, their waters will run off, and the valleys will present successions of flats with rivers running through them, instead of chains of lakes connected by natural canals. A similar state of things seems to have existed in the ancient geography of France. "Nature," says Lavergne, "has not excavated on the flanks of our Alps reservoirs as magnificent as those of Lombardy; she had, however, constructed smaller, but more numerous lakes, which the negligence of man has permitted to disappear. Auguste de Gasparin, brother of the illustrious agriculturist, demonstrated more than thirty years ago, in an original paper, that many natural dikes formerly existed in the mountain valleys, which have been swept away by the waters. He proposed to rebuild and to multiply them. This interesting suggestion has reappeared several times since, but has met with strong opposition from skilful engineers. It would, nevertheless, be well to try the experiment of creating artificial lakes which should fill themselves with the water of melting snows and deluging rains, to be drawn out in times of drought. If this plan has able opposers, it has also warm advocates. Experience alone can decide the question."[323] _Climatic Effects of Draining Lakes and Marshes._ The draining of lakes, marshes, and other superficial accumulations of moisture, reduces the water surface of a country, and, of course, the evaporation from it. Lakes, too, in elevated positions, lose a part of their water by infiltration, and thereby supply other lakes, springs, and rivulets at lower levels. Hence, it is evident that the draining of such waters, if carried on upon a large scale, must affect both the humidity and the temperature of the atmosphere, and the permanent supply of water for extensive districts.[324] _Geographical and Climatic Effects of Aqueducts, Reservoirs, and Canals._ Many processes of internal improvement, such as aqueducts for the supply of great cities, railroad cuts and embankments, and the like, divert water from its natural channels, and affect its distribution and ultimate discharge. The collecting of the waters of a considerable district into reservoirs, to be thence carried off by means of aqueducts, as, for example, in the forest of Belgrade, near Constantinople, deprives the grounds originally watered by the springs and rivulets of the necessary moisture, and reduces them to barrenness. Similar effects must have followed from the construction of the numerous aqueducts which supplied ancient Rome with such a profuse abundance of water. On the other hand, the filtration of water through the banks or walls of an aqueduct carried upon a high level across low ground, often injures the adjacent soil, and is prejudicial to the health of the neighboring population; and it has been observed in Switzerland, that fevers have been produced by the stagnation of the water in excavations from which earth had been taken to form embankments for railways. If we consider only the influence of physical improvements on civilized life, we shall perhaps ascribe to navigable canals a higher importance, or at least a more diversified influence, than to any other works of man designed to control the waters of the earth, and to affect their distribution, They bind distant regions together by social ties, through the agency of the commerce they promote; they facilitate the transportation of military stores and engines, and of other heavy material connected with the discharge of the functions of government; they encourage industry by giving marketable value to raw material and to objects of artificial elaboration which would otherwise be worthless on account of the cost of conveyance; they supply from their surplus waters means of irrigation and of mechanical power; and, in many other ways, they contribute much to advance the prosperity and civilization of nations. Nor are they wholly without geographical importance. They sometimes drain lands by conveying off water which would otherwise stagnate on the surface, and, on the other hand, like aqueducts, they render the neighboring soil cold and moist by the percolation of water through their embankments;[325] they dam up, check, and divert the course of natural currents, and deliver them at points opposite to, or distant from, their original outlets; they often require extensive reservoirs to feed them, thus retaining through the year accumulations of water--which would otherwise run off, or evaporate in the dry season--and thereby enlarging the evaporable surface of the country; and we have already seen that they interchange the flora and the fauna of provinces widely separated by nature. All these modes of action certainly influence climate and the character of terrestrial surface, though our means of observation are not yet perfected enough to enable us to appreciate and measure their effects. _Climatic and Geographical Effects of Surface and Underground Draining._ I have commenced this chapter with a description of the dikes and other hydraulic works of the Netherland engineers, because the geographical results of such operations are more obvious and more easily measured, though certainly not more important, than those of the older and more widely diffused modes of resisting or directing the flow of waters, which have been practised from remote antiquity in the interior of all civilized countries. Draining and irrigation are habitually regarded as purely agricultural processes, having little or no relation to technical geography; but we shall find that they exert a powerful influence on soil, climate, and animal and vegetable life, and may, therefore, justly claim to be regarded as geographical elements. _Surface and Under-draining and their Effects._ Superficial draining is a necessity in all lands newly reclaimed from the forest. The face of the ground in the woods is never so regularly inclined as to permit water to flow freely over it. There are, even on the hillsides, many small ridges and depressions, partly belonging to the original distribution of the soil, and partly occasioned by irregularities in the growth and deposit of vegetable matter. These, in the husbandry of nature, serve as dams and reservoirs to collect a larger supply of moisture than the spongy earth can at once imbibe. Besides this, the vegetable mould is, even under the most favorable circumstances, slow in parting with the humidity it has accumulated under the protection of the woods, and the infiltration from neighboring forests contributes to keep the soil of small clearings too wet for the advantageous cultivation of artificial crops. For these reasons, surface draining must have commenced with agriculture itself, and there is probably no cultivated district, one may almost say no single field, which is not provided with artificial arrangements for facilitating the escape of superficial water, and thus carrying off moisture which, in the natural condition of the earth, would have been imbibed by the soil. The beneficial effects of surface drainage, the necessity of extending the fields as population increased, and the inconveniences resulting from the presence of marshes in otherwise improved regions, must have suggested at a very early period of human industry the expediency of converting bogs and swamps into dry land by drawing off their waters; and it would not be long after the introduction of this practice before further acquisition of agricultural territory would be made by lowering the outlet of small ponds and lakes, and adding the ground they covered to the domain of the husbandman. All these processes belong to the incipient civilization of the ante-historical periods, but the construction of subterranean channels for the removal of infiltrated water marks ages and countries distinguished by a great advance in agricultural theory and practice, a great accumulation of pecuniary capital, and a density of population which creates a ready demand and a high price for all products of rural industry. Under-draining, too, would be most advantageous in damp and cool climates, where evaporation is slow, and upon soils where the natural inclination of surface does not promote a very rapid flow of the surface waters. All the conditions required to make this mode of rural improvement, if not absolutely necessary, at least apparently profitable, exist in Great Britain, and it is, therefore, very natural that the wealthy and intelligent farmers of England should have carried this practice farther, and reaped a more abundant pecuniary return from it, than those of any other country. Besides superficial and subsoil drains, there is another method of disposing of superfluous surface water, which, however, can rarely be practised, because the necessary conditions for its employment are not of frequent occurrence. Whenever a tenacious water-holding stratum rests on a loose, gravelly bed, so situated as to admit of a free discharge of water from or through it by means of the outcropping of the bed at a lower level, or of deep-lying conduits leading to distant points of discharge, superficial waters may be carried off by opening a passage for them through the impervious into the permeable stratum. Thus, according to Bischof, as early as the time of King Réné, in the first half of the fifteenth century, the plain of Paluns, near Marseilles, was laid dry by boring, and Wittwer informs us that drainage is effected at Munich by conducting the superfluous water into large excavations, from which it filters through into a lower stratum of pebble and gravel lying a little above the level of the river Isar.[326] So at Washington, in the western part of the city, which lies high above the rivers Potomac and Rock Creek, many houses are provided with dry wells for draining their cellars and foundations. These extend through hard tenacious earth to the depth of thirty or forty feet, when they strike a stratum of gravel, through which the water readily passes off. This practice has been extensively employed at Paris, not merely for carrying off ordinary surface water, but for the discharge of offensive and deleterious fluids from chemical and manufacturing establishments. A well of this sort received, in the winter of 1832-'33, twenty thousand gallons per day of the foul water from a starch factory, and the same process was largely used in other factories. The apprehension of injury to common and artesian wells and springs led to an investigation on this subject, in behalf of the municipal authorities, by Girard and Parent Duchatelet, in the latter year. The report of these gentlemen, published in the _Annales des Ponts et Chaussées_ for 1833, second half year, is full of curious and instructive facts respecting the position and distribution of the subterranean waters under and near Paris; but it must suffice to say that the report came to the conclusion that, in consequence of the absolute immobility of these waters, and the relatively small quantity of noxious fluid to be conveyed to them, there was no danger of the diffusion of this latter, if discharged into them. This result will not surprise those who know that, in another work, Duchatelet maintains analogous opinions as to the effect of the discharge of the city sewers into the Seine upon the waters of that river. The quantity of matter delivered by them he holds to be so nearly infinitesimal, as compared with the volume of water of the Seine, that it cannot possibly affect it to a sensible degree. I would, however, advise determined water drinkers living at Paris to adopt his conclusions, without studying his facts and his arguments; for it is quite possible that he may convert his readers to a faith opposite to his own, and that they will finally agree with the poet who held water an "ignoble beverage." _Climatic and Geographical Effects of Surface Draining._ When we remove water from the surface, we diminish the evaporation from it, and, of course, the refrigeration which accompanies all evaporation is diminished in proportion. Hence superficial draining ought to be attended with an elevation of atmospheric temperature, and, in cold countries, it might be expected to lessen the frequency of frosts. Accordingly, it is a fact of experience that, other things being equal, dry soils, and the air in contact with them, are perceptibly warmer during the season of vegetation, when evaporation is most rapid, than moist lands and the atmospheric stratum resting upon them. Instrumental observation on this special point has not yet been undertaken on a very large scale, but still we have thermometric data sufficient to warrant the general conclusion, and the influence of drainage in diminishing the frequency of frost appears to be even better established than a direct increase of atmospheric temperature. The steep and dry uplands of the Green Mountain range in New England often escape frosts when the Indian corn harvest on moister grounds, five hundred or even a thousand feet lower, is destroyed or greatly injured by them. The neighborhood of a marsh is sure to be exposed to late spring and early autumnal frosts, but they cease to be feared after it is drained, and this is particularly observable in very cold climates, as, for example, in Lapland.[327] In England, under-drains are not generally laid below the reach of daily variations of temperature, or below a point from which moisture might be brought to the surface by capillary attraction and evaporated by the heat of the sun. They, therefore, like surface drains, withdraw from local solar action much moisture which would otherwise be vaporized by it, and, at the same time, by drying the soil above them, they increase its effective hygroscopicity, and it consequently absorbs from the atmosphere a greater quantity of water than it did when, for want of under-drainage, the subsoil was always humid, if not saturated. Under-drains, then, contribute to the dryness as well as to the warmth of the atmosphere, and, as dry ground is more readily heated by the rays of the sun than wet, they tend also to raise the mean, and especially the summer temperature of the soil. So far as respects the immediate improvement of soil and climate, and the increased abundance of the harvests, the English system of surface and subsoil drainage has fully justified the eulogiums of its advocates; but its extensive adoption appears to have been attended with some altogether unforeseen and undesirable consequences, very analogous to those which I have described as resulting from the clearing of the forests. The under-drains carry off very rapidly the water imbibed by the soil from precipitation, and through infiltration from neighboring springs or other sources of supply. Consequently, in wet seasons, or after heavy rains, a river bordered by artificially drained lands receives in a few hours, from superficial and from subterranean conduits, an accession of water which, in the natural state of the earth, would have reached it only by small instalments after percolating through hidden paths for weeks or even months, and would have furnished perennial and comparatively regular contributions, instead of swelling deluges, to its channel. Thus, when human impatience rashly substitutes swiftly acting artificial contrivances for the slow methods by which nature drains the surface and superficial strata of a river basin, the original equilibrium is disturbed, the waters of the heavens are no longer stored up in the earth to be gradually given out again, but are hurried out of man's domain with wasteful haste; and while the inundations of the river are sudden and disastrous, its current, when the drains have run dry, is reduced to a rivulet, it ceases to supply the power to drive the machinery for which it was once amply sufficient, and scarcely even waters the herds that pasture upon its margin.[328] _Irrigation and its Climatic and Geographical Effects._ We know little of the history of the extinct civilizations which preceded the culture of the classic ages, and no nation has, in modern times, spontaneously emerged from barbarism, and created for itself the arts of social life.[329] The improvements of the savage races whose history we can distinctly trace are borrowed and imitative, and our theories as to the origin and natural development of industrial art are conjectural. Of course, the relative antiquity of particular branches of human industry depends much upon the natural character of soil, climate, and spontaneous vegetable and animal life in different countries; and while the geographical influence of man would, under given circumstances, be exerted in one direction, it would, under different conditions, act in an opposite or a diverging line. I have given some reasons for thinking that in the climates to which our attention has been chiefly directed, man's first interference with the natural arrangement and disposal of the waters was in the way of drainage of surface. But if we are to judge from existing remains alone, we should probably conclude that irrigation is older than drainage; for, in the regions regarded by general tradition as the cradle of the human race, we find traces of canals evidently constructed for the former purpose at a period long preceding the ages of which we have any written memorials. There are, in ancient Armenia, extensive districts which were already abandoned to desolation at the earliest historical epoch, but which, in a yet remoter antiquity, had been irrigated by a complicated and highly artificial system of canals, the lines of which can still be followed; and there are, in all the highlands where the sources of the Euphrates rise, in Persia, in Egypt, in India, and in China, works of this sort which must have been in existence before man had begun to record his own annals. In warm countries, such as most of those just mentioned, the effects I have described as usually resulting from the clearing of the forests would very soon follow. In such climates, the rains are inclined to be periodical; they are also violent, and for these reasons the soil would be parched in summer and liable to wash in winter. In these countries, therefore, the necessity for irrigation must soon have been felt, and its introduction into mountainous regions like Armenia must have been immediately followed by a system of terracing, or at least scarping the hillsides. Pasture and meadow, indeed, may be irrigated even when the surface is both steep and irregular, as may be observed abundantly on the Swiss as well as on the Piedmontese slope of the Alps; but in dry climates, plough land and gardens on hilly grounds require terracing, both for supporting the soil and for administering water by irrigation, and it should be remembered that terracing, of itself, even without special arrangements for controlling the distribution of water, prevents or at least checks the flow of rain water, and gives it time to sink into the ground instead of running off over the surface. There are few things in Continental husbandry which surprise English or American observers so much as the extent to which irrigation is employed in agriculture, and that, too, on soils, and with a temperature, where their own experience would have led them to suppose it would be injurious to vegetation rather than beneficial to it. The summers in Northern Italy, though longer, are very often not warmer than in New England; and in ordinary years, the summer rains are as frequent and as abundant in the former country as in the latter. Yet in Piedmont and Lombardy, irrigation is bestowed upon almost every crop, while in New England it is never employed at all in farming husbandry, or indeed for any purpose except in kitchen gardens, and possibly, in rare cases, in some other small branch of agricultural industry.[330] The summers in Egypt, in Syria, and in Asia Minor and even Rumelia, are almost rainless. In such climates, the necessity of irrigation is obvious, and the loss of the ancient means of furnishing it readily explains the diminished fertility of most of the countries in question.[331] The surface of Palestine, for example, is composed, in a great measure, of rounded limestone hills, once, no doubt, covered with forests. These were partially removed before the Jewish conquest.[332] When the soil began to suffer from drought, reservoirs to retain the waters of winter were hewn in the rock near the tops of the hills, and the declivities were terraced. So long as the cisterns were in good order, and the terraces kept up, the fertility of Palestine was unsurpassed, but when misgovernment and foreign and intestine war occasioned the neglect or destruction of these works--traces of which still meet the traveller's eye at every step,--when the reservoirs were broken and the terrace walls had fallen down, there was no longer water for irrigation in summer, the rains of winter soon washed away most of the thin layer of earth upon the rocks, and Palestine was reduced almost to the condition of a desert. The course of events has been the same in Idumæa. The observing traveller discovers everywhere about Petra, particularly if he enters the city by the route of Wadi Ksheibeh, very extensive traces of ancient cultivation, and upon the neighboring ridges are the ruins of numerous cisterns evidently constructed to furnish a supply of water for irrigation.[333] In primitive ages, the precipitation of winter in these hilly countries was, in great part, retained for a time in the superficial soil, first by the vegetable mould of the forests, and then by the artificial arrangements I have described. The water imbibed by the earth was partly taken up by direct evaporation, partly absorbed by vegetation, and partly carried down by infiltration to subjacent strata which gave it out in springs at lower levels, and thus a fertility of soil and a condition of the atmosphere were maintained sufficient to admit of the dense population that once inhabited those now arid wastes. At present, the rain water runs immediately off from the surface and is carried down to the sea, or is drunk up by the sands of the wadis, and the hillsides which once teemed with plenty are bare of vegetation, and seared by the scorching winds of the desert. In Southern Europe, in the Turkish Empire, and in many other countries, a very large proportion of the surface is, if not absolutely flooded, at least thoroughly moistened by irrigation, a great number of times in the course of every season, and this, especially, at periods when it would otherwise be quite dry, and when, too, the power of the sun and the capacity of the air for absorbing moisture are greatest. Hence it is obvious that the amount of evaporation from the earth in these countries, and, of course, the humidity and the temperature of both the soil and the atmosphere in contact with it, must be much affected by the practice of irrigation. The cultivable area of Egypt, or the space accessible to cultivation, between desert and desert, is more than seven thousand square statute miles. Much of the surface, though not out of the reach of irrigation, lies too high to be economically watered, and irrigation and cultivation are therefore confined to an area of five or six thousand square miles, nearly the whole of which is regularly and constantly watered when not covered by the inundation, except in the short interval between the harvest and the rise of the waters. For nearly half of the year, then, irrigation adds five or six thousand square miles, or more than a square equatorial degree, to the evaporable surface of the Nile valley, or, in other words, more than decuples the area from which an appreciable quantity of moisture would otherwise be evaporated; for after the Nile has retired within its banks, its waters by no means cover one tenth of the space just mentioned.[334] The fresh-water canals now constructing, in connection with the works for the Suez canal, will not only restore the long abandoned fields east of the Nile, but add to the arable soil of Egypt hundreds of square miles of newly reclaimed desert, and thus still further increase the climatic effects of irrigation.[335] The Nile receives not a single tributary in its course through Egypt; there is not so much as one living spring in the whole land,[336] and, with the exception of a narrow strip of coast, where the annual precipitation is said to amount to six inches, the fall of rain in the territory of the Pharaohs is not two inches in the year. The subsoil of the whole valley is pervaded with moisture by infiltration from the Nile, and water can everywhere be found at the depth of a few feet. Were irrigation suspended, and Egypt abandoned, as in that case it must be, to the operations of nature, there is no doubt that trees, the roots of which penetrate deeply, would in time establish themselves on the deserted soil, fill the valley with verdure, and perhaps at last temper the climate, and even call down abundant rain from the heavens.[337] But the immediate effect of discontinuing irrigation would be, first, an immense reduction of the evaporation from the valley in the dry season, and then a greatly augmented dryness and heat of the atmosphere. Even the almost constant north wind--the strength of which would be increased in consequence of these changes--would little reduce the temperature of the narrow cleft between the burning mountains which hem in the channel of the Nile, so that a single year would transform the most fertile of soils to the most barren of deserts, and render uninhabitable a territory that irrigation makes capable of sustaining as dense a population as has ever existed in any part of the world.[338] Whether man found the valley of the Nile a forest, or such a waste as I have just described, we do not historically know. In either case, he has not simply converted a wilderness into a garden, but has unquestionably produced extensive climatic change.[339] The fields of Egypt are more regularly watered than those of any other country bordering on the Mediterranean, except the rice grounds in Italy, and perhaps the _marcite_ or winter meadows of Lombardy; but irrigation is more or less employed throughout almost the entire basin of that sea, and is everywhere attended with effects which, if less in degree, are analogous in character to those resulting from it in Egypt. In general, it may be said that the soil is nowhere artificially watered except when it is so dry that little moisture would be evaporated from it, and, consequently, every acre of irrigated ground is so much added to the evaporable surface of the country. When the supply of water is unlimited, it is allowed, after serving its purpose on one field, to run into drains, canals, or rivers. But in most regions where irrigation is regularly employed, it is necessary to economize the water; after passing over or through one parcel of ground, it is conducted to another; no more is withdrawn from the canals at any one point than is absorbed by the soil it irrigates, or evaporated from it, and, consequently, it is not restored to liquid circulation, except by infiltration or precipitation. We are safe, then, in saying that the humidity evaporated from any artificially watered soil is increased by a quantity bearing a large proportion to the whole amount distributed over it; for most even of that which is absorbed by the earth is immediately given out again either by vegetables or by evaporation. It is not easy to ascertain precisely either the extent of surface thus watered, or the amount of water supplied, in any given country, because these quantities vary with the character of the season; but there are not many districts in Southern Europe where the management of the arrangements for irrigation is not one of the most important branches of agricultural labor. The eminent engineer Lombardini describes the system of irrigation in Lombardy as, "every day in summer, diffusing over 550,000 hectares of land 45,000,000 cubic mètres of water, which is equal to the entire volume of the Seine, at an ordinary flood, or a rise of three mètres above the hydrometer at the bridge of La Tournelle at Paris."[340] Niel states the quantity of land irrigated in the former kingdom of Sardinia, including Savoy, in 1856, at 240,000 hectares, or not much less than 600,000 acres. This is about four thirteenths of the cultivable soil of the kingdom. According to the same author, the irrigated lands in France did not exceed 100,000 hectares, or 247,000 acres, while those in Lombardy amounted to 450,000 hectares, more than 1,100,000 acres.[341] In these three states alone, then, there were more than three thousand square miles of artificially watered land, and if we add the irrigated soils of the rest of Italy, of the Mediterranean islands, of the Spanish peninsula, of Turkey in Europe and in Asia Minor, of Syria, of Egypt and the remainder of Northern Africa, we shall see that irrigation increases the evaporable surface of the Mediterranean basin by a quantity bearing no inconsiderable proportion to the area naturally covered by water within it. As near as can be ascertained, the amount of water applied to irrigated lands is scarcely anywhere less than the total precipitation during the season of vegetable growth, and in general it much exceeds that quantity. In grass grounds and in field culture it ranges from 27 or 28 to 60 inches, while in smaller crops, tilled by hand labor, it is sometimes carried as high as 300 inches.[342] The rice grounds and the _marcite_ of Lombardy are not included in these estimates of the amount of water applied. Arrangements are concluded, and new plans proposed, for an immense increase of the lands fertilized by irrigation in France and Italy, and there is every reason to believe that the artificially watered soil of the latter country will be doubled, that of France quadrupled, before the end of this century. There can be no doubt that by these operations man is exercising a powerful influence on soil, on vegetable and animal life, and on climate, and hence that in this, as in many other fields of industry, he is truly a geographical agency.[343] The quantity of water artificially withdrawn from running streams for the purpose of irrigation is such as very sensibly to affect their volume, and it is, therefore, an important element in the geography of rivers. Brooks of no trifling current are often wholly diverted from their natural channels to supply the canals, and their entire mass of water completely absorbed, so that it does not reach the river which it naturally feeds, except in such proportion as it is conveyed to it by infiltration. Irrigation, therefore, diminishes great rivers in warm countries by cutting off their sources of supply as well as by direct abstraction of water from their channels. We have just seen that the system of irrigation in Lombardy deprives the Po of a quantity of water equal to the total delivery of the Seine at ordinary flood, or, in other words, of the equivalent of a tributary navigable for hundreds of miles by vessels of considerable burden. The new canals commenced and projected will greatly increase the loss. The water required for irrigation in Egypt is less than would be supposed from the exceeding rapidity of evaporation in that arid climate; for the soil is thoroughly saturated during the inundation, and infiltration from the Nile continues to supply a considerable amount of humidity in the dryest season. Linant Bey computed that twenty-nine cubic mètres per day sufficed to irrigate a hectare in the Delta.[344] This is equivalent to a fall of rain of two millimètres and nine tenths per day, or, if we suppose water to be applied for one hundred and fifty days during the dry season, to a total precipitation of 435 millimètres, about seventeen inches and one third. Taking the area of actually cultivated soil in Egypt at the low estimate of 3,600,000 acres, and the average amount of water daily applied in both Upper and Lower Egypt at twelve hundredths of an inch in depth, we have an abstraction of 61,000,000 cubic yards, which--the mean daily delivery of the Nile being in round numbers 320,000,000 cubic yards--is nearly one fifth of the average quantity of water contributed to the Mediterranean by that river. Irrigation, as employed for certain special purposes in Europe and America, is productive of very prejudicial climatic effects. I refer particularly to the cultivation of rice in the Slave States of the American Union and in Italy. The climate of the Southern States is not necessarily unhealthy for the white man, but he can scarcely sleep a single night in the vicinity of the rice grounds without being attacked by a dangerous fever.[345] The neighborhood of the rice fields is less pestilential in Lombardy and Piedmont than in South Carolina and Georgia, but still very insalubrious to both man and beast. "Not only does the population decrease where rice is grown," says Escourrou Milliago, "but even the flocks are attacked by typhus. In the rice grounds, the soil is divided into compartments rising in gradual succession to the level of the irrigating canal, in order that the water, after having flowed one field, may be drawn off to another, and thus a single current serve for several compartments, the lowest field, of course, still being higher than the ditch which at last drains both it and the adjacent soil. This arrangement gives a certain force of hydrostatic pressure to the water with which the rice is irrigated, and the infiltration from these fields is said to extend through neighboring grounds, sometimes to the distance of not less than a myriamètre, or six English miles, and to be destructive to crops and even trees reached by it. Land thus affected can no longer be employed for any purpose but growing rice, and when prepared for that crop, it propagates still further the evils under which it had itself suffered, and, of course, the mischief is a growing one."[346] The attentive traveller in Egypt and Nubia cannot fail to notice many localities, generally of small extent, where the soil is rendered infertile by an excess of saline matter in its composition. In many cases, perhaps in all, these barren spots lie rather above the level usually flooded by the inundations of the Nile, and yet they exhibit traces of former cultivation. Recent observations in India, a notice of which I find in an account of a meeting of the Asiatic Society in the Athenæum of December 20, 1862, No. 1834, suggest a possible explanation of this fact. At this meeting, Professor Medlicott read an essay on "the saline efflorescence called 'Reh' and 'Kuller,'" which is gradually invading many of the most fertile districts of Northern and Western India, and changing them into sterile deserts. It consists principally of sulphate of soda (Glauber's salts), with varying proportions of common salt. Mr. Medlicott pronounces "these salts (which, in small quantities are favorable to fertility of soil) to be the gradual result of concentration by evaporation of river and canal waters, which contain them in very minute quantities, and with which the lands are either irrigated or occasionally overflowed." The river inundations in hot countries usually take place but once in a year, and, though the banks remain submerged for days or even weeks, the water at that period, being derived principally from rains and snows, must be less highly charged with mineral matter than at lower stages, and besides, it is always in motion. The water of irrigation, on the other hand, is applied for many months in succession, it is drawn from rivers at the seasons when their proportion of salts is greatest, and it either sinks into the superficial soil, carrying with it the saline substances it holds in solution, or is evaporated from the surface, leaving them upon it. Hence irrigation must impart to the soil more salts than natural inundation. The sterilized grounds in Egypt and Nubia lying above the reach of the floods, as I have said, we may suppose them to have been first cultivated in that remote antiquity when the Nile valley received its earliest inhabitants. They must have been artificially irrigated from the beginning; they may have been under cultivation many centuries before the soil at a lower level was invaded by man, and hence it is natural that they should be more strongly impregnated with saline matter than fields which are exposed every year, for some weeks, to the action of running water so nearly pure that it would be more likely to dissolve salts than to deposit them. INUNDATIONS AND TORRENTS. In pointing out in a former chapter the evils which have resulted from the too extensive destruction of the forests, I dwelt at some length on the increased violence of river inundations, and especially on the devastations of torrents, in countries improvidently deprived of their woods, and I spoke of the replanting of the forests as the only effectual method of preventing the frequent recurrence of disastrous floods. There are many regions where, from the loss of the superficial soil, from financial considerations, and from other causes, the restoration of the woods is not, under present circumstances, to be hoped for. Even where that measure is feasible and in actual process of execution, a great number of years must elapse before the action of the destructive causes in question can be arrested or perhaps even sensibly mitigated by it. Besides this, leaving out of view the objections urged by Belgrand and his followers to the generally received opinions concerning the beneficial influence of the forest as respects river inundations--for no one disputes its importance in preventing the formation and limiting the ravages of mountain torrents--floods will always occur in years of excessive precipitation, whether the surface of the soil be generally cleared or generally wooded. Physical improvement in this respect, then, cannot he confined to preventive measures, but, in countries subject to damage by inundation, means must he contrived to obviate dangers and diminish injuries to which human life and all the works of human industry will occasionally be exposed, in spite of every effort to lessen the frequency of their recurrence by acting directly on the causes that produce them. As every civilized country is, in some degree, subject to inundation by the overflow of rivers, the evil is a familiar one, and needs no general description. In discussing this branch of the subject, therefore, I may confine myself chiefly to the means that have been or may be employed to resist the force and limit the ravages of floods, which, left wholly unrestrained, would not only inflict immense injury upon the material interests of man, but produce geographical revolutions of no little magnitude. a. _River Embankments._ The most obvious and doubtless earliest method of preventing the escape of river waters from their natural channels, and the overflow of fields and towns by their spread, is that of raised embankments along their course. The necessity of such embankments usually arises from the gradual elevation of the bed of running streams in consequence of the deposit of the earth and gravel they are charged with in high water; and, as we have seen, this elevation is rapidly accelerated when the highlands around the headwaters of rivers are cleared of their forests. When a river is embanked at a given point, and, consequently, the water of its floods, which would otherwise spread over a wide surface, is confined within narrow limits, the velocity of the current and its transporting power are augmented, and its burden of sand and gravel is deposited at some lower point, where the rapidity of its flow is checked by a diminution in the inclination of the bed, by a wider channel, or finally by a lacustrine or marine basin which receives its waters. Wherever it lets fall solid material, its channel is raised in consequence, and the declivity of the whole bed between the head of the embankment and the slack of the stream is reduced. Hence the current, at first accelerated by confinement, is afterward checked by the mechanical resistance of the matter deposited, and by the diminished inclination of its channel, and then begins again to let fall the earth it holds in suspension, and to raise its bed at the point where its overflow had been before prevented by embankment. The bank must now be raised in proportion, and these processes would be repeated and repeated indefinitely, had not nature provided a remedy in floods, which sweep out recent deposits, burst the bonds of the river and overwhelm the adjacent country with final desolation, or divert the current into a new channel, destined to become, in its turn, the scene of a similar struggle between man and the waters. Few rivers, like the Nile, more than compensate by the fertilizing properties of their water and their slime for the damage they may do in inundations, and, consequently, there are few whose floods are not an object of dread, few whose encroachments upon their banks are not a source of constant anxiety and expense to the proprietors of the lands through which they flow. River dikes, for confining the spread of currents at high water, are of great antiquity in the East, and those of the Po and its tributaries were begun before we have any trustworthy physical or political annals of the provinces upon their borders. From the earliest ages, the Italian hydraulic engineers have stood in the front rank of their profession, and the Italian literature of this branch of material improvement is exceedingly voluminous. But the countries for which I write have no rivers like the Po, no plains like those of Lombardy, and the dangers to which the inhabitants of English and American river banks are exposed are more nearly analogous to those that threaten the soil and population in the valleys and plains of France, than to the perils and losses of the Lombard. The writings of the Italian hydrographers, too, though rich in professional instruction, are less accessible to foreigners and less adapted to popular use than those of French engineers.[347] For these reasons I shall take my citations principally from French authorities, though I shall occasionally allude to Italian writers on the floods of the Tiber, of the Arno, and some other Italian streams which much resemble those of the rivers of England and the United States. b. _Floods of the Ardèche._ The floods of mountain streams are attended with greater immediate danger to life and property than those of rivers of less rapid flow, because their currents are more impetuous, and they rise more suddenly and with less previous warning. At the same time, their ravages are confined within narrower limits, the waters retire sooner to their accustomed channel, and the danger is more quickly over, than in the case of inundations of larger rivers. The Ardèche, which has given its name to a department in France, drains a basin of 600,238 acres, or a little less than nine hundred and thirty-eight square miles. Its remotest source is about seventy-five miles, in a straight line, from its junction with the Rhone, and springs at an elevation of four thousand feet above that point. At the lowest stage of the river, the bed of the Chassezac, its largest and longest tributary, is in many places completely dry on the surface--the water being sufficient only to supply the subterranean channels of infiltration--and the Ardèche itself is almost everywhere fordable, even below the mouth of the Chassezac. But in floods, the river has sometimes risen more than sixty feet at the Pont d'Arc, a natural arch of two hundred feet chord, which spans the stream below its junction with all its important affluents. At the height of the inundation of 1827, the quantity of water passing this point--after deducting thirty per cent. for material transported with the current and for irregularity of flow--was estimated at 8,845 cubic yards to the second, and between twelve at noon on the 10th of September of that year and ten o'clock the next morning, the water discharged through the passage in question amounted to more than 450,000,000 cubic yards. This quantity, distributed equally through the basin of the river, would cover its entire area to a depth of more than five inches. The Ardèche rises so suddenly that, in the inundation of 1846, the women who were washing in the bed of the river had not time to save their linen, and barely escaped with their lives, though they instantly fled upon hearing the roar of the approaching flood. Its waters and those of its affluents fall almost as rapidly, for in less than twenty-four hours after the rain has ceased in the Cévennes, where it rises, the Ardèche returns within its ordinary channel, even at its junction with the Rhone. In the flood of 1772, the water at La Beaume de Ruoms, on the Beaume, a tributary of the Ardèche, rose thirty-five feet above low water, but the stream was again fordable on the evening of the same day. The inundation of 1827 was, in this respect, exceptional, for it continued three days, during which period the Ardèche poured into the Rhone 1,305,000,000 cubic yards of water. The Nile delivers into the sea 101,000 cubic feet or 3,741 cubic yards per second, on an average of the whole year.[348] This is equal to 323,222,400 cubic yards per day. In a single day of flood, then, the Ardèche, a river too insignificant to be known except in the local topography of France, contributed to the Rhone once and a half, and for three consecutive days once and one third, as much as the average delivery of the Nile during the same periods, though the basin of the latter river contains 500,000 square miles of surface, or more than five hundred times as much as that of the former. The average annual precipitation in the basin of the Ardèche is not greater than in many other parts of Europe, but excessive quantities of rain frequently fall in that valley in the autumn. On the 9th of October, 1827, there fell at Joyeuse, on the Beaume, no less than thirty-one inches between three o'clock in the morning and midnight. Such facts as this explain the extraordinary suddenness and violence of the floods of the Ardèche, and the basins of many other tributaries of the Rhone exhibit meteorological phenomena not less remarkable.[349] The inundation of the 10th September, 1857, was accompanied with a terrific hurricane, which passed along the eastern slope of the high grounds where the Ardèche and several other western affluents of the Rhone take their rise. The wind tore up all the trees in its path, and the rushing torrents bore their trunks down to the larger streams, which again transported them to the Rhone in such rafts that one might almost have crossed that river by stepping from trunk to trunk.[350] The Rhone, therefore, is naturally subject to great and sudden inundations, and the same remark may be applied to most of the principal rivers of France, because the geographical character of all of them is approximately the same. The height and violence of the inundations of most great rivers are determined by the degree in which the floods of the different tributaries are coincident in time. Were all the affluents of the Rhone to pour their highest annual floods into its channel at once, were a dozen Niles to empty themselves into its bed at the same moment, its water would rise to a height and rush with an impetus that would sweep into the Mediterranean the entire population of its banks, and all the works that man has erected upon the plains which border it. But such a coincidence can never happen. The tributaries of this river run in very different directions, and some of them are swollen principally by the melting of the snows about their sources, others almost exclusively by heavy rains. When a damp southeast wind blows up the valley of the Ardèche, its moisture is condensed, and precipitated in a deluge upon the mountains which embosom the headwaters of that stream, thus producing a flood, while a neighboring basin, the axis of which lies transversely or obliquely to that of the Ardèche, is not at all affected.[351] It is easy to see that the damage occasioned by such floods as I have described must be almost incalculable, and it is by no means confined to the effects produced by overflow and the mechanical force of the superficial currents. In treating of the devastations of torrents in a former chapter, I confined myself principally to the erosion of surface and the transportation of mineral matter to lower grounds by them. The general action of torrents, as there shown, tends to the ultimate elevation of their beds by the deposit of the earth, gravel, and stone conveyed by them; but until they have thus raised their outlets so as sensibly to diminish the inclination of their channels--and sometimes when extraordinary floods give the torrents momentum enough to sweep away the accumulations which they have themselves heaped up--the swift flow of their currents, aided by the abrasion of the rolling rocks and gravel, scoops their beds constantly deeper, and they consequently not only undermine their banks, but frequently sap the most solid foundations which the art of man can build for the support of bridges and hydraulic structures.[352] In the inundation of 1857, the Ardèche destroyed a stone bridge near La Beaume, which had been built about eighty years before. The resistance of the piers, which were erected on piles, the channel at that point being of gravel, produced an eddying current that washed away the bed of the river above them, and the foundation, thus deprived of lateral support, yielded to the weight of the bridge, and the piles and piers fell up stream. By a curious law of compensation, the stream which, at flood, scoops out cavities in its bed, often fills them up again as soon as the diminished velocity of the current allows it to let fall the sand and gravel with which it is charged, so that when the waters return to their usual channel, the bottom shows no sign of having been disturbed. In a flood of the Escontay, a tributary of the Rhone, in 1846, piles driven sixteen feet into its gravelly bed for the foundation of a pier were torn up and carried off, and yet, when the river had fallen to low-water mark, the bottom at that point appeared to have been raised higher than it was before the flood, by new deposits of sand and gravel, while the cut stones of the half-built pier were found buried to a great depth, in the excavation which the water had first washed out. The gravel with which rivers thus restore the level of their beds is principally derived from the crushing of the rocks brought down by the mountain torrents, and the destructive effects of inundations are immensely diminished by this reduction of large stones to minute fragments. If the blocks hurled down from the cliffs were transported unbroken to the channels of large rivers, the mechanical force of their movement would be irresistible. They would overthrow the strongest barriers, spread themselves over a surface as wide as the flow of the waters, and convert the most smiling valleys into scenes of the wildest desolation. c. _Crushing Force of Torrents._ There are few operations of nature where the effect seems more disproportioned to the cause than in the comminution of rock in the channel of swift waters. Igneous rocks are generally so hard as to be wrought with great difficulty, and they bear the weight of enormous superstructures without yielding to the pressure; but to the torrent they are as wheat to the millstone. The streams which pour down the southern scarp of the Mediterranean Alps along the Riviera di Ponente, near Genoa, have short courses, and a brisk walk of a couple of hours or even less takes you from the sea beach to the headspring of many of them. In their heaviest floods, they bring rounded masses of serpentine quite down to the sea, but at ordinary high water their lower course is charged only with finely divided particles of that rock. Hence, while, near their sources, their channels are filled with pebbles and angular fragments, intermixed with a little gravel, the proportions are reversed near their mouths, and, just above the points where their outlets are partially choked by the rolling shingle of the beach, their beds are composed of sand and gravel to the almost total exclusion of pebbles. The greatest depth of the basin of the Ardèche is seventy-five miles, but most of its tributaries have a much shorter course. "These affluents," says Mardigny, "hurl into the bed of the Ardèche enormous blocks of rock, which this river, in its turn, bears onward, and grinds down, at high water, so that its current rolls only gravel at its confluence with the Rhone."[353] Guglielmini argued that the gravel and sand of the beds of running streams were derived from the trituration of rocks by the action of the currents, and inferred that this action was generally sufficient to reduce hard rock to sand in its passage from the source to the outlet of rivers. Frisi controverted this opinion, and maintained that river sand was of more ancient origin, and he inferred from experiments in artificially grinding stones that the concussion, friction, and attrition of rock in the channel of running waters were inadequate to its comminution, though he admitted that these same causes might reduce silicious sand to a fine powder capable of transportation to the sea by the currents.[354] Frisi's experiments were tried upon rounded and polished river pebbles, and prove nothing with regard to the action of torrents upon the irregular, more or less weathered, and often cracked and shattered rocks which lie loose in the ground at the head of mountain valleys. The fury of the waters and of the wind which accompanies them in the floods of the French Alpine torrents is such, that large blocks of stone are hurled out of the bed of the stream to the height of twelve or thirteen feet. The impulse of masses driven with such force overthrows the most solid masonry, and their concussion cannot fail to be attended with the crushing of the rocks themselves.[355] d. _Inundations of 1856 in France._ The month of May, 1856, was remarkable for violent and almost uninterrupted rains, and most of the river basins of France were inundated to an extraordinary height. In the valleys of the Loire and its affluents, about a million of acres, including many towns and villages, were laid under water, and the amount of pecuniary damage was almost incalculable.[356] The flood was not less destructive in the valley of the Rhone, and in fact an invasion by a hostile army could hardly have been more disastrous to the inhabitants of the plains than was this terrible deluge. There had been a flood of this latter river in the year 1840, which, for height and quantity of water, was almost as remarkable as that of 1856, but it took place in the month of November, when the crops had all been harvested, and the injury inflicted by it upon agriculturists was, therefore, of a character to be less severely and less immediately felt than the consequences of the inundation of 1856.[357] In the fifteen years between these two great floods, the population and the rural improvements of the river valleys had much increased, common roads, bridges, and railways had been multiplied and extended, telegraph lines had been constructed, all of which shared in the general ruin, and hence greater and more diversified interests were affected by the catastrophe of 1856 than by any former like calamity. The great flood of 1840 had excited the attention and roused the sympathies of the French people, and the subject was invested with new interest by the still more formidable character of the inundations of 1856. It was felt that these scourges had ceased to be a matter of merely local concern, for, although they bore most heavily on those whose homes and fields were situated within the immediate reach of the swelling waters, yet they frequently destroyed harvests valuable enough to be a matter of national interest, endangered the personal security of the population of important political centres, interrupted communication for days and even weeks together on great lines of traffic and travel--thus severing as it were all Southwestern France from the rest of the empire--and finally threatened to produce great and permanent geographical changes. The well-being of the whole commonwealth was seen to be involved in preventing the recurrence, and in limiting the range of such devastations. The Government encouraged scientific investigation of the phenomena and their laws. Their causes, their history, their immediate and remote consequences, and the possible safeguards to be employed against them, have been carefully studied by the most eminent physicists, as well as by the ablest theoretical and practical engineers of France. Many hitherto unobserved facts have been collected, many new hypotheses suggested, and many plans, more or less original in character, have been devised for combating the evil; but thus far, the most competent judges are not well agreed as to the mode, or even the possibility, of applying a remedy. e. _Remedies against Inundations._ Perhaps no one point has been more prominent in the discussions than the influence of the forest in equalizing and regulating the flow of the water of precipitation. As we have already seen, opinion is still somewhat divided on this subject, but the conservative action of the woods in this respect has been generally recognized by the public of France, and the Government of the empire has made this principle the basis of important legislation for the protection of existing forests, and for the formation of new. The clearing of woodland, and the organization and functions of a police for its protection, are regulated by a law bearing date June 18th, 1859, and provision was made for promoting the restoration of private woods by a statute adopted on the 28th of July, 1860. The former of these laws passed the legislative body by a vote of 246 against 4, the latter with but a single negative voice. The influence of the government, in a country where the throne is so potent as in France, would account for a large majority, but when it is considered that both laws, the former especially, interfere very materially with the rights of private domain, the almost entire unanimity with which they were adopted is proof of a very general popular conviction, that the protection and extension of the forests is a measure more likely than any other to check the violence, if not to prevent the recurrence, of destructive inundations. The law of July 28th, 1860, appropriated 10,000,000 francs, to be expended, at the rate of 1,000,000 francs per year, in executing or aiding the replanting of woods. It is computed that this appropriation will secure the creation of new forest to the extent of about 250,000 acres, or one eleventh part of the soil where the restoration of the forest is thought feasible and, at the same time, specially important as a security against the evils ascribed in a great measure to its destruction. The provisions of the laws in question are preventive rather than remedial; but some immediate effect may be expected to result from them, particularly if they are accompanied with certain other measures, the suggestion of which has been favorably received. The strong repugnance of the mountaineers to the application of a system which deprives them of a part of their pasturage--for the absolute exclusion of domestic animals is indispensable to the maintenance of an existing forest and to the formation of a new--is the most formidable obstacle to the execution of the laws of 1859-'60. It is proposed to compensate this loss by a cheap system of irrigation of lower pasture grounds, consisting in little more than in running horizontal furrows along the hillsides, thus converting the scarp of the hills into a succession of small terraces which, when once turfed over, are very permanent. Experience is said to have demonstrated that this simple process suffices to retain the water of rains, of snows, and of small springs and rivulets, long enough for the irrigation of the soil, thus increasing its product of herbage in a fivefold proportion, and that it partially checks the too rapid flow of surface water into the valleys, and, consequently, in some measure obviates one of the most prominent causes of inundations.[358] It is evident that, if such results are produced by this method, its introduction upon an extensive scale must also have the same climatic effects as other systems of irrigation. Whatever may be the ultimate advantages of reclothing a large extent of the territory of France with wood, or of so shaping its surface as to prevent the too rapid flow of water over it, the results to be obtained by such processes can be realized in an adequate measure only after a long succession of years. Other steps must be taken, both for the immediate security of the lives and property of the present generation, and for the prevention of yet greater and remoter evils which are inevitable unless means to obviate them are found before it is forever too late. The frequent recurrence of inundations like those of 1856, for a single score of years, in the basins of the Rhone and the Loire, with only the present securities against them, would almost depopulate the valleys of those rivers, and produce physical revolutions in them, which, like revolutions in the political world, could never be made to "go backward." Destructive inundations are seldom, if ever, produced by precipitation within the limits of the principal valley, but almost uniformly by sudden thaws or excessive rains on the mountain ranges where the tributaries take their rise. It is therefore plain that any measures which shall check the flow of surface waters into the channels of the affluents, or which shall retard the delivery of such waters into the principal stream by its tributaries, will diminish in the same proportion the dangers and the evils of inundation by great rivers. The retention of the surface waters upon or in the soil can hardly be accomplished except by the methods already mentioned, replanting of forests, and furrowing or terracing. The current of mountain streams can be checked by various methods, among which the most familiar and obvious is the erection of barriers or dams across their channels, at points convenient for forming reservoirs large enough to retain the superfluous waters of great rains and thaws. Besides the utility of such basins in preventing floods, the construction of them is recommended by very strong considerations, such as the meteorological effects of increased evaporable surface, the furnishing of a constant supply of water for agricultural and mechanical purposes, and, finally, their value as ponds for breeding and rearing fish, and, perhaps, for cultivating aquatic vegetables. The objections to the general adoption of the system of reservoirs are these: the expense of their construction and maintenance; the reduction of cultivable area by the amount of surface they must cover; the interruption they would occasion to free communication; the probability that they would soon be filled up with sediment, and the obvious fact that when full of earth or even water, they would no longer serve their principal purpose; the great danger to which they would expose the country below them in case of the bursting of their barriers;[359] the evil consequences they would occasion by prolonging the flow of inundations in proportion as they diminished their height; the injurious effects it is supposed they would produce upon the salubrity of the neighboring districts; and, lastly, the alleged impossibility of constructing artificial basins sufficient in capacity to prevent, or in any considerable measure to mitigate, the evils they are intended to guard against. The last argument is more easily reduced to a numerical question than the others. The mean and extreme annual precipitation of all the basins where the construction of such works would be seriously proposed is already approximately known by meteorological tables, and the quantity of water, delivered by the greatest floods which have occurred within the memory of man, may be roughly estimated from their visible traces. From these elements, or from recorded observations, the capacity of the necessary reservoirs can be calculated. Let us take the case of the Ardèche. In the inundation of 1857, that river poured into the Rhone 1,305,000,000 cubic yards of water in three days. If we suppose that half this quantity might have been suffered to flow down its channel without inconvenience, we shall have about 650,000,000 cubic yards to provide for by reservoirs. The Ardèche and its principal affluent, the Chassezac, have, together, about twelve considerable tributaries rising near the crest of the mountains which bound the basin. If reservoirs of equal capacity were constructed upon all of them, each reservoir must be able to contain 54,000,000 cubic yards, or, in other words, must be equal to a lake 3,000 yards long, 1,000 yards wide, and 18 yards deep, and besides, in order to render any effectual service, the reservoirs must all have been empty at the commencement of the rains which produced the inundation. Thus far, I have supposed the swelling of the waters to be uniform throughout the whole basin; but such was by no means the fact in the inundation of 1857, for the rise of the Chassezac, which is as large as the Ardèche proper, did not exceed the limits of ordinary floods, and the dangerous excess came solely from the headwaters of the latter stream. Hence reservoirs of double the capacity I have supposed would have been necessary upon the tributaries of that river, to prevent the injurious effects of the inundation. It is evident that the construction of reservoirs of such magnitude for such a purpose is financially, if not physically, impracticable, and when we take into account a point I have just suggested, namely, that the reservoirs must be empty at all times of apprehended flood, and, of course, their utility limited almost solely to the single object of preventing inundations, the total inapplicability of such a measure in this particular case becomes still more glaringly manifest. Another not less conclusive fact is that the valleys of all the upland tributaries of the Ardèche descend so rapidly, and have so little lateral expansion, as to render the construction of capacious reservoirs in them quite impracticable. Indeed, engineers have found but two points in the whole basin suitable for that purpose, and the reservoirs admissible at these would have only a joint capacity of about 70,000,000 cubic yards, or less than one ninth part of what I suppose to be required. The case of the Ardèche is no doubt an extreme one, both in the topographical character of its basin and in its exposure to excessive rains; but all destructive inundations are, in a certain sense, extreme cases also, and this of the Ardèche serves to show that the construction of reservoirs is not by any means to be regarded as a universal panacea against floods. Nor, on the other hand, is this measure to be summarily rejected. Nature has adopted it on a great scale, on both flanks of the Alps, and on a smaller, on those of the Adirondacks and lower chains, and in this as in many other instances, her processes may often be imitated with advantage. The validity of the remaining objections to the system under discussion depends on the topography, geology, and special climate of the regions where it is proposed to establish such reservoirs. Many upland streams present numerous points where none of these objections, except those of expense and of danger from the breaking of dams, could have any application. Reservoirs may be so constructed as to retain the entire precipitation of the heaviest thaws and rains, leaving only the ordinary quantity to flow along the channel; they may be raised to such a height as only partially to obstruct the surface drainage; or they may be provided with sluices by means of which their whole contents can be discharged in the dry season and a summer crop be grown upon the ground they cover at high water. The expediency of employing them and the mode of construction depend on local conditions, and no rules of universal applicability can be laid down on the subject. It is remarkable that nations which we, in the false pride of our modern civilization, so generally regard as little less than barbarian, should have long preceded Christian Europe in the systematic employment of great artificial basins for the various purposes they are calculated to subserve. The ancient Peruvians built strong walls, of excellent workmanship, across the channels of the mountain sources of important streams, and the Arabs executed immense works of similar description, both in the great Arabian peninsula and in all the provinces of Spain which had the good fortune to fall under their sway. The Spaniards of the fifteenth and sixteenth centuries, who, in many points of true civilization and culture, were far inferior to the races they subdued, wantonly destroyed these noble monuments of social and political wisdom, or suffered them to perish, because they were too ignorant to appreciate their value, or too unskilful as practical engineers to be able to maintain them, and some of their most important territories were soon reduced to sterility and poverty in consequence. Another method of preventing or diminishing the evils of inundation by torrents and mountain rivers, analogous to that employed for the drainage of lakes, consists in the permanent or occasional diversion of their surplus waters, or of their entire currents, from their natural courses, by tunnels or open channels cut through their banks. Nature, in many cases, resorts to a similar process. Most great rivers divide themselves into several arms in their lower course, and enter the sea by different mouths. There are also cases where rivers send off lateral branches to convey a part of their waters into the channel of other streams.[360] The most remarkable of these is the junction between the Amazon and the Orinoco by the natural canal of the Cassiquiare and the Rio Negro. In India, the Cambodja and the Menam are connected by the Anam; the Saluen and the Irawaddi by the Panlaun. There are similar examples, though on a much smaller scale, in Europe. The Torneå and the Calix rivers in Lapland communicate by the Tarando, and in Westphalia, the Else, an arm of the Haase, falls into the Weser. The change of bed in rivers by gradual erosion of their banks is familiar to all, but instances of the sudden abandonment of a primitive channel are by no means wanting. At a period of unknown antiquity, the Ardèche pierced a tunnel 200 feet wide and 100 high, through a rock, and sent its whole current through it, deserting its former bed, which gradually filled up, though its course remained traceable. In the great inundation of 1827, the tunnel proved insufficient for the discharge of the water, and the river burst through the obstructions which had now choked up its ancient channel, and resumed its original course.[361] It was probably such facts as these that suggested to ancient engineers the possibility of like artificial operations, and there are numerous instances of the execution of works for this purpose in very remote ages. The Bahr Jusef, the great stream which supplies the Fayoum with water from the Nile, has been supposed, by some writers, to be a natural channel; but both it and the Bahr el Wady are almost certainly artificial canals constructed to water that basin, to regulate the level of Lake Moeris, and possibly, also, to diminish the dangers resulting from excessive inundations of the Nile, by serving as waste-weirs to discharge a part of its surplus waters. Several of the seven ancient mouths of the Nile are believed to be artificial channels, and Herodotus even asserts that King Menes diverted the entire course of that river from the Libyan to the Arabian side of the valley. There are traces of an ancient river bed along the western mountains, which give some countenance to this statement. But it is much more probable that the works of Menes were designed rather to prevent a natural, than to produce an artificial, change in the channel of the river. Two of the most celebrated cascades in Europe, those of the Teverone at Tivoli and of the Velino at Terni, owe, if not their existence, at least their position and character, to the diversion of their waters from their natural beds into new channels, in order to obviate the evils produced by their frequent floods. Remarkable works of the same sort have been executed in Switzerland, in very recent times. Until the year 1714, the Kander, which drains several large Alpine valleys, ran, for a considerable distance, parallel with the Lake of Thun, and a few miles below the city of that name emptied into the river Aar. It frequently flooded the flats along the lower part of its course, and it was determined to divert it into the Lake of Thun. For this purpose, two parallel tunnels were cut through the intervening rock, and the river turned into them. The violence of the current burst up the roof of the tunnels, and, in a very short time, wore the new channel down not less than one hundred feet, and even deepened the former bed at least fifty feet, for a distance of two or three miles above the tunnel. The lake was two hundred feet deep at the point where the river was conducted into it, but the gravel and sand carried down by the Kander has formed at its mouth a delta containing more than a hundred acres, which is still advancing at the rate of several yards a year. The Linth, which formerly sent its waters directly to the Lake of Zurich, and often produced very destructive inundations, was turned into the Wallensee about forty years ago, and in both these cases a great quantity of valuable land was rescued both from flood and from insalubrity. In Switzerland, the most terrible inundations often result from the damming up of deep valleys by ice slips or by the gradual advance of glaciers, and the accumulation of great masses of water above the obstructions. The ice is finally dissolved by the heat of summer or the flow of warm waters, and when it bursts, the lake formed above is discharged almost in an instant, and all below is swept down to certain destruction. In 1595, about a hundred and fifty lives and a great amount of property were lost by the eruption of a lake formed by the descent of a glacier into the valley of the Drance, and a similar calamity laid waste a considerable extent of soil in the year 1818. On this latter occasion, the barrier of ice and snow was 3,000 feet long, 600 thick, and 400 high, and the lake which had formed above it contained not less than 800,000,000 cubic feet. A tunnel was driven through the ice, and about 300,000,000 cubic feet of water safely drawn off by it, but the thawing of the walls of the tunnel rapidly enlarged it, and before the lake was half drained, the barrier gave way and the remaining 500,000,000 cubic feet of water were discharged in half an hour. The recurrence of these floods has since been prevented by directing streams of water, warmed by the sun, upon the ice in the bed of the valley, and thus thawing it before it accumulates in sufficient mass to threaten serious danger. In the cases of diversion of streams above mentioned, important geographical changes have been directly produced by those operations. By the rarer process of draining glacier lakes, natural eruptions of water, which would have occasioned not less important changes in the face of the earth, have been prevented by human agency. The principal means hitherto relied upon for defence against river inundations has been the construction of dikes along the banks of the streams, parallel to the channel and generally separated from each other by a distance not much greater than the natural width of the bed.[362] If such walls are high enough to confine the water and strong enough to resist its pressure, they secure the lands behind them from all the evils of inundation except those resulting from infiltration; but such ramparts are enormously costly in original construction and maintenance, and, as we have already seen, the filling up of the bed of the river in its lower course, by sand and gravel, involves the necessity of occasionally incurring new expenditures in increasing the height of the banks.[363] They are attended, too, with some collateral disadvantages. They deprive the earth of the fertilizing deposits of the waters, which are powerful natural restoratives of soils exhausted by cultivation; they accelerate the rapidity and transporting power of the current at high water by confining it to a narrower channel, and it consequently conveys to the sea the earthy matter it holds in suspension, and chokes up harbors with a deposit which it would otherwise have spread over a wide surface; they interfere with roads and the convenience of river navigation, and no amount of cost or care can secure them from occasional rupture, in case of which the rush of the waters through the breach is more destructive than the natural flow of the highest inundation.[364] For these reasons, many experienced engineers are of opinion that the system of longitudinal dikes ought to be abandoned, or, where that cannot be done without involving too great a sacrifice of existing constructions, their elevation should be much reduced, so as to present no obstruction to the lateral spread of extraordinary floods, and they should be provided with sluices to admit the water without violence whenever they are likely to be overflowed. Where dikes have not been erected, and where they have been reduced in height, it is proposed to construct, at convenient intervals, transverse embankments of moderate height running from the banks of the river across the plains to the hills which bound them. These measures, it is argued, will diminish the violence of inundations by permitting the waters to extend themselves over a greater surface and thus retarding the flow of the river currents, and will, at the same time, secure the deposit of fertilizing slime upon all the soil covered by the flood. Rozet, an eminent French engineer, has proposed a method of diminishing the ravages of inundations, which aims to combine the advantages of all other systems, and at the same time to obviate the objections to which they are all more or less liable.[365] The plan of Rozet is recommended by its simplicity and cheapness as well as its facility and rapidity of execution, and is looked upon with favor by many persons very competent to judge in such matters. He proposes to commence with the amphitheatres in which mountain torrents so often rise, by covering their slopes and filling their beds with loose blocks of rock, and by constructing at their outlets, and at other narrow points in the channels of the torrents, permeable barriers of the same material promiscuously heaped up, much according to the method employed by the ancient Romans in their northern provinces for a similar purpose. By this means, he supposes, the rapidity of the current would be checked, and the quantity of transported pebbles and gravel much diminished. When the stream has reached that part of its course where it is bordered by soil capable of cultivation, and worth the expense of protection, he proposes to place along one or both sides of the stream, according to circumstances, a line of cubical blocks of stone or pillars of masonry three or four feet high and wide, and at the distance of about eleven yards from each other. The space between the two lines, or between a line and the opposite high bank, would, of course, be determined by observation of the width of the swift-water current at high floods. As an auxiliary measure, small ditches and banks, or low walls of pebbles, should be constructed from the line of blocks across the grounds to be protected, nearly at right angles to the current, but slightly inclining downward, and at convenient distances from each other. Rozet thinks the proper interval would be 300 yards, and it is evident that, if he is right in his main principle, hedges, rows of trees, or even common fences, would in many cases answer as good a purpose as banks and trenches or low walls. The blocks or pillars of stone would, he contends, check the lateral currents so as to compel them to let fall all their pebbles and gravel in the main channel--where they would be rolled along until ground down to sand or silt--and the transverse obstructions would detain the water upon the soil long enough to secure the deposit of its fertilizing slime. Numerous facts are cited in support of the author's views, and I imagine there are few residents of rural districts whose own observation will not furnish testimony confirmatory of their soundness.[366] The deposit of slime by rivers upon the flats along their banks not only contributes greatly to the fertility of the soil thus flowed, but it subserves a still more important purpose in the general economy of nature. All running streams begin with excavating channels for themselves, or deepening the natural depressions in which they flow;[367] but in proportion as their outlets are raised by the solid material transported by their currents, their velocity is diminished, they deposit gravel and sand at constantly higher and higher points, and so at last elevate, in the middle and lower part of their course, the beds they had previously scooped out.[368] The raising of the channels is compensated in part by the simultaneous elevation of their banks and the flats adjoining them, from the deposit of the finer particles of earth and vegetable mould brought down from the mountains, without which elevation the low grounds bordering all rivers would be, as in many cases they in fact are, mere morasses. All arrangements which tend to obstruct this process of raising the flats adjacent to the channel, whether consisting in dikes which confine the waters, and, at the same time, augment the velocity of the current, or in other means of producing the last-mentioned effect, interfere with the restorative economy of nature, and at last occasion the formation of marshes where, if left to herself, she would have accumulated inexhaustible stores of the richest soil, and spread them out in plains above the reach of ordinary floods.[369] _Consequences if the Nile had been Diked._ If a system of continuous lateral dikes, like those of the Po, had been adopted in Egypt in the early dynasties, when the power and the will to undertake the most stupendous material enterprises were so eminently characteristic of the government of that country, and the waters of the annual inundation consequently prevented from flooding the land, it is conceivable that the productiveness of the small area of cultivable soil in the Nile valley might have been long kept up by artificial irrigation and the application of manures. But nature would have rebelled at last, and centuries before our time the mighty river would have burst the fetters by which impotent man had vainly striven to bind his swelling floods, the fertile fields of Egypt would have been converted into dank morasses, and then, perhaps, in some distant future, when the expulsion of man should have allowed the gradual restoration of the primitive equilibrium, would be again transformed into luxuriant garden and plough land. Fortunately, the "wisdom of Egypt" taught her children better things. They invited and welcomed, not repulsed, the slimy embraces of Nilus, and his favors have been, from the hoariest antiquity, the greatest material blessing ever bestowed upon a people.[370] The valley of the Po has probably not been cultivated or inhabited so long as that of the Nile, but embankments have been employed on its lower course for at least two thousand years, and for many centuries they have been connected in a continuous chain. I have pointed out in a former chapter the effects produced on the geography of the Adriatic by the deposit of river sediment in the sea at the mouths of the Po, the Adige, and the Brenta. If these rivers had been left unconfined, like the Nile, and allowed to spread their muddy waters at will, according to the laws of nature, the slime they have carried to the coast would have been chiefly distributed over the plains of Lombardy. Their banks would have risen as fast as their beds, the coast line would not have been extended so far into the Adriatic, and, the current of the streams being consequently shorter, the inclination of their channel and the rapidity of their flow would not have been so greatly diminished. Had man spared a reasonable proportion of the forests of the Alps, and not attempted to control the natural drainage of the surface, the Po would resemble the Nile in all its essential characteristics, and, in spite of the difference of climate, perhaps be regarded as the friend and ally, not the enemy and the invader, of the population which dwells upon its banks.[371] The Nile is larger than all the rivers of Lombardy together,[372] it drains a basin twenty times as extensive, its banks have been occupied by man probably twice as long. But its geographical character has not been much changed in the whole period of recorded history, and, though its outlets have somewhat fluctuated in number and position, its historically known encroachments upon the sea are trifling compared with those of the Po and the neighboring streams. The deposits of the Nile are naturally greater in Upper than in Lower Egypt. They are found to have raised the soil at Thebes about seven feet within the last seventeen hundred years, and in the Delta the rise has been certainly more than half as great. We shall, therefore, not exceed the truth if we suppose the annually inundated surface of Egypt to have been elevated, upon an average, ten feet, within the last 5,000 years, or twice and a half the period during which the history of the Po is known to us.[373] We may estimate the present actually cultivated area of Egypt at about 5,500 square statute miles. As I have computed in a note on page 372, that area is not more than half as extensive as under the dynasties of the Pharaohs and the Ptolemies; for--though, in consequence of the elevation of the river bed, the inundations now have a wider _natural_ spread--the industry of the ancient Egyptians conducted the Nile water over a great extent of soil it does not now reach. We may, then, adopt a mean between the two quantities, and we shall probably come near the truth if we assume the convenient number of 7,920 square statute miles as the average measure of the inundated land during the historical period. Taking the deposit on this surface at ten feet, the river sediment let fall on the soil of Egypt within the last fifty centuries would amount to fifteen cubic miles. Had the Nile been banked in, like the Po, all this deposit, except that contained in the water diverted by canals or otherwise drawn from the river for irrigation and other purposes, would have been carried out to sea.[374] This would have been a considerable quantity; for the Nile holds earth in suspension even at low water, a much larger proportion during the flood, and irrigation must have been carried on during the whole year. The precise amount which would have been thus distributed over the soil is matter of conjecture, but three cubic miles is certainly a liberal estimate. This would leave twelve cubic miles as the quantity which embankments would have compelled the Nile to transport to the Mediterranean over and above what it has actually deposited in that sea. The Mediterranean is shoal for some miles out to sea along the whole coast of the Delta, and the large bays or lagoons within the coast line, which communicate both with the river and the sea, have little depth of water. These lagoons the river deposits would have filled up, and there would still have been surplus earth enough to extend the Delta far into the Mediterranean.[375] _Deposits of the Tuscan Rivers._ The Arno, and all the rivers rising on the western slopes and spurs of the Apennines, carry down immense quantities of mud to the Mediterranean. There can be no doubt that the volume of earth so transported is very much greater than it would have been had the soil about the headwaters of those rivers continued to be protected from wash by forests; and there is as little question that the quantity borne out to sea by the rivers of Western Italy is much increased by artificial embankments, because they are thereby prevented from spreading over the surface the sedimentary matter with which they are charged. The western coast of Tuscany has advanced some miles seaward within a very few centuries. The bed of the sea, for a long distance, has been raised, and of course the relative elevation of the land above it lessened; harbors have been filled up and destroyed; long lines of coast dunes have been formed, and the diminished inclination of the beds of the rivers near their outlets has caused their waters to overflow their banks and convert them into pestilential marshes. The territorial extent of Western Italy has thus been considerably increased, but the amount of soil habitable and cultivable by man has been, in a still higher proportion, diminished. The coast of ancient Etruria was filled with great commercial towns, and their rural environs were occupied by a large and prosperous population. But maritime Tuscany has long been one of the most unhealthy districts in Christendom; the famous mart of Populonia has not an inhabitant; the coast is almost absolutely depopulated, and the malarious fevers have extended their ravages far into the interior. These results are certainly not to be ascribed wholly to human action. They are, in a large proportion, due to geological causes over which man has no control. The soil of much of Tuscany becomes pasty, almost fluid even, as soon as it is moistened, and when thoroughly saturated with water, it flows like a river. Such a soil as this would not be completely protected by woods, and, indeed, it would now be difficult to confine it long enough to allow it to cover itself with forest vegetation. Nevertheless, it certainly was once chiefly wooded, and the rivers which flow through it must then have been much less charged with earthy matter than at present, and they must have carried into the sea a smaller proportion of their sediment when they were free to deposit it on their banks than since they have been confined by dikes.[376] It is, in general, true, that the intervention of man has hitherto seemed to insure the final exhaustion, ruin, and desolation of every province of nature which he has reduced to his dominion. Attila was only giving an energetic and picturesque expression to the tendencies of human action, as personified in himself, when he said that "no grass grew where his horse's hoofs had trod." The instances are few, where a second civilization has flourished upon the ruins of an ancient culture, and lands once rendered uninhabitable by human acts or neglect have generally been forever abandoned as hopelessly irreclaimable. It is, as I have before remarked, a question of vast importance, how far it is practicable to restore the garden we have wasted, and it is a problem on which experience throws little light, because few deliberate attempts have yet been made at the work of physical regeneration, on a scale large enough to warrant general conclusions in any one class of cases. The valleys and shores of Tuscany form, however, a striking exception to this remark. The success with which human guidance has made the operations of nature herself available for the restoration of her disturbed harmonies, in the Val di Chiana and the Tuscan Maremma, is among the noblest, if not the most brilliant achievements of modern engineering, and, regarded in all its bearings on the great question of which I have just spoken, it is, as an example, of more importance to the general interests of humanity than the proudest work of internal improvement that mechanical means have yet constructed. The operations in the Val di Chiana have consisted chiefly in so regulating the flow of the surface waters into and through it, as to compel them to deposit their sedimentary matter at the will of the engineers, and thereby to raise grounds rendered insalubrious and unfit for agricultural use by stagnating water; the improvements in the Maremma have embraced both this method of elevating the level of the soil, and the prevention of the mixture of salt water with fresh in the coast marshes and shallow bays, which is a very active cause of the development of malarious influences.[377] _Improvements in the Val di Chiana._ For twenty miles or more after the remotest headwaters of the Arno have united to form a considerable stream, this river flows southeastward to the vicinity of Arezzo. It here sweeps round to the northwest, and follows that course to near its junction with the Sieve, a few miles above Florence, from which point its general direction is westward to the sea. From the bend at Arezzo, a depression called the Val di Chiana runs southeastward until it strikes into the valley of the Paglia, a tributary of the Tiber, and thus connects the basin of the latter river with that of the Arno. In the Middle Ages, and down to the eighteenth century, the Val di Chiana was often overflowed and devastated by the torrents which poured down from the highlands, transporting great quantities of slime with their currents, stagnating upon its surface, and gradually converting it into a marshy and unhealthy district, which was at last very greatly reduced in population and productiveness. It had, in fact, become so desolate that even the swallow had deserted it.[378] The bed of the Arno near Arezzo and that of the Paglia at the southern extremity of the Val di Chiana did not differ much in level. The general inclination of the valley was therefore small; it does not appear to have ever been divided into opposite slopes by a true watershed, and the position of the summit seems to have shifted according to the varying amount and place of deposit of the sediment brought down by the lateral streams which emptied into it. The length of its principal channel of drainage, and even the direction of its flow at any given point, were therefore fluctuating. Hence, much difference of opinion was entertained at different times with regard to the normal course of this stream, and, consequently, to the question whether it was to be regarded as properly an affluent of the Tiber or of the Arno. The bed of the latter river at the bend has been eroded to the depth of thirty or forty feet, and that, apparently, at no very remote period. If it were elevated to what was evidently its original height, the current of the Arno would be so much above that of the Paglia as to allow of a regular flow from its channel to the latter stream, through the Val di Chiana, provided the bed of the valley had remained at the level which excavations prove it to have had a few centuries ago, before it was raised by the deposits I have mentioned. These facts, together with the testimony of ancient geographers which scarcely admits of any other explanation, are thought to prove that all the waters of the Upper Arno were originally discharged through the Val di Chiana into the Tiber, and that a part of them still continued to flow, at least occasionally, in that direction down to the days of the Roman empire, and perhaps for some time later. The depression of the bed of the Arno, and the raising of that of the valley by the deposits of the lateral torrents and of the Arno itself, finally cut off the branch of the river which had flowed to the Tiber, and all its waters were turned into its present channel, though the principal drainage of the Val di Chiana appears to have been in a southeastwardly direction until within a comparatively recent period. In the sixteenth century, the elevation of the bed of the valley had become so considerable, that in 1551, at a point about ten miles south of the Arno, it was found to be not less than one hundred and thirty feet above that river; then followed a level of ten miles, and then a continuous descent to the Paglia. Along the level portion of the valley was a boatable channel, and lakes, sometimes a mile or even two miles in breadth, had formed at various points farther south. At this period, the drainage of the summit level might easily have been determined in either direction, and the opposite descents of the valley made to culminate at the north or at the south end of the level. In the former case, the watershed would have been ten miles south of the Arno; in the latter, twenty miles, and the division would have been not very unequal. Various schemes were suggested at this time for drawing off the stagnant waters, as well as for the future regular drainage of the valley, and small operations for those purposes were undertaken with partial success; but it was feared that the discharge of the accumulated waters into the Tiber would produce a dangerous inundation, while the diversion of the drainage into the Arno would increase the violence of the floods to which that river was very subject, and no decisive steps were taken. In 1606, an engineer whose name has not been preserved proposed, as the only possible method of improvement, the piercing of a tunnel through the hills bounding the valley on the west to convey its waters to the Ombrone, but the expense and other objections prevented the adoption of this project.[379] The fears of the Roman Government for the security of the valley of the Tiber had induced it to construct barriers across that part of the channel which lay within its territory, and these obstructions, though not specifically intended for that purpose, naturally promoted the deposit of sediment and the elevation of the bed of the valley in their neighborhood. The effect of this measure and of the continued spontaneous action of the torrents was, that the northern slope, which in 1551 had commenced at the distance of ten miles from the Arno, was found in 1605 to begin, nearly thirty miles south of that river, and in 1645 it had been removed about six miles farther in the same direction.[380] In the seventeenth century, the Tuscan and Papal Governments consulted Galileo, Torricelli, Castelli, Cassini, Viviani, and other distinguished philosophers and engineers, on the possibility of reclaiming the valley by a regular artificial drainage. Most of these eminent physicists were of opinion that the measure was impracticable, though not altogether for the same reasons; but they seem to have agreed in thinking that the opening of such channels, in either direction, as would give the current a flow sufficiently rapid to drain the lands properly, would dangerously augment the inundations of the river--whether the Tiber or the Arno--into which the waters should be turned. The general improvement of the valley was now for a long time abandoned, and the waters were allowed to spread and stagnate until carried off by partial drainage, infiltration, and evaporation. Torricelli had contended that the slope of a large part of the valley was too small to allow it to be drained by ordinary methods, and that no practicable depth and width of canal would suffice for that purpose. It could be laid dry, he thought, only by converting its surface into an inclined plane, and he suggested that this might be accomplished by controlling the flow of the numerous torrents which pour into it, so as to force them to deposit their sediment at the pleasure of the engineer, and, consequently, to elevate the level of the area over which it should be spread.[381] This plan did not meet with immediate general acceptance, but it was soon adopted for local purposes at some points in the southern part of the valley, and it gradually grew in public favor and was extended in application until its final triumph a hundred years later. In spite of these encouraging successes, however, the fear of danger to the valley of the Arno and the Tiber, and the difficulty of an agreement between Tuscany and Rome--the boundary between which states crossed the Val di Chiana not far from the halfway point between the two rivers--and of reconciling other conflicting interests, prevented the resumption of the projects for the general drainage of the valley until after the middle of the eighteenth century. In the mean time the science of hydraulics had become better understood, and the establishment of the natural law according to which the velocity of a current of water, and of course the proportional quantity discharged by it in a given time, are increased by increasing its mass, had diminished if not dissipated the fear of exposing the banks of the Arno to greater danger from inundations by draining the Val di Chiana into it. The suggestion of Torricelli was finally adopted as the basis of a comprehensive system of improvement, and it was decided to continue and extend the inversion of the original flow of the waters, and to turn them into the Arno from a point as far to the south as should be found practicable. The conduct of the works was committed to a succession of able engineers who, for a long series of years, were under the general direction of the celebrated philosopher and statesman Fossombroni, and the success has fully justified the expectations of the most sanguine advocates of the scheme. The plan of improvement embraced two branches: the one, the removal of certain obstructions in the bed of the Arno, and, consequently, the further depression of the channel of that river, in certain places, with the view of increasing the rapidity of its current; the other, the gradual filling up of the ponds and swamps, and raising of the lower grounds of the Val di Chiana, by directing to convenient points the flow of the streams which pour down into it, and there confining their waters by temporary dams until the sediment was deposited where it was needed. The economical result of these operations has been, that in 1835 an area of more than four hundred and fifty square miles of pond, marsh, and damp, sickly low grounds had been converted into fertile, healthy and well-drained soil, and, consequently, that so much territory has been added to the agricultural domain of Tuscany. But in our present view of the subject, the geographical revolution which has been accomplished is still more interesting. The climatic influence of the elevation and draining of the soil must have been considerable, though I do not know that an increase or a diminution of the mean temperature or precipitation in the valley has been established by meteorological observation. There is, however, in the improvement of the sanitary condition of the Val di Chiana, which was formerly extremely unhealthy, satisfactory proof of a beneficial climatic change. The fevers, which not only decimated the population of the low grounds but infested the adjacent hills, have ceased their ravages, and are now not more frequent than in other parts of Tuscany. The strictly topographical effect of the operations in question, besides the conversion of marsh into dry surface, has been the inversion of the inclination of the valley for a distance of thirty-five miles, so that this great plain which, within a comparatively short period, sloped and drained its waters to the south, now inclines and sends its drainage to the north. The reversal of the currents of the valley has added to the Arno a new tributary equal to the largest of its former affluents, and a most important circumstance connected with this latter fact is, that the increase of the volume of its waters has accelerated their velocity in a still greater proportion, and, instead of augmenting the danger from its inundations, has almost wholly obviated that source of apprehension. Between the beginning of the fifteenth century and the year 1761, thirty-one destructive floods of the Arno are recorded; between 1761, when the principal streams of the Val di Chiana were diverted into that river, and 1835, not one.[382] _Improvements in the Tuscan Maremme._ In the improvements of the Tuscan Maremma, more formidable difficulties have been encountered. The territory to be reclaimed was more extensive; the salubrious places of retreat for laborers and inspectors were more remote; the courses of the rivers to be controlled were longer and their natural inclination less rapid; some of them, rising in wooded regions, transported comparatively little earthy matter,[383] and above all, A like example is observed in the Anapus near Syracuse, which, below the junction of its two branches, is narrower, though swifter than either of them, and such cases are by no means unfrequent. The immediate effect of the confluence of two rivers upon the current below depends upon local circumstances, and especially upon the angle of incidence. If the two nearly coincide in direction, so as to include a small angle, the joint current will have a greater velocity than the slower confluent, perhaps even than either of them. If the two rivers run in transverse, still more if they flow in more or less opposite directions, the velocity of the principal branch will be retarded both above and below the junction, and at high water it may even set back the current of the affluent. On the other hand, the diversion of a considerable branch from a river retards its velocity below the point of separation, and here a deposit of earth in its channel immediately begins, which has a tendency to turn the whole stream into the new bed. "Theory and the authority of all hydrographical writers combine to show that the channels of rivers undergo an elevation of bed below a canal of diversion."--Letter of FOSSOMBRONI, in SALVAGNOLI, _Raccolta di Documenti_, p. 32. See the early authorities and discussions on the principle stated in the text, in FRISI, _Del modo di regolare i Fiumi e i Torrenti_, libro iii, capit. i. the coast, which is a recent deposit of the waters, is little elevated above the sea, and admits into its lagoons and the mouths of its rivers floods of salt water with every western wind, every rising tide.[384] The western coast of Tuscany is not supposed to have been an unhealthy region before the conquest of Etruria by the Romans, but it certainly became so within a few centuries after that event. This was a natural consequence of the neglect or wanton destruction of the public improvements, and especially the hydraulic works in which the Etruscans were so skilful, and of the felling of the upland forests, to satisfy the demand for wood at Rome for domestic, industrial, and military purposes. After the downfall of the Roman empire, the incursions of the barbarians, and then feudalism, foreign domination, intestine wars, and temporal and spiritual tyrannies, aggravated still more cruelly the moral and physical evils which Tuscany and the other Italian States were doomed to suffer, and from which they have enjoyed but brief respites during the whole period of modern history. The Maremma was already proverbially unhealthy in the time of Dante, who refers to the fact in several familiar passages, and the petty tyrants upon its borders often sent criminals to places of confinement in its territory, as a slow but certain mode of execution. Ignorance of the causes of the insalubrity, and often the interference of private rights,[385] prevented the adoption of measures to remove it, and the growing political and commercial importance of the large towns in more healthful localities absorbed the attention of Government, and deprived the Maremma of its just share in the systems of physical improvement which were successfully adopted in interior and Northern Italy. Before any serious attempts were made to drain or fill up the marshes of the Maremme, various other sanitary experiments were tried. It was generally believed that the insalubrity of the province was the consequence, not the cause, of its depopulation, and that, if it were once densely inhabited, the ordinary operations of agriculture, and especially the maintenance of numerous domestic fires, would restore it to its ancient healthfulness.[386] In accordance with these views, settlers were invited from various parts of Italy, from Greece, and, after the accession of the Lorraine princes, from that country also, and colonized in the Maremme. To strangers coming from soils and skies so unlike those of the Tuscan marshes, the climate was more fatal than to the inhabitants of the neighboring districts, whose constitutions had become in some degree inured to the local influences, or who at least knew better how to guard against them. The consequence very naturally was that the experiment totally failed to produce the desired effects, and was attended with a great sacrifice of life and a heavy loss to the treasury of the state. The territory known as the Tuscan Maremma, _ora maritima_, or Maremme--for the plural form is most generally used--lies upon and near the western coast of Tuscany, and comprises about 1,900 square miles English, of which 500 square miles, or 320,000 acres, are plain and marsh including 45,500 acres of water surface, and about 290,000 acres are forest. One of the mountain peaks, that of Mount Amiata, rises to the height of 6,280 feet. The mountains of the Maremma are healthy, the lower hills much less so, as the malaria is felt at some points at the height of 1,000 feet, and the plains, with the exception of a few localities favorably situated on the seacoast, are in a high degree pestilential. The fixed population is about 80,000, of whom one sixth live on the plains in the winter and about one tenth in the summer. Nine or ten thousand laborers come down from the mountains of the Maremma and the neighboring provinces into the plain, during the latter season, to cultivate and gather the crops. Out of this small number of inhabitants and strangers, 35,619 were ill enough to require medical treatment between the 1st of June, 1840, and the 1st of June, 1841, and more than one half the cases were of intermittent, malignant, gastric, or catarrhal fever. Very few agricultural laborers escaped fever, though the disease did not always manifest itself until they had returned to the mountains. In the province of Grosseto, which embraces nearly the whole of the Maremma, the annual mortality was 3.92 per cent. the average duration of life but 23.18 years, and 75 per cent. of the deaths were among persons engaged in agriculture. The filling up of the low grounds and the partial separation of the waters of the sea and the land, which had been in progress since the year 1827, now began to show very decided effects upon the sanitary condition of the population. In the year ending June 1st, 1842, the number of the sick was reduced by more than 2,000, and the cases of fever by more than 4,000. The next year, the cases of fever fell to 10,500, and in that ending June 1st, 1844, to 9,200. The political events of 1848 and the preceding and following years, occasioned the suspension of the works of improvement in the Maremma, but they were resumed after the revolution of 1859, and are now in successful progress. I have spoken, with some detail, of the improvements in the Val di Chiana and the Tuscan Maremma, because of their great relative importance, and because their history is well known; but like operations have been executed in the territory of Pisa and upon the coast of the duchy of Lucca. In the latter case, they were confined principally to prevention of the intermixing of fresh water with that of the sea. In 1741, sluices or lock gates were constructed for this purpose, and the following year, the fevers, which had been destructive to the coast population for a long time previous, disappeared altogether. In 1768 and 1769, the works having fallen to decay, the fevers returned in a very malignant form, but the rebuilding of the gates again restored the healthfulness of the shore. Similar facts recurred in 1784 and 1785, and again from 1804 to 1821. This long and repeated experience has at last impressed upon the people the necessity of vigilant attention to the sluices, which are now kept in constant repair. The health of the coast is uninterrupted, and Viareggio, the capital town of the district, is now much frequented for its sea baths and its general salubrity, at a season when formerly it was justly shunned as the abode of disease and death.[387] It is now a hundred years since the commencement of the improvements in the Val di Chiana, and those of the Maremma have been in more or less continued operation for above a generation. They have, as we have seen, produced important geographical changes in the surface of the earth and in the flow of considerable rivers, and their effects have been not less conspicuous in preventing other changes, of a deleterious character, which would infallibly have taken place if they had not been arrested by the improvements in question. It has been already stated that, in order to prevent the overflow of the valley of the Tiber by freely draining the Val di Chiana into it, the Papal authorities, long before the commencement of the Tuscan works, constructed strong barriers near the southern end of the valley, which detained the waters of the wet season until they could be gradually drawn off into the Paglia. They consequently deposited most of their sediment in the Val di Chiana and carried down comparatively little earth to the Tiber. The lateral streams contributing the largest quantities of sedimentary matter to the Val di Chiana originally flowed into that valley near its northern end; and the change of their channels and outlets in a southern direction, so as to raise that part of the valley by their deposits and thereby reverse its drainage, was one of the principal steps in the process of improvement. We have seen that the north end of the Val di Chiana near the Arno had been raised by spontaneous deposit of sediment to such a height as to interpose a sufficient obstacle to all flow in that direction. If, then, the Roman dam had not been erected, or the works of the Tuscan Government undertaken, the whole of the earth, which has been arrested by those works and employed to raise the bed and reverse the declivity of the valley, would have been carried down to the Tiber and thence into the sea. The deposit thus created, would, of course, have contributed to increase the advance of the shore at the mouth of that river, which has long been going on at the rate of three mètres and nine tenths (twelve feet and nine inches) per annum.[388] It is evident that a quantity of earth, sufficient to effect the immense changes I have described in a wide valley more than thirty miles long, if deposited at the outlet of the Tiber, would have very considerably modified the outline of the coast, and have exerted no unimportant influence on the flow of that river, by raising its point of discharge and lengthening its channel. The sediment washed into the marshes of the Maremme is not less than 12,000,000 cubic yards per annum. The escape of this quantity into the sea, which is now almost wholly prevented, would be sufficient to advance the coast line fourteen yards per year, for a distance of forty miles, computing the mean depth of the sea near the shore at twelve yards. It is true that in this case, as well as in that of other rivers, the sedimentary matter would not be distributed equally along the shore, and much of it would be carried out into deep water, or perhaps transported by the currents to distant coasts. The immediate effects of the deposit, therefore, would not be so palpable as they appear in this numerical form, but they would be equally certain, and would infallibly manifest themselves, first, perhaps, at some remote point, and afterward at or near the outlets of the rivers which produced them. _Obstruction of River Mouths._ The mouths of a large proportion of the streams known to ancient internal navigation are already blocked up by sandbars or fluviatile deposits, and the maritime approaches to river harbors frequented by the ships of Phenicia and Carthage and Greece and Rome are shoaled to a considerable distance out to sea. The inclination of almost every known river bed has been considerably reduced within the historical period, and nothing but great volume of water, or exceptional rapidity of flow, now enables a few large streams like the Amazon, the La Plata, the Ganges, and, in a less degree, the Mississippi, to carry their own deposits far enough out into deep water to prevent the formation of serious obstructions to navigation. But the degradation of their banks, and the transportation of earthy matter to the sea by their currents, are gradually filling up the estuaries even of these mighty floods, and unless the threatened evil shall be averted by the action of geological forces, or by artificial contrivances more efficient than dredging machines, the destruction of every harbor in the world which receives a considerable river must inevitably take place at no very distant date. This result would, perhaps, have followed in some incalculably distant future, if man had not come to inhabit the earth as soon as the natural forces which had formed its surface had arrived at such an approximate equilibrium that his existence on the globe was possible; but the general effect of his industrial operations has been to accelerate it immensely. Rivers, in countries planted by nature with forests and never inhabited by man, employ the little earth and gravel they transport chiefly to raise their own beds and to form plains in their basins.[389] In their upper course, where the current is swiftest, they are most heavily charged with coarse rolled or suspended matter, and this, in floods, they deposit on their shores in the mountain valleys where they rise; in their middle course, a lighter earth is spread over the bottom of their widening basins, and forms plains of moderate extent; the fine silt which floats farther is deposited over a still broader area, or, if carried out to sea, is, in great part quickly swept far off by marine currents and dropped at last in deep water. Man's "improvement" of the soil increases the erosion from its surface; his arrangements for confining the lateral spread of the water in floods compel the rivers to transport to their mouths the earth derived from that erosion even in their upper course; and, consequently, the sediment they deposit at their outlets is not only much larger in quantity, but composed of heavier materials, which sink more readily to the bottom of the sea and are less easily removed by marine currents. The tidal movement of the ocean, deep sea currents, and the agitation of inland waters by the wind, lift up the sands strewn over the bottom by diluvial streams or sent down by mountain torrents, and throw them up on dry land, or deposit them in sheltered bays and nooks of the coast--for the flowing is stronger than the ebbing tide, the affluent than the refluent wave. This cause of injury to harbors it is not in man's power to resist by any means at present available; but, as we have seen, something can be done to prevent the degradation of high grounds, and to diminish the quantity of earth which is annually abstracted from the mountains, from table lands, and from river banks, to raise the bottom of the sea. This latter cause of harbor obstruction, though an active agent, is, nevertheless, in many cases, the less powerful of the two. The earth suspended in the lower course of fluviatile currents is lighter than sea sand, river water lighter than sea water, and hence, if a land stream enters the sea with a considerable volume, its water flows over that of the sea, and bears its slime with it until it lets it fall far from shore, or, as is more frequently the case, mingles with some marine current and transports its sediment to a remote point of deposit. The earth borne out of the mouths of the Nile is in part carried over the waves which throw up sea sand on the beach, and deposited in deep water, in part drifted by the current, which sweeps east and north along the coasts of Egypt and Syria, until it finds a resting place in the northeastern angle of the Mediterranean.[390] Thus the earth loosened by the rude Abyssinian ploughshare, and washed down by the rain from the hills of Ethiopia which man has stripped of their protecting forests, contributes to raise the plains of Egypt, to shoal the maritime channels which lead to the city built by Alexander near the mouth of the Nile, and to fill up the harbors made famous by Phenician commerce. _Subterranean Waters._ I have frequently alluded to a branch of geography, the importance of which is but recently adequately recognized--the subterranean waters of the earth considered as stationary reservoirs, as flowing currents, and as filtrating fluids. The earth drinks in moisture by direct absorption from the atmosphere, by the deposition of dew, by rain and snow, by percolation from rivers and other superficial bodies of water, and sometimes by currents flowing into caves or smaller visible apertures.[391] Some of this humidity is exhaled again by the soil, some is taken up by organic growths and by inorganic compounds, some poured out upon the surface by springs and either immediately evaporated or carried down to larger streams and to the sea, some flows by subterranean courses into the bed of fresh-water rivers[392] or of the ocean, and some remains, though even here not in forever motionless repose, to fill deep cavities and underground channels.[393] In every case the aqueous vapors of the air are the ultimate source of supply, and all these hidden stores are again returned to the atmosphere by evaporation. The proportion of the water of precipitation taken up by direct evaporation from the surface of the ground seems to have been generally exaggerated, sufficient allowance not being made for moisture carried downward, or in a lateral direction, by infiltration or by crevices in the superior rocky or earthy strata. According to Wittwer, Mariotte found that but one sixth of the precipitation in the basin of the Seine was delivered into the sea by that river, "so that five sixths remained for evaporation and consumption by the organic world."[394] Lieutenant Maury--whose scientific reputation, though fallen, has not quite sunk to the level of his patriotism--estimates the annual amount of precipitation in the valley of the Mississippi at 620 cubic miles, the discharge of that river into the sea at 107 cubic miles, and concludes that "this would leave 513 cubic miles of water to be evaporated from this river basin annually."[395] In these and other like computations, the water carried down into the earth by capillary and larger conduits is wholly lost sight of, and no thought is bestowed upon the supply for springs, for common and artesian wells, and for underground rivers, like those in the great caves of Kentucky, which may gush up in fresh-water currents at the bottom of the Caribbean Sea, or rise to the light of day in the far-off peninsula of Florida. The progress of the emphatically modern science of geology has corrected these erroneous views, because the observations on which it depends have demonstrated not only the existence, but the movement, of water in nearly all geological formations, have collected evidence of the presence of large reservoirs at greater or less depths beneath surfaces of almost every character, and have investigated the rationale of the attendant phenomena. The distribution of these waters has been minutely studied with reference to a great number of localities, and though the actual mode of their vertical and horizontal transmission is still involved in much doubt, the laws which determine their aggregation are so well understood, that, when the geology of a given district is known, it is not difficult to determine at what depth water will be reached by the borer, and to what height it will rise. The same principles have been successfully applied to the discovery of small subterranean collections or currents of water, and some persons have acquired, by a moderate knowledge of the superficial structure of the earth combined with long practice, a skill in the selection of favorable places for digging wells which seems to common observers little less than miraculous. The Abbé Paramelle--a French ecclesiastic who devoted himself for some years to this subject and was extensively employed as a well-finder--states, in his work on Fountains, that in the course of thirty-four years he had pointed out more than ten thousand subterranean springs, and though his geological speculations were often erroneous, the highest scientific authorities in Europe have testified to the great practical value of his methods, and the almost infallible certainty of his predictions.[396] Babinet quotes a French proverb, "Summer rain wets nothing," and explains it as meaning that the water of such rains is "almost totally taken up by evaporation." "The rains of summer," he adds, "however abundant they may be, do not penetrate the soil to a greater depth than 15 or 20 centimètres. In summer the evaporating power of the heat is five or six times as great as in winter, and this power is exerted by an atmosphere capable of containing five times as much vapor as in winter." "A stratum of snow which prevents evaporation [from the soil] causes almost all the water that composes it to filter down into the earth, and form a reserve for springs, wells, and rivers which could not be supplied by any amount of summer rain." "This latter--useful, indeed like dew, to vegetation--does not penetrate the soil and accumulate a store to feed springs and to be brought up by them to the open air."[397] This conclusion, however applicable it may be to the climate and soil of France, is too broadly stated to be accepted as a general truth, and in countries where the precipitation is small in the winter months, familiar observation shows that the quantity of water yielded by deep wells and natural springs depends not less on the rains of summer than on those of the rest of the year, and, consequently, that much of the precipitation of that season must find its way to strata too deep to lose water by evaporation. The supply of subterranean reservoirs and currents, as well as of springs, is undoubtedly derived chiefly from infiltration, and hence it must be affected by all changes of the natural surface that accelerate or retard the drainage of the soil, or that either promote or obstruct evaporation from it. It has sufficiently appeared from what has gone before, that the spontaneous drainage of cleared ground is more rapid than that of the forest, and consequently, that the felling of the woods, as well as the draining of swamps, deprives the subterranean waters of accessions which would otherwise be conveyed to them by infiltration. The same effect is produced by artificial contrivances for drying the soil either by open ditches or by underground pipes or channels, and in proportion as the sphere of these operations is extended, the effect of them cannot fail to make itself more and more sensibly felt in the diminished supply of water furnished by wells and running springs.[398] It is undoubtedly true that loose soils, stripped of vegetation and broken up by the plough or other processes of cultivation, may, until again carpeted by grasses or other plants, absorb more rain and snow water than when they were covered by a natural growth; but it is also true that the evaporation from such soils is augmented in a still greater proportion. Rain scarcely penetrates beneath the sod of grass ground, but runs off over the surface; and after the heaviest showers a ploughed field will often be dried by evaporation before the water can be carried off by infiltration, while the soil of a neighboring grove will remain half saturated for weeks together. Sandy soils frequently rest on a tenacious subsoil, at a moderate depth, as is usually seen in the pine plains of the United States, where pools of rain water collect in slight depressions on the surface of earth, the upper stratum of which is as porous as a sponge. In the open grounds such pools are very soon dried up by the sun and wind; in the woods they remain unevaporated long enough for the water to diffuse itself laterally until it finds, in the subsoil, crevices through which it may escape, or slopes which it may follow to their outcrop or descend along them to lower strata. The readiness with which water not obstructed by impermeable strata diffuses itself through the earth in all directions--and, consequently, the importance of keeping up the supply of subterranean reservoirs--find a familiar illustration in the effect of paving the ground about the stems of vines and trees. The surface earth around the trunk of a tree may be made perfectly impervious to water, by flag stones and cement, for a distance greater than the spread of the roots; and yet the tree will not suffer for want of moisture, except in droughts severe enough sensibly to affect the supply in deep wells and springs. Both forest and fruit trees grow well in cities where the streets and courts are closely paved, and where even the lateral access of water to the roots is more or less obstructed by deep cellars and foundation walls. The deep-lying veins and sheets of water, supplied by infiltration from above, send up moisture by capillary attraction, and the pavement prevents the soil beneath it from losing its humidity by evaporation. Hence, city-grown trees find moisture enough for their roots, and though plagued with smoke and dust, often retain their freshness while those planted in the open fields, where sun and wind dry up the soil faster than the subterranean fountains can water it, are withering from drought. Without the help of artificial conduit or of water carrier, the Thames and the Seine refresh the ornamental trees that shade the thoroughfares of London and of Paris, and beneath the hot and reeking mould of Egypt, the Nile sends currents to the extremest border of its valley.[399] _Artesian Wells._ The existence of artesian wells depends upon that of subterranean reservoirs and rivers, and the supply yielded by borings is regulated by the abundance of such sources. The waters of the earth are, in many cases, derived from superficial currents which are seen to pour into chasms opened, as it were, expressly for their reception; and in others where no apertures in the crust of the earth have been detected, their existence is proved by the fact that artesian wells sometimes bring up from great depths seeds, leaves, and even living fish, which must have been carried down through channels large enough to admit a considerable stream. But in general, the sheets and currents of water reached by deep boring appear to be primarily due to infiltration from highlands where the water is first collected in superficial or subterranean reservoirs. By means of channels conforming to the dip of the strata, these reservoirs communicate with the lower basins, and exert upon them a fluid pressure sufficient to raise a column to the surface, whenever an orifice is opened.[400] The water delivered by an artesian well is, therefore, often derived from distant sources, and may be wholly unaffected by geographical or meteorological changes in its immediate neighborhood, while the same changes may quite dry up common wells and springs which are fed only by the local infiltration of their own narrow basins. In most cases, artesian wells have been bored for purely economical or industrial purposes, such as to obtain good water for domestic use or for driving light machinery, to reach saline or other mineral springs, and recently, in America, to open fountains of petroleum or rock oil. The geographical and geological effects of such abstraction of fluids from the bowels of the earth are too remote and uncertain to be here noticed;[401] but artesian wells have lately been employed in Algeria for a purpose which has even now a substantial, and may hereafter acquire a very great geographical importance. It was observed by many earlier as well as recent travellers in the East, among whom Shaw deserves special mention, that the Libyan desert, bordering upon the cultivated shores of the Mediterranean, appeared in many places to rest upon a subterranean lake at an accessible distance below the surface. The Moors are vaguely said to have _bored_ artesian wells down to this reservoir, to obtain water for domestic use and irrigation, but I do not find such wells described by any trustworthy traveller, and the universal astonishment and incredulity with which the native tribes viewed the operations of the French engineers sent into the desert for that purpose, are a sufficient proof that this mode of reaching the subterranean waters was new to them. They were, however, aware of the existence of water below the sands, and were dexterous in digging wells--square shafts lined with a framework of palm-tree stems--to the level of the sheet. The wells so constructed, though not technically artesian wells, answer the same purpose; for the water rises to the surface and flows over it as from a spring.[402] These wells, however, are too few and too scanty in supply to serve any other purposes than the domestic wells of other countries, and it is but recently that the transformation of desert into cultivable land by this means has been seriously attempted. The French Government has bored a large number of artesian wells in the Algerian desert within a few years, and the native sheikhs are beginning to avail themselves of the process. Every well becomes the nucleus of a settlement proportioned to the supply of water, and before the end of the year 1860, several nomade tribes had abandoned their wandering life, established themselves around the wells, and planted more than 30,000 palm trees, besides other perennial vegetables.[403] The water is found at a small depth, generally from 100 to 200 feet, and though containing too large a proportion of mineral matter to be acceptable to a European palate, it answers well for irrigation, and does not prove unwholesome to the natives. The most obvious use of artesian wells in the desert at present is that of creating stations for the establishment of military posts and halting places for the desert traveller; but if the supply of water shall prove adequate for the indefinite extension of the system, it is probably destined to produce a greater geographical transformation than has ever been effected by any scheme of human improvement. The most striking contrast of landscape scenery that nature brings near together in time or place, is that between the greenery of the tropics, or of a northern summer, and the snowy pall of leafless winter. Next to this in startling novelty of effect, we must rank the sudden transition from the shady and verdant oasis of the desert to the bare and burning party-colored ocean of sand and rock which surrounds it.[404] The most sanguine believer in indefinite human progress hardly expects that man's cunning will accomplish the universal fufilment of the prophecy, "the desert shall blossom as the rose," in its literal sense; but sober geographers have thought the future conversion of the sand plains of Northern Africa into fruitful gardens, by means of artesian wells, not an improbable expectation. They have gone farther, and argued that, if the soil were covered with fields and forests, vegetation would call down moisture from the Libyan sky, and that the showers which are now wasted on the sea, or so often deluge Southern Europe with destructive inundation, would in part be condensed over the arid wastes of Africa, and thus, without further aid from man, bestow abundance on regions which nature seems to have condemned to perpetual desolation. An equally bold speculation, founded on the well-known fact, that the temperature of the earth and of its internal waters increases as we descend beneath the surface, has suggested that artesian wells might supply heat for industrial and domestic purposes, for hot-house cultivation, and even for the local amelioration of climate. The success with which Count Lardarello has employed natural hot springs for the evaporation of water charged with boracic acid, and other fortunate applications of the heat of thermal sources, lend some countenance to the latter project; but both must, for the present, be ranked among the vague possibilities of science, not regarded as probable future triumphs of man over nature. _Artificial Springs._ A more plausible and inviting scheme is that of the creation of perennial springs by husbanding rain and snow water, storing it up in artificial reservoirs of earth, and filtering it through purifying strata, in analogy with the operations of nature. The sagacious Palissy--starting from the theory that all springs are primarily derived from precipitation, and reasoning justly on the accumulation and movement of water in the earth--proposed to reduce theory to practice, and to imitate the natural processes by which rain is absorbed by the earth and given out again in running fountains. "When I had long and diligently considered the cause of the springing of natural fountains and the places where they be wont to issue," says he, "I did plainly perceive, at last, that they do proceed and are engendered of nought but the rains. And it is this, look you, which hath moved me to enterprise the gathering together of rain water after the manner of nature, and the most closely according to her fashion that I am able; and I am well assured that by following the formulary of the Supreme Contriver of fountains, I can make springs, the water whereof shall be as good and pure and clear as of such which be natural."[405] Palissy discusses the subject of the origin of springs at length and with much ability, dwelling specially on infiltration, and, among other things, thus explains the frequency of springs in mountainous regions: "Having well considered the which, thou mayest plainly see the reason why there be more springs and rivulets proceeding from the mountains than from the rest of the earth; which is for no other cause but that the rocks and mountains do retain the water of the rains like vessels of brass. And the said waters falling upon the said mountains descend continually through the earth, and through crevices, and stop not till they find some place that is bottomed with stone or close and thick rocks; and they rest upon such bottom until they find some channel or other manner of issue, and then they flow out in springs or brooks or rivers, according to the greatness of the reservoirs and of the outlets thereof."[406] After a full exposition of his theory, Palissy proceeds to describe his method of creating springs, which is substantially the same as that lately proposed by Babinet in the following terms: "Choose a piece of ground containing four or five acres, with a sandy soil, and with a gentle slope to determine the flow of the water. Along its upper line, dig a trench five or six feet deep and six feet wide. Level the bottom of the trench, and make it impermeable by paving, by macadamizing, by bitumen, or, more simply and cheaply, by a layer of clay. By the side of this trench dig another, and throw the earth from it into the first, and so on until you have rendered the subsoil of the whole parcel impermeable to rain water. Build a wall along the lower line with an aperture in the middle for the water, and plant fruit or other low trees upon the whole, to shade the ground and check the currents of air which promote evaporation. This will infallibly give you a good spring which will flow without intermission and supply the wants of a whole hamlet or a large chateau."[407] Babinet states that the whole amount of precipitation on a reservoir of the proposed area, in the climate of Paris, would be about 13,000 cubic yards, not above one half of which, he thinks, would be lost, and, of course, the other half would remain available to supply the spring. I much doubt whether this expectation would be realized in practice, in its whole extent; for if Babinet is right in supposing that the summer rain is wholly evaporated, the winter rains, being much less in quantity, would hardly suffice to keep the earth saturated and give off so large a surplus. The method of Palissy, though, as I have said, similar in principle to that of Babinet, would be cheaper of execution, and, at the same time, more efficient. He proposes the construction of relatively small filtering receptacles, into which he would conduct the rain falling upon a large area of rocky hillside, or other sloping ground not readily absorbing water. This process would, in all probability, be a very successful, as well as an inexpensive, mode of economizing atmospheric precipitation, and compelling the rain and snow to form perennial fountains at will. _Economizing Precipitation._ The methods suggested by Palissy and by Babinet are of limited application, and designed only to supply a sufficient quantity of water for the domestic use of small villages or large private establishments. Dumas has proposed a much more extensive system for collecting and retaining the whole precipitation in considerable valleys, and storing it in reservoirs, whence it is to be drawn for household and mechanical purposes, for irrigation, and, in short, for all the uses to which the water of natural springs and brooks is applicable. His plan consists in draining both surface and subsoil, by means of conduits differing in construction according to local circumstances, but in the main not unlike those employed in improved agriculture, collecting the water in a central channel, securing its proper filterage, checking its too rapid flow by barriers at convenient points, and finally receiving the whole in spacious covered reservoirs, from which it may be discharged in a constant flow or at intervals as convenience may dictate.[408] There is no reasonable doubt that a very wide employment of these various contrivances for economizing and supplying water is practicable, and the expediency of resorting to them is almost purely an economical question. There appears to be no serious reason to apprehend collateral evils from them, and in fact all of them, except artesian wells, are simply indirect methods of returning to the original arrangements of nature, or, in other words, of restoring the fluid circulation of the globe; for when the earth was covered with the forest, perennial springs gushed from the foot of every hill, brooks flowed down the bed of every valley. The partial recovery of the fountains and rivulets which once abundantly watered the face of the agricultural world seems practicable by such means, even without any general replanting of the forests; and the cost of one year's warfare, if judiciously expended in a combination of both methods of improvement, would secure, to almost every country that man has exhausted, an amelioration of climate, a renovated fertility of soil, and a general physical improvement, which might almost be characterized as a new creation. CHAPTER V. THE SANDS. ORIGIN OF SAND--SAND NOW CARRIED DOWN TO THE SEA--THE SANDS OF EGYPT AND THE ADJACENT DESERT----THE SUEZ CANAL----THE SANDS OF EGYPT--COAST DUNES AND SAND PLAINS--SAND BANKS--DUNES ON COAST OF AMERICA--DUNES OF WESTERN EUROPE--FORMATION OF DUNES--CHARACTER OF DUNE SAND--INTERIOR STRUCTURE OF DUNES--FORM OF DUNES--GEOLOGICAL IMPORTANCE OF DUNES--INLAND DUNES-- AGE, CHARACTER, AND PERMANENCE OF DUNES--USE OF DUNES AS BARRIER AGAINST THE SEA--ENCROACHMENTS OF THE SEA--THE LIIMFJORD--ENCROACHMENTS OF THE SEA--DRIFTING OF DUNE SANDS--DUNES OF GASCONY--DUNES OF DENMARK--DUNES OF PRUSSIA--ARTIFICIAL FORMATION OF DUNES--TREES SUITABLE FOR DUNE PLANTATIONS--EXTENT OF DUNES IN EUROPE--DUNE VINEYARDS OF CAPE BRETON-- REMOVAL OF DUNES--INLAND SAND PLAINS--THE LANDES OF GASCONY--THE BELGIAN CAMPINE--SANDS AND STEPPES OF EASTERN EUROPE--ADVANTAGES OF RECLAIMING DUNES--GOVERNMENT WORKS OF IMPROVEMENT. _Origin of Sand._ Sand, which is found in beds or strata at the bottom of the sea or in the channels of rivers, as well as in extensive deposits upon or beneath the surface of the dry land, appears to consist essentially of the detritus of rocks. It is not always by any means clear through what agency the solid rock has been reduced to a granular condition; for there are beds of quartzose sand, where the sharp, angular shape of the particles renders it highly improbable that they have been formed by gradual abrasion and attrition, and where the supposition of a crushing mechanical force seems equally inadmissible. In common sand, the quartz grains are the most numerous; but this is not a proof that the rocks from which these particles were derived were wholly, or even chiefly, quartzose in character; for, in many composite rocks, as, for example, in the granitic group, the mica, felspar, and hornblende are more easily decomposed by chemical action, or disintegrated, comminuted, and reduced to an impalpable state by mechanical force, than the quartz. In the destruction of such rocks, therefore, the quartz would survive the other ingredients, and remain unmixed, when they had been decomposed and had entered into new chemical combinations, or been ground to slime and washed away by water currents. The greater or less specific gravity of the different constituents of rock doubtless aids in separating them into distinct masses when once disintegrated, though there are veined and stratified beds of sand where the difference between the upper and lower layers, in this respect, is too slight to be supposed capable of effecting a complete separation.[409] In cases where rock has been reduced to sandy fragments by heat, or by obscure chemical and other molecular forces, the sandbeds may remain undisturbed, and represent, in the series of geological strata, the solid formations from which they were derived. The large masses of sand not found in place have been transported and accumulated by water or by wind, the former being generally considered the most important of these agencies; for the extensive deposits of the Sahara, of the deserts of Persia, and of that of Gobi, are commonly supposed to have been swept together or distributed by marine currents, and to have been elevated above the ocean by the same means as other upheaved strata. Meteoric and mechanical influences are still active in the reduction of rocks to a fragmentary state; but the quantity of sand now transported to the sea seems to be comparatively inconsiderable, because--not to speak of the absence of diluvial action--the number of torrents emptying directly into the sea is much less than it was at earlier periods. The formation of alluvial plains in maritime bays, by the sedimentary matter brought down from the mountains, has lengthened the flow of such streams and converted them very generally into rivers, or rather affluents of rivers much younger than themselves. The filling up of the estuaries has so reduced the slope of all large and many small rivers, and, consequently, so checked the current of what the Germans call their _Unterlauf_, or lower course, that they are much less able to transport heavy material than at earlier epochs. The slime deposited by rivers at their junction with the sea, is usually found to be composed of material too finely ground and too light to be denominated sand, and it can be abundantly shown that the sandbanks at the outlet of large streams are of tidal, not of fluviatile origin, or, in lakes and tideless seas, a result of the concurrent action of waves and of wind. Large deposits of sand, therefore, must in general be considered as of ancient, not of recent formation, and many eminent geologists ascribe them to diluvial action. Staring has discussed this question very fully, with special reference to the sands of the North Sea, the Zuiderzee, and the bays and channels of the Dutch coast.[410] His general conclusion is, that the rivers of the Netherlands "move sand only by a very slow displacement of sandbanks, and do not carry it with them as a suspended or floating material." The sands of the German Ocean he holds to be a product of the "great North German drift," deposited where they now lie before the commencement of the present geological period, and he maintains similar opinions with regard to the sands thrown up by the Mediterranean at the mouths of the Nile and on the Barbary coast.[411] _Sand now carried to the Sea._ There are, however, cases where mountain streams still bear to the sea perhaps relatively small, but certainly absolutely large, amounts of disintegrated rock.[412] The quantity of sand and gravel carried into the Mediterranean by the torrents of the Maritime Alps, the Ligurian Apennines, the islands of Corsica, Sardinia, and Sicily, and the mountains of Calabria, is apparently great. In mere mass, it is possible, if not probable, that as much rocky material, more or less comminuted, is contributed to the basin of the Mediterranean by Europe, even excluding the shores of the Adriatic and the Euxine, as is washed up from it upon the coasts of Africa and Syria. A great part of this material is thrown out again by the waves on the European shores of that sea. The harbors of Luni, Albenga, San Remo, and Savona west of Genoa, and of Porto Fino on the other side, are filling up, and the coast near Carrara and Massa is said to have advanced upon the sea to a distance of 475 feet in thirty-three years.[413] Besides this, we have no evidence of the existence of deep-water currents in the Mediterranean, extensive enough and strong enough to transport quartzose sand across the sea. It may be added that much of the rock from which the torrent sands of Southern Europe are derived contains little quartz, and hence the general character of these sands is such that they must be decomposed or ground down to an impalpable slime, long before they could be swept over to the African shore. The torrents of Europe, then, do not at present furnish the material which composes the beach sands of Northern Africa, and it is equally certain that those sands are not brought down by the rivers of the latter continent. They belong to a remote geological period, and have been accumulated by causes which we cannot at present assign. The wind does not stir water to great depths with sufficient force to disturb the bottom,[414] and the sand thrown upon the coast in question must be derived from a narrow belt of sea. It must hence, in time, become exhausted, and the formation of new sandbanks and dunes upon the southern shores of the Mediterranean will cease at last for want of material.[415] But even in the cases where the accumulations of sand in extensive deserts appear to be of marine formation, or rather aggregation, and to have been brought to their present position by upheaval, they are not wholly composed of material collected or distributed by the currents of the sea; for, in all such regions, they continue to receive some small contributions from the disintegration of the rocks which underlie, or crop out through, the superficial deposits. In some instances, too, as in Northern Africa, additions are constantly made to the mass by the prevalence of sea winds, which transport, or, to speak more precisely, roll the finer beach sand to considerable distances into the interior. But this is a very slow process, and the exaggerations of travellers have diffused a vast deal of popular error on the subject. _Sands of Egypt._ In the narrow valley of the Nile--which, above its bifurcation near Cairo, is, throughout Egypt and Nubia, generally bounded by precipitous cliffs--wherever a ravine or other considerable depression occurs in the wall of rock, one sees what seems a stream of desert sand pouring down, and common observers have hence concluded that the whole valley is in danger of being buried under a stratum of infertile soil. The ancient Egyptians apprehended this, and erected walls, often of unburnt brick, across the outlet of gorges and lateral valleys, to check the flow of the sand streams. In later ages, these walls have mostly fallen into decay, and no preventive measures against such encroachments are now resorted to. But the extent of the mischief to the soil of Egypt, and the future danger from this source, have been much overrated. The sand on the borders of the Nile is neither elevated so high by the wind, nor transported by that agency in so great masses, as is popularly supposed; and of that which is actually lifted or rolled and finally deposited by air currents, a considerable proportion is either calcareous, and, therefore, readily decomposable, or in the state of a very fine dust, and so, in neither case, injurious to the soil. There are, indeed, both in Africa and in Arabia, considerable tracts of fine silicious sand, which may be carried far by high winds, but these are exceptional cases, and in general the progress of the desert sand is by a rolling motion along the surface.[416] So little is it lifted, and so inconsiderable is the quantity yet remaining on the borders of Egypt, that a wall four or five feet high suffices for centuries to check its encroachments. This is obvious to the eye of every observer who prefers the true to the marvellous; but the old-world fable of the overwhelming of caravans by the fearful simoom--which, even the Arabs no longer repeat, if indeed they are the authors of it--is so thoroughly rooted in the imagination of Christendom that most desert travellers, of the tourist class, think they shall disappoint the readers of their journals if they do not recount the particulars of their escape from being buried alive by a sand storm, and the popular demand for a "sensation" must be gratified accordingly.[417] Another circumstance is necessary to be considered in estimating the danger to which the arable lands of Egypt are exposed. The prevailing wind in the valley of the Nile and its borders is from the north, and it may be said without exaggeration that the north wind blows for three quarters of the year.[418] The effect of winds blowing up the valley is to drive the sands of the desert plateau which border it, in a direction parallel with the axis of the valley, not transversely to it; and if it ran in a straight line, the north wind would carry no desert sand into it. There are, however, both curves and angles in its course, and hence, wherever its direction deviates from that of the wind, it might receive sand drifts from the desert plain through which it runs. But, in the course of ages, the winds have, in a great measure, bared the projecting points of their ancient deposits, and no great accumulations remain in situations from which either a north or a south wind would carry them into the valley.[419] _The Suez Canal._ These considerations apply, with equal force, to the supposed danger of the obstruction of the Suez Canal by the drifting of the desert sands. The winds across the isthmus are almost uniformly from the north, and they swept it clean of flying sands long ages since. The traces of the ancient canal between the Red Sea and the Nile are easily followed for a considerable distance from Suez. Had the drifts upon the isthmus been as formidable as some have feared and others have hoped, those traces would have been obliterated, and Lake Timsah and the Bitter Lakes filled up, many centuries ago. The few particles driven by the rare east and west winds toward the line of the canal, would easily be arrested by plantations or other simple methods, or removed by dredging. The real dangers and difficulties of this magnificent enterprise--and they are great--consist in the nature of the soil to be removed in order to form the line, and especially in the constantly increasing accumulation of sea sand at the southern terminus by the tides of the Red Sea, and at the northern, by the action of the winds. Both seas are shallow for miles from the shore, and the excavation and maintenance of deep channels, and of capacious harbors with easy and secure entrances, in such localities, is doubtless one of the hardest problems offered to modern engineers for practical solution. _Sands of Egypt._ The sand let fall in Egypt by the north wind is derived, not from the desert, but from a very different source--the sea. Considerable quantities of sand are thrown up by the Mediterranean, at and between the mouths of the Nile, and indeed along almost the whole southern coast of that sea, and drifted into the interior to distances varying according to the force of the wind and the abundance and quality of the material. The sand so transported contributes to the gradual elevation of the Delta, and of the banks and bed of the river itself. But just in proportion as the bed of the stream is elevated, the height of the water in the annual inundations is increased also, and as the inclination of the channel is diminished, the rapidity of the current is checked, and the deposition of the slime it holds in suspension consequently promoted. Thus the winds and the water, moving in contrary directions, join in producing a common effect. The sand, blown over the Delta and the cultivated land higher up the stream during the inundation, is covered or mixed with the fertile earth brought down by the river, and no serious injury is sustained from it. That spread over the same ground after the water has subsided, and during the short period when the soil is not stirred by cultivation or covered by the flood, forms a thin pellicle over the surface as far as it extends, and serves to divide and distinguish the successive layers of slime deposited by the annual inundations. The particles taken up by the wind on the sea beach are borne onward, by a hopping motion, or rolled along the surface, until they are arrested by the temporary cessation of the wind, by vegetation, or by some other obstruction, and they may, in process of time, accumulate in large masses, under the lee of rocky projections, buildings, or other barriers which break the force of the wind. In these facts we find the true explanation of the sand drifts, which have half buried the Sphinx and so many other ancient monuments in that part of Egypt. These drifts, as I have said, are not primarily from the desert, but from the sea; and, as might be supposed from the distance they have travelled, they have been long in gathering. While Egypt was a great and flourishing kingdom, measures were taken to protect its territory against the encroachment of sand, whether from the desert or from the sea; but the foreign conquerors, who destroyed so many of its religious monuments, did not spare its public works, and the process of physical degradation undoubtedly began as early as the Persian invasion. The urgent necessity, which has compelled all the successive tyrannies of Egypt to keep up some of the canals and other arrangements for irrigation, was not felt with respect to the advancement of the sands; for their progress was so slow as hardly to be perceptible in the course of a single reign, and long experience has shown that, from the natural effect of the inundations, the cultivable soil of the valley is, on the whole, trenching upon the domain of the desert, not retreating before it. The oases of the Libyan, as well as of many Asiatic deserts, have no such safeguards. The sands are fast encroaching upon them, and threaten soon to engulf them, unless man shall resort to artesian wells and plantations, or to some other efficient means of checking the advance of this formidable enemy, in time to save these islands of the waste from final destruction. Accumulations of sand are, in certain cases, beneficial as a protection against the ravages of the sea; but, in general, the vicinity, and especially the shifting of bodies of this material, are destructive to human industry, and hence, in civilized countries, measures are taken to prevent its spread. This, however, can be done only where the population is large and enlightened, and the value of the soil, or of the artificial erections and improvements upon it, is considerable. Hence in the deserts of Africa and of Asia, and the inhabited lands which border on them, no pains are usually taken to check the drifts, and when once the fields, the houses, the springs, or the canals of irrigation are covered or choked, the district is abandoned without a struggle, and surrendered to perpetual desolation.[420] _Sand Dunes and Sand Plains._ Two forms of sand deposit are specially important in European and American geography. The one is that of dune or shifting hillock upon the coast, the other that of barren plain in the interior. The coast dunes are composed of sand washed up from the depths of the sea by the waves, and heaped in knolls and ridges by the winds. The sand with which many plains are covered, appears sometimes to have been deposited upon them while they were yet submerged, sometimes to have been drifted from the sea coast, and scattered over them by wind currents, sometimes to have been washed upon them by running water. In these latter cases, the deposit, though in itself considerable, is comparatively narrow in extent and irregular in distribution, while, in the former, it is often evenly spread over a very wide surface. In all great bodies of either sort, the silicious grains are the principal constituent, though, when not resulting from the disintegration of silicious rock and still remaining in place, they are generally accompanied with a greater or less admixture of other mineral particles, and of animal and vegetable remains,[421] and they are, also, usually somewhat changed in consistence by the ever-varying conditions of temperature and moisture to which they have been exposed since their deposit. Unless the proportion of these latter ingredients is so large as to create a certain adhesiveness in the mass--in which case it can no longer properly be called sand--it is infertile, and, if not charged with water, partially agglutinated by iron, lime, or other cement, or confined by alluvion resting upon it, it is much inclined to drift, whenever, by any chance, the vegetable network which, in most cases, thinly clothes and at the same time confines it, is broken. Human industry has not only fixed the flying dunes, but, by mixing clay and other tenacious earths with the superficial stratum of extensive sand plains, and by the application of fertilizing substances, it has made them abundantly productive of vegetable life. These latter processes belong to agriculture and not to geography, and, therefore, are not embraced within the scope of the present subject. But the preliminary steps, whereby wastes of loose, drifting barren sands are transformed into wooded knolls and plains, and finally, through the accumulation of vegetable mould, into arable ground, constitute a conquest over nature which precedes agriculture--a geographical revolution--and, therefore, an account of the means by which the change has been effected belongs properly to the history of man's influence on the great features of physical geography. I proceed, then, to examine the structure of dunes, and to describe the warfare man wages with the sand hills, striving on the one hand to maintain and even extend them, as a natural barrier against encroachments of the sea, and, on the other, to check their moving and wandering propensities, and prevent them from trespassing upon the fields he has planted and the habitations in which he dwells. _Coast Dunes._ Coast dunes are oblong ridges or round hillocks, formed by the action of the wind upon sands thrown up by the waves on the beach of seas, and sometimes of fresh-water lakes. On most coasts, the supply of sand for the formation of dunes is derived from tidal waves. The flow of the tide is more rapid, and consequently its transporting power greater, than that of the ebb; the momentum, acquired by the heavy particles in rolling in with the water, tends to carry them even beyond the flow of the waves; and at the turn of the tide, the water is in a state of repose long enough to allow it to let fall much of the solid matter it holds in suspension. Hence, on all low, tide-washed coasts of seas with sandy bottoms, there exist several conditions favorable to the formation of sand deposits along high-water mark.[422] If the land winds are of greater frequency, duration, or strength than the sea winds, the sands left by the retreating wave will be constantly blown back into the water; but if the prevailing air currents are in the opposite direction, the sands will soon be carried out of the reach of the highest waves, and transported continually farther and farther into the interior of the land, unless obstructed by high grounds, vegetation, or other obstacles. The tide, though a usual, is by no means a necessary condition for the accumulations of sand out of which dunes are formed. The Baltic and the Mediterranean are almost tideless seas, but there are dunes on the Russian and Prussian coasts of the Baltic, and at the mouths of the Nile and many other points on the shores of the Mediterranean. The vast shoals in the latter sea, known to the ancients as the Greater and Lesser Syrtis, are of marine origin. They are still filling up with sand, washed up from greater depths, or sometimes drifted from the coast in small quantities, and will probably be converted, at some future period, into dry land covered with sand hills. There are also extensive ranges of dunes upon the eastern shores of the Caspian, and at the southern, or rather southeastern extremity of Lake Michigan.[423] There is no doubt that this latter lake formerly extended much farther in that direction, but its southern portion has gradually shoaled and at last been converted into solid land, in consequence of the prevalence of the northwest winds. These blow over the lake a large part of the year, and create a southwardly set of the currents, which wash up sand from the bed of the lake and throw it on shore. Sand is taken up from the beach at Michigan City by every wind from that quarter, and, after a heavy blow of some hours' duration, sand ridges may be observed on the north side of the fences, like the snow wreaths deposited by a drifting wind in winter. Some of the particles are carried back by contrary winds, but most of them lodge on or behind the dunes, or in the moist soil near the lake, or are entangled by vegetables, and tend permanently to elevate the level. Like effects are produced by constant sea winds, and dunes will generally be formed on all low coasts where such prevail, whether in tideless or in tidal waters. Jobard thus describes the _modus operandi_, under ordinary circumstances, at the mouths of the Nile, where a tide can scarcely be detected: "When a wave breaks, it deposits an almost imperceptible line of fine sand. The next wave brings also its contribution, and shoves the preceding line a little higher. As soon as the particles are fairly out of the reach of the water they are dried by the heat of the burning sun, and immediately seized by the wind and rolled or borne farther inland. The gravel is not thrown out by the waves, but rolls backward and forward until it is worn down to the state of fine sand, when it, in its turn, is cast upon the land and taken up by the wind."[424] This description applies only to the common every-day action of wind and water; but just in proportion to the increasing force of the wind and the waves, there is an increase in the quantity of sand, and in the magnitude of the particles carried off from the beach by it, and, of course, every storm in a landward direction adds sensibly to the accumulation upon the shore. _Sand Banks._ Although dunes, properly so called, are found only on dry land and above ordinary high-water mark, and owe their elevation and structure to the action of the wind, yet, upon many shelving coasts, accumulations of sand much resembling dunes are formed under water at some distance from the shore by the oscillations of the waves, and are well known by the name of sand banks. They are usually rather ridges than banks, of moderate inclination, and with the steepest slope seaward; and their form differs from that of dunes only in being lower and more continuous. Upon the western coast of the island of Amrum, for example, there are three rows of such banks, the summits of which are at a distance of perhaps a couple of miles from each other; so that, including the width of the banks themselves, the spaces between them, and the breadth of the zone of dunes upon the land, the belt of moving sands on that coast is probably not less than eight miles wide. Under ordinary circumstances, sand banks are always rolling landward, and they compose the magazine from which the material for the dunes is derived. The dunes, in fact, are but aquatic sand banks transferred to dry land. The laws of their formation are closely analogous, because the action of the two fluids, by which they are respectively accumulated and built up, is very similar when brought to bear upon loose particles of solid matter. It would, indeed, seem that the slow and comparatively regular movements of the heavy, unelastic water ought to affect such particles very differently from the sudden and fitful impulses of the light and elastic air. But the velocity of the wind currents gives them a mechanical force approximating to that of the slower waves, and, however difficult it may be to explain all the phenomena that characterize the structure of the dunes, observation has proved that it is nearly identical with that of submerged sand banks. The differences of form are generally ascribable to the greater number and variety of surface accidents of the ground on which the sand hills of the land are built up, and to the more frequent changes, and wider variety of direction, in the courses of the wind. _Dunes on the Coast of America._ Upon the Atlantic coast of the United States, the prevalence of western or off-shore winds is unfavorable to the formation of dunes, and, though marine currents lodge vast quantities of sand, in the form of banks, on that coast, its shores are proportionally more free from sand hills than some others of lesser extent. There are, however, very important exceptions. The action of the tide throws much sand upon some points of the New England coast, as well as upon the beaches of Long Island and other more southern shores, and here dunes resembling those of Europe are formed. There are also extensive ranges of dunes on the Pacific coast of the United States, and at San Francisco they border some of the streets of the city. The dunes of America are far older than her civilization, and the soil they threaten or protect possesses, in general, too little value to justify any great expenditure in measures for arresting their progress or preventing their destruction. Hence, great as is their extent and their geographical importance, they have, at present, no such intimate relations to human life as to render them objects of special interest in the point of view I am taking, and I do not know that the laws of their formation and motion have been made a subject of original investigation by any American observer. _Dunes of Western Europe._ Upon the western coast of Europe, on the contrary, the ravages occasioned by the movement of sand dunes, and the serious consequences often resulting from the destruction of them, have long engaged the earnest attention of governments and of scientific men, and for nearly a century persevering and systematic effort has been made to bring them under human control. The subject has been carefully studied in Denmark and the adjacent duchies, in Western Prussia, in the Netherlands, and in France; and the experiments in the way of arresting the drifting of the dunes, and of securing them, and the lands they shelter, from the encroachments of the sea, have resulted in the adoption of a system of coast improvement substantially the same in all these countries. The sands, like the forests, have now their special literature, and the volumes and memoirs, which describe them and the processes employed to subdue them, are full of scientific interest and of practical instruction.[425] _Formation of Dunes._ The laws which govern the formation of dunes are substantially these. We have seen that, under certain conditions, sand is accumulated above high-water mark on low sea and lake shores. So long as the sand is kept wet by the spray or by capillary attraction, it is not disturbed by air currents, but as soon as the waves retire sufficiently to allow it to dry, it becomes the sport of the wind, and is driven up the gently sloping beach until it is arrested by stones, vegetables, or other obstructions, and thus an accumulation is formed which constitutes the foundation of a dune. However slight the elevation thus created, it serves to stop or retard the progress of the sand grains which are driven against its shoreward face, and to protect from the further influence of the wind the particles which are borne beyond it, or rolled over its crest, and fall down behind it. If the shore above the beach line were perfectly level and straight, the grass or bushes upon it of equal height, the sand thrown up by the waves uniform in size and weight of particles as well as in distribution, and if the action of the wind were steady and regular, a continuous bank would be formed, everywhere alike in height and cross section. But no such constant conditions anywhere exist. The banks are curved, broken, unequal in elevation; they are sometimes bare, sometimes clothed with vegetables of different structure and dimensions; the sand thrown up is variable in quantity and character; and the winds are shifting, gusty, vortical, and often blowing in very narrow currents. From all these causes, instead of uniform hills, there rise irregular rows of sand heaps, and these, as would naturally be expected, are of a pyramidal, or rather conical shape, and connected at bottom by more or less continuous ridges of the same material. On a receding coast, dunes will not attain so great a height as on more secure shores, because they are undermined and carried off before they have time to reach their greatest dimensions. Hence, while at sheltered points in Southwestern France, there are dunes three hundred feet or more in height, those on the Frisic Islands and the exposed parts of the coast of Schleswig-Holstein range only from twenty to one hundred feet. On the western shores of Africa, it is said that they sometimes attain an elevation of six hundred feet. This is one of the very few points known to geographers where desert sands are advancing seaward, and here they rise to the greatest altitude to which sand grains can be carried by the wind. The hillocks, once deposited, are held together and kept in shape, partly by mere gravity, and partly by the slight cohesion of the lime, clay, and organic matter mixed with the sand; and it is observed that, from capillary attraction, evaporation from lower strata, and retention of rain water, they are always moist a little below the surface.[426] By successive accumulations, they gradually rise to the height of thirty, fifty, sixty, or a hundred feet, and sometimes even much higher. Strong winds, instead of adding to their elevation, sweep off loose particles from their surface, and these, with others blown over or between them, build up a second row of dunes, and so on according to the character of the wind, the supply and consistence of the sand, and the face of the country. In this way is formed a belt of sand dunes, irregularly dispersed and varying much in height and dimensions, and some times many miles in breadth. On the Island of Sylt, in the German Sea, where there are several rows, the width of the belt is from half a mile to a mile. There are similar ranges on the coast of Holland, exceeding two miles in breadth, while at the mouths of the Nile they form a zone not less than ten miles wide. The base of some of the dunes in the Delta of the Nile is reached by the river during the annual inundation, and the infiltration of the water, which contains lime, has converted the lower strata into a silicious limestone, or rather a calcareous sandstone, and thus afforded an opportunity of studying the structure of that rock in a locality where its origin and mode of aggregation and solidification are known. _Character of Dune Sand._ "Dune sand," says Staring, "consists of well-rounded grains of quartz, more or less colored by iron, and often mingled with fragments of shells, small indeed, but still visible to the naked eye.[427] These fragments are not constant constituents of dune sand. They are sometimes found at the very summits of the hillocks, as at Overveen; in the King's Dune, near Egmond, they form a coarse calcareous gravel very largely distributed through the sand, while the interior dunes between Haarlem and Warmond exhibit no trace of them. It is yet undecided whether the presence or absence of these fragments is determined by the period of the formation of the dunes, or whether it depends on a difference in the process by which different dunes have been accumulated. Land shells, such as snails, for example, are found on the surface of the dunes in abundance, and many of the shelly fragments in the interior of the hillocks may be derived from the same source."[428] J. G. Kohl has some poetical thoughts upon the origin and character of the dune sands, which are worth quoting: "The sand was composed of pure transparent quartz. I could not observe this sand without the greatest admiration. If it is the product of the waves, breaking and crushing flints and fragments of quartz against each other, it is a result which could be brought about only in the course of countless ages. We need not lift ourselves to the stars, to their incalculable magnitudes and distances and numbers, in order to feel the giddiness of astonishment. Here, upon earth, in the simple sand, we find miracle enough. Think of the number of sand grains contained in a single dune, then of all the dunes upon this widely extended coast--not to speak of the innumerable grains in the Arabian, African, and Prussian deserts--this, of itself, is sufficient to overwhelm a thoughtful fancy. How long, how many times must the waves have risen and sunk in order to reduce these vast heaps to powder! "During the whole time I spent on this coast, I had always some sand in my fingers, was rubbing and rolling it about, examining it on all sides, holding a little shining grain on the tip of my finger, and thinking to myself how, in its corners, its angles, its whole configuration, it might very probably have a history longer than that of the old German nation--possibly longer than that of the human race. Where was the original quartz crystal, of which this is a fragment, first formed? To what was it once fixed? What power broke it loose? How was it beaten smaller and ever smaller by the waves? They tossed it, for æons, to and fro upon the beach, rolled it up and down, forced it to make thousands and thousands of daily voyages for millions and millions of days. Then the wind bore it away, and used it in building up a dune; there it lay for centuries, packed in with its fellows, protecting the marshes and cherished by the inhabitants, till, seized again by the pursuing sea, it fell once more into the water, there to begin the endless dance anew--and again to be swept away by the wind--and again to find rest in the dunes, a protection and a blessing to the coast. There is something mysterious about such a grain of sand, and at last I went so far as to fancy a little immortal spark linked with each one, presiding over its destiny, and sharing its vicissitudes. Could we arm our eyes with a microscope, and then dive, like a sparling, into one of these dunes, the pile, which is in fact only a heap of countless little crystal blocks, would strike us as the most marvellous building upon earth. The sunbeams would pass, with illuminating power, through all these little crystalline bodies. We should see how every sand grain is formed, by what multifarious little facets it is bounded, we should even discover that it is itself composed of many distinct particles."[429] Sand concretions form within the dunes and especially in the depressions between them. These are sometimes so extensive and impervious as to retain a sufficient supply of water to feed perennial springs, and to form small permanent ponds, and they are a great impediment to the penetration of roots, and consequently to the growth of trees planted, or germinating from self-sown seeds, upon the dunes.[430] _Interior Structure of Dunes._ The interior structure of the dunes, the arrangement of their particles, is not, as might be expected, that of an unorganized, confused heap, but they show a strong tendency to stratification. This is a point of much geological interest, because it indicates that sandstone may owe its stratified character to the action of wind as well as of water. The origin and peculiar character of these layers are due to a variety of causes. A southwest wind and current may deposit upon a dune a stratum of a given color and mineral composition, and this may be succeeded by a northwest wind and current, bringing with them particles of a different hue, constitution, and origin. Again, if we suppose a violent tempest to strew the beach with sand grains very different in magnitude and specific gravity, and, after the sand is dry, to be succeeded by a gentle breeze, it is evident that only the lighter particles will be taken up and carried to the dunes. If, after some time, the wind freshens, heavier grains will be transported and deposited on the former, and a still stronger succeeding gale will roll up yet larger kernels. Each of these deposits will form a stratum. If we suppose the tempest to be followed, after the sand is dry, not by a gentle breeze, but by a wind powerful enough to lift at the same time particles of very various magnitudes and weights, the heaviest will often lodge on the dune while the lighter will be carried farther. This would produce a stratum of coarse sand, and the same effect might result from the blowing away of light particles out of a mixed layer, while the heavier remained undisturbed.[431] Still another cause of stratification may be found in the occasional interposition of a thin layer of leaves or other vegetable remains between successive deposits, and this I imagine to be more frequent than has been generally supposed. The eddies of strong winds between the hillocks must also occasion disturbances and re-arrangements of the sand layers, and it seems possible that the irregular thickness and the strange contortions of the strata of the sandstone at Petra may be due to some such cause. A curious observation of Professor Forchhammer suggests an explanation of another peculiarity in the structure of the sandstone of Mount Seir. He describes dunes in Jutland, composed of yellow quartzose sand intermixed with black titanian iron. When the wind blows over the surface of the dunes, it furrows the sand with alternate ridges and depressions, ripples, in short, like those of water. The swells, the dividing ridges of the system of sand ripples, are composed of the light grains of quartz, while the heavier iron rolls into the depressions between, and thus the whole surface of the dune appears as if covered with a fine black network. _Form of Dunes._ The sea side of dunes, being more exposed to the caprices of the wind, is more irregular in form than the lee or land side, where the arrangement of the particles is affected by fewer disturbing and conflicting influences. Hence, the stratification of the windward slope is somewhat confused, while the sand on the lee side is found to be disposed in more regular beds, inclining landward, and with the largest particles lowest, where their greater weight would naturally carry them. The lee side of the dunes, being thus formed of sand deposited according to the laws of gravity, is very uniform in its slope, which, according to Forchhammer, varies little from an angle of 30° with the horizon, while the more exposed and irregular weather side lies at an inclination of from 5° to 10°. When, however, the outer tier of dunes is formed so near the waterline as to be exposed to the immediate action of the waves, it is undermined, and the face of the hill is very steep and sometimes nearly perpendicular. _Geological Importance of Dunes._ These observations, and other facts which a more attentive study on the spot would detect, might furnish the means of determining interesting and important questions concerning geological formations in localities very unlike those where dunes are now thrown up. For example, Studer supposes that the drifting sand hills of the African desert were originally coast dunes, and that they have been transported to their present position far in the interior, by the rolling and shifting leeward movement to which all dunes not covered with vegetation are subject. The present general drift of the sands of that desert appears to be to the southwest and west, the prevailing winds blowing from the northeast and east; but it has been doubted whether the shoals of the western coast of Northern Africa, and the sands upon that shore, are derived from the bottom of the Atlantic, in the usual manner, or, by an inverse process, from those of the Sahara. The latter, as has been before remarked, is probably the truth, though observations are wanting to decide the question.[432] There is nothing violently improbable in the supposition that they may have been first thrown up by the Mediterranean on its Libyan coast, and thence blown south and west over the vast space they now cover. But whatever has been their source and movement, they can hardly fail to have left on their route some sandstone monuments to mark their progress, such, for example, as we have seen are formed from the dune sand at the mouth of the Nile; and it is conceivable that the character of the drifting sands themselves, and of the conglomerates and sandstones to whose formation they have contributed, might furnish satisfactory evidence as to their origin, their starting point, and the course by which they have wandered so far from the sea.[433] If the sand of coast dunes is, as Staring describes it, composed chiefly of well-rounded quartzose grains, fragments of shells, and other constant ingredients, it would often be recognizable as coast sand, in its agglutinate state of sandstone. The texture of this rock varies from an almost imperceptible fineness of grain to great coarseness, and affords good facilities for microscopic observation of its structure. There are sandstones, such, for example, as are used for grindstones, where the grit, as it is called, is of exceeding sharpness; others where the angles of the grains are so obtuse that they scarcely act at all on hard metals. The former may be composed of grains of rock, disintegrated indeed, and recemented together, but not, in the meanwhile, much rolled; the latter, of sands long washed by the sea, and drifted by land winds. There is, indeed, so much resemblance between the effects of driving winds and of rolling water upon light bodies, that there would be difficulty in distinguishing them;[434] but after all, it is not probable that sandstone, composed of grains thrown up from the salt sea, and long tossed by the winds, would be identical in its structure with that formed from fragments of rock crushed by mechanical force, or disintegrated by heat, and again agglutinated without much exposure to the action of moving water.[435] _Inland Dunes._ I have met with some observations indicating a structural difference between interior and coast dunes, which might perhaps be recognized in the sandstones formed from these two species of sand hills respectively. In the great American desert between the Andes and the Pacific, Meyen found sand heaps of a perfect falciform shape.[436] They were from seven to fifteen feet high, the chord of their arc measuring from twenty to seventy paces. The slope of the convex face is described as very small, that of the concave as high as 70° or 80°, and their surfaces were rippled. No smaller dunes were observed, nor any in the process of formation. The concave side uniformly faced the northwest, except toward the centre of the desert, where, for a distance of one or two hundred paces, they gradually opened to the west, and then again gradually resumed the former position. Pöppig ascribes a falciform shape to the movable, a conical to the fixed dunes, or _medanos_, of the same desert. "The medanos," he observes, "are hillock-like elevations of sand, some having a firm, others a loose base. The former [latter], which are always crescent shaped, are from ten to twenty feet high, and have an acute crest. The inner side is perpendicular, and the outer or bow side forms an angle with a steep inclination downward. When driven by violent winds, the medanos pass rapidly over the plains. The smaller and lighter ones move quickly forward, before the larger; but the latter soon overtake and crush them, whilst they are themselves shivered by the collision. These medanos assume all sorts of extraordinary figures, and sometimes move along the plain in rows forming most intricate labyrinths. * * A plain often appears to be covered with a row of medanos, and some days afterward it is again restored to its level and uniform aspect. * * * "The medanos with immovable bases are formed on the blocks of rocks which are scattered about the plain. The sand is driven against them by the wind, and as soon as it reaches the top point, it descends on the other side until that is likewise covered; thus gradually arises a conical-formed hill. Entire hillock chains with acute crests are formed in a similar manner. * * * On their southern declivities are found vast masses of sand, drifted thither by the mid-day gales. The northern declivity, though not steeper than the southern, is only sparingly covered with sand. If a hillock chain somewhat distant from the sea extends in a line parallel with the Andes, namely, from S. S. E. to N. N. W., the western declivity is almost entirely free of sand, as it is driven to the plain below by the southeast wind, which constantly alternates with the wind from the south."[437] It is difficult to reconcile this description with that of Meyen, but if confidence is to be reposed in the accuracy of either observer, the formation of the sand hills in question must be governed by very different laws from those which determine the structure of coast dunes. Captain Gilliss, of the American navy, found the sand hills of the Peruvian desert to be in general crescent shaped, as described by Meyen, and a similar structure is said to characterize the inland dunes of the Llano Estacado and other plateaus of the North American desert, though these latter are of greater height and other dimensions than those described by Meyen. There is no very obvious explanation of this difference in form between maritime and inland sand hills, and the subject merits investigation.[438] _Age, Character, and Permanence of Dunes._ The origin of most great lines of dunes goes back past all history. There are on many coasts, several distinct ranges of sand hills which seem to be of very different ages, and to have been formed under different relative conditions of land and water.[439] In some cases, there has been an upheaval of the coast line since the formation of the oldest hillocks, and these have become inland dunes, while younger rows have been thrown up on the new beach laid bare by elevation of the sea bed. Our knowledge of the mode of their first accumulation is derived from observation of the action of wind and water in the few instances where, with or without the aid of man, new coast dunes have been accumulated, and of the influence of wind alone in elevating new sand heaps inland of the coast tier, when the outer rows are destroyed by the sea, as also when the sodded surface of ancient sands has been broken, and the subjacent strata laid open to the air. It is a question of much interest, in what degree the naked condition of most dunes is to be ascribed to the improvidence and indiscretion of man. There are, in Western France, extensive ranges of dunes covered with ancient and dense forests, while the recently formed sand hills between them and the sea are bare of vegetation, and are rapidly advancing upon the wooded dunes, which they threaten to bury beneath their drifts. Between the old dunes and the new, there is no discoverable difference in material or in structure; but the modern sand hills are naked and shifting, the ancient, clothed with vegetation and fixed. It has been conjectured that artificial methods of confinement and plantation were employed by the primitive inhabitants of Gaul; and Laval, basing his calculations on the rate of annual movement of the shifting dunes, assigns the fifth century of the Christian era as the period when these processes were abandoned.[440] There is no historical evidence that the Gauls were acquainted with artificial methods of fixing the sands of the coast, and we have little reason to suppose that they were advanced enough in civilization to be likely to resort to such processes, especially at a period when land could have had but a moderate value. In other countries, dunes have spontaneously clothed themselves with forests, and the rapidity with which their surface is covered by various species of sand plants, and finally by trees, where man and cattle and burrowing animals are excluded from them, renders it highly probable that they would, as a general rule, protect themselves, if left to the undisturbed action of natural causes. The sand hills of the Frische Nehrung, on the coast of Prussia, were formerly wooded down to the water's edge, and it was only in the last century that, in consequence of the destruction of their forests, they became moving sands.[441] There is every reason to believe that the dunes of the Netherlands were clothed with trees until after the Roman invasion. The old geographers, in describing these countries, speak of vast forests extending to the very brink of the sea; but drifting coast dunes are first mentioned by the chroniclers of the Middle Ages, and so far as we know they have assumed a destructive character in consequence of the improvidence of man.[442] The history of the dunes of Michigan, so far as I have been able to learn from my own observation, or that of others, is the same. Thirty years ago, when that region was scarcely inhabited, they were generally covered with a thick growth of trees, chiefly pines, and underwood, and there was little appearance of undermining and wash on the lake side, or of shifting of the sands, except where the trees had been cut or turned up by the roots.[443] Nature, as she builds up dunes for the protection of the sea shore, provides, with similar conservatism, for the preservation of the dunes themselves; so that, without the interference of man, these hillocks would be, not perhaps absolutely perpetual, but very lasting in duration, and very slowly altered in form or position. When once covered with the trees, shrubs, and herbaceous growths adapted to such localities, dunes undergo no apparent change, except the slow occasional undermining of the outer tier, and accidental destruction by the exposure of the interior, from the burrowing of animals, or the upturning of trees with their roots, and all these causes of displacement are very much less destructive when a vegetable covering exists in the immediate neighborhood of the breach. Before the occupation of the coasts by civilized and therefore destructive man, dunes, at all points where they have been observed, seem to have been protected in their rear by forests, which served to break the force of the winds in both directions,[444] and to have spontaneously clothed themselves with a dense growth of the various plants, grasses, shrubs, and trees, which nature has assigned to such soils. It is observed in Europe that dunes, though now without the shelter of a forest country behind them, begin to protect themselves as soon as human trespassers are excluded, and grazing animals denied access to them. Herbaceous and arborescent plants spring up almost at once, first in the depressions, and then upon the surface of the sand hills. Every seed that sprouts, binds together a certain amount of sand by its roots, shades a little ground with its leaves, and furnishes food and shelter for still younger or smaller growths. A succession of a very few favorable seasons suffices to bind the whole surface together with a vegetable network, and the power of resistance possessed by the dunes themselves, and the protection they afford to the fields behind them, are just in proportion to the abundance and density of the plants they support. The growth of the vegetable covering can, of course, be much accelerated by judicious planting and watchful care, and this species of improvement is now carried on upon a vast scale, wherever the value of land is considerable and the population dense. In the main, the dunes on the coast of the German Sea, notwithstanding the great quantity of often fertile land they cover, and the evils which result from their movement, are, upon the whole, a protective and beneficial agent, and their maintenance is an object of solicitude with the governments and people of the shores they protect.[445] _Use of Dunes as a Barrier against the Sea._ Although the sea throws up large quantities of sand on flat lee-shores, there are, as we have seen, many cases where it continually encroaches on those same shores and washes them away. At all points of the shallow North Sea where the agitation of the waves extends to the bottom, banks are forming and rolling eastward. Hence the sea sand tends to accumulate upon the coast of Schleswig-Holstein and Jutland, and were there no conflicting influences, the shore would rapidly extend itself westward. But the same waves which wash the sand to the coast undermine the beach they cover, and still more rapidly degrade the shore at points where it is too high to receive partial protection by the formation of dunes upon it. The earth of the coast is generally composed of particles finer, lighter, and more transportable by water than the sea sand. While, therefore, the billows raised by a heavy west wind may roll up and deposit along the beach thousands of tons of sand, the same waves may swallow up even a larger quantity of fine shore earth. This earth, with a portion of the sand, is swept off by northwardly and southwardly currents, and let fall at other points of the coast, or carried off, altogether, out of the reach of causes which might bring it back to its former position. Although, then, the eastern shore of the German Ocean here and there advances into the sea, it in general retreats before it, and but for the protection afforded it by natural arrangements seconded by the art and industry of man, whole provinces would soon be engulfed by the waters. This protection consists in an almost unbroken chain of sand banks and dunes, extending from the northernmost point of Jutland to the Elbe, a distance of not much less than three hundred miles, and from the Elbe again, though with more frequent and wider interruptions, to the Atlantic borders of France and Spain.[446] So long as the dunes are maintained by nature or by human art, they serve, like any other embankment or dike, as a partial or a complete protection against the encroachments of the sea; and on the other hand, when their drifts are not checked by natural processes, or by the industry of man, they become a cause of as certain, if not of as sudden, destruction as the ocean itself whose advance they retard. _Encroachments of the Sea._ The eastward progress of the sea on the Danish and Netherlandish coast, and on certain shores of the Atlantic, depends so much on local geological structure, on the force and direction of tidal and other marine currents, on the volume and rapidity of coast rivers, on the contingencies of the weather and on other varying circumstances, that no general rate can he assigned to it. At Agger, near the western end of the Liimfjord, in Jutland, the coast was washed away, between the years 1815 and 1839, at the rate of more than eighteen feet a year. The advance of the sea appears to have been something less rapid for a century before; but from 1840 to 1857, it gained upon the land no less than thirty feet a year. At other points of the shore of Jutland, the loss is smaller, but the sea is encroaching generally upon the whole line of the coast.[447] _The Liimfjord._ The irruption of the sea into the fresh-water lagoon of Liimfjord in Jutland, in 1825--one of the most remarkable encroachments of the ocean in modern times--is expressly ascribed to "mismanagement of the dunes" on the narrow neck of land which separated the fjord from the North Sea. At earlier periods, the sea had swept across the isthmus, and even burst through it, but the channel had been filled up again, sometimes by artificial means, sometimes by the operation of natural causes, and on all these occasions effects were produced very similar to those resulting from the formation of the new channel in 1825, which still remains open.[448] Within comparatively recent historical ages, the Liimfjord has thus been several times alternately filled with fresh and with salt water, and man has produced, by neglecting the dunes, or at least might have prevented by maintaining them, changes identical with those which are usually ascribed to the action of great geological causes, and sometimes supposed to have required vast periods of time for their accomplishment. "This breach," says Forchhammer, "which converted the Liimfjord into a sound, and the northern part of Jutland into an island, occasioned remarkable changes. The first and most striking phenomenon was the sudden destruction of almost all the fresh-water fish previously inhabiting this lagoon, which was famous for its abundant fisheries. Millions of fresh-water fish were thrown on shore, partly dead and partly dying, and were carted off by the people. A few only survived, and still frequent the shores at the mouth of the brooks. The eel, however, has gradually accommodated itself to the change of circumstances, and is found in all parts of the fjord, while to all other fresh-water fish, the salt water of the ocean seems to have been fatal. It is more than probable that the sand washed in by the irruption covers, in many places, a layer of dead fish, and has thus prepared the way for a petrified stratum similar to those observed in so many older formations. "As it seems to be a law of nature that animals whose life is suddenly extinguished while yet in full vigor, are the most likely to be preserved by petrification, we find here one of the conditions favorable to the formation of such a petrified stratum. The bottom of the Liimfjord was covered with a vigorous growth of aquatic plants, belonging both to fresh and to salt water, especially _Zostera marina_. This vegetation totally disappeared after the irruption, and, in some instances, was buried by the sand; and here again we have a familiar phenomenon often observed in ancient strata--the indication of a given formation by a particular vegetable species--and when the strata deposited at the time of the breach shall be accessible by upheaval, the period of eruption will be marked by a stratum of _Zostera_, and probably by impressions of fresh-water fishes. "It is very remarkable that the _Zostera marina_, a sea plant, was destroyed even where no sand was deposited. This was probably in consequence of the sudden change from brackish to salt water. * * It is well established that the Liimfjord communicated with the German Ocean at some former period. To that era belong the deep beds of oyster shells and _Cardium edule_, which are still found at the bottom of the fjord. And now, after an interval of centuries, during which the lagoon contained no salt-water shell fish, it again produces great numbers of _Mytilus edulis_. Could we obtain a deep section of the bottom, we should find beds of _Ostrea edulis_ and _Cardium edule_, then a layer of _Zostera marina_ with fresh-water fish, and then a bed of _Mytilus edulis_. If, in course of time, the new channel should be closed, the brooks would fill the lagoon again with fresh water; fresh-water fish and shell fish would reappear, and thus we should have a repeated alternation of organic inhabitants of the sea and of the waters of the land. "These events have been accompanied with but a comparatively insignificant change of land surface, while the formations in the bed of this inland sea have been totally revolutionized in character."[449] _Coasts of Schleswig-Holstein, Holland, and France._ On the islands on the coast of Schleswig-Holstein, the advance of the sea has been more unequivocal and more rapid. Near the beginning of the last century, the dunes which had protected the western coast of the island of Sylt began to roll to the east, and the sea followed closely as they retired. In 1757, the church of Rantum, a village upon that island, was obliged to be taken down in consequence of the advance of the sand hills; in 1791, these hills had passed beyond its site, the waves had swallowed up its foundations, and the sea gained so rapidly, that, fifty years later, the spot where they lay was seven hundred feet from the shore.[450] The most prominent geological landmark on the coast of Holland is the Huis te Britten, _Arx Britannica_, a fortress built by the Romans, in the time of Caligula, on the main land near the mouth of the Rhine. At the close of the seventeenth century, the sea had advanced sixteen hundred paces beyond it. The older Dutch annalists record, with much parade of numerical accuracy, frequent encroachments of the sea upon many parts of the Netherlandish coast. But though the general fact of an advance of the ocean upon the land is established beyond dispute, the precision of the measurements which have been given is open to question. Staring, however, who thinks the erosion of the coast much exaggerated by popular geographers, admits a loss of more than a million and a half acres, chiefly worthless morass;[451] and it is certain that but for the resistance of man, but for his erection of dikes and protection of dunes, there would now be left of Holland little but the name. It is, as has been already seen, still a debated question among geologists whether the coast of Holland now is, and for centuries has been, subsiding. I believe most investigators maintain the affirmative; and if the fact is so, the advance of the sea upon the land is, in part, due to this cause. But the rate of subsidence is at all events very small, and therefore the encroachments of the ocean upon the coast are mainly to be ascribed to the erosion and transportation of the soil by marine waves and currents. The sea is fast advancing at several points of the western coast of France, and unknown causes have given a new impulse to its ravages since the commencement of the present century. Between 1830 and 1842, the Point de Grave, on the north side of the Gironde, retreated one hundred and eighty mètres, or about fifty feet per year; from the latter year to 1846, the rate was increased to more than three times that quantity, and the loss in those four years was above six hundred feet. All the buildings at the extremity of the peninsula have been taken down and rebuilt farther landward, and the lighthouse of the Grave now occupies its third position. The sea attacked the base of the peninsula also, and the Point de Grave and the adjacent coasts have been for twenty years the scene of one of the most obstinately contested struggles between man and the ocean recorded in the annals of modern engineering. It cannot, indeed, be affirmed that human power is able to arrest altogether the incursions of the waves on sandy coasts, by planting the beach, and clothing the dunes with wood. On the contrary, both in Holland and on the French coast, it has been found necessary to protect the dunes themselves by piling and by piers and sea walls of heavy masonry. But experience has amply shown that the processes referred to are entirely successful in preventing the movement of the dunes, and the drifting of their sands over cultivated lands behind them; and that, at the same time, the plantations very much retard the landward progress of the waters.[452] _Drifting of Dune Sands._ Besides their importance as a barrier against the inroads of the ocean, dunes are useful by sheltering the cultivated ground behind them from the violence of the sea wind, from salt spray, and from the drifts of beach sand which would otherwise overwhelm them. But the dunes themselves, unless their surface sands are kept moist, and confined by the growth of plants, or at least by a crust of vegetable earth, are constantly rolling inward; and thus, while, on one side, they lay bare the traces of ancient human habitations or other evidences of the social life of primitive man, they are, on the other, burying fields, houses, churches, and converting populous districts into barren and deserted wastes. Especially destructive are they when, by any accident, a cavity is opened into them to a considerable depth, thereby giving the wind access to the interior, where the sand is thus first dried, and then scooped out and scattered far over the neighboring soil. The dune is now a magazine of sand, no longer a rampart against it, and mischief from this source seems more difficult to resist than from almost any other drift, because the supply of material at the command of the wind, is more abundant and more concentrated than in its original thin and widespread deposits on the beach. The burrowing of conies in the dunes is, in this way, not unfrequently a cause of their destruction and of great injury to the fields behind them. Drifts, and even inland sand hills, sometimes result from breaking the surface of more level sand deposits, far within the range of the coast dunes. Thus we learn from Staring, that one of the highest inland dunes in Friesland owes its origin to the opening of the drift sand by the uprooting of a large oak.[453] Great as are the ravages produced by the encroachment of the sea upon the western shores of continental Europe, they have been in some degree compensated by spontaneous marine deposits at other points of the coast, and we have seen in a former chapter that the industry of man has reclaimed a large territory from the bosom of the ocean. These latter triumphs are not of recent origin, and the incipient victories which paved the way for them date back perhaps as far as ten centuries. In the mean time, the dunes had been left to the operation of the laws of nature, or rather freed, by human imprudence, from the fetters with which nature had bound them, and it is scarcely three generations since man first attempted to check their destructive movements. As they advanced, he unresistingly yielded and retreated before them, and they have buried under their sandy billows many hundreds of square miles of luxuriant cornfields and vineyards and forests. _Dunes of Gascony._ On the west coast of France, a belt of dunes, varying in width from a quarter of a mile to five miles, extends from the Adour to the estuary of the Gironde, and covers an area of three hundred and seventy-five square miles. When not fixed by vegetable growths, they advance eastward at a mean rate of about one rod, or sixteen and a half feet, a year. We do not know historically when they began to drift, but if we suppose their motion to have been always the same as at present, they would have passed over the space between the sea coast and their eastern boundary, and covered the large area above mentioned, in fourteen hundred years. We know, from written records, that they have buried extensive fields and forests and thriving villages, and changed the courses of rivers, and that the lighter particles carried from them by the winds, even where not transported in sufficient quantities to form sand hills, have rendered sterile much land formerly fertile.[454] They have also injuriously obstructed the natural drainage of the maritime districts by choking up the beds of the streams, and forming lakes and pestilential swamps of no inconsiderable extent. In fact, so completely do they embank the coast, that between the Gironde and the village of Mimizan, a distance of one hundred miles, there are but two outlets for the discharge of all the waters which flow from the land to the sea; and the eastern front of the dunes is bordered by a succession of stagnant pools, some of which are more than six miles in length and breadth.[455] _The Dunes of Denmark and Prussia._ In the small kingdom of Denmark, inclusive of the duchies of Schleswig and Holstein, the dunes cover an area of more than two hundred and sixty square miles. The breadth of the chain is very various, and in some places it consists only of a single row of sand hills, while in others, it is more than six miles wide. The general rate of eastward movement of the drifting dunes is from three to twenty-four feet per annum. If we adopt the mean of thirteen feet and a half for the annual motion, the dunes have traversed the widest part of the belt in about twenty-five hundred years. Historical data are wanting as to the period of the formation of these dunes and of the commencement of their drifting; but there is recorded evidence that they have buried a vast extent of valuable land within three or four centuries, and further proof is found in the fact that the movement of the sands is constantly uncovering ruins of ancient buildings, and other evidences of human occupation, at points far within the present limits of the uninhabitable desert. Andresen estimates the average depth of the sand deposited over this area at thirty feet, which would give a cubic mile and a half for the total quantity.[456] The drifting of the dunes on the coast of Prussia commenced not much more than a hundred years ago. The Frische Nehrung is separated from the mainland by the Frische Haff, and there is but a narrow strip of arable land along its eastern borders. Hence its rolling sands have covered a comparatively small extent of dry land, but fields and villages have been buried and valuable forests laid waste by them. The loose coast row has drifted over the inland ranges, which, as was noticed in the description of these dunes on a former page, were protected by a surface of different composition, and the sand has thus been raised to a height which it could not have reached upon level ground. This elevation has enabled it to advance upon and overwhelm woods, which, upon a plain, would have checked its progress, and, in one instance, a forest of many hundred acres of tall pines was destroyed by the drifts between 1804 and 1827. _Control of Dunes by Man._ There are three principal modes in which the industry of man is brought to bear upon the dunes. First, the creation of them, at points where, from changes in the currents or other causes, new encroachments of the sea are threatened; second, the maintenance and protection of them where they have been naturally formed; and third, the removal of the inner rows where the belt is so broad that no danger is to be apprehended from the loss of them. _Artificial Formation of Dunes._ In describing the natural formation of dunes, it was said that they began with an accumulation of sand around some vegetable or other accidental obstruction to the drifting of the particles. A high, perpendicular cliff, which deadens the wind altogether, prevents all accumulation of sand; but, up to a certain point, the higher and broader the obstruction, the more sand will heap up in front of it, and the more will that which falls behind it be protected from drifting farther. This familiar observation has taught the inhabitants of the coast that an artificial wall or dike will, in many situations, give rise to a broad belt of dunes. Thus a sand dike or wall, of three or four miles in length, thrown in 1610 across the Koegras, a tide-washed flat between the Zuiderzee and the North Sea, has occasioned the formation of rows of dunes a mile in breadth, and thus excluded the sea altogether from the Koegras. A similar dike, called the Zijperzeedijk, has produced another scarcely less extensive belt in the course of two centuries. A few years since, the sea was threatening to cut through the island of Ameland, and, by encroachment on the southern side and the blowing off of the sand from a low flat which connected the two higher parts of the island, it had made such progress, that in heavy storms the waves sometimes rolled quite across the isthmus. The construction of a breakwater and a sand dike have already checked the advance of the sea, and a large number of sand hills has been formed, the rapid growth of which promises complete future security against both wind and wave. Similar effects have been produced by the erection of plank fences, and even of simple screens of wattling and reeds.[457] _Protection of Dunes._ The dunes of Holland are sometimes protected from the dashing of the waves by a _revêtement_ of stone, or by piles; and the lateral high-water currents, which wash away their base, are occasionally checked by transverse walls running from the foot of the dunes to low-water mark; but the great expense of such constructions has prevented their adoption on a large scale.[458] The principal means relied on for the protection of the sand hills are the planting of their surfaces and the exclusion of burrowing and grazing animals. There are grasses, creeping plants, and shrubs of spontaneous growth, which flourish in loose sand, and, if protected, spread over considerable tracts, and finally convert their face into a soil capable of cultivation, or, at least, of producing forest trees. Krause enumerates one hundred and seventy-one plants as native to the coast sands of Prussia, and the observations of Andresen in Jutland carry the number of these vegetables up to two hundred and thirty-four. Some of these plants, especially the _Arundo arenaria_ or _arenosa_, or _Psamma_ or _Psammophila arenaria_--Klittetag, or Hjelme in Danish, helm in Dutch, Dünenhalm, Sandschilf, or Hügelrohr in German, gourbet in French, and marram in English--are exclusively confined to sandy soils, and thrive well only in a saline atmosphere.[459] The arundo grows to the height of about twenty-four inches, but sends its strong roots with their many rootlets to a distance of forty or fifty feet. It has the peculiar property of nourishing best in the loosest soil, and a sand shower seems to refresh it as the rain revives the thirsty plants of the common earth. Its roots bind together the dunes, and its leaves protect their surface. When the sand ceases to drift, the arundo dies, its decaying roots fertilizing the sand, and the decomposition of its leaves forming a layer of vegetable earth over it. Then follows a succession of other plants which gradually fit the sand hills, by growth and decay, for forest planting, for pasturage, and sometimes for ordinary agricultural use. But the protection and gradual transformation of the dunes is not the only service rendered by this valuable plant. Its leaves are nutritious food for sheep and cattle, its seeds for poultry;[460] cordage and netting twine are manufactured from its fibres, it makes a good material for thatching, and its dried roots furnish excellent fuel. These useful qualities, unfortunately, are too often prejudicial to its growth. The peasants feed it down with their cattle, cut it for rope making, or dig it up for fuel, and it has been found necessary to resort to severe legislation to prevent them from bringing ruin upon themselves by thus improvidently sacrificing their most effectual safeguard against the drifting of the sands.[461] In 1539, a decree of Christian III, king of Denmark, imposed a fine upon persons convicted of destroying certain species of sand plants upon the west coast of Jutland. This ordinance was renewed and made more comprehensive in 1558, and in 1569 the inhabitants of several districts were required, by royal rescript, to do their best to check the sand drifts, though the specific measures to be adopted for that purpose are not indicated. Various laws against stripping the dunes of their vegetation were enacted in the following century, but no active measures were taken for the subjugation of the sand drifts until 1779, when a preliminary system of operation for that purpose was adopted. This consisted in little more than the planting of the _Arundo arenaria_ and other sand plants, and the exclusion of animals destructive to these vegetables.[462] Ten years later, plantations of forest trees, which have since proved so valuable a means of fixing the dunes and rendering them productive, were commenced, and have been continued ever since.[463] During this latter period, Brémontier, without any knowledge of what was doing in Denmark, experimented upon the cultivation of forest trees on the dunes of Gascony, and perfected a system, which, with some improvements in matters of detail, is still largely pursued on those shores. The example of Denmark was soon followed in the neighboring kingdom of Prussia, and in the Netherlands; and, as we shall see hereafter, these improvements have been everywhere crowned with most flattering success. Under the administration of Reventlov, a little before the close of the last century, the Danish Government organized a regular system of improvement in the economy of the dunes. They were planted with the arundo and other vegetables of similar habits, protected against trespassers, and at last partly covered with forest trees. By these means much waste soil has been converted into arable ground, a large growth of valuable timber obtained, and the further spread of the drifts, which threatened to lay waste the whole peninsula of Jutland, to a considerable extent arrested. In France, the operations for fixing and reclaiming the dunes--which began under the direction of Brémontier about the same time as in Denmark, and which are, in principle and in many of their details, similar to those employed in the latter kingdom--have been conducted on a far larger scale, and with greater success, than in any other country. This is partly owing to a climate more favorable to the growth of suitable forest trees than that of Northern Europe, and partly to the liberality of the Government, which, having more important landed interests to protect, has put larger means at the disposal of the engineers than Denmark and Prussia have found it convenient to appropriate to that purpose. The area of the dunes already secured from drifting, and planted by the processes invented by Brémontier and perfected by his successors, is about 100,000 acres.[464] This amount of productive soil, then, has been added to the resources of France, and a still greater quantity of valuable land has been thereby rescued from the otherwise certain destruction with which it was threatened by the advance of the rolling sand hills. The improvements of the dunes on the coast of West Prussia began in 1795, under Sören Björn, a native of Denmark, and, with the exception of the ten years between 1807 and 1817, they have been prosecuted ever since. The methods do not differ essentially from those employed in Denmark and France, though they are modified by local circumstances, and, with respect to the trees selected for planting, by climate. In 1850, between the mouth of the Vistula and Kahlberg, 6,300 acres, including about 1,900 acres planted with pines and birches, had been secured from drifting; between Kahlberg and the eastern boundary of West-Prussia, 8,000 acres; and important preliminary operations had been carried on for subduing the dunes on the west coast.[465] _Trees suited to Dune Plantations._ The tree which has been found to thrive best upon the sand hills of the French coast, and at the same time to confine the sand most firmly and yield the largest pecuniary returns, is the maritime pine, _Pinus maritima_, a species valuable both for its timber and for its resinous products. It is always grown from seed, and the young shoots require to be protected for several seasons, by the branches of other trees, planted in rows, or spread over the surface and staked down, by the growth of the _Arundo arenaria_ and other small sand plants, or by wattled hedges. The beach, from which the sand is derived, has been generally planted with the arundo, because the pine does not thrive well so near the sea; but it is thought that a species of tamarisk is likely to succeed in that latitude even better than the arundo. The shade and the protection offered by the branching top of this pine are favorable to the growth of deciduous trees, and, while still young, of shrubs and smaller plants, which contribute more rapidly to the formation of vegetable mould, and thus, when the pine has once taken root, the redemption of the waste is considered as effectually secured. In France, the maritime pine is planted on the sands of the interior as well as on the dunes of the sea coast, and with equal advantage. This tree resembles the pitch pine of the Southern American States in its habits, and is applied to the same uses. The extraction of turpentine from it begins at the age of about twenty years, or when it has attained a diameter of from nine to twelve inches. Incisions are made up and down the trunk, to the depth of about half an inch in the wood, and it is insisted that if not more than two such slits are cut, the tree is not sensibly injured by the process. The growth, indeed, is somewhat checked, but the wood becomes superior to that of trees from which the turpentine is not extracted. Thus treated, the pine continues to flourish to the age of one hundred or one hundred and twenty years, and up to this age the trees on a hectare yield annually 350 kilogrammes of essence of turpentine, and 280 kilogrammes of resin, worth together 110 francs. The expense of extraction and distillation is calculated at 44 francs, and a clear profit of 66 francs per hectare, or more than five dollars per acre, is left.[466] This is exclusive of the value of the timber, when finally cut, which, of course, amounts to a very considerable sum. In Denmark, where the climate is much colder, hardier conifers, as well as the birch and other northern trees, are found to answer a better purpose than the maritime pine, and it is doubtful whether this tree would be able to resist the winter on the dunes of Massachusetts. Probably the pitch pine of the Northern States, in conjunction with some of the American oaks, birches, and poplars, and especially the robinia or locust, would prove very suitable to be employed on the sand hills of Cape Cod and Long Island. The ailanthus, now coming into notice as a sand-loving tree, may, perhaps, serve a better purpose than any of them. _Extent of Dunes in Europe._ The dunes of Denmark, as we have seen, cover an area of two hundred and sixty square miles, or one hundred and sixty-six thousand acres; those of the Prussian coast are vaguely estimated at from eighty-five to one hundred and ten thousand acres; those of Holland at one hundred and forty thousand acres;[467] those of Gascony at about three hundred thousand acres.[468] I do not find any estimate of their extent in other provinces of France, in the duchies of Schleswig and Holstein, or in the Baltic provinces of Russia, but it is probable that the entire quantity of dune land upon the eastern shores of the Atlantic and the Baltic does not fall much short of a million of acres.[469] This vast deposit of sea sand extends along the coast for a distance of several hundred miles, and from the time of the destruction of the forests which covered it, to the year 1789, the whole line was rolling inward and burying the soil beneath it, or rendering the fields unproductive by the sand which drifted from it. At the same time, as the sand hills moved eastward, the ocean was closely following their retreat and swallowing up the ground they had covered, as fast as their movement left it bare. Planting the dunes has completely prevented the surface sands from blowing over the soil to the leeward of the plantations, and though it has not, in all cases, arrested the encroachments of the sea, it has so greatly retarded the rapidity of their advance, that sandy coasts, when once covered with forests, may be considered as substantially secure, so long as proper measures are taken for the protection of the woods. _Dune Vineyards of Cap Breton._ In the vicinity of Cap Breton in France, a peculiar process is successfully employed, both for preventing the drifting of dunes, and for rendering the sands themselves immediately productive; but this method is applicable only in exceptional cases of favorable climate and exposure. It consists in planting vineyards upon the dunes, and protecting them by hedges of broom, _Erica scoparia_, so disposed as to form rectangles about thirty feet by forty. The vines planted in these enclosures thrive admirably, and the grapes produced by them are among the best grown in France. The dunes are so far from being an unfavorable soil for the vine, that fresh sea-sand is regularly employed as a fertilizer for it, alternating every other season with ordinary manure. The quantity of sand thus applied every second year, raises the surface of the vineyard about four or five inches. The vines are cut down every year to three or four shoots, and the raising of the soil rapidly covers the old stocks. As fast as buried, they send out new roots near the surface, and thus the vineyard is constantly renewed, and has always a youthful appearance, though it may have been already planted a couple of generations. This practice is ascertained to have been followed for two centuries, and is among the oldest well-authenticated attempts of man to resist and vanquish the dunes.[470] _Removal of Dunes._ The artificial removal of dunes, no longer necessary as a protection, does not appear to have been practised upon a large scale except in the Netherlands, where the numerous canals furnish an easy and economical means of transporting the sand, and where the construction and maintenance of sea and river dikes, and of causeways and other embankments and fillings, create a great demand for that material. Sand is also employed in Holland, in large quantities, for improving the consistence of the tough clay bordering upon or underlying diluvial deposits, and for forming an artificial soil for the growth of certain garden and ornamental vegetables. When the dunes are removed, the ground they covered is restored to the domain of industry; and the quantity of land, recovered in the Netherlands by the removal of the barren sands which encumbered it, amounts to hundreds and perhaps thousands of acres.[471] _Inland Sand Plains._ The inland sand plains of Europe are either derived from the drifting of dunes or other beach sands, or consist of diluvial deposits. As we have seen, when once the interior of a dune is laid open to the wind, its contents are soon scattered far and wide over the adjacent country, and the beach sands, no longer checked by the rampart which nature had constrained them to build against their own encroachments, are also carried to considerable distances from the coast. Few regions have suffered so much from this cause in proportion to their extent, as the peninsula of Jutland. So long as the woods, with which nature had planted the Danish dunes, were spared, they seem to have been stationary, and we have no historical evidence, of an earlier date than the sixteenth century, that they had become in any way injurious. From that period, there are frequent notices of the invasions of cultivated grounds by the sands; and excavations are constantly bringing to light proof of human habitation and of agricultural industry, in former ages, on soils now buried beneath deep drifts from the dunes and beaches of the sea coast.[472] Extensive tracts of valuable plain land in the Netherlands and in France have been covered in the same way with a layer of sand deep enough to render them infertile, and they can be restored to cultivation only by processes analogous to those employed for fixing and improving the dunes.[473] Diluvial sand plains, also, have been reclaimed by these methods in the Duchy of Austria, between Vienna and the Semmering ridge, in Jutland, and in the great champaign country of Northern Germany, especially the Mark Brandenburg, where artificial forests can be propagated with great ease, and where, consequently, this branch of industry has been pursued on a great scale, and with highly beneficial results, both as respects the supply of forest products and the preparation of the soil for agricultural use. As a general rule, inland sands are looser, dryer, and more inclined to drift, than those of the sea coast, where the moist and saline atmosphere of the ocean keeps them always more or less humid and cohesive. No shore dunes are so movable as the medanos of Peru described in a passage quoted from Pöppig on a former page, or as the sand hills of Poland, both of which seem better entitled to the appellation of sand waves than those of the Sahara or of the Arabian desert. The sands of the valley of the Lower Euphrates--themselves probably of submarine origin, and not derived from dunes--are advancing to the northwest with a rapidity which seems fabulous when compared with the slow movement of the sand hills of Gascony and the Low German coasts. Loftus, speaking of Niliyya, an old Arab town a few miles east of the ruins of Babylon, says that, "in 1848, the sand began to accumulate around it, and in six years, the desert, within a radius of six miles, was covered with little, undulating domes, while the ruins of the city were so buried that it is now impossible to trace their original form or extent."[474] Loftus considers this sand flood as the "vanguard of those vast drifts which, advancing from the southeast, threaten eventually to overwhelm Babylon and Baghdad." An observation of Layard, cited by Loftus, appears to me to furnish a possible explanation of this irruption. He "passed two or three places where the sand, issuing from the earth like water, is called 'Aioun-er-rummal,' sand springs." These "springs" are very probably merely the drifting of sand from the ancient subsoil, where the protecting crust of aquatic deposit and vegetable earth has been broken through, as in the case of the drift which arose from the upturning of an oak mentioned on a former page. When the valley of the Euphrates was regularly irrigated and cultivated, the underlying sands were bound by moisture, alluvial slime, and vegetation; but now, that all improvement is neglected, and the surface, no longer watered, has become parched, powdery, and naked, a mere accidental fissure in the superficial stratum may soon be enlarged to a wide opening, that will let loose sand enough to overwhelm a province. _The Landes of Gascony._ The most remarkable sand plain of France lies at the southwestern extremity of the empire, and is generally known as the Landes, or heaths, of Gascony. Clavé thus describes it: "Composed of pure sand, resting on an impermeable stratum called _alios_, the soil of the Landes was, for centuries, considered incapable of cultivation. Parched in summer, drowned in winter, it produced only ferns, rushes, and heath, and scarcely furnished pasturage for a few half-starved flocks. To crown its miseries, this plain was continually threatened by the encroachments of the dunes. Vast ridges of sand, thrown up by the waves, for a distance of more than fifty leagues along the coast, and continually renewed, were driven inland by the west wind, and, as they rolled over the plain, they buried the soil and the hamlets, overcame all resistance, and advanced with fearful regularity. The whole province seemed devoted to certain destruction, when Brémontier invented his method of fixing the dunes by plantations of the maritime pine."[475] Although the Landes had been almost abandoned for ages, they show numerous traces of ancient cultivation and prosperity, and it is principally by means of the encroachments of the sands that they have become reduced to their present desolate condition. The destruction of the coast towns and harbors, which furnished markets for the products of the plains, the damming up of the rivers, and the obstruction of the smaller channels of natural drainage by the advance of the dunes, were no doubt very influential causes; and if we add the drifting of the sea sand over the soil, we have at least a partial explanation of the decayed agriculture and diminished population of this great waste. When the dunes were once arrested, and the soil to the east of them was felt to be secure against invasion by them, experiments, in the way of agricultural improvement, by drainage and plantation, were commenced, and they have been attended with such signal success, that the complete recovery of one of the dreariest and most extensive wastes in Europe may be considered as both a probable and a near event.[476] _The Belgian Campine._ In the northern part of Belgium, and extending across the confines of Holland, is another very similar heath plain, called the Campine. This is a vast sand flat, interspersed with marshes and inland dunes, and, until recently, considered wholly incapable of cultivation. Enormous sums have been expended in reclaiming it by draining and other familiar agricultural processes, but without results at all proportional to the capital invested. In 1849, the unimproved portion of the Campine was estimated at little less than three hundred and fifty thousand acres. The example of France has prompted experiments in the planting of trees, especially the maritime pine, upon this barren waste, and the results have been such as to show that its sands may both be fixed and made productive, not only without loss, but with positive pecuniary advantage.[477] _Sands and Steppes of Eastern Europe._ There are still unsubdued sand wastes in many parts of interior Europe not familiarly known to tourists or even geographers. "Olkuez and Schiewier in Poland," says Naumann, "lie in true sand deserts, and a boundless plain of sand stretches around Ozenstockau, on which there grows neither tree nor shrub. In heavy winds, this plain resembles a rolling sea, and the sand hills rise and disappear like the waves of the ocean. The heaps of waste from the Olkuez mines are covered with sand to the depth of four fathoms."[478] No attempts have yet been made to subdue the sands of Poland, but when peace and prosperity shall be restored to that unhappy country, there is no reasonable doubt that the measures, which have proved so successful on similar formations in Germany, may be employed with advantage in the Polish deserts. There are sand drifts in parts of the steppes of Russia, but in general the soil of those vast plains is of a different, though very varied, composition, and is covered with vegetation. The steppes, however, have many points of analogy with the sand plains of Northern Germany, and if they are ever fitted for civilized occupation, it must be by the same means, that is, by planting forests. It is disputed whether the steppes were ever wooded. They were certainly bare of forest growth at a very remote period; for Herodotus describes the country of the Scythians between the Ister and the Tanais as woodless, with the exception of the small province of Xylæa between the Dnieper and the Gulf of Perekop. They are known to have been occupied by a large nomade and pastoral population down to the sixteenth century, though these tribes are now much reduced in numbers. The habits of such races are scarcely less destructive to the forest than those of civilized life. Pastoral tribes do not employ much wood for fuel or for construction, but they carelessly or recklessly burn down the forests, and their cattle effectually check the growth of young trees wherever their range extends. At present, the furious winds which sweep over the plains, the droughts of summer, and the rights and abuses of pasturage, constitute very formidable obstacles to the employment of measures which have been attended with so valuable results on the sand wastes of France and Germany. The Russian Government has, however, attempted the wooding of the steppes, and there are thriving plantations in the neighborhood of Odessa, where the soil is of a particularly loose and sandy character.[479] The trees best suited to this locality, and, as there is good reason to suppose, to sand plains in general, is the _Ailanthus glandulosa_, or Japan varnish tree.[480] The remarkable success which has crowned the experiments with the ailanthus at Odessa, will, no doubt, stimulate to similar trials elsewhere, and it seems not improbable that the arundo and the maritime pine, which have fixed so many thousand acres of drifting sands in Western Europe, will be, partially at least, superseded by the tamarisk and the varnish tree. _Advantages of Reclaiming the Sands._ If we consider the quantity of waste land which has been made productive by the planting of the sand hills and plains, and the extent of fertile soil, the number of villages and other human improvements, and the value of the harbors, which the same process has saved from being buried under the rolling dunes, and at last swallowed up forever by the invasions of the sea, we shall be inclined to rank Brémontier and Reventlov among the greatest benefactors of their race. With the exception of the dikes of the Netherlands, their labors are the first deliberate and direct attempts of man to make himself, on a great scale, a geographical power, to restore natural balances which earlier generations had disturbed, and to atone, by acts guided by foreseeing and settled purpose, for the waste which thoughtless improvidence had created. _Government Works._ There is an important political difference between these latter works and the diking system of the Netherlandish and German coasts. The dikes originally were, and in modern times very generally have been, private enterprises, undertaken with no other aim than to add a certain quantity of cultivable soil to the former possessions of their proprietor, or sometimes of the state. In short, with few exceptions, they have been merely a pecuniary investment, a mode of acquiring land not economically different from purchase. The planting of the dunes, on the contrary, has always been a public work, executed, not with the expectation of reaping a regular direct percentage of income from the expenditure, but dictated by higher views of state economy--by the same governmental principles, in fact, which animate all commonwealths in repelling invasion by hostile armies, or in repairing the damages that invading forces may have inflicted on the general interests of the people. The restoration of the forests in the southern part of France, as now conducted by the Government of that empire, is a measure of the same elevated character as the fixing of the dunes. In former ages, forests were formed or protected simply for the sake of the shelter they afforded to game, or for the timber they yielded; but the recent legislation of France, and of some other Continental countries, on this subject, looks to more distant as well as nobler ends, and these are among the public acts which most strongly encourage the hope that the rulers of Christendom are coming better to understand the true duties and interests of civilized government. CHAPTER VI. PROJECTED OR POSSIBLE GEOGRAPHICAL CHANGES BY MAN. CUTTING OF MARINE ISTHMUSES--THE SUEZ CANAL--CANAL ACROSS ISTHMUS OF DARIEN--CANALS TO THE DEAD SEA--MARITIME CANALS IN GREECE--CANAL OF SAROS--CAPE COD CANAL--DIVERSION OF THE NILE--CHANGES IN THE CASPIAN-- IMPROVEMENTS IN NORTH AMERICAN HYDROGRAPHY--DIVERSION OF RHINE-- DRAINING OF THE ZUIDERZEE--WATERS OF THE KARST--SUBTERRANEAN WATERS OF GREECE--SOIL BELOW ROCK--COVERING ROCKS WITH EARTH--WADIES OF ARABIA PETRÆA--INCIDENTAL EFFECTS OF HUMAN ACTION--RESISTANCE TO GREAT NATURAL FORCES--EFFECTS OF MINING--ESPY'S THEORIES--RIVER SEDIMENT--NOTHING SMALL IN NATURE. _Cutting of Marine Isthmuses._ Besides the great enterprises of physical transformation of which I have already spoken, other works of internal improvement or change have been projected in ancient and modern times, the execution of which would produce considerable, and, in some cases, extremely important, revolutions in the face of the earth. Some of the schemes to which I refer are evidently chimerical; others are difficult, indeed, but cannot be said to be impracticable, though discouraged by the apprehension of disastrous consequences from the disturbance of existing natural or artificial arrangements; and there are still others, the accomplishment of which is ultimately certain, though for the present forbidden by economical considerations. When we consider the number of narrow necks or isthmuses which separate gulfs and bays of the sea from each other, or from the main ocean, and take into account the time and cost, and risks of navigation which would be saved by executing channels to connect such waters, and thus avoiding the necessity of doubling long capes and promontories, or even continents, it seems strange that more of the enterprise and money which have been so lavishly expended in forming artificial rivers for internal navigation should not have been bestowed upon the construction of maritime canals. Many such have been projected in early and in recent ages, and some trifling cuts between marine waters have been actually made, but no work of this sort, possessing real geographical or even commercial importance, has yet been effected. These enterprises are attended with difficulties and open to objections, which are not, at first sight, obvious. Nature guards well the chains by which she connects promontories with mainlands, and binds continents together. Isthmuses are usually composed of adamantine rock or of shifting sands--the latter being much the more refractory material to deal with. In all such works there is a necessity for deep excavation below low-water mark--always a matter of great difficulty; the dimensions of channels for sea-going ships must be much greater than those of canals of inland navigation; the height of the masts or smoke pipes of that class of vessels would often render bridging impossible, and thus a ship canal might obstruct a communication more important than that which it was intended to promote; the securing of the entrances of marine canals and the construction of ports at their termini would in general be difficult and expensive, and the harbors and the channel which connected them would be extremely liable to fill up by deposits washed in from sea and shore. Besides all this, there is, in many cases, an alarming uncertainty as to the effects of joining together waters which nature has put asunder. A new channel may deflect strong currents from safe courses, and thus occasion destructive erosion of shores otherwise secure, or promote the transportation of sand or slime to block up important harbors, or it may furnish a powerful enemy with dangerous facilities for hostile operations along the coast. Nature sometimes mocks the cunning and the power of man by spontaneously performing, for his benefit, works which he shrinks from undertaking, and the execution of which by him she would resist with unconquerable obstinacy. A dangerous sand bank, that all the enginery of the world could not dredge out in a generation, may be carried off in a night by a strong river flood, or a current impelled by a violent wind from an unusual quarter, and a passage scarcely navigable by fishing boats may be thus converted into a commodious channel for the largest ship that floats upon the ocean. In the remarkable gulf of Liimfjord in Jutland, nature has given a singular example of a canal which she alternately opens as a marine strait, and, by shutting again, converts into a fresh-water lagoon. The Liimfjord was doubtless originally an open channel from the Atlantic to the Baltic between two islands, but the sand washed up by the sea blocked up the western entrance, and built a wall of dunes to close it more firmly. This natural dike, as we have seen, has been more than once broken through, and it is perhaps in the power of man, either permanently to maintain the barrier, or to remove it and keep a navigable channel constantly open. If the Liimfjord becomes an open strait, the washing of sea sand through it would perhaps block up some of the belts and small channels now important for the navigation of the Baltic, and the direct introduction of a tidal current might produce very perceptible effects on the hydrography of the Cattegat. _The Suez Canal._ If the Suez Canal--the greatest and most truly cosmopolite physical improvement ever undertaken by man--shall prove successful, it will considerably affect the basins of the Mediterranean and of the Red Sea, though in a different manner, and probably in a less degree than the diversion of the current of the Nile from the one to the other--to which I shall presently refer--would do. It is, indeed, conceivable, that if a free channel be once cut from sea to sea, the coincidence of a high tide and a heavy south wind might produce a hydraulic force that would convert the narrow canal into an open strait. In such a case, it is impossible to estimate, or even to foresee, the consequences which might result from the unobstructed mingling of the flowing and ebbing currents of the Red Sea with the almost tideless waters of the Mediterranean. There can be no doubt, however, that they would be of a most important character as respects the simply geographical features and the organic life of both. But the shallowness of the two seas at the termini of the canal, the action of the tides of the one and the currents of the other, and the nature of the intervening isthmus, render the occurrence of such a cataclysm in the highest degree improbable. The obstruction of the canal by sea sand at both ends is a danger far more difficult to guard against and avert, than an irruption of the waters of either sea. There is, then, no reason to expect any change of coast lines or of natural navigable channels as a direct consequence of the opening of the Suez Canal, but it will, no doubt, produce very interesting revolutions in the animal and vegetable population of both basins. The Mediterranean, with some local exceptions--such as the bays of Calabria, and the coast of Sicily so picturesquely described by Quatrefages[481]--is comparatively poor in marine vegetation, and in shell as well as in fin fish. The scarcity of fish in some of its gulfs is proverbial, and you may scrutinize long stretches of beach on its northern shores, after every south wind for a whole winter, without finding a dozen shells to reward your search. But no one who has not looked down into tropical or subtropical seas can conceive the amazing wealth of the Red Sea in organic life. Its bottom is carpeted or paved with marine plants, with zoophytes and with shells, while its waters are teeming with infinitely varied forms of moving life. Most of its vegetables and its animals, no doubt, are confined by the laws of their organization to warmer temperatures than that of the Mediterranean, but among them there must be many, whose habitat is of a wider range, many whose powers of accommodation would enable them to acclimate themselves in a colder sea. We may suppose the less numerous aquatic fauna and flora of the Mediterranean to be equally capable of climatic adaptation, and hence, when the canal shall be opened, there will be an interchange of the organic population not already common to both seas. Destructive species, thus newly introduced, may diminish the numbers of their proper prey in either basin, and, on the other hand, the increased supply of appropriate food may greatly multiply the abundance of others, and at the same time add important contributions to the aliment of man in the countries bordering on the Mediterranean. A collateral feature of this great project deserves notice as possessing no inconsiderable geographical importance. I refer to the conduit or conduits constructed from the Nile to the isthmus, primarily to supply fresh water to the laborers on the great canal, and ultimately to serve as aqueducts for the city of Suez, and for the irrigation and reclamation of a large extent of desert soil. In the flourishing days of the Egyptian empire, the waters of the Nile were carried over important districts east of the river. In later ages, most of this territory relapsed into a desert, from the decay of the canals which once fertilized it. There is no difficulty in restoring the ancient channels, or in constructing new, and thus watering not only all the soil that the wisdom of the Pharaohs had improved, but much additional land. Hundreds of square miles of arid sand waste would thus be converted into fields of perennial verdure, and the geography of Lower Egypt would be thereby sensibly changed. If the canal succeeds, considerable towns will grow up at once at both ends of the channel, and at intermediate points, all depending on the maintenance of aqueducts from the Nile, both for water and for the irrigation of the neighboring fields which are to supply them with bread. Important interests will thus be created, which will secure the permanence of the hydraulic works and of the geographical changes produced by them, and Suez, or Port Said, or the city at Lake Timsah, may become the capital of the government which has been so long established at Cairo. _Canal across the Isthmus of Darien._ The most colossal project of canalization ever suggested, whether we consider the physical difficulties of its execution, the magnitude and importance of the waters proposed to be united, or the distance which would be saved in navigation, is that of a channel between the Gulf of Mexico and the Pacific, across the Isthmus of Darien. I do not now speak of a lock canal, by way of the Lake of Nicaragua or any other route--for such a work would not differ essentially from other canals, and would scarcely possess a geographical character--but of an open cut between the two seas. It has been by no means shown that the construction of such a channel is possible, and, if it were opened, it is highly probable that sand bars would accumulate at both entrances, so as to obstruct any powerful current through it. But if we suppose the work to be actually accomplished, there would be, in the first place, such a mixture of the animal and vegetable life of the two great oceans as I have stated to be likely to result from the opening of the Suez Canal between two much smaller basins. In the next place, if the channel were not obstructed by sand bars, it might sooner or later be greatly widened and deepened by the mechanical action of the current through it, and consequences, not inferior in magnitude to any physical revolution which has taken place since man appeared upon the earth, might result from it. What those consequences would be is in a great degree matter of pure conjecture, and there is much room for the exercise of the imagination on the subject; but, as more than one geographer has suggested, there is one possible result which throws all other conceivable effects of such a work quite into the shade. I refer to changes in the course of the two great oceanic rivers, the Gulf Stream and the corresponding current on the Pacific side of the isthmus. The warm waters which the Gulf Stream transports to high latitudes and then spreads out, like an expanded hand, along the eastern shores of the Atlantic, give out, as they cool, heat enough to raise the mean temperature of Western Europe several degrees. In fact, the Gulf Stream is the principal cause of the superiority of the climate of Western Europe over those of Eastern America and Eastern Asia in the corresponding latitudes. All the meteorological conditions of the former region are in a great measure regulated by it, and hence it is the grandest and most beneficent of all purely geographical phenomena. We do not yet know enough of the laws which govern the movements of this mighty flood of warmth and life to be able to say whether its current would be perceptibly affected by the severance of the Isthmus of Darien; but as it enters and sweeps round the Gulf of Mexico, it is possible that the removal of the resistance of the land which forms the western shore of that sea, might allow the stream to maintain its original westward direction, and join itself to the tropical current of the Pacific. The effect of such a change would be an immediate depression of the mean temperature of Western Europe to the level of that of Eastern America, and perhaps the climate of the former continent might become as excessive as that of the latter, or even a new "ice period" be occasioned by the withdrawal of so important a source of warmth from the northern zones. Hence would result the extinction of vast multitudes of land and sea plants and animals, and a total revolution in the domestic and rural economy of human life in all those countries from which the New World has received its civilized population. Other scarcely less startling consequences may be imagined as possible; but the whole speculation is too dreary, distant, and improbable to deserve to be long indulged in.[482] _Canals to the Dead Sea._ The project of Captain Allen for opening a new route to India by cuts between the Mediterranean and the Dead Sea, and between the Dead Sea and the Red Sea, presents many interesting considerations.[483] The hypsometrical observations of Bertou, Roth, and others, render it highly probable, if not certain, that the watershed in the Wadi-el-Araba between the Dead Sea and the Red Sea is not less than three hundred feet above the mean level of the latter, and if this is so, the execution of a canal from the one sea to the other is quite out of the question. But the summit level between the Mediterranean and the Jordan, near Jezreel, is believed to be little, if at all, more than one hundred feet above the sea, and the distance is so short that the cutting of a channel through the dividing ridge would probably be found by no means an impracticable undertaking. Although, therefore, we have no reason to believe it possible to open a navigable channel to the east by way of the Dead Sea, there is not much doubt that the basin of the latter might be made accessible from the Mediterranean. The level of the Dead Sea lies 1,316.7 feet below that of the ocean. It is bounded east and west by mountain ridges, rising to the height of from 2,000 to 4,000 feet above the ocean. From its southern end, a depression called the Wadi-el-Araba extends to the Gulf of Akaba, the eastern arm of the Red Sea. The Jordan empties into its northern extremity, after having passed through the Lake of Tiberias at an elevation of 663.4 feet above the Dead Sea, or 653.3 below the Mediterranean, and drains a considerable valley north of the lake, as well as the plain of Jericho, which lies between the lake and the sea. If the waters of the Mediterranean were admitted freely into the basin of the Dead Sea, they would raise its surface to the general level of the ocean, and consequently flood all the dry land below that level within the basin. I do not know that accurate levels have been taken in the valley of the Jordan above the Lake of Tiberias, and our information is very vague as to the hypsometry of the northern part of the Wadi-el-Araba. As little do we know where a contour line, carried around the basin at the level of the Mediterranean, would strike its eastern and western borders. We cannot, therefore, accurately compute the extent of now dry land which would be covered by the admission of the waters of the Mediterranean, or the area of the inland sea which would be thus created. Its length, however, would certainly exceed one hundred and fifty miles, and its mean breadth, including its gulfs and bays, could scarcely be less than fifteen, perhaps even twenty. It would cover very little ground now occupied by civilized or even uncivilized man, though some of the soil which would be submerged--for instance, that watered by the Fountain of Elisha and other neighboring sources--is of great fertility, and, under a wiser government and better civil institutions, might rise to importance, because, from its depression, it possesses a very warm climate, and might supply Southeastern Europe with tropical products more readily than they can be obtained from any other source. Such a canal and sea would be of no present commercial importance, because they would give access to no new markets or sources of supply; but when the fertile valleys and the deserted plains east of the Jordan shall be reclaimed to agriculture and civilization, these waters would furnish a channel of communication which might become the medium of a very extensive trade. Whatever might be the economical results of the opening and filling of the Dead Sea basin, the creation of a new evaporable area, adding not less than 2,000 or perhaps 3,000 square miles to the present fluid surface of Syria, could not fail to produce important meteorological effects. The climate of Syria would be tempered, its precipitation and its fertility increased, the courses of its winds and the electrical condition of its atmosphere modified. The present organic life of the valley would be extinguished, and many tribes of plants and animals would emigrate from the Mediterranean to the new home which human art had prepared for them. It is possible, too, that the addition of 1,300 feet, or forty atmospheres, of hydrostatic pressure upon the bottom of the basin might disturb the equilibrium between the internal and the external forces of the crust of the earth at this point of abnormal configuration, and thus produce geological convulsions the intensity of which cannot be even conjectured. _Maritime Canals in Greece._ A maritime canal executed and another projected in ancient times, the latter of which is again beginning to excite attention, deserve some notice, though their importance is of a commercial rather than a geographical character. The first of these is the cut made by Xerxes through the rock which connects the promontory of Mount Athos with the mainland; the other, a navigable canal through the Isthmus of Corinth. In spite of the testimony of Herodotus and Thucydides, the Romans classed the canal of Xerxes among the fables of "mendacious Greece," and yet traces of it are perfectly distinct at the present day through its whole extent, except at a single point where, after it had become so choked as to be no longer navigable, it was probably filled up to facilitate communication by land between the promontory and the country in the rear of it. If the fancy kingdom of Greece shall ever become a sober reality, escape from its tutelage and acquire such a moral as well as political status that its own capitalists--who now prefer to establish themselves and employ their funds anywhere else rather than in their native land--have any confidence in the permanency of its institutions, a navigable channel will no doubt be opened between the gulfs of Lepanto and Ægina. The annexation of the Ionian Islands to Greece will make such a work almost a political necessity, and it would not only furnish valuable facilities for domestic intercourse, but become an important channel of communication between the Levant and the countries bordering on the Adriatic, or conducting their trade through that sea. As I have said, the importance of this latter canal and of a navigable channel between Mount Athos and the continent would be chiefly commercial, but both of them would be conspicuous instances of the control of man over nature in a field where he has thus far done little to interfere with her spontaneous arrangements. If they were constructed upon such a scale as to admit of the free passage of the water through them, in either direction, as the prevailing winds should impel it, they would exercise a certain influence on the coast currents, which are important as hydrographical elements, and also as producing abrasion of the coast and a drift at the bottom of seas, and hence would be entitled to a higher rank than simply as artificial means of transit. _Canal of Saros._ It has been thought practicable to cut a canal across the peninsula of Gallipoli from the outlet of the Sea of Marmora into the Gulf of Saros. It may be doubted whether the mechanical difficulties of such a work would not be found insuperable; but when Constantinople shall recover the important political and commercial rank which naturally belongs to her, the execution of such a canal will be recommended by strong reasons of military expediency, as well as by the interests of trade. An open channel across the peninsula would divert a portion of the water which now flows through the Dardanelles, diminish the rapidity of that powerful current, and thus in part remove the difficulties which obstruct the navigation of the strait. It would considerably abridge the distance by water between Constantinople and the northern coast of the Ægean, and it would have the important advantage of obliging an enemy to maintain two blockading fleets instead of one. _Cape Cod Canal._ The opening of a navigable cut through the narrow neck which separates the southern part of Cape Cod Bay in Massachusetts from the Atlantic, was long ago suggested, and there are few coast improvements on the Atlantic shores of the United States which are recommended by higher considerations of utility. It would save the most important coasting trade of the United States the long and dangerous navigation around Cape Cod, afford a new and safer entrance to Boston harbor for vessels from Southern ports, secure a choice of passages, thus permitting arrivals upon the coast and departures from it at periods when wind and weather might otherwise prevent them, and furnish a most valuable internal communication in case of coast blockade by a foreign power. The difficulties of the undertaking are no doubt formidable, but the expense of maintenance and the uncertainty of the effects of currents setting through the new strait are still more serious objections. _Diversion of the Nile._ Perhaps the most remarkable project of great physical change, proposed or threatened in earlier ages, is that of the diversion of the Nile from its natural channel, and the turning of its current into either the Libyan desert or the Red Sea. The Ethiopian or Abyssinian princes more than once menaced the Memlouk sultans with the execution of this alarming project, and the fear of so serious an evil is said to have induced the Moslems to conciliate the Abyssinian kings by large presents, and by some concessions to the oppressed Christians of Egypt.[484] Indeed, Arabic historians affirm that in the tenth century the Ethiopians dammed the river, and, for a whole year, cut off its waters from Egypt. The probable explanation of this story is to be found in a season of extreme drought, such as have sometimes occurred in the valley of the Nile. About the beginning of the sixteenth century, Albuquerque the "Terrible" revived the scheme of turning the Nile into the Red Sea, with the hope of destroying the transit trade through Egypt by way of Kesseir. In 1525 the King of Portugal was requested by the Emperor of Abyssinia to send him engineers for that purpose; a successor of that prince threatened to attempt the project about the year 1700, and even as late as the French occupation of Egypt, the possibility of driving out the intruder by this means was suggested in England. It cannot be positively affirmed that the diversion of the waters of the Nile to the Red Sea is impossible. In the chain of mountains which separates the two valleys, Brown found a deep depression or wadi, extending from the one to the other, at no great elevation above the bed of the river. The Libyan desert is so much higher than the Nile below the junction of the two principal branches at Khartum, that there is no reason to believe a new channel for their united waters could be found in that direction; but the Bahr-el-Abiad flows through, if it does not rise in, a great table land, and some of its tributaries are supposed to communicate in the rainy season with branches of great rivers flowing in quite another direction. Hence it is probable that a portion at least of the waters of this great arm of the Nile--and perhaps a quantity the abstraction of which would be sensibly felt in Egypt--might be sent to the Atlantic by the Niger, lost in the inland lakes of Central Africa, or employed to fertilize the Libyan sand wastes. Admitting the possibility of turning the whole river into the Red Sea, let us consider the probable effect of the change. First and most obvious is the total destruction of the fertility of Middle and Lower Egypt, the conversion of that part of the valley into a desert, and the extinction of its imperfect civilization, if not the absolute extirpation of its inhabitants. This is the calamity threatened by the Abyssinian princes and the ferocious Portuguese warrior, and feared by the sultans of Egypt. Beyond these immediate and palpable consequences neither party then looked; but a far wider geographical area, and far more extensive and various human interests, would be affected by the measure. The spread of the Nile during the annual inundation covers, for many weeks, several thousand square miles with water, and at other seasons of the year pervades the same and even a larger area with moisture by infiltration. The abstraction of so large an evaporable surface from the southern shores of the Mediterranean could not but produce important effects on many meteorological phenomena, and the humidity, the temperature, the electrical condition and the atmospheric currents of Northeastern Africa might be modified to a degree that would sensibly affect the climate of Europe. The Mediterranean, deprived of the contributions of the Nile, would require a larger supply, and of course a stronger current, of water from the Atlantic through the Straits of Gibraltar; the proportion of salt it contains would be increased, and the animal life of at least its southern borders would be consequently modified; the current which winds along its southern, eastern, and northeastern shores would be diminished in force and volume, if not destroyed altogether, and its basin and its harbors would be shoaled by no new deposits from the highlands of inner Africa. In the much smaller Red Sea, more immediately perceptible, if not greater, effects, would be produced. The deposits of slime would reduce its depth, and perhaps, in the course of ages, divide it into an inland and an open sea; its waters would be more or less freshened, and its immensely rich marine fauna and flora changed in character and proportion, and, near the mouth of the river, perhaps even destroyed altogether; its navigable channels would be altered in position and often quite obstructed; the flow of its tides would be modified by the new geographical conditions; the sediment of the river would form new coast lines and lowlands, which would be covered with vegetation, and probably thereby produce sensible climatic changes. _Changes in the Caspian._ The Russian Government has contemplated the establishment of a nearly direct water communication between the Caspian Sea and the Sea of Azoff, partly by natural and partly by artificial channels, and there are now navigable canals between the Don and the Volga; but these works, though not wanting in commercial and political interest, do not possess any geographical importance. It is, however, very possible to produce appreciable geographical changes in the basin of the Caspian by the diversion of the great rivers which flow from Central Russia. The surface of the Caspian is eighty-three feet below the level of the Sea of Azoff, and its depression has been explained upon the hypothesis that the evaporation exceeds the supply derived, directly and indirectly, from precipitation, though able physicists now maintain that the sinking of this sea is due to a subsidence of its bottom from geological causes. At Tsaritsin, the Don, which empties into the Sea of Azoff, and the Volga, which pours into the Caspian, approach each other within ten miles. Near this point, by means of open or subterranean canals, the Don might be turned into the Volga, or the Volga into the Don. If we suppose the whole or a large proportion of the waters of the Don to be thus diverted from their natural outlet and sent down to the Caspian, the equilibrium between the evaporation from that sea and its supply of water might be restored, or its level even raised above its ancient limits. If the Volga were turned into the Sea of Azoff, the Caspian would be reduced in dimensions until the balance between loss and gain should be reëstablished, and it would occupy a much smaller area than at present. Such changes in the proportion of solid and fluid surface would have some climatic effects in the territory which drains into the Caspian, and on the other hand, the introduction of a greater quantity of fresh water into the Sea of Azoff would render that gulf less saline, affect the character and numbers of its fish, and perhaps be not wholly without sensible influence on the water of the Black Sea. _Improvements in North American Hydrography._ We are not yet well enough acquainted with the geography of Central Africa, or of the interior of South America, to conjecture what hydrographical revolutions might there be wrought; but from the fact that many important rivers in both continents drain extensive table lands, of very moderate inclination, there is reason to suppose that important changes in the course of rivers might be accomplished. Our knowledge of the drainage of North America is much more complete, and it is certain that there are numerous points where the courses of great rivers, or the discharge of considerable lakes, might be completely diverted, or at least partially directed into different channels. The surface of Lake Erie is 565 feet above that of the Hudson at Albany, and it is so near the level of the great plain lying east of it, that it was found practicable to supply the western section of the canal, which unites it with the Hudson, with water from the lake, or rather from the Niagara which flows out of it. Hence a channel might be constructed, which would draw off into the valley of the Genesee any desirable proportion of the water naturally discharged by the Niagara. The greatest depth of water yet sounded in Lake Erie is but two hundred and seventy feet, the mean depth one hundred and twenty. Open canals parallel with the Niagara, or directly toward the Genesee, might be executed upon a scale which would exercise an important influence on the drainage of the lake, if there were any adequate motive for such an undertaking. Still easier would it be to create additional outlets for the waters of Lake Superior at the Saut St. Mary--where the river which drains the lake descends twenty-two feet in a single mile--and thus produce incalculable effects, both upon that lake and upon the great chain of inland waters which communicate with it. The summit level between Lake Michigan and the Des Plaines, a tributary of the Mississippi, is only twenty-seven feet above the lake, and the intervening distance is but a very few miles. It has often been proposed to cut an open channel across this ridge, and there is no doubt of the practicability of the project. Were this accomplished, although such a cut would not, of itself, form a navigable canal, a part of the waters of Lake Michigan would be contributed to the Gulf of Mexico, instead of to that of St. Lawrence, and the flow might be so regulated as to keep the Illinois and the Mississippi at flood at all seasons of the year. The increase in the volume of these rivers would augment their velocity and their transporting power, and consequently, the erosion of their banks and the deposit of slime in the Gulf of Mexico, while the introduction of a larger body of cold water into the beds of these rivers would very probably produce a considerable effect on the animal life that peoples them. The diversion of water from the common basin of the great lakes through a new channel, in a direction opposite to their natural discharge, would not be absolutely without influence on the St. Lawrence, though probably the effect would be too small to be in any way perceptible. _Diversion of the Rhine._ The interference of physical improvements with vested rights and ancient arrangements, is a more formidable obstacle in old countries than in new, to enterprises involving anything approaching to a geographical revolution. Hence such projects meet with stronger opposition in Europe than in America, and the number of probable changes in the face of nature in the former continent is proportionally less. I have noticed some important hydraulic improvements as already executed or in progress in Europe, and I may refer to some others as contemplated or suggested. One of these is the diversion of the Rhine from its present channel below Ragatz, by a cut through the narrow ridge near Sargans, and the consequent turning of its current into the Lake of Wallenstadt. This would be an extremely easy undertaking, for the ridge is but twenty feet above the level of the Rhine, and hardly two hundred yards wide. There is no present adequate motive for this diversion, but it is easy to suppose that it may become advisable within no long period. The navigation of the Lake of Constance is rapidly increasing in importance, and the shoaling of the eastern end of that lake by the deposits of the Rhine may require a remedy which can be found by no other so ready means as the discharge of that river into the Lake of Wallenstadt. The navigation of this latter lake is not important, nor is it ever likely to become so, because the rocky and precipitous character of its shores renders their cultivation impossible. It is of great depth, and its basin is capacious enough to receive and retain all the sediment which the Rhine would carry into it for thousands of years. _Draining of the Zuiderzee._ I have referred to the draining of the Lake of Haarlem as an operation of great geographical as well as economical and mechanical interest. A much more gigantic project, of a similar character, is now engaging the attention of the Netherlandish engineers. It is proposed to drain the great salt-water basin called the Zuiderzee. This inland sea covers an area of not less than two thousand square miles, or about one million three hundred thousand acres. The seaward half, or that portion lying northwest of a line drawn from Enkhuizen to Stavoren, is believed to have been converted from a marsh to an open bay since the fifth century after Christ, and this change is ascribed, partly if not wholly, to the interference of man with the order of nature. The Zuiderzee communicates with the sea by at least six considerable channels, separated from each other by low islands, and the tide rises within the basin to the height of three feet. To drain the Zuiderzee, these channels must first be closed and the passage of the tidal flood through them cut off. If this be done, the coast currents will be restored approximately to the lines they followed fourteen or fifteen centuries ago, and there can be little doubt that an appreciable effect will thus be produced upon all the tidal phenomena of that coast, and, of course, upon the maritime geography of Holland. A ring dike and canal must then be constructed around the landward side of the basin, to exclude and carry off the fresh-water streams which now empty into it. One of these, the Ijssel, a considerable river, has a course of eighty miles, and is, in fact, one of the outlets of the Rhine, though augmented by the waters of several independent tributaries. These preparations being made, and perhaps transverse dikes erected at convenient points for dividing the gulf into smaller portions, the water must be pumped out by machinery, in substantially the same way as in the case of the Lake of Haarlem. No safe calculations can be made as to the expenditure of time and money required for the execution of this stupendous enterprise, but I believe its practicability is not denied by competent judges, though doubts are entertained as to its financial expediency. The geographical results of this improvement would be analogous to those of the draining of the Lake of Haarlem, but many times multiplied in extent, and its meteorological effects, though perhaps not perceptible on the coast, could hardly fail to be appreciable in the interior of Holland. _Waters of the Karst._ The singular structure of the Karst, the great limestone plateau lying to the north of Trieste, has suggested some engineering operations which might be attended with sensible effects upon the geography of the province. I have described this table land as, though now bare of forests, and almost of vegetation, having once been covered with woods, and as being completely honeycombed by caves through which the drainage of that region is conducted. Schmidl has spent years in studying the subterranean geography and hydrography of this singular district, and his discoveries, and those of earlier cave-hunters, have led to various proposals of physical improvement of a novel character. Many of the underground water courses of the Karst are without visible outlet, and, in some instances at least, they, no doubt, send their waters, by deep channels, to the Adriatic.[485] The city of Trieste is very insufficiently provided with fresh water. It has been thought practicable to supply this want by tunnelling through the wall of the plateau, which rises abruptly in the rear of the town, until some subterranean stream is encountered, the current of which can be conducted to the city. More visionary projectors have gone further, and imagined that advantage might be taken of the natural tunnels under the Karst for the passage of roads, railways, and even navigable canals. But however chimerical these latter schemes may seem, there is every reason to believe that art might avail itself of these galleries for improving the imperfect drainage of the champaign country bounded by the Karst, and that stopping or opening the natural channels might very much modify the hydrography of an extensive region. _Subterranean Waters of Greece._ There are parts of continental Greece which resemble the Karst and the adjacent plains in being provided with a natural subterranean drainage. The superfluous waters run off into limestone caves called _catavothra_ ([Greek: katabothra]). In ancient times, the entrances to the catavothra were enlarged or partially closed as the convenience of drainage or irrigation required, and there is no doubt that similar measures might be adopted at the present day with great advantage both to the salubrity and the productiveness of the regions so drained. _Soil below Rock._ One of the most singular changes of natural surface effected by man is that observed by Beechey and by Barth at Lîn Tefla, and near Gebel Genûnes, in the district of Ben Gâsi, in Northern Africa. In this region the superficial stratum originally consisted of a thin sheet of rock covering a layer of fertile earth. This rock has been broken up, and, when not practicable to find use for it in fences, fortresses, or dwellings, heaped together in high piles, and the soil, thus bared of its stony shell, has been employed for agricultural purposes.[486] If we remember that gunpowder was unknown at the period when these remarkable improvements were executed, and of course that the rock could have been broken only with the chisel and wedge, we must infer that land had at that time a very great pecuniary value, and, of course, that the province, though now exhausted, and almost entirely deserted by man, had once a dense population. _Covering Rock with Earth._ If man has, in some cases, broken up rock to reach productive ground beneath, he has, in many other instances, covered bare ledges, and sometimes extensive surfaces of solid stone, with fruitful earth, brought from no inconsiderable distance. Not to speak of the Campo Santo at Pisa, filled, or at least coated, with earth from the Holy Land, for quite a different purpose, it is affirmed that the garden of the monastery of St. Catherine at Mount Sinai is composed of Nile mud, transported on the backs of camels from the banks of that river. Parthey and older authors state that all the productive soil of the Island of Malta was brought over from Sicily.[487] The accuracy of the information may be questioned in both cases, but similar practices, on a smaller scale, are matter of daily observation in many parts of Southern Europe. Much of the wine of the Moselle is derived from grapes grown on earth carried high up the cliffs on the shoulders of men. In China, too, rock has been artificially covered with earth to an extent which gives such operations a real geographical importance, and the accounts of the importation of earth at Malta, and the fertilization of the rocks on Mount Sinai with slime from the Nile, may be not wholly without foundation. _Wadies of Arabia, Petræa._ In the latter case, indeed, river sediment might be very useful as a manure, but it could hardly be needed as a soil; for the growth of vegetation in the wadies of the Sinaitic Peninsula shows that the disintegrated rock of its mountains requires only water to stimulate it to considerable productiveness. The wadies present, not unfrequently, narrow gorges, which might easily be closed, and thus accumulations of earth, and reservoirs of water to irrigate it, might be formed which would convert many a square mile of desert into flourishing date gardens and cornfields. Not far from Wadi Feiran, on the most direct route to Wadi Esh-Sheikh, is a very narrow pass called by the Arabs El Bueb (El Bab) or, The Gate, which might be securely closed to a very considerable height, with little labor or expense. Above this pass is a wide and nearly level expanse, containing a hundred acres, perhaps much more. This is filled up to a certain regular level with deposits brought down by torrents before the Gate, or Bueb, was broken through, and they have now worn down a channel in the deposits to the bed of the wadi. If a dam were constructed at the pass, and reservoirs built to retain the winter rains, a great extent of valley might be rendered cultivable. _Incidental Effects of Human Action._ I have more than once alluded to the collateral and unsought consequences of human action as being often more momentous than the direct and desired results. There are cases where such incidental, or, in popular speech, accidental, consequences, though of minor importance in themselves, serve to illustrate natural processes; others, where, by the magnitude and character of the material traces they leave behind them, they prove that man, in primary or in more advanced stages of social life, must have occupied particular districts for a longer period than has been supposed by popular chronology. "On the coast of Jutland," says Forchhammer, "wherever a bolt from a wreck or any other fragment of iron is deposited in the beach sand, the particles are cemented together, and form a very solid mass around the iron. A remarkable formation of this sort was observed a few years ago in constructing the sea wall of the harbor of Elsineur. This stratum, which seldom exceeded a foot in thickness, rested upon common beach sand, and was found at various depths, less near the shore, greater at some distance from it. It was composed of pebbles and sand, and contained a great quantity of pins, and some coins of the reign of Christian IV, between the beginning and the middle of the seventeenth century. Here and there, a coating of metallic copper had been deposited by galvanic action, and the presence of completely oxydized metallic iron was often detected. An investigation undertaken by Councillor Reinhard and myself, at the instance of the Society of Science, made it in the highest degree probable that this formation owed its origin to the street sweepings of the town, which had been thrown upon the beach, and carried off and distributed by the waves over the bottom of the harbor."[488] These and other familiar observations of the like sort show that a sandstone reef, of no inconsiderable magnitude, might originate from the stranding of a ship with a cargo of iron,[489] or from throwing the waste of an establishment for working metals into running water which might carry it to the sea. Parthey records a singular instance of unforeseen mischief from an interference with the arrangements of nature. A landowner at Malta possessed a rocky plateau sloping gradually toward the sea, and terminating in a precipice forty or fifty feet high, through natural openings in which the sea water flowed into a large cave under the rock. The proprietor attempted to establish salt works on the surface, and cut shallow pools in the rock for the evaporation of the water. In order to fill the salt pans more readily, he sank a well down to the cave beneath, through which he drew up water by a windlass and buckets. The speculation proved a failure, because the water filtered through the porous bottom of the pans, leaving little salt behind. But this was a small evil, compared with other destructive consequences that followed. When the sea was driven into the cave by violent west or northwest winds, it shot a _jet d'eau_ through the well to the height of sixty feet, the spray of which was scattered far and wide over the neighboring gardens and blasted the crops. The well was now closed with stones, but the next winter's storms hurled them out again, and spread the salt spray over the grounds in the vicinity as before. Repeated attempts were made to stop the orifice, but at the time of Parthey's visit the sea had thrice burst through, and it was feared that the evil was without remedy.[490] I have mentioned the great extent of the heaps of oyster and other shells left by the American Indians on the Atlantic coast of the United States. Some of the Danish kitchen-middens, which closely resemble them, are a thousand feet long, from one hundred and fifty to two hundred wide, and from six to ten high. These piles have an importance as geological witnesses, independent of their bearing upon human history. Wherever the coast line appears, from other evidence, to have remained unchanged in outline and elevation since they were accumulated, they are found near the sea, and not more than about ten feet above its level. In some cases they are at a considerable distance from the beach, and in these instances, so far as yet examined, there are proofs that the coast has advanced in consequence of upheaval or of fluviatile or marine deposit. Where they are altogether wanting, the coast seems to have sunk or been washed away by the sea. The constancy of these observations justifies geologists in arguing, where other evidence is wanting, the advance of land or sea respectively, or the elevation or depression of the former, from the position or the absence of these heaps alone. Every traveller in Italy is familiar with Monte Testaccio, the mountain of potsherds, at Rome; but this deposit, large as it is, shrinks into insignificance when compared with masses of similar origin in the neighborhood of older cities. The castaway pottery of ancient towns in Magna Græcia composes strata of such extent and thickness that they have been dignified with the appellation of the ceramic formation. The Nile, as it slowly changes its bed, exposes in its banks masses of the same material, so vast that the population of the world during the whole historical period would seem to have chosen this valley as a general deposit for its broken vessels. The fertility imparted to the banks of the Nile by the water and the slime of the inundations, is such that manures are little employed. Hence much domestic waste, which would elsewhere be employed to enrich the soil, is thrown out into vacant places near the town. Hills of rubbish are thus piled up which astonish the traveller almost as much as the solid pyramids themselves. The heaps of ashes and other household refuse collected on the borders and within the limits of Cairo were so large, that the removal of them by Ibrahim Pacha has been looked upon as one of the great works of the age. The soil near cities, the street sweepings of which are spread upon the ground as manure, is perceptibly raised by them and by other effects of human industry, and in spite of all efforts to remove the waste, the level of the ground on which large towns stand is constantly elevated. The present streets of Rome are twenty feet above those of the ancient city. The Appian way between Rome and Albano, when cleared out a few years ago, was found buried four or five feet deep, and the fields along the road were elevated nearly or quite as much. The floors of many churches in Italy, not more than six or seven centuries old, are now three or four feet below the adjacent streets, though it is proved by excavations that they were built as many feet above them. _Resistance to Great Natural Forces._ I have often spoken of the greater and more subtile natural forces, and especially of geological agencies, as powers beyond human guidance or resistance. This is no doubt at present true in the main, but man has shown that he is not altogether impotent to struggle with even these mighty servants of nature, and his unconscious as well as his deliberate action may in some cases have increased or diminished the intensity of their energies. It is a very ancient belief that earthquakes are more destructive in districts where the crust of the earth is solid and homogeneous, than where it is of a looser and more interrupted structure. Aristotle, Pliny the elder, and Seneca believed that not only natural ravines and caves, but quarries, wells, and other human excavations, which break the continuity of the terrestrial strata and facilitate the escape of elastic vapors, have a sensible influence in diminishing the violence and preventing the propagation of the earth waves. In all countries subject to earthquakes this opinion is still maintained, and it is asserted that, both in ancient and in modern times, buildings protected by deep wells under or near them have suffered less from earthquakes than those the architects of which have neglected this precaution.[491] If the commonly received theory of the cause of earthquakes is true--that, namely, which ascribes them to the elastic force of gases accumulated or generated in subterranean reservoirs--it is evident that open channels of communication between such reservoirs and the atmosphere might serve as a harmless discharge of gases that would otherwise acquire destructive energy. The doubt is whether artificial excavations can be carried deep enough to reach the laboratory where the elastic fluids are distilled. There are, in many places, small natural crevices through which such fluids escape, and the source of them sometimes lies at so moderate a depth that they pervade the superficial soil and, as it were, transpire from it, over a considerable area. When the borer of an ordinary artesian well strikes into a cavity in the earth, imprisoned air often rushes out with great violence, and this has been still more frequently observed in sinking mineral-oil wells. In this latter case, the discharge of a vehement current of inflammable fluid sometimes continues for hours and even longer periods. These facts seem to render it not wholly improbable that the popular belief of the efficacy of deep wells in mitigating the violence of earthquakes is well founded. In general, light, wooden buildings are less injured by earthquakes than more solid structures of stone or brick, and it is commonly supposed that the power put forth by the earth wave is too great to be resisted by any amount of weight or solidity of mass that man can pile up upon the surface. But the fact that in countries subject to earthquakes many very large and strongly constructed palaces, temples, and other monuments have stood for centuries, comparatively uninjured, suggests a doubt whether this opinion is sound. The earthquake of the first of November, 1755, which was felt over a twelfth part of the earth's surface, was probably the most violent of which we have any clear and distinct account, and it seems to have exerted its most destructive force at Lisbon. It has often been noticed as a remarkable fact, that the mint, a building of great solidity, was almost wholly unaffected by the shock which shattered every house and church in the city, and its escape from the common ruin can hardly be accounted for except upon the supposition that its weight, compactness, and strength of material enabled it to resist an agitation of the earth which overthrew all weaker structures. On the other hand, a stone pier in the harbor of Lisbon, on which thousands of people had taken refuge, sank with its foundations to a great depth during the same earthquake; and it is plain that where subterranean cavities exist, at moderate depths, the erection of heavy masses upon them would tend to promote the breaking down of the strata which roof them over. No physicist, I believe, has supposed that man can avert the eruption of a volcano or diminish the quantity of melted rock which it pours out of the bowels of the earth; but it is not always impossible to divert the course of even a large current of lava. "The smaller streams of lava near Catania," says Ferrara, in describing the great eruption of 1669, "were turned from their course by building dry walls of stone as a barrier against them. * * * It was proposed to divert the main current from Catania, and fifty men, protected by hides, were sent with hooks and iron bars to break the flank of the stream near Belpasso.[492] When the opening was made, fluid lava poured forth and flowed rapidly toward Paterno; but the inhabitants of that place, not caring to sacrifice their own town to save Catania, rushed out in arms and put a stop to the operation."[493] In the eruption of Vesuvius in 1794, the viceroy saved from impending destruction the town of Portici, and the valuable collection of antiquities then deposited there but since removed to Naples, by employing several thousand men to dig a ditch above the town, by which the lava current was carried off in another direction.[494] _Effects of Mining._ The excavations made by man, for mining and other purposes, may sometimes occasion disturbance of the surface by the subsidence of the strata above them, as in the case of the mine of Fahlun, but such accidents must always be too inconsiderable in extent to deserve notice in a geographical point of view. Such excavations, however, may interfere materially with the course of subterranean waters, and it has even been conjectured that the removal of large bodies of metallic ore from their original deposits might, at least locally, affect the magnetic and electrical condition of the earth's crust to a sensible degree. Accidental fires in mines of coal or lignite sometimes lead to consequences not only destructive to large quantities of valuable material, but may, directly or indirectly, produce results important in geography. The coal occasionally takes fire from the miners' lights or other fires used by them, and, if long exposed to air in deserted galleries, may be spontaneously kindled. Under favorable circumstances, a stratum of coal will burn till it is exhausted, and a cavity may be burnt out in a few months which human labor could not excavate in many years. Wittwer informs us that a coal mine at St. Etienne in Dauphiny has been burning ever since the fourteenth century, and that a mine near Duttweiler, another near Epterode, and a third at Zwickau, have been on fire for two hundred years. Such conflagrations not only produce cavities in the earth, but communicate a perceptible degree of heat to the surface, and the author just quoted cites cases where this heat has been advantageously employed in forcing vegetation.[495] _Espy's Theories._ Espy's well known suggestion of the possibility of causing rain artificially, by kindling great fires, is not likely to be turned to practical account, but the speculations of this able meteorologist are not, for that reason, to be rejected as worthless. His labors exhibit great industry in the collection of facts, much ingenuity in dealing with them, remarkable insight into the laws of nature, and a ready perception of analogies and relations not obvious to minds less philosophically constituted. They have unquestionably contributed very essentially to the advancement of meteorological science. The possibility that the distribution and action of electricity may be considerably modified by long lines of iron railways and telegraph wires, is a kindred thought, and in fact rests much on the same foundation as the belief in the utility of lightning rods, but such influence is too obscure and too small to have been yet detected. _River Sediment._ The manifestation of the internal heat of the earth at any given point is conditioned by the thickness of the crust at such point. The deposits of rivers tend to augment that thickness at their estuaries. The sediment of slowly flowing rivers emptying into shallow seas is spread over so great a surface that we can hardly imagine the foot or two of slime they let fall over a wide area in a century to form an element among even the infinitesimal quantities which compose the terms of the equations of nature. But some swift rivers, rolling mountains of fine earth, discharge themselves into deeply scooped gulfs or bays, and in such cases the deposit amounts, in the course of a few years, to a mass the transfer of which from the surface of a large basin, and its accumulation at a single point, may be supposed to produce other effects than those measurable by the sounding line. Now, almost all the operations of rural life, as I have abundantly shown, increase the liability of the soil to erosion by water. Hence, the clearing of the valley of the Ganges by man must have much augmented the quantity of earth transported by that river to the sea, and of course have strengthened the effects, whatever they may be, of thickening the crust of the earth in the Bay of Bengal. In such cases, then, human action must rank among geological influences. _Nothing Small in Nature._ It is a legal maxim that "the law concerneth not itself with trifles," _de minimus non curat lex_; but in the vocabulary of nature, little and great are terms of comparison only; she knows no trifles, and her laws are as inflexible in dealing with an atom as with a continent or a planet.[496] The human operations mentioned in the last few paragraphs, therefore, do act in the ways ascribed to them, though our limited faculties are at present, perhaps forever, incapable of weighing their immediate, still more their ultimate consequences. But our inability to assign definite values to these causes of the disturbance of natural arrangements is not a reason for ignoring the existence of such causes in any general view of the relations between man and nature, and we are never justified in assuming a force to be insignificant because its measure is unknown, or even because no physical effect can now be traced to it as its origin. The collection of phenomena must precede the analysis of them, and every new fact, illustrative of the action and reaction between humanity and the material world around it, is another step toward the determination of the great question, whether man is of nature or above her. FOOTNOTES: [1] In the Middle Ages, feudalism, and a nominal Christianity whose corruptions had converted the most beneficent of religions into the most baneful of superstitions, perpetuated every abuse of Roman tyranny, and added new oppressions and new methods of extortion to those invented by older despotisms. The burdens in question fell most heavily on the provinces that had been longest colonized by the Latin race, and these are the portions of Europe which have suffered the greatest physical degradation. "Feudalism," says Blanqui, "was a concentration of scourges. The peasant, stripped of the inheritance of his fathers, became the property of inflexible, ignorant, indolent masters; he was obliged to travel fifty leagues with their carts whenever they required it; he labored for them three days in the week, and surrendered to them half the product of his earnings during the other three; without their consent he could not change his residence, or marry. And why, indeed, should he wish to marry, when he could scarcely save enough to maintain himself? The Abbot Alcuin had twenty thousand slaves, called _serfs_, who were forever attached to the soil. This is the great cause of the rapid depopulation observed in the Middle Ages, and of the prodigious multitude of monasteries which sprang up on every side. It was doubtless a relief to such miserable men to find in the cloisters a retreat from oppression; but the human race never suffered a more cruel outrage, industry never received a wound better calculated to plunge the world again into the darkness of the rudest antiquity. It suffices to say that the prediction of the approaching end of the world, industriously spread by the rapacious monks at this time, was received without terror."--_Résumé de l'Histoire du Commerce_, p. 156. The abbey of Saint-Germain-des-Prés, which, in the time of Charlemagne, had possessed a million of acres, was, down to the Revolution, still so wealthy, that the personal income of the abbot was 300,000 livres. The abbey of Saint-Denis was nearly as rich as that of Saint-Germain-des-Prés.--LAVERGNE, _Économie Rurale de la France_, p. 104. Paul Louis Courier quotes from La Bruyère the following striking picture of the condition of the French peasantry in his time: "One sees certain dark, livid, naked, sunburnt, wild animals, male and female, scattered over the country and attached to the soil, which they root and turn over with indomitable perseverance. They have, as it were, an articulate voice, and when they rise to their feet, they show a human face. They are, in fact, men; they creep at night into dens, where they live on black bread, water, and roots. They spare other men the labor of ploughing, sowing, and harvesting, and therefore deserve some small share of the bread they have grown." "These are his own words," adds Courier; "he is speaking of the fortunate peasants, of those who had work and bread, and they were then the few."--_Pétition à la Chambre des Députís pour les Villageois que l'on empêche de danser._ Arthur Young, who travelled in France from 1787 to 1789, gives, in the twenty-first chapter of his Travels, a frightful account of the burdens of the rural population even at that late period. Besides the regular governmental taxes, and a multitude of heavy fines imposed for trifling offences, he enumerates about thirty seignorial rights, the very origin and nature of some of which are now unknown, while those of some others, claimed and enforced by ecclesiastical as well as by temporal lords, are as repulsive to humanity and morality, as the worst abuses ever practised by heathen despotism. Most of these, indeed, had been commuted for money payments, and were levied on the peasantry as pecuniary imposts for the benefit of prelates and lay lords, who, by virtue of their nobility, were exempt from taxation. Who can wonder at the hostility of the French plebeian classes toward the aristocracy in the days of the Revolution? [2] The temporary depopulation of an exhausted soil may be, in some cases, a physical, though, like fallows in agriculture, a dear-bought advantage. Under favorable circumstances, the withdrawal of man and his flocks allows the earth to clothe itself again with forests, and in a few generations to recover its ancient productiveness. In the Middle Ages, worn-out fields were depopulated, in many parts of the Continent, by civil and ecclesiastical tyrannies, which insisted on the surrender of the half of a loaf already too small to sustain its producer. Thus abandoned, these lands often relapsed into the forest state, and, some centuries later, were again brought under cultivation with renovated fertility. [3] The subject of climatic change, with and without reference to human action as a cause, has been much discussed by Moreau de Jonnes, Dureau, de la Malle, Arago, Humboldt, Fuster, Gasparin, Becquerel, and many other writers in Europe, and by Noah Webster, Forry, Drake, and others in America. Fraas has endeavored to show, by the history of vegetation in Greece, not merely that clearing and cultivation have affected climate, but that change of climate has essentially modified the character of vegetable life. See his _Klima und Pflanzenwelt in der Zeit_. [4] Gods Almagt wenkte van den troon, En schiep elk volk een land ter woon: Hier vestte Zij een grondgebied, Dat Zij ons zelven scheppen liet. [5] The udometric measurements of Belgrand, reported in the _Annales Forestières_ for 1854, and discussed by Vallès in chap. vi of his _Études sur les Inondations_, constitute the earliest, and, in some respects, the most remarkable series known to me, of persevering and systematic observations bearing directly and exclusively upon the influence of human action on climate, or, to speak more accurately, on precipitation and natural drainage. The conclusions of Belgrand, however, and of Vallès, who adopts them, have not been generally accepted by the scientific world, and they seem to have been, in part at least, refuted by the arguments of Héricourt and the observations of Cantegril, Jeandel, and Belland. See chapter iii: _The Woods_. [6] Verses addressed by G. C. to Sir Walter Raleigh.--HAKLUYT, i, p. 668. [7] ----I troer, at Synets Sands er lagt i Öiet, Mens dette kun er Redskab. Synet strömmer Fra Sjælens Dyb, og Öiets fine Nerver Gaae ud fra Hjernens hemmelige Værksted. HENRIK HERTZ, _Kong René's Datter_, sc. ii. In the material eye, you think, sight lodgeth! The _eye_ is but an organ. _Seeing_ streameth From the soul's inmost depths. The fine perceptive Nerve springeth from the brain's mysterious workshop. [8] Skill in marksmanship, whether with firearms or with other projectile weapons, depends more upon the training of the eye than is generally supposed, and I have often found particularly good shots to possess an almost telescopic vision. In the ordinary use of the rifle, the barrel serves as a guide to the eye, but there are sportsmen who fire with the but of the gun at the hip. In this case, as in the use of the sling, the lasso, and the bolas, in hurling the knife (see BABINET, _Lectures_, vii, p. 84), in throwing the boomerang, the javelin, or a stone, and in the employment of the blow pipe and the bow, the movements of the hand and arm are guided by that mysterious sympathy which exists between the eye and the unseeing organs of the body. In shooting the tortoises of the Amazon and its tributaries, the Indians use an arrow with a long twine and a float attached to it. Avé-Lallemant (_Die Benutzung der Palmen am Amazonenstrom_, p. 32) thus describes their mode of aiming: "As the arrow, if aimed directly at the floating tortoise, would strike it at a small angle, and glance from its flat and wet shell, the archers have a peculiar method of shooting. They are able to calculate exactly their own muscular effort, the velocity of the stream, the distance and size of the tortoise, and they shoot the arrow directly up into the air, so that it falls almost vertically upon the shell of the tortoise, and sticks in it." Analogous calculations--if such physico-mental operations can properly be so called--are made in the use of other missiles; for no projectile flies in a right line to its mark. But the exact training of the eye lies at the bottom of all of them, and marksmanship depends almost wholly upon the power of that organ, whose directions the blind muscles implicitly follow. It is perhaps not out of place to observe here that our English word aim comes from the Latin æstimo, I calculate or estimate. See WEDGWOOD'S _Dictionary of English Etymology_, and the note to the American edition, under _Aim_. Another proof of the control of the limbs by the eye has been observed in deaf-and-dumb schools, and others where pupils are first taught to write on large slates or blackboards. The writing is in large characters, the small letters being an inch or more high. They are formed with chalk or a slate pencil firmly grasped in the fingers, and by appropriate motions of the wrist, elbow, and shoulder, not of the finger joints. Nevertheless, when a pen is put into the hand of a pupil thus taught, his handwriting, though produced by a totally different set of muscles and muscular movements, is identical in character with that which he has practised on the blackboard. It has been much doubted whether the artists of the classic ages possessed a more perfect sight than those of modern times, or whether, in executing their minute mosaics and gem engravings, they used magnifiers. Glasses ground convex have been found at Pompeii, but they are too rudely fashioned and too imperfectly polished to have been of any practical use for optical purposes. But though the ancient artists may have had a microscopic vision, their astronomers cannot have had a telescopic power of sight; for they did not discover the satellites of Jupiter, which are often seen with the naked eye at Oormeeah, in Persia, and sometimes, as I can testify by personal observation, at Cairo. For a very remarkable account of the restoration of vision impaired from age, by judicious training, see _Lessons in Life_, by TIMOTHY TITCOMB, lesson xi. [9] _Antiquity of Man_, p. 377. [10] "One of them [the Indians] seated himself near me, and made from a fragment of quartz, with a simple piece of round bone, one end of which was hemispherical, with a small crease in it (as if worn by a thread) the sixteenth of an inch deep, an arrow head which was very sharp and piercing, and such as they use on all their arrows. The skill and rapidity with which it was made, without a blow, but by simply breaking the sharp edges with the creased bone by the strength of his hands--for the crease merely served to prevent the instrument from slipping, affording no leverage--was remarkable."--_Reports of Explorations and Surveys for Pacific Railroad_, vol. ii, 1855, _Lieut._ BECKWITH'S _Report_, p. 43. It has been said that stone weapons are not found in Sicily, except in certain caves half filled with the skeletons of extinct animals. If they have not been found in that island in more easily accessible localities, I suspect it is because eyes familiar with such objects have not sought for them. In January, 1854, I picked up an arrow head of quartz in a little ravine or furrow just washed out by a heavy rain, in a field near the Simeto. It is rudely fashioned, but its artificial character and its special purpose are quite unequivocal. [11] Probably no cultivated vegetable affords so good an opportunity of studying the laws of acclimation of plants as maize or Indian corn. Maize is grown from the tropics to at least lat. 47° in Northeastern America, and farther north in Europe. Every two or three degrees of latitude brings you to a new variety, with new climatic adaptations, and the capacity of the plant to accommodate itself to new conditions of temperature and season seems almost unlimited. We may easily suppose a variety of this grain, which had become acclimated in still higher latitudes, to have been lost, and in such case the failure to raise a crop from seed brought from some distance to the south would not prove that the climate had become colder. Many persons now living remember that, when the common tomato was first introduced into Northern New England, it often failed to ripen; but, in the course of a very few years, it completely adapted itself to the climate, and now not only matures both its fruit and its seeds with as much certainty as any cultivated vegetable, but regularly propagates itself by self-sown seed. Meteorological observations, however, do not show any amelioration of the summer climate in those States within that period. See _Appendix_, No. 1. Maize and the tomato, if not new to human use, have not been long known to civilization, and were, very probably, reclaimed and domesticated at a much more recent period than the plants which form the great staples of agricultural husbandry in Europe and Asia. Is the great power of accomodation to climate possessed by them due to this circumstance? There is some reason to suppose that the character of maize has been sensibly changed by cultivation in South America; for, according to Pöppig, the ears of this grain found in old Peruvian tombs belong to varieties not now known in Peru.--_Travels in Peru_, chap. vii. [12] The cultivation of madder is said to have been introduced into Europe by an Oriental in the year 1765, and it was first planted in the neighborhood of Avignon. Of course, it has been grown in that district for less than a century; but upon soils where it has been a frequent crop, it is already losing much of its coloring properties.--LAVERGNE, _Économie Rurale de la France_, pp. 259-291. I believe there is no doubt that the cultivation of madder in the vicinity of Avignon is of recent introduction; but it appears from Fuller and other evidence, that this plant was grown in Europe before the middle of the seventeenth century. The madder brought to France from Persia may be of a different species, or, at least, variety. "Some two years since," says Fuller, "madder was sown by Sir Nicholas Crispe at Debtford, and I hope will have good success; first because it groweth in Zeland in the same (if not a more _northern_) _latitude_. Secondly, because _wild madder_ grows here in abundance; and why may not _tame madder_ if _cicurated_ by art. Lastly, because as good as any grew some thirty years since at Barn-Elms, in Surrey, though it quit not cost through some error in the first planter thereof, which now we hope will be rectified."--FULLER, _Worthies of England_, ii, pp. 57, 58. Perhaps the recent diseases of the olive, the vine, and the silkworm--the prevailing malady of which insect is supposed by some to be the effect of an incipient decay of the mulberry tree--may be, in part, due to changes produced in the character of the soil by exhaustion through long cultivation. [13] In many parts of New England there are tracts, miles in extent, and presenting all varieties of surface and exposure, which were partially cleared sixty or seventy years ago, and where little or no change in the proportion of cultivated ground, pasturage, and woodland has taken place since. In some cases, these tracts compose basins apparently scarcely at all exposed to any local influence in the way of percolation or infiltration of water toward or from neighboring valleys. But in such situations, apart from accidental disturbances, the ground is growing drier and drier, from year to year, springs are still disappearing, and rivulets still diminishing in their summer supply of water. A probable explanation of this is to be found in the rapid drainage of the surface of cleared ground, which prevents the subterranean natural reservoirs, whether cavities or merely strata of bibulous earth, from filling up. How long this process is to last before an equilibrium is reached, none can say. It may be, for years; it may be, for centuries. Livingstone states facts which favor the supposition that a secular desiccation is still going on in central Africa. When the regions where the earth is growing drier were cleared of wood, or, indeed, whether forests ever grew there, we are unable to say, but the change appears to have been long in progress. There is reason to suspect a similar revolution in Arabia Petræa. In many of the wadis, and particularly in the gorges between Wadi Feiran and Wadi Esh Sheikh, there are water-worn banks showing that, at no very remote period, the winter floods must have risen fifty feet in channels where the growth of acacias and tamarisks and the testimony of the Arabs concur to prove that they have not risen six feet within the memory or tradition of the present inhabitants. There is little probability that any considerable part of the Sinaitic peninsula has been wooded since its first occupation by man, and we must seek the cause of its increasing dryness elsewhere than in the removal of the forest. [14] The soil of newly subdued countries is generally in a high degree favorable to the growth of the fruits of the garden and the orchard, but usually becomes much less so in a very few years. Plums, of many varieties, were formerly grown, in great perfection and abundance, in many parts of New England where at present they can scarcely be reared at all; and the peach, which, a generation or two ago, succeeded admirably in the southern portion of the same States, has almost ceased to be cultivated there. The disappearance of these fruits is partly due to the ravages of insects, which have in later years attacked them; but this is evidently by no means the sole, or even the principal cause of their decay. In these cases, it is not to the exhaustion of the particular acres on which the fruit trees have grown that we are to ascribe their degeneracy, but to a general change in the condition of the soil or the air; for it is equally impossible to rear them successfully on absolutely new land in the neighborhood of grounds where, not long since, they bore the finest fruit. I remember being told, many years ago, by one of the earliest settlers of the State of Ohio, a very intelligent and observing person, that the apple trees raised there from seed sown soon after the land was cleared, bore fruit in less than half the time required to bring to bearing those reared from seed sown when the ground had been twenty years under cultivation. In the peat mosses of Denmark, Scotch firs and other trees not now growing in the same localities, are found in abundance. Every generation of trees leaves the soil in a different state from that in which it found it; every tree that springs up in a group of trees of another species than its own, grows under different influences of light and shade and atmosphere from its predecessors. Hence the succession of crops, which occurs in all natural forests, seems to be due rather to changes of condition than of climate. See chapter iii, _post_. [15] The nomenclature of meteorology is vague and sometimes equivocal. Not long since, it was suspected that the observers reporting to a scientific institution did not agree in their understanding of the mode of expressing the direction of the wind prescribed by their instructions. It was found, upon inquiry, that very many of them used the names of the compass-points to indicate the quarter _from_ which the wind blew, while others employed them to signify the quarter _toward_ which the atmospheric currents were moving. In some instances, the observers were no longer within the reach of inquiry, and of course their tables of the wind were of no value. "Winds," says Mrs. Somerville, "are named from the points whence they blow, currents exactly the reverse. An easterly wind comes from the east; whereas an easterly current comes from the west, and flows toward the east."--_Physical Geography_, p. 229. There is no philological ground for this distinction, and it probably originated in a confusion of the terminations _-wardly_ and _-erly_, both of which are modern. The root of the former ending implies the direction _to_ or _to-ward_ which motion is supposed. It corresponds to, and is probably allied with, the Latin _versus_. The termination _-erly_ is a corruption or softening of _-ernly_, easterly for easternly, and many authors of the seventeenth century so write it. In Hakluyt (i, p. 2), _easterly_ is applied to place, "_easterly_ bounds," and means _eastern_. In a passage in Drayton, "_easterly_ winds" must mean winds _from_ the east; but the same author, in speaking of nations, uses _northerly_ for _northern_. Hakewell says: "The sonne cannot goe more _southernely_ from vs, nor come more _northernely_ towards vs." Holland, in his translation of Pliny, referring to the moon has: "When shee is _northerly_," and "shee is gone _southerly_." Richardson, to whom I am indebted for the above citations, quotes a passage from Dampier where _westerly_ is applied to the wind, but the context does not determine the direction. The only example of the termination in _-wardly_ given by this lexicographer is from Donne, where it means _toward_ the west. Shakspeare, in _Hamlet_ (v. ii), uses _northerly_ wind for wind _from_ the north. Milton does not employ either of these terminations, nor were they known to the Anglo-Saxons, who, however, had adjectives of direction in _-an_ or _-en_, _-ern_ and _-weard_, the last always meaning the point _toward_ which motion is supposed, the others that _from_ which it proceeds. We use an _east_ wind, an _eastern_ wind, and an _easterly_ wind, to signify the same thing. The two former expressions are old, and constant in meaning; the last is recent, superfluous, and equivocal. See _Appendix_, No. 2. [16] I do not here speak of the vast prairie region of the Mississippi valley, which cannot properly be said ever to have been a field of British colonization; but of the original colonies, and their dependencies in the territory of the present United States, and in Canada. It is, however, equally true of the Western prairies as of the Eastern forest land, that they had arrived at a state of equilibrium, though under very different conditions. [17] The great fire of Miramichi in 1825, probably the most extensive and terrific conflagration recorded in authentic history, spread its ravages over nearly six thousand square miles, chiefly of woodland, and was of such intensity that it seemed to consume the very soil itself. But so great are the recuperative powers of nature, that, in twenty-five years, the ground was thickly covered again with trees of fair dimensions, except where cultivation and pasturage kept down the forest growth. [18] The English nomenclature of this geographical feature does not seem well settled. We have _bog_, _swamp_, _marsh_, _morass_,_ moor_, _fen_, _turf moss_, _peat moss_, _quagmire_, all of which, though sometimes more or less accurately discriminated, are often used interchangeably, or are perhaps employed, each exclusively, in a particular district. In Sweden, where, especially in the Lappish provinces, this terr-aqueous formation is very extensive and important, the names of its different kinds are more specific in their application. The general designation of all soils permanently pervaded with water is _Kärr_. The elder Læstadius divides the _Kärr_ into two genera: _Myror_ (sing. _myra_), and _Mossar_ (sing. _mosse_). "The former," he observes, "are grass-grown, and overflowed with water through almost the whole summer; the latter are covered with mosses and always moist, but very seldom overflowed." He enumerates the following species of _Myra_, the character of which will perhaps be sufficiently understood by the Latin terms into which he translates the vernacular names, for the benefit of strangers not altogether familiar with the language and the subject: 1. _Hömyror_, paludes graminosæ. 2. _Dy_, paludes profundæ. 3. _Flarkmyror_, or proper _kärr_, paludes limosæ. 4. _Fjällmyror_, paludes uliginosæ. 5. _Tufmyror_, paludes cæspitosæ. 6. _Rismyror_, paludes virgatæ. 7. _Starrängar_, prata irrigata, with their subdivisions, dry _starrängar_ or _risängar_, wet _starrängar_ and _fräkengropar_. 8. _Pölar_, laeunæ. 9. _Gölar_, fossæ inundatæ. The _Mossar_, paludes turfosæ, which are of great extent, have but two species: 1. _Torfmossar_, called also _Mossmyror_ and _Snottermyror_, and, 2. _Björnmossar_. The accumulations of stagnant or stagnating water originating in bogs are distinguished into _Tr[=a]sk_, stagna, and _Tjernar_ or _Tjärnar_ (sing. _Tjern_ or _Tjärn_), stagnatiles. _Tr[=a]sk_ are pools fed by bogs, or water emanating from them, and their bottoms are slimy; _Tjernar_ are small _Träsk_ situated within the limits of _Mossar_.--L. L. LÆSTADIUS, _om Möjligheten af Uppodlingar i Lappmarken_, pp. 23, 24. [19] Although the quantity of bog land in New England is less than in many other regions of equal area, yet there is a considerable extent of this formation in some of the Northeastern States. Dana (_Manual of Geology_, p. 614) states that the quantity of peat in Massachusetts is estimated at 120,000,000 cords, or nearly 569,000,000 cubic yards, but he does not give either the area or the depth of the deposits. In any event, however, bogs cover but a small percentage of the territory in any of the Northern States, while it is said that one tenth of the whole surface of Ireland is composed of bogs, and there are still extensive tracts of undrained marsh in England. Bogs, independently of their importance in geology as explaining the origin of some kinds of mineral coal, have a present value as repositories of fuel. Peat beds have sometimes a thickness of ten or twelve yards, or even more. A depth of ten yards would give 48,000 cubic yards to the acre. The greatest quantity of firewood yielded by the forests of New England to the acre is 100 cords solid measure, or 474 cubic yards; but this comprises only the trunks and larger branches. If we add the small branches and twigs, it is possible that 600 cubic yards might, in some cases, be cut on an acre. This is only one eightieth part of the quantity of peat sometimes found on the same area. It is true that a yard of peat and a yard of wood are not the equivalents of each other, but the fuel on an acre of deep peat is worth much more than that on an acre of the best woodland. Besides this, wood is perishable, and the quantity on an acre cannot be increased beyond the amount just stated; peat is indestructible, and the beds are always growing. [20] "Aquatic plants have a utility in raising the level of marshy grounds, which renders them very valuable, and may well be called a geological function. * * * "The engineer drains ponds at a great expense by lowering the surface of the water; nature attains the same end, gratuitously, by raising the level of the soil without depressing that of the water; but she proceeds more slowly. There are, in the Landes, marshes where this natural filling has a thickness of four mètres, and some of them, at first lower than the sea, have been thus raised and drained so as to grow summer crops, such, for example, as maize."--BOITEL, _Mise en valeur des Terres pauvres_, p. 227. The bogs of Denmark--the examination of which by Steenstrup and Vaupell has presented such curious results with respect to the natural succession of forest trees--appear to have gone through this gradual process of drying, and the birch, which grows freely in very wet soils, has contributed very effectually by its annual deposits to raise the surface above the water level, and thus to prepare the ground for the oak.--VAUPELL, _Bögens Indvandring_, pp. 39, 40. [21] Careful examination of the peat mosses in North Sjælland--which are so abundant in fossil wood that, within thirty years, they have yielded above a million of trees--shows that the trees have generally fallen from age and not from wind. They are found in depressions on the declivities of which they grew, and they lie with the top lowest, always falling toward the bottom of the valley.--VAUPELL, _Bögens Indvandring i de Danske Skove_, pp. 10, 14. [22] The locust insect, _Clitus pictus_, which deposits its eggs in the American locust, _Robinia pseudacacia_, is one of these, and its ravages have been and still are most destructive to that very valuable tree, so remarkable for combining rapidity of growth with strength and durability of wood. This insect, I believe, has not yet appeared in Europe, where, since the so general employment of the _Robinia_ to clothe and protect embankments and the scarps of deep cuts on railroads, it would do incalculable mischief. As a traveller, however, I should find some compensation for this evil in the destruction of these acacia hedges, which as completely obstruct the view on hundreds of miles of French and Italian railways, as the garden walls of the same countries do on the ordinary roads. See _Appendix_, No. 4. [23] In the artificial woods of Europe, insects are far more numerous and destructive to trees than in the primitive forests of America, and the same remark may be made of the smaller rodents, such as moles, mice, and squirrels. In the dense native wood, the ground and the air are too humid, the depth of shade too great for many tribes of these creatures, while near the natural meadows and other open grounds, where circumstances are otherwise more favorable for their existence and multiplication, their numbers are kept down by birds, serpents, foxes, and smaller predacious quadrupeds. In civilized countries, these natural enemies of the worm, the beetle and the mole, are persecuted, sometimes almost exterminated, by man, who also removes from his plantations the decayed or wind-fallen trees, the shrubs and underwood, which, in a state of nature, furnished food and shelter to the borer and the rodent, and often also to the animals that preyed upon them. Hence the insect and the gnawing quadruped are allowed to increase, from the expulsion of the police which, in the natural wood, prevent their excessive multiplication, and they become destructive to the forest because they are driven to the living tree for nutriment and cover. The forest of Fontainebleau is almost wholly without birds, and their absence is ascribed by some writers to the want of water, which, in the thirsty sands of that wood, does not gather into running brooks; but the want of undergrowth is perhaps an equally good reason for their scarcity. In a wood of spontaneous growth, ordered and governed by nature, the squirrel does not attack trees, or at least the injury he may do is too trifling to be perceptible, but he is a formidable enemy to the plantation. "The squirrels bite the cones of the pine and consume the seed which might serve to restock the wood; they do still more mischief by gnawing off, near the leading shoot, a strip of bark, and thus often completely girdling the tree. Trees so injured must be felled, as they would never acquire a vigorous growth. The squirrel is especially destructive to the pine in Sologne, where he gnaws the bark of tress twenty or twenty-five years old." But even here, nature sometimes provides a compensation, by making the appetite of this quadruped serve to prevent an excessive production of seed cones, which tends to obstruct the due growth of the leading shoot. "In some of the pineries of Brittany which produce cones so abundantly as to strangle the development of the leading shoot of the maritime pine, it has been observed that the pines are most vigorous where the squirrels are most numerous, a result attributed to the repression of the cones by this rodent."--BOITEL, _Mise en valeur des Terres pauvres_, p. 50. See _Appendix_, No. 5. [24] The terrible destructiveness of man is remarkably exemplified in the chase of large mammalia and birds for single products, attended with the entire waste of enormous quantities of flesh, and of other parts of the animal, which are capable of valuable uses. The wild cattle of South America are slaughtered by millions for their hides and horns; the buffalo of North America for his skin or his tongue; the elephant, the walrus, and the narwhal for their tusks; the cetacea, and some other marine animals, for their oil and whalebone; the ostrich and other large birds, for their plumage. Within a few years, sheep have been killed in New England by whole flocks, for their pelts and suet alone, the flesh being thrown away; and it is even said that the bodies of the same quadrupeds have been used in Australia as fuel for limekilns. What a vast amount of human nutriment, of bone, and of other animal products valuable in the arts, is thus recklessly squandered! In nearly all these cases, the part which constitutes the motive for this wholesale destruction, and is alone saved, is essentially of insignificant value as compared with what is thrown away. The horns and hide of an ox are not economically worth a tenth part as much as the entire carcass. One of the greatest benefits to be expected from the improvements of civilization is, that increased facilities of communication will render it possible to transport to places of consumption much valuable material that is now wasted because the price at the nearest market will not pay freight. The cattle slaughtered in South America for their hides would feed millions of the starving population of the Old World, if their flesh could be economically preserved and transported across the ocean. We are beginning to learn a better economy in dealing with the inorganic world. The utilization--or, as the Germans more happily call it, the Verwerthung, the _beworthing_--of waste from metallurgical, chemical, and manufacturing establishments, is among the most important results of the application of science to industrial purposes. The incidental products from the laboratories of manufacturing chemists often become more valuable than those for the preparation of which they were erected. The slags from silver refineries, and even from smelting houses of the coarser metals, have not unfrequently yielded to a second operator a better return than the first had derived from dealing with the natural ore; and the saving of lead carried off in the smoke of furnaces has, of itself, given a large profit on the capital invested in the works. A few years ago, an officer of an American mint was charged with embezzling gold committed to him for coinage. He insisted, in his defence, that much of the metal was volatilized and lost in refining and melting, and upon scraping the chimneys of the melting furnaces and the roofs of the adjacent houses, gold enough was found in the soot to account for no small part of the deficiency. [25] It is an interesting and not hitherto sufficiently noticed fact, that the domestication of the organic world, so far as it has yet been achieved, belongs, not indeed to the savage state, but to the earliest dawn of civilization, the conquest of inorganic nature almost as exclusively to the most advanced stages of artificial culture. It is familiarly known to all who have occupied themselves with the psychology and habits of the ruder races, and of persons with imperfectly developed intellects in civilized life, that although these humble tribes and individuals sacrifice, without scruple, the lives of the lower animals to the gratification of their appetites and the supply of their other physical wants, yet they nevertheless seem to cherish with brutes, and even with vegetable life, sympathies which are much more feebly felt by civilized men. The popular traditions of the simpler peoples recognize a certain community of nature between man, brute animals, and even plants; and this serves to explain why the apologue or fable, which ascribes the power of speech and the faculty of reason to birds, quadrupeds, insects, flowers, and trees, is one of the earliest forms of literary composition. In almost every wild tribe, some particular quadruped or bird, though persecuted as a destroyer of more domestic beasts, or hunted for food, is regarded with peculiar respect, one might almost say, affection. Some of the North American aboriginal nations celebrate a propitiatory feast to the manes of the intended victim before they commence a bear hunt; and the Norwegian peasantry have not only retained an old proverb which ascribes to the same animal "_ti M[oe]nds Styrke og tolv M[oe]nds Vid_," ten men's strength and twelve men's cunning, but they still pay to him something of the reverence with which ancient superstition invested him. The student of Icelandic literature will find in the saga of _Finnbogi hinn rami_ a curious illustration of this feeling, in an account of a dialogue between a Norwegian bear and an Icelandic champion--dumb show on the part of Bruin, and chivalric words on that of Finnbogi--followed by a duel, in which the latter, who had thrown away his arms and armor in order that the combatants might meet on equal terms, was victorious. Drummond Hay's very interesting work on Morocco contains many amusing notices of a similar feeling entertained by the Moors toward the redoubtable enemy of their flocks--the lion. This sympathy helps us to understand how it is that most if not all the domestic animals--if indeed they ever existed in a wild state--were appropriated, reclaimed and trained before men had been gathered into organized and fixed communities, that almost every known esculent plant had acquired substantially its present artificial character, and that the properties of nearly all vegetable drugs and poisons were known at the remotest period to which historical records reach. Did nature bestow upon primitive man some instinct akin to that by which she teaches the brute to select the nutritious and to reject the noxious vegetables indiscriminately mixed in forest and pasture? This instinct, it must be admitted, is far from infallible, and, as has been hundreds of times remarked by naturalists, it is in many cases not an original faculty but an acquired and transmitted habit. It is a fact familiar to persons engaged in sheep husbandry in New England--and I have seen it confirmed by personal observation--that sheep bred where the common laurel, as it is called, _Kalmia angustifolia_, abounds, almost always avoid browsing upon the leaves of that plant, while those brought from districts where laurel is unknown, and turned into pastures where it grows, very often feed upon it and are poisoned by it. A curious acquired and hereditary instinct, of a different character, may not improperly be noticed here. I refer to that by which horses bred in provinces where quicksands are common avoid their dangers or extricate themselves from them. See BRÉMONTIER, _Mémoire sur les Dunes, Annales des Ponts et Chaussées_, 1833: _premier sémestre_, pp. 155-157. It is commonly said in New England, and I believe with reason, that the crows of this generation are wiser than their ancestors. Scarecrows which were effectual fifty years ago are no longer respected by the plunderers of the cornfield, and new terrors must from time to time be invented for its protection. See _Appendix_, No. 6. Civilization has added little to the number of vegetable or animal species grown in our fields or bred in our folds, while, on the contrary, the subjugation of the inorganic forces, and the consequent extension of man's sway over, not the annual products of the earth only, but her substance and her springs of action, is almost entirely the work of highly refined and cultivated ages. The employment of the elasticity of wood and of horn, as a projectile power in the bow, is nearly universal among the rudest savages. The application of compressed air to the same purpose, in the blowpipe, is more restricted, and the use of the mechanical powers, the inclined plane, the wheel and axle, and even the wedge and lever, seems almost unknown except to civilized man. I have myself seen European peasants to whom one of the simplest applications of this latter power was a revelation. [26] The difference between the relations of savage life, and of incipient civilization, to nature, is well seen in that part of the valley of the Mississippi which was once occupied by the mound builders and afterward by the far less developed Indian tribes. When the tillers of the fields, which must have been cultivated to sustain the large population that once inhabited those regions perished, or were driven out, the soil fell back to the normal forest state, and the savages who succeeded the more advanced race interfered very little, if at all, with the ordinary course of spontaneous nature. [27] There is a possible--but only a possible--exception in the case of the American bison. See note on that subject in chap. iii, _post_. [28] Whatever may be thought of the modification of organic species by natural selection, there is certainly no evidence that animals have exerted upon any form of life an influence analogous to that of domestication upon plants, quadrupeds, and birds reared artificially by man; and this is as true of unforeseen as of purposely effected improvements accomplished by voluntary selection of breeding animals. [29] ----"And it may be remarked that, as the world has passed through these several stages of strife to produce a Christendom, so by relaxing in the enterprises it has learnt, does it tend downwards, through inverted steps, to wildness and the waste again. Let a people give up their contest with moral evil; disregard the injustice, the ignorance, the greediness, that may prevail among them, and part more and more with the Christian element of their civilization; and in declining this battle with sin, they will inevitably get embroiled with men. Threats of war and revolution punish their unfaithfulness; and if then, instead of retracing their steps, they yield again, and are driven before the storm, the very arts they had created, the structures they had raised, the usages they had established, are swept away; 'in that very day their thoughts perish.' The portion they had reclaimed from the young earth's ruggedness is lost; and failing to stand fast against man, they finally get embroiled with nature, and are thrust down beneath her ever-living hand."--MARTINEAU'S _Sermon_, "_The Good Soldier of Jesus Christ_." [30] The dependence of man upon the aid of spontaneous nature, in his most arduous material works, is curiously illustrated by the fact that one of the most serious difficulties to be encountered in executing the proposed gigantic scheme of draining the Zuiderzee in Holland, is that of procuring brushwood for the fascines to be employed in the embankments. See DIGGELEN'S pamphlet, "_Groote Werken in Nederland_." [31] In heavy storms, the force of the waves as they strike against a sea wall is from one and a half to two tons to the square foot, and Stevenson, in one instance at Skerryvore, found this force equal to three tons per foot. The seaward front of the breakwater at Cherbourg exposes a surface of about 2,500,000 square feet. In rough weather the waves beat against this whole face, though at the depth of twenty-two yards, which is the height of the breakwater, they exert a very much less violent motive force than at and near the surface of the sea, because this force diminishes in geometrical, as the distance below the surface increases in arithmetical proportion. The shock of the waves is received several thousand times in the course of twenty-four hours, and hence the sum of impulse which the breakwater resists in one stormy day amounts to many thousands of millions of tons. The breakwater is entirely an artificial construction. If then man could accumulate and control the forces which he is able effectually to resist, he might be said to be, physically speaking, omnipotent. [32] Some well known experiments show that it is quite possible to accumulate the solar heat by a simple apparatus, and thus to obtain a temperature which might be economically important even in the climate of Switzerland. Saussure, by receiving the sun's rays in a nest of boxes blackened within and covered with glass, raised a thermometer enclosed in the inner box to the boiling point; and under the more powerful sun of the cape of Good Hope, Sir John Herschel cooked the materials for a family dinner by a similar process, using, however, but a single box, surrounded with dry sand and covered with two glasses. Why should not so easy a method of economizing fuel be resorted to in Italy, and even in more northerly climates? The unfortunate John Davidson records in his journal that he saved fuel in Morocco by exposing his teakettle to the sun on the roof of his house, where the water rose to the temperature of one hundred and forty degrees, and, of course, needed little fire to bring it to boil. But this was the direct and simple, not the accumulated heat of the sun. [33] In the successive stages of social progress, the most destructive periods of human action upon nature are the pastoral condition, and that of incipient stationary civilization, or, in the newly discovered countries of modern geography, the colonial, which corresponds to the era of early civilization in older lands. In more advanced states of culture, conservative influences make themselves felt; and if highly civilized communities do not always restore the works of nature, they at least use a less wasteful expenditure than their predecessors in consuming them. [34] The character of geological formation is an element of very great importance in determining the amount of erosion produced by running water, and, of course, in measuring the consequences of clearing off the forests. The soil of the French Alps yields very readily to the force of currents, and the declivities of the northern Apennines are covered with earth which becomes itself a fluid when saturated with water. Hence the erosion of such surfaces is vastly greater than on many other mountains of equal steepness of inclination. This point is fully considered by the authors referred to in chap. iii, _post_. [35] The Travels of Dr. Dwight, president of Yale College, which embody the results of his personal observations, and of his inquiries among the early settlers, in his vacation excursions in the Northern States of the American Union, though presenting few instrumental measurements or tabulated results, are of value for the powers of observation they exhibit, and for the sound common sense with which many natural phenomena, such for instance as the formation of the river meadows, called "intervales," in New England, are explained. They present a true and interesting picture of physical conditions, many of which have long ceased to exist in the theatre of his researches, and of which few other records are extant. [36] The general law of temperature is that it decreases as we ascend. But, in hilly regions, the law is reversed in cold, still weather, the cold air descending, by reason of its greater gravity, into the valleys. If there be wind enough, however, to produce a disturbance and intermixture of higher and lower atmospheric strata, this exception to the general law does not take place. These facts have long been familiar to the common people of Switzerland and of New England, but their importance has not been sufficiently taken into account in the discussion of meteorological observations. The descent of the cold air and the rise of the warm affect the relative temperatures of hills and valleys to a much greater extent than has been usually supposed. A gentleman well known to me kept a thermometrical record for nearly half a century, in a New England country town, at an elevation of at least 1,500 feet above the sea. During these years his thermometer never fell lower than 26° Fahrenheit, while at the shire town of the county, situated in a basin one thousand feet lower, and ten miles distant, as well as at other points in similar positions, the mercury froze several times in the same period. [37] Railroad surveys must be received with great caution where any motive exists for _cooking_ them. Capitalists are shy of investments in roads with steep grades, and of course it is important to make a fair show of facilities in obtaining funds for new routes. Joint-stock companies have no souls; their managers, in general, no consciences. Cases can be cited where engineers and directors of railroads, with long grades above one hundred feet to the mile, have regularly sworn in their annual reports, for years in succession, that there were no grades upon their routes exceeding half that elevation. In fact, every person conversant with the history of these enterprises knows that in their public statements falsehood is the rule, truth the exception. What I am about to remark is not exactly relevant to my subject; but it is hard to "get the floor" in the world's great debating society, and when a speaker who has anything to say once finds access to the public ear, he must make the most of his opportunity, without inquiring too nicely whether his observations are "in order." I shall harm no honest man by endeavoring, as I have often done elsewhere, to excite the attention of thinking and conscientious men to the dangers which threaten the great moral and even political interests of Christendom, from the unscrupulousness of the private associations that now control the monetary affairs, and regulate the transit of persons and property, in almost every civilized country. More than one American State is literally governed by unprincipled corporations, which not only defy the legislative power, but have, too often, corrupted even the administration of justice. Similar evils have become almost equally rife in England, and on the Continent; and I believe the decay of commercial morality, and indeed of the sense of all higher obligations than those of a pecuniary nature, on both sides of the Atlantic, is to be ascribed more to the influence of joint-stock banks and manufacturing and railway companies, to the workings, in short, of what is called the principle of "associate action," than to any other one cause of demoralization. The apophthegm, "the world is governed too much," though unhappily too truly spoken of many countries--and perhaps, in some aspects, true of all--has done much mischief whenever it has been too unconditionally accepted as a political axiom. The popular apprehension of being over-governed, and, I am afraid, more emphatically the fear of being over-taxed, has had much to do with the general abandonment of certain governmental duties by the ruling powers of most modern states. It is theoretically the duty of government to provide all those public facilities of intercommunication and commerce, which are essential to the prosperity of civilized commonwealths, but which individual means are inadequate to furnish, and for the due administration of which individual guaranties are insufficient. Hence public roads, canals, railroads, postal communications, the circulating medium of exchange, whether metallic or representative, armies, navies, being all matters in which the nation at large has a vastly deeper interest than any private association can have, ought legitimately to be constructed and provided only by that which is the visible personification and embodiment of the nation, namely, its legislative head. No doubt the organization and management of these institutions by government are liable, as are all things human, to great abuses. The multiplication of public placeholders, which they imply, is a serious evil. But the corruption thus engendered, foul as it is, does not strike so deep as the rottenness of private corporations; and official rank, position, and duty have, in practice, proved better securities for fidelity and pecuniary integrity in the conduct of the interests in question, than the suretyships of private corporate agents, whose bondsmen so often fail or abscond before their principal is detected. Many theoretical statesmen have thought that voluntary associations for strictly pecuniary and industrial purposes, and for the construction and control of public works, might furnish, in democratic countries, a compensation for the small and doubtful advantages, and at the same time secure an exemption from the great and certain evils, of aristocratic institutions. The example of the American States shows that private corporations--whose rule of action is the interest of the association, not the conscience of the individual--though composed of ultra-democratic elements, may become most dangerous enemies to rational liberty, to the moral interests of the commonwealth, to the purity of legislation and of judicial action, and to the sacredness of private rights. [38] It is impossible to say how far the abstraction of water from the earth by broad-leaved field and garden plants--such as maize, the gourd family, the cabbage, &c.--is compensated by the condensation of dew, which sometimes pours from them in a stream, by the exhalation of aqueous vapor from their leaves, which is directly absorbed by the ground, and by the shelter they afford the soil from sun and wind, thus preventing evaporation. American farmers often say that after the leaves of Indian corn are large enough to "shade the ground," there is little danger that the plants will suffer from drought; but it is probable that the comparative security of the fields from this evil is in part due to the fact that, at this period of growth, the roots penetrate down to a permanently humid stratum of soil, and draw from it the moisture they require. Stirring the ground between the rows of maize with a light harrow or cultivator, in very dry seasons, is often recommended as a preventive of injury by drought. It would seem, indeed, that loosening and turning over the surface earth might aggravate the evil by promoting the evaporation of the little remaining moisture; but the practice is founded partly on the belief that the hygroscopicity of the soil is increased by it to such a degree that it gains more by absorption than it loses by evaporation, and partly on the doctrine that to admit air to the rootlets, or at least to the earth near them, is to supply directly elements of vegetable growth. [39] The vine-wood planks of the ancient great door of the cathedral at Ravenna, which measured thirteen feet in length by a foot and a quarter in width, are traditionally said to have been brought from the Black Sea, by way of Constantinople, about the eleventh or twelfth century. No vines of such dimensions are now found in any other part of the East, and, though I have taken some pains on the subject, I never found in Syria or in Turkey a vine stock exceeding six inches in diameter, bark excluded. [40] The Northmen who--as I think it has been indisputably established by Professor Rafn of Copenhagen--visited the coast of Massachusetts about the year 1000, found grapes growing there in profusion, and the vine still flourishes in great variety and abundance in the southeastern counties of that State. The townships in the vicinity of the Dighton rock, supposed by many--with whom, however, I am sorry I cannot agree--to bear a Scandinavian inscription, abound in wild vines, and I have never seen a region which produced them so freely. I have no doubt that the cultivation of the grape will become, at no distant day, one of the most important branches of rural industry in that district. [41] _Les États Unis d'Amérique en 1863_, p. 360. By "improved" land, in the reports on the census of the United States, is meant "cleared land used for grazing, grass, or tillage, or which is now fallow, connected with or belonging to a farm."--_Instructions to Marshals and Assistants, Census of 1850_, schedule 4, §§ 2, 3. [42] Cotton, though cultivated in Asia and Africa from the remotest antiquity, and known as a rare and costly product to the Latins and the Greeks, was not used by them to any considerable extent, nor did it enter into their commerce as a regular article of importation. The early voyagers found it in common use in the West Indies and in the provinces first colonized by the Spaniards; but it was introduced into the territory of the United States by European settlers, and did not become of any importance until after the Revolution. Cotton seed was sown in Virginia as early as 1621, but was not cultivated with a view to profit for more than a century afterward. Sea-island cotton was first grown on the coast of Georgia in 1786, the seed having been brought from the Bahamas, where it had been introduced from Anguilla.--BIGELOW, _Les États Unis en 1863_, p. 370. [43] The sugar cane was introduced by the Arabs into Sicily and Spain as early as the ninth century, and though it is now scarcely grown in those localities, I am not aware of any reason to doubt that its cultivation might be revived with advantage. From Spain it was carried to the West Indies, though different varieties have since been introduced into those islands from other sources. Tea is now cultivated with a certain success in Brazil, and promises to become an important crop in the Southern States of the American Union. The lemon is, I think, readily recognizable, by Pliny's description, as known to the ancients, but it does not satisfactorily appear that they were acquainted with the orange. [44] John Smith mentions, in his _Historie of Virginia_, 1624, pease and beans as having been cultivated by the natives before the arrival of the whites, and there is no doubt, I believe, that the pumpkin and several other cucurbitaceous plants are of American origin; but most, if not all the varieties of pease, beans, and other pod fruits now grown in American gardens, are from European and other foreign seed. See _Appendix_, No, 8. [45] There are some usages of polite society which are inherently low in themselves, and debasing in their influence and tendency, and which no custom or fashion can make respectable or fit to be followed by self-respecting persons. It is essentially vulgar to smoke or chew tobacco, and especially to take snuff; it is unbecoming a gentleman, to perform the duties of his coachman; it is indelicate in a lady to wear in the street skirts so long that she cannot walk without grossly soiling them. Not that all these things are not practised by persons justly regarded as gentlemen and ladies; but the same individuals would be, and feel themselves to be, much more emphatically gentlemen and ladies, if they abstained from them. [46] The name _portogallo_, so generally applied to the orange in Italy, seems to favor this claim. The orange, however, was known in Europe before the discovery of the Cape of Good Hope, and, therefore, before the establishment of direct relations between Portugal and the East. A correspondent of the _Athenæum_, in describing the newly excavated villa, which has been named Livia's Villa, near the Porta del Popolo at Rome, states that: "The walls of one of the rooms are, singularly enough, decorated with landscape paintings, a grove of palm and _orange_ trees, with fruits and birds on the branches--the colors all as fresh and lively as if painted yesterday." The writer remarks on the character of this decoration as something very unusual in Roman architecture; and if the trees in question are really orange, and not lemon trees, this circumstance may throw some doubt on the antiquity of the painting. If, on the other hand, it proves really ancient, it shows that the orange was known to the Roman painters, if not gardeners. The landscape may perhaps represent Oriental, not European scenery. The accessories of the picture would probably determine that question.--_Athenæum_, No. 1859, June 13, 1863. MÜLLER, _Das Buch der Pflanzenwelt_, p. 86, asserts that in 1802 the ancestor of all the mulberries in France, planted in 1500, was still standing in a garden in the village of Allan-Montélimart. [47] The vegetables which, so far as we know their history, seem to have been longest the objects of human care, can, by painstaking industry, be made to grow under a great variety of circumstances, and some of them--the vine for instance--prosper nearly equally well, when planted and tended, on soils of almost any geological character; but their seeds vegetate only in artificially prepared ground, they have little self-sustaining power, and they soon perish when the nursing hand of man is withdrawn from them. In range of climate, wild plants are much more limited than domestic, but much less so with regard to the state of the soil in which they germinate and grow. See _Appendix_, No. 9. Dr. Dwight remarks that the seeds of American forest trees will not vegetate when dropped on grassland. This is one of the very few errors of personal observation to be found in that author's writings. There are seasons, indeed, when few tree seeds germinate in the meadows and the pastures, and years favorable to one species are not always propitious to another; but there is no American forest tree known to me which does not readily propagate itself by seed in the thickest greensward, if its germs are not disturbed by man or animals. [48] Some years ago I made a collection of weeds in the wheatfields of Upper Egypt, and another in the gardens on the Bosphorus. Nearly all the plants were identical with those which grow under the same conditions in New England. I do not remember to have seen in America the scarlet wild poppy so common in European grainfields. I have heard, however, that it has lately crossed the Atlantic, and I am not sorry for it. With our abundant harvests of wheat, we can well afford to pay now and then a loaf of bread for the cheerful radiance of this brilliant flower. [49] Josselyn, who wrote about fifty years after the foundation of the first British colony in New England, says that the settlers at Plymouth had observed more than twenty English plants springing up spontaneously near their improvements. Every country has many plants not now, if ever, made use of by man, and therefore not designedly propagated by him, but which cluster around his dwelling, and continue to grow luxuriantly on the ruins of his rural habitation after he has abandoned it. The site of a cottage, the very foundation stones of which have been carried off, may often be recognized, years afterward, by the rank weeds which cover it, though no others of the same species are found for miles. "Mediæval Catholicism," says Vaupell, "brought us the red horsehoof--whose reddish-brown flower buds shoot up from the ground when the snow melts, and are followed by the large leaves--_lægekulsukker_ and snake-root, which grow only where there were convents and other dwellings in the Middle Ages."--_Bögens Indvandring i de Danske Skove_, pp. 1, 2. [50] VAUPELL, _Bögens Indvandring i de Danske Skove_, p. 2. [51] It is, I believe, nearly certain that the Turks inflicted tobacco upon Hungary, and probable that they in some measure compensated the injury by introducing maize also, which, as well as tobacco, has been claimed as Hungarian by patriotic Magyars. [52] Accidents sometimes limit, as well as promote, the propagation of foreign vegetables in countries new to them. The Lombardy poplar is a di[oe]cious tree, and is very easily grown from cuttings. In most of the countries into which it has been introduced the cuttings have been taken from the male, and as, consequently, males only have grown from them, the poplar does not produce seed in those regions. This is a fortunate circumstance, for otherwise this most worthless and least ornamental of trees would spread with a rapidity that would make it an annoyance to the agriculturist. See _Appendix_, No. 10. [53] Tempests, violent enough to destroy all cultivated plants, often spare those of spontaneous growth. During the present summer, I have seen in Northern Italy, vineyards, maize fields, mulberry and fruit trees completely stripped of their foliage by hail, while the forest trees scattered through the meadows, and the shrubs and brambles which sprang up by the wayside, passed through the ordeal with scarcely the loss of a leaflet. [54] The boar spear is provided with a short crossbar, to enable the hunter to keep the infuriated animal at bay after he has transfixed him. [55] Some botanists think that a species of water lily represented in many Egyptian tombs has become extinct, and the papyrus, which must have once been abundant in Egypt, is now found only in a very few localities near the mouth of the Nile. It grows very well and ripens its seeds in the waters of the Anapus near Syracuse, and I have seen it in garden ponds at Messina and in Malta. There is no apparent reason for believing that it could not be easily cultivated in Egypt, to any extent, if there were any special motive for encouraging its growth. [56] Although it is not known that man has extirpated any vegetable, the mysterious diseases which have, for the last twenty years, so injuriously affected the potato, the vine, the orange, the olive, and silk husbandry--whether in this case the malady resides in the mulberry or in the insect--are ascribed by some to a climatic deterioration produced by excessive destruction of the woods. As will be seen in the next chapter, a retardation in the period of spring has been observed in numerous localities in Southern Europe, as well as in the United States. This change has been thought to favor the multiplication of the obscure parasites which cause the injury to the vegetables just mentioned. Babinet supposes the parasites which attack the grape and the potato to be animal, not vegetable, and he ascribes their multiplication to excessive manuring and stimulation of the growth of the plants on which they live. They are now generally, if not universally, regarded as vegetable, and if they are so, Babinet's theory would be even more plausible than on his own supposition.--_Études et Lectures_, ii, p. 269. It is a fact of some interest in agricultural economy, that the oidium, which is so destructive to the grape, has produced no pecuniary loss to the proprietors of the vineyards in France. "The price of wine," says Lavergne, "has quintupled, and as the product of the vintage has not diminished in the same proportion, the crisis has been, on the whole, rather advantageous than detrimental to the country."--_Économie Rurale de la France_, pp. 263, 264. France produces a considerable surplus of wines for exportation, and the sales to foreign consumers are the principal source of profit to French vinegrowers. In Northern Italy, on the contrary, which exports little wine, there has been no such increase in the price of wine as to compensate the great diminution in the yield of the vines, and the loss of this harvest is severely felt. In Sicily, however, which exports much wine, prices have risen as rapidly as in France. Waltershausen informs us that in the years 1838-'42, the red wine of Mount Etna sold at the rate of one kreuzer and a half, or one cent the bottle, and sometimes even at but two thirds that price, but that at present it commands five or six times as much. The grape disease has operated severely on small cultivators whose vineyards only furnished a supply for domestic use, but Sicily has received a compensation in the immense increase which it has occasioned in both the product and the profits of the sulphur mines. Flour of sulphur is applied to the vine as a remedy against the disease, and the operation is repeated from two to three or four--and even, it is said, eight or ten times--in a season. Hence there is a great demand for sulphur in all the vine-growing countries of Europe, and Waltershausen estimates the annual consumption of that mineral for this single purpose at 850,000 _centner_, or more than forty thousand tons. The price of sulphur has risen in about the same proportion as that of wine.--WALTERSHAUSEN, _Ueber den Sicilianischen Ackerbau_, pp. 19, 20. [57] Some recent observations of the learned traveller Wetzstein are worthy of special notice. "The soil of the Haurân," he remarks, "produces, in its primitive condition, much wild rye, which is not known as a cultivated plant in Syria, and much wild barley and oats. These cereals precisely resemble the corresponding cultivated plants in leaf, ear, size, and height of straw, but their grains are sensibly flatter and poorer in flour."--_Reisebericht über Haurân und die Trachonen_, p. 40. [58] This remark is much less applicable to fruit trees than to garden vegetables and the cerealia. The wild orange of Florida, though once considered indigenous, is now generally thought by botanists to be descended from the European orange introduced by the early colonists. The fig and the olive are found growing wild in every country where those trees are cultivated. The wild fig differs from the domesticated in its habits, its season of fructification, and its insect population, but is, I believe, not specifically distinguishable from the garden fig, though I do not know that it is reclaimable by cultivation. The wild olive, which is so abundant in the Tuscan Maremma, produces good fruit without further care, when thinned out and freed from the shade of other trees, and is particularly suited for grafting. See SALVAGNOLI, _Memorie sulle Maremme_, pp. 63-73. See _Appendix_, No. 12. FRAAS, _Klima und Pflanzenwelt in der Zeit_, pp. 35-38, gives, upon the authority of Link and other botanical writers, a list of the native habitats of most cereals and of many fruits, or at least of localities where these plants are said to be now found wild; but the data do not appear to rest, in general, upon very trustworthy evidence. Theoretically, there can be little doubt that all our cultivated plants are modified forms of spontaneous vegetation, but the connection is not historically shown, nor are we able to say that the originals of some domesticated vegetables may not be now extinct and unrepresented in the existing wild flora. See, on this subject, HUMBOLDT, _Ansichten der Natur_, i, pp. 208, 209. The following are interesting incidents: "A negro slave of the great Cortez was the first who sowed wheat in New Spain. He found three grains of it among the rice which had been brought from Spain as food for the soldiers. In the Franciscan monastery at Quito, I saw the earthen pot which contained the first wheat sown there by Friar Jodoco Rixi, of Ghent. It was preserved as a relic." The Adams of modern botany and zoology have been put to hard shifts in finding names for the multiplied organisms which the Creator has brought before them, "to see what they would call them;" and naturalists and philosophers have shown much moral courage in setting at naught the laws of philology in the coinage of uncouth words to express scientific ideas. It is much to be wished that some bold neologist would devise English technical equivalents for the German _verwildert_, run-wild, and _veredelt_, improved by cultivation. [59] Could the bones and other relics of the domestic quadrupeds destroyed by disease or slaughtered for human use in civilized countries be collected into large deposits, as obscure causes have gathered together those of extinct animals, they would soon form aggregations which might almost be called mountains. There were in the United States, in 1860, as we shall see hereafter, nearly one hundred and two millions of horses, black cattle, sheep, and swine. There are great numbers of all the same animals in the British American Provinces, and in Mexico, and there are large herds of wild horses on the plains, and of tamed among the independent Indian tribes of North America. It would perhaps not be extravagant to suppose that all those cattle may amount to two thirds as many as those of the United States, and thus we have in North America a total of 170,000,000 domestic quadrupeds belonging to species introduced by European colonization, besides dogs, cats, and other four-footed household pets and pests, also of foreign origin. If we allow half a solid foot to the skeleton and other slowly destructible parts of each animal, the remains of these herds would form a cubical mass measuring not much short of four hundred and fifty feet to the side, or a pyramid equal in dimensions to that of Cheops, and as the average life of these animals does not exceed six or seven years, the accumulations of their bones, horns, hoofs, and other durable remains would amount to at least fifteen times as great a volume in a single century. It is true that the actual mass of solid matter, left by the decay of dead domestic quadrupeds and permanently added to the crust of the earth, is not so great as this calculation makes it. The greatest proportion of the soft parts of domestic animals, and even of the bones, is soon decomposed, through direct consumption by man and other carnivora, industrial use, and employment as manure, and enters into new combinations in which its animal origin is scarcely traceable; there is, nevertheless, a large annual residuum, which, like decayed vegetable matter, becomes a part of the superficial mould; and in any event, brute life immensely changes the form and character of the superficial strata, if it does not sensibly augment the quantity of the matter composing them. The remains of man, too, add to the earthy coating that covers the face of the globe. The human bodies deposited in the catacombs during the long, long ages of Egyptian history, would perhaps build as large a pile as one generation of the quadrupeds of the United States. In the barbarous days of old Moslem warfare, the conquerors erected large pyramids of human skulls. The soil of cemeteries in the great cities of Europe has sometimes been raised several feet by the deposit of the dead during a few generations. In the East, Turks and Christians alike bury bodies but a couple of feet beneath the surface. The grave is respected as long as the tombstone remains, but the sepultures of the ignoble poor, and of those whose monuments time or accident has removed, are opened again and again to receive fresh occupants. Hence the ground in Oriental cemeteries is pervaded with relics of humanity, if not wholly composed of them; and an examination of the soil of the lower part of the _Petit Champ des Morts_ at Pera, by the naked eye alone, shows the observer that it consists almost exclusively of the comminuted bones of his fellow man. [60] It is asserted that the bones of mammoths and mastodons, in many instances, appear to have been grazed or cut by flint arrow-heads or other stone weapons. These accounts have often been discredited, because it has been assumed that the extinction of these animals was more ancient than the existence of man. Recent discoveries render it highly probable, if not certain, that this conclusion has been too hastily adopted. Lyell observes: "These stories * * must in future be more carefully inquired into, for we can scarcely doubt that the mastodon in North America lived down to a period when the mammoth coexisted with man in Europe."--_Antiquity of Man_, p. 354. On page 143 of the volume just quoted, the same very distinguished writer remarks that man "no doubt played his part in hastening the era of the extinction" of the large pachyderms and beasts of prey; but, as contemporaneous species of other animals, which man cannot be supposed, to have extirpated, have also become extinct, he argues that the disappearance of the quadrupeds in question cannot be ascribed to human action alone. On this point it may be observed that, as we cannot know what precise physical conditions were necessary to the existence of a given extinct organism, we cannot say how far such conditions may have been modified by the action of man, and he may therefore have influenced the life of such organisms in ways, and to an extent, of which we can form no just idea. [61] Evelyn thought the depasturing of grass by cattle serviceable to its growth. "The biting of cattle," he remarks, "gives a gentle loosening to the roots of the herbage, and makes it to grow fine and sweet, and their very breath and treading as well as soil, and the comfort of their warm bodies, is wholesome and marvellously cherishing."--_Terra, or Philosophical Discourse of Earth_, p. 36. In a note upon this passage, Hunter observes: "Nice farmers consider the lying of a beast upon the ground, for one night only, as a sufficient tilth for the year. The breath of graminivorous quadrupeds does certainly enrich the roots of grass; a circumstance worthy of the attention of the philosophical farmer."--_Terra_, same page. The "philosophical farmer" of the present day will not adopt these opinions without some qualification. [62] The rat and the mouse, though not voluntarily transported, are passengers by every ship that sails from Europe to a foreign port, and several species of these quadrupeds have, consequently, much extended their range and increased their numbers in modern times. From a story of Heliogabalus related by Lampridius, _Hist. Aug. Scriptores_, ed. Casaubon, 1690, p. 110, it would seem that mice at least were not very common in ancient Rome. Among the capricious freaks of that emperor, it is said that he undertook to investigate the statistics of the arachnoid population of the capital, and that 10,000 pounds of spiders (or spiders' webs--for aranea is equivocal) were readily collected; but when he got up a mouse show, he thought ten thousand mice a very fair number. I believe as many might almost be found in a single palace in modern Rome. Rats are not less numerous in all great cities, and in Paris, where their skins are used for gloves, and their flesh, it is whispered, in some very complex and equivocal dishes, they are caught by legions. I have read of a manufacturer who contracted to buy of the rat catchers, at a high price, all the rat skins they could furnish before a certain date, and failed, within a week, for want of capital, when the stock of peltry had run up to 600,000. [63] BIGELOW, _Les États Unis en_ 1863, pp. 379, 380. In the same paragraph this volume states the number of animals slaughtered in the United States by butchers, in 1859, at 212,871,653. This is an error of the press. Number is confounded with value. A reference to the tables of the census shows that the animals slaughtered that year were estimated at 212,871,653 _dollars_; the number of head is not given. The wild horses and horned cattle of the prairies and the horses of the Indians are not included in the returns. [64] Of this total number, 2,240,000, or nearly nine per cent., are reported as working oxen. This would strike European, and especially English agriculturists, as a large proportion; but it is explained by the difference between a new country and an old, in the conditions which determine the employment of animal labor. Oxen are very generally used in the United States and Canada for hauling timber and firewood through and from the forests; for ploughing in ground still full of rocks, stumps, and roots; for breaking up the new soil of the prairies with its strong matting of native grasses, and for the transportation of heavy loads over the rough roads of the interior. In all these cases, the frequent obstructions to the passage of the timber, the plough, and the sled or cart, are a source of constant danger to the animals, the vehicles, and the harness, and the slow and steady step of the ox is attended with much less risk than the swift and sudden movements of the impatient horse. It is surprising to see the sagacity with which the dull and clumsy ox--hampered as he is by the rigid yoke, the most absurd implement of draught ever contrived by man--picks his way, when once trained to forest work, among rocks and roots, and even climbs over fallen trees, not only moving safely, but drawing timber over ground wholly impracticable for the light and agile horse. Cows, so constantly employed for draught in Italy, are never yoked or otherwise used for labor in America, except in the Slave States. [65] "About five miles from camp we ascended to the top of a high hill, and for a great distance ahead every square mile seemed to have a herd of buffalo upon it. Their number was variously estimated by the members of the party; by some as high as half a million. I do not think it any exaggeration to set it down at 200,000."--STEVENS'S _Narrative and Final Report. Reports of Explorations and Surveys for Railroad to Pacific_, vol. xii, book i, 1860. The next day, the party fell in with a "buffalo trail," where at least 100,000 were thought to have crossed a slough. [66] The most zealous and successful New England hunter of whom I have any personal knowledge, and who continued to indulge his favorite passion much beyond the age which generally terminates exploits in woodcraft, lamented on his deathbed that he had not lived long enough to carry up the record of his slaughtered deer to the number of one thousand, which he had fixed as the limit of his ambition. He was able to handle the rifle, for sixty years, at a period when the game was still nearly as abundant as ever, but had killed only nine hundred and sixty of these quadrupeds, of all species. The exploits of this Nimrod have been far exceeded by prairie hunters, but I doubt whether, in the originally wooded territory of the Union, any single marksman has brought down a larger number. [67] _Erdkunde_, viii. _Asien, 1ste Abtheilung_, pp. 660, 758. [68] See chapter iii, _post_; also HUMBOLDT, _Ansichten der Natur_, i, p. 71. From the anatomical character of the bones of the urus, or auerochs, found among the relics of the lacustrine population of ancient Switzerland, and from other circumstances, it is inferred that this animal had been domesticated by that people; and it is stated, I know not upon what authority, in _Le Alpi che cingono l'Italia_, that it had been tamed by the Veneti also. See LYELL, _Antiquity of Man_, pp. 24, 25, and the last-named work, p. 489. This is a fact of much interest, because it is, I believe, the only known instance of the extinction of a domestic quadruped, and the extreme improbability of such an event gives some countenance to the theory of the identity of the domestic ox with, and its descent from, the urus. [69] In maintaining the recent existence of the lion in the countries named in the text, naturalists have, perhaps, laid too much weight on the frequent occurrence of representations of this animal in sculptures apparently of a historical character. It will not do to argue, twenty centuries hence, that the lion and the unicorn were common in Great Britain in Queen Victoria's time, because they are often seen "fighting for the crown" in the carvings and paintings of that period. [70] Dar nach sloger schiere, einen wisent bat elch. Starcher bore biere. but einen grimmen schelch. _XVI Auentiure._ The testimony of the _Nibelungen-Lied_ is not conclusive evidence that these quadrupeds existed in Germany at the time of the composition of that poem. It proves too much; for, a few lines above those just quoted, Sigfrid is said to have killed a lion, an animal which the most patriotic Teuton will hardly claim as a denizen of mediæval Germany. [71] The wild turkey takes readily to the water, and is able to cross rivers of very considerable width by swimming. By way of giving me an idea of the former abundance of this bird, an old and highly respectable gentleman who was among the early white settlers of the West, told me that he once counted, in walking down the northern bank of the Ohio River, within a distance of four miles, eighty-four turkeys as they landed singly, or at most in pairs, after swimming over from the Kentucky side. [72] The wood pigeon has been observed to increase in numbers in Europe also, when pains have been taken to exterminate the hawk. The pigeons, which migrated in flocks so numerous that they were whole days in passing a given point, were no doubt injurious to the grain, but probably less so than is generally supposed; for they did not confine themselves exclusively to the harvests for their nourishment. [73] Pigeons were shot near Albany, in New York, a few years ago, with green rice in their crops, which it was thought must have been growing, a very few hours before, at the distance of seven or eight hundred miles. [74] Professor Treadwell, of Massachusetts, found that a half-grown American robin in confinement ate in one day sixty-eight earthworms, weighing together nearly once and a half as much as the bird himself, and another had previously starved upon a daily allowance of eight or ten worms, or about twenty per cent. of his own weight. The largest of these numbers appeared, so far as could be judged by watching parent birds of the same species, as they brought food to their young, to be much greater than that supplied to them when fed in the nest; for the old birds did not return with worms or insects oftener than once in ten minutes on an average. If we suppose the parents to hunt for food twelve hours in a day, and a nest to contain four young, we should have seventy-two worms, or eighteen each, as the daily supply of the brood. It is probable enough that some of the food collected by the parents may be more nutritious than the earthworms, and consequently that a smaller quantity sufficed for the young in the nest than when reared under artificial conditions. The supply required by growing birds is not the measure of their wants after they have arrived at maturity, and it is not by any means certain that great muscular exertion always increases the demand for nourishment, either in the lower animals or in man. The members of the English Alpine Club are not distinguished for appetites which would make them unwelcome guests to Swiss landlords, and I think every man who has had the personal charge of field or railway hands, must have observed that laborers who spare their strength the least are not the most valiant trencher champions. During the period when imprisonment for debt was permitted in New England, persons confined in country jails had no specific allowance, and they were commonly fed without stint. I have often inquired concerning their diet, and been assured by the jailers that their prisoners, who were not provided with work or other means of exercise, consumed a considerably larger supply of food than common out-door laborers. [75] I hope Michelet has good authority for this statement, but I am unable to confirm it. [76] Apropos of the sparrow--a single pair of which, according to Michelet, p. 315, carries to the nest four thousand and three hundred caterpillars or coleoptera in a week--I take from the _Record_, an English religious newspaper, of December 15, 1862, the following article communicated to a country paper by a person who signs himself "A real friend to the farmer:" "_Crawley Sparrow Club._--The annual dinner took place at the George Inn on Wednesday last. The first prize was awarded to Mr. I. Redford, Worth, having destroyed within the last year 1,467. Mr. Heayman took the second with 1,448 destroyed. Mr. Stone, third, with 982 affixed. Total destroyed, 11,944. Old birds, 8,663; young ditto, 722; eggs, 2,556." This trio of valiant fowlers, and their less fortunate--or rather less unfortunate, but not therefore less guilty--associates, have rescued by their prowess, it may be, a score of pecks of grain from being devoured by the voracious sparrow, but every one of the twelve thousand hatched and unhatched birds, thus sacrificed to puerile vanity and ignorant prejudice, would have saved his bushel of wheat by preying upon insects that destroy the grain. Mr. Redford, Mr. Heayman, and Mr. Stone ought to contribute the value of the bread they have wasted to the fund for the benefit of the Lancashire weavers; and it is to be hoped that the next Byron will satirize the sparrowcide as severely as the first did the prince of anglers, Walton, in the well known lines: "The quaint, old, cruel coxcomb in his gullet Should have a hook, and a small trout to pull it." [77] SALVAGNOLI, _Memorie sulle Maremme Toscane_, p. 143. The country about Naples is filled with slender towers fifteen or twenty feet high, which are a standing puzzle to strangers. They are the stations of the fowlers who watch from them the flocks of small birds and drive them down in to the nets by throwing stones over them. See _Appendix_, No. 14. Tschudi has collected in his little work, _Ueber die Landwirthschaftliche Bedeutung der Vögel_, many interesting facts respecting the utility of birds, and the wanton destruction of them in Italy and elsewhere. Not only the owl, but many other birds more familiarly known as predacious in their habits, are useful by destroying great numbers of mice and moles. The importance of this last service becomes strikingly apparent when it is known that the burrows of the mole are among the most frequent causes of rupture in the dikes of the Po, and, consequently, of inundations which lay many square miles under water.--_Annales des Ponts et Chaussées_, 1847, 1re sémestre, p. 150. See also VOGT, _Nützliche u. schädliche Thiere_. [78] Wild birds are very tenacious in their habits. The extension of particular branches of agriculture introduces new birds; but unless in the case of such changes in physical conditions, particular species seem indissolubly attached to particular localities. The migrating tribes follow almost undeviatingly the same precise line of flight in their annual journeys, and establish themselves in the same breeding places from year to year. The stork is a strong-winged bird and roves far for food, but very rarely establishes new colonies. He is common in Holland, but unknown in England. Not above five or six pairs of storks commonly breed in the suburbs of Constantinople along the European shore of the narrow Bosphorus, while--much to the satisfaction of the Moslems, who are justly proud of the marked partiality of so orthodox a bird--dozens of chimneys of the true believers on the Asiatic side are crowned with his nests. See _App._ No. 15. [79] It is not the unfledged and the nursing bird alone that are exposed to destruction by severe weather. Whole flocks of adult and strong-winged tribes are killed by hail. Severe winters are usually followed by a sensible diminution in the numbers of the non-migrating birds, and a cold storm in summer often proves fatal to the more delicate species. On the 10th of June, 184-, five or six inches of snow fell in Northern Vermont. The next morning I found a humming bird killed by the cold, and hanging by its claws just below a loose clapboard on the wall of a small wooden building where it had sought shelter. [80] LYELL, _Antiquity of Man_, p. 409, observes: "Of birds it is estimated that the number of those which die every year equals the aggregate number by which the species to which they respectively belong is, on the average, permanently represented." A remarkable instance of the influence of new circumstances upon birds was observed upon the establishment of a lighthouse on Cape Cod some years since. The morning after the lamps were lighted for the first time, more than a hundred dead birds of several different species, chiefly water fowl, were found at the foot of the tower. They had been killed in the course of the night by flying against the thick glass or grating of the lantern. See _Appendix_, No. 16. Migrating birds, whether for greater security from eagles, hawks, and other enemies, or for some unknown reason, perform a great part of their annual journeys by night; and it is observed in the Alps that they follow the high roads in their passage across the mountains. This is partly because the food in search of which they must sometimes descend is principally found near the roads. It is, however, not altogether for the sake of consorting with man, or of profiting by his labors, that their line of flight conforms to the paths he has traced, but rather because the great roads are carried through the natural depressions in the chain, and hence the birds can cross the summit by these routes without rising to a height where at the seasons of migration the cold would be excessive. The instinct which guides migratory birds in their course is not in all cases infallible, and it seems to be confounded by changes in the condition of the surface. I am familiar with a village in New England, at the junction of two valleys, each drained by a mill stream, where the flocks of wild geese which formerly passed, every spring and autumn, were very frequently lost, as it was popularly phrased, and I have often heard their screams in the night as they flew wildly about in perplexity as to the proper course. Perhaps the village lights embarrassed them, or perhaps the constant changes in the face of the country, from the clearings then going on, introduced into the landscape features not according with the ideal map handed down in the anserine family, and thus deranged its traditional geography. [81] The cappercailzie, or tjäder, as he is called in Sweden, is a bird of singular habits, and seems to want some of the protective instincts which secure most other wild birds from destruction. The younger Læstadius frequently notices the tjäder, in his very remarkable account of the Swedish Laplanders--a work wholly unsurpassed as a genial picture of semi-barbarian life, and not inferior in minuteness of detail to Schlatter's description of the manners of the Nogai Tartars, or even to Lane's admirable and exhaustive work on the Modern Egyptians. The tjäder, though not a bird of passage, is migratory, or rather wandering in domicile, and appears to undertake very purposeless and absurd journeys. "When he flits," says Læstadius, "he follows a straight course, and sometimes pursues it quite out of the country. It is said that, in foggy weather, he sometimes flies out to sea, and, when tired, falls into the water and is drowned. It is accordingly observed that, when he flies westwardly, toward the mountains, he soon comes back again; but when he takes an eastwardly course, he returns no more, and for a long time is very scarce in Lapland. From this it would seem that he turns back from the bald mountains, when he discovers that he has strayed from his proper home, the wood; but when he finds himself over the Baltic, where he cannot alight to rest and collect himself, he flies on until he is exhausted and falls into the sea."--PETRUS LÆSTADIUS, _Journal af första året, etc._, p. 325. [82] _Die Herzogthümer Schleswig und Holstein_, i, p. 203. [83] Gulls hover about ships in port, and often far out at sea, diligently watching for the waste of the caboose. "While the four great fleets, English, French, Turkish, and Egyptian, were lying in the Bosphorus, in the summer and autumn of 1853, a young lady of my family called my attention to the fact that the gulls were far more numerous about the ships of one of the fleets than about the others. This was verified by repeated observation, and the difference was owing no doubt to the greater abundance of the refuse from the cookrooms of the naval squadron most frequented by the birds. Persons acquainted with the economy of the navies of the states in question, will be able to conjecture which fleet was most favored with these delicate attentions. [84] Birds do not often voluntarily take passage on board ships bound for foreign countries, but I can testify to one such case. A stork, which had nested near one of the palaces on the Bosphorus, had, by some accident, injured a wing, and was unable to join his follows when they commenced their winter migration to the banks of the Nile. Before he was able to fly again, he was caught, and the flag of the nation to which the palace belonged was tied to his leg, so that he was easily identified at a considerable distance. As his wing grow stronger, he made several unsatisfactory experiments at flight, and at last, by a vigorous effort, succeeded in reaching a passing ship bound southward, and perched himself on a topsail yard. I happened to witness this movement, and observed him quietly maintaining his position as long as I could discern him with a spyglass. I suppose he finished the voyage, for he certainly did not return to the palace. [85] The enthusiasm of naturalists is not always proportioned to the magnitude or importance of the organisms they concern themselves with. It is not recorded that Adams, who found the colossal antediluvian pachyderm in a thick-ribbed mountain of Siberian ice, ran wild over his _trouvaille_; but Schmidl, in describing the natural history of the caves of the Karst, speaks of an eminent entomologist as "_der glückliche Entdecker_," the _happy_ discoverer of a new coleopteron, in one of those dim caverns. How various are the sources of happiness! Think of a learned German professor, the bare enumeration of whose Rath-ships and scientific Mitglied-ships fills a page, made famous in the annals of science, immortal, happy, by the discovery of a beetle! Had that imperial _ennuyé_, who offered a premium for the invention of a new pleasure, but read Schmidl's _Höhlen des Karstes_, what splendid rewards would he not have heaped upon Kirby and Spence! [86] I believe there is no foundation for the supposition that earthworms attack the tuber of the potato. Some of them, especially one or two species employed by anglers as bait, if natives of the woods, are at least rare in shaded grounds, but multiply very rapidly after the soil is brought under cultivation. Forty or fifty years ago they were so scarce in the newer parts of New England, that the rustic fishermen of every village kept secret the few places where they were to be found in their neighborhood, as a professional mystery, but at present one can hardly turn over a shovelful of rich moist soil anywhere, without unearthing several of them. A very intelligent lady, born in the woods of Northern New England, told me that, in her childhood, these worms were almost unknown in that region, though anxiously sought for by the anglers, but that they increased as the country was cleared, and at last became so numerous in some places, that the water of springs, and even of shallow wells, which had formerly been excellent, was rendered undrinkable by the quantity of dead worms that fell into them. The increase of the robin and other small birds which follow the settler when he has prepared a suitable home for them, at last checked the excessive multiplication of the worms, and abated the nuisance. [87] I have already remarked that the remains of extant animals are rarely, if ever, gathered in sufficient quantities to possess any geographical importance by their mere mass; but the decayed exuviæ of even the smaller and humbler forms of life are sometimes abundant enough to exercise a perceptible influence on soil and atmosphere. "The plain of Cumana," says Humboldt, "presents a remarkable phenomenon, after heavy rains. The moistened earth, when heated by the rays of the sun, diffuses the musky odor common in the torrid zone to animals of very different classes, to the jaguar, the small species of tiger cat, the cabiaï, the gallinazo vulture, the crocodile, the viper, and the rattlesnake. The gaseous emanations, the vehicles of this aroma, appear to be disengaged in proportion as the soil, which contains the remains of an innumerable multitude of reptiles, worms, and insects, begins to be impregnated with water. Wherever we stir the earth, we are struck with the mass of organic substances which in turn are developed and become transformed or decomposed. Nature in these climes seems more active, more prolific, and so to speak, more prodigal of life." [88] It is remarkable that Palissy, to whose great merits as an acute observer I am happy to have frequent occasion to bear testimony, had noticed that vegetation was necessary to maintain the purity of water in artificial reservoirs, though he mistook the rationale of its influence, which he ascribed to the elemental "salt" supposed by him to play an important part in all the operations of nature. In his treatise upon Waters and Fountains, p. 174, of the reprint of 1844, he says: "And in special, thou shalt note one point, the which is understood of few: that is to say, that the leaves of the trees which fall upon the parterre, and the herbs growing beneath, and singularly the fruits, if any there be upon the trees, being decayed, the waters of the parterre shall draw unto them the salt of the said fruits, leaves, and herbs, the which shall greatly better the water of thy fountains, and hinder the putrefaction thereof." [89] Between the years 1851 and 1853, both inclusive, the United States exported 2,665,857 pounds of beeswax, besides a considerable quantity employed in the manufacture of candles for exportation. This is an average of more than 330,000 pounds per year. The census of 1850 gave the total production of wax and honey for that year at 14,853,128 pounds. In 1860, it amounted to 26,370,813 pounds, the increase being partly due to the introduction of improved races of bees from Italy and Switzerland.--BIGELOW, _Les États Unis en 1863_, p. 376. [90] A few years ago, a laborer, employed at a North American port in discharging a cargo of hides from the opposite extremity of the continent, was fatally poisoned by the bite or the sting of an unknown insect, which ran out from a hide he was handling. [91] In many insects, some of the stages of life regularly continue for several years, and they may, under peculiar circumstances, be almost indefinitely prolonged. Dr. Dwight mentions the following remarkable case of this sort, which may be new to many readers: "While I was here [at Williamstown, Mass.], Dr. Fitch showed me an insect, about an inch in length, of a brown color tinged with orange, with two antennæ, not unlike a rosebug. This insect came out of a tea table, made of the boards of an apple tree." Dr. Dwight examined the table, and found the "cavity whence the insect had emerged into the light," to be "about two inches in length, nearly horizontal, and inclining upward very little, except at the mouth. Between the hole, and the outside of the leaf of the table, there were forty grains of the wood." It was supposed that the sawyer and the cabinet maker must have removed at least thirteen grains more, and the table had been in the possession of its proprietor for twenty years. [92] It does not appear to be quite settled whether the termites of France are indigenous or imported. See QUATREFAGES, _Souvenirs d'un Naturaliste_, ii, pp. 400, 542, 543. [93] I have seen the larva of the dragon fly in an aquarium, bite off the head of a young fish as long as itself. [94] Insects and fish--which prey upon and feed each other--are the only forms of animal life that are numerous in the native woods, and their range is, of course, limited by the extent of the waters. The great abundance of the trout, and of other more or less allied genera in the lakes of Lapland, seems to be due to the supply of food provided for them by the swarms of insects which in the larva state inhabit the waters, or, in other stages of their life, are accidentally swept into them. All travellers in the north of Europe speak of the gnat and the mosquito as very serious drawbacks upon the enjoyments of the summer tourist, who visits the head of the Gulf of Bothnia to see the midnight sun, and the brothers Læstadius regard them as one of the great plagues of sub-Arctic life. "The persecutions of these insects," says Lars Levi Læstadius [_Culex pipiens_, _Culex reptans_, and _Culex pulicaris_], "leave not a moment's peace, by day or night, to any living creature. Not only man, but cattle, and even birds and wild beasts, suffer intolerably from their bite." He adds in a note, "I will not affirm that they have ever devoured a living man, but many young cattle, such as lambs and calves, have been worried out of their lives by them. All the people of Lapland declare that young birds are killed by them, and this is not improbable, for birds are scarce after seasons when the midge, the gnat, and the mosquito are numerous."--_Om Uppodlingar i Lappmarken_, p. 50. Petrus Læstadius makes similar statements in his _Journal för första året_, p. 285. [95] It is very questionable whether there is any foundation for the popular belief in the hostility of swine and of deer to the rattlesnake, and careful experiments as to the former quadruped seem to show that the supposed enmity is wholly imaginary. Observing that the starlings, _stornelli_, which bred in an old tower in Piedmont, carried something from their nests and dropped it upon the ground, about as often as they brought food to their young, I watched their proceedings, and found every day lying near the tower numbers of dead or dying slowworms, and, in a few cases, small lizards, which had, in every instance, lost about two inches of the tail. This part I believe the starlings gave to their nestlings, and threw away the remainder. [96] Russell denies the existence of poisonous snakes in Northern Syria, and states that the last instance of death known to have occurred from the bite of a serpent near Aleppo took place a hundred years before his time. In Palestine, the climate, the thinness of population, the multitude of insects and of lizards, all circumstances, in fact, seem very favorable to the multiplication of serpents, but the venomous species, at least, are extremely rare, if at all known, in that country. I have, however, been assured by persons very familiar with Mount Lebanon, that cases of poisoning from the bite of snakes had occurred within a few years, near Hasbeiyeh, and at other places on the southern declivities of Lebanon and Hermon. In Egypt, on the other hand, the cobra, the asp, and the cerastes are as numerous as ever, and are much dreaded by all the natives, except the professional snake charmers. See _Appendix_, No. 18. [97] I use _whale_ not in a technical sense, but as a generic term for all the large inhabitants of the sea popularly grouped under that name. [98] From the narrative of Ohther, introduced by King Alfred into his translation of Orosius, it is clear that the Northmen pursued the whale fishery in the ninth century, and it appears, both from the poem called The Whale, in the Codex Exoniensis, and from the dialogue with the fisherman in the Colloquies of Aelfric, that the Anglo-Saxons followed this dangerous chase at a period not much later. I am not aware of any evidence to show that any of the Latin nations engaged in this fishery until a century or two afterward, though it may not be easy to disprove their earlier participation in it. In mediæval literature, Latin and Romance, very frequent mention is made of a species of vessel called in Latin, _baleneria_, _balenerium_, _balenerius_, _balaneria_, etc.; in Catalan, _balener_; in French, _balenier_; all of which words occur in many other forms. The most obvious etymology of these words would suggest the meaning, _whaler_, _baleinier_; but some have supposed that the name was descriptive of the great size of the ships, and others have referred it to a different root. From the fourteenth century, the word occurs oftener, perhaps, in old Catalan, than in any other language; but Capmany does not notice the whale fishery as one of the maritime pursuits of the very enterprising Catalan people, nor do I find any of the products of the whale mentioned in the old Catalan tariffs. The _whalebone_ of the mediæval writers, which is described as very white, is doubtless the ivory of the walrus or of the narwhale. [99] In consequence of the great scarcity of the whale, the use of coal gas for illumination, the substitution of other fatty and oleaginous substances, such as lard, palm oil, and petroleum, for right-whale oil and spermaceti, the whale fishery has rapidly fallen off within a few years. The great supply of petroleum, which is much used for lubricating machinery as well as for numerous other purposes, has produced a more perceptible effect on the whale fishery than any other single circumstance. According to Bigelow, _Les États Unis en 1863_, p. 346, the American whaling fleet was diminished by 29 in 1858, 57 in 1860, 94 in 1861, and 65 in 1862. The present number of American ships employed in that fishery is 353. [100] The Origin and History of the English Language, &c., pp. 423, 424. [101] Among the unexpected results of human action, the destruction or multiplication of fish, as well as of other animals, is a not unfrequent occurrence. I shall have occasion to mention on a following page the extermination of the fish in a Swedish river by a flood occasioned by the sudden discharge of the waters of a pond. Williams, in his _History of Vermont_, i, p. 149, quoted in Thompson's _Natural History of Vermont_, p. 142, records a case of the increase of trout from an opposite cause. In a pond formed by damming a small stream to obtain water power for a sawmill, and covering one thousand acres of primitive forest, the increased supply of food brought within reach of the fish multiplied them to that degree, that, at the head of the pond, where, in the spring, they crowded together in the brook which supplied it, they were taken by the hands at pleasure, and swine caught them without difficulty. A single sweep of a small scoopnet would bring up half a bushel, carts were filled with them as fast as if picked up on dry land, and in the fishing season they were commonly sold at a shilling (eightpence halfpenny, or about seventeen cents) a bushel. The increase in the size of the trout was as remarkable as the multiplication of their numbers. [102] BABINET, _Études et Lectures_, ii, pp. 108, 110. [103] THOMPSON, _Natural History of Vermont_, p. 38, and Appendix, p. 13. There is no reason to believe that the seal breeds in Lake Champlain, but the individual last taken there must have been some weeks, at least, in its waters. It was killed on the ice in the widest part of the lake, on the 23d of February, thirteen days after the surface was entirely frozen, except the usual small cracks, and a month or two after the ice closed at all points north of the place where the seal was found. [104] See page 89, note, _ante_. [105] According to Hartwig, the United Provinces of Holland had, in 1618, three thousand herring busses and nine thousand vessels engaged in the transport of these fish to market. The whole number of persons employed in the Dutch herring fishery was computed at 200,000. In the latter part of the eighteenth century, this fishery was most successfully prosecuted by the Swedes, and in 1781, the town of Gottenburg alone exported 136,649 barrels, each containing 1,200 herrings, making a total of about 164,000,000; but so rapid was the exhaustion of the fish, from this keen pursuit, that in 1799 it was found necessary to prohibit the exportation of them altogether.--_Das Leben des Meeres_, p. 182. In 1855, the British fisheries produced 900,000 barrels, or enough to supply a fish to every human inhabitant of the globe. On the shores of Long Island Sound, the white fish, a species of herring too bony to be easily eaten, is used as manure in very great quantities. Ten thousand are employed as a dressing for an acre, and a single net has sometimes taken 200,000 in a day.--DWIGHT's _Travels_, ii, pp. 512, 515. [106] The indiscriminate hostility of man to inferior forms of animated life is little creditable to modern civilization, and it is painful to reflect that it becomes keener and more unsparing in proportion to the refinement of the race. The savage slays no animal, not even the rattlesnake, wantonly; and the Turk, whom we call a barbarian, treats the dumb beast as gently as a child. One cannot live many weeks in Turkey without witnessing touching instances of the kindness of the people to the lower animals, and I have found it very difficult to induce even the boys to catch lizards and other reptiles for preservation as specimens. See _Appendix_, No. 19. The fearless confidence in man, so generally manifested by wild animals in newly discovered islands, ought to have inspired a gentler treatment of them; but a very few years of the relentless pursuit, to which they are immediately subjected, suffice to make them as timid as the wildest inhabitants of the European forest. This timidity, however, may easily be overcome. The squirrels introduced by Mayor Smith into the public parks of Boston are so tame as to feed from the hands of passengers, and they not unfrequently enter the neighboring houses. [107] A fact mentioned by Schubert--and which in its causes and many of its results corresponds almost precisely with those connected with the escape of Barton Pond in Vermont, so well known to geological students--is important, as showing that the diminution of the fish in rivers exposed to inundations is chiefly to be ascribed to the mechanical action of the current, and not mainly, as some have supposed, to changes of temperature occasioned by clearing. Our author states that, in 1796, a terrible inundation was produced in the Indalself, which rises in the Storsjö in Jemtland, by drawing off into it the waters of another lake near Ragunda. The flood destroyed houses and fields; much earth was swept into the channel, and the water made turbid and muddy; the salmon and the smaller fish forsook the river altogether, and never returned. The banks of the river have never regained their former solidity, and portions of their soil are still continually falling into the water.--_Resa genom Sverge_, ii, p. 51. [108] WITTWER, _Physikalische Geographie_, p. 142. [109] To vary the phrase, I make occasional use of _animalcule_, which, as a popular designation, embraces all microscopic organisms. The name is founded on the now exploded supposition that all of them are animated, which was the general belief of naturalists when attention was first drawn to them. It was soon discovered that many of them were unquestionably vegetable, and there are numerous genera the true classification of which is matter of dispute among the ablest observers. There are cases in which objects formerly taken for living animalcules turn out to be products of the decomposition of matter once animated, and it is admitted that neither spontaneous motion nor even apparent irritability are sure signs of animal life. [110] See an interesting report on the coral fishery, by Sant' Agabio, Italian Consul-General at Algiers, in the _Bollettino Consolare_, published by the Department of Foreign Affairs, 1862, pp. 139, 151, and in the _Annali di Agricoltura, Industria e Commercio_, No. ii, pp. 360, 373. [111] The fermentation of liquids, and in many cases the decomposition of semi-solids, formerly supposed to be owing purely to chemical action, are now ascertained to be due to vital processes of living minute organisms both vegetable and animal, and consequently to physiological, as well as to chemical forces. Even alcohol is stated to be an animal product. See an interesting article by Auguste Laugel on the recent researches of Pasteur, in the _Revue des Deux Mondes_, for September 15th, 1863. [112] The recorded evidence in support of the proposition in the text has been collected by L. F. Alfred Maury, in his _Histoire des grandes Forêts de la Gaule et de l'ancienne France_, and by Becquerel, in his important work, _Des climats et de l'Influence qu'exercent les Sols boisés et non boisés_, livre ii, chap. i to iv. We may rank among historical evidences on this point, if not technically among historical records, old geographical names and terminations etymologically indicating forest or grove, which are so common in many parts of the Eastern Continent now entirely stripped of woods--such as, in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Brühl, -wald, -wold, -wood, -shaw, -skeg, and -skov. [113] The island of Madeira, whose noble forests were devastated by fire not long after its colonization by European settlers, derives its name from the Portuguese word for wood. [114] Browsing animals, and most of all the goat, are considered by foresters as more injurious to the growth of young trees, and, therefore, to the reproduction of the forest, than almost any other destructive cause. "According to Beatson's _Saint Helena_, introductory chapter, and Darwin's _Journal of Researches in Geology and Natural History_, pp. 582, 583," says Emsmann, in the notes to his translation of Foissac, p. 654, "it was the goats which destroyed the beautiful forests that, three hundred and fifty years ago, covered a continuous surface of not less than two thousand acres in the interior of the island [of St. Helena], not to mention scattered groups of trees. Darwin observes: 'During our stay at Valparaiso, I was most positively assured that sandal wood formerly grew in abundance on the island of Juan Fernandez, but that this tree had now become entirely extinct there, having been extirpated by the goats which early navigators had introduced. The neighboring islands, to which goats have not been carried, still abound in sandal wood.'" In the winter, the deer tribe, especially the great American moose deer, subsists much on the buds and young sprouts of trees; yet--though from the destruction of the wolves or from some not easily explained cause, these latter animals have recently multiplied so rapidly in some parts of North America, that, not long since, four hundred of them are said to have been killed, in one season, on a territory in Maine not comprising more than one hundred and fifty square miles--the wild browsing quadrupeds are rarely, if ever, numerous enough in regions uninhabited by man to produce any sensible effect on the condition of the forest. A reason why they are less injurious than the goat to young trees may be that they resort to this nutriment only in the winter, when the grasses and shrubs are leafless or covered with snow, whereas the goat feeds upon buds and young shoots principally in the season of growth. However this may be, the natural law of consumption and supply keeps the forest growth, and the wild animals which live on its products, in such a state of equilibrium as to insure the indefinite continuance of both, and the perpetuity of neither is endangered until man, who is above natural law, interferes and destroys the balance. When, however, deer are bred and protected in parks, they multiply like domestic cattle, and become equally injurious to trees. "A few years ago," says Clavé, "there were not less than two thousand deer of different ages in the forest of Fontainebleau. For want of grass, they are driven to the trees, and they do not spare them. * * It is calculated that the browsing of these animals, and the consequent retardation of the growth of the wood, diminishes the annual product of the forest to the amount of two hundred thousand cubic feet per year, * * and besides this, the trees thus mutilated are soon exhausted and die. The deer attack the pines, too, tearing off the bark in long strips, or rubbing their heads against them when shedding their horns; and sometimes, in groves of more than a hundred hectares, not one pine is found uninjured by them."--_Revue des Deux Mondes_, Mai, 1863, p. 157. See also _Appendix_, No. 21. Beckstein computes that a park of 2,500 acres, containing 250 acres of marsh, 250 of fields and meadows, and the remaining 2,000 of wood, may keep 364 deer of different species, 47 wild boars, 200 hares, 100 rabbits, and an indefinite number of pheasants. These animals would require, in winter, 123,000 pounds of hay, and 22,000 pounds of potatoes, besides what they would pick up themselves. The natural forest most thickly peopled with wild animals would not, in temperate climates, contain, upon the average, one tenth of these numbers to the same extent of surface. [115] Even the volcanic dust of Etna remains very long unproductive. Near Nicolosi is a great extent of coarse black sand, thrown out in 1669, which, for almost two centuries, lay entirely bare, and can be made to grow plants only by artificial mixtures and much labor. The increase in the price of wines, in consequence of the diminution of the product from the grape disease, however, has brought even these ashes under cultivation. "I found," says Waltershausen, referring to the years 1861-'62, "plains of volcanic sand and half-subdued lava streams, which twenty years ago lay utterly waste, now covered with fine vineyards. The ashfield of ten square miles above Nicolosi, created by the eruption of 1669, which was entirely barren in 1835, is now planted with vines almost to the summits of Monte Rosso, at a height of three thousand feet."--_Ueber den Sicilianischen Ackerbau_, p. 19. [116] _A Relation of a Journey Begun An. Dom._ 1610, lib. 4, p. 260, edition of 1627. The testimony of Sandys on this point is confirmed by that of Pighio, Braccini, Magliocco, Salimbeni, and Nicola di Rubeo, all cited by Roth, _Der Vesuv._, p. 9. There is some uncertainty about the date of the last eruption previous to the great one of 1631. Ashes, though not lava, appear to have been thrown out about the year 1500, and some chroniclers have recorded an eruption in the year 1306; but this seems to be an error for 1036, when a great quantity of lava was ejected. In 1139, ashes were thrown out for many days. I take those dates from the work of Roth just cited. [117] Except upon the banks of rivers or of lakes, the woods of the interior of North America, far from the habitations of man, are almost destitute of animal life. Dr. Newberry, describing the vast forests of the yellow pine of the West, _Pinus ponderosa_, remarks: "In the arid and desert regions of the interior basin, we made whole days' marches in forests of yellow pine, of which neither the monotony was broken by other forms of vegetation, nor its stillness by the flutter of a bird or the hum of an insect."--_Pacific Railroad Report_, vol. vi, 1857. Dr. NEWBERRY's _Report on Botany_, p. 37. The wild fruit and nut trees, the Canada plum, the cherries, the many species of walnut, the butternut, the hazel, yield very little, frequently nothing, so long as they grow in the woods; and it is only when the trees around them are cut down, or when they grow in pastures, that they become productive. The berries, too--the strawberry, the blackberry, the raspberry, the whortleberry, scarcely bear fruit at all except in cleared ground. The North American Indians did not inhabit the interior of the forests. Their settlements were upon the shores of rivers and lakes, and their weapons and other relics are found only in the narrow open grounds which they had burned over and cultivated, or in the margin of the woods around their villages. The rank forests of the tropics are as unproductive of human aliment as the less luxuriant woods of the temperate zone. In Strain's unfortunate expedition across the great American isthmus, where the journey lay principally through thick woods, several of the party died of starvation, and for many days the survivors were forced to subsist on the scantiest supplies of unnutritious vegetables perhaps never before employed for food by man. See the interesting account of that expedition in _Harper's Magazine_ for March, April, and May, 1855. Clavé, as well as many earlier writers, supposes that primitive man derived his nutriment from the spontaneous productions of the wood. "It is to the forests," says he, "that man was first indebted for the means of subsistence. Exposed alone, without defence, to the rigor of the seasons, as well as to the attacks of animals stronger and swifter than himself, he found in them his first shelter, drew from them his first weapons. In the first period of humanity, they provided for all his wants: they furnished him wood for warmth, fruits for food, garments to cover his nakedness, arms for his defence."--_Études sur l'Économie Forestière_, p. 13. But the history of savage life, as far as it is known to us, presents man in that condition as inhabiting only the borders of the forest and the open grounds that skirt the waters and the woods, and as finding only there the aliments which make up his daily bread. [118] The origin of the great natural meadows, or prairies as they are called, of the valley of the Mississippi, is obscure. There is, of course, no historical evidence on the subject, and I believe that remains of forest vegetation are seldom or never found beneath the surface, even in the _sloughs_, where the perpetual moisture would preserve such remains indefinitely. The want of trees upon them has been ascribed to the occasional long-continued droughts of summer, and the excessive humidity of the soil in winter; but it is, in very many instances, certain that, by whatever means the growth of forests upon them was first prevented or destroyed, the trees have been since kept out of them only by the annual burning of the grass, by grazing animals, or by cultivation. The groves and belts of trees which are found upon the prairies, though their seedlings are occasionally killed by drought, or by excess of moisture, extend themselves rapidly over them when the seeds and shoots are protected against fire, cattle, and the plough. The prairies, though of vast extent, must be considered as a local, and, so far as our present knowledge extends, abnormal exception to the law which clothes all suitable surfaces with forest; for there are many parts of the United States--Ohio, for example--where the physical conditions appear to be nearly identical with those of the States lying farther west, but where there were comparatively few natural meadows. The prairies were the proper feeding grounds of the bison, and the vast number of those animals is connected, as cause or consequence, with the existence of those vast pastures. The bison, indeed, could not convert the forest into a pasture, but he would do much to prevent the pasture from becoming a forest. There is positive evidence that some of the American tribes possessed large herds of domesticated bisons. See HUMBOLDT, _Ansichten der Natur_, i, pp. 71-73. What authorizes us to affirm that this was simply the wild bison reclaimed, and why may we not, with equal probability, believe that the migratory prairie buffalo is the progeny of the domestic animal run wild? There are, both on the prairies, as in Wisconsin, and in deep forests, as in Ohio, extensive remains of a primitive people, who must have been more numerous and more advanced in art than the present Indian tribes. There can be no doubt that the woods where such earthworks are found in Ohio were cleared by them, and that the vicinity of these fortresses or temples was inhabited by a large population. Nothing forbids the supposition that the prairies were cleared by the same or a similar people, and that the growth of trees upon them has been prevented by fires and grazing, while the restoration of the woods in Ohio may be due to the abandonment of that region by its original inhabitants. The climatic conditions unfavorable to the spontaneous growth of trees on the prairies may be an effect of too extensive clearings, rather than a cause of the want of woods. See _Appendix_, No. 22. [119] In many parts of the North American States, the first white settlers found extensive tracts of thin woods, of a very park-like character, called "oak openings," from the predominance of different species of that tree upon them. These were the semi-artificial pasture grounds of the Indians, brought into that state, and so kept, by partial clearing, and by the annual burning of the grass. The object of this operation was to attract the deer to the fresh herbage which sprang up after the fire. The oaks bore the annual scorching, at least for a certain time; but if it had been indefinitely continued, they would very probably have been destroyed at last. The soil would have then been much in the prairie condition, and would have needed nothing but grazing for a long succession of years to make the resemblance perfect. That the annual fires alone occasioned the peculiar character of the oak openings, is proved by the fact, that as soon as the Indians had left the country, young trees of many species sprang up and grew luxuriantly upon them. See a very interesting account of the oak openings in DWIGHT's _Travels_, iv, pp. 58-63. [120] The practice of burning over woodland, at once to clear and manure the ground, is called in Swedish _svedjande_, a participial noun from the verb _att svedja_, to burn over. Though used in Sweden as a preparation for crops of rye or other grain, it is employed in Lapland more frequently to secure an abundant growth of pasturage, which follows in two or three years after the fire; and it is sometimes resorted to as a mode of driving the Laplanders and their reindeer from the vicinity of the Swedish backwoodsman's grass grounds and haystacks, to which they are dangerous neighbors. The forest, indeed, rapidly recovers itself, but it is a generation or more before the reindeer moss grows again. When the forest consists of pine, _tall_, the ground, instead of being rendered fertile by this process, becomes hopelessly barren, and for a long time afterward produces nothing but weeds and briers.--LÆSTADIUS, _Om Uppodlingar i Lappmarken_, p. 15. See also SCHUBERT, _Resa i Sverge_, ii, p. 375. In some parts of France this practice is so general that Clavé says: "In the department of Ardennes it (_le sartage_) is the basis of agriculture. The northern part of the department, comprising the arrondissements of Rocroi and Mézières, is covered by steep wooded mountains with an argillaceous, compact, moist and cold soil; it is furrowed by three valleys, or rather three deep ravines, at the bottom of which roll the waters of the Meuse, the Semoy, and the Sormonne, and villages show themselves wherever the walls of the valleys retreat sufficiently from the rivers to give room to establish them. Deprived of arable soil, since the nature of the ground permits neither regular clearing nor cultivation, the peasant of the Ardennes, by means of burning, obtains from the forest a subsistence which, without this resource, would fail him. After the removal of the disposable wood, he spreads over the soil the branches, twigs, briars, and heath, sets fire to them in the dry weather of July and August, and sows in September a crop of rye, which he covers by a light ploughing. Thus prepared, the ground yields from seventeen to twenty bushels an acre, besides a ton and a half or two tons of straw of the best quality for the manufacture of straw hats."--CLAVÉ, _Études sur l'Économie Forestière_, p. 21. Clavé does not expressly condemn the _sartage_, which indeed seems the only practicable method of obtaining crops from the soil he describes, but, as we shall see hereafter, it is regarded by most writers as a highly pernicious practice. [121] The remarkable mounds and other earthworks constructed in the valley of the Ohio and elsewhere in the territory of the United States, by a people apparently more advanced in culture than the modern Indian, were overgrown with a dense clothing of forest when first discovered by the whites. But though the ground where they were erected must have been occupied by a large population for a considerable length of time, and therefore entirely cleared, the trees which grew upon the ancient fortresses and the adjacent lands were not distinguishable in species, or even in dimensions and character of growth, from the neighboring forests, where the soil seemed never to have been disturbed. This apparent exception to the law of change of crop in natural forest growth was ingeniously explained by General Harrison's suggestion, that the lapse of time since the era of the mound builders was so great as to have embraced several successive generations of trees, and occasioned, by their rotation, a return to the original vegetation. The successive changes in the spontaneous growth of the forest, as proved by the character of the wood found in bogs, is not unfrequently such as to suggest the theory of a considerable change of climate during the human period. But the laws which govern the germination and growth of forest trees must be further studied, and the primitive local conditions of the sites where ancient woods lie buried must be better ascertained, before this theory can be admitted upon the evidence in question. In fact, the order of succession--for a rotation or alternation is not yet proved--may move in opposite directions in different countries with the same climate and at the same time. Thus in Denmark and in Holland the spike-leaved firs have given place to the broad-leaved beech, while in Northern Germany the process has been reversed, and evergreens have supplanted the oaks and birches of deciduous foliage. The principal determining cause seems to be the influence of light upon the germination of the seeds and the growth of the young tree. In a forest of firs, for instance, the distribution of the light and shade, to the influence of which seeds and shoots are exposed, is by no means the same as in a wood of beeches or of oaks, and hence the growth of different species will be stimulated in the two forests. See BERG, _Das Verdrängen der Laubwälder im Nördlichen Deutschland_, 1844. HEYER, _Das Verhalten der Waldbäume gegen Licht und Schatten_, 1852. STARING, _De Bodem van Nederland_, 1856, i, pp. 120-200. VAUPELL, _Om Bögens Indvandring i de Danske Skove_, 1857. KNORR, _Studien über die Buchen-Wirthschaft_, 1863. [122] There are, in Northern Italy and in Switzerland, joint-stock companies which insure against damage by hail, as well as by fire and lightning. Between the years 1854 and 1861, a single one of these companies, La Riunione Adriatica, paid, for damage by hail in Piedmont, Venetian Lombardy, and the Duchy of Parma, above 6,500,000 francs, or nearly $200,000 per year. [123] The _paragrandine_, or, as it is called in French, the _paragrêle_, is a species of conductor by which it has been hoped to protect the harvests in countries particularly exposed to damage by hail. It was at first proposed to employ for this purpose poles supporting sheaves of straw connected with the ground by the same material; but the experiment was afterward tried in Lombardy on a large scale, with more perfect electrical conductors, consisting of poles secured to the top of tall trees and provided with a pointed wire entering the ground and reaching above the top of the pole. It was at first thought that this apparatus, erected at numerous points over an extent of several miles, was of some service as a protection against hail, but this opinion was soon disputed, and does not appear to be supported by well-ascertained facts. The question of a repetition of the experiment over a wide area has been again agitated within a very few years in Lombardy; but the doubts expressed by very able physicists as to its efficacy, and as to the point whether hail is an electrical phenomenon, have discouraged its advocates from attempting it. [124] _Cenni sulla Importanza e Coltura dei Boschi_, p. 6. [125] _Memoria sui Boschi, etc._, p. 44. [126] _Travels in Italy_, chap. iii. [127] _Le Alpi che cingono l'Italia_, i, p. 377. [128] "Long before the appearance of man, * * * they [the forests] had robbed the atmosphere of the enormous quantity of carbonic acid it contained, and thereby transformed it into respirable air. Trees heaped upon trees had already filled up the ponds and marshes, and buried with them in the bowels of the earth--to restore it to us after thousands of ages in the form of bituminous coal and of anthracite--the carbon which was destined to become, by this wonderful condensation, a precious store of future wealth."--CLAVÉ, _Études sur l'Économie Forestière_, p. 13. This opinion of the modification of the atmosphere by vegetation is contested. [129] Schacht ascribes to the forest a specific, if not a measurable, influence upon the constitution of the atmosphere. "Plants imbibe from the air carbonic acid and other gaseous or volatile products exhaled by animals or developed by the natural phenomena of decomposition. On the other hand, the vegetable pours into the atmosphere oxygen, which is taken up by animals and appropriated by them. The tree, by means of its leaves and its young herbaceous twigs, presents a considerable surface for absorption and evaporation; it abstracts the carbon of carbonic acid, and solidifies it in wood, fecula, and a multitude of other compounds. The result is that a forest withdraws from the air, by its great absorbent surface, much more gas than meadows or cultivated fields, and exhales proportionally a considerably greater quantity of oxygen. The influence of the forests on the chemical composition of the atmosphere is, in a word, of the highest importance."--_Les Arbres_, p. 111. See _Appendix_, No. 23. [130] Composition, texture and color of soil are important elements to be considered in estimating the effects of the removal of the forest upon its thermoscopic action. "Experience has proved," says Becquerel, "that when the soil is bared, it becomes more or less heated [by the rays of the sun] according to the nature and the color of the particles which compose it, and according to its humidity, and that, in the refrigeration resulting from radiation, we must take into the account the conducting power of those particles also. Other things being equal, silicious and calcareous sands, compared in equal volumes with different argillaceous earths, with calcareous powder or dust, with humus, with arable and with garden earth, are the soils which least conduct heat. It is for this reason that sandy ground, in summer, maintains a high temperature even during the night. We may hence conclude that when a sandy soil is stripped of wood, the local temperature will be raised. After the sands follow successively argillaceous, arable, and garden ground, then humus, which occupies the lowest rank. If we represent the power of calcareous sand to retain heat by 100, we have, according to Schubler, For [silicious?] sand 95.6 " arable calcareous soil 74.8 " argillaceous earth 68.4 " garden earth 64.8 " humus 49.0 "The retentive power of humus, then, is but half as great as that of calcareous sand. We will add that the power of retaining heat is proportional to the density. It has also a relation to the magnitude of the particles. It is for this reason that ground covered with silicious pebbles cools more slowly than silicious sand, and that pebbly soils are best suited to the cultivation of the vine, because they advance the ripening of the grape more rapidly than chalky and clayey earths, which cool quickly. Hence we see that in examining the calorific effects of clearing forests, it is important to take into account the properties of the soil laid bare."--BECQUEREL, _Des Climats et des Sols boisés_, p. 137. [131] "The Washington elm at Cambridge--a tree of no extraordinary size--was some years ago estimated to produce a crop of seven millions of leaves, exposing a surface of two hundred thousand square feet, or about five acres of foliage."--GRAY, _First Lessons in Botany and Vegetable Physiology_, as quoted by COULTAS, _What may be learned from a Tree_, p. 34. [132] See, on this particular point, and on the general influence of the forest on temperature, HUMBOLDT, _Ansichten der Natur_, i, 158. [133] The radiating and refrigerating power of objects by no means depends on their form alone. Melloni cut sheets of metal into the shape of leaves and grasses, and found that they produced little cooling effect, and were not moistened under atmospheric conditions which determined a plentiful deposit of dew on the leaves of vegetables. [134] BECQUEREL, _Des Climats, etc., Discours Prélim._ vi. [135] _Travels_, i, p. 61. [136] _Le Alpi che cingono l'Italia_, pp. 370, 371. [137] BERGSÖE, _Reventlovs Virksomhed_, ii, p. 125. [138] BECQUEREL, _Des Climats, etc._, p. 179. [139] Ibid., p. 116. [140] The following well-attested instance of a local change of climate is probably to be referred to the influence of the forest as a shelter against cold winds. To supply the extraordinary demand for Italian iron occasioned by the exclusion of English iron in the time of Napoleon I, the furnaces of the valleys of Bergamo were stimulated to great activity. "The ordinary production of charcoal not sufficing to feed the furnaces and the forges, the woods were felled, the copses cut before their time, and the whole economy of the forest was deranged. At Piazzatorre there was such a devastation of the woods, and consequently such an increased severity of climate, that maize no longer ripened. An association, formed for the purpose, effected the restoration of the forest, and maize flourishes again in the fields of Piazzatorre."--Report by G. ROSA, in _Il Politecnico_, Dicembre, 1861, p. 614. Similar ameliorations have been produced by plantations in Belgium. In an interesting series of articles by Baude, entitled "Les Cotes de la Manche," in the _Revue des Deux Mondes_, I find this statement: "A spectator placed on the famous bell tower of the cathedral of Antwerp, saw, not long since, on the opposite side of the Schelde only a vast desert plain; now he sees a forest, the limits of which are confounded with the horizon. Let him enter within its shade. The supposed forest is but a system of regular rows of trees, the oldest of which is not forty years of age. These plantations have ameliorated the climate which had doomed to sterility the soil where they are planted. While the tempest is violently agitating their tops, the air a little below is still, and sands far more barren than the plateau of La Hague have been transformed, under their protection, into fertile fields."--_Revue des Deux Mondes_, January, 1859, p. 277. [141] _Cenni sulla Importanza e Coltura dei Boschi_, p. 31. [142] _La Provence au point de vue des Torrents et des Inondations_, p. 19. [143] _Ueber die Entwaldung der Gebirge_, p. 28. [144] BECQUEREL, _Des Climats, etc._, p. 9. [145] SALVAGNOLI, _Rapporto sul Bonificamento delle Maremme Toscane_, pp. xli, 124. [146] _Il Politecnico, Milano, Aprile e Maggio_, 1863, p. 35. [147] SALVAGNOLI, _Memorie sulle Maremme Toscane_, pp. 213, 214. [148] Except in the seething marshes of the tropics, where vegetable decay is extremely rapid, the uniformity of temperature and of atmospheric humidity renders all forests eminently healthful. See HOHENSTEIN's observations on this subject, _Der Wald_, p. 41. There is no question that open squares and parks conduce to the salubrity of cities, and many observers are of opinion that the trees and other vegetables with which such grounds are planted contribute essentially to their beneficial influence. See an article in _Aus der Natur_, xxii, p. 813. [149] _Memoria sui Boschi di Lombardia_, p. 45. [150] _Économie Rurale_, i, p. 22. [151] ROSSMÄSSLER, _Der Wald_, p. 158. [152] Ibid., p. 160. [153] The low temperature of air and soil at which, in the frigid zone, as well as in warmer latitudes under special circumstances, the processes of vegetation go on, seems to necessitate the supposition that all the manifestations of vegetable life are attended with an evolution of heat. In the United States, it is common to protect ice, in icehouses, by a covering of straw, which naturally sometimes contains kernels of grain. These often sprout, and even throw out roots and leaves to a considerable length, in a temperature very little above the freezing point. Three or four years since, I saw a lump of very clear and apparently solid ice, about eight inches long by six thick, on which a kernel of grain had sprouted in an icehouse, and sent half a dozen or more very slender roots into the pores of the ice and through the whole length of the lump. The young plant must have thrown out a considerable quantity of heat; for though the ice was, as I have said, otherwise solid, the pores through which the roots passed were enlarged to perhaps double the diameter of the fibres, but still not so much as to prevent the retention of water in them by capillary attraction. See _App._ 24. [154] BECQUEREL, _Des Climats, etc._, pp. 139-141. [155] Dr. Williams made some observations on this subject in 1789, and in 1791, but they generally belonged to the warmer months, and I do not know that any extensive series of comparisons between the temperature of the ground in the woods and the fields has been attempted in America. Dr. Williams's thermometer was sunk to the depth of ten inches, and gave the following results: +-------------+--------------+--------------+-------------+ | | Temperature | Temperature | | | TIME. | of ground in | of ground in | Difference. | | | pasture. | woods. | | +-------------+--------------+--------------+-------------+ | May 23 | 52 | 46 | 6 | | " 28 | 57 | 48 | 9 | | June 15 | 64 | 51 | 13 | | " 27 | 62 | 51 | 11 | | July 16 | 62 | 51 | 11 | | " 30 | 65½ | 55½ | 10 | | Aug. 15 | 68 | 58 | 10 | | " 31 | 59½ | 55 | 4½ | | Sept. 15 | 59½ | 55 | 4½ | | Oct. 1 | 59½ | 55 | 4½ | | " 15 | 49 | 49 | 0 | | Nov. 1 | 43 | 43 | 0 | | " 16 | 43½ | 43½ | 0 | +-------------+--------------+--------------+-------------+ On the 14th of January, 1791, in a winter remarkable for its extreme severity, he found the ground, on a plain open field where the snow had been blown away, frozen to the depth of three feet and five inches; in the woods where the snow was three feet deep, and where the soil had frozen to the depth of six inches before the snow fell, the thermometer, at six inches below the surface of the ground, stood at 39°. In consequence of the covering of the snow, therefore, the previously frozen ground had been thawed and raised to seven degrees above the freezing point.--WILLIAMS'S _Vermont_, i, p. 74. Bodies of fresh water, so large as not to be sensibly affected by local influences of narrow reach or short duration, would afford climatic indications well worthy of special observation. Lake Champlain, which forms the boundary between the States of New York and Vermont, presents very favorable conditions for this purpose. This lake, which drains a basin of about 6,000 square miles, covers an area, excluding its islands, of about 500 square miles. It extends from lat. 43° 30' to 45° 20', in very nearly a meridian line, has a mean width of four and a half miles, with an extreme breadth, excluding bays almost land-locked, of thirteen miles. Its mean depth is not well known. It is, however, 400 feet deep in some places, and from 100 to 200 in many, and has few shoals or flats. The climate is of such severity that it rarely fails to freeze completely over, and to be safely crossed upon the ice, with heavy teams, for several weeks every winter. THOMPSON (_Vermont_, p. 14, and Appendix, p. 9) gives the following table of the times of the complete closing and opening of the ice, opposite Burlington, about the centre of the lake, and where it is ten miles wide. +------+-------------+------------+-------+ | Year.| Closing. | Opening. | Days | | | | |closed.| +------+-------------+------------+-------+ | 1816 | February 9 | | | | 1817 | January 29 | April 16 | 78 | | 1818 | February 2 | April 15 | 72 | | 1819 | March 4 | April 17 | 44 | | 1820 |{February 3 | February | } 4 | | |{March 8 | March 12 | } | | 1821 | January 15 | April 21 | 95 | | 1822 | January 24 | March 30 | 75 | | 1823 | February 7 | April 5 | 57 | | 1824 | January 22 | February 11| 20 | | 1825 | February 9 | | | | 1826 | February 1 | March 24 | 51 | | 1827 | January 21 | March 31 | 68 | | 1828 | not closed | | | | 1829 | January 31 | April | | | 1832 | February 6 | April 17 | 70 | | 1833 | February 2 | April 6 | 63 | | 1834 | February 13 | February 20| 7 | | 1835 |{January 10 | January 23 | 18 | | |{February 7 | April 12 | 64 | | 1836 | January 27 | April 21 | 85 | | 1837 | January 15 | April 26 | 101 | | 1838 | February 2 | April 13 | 70 | | 1839 | January 25 | April 6 | 71 | | 1840 | January 25 | February 20| 26 | | 1841 | February 18 | April 19 | 61 | | 1842 | not closed | | | | 1843 | February 16 | April 22 | 65 | | 1844 | January 25 | April 11 | 77 | | 1845 | February 3 | March 26 | 51 | | 1846 | February 10 | March 26 | 44 | | 1847 | February 15 | April 23 | 68 | | 1848 | February 13 | February 26| 13 | | 1849 | February 7 | March 23 | 44 | | 1850 | not closed | | | | 1851 | February 1 | March 12 | 89 | | 1852 | January 18 | April 10 | 92 | +------+-------------+------------+-------+ In 1847, although, at the point indicated, the ice broke up on the 23d of April, it remained frozen much later at the North, and steamers were not able to traverse the whole length of the lake until May 6th. [156] We are not, indeed, to suppose that condensation of vapor and evaporation of water are going on in the same stratum of air at the same time, or, in other words, that vapor is condensed into raindrops, and raindrops evaporated, under the same conditions; but rain formed in one stratum, may fall through another, where vapor would not be condensed. Two saturated strata of different temperatures may be brought into contact in the higher regions, and discharge large raindrops, which, if not divided by some obstruction, will reach the ground, though passing all the time through strata which would vaporize them if they were in a state of more minute division. [157] It is perhaps too much to say that the influence of trees upon the wind is strictly limited to the mechanical resistance of their trunks, branches, and foliage. So far as the forest, by dead or by living action, raises or lowers the temperature of the air within it, so far it creates upward or downward currents in the atmosphere above it, and, consequently, a flow of air toward or from itself. These air streams have a certain, though doubtless a very small influence on the force and direction of greater atmospheric movements. [158] As a familiar illustration of the influence of the forest in checking the movement of winds, I may mention the well-known fact, that the sensible cold is never extreme in thick woods, where the motion of the air is little felt. The lumbermen in Canada and the Northern United States labor in the woods, without inconvenience, when the mercury stands many degrees below the zero of Fahrenheit, while in the open grounds, with only a moderate breeze, the same temperature is almost insupportable. The engineers and firemen of locomotives, employed on railways running through forests of any considerable extent, observe that, in very cold weather, it is much easier to keep up the steam while the engine is passing through the woods than in the open ground. As soon as the train emerges from the shelter of the trees the steam gauge falls, and the stoker is obliged to throw in a liberal supply of fuel to bring it up again. Another less frequently noticed fact, due, no doubt, in a great measure to the immobility of the air, is, that sounds are transmitted to incredible distances in the unbroken forest. Many instances of this have fallen under my own observation, and others, yet more striking, have been related to me by credible and competent witnesses familiar with a more primitive condition of the Anglo-American world. An acute observer of natural phenomena, whose childhood and youth were spent in the interior of one of the newer New England States, has often told me that when he established his home in the forest, he always distinctly heard, in still weather, the plash of horses' feet, when they forded a small brook nearly seven-eighths of a mile from his house, though a portion of the wood that intervened consisted of a ridge seventy or eighty feet higher than either the house or the ford. I have no doubt that, in such cases, the stillness of the air is the most important element in the extraordinary transmissibility of sound; but it must be admitted that the absence of the multiplied and confused noises, which accompany human industry in countries thickly peopled by man, contributes to the same result. We become, by habit, almost insensible to the familiar and never-resting voices of civilization in cities and towns; but the indistinguishable drone, which sometimes escapes even the ear of him who listens for it, deadens and often quite obstructs the transmission of sounds which would otherwise be clearly audible. An observer, who wishes to appreciate that hum of civic life which he cannot analyze, will find an excellent opportunity by placing himself on the hill of Capo di Monte at Naples, in the line of prolongation of the street called Spaccanapoli. It is probably to the stillness of which I have spoken, that we are to ascribe the transmission of sound to great distances at sea in calm weather. In June, 1853, I and my family were passengers on board a ship of war bound up the Ægean. On the evening of the 27th of that month, as we were discussing, at the tea table, some observations of Humboldt on this subject, the captain of the ship told us that he had once heard a single gun at sea at the distance of ninety nautical miles. The nest morning, though a light breeze had sprung up from the north, the sea was of glassy smoothness when we went on deck. As we came up, an officer told us that he had heard a gun at sunrise, and the conversation of the previous evening suggested the inquiry whether it could have been fired from the combined French and English fleet then lying at Beshika Bay. Upon examination of our position we were found to have been, at sunrise, ninety sea miles from that point. We continued beating up northward, and between sunrise and twelve o'clock meridian of the 28th, we had made twelve miles northing, reducing our distance from Beshika Bay to seventy-eight sea miles. At noon we heard several guns so distinctly that we were able to count the number. On the 29th we came up with the fleet, and learned from an officer who came on board that a royal salute had been fired at noon on the 28th, in honor of the day as the anniversary of the Queen of England's coronation. The report at sunrise was evidently the morning gun, those at noon the salute. Such cases are rare, because the sea is seldom still, and the [Greek: kymatôn anêrithmon gelasma] rarely silent, over so great a space as ninety or even seventy-eight nautical miles. I apply the epithet _silent_ to [Greek: gelasma] advisedly. I am convinced that Æschylus meant the audible laugh of the waves, which is indeed of _countless_ multiplicity, not the visible smile of the sea, which, belonging to the great expanse as one impersonation, is single, though, like the human smile, made up of the play of many features. [159] "The presence of watery vapor in the air is general. * * * Vegetable surfaces are endowed with the power of absorbing gases, vapors, and also, no doubt, the various soluble bodies which are presented to them. The inhalation of humidity is carried on by the leaves upon a large scale; the dew of a cold summer night revives the groves and the meadows, and a single shower of rain suffices to refresh the verdure of a forest which a long drought had parched."--SCHACHT, _Les Arbres_, ix, p. 340. The absorption of the vapor of water by leaves is disputed. "The absorption of watery vapor by the leaves of plants is, according to Unger's experiments, inadmissible."--WILHELM, _Der Boden und das Wasser_, p. 19. If this latter view is correct, the apparently refreshing effects of atmospheric humidity upon vegetation must be ascribed to moisture absorbed by the ground from the air and supplied to the roots. In some recent experiments by Dr. Sachs, a porous flower-pot, with a plant growing in it, was left unwatered until the earth was dry, and the plant began to languish. The pot was then placed in a glass case containing air, which was kept always saturated with humidity, but no water was supplied, and the leaves of the plant were exposed to the open atmosphere. The soil in the flower pot absorbed from the air moisture enough to revive the foliage, and keep it a long time green, but not enough to promote development of new leaves.--Id., ibid., p. 18. [160] The experiments of Hales and others, on the absorption and exhalation of water by vegetables, are of the highest physiological interest; but observations on sunflowers, cabbages, hops, and single branches of isolated trees, growing in artificially prepared soils and under artificial conditions, furnish no trustworthy data for computing the quantity of water received and given off by the natural wood. [161] In the primitive forest, except where the soil is too wet for the dense growth of trees, the ground is generally too thickly covered with leaves to allow much room for ground mosses. In the more open woods of Europe, this form of vegetation is more frequent--as, indeed, are many other small plants of a more inviting character--than in the native American forest. See, on the cryptogams and wood plants, ROSSMÄSSLER, _Der Wald_, pp. 33 _et seqq._ [162] Emerson (_Trees of Massachusetts_, p. 493) mentions a maple six feet in diameter, as having yielded a barrel, or thirty-one and a half gallons of sap in twenty-four hours, and another, the dimensions of which are not stated, as having yielded one hundred and seventy-five gallons in the course of the season. The _Cultivator_, an American agricultural journal, for June, 1842, states that twenty gallons of sap were drawn in eighteen hours from a single maple, two and a half feet in diameter, in the town of Warner, New Hampshire, and the truth of this account has been verified by personal inquiry made in my behalf. This tree was of the original forest growth, and had been left standing when the ground around it was cleared. It was tapped only every other year, and then with six or eight incisions. Dr. Williams (_History of Vermont_, i, p. 91) says: "A man much employed in making maple sugar, found that, for twenty-one days together, a maple tree discharged seven and a half gallons per day." An intelligent correspondent, of much experience in the manufacture of maple sugar, writes me that a second-growth maple, of about two feet in diameter, standing in open ground, tapped with four incisions, has, for several seasons, generally run eight gallons per day in fair weather. He speaks of a very large tree, from which sixty gallons were drawn in the course of a season, and of another, something more than three feet through, which made forty-two pounds of wet sugar, and must have yielded not less than one hundred and fifty gallons. [163] "The buds of the maple," says the same correspondent, "do not start till toward the close of the sugar season. As soon as they begin to swell, the sap seems less sweet, and the sugar made from it is of a darker color, and with less of the distinctive maple flavor." [164] "In this region, maples are usually tapped with a three-quarter inch bit, boring to the depth of one and a half or two inches. In the smaller trees, one incision only is made, two in those of eighteen inches in diameter, and four in trees of larger size. Two 3/4-inch holes in a tree twenty-two inches in diameter = 1/46 of the circumference, and 1/169 of the area of section." "Tapping does not check the growth, but does injure the quality of the wood of maples. The wood of trees often tapped is lighter and less dense than that of trees which have not been tapped, and gives less heat in burning. No difference has been observed in the starting of the buds of tapped and untapped trees."--_Same correspondent._ [165] Dr. Rush, in a letter to Jefferson, states the number of maples fit for tapping on an acre at from thirty to fifty. "This," observes my correspondent, "is correct with regard to the original growth, which is always more or less intermixed with other trees; but in second growth, composed of maples alone, the number greatly exceeds this. I have had the maples on a quarter of an acre, which I thought about an average of second-growth 'maple orchards,' counted. The number was found to be fifty-two, of which thirty-two were ten inches or more in diameter, and, of course, large enough to tap. This gives two hundred and eight trees to the acre, one hundred and twenty-eight of which were of proper size for tapping." According to the census returns, the quantity of maple sugar made in the United States in 1850 was 34,253,436 pounds; in 1860, it was 38,863,884 pounds, besides 1,944,594 gallons of molasses. The cane sugar made in 1850 amounted to 237,133,000 pounds; in 1859, to 302,205,000.--_Preliminary Report on the Eighth Census_, p. 88. According to Bigelow, _Les États Unis d'Amérique en 1863_, chap. iv, the sugar product of Louisiana alone for 1862 is estimated at 528,321,500 pounds. [166] The correspondent already referred to informs me that a black birch, tapped about noon with two incisions, was found the next morning to have yielded sixteen gallons. Dr. Williams (_History of Vermont_, i, p. 91) says: "A large birch, tapped in the spring, ran at the rate of five gallons an hour when first tapped. Eight or nine days after, it was found to run at the rate of about two and a half gallons an hour, and at the end of fifteen days the discharge continued in nearly the same quantity. The sap continued to flow for four or five weeks, and it was the opinion of the observers that it must have yielded as much as sixty barrels [1,890 gallons]." [167] "The best state of weather for a good run," says my correspondent, "is clear days, thawing fast in the daytime and freezing well at night, with a gentle west or northwest wind; though we sometimes have clear, fine, thawing days followed by frosty nights, without a good run of sap, I have thought it probable that the irregular flow of sap on different days in the same season is connected with the variation in atmospheric pressure; for the atmospheric conditions above mentioned as those most favorable to a free flow of sap are also those in which the barometer usually indicates pressure considerably above the mean. With a south or southeast wind, and in lowering weather, which causes a fall in the barometer, the flow generally ceases, though the sap sometimes runs till after the beginning of the storm. With a _gentle_ wind, south of west, maples sometimes run all night. When this occurs, it is oftenest shortly before a storm. Last spring, the sap of a sugar orchard in a neighboring town flowed the greater part of the time for two days and two nights successively, and did not cease till after the commencement of a rain storm." The cessation of the flow of sap at night is perhaps in part to be ascribed to the nocturnal frost, which checks the melting of the snow, of course diminishing the supply of moisture in the ground, and sometimes congeals the strata from which the rootlets suck in water. From the facts already mentioned, however, and from other well-known circumstances--such, for example, as the more liberal flow of sap from incisions on the south side of the trunk--it is evident that the withdrawal of the stimulating influences of the sun's light and heat is the principal cause of the suspension of the circulation in the night. [168] "The flow ceases altogether soon after the buds begin to swell."--_Letter before quoted._ [169] We might obtain a contribution to an approximate estimate of the quantity of moisture abstracted by forest vegetation from the earth and the air, by ascertaining, as nearly as possible, the quantity of wood on a given area, the proportion of assimilable matter contained in the fluids of the tree at different seasons of the year, the ages of the trees respectively, and the quantity of leaf and seed annually shed by them. The results would, indeed, be very vague, but they might serve to check or confirm estimates arrived at by other processes. The following facts are items too loose perhaps to be employed as elements in such a computation. Dr. Williams, who wrote when the woods of Northern New England were generally in their primitive condition, states the number of trees growing on an acre at from one hundred and fifty to six hundred and fifty, according to their size and the quality of the soil; the quantity of wood, at from fifty to two hundred cords, or from 238 to 952 cubic yards, but adds that on land covered with pines, the quantity of wood would be much greater. Whether he means to give the entire solid contents of the tree, or, as is usual in ordinary estimates in New England, the marketable wood only, the trunks and larger branches, does not appear. Next to the pine, the maple would probably yield a larger amount to a given area than any of the other trees mentioned by Dr. Williams, but mixed wood, in general, measures most. In a good deal of observation on this subject, the largest quantity of marketable wood I have ever known cut on an acre of virgin forest was one hundred and four cords, or 493 cubic yards, and half that amount is considered a very fair yield. The smaller trees, branches, and twigs would not increase the quantity more than twenty-five per cent., and if we add as much more for the roots, we should have a total of about 750 cubic yards. I think Dr. Williams's estimate too large, though it would fall much below the product of the great trees of the Mississippi Valley, of Oregon, and of California. It should be observed that these measurements are those of the wood as it lies when 'corded' or piled up for market, and exceed the real solid contents by not less than fifteen per cent. "In a soil of medium quality," says Clavé, quoting the estimates of Pfeil, for the climate of Prussia, "the volume of a hectare of pines twenty years old, would exceed 80 cubic mètres [42½ cubic yards to the acre]; it would amount to but 24 in a meagre soil. This tree attains its maximum of mean growth at the age of seventy-five years. At that age, in the sandy earth of Prussia, it produces annually about 5 cubic mètres, with a total volume of 311 cubic mètres per hectare [166 cubic yards per acre]. After this age the volume increases, but the mean rate of growth diminishes. At eighty years, for instance, the volume is 335 cubic mètres, the annual production 4 only. The beech reaches its maximum of annual growth at one hundred and twenty years. It then has a total volume of 633 cubic mètres to the hectare [335 cubic yards to the acre], and produces 5 cubic mètres per year."--CLAVÉ, _Études_, p. 151. These measures, I believe, include the entire ligneous product of the tree, exclusive of the roots, and express the actual solid contents. The specific gravity of maple wood is stated to be 75. Maple sap yields sugar at the rate of about one pound _wet_ sugar to three gallons of sap, and wet sugar is to dry sugar in about the proportion of nineteen to sixteen. Besides the sugar, there is a small residuum of "sand," composed of phosphate of lime, with a little silex, and it is certain that by the ordinary hasty process of manufacture, a good deal of sugar is lost; for the drops, condensed from the vapor of the boilers on the rafters of the rude sheds where the sap is boiled, have a decidedly sweet taste. [170] "The elaborated sap, passing out of the leaves, is received into the inner bark, * * * and a part of what descends finds its way even to the ends of the roots, and is all along diffused laterally into the stem, where it meets and mingles with the ascending crude sap or raw material. So there is no separate circulation of the two kinds of sap; and no crude sap exists separately in any part of the plant. Even in the root, where it enters, this mingles at once with some elaborated sap already there."--GRAY, _How Plants Grow_, § 273. [171] Ward's tight glazed cases for raising, and especially for transporting plants, go far to prove that water only circulates through vegetables, and is again and again absorbed and transpired by organs appropriated to these functions. Seeds, growing grasses, shrubs, or trees planted in proper earth, moderately watered and covered with a glass bell or close frame of glass, live for months and even years, with only the original store of air and water. In one of Ward's early experiments, a spire of grass and a fern, which sprang up in a corked bottle containing a little moist earth introduced as a bed for a snail, lived and flourished for eighteen years without a new supply of either fluid. In these boxes the plants grow till the enclosed air is exhausted of the gaseous constituents of vegetation, and till the water has yielded up the assimilable matter it held in solution, and dissolved and supplied to the roots the nutriment contained in the earth in which they are planted. After this, they continue for a long time in a state of vegetable sleep, but if fresh air and water be introduced into the cases, or the plants be transplanted into open ground, they rouse themselves to renewed life, and grow vigorously, without appearing to have suffered from their long imprisonment. The water transpired by the leaves is partly absorbed by the earth directly from the air, partly condensed on the glass, along which it trickles down to the earth, enters the roots again, and thus continually repeats the circuit. See _Aus der Natur_, 21, B. S. 537. [172] WILHELM, _Der Boden und das Wasser_, p. 18. It is not ascertained in what proportions the dew is evaporated, and in what it is absorbed by the earth, in actual nature, but there can be no doubt that the amount of water taken up by the ground, both from vapor suspended in the air and from dew, is large. The annual fall of dew in England is estimated at five inches, but this quantity is much exceeded in many countries with a clearer sky. "In many of our Algerian campaigns," says Babinet, "when it was wished to punish the brigandage of the unsubdued tribes, it was impossible to set their grain fields on fire until a late hour of the day; for the plants were so wet with the night dew that it was necessary to wait until the sun had dried them."--_Études et Lectures_, ii, p. 212. [173] "It has been concluded that the dry land occupies about 49,800,000 square statute miles. This does not include the recently discovered tracts of land in the vicinity of the poles, and allowing for yet undiscovered land (which, however, can only exist in small quantity), if we assign 51,000,000 to the land, there will remain about 146,000,000 of square miles for the extent of surface occupied by the ocean."--Sir J. F. W. HERSCHEL, _Physical Geography_, 1861, p. 19. It does not appear to which category Herschel assigns the inland seas and the fresh-water lakes and rivers of the earth; and Mrs. Somerville, who states that the "dry land occupies an area of 38,000,000 of square miles," and that "the ocean covers nearly three fourths of the surface of the globe," is equally silent on this point.--_Physical Geography_, fifth edition, p. 30. On the following page, Mrs. Somerville, in a note, cites Mr. Gardner as her authority, and says that, "according to his computation, the extent of land is about 37,673,000 square British miles, independently of Victoria Continent; and the sea occupies 110,849,000. Hence the land is to the sea as 1 to 4 nearly." Sir John F. W. Herschel makes the area of dry land and ocean together 197,000,000 square miles; Mrs. Somerville, or rather Mr. Gardner, 148,522,000. I suppose Sir John Herschel includes the islands in his aggregate of the "dry land," and the inland waters under the general designation of the "ocean," and that Mrs. Somerville excludes both. [174] It has been observed in Sweden that the spring, in many districts where the forests have been cleared off, now comes on a fortnight later than in the last century.--ASBJÖRNSEN, _Om Skovene i Norge_, p. 101. The conclusion arrived at by Noah Webster, in his very learned and able paper on the supposed change in the temperature of winter, read before the Connecticut Academy of Arts and Sciences in 1799, was as follows: "From a careful comparison of these facts, it appears that the weather, in modern winters, in the United States, is more inconstant than when the earth was covered with woods, at the first settlement of Europeans in the country; that the warm weather of autumn extends further into the winter months, and the cold weather of winter and spring encroaches upon the summer; that, the wind being more variable, snow is less permanent, and perhaps the same remark may be applicable to the ice of the rivers. These effects seem to result necessarily from the greater quantity of heat accumulated in the earth in summer since the ground has been cleared of wood and exposed to the rays of the sun, and to the greater depth of frost in the earth in winter by the exposure of its uncovered surface to the cold atmosphere."--_Collection of Papers by_ NOAH WEBSTER, p. 162. [175] I have seen, in Northern New England, the surface of the open ground frozen to the depth of twenty-two inches, in the month of November, when in the forest earth no frost was discoverable; and later in the winter, I have known an exposed sand knoll to remain frozen six feet deep, after the ground in the woods was completely thawed. [176] ----Det golde Strög i Afrika, Der Intet voxe kan, da ei det regner, Og, omvendt, ingen Regn kan falde, da Der Intet voxer. PALUDAN-MÜLLER, _Adam Homo_, ii, 408. [177] Und Stürme brausen um die Wette Vom Meer aufs Land, vom Land aufs Meer. GOETHE, _Faust, Song of the Archangels_. [178] _Études sur l'Économie Forestière_, pp. 45, 46. [179] I am not aware of any evidence to show that Malta had any woods of importance at any time since the cultivation of cotton was introduced there; and if it is true, as has been often asserted, that its present soil was imported from Sicily, it can certainly have possessed no forests since a very remote period. In Sandys's time, 1611, there were no woods in the island, and it produced little cotton. He describes it as "a country altogether champion, being no other than a rocke couered ouer with earth, but two feete deepe where the deepest; hauing but few trees but such as beare fruite. * * * So that their wood they haue from Sicilia." They have "an indifferent quantity of cotton wooll, but that the best of all other."--SANDYS, _Travels_, p. 228. [180] SCHACHT, _Les Arbres_, p. 412. [181] _What may be learned from a Tree_, p. 117. [182] _Der Wald_, p. 13. [183] _Om Skovene og deres Forhold til National[oe]conomien_, pp. 131-133. [184] _Om Skovene og om et ordnet Skovbrug i Norge_, p. 106. [185] _Études et Lectures_, iv. p. 114. [186] The supposed increase in the frequency and quantity of rain in Lower Egypt is by no means established. I have heard it disputed on the spot by intelligent Franks, whose residence in that country began before the plantations of Mehemet Aali and Ibrahim Pacha, and I have been assured by them that meteorological observations, made at Alexandria about the beginning of this century, show an annual fall of rain as great as is usual at this day. The mere fact, that it did not rain during the French occupation, is not conclusive. Having experienced a gentle shower of nearly twenty-four hours' duration in Upper Egypt, I inquired of the local governor in relation to the frequency of this phenomenon, and was told by him that not a drop of rain had fallen at that point for more than two years previous. The belief in the increase of rain in Egypt rests almost entirely on the observations of Marshal Marmont, and the evidence collected by him in 1836. His conclusions have been disputed, if not confuted, by Jomard and others, and are probably erroneous. See, FOISSAC, _Météorologie_, German translation, pp. 634-639. It certainly sometimes rains briskly at Cairo, but evaporation is exceedingly rapid in Egypt--as any one, who ever saw a Fellah woman wash a napkin in the Nile, and dry it by shaking it a few moments in the air, can testify; and a heap of grain, wet a few inches below the surface, would probably dry again without injury. At any rate, the Egyptian Government often has vast quantities of wheat stored at Boulak, in uncovered yards through the winter, though it must be admitted that the slovenliness and want of foresight in Oriental life, public and private, are such that we cannot infer the safety of any practice followed in the East, merely from its long continuance. Grain, however, may be long kept in the open air in climates much less dry than that of Egypt, without injury, except to the superficial layers; for moisture does not penetrate to a great depth in a heap of grain once well dried, and kept well aired. When Louis IX was making his preparations for his campaign in the East, he had large quantities of wine and grain purchased in the Island of Cyprus, and stored up, for two years, to await his arrival. "When we were come to Cyprus," says Joinville, _Histoire de Saint Louis_, §§ 72, 73, "we found there greate foison of the Kynge's purveyance. * * The wheate and the barley they had piled up in greate heapes in the feeldes, and to looke vpon, they were like vnto mountaynes; for the raine, the whyche hadde beaten vpon the wheate now a longe whyle, had made it to sproute on the toppe, so that it seemed as greene grasse. And whanne they were mynded to carrie it to Egypte, they brake that sod of greene herbe, and dyd finde under the same the wheate and the barley, as freshe as yf menne hadde but nowe thrashed it." [187] _Étude sur les Eaux au point de vue des Inondations_, p. 91. [188] _Économie Rurale_, ii, chap. xx, § 4, pp. 756-759. See also p. 733. [189] Jacini, speaking of the great Italian lakes, says: "A large proportion of the water of the lakes, instead of discharging itself by the Ticino, the Adda, the Oglio, the Mincio, filters through the silicious strata which underlie the hills, and follows subterranean channels to the plain, where it collects in the _fontanili_, and being thence conducted into the canals of irrigation, becomes a source of great fertility."--_La Proprietà Fondiaria, etc._, p. 144. [190] _Météorologie_, German translation by EMSMANN, p. 605. [191] _Handbuch der Physischen Geographie_, p. 658. [192] _Annales des Ponts et Chaussées_, 1854, 1st sémestre, pp. 21 _et seqq._ See the comments of VALLÈS on these observations, in his _Études sur les Inondations_, pp. 441 _et seqq._ [193] The passage in Pliny is as follows: "Nascuntur fontes, decisis plerumque silvis, quos arborum alimenta consumebant, sicut in Hæmo, obsidente Gallos Cassandro, quum valli gratia cecidissent. Plerumque vero damnosi torrentes corrivantur, detracta collibus silva continere nimbos ac digerere consueta."--_Nat. Hist._, xxxi, 30. Seneca cites this case, and another similar one said to have been observed at Magnesia, from a passage in Theophrastus, not to be found in the extant works of that author; but he adds that the stories are incredible, because shaded grounds abound most in water: ferè aquosissima sunt quæcumque umbrosissima.--_Quæst. Nat._, iii, 11. _See Appendix_, No. 26. [194] "Why go so far for the proof of a phenomenon that is repeated every day under our own eyes, and of which every Parisian may convince himself, without venturing beyond the Bois de Boulogne or the forest of Meudon? Let him, after a few rainy days, pass along the Chevreuse road, which is bordered on the right by the wood, on the left by cultivated fields. The fall of water and the continuance of the rain have been the same on both sides; but the ditch on the side of the forest will remain filled with water proceeding from the infiltration through the wooded soil, long after the other, contiguous to the open ground, has performed its office of drainage and become dry. The ditch on the left will have discharged in a few hours a quantity of water, which the ditch on the right requires several days to receive and carry down to the valley."--CLAVÉ, _Études, etc._, pp. 53, 54. [195] VALLÈS, _Études sur les Inondations_, p. 472. [196] _Économie Rurale_, p. 730. [197] _Ueber die Entwaldung der Gebirge_, pp. 20 _et seqq._ [198] _Physische Geographie_, p. 32. [199] _The Trees of America_, pp. 50, 51. [200] THOMPSON's _Vermont_, appendix, p. 8. [201] _Trees of America_, p. 48. [202] Dumont, following Dansse, gives an interesting extract from the Misopogon of the Emperor Julian, showing that, in the fourth century, the Seine--the level of which now varies to the extent of thirty feet between extreme high and extreme low water mark--was almost wholly exempt from inundations, and flowed with a uniform current through the whole year. "Ego olim eram in hibernis apud caram Lutetiam, [sic] enim Galli Parisiorum oppidum appellant, quæ insula est non magna, in fluvio sita, qui eam omni ex parte eingit. Pontes sublicii utrinque ad eam ferunt, raròque fluvius minuitur ae crescit; sed qualis æstate, talis esse solet hyeme."--_Des Travaux Publics dans leur Rapports avec l'Agriculture_, p. 361, note. As Julian was six years in Gaul, and his principal residence was at Paris, his testimony as to the habitual condition of the Seine, at a period when the provinces where its sources originate were well wooded, is very valuable. [203] Almost every narrative of travel in those countries which were the earliest seats of civilization, contains evidence of the truth of these general statements, and this evidence is presented with more or less detail in most of the special works on the forest which I have occasion to cite. I may refer particularly to HOHENSTEIN, _Der Wald_, 1860, as full of important facts on this subject. See also CAIMI, _Cenni sulla Importanza dei Boschi_, for some statistics not readily found elsewhere, on this and other topics connected with the forest. [204] Stanley, citing SELDEN, _De Jure Naturali_, book vi, and FABRICIUS, _Cod. Pseudap._ V. T., i, 874, mentions a remarkable Jewish tradition of uncertain but unquestionably ancient date, which is among the oldest evidences of public respect for the woods, and of enlightened views of their importance and proper treatment: "To Joshua a fixed Jewish tradition ascribed ten decrees, laying down precise rules, which were instituted to protect the property of each tribe and of each householder from lawless depredation. Cattle, of a smaller kind, were to be allowed to graze in thick woods, not in thin woods; in woods, no kind of cattle without the owner's consent. Sticks and branches might be gathered by any Hebrew, but not cut. * * * Woods might be pruned, provided they were not olives or fruit trees, and that there was sufficient shade in the place."--_Lectures on the History of the Jewish Church_, part i, p. 271. [205] There seems to have been a tendency to excessive clearing in Central and Western, earlier than in Southeastern France. Wise and good Bernard Palissy--one of those persecuted Protestants of the sixteenth century, whose heroism, virtue, refinement, and taste shine out in such splendid contrast to the brutality, corruption, grossness, and barbarism of their oppressors--in the _Recepte Véritable_, first printed in 1563, thus complains: "When I consider the value of the least clump of trees, or even of thorns, I much marvel at the great ignorance of men, who, as it seemeth, do nowadays study only to break down, fell, and waste the fair forests which their forefathers did guard so choicely. I would think no evil of them for cutting down the woods, did they but replant again some part of them; but they care nought for the time to come, neither reck they of the great damage they do to their children which shall come after them."--_[OE]uvres Complètes de Bernard Palissy_, 1844, p. 88. [206] The great naval and commercial marines of Venice and of Genoa must have occasioned an immense consumption of lumber in the Middle Ages, and the centuries immediately succeeding those commonly embraced in that designation. The marine construction of that period employed larger timbers than the modern naval architecture of most commercial countries, but apparently without a proportional increase of strength. The old modes of ship building have been, to a considerable extent, handed down to the present day in the Mediterranean, and an American or an Englishman looks with astonishment at the huge beams and thick planks so often employed in the construction of very small vessels navigating that sea. According to Hummel, the desolation of the Karst, the high plateau lying north of Trieste, now one of the most parched and barren districts in Europe, is owing to the felling of its woods to build the navies of Venice. "Where the miserable peasant of the Karst now sees nothing but bare rock swept and scoured by the raging Bora, the fury of this wind was once subdued by mighty firs, which Venice recklessly cut down to build her fleets."--_Physische Geographie_, p. 32. See _Appendix_, No. 27. [207] _Le Alpi che cingono l'Italia_, i, p. 367. [208] See the periodical _Politecnico_, published at Milan, for the month of May, 1862, p. 234. [209] _Annali di Agricoltura, Industria e Commercio_, vol. i, p. 77. [210] HOLINSHED, reprint of 1807, i, pp. 357, 358. It is evident from this passage, and from another on page 397 of the same volume, that, though sea coal was largely exported to the Continent, it had not yet come into general use in England. It is a question of much interest, when coal was first employed in England for fuel. I can find no evidence that it was used as a combustible until more than a century after the Norman conquest. It has been said that it was known to the Anglo-Saxon population, but I am acquainted with no passage in the literature of that people which proves this. The dictionaries explain the Anglo-Saxon word _græfa_ by sea coal. I have met with this word in no Anglo-Saxon work, except in the _Chronicle_, A. D. 852, from a manuscript certainly not older than the twelfth century, and in that passage it may as probably mean peat as coal, and quite as probably something else as either. Coal is not mentioned in King Alfred's Bede, in Glanville, or in Robert of Gloucester, though all these writers speak of jet as found in England, and are full in their enumeration of the mineral products of the island. England was anciently remarkable for its forests, but Cæsar says it wanted the _fagus_ and the _abies_. There can be no doubt that _fagus_ means the beech, which, as the remains in the Danish peat mosses show, is a tree of late introduction into Denmark, where it succeeded the fir, a tree not now native to that country. The succession of forest crops seems to have been the same in England; for Harrison, p. 359, speaks of the "great store of firre" found lying "at their whole lengths" in the "fens and marises" of Lancashire and other counties, where not even bushes grew in his time. We cannot be sure what species of evergreen Cæsar intended by _abies_. The popular designations of spike-leaved trees are always more vague and uncertain in their application than those of broad-leaved trees. _Pinus_, _pine_, has been very loosely employed even in botanical nomenclature, and _Kiefer_, _Fichte_, and _Tanne_ are often confounded in German.--ROSSMÄSSLER, _Der Wald_, pp. 256, 289, 324. If it were certain that the _abies_ of Cæsar was the fir formerly and still found in peat mosses, and that he was right in denying the existence of the beech in England in his time, the observation would be very important, because it would fix a date at which the fir had become extinct, and the beech had not yet appeared in the island. The English oak, though strong and durable, was not considered generally suitable for finer work in the sixteenth century. There were, however, exceptions. "Of all in Essex," observes HARRISON, _Holinshed_, i, p. 357, "that growing in Bardfield parke is the finest for ioiners craft: for oftentimes haue I seene of their workes made of that oke so fine and faire, as most of the wainescot that is brought hither out of Danske; for our wainescot is not made in England. Yet diuerse haue assaied to deale without [with our] okes to that end, but not with so good successe as they haue hoped, bicause the ab or iuice will not so soone be remoued and cleane drawne out, which some attribute to want of time in the salt water." This passage is also of interest as showing that soaking in salt water, as a mode of seasoning, was practised in Harrison's time. But the importation of wainscot, or boards for ceiling, panelling, and otherwise finishing rooms, which was generally of oak, commenced three centuries before the time of Harrison. On page 204 of the _Liber Albus_--a book which could have been far more valuable if the editor had given us the texts, with his learned notes, instead of a translation--mention is made of "squared oak timber," brought in from the country by carts, and of course of domestic growth, as free of city duty or octroi, and of "planks of oak" coming in in the same way as paying one plank a cartload. But in the chapter on the "Customs of Billyngesgate," pp. 208, 209, relating to goods imported from foreign countries, a duty of one halfpenny is imposed on every hundred of boards called "weynscotte," and of one penny on every hundred of boards called "Rygholt." The editor explains "Rygholt" as "wood of Riga." This was doubtless pine or fir. The year in which these provisions were made does not appear, but they belong to the reign of Henry III. [211] In a letter addressed to the Minister of Public Works, after the terrible inundations of 1857, the Emperor thus happily expressed himself: "Before we seek the remedy for an evil, we inquire into its cause. Whence come the sudden floods of our rivers? From the water which falls on the mountains, not from that which falls on the plains. The waters which fall on our fields produce but few rivulets, but those which fall on our roofs and are collected in the gutters, form small streams at once. Now, the roofs are mountains--the gutters are valleys." "To continue the comparison," observes D'Héricourt, "roofs are smooth and impermeable, and the rain water pours rapidly off from their surfaces; but this rapidity of flow would be greatly diminished if the roofs were carpeted with mosses and grasses; more still, if they were covered with dry leaves, little shrubs, strewn branches, and other impediments--in short, if they were wooded."--_Annales Forestières, Déc._, 1857, p. 311. [212] "The roots of vegetables," says D'Héricourt, "perform the office of a perpendicular drainage analogous to that which has been practised with success in Holland and in some parts of the British Islands. This system consists in driving down three or four thousand stakes upon a hectare; the rain water filters down along the stakes, and, in certain cases, as favorable results are obtained by this method as by horizontal drains."--_Annales Forestières_, 1857, p. 312. [213] The productiveness of Egypt has been attributed too exclusively to the fertilizing effects of the slime deposited by the inundations of the Nile; for in that climate a liberal supply of water would produce good crops on almost any ordinary sand, while, without water, the richest soil would yield nothing. The sediment deposited annually is but a very small fraction of an inch in thickness. It is alleged that in quantity it would be hardly sufficient for a good top dressing, and that in quality it is not chemically distinguishable from the soil inches or feet below the surface. But to deny, as some writers have done, that the slime has any fertilizing properties at all, is as great an error as the opposite one of ascribing all the agricultural wealth of Egypt to that single cause of productiveness. Fine soils deposited by water are almost uniformly rich in all climates; those brought down by rivers, carried out into salt water, and then returned again by the tide, seem to be more permanently fertile than any others. The polders of the Netherland coast are of this character, and the meadows in Lincolnshire, which have been covered with slime by _warping_, as it is called, or admitting water over them at high tide, are remarkably productive. See _Appendix_, No. 28. [214] "The laws against clearing have never been able to prevent these operations when the proprietor found his advantage in them, and the long series of royal ordinances and decrees of parliaments, proclaimed from the days of Charlemagne to our own, with a view of securing forest property, have served only to show the impotence of legislative notion on this subject."--CLAVÉ, _Études sur l'Économie Forestière_, p. 32. "A proprietor can always contrive to clear his woods, whatever may be done to prevent him; it is a mere question of time, and a few imprudent cuttings, a few abuses of the right of pasturage, suffice to destroy a forest in spite of all regulations to the contrary."--DUNOYER, _De la Liberté du Travail_, ii, p. 452, as quoted by Clavé, p. 353. Both authors agree that the preservation of the forests in France is practicable only by their transfer to the state, which alone can protect them and secure their proper treatment. It is much to be feared that even this measure would be inadequate to save the forests of the American Union. There is little respect for public property in America, and the Federal Government, certainly, would not be the proper agent of the nation for this purpose. It proved itself unable to protect the live-oak woods of Florida, which were intended to be preserved for the use of the navy, and it more than once paid contractors a high price for timber stolen from its own forests. The authorities of the individual States might be more efficient. [215] See the lively account of the sale of a communal wood in BERLEPSCH, _Die Alpen, Holzschläger und Flösser_. [216] Streffleur (_Ueber die Natur und die Wirkungen der Wildbäche_, p. 3) maintains that all the observations and speculations of French authors on the nature of torrents had been anticipated by Austrian writers. In proof of this assertion he refers to the works of Franz von Zallinger, 1778, Von Arretin, 1808, Franz Duile, 1826, all published at Innsbruck, and HAGEN's _Beschreibung neuerer Wasserbauwerke_, Königsberg, 1826, none of which works are known to me. It is evident, however, that the conclusions of Surell and other French writers whom I cite, are original results of personal investigation, and not borrowed opinions. [217] Whether Palissy was acquainted with this ancient practice, or whether it was one of those original suggestions of which his works are so full, I know not; but in his treatise, _Des Eaux et Fontaines_, he thus recommends it, by way of reply to the objections of "Théorique," who had expressed the fear that "the waters which rush violently down from the heights of the mountain would bring with them much earth, sand, and other things," and thus spoil the artificial fountain that "Practique" was teaching him to make: "And for hindrance of the mischiefs of great waters which may be gathered in few hours by great storms, when thou shalt have made ready thy parterre to receive the water, thou must lay great stones athwart the deep channels which lead to thy parterre. And so the force of the rushing currents shall be deadened, and thy water shall flow peacefully into his cisterns."--_[OE]uvres Complètes_, p. 173. [218] Ladoucette says the peasant of Dévoluy "often goes a distance of five hours over rocks and precipices for a single [man's] load of wood;" and he remarks on another page, that "the justice of peace of that canton had, in the course of forty-three years, but once heard the voice of the nightingale."--_Histoire, etc., des Hautes Alpes_, pp. 220, 434. [219] The valley of Embrun, now almost completely devastated, was once remarkable for its fertility. In 1806, Héricart de Thury said of it: "In this magnificent valley nature had been prodigal of her gifts. Its inhabitants have blindly revelled in her favors, and fallen asleep in the midst of her profusion."--BECQUEREL, _Des Climats, etc._, p. 314. [220] In the days of the Roman empire the Durance was a navigable river, with a commerce so important that the boatmen upon it formed a distinct corporation.--LADOUCETTE, _Histoire, etc., des Hautes Alpes_, p. 354. Even as early as 1789, the Durance was computed to have already covered with gravel and pebbles not less than 130,000 acres, "which, but for its inundations, would have been the finest land in the province."--ARTHUR YOUNG, _Travels in France_, vol. i, ch. i. [221] Between 1851 and 1856 the population of Languedoc and Provence had increased by 101,000 souls. The augmentation, however, was wholly in the provinces of the plains, where all the principal cities are found. In these provinces the increase was 204,000, while in the mountain provinces there was a diminution of 103,000. The reduction of the area of arable land is perhaps even more striking. In 1842, the department of the Lower Alps possessed 99,000 hectares, or nearly 245,000 acres, of cultivated soil. In 1852, it had but 74,000 hectares. In other words, in ten years 25,000 hectares, or 61,000 acres, had been washed away or rendered worthless for cultivation, by torrents and the abuses of pasturage.--CLAVÉ, _Études_, pp. 66, 67. [222] The Skalära-Tobel, for instance, near Coire. See the description in BERLEPSCH, _Die Alpen_, pp. 169 _et seqq_, or in Stephen's English translation. The recent change in the character of the Mella--a river anciently so remarkable for the gentleness of its current that it was specially noticed by Catullus as flowing _molli flumine_--deserves more than a passing remark. This river rises in the mountain chain east of Lake Iseo, and traversing the district of Brescia, empties into the Oglio after a course of about seventy miles. The iron works in the upper valley of the Mella had long created a considerable demand for wood, but their operations were not so extensive as to occasion any very sudden or general destruction of the forests, and the only evil experienced from the clearings was the gradual diminution of the volume of the river. Within the last twenty years, the superior quality of the arms manufactured at Brescia has greatly enlarged the sale of them, and very naturally stimulated the activity of both the forges and of the colliers who supply them, and the hillsides have been rapidly stripped of their timber. Up to 1850, no destructive inundation of the Mella had been recorded. Buildings in great numbers had been erected upon its margin, and its valley was conspicuous for its rural beauty and its fertility. But when the denudation of the mountains had reached a certain point, avenging nature began the work of retribution. In the spring and summer of 1850 several new torrents were suddenly formed in the upper tributary valleys, and on the 14th and 15th of August in that year, a fall of rain, not heavier than had been often experienced, produced a flood which not only inundated much ground never before overflowed, but destroyed a great number of bridges, dams, factories, and other valuable structures, and, what was a far more serious evil, swept off from the rocks an incredible extent of soil, and converted one of the most beautiful valleys of the Italian Alps into a ravine almost as bare and as barren as the savagest gorge of Southern France. The pecuniary damage was estimated at many millions of francs, and the violence of the catastrophe was deemed so extraordinary, even in a country subject to similar visitations, that the sympathy excited for the sufferers produced, in five months, voluntary contributions for their relief to the amount of nearly $200,000--_Delle Inondazioni del Mella, etc., nella notte del 14 al 15 Agosto_, 1850. The author of this remarkable pamphlet has chosen as a motto a passage from the Vulgate translation of Job, which is interesting as showing accurate observation of the action of the torrent: "Mons cadens definit, et saxum transfertur de loco suo; lapides excavant aquæ et alluvione paullatim terra consumitur."--_Job_ xiv, 18, 19. The English version is much less striking, and gives a different sense. [223] Streffleur quotes from Duile the following observations: "The channel of the Tyrolese brooks is often raised much above the valleys through which they flow. The bed of the Fersina is elevated high above the city of Trient, which lies near it. The Villerbach flows at a much more elevated level than that of the market place of Neumarkt and Vill, and threatens to overwhelm both of them with its waters. The Talfer at Botzen is at least even with the roofs of the adjacent town, if not above them. The tower steeples of the villages of Schlanders, Kortsch, and Laas, are lower than the surface of the Gadribach. The Saldurbach at Schluderns menaces the far lower village with destruction, and the chief town, Schwaz, is in similar danger from the Lahnbach."--STREFFLEUR, _Ueber die Wildbäche, etc._, p. 7. [224] The snow drifts into the ravines and accumulates to incredible depths, and the water resulting from its dissolution and from the deluging rains which fall in spring, and sometimes in the summer, being confined by rocky walls on both sides, rises to a very great height, and of course acquires an immense velocity and transporting power in its rapid descent to its outlet from the mountain. In the winter of 1842--'3, the valley of the Doveria, along which the Simplon road passes, was filled with solid snowdrifts to the depth of a hundred feet above the carriage road, and the sledge track by which passengers and the mails were carried ran at that height. Other things being equal, the transporting power of the water is greatest where its flow is most rapid. This is usually in the direction of the axis of the ravine. As the current pours out of the gorge and escapes from the lateral confinement of its walls, it spreads and divides itself into numerous smaller streams, which shoot out from the mouth of the valley, as from a centre, in different directions, like the ribs of a fan from the pivot, each carrying with it its quota of stones and gravel. The plain below the point of issue from the mountain is rapidly raised by newly formed torrents, the elevation depending on the inclination of the bed and the form and weight of the matter transported. Every flood both increases the height of this central point and extends the entire circumference of the deposit. The stream retaining most nearly the original direction moves with the greatest momentum, and consequently transports the solid matter with which it is charged to the greatest distance. The untravelled reader will comprehend this the better when he is informed that the southern slope of the Alps generally rises suddenly out of the plain, with no intervening hill to break the abruptness of the transition, except those consisting of comparatively small heaps of its own debris brought down by ancient glaciers or recent torrents. The torrents do not wind down valleys gradually widening to the rivers or the sea, but leap at once from the flanks of the mountains upon the plains below. This arrangement of surfaces naturally facilitates the formation of vast deposits at their points of emergence, and the centre of the accumulation in the case of very small torrents is not unfrequently a hundred feet high, and sometimes very much more. Torrents and the rivers that receive them transport mountain debris to almost incredible distances. Lorentz, in an official report on this subject, as quoted by Marschand from the Memoirs of the Agricultural Society of Lyons, says: "The felling of the woods produces torrents which cover the cultivated soil with pebbles and fragments of rock, and they do not confine their ravages to the vicinity of the mountains, but extend them into the fertile fields of Provence and other departments, to the distance of forty or fifty leagues."--_Entwaldung der Gebirge_, p. 17. [225] The precipitous walls of the Val de Lys, and more especially of the Val Doveria, though here and there shattered, show in many places a smoothness of face over a large vertical plane, at the height of hundreds of feet above the bottom of the valley, which no known agency but glacier ice is capable of producing, and of course they can have undergone no sensible change at those points for a vast length of time. The beds of the rivers which flow through those valleys suffer lateral displacement occasionally, where there is room for the shifting of the channel; but if any elevation or depression takes place in them, it is too slow to be perceptible except in case of some merely temporary obstruction. [226] Lombardini found, twenty years ago, that the mineral matter brought down to the Po by its tributaries was, in general, comminuted to about the same degree of fineness as the sands of its bed at their points of discharge. In the case of the Trebbia, which rises high in the Apennines and empties into the Po at Piacenza, it was otherwise, that river rolling pebbles and coarse gravel into the channel of the principal stream. The banks of the other affluents--excepting some of those which discharge their waters into the great lakes--then either retained their woods, or had been so long clear of them, that the torrents had removed most of the disintegrated and loose rock in their upper basins. The valley of the Trebbia had been recently cleared, and all the forces which tend to the degradation and transportation of rock were in full activity.--_Notice sur les Rivières de la Lombardie, Annales des Ponts et Chaussées_, 1847, 1er sémestre, p. 131. Since the date of Lombardini's observations, many Alpine valleys have been stripped of their woods. It would be interesting to know whether any sensible change has been produced in the character or quantity of the matter transported by them to the Po. [227] In proportion as the dikes are improved, and breaches and the escape of the water through them are less frequent, the height of the annual inundations is increased. Many towns on the banks of the river, and of course within the system of parallel embankments, were formerly secure from flood by the height of the artificial mounds on which they were built; but they have recently been obliged to construct ring dikes for their protection.--BAUMGARTEN, after LOMBARDINI, in the paper last quoted, pp. 141, 147. [228] Three centuries ago, when the declivities of the mountains still retained a much larger proportion of their woods, the moderate annual floods of the Po were occasioned by the melting of the snows, and, as appears by a passage of Tasso quoted by Castellani (_Dell' Influenza delle Selve_, i, p. 58, note), they took place in May. The much more violent inundations of the present century are due to rains, the waters of which are no longer retained by a forest soil, but conveyed at once to the rivers--and they occur almost uniformly in the autumn or late summer. Castellani, on the page just quoted, says that even so late as about 1780, the Po required a heavy rain of a week to overflow its banks, but that forty years later, it was sometimes raised to full flood in a single day. [229] This change of coast line cannot be ascribed to upheaval, for a comparison of the level of old buildings--as, for instance, the church of San Vitale and the tomb of Theodoric at Ravenna--with that of the sea, tends to prove a depression rather than an elevation of their foundations. A computation by a different method makes the deposits at the mouth of the Po 2,123,000 mètres less; but as both of them omit the gravel and silt rolled, if not floated, down at ordinary and low water, we are safe in assuming the larger quantity.--_Article last quoted_, p. 174. (See note, p. 329) [230] Mengotti estimated the mass of solid matter annually "united to the waters of the Po" at 822,000,000 cubic mètres, or nearly twenty times as much as, according to Lombardini, that river delivers into the Adriatic. Castellani supposes the computation of Mengotti to fall much below the truth, and there can be no doubt that a vastly larger quantity of earth and gravel is washed down from the Alps and the Apennines than is carried to the sea.--CASTELLANI, _Dell' Immediata Influenza delle Selve sul corso delle Acque_, i, pp. 42, 43. I have contented myself with assuming less than one fifth of Mengotti's estimate. [231] BAUMGARTEN, _An. des Ponts et Chaussées_, 1847, 1er sémestre, p. 175. [232] The total superficies of the basin of the Po, down to Ponte Lagoscuro [Ferrara]--a point where it has received all its affluents--is 6,938,200 hectares, that is, 4,105,600 in mountain lands, 2,832,600 in plain lands.--DUMONT, _Travaux Publics, etc._, p. 272. These latter two quantities are equal respectively to 10,145,348, and 6,999,638 acres, or 15,852 and 10,937 square miles. [233] I do not use the numbers I have borrowed or assumed as factors the value of which is precisely ascertained; nor, for the purposes of the present argument, is quantitative exactness important. I employ numerical statements simply as a means of aiding the imagination to form a general and certainly not extravagant idea of the extent of geographical revolutions which man has done much to accelerate, if not, strictly speaking, to produce. There is an old proverb, _Dolus latet in generalibus_, and Arthur Young is not the only public economist who has warned his readers against the deceitfulness of round numbers. I think, on the contrary, that vastly more error has been produced by the affectation of precision in cases where precision is impossible. In all the great operations of terrestrial nature, the elements are so numerous and so difficult of exact appreciation, that, until the means of scientific observation and measurement are much more perfected than they now are, we must content ourselves with general approximations. I say _terrestrial_ nature, because in cosmical movements we have fewer elements to deal with, and may therefore arrive at much more rigorous accuracy in determination of time and place than we can in fixing and predicting the quantities and the epochs of variable natural phenomena on the earth's surface. The value of a high standard of accuracy in scientific observation can hardly be overrated; but habits of rigorous exactness will never be formed by an investigator who allows himself to trust implicitly to the numerical precision of the results of a few experiments. The wonderful accuracy of geodetic measurements in modern times is, in general, attained by taking the mean of a great number of observations at every station, and this final precision is but the mutual balance and compensation of numerous errors. Travellers are often misled by local habits in the use of what may be called representative numbers, where a definite is put for an indefinite quantity. A Greek, who wished to express the notion of a great, but undetermined number, used "myriad, or ten thousand;" a Roman, "six hundred;" an Oriental, "forty," or, at present, very commonly, "fifteen thousand." Many a tourist has gravely repeated, as an ascertained fact, the vague statement of the Arabs and the monks of Mount Sinai, that the ascent from the convent of St. Catherine to the summit of Gebel Moosa counts "fifteen thousand" steps, though the difference of level is barely two thousand feet, and the "Forty" Thieves, the "forty" martyr monks of the convent of El Arbain--not to speak of a similar use of this numeral in more important cases--have often been understood as expressions of a known number, when in fact they mean simply _many_. The number "fifteen thousand" has found its way to Rome, and De Quincey seriously informs us, on the authority of a lady who had been at much pains to ascertain the _exact_ truth, that, including closets large enough for a bed, the Vatican contains fifteen thousand rooms. Any one who has observed the vast dimensions of most of the apartments of that structure will admit that we make a very small allowance of space when we assign a square rod, sixteen and a half feet square, to each room upon the average. On an acre, there might be one hundred and sixty such rooms, including partition walls; and, to contain fifteen thousand of them, a building must cover more than nine acres, and be ten stories high, or possess other equivalent dimensions, which, as every traveller knows, many times exceeds the truth. That most entertaining writer, About, reduces the number of rooms in the Vatican, but he compensates this reduction by increased dimensions, for he uses the word _salle_, which cannot be applied to closets barely large enough to contain a bed. According to him, there are in that "presbytère," as he irreverently calls it, twelve thousand large rooms [_salles_], thirty courts, and three hundred staircases.--_Rome Contemporaire_, p. 68. The pretended exactness of statistical tables is generally little better than an imposture; and those founded not on direct estimation by competent observers, but on the report of persons who have no particular interest in knowing, but often have a motive for distorting, the truth--such as census returns--are commonly to be regarded as but vague guesses at the actual fact. Fuller, who, for the combination of wit, wisdom, fancy, and personal goodness, stands first in English literature, thus remarks on the pretentious exactness of historical and statistical writers: "I approve the plain, country By-word, as containing much Innocent Simplicity therein, _'Almost and very nigh Have saved many a Lie.'_ So have the Latines their _prope_, _fere_, _juxta_, _circiter_, _plus minus_, used in matters of fact by the most authentic Historians. Yea, we may observe that the Spirit of Truth itself, where _Numbers_ and _Measures_ are concerned, in Times, Places, and Persons, useth the aforesaid Modifications, save in such cases where some mystery contained in the number requireth a particular specification thereof: In Times. | In Places. | In Person. | | Daniel, 5:33. | Luke, 24:13. | Exodus, 12:37. Luke, 3:23. | John, 6:19. | Acts, 2:41. None therefore can justly find fault with me, if, on the like occasion, I have secured myself with the same Qualifications. Indeed, such Historians who grind their Intelligence to the _powder of fraction_, pretending to _cleave the pin_, do sometimes _misse the But_. Thus, one reporteth, how in the Persecution under _Dioeletian_, there were neither under nor over, but just _nine hundred ninety-nine_ martyrs. Yea, generally those that trade in such _Retail-ware_, and deal in such small parcells, may by the ignorant be commended for their _care_, but condemned by the judicious for their ridiculous _curiosity_."--_The History of the Worthies of England_, i, p. 59. [234] SURELL, _Les Torrents des Hautes Alpes_, chap. xxiv. In such cases, the clearing of the ground, which, in consequence of a temporary diversion of the waters, or from some other cause, has become rewooded, sometimes renews the ravages of the torrent. Thus, on the left bank of the Durance, a wooded declivity had been formed by the debris brought down by torrents, which had extinguished themselves after having swept off much of the superficial strata of the mountain of Morgon. "All this district was covered with woods, which have now been thinned out and are perishing from day to day; consequently, the torrents have recommenced their devastations, and if the clearings continue, this declivity, now fertile, will be ruined, like so many others."--Id., p. 155. [235] Where a torrent has not been long in operation, and earth still remains mixed with the rocks and gravel it heaps up at its point of eruption, vegetation soon starts up and prospers, if protected from encroachment. In Provence, "several communes determined, about ten years ago, to reserve the soils thus wasted, that is, to abandon them for a certain time, to spontaneous vegetation, which was not slow in making its appearance."--BECQUEREL, _Des Climats_, p. 315. [236] Rock is permeable by water to a greater extent than is generally supposed. Freshly quarried marble, and even granite, as well as most other stones, are sensibly heavier, as well as softer and more easily wrought, than after they are dried and hardened by air-seasoning. Many sandstones are porous enough to serve as filters for liquids, and much of that of Upper Egypt and Nubia hisses audibly when thrown into water, from the escape of the air forced out of it by hydrostatic pressure and the capillary attraction of the pores for water. See _Appendix_, No. 29. [237] Palissy had observed the action of frost in disintegrating rock, and he thus describes it, in his essay on the formation of ice: "I know that the stones of the mountains of Ardennes be harder than marble. Nevertheless, the people of that country do not quarry the said stones in winter, for that they be subject to frost; and many times the rocks have been seen to fall without being cut, by means whereof many people have been killed, when the said rocks were thawing." Palissy was ignorant of the expansion of water in freezing--in fact he supposed that the mechanical force exerted by freezing water was due to compression, not dilatation--and therefore he ascribes to thawing alone effects resulting not less from congelation. Various forces combine to produce the stone avalanches of the higher Alps, the fall of which is one of the greatest dangers incurred by the adventurous explorers of those regions--the direct action of the sun upon the stone, the expansion of freezing water, and the loosening of masses of rock by the thawing of the ice which supported them or held them together. [238] WESSELY, _Die Oesterreichischen Alpenländer und ihre Forste_, pp. 125, 126. Wessely records several other more or less similar occurrences in the Austrian Alps. Some of them, certainly, are not to be ascribed to the removal of the woods, but in most cases they are clearly traceable to that cause. [239] BIANCHI, Appendix to the Italian translation of Mrs. SOMERVILLE's _Physical Geography_, p. xxxvi. [240] See in KOHL, _Alpenreisen_, i, 120, an account of the ruin of fields and pastures, and even of the destruction of a broad belt of forest, by the fall of rocks in consequence of cutting a few large trees. Cattle are very often killed in Switzerland by rock avalanches, and their owners secure themselves from loss by insurance against this risk as against damage by fire or hail. [241] _Entwaldung der Gebirge_, p. 41. [242] The importance of the wood in preventing avalanches is well illustrated by the fact that, where the forest is wanting, the inhabitants of localities exposed to snow slides often supply the place of the trees by driving stakes through the snow into the ground, and thus checking its propensity to slip. The woods themselves are sometimes thus protected against avalanches originating on slopes above them, and as a further security, small trees are cut down along the upper line of the forest, and laid against the trunks of larger trees, transversely to the path of the slide, to serve as a fence or dam to the motion of an incipient avalanche, which may by this means be arrested before it acquires a destructive velocity and force. [243] The tide rises at Quebec to the height of twenty-five feet, and when it is aided by a northeast wind, it flows with almost irresistible violence. Rafts containing several hundred thousand cubic feet of timber are often caught by the flood tide, torn to pieces, and dispersed for miles along the shores. [244] One of these, the Baron of Renfrew--so named from one of the titles of the kings of England--built thirty or forty years ago, measured 5,000 tons. They were little else than rafts, being almost solid masses of timber designed to be taken to pieces and sold as lumber on arriving at their port of destination. The lumber trade at Quebec is still very large. According to a recent article in the _Revue des Deux Mondes_, that city exported, in 1860, 30,000,000 cubic feet of squared timber, and 400,000,000 square feet of "planches." The thickness of the boards is not stated, but I believe they are generally cut an inch and a quarter thick for the Quebec trade, and as they shrink somewhat in drying, we may estimate ten square for one cubic foot of boards. This gives a total of 70,000,000 cubic feet. The specific gravity of white pine is .554, and the weight of this quantity of lumber, very little of which is thoroughly seasoned, would exceed a million of tons, even supposing it to consist wholly of wood as light as pine. New Brunswick, too, exports a large amount of lumber. [245] This name, from the French _chantier_, which has a wider meaning, is applied in America to temporary huts or habitations erected for the convenience of forest life, or in connection with works of material improvement. [246] Trees differ much in their power of resisting the action of forest fires. Different woods vary greatly in combustibility, and even when their bark is scarcely scorched, they are, partly in consequence of physiological character, and partly from the greater or less depth at which their roots habitually lie below the surface, very differently affected by running fires. The white pine, _Pinus strobus_, as it is the most valuable, is also perhaps the most delicate tree of the American forest, while its congener, the Northern pitch pine, _Pinus rigida_, is less injured by fire than any other tree of that country. I have heard experienced lumbermen maintain that the growth of this pine was even accelerated by a fire brisk enough to destroy all other trees, and I have myself seen it still flourishing after a conflagration which had left not a green leaf but its own in the wood, and actually throwing out fresh foliage, when the old had been quite burnt off and the bark almost converted into charcoal. The wood of the pitch pine is of comparatively little value for the joiner, but it is useful for very many purposes. Its rapidity of growth in even poor soils, its hardihood, and its abundant yield of resinous products, entitle it to much more consideration, as a plantation tree, than it has hitherto received in Europe or America. [247] Between fifty and sixty years ago, a steep mountain with which I am very familiar, composed of metamorphic rock, and at that time covered with a thick coating of soil and a dense primeval forest, was accidentally burnt over. The fire took place in a very dry season, the slope of the mountain was too rapid to retain much water, and the conflagration was of an extraordinarily fierce character, consuming the wood almost entirely, burning the leaves and combustible portion of the mould, and in many places cracking and disintegrating the rock beneath. The rains of the following autumn carried off much of the remaining soil, and the mountain side was nearly bare of wood for two or three years afterward. At length, a new crop of trees sprang up and grew vigorously, and the mountain is now thickly covered again. But the depth of mould and earth is too small to allow the trees to reach maturity. When they attain to the diameter of about six inches, they uniformly die, and this they will no doubt continue to do until the decay of leaves and wood on the surface, and the decomposition of the subjacent rock, shall have formed, perhaps hundreds of years hence, a stratum of soil thick enough to support a full-grown forest. [248] The growth of the white pine, on a good soil and in open ground, is rather rapid until it reaches the diameter of a couple of feet, after which it is much slower. The favorite habitat of this tree is light sandy earth. On this soil, and in a dense wood, it requires a century to attain the diameter of a yard. Emerson (_Trees of Massachusetts_, p. 65), says that a pine of this species, near Paris, "thirty years planted, is eighty feet high, with a diameter of three feet." He also states that ten white pines planted at Cambridge, Massachusetts, in 1809 or 1810, exhibited, in the winter of 1841 and 1842, an average of twenty inches diameter at the ground, the two largest measuring, at the height of three feet, four feet eight inches in circumference; and he mentions another pine growing in a rocky swamp, which, at the age of thirty-two years, "gave seven feet in circumference at the but, with a height of sixty-two feet six inches." This latter I suppose to be a seedling, the others _transplanted_ trees, which might have been some years old when placed where they finally grew. The following case came under my own observation: In 1824, a pine tree, so small that a young lady, with the help of a lad, took it up from the ground and carried it a quarter of a mile, was planted near a house in a town in Vermont. It was occasionally watered, but received no other special treatment. I measured this tree in 1860, and found it, at four feet from the ground, and entirely above the spread of the roots, two feet and four inches in diameter. It could not have been more than three inches through when transplanted, and must have increased its diameter twenty-five inches in thirty-six years. [249] WILLIAMS, _History of Vermont_, ii, p. 53. DWIGHT's _Travels_, iv, p. 21, and iii, p. 36. EMERSON, _Trees of Massachusetts_, p. 61. PARISH, _Life of President Wheelock_, p. 56. [250] The forest trees of the Northern States do not attain to extreme longevity in the dense woods. Dr. Williams found that none of the huge pines, the age of which he ascertained, exceeded three hundred and fifty or four hundred years, though he quotes a friend who thought he had noticed trees considerably older. The oak lives longer than the pine, and the hemlock spruce is perhaps equally long lived. A tree of this latter species, cut within my knowledge in a thick wood, counted four hundred and eighty-six, or, according to another observer, five hundred annual circles. Great luxuriance of animal and vegetable production is not commonly accompanied by long duration of the individual. The oldest men are not found in the crowded city; and in the tropics, where life is prolific and precocious, it is also short. The most ancient forest trees of which we have accounts have not been those growing in thick woods, but isolated specimens, with no taller neighbor to intercept the light and heat and air, and no rival to share the nutriment afforded by the soil. The more rapid growth and greater dimensions of trees standing near the boundary of the forest, are matters of familiar observation. "Long experience has shown that trees growing on the confines of the wood may be cut at sixty years of age as advantageously as others of the same species, reared in the depth of the forest, at a hundred and twenty. We have often remarked, in our Alps, that the trunk of trees upon the border of a grove is most developed or enlarged upon the outer or open side, where the branches extend themselves farthest, while the concentric circles of growth are most uniform in those entirely surrounded by other trees, or standing entirely alone."--A. and G. VILLA, _Necessità dei Boschi_, pp. 17, 18. [251] Caimi states that "a single flotation in the Valtelline in 1839, caused damages alleged to amount to more than $800,000, and actually appraised at $250,000."--_Cenni sulla Importanza e Coltura dei Boschi_, p. 65. [252] Most physicists who have investigated the laws of natural hydraulics maintain that, in consequence of direct obstruction and frictional resistance to the flow of the water of rivers along their banks, there is both an increased rapidity of current and an elevation of the water in the middle of the channel, so that a river presents always a convex surface. The lumbermen deny this. They affirm that, while rivers are rising, the water is highest in the middle of the channel, and tends to throw floating objects shoreward; while they are falling, it is lowest in the middle, and floating objects incline toward the centre. Logs, they say, rolled into the water during the rise, are very apt to lodge on the banks, while those set afloat during the falling of the waters keep in the current, and are carried without hindrance to their destination. Foresters and lumbermen, like sailors and other persons whose daily occupations bring them into contact, and often, into conflict, with great natural forces, have many peculiar opinions, not to say superstitions. In one of these categories we must rank the universal belief of lumbermen, that with a given head of water, and in a given number of hours, a sawmill cuts more lumber by night than by day. Having been personally interested in several sawmills, I have frequently conversed with sawyers on this subject, and have always been assured by them that their uniform experience established the fact that, other things being equal, the action of the machinery of sawmills is more rapid by night than by day. I am sorry--perhaps I ought to be ashamed--to say that my scepticism has been too strong to allow me to avail myself of my opportunities of testing this question by passing a night, watch in hand, counting the strokes of a millsaw. More unprejudiced, and I must add, very intelligent and credible persons have informed me that they have done so, and found the report of the sawyers abundantly confirmed. A land surveyor, who was also an experienced lumberman, sawyer, and machinist, a good mathematician and an exact observer, has repeatedly told me, that he had very often "timed" sawmills, and found the difference in favor of night work above thirty per cent. _Sed quære._ [253] For many instances of this sort, see BECQUEREL, _Des Climats, etc._, pp. 301-303. In 1664, the Swedes made an incursion into Jutland and felled a considerable extent of forest. After they retired, a survey of the damage was had, and the report is still extant. The number of trees cut was found to be 120,000, and as an account was kept of the numbers of each species of tree, the document is of interest in the history of the forest, as showing the relative proportions between the different trees which composed the wood. See VAUPELL. _Bögens Indvandring_, p. 35, and _Notes_, p. 55. [254] Since writing this paragraph, I have fallen upon--and that in a Spanish author--one of those odd coincidences of thought which every man of miscellaneous reading so often meets with. Antonio Ponz (_Viage de España_, i, prólogo, p. lxiii), says: "Nor would this be so great an evil, were not some of them declaimers against _trees_, thereby proclaiming themselves, in some sort, enemies of the works of God, who gave us the leafy abode of Paradise to dwell in, where we should be even now sojourning, but for the first sin, which expelled us from it." I do not know at what period the two Castiles were bared of their woods, but the Spaniard's proverbial "hatred of a tree" is of long standing. Herrera vigorously combats this foolish prejudice; and Ponz, in the prologue to the ninth volume of his journey, says that many carried it so far as wantonly to destroy the shade and ornamental trees planted by the municipal authorities. "Trees," they contended, and still believe, "breed birds, and birds eat up the grain." Our author argues against the supposition of the "breeding of birds by trees," which, he says, is as absurd as to believe that an elm tree can yield pears; and he charitably suggests that the expression is, perhaps, a _manière de dire_, a popular phrase, signifying simply that trees harbor birds. [255] Religious intolerance had produced similar effects in France at an earlier period. "The revocation of the edict of Nantes and the dragonnades occasioned the sale of the forests of the unhappy Protestants, who fled to seek in foreign lands the liberty of conscience which was refused to them in France. The forests were soon felled by the purchasers, and the soil in part brought under cultivation."'--BECQUEREL, _Des Climats, etc._, p. 303. [256] The American reader must be reminded that, in the language of the chase and of the English law, a "forest" is not necessarily a wood. Any large extent of ground, withdrawn from cultivation, reserved for the pleasures of the chase, and allowed to clothe itself with a spontaneous growth, serving as what is technically called "cover" for wild animals, is, in the dialects I have mentioned, a forest. When, therefore, the Norman kings afforested the grounds referred to in the text, it is not to be supposed that they planted them with trees, though the protection afforded to them by the game laws would, if cattle had been kept out, soon have converted them into real woods. [257] _Histoire des Paysans_, ii, p. 190. The work of Bonnemère is of great value to those who study the history of mediæval Europe from a desire to know its real character, and not in the hope of finding apparent facts to sustain a false and dangerous theory. Bonnemère is one of the few writers who, like Michelet, have been honest enough and bold enough to speak the truth with regard to the relations between the church and the people in the Middle Ages. [258] It is painful to add that a similar outrage was perpetrated a very few years ago, in one of the European states, by a prince of a family now dethroned. In this case, however, the prince killed the trespasser with his own hand, his sergeants refusing to execute his mandate. [259] GUILLAUME DE NANGIS, as quoted in the notes to JOINVILLE, _Nouvelle Collection des Mémoires, etc._, par Michaud et Poujoulat, première série, i, p. 335. Persons acquainted with the character and influence of the mediæval clergy will hardly need to be informed that the ten thousand livres never found their way to the royal exchequer. It was easy to prove to the simple-minded king that, as the profits of sin were a monopoly of the church, he ought not to derive advantage from the commission of a crime by one of his subjects; and the priests were cunning enough both to secure to themselves the amount of the fine, and to extort from Louis large additional grants to carry out the purposes to which they devoted the money. "And though the king did take the moneys," says the chronicler, "he put them not into his treasury, but turned them into good works; for he builded therewith the maison-Dieu of Pontoise, and endowed the same with rents and lands; also the schools and the dormitory of the friars preachers of Paris, and the monastery of the Minorite friars." [260] _Histoire des Paysans_, ii, p. 200. [261] The following details from Bonnemère will serve to give a more complete idea of the vexatious and irritating nature of the game laws of France. The officers of the chase went so far as to forbid the pulling up of thistles and weeds, or the mowing of any unenclosed ground before St. John's day [24th June], in order that the nests of game birds might not be disturbed. It was unlawful to fence-in any grounds in the plains where royal residences were situated; thorns were ordered to be planted in all fields of wheat, barley, or oats, to prevent the use of ground nets for catching the birds which consumed, or were believed to consume, the grain, and it was forbidden to cut or pull stubble before the first of October, lest the partridge and the quail might be deprived of their cover. For destroying the eggs of the quail, a fine of one hundred livres was imposed for the first offence, double that amount for the second, and for the third the culprit was flogged and banished for five years to a distance of six leagues from the forest.--_Histoire des Paysans_, ii, p. 202, text and notes. Neither these severe penalties, nor any provisions devised by the ingenuity of modern legislation, have been able effectually to repress poaching. "The game laws," says Clavé, "have not delivered us from the poachers, who kill twenty times as much game as the sportsmen. In the forest of Fontainebleau, as in all those belonging to the state, poaching is a very common and a very profitable offence. It is in vain that the gamekeepers are on the alert night and day, they cannot prevent it. Those who follow the trade begin by carefully studying the habits of the game. They will lie motionless on the ground, by the roadside or in thickets, for whole days, watching the paths most frequented by the animals," &c.--_Revue des Deux Mondes_, Mai, 1863, p. 160. The writer adds many details on this subject, and it appears that, as there are "beggars on horseback" in South America, there are poachers in carriages in France. [262] "Whole trees were sacrificed for the most insignificant purposes; the peasants would cut down two firs to make a single pair of wooden shoes."--MICHELET, as quoted by CLAVÉ, _Études_, p. 24. A similar wastefulness formerly prevailed in Russia, though not from the same cause. In St. Pierre's time, the planks brought to St. Petersburg were not sawn, but hewn with the axe, and a tree furnished but a single plank. [263] "A hundred and fifty paces from my house is a hill of drift sand, on which stood a few scattered pines. _Pinus sylvestris_, and _Sempervivum tectorum_ in abundance, _Statice armeria_, _Ammone vernalis_, _Dianthus carthusianorum_, with other sand plants, were growing there. I planted the hill with a few birches, and all the plants I have mentioned completely disappeared, though there were many naked spots of sand between the trees. It should be added, however, that the hillock is more thickly wooded than before. * * * It seems then that _Sempervivum tectorum_, &c., will not bear the neighborhood of the birch, though growing well near the _Pinus sylvestris_. I have found the large red variety of _Agaricus deliciosus_ only among the roots of the pine; the greenish-blue _Agaricus deliciosus_ among alder roots, but not near any other tree. Birds have their partialities among trees and shrubs. The _Silviæ_ prefer the _Pinus Larix_ to other trees. In my garden this _Pinus_ is never without them, but I never saw a bird perch on _Thuja occidenialis_ or _Juniperus sabina_, although the thick foliage of these latter trees affords birds a better shelter than the loose leafage of other trees. Not even a wren ever finds its way to one of them. Perhaps the scent of the _Thuja_ and the _Juniperus_ is offensive to them. I have spoiled one of my meadows by cutting away the bushes. It formerly bore grass four feet high, because many umbelliferous plants, such as _Heracleum spondylium_, _Spiræa ulmaria_, _Laserpitium latifolia_, &c., grew in it. Under the shelter of the bushes these plants ripened and bore seed, but they gradually disappeared as the shrubs were extirpated, and the grass now does not grow to the height of more than two feet, because it is no longer obliged to keep pace with the umbellifera which flourished among it." See a paper by J. G. BÜTTNER, of Kurland, in BERGHAUS' _Geographisches Jahrbuch_, 1852, No. 4, pp. 14, 15. These facts are interesting as illustrating the multitude of often obscure conditions upon which the life or vigorous growth of smaller organisms depends. Particular species of truffles and of mushrooms are found associated with particular trees, without being, as is popularly supposed, parasites deriving their nutriment from the dying or dead roots of those trees. The success of Rousseau's experiments seem decisive on this point, for he obtains larger crops of truffles from ground covered with young seedling oaks than from that filled with roots of old trees. See an article on Mont Ventoux, by Charles Martins, in the _Revue des Deux Mondes_, Avril, 1863, p. 626. It ought to be much more generally known than it is that most, if not, all mushrooms, even of the species reputed poisonous, may be rendered harmless and healthful as food by soaking them for two hours in acidulated or salt water. The water requires two or three spoonfuls of vinegar or two spoonfuls of gray salt to the quart, and a quart of water is enough for a pound of sliced mushrooms. After thus soaking, they are well washed in fresh water, thrown into cold water, which is raised to the boiling point, and, after remaining half an hour, taken out and again washed. Gérard, to prove that "crumpets is wholesome," ate one hundred and seventy-five pounds of the most poisonous mushrooms thus prepared, in a single month, fed his family _ad libitum_ with the same, and finally administered them, in heroic doses, to the members of a committee appointed by the Council of Health of the city of Paris. See FIGUIER, _L'Année Scientifique_, 1862, pp. 353, 384. See _Appendix_, No. 31. It has long been known that the Russian peasantry eat, with impunity, mushrooms of species everywhere else regarded as very poisonous. Is it not probable that the secret of rendering them harmless--which was known to Pliny, though since forgotten in Italy--is possessed by the rustic Muscovites? [264] _Physikalische Geographie_, p. 486. [265] _Origin of Species_, American edition, p. 69. [266] Writers on vegetable physiology record numerous instances where seeds have grown after lying dormant for ages. The following cases, mentioned by Dr. Dwight (_Travels_, ii, pp. 438, 439), may be new to many readers: "The lands [in Panton, Vermont], which have here been once cultivated, and again permitted to lie waste for several years, yield a rich and fine growth of hickory [_Carya porcina_]. Of this wood there is not, I believe, a single tree in any original forest within fifty miles from this spot. The native growth was here white pine, of which I did not see a single stem in a whole grove of hickory." The hickory is a walnut, bearing a fruit too heavy to be likely to be carried fifty miles by birds, and besides, I believe it is not eaten by any bird indigenous to Vermont. "A field, about five miles from Northampton, on an eminence called Rail Hill, was cultivated about a century ago. The native growth here, and in all the surrounding region, was wholly oak, chestnut, &c. As the field belonged to my grandfather, I had the best opportunity of learning its history. It contained about five acres, in the form of an irregular parallelogram. As the savages rendered the cultivation dangerous, it was given up. On this ground there sprang up a grove of white pines covering the field and retaining its figure exactly. So far as I remember, there was not in it a single oak or chestnut tree. * * * There was not a single pine whose seeds were, or, probably, had for ages been, sufficiently near to have been planted on this spot. The fact that these white pines covered this field exactly, so as to preserve both its extent and its figure, and that there were none in the neighborhood, are decisive proofs that cultivation brought up the seeds of a former forest within the limits of vegetation, and gave them an opportunity to germinate." [267] Quaint old Valvasor had observed the subduing influence of nature's solitudes. In describing the lonely Canker-Thal, which, though rocky, was in his time well wooded with "fir, larches, beeches, and other trees," he says: "Gladsomeness and beauty, which dwell in many valleys, may not be looked for there. The journey through it is cheerless, melancholy, wearisome, and serveth to temper and mortify over-joyousness of thought. * * * In sum it is a very wild, wherein the wildness of human pride doth grow tame."--_Ehre der Crain_, i, p. 136, b. [268] Valvasor says, in the same paragraph from which I have just quoted, "In my many journeys through this valley, I did never have sight of so much as a single bird." [269] Smela, in the government of Kiew, has, for some years, not suffered at all from the locusts, which formerly came every year in vast swarms, and the curculio, so injurious to the turnip crops, is less destructive there than in other parts of the province. This improvement is owing partly to the more thorough cultivation of the soil, partly to the groves which are interspersed among the plough lands. * * * When in the midst of the plains woods shall be planted and filled with insectivorous birds, the locusts will cease to be a plague and a terror to the farmer.--RENTZSCH, _Der Wald_, pp. 45, 46. [270] England is, I believe, the only country where private enterprise has pursued sylviculture on a really great scale, though admirable examples have been set in many others on both sides of the Atlantic. In England the law of primogeniture, and other institutions and national customs which tend to keep large estates long undivided and in the same line of inheritance, the wealth of the landholders, and the difficulty of finding safe and profitable investments of capital, combine to afford encouragements for the plantation of forests, which nowhere else exist in the same degree. The climate of England, too, is very favorable to the growth of forest trees, though the character of surface secures a large part of the island from the evils which have resulted from the destruction of the woods elsewhere, and therefore their restoration is a matter of less geographical importance in England than on the Continent. [271] The preservation of the woods on the eastern frontier of France, as a kind of natural abattis, is also recognized by the Government of that country as an important measure of military defence, though there have been conflicting opinions on the subject. [272] Let us take the supply of timber for railroad ties. According to Clavé (p. 248), France has 9,000 kilomètres of railway in operation, 7,000 in construction, half of which is built with a double track. Adding turnouts and extra tracks at stations, the number of ties required for a single track is stated at 1,200 to the kilomètre, or, as Clavé computes, for the entire network of France, 58,000,000. As the schoolboys say, "this sum does not prove;" for 16,000 + 8,000 for the double track halfway = 24,000, and 24,000 × 1,200 = 28,800,000. According to Bigelow (_Les États Unis en 1863_, p. 439), the United States had in operation or construction on the first of January, 1862, 51,000 miles, or about 81,000 kilomètres of railroad, and the military operations of the present civil war are rapidly extending the system. Allowing the same proportion as in France, the American railroads required 97,200,000 ties in 1862. The consumption of timber in Europe and America during the present generation, occasioned by this demand, has required the sacrifice of many hundred thousand acres of forest, and if we add the quantity employed for telegraph posts, we have an amount of destruction, for entirely new purposes, which is really appalling. The consumption of wood for lucifer matches is enormous, and I have heard of several instances where tracts of pine forest, hundreds and even thousands of acres in extent, have been purchased and felled, solely to supply timber for this purpose. The demand for wood for small carvings and for children's toys is incredibly large. Rentzsch states the export of such objects from the town of Sonneberg alone to have amounted, in 1853, to 60,000 centner, or three thousand tons' weight.--_Der Wald_, p. 68. See _Appendix_, No. 33. The importance of so managing the forest that it may continue indefinitely to furnish an adequate supply of material for naval architecture is well illustrated by some remarks of the same author in the valuable little work just cited. He suggests that the prosperity of modern England is due, in no small degree, to the supplies of wood and other material for building and equipping ships, received from the forests of her colonies and of other countries with which she has maintained close commercial relations, and he adds: "Spain, which by her position seemed destined for universal power, and once, in fact, possessed it, has lost her political rank, because during the unwise administration of the successors of Philip II, the empty exchequer could not furnish the means of building new fleets; for the destruction of the forests had raised the price of timber above the resources of the state."--_Der Wald_, p. 63. The market price of timber, like that of all other commodities, may be said, in a general way, to be regulated by the laws of demand and supply, but it is also controlled by those seemingly unrelated accidents which so often disappoint the calculations of political economists in other branches of commerce. A curious case of this sort is noticed by CERINI, _Dell' Impianto e Conservazione dei Boschi_, p. 17: "In the mountains on the Lago Maggiore, in years when maize is cheap, the woodcutters can provide themselves with corn meal enough for a week by three days' labor, and they refuse to work the remaining four. Hence the dealers in wood, not being able to supply the demand, for want of laborers, are obliged to raise the price for the following season, both for timber and for firewood; so that a low price of grain occasions a high price of building lumber and of fuel. The consequence is, that though the poor have supplied themselves cheaply with food, they must pay dear for firewood, and they cannot get work, because the high price of lumber has discouraged repairs and building, the expense of which landed proprietors cannot undertake when their incomes have been reduced by sales of grain at low rates, and hence there is not demand enough for lumber to induce the timber merchants to furnish employment to the woodmen." [273] Besides the substitution of iron for wood, a great saving of consumption of this latter material has been effected by the revival of ancient methods of increasing its durability, and the invention of new processes for the same purpose. The most effectual preservative yet discovered for wood employed on land, is sulphate of copper, a solution of which is introduced into the pores of the wood while green, by soaking, by forcing-pumps, or, most economically, by the simple pressure of a column of the fluid in a small pipe connected with the end of the piece of timber subjected to the treatment. Clavé (_Études Forestières_, pp. 240-249) gives an interesting account of the various processes employed for rendering wood imperishable, and states that railroad ties injected with sulphate of copper in 1846, were found absolutely unaltered in 1855; and telegraphic posts prepared two years earlier, are now in a state of perfect preservation. For many purposes, the method of injection is too expensive, and some simpler process is much to be desired. The question of the proper time of felling timber is not settled, and the best modes of air, water, and steam seasoning are not yet fully ascertained. Experiments on these subjects would be well worth the patronage of governments in new countries, where they can be very easily made, without the necessity of much waste of valuable material, and without expensive arrangements for observation. The practice of stripping living trees of their bark some years before they are felled, is as old as the time of Vitruvius, but is much less followed than it deserves, partly because the timber of trees so treated inclines to crack and split, and partly because it becomes so hard as to be wrought with considerable difficulty. In America, economy in the consumption of fuel has been much promoted by the substitution of coal for wood, the general use of stoves both for wood and coal, and recently by the employment of anthracite in the furnaces of stationary and locomotive steam-engines. All the objections to the use of anthracite for this latter purpose appear to have been overcome, and the improvements in its combustion have been attended with a great pecuniary saving, and with much advantage to the preservation of the woods. The employment of coal has produced a great reduction in the consumption of fire wood in Paris. In 1815, the supply of fire wood for the city required 1,200,000 stères, or cubic mètres; in 1859, it had fallen to 501,805, while, in the mean time, the consumption of coal had risen from 600,000 to 432,000,000 metrical quintals. See CLAVÉ, _Études_, p. 212. I think there must be some error in this last sum, as 432 millions of metrical quintals would amount to 43 millions of tons, a quantity which it is difficult to suppose could be consumed in the city of Paris. The price of fire wood has scarcely advanced at all in Paris for half a century, though that of timber generally has risen enormously. [274] In the first two years of the present civil war in the United States, twenty-eight thousand walnut trees were felled to supply a single European manufactory of gunstocks for the American market. [275] Among the indirect proofs of the comparatively recent existence of extensive forests in France, may be mentioned the fact, that wolves were abundant, not very long since, in parts of the empire where there are now neither wolves nor woods to shelter them. Arthur Young more than once speaks of the "innumerable multitudes" of these animals which infested France in 1789, and George Sand states, in the _Histoire de ma Vie_, that some years after the restoration of the Bourbons, they chased travellers on horseback in the Southern provinces, and literally knocked at the doors of her father-in-law's country seat. [276] In the _Recepte Véritable_, Palissy having expressed his indignation at the folly of men in destroying the woods, his interlocutor defends the policy of felling them, by citing the example of "divers bishops, cardinals, priors, abbots, monkeries, and chapters, which, by cutting their woods, have made three profits," the sale of the timber, the rent of the ground, and the "good portion" they received of the grain grown by the peasants upon it. To this argument, Palissy replies: "I cannot enough detest this thing, and I call it not an error, but a curse and a calamity to all France; for when forests shall be cut, all arts shall cease, and they which practise them shall be driven out to eat grass with Nebuchadnezzar and the beasts of the field. I have divers times thought to set down in writing the arts which shall perish when there shall be no more wood; but when I had written down a great number, I did perceive that there could be no end of my writing, and having diligently considered, I found there was not any which could be followed without wood." * * "And truly I could well allege to thee a thousand reasons, but 'tis so cheap a philosophy, that the very chamber wenches, if they do but think, may see that without wood, it is not possible to exercise any manner of human art or cunning."--_[OE]uvres de_ BERNARD PALISSY, p. 89. [277] Since writing the above paragraph, I have found the view I have taken of this point confirmed by the careful investigations of Rentzsch, who estimates the proper proportion of woodland to entire surface at twenty-three per cent. for the interior of Germany, and supposes that near the coast, where the air is supplied with humidity by evaporation from the sea, it might safely be reduced to twenty per cent. See Rentzsch's very valuable prize essay, _Der Wald im Haushalt der Natur und der Volkswirthschaft_, cap. viii. The due proportion in France would considerably exceed that for the German States, because France has relatively more surface unfit for any growth but that of wood, because the form and geological character of her mountains expose her territory to much greater injury from torrents, and because at least her southern provinces are more frequently visited both by extreme drought and by deluging rains. [278] _Études sur l'Économie Forestière_, p. 261. Clavé adds (p. 262): "The Russian forests are very unequally distributed through the territory of this vast empire. In the north they form immense masses, and cover whole provinces, while in the south they are so completely wanting that the inhabitants have no other fuel than straw, dung, rushes, and heath." * * * "At Moscow, firewood costs thirty per cent. more than at Paris, while, at the distance of a few leagues, it sells for a tenth of that price." This state of things is partly due to the want of facilities of transportation, and some parts of the United States are in a similar condition. During a severe winter, six or seven years ago, the sudden freezing of the canals and rivers, before a large American town had received its usual supply of fuel, occasioned an enormous rise in the price of wood and coal, and the poor suffered severely for want of it. Within a few hours of the city were large forests and an abundant stock of firewood felled and prepared for burning. This might easily have been carried to town by the railroads which passed through the woods; but the managers of the roads refused to receive it as freight, because the opening of a new market for wood might raise the price of the fuel they employed for their locomotives. Hohenstein, who was long professionally employed as a forester in Russia, describes the consequences of the general war upon the woods in that country as already most disastrous, and as threatening still more ruinous evils. The river Volga, the life artery of Russian internal commerce, is drying up from this cause, and the great Muscovite plains are fast advancing to a desolation like that of Persia.--_Der Wald_, p. 223. The level of the Caspian Sea is eighty-three feet lower than that of the Sea of Azoff, and the surface of Lake Aral is fast sinking. Von Baer maintains that the depression of the Caspian was produced by a sudden subsidence, from geological causes, and not gradually by excess of evaporation over supply. See _Kaspische Studien_, p. 25. But this subsidence diminished the area and consequently the evaporation of that sea, and the rivers which once maintained its ancient equilibrium ought to raise it to its former level, if their own flow had not been diminished. It is, indeed, not proved that the laying bare of a wooded country diminishes the total annual precipitation upon it; but it is certain that the summer evaporation from the surface of a champaign region, like that through which the Volga, its tributaries, and the feeders of Lake Aral flow, is increased by the removal of its woods. Hence, though as much rain may still fall in the valleys of those rivers as when their whole surface was covered with forests, a less quantity of water may be delivered by them since their basins were cleared, and therefore the present condition of the inland waters in question may be due to the removal of the forests in their basins. [279] Rentzsch _(Der Wald, etc._, pp. 123, 124) states the proportions of woodland in different European countries as follows: ---------------+----------+----------- | |Acres per | Per cent.| head of | |population. ---------------+----------+----------- Germany | 26.58 | 0.6638 Great Britain | 5. | 0.1 France | 16.79 | 0.3766 Russia | 30.90 | 4.28 Sweden | 60. | 8.55 Norway | 66. | 24.61 Denmark | 5.50 | 0.22 Switzerland | 15. | 0.396 Holland | 7.10 | 0.12 Belgium | 18.52 | 0.186 Spain | 5.52 | 0.291 Portugal | 4.40 | 0.182 Sardinia | 12.29 | 0.223 Naples | 9.43 | 0.138 ---------------+----------+----------- Probably no European countries can so well dispense with the forests, in their capacity of conservative influences, as England and Ireland. Their insular position and latitude secure an abundance of atmospheric moisture, and the general inclination of surface is not such as to expose it to special injury from torrents. The due proportion of woodland in England and Ireland is, therefore, almost purely an economical question, to be decided by the comparative direct pecuniary return from forest growth, pasturage, and plough land. In Scotland, where the country is for the most part more broken and mountainous, the general destruction of the forests has been attended with very serious evils, and it is in Scotland that many of the most extensive British forest plantations have now been formed. But although the inclination of surface in Scotland is rapid, the geological constitution of the soil is not of a character to promote such destructive degradation by running water as in Southern France, and it has not to contend with the parching droughts by which the devastations of the torrents are rendered more injurious in that part of the French empire. In giving the proportion of woodland to population, I compute Rentzsch's Morgen at .3882 of an English acre, because I find, by Alexander's most accurate and valuable Dictionary of Weights and Measures, that this is the value of the Dresden Morgen, and Rentzsch is a Saxon writer. In the different German States, there are more than twenty different land measures known by the name of Morgen, varying from about one third of an acre to more than three acres in value. When will the world be wise enough to unite in adopting the French metrical and monetary systems? As to the latter, never while Christendom continues to be ruled by money changers, who can compel you to part with your sovereigns in France at twenty-five francs, and in England to accept fifteen shillings for your napoleons. I speak as a sufferer. _Experto crede Roberto._ [280] According to the maxims of English jurisprudence, the common law consists of general customs so long established that "the memory of man runneth not to the contrary." In other words, long custom makes law. In new countries, the change of circumstances creates new customs, and, in time, new law, without the aid of legislation. Had the American colonists observed a more sparing economy in the treatment of their woods, a new code of customary forest law would have sprung up and acquired the force of a statute. Popular habit was fast elaborating the fundamental principles of such a code, when the rapid increase in the value of timber, in consequence of the reckless devastation of the woodlands, made it the interest of the proprietors to interfere with this incipient system of forest jurisprudence, and appeal to the rules of English law for the protection of their woods. The courts have sustained these appeals, and forest property is now legally as inviolable as any other, though common opinion still combats the course of judicial decision on such questions. In the United States, swarms of honey bees, on leaving the parent hive, often take up their quarters in hollow trees in the neighboring woods. By the early customs of New England, the finder of a "bee tree" on the land of another owner was regarded as entitled to the honey by right of discovery; and as a necessary incident of that right, he might cut the tree, at the proper season, without asking permission of the proprietor of the soil. The quantity of "wild honey" in a tree was often large, and "bee hunting" was so profitable that it became almost a regular profession. The "bee hunter" sallied forth with a small box containing honey and a little vermilion. The bees which were attracted by the honey marked themselves with the vermilion, and hence were more readily followed in their homeward flight, and recognized when they returned a second time for booty. When loaded with spoil, this insect returns to his hive by the shortest route, and hence a straight line is popularly called in America a "bee line." By such a line, the hunter followed the bees to their sylvan hive, marked the tree with his initials, and returned to secure his prize in the autumn. When the right of the "bee hunter" was at last disputed by the land proprietors, it was with difficulty that judgments could be obtained, in inferior courts, in favor of the latter, and it was only after repeated decisions of the higher legal tribunals that the superior right of the owner of the soil was at last acquiesced in. [281] _Étude sur le Reboisement des Montagnes_, p. 5. [282] "In America," says Clavé (p. 124, 125), "where there is a vast extent of land almost without pecuniary value, but where labor is dear and the rate of interest high, it is profitable to till a large surface at the least possible cost; _extensive_ cultivation is there the most advantageous. In England, France, and Germany, where every corner of soil is occupied, and the least bit of ground is sold at a high price, but where labor and capital are comparatively cheap, it is wisest to employ _intensive_ cultivation. * * * All the efforts of the cultivator ought to be directed to the obtaining of a given result with the least sacrifice, and there is equally a loss to the commonwealth if the application of improved agricultural processes be neglected where they are advantageous, or if they be employed where they are not required. * * * In this point of view, sylviculture must follow the same laws as agriculture, and, like it, be modified according to the economical conditions of different states. In countries abounding in good forests, and thinly peopled, elementary and cheap methods must be pursued; in civilized regions, where a dense population requires that the soil shall be made to produce all it can yield, the regular artificial forest, with all the processes that science teaches, should be cultivated. It would be absurd to apply to the endless woods of Brazil and of Canada the method of the Spessart by "double stages," and not less so in our country, where every yard of ground has a high value, to leave to nature the task of propagating trees, and to content ourselves with cutting, every twenty or twenty-five years, the meagre growths that chance may have produced." [283] It is often laid down as a universal law, that the wood of trees of slow vegetation is superior to that of quick growth. This is one of those commonplaces by which men love to shield themselves from the labor of painstaking observation. It has, in fact, so many exceptions, that it may be doubted whether it is in any sense true. Most of the cedars are slow of growth; but while the timber of some of them is firm and durable, that of others is light, brittle, and perishable. The hemlock spruce is slower of growth than the pines, but its wood is of very little value. The pasture oak and beech show a breadth of grain--and, of course, an annual increment--twice as great as trees of the same species grown in the woods; and the American locust, _Robinia pseudacacia_, the wood of which is of extreme toughness and durability, is, of all trees indigenous to Northeastern America, by far the most rapid in growth. As an illustration of the mutual interdependence of the mechanic arts, I may mention that in Italy, where stone, brick, and plaster are almost the only materials used in architecture, and where the "hollow ware" kitchen implements are of copper or of clay, the ordinary tools for working wood are of a very inferior description, and the locust timber is found too hard for their temper. Southey informs us, in "Espriella's Letters," that when a small quantity of mahogany was brought to England, early in the last century, the cabinetmakers were unable to use it, from the defective temper of their tools, until the demand for furniture from the new wood compelled them to improve the quality of their implements. In America, the cheapness of wood long made it the preferable material for almost all purposes to which it could by any possibility be applied. The mechanical cutlery and artisans' tools of the United States are of admirable temper, finish, and convenience, and no wood is too hard, or otherwise too refractory, to be wrought with great facility, both by hand tools and by the multitude of ingenious machines which the Americans have invented for this purpose. [284] _Études Forestières_, p. 7. [285] _Études Forestières_, p. 7. [286] For very full catalogues of American forest trees, and remarks on their geographical distribution, consult papers on the subject by Dr. J. G. Cooper, in the Report of the Smithsonian Institution for 1858, and the Report of the United States Patent Office, Agricultural Division, for 1860. [287] Although Spenser's catalogue of trees occurs in the first canto of the first book of the "Faëry Queene"--the only canto of that exquisite poem actually read by most students of English literature--it is not so generally familiar as to make the quotation of it altogether superfluous: VII. Enforst to seeke some covert nigh at hand, A shadie grove not farr away they spide, That promist ayde the tempest to withstand; Whose loftie trees, yelad with sommers pride, Did spred so broad, that heavens light did hide, Not perceable with power of any starr: And all within were pathes and alleies wide, With footing worne, and leading inward farr; Faire harbour that them seems; so in they entred ar. VIII. And foorth they passe, with pleasure forward led, Joying to heare the birdes sweete harmony, Which therein shrouded from the tempest dred, Seemd in their song to scorne the cruell sky. Much can they praise the trees so straight and hy, The sayling pine; the cedar stout and tall; The vine-propp elm; the poplar never dry; The builder oake, sole king of forrests all; The aspine good for staves; the cypresse funerall; IX. The laurell, meed of mightie conquerours And poets sage; the firre that weepeth still; The willow, worne of forlorn paramours; The eugh, obedient to the benders will; The birch for shaftes; the sallow for the mill; The mirrhe sweete-bleeding in the bitter wound; The warlike beech; the ash for nothing ill; The fruitfull olive; and the platane round; The carver holme; the maple seeldom inward sound. [288] The walnut is a more valuable tree than is generally supposed. It yields one third of the oil produced in France, and in this respect occupies an intermediate position between the olive of the south, and the oleaginous seeds of the north. A hectare (about two and a half acres), will produce nuts to the value of five hundred francs a year, which cost nothing but the gathering. Unfortunately, its maturity must be long waited for, and more nut-trees are felled than planted. The demand for its wood in cabinet work is the principal cause of its destruction. See LAVERGNE, _Économie Rurale de la France_, p. 253. According to Cosimo Ridolfi (Lezioni Orali, ii. p. 424), France obtains three times as much oil from the walnut as from the olive, and nearly as much as from all oleaginous seeds together. He states that the walnut bears nuts at the age of twenty years, and yields its maximum product at seventy, and that a hectare of ground, with thirty trees, or twelve to the acre, is equal to a capital of twenty-five hundred francs. The nut of this tree is known in the United States as the "English walnut." The fruit and the wood much resemble those of the American black walnut, _Juglans nigra_, but for cabinet work the American is the more beautiful material, especially when the large knots are employed. The timber of the European species, when straight grained, and _clear_, or free from knots, is, for ordinary purposes, better than that of the American black walnut, but bears no comparison with the wood of the hickory, when strength combined with elasticity is required, and its nut is very inferior in taste to that of the shagbark, as well as to the butternut, which it somewhat resembles. "The chestnut is more valuable still, for it produces on a sterile soil, which, without it, would yield only ferns and heaths, an abundant nutriment for man."--LAVERGNE, _Économie Rurale de la France_, p. 253. I believe the varieties developed by cultivation are less numerous in the walnut than in the chestnut, which latter tree is often grafted in Southern Europe. [289] This fir is remarkable for its tendency to cicatrize or heal over its stumps, a property which it possesses in common with some other firs, the maritime pine, and the European larch. When these trees grow in thick clumps, their roots are apt to unite by a species of natural grafting, and if one of them be felled, although its own proper rootlets die, the stump may continue, sometimes for a century, to receive nourishment from the radicles of the surrounding trees, and a dome of wood and bark of considerable thickness be formed over it. The cicatrization is, however, only apparent, for the entire stump, except the outside ring of annual growth, soon dies, and even decays within its covering, without sending out new shoots. [290] At the age of twelve or fifteen years, the cork tree is stripped of its outer bark for the first time. This first yield is of inferior quality, and is employed for floats for nets and buoys, or burnt for lampblack. After this, a new layer of cork, an inch or an inch and a quarter in thickness, is formed about once in ten years, and is removed in large sheets without injury to the tree, which lives a hundred and fifty years or more. According to Clavé (p. 252), the annual product of a forest of cork oaks is calculated at about 660 kilogrammes, worth 150 francs, to the hectare, which, deducting expenses, leaves a profit of 100 francs. This is about equal to 250 pound weight, and eight dollars profit to the acre. The cork oaks of the national domain in Algeria cover about 500,000 acres, and are let to individuals at rates which are expected, when the whole is rented, to yield to the state a revenue of about $2,000,000. George Sand, in the _Histoire de ma Vie_, speaks of the cork forests in Southern France as among the most profitable of rural possessions, and states, what I do not remember to have seen noticed elsewhere, that Russia is the best customer for cork. The large sheets taken from the trees are slit into thin plates, and used to line the walls of apartments in that cold climate. [291] The walnut, the chestnut, the apple, and the pear are common to the border between the countries I have mentioned, but the range of the other trees is bounded by the Alps, and by a well-defined and sharply drawn line to the west of those mountains. I cannot give statistical details as to the number of any of the trees in question, or as to the area they would cover if brought together in a given country. From some peculiarity in the sky of Europe, cultivated plants will thrive, in Northern Italy, in Southern France, and even in Switzerland, under a depth of shade where no crop, not even grass, worth harvesting, would grow in the United States with an equally high summer temperature. Hence the cultivation of all these trees is practicable in Europe to a greater extent than would be supposed reconcilable with the interests of agriculture. Some idea of the importance of the olive orchards may be formed from the fact that Sicily alone, an island scarcely exceeding 10,000 square miles in area, of which one third at least is absolutely barren, has exported to the single port of Marseilles more than 2,000,000 pounds weight of olive oil per year, for the last twenty years. [292] It is hard to say how far the peculiar form of the graceful crown of this pine is due to pruning. It is true that the extremities of the topmost branches are rarely lopped, but the lateral boughs are almost uniformly removed to a very considerable height, and it is not improbable that the shape of the top is thereby affected. [293] Besides this, in a country so diversified in surface--I wish we could with the French say _accidented_--as Italy with the exception of the champaign region drained by the Po, every new field of view requires either an extraordinary _coup d'[oe]il_ in the spectator, or a long study, in order to master its relief, its plans, its salient and retreating angles. In summer, the universal greenery confounds light and shade, distance and foreground; and though the impression upon a traveller, who journeys for the sake of "sensations," may be strengthened by the mysterious annihilation of all standards for the measurement of space, yet the superior intelligibility of the winter scenery of Italy is more profitable to those who see with a view to analyze. [294] Copse, or coppice, from the French _couper_, to cut, signifies properly a wood the trees of which are cut at certain periods of immature growth, and allowed to shoot up again from the roots; but it has come to signify, very commonly, a young wood, grove, or thicket, without reference to its origin, or to its character of a forest crop. [295] It has been recently stated, upon the evidence of the Government foresters of Greece, and of the queen's gardener, that a large wood has been discovered in Arcadia, consisting of a fir which has the property of sending up both vertical and lateral shoots from the stump of felled trees and forming a new crown. It was at first supposed that this forest grew only on the "mountains," of which the hero of About's most amusing story, _Le Roi des Montagnes_, was "king;" but it is now said that small stumps, with the shoots attached, have been sent to Germany, and recognized by able botanists as true natural products. [296] Natural forests are rarely, if ever, composed of trees of a single species, and experience has shown that oaks and other broad-leaved trees, planted as artificial woods, require to be mixed, or associated with others of different habits. In the forest of Fontainebleau, "oaks, mingled with beeches in due proportion," says Clavé, "may arrive at the age of five or six hundred years in full vigor, and attain dimensions which I have never seen surpassed; when, however, they are wholly unmixed with other trees, they begin to decay and die at the top, at the age of forty or fifty years, like men, old before their time, weary of the world, and longing only to quit it. This has been observed in most of the oak plantations of which I have spoken, and they have not been able to attain to full growth. When the vegetation was perceived to languish, they were cut, in the hope that this operation would restore their vigor, and that the new shoots would succeed better than the original trees; and, in fact, they seemed to be recovering for the first few years. But the shoots were soon attacked by the same decay, and the operation had to be renewed at shorter and shorter intervals, until at last it was found necessary to treat as coppices plantations originally designed for the full-growth system. Nor was this all: the soil, periodically bared by these cuttings, became impoverished, and less and less suited to the growth of the oak. * * * It was then proposed to introduce the pine and plant with it the vacancies and glades. * * * By this means, the forest was saved from the ruin which threatened it, and now more than 10,000 acres of pines, from fifteen to thirty years old, are disseminated at various points, sometimes intermixed with broad-leaved trees, sometimes forming groves by themselves."--_Revue des Deux Mondes_, Mai, 1863, pp. 153, 154. The forests of Denmark, which, in modern times, have been succeeded by the beech--a species more inclined to be exclusive than any other broad-leaved tree--were composed of birches, oaks, firs, aspens, willows, hazel, and maple, the first three being the leading species. At present, the beech greatly predominates.--VAUPELL, _Bögens Indvandring_, pp. 19, 20. [297] _Études Forestières_, p. 89. [298] The grounds which it is most important to clothe with wood as a conservative influence, and which, also, can best be spared from agricultural use, are steep hillsides. But the performance of all the offices of the forester to the tree--seeding, planting, thinning, and finally felling and removing for consumption--is more laborious upon a rapid declivity than on a level soil, and at the same time it is difficult to apply irrigation or manures to trees so situated. Experience has shown that there is great advantage in terracing the face of a hill before planting it, both as preventing the wash of the earth by checking the flow of water down its slope, and as presenting a surface favorable for irrigation, as well as for manuring and cultivating the tree. But even without so expensive a process, very important results have been obtained by simply ditching declivities. "In order to hasten the growth of wood on the flanks of a mountain, Mr. Eugène Chevandier divided the slope into zones forty or fifty feet wide, by horizontal ditches closed at both ends, and thereby obtained, from firs of different ages, shoots double the dimensions of those which grew on a dry soil of the same character, where the water was allowed to run off without obstruction."--DUMONT, _Des Travaux Publics, etc._, pp. 94-96. The ditches were about two feet and a half deep, and three feet and a half wide, and they cost about forty francs the hectare, or three dollars the acre. This extraordinary growth was produced wholly by the retention of the rain water in the ditches, whence it filtered through the whole soil and supplied moisture to the roots of the trees. It may be doubted whether in a climate cold enough to freeze the entire contents of the ditches in winter, it would not be expedient to draw off the water in the autumn, as the presence of so large a quantity of ice in the soil might prove injurious to trees too young and small to shelter the ground effectually against frost. Chevandier computes that, if the annual growth of the pine in the marshy soil of the Vosges be represented by one, it will equal two in dry ground, four or five on slopes so ditched or graded as to retain the water flowing upon them from roads or steep declivities, and six where the earth is kept constantly moist by infiltration from running brooks.--_Comptes Rendus à l'Académie des Sciences_--t. xix, Juillet, Dec., 1844, p. 167. The effect of accidental irrigation is well shown in the growth of the trees planted along the canals of irrigation which traverse the fields in many parts of Italy. They flourish most luxuriantly, in spite of continual lopping, and yield a very important contribution to the stock of fuel for domestic use; while trees, situated so far from canals as to be out of the reach of infiltration from them, are of much slower growth, under circumstances otherwise equally favorable. In other experiments of Chevandier, under better conditions, the yield of wood was increased, by judicious irrigation, in the ratio of seven to one, the profits in that of twelve to one. At the Exposition of 1855, Chambrelent exhibited young trees, which, in four years from the seed, had grown to the height of sixteen and twenty feet, and the diameter of ten and twelve inches. Chevandier experimented with various manures, and found that some of them might be profitably applied to young, but not to old trees, the quantity required in the latter case being too great. Wood ashes and the refuse of soda factories are particularly recommended. I have seen an extraordinary growth produced in fir trees by the application of soapsuds. [299] Although the economy of the forest has received little attention in the United States, no lover of American nature can have failed to observe a marked difference between a native wood from which cattle are excluded and one where they are permitted to browse. A few seasons suffice for the total extirpation of the "underbrush," including the young trees on which alone the reproduction of the forest depends, and all the branches of those of larger growth which hang within reach of the cattle are stripped of their buds and leaves, and soon wither and fall off. These effects are observable at a great distance, and a wood pasture is recognized, almost as far as it can be seen, by the regularity with which its lower foliage terminates at what Ruskin somewhere calls the "cattle line." This always runs parallel to the surface of the ground, and is determined by the height to which domestic quadrupeds can reach to feed upon the leaves. In describing a visit to the grand-ducal farm of San Rossore near Pisa, where a large herd of camels is kept, Chateauvieux says: "In passing through a wood of evergreen oaks, I observed that all the twigs and foliage of the trees were clipped up to the height of about twelve feet above the ground, without leaving a single spray below that level. I was informed that the browsing of the camels had trimmed the trees as high as they could reach."--LULLIN DE CHATEAUVIEUX, _Lettres sur l'Italie_, p. 113. The removal of the shelter afforded by the brushwood and the pendulous branches of trees permits drying and chilling winds to parch and cool the ground, and of course injuriously affects the growth of the wood. But this is not all. The tread of quadrupeds exposes and bruises the roots of the trees, which often die from this cause, as any one may observe by following the paths made by cattle through woodlands. [300] I have remarked elsewhere that most insects which deposit and hatch their eggs in the wood of the natural forest confine themselves to dead trees. Not only is this the fact, but it is also true that many of the borers attack only freshly cut timber. Their season of labor is a short one, and unless the tree is cut during this period, it is safe from them. In summer you may hear them plying their augers in the wood of a young pine with soft green bark, as you sit upon its trunk, within a week after it has been felled, but the windfalls of the winter lie uninjured by the worm and even undecayed for centuries. In the pine woods of New England, after the regular lumberman has removed the standing trees, these old trunks are hauled out from the mosses and leaves which half cover them, and often furnish excellent timber. The slow decay of such timber in the woods, it may be remarked, furnishes another proof of the uniformity of temperature and humidity in the forest, for the trunk of a tree lying on grass or plough land, and of course exposed to all the alternations of climate, hardly resists complete decomposition for a generation. The forests of Europe exhibit similar facts. Wessely, in a description of the primitive wood of Neuwald in Lower Austria, says that the windfalls required from 150 to 200 years for entire decay.-_-Die Oesterreichischen Alpenländer und ihre Forste_, p. 312. [301] VAUPELL, _Bögens Indvandring i de Danske Skove_, pp. 29, 46. Vaupell further observes, on the page last quoted: "The removal of leaves is injurious to the forest, not only because it retards the growth of trees, but still more because it disqualifies the soil for the production of particular species. When the beech languishes, and the development of its branches is less vigorous and its crown less spreading, it becomes unable to resist the encroachments of the fir. This latter tree thrives in an inferior soil, and being no longer stifled by the thick foliage of the beech, it spreads gradually through the wood, while the beech retreats before it and finally perishes." The study of the natural order of succession in forest trees is of the utmost importance in sylviculture, because it guides us in the selection of the species to be employed in planting a new or restoring a decayed forest. When ground is laid bare both of trees and of vegetable mould, and left to the action of unaided and unobstructed nature, she first propagates trees which germinate and grow only under the influence of a full supply of light and air, and then, in succession, other species, according to their ability to bear the shade and their demand for more abundant nutriment. In Northern Europe, the larch, the white birch, the aspen, first appear; then follow the maple, the alder, the ash, the fir; then the oak and the linden; and then the beech. The trees called by these respective names in the United States are not specifically the same as their European namesakes, nor are they always even the equivalents of these latter, and therefore the order of succession in America would not be precisely as indicated by the foregoing list, but it nevertheless very nearly corresponds to it. It is thought important to encourage the growth of the beech in Denmark and Northern Germany, because it upon the whole yields better returns than other trees, and particularly because it appears not to exhaust, but on the contrary to enrich the soil; for by shedding its leaves it returns to it most of the nutriment it has drawn from it, and at the same time furnishes a solvent which aids materially in the decomposition of its mineral constituents. When the forest is left to itself, the order of succession is constant, and its occasional inversion is always explicable by some human interference. It is curious that the trees which require most light are content with the poorest soils, and _vice versa_. The trees which first appear are also those which propagate themselves farthest to the north. The birch, the larch, and the fir bear a severer climate than the oak, the oak than the beech. "These parallelisms," says Vaupell, "are very interesting, because they are entirely independent of each other," and each prescribes the same order of succession.--_Bögens Indvandring_, p. 42. [302] When vigorous young locusts, of two or three inches in diameter, are polled, they throw out a great number of very thick-leaved shoots, which arrange themselves in a globular head, so unlike the natural crown of the acacia, that persons familiar only with the untrained tree often take them for a different species. [303] The two ideas expressed in the text are not exactly equivalent, because, though the consumption of animal food diminishes the amount of vegetable aliment required for human use, yet the animals themselves consume a great quantity of grain and roots grown on ground ploughed and cultivated as regularly and as laboriously as any other. The 170,000,000 bushels of oats raised in the United States in 1860, and fed to the 6,000,000 horses, the potatoes, the turnips, and the maize employed in fattening the oxen, the sheep, and the swine slaughtered the same year, occupied an extent of ground which, cultivated by hand labor and with Chinese industry and skill, would probably have produced a quantity of vegetable food equal in alimentary power to the flesh of the quadrupeds killed for domestic use. Hence, so far as the naked question of _amount_ of aliment is concerned, the meadows and the pastures might as well have remained in the forest condition. [304] According to Clavé (_Études_, p. 159), the net revenue from the forests of the state in France, making no allowance for interest on the capital represented by the forest, is two dollars per acre. In Saxony it is about the same, though the cost of administration is twice as much as in France; in Würtemberg it is about a dollar an acre; and in Prussia, where half the income is consumed in the expenses of administration, it sinks to less than half a dollar. This low rate in Prussia is partly explained by the fact that a considerable proportion of the annual product of wood is either conceded to persons claiming prescriptive rights, or sold, at a very small price, to the poor. Taking into account the capital invested in forest land, and adding interest upon it, Pressler calculates that a pine wood, managed with a view to felling it when eighty years old, would yield only one eighth of one per cent. annual profit; a fir wood, at one hundred years, one sixth of one per cent.; a beech wood, at one hundred and twenty years, one fourth of one per cent. The same author (p. 335) gives the net income of the New forest in England, over and above expenses, interest not computed, at twenty-five cents per acre only. In America, where no expense is bestowed upon the woods, the annual growth would generally be estimated much higher. [305] It is rare that a middle-aged American dies in the house where he was born, or an old man even in that which he has built; and this is scarcely less true of the rural districts, where every man owns his habitation, than of the city, where the majority live in hired houses. This life of incessant flitting is unfavorable for the execution of permanent improvements of every sort, and especially of those which, like the forest, are slow in repaying any part of the capital expended in them. It requires a very generous spirit in a landholder to plant a wood on a farm he expects to sell, or which he knows will pass out of the hands of his descendants at his death. But the very fact of having begun a plantation would attach the proprietor more strongly to the soil for which he had made such a sacrifice; and the paternal acres would have a greater value in the eyes of a succeeding generation, if thus improved and beautified by the labors of those from whom they were inherited. Landed property, therefore, the transfer of which is happily free from every legal impediment or restriction in the United States, would find, in the feelings thus prompted, a moral check against a too frequent change of owners, and would tend to remain long enough in one proprietor or one family to admit of gradual improvements which would increase its value both to the possessor and to the state. [306] It has been often asserted by eminent writers that a part of the fens in Lincolnshire was reclaimed by sea dikes under the government of the Romans. I have found no ancient authority in support of this allegation, nor can I refer to any passage in Roman literature in which sea dikes are expressly mentioned otherwise than as walls or piers, except that in Pliny (_Hist. Nat._ xxxvi, 24), where it is said that the Tyrrhenian sea was excluded from the Lucrine lake by dikes. [307] A friend has recently suggested to me an interesting illustration of the applicability of military instrumentalities to pacific art. The sale of gunpowder in the United States, he informs me, is smaller since the commencement of the present rebellion than before, because the war has caused the suspension of many public and private improvements, in the execution of which great quantities of powder were used for blasting. It is alleged that the same observation was made in France during the Crimean war, and that, in general, not ten per cent. of the powder manufactured on either side of the Atlantic is employed for military purposes. It is a fact not creditable to the moral sense of modern civilization, that very many of the most important improvements in machinery and the working of metals have originated in the necessities of war, and that man's highest ingenuity has been shown, and many of his most remarkable triumphs over natural forces achieved, in the contrivance of engines for the destruction of his fellow man. The military material employed by the first Napoleon has become, in less than two generations, nearly as obsolete as the sling and stone of the shepherd, and attack and defence now begin at distances to which, half a century ago, military reconnoissances hardly extended. Upon a partial view of the subject, the human race seems destined to become its own executioner--on the one hand, exhausting the capacity of the earth to furnish sustenance to her taskmaster; on the other, compensating diminished production by inventing more efficient methods of exterminating the consumer. But war develops great civil virtues, and brings into action a degree and kind of physical energy which seldom fails to awaken a new intellectual life in a people that achieves great moral and political results through great heroism and endurance and perseverance. Domestic corruption has destroyed more nations than foreign invasion, and a people is rarely conquered till it has deserved subjugation. [308] STARING, _Voormaals en Thans_, p. 150. [309] Idem, p. 163. Much the largest proportion of the lands so reclaimed, though for the most part lying above low-water tidemark, are at a lower level than the Lincolnshire fens, and more subject to inundation from the irruptions of the sea. [310] _Die Inseln und Marschen der Herzogthümer Schleswig und Holstein_, iii, p. 151. [311] The purely agricultural island of Pelworm, off the coast of Schleswig, containing about 10,000 acres, annually expends for the maintenance of its dikes not less than £6,000 sterling, or nearly $30,000.--J. G. KOHL, _Inseln und Marschen Schleswig's und Holstein's_, ii, p. 394. The original cost of the dikes of Pelworm is not stated. "The greatest part of the province of Zeeland is protected by dikes measuring 250 miles in length, the maintenance of which costs, in ordinary years, more than a million guilders [above $400,000]. * * * The annual expenditure for dikes and hydraulic works in Holland is from five to seven million guilders" [$2,000,000 to $2,800,000].--WILD, _Die Niederlande_, i, p. 62. One is not sorry to learn that the Spanish tyranny in the Netherlands had some compensations. The great chain of ring dikes which surrounds a large part of Zeeland is due to the energy of Caspar de Robles, the Spanish governor of that province, who in 1570 ordered the construction of these works at the public expense, as a substitute for the private embankments which had previously partially served the same purpose.--WILD, _Die Niederlande_, i, p. 62. [312] STARING, _Voormaals en Thans_, p. 163. [313] _Voormaals en Thans_, pp. 150, 151. [314] STARING, _Voormaals en Thans_, p. 152. Kohl states that the peninsula of Diksand on the coast of Holstein consisted, at the close of the last century, of several islands measuring together less than five thousand acres. In 1837 they had been connected with the mainland, and had nearly doubled in area.--_Inseln u. Marschen Schlesw. Holst._, iii, p. 262. [315] The most instructive and entertaining of tourists, J. G. Kohl--so aptly characterized by Davies as the "Herodotus of modern Europe"--furnishes a great amount of interesting information on the dikes of the Low German seacoast, in his _Inseln und Marschen der Herzogthümer Schleswig und Holstein_. I am acquainted with no popular work on this subject which the reader can consult with greater profit. See also STARING, _Voormaals en Thans_, and _De Bodem van Nederland_, on the dikes of the Netherlands. [316] The inclination varies from one foot rise in four of base to one foot in fourteen.--KOHL, iii, p. 210. [317] The dikes are sometimes founded upon piles, and sometimes protected by one or more rows of piles driven deeply down into the bed of the sea in front of them. "Triple rows of piles of Scandinavian pine," says Wild, "have been driven down along the coast of Friesland, where there are no dunes, for a distance of one hundred and fifty miles. The piles are bound together by strong cross timbers and iron clamps, and the interstices filled with stones. The ground adjacent to the piling is secured with fascines, and at exposed points heavy blocks of stone are heaped up as an additional protection. The earth dike is built behind the mighty bulwark of this breakwater, and its foot also is fortified with stones." * * * "The great Helder dike is about five miles long and forty feet wide at the top, along which runs a good road. It slopes down two hundred feet into the sea, at an angle of forty degrees. The highest waves do not reach the summit, the lowest always cover its base. At certain distances, immense buttresses, of a height and width proportioned to those of the dike, and even more strongly built, run several hundred feet out into the rolling sea. This gigantic artificial coast is entirely composed of Norwegian granite."--WILD, _Die Niederlande_, i, pp. 61, 62. [318] The shaking of the ground, even when loaded with large buildings, by the passage of heavy carriages or artillery, or by the march of a body of cavalry or even infantry, shows that such causes may produce important mechanical effects on the condition of the soil. The bogs in the Netherlands, as in most other countries, contain large numbers of fallen trees, buried to a certain depth by earth and vegetable mould. When the bogs are dry enough to serve as pastures, it is observed that trunks of these ancient trees rise of themselves to the surface. Staring ascribes this singular phenomenon to the agitation of the ground by the tread of cattle. "When roadbeds," observes he, "are constructed of gravel and pebbles of different sizes, and these latter are placed at the bottom without being broken and rolled hard together, they are soon brought to the top by the effect of travel on the road. Lying loosely, they undergo some motion from the passage of every wagon wheel and the tread of every horse that passes over them. This motion is an oscillation or partial rolling, and as one side of a pebble is raised, a little fine sand or earth is forced under it, and the frequent repetition of this process by cattle or carriages moving in opposite directions brings it at last to the surface. We may suppose that a similar effect is produced on the stems of trees in the bogs by the tread of animals."--_De Bodem van Nederland_, i, pp. 75, 76. It is observed in the Northern United States, that when soils containing pebbles are cleared and cultivated, and the stones removed from the surface, new pebbles, and even bowlders of many pounds weight, continue to show themselves above the ground, every spring, for a long series of years. In clayey soils the fence posts are thrown up in a similar way, and it is not uncommon to see the lower rail of a fence thus gradually raised a foot or even two feet above the ground. This rising of stones and fences is popularly ascribed to the action of the severe frosts of that climate. The expansion of the ground, in freezing, it is said, raises its surface, and, with the surface, objects lying near or connected with it. When the soil thaws in the spring, it settles back again to its former level, while the pebbles and posts are prevented from sinking as low as before by loose earth which has fallen under them. The fact that the elevation spoken of is observed only in the spring, gives countenance to this theory, which is perhaps applicable also to the cases stated by Staring, and it is probable that the two causes above assigned concur in producing the effect. The question of the subsidence of the Netherlandish coast has been much discussed. Not to mention earlier geologists, Venema, in several essays, and particularly in _Het Dalen van de Noordelijke Kuststreken van ons Land_, 1854, adduces many facts and arguments to prove a slow sinking of the northern provinces of Holland. Laveleye (_Affaissement du sol et envasement des fleuves survenus dans les temps historiques_, 1859), upon a still fuller investigation, arrives at the same conclusion. The eminent geologist Staring, however, who briefly refers to the subject in _De Bodem van Nederland_, i, p. 356 _et seqq._, does not consider the evidence sufficient to prove anything more than the sinking of the surface of the polders from drying and consolidation. [319] The elevation of the lands enclosed by dikes--or _polders_, as they are called in Holland--above low water mark, depends upon the height of the tides, or, in other words, upon, the difference between ebb and flood. The tide cannot deposit earth higher than it flows, and after the ground is once enclosed, the decay of the vegetables grown upon it and the addition of manures do not compensate the depression occasioned by drying and consolidation. On the coast of Zeeland and the islands of South Holland, the tides, and of course the surface of the lands deposited by them, are so high that the polders can be drained by ditching and sluices, but at other points, as in the enclosed grounds of North Holland on the Zuiderzee, where the tide rises but three feet or even less, pumping is necessary from the beginning.--STARING, _Voormaals en Thans_, p. 152. [320] The principal engine--called the Leeghwater, from the name of an engineer who had proposed the draining of the lake in 1641--was of 500 horse power, and drove eleven pumps making six strokes per minute. Each pump raised six cubic mètres, or nearly eight cubic yards of water to the stroke, amounting in all to 23,760 cubic mètres, or above 31,000 cubic yards, the hour.--WILD, _Die Niederlande_, i, p. 87. [321] In England and New England, where the marshes have been already drained or are of comparatively small extent, the existence of large floating islands seems incredible, and has sometimes been treated as a fable, but no geographical fact is better established. Kohl (_Inseln und Marschen Schleswig-Holsteins_, iii, p. 309) reminds us that Pliny mentions among the wonders of Germany the floating islands, covered with trees, which met the Roman fleets at the mouths of the Elbe and the Weser. Our author speaks also of having visited, in the territory of Bremen, floating moors, bearing not only houses but whole villages. At low stages of the water these moors rest upon a bed of sand, but are raised from six to ten feet by the high water of spring, and remain afloat until, in the course of the summer, the water beneath is exhausted by evaporation and drainage, when they sink down upon the sand again. See _Appendix_, No. 40. Staring explains, in an interesting way, the whole growth, formation, and functions of floating fens or bogs, in his very valuable work, _De Bodem van_ _Nederland_, i, pp. 36-43. The substance of his account is as follows: The first condition for the growth of the plants which compose the substance of turf and the surface of the fens, is stillness of the water. Hence they are not found in running streams, nor in pools so large as to be subject to frequent agitation by the wind. For example, not a single plant grew in the open part of the Lake of Haarlem, and fens cease to form in all pools as soon as, by the cutting of the turf for fuel or other purposes, their area is sufficiently enlarged to be much acted on by wind. When still water above a yard deep is left undisturbed, aquatic plants of various genera, such us Nuphar, Nymphæa, Limnanthemum, Stratiotes, Polygonum, and Potamogeton, fill the bottom with roots and cover the surface with leaves. Many of the plants die every year, and prepare at the bottom a soil fit for the growth of a higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex, Lythrum, Pedicularis, Spiræa, Polystichum, Comarum, Caltha, &c., &c. In the course of twenty or thirty years the muddy bottom is filled with roots of aquatic and marsh plants, which are lighter than water, and if the depth is great enough to give room for detaching this vegetable network, a couple of yards for example, it rises to the surface, bearing with it, of course, the soil formed above it by decay of stems and leaves. New genera now appear upon the mass, such as Carex, Menyanthes, and others, and soon thickly cover it. The turf has now acquired a thickness of from two to four feet, and is called in Groningen _lad_; in Friesland, _til_, _tilland_, or _drijftil_; in Overijssel, _krag_; and in Holland, _rietzod_. It floats about as driven by the wind, gradually increasing in thickness by the decay of its annual crops of vegetation, and in about half a century reaches the bottom and becomes fixed. If it has not been invaded in the mean time by men or cattle, trees and arborescent plants, Alnus, Salix, Myrica, &c. appear, and these contribute to hasten the attachment of the turf to the bottom, both by their weight and by sending their roots quite through into the ground. This is the regular method employed by nature for the gradual filling up of shallow lakes and pools, and converting them first into morass and then into dry land. Whenever therefore man removes the peat or turf, he exerts an injurious geographical agency, and, as I have already said, there is no doubt that the immense extension of the inland seas of Holland in modern times is owing to this and other human imprudences. "Hundreds of hectares of floating pastures," says our author, "which have nothing in their appearance to distinguish them from grass lands resting on solid bog, are found in Overijssel, in North Holland and near Utrecht. In short, they occur in all deep bogs, and wherever deep water is left long undisturbed." In one case, a floating island, which had attached itself to the shore, continued to float about for a long time after it was torn off by a flood, and was solid enough to keep a pond of fresh water upon it sweet, though the water in which it was swimming had become brackish from the irruption of the sea. After the hay is cut, cattle are pastured upon those islands, and they sometimes have large trees growing upon them. When the turf or peat has been cut, leaving water less than a yard deep, Equisetum limosum grows at once, and is followed by the second class of marsh plants mentioned above. Their roots do not become detached from the bottom in such shallow water, but form ordinary turf or peat. These processes are so rapid that a thickness of from three to six feet of turf is formed in half a century, and many men have lived to mow grass where they had fished in their boyhood, and to cut turf twice in the same spot. Captain Gilliss says that before Lake Taguataga in Chili was drained, there were in it islands composed of dead plants matted together to a thickness of from four to six feet, and with trees of medium size growing upon them. These islands floated before the wind "with their trees and browsing cattle."--_United States Naval Astronomical Expedition to the Southern Hemisphere_, i, pp. 16, 17. [322] A considerable work of this character is mentioned by Captain Gilliss as having been executed in Chili, a country to which we should have hardly looked for an improvement of such a nature. The Lake Taguataga was partially drained by cutting through a narrow ridge of land, not at the natural outlet, but upon one side of the lake, and eight thousand acres of land covered by it were gained for cultivation.--_U. S. Naval Astronomical Expedition to the Southern Hemisphere_, i, pp. 16, 17. [323] _Économie Rurale de la France_, p. 289. [324] In a note on a former page of this volume I noticed an observation of Jacini, to the effect that the great Italian lakes discharge themselves partly by infiltration beneath the hills which bound them. The amount of such infiltration must depend much upon the hydrostatic pressure on the walls of the lake basins, and, of course, the lowering of the surface of these lakes, by diminishing that pressure, would diminish also the infiltration. It is now proposed to lower the level of the Lake of Como some feet by deepening its outlet. It is possible that the effect of this may manifest itself in a diminution of the water in springs and _fontanili_ or artesian wells in Lombardy. See _Appendix_, No. 43. [325] Simonde, speaking of the Tuscan canals, observes: "But inundations are not the only damage caused by the waters to the plains of Tuscany. Raised, as the canals are, above the soil, the water percolates through their banks, penetrates every obstruction, and, in spite of all the efforts of industry, sterilizes and turns to morasses fields which nature and the richness of the soil seemed to have designed for the most abundant harvests. In ground thus pervaded with moisture, or rendered _cold_, as the Tuscans express it, by the filtration of the canal water, the vines and the mulberries, after having for a few years yielded fruit of a saltish taste, rot and perish. The wheat decays in the ground, or dies as soon as it sprouts. Winter crops are given up, and summer cultivation tried for a time; but the increasing humidity, and the saline matter communicated to the earth--which affects the taste of all its products, even to the grasses, which the cattle refuse to touch--at last compel the husbandman to abandon his fields, and leave uncultivated a soil that no longer repays his labor."--_Tableau de l'Agriculture Toscane._ pp. 11, 12. [326] _Physikalische Geographie_, p. 288. Draining by driving down stakes, mentioned in a note in a chapter on the woods, _ante_, is a process of the same nature. [327] "The simplest backwoodsman knows by experience that all cultivation is impossible in the neighborhood of bogs and marshes. Why is a crop near the borders of a marsh cut off by frost, while a field upon a hillock, a few stone's throws from it, is spared?"--LARS LEVI LÆSTADIUS, _Om Uppodlingar i Lappmarken_, pp. 69, 74. [328] Babinet condemns even the general draining of marshes. "Draining," says he, "has been much in fashion for some years. It has been a special object to dry and fertilize marshy grounds. My opinion has always been that excessive dryness is thus produced, and that other soils in the neighborhood are sterilized in proportion." [329] I ought perhaps to except the Mexicans and the Peruvians, whose arts and institutions are not yet shown to be historically connected with those of any more ancient people. The lamentable destruction of so many memorials of these tribes, by the ignorance and bigotry of the so-called Christian barbarians who conquered them, has left us much in the dark as to many points of their civilization; but they seem to have reached that stage where continued progress in knowledge and in power over nature is secure, and a few more centuries of independence might have brought them to originate for themselves most of the great inventions which the last four centuries have bestowed upon man. [330] The necessity of irrigation in the great alluvial plain of Northern Italy is partly explained by the fact that the superficial stratum of fine earth and vegetable mould is very extensively underlaid by beds of pebbles and gravel brought down by mountain torrents at a remote epoch. The water of the surface soil drains rapidly down into these loose beds, and passes off by subterranean channels to some unknown point of discharge; but this circumstance alone is not a sufficient solution. Is it not possible that the habits of vegetables, grown in countries where irrigation has been immemorially employed, have been so changed that they require water under conditions of soil and climate where their congeners, which have not been thus indulgently treated, do not? There are some atmospheric phenomena in Northern Italy, which an American finds it hard to reconcile with what he has observed in the United States. To an American eye, for instance, the sky of Piedmont, Lombardy, and the northern coast of the Mediterranean, is always whitish and curdled, and it never has the intensity and fathomless depth of the blue of his native heavens. And yet the heat of the sun's rays, as measured by sensation, and, at the same time, the evaporation, are greater than they would be with the thermometer at the same point in America. I have frequently felt in Italy, with the mercury below 60° Fahrenheit, and with a mottled and almost opaque sky, a heat of solar irradiation which I can compare to nothing but the scorching sensation experienced in America at a temperature twenty degrees higher, during the intervals between showers, or before a rain, when the clear blue of the sky seems infinite in depth and transparency. Such circumstances may create a necessity for irrigation where it would otherwise be superfluous, if not absolutely injurious. In speaking of the superior apparent clearness of the _sky_ in America, I confine myself to the concave vault of the heavens, and do not mean to assert that terrestrial objects are generally visible at greater distances in the United States than in Italy. Indeed I am rather disposed to maintain the contrary; for though I know that the lower strata of the atmosphere in Europe never equal in transparency the air near the earth in New Mexico, Peru, and Chili, yet I think the accidents of the coast line of the Riviera, as, for example, between Nice and La Spezia, and those of the incomparable Alpine panorama seen from Turin, are distinguishable at greater distances than they would be in the United States. [331] In Egypt, evaporation and absorption by the earth are so rapid, that all annual crops require irrigation during the whole period of their growth. As fast as the water retires by the subsidence of the annual inundation, the seed is sown upon the still moist uncovered soil, and irrigation begins at once. Upon the Nile, you hear the creaking of the water wheels, and sometimes the movement of steam pumps, through the whole night, while the poorer cultivators unceasingly ply the simple _shadoof_, or bucket-and-sweep, laboriously raising the water from trough to trough by as many as six or seven stages when the river is low. The bucket is of flexible leather, with a stiff rim, and is emptied into the trough, not by inverting it like a wooden bucket, but by putting the hand beneath and pushing the bottom up till the water all runs out over the brim, or, in other words, by turning the vessel inside out. The quantity of water thus withdrawn from the Nile is enormous. Most of this is evaporated directly from the surface or the superficial strata, but some moisture percolates down and oozes through the banks into the river again, while a larger quantity sinks till it joins the slow current of infiltration by which the Nile water pervades the earth of the valley to the distance, at some points, of not less than fifty miles. [332] "Forests," "woods," and "groves," are very frequently mentioned in the Old Testament as existing at particular places, and they are often referred to by way of illustration, as familiar objects. "Wood" is twice spoken of as a material in the New Testament, but otherwise--at least according to Cruden--not one of the above words occurs in that volume. This interesting fact, were other evidence wanting, would go far to prove that a great change had taken place in this respect between the periods when the Old Testament and the New were respectively composed; for the scriptural writers, and the speakers introduced into their narratives, are remarkable for their frequent allusions to the natural objects and the social and industrial habits which characterized their ages and their country. See _Appendix_, No. 44. Solomon anticipated Chevandier in the irrigation of forest trees: "I made me pools of water, to water therewith the wood that bringeth forth trees."--_Ecclesiastes_ ii, 6. [333] One of these, upon Mount Hor, two stories in height, is still in such preservation that I found not less than ten feet of water in it in the month of June, 1851. The brook Ain Musa, which runs through the city of Petra and finally disappears in the sands of Wadi el Araba, is a considerable river in winter, and the inhabitants of that town were obliged to excavate a tunnel through the rock near the right bank, just above the upper entrance of the Sik, to discharge a part of its swollen current. The sagacity of Dr. Robinson detected the necessity of this measure, though the tunnel, the mouth of which was hidden by brushwood, was not discovered till some time after his visit. I even noticed unequivocal remains of a sluice by which the water was diverted to the tunnel near the arch that crosses the Sik. Immense labor was also expended in widening the natural channel at several points below the town, to prevent the damming up and setting back of the water--a fact I believe not hitherto noticed by travellers. The Fellahheen above Petra still employ the waters of Ain Musa for irrigation, and in summer the superficial current is wholly diverted from its natural channel for that purpose. At this season, the bed of the brook, which is composed of pebbles, gravel, and sand, is dry in the Sik and through the town; but the infiltration is such that water is generally found by digging to a small depth in the channel. Observing these facts in a visit to Petra in the summer, I was curious to know whether the subterranean waters escaped again to daylight, and I followed the ravine below the town for a long distance. Not very far from the upper entrance of the ravine, arborescent vegetation appeared upon its bottom, and as soon as the ground was well shaded, a thread of water burst out. This was joined by others a little lower down, and, at the distance of a mile from the town, a strong current was formed and ran down toward Wadi el Araba. [334] The authorities differ as to the extent of the cultivable and the cultivated soil of Egypt. Lippincott's, or rather Thomas and Baldwin's, _Gazetteer_--a work of careful research--estimates "the whole area comprised in the valley [below the first cataract] and delta," at 11,000 square miles. Smith's _Dictionary of the Bible_, article "Egypt," says: "Egypt has a superficies of about 9,582 square geographical miles of soil, which the Nile either does or can water and fertilize. This computation includes the river and lakes as well as sundry tracts which can be inundated, and the whole space either cultivated or fit for cultivation is no more than about 5,626 square miles." By geographical mile is here meant, I suppose, the nautical mile of sixty to an equatorial degree, or about 2,025 yards. The whole area, then, by this estimate, is 12,682 square statute or English miles, that of the space "cultivated or fit for cultivation," 7,447. Smith's _Dictionary of Greek and Roman Geography_, article "Ægyptus," gives 2,255 square miles as the area of the valley between Syene and the bifurcation of the Nile, exclusive of the Fayoom, which is estimated at 340. The area of the Delta is stated at 1,976 square miles between the main branches of the river, and, including the irrigated lands east and west of those branches, at 4,500 square miles. This latter work does not inform us whether these are statute or nautical miles, but nautical miles must be intended. Other writers give estimates differing considerably from those just cited. The latest computations I have seen are those in the first volume of Kremer's _Ægypten_, 1863. This author (pp. 6, 7) assigns to the Delta an area of 200 square German geographical miles (fifteen to the degree); to all Lower Egypt, including, of course, the Delta, 400 such miles. These numbers are equal, respectively, to 4,239 and 8,478 square statute miles, and the great lagoons are embraced in the areas computed. Upper Egypt (above Cairo) is said (p. 11) to contain 4,000,000 feddan of _culturfläche_, or cultivable land. The feddan is stated (p. 37) to contain 7,333 square piks, the pik being 75 centimètres, and it therefore corresponds almost exactly to the English acre. Hence, according to Kremer, the cultivable soil of Upper Egypt is 6,250 square statute miles, or twice as much as the whole area of the valley between Syene and the bifurcation of the Nile, according to Smith's _Dictionary of Greek and Roman Geography_. I suspect that 4,000,000 feddan is erroneously given as the cultivable area of Upper Egypt alone, when in fact it should be taken for the arable surface of both Lower and Upper Egypt; for from the statistical tables in the same volume, it appears that 3,317,125 feddan, or 5,253 square statute miles, were cultivated, in both geographical divisions, in the year referred to in the tables, the date of which is not stated. The area which the Nile would now cover at high water, if left to itself, is greater than in ancient times, because the bed of the river has been elevated, and consequently the lateral spread of the inundation increased. See SMITH'S _Dictionary of Geography_, article "Ægyptus." But the industry of the Egyptians in the days of the Pharaohs and the Ptolomies carried the Nile-water to large provinces which have now been long abandoned and have relapsed into the condition of a desert. "Anciently," observes the writer of the article "Egypt" in Smith's _Dictionary of the Bible_, "2,735 square miles more [about 3,700 square statute miles] may have been cultivated. In the best days of Egypt, probably all the land was cultivated that could be made available for agricultural purposes, and hence we may estimate the ancient arable area of that country at not less than 11,000 square statute miles, or fully double its present extent." [335] A canal has been constructed, and new ones are in progress, to convey water from the Nile to the city of Suez, and to various points on the line of the ship canal, with the double purpose of supplying fresh water to the inhabitants and laborers, and of irrigating the adjacent soil. The area of land which may be thus reclaimed and fertilized is very large, but the actual quantity which it will be found economically expedient to bring under cultivation cannot now be determined. [336] The so-called spring at Heliopolis is only a thread of water infiltrated from the Nile or the canals. [337] The date and the doum palm, the _sont_ and many other acacias, the caroub, the sycamore, and other trees, grow well in Egypt without irrigation, and would doubtless spread through the entire valley in a few years. [338] Wilkinson has shown that the cultivable soil of Egypt has not been diminished by encroachment of the desert sands, or otherwise, but that, on the contrary, it must have been increased since the age of the Pharaohs. The Gotha _Almanac_ for 1862 states the population of Egypt in 1859 at 5,125,000 souls; but this must be a great exaggeration, even supposing the estimate to include the inhabitants of Nubia, and of much other territory not geographically belonging to Egypt. In general, the population of that country has been estimated at something more than three millions, or about six hundred to the square mile; but with a better government and better social institutions, the soil would sustain a much greater number, and in fact it is believed that in ancient times its inhabitants were twice, perhaps even thrice, as numerous as at present. Wilkinson (_Handbook for Travellers in Egypt_, p. 10) observes that the total population, which two hundred years ago was estimated at 4,000,000, amounted till lately only to about 1,800,000 souls, having been reduced since 1800 from 2,500,000 to that number. [339] Ritter supposes Egypt to have been a sandy desert when it was first occupied by man. "The first inhabitant of the sandy valley of the Nile was a desert dweller, as his neighbors right and left, the Libyan, the nomade Arab, still are. But the civilized people of Egypt transformed, by canals, the waste into the richest granary of the world; they liberated themselves from the shackles of the rock and sand desert, in the midst of which, by a wise distribution of the fluid through the solid geographical form, by irrigation in short, they created a region of culture most rich in historical monuments."--_Einleitung zur allgemeinen vergleichenden Geographie_, pp. 165, 166. This view seems to me highly improbable; for though, by canals and embankments, man has done much to modify the natural distribution of the waters of the Nile, and possibly has even transferred its channel from one side of the valley to the other, yet the annual inundation is not his work, and the river must have overflowed its banks and carried spontaneous vegetation with its waters, as well before as since Egypt was first occupied by the human family. There is, indeed, some reason to suppose that man lived upon the banks of the Nile when its channel was much lower, and the spread of its inundations much narrower than at present; but wherever its flood reached, there the forest would propagate itself, and its shores are much more likely to have been morasses than sands. [340] _Memorie sui progetti per l'estensione dell' Irrigazione, etc., il Politecnico_, for January, 1863, p. 6. [341] NIEL, _L'Agriculture des États Sardes_, p. 232. [342] NIEL, _Agriculture des États Sardes_, p. 237. Lombardini's computation just given allows eighty-one cubic mètres per day to the hectare, which, supposing the season of irrigation to be one hundred days, is equal to a precipitation of thirty-two inches. But in Lombardy, water is applied to some crops during a longer period than one hundred days; and in the _marcite_ it flows over the ground even in winter. According to Boussingault (_Économie Rurale_, ii, p. 246) grass grounds ought to receive, in Germany, twenty-one centimètres of water per week, and with less than half that quantity it is not advisable to incur the expense of supplying it. The ground is irrigated twenty-five or thirty times, and if the full quantity of twenty-one centimètres is applied, it receives about two hundred inches of water, or six times the total amount of precipitation. Puvis, quoted by Boussingault, after much research comes to the conclusion that a proper quantity is twenty centimètres applied twenty-five or thirty times, which corresponds with the estimate just stated. Puvis adds--and, as our author thinks, with reason--that this amount might be doubled without disadvantage. Boussingault observes that rain water is vastly more fertilizing than the water of irrigating canals, and therefore the supply of the latter must be greater. This is explained partly by the different character of the substances held in solution or suspension by the waters of the earth and of the sky, partly by the higher temperature of the latter, and, possibly, partly also by the mode of application--the rain being finely divided in its fall or by striking plants on the ground, river water flowing in a continuous sheet. The temperature of the water is thought even more important than its composition. The sources which irrigate the _marcite_ of Lombardy--meadows so fertile that less than an acre furnishes grass for a cow the whole year--are very warm. The ground watered by them never freezes, and a first crop, for soiling, is cut from it in January or February. The Canal Cavour, just now commenced--which is to take its supply from the Po at Chivasso, fourteen or fifteen miles below Turin--will furnish water of much higher fertilizing power than that derived from the Dora Baltea and the Sesia, both because it is warmer, and because it transports a more abundant and a richer sediment than the latter streams, which are fed by Alpine icefields and melting snows, and which flow, for long distances, in channels ground smooth and bare by ancient glaciers, and not now contributing much vegetable mould or fine slime to their waters. [343] It belongs rather to agriculture than to geography to discuss the quality of the crops obtained by irrigation, or the permanent effects produced by it on the productiveness of the soil. There is no doubt, however, that all crops which can be raised without watering are superior in flavor and in nutritive power to those grown by the aid of irrigation. Garden vegetables, particularly, profusely watered, are so insipid as to be hardly eatable. Wherever irrigation is practised, there is an almost irresistible tendency, especially among ignorant cultivators, to carry it to excess; and in Piedmont and Lombardy, if the supply of water is abundant, it is so liberally applied as sometimes not only to injure the quality of the product, but to drown the plants and diminish the actual weight of the crop. Professor Liebig, in his _Modern Agriculture_, says: "There is not to be found in chemistry a more wonderful phenomenon, one which more confounds all human wisdom, than is presented by the soil of a garden or field. By the simplest experiment, any one may satisfy himself that rain water filtered through field or garden soil does not dissolve out a trace of potash, silicic acid, ammonia, or phosphoric acid. The soil does not give up to the water one particle of the food of plants which it contains. The most continuous rains cannot remove from the field, except mechanically, any of the essential constituents of its fertility." "The soil not only retains firmly all the food of plants which is actually in it, but its power to preserve all that may be useful to them extends much farther. If rain or other water holding in solution ammonia, potash, and phosphoric and silicic acids, be brought in contact with soil, these substances disappear almost immediately from the solution; the soil withdraws them from the water. Only such substances are completely withdrawn by the soil as are indispensable articles of food for plants; all others remain wholly or in part in solution." The first of the paragraphs just quoted is not in accordance with the alleged experience of agriculturists in those parts of Italy where irrigation is most successfully applied. They believe that the constituents of vegetable growth are washed out of the soil by excessive and long-continued watering. They consider it also established as a fact of observation, that water which has flowed through or over rich ground is far more valuable for irrigation than water from the same source, which has not been impregnated with fertilizing substances by passing through soils containing them; and, on the other hand, that water, rich in the elements of vegetation, parts with them in serving to irrigate a poor soil, and is therefore less valuable as a fertilizer of lower grounds to which it may afterward be conducted. The practice of irrigation--except in mountainous countries where springs and rivulets are numerous--is attended with very serious economical, social, and political evils. The construction of canals and their immensely ramified branches, and the grading and scarping of the ground to be watered, are always expensive operations, and they very often require an amount of capital which can be commanded only by the state, by moneyed corporations, or by very wealthy proprietors; the capacity of the canals must be calculated with reference to the area intended to be irrigated, and when they and their branches are once constructed, it is very difficult to extend them, or to accommodate any of their original arrangements to changes in the condition of the soil, or in the modes or objects of cultivation; the flow of the water being limited by the abundance of the source or the capacity of the canals, the individual proprietor cannot be allowed to withdraw water at will, according to his own private interest or convenience, but both the time and the quantity of supply must be regulated by a general system applicable, as far as may be, to the whole area irrigated by the same canal, and every cultivator must conform his industry to a plan which may be quite at variance with his special objects or with his views of good husbandry. The clashing interests and the jealousies of proprietors depending on the same means of supply are a source of incessant contention and litigation, and the caprices or partialities of the officers who control, or of contractors who farm the canals, lead not unfrequently to ruinous injustice toward individual landholders. These circumstances discourage the division of the soil into small properties, and there is a constant tendency to the accumulation of large estates of irrigated land in the hands of great capitalists, and consequently to the dispossession of the small cultivators, who pass from the condition of owners of the land to that of hireling tillers. The farmers are no longer yeomen, but peasants. Having no interest in the soil which composes their country, they are virtually expatriated, and the middle class, which ought to constitute the real physical and moral strength of the land, ceases to exist as a rural estate, and is found only among the professional, the mercantile, and the industrial population of the cities. [344] BOUSSINGAULT, _Économie Rurale_, ii, pp. 248, 249. [345] The cultivation of rice is so prejudicial to health everywhere that nothing but the necessities of a dense population can justify the sacrifice of life it costs in countries where it is pursued. It has been demonstrated by actual experiment, that even in Mississippi, cotton can be advantageously raised by the white man without danger to health; and in fact, a great deal of the cotton brought to the Vicksburg market for some years past has been grown exclusively by white labor. There is no reason why the cultivation of cotton should be a more unhealthy occupation in America than it is in other countries where it was never dreamed of as dangerous, and no well-informed American, in the Slave States or out of them, believes that the abolition of slavery in the South would permanently diminish the cotton crop of those States. [346] _L'Italie à propos de l'Exposition de Paris_, p. 92. [347] The very valuable memoirs of Lombardini, _Cenni idrografi sulla Lombardia, Intorno al sistema idraulico del Po_, and other papers on similar subjects, were published in periodicals little known out of Italy; and the _Idraulica Pratica_ of Mari has not, I believe, been translated into French or English. These works, and other sources of information equally inaccessible out of Italy, have been freely used by Baumgarten, in a memoir entitled _Notice sur les Rivières de la Lombardie_, in the _Annales des Ponts et Chaussées_, 1847, 1er sémestre, pp. 129 _et seqq._, and by Dumont, _Des Travaux Publics dans leurs Rapports avec l'Agriculture_, note, viii, pp. 269 _et seqq._ For the convenience of my readers, I shall use these two articles instead of the original authorities on which they are founded. [348] Sir John F. W. Herschel, citing Talabot as his authority, _Physical Geography_ (24). In an elaborate paper on "Irrigation," printed in the _United States Patent Report_ for 1860, p. 169, it is stated that the volume of water poured into the Mediterranean by the Nile in twenty-four hours, at low water, is 150,566,392,368 cubic mètres; at high water, 705,514,667,440 cubic mètres. Taking the mean of these two numbers, the average daily delivery of the Nile would be 428,081,059,808 cubic mètres, or more than 550,000,000,000 cubic yards. There is some enormous mistake, probably a typographical error, in this statement, which makes the delivery of the Nile seventeen hundred times as great as computed by Talabot, and many times more than any physical geographer has ever estimated the quantity supplied by all the rivers on the face of the globe. [349] The Drac, a torrent emptying into the Isère a little below Grenoble, has discharged 5,200, the Isère, which receives it, 7,800 cubic yards, and the Durance an equal quantity, per second.--MONTLUISANT, _Note sur les Desséchements, etc., Annales des Ponts et Chaussées_, 1833, 2me sémestre, p. 288. The floods of some other French rivers scarcely fall behind those of the Rhone. The Loire, above Roanne, has a basin of 2,471 square miles, or about twice and a half the area of that of the Ardèche. In some of its inundations it has delivered above 9,500 cubic yards per second.--BELGRAND, _De l'Influence des Forêts, etc., Annales des Ponts et Chaussées_, 1854, 1er sémestre, p. 15, note. [350] The original forests in which the basin of the Ardèche was rich have been rapidly disappearing, for many years, and the terrific violence of the inundations which are now laying it waste is ascribed, by the ablest investigators, to that cause. In an article inserted in the _Annales Forestières_ for 1843, quoted by Hohenstein, _Der Wald_, p. 177, it is said that about one third of the area of the department had already become absolutely barren, in consequence of clearing, and that the destruction of the woods was still going on with great rapidity. New torrents were constantly forming, and they were estimated to have covered more than 70,000 acres of good land, or one eighth of the surface of the department, with sand and gravel. [351] "There is no example of a coincidence between great floods of the Ardèche and of the Rhone, all the known inundations of the former having taken place when the latter was very low."--MARDIGNY, _Mémoire sur les Inondations des Rivières de l'Ardèche_, p. 26. I take this occasion to acknowledge myself indebted to the interesting memoir just quoted for all the statements I make respecting the floods of the Ardèche, except the comparison of the volume of its waters with that of the Nile, and the computation with respect to the capacity required for reservoirs to be constructed in its basin. [352] In some cases where the bed of rapid Alpine streams is composed of very hard rock--as is the case in many of the valleys once filled by ancient glaciers--and especially where they are fed by glaciers not overhung by crumbling cliffs, the channel may remain almost unchanged for centuries. This is observable in many of the tributaries of the Dora Baltea, which drains the valley of the Aosta. Several of these small rivers are spanned by more or less perfect Roman bridges--one of which, that over the Lys at Pont St. Martin, is still in good repair and in constant use. An examination of the rocks on which the abutments of this and some other similar structures are founded, and of the channels of the rivers they cross, shows that the beds of the streams cannot have been much elevated or depressed since the bridges were built. In other cases, as at the outlet of the Val Tournanche at Chatillon, where a single rib of a Roman bridge still remains, there is nothing to forbid the supposition that the deep excavation of the channel may have been partly effected at a much later period. See _App._, No. 45. [353] _Mémoire sur les Inondations des Rivières de l'Ardèche_, p. 16. "The terrific roar, the thunder of the raging torrents proceeds principally from the stones which are rolled along in the bed of the stream. This movement is attended with such powerful attrition that, in the Southern Alps, the atmosphere of valleys where the limestone contains bitumen, has, at the time of floods, the marked bituminous smell produced by rubbing pieces of such limestone together."--WESSELY, _Die Oesterreichischien Alpenländer_, i, p. 113. See _Appendix_, No. 48. [354] FRISI, _Del modo di regolare i Fiumi e i Torrenti_, pp. 4-19. [355] SURELL, _Étude sur les Torrents_, pp. 31-36. [356] CHAMPION, _Les Inondations en France_, iii, p. 156, note. [357] Notwithstanding this favorable circumstance, the damage done by the inundation of 1840 in the valley of the Rhone was estimated at seventy-two millions of francs.--CHAMPION, _Les Inondations en France_, iv, p. 124. Several smaller floods of the Rhone, experienced at a somewhat earlier season of the year in 1846, occasioned a loss of forty-five millions of francs. "What if," says Dumont, "instead of happening in October, that is between harvest and seedtime, they had occurred before the crops were secured? The damage would have been counted by hundreds of millions."--_Des Travaux Publics_, p. 99, note. [358] TROY, _Étude sur le Reboisement des Montagnes_, §§ 6, 7, 21. [359] For accounts of damage from the bursting of reservoirs, see VALLÉE, _Mémoire sur les Reservoirs d'Alimentation des Canaux, Annales des Ponts et Chaussées_, 1833, 1er sémestre, p. 261. [360] Some geographical writers apply the term _bifurcation_ exclusively to this intercommunication of rivers; others, with more etymological propriety, use it to express the division of great rivers into branches at the head of their deltas. A technical term is wanting to designate the phenomenon mentioned in the text. [361] MARDIGNY, _Mémoire sur les Inondations de l'Ardèche_, p. 13. [362] In the case of rivers flowing through wide alluvial plains and much inclined to shift their beds, like the Po, the embankments often leave a very wide space between them. The dikes of the Po are sometimes three or four miles apart.--BAUMGARTEN, after LOMBARDINI, _Annales des Ponts et Chaussées_, 1847, 1er sémestre, p. 149. [363] It appears from the investigations of Lombardini that the rate of elevation of the bed of the Po has been much exaggerated by earlier writers, and in some parts of its course the change is so slow that its level may be regarded as nearly constant.--BAUMGARTEN, volume before cited, pp. 175, et seqq. See _Appendix_, No. 49. If the western coast of the Adriatic is undergoing a secular depression, as many circumstances concur to prove, the sinking of the plain near the coast may both tend to prevent the deposit of sediment in the river bed by increasing the velocity of its current, and compensate the elevation really produced by deposits, so that no sensible elevation would result, though much gravel and slime might be let fall. [364] To secure the city of Sacramento in California from the inundations to which it is subject, a dike or levée was built upon the bank of the river and raised to an elevation above that of the highest known floods, and it was connected, below the town, with grounds lying considerably above the river. On one occasion a breach in the dike occurred above the town at a very high stage of the flood. The water poured in behind it, and overflowed the lower part of the city, which remained submerged for some time after the river had retired to its ordinary level, because the dike, which had been built to keep the water _out_, now kept it _in_. According to Arthur Young, on the lower Po, where the surface of the river has been elevated much above the level of the adjacent fields by diking, the peasants in his time frequently endeavored to secure their grounds against threatened devastation through the bursting of the dikes, by crossing the river when the danger became imminent and opening a cut in the opposite bank, thus saving their own property by flooding their neighbors'. He adds, that at high water the navigation of the river was absolutely interdicted, except to mail and passenger boats, and that the guards fired upon all others; the object of the prohibition being to prevent the peasants from resorting to this measure of self-defence.--_Travels in Italy and Spain_, Nov. 7, 1789. In a flood of the Po in 1839, a breach of the embankment took place at Bonizzo. The water poured through and inundated 116,000 acres, or 181 square miles, of the plain, to the depth of from twenty to twenty-three feet in its lower parts.--BAUMGARTEN, after LOMBARDINI, volume before cited, p. 152. [365] MOYENS _de forcer les Torrents de rendre une partie du sol qu'ils ravagent, et d'empêcher les grandes Inondations_. [366] The effect of trees and other detached obstructions in checking the flow of water is particularly noticed by Palissy in his essay on _Waters and Fountains_, p. 173, edition of 1844. "There be," says he, "in divers parts of France, and specially at Nantes, wooden bridges, where, to break the force of the waters and of the floating ice, which might endamage the piers of the said bridges, they have driven upright timbers into the bed of the rivers above the said piers, without the which they should abide but little. And in like wise, the trees which be planted along the mountains do much deaden the violence of the waters that flow from them." [367] I do not mean to say that all rivers excavate their own valleys, for I have no doubt that in the majority of cases such depressions of the surface originate in higher geological causes, and hence the valley makes the river, not the river the valley. But even if we suppose a basin of the hardest rock to be elevated at once, completely formed, from the submarine abyss where it was fashioned, the first shower of rain that falls upon it after it rises to the air, while its waters will follow the lowest lines of the surface, will cut those lines deeper, and so on with every successive rain. The disintegrated rock from the upper part of the basin forms the lower by alluvial deposit, which is constantly transported farther and farther until the resistance of gravitation and cohesion balances the mechanical force of the running water. Thus plains, more or less steeply inclined, are formed, in which the river is constantly changing its bed, according to the perpetually varying force and direction of its currents, modified as they are by ever-fluctuating conditions. Thus the Po is said to have long inclined to move its channel southward in consequence of the superior mechanical force of its northern affluents. A diversion of these tributaries from their present beds, so that they should enter the main stream at other points and in different directions, might modify the whole course of that great river. But the mechanical force of the tributary is not the only element of its influence on the course of the principal stream. The deposits it lodges in the bed of the latter, acting as simple obstructions or causes of diversion, are not less important agents of change. [368] The distance to which a new obstruction to the flow of a river, whether by a dam or by a deposit in its channel, will retard its current, or, in popular phrase, "set back the water," is a problem of more difficult practical solution than almost any other in hydraulics. The elements--such as straightness or crookedness of channel, character of bottom and banks, volume and previous velocity of current, mass of water far above the obstruction, extraordinary drought or humidity of seasons, relative extent to which the river may be affected by the precipitation in its own basin, and by supplies received through subterranean channels from sources so distant as to be exposed to very different meteorological influences, effects of clearing and other improvements always going on in new countries--are all extremely difficult, and some of them impossible, to be known and measured. In the American States, very numerous watermills have been erected within a few years, and there is scarcely a stream in the settled portion of the country which has not several milldams upon it. When a dam is raised--a process which the gradual diminution of the summer currents renders frequently necessary--or when a new dam is built, it often happens that the meadows above are flowed, or that the retardation of the stream extends back to the dam next above. This leads to frequent lawsuits. From the great uncertainty of the facts, the testimony is more conflicting in these than in any other class of cases, and the obstinacy with which "water causes" are disputed has become proverbial. The subterranean courses of the waters form a subject very difficult of investigation, and it is only recently that its vast importance has been recognized. The interesting observations of Schmidt on the caves of the Karst and their rivers throw much light on the underground hydrography of limestone districts, and serve to explain how, in the low peninsula of Florida, rivers, which must have their sources in mountains a hundred or more miles distant, can pour out of the earth in currents large enough to admit of steamboat navigation to their very basins of eruption. Artesian wells are revealing to us the existence of subterranean lakes and rivers sometimes superposed one above another in successive sheets; but the still more important subject of the absorption of water by earth and its transmission by infiltration is yet wrapped in great obscurity. [369] The sediment of the Po has filled up some lagoons and swamps in its delta, and converted them into comparatively dry land; but, on the other hand, the retardation of the current from the lengthening of its course, and the diminution of its velocity by the deposits at its mouth, have forced its waters at some higher points to spread in spite of embankments, and thus fertile fields have been turned into unhealthy and unproductive marshes.--See BOTTER, _Sulla condizione dei Terreni Maremmani nel Ferrarese. Annali di Agricoltura, etc._, Fasc. v, 1863. [370] Deep borings have not detected any essential difference in the quantity or quality of the deposits of the Nile for forty or fifty, or, as some compute, for a hundred centuries. From what vast store of rich earth does this river derive the three or four inches of fertilizing material which it spreads over the soil of Egypt every hundred years? Not from the White Nile, for that river drops nearly all its suspended matter in the broad expansions and slow current of its channel south of the tenth degree of north latitude. Nor does it appear that much sediment is contributed by the Bahr-el-Azrek, which flows through forests for a great part of its course. I have been informed by an old European resident of Egypt who is very familiar with the Upper Nile, that almost the whole of the earth with which its waters are charged is brought down by the Takazzé. [371] It is very probably true that, as Lombardini supposes, the plain of Lombardy was anciently covered with forests and morasses (Baumgarten, l. c. p. 156); but, had the Po remained unconfined, its deposits would have raised its banks as fast as its bed, and there is no obvious reason why this plain should be more marshy than other alluvial flats traversed by great rivers. Its lower course would possibly have become more marshy than at present, but the banks of its middle and upper course would have been in a better condition for agricultural use than they now are. [372] From daily measurements during a period of fourteen years--1827 to 1840--the mean delivery of the Po at Ponte Lagoscuro, below the entrance of its last tributary, is found to be 1,720 cubic mètres, or 60,745 cubic feet, per second. Its smallest delivery is 186 cubic mètres, or 6,569 cubic feet, its greatest 5,156 cubic mètres, or 182,094 cubic feet.--BAUMGARTEN, following LOMBARDINI, volume before cited, p. 159. The average delivery of the Nile being 101,000 cubic feet per second, it follows that the Po contributes to the Adriatic six tenths as much water as the Nile to the Mediterranean--a result which will surprise most readers. [373] We are quite safe in supposing that the valley of the Nile has been occupied by man at least 5,000 years. The dates of Egyptian chronology are uncertain, but I believe no inquirer estimates the age of the great pyramids at less than forty centuries, and the construction of such works implies an already ancient civilization. [374] There are many dikes in Egypt, but they are employed in but a very few cases to exclude the waters of the inundation. Their office is to retain the water received at high Nile into the inclosures formed by them until it shall have deposited its sediment or been drawn out for irrigation; and they serve also as causeways for interior communication during the floods. The Egyptian dikes, therefore, instead of forcing the river, like those of the Po, to transport its sediment to the sea, help to retain the slime, which, if the flow of the current over the land were not obstructed, might be carried back into the channel, and at last to the Mediterranean. [375] The Mediterranean front of the Delta may be estimated at one hundred and fifty miles in length. Two cubic miles of earth would more than fill up the lagoons on the coast, and the remaining ten, even allowing the mean depth of the water to be twenty fathoms, which is beyond the truth, would have been sufficient to extend the coast line about three miles farther seaward, and thus, including the land gained by the filling up of the lagoons, to add more than five hundred square miles to the area of Egypt. Nor is this all; for the retardation of the current, by lengthening the course and consequently diminishing the inclination of the channel, would have increased the deposit of suspended matter, and proportionally augmented the total effect of the embankment. [376] For the convenience of navigation, and to lessen the danger of inundation by giving greater directness, and, of course, rapidity to the current, bends in rivers are sometimes cut off and winding channels made straight. This process has the same general effects as diking, and therefore cannot be employed without many of the same results. This practice has often been resorted to on the Mississippi with advantage to navigation, but it is quite another question whether that advantage has not been too dearly purchased by the injury to the banks at lower points. If we suppose a river to have a navigable course of 1,600 miles as measured by its natural channel, with a descent of 800 feet, we shall have a fall of six inches to the mile. If the length of channel be reduced to 1,200 miles by cutting off bends, the fall is increased to eight inches per mile. The augmentation of velocity consequent upon this increase of inclination is not computable without taking into account other elements, such as depth and volume of water, diminution of direct resistance, and the like, but in almost any supposable case, it would be sufficient to produce great effects on the height of floods, the deposit of sediment in the channel, on the shores, and at the outlet, the erosion of banks and other points of much geographical importance. The Po, in those parts of its course where the embankments leave a wide space between, often cuts off bends in its channel and straightens its course. These short cuts are called _salti_, or leaps, and sometimes reduce the distance between their termini by several miles. In 1777, the salto of Cottaro shortened a distance of 7,000 mètres by 5,000, or, in other words, reduced the length of the channel more than three miles; and in 1807 and 1810 the two salti of Mezzanone effected a reduction of distance to the amount of between seven and eight miles.--BAUMGARTEN, l. c. p. 38. [377] The fact, that the mixing of salt and fresh water in coast marshes and lagoons is deleterious to the sanitary condition of the vicinity, seems almost universally admitted, though the precise reason why a mixture of both should be more injurious than either alone, is not altogether clear. It has been suggested that the admission of salt water to the lagoons and rivers kills many fresh water plants and animals, while the fresh water is equally fatal to many marine organisms, and that the decomposition of the remains originates poisonous miasmata. Other theories however have been proposed. The whole subject is fully and ably discussed by Dr. Salvagnoli Marchetti in the appendix to his valuable _Rapporto sul Bonificamento delle Maremme Toscane_. See also the _Memorie Economico-Statistiche sulle Maremme Toscane_, of the same author. [378] This curious fact is thus stated in the preface to Fossombroni (_Memorie sopra la Val di Chiana_, edition of 1835, p. xiii), from which also I borrow most of the data hereafter given with respect to that valley: "It is perhaps not universally known, that the swallows, which come from the north [south] to spend the summer in our climate, do not frequent marshy districts with a malarious atmosphere. A proof of the restoration of salubrity in the Val di Chiana is furnished by these aerial visitors, which had never before been seen in those low grounds, but which have appeared within a few years at Forano and other points similarly situated." Is the air of swamps destructive to the swallows, or is their absence in such localities merely due to the want of human habitations, near which this half-domestic bird loves to breed, perhaps because the house fly and other insects which follow man are found only in the vicinity of his dwellings? In almost all European countries, the swallow is protected, by popular opinion or superstition, from the persecution to which almost all other birds are subject. It is possible that this respect for the swallow is founded upon ancient observation of the fact just stated on the authority of Fossombroni. Ignorance mistakes the effect for the cause, and the absence of this bird may have been supposed to be the occasion, not the consequence, of the unhealthiness of particular localities. This opinion once adopted, the swallow would become a sacred bird, and in process of time fables and legends would be invented to give additional sanction to the prejudices which protected it. The Romans considered the swallow as consecrated to the Penates, or household gods, and according to Peretti (_Le Serate del Villaggio_, p. 168) the Lombard peasantry think it a sin to kill them, because they are _le gallinelle del Signore_, the chickens of the Lord. The following little Tuscan _rispetto_ from Gradi (_Racconti Popolari_, p. 33) well expresses the feeling of the peasantry toward this bird: O rondinella che passi lo mare Torna 'ndietro, vo' dirti du' parole; Dammi 'na penna delle tue bell' ale, Vo' scrivere 'na lettera al mi' amore; E quando l' avrò scritta 'n carta bella, Ti renderò la penna, o rondinella; E quando l' avrò scritta 'n carta bianca, Ti renderò la penna che ti manca; E quando l' avrò scritta in carta d' oro, Ti renderò la penna al tuo bel volo. O swallow, that fliest beyond the sea, Turn back! I would fain have a word with thee. A feather oh grant, from thy wing so bright! For I to my sweetheart a letter would write; And when it is written on paper fine I'll give thee, O swallow, that feather of thine; --On paper so white, and I'll give thee back, O pretty swallow, the pen thou dost lack; --On paper of gold, and then I'll restore To thy beautiful pinion the feather once more. Popular traditions and superstitions are so closely connected with localities, that, though an emigrant people may carry them to a foreign land, they seldom survive a second generation. The swallow, however, is still protected in New England by prejudices of transatlantic origin; and I remember hearing, in my childhood, that if the swallows were killed, the cows would give bloody milk. [379] MOROZZI, _Dello stato antico e moderno del fiume Arno_, ii, p. 42. [380] MOROZZI, _Dello stato, etc., dell' Arno_, ii, pp. 39, 40. [381] Torricelli thus expressed himself on this point: "If we content ourselves with what nature has made practicable to human industry, we shall endeavor to control, as far as possible, the outlets of these streams, which, by raising the bed of the valley with their deposits, will realize the fable of the Tagus and the Pactolus, and truly roll golden sands for him that is wise enough to avail himself of them."--FOSSOMBRONI, _Memorie sopra la Val di Chiana_, p. 219. [382] Arrian observes that at the junction of the Hydaspes and the Acesines, both of which are described as wide streams, "one very narrow river is formed of two confluents, and its current is very swift."--ARRIAN, _Alex. Anab._, vi, 4. [383] This difficulty has been remedied as to one important river of the Maremma, the Pecora, by clearings recently executed along its upper course. "The condition of this marsh and of its affluents are now, November, 1859, much changed, and it is advisable to prosecute its improvement by deposits. In consequence of the extensive felling of the woods upon the plains, hills, and mountains of the territory of Massa and Scarlino, within the last ten years, the Pecora and other affluents of the marsh receive, during the rains, water abundantly charged with slime, so that the deposits within the first division of the marsh are already considerable, and we may now hope to see the whole marsh and pond filled up in a much shorter time than we had a right to expect before 1850. This circumstance totally changes the terms of the question, because the filling of the marsh and pond, which then seemed almost impossible on account of the small amount of sediment deposited by the Pecora, has now become practicable."--SALVAGNOLI, _Rapporto sul Bonificamento delle Maremme Toscane_, pp. li, lii. The annual amount of sediment brought down by the rivers of the Maremma is computed at more than 12,000,000 cubic yards, or enough to raise an area of four square miles one yard. Between 1830 and 1859 more than three times that quantity was deposited in the marsh and shoal water lake of Castiglione alone.--SALVAGNOLI, _Raccolta di Documenti_, pp. 74, 75. [384] The tide rises ten inches on the coast of Tuscany. See Memoir by FANTONI, in the appendix to SALVAGNOLI, _Rapporto_, p. 189. On the tides of the Mediterranean, see BÖTTGER, _Das Mittelmeer_, p. 190. Not having Admiral Smyth's Mediterranean--on which Böttger's work is founded--at hand, I do not know how far credit is due to the former author for the matter contained in the chapter referred to. [385] In Catholic countries, the discipline of the church requires a _meagre_ diet at certain seasons, and as fish is not flesh, there is a great demand for that article of food at those periods. For the convenience of monasteries and their patrons, and as a source of pecuniary emolument to ecclesiastical establishments and sometimes to lay proprietors, great numbers of artificial fish ponds were created during the Middle Ages. They were generally shallow pools formed by damming up the outlet of marshes, and they were among the most fruitful sources of endemic disease, and of the peculiar malignity of the epidemics which so often ravaged Europe in those centuries. These ponds, in religious hands, were too sacred to be infringed upon for sanitary purposes, and when belonging to powerful lay lords they were almost as inviolable. The rights of fishery were a standing obstacle to every proposal of hydraulic improvement, and to this day large and fertile districts in Southern Europe remain sickly and almost unimproved and uninhabited, because the draining of the ponds upon them would reduce the income of proprietors who derive large profits by supplying the faithful, in Lent, with fish, and with various species of waterfowl which, though very fat, are, ecclesiastically speaking, meagre. [386] Macchiavelli advised the Government of Tuscany "to provide that men should restore the wholesomeness of the soil by cultivation, and purify the air by fires."--SALVAGNOLI, _Memorie_, p. 111. [387] GIORGINI, _Sur les causes de l'Insalubrité de l'air dans le voisinage des marais, etc., lue à l'Académie des Sciences à Paris_, le 12 Juillet, 1825. Reprinted in SALVAGNOLI, _Rapporto, etc._, appendice, p. 5, _et seqq._ [388] See the careful estimates of ROSET, _Moyens de forcer les Torrents, etc._, pp. 42, 44. [389] Rivers which transport sand, gravel, pebbles, heavy mineral matter in short, tend to raise their own beds; those charged only with fine, light earth, to cut them deeper. The prairie rivers of the West have deep channels, because the mineral matter they carry down is not heavy enough to resist the impulse of even a moderate current, and those tributaries of the Po which deposit their sediment in the lakes--the Ticino, the Adda, the Oglio, and the Mincio--flow, in deep cuts, for the same reason.--BAUMGARTEN, l. c., p. 132. [390] "The stream carries this mud, &c., at first farther to the east, and only lets it fall where the force of the current becomes weakened. This explains the continual advance of the land seaward along the Syrian coast, in consequence of which Tyre and Sidon no longer lie on the shore, but some distance inland. That the Nile contributes to this deposit may easily be seen, even by the unscientific observer, from the stained and turbid character of the water for many miles from its mouths. A somewhat alarming phenomenon was observed in this neighborhood in 1801, on board the English frigate Romulus, Captain Culverhouse, on a voyage from Acre to Abukir. Dr. E. D. Clarke, who was a passenger on board this ship, thus describes it: "'26th July.--To-day, Sunday, we accompanied the captain to the wardroom to dine, as usual, with his officers. While we were at table, we heard the sailors who were throwing the lead suddenly cry out: "Three and a half!" The captain sprang up, was on deck in an instant, and, almost at the same moment, the ship slackened her way, and veered about. Every sailor on board supposed she would ground at once. Meanwhile, however, as the ship came round, the whole surface of the water was seen to be covered with thick, black mud, which extended so far that it appeared like an island. At the same time, actual land was nowhere to be seen--not even from the masthead--nor was any notice of such a shoal to be found on any chart on board. The fact is, as we learned afterward, that a stratum of mud, stretching from the mouths of the Nile for many miles out into the open sea, forms a movable deposit along the Egyptian coast. If this deposit is driven forward by powerful currents, it sometimes rises to the surface, and disturbs the mariner by the sudden appearance of shoals where the charts lead him to expect a considerable depth of water. But these strata of mud are, in reality, not in the least dangerous. As soon as a ship strikes them they break up at once, and a frigate may hold her course in perfect safety where an inexperienced pilot, misled by his soundings, would every moment expect to be stranded.'"--BÖTTGER, _Das Mittelmeer_, pp. 188, 189. [391] The caves of Carniola receive considerable rivers from the surface of the earth, which cannot, in all cases, be identified with streams flowing out of them at other points, and like phenomena are not uncommon in other limestone countries. The cases are certainly not numerous where marine currents are known to pour continuously into cavities beneath the surface of the earth, but there is at least one well-authenticated instance of this sort--that of the mill streams at Argostoli in the island of Cephalonia. It had been long observed that the sea water flowed into several rifts and cavities in the limestone rocks of the coast, but the phenomenon has excited little attention until very recently. In 1833, three of the entrances were closed, and a regular channel, sixteen feet long and three feet wide, with a fall of three feet, was cut into the mouth of a larger cavity. The sea water flowed into this canal, and could be followed eighteen or twenty feet beyond its inner terminus, when it disappeared in holes and clefts in the rock. In 1858, the canal had been enlarged to the width of five feet and a half, and a depth of a foot. The water pours rapidly through the canal into an irregular depression and forms a pool, the surface of which is three or four feet below the adjacent soil, and about two and a half or three feet below the level of the sea. From this pool it escapes through several holes and clefts in the rock, and has not yet been found to emerge elsewhere. There is a tide at Argostoli of about six inches in still weather, but it is considerably higher with a south wind. I do not find it stated whether water flows through the canal into the cavity at low tide, but it distinctly appears that there is no refluent current, as of course there could not be from a basin so much below the sea. Mousson found the delivery through the canal to be at the rate of 24.88 cubic feet to the second; at what stage of the tide does not appear. Other mills of the same sort have been erected, and there appear to be several points on the coast where the sea flows into the land. Various hypotheses have been suggested to explain this phenomenon, some of which assume that the water descends to a great depth beneath the crust of the earth, but the supposition of a difference of level in the surface of the sea on the opposite sides of the island, which seems confirmed by other circumstances, is the most obvious method of explaining these singular facts. If we suppose the level of the water on one side of the island to be raised by the action of currents three or four feet higher than on the other, the existence of cavities and channels in the rock would easily account for a subterranean current beneath the island, and the apertures of escape might be so deep or so small as to elude observation. See _Aus der Natur_, vol. 19, pp. 129, _et seqq._ See _Appendix_, No. 53. [392] "The affluents received by the Seine below Rouen are so inconsiderable, that the augmentation of the volume of that river must be ascribed principally to springs rising in its bed. This is a point of which engineers now take notice, and M. Belgrand, the able officer charged with the improvement of the navigation of the Seine between Paris and Rouen, has devoted much attention to it."--BABINET, _Études et Lectures_, iii, p. 185. On page 232 of the volume just quoted, the same author observes: "In the lower part of its course, from the falls of the Oise, the Seine receives so few important affluents, that evaporation alone would suffice to exhaust all the water which passes under the bridges of Paris." This supposes a much greater amount of evaporation than has been usually computed, but I believe it is well settled that the Seine conveys to the sea much more water than is discharged into it by all its superficial branches. [393] Girard and Duchatelet maintain that the subterranean waters of Paris are absolutely stagnant. See their report on drainage by artesian wells, _Annales des Ponts et Chaussées_, 1833, 2me sémestre, pp. 313, _et seqq._ This opinion, if locally true, cannot be generally so, for it is inconsistent with the well-known fact that the very first eruption of water from a boring often brings up leaves and other objects which must have been carried into the underground reservoirs by currents. [394] _Physikalische Geographie_, p. 286. It does not appear whether this inference is Mariotte's or Wittwer's. I suppose it is a conclusion of the latter. [395] _Physical Geography of the Sea._ Tenth edition. London, 1861, § 274. [396] PARAMELLE, _Quellenkunde, mit einem Vorwort von_ B. COTTA, 1856. [397] _Études et Lectures_, vi, p. 118. [398] "The area of soil dried by draining is constantly increasing, and the water received by the surface from atmospheric precipitation is thereby partly conducted into new channels, and, in general, carried off more rapidly than before. Will not this fact exert an influence on the condition of many springs, whose basin of supply thus undergoes a partial or complete transformation? I am convinced that it will, and it is important to collect data for solving the question." BERNHARD COTTA, Preface to PARAMELLE, _Quellenkunde_ (German translation), pp. vii, viii. See _Appendix_, No. 54. [399] See the interesting observations of KRIEGK on this subject, _Schriften zur allgemeinen Erdkunde_, cap. iii, § 6, and especially the passages in RITTER'S _Erdkunde_, vol. i, there referred to. Laurent, (_Mémoires sur le Sahara Oriental_, pp. 8, 9), in speaking of a river at El-Faid, "which, like all those of the desert, is, most of the time, without water," observes, that many wells are dug in the bed of the river in the dry season, and that the subterranean current thus reached appears to extend itself laterally, at about the same level, at least a kilomètre from the river, as water is found by digging to the depth of twelve or fifteen mètres at a village situated at that distance from the bank. The most remarkable case of infiltration known to me by personal observation is the occurrence of fresh water in the beach sand on the eastern side of the Gulf of Akaba, the eastern arm of the Red Sea. If you dig a cavity in the beach near the sea level, it soon fills with water so fresh as not to be undrinkable, though the sea water two or three yards from it contains even more than the average quantity of salt. It cannot be maintained that this is sea water freshened by filtration through a few feet or inches of sand, for salt water cannot be deprived of its salt by that process. It can only come from the highlands of Arabia, and it would seem that there must exist some large reservoir in the interior to furnish a supply which, in spite of evaporation, holds out for months after the last rains of winter, and perhaps even through the year. I observed the fact in the month of June. The precipitation in the mountains that border the Red Sea is not known by pluviometric measurement, but the mass of debris brought down the ravines by the torrents proves that their volume must be large. The proportion of surface covered by sand and absorbent earth, in Arabia Petræa and the neighboring countries, is small, and the mountains drain themselves rapidly into the wadies or ravines where the torrents are formed; but the beds of earth and disintegrated rock at the bottom of the valleys are of so loose and porous texture, that a great quantity of water is absorbed in saturating them before a visible current is formed on their surface. In a heavy thunder storm, accompanied by a deluging rain, which I witnessed at Mount Sinai in the month of May, a large stream of water poured, in an almost continuous cascade, down the steep ravine north of the convent, by which travellers sometimes descend from the plateau between the two peaks, but after reaching the foot of the mountain, it flowed but a few yards before it was swallowed up in the sands. [400] It is conceivable that in large and shallow subterranean basins the superincumbent earth may rest upon the water and be partly supported by it. In such case the weight of the earth would be an additional, if not the sole, cause of the ascent of the water through the tubes of artesian wells. The elasticity of gases in the cavities may also aid in forcing up water. A French engineer, M. Mullot, invented a simple method of bringing to the surface water from any one of several successive accumulations at different depths, or of raising it, unmixed, from two or more of them at once. It consists in employing concentric tubes, one within the other, leaving a space for the rise of water between them, and reaching each to the sheet from which it is intended to draw. [401] Many more or less probable conjectures have been made on this subject, but thus far I am not aware that any of the apprehended results have been actually shown to have happened. In an article in the _Annales des Ponts et Chaussées_ for July and August, 1839, p. 131, it was suggested that the sinking of the piers of a bridge at Tours in France was occasioned by the abstraction of water from the earth by artesian wells, and the consequent withdrawal of the mechanical support it had previously given to the strata containing it. A reply to this article will be found in VIOLETT, _Théorie des Puits Artésiens_, p. 217. In some instances the water has rushed up with a force which seemed to threaten the inundation of the neighborhood, and even the washing away of much soil; but in those cases the partial exhaustion of the supply, or the relief of hydrostatic or elastic pressure, has generally produced a diminution of the flow in a short time, and I do not know that any serious evil has ever been occasioned in this way. [402] See a very interesting account of these wells, and of the workmen who clean them out when obstructed by sand brought up with the water, in Laurent's memoir on the artesian wells recently bored by the French Government in the Algerian desert, _Mémoire sur le Sahara Oriental, etc._, pp. 19, _et seqq._ Some of the men remained under water from two minutes to two minutes and forty seconds. Several officers are quoted as having observed immersions of three minutes' duration, and M. Berbrugger alleges that he witnessed one of five minutes and fifty-five seconds. The shortest of these periods is longer than the best pearl diver can remain below the surface of salt water. The wells of the Sahara are from twenty to eighty mètres deep. It has often been asserted that the ancient Egyptians were acquainted with the art of boring artesian wells. Parthey, describing the Little Oasis, mentions ruins of a Roman aqueduct, and observes: "It appears from the recent researches of Aim, a French engineer, that these aqueducts are connected with old artesian wells, the restoration of which would render it practicable to extend cultivation much beyond its present limits. This agrees with ancient testimony. It is asserted that the inhabitants of the oases sunk wells to the depth of 200, 300, and even 500 ells, from which affluent streams of water poured out. See OLYMPIODORUS in _Photii Bibl._, cod. 80, p. 61, l. 17, ed. Bekk."--PARTHEY, _Wanderungen_, ii, p. 528. In a paper entitled, _Note relative à l'execution d'un Puits Artésien en Egypte sous la XVIII dynastie_, presented to the Académie des Inscriptions et Belles Lettres, on the 12th of November, 1852, M. Lenormant endeavors to show that a hieroglyphic inscription found at Contrapscelcis proves the execution of a work of this sort in the Nubian desert, at the period indicated in the title to his paper. The interpretation of the inscription is a question for Egyptologists; but if wells were actually bored through the rock by the Egyptians after the Chinese or the European fashion, it is singular that among the numerous and minute representations of their industrial operations, painted or carved on the walls of their tombs, no trace of the processes employed for so remarkable and important a purpose should have been discovered. See _Appendix_, No. 56. It is certain that artesian wells have been common in China from a very remote antiquity, and the simple method used by the Chinese--where the borer is raised and let fall by a rope, instead of a rigid rod--has been lately been employed in Europe with advantage. Some of the Chinese wells are said to be 3,000 feet deep; that of Neusalzwerk in Silesia--the deepest in Europe--is 2,300. A well was bored at St. Louis, in Missouri, a few years ago, to supply a sugar refinery, to the depth of 2,199 feet. This was executed by a private firm in three years, at the expense of only $10,000. Another has since been bored at the State capitol at Columbus, Ohio, 2,500 feet deep, but without obtaining the desired supply of water. [403] "In the anticipation of our success at Oum-Thiour, every thing had been prepared to take advantage of this new source of wealth without a moment's delay. A division of the tribe of the Selmia, and their sheikh, Aïssa ben Shâ, laid the foundation of a village as soon as the water flowed, and planted twelve hundred date palms, renouncing their wandering life to attach themselves to the soil. In this arid spot, life had taken the place of solitude, and presented itself, with its smiling images, to the astonished traveller. Young girls were drawing water at the fountain; the flocks, the great dromedaries with their slow pace, the horses led by the halter, were moving to the watering trough; the hounds and the falcons enlivened the group of party-colored tents, and living voices and animated movement had succeeded to silence and desolation."--LAURENT, _Mémoires sur le Sahara_, p. 85. [404] The variety of hues and tones in the local color of the desert is, I think, one of the phenomena which most surprise and interest a stranger to those regions. In England and the United States, rock is so generally covered with moss or earth, and earth with vegetation, that untravelled Englishmen and Americans are not very familiar with naked rock as a conspicuous element of landscape. Hence, in their conception of a bare cliff or precipice, they hardly ascribe definite color to it, but depict it to their imagination as wearing a neutral tint not assimilable to any of the hues with which nature tinges her atmospheric or paints her organic creations. There are certainly extensive desert ranges, chiefly limestone formations, where the surface is either white, or has weathered down to a dull uniformity of tone which can hardly be called color at all; and there are sand plains and drifting hills of wearisome monotony of tint. But the chemistry of the air, though it may tame the glitter of the limestone to a dusky gray, brings out the green and brown and purple of the igneous rocks, and the white and red and blue and violet and yellow of the sandstone. Many a cliff in Arabia Petræa is as manifold in color as the rainbow, and the veins are so variable in thickness and inclination, so contorted and involved in arrangement, as to bewilder the eye of the spectator like a disk of party-colored glass in rapid revolution. In the narrower wadies, the mirage is not common; but on broad expanses, as at many points between Cairo and Suez, and in Wadi el Araba, it mocks you with lakes and land-locked bays, studded with islands and fringed with trees, all painted with an illusory truth of representation absolutely indistinguishable from the reality. The checkered earth, too, is canopied with a heaven as variegated as itself. You see, high up in the sky, rosy clouds at noonday, colored probably by reflection from the ruddy mountains, while near the horizon float cumuli of a transparent ethereal blue, seemingly balled up out of the clear cerulean substance of the firmament, and detached from the heavenly vault, not by color or consistence, but solely by the light and shade of their prominences. [405] _[OE]uvres de Palissy, Des Eaux et Fontaines_, p. 157. [406] Id., p. 166. See _Appendix_, No. 57. [407] BABINET, _Études et Lectures sur les Sciences d'Observation_, ii, p. 225. Our author precedes his account of his method with a complaint which most men who indulge in thinking have occasion to repeat many times in the course of their lives. "I will explain to my readers the construction of artificial fountains according to the plan of the famous Bernard de Palissy, who, a hundred and fifty [three hundred] years ago, came and took away from me, a humble academician of the nineteenth century, this discovery which I had taken a great deal of pains to make. It is enough to discourage all invention when one finds plagiarists in the past as well as in the future!" (P. 224.) [408] M. G. DUMAS, _La Science des Fontaines_, 1857. [409] In the curiously variegated sandstone of Arabia Petræa--which is certainly a reaggregation of loose sand derived from particles of older rocks--the contiguous veins frequently differ very widely in color, but not sensibly in specific gravity or in texture; and the singular way in which they are now alternated, now confusedly intermixed, must be explained otherwise than by the weight of the respective grains which compose them. They seem, in fact, to have been let fall by water in violent ebullition or tumultuous mechanical agitation, or by a succession of sudden aquatic or aerial currents flowing in different directions and charged with differently colored matter. [410] _De Bodem van Nederland_, i, pp. 243, 246-377, _et seqq._ See also the arguments of Brémontier as to the origin of the dune sands of Gascony, _Annales des Ponts et Chaussées_, 1833, 1er sémestre, pp. 158, 161. Brémontier estimates the sand annually thrown up on that coast at five cubic toises and two feet to the running toise (ubi supra, p. 162), or rather more than two hundred and twenty cubic feet to the running foot. Laval, upon observations continued through seven years, found the quantity to be twenty-five mètres per running mètre, which is equal to two hundred and sixty-eight cubic feet to the running foot.--_Annales des Ponts et Chaussées_, 1842, 2me sémestre, p. 229. These computations make the proportion of sand deposited on the coast of Gascony three or four times as great as that observed by Andresen on the shores of Jutland. Laval estimates the total quantity of sand annually thrown up on the coast of Gascony at 6,000,000 cubic mètres, or more than 7,800,000 cubic yards. [411] _De Bodem van Nederland_, i, p. 339. [412] The conditions favorable to the production of sand from disintegrated rock, by causes now in action, are perhaps nowhere more perfectly realized than in the Sinaitic Peninsula. The mountains are steep and lofty, unprotected by vegetation or even by a coating of earth, and the rocks which compose them are in a shattered and fragmentary condition. They are furrowed by deep and precipitous ravines, with beds sufficiently inclined for the rapid flow of water, and generally without basins in which the larger blocks of stone rolled by the torrents can be dropped and left in repose; there are severe frosts and much snow on the higher summits and ridges, and the winter rains are abundant and heavy. The mountains are principally of igneous formation, but many of the less elevated peaks are capped with sandstone, and on the eastern slope of the peninsula you may sometimes see, at a single glance, several lofty pyramids of granite, separated by considerable intervals, and all surmounted by horizontally stratified deposits of sandstone often only a few yards square, which correspond to each other in height, are evidently contemporaneous in origin, and were once connected in continuous beds. The degradation of the rock on which this formation rests is constantly bringing down masses of it, and mingling them with the basaltic, porphyritic, granitic, and calcareous fragments which the torrents carry down to the valleys, and, through them, in a state of greater or less disintegration, to the sea. The quantity of sand annually washed into the Red Sea by the larger torrents of the Lesser Peninsula, is probably at least equal to that contributed to the ocean by any streams draining basins of no greater extent. Absolutely considered, then, the mass may be said to be large, but it is apparently very small as compared with the sand thrown up by the German Ocean and the Atlantic on the coasts of Denmark and of France. There are, indeed, in Arabia Petræa, many torrents with very short courses, for the sea waves in many parts of the peninsular coast wash the base of the mountains. In these cases, the debris of the rocks do not reach the sea in a sufficiently comminuted condition to be entitled to the appellation of sand, or even in the form of well-rounded pebbles. The fragments retain their angular shape, and, at some points on the coast, they become cemented together by lime or other binding substances held in solution or mechanical suspension in the sea water, and are so rapidly converted into a singularly heterogeneous conglomerate, that one deposit seems to be consolidated into a breccia before the next winter's torrents cover it with another. In the northern part of the peninsula there are extensive deposits of sand intermingled with agate pebbles and petrified wood, but these are evidently neither derived from the Sinaitic group, nor products of local causes known to be now in action. I may here notice the often repeated but mistaken assertion, that the petrified wood of the Western Arabian desert consists wholly of the stems of palms, or at least of endogenous vegetables. This is an error. I have myself picked up in that desert, within the space of a very few square yards, fragments both of fossil palms, and of at least two petrified trees distinctly marked as of exogenous growth both by annular structure and by knots. In ligneous character, one of these almost precisely resembles the grain of the extant beech, and this specimen was wormeaten before it was converted into silex. [413] BÖTTGER, _Das Mittelmeer_, p. 128. [414] The testimony of divers and of other observers on this point is conflicting, as might be expected from the infinite variety of conditions by which the movement of water is affected. It is generally believed that the action of the wind upon the water is not perceptible at greater depths than from fifteen feet in ordinary, to eighty or ninety in extreme cases; but these estimates are probably very considerably below the truth. Andresen quotes Brémontier as stating that the movement of the waves sometimes extends to the depth of five hundred feet, and he adds that others think it may reach to six or even seven hundred feet below the surface.--ANDRESEN, _Om Klitformationen_, p. 20. Many physicists now suppose that the undulations of great bodies of water reach even deeper. But a movement of undulation is not necessarily a movement of translation, and besides, there is very frequently an undertow, which tends to carry suspended bodies out to sea as powerfully as the superficial waves to throw them on shore. Sandbanks sometimes recede from the coast, instead of rolling toward it. Reclus informs us that the Mauvaise, a sandbank near the Point de Grave, on the Atlantic coast of France, has moved five miles to the west in less than a century.--_Revue des Deux Mondes_, for December, 1862, p. 905. The action of currents may, in some cases, have been confounded with that of the waves. Sea currents, strong enough, possibly, to transport sand for some distance, flow far below the surface in parts of the open ocean, and in narrow straits they have great force and velocity. The divers employed at Constantinople in 1853 found in the Bosphorus, at the depth of twenty-five fathoms and at a point much exposed to the wash from Galata and Pera, a number of bronze guns supposed to have belonged to a ship of war blown up about a hundred and fifty years before. These guns were not covered by sand or slime, though a crust of earthy matter, an inch in thickness, adhered to their upper surfaces, and the bottom of the strait appeared to be wholly free from sediment. The current was so powerful at this depth that the divers were hardly able to stand, and a keg of nails, purposely dropped into the water, in order that its movements might serve as a guide in the search for a bag of coin accidentally lost overboard from a ship in the harbor, was rolled by the stream several hundred yards before it stopped. [415] Few seas have thrown up so much sand as the shallow German Ocean; but there is some reason to think that the amount of this material now cast upon its northern shores is less than at some former periods, though no extensive series of observations on this subject has been recorded. On the Spit of Agger, at the present outlet of the Liimfjord, Andresen found the quantity during ten years, on a beach about five hundred and seventy feet broad, equal to an annual deposit of an inch and a half over the whole surface.--_Om Klitformationen_, p. 56. This gives seventy-one and a quarter cubic feet to the running foot--a quantity certainly much smaller than that cast up by the same sea on the shores of the Dano-German duchies and of Holland, and, as we have seen, scarcely one fourth of that deposited by the Atlantic on the coast of Gascony. See _ante_, p. 453, note. [416] Sand heaps, three and even six hundred feet high, are indeed formed by the wind, but this is effected by driving the particles up an inclined plane, not by lifting them. Brémontier, speaking of the sand hills on the western coast of France, says: "The particles of sand composing them are not large enough to resist wind of a certain force, nor small enough to be taken up by it, like dust; they only roll along the surface from which they are detached, and, though moving with great velocity, they rarely rise to a greater height than three or four inches."--_Mémoire sur les Dunes, Annales des Ponts et Chaussées_, 1833, 1er sémestre, p. 148. Andresen says that a wind, having a velocity of forty feet per second, is strong enough to raise particles of sand as high as the face and eyes of a man, but that, in general, it rolls along the ground, and is scarcely ever thrown more than to the height of a couple of yards from the surface. Even in these cases, it is carried forward by a hopping, not a continuous, motion; for a very narrow sheet or channel of water stops the drift entirely, all the sand dropping into it until it is filled up. The character of the motion of sand drifts is well illustrated by an interesting fact not much noticed hitherto by travellers in the East. In situations where the sand is driven through depressions in rock beds, or over deposits of silicious pebbles, the surface of the stone is worn and smoothed much more effectually than it could be by running water, and you may pick up, in such localities, rounded, irregularly broken fragments of agate, which have received from the attrition of the sand as fine a polish as could be given them by the wheel of the lapidary. Very interesting observations on the polishing of hard stones by drifting sand will be found in the Geological Report of William P. Blake: _Pacific Railroad Report_, vol. v, pp. 92, 230, 231. The same geologist observes, p. 242, that the sand of the Colorado desert does not rise high in the air, but bounds along on the surface or only a few inches above it. [417] Wilkinson says that, in much experience in the most sandy parts of the Libyan desert, and much inquiry of the best native sources, he never saw or heard of any instance of danger to man or beast from the mere accumulation of sand transported by the wind. Chesney's observations in Arabia, and the testimony of the Bedouins he consulted, are to the same purpose. The dangers of the simoom are of a different character, though they are certainly aggravated by the blinding effects of the light particles of dust and sand borne along by it, and by that of the inhalation of them upon the respiration. [418] In the narrow valley of the Nile, bounded as it is, above the Delta, by high cliffs, all air currents from the northern quarter become north winds, though, of course varying in partial direction, in conformity with the sinuosities of the valley. Upon the desert plateau they incline westward, and have already borne into the valley the sands of the eastern banks, and driven those of the western quite out of the Egyptian portion of the Nile basin. [419] "The North African desert falls into two divisions: the Sahel, or western, and the Sahar, or eastern. The sands of the Sahar were, at a remote period, drifted to the west. In the Sahel, the prevailing east winds drive the sand-ocean with a progressive westward motion. The eastern half of the desert is swept clean."--NAUMANN, _Geognosie_, ii, p. 1173. [420] In parts of the Algerian desert, some efforts are made to retard the advance of sand dunes which threaten to overwhelm villages. "At Debila," says Laurent, "the lower parts of the lofty dunes are planted with palms, * * * but they are constantly menaced with burial by the sands. The only remedy employed by the natives consists in little dry walls of crystallized gypsum, built on the crests of the dunes, together with hedges of dead palm leaves. These defensive measures are aided by incessant labor; for every day the people take up in baskets the sand blown over to them the night before and carry it back to the other side of the dune."--_Mémoires sur le Sahara_, p. 14. [421] Organic constituents, such as comminuted shells, and silicious and calcareous exuviæ of infusorial animals and plants, are sometimes found mingled in considerable quantities with mineral sands. These are usually the remains of aquatic vegetables or animals, but not uniformly so, for the microscopic organisms, whose flinty cases enter so largely into the sandbeds of the Mark of Brandenburg, are still living and prolific in the dry earth. See WITTWER, _Physikalische Geographie_, p. 142. The desert on both sides of the Nile is inhabited by a land snail, and thousands of its shells are swept along and finally buried in the drifts by every wind. Every handful of the sand contains fragments of them. FORCHHAMMER, in LEONHARD Und BRONN's _Jahrbuch_, 1841, p. 8, says of the sand hills of the Danish coast: "It is not rare to find, high in the knolls, marine shells, and especially those of the oyster. They are due to the oyster eater [_Hæmalopus ostralegus_], which carries his prey to the top of the dunes to devour it." See also STARING, _De Bodem van_, N. I. p. 321. [422] There are various reasons why the formation of dunes is confined to low shores, and this law is so universal, that when bluffs are surmounted by them, there is always cause to suspect upheaval, or the removal of a sloping beach in front of the bluff, after the dunes were formed. Bold shores are usually without a sufficient beach for the accumulation of large deposits; they are commonly washed by a sea too deep to bring up sand from its bottom; their abrupt elevation, even if moderate in amount, would still be too great to allow ordinary winds to lift the sand above them; and their influence in deadening the wind which blows toward them would even more effectually prevent the raising of sand from the beach at their foot. Forchhammer, describing the coast of Jutland, says that, in high winds, "one can hardly stand upon the dunes, except when they are near the water line and have been cut down perpendicularly by the waves. Then the wind is little or not at all felt--a fact of experience very common on our coasts, observed on all the steep shore bluffs of two hundred feet in height, and, in the Faroe Islands, on precipices two thousand feet high. In heavy gales in those islands, the cattle fly to the very edge of the cliffs for shelter, and frequently fall over. The wind, impinging against the vertical wall, creates an ascending current which shoots somewhat past the crest of the rock, and thus the observer or the animal is protected against the tempest by a barrier of air."--LEONHARD und BRONN, _Jahrbuch_, 1841, p. 3. The calming, or rather diversion, of the wind by cliffs extends to a considerable distance in front of them, and no wind would have sufficient force to raise the sand vertically, parallel to the face of a bluff, even to the height of twenty feet. It is very commonly believed that it is impossible to grow forest trees on sea-shore bluffs, or points much exposed to strong winds. The observations just cited tend to show that it would not be difficult to protect trees from the mechanical effect of the wind, by screens much lower than the height to which they are expected to grow. Recent experiments confirm this, and it is found that, though the outer row or rows may suffer from the wind, every tree shelters a taller one behind it. Extensive groves have thus been formed in situations where an isolated tree would not grow at all. Piper, in his _Trees of America_, p. 19, gives an interesting account of Mr. Tudor's success in planting trees on the bleak and barren shore of Nahant. "Mr. Tudor," observes he, "has planted more than ten thousand trees at Nahant, and, by the results of his experiments, has fully demonstrated that trees, properly cared for in the beginning, may be made to grow up to the very bounds of the ocean, exposed to the biting of the wind and the spray of the sea. The only shelter they require is, at first, some interruption to break the current of the wind, such as fences, houses, or other trees." [423] The careful observations of Colonel J. D. Graham, of the United States Army, show a tide of about three inches in Lake Michigan. See "A Lunar Tidal Wave in the North American Lakes," demonstrated by Lieut.-Colonel J. D. Graham, in the fourteenth volume of the _Proceedings of the American Association for the Advancement of Science_. [424] STARING, _De Bodem van Nederland_, i, p. 327, note. [425] The principal special works and essays on this subject known to me are: BRÉMONTIER, _Mémoire sur les Dunes, etc._, 1790, reprinted in _Annales des Ponts et Chaussées_, 1833, 1er sémestre, pp. 145-186. _Rapport sur les differents Mémoires de M. Brémontier_, par LAUMONT et autres, 1806, same volume, pp. 192, 224. LEFORT, _Notice sur les Travaux de Fixation des Dunes, Annales des Ponts et Chaussées_, 1831, 2me sémestre, pp. 320-332. FORCHHAMMER, _Geognostische Studien am Meeres Ufer_, in LEONHARD und BRONN, _Jahrbuch, etc._, 1841, pp. 1, 38. J. G. KOHL, _Die Inseln und Marschen der Herzogthümer Schleswig und Holstein_, 1846, vol. ii, pp. 112-162, 193-204. LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des Ponts et Chaussées_, 1847, 2me sémestre, pp. 218-268. G. C. A. KRAUSE, _Der Dünenbau auf den Ostsee-Küsten West-Preussens_, 1850, 1 vol. 8vo. W. C. H. STARING, _De Bodem van Nederland_, 1856, vol. i, pp. 310-341, and 424-431. Same author, _Voormaals en Thans_, 1858, pages cited. C. C. ANDRESEN, _Om Klitformationen og Klittens Behandling og Bestyrelse_, 1861, 1 vol. 8vo, x, 392 pp., much the most complete treatise on the subject. ANDRESEN cites, upon the origin of the dunes: HULL, _Over den Oorsprong en de Geschiedenis der Hollandsche Duinen_, 1838, and GROSS's _Veiledning ved Behandlingen af Sandflugtstrækningerne_, 1847; and upon the improvement of sand plains by planting, PANNEWITZ, _Anleitung zum Anbau der Sandflächen_, 1832. I am not acquainted with either of the latter two works but I have consulted with advantage, on this subject, DELAMARRE, _Historique de la Création d'une Richesse millionaire par la culture des Pins_, 1827; BOITEL, _Mise en valeur des terres pauvres par le Pin maritime_, 1857; and BRINCKEN, _Ansichten über die Bewaldung der Steppen des Europäischen Russlands_, 1854. [426] "Dunes are always full of water, from the action of capillary attraction. Upon the summits, one seldom needs to dig more than a foot to find the sand moist, and in the depressions, fresh water is met with near the surface."--FORCHHAMMER, in LEONHARD und BRONN, for 1841, p. 5, note. On the other hand, Andresen, who has very carefully investigated this as well as all other dune phenomena, maintains that the humidity of the sand ridges cannot be derived from capillary attraction. He found by experiment that drift sand was not moistened to a greater height than eight and a half inches, after standing a whole night in water. He states the minimum of water contained by the sand of the dunes, one foot below the surface, after a long drought, at two per cent., the maximum, after a rainy month, at four per cent. At greater depths the quantity is larger. The hygroscopicity of the sand of the coast of Jutland he found to be thirty-three per cent. by measure, or 21.5 by weight. The annual precipitation on that coast is twenty-seven inches, and, as the evaporation is about the same, he argues that rain water does not penetrate far beneath the surface of the dunes, and concludes that their humidity can be explained only by evaporation from below.--_Om Klitformationen_, pp. 106-110. In the dunes of Algeria, water is so abundant that wells are constantly dug in them at high points on their surface. They are sunk to the depth of three or four mètres only, and the water rises to the height of a mètre in them.--LAURENT, _Mémoire sur le Sahara_, pp. 11, 12, 13. The same writer observes (p. 14) that the hollows in the dunes are planted with palms which find moisture enough a little below the surface. It would hence seem that the proposal to fix the dunes which are supposed to threaten the Suez Canal, by planting the maritime pine and other trees upon them, is not altogether so absurd as it is thought to be by some of those disinterested philanthropists of other nations who are distressed with fears that French capitalists will lose the money they have invested in that great undertaking. Ponds of water are often found in the depressions between the sand hills of the dune chains in the North American desert. [427] According to the French authorities, the dunes of France are not always composed of quartzose sand. "The dune sands" of different characters, says Brémontier, "partake of the nature of the different materials which compose them. At certain points on the coast of Normandy they are found to be purely calcareous; they are of mixed composition on the shores of Brittany and Saintonge, and generally quartzose between the mouth of the Gironde and that of the Adour."--_Mémoire sur les Dunes, Annales des Ponts et Chaussées_, t. vii, 1833, 1er sémestre, p. 146. In the dunes of Long Island and of Jutland, there are considerable veins composed almost wholly of garnet. For a very full examination of the mechanical and chemical composition of the dune sands of Jutland, see ANDRESEN, _Om Klitformationen_, p. 110. [428] _De Bodem van Nederland_, i, p. 323. [429] J. G. KOHL, _Die Inseln und Marschen der Herzogthümer Schleswig und Holstein_, ii, p. 200. [430] STARING, _De Bodem van Nederland_, i, p. 317. See also, BERGSÖE, _Reventov's Virksomhed_, ii, p. 11. "In the sand-hill ponds mentioned in the text, there is a vigorous growth of bog plants accompanied with the formation of peat, which goes on regularly as long as the dune sand does not drift. But if the surface of the dunes is broken, the sand blows into the ponds, covers the peat, and puts an end to its formation. When, in the course of time, marine currents cut away the coast, the dunes move landward and fill up the ponds, and thus are formed the remarkable strata of fossile peat called Martörv, which appears to be unknown to the geologists of other parts of Europe."--FORCHHAMMER, in LEONHARD und BRONN, 1841, p. 13. [431] The lower strata must be older than the superficial layers, and the particles which compose them may in time become more disintegrated, and therefore finer than those deposited later and above them. [432] "On the west coast of Africa the dunes are drifting seawards, and always receiving new accessions from the Sahara. They are constantly advancing out into the sea." See _ante_, p. 16, note.--NAUMANN, _Geognosie_, ii, p. 1172. See _Appendix_, No. 58. [433] Forchhammer, after pointing out the coincidence between the inclined stratification of dunes and the structure of ancient tilted rocks, says: "But I am not able to point out a sandstone formation corresponding to the dunes. Probably most ancient dunes have been destroyed by submersion before the loose sand became cemented to solid stone, but we may suppose that circumstances have existed somewhere which have preserved the characteristics of this formation."--LEONHARD und BRONN, 1841, p. 8, 9. Such formations, however, certainly exist. I find from Laurent (_Mémoire sur le Sahara, etc._, p. 12), that in the Algerian desert there exist "sandstone formations" not only "corresponding to the dunes," but actually consolidated within them. "A place called El-Mouia-Tadjer presents a repetition of what we saw at El-Baya; one of the funnels formed in the middle of the dunes contains wells from two mètres to two and a half in depth, dug in a sand which pressure, and probably the presence of certain salts, have cemented so as to form true sandstone, soft indeed, but which does not yield except to the pickaxe. These sandstones exhibit an inclination which seems to be the effect of wind; for they conform to the direction of the sands which roll down a scarp occasioned by the primitive obstacle." See _Appendix_, No. 59. The dunes near the mouth of the Nile, the lower sands of which have been cemented together by the infiltration of Nile water, would probably show a similar stratification in the sandstone which now forms their base. [434] Forchhammer ascribes the resemblance between the furrowing of the dune sands and the beach ripples, not to the similarity of the effect of wind and water upon sand, but wholly to the action of the former fluid; in the first instance, directly, in the latter, through the water. "The wind ripples on the surface of the dunes precisely resemble the water ripples of sand flats occasionally overflowed by the sea; and with the closest scrutiny, I have never been able to detect the slightest difference between them. This is easily explained by the fact, that the water ripples are produced by the action of light wind on the water which only transmits the air waves to the sand."--LEONHARD und BRONN, 1841, pp. 7, 8. [435] American observers do not agree in their descriptions of the form and character of the sand grains which compose the interior dunes of the North American desert. C. C. Parry, geologist to the Mexican Boundary Commission, in describing the dunes near the station at a spring thirty-two miles west from the Rio Grande at El Paso, says: "The separate grains of the sand composing the sand hills are seen under a lens to be angular, and not rounded, as would be the case in regular beach deposits."--_U. S. Mexican Boundary Survey, Report of_, vol. i, _Geological Report of C. C. Parry_, p. 10. In the general description of the country traversed, same volume, p. 47, Colonel Emory says that on an "examination of the sand with a microscope of sufficient power," the grains are seen to be angular, not rounded by rolling in water. On the other hand, Blake, in _Geological Report, Pacific Railroad Rep._, vol. v, p. 119, observes that the grains of the dune sand, consisting of quartz, chalcedony, carnelian, agate, rose quartz, and probably chrysolite, were much rounded; and on page 241, he says that many of the sand grains of the Colorado desert are perfect spheres. On page 20 of a report in vol. ii of the _Pacific Railroad Report_, by the same observer, it is said that an examination of dune sands brought from the Llano Estacado by Captain Pope, showed the grains to be "much rounded by attrition." The sands described by Mr. Parry and Colonel Emory are not from the same localities as those examined by Mr. Blake, and the difference in their character may denote a difference of origin or of age. [436] LAURENT (_Mémoire sur le Sahara_, pp. 11, 12, and elsewhere) speaks of a funnel-shaped depression at a high point in the dunes, as a characteristic feature of the sand hills of the Algerian desert. This seems to be an approximation to the crescent form noticed by Meyen and Pöppig in the inland dunes of Peru. [437] _Travels in Peru_, New York, 1848, chap. ix. [438] Notwithstanding the general tendency of isolated coast dunes and of the peaks of the sand ridges to assume a conical form, Andresen states that the hills of the inner or landward rows are sometimes _bow-shaped_, and sometimes undulating in outline.--_Om Klitformationen_, p. 84. He says further that: "Before an obstruction, two or three feet high and considerably longer, lying perpendicularly to the direction of the wind, the sand is deposited with a windward angle of from 6° to 12°, and the bank presents a concave face to the wind, while, behind the obstruction, the outline is convex;" and he lays it down as a general rule, that a slope, _from_ which sand is blown, is left with a concavity of about one inch of depth to four feet of distance; a slope, _upon_ which sand is dropped by the wind, is convex. It appears from Andresen's figures, however, that the concavity and convexity referred to, apply, not to the _horizontal longitudinal_ section of the sand bank, as his language unexplained by the drawings might be supposed to mean, but to the _vertical cross-section_, and hence the dunes he describes, with the exception above noted, do not correspond to those of the American deserts.--_Om Klitformationen_, p. 86. The dunes of Gascony, which sometimes exceed three hundred feet in height, present the same concavity and convexity of _vertical_ cross-section. The slopes of these dunes are much steeper than those of the Netherlands and the Danish coast; for while all observers agree in assigning to the seaward and landward faces of those latter, respectively, angles of from 5° to 12°, and 30° with the horizon, the corresponding faces of the dunes of Gascony present angles of from 10° to 25°, and 50° to 60°.--LAVAL, _Mémoire sur les Dunes de Gascogne, Annales des Ponts et Chaussées_, 1847, 2me sémestre. [439] Krause, speaking of the dunes on the coast of Prussia, says: "Their origin belongs to three different periods, in which important changes in the relative level of sea and land have unquestionably taken place. * * * Except in the deep depressions between them, the dunes are everywhere sprinkled, to a considerable height, with brown oxydulated iron, which has penetrated into the sand to the depth of from three to eighteen inches, and colored it red. * * * Above the iron is a stratum of sand differing in composition from ordinary sea sand, and on this, growing woods are always found. * * * The gradually accumulated forest soil occurs in beds of from one to three feet thick, and changes, proceeding upward, from gray sand to black humus." Even on the third or seaward range, the sand grasses appear and thrive luxuriantly, at least on the west coast, though. Krause doubts whether the dunes of the east coast were ever thus protected.--_Der Dünenbau_, pp. 8, 11. [440] LAVAL, _Mémoire sur les Dunes de Gascogne, Annales des Ponts et Chaussées_, 1847, 2me sémestre, p. 231. The same opinion had been expressed by BRÉMONTIER, _Annales des Ponts et Chaussées_, 1833, 1er sémestre, p. 185. [441] "In the Middle Ages," says Willibald Alexis, as quoted by Müller, _Das Buch der Pflanzenwelt_ i, p. 16, "the Nehrung was extending itself further, and the narrow opening near Lochstadt had filled itself up with sand. A great pine forest bound with its roots the dune sand and the heath uninterruptedly from Danzig to Pillau. King Frederick William I was once in want of money. A certain Herr von Korff promised to procure it for him, without loan or taxes, if he could be allowed to remove something quite useless. He thinned out the forests of Prussia, which then, indeed, possessed little pecuniary value; but he felled the entire woods of the Frische Nehrung, so far as they lay within the Prussian territory. The financial operation was a success. The king had money, but in the elementary operation which resulted from it, the state received irreparable injury. The sea winds rush over the bared hills; the Frische Haff is half-choked with sand; the channel between Elbing, the sea, and Königsberg is endangered, and the fisheries in the Haff injured. The operation of Herr von Korff brought the king 200,000 thalers. The state would now willingly expend millions to restore the forests again." [442] STARING, _Voormaals en Thans_, p. 231. Had the dunes of the Netherlandish and French coasts, at the period of the Roman invasion, resembled the moving sand hills of the present day, it is inconceivable that they could have escaped the notice of so acute a physical geographer as Strabo; and the absolute silence of Cæsar, Ptolemy, and the encyclopædic Pliny, respecting them, would be not less inexplicable. The Old Northern language, the ancient tongue of Denmark, though rich in terms descriptive of natural scenery, had no name for dune, nor do I think the sand hills of the coast are anywhere noticed in Icelandic literature. The modern Icelanders, in treating of the dunes of Jutland, call them _klettr_, hill, cliff, and the Danish _klit_ is from that source. The word Düne is also of recent introduction into German. Had the dunes been distinguished from other hillocks, in ancient times, by so remarkable a feature as the propensity to drift, they would certainly have acquired a specific name in both Old Northern and German. So long as they were wooded knolls, they needed no peculiar name; when they became formidable, from the destruction of the woods which confined them, they acquired a designation. [443] The sands of Cape Cod were partially, if not completely, covered with vegetation by nature. Dr. Dwight, describing the dunes as they were in 1800, says: "Some of them are covered with beach grass; some fringed with whortleberry bushes; and some tufted with a small and singular growth of oaks. * * * The parts of this barrier, which are covered with whortleberry bushes and with oaks, have been either not at all, or very little blown. The oaks, particularly, appear to be the continuation of the forests originally formed on this spot. * * * They wore all the marks of extreme age; were, in some instances, already decayed, and in others decaying; were hoary with moss, and were deformed by branches, broken and wasted, not by violence, but by time."--_Travels_, iii, p. 91. [444] Bergsöe (_Reventlovs Virksomhed_, ii, 3) states that the dunes on the west coast of Jutland were stationary before the destruction of the forests to the east of them. The felling of the tall trees removed the resistance to the lower currents of the westerly winds, and the sands have since buried a great extent of fertile soil. See also same work, ii, p. 124. [445] "We must, therefore, not be surprised to see the people here deal as gingerly with their dunes, as if treading among eggs. He who is lucky enough to own a molehill of dune pets it affectionately, and spends his substance in cherishing and fattening it. That fair, fertile, rich province, the peninsula of Eiderstädt in the south of Friesland, has, on the point toward the sea, only a tiny row of dunes, some six miles long or so; but the people talk of their fringe of sand hills as if it were a border set with pearls. They look upon it as their best defence against Neptune. They have connected it with their system of dikes, and for years have kept sentries posted to protect it against wanton injury."--J. G. KOHL, _Die Inseln u. Marschen Schleswig-Holsteins_, ii, p. 115. [446] Sand banks sometimes connect themselves with the coast at both ends, and thus cut off a portion of the sea. In this case, as well as when salt water is enclosed by sea dikes, the water thus separated from the ocean gradually becomes fresh, or at least brackish. The Haffs, or large expanses of fresh water in Eastern Prussia--which are divided from the Baltic by narrow sand banks called Nehrungen, or, at sheltered points of the coast, by fluviatile deposits called Werders--all have one or more open passages, through which the water of the rivers that supply them at last finds its way to the sea. [447] ANDRESEN, _Om Klitformationen_, pp. 68-72. [448] Id., pp. 231, 232. Andresen's work, though printed in 1861, was finished in 1859. Lyell (_Antiquity of Man_, 1863, p. 14) says: "Even in the course of the present century, the salt waters have made one eruption into the Baltic by the Liimfjord, although they have been now again excluded." [449] FORCHHAMMER, _Geognostische Studien am Meeres-Ufer_. LEONHARD und BRONN, _Jahrbuch_, 1841, pp. 11, 13. [450] ANDRESEN, _Om Klitformationen_, pp. 68, 72. [451] _Voormaals en Thans_, pp. 126, 170. [452] See a very interesting article entitled "Le Littoral de la France," by ÉLISÉE RECLUS, in the _Revue des Deux Mondes_, for December, 1862, pp. 901, 936. [453] _De Bodem van Nederland_, i, p. 425. See _Appendix_, No. 60. [454] The movement of the dunes has been hardly less destructive on the north side of the Gironde. Sea the valuable article of ÉLISÉE RECLUS already referred to, in the _Revue des Deux Mondes_, for December, 1862, entitled "Le Littoral de la France." [455] LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des Ponts et Chaussées_, 1847, p. 223. The author adds, as a curious and unexplained fact, that some of these pools, though evidently not original formations but mere accumulations of water dammed up by the dunes, have, along their western shore, near the base of the sand hills, a depth of more than one hundred and thirty feet, and hence their bottoms are not less than eighty feet below the level of the lowest tides. Their western banks descend steeply, conforming nearly to the slope of the dunes, while on the northeast and south the inclination of their beds is very gradual. The greatest depth of these pools corresponds to that of the sea ten miles from the shore. Is it possible that the weight of the sands has pressed together the soil on which they rest, and thus occasioned a subsidence of the surface extending beyond their base? See _Appendix_, No. 61. [456] ANDRESEN, _Om Klitformationem_, pp. 56, 79, 82. [457] STARING, _De Bodem van Nederland_, i, pp. 329-331. Id., _Voormaals en Thans_, p. 163. ANDRESEN, _Om Klitformationen_, pp. 280, 295. The creation of new dunes, by the processes mentioned in the text, seems to be much older in Europe than the adoption of measures for securing them by planting. Dr. Dwight mentions a case in Massachusetts, where a beach was restored, and new dunes formed, by planting beach grass. "Within the memory of my informant, the sea broke over the beach which connects Truro with Province Town, and swept the body of it away for some distance. The beach grass was immediately planted on the spot; in consequence of which the beach was again raised to a sufficient height, and in various places into hills."--_Dwight's Travels_, iii, p. 93. [458] STARING, i, pp. 310, 332. [459] There is some confusion in the popular use of these names, and in the scientific designations of sand plants, and they are possibly applied to different plants in different places. Some writers style the gourbet _Calamagrostis arenaria_, and distinguish it from the Danish Klittetag or Hjelme. [460] Bread, not indeed very palatable, has been made of the seeds of the arundo, but the quantity which can be gathered is not sufficient to form an important economical resource.----ANDRESEN, _Om Klitformationen_, p. 160. [461] BERGSÖE, _Reventlovs Virksomhed_, ii, p. 4. [462] Measures were taken for the protection of the dunes of Cape Cod, in Massachusetts, during the colonial period, though I believe they are now substantially abandoned. A hundred years ago, before the valley of the Mississippi, or even the rich plains of Central and Western New York, were opened to the white settler, the value of land was relatively much greater in New England than it is at present, and consequently some rural improvements were then worth making, which would not now yield sufficient returns to tempt the investment of capital. The money and the time required to subdue and render productive twenty acres of sea sand on Cape Cod, would buy a "section" and rear a family in Illinois. The son of the Pilgrims, therefore, abandons the sand hills, and seeks a better fortune on the fertile prairies of the West. Dr. Dwight, who visited Cape Cod in the year 1800, after describing the "beach grass, a vegetable bearing a general resemblance to sedge, but of a light bluish-green, and of a coarse appearance," which "flourishes with a strong and rapid vegetation on the sands," observes that he received "from a Mr. Collins, formerly of Truro, the following information:" "When he lived at Truro, the inhabitants were, under the authority of law, regularly warned in the month of April, yearly, to plant beach grass, as, in other towns of New England, they are warned to repair highways. It was required by the laws of the State, and under the proper penalties for disobedience; being as regular a public tax as any other. The people, therefore, generally attended and performed the labor. The grass was dug in bunches, as it naturally grows; and each bunch divided into a number of smaller ones. These were set out in the sand at distances of three feet. After one row was set, others were placed behind it in such a manner as to shut up the interstices; or, as a carpenter would say, so as to break the joints. * * * When it is once set, it grows and spreads with rapidity. * * * The seeds are so heavy that they bend down the heads of the grass; and when ripe, drop directly down by its side, where they immediately vegetate. Thus in a short time the ground is covered. "Where this covering is found, none of the sand is blown. On the contrary, it is accumulated and raised continually as snow gathers and rises among bushes, or branches of trees cut and spread upon the earth. Nor does the grass merely defend the surface on which it is planted; but rises, as that rises by new accumulations; and always overtops the sand, however high that may be raised by the wind."--_Dwight's Travels in New England and New York_, ii, p. 92, 93. This information was received in 1800, and it relates to a former state of things, probably more than twenty years previous, and earlier than 1779, when the Government of Denmark first seriously attempted the conquest of the dunes. The depasturing of the beach grass--a plant allied in habits, if not in botanical character, to the arundo--has been attended with very injurious effects in Massachusetts. Dr. Dwight, after referring to the laws for its propagation, already cited, says: "The benefit of this useful plant, and of these prudent regulations, is, however, in some measure lost. There are in Province Town, as I was informed, one hundred and forty cows. These animals, being stinted in their means of subsistence, are permitted to wander, at times, in search of food. In every such case, they make depredations on the beach grass, and prevent its seeds from being formed. In this manner the plant is ultimately destroyed."--_Travels_, iii, p. 94. On page 101 of the same volume, the author mentions an instance of great injury from this cause. "Here, about one thousand acres were entirely blown away to the depth, in many places, of ten feet. * * * Not a green thing was visible except the whortleberries, which tufted a few lonely hillocks rising to the height of the original surface and prevented by this defence from being blown away also. These, although they varied the prospect, added to the gloom by their strongly picturesque appearance, by marking exactly the original level of the plain, and by showing us in this manner the immensity of the mass which had been thus carried away by the wind. The beach grass had been planted here, and the ground had been formerly enclosed; but the gates had been left open, and the cattle had destroyed this invaluable plant." [463] ANDRESEN, _Om Klitformationen_, pp. 237, 240. [464] "These plantations, perseveringly continued from the time of Brémontier now cover more than 40,000 hectares, and compose forests which are not only the salvation of the department, but constitute its wealth."--CLAVÉ, _Études Forestières_, p. 254. Other authors have stated the plantations of the French dunes to be much more extensive. [465] KRUSE, _Dünenbau_, pp. 34, 38, 40. [466] These processes are substantially similar to those employed in the pineries of the Carolinas, but they are better systematized and more economically conducted in France. In the latter country, all the products of the pine, even to the cones, find a remunerating market, while, in America, the price of resin is so low, that in the fierce steamboat races on the great rivers, large quantities of it are thrown into the furnaces to increase the intensity of the fires. In a carefully prepared article on the Southern pineries published in an American magazine--I think Harper's--a few years ago, it was stated that the resin from the turpentine distilleries was sometimes allowed to run to waste; and the writer, in one instance, observed a mass, thus rejected as rubbish, which was estimated to amount to two thousand barrels. See _Appendix_, No. 62. [467] ANDRESEN, _Om Klitformationen_, pp. 78, 262, 275. [468] LAVAL, _Mémoire sur les Dunes du Golfe de Gascogne, Annales des Ponts et Chaussées_, 1847, 2me sémestre, p. 261. See _Appendix_, No. 63. [469] There are extensive ranges of dunes on various parts of the coasts of the British Islands, but I find no estimate of their area. Pannewitz (_Anleitung zam Anbau der Sandflächen_), as cited by Andresen (_Om Klitformationen_, p. 45), states that the drifting sands of Europe, including, of course, sand plains as well as dunes, cover an extent of 21,000 square miles. This is, perhaps, an exaggeration, though there is, undoubtedly, much more desert land of this description on the European continent than has been generally supposed. There is no question that most of this waste is capable of reclamation by simple planting, and no mode of physical improvement is better worth the attention of civilized Governments than this. There are often serious objections to extensive forest planting on soils capable of being otherwise made productive, but they do not apply to sand wastes, which, until covered by woods, are not only a useless incumbrance, but a source of serious danger to all human improvements in the neighborhood of them. [470] BOITEL, _Mise en valeur des Terres pauvres par le Pin maritime_, pp. 212, 218. [471] See _Appendix_, No. . [472] For details, consult ANDRESEN, _Om Klitformationen_, pp. 223, 236. [473] When the deposit is not very deep, and the adjacent land lying to the leeward of the prevailing winds is covered with water, or otherwise worthless, the surface is sometimes freed from the drifts by repeated harrowings, which loosen the sand, so that the wind takes it up and transports it to grounds where accumulations of it are less injurious. [474] _Travels and Researches in Chaldæa_, chap. ix. [475] _Études Forestières_, p. 253. [476] LAVERGNE, _Économie Rurale de la France_, p. 300, estimates the area of the Landes of Gascony at 700,000 hectares, or about 1,700,000 acres. The same author states (p. 304), that when the Moors were driven from Spain by the blind cupidity and brutal intolerance of the age, they demanded permission to establish themselves in this desert; but political and religious prejudices prevented the granting of this liberty. At this period the Moors were a far more cultivated people than their Christian persecutors, and they had carried many arts, that of agriculture especially, to a higher pitch than any other European nation. But France was not wise enough to accept what Spain had cast out, and the Landes remained a waste for three centuries longer. See _Appendix_, No. 64. The forest of Fontainebleau, which contains above 40,000 acres, is not a plain, but its soil is composed almost wholly of sand, interspersed with ledges of rock. The sand forms not less than ninety-eight per cent. of the earth, and, as it is almost without water, it would be a drifting desert but for the artificial propagation of forest trees upon it. [477] _Économie Rurale de la Belgique, par_ EMILE DE LAVELEYE, _Revue des Deux Mondes_, Juin, 1861, pp. 617-644. [478] _Geognosie_, ii, p. 1173. [479] According to HOHENSTEIN, _Der Wald_, pp. 228, 229, an extensive plantation of pines--a tree new to Southern Russia--was commenced in 1842, on the barren and sandy banks of the Ingula, near Elisabethgrod, and has met with very flattering success. Other experiments in sylviculture at different points on the steppes promise valuable results. [480] "Sixteen years ago," says an Odessa landholder, "I attempted to fix the sand of the steppes, which covers the rocky ground to the depth of a foot, and forms moving hillocks with every change of wind. I tried acacias and pines in vain; nothing would grow in such a soil. At length I planted the varnish tree, or _ailanthus_, which succeeded completely in binding the sand." This result encouraged the proprietor to extend his plantations over both dunes and sand steppes, and in the course of sixteen years this rapidly growing tree had formed real forests. Other landowners have imitated his example with great advantage.--RENTSCH, _Der Wald_, p. 44, 45. [481] _Souvenirs d'un Naturaliste_, i, pp. 204 _et seqq._ [482] "If we suppose the narrow isthmus of Central America to be sunk in the ocean, the warm equatorial current would no longer follow its circuitous route around the Gulf of Mexico, but pour itself through the new opening directly into the Pacific. We should then lose the warmth of the Gulf Stream, and cold polar currents flowing farther southward would take its place and be driven upon our coasts by the western winds. The North Sea would resemble Hudson's Bay, and its harbors be free from ice at best only in summer. The power and prosperity of its coasts would shrivel under the breath of winter, as a medusa thrown on shore shrinks to an insignificant film under the influence of the destructive atmosphere. Commerce, industry, fertility of soil, population, would disappear, and the vast waste--a new Labrador--would become a worthless appendage of some clime more favored by nature."--HARTWIG, _Das Leben des Meeres_, p. 70. [483] I know nothing of Captain Allen's work but its title and its subject. Very probably he may have anticipated many of the following speculations, and thrown light on points upon which I am ignorant. [484] "Some haue writt[=e], that by certain kings inhabiting aboue, the _Nilus_ should there be stopped; & at a time prefixt, let loose vpon a certaine tribute payd them by the _Aegyptians_. The error springing perhaps fr[=o] a truth (as all wandring reports for the most part doe) in that the _Sultan_ doth pay a certaine annuall summe to the _Abissin_ Emperour for not diuerting the course of the Riuer, which (they say) he may, or impouerish it at the least."--GEORGE SANDYS, _A Relation of a Journey, etc._, p. 98. [485] The Recca, a river with a considerable current, has been satisfactorily identified with a stream flowing through the cave of Trebich, and with the Timavo--the Timavus of Virgil and the ancient geographers--which empties through several mouths into the Adriatic between Trieste and Aquileia. The distance from Trieste to a suitable point in the grotto of Trebich is thought to be less than three miles, and the difficulties in the way of constructing a tunnel do not seem formidable. The works of Schmidl, _Die Höhlen des Karstes_, and _Der unterirdische Lauf der Recca_, are not common out of Germany, but the reader will find many interesting facts derived from them in two articles entitled _Der unterirdische Lauf der Recca_, in _Aus der Natur_, xx, pp. 250-254, 263-266. [486] BARTH, _Wanderungen durch die Küsten des Mittelmeeres_, i, p. 353. In a note on page 380, of the same volume, Barth cites Strabo as asserting that a similar practice prevailed in Iapygia; but it may be questioned whether the epithet [Greek: tracheia], applied by Strabo to the original surface, necessarily implies that it was covered with a continuous stratum of rock. [487] PARTHEY, _Wanderungen durch Sicilien und die Levante_, i, p. 404. [488] _Geognostische Studien am Meeres Ufer_, LEONHARD und BRONN, _Jahrbuch_, 1841, pp. 25, 26. [489] KOHL, _Schleswig-Holstein_, ii, p. 45. [490] _Wanderungen durch Sicilien und die Levante_, i, p. 406. [491] LANDGREBE, _Naturgeschichte der Vulkane_, ii, pp. 19, 20. [492] Soon after the current issues from the volcano, it is covered above and at its sides, and finally in front, with scoriæ, formed by the cooling of the exposed surface, which bury and conceal the fluid mass. The stream rolls on under the coating, and between the walls of scoriæ, and it was the lateral crust which was broken through by the workmen mentioned in the text. The distance to which lava flows, before its surface begins to solidify, depends on its volume, its composition, its temperature and that of the air, the force with which it is ejected, and the inclination of the declivity over which it runs. In most cases it is difficult to approach the current at points where it is still entirely fluid, and hence opportunities of observing it in that condition are not very frequent. In the eruption of February, 1850, on the east side of Vesuvius, I went quite up to one of the outlets. The lava shot out of the orifice upward with great velocity, like the water from a spring, in a stream eight or ten feet in diameter, throwing up occasionally volcanic bombs, but it immediately spread out on the declivity down which it flowed, to the width of several yards. It continued red hot in broad daylight, and without a particle of scoriæ on its surface, for a course of at least one hundred yards. At this distance, the suffocating, sulphurous vapors became so dense that I could follow the current no farther. The undulations of the surface were like those of a brook swollen by rain. I estimated the height of the waves at five or six inches by a breadth of eighteen or twenty. To the eye, the fluidity of the lava seemed as perfect as that of water, but masses of cold lava weighing ten or fifteen pounds floated upon it like cork. The heat emitted by lava currents seems extremely small when we consider the temperature required to fuse such materials and the great length of time they take in cooling. I saw at Nicolosi ancient oil jars, holding a hundred gallons or more, which had been dug out from under a stream of old lava above that town. They had been very slightly covered with volcanic ashes before the lava flowed over them, but the lead with which holes in them had been plugged was not melted. The current that buried Mompiliere in 1669 was thirty-five feet thick, but marble statues, in a church over which the lava formed an arch, were found uncalcined and uninjured in 1704. See SCROPE, _Volcanoes_, chap. VI. § 6. [493] FERRARA, _Descrizione dell' Etna_, p. 108. [494] LANGREBE, _Naturgeschichte der Vulkane_, ii, p. 82. [495] _Physikalische Geographie_, p. 168. Beds of peat, accidentally set on fire, sometimes continue to burn for months. I take the following account of a case of this sort from a recent American journal: "A CURIOUS PHENOMENON.--When the track of the railroad between Brunswick and Bath was being graded, in crossing a meadow near the populous portion of the latter city, the 'dump' suddenly took on a sinking symptom, and down went the twenty feet fill of gravel, clay, and broken rocks, out of sight, and it was a long, _long_ time before dirt trains could fill the capacious stomach that seemed ready to receive all the solid material that could be turned into it. The difficulty was at length overcome, but all along the side of the sinkage the earth was thrown up, broken into yawning chasms, and the surface was thus elevated above its old watery level. Since that time this ground, thus slightly elevated, has been cultivated, and has yielded enormously of whatever the owner seemed disposed to plant upon it. Some three months ago, by some means unknown to us, the underlying peat took fire, and for weeks, as we had occasion to pass it, we noticed the smoke arising from the smouldering combustion beneath the surface. Rains fell, but the fire burned, and the smoke continued to arise. Monday we had occasion to pass the spot, and though nearly a week's rain had been drenching the ground, and though the surface was whitened with snow, and though pools of water were standing upon the surface in the immediate neighborhood, still the everlasting subterranean fire was burning, and the smoke arising through the snow." [496] One of the sublimest, and at the same time most fearful suggestions that have been prompted by the researches of modern science, was made by Babbage in the ninth chapter of his _Ninth Bridgewater Treatise_. I have not the volume at hand, but the following explanation will recall to the reader, if it does not otherwise make intelligible, the suggestion I refer to. No atom can be disturbed in place, or undergo any change of temperature, of electrical state, or other material condition, without affecting, by attraction or repulsion or other communication, the surrounding atoms. These, again, by the same law, transmit the influence to other atoms, and the impulse thus given extends through the whole material universe. Every human movement, every organic act, every volition, passion, or emotion, every intellectual process, is accompanied with atomic disturbance, and hence every such movement, every such act or process affects all the atoms of universal matter. Though action and reaction are equal, yet reaction does not restore disturbed atoms to their former place and condition, and consequently the effects of the least material change are never cancelled, but in some way perpetuated, so that no action can take place in physical, moral, or intellectual nature, without leaving all matter in a different state from what it would have been if such action had not occurred. Hence, to use language which I have employed on another occasion: there exists, not alone in the human conscience or in the omniscience of the Creator, but in external material nature, an ineffaceable, imperishable record, possibly legible even to created intelligence, of every act done, every word uttered, nay, of every wish and purpose and thought conceived by mortal man, from the birth of our first parent to the final extinction of our race; so that the physical traces of our most secret sins shall last until time shall be merged in that eternity of which not science, but religion alone, assumes to take cognizance. APPENDIX. No. 1 (page 19, _note_). It may be said that the cases referred to in the note on p. 19--and indeed all cases of a supposed acclimation consisting in physiological changes--are instances of the origination of new varieties by natural selection, the hardier maize, tomato, and other vegetables of the North, being the progeny of seeds of individuals endowed, exceptionally, with greater power of resisting cold than belongs in general to the species which produced them. But, so far as the evidence of change of climate, from a difference in vegetable growth, is concerned, it is immaterial whether we adopt this view or maintain the older and more familiar doctrine of a local modification of character in the plants in question. No. 2 (page 24, _note_). The adjectives of direction in _-erly_ are not unfrequently used to indicate, in a loose way, the course of winds blowing from unspecified points between N.E. and S.E.; S.E. and S.W.; S.W. and N.W. or N.W. and N.E. If the employment of these words were understood to be limited to thus expressing a direction nearer to the cardinal point from whose name the adjective is taken than to any other cardinal point, they would be valuable elements of English meteorological nomenclature. No. 3 (page 31). I find a confirmation of my observations on the habits of the beaver as a geographical agency, in a report of the proceedings of the British Association, in the London Athenæum of October 8, 1864, p. 469. It is there stated that Viscount Milton and Dr. Cheadle, in an expedition across the Rocky Mountains by the Yellow Head, or Leather Pass, observed that "a great portion of the country to the east of the mountains" had been "completely changed in character by the agency of the beaver, which formerly existed here in enormous numbers. The shallow valleys were formerly traversed by rivers and chains of lakes which, dammed up along their course at numerous points, by the work of those animals, have become a series of marshes in various stages of consolidation. So complete has this change been, that hardly a stream is found for a distance of two hundred miles, with the exception of the large rivers. The animals have thus destroyed, by their own labors, the waters necessary to their own existence." When the process of "consolidation" shall have been completed, and the forest reëstablished upon the marshes, the water now diffused through them will be collected in the lower or more yielding portions, cut new channels for their flow, become running brooks, and thus restore the ancient aspect of the surface. No. 4 (page 33, _note_). The lignivorous insects that attack living trees almost uniformly confine their ravages to trees already unsound or diseased in growth from the depredations of leaf-eaters, such as caterpillars and the like, or from other causes. The decay of the tree, therefore, is the cause not the consequence of the invasions of the borer. This subject has been discussed by Perris in the _Annales de la Société Entomologique de la France_, for 1851 (?), and his conclusions are confirmed by the observations of Samanos, who quotes, at some length, the views of Perris. "Having, for fifteen years," says the latter author, "incessantly studied the habits of lignivorous insects in one of the best wooded regions of France, I have observed facts enough to feel myself warranted in expressing my conclusions, which are: that insects in general--I am not speaking of those which confine their voracity to the leaf--do not attack trees in sound health, and they assail those only whose normal conditions and functions have been by some cause impaired." See, more fully, Samanos, _Traité de la Culture du Pin Maritime_, Paris, 1864, pp. 140-145. No. 5 (page 34, _note_). Very interesting observations, on the agency of the squirrel and other small animals in planting and in destroying nuts and other seeds of trees, may be found in a paper on the Succession of Forests in Thoreau's _Excursions_, pp. 135 _et seqq._ I once saw several quarts of beech-nuts taken from the winter quarters of a family of flying squirrels in a hollow tree. The kernels were neatly stripped of their shells and carefully stored in a dry cavity. No. 6 (page 40, _note_). Schroeder van der Kolk, in _Het Verschil tusschen den Psychischen Aanleg van het Dier en van den Mensch_, cites from Burdach and other authorities many interesting facts respecting instincts lost, or newly developed and become hereditary, in the lower animals, and he quotes Aristotle and Pliny as evidence that the common quadrupeds and fowls of our fields and our poultry yards were much less perfectly domesticated in their times than long, long ages of servitude have now made them. Perhaps the half-wild character ascribed by P. Læstadius and other Swedish writers to the reindeer of Lapland, may be in some degree due to the comparative shortness of the period during which he has been partially tamed. The domestic swine bred in the woods of Hungary and the buffaloes of Southern Italy are so wild and savage as to be very dangerous to all but their keepers. The former have relapsed into their original condition, the latter have not yet been reclaimed from it. Among other instances of obliterated instincts, Schroeder van der Kolk states that in Holland, where, for centuries, the young of the cow has been usually taken from the dam at birth and fed by hand, calves, even if left with the mother, make no attempt to suck; while in England, where calves are not weaned until several weeks old, they resort to the udder as naturally as the young of wild quadrupeds.--_Ziel en Ligchaam_, p. 128, _n._ No. 7 (page 60, _first note_). At Piè di Mulera, at the outlet of the Val Anzasca, near the principal hotel, is a vine measuring thirty-one inches in circumference. The door of the chapter-hall in the cloister of the church of San Giovanni, at Saluzzo, is of vine wood, and the boards of which the panels were made could not have been less than ten inches wide. Statues and other objects of considerable dimensions, of vine wood, are mentioned by ancient writers. No. 8 (page 63, _second note_). Cartier, A. D. 1535-'6, mentions "vines, great melons, cucumbers, gourds [courges], pease, beans of various colors, but not like ours," as common among the Indians of the banks of the St. Lawrence.--_Bref Recit_, etc., reprint. Paris, 1863, pp. 13, a; 14, b; 20, b; 31, a. No. 8 (page 65, _second paragraph_). It may be considered very highly probable, if not certain, that the undiscriminating herbalists of the sixteenth century must have overlooked many plants native to this island. An English botanist, in an hour's visit to Aden, discovered several species of plants on rocks always reported, even by scientific travellers, as absolutely barren. But after all, it appears to be well established that the original flora of St. Helena was extremely limited, though now counting hundreds of species. No. 9 (page 66, _first note_). Although the vine _genus_ is very catholic and cosmopolite in its habits, yet particular _varieties_ are extremely fastidious and exclusive in their requirements as to soil and climate. The stocks of many celebrated vineyards lose their peculiar qualities by transplantation, and the most famous wines are capable of production only in certain well-defined, and for the most part narrow districts. The Ionian vine which bears the little stoneless grape known in commerce as the Zante currant, has resisted almost all efforts to naturalize it elsewhere, and is scarcely grown except in two or three of the Ionian islands and in a narrow territory on the northern shores of the Morea. No. 10 (page 68, _first note_). In most of the countries of Southern Europe, sheep and beeves are wintered upon the plains, but driven in the summer to mountain pastures at many days' distance from the homesteads of their owners. They transport seeds in their coats in both directions, and hence Alpine plants often shoot up at the foot of the mountains, the grasses of the plain on the borders of the glaciers; but in both cases, they usually fail to propagate themselves by ripening their seed. This explains the scattered tufts of common clover, with pale and flaccid blossoms, which are sometimes seen at heights exceeding 7,000 feet above the sea. No. 11 (page 73, _last paragraph_). The poisonous wild parsnip, which is very common in New England, is popularly believed to be identical with the garden parsnip, and differenced only by conditions of growth, a richer soil depriving it, it is said, of its noxious properties. Many wild medicinal plants, such as pennyroyal for example, are so much less aromatic and powerful, when cultivated in gardens, than when self-sown on meagre soils, as to be hardly fit for use. No. 12 (page 74, _second note_). See in Thoreau's _Excursions_, an interesting description of the wild apple-trees of Massachusetts. No. 13 (page 86, _first paragraph_). It is said at Courmayeur that a very few ibexes of a larger variety than those of the Cogne mountains, still linger about the Grande Jorasse. No. 14 (page 92, _first note_). In Northern and Central Italy, one often sees hillocks crowned with grove-like plantations of small trees, much resembling large arbors. These serve to collect birds, which are entrapped in nets in great numbers. These plantations are called _ragnaje_, and the reader will find, in Bindi's edition of Davanzati, a very pleasant description of a ragnaja, though its authorship is not now ascribed to that eminent writer. No. 15 (page 93, _second note_). The appearance of the dove-like grouse, _Tetrao paradoxus_, or _Syrrhaptes Pallasii_, in various parts of Europe, in 1859 and the following years, is a noticeable exception to the law of regularity which seems to govern the movements and determine the habitat of birds. The proper home of this bird is the steppes of Tartary, and it is not recorded to have been observed in Europe, or at least west of Russia, until the year abovementioned, when many flocks of twenty or thirty, and even a hundred individuals, were seen in Bohemia, Germany, Holland, Denmark, England, Ireland, and France. A considerable flock frequented the Frisian island of Borkum for more than five months. It was hoped they would breed and remain permanently in the island, but this expectation has been disappointed, and the steppe-grouse seems to have disappeared again altogether. No. 16 (page 94, _note_). From an article by A. Esquiros, in the _Revue des Deux Mondes_ for Sept. 1, 1864, entitled, _La vie Anglaise_, p. 119, it appears that such occurrences as that stated in the note are not unfrequent on the British coast. No. 17 (page 100, _first paragraph_). I cannot learn that caprification is now practised in Italy, but it is still in use in Greece. No. 18 (page 112, _first note_). The recent great multiplication of vipers in some parts of France, is a singular and startling fact. Toussenel, quoting from official documents, states, that upon the offer of a reward of fifty centimes, or ten cents, a head, _twelve thousand_ vipers were brought to the prefect of a single department, and that in 1859 fifteen hundred snakes and twenty quarts of snakes' eggs were found under a farm-house hearthstone. The granary, the stables, the roof, the very beds swarmed with serpents, and the family were obliged to abandon its habitation. Dr. Viaugrandmarais, of Nantes, reported to the prefect of his department more than two hundred recent cases of viper bites, twenty-four of which proved fatal.--_Tristia_, p. 176 _et seqq._ No. 19 (page 121, _first note_). The Beduins are little given to the chase, and seldom make war on the game birds and quadrupeds of the desert. Hence the wild animals of Arabia are less timid than those of Europe. On one occasion, when I was encamped during a sand storm of some violence in Arabia Petræa, a wild pigeon took refuge in one of our tents which had not been blown down, and remained quietly perched on a boy in the midst of four or five persons, until the storm was over, and then took his departure, _insalutato hospite_. No. 20 (page 122). It is possible that time may modify the habits of the fresh water fish of the North American States, and accommodate them to the now physical conditions of their native waters. Hence it may be hoped that nature, even unaided by art, will do something toward restoring the ancient plenty of our lakes and rivers. The decrease of our fresh water fish cannot be ascribed alone to exhaustion by fishing, for in the waters of the valleys and flanks of the Alps, which have been inhabited and fished ten times as long by a denser population, fish are still very abundant, and they thrive and multiply under circumstances where no American species could live at all. On the southern slope of those mountains, trout are caught in great numbers, in the swift streams which rush from the glaciers, and where the water is of icy coldness, and so turbid with particles of fine-ground rock, that you cannot see an inch below the surface. The glacier streams of Switzerland, however, are less abundant in fish. No. 21 (page 131, _note_). Vaupell, though agreeing with other writers as to the injury done to the forest by most domestic animals--which he illustrates in an interesting way in his posthumous work, _The Danish Woods_--thinks, nevertheless, that at the season when the mast is falling swine are rather useful than otherwise to forests of beech and oak, by treading into the ground and thus sowing beechnuts and acorns, and by destroying moles and mice.--_De Danske Skore_, p. 12. No. 22 (page 135, _note_). The able authors of Humphreys and Abbot's most valuable Report on the Physics and Hydraulics of the Mississippi, conclude that the delta of that river began its encroachments on the Gulf of Mexico not more than 4,400 years ago, before which period they suppose the Mississippi to have been "a comparatively clear stream," conveying very little sediment to the sea. The present rate of advance of the delta is 262 feet a year, and there are reasons for thinking that the amount of deposit has long been approximately constant.--_Report_, pp. 435, 436. The change in the character of the river must, if this opinion is well founded, be due to some geological revolution, or at least convulsion, and the hypothesis of the former existence of one or more great lakes in its upper valley, whose bottoms are occupied by the present prairie region, has been suggested. The shores of these supposed lakes have not, I believe, been traced, or even detected, and we cannot admit the truth of this hypothesis without supposing changes much more extensive than the mere bursting of the barrier which confined the waters. No. 23 (page 143, _note_). See on this subject a paper by J. Jamin, in the _Revue des Deux Mondes_ for Sept. 15, 1864; and, on the effects of human industry on the atmosphere, an article in _Aus der Natur_, vol. 29, 1864, pp. 443, 449, 465 _et seqq._ No. 24 (page 159, _second paragraph_). All evergreens, even the broad-leaved trees, resist frosts of extraordinary severity better than the deciduous trees of the same climates. Is not this because the vital processes of trees of persistent foliage are less interrupted during winter than those of trees which annually shed their leaves, and therefore more organic heat is developed? No. 25 (page 191, _first paragraph_). In discussing the influence of mountains on precipitation, meteorologists have generally treated the popular belief, that mountains "attract" to them clouds floating within a certain distance from them, as an ignorant prejudice, and they ascribe the appearance of clouds about high peaks solely to the condensation of the humidity of the air carried by atmospheric currents up the slopes of the mountain to a colder temperature. But if mountains do not really draw clouds and invisible vapors to them, they are an exception to the universal law of attraction. The attraction of the small Mount Shehallien was found sufficient to deflect from the perpendicular, by a measurable quantity, a plummet weighing but a few ounces. Why, then, should not greater masses attract to them volumes of vapor weighing hundreds of tons, and floating freely in the atmosphere within moderate distances of the mountains? No. 26 (page 198, _note_). Élisée Redus ascribes the diminution of the ponds which border the dunes of Gascony to the absorption of their water by the trees which have been planted upon the sands.--_Revue des Deux Mondes_, 1 Aug., 1863, p. 694. No. 27 (page 219, _note_). The waste of wood in European carpentry was formerly enormous, the beams of houses being both larger and more numerous than permanence or stability required. In examining the construction of the houses occupied by the eighty families which inhabit the village of Faucigny, in Savoy, in 1834, the forest inspector found that _fifty thousand_ trees had been employed in building them. The builders "seemed," says Hudry-Menos, "to have tried to solve the problem of piling upon the walls the largest quantity of timber possible without crushing them."--_Revue des Deux Mondes_, 1 June, 1864, p. 601. No. 28 (page 231, _note_). In a remarkable pamphlet, to which I shall have occasion to refer more than once hereafter, entitled _Avant-projet pour la création d'un sol fertile à la surface des Landes de Gascogne_, Duponchel argues with much force, that the fertilizing properties of river-slime are generally due much more to its mineral than to its vegetable constituents. No. 29 (page 265, _note_). Even the denser silicious stones are penetrable by fluids and the coloring matter they contain, to such an extent that agates and other forms of silex may be artificially stained through their substance. This art was known to and practised by the ancient lapidaries, and it has been revived in recent times. No. 30 (page 268). There is good reason for thinking that many of the earth and rock slides in the Alps occurred at an earlier period than the origin of the forest vegetation which, in later ages, covered the flanks of those mountains. See _Bericht über die Untersuchung der Schweizerischen Hochgebirgswaldungen_. 1862. P. 61. Where more recent slides have been again clothed with woods, the trees, shrubs, and smaller plants which spontaneously grow upon them are usually of different species from those observed upon soil displaced at remote periods. This difference is so marked that the site of a slide can often be recognized at a great distance by the general color of the foliage of its vegetation. No. 31 (page 286, _note_). It should have been observed that the venomous principle of poisonous mushrooms is not decomposed and rendered innocent by the process described in the _note_. It is merely extracted by the acidulated or saline water employed for soaking the plants, and care should be taken that this water be thrown away out of the reach of mischief. No. 32 (page 293, _note_). Gaudry estimates the ties employed in the railways of France at thirty millions, to supply which not less than two millions of large trees have been felled. These ties have been, upon the average, at least once renewed, and hence we must double the number of ties and of trees required to furnish them.--_Revue des Deux Mondes_, 15 July, 1863, p. 425. No. 33 (page 294, _second paragraph of note_). After all, the present consumption of wood and timber for fuel and other domestic and rural purposes, in many parts of Europe, seems incredibly small to an American. In rural Switzerland, the whole supply of firewood, fuel for small smitheries, dairies, breweries, brick and lime kilns, distilleries, fences, furniture, tools, and even house building--exclusive of the small quantity derived from the trimmings of fruit trees, grape vines and hedges, and from decayed fences and buildings--does not exceed an average of _two hundred and thirty cubic feet_, or less than two cords, a year per household. The average consumption of wood in New England for domestic fuel alone, is from five to ten times as much as Swiss families require for all the uses above enumerated. But the existing habitations of Switzerland are sufficient for a population which increases but slowly, and in the peasants' houses but a single room is usually heated. See _Bericht über die Untersuchung der Schweiz. Hochgebirgswaldungen_, pp. 85-89. No. 34 (page 304). Among more recent manuals may be mentioned: _Les Études de Maitre Pierre._ Paris, 1864. 12mo; BAZELAIRE, _Traité de Reboisement_. 2d edition, Paris, 1864; and, in Italian, SIEMONI, _Manuale teorico-pratico d'arte Forestale_. Firenze, 1864. 8vo. A very important work has lately been published in France by Viscount de Courval, which is known to me only by a German translation published at Berlin, in 1864, under the title, _Das Aufästen der Waldbäume_. The principal feature of De Courval's very successful system of sylviculture, is a mode of trimming which compels the tree to develop the stem by reducing the lateral ramification. Beginning with young trees, the buds are rubbed off from the stems, and superfluous lateral shoots are pruned down to the trunk. When large trees are taken in hand, branches which can be spared, and whose removal is necessary to obtain a proper length of stem, are very smoothly cut off quite close to the trunk, and the exposed surface is _immediately_ brushed over with mineral-coal tar. When thus treated, it is said that the healing of the wound is perfect, and without any decay of the tree. No. 35 (page 313). The most gorgeous autumnal coloring I have observed in the vegetation of Europe, has been in the valleys of the Durance and its tributaries in Dauphiny. I must admit that neither in variety nor in purity and brilliancy of tint, does this coloring fall much, if at all, short of that of the New England woods. But there is this difference: in Dauphiny, it is only in small shrubs that this rich painting is seen, while in North America the foliage of large trees is dyed in full splendor. Hence the American woodland has fewer broken lights and more of what painters call breadth of coloring. Besides this, the arrangement of the leafage in large globular or conical masses, affords a wider scale of light and shade, thus aiding now the gradation, now the contrast of tints, and gives the American October landscape a softer and more harmonious tone than marks the humble shrubbery of the forest hill-sides of Dauphiny. Thoreau--who was not, like some very celebrated landscape critics of the present day, an outside spectator of the action and products of natural forces, but, in the old religious sense, an _observer_ of organic nature, living, more than almost any other descriptive writer, among and with her children--has a very eloquent paper on the "Autumnal Tints" of the New England landscape.--See his _Excursions_, pp. 215 _et seqq._ Few men have personally noticed so many facts in natural history accessible to unscientific observation as Thoreau, and yet he had never seen that very common and striking spectacle, the phosphorescence of decaying wood, until, in the latter years of his life, it caught his attention in a bivouac in the forests of Maine. He seems to have been more excited by this phenomenon than by any other described in his works. It must be a capacious eye that takes in all the visible facts in the history of the most familiar natural object.--_The Maine Woods_, p. 184. "The luminous appearance of bodies projected against the sky adjacent to the rising" or setting sun, so well described in Professor Necker's Letter to Sir David Brewster, is, as Tyndall observes, "hardly ever seen by either guides or travellers, though it would seem, _prima facie_, that it must be of frequent occurrence." See TYNDALL, _Glaciers of the Alps_. Part I. Second ascent of Mont Blanc. Judging from my own observation, however, I should much doubt whether this brilliant phenomenon can be so often seen in perfection as would be expected; for I have frequently sought it in vain at the foot of the Alps, under conditions apparently otherwise identical with those where, in the elevated Alpine valleys, it shows itself in the greatest splendor. No. 36 (page 314). European poets, whose knowledge of the date palm is not founded on personal observation, often describe its trunk as not only slender, but particularly _straight_. Nothing can be farther from the truth. When the Orientals compare the form of a beautiful girl to the stem of the palm, they do not represent it as rigidly straight, but on the contrary as made up of graceful curves, which seem less like permanent outlines than like flowing motion. In a palm grove, the trunks, so far from standing planted upright like the candles of a chandelier, bend in a vast variety of curves, now leaning towards, now diverging from, now crossing, each other, and among a hundred you will hardly see two whose axes are parallel. No. 37 (page 316, _first note_). Charles Martin ascribes the power of reproduction by shoots from the stump to the cedar of Mount Atlas, which appears to be identical with the cedar of Lebanon.--_Revue des Deux Mondes_, 15 July, 1864, p. 315. No. 38 (page 332). In an interesting article on recent internal improvements in England, in the London Quarterly Review for January, 1858, it is related that in a single rock cutting on the Liverpool and Manchester railway, 480,000 cubic yards of stone were removed; that the earth excavated and removed in the construction of English railways up to that date, amounted to a hundred and fifty million cubic yards, and that at the Round Down Cliff, near Dover, a single blast of nineteen thousand pounds of powder blew down a thousand million tons of chalk, and covered fifteen acres of land with the fragments. No. 39 (page 339). According to Reventlov, whose work is one of the best sources of information on the subject of diking-in tide-washed flats, _Salicornia herbacea_ appears as soon as the flat is raised high enough to be dry for three hours at ordinary ebb tide, or, in other words, where the ordinary flood covers it to a depth of not more than two feet. At a flood depth of one foot, the _Salicornia_ dies and is succeeded by various sand plants. These are followed by _Poa distans_ and _Poa maritima_ as the ground is raised by further deposits, and these plants finally by common grasses. The _Salicornia_ is preceded by _confervæ_, growing in deeper water, which spread over the bottom, and when covered by a fresh deposit of slime reappear above it, and thus vegetable and alluvial strata alternate until the flat is raised sufficiently high for the growth of _Salicornia_.--_Om Marskdannelsen paa Vestkysten af Hertugdömmet Slesvig_, pp. 7, 8. No. 40 (page 348, _note_). The drijftil employed for the ring dike of the Lake of Haarlem, was in part cut in sections fifty feet long by six or seven wide, and these were navigated like rafts to the spot where they were sunk to form the dike.--EMILE DE LAVELEYE, _Revue des Deux Mondes_, 15 Sept., 1863, p. 285. No. 41 (page 352, _last paragraph_). See on the influence of the improvements in question on tidal and other marine currents, Staring, _De Bodem van Nederland_, I. p. 279. Although the dikes of the Netherlands and the adjacent states have protected a considerable extent of coast from the encroachments of the sea, and have won a large tract of cultivable land from the dominion of the waters, it has been questioned whether a different method of accomplishing these objects might not have been adopted with advantage. It has been suggested that a system of inland dikes and canals, upon the principle of those which, as will be seen in a subsequent part of the chapter on the waters, have been so successfully employed in the Val di Chiana and in Egypt, might have elevated the low grounds above the ocean tides, by spreading over them the sediment brought down by the Rhine, the Maes, and the Scheld. If this process had been introduced in the Middle Ages and constantly pursued to our times, the superficial and coast geography, as well as the hydrography of the countries in question, would undoubtedly have presented an aspect very different from their present condition; and by combining the process with a system of maritime dikes, which would have been necessary, both to resist the advance of the sea and to retain the slime deposited by river overflows, it is possible that the territory of those states would have been as extensive as it now is, and, at the same time, more elevated by several feet. But it must be borne in mind that we do not know the proportions in which the marine deposits that form the polders have been derived from materials brought down by these rivers or from other more remote sources. Much of the river slime has no doubt been transported by marine currents quite beyond the reach of returning streams, and it is uncertain how far this loss has been balanced by earth washed by the sea from distant shores and let fall on the coasts of the Netherlands and other neighboring countries. We know little or nothing of the quantity of solid matter brought down by the rivers of Western Europe in early ages, but, as the banks of those rivers are now generally better secured against wash and abrasion than in former centuries, the sediment transported by them must be less than at periods nearer the removal of the primitive forests of their valleys. Klöden states the quantity of sedimentary matter now annually brought down by the Rhine at Bonn to be sufficient only to cover a square English mile to the depth of a little more than a foot.--_Erdkunde_, I. p. 384. No. 42 (page 358, _first paragraph_). Meteorological observations have been regularly recorded at Zwanenburg, near the north end of the Lake of Haarlem, for more than a century, and since 1845 a similar register has been kept at the Helder, forty or fifty miles farther north. In comparing these two series of observations, it is found that about the end of the year 1852, when the drawing off of the waters of the Lake of Haarlem was completed, and the preceding summer had dried the grounds laid bare so as greatly to reduce the evaporable surface, a change took place in the relative temperature of the two stations. Taking the mean of every successive period of five days from 1845 to 1852, the temperature at Zwanenburg was thirty-three hundredths of a centigrade degree _lower_ than at the Helder. Since the end of 1852, the thermometer at Zwanenburg has stood, from the 11th of April to the 20th of September inclusive, twenty-two hundredths of a degree _higher_ than at the Helder, but from the 14th of October to the 17th of March, it has averaged one-tenth of a degree _lower_ than its mean between the same dates before 1853. There is no reasonable doubt that these differences are due to the draining of the lake. There has been less refrigeration from evaporation in summer, and the ground has absorbed more solar heat at the same period, while in the winter it has radiated more warmth then when it was covered with water. Doubtless the quantity of humidity contained in the atmosphere has also been affected by the same cause, but observations do not appear to have been made on that point. See KRECKE, _Het Klimaat van Nederland_, II. 64. No. 43 (page 358, _note_). In the course of the present year (1864), there have been several land slips on the borders of the Lake of Como, and in one instance the grounds of a villa lying upon the margin of the water suffered a considerable displacement. If the lake should be lowered to any considerable extent, in pursuance of the plan mentioned in the note on page 358, there is ground to fear that the steep shores of the lake might, at some points, be deprived of a lateral pressure requisite to their stability, and slide into the water as on the Lake of Lungern. See p. 356. No. 44 (page 369, _last paragraph but one of note_). In like manner, while the box, the cedar, the fir, the oak, the pine, "beams," and "timber," are very frequently mentioned in the Old Testament, not one of these words is found in the New, _except_ the case of the "beam in the eye," in the parable in Matthew and Luke. No. 45 (page 375, _note_). In all probability, the real change effected by human art in the superficial geography of Egypt, is the conversion of pools and marshes into dry land, by a system of transverse dikes, which compelled the flood water to deposit its sediment on the banks of the river instead of carrying it to the sea. The _colmate_ of modern Italy were thus anticipated in ancient Egypt. No. 46 (page 378). We have seen in _Appendix_, No. 42, _ante_, that the mean temperature of a station on the borders of the Lake of Haarlem--a sheet of water formerly covering sixty-two and a half square English miles--for the period between the 11th of April and the 20th of September, had been raised not less than a degree of Fahrenheit by the draining of that lake; or, to state the case more precisely, that the formation of the lake, which was a consequence of man's improvidence, had reduced the temperature one degree F. below the natural standard. The artificially irrigated lands of France, Piedmont, and Lombardy, taken together, are fifty times as extensive as the Lake of Haarlem, and they are situated in climates where evaporation is vastly more rapid than in the Netherlands. They must therefore, no doubt, affect the local climate to a far greater extent than has been observed in connection with the draining of the lake in question. I do not know that special observations have been made with a view to measure the climatic effects of irrigation, but in the summer I have often found the _morning_ temperature, when the difference would naturally be least perceptible, on the watered plains of Piedmont, nine miles south of Turin, several degrees lower than that recorded at an observatory in the city. No. 47 (page 391, _note_). The Roman aqueduct known as the Pont du Gard, near Nismes, was built, in all probability, nineteen centuries ago. The bed of the river Gardon, a rather swift stream, which flows beneath it, can have suffered but a slight depression since the piers of the aqueduct were founded. No. 48 (page 393, _first note_). Duponchel makes the following remarkable statement: "The river Herault rises in a granitic region, but soon reaches calcareous formations, which it traverses for more than sixty kilometres, rolling through deep and precipitous ravines, into which the torrents are constantly discharging enormous masses of pebbles belonging to the hardest rocks of the Jurassian period. These debris, continually renewed, compose, even below the exit of the gorge where the river enters into a regular channel cut in a tertiary deposit, broad beaches, prodigious accumulations of rolled pebbles, extending several kilometres down the stream, but they diminish in size and weight so rapidly that above the mouth of the river, which is at a distance of thirty or thirty-five kilometres from the gorge, every trace of calcareous matter has disappeared from the sands of the bottom, which are exclusively silicious."--_Avant-projet pour la création d'un sol fertile_, etc., p. 20. No. 49 (page 404, _first paragraph of second note_). The length of the lower course of the Po having been considerably increased by the filling up of the Adriatic with its deposits, the velocity of the current ought, _prima facie_, to have been diminished and its bed raised in proportion. There are grounds for believing that this has happened in the case of the Nile, and one reason why the same effect has not been more sensibly perceptible in the Po is, that the confinement of the current by continuous embankments gives it a high-water velocity sufficient to sweep out deposits let fall at lower stages and slower movements of the water. Torrential streams tend first to excavate, then to raise, their beds. No general law on this point can be stated in relation to the middle and lower course of rivers. The conditions which determine the question of the depression or elevation of a river bed are too multifarious, variable, and complex to be subjected to formulæ, and they can scarcely even be enumerated. See, however, note on p. 431. No. 50 (page 406, _first paragraph_). The system proposed in the text is substantially the Egyptian method, the Nile dikes having been constructed rather to retain than to exclude the water. The waters of rivers which flow down planes of gentle inclination, deposit in their inundations the largest proportion of their sediment as soon as, by overflowing their banks, they escape from the swift current of the channel, and consequently the immediate banks of such rivers become higher than the grounds lying farther from the stream. In the "intervals," or "bottoms," of the great North American rivers, the alluvial banks are elevated and dry, the flats more remote from the river lower and swampy. This is generally observable in Egypt, though less so than in the valley of the Mississippi, where, below Cape Girardeau, the alluvial banks constitute natural glacis descending as you recede from the river, at an average of seven feet in the first mile.--HUMPHREYS AND ABBOT'S _Report_, pp. 96, 97. The Egyptian crossdikes, by retaining the water of the inundations, compel it to let fall its remaining slime, and hence the elevation of the remoter land goes on at a rate not very much slower than that of the immediate banks. Probably transverse embankments would produce the same effect in the Mississippi valley. In the great floods of this river, it is observed that, at a certain distance from the channel, the bottoms, though lower than the banks, are flooded to a less depth. See cross sections in Plate IV. of Humphreys and Abbot's Report. This apparently anomalous fact is due, I suppose, to the greater swiftness of the current of the overflowing water in the low grounds, which are often drained through the channels of rivers whose beds lie at a lower level than that of the Mississippi, or by the bayous which are so characteristic a feature of the geography of that valley. A judicious use of dikes would probably convert the swamps of the lower Mississippi valley into a region like Egypt. No. 51 (_second note_). The mean discharge of the Mississippi is 675,000 cubic feet per second, and, accordingly, that river contributes to the sea about eleven times as much water as the Po, and more than sis and a half times as much as the Nile. The discharge of the Mississippi is estimated at one-fourth of the precipitation in its basin, certainly a very large proportion, when we consider the rapidity of evaporation in many parts of the basin, and the probable loss by infiltration.--HUMPHREYS AND ABBOT'S _Report_, p. 93. No. 52 (page 423, _first paragraph_). Artificially directed currents of water have been advantageously used in civil engineering for displacing and transporting large quantities of earth, and there is no doubt that this agency might be profitably employed to a far greater extent than has yet been attempted. Some of the hydraulic works in California for washing down masses of auriferous earth are on a scale stupenduous enough to produce really important topographical changes. No. 53 (page 435, _first note_). I have lately been informed by a resident of the Ionian Islands, who is familiar with this phenomenon, that the sea flows uninterruptedly into the sub-insular cavities, at all stages of the tide. No. 54 (page 438, _note_). It is observed in Cornwall that deep mines are freer from water in artificially well-drained, than in undrained agricultural districts.--ESQUIROS, _Revue des Deux Mondes_, Nov. 15, 1863, p. 430. No. 55 (page 441). See, on the Artesian wells of the Sahara, and especially on the throwing up of living fish by them, an article entitled, _Le Sahara_, etc., by Charles Martins, in the _Revue des Deux Mondes_ for August 1, 1864, pp. 618, 619. No. 56 (page 444, _first note_). From the article in the _Rev. des Deux Mondes_, referred to in the preceding note, it appears that the wells discovered by Ayme were truly artesian. They were bored in rock, and provided at the outlet with a pear-shaped valve of stone, by which the orifice could be closed or opened at pleasure. No. 57 (page 447, _second note_). Hull ingeniously suggests that, besides other changes, fine sand intermixed with or deposited above a coarser stratum, as well as the minute particles resulting from the disintegration of the latter, may be carried by rain in the case of dunes, or by the ordinary action of sea water in that of subaqueous sandbanks, down through the interstices in the coarser layer, and thus the relative position of fine sand and gravel may be more or less changed.--_Oorsprong der Hollandsche Duinen_, p. 103. No. 58 (page 479). It appears from Laurent, that marine shells, of extant species, are found in the sands of the Sahara, far from the sea, and even at considerable depths below the surface.--_Mémoires sur le Sahara Oriental_, p. 62. This observation has been confirmed by late travellers, and is an important link in the chain of evidence which tends to prove that the upheaval of the Libyan desert is of comparatively recent date. No. 59 (p. 480). "At New Quay [in England] the dune sands are converted to stone by an oxyde of iron held in solution by the water which pervades them. This stone, which is formed, so to speak, under our eye, has been found solid enough to be employed for building."--ESQUIROS, _L'Angleterre et la vie Anglaise_, _Revue des Deux Mondes_, 1 March, 1864, pp. 44, 45. No. 60 (page 496, _first paragraph_). In Ditmarsh, the breaking of the surface by the man[oe]uvering of a corps of cavalry let loose a sand-drift which did serious injury before it was subdued.--KOHL, _Inseln u. Marschen._ etc., III. p. 282. Similar cases have occurred in Eastern Massachusetts, from equally slight causes.--See THOREAU, _A Week on the Concord and Merrimack Rivers_, pp. 151-208. No. 61 (page 497, _last note_). A more probable explanation of the fact stated in the note is suggested by Èlisée Reclus, in an article entitled, _Le Littoral de la France_, in the _Revue des Deux Mondes_ for Sept. 1, 1864, pp. 193, 194. This able writer believes such pools to be the remains of ancient maritime bays, which have been cut off from the ocean by gradually accumulated sand banks raised by the waves and winds to the character of dunes. No. 62 (page 506, _note_). The statement in the note is confirmed by Olmsted: "There is not a sufficient demand for rosin, except of the first qualities, to make it worth transporting from the inland distilleries; it is ordinarily, therefore, conducted off to a little distance, in a wooden trough, and allowed to flow from it to waste upon the ground. At the first distillery I visited, which had been in operation but one year, there lay a congealed pool of rosin, estimated to contain over three thousand barrels."--_A Journey in the Seaboard Slave States_, 1863, p. 345. No. 63 (page 507). In an article on the dunes of Europe, in Vol. 29 (1864) of _Aus der Natur_, p. 590, the dunes are estimated to cover, on the islands and coasts of Schleswig Holstein, in Northwest Germany, Denmark, Holland, and France, one hundred and eighty-one German, or nearly four thousand English square miles; in Scotland, about ten German, or two hundred and ten English miles; in Ireland, twenty German, or four hundred and twenty English miles; and in England, one hundred and twenty German, or more than twenty-five hundred English miles. No. 64 (page 512, _last paragraph_). For a brilliant account of the improvement of the Landes, see Edmond About, _Le Progrès_, Chap, VII. In the memoir referred to in _Appendix_, No. 48, _ante_, Duponchel proposes the construction of artificial torrents to grind calcareous rock to slime by rolling and attrition in its bed, and, at the same time, the washing down of an argillaceous deposit which is to be mixed with the calcareous slime and distributed over the Landes by watercourses constructed for the purpose. By this means, he supposes that a highly fertile soil could be formed on the surface, which would also be so raised by the process as to admit of freer drainage. That nothing may be wanting to recommend this project, Duponchel suggests that, as some of the rivers of Western France are auriferous, it is probable that gold enough may be collected from the washings to reduce the cost of the operations materially. No. 65 (page 528, _first paragraph_). The opening of a channel across Cape Cod would have, though perhaps to a smaller extent, the same effects in interchanging the animal life of the southern and northern shores of the isthmus, as in the case of the Suez canal; for although the breadth of Cape Cod does not anywhere exceed twenty miles, and is in some places reduced to one, it appears from the official reports on the Natural History of Massachusetts, that the population of the opposite waters differs widely in species. Not having the original documents at hand, I quote an extract from the _Report on the Invertebrate Animals of Mass._, given by Thoreau, _Excursions_, p. 69: "The distribution of the marine shells is well worthy of notice as a geological fact. Cape Cod, the right arm of the Commonwealth, reaches out into the ocean some fifty or sixty miles. It is nowhere many miles wide; but this narrow point of land has hitherto proved a barrier to the migration of many species of mollusca. Several genera and numerous species, which are separated by the intervention of only a few miles of land, are effectually prevented from mingling by the Cape, and do not pass from one side to the other * * * * Of the one hundred and ninety-seven marine species, eighty-three do not pass to the south shore, and fifty are not found on the north shore of the Cape." Probably the distribution of the species of mollusks is affected by unknown local conditions, and therefore an open canal across the Cape might not make every species that inhabits the waters on one side common to those of the other; but there can be no doubt that there would be a considerable migration in both directions. The fact stated in the report may suggest an important caution in drawing conclusions upon the relative age of formations from the character of their fossils. Had a geological movement or movements upheaved to different levels the bottoms of waters thus separated by a narrow isthmus, and dislocated the connection between those bottoms, naturalists, in after ages, reasoning from the character of the fossil faunas, might have assigned them to different, and perhaps very widely distant, periods. No. 66 (page 548, _first paragraph_). To the geological effects of the thickening of the earth's crust in the Bay of Bengal, are to be added those of thinning it on the highlands where the Ganges rises. The same action may, as a learned friend suggests to me, even have a cosmical influence. The great rivers of the earth, taken as a whole, transport sediment from the polar regions in an equatorial direction, and hence tend to increase the equatorial diameter, and at the same time, by their inequality of action, to a continual displacement of the centre of gravity, of the earth. The motion of the globe and of all bodies affected by its attraction, is modified by every change of its form, and in this case we are not authorized to say that such effects are in any way compensated. INDEX Abbeys of St. Germain and St. Denis, revenues of, 6. Adirondack forest, 235; lakes of, 357. Ailanthus glandulosa, 515. Akaba, gulf of, infiltration of fresh water in, 440. Albano, lake of, artificial lowering of, 353. Algeria, deserts of, artesian wells in, 443; sand dunes of, 463; consolidated dunes, 480. Alpaca, South American, 83. Amazon, Indians of, 11. Ameland, island of, 499. America, North, primitive physical condition of, 27, 43; forests of, 28; possibility of noting its physical changes, 52; by scientific observation, 53; forest trees of, 274; sand dunes of, 469; proposed changes in hydrography of, 532. Animal life, sympathy of ruder races with, 39; instinct, fallibility of, 40; hostility of civilized man to inferior forms of, 121. Animals, wild, action of on vegetation, 78. Aphis, the European, 104. Apennines, effects of felling the woods on, 150, 152. Appian way, the, 542. Aqueducts, geographical and climatic effects of, 358. Arabia Petræa, surface drainage of, 440; sandstone of, 452; sands and petrified wood of, 455; wadies of, 538. Aragua, valley of, Venezuela, 202. Ararat, Mt., phenomenon of vegetation on, 287. Ardèche, l', department of, 152; destruction of forests in, 389. -- river and basin, floods of, 386; supply of water to the Rhone, 388, 398; violence of inundations of, 388; damage done by, 390; effect on river beds, 391; force of its affluents, 392. Argostoli, Cephalonia, millstreams of, 434. Armenia, ancient irrigation of, 366. Arno, the river, deposits of, 414; upper course of in the Val di Chiana, 417, 420. Artesian wells, their sources, 441; usual objects, 442; occasional effects, 442; employment in the Algerian desert, 443; by the French Government, 444; success and probable results of, 445; known to the ancients, 443; depth of, 444. Arundo arenaria, 501. Ascension, island of, 205. Auk, the wingless, extirpation of, 95. Australia a field of physical observation, 51. Avalanches, Alpine, various causes of, 266; by felling trees, 270. Azoff, sea of, proposed changes, 531. Babinet, plan for artificial springs, by, 448. Baikal Lake, the fish of, 117. Baltic Sea, sand dunes of, 467. Barcelonette, valley of, former fertility, 243; present degradation of, 244. Bavaria, scarcity of fuel in, 299. Bear, the mythical character of, 40. Beaver, the, agency in forming bogs, 31; cause of its increased numbers, 84. Bee, the honey, products of, 105; introduction in United States, 106. Belgium, effect of plantations in, 152; Campine of, 513. Ben Gâsi, district of, rock formation in, 537. Bergamo, change of climate in the valley of, 151. Bibliographical list of authorities, vii. Birch tree (black and yellow), produce of, 171. Birds, number of, in United States, 86; the turkey, dove, pigeon, 87; as sowers and consumers of seeds, 87; as destroyers of insects, 89; injurious extirpation of, 90; wanton destruction of, 92; weakness of, 93; instinct of migratory, 94; extinction of species, 95; commercial value of, 97; introduction of species, 98. Bison, the American, 78; number and migrations of, 81, 83; domesticated, 135. Blackbird, the proscription of, 91. Bogs, formation and nomenclature of, 29-32; of New England, 29; repositories of fuel, 30. Brémontier, system of dune plantations of, 503; a benefactor to his race, 515. Breton, Cap, dune vineyards of, 508. Busbequius' letters, 64. Camel, the, transfer and migrations of, 83; injurious to vegetation, 132. Campine of Belgium, 513. Canada thistle, the, 68. Canals, geographic and climatic effects of, 359; injurious effects of Tuscan, 359; projected, Suez, 519; Isthmus of Darien, 522; to the Dead Sea, 524; maritime, in Greece, 526; Saros, 527; Cape Cod, 528; the Don and the Volga, 531; Lake Erie and the Genesee, 532; Lake Michigan and the Mississippi, 533. Cape Cod, sand dunes of, 487; legislative protection of, 502; vegetation of, 503; projected canal through, 528. Cappercailzie, the, extinction of, in Britain, 96. Carniola, caves of, 434. Caspian Sea, proposed changes in its basin, 531. Catania, lava streams of, 544. Catavothra of Greece, 536. Cévennes, effects of clearing the, 153. Champlain, lake, dates of its congelation, 163. Cherbourg, breakwater of, 46, 332. Chiana, Val di, description and character of, 417-420; plans for its restoration, 420; artificial drainage of, attempted, 421; successfully executed, 423. Clergy, mediæval, their character, 282. Climatic change, discussions of, 9; how tested, 20; causes producing, in New England, Africa, Arabia Petræa, 20-22; man's action on, difficult to ascertain, 51; deterioration, 71. Coal mines, combustion of, 546. Coal, sea, early use of, for fuel, 222; increased use of, in Paris, 295. Coast line, change of, from natural causes, 331; subject to human guidance, 332. Cochineal insect transferred to Spain, 105. Cochituate Aqueduct, Boston, 103. Col Isoard, valley of, devastated, 242. Commerce, modern, on what dependent, 60. Como, lake of, proposed lowering of, 358. Constance, lake of, 534. Cork-oak tree, yield of, 311. Corporations, social and political, influence of, 54. Cosmical influences, 13. Cotton, early cultivation of, 61; can be raised by white labor, 381. Crawley Sparrow Club, 90. Currents, sea, strength of, 456; in the Bosphorus, 457. Cuyahoga river, 208. Cypress tree, its beauty, 314. Darien, Isthmus of, proposed canal across, 522; conjectural effects of, 523. Dead Sea, projected canals to, 524; possible results of, 525. Deer, numbers of, in United States; 82; tame, injurious to trees, 130. Denmark, peat mosses of, 22; dunes of, 497; extent and movement of, 498; legislative protection of, 501, 504. Desert, the, richness of local color, 445; mirage in, 446. Des Plaines river, 533. Despotism a cause of physical decay, 5. Dikes, recovery of land by, in the Netherlands, 335; early usage and immense extent of, 336; encouraged by the Spaniards, 337; details of their construction and effect on the land gained, 340-345; in Egypt, 413. Dinornis, or moa, recent extirpation of, in New Zealand, 95. Dodo, the, extirpation of, 95. Domestic animals, action of, on vegetation, 79; origin and transfer of, 82; injurious to the forest growth, 130. Don river, proposed diversion of, 531. Draining a geographical element, 360; superficial, its necessity in forest lands, 363; effect on temperature, 364; underground, _ib._; extensive use of, in England, 362; affects the atmosphere, 364; disturbs the equilibrium of river supply, 365; by boring, 362; in France, &c., 362; Paris, 363. Drance, Switzerland, glacier lake of, 403. Dry land and water, relative extent of, 178. Dwight, Dr., Travels in the United States, characterized, 52. Earth, fertile, below the rock, 537; transported to cover rocky surfaces, 537. Earthquakes, effects of, 542; causes and possible prevention of, 543; of Lisbon, 544. Earthworm, utility of, in agriculture, 100; multiplication of, in New England, 101. Egypt, catacombs, 70; papyrus or water lily, 70; poisonous snakes of, 112; supposed increase of rain in, 190; productiveness of, 230; necessity and extent of irrigation in, 368, 373; cultivated soil of, 372, 374; population of, 374; amount of water used for irrigation, 380; saline deposits, 382; artificial river courses of, 402; cultivated area of, 412; sands of, 458; their prevalence and extent, 459; source of, 461; action on the Delta and cultivated land, 462; effect of the diversion of the Nile on, 529; refuse heaps near Cairo, 541. Eland, the, preserved in Prussia, 86. Elm, the Washington, Cambridge, 146. Elsineur, artificial formation in harbor of, 539. England, forest economy of, 221; large extent of ornamental plantations, 222; Forests of, described by Cæsar, 222; private enterprise in sylviculture, 292; sand dunes of, 507. Enguerrand de Coucy, cruelty of, 281. Erie Canal, the, influence on the fauna and flora of its region, 116; lake, depth and level of, 532; proposed canal from, 532. Espy's theories of artificial rain, 547. Etna, volcanic lava and dust, 131. Euphrates, sand plains in the valley of, 511. Eye, cultivation of the, 11; control of the limbs by, 12; trained by the study of physical geography, 12. Feudalism, pernicious influence of, 6. Fir tree, the, its products, 311. Fire weed, in burnt forests of the United States, 287. Fish, destruction of, by man, 112, 114, 120, 122; voracity of, 114; introduction and breeding of foreign, 116; naturalization of, 117; inferiority of the artificially fattened, 121. Fish, shell, extensive remains of, in United States, 117; of Indian origin, 128. Fish ponds of Catholic countries, 426. Fontainebleau, forest of, 34, 130; poaching in, 284; its renovation, 316; soil of, 513. Food, ancient arts of preservation of, 18. Forest, the, influence of, on the humidity of air, 162; do. of earth, 165; as organic, 166; balance of conflicting influences in, 176; influence on temperature, 178; on precipitation, 181, 196; in South America, 184; the Canary Islands and Asia Minor, 185; Peru, 188; Palestine, Southern France, Scotland and Egypt, 189; influence of, on humidity of soil, 196; on springs, 197; in Venezuela, 202; New Granada, 204; Switzerland and France, 205, 208; United States, 207; in winter, 210; general consequences of its destruction, 214; on the earth, springs, rivers, 215; literature of, in France, 217; Germany, 218; Italy, 218; England, 221; influence of, on inundations, 223; in North America, 225; disputed effects of, in Europe, 228; principal causes of its destruction, 270; in British America, 271; in Europe, 279; royal forests, 280; effects of the Revolution on, in France, 284; utility of, for the preservation of smaller plants, 286, 290; do. of birds, 291; economic utility of, and necessity for its restoration, 292; extent of, in Europe, 296; proportion in different countries of, 300; of the United States and Canada, 300; economy of, 303; management of, in France, 304; European forests, all of artificial growth, 305; artificial and natural, their respective advantages, 307; American do., their peculiar characteristics, 313; economic action of cattle on, 325; duty of preserving, 327; average revenue from, 327; regulated by laws in France, 395. See _Trees_, _Woods_. Forests of North America, balance of geographical elements in, 27; agency of quadrupeds and insects in, 32; injury to, by insects, 33; meteorological importance of, 139. Forest laws, mediæval, character of, 217; do. Jewish, 217; severity of, in France and England, 280; under Louis IX., 281; of America, created by circumstances, 302. France, forest literature and economy of, 217; legislation on forests, 233; -- Southeastern, former physical state of, 237; altered condition of, 239; royal forests of, and forest laws, 280; extent of, in, 296; ancient lakes of, 357; inundations of 1856 in, 393; remedies against inundations in, 395; sand dunes of Western, 485; encroachments of the sea on, 494. French peasantry, described by La Bruyere, 6; do. Arthur Young, 7; of Chambord, 283. Friesland, sand dunes of, 489. Fucinus Lake (Lago di Celano), drainage of, by the Romans, 354; moderns, 355. Game Laws, effect on the numbers of birds in France, 91; in England and Italy, 92; severity of, in France, 283; unable to stop poaching, 284. Ganges, valley of the, 548. Gascony, coast sands of, 453; dunes of, 496; extent and advance of, 497; fixing and reclaiming of, 504; Landes of, 511; their reclamation, 512. Geological influences, 13. Geographers, new school of, 8. Geographical influence of changes produced by man, 352. Geography, modern, improved form of, 57. German Ocean, sands of, 454, 457. Germany, extent of forests in, 299. Glacier lakes in Switzerland, 403. Goat, the Cashmere or Thibet, 83. Gold fish, the migration from China, 116. Goldau, Switzerland, destruction of, 268. Grape disease, its economic effect in France, Italy, Sicily, 72. Grasshopper, the rapid increase in America, 291. Gravedigger beetle, the, 107. Greece, proposed maritime canals in, through the Corinthian Isthmus, 526; Mount Athos, 527; subterranean waters of, 536. Gulls, sea, habits of, 98. Gulf stream, the, 523. Gunpowder chiefly used for industrial purposes, 335. Haarlem Lake, origin and extent of, 346, 347; reasons for draining it, 348; means employed, 349; successful results, 350. Hauran, the productions of, its soil, 74. Heilbronn, springs at, 207. Herring fishery, produce of, 120. Hessian fly, introduction of in the United States, 104. Honey bee, the wild, New England, legal usage, 302. Humid air, movement of, 183. Hunter in New England, exploits of, 82. Ibex, the Alpine, 86. India, saline efflorescence of its soil, 382; natural connection of rivers in, 401. Insects, injurious to vegetable life, 33; utility of, 99; agency in the fertilization of orchids, 102; mass of their exuviæ in South America, 102; introduction of injurious species, 104, 106; ravages of, 105; tenacity of life in, 106; the carnivorous, useful to man, 107; destruction of, by fish, 108; abundance of, in Northern Europe, 108; destruction of, by birds, 109; do. quadrupeds, 110; do. reptiles, 110; do not multiply in the forest, 291; confine themselves to dead trees, 322. Inundations, influence of the forest on, 223; of the German Ocean, 334; means for obviating, 384; of 1856 in France, 393; remedies against, 395; legislative regulation of the woodlands in France for prevention of, 396; proposed basins of reception, 398; do. in Peru and Spain, 400; Rozet's plan for diminishing, 406. Irrigation, remote date of in ancient nations, 366; among Mexicans and Peruvians, 366; its necessity in hot climates, 367; in Europe, 367; in Palestine, 368; in Idumæa, 370; Egypt, 371, 373; quantity of water so applied, 376, 377; extent of lands irrigated, 396; effects of, 378; on river supply, 380; on human health, 381; saline deposits from, in India and Egypt, 382; effect of, on vegetable crops, 378; on the soil, 379; economic evils of, 379. Islands, floating, in Holland and South America, 349, 351. Ijssel river, Holland, 535. Italy, effects of the denudation of its forests, 220; political condition adverse to their preservation, 219; beauty of its winter scenery, 314; extent of irrigation in, 368; atmospheric phenomena of Northern, 368. Jupiter, satellites of, visible to the eye, 12. Jutland, effects of felling the woods in, 150; destruction of forests in, 279; encroachments of the sea on, 491. Kander river, Switzerland, artificial course of, 403. Karst, the subterranean waters of, 536. Kjökkenmöddinger in Denmark, 16; their extent, 540. Kohl, J. G., "the Herodotus of modern Europe," 340; on dune sand, 475. Labruguière, commune of, 208. Læstadius, account of the Swedish Laplanders, 96. Lakes, draining of, by steam hydraulic engines, 346; natural process of filling up by aquatic vegetation, 349; lowering of, in ancient and modern times, 353; in Italy, 354; in Switzerland, 356; inconvenient consequences of, 356; mountain, their disappearance, 357. Landscape beauty, insensibility of the ancients to, 2; of the oasis and the desert, 445. Lava currents, diversion of their course, 544; from Vesuvius, phenomena of, 545; heat emitted by, 545. Life, balance of animal and vegetable, 103. Liimfjord, the, irruption of the sea into, 491; aquatic vegetation of, 492; original state of, 519. Lion, an inhabitant of Europe, 85. Lisbon, earthquake of, 544. Locust, the, does not multiply in woods, 296; tree and insect, 32. Lombardy, statistics of irrigation in, 376. Louis IX., of France, clemency of, 282. Lower Alps, department of, ravages of torrents in, 246. Lumber trade of Quebec, 271; of United States, 1850-'60, 301. Lungern, lake of, lowering of, 356. Madagascar, gigantic bird of, 96; the ai-ai of, 110. Madder, early cultivation of, in Europe, 20. Madeira, named from its forests, 129. Maize, early cultivation of, law of its acclimation, 19; native country of, 73. Malta, transported soil of, 538; salt works at, 540. Man, reaction of, on nature, 8; insufficiency of data, 9; geographical influence of, 13; physical revolutions wrought by, 14; unpremeditated results of conscious action, 15; ancient relics of, in old geological formations, 16; mechanical effects of, on the earth's surface, 25; destructiveness of, 35; in animal life and inorganic nature, 36-39; character of his action compared with that of brutes, 42; subversive of the balance of nature, 43; sometimes exercised for good, 44; present limits to, 45; transfer of vegetable life by, 59; remains of, 76; contemporary with the mammoth, 77; agency in the extermination of birds, 96; do. introduction of species, 98; increase of insect life, 104; introduction of new forms of do. by, 105; destruction of fish by, 112, 120, 122; extirpation of aquatic animals by, 119; possible control of minute organisms, 125; his first physical conquest, 135; his action on land and the waters, 330; possible geographical changes by, 517; incidental effects of his action, 539; illimitable and ever enduring do., 548. Maremme of Tuscany, ancient and mediæval state of, 425; extent of, 427; inhabitants, 428; improvement of, 429; sedimentary deposits of, 425, 430. Marine isthmuses, cutting of, 517; its difficulties, 518; sometimes done by nature, 519. Marmato in Popayan, 205. Marshes, climatic effects of draining, 358; insalubrity of mixture of fresh and salt water in, 417. Mechanic arts, illustration of their mutual interdependence, 307. Medanos of the South American desert, 482. Mediterranean Sea, tides of, 425; sand dunes of, 467; poor in organic life, 520. Mella, the river, Italy, 248. Meteorology, uncertainty and late rise of, 16, 22; varying nomenclature of, 23; precipitation and evaporation, 24. Michigan, lake, sand dunes of, 467; originally wooded, 487; proposed diversion of its waters, 532. Mining excavations, effects of, 545. Minute organisms, their offices, 123; universal diffusion and products of, 124, 127; possible control of their agency by man, 125; the coral insect, 125; the diatomaceæ, 126. Miramichi, great fire of, 28. Mistral in France, 153. Mississippi river, "cut offs" and their effect, 415; precipitation in the valley of, 436; projected canal to, 533. Mountain slides, their cause, 265, 268; their frequency in the Alps, 267. Mountainous countries, their liability to physical degradation, 50. Monte Testaccio, Rome, 541. Moose deer, the American, rapid multiplication of, 130. Mushrooms, poisonous, how to render harmless, 286. Natural forces, accumulation of, 46; resistance to, 542. Nature, man's reaction on, 8; observation of, 10; stability of, 27, 34; restoration of disturbed harmonies of, 35; nothing small in, 548. Naturalists, enthusiasm of, 99. Netherlands, ancient inundations of, 334; recovery of land by diking, 334; the practice derived from the Romans, 335; extent of land gained from the sea, 336; do. lost by incursions of do., 337; character of lands gained, 338; natural process of recovery, 339; grandeur of the dike system of, 340; method of their construction in, 341; modes of protection, 343; various uses of, 343; effect on the level of the land, 344; drainage of do., 345; primitive condition of, 351; effects on the social, moral, and economic interests of the people of, 351; sand dunes of, 486; encroachments of the sea on, 494; artificial dunes in, 499; protection of dunes in, 500; removal of do., 509. Nile, the river, valley of, 374; its ancient state, 375; inundations of, 385; water delivery of, 387; artificial mouths of, 402; consequences of diking, 410, 413; richness of its deposits, 411; extent of do., 412; mud banks caused by its deposits, 433; sand dunes at its mouths, 468; conduits for irrigation, 521; proposed diversion of, 528; not impossible, 529; effects of, 530; ceramic banks of, 541. Northmen in New England, 60. Nubians, Nile boats of the, 17. Numbers, the frequent error in too definite statements of, 260; oriental and Italian usage of, 261. Oak, the English, early uses in the arts, 223; "openings" of North America, 136. Ohio, mounds of, 18; remains of a primitive people in, 135, 138; apple trees of, 22. Old World, former populousness of, 4; physical decay of, 3; present desolation of, 5; its causes, 5; ancient climate of, 19; physical restoration of, 47. Olive tree, the wild, 74; importance of, 312. Orange tree known to the ancients, 64; the wild, 74. Orchids, fertilization of, by insects, 102. Organic life embraced in modern geography, 57; its geological agency, 75; geographical importance of, 7; bones and relics of, human and animal, 76. Ostrich, the, diminution of its numbers, 97. Ottaquechee river, Vermont, transporting power of, 253. Otter, the American, voracity of, 120. Oxen, agricultural uses of, in United States, 80. Oyster, the, transplantation of, 118. Palestine, ancient terrace culture and irrigation of, 369; disastrous effects of its neglect, 370. Palissy, Bernard, character of, 218; plan for artificial springs, 447. Paragrandini of Lombardy, 141. Paramelle, the Abbé, on fountains, 437. Peat beds, accidental burning of, 546; -- mosses of Denmark, 32. Pecora, river of the Maremma, its deposits, 425. Peru, ancient progress in the arts, 366; basins of reception in, 400. Petra, in Idumæa, ancient irrigation at, 370. Phosphorescence of the sea unknown to the ancients, 114. Physical decay of the earth's surface, 3; its causes, 5; arrest of, in new countries, 48; forms and formations predisposing to, 49. Physical geography, study of recommended, 12; restoration of the earth, 8; importance and possibility of, 26; of disturbed harmonies, 35; of the Old World, 47. Pine, the American, former ordinary dimensions of, 275; how affected by the accidents of its growth, 306; the maritime, on dune sands in France, 506; the pitch, hardihood of, 273; umbrella, the, most elegant of trees, 309, 313; the white, rapidity of its growth, 274. Pinus cembra of Switzerland, 309. Pisciculture, its valuable results, 118. Plants, cultivated, uncertain identity of ancient and modern, 19; do. of wild and domestic species, 73; changes of habit by domestication, 19; geographical influence of, 58; foreign, grown in United States, 61; American, grown in Europe, 63; modes of introduction, 64; accidental do., 66; power of accommodation of, 65; how affected by transfer, 68; tenacity of life in wild species, 69; extirpation of, 70; domestic origin of, 72; species employed for protection of sand dunes, 500. Pliny, the elder, theory of springs, 198, 216. Po, river, ancient state of its basin, 255; modern changes, 256; its floods, tributaries, and deposits, 256-261, 405; embankments of, 385, 404; sediment of, 410; age and consequences of its embankments, 411; mean delivery of, 412; _salti_ of, 415. Poland, sand plains of, 514. Poplar, the Lombardy, 68; characterized, 313. Potato, native country of, 73. Prairies, conjectural origin of, 134. Provence, physical structure of, 237; ancient state of, 238; destructive action of torrents on, 236; Alps of, 245. Prussia, sand dunes of, 485; drifting of, 498; measures for reclaiming of, 505. Quadrupeds, number in United States, 79; extirpation of, 84. Quebec, high tides of, 271; lumber trade of, 272. Railways, scientific uses of, 53. Rain water, its absorption and infiltration, 438, 439; economizing its precipitation, 449. Ravenna, cathedral of, 60; pine woods of, 150. Red Sea, richness of, in organic life, 320; diversion of the Nile to, its effects, 530. Reindeer, the, 83. Reservoirs, geographic and climatic effects of, 258. Reventlov's organization of dune economy in Denmark, 504; a benefactor to his race, 515. Rhine, river, proposed diversion of, 533. Rice, cultivation of, 381. Rivers, transporting power of, 252; in Vermont, 253; their origin, 262; injury to their banks by lumbermen, 277; conditions of their rise and fall, 278; mutual action of rivers and valleys, 408; effect of obstructions in, 409; subterranean course of, 409; confluences of, effect on the current below, 424; sediment of, its extent, 547. River beds, natural change of, 401; artificial do. in Egypt, 402; Italy and Switzerland, 403. River deposits, 408; of the Nile, 410; the Po, 411; the Tuscan rivers, 414. River embankments, 384; their use, 404; disadvantages, 405; transverse do., superiority of, 406; effects of, 409. River mouths, obstructions of, 430; by sand banks, 431; accelerated by man's influence, 432; effect of tidal movements, 432. Robin, the American, voracity of, 88. Rock generally permeable by water, 265. Roman empire, natural advantages of its territory, 1; increased by intelligent labor, 2; physical decay of, 3; present desolation, 4; caused by its despotism and oppression, 5. Rozet's plan for diminishing inundations, 406. Rude tribes, continuity of arts among, 17; commerce of, 18; relations to organic life, 39; and to nature, 41. Russia, diminution of forests in, 298; effects of, on rivers and lakes, 299; sand drifts of the steppes of, 514; attempts to reclaim them, 515. Sacramento City, California, effect of river dike at, 405. Sand, its composition and origin, 452; action of rivers, 453; ancient deposits of, 454, 456; amount of, carried to the Mediterranean, 455; of Egypt, 458, 461; movement of, by the wind, 459; drifts of, from the sea, 461; dangers of accumulation of, 463; two forms of deposit, 463; drifting of dune, 495. Sand banks, aquatic, 468; movement of, 469; connect themselves with the coast, 490. Sand dunes, how formed, 464; utilization of, 465; inland, of the South American desert, 482; their peculiarities, 483; age, character, and permanence of, 484; naturally wooded, 486; not noticed by ancient writers, 487; management of, 488; coast, sources of supply, 465; law of their formation, 466, 471, 483; of the Mediterranean, 467; of Lake Michigan, 467; of the Nile mouths, 468; of America, 469; of Western Europe, 470; literature of, 471; height of, 472; humidity of, 473; of Cape Cod, 487; character of their sand, 474, 481; concretion within, 476; interior structure of, 477; general form of, 478; geological importance of, 479; composition of sandstone, 481; as barriers against the sea, 489; in Western Europe, 490; extent of, 507; of Gascony, 496; of Denmark, 497; of Prussia, 497; artificial formation of, in Holland, 499; protection of, 500; by vegetation, 501; trees adapted to, 505; removal of, 509. Sand-dune vineyard of Cap Breton, 508. Sand plains, mode of deposit, 464; constituent parts, 464; inland, of Europe, 509; landes of Gascony, 511; Belgium, 513; Eastern Europe, 513; advantages of reclaiming, 515; private and public enterprise, 516. Sand springs, 511. Sandal wood extirpated in Juan Fernandez, 130. Saros, projected canal of, 527. Sawmills, action of their machinery more rapid by night, 278. Schelk, the extirpation of, 85. Schleswig-Holstein, encroachments of the sea on, 493. Scientific observation, practical lessons of, 54-56. Sea, the, exclusion of, by dikes, in Lincolnshire, 333; encroachments of, 490; coast, 491; the Liimfjord, 491; Schleswig-Holstein, 493; Holland, 494; France, 494. Sea cow, Steller's, extirpation of, 119. Seal, the, in Lake Champlain, 117; voracity of, 120. Seeds, vitality of, as preserved by the forest, 287, 289. Seine river, ancient level of, 214; affluents of, 435. Ship building of the middle ages, Venice and Genoa, 218. Siberia, ice ravine in, 158. Sicily, stone weapons found in, 18; sulphur mines of, 72; olive oil crop of, 312. Silkworm, introduction in South America, 105. Sinai, Mt., rain torrent at, 441; production of sand in peninsula of, 454; garden of monastery at, 537. Snakes, destructive to insects, 110; tenacity of species, 111; number of, in Palestine and Egypt, 111. Snow, action of the woods on, 211; experiments on, 212. Soils, amount of thermoscopic action on various, 144; mechanical effects of shaking in the Netherlands, 344; effect of frost on, in United States, 344. Solar heat, economic employment of, 47. Solitary, the, extirpation of, 95. Sound, transmission of, in still air, 165. Springs, artificial, proposed by Palissy, 447; by Babinet, 448. Spain, neglect of forest culture in, 279. Squirrel, the, destructiveness of, in forests, 34; of Boston, 121. St. Helena, flora of, 65; destruction of its forests, 130. Staffordshire, phenomena of vegetation in, 288. Starlings, habits of, in Piedmont, 111. Stork, the, geographical range of, 93; anecdote of a, 99. Subterranean waters, their origin, 434; sources of supply, 435; reservoirs and currents of, 438; diffusion of, in the soil, 439; importance, 440; of the Karst, 535; of Greece, 536. Suez canal, the, danger from sand drifts, 461; effect on the Mediterranean and Red Sea basins, 520. Sugar cane, culture of, 62. Sugar-maple tree, produce of, 169. Summer dikes of Holland, 342. Sunflowers, effect of plantations of, 154. Swallow, the, popular superstitions respecting, 418. Switzerland, ancient lacustrine habitations of, 16, 70, 83. Sylt Island, sand dunes of, 474; encroachments of the sea on, 493. Sylviculture, best manuals of practice of, 304; when and how profitable, 305; its methods, 315; the _taillis_ treatment, 315; the _futaie_ do., 317; beneficial effects of irrigation, 319; exclusion of animals, 321; removal of leaves, &c., 322; topping and trimming, 324. Taguataga Lake, Chili, 355. Tea plant, the, cultivated in America, 62. Temperature, general law of, 52. Teredo, the general diffusion of, 107. Termite, or white ant, ravages of, 107. Teverone, cascade of, Tivoli, 402. Timber, general superiority of cultivated, 305; slow decay of, in forest, 322. Tobacco an American plant, 68; introduction in Hungary, 67. Tocat, Asia Minor, oak woods of, 186. Tomato, the, introduction to New England, 19. Torricelli, successful plan for draining the Val di Chiana, 421. Torrents, destructive action of, 231; means of prevention, 233; ravages of, in Southeastern France, 237; Provence, 239; Upper Alps, 240; Lower Alps, 246; action of, in elevating the beds of mainland streams, 249; in excavating ravines, 250; transporting power of, 251; signs of, extinguished, 263; crushing force of, 392. Trees, as organisms, specific temperature of, 156; moisture given out by, 158; total influence on temperature, 159; absorption of water by, 166; flow of sap, 169; absorption of moisture by foliage of, 172; exhalation of do., 174; consequent refrigeration, 175; amount of ligneous products of, 173; protection against avalanches afforded by, 269; power of resisting the action of fire, 273; American forest trees, 274; their dimensions, 275; change in relative proportions of height and diameter, 276; comparative longevity of, 277; European and American compared, 308; species more numerous in America, 309; Spenser's catalogue of, 308; interchange of European and American species, 310; species of Southern Europe and their extent, 312; natural order of succession in, 323. See _Forest_, _Woods_. Trieste, proposed supply of water to, 536. Trout, the American, 115, 117, 121. Tuscany, rivers of, their deposits, 414; physical restoration in, 416; improvements in Val di Chiana, 417; do. in the Maremma, 424. Tyrolese rivers, elevation of their beds, 249. Ubate, lakes of, New Granada, 204. Undulation of water, 456. United States, foreign plants grown in, 61; weight of annual harvest in, 62; number of quadrupeds in, 79; of birds, 86; effect of felling woods on its climate, 180; forests of, 300; instability of life in, 328. Upper Alps, department of, ravages of torrents in, 240. Urus, or auerochs, domesticated by man, 83; extirpation of, 85. Val de Lys, evidence of glacier action in, 252. Vegetable life, transfer by man's action, 59. Velino, cascade of, Tivoli, 402. Vesuvius, vegetation on, 131; eruption of February, 1851, 544. Volcanic action, resistance to, 544; matter, vegetation in, 131. Volga river, proposed diversion of, 531. Walcheren, formation of the island, 340. Wallenstadt, lake of, 534. Walnut tree, consumption of, for gun stocks, 296; oil yielded by, 310. Ward's cases for plants, 175. Waste products, utilization of, 37. Weeds common to Old and New World, 66; extirpated in China, &c., 71. Whale, the, food of, 113; destruction of, 114. Whale fishery, date of its commencement unknown, 112; in the middle ages, 112; American, 113. Wheat, its asserted origin, 73; introduction to America, 74. Wild animals, number of, 84. Wild organisms, vegetable and animal, tenacity of life in, 69. Willow, the weeping, introduction in Europe, 64. Wolf, increase of the, 84; prevalence in forests of France, 296. Wolf Spring, Soubey, 206. Wood, increased demand for, 293; ship building, railroads, &c., 294; market price of, 294; replaced by iron in the arts, 295; means of increasing its durability, 295; how affected by rapid growth, 306; facilities for working, 307. Woods, habitable earth originally covered by, 128; conditions of their propagation, 131; destructive agency of man and domestic animals, 132; do not furnish food for man, 133; first removal of, 134; burning of, 136; in Sweden and France, 137; effect on the soil, 138; destruction of, its effect, 139; electrical influence of, 140; chemical influence of, 142; influence on temperature, 143; absorbing and emitting surface of, 144; in summer and winter, 147; dead products of, 148; as a shelter, 149; in France, 149, 151; New England, 149; Italy and Jutland, 150; as a protection against malaria, 154; tend to mitigate extremes of temperature, 155. See _Forest_, _Trees_. Wood mosses and fungi, absorbent of moisture, 168. Woodpecker, the, destroyer of insects, 109. Yak, or Tartary ox, the, 83. Yew tree, geographical range of, 70. Zeeland, province, formation of, 339. Zostera marina, 492. Zuiderzee, proposed drainage of, 534; means of, and geographical results, 535. THE END. * * * * * FORSYTH'S "CICERO." A New Life of Cicero. BY WILLIAM FORSYTH, M. A., Q. C. With Twenty Illustrations. 2 vols. crown octavo. Printed on tinted and laid paper. Price, $5.00. The object of this work is to exhibit Cicero not merely as a Statesman and an Orator, but as he was at home in the relations of private life, as a Husband, a Father, a Brother, and a Friend. His letters are full of interesting details, which enable us to form a vivid idea of how the old Romans lived 2,000 years ago; and the Biography embraces not only a History of Events, as momentous as any in the annals of the world, but a large amount of Anecdote and Gossip, which amused the generation that witnessed the downfall of the Republic. The _London Athenæuem_ says: "Mr. Forsyth has rightly aimed to set before us a portrait of Cicero in the modern style of biography, carefully gleaning from his extensive correspondence all those little traits of character and habit which marked his private and domestic life. These volumes form a very acceptable addition to the classic library. The style is that of a scholar and a man of taste." From the _Saturday Review_:--"Mr. Forsyth has discreetly told his story, evenly and pleasantly supplied it with apt illustrations from modern law, eloquence, and history, and brought Cicero as near to the present time as the differences of age and manners warrant. * * * These volumes we heartily recommend as both a useful and agreeable guide to the writings and character of one who was next in intellectual and political rank to the foremost man of all the world, at a period when there were many to dispute with him the triple crown of forensic, philosophic, and political composition." "A scholar without pedantry, and a Christian without cant, Mr. Forsyth seems to have seized with praiseworthy tact the precise attitude which it behoves a biographer to take when narrating the life, the personal life, of Cicero. Mr. Forsyth produces what we venture to say will become one of _the classics of English biographical literature_, and will be welcomed by readers of all ages and both sexes, of all professions and of no profession at all."--_London Quarterly._ "This book is a valuable contribution to our Standard Literature. It is a work which will aid our progress towards the truth; it lifts a corner of the veil which has hung over the scenes and actors of times so full of ferment, and allows us to catch a glimpse of the stage upon which the great drama was played."--_North American Review._ _Copies sent by mail, post paid, on receipt of price._ LORD DERBY'S "HOMER." The Iliad of Homer. RENDERED INTO ENGLISH BLANK VERSE BY EDWARD, EARL OF DERBY. From the fifth London Edition. Two volumes, royal octavo, on tinted paper. Price $7.50 per vol. Extracts from Notices and Reviews from the English Quarterlies, &c. "The merits of Lord Derby's translation may be summed up in one word: "it is eminently attractive; it is instinct with life; it may be read with fervent interest; it is immeasurably nearer than Pope to the text of the original. * * * We think that Lord Derby's translation will not only be read, but read over and over again. * * * Lord Derby has given to England a version far more closely allied to the original, and superior to any that has yet been attempted in the blank verse of our language."--_Edinburgh Review, January 1865._ "As often as we return from even the best of them (other translations) to the translation before us, we find ourselves in a purer atmosphere of taste. We find more spirit, more tact in avoiding either trivial or conceited phrases, and altogether a presence of merits, and an absence of defects which continues, as we read, to lengthen more and more the distance between Lord Derby and the foremost of his competitors."--_London Quarterly Review, January, 1865._ "While the versification of Lord Derby is such as Pope himself would have admired, his Iliad is in all other essentials superior to that of his great rival. For the rest, if Pope is dethroned what remains? * * * It is the Iliad we would place in the hands of English readers as the truest counterpart of the original, the nearest existing approach to a reproduction of that original's matchless feature."--_Saturday Review._ "Among those curiosities of literature which are also its treasures, Lord Derby's translation of Homer must occupy a very conspicuous place. * * * Lord Derby's work is, on the whole, more remarkable for the constancy of its excellence and the high level which it maintains throughout, than for its special bursts of eloquence. It is uniformly worthy of itself and its author."--_The Reader._ "Whatever may be the ultimate fate of this poem--whether it take sufficient hold of the public mind to satisfy that demand for a translation of Homer which we have alluded to, and thus become a permanent classic of the language, or whether it give place to the still more perfect production of some yet unknown poet--it must equally be considered a splendid performance; and for the present we have no hesitation in saying that it is by far the best representation of Homer's Iliad in the English language." AMERICAN NOTICES. The _Publishers Circular_ says:--At the advanced age of sixty-five, the Earl of Derby, leader of the Tory party in England, has published a translation of Homer, in blank verse. Nearly all the London critics unite in declaring, with _The Times_, "that it is by far the best representation of Homer's 'Iliad' in the English language." His purpose was to produce a translation, and not a paraphrase--fairly and honestly giving the sense of every passage and of every line. Without doubt the greatest of all living British orators, he has now shown high poetic power as well as great scholarship. From the _New York World_:--"The reader of English, who seeks to know what Homer really was, and in what fashion he thought and felt and wrote, will owe to Lord Derby his first honest opportunity of doing so. The Earl's translation is devoid alike of pretension and of prettiness. It is animated in movement, simple and representative to phraseology, breezy in atmosphere, if we may so speak, and pervaded by a refinement of taste which is as far removed from daintiness or effeminacy as can well be imagined." _Copies sent by mail, post paid, on receipt of price._ TRANSCRIBER'S NOTES: 1. Passages in italics are surrounded by _underscores_. 2. The original text includes Greek characters. For this text version these letters have been replaced with transliterations. 3. Certain words use "oe" ligature in the original, indicated by [oe] and [OE]. 4. The letters with macron are represented within square braces with an equals sign preceding it. For example, letter a with macron is indicated by [=a]. 5. In this text version, some of the references to appendix notes within footnotes were incorrect which have been corrected. Also, errors found in page references within Appendix have been corrected. 
6019	----	THE EARTH AS MODIFIED BY HUMAN ACTION. A NEW EDITION OF MAN AND NATURE. BY GEORGE P. MARSH. "Not all the winds, and storms, and earthquakes, and seas, and seasons of the world, have done so much to revolutionize the earth as MAN, the power of an endless life, has done since the day he came forth upon it, and received dominion over it."--H. Bushnell, Sermon on the Power of an Endless Life. 1874. PREFACE TO THE FIRST EDITION. The object of the present volume is: to indicate the character and, approximately, the extent of the changes produced by human action in the physical conditions of the globe we inhabit; to point out the dangers of imprudence and the necessity of caution in all operations which, on a large scale, interfere with the spontaneous arrangements of the organic or the inorganic world; to suggest the possibility and the importance of the restoration of disturbed harmonies and the material improvement of waste and exhausted regions; and, incidentally, to illustrate the doctrine that man is, in both kind and degree, a power of a higher order than any of the other forms of animated life, which, like him, are nourished at the table of bounteous nature. In the rudest stages of life, man depends upon spontaneous animal and vegetable growth for food and clothing, and his consumption of such products consequently diminishes the numerical abundance of the species which serve his uses. At more advanced periods, he protects and propagates certain esculent vegetables and certain fowls and quadrupeds, and, at the same time, wars upon rival organisms which prey upon these objects of his care or obstruct the increase of their numbers. Hence the action of man upon the organic world tends to derange its original balances, and while it reduces the numbers of some species, or even extirpates them altogether, it multiplies other forms of animal and vegetable life. The extension of agricultural and pastoral industry involves an enlargement of the sphere of man's domain, by encroachment upon the forests which once covered the greater part of the earth's surface otherwise adapted to his occupation. The felling of the woods has been attended with momentous consequences to the drainage of the soil, to the external configuration of its surface, and probably, also, to local climate; and the importance of human life as a transforming power is, perhaps, more clearly demonstrable in the influence man has thus exerted upon superficial geography than in any other result of his material effort. Lands won from the woods must be both drained and irrigated; river-banks and maritime coasts must be secured by means of artificial bulwarks against inundation by inland and by ocean floods; and the needs of commerce require the improvement of natural and the construction of artificial channels of navigation. Thus man is compelled to extend over the unstable waters the empire he had already founded upon the solid land. The upheaval of the bed of seas and the movements of water and of wind expose vast deposits of sand, which occupy space required for the convenience of man, and often, by the drifting of their particles, overwhelm the fields of human industry with invasions as disastrous as the incursions of the ocean. On the other hand, on many coasts, sand-hills both protect the shores from erosion by the waves and currents, and shelter valuable grounds from blasting sea-winds. Man, therefore, must sometimes resist, sometimes promote, the formation and growth of dunes, and subject the barren and flying sands to the same obedience to his will to which he has reduced other forms of terrestrial surface. Besides these old and comparatively familiar methods of material improvement, modern ambition aspires to yet grander achievements in the conquest of physical nature, and projects are meditated which quite eclipse the boldest enterprises hitherto undertaken for the modification of geographical surface. The natural character of the various fields where human industry has effected revolutions so important, and where the multiplying population and the impoverished resources of the globe demand new triumphs of mind over matter, suggests a corresponding division of the general subject, and I have conformed the distribution of the several topics to the chronological succession in which man must be supposed to have extended his sway over the different provinces of his material kingdom. I have, then, in the introductory chapter, stated, in a comprehensive way, the general effects and the prospective consequences of human action upon the earth's surface and the life which peoples it. This chapter is followed by four others in which I have traced the history of man's industry as exerted upon Animal and Vegetable Life, upon the Woods, upon the Waters, and upon the Sands; and to these I have added a concluding chapter upon Man. It is perhaps superfluous to add, what indeed sufficiently appears upon every page of the volume, that I address myself not to professed physicists, but to the general intelligence of observing and thinking men; and that my purpose is rather to make practical suggestions than to indulge in theoretical speculations more properly suited to a different class from that for which I write. GEORGE P. MARSH. December 1, 1868. PREFACE TO THE PRESENT EDITION. In preparing for the press an Italian translation of this work, published at Florence in 1870, I made numerous corrections in the statement of both facts and opinions; I incorporated into the text and introduced in notes a large amount of new data and other illustrative matter; I attempted to improve the method by differently arranging many of the minor subdivisions of the chapters; and I suppressed a few passages which teemed to me superfluous. In the present edition, which is based on the Italian translation, I have made many further corrections and changes of arrangement of the original matter; I have rewritten a considerable portion of the work, and have made, in the text and in notes, numerous and important additions, founded partly on observations of my own, partly on those of other students of Physical Geography, and though my general conclusions remain substantially the same as those I first announced, yet I think I may claim to have given greater completeness and a more consequent and logical form to the whole argument Since the publication of the original edition, Mr. Elisee Reclus, in the second volume of his admirable work, La Terre (Paris, 1868), lately made accessible to English-reading students, has treated, in a general way, the subject I have undertaken to discuss. He has, however, occupied himself with the conservative and restorative, rather than with the destructive, effects of human industry, and he has drawn an attractive and encouraging picture of the ameliorating influences of the action of man, and of the compensations by which he, consciously or unconsciously, makes amends for the deterioration which he has produced in the medium he inhabits. The labors of Mr. Reclus, therefore, though aiming at a much higher and wider scope than I have had in view, are, in this particular point, a complement to my own. I earnestly recommend the work of this able writer to the attention of my readers. George P. Marsh Rome, May 1, 1878. BIBLIOGRAPHICAL LIST OF WORKS CONSULTED IN THE PREPARATION OF THIS VOLUME. Amersfoordt, J.P. Het Haarlemmermeer, Oorsprong, Geschiedenis, Droogmaking. Haarlem, 1857. 8vo. Andresen, C.C. Om Klitformationen og Klittens Behandling og Bestyrelse. Kjobenhavn, 1861. 8vo. Annali di Agricoltura, Industria e Commercio. Pubblicati per cura del Ministero d'Agricoltura, Industria e Commercio. Faso i-v. Torino, 1862-'3. 8vo. Arago, F. Extracts from, in Becquerel, Des Climate. Arriani, Opera. Lipsiae, 1856. 2 vols. 12mo. Asbjornen, P.Chr. Om Skoveno og om et ordnet Skovbrug i Norge. Christiania, 1855. 12mo. Aus der Natur. Die neuesten Entdeckungen auf dem Gebiete der Naturwissenschaften. Leipzig, various years. 20 vols. 8vo. Ave-Lallemant, K.C.B. Die Benutzung der Palmen am Amazonenstrom in der Oekonomie der Indier. Hamburg, 1861. 18mo. Babinet. Etudes et Lectures sur les Sciences d'Obsorvation. Paris, 1855- 1863. 7 vols. 18mo. Baer, von. Kaspische Studien. St. Petersburg, 1855-1859. 8vo. Barth, Heinrich. Wanderungen durch die Kustenlander des Mittelmeeres. V.1. Berlin, 1849. 8vo. Barth, J.B. Om Skovene i deres Forhold til Nationaloeconomien. Christiania, 1857. 8vo. Baude, J.J. Les Cotes de la Manche, Revue des Deux Mondes, 15 Janvier, 1859. Baumgarten. Notice sur les Rivieres de la Lombardie; in Annales des Ponts et Chaussees, 1847, 1er semestre, pp. 129-199. Beckwith, Lieut. Report in Pacific Railroad Report, vol. Ii. Becquerel. Des Climats et de l'Influence qu'exercent les Sols bolses et non-boises. Paris, 1858. 8vo. ----Elements de Physique Terrestre et de Meteorologie. Paris, 1847. 8vo. Belgrand. De l'Influence des Forets sur l'ecoulement des Eaux Pluviales; in Annales des Ponts et Chaussees, 1854, ler semestre, pp. 1, 27. Berg, Edmund von. Das Verdrangen der Laubwalder im Nordlichen Deutschlande durch die Fichte und die Kiefer. Darmstadt, 1844. 8vo. Bergsoe, A.F. Greve Ch. Ditlev Frederik Reventlovs Virksomhed som Kongens Embedsmand og Statens Borger. Kjobenhavn, 1837. 2 vols. 8vo. Berlepsch, H. Die Alpen in Natur-und Lebensbildern. Leipzig, 1862. 8vo. Bianchi, Celestino. Compendio di Geografia Fisica Speciale d'Italia. Appendice alla traduzione Italiana della Geog.-Fisica di Maria Somerville. Firenze, 1861. (2d vol. of translation.) Bigelow, John. Les Etats Unis d'Amerique en 1868. Paris, 1868. 8vo. Blake, Wm. P. Reports in Pacific Railroad Report, vols. ii and v. Blanqui. Memoire sur les Populations des Hautes Alpes; in Memoires de l'Academie del Sciences Morales et Politiques, 1843. ----Voyage en Bulgarie. Paris, 1843. 12mo. ----Precis Elementaire d'Economie Politique, suivi du Resume de l'Histoire du Commerce et de l'Industrie. Paris, 1857. 12mo. Boitel, Amedee. Mise en valeur des Terres pauvres par le Pin Maritime. 2d edition. Paris, 1857. 8vo. Bonnemere, Eugene. Histoire des Paysons depuis la fin du Moyen Age jusqu'a nos jours. Paris, 1856. 2 vols. 8vo. Bottger, C. Das Mittelmeer. Leipzig, 1859. Boussingault, J.B. Economie Rurale consideree dans ses Rapports avec la Chimie, la Physique, et la Meteorologie. 2d edition. Paris, 1851. 2 vols. 8vo. Bremontier, N.T. Memoire sur les Dunes; in Annales des Ponts et Chaussees, 1833, ler semestre, pp. 145, 228. Brincken, J. von den. Ausichten uber die Bewaldung der Steppen des Europaeischen Russland. Braunschweig, 1854. 4to. Buttner, J.G. Zur Physikalischen Geographie; in Berghaus, Geographisches Jabrbuch, No. iv, 1852, pp. 9-19. Caimi, Pietro. Conni sulla Importanza e Coltura del Boschi. Milano, 1857. 8vo. Cantegril, and others. Extracts in Comptes Rendus a l'Academie des Sciences. Paris, 1861. Castellani. Dell' immediata influenza delle Selve sul corso delle acqua. Torino, 1818, 1819. 2 vols. 4to. Census of the United States for 1860. Preliminary Report on, Washington, 1862. 8vo. Cerini, Giuseppe. Dell' Impianto e Conservazione dei Boschi. Milano, 1844. 8vo. Champion, Maurice. Les Inondations en France depuis le VIme Siecle jusqu'a nos jours. Paris, 1858, 1862. Vols. i-iv, 8vo. Chateauvieux, F. Lullin de. Lettres sur l'Italie. Seconde edition, Geneve, 1834. 8vo. Chevandier. Extracts in Comptes Rendus a l'Academie des Sciences. Juillet-Decembre, 1844. Paris. Clave, Jules. Etudes sur l'Economie Forestiere. 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Reisebericht uber Hanran und die Trachonen. Berlin, 1860. 8vo. Wild, Albert. Die Niederlande. Leipzig, 1862. 2 vols. 8vo. Wilhelm, Gustav. Der Boden und das Wasser. Wien, 1861. 8vo. Williams, Dr. History of Vermont. 2 vols. 8vo. Wittwer, W.C. Die Physikalische Geographie. Leipzig, 1855. 8vo. Young, Arthur. Voyages en France, pendant les annees 1787, 1788, 1789, procedee d'une introduction par Lavergne. Paris, 1860. 2 vols. 12mo. ----Voyages en Italie et en Espagne, pendant les annees 1787, 1789. Paris, 1860. 1 vol. 12mo. TABLE OF CONTENTS CHAPTER I. INTRODUCTORY Natural Advantages of the Territory of the Roman Empire--Physical Decay of that Territory--Causes of the Decay--Reaction of Man on Nature--Observation of Nature--Uncertainty of Our Historical Knowledge of Ancient Climates--Uncertainty of Modern Meteorology--Stability of Nature--Formation of Bogs--Natural Conditions Favorable to Geographical Change--Destructiveness of Man--Human and Brute Action Compared--Limits of Human Power--Importance of Physical Conservation and Restoration--Uncertainty as to Effects of Human Action CHAPTER II. TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES. Modern Geography takes Account of Organic Life--Geographical Importance of Plants--Origin of Domestic Vegetables--Transfer of Vegetable Life--Objects of Modern Commerce--Foreign Plants, how Introduced--Vegetable Power of Accommodation--Agricultural Products of the United States--Useful American Plants Grown in Europe--Extirpation of Vegetables--Animal Life as a Geological and Geographical Agency--Origin and Transfer of Domestic Quadrupeds--Extirpation of Wild Quadrupeds--Large Marine Animals Relatively Unimportant in Geography--Introduction and Breeding of Fish--Destruction of Fish--Geographical Importance of Birds--Introduction of Birds--Destruction of Birds--Utility and Destruction of Reptiles--Utility of Insects and Worms--Injury to the Forest by Insects--Introduction of Insects--Destruction of Insects--Minute Organisms CHAPTER III. THE WOODS. The Habitable Earth Originally Wooded--General Meteorological Influence of the Forest--Electrical Action of Trees--Chemical Influence of Woods--Trees as Protection against Malaria--Trees as Shelter to Ground to the Leeward--Influence of the Forest as Inorganic on Temperature--Thermometrical Action of Trees as Organic--Total Influence of the Forest on Temperature--Influence of Forests as Inorganic on Humidity of Air and Earth--Influence as Organic--Balance of Conflicting Influences--Influence of Woods on Precipitation--Total Climatic Action of the Forest--Influence of the Forest on Humidity of Soil--The Forest in Winter--Summer Rain, Importance of--Influence of the Forest on the Flow of Springs--Influence of the Forest on Inundations and Torrents--Destructive Action of Torrents--Floods of the Ardeche--Excavation by Torrents--Extinction of Torrents--Crushing Force of Torrents--Transporting Power of Water--The Po and its Deposits--Mountain Slides--Forest as Protection against Avalanches--Minor Uses of the Forest--Small Forest Plants and Vitality of Seeds--Locusts do not Breed in Forests--General Functions of Forest--General Consequences of Destruction of--Due Proportion of Woodland--Proportion of Woodland in European Countries--Forests of Great Britain--Forests of France--Forests of Italy--Forests of Germany--Forests of United States--American Forest Trees--European and American Forest Trees Compared--The Forest does not furnish Food for Man--First Removal of the Forest--Principal Causes of Destruction of Forest--Destruction and Protection of Forests by Governments--Royal Forests and Game-laws--Effects of the French Revolution--Increased Demand for Lumber--Effects of Burning Forest--Floating of Timber--Restoration of the Forest--Economy of the Forest--Forest Legislation--Plantation of Forests In America--Financial Results of Forest Plantations--Instability of American Life CHAPTER IV. THE WATERS. Land Artificially Won from the Waters--Great Works of Material Improvement--Draining of Lincolnshire Fens--Incursions of the Sea in the Netherlands--Origin of Sea-dikes--Gain and Loss of Land in the Netherlands--Marine Deposits on the Coast of Netherlands--Draining of Lake of Haarlem--Draining of the Zuiderzee--Geographical Effects of--Improvements in the Netherlands--Ancient Hydraulic Works--Draining of Lake Celano by Prince Torlonia--Incidental Consequences of Draining Lakes--Draining of Marshes--Agricultural Draining--Meteorological Effects of Draining--Geographical Effects of Draining--Geographical Effects of Aqueducts and Canals--Antiquity of Irrigation--Irrigation in Palestine, India, and Egypt--Irrigation in Europe--Meteorological Effects of Irrigation--Water withdrawn from Rivers for Irrigation--Injurious Effects of Rice-culture--Salts Deposited by Water of Irrigation--Subterranean Waters--Artesian Wells--Artificial Springs--Economizing Precipitation--Inundations in France--Basins of Reception--Diversion of Rivers--Glacier Lakes--River Embankments--Other Remedies against Inundations--Dikes of the Nile--Deposits of Tuscan Rivers--Improvements in Tuscan Maremma--Improvements in Val di Chiana--Coast of the Netherlands CHAPTER V. THE SANDS. Origin of Sand--Sand now Carried to the Sea--Beach Sands of Northern Africa--Sands of Egypt--Sand Dunes and Sand Plains--Coast Dunes--Sand Banks--Character of Dune Sand--Interior Structure of Dunes--Geological Importance of Dunes--Dunes on American Coasts--Dunes of Western Europe--Age, Character, and Permanence of Dunes--Dunes as a Barrier against the Sea--Encroachments of the Sea--Liimfjord--Coasts of Schleswig-Holstein, Netherlands, and France--Movement of Dunes--Control of Dunes by Man--Inland Dunes--Inland Sand Plains CHAPTER VI. GREAT PROJECTS OF PHYSICAL CHANGE ACCOMPLISHED OR PROPOSED BY MAN. Cutting of Isthmuses--Canal of Suez--Maritime Canals in Greece--Canals to Dead Sea--Canals to Libyan Desert--Maritime Canals in Europe--Cape Cod Canal--Changes in Caspian--Diversion of the Nile--Diversion of the Rhine--Improvements in North American Hydrography--Soil below Rock--Covering Rock with Earth--Desert Valleys--Effects of Mining--Duponchel's Plans of Improvement--Action of Man on the Weather--Resistance to Great Natural Forces--Incidental Effects of Human Action--Nothing Small In Nature THE EARTH AS MODIFIED BY HUMAN ACTION. CHAPTER 1. INTRODUCTORY. Natural Advantages of the Territory of the Roman Empire.--Physical Decay of that Territory.--Causes of the Decay.--Reaction of Man on Nature.-- Observation of Nature.--Uncertainty of Our Historical Knowledge of Ancient Climates.--Uncertainty of Modern Meteorology.--Stability of Nature.--Formation of Bogs--Natural Conditions Favorable to Geographical Change.--Destructiveness of Man--Human and Brute Action Compared.--Limits of Human Power.--Importance of Physical Conservation and Restoration--Uncertainty as to Effects of Human Action. Natural Advantages of the Territory of the Roman Empire. The Roman Empire, at the period of its greatest expansion, comprised the regions of the earth most distinguished by a happy combination of physical conditions. The provinces bordering on the principal and the secondary basins of the Mediterranean enjoyed in healthfulness and equability of climate, in fertility of soil, in variety of vegetable and mineral products, and in natural facilities for the transportation and distribution of exchangeable commodities, advantages which have not been possessed in any equal degree by any territory of like extent in the Old World or the New. The abundance of the land and of the waters adequately supplied every material want, ministered liberally to every sensuous enjoyment. Gold and silver, indeed, were not found in the profusion which has proved so baneful to the industry of lands richer in veins of the precious metals; but mines and river beds yielded them in the spare measure most favorable to stability of value in the medium of exchange, and, consequently, to the regularity of commercial transactions. The ornaments of the barbaric pride of the East, the pearl, the ruby, the sapphire, and the diamond--though not unknown to the luxury of a people whose conquests and whose wealth commanded whatever the habitable world could contribute to augment the material splendor of their social life--were scarcely native to the territory of the empire; but the comparative rarity of these gems in Europe, at somewhat earlier periods, was, perhaps, the very circumstance that led the cunning artists of classic antiquity to enrich softer stones with engravings, which invest the common onyx and cornelian with a worth surpassing, in cultivated eyes, the lustre of the most brilliant oriental jewels. Of these manifold blessings the temperature of the air, the distribution of the rains, the relative disposition of land and water, the plenty of the sea, the composition of the soil, and the raw material of the primitive arts, were wholly gratuitous gifts. Yet the spontaneous nature of Europe, of Western Asia, of Libya, neither fed nor clothed the civilized inhabitants of those provinces. The luxuriant harvests of cereals that waved on every field from the shores of the Rhine to the banks of the Nile, the vines that festooned the hillsides of Syria, of Italy and of Greece, the olives of Spain, the fruits of the gardens of the Hesperides, the domestic quadrupeds and fowls known in ancient rural husbandry--all these were original products of foreign climes, naturalized in new homes, and gradually ennobled by the art of man, while centuries of persevering labor were expelling the wild vegetation, and fitting the earth for the production of more generous growths. Every loaf was eaten in the sweat of the brow. All must be earned by toil. But toil was nowhere else rewarded by so generous wages; for nowhere would a given amount of intelligent labor produce so abundant, and, at the same time, so varied returns of the good things of material existence. Physical Decay of the Territory of the Roman Empire. If we compare the present physical condition of the countries of which I am speaking, with the descriptions that ancient historians and geographers have given of their fertility and general capability of ministering to human uses, we shall find that more than one-half their whole extent--not excluding the provinces most celebrated for the profusion and variety of their spontaneous and their cultivated products, and for the wealth and social advancement of their inhabitants--is either deserted by civilized man and surrendored to hopeless desolation, or at least greatly reduced in both productiveness and population. Vast forests have disappeared from mountain spurs and ridges; the vegetable earth accumulated beneath the trees by the decay of leaves and fallen trunks, the soil of the alpine pastures which skirted and indented the woods, and the mould of the upland fields, are washed away; meadows, once fertilized by irrigation, are waste and unproductive because the cisterns and reservoirs that supplied the ancient canals are broken, or the springs that fed them dried up; rivers famous in history and song have shrunk to humble brooklets; the willows that ornamented and protected the banks of the lesser watercourses are gone, and the rivulets have ceased to exist as perennial currents, because the little water that finds its way into their old channels is evaporated by the droughts of summer, or absorbed by the parched earth before it reaches the lowlands; the beds of the brooks have widened into broad expanses of pebbles and gravel, over which, though in the hot season passed dryshod, in winter sealike torrents thunder; the entrances of navigable streams are obstructed by sandbars; and harbors, once marts of an extensive commerce, are shoaled by the deposits of the rivers at whose mouths they lie; the elevation of the beds of estuaries, and the consequently diminished velocity and increased lateral spread of the streams which flow into them, have converted thousands of leagues of shallow sea and fertile lowland into unproductive and miasmatic morasses. Besides the direct testimony of history to the ancient fertility of the now exhausted regions to which I refer--Northern Africa, the greater Arabian peninsula, Syria, Mesopotamia, Armenia and many other provinces of Asia Minor, Greece, Sicily, and parts of even Italy and Spain--the multitude and extent of yet remaining architectural ruins, and of decayed works of internal improvement, show that at former epochs a dense population inhabited those now lonely districts. Such a population could have been sustained only by a productiveness of soil of which we at present discover but slender traces; and the abundance derived from that fertility serves to explain how large armies, like those of the ancient Persians, and of the Crusaders and the Tartars in later ages, could, without an organized commissariat, secure adequate supplies in long marches through territories which, in our times, would scarcely afford forage for a single regiment. It appears then, that the fairest and fruitfulest provinces of the Roman Empire, precisely that portion of terrestrial surface, in short, which, about the commencement of the Christian era, was endowed with the greatest superiority of soil, climate, and position, which had been carried to the highest pitch of physical improvement, and which thus combined the natural and artificial conditions best fitting it for the habitation and enjoyment of a dense and highly refined and cultivated population, are now completely exhausted of their fertility, or so diminished in productiveness, as, with the exception of a few favored oases that have escaped the general ruin, to be no longer capable of affording sustenance to civilized man. If to this realm of desolation we add the now wasted and solitary soils of Persia and the remoter East that once fed their millions with milk and honey, we shall see that a territory larger than all Europe, the abundance of which sustained in bygone centuries a population scarcely inferior to that of the whole Christian world at the present day, has been entirely withdrawn from human use, or, at best, is thinly inhabited by tribes too few in numbers, too poor in superfluous products, and too little advanced in culture and the social arts, to contribute anything to the general moral or material interests of the great commonwealth of man. Causes of this Decay. The decay of these once flourishing countries is partly due, no doubt, to that class of geological causes whose action we can neither resist nor guide, and partly also to the direct violence of hostile human force; but it is, in a far greater proportion, either the result of man's ignorant disregard of the laws of nature, or an incidental consequence of war and of civil and ecclesiastical tyranny and misrule. Next to ignorance of these laws, the primitive source, the causa causarum, of the acts and neglects which have blasted with sterility and physical decrepitude the noblest half of the empire of the Caesars, is, first, the brutal and exhausting despotism which Rome herself exercised over her conquered kingdoms, and even over her Italian territory; then, the host of temporal and spiritual tyrannies which she left as her dying curse to all her wide dominion, and which, in some form of violence or of fraud, still brood over almost every soil subdued by the Roman legions. [Footnote: In the Middle Ages, feudalism, and a nominal Christianity, whose corruptions had converted the most beneficent of religions into the most baneful of superstitions, perpetuated every abuse of Roman tyranny, and added new oppressions and new methods of extortion to those invented by older despotisms. The burdens in question fell most heavily on the provinces that had been longest colonized by the Latin race, and those are the portions of Europe which have suffered the greatest physical degradation. "Feudalism," says Blanqui, "was a concentration of scourges. The peasant, stripped of the inheritance of his fathers, became the property of inflexible, ignorant, indolent masters; he was obliged to travel fifty leagues with their carts whenever they required it; he labored for them three days in the week, and surrendered to them half the product of his earnings during the other three; without their consent he could not change his residence, or marry. And why, indeed, should he wish to marry, when he could scarcely save enough to maintain himself The Abbot Alcuin had twenty thousand slaves, called SERFS, who were forever attached to the soil. This is the great cauue of the rapid depopulation observed in the Middle Ages, and of the prodigious multitude of monasteries which sprang up on every side. It was doubtless a relief to such miserable men to find in the cloisters a retreat from oppression; but the human race never suffered a more cruel outrage, industry never received a wound better calculated to plunge the world again into the darkness of the rudest antiquity. It suffices to say that the prediction of the approaching end of the world, industriously spread by the rapacious monks at this time, was received without terror."--Resume de l'Histoire du Commerce, p. 156.] Man cannot struggle at once against human oppression and the destructive forces of inorganic nature. "When both are combined against him, he succumbs after a shorter or longer struggle, and the fields he has won from the primeval wood relapse into their original state of wild and luxuriant, but unprofitable forest growth, or fall into that of a dry and barren wilderness. The abbey of Saint-Germain-des-Pres, which, in the time of Charlemagne, had possessed a million of acres, was, down to the Revolution, still so wealthy, that the personal income of the abbot was 300,000 livres. Theabbey of Saint-Denis was nearly as rich as that of Saint-Germain-des-Pres.--Lavergne, Economie Rurale de la France, p. 104. Paul Louis Courier quotes from La Bruyere the following striking picture of the condition of the French peasantry in his time: "One sees certain dark, livid, naked, sunburnt, wild animals, male and female, scattered over the country and attached to the soil, which they root and turn over with indomitable perseverance. They have, as it were, an articulate voice, and when they rise to their feet, they show a human face. They are, in fact, men; they creep at night into dens, where they live on black bread, water, and roots. They spare other men the labor of ploughing, Bowing, and harvesting, and therefore deserve some small share of the bread they have grown." "These are his own words," adds Courier, "and he is speaking of the fortunate peasants, of those who had work and bread, and they were then the few."--Petition a la Chambre des Deputes pour les Villageois l'en empeche ce danser. Arthur Young, who travelled in France from 1787 to 1789, gives, in the twenty-first chapter of his Travels, a frightful account of the burdens of the rural population even at that late period. Besides the regular governmental taxes, and a multitude of heavy fines imposed for trifling offense, he enumerates about thirty seignorial rights, the very origin and nature of some of which are now unknown, while those of some others are as repulsive to humanity and morality, as the worst abuses ever practised by heathen despotism. But Young underrates the number of these oppressive impositions. Moreau de Jonnes, a higher authority, asserts that in a brief examination he had discovered upwards of three hundred distinct lights of the feudatory over the person or the property of his vassal. See Etat Economique et Social de la France, Paris, 1890, p. 389. Most of these, indeed, had been commuted for money payments, and were levied on the peasantry as pecuniary imposts for the benefit of prelates and lay lords, who, by virtue of their nobility, were exempt from taxation. The collection of the taxes was enforced with unrelenting severity. On one occasion, in the reign of Louis XIV., the troops sent out against the recreant peasants made more than 3,000 prisoners, of whom 400 were condemned to the galleys for life, and a number so large that the government did not dare to disclose it, were hung on trees or broken on the wheel.--Moreau de Jonnes, Etat Economique et Social de la France, p. 420. Who can wonder at the hostility of the French plebeian classes towards the aristocracy in the days of the Revolution? Rome imposed on the products of agricultural labor in the rural districts taxes which the sale of the entire harvest would scarcely discharge; she drained them of their population by military conscription; she impoverished the peasantry by forced and unpaid labor on public works; she hampered industry and both foreign and internal commerce by absurd restrictions and unwise regulations. [Footnote: Commerce, in common with all gainful occupations except agriculture, was despised by the Romans, and the exercise of it was forbidden to the higher ranks. Cicero, however, admits that though retail trade, which could only prosper by lying and knavery, was contemptible, yet wholesale commerce was not altogether to be condemned, and might even be laudable, provided the merchant retired early from trade and invested his gaits in farm lands.--De Officiis, lib. i.,42.] Hence, large tracts of land were left uncultivated, or altogether deserted, and exposed to all the destructive forces which act with such energy on the surface of the earth when it is deprived of those protections by which nature originally guarded it, and for which, in well-ordered husbandry, human ingenuity has contrived more or less efficient substitutes. [Footnote: The temporary depopulation of an exhausted soil may be, in some cases, a physical, though, like fallows in agriculture, a dear-bought advantage. Under favorable circumstances, the withdrawal of man and his flocks allows the earth to clothe itself again with forests, and in a few generations to recover its ancient productiveness. In the Middle Ages, worn-out fields were depopulated, in many parts of the Continent, by civil and ecclesiastical tyrannies, which insisted on the surrender of the half of a loaf already too small to sustain its producer. Thus abandoned, these lands often relapsed into the forest state, and, some centuries later, were again brought under cultivation with renovated fertility.] Similar abuses have tended to perpetuate and extend these evils in later ages, and it is but recently that, even in the most populous parts of Europe, public attention has been half awakened to the necessity of restoring the disturbed harmonies of nature, whose well-balanced influences are so propitious to all her organic offspring, and of repaying to our great mother the debt which the prodigality and the thriftlessness of former generations have imposed upon their successors--thus fulfilling the command of religion and of practical wisdom, to use this world as not abusing it. Reaction of Man on Nature. The revolutions of the seasons, with their alternations of temperature and of length of day and night, the climates of different zones, and the general conditions and movements of the atmosphere and the seas, depend upon causes for the most part cosmical, and, of course, wholly beyond our control. The elevation, configuration, and composition of the great masses of terrestrial surface, and the relative extent and distribution of land and water, are determined by geological influences equally remote from our jurisdiction. It would hence seem that the physical adaptation of different portions of the earth to the use and enjoyment of man is a matter so strictly belonging to mightier than human powers, that we can only accept geographical nature as we find her, and be content with such soils and such skies as she spontaneously offers. But it is certain that man has reacted upon organized and inorganic nature, and thereby modified, if not determined, the material structure of his earthly home. The measure of that reaction manifestly constitutes a very important element in the appreciation of the relations between mind and matter, as well as in the discussion of many purely physical problems. But though the subject has been incidentally touched upon by many geographers, and treated with much fulness of detail in regard to certain limited fields of human effort and to certain specific effects of human action, it has not, as a whole, so tar as I know, been made matter of special observation, or of historical research, by any scientific inquirer. Indeed, until the influence of geographical conditions upon human life was recognized as a distinct branch of philosophical investigation, there was no motive for the pursuit of such speculations; and it was desirable to inquire how far we have, or can, become the architects of our own abiding place, only when it was known how the mode of our physical, moral, and intellectual being is affected by the character of the home which Providence has appointed, and we have fashioned, for our material habitation. [Footnote:Gods Almagt wenkte van den troon, En schiep elk volk een land ter woon: Hier vestte Zij een grondgebied, Dat Zij ona zelven scheppon llet.] It is still too early to attempt scientific method in discussing this problem, nor is our present store of the necessary facts by any means complete enough to warrant me in promising any approach to fulness of statement respecting them. Systematic observation in relation to this subject has hardly yet begun, and the scattered data which have chanced to be recorded have never been collected. It has now no place in the general scheme of physical science, and is matter of suggestion and speculation only, not of established and positive conclusion. At present, then, all that I can hope is to excite an interest in a topic of much economical importance, by pointing out the directions and illustrating the modes in which human action has been, or may be, most injurious or most beneficial in its influence upon the physical conditions of the earth we inhabit We cannot always distinguish between the results of man's action and the effects of purely geological or cosmical causes. The destruction of the forests, the drainage of lakes and marshes, and the operations of rural husbandry and industrial art have unquestionably tended to produce great changes in the hygrometric, thermometric, electric, and chemical condition of the atmosphere, though we are not yet able to measure the force of the different elements of disturbance, or to say how far they have been neutralised by each other, or by still obscurer influences; and it is equally certain that the myriad forms of animal and vegetable life, which covered the earth when man first entered upon the theatre of a nature whose harmonies he was destined to derange, have been, through his interference, greatly changed in numerical proportion, sometimes much modified in form and product, and sometimes entirely extirpated. [Footnote: Man has not only subverted the natural numerical relations of wild as well as domestic quadrupeds, fish, birds, reptile, insect, and common plants, and even of still humbler tribes of animal and vegetable life, but he has effected in the forms, habits, nutriment and products of the organisms which minister to his wants and his pleasures, changes which, more than any other manifestaion of human energy, resemble the exercise of a creative power. Even wild animals have been compelled by him, through the destruction of plants and insects which furnished their proper aliment, to resort to food belonging to a different kingdom of nature. Thus a New Zealand bird, originally granivorous and insectivorous, has become carnivorous, from the want of its natural supplies, and now tears the fleeces from the backs of the sheep, in order to feed on their living flesh. All these changes have exercised more or less direct or indirect action on the inorganic surface of the globe; and the history of the geographical revolutions thus produced would furnish ample material for a volume. The modification of organic species by domestication is a branch of philosophic inquiry which we may almost say has been created by Darwin; but the geographical results of these modifications do not appear to have yet been made a subject of scientific investigation. I do not know that the following passage from Pliny has ever been cited in connection with the Darwinian theories but it is worth a reference: "But behold a very strange and new fashion of them [cucumbers] in Campane, for there you shall have abundance of them come up in forme of a Quince. And as I heare say, one of the channced so to grow first at a very venture; but afterwards from the seed of it came a whole race and progenie of the like, which therefore they call Melonopopones, as a man would say, the Quince-pompions or cucumbers"--Pliny, Nat. Hist., Holland's translation, book xix, c.5 The word cucumis used in the original of this passage embraces many of the cucurbitaceae, but the context shows that here means the cucumber. The physical revolutions thus wrought by man have not indeed all been destructive to human interests, and the heaviest blows he has inflicted upon nature have not been wholly without their compensations. Soils to which no nutritious vegetable was indigenous, countries which once brought forth but the fewest products suited for the sustenance and comfort of man--while the severity of their climates created and stimulated the greatest number and the most imperious urgency of physical wants--surfaces the most rugged and intractable, and least blessed with natural facilities of communication, have been brought in modern times to yield and distribute all that supplies the material necessities, all that contributes to the sensuous enjoyments and conveniences of civilized life. The Scythia, the Thule, the Britain, the Germany, and the Gaul which the Roman writers describe in such forbidding terms, have been brought almost to rival the native luxuriance and easily won plenty of Southern Italy; and, while the fountains of oil and wine that refreshed old Greece and Syria and Northern Africa have almost ceased to flow, and the soils of those fair lands are turned to thirsty and inhospitable deserts, the hyperborean regions of Europe have learnod to conquer, or rather compensate, the rigors of climate, and have attained to a material wealth and variety of product that, with all their natural advantages, the granaries of the ancient world can hardly be said to have enjoyed. Observation of Nature. In these pages it is my aim to stimulate, not to satisfy, curiosity, and it is no part of my object to save my readers the labor of observation or of thought. For labor is life, and Death lives where power lives unused. [Footnote: Verses addressed by G. C. to Sir Walter Raleigh.--Haklutt, i., p. 608.] Self is the schoolmaster whose lessons are best worth his wages; and since the subject I am considering has not yet become a branch of formal instruction, those whom it may interest can, fortunately, have no pedagogue but themselves. To the natural philosopher, the descriptive poet, the painter, the sculptor, and indeed every earnest observer, the power most important to cultivate, and, at the same time, hardest to acquire, is that of seeing what is before him. Sight is a faculty; seeing, an art. The eye is a physical but not a self-acting apparatus, and in general it sees only what it seeks. Like a mirror, it reflects objects presented to it; but it may be as insensible as a mirror, and not consciously perceive what it reflects. [Footnote: --I troer, at Synets Sands er lagt i Oiet, Mens dette kun er Redskab. Synet strommer Fra Sjaelens Dyb, og Oiets fine Nerver Gaae ud fra Hjernens hemmelige Vaerksted. Henrik Hertz, Kong Rene's Datter, sc. ii. In the material eye, you think, sight lodgeth! The EYE is but an organ. SEEING streameth from the soul's inmost depths. The fine perceptive Nerve springeth from the brain's mysterious workshop.] It has been maintained by high authority, that the natural acuteness of our sensuous faculties cannot be heightened by use, and hence, that the minutest details of the image formed on the retina are as perfect in the most untrained as in the most thoroughly disciplined organ. This may be questioned, and it is agreed on all hands that the power of multifarious perception and rapid discrimination may be immensely increased by well-directed practice. [Footnote: Skill in marksmanship, whether with firearms or with other projectile weapons, depends more upon the training of the eye than is generally supposed, and I have often found particularly good shots to possess an almost telescopic vision. In the ordinary use of the rifle, the barrel is guided by the eye, but there are sportemen who fire with the butt of the gun at the hip. In this case, as in the use of the sling, the lasso, and the bolas, in hurling the knife (see Babinet, Lectures, vii., p. 84), in throwing the boomerang, the javelin, or a stone, and in the employment of the blowpipe and the bow, the movements of the hand and arm are guided by that mysterious sympathy which exists between the eye and the unseeing organs of the body. "Some men wonder whye, in casting a man's eye at the marke, the hand should go streighte. Surely if he considered the nature of a man's eye he would not wonder at it: for this I am certaine of, that no servaunt to his maister, no childe to his father, is so obedient, as every joynte and peece of the bodye is to do whatsover the eye biddes."--Roger Ascham, Taxophilus, Book ii. In shooting the tortoises of the Amazon and its tributaries, the Indians use an arrow with a long twine and a float attached to it. Ave-Lallemant (Die Benutzung der Palmen am Amazonenstrom, p. 32) thus describes their mode of aiming: "As the arrow, if aimed directly at the floating tortoise, would strike it at a small angle and glance from its fiat and wet shell, the archers have a peculiar method of shooting. They are able to calculate exactly their own muscular effort, the velocity of the stream, the distance and size of the tortoise, and they shoot the arrow directly up into the air, so that it falls almost vertically upon the shell of the tortoise, and sticks in it." Analogous calculations--if such physico-mental operations can property be so called--are made in the use of other missiles; for no projectile flies in a right line to its mark. But the exact training of the eye lies at the bottom of them all, and marksmanship depends almost wholly upon the power of that organ, whose directions the blind muscles implicitly follow. Savages accustomed only to the use of the bow become good shots with firearms after very little practice. It is perhaps not out of place to observe here that our English word aim comes from the Latin aestimo, I calculate or estimate. See Wedgwood's Dictionary of English Etymology, and the note to the American edition, under Aim. Another proof of the control of the limbs by the eye has been observed in deaf-and-dumb schools, and others where pupils are first taught to write on large slates or blackboards. The writing is in large characters, the small letters being an inch or more high. They are formed with chalk or a slate pencil firmly grasped in the fingers, and by appropriate motions of the wrist, elbow, and shoulder, not of the finger joints. Nevertheless, when a pen is put into the hand of a pupil thus taught, his handwriting, though produced by a totally different set of muscles and muscular movements, is identical in character with that which he has practised on the blackboard. For a very remarkable account of the restoration of vision impaired from age, by judicious training, see Lessons in Life, by Timothy Titcomb, lesson xi. It has been much doubted whether the artists of the classic ages possessed a more perfect light than those of modern times, or whether, in executing their minute mosaics and gem engravings, they need magnifiers. Glasses ground convex have been found at Pompeii, but they are too rudely fashioned and too imperfectly polished to have been of any practical use for optical purposes. But though the ancient artists may have had a microscopic vision, their astronomers cannot have had a telescopic power of sight; for they did not discover the satellites of Jupiter, which are often seen with the naked eye at Oormeeah, in Persia, and sometimes, as I can testify by personal observation, at Cairo.] This exercise of the eye I desire to promote, and, next to moral and religious doctrine, I know no more important practical lessons in this earthly life of ours--which, to the wise man, is a school from the cradle to the grave--than those relating to the employment of the sense of vision in the study of nature. The pursuit of physical geography, embracing actual observation of terrestrial surface, affords to the eye the best general training that is accessible to all. The majority of even cultivated men have not the time and means of acquiring anything beyond a very superficial acquaintance with any branch of physical knowledge. Natural science has become so vastly extended, its recorded facts and its unanswered questions so immensely multiplied, that every strictly scientific man must be a specialist, and confine the researches of a whole life within a comparatively narrow circle. The study I am recommending, in the view I propose to take of it, is yet in that imperfectly developed state which allows its votaries to occupy themselves with broad and general views attainable by every person of culture, and it does not now require a knowledge of special details which only years of application can master. It may be profitably pursued by all; and every traveller, every lover of rural scenery, every agriculturist, who will wisely use the gift of sight, may add valuable contributions to the common stock of knowledge on a subject which, as I hope to convince my readers, though long neglected, and now inartificially presented, is not only a very important but a very interesting field of inquiry. Measurement of Man's Influence. The exact measurement of the geographical and climatic changes hitherto effected by man is impracticable, and we possess, in relation to them, the means of only qualitative, not quantitative analysis. The fact of such revolutions is established partly by historical evidence, partly by analogical deduction from effects produced, in our own time, by operations similar in character to those which must have taken place in more or less remote ages of human action. Both sources of information are alike defective in precision; the latter, for general reasons too obvious to require specification; the former, because the facts to which it bears testimony occurred before the habit or the means of rigorously scientific observation upon any branch of physical research, and especially upon climatic changes, existed. UNCERTAINTY OF OUR HISTORICAL CONCLUSIONS ON ANCIENT CLIMATES. The invention of measures of heat and of atmospheric moisture, pressure, and precipitation, is extremely recent. Hence, ancient physicists have left us no thermometric or barometric records, no tables of the fall, evaporation, and flow of waters, and even no accurate maps of coast lines and the course of rivers. Their notices of these phenomena are almost wholly confined to excessive and exceptional instances of high or of low temperatures, extraordinary falls of rain and snow, and unusual floods or droughts. Our knowledge of the meteorological condition of the earth, at any period more than two centuries before our own time, is derived from these imperfect details, from the vague statements of ancient historians and geographers in regard to the volume of rivers and the relative extent of forest and cultivated land, from the indications furnished by the history of the agriculture and rural economy of past generations, and from other almost purely casual sources of information. [Footnote: The subject of climatic change, with and without reference to human action as a cause, has been much discussed by Moreau de Jonnes, Dureau de la Malle, Arago, Humboldt, Fuster, Gasparin, Becquerel, Schleiden, and many other writers in Europe, and by Noah Webster, Forry, Drake, and others in America. Fraas has endeavored to show, by the history of vegetation in Greece, not merely that clearing and cultivation have affected climate, but that change of climate has essentially modified the character of vegetable life. See his Klima und Pflansenwelt in der Zeit.] Among these latter we must rank certain newly laid open fields of investigation, from which facts bearing on the point now under consideration have been gathered. I allude to the discovery of artificial objects in geological formations older than any hitherto recognized as exhibiting traces of the existence of man; to the ancient lacustrine habitations of Switzerland and of the terremare of Italy, [Footnote: See two learned articles by Pigorini, in the Nuova Antologia for January and October, 1870.] containing the implements of the occupants, remains of their food, and other relics of human life; to the curious revelations of the Kjokkenmoddinger, or heaps of kitchen refuse, in Denmark and elsewhere, and of the peat mosses in the same and other northern countries; to the dwellings and other evidences of the industry of man in remote ages sometimes laid bare by the movement of sand dunes on the coasts of France and of the North Sea; and to the facts disclosed on the tide-washed flats of the latter shores by excavations in Halligs or inhabited mounds which were probably raised before the era of the Roman Empire. [Footnote: For a very picturesque description of the Halligs, see Pliny, N.H., Book xvi, c. 1.] These remains are memorials of races which have left no written records, which perished at a period beyond the reach of even historical tradition. The plants and animals that furnished the relics found in the deposits were certainly contemporaneous with man; for they are associated with his works, and have evidently served his uses. In some cases, the animals belonged to species well ascertained to be now altogether extinct; in some others, both the animals and the vegetables, though extant elsewhere, have ceased to inhabit the regions where their remains are discovered. From the character of the artificial objects, as compared with others belonging to known dates, or at least to known periods of civilization, ingenious inferences have been drawn as to their age; and from the vegetable remains which accompany them, as to the climates of Central and Northern Europe at the time of their production. There are, however, sources of error which have not always been sufficiently guarded against in making these estimates. When a boat, composed of several pieces of wood fastened together by pins of the same material, is dug out of a bog, it is inferred that the vessel, and the skeletons and implements found with it, belong to an age when the use of iron was not known to the builders. But this conclusion is not warranted by the simple fact that metals were not employed in its construction; for the Nubians at this day build boats large enough to carry half a dozen persons across the Nile, out of small pieces of acacia wood pinned together entirely with wooden bolts, and large vessels of similar construction are used by the islanders of the Malay archipelago. Nor is the occurrence of flint arrow heads and knives, in conjunction with other evidences of human life, conclusive proof as to the antiquity of the latter. Lyell informs us that some Oriental tribes still continue to use the same stone implements as their ancestors, "after that mighty empires, where the use of metals in the arts was well known, had flourished for three thousand years in their neighborhood;" [Footnote: Antiquity of Man, p. 377.] and the North American Indians now manufacture weapons of stone, and even of glass, chipping them in the latter case out of the bottoms of thick bottles, with great facility. [Footnote: "One of the Indians seated himself near me, and made from a fragment of quartz, with a simple piece of round bone, one end of which was hemispherical, with a small crease in it (as if worn by a thread) the sixteenth of an inch deep, an arrow head which was very sharp and piercing, and such as they use on all their arrows. The skill and rapidity with which it was made, without a blow, but by simply breaking the sharp edges with the creased bone by the strength of his hands--for the crease merely served to prevent the instrument from slipping, affording no leverage--was remarkable."--Reports of Explorations and Surveys for Pacific Railroad, vol. ii., 1855, Lieut. Beckwith'S Report, p. 43. See also American Naturalist for May, 1870, and especially Stevens, Flint Chips, London, 1870, pp. 77 et seq. Mariette Bey lately saw an Egyptian barber shave the head of an Arab with a flint razor.] We may also be misled by our ignorance of the commercial relations existing between savage tribes. Extremely rude nations, in spite of their jealousies and their perpetual wars, sometimes contrive to exchange the products of provinces very widely separated from each other. The mounds of Ohio contain pearls, thought to be marine, which must have come from the Gulf of Mexico, or perhaps even from California, and the knives and pipes found in the same graves are often formed of far-fetched material, that was naturally paid for by some home product exported to the locality whence the material was derived. The art of preserving fish, flesh, and fowl by drying and smoking is widely diffused, and of great antiquity. The Indians of Long Island Sound are said to have carried on a trade in dried shell fish with tribes residing very far inland. From the earliest ages, the inhabitants of the Faroe and Orkney Islands, and of the opposite mainland coasts, have smoked wild fowl and other flesh. Hence it is possible that the animal and the vegetable food, the remains of which are found in the ancient deposits I am speaking of, may sometimes have been brought from climates remote from that where it was consumed. The most important, as well as the most trustworthy conclusions with respect to the climate of ancient Europe and Asia, are those drawn from the accounts given by the classical writers of the growth of cultivated plants; but these are by no means free from uncertainty, because we can seldom be sure of an identity of species, almost never of an identity of race or variety, between vegetables known to the agriculturists of Greece and Rome and those of modern times which are thought most nearly to resemble them. Besides this, there is always room for doubt whether the habits of plants long grown in different countries may not have been so changed by domestication or by natural selection, that the conditions of temperature and humidity which they required twenty centuries ago were different from those at present demanded for their advantageous cultivation. [Footnote: Probably no cultivated vegetable affords so good an opportunity of studying the law of acclimation of plants as maize or Indian corn. Maize is grown from the tropics to at least lat. 47 degrees in Northeastern America, and farther north in Europe. Every two or three degrees of latitude brings you to a new variety with new climatic adaptations, and the capacity of the plant to accommodate itself to new conditions of temperature and season seems almost unlimited. Many persons now living remember that, when the common tomato was first introduced into Northern New England, it often failed to ripen; but, in the course of a very few years, it completely adapted itself to the climate, and now not only matures both its fruit and its seeds with as much certainty as any cultivated vegetable, but regularly propagates itself by self-sown seed. Meteorological observations, however, do not show any amelioration of the summer climate in those States within that period. It may be said that these cases--and indeed all cases of a supposed acclimation consisting in physiological changes--are instances of the origination of new varieties by natural selection, the hardier maize, tomato, and other vegetables of the North, being the progeny of seeds of individuals endowed, exceptionally, with greater power of resisting cold than belongs in general to the species which produced them. But, so far as the evidence of change of climate, from a difference in vegetable growth, is concerned, it is immaterial whether we adopt this view or maintain the older and more familiar doctrine of a local modification of character in the plants in question. Maize and the tomato, if not new to human use, have not been long known to civilization, and were, very probably, reclaimed and domesticated at a much more recent period than the plants which form the great staples of agricultural husbandry in Europe and Asia. Is the great power of accommodation to climate possessed by them due to this circumstance There is some reason to suppose that the character of maize has been sensibly changed by cultivation in South America; for, according to Tschudi, the ears of this grain found in old Peruvian tombs belong to varieties not now known in Peru.--Travels in Peru, chap. vii. See important observations in Schubeler, Die Pflanzenwelt Norwegans (Allgemeiner Theil), Christinania, 1873, 77 and following pp.] Even if we suppose an identity of species, of race, and of habit to be established between a given ancient and modern plant, the negative fact that the latter will not grow now where it flourished two thousand years ago does not in all cases prove a change of climate. The same result might follow from the exhaustion of the soil, [Footnote: The cultivation of madder is said to have been introduced into Europe by an Oriental in the year 1765, and it was first planted in the neighborhood of Avignon. Of course, it has been grown in that district for less than a century; but upon soils where it has been a frequent crop, it is already losing much of its coloring properties.--Lavergne, Economic Rurale de la France, pp. 250-201. I believe there is no doubt that the cultivation of madder in the vicinity of Avignon is of recent introduction; but it is certain that it was grown by the ancient Romans, and throughout nearly all Europe in the middle ages. The madder brought from Persia to France, may belong to a different species, or at least variety.] or from a change in the quantity of moisture it habitually contains. After a district of country has been completely or even partially cleared of its forest growth, and brought under cultivation, the drying of the soil, under favorable circumstances, goes on for generations, perhaps for ages. [Footnote: In many parts of New England there are tracts, many square miles in extent and presenting all varieties of surface and exposure, which were partially cleared sixty or seventy years ago, and where little or no change in the proportion of cultivated ground, pasturage, and woodland has taken place since. In some cases, these tracts compose basins apparently scarcely at all exposed to any local influence in the way of percolation or infiltration of water towards or from neighboring valleys. But in such situations, apart from accidental disturbances, the ground is growing drier and drier from year to year, springs are still disappearing, and rivulets still diminishing in their summer supply of water. A probable explanation of this is to be found in the rapid drainage of the surface of cleared ground, which prevents the subterranean natural reservoirs, whether cavities or merely strata of bibulous earth, from filling up. How long this process is to last before an equilibrium is reached, none can say. It may be, for years; it may be, for centuries. Livingstone states facts which strongly favor the supposition that a secular desiccation is still going on in central Africa, and there is reason to suspect that a like change is taking place in California. When the regions where the earth is growing drier were cleared of wood, or, indeed, whether forests ever grew there, we are unable to say, but the change appears to have been long in progress. A similar revolution appears to have occurred in Arabia Petraea. In many of the wadis, and particularly in the gorges between Wadi Feiran and Wadi Esh Sheikh, there are water-worn banks showing that, at no very remote period, the winter floods must have risen fifty feet in channels where the growth of acacias and tamarisks and the testimony of the Arabs concur to prove that they have not risen six feet within the memory or tradition of the present inhabitants. Recent travellers have discovered traces of extensive ancient cultivation, and of the former existence of large towns in the Tih desert, in localities where all agriculture is now impossible for want of water. Is this drought due to the destruction of ancient forests or to some other cause? For important observations on supposed changes of climate in our Western prairie region, from cultivation of the soil and the introduction of domestic cattle, see Bryant's valuable Forest Trees, 1871, chapter v., and Hayden, Preliminary Report on Survey of Wyoming, p. 455. Some physicists believe that the waters of our earth are, from chemical of other less known causes, diminishing by entering into new inorganic combinations, and that this element will finally disappear from the globe.] In other cases, from injudicioua husbandry, or the diversion or choking up of natural water-courses, it may become more highly charged with humidity. An increase or diminution of the moisture of a soil almost necessarily supposes an elevation or a depression of its winter or its summer heat, and of its extreme if not of its mean annual temperature, though such elevation or depression may be so slight as not sensibly to raise or lower the mercury in a thermometer exposed to the open air. Any of these causes, more or less humidity, or more or less warmth of soil, would affect the growth both of wild and of cultivated vegetation, and consequently, without any appreciable change in atmospheric temperature, precipitation, or evaporation, plants of a particular species might cease to be advantageously cultivated where they had once been easily reared. [Footnote: The soil of newly subdued countries is generally highly favorable to the growth of the fruits of the garden and the orchard, but usually becomes much less so in a very few years. Plums, of many varieties, were formerly grown, in great perfection and abundance, in many parts of New England where at present they can scarcely be reared at all; and the peach, which, a generation or two ago, succeeded admirably in the southern portion of the same States, has almost ceased to be cultivated there. The disappearance of these fruits is partly due to the ravages of insects, which have in later years attacked them; but this is evidently by no means the sole, or even the principal cause of their decay. In these cases, it is not to the exhaustion of the particular acres on which the fruit trees have grown that we are to ascribe their degeneracy, but to a general change in the condition of the soil or the air; for it is equally impossible to rear them successfully on absolutely new land in the neighborhood of grounds where, not long since, they bore the finest fruit. I remember being told, many years ago, by intelligent early settlers of the State of Ohio, that the apple trees raised there from seed sown soon after the land was cleared, bore fruit in less than half the time required to bring to bearing those reared from seed gown when the ground had been twenty years under cultivation. Analogous changes occur slowly and almost imperceptibly even in spontaneous vegetation. In the peat mosses of Denmark, Scotch firs and other trees not now growing in the same localities, are found in abundance. Every generation of trees leaves the soil in a different state from that in which it found it; every tree that springs up in a group of trees of another species than its own, grows under different influences of light and shade and atmosphere from its predecessors. Hence the succession of crops, which occurs in all natural forests, seems to be due rather to changes of condition than of climate. See chapter iii., post.] Uncertainty of Modern Meteorology. We are very imperfectly acquainted with the present mean and extreme temperature, or the precipitation and the evaporation of any extensive region, even in countries most densely peopled and best supplied with instruments and observers. The progress of science is constantly detecting errors of method in older observations, and many laboriously constructed tables of meteorological phenomena are now thrown aside as fallacious, and therefore worse than useless, because some condition necessary to secure accuracy of result was neglected, in obtaining and recording the data on which they were founded. To take a familiar instance: it is but recently that attention has been drawn to the great influence of slight differences in station upon the results of observations of temperature and precipitation. Two thermometers hung but a few hundred yards from each other differ not unfrequently five, sometimes even ten degrees in their readings; [Footnote: Tyndall, in a lecture on Radiation, expresses the opinion that from ten to fifteen per cent. of the heat radiated from the earth is absorbed by aqueous vapor within ten feet of the earth's surface.--Fragments of Science, 3d edition, London, 1871, p. 203. Thermometers at most meteorological stations, when not suspended at points regulated by the mere personal convenience of the observer, are hung from 20 to 40 feet above the ground. In such positions they are less exposed to disturbance from the action of surrounding bodies than at a lower level, and their indications are consequently more uniform; but according to Tyndall's views they do not mark the temperature of the atmospheric stratum in which nearly all the vegetables useful to man, except forest trees, bud and blossom and ripen, and in which a vast majority of the ordinary operations of material life are performed. They give the rise and fall of the mercury at heights arbitrarily taken, without reference to the relations of temperature to human interests, or to any other scientific consideration than a somewhat less liability to accidental disturbance.] and when we are told that the annual fall of rain on the roof of the observatory at Paris is two inches less than on the ground by the side of it, we may see that the height of the rain-gauge above the earth is a point of much consequence in making estimates from its measurements. [Footnote: Careful observations by the late lamented Dallas Bache appeared to show that there is no such difference in the quantity of precipitation falling at slightly different levels as has been generally supposed. The apparent difference was ascribed by Prof. Bache to the irregular distribution of the drops of rain and flakes of snow, exposed, as they are, to local disturbances by the currents of air around the corners of buildings or other accidents of the surface. This consideration much increases the importance of great care in the selection of positions for rain-gauges. But Mr. Bache's conclusions seem not to be accepted by late experimenters in England. See Quarterly Journal of Science for January, 1871, p. 123.] The data from which results have been deduced with respect to the hygrometrical and thermometrical conditions, to the climate in short, of different countries, have very often been derived from observations at single points in cities or districts separated by considerable distances. The tendency of errors and accidents to balance each other authorizes us, indeed, to entertain greater confidence than we could otherwise feel in the conclusions drawn from such tables; but it is in the highest degree probable that they would be much modified by more numerous series of observations, at different stations within narrow limits. [Footnote: The nomenclature of meteorology is vague and sometimes equivocal. Not long since, it was suspected that the observers reporting to a scientific institution did not agree in their understanding of the mode of expressing the direction of the wind prescribed by their instructions. It was found, upon inquiry, that very many of them used the names of the compass-points to indicate the quarter FROM which the wind blew, while others employed them to signify the quarter TOWARDS which the atmospheric currents were moving. In some instances, the observers were no longer within the reach of inquiry, and of course their tables of the wind were of no value. "Winds," says Mrs. Somerville, "are named from the points whence they blow, currents exactly the reverse. An easterly wind comes from the east; whereas on easterly current comes from the west, and flows towards the east."--Physical Geography, p. 229. There is no philological ground for this distinction, and it probably originated in a confusion of the terminations -WARDLY and -ERLY, both of which are modern. The root of the former ending implies the direction TO or TO-WARDS which motion is supposed. It corresponds to, and is probably allied with, the Latin VERSUS. The termination -ERLY is a corruption or softening of -ERNLY, easterly for easternly, and many authors of the nineteenth century so write it. In Haklnyt (i., p. 2), EASTERLY is applied to place, "EASTERLY bounds," and means EASTERN. In a passage in Drayton, "EASTERLY winds" must mean winds FROM the east; but the same author, in speaking of nations, uses NORTHERLY for NORTHERN. Lakewell says: "The sonne cannot goe more SOUTHERNLY from us, nor come more NORTHERNLY towards us." Holland, in his translation of Pliny, referring to the moon, has: "When shee is NORTHERLY," and "shee is gone SOUTHERLY." Richardson, to whom I am indebted for the above citations, quotes a passage from Dampier where WESTERLY is applied to the wind, but the context does not determine the direction. The only example of the termination -WARDLY given by this lexicographer is from Donne, where it means TOWARDS the west. Shakespeare, in Hamlet(v., ii.), uses NORTHERLY wind for wind FROM the north. Milton does not employ either of these terminations, nor were they known to the Anglo-Saxons, who, however, had adjectives of direction in -AN or -EN, -ern and -weard, the last always meaning the point TOWARDS which motion in supposed, the others that FROM which it proceeds. The vocabulary of science has no specific name for one of the most important phenomena in meteorology--I mean for watery vapor condensed and rendered visible by cold. The Latins expressed this condition of water by the word vapor. For INVISIBLE vapor they had no name, because they did not know that it existed, and Van Helmont was obliged to invent a word, gas, as a generic name for watery and other fluids in the invisible state. The moderns have perverted the meaning of the word vapor, and in science its use is confined to express water in the gaseous and invisible state. When vapor in rendered visible by condensation, we call it fog or mist--between which two words there is no clearly established distinction--if it is lying on or near the surface of the earth or of water; when it floats in the air we call it cloud. But these words express the form and position of the humid aggregation, not the condition of the water-globules which compose it. The breath from our mouths, the steam from an engine, thrown out into cold air, become visible, and consist of water in the same state as in fog or cloud; but we do not apply those terms to these phenomena. It would be an improvement in meteorological nomenclature to restore vapor to its original meaning, and to employ a new word, such for example as hydrogas, to explain the new scientific idea of water in the invisible state.] There is one branch of research which is of the utmost importance in reference to these questions, but which, from the great difficulty of direct observation upon it, has been less successfully studied than almost any other problem of physical science. I refer to the proportions between precipitation, superficial drainage, absorption, and evaporation. Precise actual measurement of these quantities upon even a single acre of ground is impossible; and in all cabinet experiments on the subject, the conditions of the surface observed are so different from those which occur in nature, that we cannot safely reason from one case to the other. In nature, the inclination and exposure of the ground, the degree of freedom or obstruction of the flow of water over the surface, the composition and density of the soil, the presence or absence of perforations by worms and small burrowing quadrupeds--upon which the permeability of the ground by water and its power of absorbing and retaining or transmitting moisture depend--its temperature, the dryness or saturation of the subsoil, vary at comparatively short distances; and though the precipitation upon very small geographical basins and the superficial flow from them may be estimated with an approach to precision, yet even here we have no present means of knowing how much of the water absorbed by the earth is restored to the atmosphere by evaporation, and how much carried off by infiltration or other modes of underground discharge. When, therefore, we attempt to use the phenomena observed on a few square or cubic yards of earth, as a basis of reasoning upon the meteorology of a province, it is evident that our data must be insufficient to warrant positive general conclusions. In discussing the climatology of whole countries, or even of comparatively small local divisions, we may safely say that none can tell what percentage of the water they receive from the atmosphere is evaporated; what absorbed by the ground and conveyed off by subterranean conduits; what carried down to the sea by superficial channels; what drawn from the earth or the air by a given extent of forest, of short pasture vegetation, or of tall meadow-grass; what given out again by surfaces so covered, or by bare ground of various textures and composition, under different conditions of atmospheric temperature, pressure, and humidity; or what is the amount of evaporation from water, ice, or snow, under the varying exposures to which, in actual nature, they are constantly subjected. If, then, we are so ignorant of all these climatic phenomena in the best-known regions inhabited by man, it is evident that we can rely little upon theoretical deductions applied to the former more natural state of the same regions--less still to such as are adopted with respect to distant, strange, and primitive countries. STABILITY OF NATURE. Nature, left undisturbed, so fashions her territory as to give it almost unchanging permanence of form, outline, and proportion, except when shattered by geologic convulsions; and in these comparatively rare cases of derangement, she sets herself at once to repair the superficial damage, and to restore, as nearly as practicable, the former aspect of her dominion. In new countries, the natural inclination of the ground, the self-formed slopes and levels, are generally such as best secure the stability of the soil. They have been graded and lowered or elevated by frost and chemical forces and gravitation and the flow of water and vegetable deposit and the action of the winds, until, by a general compensation of conflicting forces, a condition of equilibrium has been readied which, without the action of main, would remain, with little fluctuation, for countless ages. We need not go far back to reach a period when, in all that portion of the North American continent which has been occupied by British colonization, the geographical elements very nearly balanced and compensated each other. At the commencement of the seventeenth century, the soil, with insignificant exceptions, was covered with forests; [Footnote: I do not here speak of the vast prairie region of the Mississippi valley, which cannot properly said ever to have been a field of British colonization; but of the original colonies, and their dependencies in the territory of the present United States, and in Canada. It is, however, equally true of the Western prairies as of the Eastern forest land, that they had arrived at a state of equilibrium, though under very different conditions.] and whenever the Indian, in consequence of war or the exhaustion of the beasts of the chase, abandoned the narrow fields he had planted and the woods he had burned over, they speedily returned, by a succession of herbaceous, arborescent, and arboreal growths, to their original state. Even a single generation sufficed to restore them almost to their primitive luxuriance of forest vegetation. [Footnote: The great fire of Miramichi in 1825, probably the most extensive and terrific conflagration recorded in authentic history, spread its ravages over nearly six thousand square miles, chiefly of woodland, and was of such intensity that it seemed to consume the very soil itself. But so great are the recuperative powers of nature, that, in twenty-five years, the ground was thickly covered again with tree of fair dimensions, except where cultivation and pasturage kept down the forest growth.] The unbroken forests had attained to their maximum density and strength of growth, and, as the older trees decayed and fell, they were succeeded by new shoots or seedlings, so that from century to century no perceptible change seems to have occurred in the wood, except the slow, spontaneous succession of crops. This succession involved no interruption of growth, and but little break in the "boundless contiguity of shade;" for, in the husbandry of nature, there are no fallows. Trees fall singly, not by square roods, and the tall pine is hardly prostrate, before the light and heat, admitted to the ground by the removal of the dense crown of foliage which had shut them out, stimulate the germination of the seeds of broad-leaved trees that had lain, waiting this kindly influence, perhaps for centuries. FORMATION OF BOGS. Two natural causes, destructive in character, were, indeed, in operation in the primitive American forests, though, in the Northern colonies, at least, there were sufficient compensations; for we do not discover that any considerable permanent change was produced by them. I refer to the action of beavers and of fallen trees in producing bogs, [Footnote: The English nomenclature of this geographical feature does not seem well settled. We have bog, swamp, marsh, morass, moor, fen, turf-moss, peat-moss, quagmire, all of which, though sometimes more or less accurately discriminated, are often used interchangeably, or are perhaps employed, each exclusively, in a particular district. In Sweden, where, especially in the Lappish provinces, this terr-aqueous formation is very extensive and important, the names of its different kinds are more specific in their application. The general designation of all soils permanently pervaded with water is Karr. The elder Laestadius divides the Karr into two genera: Myror (sing. myra), and Mossar (sing. mosse). "The former," he observes, "are grass-grown, and overflowed with water through almost the whole summer; the latter are covered with mosses and always moist, but very seldom overflowed." He enumerates the following species of Myra, the character of which will perhaps be sufficiently understood by the Latin terms into which he translates the vernacular names, for the benefit of strangers not altogether familiar with the language and the subject: 1. Homyror, paludes graminosae. 2. Dy, paludes profundae. 3. Flarkmyror, or proper karr, paludes limosae. 4. Fjalimyror, paludes uliginosae. 5. Tufmyror, paludes caespitosae. 6. Rismyror, paludes virgatae. 7. Starrangar, prata irrigata, with their subdivisions, dry starrungar or risangar, wet starrangar and frakengropar. 8. Polar, lacunae. 9. Golar, fossae inundatae. The Mossar, paludes turfosae, which are of great extent, have but two species: 1. Torfmossar, called also Mossmyror and Snottermyror, and, 2. Bjornmossar. The accumulations of stagnant or stagnating water originating in bogs are distinguished into Trask, stagna, and Tjernar or Tjarnar (sing. Tjern or Tjarn), stagnatiles. Trask are pools fed by bogs, or water emanating from them, and their bottoms are slimy; Tjernar are small Trask situated within the limits of Mossar.--L.L. Laestadius, om Mojligheten af Uppodlingar i Lappmarken, pp. 23, 24. Although the quantity of bog land in New England is less than in many other regions of equal area, yet there is a considerable extent of this formation in some of the Northeastern States. Dana (Manual of Geology, p. 614) states that the quantity of peat in Massachusetts is estimated at 120,000,000 cords, or nearly 569,000,000 cubic yards, but he does not give either the area or the depth of the deposits. In any event, however, bogs cover but a small percentage of the territory in any of the Northern States, while it is said that one tenth of the whole surface of Ireland is composed of bogs, and there are still extensive tracts of undrained marsh in England. The amount of this formation in Great Britain is estimated at 6,000,000 acres, with an average depth of twelve feet, which would yield 21,600,000 tons of air-dried peat.--Asbjornsen, Tore og Torodrift, Christiania, 1868, p. 6. Peat beds have sometimes a thickness of ten or twelve yards, or even more. A depth of ten yards would give 48,000 cubic yards to the acre. The greatest quantity of firewood yielded by the forests of New England to the acre is 100 cords solid measure, or 474 cubic yards; but this comprises only the trunks and larger branches. If we add the small branches and twigs, it is possible that 600 cubic yards might, in some cases, be cut on an acre. This is only one eightieth part of the quantity of peat sometimes found on the same area. It is true that a yard of peat and a yard of wood are not the equivalents of each other, but the fuel on an acre of deep peat is worth much more than that on an acre of the best woodland. Besides this, wood is perishable, and the quantity of an acre cannot be increased beyond the amount just stated; peat is indestructible, and the beds are always growing. See post, Chap. IV. Cold favors the conversion of aquatic vegetables into peat. Asbjornsen says some of the best peat he has met with is from a bog which is frozen for forty weeks in the year. The Greeks and Romans were not acquainted with the employment of peat as fuel, but it appears from a curious passage which I have already cited from Pliny, N. H., book xvi., chap. 1, that the inhabitants of the North Sea coast used what is called kneaded turf in his time. This is the finer and more thoroughly decomposed matter lying at the bottom of the peat, kneaded by the hands, formed into small blocks and dried. It is still prepared in precisely the same way by the poorer inhabitants of those shores. But though the Low German tribes, including probably the Anglo-Saxons, have used peat as fuel from time immemorial, it appears not to have been known to the High Germans until a recent period. At least, I can find neither in Old nor in Middle High German lexicons and glossaries any word signifying peat. Zurb indeed is found in Graff as an Old High German word, but only in the sense of grass-turf, or greensward. Peat bogs of vast extent occur in many High German localities, but the former abundance of wood in the same regions rendered the use of peat unnecessary.] and of smaller animals, insects, and birds, in destroying the woods. [Footnote: See Chapter II., post.] Bogs generally originate in the checking of watercourses by the falling of timber or of earth and rocks, or by artificial obstructions across their channels. If the impediment is sufficient to retain a permanent accumulation of water behind it, the trees whose roots are overflowed soon perish, and then by their fall increase the obstruction, and, of course, occasion a still wider spread of the stagnating stream. This process goes on until the water finds a new outlet, at a higher level, not liable to similar interruption. The fallen trees not completely covered by water are soon overgrown with mosses; aquatic and semiaquatic plants propagate themselves, and spread until they more or less completely fill up the space occupied by the water, and the surface is gradually converted from a pond to a quaking morass. The morass is slowly solidified by vegetable production and deposit, then very often restored to the forest condition by the growth of black ashes, cedars, or, in southern latitudes, cypresses, and other trees suited to such a soil, and thus the interrupted harmony of nature is at last reestablished. [Footnote: "Aquatic plants have a utility in raising the level of marshy grounds, which renders them very valuable, and may well be called a geological function. The engineer drains ponds at a great expense by lowering the surface of the water; nature attains the same end, gratuitously, by raising the level of the soil without depressing that of the water; but she proceeds more slowly. There are, in the Landes, marshes where this natural filling has a thickness of four metres, and some of them, at first lower than the sea, have been thus raised and drained so as to grow summer crops, such, for example, as maize."--Boitel, Mise en valeur des Terres pauvres, p. 227. The bogs of Denmark--the examination of which by Steenstrap and Vaupell has presented such curious results with respect to the natural succession of forest trees--appear to have gone through this gradual process of drying, and the birch, which grow freely in very wet soils, has contributed very effectually by its annual deposits to raise the surface above the water level, and thus to prepare the ground for the oak.--Vaupell, Bogens Indvandring, pp. 39, 40. The growth of the peat not unfrequently raises the surface of bogs considerably above the level of the surrounding country, and they sometimes burst and overflow lower grounds with a torrent of mud and water as destructive as a current of lava.] In countries somewhat further advanced in civilization than those occupied by the North American Indians, as in mediaeval Ireland, the formation of bogs may be commenced by the neglect of man to remove, from the natural channels of superficial drainage, the tops and branches of trees felled for the various purposes to which wood is applicable in his rude industry; and, when the flow of the water is thus checked, nature goes on with the processes I have already described. In such half-civilized regions, too, windfalls are more frequent than in those where the forest is unbroken, because, when openings have been made in it for agricultural or other purposes, the entrance thus afforded to the wind occasions the sudden overthrow of hundreds of trees which might otherwise have stood for generations and have fallen to the ground, only one by one, as natural decay brought them down. [Footnote: Careful examination of the peat mosses in North Sjaelland--which are so abundant in fossil wood that, within thirty years, they have yielded above a million of trees--shows that the trees have generally fallen from age and not from wind. They are found in depressions on the declivities of which they grew, and they lie with the top lowest, always falling towards the bottom of the valley.--Vaupell, Bogens Indvandring i de Danske Skove, pp. 10,14.] Besides this, the flocks bred by man in the pastoral state keep down the incipient growth of trees on the half-dried bogs, and prevent them from recovering their primitive condition. Young trees in the native forest are sometimes girdled and killed by the smaller rodent quadrupeds, and their growth is checked by birds which feed on the terminal bud; but these animals, as we shall see, are generally found on the skirts of the wood only, not in its deeper recesses, and hence the mischief they do is not extensive. In fine, in countries untrodden by man, the proportions and relative positions of land and water, the atmospheric precipitation and evaporation, the thermometric mean, and the distribution of vegetable and animal life, are maintained by natural compensations, in a state of approximate equilibrium, and are subject to appreciable change only from geological influences so slow in their operation that the geographical conditions may be regarded as substantially constant and immutable. NATURAL CONDITIONS FAVORABLE TO GEOGRAPHICAL CHANGE. There are, nevertheless, certain climatic conditions and certain forms and formations of terrestrial surface, which tend respectively to impede and to facilitate the physical degradation both of new countries and of old. If the precipitation, whether great or small in amount, be equally distributed through the seasons, so that there are neither torrential rains nor parching droughts, and if, further, the general inclination of ground be moderate, so that the superficial waters are carried off without destructive rapidity of flow, and without sudden accumulation in the channels of natural drainage, there is little danger of the degradation of the soil in consequence of the removal of forest or other vegetable covering, and the natural face of the earth may be considered as virtually permanent. These conditions are well exemplified in Ireland, in a great part of England, in extensive districts in Germany and France, and, fortunately, in an immense proportion of the valley of the Mississippi and the basin of the great American lakes, as well as in many parts of the continents of South America and of Africa, and it is partly, though by no means entirely, owing to topographical and climatic causes that the blight, which has smitten the fairest and most fertile provinces of Imperial Rome, has spared Britannia, Germania, Pannonia, and Moesia, the comparatively inhospitable homes of barbarous races, who, in the days of the Caesars, were too little advanced in civilized life to possess either the power or the will to wage that war against the order of nature which seems, hitherto, an almost inseparable condition precedent of high social culture, and of great progress in fine and mechanical art. Destructive changes are most frequent in countries of irregular and mountainous surface, and in climates where the precipitation is confined chiefly to a single season, and where, of course, the year is divided into a wet and a dry period, as is the case throughout a great part of the Ottoman empire, and, indeed, in a large proportion of the whole Mediterranean basin. In mountainous countries various causes combine to expose the soil to constant dangers. The rain and snow usually fall in greater quantity, and with much inequality of distribution; the snow on the summits accumulates for many months in succession, and then is not unfrequently almost wholly dissolved in a single thaw, so that the entire precipitation of months is in a few hours hurried down the flanks of the mountains, and through the ravines that furrow them; the natural inclination of the surface promotes the swiftness of the gathering currents of diluvial rain and of melting snow, which soon acquire an almost irresistible force and power of removal and transportation; the soil itself is less compact and tenacious than that of the plains, and if the sheltering forest has been destroyed, it is contined by few of the threads and ligaments by which nature had bound it together, and attached it to the rocky groundwork. Hence every considerable shower lays bare its roods of rock, and the torrents sent down by the thaws of spring, and by occasional heavy discharges of the summer and autumnal rains, are seas of mud and rolling stones that sometimes lay waste and bury beneath them acres, and even miles, of pasture and field and vineyard. [Footnote: The character of geological formation is an element of very great importance in determining the amount of erosion produced by running water, and, of course, in measuring the consequences of clearing off the forests. The soil of the French Alps yields very readily to the force of currents, and the declivities of the northern Apennines, as well as of many minor mountain ridges in Tuscany and other parts or Italy, are covered with earth which becomes itself almost a fluid when saturated with water. Hence the erosion of such surfaces is vastly greater than on many other mountains of equal steepness of inclination. The traveller who passes over the route between Bologna and Florence, and the Perugia and the Siena roads from the latter city to Rome, will have many opportunities of observing such localities.] Destructiveness of Man. Man has too long forgotten that the earth was given to him for usufruct alone, not for consumption, still less for profligate waste. Nature has provided against the absolute destruction of any of her elementary matter, the raw material of her works; the thunderbolt and the tornado, the most convulsive throes of even the volcano and the earthquake, being only phenomena of decomposition and recomposition. But she has left it within the power of man irreparably to derange the combinations of inorganic matter and of organic life, which through the night of aeons she had been proportioning and balancing, to prepare the earth for his habitation, when in the fulness of time his Creator should call him forth to enter into its possession. Apart from the hostile influence of man, the organic and the inorganic world are, as I have remarked, bound together by such mutual relations and adaptations as secure, if not the absolute permanence and equilibrium of both, a long continuance of the established conditions of each at any given time and place, or at least, a very slow and gradual succession of changes in those conditions. But man is everywhere a disturbing agent. Wherever he plants his foot, the harmonies of nature are turned to discords. The proportions and accommodations which insured the stability of existing arrangements are overthrown. Indigenous vegetable and animal species are extirpated, and supplanted by others of foreign origin, spontaneous production is forbidden or restricted, and the face of the earth is either laid bare or covered with a new and reluctant growth of vegetable forms, and with alien tribes of animal life. These intentional changes and substitutions constitute, indeed, great revolutions; but vast as is their magnitude and importance, they are, as we shall see, insignificant in comparison with the contingent and unsought results which have flowed from them. The fact that, of all organic beings, man alone is to be regarded as essentially a destructive power, and that he wields energies to resist which Nature--that nature whom all material life and all inorganic substance obey--is wholly impotent, tends to prove that, though living in physical nature, he is not of her, that he is of more exalted parentage, and belongs to a higher order of existences, than those which are born of her womb and live in blind submission to her dictates. There are, indeed, brute destroyers, beasts and birds and insects of prey--all animal life feeds upon, and, of course, destroys other life,--but this destruction is balanced by compensations. It is, in fact, the very means by which the existence of one tribe of animals or of vegetables is secured against being smothered by the encroachments of another; and the reproductive powers of species, which serve as the food of others, are always proportioned to the demand they are destined to supply. Man pursues his victims with reckless destructiveness; and, while the sacrifice of life by the lower animals is limited by the cravings of appetite, he unsparingly persecutes, even to extirpation, thousands of organic forms which he cannot consume. [Footnote: The terrible destructiveness of man is remarkably exemplified in the chase of large mammalia and birds for single products, attended with the entire waste of enormous quantities of flesh, and of other parts of the animal which are capable of valuable uses. The wild cattle of South America are slaughtered by millions for their hides and hairs; the buffalo of North America for his skin or his tongue; the elephant, the walrus, and the narwhal for their tusks; the cetacen, and some other marine animals, for their whalebone and oil; the ostrich and other large birds, for their plumage. Within a few years, sheep have been killed in New England, by whole flocks, for their pelts and suet alone, the flesh being thrown away; and it is even said that the bodies of the same quadrupeds have been used in Australia as fuel for limekilns. What a vast amount of human nutriment, of bone, and of other animal products valuable in the arts, is thus recklessly squandered! In nearly all these cases, the part which constitutes the motive for this wholesale destruction, and is alone saved, is essentially of insignificant value as compared with what is thrown away. The horns and hide of an ox are not economically worth a tenth part as much as the entire carcass. During the present year, large quantities of Indian corn have been used as domestic fuel, and even for burning lime, in Iowa and other Western States. Corn at from fifteen to eighteen cents per bushel is found cheaper than wood at from five to seven dollars per cord, or coal at six or seven dollars per ton.-Rep. Agric. Dept., Nov. and Dec., 1872, p. 487. One of the greatest benefits to be expected from the improvement civilization is, that increased facilities of communication will render it possible to transport to places of consumption much valuable material that is now wasted because the price at the nearest market will not pay freight. The cattle slaughtered in South America for their hides would feed millions of the starving population of the Old World, if their flesh could be economically preserved and transported across the ocean. This, indeed, is already done, but on a scale which, though absolutely considerable, is relatively insignificant. South America sends to Europe a certain quantity of nutriment in the form of meat extracts, Liebig's and others; and preserved flesh from Australia is beginning to figure in the English market. We are beginning to learn a better economy in dealing with the inorganic world. The utilization--or, as the Germans more happily call it, the Verwerthung, the BEWORTHING--of waste from metallurgical, chemical, and manufacturing establishments, is among the most important results of the application of science to industrial purposes. The incidental products from the laboratories of manufacturing chemists often become more valuable than those for the preparation of which they were erected. The slags front silver refineries, and even from smelting houses of the coarser metals, have not unfrequently yielded to a second operator a better return than the first had derived from dealing with the natural ore; and the saving of lead carried off in the smoke of furnaces has, of itself, given a large profit on the capital invested in the works. According to Ure's Dictionary of Arts, see vol. ii., p. 832, an English miner has constructed flues five miles in length for the condensation of the smoke from his lead-works, and makes thereby an annual saving of metal to the value of ten thousand pounds sterling. A few years ago, an officer of an American mint was charged with embezzling gold committed to him for coinage. He insisted, in his defence, that much of the metal was volatilized and lost in refining and melting, and upon scraping the chimneys of the melting furnaces and the roofs of the adjacent houses, gold enough was found in the soot to account for no small part of the deficiency. The substitution of expensive machinery for manual labor, even in agriculture--not to speak of older and more familiar applications--besides being highly remunerative, has better secured the harvests, and it is computed that the 230,000 threshing machines used in the United States in 1870 obtained five per cent. more grain from the sheaves which passed through them than could have been secured by the use of the flail. The cotton growing States in America produce annually nearly three million tons of cotton seed. This, until very recently, has been thrown away as a useless incumbrance, but it is now valued at ten or twelve dollars per ton for the cotton fibre which adheres to it, for the oil extracted from it, and for the feed which the refuse furnishes to cattle. The oil--which may be described as neutral--is used very largely for mixing with other oils, many of which bear a large proportion of it without injury to their special properties. There are still, however, cases of enormous waste in many mineral and mechanical industries. Thus, while in many European countries common salt is a government monopoly, and consequently so dear that the poor do not use as much or it as health requires, in others, as in Transylvania, where it is quarried like stone, the large blocks only are saved, the fragments, to the amount of millions of hundred weights, being thrown away.--Bonar, Transylvania, p. 455, 6. One of the most interesting and important branches of economy at the present day is the recovery of agents such as ammonia and ethers which had been utilized in chemical manufactures, and re-employing them indefinitely afterwards in repeating the same process. Among the supplemental exhibitions which will be formed in connection with the Vienna Universal Exhibition is to be one showing what steps have been taken since 1851 (the date of the first London Exhibition) in the utilization of substances previously regarded as waste. On the one hand will be shown the waste products in all the industrial processes included in the forthcoming Exhibition; on the other hand, the useful products which have been obtained from such wastes since 1851. This is intended to serve as an incentive to further researches in the same important direction.] The earth was not, in its natural condition, completely adapted to the use of man, but only to the sustenance of wild animals and wild vegetation. These live, multiply their kind in just proportion, and attain their perfect measure of strength and beauty, without producing or requiring any important change in the natural arrangements of surface, or in each other's spontaneous tendencies, except such mutual repression of excessive increase as may prevent the extirpation of one species by the encroachments of another. In short, without man, lower animal and spontaneous vegetable life would have been practically constant in type, distribution, and proportion, and the physical geography of the earth would have remained undisturbed for indefinite periods, and been subject to revolution only from slow development, from possible, unknown cosmical causes, or from geological action. But man, the domestic animals that serve him, the field and garden plants the products of which supply him with food and clothing, cannot subsist and rise to the full development of their higher properties, unless brute and unconscious nature be effectually combated, and, in a great degree, vanquished by human art. Hence, a certain measure of transformation of terrestrial surface, of suppression of natural, and stimulation of artificially modified productivity becomes necessary. This measure man has unfortunately exceeded. He has felled the forests whose network of fibrous roots bound the mould to the rocky skeleton of the earth; but had he allowed here and there a belt of woodland to reproduce itself by spontaneous propagation, most of the mischiefs which his reckless destruction of the natural protection of the soil has occasioned would have been averted. He has broken up the mountain reservoirs, the percolation of whose waters through unseen channels supplied the fountains that refreshed his cattle and fertilized his fields; but he has neglected to maintain the cisterns and the canals of irrigation which a wise antiquity had constructed to neutralize the consequences of its own imprudence. While he has torn the thin glebe which confined the light earth of extensive plains, and has destroyed the fringe of semi-aquatic plants which skirted the coast and checked the drifting of the sea sand, he has failed to prevent the spreading of the dunes by clothing them with artificially propagated vegetation. He has ruthlessly warred on all the tribes of animated nature whose spoil he could convert to his own uses, and he has not protected the birds which prey on the insects most destructive to his own harvests. Purely untutored humanity, it is true, interferes comparatively little with the arrangements of nature, [Footnote: It is an interesting and not hitherto sufficiently noticed fact, that the domestication of the organic world, so far as it has yet been achieved, belongs, not indeed to the savage state, but to the earliest dawn of civilization, the conquest of inorganic nature almost as exclusively to the most advanced stages of artificial culture. Civilization has added little to the number of vegetable or animal species grown in our fields or bred in our folds--the cranberry and the wild grape being almost the only plants which the Anglo-American has reclaimed out of our most native flora and added to his harvests--while, on the contrary, the subjugation of the inorganic forces, and the consequent extension of man's sway over, not the annual products of the earth only, but her substance and her springs of action, is almost entirely the work of highly refined and cultivated ages. The employment of the elasticity of wood and of horn, as a projectile power in the bow, is nearly universal among the rudest savages. The application of compressed air to the same purpose, in the blowpipe, is more restricted, and the use of the mechanical powers, the inclined plane, the wheel and axle, and even the wedge and lever, seems almost unknown except to civilized man. I have myself seen European peasants to whom one of the simplest applications of this latter power was a revelation. It is familiarly known to all who have occupied themselves with the psychology and habits of the ruder races, and of persons with imperfectly developed intellects in civilized life, that although these humble tribes and individuals sacrifice, without scruple, the lives of the lower animals to the gratification of their appetites and the supply of their other physical wants, yet they nevertheless seem to cherish with brutes, and even with vegetable life, sympathies which are much more feebly felt by civilized men. The popular traditions of the simpler peoples recognize a certain community of nature between man, brute animals, and even plants; and this serves to explain why the apologue or fable, which ascribes the power of speech and the faculty of reason to birds, quadrupeds, insects, flowers, and trees, is one of the earliest forms of literary composition. In almost every wild tribe, some particular quadruped or bird, though persecuted as a destroyer of other animals more useful to man, or hunted for food, is regarded with peculiar respect, one might almost say, affection. Some of the North American aboriginal nations celebrate a propitiatory feast to the manes of the intended victim before they commence a bear hunt; and the Norwegian peasantry have not only retained an old proverb which ascribes to the same animal "ti Maends Styrke og tolo Maends Vid," ten men's strength and twelve men's cunning, but they still pay to him something of the reverence with which ancient superstition invested him. The student of Icelandic literature will find in the saga of Finnbogi hinn rami a curious illustration of this feeling, in an account of a dialogue between a Norwegian bear and an Icelandic champion--dumb show on the part of Bruin, and chivalric words on that of Finnbogi--followed by a duel, in which the latter, who had thrown away his arms and armor in order that the combatants might meet on equal terms, was victorious. See also Friis, Lappisk Mythologi, Christiania, 1871, section 37, and the earlier authors there cited. Drummond Hay's very interesting work on Morocco contains many amusing notices of a similar feeling entertained by the Moors towards the redoubtable enemy of their flocks--the lion. This sympathy helps us to understand how it is that most if not all the domestic animals--if indeed they ever existed in a wild state--were appropriated, reclaimed and trained before men had been gathered into organized and fixed communities, that almost every known esculent plant had acquired substantially its present artificial character, and that the properties of nearly all vegetable drugs and poisons were known at the remotest period to which historical records reach. Did nature bestow upon primitive man some instinct akin to that by which she has been supposed to teach the brute to select the nutritious and to reject the noxious vegetables indiscriminately mixed in forest and pasture? This instinct, it must be admitted, is far from infallible, and, as has been hundreds of times remarked by naturalists, it is in many cases not an original faculty but an acquired and transmitted habit. It is a fact familiar to persons engaged in sheep husbandry in New England--and I have seen it confirmed by personal observation--that sheep bred where the common laurel, as it is called, Kalmia angustifolia, abounds, almost always avoid browsing upon the leaves of that plant, while those brought from districts where laurel is unknown, and turned into pastures where it grows, very often feed upon it and are poisoned by it. A curious acquired and hereditary instinct, of a different character, may not improperly be noticed here. I refer to that by which horses bred in provinces where quicksands are common avoid their dangers or extricate themsleves from them. See Bremontier, Memoire sur les Dunes, Annales des Ponts et Chaussees, 1833; premier semestre, pp. 155-157. It is commonly said in New England, and I believe with reason, that the crows of this generation are wiser than their ancestors. Scarecrows which were effectual fifty yeara ago are no longer respected by the plunderers of the cornfield, and new terrors must from time to time be invented for its protection. Schroeder van der Kolk, in Het Verschil tusschen den Psychischen, Aanleg van het Dier en van den Mensch, cites many interesting facts respecting instincts lost, or newly developed and become hereditary, in the lower animals, and he quotes Aristotle and Pliny as evidence that the common quadrupeds and fowls of our fields and our poultry yards were much less perfectly domesticated in their times than long, long ages of servitude have now made them. Among other inntances of obliterated instincts, this author states that in Holland, where, for centuries, the young of the cow has been usually taken from the dam at birth and fed by hand, calves, even if left with the mother, make no attempt to suck; while in England, where calves are not weaned until several weeks old, they resort to the udder as naturally as the young of wild quadrupeds.-Ziel en Ligchaam, p. 128. n. Perhaps the half-wild character ascribed by P. Laestadius and other Swedish writers to the reindeer of Lapland, may be in some degree due to the comparative shortness of the period during which he has been partially tamed. The domestic swine bred in the woods of Hungary and the buffalo of Southern Italy are so wild and savage as to be very dangerous to all but their keepers. The former have relapsed into their original condition, the latter, perhaps, have never been fully reclaimed from it.] and the destructive agency of man becomes more and more energetic and unsparing as he advances in civilization, until the impoverishment with which his exhaustion of the natural resources of the soil is threatening him, at last awakens him to the necessity of preserving what is left, if not of restoring what has been wantonly wasted. The wandering savage grows no cultivated vegetable, fells no forest, and extirpates no useful plant, no noxious weed. If his skill in the chase enables him to entrap numbers of the animals on which he feeds, he compensates this loss by destroying also the lion, the tiger, the wolf, the otter, the seal, and the eagle, thus indirectly protecting the feebler quadrupeds and fish and fowls, which would otherwise become the booty of beasts and birds of prey. But with stationary life, or at latest with the pastoral state, man at once commences an almost indiscriminate warfare upon all the forms of animal and vegetable existence around him, and as he advances in civilization, he gradually eradicates or transforms every spontaneous product of the soil he occupies. [Footnote: The difference between the relations of savage life, and of incipient civilization, to nature, is well seen in that part of the valley of the Mississippi which was once occupied by the mound builders and afterwards by the far less developed Indian tribes. When the tillers of the fields, which must have been cultivated to sustain the large population that once inhabited those regions, perished, or were driven out, the soil fell back to the normal forest state, and the savages who succeeded the more advanced race interfered very little, if at all, with the ordinary course of spontaneous nature.] Human and Brute Action Compared. It is maintained by authorities as high as any known to modern science, that the action of man upon nature, though greater in DEGREE, does not differ in KIND from that of wild animals. It is perhaps impossible to establish a radical distinction in genere between the two classes of effects, but there is an essential difference between the motive of action which calls out the energies of civilized man and the mere appetite which controls the life of the beast. The action of man, indeed, is frequently followed by unforeseen and undesired results, yet it is nevertheless guided by a self-conscious will aiming as often at secondary and remote as at immediate objects. The wild animal, on the other hand, acts instinctively, and, so far as we are able to perceive, always with a view to single and direct purposes. The backwoodsman and the beaver alike fell trees; the man that he may convert the forest into an olive grove that will mature its fruit only for a succeeding generation, the beaver that he may feed upon the bark of the trees or use them in the construction of his habitation. The action of brutes upon the material world is slow and gradual, and usually limited, in any given case, to a narrow extent of territory. Nature is allowed time and opportunity to set her restorative powers at work, and the destructive animal has hardly retired from the field of his ravages before nature has repaired the damages occasioned by his operations. In fact, he is expelled from the scene by the very efforts which she makes for the restoration of her dominion. Man, on the contrary, extends his action over vast spaces, his revolutions are swift and radical, and his devastations are, for an almost incalculable time after he has withdrawn the arm that gave the blow, irreparable. The form of geographical surface, and very probably the climate of a given country, depend much on the character of the vegetable life belonging to it. Man has, by domestication, greatly changed the habits and properties of the plants he rears; he has, by voluntary selection, immensely modified the forms and qualities of the animated creatures that serve him; and he has, at the same time, completely rooted out many forms of animal if not of vegetable being. [Footnote: Whatever may be thought of the modification of organic species by natural selection, there is certainly no evidence that animals have exerted upon any form of life an influence analogous to that of domestication upon plants, quadrupeds, and birds reared artificially by man; and this is as true of unforeseen as of purposely effected improvements accomplished by voluntary selection of breeding animals. It is true that nature employs birds and quadrupeds for the dissemination of vegetable and even of animal species. But when the bird drops the seed of a fruit it has swallowed, and when the sheep transports in its fleece the seed-vessel of a burdock from the plain to the mountain, its action is purely mechanical and unconscious, and does not differ from that of the wind in producing the same effect.] What is there, in the influence of brute life, that corresponds to this We have no reason to believe that, in that portion of the American continent which, though peopled by many tribes of quadruped and fowl, remained uninhabited by man or only thinly occupied by purely, savage tribes, any sensible geographical change had occurred within twenty centuries before the epoch of discovery and colonization, while, during the same period, man had changed millions of square miles, in the fairest and most fertile regions of the Old World, into the barrenest deserts. The ravages committed by man subvert the relations and destroy the balance which nature had established between her organized and her inorganic creations, and she avenges herself upon the intruder, by letting loose upon her defaced provinces destructive energies hitherto kept in check by organic forces destined to be his best auxiliaries, but which he has unwisely dispersed and driven from the field of action. When the forest is gone, the great reservoir of moisture stored up in its vegetable mould is evaporated, and returns only in deluges of rain to wash away the parched dust into which that mould has been converted. The well-wooded and humid hills are turned to ridges of dry rock, which encumbers the low grounds and chokes the watercourses with its debris, and--except in countries favored with an equable distribution of rain through the seasons, and a moderate and regular inclination of surface--the whole earth, unless rescued by human art from the physical degradation to which it tends, becomes an assemblage of bald mountains, of barren, turfless hills, and of swampy and malarious plains. There are parts of Asia Minor, of Northern Africa, of Greece, and even of Alpine Europe, where the operation of causes set in action by man has brought the face of the earth to a desolation almost as complete as that of the moon; and though, within that brief space of time which we call "the historical period," they are known to have been covered with luxuriant woods, verdant pastures, and fertile meadows, they are now too far deteriorated to be reclaimable by man, nor can they become again fitted for human use, except through great geological changes, or other mysterious influences or agencies of which we have no present knowledge, and over which we have no prospective control. The earth is fast becoming an unfit home for its noblest inhabitant, and another era of equal human crime and human improvidence, and of like duration with that through which traces of that crime and that improvidence extend, would reduce it to such a condition of impoverished productiveness, of shattered surface, of climatic excess, as to threaten the depravation, barbarism, and perhaps even extinction of the species. [Footnote: ---"And it may be remarked that, as the world has passed through these several stages of strife to produce a Christendom, so by relaxing in the enterprises it has learnt, does it tend downwards, through inverted steps, to wildness and the waste again. Let a people give up their contest with moral evil; disregard the injustice, the ignorance, the greediness, that may prevail among them, and part more and more with the Christian element of their civilization; and in declining this battle with sin, they will inevitably get embroiled with men. Threats of war and revolution punish their unfaithfulness; and if then, instead of retracing their steps, they yield again, and are driven before the storm, the very arts they had created, the structures they had raised, the usages they had established, are swept away; 'in that very day their thoughts perish.' The portion they had reclaimed from the young earth's ruggedness is lost; and failing to stand fast against man, they finally get embroiled with nature, and are thrust down beneath her ever-living hand .-Martineau's Sermon, "The Good Soldier of Jesus Christ."] Physical Improvement. True, there is a partial reverse to this picture. On narrow theatres, new forests have been planted; inundations of flowing streams restrained by heavy walls of masonry and other constructions; torrents compelled to aid, by depositing the slime with which they are charged, in filling up lowlands, and raising the level of morasses which their own overflows had created; ground submerged by the encroachments of the ocean, or exposed to be covered by its tides, has been rescued from its dominion by diking; swamps and even lakes have been drained, and their beds brought within the domain of agricultural industry; drifting coast dunes have been checked and made productive by plantation; seas and inland waters have been repeopled with fish, and even the sands of the Sahara have been fertilized by artesian fountains. These achievements are more glorious than the proudest triumphs of war, but, thus far, they give but faint hope that we shall yet make full atonement for our spendthrift waste of the bounties of nature. [Footnote: The wonderful success which has attended the measures for subduing torrents and preventing inundations employed in Southern France since 1863 and described in Chapter III., post, ought to be here noticed as a splendid and most encouraging example of well-directed effort in the way of physical restoration.] Limits Of Human Power. It is on the one hand, rash and unphilosophical to attempt to set limits to the ultimate power of man over inorganic nature, and it is unprofitable, on the other, to speculate on what may be accomplished by the discovery of now unknown and unimagined natural forces, or even by the invention of new arts and new processes. But since we have seen aerostation, the motive power of elastic vapors, the wonders of modern telegraphy, the destructive explosiveness of gunpowder, of nitro-glycerine, and even of a substance so harmless, unresisting, and inert as cotton, there is little in the way of mechanical achievement which seems hopelessly impossible, and it is hard to restrain the imagination from wandering forward a couple of generations to an epoch when our descendants shall have advanced as far beyond us in physical conquest, as we have marched beyond the trophies erected by our grandfathers. There are, nevertheless, in actual practice, limits to the efficiency of the forces which we are now able to bring into the field, and we must admit that, for the present, the agencies known to man and controlled by him are inadequate to the reducing of great Alpine precipices to such slopes as would enable them to support a vegetable clothing, or to the covering of large extents of denuded rock with earth, and planting upon them a forest growth. Yet among the mysteries which science is hereafter to reveal, there may be still undiscovered methods of accomplishing even grander wonders than these. Mechanical philosophers have suggested the possibility of accumulating and treasuring up for human use some of the greater natural forces, which the action of the elements puts forth with such astonishing energy. Could we gather, and bind, and make subservient to our control, the power which a West Indian hurricane exerts through a small area in one continuous blast, or the momentum expended by the waves in a tempestuous winter, upon the breakwater at Cherbourg, [Footnote: In heavy storms, the force of the waves as they strike against a sea-wall is from one and a half to two tons to the square foot, and Stevenson, in one instance at Skerryvore and in another at the Bell Rock lighthouse, found this force equal to nearly three tons per foot. The seaward front of the breakwater at Cherbourg exposes a surface about 2,500,000 square feet. In rough weather the waves beat against this whole face, though at the depth of twenty-two yards, which is the height of the breakwater, they exert a very much less violent motive force than at and near the surface of the sea, because this force diminishes in geometrical, and the distance below the surface increases in arithmetical, proportion. The shock of the waves is received several thousand times in the course of twenty four hours, and hence the sum of impulse which the breakwater resists in one stormy day amounts to many thousands of millions of tons. The breakwater is entirely an artificial construction. If then man could accumulate and control the forces which he is able effectually to resist, he might be said to be physically speaking, omnipotent.] or the lifting power of the tide, for a month, at the head of the Bay of Fundy, or the pressure of a square mile of sea water at the depth of five thousand fathoms, or a moment of the might of an earthquake or a volcano, our age--which moves no mountains and casts them into the sea by faith alone--might hope to scarp the ragged walls of the Alps and Pyrenees and Mount Taurus, robe them once more in a vegetation as rich as that of their pristine woods, and turn their wasting torrents into refreshing streams. [Footnote: Some well-known experiments show that it is quite possible to accumulate the solar heat by a simple apparatus, and thus to obtain a temperature which might be economically important even in the climate of Switzerland. Saussure, by receiving the sun's rays in a nest of boxes blackened within and covered with glass, raised a thermometer enclosed in the inner box to the boiling point; and under the more powerful sun of the Cape of Good Hope, Sir John Hershel cooked the materials for a family dinner by a similar process, using however, but at single box, surrounded with dry sand and covered with two glasses. Why should not so easy a method of economizing fuel be resorted to in Italy, in Spain, and even in more northerly climate The unfortunate John Davidson records in his journal that he saved fuel in Morocco by exposing his teakettle to the sun on the roof of his house, where the water rose to the temperature of one hundred and forty degrees, and, of course, needed little fire to bring it to boil. But this was the direct and simple, not the concentrated or accumulated heat of the sun. On the utilizing of the solar heat, simply as heat, see the work of Mouchot, La Chaleur solaire et ses applications industrielles. Paris, 1860. The reciprocal convertibility of the natural forces has suggested the possibility of advantageously converting the heat of the sun into mechanical power. Ericsson calculates that in all latitudes between the equator and 45 degrees, a hundred square feet of surface exposed to the solar rays develop continuously, for nine hours a day on an average, eight and one fifth horse-power. I do not know that any attempts have been made to accumulate and store up, for use at pleasure, force derived from this powerful source.] Could this old world, which man has overthrown, be rebuilded, could human cunning rescue its wasted hillsides and its deserted plains from solitude or mere nomade occupation, from barrenness, from nakedness, and from insalubrity, and restore the ancient fertility and healthfulness of the Etruscan sea coast, the Campagna and the Pontine marshes, of Calabria, of Sicily, of the Peloponnesus and insular and continental Greece, of Asia Minor, of the slopes of Lebanon and Hermon, of Palestine, of the Syrian desert, of Mesopotamia and the delta of the Euphrates, of the Cyrenaica, of Africa proper, Numidia, and Mauritania, the thronging millions of Europe might still find room on the Eastern continent, and the main current of emigration be turned towards the rising instead of the setting sun. But changes like these must await not only great political and moral revolutions in the governments and peoples by whom these regions are now possessed, but, especially, a command of pecuniary and of mechanical means not at present enjoyed by these nations, and a more advanced and generally diffused knowledge of the processes by which the amelioration of soil and climate is possible than now anywhere exists. Until such circumstances shall conspire to favor the work of geographical regeneration, the countries I have mentioned, with here and there a local exception, will continue to sink into yet deeper desolation, and in the meantime the American continent, Southern Africa, Australia, New Zealand, and the smaller oceanic islands, will be almost the only theatres where man is engaged, on a great scale, in transforming the face of nature. IMPORTANCE OF PHYSICAL CONSERVATION, AND RESTORATION. Comparatively short as is the period through which the colonization of foreign lands by European emigrants extends, great and, it is to be feared, sometimes irreparable injury has already been done in the various processes by which man seeks to subjugate the virgin earth; and many provinces, first trodden by the homo sapiens Europae within the last two centuries, begin to show signs of that melancholy dilapidation which is now driving so many of the peasantry of Europe from their native hearths. It is evidently a matter of great moment, not only to the population of the states where these symptoms are manifesting themselves, but to the general interests of humanity, that this decay should be arrested, and that the future operations of rural husbandry and of forest industry, in districts yet remaining substantially in their native condition, should be so conducted as to prevent the widespread mischiefs which have been elsewhere produced by thoughtless or wanton destruction of the natural safeguards of the soil. This can be done only by the diffusion of knowledge on this subject among the classes that, in earlier days, subdued and tilled ground in which they had no vested rights, but who, in our time, own their woods, their pastures, and their ploughlands as a perpetual possession for them and theirs, and have, therefore, a strong interest in the protection of their domain against deterioration. PHYSICAL RESTORATION. Many circumstances conspire to invest with great present interest the questions: how far man can permanently modify and ameliorate those physical conditions of terrestrial surface and climate on which his material welfare depends; how far he can compensate, arrest, or retard the deterioration which many of his agricultural and industrial processes tend to produce; and how far he can restore fertility and salubrity to soil which his follies or his crimes have made barren or pestilential. Among these circumstances, the most prominent, perhaps, is the necessity of providing new homes for a European population which is increasing more rapidly than its means of subsistence, new physical comforts for classes of the people that have now become too much enlightened and have imbibed too much culture to submit to a longer deprivation of a share in the material enjoyments which the privileged ranks have hitherto monopolized. To supply new hives for the emigrant swarms, there are, first, the vast unoccupied prairies and forests of America, of Australia, and of many other great oceanic islands, the sparsely inhabited and still unexhausted soils of Southern and even Central Africa, and, finally, the impoverished and half-depopulated shores of the Mediterranean, and the interior of Asia Minor and the farther East. To furnish to those who shall remain after emigration shall have conveniently reduced the too dense population of many European states, those means of sensuous and of intellectual well-being which are styled "artificial wants" when demanded by the humble and the poor, but are admitted to be "necessaries" when claimed by the noble and the rich, the soil must be stimulated to its highest powers of production, and man's utmost ingenuity and energy must be tasked to renovate a nature drained, by his improvidence, of fountains which a wise economy would have made plenteous and perennial sources of beauty, health, and wealth. In those yet virgin lands which the progress of modern discovery in both hemispheres has brought and is still bringing to the knowledge and control of civilized man, not much improvement of great physical conditions is to be looked for. The proportion of forest is indeed to be considerably reduced, superfluous waters to be drawn off, and routes of internal communication to be constructed; but the primitive geographical and climatic features of these countries ought to be, as far as possible, retained. In reclaiming and reoccupying lands laid waste by human improvidence or malice, and abandoned by man, or occupied only by a nomade or thinly scattered population, the task of the pioneer settler is of a very different character. He is to become a co-worker with nature in the reconstruction of the damaged fabric which the negligence or the wantonness of former lodgers has rendered untenantable. He must aid her in reclothing the mountain slopes with forests and vegetable mould, thereby restoring the fountains which she provided to water them; in checking the devastating fury of torrents, and bringing back the surface drainage to its primitive narrow channels; and in drying deadly morasses by opening the natural sluices which have been choked up, and cutting new canals for drawing off their stagnant waters. He must thus, on the one hand, create new reservoirs, and, on the other, remove mischievous accumulations of moisture, thereby equalizing and regulating the sources of atmospheric humidity and of flowing water, both which are so essential to all vegetable growth, and, of course, to human and lower animal life. I have remarked that the effects of human action on the forms of the earth's surface could not always be distinguished from those resulting from geological causes, and there is also much uncertainty in respect to the precise influence of the clearing and cultivating of the ground, and of other rural operations, upon climate. It is disputed whether either the mean or the extremes of temperature, the periods of the seasons, or the amount or distribution of precipitation and of evaporation, in any country whose annals are known, have undergone any change during the historical period. It is, indeed, as has been already observed, impossible to doubt that many of the operations of the pioneer settler TEND to produce great modifications in atmospheric humidity, temperature, and electricity; but we are at present unable to determine how far one set of effects is neutralized by another, or compensated by unknown agencies. This question scientific research is inadequate to solve, for want of the necessary data; but well conducted observation, in regions now first brought under the occupation of man, combined with such historical evidence as still exists, may be expected at no distant period to throw much light on this subject. Australia and New Zealand are, perhaps, the countries from which we have a right to expect the fullest elucidation of these difficult and disputable problems. Their colonization did not commence until the physical sciences had become matter of utmost universal attention, and is, indeed, so recent that the memory of living men embraces the principal epochs of their history; the peculiarities of their fauna, their flora, and their geology are such as to have excited for them the liveliest interest of the votaries of natural science; their mines have given their people the necessary wealth for procuring the means of instrumental observation, and the leisure required for the pursuit of scientific research; and large tracts of virgin forest and natural meadows are rapidly passing under the control of civilized man. Here, then, exist greater facilities and stronger motives for the careful study of the topics in question than have ever been found combined in any other theatre of European colonization. In North America, the change from the natural to the artificial condition of terrestrial surface began about the period when the most important instruments of meteorological observation were invented. The first settlers in the territory now constituting the United States and the British American provinces had other things to do than to tabulate barometrical and thermometrical readings, but there remain some interesting physical records from the early days of the colonies, [Footnote: The Travels of Dr. Dwight, president of Yale College, which embody the results of his personal observations, and of his inquiries among the early settlers, in his vacation excursions in the Northern States of the American Union, though presenting few instrumental measurements or tabulated results, are of value for the powers of observation they exhibit, and for the sound common sense with which many natural phenomena, such for instance as the formation of the river meadows, called "intervales," in New England, are explained. They present a true and interesting picture of physical conditions, many of which have long ceased to exist in the theatre of his researches, and of which few other records are extant.] and there is still an immense extent of North American soil where the industry and the folly of man have as yet produced little appreciable change. Here, too, with the present increased facilities for scientific observation, the future effects, direct a contingent, of man's labors, can be measured, and such precautions taken in those rural processes which we call improvements, as to mitigate evils, perhaps, in some degree, inseparable from every attempt to control the action of natural laws. In order to arrive at safe conclusions, we must first obtain a more exact knowledge of the topography, and of the present superficial and climatic condition of countries where the natural surface is as yet more or less unbroken. This can only be accomplished by accurate surveys, and by a great mutiplication of the points of meteorological registry, [Footnote: The general law of tempeture is that it decreases as we ascend. But in hilly areas the law is reversed in cold, still weather, the cold air descending, by reason of its greater gravity, into the valleys. If there be wind enough however, to produce a disturbance and intermixture of higher and lower atmospheric strata, this exception to the general law does not take place. These facts have long been familiar to the common people of Switzerland and of New England, but their importance has not been sufficiently taken into account in the discussion of meterological observations. The descent of the cold air and the rise of the warm effect the relative temperatures of hills and valleys to a much greater extent that has been usually supposed. A gentleman well known to me kept a thermometrical record for nearly a half century in a New England county town, at an elevation of at least 1,5000 feet above the sea. During these years his thermometer never fell lower that 26 degrees Farrenheit, while at the shire town of the county, situated in a basin thousand feet lower, and only tem miles distant, as well as at other points in similar positions, the mercury froze several times in the same period] already so numerous; and as, moreover, considerable changes in the proportion of forest and of cultivated land, or of dry and wholly or partially submerged surface, will often take place within brief periods, it is highly desirable that the attention of observers, in whose neighborhood the clearing of the soil, of the drainage of lakes and swamps, or other great works of rural improvement, are going on or meditated, should be especially drawn not only to revolutions in atmospheric tempeture and precipitation, but to the more easily ascertained and perhaps more important local changes produced by these operations in the temperature and the hygrometric state of the superficial strata of the earth, and in its spontaneous vegetable and animal products. The rapid extension of railroads, which now everywhere keep pace with, and sometimes even precede, the occupation of new soil for agricultural purposes, furnishes great facilities for enlarging our knowledge of the topography of the territory they traverse, because their cuttings reveal the composition and general structure of surface, and the inclination and elevation of their lines constitute known hypsometrical sections, which give numerous points of departure for the measurement of higher and lower stations, and of course for determining the relief and depression of surface, the slope of the beds of watercourses, and many other not less important questions. [Footnote: Railroad surveys must be received with great caution where any motive exists for COOKING them. Capitalists are shy of investments in roads with steep grades, and of course it is important to make a fair show of facilities in obtaining funds for new routes. Joint-stock companies have no souls; their managers, in general, no consciences. Cases can be cited where engineers and directors of railroads, with long grades above one hundred foot to the mile, have regularly sworn in their annual reports, for years in succession, that there were no grades upon their routes exceeding half that elevation. In fact, every person conversant with the history of these enterprises knows that in their public statements falsehood is the rule, truth the exception. What I am about to remark is not exactly relevant to my subject; but it is hard to "get the floor" in the world's great debating society, and when a speaker who has anything to say once finds access to the public ear, he must make the must of his opportunity, without inquiring too nicely whether his observations are "in order." I shall harm no honest man by endeavoring, as I have often done elsewhere, to excite the attention of thinking and conscientious men to the dangers which threaten the great moral and even political interests of Christendom, from the unscrupulousness of the private associations that now control the monetary affairs, and regulate the transit of persons and property, in almost every civilized country. More than one American State is literally governed by unprincipled corporations, which not only defy the legislative power, but have, too often, corrupted even the administration of justice. The tremendous power of these associations is due not merely to pecuniary corruption, but partly to an old legal superstition--fostered by the decision of the Supreme Court of the United States in the famous Dartmouth College case--in regard to the sacredness of corporate prerogatives. There is no good reason why private rights derived from God and the very constitution of society should be less respected than privileges granted by legislatures. It should never be forgotten that no privilege can be a right, and legislative bodies ought never to make a grant to a corporation, without express reservation of what many sound jurists now hold to be involved in the very nature of such grants, the power of revocation. Similar evils have become almost equally rife in England, and on the Continent; and I believe the decay of commercial morality, and of the sense of all higher obligations than those of a pecuniary nature, on both sides of the Atlantic, is to be ascribed more to the influence of joint-stock banks and manufacturing and railway companies, to the workings, in short, of what is called the principle of "associate action," than to any other one cause of demoralization. The apophthegm, "the world is governed too much," though unhappily too truly spoken of many countries--and perhaps, in some aspects, true of all--has done much mischief whenever it has been too unconditionally accepted as a political axiom. The popular apprehension of being over-governed, and, I am afraid, more emphatically the fear of being over-taxed, has had much to do with the general abandonment of certain governmental duties by the ruling powers of most modern states. It is theoretically the duty of government to provide all those public facilities of intercommunication and commerce, which are essential to the prosperity of civilized commonwealths, but which individual means are inadequate to furnish, and for the due administration of which individual guarantees are insufficient. Hence public roads, canals, railroads, postal communications, the circulating medium of exchange whether metallic or representative, armies, navies, being all matters in which the nation at large has a vastly deeper interest than any private association can have, ought legitimately to be constructed and provided only by that which is the visible personification and embodiment of the nation, namely, its legislative head. No doubt the organization and management of those insitutions by government are liable, as are all things human, to great abuses. The multiplication of public placeholders, which they imply, is a serious evil. But the corruption thus engendered, foul as it is, does not strike so deep as the rottenness of private corporations; and official rank, position, and duty have, in practice, proved better securities for fidelity and pecuniary integrity in the conduct of the interests in question, than the suretyships of private corporate agents, whose bondsmen so often fail or abscond before their principal is detected. Many theoretical statesmen have thought that voluntary associations for strictly pecuniary and industrial purposes, and for the construction and control of public works, might furnish, in democratic countries, a compensation for the small and doubtful advantages, and at the same time secure an exemption from the great and certain evils, of aristocratic institutions. The example of the American States shows that private corporations--whose rule of action is the interest of the association, not the conscience of the individual--though composed of ultra-democratic elements, may become most dangerous enemies to rational liberty, to the moral interests of the commonwealth, to the purity of legislation and of judicial action, and to the sacredness of private rights.] The geological, hydrographical, and topographical surveys, which almost every general and even local government of the civilized world is carrying on, are making yet more important contributions to our stock of geographical and general physical knowledge, and, within a comparatively short space, there will be an accumulation of well established constant and historical facts, from which we can safely reason upon all the relations of action and reaction between man and external nature. But we are, even now, breaking up the floor and wainscoting and doors and window frames of our dwelling, for fuel to warm our bodies and to seethe our pottage, and the world cannot afford to wait till the slow and sure progress of exact science has taught it a better economy. Many practical lessons have been learned by the common observation of unschooled men; and the teachings of simple experience, on topics where natural philosophy has scarcely yet spoken, are not to be despised. In these humble pages, which do not in the least aspire to rank among scientific expositions of the laws of nature, I shall attempt to give the most important practical conclusions suggested by the history of man's efforts to replenish the earth and subdue it; and I shall aim to support those conclusions by such facts and illustrations only as address themselves to the understanding of every intelligent reader, and as are to be found recorded in works capable of profitable perusal, or at least consultation, by persons who have not enjoyed a special scientific training. CHAPTER II. TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL SPECIES. Modern geography takes account of organic life--Geographical importance of plants--Origin of domestic vegetables-Transfer of vegetable life--Objects of modern commerce-Foreign plants, how introduced--Vegetable power of accommodation--Agricultural products of the United States--Useful American plants grown in Europe--Extirpation of vegetables--Animal life as a geological and geographical agency--Origin and transfer of domestic quadrupeds--Extirpation of wild quadrupeds--Large marine animals relatively unimportant in geography--Introduction and breeding of fish--Destruction of fish--Geographical importance of birds--Introduction of birds--Destruction of birds--Utility and destruction of reptiles--Utility of insects and worms--Injury to the forest by insects--Introduction of insects--Destruction of insects--Minute organisms. MODERN GEOGRAPHY EMBRACES ORGANIC LIFE. It was a narrow view of geography which confined that science to delineation of terrestrial surface and outline, and to description of the relative position and magnitude of land and water. In its improved form it embraces not only the globe itself and the atmosphere which bathes it, but the living things which vegetate or move upon it, the varied influences they exert upon each other, the reciprocal action and reaction between them and the earth they inhabit. Even if the end of geographical studies were only to obtain a knowledge of the external forms of the mineral and fluid masses which constitute the globe, it would still be necessary to take into account the element of life; for every plant, every animal, is a geographical agency, man a destructive, vegetables, and in some cases even wild beasts, restorative powers. The rushing waters sweep down earth from the uplands; in the first moment of repose, vegetation seeks to reestablish itself on the bared surface, and, by the slow deposit of its decaying products, to raise again the soil which the torrent lhad lowered. So important an element of reconstruction in this, that it has been seriously questioned whether, upon the whole, vegetation does not contribute as much to elevate, as the waters to depress, the level of the surface. Whenever man has transported a plant from its native habitat to a new soil, he has introduced a new geographical force to act upon it, and this generally at the expense of some indigenous growth which the foreign vegetable has supplanted. The new and the old plants are rarely the equivalents of each other, and the substitution of an exotic for a native tree, shrub, or grass, increases or diminishes the relative importance of the vegetable element in thegeography of the country to which it is removed. Further, man sows that he may reap. The products of agricultural industry are not suffered to rot upon the ground, and thus raise it by an annual stratum of new mould. They are gathered, transported to greater or less distances, and after they have served their uses in human economy, they enter, on the final decomposition of their elements, into new combinations, and are only in smnall proportion returned to the soil on which they grew. The roots of the grasses, and of many other cultivated plants, however, usually remain and decay in the earth, and contribute to raise its surface, though certainly not in the same degree as the forest. The smaller vegetables which have taken the place of trees unquestionably perform many of the same functions. They radiate heat, they absorb gases, and exhale uncombined gases and watery vapor, and consequently act upon the chemical constitution and hygrometrical condition of the air, their roots penetrate the earth to greater depths than is commonly supposed, and form an inextricable labyrinth of filaments which bind the soil together and prevent its erosion by water. The broad-leaved annuals and perennials, too, shade the ground, and prevent the evaporation of moisture from its surface by wind and sun. [Footnote: It is impossible to say how far the abstraction of water from the earth by broad-leaved field and garden plants--such as maize, the gourd family, the cabbage, &c.--is compensated by the condensation of dew, which sometimes pours from them in a stream, by the exhalation of aqueous vapor from their leaves, which is directly absorbed by the ground, and by the shelter they afford the soil from sun and wind, thus preventing evaporation. American farmers often say that after the leaves of Indian corn are large enough to "shade the ground," there is little danger that the plants will suffer from drought; but it is probable that the comparative security of the fields from this evil is in port due to the fact that, at thin period of growth, the roots penetrate down to a permanently humid stratum of soil, and draw from it the moisture they require. Stirring the ground between the rows of maize with a light harrow or cultivator, in very dry seasons, is often recommended as a preventive of injury by drought. It would seem, indeed, that loosening and turning over the surface earth might aggravate the evil by promoting the evaporation of the little remaining moisture; but the practice is founded partly on the belief that the hygroscopicity of the soil is increased by it to such a degree that it gains more by absorption than it loses by evaporation, and partly on the doctrine that to admit air to the rootlets, or at least to the earth near them, is to supply directly elements of vegetable growth.] At a certain stage of growth, grass land is probably a more energetic evaporator and refrigerator than even the forest, but this powerful action is exerted, in its full intensity, for a comparatively short time only, while trees continue such functions, with unabated vigor, for many months in succession. Upon the whole, it seems quite certain, that no cultivated ground is as efficient in tempering climatic extremes, or in conservation of geographical surface and outline, as is the soil which nature herself has planted. ORIGIN OF DOMESTIC PLANTS. One of the most important questions connected with our subject is: how far we are to regard our cereal grains, our esculent bulbs and roots, and the multiplied tree fruits of our gardens, as artificially modified and improved forms of wild, self-propagating vegetation. The narratives of botanical travellers have often announced the discovery of the original form and habitat of domesticated plants, and scientific journals have described the experiments by which the identity of particular wild and cultivated vegetables has been thought to be established. It is confidently affirmed that maize and the potato--which we must suppose to have been first cultivated at a much later period than the breadstuffs and most other esculent vegetables of Europe and the East--are found wild and self-propagating in Spanish America, though in forms not recognizable by the common observer as identical with the familiar corn and tuber of modern agriculture. It was lately asserted, upon what seemed very strong evidence, that the Aegilops ovata, a plant growing wild in Southern France, had been actually converted into common wheat; but, upon a repetition of the experiments, later observers have declared that the apparent change was only a case of temporary hybridation or fecundation by the pollen of true wheat, and that the grass alleged to be transformed into wheat could not be perpetuated as such from its own seed. The very great modifications which cultivated plants are constantly undergoing under our eyes, and the numerous varieties and races which spring up among them, certainly countenance the doctrine, that every domesticated vegetable, however dependent upon human care for growth and propagation in its present form, may have been really derived, by a long Succession of changes, from some wild plant not now perhaps much resembling it. [Footnote: What is the possible limit of such changes, we do not know, but they may doubtless be carriad vastly beyond what experience has yet shown to be practicable. Civilized man has experimented little on wild plants, and especially on forest trees. He has indeed improved the fruit, and developed new varieties, of the chestnut, by cultivation, and it is observed that our American forest-tree nuts and berries, such as the butternut and thewild mulberry, become larger and better flavored in a single generation by planting and training. (Bryant, Forest Trees, 1871, pp. 99, 115.) Why should not the industry and ingenuity which have wrought such wonders in our horticulture produce analogous results when applied to the cultivation and amelioration of larger vegetables Might not, for instance, the ivory nut, the fruit of the Phytelephas macrocarpa, possibly be so increased in size as to serve nearly all the purposes of animal ivory now becoming so scarce Might not the various milk-producing trees become, by cultivation, a really important source of nutriment to the inhabitants of warm climates In short, there is room to hope incalculable advantage from the exercise of human skill in the improvement of yet untamed forms of vegetable life.] But it is, in every case, a question of evidence. The only satisfactory proof that a given wild plant is identical with a given garden or field vegetable, is the test of experiment, the actual growing of the one from the seed of the other, or the conversion of the one into the other by transplantation and change of conditions. [Footnote: The poisonous wild parsnip of New England has been often asserted to be convertible into the common garden parsnip by cultivation, or rather to be the same vegetable growing under different conditions, and it is said to be deprived of its deleterious qualities simply by an increased luxuriance of growth in rich, tilled earth. Wild medicinal plants, so important in the rustic materia medica of New England--such as pennyroyal, for example--are generally much less aromatic and powerful when cultivated in gardens than when self-sown on meagre soils. On the other hand, the cinchona, lately introduced from South America into British India and carefully cultivated there, is found to be richer in quinine than the American tree.] It is hardly contended that any of the cereals or other plants important as human aliment, or as objects of agricultural industry, exist and propagate themselves uncultivated in the same form and with the same properties as when sown and reared by human art. [Footnote: Some recent observations of Wetzatein are worthy of special notice. "The soil of the Hauran," he remarks, "produces, in its primitive condition, much wild rye, which is not known as a cultivated plant in Syria, and much wild barley and oats. These cereals precisely resemble the corresponding cultivated plants in leaf, ear, size, and height of straw, but their grains are sensibly flatter and poorer in flour."--Reisebericht uber Hauran und die Trachenen, p. 40. Some of the cereals are, to a certain extent, self-propagating in the soil and climate of California. "VOLUNTEER crops are grown from the seed which falls out in harvesting. Barley has been known to volunteer five crops in succession."--Prayer-Frowd, Six Months in California, p. 189.] In fact, the cases are rare where the identity of a wild with a domesticated plant is considered by the best authorities as conclusively established, and we are warranted in affirming of but few of the latter, as a historically known or experimentally proved fact, that they ever did exist, or could exist, independently of man. [Footnote: This remark is much less applicable to fruit trees than to garden vegetables and the cerealia. The wild orange of Florida, though once considered indigenous, is now generally thought by botanists to be descended from the European orange introduced by the early colonists. On the wild apple trees of Massachusetts see an interesting chapter in Thoreau, Excursions. The fig and the olive are found growing wild in every country where those trees are cultivated The wild fig differs from the domesticated in its habits, its season of fructification, and its insect population, but is, I believe, not specifically distinguishable from the garden fig, though I do not know that it is reclaimable by cultivation. The wild olive, which is so abundant in the Tuscan Maremma, produces good fruit without further care, when thinned out and freed from the shade of other trees, and is particularly suited for grafting. See Salvagnoli, Memorie sulle Maremme, pp. 63-73. The olive is indigenous in Syria and in the Punjaub, and forms vast forests in the Himalayas at from 1,400 to 2,100 feet above the level of the sea.--Cleghorn, Memoir on the Timber procured from the Indus, etc., pp. 8-15. Fraas, Klima und Pfanzenwelt in der Zeit, pp. 35-38, gives, upon the authority of Link and other botanical writers, a lift of the native habitats of most cereals and of many fruits, or at least of localities where those plants are said to be now found wild; but the data do not appear to rest, in general, upon very trustworthy evidence. Theoretically, there can be little doubt that all our cultivated plants are modified forms of spontaneous vegetation, though the connection is not historically shown, nor are we able to say that the originals of some domesticated vegetables may not be now extinct and unrepresented in the existing wild flora. See, on this subject, Humboldt, Ansichten der Natur, i., pp. 208, 209. The Adams of modern botany and zoology have been put to hard shifts in finding names for the multiplied organisms which the Creator has brought before them, "to see what they would call them;" and naturalists and philosophers have shown much moral courage in setting at naught the law of philology in the coinage of uncouth words to express scientific Ideas. It is much to be wished that some bold neologist would devise English technical equivalents for the German verwildert, run-wild, and veredelt, improved by cultivation.] Transfer of Vegetable Life. It belongs to vegetable and animal geography, which are almost sciences of themselves, to point out in detail what man has done to change the distribution of plants and of animated life and to revolutionize the aspect of organic nature; but some of the more important facts bearing on the first branch of this subject may pertinently be introduced here. Most of the cereal grains, the pulse, the edible roots, the tree fruits, and other important forms of esculent vegetation grown in Europe and the United States are believed, and--if the testimony of Pliny and other ancient naturalists is to be depended upon--many of them are historically known, to have originated in the temperate climates of Asia. The agriculture of even so old a country as Egypt has been almost completely revolutionized by the introduction of foreign plants, within the historical period. "With the exception of wheat," says Hehn, "the Nile valley now yields only new products, cotton, rice, sugar, indigo, sorghum, dates," being all unknown to its most ancient rural husbandry. [Footnote: On these points see the learned work of Hehn, Kultur. Pflanzen und Thiere in ihrem Uebergang aus Asien, 1870. On the migration of plants generally, see Lyell, Principles of Geology, 10th ed., vol. ii., c.] The wine grape has been thought to be truly indigenous only in the regions bordering on the eastern end of the Black Sea, where it now, particularly on the banks of the Rion, the ancient Phasis, propagates itself spontaneously, and grows with unexampled luxuriance. [Footnote: The vine-wood planks of the ancient great door of the cathedral at Ravenna, which measured thirteen feet in length by a foot and a quarter in width, are traditionally said to have boon brought from the Black Sea, by way of Constantinople, about the eleventh or twelfth century. Vines of such dimension are now very rarely found in any other part of the East, and, though I have taken some pains on the subject, I never found in Syria or in Turkey a vine stock exceeding six inches in diameter, bark excluded. Schulz, however, saw at Beitschin, near Ptolemais, a vine measuring eighteen inches in diameter. Strabo speaks of vine-stocks in Margiana (Khorasan) of such dimension that two men, with outstretched arms, could scarcely embrace them. See Strabo, ed. Casaubon, pp. 78, 516, 826. Statues of vine wood are mentioned by ancient writers. Very large vine-stems are not common in Italy, but the vine-wood panels of the door of the chapter-hall of the church of St. John at Saluzzo are not less than ten inches in width, and I observed not long since, in a garden at Pie di Mulera, a vine stock with a circumference of thirty inches.] But some species of the vine seem native to Europe, and many varieties of grape have been too long known as common to every part of the United States to admit of the supposition that they were introduced by European colonists. [Footnote: The Northmen who--as I think it has been indisputably established by Professor Rafn of Copenhagen--visited the coast of Massachusetts about theyear 1000, found grapes growing there in profusion, and the wild vine still flourishes in great variety and abundance in the southeastern counties of that State. The townships in the vicinity of the Dighton rock, supposed by many--with whom, however, I am sorry I cannot agree--to bear a Scandinavian inscription, abound in wild vines. According to Laudonniere, Histoire Notable de la Florida, reprint, Paris, 1853, p 5, the French navigators in 1562 found in that peninsula "wild vines which climb the trees and produce good grapes."] OBJECTS OF MODERN COMMERCE. It is an interesting fact that the commerce--or at least the maritime carrying trade--and the agricultural and mechanical industry of the world are, in very large proportion, dependent on vegetable and animal products little or not at all known to ancient Greek, Roman, and Jewish civilization. In many instances, the chief supply of these articles comes from countries to which they are probably indigenous, and where they are still almost exclusively grown; but in most cases, the plants or animals from which they are derived have been introduced by man into regions now remarkable for their successful cultivation, and that, too, in comparatively recent times, or, in other words, within two or three centuries. Something of detail on this subject cannot, I think, fail to prove interesting. Pliny mentions about thirty or forty oils as known to the ancients, of which only olive, sesame, rape seed and walnut oil--for except in one or two doubtful passages I find in this author no notice of linseed oil--appear to have been used in such quantities as to have had any serious importance in the carrying trade. At the present time, the new oils, linseed oil, the oil of the whale and other largeo marine animals, petroleum--of which the total consumption of the world in 1871 is estimated at 6,000,000 barrels, the port of Philadelphia alone exporting 56,000,000 gallons in that year--palm-oil recently introduced into commerce, and now imported into England from the coast of Africa at the rate of forty or fifty thousand tuns a year, these alone undoubtedly give employment to more shipping than the whole commerce of Italy--with the exception of wheat--at the most flourishing period of the Roman empire. [Footnote: A very few years since, the United States had more than six hundred large ships engaged in the whale fishery, and the number of American whalers, in spite of the introduction of many now sources of oils, still amounts to two hundred and fifty. The city of Rome imported from Sicily, from Africa, and from the Levant, enormous quantities of grain for gratuitous distribution among the lower classes of the capital. The pecuniary value of the gems, the spices, the unguents, the perfumes, the cosmetics and the tissues, which came principally from the East, was great, but these articles were neither heavy nor bulky and their transportation required but a small amount of shipping. The marbles, the obelisks, the statuary and other objects of art plundered in conquered provinces by Roman generals and governors, the wild animals, such as elephants, rhinoceroses, hippopotami, camelopards and the larger beasts of prey imported for slaughter at the public games, and the prisoners captured in foreign wars and brought to Italy for sale as slaves or butchery as gladiators, furnished employment for much more tonnage than all the legitimate commerce of the empire, with the possible exception of wheat. Independently of the direct testimony of Latin authors, the Greek statuary, the Egyptian obelisks, and the vast quantities of foreign marbles, granite, parphyry, basalt, and other stones used in sculpture and in architecture, which have been found in the remains of ancient Rome, show that the Imperial capital must have employed an immense amount of tonnage in the importation of heavy articles for which there could have been no return freight, unless in the way of military transportation. Some of the Egyptian obelisks at Rome weigh upwards of four hundred tons, and many of the red granite columns from the same country must have exceeded one hundred tons. Greek and African marbles were largely used not only for columns, contablatures, and solid walls, but for casing the exterior and veneering the interior of public and private buildings. Scaurus imported, for the scene alone of a temporary theatre designed to stand scarcely for a month, three hundred and sixty columns, which were disposed in three tiers, the lower range being forty-two feet in height--See Pliny, Nat. Hist., Lib. xxxvi. Italy produced very little for export, and her importations, when not consisting of booty, were chiefly paid for in coin which was principally either the spoil of war or the fruit of official extortion.] England imports annually about 600,000 tons of sugar, 100,000 tons of jute, and about the same quantity of esparto, six million tons of cotton, of which the value of $30,000,000 is exported again in the form of manufactured, goods--including, by a strange industrial revolution, a large amount of cotton yarn and cotton tissues sent to India and directly or indirectly paid for by raw cotton to be manufactured in England--30,000 tons of tobacco, from 100,000 to 350,000 tons of guano, hundreds of thousands of tons of tea, coffee, cacao, caoutchone, gutta-percha and numerous other important articles of trade wholly unknown, as objects of commerce, to the ancient European world; and this immense importation is balanced by a corresponding amount of exportation, not consisting, however, by any means, exclusively of articles new to commerce. [Footnote: Many of these articles would undoubtedly have been made known to the Greeks and Romans and have figured in their commerce, but for the slowness and costliness of ancient navigation, which, in the seas familiar to them, was suspended for a full third of the year from the inability of their vessels to cope with winter weather. The present speed and economy of transportation have wrought and are still working strange commercial and industrial revolutions. Algeria now supplies Northern Germany with fresh cauliflowers, and in the early spring the market-gardeners of Naples find it more profitable to send their first fruits to St. Petersburg than to furnish them to Florence and Rome.] FOREIGN PLANTS, HOW INTRODUCED. Besides the vegetables I have mentioned, we know that many plants of smaller economical value have been the subjects of international exchange in very recent times. Busbequius, Austrian ambassador at Constantinople about the middle of the sixteenth century--whose letters contain one of the best accounts of Turkish life which have appeared down to the present day--brought home from the Ottoman capital the lilac and the tulip. The Belgian Clusius about the same time introduced from the East the horse chestnut, which has since wandered to America. The weeping willows of Europe and the United States are said to have sprung from a slip received from Smyrna by the poet Pope; and planted by him in an English garden; Drouyn de l'IIuys, in a discourse delivered before the French Societe d'Acclimatation, in 1860, claims for Rabelais the introduction of the melon, the artichoke and the Alexandria pink into France; and the Portuguese declare that the progenitor of all the European and American oranges was an Oriental tree transplanted to Lisbon, and still living in the last generation. [Footnote: The name portogallo, so generally applied to the orange in Italy, seems to favor this claim. The orange, however, was known in Europe before the discovery of the Cape of Good Hope, and therefore, before the establishment of direct relations between Portugal and the East.--See Amari, Storia del Musulmani in Sicilia, vol ii., p. 445. The date-palms of eastern and southern Spain were certainly introduced by the Moors. Leo Von Rozmital, who visited Barcelona in 1476, says that the date-tree grew in great abundance in the environs of that city and ripened its fruit well. It is now scarcely cultivated further north than Valencia. It is singular that Ritter in his very full monograph on the palm does not mention those of Spain. On the introduction of conifera into England see an interesting article in the Edinburgh Review of October, 1864. Muller, Das Buch der Pfianzenrodt, p. 86, asserts that in 1802 the ancestor of all the mulberries in France, planted in 1500, was still standing in a garden in the village of Allan-Montelimart.] The present favorite flowers of the parterres of Europe have been imported from America, Japan and other remote Oriental countries, within a century and a half, and, in fine, there are few vegetables of any agricultural importance, few ornamental trees or decorative plants, which are not now common to the three civilized continents. The statistics of vegetable emigration exhibit numerical results quite surprising to those not familiar with the subject. The lonely island of St. Helena is described as producing, at the time of its discovery in the year 1501, about sixty vegetable species, including some three or four known to grow elsewhere also. [Footnote: It may be considered very highly probable, if not certain, that the undiscriminating herbalists of the sixteenth century must have overlooked many plants native to this island. An English botanist, in an hour's visit to Aden, discovered several species of plants on rocks always reported, even by scientific travellers, as absolutely barren. But after all, it appears to be well established that the original flora of St. Helena was extremely limited, though now counting hundreds of species.] At the present time its flora numbers seven hundred and fifty species--a natural result of the position of the island as the half-way house on the great ocean highway between Europe and the East. Humboldt and Bonpland found, among the unquestionably indigenous plants of tropical America, monocotyledons only, all the dicotyledons of those extensive regions having been probably introduced after the colonization of the New World by Spain. The seven hundred new species which have found their way to St. Helena within three centuries and a half, were certainly not all, or ever in the largest proportion, designedly planted there by human art, and if we were well acquainted with vegetable emigration, we should probably be able to show that man has intentionally transferred fewer plants than he has accidentally introduced into countries foreign to them. After the wheat, follow the tares that infest it. The woods that grow among the cereal grains, the pests of the kitchen garden, are the same in America as in Europe. [Footnote: Some years ago I made a collection of weeds in the wheatfields of Upper Egypt, and another in the gardens on the Bosphorus. Nearly all the plants were identical with those which grow under the same conditions in New England. I do not remember to have seen in America the scarlet wild poppy so common in European grainfields. I have heard, however, that it has lately crossed the Atlantic, and I am not sorry for it. With our abundant harvests of wheat, we can well afford to pay now and then a loaf of bread for the cheerful radiance of this brilliant flower.] The overturning of a wagon, or any of the thousand accidents which befall the emigrant in his journey across the Western plains, may scatter upon the ground the seeds he designed for his garden, and the herbs which fill so important a place in the rustic materia medica of the Eastern States, spring up along the prairie paths but just opened by the caravan of the settler. [Footnote: Josselyn, who wrote about fifty years after the foundation of the first British colony in New England, says that the settlers at Plymouth had observed more than twenty English plants springing up spontaneously near their improvements. Every country has many plants not now, if ever, made use of by man, and therefore not designedly propagated by him, but which cluster around his dwelling, and continue to grow luxuriantly on the ruins of his rural habitation after he has abandoned it. The site of a cottage, the very foundation stones of which have been carried off, may often be recognized, years afterwards, by the rank weeds which cover it, though no others of the same species are found for miles. "Mediaeval Catholicism," says Vaupell, "brought us the red horsehoof--whose reddish-brown flower buds shoot up from the ground when the snow melts, and are followed by the large leaves--comfrey and snake-root, which grow only where there were convents and other dwellings in the Middle Ages."--Bogens Indvandring & de Daneke Skove, pp. 1, 2. ] Introduction of Foreign Plants. "A negro slave of the great Cortez," says Humboldt, "was the first who sowed wheat in New Spain. He found three grains of it among the rice which had been brought from Spain as food for the soldiers." About twenty years ago, a Japanese forage plant, the Lesperadeza striata, whose seeds had been brought to the United States by some unknown accident made its appearance in one of the Southern States. It spread spontaneously in various directions, and in a few years was widely diffused. It grows upon poor and exhausted soils, where the formation of a turf or sward by the ordinary grasses would be impossible, and where consequently no regular pastures or meadows can exist. It makes excellent fodder for stock, and though its value is contested, it is nevertheless generally thought a very important addition to the agricultural resources of the South. [Footnote: Accidents sometimes limit, as well as promote the propagation of foreign vegetables in countries new to them. The Lombardy poplar is a deciduous tree, and is very easily grown from cuttings. In most of the countries into which it has been introduced the cuttings hare been taken from the male, and as, consequently, males only have grown from them, the poplar does not produce seed in those regions. This is a fortunate circumstance, for otherwise this most worthless and least ornamental of trees would spread with a rapidity that would make it an annoyance to the agriculturist.] In most of the Southern countries of Europe, the sheep and horned cattle winter on the plains, but in the summer are driven, sometimes many days' journey, to mountain pastures. Their coats and fleeces transport seeds in both directions. Hence we see Alpine plants in champaign districts, the plants of the plains on the borders of the glaciers, though in neither case do these vegetables ripen their seeds and propagate themselves. This explains the occurrence of tufts of common red clover with pallid and sickly flowers, on the flanks of the Alps at heights exceeding seven thousand feet. The hortus siccus of a botanist may accidentally sow seeds from the foot of the Himalayas on the plains that skirt the Alps; and it is a fact of very familiar observation, that exotics, transplanted to foreign climates suited to their growth, often escape from the flower garden and naturalize themselves among the spontaneous vegetation of the pastures. When the cases containing the artistic treasures of Thorvaldsen wore opened in the court of the museum where they are deposited, the straw and grass employed in packing them were scattered upon the ground, and the next season there sprang up from the seeds no less than twenty-five species of plants belonging to the Roman campagna, some of which were preserved and cultivated as a new tribute to the memory of the great Scandinavian sculptor, and at least four are said to have spontaneously naturalized themselves about Copenhagen. [Footnote: Vaupell, Bogens Indvandring i de Danske Skove, p. 2.] The Turkish armies, in their incursions into Europe, brought Eastern vegetables in their train, and left the seeds of Oriental wall plants to grow upon the ramparts of Buda and Vienna. [Footnote: I believe it is certain that the Turks introduced tobacco into Hungary, and probable that they in some measure compensated, the injury by introducing maize also, which, as well as tobacco, has been claimed as Hungarian by patriotic Magyars.] In the campaign of 1814, the Russian troops brought, in the stuffing of their saddles and by other accidental means, seeds from the banks of the Dnieper to the valley of the Rhine, and even introduced the plants of the steppes into the environs of Paris. The forage imported for the French army in the war of 1870-1871 has introduced numerous plants from Northern Africa and other countries into France, and this vegetable emigration is so extensive and so varied in character, that it will probably have an important botanical, and even economical, effect on the flora of that country. [Footnote: In a communication lately made to the French Academy, M. Vibraye gives numerous interesting details on this subject, and says the appearance of the many new plants observed in France in 1871, "results from forage supplied from abroad, the seeds of which had fallen upon the ground. At the present time, several Mediterranean plants, chiefly Algerian, having braved the cold of an exceptionally severe winter, are being largely propagated, forming extensive meadows, and changing soil that was formerly arid and produced no vegetable of importance into veritable oases." See Nature, Aug. 1, 1872, p. 263. We shall see on a following page that canals are efficient agencies in the unintentional interchange of organic life, vegetable as well as animal, between regions connected by such channels.] The Canada thistle, Erigeron Canadense, which is said to have accompanied the early French voyagers to Canada from Normandy, is reported to have been introduced into other parts of Europe two hundred years ago by a seed which dropped out of the stuffed skin of an American bird. VEGETABLE POWER OF ACCOMMODATION. The vegetables which, so far as we know their history, seem to have been longest objects of human care, can, by painstaking industry, be made to grow under a great variety of circumstances, and some of them prosper nearly equally well when planted and tended on soils of almost any geological character; but the seeds of most of them vegetate only in artificially prepared ground, they have little self-sustaining power, and they soon perish when the nursing hand of man is withdrawn from them. The vine genus is very catholic and cosmopolite in its habits, but particular varieties are extremely fastidious and exclusive in their requirements as to soil and climate. The stocks of many celebrated vineyards lose their peculiar qualities by transplantation, and the most famous wines are capable of production only in certain well-defined and for the most part narrow districts. The Ionian vine which bears the little stoneless grape known in commerce as the Zante currant, has resisted almost all efforts to naturalize it elsewhere, and is scarcely grown except in two or three of the Ionian islands and in a narrow territory on the northern shores of the Morea. The attempts to introduce European varieties of the vine into the United States have not been successful except in California, [Footnote: In 1869, a vine of a European variety planted in Sta. Barbara county in 1833 measured a foot in diameter four foot above the ground. Its ramifications covered ten thousand square feet of surface and it annually produces twelve thousand pounds of grapes. The bunches are sixteen or eighteen inches long, and weigh six or seven pounds.-Letter from Commissioner of Land-Office, dated May 13, 1860.] and it may be stated as a general rule that European forest and ornamental trees are not suited to the climate of North America, and that, at the same time, American garden vegetables are less luxuriant, productive and tasteful in Europe than in the United States. The saline atmosphere of the sea is specially injurious both to seeds and to very many young plants, and it is only recently that the transportation of some very important vegetables across the ocean lines been made practicable, through the invention of Ward's air-tight glass cases. By this means large numbers of the trees which produce the Jesuit's bark were successfully transplanted from America to the British possessions in the East, where this valuable plant may now be said to have become fully naturalized. [Footnote: See Cleghorn, Forests and Gardens of South India, Edinburgh, 1861, and The British Parliamentary return on the Chinchona Plant, 1866. It has been found that the seeds of several species of CINCHONA preserve their vitality long enough to be transported to distant regions. The swiftness of steam navigation render it possible to transport to foreign countries not only seeds but delicate living plants which could not have borne a long voyage by sailing vessels.] Vegetables, naturalized abroad either by accident or design, sometimes exhibit a greatly increased luxuriance of growth. The European cardoon, an esculent thistle, has broken out from the gardens of the Spanish colonies on the La Plata, acquired a gigantic stature, and propagated itself, in impenetrable thickets, over hundreds of leagues of the Pampas; and the Anacharis alsinastrum, a water plant not much inclined to spread in its native American habitat, has found its way into English rivers, and extended itself to such a degree as to form a serious obstruction to the flow of the current, and even to navigation. Not only do many wild plants exhibit a remarkable facility of accommodation, but their seeds usually possess great tenacity of life, and their germinating power resists very severe trials. Hence, while the seeds of many cultivated vegetables lose their vitality in two or three years, and can be transported safely to distant countries only with great precautions, the weeds that infest those vegetables, though not cared for by man, continue to accompany him in his migrations, and find a new home on every soil he colonizes. Nature fights in defence of her free children, but wars upon them when they have deserted her banners and tamely submitted to the domination of man. [Footnote: Tempests, violent enough to destroy all cultivated plants, frequently spare those of spontaneous growth. I have often seen in Northern Italy, vineyards, maize fields, mulberry and fruit trees completely stripped of their foliage by hail, while the forest trees scattered through the meadows, and the shrubs and brambles which sprang up by the wayslde, passed through the ordeal with scarcely the loss of a leaflet.] Indeed, the faculty of spontaneous reproduction and perpetuation necessarily supposes a greater power of accommodation, within a certain range, than we find in most domesticated plants, for it would rarely happen that the seed of a wild plant would fall into ground as nearly similar, in composition and condition, to that where its parent grew, as the soils of different fields artificially prepared for growing a particular vegetable are to each other. Accordingly, though every wild species affects a habitat of a particular character, it is found that, if accidentally or designedly sown elsewhere, it will grow under conditions extremely unlike those of its birthplace. Cooper says: "We cannot say positively that any plant is uncultivable ANYWHERE until it has been tried;" and this seems to be even more true of wild than of domesticated vegetation. The wild plant is much hardier than the domesticated vegetable, and the same law prevails in animated brute and even human life. The beasts of the chase are more capable of endurance and privation and more tenacious of life, than the domesticated animals which most nearly resemble them. The savage fights on, after he has received half a dozen mortal wounds, the least of which would have instantly paralyzed the strength of his civilized enemy, and, like the wild boar, he has been known to press forward along the shaft of the spear which was trans-piercing his vitals, and to deal a deathblow on the soldier who wielded it. True, domesticated plants can be gradually acclimatized to bear a degree of heat or of cold, which, in their wild state, they would not have supported; the trained English racer out-strips the swiftest horse of the pampas or prairies, perhaps even the less systematically educated courser of the Arab; the strength of the European, as tested by the dynamometer, is greater than that of the New Zealander. But all these are instances of excessive development of particular capacities and faculties at the expense of general vital power. Expose untamed and domesticated forms of life, together, to an entire set of physical conditions equally alien to the former habits of both, so that every power of resistance and accommodation shall be called into action, and the wild plant or animal will live, while the domesticated will perish. AGRICULTURAL PRODUCTS OF THE UNITED STATES. According to the census of 1870, the United States had, on the first of June in that year, in round numbers, 189,000,000 acres of improved land, the quantity having been increased by 16,000,000 acres within the ten years next preceding. [Footnote: Ninth Census of the United States, 1872, p. 841. By "improved" land, in the reports on the census of the United States, is meant "cleared land" used for grazing, grass, or tillage, or which is now fallow, connected with or belonging to a farm."--Instructions to Marshals and Assistants, Census of 1870.] Not to mention less important crops, this land produced, in the year ending on the day last mentioned, in round numbers, 288,000,000 bushels of wheat, 17,000,000 bushels of rye, 282,000,000 bushels of oats, 6,000,000 bushels of peas and beans, 30,000,000 bushels of barley, orchard fruits to the value of $47,000,000, 640,000 bushels of cloverseed, 580,000 bushels of other grass seed, 13,000 tons of hemp, 27,000,000 pounds of flax, and 1,730,000 bushels of flaxseed. These vegetable growths were familiar to ancient European agriculture, but they were all introduced into North America after the close of the sixteenth century. Of the fruits of agricultural industry unknown to the Greeks and Romans, or too little employed by them to be of any commercial importance, the United States produced, in the same year, 74,000,000 pounds of rice, 10,000,000 bushels of buckwheat, 3,000,000 bales of cotton, [Footnote: Cotton, though cultivated in Asia from the remotest antiquity, and known as a rare and costly product to the Latins and the Greeks, was not used by them except as an article of luxury, nor did it enter into their commerce to any considerable extent as a regular object of importation. The early voyagers found it in common use in the West Indies and in the provinces first colonized by the Spaniards; but it was introduced into the territory of the United States by European settlers, and did not become of any importance until after the Revolution. Cottonseed was sown in Virginia as early as 1621, but was not cultivated with a view to profit for more than a century afterwards. Sea-island cotton was first grown on the coast of Georgia in 1786, the seed having been brought from the Bahamas, when it had been introduced from Anguilla--BIGELOW, Les Etats-Unis en 1868, p. 370]. 87,000 hogsheads of cane sugar, 6,600,000 gallons of cane molasses, 16,000,000 gallons of sorghum molasses, all yielded by vegetables introduced into that country within two hundred years, and--with the exception of buckwheat, the origin of which is uncertain, and of cotton--all, directly or indirectly, from the East Indies; besides, from indigenous plants unknown to ancient agriculture, 761,000,000 bushels of Indian corn, 263,000,000 pounds of tobacco, 143,000,000 bushels of potatoes, 22,000,000 bushels of sweet potatoes, 28,000,000 pounds of maple sugar, and 925,000 gallons of maple molasses. [Footnote: There is a falling off since 1860 of 11,000,000 pounds in the quantity of maple sugar and of more than a million gallons of maple molasses. The high price of cane sugar during and since the late civil war must have increased the product of maple sugar and molasses beyond what it otherwise would have been, but the domestic warfare on the woods has more than compensated this cause of increase.] To all this we are to add 27,000,000 tons of hay,--produced partly by new, partly by long known, partly by exotic and partly by native herbs and grasses, the value of $21,000,000 in garden vegetables chiefly of European or Asiatic origin, 3,000,000 gallons of wine, and many minor agricultural products. [Footnote: Raenie, Bochmeria tenacissima, a species of Chinese nettle producing a fibre which may be spun and woven, and which unites many of the properties of silk and of linen, has been completely naturalized in the United States, and results important to the industry of the country are expected from it.] The weight of this harvest of a year would be many times the tonnage of all the shipping of the United States at the close of the year 1870--and, with the exception of the maple sugar, the maple molasses, and the products of the Western prairie lands and of some small Indian clearings, it was all grown upon lands wrested from the forest by the European race within little more than two hundred years. The wants of Europe have introduced into the colonies of tropical America the sugar cane, [Footnote: The sugar cane was introduced by the Arabs into Sicily and Spain as early as the ninth century, and though it is now scarcely grown in those localities, I am not aware of any reason to doubt that its cultivation might be revived with advantage. From Spain it was carried to the West Indies, though different varieties have since been introduced into those Islands from other sources.] the coffee plant, the orange and the lemon, all of Oriental origin, have immensely stimulated the cultivation of the former two in the countries of which they are natives, and, of course, promoted agricultural operations which must have affected the geography of those regions to an extent proportionate to the scale on which they have been pursued. USEFUL AMERICAN PLANTS GROWN IN EUROPE. America has partially repaid her debt to the Eastern continent. Maize and the potato are very valuable additions to the field agriculture of Europe and the East, and the tomato is no mean gift to the kitchen gardens of the Old World, though certainly not an adequate return for the multitude of esculent roots and leguminous plants which the European colonists carried with them. [Footnote: John Smith mentions, In his Historie of Virginia, 1624, pease and beans as having been cultivated by the natives before the arrival of the whites, and there is no doubt, I believe, that several common cucurbitaceous plants are of American origin; but most, if not all the varieties of pease, beans, and other pod fruits now grown in American gardens, are from European and other foreign seed. Cartier, A.D. 1535-'6, mentions "vines, great melons, cucumbers, gourds [courges], pease, beans of various colors, but not like ours," as common among the Indians of the banks of the St. Lawrence--Bref Recit, etc., reprint. Paris, 1863, pp. 13, a; 14, b; 20, b; 31, a.] I wish I could believe, with some, that America is not alone responsible for the introduction of the filthy weed, tobacco, the use of which is the most vulgar and pernicious habit engrafted by the semi-barbarism of modern civilization upon the less multifarious sensualism of ancient life; but the alleged occurrence of pipe-like objects in old Sclavonic, and, it has been said, in Hungarian sepulchres, is hardly sufficient evidence to convict those races of complicity in this grave offence against the temperance and the refinement of modern society. EXTIRPATION OF VEGETABLES. Lamentable as are the evils produced by the too general felling of the woods in the Old World, I believe it does not appear that any species of native forest tree has yet been extirpated by man on the Eastern continent. The roots, stumps, trunks, and foliage found in bogs are recognized as belonging to still extant species. Except in some few cases where there is historical evidence that foreign material was employed, the timber of the oldest European buildings, and even of the lacustrine habitations of Switzerland, is evidently the product of trees still common in or near the countries where such architectural remains are found; nor have the Egyptian catacombs themselves revealed to us the former existence of any woods not now familiar to us as the growth of still living trees. [Footnote: Some botanists think that a species of water lily represented in many Egyptian tombs has become extinct, and the papyrus, which must have once been abundant in Egypt, is now found only in a very few localities near the mouth of the Nile. It grows very well and ripens its seeds in the waters of the Anapus near Syracuse, and I have seen it in garden ponds at Messina and in Malta. There is no apparent reason for believing that it could not be easily cultivated in Egypt, to any extent, if there were any special motive for encouraging its growth. Silphium, a famous medicinal plant of Lybia and of Persia, seems to have disappeared entirely. At any rate there is no proof that it now exists in either of those regions. The Silphium of Greek and Roman commerce appears to have come wholly from Cyrene, that from the Asiatic deserts being generally of less value, or, as Strabo says, perhaps of an inferior variety. The province near Cyrene which produced it was very limited, and according to Strabo (ed. Casaubon, p. 837), it was at one time almost entirely extirpated by the nomade Africans who invaded the province and rooted out the plant. The vegetable which produced the Balm of Gilead has not been found in modern times, although the localities in which it anciently grew have been carefully explored.] It is, however, said that the yew tree, Taxus baccata, formerly very common in England, Germany, and--as we are authorized to infer from Theophrastus--in Greece, has almost wholly disappeared from the latter country, and seems to be dying out in Germany. The wood of the yew surpasses that of almost any other European tree in closeness and fineness of grain, and it is well known for the elasticity which of old made it so great a favorite with the English archer. It is much in request among wood carvers and turners, and the demand for it explains, in part, its increasing scarcity. It is also asserted that no insect depends upon it for food or shelter, or aids in its fructification, and birds very rarely feed upon its berries: these are circumstances of no small importance, because the tree hence wants means of propagation or diffusion common to so many other plants. But it is alleged that the reproductive power of the yew is exhausted, and that it can no longer be readily propagated by the natural sowing of its seeds, or by artificial methods. If further investigation and careful experiment should establish this fact, it will go far to show that a climatic change, of a character unfavorable to the growth of the yew, has really taken place in Germany, though not yet proved by instrumental observation, and the most probable cause of such change would be found in the diminution of the area covered by the forests. The industry of man is said to have been so successful in the local extirpation of noxious or useless vegetables in China, that, with the exception of a few water plants in the rice grounds, it is sometimes impossible to find a single weed in an extensive district; and the late eminent agriculturist, Mr. Coke, is reported to have offered in vain a considerable reward for the detection of a weed in a large wheatfield on his estate in England. In these cases, however, there is no reason to suppose that diligent husbandry has done more than to eradicate the pests of agriculture within a comparatively limited area, and the cockle and the darnel will probably remain to plague the slovenly cultivator as long as the cereal grains continue to bless him. [Footnote: Although it is not known that man has absolutely extirpated any vegetable, the mysterious diseases which have, for the last twenty years, so injuriously affected the potato, the vine, the orange, the olive, and silk husbandry, are ascribed by some to a climatic deterioration produced by excessive destruction of the woods. As will be seen in the next chapter, a retardation in the period of spring has been observed in numerous localities in Southern Europe, as well as in the United States, and this change has been thought to favor the multiplication of the obscure parasites which causee the injury to the vegetables mentioned. Babinet supposes the parasites which attack the grape and the potato to be animal, not vegetable, and he ascribes their multiplication to excessive manuring and stimulation of the growth of the plants on which they live. They are now generally, it not universally, regarded as vegetable, and if they are so, Babinet's theory would be even more plausible than on his own supposition.--Etudes et lectures, ii, p. 269. It is a fact of some interest in agricultural economy, that the oidium, which is so destructive to the grape, has produced no pecuniary loss to the proprietors of the vineyards in France. "The price of wine," says Lavergne, "has quintupled, and as the product of the vintage has not diminished in the same proportion, the crisis has been, on the whole, rather advantageous than detrimental to the country."--Economie rurale de la France, pp. 263, 264. France produces a large surplus of wines for exportation, and the sales to foreign consumers are the principal source of profit to French vinegrowers. In Northern Italy, on the contrary, which exports little wine, there has been no such increase in the price of wine as to compensate the great diminution in the yield of the vines, and the loss of this harvest is severely felt. In Sicily, however, which exports much wine, prices have risen as rapidly as in France. Waltershausen informs us that in the years 1838-'42, the red wine of Mount Etna sold at the rate of one kreuzer and a half, or one cent the bottle, and sometimes even at but two thirds that price, but that at present it commands five or six times as much. The grape disease has operated severely on small cultivators whose vineyards only furnished a supply for domestic use, but Sicily has received a compensation in the immense increase which it has occasioned in both the product and the profits of the sulphur mines. Flour of sulphur is applied to the vine as a remedy against the disease, and the operation is repeated from two to three or four--and sometimes even eight or ten--times in a season. Hence there is a great demand for sulphur in all the vine-growing countries of Europe, and Waltershausen estimates the annual consumption of that mineral for this single purpose at 850,000 centner, or more than forty thousand tons. The price of sulphur has risen in about the same proportion as that of the wine.--Waltershausen, Ueber den Sicilianischen Ackerbau, pp. 19, 20.] All the operations of rural husbandry are destructive to spontaneous vegetation by the voluntary substitution of domestic for wild plants, and, as we have seen, the armies of the colonist are attended by troops of irregular and unrecognized camp-followers, which soon establish and propagate themselves over the new conquests. These unbidden and hungry guests--the gipsies of the vegetable world--often have great aptitude for accommodation and acclimation, and sometimes even crowd out the native growth to make room for themselves. The botanist Latham informs us that indigenous flowering plants, once abundant on the North-Western prairies, have been so nearly extirpated by the inroads of half-wild vegetables which have come in the train of the Eastern immigrant, that there is reason to fear that, in a few years, his herbarium will constitute the only evidence of their former existence. [Footnote: Report of Commissioner of Agriculture of the United States for 1870.] There are plants--themselves perhaps sometimes stragglers from their proper habitat--which are found only in small numbers and in few localities. These are eagerly sought by the botanist, and some such species are believed to be on the very verge of extinction, from the zeal of collectors. ANIMAL LIFE AS A GEOLOGICAL AND GEOGRAPHICAL AGENCY. The quantitative value of animated life, as a geological agency, seems to be inversely as the volume of the individual organism; for nature supplies by numbers what is wanting in the bulk of the animal out of whose remains or structures she forms strata covering whole provinces, and builds up from the depths of the sea large islands, if not continents. There are, it is true, near the mouths of the great Siberian rivers which empty themselves into the Polar Sea, drift islands composed, in an incredibly large proportion, of the bones and tusks of elephants, mastodons, and other huge pachyderms, and many extensive caves in various parts of the world are half filled with the skeletons of quadrupeds, sometimes lying loose in the earth, sometimes cemented together into an osseous breccia by a calcareous deposit or other binding material. These remains of large animals, though found in comparatively late formations, generally belong to extinct species, and their modern congeners or representatives do not exist in sufficient numbers to be of sensible importance in geology or in geography by the mere mass of their skeletons. [Footnote: Could the bones and other relics of the domestic quadrupeds destroyed by disease or slaughtered for human use in civilized countries be collected into large deposits, as obscure causes have gathered together those of extinct animals, they would soon form aggregations which might almost be called mountains. There were in the United States, in 1870, as we shall see hereafter, nearly one hundred millions of horses, black cattle, sheep, and swine. There are great numbers of all the same animals in the British American Provinces and in Mexico, and there are large herds of wild horses on the plains, and of tamed among the independent Indian tribes of North America. It would perhaps not be extravagant to suppose that all these cattle may amount to two thirds as many as those of the United States, and thus we have in North America a total of 160,000,000 domestic quadrupeds belonging to species introduced by European colonization, besides dogs, cats, and other four-footed household pets and pests, also of foreign origin. If we allow half a solid foot to the skeleton and other slowly destructible parts of each animal, the remains of these herds would form a cubical mass measuring not much short of four hundred and fifty feet to the side, or a pyramid equal in dimensions to that of Cheops, and as the average life of these animals does not exceed six or seven years, the accumulations of their bones, horns, hoofs, and other durable remains would amount to at least fifteen times as great a volume in a single century. It is true that the actual mass of solid matter, left by the decay of dead domestic quadrupeds and permanently added to the crust of the earth, is not so great as this calculation makes it. The greatest proportion of the soft parts of domestic animals, and even of the bones, is soon decomposed, through direct consumption by man and other carnivora, industrial use, and employment as manure, and enters into new combinations in which its animal origin is scarcely traceable; there is, nevertheless, a large annual residuum, which, like decayed vegetable matter, becomes a part of the superficial mould; and in any event, brute life immensely changes the form and character of the superficial strata, if it does not sensibly augment the quantity of the matter composing them. The remains of man, too, add to the earthy coating that covers the face of the globe. The human bodies deposited in the catacombs during the long, long ages of Egyptian history, would perhaps build as large a pile as one generation of the quadrupeds of the United States. In the barbarous days of old Moslem warfare, the conquerors erected large pyramids of human skulls. The soil of cemeteries in the great cities of Europe has sometimes been raised several feet by the deposit of the dead during a few generations. In the East, Turks and Christians alike bury bodies but a cople of feet beneath the sculptures of the ignoble poor, and of those whose monuments time or accident has removed, are opened again and again to receive fresh occupants. Hence the ground in Oriental cemeteries is pervaded with relics of humanity, of not wholly composed of them; and an examination of the soil of the lower part of the Petit Champ des Morts, at Pera, by the naked eye alone, shows the observer that it consists almost exclusively of the comminuted bones of his fellow-man.] But the vegetable products found with them, and, in rare cases, in the stomachs of some of them, are those of yet extant plants; and besides this evidence, the discovery of works of human art, deposited in juxtaposition with fossil bones, and evidently at the same time and by the same agency which buried these latter--not to speak of human bones found in the same strata--proves that the animals whose former existence they testify were contemporaneous with man, and possibly even extirpated by him. [Footnote: The bones of mammoths and mastodons, in many instances, appear to have been grazed or cut by flint arrow-heads or other stone weapons, and the bones of animals now extinct are often wrought into arms and utensils, or split to extract the marrow. These accounts have often been discredited, because it has been assumed that the extinction of these animals was more ancient than the existence of man. Recent discoveries render it certain that this conclusion has been too hastily adopted. On page 143 of the Antiquity of Man, Lyell remarks that man "no doubt played his part in hastening the era of the extincion" of the large pachyderms and beasts of prey; but, as contemporaneous species of other animals, which man cannot be supposed to have extirpated, have also become extinct, he argues that the disappearance of the quadrupeds in question cannot be ascribed to human action alone. On this point it may be observed that, as we cannot know what precise physical conditions were necessary to the existence of a given extinct organism, we cannot say how far such conditions may have been modified by the action of man, and he may therefore have influenced the life of such organisms in ways, and to an extent, of which we can form no just idea.] I do not propose to enter upon the thorny question, whether the existing races of man are genealogically connected with these ancient types of humanity, and I advert to these facts only for the sake of the suggestion, that man, in his earliest known stages of existence, was probably a destructive power upon the earth, though perhaps not so emphatically as his present representatives. The larger wild animals are not now numerous enough in any one region to form extensive deposits by their remains; but they have, nevertheless, a certain geographical importance. If the myriads of large browsing and grazing quadrupeds which wander over the plains of Southern Africa--and the slaughter of which by thousands is the source of a ferocious pleasure and a brutal triumph to professedly civilized hunters--if the herds of the American bison, which are numbered by hundreds of thousands, do not produce visible changes in the forms of terrestrial surface, they have at least an immense influence on the growth and distribution of vegetable life, and, of course, indirectly upon all the physical conditions of soil and climate between which and vegetation a mutual interdependence exists. In the preceding chapter I referred to the agency of the beaver in the formation of bogs as producing sensible geographical effects. I am disposed to think that more bogs in the Northern States owe their origin to beavers than to accidental obstructions of rivulets by wind-fallen or naturally decayed trees; for there are few swamps in those States, at the outlets of which we may not, by careful search, find the remains of a beaver dam. The beaver sometimes inhabits natural lakelets and even large rivers like the Upper Mississippi, when the current is not too rapid, but he prefers to owe his pond to his own ingenuity and toil. The reservoir once constructed, its inhabitants rapidly multiply so long as the trees, and the harvests of pond lilies and other aquatic plants on which this quadruped feeds in winter, suffice for the supply of the growing population. But the extension of the water causes the death of the neighboring trees, and the annual growth of those which could be reached by canals and floated to the pond soon becomes insufficient for the wants of the community, and the beaver metropolis now sends out expeditions of discovery and colonization. The pond gradually fills up, by the operation of the same causes as when it owes its existence to an accidental obstruction, and when, at last, the original settlement is converted into a bog by the usual processes of vegetable life, the remaining inhabitants abandon it and build on some virgin brooklet a new city of the waters. [Footnote: I find confirmation of my own observations on this point (published in 1863) in the North-West Passage by Land of Milton and Cheadle, London, 1865. These travellers observed "a long chain of marshes formed by the damming up of a stream which had now ceased to exist," Chap. X. In Chap. XII, they state that "nearly every stream between the Pembina and the Athabasca--except the large river McLeod--appeared to have been destroyed by the agency of the beaver," and they question whether the vast extent of swampy ground in that region "has not been brought to this condition by the work of beavers who have thus destroyed, by their own labor, the streams necessary to their own existence." But even here nature provides a remedy, for when the process of "consolidation" referred to in treating of bogs in the first chapter shall have been completed, and the forest re-established upon the marshes, the water now diffused through them will be collected in the lower or more yielding portions, cut new channels for their flow, become running brooks, and thus restore the ancient aspect of the surface. The authors add the curious observation that the beavers of the present day seem to be a degenerate race, as they neither fell huge trees not construct great dams, while their progenitors cut down trees two feet in diameter and dammed up rivers a hundred feet in width. The change in the habits of the beaver is probably due to the diminution of their numbers since the introduction of fire-arms, and to the tact that their hydraulic operations are more frequently interrupted by the encroachments of man. In the valley of the Yellowstone, which has but lately been much visited by the white man, Hayden saw stumps of trees thirty inches in diameter which had been cut down by beavers. --Geological Survey of Wyoming, p. 135. The American beaver closely resembles his European congener, and I believe most naturalists now regard them as identical. A difference of speceies has been inferred from a difference in their modes of life, the European animal being solitary and not a builder, the American gregarious and constructive. But late careful researches in Germany have shown the former existence of numerous beaver dams in that country, though the animal, having becaome rare to form colonies, has of course ceased to attempt works which require the co-operation of numerous individuals.--Schleiden, Fur Baum und Wald Leipzig, 1870, p. 68. On the question of identity and on all others relating to this interesting animal, see L.H. Morgan's important monograph, The American Beaver and his Works, Philadelphia, 1868. Among the many new facts observed by this investigator is the construction of canals by the beaver to float trunks and branches of trees to his ponds. These canals are sometimes 600 to 700 feet long, with a width of two or three feet and a depth of one to one and a half.] INFLUENCE OF ANIMAL LIFE ON VEGETATION The influence of wild quadrupeds upon vegetable life have been little studied, and not many facts bearing upon it have been recorded, but, so far as it is known, it appears to be conservative rather than pernicious. Few wild animals depend for their subsistence on vegetable products obtainable only by the destruction of the plant, and they seem to confine their consumption almost exclusively to the annual harvest of leaf or twig, or at least of parts of the vegetable easily reproduced. If there are exceptions to this rule, they are in cases where the numbers of the animal are so proportioned to the abundance of the vegetable that there is no danger of the extermination of the plant from the voracity of the quadruped, or of the extinction of the quadruped from the scarcity of the plant. [Footnote: European foresters speak of the action of the squirrel as injurious to trees. Doubtless this is sometimes true in the case of artificial forests, but in woods of spontaneous growth, ordered and governed by nature, the squirrel does not attack trees, or at least the injury he may do is too trifling to be perceptible, but he is a formidable enemy to the plantation. "The squirrels bite the cones of the pine and consume the seed which might serve to restock the wood; they do still more mischief by gnawing off, near the leading shoot, a strip of bark, and thus often completely girdling the tree. Trees so injured must be felled, as they would never acquire a vigorous growth. The squirrel is especially destructive to the pine in Sologne, where he gnaws the bark of trees twenty or twenty-five years old." But even here, nature sometimes provides a compensation, by making the appetite of this quadruped serve to prevent an excessive production of seed cones, which tends to obstruct the due growth of the leading shoot. "In some of the pineries of Brittany which produce cones so abundantly as to strangle the development of the leading shoot of the maritime pine, it has been observed that the pines are most vigorous where the squirrels are most numerous, a result attributed to the repression of the cones by this rodent."--Boitel, Mise en valeur des Terres pauvres, p. 50. Very interesting observations, on the agency of the squirrel and other small animals in planting and in destroying nuts and other seeds of trees, may be found in a paper on the Succession of Forests in Thoreau's Excursions, pp. 135 et seqq. I once saw several quarts of beech-nuts taken from the winter quarters of a family of flying squirrels in a hollow tree. The kernels were neatly stripped of the shells and carefully stored in a dry cavity.] In diet and natural wants the bison resembles the ox, the ibex and the chamois assimilate themselves to the goat and the sheep; but while the wild animal does not appear to be a destructive agency in the garden of nature, his domestic congeners are eminently so. [Footnote: Evelyn thought the depasturing of grass by cattle serviceable to its growth. "The biting of cattle," he remarks, "gives a gentle loosening to the roots of the herbage, and makes it to grow fine and sweet, and their very breath and treading as well as soil, and the comfort of their warm bodies, is wholesome and marvellously cherishing."--Terra, or Philosophical Discourses of Earth, p. 86. In a note upon this passage, Hunter observes: "Nice farmers consider the lying of a beast upon the ground, for one night only, as a sufficient tilth for the year. The breath of graminivorous quadrupeds does certainly enrich the roots of grass; a circumstance worthy of the attention of the philosophical farmer."--Terra, same page. The "philosophical farmer" of the present day will not adopt these opinions without some qualification, and they certainly are not sustained by American observation. The Report of the Department of Agriculture for March and April, 1872, states that the native grasses are disappearing from the prairies of Texas, especially on the bottom-lands, depasturing of cattle being destructive to them.] This is partly from the change of habits resulting from domestication and association with man, partly from the fact that the number of reclaimed animals is not determined by the natural relation of demand and spontaneous supply which regulates the multiplication of wild creatures, but by the convenience of man, who is, in comparatively few things, amenable to the control of the merely physical arrangements of nature. When the domesticated animal escapes from human jurisdiction, as in the case of the ox, the horse, the goat, and perhaps the ass--which, so far as I know, are the only well-authenticated instances of the complete emancipation of household quadrupeds--he becomes again an unresisting subject of nature, and all his economy is governed by the same laws as that of his fellows which have never been enslaved by man; but, so long as he obeys a human lord, he is an auxiliary in the warfare his master is ever waging against all existences except those which he can tame to a willing servitude. ORIGIN AND TRANSFER OF DOMESTIC QUADRUPEDS. Civilization is so intimately associated with certain inferior forms of animal life, if not dependent on them, that cultivated man has never failed to accompany himself, in all his migrations, with some of these humble attendants. The ox, the horse, the sheep, and even the comparatively useless dog and cat, as well as several species of poultry, are voluntarily transferred by every emigrant colony, and they soon multiply to numbers far exceeding those of the wild genera most nearly corresponding to them. [Footnote: The rat and the mouse, though not voluntarily transported, are passengers by every ship that sails for a foreign port, and several species of these quadrupeds have, consequently, much extended their range and increased their numbers in modern times. From a story of Heliogabalus related by Lampridius, Hist. Aug. Scriptores, ed. Casaubon, 1690, p. 110, it would seem that mice at least were not very common in ancient Rome. Among the capricious freaks of that emperor, it is said that he undertook to investigate the statistics of the arachnoid population of the capital, and that 10,000 pounds of spiders (or spiders' webs--for aranea is equivocal) were readily collected; but when he got up a mouse-show, he thought ten thousand mice a very fair number. Rats are not less numerous in all great cities; and in Paris, where their skins are used for gloves, and their flesh, it is whispered, in some very complex and equivocal dishes, they are caught by legions. I have read of a manufacturer who contracted to buy of the rat-catchers, at a high price, all the rat-skins they could furnish before a certain date, and failed, within a week, for want of capital, when the stock of peltry had run up to 600,000. Civilization has not contented itself with the introduction of domestic animals alone. The English sportsman imports foxes from the continent, and Grimalkin-like turns them loose in order that he may have the pleasure of chasing them afterwards.] Of the origin of our domestic animals, we know historically nothing, because their domestication belongs to the ages which preceded written annals; but though they cannot all be specifically identified with now extant wild animals, it is presumable that they have been reclaimed from an originally wild state. Ancient writers have preserved to us fewer data respecting the introduction of domestic animals into new countries than respecting the transplantation of domestic vegetables. Ritter, in his learned essay on the camel, has shown that this animal was not employed by the Egyptians until a comparatively late period in their history; [Footnote: The horse and the ass were equally unknown to ancient Egypt, and do not appear in the sculptures before the XV. and XVI. dynasties. But even then, the horse was only known as a draught animal, and the only representation of a horseman yet found in the Egyptian tombs is on the blade of a battle axe of uncertain origin and period.] that he was unknown to the Carthaginians until after the downfall of their commonwealth; and that his first appearance in Western Africa is more recent still. The Bactrian camel was certainly brought from Asia Minor to the Northern shores of the Black Sea, by the Goths, in the third or fourth century, and the buffalo first appeared in Italy about A.D. 600, though it is unknown whence or by whom he was introduced. [Footnote: Erdkunde, viii., Asien, 1ste Abtheuung, pp. 660,758. Hehn, Kuttonpflanzen, p. 845.] The Arabian single-humped camel, or dromedary, has been carried to the Canary Islands, partially introduced into Australia, Greece, Spain, and even Tuscany, experimented upon to little purpose in Venezuela, and finally imported by the American Government into Texas and New Mexico, where it finds the climate and the vegetable products best suited to its wants, and promises to become a very useful agent in the promotion of the special civilization for which those regions are adapted. Quadrupeds, both domestic and wild, bear the privations and discomforts of long voyages better than would be supposed. The elephant, the giraffe, the rhinoceros, and even the hippopotamus, do not seem to suffer much at sea. Some of the camels imported by the U.S. government into Texas from the Crimea and Northern Africa were a whole year on shipboard. On the other hand, George Sand, in Un Hiver au Midi, gives an amusing description of the sea-sickness of swine in the short passage from the Baleares to Barcelona. America had no domestic quadruped but a species of dog, the lama tribe, and, to a certain extent, the bison or buffalo. [Footnote: See Chapter III., post; also Humboldt, Ansichten der Natur, i., p. 71. From the anatomical character of the bones of the urus, or auerochs, found among the relics of the lacustrine population of ancient Switzerland, and from other circumstances, it is inferred that this animal had been domesticated by that people; and it is stated, I know not upon what authority, in Le Alpi che cingono l'Italia, that it had been tamed by the Veneti also. See Lyell, Antiquity of Man, pp. 24, 25, and the last-named work, p. 480. This is a fact of much interest, because it is one of the very few HISTORICALLY known instances of the extinction of a domestic quadruped, and the extreme improbability of such an event gives some countenance to the theory of the identity of the domestic ox with, and its descent from, the urus.]Of course, it owes the horse, the ass, the ox, the sheep, the goat, and the swine, as does also Australia, to European colonization. Modern Europe has, thus far, not accomplished much in the way of importation of new animals, though some interesting essays have been made. The reindeer was successfully introduced into Iceland about a century ago, while similar attempts failed, about the same time, in Scotland. The Cashmere or Thibet goat was brought to France a generation since, and succeeds well. The same or an allied species and the Asiatic buffalo were carried to South Carolina about the year 1850, and the former, at least, is thought likely to prove of permanent value in the United States. [Footnote: The goat introduced into South Carolina was brought from the district of Angora, in Asia Minor, which has long been celebrated for flocks of this valuable animal. It is calculated that more than a million of these goats are raised in that district, and it is commonly believed that the Angora goat and its wool degenerate when transported. Probably this is only an invention of the shepherds to prevent rivals from attempting to interfere with so profitable a monopoly. But if the popular prejudice has any foundation, the degeneracy is doubtless to be attributed to ignorance of the special treatment which long experience has taught the Angora shepherds, and the consequent neglect of such precautions as are necessary to the proper care of the animal. Throughout nearly the whole territory of the United States the success of the Angora goat is perfect, and it would undoubtedly thrive equally well in Italy, though it is very doubtful whether in either country the value of its fleece would compensate the damage it would do to the woods.] The yak, or Tartary ox, seems to thrive in France, and it is hoped that success will attend the present efforts to introduce the South American alpaca into Europe. [Footnote: The reproductive powers of animals, as well as of plants, seem to be sometimes stimulated in an extraordinary way by transfer to a foreign clime. The common warren rabbit introduced by the early colonists into the island of Madeira multiplied to such a degree as to threaten the extirpation of vegetation, and in Australia the same quadruped has become so numerous as to be a very serious evil. The colonists are obliged to employ professional rabbit-hunters, and one planter has enclosed his grounds by four miles of solid wall, at an expense of $6,000, to protect his crops against those ravagers.--Revue des Eaux et Forets, 1870, p. 38.] According to the census of the United States for 1870, [Footnote: In the enumeration of farm stock, "sucking pigs, spring lambs, and calves," are omitted. I believe they are included in the numbers reported by the census of 1860. Horses and horned cattle in towns and cities were excluded from both enumerations, the law providing for returns on these points from rural districts only. On the whole, there is a diminution in the number of all farm stock, except sheep, since 1860. This is ascribed by the Report to the destruction of domestic quadrupeds during the civil war, but this hardly explains the reduction in the number of swine from 39,000,000 in 1800 to 25,000,000 in 1870.] the total number of horses in all the States of the American Union, was, in round numbers, 7,100,000; of asses and mules, 1,100,000; of the ox tribe, 25,000,000; of sheep, 28,000,000; and of swine, 25,000,000. The only indigenous North American quadruped sufficiently gregarious in habits, and sufficiently multiplied in numbers, to form really large herds, is the bison, or, as he is commonly called in America, the buffalo; and this animal is confined to the prairie region of the Mississippi basin, a small part of British America, and Northern Mexico. The engineers sent out to survey railroad routes to the Pacific estimated the number of a single herd of bisons seen within the last fifteen years on the great plains near the Upper Missouri, at not less than 200,000, and yet the range occupied by this animal is now very much smaller in area than it was when the whites first established themselves on the prairies. [Footnote: "About five miles from camp we ascended to the top of a high hill, and for a great distance ahead every square mile seemed to have a herd of buffalo upon it. Their number was variously estimated by the members of the party; by some as high as half a million. I do not think it any exaggeration to set it down at 200,000." Steven's Narrative and Final Report. Reports of Explorations and Surveys for Railroad to Pacific, vol xii, book i., 1860. The next day the party fell in with a "buffalo trail," where at least 100,000 were thought to have crossed a slough. As late as 1868, Sheridan's party estimated the number of bisons seen by them in a single day at 200,000.--Sheridan's Troopers on the Border, 1868, p. 41.] But it must be remarked that the American buffalo is a migratory animal, and that, at the season of his annual journeys, the whole stock of a vast extent of pasture-ground is collected into a single army, which is seen at or very near any one point only for a few days during the entire season. Hence there is risk of great error in estimating the numbers of the bison in a given district from the magnitude of the herds seen at or about the same time at a single place of observation; and, upon the whole, it is neither proved nor probable that the bison was ever, at any one time, as numerous in North America as the domestic bovine species is at present. The elk, the moose, the musk ox, the caribou, and the smaller quadrupeds popularly embraced under the general name of deer, though sufficient for the wants of a sparse savage population, were never numerically very abundant, and the carnivora which fed upon them were still less so. It is almost needless to add that the Rocky Mountain sheep and goat must always have been very rare. Summing up the whole, then, it is evident that the wild quadrupeds of North America, even when most numerous, were few compared with their domestic successors, that they required a much less supply of vegetable food, and consequently were far less important as geographical elements than the many millions of hoofed and horned cattle now fed by civilized man on the same continent. EXTIRPATION OF WILD QUADRUPEDS. Although man never fails greatly to diminish, and is perhaps destined ultimately to exterminate, such of the larger wild quadrupeds as he cannot profitably domesticate, yet their numbers often fluctuate, and oven after they seem almost extinct, they sometimes suddenly increase, without any intentional steps to promote such a result on his part. During the wars which followed the French Revolution, the wolf multiplied in many parts of Europe, partly because the hunters were withdrawn from the woods to chase a nobler game, and partly because the bodies of slain men and horses supplied this voracious quadraped with more abundant food. [Footnote: During the late civil war in America, deer and other animals of the chase multiplied rapidly in the regions of the Southern States which were partly depopulated and deprived of their sportsmen by the military operations of the contest, and the bear is said to have reappeared in districts where he had not been seen in the memory of living man.] The same animal became again more numerous in Poland after the general disarming of the rural population by the Russian Government. On the other hand, when the hunters pursue the wolf, the graminivorous wild quadrupeds increase, and thus in turn promote the multiplication of their great four-footed destroyer by augmenting the supply of his nourishment. So long as the fur of the beaver was extensively employed as a material for hats, it bore a very high price, and the chase of this quadruped was so keen that naturalists feared its speedy extinction. When a Parisian manufacturer invented the silk hat, which soon came into almost universal use, the demand for beavers' fur fell off, and the animal--whose habits are an important agency in the formation of bogs and other modifications of forest nature--immediately began to increase, reappeared in haunts which he had long abandoned, and can no longer be regarded as rare enough to be in immediate danger of extirpation. Thus the convenience or the caprice of Parisian fashion has unconsciously exercised an influence which may sensibly affect the physical geography of a distant continent. Since the invention of gunpowder, gome quadrupeds have completely disappeared from many European and Asiatic countries where they were formerly numerous. The last wolf was killed in Great Britain two hundred years ago, and the bear was extirpated from that island still earlier. The lion is believed to have inhabited Asia Minor and Syria, and probably Greece and Sicily also, long after the commencement of the historical period, and he is even said to have been not yet extinct in the first-named two of these countries at the time of the first Crusade. [Footnote: In maintaining the recent existence of the lion in the countries named in the text, naturalists have, perhaps, laid. too much weight on the frequent occurrence of representations of this animal in sculptures apparently of a historical character. It will not do to argue, twenty centuries hence, that the lion and the unicorn were common in Great Britain in Queen Victoria's time because they are often seen "fighting for the crown" in the carvings and paintings of that period. Many paleontolgists, however, identify the great cat-like animal, whose skeletons are frequently found in British bone-caves, with the lion of our times. The leopard (panthera), though already growing scarce, was found in Cilicia in Cicero's time. See his letter to Coelius, Epist. ad Diversos, Lib. II., Ep. 11. The British wild ox is extinct except in a few English and Scottish parks, while in Irish bogs of no great apparent antiquity are found antlers which testify to the former existence of a stag much larger than any extant European species. Two large graminivorous or browsing quadrupeds, the ur and the schelk, once common in Germany, have been utterly extirpated, the eland and the auerochs nearly so. The Nibelungen-Lied, which, in the oldest form preserved to us, dates from about the year 1200, though its original composition no doubt belongs to an earlier period, thus sings: Then slowe the dowghtie Sigfrid a wisent and an elk, he smote four stoute uroxen and a grim and sturdie schelk. [Footnote: Dar nach sluoger schiere, einen wisent unde elch. Starker ure viere, unt einen grimmen schelch. XVI. Aventiure. The testimony of the Nibelungen-Lied is not conclusive evidence that these quadrupeds existed in Germany at the time of the composition of that poem. It proves too much; for, a few lines above those just quoted, Sigfrid is said to have killed a lion, an animal which the most patriotic Teuton will hardly claim as a denizen of mediaeval Germany.] Modern naturalists identify the elk with the eland, the wisent with the auerochs. The period when the ur and the schelk became extinct is not known. The auerochs survived in Prussia until the middle of the last century, but unless it is identical with a similar quadruped said to be found on the Caucasus, it now exists only in the Russian imperial forest of Bialowitz where about a thousand are still preserved, and in some great menageries, as for example that at Schonbrunn, near Vienna, which, in 1852, had four specimens. The eland, which is closely allied to the American wapiti if not specifically the same animal, is still kept in the royal preserves of Prussia, to the number of four or five hundred individuals. The chamois is becoming rare, and the ibex or steinbock, once common in all the high Alps, is now believed to be confined to the Cogne mountains in Piedmont, between the valleys of the Dora Baltea and the Orco, though it is said that a few still linger about the Grandes Jorasses near Cormayeur. The chase, which in early stages of human life was a necessity, has become with advancing civilization not merely a passion but a dilettanteism, and the cruel records of this pastime are among the most discreditable pages in modern literature. It is true that in India and other tropical countries, the number and ferocity of the wild beasts not only justify but command a war of extermination against them, but the indiscriminate slaughter of many quadrupeds which are favorite objects of the chase can urge no such apology. Late official reports from India state the number of human victims of the tiger, the leopard, the wolf and other beasts of prey, in ten "districts," at more then twelve thousand within three years, and we are informed on like authority that within the last six years more than ten thousand men, women, and children have perished in the same way in the Presidency of Bengal alone. One tiger, we are told, had killed more than a hundred people, and finally stopped the travel on an important road, and another had caused the desertion of thirteen villages and thrown 250 square miles out of cultivation. In such facts we find abundant justification of the slaying of seven thousand tigers, nearly six thousand leopards, and twenty-five hundred other ravenous beasts in the Bengal Presidency, in the space of half a dozen years. But the humane reader will not think the value of the flesh, the skin, and other less important products of inoffensive quadrupeds a satisfactory excuse for the ravages committed upon them by amateur sportsmen as well as by professional hunters. In 1861, it was computed that the supply of the English market with ivory cost the lives of 8,000 elephants. Others make the number much larger and it is said that half as much ivory is consumed in the United States as in Great Britain. In Ceylon, where the elephants are numerous and destructive to the crops, as well as dangerous to travellers, while their tusks are small and of comparatively little value, the government pays a small reward for killing them. According to Sir Emerson Tennant, [Footnote: Natural History of Ceylon, chap. iv.] in three years prior to 1848, the premium was paid for 3,500 elephants in a part of the northern district, and between 1851 and 1856 for 2,000 in the southern district. Major Rogers, famous as an elephant shooter in Ceylon, ceased to count his victims after he had slain 1,300, and Cumming in South Africa sacrificed his hecatombs every month. In spite of the rarity of the chamois, his cautious shyness, and the comparative inaccessibility of his favorite haunts, Colani of Pontresina, who died in 1837, had killed not less than 2,000 of these animals; Kung, who is still living in the Upper Engadine, 1,500; Hitz, 1,300, and Zwichi an equal number; Soldani shot 1,100 or 1,200 in the mountains which enclose the Val Bregaglia, and there are many living hunters who can boast of having killed from 500 to 800 of these interesting quadrupeds. [Footnote: Although it is only in the severest cold of winter that the chamois descends to the vicinity of grounds occupied by man, its organization does not confine it to the mountains. In the royal park of Racconigi, on the plain a few miles from Turin, at a height of less than 1,000 feet, is kept a herd of thirty or forty chamois, which thrive and breed apparently as well as in the Alps.] In America, the chase of the larger quadrupeds is not less destructive. In a late number of the American Naturalist, the present annual slaughter of the bison is calculated at the enormous number of 500,000, and the elk, the moose, the caribou, and the more familiar species of deer furnish, perhaps, as many victims. The most fortunate deer-hunter I have personally known in New England had killed but 960; but in the northern part of the State of New York, a single sportsman is said to have shot 1,500, and this number has been doubtless exceeded by zealous Nimrods of the West. But so far as numbers are concerned, the statistics of the furtrade furnish the most surprising results. Russia sends annually to foreign markets not less than 20,000,000 squirrel skins, Great Britain has sometimes imported from South America 600,000 nutria skins in a year. The Leipzig market receives annually nearly 200,000 ermine, and the Hudson Bay Company is said to have occasionally burnt 20,000 ermine skins in order that the market might not be overstocked. Of course natural reproduction cannot keep pace with this enormous destruction, and many animals of much interest to natural science are in imminent danger of final extirpation. [Footnote: Objectionable as game laws are, they have done something to prevent the extinction of many quadrupeds, which naturalists would be loth to lose, and, as in the case of the British ox, private parks and preserves have saved other species from destruction. Some few wild aminals, such as the American mink, for example, have been protected and bred with profit, and in Pennsylvania an association of gentlemen has set apart, and is about enclosing, a park of 16,000 acres for the breeding of indigenous quadrupeds and fowls.] LARGE MARINE ANIMALS RELATIVELY UNIMPORTANT IN GEOGRAPHY. Vast as is the bulk of some of the higher orders of aquatic animals, their remains are generally so perishable that, even where most abundant, they do not appear to be now forming permanent deposits of any considerable magnitude; but it is quite otherwise with shell-fish, and, as we shall see hereafter, with many of the minute limeworkers of the sea. There are, on the southern coast of the United States, beds of shells so extensive that they were formerly supposed to have been naturally accumulated, and were appealed to as proofs of an elevation of the coast by geological causes; but they are now ascertained to have been derived chiefly from oysters and other shell-fish, consumed in the course of long ages by the inhabitants of Indian towns. The planting of a bed of oysters in a new locality might very probably lead, in time, to the formation of a bank, which, in connection with other deposits, might perceptibly affect the line of a coast, or, by changing the course of marine currents, or the outlet of a river, produce geographical changes of no small importance. INTRODUCTION AND BREEDING OF FISH. The introduction and successful breeding of fish or foreign species appears to have been long practised in China, and was not unknown to the Greeks and Romans. [Footnote: The observations of COLUMELLA, de Re Rustica, lib. viii., sixteenth and following chapters, on fish-breeding, are interesting. The Romans not only stocked natural but constructed artificial ponds, of both fresh and salt water, and cut off bays of the sea for this purpose. They also naturalized various species of sea-fish in fresh water.] This art has been revived in modern times, but thus far without any important results, economical or physical, though there seems to be good reason to believe it may be employed with advantage on an extended scale. As in the case of plants, man has sometimes undesignedly introduced now species of aquatic animals into countries distant from their birthplace. The accidental escape of the Chinese goldfish from ponds where they were bred as a garden ornament, has peopled some European, and it is said American streams with this species. Canals of navigation and irrigation interchange the fish of lakes and rivers widely separated by natural barriers, as well as the plants which drop their seeds into the waters. The Erie Canal, as measured by its own channel, has a length of about three hundred and sixty miles, and it has ascending and descending locks in both directions. By this route, the fresh-water fish of the Hudson and the Upper Lakes, and some of the indigenous vegetables of these respective basins, have intermixed, and the fauna and flora of the two regions have now more species common to both than before the canal was opened. [Footnote: The opening or rather the reconstruction of the Claudian emissary by Prince Torlonia, designed to drain the Lake Fucinus, or Celano, has introduced the fish of that lake into the Liri or Garigliano which received the discharge from the lake.--Dorotea, Sommario storico dell' Alieutica, p. 60.]The opening of the Suez Canal will, no doubt, produce very interesting revolutions in the animal and vegetable population of both basins. The Mediterranean, with some local exceptions--such as the bays of Calabria, and the coast of Sicily so picturesquely described by Quatrefages [Footnote: Souvenire d'un Naturaliste, i., pp. 204 et seqq.]-is comparatively poor in marine vegetation, and in shell as well as in fin fish. The scarcity of fish in some of its gulfs is proverbial, and you may scrutinize long stretches of beach on its northern shores, after every south wind for a whole winter, without finding a dozen shells to reward your search. But no one who has not looked down into tropical or subtropical seas can conceive the amazing wealth of the Red Sea in organic life. Its bottom is carpeted or paved with marine plants, with zoophytes and with shells, while its waters are teeming with infinitely varied forms of moving life. Most of its vegetables and its animals, no doubt, are confined by the laws of their organization to a warmer temperature than that of the Mediterranean, but among them there must be many whose habitat is of a wider range, many whose powers of accommodation would enable them to acclimate themselves in a colder sea. We may suppose the less numerous aquatic fauna and flora of the Mediterranean to be equally capable of climatic adaptation, and hence there will be a partial interchange of the organic population not already common to both seas. Destructive species, thus newly introduced, may diminish the numbers of their proper prey in either basin, and, on the other hand, the increased supply of appropriate food may greatly multiply the abundance of others, and at the same time add important contributions to the aliment of man in the countries bordering on the Mediterranean. [Footnote: The dissolution of the salts in the bed of the Bitter Lake impregnated the water admitted from the Red Sea so highly that for some time fish were not seen in that basin. The flow of the current through the canal has now reduced the proportion of saline matter to five per cent, and late travellers speak of fish as abundant in its waters.] Some accidental attraction not unfrequently induces fish to follow a vessel for days in succession, and they may thus be enticed into zones very distant from their native habitat. Several years ago, I was told at Constantinople, upon good authority, that a couple of fish, of a species wholly unknown to the natives had just been taken in the Bosphorus. They were alleged to have followed an English ship from the Thames, and to have been frequently observed by the crew during the passage; but I was unable to learn their specific character. [Footnote: Seven or eight years ago, the Italian government imported from France a dredging machine for use in the harbor of La Spezia. The dredge brought attached to its hull a shell-fish not known in Italian waters. The mollusk, finding the local circumstances favorable, established itself in this new habitat, multiplied rapidly, and is now found almost everywhere on the west coast of the Peninsula.] Many of the fish which pass the greater part of the year in salt water spawn in fresh, and some fresh-water species, the common brook-trout of New England for instance, which under ordinary circumstances never visit the sea, will, if transferred to brooks emptying directly into the ocean, go down into the salt water after spawning-time, and return again the next season. Some sea fish have been naturalized in fresh water, and naturalists have argued from the character of the fish of Lake Baikal, and especially from the existence of the seal in that locality, that all its inhabitants were originally marine species, and have changed their habits with the gradual conversion of the saline waters of the lake-once, as is assumed, a maritime bay-into fresh. [Footnote: Babinet, Etudes et Lectures, ii, pp. 108,110.] The presence of the seal is hardly conclusive on this point, for it is sometimes seen in Lake Champlain at the distance of some hundreds of miles from even brackish water. One of these animals was killed on the ice in that lake in February, 1810, another in February, 1846, [Footnote: Thompson, Natural History of Vermont, p. 38, and Appendix, p. 18. There is no reason to believe that the seal breeds in Lake Champlain, but the individual last taken there must have been some weeks, at least, in its waters. It was killed on the ice in the widest part of the lake, on the 23d of February, thirteen days after the surface was entirely frozen, except the usual small cracks, and a month or two after the ice closed at all points north of the place where the seal was found.] and remains of the seal have been found at other times in the same waters. The intentional naturalization of foreign fish, as I have said, has not thus far yielded important fruits; but though this particular branch of what is called, not very happily, pisciculture, has not yet established its claims to the attention of the physical geographer or the political economist, the artificial breeding of domestic fish, of the lobster and other crustacea, has already produced very valuable results, and is apparently destined to occupy an extremely conspicuous place in the history of man's efforts to compensate his prodigal waste of the gifts of nature. The arrangements for breeding fish in the Venetian lagoon of Comacchio date far back in the Middle Ages, but the example does not seem to have been followed elsewhere in Europe at that period, except in small ponds where the propagation of the fish was left to nature without much artificial aid. The transplantation of oysters to artificial ponds has long been common, and it appears to have recently succeeded well on a large scale in the open sea on the French coast. A great extension of this fishery is hoped for, and it is now proposed to introduce upon the same coast the American soft clam, which is so abundant in the tide-washed beach sands of Long Island Sound as to form an important article in the diet of the neighboring population. Experimental pisciculture has been highly successful in the United States, and will probably soon become a regular branch of rural industry, especially as Congress, at the session of 1871-2, made liberal provision for its promotion. The restoration of the primitive abundance of salt and fresh water fish, is perhaps the greatest material benefit that, with our present physical resources, governments can hope to confer upon their subjects. The rivers, lakes, and seacoasts once restocked, and protected by law from exhaustion by taking fish at improper seasons, by destructive methods, and in extravagant quantities, would continue indefinitely to furnish a very large supply of most healthful food, which, unlike all domestic and agricultural products, would spontaneously renew itself and cost nothing but the taking. There are many sterile or wornout soils in Europe so situated that they might, at no very formidable cost, be converted into permanent lakes, which would serve not only as reservoirs to retain the water of winter rains and snow, and give it out in the dry season for irrigation, but as breeding ponds for fish, and would thus, without further cost, yield a larger supply of human food than can at present be obtained from them even at a great expenditure of capital and labor in agricultural operations. [Footnote: See Ackerhof, Die Nutzung der Seiche und Gewasser. Quedlinburg, 1860.] The additions which might be made to the nutriment of the civilized world by a judicious administration of the resources of the waters, would allow some restriction of the amount of soil at present employed for agricultural purposes, and a corresponding extension of the area of the forest, and would thus facilitate a return to primitive geographical arrangements which it is important partially to restore. Destruction of Fish. The inhabitants of the waters seem comparatively secure from human pursuit or interference by the inaccessibility of their retreats, and by our ignorance of their habits--a natural result of the difficulty of observing the ways of creatures living in a medium in which we cannot exist. Human agency has, nevertheless, both directly and incidentally, produced great changes in the population of the sea, the lakes, and the rivers, and if the effects of such revolutions in aquatic life are apparently of small importance in general geography, they are still not wholly inappreciable. The great diminution in the abundance of the larger fish employed for food or pursued for products useful in the arts is familiar, and when we consider how the vegetable and animal life on which they feed must be effected by the reduction of their numbers, it is easy to see that their destruction may involve considerable modifications in many of the material arrangements of nature. The whale [Footnote: I use WHALE not in a technical sense, but as a generic term for all the large inhabitants of the sea popularly grouped under that name. The Greek kaetos and Latin Balaena, though sometimes, especially in later classical writers, specifically applied to true cetaceans, were generally much more comprehensive in their signification than the modern word whale. This appears abundantly from the enumeration of the marine animals embraced by Oppian under the name <Greek: kaetos>, in the first book of the Halieutica. There is some confusion in Oppian's account of the fishery of the <Greek: kaetos> in the fifth book of the Halieutica. Part of it is probably to be understood of cetaceans which have GROUNDED, as some species often do; but in general it evidently applies to the taking of large fish--sharks, for example, as appear by the description of the teeth--with hook and bait.] does not appear to have been an object of pursuit by the ancients, for any purpose, nor do we know when the whale fishery first commenced. It was, however, very actively prosecuted in the Middle Ages, and the Biscayans seem to have been particularly successful in this as indeed in other branches of nautical industry. [Footnote: From the narrative of Ohther, introduced by King Alfred into his translation of Orosius, it is clear that the Northmen pursued the whale fishery in the ninth century, and it appears, both from the poem called The Whale, in the Codex Exoniensis, and from the dialogue with the fisherman in the Colloquies of Aelfric, that the Anglo-Saxons followed this dangerous chore at a period not much later. I am not aware of any evidence to show that any of the Latin nationals engaged in this fishery until a century or two afterward, though it may not be easy to disprove their earlier participation in it. In mediaeval literature, Latin and Romance, very frequent mention is made of a species of vessel called in Latin baleneria, balenerium, balenerius, balaneria, etc.; in Catalan, balener; in French, balenier; all of which words occur the many other forms. The most obvious etymology of these words would suggest the meaning, whaler, baleinier; but some have supposed that the name was descriptive of the great size of the ships, and others have referred it to a different root. From the fourteenth century, the word occurs oftener, perhaps, in old Catalan, than in any other language; but Capmany does not notice the whale fishery as one of the maritime pursuits of the very enterprising Catalan people, nor do I find any of the products of the whale mentioned in the old Catalan tariffs. The WHALEBONE of the mediaeval writers, which is described as very white, is doubtless the ivory of the walrus or of the narwhale.] Five hundred years ago, whales abounded in every sea. They long since became so rare in the Mediterranean as not to afford encouragement for the fishery as a regular occupation; and the great demand for oil and whalebone for mechanical and manufacturing purposes, in the present century, has stimulated the pursuit of the "hugest of living creatures" to such activity, that he has now almost wholly disappeared from many favorite fishing grounds, and in others is greatly diminished in numbers. What special functions, besides his uses to man, are assigned to the whale in the economy of nature, wo do not know; but some considerations, suggested by the character of the food upon which certain species subsist, deserve to be specially noticed. None of the great mammals grouped under the general name of whale are rapacious. They all live upon small organisms, and the most numerous species feed almost wholly upon thesoft gelatinous mollusks in which the sea abounds in all latitudes. We cannot calculate even approximately the number of the whales, or the quantity of organic nutriment consumed by an individual, and of course we can form no estimate of the total amount of animal matter withdrawn by them, in a given period, from the waters of the sea. It is certain, however, that it must have been enormous when they were more abundant, and that it is still very considerable. In 1846 the United States had six hundred and seventy-eight whaling ships chiefly employed in the Pacific, and the product of the American whale fishery for the year ending June 1st, 1860, was seven millions and a half of dollars. [Footnote: In consequence of the great scarcity of the whale, the use of coal-gas for illumination, the substitution of other fatty and oleaginous substances, such as lard, palm-oil, and petroleum for right-whale oil and spermaceti, the whale fishery has rapidly fallen off within a few years. The great supply of petroleum, which is much used for lubricating machinery as well as for numerous other purposes, has produced a more perceptible effect on the whale fishery than any other single circumstance. According to Bigelow, Les Etats-Unis en 1863, p. 346, the American whaling fleet was diminished by 29 in 1858, 57 in 1860, 94 in 1861, and 65 in 1862. The number of American ships employed in that fishery in 1862 was 353. In 1868, the American whaling fleet was reduced to 223. The product of the whale fishery in that year was 1,485,000 gallons of sperm oil, 2,065,612 gallons of train oil, and 901,000 pounds of whalebone. The yield of the two species of whale is about the same, being estimated at from 4,000 to 5,000 gallons for each fish. Taking the average at 4,500 gallons, the American whalers must have captured 789 whales, besides, doubtless, many which were killed or mortally wounded and not secured. The returns for the year are valued at about five million and a half dollars. Mr. Cutts, from a report by whom most of the above facts are taken, estimates the annual value of the "products of the sea" at $90,000,000. According to the New Bedford Standard, the American whalers numbered 722, measuring 230,218 tons, in 1846. On the 31st December, 1872, the number was reduced to 204, with a tonnage of 47,787 tons, and the importation of whale and sperm oil amounted in that year to 79,000 barrels. Svend Foyn, an energetic Norwegian, now carries on the whale fishery in the Arctic Ocean in a steamer of 20 horse-power, accompanied by freight-ships for the oil. The whales are killed by explosive shells fired from a small cannon. The number usually killed by Foyn is from 35 to 45 per year.--The Commerce in the Products of the Sea, a report by Col. R. D. Cutts, communicated to the U. S. Senate. Washington, 1872.] The mere bulk of the whales destroyed in a single year by the American and the European vessels engaged in this fishery would form an island of no inconsiderable dimensions, and each one of those taken must have consumed, in the course of his growth, many times his own weight of mollusks. The destruction of the whales must have been followed by a proportional increase of the organisms they feed upon, and if we had the means of comparing the statistics of these humble forms of life, for even so short a period as that between the years 1760 and 1860, we should find a difference possibly sufficient to suggest an explanation of some phenomena at present unaccounted for. For instance, as I have observed in another work, [Footnote: The Origin and History of the English Language, &c., pp. 423, 424.] the phosphorescence of the sea was unknown to ancient writers, or at least scarcely noticed by them, and even Homer--who, blind as tradition makes him when he composed his epics, had seen, and marked, in earlier life, all that the glorious nature of the Mediterranean and its coasts discloses to unscientific observation--nowhere alludes to this most beautiful and striking of maritime wonders. In the passage just referred to, I have endeavored to explain the silence of ancient writers with respect to this as well as other remarkable phenomena on psychological grounds; but is it not possible that, in modern times, the animalculae which produce it may have immensely multiplied, from the destruction of their natural enemies by man, and hence that the gleam shot forth by their decomposition, or by their living processes, is both more frequent and more brilliant than in the days of classic antiquity? Although the whale does not prey upon smaller creatures resembling himself in form and habits, yet true fishes are extremely voracious, and almost every tribe devours unsparingly the feebler species, and even the spawn and young of its own. [Footnote: Two young pickerel, Gystes fasciatus, five inches long, ate 128 minnows, an inch long, the first day they were fed, 132 the second, and 150 the third.--Fifth Report of Commissioners of Massachusetts for Introduction of Fish. 1871. p. 17.] The enormous destruction of the shark [Footnote: The shark is pursued in all the tropical and subtropical seas for its fins--for which there is a great demand in China as an article of diet--its oil and other products. About 40,000 are taken annually in the Indian Ocean and the contiguous seas. In the North Sea and the Arctic Ocean large numbers are annually caught. See MERK. Waarenlexikon--a work of great accuracy and value (Leipzig, 1870), article Haifisch.] the pike, the trout family, and other ravenous fish, as well as of the fishing birds, the seal, and the otter, by man, would naturally have occasioned a great increase in the weaker and more defenceless fish on which they feed, had he not been as hostile to them also as to their persecutors. Destruction of Aquatic Animals. It does not seem probable that man, with all his rapacity and all his enginery, will succeed in totally extirpating any salt-water fish, but he has already exterminated at least one marine warm-blooded animal--Steller's sea cow--and the walrus, the sea lion, and other large amphibia, as well as the principal fishing quadrupeds, are in imminent danger of extinction. Steller's sea cow, Rhytina Stelleri, was first seen by Europeans in the year 1741, on Bering's Island. It was a huge amphibious mammal, weighing not less than eight thousand pounds, and appears to have been confined exclusively to the islands and coasts in the neighborhood of Bering's Strait. Its flesh was very palatable, and the localities it frequented were easily accessible from the Russian establishments in Kamtschatka. As soon as its existence and character, and the abundance of fur animals in the same waters, were made known to the occupants of those posts by the return of the survivors of Bering's expedition, so active a chase was commenced against the amphibia of that region, that, in the course of twenty-seven years, the sea cow, described by Steller as extremely numerous in 1741, is believed to have been completely extirpated, not a single individual having been seen since the year 1768. The various tribes of seals [Footnote: The most valuable variety of fur seal, formerly abundant in all cold latitudes, is stated to have been completely exterminated in the Southern hemisphere, and to be now found only on one or two small islands of the Aleutian group. In 1867 more than 700,000 seal skins were imported into Great Britain, and at least 600,000 seals are estimated to have been taken in 1870. These numbers do not include the seals killed by the Esquimaux and other rude tribes.] in the Northern and Southern Pacific, the walrus [Footnote: In 1868, a few American ships engaged in the North Pacific whale fishery turned their attention to the walrus, and took from 200 to 600 each. In 1869 other whalers engaged in the same pursuit, and in 1870 the American fleet is believed to have destroyed not less than fifty thousand of these animals. They yield about twenty gallons of oil and four or five pounds of ivory each.] and the sea otter, are already so reduced in numbers that they seem destined soon to follow the sea cow, unless protected by legislation stringent enough, and a police energetic enough, to repress the ardent cupidity of their pursuers. The seals, the otter tribe, and many other amphibia which feed almost exclusively upon fish, are extremely voracious, and of course their destruction or numerical reduction must have favored the multiplication of the species of fish principally preyed upon by them. I have been assured by the keeper of several young seals that, if supplied at frequent intervals, each seal would devour not less than fourteen pounds of fish, or about a quarter of his own weight, in a day. A very intelligent and observing hunter, who has passed a great part of his life in the forest, after carefully watching the habits of the fresh-water otter of the North American States, estimates their consumption of fish at about four pounds per day. Man has promoted the multiplication of fish by making war on their brute enemies, but he has by no means thereby compensated his own greater destructiveness. [Footnote: According to Hartwig, the United Provinces of Holland had, in 1618, three thousand herring busses, and nine thousand vessels engaged in the transport of these fish to market. The whole number of persons employed in the Dutch herring fishery was computed at 200,000. In the latter part of the eighteenth century, this fishery was most successfully prosecuted by the Swedes, and in 1781, the town of Gottenburg alone exported 136,649 barrels, each containing 1,200 herrings, making a total of about 164,000,000; but so rapid was the exhaustion of the fish, from this keen pursuit, that in 1799 it was found necessary to prohibit the exportation of them altogether.--Das Leben des Meeres, p. 182. In 1855, the British fisheries produced 900,000 barrels, or almost enough to supply a fish to every human inhabitant of the globe. On the shores of Long Island Sound, the white fish, a species of herring too bony to be easily eaten, is used as manure in very great quantities. Ten thousand are employed as a dressing for an acre, and a single net has sometimes taken 200,000 in a day.--Dwight's Travels, ii. pp. 512, 515. The London Times of May 11, 1872, informs us that 1,100 tons of mackerel estimated to weigh one pound each had recently been taken in a single night at a fishing station on the British coast. About ten million eels are sold annually in Billingsgate market, but vastly greater numbers of the young fry, when but three or four inches long, are taken. So abundant are they at the mouths of many French and English rivers, that they are carried into the country by cart-loads, and not only eaten, but given to swine or used as manure.] The bird and beast of prey, whether on land or in the water, hunt only as long as they feel the stimulus of hunger, their ravages are limited by the demands of present appetite, and they do not wastefully destroy what they cannot consume. Man, on the contrary, angles to-day that he may dine to-morrow; he takes and dries millions of fish on the banks of Newfoundland and the coast of Norway, that the fervent Catholic of the shores of the Mediterranean may have wherewithal to satisfy the cravings of the stomach during next year's Lent, without violating the discipline of the papal church; [Footnote: The fisheries of Sicily alone are said to yield 20,000 tons of tunny a year. The tunny is principally consumed in Italy during Lent, and a large proportion of the twenty millions of codfish taken annually at the Lofoden fishery on the coast of Norway is exported to the Mediterranean.] and all the arrangements of his fisheries are so organized as to involve the destruction of many more fish than are secured for human use, and the loss of a large proportion of the annual harvest of the sea in the process of curing, or in transportation to the places of its consumption. [Footnote According to Berthelote, in the Gulf of Lyons, between Marseilles and the easternmost spur of the Pyrenees, about 5,000,000 small fish ate taken annually with the drag-net, and not lees than twice as many more, not to spekak of spawn, are destroyed by the use of this act. Between 1861 and 1865 France imported from Norway, for use as bait in the Sardine fishery, cod-roes to the value of three million francs.--Cutts, Report on Commerce in the Products of the Sea, 1872, p. 82. The most reckless waste of aquatic life I remember to have seen noticed, if we except the destruction of herring and other fish with upawn, is that of the eggs of the turtle in the Amazon for the sake of the oil extracted from then. Bates estimates the eggs thus annually sacrificed at 48,000,000.-Naturalits inthe Amazon, 2d edition, 1864, p. 805.] Fish are more affected than quadrupeds by slight and even imperceptible differences in their breeding places and feeding grounds. Every river, every brook, every lake stamps a special character upon its salmon, its shad, and its trout, which is at once recognized by those who deal in or consume them. No skill can give the fish fattened by food selected and prepared by man the flavor of those which are nourished at the table of nature, and the trout of the artificial pouds in Germany and Switzerland are so inferior to the brook-fish of the same species and climate, that it is hard to believe them identical. The superior sapidity of the American trout and other fresh-water fishes to the most nearly corresponding European species, which is familiar to every one acquainted with both continents, is probably due less to specific difference than to the fact that, even in the parts of the New World which have been longest cultivated, wild nature is not yet tamed down to the character it has assumed in the Old, and which it will acquire in America also when her civilization shall be as ancient as is now that of Europe. [Footnote: It is possible that time may modify the habits of the fresh-water fish the North American States, and accommodate them to the new physical conditions of their native waters. Hence it may be hoped that nature, even unaided by art, will do something towards restoring the ancient plenty of our lakes and rivers. The decrease of our fresh-water fish cannot be alone to exhaustion by fishing, for in the waters of the valleys and flanks of the Alps, which have been inhabited and fished ten times as long by a denser population, fish are still very abundant, and they thrive and multiply under circumstances where no American species could live at all. On the southern slope of those mountains, trout are caught in great numbers, in the swift streams which rush from the glaciers, and where the water is of icy coldness, and so turbid with particles of fine-ground rock, that you cannot see an inch below the surface. The glacier streams of Switzerland, however, are less abundant in fish.] Man has hitherto hardly anywhere produced such climatic or other changes as would suffice of themselves totally to banish the wild inhabitants of the dry land, and thedisappearance of the native birds and quadrupeds from particular localities is to be ascribed quite as much to his direct persecutions as to the want of forest shelter, of appropriate food, or of other conditions indispensable to their existence. But almost all the processes of agriculture, and of mechanical and chemical industry, are fatally destructive to aquatic animals within reach of their influence. When, in consequence of clearing the woods, the changes already described as thereby produced in the beds and currents of rivers, are in progress, the spawning grounds of fish, are exposed from year to year to a succession of mechanical disturbances; the temperature of the water is higher in summer, colder in winter, than when it was shaded and protected by wood; the smaller organisms, which formed the sustenance of the young fry, disappear or are reduced in numbers, and new enemies are added to the old foes that preyed upon them; the increased turbidness of the water in the annual inundations chokes the fish; and, finally, the quickened velocity of its current sweeps them down into the larger rivers or into the sea, before they are yet strong enough to support so great a change of circumstances. [Footnote: A fact mentioned by Schubert--and which in its causes and many of its results corresponds almost precisely with those connected with the escape of Barton Pond in Vermont, so well known to geological students--is important, as showing that the diminution of the fish in rivers exposed to inundations is chiefly to be ascribed to the mechanical action of the current, and not mainly, as some have supposed, to changes of temperature occasioned by clearing. Our author states that, in 1796, a terrible inundation was produced in the Indalself, which rises in the Storsjo in Jemtland, by drawing off into it the waters of another lake near Ragunda. The flood destroyed houses and fields; much earth was swept into the channel, and the water made turbid and muddy; the salmon and the smaller fish forsook the river altogether, and never returned. The banks of the river have never regained their former solidity, and portions of their soil are still continually falling into the water and destroying its purity.--Resa genom Sverge, ii, p. 61.] Industrial operations are not less destructive to fish which live or spawn in fresh water. Mill-dams impede their migrations, if they do not absolutely prevent them, the sawdust from lumber mills clogs their gills, and the thousand deleterious mineral substances, discharged into rivers from metallurgical, chemical, and manufacturing establishments, poison them by shoals. [Footnote: The mineral water discharged from a colliery on the river Doon in Scotland discolored the stones in the bed of the river, and killed the fish for twenty miles below. The fish of the streams in which hemp is macerated in Italy are often poisoned by the juices thus extracted from the plant.-Dorotea, Sommario della storia dell' Alieutica, pp. 64, 65.] We have little evidence that any fish employed as human food has naturally multiplied in modern times, while all the more valuable tribes have been immensely reduced in numbers. This reduction must have affected the more voracious species not used as food by man, and accordingly the shark, and other fish of similar habits, even when not objects of systematic pursuit, are now comparatively rare in many waters where they formerly abounded. The result is, that man has greatly reduced thenumbers of all larger marine animals, and consequently indirectly favored the multiplication of the smaller aquatic organisms which entered into their nutriment. This change in the relations of the organic and inorganic matter of the sea must have excercised an influence on the latter. What that influence has been we cannot say, still less can we predict what it will be hereafter; but its action is not for that reason the less certain. [Footnote: Among the unexpected results of human action, the destruction or multiplication of fish, as well as of other animals, is a not unfrequent occurrence. Footnote: Williams, in his History of Vermont, i., p. 140, records such a case of the increase of trout. In a pond formed by damming a small stream to obtain water power for a sawmill, and covering one thousand acres of primitive forest, the increased supply of food brought within reach of the fish multiplied them to that degree, that, at the head of the pond, where, in the spring, they crowded together in the brook which supplied it, they were taken by the hands at pleasure, and swine caught them without difficulty. A single sweep of a small scoopnet would bring up half a bushel, carts were filled with them as fast as if picked up on dry land, and in the fishing season they were commonly sold at a shilling (eightpence halfpenny, or about seventeen cents) a bushel. The increase in the size of the trout was as remarkable as the multiplication of their numbers. The construction of dams and mills is destructive to many fish, but operates as a protection to their prey. The mills on Connecticut River greatly diminished the number of the salmon, but the striped bass, on which the salmon feeds, multiplied in proportion.--Dr. Dwight, Travels, vol. ii., p. 323.] Geographical Importance of Birds. Wild birds form of themselves a very conspicuous and interesting feature in the staffage, as painters call it, of the natural landscape, and they are important elements in the view we are taking of geography, whether we consider their immediate or their incidental influence. Birds affect vegetation directly by sowing seeds and by consuming them; they affect it indirectly by destroying insects injurious, or, in some cases, beneficial to vegetable life. Hence, when we kill a seed-sowing bird, we check the dissemination of a plant; when we kill a bird which digests the seed it swallows, we promote the increase of a vegetable. Nature protects the seeds of wild, much more effectually than those of domesticated plants. The cereal grains are completely digested when consumed by birds, but the germ of the smaller stone fruits and of very many other wild vegetables is uninjured, perhaps even stimulated to more vigorous growth, by the natural chemistry of the bird's stomach. The power of flight and the restless habits of the bird enable it to transport heavy seeds to far greater distances than they could be carried by the wind. A swift-winged bird may drop cherry stones a thousand miles from the tree they grow on; a hawk, in tearing a pigeon, may scatter from its crop the still fresh rice it had swallowed at a distance of ten degrees of latitude, and thus the occurrence of isolated plants in situations where their presence cannot otherwise well be explained, is easily accounted for. [Footnote: Pigeons were shot near Albany, in New York, a few years ago, with green rice in their crops, which it was thought must have been growing, a very few hours before, at the distance of seven or eight hundred miles. The efforts of the Dutch to confine the cultivation of the nutmeg to the island of Banda are said to have been defeated by the birds, which transported this heavy fruit to other islands.] There is a large class of seeds apparently specially fitted by nature for dissemination by animals. I refer to those which attach themselves, by means of hooks, or by viscous juices, to the coats of quadrupeds and the feathers of birds, and are thus transported wherever their living vehicles may chance to wander. Some birds, too, deliberately bury seeds in the earth, or in holes excavated by them in the bark of trees, not indeed with a foresight aiming directly at the propagation of the plant, but from apparently purposeless secretiveness, or as a mode of preserving food for future use. The tame fowls play a much less conspicuous part in rural life than the quadrupeds, and, in their relations to the economy of nature, they are of very much less moment than four-footed animals, or than the undomesticated birds. The domestic turkey [Footnote: The wild turkey takes readily to the water, and is able to cross rivers of very considerable width by swimming. By way of giving me an idea of the former abundance of this bird, an old and highly respectable gentleman who was among the early white settlers of the West, told me that he once counted, in walking down the northern bank of the Ohio River, within a distance of four miles, eighty-four turkeys as they landed singly, or at most in pairs, after swimming over from the Kentucky side.] is probably more numerous in the territory of the United States than the wild bird of the same species ever was, and the grouse cannot, at the period of their greatest abundance, have counted as many as we now number of the common hen. The dove, however, must fall greatly short of the wild pigeon in multitude, and it is hardly probable that the flocks of domestic geese and ducks are as numerous as once wore those of their wild congeners. The pigeon, indeed, seems to have multiplied immensely, for some years after the first clearings in the woods, because the settlers warred unsparingly upon the hawk, while the crops of grain and other vegetable growths increased the supply of food within the reach of the young birds, at the age when their power of flight is not yet great enough to enable them to seek it over a wide area. [Footnote: The wood-pigeon, as well as the domestic dove, has been observed to increase in numbers in Europe also, when pains have been taken to exterminate the hawk. The American pigeons, which migrated in flocks so numerous that they were whole days in passing a given point, were no doubt injurious to the grain, but probably less so than is generally supposed; for they did not confine themselves exclusively to the harvests for their nourishment. ] The pigeon is not described by the earliest white inhabitants of the American States as filling the air with such clouds of winged life as astonished naturalists in the descriptions of Audubon, and, at the present day, the net and the gun have so reduced its abundance, that its appearance in large numbers is recorded only at long intervals, and it is never seen in the great flocks remembered by many still living observers as formerly very common. INTRODUCTION OF BIRDS. Man has undesignedly introduced into now districts perhaps fewer species of birds than of quadrupeds; [Footnote: The first mention I have found of the naturalization of a wild bird in modern Europe is in the Menagiana, vol. iii., p. 174, edition of 1715, where it is stated that Rene, King of Sicily and Duke of Anjou, who died in 1480, introduced the red-legged partridge into the latter country. Attempts have been made, and I believe with success, to naturalize the European lark on Long Island, and the English sparrow has been introduced into various parts of the Northern States, where he is useful by destroying noxious insects and worms not preyed upon by native birds. The humming-bird has resisted all efforts to acclimate him in Europe, though they have not unfrequently survived the passage across the ocean. In Switzerland and some other parts of Europe the multiplication of insectivorous birds is encouraged by building nests for them, and it is alleged that both fruit and forest trees have been essentially benefited by the protection thus afforded them.] but the distribution of birds is very much influenced by the character of his industry, and the transplantation, of every object of agricultural production is, at a longer or shorter interval, followed by that of the birds which feed upon its seeds, or more frequently upon the insects it harbors. The vulture, the crow, and other winged scavengers, follow the march of armies as regularly as the wolf. Birds accompany ships on long voyages, for the sake of the offal which is thrown overboard, and, in such cases, it might often happen that they would breed and become naturalized in countries where they had been unknown before. [Footnote: Gulls hover about ships in port, and often far out at sea, diligently watching for the waste of the caboose. While the four great fleets, English, French, Turkish, and Egyptian, were lying in the Bosphorus, in the summer and autumn of 1853, a young lady of my family called my attention to the fact that the gulls were far more numerous about the ships of one of the fleets than about the others. This was verified by repeated observation, and the difference was owing no doubt to the greater abundance of the refuse from the cookrooms of the naval squadron most frequented by the birds. Persons acquainted with the economy of the navies of the states in question, will be able to conjecture which fleet was most favored with these delicate attentions. The American gull follows the steamers up the Mississippi, and has been shot 1,500 miles from the sea.] There is a familiar story of an English bird which built its nest in an unused block in the rigging of a ship, and made one or two short voyages with the vessel while hatching its eggs. Had the young become fledged while lying in a foreign harbor, they would of course have claimed the rights of citizenship in the country where they first took to the wing. [Footnote: Birds do not often voluntarily take passage on board ships bound for foreign countries, but I can testify to one such case. A stork, which had nested near one of the palaces on the Bosphorus, had, by some accident, injured a wing, and was unable to join his fellows when they commenced their winter migration to the banks of the Nile. Before he was able to fly again, he was caught, and the flag of the nation to which the palace belonged was tied to his leg, so that he was easily identified at a considerable distance. As his wing grew stronger, he made several unsatisfactory experiments at flight, and at last, by a vigorous effort, succeeded in reaching a passing ship bound southward, and perched himself on a topsail-yard. I happened to witness this movement, and observed him quietly maintaining his position as long as I could discern him with a spy-glass. I supposed he finished the voyage, for he certainly did not return to the palace.] An unfortunate popular error greatly magnifies the injury done to the crops of grain and leguminous vegetables by wild birds. Very many of those generally supposed to consume large quantities of the seeds of cultivated plants really feed almost exclusively upon insects, and frequent the wheatfields, not for the sake of the grain, but for the eggs, larvae, and fly of the multiplied tribes of insect life which are so destructive to the harvests. This fact has been so well established by the examination of the stomachs of great numbers of birds in Europe and the United States, at different seasons of the year, that it is no longer open to doubt, and it appears highly probable that even the species which consume more or less grain generally make amends by destroying insects whose ravages would have been still more injurious. [Footnote: Even the common crow has found apologists, and it has been asserted that he pays for the Indian corn he consumes by destroying the worms and larva which infest that plant. Professor Treadwell, of Massachusetts, found that a half-grown American robin in confinement ate in one day sixty-eight worms, weighing together nearly once and a half as much as the bird himself, and another had previously starved upon a daily allowance of eight or ten worms, or about twenty per cent. of his own weight. The largest of these numbers appeared, so far as could be judged by watching parent birds of the same species, as they brought food to their young, to be much greater than that supplied to them when fed in the nest; for the old birds did not return with worms or insects oftener than once in ten minutes on an average. It we suppose the parents to hunt for food twelve hours in a day, and a nest to contain four young, we should have seventy-two worms, or eighteen each, as the daily supply of the brood. It is probable enough that some of the food collected by the parents may be more nutritious than the earthworms, and consequently that a smaller quantity sufficed for the young in the nest than when reared under artificial conditions. The supply required by growing birds is not the measure of their wants after they have arrived at maturity, and it is not by any means certain that great muscular exertion always increases the demand for nourishment, either in the lower animals or in man. The members of the English Alpine Club are not distinguished for appetites which would make them unwelcome guests to Swiss landlords, and I think every man who has had the personal charge of field or railway hands, must have observed that laborers who spare their strength the least are not the most valiant trencher champions. During the period when imprisonment for debt was permitted in New England, persons confined in country jails had no specific allowance, and they were commonly fed without stint. I have often inquired concerning their diet, and been assured by the jailers that their prisoners, who were not provided with work or other means of exercise, consumed a considerably larger supply of food than common out-door laborers.] On this subject, we have much other evidence besides that derived from dissection. Direct observation has shown, in many instances, that the destruction of wild birds has been followed by a great multiplication of noxious insects, and, on the other hand, that these latter have been much reduced in numbers by the protection and increase of the birds that devour them. Many interesting facts of this nature have been collected by professed naturalists, but I shall content myself with a few taken from familiar and generally accessible sources. The following extract is from Michelet, L'Oiseau, pp. 169,170: "The STINGY farmer--an epithet justly and feelingly bestowed by Virgil. Avaricious, blind, indeed, who proscribes the birds--those destroyers of insects, those defenders of his harvests. Not a grain for the creature which, during the rains of winter, hunts the future insect, finds out the nests of the larvae, examines, turns over every leaf, and destroys, every day, thousands of incipient caterpillars. But sacks of corn for the mature insect, whole fields for the grasshoppers, which the bird would have made war upon. With eyes fixed upon his furrow, upon the present moment only, without seeing and without foreseeing, blind to the great harmony which is never broken with impunity, he has everywhere demanded or approved laws for the extermination of that necessary ally of his toil--the insectivorous bird. And the insect has well avenged the bird. It has become necessary to revoke in haste the proscription. In the Isle of Bourbon, for instance, a price was set on the head of the martin; it disappeared, and the grasshopper took possession of the island, devouring, withering, scorching with a biting drought all that they did not consume. In North America it has been the same with the starling, the protector of Indian corn. [Footnote: I hope Michelet has good authority for this statement, but I am unable to confirm it.] Even the sparrow, which really does attack grain, but which protects it still more, the pilferer, the outlaw, loaded with abuse and smitten with curses--it has been found in Hungary that they were likely to perish without him, that he alone could sustain the mighty war against the beetles and the thousand winged enemies that swarm in the lowlands; they have revoked the decree of banishment, recalled in haste this valiant militia, which, though deficient in discipline, is nevertheless the salvation of the country. [Footnote: Apropos of the sparrow--a single pair of which, according to Michelet, p. 315, carries to the nest four thousand and three hundred caterpillar or coleoptera in a week--I find in an English newspaper a report of a meeting of a "Sparrow Club," stating that the member who took the first prize had destroyed 1,467 of these birds within the year, and that the prowess of the other members had brought the total number up to 11,944 birds, besides 2,553 eggs. Every one of the fourteen thousand hatched and unhatched birds, thus sacrificed to puerile vanity and ignorant prejudice, would have saved his bushel of wheat by preying upon insects that destroy the grain.] "Not long since, in the neighborhood of Ronen and in the valley of Monville, the blackbird was for some time proscribed. The beetles profited well by this proscription; their larvae, infinitely multiplied, carried on their subterranean labors with such success, that a meadow was shown me, the surface of which was completely dried up, every herbaceous root was consumed, and the whole grassy mantle, easily loosened, might have been rolled up and carried away like a carpet." The general hostility of the European populace to the smaller birds is, in part, the remote effect of the reaction created by the game laws. When the restrictions imposed upon the chase by those laws were suddenly removed in France, the whole people at once commenced a destructive campaign against every species of wild animal. Arthur Young, writing in Provence, on the 30th of August, 1789, soon after the National Assembly had declared the chase free, thus complains of the annoyance he experienced from the use made by the peasantry of their newly-won liberty. "One would think that every rusty firelock in all Provence was at work in the indiscriminate destruction of all the birds. The wadding buzzed by my ears, or fell into my carriage, five or six times in the course of the day." ... "The declaration of the Assembly that every man is free to hunt on his own land ... has filled all France with an intolerable cloud of sportsmen. ... The declaration speaks of compensations and indemnities [to the seigneurs], but the ungovernable populace takes advantage of the abolition of the game laws and laughs at the obligation imposed by the decree." The contagious influence of the French Revolution occasioned the removal of similar restrictions, with similar results, in other countries. The habits then formed have become hereditary on the Continent, and though game laws still exist in England, there is little doubt that the blind prejudices of the ignorant and half-educated classes in that country against birds are, in some degree, at least, due to a legislation, which, by restricting the chase of game worth killing, drives the unprivileged sportsman to indemnify himself by slaughtering all wild life which is not reserved for the amusement of his betters. Hence the lord of the manor buys his partridges and his hares by sacrificing the bread of his tenants, and so long as the members of "Sparrow Clubs" are forbidden to follow higher game, they will suicidally revenge themselves by destroying the birds which protect their wheatfields. On the Continent, and especially in Italy, the comparative scarcity and dearness of animal food combine with the feeling I have just mentioned to stimulate still further the destructive passions of the fowler. In the Tuscan province of Grosseto, containing less than 2,000 square miles, nearly 300,000 thrushes and other small birds are annually brought to market. [Footnote: Salvagnoli, Memorie sulle Maremme Toscane, p. 143. The country about Naples is filled with slender towers fifteen or twenty feet high, which are a standing puzzle to strangers. They are the stations of the fowlers who watch from them the flocks of small birds and drive them down into the nets by throwing stones over them. In Northern and Central Italy, one often sees hillocks crowned with grove-like plantations of small trees, much resembling large arbors. These serve to collect birds, which are entrapped in nets in great numbers. These plantatious are called ragnaje, and the reader will find, in Bindi's edition of Davanzati, a very pleasant description of a ragnaja, though its authorship is not now ascribed to that eminent writer. Tschudi has collected in his little work, Ueber die Landwirthschaftliche Bedeutung der Vogel, many interesting facts respecting the utility of birds, and, the wanton destruction of them in Italy and elsewhere. Not only the owl, but many other birds more familiarly known as predacious in their habits, are useful by destroying great numbers of mice and moles. The importance of this last service becomes strikingly apparent when it is known that the burrows of the moles are among the most frequent causes of rupture in the dikes of the Po, and, consequently, of inundations which lay many square miles of land under water. See Annales des Ponts et Chaussees, 1847, 1 semestre, p. 150; VOGT, Nutzliche und schadliche Thiere; and particularly articles in the Giornale del Club Alpino, vol. iv., no. 15, and vol. v., no. 16. See also in Aus der Natur, vol. 54, p. 707, an article entitled Nutzen der Vogel fur die Landwirthschaft, where it is affirmed that "without birds no agriculture or even vegetation would be possible." In an interesting memoir by Rondani, published in the Bolletino del Comizio agrario di Parma for December, 1868, it is maintained that birds are often injurious to the agriculturist, by preying not only on noxious insects, but sometimes exclusively, or at least by preference, on entomophagous tribes which would otherwise destroy those injurious to cultivated plants. See also articles by Prof. Sabbioni in the Giornale di Agricoltura di Bologna, November and December, 1870, and other articles in the same journal of 15th and 30th April, 1870.] Birds are less hardy in constitution, they possess less facility of accommodation, [Footnote: Wild birds are very tenacious in their habits. The extension of particular branches of agriculture introduces new birds; but unless in the case of such changes in physical conditions, particular species seem indissolubly attached to particular localities. The migrating tribes follow almost undeviatingly the same precise line of flight in their annual journeys, and establish themselves in the same breeding-places from year to year. The stork is a strong-winged bird and roves far for food, but very rarely establishes new colonies. He is common in Holland, but unknown in England. Not above five or six pairs of storks commonly breed in the suburbs of Constantinople along the European shore of the narrow Bosphorous, while--much to the satisfaction of the Moslems, who are justly proud of the marked partiality of so orthodox a bird--dozens of chimneys of the true believers on the Asiatic side are crowned with his nests. The appearance of the dove-like grouse, Tetrao paradoxus, or Syrrhaptus Pallassi, in various parts of Europe, in 1850 and the following years, is a noticable exception to the law of regularity which seems to govern the movements and determine the habitat of birds. The proper home of this bird is the Steppes of Tartary, and it is no recorded to have been observed in Europe, or at least west of Russia, until the year above mentioned, when many flocks of twenty or thirty, and even a hundred individuals, were seen in Bohemia, Germany, Holland, Denmark, England, Ireland, and France. A considerable flock frequented the Frisian island of Borkum for more than five months. It was hoped that they would breed and remain permanently in the island but this expectation has now been disappointed, and the steppe-grouse seems to have disappeared again altogether.] and they are more severely affected by climatic excess than quadrupeds. Besides, they generally want the special means of shelter against the inclemency of the weather and against pursuit by their enemies, which holes and dens afford to burrowing animals and to some larger beasts of prey. The egg is exposed to many dangers before hatching, and the young bird is especially tender, defenceless, and helpless. Every cold rain, every violent wind, every hailstorm during the breeding season, destroys hundreds of nestlings, and the parent often perishes with her progeny while brooding over it in the vain effort to protect it. [Footnote: It is not the unfledged and the nursing bird alone that are exposed to destruction by severe weather. Whole flocks of adult and strong-winged tribes are killed by hail. Severe winters are usually followed by a sensible diminution in the numbers of the non-migrating birds, and a cold storm in summer often proves fatal to the more delicate species. On the 10th of June, 184-, five or six inches of snow fell in Northern Vermont. The next morning I found a hummingbird killed by the cold, and hanging by its claws just below a loose clapboard on the wall of a small wooden building where it had sought shelter.] The great proportional numbers of birds, their migratory habits, and the ease with which, by their power of flight they may escape most dangers that beset them, would seem to secure them from extirpation, and even from very great numerical reduction. But experience shows that when not protected by law, by popular favor or superstition, or by other special circumstances, they yield very readily to the hostile influences of civilization, and, though the first operations of the settler are favorable to the increase of many species, the great extension of rural and of mechanical industry is, in a variety of ways, destructive even to tribes not directly warred upon by man. [Footnote: Lyell, Antiquity of Man, p. 400, observes: "Of birds it is estimated that the number of those which die every year equals the aggregate number by which the species to which they respectively belong is, on the average, permanently represented." A remarkable instance of the influence of new circumstances upon birds was observed upon the establishment of a light-house on Cape Cod some years since. The morning after the lamps were lighted for the first time, more than a hundred dead birds of several different species, chiefly water-fowl, were found at the foot of the tower. They had been killed in the course of the night by flying against the thick glass or grating of the lantern. From an article by A. Esquiros, in the Revue des Deux Mondes for Sept. 1, 1864, entitled, La vie Anglaise, p. 110, it appears that such occurrences as that stated in the note have been not unfrequent on the British coast. Are the birds thus attracted by new lights, flocks in migration? Migrating birds, whether for greater security from eagles, hawks, and other enemies, or for some unknown reason, perform a great part of their annual journeys by night; and it is observed in the Alps that they follow the high roads in their passage across the mountains. This is partly because the food in search of which they must sometimes descend is principally found near the roads. It is, however, not altogether for the sake of consorting with man, or of profiting by his labors, that their line of flight conforms to the paths he has traced, but rather because the great roads are carried through the natural depressions in the chain, and hence the birds can cross the summit by these routes without rising to a height where at the seasons of migration the cold would be excessive. The instinct which guides migratory birds in their course is not in all cases infallible, and it seems to be confounded by changes in the condition of the surface. I am familiar with a village in New England, at the junction of two valleys, each drained by a mill-stream, where the flocks of wild geese which formerly passed, every spring and autumn, were very frequently lost, as it was popularly phrased, and I have often heard their screams in the night as they flew wildly about in perplexity as to the proper course. Perhaps the village lights embarrassed them, or perhaps the constant changes in the face of the country, from the clearings then going on, introduced into the landscape features not according with the ideal map handed down in the anserine family, and thus deranged its traditional geography.] Nature sets bounds to the disproportionate increase of birds, while at the same time, by the multitude of their resources, she secures them from extinction through her own spontaneous agencies. Man both preys upon them and wantonly destroys them. The delicious flavor of game-birds, and the skill implied in the various arts of the sportsman who devotes himself to fowling, make them favorite objects of the chase, while the beauty of their plumage, as a military and feminine decoration, threatens to involve the sacrifice of the last survivor of many once numerous species. Thus far, but few birds described by ancient or modern naturalists are known to have become absolutely extinct, though there are some cases in which they are ascertained to have utterly disappeared from the face of the earth in very recent times. The most familiar instances are those of the dodo, a large bird peculiar to the Mauritius or Isle of France, exterminated about the year 1690, and now known only by more or less fragmentary skeletons, and the solitary, which inhabited the islands of Bourbon and Rodriguez, but has not been seen for more than a century. A parrot and some other birds of the Norfolk Island group are said to have lately become extinct. The wingless auk, Alca impennis, a bird remarkable for its excessive fatness, was very abundant two or three hundred years ago in the Faroe Islands, and on the whole Scandinavian seaboard. The early voyagers found either the same or a closely allied species, in immense numbers, on all the coasts and islands of Newfoundland. The value of its flesh and its oil made it one of the most important resources of the inhabitants of those sterile regions, and it was naturally an object of keen pursuit. It is supposed to be now completely extinct, and few museums can show even its skeleton. There seems to be strong reason to believe that modern civilization is guiltless of one or two sins of extermination which have been committed in recent ages. Now Zealand formerly possessed several species of dinornis, one of which, called moa by the islanders, was larger than the ostrich. The condition in which the bones of these birds have been found and the traditions of the natives concur to prove that, though the aborigines had probably extirpated them before the discovery of New Zealand by the whites, they still existed at a comparatively late period. The same remarks apply to a winged giant the eggs of which have been brought from Madagascar. This bird must have much exceeded the dimensions of the moa, at least so far as we can judge from the egg, which is eight times as large as the average size of the ostrich egg, or about one hundred and fifty times that of the hen. But though we have no evidence that man has exterminated many species of birds, we know that his persecutions have caused their disappearance from many localities where they once were common, and greatly diminished their numbers in others. The cappercailzie, Tetrao urogallus, the finest of the grouse family, formerly abundant in Scotland, had become extinct in Great Britain, but has been reintroduced from Sweden. [Footnote: Thecappercailzie, or tjader, as he is called in Sweden, is a bird of singular habits, and seems to want some of the protective instincts which secure most other wild birds from destruction. The younger Laestadius frequently notices the tjader, in his very remarkable account of the Swedish Laplanders. The tjader, though not a bird of passage, is migratory, or rather wandering in domicile, and appears to undertake very purposeless and absurd journeys. "When he flits," says Laestadius, "he follows a straight course, and sometimes pursues it quite out of the country. It is said that, in foggy weather, he sometimes flies out to sea, and, when tired, falls into the water and is drowned. It is accordingly observed that, when he flies westwardly, towards the mountains, he soon comes back again; but when he takes an eastwardly course, he returns no more, and for a long time is very scarce in Lapland. From this it would seem that he turns back from the bald mountains, when he discovers that he has strayed from his proper home, the wood; but when he finds himself over the Baltic, where he cannot alight to rest and collect himself, he flies on until he is exhausted and falls into the sea."--Petrus Laestadius, Journal of forsta aret, etc., p. 325.] The ostrich is mentioned, by many old travellers, as common on the Isthmus of Suez down to the middle of the seventeenth century. It appears to have frequented Palestine, Syria, and even Asia Minor at earlier periods, but is now rarely found except in the seclusion of remoter deserts. [Footnote: Frescobaldi saw ostriches between Suez and Mt. Sinai. Viaggio in Terra Santa, p. 65. See also Vansler, Voyage d'Egypte, p. 103, and an article in Petermann, Mittheilungen, 1870, p. 880, entitled Die Verbreitung des Straussee in Asien.] The modern increased facilities of transportation have brought distant markets within reach of the professional hunter, and thereby given a new impulse to his destructive propensities. Not only do all Great Britain and Ireland contribute to the supply of game for the British capital, but the canvas-back duck of the Potomac, and even the prairie hen from the basin of the Mississippi, may be found at the stalls of the London poulterer. Kohl [Footnote: Die Herzogthumer Schleswig und Holstein, i., p. 203.] informs us that, on the coasts of the North Sea, twenty thousand wild ducks are usually taken in the course of the season in a single decoy, and sent to the large maritime towns for sale. The statistics of the great European cities show a prodigious consumption of game-birds, but the official returns fall far below the truth, because they do not include the rural districts, and because neither the poacher nor his customers report the number of his victims. Reproduction, in cultivated countries, cannot keep pace with this excessive destruction, and there is no doubt that all the wild birds which are chased for their flesh or their plumage are diminishing with a rapidity which justifies the fear that the last of them will soon follow the dodo and the wingless auk. Fortunately the larger birds which are pursued for their flesh or for their feathers, and those the eggs of which are used as food, are, so far as we know the functions appointed to them by nature, not otherwise specially useful to man, and, therefore, their wholesale destruction is an economical evil only in the same sense in which all waste of productive capital is an evil. [Footnote: The increased demand for animal oils for the use of the leather-dresses is now threatening the penguin with the fate of the wingless auk. According to the Report of the Agricultural Department of the U. S. for August and September, 1871, p. 840, small vessels are fitted out for the chase of this bird, and return from a six week's cruise with 25,000 or 30,000 gallons of oil. About eleven birds are required for a gallon, and consequently the vessels take upon an average 800,000 penguins each.] If it were possible to confine the consumption of game-fowl to a number equal to the annual increase, the world would be a gainer, but not to the same extent as it would be by checking the wanton sacrifice of millions of the smaller birds, which are of no real value as food, but which, as we have seen, render a most important service by battling, in our behalf, as well as in their own, against the countless legions of humming and of creeping things, with which the prolific powers of insect life would otherwise cover the earth. Utility and Destruction of Reptiles. The disgust and fear with which the serpent is so universally regarded expose him to constant persecution by man, and perhaps no other animal is so relentlessly sacrificed by him. Nevertheless, snakes as well as lizards and other reptiles are not wholly useless to their great enemy. The most formidable foes of the insect, and even of the small rodents, are the reptiles. The chameleon approaches the insect perched upon the twig of a tree, with an almost imperceptible slowness of motion, until, at the distance of a foot, he shoots out his long, slimy tongue, and rarely fails to secure the victim. Even the slow toad catches the swift and wary housefly in the same manner; and in the warm countries of Europe, the numerous lizards contribute very essentially to the reduction of the insect population, which they both surprise in the winged state upon walls and trees, and consume as egg, worm, and chrysalis, in their earlier metamorphoses. The serpents feed much upon insects, as well as upon mice, moles, and small reptiles, including also other snakes. In temperate climates, snakes are consumed by scarcely any beast or bird of prey except the stork, and they have few dangerous enemies but man, though in the tropics other animals prey upon them. [Footnote: It is very questionable whether there is any foundation for the popular belief in the hostility of swine and of deer to the rattlesnake, and careful experiments as to the former quadruped seem to show that the supposed enmity is wholly imaginary. It is however affirmed in an article in Nature, June 11, 1872, p. 215, that the pigs have exterminated the rattlesnake in some parts of Oregon, and that swine are destructive to the cobra de capello in India. Observing that the starlings, stornelli, which bred in an old tower in Piedmont, carried something from their nests and dropped it upon the ground about as often they brought food to their young, I watched their proceedings, and found every day lying near the tower numbers of dead or dying slowworms, and, in a few cases, small lizards, which had, in every Instance, lost about two inches of the tail. This part I believe the starlings gave to their nestlings, and threw away the remainder.] It is doubtful whether any species of serpent has been exterminated within the human period, and even the dense population of China has not been able completely to rid itself of the viper. They have, however, almost entirely disappeared from particular localities. The rattlesnake is now wholly unknown in many large districts where it was extremely common half a century ago, and Palestine has long been, if not absolutely free from venomous serpents, at least very nearly so. [Footnote: Russell denies the existence of poisonous snakes in Northern Syria, and states that the last instance of death known to have occurred from the bite of a serpent near Aleppo took place a hundred years before his time. In Palestine, the climate, the thinness of population, the multitude of insects and of lizards, all circumstances, in fact, seem very favorable to the multiplication of serpents, but the venomous species, at least, are extremely rare, if at all known, in that country. I have, however, been assured by persons very familiar with Mount Lebanon, that cases of poisoning from the bite of snakes had occurred within a few years, near Hasbeiyeh, and at other places on the southern declivities of Lebanon and Hermon. In Egypt, on the other hand, the cobra, the asp, and the cerastes are as numerous as ever, and are much dreaded by all the natives except the professional snake charmers. The recent great multiplication of vipers in some parts of France is a singular and startling fact. Toussenel, quoting from official documents, states, that upon the offer of a reward of fifty centimes, or ten cents, a head, TWELVE THOUSAND vipers were brought to the prefect of a single department, and that in 1850 fifteen hundred snakes and twenty quarts of snakes' eggs were found under a farm-house hearthstone. The granary, the stables, the roof, the very beds swarmed with serpents, and the family were obliged to abandon its habitation. Dr. Viaugrandmarais, of Nantes, reported to the prefect of his department more than two hundred recent cases of viper bites, twenty-four of which proved fatal.--Tristia, p. 176 et seqq. According to the Journal del Debats for Oct. 1st, 1867, the Department of the Cote d'Or paid in the year 1866 eighteen thousand francs for the destruction of vipers. The reward was thirty centimes a head, and consequently the number killed was about sixty thousand. A friend residing in that department informs me that it was strongly suspected that many of these snakes were imported from other departments for the sake of the premium. In Nature for 1870 and 1871 we are told that the number of deaths from the bites of venomous serpents in the Bengal Presidency, in the year 1869, was 11,416, and that in the whole of British India not less than 40,000 human lives are annually lost from this cause. In one small department, a reward of from three to six pence a head for poisonous serpents brought in 1,200 a day, and in two months the government paid L10,000 sterling for their destruction.] The serpent does not appear to have any natural limit of growth, and we are therefore not authorized wholly to discredit the evidence of ancient naturalists in regard to the extraordinary dimensions which those reptiles are said by them to have sometimes attained. The use of firearms has enabled man to reduce the numbers of the larger serpents, and they do not often escape him long enough to arrive at the size ascribed to them by travellers a century or two ago. Captain Speke, however, shot a serpent in Africa which measured fifty-one and a half feet in length. Some enthusiastic entomologist will, perhaps, by and by discover that insects and worms are as essential as the larger organisms to the proper working of the great terraqueous machine, and we shall have as eloquent pleas in defence of the mosquito, and perhaps oven of the tzetze-fly, as Toussenel and Michelet have framed in behalf of the bird. The silkworm, the lac insect, and the bee need no apologist; a gallnut produced by the puncture of a cynips on a Syrian oak is a necessary ingredient in the ink I am writing with, and from my windows I recognize the grain of the kermes and the cochineal in the gay habiliments of the holiday groups beneath them. These humble forms of being are seldom conspicuous by more mass, and though the winds and the waters sometimes sweep together large heaps of locusts and even of may-flies, their remains are speedily decomposed, their exuviae and their structures form no strata, and still less does nature use them, as she does the calcareous and silicious cases and dwellings of animalcular species, to build reefs and spread out submarine deposits, which subsequent geological action may convert into islands and even mountains. [Footnote: Although the remains of extant animals are rarely, if ever, gathered In sufficient quantities to possess any geographical importance by their mere mass, the decayed exuviae of even the smaller and humbler forms of life are sometimes abundant enough to exercise a perceptible influence on soil and atmosphere. "The plain of Cumana," saya Humboldt, "presents a remarkable phenomenon, after heavy rains. The moistened earth, when heated by the rays of the sun, diffuses the musky odor common in the torrid zone to animals of very different classes, to the jaguar, the small species of tiger-cat, the cabiai, the gallinazo vulture, the crocodile, the viper, and the rattlesnake. The gaseous emanations, the vehicles of this aroma, appear to be disengaged in proportion as the soil, which contains the remains of an innumerable multitude of reptiles, worms, and insects, begins to be impregnated with water. Wherever we stir the earth, we are struck with the mass of organic substances which in turn are developed and become transformed or decomposed. Nature in these climes seems more active, more prolific, and, so to speak, more prodigal of life."] But the action of the creeping and swarming things of the earth, though often passed unnoticed, is not without important effects in the general economy of nature. The geographical importance of insects proper, as well as of worms, depends principally on their connection with vegetable life as agents of its fecundation, and of its destruction. We learn from Darwin, "On Various Contrivances by which British and Foreign Orchids are Fertilized by Insects," that some six thousand species of orchids are absolutely dependent upon the agency of insects for their fertilization, and that consequently, were those plants unvisited by insects, they would all rapidly disappear. What is true of the orchids is more or less true of many other vegetable families. [Footnote: Later observations of Darwin and other naturalists have greatly raised former estimates of the importance of insect life in the fecundation of plants, and among other remarkable discoveries it has been found that, in many cases at least, insects are necessary even to monoecious vegetables, because the male flower does not impregnate the female growing on the same stem, and the latter can be fecundated only by pollen supplied to it by insects from another plant of the same species. "Who would ever have thought," says Preyer, "that the abundance and beauty of the pansy and of the clover were dependent upon the number of cats and owls But so it is. The clover and the pansy cannot exist without the bumble-bee, which, in search of his vegetable nectar, transports unconciously the pollen from the masculine to the feminine flower, a service which other insects perform only partially for these plants. Their existence therefore depends upon that of the bumble-bee. The mice make war upon this bee. In their fondness for honey they destroy the nest and at the same time the bee. The principal enemies of mice are cats and owls, and therefore the finest clovers and the most beautiful pansies are found near villages where cats and owls abound."--Preyer, Der Kampf um daas Dasein, p. 22. See also Delpino, Pensieri sulla biologia vegetale, and other works of the same able observer on vegetable physiology.] We do not know the limits of this agency, and many of the insects habitually regarded as unqualified pests, may directly or indirectly perform functions as important to the most valuable plants as the services rendered by certain tribes to the orchids. I say directly or indirectly, because, besides the other arrangements of nature for chocking the undue multiplication of particular species, she has established a police among insects themselves, by which some of them keep down or promote the increase of others; for there are insects, as well as birds and beasts, of prey. The existence of an insect which fertilizes a useful vegetable may depend on that of another insect which constitutes his food in some stage of his life, and this other again may be as injurious to some plant as his destroyer is to a different species. The ancients, according to Pliny, were accustomed to hang branches of the wild fig upon the domestic tree, in order that the insects which frequented the former might hasten the ripening of the cultivated fig by their punctures--or, as others suppose, might fructify it by transporting to it the pollen of the wild fruit--and this process, called caprification, is not yet entirely obsolete. [Footnote: The utility of caprification has been a good deal disputed, and it has, I believe, been generally abandoned in Italy, though still practised in Greece. See Browne, The Trees of America, p. 475, and on caprification in Kabylia, N. Bibesco, Les Kabyles du Djardjura, in Revue des Deux Mondes for April 1st, 1805, p. 580; also, Aus der Natur, vol. xxx., p. 684, and Phipson, Utilization of Minute Life, p. 50. In some parts of Sicily, sprigs of mint, mentha pulegium, are used instead of branches of the wild for caprification. Pitre, Usi popolari Siciliani, 1871, p. 18.] The perforations of the earthworms and of many insect larvae mechanically affect the texture of the soil and its permeability by water, and they therefore have a certain influence on the form and character of terrestrial surface. The earthworms long ago made good their title to the respect and gratitude of the farmer as well as of the angler. Their utility has been pointed out in many scientific as well as in many agricultural treatises. The following extract from an essay on this subject will answer my present purpose: "Worms are great assistants to the drainer, and valuable aids to the fanner in keeping up the fertility of the soil. They love moist, but not wet soils; they will bore down to, but not into water; they multiply rapidly on land after drainage, and prefer a deeply-dried soil. On examining part of a field which had been deeply drained, after long-previous shallow drainage, it was found that the worms had greatly increased in number, and that their bores descended quite to the level of the pipes. Many worm-bores were large enough to receive the little finger. A piece of land near the sea, in Lincolnshire, over which the sea had broken and killed all the worms, remained sterile until the worms again inhabited it. A piece of pasture land, in which worms were in such numbers that it was thought their casts interfered too much with its produce, was rolled at night in order to destroy the worms. The result was, that the fertility of the field greatly declined, nor was it restored until they had recruited their numbers, which was aided by collecting and transporting multitudes of worms from the fields. "The great depth into which worms will bore, and from which they push up fine fertile soil, and cast it on the surface, have been well shown by the fact that in a few years they have actually elevated the surface of fields by a largo layer of rich mould, several inches thick, thus affording nourishment to the roots of grasses, and increasing the productiveness of the soil." It should be added that the writer quoted, and all others who have discussed the subject, have, so far as I know, overlooked one very important element in the fertilization produced by earthworms. I refer to the enrichment of the soil by their excreta during life, and by the decomposition of their remains when they die. Themanure thus furnished is as valuable as the like amount of similar animal products derived from higher organisms, and when we consider the prodigious numbers of these worms found on a single square yard of some soils, we may easily see that they furnish no insignificant contribution to the nutritive material required for the growth of plants. [Footnote: I believe there is no foundation for the supposition that earthworms attack the tuber of the potato. Some of them, especially one or two species employed by anglers as bait, if natives of the woods, are at least rare in shaded grounds, but multiply very rapidly after the soil is brought under cultivation. Forty or fifty years ago they were so scarce in the newer parts of New England, that the rustic fishermen of every village kept secret the few places where they were to be found in their neighborhood, as a professional mystery, but at present one can hardly turn over a shovelfull of rich moist soil anywhere, without unearthing several of them. A very intelligent lady, born in the woods of Northern New England, told me that, in her childhood, these worms were almost unknown in that region, though anxiously sought for by the anglers, but that they increased as the country was cleared, and at last became so numerous in some places, that the water of springs, and even of shallow wells, which had formerly been excellent, was rendered undrinkable by the quantity of dead worms that fell into them. The increase of the robin and other small birds which follow the settler when he has prepared a suitable home for them, at last checked the excessive multiplication of the worms, and abated the nuisance.] The carnivorous and often herbivorous insects render another important service to man by consuming dead and decaying animal and vegetable matter, the decomposition of which would otherwise fill the air with effluvia noxious to health. Some of them, the grave-digger beetle, for instance, bury the small animals in which they lay their eggs, and thereby prevent the escape of the gases disengaged by putrefaction. The prodigious rapidity of development in insect life, the great numbers of the individuals in many species, and the voracity of most of them while in the larva state, justify the appellation of nature's scavengers which has been bestowed upon them, and there is very little doubt that, in warm countries, they consume a larger quantity of putrescent organic matter than the quadrupeds and birds which feed upon such aliment. INJURY TO THE FOREST BY INSECTS. The action of the insect on vegetation, as we have thus far described it, is principally exerted on smaller and less conspicuous plants, and it is therefore matter rather of agricultural than of geographical interest. But in the economy of the forest European writers ascribe to insect life an importance which it has not reached in America, where the spontaneous woods are protected by safeguards of nature's own devising. The insects which damage primitive forests by feeding upon products of trees essential to their growth, are not numerous, nor is their appearance, in destructive numbers, frequent, and those which perforate the stems and branches, to deposit and hatch their eggs, more commonly select dead trees for that purpose, though, unhappily, there are important exceptions to this latter remark. [Footnote: The locust Insect, Clitus pictus, which deposits its eggs in the American locust, Robinia pseudacacia, is one of these, and its ravages have been and still are more destructive to that very valuable tree, so remarkable for combining rapidity of growth with strength and durability of wood. This insect, I believe, has not yet appeared in Europe, where, since the so general employment of the Robinia to clothe and protect embankments and the scarps of deep cuts on railroads, it would do incalculable mischief. As a traveller, however, I should find some compensation for this evil in the destruction of these acacia hedges, which as completely obstruct the view on hundreds of miles of French and Italian railways, as do the garden walls of the same countries on the ordinary roads. The lignivorous insects that attack living trees almost uniformly confine their ravages to trees already unsound or diseased in growth from the depredations of leaf-eaters, such as caterpillars and the like, or from other causes. The decay of the tree, therefore, is the cause not the consequence of the invasions of the borer. This subject has been discussed by Perris in the Annales de la Societe Entomologique de la France for 1852, and his conclusions are confirmed by the observations of Samanos, who quotes, at some length, the views of Perris. "Having, for fifteen years," says the latter author, "incessantly studied the habits of lignivorous insects in one of the best wooded regions of France, I have observed facts enough to feel myself warranted in expressing my conclusions, which are: that insects in general--I am trees in sound health, and they assail those only whose normal conditions and functions have been by some cause impaired." See, more fully, Samanos, Traite de la Culture du Pin Maritime, Paris, 1864, pp. 140-145, and Siemoni, Manuale dell' Arte Forestale. 2d edition. Florence, 1872.] I do not know that we have any evidence of the destruction or serious injury of American forests by insects before or even soon after the period of colonization; but since the white man has laid bare a vast proportion of the earth's surface, and thereby produced changes favorable, perhaps, to the multiplication of these pests, they have greatly increased in numbers, and, apparently, in voracity also. Not many years ago, the pines on thousands of acres of land in North Carolina were destroyed by insects not known to have ever done serious injury to that tree before. In such cases as this and others of the like sort, there is good reason to believe that man is the indirect cause of an evil for which he pays so heavy a penalty. Insects increase whenever the birds which feed upon them disappear. Hence, in the wanton destruction of the robin and other insectivorous birds, the bipes implumis, the featherless biped, man, is not only exchanging the vocal orchestra which greets the rising sun for the drowny beetle's evening drone, and depriving his groves and his fields of their fairest ornament, but he is waging a treacherous warfare on his natural allies. [Footnote: In the artificial woods of Europe, insects are far more numerous and destructive to trees than in the primitive forests of America, and the same remark may be made of the smaller rodents, such as moles, mice, and squirrels. In the dense native wood, the ground and the air are too humid, the depth of shade too great, for many tribes of these creatures, while near the natural meadows and other open grounds, where circumstances are otherwise more favorable for their existence and multiplication, their numbers are kept down by birds, serpents, foxes, and smaller predacious quadrupeds. In civilized countries these natural enemies of the worm, the beetle, and the mole, are persecuted, sometimes almost exterminated, by man, who also removes from his plantations the decayed or wind-fallen trcea, the shrubs and underwood, which, in a state of nature, furnished food and shelter to the borer and the rodent, and often also to the animals that preyed upon them. Hence the insect and the gnawing quadruped are allowed to increase, from the expulsion of the police which, in the natural wood, prevent their excessive multiplication, and they become destructive to the forest because they are driven to the living tree for nutriment and cover. The forest of Fontainebleau is almost wholly without birds, and their absence is ascribed by some writers to the want of water, which, in the thirsty sands of that wood, does not gather into running brooks; but the want of undergrowth is perhaps an equally good reason for their scarcity. On the other hand, the thinning out of the forest and the removal of underwood and decayed timber, by which it is brought more nearly to the condition of an artificial wood, is often destructive to insect tribes which, though not injurious to trees, are noxious to man. Thus the troublesome woodtick, formerly very abundant in the North Eastern, as it unhappily still is in native forests in the Southern and Western States, has become nearly or quite extinct in the former region since the woods have been reduced in extent and laid more open to the sun and air.--Asa Fitch, in Report of New York Agricultural Society for 1870, pp. 868,864.] Introduction of Insects. The general tendency of man's encroachments upon spontaneous nature has been to increase insect life at the expense of vegetation and of the smaller quadrupeds and birds. Doubtless there are insects in all woods, but in temperate climates they are comparatively few and harmless, and the most numerous tribes which breed in the forest, or rather in its waters, and indeed in all solitudes, are those which little injure vegetation, such as mosquitoes, gnats, and the like. With the cultivated plants of man come the myriad tribes which feed or breed upon them, and agriculture not only introduces new speciss, but so multiplies the number of individuals as to defy calculation. Newly introduced vegetables frequently escape for years the insect plagues which had infested them in their native habitat; but the importation of other varieties of the plant, the exchange of seed, or some more accident, is sure in the long run to carry the egg, the larva, or the chrysalis to the most distant shores where the plant assigned to it by nature as its possession has preceded it. For many years after the colonization of the United States, few or none of the insects which attack wheat in its different stages of growth, were known in America. During the Revolutionary war, the Hessian fly, Cecidomyia destructrix, made its appearance, and it was so called because it was first observed in the year when the Hessian troops were brought over, and was popularly supposed to have been accidentally imported by those unwelcome strangers. Other destroyers of cereal grains have since found their way across the Atlantic, and a noxious European aphis has first attacked the American wheatfields within the last fifteen years. Unhappily, in these cases of migration, the natural corrective of excessive multiplication, the parasitic or voracious enemy of the noxious insect, does not always accompany the wanderings of its prey, and the bane long precedes the antidote. Hence, in the United States, the ravages of imported insects injurious to cultivated crops, not being checked by the counteracting influences which nature had provided to limit their devastations in the Old World, are more destructive than in Europe. It is not known that the wheat midge is preyed upon in America by any other insect, and in seasons favorable to it, it multiplies to a degree which would prove almost fatal to the entire harvest, were it not that, in the great territorial extent of the United States, there is room for such differences of soil and climate as, in a given year, to present in one State all the conditions favorable to the increase of a particular insect, while in another, the natural influences are hostile to it. The only apparent remedy for this evil is, to balance the disproportionate development of noxious foreign species by bringing from their native country the tribes which prey upon them. This, it seems, has been attempted. The United States Census Report for 1860, p. 82, states that the New York Agricultural Society "has introduced into this country from abroad certain parasites which Providence has created to counteract the destructive powers of some of these depredators." [Footnote: On parasitic and entomophagous insects, see a paper by Rondani referred to p. 119 ante.] This is, however, not the only purpose for which man has designedly introduced foreign forms of insect life. The eggs of the silkworm are known to have been brought from the farther East to Europe in the sixth century, and new silk-spinners which feed on the castor-oil bean and the ailanthus, have recently been reared in France and in South America with promising success. [Footnote: The silkworm which feeds on the ailanthus has naturalized itself in the United States, but also the promises of its utility have not been realized.] The cochineal, long regularly bred in aboriginal America, has been transplanted to Spain, and both the kermes insect and the cantharides have been transferred to other climates than their own. The honey--bee must be ranked next to the silkworm in economical importance. This useful creature was carried to the United States by European colonists, in the latter part of theseventeenth century; it did not cross the Mississippi till the close of the eighteenth, and it is only in 1853 that it was transported to California, where it was previously unknown. The Italian bee, which seldom stings, has lately been introduced into the United States. [Footnote: Bee husbandry, now very general in Switzerland and other Alpine regions, was formerly an important branch of industry in Italy. It has lately been revived and is now extensively prosecuted it that country. It is interesting to observe that many of the methods recently introduced into this art in England and United States, such for example as the removable honey--boxes, are reinventions of Italian systeams at least three hundred years old. See Gallo, Le Venti Giornate dell' Agricultura, cap. XV. The temporary decline of this industry in Italy was doubtless in great measure due to the use of sugar which had taken the place of honed, but perhaps also in part to the decrease of the wild vegetation from which the bee draws more or less of his nutriment. A new was-producing insect, a species of coccus, very abundant in China, where its annual produce is said to amount to the value of ten millions of francs, has recently attracted notice in France. The wax is white, resembling spermaceti, and is said to be superior to that of the bee.] The insects and worms intentionally transplanted by man bear but a small portion to those accidentally introduced by him. Plants and animals often carry their parasites with them, and the traffic of commercial countries, which exchange their products with every zone and every stage of social existence, cannot fail to transfer in both directions the minute organisms that are, in one way or another associated with almost every object important to the material interests of man. [Footnote: A few years ago, a laborer, employed at a North American port in discharging a cargo of hides from the opposite extremity of the continent, was fatally poisoned by the bite or the sting of an unknown insect, which ran out from a hide he was handling. The Phylloxera vastatrix, the most destructive pest which has ever attacked European vineyards--for its ravages are fatal not merely to the fruit, but to the vine itself--in said by many entomologists to be of American origin, but I have seen no account of the mode of its introduction.] The tenacity of life possessed by many insects, their prodigious fecundity, the length of time they often remain in the different phases of their existence, [Footnote: In many insects, some of the stages of life regularly continue for several years, and they may, under peculiar circumstances, be almost indefinitely prolonged. Dr. Dwight mentions the following remarkable case of this sort: "I saw here an insect, about an inch in length, of a brown color tinged with orange, with two antennae, not unlike a rosebug. This insect came out of a tea-table made of the boards of an apple-tree." Dr. Dwight found the "cavity whence the insect had emerged into the light," to be "about two inches in length. Between the hole, and the outside of the leaf of the table, there were forty grains of the wood." It was supposed that the sawyer and the cabinet-maker must have removed at least thirteen grains more, and the table had been in the possession of its proprietor for twenty years.] the security of the retreats into which their small dimensions enable them to retire, are all circumstances very favorable not only to the perpetuity of their species, but to their transportation to distant climates and their multiplication in their new homes. The teredo, so destructive to shipping, has been carried by the vessels whose wooden walls it mines to almost every part of the globe. The termite, or white ant, is said to have been brought to Rochefort by the commerce of that port a hundred years ago. [Footnote: It does not appear to be quite settled whether the termites of France are indigenous or imported. See Quatrefaces, Souvenirs d'un naturaliste, ii., pp. 400, 542, 543. The white ant has lately appeared at St. Helena and is in a high degree destructive, no wood but teak, and even that not always, resisting it.--Nature for March 2d, 1871, p. 362.] This creature is more injurious to wooden structures and implements than any other known insect. It eats out almost the entire substance of the wood, leaving only thin partitions between the galleries it excavates in it; but as it never gnaws through the surface to the air, a stick of timber may be almost wholly consumed without showing any external sign of the damage it has sustained. The termite is found also in other parts of France, and particularly at Rochelle, where, thus far, its ravages are confined to a single quarter of the city. A borer, of similar habits, is not uncommon in Italy, and you may see in that country handsome chairs and other furniture which have been reduced by this insect to a framework of powder of post, covered, and apparently held together, by nothing but the varnish. DESTRUCTION OF INSECTS. It is well known to naturalists, but less familiarly to common observers, that the aquatic larvae of some insects which in other stages of their existence inhabit the land, constitute, at certain seasons, a large part of the food of fresh-water fish, while other larvae, in their turn, prey upon the spawn and even the young of their persecutors. [Footnote: I have seen the larva of the dragon-fly in an aquarium bite off the head of a young fish as long as itself.] The larvae of the mosquito and the gnat are the favorite food of the trout in the wooded regions where those insects abound. [Footnote: Insects and fish--which prey upon and feed each other--are the only forms of animal life that are numerous in the native woods, and their range is, of course, limited by the extent of the waters. The great abundance of the trout, and of other more or less allied genera in the lakes of Lapland, seems to be due to the supply of food provided for them by the swarms of insects which in the larva state inhabit the waters, or, in other stages of their life, are accidentally swept into them. All travellers in the north of Europe speak of the gnat and the mosquito as very serious drawbacks upon the enjoyments of the summer tourist, who visits the head of the Gulf of Bothnia to see the midnight sun, and the brothers Laestadius regard them as one of the great plagues of sub-arctic life. "The persecutions of these insects," says Lars Levi Laestadius [Culex pipiens, Culex reptans, and Culex pulicaris], "leave not a moment's peace, by day or night, to any living creature. Not only man, but cattle, and even birds and wild beasts, suffer intolerably from their bite." He adds in a note, "I will not affirm that they have ever devoured a living man, but many young cattle, such as lambs and calves, have been worried out of their lives by them. All the people of Lapland declare that young birds are killed by them, and this is not improbable, for birds are scarce after seasons when the midge, the gnlat, and the mosquito are numerous."--Om Uppodlingar i Lappmarken, p. 50. Petrus Laestadius makes similar statements in his Journal for forsta urst, p. 283.] Earlier in the year the trout feeds on the larvae of the May fly, which is itself very destructive to the spawn of the salmon, and hence, by a sort of house-that-Jack-built, the destruction of the mosquito, that feeds the trout that preys on the May fly that destroys the eggs that hatch the salmon that pampers the epicure, may occasion a scarcity of this latter fish in waters where he would otherwise be abundant. Thus all nature is linked together by invisible bonds, and every organic creature, however low, however feeble, however dependent, is necessary to the well-being of some other among the myriad forms of life with which the Creator has peopled the earth. I have said that man has promoted the increase of the insect and the worm, by destroying the bird and the fish which feed upon them. Many insects, in the four different stages of their growth, inhabit in succession the earth, the water, and the air. In each of these elements they have their special enemies, and, deep and dark as are the minute recesses in which they hide themselves, they are pursued to the remotest, obscurest corners by the executioners that nature has appointed to punish their delinquencies, and furnished with cunning contrivances for ferreting out the offenders and dragging them into the light of day. One tribe of birds, the woodpeckers, seems to depend for subsistence almost wholly on those insects which breed in dead or dying trees, and it is, perhaps, needless to say that the injury these birds do the forest is imaginary. They do not cut holes in the trunk of the tree to prepare a lodgment for a future colony of boring larvae, but to extract the worm which has already begun his mining labors. Hence these birds are not found where the forester removes trees as fast as they become fit habitations for such insects. In clearing new lands in the United States, dead trees, especially of the spike-leaved kinds, too much decayed to serve for timber, and which, in that state, are worth little for fuel, are often allowed to stand until they fall of themselves. Such stubs, as they are popularly called, are filled with borers, and often deeply cut by the woodpeckers, whose strong bills enable them to penetrate to the very heart of the tree and drag out the lurking larvae. After a few years, the stubs fall, or, as wood becomes valuable, are cut and carried off for firewood, and, at the same time, the farmer selects for felling, in the forest he has reserved as a permanent source of supply of fuel and timber, the decaying trees which, like the dead stems in the fields, serve as a home for both the worm and his pursuer. We thus gradually extirpate this tribe of insects, and, with them, the species of birds which subsist principally upon them. Thus the fine, large, red-headed woodpecker, Picus erythrocephalus, formerly very common in New England, has almost entirely disappeared from those States, since the dead trees are gone, and the apples, his favorite vegetable food, are less abundant. There are even large quadrupeds which feed almost exclusively upon insects. The ant-bear is strong enough to pull down the clay houses built by the species of termites that constitute his ordinary diet, and the curious ai-ai, a climbing quadruped of Madagascar, is provided with a very slender, hook-nailed finger, long enough to reach far into a hole in the trunk of a tree, and extract the worm which bored it. [Footnote: On the destruction of insects by reptiles, see page 125 ante.] Minute Organisms. Besides the larger inhabitants of the land and of the sea, the quadrupeds, the reptiles, the birds, the amphibia, the crustacea, the fish, the insects, and the worms, there are other countless forms of vital being. Earth, water, the ducts and fluids of vegetable and of animal life, the very air we breathe, are peopled by minute organisms which perform most important functionsin both the living and the inanimate kingdoms of nature. Of the offices assigned to these creatures, the most familiar to common observation is the extraction of lime, and, more rarely, of silex, from the waters inhabited by them, and the deposit of these minerals in a solid form, either as the material of their habitations or as the exuviae of their bodies. The microscope and other means of scientific observation assure us that the chalk-beds of England and of France, the coral reefs of marine waters in warm climates, vast calcareous and silicious deposits in the sea and in many fresh-water ponds, the common polishing earths and slates, and many species of apparently dense and solid rock, are the work of the humble organisms of which I speak, often, indeed, of animaculae so small as to become visible only by the aid of lenses magnifying thousands of times the linear measures. It is popularly supposed that animalculae, or what are commonly embraced under the vague name of infusoria, inhabit the water alone, but naturalists have long known that the atmospheric dust transported by every wind and deposited by every calm is full of microscopic life or of its relics. The soil on which the city of Berlin stands, contains, at the depth of ten or fifteen feet below the surface, living elaborators of silex; [Footnote: Wittwer, Physikalische Geographie, p. 142.] and a microscopic examination of a handful of earth connected with the material evidences of guilt has enabled the naturalist to point out the very spot where a crime was committed. It has been computed that one-sixth part of the solid matter let fall by great rivers at their outlets consists of still recognizable infusory shells and shields, and, as the friction of rolling water must reduce many of these fragile structures to a state of comminution which even the microscope cannot resolve into distinct particles and identify as relics of animal or of vegetable life, we must conclude that a considerably larger proportion of river deposits is really the product of animalcules. [Footnote: To vary the phrase, I make occasional use of animaloule, which, as a popular designation, embraces all microscopic organisms. The name is founded on the now exploded supposition that all of them are animated, which was the general belief of naturalists when attention was first drawn to them. It was soon discovered that many of them were unquestionably vegetable, and there are numerous genera the true classification of which is a matter of dispute among the ablest observers. There are cases in which objects formerly taken for living animalcules turn out to be products of the decomposition of matter once animated, and it is admitted that neither spontaneous motion nor even apparent irritability are sure signs of animal life.] It is evident that the chemical, and in many cases mechanical, character of a great number of the objects important in the material economy of human life, must be affected by the presence of so large an organic element in their substance, and it is equally obvious that all agricultural and all industrial operations tend to disturb the natural arrangements of this element, to increase or to diminish the special adaptation of every medium in which it lives to the particular orders of being inhabited by it. The conversion of woodland into pasturage, of pasture into plough land, of swamp or of shallow sea into dry ground, the rotations of cultivated crops, must prove fatal to millions of living things upon every rood of surface thus deranged by man, and must, at the same time, more or less fully compensate this destruction of life by promoting the growth and multiplication of other tribes equally minute in dimensions. I do not know that man has yet endeavored to avail himself, by artificial contrivances, of the agency of these wonderful architects and manufacturers. We are hardly well enough acquainted with their natural economy to devise means to turn their industry to profitable account, and they are in very many cases too slow in producing visible results for an age so impatient as ours. The over-civilization of the nineteenth century cannot wait for wealth to be amassed by infinitesimal gains, and we are in haste to SPECULATE upon the powers of nature, as we do upon objects of bargain and sale in our trafficking one with another. But there are still some cases where the little we know of a life, whose workings are invisible to the naked eye, suggests the possibility of advantageously directing the efforts of troops of artisans that we cannot see. Upon coasts occupied by the corallines, the reef-building animalcule does not work near the mouth of rivers. Hence the change of the outlet of a stream, often a very busy matter, may promote the construction of a barrier to coast navigation at one point, and check the formation of a reef at another, by diverting a current of fresh water from the former and pouring it into the sea at the latter. Cases may probably be found, in tropical seas, where rivers have prevented the working of the coral animalcules in straits separating islands from each other or from the mainland. The diversion of such streams might remove this obstacle, and reefs consequently be formed which should convert an archipelago into a single large island, and finally join that to the neighboring continent. Quatrefages proposed to destroy the teredo in harbors by impregnating the water with a mineral solution fatal to them. Perhaps the labors of the coralline animals might be arrested over a considerable extent of sea-coast by similar means. The reef-builders are leisurely architects, but the precious coral is formed so rapidly that the beds may be refished advantageously as often as once in ten years. [Footnote: The smallest twig of the precious coral thrown back into the sea attaches itself to the bottom or a rock, and grows as well as on its native stem. See an interesting report on the coral fishery, by Sant' Agabio, Italian Consul-General at Algiers, in the Bollettino Consolare, published by the Department of Foreign Affairs, 1862, pp. 139, 151, and in the Annali di Agricoltura Industria e Commercio, No. ii., pp. 300, 373.] It does not seem impossible that branches of this coral might be attached to the keel of a ship and transplanted to the American coast, where the Gulf stream would furnish a suitable temperature beyond the climatic limits that otherwise confine its growth; and thus a new source of profit might perhaps be added to the scanty returns of the hardy fisherman. In certain geological formations, the diatomaceae deposit, at the bottom of fresh-water ponds, beds of silicious shields, valuable as a material for a species of very light firebrick, in the manufacture of water-glass and of hydraulic cement, and ultimately, doubtless, in many yet undiscovered industrial processes. An attentive study of the conditions favorable to the propagation of the diatomaceae might perhaps help us to profit directly by the productivity of this organism, and, at the same time, disclose secrets of nature capable of being turned to valuable account in dealing with silicious rocks, and the metal which is the base of them. Our acquaintance with the obscure and infinitesimal life of which I have now been treating is very recent, and still very imperfect. We know that it is of vast importance in geology, but we are so ambitious to grasp the great, so little accustomed to occupy ourselves with the minute, that we are not yet prepared to enter seriously upon the question how far we can control and utilize the operations, not of unembodied physical forces merely, but of beings, in popular apprehension, almost as immaterial as they. Disturbance of Natural Balances. It is highly probable that the reef-builders and other yet unstudied minute forms of vital existence have other functions in the economy of nature besides aiding in the architecture of the globe, and stand in important relations not only to man but to the plants and the larger sentient creatures over which he has dominion. The diminution or multiplication of these unseen friends or foes may be attended with the gravest consequences to all his material interests, and he is dealing with dangerous weapons whenever he interferes with arrangements pre-established by a power higher than his own. The equation of animal and vegetable life is too complicated a problem for human intelligence to solve, and we can never know how wide a circle of disturbance we produce in the harmonics of nature when we throw the smallest pebble into the ocean of organic being. This much, however, the facts I have hitherto presented authorize us to conclude: as often as we destroy the balance by deranging the original proportions between different orders of spontaneous life, the law of self-preservation requires us to restore the equilibrium, by either directly returning the weight abstracted from one scale, or removing a corresponding quantity from the other. In other words, destruction must be either repaired by reproduction, or compensated by new destruction in an opposite quarter. The parlor aquarium has taught even those to whom it is but an amusing toy, that the balance of animal and vegetable life must be preserved, and that the excess of either is fatal to the other, in the artificial tank as well as in natural waters. A few years ago, the water of the Cochituato aqueduct at Boston became so offensive in smell and taste as to be quite unfit for use. Scientific investigation found the cause in the too scrupulous care with which aquatic vegetation had been excluded from the reservoir, and the consequent death and decay of the animalculae, which could not be shut out, nor live in the water without the vegetable element. [Footnote: It is remarkable that Pulisay, to whose great merits as an acute observer I am happy to have frequent occasion to bear testimony, had noticed that vegetation was necessary to maintain the purity of water in artificial reservoirs, though he mistook the rationale of its influence, which he ascribed to the elemental "salt" supposed by him to play an important part in all the operations of nature. In his treatise upon Waters and Fountains, p. 174, of the reprint of 1844, he says: "And in special, thou shalt note one point, the which is understood of few: that is to say, that the leaves of the trees which fall upon the parterre, and the herbs growing beneath, and singularly the fruits, if any there be upon the trees, being decayed, the waters of the parterre shall draw onto them the salt of the said fruits, leaves, and herbs, the which shall greatly better the water of thy fountains, and hinder the putrefaction thereof."] Animalcular Life. Nature has no unit of magnitude by which she measures her works. Man takes his standards of dimension from himself. The hair's breadth was his minimum until the microscope told him that there are animated creatures to which one of the hairs of his head is a larger cylinder than is the trunk of the giant California sequoia to him. He borrows his inch from the breadth of his thumb, his palm and span from the width of his hand and the spread of his fingers, his foot from the length of the organ so named; his cubit is the distance from the tip of his middle finger to his elbow, and his fathom is the space he can measure with his outstretched arms. [Footnote: The French metrical system seems destined to be adopted throughout the civilized world. It is indeed recommended by great advantages, but it is very doubtful whether they are not more than counterbalanced by the selection of too large a unit of measure, and by the inherent intractability of all decimal systems with reference to fractional divisions. The experience of the whole world has established the superior convenience of a smaller unit, such as the braccio, the cubit, the foot, and the palm or span, and in practical life every man finds that he haa much more frequent occasion to use a fraction than a multiple of the metre. Of course, he must constantly employ numbers expressive of several centimetres or millimetres instend of the name of a single smaller unit than the metre. Besides, the metre is not divisible into twelfths, eighths, sixths, or thirds, or the multiples of any of these proportions, two of which at least--the eighth and the third--are of as frequent use as any other fractions. The adoption of a fourth of the earth's circumference as a base for the new measures was itself a departure from the decimal system. Had the Commissioners taken the entire circumference as a base, and divided it into 100,000,000 instead of 10,000,000 parts, we should have had a unit of about sixteen inches, which, as a compromise between the foot and the cubit, would have been much better adapted to universal use than so large a unit as the metre.] To a being who instinctively finds the standard of all magnitudes in his own material frame, all objects exceeding his own dimensions are absolutely great, all falling short of them absolutely small. Hence we habitually regard the whale and the elephant as essentially large and therefore important creatures, the animalcule as an essentially small and therefore unimportant organism. But no geological formation owes its origin to the labors or the remains of the huge mammal, while the animalcule composes, or has furnished, the substance of strata thousands of feet in thickness, and extending, in unbroken beds, over many degrees of terrestrial surface. If man is destined to inhabit the earth much longer, and to advance in natural knowledge with the rapidity which has marked his progress in physical science for the last two or three centuries, he will learn to put a wiser estimate on the works of creation, and will derive not only great instruction from studying the ways of nature in her obscurest, humblest walks, but great material advantage from stimulating her productive energies in provinces of her empire hitherto regarded as forever inaccessible, utterly barren. [Footnote: The fermentation of liquids, and in many cases the decomposition of semi-solids, formerly supposed to be owing purely to chemical action, are now ascribed by many chemists to vital processes of living minute organisms, both vegetable and animal, and consequently to physiological as well as to chemical forces. Even alcohol is stated to be an animal product. The whole subject of animalcular, or rather minute organic, life, has assumed a now and startling importance from the recent researches of naturalists and physiologists, in the agency of such life, vegetable or animal, in exciting and communicating contagious diseases, and it is extremely probable that what are vaguely called germs, to whichever of the organic kingdoms they may be assigned, creatures inhabiting various media, and capable of propagating their kind and rapidly multiplying, are the true seeds of infection and death in the maladies now called zymotic, as well perhaps as in many others. The literature of this subject is now very voluminous. For observations with high microscopic power on this subject, see Beale, Disease Germs, their supposed Nature, and Disease Germs, their real Nature, both published in London in 1870. The increased frequency of typhoidal, zymotic, and malarious diseases in some parts of the United States, and the now common occurrence of some of them in districts where they were unknown forty years ago, are startling facts, and it is a very interesting question how far man's acts or neglects may have occasioned the change. See Third Anual Report of Massachusetts State Board of Health for 1873. The causes and remedies of the insalubrity of Rome and its environs have been for some time the object of careful investigation, and many valuable reports have been published on the subject. Among the most recent of these are: Relazione sulle condizioni agrarie ed igieniche della Campagna di Roma, per Raffaele Pareto; Cenni Storici sulla questione dell' Agro Romano di G. Guerzoni; Cenni sulle condizioni Fisico-economiche di Roma per F. Giordano; and a very important paper in the journal Lo Sperimentale for 1870, by Dr. D. Pantaleoni. There are climates, parts of California, for instance, where the flesh of dead animals, freely exposed, shows no tendency to putrefaction but dries up and may be almost indefinitely preserved in this condition. Is this owing to the absence of destructive animalcular life in such localities, and has man any agency in the introduction and naturalization of these organisms in regions previously not infested by them ] CHAPTER III. THE WOODS. The habitable earth originally wooded--General meteorological influence of the forest--Electrical action of trees--Chemical influence of woods--Trees as protection against malaria--Trees as shelter to ground to the leeward--Influence of the forest as inorganic on temperature--Thermometrical action of trees as organic--Total influence of the forest on temperature--Influence of forests as inorganic on humidity of air and earth--Influence as organic--Balance of conflicting influences--Influence of woods on precipitation--Total climatic action of the forest--Influence of the forest on humidity of soil--The forest in winter--Summer rain, importance of--Influence of the forest on the flow of springs--Influence of the forest on inundations and torrents--Destructive action of torrents--Floods of the Ardeche--Excavation by torrents--Extinction of torrents--Crushing force of torrents--Transporting power of water--The Po and its deposits--Mountain slides--Forest as protection against avalanches--Minor uses of the forest--Small forest plants and vitality of seeds--Locusts do not breed in forests--General functions of forest--General consequences of destruction of--Due proportion of woodland--Proportion of woodland in European countries--Forests of Great Britain--Forests of France--Forests of Italy--Forests of Germany--Forests of United States--American forest trees--European and American forest trees compared--The forest does not furnish food for man--First removal of the forest--Principal causes of destruction of forest--Destruction and protection of forests by governments--Royal forests and game-laws--Effects of the French revolution--Increased demand for lumber--Effects of burning forest--Floating of timber--Restoration of the forest--Economy of the forest--Forest legislation--Plantation of forests in America--Financial results of forest plantations--Instability of American life. The Habitable Earth originally Wooded. There is good reason to believe that the surface of the habitable earth, in all the climates and regions which have been the abodes of dense and civilized populations, was, with few exceptions, already covered with a forest growth when it first became the home of man. This we infer from the extensive vegetable remains--trunks, branches, roots, fruits, seeds, and leaves of trees--so often found in conjunction with works of primitive art, in the boggy soil of districts where no forests appear to have existed within the eras through which written annals reach; from ancient historical records, which prove that large provinces, where the earth has long been wholly bare of trees, were clothed with vast and almost unbroken woods when first made known to Greek and Roman civilization; [Footnote: The recorded evidence in support of the proposition in the text has been collected by L. F. Alfred Maury, in his Histoire des grandes Forets de la Gauls et de l'ancienne France, and by Becquerel, in his important work, Des climats et de l'Influence qu'exercent les Sols boises et non boises, livre ii., chap. i. to iv. We may rank among historical evidences on this point, if not technically among historical records, old geographical names and terminations etymologically indicating forest or grove, which are so common in many parts of the Eastern Continent now entirely stripped of woods--such as, in Southern Europe, Breuil, Broglio, Brolio, Brolo; in Northern, Bruhl, and the endings -dean, -den, -don, -ham, -holt, -horst, -hurst, -lund, -shaw, -shot, -skog, -skov, -wald, -weald, -wold, -wood.] and from the state of much of North and of South America, as well as of many islands, when they were discovered and colonized by the European race. [Footnote: The island of Madeira, whose noble forests wore devastated by fire not Iong after its colonization by European settlors, takes its name from the Portuguese word tor wood.] These evidences are strengthened by observation of the natural economy of our time; for, whenever a tract of country once inhabited and cultivated by man, is abandoned by him and by domestic animals, and surrendered to the undisturbed influences of spontaneous nature, its soil sooner of later clothes itself with herbaceous and arborescent plants, and, at no long interval, with a dense forest growth. Indeed, upon surfaces of a certain stability and not absolutely precipitous inclination the special conditions required for the spontaneous propagation of trees may all be negatively expressed and reduced to these three: exemption from defect or excess of moisture, from perpetual frost, and from the depredations of man and browsing quadrupeds. Where these requisites are secured, the hardest rock is as certain to be overgrown with wood as the most fertile plain, though, for obvious reasons, the process is slower in the former than in the latter case. Lichens and mosses first prepare the way for a more highly organized vegetation. They retain the moisture of rains and dews, and bring it to act, in combination with the gases evolved by their organic processes, in decomposing the surface of the rocks they cover; they arrest and confine the dust which the wind scatters over them, and their final decay adds new material to the soil already half formed beneath and upon them. A very thin stratum of mould is sufficient for the germination of seeds of the hardy evergreens and birches, the roots of which are often found in immediate contact with the rock, supplying their trees with nourishment from a soil deepened and enriched by the decomposition of their own foliage, or sending out long rootlets into the surrounding earth in search of juices to feed them. The eruptive matter of volcanoes, forbidding as is its aspect, does not refuse nutriment to the woods. The refractory lava of Etna, it is true, remains long barren, and that of the great eruption of 1669 is still almost wholly devoid of vegetation. [Footnote: Even the volcanic dust of Etna remains very long unproductive. Near Nicolosi is a great extent of coarse black sand, thrown out in 1669, which, for almost two centuries, lay entirely bare, and can be made to grow plants only by artificial mixtures and much labor. The increase in the price of wines, in consequence of the diminution of the product from the grape disease, however, has brought even these ashes under cultivation. "I found," says Waltershausen, referring to the years 1861-62, "plains of volcanic sand and half-subdued lava streams, which twenty years ago lay utterly waste, now covered with fine vineyards. The ashfield of ten square miles above Nicolosi, created by the eruption of 1669, which was entirely barren in 1835, is now planted with vines almost to the summits of Monte Rosso, at a height of three thousand feet" Ueber den Sicilianischen Ackerbau, p. 19.] But the cactus is making inroads even here, while the volcanic sand and molten rock thrown out by Vesuvius soon become productive. Before the great eruption of 1631 even the interior of the crater was covered with vegetation. George Sandys, who visited Vesuvius in 1611, after it had reposed for several centuries, found the throat of the volcano at the bottom of the crater "almost choked with broken rocks and trees that are falne therein." "Next to this," he continues, "the matter thrown up is ruddy, light, and soft: more removed, blacke and ponderous: the uttermost brow, that declineth like the seates in a theater, flourishing with trees and excellent pasturage. The midst of the hill is shaded with chestnut trees, and others bearing sundry fruits." [Footnote: A Relation of a Journey Begun An. Dom. 1610, lib. 4, p. 260, edition of 1615. The testimony of Sandys on this point is confirmed by that of Pighio, Braccini, Magliocco, Salimbeni, and Nicola di Rubco, all cited by Roth, Der Vesuv., p. 9. There is some uncertainty about the date of the last eruption previous to the great one of 163l. Ashes, though not lava, appear to have been thrown out about the year 1500, and some chroniclers have recorded an eruption in the year 1306; but this seems to be an error for 1036, when a great quantity of lava was ejected. In 1130, ashes were thrown out for many days. I take these dates from the work of Roth just cited.] I am convinced that forests would soon cover many parts of the Arabian and African deserts, if man and domestic animals, especially the goat and the camel, were banished from them. The hard palate and tongue and strong teeth and jaws of this latter quadruped enable him to break off and masticate tough and thorny branches as large as the finger. He is particularly fond of the smaller twigs, leaves, and seed-pods of the sont and other acacias, which, like the American Robinia, thrive well on dry and sandy soils, and he spares no tree the branches of which are within his reach, except, if I remember right, the tamarisk that produces manna. Young trees sprout plentifully around the springs and along the winter water-courses of the desert, and these are just the halting stations of the caravans and their routes of travel. In the shade of these trees, annual grasses and perennial shrubs shoot up, but are mown down by the hungry cattle of the Bedouin, as fast as they grow. A few years of undisturbed vegetation would suffice to cover such points with groves, and these would gradually extend themselves over soils where now scarcely any green thing but the bitter colocynth and the poisonous foxglove is ever seen. General Meteorological Influence of the Forest. The physico-geographical influence of forests may be divided into two great classes, each having an important influence on vegetable and on animal life in all their manifestations, as well as on every branch of rural economy and productive industry, and, therefore, on all the material interests of man. The first respects the meteorology of the countries exposed to the action of these influences; the second, their superficial geography, or, in other words, the configuration, consistence, and clothing of their surface. For reasons assigned in the first chapter, and for others that will appear hereafter, the meteorological or climatic branch of the subject is the most obscure, and the conclusions of physicists respecting it are, in a great degree, inferential only, not founded on experiment or direct observation. They are, as might be expected, somewhat discordant, though one general result is almost universally accepted, and seems indeed too well supported to admit of serious question, and it may be considered as established that forests tend to mitigate, at least within their own precincts, extremes of temperature, humidity, and drought. By what precise agencies the meteorological effects of the forest are produced we cannot say, because elements of totally unknown value enter into its action, and because the relative intensity of better understood causes cannot be measured or compared. I shall not occupy much space in discussing questions which at present admit of no solution, but I propose to notice all the known forces whose concurrent or conflicting energies contribute to the general result, and to point out, in some detail, the value of those influeuces whose mode of action has been ascertained. Electrical Influence of Trees. The properties of trees, singly and in groups, as exciters or conductors of electricity, and their consequent influence upon the electrical state of the atmosphere, do not appear to have been much investigated; and the conditions of the forest itself are so variable and so complicated, that the solution of any general problem respecting its electrical influence would be a matter of extreme difficulty. It is, indeed, impossible to suppose that a dense cloud, a sea of vapor, can pass over miles of surface bristling with good conductors, without undergoing and producing some change of electrical condition. Hypothetical cases may be put in which the character of the change could be deduced from the known laws of electrical action. But in actual nature, the elements are too numerous for us to seize. The true electrical condition of neither cloud nor forest could be known, and it could seldom be predicted whether the vapors would be dissolved as they floated over the wood, or discharged upon it in a deluge of rain. With regard to possible electrical influences of the forest, wider still in their range of action, the uncertainty is even greater. The data which alone could lead to positive, or even probable, conclusions are wanting, and we should, therefore, only embarrass our argument by any attempt to discuss this meteorological element, important as it may be, in its relations of cause and effect to more familiar and bettor understood meteoric phenomena. It may, however, be observed that hail-storms--which were once generally supposed, and are still held by many, to be produced by a specific electrical action, and which, at least, appear to be always accompanied by electrical disturbances--are believed, in all countries particularly exposed to that scourge, to have become more frequent and destructive in proportion as the forests have been cleared. Caimi observes: "When the chains of the Alps and the Apennines had not yet been stripped of their magnificent crown of woods, the May hail, which now desolates the fertile plains of Lombardy, was much less frequent; but since the general prostration of the forest, these tempests are laying waste even the mountain-soils whose older inhabitants scarcely knew this plague. [Footnote: There are, in Northern Italy and in Switzerland, joint-stock companies which insure against damage by hail, as well as by fire and lightning. Between the years 1854 and 1861, a single one of these companies, La Riunione Adriatica, paid, for damage by hail in Piedmont, Venetian Lombardy, and the Duchy of Parma, above 6,500,000 francs, or nearly $200,000 per year.] The paragrandini, [Footnote: The paragrandine, or, as it is called in French, the paragrele, is a species of conductor by which it has been hoped to protect the harvests in countries particularly exposed to damage by hail. It was at first proposed to employ for this purpose poles supporting sheaves of straw connected with the ground by the same material; but the experiment was afterwards tried in Lombardy on a large scale, with more perfect electrical conductors, consisting of poles secured to the top of tall trees and provided with a pointed wire entering the ground and reaching above the top of the pole. It was at first thought that this apparatus, erected at numerous points over an extent of several miles, was of some service as a protection against hail, but this opinion was soon disputed, and does not appear to be supported by well-ascertained facts. The question of a repetition of the experiment over a wide area has been again agitated within a very few years in Lombardy; but the doubts expressed by very able physicists as to its efficacy, and as to the point whether hail is an electrical phenomenon, have discouraged its advocates from attempting it.] which the learned curate of Rivolta advised to erect, with sheaves of straw set up vertically, over a great extent of cultivated country, are but a Liliputian imago of the vast paragrandini, pines, larches, and fire, which nature had planted by millions on the crests and ridges of the Alps and the Apennines." [Footnote: Cenni sulla Importansa e Coltura dei Boschi, p. 6.] "Electrical action being diminished," says Meguscher, "and the rapid congelation of vapors by the abstraction of heat being impeded by the influence of the woods, it is rare that hail or waterspouts are produced within the precincts of a large forest when it is assailed by the tempest." [Footnote: Memoria sui Boschi, etc., p. 44.] Arthur Young was told that since the forests which covered the mountains between the Riviera and the county of Montferrat had disappeared, hail had become more destructive in the district of Acqui, [Footnote: Travels in Italy, chap. iii.] and a similar increase in the frequency and violence of hail-storms in the neighborhood of Saluzzo and Mondovi, the lower part of the Valtelline, and the territory of Verona and Vicenza, is probably to be ascribed to a similar cause. [Footnote: Le Alpi che cingono l'Italia, i., p. 377. See "On the Influence of the Forest in Preventing Hail-storms," a paper by Becquerel, in the Memoires de l'Academie des Sciences, vol. xxxv. The conclusion of this eminent physicist is, that woods do excercise, both within their own limits and in their vicinity, the influence popularly ascribed to them in this respect, and that the effect is probably produced partly by mechanical and partly by electrical action.] Chemical Influence of the Forest. We know that the air in a close apartment is appreciably affected through the inspiration and expiration of gases by plants growing in it. The same operations are performed on a gigantic scale by the forest, and it has even been supposed that the absorption of carbon, by the rank vegetation of earlier geological periods, occasioned a permanent change in the constitution of the terrestrial atmosphere. [Footnote: "Long before the appearance of man, ... they [the forests] had robbed the atmosphere of the enormous quantity of carbonic acid it contained, and thereby transformed it into respirable air. Trees heaped upon trees had already filled up the ponds and marshes, and buried with them in the bowels of the earth--to restore it to us, after thousands of ages, in the form of bituminous coal and of anthracite--the carbon which was destined to become, by this wonderful condensation, a precious store of future wealth."--Clave, Etudes sur l'Economie Forestiere, p. 13. This opinion of the modification of the atmosphere by vegetation is contested. Mossman ascribes the great luxuriance and special character of the Australian and New Zealand forests, as well as other peculiarities of the vegetation of the Southern hemisphere, to a supposed larger proportion of carbon in the atmosphere of that hemisphere, though the fact of such excess does not appear to have been established by chemical analysis. Mossman, Origin of the Seasons. Edinburgh, 1869. Chaps. xvi. and xvil.] To the effects thus produced are to be added those of the ultimate gaseous decomposition of the vast vegetable mass annually shed by trees, and of their trunks and branches when they fall a prey to time. But the quantity of gases thus abstracted from and restored to the atmosphere is inconsiderable--infinitesimal, one might almost say--in comparison with the ocean of air from which they are drawn and to which they return; and though the exhalations from bogs, and other low grounds covered with decaying vegetable matter, are highly deleterious to human health, yet, in general, the air of the forest is hardly chemically distinguishable from that of the sand plains, and we can as little trace the influence of the woods in the analysis of the atmosphere, as we can prove that the mineral ingredients of landsprings sensibly affect the chemistry of the sea. I may, then, properly dismiss the chemical, as I have done the electrical, influences of the forest, and treat them both alike, if not as unimportant agencies, at least as quantities of unknown value in our meteorological equation. [Footnote: Schacht ascribes to the forest a specific, if not a measurable, influence upon the constitution of the atmosphere. "Plants imbibe from the air carbonic acid and other gaseous or volatile products exhaled by animals or developed by the natural phenomena of decomposition. On the other hand, the vegetable pours into the atmosphere oxygen, which is taken up by animals and appropriated by them. The tree, by means of its leaves and its young herbaceous twigs, presents a considerable surface for absorption and evaporation; it abstracts the carbon of carbonic acid, and solidifies it in wood, fecula, and a multitude of other compounds. The result is that a forest withdraws from the air, by its great absorbent surface, much more gas than meadows or cultivated fields, and exhales proportionally a considerably greater quantity of oxygen. The influence of the forests on the chemical composition of the atmosphere is, in a word, of the highest importance."--Les Arbres, p. 111. See on this subject a paper by J. Jamin, in the Revue des Deux Mondes for Sept. 15, 1864; and, on the effects of human industry on the atmosphere, an article in Aus der Natur, vol. 29, 1864, pp. 443, 449, 465, et seq. See also Alfred Maury, Les Forete de la Gaule, p. 107.] Our inquiries upon this branch of the subject will accordingly be limited to the thermometrical and hygrometrical influences of the woods. There is, however, a special protective function of the forest, perhaps, in part, of a chemical nature, which may be noticed here. Trees as a Protection against Malaria. The influence of forests in preventing the diffusion of miasmatic vapors is not a matter of familiar observation, and perhaps it does not come strictly within the sphere of the present inquiry, but its importance will justify me in devoting some space to the subject. "It has been observed" (I quote from Becquerel) "that humid air, charged with miasmata, is deprived of them in passing through the forest. Rigaud de Lille observed localities in Italy where the interposition of a screen of trees preserved everything beyond it, while the unprotected grounds were subject to fevers." [Footnote: Becquerel, Des Climats, etc., p. 9.] Few European countries present better opportunities for observation on this point than Italy, because in that kingdom the localities exposed to miasmatic exhalations are numerous, and belts of trees, if not forests, are of so frequent occurrence that their efficacy in this respect can be easily tested. The belief that rows of trees afford an important protection against malarious influences is very general among Italians best qualified by intelligence and professional experience to judge upon the subject. The commissioners, appointed to report on the measures to be adopted for the improvement of the Tuscan Maremme, advised the planting of three or four rows of poplars, Populus alla, in such directions as to obstruct the currents of air from malarious localities, and thus intercept a great proportion of the pernicious exhalations." [Footnote: Salvagnoli, Rapporto sul Bonificamento delle Maremme Toscane, pp. xii., 124.] Maury believed that a few rows of sunflowers, planted between the Washington Observatory and the marshy banks of the Potomac, had saved the inmates of that establishment from the intermittent fevers to which they had been formerly liable. Maury's experiments have been repeated in Italy. Large plantations of sunflowers have been made upon the alluvial deposits of the Oglio, above its entrance into the Lake of Iseo, near Pisogne, and it is said with favorable results to the health of the neighborhood. [Footnote: Il Politecnico, Milano, Aprile e Maggio, 1863, p. 35.] In fact, the generally beneficial effects of a forest wall or other vegetable screen, as a protection against noxious exhalations from marshes or other sources of disease, situated to the windward of them, are very commonly admitted. It is argued that, in these cases, the foliage of trees and of other vegetables exercises a chemical as well as a mechanical effect upon the atmosphere, and some, who allow that forests may intercept the circulation of the miasmatic effluvia of swampy soils, or even render them harmless by decomposing them, contend, nevertheless, that they are themselves active causes of the production of malaria. The subject has been a good deal discussed in Italy, and there is some reason to think that under special circumstances the influence of the forest in this respect may be prejudicial rather than salutary, though this does not appear to be generally the case. [Footnote: Salvagnoli, Memorie sulle Maremme Toscane, pp. 213, 214. The sanitary action of the forest has been lately matter of much attention in Italy. See Rendiconti del Congresso Medico del 1869 a Firenze, and especially the important observations of Selmi, Il Miasma Palustre, Padua, 1870, pp. 100 et seq. This action is held by this able writer to be almost wholly chemical, and he earnestly recommends the plantation of groves, at least of belts of trees, as an effectual protection against the miasmatic influence of marshes. Very interesting observations on this point will be found in Ebermayer, Die Physikalischen Einwirkungen des Waldes, Aschaffenburg, 1873, B. I., pp. 237 et seq., where great importance is ascribed to the development of ozone by the chemical action of the forest. The beneficial influence of the ozone of the forest atmosphere on the human system is, however, questioned by some observers. See also the able memoir: Del Miasma vegetale e delle Malattis Miasmatiche of Dr D. Pantaleoni in Lo Sperimentale, vol. xxii., 1870. The necessity of such hygienic improvements as shall render the new capital of Italy a salubrious residence gives great present importance to this question, and it is much to be hoped that the Agro Romano, as well as more distant parts of the Campagna, will soon be dotted with groves and traversed by files of rapidly growing trees. Many forest trees grow with great luxuriance in Italy, and a moderate expense in plantation would in a very few years determine whether any amelioration of the sanitary condition of Rome can be expected from this measure. It is said by recent writers that in India the villages of the natives and the encampments of European troops, situated in the midst or in the neighborhood of groves and of forests, are exempt from cholera. Similar observations were also made in 18S4 in Germany when this terrible disease was raging there. It is hence inferred that forests prevent the spreading of this malady, or rather the development of those unknown influences of which cholera is the result. These influences, if we may believe certain able writers on medical subjects, are telluric rather than meteoric; and they regard it as probable that the uniform moisture of soil in forests may be the immediate cause of the immunity enjoyed by such localities. See an article by Pettenkofer in the Sud-Deutsche Presse, August, 1869; and the observations of Ebermayer in the work above quoted, pp. 246 et seq. In Australia and New Zealand, as well as generally in the Southern Hemisphere, the indigenous trees are all evergreens, and even deciduous trees introduced from the other side of the equator become evergreen. In those regions, even in the most swampy localities, malarious diseases are nearly, if not altogether, unknown. Is this most important fact due to the persistence of the foliage Mossman, Origin of Climates, pp. 374, 393, 410, 425, et seq.] It is, at all events, well known that the great swamps of Virginia and the Carolinas, in climates nearly similar to that of Italy, are healthy even to the white man, so long as the forests in and around them remain, but become very insalubrious when the woods are felled. [Footnote: Except in the seething marshes of northern tropical and subtropical regions, where vegetable decay is extremely rapid, the uniformity of temperature and of atmospheric humidity renders all forests eminently healthful. See Hohensten's observations on this subject, Der Wald, p. 41; also A. Maury, Les Forets de la Gaule, p. 7. The flat and marshy district of the Sologne in France was salubrious until its woods were felled. It then became pestilential, but within the last few years its healthfulness has been restored by forest plantations. Jules Clave in Revue des Deux Mondes for 1st March, 1866, p. 209. There is no question that open squares and parks conduce to the salubrity of cities, and many observers are of opinion that the trees and other vegetables with which such grounds are planted contribute essentially to their beneficial influence. See an article in Aus der Natur, xxii, p. 813.] Trees as Shelter to Ground to the Leeward. As a mechanical obstruction, trees impede the passage of air-currents over the ground, which, as is well known, is one of the most efficient agents in promoting evaporation and the refrigeration resulting from it. [Footnote: It is perhaps too much to say that the influence of trees upon the wind is strictly limited to the mechanical resistance of their trunks, branches, and foliage. So far as the forest, by dead or by living action, raises or lowers the temperature of the air within it, so far it creates upward or downward currents in the atmosphere above it, and, consequently, a flow of air towards or from itself. These air-streams have a certain, though doubtless a very small, influence on the force and direction of greater atmospheric movements.] In the forest, the air is almost quiescent, and moves only as local changes of temperature affect the specific gravity of its particles. Hence there is often a dead calm in the woods when a furious blast is raging in the open country at a few yards' distance. The denser the forest--as, for example, where it consists of spike-leaved trees, or is thickly intermixed with them--the more obvious is its effect, and no one can have passed from the field to the wood in cold, windy weather, without having remarked it. [Footnote: As a familiar illustration of the influence of the forest in checking the movement of winds, I may mention the well-known fact, that the sensible cold is never extreme in thick woods, where the motion of the air is little felt. The lumbermen in Canada and the Northern United States labor in the woods, without inconvenience, when the mercury stands many degrees below the zero of Fahrenheit, while in the open grounds, with only a moderate breeze, the same temperature is almost insupportable. The engineers and firemen of locomotives, employed on railways running through forests of any considerable extent, observe that, in very cold weather, it is much easier to keep up the steam while the engine is passing through the woods than in the open ground. As soon as the train emerges from the shelter of the trees the steam-gauge falls, and the stoker is obliged to throw in a liberal supply of fuel to bring it up again. Another less frequently noticed fact, due, no doubt, in a great measure to the immobility of the air, is, that sounds are transmitted to incredible distances in the unbroken forest. Many instances of this have fallen under my own observation, and others, yet more striking, have been related to me by credible and competent witnesses familiar with a more primitive condition of the Anglo-American world. An acute observer of natural phenomena, whose childhood and youth were spent in the interior of one of the newer New England States, has often told me that when he established his home in the forest, he always distinctly heard, in still weather, the plash of horses' feet, when they forded a small brook nearly seven-eighths of a mile from his house, though a portion of the wood that intervened consisted of a ridge seventy or eighty feet higher than either the house or the ford. I have no doubt that, in such cases, the stillness of the air is the most important element in the extraordinary transmissibilty of sound; but it must be admitted that the absence of the multiplied, and confused noises, which accompany human industry in countries thickly peopled by man, contributes to the same result. We become, by habit, almost insensible to the familiar and never-resting voices of civilization in cities and towns; but the indistinguishable drone, which sometimes escapes even the ear of him who listens for it, deadens and often quite obstructs the transmission of sounds which would otherwise be clearly audible. An observer, who wishes to appreciate that hum of civic life which he cannot analyze, will find an excellent opportunity by placing himself on the hill of Capo di Monte at Naples, in the line of prolongation of the street called Spaccanapoli. It is probably to the stillness of which I have spoken that we are to ascribe the transmission of sound to great distances at sea in calm weather. In June, 1853, I and my family were passengers on board a ship-of-war bound up the Aegean. On the evening of the 27th of that month, as we were discussing, at the tea-table, some observations of Humboldt on this subject, the captain of the ship told us that he had once heard a single gun at sea at the distance of ninety nautical miles. The next morning, though a light breeze had sprung up from the north, the sea was of glassy smoothness when we went on deck. As we came up, an officer told us that he had heard a gun at sunrise, and the conversation of the previous evening suggested the inquiry whether it could have been fired from the combined French and English fleet then lying at Beshika Bay. Upon examination of our position we were found to have been, at sunrise, ninety sea miles from that point. We continued beating up northwards, and between sunrise and twelve o'clock meridian of the 28th, we had made twelve miles northing, reducing our distance from Beshika Bay to seventy-eight sea miles. At noon we heard several guns so distinctly that we were able to count the number. On the 29th we came up with the fleet, and learned from an officer who came on board that a royal salute had been fired at noon on the 28th, in honor of the day as the anniversary of the Queen of England's coronation. The report at sunrise was evidently the morning gun, those at noon the salute. Such cases are rare, because the sea is seldom still, and the [word in Greek] rarely silent, over so great a space as ninety or even seventy-eight nautical miles. I apply the epithet silent to [word in Greek] advisedly. I am convinced that Aeschylus meant the audible laugh of the waves, which is indeed of COUNTLESS multiplicity, not the visible smile of the sea, which, belonging to the great expanse as one impersonation, is single, though, like the human smile, made up of the play of many features.] The action of the forest, considered merely as a mechanical shelter to grounds lying to the leeward of it, might seem to be an influence of too restricted a character to deserve much notice; but many facts concur to allow that it is a most important element in local climate. It is evident that the effect of the forest, as a mechanical impediment to the passage of the wind, would extend to a very considerable distance above its own height, and hence protect while standing, or lay open when felled, a much larger surface than might at first thought be supposed. The atmosphere, movable as are its particles, and light and elastic as are its masses, is nevertheless held together as a continuous whole by the gravitation of its atoms and their consequent pressure on each other, if not by attraction between them, and, therefore, an obstruction which mechanically impedes the movement of a given stratum of air will retard the passage of the strata above and below it. To this effect may often be added that of an ascending current from the forest itself, which must always exist when the atmosphere within the wood is warmer than the stratum of air above it, and must be of almost constant occurrence in the case of cold winds, from whatever quarter, because the still air in the forest is slow in taking up the temperature of the moving columns and currents around and above it. Experience, in fact, has shown that mere rows of trees, and even much lower obstructions, are of essential service in defending vegetation against the action of the wind. Hardy proposes planting, in Algeria, belts of trees at the distance of one hundred metres from each other, as a shelter which experience had proved to be useful in France. [Footnote: Becquerel, Des Climats, etc., p. 179.] "In the valley of the Rhone," says Becquerel, "a simple hedge, two metres in height, is a sufficient protection for a distance of twenty-two metres." [Footnote: Ibid., p. 116. Becquerel's views have been amply confirmed by recent extensive experiments on the bleak, stony, and desolate plain of the Cran in the Department of the Bouches-du-Rhone, which had remained a naked waste from the earliest ages of history. Belts of trees prove a secure protection even against the furious and chilly blasts of the Mistral, and in this shelter plantations of fruit-trees and vegetables, fertilized by the waters and the slime of the Durance, which are conducted and distributed over the Cran, thrive with the greatest luxuriance. [Footnote: Surrell, Etude sur les Torrents, 2d edition, 1872, ii, p. 85.] The mechanical shelter acts, no doubt, chiefly as a defence against the mechanical force of the wind, but its uses are by no means limited to this effect. If the current of air which it resists moves horizontally, it would prevent the access of cold or parching blasts to the ground for a great distance; and did the wind even descend at a large angle with the surface, still a considerable extent of ground would be protected by a forest to the windward of it. In the report of a committee appointed in 1836 to examine an article of the forest code of France, Arago observes; "If a curtain of forest on the coasts of Normandy and of Brittany were destroyed, these two provinces would become accessible to the winds from the west, to the mild breezes of the sea. Hence a decrease of the cold of winter. If a similar forest were to be cleared on the eastern border of France, the glacial east wind would prevail with greater strength, and the winters would become more severe. Thus the removal of a belt of wood would produce opposite effects in the two regions." [Footnote: Becquerel, Des Climats, etc., Discours Prelim., vi.] This opinion receives confirmation from an observation of Dr. Dwight, who remarks, in reference to the woods of New England: "Another effect of removing the forest will be the free passage of the winds, and among them of the southern winds, over the surface. This, I think, has been an increasing fact within my own remembrance. As the cultivation of the country has extended further to the north, the winds from the south have reached distances more remote from the ocean, and imparted their warmth frequently, and in such degrees as, forty years since, were in the same places very little known. This fact, also, contributes to lengthen the summer and to shorten the winter half of the year." [Footnote: Travels, i., p. 61.] It is thought in Italy that the clearing of the Apennines has very materially affected the climate of the valley of the Po. It is asserted in Le Alpi che cingono l'Italia that: "In consequence of the felling of the woods on the Apennines, the sirocco prevails greatly on the right bank of the Po, in the Parmesan territory, and in a part of Lombardy; it injures the harvests and the vineyards, and sometimes ruins the crops of the season. To the same cause many ascribe the meteorological changes in the precincts of Modena and of Reggio. In the communes of these districts, where formerly straw roofs resisted the force of the winds, tiles are now hardly sufficient; in others, where tiles answered for roofs, large slabs of stone are now ineffectual; and in many neighboring communes the grapes and the grain are swept off by the blasts of the south and south-west winds." According to the same authority, the pinery of Porto, near Ravenna--which is twenty miles long, and is one of the oldest pine woods in Italy--having been replanted with resinous trees after it was unfortunately cut, has relieved the city from the sirocco to which it had become exposed, and in a great degree restored its ancient climate. [Footnote: Le Alpi che cingono l'Italia, pp. 370, 371.] The felling of the woods on the Atlantic coast of Jutland has exposed the soil not only to drifting sands, but to sharp sea-winds, that have exerted a sensible deteriorating effect on the climate of that peninsula, which has no mountains to serve at once as a barrier to the force of the winds, and as a storehouse of moisture received by precipitation or condensed from atmospheric vapors. [Footnote: Bergsoe, Reventlovs Virksomhed, ii., p. 125. The following well-attested instance of a local change of climate is probably to be referred to the influence of the forest as a shelter against cold winds. To supply the extraordinary demand for Italian iron occasioned by the exclusion of English iron in the time of Napoleon I., the furnaces of the valleys of Bergamo were stimulated to great activity. "The ordinary production of charcoal not sufficing to feed the furnaces and the forges, the woods were felled, the copses cut before their time, and the whole economy of the forest was deranged. At Piazzatorre there was such a devastation of the woods, and consequently such an increased severity of climate, that maize no longer ripened. An association, formed for the purpose, effected the restoration of the forest, and maize flourishes again in the fields of Piazzatorre." --Report by G. Rosa, in Il Politecnico, Dicembre, 1861, p. 614. Similar ameliorations have been produced by plantations in Belgium. In an interesting series of articles by Bande, entitled, "Les Cotes de la Manche," in the Revue des Deux Mondes, I find this statement: "A spectator, placed on the famous bell-tower of the cathedral of Antwerp, saw, not long since, on the opposite side of the Schelde, only a vast desert plain; now he sees a forest, the limits of which are confounded with the horizon. Let him enter within its shade. The supposed forest is but a system of regular rows of trees, the oldest of which is not forty years of age. These plantations have ameliorated the climate which had doomed to sterility the soil where they are planted. While the tempest is violently agitating their tops, the air a little below is still, and sands far more barren than the plateau of La Hague have been transformed, under their protection, into fertile fields."--Revue des Deux Mondes, January, 1859, p. 277.] The local retardation of spring, so much complained of in Italy, France, and Switzerland, and the increased frequency of late frosts at that season, appear to be ascribable to the admission of cold blasts to the surface, by the felling of the forests which formerly both screened it as by a wall, and communicated the warmth of their soil to the air and earth to the leeward. Caimi states that since the cutting down of the woods of the Apennines, the cold winds destroy or stunt the vegetation, and that, in consequence of "the usurpation of winter on the domain of spring," the district of Mugello has lost all its mulberries, except the few which find in the lee of buildings a protection like that once furnished by the forest. [Footnote: Cenni sulla Importanza e Coltura dei Boschi, p. 31.] The department of Ardeche, which now contains not a single considerable wood, has experienced within thirty years a climatic disturbance, of which the late frosts, formerly unknown in the country, are one of the most melancholy effects. Similar results have been observed in the plain of Alsace, in consequence of the denudation of several of the crests of the Vosges. [Footnote: Clave, Etudes, p. 44.] [Footnote It has been observed in Sweden that the spring, in many districts where the forests have been cleared off, now comes on a fortnight later than in the last century.--Asbjornsen, Om Skovene i norge, p. 101.] Dussard, as quoted by Ribbe, [Footnote: La Provence au point de vue des Torrents et des Inondations, p. 10. Dussard is doubtless historically inaccurate in making the origin of the mistral so late as the time of Augustus. Diodorus Siculus, who was a contemporary of Julius Caesar, describes the north-west winds in Gaul as violent enough to hurl along stones as large as the fist with clouds of sand and gravel, to strip travellers of their arms and clothing, and to throw mounted men from their horses. Bibliotheca Historica, lib. v., c. xxvi. Diodorus, it is true, is speaking of the climate of Gaul in general, but his description can hardly refer to anything but the mistral of South-eastern France.] maintains that even the MISTRAL, or north-west wind, whose chilling blasts are so fatal to tender vegetation in the spring, "is the child of man, the result of his devastations." "Under the reign of Augustus," continues he, "the forests which protected the Cevennes were felled, or destroyed by fire, in mass. A vast country, before covered with impenetrable woods--powerful obstacles to the movement and even to the formation of hurricanes--was suddenly denuded, swept bare, stripped, and soon after, a scourge hitherto unknown, struck terror over the land from Avignon to the Bouches-du-Rhone, thence to Marseilles, and then extended its ravages, diminished indeed by a long career which had partially exhausted its force, over the whole maritime frontier. The people thought this wind a curse sent of God. They raised altars to it and offered sacrifices to appease its rage." It seems, however, that this plague was less destructive than at present, until the close of the sixteenth century, when further clearings had removed most of the remaining barriers to its course. Up to that time, the north-west wind appears not to have attained to the maximum of specific effect which now characterizes it as a local phenomenon. Extensive districts, from which the rigor of the seasons has now banished valuable crops, were not then exposed to the loss of their harvests by tempests, cold, or drought. The deterioration was rapid in its progress. Under the Consulate, the clearings had exerted so injurious an effect upon the climate, that the cultivation of the olive had retreated several leagues, and since the winters and springs of 1820 and 1836, this branch of rural industry has been abandoned in a great number of localities where it was advantageously pursued before. The orange now flourishes only at a few sheltered points of the coast, and it is threatened even at Hyeres, where the clearing of the hills near the town has proved very prejudicial to this valuable tree. Marchand informs us that, since the felling of the woods, late spring frosts are more frequent in many localities north of the Alps; that fruit-trees thrive no longer, and that it is difficult even to raise young fruit-trees. [Footnote: Ueber die Entwaldung der Gebirge, p. 28. Interesting facts and observations on this point will be found in the valuable Report on the Effects of the Destruction of the Forests in Wisconsin, by LAPHAM and others, pp. 6, 18, 20.] Influence of the Forest, considered as Inorganic Matter, on Temperature. The evaporation of fluids, and the condensation and expansion of vapors and gases, are attended with changes of temperature; and the quantity of moisture which the air is capable of containing, and of course, other things being equal, the evaporation, rise and fall with the thermometer. The hygroscopical and the thermoscopical conditions of the atmosphere are, therefore, inseparably connected as reciprocally dependent quantities, and neither can be fully discussed without taking notice of the other. The leaves of living trees exhale enormous quantities of gas and of aqueous vapor, and they largely absorb gases, and, under certain conditions, probably also water. Hence they affect more or less powerfully the temperature as well as the humidity of the air. But the forest, regarded purely as inorganic matter, and without reference to its living processes of absorption and exhalation of gases and of water, has, as an absorbent, a radiator and a conductor of heat, and as a mere covering of the ground, an influence on the temperature of the air and the earth, which may be considered by itself. Absorbing and Emitting Surface. A given area of ground, as estimated by the every-day rule of measurement in yards or acres, presents always the same apparent quantity of absorbing, radiating, and reflecting surface; but the real extent of that surface is very variable, depending, as it does, upon its configuration, and the bulk and form of the adventitious objects it bears upon it; and, besides, the true superficies remaining the same, its power of absorption, radiation, reflection, and conduction of heat will be much affected by its consistence, its greater or less humidity, and its color, as well as by its inclination of plane and exposure. An acre of clay, rolled hard and smooth, would have great reflecting power, but its radiation would be much increased by breaking it up into clods, because the actually exposed surface would be greater, though the outline of the field remained the same. The inequalities, natural or artificial, which always occur in the surface of ordinary earth, affect in the same way its quantity of superficies acting upon the temperature of the atmosphere, and acted on by it, though the amount of this action and reaction is not susceptible of measurement. Analogous effects are produced by other objects, of whatever form or character, standing or lying upon the earth, and no solid can be placed upon a flat piece of ground, without itself exposing a greater surface than it covers. This applies, of course, to forest trees and their leaves, and indeed to all vegetables, as well as to other prominent bodies. If we suppose forty trees to be planted on an acre, one being situated in the centre of every square of two rods the side, and to grow until their branches and leaves everywhere meet, it is evident that, when in full foliage, the trunks, branches, and leaves would present an amount of thermoscopic surface much greater than that of an acre of bare earth; and besides this, the fallen leaves lying scattered on the ground, would somewhat augment the sum-total. [Footnote: "The Washington elm at Cambridge--a tree of no extraordinary size--was some years ago estimated to produce a crop of seven millions of leaves, exposing a surface of two hundred thousand square feet, or about five acres of foliage."--Gray, First Lessons in Botany and Vegetable Physiology.] On the other hand, the growing leaves of trees generally form a succession of stages, or, loosely speaking, layers, corresponding to the annual growth of the branches, and more or less overlying each other. This disposition of the foliage interferes with that free communication between sun and sky above, and leaf-surface below, on which the amount of radiation and absorption of light depends. From all these considerations, it appears that though the effective thermoscopic surface of a forest in full leaf does not exceed that of bare ground in the same proportion as does its measured superficies, yet the actual quantity of area capable of receiving and emitting heat must be greater in the former than in the latter case. [Footnote: See, on this particular point, and on the general influence of the forest on temperature, Humboldt, Ansichten der Natur, i., 158.] It must further be remembered that the form and texture of a given surface are important elements in determining its thermoscopic character. Leaves are porous, and admit air and light more or less freely into their substance; they are generally smooth and even glazed on one surface; they are usually covered on one or both sides with spicula, and they very commonly present one or more acuminated points in their outline--all circumstances which tend to augment their power of emitting heat by reflection or radiation. Direct experiment on growing trees is very difficult, nor is it in any case practicable to distinguish how far a reduction of temperature produced by vegetation is due to radiation, and how far to exhalation of the gaseous and watery fluids of the plant; for both processes usually go on together. But the frigorific effect of leafy structure is well observed in the deposit of dew and the occurrence of hoarfrost on the foliage of grasses and other small vegetables, and on other objects of similar form and consistence, when the temperature of the air a few feet above has not been brought down to the dew-point, still less to 32 degrees, the degree of cold required to congeal dew to frost. [Footnote: The leaves and twigs of plants may be reduced by radiation to a temperature lower than that of the ambient atmosphere, and even be frozen when the air in contact with them is above 32 degrees. Their temperature may be communicated to the dew deposited on them and thus this dew be converted into frost when globules of watery fluid floating in the atmosphere near them, in the condition of fog or vapor, do not become congealed. It has long been known that vegetables can be protected against frost by diffusing smoke through the atmosphere above them. This method has been lately practised in France on a large scale: vineyards of forty or fifty acres have been protected by placing one or two rows of pots of burning coal-tar, or of naphtha, along the north side of the vineyard, and thus keeping up a cloud of smoke for two or three hours before and after sunrise. The expense is said to be small, and probably it might be reduced by mixing some less combustible substance, as earth, with the fluid, and thus checking its too rapid burning. The radiating and refrigerating power of objects by no means depends on their form alone. Melloni cut sheets of metal into the shape of leaves and grasses, and found that they produced little cooling effect, and were not moistened under atmospheric conditions which determined a plentiful deposit of dew on the leaves of vegetables.] We are also to take into account the action of the forest as a conductor of heat between the atmosphere and the earth. In the most important countries of America and Europe, and especially in those which have suffered most from the destruction of the woods, the superficial strata of the earth are colder in winter, and warmer in summer, than those a few inches lower, and their shifting temperature approximates to the atmospheric mean of the respective seasons. The roots of large trees penetrate beneath the superficial strata, and reach earth of a nearly constant temperature, corresponding to the mean for the entire year. As conductors, they convey the heat of the atmosphere to the earth when the earth is colder than the air, and transmit it in the contrary direction when the temperature of the earth is higher than that of the atmosphere. Of course, then, as conductors, they tend to equalize the temperature of the earth and the air. In countries where the questions I am considering have the greatest practical importance, a very large proportion, if not a majority, of the trees are of deciduous foliage, and their radiating as well as their shading surface is very much greater in summer than in winter. In the latter season, they little obstruct the reception of heat by the ground or the radiation from it; whereas, in the former, they often interpose a complete canopy between the ground and the sky, and materially interfere with both processes. Dead Products of Trees. Besides this various action of standing trees, considered as inorganic matter, the forest exercises, by the annual moulting of its foliage, still another influence on the temperature of the earth, and, consequently, of the atmosphere which rests upon it. If we examine the constitution of the superficial soil in a primitive or an old and undisturbed artificially planted wood, we find, first, a deposit of undecayed leaves, twigs, and seeds, lying in loose layers on the surface; then, more compact beds of the same materials in incipient, and, as we descend, more and more advanced, stages of decomposition; then, a mass of black mould, in which traces of organic structure are hardly discoverable except by microscopic examination; then, a stratum of mineral soil, more or less mixed with vegetable matter carried down into it by water, or resulting from the decay of roots; and, finally, the inorganic earth or rock itself. Without this deposit of the dead products of trees, this latter would be the superficial stratum, and as its powers of absorption, radiation, and conduction of heat would differ essentially from those of the layers with which it has been covered by the droppings of the forest, it would act upon the temperature of the atmosphere, and be acted on by it, in a very different way from the leaves and mould which rest upon it. Dead leaves, still entire, or partially decayed, are very indifferent conductors of light, and, therefore, though they diminish the warming influence of the summer sun on the soil below them, they, on the other hand, prevent the escape of heat from that soil in winter, and, consequently, in cold climates, even when the ground is not covered by a protecting mantle of snow, the earth does not freeze to as great a depth in the wood as in the open field. Specific Heat. Trees, considered as organisms, produce in themselves, or in the air, a certain amount of heat, by absorbing and condensing atmospheric gases, and they exert an opposite influence by absorbing water and exhaling it in the form of vapor; but there is still another mode by which their living processes may warm the air around them, independently of the thermometric effects of condensation and evaporation. The vital heat of a dozen persons raises the temperature of a room. If trees possess a specific temperature of their own, an organic power of generating heat like that with which the warm-blooded animals are gifted, though by a different process, a certain amount of weight is to be ascribed to this element in estimating the action of the forest upon atmospheric temperature. Boussingault remarks: "In many flowers there has been observed a very considerable evolution of heat, at the approach of fecundation. In certain arums the temperature rises to 40 degrees or 50 degrees Cent. [= 104 degrees or 122 degrees Fahr.] It is very probable that this phenomenon in general, and varies only in the intensity which it is manifested." [Footnote: Economie Rurale, i., p. 22.] If we suppose the fecundation of the flowers of forest trees to be attended with a tenth only of this calorific power, they could not fail to exert an important influence on the warmth of the atmospheric strata in contact with them. Experiments by Meguscher, in Lombardy, led that observer to conclude "that the wood of a living tree maintains a temperature of + 12 degrees or 18 degrees Cent. [= 54 degrees, 56 degrees Fahr.] when the temperature of the air stands at 3 degrees, 7 degrees, and 8 degrees [= 37 degrees, 46 degrees, 47 degrees F.] above zero, and that the internal warmth of the tree does not rise and fall in proportion to that of the atmosphere. So long as the latter is below 18 degrees [= 67 degrees Fahr.], that of the tree is always the highest; but if the temperature of the air rises to 18 degrees, that of the vegetable growth is the lowest. Since then, trees maintain at all seasons a constant mean temperature of 12 degrees [= 54 degrees Fahr.], it is easy to see why the air in contact with the forest must be warmer in winter, cooler in summer than in situations where it is deprived of that influence." [Footnote: Memoria Sur Boschi Della Lombardia, p. 45. The results of recent experiments by Becquerel do not accord with those obtained by Meguscher, and the former eminent physicist holds that "a tree is warmed in the air like any inert body." At the same time he asserts, as a fact well ascertained by experiment, that "vegetables possess in themselves the power or resisting extreme cold for a certain length of time,.... and hence it is believed that there may exist in the organism of plants a force, independent of the conduction of caloric, which resists a degree of cold above the freezing-point." In a following page he cites observations made by Bugeaud, under the parallel of 58 degrees N. L., between the months of November and June, during most of which time, of course, vegetable life was in its deepest lethargy. Bugeaud found that when the temperature of the air was at -34.60 degrees, that of a poplar was only at -29.70 degrees, which certainly confirms the doctrine that trees exercise a certain internal resistance against cold.] Professor Henry says: "As a general deduction from chemical and mechanical principles, we think no change of temperature is ever produced where the actions belonging to one or both of these principles are not present. Hence, in midwinter, when all vegetable functions are dormant, we do not believe that any heat is developed by a tree, or that its interior differs in temperature from its exterior further than it is protected from the external air. The experiments which have been made on this point, we think, have been directed by a false analogy. During the active circulation of the sap and the production of new tissue, variations of temperature belonging exclusively to the plant may be observed; but it is inconsistent with general principles that heat should be generated where no change is taking place." [Footnote: United States Patent Office Report for 1857, p. 504.] There can be no doubt that moisture is given, out by trees and evaporated in extremely cold winter weather, and unless new fluid were supplied from the roots by the exercise of some vital function, the tree would be exhausted of its juices before winter was over. But this is not observed to be the fact, and, though the point is disputed, respectable authorities declare that "wood felled in the depth of winter is the heaviest and fullest of sap." [Footnote: Rossmassler, Der Wald, p. 158.] Warm weather in winter, of too short continuance to affect the temperature of the ground sensibly, stimulates a free flow of sap in the maple. Thus, in the last week of December, 1862, and the first week of January, 1863, sugar was made from that tree in various parts of New England. "A single branch of a tree, admitted into a warm room in winter through an aperture in a window, opened its buds and developed its leaves, while the rest of the tree in the external air remained in its winter sleep." [Footnote: Ibid., p. 160.] Like facts are matter of every-day observation in graperies where the vine is often planted outside the wall, the stem passing through an aperture into the warm interior. The roots, of course, stand in ground of the ordinary winter temperature, but vegetation is developed in the branches at the pleasure of the gardener. The roots of forest trees in temperate climates remain, for the most part, in a moist soil, of a temperature not much below the annual mean, through the whole winter; and we cannot account for the uninterrupted moisture of the tree, unless we suppose that the roots furnish a constant supply of water. Atkinson describes a ravine in a valley in Siberia, which was filled with ice to the depth of twenty-five feet. Poplars were growing in this ice, which was thawed to the distance of some inches from the stem. But the surface of the soil beneath it must have remained still frozen, for the holes around the trees were full of water resulting from its melting, and this would have escaped below if the ground had been thawed. In this case, although the roots had not thawed the thick covering of earth above them, the trunks must have melted the ice in contact with them. The trees, when observed by Atkinson, were in full leaf, but it does not appear at what period the ice around their stems had melted. From these facts, and others of the like sort, it would seem that "all vegetable functions are" not absolutely "dormant in winter, and, therefore, that trees may give out SOME heat even at that season." [Footnote: All evergreens, even the broad-leaved trees, resist frosts of extraordinary severity better than the deciduous trees of the same climates. Is not this because the vital processes of trees of persistent foliage are less interrupted during winter than those of trees which annually shed their leaves, and that therefore more organic heat is developed? In crossing Mont Cenis in October, 1869, when the leaves of the larches on the northern slope and near the top of the mountain were entirely dead and turned brown, I observed that these trees were completely white with hoar-frost. It was a wonderful sight to see how every leaf was covered with a delicate deposit of frozen aqueous vapor, which gave the effect of the most brilliant silver. On the other band, the evergreen coniferae, which were growing among the larches, and therefore in the same conditions of exposure, were almost entirely free from frost. The contrast between the verdure of the leaves of the evergreens and the crystalline splendor of those of the larches was strikingly beautiful. Was this fact due to a difference in the color and structure of the leaves, or rather is it a proof of a vital force of resistance to cold in the living foliage of the evergreen tree The low temperature of air and soil at which, in the frigid zone, as well as in warmer latitudes under special circumstances, the processes of vegetation go on, seems to necessitate the supposition that all the manifestations of vegetable life are attended with an evolution of heat. In the United States it is common to protect ice, in ice-houses, by a covering of straw, which naturally sometimes contains kernels of grain. These often sprout, and even throw out roots and leaves to a considerable length, in a temperature very little above the freezing-point. Three or four years since I saw a lump of very clear and apparently solid ice, about eight inches long by six thick, on which a kernel of grain had sprouted in an ice-house, and sent half a dozen or more very slender roots into the pores of the ice and through the whole length of the lump. The young plant must have thrown out a considerable quantity of heat; for though the ice was, as I have said, otherwise solid, the pores through which the roots passed were enlarged to perhaps double the diameter of the fibres, but still not so much as to prevent the retention of water in them by capillary attraction.] It does not appear that observations have been made on the special point of the development of heat in forest trees during florification, or at any other period of intense vital action; and hence an important element in the argument remains undetermined. The "circulation of the sap" commences at a very early period in the spring, and the temperature of the air in contact with trees may then be sufficiently affected by heat evolved in the vital processes of vegetation, to raise the thermometric mean of wooded countries for that season, and, of course, for the year. The determination of this point is of much greater importance to vegetable physiology than the question of the winter temperature of trees, because a slight increment of heat in the trees of a forest might so affect the atmosphere in contact with them as to make possible the growing of many plants in or near the wood which could not otherwise he reared in that climate. The evaporation of the juices of trees and other plants is doubtless their most important thermoscopic function, and as recent observations lead to the conclusion that the quantity of moisture exhaled by vegetables has been hitherto underrated, we must ascribe to this element a higher value than has been usually assigned to it as a meteorological influence. The exhalation and evaporation of the juices of trees, by whatever process effected, take up atmospheric heat and produce a proportional refrigeration. This effect is not less real, though to common observation less sensible, in the forest than in meadow or pasture land, and it cannot be doubted that the local temperature is considerably affected by it. But the evaporation that cools the air diffuses through it, at the same time, a medium which powerfully resists the escape of heat from the earth by radiation. Visible vapors, fogs and clouds, it is well known, prevent frosts by obstructing radiation, or rather by reflecting back again the heat radiated by the earth, just as any mechanical screen would do. On the other hand, fogs and clouds intercept the rays of the sun also, and hinder its heat from reaching the earth. The invisible vapors given out by leaves impede the passage of heat reflected and radiated by the earth and by all terrestrial objects, bat oppose much less resistance to the transmission of direct solar heat, and indeed the beams of the sun seem more scorching when received through clear air charged with uncondensed moisture than after passing through a dry atmosphere. Hence the reduction of temperature by the evaporation of moisture from vegetation, though sensible, is less than it would be if water in the gaseous state were as impervious to heat given out by the sun as to that emitted by terrestrial objects. Total Influence of the Forest on Temperature. It has not yet been found practicable to measure, sum up, and equate the total influence of the forest, its processes and its products, dead and living, upon temperature, and investigators differ much in their conclusions on this subject. It seems probable that in every particular case the result is, if not determined, at least so much modified by local conditions which are infinitely varied, that no general formula is applicable to the question. In the report to which I referred on page 163, Gay-Lussac says; "In my opinion we have not yet any positive proof that the forest has, in itself, any real influence on the climate of a great country, or of a particular locality. By closely examining the effects of clearing off the woods, we should perhaps find that, far from being an evil, it is an advantage; but these questions are so complicated when they are examined in a climatological point of view, that the solution of them is very difficult, not to say impossible." Becquerel, on the other hand, considers it certain that in tropical climates the destruction of the forests is accompanied with an elevation of the mean temperature, and he thinks it highly probable that it has the same effect in the temperate zones. The following is the substance of his remarks on this subject: "Forests act as frigorific causes in three ways: "1. They shelter the ground against solar irradiation and maintain a greater humidity. "2. They produce a cutaneous transpiration by the leaves. "3. They multiply, by the expansion of their branches, the surfaces which are cooled by radiation. "These three causes acting with greater or less force, we must, in the study of the climatology of a country, take into account the proportion between the area of the forests and the surface which is bared of trees and covered with herbs and grasses. "We should be inclined to believe, a priori, according to the foregoing considerations, that the clearing of the woods, by raising the temperature and increasing the dryness of the air, ought to react on climate. There is no doubt that, if the vast desert of the Sahara were to become wooded in the course of ages, the sands would cease to be heated as much as at the present epoch, when the mean temperature is twenty-nine degrees [Centigrade, = 85 degrees Fahr.]. In that case, the ascending currents of warm air would cease, or be less warm, and would not contribute, by descending in our latitudes, to soften the climate of Western Europe. Thus the clearing of a great country may react on the climates of regions more or less remote from it. "The observations by Boussingault leave no doubt on this point. This writer determined the mean temperature of wooded and of cleared points, under the same latitude, and at the same elevation above the sea, in localities comprised between the eleventh degree of north and the fifth degree of south latitude, that is to say, in the portion of the tropics nearest to the equator, and where radiation tends powerfully during the night to lower the temperature under a sky without clouds." [Footnote: Becquerel, Des Climats, etc., pp. 139-141.] The result of these observations, which has been pretty generally adopted by physicists, is that the mean temperature of cleared land in the tropics appears to be about one degree Centigrade, or a little less than two degrees of Fahrenheit, above that of the forest. On page 147 of the volume just cited, Becquerel argues that, inasmuch as the same and sometimes a greater difference is found in favor of the open ground, at points within the tropics so elevated as to have a temperate or even a polar climate, we must conclude that theforests in Northern America exert a refrigerating influence equally powerful. But the conditions of the soil are so different in the two regions compared, that I think we cannot, with entire confidence, reason from the one to the other, and it is much to be desired that observations be made on the summer and winter temperature of both the air and the ground in the depths of the North American forests, before it is too late. Recent inquiries have introduced a new element into the problem of the influence of the forest on temperature, or rather into the question of the thermometrical effects of its destruction. I refer to the composition of the soil in respect to its hygroscopicity or aptitude to absorb humidity, whether in a liquid or a gaseous form, and to the conducting power of the particles of which it is composed. [Footnote: Composition, texture, and color of soil are important elements to be considered in estimating the effects of the removal of the forest upon its thermoscopic action. "Experience has proved," says Becquerel, "that when the soil is bared, it becomes more or less heated [by the rays of the sun] according to the nature and the color of the particles which compose it, and according to its humidity, and that, in the refrigeration resulting from radiation, we must take into the account the conducting power of those particles also. Other things being equal, siliceous and calcareous sands, compared in equal volumes with different argillaceous earths, with calcareous powder or dust, with humus, with arable and with garden earth, are the soils which least conduct heat. It is for this reason that sandy ground, in summer, maintains a high temperature even during the night. We may hence conclude that when a sandy soil is stripped of wood, the local temperature will be raised. After the sands follow successively argillaceous, arable, and garden ground, then humus, which occupies the lowest rank. "The retentive power of humus is but half as great as that of calcareous sand. We will add that the power or retaining heat is proportional to the density. It has also a relation to the magnitude of the particles. It is for this reason that ground covered with siliceous pebbles cools more slowly than siliceous sand, and that pebbly soils are best suited to the cultivation of the vine, because they advance the ripening of the grape more rapidly than chalky and clayey earths, which cool quickly. Hence we see that in examining the calorific effects of clearing forests, it is important to take into account the properties of the soil laid bare."--Becquerel, Des Climats et des Sols boises, p. 137.] The hygroscopicity of humus or vegetable earth is much greater than that of any mineral soil, and consequently forest ground, where humus abounds, absorbs the moisture of the atmosphere more rapidly and in larger proportion than common earth. The condensation of vapor by absorption develops heat, and consequently elevates the temperature of the soil which absorbs it, together with that of air in contact with the surface. Von Babo found the temperature of sandy ground thus raised from 68 degrees to 80 degrees F., that of soil rich in humus from 68 degrees to 88 degrees. The question of the influence of the woods on temperature does not, in the present state of our knowledge, admit of precise solution, and, unhappily, the primitive forests are disappearing so rapidly before the axe of the woodman, that we shall never be able to estimate with accuracy the climatological action of the natural wood, though all the physical functions of artificial plantations will, doubtless, one day be approximately known. But the value of trees as a mechanical screen to the soil they cover, and often to ground far to the leeward of them, is most abundantly established, and this agency alone is important enough to justify extensive plantation in all countries which do not enjoy this indispensable protection. Influence of Forests as Inorganic on the Humidity of the Air and the Earth. The most important hygroscopic as well as thermoscopic influence of the forest is, no doubt, that which it exercises on the humidity of the air and the earth, and this climatic action it exerts partly as dead, partly as living matter. By its interposition as a curtain between the sky and the ground it both checks evaporation from the earth, and mechanically intercepts a certain proportion of the dew and the lighter showers, which would otherwise moisten the surface of the soil, and restores it to the atmosphere by exhalation; [Footnote: Mangotti had observed and described, in his usual picturesque way, the retention of rain-water by the foliage and bark of trees, but I do not know that any attempts were made to measure the quantity thus intercepted before the experiments of Becquerel, communicated to the Academy of Sciences in 1866. These experiments embraced three series of observations continued respectively for periods of a year, a month, and two days. According to Becquerel's measurements, the quantity falling on bare and on wooded soil respectively was as 1 to 0.07; 1 to 0.5; and 1 to 0.6, or, in other words, he found that only from five-tenths to sixty-seven hundredths of the precipitation reached the ground.--Comptes Rendus de l'Academie des Sciences, 1866. It seemed, indeed, improbable that in rain-storms which last not hours but whole days in succession, so large a proportion of the downfall should continue to be intercepted by forest vegetation after the leaves, the bark, and the whole framework of the trees were thoroughly wet, but the conclusions of this eminent physicist appear to have been generally accepted until the very careful experiments of Mathieu at the Forest-School of Nancy were made known. The observations of Mathieu were made in a plantation of deciduous trees forty-two years old, and were continued through the entire years 1866, 1867, and 1868. The result was that the precipitation in the wood was to that in an open glade of several acres near the forest station as 043 to 1,000, and the proportion in each of the three years was nearly identical. According to Mathieu, then, only 57 thousandths or 5.7 per cent of the precipitation is intercepted by trees.--Surrell, Etude sur les Torrents, 2d ed., ii., p. 98. By order of the Direction of the Forests of the Canton of Berne, a series of experiments on this subject was commenced at the beginning of the year 1869. During the first seven months of the year (the reports for which alone I have seen), including, of course, the season when the foliage is most abundant, as well as that when it is thinnest, the pluviometers in the woods received only fifteen per cent less than those in the open grounds in the vicinity.--Risler, in Revue des Eaux et Forets, of 10th January, 1870.] while in heavier rains, the large drops which fall upon the leaves and branches are broken into smaller ones, and consequently strike the ground with less mechanical force, or are perhaps even dispersed into vapor without reaching it. [Footnote: We are not, indeed, to suppose that the condensation of vapor and the evaporation of water are going on in the same stratum of air at the same time, or, in other words, that vapor is condensed into rain-drops, and rain-drops evaporated, under the same conditions; but rain formed in one stratum may fall through another, where vapor would not be condensed. Two saturated strata of different temperatures may be brought into contact in the higher regions, and discharge large rain-drops, which, it not divided by some obstruction, will reach the ground, though passing through strata which would vaporize them if they were in a state of more minute division.] The vegetable mould, resulting from the decomposition of leaves and of wood, serves as a perpetual mulch to forest-soil by carpeting the ground with a spongy covering which obstructs the evaporation from the mineral earth below, [Footnote: The only direct experiments known to me on the evaporation from the SURFACE of the forest are those of Mathieu.--Surrell, Etude sur les Torrents, 2d ed., ii, p. 99. These experiments were continued from March to December, inclusive, of the year 1868. It was found that during those months the evaporation from a recipient placed on the ground in a plantation of deciduous trees sixty-two years old, was less than one-fifth of that from a recipient of like form and dimensions placed in the open country.] drinks up the rains and melting snows that would otherwise flow rapidly over the surface and perhaps be conveyed to the distant sea, and then slowly gives out, by evaporation, infiltration, and percolation, the moisture thus imbibed. The roots, too, penetrate far below the superficial soil, conduct water along their surface to the lower depths to which they reach, and thus by partially draining the superior strata, remove a certain quantity of moisture out of the reach of evaporation. The Forest as Organic. These are the principal modes in which the humidity of the atmosphere is affected by the forest regarded as lifeless matter. Let us inquire how its organic processes act upon this meteorological element. The commonest observation shows that the wood and bark of living trees are always more or less pervaded with watery and other fluids, one of which, the sap, is very abundant in trees of deciduous foliage when the buds begin to swell and the leaves to develop themselves in the spring. This fluid is drawn principally, if not entirely, from the ground by the absorbent action of the roots, for though Schacht and some other eminent botanical physiologists have maintained that water is absorbed by the leaves and bark of trees, yet most experiments lead to the contrary result, and it is now generally held that no water is taken in by the pores of vegetables. Late observations by Cailletet, in France, however, tend to the establishment of a new doctrine on this subject which solves many difficulties and will probably be accepted by botanists as definitive. Cailletet finds that under normal conditions, that is, when the soil is humid enough to supply sufficient moisture through the roots, no water is absorbed by the leaves, buds, or bark of plants, but when the roots are unable to draw from the earth the requisite quantity of this fluid, the vegetable pores in contact with the atmosphere absorb it from that source. Popular opinion, indeed, supposes that all the vegetable fluids, during the entire period of growth, are drawn from the bosom of the earth, and that the wood and other products of the tree are wholly formed from matter held in solution in the water abstracted by the roots from the ground. This is an error, for the solid matter of the tree, in a certain proportion not important to our present inquiry, is received from the atmosphere in a gaseous form, through the pores of the leaves and of the young shoots, and, as we have just seen, moisture is sometimes supplied to trees by the atmosphere. The amount of water taken up by the roots, however, is vastly greater than that imbibed through the leaves and bark, especially at the season when the sap is most abundant, and when the leaves are yet in embryo. The quantity of water thus received from the air and the earth, in a single year, even by a wood of only a hundred acres, is very great, though experiments are wanting to furnish the data for even an approximate estimate of its measure; for only the vaguest conclusions can be drawn from the observations which have been made on the imbibition and exhalation of water by trees and other plants reared in artificial conditions diverse from those of the natural forest. [Footnote: The experiments of Hales and others on the absorption and exhalation of vegetables are of high physiological interest; but observations on sunflowers, cabbages, hops, and single branches of isolated trees, growing in artificially prepared soils and under artificial conditions, furnish no trustworthy data for computing the quantity of water received and given off by the natural wood.] Flow of Sap. The amount of sap which can be withdrawn from living trees furnishes, not indeed a measure of the quantity of water sucked up by their roots from the ground--for we cannot extract from a tree its whole moisture--but numerical data which may aid the imagination to form a general notion of the powerful action of the forest as an absorbent of humidity from the earth. The only forest-tree known to Europe and North America, the sap of which is largely enough applied to economical uses to have made the amount of its flow a matter of practical importance and popular observation, is the sugar maple, Acer saccharinum, of the Anglo-American Provinces and States. In the course of a single "sugar season," which lasts ordinarily from twenty-five to thirty days, a sugar maple two feet in diameter will yield not less than twenty gallons of sap, and sometimes much more. [Footnote: Emerson (Trees of Massachusetts. p. 403) mentions a maple six feet in diameter, as having yielded a barrel, or thirty-one and a half gallons, of sap in twenty-four hours, and another, the dimensions of which are not stated, as having yielded one hundred and seventy-five gallons in the course of the season. The Cultivator, an American agricultural journal, for June, 1842, states that twenty gallons of sap were drawn in eighteen hours from a single maple, two and a half feet in diameter, in the town of Warner, New Hampshire, and the truth of this account has been verified by personal inquiry made in my behalf. This tree was of the original forest growth, and had been left standing when the ground around it was cleared. It was tapped only every other year, and then with six or eight incisions. Dr. Williams (History of Vermont, i., p. 01) says: "A man much employed in milking maple sugar, found that, for twenty-one days together, a maple-tree discharged seven and a half gallons per day." An intelligent correspondent, of much experience in the manufacture of maple sugar, writes me that a second-growth maple, of about two feet in diameter, standing in open ground, tapped with four incisions, has, for several seasons, generally run eight gallons per day in fair weather. He speaks of a very large tree, from which sixty gallons were drawn in the course of a season, and of another, something more than three feet through, which made forty-two pounds of wet sugar, and must have yielded not less than one hundred and fifty gallons.] This, however, is but a trifling proportion of the water abstracted from the earth by the roots during this season; for all this fluid runs from two or three incisions or auger-holes, so narrow as to intercept the current of comparatively few sap vessels, and besides, experience shows that large as is the quantity withdrawn from the circulation, it is relatively too small to affect very sensibly the growth of the tree. [Footnote: Tapping does not check the growth, but does injure the quality of the wood of maples. The wood of trees often tapped is lighter and less dense than that of trees which have not been tapped, and gives less heat in burning. No difference has been observed in the bursting of the buds of tapped and untapped trees.] The number of large maple-trees on an acre is frequently not less than fifty, [Footnote: Dr. Rush, in a letter to Jefferson, states the number of maples fit for tapping on an acre at from thirty to fifty. "This," observes my correspondent, "is correct with regard to the original growth, which is always more or less intermixed with other trees; but in second growth, composed of maples alone, the number greatly exceeds this. I have had the maples on a quarter of an acre, which I thought about an average of second-growth 'maple orchards,' counted. The number was found to be fifty-two, of which thirty-two were ten inches or more in diameter, and, of course, large enough to tap. This gives two hundred and eight trees to the acre, one hundred and twenty-eight of which were of proper size for tapping."] and of course the quantity of moisture abstracted from the soil by this tree alone is measured by thousands of gallons to the acre. The sugar orchards, as they are called, contain also many young maples too small for tapping, and numerous other trees--two of which, at least, the black birch, Betula lenta, and yellow birch, Betula excelsa, both very common in the same climate, are far more abundant in sap than the maple [Footnote: The correspondent already referred to informs me that a black birch, tapped about noon with two incisions, was found the next morning to have yielded sixteen gallons. Dr. Williams (History of Vermont, i., p. 91) says: "A large birch, tapped in the spring, ran at the rate of five gallons an hour when first tapped. Eight or nine days after, it was found to run at the rate of about two and a half gallons an hour, and at the end of fifteen days the discharge continued in nearly the same quantity. The sap continued to flow for four or five weeks, and it was the opinion of the observers that it must have yielded as much as sixty barrels [l,800 gallons]."]--are scattered among the sugar-trees; for the North American native forests are remarkable for the mixture of their crops. The sap of the maple, and of other trees with deciduous leaves which grow in the same climate, flows most freely in the early spring, and especially in clear weather, when the nights are frosty and the days warm; for it is then that the melting snows supply the earth with moisture in the justest proportion, and that the absorbent power of the roots is stimulated to its highest activity. When the buds are ready to burst, and the green leaves begin to show themselves beneath their scaly covering, the ground has become drier, the absorption by the roots is diminished, and the sap, being immediately employed in the formation of the foliage, can be extracted from the stem in only small quantities. Absorption and Exhalation by Foliage. The leaves now commence the process of absorption, and imbibe both uncombined gases and an unascertained but probably inconsiderable quantity of aqueous vapor from the humid atmosphere of spring which bathes them. The organic action of the tree, as thus far described, tends to the desiccation of air and earth; but when we consider what volumes of water are daily absorbed by a large tree, and how small a proportion of the weight of this fluid consists of matter which, at the period when the flow of sap is freest, enters into new combinations, and becomes a part of the solid framework of the vegetable, or a component of its deciduous products, it becomes evident that the superfluous moisture must somehow be carried back again almost as rapidly as it flows into the tree. At the very commencement of vegetation in spring, some of this fluid certainly escapes through the buds, the nascent foliage, and the pores of the bark, and vegetable physiology tells us that there is a current of sap towards the roots as well as from them. [Footnote: "The elaborated sap, passing out of the leaves, is received into the inner bark, . . . and a part of what descends finds its way even to the ends of the roots, and is all along diffused laterally into the stem, where it meets and mingles with the ascending crude sap or raw material. So there is no separate circulation of the two kinds of sap; and no crude sap exists separately in any part of the plant. Even in the root, where it enters, this mingles at once with some elaborated sap already there."--Gray, How Plants Grow, Section 273.] I do not know that the exudation of water into the earth, through the bark or at the extremities of these latter organs, has been proved, but the other known modes of carrying off the surplus do not seem adequate to dispose of it at the almost leafless period when it is most abundantly received, and it is possible that the roots may, to some extent, drain as well as flood the water-courses of their stem. Later in the season the roots absorb less, and the now developed leaves exhale an increased quantity of moisture into the air. In any event, all the water derived by the growing tree from the atmosphere and the ground is parted with by transpiration or exudation, after having surrendered to the plant the small proportion of matter required for vegetable growth which it held in solution or suspension. [Footnote: Ward's tight glazed cases for raising and especially for transporting plants, go far to prove that water only circulates through vegetables, and is again and again absorbed and transpired by organs appropriated to these functions. Seeds, growing grasses, shrubs, or trees planted in proper earth, moderately watered and covered with a glass bell or close frame of glass, live for months, and even years, with only the original store of air and water. In one of Ward's early experiments, a spire of grass and a fern, which sprang up in a corked bottle containing a little moist earth introduced as a bed for a snail, lived and flourished for eighteen years without a new supply of either fluid. In these boxes the plants grow till the enclosed air is exhausted of the gaseous constituents of vegetation, and till the water has yielded up the assimilable matter it held in solution, and dissolved and supplied to the roots the nutriment contained in the earth in which they are planted. After this, they continue for a long time in a state of vegetable sleep, but if fresh air and water be introduced into the cases, or the plants be transplanted into open ground, they rouse themselves to renewed life, and grow vigorously, without appearing to have suffered from their long imprisonment. The water transpired by the leaves is partly absorbed by the earth directly from the air, partly condensed on the glass, along which it trickles down to the earth, enters the roots again, and thus continually repeats the circuit. See Aus der Natur, 21, B. S. 537.] The hygrometrical equilibrium is then restored, so far as this: the tree yields up again the moisture it had drawn from the earth and the air, though it does not return it each to each; for the vapor carried off by transpiration greatly exceeds the quantity of water absorbed by the foliage from the atmosphere, and the amount, if any, carried back to the ground by the roots. The present estimates of some eminent vegetable physiologists in regard to the quantity of aqueous vapor exhaled by trees and taken up by the atmosphere are much greater than those of former inquirers. Direct and satisfactory experiments on this point are wanting, and it is not easy to imagine how they could be made on a sufficiently extensive and comprehensive scale. Our conclusions must therefore be drawn from observations on small plants, or separate branches of trees, and of course are subject to much uncertainty. Nevertheless, Schleiden, arguing from such analogies, comes to the surprising result, that a wood evaporates ten times as much water as it receives from atmospheric precipitation. [Footnote: Fur Baum und Wald, pp. 46, 47, notes. Pfaff, too, experimenting on branches of a living oak, weighed immediately after being cut from the tree, and again after an exposure to the air for three minutes, and computing the superficial measure of all the leaves of the tree, concludes that an oak-tree evaporates, during the season of growth, eight and a half times the mean amount of rain-fall on an area equal to that shaded by the tree.] In the Northern and Eastern States of the Union, the mean precipitation during the period of forest growth, that is from the swelling of the buds in the spring to the ripening of the fruit, the hardening of the young shoots, and the full perfection of the other annual products of the tree, exceeds on the average twenty-four inches. Taking this estimate, the evaporation from the forest would be equal to a precipitation of two hundred and forty inches, or very nearly one hundred and fifty standard gallons to the square foot of surface. The first questions which suggest themselves upon this statement are: what becomes of this immense quantity of water and from what source does the tree derive it We are told in reply that it is absorbed from the air by the humus and mineral soil of the wood, and supplied again to the tree through its roots, by a circulation analogous to that observed in Ward's air-tight cases. When we recall the effect produced on the soil even of a thick wood by a rain-fall of one inch, we find it hard to believe that two hundred and forty times that quantity, received by the ground between early spring and autumn, would not keep it in a state of perpetual saturation, and speedily convert the forest into a bog. No such power of absorption of moisture by the earth from the atmosphere, or anything approaching it, has ever been shown by experiment, and all scientific observation contradicts the supposition. Schubler found that in seventy-two hours thoroughly dried humus, which is capable of taking up twice its own weight of water in the liquid state, absorbed from the atmosphere only twelve per cent. of its weight of humidity; garden-earth five and one-fifth per cent. and ordinary cultivated soil two and one-third per cent. After seventy-two hours, and, in most of his experiments with thirteen different earths, after forty-eight hours, no further absorption took place. Wilhelm, experimenting with air-dried field-earth, exposed to air in contact with water and protected by a bell-glass, found that the absorption amounted in seventy-two hours to two per cent. and a very small fraction, nearly the whole of which was taken up in the first forty-eight hours. In other experiments with carefully heat-dried field-soil, the absorption was five per cent. in eighty-four hours, and when the water was first warmed to secure the complete saturation of the air, air-dried garden-earth absorbed five and one-tenth per cent. in seventy-two hours. In nature, the conditions are never so favorable to the absorption of vapor as in those experiments. The ground is more compact and of course offers less surface to the air, and, especially in the wood, it is already in a state approaching saturation. Hence, both these physicists conclude that the quantity of aqueous vapor absorbed by the earth from the air is so inconsiderable "that we can ascribe to it no important influence on vegetation." [Footnote: Wilhelm, Der Boden und das Wasser, pp. 14,20.] Besides this, trees often grow luxuriantly on narrow ridges, on steep declivities, on partially decayed stumps many feet above the ground, on walls of high buildings, and on rocks, in situations where the earth within reach of their roots could not possibly contain the tenth part of the water which, according to Schleiden and Pfaff, they evaporate in a day. There are, too, forests of great extent on high bluffs and well-drained table-lands, where there can exist, neither in the subsoil nor in infiltration from neighboring regions, an adequate source of supply for such consumption. It must be remembered, also, that in the wood the leaves of the trees shade each other, and only the highest stratum of foliage receives the full influence of heat and light; and besides, the air in the forest is almost stagnant, while in the experiments of Unger, Marshal, Vaillant, Pfaff and others, the branches were freely exposed to light, sun, and atmospheric currents. Such observations can authorize no conclusions respecting the quantitative action of leaves of forest trees in normal conditions. Further, allowing two hundred days for the period of forest vital action, the wood must, according to Schleiden's position, exhale a quantity of moisture equal to an inch and one-fifth of precipitation per day, and it is hardly conceivable that so large a volume of aqueous vapor, in addition to the supply from other sources, could be diffused through the ambient atmosphere without manifesting its presence by ordinary hygrometrical tests much more energetically than it has been proved to do, and in fact, the observations recorded by Ebermayer show that though the RELATIVE humidity of the atmosphere is considerably greater in the cooler temperature of the wood, its ABSOLUTE humidity does not sensibly differ from that of the air in open ground. [Footnote: Ebermeyer, Die Physikalischen, Einwirkungen des Waldes, i., pp. 150 et seqq. It may be well here to guard my readers against the common error which supposes that a humid condition of the AIR is necessarily indicated by the presence of fog or visible vapor. The air is rendered humid by containing INVISIBLE vapor, and it becomes drier by the condensation of such vapor into fog, composed of solid globules or of hollow vesicles of water--for it is a disputed point whether the particles of fog are solid or vesicular. Hence, though the ambient atmosphere may hold in suspension, in the form of fog, water enough to obscure its transparency, and to produce the sensation of moisture on the skin, the air, in which the finely divided water floats, may be charged with even less than an average proportion of humidity.] The daily discharge of a quantity of aqueous vapor corresponding to a rain-fall of one inch and a fifth into the cool air of the forest would produce a perpetual shower, or at least drizzle, unless, indeed, we suppose a rapidity of absorption and condensation by the ground, and of transmission through the soil to the roots and through them and the vessels of the tree to the leaves, much greater than has been shown by direct observation. Notwithstanding the high authority of Schleiden, therefore, it seems impossible to reconcile his estimates with facts commonly observed and well established by competent investigators. Hence the important question of the supply, demand, and expenditure of water by forest vegetation must remain undecided, until it can be determined by something approaching to satisfactory direct experiment. [Footnote: According to Cezanne, Surrell, Etude sur les Torrents, 2e edition, ii., p. 100, experiments reported in the Revue des Eaux et Forets for August, 1868, showed the evaporation from a living tree to be "almost insignificant." Details are not given.] Balance of Conflicting Influences of Forest on Atmospheric Heat and Humidity. We have shown that the forest, considered as dead matter, tends to diminish the moisture of the air, by preventing the sun's rays from reaching the ground and evaporating the water that falls upon the surface, and also by spreading over the earth a spongy mantle which sucks up and retains the humidity it receives from the atmosphere, while, at the same time, this covering acts in the contrary direction by accumulating, in a reservoir not wholly inaccessible to vaporizing influences, the water of precipitation which might otherwise suddenly sink deep into the bowels of the earth, or flow by superficial channels to other climatic regions. We now see that, as a living organism, it tends, on the one hand, to diminish the humidity of the air by sometimes absorbing moisture from it, and, on the other, to increase that humidity by pouring out into the atmosphere, in a vaporous form, the water it draws up through its roots. This last operation, at the same time, lowers the temperature of the air in contact with or proximity to the wood, by the same law as in other cases of the conversion of water into vapor. As I have repeatedly said, we cannot measure the value of any one of those elements of climatic disturbance, raising or lowering of temperature, increase or diminution of humidity, nor can we say that in any one season, any one year, or any one fixed cycle, however long or short, they balance and compensate each other. They are sometimes, but certainly not always, contemporaneous in their action, whether their tendency is in the same or in opposite directions, and, therefore, their influence is sometimes cumulative, sometimes conflicting; but, upon the whole, their general effect is to mitigate extremes of atmospheric heat and cold, moisture and drought. They serve as equalizers of temperature and humidity, and it is highly probable that, in analogy with most other works and workings of nature, they, at certain or uncertain periods, restore the equilibrium which, whether as lifeless masses or as living organisms, they may have temporarily disturbed. [Footnote: There is one fact which I have nowhere seen noticed, but which seems to me to have an important bearing on the question whether forests tend to maintain an equilibrium between the various causes of hygroscopic action, and consequently to keep the air within their precincts in an approximately constant condition, so far as this meteorological element is concerned. I refer to the absence of fog or visible vapor in thick woods in full leaf, even when the air of the neighboring open grounds is so heavily charged with condensed vapor as completely to obscure the sun. The temperature of the atmosphere in the forest is not subject to so sudden and extreme variations as that of cleared ground, but at the same time it is far from constant, and so large a supply of vapor as is poured out by the foliage of the trees could not fail to be sometimes condensed into fog by the same causes as in the case of the adjacent meadows, which are often covered with a dense mist while the forest-air remains clear, were there not some potent counteracting influence always in action. This influence, I believe, is to be found partly in the equalization of the temperature of the forest, and partly in the balance between the humidity exhaled by the trees and that absorbed and condensed invisibly by the earth.] When, therefore, man destroys these natural harmonizors of climatic discords, he sacrifices an important conservative power, though it is far from certain that he has thereby affected the mean, however much he may have exaggerated the extremes of atmospheric temperature and humidity, or, in other words, may have increased the range and lengthened the scale of thermometric and hygrometric variation. Special Influence of Woods on Precipitation. With the question of the action of forests upon temperature and upon atmospheric humidity is intimately connected that of their influence upon precipitation, which they may affect by increasing or diminishing the warmth of the air and by absorbing or exhaling uncombincd gas and aqueous vapor. The forest being a natural arrangement, the presumption is that it exercises a conservative action, or at least a compensating one, and consequently that its destruction must tend to produce pluviometrical disturbances as well as thermometrical variations. And this is the opinion of perhaps the greatest number of observers. Indeed, it is almost impossible to suppose that, under certain conditions of time and place, the quantity and the periods of rain should not depend, more or less, upon the presence or absence of forests; and without insisting that the removal of the forest has diminished the sum-total of snow and rain, we may well admit that it has lessened the quantity which annually falls within particular limits. Various theoretical considerations make this probable, the most obvious argument, perhaps, being that drawn from the generally admitted fact, that the summer and even the mean temperature of the forest is below that of the open country in the same latitude. If the air in a wood is cooler than that around it, it must reduce the temperature of the atmospheric stratum immediately above it, and, of course, whenever a saturated current sweeps over it, it must produce precipitation which would fall upon it, or at a greater or less distance from it. We must here take into the account a very important consideration. It is not universally or even generally true, that the atmosphere returns its condensed humidity to the local source from which it receives it. The air is constantly in motion, --howling tempests scour amain From sea to land, from land to sea; [Footnote: Und Sturme brausen um die Wette Vom Meer aufs Land, vom Land aufs Meer. Goethe, Faust, Song of the Archangels.] and, therefore, it is always probable that the evaporation drawn up by the atmosphere from a given river, or sea, or forest, or meadow, will be discharged by precipitation, not at or near the point where it rose, but at a distance of miles, leagues, or even degrees. The currents of the upper air are invisible, and they leave behind them no landmark to record their track. We know not whence they come, or whither they go. We have a certain rapidly increasing acquaintance with the laws of general atmospheric motion, but of the origin and limits, the beginning and end of that motion, as it manifests itself at any particular time and place, we know nothing. We cannot say where or when the vapor, exhaled to-day from the lake on which we float, will be condensed and fall; whether it will waste itself on a barren desert, refresh upland pastures, descend in snow on Alpine heights, or contribute to swell a distant torrent which shall lay waste square miles of fertile corn-land; nor do we know whether the rain which feeds our brooklets is due to the transpiration from a neighboring forest, or to the evaporation from a far-off sea. If, therefore, it were proved that the annual quantity of rain and dew is now as great on the plains of Castile, for example, as it was when they were covered with the native forest, it would by no means follow that those woods did not augment the amount of precipitation elsewhere. The whole problem of the pluviometrical influence of the forest, general or local, is so exceedingly complex and difficult that it cannot, with our present means of knowledge, be decided upon a priori grounds. It must now be regarded as a question of fact which would probably admit of scientific explanation if it were once established what the actual fact is. Unfortunately, the evidence is conflicting in tendency, and sometimes equivocal in interpretation, but I believe that a majority of the foresters and physicists who have studied the question are of opinion that in many, if not in all cases, the destruction of the woods has been followed by a diminution in the annual quantity of rain and dew. Indeed, it has long been a popularly settled belief that vegetation and the condensation and fall of atmospheric moisture are reciprocally necessary to each other, and even the poets sing of Afric's barren sand, Where nought can grow, because it raineth not, And where no rain can fall to bless the land, Because nought grows there. [Footnote: Det golde Strog i Afrika, Der Intet voxe kan, da ei det regner, Og, omvendt, ingen Regn kan falde, da Der Intet voxer. Paudan-Muller, Adam Hamo, ii., 408.] Before going further with the discussion, however, it is well to remark that the comparative rarity or frequency of inundations in earlier or later centuries is not necessarily, in most cases not probably, entitled to any weight whatever, as a proof that more or less rain fell formerly than now; because the accumulation of water in the channel of a river depends far less upon the quantity of precipitation in its valley, than upon the rapidity with which it is conducted, on or under the surface of the ground, to the central artery that drains the basin. But this point will be more fully discussed in a subsequent chapter. In writers on the subject we are discussing, we find many positive assertions about the diminution of rain in countries which have been stripped of wood within the historic period, but these assertions very rarely rest upon any other proof than the doubtful recollection of unscientific observers, and I am unable to refer to a single instance where the records of the rain-gauge, for a considerable period before and after the felling or planting of extensive woods, can be appealed to in support of either side of the question. The scientific reputation of many writers who have maintained that precipitation has been diminished in particular localities by the destruction of forests, or augmented by planting them, has led the public to suppose that their assertions rested on sufficient proof. We cannot affirm that in none of these cases did such proof exist, but I am not aware that it has ever been produced. [Footnote: Among recent writers, Clave, Schacht, Sir John F. W. Herschel, Hohenstein, Barth, Asbjornsen, Boussingault, and others, maintain that forests tend to produce rain and clearings to diminish it, and they refer to numerous facts of observation in support of this doctrine; but in none of these does it appear that these observations are supported by actual pluviometrical measure. So far as I know, the earliest expression of the opinion that forests promote precipitation is that attributed to Christopher Columbus, in the Historie del S. D. Fernando Colombo, Venetia, 157l, cap. lviii., where it is said that the Admiral ascribed the daily showers which fell in the West Indies about vespers to "the great forests and trees of those countries," and remarked that the same effect was formerly produced by the same cause in the Canary and Madeira Islands and in the Azores, but that "now that the many woods and trees that covered them have been felled, there are not produced so many clouds and rains as before." Mr. H. Harrisse, in his very learned and able critical essay, Fernand Colomb, sa Vie et ses Oeuvres, Paris, 1872, has made it at least extremely probable that the Historie is a spurious work. The compiler may have found this observation in some of the writings of Columbus now lost, but however that may be, the fact, which Humboldt mentions in Cosmos with much interest, still remains, that the doctrine in question was held, if not by the great discoverer himself, at least by one of his pretended biographers, as early as the year 1571.] The effect of the forest on precipitation, then, is by no means free from doubt, and we cannot positively affirm that the total annual quantity of rain is even locally diminished or increased by the destruction of the woods, though both theoretical considerations and the balance of testimony strongly favor the opinion that more rain falls in wooded than in open countries. One important conclusion, at least, upon the meteorological influence of forests is certain and undisputed: the proposition, namely, that, within their own limits, and near their own borders, they maintain a more uniform degree of humidity in the atmosphere than is observed in cleared grounds. Scarcely less can it be questioned that they tend to promote the frequency of showers, and, if they do not augment the amount of precipitation, they probably equalize its distribution through the different seasons. [Footnote: The strongest direct evidence which I am able to refer to in support of the proposition that the woods produce even a local augmentation of precipitation is furnished by the observations of Mathieu, sub-director of the Forest-School at Nancy. His pluviometrical measurements, continued for three years, 1866-1868, show that during that period the annual mean of rain-fall in the centre of the wooded district of Cinq-Tranchees, at Belle Fontaine on the borders of the forest, and at Amance, in an open cultivated territory in the same vicinity, was respectively as the numbers 1,000, 957, and 853. The alleged augmentation of rain-fall in Lower Egypt, in consequence of large plantations by Mehemet Ali, is very frequently appealed to as a proof of this influence of the forest, and this case has become a regular common-place in all discussions of the question. It is, however, open to the same objection as the alleged instances of the diminution of precipitation in consequence of the felling of the forest. This supposed increase in the frequency and quantity of rain in Lower Egypt is, I think, an error, or at least not an established fact. I have heard it disputed on the spot by intelligent Franks, whose residence in that country began before the plantations of Mehemet Ali and Ibrahim Pacha, and I have been assured by them that meterological observations, made at Alexandria about the begiuning of this century, show an annual fall of rain as great as is usual at this day. The mere fact that it did not rain during the French occupation is not conclusive. Having experienced a gentle shower of nearly twenty-four hours' duration in Upper Egypt, I inquired of the local governor in relation to the frequency of this phenomenon, and was told by him that not of drop of rain had fallen at that point for more than two years previous. The belief in the increase of rain in Egypt rests almost entirely on the observations of Marshal Marmont, and the evidence collected by him in 1836. His conclusions have been disputed, if not confuted, by Joinard and others, and are probably erroneous. See Foissac, Meteorologie, German translation, pp. 634-639. It certainly sometimes rains briskly at Cairo, but evaporation is exceedingly rapid in Egypt--as any one who ever saw a Fellah woman wash a napkin in the Nile, and dry it by shaking it a few moments in the air, can testify; and a heap of grain, wet a few inches below the surface, would probably dry again without injury. At any rate, the Egyptian Government often has vast quantities of wheat stored at Boulak in uncovered yards through the winter, though it must be admitted that the slovenliness and want of foresight in Oriental life, public and private, are such that we cannot infer the safety of any practice followed in the East merely from its long continuance. Grain, however, may be long kept in the open air in climates much less dry than that of Egypt, without injury, except to the superficial layers; for moisture does not penetrate to a great depth in a heap of grain once well dried and kept well aired. When Louis IX. was making his preparations for his campaign in the East, he had large quantities of wine and grain purchased in the Island of Cyprus, and stored up for two years to await his arrival. "When we were come to Cyprus," says Joinville, Histoire de Saint Louis, Section 72, 73, "we found there greate foison of the Kynge's purveyance. . . The wheate and the barley they had piled up in greate heapes in the feeldes, and to looke vpon, they were like vnto mountaynes; for the raine, the whyche hadde beaten vpon the wheate now a longe whyle, had made it to sproute on the toppe, so that it seemed as greene grasse. And whanne they were mynded to carrie it to Egypte, they brake that sod of greene herbe, and dyd finde under the same the wheate and the barley, as freshe as yf menne hadde but nowe thrashed it."] Total Climatic Influence of the Forest. Aside from the question of local disturbances and their compensations, it does not seem probable that the forests sensibly affect the general mean of atmospheric temperature of the globe, or the total quantity of precipitation, or even that they had this influence when their extent was vastly greater than at present. The waters cover about three-fourths of the face of the earth, and if we deduct the frozen zones, the peaks and crests of lofty mountains and their craggy slopes, the Sahara and other great African and Asiatic deserts, and all such other portions of the solid surface as are permanently unfit for the growth of wood, we shall find that probably not one-tenth of the total superficies of our planet was ever, at any one time in the present geological period, covered with forests. Besides this, the distribution of forest land, of desert, and of water, is such as to reduce the possible influence of the woods to a low expression; for the forests are, in large proportion, situated in cold or temperate climates, where the action of the sun is comparatively feeble both in elevating temperature and in promoting evaporation; while, in the torrid zone, the desert and the sea--the latter of which always presents an evaporable surface--enormously preponderate. It is, upon the whole, not probable that so small an extent of forest, so situated, could produce a sensible influence on the general climate of the globe, though it might appreciably affect the local action of all climatic elements. The total annual amount of solar heat absorbed and radiated by the earth, and the sum of terrestrial evaporation and atmospheric precipitation, must be supposed constant; but the distribution of heat and of humidity is exposed to disturbance in both time and place by a multitude of local causes, among which the presence or absence of the forest is doubtless one. So far as we are able to sum up the results, it would appear that, in countries in the temperate zone still chiefly covered with wood, the summers would be cooler, moister, shorter, the winters milder, drier, longer, than in the same regions after the removal of the forest, and that the condensation and precipitation of atmospheric moisture would be, if not greater in total quantity, more frequent and less violent in discharge. The slender historical evidence we possess seems to point to the same conclusion, though there is some conflict of testimony and of opinion on this point. Among the many causes which, as we have seen, tend to influence the general result, the mechanical action of the forest, if not more important, is certainly more obvious and direct than the immediate effects of its organic processes. The felling of the woods involves the sacrifice of a valuable protection against the violence of chilling winds and the loss of the shelter afforded to the ground by the thick coating of leaves which the forest sheds upon it and by the snow which the woods prevent from blowing away, or from melting in the brief thaws of winter. I have already remarked that bare ground freezes much deeper than that which is covered by beds of leaves, and when the earth is thickly coated with snow, the strata frozen before it fell begin to thaw. It is not uncommon to find the ground in the woods, where the snow lies two or three feet deep, entirely free from frost, when the atmospheric temperature has been for several weeks below the freezing-point, and for some days even below the zero of Fahrenheit. When the ground is cleared and brought under cultivation, the leaves are ploughed into the soil and decomposed, and the snow, especially upon knolls and eminences, is blown off, or perhaps half thawed, several times during the winter. The water from the melting snow runs into the depressions, and when, after a day or two of warm sunshine or tepid rain, the cold returns, it is consolidated to ice, and the bared ridges and swells of earth are deeply frozen. [Footnote: I have seen, in Northern New England, the surface of the open ground frozen to the depth of twenty-two inches, in the month of November, when in the forest-earth no frost was discoverable; and later in the winter, I have known an exposed sand-knoll to remain frozen six feet deep, after the ground in the woods was completely thawed.] It requires many days of mild weather to raise the temperature of soil in this condition, and of the air in contact with it, to that of the earth in the forests of the same climatic region. Flora is already plaiting her sylvan wreath before the corn-flowers which are to deck the garland of Ceres have waked from their winter's sleep; and it is probably not a popular error to believe that, where man has substituted his artificial crops for the spontaneous harvest of nature, spring delays her coming. [Footnote: The conclusion arrived at by Noah Webster, in his very learned and able paper on the supposed change in the temperature of winter, read before the Connecticut Academy of Arts and Sciences in 1799, was as follows: "From a careful comparison of these facts, it appears that the weather, in modern winters, in the United States, is more inconstant than when the earth was covered with woods, at the first settlement of Europeans in the country; that the warm weather of autumn extends further into the winter months, and the cold weather of winter and spring encroaches upon the summer; that, the wind being more variable, snow is less permanent, and perhaps the same remark may be applicable to the ice of the rivers. These effects seem to result necessarily from the greater quantity of heat accumulated in the earth in summer since the ground has been cleared of wood and exposed to the rays of the sun, and to the greater depth of frost in the earth in winter by the exposure of its uncovered surface to the cold atmosphere."--Collection of Papers by Noah Webster, p. 162.] There are, in the constitution and action of the forest, many forces, organic and inorganic, which unquestionably tend powerfully to produce meteorological effects, and it may, therefore, be assumed as certain that they must and do produce such effects, UNLESS they compensate and balance each other, and herein lies the difficulty of solving the question. To some of these elements late observations give a new importance. For example, the exhalation of aqueous vapor by plants is now believed to be much greater, and the absorption of aqueous vapor by them much less, than was formerly supposed, and Tyndall's views on the relations of vapor to atmospheric heat give immense value to this factor in the problem. In like manner the low temperature of the surface of snow and the comparatively high temperature of its lower strata, and its consequent action on the soil beneath, and the great condensation of moisture by snow, are facts which seem to show that the forest, by protecting great surfaces of snow from melting, must inevitably exercise a great climatic influence. If to these influences we add the mechanical action of the woods in obstructing currents of wind, and diminishing the evaporation and refrigeration which such currents produce, we have an accumulation of forces which MUST manifest great climatic effects, unless--which is not proved and cannot be presumed--they neutralize each other. These are points hitherto little considered in the discussion, and it seems difficult to deny that as a question of ARGUMENT, the probabilities are strongly in favor of the meteorological influence of the woods. The EVIDENCE, indeed, is not satisfactory, or, to speak more accurately, it is non-existent, for there really is next to no trustworthy proof on the subject, but it appears to me a case where the burden of proof must be taken by those who maintain that, as a meteorological agent, the forest is inert. The question of a change in the climate of the Northern American States is examined in the able Meteorological Report of Mr. Draper, Director of the New York Central Park Observatory, for 1871. The result arrived at by Mr. Draper is, that there is no satisfactory evidence of a diminution in the rainfall, or of any other climatic change in the winter season, in consequence of clearing of the forests or other human action. The proof from meteorological registers is certainly insufficient to establish the fact of a change of climate, but, on the other hand, it is equally insufficient to establish the contrary. Meteorological stations are too few, their observations, in many cases, extend over a very short period, and, for reasons I have already given, the great majority of their records are entitled to little or no confidence. [Footnote: Since these pages were written, the subject of forest meteorology has received the most important contribution ever made to it, in several series of observations at numerous stations in Bavaria, from the year 1866 to 1871, published by Ebermayer, at Aschaffenburg, in 1873, under the title: Die Physikalischen Einwirkungen des Waldes auf Luft und Boden, und seine Klimatologische und Hygienische Bedeutung. I. Band. So far as observations of only five years' duration can prove anything, the following propositions, not to speak of many collateral and subsidiary conclusions, seem to be established, at least for the localities where the observations were made: 1. The yearly mean temperature of wooded soils, at all depths, is lower than that of open grounds, p. 85. This conclusion, it may be remarked, is of doubtful applicability in regions of excessive climate like the Northern United States and Canada, where the snow keeps the temperature of the soil in the forest above the freezing-point, for a large part and sometimes the whole of the winter, while in unwooded ground the earth remains deeply frozen. 2. The yearly mean atmospheric temperature, other things being equal, is lower in the forest than in cleared grounds, p. 84. 3. Climates become excessive in consequence of extensive clearings, p. 117. 4. The ABSOLUTE humidity of the air in the forest is about the same as in open ground, while the RELATIVE humidity is greater in the former than in the latter case, on account of the lower temperature of the atmosphere in the wood, p. 150. 5. The evaporation from an exposed surface of water in the forest is sixty-four per cent. less than in unwooded grounds, pp. 159,161. 6. About twenty-six per cent. of the precipitation is interrupted and prevented from reaching the ground by the foliage and branches of forest trees, p. 194. 7. In the interior of thick woods, the evaporation from water and from earth is much less than the precipitation, p. 210. 8. The loss of the water of precipitation intercepted by the trees in the forest is compensated by the smaller evaporation from the ground, p. 219. 9. In elevated regions and during the summer half of the year, woods tend to increase the precipitation, p. 202.] Influence of the Forest on the Humidity of the Soil. I have hitherto confined myself to the influence of the forest on meteorological conditions, a subject, as has been seen, full of difficulty and uncertainty. Its comparative effects on the temperature, the humidity, the texture and consistence, the configuration and distribution of the mould or arable soil, and, very often, of the mineral strata below, and on the permanence and regularity of springs and greater superficial water-courses, are much less disputable as well as more easily estimated and more important, than its possible value as a cause of strictly climatic equilibrium or disturbance. The action of the forest on the earth is chiefly mechanical, but the organic process of absorption of moisture by its roots affects the quantity of water contained in the vegetable mould and in the mineral strata near the surface, and, consequently, the consistency of the soil. In treating of the effects of trees on the moisture of the atmosphere, I have said that the forest, by interposing a canopy between the sky and the ground, and by covering the surface with a thick mantle of fallen leaves, at once obstructed insulation and prevented the radiation of heat from the earth. These influences go far to balance each other; but familiar observation shows that, in summer, the forest-soil is not raised to so high a temperature as open grounds exposed to irradiation. For this reason, and in consequence of the mechanical resistance opposed by the bed of dead leaves to the escape of moisture, we should expect that, except after recent rains, the superficial strata of woodland-soil would be more humid than that of cleared land. This agrees with experience. The soil of the natural forest is always moist, except in the extremest droughts, and it is exceedingly rare that a primitive wood suffers from want of humidity. How far this accumulation of water affects the condition of neighboring grounds by lateral infiltration, we do not know, but we shall see, in a subsequent chapter, that water is conveyed to great distances by this process, and we may hence infer that the influence in question is an important one. It is undoubtedly true that loose soils, stripped of vegetation and broken up by the plough or other processes of cultivation, may, until again carpeted by grasses or other plants, absorb more rain and snow-water than when they were covered by a natural growth; but it is also true that the evaporation from such soils is augmented in a still greater proportion. Rain scarcely penetrates beneath the sod of grass-ground, but runs off over the surface; and after the heaviest showers a ploughed field will often be dried by evaporation before the water can be carried off by infiltration, while the soil of a neighboring grove will remain half saturated for weeks together. Sandy soils frequently rest on a tenacious subsoil, at a moderate depth, as is usually seen in the pine plains of the United States, where pools of rain-water collect in slight depressions on the surface of earth the upper stratum of which is as porous as a sponge. In the open grounds such pools are very soon dried up by the sun and wind; in the woods they remain unevaporated long enough for the water to diffuse itself laterally until it finds, in the subsoil, crevices through which it may escape, or slopes which it may follow to their outcrop or descend along them to lower strata. Drainage by Roots of Trees. Becquerel notices a special function of the forest to which I have already alluded, but to which sufficient importance has not, until very recently, been generally ascribed. I refer to the mechanical action of the roots as conductors of the superfluous humidity of the superficial earth to lower strata. The roots of trees often penetrate through subsoil almost impervious to water, and in such cases the moisture, which would otherwise remain above the subsoil and convert the surface-earth into a bog, follows the roots downwards and escapes into more porous strata or is received by subterranean canals or reservoirs. [Footnote: "The roots of vegetables," says d'Hericourt, "perform the office of draining in a manner analogous to that artificially practised in parts of Holland and the British islands. This method consists in driving deeply down into the soil several hundred stakes to the acre; the water filters down along the stakes, and in some cases as favorable results have been obtained by this means as by horizontal drains."-Annales Forestieres, 1837, p. 312.] When the forest is felled, the roots perish and decay, the orifices opened by them are soon obstructed, and the water, after having saturated the vegetable earth, stagnates on the surface and transforms it into ponds and morasses. Thus in La Brenne, a tract of 200,000 acres resting on an impermeable subsoil of argillaceous earth, which ten centuries ago was covered with forests interspersed with fertile and salubrious meadows and pastures, has been converted, by the destruction of the woods, into a vast expanse of pestilential pools and marshes. In Sologne the same cause has withdrawn from cultivation and human inhabitation not less than 1,100,000 acres of ground once well wooded, well drained, and productive. It is an important observation that the desiccating action of trees, by way of drainage or external conduction by the roots, is greater in the artificial than in the natural wood, and hence that the surface of the ground in the former is not characterized by that approach to a state of saturation which it so generally manifests in the latter. In the spontaneous wood, the leaves, fruits, bark, branches, and dead trunks, by their decayed material and by the conversion of rock into loose earth through the solvent power of the gases they develop in decomposition, cover the ground with an easily penetrable stratum of mixed vegetable and mineral matter extremely favorable to the growth of trees, and at the same time too retentive of moisture to part with it readily to the capillary attraction of the roots. The trees, finding abundant nutriment near the surface, and so sheltered against the action of the wind by each other as not to need the support of deep and firmly fixed stays, send their roots but a moderate distance downwards, and indeed often spread them out like a horizontal network almost on the surface of the ground. In the artificial wood, on the contrary, the spaces between the trees are greater; they are obliged to send their roots deeper both for mechanical support and in search of nutriment, and they consequently serve much more effectually as conduits for perpendicular drainage. It is only under special circumstances, however, that this function of the forest is so essential a conservative agent as in the two cases just cited. In a champaign region insufficiently provided with natural channels for the discharge of the waters, and with a subsoil which, though penetrable by the roots of trees, is otherwise impervious to water, it is of cardinal importance; but though trees everywhere tend to carry off the moisture of the superficial strata by this mode of conduction, yet the precise condition of soil which I have described is not of sufficiently frequent occurrence to have drawn much attention to this office of the wood. In fact, in most soils, there are counteracting influences which neutralize, more or less effectually, the desiccative action of roots, and in general it is as true as it was in Seneca's time, that "the shadiest grounds are the moistest." [Footnote: Seneca, Questiones Naturales, iii. 11, 2.] It is always observed in the American States, that clearing the ground not only causes running springs to disappear, but dries up the stagnant pools and the spongy soils of the low grounds. The first roads in those States ran along the ridges, when practicable, because there only was the earth dry enough to allow of their construction, and, for the same reason, the cabins of the first settlers were perched upon the hills. As the forests have been from time to time removed, and the face of the earth laid open to the air and sun, the moisture has been evaporated, and the removal of the highways and of human habitations from the bleak hills to the sheltered valleys, is one of the most agreeable among the many improvements which later generations have witnessed in the interior of the Northern States. [Footnote: The Tuscan poet Ginati, who hod certainly had little opportunity of observing primitive conditions of nature and of man, was aware that such must have been the course of things in new countries. "You know," says he in a letter to a friend, "that the hills were first occupied by man, because stagnant waters, and afterwards continual wars, excluded men from the plains. But when tranquillity was established and means provided for the discharge of the waters, the low grounds were soon covered with human habitations."-- Letters, Firenze, 1864, p. 98.] Recent observers in France affirm that evergreen trees exercise a special desiccating action on the soil, and cases are cited where large tracts of land lately planted with pines have been almost completely drained of moisture by some unknown action of the trees. It is argued that the alleged drainage is not due to the conducting power of the roots, inasmuch as the roots of the pine do not descend lower than those of the oak and other deciduous trees which produce no such effect, and it is suggested that the foliage of the pine continues to exhale through the winter a sufficient quantity of moisture to account for the drying up of the soil. This explanation is improbable, and I know nothing in American experience of the forest which accords with the alleged facts. It is true that the pines, the firs, the hemlock, and all the spike-leaved evergreens prefer a dry soil, but it has not been observed that such soils become less dry after the felling of their trees. The cedars and other trees of allied families grow naturally in moist ground, and the white cedar of the Northern States, Thuya occidentalis, is chiefly found in swamps. The roots of this tree do not penetrate deeply into the earth, but are spread out near the surface, and of course do not carry off the waters of the swamp by perpendicular conduction. On the contrary, by their shade, the trees prevent the evaporation of the superficial water; but when the cedars are felled, the swamp--which sometimes rather resembles a pool filled with aquatic trees than a grove upon solid ground--often dries up so completely as to be fit for cultivation without any other artificial drainage than, in the ordinary course of cultivation, is given to other new soils. [Footnote: A special dessicative influence has long been ascribed to the maritime pine, which has been extensively planted on the dunes and sand-plains of western France, and it is well established that, under certain conditions, all trees, whether evergreen or deciduous, exercise this function, but there is no convincing proof that in the cases now referred to there is any difference in the mode of action of the two classes of trees. An article by D'Arbois de Jubainville in the Revue des Eaux et Forets for April, 1869, ascribing the same action to the Pinus sylvestris, has excited much attention in Europe, and the facts stated by this writer constitute the strongest evidence known to me in support of the alleged influence of evergreen trees, as distinguished from the draining by downward conduction, which is a function exercised by all trees, under ordinary circumstances, in proportion to their penetration of a bibulous subsoil by tap or other descending roots. The question has been ably discussed by Beraud in the Revue des Deux Mondes for April, 1870, the result being that the drying of the soil by pines is due simply to conduction by the roots, whatever may be the foliage of the tree. See post: Influence of the Forest on Flow of Springs. It is however certain, I believe, that evergreens exhale more moisture in winter than leafless deciduous trees, and consequently some weight is to be ascribed to this element.] The Forest in Winter. The influence of the woods on the flow of springs, and consequently on the supply for the larger water-courses, naturally connects itself with the general question of the action of the forest on the humidity of the ground. But the special condition of the woodlands, as affected by snow and frost in the winter of excessive climates, like that of the United States, has not been so much studied as it deserves; and as it has a most important bearing on the superficial hydrology of the earth, I shall make some observations upon it before I proceed to the direct discussion of the influence of the forest on the flow of springs. To estimate rightly the importance of the forest in our climate as a natural apparatus for accumulating the water that falls upon the surface and transmitting it to the subjacent strata, we must compare the condition and properties of its soil with those of cleared and cultivated earth, and examine the consequently different action of these soils at different seasons of the year. The disparity between them is greatest in climates where, as in the Northern American States and in the extreme North of Europe, the open ground freezes and remains impervious to water during a considerable part of the winter; though, even in climates where the earth does not freeze at all, the woods have still an important influence of the same character. The difference is yet greater in countries which have regular wet and dry seasons, rain being very frequent in the former period, while, in the latter, it scarcely occurs at all. These countries lie chiefly in or near the tropics, but they are not wanting in higher latitudes; for a large part of Asiatic and even of European Turkey is almost wholly deprived of summer rains. In the principal regions occupied by European cultivation, and where alone the questions discussed in this volume are recognized as having, at present, any practical importance, more or less rain falls at all seasons, and it is to these regions that, on this point as well as others, I chiefly confine my attention. Importance of Snow. Recent observations in Switzerland give a new importance to the hygrometrical functions of snow, and of course to the forest as its accumulator and protector. I refer to statements of the condensation of atmospheric vapor by the snows and glaciers of the Rhone basin, where it is estimated to be nearly equal to the entire precipitation of the valley. Whenever the humidity of the atmosphere in contact with snow is above the point of saturation at the temperature to which the air is cooled by such contact, the superfluous moisture is absorbed by the snow or condensed and frozen upon its surface, and of course adds so much to the winter supply of water received from the snow by the ground. This quantity, in all probability, much exceeds the loss by evaporation, for during the period when the ground is covered with snow, the proportion of clear dry weather favorable to evaporation is less than that of humid days with an atmosphere in a condition to yield up its moisture to any bibulous substance cold enough to condense it. [Footnote: The hard snow-crust, which in the early spring is a source of such keen enjoyment to the children and youth of the North--and to many older persons in whom the love of nature has kept awake a relish for the simple pleasures of rural life--is doubtless due to the congelation of the vapor condensed by the snow rather than to the thawing and freezing of the superficial stratum; for when the surface is melted by the sun, the water is taken up by the absorbent mass beneath before the temperature falls low enough to freeze it.] In our Northern States, irregular as is the climate, the first autumnal snows pretty constantly fall before the ground is frozen at all, or when the frost extends at most to the depth of only a few inches. [Footnote: The hard autumnal frosts are usually preceded by heavy rains which thoroughly moisten the soil, and it is a common saying in the North that "the ground will not freeze till the swamps are full."] In the woods, especially those situated upon the elevated ridges which supply the natural irrigation of the soil and feed the perennial fountains and streams, the ground remains covered with snow during the winter; for the trees protect the snow from blowing from the general surface into the depressions, and new accessions are received before the covering deposited by the first fall is melted. Snow is of a color unfavorable for radiation, but, even when it is of considerable thickness, it is not wholly impervious to the rays of the sun, and for this reason, as well as from the warmth of lower strata, the frozen crust of the soil, if one has been formed, is soon thawed, and does not again fall below the freezing-point during the winter. [Footnote: Dr. Williams, of Vermont, made some observations on the comparative temperature of the soil in open and in wooded ground In the years 1789 and 1791, but they generally belonged to the warmer months, and I do not know that any extensive series of comparisons between the temperature of the ground in the woods and in the fields has been attempted in America. Dr. Williams's thermometer was sunk to the depth of ten inches, and gave the following results: ---- | Temperature | Temperature | Time. | of ground in| of ground in| Difference. | pasture. | woods. | ---- May 23......................| 52 | 46 | 6 " 28......................| 57 | 48 | 9 June 15......................| 64 | 51 | 13 " 27......................| 62 | 51 | 11 July 16......................| 62 | 51 | 11 " 30......................| 65 1/2 | 55 1/2 | 10 Aug. 15......................| 68 | 58 | 10 " 31......................| 59 1/2 | 55 | 4 1/2 Sept.15......................| 59 1/2 | 55 | 4 1/2 Oct. 1......................| 59 1/2 | 55 | 4 1/2 " 15......................| 49 | 49 | 0 Nov. 1......................| 43 | 43 | 0 " 16......................| 43 1/2 | 43 1/2 | 0 On the 14th of January, 1791, in a winter remarkable for its extreme severity, he found the ground, on a plain open field where the snow had been blown away, frozen to the depth of three feet and five inches; in the woods where the snow was three feet deep, and where the soil had frozen to the depth of six inches before the snow fell, the thermometer, at six inches below the surface of the ground, stood at 39 degrees. In consequence of the covering of the snow, therefore, the previously frozen ground had been thawed and raised to seven degrees above the freezing-point.--William's Vermont, i., p. 74. Boussingault's observations are important. Employing three thermometers, one with the bulb an inch below the surface of powdery snow; one on the surface of the ground beneath the snow, then four inches deep; and one in the open air, forty feet above the ground, on the north side of a building, he found, at 5 P.M., the FIRST thermometer at -1.5 degrees Centigrade, the second at 0 degrees, and the THIRD at + 2.5 degrees; at 7 A.M. the next morning, the first stood at -12 degrees, the second at -3.5 degrees and the third at -3 degrees; at 5.30 the same evening No. 1 stood at -1.4 degrees, No. 2 at 0 degrees, and No. 3 at + 3 degrees. Other experiments were tried, and though the temperature was affected by the radiation, which varied with the hour of the day and the state of the sky, the upper surface of the snow was uniformly colder than the lower, or than the open air. According to the Report of the Department of Agriculture for May and June, 1872, Mr. C. G. Prindle, of Vermont, in the preceding winter, found, for four successive days, the temperature immediately above the snow at 13 degrees below zero; beneath the snow, which was but four inches deep, at 19 degrees above zero; and under a drift two feet deep, at 27 degrees above. On the borders and in the glades of the American forest, violets and other small plants begin to vegetate as soon as the snow has thawed the soil around their roots, and they are not unfrequently found in full flower under two or three feet of snow.--American Naturalist, May, 1869, pp. 155, 156. In very cold weather, when the ground is covered with light snow, flocks of the grouse of the Eastern States often plunge into the snow about sunset, and pass the night in this warm shelter. If the weather moderates before morning, a frozen crust is sometimes formed on the surface too strong to be broken by the birds, which consequently perish.] The snow in contact with the earth now begins to melt, with greater or less rapidity, according to the relative temperature of the earth and the air, while the water resulting from its dissolution is imbibed by the vegetable mould, and carried off by infiltration so fast that both the snow and the layers of leaves in contact with it often seem comparatively dry, when, in fact, the under-surface of the former is in a state of perpetual thaw. No doubt a certain proportion of the snow is given off to the atmosphere by direct evaporation, but in the woods, the protection against the sun by even leafless trees prevents much loss in this way, and besides, the snow receives much moisture from the air by absorption and condensation. Very little water runs off in the winter by superficial water-courses, except in rare cases of sudden thaw, and there can be no question that much the greater part of the snow deposited in the forest is slowly melted and absorbed by the earth. The immense importance of the forest, as a reservoir of this stock of moisture, becomes apparent, when we consider that a large proportion of the summer rain either flows into the valleys and the rivers, because it falls faster than the ground can imbibe it; or, if absorbed by the warm superficial strata, is evaporated from them without sinking deep enough to reach wells and springs, which, of course, depend much on winter rains and snows for their entire supply. This observation, though specially true of cleared and cultivated grounds, is not wholly inapplicable to the forest, particularly when, as is too often the case in Europe, the underwood and the decaying leaves are removed. The quantity of snow that falls in extensive forests, far from the open country, has seldom been ascertained by direct observation, because there are few meteorological stations in or near the forest. According to Thompson, [Footnote: Thompson's Vermont, Appendix, p. 8.] the proportion of water which falls in snow in the Northern States does not exceed one-fifth of the total precipitation, but the moisture derived from it is doubtless considerably increased by the atmospheric vapor absorbed by it, or condensed and frozen on its surface. I think I can say from experience--and I am confirmed in this opinion by the testimony of competent observers whose attention has been directed specially to the point--that though much snow is intercepted by the trees, and the quantity on the ground in the woods is consequently less than in open land in the first part of the winter, yet most of what reaches the ground at that season remains under the protection of the wood until melted, and as it occasionally receives new supplies the depth of snow in the forest in the latter half of winter is considerably greater than in the cleared fields. Careful measurements in a snowy region in New England, in the month of February, gave a mean of 38 inches in the open ground and 44 inches in the woods. [Footnote: As the loss of snow by evaporation has been probably exaggerated by popular opinion, an observation or two on the subject may not be amiss in this place. It is true that in the open grounds, in clear weather and with a dry atmosphere, snow and ice are evaporated with great rapidity even when the thermometer is much below the freezing-point; and Darwin informs us that the snow on the summit of Aconcagua, 23,000 feet high, and of course in a temperature of perpetual frost, is sometimes carried off by evaporation. The surface of the snow in our woods, however, does not indicate much loss in this way. Very small deposits of snow-flakes remain unevaporated in the forest, for many days after snow which fell at the same time in the cleared field has disappeared without either a thaw to melt it or a wind powerful enough to drift it away. Even when bared of their leaven, the trees of a wood obstruct, in an important degree, both the direct action of the sun's rays on the snow and the movement of drying and thawing winds. Dr. Piper (Trees of America, p. 48) records the following observations: "A body of snow, one foot in depth and sixteen feet square, was protected from the wind by a tight board fence about five feet high, while another body of snow, much more sheltered from the sun than the first, six feet in depth, and about sixteen feet square, was fully exposed to the wind. When the thaw came on, which lasted about a fortnight, the larger body of snow was entirely dissolved in less than a week, while the smaller body was not wholly gone at the end of the second week. "Equal quantities of snow were placed in vessels of the samekind and capacity, the temperature of the air being seventy degrees. In the one case, a constant current of air was kept passing over the open vessel, while the other was protected by a cover. The snow in the first was dissolved in sixteen minutes, while the latter had a small unthawed proportion remaining at the end of eighty-five minutes." The snow in the woods is protected in the same way, though not literally to the same extent, as by the fence in one of these cases and the cover in the other.] The general effect of the forest in cold climates is to assimilate the winter state of the ground to that of wooded regions under softer skies; and it is a circumstance well worth noting, that in Southern Europe, where Nature has denied to the earth a warm winter-garment of flocculent snow, she has, by one of those compensations in which her empire is so rich, clothed the hillsides with umbrella and other pines, ilexes, cork-oaks, bays and other trees of persistent foliage, whose evergreen leaves afford to the soil a protection analogous to that which it derives from snow in more northern climates. The water imbibed by the soil in winter sinks until it meets a more or less impermeable or a saturated stratum, and then, by unseen conduits, slowly finds its way to the channels springs, or oozes out of the ground in drops which unite in rills, and so all is conveyed to the larger streams, and by them finally to the sea. The water, in percolating through the vegetable and mineral layers, acquires their temperature, and is chemically affected by their action, but it carries very little matter in mechanical suspension. The process I have described is a slow one, and the supply of moisture derived from the snow, augmented by the rains of the following seasons, keeps the forest-ground, where the surface is level or but moderately inclined, in a state of approximate saturation throughout almost the whole year. [Footnote: The statements I have made, here and elsewhere, respecting the humidity of the soil in natural forests, have been, I understand, denied by Mr. T. Meehan, a distinguished American naturalist, in a paper which I have not seen He is quoted as maintaining, among other highly questionable propositions that no ground is "so dry in its subsoil as that which sustains a forest on its surface." In open, artificially planted woods, with a smooth and regular surface, and especially in forests where the fallen leaves and branches are annually burnt or carried off, both the superficial and the subjacent strata may under certain circumstances, become dry, but this rarely, if ever, happens in a wood of spontaneous growth, undeprived of the protection afforded by its own droppings, and of the natural accidents of surface which tend to the retention of water. See, on this point, a very able article by Mr. Henry Stewart, in the New York Tribune of November 23, 1873.] It may be proper to observe here that in Italy, and in many parts of Spain and France, the Alps, the Apennines, and the Pyrenees, not to speak of less important mountains, perform the functions which provident nature has in other regions assigned to the forest, that is, they act as reservoirs wherein is accumulated in winter a supply of moisture to nourish the parched plains during the droughts of summer. Hence, however enormous may be the evils which have accrued to the above-mentioned countries from the destruction of the woods, the absolute desolation which would otherwise have smitten them through the folly of man, has been partially prevented by those natural dispositions, by means of which there are stored up in the glaciers, in the snow-fields, and in the basins of mountains and valleys, vast deposits of condensed moisture which are afterwards distributed in a liquid form during the season in which the atmosphere furnishes a slender supply of the beneficent fluid so indispensable to vegetable and animal life. [Footnote: The accumulation of snow and ice upon the Alps and other mountains--which often fills up valleys to the height of hundreds of feet--is due not only to the fall or congealed and crystallized vapor in the form of snow, to the condensation of atmospheric vapor on the surface of snow-fields and glaciers, and to a temperature which prevents the rapid melting of snow, but also to the well-known fact that, at least up to the height of 10,000 feet, rain and snow are more abundant on the mountains than at lower levels. But another reason may be suggested for the increase of atmospheric humidity, and consequently of the precipitation of aqueous vapor on mountain chains. In discussing the influence of mountains on precipitation, meteorologists have generally treated the popular belief, that mountains "attract" to them clouds floating within a certain distance from them, as an ignorant prejudice, and they ascribe the appearance of clouds about high peaks solely to the condensation of the humidity of the air carried by atmospheric currents up the slopes of the mountain to a colder temperature. But if mountains do not really draw clouds and invisible vapors to them, they are an exception to the universal law of attraction. The attraction of the small Mount Shehallien was found sufficient to deflect from the perpendicular, by a measurable quantity, a plummet weighing but a few ounces. Why, then, should not greater masses attract to them volumes of vapor weighing many tons, and floating freely in the atmosphere within moderate distances of the mountains ] Summer Rains, Importance of. Babinet quotes a French proverb: "Summer rain wets nothing," and explains it by saying that at that season the rainwater is "almost entirely carried off by evaporation." "The rains of summer," he adds, "however abundant they may be, do not penetrate the soil beyond the depth of six or eight inches. In summer the evaporating power of the heat is five or six times greater than in winter, and this force is exerted by an atmosphere capable of containing five or six times as much vapor as in winter." "A stratum of snow which prevents evaporation [from the ground], causes almost all the water that composes it to filter into the earth, and forms a provision for fountains, wells, and streams which could not be furnished by any quantity whatever of summer rain. This latter, useful to vegetation like the dew, neither penetrates the soil nor accumulates a store to supply the springs and to be given out again into the open air." [Footnote: Etudes et Lectures, vol. vi., p. 118. The experiments or Johnstrup in the vicinity of Copenhagen, where the mean annual precipitation is 23 1/2 inches, and where the evaporation must be less than in the warmer and drier atmosphere of France, form the most careful series of observations on this subject which I have met with. Johnstrup found that at the depth at a metre and a half (50 inches) the effects of rain and evaporation were almost imperceptible, and became completely so at a depth of from two to three metres (6 1/2 to 10 feet). During the summer half of the year the evaporation rather exceeded the rainfall; during the winter half the entire precipitation was absorbed by the soil and transmitted to lower strata by infiltration. The stratum between one metre and a half (50 inches) and three metres (10 feet) from the surface was then permanently in the condition of a saturated sponge, neither receiving nor losing humidity during the summer half of the year, but receiving from superior, and giving off to lower, strata an equal amount of moisture during the winter half.--Johnstrup, Om Fugtighedens Bezagelse i den naturlige Jordbund. Kjobenhavn, 1866.] This conclusion, however applicable to the climate and to the soil of France, is too broadly stated to be received as a general truth; and in countries like the United States, where rain is comparatively rare during the winter and abundant during the summer half of the year, common observation shows that the quantity of water furnished by deep wells and by natural springs depends almost as much upon the rains of summer as upon those of the rest of the year, and consequently that a large portion of the rain of that season must find its way into strata too deep for the water to be wasted by evaporation. [Footnote: According to observations at one hundred military stations in the United States, the precipitation ranges from three and a quarter inches at Fort Yuma in California to about seventy-two inches at Fort Pike, Louisiana, the mean for the entire territory, not including Alaska, being thirty-six inches. In the different sections of the Union it is as follows: North-eastern States.................. 41 inches, New York.............................. 36 " Middle States......................... 40 1/2 " Ohio.................................. 40 " Southern States....................... 51 " S. W. States and Indian Territories... 39 1/2 " Western States and Territories........ 30 " Texas and New Mexico.................. 24 1/2 " California............................ 18 1/2 " Oregon and Washington Territory....... 50 " The mountainous regions, it appears, do not recieve the greatest amount of precipitation. The avenge downfall of the Southern States bordering on the Atlantic and the Gulf of Mexico exceeds the mean of the whole United States, being no less than fifty-one inches, while on the Pacific coast it ranges from fifty to fifty-six inches. As a general rule, it may be stated that at the stations on or near the sea-coast the precipitation is greatest in the spring months, though there are several exceptions to this remark, and at a large majority of the stations the downfall is considerably greater in the summer months than at any other season.] Dalton's experiments in the years 1796, 1797, and 1798 appeared to show that the mean absorption of the downfall by the earth in those years was twenty-nine per cent. Dickinson, employing the same apparatus for eight years, found the absorption to vary widely in different years, the mean being forty-seven per cent. Charnock's experiments in two years show an absorption of from seventeen to twenty-seven per cent.] Besides, even admitting that the water from summer rains is so completely evaporated as to contribute nothing directly to the supply of springs, it at least tends indirectly to maintain their flow, because it saturates in part the atmosphere, and at the same time it prevents the heat of the sun from drying the earth to still greater depths, and bringing within the reach of evaporation the moisture of strata which ordinarily do not feel the effects of solar irradiation. Influence of the Forest on the Flow of Springs. It is an almost universal and, I believe, well-founded opinion, that the protection afforded by the forest against the escape of moisture from its soil by superficial flow and evaporation insures the permanence and regularity of natural springs, not only within the limits of the wood, but at some distance beyond its borders, and thus contributes to the supply of an element essential to both vegetable and animal life. As the forests are destroyed, the springs which flowed from the woods, and, consequently, the greater water-courses fed by them, diminish both in number and in volume. This fact is so familiar throughout the American States and the British Provinces, that there are few old residents of the interior of those districts who are not able to testify to its truth as a matter of personal observation. My own recollection suggests to me many instances of this sort, and I remember one case where a small mountain spring, which disappeared soon after the clearing of the ground where it rose, was recovered about twenty years ago, by simply allowing the bushes and young trees to grow up on a rocky knoll, not more than half an acre in extent, immediately above the spring. The ground was hardly shaded before the water reappeared, and it has ever since continued to flow without interruption. The hills in the Atlantic States formerly abounded in springs and brooks, but in many parts of these States which were cleared a generation or two ago, the hill-pastures now suffer severely from drought, and in dry seasons furnish to cattle neither grass nor water. Almost every treatise on the economy of the forest adduces facts in support of the doctrine that the clearing of the woods tends to diminish the flow of springs and the humidity of the soil, and it might seem unnecessary to bring forward further evidence on this point. [Footnote: "Why go so far for the proof of a phenomenon that is repeated every day under our own eyes, and of which every Parisian may convince himself, without venturing beyond the Bois de Boulogne or the forest of Meudon Let him, after a few rainy days, pass alone the Chevreuse road, which is bordered on the right by the wood, on the left by cultivated fields. The fall of water and the continuance of the rain have been the same on both sides; but the ditch on the side of the forest will remain filled with water proceeding from the infiltration through the wooded soil, long after the other, contiguous to the open ground, has performed its office of drainage and become dry. The ditch on the left will have discharged in a few hours a quantity of water, which the ditch on the right requires several days to receive and carry down to the valley."--Clave, Etudes, etc., pp. 53, 54.] But the subject is of too much practical importance and of too great philosophical interest to be summarily disposed of; and it ought to be noticed that there is at least one case--that of some loose sandy soils which, as observed by Valles, [Footnote: Valles, Etudes sur les Inondations, p. 472.] when bared of wood very rapidly absorb and transmit to lower strata the water they receive from the atmosphere--where the removal of the forest may increase the flow of springs at levels below it, by exposing to the rain and melted snow a surface more bibulous, and at the same time less retentive, than its original covering. Under such circumstances, the water of precipitation, which had formerly been absorbed by the vegetable mould and retained until it was evaporated, might descend through porous earth until it meets an impermeable stratum, and then be conducted along it, until, finally, at the outcropping of this stratum, it bursts from a hillside as a running spring. But such instances are doubtless too rare to form a frequent or an important exception to the general law, because it is very seldom the case that such a soil as has just been supposed is covered by a layer of vegetable earth thick enough to retain, until it is evaporated, all the rain that falls upon it, without imparting any water to the strata below it. If we look at the point under discussion as purely a question of fact, to be determined by positive evidence and not by argument, the observations of Boussingault are, both in the circumstances they detail and in the weight to be attached to the testimony, among the most important yet recorded. The interest of the question will justify me in giving, nearly in Boussingault's own words, the facts and some of the remarks with which he accompanies the detail of them. "In many localities," he observes, [Footnote: Economie Rurale t. ii, p. 780.] "it has been thought that, within a certain number of years, a sensible diminution has been perceived in the volume of water of streams utilized as a motive-power; at other points, there are grounds for believing that rivers have become shallower, and the increasing breadth of the belt of pebbles along their banks seems to prove the loss of a part of their water; and, finally, abundant springs have almost dried up. These observations have been principally made in valleys bounded by high mountains, and it has been noticed that this diminution of the waters has immediately followed the epoch when the inhabitants have begun to destroy, unsparingly, the woods which were spread over the face of the land. "And here lies the practical point of the question; for if it is once established that clearing diminishes the volume of streams, it is less important to know to what special cause this effect is due. The rivers which rise within the valley of Aragua, having no outlet to the ocean, form, by their union, the Lake of Tacarigua or Valencia, having a length of about two leagues and a half [= 7 English miles]. At the time of Humboldt's visit to the valley of Aragua, the inhabitants were struck by the gradual diminution which the lake had been undergoing for thirty years. In fact, by comparing the descriptions given by historians with its actual condition, even making large allowance for exaggeration, it was easy to see that the level was considerably depressed. The facts spoke for themselves. Oviedo, who, toward the close of the sixteenth century, had often traversed the valley of Aragua, says positively that New Valencia was founded, in 1555, at half a league from the Lake of Tacarigua; in 1800, Humboldt found this city 5,260 metres [= 3 1/2 English miles] from the shore. "The aspect of the soil furnished new proofs. Many hillocks on the plain retain the name of islands, which they more justly bore when they were surrounded by water. The ground laid bare by the retreat of the lake was converted into admirable plantations; and buildings erected near the lake showed the sinking of the water from year to year. In 1796, new islands made their appearance. A fortress built in 1740 on the island of Cabrera, was now on a peninsula; and, finally, on two granitic islands, those of Cura and Cabo Blanco, Humboldt observed among the shrubs, somo metres above the water, fine sand filled with helicites. "These clear and positive facts suggested numerous explanations, all assuming a subterranean outlet, which permitted the discharge of the water to the ocean. Humboldt disposed of these hypotheses, and did not hesitate to ascribe the diminution of the waters of the lake to the numerous clearings which had been made in the valley of Aragua within half a century." Twenty-two years later, Boussingault explored the valley of Aragua. For some years previous, the inhabitants had observed that the waters of the lake were no longer retiring, but, on the contrary, were sensibly rising. Grounds, not long before occupied by plantations, were submerged. The islands of Nuevas Aparecidas, which appeared above the surface in 1796, had again become shoals dangerous to navigation. Cabrera, a tongue of land on the north side of the valley, was so narrow that the least rise of the water completely inundated it. A protracted north wind sufficed to flood the road between Maracay and New Valencia. The fears which the inhabitants of the shores had so long entertained were reversed. Those who had explained the diminution of the lake by the supposition of subterranean channels were suspected of blocking them up, to prove themselves in the right. During the twenty-two years which had elapsed, the valley of Aragua had been the theatre of bloody struggles, and war had desolated these smiling lands and decimated their population. At the first cry of independence a great number of slaves found their liberty by enlisting under the banners of the new republic; the great plantations were abandoned, and the forest, which in the tropics so rapidly encroaches, had soon recovered a large proportion of the soil which man had wrested from it by more than a century of constant and painful labor. Boussingault proceeds to state that two lakes near Ubate, in New Granada, had formed but one, a century before his visit; that the waters were gradually retiring, and the plantations extending over the abandoned bed; that, by inquiry of old hunters and by examination of parish records, he found that extensive clearings had been made and were still going on. He found, also, that the length of the Lake of Fuquene, in the same valley, had, within two centuries, been reduced from ten leagues to one and a half, its breadth from three leagues to one. At the former period, the neighboring mountains were well wooded, but at the time of his visit the mountains had been almost entirely stripped of their wood. Our author adds that other cases, similar to those already detailed, might be cited, and he proceeds to show, by several examples, that the waters of other lakes in the same regions, where the valleys had always been bare of wood, or where the forests had not been disturbed, had undergone no change of level. Boussingault further states that the lakes of Switzerland have sustained a depression of level since the too prevalent destruction of the woods, and arrives at the general conclusion that, "in countries where great clearings have been made, there has most probably been a diminution in the living waters which flow upon the surface of theground." This conclusion he further supports by two examples: one, where a fine spring, at the foot of a wooded mountain in the Island of Ascension, dried up when the mountain was cleared, but reappeared when the wood was replanted; the other at Marmato, in the province of Popayan, where the streams employed to drive machinery were much diminished in volume, within two years after the clearing of the heights from which they derived their supplies. This latter is an interesting case, because, although the rain-gauges, established as soon as the decrease of water began to excite alarm, showed a greater fall of rain for the second year of observation than the first, yet there was no appreciable increase in the flow of the mill-streams. From these cases, the distinguished physicist infers that very restricted local clearings may diminish and even suppress springs and brooks, without any reduction in the total quantity of rain. It will have been noticed that these observations, with the exception of the last two cases, do not bear directly upon the question of the diminution of springs by clearings, but they logically infer it from the subsidence of the natural reservoirs which springs once filled. There is, however, no want of positive evidence on this subject. Marchand cites the following instances: "Before the felling of the woods, within the last few years, in the valley of the Soulce, the Combe-es-Monnin and the Little Valley, the Sorne furnished a regular and sufficient supply of water for the ironworks of Unterwyl, which was almost unaffected by drought or by heavy rains. The Sorne has now become a torrent, every shower occasions a flood, and after a few days of fine weather, the current falls so low that it has been necessary to change the water-wheels, because those of the old construction are no longer able to drive the machinery, and at last to introduce a steam-engine to prevent the stoppage of the works for want of water. "When the factory of St. Ursanne was established, the river that furnished its power was abundant, and had, from time immemorial, sufficed for the machinery of a previous factory. Afterwards, the woods near its sources were cut. The supply of water fell off in consequence, the factory wanted water for half the year, and was at last obliged to stop altogether. "The spring of Combefoulat, in the commune of Seleate, was well known as one of the best in the country; it was remarkably abundant, and sufficient, in the severest droughts, to supply all the fountains of the town; but as soon as considerable forests were felled in Combe-de-pre Martin and in the valley of Combefoulat, the famous spring, which lies below these woods, has become a mere thread of water, and disappears altogether in times of drought. "The spring of Varieux, which formerly supplied the castle of Pruntrut, lost more than half its water after the clearing of Varieux and Rougeoles. These woods have been replanted, the young trees are growing well, and, with the woods, the waters of the spring are increasing. "The Dog Spring between Pruntrut and Bressancourt has entirely vanished since the surrounding forest-grounds were brought under cultivation. "The Wolf Spring, in the commune of Soubey, furnishes a remarkable example of the influence of the woods upon fountains. A few years ago this spring did not exist. At the place where it now rises, a small thread of water was observed after very long rains, but the stream disappeared with the rain. The spot is in the middle of a very steep pasture inclining to the south. Eighty years ago, the owner of the land, perceiving that young firs were shooting up in the upper part of it, determined to let them grow, and they soon formed a flourishing grove. As soon as they were well grown, a fine spring appeared in place of the occasional rill, and furnished abundant water in the longest droughts. For forty or fifty years this spring was considered the best in the Clos du Doubs. A few years since, the grove was felled, and the ground turned again to a pasture. The spring disappeared with the wood, and is now as dry as it was ninety years ago." [Footnote: Ueber Die Entwaldung Der Gebirge, pp. 20 et seqq.] Siemoni gives the following remarkable facts from his own personal observation: "In a rocky nook near the crest of a mountain in the Tuscan Apennines, there flowed a clear, cool, and perennial fountain, uniting three distinct springs in a single current. The ancient beeches around and particularly above the springs were felled. On the disappearance of the wood, the springs ceased to flow, except in a thread of water in rainy weather, greatly inferior in quality to that of the old fountain. The beeches were succeeded by firs, and as soon as they had grown sufficiently to shade the soil, the springs begun again to flow, and they gradually returned to their former abundance and quality." [Footnote: Manuale D'arte Forestale. 2me editione, p. 492.] This and the next preceding case are of great importance both as to the action of the wood in maintaining springs, and particularly as tending to prove that evergreens do not exercise the desiccative influence ascribed to them in France. The latter instance shows, too, that the protective influence of the wood extends far below the surface, for the quality of the water was determined, no doubt, by the depth from which it was drawn. The slender occasional supply after the beeches were cut was rain-water which soaked through the superficial humus and oozed out at the old orifices, carrying the taste and temperature of the vegetable soil with it; the more abundant and grateful water which flowed before the beeches were cut, and after the firs were well grown, came from a deeper source and had been purified, and cooled to the mean temperature of the locality, by filtering through strata of mineral earth. "The influence of the forest on springs," says Hummel, "is strikingly shown by an instance at Heilbronn. The woods on the hills surrounding the town are cut in regular succession every twentieth year. As the annual cuttings approach a certain point, the springs yield less water, some of them none at all; but as the young growth shoots up, they flow more and more freely, and at length bubble up again in all their original abundance." [Footnote: Physische Geographie, p. 32.] Dr. Piper states the following case: "Within about half a mile of my residence there is a pond upon which mills have been standing for a long time, dating back, I believe, to the first settlement of the town. These have been kept in constant operation until within some twenty or thirty years, when the supply of water began to fail. The pond owes its existence to a stream that has its source in the hills which stretch some miles to the south. Within the time mentioned, these hills, which were clothed with a dense forest, have been almost entirely stripped of trees; and to the wonder and loss of the mill-owners, the water in the pond has failed, except in the season of freshets; and, what was never heard of before, the stream itself has been entirely dry. Within the last ten years a new growth of wood has sprung up on most of the land formerly occupied by the old forest; and now the water runs through the year, notwithstanding the great droughts of the last few years, going back from 1856." Dr. Piper quotes from a letter of William C. Bryant the following remarks: "It is a common observation that our summers are becoming drier and our streams smaller. Take the Cuyahoga as an illustration. Fifty years ago large barges loaded with goods went up and down that river, and one of the vessels engaged in the battle of Lake Erie, in which the gallant Perry was victorious, was built at Old Portage, six miles north of Albion, and floated down to the lake. Now, in an ordinary stage of the water, a canoe or skiff can hardly pass down the stream. Many a boat of fifty tons burden has been built and loaded in the Tuscarawas, at New Portage, and sailed to New Orleans without breaking bulk. Now, the river hardly affords a supply of water at New Portage for the canal. The same may be said of other streams--they are drying up. And from the same cause--the destruction of our forests--our summers are growing drier and our winters colder." [Footnote: The Trees of America, pp. 50, 51.] No observer has more carefully studied the influence of the forest upon the flow of the waters, or reasoned more ably on the ascertained phenomena, than Cantegril. The facts presented in the following case, communicated by him to the Ami des Sciences for December, 1859, are as nearly conclusive as any single instance well can be: "In the territory of the commune of Labruguiere there is a forest of 1,834 hectares [4,530 acres], known by the name of the Forest of Montaut, and belonging to that commune. It extends along thenorthern slope of the Black Mountains. The soil is granitic, the maximum altitude 1,243 metres [4,140 feet], and the inclination ranges between 15 and 60 to 100. "A small current of water, the brook of Caunan, takes its rise in this forest, and receives the waters of two-thirds of its surface. At the lower extremity of the wood and on the stream are several fulleries, each requiring a force of eight horse-power to drive the water-wheels which work the stampers. The commune of Labruguiere had been for a long time famous for its opposition to forest laws. Trespasses and abuses of the right of pasturage had converted the wood into an immense waste, so that this vast property now scarcely sufficed to pay the expense of protecting it, and to furnish the inhabitants with a meagre supply of fuel. While the forest was thus ruined, and the soil thus bared, the water, after every abundant rain, made an eruption into the valley, bringing down a great quantity of pebbles which still clog the current of the Caunan. The violence of the floods was sometimes such that they were obliged to stop the machinery for some time. During the summer another inconvenience was felt. If the dry weather continued a little longer than usual, the delivery of water became insignificant. Each fullery could for the most part only employ a single set of stampers, and it was not unusual to see the work entirely suspended. "After 1840, the municipal authority succeeded in enlightening the population as to their true interests. Protected by a more watchful supervision, aided by well-managed replantation, the forest has continued to improve to the present day. In proportion to the restoration of the forest, the condition of the manufactories has become less and less precarious, and the action of the water is completely modified. For example, sudden and violent floods, which formerly made it necessary to stop the machinery, no longer occur. There is no increase in the delivery until six or eight hours after the beginning of the rain; the floods follow a regular progression till they reach their maximum, and decrease in the same manner. Finally, the fulleries are no longer forced to suspend work in summer; the water is always sufficiently abundant to allow the employment of two sets of stampere at least, and often even of three. "This example is remarkable in this respect, that, all other circumstances having remained the same, the changes in the action of the stream can be attributed only to the restoration of the forest--changes which may be thus summed up: diminution of flood-water during rains--increase of delivery at other seasons." Becquerel and other European writers adduce numerous other cases where the destruction of forests has caused the disappearance of springs, a diminution in the volume of rivers, and a lowering of the level of lakes, and in fact, the evidence in support of the doctrine I have been maintaining on this subject seems to be as conclusive as the nature of the case admits. [Footnote: See, in the Revue des Eaux et Forets for April, 1867, an article entitled De l'influence des Forets sur le Regime des Eaux, and the papers in previous numbers of the same journal therein referred to.] We cannot, it is true, arrive at the same certainty and precision of result in these inquiries as in those branches of physical research where exact quantitative appreciation is possible, and we must content ourselves with probabilities and approximations. We cannot positively affirm that the precipitation in a given locality is increased by the presence, or lessened by the destruction, of the forest, and from our ignorance of the subterranean circulation of the waters, we cannot predict, with certainty, the drying up of a particular spring as a consequence of the felling of the wood which shelters it; but the general truth, that the flow of springs and the normal volume of rivers rise and fall with the extension and the diminution of the woods where they originate and through which they run, is as well established as any proposition in the science of physical geography. [Footnote: Some years ago it was popularly believed that the volume of the Mississippi, like that of the Volga and other rivers of the Eastern Hemisphere, was diminished by the increased evaporation from its basin and the drying up of the springs in consequence of the felling of the forests in the vicinity of the source of its eastern affluents. The boatmen of this great river and other intelligent observers now assure us, however, that the mean and normal level of the Mississippi has risen within a few years, and that in consequence the river is navigable at low water for boats of greater draught and at higher points in its course than was the case twenty-five years ago. This supposed increase of volume has been attributed by some to the recent re-wooding of the prairies, but the plantations thus far made are not yet sufficiently extensive to produce an appreciable effect of this nature; and besides, while young trees have covered some of the prairies, the destruction of the forest has been continued perhaps in a greater proportion in other parts of the basin of the river. A more plausible opinion is that the substitution of ground that is cultivated, and consequently spongy and absorbent, for the natural soil of the prairies, has furnished a reservoir for the rains which are absorbed by the earth and carried gradually to the river by subterranean flow, instead of running off rapidly from the surface, or, as is more probable, instead of evaporating or being taken up by the vigorous herbaceous vegetation which covers the natural prairie. A phenomenon so contrary to common experience, as would be a permanent increase in the waters of a great river, will not be accepted without the most convincing proofs. The present greater facility of navigation may be attributed to improvements in the model of the boats, to the removing of sand-banks and other impediments to the flow of the waters, or to the confining of these waters in a narrower channel, by extending the embankments of the river, or to yet other causes. So remarkable a change could not have escaped the notice of Humphreys and Abbot, whose most able labors comprise the years 1850-1861, had it occurred during that period or at any former time within the knowledge of the many observers they consulted; but no such fact is noticed in their exhaustive report. However, even if an increase in the volume of the Mississippi, for a period of ten or twenty years, were certain, it would still be premature to consider this increase as normal and constant, since it might very well be produced by causes yet unknown and analogous to those which influence the mysterious advance and retreat of those Alpine ice-rivers, the glaciers. Among such causes we may suppose a long series of rainy seasons in regions where important tributaries have their far-off and almost unknown sources; and with no less probability, we may conceive of the opening of communications with great subterranean reservoirs, which may from year to year empty large quantities of water into the bed of the stream; or the closing up of orifices through which a considerable portion of the water of the river once made its way for the supply of such reservoirs.--See upon this point, Chap. IV., Of Subterranean Waters; post.] Of the converse proposition, namely, that the planting of new forests gives rise to new springs and restores the regular flow of rivers, I find less of positive proof, however probable it may be that such effects would follow. [Footnote: According to the Report of the Department of Agriculture for February, 1872, it is thought in the Far West that the young plantations have already influenced the water-courses in that region, and it is alleged that ancient river-beds, never known to contain water since the settlement of the country, have begun to flow since these plantations were commenced. See also Hayden, Report on Geological Survey of Wyoming, 1870, p. 104, and Bryant. Forest Trees, 1871, chap. iv. In the Voyage autour du Monde of the Comte da Beauvoir, chap. x., this passage occurs: Dr. Muller, Director of the Botanic Garden at Melbourne, "has distributed through the interior of Australia millions of seedling trees from his nursuries. Small rivulets are soon formed under the young wood; the results are superb, and the observation of every successive year confirms them. On bare soils he has created, at more than a hundred points, forests and water-courses."] A reason for the want of evidence on the subject may be, that, under ordinary circumstances, the process of conversion of bare ground to soil with a well-wooded surface is so gradual and slow, and the time required for a fair experiment is consequently so long, that many changes produced by the action of the new geographical element escape the notice and the memory of ordinary observers. The growth of a forest, including the formation of a thick stratum of vegetable mould beneath it, is the work of a generation, its destruction may be accomplished in a day; and hence, while the results of the one process may, for a considerable time, be doubtful if not imperceptible, those of the other are immediate and readily appreciable. Fortunately, the plantation of a wood produces other beneficial consequences which are both sooner realized and more easily estimated; and though he who drops the seed is sowing for a future generation as well as for his own, the planter of a grove may hope himself to reap a fair return for his expenditure and his labor. Influence of the Forest on Inundations and Torrents. Inasmuch as it is not yet proved that the forests augment or diminish the precipitation in the regions they principally cover, we cannot positively affirm that their presence or absence increases or lessens the total volume of the water annually delivered by great rivers or by mountain torrents. It is nevertheless certain that they exercise an action on the discharge of the water of rain and snow into the valleys, ravines, and other depressions of the surface, where it is gathered into brooks and finally larger currents, and consequently influence the character of floods, both in rivers and in torrents. For this reason, river inundations and the devastations of torrents, and the geographical effects resulting from them, so far as they are occasioned or modified by the action of forests or of the destruction of the woods, may properly be discussed in this chapter, though they might seem otherwise to belong more appropriately to another division of this work. Besides the climatic question, which I have already sufficiently discussed, and the obvious inconveniences of a scanty supply of charcoal, of fuel, and of timber for architectural and naval construction and for the thousand other uses to which wood is applied in rural and domestic economy, and in the various industrial processes of civilized life, the attention of European foresters and public economists has been specially drawn to three points, namely: the influence of the forests on the permanence and regular flow of springs or natural fountains; on inundations by the overflow of rivers; and on the abrasion of soil and the transportation of earth, gravel, pebbles, and even of considerable masses of rock, from higher to lower levels, by torrents. There are, however, connected with this general subject, several other topics of minor or strictly local interest, or of more uncertain character, which I shall have occasion more fully to speak of hereafter. The first of these three principal subjects--the influence of the woods on springs and other living waters--has been already considered; and if the facts stated in that discussion are well established, and the conclusions I have drawn from them are logically sound, it would seem to follow, as a necessary corollary, that the action of the forest is as important in diminishing the frequency and violence of river-floods as in securing the permanence and equability of natural fountains; for any cause which promotes the absorption and accumulation of the water of precipitation by the superficial strata of the soil, to be slowly given out by infiltration and percolation, must, by preventing the rapid flow of surface-water into the natural channels of drainage, tend to check the sudden rise of rivers, and, consequently, the overflow of their banks, which constitutes what is called inundation. The surface of a forest, in its natural condition, can never pour forth such deluges of water as flow from cultivated soil. Humus, or vegetable mould, is capable of absorbing almost twice its own weight of water. The soil in a forest of deciduous foliage is composed of humus, more or less unmixed, to the depth of several inches, sometimes even of feet, and this stratum is usually able to imbibe all the water possibly resulting from the snow which at any one time covers, or the rain which in any one shower falls upon it. But the vegetable mould does not cease to absorb water when it becomes saturated, for it then gives off a portion of its moisture to the mineral earth below, and thus is ready to receive a new supply; and, besides, the bed of leaves not yet converted to mould takes up and retains a very considerable proportion of snow-water, as well as of rain. The stems of trees, too, and of underwood, the trunks and stumps and roots of fallen timber, the mosses and fungi and the numerous inequalities of the ground observed in all forests, oppose a mechanical resistance to the flow of water over the surface, which sensibly retards the rapidity of its descent down declivities, and diverts and divides streams which may have already accumulated from smaller threads of water. [Footnote: In a letter addressed to the Minister of Public Works, after the terrible inundations of 1857, the late Emperor of France thus happily expressed himself: "Before we seek the remedy for an evil, we inquire into its cause. Whence come the sudden floods of our rivers From the water which falls on the mountains, not from that which falls on the plains. The waters which fall on our fields produce but few rivulets, but these which fall on our roofs and are collected in the gutters, form small streams at once. Now, the roofs are mountains--the gutters are valleys." "To continue the comparison," observes D'Hericourt, "roofs are smooth and impermeable, and the rain-water pours rapidly off from their surfaces; but this rapidity of flow would be greatly diminished if the roofs were carpeted with mosses and grasses; more still, if they were covered with dry leaves, little shrubs, strewn branches, and other impediments--in short, if they were wooded."--Annales Forestieres, Dec. 1857, p. 311. The mosses and fungi play a more important part in regulating the humidity of the air and of the soil than writers on the forest have usually assigned to them. They perish with the trees they grow on; but, in many situations, nature provides a compensation for the tree-mosses and fungi in ground species, which, on cold soils, especially those with a northern exposure, spring up abundantly both before the woods are felled, and when the land is cleared and employed for pasturage, or deserted. These humble plants discharge a portion of the functions appropriated to the wood, and while they render the soil of improved lands much less fit for agricultural use, they, at the same time, prepare it for the growth of a new harvest of trees, when the infertility they produce shall have driven man to abandon it and suffer it to relapse into the hands of nature. In primitive forests, when the ground is not too moist to admit of a dense growth of trees, the soil is generally so thickly covered with leaves that there is little room for ground mosses and mushrooms. In the more open artificial woods of Europe these forms of vegetation, as well as many more attractive plants, are more frequent than in the native groves of America. See, on cryptogamic and other wood plants, Rossmassler, Der Wald, pp. 82 et seqq., and on the importance of such vegetables in checking the flow of water, Mengotti, Idraulica Fisica e Sperimentale, chapters xvi. and xvii. No writer known to me has so well illustrated this function of forest vegetation as Mengotti, though both he and Rossmassler ascribe to plants a power of absorbing water from the atmosphere which they do not possess, or rather can only rarely exercise.] The value of the forest as a mechanical check to a too rapid discharge of rain-water was exemplified in numerous instances in the great floods of 1866 and 1868, in France and Switzerland, and I refer to the observations made on those occasions as of special importance because no previous inundations in those countries had been so carefully watched and so well described by competent investigators. In the French Department of Lozere, which was among those most severely injured by the inundation of 1866--an inundation caused by diluvial rains, not by melted snow--it was everywhere remarked that "grounds covered with wood sustained no damage even on the steepest slopes, while in cleared and cultivated fields the very soil was washed away and the rocks laid bare by the pouring rain." [Footnote: See, for other like observations, an article entitled Le Reboisement et les Inondations, in the Revue des Eaux et Forets of September, 1868] The Italian journals of the day state that the province of Brescia and a part of that of Bergamo, which have heretofore been exposed to enormous injury, after every heavy rain, from floods of the four principal streams which traverse them, in a great degree escaped damage in the terrible inundation of October, 1872, and their immunity is ascribed to the forestal improvements executed by the former province, within ten or twelve years, in the Val Camonica and in the upper basins of the other rivers which drain that territory. Similar facts were noticed in the extraordinary floods of September and October, 1868, in the valley of the Upper Rhine, and Coaz makes the interesting observation that not even dense greensward was so efficient a protection to the earth as trees, because the water soaked through the sod and burst it up by hydrostatic pressure. [Footnote: Die Hochwasser in 1868 im Bandnerischen Rheingebiet, pp. 12, 68. Observations of Forster, cited by Cezanne from the Annales Forestieres for 1859, p. 358, are not less important than those adduced in the text. The field of these observations was a slope of 45 degrees divided into three sections, one luxuriantly wooded from summit to base with oak and beech, one completely cleared through its whole extent, and one cleared in its upper portion, but retaining a wooded belt for a quarter of the height of the slope, which was from 1,360 to 1,800 feet above the brook at its foot. In the first section, comprising six-sevenths of the whole surface, the rains had not produced a single ravine; in the second, occupying about a tenth of the ground, were three ravines, increasing in width from the summit to the valley beneath, where they had, all together, a cross-section of 600 square feet; in the third section, of about the same extent as the second, four ravines had been formed, widening from the crest of the slope to the belt of wood, where they gradually narrowed and finally disappeared. For important observations to the same purpose, see Marchand, Les Torrents des Alpes, in Revue des Eaux et Forets for September, 1871.] The importance of the mechanical resistance of the wood to the flow of water OVER THE SURFACE has, however, been exaggerated by some writers. Rain-water is generally absorbed by the forest-soil as fast as it falls, and it is only in extreme cases that it gathers itself into a superficial sheet or current overflowing the ground. There is, nevertheless, besides the absorbent power of the soil, a very considerable mechanical resistance to the transmission of water BENEATH the surface through and along the superior strata of the ground. This resistance is exerted by the roots, which both convey the water along their surface downwards, and oppose a closely wattled barrier to its descent along the slope of the permeable strata which have absorbed it. [Footnote: In a valuable report on a bill for compelling the sale of waste communal lands, now pending in the Parliament of Italy, Senator Torelli, an eminent man of science, calculates that four-fifths of the precipitation in the forest are absorbed by the soil, or detained by the obstructions of the surface, only one-fifth being delivered to the rivers rapidly enough to create danger of floods, while in open grounds, in heavy rains, the proportions are reversed. Supposing a rain-fall of four inches, an area measuring 100,000 acres, or a little more than four American townships, would receive 53,777,777 cubic yards of water. Of this quantity it would retain, or rather detain, if wooded, 41,000,000 yards, if bare, only 11,000,000. The difference of discharge from wooded and unwooded soils is perhaps exaggerated in Col. Torelli's report, but there is no doubt that in very many cases it is great enough to prevent, or to cause, destructive inundations.] Rivers fed by springs and shaded by woods are comparatively uniform in volume, in temperature, and in chemical composition. [Footnote: Dumont gives an interesting extract from the Misopogon of the Emperor Julian, showing that, in the fourth century, the Seine--the level of which now varies to the extent of thirty feet between extreme high and extreme low water mark--was almost wholly exempt from inundations, and flowed with a uniform current through the whole year. "Ego olim eram in hibernis apud curam Lutetiam, [sic] enim Galli Parisiorum oppidum appellant, quae insula est non magna, in fluvio sita, qui eam omni ex parte cingit. Pontes sublicii utrinque ad eam ferunt, raroque fluvius minuitur ac crescit; sed qualis aestate talis esse solet hyeme."--Des Travaux Publics dans leur Rapports avec l'Agriculture, p. 361, note. As Julian was six years in Gaul, and his principal residence was at Paris, his testimony as to the habitual condition of the Seine, at a period when the provinces where its sources originate were well wooded, is very valuable.] Their banks are little abraded, nor are their courses much obstructed by fallen timber, or by earth and gravel washed down from the highlands. Their channels are subject only to slow and gradual changes, and they carry down to the lakes and the sea no accumulation of sand or silt to fill up their outlets, and, by raising their beds, to force them to spread over the low grounds near their mouth. [Footnote: Forest rivers seldom if ever form large sedimentary deposits at their points of discharge into lakes or larger streams, such accumulations beginning or at least advancing far more rapidly, after the valleys are cleared.] Causes of Inundations. The immediate cause of river inundations is the flow of superficial and subterranean waters into the beds of rivers faster than those channels can discharge them. The insufficiency of the channels is occasioned partly by their narrowness and partly by obstructions to their currents, the most frequent of which is the deposit of sand, gravel, and pebbles in their beds by torrential tributaries during the floods. [Footnote: The extent of the overflow and the violence of the current in river- floods are much affected by the amount of sedimentary matter let fall in their channels by their affluents, which have usually a swifter flow than the main stream, and consequently deposit more or less of their transported material when they join its more slowly-moving waters. Such deposits constitute barriers which at first check the current and raise its level, and of course its violence at lower points is augmented, both by increased volume and by the solid material it carries with it, when it acquires force enough to sweep away the obstruction.--Risler, Sur L influence des Forets sur les Cours d eau, in Revue des Eaux et Forets, 10th January, 1870. In the flood of 1868 the torrent Illgraben, which had formerly spread its water and its sediment over the surface of a vast cone of dejection, having been forced, by the injudicious confinement of its current to a single channel, to discharge itself more directly into the Rhone, carried down a quantity of gravel, sand, and mud, sufficient to dam that river for a whole hour, and in the same great inundation the flow of the Rhine at Thusis was completely arrested for twenty minutes by a similar discharge from the Nolla. Of course, when the dam yielded to the pressure of the accumulated water, the damage to the country below was far greater than it would have ben had the currents of the rivers not been thus obstructed.--Marchand, Les Torrents des Alpes, in Revue des Eaux et Forets, Sept., 1871.] In accordance with the usual economy of nature, we should presume that she had everywhere provided the means of discharging, without disturbance of her general arrangements or abnormal destruction of her products, the precipitation which she sheds upon the face of the earth. Observation confirms this presumption, at least in the countries to which I confine my inquiries; for, so far as we know the primitive conditions of the regions brought under human occupation within the historical period, it appears that the overflow of river-banks was much less frequent and destructive than at the present day, or, at least, that rivers rose and fell less suddenly, before man had removed the natural checks to the too rapid drainage of the basins in which their tributaries originate. The affluents of rivers draining wooded basins generally transport, and of course let fall, little or no sediment, and hence in such regions the special obstruction to the currents of water-courses to which I have just alluded does not occur. The banks of the rivers and smaller streams in the North American colonies were formerly little abraded by the currents. [Footnote: In primitive countries, running streams are very generally fringed by groves, for almost every river is, as Pliny, Nat. Hist., v. 10, says of the Upper Nile, an opifex silvarum, or, to use the quaint and picturesque language of Holland's translation, "makes shade of woods as he goeth."] Even now the trees come down almost to the water's edge along the rivers, in the larger forests of the United States, and the surface of the streams seems liable to no great change in level or in rapidity of current. [Footnote: A valuable memoir by G. Doni, in the Rivista Forestale for October, 1863, p. 438, is one of the best illustrations I can cite of the influence of forests in regulating and equalizing the flow of running water, and of the comparative action of water-courses which drain wooded valleys and valleys bared of trees, with regard to the erosion of their banks and the transportation of sediment. "The Sestajone," remarks this writer, "and the Lima, are two considerable torrents which collect the waters of two great valleys of the Tuscan Apennines, and empty them into the Serchio. At the junction of these two torrents, from which point the combined current takes the name of Lima, a curious phenomenon is observed, which is in part easily explained. In rainy weather the waters of the Sestajone are in volume only about one-half those of the Lima, and while the current of the Lima is turbid and muddy, that of the Sestajone appears limpid and I might almost say drinkable. In clear weather, on the contrary, the waters of the Sestajone are abundant and about double those of the Lima. Now the extent of the two valleys is nearly equal, but the Sestajone winds down between banks clothed with firs and beeches, while the Lima flows through a valley that has been stripped of trees, and in great part brought under cultivation." The Sestajone and the Lima are neither of them what is technically termed a torrent--a name strictly applicable only to streams whose current is not derived from springs and perennial, but is the temporary effect of a sudden accumulation of water from heavy rains or from a rapid melting of the snows, while their beds are dry, or nearly so, at other times. The Lima, however, in a large proportion of its course, has the erosive character of a torrent, for the amount of sediment which it carries down, even when it is only moderately swollen by rains, surpasses almost everything of the kind which I have observed, under analogous circumstances, in Italy. Still more striking is the contrast in the regime of the Saint-Phalez and the Combe-d'Yeuse in the Department of Vancluse, the latter of which became subject to the most violent torrential floods after the destruction of the woods of its basin between 1823 and 1833, but has now been completely subdued, and its waters brought to a peaceful flow, by replanting its valley. See Labussiere, Revue Agric. et Forestiere de Provence, 1866, and Revue des Eaux et Forets, 1866.] Inundations in Winter. In the Northern United States, although inundations are not very unfrequently produced by heavy rains in the height of summer, it will be found generally true that the most rapid rise of the waters, and, of course, the most destructive "freshets," as they are called in America, are occasioned by the sudden dissolution of the snow before the open ground is thawed in the spring. It frequently happens that a powerful thaw sets in after a long period of frost, and the snow which had been months in accumulating is dissolved and carried off in a few hours. When the snow is deep, it, to use a popular expression, "takes the frost out of the ground" in the woods, and, if it lies long enough, in the fields also. But the heaviest snows usually fall after midwinter, and are succeeded by warm rains or sunshine, which dissolve the snow on the cleared land before it has had time to act upon the frost-bound soil beneath it. In this case, the snow in the woods is absorbed as fast as it melts, by the soil it has protected from freezing, and does not materially contribute to swell the current of the rivers. If the mild weather, in which great snow-storms usually occur, does not continue and become a regular thaw, it is almost sure to be followed by drifting winds, and the inequality with which they distribute the snow over the cleared ground leaves the ridges of the surface-soil comparatively bare, while the depressions are often filled with drifts to the height of many feet. The knolls become frozen to a great depth; succeeding partial thaws melt the surface-snow, and the water runs down into the furrows of ploughed fields, and other artificial and natural hollows, and then often freezes to solid ice. In this state of things, almost the entire surface of the cleared land is impervious to water, and from the absence of trees and the general smoothness of the ground, it offers little mechanical resistance to superficial currents. If, under these circumstances, warm weather accompanied by rain occurs, the rain and melted snow are swiftly hurried to the bottom of the valleys and gathered to raging torrents. It ought further to be considered that, though the lighter ploughed soils readily imbibe a great deal of water, yet grass-lands, and all the heavy and tenacious earths, absorb it in much smaller quantities, and less rapidly than the vegetable mould of the forest. Pasture, meadow, and clayey soils, taken together, greatly predominate over sandy ploughed fields, in all large agricultural districts, and hence, even if, in the case we are supposing, the open ground chance to have boon thawed before the melting of the snow which covers it, it is already saturated with moisture, or very soon becomes so, and, of course, cannot relieve the pressure by absorbing more water. The consequence is that the face of the country is suddenly flooded with a quantity of melted snow and rain equivalent to a fall of six or eight inches of the latter, or even more. This runs unobstructed to rivers often still-bound with thick ice, and thus inundations of a fearfully devastating character are produced. The ice bursts, from the hydrostatic pressure from below, or is violently torn up by the current, and is swept by the impetuous stream, in large masses and with resistless fury, against banks, bridges, dams, and mills erected near them. The bark of the trees along the rivers is often abraded, at a height of many feet above the ordinary water-level, by cakes of floating ice, which are at last stranded by the receding flood on meadow or ploughland, to delay, by their chilling influence, the advent of the tardy spring. Another important effect of the removal of the forest shelter in cold climates may be noticed here. We have observed that the ground in the woods either does not freeze at all, or that if frozen it is thawed by the first considerable snow-fall. On the contrary, the open ground is usually frozen when the first spring freshet occurs, but is soon thawed by the warm rain and melting snow. Nothing more effectually disintegrates a cohesive soil than freezing and thawing, and the surface of earth which has just undergone those processes is more subject to erosion by running water than under any other circumstances. Hence more vegetable mould is washed away from cultivated grounds in such climates by the spring floods than by the heaviest rain at other seasons. In the warm climates of Southern Europe, as I have already said, the functions of the forest, so far as the disposal of the water of precipitation is concerned, are essentially the same at all seasons, and are analogous to those which it performs in the Northern United States in summer. Hence, in the former countries, the winter floods have not the characteristics which mark them in the latter, nor is the conservative influence of the woods in winter relatively so important, though it is equally unquestionable. If the summer floods in the United States are attended with less pecuniary damage than those of the Loire and other rivers of France, the Po and its tributaries in Italy, the Emme and her sister torrents which devastate the valleys of Switzerland, it is partly because the banks of American rivers are not yet lined with towns, their shores and the bottoms which skirt them not yet covered with improvements whose cost is counted by millions, and, consequently, a smaller amount of property is exposed to injury by inundation. But the comparative exemption of the American people from the terrible calamities which the overflow of rivers has brought on some of the fairest portions of the Old World, is, in a still greater degree, to be ascribed to the fact that, with all our thoughtless improvidence, we have not yet bared all the sources of our streams, not yet overthrown all the barriers which nature has erected to restrain her own destructive energies. Let us be wise in time, and profit by the errors of our older brethren! The influence of the forest in preventing inundations has been very generally recognized, both as a theoretical inference and as a fact of observation; but the eminent engineer Belgrand and his commentator Valles have deduced an opposite result from various facts of experience and from scientific considerations. They contend that the superficial drainage is more regular from cleared than from wooded ground, and that clearing diminishes rather than augments the intensity of inundations. Neither of these conclusions appears to be warranted by their data or their reasoning, and they rest partly upon facts, which, truly interpreted, are not inconsistent with the received opinions on these subjects, partly upon assumptions which are contradicted by experience. Two of these latter are, first, that the fallen leaves in the forest constitute an impermeable covering of the soil over, not through, which the water of rains and of melting snows flows off, and secondly, that the roots of trees penetrate and choke up the fissures in the rocks, so as to impede the passage of water through channels which nature has provided for its descent to lower strata. As to the first of those, we may appeal to familiar facts within the personal knowledge of every man acquainted with the operations of sylvan nature. Rain-water never, except in very trifling quantities, flows over the leaves in the woods in summer or autumn. Water runs over them only in the spring, in the rare cases when they have been pressed down smoothly and compactly by the weight of the snow--a state in which they remain only until they are dry, when shrinkage and the action of the wind soon roughen the surface so as effectually to stop, by absorption, all flow of water. I have observed that when a sudden frost succeeds a thaw at the close of the winter, after the snow has principally disappeared, the water in and between the layers of leaves sometimes freezes into a solid crust, which allows the flow of water over it. But this occurs only in depressions and on a very small scale; and the ice thus formed is so soon dissolved that no sensible effect is produced on the escape of water from the general surface. As to the influence of roots upon drainage, we have seen that there is no doubt that they, independently of their action as absorbents, mechanically promote it. Not only does the water of the soil follow them downwards, but their swelling growth powerfully tends to enlarge, not to obstruct, the crevices of rock into which they enter; and as the fissures in rocks are longitudinal, not mere circular orifices, every line of additional width gained by the growth of roots within them increases the area of the crevice in proportion to its length. Consequently, the widening of a fissure to the extent of one inch might give an additional drainage equal to a square foot of open tubing. The observations and reasonings of Belgrand and Valles, though their conclusions have not been accepted by many, are very important in one point of view. There writers insist much on the necessity of taking into account, in estimating the relations between precipitation and evaporation, the abstraction of water from the surface and surface-currents, by absorption and infiltration--an element unquestionably of great value, but hitherto much neglected by meteorological inquirers, who have very often reasoned as if the surface-earth were either impermeable to water or already saturated with it; whereas, in fact, it is a sponge, always imbibing humidity and always giving it off, not by evaporation only, but by infiltration and percolation. The remarkable historical notices of inundations in France in the Middle Ages collected by Champion [Footnote: Les Inondations en France depuis le VIe siecle jusqu'a nos jours, 6 vols, 8vo. Paris, 1858-64. See a very able review of this learned and important work by Prof. Messedaglia, read before the Academy of Agriculture at Verona in 1864.] are considered by many as furnishing proof, that when that country was much more generally covered with wood than it now is, destructive inundations of the French rivers were not less frequent than they are in modern days. But this evidence is subject to this among other objections: we know, it is true, that the forests of certain departments of France were anciently much more extensive than at the present day; but we know also that in many portions of that country the soil has been bared of its forests, and then, in consequence of the depopulation of great provinces, left to reclothe itself spontaneously with trees, many times during the historic period; and our acquaintance with the forest topography of ancient Gaul or of mediaeval France is neither sufficiently extensive nor sufficiently minute to permit us to say, with certainty, that the sources of this or that particular river were more or less sheltered by wood at any given time, ancient or mediaeval, than at present. [Footnote: Alfred Maury has, nevertheless, collected, in his erudite and able work, Les Forets de la Gaule et de l'ancienne France, Paris, 1867, an immense amount of statistical detail on the extent, the distribution, and the destruction of the forests of France, but it still remains true that we can very seldom pronounce on the forestal condition of the upper valley of a particular river at the time of a given inundation in the ancient or the mediaeval period.] I say the sources of the rivers, because the floods of great rivers are occasioned by heavy rains and snows which fall in the more elevated regions around the primal springs, and not by precipitation in the main valleys or on the plains bordering on the lower course. The destructive effects of inundations, considered simply as a mechanical power by which life is endangered, crops destroyed, and the artificial constructions of man overthrown, are very terrible. Thus far, however, the flood is a temporary and by no means an irreparable evil, for if its ravages end here, the prolific powers of nature and the industry of man soon restore what had been lost, and the face of the earth no longer shows traces of the deluge that had overwhelmed it. Inundations have even their compensations. The structures they destroy are replaced by better and more secure erections, and if they sweep off a crop of corn, they not unfrequently leave behind them, as they subside, a fertilizing deposit which enriches the exhausted field for a succession of seasons. [Footnote: The productiveness of Egypt has been attributed too exclusively to the fertilizing effects of the slime deposited by the inundations of the Nile; for in that climate a liberal supply of water would produce good crops on almost any ordinary sand, while, without water, the richest soil would yield nothing. The sediment deposited annually is but a very small fraction of an inch in thickness. It is alleged that in quantity it would be hardly sufficient for a good top-dressing, and that in quality it is not chemically distinguishable from the soil inches or feet below the surface. But to deny, as some writers have done, that the slime has any fertilizing properties at all, is as great a error as the opposite one of ascribing all the agricultural wealth of Egypt to that single cause of productiveness. Fine soils deposited by water are almost uniformly rich in all climates; those brought down by rivers, carried out into salt-water, and then returned again by the tide, seem to be more permanently fertile than any others. The polders of the Netherland coast are of this character, and the meadows in Lincolnshire, which have been covered with slime by warping, as it is called, or admitting water over them at high tide, are remarkably productive. Recent analysis is said to have detected in the water of the Nile a quantity of organic matter--derived mainly, no doubt, from the decayed vegetation it bears down from its tropical course--sufficiently large to furnish an important supply of fertilizing ingredients to the soil. It is computed that the Durance--a river fed chiefly by torrents, of great erosive power--carries down annually solid material enough to cover 272,000 acres of soil with a deposit of two-fifths of an inch in thickness, and that this deposit contains, in the combination most favorable to vegetation, more azote than 110,000 tons of guano, and more carbon than 121,000 acres of woodland would assimilate in a year. Elisee Reclus, La Terre, vol. i., p. 467. On the chemical composition, quantity, and value of the solid matter transported by river, see Herve Magnon, Sur l'Emploi des Eaux dans les Irrigations, 8vo. Paris, 1869, pp. 132 et seqq. Duponchel, Traite d'Hydraulique et de Geologie Agricoles. Paris, 1868, chap. i., xii., and xiii.] If, then, the too rapid flow of the surface-waters occasioned no other evil than to produce, once in ten years upon the average, an inundation which should destroy the harvest of the low grounds along the rivers, the damage would be too inconsiderable, and of too transitory a character, to warrant the inconveniences and the expense involved in the measures which the most competent judges in many parts of Europe believe the respective governments ought to take to obviate it. Destructive Action of Torrents. But the great, the irreparable, the appalling mischiefs which have already resulted, and which threaten to ensue on a still more extensive scale hereafter, from too rapid superficial drainage, are of a properly geographical, we may almost say geological, character, and consist primarily in erosion, displacement, and transportation of the superficial strata, vegetable and mineral--of the integuments, so to speak, with which nature has clothed the skeleton frame-work of the globe. It is difficult to convey by description an idea of the desolation of the regions most exposed to the ravages of torrent and of flood; and the thousands who, in these days of swift travel, are whirled by steam near or even through the theatres of these calamities, have but rare and imperfect opportunities of observing the destructive causes in action. Still more rarely can they compare the past with the actual condition of the provinces in question, and trace the progress of their conversion from forest-crowned hills, luxuriant pasture grounds, and abundant cornfields and vineyards well watered by springs and fertilizing rivulets, to bald mountain ridges, rocky declivities, and steep earth-banks furrowed by deep ravines with beds now dry, now filled by torrents of fluid mud and gravel hurrying down to spread themselves over the plain, and dooming to everlasting barrenness the once productive fields. In surveying such scenes, it is difficult to resist the impression that nature pronounced a primal curse of perpetual sterility and desolation upon these sublime but fearful wastes, difficult to believe that they wore once, and but for the folly of man might still be, blessed with all the natural advantages which Providence has bestowed upon the most favored climes. But the historical evidence is conclusive as to the destructive changes occasioned by the agency of man upon the flanks of the Alps, the Apennines, the Pyrenees, and other mountain ranges in Central and Southern Europe, and the progress of physical deterioration has been so rapid that, in some localities, a single generation has witnessed the beginning and the end of the melancholy revolution. I have stated, in a general way, the nature of the evils in question, and of the processes by which they are produced; but I shall make their precise character and magnitude better understood by presenting some descriptive and statistical details of facts of actual occurrence. I select for this purpose the south-eastern portion of France, not because that territory has suffered more severely than some others, but because its deterioration is comparatively recent, and has been watched and described by very competent and trustworthy observers, whose reports are more easily accessible than those published in other countries. [Footnote: Streffleur (Ueber die Natur und die Wirkungen der Wildbuche, p. 3) maintains that all the observations and speculations of French authors on the nature of torrents had been anticipated by Austrian writers. In proof of this assertion he refers to the works of Franz von Zallinger, 1778, Von Arretin, 1808, Franz Duile, 1826, all published at Innsbruck, and Hagenus Beschreibung neuerer Wasserbauwerke, Konigsberg, 1826, none of which works are known to me. It is evident, however, that the conclusions of Surell and other French writers whom I cite, are original results of personal investigation, and not borrowed opinions.] The provinces of Dauphiny and Provence comprise a territory of fourteen or fifteen thousand square miles, bounded north-west by the Isere, north-east and east by the Alps, south by the Mediterranean, west by the Rhone, and extending from 42 degrees to about 45 degrees of north latitude. The surface is generally hilly and even mountainous, and several of the peaks in Dauphiny rise above the limit of perpetual snow. Except upon the mountain ridges, the climate, as compared with that of the United States in the same latitude, is extremely mild. Little snow falls, except upon the higher mountains, the frosts are light, and the summers long, as might, indeed, be inferred from the vegetation; for in the cultivated districts, the vine and the fig everywhere flourish; the olive thrives as far north as 43 and one half degrees, and upon the coast grow the orange, the lemon, and the date-palm. The forest trees, too, are of southern type, umbrella pines, various species of evergreen oaks, and many other trees and shrubs of persistent broad-leaved foliage, characterizing the landscape. The rapid slope of the mountains naturally exposed these provinces to damage by torrents, and the Romans diminished their injurious effects by erecting, in the beds of ravines, barriers of rocks loosely piled up, which permitted a slow escape of the water, but compelled it to deposit above the dikes the earth and gravel with which it was charged. [Footnote: Whether Palissy was acquainted with this ancient practice, or whether it was one of those original suggestions of which his works are so full, I know not, but in his treatise, Des Eaux et Fontaines, he thus recommends it, by way of reply to the objections of "Theorique," who had expressed the fear that "the waters which rush violently down from the heights of the mountain would bring with them much earth, sand, and other things," and thus spoil the artificial fountain that "Practique" was teaching him to make: "And for hindrance of the mischiefs of great waters which may be gathered in a few hours by great storms, when thou shalt have made ready thy parterre to receive the water, thou must lay great atones athwart the deep channels which lead to thy parterre. And so the force of the rushing currents shall be deadened, and thy water shall flow peacefully into his cisterns."--Oeuvres Completes, p. 178.] At a later period the Crusaders brought home from Palestine, with much other knowledge gathered from the wiser Moslems, the art of securing the hillsides and making them productive by terracing and irrigation. The forests which covered the mountains secured an abundant flow of springs, and the process of clearing the soil went on so slowly that, for centuries, neither the want of timber and fuel, nor the other evils about to be depicted, were seriously felt. Indeed, throughout the Middle Ages, these provinces were well wooded, and famous for the fertility and abundance, not only of the low grounds, but of the hills. Such was the state of things at the close of the fifteenth century. The statistics of the seventeenth show that while there had been an increase of prosperity and population in Lower Provence, as well as in the correspondingly situated parts of the other two provinces I have mentioned, there was an alarming decrease both in the wealth and in the population of Upper Provence and Dauphiny, although, by the clearing of the forests, a great extent of plough-land and pasturage had been added to the soil before reduced to cultivation. It was found, in fact, that the augmented violence of the torrents had swept away, or buried in sand and gravel, more land than had been reclaimed by clearing; and the taxes computed by fires or habitations underwent several successive reductions in consequence of the gradual abandonment of the wasted soil by its starving occupants. The growth of the large towns on and near the Rhone and the coast, their advance in commerce and industry, and the consequently enlarged demand for agricultural products, ought naturally to have increased the rural population and the value of their lands; but the physical decay of the uplands was such that considerable tracts were deserted altogether, and in Upper Provence, the fires which, in 1471 counted 897, were reduced to 747 in 1699, to 728 in 1733, and to 635 in 1776. [Footnote: These facts I take from the La Provence au point de vue des Bois, des Torrents et des Inondations, of Charles de Ribbe, one of the highest authorities.] Surell--whose admirable work, Etude sur les Torrents des Hautes Alpes, first published in 1841, [Footnote: A second edition of this work, with an additional volume of great value by Ernest Cezanne, was published at Paris, in two 8vo volumes, in 1871-72.] presents a most appalling picture of the desolations of the torrent, and, at the same time, the most careful studies of the history and essential character of this great evil--in speaking of the valley of Devoluy, on page 152, says: "Everything concurs to show that it was anciently wooded. In its peat-bogs are found buried trunks of trees, monuments of its former vegetation. In the framework of old houses, one sees enormous timber, which is no longer to be found in the district. Many localities, now completely bare, still retain the name of 'wood,' and one of them is called, in old deeds, Comba nigra [Black forest or dell], on account of its dense woods. These and many other proofs confirm the local traditions which are unanimous on this point. "There, as everywhere in the Upper Alps, the clearings began on the flanks of the mountains, and were gradually extended into the valleys and then to the highest accessible peaks. Then followed the Revolution, and caused the destruction of the remainder of the trees which had thus far escaped the woodman's axe." In a note to this passage the writer says: "Several persons have told me that they had lost flocks of sheep, by straying, in the forests of Mont Auroux, which covered the flanks of the mountain from La Cluse to Agneres. These declivities are now as bare as the palm of the hand." The ground upon the steep mountains being once bared of trees, and the underwood killed by the grazing of horned cattle, sheep, and goats, every depression becomes a water-course. "Every storm," says Surell, page 153, "gives rise to a new torrent. [Footnote: No attentive observer can frequent the southern flank of the Piedmontese Alps or the French province of Dauphiny, for half a dozen years, without witnessing with his own eyes the formation and increase of new torrents. I can bear personal testimony to the conversion of more than one grassy slope into the bed of a furious torrent by baring the hills above of their woods.] Examples of such are shown, which, though not yet three years old, have laid waste the finest fields of their valleys, and whole villages have narrowly escaped being swept into ravines formed in the course of a few hours. Sometimes the flood pours in a sheet over the surface, without ravine or even bed, and ruins extensive grounds, which are abandoned forever." I cannot follow Surell in his description and classification of torrents, and I must refer the reader to his instructive work for a full exposition of the theory of the subject. In order, however, to show what a concentration of destructive energies may be effected by felling the woods that clothe and support the sides of mountain abysses, I cite his description of a valley descending from the Col Isoard, which he calls "a complete type of a basin of reception," that is, a gorge which serves as a common point of accumulation and discharge for the waters of several lateral torrents. "The aspect of the monstrous channel," says he, "is frightful. Within a distance of less than two English miles, more than sixty torrents hurl into the depths of the gorge the debris torn from its two flanks. The smallest of these secondary torrents, if transferred to a fertile valley, would be enough to ruin it." The eminent political economist Blanqui, in a memoir read before the Academy of Moral and Political Science on the 25th of November, 1843, thus expresses himself: "Important as are the causes of impoverishment already described, they are not to be compared to the consequences which have followed from the two inveterate evils of the Alpine provinces of France, the extension of clearing and the ravages of torrents. ... The most important result of this destruction is this; that the agricultural capital, or rather the ground itself--which, in a rapidly increasing degree, is daily swept away by the waters--is totally lost. Signs of unparalleled destitution are visible in all the mountain zone, and the solitudes of those districts are assuming an indescribable character of sterility and desolation. The gradual destruction of the woods has, in a thousand localities, annihilated at once the springs and the fuel. Between Grenoble and Briancon, in the valley of the Romanche, many villages are so destitute of wood that they are reduced to the necessity of baking their bread with sun-dried cow-dung, and even this they can afford to do but once a year. "Whoever has visited the valley of Barcelonette, those of Embrun, and of Verdun, and that Arabia Petraea of the department of the Upper Alps, called Devoluy, knows that there is no time to lose--that in fifty years from this date France will be separated from Savoy, as Egypt from Syria, by a desert." [Footnote: Ladoucette says the peasant of Devoluy "often goes a distance of five hours over rocks and precipices for a single [man's] load of wood;" and he remarks on another page, that "the justice of peace of that canton had, in the course of forty-three years, but once heard the voice of the nightingale."--Histoire, etc, des Hautes Alpes, pp. 220, 434.] It deserves to be specially noticed that the district here referred to, though now among the most hopelessly waste in France, was very productive even down to so late a period as the commencement of the French Revolution. Arthur Young, writing in 1789, says: "About Barcelonette and in the highest parts of the mountains, the hill-pastures feed a million of sheep, besides large herds of other cattle;" and he adds: "With such a soil and in such a climate, we are not to suppose a country barren because it is mountainous. The valleys I have visited are, in general, beautiful." [Footnote: The valley of Embrun, now almost completely devastated, was once remarkable for its fertility. In 1800, Hericart de Thury said of it: "In this magnificent valley nature had been prodigal of her gifts. Its inhabitants have blindly revelled in her favors, and fallen asleep in the midst of her profusion."--Becquerel, Des Climats, etc., p. 314.] He ascribes the same character to the provinces of Dauphiny, Provence, and Auvergne, and, though he visited, with the eye of an attentive and practised observer, many of the scenes since blasted with the wild desolation described by Blanqui, the Durance and a part of the course of the Loire are the only streams he mentions as inflicting serious injury by their floods. The ravages of the torrents had, indeed, as we have seen, commenced earlier in some other localities, but we are authorized to infer that they were, in Young's time, too limited in range, and relatively too insignificant, to require notice in a general view of the provinces where they have now ruined so large a proportion of the soil. But I resume my citations. "I do not exaggerate," says Blanqui. "When I shall have finished my description and designated localities by their names, there will rise, I am sure, more than one voice from the spots themselves, to attest the rigorous exactness of this picture of their wretchedness. I have never seen its equal even in the Kabyle villages of the province of Constantine; for there you can travel on horseback, and you find grass in the spring, whereas in more than fifty communes in the Alps there is absolutely nothing. "The clear, brilliant, Alpine sky of Embrun, of Gap, of Barcelonette, and of Digne, which for months is without a cloud, produces droughts interrupted only by diluvial rains like those of the tropics. The abuse of the right of pasturage and the felling of the woods have stripped the soil of all its grass and all its trees, and the scorching sun bakes it to the consistence of porphyry. When moistened by the rain, as it has neither support nor cohesion, it rolls down to the valleys, sometimes in floods resembling black, yellow, or reddish lava, sometimes in streams of pebbles, and over huge blocks of stone, which pour down with a frightful roar, and in their swift course exhibit the most convulsive movements. If you overlook from an eminence one of these landscapes furrowed with so many ravines, it presents only images of desolation and of death. Vast deposits of flinty pebbles, many feet in thickness, which have rolled down and spread far over the plain, surround large trees, bury even their tops, and rise above them, leaving to the husbandman no longer a ray of hope. One can imagine no sadder spectacle than the deep fissures in the flanks of the mountains, which seem to have burst forth in eruption to cover the plains with their ruins. Those gorges, under the influence of the sun which cracks and shivers to fragments the very rocks, and of the rain which sweeps them down, penetrate deeper and deeper into the heart of the mountain, while the beds of the torrents issuing from them are sometimes raised several feet in a single year, by the debris, so that they reach the level of the bridges, which, of course, are then carried off. The torrent-beds are recognized at a great distance, as they issue from the mountains, and they spread themselves over the low grounds, in fan-shaped expansions, like a mantle of stone, sometimes ten thousand feet wide, rising high at the centre, and curving towards the circumference till their lower edges meet the plain. "Such is their aspect in dry weather. But no tongue can give an adequate description of their devastations in one of those sudden floods winch resemble, in almost none of their phenomena, the action of ordinary river-water. They are now no longer overflowing brooks, but real seas, tumbling down in cataracts, and rolling before them blocks of stone, which are hurled forwards by the shock of the waves like balls shot out by the explosion of gunpowder. Sometimes ridges of pebbles are driven down when the transporting torrent does not rise high enough to show itself, and then the movement is accompanied with a roar louder than the crash of thunder. A furious wind precedes the rushing water and announces its approach. Then comes a violent eruption, followed by a flow of muddy waves, and after a few hours all returns to the dreary silence which at periods of rest marks these abodes of desolation. [Footnote: These explosive gushes of mud and rock appear to be occasioned by the caving-in of large masses of earth from the banks of the torrent, which dam up the stream and check its flow until it has acquired volume enough to burst the barrier and carry all before it. In 1827, such a sudden eruption of a torrent, after the current had appeared to have ceased, swept off forty-two houses and drowned twenty-eight persons in the village of Goncelin, near Grenoble, and buried with rubbish a great part of the remainder of the village." The French traveller, D'Abbadie, relates precisely similar occurrences as not unfrequent in the mountains of Abyssinia.--Surrell, Etudes, etc; 2d edition, pp. 224, 295.] "The elements of destruction are increasing in violence. The devastation advances in geometrical progression as the higher slopes are bared of their wood, and 'the ruin from above,' to use the words of a peasant, 'helps to hasten the desolation below.' "The Alps of Provence present a terrible aspect. In the more equable climate of Northern France, one can form no conception of those parched mountain gorges where not even a bush can be found to shelter a bird, where, at most, the wanderer sees in summer here and there a withered lavender, where all the springs are dried up, and where a dead silence, hardly broken by even the hum of an insect, prevails. But if a storm bursts forth, masses of water suddenly shoot from the mountain heights into the shattered gulfs, waste without irrigating, deluge without refreshing the soil they overflow in their swift descent, and leave it even more seared than it was from want of moisture. Man at last retires from the fearful desert, and I have, the present season, found not a living soul in districts where I remember to have enjoyed hospitality thirty years ago." In 1853, ten years after the date of Blanqui's memoir, M. de Bonville, prefect of the Lower Alps, addressed to the Government a report in which the following passages occur: "It is certain that the productive mould of the Alps, swept off by the increasing violence of that curse of the mountains, the torrents, is daily diminishing with fearful rapidity. All our Alps are wholly, or in large proportion, bared of wood. Their soil, scorched by the sun of Provence, cut up by the hoofs of the sheep, which, not finding on the surface the grass they require for their sustenance, gnaw and scratch the ground in search of roots to satisfy their hunger, is periodically washed and carried off by melting snows and summer storms. "I will not dwell on the effects of the torrents. For sixty years they have been too often depicted to require to be further discussed, but it is important to show that their ravages are daily extending the range of devastation. The bed of the Durance, which now in some places exceeds a mile and a quarter in width, and, at ordinary times, has a current of water less than eleven yards wide, shows something of the extent of the damage." [Footnote: In the days of the Roman Empire the Durance was a navigable, or at least a boatable, river, with a commerce so important that the boatmen upon it formed a distinct corporation.--Ladoucette, Histoire, etc., des Hautes Alpes, p. 354. Even as early as 1789 the Durance was computed to have already covered with gravel and pebbles not less than 130,000 acres, "which, but for its inundations, would have been the finest land in the province."--Arthur Young, Travels in France, vol i., ch. i.] Where, ten years ago, there were still woods and cultivated grounds to be seen, there is now but a vast torrent; there is not one of our mountains which has not at least one torrent, and new ones are daily forming. "An indirect proof of the diminution of the soil is to be found in the depopulation of the country. In 1852 I reported to the General Council that, according to the census of that year, the population of the department of the Lower Alps had fallen off no less than 5,000 souls in the five years between 1846 and 1851. "Unless prompt and energetic measures are taken, it is easy to fix the epoch when the French Alps will be but a desert. The interval between 1851 and 1856 will show a further decrease of population. In 1862 the ministry will announce a continued and progressive reduction, in the number of acres devoted to agriculture; every year will aggravate the evil and in half a century France will count more ruins, and a department the less." Time has verified the predictions of De Bonville. The later census returns show a progressive diminution in the population of the departments of the Lower Alps, the Isere, Drome, Ariege, the Upper and the Lower Pyrenees, Lozere, the Ardennes, Doubs, the Vosges, and, in short, in all the provinces formerly remarkable for their forests. This diminution is not to be ascribed to a passion for foreign emigration, as in Ireland, and in parts of Germany and of Italy; it is simply a transfer of population from one part of the empire to another, from soils which human folly has rendered uninhabitable, by ruthlessly depriving them of their natural advantages and securities, to provinces where the face of the earth was so formed by nature as to need no such safeguards, and where, consequently, she preserves her outlines in spite of the wasteful improvidence of man. [Footnote: Between 1851 and 1856 the population of Languedoc and Provence had increased by 101,000 souls. The augmentation, however, was wholly in the provinces of the plains, where all the principal cities are found. In these provinces the increase was 204,000, while in the mountain provinces there was a diminution of 103,000. The reduction of the area of arable land is perhaps even more striking. In 1842 the department of the Lower Alps possessed 90,000 hectares, or nearly 245,000 acres, of cultivated soil. In 1852 it had but 74,000 hectares. In other words, in ten years 25,000 hectares, or 61,000 acres, had been washed away, or rendered worthless for cultivation, by torrents and the abuses of pasturage.--Clave, Etudes, pp. 66, 67.] Floods of the Ardeche. The River Ardeche, in the French department of that name, has a perennial current in a considerable part of its course, and therefore is not, technically speaking, a torrent; but the peculiar character and violence of its floods is due to the action of the torrents which discharge themselves into it in its upper valley, and to the rapidity of the flow of the water of precipitation from the surface of a basin now almost bared of its once luxuriant woods. [Footnote: The original forests in which the basin of the Ardeche was rich have been rapidly disappearing for many years, and the terrific violence of the inundations which are now laying it waste is ascribed, by the ablest investigators, to that cause. In an article inserted in the Annales Forestieres for 1843, quoted by Hohenstein, Der Wald, p. 177, it is said that about one-third of the area of the department had already become absolutely barren, in consequence of clearing, and that the destruction of the woods was still going on with great rapidity. New torrents were constantly forming, and they were estimated to have covered more than 70,000 acres of good land, or one-eighth of the surface of the department, with sand and gravel.] A notice of these floods may therefore not inappropriately be introduced in this place. The floods of the Ardeche and other mountain streams are attended with greater immediate danger to life and property than those of rivers of less rapid flow, because their currents are more impetuous, and they rise more suddenly and with less previous warning. At the same time, their ravages are confined within narrower limits, the waters retire sooner to their accustomed channel, and the danger is more quickly over, than in the case of inundations of larger rivers. The Ardeche drains a basin of 600,238 acres, or a little less than nine hundred and thirty-eight square miles. Its remotest source is about seventy-five miles, in a straight line, from its junction with the Rhone, and springs at an elevation of four thousand feet above that point. At the lowest stage of the river, the bed of the Chassezac, its largest and longest tributary, is in many places completely dry on the surface--the water being sufficient only to supply the subterranean channels of infiltration--and the Ardeche itself is almost everywhere fordable, even below the mouth of the Chassezac. But in floods, the river has sometimes risen more than sixty feet at the Pont d'Arc, a natural arch of two hundred feet chord, which spans the stream below its junction with all its important affluents. At the height of the inundation of 1857, the quantity of water passing this point--after deducting thirty per cent. for material transported with the current and for irregularity of flow--was estimated at 8,845 cubic yards to the second, and between twelve o'clock at noon on the 10th of September of that year and ten o'clock the next morning, the water discharged through the passage in question amounted to more than 450,000,000 cubic yards. This quantity, distributed equally through the basin of the river, would cover its entire area to a depth of more than five inches. The Ardeche rises so suddenly that, in the inundation of 1846, the women who were washing in the bed of the river had not time to save their linen, and barely escaped with their lives, though they instantly fled upon hearing the roar of the approaching flood. Its waters and those of its affluents fall almost as rapidly, for in less than twenty-four hours after the rain has ceased in the Cevennes, where it rises, the Ardeche returns within its ordinary channel, even at its junction with the Rhone. In the flood of 1772, the water at La Beaume de Ruoms, on the Beaume, a tributary of the Ardeche, rose thirty-five feet above low water but the stream was again fordable on the evening of the same day. The inundation of 1827 was, in this respect, exceptional, for it continued three days, during which period the Ardeche poured into the Rhone 1,305,000,000 cubic yards of water. The Nile delivers into the sea 101,000 cubic feet or 3,741 cubic yards per second, on an average of the whole year. [Footnote: Sir John F. Herschel, citing Talabot as his authority, Physical Geography (24). In an elaborate paper on "Irrigation," printed in the United States Patent Report for 1860, p. 169, it is stated that the volume of water poured into the Mediterranean by the Nile in twenty-four hours, at low water, is 150,566,392,368 cubic meters; at high water, 705,514,667,440 cubic metres. Taking the mean of these two numbers, the average daily delivery of the Nile would be 428,081,059,808 cubic metres, or more than 550,000,000,000 cubic yards. There is some enormous mistake, probably a typographical error, in this statement, which makes the delivery of the Nile seventeen hundred times as great as computed by Talabot, and more than physical geographers have estimated the quantity supplied by all the rivers on the face of the globe.] This is equal to 323,222,400 cubic yards per day. In a single day of flood, then, the Ardeche, a river too insignificant to be known except in the local topography of France, contributed to the Rhone once and a half, and for three consecutive days once and one third, as much as the average delivery of the Nile during the same periods, though the basin of the latter river probably contains 1,000,000 square miles of surface, or more than one thousand times as much as that of the former. The average annual precipitation in the basin of the Ardeche is not greater titan in many other parts of Europe, but excessive quantities of rain frequently fall in that valley in the autumn. On the 9th. of October, 1827, there fell at Joyeuse, on the Beaume, no less than thirty-one inches between three o'clock in the morning and midnight. Such facts as this explain the extraordinary suddenness and violence of the floods of the Ardeche, and the basins of many other tributaries of the Rhone exhibit meteorological phenomena not less remarkable. [Footnote: The Drac, a torrent emptying into the Isere a little below Grenoble, has discharged 5,200, the Isere, which receives it, 7,800 cubic yards, and the Durance, above its junction with the Isere, an equal quantity, per second.--Montluisant, Note sur les Dessechements, etc., Annales des Ponts et Chaussees, 1833, 2me semestre p. 288. The Upper Rhone, which drains a basin of about 1,900 square miles, including seventy-one glaciers, receives many torrential affluents, and rain-storms and thaws are sometimes extensive enough to affect the whole tributary system of its narrow valley. In such cases its current swells to a great volume, but previously to the floods of the autumn of 1868 it was never known to reach a discharge of 2,600 cubic yards to the second. On the 28th of September in that year, however, its delivery amounted to 3,700 cubic yards to the second, which is about equal to the mean discharge of the Nile.--Berichte der Experten-Commission uber die Ueberschaeemmungen im Jahr 1868, pp. 174,175. The floods of some other French rivers, which have a more or less torrential character, scarcely fall behind those of the Rhone. The Loire, above Roanne, has a basin of 2,471 square miles, or about twice and a half the area of that of the Ardeche. In some of its inundations it has delivered above 9,500 cubic yards per second, or 400 times its low-water discharge.--Belgrand, De l'Influence des Forets, etc., Annales des Ponts et Chaussees, 1854, 1er semestre, p.15, note. The ordinary low-water discharge of the Seine at Paris is nearly 100 cubic yards per second. Belgrand gives a list of eight floods of that river within the last two centuries, in which it has delivered thirty times that quantity.] The Rhone, therefore, is naturally subject to great and sudden inundations, and the same remark may be applied to most of the principal rivers of France, because the geographical character of all of them is approximately the same. The volume of water in the floods of most great rivers is determined by the degree in which the inundations of the different tributaries are coincident in time. Were all the affluents of the Lower Rhone to pour their highest annual floods into its channel at once--as the smaller tributaries of the Upper Rhone sometimes do--were a dozen Niles to empty themselves into its bed at the same moment, its water would rise to a height and rush with an impetus that would sweep into the Mediterranean the entire population of its banks, and all the works that man has erected upon the plains which border it. But such a coincidence can never happen. The tributaries of this river run in very different directions, and some of them are swollen principally by the melting of the snows about their sources, others almost exclusively by heavy rains. When a damp southeast wind blows up the valley of the Ardeche, its moisture is condensed, and precipitated in a deluge upon the mountains which embosom the headwaters of that stream, thus producing a flood, while a neighboring basin, the axis of which lies transversely or obliquely to that of the Ardeche, is not at all affected. [Footnote: "There is no example of a coincidence between great floods of the Ardeche and of the Rhone, all the known inundations of the former having taken place when the latter was very low."--MARDIGNY, Memoire sur les Inondations des Rivieres de l'Ardeche, p. 26. The same observation may be applied to the tributaries of the Po, their floods being generally successive, not contemporaneous. The swelling of the affluents of the Amazon, and indeed of most large rivers, is regulated by a similar law. See Messedaglia, Analisi dell' opera di Champion, etc., p. 103. The floods of the affluents of the Tiber form an exception to this law, being generally coincident, and this is one of the explanations of the frequency of destructive inundations in that river.--Lombardini, Guida allo Studio dell' Idrologia, ff. 68; same author, Esame degli studi sul Tevere. I take this occasion to acknowledge myself indebted to Mardigny's interesting memoir just quoted for all the statements I make respecting the floods of the Ardeche, except the comparison of the volume of its water with that of the Nile.] It is easy to see that the damage occasioned by such floods as I have described must be almost incalculable, and it is by no means confined to the effects produced by overflow and the mechanical force of the superficial currents. In treating of the devastations of torrents, I have hitherto confined myself principally to the erosion of surface and the transportation of mineral matter to lower grounds by them. The general action of torrents, as thus fur shown, tends to the ultimate elevation of their beds by the deposit of the earth, gravel, and stone conveyed by them; but until they have thus raised their outlets so as sensibly to diminish the inclination of their channels--and sometimes when extraordinary floods give the torrents momentum enough to sweep away the accumulations which they have themselves heaped up--the swift flow of their currents, aided by the abrasion of the rolling rocks and gravel, scoops their beds constantly deeper, and they consequently not only undermine their banks, but frequently sap the most solid foundations which the art of man can build for the support of bridges and hydraulic structures. [Footnote: In some cases where the bed of rapid Alpine streams is composed of very hard rock--as is the case in many of the valleys once filled by ancient glaciers--and especially where they are fed by glaciers not overhung by crumbling cliffs, the channel may remain almost unchanged for centuries. This is observable in many of the tributaries of the Dora Baltea, which drains the valley of Aosta. Several of these small rivers are spanned by more or less perfect Roman bridges--one of which, that over the Lys at Pont St. Martin, is still in good repair and in constant use. An examination of the rocks on which the abutments of this and some other similar structures are founded, and of the channels of the rivers they cross, shows that the beds of the streams cannot have been much elevated or depressed since the bridges were built. In other cases, as at the outlet of the Val Tournanche at Chatillon, where a single rib of a Roman bridge still remains, there is nothing to forbid the supposition that the deep excavation of the channel may have been partly effected at much later period. The Roman aqueduct known as the Pont du Gard, near Nismes, was built, in all probability, nineteen centuries ago. The bed of the river Gardon, a rather swift stream, which flows beneath it, can have suffered but slight depression since the piers of the aqueduct were founded.] In the inundation of 1857, the Ardeche destroyed a stone bridge near La Beaume, which had been built about eighty years before. The resistance of the piers, which were erected on piles, the channel at that point being of gravel, produced an eddying current that washed away the bed of the river above them, and the foundation, thus deprived of lateral support, yielded to the weight of the bridge, and the piles and piers fell up-stream. By a curious law of compensation, the stream which, at flood, scoops out cavities in its bed, often fills them up again as soon as the diminished velocity of the current allows it to let fall the sand and gravel with which it is charged, so that when the waters return to their usual channel, the bottom shows no sign of having been disturbed. In a flood of the Escontay, a tributary of the Rhone, in 1846, piles driven sixteen feet into its gravelly bed for the foundation of a pier were torn up and carried off, and yet, when the river had fallen to low-water mark, the bottom at that point appeared to have been raised higher than it was before the flood, by new deposits of sand and gravel, while the cut stones of the half-built pier were found buried to a great depth in the excavation which the water had first washed out. The gravel with which rivers thus restore the level of their beds is principally derived from the crushing of the rocks brought down by the mountain torrents, and the destructive effects of inundations are immensely diminished by this reduction of large stones to minute fragments. If the blocks hurled down from the cliffs were transported unbroken to the channels of large rivers, the mechanical force of their movement would be irresistible. They would overthrow the strongest barriers, spread themselves over a surface as wide as the flow of the waters, and convert the most smiling valleys into scenes of the wildest desolation. As I have before remarked, I have taken my illustrations of the action of torrents and mountain streams principally from French authorities, because the facts recorded by them are chiefly of recent occurrence, and as they have been collected with much care and described with great fulness of detail, the information furnished by them is not only more trustworthy, but both more complete and more accessible than that which can be gathered from any other source. It is not to be supposed, however, that the countries adjacent to France have escaped the consequences of a like improvidence. The southern flanks of the Alps, and, in a less degree, the northern slope of these mountains and the whole chain of the Pyrenees, afford equally striking examples of the evils resulting from the wanton sacrifice of nature's safeguards. But I can afford space for few details, and as an illustration of the extent of these evils in Italy, I shall barely observe that it was calculated ten years ago that four-tenths of the area of the Ligurian provinces had been washed away or rendered incapable of cultivation in consequence of the felling of the woods. [Footnote: Annali di Agricoltura, Industria e Commercio, vol. i., p. 77. Similar instances of the erosive power of running water might be collected by hundreds from the narratives of travellers in warm countries. The energy of the torrents of the Himalayas is such that the brothers Schlagintweit believe that they will cut gorges through that lofty chain wide enough to admit the passage of currents of warm wind from the south, and thereby modify the climate of the countries lying to the north of the mountains.] Highly colored as these pictures seem, they are not exaggerated, although the hasty tourist through Southern France, Switzerland, the Tyrol, and Northern Italy, finding little in his high-road experiences to justify them, might suppose them so. The lines of communication by locomotive-train and diligence lead generally over safer ground, and it is only when they ascend the Alpine passes and traverse the mountain chains, that scenes somewhat resembling those just described fall under the eye of the ordinary traveller. But the extension of the sphere of devastation, by the degradation of the mountains and the transportation of their debris, is producing analogous effects upon the lower ridges of the Alps and the plains which skirt them; and even now one needs but an hour's departure from some great thoroughfares to reach sites where the genius of destruction revels as wildly as in the most frightful of the abysses which Blanqui has painted. [Footnote: The Skalara-Tobel, for instance, near Coire. See the description of this and other like scenes in Berlepsch, Die Alpen, pp. 169 et seqq., or in Stephen's English translation. About an hour from Thusis, on the Splagen road, "opens the awful chasm of the Nolla which a hundred years ago poured its peaceful waters through smiling meadows protected by the wooded slopes of the mountains. But the woods were cut down and with them departed the rich pastures, the pride of the valley, now covered with piles of rock and rubbish swept down from the mountains. This result is the more to be lamented as it was entirely compassed by the improvidence of man in thinning the forests."--Morell, Scientific Guide to Switzerland, p. 100. The recent change in the character of the Mella--a river anciently so remarkable for the gentleness of its current that it was specially noticed by Catullus as flowing molli flumine--deserves more than a passing remark. This river rises in the mountain-chain east of Lake Iseo, and traversing the district of Brescia, empties into the Oglio after a course of about seventy miles. The iron-works in the upper valley of the Mella had long created a considerable demand for wood, but their operations were not so extensive as to occasion any very sudden or general destruction of the forests, and the only evil experienced from the clearings was the gradual diminution of the volume of the river. Within the last thirty years, the superior quality of the arms manufactured at Brescia has greatly enlarged the sale of them, and very naturally stumulated the activity of both the forges and of the colliers who supply them, and the hillsides have been rapidly stripped of their timber. Up to 1850, no destructive inundation of the Mella had been recorded. Buildings in great numbers had been erected upon its margin, and its valley was conspicuous for its rural beauty and its fertility. But when the denudation of the mountains had reached a certain point, avenging nature began the work of retribution. In the spring and summer of 1850 several new torrents were suddenly formed in the upper tributary valleys, and on the 14th and 15th of August in that year a fall of rain, not heavier than had been often experienced, produced a flood which not only inundated much ground never before overflowed, but destroyed a great number of bridges, dams, factories, and other valuable structures, and, what was a far more serious evil, swept off from the rocks an incredible extent of soil, and converted one of the most beautiful valleys of the Italian Alps into a ravine almost us bare and as barren as the savagest gorge of Southern France. The pecuniary damage was estimated at many millions of francs, and the violence of the catastrophe was deemed so extraordinary, even in a country subject to similar visitations, that the sympathy excited for the sufferers produced, in five months, voluntary contributions for their relief to the amount of nearly $200,000.--Delle Inondazioni del Mella, etc., nella notte del 14 al 15 Agosto, 1850. The author of this pamphlet has chosen as a motto a passage from the Vulgate translation of Job, which is interesting as showing accurate observation of the action of the torrent: "Mons cadens definit, et saxum transfertur de loco suo; lapides excavant aquae et alluvione paullatim terra consumitur."--Job xiv. 18, 19. The English version is much less striking, and gives a different sense. The recent date of the change in the character of the Mella is contested, and it is possible that, though the extent of the revolution is not exaggerated, the rapidity with which it has taken place may have been.] There is one effect of the action of torrents which few travellers on the Continent are heedless enough to pass without notice. I refer to the elevation of the beds of mountain streams in consequence of the deposit of the debris with which they are charged. To prevent the spread of sand and gravel over the fields and the deluging overflow of the raging waters, the streams are confined by walls and embankments, which are gradually built higher and higher as the bed of the torrent is raised, so that, to reach a river, you ascend from the fields beside it; and sometimes the ordinary level of the stream is above the streets and even the roofs of the towns through which it passes. [Footnote: Streffleur quotes from Duile the following observations: "The channel of the Tyrelese brooks is often raised much above the valleys through which they flow. The bed of the Fersina is elevated high above the city of Trent, which lies near it. The Villerbach flows at a much more elevated level than that of the market-place of Neumarkt and Vill, and threatens to overwhelm both of them with its waters. The Talfer at Botzen is at least even with the roofs of the adjacent town, if not above them. The tower-steeples of the villages of Schlanders, Kortsch, and Laas, are lower than the surface of the Gadribach. The Saldurbach at Schluderus menaces the far lower village with destruction, and the chief town, Schwaz, is in similar danger from the Lahnbach."--Streffleur, Ueber die Wildbuche, etc., p. 7.] The traveller who visits the depths of an Alpine ravine, observes the length and width of the gorge and the great height and apparent solidity of the precipitous walls which bound it, and calculates the mass of rock required to fill the vacancy, can hardly believe that the humble brooklet which purls at his feet has been the principal agent in accomplishing this tremendous erosion. Closer observation will often teach him, that the seemingly unbroken rock which overhangs the valley is full of cracks and fissures, and really in such a state of disintegration that every frost must bring down tons of it. If he computes the area of the basin which finds here its only discharge, he will perceive that a sudden thaw of the winter's deposit of snow, or one of those terrible discharges of rain so common in the Alps, must send forth a deluge mighty enough to sweep down the largest masses of gravel and of rock. The simple measurement of the cubical contents of the semicircular hillock which he climbed before he entered the gorge, the structure and composition of which conclusively show that it must have been washed out of this latter by torrential action, will often account satisfactorily for the disposal of most of the matter which once filled the ravine. When a torrent escapes from the lateral confinement of its mountain walls and pours out of the gorge, it spreads and divides itself into numerous smaller streams which shoot out from the mouth of the ravine as from a centre, in different directions, like the ribs of a fan from the pivot, each carrying with it its quota of stones and gravel. The plain below the point of issue from the mountain is rapidly raised by newly-formed torrents, the elevation depending on the inclination of the bed and the form and weight of the matter transported. Every flood both increases the height of this central point and extends the entire circumference of the deposit. Other things being equal, the transporting power of the water is greatest where its flow is most rapid. This is usually in the direction of the axis of the ravine. The stream retaining most nearly this direction moves with the greatest momentum, and consequently transports the solid matter with which it is charged to the greatest distance. The untravelled reader will comprehend this the better when he is informed that the southern slope of the Alps generally rises suddenly out of the plain, with no intervening hill to break the abruptness of the transition, except those consisting of comparatively small heaps of its own debris brought down by ancient glaciers or recent torrents. The torrents do not wind down valleys gradually widening to the rivers or the sea, but leap at once from the flanks of the mountains upon the plains below. This arrangement of surfaces naturally facilitates the formation of vast deposits at their points of emergence, and the centre of the accumulation in the case of very small torrents is not unfrequently a hundred feet high, and sometimes very much more. The deposits of the torrent which has scooped out the Nantzen Thal, a couple of miles below Brieg in the Valais, have built up a semicircular hillock, which most travellers by the Simplon route pass over without even noticing it, though it is little inferior in dimensions to the great cones of dejection described by Blanqui. The principal course of the torrent having been--I know not whether spontaneously or artificially--diverted towards the west, the eastern part of the hill has been gradually brought under cultivation, and there are many trees, fields, and houses upon it; but the larger western part is furrowed with channels diverging from the summit of the deposit at the outlet of the Nantzen Thal, which serve as the beds of the water-courses into which the torrent has divided itself. All this portion of the hillock is subject to inundation after long and heavy rain, and as I saw it in the great flood of October, 1866, almost its whole surface seemed covered with an unbrokun sheet of rushing water. The semi-conical deposit of detritus at the mouth of the Litznerthal, a lateral branch of the valley of the Adige, at the point where the torrent pours out of the gorge, is a thousand feet high and, measuring along the axis of the principal current, two and a half miles long. [Footnote: Sonklar, Die Octzthaler Gebirgsgruppe, 1861, p. 231.] The solid material of this hillock--which it is hardly an exaggeration to call a mountain, the work of a single insignificant torrent and its tributaries--including what the river which washes its base has carried off in a comparatively few years, probably surpasses the mass of the stupendous pyramid of the Matterhorn. In valleys of ancient geological formation, which extend into the very heart of the mountains, the streams, though rapid, have often lost the true torrential character, if, indeed, they ever possessed it. Their beds have become approximately constant, and their walls no longer crumble and fall into the waters that wash their bases. The torrent-worn ravines, of which I have spoken, are of later date, and belong more properly to what may be called the crust of the Alps, consisting of loose rocks, of gravel, and of earth, strewed along the surface of the great declivities of the central ridge, and accumulated thickly between their solid buttresses. But it is on this crust that the mountaineer dwells. Here are his forests, here his pastures, and the ravages of the torrent both destroy his world, and convert it into a source of overwhelming desolation to the plains below. I do not mean to assert that all the rocky valleys of the Alps have been produced by the action of torrents resulting from the destruction of the forests. The greater, and many of the smaller channels, by which that chain is drained, owe their origin to higher causes. They are primitive fissures, ascribable to disruption in upheaval or other geological convulsion, widened and scarped, and often even polished, so to speak, by the action of glaciers during the ice period, and but little changed in form by running water in later eras. It has been contended that all rivers which take their rise in mountains originated in torrents. These, it is said, have lowered the summits by gradual erosion, and, with the material thus derived, have formed shoals in the sea which once beat against the cliffs; then, by successive deposits, gradually raised them above the surface, and finally expanded them into broad plains traversed by gently flowing streams. If we could get back to earlier geological periods, we should find this theory often verified, and we cannot fail to see that the torrents go on at the present hour, depressing still lower the ridges of the Alps and the Apennines, raising still higher the plains of Lombardy and Provence, extending the coast still farther into the Adriatic and the Mediterranean, reducing the inclination of their own beds and the rapidity of their flow, and thus tending to become river-like in character. We cannot measure the share which human action has had in augmenting the intensity of causes of mountain degradation, and of the formation of plains and marshes below, but we know that the clearing of the woods has, in some cases, produced, within two or three generations, effects as blasting as those generally ascribed to geological convulsions, and has laid waste the face of the earth more hopelessly than if it had been buried by a current of lava or a shower of volcanic sand. New torrents are forming every year in the Alps. Tradition, written records, and analogy concur to establish the belief that the ruin of most of the now desolate valleys in those mountains is to be ascribed to the same cause, and authentic descriptions of the irresistible force of the torrent show that, aided by frost and heat, it is adequate to level Mont Blanc and Monte Rosa themselves, unless new upheavals shall maintain their elevation. There are cases where torrents cease their ravages of themselves, in consequence of some change in the condition of the basin where they originate, or of the face of the mountain at a higher level, while the plain or the sea below remains in substantially the same state as before. If a torrent rises in a small valley containing no great amount of earth and of disintegrated or loose rock, it may, in the course of a certain period, wash out all the transportable material, and if the valley is then left with solid walls, it will cease to furnish debris to be carried down by floods. If, in this state of things, a new channel be formed at an elevation above the head of the valley, it may divert a part or even the whole of the rain-water and melted snow which would otherwise have flowed into it, and the once furious torrent now sinks to the rank of a humble and harmless brooklet. "In traversing this department," says Suroll, "one often sees, at the outlet of a gorge, a flattened hillock, with a fan-shaped outline and regular slopes; it is the bed of dejection of an ancient torrent. It sometimes requires long and careful study to detect the primitive form, masked as it is by groves of trees, by cultivated fields, and often by houses, but, when examined closely, and from different points of view, its characteristic figure manifestly appears, and its true history cannot be mistaken. Along the hillock flows a streamlet, issuing from the ravine, and quietly watering the fields. This was originally a torrent, and in the background may be discovered its mountain basin. Such EXTINGUISHED torrents, if I may use the expression, are numerous." [Footnote: Surrell, Les Torrents des Hautes Alpes, chap. xxiv. In such cases, the clearing of the ground, which, in consequence of a temporary diversion of the waters, or from some other cause, has become rewooded, sometimes renews the ravages of the torrent. Thus, on the left bank of the Durance, a wooded declivity had been formed by the debris brought down by torrents, which had extinguished themselves after having swept off much of the superficial strata of the mountain of Morgon. "All this district was covered with woods, which have now been thinned out and are perishing from day to day; consequently, the torrents have recommenced their devastations, and if the clearings continue, this declivity, now fertile, will he ruined, like so many others."--Ibid, p. 155.] But for the intervention of man and domestic animals, these latter beneficent revolutions would occur more frequently, proceed more rapidly. The new scarped mountains, the hillocks of debris, the plains elevated by sand and gravel spread over them, the shores freshly formed by fluviatile deposits, would clothe themselves with shrubs and trees, the intensity of the causes of degradation would be diminished, and nature would thus regain her ancient equilibrium. But these processes, under ordinary circumstances, demand, not years, generations, but centuries; [Footnote: Where a torrent has not been long in operation, and earth still remains mixed with the rocks and gravel it heaps up at its point of eruption, vegetation soon starts up and prospers, it protected from encroachment. In Provence, "several communes determined, about ten years ago, to reserve the soils thus wasted, that is, to abandon them for a certain time, to spontaneous vegetation, which was not slow in making its appearance."-Becquerel, Des Climats, p. 815.] and man, who even now finds scarce breathing-room on this vast globe, cannot retire from the Old World to some yet undiscovered continent, and wait for the slow action of such causes to replace, by a new creation, the Eden he has wasted. Crushing Force of Torrents. I must here notice a mechanical effect of the rapid flow of the torrent, which is of much importance in relation to the desolating action it exercises by covering large tracts of cultivated ground with infertile material. The torrent, as we have seen, shoots or rolls forwards, with great velocity, masses and fragments of rock, and sometimes rounded pebbles from more ancient formations. Every inch of this violent movement is accompanied with crushing concussion, or, at least, with great abrasion of the mineral material, and, as you follow it along the course of the waters which transport it, you find the stones gradually rounding off in form, and diminishing in size, until they pass successively into gravel, and, in the beds of the rivers to which the torrents convey it, sand, and lastly impalpable slime. There are few operations of nature where the effect seems more disproportioned to the cause than in the crushing and comminution of rock in the channel of swift waters. Igneous rocks are generally so hard as to be wrought with great difficulty, and they bear the weight of enormous superstructures without yielding to the pressure; but to the torrent they are as wheat to the millstone. The streams which pour down the southern scarp of the Mediterranean Alps along the Riviera di Ponente, near Genoa, have short courses, and a brisk walk of a couple of hours or even less takes you from the sea-beach to the headspring of many of them. In their heaviest floods, they bring rounded masses of serpentine quite down to the sea, but at ordinary high water their lower course is charged only with finely divided particles of that rock. Hence, while, near their sources, their channels are filled with pebbles and angular fragments, intermixed with a little gravel, the proportions are reversed near their months, and, just above the points where their outlets are partially choked by the rolling shingle of the beach, their beds are composed of sand and gravel to the almost total exclusion of pebbles. Guglielmini argued that the gravel and sand of the beds of running streams were derived from the trituration of rocks by the action of the currents, and inferred that this action was generally sufficient to reduce hard rock to sand in its passage from the source to the outlet of rivers. Frisi controverted this opinion, and maintained that river-sand was of more ancient origin, and he inferred from experiments in artificially grinding stones that the concussion, friction, and attrition of rock in the channel of running waters were inadequate to its comminution, though he admitted that these same causes might reduce silicious sand to a fine powder capable of transportation to the sea by the currents. [Footnote: Frisi, Del modo di regolare i Fiumi e i Torrenti, pp. 4-19. See in Lombardini, Sulle Inondazioni in Francia, p. 87, notices of the action of currents transporting only fine material in wearing down hard rock. In the sluices for gold-washing in California having a grade of 1 to 14 1/2, and paved with the hardest stones, the wear of the bottom is at the rate of two inches in three months.--Raymond, Mineral Statistics, 1870, p. 480.] Frisi's experiments were tried upon rounded and polished river-pebbles, and prove nothing with regard to the action of torrents upon the irregular, more or less weathered, and often cracked and shattered rocks which lie loose in the ground at the head of mountain valleys. The fury of the waters and of the wind which accompanies them in the floods of the French Alpine torrents is such, that large blocks of stone are hurled out of the bed of the stream to the height of twelve or thirteen feet. [Footnote: Surrell, Etude sur les Torrents, pp. 81-86.] The impulse of masses driven with such force overthrows the most solid masonry, and their concussion cannot fail to be attended with the crushing of the rocks themselves. The greatest depth of the basin of the Ardeche is seventy-five miles, but most of its tributaries have a much shorter course. "These affluents," says Mardigny, "hurl into the bed of the Ardeche enormous blocks of rock, which this river, in its turn bears onwards, and grinds down, at high water, so that its current rolls only gravel at its confluence with the Rhone." [Footnote: At Rinkenberg, on the right bank of the Vorder Rhein, in the flood of 1868, a block of stone computed to weigh nearly 9,000 cwt. was carried bodily forwards, not rolled, by a torrent, a distance of three-quarter of a mile.--Coaz, die Hochwasser im 1868, p. 54. Memoire sur les Inondations des Rivieres de l'Ardeche, p. 16. "The terrific roar, the thunder of the raging torrents proceeds principally from the stones which are rolled along in the bed of the stream. This movement is attended with such powerful attrition that, in the Southern Alps, the atmosphere of valleys where the limestone contains bitumen, has, at the time of floods, the marked bituminous smell produced by rubbing pieces of such limestone together."--Wessely, Die Oesterreichischen Alpenlander, i., p. 113.] Duponchel makes the following remarkable statement: "The river Herault rises in a granitic region, but soon reaches calcareous formations, which it traverses for more than sixty kilometres, rolling through deep and precipitous ravines, into which the torrents are constantly discharging enormous masses of pebbles belonging to the hardest rocks of the Jurassian period. These debris, continually renewed, compose, even below the exit of the gorge where the river enters into a regular channel cut in a tertiary deposit, broad beaches, prodigious accumulations of rolled pebbles, extending several kilometres down the stream, but they diminish in size and weight so rapidly that above the mouth of the river, which is at a distance of thirty or thirty-five kilometres from the gorge, every trace of calcareous matter has disappeared from the sands of the bottom, which are exclusively silicious." [Footnote: Avant-projet pour la creation d'un sol fertile, p. 20.] Similar effects of the rapid flow of water and the concussion of stones against each other in river-beds may be observed in almost every Alpine gorge which serves as the channel of a swift stream. The tremendous cleft through which the well-known Via Mala is carried receives, every year, from its own crumbling walls and from the Hinter Rhein and its mild tributaries, enormous quantities of rock, in blocks and boulders. In fact, the masses hurled into it in a single flood like those of 1868 would probably fill it up, at its narrow points, to the level of the road 400 feet above its bottom, were not the stones crushed and carried off by the force of the current. Yet below the outlet at Thusis only small rounded boulders, pebbles, and gravel, not rock, are found in the bed of the river. The Swiss glaciers bring down thousands of cubic yards of hard rock every season. Where the glacier ends in a plain or wide valley, the rocks are accumulated in a terminal moraine, but in numerous instances the water which pours from the ice-river has forces enough to carry down to larger streams the masses delivered by the glacier, and there they, with other stones washed out from the earth by the current, are ground down, so that few of the affluents of the Swiss lakes deliver into them anything but fine sand and slime. Great rivers carry no boulders to the sea, and, in fact, receive none from their tributaries. Lombardini found, twenty years ago, that the mineral matter brought down to the Po by its tributaries was, in general, comminuted to about the same degree of fineness as the sands of its bed at their points of discharge. In the case of the Trebbia, which rises high in the Apennines and empties into the Po at Piacenza, it was otherwise, that river rolling pebbles and coarse gravel into the channel of the principal stream. The banks of the other affluents--excepting some of those which discharge their waters into the great lakes--then either retained their woods, or had been so long clear of them that the torrents had removed most of the disintegrated and loose rock in their upper basins. The valley of the Trebbia had been recently cleared, and all the forces which tend to the degradation and transportation of rock were in full activity. [Footnote: Since the date of Lombardini's observations, many Alpine valleys have been stripped of their woods. It would be interesting to know whether any sensible change has been produced in the character or quantity of the matter transported by the rivers to the Po.--Notice sur les Rivieres de la Lombardie, Annales des Ponts et Chaussees, 1847, 1er semestre, p. 131.] Transporting Power of Water. But the geographical effects of the action of torrents are not confined to erosion of earth and comminution of rock; for they and the rivers to which they contribute transport the debris of the mountains to lower levels and spread them out over the dry land and the bed of the sea, thus forming alluvial deposits, sometimes of a beneficial, sometimes of an injurious, character, and of vast extent. [Footnote: Lorentz, in an official report quoted by Marchand, says: "The felling of the woods produces torrents which cover the cultivated soil with pebbles and fragments of rock, and they do not confine their ravages to the vicinity of the mountains, but extend them into the fertile fields of Provence and other departments, to the distance of forty or fifty leagues."--Entwaldung der Gebirge, p. 17.] A mountain rivulet swollen by rain or melted snow, when it escapes from its usual channel and floods the adjacent fields, naturally deposits pebbles and gravel upon them; but even at low water, if its course is long enough for its grinding action to have full scope, it transports the solid material with which it is charged to some larger stream, and there lets it fall in a state of minute division, and at last the spoil of the mountain is used to raise the level of the plains or carried down to the sea. An instance that fell under my own observation, in 1857, will serve to show something of the eroding and transporting power of streams which, in these respects, fall incalculably below the torrents of the Alps. In a flood of the Ottaquechee, a small river which flows through Woodstock, Vermont, a mill-dam on that stream burst, and the sediment with which the pond was filled, estimated after careful measurement at 13,000 cubic yards, was carried down by the current. Between this dam and the slackwater of another, four miles below, the bed of the stream, which is composed of pebbles interspersed in a few places with larger stones, is about sixty-five feet wide, though, at low water, the breadth of the current is considerably less. The sand and fine gravel were smoothly and evenly distributed over the bed to a width of fifty-five or sixty feet, and, for a distance of about two miles, except at two or three intervening rapids, filled up all the interstices between the stones, covering them to the depth of nine or ten inches, so as to present a regularly formed concave channel, lined with sand, and reducing the depth of water, in some places, from five or six feet to fifteen or eighteen inches. Observing this deposit after the river had subsided and become so clear that the bottom could be seen, I supposed that the next flood would produce an extraordinary erosion of the banks and some permanent changes in the channel of the stream, in consequence of the elevation of the bed and the filling up of the spaces between the stones through which formerly much water had flowed; but no such result followed. The spring freshet of the next year entirely washed out the sand its predecessor had left, deposited some of it in ponds and still-water reaches below, carried the residue beyond the reach of observation, and left the bed of the river almost precisely in its former condition, though, of course, with the displacement of the pebbles which every flood produces in the channels of such streams. The pond, though often previously discharged by the breakage of the dam, had then been undisturbed for about twenty-five years, and its contents consisted almost entirely of sand, the rapidity of the current in floods being such that it would let fall little lighter sediment, even above an obstruction like a dam. The quantity I have mentioned evidently bears a very inconsiderable proportion to the total erosion of the stream during that period, because the wash of the banks consists chiefly of fine earth rather than of sand, and after the pond was once filled, or nearly so, even this material could no longer be deposited in it. The fact of the complete removal of the deposit I have described between the two dams in a single freshet, shows that, in spite of considerable obstruction from roughness of bed, large quantities of sand may be taken up and carried off by streams of no great rapidity of inclination; for the whole descent of the bed of the river between the two dams--a distance of four miles--is but sixty feet, or fifteen feet to the mile. [Footnote: In a sheet-iron siphon, 1,000 feet long, with a diameter of four inches, having the entrance 18 feet, the orifice of discharge 40 feet below the summit of the curve, employed in draining a mine In California, the force of the current was such as to carry through the tube great quantities of sand and coarse gravel, some of the grains of which were as large as an English walnut. --Raymond, Mining Statistics, 1870, p. 602.] The facts which I have adduced may aid us in forming an idea of the origin and mode of transportation of the prodigious deposits at the mouth of great rivers like the Mississippi, the Nile, the Ganges, and the Hoang-Ho, the delta of which last river, composed entirely of river sediment, has a superficial extent of not less than 96,500 square miles. But we shall obtain a clearer conception of the character of this important geographical process by measuring, more in detail, the mass of earth and rock which a well--known river and its tributaries have washed from the mountains and transported to the plains or the sea, within the historic period. The Po and its Deposits. The current of the River Po, for a considerable distance after its volume of water is otherwise sufficient for continuous navigation, is too rapid for that purpose until near Cremona, where its velocity becomes too much reduced to transport great quantities of mineral matter, except in a state of minute division. Its southern affluents bring down from the Apennines a large quantity of fine earth from various geological formations, while its Alpine tributaries west of the Ticino are charged chiefly with rock ground down to sand or gravel. The bed of the river has been somewhat elevated by the deposits in its channel, though not by any means above the level of the adjacent plains as has been so often represented. The dikes, which confine the current at high water, at the same time augment its velocity and compel it to carry most of its sediment to the Adriatic. It has, therefore, raised neither its own channel nor its alluvial shores, as it would have done if it had remained unconfined. But, as the surface of the water in floods is above the general level of the plains through which it flows, the Po can, at that period, receive no contributions of earth from the washing of the fields of Lombardy, and there is no doubt that a large proportion of the sediment it now deposits at its mouth descended from the Alps in the form of rock, though reduced by the grinding action of the waters, in its passage seaward, to the condition of fine sand, and often of silt. We know little of the history of the Po, or of the geography of the coast near the point where it enters the Adriatic, at any period more than twenty centuries before our own. Still less can we say how much of the plains of Lombardy had been formed by its action, combined with other causes, before man accelerated its levelling operations by felling the first woods on the mountains whence its waters are derived. But we know that since the Roman conquest of Northern Italy, its deposits have amounted to a quantity which, if recemented into rock, recombined into gravel, common earth, and vegetable mould, and restored to the situations where eruption or upheaval originally placed or vegetation deposited it, would fill up hundreds of deep ravines in the Alps and Apennines, change the plan and profile of their chains, and give their southern and northern faces respectively a geographical aspect very different from that they now present. Ravenna, forty miles south of the principal mouth of the Po, was built like Venice, in a lagoon, and the Adriatic still washed its walls at the commencement of the Christian era. The mud of the Po has filled up the lagoon, and Ravenna is now four miles from the sea. The town of Adria, which lies between the Po and the Adige, at the distance of some four or five miles from each, was once a harbor famous enough to have given its name to the Adriatic Sea, and it was still accessible to large vessels, if not by the open sea at least by lagoons, in the time of Augustus. The combined action of the two rivers has so advanced the coast-line that Adria is now more than fourteen miles inland, and, in other places, the deposits made within the same period by these and other neighboring streams have a width of twenty miles. What proportion of the earth with which they are charged these rivers have borne out into deep water, during the last two thousand years, we do not know, but as they still transport enormous quantities, as the North Adriatic appears to have shoaled rapidly, and as long islands, composed in great part of fluviatile deposits, have formed opposite their mouths, it must evidently have been very great. The floods of the Po occur but once, or sometimes twice, in a year. [Footnote: In the earlier medieval centuries, when the declivities of the mountains still retained a much larger proportion of their woods, the moderate annual floods of the Po were occasioned by the melting of the snows on the lower slopes, and, according to a passage of Tasso quoted by Castellani (Dell' Influenza delle Selve, i., p. 58, note), they took place in May. The usually more violent inundations of later ages are due to rains, the waters of which are no longer retained by a forest-soil, but conveyed at once to the rivers--and they occur almost uniformly in the autumn or late summer. Castellani, on the page just quoted, says that even so late as about 1780, the Po required a heavy rain of a week to overflow its banks, but that forty years later it was sometimes raised to full flood in a single day. Pliny says: "The Po, which is inferior to no river in swiftness of current, is in flood about the rising of the dog-star, the snow then melting, and though so rapid in flow, it washes nothing from the soil, but leaves it increased in fertility."--Natural History, Book iii, 20. The first terrible inundation of the Po in 1872 took place in May, and appears to have been occasioned by heavy rains on the southern flank of the Alps, and to have received little accession from snow. The snow on the higher Alps does not usually thaw so as to occasion floods before August, and often considerably later. The more destructive flood of October, 1872, was caused both by thaws in the high mountains and by an extraordinary fall of rain. See River Embankments; post. Pliny's remark as to enrichment of the soil by the floods appear to be verified in the case of that of October, 1872, for it is found that the water has left very extensively a thick deposit of slime on the fields. See a list of the historically known great inundations of the Po by the engineer Zuccholli in Torelli, Progetto di Legge per la Vendita di Beni incolti. Roma, 1873.] At other times, its waters are comparatively limpid and seem to hold no great amount of mud or fine sand in mechanical suspension; but at high water it contains a large proportion of solid matter, and, according to Lombardini, it annually transports to the shores of the Adriatic not less than 42,760,000 cubic metres, or very nearly 55,000,000 cubic yards, which carries the coast-line out into the sea at the rate of more than 200 feet in a year. [Footnote: This change of coast-line cannot be ascribed to upheaval, for a comparison of the level of old buildings--as, for instance, the church of San Vitale and the tomb of Theodoric at Ravenna--with that of the sea, tends to prove a depression rather than an elevation of their foundations. A computation by a different method makes the deposits at the mouth of the Po 2,123,000 metres less; but as both of them omit the gravel and silt carried down at ordinary and low water, we are safe in assuming the larger quantity.] The depth of the annual deposit is stated at eighteen centimetres, or rather more than seven inches, and it would cover an area of not much less than ninety square miles with a layer of that thickness. The Adige, also, brings every year to the Adriatic many million cubic yards of Alpine detritus, and the contributions of the Brenta from the same source are far from inconsiderable. The Adriatic, however, receives but a small proportion of the soil and rock washed away from the Italian slope of the Alps and the northern declivity of the Apennines by torrents. Nearly the whole of the debris thus removed from the southern face of the Alps between Monte Rosa and the sources of the Adda--a length of watershed [Footnote: Sir John F. W. Herschel (Physical Geography, 137, and elsewhere) spells this word water-sched, because he considers it a translation, or rather an adoption, of the German "Wasser-scheide, separation of the waters, not water-SHED the slope DOWN WHICH the waters run." As a point of historical etymology, it is probable that the word in question was suggested to those who first used it by the German Wasserscheide; but the spelling WATER-SCHED, proposed by Herschel, is objectionable, both because SCH is a combination of letters wholly unknown to modern English orthography, and properly representing no sound recognized in English orthoepy, and for the still better reason that WATER-SHED, in the sense of DIVISION-OF-THE-WATERS, has a legitimate English etymology. The Anglo-Saxon sceadan meant both to separate or divide, and to shade or shelter. It is the root of the English verbs TO SHED and TO SHADE, and in the former meaning is the A. S. equivalent of the German verb scheiden. SHED in Old English had the meaning to SEPARATE or DISTINGUISH. It is so used in the Owl and the Nightingale, v. 107. Palsgrave (Lesclarcissement, etc., p. 717) defines I SHEDE, I departe thinges asonder; and the word still means TO DIVIDE in several English local dialects. Hence, watershed, the division or separation of the waters, is good English both in etymology and in spelling.] not less than one hundred and fifty miles--is arrested by the still waters of the Lakes Maggiore and Como, and some smaller lacustrine reservoirs, and never reaches the sea. The Po is not continuously embanked except for the lower half of its course. Above Cremona, therefore, it spreads and deposits sediment over a wide surface, and the water withdrawn from it for irrigation at lower points, as well as its inundations in the occasional ruptures of its banks, carry over the adjacent soil a large amount of slime. [Footnote: The quantity of sediment deposited by the Po on the plains which border it, before the construction of the continuous dikes and in the floods which occasionally burst through them, is vast, and the consequent elevation of those plains is very considerable. I do not know that this latter point has been made a subject of special investigation, but vineyards, with the vines still attached to the elms which supported them, have been found two or three yards below the present surface at various points on the plains of Lombardy.] If to the estimated annual deposits of the Po at its mouth, we add the earth and sand transported to the sea by the Adige, the Brenta, and other less important streams, the prodigious mass of detritus swept into Lago Maggioro by the Tosa, the Maggia, and the Ticino, into the lake of Como by the Maira and the Adda, into the lakes of Garda, Lugano, Iseo, and Idro, by their affluents, [Footnote: The Po receives about four-tenths of its waters from these lakes. See Lombardini, Dei cangiamenti nella condizione del Po, p. 29. All the sediment carried into the lakes by their tributaries is deposited in them, and the water which flows out of them is perfectly limpid. From their proximity to the Alps and the number of torrents which empty into them, they no doubt receive vastly more transported matter than is contributed to the Po by the six-tenths of its waters received from other sources.] and the yet vaster heaps of pebbles, gravel, and earth permanently deposited by the torrents near their points of eruption from mountain gorges, or spread over the wide plains at lower levels, we may safely assume that we have an aggregate of not less than ten times the quantity carried to the Adriatic by the Po, or 550,000,000 cubic yards of solid matter, abstracted every year from the Italian Alps and the Apennines, and removed out of their domain by the force of running water. [Footnote: Mengotti estimated the mass of solid matter annually "united to the waters of the Po" at 822,000,000 cubic metres, or nearly twenty times as much as, according to Lombardini, that river delivers into the Adriatic. Castellani supposes the computation of Mengotti to fall much below the truth, and there can be no doubt that a vastly larger quantity of earth and gravel is washed down from the Alps and the Apennines than is carried to the sea.--Castellani, Dell Immediata Influenza delle Salce sul corso delle Acqua, i., pp. 42,43. I have contented myself with assuming less than one-half of Mengotti's estimate.] The present rate of deposit at the mouth of the Po has continued since the year 1600, the previous advance of the coast, after the year 1200, having been only one-third as rapid. The great increase of erosion and transport is ascribed by Lombardini chiefly to the destruction of the forests in the basin of that river and the valleys of its tributaries, since the beginning of the seventeenth century. [Footnote: Baumgarten, An. des Ponts et Chaussees, 1847, 1er semestre, p. 175.] We have no data to show the rate of deposit in any given century before the year 1200, and it doubtless varied according to the progress of population and the consequent extension of clearing and cultivation. The transporting power of torrents is greatest soon after their formation, because at that time their points of delivery are lower, and, of course, their general slope and velocity more rapid, than after years of erosion above, and deposit below, have depressed the beds of their mountain valleys, and elevated the channels of their lower course. Their eroding action also is most powerful at the same period, both because their mechanical force is then greatest, and because the loose earth and stones of freshly cleared forest-ground are most easily removed. Many of the Alpine valleys west of the Ticino--that of the Dora Baltea, for instance--were nearly stripped of their forests in the days of the Roman Empire, others in the Middle Ages, and, of course, there must have been, at different periods before the year 1200, epochs when the erosion and transportation of solid matter from the Alps and the Apennines were at least as great as since the year 1600. Upon the whole, we shall not greatly err if we assume that, for a period of not less than two thousand years, the walls of the basin of the Po--the Italian slope of the Alps, and the northern and north-eastern declivities of the Apennines--have annually sent down into the lakes, the plains, and the Adriatic, not less than 375,000,000 cubic yards of earth and disintegrated rock. We have, then, an aggregate of 750,000,000,000 cubic yards of such material, which, allowing to the mountain surface in question an area of 50,000,000,000 square yards, would cover the whole to the depth of fifteen yards. [Footnote: The total superficies of the basin of the Po, down to Ponte Lagoscuro [Ferrara]--a point where it has received all its affluents--is 6,938,200 hectares, that is, 4,105,600 in mountain lands, 2,832,600 in plain lands.--Dumont, Travaux Publics, etc., p. 272. These latter two quantities are equal respectively to 10,145,348, and 6,999,638 acres, or 15,852 and 10,937 square miles.] There are very large portions of this area, where, as we know from ancient remains--roads, bridges, and the like--from other direct testimony, and from geological considerations, very little degradation has taken place within twenty centuries, and hence the quantity to be assigned to localities where the destructive causes have been most active is increased in proportion. If this vast mass of pulverized rock and earth were restored to the localities from which it was derived, it certainly would not obliterate valleys and gorges hollowed out by great geological causes, but it would reduce the length and diminish the depth of ravines of later formation, modify the inclination of their walls, reclothe with earth many bare mountain ridges, essentially change the line of junction between plain and mountain, and carry back a long reach of the Adriatic coast many miles to the west. [Footnote: I do not use these quantities as factors the value of which is precisely ascertained; nor, for the purposes of the present argument, is quantitative exactness important. I employ numerical statements simply as a means of aiding the imagination to form a general and certainly not extravagant idea of the extent of geographical revolutions which man has done much to accelerate, if not, strictly speaking, to produce. There is an old proverb, Dolus latet in generalibus, and Arthur Young in not the only public economist who has warned his readers against the deceitfulness of round numbers. I think, on the contrary, that vastly more error has been produced by the affectation of precision in cases where precision is impossible. In all the great operations of terrestrial nature, the elements are so numerous and so difficult of exact appreciation, that, until the means of scientific observation and measurement are much more perfected than they now are, we must content ourselves with general approximations. I say TERRESTRIAL nature, because in cosmical movements we have fewer elements to deal with, and may therefore arrive at much more rigorous proportional accuracy in determination of time and place than we can in fixing and predicting the quantities and the epochs of variable natural phenomena on the earth's surface. Travellers are often misled by local habits in the use of what may be called representative numbers, where a definite is put for an indefinite quantity. A Greek, who wished to express the notion of a great but undetermined number, "myriad, or ten thousand;" a Roman, "six hundred;" an Oriental, "forty," or, at present, very commonly, "fifteen thousand." Many a tourist has gravely repeated, as an ascertained fact; the vague statement of the Arabs and the monks of Mount Sinai, that the ascent from the convent of St. Catherine to the summit of Gebel Moosa counts "fifteen thousand" steps, though the difference of level is two thousand feet; and the "Forty" Thieves, the "forty" martyr-monks of the convent of El Arbain--not to speak of a similar use of this numeral in more important cases--have often been understood as expressions of a known number, when in fact they mean simply MANY. The number "fifteen thousand" has found its way to Rome, and De Quincey seriously informs us, on the authority of a lady who had been at much pains to ascertain the EXACT truth, that, including closets large enough for a bed, the Vatican contains fifteen thousand rooms. Any one who has observed the vast dimensions of most of the apartments of that structure will admit that we make a very small allowance of space when we assign a square rod, sixteen and a half feet square, to each room upon the average. On an acre, there might be one hundred and sixty such rooms, including partition walls; and, to contain fifteen thousand of them, a building must cover more than nine acres, and be ten stories high, or possess other equivalent dimensions, which, as every traveller knows, many times exceeds the truth. The value of a high standard of accuracy in scientific observation can hardly be overrated; but habits of rigorous exactness will never be formed by an investigator who allows himself to trust implicitly to the numerical precision or the results of a few experiments. The wonderful accuracy of geodetic measurements in modern times is, in general, attained by taking the mean of a great number of observations at every station, and this final precision is but the mutual balance and compensation of numerous errors. The pretended exactness of statistical tables is too often little better than an imposture; and those founded not on direct estimation by competent observers, but on the report of persons who have no particular interest in knowing the truth, but often have a motive for distorting it, are commonly to be regarded as but vague guesses at the actual fact.] It is, indeed, not to be supposed that all the degradation of the mountains is due to the destruction of the forests--that the flanks of every Alpine valley in Central Europe below the snow-line were once covered with earth and green with woods, but there are not many particular cases in which we can, with certainty, or even with strong probability, affirm the contrary. Mountain Slides. Terrible as are the ravages of the torrent and the river-flood, the destruction of the woods exposes human life and industry to calamities even more appalling than those which I have yet described. The slide in the Notch of the White Mountains, by which the Willey family lost their lives, is an instance of the sort I refer to, though I am not able to say that in this particular case the slip of the earth and rock was produced by the denudation of the surface. It may have been occasioned by this cause, or by the construction of the road through the Notch, the excavations for which, perhaps, cut through the natural buttresses that supported the sloping strata above. Not to speak of the fall of earth when the roots which held it together, and the bed of leaves and mould which sheltered it both from disintegrating frost and from sudden drenching and dissolution by heavy showers, are gone, it is easy to see that, in a climate with severe winters, the removal of the forest, and, consequently, of the soil it had contributed to form, might cause the displacement and descent of great masses of rock. The woods, the vegetable mould, and the soil beneath, protect the rocks they cover from the direct action of heat and cold, and from the expansion and contraction which accompany them. Most rocks, while covered with earth, contain a considerable quantity of water. [Footnote: Rock is permeable by water to a greater extent than is generally supposed. Freshly quarried marble, and even granite, as well as most other stones, are sensibly heavier, as well as softer and more easily wrought, than after they are dried and hardened by air-seasoning. Many sandstones are porous enough to serve as filters for liquids, and much of that of Upper Egypt and Nubia hisses audibly when thrown into water, from the escape of the air forced out of it by hydrostatic pressure and the capillary attraction of the pores for water. Even the denser silicious stones are penetrable by fluids and the coloring matter they contain, to such an extent that agates and other forms of silex may be artificially stained through their substance. The colors of the stones cut at Oberstein are generally produced, or at least heightened, by art. This art was known to and practised by the ancient lapidaries, and it has been revived in recent times.] A fragment of rock pervaded with moisture cracks and splits, if thrown into a furnace, and sometimes with a loud detonation; and it is a familiar observation that the fire, in burning over newly cleared lands, breaks up and sometimes almost pulverizes the stones. This effect is due partly to the unequal expansion of the stone, partly to the action of heat on the water it contains in its pores. The sun, suddenly let in upon rock which had been covered with moist earth for centuries, produces more or less disintegration in the same way, and the stone is also exposed to chemical influences from which it was sheltered before. But in the climate of the United States as well as of the Alps, frost is a still more powerful agent in breaking up mountain masses. The soil that protects the lime and sandstone, the slate and the granite from the influence of the sun, also prevents the water which filters into their crevices and between their strata from freezing in the hardest winters, and the moisture descends, in a liquid form, until it escapes in springs, or passes off by deep subterranean channels. But when the ridges are laid bare, the water of the autumnal rains fills the minutest pores and veins and fissures and lines of separation of the rocks, then suddenly freezes, and bursts asunder huge, and apparently solid blocks of adamantine stone. [Footnote: Palissy had observed the action of frost in disintegrating rock, and he thus describes it, in his essay on the formation of ice: "I know that the stones of the mountains of Ardennes be harder than marble. Nevertheless, the people of that country do not quarry the said stones in winter, for that they be subject to frost; and many times the rocks have been seen to fall without being cut, by means whereof many people have been killed, when the said rocks were thawing." Palissy was ignorant of the expansion of water in freezing--in fact, he supposed that the mechanical force exerted by freezing-water was due to compression, not dilatation--and therefore he ascribes to thawing alone effects resulting not less from congelation. Various forces combine to produce the stone avalanches of the higher Alps, the fall of which is one of the greatest dangers incurred by the adventurous explorers of those regions--the direct action of the sun upon the stone, the expansion of freezing-water, and the loosening of masses of rock by the thawing of the ice which supported them or held them together.] Where the strata are inclined at a considerable angle, the freezing of a thin film of water over a large interstratal area might occasion a slide that should cover miles with its ruins; and similar results might be produced by the simple hydrostatic pressure of a column of water, admitted, by the removal of the covering of earth, to flow into a crevice faster than it could escape through orifices below. Earth or rather mountain slides, compared to which the catastrophe that buried the Willey family in New Hampshire was but a pinch of dust, have often occurred in the Swiss, Italian, and French Alps. The land-slip, which overwhelmed, and covered to the depth of seventy feet, the town of Plurs in the valley of the Maira, on the night of the 4th of September, 1618, sparing not a soul of a population of 2,430 inhabitants, is one of the most memorable of these catastrophes, and the fall of the Rossberg or Rufiberg, which destroyed the little town of Goldan in Switzerland, and 450 of its people, on the 2d of September, 1806, is almost equally celebrated. In 1771, according to Wessely, the mountain-peak Piz, near Alleghe in the province of Belluno, slipped into the bed of the Cordevole, a tributary of the Piave, destroying in its fall three hamlets and sixty lives. The rubbish filled the valley for a distance of nearly two miles, and, by damming up the waters of the Cordevole, formed a lake about three miles long, and a hundred and fifty feet deep, which still subsists, though reduced to half its original length by the wearing down of its outlet. [Footnote: Wessely, Die Oesterreichischen Alpenlander und ihre Forste, pp. 125, 126. Wessely records several other more or less similar occurrences in the Austrian Alps. Some of them, certainly, are not to be ascribed to the removal of the woods, but in most cases they are clearly traceable to that cause. See Revue des Eaux et Forets for 1860, pp. 182, 205.] The important provincial town of Veleia, near Piacenza, where many interesting antiquities have been discovered within a few years, was buried by a vast land-slip, probably about the time of Probus, but no historical record of the event has survived to us. On the 14th of February, 1855, the hill of Belmonte, a little below the parish of San Stefano, in Tuscany, slid into the valley of the Tiber, which consequently flooded the village to the depth of fifty feet, and was finally drained off by a tunnel. The mass of debris is stated to have been about 3,500 feet long, 1,000 wide, and not less than 600 high. [Footnote: Bianchi, Appendix to the Italian translation of Mrs. Somerville'S Physical Geography, p. xxxvi.] Occurrences of this sort have been so numerous in the Alps and Apennines, that almost every Italian mountain commune has its tradition, its record, or its still visible traces of a great land-slip within its own limits. The old chroniclers contain frequent notices of such calamities, and Giovanni Villani even records the destruction of fifty houses and the loss of many lives by a slide of what seems to have been a spur of the hill of San Giorgio in the city of Florence, in the year 1284. [Footnote: Cronica di Giovani Villani, lib. vii., cap. 97. For descriptions of other slides in Italy, see same author, lib. xi, cap. 26; Fanfani, Antologia Italiana, parte ii., p. 95; Giuliani, Linguaggio vivente della Toscana, 1865, lettera 63.] Such displacements of earth and rocky strata rise to the magnitude of geological convulsions, but they are of so rare occurrence in countries still covered by the primitive forest, so common where the mountains have been stripped of their native covering, and, in many cases, so easily explicable by the drenching of incohesive earth from rain, or the free admission of water between the strata of rocks--both of which a coating of vegetation would have prevented--that we are justified in ascribing them for the most part to the same cause as that to which the destructive effects of mountain torrents are chiefly due--the felling of the woods. [Footnote: There is good reason for thinking that many of the earth and rock slides in the Alps occurred at an earlier period than the origin of the forest vegetation which, in later ages, covered the flanks of those mountains. See Bericht uber die Untersuchung der Schweizerischen Hochgebirgswaldungen, 1862, p. 61. Where more recent slides have been again clothed with woods, the trees, shrubs, and smaller plants which spontaneously grow upon them are usually of different species from those observed upon soil displaced at remote periods. This difference is so marked that the site of a slide can often be recognized at a great distance by the general color of the foliage of its vegetation.] In nearly every case of this sort the circumstances of which are known--except the rare instances attributable to earthquakes--the immediate cause of the slip has been the imbibition of water in large quantities by bare earth, or its introduction between or beneath solid strata. If water insinuates itself between the strata, it creates a sliding surface, or it may, by its expansion in freezing, separate beds of rock, which had been nearly continuous before, widely enough to allow the gravitation of the superincumbent mass to overcome the resistance afforded by inequalities of face and by friction; if it finds its way beneath hard earth or rock reposing on clay or other bedding of similar properties, it converts the supporting layer into a semi-fluid mud, which opposes no obstacle to the sliding of the strata above. The upper part of the mountain which buried Goldau was composed of a hard but brittle conglomerate, called nagelflue, resting on unctuous clay, and inclining rapidly towards the village. Much earth remained upon the rock, in irregular masses, but the woods had been felled, and the water had free access to the surface, and to the crevices which sun and frost had already produced in the rock, and, of course, to the slimy stratum beneath. The whole summer of 1806 had been very wet, and an almost incessant deluge of rain had fallen the day preceding the catastrophe, as well as on that of its occurrence. All conditions, then, were favorable to the sliding of the rock, and, in obedience to the laws of gravitation, it precipitated itself into the valley as soon as its adhesion to the earth beneath it was destroyed by the conversion of the latter into a viscous paste. The mass that fell measured between two and a half and three miles in length by one thousand feet in width, and its average thickness is thought to have been about a hundred feet. The highest portion of the mountain was more than three thousand feet above the village, and the momentum acquired by the rocks and earth in their descent carried huge blocks of stone far up the opposite slope of the Rigi. The Piz, which fell into the Cordevole, rested on a steeply inclined stratum of limestone, with a thin layer of calcareous marl intervening, which, by long exposure to frost and the infiltration of water, had lost its original consistence, and become a loose and slippery mass instead of a cohesive and tenacious bed. Protection against Avalanches. In Switzerland and other snowy and mountainous countries, forests render a most important service by preventing the formation and fall of destructive avalanches, and in many parts of the Alps exposed to this catastrophe, the woods are protected, though too often ineffectually, by law. No forest, indeed, could arrest a large avalanche once in full motion, but the mechanical resistance afforded by the trees prevents their formation, both by obstructing the wind, which gives to the dry snow of the Staub-Lawine, or dust-avalanche, its first impulse, and by checking the disposition of moist snow to gather itself into what is called the Rutsch-Lawine, or sliding avalanche. Marchand states that, the very first winter after the felling of the trees on the higher part of a declivity between Sannen and Gsteig where the snow had never been known to slide, an avalanche formed itself in the clearing, thundered down the mountain, and overthrew and carried with it a hitherto unviolated forest to the amount of nearly a million cubic feet of timber. [Footnote: Entwaldung der Gebirge, p. 41.] Elisee Reclus informs us in his remarkable work, La Terre, vol. i., p. 212, that a mountain, which rises to the south of the Pyrenaean village Araguanet in the upper valley of the Neste, having been partially stripped of its woods, a formidable avalanche rushed down from a plateau above in 1846, and swept off more than 15,000 pine-trees. The path once opened down the flanks of the mountain, the evil is almost beyond remedy. The snow sometimes carries off the earth from the face of the rock, or, if the soil is left, fresh slides every winter destroy the young plantations, and the restoration of the wood becomes impossible. The track widens with every new avalanche. Dwellings and their occupants are buried in the snow, or swept away by the rushing mass, or by the furious blasts it occasions through the displacement of the air; roads and bridges are destroyed; rivers blocked up, which swell till they overflow the valley above, and then, bursting their snowy barrier, flood the fields below with all the horrors of a winter inundation. [Footnote: The importance of the wood in preventing avalanches is well illustrated by the fact that, where the forest is wanting, the inhabitants of localities exposed to snow-slides often supply the place of the trees by driving stakes through the snow into the ground, and thus checking its propensity to slip. The woods themselves are sometimes thus protected against avalanches originating on slopes above them, and as a further security, small trees are cut down along the upper line of the forest, and laid against the trunks of larger trees, transversely to the path of the slide, to serve as a fence or dam to the motion of an incipient avalanche, which may by this means be arrested before it acquires a destructive velocity and force. In the volume cited in the text, Reclus informs us that "the village and the great thermal establishment of Bareges in the Pyrenees were threatened yearly by avalanches which precipitated themselves from a height of 1,200 metres and at an angle of 35 degrees; so that the inhabitants had been obliged to leave large spaces between the different quarters of the town for the free passage of the descending masses. Attempts have been recently made to prevent those avalanches by means similar to those employed by the Swiss mountaineers. They cut terraces three or four yards in width across the mountain slopes and supported these terraces by a row of iron piles. Wattled fences, with here and there a wall of stone, shelter the young shoots of trees, which grow up by degrees under the protection of these defences. Until natural trees are ready to arrest the snows, these artificial supports take their place and do their duty very well. The only avalanche which swept down the slope in the year 1860, when these works were completed, did not amount to 350 cubic yards, while the masses which fell before this work was undertaken contained from 75,000 to 80,000 cubic yards."--La Terre, vol. i., p. 233.] Minor Uses of the Forest. Besides the important conservative influences of the forest and its value as the source of supply of a material indispensable to all the arts and industries of human life, it renders other services of a less obvious and less generally recognized character. Woods often subserve a valuable purpose in preventing the fall of rocks, by mere mechanical resistance. Trees, as well as herbaceous vegetation, grow in the Alps upon declivities of surprising steepness of inclination, and the traveller sees both luxuriant grass and flourishing woods on slopes at which the soil, in the dry air of lower regions, would crumble and fall by the weight of its own particles. When loose rocks lie scattered on the face of these declivities, they are held in place by the trunks of the trees, and it is very common to observe a stone that weighs hundreds of pounds, perhaps even tons, resting against a tree which has stopped its progress just as it was beginning to slide down to a lower level. When a forest in such a position is cut, these blocks lose their support, and a single wet season is enough not only to bare the face of a considerable extent of rock, but to cover with earth and stone many acres of fertile soil below. [Footnote: See in Kohl, Alpenreisen, i., 120, an account of the ruin of fields and pastures, and even of the destruction of a broad belt of forest, by the fall of rocks in consequence of cutting a few large trees. Cattle are very often killed in Switzerland by rock-avalanches, and their owners secure themselves from loss by insurance against this risk as against damage by fire or hail.] In alluvial plains and on the banks of rivers trees are extremely useful as a check to the swift flow of the water in inundations, and the spread of the mineral material it transports; but this will be more appropriately considered in the chapter on the Waters; and another most important use of the woods, that of confining the loose sands of dunes and plains, will be treated of in the chapter on the Sands. Small Forest Plants, and Vitality of Seed. Another function of the woods, to which I have barely alluded, deserves a fuller notice than can be bestowed upon it in a treatise the scope of which is purely economical. The forest is the native habitat of a large number of humbler plants, to the growth and perpetuation of which its shade, its humidity, and its vegetable mould appear to be indispensable necessities. [Footnote: "A hundred and fifty paces from my house is a hill of drift-sand, on which stood a few scattered pines (Pinus sylvestris). Sempervivum tectorum in abundance, Statice armeria, Ammone vernalis, Dianthus carthusianorum, with other sand-plants, were growing there. I planted the hill with a few birches, and all the plants I have mentioned completely disappeared, though there were many naked spots of sand between the trees. It should be added, however, that the hillock is more thickly wooded than before. . . . It seems then that Sempervivum tectorum, etc., will not bear the neighborhood of the birch, though growing well near the Pinus sylvestris. I have found the large red variety of Agaricus deliciosus only among the roots of the pine; the greenish-blue Agaricus deliciosus among alder roots, but not near any other tree. Birds have their partialities among trees and shrubs. The Silvioe prefer the Pinus Larix to other trees. In my garden this Pinus is never without them, but I never saw a bird perch on Thuja occidentalis or Juniperus sabina, although the thick foliage of these latter trees affords birds a better shelter than the loose leafage of other trees. Not even a wren ever finds its way to one of them. Perhaps the scent of the Thuja and the Juniperus is offensive to them. I have spoiled one of my meadows by cutting away the bushes. It formerly bore grass four feet high, because many umbelliferous plants, such as Heracleum spondylium, Spiraea ulmaria, Laserpitium latifolia, etc., grew in it. Under the shelter of the bushes these plants ripened and bore seed, but they gradually disappeared as the shrubs wore extirpated, and the grass now does not grow to the height of more than two feet, because it is no longer obliged to keep pace with the umbellifera which flourished among it." See a paper by J.G. Buttner, of Kurland, in Berghaus s Geographicsches Jahrbuch, 1852, No. 4, pp. 14, 15. These facts are interesting as illustrating the multitude of often obscure conditions upon which the life or vigorous growth of smaller organisms depends. Particular species of truffles and of mushrooms are found associated with particular trees, without being, as is popularly supposed, parasites deriving their nutriment from the dying or dead roots of those trees. The success of Rousseau's experiments seem decisive on this point, for he obtains larger crops of truffles from ground covered with young seedling oaks than from that filled with roots of old trees. See an article on Mont Ventoux, by Charles Martins, in the Revue des Deux Mondes, Avril, 1863, p. 626. It ought to be much more generally known than it is, that most if not all mushrooms, even of the species reputed poisonous, may be rendered harmless and healthful as food by soaking them for two hours in acidulated or salt water. The water requires two or three spoonfuls of vinegar or two spoonful of gray salt to the quart, and a quart of water is enough for a pound of sliced mushrooms. After thus soaking, they are well washed in fresh water, thrown into cold water, which is raised to the boiling-point, and, after remaining half an hour, taken out and again washed, Gerard, to prove that "crumpets is wholesome," ate one hundred and seventy-five pounds of the most poisonous mushrooms thus prepared, in a single month, fed his family ad libitum with the same, and finally administered them, in heroic doses, to the members of a committee appointed by the Council of Health of the city of Paris. See Figuier, L'Annee Scientifique, 1862, pp. 353, 384. It should be observed that the venomous principle of poisonous mushrooms is not decomposed and rendered innocent by the process described in the note. It is merely extracted by the acidulated or saline water employed for soaking the plants, and care should be taken that this water be thrown away out of the reach of mischief. It has long been known that the Russian peasantry eat, with impunity, mushrooms of species everywhere else regarded as very poisonous. Is it not probable that the secret of rendering them harmless--which was known to Pliny, though since forgotten in Italy--is possessed by the rustic Muscovites ] We cannot positively say that the felling of the woods in a given vegetable province would involve the final extinction of the smaller plants which are found only within their precincts. Some of these, though not naturally propagating themselves in the open ground, may perhaps germinate and grow under artificial stimulation and protection, and finally become hardy enough to maintain an independent existence in very different circumstances from those which at present seem essential to their life. Besides this, although the accounts of the growth of seeds, which have lain for ages in the ashy dryness of Egyptian catacombs, are to be received with great caution, or, more probably, to be rejected altogether, yet their vitality seems almost imperishable while they remain in the situations in which nature deposits them. When a forest old enough to have witnessed the mysteries of the Druids is felled, trees of other species spring up in its place; and when they, in their turn, fall before the axe, sometimes even as soon as they have spread their protecting shade over the surface, the germs which their predecessors had shed years, perhaps centuries before, sprout up, and in due time, if not choked by other trees belonging to a later stage in the order of natural succession, restore again the original wood. In these cases, the seeds of the new crop may have been brought by the wind, by birds, by quadrupeds, or by other causes; but, in many instances, this explanation is not probable. When newly cleared ground is burnt over in the United States, the ashes are hardly cold before they are covered with a crop of fire-weed, Senecio hieracifolius, a tall, herbaceous plant, very seldom seen growing under other circumstances, and often not to be found for a distance of many miles from the clearing. Its seeds, whether the fruit of an ancient vegetation or newly sown by winds or birds, require either a quickening by a heat which raises to a certain high point the temperature of the stratum where they lie buried, or a special pabulum furnished only by the combustion of the vegetable remains that cover the ground in the woods. Earth brought up from wells or other excavations soon produces a harvest of plants often very unlike those of the local flora, and Hayden informs us that on our great Western desert plains, "wherever the earth is broken up, the wild sun-flower (Helianthus) and others of the taller-growing plants, though previously unknown in the vicinity, at once spring up, almost as if spontaneous generation had taken place." [Footnote: Geological Survey of Wyoming, p. 455.] Moritz Wagner, as quoted by Wittwer, [Footnote: Physikalische Geographie, p. 486.] remarks in his description of Mount Ararat: "A singular phenomenon to which my guide drew my attention is the appearance of several plants on the earth-heaps left by the last catastrophe [an earthquake], which grow nowhere else on the mountain, and had never been observed in this region before. The seeds of these plants were probably brought by birds, and found in the loose, clayey soil remaining from the streams of mud, the conditions of growth which the other soil of the mountain refused them." This is probable enough, but it is hardly less so that the flowing mud brought them up to the influence of air and sun, from depths where a previous convulsion had buried them ages before. Seeds of small sylvan plants, too deeply buried by successive layers of forest foliage and the mould resulting from its decomposition to be reached by the plough when the trees are gone and the ground brought under cultivation, may, if a wiser posterity replants the wood which sheltered their parent stems, germinate and grow, after lying for generations in a state of suspended animation. Darwin says: "On the estate of a relation there was a large and extremely barren heath, which had never been touched by the hand of man, but several hundred acres of exactly the same nature had been enclosed twenty-five years previously and planted with Scotch fir. The change in the native vegetation of the planted part of the heath was most remarkable--more than is generally seen in passing from one quite different soil to another; not only the proportional numbers of the heath-plants were wholly changed, but TWELVE SPECIES of plants (not counting grasses and sedges) flourished in the plantation which could not be found on the heath." [Footnote: Origin of Species, American edition, p. 60.] Had the author informed us that these twelve plants belonged to species whose seeds enter into the nutriment of the birds which appeared with the young wood, we could easily account for their presence in the soil; but he says distinctly that the birds were of insectivorous species, and it therefore seems more probable that the seeds had been deposited when an ancient forest protected the growth of the plants which bore them, and that they sprang up to new life when a return of favorable conditions awaked them from a sleep of centuries. Darwin indeed says that the heath "had never been touched by the hand of man." Perhaps not, after it became a heath; but what evidence is there to control the general presumption that this heath was preceded by a forest, in whose shade the vegetables which dropped the seeds in question might have grown [Footnote: Writers on vegetable physiology record numerous instances where seeds have grown after lying dormant for ages. The following cases are mentioned by Dr. Dwight (Travels, ii., pp. 438, 430). "The lands [in Panton, Vermont], which have here been once cultivated, and again permitted to lie waste for several years, yield a rich and fine growth of hickory [Carya Porcina]. Of this wood there is not, I believe, a single tree in any original forest within fifty miles from this spot. The native growth was here white pine, of which I did not see a single stem in a whole grove of hickory." The hickory is a walnut, bearing a fruit too heavy to be likely to be carried fifty miles by birds, and besides, I believe it is not eaten by any bird indigenous to Vermont. We have seen, however, on a former page, that birds transport the nutmeg, which when fresh is probably as heavy as the walnut, from one inland of the Indian archipelago to another. "A field, about five miles from Northampton, on an eminence called Rail Hill, was cultivated about a century ago. The native growth here, and in all the surrounding region, was wholly oak, chestnut, etc. As the field belonged to my grandfather, I had the best opportunity of learning its history. It contained about five acres, in the form of an irregular parallelogram. As the savages rendered the cultivation dangerous, it was given up. On this ground there sprang up a grove of white pines covering the field and retaining its figure exactly. So far as I remember, there was not in it a single oak or chestnut tree ... There was not a single pine whose seeds were, or, probably, had for ages been, sufficiently near to have been planted on this spot. The fact that these white pines covered this field exactly, go as to preserve both its extent and its figure, and that there were none in the neighborhood, are decisive proofs that cultivation brought up the seeds of a former forest within the limits of vegetation, and gave them an opportunity to germinate." See, on the Succession of the Forest, Thoreau, Excursions, p. l35 et seqq.] Although, therefore, the destruction of a wood and the reclaiming of the soil to agricultural uses suppose the death of its smaller dependent flora, these revolutions do not exclude the possibility of its resurrection. In a practical view of the subject, however, we must admit that when the woodman fells a tree he sacrifices the colony of humbler growths which had vegetated under its protection. Some wood-plants are known to possess valuable medicinal properties, and experiment may show that the number of these is greater than we now suppose. Few of them, however, have any other economical value than that of furnishing a slender pasturage to cattle allowed to roam in the woods; and even this small advantage is far more than compensated by the mischief done to the young trees by browsing animals. Upon the whole, the importance of this class of vegetables, as physic or as food, is not such as to furnish a very telling popular argument for the conservation of the forest as a necessary means of their perpetuation. More potent remedial agents may supply their place in the materia medica, and an acre of grass-land yields more nutriment for cattle than a range of a hundred acres of forest. But he whose sympathies with nature have taught him to feel that there is a fellowship between all God's creatures; to love the brilliant ore better than the dull ingot, iodic silver and crystallized red copper better than the shillings and the pennies forged from them by the coiner's cunning; a venerable oak-tree than the brandy-cask whose staves are split out from its heart-wood; a bed of anemones, hepaticas, or wood violets than the leeks and onions which he may grow on the soil they have enriched and in the air they made fragrant--he who has enjoyed that special training of the heart and intellect which can be acquired only in the unviolated sanctuaries of nature, "where man is distant, but God is near"--will not rashly assert his right to extirpate a tribe of harmless vegetables, barely because their products neither tickle his palate nor fill his pocket; and his regret at the dwindling area of the forest solitude will be augmented by the reflection that the nurselings of the woodland perish with the pines, the oaks, and the beeches that sheltered them. [Footnote: Quaint old Valvasor had observed the subduing influence of nature's solitudes. In describing the lonely Canker-Thal, which, though rocky, was in his time well wooded with "fir, larches, beeches and other trees," he says: "Gladsomeness and beauty, which dwell in many valleys, may not be looked for there. The journey through it is cheerless, melancholy, wearisome, and serveth to temper and mortify orer-joyousness of thought ... In sum it is a very desert, wherein the wildness of human pride doth grow tame."--Ehre der Crain, i., p. 186, b.] Although, as I have said in a former chapter, birds do not frequent the deeper recesses of the wood, yet a very large proportion of them build their nests in trees, and find in their foliage and branches a secure retreat from the inclemencies of the seasons and the pursuit of the reptiles and quadrupeds which prey upon them. The borders of the forests are vocal with song; and when the gray and dewy morning calls the creeping things of the earth out of their night-cells, it summons from the neighboring wood legions of their winged enemies, which swoop down upon the fields to save man's harvests by devouring the destroying worm, and surprising the lagging beetle in his tardy retreat to the dark cover where he lurks through the hours of daylight. The insects most injurious to the rural industry of the garden and the ploughland do not multiply in or near the woods. The locust, which ravages the East with its voracious armies, is bred in vast open plains which admit the full heat of the sun to hasten the hatching of the eggs, gather no moisture to destroy them, and harbor no bird to feed upon thelarvae. [Footnote: Smela, in the government of Kiew, has, for some years, not suffered at all from the locusts, which formerly came every year in vast swarms, and the curculio, so injurious to the turnip crops, is less destructive there than in other parts of the province. This improvement is owing partly to the more thorough cultivation of the soil, partly to the groves which are interspersed among the ploughlands. ... When in the midst of the plains woods shall be planted and filled with insectivorous birds, the locusts will cease to be a plague and a terror to the farmer.--Rentzsch, Der Wald, pp. 45, 46.] It is only since the felling of the forests of Asia Minor and Cyrene that the locust has become so fearfully destructive in those countries; and the grasshopper, which now threatens to be almost as great a pest to the agriculture of some North American soils, breeds in seriously injurious numbers only where a wide extent of surface is bare of woods. General Functions of Forests. In the preceding pages we have seen that the electrical and chemical action of the forest, though obscure, exercises probably a beneficial, certainly not an injurious, influence on the composition and condition of the atmosphere; that it serves as a protection against the diffusion of miasmatic exhalations and malarious poisons; that it performs a most important function as a mechanical shelter from blasting winds to grounds and crops in the lee of it; that, as a conductor of heat, it tends to equalize the temperature of the earth and the air; that its dead products form a mantle over the surface, which protects the earth from excessive heat and cold; that the evaporation from the leaves of living trees, while it cools the air around them, diffuses through the atmosphere a medium which resists the escape of warmth from the earth by radiation, and hence that its general effect is to equilibrate caloric influences and moderate extremes of temperature. We have seen, further, that the forest is equally useful as a regulator of terrestrial and of atmospheric humidity, preventing by its shade the drying up of the surface by parching winds and the scorching rays of the sun, intercepting a part of the precipitation, and pouring out a vast quantity of aqueous vapor into the atmosphere; that if it does not increase the amount of rain, it tends to equalize its distribution both in time and in place; that it preserves a hygrometric equilibrium in the superior strata of the earth's surface; that it maintains and regulates the flow of springs and rivulets; that it checks the superficial discharge of the waters of precipitation and consequently tends to prevent the sudden rise of rivers, the violence of floods, the formation of destructive torrents, and the abrasion of the surface by the action of running water; that it impedes the fall of avalanches and of rocks, and destructive slides of the superficial strata of mountains; that it is a safeguard against the breeding of locusts, and finally that it furnishes nutriment and shelter to many tribes of animal and of vegetable life which, if not necessary to man's existence, are conducive to his rational enjoyment. In fine, in well-wooded regions, and in inhabited countries where a due proportion of soil is devoted to the growth of judiciously distributed forests, natural destructive tendencies of all sorts are arrested or compensated, and man, bird, beast, fish, and vegetable alike find a constant uniformity of condition most favorable to the regular and harmonious coexistence of them all. General Consequences of the Destruction of the Forest. With the extirpation of the forest, all is changed. At one season, the earth parts with its warmth by radiation to an open sky--receives, at another, an immoderate heat from the unobstructed rays of the sun. Hence the climate becomes excessive, and the soil is alternately parched by the fervors of summer, and seared by the rigors of winter. Bleak winds sweep unresisted over its surface, drift away the snow that sheltered it from the frost, and dry up its scanty moisture. The precipitation becomes as irregular as the temperature; the melting snows and vernal rains, no longer absorbed by a loose and bibulous vegetable mould, rush over the frozen surface, and pour down the valleys seawards, instead of filling a retentive bed of absorbent earth, and storing up a supply of moisture to feed perennial springs. The soil is bared of its covering of leaves, broken and loosened by the plough, deprived of the fibrous rootlets which held it together, dried and pulverized by sun and wind, and at last exhausted by new combinations. The face of the earth is no longer a sponge, but a dust-heap, and the floods which the waters of the sky pour over it hurry swiftly along its slopes, carrying in suspension vast quantities of earthy particles which increase the abrading power and mechanical force of the current, and, augmented by the sand and gravel of falling banks, fill the beds of the streams, divert them into new channels, and obstruct their outlets. The rivulets, wanting their former regularity of supply and deprived of the protecting shade of the woods, are heated, evaporated, and thus reduced in their summer currents, but swollen to raging torrents in autumn and in spring. From these causes, there is a constant degradation of the uplands, and a consequent elevation of the beds of water-courses and of lakes by the deposition of the mineral and vegetable matter carried down by the waters. The channels of great rivers become unnavigable, their estuaries are choked up, and harbors which once sheltered large navies are shoaled by dangerous sand-bars. The earth, stripped of its vegetable glebe, grows less and less productive, and, consequently, less able to protect itself by weaving a new network of roots to bind its particles together, a new carpeting of turf to shield it from wind and sun and scouring rain. Gradually it becomes altogether barren. The washing of the soil from the mountains leaves bare ridges of sterile rock, and the rich organic mould which covered them, now swept down into the dank low grounds, promotes a luxuriance of aquatic vegetation, that breeds fever, and more insidious forms of mortal disease, by its decay, and thus the earth is rendered no longer fit for the habitation of man. [Footnote: Almost every narrative of travel in those countries which were the earliest seats of civilization, contains evidence of the truth of these general statements, and this evidence is presented with more or less detail in most of the special works on the forest which I have occasion to cite. I may refer particularly to Hohenstein, Der Wald, 1860, as full of important facts on this subject. See also Caimi, Cenni sulla Importanza dei Boschi, for some statistics, not readily found elsewhere, on this and other topics connected with the forest.] To the general truth of this sad picture there are many exceptions, even in countries of excessive climates. Some of these are due to favorable conditions of surface, of geological structure, and of the distribution of rain; in many others, the evil consequences of man's improvidence have not yet been experienced, only because a sufficient time has not elapsed, since the felling of the forest, to allow them to develop themselves. But the vengeance of nature for the violation of her harmonies, though slow, is sure, and the gradual deterioration of soil and climate in such exceptional regions is as certain to result from the destruction of the woods as is any natural effect to follow its cause. Due Proportion of Woodland. The proportion of woodland that ought to be permanently maintained for its geographical and atmospheric influences varies according to the character of soil, surface, and climate. In countries with a humid sky, or moderately undulating surface and an equable temperature, a small extent of forest, enough to serve as a mechanical screen against the action of the wind in localities where such protection is needed, suffices. But most of the territory occupied by civilized man is exposed, by the character of its surface and its climate, to a physical degradation which cannot be averted except by devoting a large amount of soil to the growth of the woods. From an economical point of view, the question of the due proportion of forest is not less complicated or less important than in its purely physical aspects. Of all the raw materials which nature supplies for elaboration by human art, wood is undoubtedly the most useful, and at the same time the most indispensable to social progress. [Footnote: In an imaginary dialogue in the Recepte Veritable, the author, Palissy, having expressed his indignation at the folly of men in destroying the woods, his interlocutor defends the policy of felling them, by citing the example of "divers bishops, cardinals, priors, abbots, monkeries and chapters, which, by cutting their woods, have made three profits, "the sale of the timber, the rent of the ground, and the "good portion" they received of the grain grown by the peasants upon it. To this argument Palissy replies: "I cannot enough detest this thing, and I call it not an error, but a curse and a calamity to all France; for when forests shall be cut, all arts shall cease, and they which practise them shall be driven out to eat grass with Nebuchadnezzar and the beasts of the field. I have divers times thought to set down in writing the arts which shall perish when there shall be no more wood; but when I had written down a great number, I did perceive that there could be no end of my writing, and having diligently considered, I found there was not any which could be followed without wood." ... "And truly I could well allege to thee a thousand reasons, but 'tis so cheap a philosophy, that the very chamber-wenches, it they do but think, may see that without wood, it is not possible to exercise any manner of human art or cunning."--Oeuvres de Bernard Pallisy . Paris, 1844, p. 89.] The demand for wood, and of course the quantity of forest required to furnish it, depend upon the supply of fuel from other sources, such as peat and coal, upon the extent to which stone, brick, or metal can advantageously be substituted for wood in building, upon the development of arts and industries employing wood and other forest products as materials, and upon the cost of obtaining them from other countries, or upon their commercial value as articles of export. Upon the whole, taking civilized Europe and America together, it is probable that from twenty to twenty-five per cent. of well-wooded surface is indispensable for the maintenance of normal physical conditions, and for the supply of materials so essential to every branch of human industry and every form of social life as those which compose the harvest of the woods. There is probably no country--there are few large farms even--where at least one-fourth of the soil is not either unfit for agricultural use, or so unproductive that, as pasture or as ploughland, it yields less pecuniary return than a thrifty wood. Every prairie has its sloughs where willows and poplars would find a fitting soil, every Eastern farm its rocky nooks and its barren hillsides suited to the growth of some species from our rich forest flora, and everywhere belts of trees might advantageously be planted along the roadsides and the boundaries and dividing fences. In most cases, it will be found that trees may be made to grow well where cultivated crops will not repay the outlay of tillage, and it is a very plain dictate of sound economy that if trees produce a better profit than the same ground would return if devoted to grass or grain, the wood should be substituted for the field. Woodland in European Countries. In 1862, Rentzsch calculated the proportions of woodland in different European countries as follows: [Footnote: Der Wald, pp. 123, 124.] Norway.................................. 66 per cent. Sweden.................................. 60 " Russia.................................. 30.00 " Germany................................. 26.58 " Belgium................................. 18.52 " France.................................. 16.79 " Switzerland............................. 15 " Sardinia................................. 12.29 Neapolitan States........................ 9.43 " Holland.................................. 7.10 " Spain.................................... 5.52 " Denmark.................................. 5.50 " Great Britain............................ 5 " Portugal................................. 4.40 " The large proportion of woodland in Norway and Sweden is in a great measure to be ascribed to the mountainous character of the surface, which renders the construction of roads difficult and expensive, and hence the forests are comparatively inaccessible, and transportation is too costly to tempt the inhabitants to sacrifice their woods for the sake of supplying distant markets. The industries which employ wood as a material have only lately been much developed in these countries, and though the climate requires the consumption of much wood as a fuel, the population is not numerous enough to create, for this purpose, a demand exceeding the annually produced supply, or to need any great extension of cleared ground for agricultural purposes. Besides this, in many places peat is generally employed as domestic fuel. Hence, though Norway has long exported a considerable quantity of lumber, [Footnote: Railway-ties, or, as they are called in England, sleepers, are largely exported from Norway to India, and sold at Calcutta at a lower price than timber of equal quality can be obtained from the native woods.--Reports on Forest Conservancy, vol. i., pt. ii., p. 1533. From 1861 to 1870 Norway exported annually, on the average, more than 60,000,000 cubic feet of lumber.--Wulfsberg, Norges Velstandskilder. Christiania, 1872.] and the iron and copper works of Sweden consume charcoal very largely, the forests have not diminished rapidly enough to produce very sensible climatic or even economic evils. At the opposite end of the scale we find Holland, Denmark, Great Britain, Spain, and Portugal. In the three first-named countries a cold and humid climate renders the almost constant maintenance of domestic fires a necessity, while in Great Britain especially the demand of the various industries which depend on wood as a material, or on mechanical power derived from heat, are very great. Coal and peat serve as a combustible instead of wood in them all, and England imports an immense quantity of timber from her foreign possessions. Fortunately, the character of soil, surface, and climate renders the forest of less importance as a geographical agent in these northern regions than in Spain and Portugal, where all physical conditions concur to make a large extent of forest an almost indispensable means of industrial progress and social advancement. Rentzsch, in fact, ascribes the political decadence of Spain almost wholly to the destruction of the forest. "Spain," observes he, "seemed destined by her position to hold dominion over the world, and this in fact she once possessed. But she has lost her political ascendancy, because, during the feeble administration of the successors of Philip II., her exhausted treasury could not furnish the means of creating new fleets, the destruction of the woods having raised the price of timber above the means of the state." [Footnote: Der Wald, p. 63. Antonio Ponz (Viage de Espana, i., prologo, p. lxiii.), says: "Nor would this be so great an evil, were not some of them declaimers against TREES, thereby proclaiming themselves, in some sort, enemies of the works of God, who gave us the leafy abode of Paradise to dwell in, where we should be even now sojourning, but for the first sin, which expelled us from it." I do not know at what period the two Castiles were bared of their woods, but the Spaniard's proverbial "hatred of a tree" is of long standing. Herrera combats this foolish prejudice; and Ponz, in the prologue to the ninth volume of his journey, says that many carried it so far as wantonly to destroy the shade and ornamental trees planted by the municipal authorities. "Trees," they contended, and still believe, "breed birds, and birds eat up the grain." Our author argues against the supposition of the "breeding of birds by trees," which, he says, is as absurd as to believe that an elm-tree can yield pears; and he charitably suggests that the expression is, perhaps, a maniere de dire, a popular phrase, signifying simply that trees harbor birds.] On the other hand, the same writer argues that the wealth and prosperity of modern England are in great part due to the supply of lumber, as well as of other material for ship-building, which she imports from her colonies and other countries with which she maintains commercial relations. Forests of Great Britain. The proportion of forest is very small in Great Britain, where, as I have said, on the one hand, a prodigious industrial activity requires a vast supply of ligneous material, but where, on the other, the abundance of coal, which furnishes a sufficiency of fuel, the facility of importation of timber from abroad, and the conditions of climate and surface combine to reduce the necessary quantity of woodland to its lowest expression. With the exception of Russia, Denmark, and parts of Germany, no European countries can so well dispense with the forests, in their capacity of conservative influences, as England and Ireland. Their insular position and latitude secure an abundance of atmospheric moisture; the general inclination of surface is not such as to expose it to special injury from torrents, and it is probable that the most important climatic action exercised by the forest in these portions of the British empire, is in its character of a mechanical screen against the effects of wind. The due proportion of woodland in England and Ireland is, therefore, a question not of geographical, but almost purely of economical, expediency, to be decided by the comparative direct pecuniary return from forest-growth, pasturage, and ploughland. Contrivances for economizing fuel came later into use in the British Islands than on the Continent. Before the introduction of a system of drainage, the soil, like the sky, was, in general, charged with humidity; its natural condition was unfavorable for the construction and maintenance of substantial common roads, and the transportation of so heavy a material as coal, by land, from the remote counties where alone it was mined in the Middle Ages, was costly and difficult. For all these reasons, the consumption of wood was large, and apprehensions of the exhaustion of the forests were excited at an early period. Legislation there, as elsewhere, proved ineffectual to protect them, and many authors of the sixteenth century express fears of serious evils from the wasteful economy of the people in this respect. Harrison, in his curious chapter "Of Woods and Marishes" in Holinshed's compilation, complains of the rapid decrease of the forests, and adds: "Howbeit thus much I dare affirme, that if woods go so fast to decaie in the next hundred yeere of Grace, as they haue doone and are like to doo in this, . . . it is to be feared that the fennie bote, broome, turfe, gall, heath, firze, brakes, whinnes, ling, dies, hassacks, flags, straw, sedge, reed, rush, and also seacole, will be good merchandize euen in the citie of London, whereunto some of them euen now haue gotten readie passage, and taken up their innes in the greatest merchants' parlours . . . . I would wish that I might liue no longer than to see foure things in this land reformed, that is: the want of discipline in the church: the couetous dealing of most of our merchants in the preferment of the commodities of other countries, and hinderance of their owne: the holding of faires and markets vpon the sundaie to be abolished and referred to the wednesdaies: and that euerie man, in whatsoeuer part of the champaine soile enioieth fortie acres of land, and vpwards, after that rate, either by free deed, copie hold, or fee farme, might plant one acre of wood, or sowe the same with oke mast, hasell, beech, and sufficient prouision be made that it may be cherished and kept. But I feare me that I should then liue too long, and so long, that I should either be wearie of the world, or the world of me." [Footnote: Holinshed, reprint of 1807, i., pp. 357, 358. It is evident from this passage, and from another on page 397 of the same volume, that, though seacoal was largely exported to the Continent, it had not yet come into general use in England. It is a question of much interest, when mineral coal was first employed in England for fuel. I can find no evidence that it was used as a combustible until more than a century after the Norman conquest. It has been said that it was known to the Anglo-Saxon population, but I am acquainted with no passage in the literature of that people which proves this. The dictionaries explain the Anglo-Saxon word grofa by sea-coal. I have met with this word in no Anglo-Saxon work, except in the Chronicle, A.D. 852, from a manuscript certainly not older than the 12th century, and in two citations from Anglo-Saxon charters, one published by Kemble in Codex Diplomaticus, the other by Thorpe in Diplomatarium Anglicum, in all which passages it more probably means peat than mineral coal. According to Way, Promptorium Parrulorum, p. 506, note, the Catholicon Anglicanum has "A turfe grafte, turbarium." Grafte is here evidently the same word as the A.-S. grafa, and the Danish Torvegraf, a turf-pit, confirms this opinion. Coal is not mentioned in King Alfred's Bede, in Neckam, in Glanville or in Robert of Gloucester, though the two latter writers speak of the allied mineral, jet, and are very full in their enumeration of the mineral productions of the island. In a Latin poem ascribed to Giraldus Cambrensis, who died after the year 1220, but found also in the manuesripts of Walter Mapes (see Camden Society edition, pp. 131 and 350), and introduced into Higden's Polychronicon (London, 1865, pp. 398, 399), carbo sub terra cortice, which can mean nothing but pit-coal, is enumerated among the natural commodities of England. Some of the translations of the 13th and 14th century render carbo by cool or col, some by gold, and some omit this line, as well as others unintelligible to the translators. Hence, although Giraldus was acquainted with coal, it certainly was not generally known to English writers until at least a century after the time of that author. The earliest mediaeval notice of mineral coal I have met with is in a passage cited by Ducange from a document of the year 1198, and it is an etymological observation of some interest, that carbones ferrei, as sea-coal is called in the document, are said by Ducange to have been known in France by the popular name of hulla, a word evidently identical with the modern French houille and the Cornish Huel, which in the form wheal is an element in the name of many mining localities. England was anciently remarkable for its forests, but Caesar says it wanted the fagus and the abies. There can be no doubt that fagus means the beech, which, as the remains in the Danish peat-mosses show, is a tree of late introduction into Denmark, where it succeeded the fir, a tree not now native to that country. The succession of forest crops seems to have been the same in England; for Harrison, p. 359, speaks of the "great store of firre" found lying "at their whole lengths" in the "fens and marises" of Lancashire and other counties, where not even bushes grew in his time. We cannot be sure what species of evergreen Caesar intended by abies. The popular designations of spike-leaved trees are always more vague and uncertain in their application than those of broad-leaved trees. PINUS, PINE, has been very loosely employed even in botanical nomenclature, and KIEFER, FICHTE, and TANNE are often confounded in German.--Rossmassler, Der Wald, pp. 256, 289, 324. A similar confusion in the names of this family of trees exists in India. Dr. Cleghorn, Inspector-General of the Indian Forests, informs us in his official Circular No. 2, that the name of deodar is applied in some provinces to a cypress, in some to a cedar, and in others to a juniper. If it were certain that the abies of Caesar was the fir formerly and still found in peat-mosses, and that he was right in denying the existence of the beech in England in his time, the observation would be very important, because it would fix a date at which the fir had become extinct, and the beech had not yet appeared in the island. The English oak, though strong and durable, was not considered generally suitable for finer work in the sixteenth century. There were, however, exceptions. "Of all in Essex," observes Harrison, Holinshed, i., p. 357, "that growing in Bardfield parke is the finest for ioiners craft; for oftentimes haue I seene of their workes made of that oke so fine and faire, as most of the wainescot that is brought hither out of Danske [Danzig]; for our wainescot is not made in England. Yet diuerse haue assaied to deale with our okes to that end, but not with so good successe as they haue hoped, bicause the ab or iuice will not so soone be removed and cleane drawne out, which some attribute to want of time in the salt water." This passage is also of interest as showing that soaking in salt-water, as a mode of seasoning, was practised in Harrison's time. But the importation of wainscot, or boards for ceiling, panelling, and otherwise finishing rooms, which was generally of oak, commenced at least three centuries before the time of Harrison. On page 204 of the Liber Albus mention is made of "squared oak timber," brought in from the country by carts, and of course of domestic growth, as free of city duty or octroi, and of "planks of oak" coming in in the same way as paying one plank a cart-load. But in the chapter on the "Customs of Billyngesgate," pp. 208, 209, relating to goods imported from foreign countries, an import duty of one halfpenny is imposed on every hundred of boards called "weynscotte"--a term formerly applied only to oak--and of one penny on every hundred of boards called "Rygholt." The editor explains "Rygholt" as "wood of Riga." This was doubtless pine or fir. The year in which these provisions were made does not appear, but they belong to the reign of Henry III.] Evelyn's "Silva," the first edition of which appeared in 1664, rendered an extremely important service to the cause of the woods, and there is no doubt that the ornamental plantations in which England far surpasses all other countries, are, in some measure, the fruit of Evelyn's enthusiasm. In England, however, arboriculture, the planting and nursing of single trees, has, until comparatively recent times, been better understood than sylviculture, the sowing and training of the forest. But this latter branch of rural improvement now receives great attention from private individuals, though, so far as I know, not from the National Government, except in the East Indian provinces, where the forestal department has assumed great importance. [Footnote: The improvidence of the population under the native and early foreign governments has produced great devastations in the forests of the British East Indian provinces, and the demands of the railways for fuel and timber have greatly augmented the consumption of lumber, and of course contributed to the destruction of the woods. The forests of British India are now, and for several years have been, under the control of an efficient governmental organization, with great advantage both to the government and to the general private interests of the people. The official Reports on Forest Conservancy from May, 1862, to August, 1871, in 4 vols. folio, contain much statistical and practical information on all subjects connected with the administration of the forest.] In fact, England is, I believe, the only European country where private enterprise has pursued sylviculture on a really great scale, though admirable examples have been set in many others. In England the law of primogeniture, and other institutions and national customs which tend to keep large estates long undivided and in the same line of inheritance, the wealth of the landholders, the special adaptation of the climate to the growth of forest-trees, and the difficulty of finding safe and profitable investments of capital, combine to afford encouragements for the plantation of forests, which scarcely exist elsewhere in the same degree. In Scotland, where the country is for the most part broken and mountainous, the general destruction of the forests has been attended with very serious evils, and it is in Scotland that many of the most extensive British forest plantations have now been formed. But although the inclination of surface in Scotland is rapid, the geological constitution of the soil is not of a character to promote such destructive degradation by running water as in Southern France, and it has not to contend with the parching droughts by which the devastations of the torrents are rendered more injurious in those provinces. It is difficult to understand how either law or public opinion, in a country occupied by a dense and intelligent population, and, comparatively speaking, with an infertile soil, can tolerate the continued withdrawal of a great portion of the territory from the cultivation of trees and from other kinds of rural economy, merely to allow wealthy individuals to amuse themselves with field-sports. In Scotland, 2,000,000 acres, as well suited to the growth of forests and for pasture as is the soil generally, are withheld from agriculture, that they may be given up to herds of deer protected by the game laws. A single nobleman, for example, thus appropriates for his own pleasures not less than 100,000 acres. [Footnote: Robertson, Our Deer Forests. London, 1867.] In this way one-tenth of all the land of Scotland is rendered valueless in an economical point of view--for the returns from the sale of the venison and other game scarcely suffice to pay the game-keepers and other incidental expenses--and in these so-called FORESTS there grows neither building timber nor fire-wood worth the cutting, as the animals destroy the young shoots. Forests of France. The preservation of the woods was one of the wise measures recommended to France by Sully, in the time of Henry IV., but the advice was little heeded, and the destruction of the forests went on with such alarming rapidity, that, two generations later, Colbert uttered the prediction: "France will perish for want of wood." Still, the extent of wooded soil was very great, and the evils attending its diminution were not so sensibly felt, that either the government or public opinion saw the necessity of authoritative interference, and in 1750 Mirabeau estimated the remaining forests of the kingdom at seventeen millions of hectares [42,000,000 acres]. In 1860 they were reduced to eight millions [19,769,000 acres], or at the rate of 82,000 hectares [202,600 acres] per year. Troy, from whose valuable pamphlet, Etude sur le Reboisement des Montagnes, I take these statistical details, supposes that Mirabeau's statement may have been an extravagant one, but it still remains certain that the waste has been enormous; for it is known that, in some departments, that of Ariege, for instance, clearing has gone on during the last half-century at the rate of three thousand acres a year, and in all parts of the empire trees have been felled faster than they have grown. [Footnote: Among the indirect proofs of the comparatively recent existence of extensive forests in France, may be mentioned the fact that wolves were abundant, not very long since, in parts of the empire where there are now neither wolves nor woods to shelter them. Arthur Young more than once speaks of the "innumerable multitudes" of these animals which infested France in 1789, and George Sand states, in the Histoire de ma Vie, that some years after the restoration of the Bourbons, they chased travellers on horseback in the southern provinces, and literally knocked at the doors of her father-in-law's country seat. Eugenie de Guerin, writing from Rayssac in Languedoc in 1831 speaks of hearing the wolves fighting with dogs in the night under her very windows. Lettres, 2d ed., p. 6. There seems to have been a tendency to excessive clearing in Central and Western, earlier than in South-eastern, France. Bernard Palissy, in the Recepte Veritable, first printed in 1563, thus complains: "When I consider the value of the least clump of trees, or even of thorns, I much marvel at the great ignorance of men, who, as it seemeth, do nowadays study only to break down, fell, and waste the fair forests which their forefathers did guard so choicely. I would think no evil of them for cutting down the woods, did they but replant again some part of them; but they care nought for the time to come, neither reck they of the great damage they do to their children which shall come after them."--Oeuvres Completes de Bernard Pallisy, 1844, p. 88.] The total area of France in Mirabeau's time, excluding Savoy, but including Alsace and Lorraine, was about one hundred and thirty-one millions of acres. The extent of forest supposed by Mirabeau would be about thirty-two per cent. of the whole territory. In a country and a climate where the conservative influences of the forest are so necessary as in France, trees must cover a large surface and be grouped in large masses, in order to discharge to the best advantage the various functions assigned to them by nature. The consumption of wood is rapidly increasing in that empire, and a large part of its territory is mountainous, sterile, and otherwise such in character or situation that it can be more profitably devoted to the growth of wood than to any agricultural use. Hence it is evident that the proportion of forest in 1750, taking even Mirabeau's large estimate, was not very much too great for permanent maintenance, though doubtless the distribution was so unequal that it would have been sound policy to fell the woods and clear land in some provinces, while large forests should have been planted in others. [Footnote: The view I have taken of this point is confirmed by the careful investigation of Rentzsch, who estimates the proper proportion of woodland to entire surface at twenty-three per cent. for the interior of Germany, and supposes that near the coast, where the air is supplied with humidity by evaporation from the sea, it might safely be reduced to twenty per cent. See Rentzsch's very valuable prize essay, Der Wald im Haushalt der Natur und der Volkswirthschaft. cap. viii. The due proportion in France would considerably exceed that for the German States, because France has relatively more surface unfit for any growth but that of wood, because the form and geological character of her mountains expose her territory to much greater injury from torrents, and beause at least her southern provinces are more frequently visited both by extreme droughts and by deluging rains.] During the period in question France neither exported manufactured wood or rough timber, nor derived important collateral advantages of any sort from the destruction of her forests. She is consequently impoverished and crippled to the extent of the difference between what she actually possesses of wooded surface and what she ought to have retained. [Footnote: In 1863, France imported lumber to the value of twenty-five and a half millions of dollars, and exported to the amount of six and a half millions of dollars. The annual consumption of France was estimated in 1866 at 212,000,000 cubic feet for building and manufacturing, and 1,588,300,000 for firewood and charcoal. The annual product of the forest-soil of France does not exceed 70,000,000 cubic feet of wood fit for industrial use, and 1,300,000,000 cubic feet consumed as fuel. This estimate does not include the product of scattered trees on private grounds, but the consumption is estimated to exceed the production of the forests by the amount of about twenty millions of dollars. It is worth noticing that the timber for building and manufacturing produced in France comes almost wholly from the forests of the state or of the communes.--Jules Clave, in Revue des Deux Mondes for March 1, 1866, p. 207.] The force of the various considerations which have been suggested in regard to the importance of the forest has been generally felt in France, and the subject has been amply debated special treatises, in scientific journals, and by the public press, as well as in the legislative body of that country. Perhaps no one point has been more prominent in the discussions than the influence of the forest in equalizing and regulating the flow of the water of precipitation. Opinion is still somewhat divided on this subject, but the value of the woods as a safeguard against the ravages of torrents is universally acknowledged, and it is hardly disputed that the rise of river-floods is, even if as great, at least less sudden in streams having their sources in well-wooded territory. Upon the whole, the conservative action of the woods in regard to torrents and to inundations has ben generally recognized by the public of France as a matter of prime importance, and the Government of the empire has made this principle the basis of a special system of legislation for the protection of existing forests, and for the formation of new. The clearing of woodland, and the organization and functions of a police for its protection, are regulated by a law bearing date June 18th, 1859, and provision was made for promoting the restoration of private woods by a statute adopted on the 28th of July, 1860. The former of these laws passed the legislative body by a vote of 246 against 4, the latter with but a single negative voice. The influence of the Government, in a country where the throne is as potent as in France, would account for a large majority, but when it is considered that both laws, the former especially, interfere very materially with the rights of private domain, the almost entire unanimity with which they were adopted is proof of a very general popular conviction, that the protection and extension of the forests is a measure more likely than any other to arrest the devastations of the torrents and check the violence, if not to prevent the recurrence, of destructive river inundations. The law of July 28th, 1860, appropriated 10,000,000 francs, to be expended, at the rate of 1,000,000 francs per year, in executing or aiding the replanting of woods. It is computed that this appropriation--which, considering the vast importance of the subject, does not seem extravagant for a nation rich enough to be able to expend annually six hundred times that sum in the maintenance of its military establishments in times of peace--will secure the creation of new forest to the extent of about 200,000 acres, or one fourteenth part of the soil, where the restoration of the woods is thought feasible, and, at the same time, specially important as a security against the evils ascribed, in a great measure, to its destruction. [Footnote: In 1848 the Government of the so-called French Republic sold to the Bank of France 187,000 acres of public forests, and notwithstanding the zeal with which the Imperial Government had pressed the protective Iegislation of 1860, it introduced, into the Legislative Assembly in 1865 a bill for the sale, and consequently destruction, of the forests of the state to the amount of one hundred million francs. The question was much debated in the Assembly, and public opinion manifested itself so energetically against the measure that the ministry felt itself compelled to withdraw it. See the discussions in D'Alienation des Forets de l'Etat. Paris, 1865. The late Imperial Government sold about 170,000 acres of woodland between 1852 and 1866, both inclusive. The other Governments, since the restoration of the Bourbons in 1814, alienated more than 700,000 acres of the public forests, exclusive of sales between 1836 and 1857, which are not reported.--Annuaire des Eaux et Forets, 1872, p. 9.] In 1865 the Legislative Assembly passed a bill amendatory of the law of 1860, providing, among other things, for securing the soil in exposed localities by grading, and by promoting the growth of grass and the formation of greensward over the surface. This has proved a most beneficial measure, and its adoption under corresponding conditions in the United States is most highly to be recommended. The leading features of the system are: 1. Marking out and securing from pasturage and all other encroachments a zone along the banks and around the head of ravines. 2. Turfing this zone, which in France accomplishes itself, if not spontaneously, at least with little aid from art. 3. Consolidation of the scarps of the ravines by grading and wattling and establishing barriers, sometimes of solid masonry, but generally of fascines or any other simple materials at hand, across the bed of the stream. 4. Cutting banquettes or narrow terraces along the scarps, and planting rows of small deciduous trees and arborescent shrubs upon them, alternating with belts of grass obtained by turfing with sods or sowing grass-seeds. Planting the banquettes and slopes with bushes, and sowing any other vegetables with tenacious roots, is also earnestly recommended. [Footnote: See a description of similar processes recommended and adopted by Mengotti, in his Idraulica, vol. ii., chap. xvii.] Remedies against Torrents. The rural population, which in France is generally hostile to all forest laws, soon acquiesced in the adoption of this system, and its success has far surpassed all expectation. At the end of the year 1868 about 190,000 acres had been planted with trees, [Footnote: Travellers spending the winter at Nice may have a good opportunity of studying the methods of forming and conducting the rewooding of mountain slopes, under the most unfavorable conditions, by visiting Mont Boron, in the immediate vicinity of that city, and other coast plantations in that province, where great difficulties have been completely overcome by the skill and perseverance of French foresters. See Les Forets des Maures, Revue des Eaux et Forets, January, 1869.] and nearly 7,000 acres well turfed over in the Department of the Hautes Alpes. Many hundred ravines, several of which had been the channels of formidable torrents, had been secured by barriers, grading and planting, and according to official reports the aspect of the mountains in the Department, wherever these methods were employed, had rapidly changed. The soil had acquired such stability that the violent rains of 1868, so destructive elsewhere, produced no damage in the districts which had been subjected to these operations, and numerous growing torrents which threatened irreparable mischief had been completely extinguished, or at least rendered altogether harmless. [Footnote: For ample details of processes and results, see the second volume of Surrell, Etudes sur les Torrents, Paris, 1872, and a Report by De La Grye, in the Revue des Eaux et Forets for January, 1869.] Besides the processes directed by the Government of France, various subsidiary measures of an easily and economically practicable character have been suggested. Among them is one which has long been favorably known in our Southern States under the name of circling, and the adoption of which in hilly regions in other States is to be strongly recommended. It is simply a method of preventing the wash of surface by rains, and at the same time of providing a substitute for irrigation of steep pasture-grounds, consisting in little more than in running horizontal furrows along the hillsides, thus converting the scarp of the hills into a succession of small terraces which, when once turfed over, are very permanent. Experience is said to have demonstrated that this simple process at least partially checks the too rapid flow of surface-water into the valleys, and, consequently, in a great measure obviates one of the most prominent causes of inundations, and that it suffices to retain the water of rains, of snows, and of small springs, long enough for the irrigation of the soil, thus increasing its product of herbage in a fivefold proportion. [Footnote: Troy, Etude sur le Reboisement des Montagnes, sections 6, 7, 21.] As a further recommendation, it may be observed that this process is an admirable preparation of the ground for forest plantations, as young trees planted on the terraces would derive a useful protection from the form of the surface and the coating of turf, and would also find a soil moist enough to secure their growth. Forests of Italy. According to the most recent statistics, Italy has 17.64 per cent. of woodland, [Footnote: Siemoni, Manuale d'Arte Forestale, 2 ediz., Firenze, 1872, p. 542.] a proportion which, considering the character of climate and surface, the great amount of soil which is fit for no other purpose than the growth of trees, and the fact that much of the land classed as forest is either very imperfectly wooded, or covered with groves badly administered, and not in a state of progressive improvement, might advantageously be doubled. Taking Italy as a whole, we may say that she is eminently fitted by climate, soil, and superficial formation, to the growth of a varied and luxuriant arboreal vegetation, and that in the interests of self-protection, the promotion of forestal industry is among the first duties of her people. There are in Western Piedmont valleys where the felling of the woods has produced consequences geographically and economically as disastrous as in South-eastern France, and there are many other districts in the Alps and the Apennines where human improvidence has been almost equally destructive. Some of these regions must be abandoned to absolute desolation, and for others the opportunity of physical restoration is rapidly passing away. But there are still millions of square miles which might profitably be planted with forest-trees, and thousands of acres of parched and barren hillside, within sight of almost every Italian provincial capital, which might easily and shortly be reclothed with verdant woods. [Footnote: To one accustomed to the slow vegetation of less favored climes, the rapidity of growth in young plantations in Italy seems almost magical. The trees planted along the new drives and avenues in Florence have attained in three or four years a development which would require at least ten in our Northern States. This, it is true, is a special case, for the trees have been planted and tended with a skill and care which cannot be bestowed upon a forest; but the growth of trees little cared for is still very rapid in Italy. According to Toscanelli, Economia rurale nella Provincia di Pisa, p. 8, note--one of the most complete, curious, and instructive pictures of rural life which exists in any literature--the white poplar, Populus alba, attains in the valley of the Serchio a great height, with a mean diameter of two feet, in twenty years. Solmi states in his Miasma Palustre, p. 115, that the linden reaches a diameter of sixteen inches in the same period. The growth of foreign trees is sometimes extremely luxuriant in Italy. Two Atlas cedars, at the well-known villa of Careggi, near Florence, grown from seed sown in 1850, measure twenty inches in diameter, above the swell of the roots, with an estimated height of sixty feet.] The denudation of the Central and Southern Apennines and of the Italian declivity of the Western Alps began at a period of unknown antiquity, but it does not seem to have been carried to a very dangerous length until the foreign conquests and extended commerce of Rome created a greatly increased demand for wood for the construction of ships and for military material. [Footnote: An interesting example of the collateral effects of the destruction of the forests in ancient Italy may be found in old Roman architecture. In the oldest brick constructions of Rome the bricks are very thin, very thoroughly burnt, and laid with a thick stratum of mortar between the courses. A few centuries later the bricks were thicker and less well burnt, and the layers of mortar were thinner. In the Imperial period the bricks were still thicker, generally soft-burnt, and with little mortar between the courses. This fact, I think, is due to the abundance and cheapness of fuel in earlier, and its growing scarceness and dearness in later, ages. When wood cost little, constructors could afford to burn their brick thoroughly, and to burn and use a great quantity of lime. As the price of fire-wood advanced, they were able to consume less fuel in brick- and lime-kilns, and the quality and quantity of brick and lime used in building were gradually reversed in proportion. The multitude of geographical designations in Italy which indicate the former existence of forests show that even in the Middle Ages there were woods where no forest-trees are now to be found. There are hundreds of names of mediaeval towns derived from abete, acero, carpino, castagno, faggio, frassino, pino, quercia, and other names of trees.] The Eastern Alps, the Western Apennines, and the Maritime Alps retained their forests much later; but even here the want of wood, and the injury to the plains and the nagivation of the rivers by sediment brought down by the torrents, led to legislation for the protection of the forests, by the Republic of Venice, at various periods between the fifteenth and the nineteenth centuries, [Footnote: See A. de Bereuger's valuable Saggio Storico della Legislazione Veneta Forestale. Venezia, 1863. We do not find in the Venetian forestal legislation much evidence that geographical arguments were taken into account by the lawgivers, who seem to have had an eye only to economical considerations. According to Hummel, the desolation of the Karst, the high plateau lying north of Trieste, now one of the most parched and barren districts in Europe, is owing to the felling of the woods, centuries ago, to build the navies of Venice. "Where the miserable peasant of the Karst now sees nothing but bare rock swept and scoured by the raging Bora, the fury of this wind was once subdued by mighty firs, which Venice recklessly cut down to build her fleets."--Physische Geographie, p. 32.] by that of Genoa as early at least as the seventeenth; and both these Governments, as well as several others, passed laws requiring the proprietors of mountain-lands to replant the woods. These, however, seem to have been little observed, and it is generally true that the present condition of the forest in Italy is much less due to the want of wise legislation for its protection than to the laxity of the Governments in enforcing their laws. It is very common in Italy to ascribe to the French occupation under the first Empire all the improvements and all the abuses of recent times, according to the political sympathies of the individual; and the French are often said to have prostrated every forest which has disappeared within this century. But, however this may be, no energetic system of repression or restoration was adopted by any of the Italian States after the downfall of the Empire, and the taxes on forest property in some of them were so burdensome that rural municipalities sometimes proposed to cede their common woods to the Government, without any other compensation than the remission of the taxes imposed on forest-lands. [Footnote: See the Politecnico for the month of May, 1862, p. 234.] Under such circumstances, woodlands would soon become disafforested, and where facilities of transportation and a good demand for timber have increased the inducements to fell it, as upon the borders of the Mediterranean, the destruction of the forest and all the evils which attend it have gone on at a seriously alarming rate. Gallenga gives a striking account of the wanton destruction of the forests in Northern Italy within his personal recollection, [Footnote: "Far away in the darkest recesses of the mountains a kind of universal conspiracy seems to have been got up among these Alpine people,--a destructive mania to hew and sweep down everything that stands on roots."--Country Life in Piedmont, p. 134. "There are huge pyramids of mountains now bare and bleak from base to summit, which men still living and still young remember seeing richly mantled with all but primeval forests."--Ibid., p. 135.] and there are few Italians past middle life whose own memory will not supply similar reminiscences. The clearing of the mountain valleys of the provinces of Bergamo and of Bescia is recent, and Lombardini informs us the felling of the woods in the Valtelline commenced little more than forty years ago. Although no country has produced more able writers on the value of the forest and the general consequences of its destruction than Italy, yet the specific geographical importance of the woods, except as a protection against inundations, has not been so clearly recognized in that country as in the States bordering it on the north and west. It is true that the face of nature has been as completely revolutionized by man, and that the action of torrents has created almost as wide and as hopeless devastation in Italy as in France; but in the French Empire the recent desolation produced by clearing the forests is more extensive, has been more suddenly effected, has occurred in less remote and obscure localities, and therefore, excites a livelier and more general interest than in Italy, where public opinion does not so readily connect the effect with its true cause. Italy, too, from ancient habit, employs little wood in architectural construction; for generations she has maintained no military or commercial marine large enough to require exhaustive quantities of timber, [Footnote: The great naval and commercial marines of Venice and of Genoa must have occasioned an immense consumption of lumber in the Middle Ages, and the centuries immediately succeeding those commonly embraced in that designation. The marine construction of that period employed larger timbers than the modern naval architecture of most commercial countries, but apparently without a proportional increase of strength. The old modes of ship-building have been, to a considerable extent, handed down to very recent times in the Mediterranean, and though better models and modes of construction are now employed in Italian shipyards, an American or an Englishman looks with astonishment at the huge beams and thick planks so often employed in the construction of very small vessels navigating that sea, and not yet old enough to be broken up as unseaworthy.] and the mildness of her climate makes small demands on the woods for fuel. Besides these circumstances, it must be remembered that the sciences of observation did not become knowledges of practical application till after the mischief was already mainly done and even forgotten in Alpine Italy, while its evils were just beginning to be sensibly felt in France when the claims of natural philosophy as a liberal study were first acknowledged in modern Europe. The former political condition of the Italian Peninsula would have effectually prevented the adoption of a general system of forest economy, however clearly the importance of a wise administration of this great public interest might have been understood. The woods which controlled and regulated the flow of the river-sources were very often in one jurisdiction, the plains to be irrigated, or to be inundated by floods and desolated by torrents, in another. Concert of action, on such a subject, between a multitude of jealous petty sovereignties, was obviously impossible, and nothing but the permanent union of all the Italian States under a single government can render practicable the establishment of such arrangements for the conservation and restoration of the forests, and the regulation of the flow of the waters, as are necessary for the full development of the yet unexhausted resources of that fairest of lands, and even for the maintenance of the present condition of its physical geography. The Forests of Germany. Germany, including a considerable part of the Austrian Empire, from character of surface and climate, and from the attention which has long been paid in all the German States to sylviculture, is in a far better condition in this respect than its more southern neighbors; and though in the Alpine provinces of Bavaria and Austria the corresponding districts of Switzerland, Italy, and France, has produced effects hardly less disastrous, [Footnote: As an instance of the scarcity of fuel in some parts of the territory of Bavaria, where, not long since, wood abounded, I may mention the fact that the water of salt-springs is, in some instances, conveyed to the distance of sixty miles, in iron pipes, to reach a supply of fuel for boiling it down. In France, the juice of the sugar-beet is sometimes carried three or four miles in pipes for the same reason. Many of my readers may remember that it was not long ago proposed to manufacture the gas for the supply of London at the mouths of the coal- mines, and convey it to the city in pipes, thus saving the transportation of the coal; but as the coke and mineral tar would still have remained to be disposed of, the operation would probably not have proved advantageous. Great economy in the production of petroleum has resulted from the application of cast-iron tubes to the wells instead of barrels; the oil is thus carried over the various inequalities of surface for three or four miles to the tanks on the railroads, and forced into them by steam-engines. The price of transport is thus reduced one-fifth.] yet, as a whole, the German States, as Siemoni well observes, must be considered as in this respect the model countries of Europe. Not only is the forest area in general maintained without diminution, but new woods are planted where they are specially needed, [Footnote: The Austrian Government is making energetic efforts for the propagation of forests on the desolate waste of the Karst. The difficulties from drought and from the violence of the winds, which might prove fatal to young and even to somewhat advanced plantations, are very serious, but in 1866 upwards of 400,000 trees had been planted and great quantities of seeds sown. Thus far, the results of this important experiment are said to be encouraging. See the Chronique Forestiere in the Revue des Eaux et Forets, Feb. 1870.] and, though the slow growth of forest-trees in those climates reduces the direct pecuniary returns of woodlands to a minimum, the governments wisely persevere in encouraging this industry. The exportation of sawn lumber from Trieste is large, and in fact the Turkish and Egyptian markets are in great part supplied from this source. [Footnote: For information respecting the forests of Germany, as well as other European countries, see, besides the works already cited, the very valuable Manuale d'Arts Forestale of Siemoni, 2de edizione, Firenze, 1872.] Forests of Russia. Russia, which we habitually consider as substantially a forest country--which has in fact a large proportion of woodland--is beginning to suffer seriously for want of wood. Jourdier observes: "Instead of a vast territory with immense forests, which we expect to meet, one sees only scattered groves thinned by the wind or by the axe of the moujik, grounds cut over and more or less recently cleared for cultivation. There is probably not a single district in Russia which has not to deplore the ravages of man or of fire, those two great enemies of Muscovite sylviculture. This is so true, that clear-sighted men already foresee a crisis which will become terrible, unless the discovery of great deposits of some new combustible, as pit-coal or anthracite, shall diminish its evils." [Footnote: Clave, Etudes sur l'Economie Forestiere, p. 261. Clave adds (p. 262): "The Russian forests are very unequally distributed through the territory of this vast empire. In the north they form immense masses, and cover whole provinces, while in the south they are so completely wanting that the inhabitants have no other fuel than straw, dung, rushes, and heath." ... "At Moscow, firewood costs thirty per cent. more than at Paris, while, at the distance of a few leagues, it sells for a tenth of that price." This state of things is partly due to the want of facilities of transportation, and some parts of the United States are in a similar condition. During a severe winter, ten or twelve years ago, the sudden freezing of the canals and rivers, before a large American town had received its usual supply of fuel, occasioned an enormous rise in the price of wood and coal, and the poor suffered severely for want of it. Within a few hours of the city were large forests and an abundant stock of firewood felled and prepared for burning. This might easily have been carried to town by the railroads which passed through the woods; but the managers of the roads refused to receive it as freight, because a rival market for wood might raise the price of the fuel they employed for their locomotives. Truly, our railways "want a master." Hohenstein, who was long professionally employed as a forester in Russia, describes the consequences of the general war upon the woods in that country as already most disastrous, and as threatening still more ruinous evils. The river Volga, the life artery of Russian internal commerce, is drying up from this cause, and the great Muscovite plains are fast advancing to a desolation like that of Persia.--Der Wald, p. 223. The level of the Caspian Sea is eighty-three feet lower than that of the Sea of Azoff, and the surface of Lake Aral is fast sinking. Von Baer maintains that the depression of the Caspian was produced by a sudden subsidence, from ecological causes, and not gradually by excess of evaporation over supply. See Kaspische Studien, p. 25. But this subsidence diminished the area and consequently the evaporation of that sea, and the rivers which once maintained its ancient equilibrium ought to have raised it to its former level, if their own flow had not been diminished. It is, indeed, not proved that the laying bare of a wooded country diminishes the total annual precipitation upon it; but it is certain that the summer delivery of water from the surface of a champaign region, like that through which the Volga, its tributaries, and the feeders of Lake Aral, flow, is lessened by the removal of its woods. Hence, though as much rain may still fall in the valleys of those rivers as when their whole surface was covered with forests, more moisture may be carried off by evaporation, and a less quantity of water be discharged by the rivers since their basins were cleared, and therefore the present condition of the inland waters in question may be due to the removal of the forests in their valleys and the adjacent plains.] Forests of United States. I greatly doubt whether any one of the American States, except, perhaps, Oregon, has, at this moment, more woodland than it ought permanently to preserve, though, no doubt, a different distribution of the forests in all of them might be highly advantageous. It is, perhaps, a misfortune to the American Union that the State Governments have so generally disposed of their original domain to private citizens. It is true that public property is not sufficiently respected in the United States; and within the memory of almost every man of mature age, timber was of so little value in the northernmost States that the owners of private woodlands submitted, almost without complaint, to what would be regarded elsewhere as very aggravated trespasses upon them. [Footnote: According to the maxims of English jurisprudence, the common law consists of general customs so long established that "the memory of man runneth not to the contrary." In other words, long custom makes law. In new countries, the change of circumstances creates new customs, and, in time, new law, without the aid of legislation. Had the American colonists observed a more sparing economy in the treatment of their woods, a new code of customary forest-law would have sprung up and acquired the force of a statute. Popular habit was fast elaborating the fundamental principles of such a code, when the rapid increase in the value of timber, in consequence of the reckless devastation of the woodlands, made it the interest of the proprietors to interfere with this incipient system of forest jurisprudence, and appeal to the rules of English law for the protection of their woods. The courts have sustained these appeals, and forest property is now legally as inviolable as any other, though common opinion still combats the course of judicial decision on such questions.] Persons in want of timber helped themselves to it wherever they could find it, and a claim for damages, for so insignificant a wrong as cutting down and carrying off a few pine or oak trees, was regarded as a mean-spirited act in a proprietor. The habits formed at this period are not altogether obsolete, and even now the notion of a common right of property in the woods still lingers, if not as an opinion at least as a sentiment. Under such circumstances it has been difficult to protect the forest, whether it belong to the State or to individuals. Property of this kind is subject to plunder, as well as to frequent damage by fire. The destruction from these causes would, indeed, considerably lessen, but would by no means wholly annihilate the climatic and geographical influences of the forest, or ruinously diminish its value as a regular source of supply of fuel and timber. It is evidently a matter of the utmost importance that the public, and especially land-owners, be roused to a sense of the dangers to which the indiscriminate clearing of the woods may expose not only future generations, but the very soil itself. Some of the American States, as well as the Governments of many European colonies, still retain the ownership of great tracts of primitive woodland. The State of New York, for example, has, in its north-eastern counties, a vast extent of territory in which the lumberman has only here and there established his camp, and where the forest, though interspersed with permanent settlements, robbed of some of its finest pine groves, and often ravaged by devastating fires, still covers far the largest proportion of the surface. Through this territory the soil is generally poor, and even the new clearings have little of the luxuriance of harvest which distinguishes them elsewhere. The value of the land for agricultural uses is therefore very small, and few purchases are made for any other purpose than to strip the soil of its timber. It has been often proposed that the State should declare the remaining forest the inalienable property of the commonwealth, but I believe the motive of the suggestion has originated rather in poetical than in economical views of the subject. Both these classes of considerations have a real worth. It is desirable that some large and easily accessible region of American soil should remain, as far as possible, in its primitive condition, at once a museum for the instruction of the student, a garden for the recreation of the lover of nature, and an asylum where indigenous tree, and humble plant that loves the shade, and fish and fowl and four-footed beast, may dwell and perpetuate their kind, in the enjoyment of such imperfect protection as the laws of a people jealous of restraint can afford them. The immediate loss to the public treasury from the adoption of this policy would be inconsiderable, for these lands are sold at low rates. The forest alone, economically managed, would, without injury, and even with benefit to its permanence and growth, soon yield a regular income larger than the present value of the fee. The collateral advantages of the preservation of these forests would be far greater. Nature threw up those mountains and clothed them with lofty woods, that they might serve as a reservoir to supply with perennial waters the thousand rivers and rills that are fed by the rains and snows of the Adirondacks, and as a screen for the fertile plains of the central counties against the chilling blasts of the north wind, which meet no other barrier in their sweep from the Arctic pole. The climate of Northern New York even now presents greater extremes of temperature than that of Southern France. The long-continued cold of winter is more intense, the short heats of summer even fiercer than in Provence, and hence the preservation of every influence that tends to maintain an equilibrium of temperature and humidity is of cardinal importance. The felling of the Adirondack woods would ultimately involve for Northern and Central New York consequences similar to those which have resulted from the laying bare of the southern and western declivities of the French Alps and the spurs, ridges, and detached peaks in front of them. It is true that the evils to be apprehended from the clearing of the mountains of New York may be less in degree than those which a similar cause has produced in Southern France, where the intensity of its action has been increased by the inclination of the mountain declivities, and by the peculiar geological constitution of the earth. The degradation of the soil is, perhaps, not equally promoted by a combination of the same circumstances, in any of the American Atlantic States, but still they have rapid slopes and loose and friable soils enough to render widespread desolation certain, if the further destruction of the woods is not soon arrested. The effects of clearing are already perceptible in the comparatively unviolated region of which I am speaking. The rivers which rise in it flow with diminished currents in dry seasons, and with augmented volumes of water after heavy rains. They bring down larger quantities of sediment, and the increasing obstructions to the navigation of the Hudson, which are extending themselves down the channel in proportion as the fields are encroaching upon the forest, give good grounds for the fear of irreparable injury to the commerce of the important towns on the upper waters of that river, unless measures are taken to prevent the expansion of "improvements" which have already been carried beyond the demands of a wise economy. In the Eastern United States the general character of the climate, soil, and surface is such, that for the formation of very destructive torrents a much longer time is required than would be necessary in the mountainous provinces of Italy or of France. But the work of desolation has begun even there, and wherever a rapid mountain-slope has been stripped of wood, incipient ravines already plough the surface, and collect the precipitation in channels which threaten serious mischief in the future. There is a peculiar action of this sort on the sandy surface of pine-forests and in other soils that unite readily with water, which has excited the attention of geographers and geologists. Soils of the first kind are found in all the Eastern States; those of the second are more frequent in the exhausted counties of Maryland, where tobacco is cultivated, and in the more southern territories of Georgia and Alabama. In these localities the ravines which appear after the cutting of the forest, through some accidental disturbance of the surface, or, in some formations, through the cracking of the soil in consequence of great drought or heat, enlarge and extend themselves with fearful rapidity. In Georgia and in Alabama, Lyell saw "the beginning of the formation of hundreds of valleys in places where the primitive forest had been recently cut down." One of these, in Georgia, in a soil composed of clay and sand produced by the decomposition in situ of hornblendic gneiss with layers and veins of quartz, "and which did not exist before the felling of the forest twenty years previous," he describes as more than 55 feet in depth, 300 yards in length, and from 20 to 180 feet in breadth. Our author refers to other cases in the same States, "where the cutting down of the trees, which had prevented the rain from collecting into torrents and running off in sudden land-floods, has given rise to ravines from 70 to 80 feet deep." [Footnote: Lyell, Principles of Geology, 10th ed., vol i., 345-6.] Similar results often follow in the North-eastern States from cutting the timber on the "pine plains," where the soil is usually of a sandy composition and loose texture. American Forest-Trees. The remaining forests of the Northern States and of Canada no longer boast the mighty pines which almost rivalled the gigantic sequoia and redwood of California; and the growth of the larger forest-trees is so slow, after they have attained to a certain size, that if every pine and oak were spared for two centuries, the largest now standing would not reach the stature of hundreds recorded to have been cut within two or three generations. [Footnote: The growth of the white pine, on good soil and in open ground, is rather rapid until it reaches the diameter of a couple of feet, after which it is much slower. The favorite habitat of this tree is light, sandy earth. On this soil, and in a dense wood, it requires a century to attain the diameter of a yard. Emerson (Trees of Massachusetts, p. 65), says that a pine of this species, near Paris, "thirty years planted, is eighty feet high, with a diameter of three feet." He also states that ten white pines planted at Cambridge, Massachusetts in 1809 or 1810, exhibited, in the winter of 1841 and 1842, an average of twenty inches diameter at the ground, the two largest measuring, at the height of three feet, four feet eight inches in circumference; and he mentions another pine growing in a rocky swamp, which at the age of thirty-two years, "gave seven feet in circumference at the but, with a height of sixty-two feet six inches." This latter I suppose to be a seedling, the others TRANSPLANTED trees, which might have been some years old when placed where they finally grew. The following case came under my own observation: In 1824 a pine-tree, so small that a young lady, with the help of a lad, took it up from the ground and carried it a quarter of a mile, was planted near a house in a town in Vermont. It was occasionally watered, but received no other special treatment. I measured this tree in 1860, and found it, at four feet from the ground, and entirely above the spread of the roots, two feet and four inches in diameter. A new measurement in 1871 gave a diameter of two feet eight inches, being an increase of four inches in eleven years, a slower rate than that of preceding years. It could not have been more than three inches through when transplanted, and up to 1860 must have increased its diameter at the rate of about seven-tenths of an inch per year, almost double its later growth. In 1871 the crown had a diameter of 63 feet. In the same neighborhood, elms transplanted in 1803, when they were not above three or four inches through, had attained, in 1871, a diameter of from four feet to four feet two inches, with a spread of crown of from 90 to 112 feet. Sugar-maples, transplanted in 1822, at about the same size, measured two feet three inches through. This growth undoubtedly considerably exceeds that of trees of the same species in the natural forest, though the transplanted trees had received no other fertilizing application than an unlimited supply of light and air.] Dr. Williams, who wrote about sixty years ago, states the following as the dimensions of "such trees as are esteemed large ones of their kind in that part of America" [Vermont], qualifying his account with the remark that his measurements "do not denote the greatest which nature has produced of their particular species, but the greatest which are to be found in most of our towns." Diameter. Height. Pine.......... 6 feet, 247 feet. Maple......... 5 " 9 inches \ Buttonwood.... 5 " 6 " | Elm........... 5 " | Hemlock....... 4 " 9 " | Oak........... 4 " > From 100 to 200 feet. Basswood...... 4 " | Ash........... 4 " | Birch......... 4 " / He adds a note saying that a white pine was cut in Dunstable, New Hampshire, in the year 1736, the diameter of which was seven feet and eight inches. Dr. Dwight says that a fallen pine in Connecticut was found to measure two hundred and forty-seven feet in height, and adds: "A few years since, such trees were in great numbers along the northern parts of Connecticut River." In another letter, he speaks of the white pine as "frequently six feet in diameter, and two hundred and fifty feet in height," and states that a pine had been cut in Lancaster, New Hampshire, which measured two hundred and sixty-four feet, Emerson wrote in 1846: "Fifty years ago, several trees growing on rather dry land in Blandford, Massachusetts, measured, after they were felled, two hundred and twenty-three feet." All these trees are surpassed by a pine felled at Hanover, New Hampshire, about a hundred years ago, and described as measuring two hundred and seventy-four feet. [Footnote: Williams, History of Vermont, ii., p. 53. Dwight s Travels, iv., p. 21, and iii, p. 36. Emerson, Trees of Massachusetts, p. 61. Parish, Life of President Wheelock, p. 56.] These descriptions, it will be noticed, apply to trees cut from seventy to one hundred and forty years since. Persons, whom observation has rendered familiar with the present character of the American forest, will be struck with the smallness of the diameter which Dr. Williams and Dr. Dwight ascribe to trees of such extraordinary height. Individuals of the several species mentioned in Dr. Williams's table are now hardly to be found in the same climate, exceeding one-half or at most two-thirds of the height which he assigns to them; but, except in the case of the oak and the pine, the diameter stated by him would not be thought very extraordinary in trees of far less height, now standing. Even in the species I have excepted, those diameters, with half the heights of Dr. Williams, might perhaps be paralleled at the present time; and many elms, transplanted, at a diameter of six inches, within the memory of persons still living, measure four and sometimes even five feet through. For this change in the growth of forest-trees there are two reasons: the one is, that the great commercial value of the pine and the oak have caused the destruction of all the best--that is, the tallest and straightest-- specimens of both; the other, that the thinning of the woods by the axe of the lumberman has allowed the access of light and heat and air to trees of humbler worth and lower stature, which have survived their more towering brethren. These, consequently, have been able to expand their crowns and swell their stems to a degree not possible so long as they were overshadowed and stifled by the lordly oak and pine. While, therefore, the New England forester must search long before he finds a pine fit to be the mast Of some great ammiral, beeches and elms and birches, as sturdy as the mightiest of their progenitors, are still no rarity. [Footnote: The forest-trees of the Northern States do not attain to extreme longevity in the dense woods. Dr. Williams found that none of the huge pines, the age of which he ascertained, exceeded three hundred and fifty or four hundred years, though he quotes a friend who thought he had noticed trees considerably older. The oak lives longer than the pine, and the hemlock-spruce is perhaps equally long lived. A tree of this latter species, cut within my knowledge in a thick wood, counted four hundred and eighty-six, or, according to another observer, five hundred annual circles. Great luxuriance of animal and vegetable production is not commonly accompanied by long duration of the individual. The oldest men are not found in the crowded city; and in the tropics, where life is prolific and precocious, it is also short. The most ancient forest-trees of which we have accounts have not been those growing in thick woods, but isolated specimens, with no taller neighbor to intercept the light and heat and air, and no rival to share the nutriment afforded by the soil. The more rapid growth and greater dimensions of trees standing near the boundary of the forest, are matters of familiar observation. "Long experience has shown that trees growing on the confines of the wood may be cut at sixty years of age as advantageously as others of the same species, reared in the depth of the forest, at a hundred and twenty. We have often remarked, in our Alps, that the trunk of trees upon the border of a grove is most developed or enlarged upon the outer or open side, where the branches extend themselves farthest, while the concentric circles of growth are most uniform in those entirely surrounded by other trees, or standing entirely alone."--A. and G. Villa, Necessita dei Boschi pp. 17, 18.] California fortunately still preserves her magnificent sequoias, which rise to the height of three hundred feet, and sometimes, as we are assured, even to three hundred and sixty and four hundred feet, and she has also pines and cedars of scarcely inferior dimensions. The public being now convinced of the importance of preserving these colossal trees, it is very probable that the fear of their total destruction may prove groundless, and we may still hope that some of them may survive even till that distant future when the skill of the forester shall have raised from their seeds a progeny as lofty and as majestic as those which now exist. [Footnote: California must surrender to Australia the glory of possessing the tallest trees. According to Dr. Mueller, Director of the Government Botanic Garden at Melbourne, a Eucalyptus, near Healesville, measured 480 feet in height. Later accounts speak of trees of the same species fully 500 feet in height. See Schleiden, Fur Baum und Wald, p. 21. If we may credit late reports, the growth of the eucalyptus is so rapid in California, that the child is perhaps now born who will see the tallest sequoia overtopped by this new vegetable emigrant from Australia.] European and American Trees compared. The woods of North America are strikingly distinguished from those of Europe by the vastly greater variety of species they contain. According to Clave, there are in "France and in most parts of Europe only about twenty forest-trees, five or six of which are spike-leaved and resinous, the remainder broad-leaved." [Footnote: Etudes Forestieres, p. 7.] Our author, however, doubtless means genera, though he uses the word especes. Rossmassler enumerates fifty-seven species of forest-trees as found in Germany, but some of these are mere shrubs, some are fruit and properly garden trees, and some others are only varieties of familiar species. The valuable manual of Parade describes about the same number, including, however, two of American origin--the locust, Robinia pseudacacia, and the Weymouth or white pine, Pinus Strobus--and the cedar of Lebanon from Asia, which, or at least a very closely allied species, is indigenous in Algeria also. We may then safely say that Europe does not possess above forty or fifty native trees of such economical value as to be worth the special care of the forester, while the oak alone numbers more than thirty species in the United States, [Footnote: For full catalogues of American forest-trees, and remarks on their geographical distribution, consult papers on the subject by Dr. J. G. Cooper, in the Report of the Smithsonian Institution for 1858, and the Report of the United States Patent Office, Agricultural Division, for 1860.] and some other North American genera are almost equally diversified. [Footnote: Although Spenser's catalogue of trees occurs in the first canto of the first book of the "Faery Queene"--the only canto of that exquisite poem actually read by most students of English literature--it is not so generally familiar as to make the quotation of it altogether superfluous: VII. Enforst to seeke some covert nigh at hand, A shadic grove not farr away they spide, That promist ayde the tempest to withstand; Whose loftie trees, yclad with sommers pride, Did spred so broad, that heavens light did hide, Not perceable with power of any starr: And all within were pathes and alleies wide, With footing worne, and leading inward farr; Faire harbour that them seems; so in they entered ar. VIII. And foorth they passe, with pleasure forward led, Joying to heare the birdes sweete harmony. Which therein shrouded from the tempest dred, Seemd in their song to scorne the cruell sky. Much can they praise the trees so straight and hy, The sayling pine; the cedar stout and tall; The vine-propp elm; the poplar never dry; The builder oake, sole king of forrests all; The aspine good for staves; the cypresse funerall; IX. The laurell, meed of mightie conquerours And poets sage; the firre that weepeth still; The willow, worne of forlorn paramours; The eugh, obedient to the benders will; The birch for shaftes; the sallow for the mill; The mirrhe sweete-bleeding in the bitter wound; The warlike beech; the ash for nothing ill; The fruitfull olive; and the platane round; The carver holme; the maple seeldom inward sound. Although the number of SPECIES of American forest-trees is much larger than of European, yet the distinguishable VARIETIES are relatively more numerous in the Old World, even in the case of trees not generally receiving special care. This multiplication of varieties is no doubt a result, though not a foreseen or intended one, of human action; for the ordinary operations of European forest economy expose young trees to different conditions from those presented by nature, and new conditions produce new forms. All European woods, except in the remote North, even if not technically artificial forests, acquire a more or less artificial character from the governing hand of man, and the effect of this interference is seen in the constant deviation of trees from the original type. The holly, for example, even when growing as absolutely wild as any tree can ever grow in countries long occupied by man, produces numerous varieties, and twenty or thirty such, not to mention intermediate shades, are described and named as recognizably different, in treatises on the forest-trees of Europe.] While the American forest flora has made large contributions to that of Europe, comparatively few European trees have been naturalized in the United States, and as a general rule the indigenous trees of Europe do not succeed well in our climate. The European mountain-ash--which in beauty, dimensions, and healthfulness of growth is superior to our own [Footnote: In the Northern Tyrol mountain-ashes fifteen inches in diameter are not uncommon. The berries are distilled with grain to flavor the spirit.]--the horse-chestnut, and the abele, or silver poplar, are valuable additions to the ornamental trees of North America. The Swiss arve or zirbelkiefer, Pinus cembra, which yields a well-flavored edible seed and furnishes excellent wood for carving, the umbrella-pine, [Footnote: The mountain ranges of our extreme West produce a pine closely resembling the European umbrella-pine.] which also bears a seed agreeable to the taste, and which, from the color of its foliage and the beautiful form of its dome-like crown, is among the most elegant of trees, the white birch of Central Europe, with its pendulous branches almost rivalling those of the weeping willow in length, flexibility, and gracefulness of fall, and, especially, the "cypresse funerall," might be introduced into the United States with great advantage to the landscape. The European beech and chestnut furnish timber of far better quality than that of their American congeners. The fruit of the European chestnut, though inferior to the American in sweetness and flavor, is larger, and is an important article of diet among the French and Italian peasantry. The walnut of Europe, though not equal to some of the American species in beauty of growth or of wood, or to others in strength and elasticity of fibre, is valuable for its timber and its oil. [Footnote: The walnut is a more valuable tree than is generally supposed. It yields one-third of the oil produced in France, and in this respect occupies an intermediate position between the olive of the south and the oleaginous seeds of the north. A hectare (about two and a half acres) will produce nuts to the value of five hundred francs a year, which cost nothing but the gathering. Unfortunately, its maturity must be long waited for, and more nut-trees are felled than planted. The demand for its wood in cabinet-work is the principal cause of its destruction. See Lavergne, Economie Rurale de la France, p. 253. According to Cosimo Ridolfi (Lezioni Orali, ii., p. 424), France obtains three times as much oil from the walnut as from the olive, and nearly as much as from all oleaginous seeds together. He states that the walnut bears nuts at the age of twenty years, and yields its maximum product at seventy, and that a hectare of ground, with thirty trees, or twelve to the acre, is equal to a capital of twenty-five hundred francs. The nut of this tree is known in the United States as the "English walnut." The fruit and the wood much resemble those of the American black walnut, Juglans nigra, but for cabinet-work the American is the more beautiful material, especially when the large knots are employed. The timber or the European species, when straight-grained, and clear, or free from knots, is, for ordinary purposes, better than that of the American black walnut, but bears no comparison with the wood of the hickory, when strength combined with elasticity is required, and its nut is very inferior in taste to that of the shagbark, as well as to the butternut, which it somewhat resembles. "The chestnut is more valuable still, for it produces on a sterile soil, which, without it, would yield only ferns and heaths, an abundant nutriment for man."--Lavergne, Economie Rurale de la France, p. 253. I believe the varieties developed by cultivation are less numerous in the walnut than is the chestnut, which latter tree is often grafted in Southern Europe. The chestnut crop of France was estimated in 1848 at 3,478,000 hectolitres, or 9,877,520 Winchester bushels, and valued at 13,528,000 francs, or more than two million and a half dollars. In Tuscany the annual yield is computed at about 550,000 bushels. The Tuscan peasants think the flour of the dried chestnut not less nutritious than Indian cornmeal, and it sells at the same price, or about three cents per English pound, in the mountains, and four cents in the towns.] The maritime pine, which has proved of such immense use in fixing drifting sands in France, may perhaps be better adapted to this purpose than any of the pines of the New World, and it is of great importance for its turpentine, resin, and tar. The epicea, or common fir, Abies picea, Abies excelsa, Picea excelsa, abundant in the mountains of France and the contiguous country, is known for its product, Burgundy pitch, and, as it flourishes in a greater variety of soil and climate than almost any other spike-leaved tree, it might be well worth transplantation. [Footnote: This fir is remarkable for its tendency to cicatrize or heal over its stumps, a property which it possesses in common with some other firs, the maritime pine, and the European larch. When these trees grow in thick clumps, their roots are apt to unite by a species of natural grafting, and if one of them be felled, although its own proper rootlets die, the stump may continue, sometimes for a century, to receive nourishment from the radicles of the surrounding trees, and a dome of wood and bark of considerable thickness be formed over it. The healing is, however, only apparent, for the entire stump, except the outside ring of annual growth, soon dies, and even decays within its covering, without sending out new shoots. See Monthly Report, Department of Agriculture, for October, 1872.] The cork oak has been introduced into California and some other parts of the United States, I believe, and would undoubtedly thrive in the Southern section of the Union. [Footnote: At the age of twelve or fifteen years, the cork-tree is stripped of its outer bark for the first time. This first yield is of inferior quality, and it employed for floats for nets and buoys, or burnt for lampblack. After this, a new layer of cork, an inch or an inch and a quarter in thickness, is formed about one in ten years, and is removed in large sheets without injury to the tree, which lives a hundred and fifty years or more. According to Clave (p. 252), the annual product of a forest of cork oaks is calculated at about 660 kilogrammes, worth 150 frances, to the hectare, which, deducting expenses, leaves a profit of 100 francs. This is about equal to 250 pound weight, and eight dollars profit to the acre. The cork oaks of the national domain in Algeria cover about 500,000 acres, and are let to individuals at rates which are expected, when the whole is rented, to yield to the state revenue of about $2,000,000. George Sand, in the Histoire de ma Vie, speaks of the cork-forests in Southern France as among the most profitable of rural possessions, and states, what I do not remember to have seen noticed elsewhere, that Russia is the best customer for cork. The large sheets taken from the trees are slit into thin plates, and used to line the walls of apartments in that cold climate. On the cultivation and management of the cork oak, see Des Incendies et de la culture du Chene-liege, in Revue das Eaux et Forets for February, 1869.] the walnut, the chestnut, the cork oak, the mulberry, the olive, the orange, the lemon, the fig, and the multitude of other trees which, by their fruit, or by other products, yield an annual revenue, nature has provided Southern Europe with a partial compensation for the loss of the native forest. It is true that these trees, planted as most of them are at such distances as to admit of cultivation, or of the growth of grass among them, are but an inadequate substitute for the thick and shady wood; but they perform to a certain extent the same offices of absorption and transpiration, they shade the surface of the ground, they serve to break the force of the wind, and on many a steep declivity, many a bleak and barren hillside, the chestnut binds the soil together with its roots, and prevents tons of earth and gravel from washing down upon the fields and the gardens. Fruit-trees are not wanting, certainly, north of the Alps. The apple, the pear, and the prune are important in the economy both of man and of nature, but they are far less numerous in Switzerland and Northern France than are the trees I have mentioned in Southern Europe, both because they are in general less remunerative, and because the climate, in higher latitudes, does not permit the free introduction of shade trees into grounds occupied for agricultural purposes. [Footnote: The walnut, the chestnut, the apple, and the pear are common to the border between the countries I have mentioned, but the range of the other trees is bounded by the Alps, and by a well-defined and sharply drawn line to the west of those mountains. From some peculiarity in the sky of Europe, cultivated plants will thrive, in Northern Italy, in Southern France, and even in Switzerland, under a depth of shade where no crop, not even grass, worth harvesting, would grow in the United States with an equally high summer temperature. Hence the cultivation of all these trees is practicable in Europe to a greater extent than would be supposed reconcilable with the interests of agriculture. Some idea of the importance of the olive orchards may be formed from the fact that Sicily alone, an island scarcely exceeding 10,000 square miles in area, of which one-third at least is absolutely barren, has exported to the single port of Marseilles more than 2,000,000 pounds weight olive-oil per year, for the last thirty years. According to Cosimo Ridolfi, Lezioni Orali, vol. ii., p. 340, in a favorable soil and climate the average yield of oil from poorly manured trees, which compose the great majority, is six English pounds, while with the best cultivation it rises to twenty-three pounds. The annual production of olive-oil in the whole of Italy is estimated at upwards of 850,000,000 pounds, and if we allow twelve pounds to the tree, we have something more than 70,000,000 trees. The real number of trees is, however, much greater than this estimate, for in Tuscany and many other parts of Italy the average yield of oil per tree does not exceed two pounds, and there are many millions of young trees not yet in bearing. Probably we shall not exaggerate if we estimate the olive trees of Italy at 100,000,000, and as there are about a hundred trees to the acre, the quantity of land devoted to the cultivation of the olive may be taken at a million acres. Although olive-oil is much used in cookery in Italy, lard is preferred as more nutritious. Much American lard is exported to South-eastern Italy, and olive-oil is imported in return.] The multitude of species, intermixed as they are in their spontaneous growth, gives the American forest landscape a variety of aspect not often seen in the woods of Europe, and the gorgeous tints, which nature repeats from the dying dolphin to paint the falling leaf of the American maples, oaks, and ash trees, clothe the hillsides and fringe the water-courses with a rainbow splendor of foliage, unsurpassed by the brightest groupings of the tropical flora. It must be confessed, however, that both the northern and the southern declivities of the Alps exhibit a nearer approximation to this rich and multifarious coloring of autumnal vegetation than most American travellers in Europe are willing to allow; and, besides, the small deciduous shrubs which often carpet the forest-glades of these mountains are dyed with a ruddy and orange glow, which, in the distant landscape, is no mean substitute for the scarlet and crimson and gold and amber of the transatlantic woodland. [Footnote: The most gorgeous autumnal coloring I have observed in the vegetation of Europe has been in the valleys of the Durance and its tributaries in Dauphiny. I must admit that neither in variety nor in purity and brilliancy of tint, does this coloring fall much, if at all, short of that of the New England woods. But there is this difference: in Dauphiny, it is only in small shrubs that this rich painting is seen, while in North America the foliage of large trees is dyed in full splendor. Hence the American woodland has fewer broken lights and more of what painters call breadth of coloring. Besides this, the arrangement of the leafage in large globular or conical masses, affords a wider scale of light and shade, thus aiding now the gradation now the contrast of tints, and gives the American October landscape a softer and more harmonious tone than marks the humble shrubbery of the forest hillsides of Dauphiny. Thoreau--who was not, like some very celebrated landscape critics of the present day, an outside spectator of the action and products of natural forces, but, in the old religious sense, an OBSERVER of organic nature, living, more than almost any other descriptive writer, among and with her children--had a very eloquent paper on the "Autumnal Tints" of the New England landscape.--See his Excursions, pp. 215 et seqq. Few men have personally noticed so many facts in natural history accessible to unscientific observation as Thoreau, and yet he had never seen that very common and striking spectacle, the phosphorescence of decaying wood, until, in the latter years of his life, it caught his attention in a bivouac in the forests of Maine. He seems to have been more excited by this phenomenon than by any other described in his works. It must be a capacious eye that takes in all the visible facts in the history of the most familiar natural object.--The Maine Woods, p. 184.] I admit, though not without reluctance, that the forest-trees of Central and Southern Europe have a great advantage over our own in the corresponding latitudes, in density of foliage as well as in depth of color and persistence of the leaves in deciduous species. An American, who, after a long absence from the United States, returns in the full height of summer, is painfully surprised at the thinness and poverty of the leafage even of the trees which he had habitually regarded as specially umbrageous, and he must wait for the autumnal frosts before he can recover his partiality for the glories of his native woods. None of our north-eastern evergreens resemble the umbrella pine sufficiently to be a fair object of comparison with it. A cedar, very common above the Highlands on the Hudson, and elsewhere, is extremely like the cypress, straight, slender, with erect, compressed ramification, and feathered to the ground, but its foliage is neither so dark nor so dense, the tree does not attain the majestic height of the cypress, nor has it the lithe flexibility of that tree. [Footnote: The cold winter, or rather spring, of 1872 proved fatal to many cypresses as well as olive trees in the Val d'Arno. The cypress, therefore, could be introduced only into California and our Southern States.] In mere shape, the Lombardy poplar nearly resembles this latter, but it is almost a profanation to compare the two, especially when they are agitated by the wind; for under such circumstances, the one is the most majestic, the other the most ungraceful, or--if I may apply such an expression to anything but human affectation of movement--the most awkward of trees. The poplar trembles before the blast, flutters, struggles wildly, dishevels its foliage, gropes around with its feeble branches, and hisses as in impotent passion. The cypress gathers its limbs still more closely to its stem, bows a gracious salute rather than an humble obeisance to the tempest, bends to the wind with an elasticity that assures you of its prompt return to its regal attitude, and sends from its thick leaflets a murmur like the roar of the far-off ocean. The cypress and the umbrella-pine are not merely conventional types of the Italian landscape. They are essential elements in a field of rural beauty which can be seen in perfection only in the basin of the Mediterranean, and they are as characteristic of this class of scenery as is the date-palm of the oases of the Eastern desert. There is however, this difference: a single cypress or pine is often enough to shed beauty over a wide area; the palm is a social tree, and its beauty is not so much that of the individual as of the group. [Footnote: European poets, whose knowledge of the date-palm is not founded on personal observation, often describe its trunk as not only slender, but particularly STRAIGHT. Nothing can be farther from the truth. When the Orientals compare the form of a beautiful girl to the stem of the palm, they do not represent it as rigidly straight, but on the contrary as made up of graceful curves, which seem less like permanent outlines than like flowing motion. In a palm grove, the trunks, so far from standing planted upright like the candles of a chandelier, bend in a vast variety of curves, now leaning towards, now diverging from, now crossing, each other, and among a hundred you will hardly see two whose axes are parallel.] The frequency of the cypress and the pine--combined with the fact that the other trees of Southern Europe which most interest a stranger from the north, the orange and the lemon, the cork oak, the ilex, the myrtle, and the laurel, are evergreens--goes far to explain the beauty of the winter scenery of Italy. Indeed, it is only in the winter that a tourist who confines himself to wheel-carriages and high roads can acquire any notion of the face of the earth, and form any proper geographical image of that country. At other seasons, not high walls only, but equally impervious hedges, and now, unhappily, acacias thickly planted along the railway routes, confine the view so completely, that the arch of a tunnel, or a night-cap over the traveller's eyes, is scarcely a more effectual obstacle to the gratification of his curiosity. [Footnote: Besides this, in a country so diversified in surface as Italy, with the exception of the champaign region drained by the Po, every new field of view requires either an extraordinary coup d'oeil in the spectator, or a long study, in order to master its relief, its plans, its salient and retreating angles. In summer, except of course in the bare mountains, the universal greenery confounds light and shade, distance and foreground; and though the impression upon a traveller, who journeys for the sake of "sensations," may be strengthened by the mysterious annihilation of all standards for the measurement of space, yet the superior intelligibility of the winter scenery of Italy is more profitable to those who see with a view to analyze.] The Forest does not furnish Food for Man. In a region absolutely covered with trees, human life could not long be sustained, for want of animal and vegetable food. The depths of the forest seldom furnish either bulb or fruit suited to the nourishment of man; and the fowls and beasts on which he feeds are scarcely seen except upon the margin of the wood, for here only grow the shrubs and grasses, and here only are found the seeds and insects, which form the sustenance of the non-carnivorous birds and quadrupeds. [Footnote: Clave, as well as many earlier writers, supposes that primitive man derived his nutriment from the spontaneous productions of the wood. "It is to the forests," says he, "that man was first indebted for the means of subsistence. Exposed alone, without defence, to the rigor of the seasons, as well as to the attacks of animals stronger and swifter than himself, he found in them his first shelter, drew from them his first weapons. In the first period of humanity, they provided for all his wants: they furnished him wood for warmth, fruits for food, garments to cover his nakedness, arms for his defence."--Etudes sur l'Economie Forestiere, p. 13. But the history of savage life, as far as it is known to us, presents man in that condition as inhabiting only the borders of the forest and the open grounds that skirt the waters and the woods, and as finding only there the aliments which make up his daily bread. The villages of the North American Indians were upon the shores of rivers and lakes, and their weapons and other relics are found only in the narrow open grounds which they had burned over and cultivated, or in the margin of the woods around their hamlets. Except upon the banks of rivers or of lakes, the woods of the interior of North America, far from the habitations of man, are almost destitute of animal life. Dr. Newberry, describing the vast forests of the yellow pine of the West, Pinus ponderosa, remarks: "In the arid and desert regions of the interior basin, we made whole days' marches in forests of yellow pine, of which neither the monotony was broken by other forms of vegetation, nor its stillness by the flutter of a bird or the hum of an insect."--Pacific Railroad Report, vol. vi., 1857. Dr. Newberry's Report on Botany, p. 37. Cheadle and Milton's North-west Passage confirms these statements. Valvasor says, in a paragraph already quoted, "In my many journeys through this valley, I did never have sight of so much as a single bird." The wild fruit and nut trees, the Canada plum, the cherries, the many species of walnut, the butternut, the hazel, yield very little, frequently nothing, so long as they grow in the woods; and it is only when the trees around them are cut down, or when they grow in pastures, that they become productive. The berries, too--the strawberry, the blackberry, the raspberry, the whortleberry, scarcely bear fruit at all except in cleared ground. The rank forests of the tropics are as unproductive of human aliment as the less luxuriant woods of the temperate zone. In Strain's unfortunate expedition across the great American isthmus, where the journey lay principally through thick woods, several of the party died of starvation, and for many days the survivors were forced to subsist on the scantiest supplies of unnutritious vegetables perhaps never before employed for food by man. See the interesting account of that expedition in Harper's Magazine for March, April, and May, 1855.] First Removal of the Forest. When multiplying man had filled the open grounds along the margin of the rivers, the lakes, and the sea, and sufficiently peopled the natural meadows and savannas of the interior, where such existed, he could find room for expansion and further growth only by the removal of a portion of the forest that hemmed him in. The destruction of the woods, then, was man's first geographical conquest, his first violation of the harmonies of inanimate nature. Primitive man had little occasion to fell trees for fuel, or for the construction of dwellings, boats, and the implements of his rude agriculture and handicrafts. Windfalls would furnish a thin population with a sufficient supply of such material, and if occasionally a growing tree was cut, the injury to the forest would be too insignificant to be at all appreciable. The accidental escape and spread of fire or possibly, the combustion of forests by lightning, must have first suggested the advantages to be derived from the removal of too abundant and extensive woods, and at the same time, have pointed out a means by which a large tract of surface could readily be cleared of much of this natural incumbrance. As soon as agriculture had commenced at all, it would be observed that the growth of cultivated plants, as well as of many species of wild vegetation, was particularly rapid and luxuriant on soils which had been burned over, and thus a new stimulus would be given to the practice of destroying the woods by fire, as a means of both extending the open grounds, and making the acquisition of a yet more productive soil. After a few harvests had exhausted the first rank fertility of this virgin mould, or when weeds and briers and the sprouting roots of the trees had begun to choke the crops of the half-subdued soil, the ground would be abandoned for new fields won from the forest by the same means, and the deserted plain or hillock would soon clothe itself anew with shrubs and trees, to be again subjected to the same destructive process, and again surrendered to the restorative powers of vegetable nature. [Footnote: In many parts of the North American States, the first white settlers found extensive tracts of thin woods, of a very park-like character, called "oak-openings," from the predominance of different species of that tree upon them. These were the semi-artificial pasture-grounds of the Indians, brought into that state, and so kept, by partial clearing, and by the annual burning of the grass. The object of this operation was to attract the deer to the fresh herbage which sprang up after the fire. The oaks bore the annual scorching at least for a certain time; but if it had been indefinitely continued, they would very probably have been destroyed at last. The soil would have then been much in the prairie condition, and would have needed nothing but grazing for a long succession of years to make the resemblance perfect. That the annual fires alone occasioned the peculiar character of the oak-openings, is proved by the fact that as soon as the Indians had left the country, young trees of many species sprang up and grew luxuriantly upon them. See a very interesting account of the oak-openings in Dwight s Travels, iv., pp. 58-63. This rude economy would be continued for generations, and, wasteful as it is, is still largely pursued in Northern Sweden, Swedish Lapland, and sometimes even in France and the United States. [Footnote: The practice of burning over woodland, at once to clear and manure the ground, is called in Swedieh svedjande, a participial noun from the verb att svedja, to burn over. Though used in Sweden as a preparation for crops of rye or other grain, it is employed in Lapland more frequently to secure an abundant growth of pasturage, which follows in two or three years after the fire; and it is sometimes resorted to as a mode of driving the Laplanders and their reindeer from the vicinity of the Swedish backwoodsman's grass-grounds and hay-stacks, to which they are dangerous neighbors. The forest, indeed, rapidly recovers itself, but it is a generation or more before the reindeer-moss grows again. When the forest consists of pine, tall, the ground, instead of being rendered fertile by this process, becomes hopelessly barren, and for a long time afterwards produces nothing but weeds and briers.--Laestadius, Om Uppodlingar i Lappmarken, p. 15. See also Schubert, Resa i Sverge, ii., p. 375. In some parts of France this practice is so general that Clave says: "In the department of Ardennes it (le sartage) is the basis of agriculture."] Principal Causes of the Destruction of the Forest. The needs of agriculture are the most familiar cause of the destruction of the forest in new countries; for not only does an increasing population demand additional acres to grow the vegetables which feed it and its domestic animals, but the slovenly husbandry of the border settler soon exhausts the luxuriance of his first fields, and compels him to remove his household gods to a fresher soil. The extent of cleared ground required for agricultural use depends very much on the number and kinds of the cattle bred. We have seen, in a former chapter, that, in the United States, the domestic quadrupeds amount to more than a hundred millions, or nearly three times the number of the human population of the Union. In many of the Western States, the swine subsist more or less on acorns, nuts, and other products of the woods, and the prairies, or natural meadows of the Mississippi valley, yield a large amount of food for beast, as well as for man. With these exceptions, all this vast army of quadrupeds is fed wholly on grass, grain, pulse, and roots grown on soil reclaimed from the forest by European settlers. It is true that the flesh of domestic quadrupeds enters very largely into the aliment of the American people, and greatly reduces the quantity of vegetable nutriment which they would otherwise consume, so that a smaller amount of agricultural product is required for immediate human food, and, of course, a smaller extent of cleared land is needed for the growth of that product, than if no domestic animals existed. But the flesh of the horse, the ass, and the mule is not consumed by man, and the sheep is reared rather for its fleece than for food. Besides this, the ground required to produce the grass and grain consumed in rearing and fattening a grazing quadruped, would yield a far larger amount of nutriment, if devoted to the growing of breadstuffs, than is furnished by his flesh; and, upon the whole, whatever advantages may be reaped from the breeding of domestic cattle, it is plain that the cleared land devoted to their sustenance in the originally wooded part of the United States, after deducting a quantity sufficient to produce an amount of aliment equal to their flesh, still greatly exceeds that cultivated for vegetables, directly consumed by the people of the same regions; or, to express a nearly equivalent idea in other words, the meadow and the pasture, taken together, much exceed the ploughland. [Footnote: The two ideas expressed in the text are not exactly equivalent, because, though the consumption of animal food diminishes the amount of vegetable aliment required for human use, yet the animals themselves consume a great quantity of grain and roots grown on ground ploughed and cultivated as regularly and as laboriously as any other. The 280,000,000 bushels of oats raised in the United States in 1870, and fed to the 7,000,000 horses, the potatoes, the turnips, and the maize employed in fattening the oxen, the sheep, and the swine slaughtered the same year, occupied an extent of ground which, cultivated by hand-labor and with Chinese industry and skill, would probably have produced a quantity of vegetable food equal in alimentary power to the flesh of the quadrupeds killed for domestic use. Hence, so far as the naked question of AMOUNT of aliment is concerned, the meadows and the pastures might as well have remained in the forest condition. It must, however, be borne in mind that animal labor, if not a necessary, is probably an economical, force in agricultural occupations, and that without animal manure many branches of husbandry could hardly be carried on at all. At the same time, the introduction of machinery into rural industry, and of artificial, mineral, and fossil manures, is working great revolutions, and we may find at some future day that the ox is no longer necessary as a help to the farmer.] Governments and military commanders have at different periods deliberately destroyed forests by fire or the axe, because they afforded a retreat to robbers, outlaws, or enemies, and this was one of the hostile measures practised by both Julius Caesar and the Gauls in the Roman war of conquest against that people. It was also resorted to in the Mediterranean provinces of France, then much infested by robbers and deserters, as late as the reign of Napoleon I., and is said to have been employed by the early American colonists in their exterminating wars with the native Indians. [Footnote: For many instances of this sort, see Maury, Les Forets de la Gaule, pp. 3-5, and Becquerel, Des Climats, etc., pp. 301-303. In 1664 the Swedes made an incursion into Jutland and felled a considerable extent of forest. After they retired, a survey of the damage was had, and the report is still extant. The number of trees cut was found to be 120,000, and as an account was taken of the numbers of each species of tree, the document is of much interest in the history of the forest, as showing the relative proportions between the different trees which at that time composed the wood. See Vaupell, Bogens Indvandring, p. 35, and Notes, p. 55.] In the Middle Ages, as well as in earlier and later centuries, attempts have been made to protect the woods by law, [Footnote: Stanley, quoting Selden, De Jure Naturali, lib. vi., and Fabricius, Cod. Psedap., V. T., i. 874, mentions a noteworthy Hebrew tradition of uncertain date, but unquestionably very ancient, which is one of the oldest proofs of a public respect for the woods. "A Hebrew tradition attributes to Joshua ten statutes, containing precise regulations for the protection of the property of every tribe and of every head of a family against irregular depredations. Small quadrupeds were allowed to pasture in dense woods, not in thin ones; but no animal could feed in any forest without the consent of the proprietor of the soil. Every Hebrew might pick up fallen boughs and twigs, but was not permitted to cut them. Trees might be pruned for the trimmings, with the exception of the olive and other fruit-trees, and provided there was sufficient shade in the place."--Lectures on the History of the Jewish Church, part i., p. 271. Alfred Maury mentions several provisions taken from the laws of the Indian legislator Manu, on the same subject.--Les Forets de la Gaule, p. 9. The very ancient Tables of Heracles contain provisions for the protection of woods, but whether these referred only to sacred groves, to public forests, or to leased lands, is not clear.] as necessary for the breeding of deer, wild boars, and other game, or for the more reasonable purpose of furnishing a supply of building timber and fuel for future generations. It was reserved for more advanced ages to appreciate the geographical importance of the woods, and it is only in the most recent times, only in a few countries of Europe, that the general destruction of the forests has been recognized as the most potent among the many causes of the physical deterioration of the earth. [Footnote: We must perhaps make an exception in favor of the Emperor Constantine, who commenced the magnificent series of aqueducts and cisterns which still supply Constantinople with water, and enacted strict laws for the protection of the forest of Belgrade, in which rise the springs that feed the aqueducts. See an article by Mr. H. A. Homes on the Water-Supply of Constantinople in the Albany Argus of June 6, 1872.] Royal Forests and Game Laws. The French authors I have quoted, as well as many other writers of the same nation, refer to the French Revolution as having given a new impulse to destructive causes which were already threatening the total extermination of the woods. [Footnote: Religious intolerance had produced similar effects in France at an earlier period. "The revocation of the edict of Nantes and the dragonnades occasioned the sale of the forests of the unhappy Protestants, who fled to seek in foreign lands the liberty of conscience which was refused to them in France. The forests were soon felled by the purchasers, and the soil in part brought under cultivation."--Becquerel, Des Climats, etc, p. 303.] The general crusade against the forests, which accompanied that important event, is to be ascribed, in a considerable degree, to political resentments. The forest codes of the mediaeval kings, and the local "coutumes" of feudalism, contained many severe and even inhuman provisions, adopted rather for the preservation of game than from any enlightened views of the more important functions of the woods. Ordericus Vitalis informs us that William the Conqueror destroyed sixty parishes and drove out their inhabitants, in order that he might turn their lands into a forest, [Footnote: The American reader must be reminded that, in the language of the chase and of the English law, a "forest" is not necessarily a wood. Any large extent of ground, withdrawn from cultivation, reserved for the pleasures of the chase, and allowed to clothe itself with a spontaneous growth, serving as what is technically called "cover" for wild animals, is, in the dialects I have mentioned, a forest. When, therefore, the Norman kings afforested the grounds referred to in the text, it is not to be supposed that they planted them with trees, though the protection afforded to them by the game laws would, if cattle had been kept out, soon have converted them into real woods.] to be reserved as a hunting-ground for himself and his posterity, and he punished with death the killing of a deer, wild boar, or even a hare. His successor, William Rufus, according to the Histoire des Ducs de Normandie et des Rois d'Angleterre, p. 67, "was hunting one day in a new forest, which he had caused to be made out of eighteen parishes that he had destroyed, when, by mischance, he was killed by an arrow wherewith Tyreus de Rois [Sir Walter Tyrell] thought to slay a beast, but missed the beast, and slew the king, who was beyond it. And in this very same forest, his brother Richard ran so hard against a tree that he died of it. And men commonly said that these things were because they had so laid waste and taken the said parishes." These barbarous acts, as Bonnemere observes, [Footnote: Histoire des Paysans, ii., p. 190. The work of Bonnemere is of great value to those who study the history of mediaeval Europe from a desire to know its real character, and not in the hope of finding apparent facts to sustain a false and dangerous theory. Bonnemere is one of the few writers who, like Michelet, have been honest enough and bold enough to speak the truth with regard to the relations between the church and the people in the Middle Ages.] were simply the transfer of the customs of the French kings, of their vassals, and even of inferior gentlemen, to conquered England. "The death of a hare," says our author, "was a hanging matter, the murder of a plover a capital crime. Death was inflicted on those who spread nets for pigeons; wretches who had drawn a bow upon a stag were to be tied to the animal alive; and among the seigniors it was a standing excuse for having killed game on forbidden ground, that they aimed at a serf." The feudal lords enforced these codes with unrelenting rigor, and not unfrequently took the law into their own hands. In the time of Louis IX., according to William of Nangis, "three noble children, born in Flanders, who were sojourning at the abbey of St. Nicholas in the Wood, to learn the speech of France, went out into the forest of the abbey, with their bows and iron-headed arrows, to disport them in shooting hares, chased the game, which they had started in the wood of the abbey, into the forest of Enguerrand, lord of Coucy, and were taken by the sergeants which kept the wood. When the fell and pitiless Sir Enguerrand knew this, he had the children straightway hanged without any manner of trial." [Footnote: It is painful to add that a similar outrage was perpetrated a very few years ago, in one of the European states, by a prince of a family now dethroned. In this case, however, the prince killed the trespasser with his own hand, his sergeants refusing to execute his mandate.] The matter being brought to the notice of good King Louis, Sir Enguerrand was summoned to appear, and, finally, after many feudal shifts and dilatory pleas, brought to trial before Louis himself and a special council. Notwithstanding the opposition of the other seigniors, who, it is needless to say, spared no efforts to save a peer, probably not a greater criminal than themselves, the king was much inclined to inflict the punishment of death on the proud baron. "If he believed," said he, "that our Lord would be as well content with hanging as with pardoning, he would hang Sir Enguerrand in spite of all his barons;" but noble and clerical interests unfortunately prevailed. The king was persuaded to inflict a milder retribution, and the murderer was condemned to pay ten thousand livres in coin, and to "build for the souls of the three children two chapels wherein mass should be said every day." [Footnote: Guillame De Nangis, as quoted in the notes to Joinville, Nouvelle Collection des Memoires, etc., par Michaud et Poujoulat, premiere serie, i., p. 335. Persons acquainted with the character and influence of the mediaeval clergy will hardly need to be informed that the ten thousand livres never found their way to the royal exchequer. It was easy to prove to the simple-minded king that, as the profits of sin were a monopoly of the church, he ought not to derive advantage from the commission of a crime by one of his subjects; and the priests were cunning enough both to secure to themselves the amount of the fine, and to extort from Louis large additional grants to carry out the purposes to which they devoted the money. "And though the king did take the moneys," says the chronicler, "he put them not into his treasury, but turned them into good works; for he builded therewith the maison-Dieu of Pontoise, and endowed the same with rents and lands; also the schools and the dormitory of the friars preachers of Paris, and the monastery of the Minorite friars."] The hope of shortening the purgatorial term of the young persons, by the religious rites to be celebrated in the chapels, was doubtless the consideration which operated most powerfully on the mind of the king; and Europe lost a great example for the sake of a mass. The desolation and depopulation, resulting from the extension of the forest and the enforcement of the game laws, induced several of the French kings to consent to some relaxation of the severity of these latter. Francis I., however, revived their barbarous provisions, and, according to Bonnemere, even so good a monarch as Henry IV. re-enacted them, and "signed the sentence of death upon peasants guilty of having defended their fields against devastation by wild beasts." "A fine of twenty livres," he continues, "was imposed on every one shooting at pigeons, which, at that time, swooped down by thousands upon the new-sown fields and devoured the seed. But let us count even this a progress, for we have seen that the murder of a pigeon had been a capital crime." [Footnote: Histoire des Paysans, ii., p. 200.] Not only were the slightest trespasses on the forest domain--the cutting of an oxgoad, for instance--severely punished, but game animals were still sacred when they had wandered from their native precincts and were ravaging the fields of the peasantry. A herd of deer or of wild boars often consumed or trod down a harvest of grain, the sole hope of the year for a whole family; and the simple driving out of such animals from this costly pasturage brought dire vengeance on the head of the rustic, who had endeavored to save his children's bread from their voracity. "At all times," says Paul Louis Courier, speaking in the name of the peasants of Chambord, in the "Simple Discours," "the game has made war upon us. Paris was blockaded eight hundred years by the deer, and its environs, now so rich, so fertile, did not yield bread enough to support the gamekeepers." [Footnote: The following details from Bonnemere will serve to give a more complete idea of the vexatious and irritating nature of the game laws of France. The officers of the chase went so far as to forbid the pulling up of thistles and weeds, or the mowing of any unenclosed ground before St. John's day (24th June), in order that the nests of game birds might not be disturbed. It was unlawful to fence-in any grounds in the plains where royal residences were situated; thorns were ordered to be planted in all fields of wheat, barley, or oats, to prevent the use of ground-nets for catching the birds which consumed, or were believed to consume, the grain, and it was forbidden to cut or pull stubble before the first of October, lest the partridge and the quail might be deprived of their cover. For destroying the eggs of the quail, a fine of one hundred livres was imposed for the first offence, double that amount for the second, and for the third the culprit was flogged and banished for five years to a distance of six leagues from the forest.--Histoire des Paysans, ii., p. 202, text and notes. Neither these severe penalties, nor any provisions devised by the ingenuity of modern legislation, have been able effectually to repress poaching. "The game laws," says Clave, "have not delivered us from the poachers, who kill twenty times as much game as the sportsmen. In the forest of Fontainebleau, as in all those belonging to the state, poaching is a very common and a very profitable offence. It is in vain that the gamekeepers are on the alert night and day, they cannot prevent it. Those who follow the trade begin by carefully studying the habits of the game. They will lie motionless on the ground, by the roadside or in thickets, for whole days, watching the paths most frequented by the animals," etc.--Revue des Deux Mondes, Mai, 1863, p. 160. The writer adds many details on this subject, and it appears that, as there are "beggars on horseback" in South America, there are poachers in carriages in France.] The Tiers Etat declared, in 1789, "the most terrible scourge of agriculture is the abundance of wild game, a consequence of the privileges of the chase; the fields are wasted, the forests ruined, and the vines gnawed down to the roots." Effects of the French Revolution. The abrogation of the game laws and of the harsh provisions of the forestal code was one of the earliest measures of the revolutionary government; and the removal of the ancient restrictions on the chase and of the severe penalties imposed on trespassers upon the public forests, was immediately followed by unbridled license in the enjoyment of the newly conceded rights. In the popular mind the forest was associated with all the abuses of feudalism, and the evils the peasantry had suffered from the legislation which protected both it and the game it sheltered, blinded them to the still greater physical mischiefs which its destruction was to entail upon them. No longer under the safeguard of the law, the crown forests and those of the great lords were attacked with relentless fury, unscrupulously plundered and wantonly laid waste, and even the rights of property in small private woods ceased to be respected. [Footnote: "Whole trees were sacrificed for the most insignificant purposes; the peasants would cut down two firs to make a single pair of wooden shoes."--Michelet, as quoted by Clave. Etudes, p. 24. A similar wastefulness formerly prevailed in Russia, though not from the same cause. In St. Pierre's time, the planks brought to St. Petersburg were not sawn, but hewn with the axe, and a tree furnished but a single plank.] Various absurd theories, some of which are not even yet exploded, were propagated with regard to the economical advantages of converting the forest into pasture and plough-land, the injurious effects of the woods upon climate, health, facility of internal communication, and the like. Thus resentful memory of the wrongs associated with the forest, popular ignorance, and the cupidity of speculators cunning enough to turn these circumstances to profitable account, combined to hasten the sacrifice of the remaining woods, and a waste was produced which hundreds of years and millions of treasure will hardly repair. In the era of savage anarchy which followed the beneficent reforms of 1789, economical science was neglected, and statistical details upon the amount of the destruction of woods during that period are wanting. But it is known to have been almost incalculably rapid, and the climatic and financial evils, which elsewhere have been a more gradual effect of this cause, began to make themselves felt in France within three or four years after that memorable epoch. [Footnote: See Becquerel, Memoire sur les Forets, in the Mem. de l'Academie des Sciences, c. XXXV., p. 411 et seqq. Similar circumstances produced a like result, though on a far smaller scale, in Italy, at a very recent period. Gallenga says: "The destruction of the majestic timber [between the Vals Sesia and Sessera] dates no farther back than 1848, when, on the first proclamation of the Constitution, the ignorant boor had taken it for granted that all the old social ties would be loosened, and therefore the old forest-laws should be at once set at naught."--Country Life in Piedmont, p. 136.] Increased Demand for Lumber. With increasing population and the development of new industries, come new drains upon the forest from the many arts for which wood is the material. The demands of the near and the distant market for this product excite the cupidity of the hardy forester, and a few years of that wild industry of which Springer's "Forest Life and Forest Trees" so vividly depicts the dangers and the triumphs, suffice to rob the most inaccessible glens of their fairest ornaments. The value of timber increases with its dimensions in almost geometrical proportion, and the tallest, most vigorous, and most symmetrical trees fall the first sacrifice. This is a fortunate circuinritiinco for the remainder of the wood; for the impatient lumberman contents himself with felling a few of the best trees, and then hurries on to take his tithe of still virgin groves. The vast extension of railroads, of manufactures and the mechanical arts, of military armaments, and especially of the commercial fleets and navies of Christendom, within the present century, has incredibly augmented the demand for wood, [Footnote: Let us take the supply of timber for railroad-ties. According to Clave (p. 248), France had, in 1862, 9,000 kilometres of railway in operation, 7,000 in construction, half of which is built with a double track. Adding turn-outs and extra tracks at stations, the number of ties required for a single track is stated at 1,200 to the kilometre, or, as Clave computes, for the entire network of France, 58,000,000. This number is too large, for 16,000 + 8,000 for the double track halfway = 24,000, and 24,000 x 1,200 = 28,800,000. In an article in the Revue des Deux Mondes, July, 1863, Gandy states that 2,000,000 trees had been felled to furnish the ties for the French railroads, and as the ties must be occasionally renewed, and new railways have been constructed since 1863, we may probably double this number. The United States had in operation on the first of January, 1872, 61,000 miles, or about 97,000 kilometres, of railroad. Allowing the same proportion as in France, the American railroads required 116,400,000 ties. The Report of the Agricultural Department of the United States for November and December, 1869, estimates the number of ties annually required for our railways at 30,000,000, and supposes that 150,000 acres of the best woodland must be felled to supply this number. This is evidently an error, perhaps a misprint for 15,000. The same authority calculates the annual expenditure of the American railroads for lumber for buildings, repairs, and cars, at $38,000,000, and for locomotive fuel, at the rate of 10,000 cords of wood per day, at $50,000,000. The walnut trees cut in Italy and France to furnish gunstocks to the American army, during our late civil war, would alone have formed a considerable forest. A single establishment in Northern Italy used twenty-eight thousand large walnut trees for that purpose in the years 1862 and 1863. The consumption of wood for lucifer matches is enormous, and I have heard of several instances where tracts of pine forest, hundreds and even thousands of acres in extent, have been purchased and felled, solely to supply timber for this purpose. The United States government tax, at one cent per hundred, produces $2,000,000 per year, which shows a manufacture of 20,000,000,000 matches. Allowing nothing for waste, there are about fifty matches to the cubic inch of wood, or 86,400 to the cubic foot, making in all upwards of 230,000 cubic feet, and, as only straight-grained wood, free from knots, can be used for this purpose, the sacrifice of not less than three or four thousand well-grown pines is required for this purpose. If we add to all this the supply of wood for telegraph-posts, wooden pavements, wooden wall tapestry-paper, shoe-pegs, and even wooden nails, which have lately come into use--not to speak of numerous other recent applications of this material which American ingenuity has devised--we have an amount of consumption, for entirely new purposes, which is really appalling. Wooden field and garden fences are very generally used in America, and some have estimated the consumption of wood for this purpose as not less than that for architectural uses. Fully one-half our vast population is lodged in wooden houses, and barns and country out-houses of all descriptions are almost universally of the same material. The consumption of wood in the United States as fuel for domestic purposes, for charcoal, for brick and lime kilns, for breweries and distilleries, for steamboats, and many other uses, defies computation, and is vastly greater than is employed in Europe for the same ends. For instance, in rural Switzerland, cold as is the winter climate, the whole supply of wood for domestic fires, dairies, breweries, distilleries, brick and lime kilns, fences, furniture, tools, and even house-building and small smitheries, exclusive of the small quantity derived from the trimmings of fruit-trees, grape-vines, and hedges, and from decayed fences and buildings, does not exceed TWO HUNDRED AND THIRTY CUBIC FEET, or less than two cords a year, per household.--See Bericht uber die Untersuchung der Schweiz Hochgebirgswaldungen, pp. 85-89. In 1789, Arthur Young estimated the annual consumption of firewood by single families in France at from two and a half to ten Paris cords of 134 cubic feet.--Travels, vol. ii., chap. xv. The report of the Commissioners on the Forests of Wisconsin, 1867, allows three cords of wood to each person for household fires alone. Taking families at an average of five persons, we have eight times the amount consumed by an equal number of persons in Switzerland for this and all other purposes to which this material in ordinarily applicable. I do not think the consumption in the North-eastern States is at all less than the calculation for Wisconsin. Evergreen trees are often destroyed in immense numbers in the United States for the purpose of decoration of churches and on other festive occasions. The New York city papers reported that 113,000 young evergreen trees, besides 20,000 yards of small branches twirled into festoons, were sold in the markets of that city, for this use, at Christmas, in 1869. At the Cincinnati Industrial Exhibition of 1873, three miles of evergreen festoons were hung upon the beams and rafters of the "Floral Hall." Important statistics on the consumption and supply of wood in the United States will be found in a valuable paper by the Rev. Frederick Starr, Jr., in the Transactions of the Agricultural Society for--. Of course, there is a vast consumption of ligneous material for all these uses in Europe, but it is greatly less than at earlier periods. The waste of wood in European carpentry was formerly enormous, the beams of houses being both larger and more numerous than permanence or stability required. In examining the construction of the houses occupied by the eighty families which inhabit the village of Faucigny, in Savoy, in 1854, the forest inspector found that FIFTY THOUSAND trees had been employed in building them. The builders "seemed," says Hudry-Menos, "to have tried to solve the problem of piling upon the walls the largest quantity of timber possible without crushing them."--Revue des Deux Mondes, 1st June, 1864, p. 601. European statistics present comparatively few facts on this subject, of special interest to American readers, but it is worth noting that France employs 1,500,000 cubic feet of oak per year for brandy and wine casks, which is about half her annual consumption of that material; and it is not a wholly insignificant fact that, according to Rentzach, the quantity of wood used in parts of Germany for small carvings and for children's toys is so largs, that the export of such objects from the town of Sonneberg alone, amounted, in 1853, to 60,000 centner, or three thousand tons' weight.--Der Wald, p. 68. In an article in the Revue des Eaux et Forets for November, 1868, it is stated that 200,000 dozens of drums for boys aro manufactured per month in Paris. This is equivalent to 28,800,000 per year, for which 56,000,000 drumsticks are required, and the writer supposes that the annual growth of 50,000 acres of woodland would not more than supply the material. In the same article the consumption of matches in France is given at 7,200,000,000, and the quantity of lumber annually required for this manufacture is computed at 80,000 steres, or cubic metres--evidently an erroneous calculation.] and but for improvements in metallurgy and the working of iron, which have facilitated the substitution of that metal for wood, the last twenty-five years would have almost stripped Europe of her last remaining tree fit for these uses. [Footnote: Besides the substitution of iron for wood, a great saving of consumption of this latter material has been effected by the revival of ancient methods of increasing its durability, and the invention of new processes for the same purpose. The most effectual preservative yet discovered for wood employed on land, is sulphate of copper, a solution of which is introduced into the pores of the wood while green, by soaking, by forcing-pumps, or, most economically, by the simple pressure of a column of the fluid in a small pipe connected with the end of the piece of timber subjected to the treatment. Clave (Etudes Forestieres, pp. 240-249) gives an interesting account of the various processes employed for rendering wood imperishable, and states that railroad-ties injected with sulphate of copper in 1846, were found absolutely unaltered in 1855; and telegraphic posts prepared two years earlier, are now in a state of perfect preservation. For many purposes, the method of injection is too expensive, and some simpler process is much to be desired. The question of the proper time of felling timber is not settled, and the best modes of air, water, and steam seasoning are not yet fully ascertained. Experiments on these subjects would be well worth the patronage of Governments in new countries, where they can be very easily made, without the necessity of much waste of valuable material, and without expensive arrangements for observation. The practice of stripping living trees of their bark some years before they are felled, is as old as the time of Vitruvius, but is much less followed than it deserves, partly because the timber of trees so treated inclines to crack and split, and partly because it becomes so hard as to be wrought with considerable difficulty. In America, economy in the consumption of fuel has been much promoted by the substitution of coal for wood, the general use of stoves both for wood and coal, and recently by the employment of anthracite in the furnaces of stationary and locomotive steam-engines. All the objections to the use of anthracite for this latter purpose appear to have been overcome, and the improvements in its combustion have been attended with a great pecuniary saving, and with much advantage to the preservation of the woods. The employment of coal has produced a great reduction in the consumption of firewood in Paris. In 1815, the supply of firewood for the city required 1,200,000 steres, or cubic metres; in 1859 it had fallen to 501,805, while, in the meantime, the consumption of coal had risen from 600,000 to 4,320,000 metrical quintals. See Clave, Etudes, p. 212. In 1869 Paris consumed 951,157 steres of firewood, 4,902,414 hectolitres, or more than 13,000,000 bushels, of charcoal, and 6,872,000 metrical quintals, or more than 7,000,000 tons of mineral coal.--Annuaire de la Revue des Eaux et Forets for 1872, p. 26. The increase in the price of firewood at Paris, within a century, has been comparatively small, while that of timber and of sawed lumber has increased enormously.] I have spoken of the foreign demand for American agricultural products as having occasioned an extension of cultivated ground, which had led to clearing land not required by the necessities of home consumption. But the forest itself has become, so to speak, an article of exportation. England, as we have seen, imported oak and pine from the Baltic ports more than six hundred years ago. She has since drawn largely on the forests of Norway, and for many years has received vast quantities of lumber from her American possessions. The unparalleled facilities for internal navigation, afforded by the numerous rivers of the present and former British colonial possessions in North America, have proved very fatal to the forests of that continent. Quebec became many years ago a centre for a lumber trade, which, in the bulk of its material, and, consequently, in the tonnage required for its transportation, rivalled the commerce of the greatest European cities. Immense rafts were collected at Quebec from the great Lakes, from the Ottawa, and from all the other tributaries which unite to swell the current of the St. Lawrence and help it to struggle against its mighty tides. [Footnote: The tide rises at Quebec to the height of twenty-five feet, and when it is aided by a north-east wind, it flows with almost irresistible violence. Rafts containing several hundred thousand cubic feet of timber are often caught by the flood-tide, torn to pieces, and dispersed for miles along the shores.] Ships, of burden formerly undreamed of, have been built to convey the timber to the markets of Europe, and during the summer months the St. Lawrence is almost as crowded with shipping as the Thames. [Footnote: One of these, the Baron of Renfrew--so named from one of the titles of the kings of England--built forty or fifty years ago, measured 5,000 tons. They were little else than rafts, being almost solid masses of timber designed to be taken to pieces and sold as lumber on arriving at their port of destination. The lumber trade at Quebec is still very large. According to an article in the Revue des Deux Mondes, that city exported, in 1860, 30,000,000 cubic feet of squared timber, and 400,000,000 square feet of "planches." The thickness of the boards is not stated, but I believe they are generally cut an inch and a quarter thick for the Quebec trade, and as they shrink somewhat in drying, we may estimate ten square for one cubic foot of boards. This gives a total of 70,000,000 cubic feet. The specific gravity of white pine is .554, and the weight of this quantity of lumber, very little of which is thoroughly seasoned, would exceed a million of tons, even supposing it to consist wholly of wood as light as pine. The London Times of Oct. 10, 1871, states the exportation of lumber from Canada to Europe, in 1870, at 200,000,000 cubic feet, and adds that more than three times that quantity was sent from the same province to the United States. A very large proportion of this latter quantity goes to Burlington, Vermont, whence it is distributed to other parts of the Union. There must, I think, be some error or exaggeration in these figures. Perhaps instead of cubic feet we should read square feet. Two hundred millions of cubic feet of timber would require more than half the entire tonnage of England for its transportation. I suppose the quantities in the following estimates, from a carefully prepared article in the St. Louis Republican, must be understood as meaning square or superficial feet, board measure, allowing a thickness of one inch: "The lumber trade of Michigan, Wisconsin, and Minnesota, for the year 1869, shows the amount cut as being 2,029,372,255 feet for the State of Michigan, and 317,400,000 feet for the State of Minnesota, and 964,600,000 feet for the State of Wisconsin. This includes the lake shore and the whole State of Wisconsin, which heretofore has been difficult to get a report from. The total amount cut in these States was 3,311,372,255 feet, and that to obtain this quantity there have been shipped 883,032 acres, or 1,380 square miles of pine have been removed. It is calculated that 4,000,000 acres of land still remain unstripped in Michigan, which will yield 15,000,000,000 feet of lumber; while 3,000,000 acres arc still standing in Wisconsin, which will yield 11,250,000,000 feet, and that which remains in Minnesota, taking the estimate of a few years since of that which was surveyed and unexplored, after deducting the amount cut the past few years, we find 3,630,000 acres to be the proper estimate of trees now standing which will yield 32,362,500,000 feet of lumber. This makes a total of 15,630,000 acres of pine lands, which remain standing in the above States, that will yield 58,612,500,000 feet of lumber, and it is thought that fifteen or twenty years will be required to cut and send to market the trees now standing." See also Bryant, Forest Trees, chap. iv.] Effects of Forest Fires. The operations of the lumberman involve other dangers to the woods besides the loss of the trees felled by him. The narrow clearings around his shanties form openings which let in the wind, and thus sometimes occasion the overthrow of thousands of trees, the fall of which dams up small streams, and creates bogs by the spreading of the waters, while the decaying trunks facilitate the multiplication of the insects which breed in dead wood and are, some of them, injurious to living trees. The escape and spread of camp-fires, however, is the most devastating of all the causes of destruction that find their origin in the operations of the lumberman. The proportion of trees fit for industrial uses is small in all primitive woods. Only these fall before the forester's axe, but the fire destroys, almost indiscriminately, every age and every species of tree. [Footnote: Trees differ in their power of resisting the action of forest fires. Different woods vary greatly in combustibility, and even when the bark is scarcely scorched, trees are, partly in consequence of physiological character, and partly from the greater or less depth at which their roots habitually lie below the surface, differently affected by running fires. The white pine, Pinus strobus, as it is the most valuable, is also perhaps the most delicate tree of the American forest, while its congener, the Northern pitch-pine, Pinus rigida, is less injured by fire than any other tree of that country. I have heard experienced lumbermen maintain that the growth of this pine was even accelerated by a fire brisk enough to destroy all other trees, and I have myself seen it still flourishing after a conflagration which had left not a green leaf but its own in the wood, and actually throwing out fresh foliage, when the old had been quite burnt off and the bark almost converted into charcoal. The wood of the pitch-pine is of comparatively little value for the joiner, but it is useful for very many purposes. Its rapidity of growth in even poor soils, its hardihood, and its abundant yield of resinous products, entitle it to much more consideration, as a plantation tree, than it has hitherto received in Europe or America.] While, then, without fatal injury to the younger growths, the native forest will bear several "cuttings over" in a generation--for the increasing value of lumber brings into use, every four or five years, a quality of timber which had been before rejected as unmarketable--a fire may render the declivity of a mountain unproductive for a century. [Footnote: Between sixty and seventy years ago, a steep mountain with which I am familiar, composed of metamorphic rock, and at that time covered with a thick coating of soil and a dense primeval forest, was accidentally burnt over. The fire took place in a very dry season, the slope of the mountain was too rapid to retain much water, and the conflagration was of an extraordinarily fierce character, consuming the wood almost entirely, burning the leaves and combustible portion of the mould, and in the many places cracking and disintegrating the rock beneath. The rains of the following autumn carried off much of the remaining soil, and the mountain-side was nearly bare of wood for two or three years afterwards. At length a new crop of trees sprang up and grew vigorously, and the mountain is now thickly covered again. But the depth of mould and earth is too small to allow the trees to reach maturity. When they attain to the diameter of about six inches, they uniformly die, and this they will no doubt continue to do until the decay of leaves and wood on the surface, and the decomposition of the subjacent rock, shall have formed, perhaps hundreds of years hence, a stratum of soil thick enough to support a full-grown forest. Under favorable conditions, however, as in the case of the fire of Miramichi, a burnt forest renews itself rapidly and permanently.] Aside from the destruction of the trees and the laying bare of the soil, and consequently the freer admission of sun, rain, and air to the ground, the fire of itself exerts an important influence on its texture and condition. It cracks and sometimes even pulverizes the rocks and stones upon and near the surface; [Footnote: In the burning over of a hill-forest in the Lower Engadine, in September, 1865, the fire was intense as to shatter and calcine the rocks on the slope, and their fragments were precipitated into the valley below.--Ricista Firrestate del Regna d'Italia, Ottobro, 1865, 1865, p. 474.] it consumes a portion of the half-decayed vegetable mould which served to hold its mineral particles together and to retain the water of precipitation, and thus loosens, pulverizes, and dries the earth; it destroys reptiles, insects, and worms, with their eggs, and the seeds of trees and of smaller plants; it supplies, in the ashes which it deposits on the surface, important elements for the growth of a new forest clothing, as well as of the usual objects of agricultural industry; and by the changes thus produced, it fits the ground for the reception of a vegetation different in character from that which had spontaneously covered it. These new conditions help to explain the natural succession of forest crops, so generally observed in all woods cleared by fire and then abandoned. There is no doubt, however, that other influences contribute to the same result, because effects more or less analogous follow when the trees are destroyed by other causes, as by high winds, by the woodman's axe, and even by natural decay. [Footnote: The remarkable mounds and other earthworks constructed in the valley of the Ohio and elsewhere in the territory of the United States, by a people apparently more advanced in the culture than the modern Indian, were overgrown with a dense clothing of forest when first discovered by the whites. But though the ground where they were erected must have been occupied by a large population for a considerable leagth of time, and therefore entirely cleared, the trees which grew upon the ancient fortresses and the adjacent lands were not distinguishable in species, or even in dimensions and character of growth, from the neighboring forests, where the soil seemed never to have been disturbed. This apparent exception to the law of change of crop in natured forest growth was ingeniously explained by General Harrison's suggestion, that the lapse of time since the era of the mound-builders was so great as to have embraced several successive generations of trees, and occasioned, by their rotation, a return to the original vegetation. The succesive changes in the spontaneous growth of the forest, as proved by the character of the wood found in bogs, are such as to have suggested the theory of a considerable change of climate during the human period. But strobus, as it is the most valuable, is also perhaps the most delicate tree of the American forest, while its congener, the Northern pitch-pine, Pinus rigida, is less injured by fire than any other tree of that country. I have heard experienced lumbermen maintain that the growth of this pine was even accelerated by a fire brisk enough to destroy all other trees, and I have myself seen it still flourishing after a conflagration which had left not a green leaf but its own in the wood, and actually throwing out fresh foliage, when the old had been quite burnt off and the bark almost converted into charcoal. The wood of the pitch-pine is of comparatively little value for the joiner, but it is useful for very many purposes. Its rapidity of growth in even poor soils, its hardihood, and its abundant yield of resinous products, entitle it to much more consideration, as a plantation tree, than it has hitherto received in Europe or America.] without fatal injury to the younger growths, the native forest will hear several "cuttings over" in a generation--for the increasing value of lumber brings into use, every four or five years, a quality of timber which had been before rejected as unmarketable--a fire may render the declivity of a mountain unproductive for a century. [Footnote: Between sixty and seventy years ago, a steep mountain with which I am familiar, composed of metamorphic rock, and at that time covered with a thick coating of soil and a dense primeval forest, was accidentally burnt over. The fire took place in a very dry season, the slope of the mountain was too rapid to retain much water, and the conflagration was of an extraordinarily fierce character, consuming the wood almost entirely, burning the leaves and combustible portion of the mould, and in many places cracking and disintegrating the rock beneath. The rains of the following autumn carried off much of the remaining soil, and the mountain-side was nearly bare of wood for two or three years afterwards. At length a new crop of trees sprang up and grew vigorously, and the mountain is now thickly covered again. But the depth of mould and earth is too small to allow the trees to reach maturity. When they attain to the diameter of about six inches, they uniformly die, and this they will no doubt continue to do until the decay of leaves and wood on the surface, and the decomposition of the subjacent rock, shall have formed, perhaps hundreds of years hence, a stratum of soil thick enough to support a full-grown forest. Under favorable conditions, however, as in the case of the fire of Miramichi, a burnt forest renews itself rapidly and permanently.] Aside from the destruction of the trees and the laying bare of the soil, and consequently the freer admission of sun, rain, and air to the ground, the fire of itself exerts an important influence on its texture and condition. It cracks and sometimes even pulverizes the rocks and stones upon and near the surface; [Footnote: In the burning over of a hill-forest in the Lower Engadine, in September, 1865, the fire was so intense as to shatter and calcine the rocks on the slope, and their fragments were precipitated into the valley below.--Rivista Forestale del Regno d'Italia, Ottobre, 1865, p. 474.] it consumes a portion of the half-decayed vegetable mould which served to hold its mineral particles together and to retain the water of precipitation, and thus loosens, pulverizes, and dries the earth; it destroys reptiles, insects, and worms, with their eggs, and the seeds of trees and of smaller plants; it supplies, in the ashes which it deposits on the surface, important elements for the growth of a new forest clothing, as well as of the usual objects of agricultural industry; and by the changes thus produced, it fits the ground for the reception of a vegetation different in character from that which had spontaneously covered it. These new conditions help to explain the natural succession of forest crops, so generally observed in all woods cleared by fire and then abandoned. There is no doubt, however, that other influences contribute to the same result, because effects more or less analogous follow when the trees are destroyed by other causes, as by high winds, by the woodman's axe, and even by natural decay. [Footnote: The remarkable mounds and other earthworks constructed in the valley of the Ohio and elsewhere in the territory of the United States, by a people apparently more advanced in culture than the modern Indian, were overgrown with a dense clothing of forest when first discovered by the whites. But though the ground where they were erected must have been occupied by a large population for a considerable length of time, and therefore entirely cleared, the trees which grew upon the ancient fortresses and the adjacent lands were not distinguishable in species, or even in dimensions and character of growth, from the neighboring forests, where the soil seemed never to have been disturbed. This apparent exception to the law of change of crop in natural forest growth was ingeniously explained by General Harrison's suggestion, that the lapse of time since the era of the mound-builders were so great as to have embraced several successive generations of trees, and occasioned, by their rotation, a return to the original vegetation. The successive changes in the spontaneous growth of the forest, as proved by the character of a wood found in bogs, are such as to have suggested the theory of a considerable change of the climate during the human period. But this theory cannot be admitted upon the evidence in question. In fact, the order of succession--for a rotation or alternation is neither proved nor probable--may be made to move in opposite directions in different countries with the same climate and at the same time. Thus in Denmark and in Holland the spike-leaved firs have given place to the broad-leaved beech, while in Northern Germany the process has been reversed, and evergreens have supplanted the oaks and birches of deciduous foliage. The principal determining cause seems to be the influence of light upon the germination of the seeds and the growth of the young tree. In a forest of firs, for instance, the distribution of the light and shade, to the influence of which seeds and shoots are exposed, is by no means the same as in a wood of beeches or of oaks, and hence the growth of different species will be stimulated in the two forests. When ground is laid bare both of trees and of vegetable mould, and left to the action of unaided and unobstructed nature, she first propagates trees which germinate and grow only under the influence of a full supply of light and air, and then, in succession, other species, according to their ability to bear the shade and their demand for more abundant nutriment. In Northern Europe the large, the white birch, the aspen, first appear; then follow the maple, the alder, the ash, the fir; then the oak and the linden; and then the beech. The trees called by these respective names in the United States are not specifically the same as their European namesakes, nor are they always even the equivalents of these latter, and therefore the order of succession in America would not be precisely as indicated by the foregoing list, but, so far as is known, it nevertheless very nearly corresponds to it. It is thought important to encourage the growth of the beech in Denmark and Northern Germany, because it upon the whole yields better returns than other trees, and does not exhaust, but on the contrary enriches, the soil; for by shedding its leaves it returns to it most of the nutriment it has drawn from it, and at the same time furnishes a solvent which aids materially in the decomposition of its mineral constituents. When the forest is left to itself, the order of succession is constant, and its occasional inversion is always explicable by some human interference. It is curious that the trees which require most light are content with the poorest soils, and vice versa. The trees which first appear are also those which propagate themselves farthest to the north. The birch, the larch, and the fir bear a severer climate than the oak, the oak than the beech. "These parallelisms," says Vaupell, "are very interesting, because, though they are entirely independent of each other," they all prescribe the same order of succession.--Bogens Indvandring, p. 42. See alo Berg, Das Verdrangen der Laubralder im Nordlichen Deutschland, 1844. Heyer, Das Verhalten der Waldbaume gegen Licht und Schatten, 1852. Staring, De Bodem van Nederland, 1856, i., pp. 120-200. Vaupell, De Danske Skove, 1863. Knorr, Studien uber die Buchen-Wirthschaft, 1863. A. Maury, Les Forets de la Gaule, pp. 73, 74, 377, 384.] Another evil, sometimes of serious magnitude, which attends the operations of the lumberman, is the injury to the banks of rivers from the practice of floating. I do not here allude to rafts, which, being under the control of those who navigate them, may be so guided as to avoid damage to the shore, but to masts, logs, and other pieces of timber singly entrusted to the streams, to be conveyed by their currents to sawmill ponds, or to convenient places for collecting them into rafts. The lumbermen usually haul the timber to the banks of the rivers in the winter, and when the spring floods swell the streams and break up the ice, they roll the logs into the water, leaving them to float down to their destination. If the transporting stream is too small to furnish a sufficient channel for this rude navigation, it is sometimes dammed up, and the timber collected in the pond thus formed above the dam. When the pond is full, a sluice is opened, or the dam is blown up or otherwise suddenly broken, and the whole mass of lumber above it is hurried down with the rolling flood. Both of these modes of proceeding expose the banks of the rivers employed as channels of flotation to abrasion, [Footnote: Caimi states that "a single flotation in the Valtelline, in 1830, caused damages appraised at $250,000."--Cenni sulla Importanza e Coltura dei Boschi, p. 65.] and in some of the American States it has been found necessary to protect, by special legislation, the lands through which they flow from the serious injury sometimes received through the practices I have described. [Footnote: Many physicists who have investigated the laws of natural hydraulics maintain that, in consequence of direct obstruction and frictional resistance to the flow of the water of rivers along their banks, there is both an increased rapidity of current and an elevation of the water in the middle of the channel, so that a river presents always a convex surface. Others have thought that the acknowledged greater swiftness of the central current must produce a depression in that part of the stream. The lumbermen affirm that, while rivers are rising, the water is highest in the middle of the channel, and tends to throw floating objects shorewards; while they are falling, it is lowest in the middle, and floating objects incline towards the centre. Logs, they say, rolled into the water during the rise, are very apt to lodge on the banks, while those set afloat during the falling of the waters keep in the current, and are carried without hindrance to their destination, and this law, which has been a matter of familiar observation among woodmen for generations, is now admitted as a scientific truth. Foresters and lumbermen, like sailors and other persons whose daily occupations bring them into contact, and often into conflict, with great natural forces, have many peculiar opinions, not to say superstitious. In one of these categories we must rank the universal belief of lumbermen, that with a given head of water, and in a given number of hours, a sawmill cuts more lumber by night than by day. Having been personally interested in several sawmills, been assured by them that their uniform experiences established the fact that, other things being equal, the action of the machinery of sawmills is more rapid by night than by day. I am sorry--perhaps I ought to be ashamed--to say that my skepticism has been too strong to allow me to avail myself of my ooportunites of testing this question by passing a night, watch in hand, counting the strokes of a millisaw. More unprejudiced, and, I must add, very intelligent and credible persons have informed me that they have done so, and found the report of the sawyers abundantly confirmed. A land surveyor, who was also an experienced lumberman, sawyer, and machinist, a good mathematician, and an accurate observer, has repeatedly told me that he had very often "timed" sawmills, and before the difference in favor of night-work above thirty per cent. Sed quaere.] Restoration of the Forest. In most countries of Europe--and I fear in many parts of the United States--the woods are already so nearly extirpated, that the mere protection of those which now exist is by no means an adequate security against a great increase of the evils which have already resulted from the diminution of them. Besides this, experience has shown that where the destruction of the woods has been carried beyond a certain point, no coercive legislation can absolutely secure the permanence of the remainder, especially if it is held by private hands. The creation of new forests, therefore, is generally recognized, wherever the subject has received the attention it merits, as an indispensable measure of sound public economy. Enlightened individuals in some European states, the Governments in others, have made extensive plantations, and France, particularly, has now set herself energetically at work to restore the woods in her southern provinces, and thereby to prevent the utter depopulation and waste with which that once fertile soil and genial climate are threatened. The objects of the restoration of the forest are as multifarious as the motives that have led to its destruction, and as the evils which that destruction has occasioned. It is hoped that the replanting of the mountain slopes, and of bleak and infertile plains, will diminish the frequency and violence of river inundations, prevent the formation of new torrents and check the violence of those already existing, mitigate the extremes of atmospheric temperature, humidity, and precipitation, restore dried-up springs, rivulets, and sources of irrigation, shelter the fields from chilling and from parching winds, arrest the spread of miasmatic effluvia, and, finally, furnish a self-renewing and inexhaustible supply of a material indispensable to so many purposes of domestic comfort, and to the successful exercise of every art of peace, every destructive energy of war. [Footnote: The preservation of the woods on the former eastern frontier of France, as a kind of natural abattis, was recognized by the Government of that country as an important measure of military defence, though there have been conflicting opinions on the subject.] The Economy of the Forest. The legislation of European states upon sylviculture, and the practice of that art, divide themselves into two great branches--the preservation of existing forests, and the creation of new. Although there are in Europe many forests neither planted nor regularly trained by man, yet from the long operation of causes already set forth, what is understood in America and other new countries by the "primitive forest," no longer exists in the territories which were the seats of ancient civilization and empire, except upon a small scale, and in remote and almost inaccessible glens quite out of the reach of ordinary observation. The oldest European woods are indeed native, that is, sprung from self-sown seed, or from the roots of trees which have been felled for human purposes; but their growth has been controlled, in a variety of ways, by man and by domestic animals, and they almost uniformly present more or less of an artificial character and arrangement. Both they and planted forests--which, though certainly not few, are of comparatively recent date in Europe--demand, as well for protection as for promotion of growth, a treatment different in some respects from that which would be suited to the character and wants of the virgin wood. On this latter branch of the subject, the management of the primitive wood, experience and observation have not yet collected a sufficient stock of facts to serve for the construction of a complete system of this department of sylviculture; but the government of the forest as it exists in France--the different zones and climates of which country present many points of analogy with those of the United States and of some of the British colonies--has been carefully studied, and several manuals of practice have been prepared for the foresters of that empire. I believe the Cours Elementaire de Culture des Bois cree a l'Ecole Forestiere de Nancy, par M. Lorentz, complete et public par A. Parade, with a supplement under the title of Cours d'Amenagement des Forets, par Henri Nanquette, has been generally considered the best of these. The Etudes sur l'Economie Forestiere, par Jules Clave, which I have often quoted, presents a great number of interesting views on this subject, but it is not designed as a practical guide, and it does not profess to be sufficiently specific in its details to serve that purpose. [Footnote: Among more recent manuals may be mentioned: in French, Les Etudes de Maitre Pierre, Paris, 1864, 12mo; Bazelaire, Traite de Roboisement, 2d edition. Paris 1864; Paston, L'Amenagemend des Forets, Paris, 1867; in English, Gregor, Arboriculture, Edinburgh, 1868: in Italian, Siemoni 's very valuable Manuale teorico-pratico d'Arte Forestale, 2d ediz., Firenze, 1872; the excellent work of Cerini, Dei Vantaggi di Societe, por l'Impianto e Conservazione dei Boschi, Milano, 1844, 8vo; and the prize essay of Meguscher, Memoria sui Boschi, etc., 2d edizione, Milano, 1859, 8vo. Another very important treatise of the uses of the forest, though not a manual of sylviculture, is Schleiden, Fur Baum und Wald, Leipzig, 1870.]Notwithstanding the difference of conditions between the aboriginal and the trained forest, the judicious observer who aims at the preservation of the former will reap much instruction from the treatises I have cited, and I believe he will be convinced that the sooner a natural wood is brought into the state of an artificially regulated one, the better it is for all the multiplied interests which depend on the wise administration of this branch of public economy. One consideration bearing on this subject has received less attention than it merits, because most persons interested in such questions have not opportunities for the comparison I refer to. I mean the great general superiority of cultivated timber to that of strictly spontaneous growth. I say GENERAL superiority, because there are exceptions to the rule. The white pine, Pinus strobus, for instance, and other trees of similar character and uses, require, for their perfect growth and best ligneous texture, a density of forest vegetation around them, which protects them from too much agitation by wind, and from the persistence of the lateral branches which fill the wood with knots. A pine which has grown under those conditions possesses a tall, straight stem, admirably fitted for masts and spars, and, at the same time, its wood is almost wholly free from knots, is regular in annular structure, soft and uniform in texture, and, consequently, superior to almost all other timber for joinery. If, while a large pine is spared, the broad-leaved or other smaller trees around it are felled, the swaying of the tree from the action of the wind mechanically produces separations between the layers of annual growth, and greatly diminishes the value of the timber. The same defect is often observed in pines which, from some accident of growth, have much overtopped their fellows in the virgin forest. The white pine, growing in the fields, or in open glades in the woods, is totally different from the true forest-tree, both in general aspect and in quality of wood. Its stem is much shorter, its top less tapering, its foliage denser and more inclined to gather into tufts, its branches more numerous and of larger diameter, its wood shows much more distinctly the divisions of annual growth, is of coarser grain, harder and more difficult to work into mitre-joints. Intermixed with the most valuable pines in the American forests, are met many trees of the character I have just described. The lumbermen call them "saplings," and generally regard them as different in species from the true white pine, but botanists are unable to establish a distinction between them, and as they agree in almost all respects with trees grown in the open grounds from known white-pine seedlings, I believe their peculiar character is due to unfavorable circumstances in their early growth. The pine, then, is an exception to the general rule as to the inferiority of the forest to the open-ground tree. The pasture oak and pasture beech, on the contrary, are well known to produce far better timber than those grown in the woods, and there are few trees to which the remark is not equally applicable. [Footnote: It is often laid down as a universal law, that the wood of trees of slow vegetation is superior to that of quick growth. This is one of those commonplaces by which men love to shield themselves from the labor of painstaking observation. It has, in fact, so many exceptions, that it may be doubted in whether it is in any sense true. Most of the cedars are slow of growth; but while the timber of some of them is firm and durable, that of others is light, brittle, and perishable. The hemlock-spruce is slower of growth than the pines, but its wood is of very little value. The pasture oak and beech show a breadth of grain--and, of course, an annual increment--twice as great as trees of the same species grown in the woods; and the American locust, Robinia pseudacacia, the wood of which is of extreme toughness and durability, is, of all trees indigenous to North-eastern America, by far the most rapid in growth. Some of the species of the Australian Eucalyptus furnish wood of remarkable strength and durability, and yet the eucalyptus is surpassed by no known tree in rapidity of growth. As an illustration of the mutual interdependence of the mechanic arts, I may mention that in Italy, where stone, brick, and plaster are almost the only materials used in architecture, and where the "hollow ware" kitchen implements are of copper or of clay, the ordinary tools for working wood are of a very inferior description, and the locust timber is found too hard for their temper. At the same time the work of the Italian stipettai, or cabinet-makers, and carvers in wood, who take pains to provide themselves with tools of better metal, is wholly unsurpassed in finish and in accuracy of adjustment as well as in taste. When a small quantity of mahogany was brought to England, early in the last century, the cabinet-makers were unable to use it, from the defective temper of their tools, until the demand for furniture from the new wood compelled them to improve the quality of their implements. In America, the cheapness of wood long made it the preferable material for almost all purposes to which it could by any possibility be applied. The mechanical cutlery and artisans' tools of the United States are of admirable temper, finish, and convenience, and no wood is too hard, or otherwise too refractory, to be wrought with great facility, both by hand-tools and by the multitude of ingenious machines which the Americans have invented for this purpose.] Another advantage of the artificially regulated forest is, that it admits of such grading of the ground as to favor the retention or discharge of water at will, while the facilities it affords for selecting and duly proportioning, as well as properly spacing, and in felling and removing, from time to time, the trees which compose it, are too obvious to require to be more than hinted at. In conducting these operations, we must have a diligent eye to the requirements of nature, and must remember that a wood is not an arbitrary assemblage of trees to be selected and disposed according to the caprice of its owner. "A forest," says Clave, "is not, as is often supposed, a simple collection of trees succeeding each other in long perspective, without bond of union, and capable of isolation from each other; it is, on the contrary, a whole, the different parts of which are interdependent upon each other, and it constitutes, so to speak, a true individuality. Every forest has a special character, determined by the form of the surface it grows upon, the kinds of trees that compose it, and the manner in which they are grouped." The art, or, as the Continental foresters rather ambitiously call it, the science of sylviculture has been so little pursued in England and America, that its nomenclature has not been introduced into the English vocabulary, and it would not be possible to describe its processes with technical propriety of language, without occasionally borrowing a word from the forest literature of France and Germany. A full discussion of the methods of sylviculture would, indeed, be out of place in a work like the present, but the want of conveniently accessible means of information on the subject, in the United States, will justify me in presenting it with somewhat more of detail than would otherwise be pertinent. The two best known methods of treating already existing forests are those distinguished as the TAILLIS, copse or coppice treatment, [Footnote: COPSE, or COPPICE, from the French COUPER, to cut, means properly a wood, the trees of which are cut at certain periods of immature growth, and allowed to shoot up again from the roots; but it has come to signify, very commonly, a young wood, grove, or thicket, without reference to its origin, or to the character of a forest crop.] and the FUTAIE, for which I find no English equivalent, but which may not inappropriately be called the FULL-GROWTH system. A TAILLIS, copse, or coppice, is a wood composed of shoots from the roots of trees previously cut for fuel and timber. The shoots are thinned out from time to time, and finally cut, either after a fixed number of years, or after the young trees have attained to certain dimensions, their roots being then left to send out a new progeny as before. This is the cheapest method of management, and therefore the best whenever the price of labor and of capital bears a high proportion to that of land and of timber; but it is essentially a wasteful economy. [Footnote: "In America," says Clave (p. 124, 125), "where there is a vast extent of land almost without pecuniary value, but where labor is dear and the rate of interest high, it is profitable to till a large surface at the least possible cost. EXTENSIVE cultivation is there the most advantageous. In England, France, and Germany, where every corner of soil is occupied, and the least bit of ground is sold at a high price, but where labor and capital are comparatively cheap is wisest to employ INTENSIVE cultivation. ... All the efforts of the cultivator ought to be directed to the obtaining of a given result with the least sacrifice, and there is equally a loss to the commonwealth if the application of improved agricultural processes be neglected where they are advantageous, or if they be employed where they are not required. ... In this point of view, sylviculture must follow the same laws as agriculture, and, like it, be modified according to the economical conditions of different states. In countries abounding in good forests, and thinly peopled, elementary and cheap methods must be pursued; in civilized regions, where a dense population requires that the soil shall be made to produce all it can yield, the regular artificial forest, with all the processes that science teaches, should be cultivated. It would be absurd to apply to the endless woods of Brazil and of Canada the method of the Spessart by "double stages," but not less so in our country, where every yard of ground has a high value, to leave to nature the task of propagating trees, and to content ourselves with cutting, every twenty or twenty-five years, the meagre growths that chance may have produced."] If the woodland is, in the first place, completely cut over as is found most convenient in practice, the young shoots have neither the shade nor the protection from wind so important to forest growth, and their progress is comparatively slow, while at the same time, the thick clumps they form choke the seedlings that may have sprouted near them. [Footnote: In ordinary coppices, there are few or no seedlings, because the young shoots are cut before they are old enough to mature fertile seed, and this is one of the strongest objections to the system.] The evergreens, once cut do not shoot up again, [Footnote: It was not long ago stated, upon the evidence of the Government foresters of Greece, and of the queen's gardener, that a large wood has been discovered in Arcadia, consisting of a fir which has the property of sending up both vertical and lateral shoots from the stump of felled trees and forming a new crown. It was at first supposed that this forest grew only on the "mountains," of which the hero of About's most amusing story, Le Roi des Montagnes, was "king;" but stumps, with the shoots attached, have been sent to Germany, and recognized by able botanists as true natural products, and the fact must now be considered as established. Daubeny refers to Theophrastus as ascribing this faculty of reproduction to the 'Elate [word in greek] or fir, but he does not cite chapter and verse, and I have not been able to find the passage. The same writer mentions a case where an entire forest of the common fir in France had been renewed in this way.--Trees and Shrubs of the Ancients, 1865, pp. 27-28. The American Northern pitch possesses the same power in a certain degree. According to Charles Martins, the cedar of Mount Atlas--which, if not identical with the cedar of Lebanon, is closely allied to it--possesses the same power.--Revue des Deux Mondes, July 15, 1864, p. 315.] and the mixed character of the forest--in many respects an important advantage, if not an indispensable condition of growth--is lost; [Footnote: Natural forests are rarely, if ever, composed of trees of a single species, and experience has shown that oaks and other broad-leaved trees, planted as artificial woods, require to be mixed, or associated with others of different habits. In the forest of Fontainebleau, "oaks, mingled with beeches in due proportion," says Clave, "may arrive at the age of five or six hundred years in full vigor, and attain dimensions which I have never seen surpassed; when, however, they are wholly unmixed with other trees, they begin to decay and die at the top, at the age of forty or fifty years, like men, old before their time, weary of the world, and longing only to quit it. This has been observed in most of the oak plantations of which I have spoken, and they have not been able to attain to full growth. When the vegetation was perceived to languish, they were cut, in the hope that this operation would restore their vigor, and that the new shoots would succeed better than the original trees; and, in fact, they seemed to be recovering for the first few years. But the shoots were soon attacked by the same decay, and the operation had to be renewed at shorter and shorter intervals, until at last it was found necessary to treat as coppices plantations originally designed for the full-growth system. Nor was this all: the soil, periodically bared by these cuttings, became impoverished, and less and less suited to the growth of the oak. ... It was then proposed to introduce the pine and plant with it the vacancies and glades. "... By this means, the forest was saved from the ruin which threatened it, and now more than 10,000 acres of pines, from fifteen to thirty years old are disseminated at various points, sometimes intermixed with broad-leaved trees, sometimes forming groves by themselves"--Revue des Deux Mondes, Mai, 1863, pp. 153, 154.] and besides this, large wood of any species cannot be grown in this method because trees which shoot from decaying stumps and their dying roots, become hollow or otherwise unsound before they acquire their full dimensions. A more fatal objection still, is, that the roots of trees will not bear more than two or three, or at most four cuttings of their shoots before their vitality is exhausted, and the wood can then be restored only by replanting entirely. The period of cutting coppices varies in Europe from fifteen to forty years, according to soil, species, and rapidity of growth. In the futaie, or full-growth system, the trees are allowed to stand as long as they continue in healthy and vigorous growth. This is a shorter period than would be at first supposed, when we consider the advanced age and great dimensions to which, under favorable circumstances, many forest-trees attain in temperate climates. But, as every observing person familiar with the forest is aware, these are exceptional cases, just as are instances of great longevity or of gigantic stature among men. Able vegetable physiologists have maintained that the tree, like most fish and reptiles, has no natural limit of life or of growth, and that the only reason why our oaks and our pines do not reach the age of twenty centuries and the height of a hundred fathoms, is, that in the multitude of accidents to which they are exposed, the chances of their attaining to such a length of years and to such dimensions of growth are millions to one against them. But another explanation of this fact is possible. In trees affected by no discoverable external cause of death, decay begins at the topmost branches, which seem to wither and die for want of nutriment. The mysterious force by which the sap is carried from the roots to the utmost twigs, cannot be conceived to be unlimited in power, and it is probable that it differs in different species, so that while it may suffice to raise the fluid to the height of five hundred feet in the eucalyptus, it may not be able to carry it beyond one hundred and fifty in the oak. The limit may be different, too, in different trees of the same species, not from defective organization in those of inferior growth, but from more or less favorable conditions of soil, nourishment, and exposure. Whenever a tree attains to the limit beyond which its circulating fluids cannot rise, we may suppose that decay begins, and death follows from want of nutrition at the extremities, and from the same causes which bring about the same results in animals of limited size--such, for example, as the interruption of functions essential to life, in consequence of the clogging up of ducts by matter assimilable in the stage of growth, but no longer so when increment has ceased. In the natural woods we observe that, though, among the myriads of trees which grow upon a square mile, there are several vegetable giants, yet the great majority of them begin to decay long before they have attained their maximum of stature, and this seems to be still more emphatically true of the artificial forest. In France, according to Clave, "oaks, in a suitable soil, may stand, without exhibiting any sign of decay, for two or three hundred years; the pines hardly exceed one hundred and twenty, and the soft or white woods [bois blancs], in wet soils, languish, and die before reaching the fiftieth year." [Footnote: Etudes Forestieres, p. 80.] These ages are certainly below the average of those of American forest-trees, and are greatly exceeded in very numerous well-attested instances of isolated trees in Europe. The former mode of treating the futaie, called the garden system, was to cut the trees individually as they arrived at maturity, but, in the best regulated forests, this practice has been abandoned for the German method, which embraces not only the securing of the largest immediate profit, but the replanting of the forest, and the care of the young growth. This is effected in the case of a forest, whether natural or artificial, which is to be subjected to regular management, by three operations. The first of these consists in felling about one-third of the trees, in such way as to leave convenient spaces for the growth of seedlings. The remaining two-thirds are relied upon to replant the vacancies, by natural sowing, which they seldom or never fail to do. The seedlings are watched, are thinned out when too dense, and the ill-formed and sickly, as well as those of species of inferior value, and the shrubs and thorns which might otherwise choke or too closely shade them, are pulled up. When they have attained sufficient strength and development of foliage to require, or at least to bear, more light and air, the second step is taken, by removing a suitable proportion of the old trees which had been spared at the first cutting; and when, finally, the younger trees are hardened enough to bear frost and sun without other protection than that which they mutually give to each other, the remainder of the original forest is felled, and the wood now consists wholly of young and vigorous trees. This result is obtained after about twenty years. At convenient periods, the unhealthy stocks and those injured by wind or other accidents are removed, and in some instances the growth of the remainder is promoted by irrigation or by fertilizing applications. [Footnote: The grounds which it is most important to clothe with wood as a conservative influence, and which, also, can best be spared from agricultural use, are steep hillsides. But the performance of all the offices of the forester to the tree--seeding, planting, thinning, trimming, and finally felling and removing for consumption--is more laborious upon a rapid declivity than on a level soil, and at the same time it is difficult to apply irrigation or manures to trees so situated. Experience has shown that there in great advantage in terracing the face of a hill before planting it, both as preventing the wash of the earth by checking the flow of water down its slope, and as presenting a surface favorable for irrigation, as well as for manuring and cultivating the tree. But even without so expensive a process, very important results have been obtained by simply ditching declivities. "In order to hasten the growth of wood on the flanks of a mountain, Mr. Eugene Chevandier divided the slope into zones forty or fifty feet wide, by horizontal ditches closed at both ends, and thereby obtained, from firs of different ages, shoots double the dimensions of those which grew on a dry soil of the same character, where the water was allowed to run off without obstruction."--Dumont, Des Travaux Publics, etc., pp. 94-96. The ditches were about two feet and a half deep, and three feet and a half wide, and they cost about forty francs the hectare, or three dollars the acre. This extraordinary growth was produced wholly by the retention of the rain-water in the ditches, whence it filtered through the whole soil and supplied moisture to the roots of the trees. It may be doubted whether in a climate cold enough to freeze the entire contents of the ditches in winter, it would not be expedient to draw off the water in the autumn, as the presence of so large a quantity of ice in the soil might prove injurious to trees too young and small to shelter the ground effectually against frost. Chevandier computes that, if the annual growth of the pine in the marshy and too humid soil of the Vosges be represented by one, it will equal two in ordinary dry ground, four or five on slopes so ditched or graded as to retain the water flowing upon them from roads or steep declivities, and six where the earth is kept sufficiently moist by infiltration from running brooks.--Comptes Rendus a l'Academie des Sciences, t. xix., Juillet, Dec., 1844, p. 167. The effect of accidental irrigation in well shown in the growth of the trees planted along the canals of irrigation which traverse the fields in many parts of Italy. They nourish most luxuriantly, in spite of continual lopping, and yield a very important contribution to the stock of fuel for domestic use while trees, situated so far from canals as to be out of the reach of infiltration from them, are of much slower growth, under circumstances otherwise equally favorable. In other experiments of Chevandier, under better conditions, the yield of wood was increased, by judicious irrigation, in the ratio of seven to one, the profits in that of twelve to one. At the Exposition of 1855, Chambrelent exhibited young trees, which, in four years from the seed, had grown to the height of sixteen and twenty feet, and the circumference of ten and twelve inches. Chevandier experimented with various manures, and found that some of them might be profitably applied to young but not to old trees, the quantity required in the latter case being too great. Wood-ashes and the refuse of soda factories are particularly recommended. See, on the manuring of trees, Chevandier, Recherches sur l'emploi de divers amendements, etc., Paris, 1852, and Koderle, Grundsatze der Kunstlichen Dungung im Forstculturwesen. Wien, 1865. I have seen an extraordinary growth produced in fir-trees by the application of soapsuds; in a young and sickly cherry-tree, by heaping the chips and dust from a marble-quarry, to the height of two or three feet, over the roots and around the stem; and cases have come to my knowledge where like results followed the planting of vines and trees in holes half filled with fragments of plaster-castings, and mortar from old buildings. Chevandier's experiments in the irrigation of the forest would not have been a "new thing under the sun" to wise King Solomon, for that monarch saya: "I made me pools of water, to water therewith, the wood that bringeth forth trees." Eccles. ii. 6.] When the forest is approaching maturity, the original processes already described are repeated; and as, in different parts of an extensive forest, they would take place at different times in different zones, it would afford indefinitely an annual crop of small wood, fuel, and timber. The duties of the forester do not end here, for it sometimes happens that the glades left by felling the older trees are not sufficiently seeded, or that the species, or essences, as the French oddly call them, are not duly proportioned in the new crop. In this case, seed must be artificially sown, or young trees planted in the vacancies. Besides this, all trees, whether grown for fruit, for fuel, or for timber, require more or less training in order to yield the best returns. The experiments of the Vicomte de Courval in sylviculture throw much light on this subject, and show, in a most interesting way, the importance of pruning forest-trees. The principal feature of De Courval's very successful method is a systematical mode of trimming which compels the tree to develop the stem, by reducing the lateral ramification. Beginning with young trees, the buds are rubbed off from the stems, and superfluous lateral shoots are pruned down to the trunk. When large trees are taken in hand, branches which can be spared, and whose removal is necessary to obtain a proper length of stem, are very smoothly cut off quite close to the trunk, and the exposed surface is IMMEDIATELY brushed over with mineral-coal tar. When thus treated, it is said that the healing of the wound is perfect, and without any decay of the tree. Trees trained by De Courval's method, which is now universally approved and much practised in France, rapidly attained a great height. They grow with remarkable straightness of stem and of grain, and their timber commands the highest price. [Footnote: See De Courval, Taille et conduite des Arbres forestieres et autres arbres de grande dimension. Paris, 1861. The most important part of Viscount de Courval's system will be found in L'Elagage des Arbres, par le Comte A. Des Cars, an admirable little treatise, of which numerous editions, at the price of one franc, have been printed since the first, of 1864, and which ought to be translated and published without delay in the United States.] A system of plantation, specially though not exclusively suited to very moist soils, recommended by Duhamel a hundred years ago, has been revived in Germany, within about twenty years, with much success. It is called hill-planting, and consists in placing the young tree upright on the greensward with its roots properly spread out, and then covering the roots and supporting the trunk by thick sods cut so as to form a circular hillock around it. [Footnote: See Manteuffel, L'Art de Planter, traduit par Stumper. Paris, 1868.] By this method it is alleged trees can be grown advantageously both in dry ground and on humid soils, where they would not strike root if planted in holes after the usual mauner. If there is any truth in the theory of a desiccating action in evergreen trees, plantations of this sort might have a value as drainers of lands not easily laid dry by other processes. There is much ground on the great prairies of the West, where experiments with this method of planting are strongly to be recommended. It is common in Europe to permit the removal of the fallen leaves and fragments of bark and branches with which the forest-soil is covered, and sometimes the cutting of the lower twigs of evergreens. The leaves and twigs are principally used as litter for cattle, and finally as manure, the bark and wind-fallen branches as fuel. By long usage, sometimes by express grant, this privilege has become a vested right of the population in the neighborhood of many public and even large private forests; but it is generally regarded as a serious evil. To remove the leaves and fallen twigs is to withdraw much of the pabulum upon which the tree was destined to feed. The small branches and leaves are the parts of the tree which yield the largest proportion of ashes on combustion, and of course they supply a great amount of nutriment for the young shoots. "A cubic foot of twigs," says Vaupell, "yields four times as much ashes as a cubic foot of stem wood. ... For every hundred weight of dried leaves carried off from a beech forest, we sacrifice a hundred and sixty cubic feet of wood. The leaves and the mosses are a substitute, not only for manure, but for ploughing. The carbonic acid given out by decaying leaves, when taken up by water, serves to dissolve the mineral constituents of the soil, and is particularly active in disintegrating feldspar and the clay derived from its decomposition. ... The leaves belong to the soil. Without them it cannot preserve its fertility, and cannot furnish nutriment to the beech. The trees languish, produce seed incapable of germination, and the spontaneous self-sowing, which is an indispensable element in the best systems of sylviculture, fails altogether in the bared and impoverished soil." [Footnote: Vaupell, Bogens Indvandring i de Danske Skove, pp. 29, 46. Vaupell further observes, on the page last quoted: "The removal of leaves is injurious to the forest, not only because it retards the growth of trees, but still more because it disqualifies the soil for the production of particular species. When the beech languishes, and the development of its branches is less vigorous and its crown less spreading, it becomes unable to resist the encroachments of the fir. This latter tree thrives in an inferior soil, and being no longer stifled by the thick foliage of the beech, it spreads gradually through the wood, while the beech retreats before it and finally perishes." Schleiden confirms the opinion of Vaupell, and adds many important observations on this subject.--Fur Baum und Wald, pp. 64, 65.] Besides these evils, the removal of the leaves deprives the soil of much of that spongy character which gives it such immense value as a reservoir of moisture and a regulator of the flow of springs; and, finally, it exposes the surface-roots to the drying influence of sun and wind, to accidental mechanical injury from the tread of animals or men, and, in cold climates, to the destructive effects of frost. Protection against Wild Animals. It is often necessary to take measures for the protection of young trees against the rabbit, the mole, and other rodent quadrupeds, and of older ones against the damage done by the larvae of insects hatched upon the surface or in the tissues of the bark, or even in the wood itself. The much greater liability of the artificial than of the natural forest to injury from this cause is perhaps the only point in which the superiority of the former to the latter is not as marked as that of any domesticated vegetable to its wild representative. But the better quality of the wood and the much more rapid growth of the trained and regulated forest are abundant compensations for the loss thus occasioned, and the progress of entomological science will, perhaps, suggest new methods of preventing the ravages of insects. Thus far, however, the collection and destruction ofthe eggs, by simple but expensive means, has proved the most effectual remedy. [Footnote: I have remarked elsewhere that most insects which deposit and hatch their eggs in the wood of the natural forest confine themselves to dead trees. Not only is this the fact, but it is also true that many of the borers attack only freshly-cut timber. Their season of labor is a short one, and unless the tree is cut during this period, it is safe from them. In summer you may hear them plying their augers in the wood of a young pine with soft, green bark, as you sit upon its trunk, within a week after it has been felled, but the windfalls of the winter lie uninjured by the worm and even undecayed for centuries. In the pine woods of New England, after the regular lumberman has removed the standing trees, these old trunks are hauled out from the mosses and leaves which half cover them, and often furnish excellent timber. The slow decay of such timber in the woods, it may be remarked, furnishes another proof of the uniformity of temperature and humidity in the forest, for the trunk of a tree lying on grass or ploughland, and of course exposed to all the alternations of climate, hardly resists complete decomposition for a generation. The forests of Europe exhibit similar facts. Wessely, in a description of the primitive wood of Neuwald in Lower Austria, says that the windfalls required from 150 to 200 years for entire decay.--Die Oesterreichischen Alpenlander und ihre Forste, p. 312. The comparative immunity of the American native forests from attacks by insects is perhaps in some degree due to the fact that the European destructive tribes have not yet found their way across the ocean, and that our native species are less injurious to living trees. On the European lignivorous insects, see Siemoni, Manuale d'Arte Forestale, 2d edizione, pp. 369-379.] Exclusion of Domestic Quadrupeds. But probably the most important of all rules for the government of the forest, whether natural or artificial, is that which prescribes the absolute exclusion of all domestic quadrupeds, except swine, from every wood which is not destined to be cleared. No growth of young trees is possible where horned cattle, sheep, or goats, or even horses, are permitted to pasture at any season of the year, though they are doubtless most destructive when trees are in leaf. [Footnote: Although the economy of the forest has received little attention in the United States, no lover of American nature can have failed to observe a marked difference between a native wood from which cattle are excluded and one where they are permitted to browse. A few seasons suffice for the total extirpation of the "underbrush," including the young trees on which alone the reproduction of the forest depends, and all the branches of those of larger growth which hang within reach of the cattle are stripped of their buds and leaves, and soon wither and fall off. These effects are observable at a great distance, and a wood-pasture is recognized, almost as far as it can be seen, by the regularity with which its lower foliage terminates at what Ruskin somewhere calls the "cattle-line." This always runs parallel to the surface of the ground, and is determined by the height to which domestic quadrupeds can reach to feed upon the leaves. In describing a visit to the grand-ducal farm of San Rossore near Pisa, where a large herd of camels is kept, Chateauvieux says: "In passing through a wood of evergreen oaks, I observed that all the twigs and foliage of the trees were clipped up to the height of about twelve feet above the ground, without leaving a single spray below that level. I was informed that the browsing of the camels had trimmed the trees as high as they could reach." F. Lullin De Chateuvieux, Lettres sur l'Italie, p. 118. Browsing animals, and most of all the goat, are considered by foresters as more injurious to the growth of young trees, and, therefore, to the reproduction of the forest, than almost any other destructive cause. According to Beatson's Saint Helena, introductory chapter, and Darwin's Journal of Researches in Geology and Natural History, pp. 582, 583, it was the goats which destroyed the beautiful forests that, three hundred and fifty years ago, covered a continuous surface of not less than two thousand acres in the interior of the island [of St. Helena], not to mention scattered groups of trees. Darwin observes: "During our stay at Valparaiso, I was most positively assured that sandal-wood formerly grew in abundance on the island of Juan Fernandez, but that this tree had now become entirely extinct there, having been extirpated by the goats which early navigators had introduced. The neighboring islands, to which goats have not been carried, still abound in sandal-wood." In the winter, the deer tribe, especially the great American moose-deer, subsists much on the buds and young sprouts of trees; yet--though from the destruction of the wolves or from some not easily explained cause, these latter animals have recently multiplied so rapidly in some parts of North America, that, not long since, four hundred of them are said to have been killed, in one season, on a territory in Maine not comprising more than one hundred and fifty square miles--the wild browsing quadrupeds are rarely, if ever, numerous enough in regions uninhabited by man to produce any sensible effect on the condition of the forest. A reason why they are less injurious than the goat to young trees may be that they resort to this nutriment only in the winter, when the grasses and shrubs are leafless or covered with snow, whereas the goat feeds upon buds and young shoots principally in the season of growth. However this may be, the natural law of consumption and supply keeps the forest growth, and the wild animals which live on its products, in such a state of equilibrium as to insure the indefinite continuance of both, and the perpetuity of neither is endangered until man interferes and destroys the balance. When, however, deer are bred and protected in parks, they multiply like domestic cattle, and become equally injurious to trees. "A few years ago," says Clave, "there were not less than two thousand deer of different ages in the forest of Fontainebleau. For want of grass, they are driven to the trees, and they do not spare them ... It is calculated that the browsing of these animals, and the consequent retardation of the growth of the wood, diminishes the annual product of the forest to the amount of two hundred thousand cubic feet per year, ... and besides this, the trees thus mutilated are soon exhausted and die. The deer attack the pines, too, tearing off the bark in long strips, or rubbing theie heads against them when shedding their horns; and sometimes, in groves of more than a hundred hectares, not one pine is found uninjured by them."--Revue des Deux Mondes, Mai, 1863, p. 157. Vaupell, though agreeing with other writers as to the injury done to the forest by most domestic animals and by half-tamed deer--which he illustrates in an interesting way in his posthumous work, The Danish Woods--thinks, nonetheless, that at the season when the mast is falling, swine are rather useful than otherwise to forests of beech and oak, by treading into the ground and thus sowing beechnuts and acorns, and by destroying moles and mice.--De Danake Skore, p. 12. Meguschor is of the same opinion, and adds that swine destroy injurious insects and their larvae.--Memoria, etc., p. 233. Beckstein computes that a park of 2,500 acres, containing 250 acres of marsh, 250 of fields and meadows, and the remaining 2,000 of wood, mny keep 364 deer of different species, 47 wild boars, 200 hares, 100 rabbits, and an indefinite number of pheasants. These animals would require, in winter, 123,000 pounds of hay, and 22,000 pounds of potatoes, besides what they would pick up themselves. The natural forest most thickly peopled with wild animals would not, in temperate climates, contain, upon the average, one-tenth of these numbers to the same extent of surface.] These animals browse upon the terminal buds and the tender branches, thereby stunting, if they do not kill, the young trees, and depriving them of all beauty and vigor of growth. Forest Fires. The difficulty of protecting the woods against accidental or incendiary fires is one of the most discouraging circumstances attending the preservation of natural and the plantation of artificial forests. [Footnote: The disappearance of the forests of ancient Gaul and of mediaeval France has been ascribed by some writers as much to accidental fires as to the felling of the trees. All the treatises on sylviculture are full of narratives of forest fires. The woods of Corsica and Sardinia have suffered incalculable injury from this cause, and notwithstanding the resistance of the cork-tree to injury from common fires, the government forests of this valuable tree in Algeria have been lately often set on fire by the natives and have sustained immense damage. See an article by Ysabeau in the Annales Forestieres, t. iii., p. 439; Della Marmora, Voyage en Sardaigne, 2d edition, t. i., p. 426; Rivista Forestale del Regno d'Italia, October, 1865, p. 474. Five or six years ago I saw in Switzerland a considerable forest, chiefly of young trees, which had recently been burnt over. I was told that the poor of the commune had long enjoyed a customary privilege of carrying off dead wood and windfalls, and that they had set the forest on fire to kill the trees and so increase the supply of their lawful plunder. The customary rights of herdsmen, shepherds, and peasants in European forests are often an insuperable obstacle to the success of attempts to preserve the woods or to improve their condition. See, on this subject, Alfred Maury, Les anciens Forets de la Gaule, chap. xxix.] In the spontaneous wood the spread of fire is somewhat retarded by the general humidity of the soil and of the beds of leaves which cover it. But in long droughts the superficial layer of leaves and the dry fallen branches become as inflammable as tinder, and the fire spreads with fearful rapidity, until its further progress is arrested by want of material, or, more rarely, by heavy rains, sometimes caused, as many meteorologists suppose, by the conflagration itself. In the artificial forest the annual removal of fallen or half-dried trees and the leaves and other droppings of the wood, though otherwise a very injurious practice, much diminishes the rapid spread of fires; and the absence of combustible underwood and the greater distance between the trees are additional safeguards. But, on the other hand, the comparative dryness of the soil, and of any leaves or twigs which may remain upon it, and the greater facility for the passage of wind-currents through a regularly planted and more open wood, are circumstances unfavorable to the security of the trees against this formidable danger. The natural forest, unless isolated and of small extent, can be protected from fire only by a vigilance too costly to be systematically practised. But the artificial wood may be secured by a network of ditches and of paths or occasional open glades, which both check the running of the fire and furnish the means of approaching and combating it. [Footnote: It is stated that in the pine woods of the Landes of Gascony a fire has never been known to cross a railway-track or a common road. See Des Incendies, etc., dans la Region des Maures in the Revue des Eaux et Forets for February, 1869. Many other important articles on this subject will be found in other numbers of the same very valuable periodical.] The experience of 1871 ought not to be wholly without value as a lesson. It is not possible to estimate the damage by forest fires in that disastrous year, in what were lately the North-western States, and in Canada, but as the demand for lumber, and consequently, its market price, are rising at a rate higher than the interest on capital, in a geometrical ratio, one may almost say it is probable that ten years hence those fires will be thought to have diminished the national wealth by a larger amount than even the terrible conflagration at Chicago. There is no good reason why insurance companies should not guarantee the proprietor of a wood as well as the owner of a house against damage by fire. In Europe there is no conceivable liability to pecuniary loss which may not be insured against. The American companies might at first be embarrassed in estimating the risk, but the experience of a few years would suggest safe principles, and all parties would find advantage in this extension of security. Forest Legislation. I have alleged sufficient reasons for believing that a desolation, like that which has overwhelmed many once beautiful and fertile regions of Europe, awaits an important part of the territory of the United States, and of other comparatively new countries over which European civilization is now extending its sway, unless prompt measures are taken to check the action of destructive causes already in operation. It is almost in vain to expect that mere restrictive legislation can do anything effectual to arrest the progress of the evil in those countries, except so far as the state is still the proprietor of extensive forests. Woodlands which have passed into private hands will everywhere be managed, in spite of legal restrictions, upon the same economical principles as other possessions, and every proprietor will, as a general rule, fell his woods, unless he believes that it will be for his pecuniary interest to preserve them. Few of the new provinces which the last three centuries have brought under the control of the European race, would tolerate any interference by the law-making power with what they regard as the most sacred of civil rights--the right, namely, of every man to do what he will with his own. In the Old World, even in France, whose people, of all European nations, love best to be governed and are least annoyed by bureaucratic supervision, law has been found impotent to prevent the destruction, or wasteful economy, of private forests; and in many of the mountainous departments of that country, man is at this moment so fast laying waste the face of the earth, that the most serious fears are entertained, not only of the depopulation of those districts, but of enormous mischiefs to the provinces contiguous to them. [Footnote: "The laws against clearing have never been able to prevent these operations when the proprietor found his advantage in them, and the long series of royal ordinances and decrees of parliaments, proclaimed from the days of Charlemagne to our own, with a view of securing forest property against the improvidence of its owners, have served only to show the impotence of legislative action on this subject."--Clave, Etudes sur l'Economie Forestiere, p. 32. "A proprietor can always contrive to clear his woods, whatever may be done to prevent him; it is a mere question of time, and a few imprudent cuttings, a few abuses of the right of pasturage, suffice to destry a forest in spite of all regulations to the contrary."--Dunoyer, De la Liberte du Travail, ii., p. 452, as quoted by Clave, p. 353. Both authors agree that the preservation of the forests in France is practicable only by their transfer to the state, which alone can protect them and secure their proper treatment. It is much to be feared that even this measure would be inadequate to preserve the forests of the American Union. There is little respect for public property in America, and the Federal Government, certainly, would not be the proper agent of the nation for this purpose. It proved itself unable to protect the live-oak woods of Florida, which were intended to be preserved for the use of the navy, and it more than once paid contractors a high price for timber stolen from its own forests. The authorities of the individual States might be more efficient.] The only legal provisions from which anything is to be hoped, are such as shall make it a matter of private advantage to the landholder to spare the trees upon his grounds, and promote the growth of the young wood. Much may be done by exempting standing forests from taxation, and by imposing taxes on wood felled for fuel or for timber, something by more stringent provisions against trespasses on forest property, and something by premiums or honorary distinctions for judicious management of the woods; and, in short, in this matter rewards rather than punishments must be the incentives to obedience even to a policy of enlightened self-interest. It might be difficult to induce governments, general or local, to make the necessary appropriations for such purposes, but there can be no doubt that it would be sound economy in the end. In countries where there exist municipalities endowed with an intelligent public spirit, the purchase and control of forests by such corporations would often prove advantageous; and in some of the provinces of Northern Lombardy, experience has shown that such operations may be conducted with great benefit to all the interests connected with the proper management of the woods. In Switzerland, on the other hand, except in some few cases where woods have been preserved as a defence against avalanches, the forests of the communes have been of little advantage to the public interests, and have very generally gone to decay. [Footnote: A better economy has been of late introduced into the management of the forest in Switzerland. Excellent official reports on the subject have been published and important legal provisions adopted.] The rights of pasturage, everywhere destructive to trees, combined with toleration of trespasses, have so reduced their value, that there is, too often, nothing left that is worth protecting. In the canton of Ticino, the peasants have very frequently voted to sell the town-woods and divide the proceeds among the corporators. The sometimes considerable sums thus received are squandered in wild revelry, and the sacrifice of the forests brings not even a momentary benefit to the proprietors. [Footnote: See in Berlepscu, Die Alpen, chapter Holzschlager und Flosser, a lively account of the sale of a communal wood.] Fortunately for the immense economical and sanitary interests involved in this branch of rural and industrial husbandry, public opinion in many parts of the United States is thoroughly roused to the importance of the subject. In the Eastern States, plantations of a certain extent have been made, and a wiser system is pursued in the treatment of the remaining native woods. [Footnote: When the census of 1860 was taken, the States of Maine and New York produced and exported lumber in abundance. Neither of them now has timber enough for domestic use, and they are both compelled to draw much of their supply from Canada and the West.] Important experiments have been tried in Massachusetts on the propagation of forest-trees on seashore bluffs exposed to strong winds. This had been generally supposed to be impossible, but the experiments in question afford a gratifying proof that this is an erroneous opinion. Piper gives an interesting account of Mr. Tudor's success in planting trees on the bleak and barren shore of Nahant. "Mr. Tudor," observes he, "has planted more than ten thousand trees at Nahaut, and, by the results of his experiments, has fully demonstrated that trees, properly cared for in the beginning, may be made to grow up to the very bounds of the ocean, exposed to the biting of the wind and the spray of the sea. The only shelter they require is, at first, some interruption to break the current of the wind, such as fences, houses, or other trees." [Footnote: Trees of America, p. 10.] Young trees protected against the wind by a fence will somewhat overtop their shelter, and every tree will serve as a screen to a taller one behind it. Extensive groves have thus been formed in situations where an isolated tree would not grow at all. The people of the Far West have thrown themselves into the work, we cannot say of restoration, but rather of creation, of woodland, with much of the passionate energy which marks their action in reference to other modes of physical improvement. California has appointed a State forester with a liberal salary, and made such legal provisions and appropriations as to render the discharge of his duties effectual. The hands that built the Pacific Railroad at the rate of miles in a day are now busy in planting belts of trees to shelter the track from snow- drifts, and to supply, at a future day, timber for ties and fuel for the locomotives. The settlers on the open plains, too, are not less actively engaged in the propagation of the woods, and if we can put faith in the official statistics on the subject, not thousands but millions of trees are annually planted on the prairies. These experiments are of much scientific as well as economical interest. The prairies have never been wooded, so far as we know their history, and it has been contended that successful sylviculture would be impracticable in those regions from the want of rain. But we are acquainted with no soil and climate which favor the production of herbage and forbid the rearing of trees, and, as Bryant well observes, "it seems certain that where grass will grow trees may be made to grow also." [Footnote: The origin of our Western treeless prairies and plains, as of the Russian steppes, which much resemble them, is obscure, but the want of forests upon them, seems to be due to climatic conditions and especially to a want of spring and summer rains, which prevents the spontaneous formation of forests upon them, though not necessarily the growth of trees artificially planted and cared for. Climatic conditions more or less resembling those of our Western territories produce analogous effects in India. Much valuable information on the relations between climate and forest vegetation will be found in an article by Dr. Brandis, On the Distribution of Forests in India, in Ocean Highways for October, 1872. In the more eastwardly prairie region fires have done much to prevent the spread of the native groves, and throughout the whole woodless plains the pastorage of the buffalo alone would suffice to prevent a forest growth. The prairies were the proper feeding-grounds of the bison, and the vast number of those animals is connected, as cause or consequence, with the existence of these vast pastures. The bison, indeed, could not convert the forest into a pasture, but he would do much to prevent the pasture from becoming a forest. There is positive evidence that some of the American tribes possessed large herds of domesticated bisons. See Humboldt, Ansichten der Natur, i., pp. 71-73. What authorizes us to affirm that this was simply the wild bison reclaimed, and why may we not, with equal probability, believe that the migratory prairie-buffalo is the progeny of the domestic animal run wild? There are, both on the prairies, as in Wisconsin, and in deep forests, as in Ohio, extensive remains of a primitive people, who must have been more numerous and more advanced in art than the present Indian tribes. There can be no doubt that the woods where such earthworks are found in Ohio were cleared by them, and that the vicinity of these fortresses or temples was inhabited by a large population. Nothing forbids the supposition that the prairies were cleared by the same or a similar people, and that the growth of trees upon them has been prevented by fires and grazing, while the restoration of the woods in Ohio may be due to the abandonment of that region by its original inhabitants. The climatic conditions unfavorable to the spontaneous growth of trees on the prairies may possibly be an effect of too extensive clearings, rather than a cause of the want of woods. It is disputed whether the steppes of Russia were ever wooded. They were certainly bare of forest growth at a very remote period; for Herodotus describes the country of the Scythians between the Ister and the Tanais as woodless, with the exception of the small province of Xylaea between the Dnieper and the Gulf of Perekop. They are known to have been occupied by a large nomade and pastoral population down to the sixteenth century, though these tribes are now much reduced in numbers. The habits of such races are scarcely less destructive to the forest than those of civilized life. Pastoral tribes do not employ much wood for fuel or for construction, but they carelessly or recklessly burn down the forests, and their cattle effectually check the growth of young trees wherever their range extends. At present, the furious winds which sweep over the plains, the droughts of summer, and the rights and abuses of pasturage, constitute very formidable obstacles to the employment of measures which have been attended with so valuable results on the sand-wastes of France and Germany. The Russian Government has, however, attempted the wooding of the steppes, and there are thriving plantations in the neighborhood of Odessa, where the soil is of a particularly loose and sandy character. The tree best suited to this locality, and, as there is good reason to suppose, to sand plains in general, is the Ailanthus glandulosa, or Japan varnish-tree. The remarkable success which has crowned the experiments with the ailanthus at Odessa, will, no doubt, stimulate to similar trials elsewhere, and it seems not improbable that the arundo and the maritime pine, which have fixed so many thousand acres of drifting sands in Western Europe, will be, partially at leaat, superseded by the tamarisk and the varnish-tree. According to Hohenstein, Der Wald, pp. 228, 229, an extensive plantation of pines--a tree new to Southern Russia--was commenced in 1842, on the barren and sandy banks of the Ingula, near Elisabethgrod, and has met with very flattering success. Other experiments in sylviculture at different points on the steppes promise valuable results.] In any case the question will now be subjected to a practical test, and the plantations are so extensive, and, as is reported, so thrifty in growth, that one generation will suffice to determine with certainty and precision how far climate is affected by clothing with wood a vast territory naturally destitute of that protection. I have thus far spoken only of the preservation and training of existing woods, not of the planting of new forests, because European experience, to which alone we can appeal, is conversant only with conditions so different from those of our own climate, soil, and arboreal vegetation, that precedents drawn from it cannot be relied upon as entirely safe rules for our guidance in that branch of rural economy. [Footnote: Many valuable suggestions on this subject will be found in Bryant, Forest Trees, chap. vi. et seqq.] I apprehend that one rule, which is certainly alike applicable to both sides of the Atlantic--that, namely, of the absolute exclusion of domestic quadrupeds from all woods, old or young, not destined for the axe--would be least likely to be observed in our practice. The need of shade for cattle, and our inveterate habits in this respect, are much more serious obstacles to compliance with this precept than any inherent difficulty in the thing itself; for there is no good reason why our cattle may not be kept out of our woods as well as out of our wheatfields. When forest-planting is earnestly and perseveringly practised, means of overcoming this difficulty will be found, and our husbandry will be modified to meet the exigency. The best general advice that can be offered, in the want of an experimental code, is to make every plantation consist of a great variety of trees, and this not only because nature favors a diversified forest-crop, but because the chances of success among a multitude of species are far greater than if we confine ourselves to one or two. It will doubtless be found that in our scorching summer, especially on bare plains, shade for young plants is even more necessary than in most parts of Europe, and hence a fair proportion of rapidly growing trees and shrubs, even if themselves of little intrinsic value, ought to be regarded as an indispensable feature in every young plantation. These trees should be of species which bear a full supply of air and light, and therefore, in the order of nature, precede those which are of greater value for the permanent wood; and it would be a prudent measure to seed the ground with a stock of such plants, a year or two before sowing or transplanting the more valuable varieties. More specific rules than these cannot at present well be given, but very brief experiments, even if not in all respects wisely conducted, will suffice to determine the main question: whether in a given locality this or that particular tree can advantageously be propagated or introduced. The special processes of arboriculture suited to the ends of the planter may be gathered partly from cautious imitation of European practice, and partly from an experience which, though not pronouncing definitively in a single season, will, nevertheless, suggest appropriate methods of planting and training the wood within a period not disproportioned to the importance of the object. [Footnote: For very judicious suggestions on experiments in sylviculture, see the Rev. Frederick Starr's remarkable paper on the American Forests in the Transactions of the Agricultural Society for -.] The growth of arboreal vegetation is comparatively slow, and we are often told that, though he who buries an acorn may hope to see it shoot up to a miniature resemblance of the majestic tree which shall shade his remote descendants, yet the longest life hardly embraces the seedtime and the harvest of a forest. The planter of a wood, it is said, must be actuated by higher motives than those of an investment, the profits of which consist in direct pecuniary gain to himself or even to his posterity; for if, in rare cases, an artificial forest may, in a generation or two, more than repay its original cost, still, in general, the value of its timber will not return the capital expended and the interest accrued. [Footnote: According to Clave (Etudes, p. 159), the net revenue from the forests of the state in France, making no allowance for interest on the capital represented by the forest, is two dollars per acre. In Saxony it is about the same, though the cost of administration is twice as much as in France; in Wurtemberg it is about a dollar an acre; and in Prussia, where half the income is consumed in the expenses of administration, it sinks to less than half a dollar. This low rate in Prussia and other German states is partly explained by the fact that a considerable proportion of the annual product of the wood is either conceded to persons claiming prescriptive rights, or sold, at a very small price, to the poor. Taking into account the capital invested in forest-land, and adding interest upon it, Pressler calculates that a pine wood, managed with a view to felling it when eighty years old, would yield one-eighth of one per cent. annual profit; a fir wood, at one hundred years, one-sixth of one per cent.; a beech wood, at one hundred and twenty years, one-fourth of one per cent. The same author gives the net income of the New Forest in England, over and above expenses, interest not computed, at twenty-five cents per acre only. In America, where no expense is bestowed upon the woods, the value of the annual growth has generally been estimated much higher. Forest-trees are often planted in Europe for what may be called an early crop. Thus in Germany acorns are sown and the young seedlings cultivated like ordinary field-vegetables, and cut at the age of a very few years for the sake of the bark and young twigs used by tanners. In England, trees are grown at the rate of two thousand to the acre, and cut for props in the mines at the diameter of a few inches. Plantations for hoop-poles, and other special purposes requiring small timber, would, no doubt, often prove high remunerative.] But the modern improved methods of sylviculture show vastly more favorable financial results; and when we consider the immense collateral advantages derived from the presence of the forest, the terrible evils necessarily resulting from its destruction, we cannot but admit that the preservation of existing woods, and the more costly extension and creation of them where they have been unduly reduced or have never existed, are among the plainest dictates of self-interest and most obvious of the duties which this age owes to those that are to come after it. Financial Results of Forest Plantation. Upon the whole, I am persuaded that the financial statistics which are found in French and German authors, as the results of European experience in forest economy, present the question under a too unfavorable aspect; and therefore these calculations ought not to discourage landed proprietors from making experiments on this subject. These statistics apply to woods whose present condition is, in an eminent degree, the effect of previous long-continued mismanagement; and there is much reason to believe that in the propitious climate of the United States new plantations, regulated substantially according to the methods of De Courval, Chambrelent, and Chevandier, and accompanied with the introduction of exotic trees, as, for example, the Australian caruarina and eucalyptus [Footnote: Although the eucalyptus thrives admirably in Algeria--where it attains a height of from fifty to sixty feet, and a diameter of fifteen or sixteen inches, in six years from the seed--and in some restricted localities in Southern Europe, it will not bear the winters even of Florence, and consequently cannot be expected to flourish in any part of the United States except the extreme South and California. The writer of a somewhat enthusiastic article on this latter State, in Harper's Monthly for July, 1872, affirms that he saw a eucalyptus "eight years from a small cutting, which was seventy-five feet in height, and two feet and a half in diameter at the base." The paulownia, which thrives in Northern Italy, has a wood of little value, but the tree would serve well as a shelter for seedlings and young plants of more valuable species, and in other cases where a temporary shade is urgently needed. The young shoots, from a stem polled the previous season, almost surpass even the eucalyptus in rapidity of growth. Such a shoot from a tree not six inches in diameter, which I had an opportunity of daily observing, from the bursting out of the bud from the bark of the parent stem in April till November of the same year, acquired in that interval a diameter of between four and five inches and a height of above twenty feet.] which, latter, it is said, has a growth at least five, and, according to some, ten times more rapid than that of the oak--would prove good investments even in an economical aspect. [Footnote: The economical statistics of Grigor, Arboriculture, Edinburgh, 1868, are very encouraging. In the preface to that work the author says: "Having formed several large plantations nearly forty years ago, which are still standing, in the Highlands of Scotland, I can refer to them as, after paying every expense, yielding a revenue equal to that of the finest arable land in the country, where the ground previously to these formations was not worth a shilling an acre." See also Hartig, Ueber den Wachsthumsgang und Ertrag der Buche, Eiche und Kiefer, 1869, and especially Bryant, Forest Trees, chap. ix.] There is no doubt that they would pay the expenses of their planting at no distant period, at least in every case where irrigation is possible, and in very many situations, terraces, ditches, or even horizontal furrows upon the hillsides, would answer as a substitute for more artificial irrigation. Large proprietors would receive important indirect benefits from the shelter and the moisture which forests furnish for the lands in their neighborhood, and eventually from the accumulation of vegetable mould in the woods. [Footnote: The fertility of newly cleared land is by no means due entirely to the accumulation of decayed vegetable matter on its surface, and to the decomposition of the mineral constituents of the soil by the gases emitted by the fallen leaves. Sachs has shown that the roots of living plants exercise a most powerful solvent action on rocks, and hence stones are disintegrated and resolved into elements of vegetable nutrition, by the chemical agency of the forest, more rapidly than by frost, rain, and other meteorological influences.] The security of the investment, as in the case of all real-estate, is a strong argument for undertaking such plantations, and a moderate amount of government patronage and encouragement would be sufficient to render the creation of new forests an object of private interest as well as of public advantage, especially in a country where the necessity is so urgent and the climate so favorable as in the United States. Instability of American Life. All human institutions, associate arrangements, modes of life, have their characteristic imperfections. The natural, perhaps the necessary defect of ours, is their instability, their want of fixedness, not in form only, but even in spirit. The face of physical nature in the United States shares this incessant fluctuation, and the landscape is as variable as the habits of the population. It is time for some abatement in the restless love of change which characterizes us, and makes us almost a nomade rather than a sedentary people. [Footnote: It is rare that a middle-aged American dies in the house where he was born, or an old man even in that which he has built; and this is scarcely less true of the rural districts, where every man owns his habitation, than of the city, where the majority live hired houses. This life of incessant flitting is unfavorable for the execution of permanent improvements of every sort, and especially of those which, like the forest, are slow in repaying any part of the capital expended in them. It requires a very generous spirit in a landholder to plant a wood on a farm he expects to sell, or which he knows will pass out of the hands of his descendants at his death. But the very fact of having begun a plantation would attach the proprietor more strongly to the soil for which he had made such a sacrifice; and the paternal acres would have a greater value in the eyes of a succeeding generation, if thus improved and beautified by the labors of those from whom they were inherited. Landed property, therefore, the transfer of which is happily free from every legal impediment or restriction in the United States, would find, in the feelings thus prompted, a moral check against a too frequent change of owners, and would tend to remain long enough in one proprietor or one family to admit of gradual improvements which would increase its value both to the possessor and to the state.] We have now felled forest enough everywhere, in many districts far too much. Let us restore this one element of material life to its normal proportions, and devise means of maintaining the permanence of its relations to the fields, the meadows, and the pastures, to the rain and the dews of heaven, to the springs and rivulets with which it waters the earth. The establishment of an approximately fixed ratio between the two most broadly characterized distinctions of rural surface--woodland and ploughland--would involve a certain persistence of character in all the branches of industry, all the occupations and habits of life, which depend upon or are immediately connected with either, without implying a rigidity that should exclude flexibility of accommodation to the many changes of external circumstance which human wisdom can neither prevent nor foresee, and would thus help us to become, more emphatically, a well-ordered and stable commonwealth, and, not less conspicuously, a people of progress. CHAPTER IV. THE WATERS. Land Artificially won from the Waters--Great Works of Material Improvement--Draining of Lincolnshire Fens--Incursions of the Sea in the Netherlands--Origin of Sea-dikes--Gain and Loss of Land in the Netherlands--Marine Deposits on the Coast of Netherlands--Draining of Lake of Haarlem--Draining of the Zuiderzee--Geographical Effects of Improvements in the Netherlands--Ancient Hydraulic Works--Draining of Lake Celano by Prince Torlonia--Incidental Consequences of draining Lakes--Draining of Marshes--Agricultural Draining--Meteorological Effects of Draining--Geographical Effects of Draining--Geographical Effects of Aqueducts and Canals--Antiquity of Irrigation--Irrigation in Palestine, India, and Egypt--Irrigation in Europe--Meteorological Effects of Irrigation--Water withdrawn from Rivers for Irrigation--Injurious Effects of Rice-culture--Salts Deposited by Water of Irrigation--Subterranean Waters--Artesian Wells--Artificial Springs--Economizing Precipitation--Inundations in France--Basins of Reception--Diversion of Rivers--Glacier Lakes--River Embankments--Other Remedies against Inundations--Dikes of the Nile--Deposits of Tuscan Rivers--Improvements in Tuscan Maremma--Improvements in Val di Chiana--Coast of the Netherlands. Land artificially won from the Waters. Man, as we have seen, has done much to revolutionize the solid surface of the globe, and to change the distribution and proportions, if not the essential character, of the organisms which inhabit the land and even the waters. Besides the influence thus exerted upon the life which peoples the sea, his action upon the land has involved a certain amount of indirect encroachment upon the territorial jurisdiction of the ocean. So far as he has increased the erosion of running waters by the destruction of the forest or by other operations which lessen the cohesion of the soil, he has promoted the deposit of solid matter in the sea, thus reducing the depth of marine estuaries, advancing the coast-line, and diminishing the area covered by the waters. He has gone beyond this, and invaded the realm of the ocean by constructing within its borders wharves, piers, light-houses, breakwaters, fortresses, and other facilities for his commercial and military operations; and in some countries he has permanently rescued from tidal overflow, and even from the very bed of the deep, tracts of ground extensive enough to constitute valuable additions to his agricultural domain. The quantity of soil gained from the sea by these different modes of acquisition is, indeed, too inconsiderable to form an appreciable element in the comparison of the general proportion between the two great forms of terrestrial surface, land and water; but the results of such operations, considered in their physical and their moral bearings, are sufficiently important to entitle them to special notice in every comprehensive view of the relations between man and nature. There are cases, as on the western shores of the Baltic, where, in consequence of the secular elevation of the coast, the sea appears to be retiring; others, where, from the slow sinking of the land, it seems to be advancing. These movements depend upon geological causes wholly out of our reach, and man can neither advance nor retard them. [Footnote: It is possible that the weight of the sediment let fall at the mouths of great rivers, like the Ganges, the Mississippi, and the Po, may cause the depression of the strata on which they are deposited, and hence if man promotes the erosion and transport of earthy material by rivers, he augments the weight of the sediment they convey into their estuaries, and consequently his action tends to accelerate such depression. There are, however, cases where, in spite of great deposits of sediment by rivers, the coast is rising. Further, the manifestation of the internal heat of the earth at any given point is conditioned by the thickness of the crust at such point. The deposits of rivers tend to augment that thickness at their estuaries. The sediment of slowly-flowing rivers emptying into shallow seas is spread over so great a surface that we can hardly imagine the foot or two of slime they let fall over a wide area in a century to form an element among even the infinitesimal quantities which compose the terms of the equations of nature. But some swift rivers, rolling mountains of fine earth, discharge themselves into deeply scooped gulfs or bays, and in such cases the deposit amounts, in the course of a few years, to a mass the transfer of which from the surface of a large basin, and its accumulation at a single point, may be supposed to produce other effects than those measurable by the sounding-line. Now, almost all the operations of rural life, as I have abundantly shown, increase the liability of the soil to erosion by water. Hence, the clearing of the valley of the Ganges, for example, by man, must have much augmented the quantity of earth transported by that river to the sea, and of course have strengthened the effects, whatever they may be, of thickening the crust of the earth in the Bay of Bengal. In such cases, then, human action must rank among geological influences. To the geological effects of the thickening of the earth's crust in the Bay of Bengal, are to be added those of thinning it on the highlands where the Ganges rises. The same action may, as a learned friend suggests to me, even have a cosmical influence. The great rivers of the earth, taken as a whole, transport sediment from the polar regions in an equatorial direction, and hence tend to increase the equatorial diameter, and at the same time, by their inequality of action, to a continual displacement of the centre of gravity, of the earth. The motion of the globe, and of all bodies affected by its attraction, is modified by every change of its form, and in this case we are not authorized to say that such effects are in any way compensated.] There are also cases where similar apparent effects are produced by local oceanic currents, by river deposit or erosion, by tidal action, or by the influence of the wind upon the waves and the sands of the seabeach. A regular current may drift suspended earth and seaweed along a coast until they are caught by an eddy and finally deposited out of the reach of further disturbance, or it may scoop out the bed of the sea and undermine promontories and headlands; a powerful river, as the wind changes the direction of its flow at its outlet, may wash away shores and sandbanks at one point to deposit their material at another; the tide or waves, stirred to unusual depths by the wind, may gradually wear down the line of coast, or they may form shoals and coast-dunes by depositing the sand they have rolled up from the bottom of the ocean. These latter modes of action are slow in producing effects sufficiently important to be noticed in general geography, or even to be visible in the representations of coast-line laid down in ordinary maps; but they nevertheless form conspicuous features in local topography, and they are attended with consequences of great moment to the material and the moral interests of men. The forces which produce these limited results are all in a considerable degree subject to control, or rather to direction and resistance, by human power, and it is in guiding, combating, and compensating them that man has achieved some of his most remarkable and most honorable conquests over nature. The triumphs in question, or what we generally call harbor and coast improvements, whether we estimate their value by the money and labor expended upon them, or by their bearing upon the interests of commerce and the arts of civilization, must take a very high rank among the great works of man, and they are fast assuming a magnitude greatly exceeding their former relative importance. The extension of commerce and of the military marine, and especially the introduction of vessels of increased burden and deeper draught of water, have imposed upon engineers tasks of a character which a century ago would have been pronounced, and, in fact, would have been, impracticable; but necessity has stimulated au ingenuity which has contrived means of executing them, and which gives promise of yet greater performance in time to come. Indeed, although man, detached from the solid earth, is almost powerless to struggle against the sea, he is fast becoming invincible by it so long as his foot is planted on the shore, or even on the bottom of the rolling ocean; and though on some battle-fields between the waters and the land he is obliged slowly to yield his ground, yet he retreats still facing the foe, and will finally be able to say to the sea, "Thus far shalt thou come and no farther, and here shall thy proud waves be stayed!" [Footnote: It is, nevertheless, remarkable that in the particular branch of coast engineering where great improvements are most urgently needed, comparatively little has been accomplished. I refer to the creation of artificial harbors, and of facilities for loading and discharging ships. The whole coast of Italy is, one may almost say, harborless and even, wharfless, and there are many thousands of miles of coast in rich commercial countries in Europe, where vessels can neither lie in safety for a single day, nor even, in better protected heavens, ship or land their passengers or cargoes except by the help of lighters, and other not less clumsy contrivances. It is strange that such enormous inconveniences are borne with so little effort to remove them, and especially that break-waters are rarely constructed by Governments except for the benefit of the military marine.] Great Works of Material Improvement. Men have ceased to admire the vain exercise of power which heaped up the great pyramid to gratify the pride of a despot with a giant sepulchre; for many great harbors, many important lines of internal communication, in the civilized world, now exhibit works which in volume and weight of material surpass the vastest remains of ancient architectural art, and demand the exercise of far greater constructive skill and involve a much heavier pecuniary expenditure than would now be required for the building of the tomb of Cheops. It is computed that the great pyramid, the solid contents of which when complete were about 3,000,000 cubic yards, could be erected for a million of pounds sterling. The breakwater at Cherbourg, founded in rough water sixty feet deep, at an average distance of more than two miles from the shore, contains double the mass of the pyramid, and many a comparatively unimportant canal has been constructed at twice the cost which would now build that stupendous monument. The description of works of harbor and coast improvement which have only an economical value, not a true geographical importance, does not come within the plan of the present volume, and in treating this branch of my subject, I shall confine myself to such as are designed either to gain new soil by excluding the waters from grounds which they had permanently or occasionally covered, or to resist new encroachments of the sea upon the land. [Footnote: Some notice of great works executed by man in foreign lands, and probably not generally familiar to my readers, may, however, prove not uninteresting. The desaguadero, or canal constructed by the Viceroy Revillagigedo to prevent the inundation of the city of Mexico by the lakes in its vicinity, besides subsidiary works of great extent, has a cutting half a mile long, 1,000 feet wide, and from 150 to 200 feet deep.--Hoffmann, Encyclopaedie, art. Mexico. The adit which drains the mines of Gwennap in Cornwall, with its branches, is thirty miles long. Those of the silver mines of Saxony are scarcely less extensive, and the Ernst-August-Stollen, or great drain of the mines of the Harz, is fifteen miles long. The excavation for the Suez Canal were computed at 75,000,000 cubic metres, or about 100,000,000 cubic yards, and those of the Ganges Canal, which, with its branches, had a length of 3,000 miles, amount to nearly the same quantity. The quarries at Maestricht have undermined a space of sixteen miles by six, or more than two American townships, and the catacombs of Rome, in part, at least, originally quarries, have a lineal extent of five hundred and fifty miles. The catacombs of Paris required the excavation of 13,000,000 cubic yards of stone, or more than four times the volume of the great pyramid. The excavation for the Mt. Cenis tunnel, eight miles in length, wholly through solid rock, amounted to more than 900,000 cubic yards, and 16,000,000 of brick were employed for the lining. In an article on recent internal improvements in England, in the London Quarterly Review for January, 1858, it is stated that in a single rock-cutting on the Liverpool and Manchester railway, 480,000 cubic yards of stone were removed; that the earth excavated in the construction of English railways up to that date amounted to a hundred and fifty million cubic yards, and that at the Round Down Cliff, near Dover, a single blast of nineteen thousand pounds of powder blew down a thousand million tons of chalk, and covered fifteen acres of land with the fragments. In 1869, a mass of marble equal to one and a half times the cubical contents of the Duomo at Florence, or about 450,000 cubic yards, was thrown down at Carrara by one blast, and two hours after, another equal mass, which had been loosened by the explosion, fell of itself. Zolfanelli, La Lunigiana, p. 43. The coal yearly extracted from the mines of England averages not less than 100,000,000 tons. The specific gravity of British coal ranges from 1.20 to 1.35, and consequently we may allow a cubic yard to the ton. If we add the earth and rock removed in order to reach the coal, we shall have a yearly amount of excavation for this one object equal to more than thirty times the volume of the pyramid of Cheops. These are wonderful achievements of human industry; but the rebuilding of Chicago within a single year after the great fire--not to speak of the extraordinary material improvements previously executed at that city--surpasses them all, and it probably involved the expenditure of a sum of muscular and of moral energy which has never before been exerted in the accomplishment of a single material object, within a like period.] Draining of Lincolnshire Fens. The draining of the Lincolnshire fens in England, which has converted about 400,000 acres of marsh, pool, and tide-washed flat into ploughland and pasturage, is a work, or rather series of works, of great magnitude, and it possesses much economical, and, indeed, no trifling geographical, importance. Its plans and methods were, at least in part, borrowed from the example of like improvements in Holland, and it is, in difficulty and extent, inferior to works executed for the same purpose on the opposite coast of the North Sea, by Dutch, Frisie, and Low German engineers. The space I can devote to such operations will be better employed in describing the latter, and I content myself with the simple statement I have already made of the quantity of worthless and even pestilential land which has been rendered both productive and salubrious in Lincolnshire, by diking out the sea, and the rivers which traverse the fens of that country. The almost continued prevalence of west winds upon both coasts of the German Ocean occasions a constant set of the currents of that sea to the east, and both for this reason and on account of the greater violence of storms from the former quarter, the English shores of the North Sea are less exposed to invasion by the waves than those of the Netherlands and the provinces contiguous to them on the north. The old Netherlandish chronicles are filled with the most startling accounts of the damage done by the irruptions of the ocean, from west winds or extraordinarily high tides, at times long before any considerable extent of seacoast was diked. Several hundreds of those terrible inundations are recorded, and in many of them the loss of human lives is estimated as high as one hundred thousand. It is impossible to doubt that there must be enormous exaggeration in these numbers; for, with all the reckless hardihood shown by men in braving the dangers and privations attached by nature to their birthplace, it is inconceivable that so dense a population as such wholesale destruction of life supposes could find the means of subsistence, or content itself to dwell, on a territory liable, a dozen times in a century, to such fearful devastation. There can be no doubt, however, that the low continental shores of the German Ocean very frequently suffered immense injury from inundation by the sea, and it is natural, therefore, that the various arts of resistance to the encroachments of the ocean, and, finally, of aggressive warfare upon its domain, and of permanent conquest of its territory, should have been earlier studied and carried to higher perfection in the latter countries, than in England, which had less to lose or to gain by the incursions or the retreat of the waters. Indeed, although the confinement of swelling rivers by artificial embankments is of great antiquity, I do not know that the defence or acquisition of land from the sea by diking was ever practised on a large scale until systematically undertaken by the Netherlanders, a few centuries after the commencement of the Christian era. The silence of the Roman historians affords a strong presumption that this art was unknown to the inhabitants of the Netherlands at the time of the Roman invasion, and the elder Pliny's description of the mode of life along the coast which has now been long diked in, applies precisely to the habits of the people who live on the low islands and mainland flats lying outside of the chain of dikes, and wholly unprotected by embankments of any sort. Origin of Sea-dikes. It has been conjectured, and not without probability, that the causeways built by the Romans across the marshes of the Low Countries, in their campaigns against the Germanic tribes, gave the natives the first hint of the utility which might be derived from similar constructions applied to a different purpose. [Footnote: It has often been alleged by eminent writers that a part of the fens in Lincolnshire was reclaimed by sea-dikes under the government of the Romans. I have found no ancient authority in support of this assertion, nor can I refer to any passage in Roman literature in which sea-dikes are expressly mentioned otherwise than as walls or piers, except that in Pliny (Hist. Nat. xxxvi. 24), where it is said that the Tyrrhenian Sea was excluded from the Lucrino Lake by dikes. Dugdale, whose enthusiasm for his subject led him to believe that recovering from the sea land subject to be flooded by it, was of divine appointment, because God said: "Let the waters under the heavens be gathered together unto one place and let the dry land appear," unhesitatingly ascribes the reclamation of the Lincolnshire fens to the Romans, though he is able to cite but one authority, a passage in Tacitus's Life of Agricola which certainly has no such meaning, in support of the assertion.--History of Embankment and Drainage, 2d edition, 1772.] If this is so, it is one of the most interesting among the many instances in which the arts and enginery of war have been so modified as to be eminently promotive of the blessings of peace, thereby in some measure compensating the wrongs and sufferings they have inflicted on humanity. [Footnote: It is worth mentioning, as an illustration of the applicability of military instrumentalities to pacific art, that the sale of gunpowder in the United States was smaller during the late rebellion than before, because the war caused the suspension of many public and private improvements, in the execution of which great quantities of powder were used for blasting. The same observation was made in France during the Crimean war, and it is alleged that, in general, not ten per cent. of the powder manufactured on either either side of the Atlantic is employed for military purposes. The blasting for the Mount Cenis tunnel consumed gunpowder enough to fill more than 200,000,000 musket cartridges. It is a fact not creditable to the moral sense of modern civilization, that very many of the most important improvements in machinery and the working of metals have originated in the necessities of war, and that man's highest ingenuity has been shown, and many of his most remarkable triumphs over natural forces achieved, in the contrivance of engines for the destruction of his fellow-man. The military material employed by the first Napoleon has become, in less than two generations, nearly as obsolete as the sling and stone of the shepherd, and attack and defence now begin at distances to which, half a century ago, military reconnaissances hardly extended. Upon a partial view of the subject, the human race seems destined to become its own executioner--on the one hand, exhausting the capacity of the earth to furnish sustenance to her taskmaster; on the other, compensating diminished production by inventing more efficient methods of exterminating the consumer. At the present moment, at an epoch of universal peace, the whole civilized world with the happy exception of our own country, is devoting its utmost energies, applying the highest exercise of inventive genius, to the production of new engines of war; and the last extraordinary rise in the price of iron and copper is in great part due to the consumption of these metals in the fabrication of arms and armed vessels. The simple substitution of sheet-copper for paper and other materials in the manufacture of cartridges has increased the market-price of copper by a large percentage on its former cost. But war develops great civil virtues, and brings into action a degree and kind of physical energy which seldom fails to awaken a new intellectual life in a people that achieves great moral and political results through great heroism and endurance and perseverance. Domestic corruption has destroyed more nations than foreign invasion, and a people is rarely conquered till it has deserved subjugation.] The Lowlanders are believed to have secured some coast and bay islands by ring-dikes and to have embanked some fresh-water channels, as early as the eighth or ninth century; but it does not appear that sea-dikes, important enough to be noticed in historical records, were constructed on the mainland before the thirteenth century. The practice of draining inland accumulations of water, whether fresh or salt, for the purpose of bringing under cultivation the ground they cover, is of later origin, and is said not to have been adopted until after the middle of the fifteenth century. [Footnote: Staring, Voormaals en Thans, p. 150.] Gain and Loss of Land in the Netherlands. The total amount of surface gained to the agriculture of the Netherlands by diking out the sea and by draining shallow bays and lakes, is estimated by Staring at three hundred and fifty-five thousand bunder or hectares, equal to eight hundred and seventy-seven thousand two hundred and forty acres, which is one-tenth of the area of the kingdom. [Footnote: Idem, p. 163. Much the largest proportion of the lands so reclaimed, though for the most part lying above low-water tidemark, are at a lower level than the Lincolnshire fens, and more subject to inundation from the irruptions of the sea.] In very many instances the dikes have been partially, in some particularly exposed localities totally, destroyed by the violence of the sea, and the drained lands again flooded. In some cases the soil thus painfully won from the ocean has been entirely lost; in others it has been recovered by repairing or rebuilding the dikes and pumping out the water. Besides this, the weight of the dikes gradually sinks them into the soft soil beneath, and this loss of elevation must be compensated by raising the surface, while the increased burden thus added tends to sink them still lower. "Tetens declares," says Kohl, "that in some places the dikes have gradually sunk to the depth of sixty or even a hundred feet." [Footnote: Die Inseln und Marschen der Herzogthamer Schleswig und Holstein, iii., p. 151.] For these reasons, the processes of dike-building have been almost everywhere again and again repeated, and thus the total expenditure of money and of labor upon the works in question is much greater than would appear from an estimate of the actual cost of diking-in a given extent of coast-land and draining a given area of water-surface. [Footnote: The purely agricultural island of Pelworm, off the coast of Schleswig, containing about 10,000 acres, annually expends for the maintenance of its dikes not less than L6,000 sterling, or nearly $30,000.--J. G. Kohl, Inseln und Marschen Schleswig's und Holstein's, ii., p. 394. The original cost of the dikes of Pelworm is not stated. "The greatest part of the province of Zeeland is protected by dikes measuring 250 miles in length, the maintenance of which costs, in ordinary years, more than a million guilders [above $400,000] ... The annual expenditure for dikes and hydraulic works in Holland is from five to seven million guilders" [$2,000,000 to $2,800,000].--Wild, Die Niederlande, i., p. 62. One is not sorry to learn that the Spanish tyranny in the Netherlands had some compensations. The great chain of ring-dikes which surrounds a large part of Zeeland is due to the energy of Caspar de Robles, the Spanish governor of that province, who in 1570 ordered the construction of these works at the public expense, as a substitute for the private embankments which had previously partially served the same purpose.--Wild, Die Niederlande, i., p. 62.] Loss of Land by Incursions of Sea. On the other hand, by erosion of the coast-line, the drifting of sand-dunes into the interior, and the drowning of fens and morasses by incursions of the sea--all caused, or at least greatly aggravated, by human improvidence--the Netherlands have lost a far larger area of land since the commencement of the Christian era than they have gained by diking and draining. Staring despairs of the possibility of calculating the loss from the first-mentioned two causes of destruction, but he estimates that not less than six hundred and forty thousand bunder, or one million five hundred and eighty-one thousand acres, of fen and marsh have been washed away, or rather deprived of their vegetable surface and covered by water; and thirty-seven thousand bunder, or ninety-one thousand four hundred acres, of recovered land, have been lost by the destruction of the dikes which protected them. [Footnote: Staring, Voormaals en Thans, p. 163.] The average value of land gained from the sea is estimated at about nineteen pounds sterling, or ninety dollars, per acre; while the lost fen and morass was not worth more than one twenty-fifth part of the same price. The ground buried by the drifting of the dunes appears to have been almost entirely of this latter character, and, upon the whole, there is no doubt that the soil added by human industry to the territory of the Netherlands, within the historical period, greatly exceeds in pecuniary value that which has fallen a prey to the waves during the same era. Upon most low and shelving coasts, like those of the Netherlands, the maritime currents are constantly changing, in consequence of the variability of the winds, and the shifting of the sand-banks, which the currents themselves now form and now displace. While, therefore, at one point the sea is advancing landward, and requiring great effort to prevent the undermining and washing away of the dikes, it is shoaling at another by its own deposits, and exposing, at low water, a gradually widening belt of sands and ooze. The coast-lands selected for diking-in are always at points where the sea is depositing productive soil. The Eider, the Elbe, the Weser, the Ems, the Rhine, the Maas, and the Schelde bring down large quantities of fine earth. The prevalence of west winds prevents the waters from carrying this material far out from the coast, and it is at last deposited northward or southward from the mouth of the rivers which contribute it, according to the varying drift of the currents. Marine Deposits. The process of natural deposit which prepares the coast for diking-in is thus described by Staring: "All sea-deposited soil is composed of the same constituents. First comes a stratum of sand, with marine shells, or the shells of mollusks living in brackish water. If there be tides, and, of course, flowing and ebbing currents, mud is let fall upon the sand only after the latter has been raised above low-water mark; for then only, at the change from flood to ebb, is the water still enough to form a deposit of so light a material. Where mud is found at great depths, as, for example, in a large proportion of the Ij, it is a proof that at this point there was never any considerable tidal flow or other current. ... The powerful tidal currents, flowing and ebbing twice a day, drift sand with them. They scoop out the bottom at one point, raise it at another, and the sand-banks in the current are continually shifting. As soon as a bank raises itself above low-water mark, flags and reeds establish themselves upon it. The mechanical resistance of these plants checks the retreat of the high water and favors the deposit of the earth suspended in it, and the formation of land goes on with surprising rapidity. When it has risen to high-water level, it is soon covered with grasses, and becomes what is called schor in Zeeland, kwelder in Friesland. Such grounds are the foundation or starting-point of the process of diking. When they are once elevated to the flood-tide level, no more mud is deposited upon them except by extraordinary high tides. Their further rise is, accordingly, very slow, and it is seldom advantageous to delay longer the operation of diking." [Footnote: Voormaals en Thans, pp. 150, 151. According to Reventlov, confercae first appear at the bottom in shoal water, then, after the deposit has risen above the surface, Salicornia herbacea. The Salicornia is followed by various sand-plants, and so the ground rises, by Poa distans and Poa maritum, and finally common grasses establish themselves.--Om Markdannelsen poa Vestkyeten of Slesvig, pp. 7, 8.] Sea-dikes of the Netherlands. The formation of new banks by the sea is constantly going on at points favorable for the deposit of sand and earth, and hence opportunity is continually afforded for enclosure of new land outside of that already diked in, the coast is fast advancing seaward, and every new embankment increases the security of former enclosures. The province of Zeeland consists of islands washed by the sea on their western coasts, and separated by the many channels through which the Schelde and some other rivers find their way to the ocean. In the twelfth century these islands were much smaller and more numerous than at present. They have been gradually enlarged, and, in several instances, at last connected by the extension of their system of dikes. Walcheren is formed of ten islets united into one about the end of the fourteenth century. At the middle of the fifteenth century, Goeree and Overflakkee consisted of separate islands, containing altogether about ten thousand acres; by means of above sixty successive advances of the dikes, they have been brought to compose a single island, whose area is not less than sixty thousand acres. [Footnote: Staring, Voormaals en Thans, p, 152. Kohl states that the peninsula of Diksand on the coast of Holstein consisted, at the close of the last century, of several islands measuring together less than five thousand acres. In 1837 they had been connected with the mainland, and had nearly doubled in area.--Inseln u. Marschen Schlene, Holst., iii., p. 202] In the Netherlands--which the first Napoleon characterized as a deposit of the Rhine, and as, therefore, by natural law, rightfully the property of him who controlled the sources of that great river--and on the adjacent Frisie, Low German, and Danish shores and islands, sea and river dikes have been constructed on a grander and more imposing scale than in any other country. The whole economy of the art has been there most thoroughly studied, and the literature of the subject is very extensive. For my present aim, which is concerned with results rather than with processes, it is not worth while to refer to professional treatises, and I shall content myself with presenting such information as can be gathered from works of a more popular character. The superior strata of the lowlands upon and near the coast are, as we have seen, principally composed of soil brought down by the great rivers I have mentioned, and either directly deposited by them upon the sands of the bottom, or carried out to sea by their currents, and then, after a shorter or longer exposure to the chemical and mechanical action of salt-water and marine currents, restored again to the land by tidal overflow and subsidence from the waters in which it was suspended. At a very remote period the coast-flats were, at many points, raised so high by successive alluvious or tidal deposits as to be above ordinary high-water level, but they were still liable to occasional inundation from river-floods, and from the seawater also, when heavy or long-continued west winds drove it landwards. The extraordinary fertility of this soil and its security as a retreat from hostile violence attracted to it a considerable population, while its want of protection against inundation exposed it to the devastations of which the chroniclers of the Middle Ages have left such highly colored pictures. The first permanent dwellings on the coast-flats were erected upon artificial mounds, and many similar precarious habitations still exist on the unwalled islands and shores beyond the chain of dikes. River embankments, which, as is familiarly known, have from the earliest antiquity been employed in many countries where sea-dikes are unknown, were probably the first works of this character constructed in the Low Countries, and when two neighboring streams of fresh water had been embanked, the next step in the process would naturally be to connect the river-walls together by a transverse dike or raised causeway, which would serve as a means of communication between different hamlets and at the same time secure the intermediate ground both against the backwater of river-floods and against overflow by the sea. The oldest true sea-dikes described in historical records, however, are those enclosing islands in the estuaries of the great rivers, and it is not impossible that the double character they possess as a security against maritime floods and as a military rampart, led to their adoption upon those islands before similar constructions had been attempted upon the mainland. At some points of the coast, various contrivances, such as piers, piles, and, in fact, obstructions of all sorts to the ebb of the current, are employed to facilitate the deposit of slime, before a regular enclosure is commenced. Usually, however, the first step is to build low and cheap embankments, extending from an older dike, or from high ground, around the parcel of flat intended to be secured. These are called summer dikes. They are erected when a sufficient extent of ground to repay the cost has been elevated enough to be covered with coarse vegetation fit for pasturage. They serve both to secure the ground from overflow by the ordinary flood-tides of mild weather, and to retain the slime deposited by very high water, which would otherwise be partly carried off by the retreating ebb. The elevation of the soil goes on slowly after this; but when it has at last been sufficiently enriched, and raised high enough to justify the necessary outlay, permanent dikes are constructed by which the water is excluded at all seasons. These embankments are constructed of sand from the coast-dunes or from sand-banks, and of earth from the mainland or from flats outside the dikes, bound and strengthened by fascines, and provided with sluices, which are generally founded on piles and of very expensive construction, for drainage at low water. The outward slope of the sea-dikes is gentle, experience having shown that this form is least exposed to injury both from the waves and from floating ice, and the most modern dikes are even more moderate in the inclination of the seaward scarp than the older ones. [Footnote: The inclination varies from one foot rise in four of base to one foot in fourteen.--Kohl, iii., p. 210.] The crown of the dike, however, for the last three or four feet of its height, is much steeper, being intended rather as a protection against the spray than against the waves, and the inner slope is always comparatively abrupt. The height and thickness of dikes varies according to the elevation of the ground they enclose, the rise of the tides, the direction of the prevailing winds, and other special causes of exposure, but it may be said that they are, in general, raised from fifteen to twenty feet above ordinary high-water mark. The water-slopes of river-dikes are protected by plantations of willows or strong semi-aquatic shrubs or grasses, but as these will not grow upon banks exposed to salt-water, sea-dikes must be faced with stone, fascines, or some other revetement. [Footnote: The dikes are sometimes founded upon piles, and sometimes protected by one or more rows of piles driven deeply down into the bed of the sea in front of them. "Triple rows of piles of Scandinavian pine," says Wild, "have been driven down along the coast of Friesland, where there are no dunes, for a distance of one hundred and fifty miles. The piles are bound together by strong cross-timbers and iron clamps, and the interstices filled with stones. The ground adjacent to the piling is secured with fascines, and at exposed points heavy blocks of stone are heaped up as an additional protection. The earth-dike is built behind the mighty bulwark of this breakwater, and its foot also is fortified with stones." ... "The great Helder dike is about five miles long and forty feet wide at the top, along which runs a good road. It slopes down two hundred feet into the sea, at an angle of forty degrees. The highest waves do not reach the summit, the lowest always cover its base. At certain distances, immense buttresses, of a height and width proportioned to those of the dike, and even more strongly built, run several hundred feet out into the rolling sea. This gigantic artificial coast is entirely composed of Norwegian granite."--Wild, Die Niederlande, i., pp. 61, 62.] Upon the coast of Schleswig and Holstein, where the people have less capital at their command, they defend their embankments against ice and the waves by a coating of twisted straw or reeds, which must be renewed as often as once, sometimes twice a year. The inhabitants of these coasts call the chain of dikes "the golden border," a name it well deserves, whether we suppose it to refer to its enormous cost, or, as is more probable, to its immense value as a protection to their fields and their firesides. When outlying flats are enclosed by building new embankments the old interior dikes are suffered to remain, both as an additional security against the waves, and because the removal of them would be expensive. They serve, also, as roads or causeways, a purpose for which the embankments nearest the sea are seldom employed, because the whole structure might be endangered from the breaking of the turf by wheels and the hoofs of horses. Where successive rows of dikes have been thus constructed, it is observed that the ground defended by the more ancient embankments is lower than that embraced within the newer enclosures, and this depression of level has been ascribed to a general subsidence of the coast from geological causes; [Footnote: A similar subsidence of the surface is observed in the diked ground of the Lincolnshire fens, where there is no reason to suspect a general depression from geological causes.] but the better opinion seems to be that it is, in most cases, due merely to the consolidation and settling of the earth from being more effectually dried, from the weight of the dikes, from the tread of men and cattle, and from the movement of the heavy wagons which carry off the crops. [Footnote: The shaking of the ground, even when loaded with large buildings, by the passage of heavy carriages or artillery, or by the march of a body of cavalry or even infantry, shows that such causes may produce important mechanical effects on the condition of the soil. The bogs in the Netherlands, as in most other countries, contain large numbers of fallen trees, buried to a certain depth by earth and vegetable mould. When the bogs are dry enough to serve as pastures, it is observed that trunks of these ancient trees rise of themselves to the surface. Staring ascribes this singular phenomenon to the agitation of the ground by the tread of cattle. "When roadbeds," observes he, "are constructed of gravel and pebbles of different sizes, and these latter are placed at the bottom without being broken and rolled hard together, they are soon brought to the top by the effect of travel on the road. Lying loosely, they undergo some motion from the passage of every wagon-wheel and the tread of every horse that passes over them. This motion is an oscillation or partial rolling, and as one side of a pebble is raised, a little fine sand or earth is forced under it, and the frequent repetition of this process by cattle or carriages moving in opposite directions brings it at last to the surface. We may suppose that a similar effect is produced on the stems of trees in the bogs by the tread of animals."--De Bodem van Nederland, i., pp. 75, 76. It is observed in the Northern United States, that when soils containing pebbles are cleared and cultivated, and the stones removed from the surface, new pebbles, and even bowlders of many pounds weight, continue to show themselves above the ground, every spring, for a long series of years. In clayey soils the fence-posts are thrown up in a similar way, and it is not uncommon to see the lower rail of a fence thus gradually raised a foot or even two feet above the ground. This rising of stones and fences is popularly ascribed to the action of the severe frosts of that climate. The expansion of the ground, in freezing, it is said, raises its surface, and, with the surface, objects lying near or connected with it. When the soil thaws in the spring, it settles back again to its former level, while the pebbles and posts are prevented from sinking as low as before by loose earth which has fallen under them. The fact that the elevation spoken of is observed only in the spring gives countenance to this theory, which is perhaps applicable also to the cases stated by Staring, and it is probable that the two causes above assigned concur in producing the effect. The question of the subsidence of the Netherlandish coast has been much discussed. Not to mention earlier geologists, Venema, in several essays, and particularly in Het Dalen van de Noordelijke Kuststreken van ons Land, 1854, adduces many facts and arguments to prove a slow sinking of the northere provinces of Holland. Laveleye (Affaissement du sol at envasement des fleuves survenus dans les temps historiques, 1859), upon a still fuller investigation, arrives at the same conclusion. The eminent geologist Staring, however, who briefly refers to the subject in De Bodem van Nederland, i., p. 356 et seqq., does not consider the evidence sufficient to prove anything more than the sinking of the surface of the polders from drying and consolidation.--See Elisee Reclus, La Terre, vol. i., pp. 730, 732.] Notwithstanding this slow sinking, most of the land enclosed by dikes is still above low-water mark, and can, therefore, be wholly or partially freed from rain-water, and from that received by infiltration from higher ground, by sluices opened at the ebb of the tide. For this purpose the land is carefully ditched, and advantage is taken of every favorable occasion for discharging the water through the sluices. But the ground cannot be effectually drained by this means, unless it is elevated four or five feet, at least, above the level of the ebb-tide because the ditches would not otherwise have a sufficient descent to carry the water off in the short interval between ebb and flow, and because the moisture of the saturated sub-soil is always rising by capillary attraction. Whenever, therefore, the soil has sunk below the level I have mentioned, and in cases where its surface has never been raised above it, pumps, worked by wind or some other mechanical power, must be very frequently employed to keep the land dry enough for pasturage and cultivation. [Footnote: The elevation of the lands enclosed by dikes--or polders, as they are called in Holland--above low-water mark, depends upon the height of the tides or, in other words, upon the difference between ebb and flood. The tide cannot deposit earth higher than it flows, and after the ground is once enclosed, the decay of the vegetables grown upon it and the addition of manures do not compensate the depression occasional by drying and consolidation. On the coast of Zeeland and the islands of South Holland, the tides, and of course the surface of the lands deposited by them, are so high that the polders can be drained by ditching and sluices, but at other points, as in the enclosed grounds of North Holland on the Zuiderzee, where the tide rises but three feet or even less, pumping is necessary from the beginning.--Staring, Voormaals en Thans, p. 152] DRAINING OF THE LAKE OF HAARLEM. The substitution of steam-engines for the feeble and uncertain action of windmills, in driving pumps, has much facilitated the removal of water from the polders as well as the draining of lakes, marshes, and shallow bays, and thus given such an impulse to these enterprises, that not less than one hundred and ten thousand acres wore reclaimed from the waters, and added to the agricultural domain of the Netherlands, between 1815 and 1855. The most important of these undertaking was the draining of the Lake of Haarlem, and for this purpose some of the most powerful hydraulic engines over constructed were designed and executed. [Footnote: The principal engine, of 500 horse-power, drove eleven pumps with a total delivery of 31,000 cubic yards per hour.--Wild, Die Netherland, i., p. 87.] The origin of this lake is unknown. It is supposed by some geographers to be a part of an ancient bed of the Rhine, the channel of which, as there is good reason to believe, has undergone great changes since the Roman invasion of the Netherlands; by others it is thought to have once formed an inland marine channel, separated from the sea by a chain of low islands, which the sand washed up by the tides has since connected with the mainland and converted into a continuous line of coast. The best authorities, however, find geological evidence that the surface occupied by the lake was originally a marshy tract containing within its limits little solid ground, but many ponds and inlets, and much floating as well as fixed fen. In consequence of the cutting of turf for fuel, and the destruction of the few trees and shrubs which held the loose soil together with their roots, the ponds are supposed to have gradually extended themselves, until the action of the wind upon their enlarged surface gave their waves sufficient force to overcome the resistance of the feeble barriers which separated them, and to unite them all into a single lake. Popular tradition, it is true, ascribes the formation of the Lake of Haarlem to a single irruption of the sea, at a remote period, and connects it with one or another of the destructive inundations of which the Netherland chronicles describe so many; but on a map of the year 1531, a chain of four smaller waters occupies nearly the ground afterwards covered by the Lake of Haarlem, and they have most probably been united by gradual encroachments resulting from the improvident practices above referred to, though no doubt the consummation may have been hastened by floods, and by the neglect to maintain dikes, or the intentional destruction of them, in the long wars of the sixteenth century. The Lake of Haarlem was a body of water not far from fifteen miles in length, by seven in greatest width, lying between the cities of Amsterdam and Leyden, running parallel with the coast of Holland at the distance of about five miles from the sea, and covering an area of about 45,000 acres. By means of the Ij, it communicated with the Zuiderzee, the Mediterranean of the Netherlands, and its surface was little above the mean elevation of that of the sea. Whenever, therefore, the waters of the Zuiderzee were acted upon by strong north-west winds, those of the Lake of Haarlem were raised proportionally and driven southwards, while winds from the south tended to create a flow in the opposite direction. The shores of the lake were everywhere low, and though between the years 1767 and 1848 more than $1,700,000 had been expended in checking its encroachments, it often burst its barriers, and produced destructive inundations. In November, 1836, a south wind brought its waters to the very gates of Amsterdam, and in December of the same year, in a north-west gale, they overflowed twenty thousand acres of land at the southern extremity of the lake, and flooded a part of the city of Leyden. The depth of water in the lake did not, in general, exceed fourteen feet, but the bottom was a semi-fluid ooze or slime, which partook of the agitation of the waves, and added considerably to their mechanical force. Serious fears were entertained that the lake would form a junction with the inland waters of the Legmeer and Mijdrecht, swallow up a vast extent of valuable soil, and finally endanger the security of a large proportion of the land which the industry of Holland had gained in the course of centuries from the ocean. For this reason, and for the sake of the large addition the bottom of the lake would make to the cultivable soil of the state, it was resolved to drain it, and the preliminary steps for that purpose were commenced in the year 1840. The first operation was to surround the entire lake with a ring-canal and dike, in order to cut off the communication with the Ij, and to exclude the water of the streams and morasses which discharged themselves into it from the land side. The dike was composed of different materials, according to the means of supply at different points, such as sand from the coast-dunes, earth and turf excavated from the line of the ring-canal, and floating turf, [Footnote: In England and New England, where the marshes have been already drained or are of comparatively small extent, the existence of large floating islands seems incredible, and has sometimes been treated as a fable, but no geographical fact is better established. Kohl (Inseln und Marschen Schleswig-Holsteins, iii., p. 309) reminds us that Pliny mentions among the wonders of Germany the floating islands, covered with trees, which met the Roman fleets at the mouths of the Elbe and the Weser. Our author speaks also of having visited, in the territory of Bremen, floating moors, bearing not only houses but whole villages. At low stages of the water these moors rest upon a bed of sand, but are raised from six to ten feet by the high water of spring, and remain afloat until, in the course of the summer, the water beneath is exhausted by evaporation and drainage, when they sink down upon the sand again. Staring explains, in an interesting way, the whole growth, formation, and functions of floating fens or bogs, in his very valuable work, De Bodem van Nederland, i., pp. 36-43. The substance of his account is as follows: The turf and the surface of the fens, is stillness of the water. Hence they are not found in running streams, nor in pools so large as to be subject to frequent agitation by the wind. For example, not a single plant grew in the open part of the Lake of Haarlem, and fens cease to form in all pools as soon as, by the cutting of the turf for fuel or other purposes, their area is sufficiently enlarged to be much acted on by wind. When still water above a yard deep is left undisturbed, aquatic plants of various genera, such as Nuphar, Nymphaea, Limnanthemum, Stratiotes, Polygonum, and Potamogeton, fill the bottom with roots and cover the surface with leaves. Many of the plants die every year, and prepare at the bottom a soil fit for the growth of a higher order of vegetation, Phragmites, Acorus, Sparganium, Rumex, Lythrum, Pedicularis, Spiraea, Polystichum, Comarum, Caltha, etc., etc. In the course of twenty or thirty years the muddy bottom is filled with roots of aquatic and marsh plants, which are lighter than water, and if the depth is great enough to give room for detaching this vegetable network, a couple of yard for example, it rises to the surface, bearing with it, of course, the soil formed above it by decay of stems and leaves. New genera now appear upon the mass, such a Carex, Menyanthes, and others, and soon thicky cover it. The turf has now acquired a thickness of from two to four feet, and is called in Groningen lad; in Friesland, til, tilland, or drifftil; in Overijsse, krag; and in Holland, rietzod. It floats about as driven by the wind, gradually increasing in thickness by the decay of its annual crops of vegetation, and in about half a century reaches the bottom and becomes fixed. If it has not been invaded in the meantime by men or cattle, trees and arborescent plants, Alnus, Salix, Myrica, etc., appear, and these contribute to hasten the attachment of the turf to the bottom, both by their weight and by sending their roots quite through into the ground." This is the regular method employed by nature for the gradual filling up of shallow lakes and pools, and converting them first into morass and then into dry land. Whenever, therefore, man removes the peat or turf, he exerts an injurious geographical agency, and, as I have already said, there is no doubt that the immense extension of the inland seas of Holland in modern times is owing to this and other human imprudences. "Hundreds of hectares of floating pastures," says our author, "which have nothing in their appearance to distinguish them from grass-lands resting on solid bog, are found in Overijssel, in North Holland, and near Utrecht. In short, they occur in all deep bogs, and wherever deep water is left long undisturbed." In one case a floating island, which had attached itself to the shore, continued to float about for a long time after it was torn off by a flood, and was solid enough to keep a pond of fresh water upon it sweet, though the water in which it was swimming had become brackish from the irruption of the sea. After the hay is cut, cattle are pastured, and occasionally root-crops grown upon these islands, and they sometimes have large trees growing upon them. When the turf or peat has been cut, leaving water less than a yard deep, Equisetum limosum grows at once, and is followed by the second class of marsh plants mentioned above. Their roots do not become detached from the bottom in such shallow water, but form ordinary turf or peat. These processes are so rapid that a thickness of from three to six feet of turf is formed in half a century, and many men have lived to mow grass where they had fished in their boyhood, and to cut turf twice in the same spot. In Ireland the growth of peat is said to be much more rapid. Elisee Reclus, La Terre, i., 591, 592. But see Asbjornsen, Torv og Torvdrift, ii., 29, 30. Captain Gilliss says that before Lake Taguataga in Chili was drained, there were in it islands composed of dead plants matted together to a thickness of from four to six feet, and with trees of medium size growing upon them. These islands floated before the wind "with their trees and browsing cattle."--United States Naval Astronomical Expedition to the Southern Hemisphere, i., pp. 16, 17.] fascines being everywhere used to bind and compact the mass together. This operation was completed in 1848, and three steam-pumps were then employed for five years in discharging the water. The whole enterprise was conducted at the expense of the state, and in 1853 the recovered lands were offered for sale for its benefit. Up to 1858, forty-two thousand acres had been sold at not far from sixteen pounds sterling or seventy-seven dollars an acre, amounting altogether to L661,000 sterling or $3,200,000. The unsold lands were valued at more than L6,000 or nearly $30,000, and as the total cost was L764,500 or about $3,700,000, the direct loss to the state, exclusive of interest on the capital expended, may be stated at L100,000 or something less than $500,000. The success of this operation has encouraged others of like nature in Holland. The Zuid Plas, which covered 11,500 acres and was two feet deeper than the Lake of Haarlem, has been drained, and a similar work now in course of execution on an arm of the Scheld, will recover about 35,000 acres. In a country like the United States, of almost boundless extent of sparsely inhabited territory, such an expenditure for such an object would be poor economy. But Holland has a narrow domain, great pecuniary resources, an excessively crowded population, and a consequent need of enlarged room and opportunity for the exercise of industry. Under such circumstances, and especially with an exposure to dangers so formidable, there is no question of the wisdom of the measure. It has already provided homes and occupation for more than five thousand citizens, and furnished a profitable investment for a private capital of not less than L400,000 sterling or $2,000,000, which has been expended in improvements over and above the purchase money of the soil; and the greater part of this sum, as well as of the cost of drainage, has been paid as a compensation for labor. The excess of governmental expenditure over the receipts, if employed in constructing ships of war or fortifications, would have added little to the military strength of the kingdom; but the increase of territory, the multiplication of homes and firesides which the people have an interest in defending, and the augmentation of agricultural resources, constitute a stronger bulwark against foreign invasion than a ship of the line or a fortress armed with a hundred cannon. Draining of the Zuiderzee. I have referred to the draining of the Lake of Haarlem as an operation of great geographical as well as economical and mechanical interest. A much more gigantic project, of a similar character, is now engaging the attention of the Netherlandish engineers. It is proposed to drain the great salt-water basin called the Zuiderzee. This inland sea covers an area of not less than two thousand square miles, or about one million three hundred thousand acres. The seaward half, or that portion lying north-west of a line drawn from Enkhuizen to Stavoren, is believed to have been converted from a marsh to an open bay since the fifth century after Christ, and this change is ascribed, partly if not wholly, to the interference of man with the order of nature. The Zuiderzee communicates with the sea by at least six considerable channels, separated from each other by low islands, and the tide rises within the basin to the height of three feet. To drain the Zuiderzee, these channels must first be closed and the passage of the tidal flood through them cut off. If this be done, the coast currents will be restored approximately to the lines they followed fourteen or fifteen centuries ago, and thero can be little doubt that an appreciable effect will thus be produced upon all the tidal phenomena of that coast, and, of course, upon the maritime geography of Holland. A ring-dike and canal must then be constructed around the landward side of the basin, to exclude and carry off the freshwater streams which now empty into it. One of these, the Ijssel, a considerable river, has a course of eighty miles, and is, in fact, one of the outlets of the Rhine, though augmented by the waters of several independent tributaries. These preparations being made, and perhaps transverse dikes erected at convenient points for dividing the gulf into smaller portions, the water must be pumped out by machinery, in substantially the same way as in the case of the Lake of Haarlem. [Footnote: The dependence of man upon the aid of spontaneous nature, in his most arduous material works, is curiously illustrated by the fact that one of the most serious difficulties to be encountered in executing this gigantic scheme is that of procuring brushwood for the fascines to be employed in the embankments. See Diggelen's pamphlet, "Groote Werken in Nederland."] No safe calculations can be made as to the expenditure of time and money required for the execution of this stupendous enterprise, but I believe its practicability is not denied by competent judges, though doubts are entertained as to its financial expediency. [Footnote: The plan at present most in favor is that which proposes the drainage of only a portion of the southern half of the Zuiderzee, which covers not far from 400,000 acres. The project for the construction of a ship-canal directly from Amsterdam to the North Sea, now in course of execution, embraces the drainage of the Ij, a nearly land-locked basin communicating with the Zuiderzee and covering more than 12,000 acres. See official reports on these projects in Droogmaking vom het zuidelyk gedeelte der Zuiderzee, te s' Gravenhage, 1868, 4to.] The geographical results of this improvement would be analogous to those of the draining of the Lake of Haarlem, but many times multiplied in extent, and its meteorological effects, though perhaps not perceptible on the coast, could hardly fail to be appreciable in the interior of Holland. The bearing of the works I have noticed, and of others similar in character, upon the social and moral, as well as the purely economical, interests of the people of the Netherlands, has induced me to describe them more in detail than the general purpose of this volume may be thought to justify; but if we consider them simply from a geographical point of view, we shall find that they are possessed of no small importance as modifications of the natural condition of terrestrial surface. There is good reason to believe that before the establishment of a partially civilized race upon the territory now occupied by Dutch, Frisic, and Low German communities, the grounds not exposed to inundation were overgrown with dense woods; that the lowlands between these forests and the sea-coasts were marshes, covered and partially solidified by a thick matting of peat-plants and shrubs interspersed with trees; and that even the sand-dunes of the shore were protected by a vegetable growth which, in a great measure, prevented the drifting and translocation of them. The present causes of river and coast erosion existed, indeed, at the period in question; but some of them must have acted with less intensity, there were strong natural safeguards against the influence of marine and fresh-water currents, and the conflicting tendencies had arrived at a condition of approximate equilibrium, which permitted but slow and gradual changes in the face of nature. The destruction of the forests around the sources and along the valleys of the rivers by man gave them a more torrential character. The felling of the trees, and the extirpation of the shrubbery upon the fens by domestic cattle, deprived the surface of its cohesion and consistence, and the cutting of peat for fuel opened cavities in it, which, filling at once with water, rapidly extended themselves by abrasion of their borders, and finally enlarged to pools, lakes, and gulfs, like the Lake of Haarlem and the northern part of the Zuiderzee. The cutting of the wood and the depasturing of the grasses upon the sand-dunes converted them from solid bulwarks against the ocean to loose accumulations of dust, which every sea-breeze drove farther landward, burying, perhaps, fertile soil and choking up water-courses on one side, and exposing the coast to erosion by the sea upon the other. Geographical Effect of Physical Improvements in the Netherlands. The changes which human action has produced within twenty centuries in the Netherlands and the neighboring provinces, are, certainly of no small geographical importance, considered simply as a direct question of loss and gain of territory. They have also, as we shall see hereafter, undoubtedly been attended with some climatic consequences, they have exercised a great influence on the spontaneous animal and vegetable life of this region, and they cannot have failed to produce effects upon tidal and other oceanic currents, the range of which may be very extensive. The force of the tidal wave, the height to which it rises, the direction of its currents, and, in fact, all the phenomena which characterize it, as well as all the effects it produces, depend as much upon the configuration of the coast it washes, and the depth of water, and form of bottom near the shore, as upon the attraction which occasions it. Every one of the terrestrial conditions which affect the character of tidal and other marine currents has been very sensibly modified by the operations I have described, and on this coast, at least, man has acted almost as powerfully on the physical geography of the sea as on that of the land. [Footnote: See, on the influence of the artificial modification of the coast-line on tides and other marine currents, Staring, De Bodem van Nederland, i., p. 279.] Ancient Hydraulic Works. The hydraulic works of the Netherlands and of the neighboring states are of such magnitude that--with the exception of the dikes of the Mississippi--they quite throw into the shade all other known artificial arrangements for defending the land against the encroachments of the rivers and the sea, and for reclaiming to the domain of agriculture and civilization soil long covered by the waters. But although the recovery and protection of lands flooded by the sea seems to be an art wholly of Netherlandish origin, we have abundant evidence that, in ancient as well as in comparatively modern times, great enterprises more or less analogous in character have been successfully undertaken, both in inland Europe and in the less familiar countries of the East. In many cases no historical record remains to inform us when or by whom such works were constructed. The Greeks and Romans, the latter especially, were more inclined to undertake and carry out stupendous material enterprises than to boast of them; and many of the grandest and most important constructions of those nations are absolutely unnoticed by contemporary annalists, and are first mentioned by writers living after all knowledge of the epochs of the projectors of these works had perished. Thus the aqueduct known as the Pont du Gard, near Nimes, which, though not surpassing in volume or in probable cost other analogous constructions of ancient and of modern ages, is yet among the most majestic and imposing remains of ancient civil architecture, is not so much as spoken of by any Roman author, [Footnote: One reason for the silence of Roman writers in respect to great material improvements which had no immediate relation to military or political objects, is doubtless the contempt in which mechanical operations and mechanical contrivances were held by that nation of spoilers. Even the engineer, upon whose skill the attack or defence of a great city depended, was only praefectus fabrum, the master-artisan, and had no military rank or command. This prejudice continued to a late period in the Middle Ages, and the chiefs of artillery were equally without grade or title as soldiers. "The occupations of all artisans," says Cicero, "are base, and the shop can have nothing of the respectable." De Officiis, 1, i., 42. The position of the surgeon relatively to the physician, in England, is a remnant of the same prejudice, which still survives in full vigor in Italy, with regard to both trade and industry. See p. 6, ante.] and we are in absolute ignorance of the age or the construction of the remarkable tunnel cut to drain Lake Copais in Boeotia. This lake, now reduced by sedimentary deposit and the growth of aquatic and semi-aquatic vegetation to the condition of a marsh, was originally partially drained by natural subterranean outlets in the underlying limestone rock, many of which still exist. But these emissaries, or katavothra, as they are called in both ancient and modern Greek, were insufficient for the discharge of the water, and besides, they were constantly liable to be choked by earth and vegetables, and in such cases the lake rose to a height which produced much injury. To remedy this evil and secure a great accession of fertile soil, at some period anterior to the existence of a written literature in Greece and ages before the time of any prose author whose works have come down to us, two tunnels, one of them four miles long, and of course not inferior to the Torlonian emissary in length, were cut through the solid rock, and may still be followed throughout their whole extent. They were repaired in the time of Alexander the Great, in the fourth century before Christ, and their date was at that time traditionally referred to the reign of rulers who lived as early as the period of the Trojan war. One of the best known hydraulic works of the Romans is the tunnel which serves to discharge the surplus waters of the Lake of Albano, about fourteen miles from Rome. This lake, about six miles in circuit, occupies one of the craters of an extinct volcanic range, and the surface of its waters is about nine hundred feet above the sea. It is fed by rivulets and subterranean springs originating in the Alban Mount, or Monte Cavo, the most elevated peak of the volcanic group just mentioned, which rises to the height of about three thousand feet. At present the lake has no discoverable natural outlet, and it is not known that the water ever stood at such a height as to flow regularly over the lip of the crater. It seems that at the earliest period of which we have any authentic memorials, its level was usually kept by evaporation, or by discharge through subterranean channels, considerably below the rim of the basin which encompassed it, but in the year 397 B.C., the water, either from the obstruction of such channels, or in consequence of increased supplies from unknown sources, rose to such a height as to flow over the edge of the crater, and threaten inundation to the country below by bursting through its walls. To obviate this danger, a tunnel for carrying off the water was pierced at a level much below the height to which it had risen. This gallery, cut entirely with the chisel through the rock for a distance of six thousand feet, or nearly a mile and one-seventh, is still in so good condition as to serve its original purpose. The fact that this work was contemporaneous with the siege of Veii, has given to ancient annalists occasion to connect the two events, but modern critics are inclined to reject Livy's account of the matter, as one of the many improbable fables which disfigure the pages of that historian. It is, however, repeated by Cicero and by Dionysius of Halicarnassus, and it is by no means impossible that, in an age when priests and soothsayers monopolized both the arts of natural magic and the little which yet existed of physical science, the Government of Rome, by their aid, availed itself at once of the superstition and of the military ardor of its citizens to obtain their sanction to an enterprise which sounder arguments might not have induced them to approve. Still more remarkable is the tunnel cut by the Emperor Claudius to drain the Lake Fucinus, now Lago di Celano, in the former Neapolitan territory, about fifty miles eastward of Rome. This lake, as far as its history is known, has varied very considerably in its dimensions at different periods, according to the character of the seasons. It lies 2,200 feet above the sea, and has no visible outlet, but was originally either drained by natural subterranean conduits, or kept within certain extreme limits by evaporation. In years of uncommon moisture it spread over the adjacent soil and destroyed the crops; in dry seasons it retreated, and produced epidemic disease by poisonous exhalations from the decay of vegetable and animal matter upon its exposed bed. Julius Caesar had proposed the construction of a tunnel to lower the bed of the lake and provide a regular discharge for its waters, but the enterprise was not actually undertaken until the reign of Claudius, when--after a temporary failure, from errors in levelling by the engineers, as was pretended at the time, or, as now appears certain, in consequence of frauds by the contractors in the execution of the work--it was at least partially completed. From this imperfect construction, it soon got out of repair, but was restored by Hadrian, and is said to have answered its design for some centuries. [Footnote: The fact alluded to in a note on p. 97, ante, that since the opening of a communication between Lake Celano and the Garigliano by the works noticed in the text, fish, of species common in the lake, but not previously found in the river, have become naturalized in the Garigliano, is a circumstance of some weight as evidence that the emissary was not actually open in ancient times; for if the waters had been really connected, the fish of the lake would naturally have followed the descending current and established themselves in the river as they have done now.] In the barbarism which followed the downfall of the empire, it again fell into decay, and though numerous attempts were made to repair it during the Middle Ages, no tolerable success seems to have attended any of these efforts until the present generation. Draining of Lake Celano by Prince Torlonia. Works have been some years in progress and are now substantially completed, at a cost of about six millions of dollars, for restoring, or rather enlarging and rebuilding, this ancient tunnel, upon a scale of grandeur which does infinite honor to the liberality and public spirit of the projectors, and with an ingenuity of design and a constructive skill which reflect the highest credit upon the professional ability of the engineers who have planned the works and directed their execution. The length of the Roman tunnel was 18,634 feet, or rather more than three miles and a half, but as the new emissary is designed to drain the lake to the bottom, it must be continued to the lowest part of the basin. It will consequently have a length of not less than 21,000 feet, and, of course, is among the longest subterranean galleries in Europe. Many curious particulars in the design and execution of the original work have been observed in the course of the restoration, but these cannot here be noticed. The difference between the lowest and highest known levels of the surface of the lake is rather more than forty feet and the difference between the areas covered by water at these levels is not less than nine thousand acres. The complete drainage of the lake, including the ground occasionally flooded, will recover, for agricultural occupation, and permanently secure from inundation, about forty-two thousand acres of as fertile soil as any in Italy. [Footnote: Springs rising in the bottom of the lake have materially impeded the process of drainage, and some engineers believe that they will render the complete discharge of the waters impossible. It appears that the earthy and rocky strata underlying the lake are extremely porous, and that the ground already laid dry on the surface absorbs an abnormally large proportion of the precipitation upon it. These strata, therefore, constitute a reservoir which contributes to maintain the spring fed chiefly, no doubt, by underground channels from the neighboring mountains. But it is highly probable that, after a certain time, the process of natural desiccation noticed in note to p. 20, ante, will drain this reservoir, and the entire removal of the surface-water will then become practicable.] The ground already dry enough for cultivation furnishes occupation and a livelihood for a population of 16,000 persons, and it is thought that this number will be augmented to 40,000 when the drainage shall be completely effected. The new tunnel follows the line of the Claudian emissary--which though badly executed was admirably engineered--but its axis is at a somewhat lower level than that of the old gallery, and its cross-section is about two hundred and fifteen square feet, allowing a discharge of about 2,400 cubic feet to the second, while the Roman work had a cross-section of only one hundred and two square feet, with a possible delivery of 424 cubic feet to the second. In consequence of the nature of the rock and of the soil, which had been loosened and shattered by the falling in of much of the crown and walls of the old tunnel--every stone of which it was necessary to remove in the progress of the work--and the great head of water in the lake from unusually wet seasons, the technical difficulties to be surmounted were most baffling and discouraging in character, and of such extreme gravity that it may well be doubted whether the art of engineering has anywhere triumphed over more serious obstacles. This great "victory of peace"--probably the grandest work of physical improvement ever effected by the means, the energy, and the munificence of a single individual--is of no small geographical and economical, as well as sanitary, importance, but it has a still higher moral value as an almost unique example of the exercise of public spirit, courage, and perseverance in the accomplishment of a noble and beneficent enterprise by a private citizen. [Footnote: The draining of Lake Celano was undertaken by a company, but Prince Alessandro Torlonia of Rome bought up the interest of all the shareholders and has executed the entire work at his own private expense. Montricher, the celebrated constructor of the great aqueduct of Marseilles, was the engineer who designed and partly carried out the plans, and after his lamentable death the work has been directed with equal ability by Bermont and Brisse.--See Leon De Rothou, Prosciugamento del Lago Fucino, 8vo. Firenza, 1871.] The crater-lake of Nemi, in the same volcanic region as that of Albano, is also drained by a subterranean tunnel probably of very ancient construction, and the Valle-Riccia appears to have once been the basin of a lake long since laid dry, but whether by the bursting of its banks or by human art we are unable to say. The success of the Lake Celano tunnel has suggested other like improvements in Italy. A gallery has been cut, under circumstances of great difficulty, to drain Lake Agnano near Naples, and a project for the execution of a similar operation on the Lake of Perugia, the ancient Trasimenus, which covers more than 40,000 acres, is under discussion. Many similar enterprises have been conceived and executed in modern times, both for the purpose of reclaiming land covered by water and for sanitary reasons. [Footnote: A considerable work of this character is mentioned by Captain Gilliss as having been executed in Chili, a country to which we should hardly have looked for an improvement of such a nature. The Lake Taguataga was partially drained by cutting through a narrow ridge of land, not at the natural outlet, but upon one side of the lake, and eight thousand acres of land covered by it were gained for cultivation.--U. S. Naval Astronomical Expedition to the Southern Hemisphere, i., pp. 16, 17. Lake Balaton and the Neusiedler Sea in Hungary have lately been, at least partially, drained. The lakes of Neuchatel, Bienne, and Morat, in Switzerland, have been connected and the common level of all of them lowered about four feet. The works now in operation will produce, in the course of the year 1874, a further depression of four feet, and recover for agricultural use more than twelve thousand acres of fertile soil.] They are sometimes attended with wholly unexpected evils, as, for example, in the case of Barton Pond, in Vermont, and in that of a lake near Ragunda in Sweden, already mentioned on a former page. Another still less obvious consequence of the withdrawal of the waters has occasionally been observed in these operations. The hydrostatic force with which the water, in virtue of its specific gravity, presses against the banks that confine it, has a tendency to sustain them whenever their composition and texture are not such as to expose them to softening and dissolution by the infiltration of the water. If, then, the slope of the banks is considerable, or if the earth of which they are composed rests on a smooth and slippery stratum inclining towards the bed of the lake, they are liable to fall or slide forward when the mechanical support of the water is removed, and this sometimes happens on a considerable scale. A few years ago the surface of the Lake of Lungern, in the Canton of Unterwalden, in Switzerland, was lowered by driving a tunnel about a quarter of a mile long through the narrow ridge, called the Kaiserstuhl, which forms a barrier at the north end of the basin. When the water was drawn off, the banks, which are steep, cracked and burst, several acres of ground slid down as low as the water receded, and even the whole village of Lungern was thought to be in no small danger. [Footnote: In the course of the year 1864 there were slides of the banks of the Lake of Como, and in one case the grounds of a villa near the water suffered a considerable displacement. More important slips occurred at Fesiolo on the shore of Lago Maggiore in 1867 and 1869, and on the Lake of Orta in 1868. These occurrences excited some apprehensions in regard to the possible effects of projects then under discussion for lowering the level of some of the Italian lakes, to obtain an increased supply of water for irrigation and as a mechanical power, but as it was not proposed to depress the surface below the lowest natural low-water level, there seems to have been little ground for the fears expressed. See, for important observations on the character and probable results of these projects, Tagliasecchi, Nostizie etc. del Canali dell' Alta Lombardia, Milano, 1871. Jacini says: "A large proportion of the water of the lakes, instead of discharging itself by the Ticino, the Adda, the Oglio, the Mincio, filters through the silicious strata which underlie the hills, and follows subterranean channels to the plain, where it collects in the fontanili, and being thence conducted into the canals of irrigation, becomes a source of great fertility."--La Proprieta Fondiaria, etc., p.144. The quantity of water escaping from the lakes by infiltration depends much on the hydrostatic pressure on the bottom and the walls of the lake-basins, and consequently the depression of the lake surface, diminishing this pressure, would diminish the infiltration. Hence it is possible that the lowering of the level of these lakes would manifest itself in a decreased supply of water for the springs, fontanili, and wells of Lombardy.] Mountain Lakes. Other inconveniences of a very serious character have often resulted from the natural wearing down, or, much more frequently, the imprudent destruction, of the barriers which confine mountain lakes. In their natural condition, such basins serve both to receive and retain the rocks and other detritus brought down by the torrents which empty into them, and to check the impetus of the rushing waters by bringing them to a temporary pause; but if the outlets are lowered so as to drain the reservoirs, the torrents continue their rapid flow through the ancient bed of the basins, and carry down with them the sand and gravel with which they are charged, instead of depositing their burden as before in the still waters of the lakes. It is a common opinion in America that the river meadows, bottoms, or intervales, as they are popularly called, are generally the beds of ancient lakes which have burst their barriers and left running currents in their place. It was shown by Dr. Dwight, many years ago, that this is very far from being universally true; but there is no doubt that mountain lakes were of much more frequent occurrence in primitive than in modern geography, and there are many chains of such still existing in regions where man has yet little disturbed the original features of the earth. In the long valleys of the Adirondack range in Northern New York, and in the mountainous parts of Maine, eight, ten, and even more lakes and lakelets are sometimes found in succession, each emptying into the next lower pool, and so all at last into some considerable river. When the mountain slopes which supply these basins shall be stripped of their woods, the augmented swelling of the lakes will break down their barriers, their waters will run off, and the valleys will present successions of flats with rivers running through them, instead of chains of lakes connected by natural canals. A similar state of things seems to have existed in the ancient geography of France. "Nature," says Lavergne, "has not excavated on the flanks of our Alps reservoirs as magnificent as those of Lombardy; she had, however, constructed smaller but more numerous lakes, which the improvidence of man has permitted to disappear. Auguste de Gasparin demonstrated more than thirty years ago that many natural dikes formerly existed in the mountain valleys, which have been swept away by the waters." [Footnote: Economie Rurale de la France, p. 289.] Many Alpine valleys in Switzerland and Italy present unquestionable evidence of the former existence of chains of lakes in their basins, and this may be regarded as a general fact in regard to the primitive topography of mountainous regions. Where the forests have not been destroyed, the lakes remain as characteristic features of the geographical surface. But when the woods are felled, these reservoirs are sooner or later filled up by wash from the shores, and of course disappear. Geologists have calculated the period when the bottom of the Lake of Geneva will be levelled up and its outlet worn down. The Rhone will then flow, in an unbroken current, from its source in the great Rhone glacier to the Mediterranean Sea. Draining of Swamps. The reclamation of bogs and swamps by draining off the surface-water is doubtless much more ancient than the draining of lakes. The beneficial results of the former mode of improvement are more unequivocal, and balanced by fewer disadvantages, and, at the same time, the processes by which it is effected are much simpler and more obvious. It has accordingly been practised through the whole historical period, and in recent times operations for this purpose have assumed a magnitude, and been attended with economical as well as sanitary and geographical effects, which entitle them to a high place in the efforts of man to ameliorate the natural conditions of the soil he occupies. The methods by which the draining of marshes is ordinarily accomplished are too familiar, and examples of their successful employment too frequent, to require description, and I shall content myself, for the moment, with a brief notice of some recent operations of this sort which are less generally known than their importance merits. Within the present century more than half a million acres of swamp-land have been drained and brought under cultivation in Hungary, and works are in progress which will ultimately recover a still larger area for human use. The most remarkable feature of these operations, and at the same time the process which has been most immediately successful and remunerative, is what is called in Europe the regulation of water-courses, and especially of the River Theiss, on the lower course of which stream alone not less than 250,000 acres of pestilential and wholly unproductive marsh have been converted into a healthful region of the most exuberant fertility. The regulation of a river consists in straightening its channel by cutting off bends, securing its banks from erosion by floods, and, where necessary, by constructing embankments to confine the waters and prevent them from overflowing and stagnating upon the low grounds which skirt their current. In the course of the Theiss about sixty bends, including some of considerable length, have been cut off, and dikes sufficient for securing the land along its banks against inundation have been constructed. Many thousand acres of land have been recently permanently improved in Italy by the draining of swamps, and extensive operations have been projected and commenced on the lower Rhone, and elsewhere in France, with the same object. [Footnote: Very interesting and important experiments, on the practicability of washing out the salt from seacoast lands too highly impregnated with that mineral to be fit for cultivation, are now in progress near the mouth of the Rhone, where millions of acres of marshy soil can easily be recovered, if these experiments are successful. See Duponchel, Traite d'Hydraulique et de Geologie agricoles. Paris, 1868, chap. xi. and xii. In the neighborhood of Ferrara are pools and marshes covering nearly two hundred square miles, or a surface more than equal to eight American townships. Centrifugal steam-pumps, of 2,000 horse-power, capable of discharging more than six hundred and fifty millions of gallons of water per day have lately been constructed in England for draining these marshes. This discharge is equal to an area of 640 acres, or a mile square, with nearly three feet of water.] But there is probably no country where greater improvements of this sort have either been lately effected, or are now in course of accomplishment, than in our own. Not to speak of well-known works on the New Jersey seacoast and the shores of Lake Michigan, the people of the new State of California are engaging in this mode of subduing nature with as much enterprise and energy as they have shown in the search for gold. The Report of the Agricultural Department of the United States for January, 1872, notices, with more or less detail, several highly successful experiments in California in the way of swamp-drainage and securing land from overflow, and it appears that not far from 200,000 acres have either very recently undergone or will soon be subjected to this method of improvement. Agricultural Draining. I have commenced this chapter with a description of the dikes and other hydraulic works of the Netherland engineers, because both the immediate and the remote results of such operations are more obvious and more easily measured, though certainly not more important, than those of much older and more widely diffused modes of resisting or directing the flow of waters, which have been practised from remote antiquity in the interior of all civilized countries. Draining and irrigation are habitually regarded as purely agricultural processes, having little or no relation to technical geography; but we shall find that they exert a powerful influence on soil, climate, and animal and vegetable life, and may, therefore, justly claim to be regarded as geographical elements. Superficial draining is a necessity in all lands newly reclaimed from the forest. The face of the ground in the woods is never so regularly inclined as to permit water to flow freely over it. There are, even on the hillsides, small ridges depressions, partly belonging to the original distribution of the soil, and partly occasioned by irregularities in the growth and deposit of vegetable matter. These, in the husbandry of nature, serve as dams and reservoirs to collect a larger supply of moisture than the spongy earth can at once imbibe. Besides this, the vegetable mould is, even under the most favorable circumstances, slow in parting with the humidity it has accumulated under the protection of the woods, and the infiltration from neighboring forests contributes to keep the soil of small clearings too wet for the advantageous cultivation of artificial crops. For these reasons, surface draining must have commenced with agriculture itself, and there is probably no cultivated district, one may almost say no single field, which is not provided with artificial arrangements for facilitating the escape of superficial water, and thus carrying off moisture which, in the natural condition of the earth, would have been imbibed by the soil. All these processes belong to the incipient civilization of the ante-historical periods, but the construction of subterranean channels for the removal of infiltrated water marks ages and countries distinguished by a great advance in agricultural theory and practice, a great accumulation of pecuniary capital and a density of population which creates a ready demand and a high price for all products of rural industry. Under draining, too, would be most advantageous in damp and cool climates, where evaporation is slow, and upon soils where the natural inclination of surface does not promote a very rapid flow of the surface-waters. All the conditions required to make this mode of rural improvement, if not absolutely necessary, at least profitable, exist in Great Britain, and it is, therefore, very natural that the wealthy and intelligent farmers of England should have carried this practice farther, and reaped a more abundant pecuniary return from it, than those of any other country. Besides superficial and subsoil drains, there is another method of disposing of superfluous surface-water, which, however, can rarely be practised, because the necessary conditions for its employment are not of frequent occurrence. Whenever a tenacious water-holding stratum rests on a loose, gravelly bed so situated as to admit of a free discharge of water from or through it by means of the outcropping of the bed at a lower level, or of deep-lying conduits leading to distant points of discharge, superficial waters may be carried off by opening a passage for them through the impervious into the permeable stratum. Thus, according to Bischof, as early as the time of King Rene, in the first half of the fifteenth century, when subsoil drainage was scarcely known, the plain of Paluns, near Marseilles, was laid dry by boring, and Wittwer informs us that drainage is effected at Munich by conducting the superfluous water into large excavations, from which it filters through into a lower stratum of pebble and gravel lying a little above the level of the river Isar. [Foonote: Physikalische Geographie, p. 288. This method is now frequently employed in France. Details as to the processes will be found in Mangon Pratique du Drainage, pp. 78 et seqq. Draining by driving down stakes mentioned in a note in the chapter on the Woods, ante, is a process of the same nature. In the United States, large tracts of marshy ground, and even shallow lakes of considerable extent, have been sufficiently drained not only for pasturage but for cultivation, without resort to any special measures for effecting that end. The ordinary processes of rural improvement in the vicinity, such as felling woods upon and around such grounds, and the construction of roads, the side ditches of which act as drains, over or near them, aided now and then by the removal of a fallen tree or other accidental obstruction in the beds of small streams which flow from them, often suffice to reclaim miles square of unproductive swamp and water. See notes on p. 20, and on cedar swamps, p. 208, ante.] So at Washington, in the western part of the city, which lies high above the rivers Potomac and Rock Creek, many houses are provided with dry wells for draining their cellars and foundations. These extend through hard, tenacious earth to the depth of thirty or forty feet, when they strike a stratum of gravel, through which the water readily passes off. This practice has been extensively employed at Paris, not merely for carrying off ordinary surface-water, but for the discharge of offensive and deleterious fluids from chemical and manufacturing establishments. A well of this sort received, in the winter of 1832-'33, twenty thousand gallons per day of the foul water from a starch factory, and the same process was largely used in other factories. The apprehension of injury to common and artesian wells and springs led to an investigation on this subject by Girard and Parent Duchatelet, in the latter year. The report of these gentlemen, published in the Annales des Ponts et Chaussees for 1833, second half-year, is full of curious and instructive facts respecting the position and distribution of the subterranean waters under and near Paris; but it must suffice to say that the report came to the conclusion that, in consequence of the absolute immobility of these waters, and the relatively small quantity of noxious fluid to be conveyed to them, there was no danger of the diffusion of such fluid if discharged into them. This result will not surprise those who know that, in another work, Duchatelet maintains analogous opinions as to the effect of the discharge of the city sewers into the Seine or the waters of that river. The quantity of matter delivered by them he holds to be so nearly infinitesimal, as compared with the volume of water of the river, that it cannot possibly affect it to a sensible degree, and therefore cannot render the Seine water unfit for drinking. [Foonote: Coste found, in his experiments on pisciculture, that the fermentation, which takes place in the water of the Seine in consequence of the discharge of the drains into the river, destroyed a large proportion of the eggs of fish in his breeding basins. Analysis of Seine water by Boussingault in 1855 detected a considerable quantity of ammonia.] Meteorological Effects of Draining. The draining of lakes diminishes the water-surface of the soil, and consequently, in many cases, the evaporation from it, as well as the refrigeration which attends all evaporation. [Footnote: The relative evaporating action of earth and water is a very complicated problem, and the results of observation on the subject are conflicting. Schubler found that at Geneva the evaporation from bare loose earth, in the months of December, January, and February, was from two and a half to nearly six times as great as from a like surface of water in the other months. The evaporation from water was from about once and a half to six times as great as from earth. Taking the whole year together, the evaporation from the two surfaces was 199 lines from earth and 536 lines from water. Experiments by Van der Steer, at the Helder, in the years 1861 and 1862, showed, for the former year, an evaporation of 602.9 millimetres from water, 1399.6 millimetres from ground covered with clover and other grasses; in 1862, the evaporation from water was 584.5 millimetres, from grassground, 875.5. --Wilhelm, Der Boden und das Wasser, p. 57; Krecke, Het Klimaat van Nederland, ii., p. 111. On the other hand, the evaporation from the Nile in Egypt and Nubia is stated to be three times as great as that from an equal surface of the soil which borders it.--Lombardini, Saggio Idrologico sul Nilo, Milano, 1864, and Appendix. The relative thermometrical conditions of land and water in the same vicinity are constantly varying, and the hygrometrical state of both is equally unstable. Consequently there is no general formula to express the proportionate evaporation from fluid and solid geographical surfaces.] On the other hand, if the volume of water abstracted is great, its removal deprives its basin of an equalizing and moderating influence; for large bodies of water take very slowly the temperature of the air in contact with their surface, and are almost constantly either sending off heat into the atmosphere or absorbing heat from it. Besides, as we have seen, lakes in elevated positions discharge more or less water by infiltration, and contribute it by the same process to other lakes, to springs, and to rivulets, at lower levels. Hence the draining of lakes, on a considerable scale, must modify both the humidity and the temperature of the atmosphere of the neighboring regions, and the permanent supply of ground-water for the lands lying below them. Meteorological Action of Marshes. The shallow water of marshes, indeed, performs this latter function, but, under ordinary circumstances, marshes exercise in but a very small degree the compensating meteorological action which I have ascribed to large expansions of deeper water. The direct rays of the sun and the warmth of the atmosphere penetrate to the soil beneath, and raise the temperature of the water which covers it; and there is usually a much greater evaporation from marshes than from lakes in the same region during the warmer half of the year. This evaporation implies refrigeration, and consequently the diminution of evaporation by the drainage of swamps tends to prevent the lowering of the atmospheric temperature, and to lessen the frequency and severity of frosts. Accordingly it is a fact of experience that, other things being equal, dry soils, and the air in contact with them, are perceptibly warmer during the season of vegetation, when evaporation is most rapid, than moist lands and the atmospheric stratum resting upon them. Instrumental observation on this special point has not yet been undertaken on a large scale, but still we have thermometric data sufficient to warrant the general conclusion, and the influence of drainage in diminishing the frequency of frost appears to be even better established than a direct increase of atmospheric temperature. The steep and dry uplands of the Green Mountain range in New England often escape frosts when the Indian-corn harvest on moister grounds, five hundred or even a thousand feet lower, is destroyed or greatly injured by them. The neighborhood of a marsh is sure to be exposed to late spring and early autumnal frosts, but they cease to be feared after it is drained, and this is particularly observable in very cold climates, as, for example, in Lapland. [Footnote: "The simplest backwoodsman knows by experiences that all cultivation is impossible in the neighborhood of bogs and marshes. Why is a crop near the borders of a marsh out off by frost, while a field upon a hillock, a few stone's throws from it, is spared "--Lars Levi Laestadius, Om Uppoldingar Lappmarrken, pp. 69, 74.] In England, under-drains are not generally laid below the reach of daily variations of temperature, or below a point from which moisture, if not carried off by the drains, might be brought to the surface by capillary attraction, and evaporated by the heat of the sun. They, therefore, like surface-drains, withdraw from local solar action much moisture which would otherwise be vaporized by it, and, at the same time, by drying the soil above them, they increase its effective hygroscopicity, and it consequently absorbs from the atmosphere a greater quantity of water than it did when, for want of under-drainage, the subsoil was always humid, if not saturated. [Footnote: Mangon thinks that the diminution of evaporation by agricultural drainage corresponds, in certain circumstances, to five per cent. of the heat received from the sun by the same surface in a year. He cites observations by Parkes, showing a difference in temperature of 5.5 degrees (centigrade ) in favor of drained, as compared with undrained, ground in the same vicinity.--Instructions pratiques sur le Drainage, pp. 227, 228. The diminution of evaporation is not the only mode in which under-draining affects the temperature. The increased effective hygroscopicity of the soil increases its absorbent action, and the condensation of atmospheric vapor thus produced is attended with the manifestation of heat.] Under-drains, then, contribute to the dryness as well as to the warmth of the atmosphere, and, as dry ground is more readily heated by the rays of the sun than wet, they tend also to raise the mean, and especially the summer, temperature of the soil. Effects of Draining Lake of Haarlem. The meteorological influence of the draining of lakes and of humid soils has not, so far as I know, received much attention from experimental physicists; but we are not altogether without direct proof in support of theoretical and a priori conclusions. Thermometrical observations have been regularly made at Zwanenburg, near the northern extremity of the Lake of Haarlem, for more than a century; and since 1845 a similiar registry has been kept at the Helder, forty or fifty miles more to the north. In comparing these two series of observations, it is found that towards the end of 1852, when the draining of the lake was finished, and the following summer had completely dried the newly exposed soil--and, of course, greatly diminished the water-surface--a change took place in the relative temperature of those two stations. Taking the mean of each successive period of five days, from 1845 to 1852, both inclusive, the temperature of Zwanenburg was thirty-three hundredths of a degree centigrade LOWER than at the Helder. From the end of 1852 the thermometer at Zwanenburg has stood, from the 11th of April to the 20th of September, twenty-two hundredths of a degree HIGHER than that at Helder; but from the 14th of October to the 17th of March, it has marked one-tenth of a degree LOWER than its mean between the same dates before 1853. [Footnote: Krecke, Het Klimaat van Nederland, ii., p. 64.] There is no reason to doubt that these differences are due to the draining of the lake. In summer, solar irradiation has acted more powerfully on the now exposed earth and of course on the air in contact with it; and there is no longer a large expanse of water still retaining and of course imparting something of the winter temperature; in winter, the earth has lost more heat by radiation than when covered by water and the influence of the lake, as a reservoir of warmth accumulated in summer and gradually given out in winter, was of course lost by its drainage. Doubtless the quantity of moisture contained in the atmosphere has been modified by the same cause, but it does not appear that observations have been made upon this point. Facts lately observed by Glaisher tend to prove an elevation of not far from two degrees in the mean temperature of England during the course of the last hundred years. For reasons which I have explained elsewhere, the early observations upon which these conclusions are founded do not deserve entire confidence; but admitting the fact of the alleged elevation, its most probable explanation would be found in the more thorough draining of the soil by superficial and by subterranean conduits. So far as respects the immediate improvement of soil and climate, and the increased abundance of the harvests, the English system of surface and subsoil drainage has fully justified the eulogiums of its advocates; but its extensive adoption appears to have been attended with some altogether unforeseen and undesirable consequences, very analogous to those which I have described as resulting from the clearing of the forests. The under-drains carry off very rapidly the water imbibed by the soil from precipitation, and through infiltration from neighboring springs or other sources of supply. Consequently, in wet seasons, or after heavy rains, a river bordered by artificially drained lands receives in a few hours, from superficial and from subterranean conduits, an accession of water which, in the natural state of the earth, would have reached it only by small instalments after percolating through hidden paths for weeks or even months, and would have furnished perennial and comparatively regular contributions, instead of swelling deluges, to its channel. Thus, when human impatience rashly substitutes swiftly acting artificial contrivances for the slow methods by which nature drains the surface and superficial strata of a river-basin, the original equilibrium is disturbed, the waters of the heavens are no longer stored up in the earth to be gradually given out again, but are hurried out of man's domain with wasteful haste; and while the inundations of the river are sudden and disastrous, its current, when the drains have run dry, is reduced to a rivulet, it ceases to supply the power to drive the machinery for which it was once amply sufficient, and scarcely even waters the herds that pasture upon its margin. The water of subterranean currents and reservoirs, as well as that of springs and common wells, is doubtless principally furnished by infiltration, and hence its quantity must vary with every change of natural surface which tends to accelerate or to retard the drainage of the surface-soil. The drainage of marshes, therefore, and all other methods of drying the superficial strata, whether by open ditches or by underground tubes or drains, has the same effect as clearing off the forest in depriving the subterranean waters of accessions which they would otherwise receive by infiltration, and in proportion as the sphere of such operation is extended, their influence will make itself felt in the diminished supply of water in springs and wells. [Footnote: Babinet condemns the general draining of marshes. "Draining," says he, "has been much in vogue for some years, and it has been a special object to dry and fertilize marshy grounds. I believe that excessive dryness is thus produced, and that other soils in the neighborhood are sterilized in proportion."--Etudes et Lectures, iv., p. 118. "The extent of soil artificially dried by drainage is constantly increasing, and the water received by the surface from precipitation flows off by new channels, and is in general carried off more rapidly than before. Must not this fact exercise an influence on the regime of springs whose basin of supply thus undergoes a more or less complete transformation "--Bernhard Cotta, Preface to Paramelle, Quellenkunde, p. vii., viii. The effects of agricultural drainage are perceptible at great depths. It has been observed in Cornwall that deep mines are more free from water in well-drained districts than in those where drainage is not generally practised.--Esquiros, Revue des Deux Mondes, 15 Nov., 1863, p. 430. See also Asbjornsen, Torv og Torvdrift, p. 31.] Geographical and Meteorological Effects of Aqueducts, Reservoirs, and Canals. Many of the great processes of internal improvement, such as aqueducts for the supply of great cities, railroad cuts and embankments, and the like, divert water from its natural channels and affect its distribution and ultimate discharge. The collecting of the waters of a considerable district into reservoirs, to be thence carried off by means of aqueducts, as, for example, in the forest of Belgrade, near Constantinople, deprives the grounds originally watered by the springs and rivulets of the necessary moisture, and reduces them to barrenness. [Footnote: See a very interesting paper on the Water-Supply of Constantinople, by Mr. Homes, of the New York State Library, in the Albany Argus of June 6, 1872. The system of aqueducts for the supply of water to that city was commenced by Constantine, and the great aqueduct, frequently ascribed to Justinian, which is 840 feet long and 112 feet high, is believed to have been constructed during the reign of the former emperor.] Similar effects must have followed from the construction of the numerous aqueducts which supplied ancient Rome with such a profuse abundance of water. [Footnote: The unhealthiness of the Roman Campagna is ascribed by many mediaeval as well as later writers to the escape of water from the ancient aqueducts, which had fallen out of repair from neglect, or been broken down by enemies in the sieges of Rome.] On the other hand, the filtration of water through the banks or walls of an aqueduct carried upon a high level across low ground, often injures the adjacent soil, and is prejudicial to the health of the neighboring population; and it has been observed in Switzerland and elsewhere, that fevers have been produced by the stagnation of the water in excavations from which earth had been taken to form embankments for railways. If we consider only the influence of physical improvements on civilized life, we shall perhaps ascribe to navigable canals a higher importance, or at least a more diversified influence, than to aqueducts or to any other works of man designed to control the waters of the earth, and to affect their distribution. They bind distant regions together by social ties, through the agency of the commerce they promote; they facilitate the transportation of military stores and engines, and of other heavy material connected with the discharge of the functions of government; they encourage industry by giving marketable value to raw material and to objects of artificial elaboration which would otherwise be worthless on account of the cost of conveyance; they supply from their surplus waters means of irrigation and of mechanical power; and, in many other ways, they contribute much to advance the prosperity and civilization of nations. Nor are they wholly without geographical importance. They sometimes drain lands by conveying off water which would otherwise stagnate on the surface, and, on the other hand, like aqueducts, they render the neighboring soil cold and moist by the percolation of water through their embankments; [Footnote: Sismondi, speaking of the Tuscan canals, observes: "But inundations are not the only damage caused by the waters to the plains of Tuscany. Raised, as the canals are, above the soil, the water percolates through their banks, penetrates every obstruction, and, in spite of all the efforts of industry, sterilizes and turns to morasses fields which nature and the richness of the soil seemed to have designed for the most abundant harvests. In ground thus pervaded with moisture, or rendered COLD, as the Tuscans express it, by the filtration of the canal-water, the vines and the mulberries, after having for a few years yielded fruit of a saltish taste, rot and perish. The wheat decays in the ground, or dies as soon as it sprouts. Winter crops are given up, and summer cultivation tried for a time; but the increasing humidity, and the saline matter communicated to the earth--which affects the taste of all its products, even to the grasses, which the cattle refuse to touch--at last compel the husbandman to abandon his fields and leave uncultivated a soil that no longer repays his labor."--Tableau de l'Agriculture Toscane, pp. 11, 12.] they dam up, check, and divert the course of natural currents, and deliver them at points opposite to, or distant from, their original outlets; they often require extensive reservoirs to feed them thus retaining through the year accumulations of water--which would otherwise run off, or evaporate in the dry season--and thereby enlarging the evaporable surface of the country; and we have already seen that they interchange the flora and the fauna of provinces widely separated by nature. All these modes of action certainly influence climate and the character of terrestrial surface, though our means of observation are not yet perfected enough to enable us to appreciate and measure their effects. Antiquity of Irrigation. We know little of the history of the extinct civilizations which preceded the culture of the classic ages, and no nation has, in modern times, spontaneously emerged from barbarian and created for itself the arts of social life. [Footnote: I ought perhaps to except the Mexicans and the Peruvians, whose arts and institutions are not yet shown to be historically connected with those of any more ancient people. The lamentable destruction of so many memorials of these tribes, by the ignorance and bigotry of the so-called Christian barbarians who conquered them, has left us much in the dark as to many points of their civilization; but they seem to have reached that stage where continued progress in knowledge and in power over nature is secure, and a few more centuries of independence might have brought them to originate for themselves most of the great inventions which the last four centuries have bestowed upon man.] The improvements of the savage races whose history we can distinctly trace are borrowed and imitative, and our theories as to the origin and natural development of industrial art are conjectural. Of course, the relative antiquity of particular branches of human industry depends much upon the natural character of soil, climate, and spontaneous vegetable and animal life in different countries; and while the geographical influence of man would, under given circumstances, be exerted in one direction, it would, under different conditions, act in an opposite or a diverging line. I have given some reasons for thinking that in the climates to which our attention has been chiefly directed, man's first interference with the natural arrangement and disposal of the waters was in the way of drainage of surface. But if we are to judge from existing remains alone, we should probably conclude that irrigation is older than drainage; for, in the regions regarded by general tradition as the cradle of the human race, we find traces of canals evidently constructed for the former purpose at a period long preceding the ages of which we have any written memorials. There are, in ancient Armenia, extensive districts which were already abandoned to desolation at the earliest historical epoch, but which, in a yet remoter antiquity, had been irrigated by a complicated and highly artificial system of canals, the lines of which can still be followed; and there are, in all the highlands where the sources of the Euphrates rise, in Persia, in Egypt, in India, and in China, works of this sort which must have been in existence before man had begun to record his own annals. In warm countries, such as most of those just mentioned, the effects I have described as usually resulting from the clearing of the forests would very soon follow. In such climates, the rains are inclined to be periodical; they are also violent, and for these reasons the soil would be parched in summer and liable to wash in winter. In these countries, therefore, the necessity for irrigation must soon have been felt, and its introduction into mountainous regions like Armenia must have been immediately followed by a system of terracing, or at least scarping the hillsides. Pasture and meadow, indeed, may be irrigated even when the surface is both steep and irregular, as may be observed abundantly on the Swiss as well as on the Piedmontese slope of the Alps; but in dry climates, ploughland and gardens on hilly grounds require terracing, both for supporting the soil and for administering water by irrigation, and it should be remembered that terracing, of itself, even without special arrangements for controlling the distribution of water, prevents or at least checks the flow of rain-water, and gives it time to sink into the ground instead of running off over the surface. The summers in Egypt, in Syria, and in Asia Minor and even Rumelia, are almost rainless. In such climates, the neccssity of irrigation is obvious, and the loss of the ancient means of furnishing it helps to explain the diminished fertility of most of the countries in question. [Footnote: In Egypt, evaporation and absorption by the earth are so rapid, that all annual crops require irrigation during the whole period of their growth. As fast as the water retires by the subsidence of the annual inundation, the seed is sown upon the still moist, uncovered soil, and irrigation begins at once. Upon the Nile, you hear the creaking of the water-wheels, and sometimes the movement of steam-pumps, through the whole night, while the poorer cultivators unceasingly ply the simple shadoof, or bucket-and-sweep, laboriously raising the water from trough to trough by as many as six or seven stages when the river is low. The bucket is of flexible leather, with a stiff rim, and is emptied into the trough, not by inverting it like a wooden bucket, but by putting the hand beneath and pushing the bottom up till the water all runs out over the brim, or, in other words, by turning the vessel inside out. The quantity of water thus withdrawn from the Nile is enormous. Most of this is evaporated directly from the surface or the superficial strata, but some moisture percolates down and oozes through the banks into the river again, while a larger quantity sinks till it joins the slow current of infiltration by which the Nile water pervades the earth of the valley to the distance, at some points, of not less than fifty miles.] The surface of Palestine, for example, is composed, in a great measure, of rounded limestone hills, once, no doubt, covered with forests. These were partially removed before the Jewish conquest. [Footnote: "Forests," "woods," and "groves," are frequently mentioned in the Old Testament as existing at particular places, and they are often referred to by way of illustration, as familiar objects. "Wood" is twice spoken of as a material in the New Testament, but otherwise--at least according to Cruden--not one of the above words occurs in that volume. In like manner, while the box, the cedar, the fir, the oak, the pine, "beams," and "timber," are very frequently mentioned in the Old Testament, not one of these words is found in the New, EXCEPT the case of the "beam in the eye," in the parable in Matthew and Luke. This interesting fact, were other evidence wanting, would go far to prove that a great change had taken place in this respect between the periods when the Old Testament and the New were respectively composed; for the scriptural writers, and the speakers introduced into their narratives, are remarkable for their frequent allusions to the natural objects and the social and industrial habits which characterized their ages and their country.] When the soil began to suffer from drought, reservoirs to retain the waters of winter were hewn in the rock near the tops of the hills, and the declivities were terraced. So long as the cisterns were in good order, and the terraces kept up, the fertility of Palestine was unsurpassed, but when misgovernment and foreign and intestine war occasioned the neglect or destruction of these works--traces of which still meet the traveller's eye at every step,--when the reservoirs were broken and the terrace walls had fallen down, there was no longer water for irrigation in summer, the rains of winter soon washed away most of the thin layer of earth upon the rocks, and Palestine was reduced almost to the condition of a desert. The course of events has been the same in Idumaea. The observing traveller discovers everywhere about Petra, particularly if he enters the city by the route of Wadi Ksheibeh, very extensive traces of ancient cultivation, and upon the neighboring ridges are the ruins of numerous cisterns evidently constructed to furnish a supply of water for irrigation. [Footnote: One of these on Mount Hor, two stories deep, is in such good preservation, although probably not repaired for many centuries, that I found ten feet of water in it in June, 1851.] In primitive ages, the precipitation of winter in these hilly countries was, in great part, retained for a time in the superficial soil, first by the vegetable mould of the forests, and then by the artificial arrangements I have described. The water imbibed by the earth was partly taken up by direct evaporation, partly absorbed by vegetation, and partly carried down by infiltration to subjacent strata which gave it out in springs at lower levels, and thus a fertility of soil and a condition of the atmosphere were maintained sufficient to admit of the dense population that once inhabited those now arid wastes. At present, the rain-water runs immediately off from the surface and is carried down to the sea, or is drunk up by the sands of the wadis, and the hillsides which once teemed with plenty are bare of vegetation, and seared by the scorching winds of the desert. In fact, climatic conditions render irrigation a necessity in all the oriental countries which have any importance in ancient or in modern history, and there can be no doubt that this diffusion of water over large surfaces has a certain reaction on climate. Some idea of the extent of artificially watered soil in India may be formed from the fact that in fourteen districts of the Presidency of Madras, not less than 43,000 reservoirs, constructed by the ancient native rulers for the purpose of irrigation, are now in use, and that there are in those districts at least 10,000 more which are in ruins and useless. These reservoirs are generally formed by damming the outlets of natural valleys; and the dams average half a mile in length, though some of them are thirty miles long and form ponds covering from 37,000 to 50,000 acres. The areas of these reservoirs alone considerably increase the water-surface, and each one of them irrigates an extent of cultivated ground much larger than itself. Hence there is a great augmentation of humid surface from those constructions. [Footnote: The present government of India obtains the same result more economically and advantageously by constructing in many provinces of that vast empire canals of great length and capacity, which not only furnish a greater supply of water than the old reservoirs, but so distribute it as to irrigate a larger area than could be watered by any system of artificial basins. The excavacations for the Ganges Canal were nearly equal to those for the Suez Canal, falling little short of 100,000 cubic yards, without counting feeders and accessory lines amounting to a length of 3,000 miles. This canal, according to a recent article in the London Times, waters a tract of land 320 miles long by 50 broad. The Jumna Canal, 130 miles long, with 608 miles of distributing branches, waters a territory 120 miles long with a breadth of 15 miles. Other statements estimate the amount of land actually under irrigation in British India at 6,000,000 acres, and add that canals now in construction will water as much more. The Indian irrigation canals are generally navigable, some of them by boats of large tonnage, and the canals return a net revenue of from five to twenty per cent. on their cost.] The cultivable area of Egypt, or the space between desert and desert where cultivation would be possible, is now estimated at ten thousand square statute miles. [Footnote: The area which the waters of the Nile, left to themselves, would now cover is greater than it would have been in ancient times, because the bed of the river has been elevated, and consequently the lateral spread of the inundation increased. See Smith's Dictionary of Geography, article "Aegyptus". But the industry of the Egyptians in the days of the Pharaohs and the Ptolemies carried the Nile-water to large provinces, which have now been long abandoned and have relapsed into the condition of desert. "Anciently," observes the writer of the article "Egypt" in Smith's Dictionary of the Bible, "2,735 square miles more [about 3,700 square statute miles] may have been cultivated. In the best days of Egypt, probably all the land was cultivated that could be made available for agricultural purposes, and hence we may estimate the ancient arable area of that country at not less than 11,000 square statute miles, or fully double its present extent." According to an article in the Bollettino della Societa Geografica Italiana, vol. v., pt. iii., p. 210, the cultivated soil of Egypt in 1869 amounted to 4,500,000 acres, and the remaining soil capable of cultivation was estimated at 2,000,000 acres.] Much of the surface, though not out of the reach of irrigation, lies too high to be economically watered, and irrigation and cultivation are therefore at present confined to an area of seven thousand square miles, nearly the whole of which is regularly and constantly watered when not covered by the inundation, except in the short interval between the harvest and the rise of the waters. For nearly half of the year, then, irrigation adds seven thousand square miles to the humid surface of the Nile valley, or, in other words, more than decuples the area from which an appreciable quantity of moisture would otherwise be evaporated; for after the Nile has retired within its banks, its waters by no means cover one-tenth of the space just mentioned. The Nile receives not a single tributary in its course below Khartoum; there is not so much as one living spring in the whole land, [Footnote: The so-called spring at Heliopolis is only a thread of water infiltrated from the Nile or the canals.] and, with the exception of a narrow strip of coast, where the annual precipitation is said to amount to six inches, the fall of rain in the territory of the Pharaohs is not two inches in the year. The subsoil of the whole valley is pervaded with moisture by infiltration from the Nile, and water can everywhere be found at the depth of a few feet. Were irrigation suspended, and Egypt abandoned, as in that case it must be, to the operations of nature, there is no doubt that trees, the roots of which penetrate deeply, would in time establish themselves on the deserted soil, fill the valley with verdure, and perhaps at last temper the climate, and even call down abundant rain from the heavens. [Footnote: The date and the doum palm, the sont and many other acacias, the caroub, the sycamore and other trees grow in Egypt without irrigation, and would doubtless spread through the entire valley in a few years.] But the immediate effect of discontinuing irrigation would be, first, an immense reduction of the evaporation from the valley in the dry season, and then a greatly augmented dryness and heat of the atmosphere. Even the almost constant north wind--the strength of which would be increased in consequence of these changes--would little reduce the temperature of the narrow cleft between the burning mountains which hem in the channel of the Nile, so that a single year would transform the most fertile of soils to the most barren of deserts, and render uninhabitable a territory that irrigation makes capable of sustaining as dense a population as has ever existed in any part of the world. [Footnote: Wilkinson states that the total population, which, two hundred years ago, was estimated at 4,000,000, amounted till lately to only about 1,800,000 souls, having been reduced since the year 1800 from 2,500,000 to less than 2,000,000.--Handbook for Travellers in Egypt. p. 10. The population at the end of the year 1869 is computed at 5,215,000.--Bollettino della Soc. Geog. Ital., vol. v., pt. iii., p. 215. This estimate doubtless includes countries bordering on the upper Nile not embraced in Wilkinson's statistics.] Whether man found the valley of the Nile a forest, or such a waste as I have just described, we do not historically know. In either case, he has not simply converted a wilderness into a garden, but has unquestionably produced extensive climatic change. [Footnote: Ritter supposes Egypt to have been a sandy desert when it was first occupied by man. "The first inhabitant of the sandy valley of the Nile was a desert-dweller, as his neighbors right and left, the Libyan, the nomade Arab, still are. But the civilized people of Egypt transformed, by canals, the waste into the richest granary of the world; they liberated themselves from the shackles of the rock and sand desert, in the midst of which, by a wise distribution of the fluid through the solid geographical form, by irrigation in short, they created a region of culture most rich in historical monuments."--Einleitung zur allgemeinen vergleichenden Geographie, pp. 165, 166. This view seems to me highly improbable; for great rivers, in warm climates, are never bordered by sandy plains. A small stream may be swallowed up by sands, but if the volume of water is too large to be carried off by evaporation or drank up by absorption, it saturates its banks with moisture, and unless resisted by art, converts them into marshes covered with aquatio vegetation. By canals and embankments, man has done much to modify the natural distribution of the waters of the Nile; yet the annual inundation is not his work, and the river must have overflowed its banks and carried spontaneous vegetation with its waters, as well before as since Egypt was first occupied by the human family. There is, indeed, some reason to suppose that man lived upon the banks of the Nile when its channel was much lower, and the spread of its inundations much narrower, than at present; but wherever its flood reached, there the forest would propagate itself, and its shores would certainly have been morasses rather than sands. The opinions of Ritter on this subject are not only improbable, but they are contradictory to the little historical testimony we possess. Herodotus informs us in Euterpe that except the province of Thebes, all Egypt, that is to say, the whole of the Delta and of middle Egypt extending to Hemopolis Magna in N. L. 27 degrees 45 minutes, was originally a morass. This morass was doubtless in great part covered with trees, and hence, in the most ancient hieroglyphical records, a tree is the sign for the cultivated land between the desert and the channel of the Nile. In all probability, the real change effected by human art in the superficial geography of Egypt is the conversion of pools and marshes into dry land, by a system of transverse dikes, which compelled the flood-water to deposit its sediment on the banks of the river instead of carrying it to the sea. The colmate of modern Italy were thus anticipated in ancient Egypt.] The fields of Egypt are more regularly watered than those of any other country bordering on the Mediterranean, except the rice-grounds in Italy, and perhaps the marcite or winter meadows of Lombardy; but irrigation is more or less employed throughout almost the entire basin of that sea, and is everywhere attended with effects which, if less in degree, are analogous in character, to those resulting from it in Egypt. There are few things in European husbandry which surprise English or American observers so much as the extent to which irrigation is employed in agriculture, and that, too, on soils, and with a temperature, where their own experience would have led them to suppose it would be injurious to vegetation rather than beneficial to it. In Switzerland, for example, grass-grounds on the very borders of glaciers are freely irrigated, and on the Italian slope of the Alps water is applied to meadows at heights exceeding 6,000 feet. The summers in Northern Italy, though longer, are very often not warmer than in the Northern United States; and in ordinary years, the summer rains are as frequent and as abundant in the former country as in the latter. [Footnote: The mean annual precipitation in Lombardy is thirty-six inches, of which nearly two-thirds fall during the season of irrigation. The rain-fall is about the same in Piedmont, though the number of days in the year classed as "rainy" is said to be but twenty-four in the former province while it is seventy in the latter.--Baird Smith, Italian Irrigation, vol. i., p. 196. The necessity of irrigation in the great alluivial plain of Northern Italy is partly explained by the fact that the superficial stratum of fine earth and vegetable mould is very extensively underlaid by beds of pebbles and gravel brought down by mountain torrents at a remote epoch. The water of the surface-soil drains rapdily down into these loose beds, and passes off by subterranean channels to some unknown point of discharge; but this circumstance alone is not a sufficient solution. It is not possible that the habits of vegetables, grown in countries where irrigation has been immemorially employed, have been so changed that they require water under conditions of soil and climate where their congeners, which have not been thus indulgently treated, do not It is a remarkable fact that during the season of irrigation, when large tracts of surface are almost constantly saturated with water, there is an extraordinary dryness in the atmosphere of Lombardy, the hygrometer standing for days together a few degrees only above zero, while in winter the instrument indicates extreme humidity of the air, approaching to total saturation.--Baird Smith, Italian Irrigation, i., p. 189. There are some atmospheric phenomena in Northern Italy, which an American finds it hard to reconcile with what he has observed in the United States. To an American eye, for instance, the sky of Piedmont, Lombardy, and the northern coast of the Mediterranean, is always whitish and curdled, and it never has the intensity and fathomless depth of the blue of his native heavens. And yet the heat of the sun's rays, as measured by sensation, and, at the same time, the evaporation, are greater than they would be with the thermometer at the same point in America. I have frequently felt in Italy, with the mercury below 60 degrees Fahrenheit, and with a mottled and almost opaque sky, a heat of solar irradiation which I can compare to nothing but the scorching sensation experienced in America at a temperature twenty degrees higher, during the intervals between showers, or before a rain, when the clear blue of the sky seems infinite in depth and transparency. Such circumstances may create a necessity for irrigation where it would otherwise be superfluous, if not absolutely injurious. In speaking of the superior apparent clearness of the SKY in America, I confine myself to the concave vault of the heavens, and do not mean to assert that terrestrial objects are generally visible at greater distances in the United States than in Italy. Indeed, I am rather disposed to maintain the contrary; for though I know that the lower strata of the atmosphere in Europe never equal in transparency the air near the earth in New Mexico, Peru, and Chili, yet I think the accidents of the coast-line of the Riviera, as, for example, between Nice and La Spezia, and those of the incomparable Alpine panorama seen from Turin, are distinguishable at greater distances than they would be in the United States.] Yet in Piedmont and Lombardy irrigation is bestowed upon almost every crop, while in our Northern States it is never employed at all in farming husbandry, or indeed for any purpose except in kitchen-gardens, and possibly, in rare cases, in some other small branch of agricultural industry. [Footnote: In our comparatively rainless Western territory, irrigation is extensively and very beneficially employed. In the Salt Lake valley and in California, hundreds if not thousands of miles of irrigation canals have been constructed, and there is little doubt that artificially watering the soil will soon be largely resorted to in the older States. See valuable observations on this subject in Hayden, Preliminary Report on Geological Survey of Wyoming, 1870, pp. 194, 195, 258-261.] In general, it may be said that irrigation is employed only in the seasons when the evaporating power of the sun and the capacity of the air for absorbing humidity are greatest, or, in other words, that the soil is nowhere artificially watered except when it is so dry that little moisture would be evaporated from it, and, consequently, every acre of irrigated ground is so much added to the evaporable surface of the country. When the supply of water is unlimited, it is allowed, after serving its purpose on one field, to run into drains, canals, or rivers. But in most regions where irrigation is regularly employed, it is necessary to economize the water; after passing over or through one parcel of ground, it is conducted to another; no more is usually withdrawn from the canals at anyone point than is absorbed by the soil it irrigates, or evaporated from it, and, consequently, it is not restored to liquid circulation, except by infiltration or precipitation. We are safe, then, in saying that the humidity evaporated from any artificially watered soil is increased by a quantity bearing a large proportion to the whole amount distributed over it, for most even of that which is absorbed by the earth is immediately given out again either by vegetables or by evaporation; and the hygrometrical and thermometrical condition of the atmosphere in irrigated countries is modified proportionally to the extent of the practice. It is not easy to ascertain precisely either the extent of surface thus watered, or the amount of water supplied, in any given country, because these quantities vary with the character of the season; but there are not many districts in Southern Europe where the management of the arrangements for irrigation is not one of the most important branches of agricultural labor. The eminent engineer Lombardini describes the system of irrigation in Lombardy as, "every day in summer, diffusing over 550,000 hectares [1,375,000 acres] of land 45,000,000 cubic metres [nearly 600,000,000 cubic yards] of water, which is equal to the entire volume of the Seine, at an ordinary flood, or a rise of three metres above the hydrometer at the bridge of La Tournelle at Paris." [Footnote: Memorie sui progetti per Pestensions dell' Irrigazione, etc., il Politecniso, for January, 1868, p. 6.] Niel states the quantity of land irrigated in the former kingdom of Sardinia, including Savoy, in 1856, at 240,000 hectares, or not much Ices than 600,000 acres. This is about four-thirteenths of the cultivable soil of the kingdom. According to the same author, the irrigated lands in Franco did not exceed 100,000 hectares, or 247,000 acres, while those in Lombardy amounted to 450,000 hectares, more than 1,100,000 acres. [Footnote: Niel, L'Agriculture des Etats Sardes, p. 232. This estimate, it will be observed, is 275,000 acres less than that of Lombardini.] In these three states alone, then, there were more than three thousand square miles of artificially watered land, and if we add the irrigated soils of the rest of Italy, [Footnote: In 1865 the total quantity of irrigated lands in the kingdom of Italy was estimated at 1,357,677 hectares, or 2,000,000 acres, of which one-half is supplied with water by artificial canals. The Canal Cavour adds 250,000 acres to the above amount. The extent of artificially watered ground in Italy is consequently equal to the entire area of the States of Delaware and Rhode Island.--See the official report, Sulle Bonificazione, Risaie, ed Irrigazioni, 1865, p. 269.] of the Mediterranean islands, of the Spanish peninsula, of Turkey in Europe and in Asia Minor, of Syria, of Egypt and the remainder of Northern Africa, we shall see that irrigation increases the evaporable surface of the Mediterranean basin by a quantity bearing no inconsiderable proportion to the area naturally covered by water within it. Arrangements are concluded, and new plans proposed, for an immense increase of the lands fertilized by irrigation in France and in Belgium, as well as in Spain and Italy, and there is every reason to believe that the artificially watered soil of the latter country will be doubled, that of France quadrupled, before the end of this century. There can be no doubt that by these operations man is exercising a powerful influence on the soil, on vegetable and animal life, and on climate, and hence that in this, as in many other fields of industry, he is truly a geographical agency. [Footnote: It belongs rather to agriculture than to geography to discuss the quality of the crops obtained by irrigation, or the permanent effects produced by it on the productiveness of the soil. There is no doubt, however, that all crops which can be raised without watering are superior in flavor and in nutritive power to those grown by the aid of irrigation. Garden vegetables, particularly, profusely watered, are so insipid as to be hardly eatable. Wherever irrigation is practised, there is an almost irresistible tendency, especially among ignorant cultivators, to carry it to excess; and in Piedmont and Lombardy, if the supply of water is abundant, it is so liberally applied as sometimes not only to injure the quality of the product, but to drown the plants and diminish the actual weight of the crop. Grass-lands are perhaps an exception to this remark, as it seems almost impossible to apply too much water to them, provided it be kept in motion and not allowed to stagnate on the surface. Protestor Liebig, in his Modern Agriculture, says: "There is not to be found in chemistry a more wonderful phenomenon, one which more confounds all human wisdom, than is presented by the soil of a garden or field. By the simplest experiment, any one may satisfy himself that rain-water filtered through field or garden soil does not dissolve out a trace of potash, silicic acid, ammonia, or phosphoric acid. The soil does not give up to the water one particle of the food of plants which it contains. The most continuous rains cannot remove from the field, except mechanically, any of the essential constituents of ite fertility." "The soil not only retains firmly all the food of plants which is actually in it, but its power to preserve all that may be useful to them extends much farther. If rain or other water holding in solution ammonia, potash, and phosphoric and silicic acids, be brought in contact with soil, these substances disappear almost immediately from the solution; the soil withdraws them from the water. Only such substances are completely withdrawn by the soil as are indispensable articles of food for plants; all others remain wholly or in part in solution." These opinions were confirmed, soon after their promulgation, by the experimental researches of other chemists, but are now questioned, and they are not strictly in accordance with the alleged experience of agriculturists in those parts of Italy where irrigation is most successfully applied. They believe that the constituents of vegetable growth are washed out of the soil by excessive and long-continued watering. They consider it also established as a fact of observation, that water which has flowed through or over rich ground is more valuable for irrigation than water from the same source, which has not been impregnated with fertilizing substances by passing through soils containing them; and, on the other hand, that water, rich in the elements of vegetation, parts with them in serving to irrigate a poor soil, and is therefore less valuable as a fertilizer of lower grounds to which it may afterward be conducted. See Baird Smith, Italian Irrigation, i., p. 25; Scott Moncrieff, Irrigation in Southern Europe, pp. 34, 87, 89; Lombardini, Sulle Inondazioni etc., p. 73; Mangon, Les Irrigations, p. 48. The practice of irrigation--except in mountainous countries where springs and rivulets are numerous--is attended with very serious economical, social, and political evils. The construction of canals and their immensely ramified branches, and the grading and scarping of the ground to be watered, are always expensive operations, and they very often require an amount of capital which can be commanded only by the state, by moneyed corporations, or by very wealthy proprietors; the capacity of the canals must be calculated with reference to the area intended to be irrigated, and when they and their branches are once constructed, it in very difficult to extend them, or to accommodate any of their original arrangements to changes in the condition of the soil, or in the modes or objects of cultivation; the flow of the water being limited by the abundance of the source or the capacity of the canals, the individual proprietor cannot be allowed to withdraw water at will, according to his own private interest or convenience, but both the time and the quantity of supply must be regulated by a general system applicable, as far as may be, to the whole area irrigated by the same canal, and every cultivator must conform his industry to a plan which may be quite at variance with his special objects or with his views of good husbandry. The clashing interests and the jealousies of proprietors depending on the same means of supply are a source of incessant contention and litigation, and the caprices or partialities of the officers who control, or of contractors who farm, the canals, lead not unfrequently to ruinous injustice towards individual landholders. These circumstances discourage the division of the soil into small properties, and there is a constant tendency to the accumulation of large estates of irrigated land in the hands of great capitalists, and consequently to the dispossession of the small cultivators, who pass from the condition of owners of the land to that of hireling tillers. Though farmers are no longer yeomen, but peasants. Having no interest in the soil which composes their country, they are virtually expatriated, and the middle class, which ought to constitute the real physical and moral strength of the land, ceases to exist as a rural estate, and is found only among the professional, the mercantile, and the industrial population of the cities.--See, on the difficulty of regulating irrigation by law, Negri, Idea su una Legge in materia di Acqua, 1864; and Agmard, Irrigations du Midi de L'Europe' where curious and important remarks on the laws and usages of the Spanish Moors and the Spaniards, in respect to irrigation, will be found. The Moors were so careful in maintaining the details of their system, that they kept in publio offices bronze models of their dams and sluices, as guides for repairs and rebuilding. Some of these models are still preserved. --Ibidem, pp. 204, 205. For an account of recent irrigation works in Spain, see Spon, Dictionary of Engineering, article Irrigation. As near as can be ascertained, the amount of water applied to irrigated lands is scarcely anywhere less than the total precipitation during the season of vegetable growth, and in general it much exceeds that quantity. In grass-grounds and in field-culture it ranges from 27 or 28 to 60 inches, while in smaller crops, tilled by hand-labor, it is sometimes carried as high as 300 inches. [Footnote: Niel, Agriculture des Etata Sardes, p. 237. Lombardini's computation just given allows eighty-one cubic metres per day to the hectare [two hundred and sixty cubic yards to the acre], which, supposing the season of irrigation to be one hundred days, in equal to a precipitation of thirty-two inches. But in Lombardy, water in applied to some crops during a longer period than one hundred days; and in the marcite it flows over the ground even in winter. According to Boussingault (Economie Rurale, ii., p. 240), grass-grounds ought to receive, in Germany, twenty-one centimetres of water per week, and with less than half that quantity it is not advisable to incur the expense of supplying it. The ground is irrigated twenty-five or thirty times, and if the full quantity of twenty-one centimetres is applied, it receives more than two hundred inches of water, or six times the total amount of precipitation. Puvis, quoted by Boussingault, after much research comes to the conclusion that a proper quantity is twenty centimetres [eight inches] applied twenty-five or thirty times, which corresponds with the estimate just stated. Puvis adds--and, as our author thinks, with reason--that this amount might be doubled without disadvantage.--Ibidem, ii., p. 248, 249. In some parts of France this quantity is immensely exceeded, and it is very important to observe, with reference to the employment of irrigation in our Northern States, that water is most freely supplied in the COLDER provinces. Thus, in the Vosges, meadows are literally flooded for weeks together, and while in the department of Vancluse a meadow may receive, in five waterings of six and a half hours each, twenty-one inches of wnter, in the Vosges it might be deluged for twenty-four hundred hours in six applications, the enormous quantity of thirteen hundred feet of water flowing over it. See the important work of Herve Mangon, Sur l'emploi des eaux dans les Irrigations, chap. ix. Boussingault observes that rain-water is vastly more fertilizing than the water of irrigating canals, and therefore the supply of the latter must be greater. This is explained partly by the different character of the substances held in solution or suspension by the waters of the earth and of the sky, partly by the higher temperature of the latter, and, possibly, partly also by the mode of application--the rain being finely divided in its fall or by striking plants on the ground, river-water flowing in a continuous sheet. The temperature of the water is thought even more important than its composition. The sources which irrigate the marcite of Lombardy--meadows so fertile that less than an acre furnishes grass for a cow the whole year--are very warm. The ground watered by them never freezes, and a first crop, for soiling, is cut from it in January or February. The Canal Cavour--which takes its supply chiefly from the Po at Chivasso, fourteen or fifteen miles below Turin--furnishes water of much higher fertilizing power than that derived from the Dora Baltea and the Sesia, both because it is warmer, and because it transports a more abundant and a richer sediment than the latter streams, which are fed by Alpine ice-fields and melting snows, and which flow, for long distances, in channels ground smooth and bare by ancient glaciers and not now contributing much vegetable mould or fine slime to their waters.] The rice-grounds and the marcite of Lombardy are not included in these estimates of the amount of water applied. [Footnote: About one-seventh of the water which flows over the marcite is absorbed by the soil of those meadows or evaporated from their surface, and consequently six-sevenths of the supply remain for use on ground at lower levels.] The meteorological effect of irrigation on a large scale, which would seem prima facie most probable, would be an increase of precipitation in the region watered. [Footnote: On the pluviometric effect of irrigation, see Lombardini, Sulle Inondazioni, etc., p. 72, 74; the same author, Essai Hydrologique sur le Nil, p. 32; Messedaglia, Analisi dell' opera di Champion, pp. 96, 97, note; and Baird Smith, Italian Irrigation, i., pp. 189, 190. In an article in Aus der Natur, vol. 57, p. 443, it is stated that the rain on the Isthmus of Suez has increased since the opening of the canal, and has enlarged the evaporable surface of the country; but this cannot be accepted as an established fact without further evidence.] Hitherto scientific observation has recorded no such increase, but in a question of so purely local a character, we must ascribe very great importance to a consideration which I have noticed elsewhere, but which, has been frequently overlooked by meteorologists, namely, that vapors exhaled in one district may very probably be condensed and precipitated in another very distant from their source. If then it were proved that an extension of irrigated soil was not followed by an increase of rain-fall in the same territory, the probability that the precipitation was augmented SOMEWHERE would not be in the least diminished. But though we cannot show that in the irrigated portions of Italy the summer rain is more abundant than it was before irrigation was practised--for we know nothing of the meteorological conditions of that country at so remote a period--the fact that there is a very considerable precipitation in the summer months in Lombardy is a strong argument in favor of such increase. In the otherwise similar climate of Rumelia and of much of Asia Minor, irrigation is indeed practiced, but in a relatively small proportion. In those provinces there is little or no summer rain. Is it not highly probable that the difference between Italy and Turkey in this respect is to be ascribed, in part at least, to extensive irrigation in the former country, and the want of it in the latter It is true that, in its accessible strata, the atmosphere of Lombardy is extremely dry during the period of irrigation, but it receives an immense quantity of moisture by the evaporation from the watered soil, and the rapidity with which the aqueous vapor is carried up to higher regions--where, if not driven elsewhere by the wind, it would be condensed by the cold into drops of rain or at least visible clouds--is the reason why it is so little perceptible in the air near the ground. [Footnote: Is not the mottled appearance of the upper atmosphere in Italy, which I have already noticed, perhaps due in part to the condensation of the aqueous vapor exhaled by watered ground ] But the question of an influence on temperature rests on a different ground; for though the condensation of vapor may not take place within days of time and degrees of distance from the hour and the place where it was exhaled from the surface, a local refrigeration must necessarily accompany a local evaporation. Hence, though the summer temperature of Lombardy is high, we are warranted in affirming that it must have been still higher before the introduction of irrigation, and would again become so if that practice were discontinued. [Footnote: I do not know that observations have been made on the thermometric influence of irrigation, but I have often noticed that, on the irrigated plains of Piedmont ten miles south of Turin, the morning temperature in summer was several degrees below that marked at the Observatory in the city.] The quantity of water artificially withdrawn from running streams for the purpose of irrigation is such as very sensibly to affect their volume, and it is, therefore, an important element in the geography of rivers. Brooks of no trifling current are often wholly diverted from their natural channels to supply the canals, and their entire mass of water is completely absorbed or evaporated, so that only such proportion as is transmitted by infiltration reaches the river they originally fed. Irrigation, therefore, diminishes great rivers in warm countries by cutting off their sources of supply as well as by direct abstraction of water from their main channels. We have just seen that the system of irrigation in Lombardy deprives the Po of a quantity of water equal to the total delivery of the Seine at ordinary flood, or, in other words, of the equivalent of a tributary navigable for hundreds of miles by vessels of considerable burden. The new canals executed and projected will greatly increase the loss. The water required for irrigation in Egypt is less than would be supposed from the exceeding rapidity of evaporation in that arid climate; for the soil is thoroughly saturated during the inundation, and infiltration from the Nile continues to supply a considerable amount of humidity in the dryest season. Linant Bey computed that, in the Delta, fifteen and one-third cubic yards per day sufficed to irrigate an acre. If we suppose water to be applied for one hundred and fifty days during the season of growth, this would be equivalent to a total precipitation of about seventeen inches and one-third. Taking the area of actually cultivated soil in Egypt at the estimate of 4,500,000 acres, and the average amount of water daily applied in both Upper and Lower Egypt at twelve hundredths of an inch in depth, we have an abstraction of about 74,000,000 cubic yards, which--the mean daily delivery of the Nile being in round numbers 320,000,000 cubic yards--is twenty-three per cent of the average quantity of water contributed to the Mediterranean by that river. [Footnote: The proportion of the waters of the Nile withdrawn for irrigation is greater than this calculation makes it. The quantity required for an acre is less in the Delta than in Upper Egypt, both because the soil of the Delta, to which Linant Bey's estimate applies, lies little higher than the surface of the river, and is partly saturated by infiltration, and because near the sea, in N. L. 30 degrees, evaporation is much less rapid than it is several degrees southwards and in the vicinity of a parched desert.] In estimating the effect of this abstraction of water upon the volume of great rivers, especially in temperate climates and in countries with a hilly surface, we must remember that all the water thus withdrawn--except that which is absorbed by vegetation, that which enters into new inorganic compounds, and that which is carried off by evaporation--is finally restored to the original current by superficial flow or by infiltration. It is generally estimated that from one-third to one-half of the water applied to the fields is absorbed by the earth, and this, with the deductions just given, is returned to the river by direct infiltration, or descends through invisible channels to moisten lower grounds, and thence in part escapes again into the bed of the river, by similar conduits, or in the form of springs and rivulets. Interesting observations have lately been made on this subject in France and important practical results arrived at. It was maintained that mountain irrigation is not ultimately injurious to that of the plains below, because lands liberally watered in the spring, when the supply is abundant, act as reservoirs, storing up by absorption water which afterwards filters down to lower grounds or escapes into the channel of the river and keeps up its current in the dry summer months, so as to compensate for what, during those months, is withdrawn from it for upland irrigation. Careful investigation showed that though this proposition is not universally true, it is so in many cases, and there can be no doubt that the loss in the volume of rivers by the abstraction of water for irrigation is very considerably less than the measure of the quantity withdrawn. [Footnote: See Vigan, Etude sur les Irrigations, Paris, 1867; and Scott Moncrieff, Irrigation in Southern Europe, pp. 89, 90. The brook Ain Musa, which runs through the ruined city of Petra and finally disappears in the sands of Wadi el Araba, is a considerable stream in winter, and the inhabitants of that town were obliged to excavate a tunnel through the rock near the right bank, just above the upper entrance of the narrow Sik, to discharge a part of its swollen current. The sagacity of Dr. Robinson detected the necessity of this measure, though the tunnel, the mouth of which was hidden by brushwood, was not discovered till some time after his visit. I even noticed, near the arch that crosses the Sik, unequivocal remains of a sluice by which the water was diverted to the tunnel. Immense labor was also expended in widening the natural channel at several points below the town, to prevent the damming up and setting back of the water--a fact I believe not hitherto noticed by travellers. The Fellahheen above Petra still employ the waters of Ain Musa for irrigation, and in summer the superficial current is wholly diverted from its natural channel for that purpose. At this season, the bed of the brook, which is composed of pebbles, gravel, and sand, is dry in the Sik and through the town; but the infiltration is such that water is generally found by digging to a small depth in the channel. Observing these facts in a visit to Petra in the summer, I was curious to know whether the subterranean waters escaped again to daylight, and I followed the ravine below the town for a long distance. Not very far from the upper entrance of the ravine, arborescent vegetation appeared upon its bottom, and as soon as the ground was well shaded, a thread of water burst out. This was joined by others a little lower down, and, at the distance of a mile from the town, a strong current was formed and ran down towards Wadi el Araba. Similar facts are observed in all countries where the superficial current of water-courses is diverted from their bed for irrigation, but this case is of special interest because it shows the extent of absorption and infiltration even in the torrid climate of Arabia. See Baird Smith, Italian Irrigation, vol. i., pp. 172, 386 and 387.] Irrigation, as employed for certain special purposes in Europe and America, is productive of very prejudicial climatic effects. I refer particularly to the cultivation of rice in the Southern States of the American Union and in Italy. The climate of the Southern States is in general not necessarily unhealthy for the white man, but he can scarcely sleep a single night in the vicinity of the rice-grounds without being attacked by a dangerous fever. The neighborhood of the rice-fields is possibly less pestilential in Lombardy and Piedmont than in South Carolina and Georgia, but still very insalubrious to both man and beast. "Not only does the population decrease where rice is grown," says Escourron-Milliago, "but even the flocks are attacked by typhus. In the rice-grounds the soil is divided into compartments rising in gradual succession to the level of the irrigating canal, in order that the water, after having flowed one field, may be drawn off to another, and thus a single current serve for several compartments, the lowest field, of course, still being higher than the ditch which at last drains both it and the adjacent soil. This arrangement gives a certain force of hydrostatic pressure to the water with which the rice is irrigated, and the infiltration from these fields is said to extend through neighboring grounds, sometimes to the distance of not less than a myriametre, or six English miles, and to be destructive to crops and even trees reached by it. Land thus affected can no longer be employed for any purpose but growing rice, and when prepared for that crop, it propagates still further the evils under which it had itself suffered, and, of course, the mischief is a growing one." [Footnote: Escourrou-Milliago, D'Italie a propos de l'Exposition de Paris, 1856, p. 92. According to an article in the Gazzetto di Torino for the 17th of January, 1869, the deaths from malarious fever in the Canavese district--which is asserted to have been altogether free from this disease before the recent introduction of rice-culture--between the 1st of January and the 15th of October, 1868, were two thousand two hundred and fifty. The extent of the injurious influence of this very lucrative branch of rural industry in Italy is contested by the rice-growers. But see Secondo Laura, Le Risaje, Torino, 1869; Selmi, Il Miasma Palustre, p. 89; and especially Carlo Livi, Della coltivazione del Riso in Italia, in the Nuova Antologia for July, 1871, p. 599 et seqq. According to official statistics, the rice-grounds of Italy, including the islands, amounted in 1866 to 450,000 acres. It is an interesting fact in relation to geographical and climatic conditions, that while little rice is cultivated SOUTH of N. L. 44 degrees in Italy, little is grown in the United States NORTH of 35 degrees. To the southward of the great alluvial plain of the Po, the surface is in general too much broken to admit of the formation of level fields of much extent, and where the ground is suitable, the supply of water is often insufficient. The Moors introduced the cultivation of rice into Spain at an early period of their dominion in that country. The Spaniards sowed rice in Lombardy and in the Neapolitan territory in the 16th century; but besides the want of water and of level ground convenient for irrigation, rice-husbandry has proved so much more pestilential in Southern than in Northern Italy that it has long been discouraged by the Neapolitan government.] Salts deposited by Water of Irrigation. The attentive traveller in Egypt and Nubia cannot fail to notice many localities, generally of small extent, where the soil is rendered infertile by an excess of saline matter in its composition. In many cases, perhaps in all, these barren spots lie rather above the level usually flooded by the inundations of the Nile, and yet they exhibit traces of former cultivation. Observations in India suggest a possible explanation of this fact. A saline efflorescence called "Reh" and "Kuller" is gradually invading many of the most fertile districts of Northern and Western India, and changing them into sterile deserts. It consists principally of sulphate of soda (Glauber's salts), with varying proportions of common salt. These salts (which in small quantities are favorable to fertility of soil) are said to be the gradual result of concentration by evaporation of river and canal waters, which contain them in very minute quantities, and with which the lands are either irrigated or occasionally overflowed. The river inundations in hot countries usually take place but once in a year, and, though the banks remain submerged for days or even weeks, the water at that period, being derived principally from rains and snows, must be less highly charged with mineral matter than at lower stages, and besides, it is always in motion. The water of irrigation, on the other hand, is applied for many months in succession, it is drawn from rivers and canals at the seasons when the proportion of salts is greatest, and it either sinks into the superficial soil, carrying with it the saline substances it holds in solution, or is evaporated from the surface, leaving them upon it. Hence irrigation must impart to the soil more salts than natural inundation. The sterilized grounds in Egypt and Nubia lying above the reach of the floods, as I have said, we may suppose them to have been first cultivated in that remote antiquity when the Nile valley received its earliest inhabitants, and when its lower grounds were in the condition of morasses. They must have been artificially irrigated from the beginning; they may have been under cultivation many centuries before the soil at a lower level was invaded by man, and hence it is natural that they should be more strongly impregnated with saline matter than fields which are exposed every year, for some weeks, to the action of running water so nearly pure that it would be more likely to dissolve salts than to deposit them. SUBTERRANEAN WATERS. I have frequently alluded to a branch of physical geography, the importance of which is but recently adequately recognized--the subterranean waters of the earth considered as stationary reservoirs, as flowing currents, and as filtrating fluids. The earth drinks in moisture by direct absorption from the atmosphere, by the deposition of dew, by rain and snow, by percolation from rivers and other superficial bodies of water, and sometimes by currents flowing into caves or smaller visible apertures. [Footnote: The great limestone plateau of the Karst in Carniola is completely honey-combed by caves through which the drainage of that region is conducted. Rivers of considerable volume pour into some of these caves and can be traced underground to their exit. Thus the Recca has been satisfactorily identified with a stream flowing through the cave of Trebich, and with the Timavo--the Timavus of Virgil and the ancient geographers--which empties through several mouths into the Adriatic between Trieste and Aquileia. The city of Trieste is very insufficiently supplied with fresh water. It has been thought practicable to supply this want by tunnelling through the wall of the plateau, which rises abruptly in the rear of the town, until some subterranean stream is encountered, the current of which can be conducted to the city. More visionary projectors have gone further, and imagined that advantage might be taken of the natural tunnels under the Karst for the passage of roads, railways, and even navigable canals. But however chimerical these latter schemes may seem, there is every reason to believe that art might avail itself of these galleries for improving the imperfect drainage of the champaign country bounded by the Karst, and that stopping or opening the natural channels might very much modify the hydrography of an extensive region. See in Aus des Natur, xx., pp. 250-254, 263-266, two interesting articles founded on the researches of Schmidt. The cases are certainly not numerous where marine currents are known to pour continuously into cavities beneath the surface of the earth, but there is at least one well-authenticated instance of this sort--that of the mill-stream at Argostoli in the island of Cephalonia. It had been long observed that the sea-water flowed into several rifts and cavities in the limestone rocks of the coast, but the phenomenon has excited little attention until very recently. In 1833, three of the entrances were closed, and a regular channel, sixteen feet long and three feet wide, with a fall of three feet, was cut into the mouth of a larger cavity. The sea-water flowed into this canal, and could be followed eighteen or twenty feet beyond its inner terminus, when it disappeared in holes and clefts in the rock. In 1858 the canal had been enlarged to thewidth of five feet and a half, and a depth of a foot. The water pours rapidly through the canal into an irregular depression and forms a pool, the surface of which is three or four feet below the adjacent soil, and about two and a half or three feet below the level of the sea. From this pool it escapes through several holes and clefts in the rock, and has not yet been found to emerge elsewhere. There is a tide at Argostoli of about six inches in still weather, but it is considerably higher with a south wind. I do not find it stated whether water flows through the canal into the cavity at low tide, but it distinctly appears that there is no refluent current, as of course there could not be from a base so much below the sea. Mousson found the delivery through the canal to be at the rate of 24.88 cubic feet to the second; at what stage of the tide does not appear. Other mills of the same sort have been erected, and there appear to be several points on the coast where the sea flows into the land. Various hypotheses have been suggested to explain this phenomenon, some of which assume that the water descends to a great depth beneath the crust of the earth; but the supposition of a difference of level in the surface of the sea on the opposite sides of the island, which seems confirmed by other circumstances, is the most obvious method of explaining these singular facts. If we suppose the level of the water on one side of the island to be raised by the action of currents three or four feet higher than on the other, the existence of cavities and channels in the rock would easily account for a subterranean current beneath the island, and the apertures of escape might be so deep or so small as to elude observation. See Aus der Natur, vol. xix., pp. 129 et seqq. I have lately been informed by a resident of the Ionian Islands, who is familiar with the locality, that the sea flows uninterruptedly into the sub-insular cavities, at all stages of the tide.] Some of this humidity is exhaled again by the soil, some is taken up by organic growths and by inorganic compounds, some poured out upon the surface by springs and either immediately evaporated or carried down to larger streams and to the sea, some flows by subterranean courses into the bed of fresh-water rivers [Footnote: "The affluents received by the Seine below Rouen are so inconsiderable, that the augmentation of the volume of that river must be ascribed principally to springs rising in its bed. This is a point of which engineers now take notice, and M. Belgrand, the able officer charged with the improvement of the navigation of the Seine between Paris and Rouen, has devoted much attention to it."--Babinet, Etudes et Lectures, iii., p. 185. On page 232 of the volume just quoted, the same author observes: "In the lower part of its course, from the falls of the Oise, the Seine receives so few important affluents, that evaporation alone would suffice to exhaust all the water which passes under the bridges of Paris." This supposes a much greater amount of evaporation than has been usually computed, but I believe it is well settled that the Seine conveys to the sea much more water than is discharged into it by all its superficial branches. Babinet states the evaporation from the surface of water at Paris to be twice as great as the precipitation. Belgrand supposes that the floods of the Seine at Paris are not produced by the superficial flow of the water of precipitation into its channel, but from the augmented discharge of its remote mountain sources, when swollen by the rains and melted snows which percolate through the permeable strata in its upper course.--Annales des Ponts et Chaussees, 1851, vol. i.] or of the ocean, and some remains, though even here not in forever motionless repose, to fill deep cavities and underground channels. In every case the aqueous vapors of the air are the ultimate source of supply and all these hidden stores are again returned to the atmosphere by evaporation. The proportion of the water of precipitation taken up by direct evaporation from the surface of the ground seems to have been generally exaggerated, sufficient allowance not being made for moisture carried downwards or in a lateral direction by infiltration or by crevices in the superior rocky or earthy strata. According to Wittwer, Mariotte found that but one-sixth of the precipitation in the basin of the Seine was delivered into that sea by the river, "so that five-sixths remained for evaporation and consumption by the organic world." [Footnote: Physicalische Geographie, p. 286. It does not appear whether this inference is Mariotte's or Wittwer's. I suppose it is a conclusion of the latter. According to Valles, the Seine discharges into the sea thirty per cent. of the precipitation in its valley, while the Po delivers into the Adriatic two-thirds and perhaps even three-quarters of the total down-fall of its basin. The differences between the tributaries of the Mississippi in this respect are remarkable, the Missouri discharging only fifteen per cent., the Yazoo not less than ninety. The explanation of these facts is found in the geographical and geological character of the valleys of these rivers. The Missouri flows with a rapid current through an irregular country, the Yazoo has a very slow flow through a low, alluvial region which is kept constantly almost saturated by infiltration.] Maury estimates the annual amount of precipitation in the valley of the Mississippi at 620 cubic miles, the discharge of that river into the sea at 107 cubic miles, and concludes that "this would leave 513 cubic miles of water to be evaporated from this river-basin annually." [Footnote: Physical Geography of the Sea. Tenth edition. London, 1861, Section 274.] In these and other like computations, the water carried down into the earth by capillary and larger conduits is wholly lost sight of, and no thought is bestowed upon the supply for springs, for common and artesian wells, and for underground rivers, like those in the great caves of Kentucky, which may gush up in fresh-water currents at the bottom of the Caribbean Sea, or rise to the light of day in the far-off peninsula of Florida. [Footnote: In the low peninsula of Florida, rivers, which must have their sources in mountains hundreds of miles distant, pour forth from the earth with a volume sufficient to permit steamboats to ascend to their basins of eruption. In January, 1857, a submarine fresh-water river burst from the bottom of the sea not far from the southern extremity of the peninsula, and for a whole month discharged a current not inferior in volume to the river Mississippi, or eleven times the mean delivery of the Po, and more than six times that of the Nile. We can explain this phenomenon only by supposing that the bed of the sea was suddenly burst up by the hydrostatic upward pressure of the water in a deep reservoir communicating with some great subterranean river or receptacle in the mountains of Georgia or of Cuba, or perhaps even in the valley of the Mississippi.--Thomassy, Essai sur l'Hydrologie. Late southern journals inform us that the creek under the Natural Bridge in Virginia has suddenly disappeared, being swallowed up by newly formed fissures, of unknown depth, in its channel. It does not appear that an outlet for the waters thus absorbed has been discovered, and it is not improbable that they are filling some underground cavity like that which supplied the submarine river just mentioned.] The progress of the emphatically modern science of geology has corrected these erroneous views, because the observations on which it depends have demonstrated not only the existence, but the movement, of water in nearly all geological formations, have collected evidence of the presence of large reservoirs at greater or less depths beneath surfaces of almost every character, and have investigated the rationale of the attendant phenomena. [Footnote: See especially Stoppani, Corso di Geologia, i., pp. 270 et seqq.] The distribution of these waters has been minutely studied with reference to a great number of localities, and though the actual mode and rate of their vertical and horizontal transmission is still involved in much obscurity, the laws which determine their aggregation are so well understood, that, when the geology of a given district is known, it is not difficult to determine at what depth water will be reached by the borer, and to what height it will rise. The same principles have been successfully applied to the discovery of small subterranean collections or currents of water, and some persons have acquired, by a moderate knowledge of the superficial structure of the earth combined with long practice, a skill in the selection of favorable places for digging wells which seems to common observers little less than miraculous. The Abbe Paramelle--a French ecclesiastic who devoted himself for some years to this subject and was extensively employed as a well-finder--states, in his work on Fountains, that in the course of thirty-four years he had pointed out more than ten thousand subterranean springs; and though his geological speculations were often erroneous, high scientific authorities have testified to the great practical value of his methods, and the general accuracy of his predictions. [Footnote: Paramelle, Quellenkunde, mit einem Vorwort von B. Cotta. 1856.] Hydrographical researches have demonstrated the existence of subterranean currents and reservoirs in many regions where superficial geology had not indicated their probable presence. Thus, a much larger proportion of the precipitation in the valley of the Tiber suddenly disappears than can be accounted for by evaporation and visible flow into the channel of the river. Castelli suspected that the excess was received by underground caverns, and slowly conducted by percolation to the bed of the Tiber. Lombardini--than whom there is no higher authority--concludes that the quantity of water gradually discharged into the river by subterranean conduits, is not less than three-quarters of the total delivery of its basin. [Footnote: See Lombardini, Importanza degli studi sulla Statistica da Fiumi, p. 27; also, same author, Sulle Inondazioni avvenute in Francia, etc., p. 29.] What is true of the hydrology of the Tiber is doubtless more or less true of that of other rivers, and the immense value of natural arrangements which diminish the danger of sudden floods by retaining a large proportion of the precipitation, and of an excessive reduction of river currents in the droughts of summer, by slowly conducting into their beds water accumulated and stored up in subterranean reservoirs in rainy seasons, is too obvious to require to be dwelt upon. The readiness with which water not obstructed by impermeable strata diffuses itself through the earth in all directions--and consequently, the importance of keeping up the supply of subterranaean reservoirs--find a familiar illustration in the effect of paving the ground about the stems of vines and trees. The surface-earth around the trunk of a tree may be made almost impervious to water, by flagstones and cement, for a distance as great as the spread of the roots; and yet the tree will not suffer for want of moisture, except in droughts severe enough sensibly to affect the supply in deep wells and springs. Both forest and fruit trees attain a considerable age and size in cities where the streets and courts are closely paved, and where even the lateral access of water to the roots is more or less obstructed by deep cellars and foundation walls. The deep-lying veins and sheets of water, supplied by infiltration from often comparatively distant sources, send up moisture by capillary attraction, and the pavement prevents the soil beneath it from losing its humidity by evaporation. Hence, city-grown trees find moisture enough for their roots, and though plagued with smoke and dust, often retain their freshness, while those planted in the open fields, where sun and wind dry up the soil faster than the subterranean fountains can water it, are withering from drought. [Footnote: The roots of trees planted in towns do not depend exclusively on infiltration for their supply of water, for they receive a certain amount of both moisture and air through the interstices between the paving-stones; but where wide surfaces of streets and courts are paved with air and water tight asphaltum, as in Paris, trees suffer from the diminished supply of these necessary elements.] Without the help of artificial conduit or of water-carrier, the Thames and the Seine refresh the ornamental trees that shade the thoroughfares of London and of Paris, and beneath the hot and reeking mould of Egypt, the Nile sends currents to the extremest border of its valley. [Footnote: See the interesting observations of Krieck on this subject, Schriften zur allgemeinen Erdkunde, cap. iii., Section 6, and especially the passages in Ritter s Erdkunde, vol. i., there referred to. The tenacity with which the parched soil of Egypt retains the supply of moisture it receives from the Nile is well illustrated by observations of Girard cited by Lombardini from the Memoires de l'Academie des Sciences, t. ii., 1817. Girard dug wells at distances of 3,200, 1,800, and 1,200 metres from the Nile, and after three months of low water in the river, found water in the most remote well, at 4m. 97, in the next at 4m. 23, and in that nearest the bank at 3m. 44 above the surface of the Nile. The fact that the water was highest in the most distant well appears to show that it was derived from the inundation and not, by lateral infiltration, from the river. But water is found beneath the sands at points far above and beyond the reach of the inundations, and can be accounted for only by subterranean percolation from the Nile. At high flood, the hydrostatic pressure on the banks, combined with capillary attribution, sends water to great horizontal distances through the loose soil; at low water the current is reversed, and the moisture received from the river is partly returned, and may often be seen oozing from the banks into the river.--Clot Bey, Apercu sur l'Egypte, i., 128. Laurent (Memoires sur le Sahara Oriental, pp. 8, 9), in speaking of a river at El-Faid, "which, like all those of the desert, is, most of the time, without water," observes, that many wells are dug in the bed of the river in the dry season, and that the subterranean supply of water thus reached extends itself laterally, at about the same level, at least a kilometre from the river, as water is found by digging to the depth of twelve or fifteen metres at a village situated at that distance from the bank. Recent experiments, however, have shown that in the case of rivers flowing through thickly peopled regions, and especially where the refuse from industrial establishments is discharged into them, the finely comminuted material received from sewers and factories sometimes clogs up the interstices between the particles of sand and gravel which compose the bed and banks, and the water is consequently confined to the channel and no longer diffuses itself laterally through the adjacent soil. This obstruction of course acts in both directions, according to circumstances. In one case, it prevents the escape of river-water and tends to maintain a full flow of the current; in another it intercepts the supply the river might otherwise receive by infiltration from the land, and thus tends to reduce the volume of the stream. In some instances pits have been sunk along the banks of large rivers and the water which filters into them pumped up to supply aqueducts. This method often succeeds, but where the bed of the stream has been rendered impervious by the discharge of impurities into it, it cannot be depended upon. The tubular wells generally known as the American wells furnish another proof of the free diffusion and circulation of water through the soil. I do not know the date of the first employment of these tubes in the United States, but as early as 1861, the Chevalier Calandra used wooden tubes for this pose in Piedmont, with complete success. See the interesting pamphlet, Sulla Estrazione delle Acque Sotterrance, by C. Calandra. Torino, 1867. The most remarkable case of infiltration known to me by personal observation is the occurrence of fresh water in the beach-sand on the eastern side of the Gulf of Akaba, the eastern arm of the Red Sea. If you dig a cavity in the beach near the sea-level, it soon fills with water so fresh as not to be undrinkable, though the sea-water two or three yards from it contains even more than the average quantity of salt. It cannot be maintained that this is sea-water freshed by filtration through a few feet or inches of sand, for salt-water cannot be deprived of its salt by that process. It can only come from the highlands of Arabia, and it would seem that there must exist some large reservoir in the interior to furnish a supply which, in spite of evaporation, holds out for months after the last rains of winter, and perhaps even through the year. I observed the fact in the month of June. See Robinson, Biblical Researches, 1857, vol i., p. 167. The precipitation in the mountains that border the Red Sea is not known by pluviometric measurement, but the mass of debris brought down the ravines by the torrents proves that their volume must be large. The proportion of surface covered by sand and absorbent earth, in Arabia Petraea and the neighboring countries, is small, and the mountains drain themselves rapidly into the wadies or ravines where the torrents are formed; but the beds of earth and disintegrated rock at the bottom of the valleys are of so loose and porous texture, that a great quantity of water is absorbed in saturating them before a visible current is formed on their surface. In a heavy thunder-storm, accompanied by a deluging rain, which I witnessed at Mount Sinai in the month of May, a large stream of water poured, in an almost continuous cascade, down the steep ravine north of the convent, by which travellers sometimes descend from the plateau between the two peaks, but after reaching the foot of the mountain, it flowed but a few yards before it was swallowed up in the sands. Fresh-water wells are not unfrequently found upon the borders of ocean beaches. In the dry summer of 1870, drinkable water was procured in many places on the coast of Liguria by digging to the depth of a yard in the beach-sands. Tubular wells reach fresh water at twelve or fifteen feet below the surface on the sandy plains of Cape Cod. In this latter case, the supply is more probably derived directly from precipitation than from lateral infiltration.] Artesian Wells. The existence of artesian wells depends upon that of subterranean reservoirs and rivers, and the supply yielded by borings is regulated by the abundance of such sources. The waters of the earth are, in many cases, derived from superficial currents which are seen to pour into chasms opened, as it were, expressly for their reception; and in others, where no apertures in the crust of the earth have been detected, their existence is proved by the fact that artesian wells sometimes bring up from great depths seeds, leaves, and even living fish, which must have been carried down through channels large enough to admit a considerable stream. [Footnote: Charles Martins, Le Sahara, in Revue des Deux Mondes, Sept. 1, 1864, p. 619; Stoppani, Corso di Geologia, i., 281; Desor, Die Sahara, Basel, 1871, pp. 50, 51.] But in general, the sheet and currents of water reached by deep boring appear to be primarily due to infiltration from highlands where the water is first collected in superficial or subterranean reservoirs. By means of channels conforming to the dip of the strata, these reservoirs communicate with the lower basins, and exert upon them a fluid pressure sufficient to raise a column to the surface, whenever an orifice is opened. [Footnote: It is conceivable that in shallow subterranean basins superincumbered mineral strata may rest upon the water and be partly supported by it. In such case the weight of such strata would be an additional, if not the sole, cause of the ascent of the water through the tubes of artesian wells. The ascent of petroleum in the artesian oil-wells in Pennsylvania, and, in many cases, of salt-water in similar tubes, can hardly be ascribed to hydrostatic pressure, and there is much difficulty in accounting for the rise of water in artesian wells in many parts of the African desert on that principle. Perhaps the elasticity of gases, which probably aids in forcing up petroleum and saline waters, may be, not unfrequently, an agency in causing the flow of water in common artesian borings. It is said that artesian wells lately bored in Chicago, some to the depth of 1,600 feet, raise water to the height of 100 feet above the surface. What is the source of the pressure ] The water delivered by an artesian well is, therefore, often derived from distant sources, and may be wholly unaffected by geographical or meteorological changes in its immediate neighborhood, while the same changes may quite dry up common wells and springs which are fed only by the local infiltration of their own narrow basins. In most cases, artesian wells have been bored for purely economical or industrial purposes, such as to obtain good water for domestic use or for driving light machinery, to reach saline or other mineral springs, and recently, in America, to open fountains of petroleum or rock-oil. The geographical and geological effects of such abstraction of fluids from the bowels of the earth are too remote and uncertain to be here noticed; [Footnote: Many more or less probable conjectures have been made on this subject but thus far I am not aware that any of the apprehended results have been actually shown to have happened. In an article in the Annales des Ponts et Chaussees for July and August, 1839, p. 131, it was suggested that the sinking of the piers of a bridge at Tours in France was occasioned by the abstraction of water from the earth by artesian wells, and the consequent withdrawal of the mechanical support it had previously given to the strata containing it. A reply to this article will be found in Viollet, Theorie des Puits Artesiens, p. 217. In some instances the water has rushed up with a force which seemed to threaten the inundation of the neighborhood, and even the washing away of much soil; but in those cases the partial exhaustion of the supply, or the relief of hydrostatic or elastic pressure, has generally produced a diminution of theflow in a short time, and I do not know that any serious evil has everbeen occasioned in this way. In April, 1866, a case of this sort occurred in boring an artesian well near the church of St. Agnes at Venice. When the drill reached the depth of 160 feet, a jet of mud and water was shot up to the height of 130 feet above the surface, and continued to flow with gradually diminishing force for about eight hours.] but artesian wells have lately been employed in Algeria for a purpose which has even now a substantial, and may hereafter acquire a very great geographical importance. It was observed by many earlier as well as recent travellers in the East, among whom Shaw deserves special mention, that the Libyan desert, bordering upon the cultivated shores of the Mediterranean, appeared in many places to rest upon a subterranean lake at an accessible distance below the surface. The Moors are vaguely said to bore artesian wells down to this reservoir, to obtain water for domestic use and irrigation, and there is evidence that this art was practised in Northern Africa in the Middle Ages. But it had been lost by the modern Moors, and the universal astonishment and incredulity with which the native tribes viewed the operations of the French engineers sent into the desert for that purpose, are a sufficient proof that this mode of reaching the subterranean waters was new to them. They were, however, aware of the existence of water below the sands, and were dexterous in digging wells--square shafts lined with a framework of palm-tree stems--to the level of the sheet. The wells so constructed, though not technically artesian wells, answer the same purpose; for the water rises to the surface and flows over it as from a spring. [Footnote: See a very interesting account of these wells, and of the workmen who clean them out when obstructed by sand brought up with the water, in Laurent's memoir on the artesian wells recently bored by the French Government in the Algerian desert. Mimoire sur le Sahara Oriental, etc., pp. et seqq. Some of the men remained under water from two minutes to two minutes and forty seconds. Several officers are quoted as having observed immersions of three minutes' duration, and M. Berbrugger witnessed ona of six minutes and five seconds and another of five minutes and fifty-five seconds. The shortest of these periods is longer than the best pearl-diver can remain below the surface of salt-water. The wells of the Sahara are from twenty to eighty metres deep.-Desor, Die Sahara, Basel, 1871, p. 43. The ancient Egyptians were acquainted with the art of boring artesian wells. Ayme, a French engineer in the service of the Pacha of Egypt, found several of these old wells, a few years ago, in the oases. They differed little from modern artesian wells, but were provided with pear-shaped valves of stone for closing them when water was not needed. When freed from the sand and rubbish with which they were choked, they flowed freely and threw up fish large enough for the table. The fish were not blind, as cave-fish often are, but were provided with eyes, and belonged to species common in the Nile. The sand, too, brought up with them resembled that of the bed of that river. Hence it is probable that they were carried to the oases by subterranean channels from the Nile.--Desor, Die Sahara, Basel, 1871, p. 28; Stoppani, Corso di Geologia, i., p. 281. Barth speaks of common wells in Northern Africa from 200 to 360 feet deep.--Reisen in Africa, ii., p. 180. It is certain that artesian wells have been common in China from a very remote antiquity, and the simple method used by the Chinese--where the drill is raised and let fall by a rope, instead of a rigid rod--has lately been employed in Europe with advantage. Some of the Chinese wells are said to be 3,000 feet deep; that of Neusalzwerk in Silesia is 2,300. A well was bored at St. Louis, in Missouri, a few years ago, to supply a sugar refinery, to the depth of 2,199 feet. This was executed by a private firm in three years, at the expense of only $10,000. Four years since the boring was recommenced in this well and reached a depth of 3,150 feet, but without a satisfactory result. Another artesian well was sunk at Columbus, in Ohio, to the depth of 2,500 feet, but without obtaining the desired supply of water. Perhaps, however, the artesian well of the greatest depth ever executed until very recently, is that bored within the last six or seven years, for the use of an Insane Asylum near St. Louis. This well descends to the depth of three thousand eight hundred and forty-three feet, but the water which it furnishes is small in quantity and of a quality that cannot be used for ordinary domestic purposes. The bore has a diameter of six inches to the depth of 425 feet, and after that it is reduced to four inches. For about three thousand feet the strata penetrated were of carboniferous and magnesian limestone alternating with sandstone. The remainder of the well passes through igneous rock. At St. Louis the Missouri and Mississippi rivers are not more than twenty miles distant from each other, and it is worthy of note that the waters of neither of those two rivers appear to have opened for themselves a considerable subterranean passage through the rocky strata of the peninsula which separates them. When in boring an artesian well water is not reached at a moderate depth, it is not always certain that it will be found by driving the drill still lower. In certain formations, water diminshes as we descend, and it seems probable that, except in case of caverns and deep fissures, the weight of the superincumbent mineral strata so compresses the underlying ones, at no very great distance below the surface, as to render them impermeable to water and consequently altogether dry. See London Quarterly Journal of Science, No. xvii., Jan., 1868, p. 18, 19. In the silver mines of Nevada water is scarcely found at depths below 1,000 feet, and at 1,200 feet from the surface the earth is quite dry.--American Annual of Scientific Discovery for 1870, p. 75. Similar facts are observed in Australia. The Pleasant Creek News writes: "A singular and unaccountable feature in connection with our deep quartz mines is being developed daily, which must surprise those well experienced in mining matters. It is the decrease of water as the greater depths are reached. In the Magdala shaft at 950 ft. the water has decreased to a MINIMUM; in the Crown Cross Reef Company's shaft, at 800 ft., notwithstanding the two reefs recently struck, no extra water has been met with; and in the long drive of the Extended Cross Reef Company, at a depth of over 800 ft., the water is lighter than it was nearer the surface." Boring has been carried to a great depth at Sperenberg near Berlin, where, in 1871, the drill had descended 5,500 feet below the surface, passing through a stratum of salt for the last 3,200 feet; but the drilling was still in progress, the whole thickness of the salt-bed not having been penetrated.--Aus der Natur, vol. 55, p. 208. The facts that there are mines extending two miles under the bed of the sea, which are not particularly subject to inconvenience from water, that little water was encountered in the Mt. Cenis tunnel, 3500 feet below the surface, and that at Scarpa, not far from Tivoli, there is an ancient well 1700 feet deep with but eighteen feet of water, may also be cited as proofs that water is not universally diffused at great distances beneath the surface.] These wells, however, are too few and too scanty in supply to serve any other purposes than the domestic wells of other countries, and it is but recently that the transformation of desert into cultivable land by this means has been seriously attempted. The French Government has bored a large number of artesian wells in the Algerian desert within a few years, and the native sheikhs are beginning to avail themselves of the process. Every well becomes the nucleus of a settlement proportioned to the supply of water, and before the end of the year 1860, several nomade tribes had abandoned their wandering life, established themselves around the wells, and planted more than 30,000 palm trees, besides other perennial vegetables. [Footnote: "In the anticipation of our success at Oum-Thiour, everything had been prepared to take advantage of this new source of wealth without a moment's delay. A division of the tribe of the Selmia, and their sheikh, Aissa ben Sha, laid the foundation of a village as soon as the water flowed, and planted twelve hundred date-palms, renouncing their wandering life to attach themselves to the soil. In this arid spot, life had taken the place of solitude, and presented itself, with its smiling images, to the astonished traveller. Young girls were drawing water at the fountain; the flocks, the great dromedaries with their slow pace, the horses led by the halter, were moving to the watering trough; the hounds and the falcons enlivened the group of party-colored tents, and living voices and animated movement had succeeded to silence and desolation."--Laurent, Memoires sur le Sahara, p. 85. Between 1856 and 1864 the French engineers had bored 83 wells in the Hodna and the Sahara of the Province of Constantine, yielding, all together, 9,000 gallons a minute, and irrigating more than 125,000 date-palms. Reclus, La Terre, i., p. 110.] The water is found at a small depth, generally from 100 to 200 feet, and though containing too large a proportion of mineral matter to be acceptable to a European palate, it answers well for irrigation, and does not prove unwholesome to the natives. The most obvious use of artesian wells in the desert at present is that of creating stations for the establishment of military posts and halting-places for the desert traveller; but if the supply of water shall prove adequate for the indefinite extension of the system, it is probably destined to produce a greater geographical transformation than has ever been effected by any scheme of human improvement. The most striking contrast of landscape scenery that nature brings near together in time or place, is that between the greenery of the tropics, or of a northern summer, and the snowy pall of leafless winter. Next to this in startling novelty of effect, we must rank the sudden transition from the shady and verdant oasis of the desert to the bare and burning party-colored ocean of sand and rock which surrounds it. [Footnote: The variety of hues and tones in the local color of the desert is, I think, one of the phenomena which most surprise and interest a stranger to those regions. In England and the United States, rock is so generally covered with moss or earth, and earth with vegetation, that untravelled Englishmen and Americans are not very familiar with naked rock as a conspicuous element of landscape. Hence, in their conception of a bare cliff or precipice, they hardly ascribe definite color to it, but depict it to their imagination as wearing a neutral tint not assimilable to any of the hues with which nature tinges her atmospheric or paints her organic creations. There are certainly extensive desert ranges, chiefly limestone formations, where the surface is either white, or has weathered down to a dull uniformity of tone which can hardly be called color at all; and there are sand plains and drifting hills of wearisome monotony of tint. But the chemistry of the air, though it may tame the glitter of the limestone to a dusky gray, brings out the green and brown and purple of the igneous rocks, and the white and red and blue and violet and yellow of the sandstone. Many a cliff in Arabia Petraea is as manifold in color as the rainbow, and the veins are so variable in thickness and inclination, so contorted and involved in arrangement, as to bewilder the eye of the spectator like a disk of party-colored glass in rapid evolution. In the narrower wadies the mirage is not common; but on broad expanses, as at many points between Cairo and Suez, and in Wadi el Araba, it mocks you with lakes and land-locked bays, studded with inlands and fringed with trees, all painted with an illusory truth of representation absolutely indistinguishable from the reality. The checkered earth, too, is canopied with a heaven as variegated as itself. You see, high up in the sky, rosy clouds at noonday, colored probably by reflection from the ruddy mountains, while near the horizon float cumuli of a transparent, ethereal blue, seemingly balled up out of the clear cerulean substance of the firmament, and detached from the heavenly vault, not by color or consistence, but solely by the light and shade of their salient and retreating outlines.] The most sanguine believer in indefinite human progress hardly expects that man's cunning will accomplish the universal fulfilment of the prophecy, "the desert shall blossom as the rose," in its literal sense; but sober geographers have thought the future conversion of the sand plains of Northern Africa into fruitful gardens, by means of artesian wells, not an improbable expectation. They have gone farther, and argued that, if the soil were covered with fields and forests, vegetation would call down moisture from the Libyan sky, and that the showers which are now wasted on the sea, or so often deluge Southern Europe with destructive inundation, would in part be condensed over the arid wastes of Africa, and thus, without further aid from man, bestow abundance on regions which nature seems to have condemned to perpetual desolation. An equally bold speculation, founded on the well-known fact that the temperature of the earth and of its internal waters increases as we descend beneath the surface, has suggested that artesian wells might supply heat for industrial and domestic purposes, for hot-house cultivation, and even for the local amelioration of climate. The success with which Count Lardarel has employed natural hot springs for the evaporation of water charged with boracic acid, and other fortunate applications of the heat of thermal sources, lend some countenance to the latter project; but both must, for the present, be ranked among the vague possibilities of science, not regarded as probable future triumphs of man over nature. Artificial Springs A more plausible and inviting scheme is that of the creation of perennial springs by husbanding rain and snow water, storing it up in artificial reservoirs of earth, and filtering it through purifying strata, in analogy with the operations of nature. The sagacious Palissy--starting from the theory that all springs are primarily derived from precipitation, and reasoning justly on the accumulation and movement of water in the earth--proposed to reduce theory to practice, and to imitate the natural processes by which rain is absorbed by the earth and given out again in running fountains. "When I had long and diligently considered the cause of the springing of natural fountains and the places where they be wont to issue," says he, "I did plainly perceive, at last, that they do proceed and are engendered of nought but the rains. And it is this, look you, which hath moved me to enterprise the gathering together of rain-water after the manner of nature, and the most closely according to her fashion that I am able; and I am well assured that by following the formulary of the Supreme Contriver of fountains, I can make springs, the water whereof shall be as good and pure and clear as of such which be natural." [Footnote: Oeuvres de Palissy, Des Eaux et Fontaines, p. 157.] Palissy discusses the subject of the origin of springs at length and with much ability, dwelling specially on infiltration, and, among other things, thus explains the frequency of springs in mountainous regions: "Having well considered the which, thou mayest plainly see the reason why there be more springs and rivulets proceeding from the mountains than from the rest of the earth; which is for no other cause but that the rocks and mountains do retain the water of the rains like vessels of brass. And the said waters falling upon the said mountains descend continually through the earth, and through crevices, and stop not till they find some place that is bottomed with stone or close and thick rocks; and they rest upon such bottom until they find some channel or other manner of issue, and then they flow out in springs or brooks or rivers, according to the greatness of the reservoirs and of the outlets thereof." [Footnote: Id., p. 166. Palissy's method has recently been tried with good success in various parts of France.] After a full exposition of his theory, Palissy proceeds to describe his method of creating springs, which is substantially the same as that lately proposed by Babinet in the following terms: "Choose a piece of ground containing four or five acres, with a sandy soil, and with a gentle slope to determine the flow of the water. Along its upper line, dig a trench five or six feet deep and six feet wide. Level the bottom of the trench, and make it impermeable by paving, by macadamizing, by bitumen, or, more simply and cheaply, by a layer of clay. By the side of this trench dig another, and throw the earth from it into the first, and so on until you have rendered the subsoil of the whole parcel impermeable to rain-water. Build a wall along the lower line with an aperture in the middle for the water, and plant fruit or other low trees upon the whole, to shade the ground and check the currents of air which promote evaporation. This will infallibly give you a good spring which will flow without intermission, and supply the wants of a whole hamlet or a large chateau." [Footnote: Babinet, Etudes et Lectures sur les Sciences d'Observation, ii., p. 225. Our author precedes his account of his method with a complaint which most men who indulge in thinking have occasion to repeat many times in the course of their lives. "I will explain to my readers the construction of artificial fountains according to the plan of the famous Bernard de Palissy, who, a hundred and fifty [three hundred] years ago, came and took away from me, a humble academician of the nineteenth century, this discovery which I had taken a great deal of pains to make. It is enough to discourage all invention when one finds plagiarists in the past as well as in the future!" (P. 224.)] Babinet states that the whole amount of precipitation on a reservoir of the proposed area, in the climate of Paris, would be about 13,000 cubic yards, not above one half of which, he thinks, would be lost, and, of course, the other half would remain available to supply the spring. I much doubt whether this expectation would be realized in practice, in its whole extent; for if Babinet is right in supposing that the summer rain is wholly evaporated, the winter rains, being much less in quantity, would hardly suffice to keep the earth saturated and give off so large a surplus. The method of Palissy, though, as I have said, similar in principle to that of Babinet, would be cheaper of execution, and, at the same time, more efficient. He proposes the construction of relatively small filtering receptacles, into which he would conduct the rain falling upon a large area of rocky hillside, or other sloping ground not readily absorbing water. This process would, in all probability, be a very successful, as well as an inexpensive, mode of economizing atmospheric precipitation, and compelling the rain and snow to form perennial fountains at will. Economizing Precipitation. The methods suggested by Palissy and by Babinet are of limited application, and designed only to supply a sufficient quantity of water for the domestic use of small villages or large private establishments. Dumas has proposed a much more extensive system for collecting and retaining the whole precipitation in considerable valleys, and storing it in reservoirs, whence it is to be drawn for household and mechanical purposes, for irrigation, and, in short, for all the uses to which the water of natural springs and brooks is applicable. His plan consists in draining both surface and subsoil, by means of conduits differing in construction according to local circumstances, but in the main not unlike those employed in improved agriculture, collecting the water in a central channel, securing its proper filterage, checking its too rapid flow by barriers at convenient points, and finally receiving the whole in spacious, covered reservoirs, from which it may he discharged in a constant flow or at intervals as convenience may dictate. [Footnote: M. G. Dumas, La Science des Fontaines, 1857.] There is no reasonable doubt that a very wide employment of these various contrivances for economizing and supplying water is practicable, and the expediency of resorting to them is almost purely an economical question. There appears to be no serious reason to apprehend collateral evils from them, and in fact all of them, except artesian wells, are simply indirect methods of returning to the original arrangements of nature, or, in other words, of restoring the fluid circulation of the globe; for when the earth was covered with the forest, perennial springs gushed from the foot of every hill, brooks flowed down the bed of every valley. The partial recovery of the fountains and rivulets which once abundantly watered the face of the agricultural world seems practicable by such means, even without any general replanting of the forests; and the cost of one year's warfare--or in some countries of that armed peace which has been called "Platonic war"--if judiciously expended in a combination of both methods of improvement, would secure, to almost every country that man has exhausted, an amelioration of climate, a renovated fertility of soil, and a general physical improvement, which might almost be characterized as a new creation. Inundations and Torrents. In pointing out in a former chapter the evils which have resulted from the too extensive destruction of the forests, I dwelt at some length on the increased violence of river inundations, and especially on the devastations of torrents, in countries improvidently deprived of their woods, and I spoke of the replanting of the forests as probably the most effectual method of preventing the frequent recurrence of disastrous floods. There are many regions where, from the loss of the superficial soil, from financial considerations, and from other special causes, the general restoration of the woods is not, under present circumstances, either possible or desirable. In all inhabited countries, the necessities of agriculture and other considerations of human convenience will always require the occupation of much the largest proportion of the surface for purposes inconsistent with the growth of extensive forests. Even where large plantations are possible and in actual process of execution, many years must elapse before the action of the destructive causes in question can be arrested or perhaps even sensibly mitigated by their influence; and besides, floods will always occur in years of excessive precipitation, whether the surface of the soil be generally cleared or generally wooded. [Footnote: All the arrangements of rural husbandry, and we might say of civilised occupancy of the earth, are such as necessarily to increase the danger and the range of floods by promoting the rapid discharge of the waters of precipitation. Superficial, if not subterranean, drainage is a necessary condition of all agriculture. There is no field which has not some artificial disposition for this purpose, and even the furrows of ploughed land, if the surface is inclined, and especially when it if frozen, serve rather to carry off than to retain water. As Bacquerel has observed, common road and railway ditches are among the most efficient conduits for the discharge of surface-water which man has yet constructed, and of course they are powerful agents in causing river inundations. All these channels are, indeed, necessary for the convenience of man, but this convenience, like every other interference with the order of nature, must often be purchased at a heavy cost.] Physical improvement in this respect, then, cannot be confined to merely preventive measures, but, in countries subject to damage by inundation, means must be contrived to obviate dangers and diminish injuries to which human life and all the works of human industry will occasionally be exposed, in spite of every effort to lessen the frequency of their recurrence by acting directly on the causes that produce them. As every civilized country is, in some degree, subject to inundation by the overflow of rivers, the evil is a familiar one, and needs no general description. In discussing this branch of the subject, therefore, I may confine myself chiefly to the means that have been or may be employed to resist the force and limit the ravages of floods, which, left wholly unrestrained, would not only inflict immense injury upon the material interests of man, but produce geographical revolutions of no little magnitude. Inundations of 1856 in France. The month of May, 1856, was remarkable for violent and almost uninterrupted rains, and most of the river-basins of France were inundated to an extraordinary height. In the val-leys of the Loire and its aflluents, about a million of acres, including many towns and villages, were laid under water, and the amount of pecuniary damage was almost incalculable. [Footnote: Champion, Les Inondations en France, iii., p.156, note.] The flood was not less destructive in the valley of the Rhone, and in fact an invasion by a hostile army could hardly have been more disastrous to the inhabitants of the plains than was this terrible deluge. There had been a flood of this latter river in the year 1840, which, for height and quantity of water, was almost as remarkable as that of 1856, but it took place in the month of November, when the crops had all been harvested, and the injury inflicted by it upon agriculturists was, therefore, of a character to be less severely and less immediately felt than the consequences of the inundation of 1856. [Footnote: Notwithstanding this favorable circumstance, the damage done by the inundation of 1840 in the valley of the Rhone was estimated at seventy-two millions of francs.--Champion, Les Inondations en France, iv., p. 124. Several smaller floods of the Rhone, experienced at a somewhat earlier season of the year in 1846, occasioned a loss of forty-five millions of francs. "What if," says Dumont, "instead of happening in October, that is, between harvest and seedtime, they had occurred before the crops were secured The damage would have been counted by hundreds of millions."--Des Travaux Publics, p. 99, note.] In the fifteen years between these two great floods, the population and the rural improvements of the river valleys had much increased, common roads, bridges, and railways had been multiplied and extended, telegraph lines had been constructed, all of which shared in the general ruin, and hence greater and more diversified interests were affected by the catastrophe of 1856 than by any former like calamity. The great flood of 1840 had excited the attention and roused the sympathies of the French people, and the subject was invested with new interest by the still more formidable character of the inundations of 1856. It was felt that these scourges had ceased to be a matter of merely local concern, for, although they bore most heavily on those whose homes and fields were situated within the immediate reach of the swelling waters, yet they frequently destroyed harvests valuable enough to be a matter of national interest, endangered the personal security of the population of important political centres, interrupted communication for days and even weeks together on great lines of traffic and travel--thus severing, as it were, all South-western France from the rest of the empire--and finally threatened to produce great and permanent geographical changes. The well-being of the whole commonwealth was seen to be involved in preventing the recurrence and in limiting the range of such devastations. The Government encouraged scientific investigation of the phenomena and their laws. Their causes, their history, their immediate and remote consequences, and the possible safeguards to be employed against them, have been carefully studied by the most eminent physicists, as well as by the ablest theoretical and practical engineers of France. Many hitherto unobserved facts have been collected, many new hypotheses suggested, and many plans, more or less original in character, have been devised for combating the evil; but thus far, the most competent judges are not well agreed as to the mode, or even the possibility, of applying an effectual remedy. I have noticed in the next preceding chapter the recent legislation of France upon the preservation and restoration of the forests, with reference to their utility in subduing torrents and lessening the frequency and diminishing the violence of river inundations. The provisions of those laws are preventive rather than remedial, but most beneficial effects have already been experienced from the measures adopted in pursuance of them, though sufficient time has not yet elapsed for the complete execution of the greater operations of the system. Basins of Reception. Destructive inundations of large rivers are seldom, if ever, produced by precipitation within the limits of the principal valley, but almost uniformly by sudden thaws or excessive rains on the mountain ranges where the tributaries take their rise. It is therefore plain that any measures which shall check the flow of surface-waters into the channels of the affluents, or which shall retard the delivery of such waters into the principal stream by its tributaries, will diminish in the same proportion the dangers and the evils of inundation by great rivers. The retention of the surface-waters upon or in the soil can hardly be accomplished except by the methods already mentioned, replanting of forests, and furrowing or terracing. The current of mountain streams can be checked by various methods, among which the most familiar and obvious is the erection of barriers or dams across their channels, at points convenient for forming reservoirs large enough to retain the superfluous waters of great rains and thaws. [Footnote: On the construction of temporary and more permanent barriera to the curreuts of torrents and rivulets, see Marchand, Les Torrents des Alpes, in Recue des Eaux et Forets for October and November, 1871.] Besides the utility of such basins in preventing floods, the construction of them is recommended by very strong considerations, such as the furnishing of a constant supply of water for agricultural and mechanical purposes, and, also, their value as ponds for breeding and rearing fish, and, perhaps, for cultivating aquatic vegetables. [Footnote: In reference to the utilization of artificial as well as natural reservoirs, see Ackerhof, Die Nutruny der Teiche und Gewasser, Quadlinburg, 1869.] The objections to the general adoption of the system of reservoirs are these: the expense of their construction and maintenance; the reduction of cultivable area by the amount of surface they must cover; the interruption they would occasion to free communication; the probability that they would soon be filled up with sediment, and the obvious fact that when full of earth, or even water, they would no longer serve their principal purpose; the great danger to which they would expose the country below them in case of the bursting of their barriers; [Footnote: For accounts of damage from the bursting of reservoirs, see Vallee, Memoire sur les Reservoir d'Alimentation des Canaux, Annales des Ponts et Chaussees, 1833, 1er semestre, p.261. The dam of the reservoir of Puentes in Spain, which was one hundred and sixty feet high, after having discharged its functions for eleven years, burst, in 1802, in consequence of a defect in its foundations, and the eruption of the water destroyed or seriously injured eight hundred houses, and produced damage to the amount of more than a million dollars.--Aynard, Irrigations du Midi d l'Europe, pp. 257-259.] the evil consequences they would occasion by prolonging the flow of inundations in proportion as they diminished their height; the injurious effects it is supposed they would produce upon the salubrity of the neighbouring districts; and, lastly, the alleged impossibility of constructing artificial basins sufficient in capacity to prevent, or in any considerable measure to mitigate, the evils they are intended to guard against. The last argument is more easily reduced to a numerical question than the others. The mean and extreme annual precipitation of all the basins where the construction of such works would be seriously proposed is already approximately known by meteorological tables, and the quantity of water, delivered by the greatest floods which have occurred within the memory of man, may be roughly estimated from their visible traces. From these elements, or from meteorological records, the capacity of the necessary reservoirs can be calculated. Let us take the case of the Ardeche. In the inundation of 1857, that river poured into the Rhone 1,305,000,000 cubic yards of water in three days. If we suppose that half this quantity might have been suffered to flow down its channel without inconvenience, we shall have about 650,000,000 cubic yards to provide for by reservoirs. The Ardeche and its principal affluent, the Chassezae, have, together, about twelve considerable tributaries rising near the crest of the mountains which bound the basin. If reservoirs of equal capacity were constructed upon all of them, each reservoir must be able to contain 54,000,000 cubic yards, or, in other words, must be equal to a lake 3,000 yards long, 1,000 yards wide, and 18 yards deep, and besides, in order to render any effectual service, the reservoirs must all have been empty at the commencement of the rains which produced the inundation. Thus far I have supposed the swelling of the waters to be uniform throughout the whole basin; but such was by no means the fact in the inundation of 1857, for the rise of the Chassezae, which is as large as the Ardeche proper, did not exceed the limits of ordinary floods, and the dangerous excess came solely from the headwaters of the latter stream. Hence reservoirs of double the capacity I have supposed would have been necessary upon the tributaries of that river, to prevent the injurious effects of the inundation. It is evident that the construction of reservoirs of such magnitude for such a purpose is financially, if not physically, impracticable, and when we take into account a point I have just suggested, namely, that the reservoirs must be empty at all times of apprehended flood, and, of course, their utility limited almost solely to the single object of preventing inundations, the total inapplicability of such a measure in this particular case becomes still more glaringly manifest. Another not less conclusive fact is, that the valleys of all the upland tributaries of the Ardeche descend so rapidly, and have so little lateral expansion, as to render the construction of capacious reservoirs in them quite impracticable. Indeed, engineers have found but two points in the whole basin suitable for that purpose, and the reservoirs admissible at these would have only a joint capacity of about 70,000,000 cubic yards, or less than one-ninth part of what I suppose to be required. The case of the Ardeche is no doubt an extreme one, both in the topographical character of its basin and in its exposure to excessive rains; but all destructive inundations are, in a certain sense, extreme cases also, and this of the Ardeche serves to show that the construction of reservoirs is not by any means to be regarded as a universal panacea against floods. Nor, on the other hand, is this measure to be summarily rejected. Nature has adopted it on a great scale, on both flanks of the Alps, and on a smaller, on those of the Adirondacks and of many lower chains. The quantity of water which, in great rains or sudden thaws, rushes down the steep declivities of the Alps, is so vast that the channels of the Swiss and Italian rivers would be totally incompetent to carry it off as rapidly as it would pour into them, were it not absorbed by the capacious basins which nature has scooped out for its reception, freed from the transported material which adds immensely both to the volume and to the force of its current, and then, after some reduction by evaporation and infiltration, gradually discharged into the beds of the rivers. In the inundation of 1829 the water discharged into Lake Como from the 15th to the 20th of September amounted to 2,600 cubic yards the second, while the outflow from the lake during the same period was only at the rate of about 1,050 cubic yards to the second. In those five days, then, the lake accumulated 670,000,000 cubic yards of superfluous water, and of course diminished by so much the quantity to be disposed of by the Po. [Footnote: Baird Smith, Italian Irrigation, i., p. 176.] In the flood of October, 1868, the surface of Lago Maggiore was raised twenty-five feet above low-water mark in the course of a few hours. [Footnote: Bollettino della Societa Geog. Italiana, iii., p. 466.] There can be no doubt that without such detention of water by the Lakes Como, Maggiore, Garda, and other subalpine basins, almost the whole of Lombardy would have been irrecoverably desolated, or rather, its great plain would never have become anything but a vast expanse of river-beds and marshes; for the annual floods would always have prevented the possibility of its improvement by man. [Footnote: See, as to the probable effects of certain proposed hydraulic works at the outlet of Lake Maggiore on the action of the lake as a regulating reservoir, Tagliasecchi, Notizie sui Canali dell' Alta Lombardia, Milano, 1869.] Lake Bourget in Savoy, once much more extensive than it is at present, served, and indeed still serves, a similar purpose in the economy of nature. In a flood of the Rhone, in 1863, this lake received from the overflow of that river, which does not pass through it, 72,000,000 cubic yards of water, and of course moderated, to that extent, the effects of the inundation below. [Footnote: Elisee Recluse, La Terre, i., p. 460.] In fact, the alluvial plains which border the course of most considerable streams, and are overflowed in their inundations, either by the rise of the water to a higher level than that of their banks, or by the bursting of their dikes, serve as safety-valves for the escape of their superfluous waters. The current of the Po, spreading over the whole space between its widely separated embankments, takes up so much water in its inundations, that, while a little below the outlet of the Ticino the discharge of the channel is sometimes not less than 19,500 cubic yards to the second, it has never exceeded 6,730 yards at Ponte Lagoscuro, near Ferrara. The currents of the Mississippi, the Rhone, and of many other large rivers, are modified in the same way. In the flood of 1858, the delivery of the Mississippi, a little below the month of the Ohio, was 52,000 cubic yards to the second, but at Baton Rouge, though of course increased by the waters of the Arkansas, the Yazoo, and other smaller tributaries, the discharge was reduced to 46,760 cubic yards. We rarely err when we cautiously imitate the processes of nature, and there are doubtless many cases where artificial basins of reception and lateral expansions of river-beds might be employed with advantage. Many upland streams present points where none of the objections usually urged against artificial reservoirs, except those of expense and of danger from the breaking of dams, could have any application. Reservoirs may be so constructed as to retain the entire precipitation of the heaviest thaws and rains, leaving only the ordinary quantity to flow along the channel; they may be raised to such a height as only partially to obstruct the surface drainage; or they may be provided with sluices by means of which their whole contents can be discharged in the dry season and a summer crop be grown upon the ground they cover at high water. The expediency of employing them and the mode of construction depend on local conditions, and no rules of universal applicability can be laid down on the subject. [Footnote: The insufficiency of artificial basins of reception as a means of averting the evils resulting from the floods of great rivers has been conclusively shown, in reference to a most important particular case--that of the Mississippi--by Humphreys and Abbot, in their admirable monograph of that river.] It is remarkable that nations which we, in the inflated pride of our modern civilization, so generally regard as little less than barbarian, should have long preceded Christian Europe in the systematic employment of great artificial basins for the various purposes they are calculated to subserve. The ancient Peruvians built strong walls, of excellent workmanship, across the channels of the mountain sources of important streams, and the Arabs executed immense works of similar description, both in the great Arabian peninsula and in all the provinces of Spain which had the good fortune to fall under their sway. The Spaniards of the fifteenth and sixteenth centuries, who, in many points of true civilization and culture, were far inferior to the races they subdued, wantonly destroyed these noble monuments of social and political wisdom, or suffered them to perish, because they were too ignorant to appreciate their value, or too unskilful as practical engineers to be able to maintain them, and some of their most important territories were soon reduced to sterility and poverty in consequence. Diversion of Rivers. Another method of preventing or diminishing the evils of inundation by torrents and mountain rivers, analogous to that employed for the drainage of lakes, consists in the permanent or occasional diversion of their surplus waters, or of their entire currents, from their natural courses, by tunnels or open channels cut through their banks. Nature, in many cases, resorts to a similar process. Most great rivers divide themselves into several arms in their lower course, and enter the sea by different mouths. There are also cases where rivers send off lateral branches to convey a part of their waters into the channel of other streams. [Footnote: Some geographical writers apply the term bifurcation exclusively to this intercommunication of rivers; others, with more etymological propriety, use it to express the division of great rivers into branches at the head of their deltas. A technical word is wanting to designate the phenomenon mentioned in the text, and there is no valid objection to the employment of the anatomical term anastomosis for this purpose.] The most remarkable of these is the junction between the Amazon and the Orinoco by the natural canal of the Cassiquiare and the Rio Negro. In India, the Cambodja and the Menam are connected by the Anam; the Saluen and the Irawaddi by the Panlaun. There are similar examples, though on a much smaller scale, in Europe. The Tornea, and the Calix rivers in Lapland communicate by the Tarando, and in Westphalia, the Else, an arm of the Haase, falls into the Weser. [Footnote: The division of the currents of rivers, as a means of preventing the overflow of their banks, is by no means a remedy capable of general application, even when local conditions are favorable to the construction of an emissary. The velocity of a stream, and consequently its delivery in a given time, are frequently diminished in proportion to the diminution of the volume by diversion; and on the other hand, the increase of volume by the admission of a new tributary increases proportionally the velocity and the quantity of water delivered. Emissaries may, nevertheless, often be useful in carrying off water which has already escaped from the channel and which would otherwise become stagnant and prevent further lateral discharge from the main current, and it is upon this principle that Humphreys and Abbot think a canal of diversion at Lake Providence might be advisable. Emissaries serve an important purpose in the lower course of rivers where the bed is nearly a dead level and the water moves from previously acquired momentum and the pressure of the current above, rather than by the force of gravitation, and it is, in general, only under such circumstances, as for example in the deltas at the mouths of great rivers, that nature employs them.] The change of bed in rivers by gradual erosion of their banks is familiar to all, but instances of the sudden abandonment of a primitive channel are by no means wanting. At a period of unknown antiquity, the Ardeche pierced a tunnel 200 feet wide and 100 high, through a rock, and sent its whole current through it, deserting its former bed, which gradually filled up, though its course remained traceable. In the great inundation of 1827, the tunnel proved insufficient for the discharge of the water, and the river burst through the obstructions which had now choked up its ancient channel, and resumed its original course. [Footnote: Mardigny, Memoire sur les Inondations de l'Ardeche, p. 13.] It was probably such facts as these that suggested to ancient engineers the possibility of like artificial operations, and there are numerous instances of the execution of works for this purpose in very remote ages. The Bahr Jusef, the great stream which supplies the Fayoum with water from the Nile, has been supposed, by some writers, to be a natural channel; but both it and the Bahr el Wady are almost certainly artificial canals constructed to water that basin, to regulate the level of Lake Meeris, and possibly, also, to diminish the dangers resulting from excessive inundations of the Nile, by serving as waste-weirs to discharge a part of its overflowing waters. [Footnote: The starting-points of these anals were far up the Nile, and of course at a comparatively high level, and it is probable that they received water only during the inundation. Linant Bey calculates the capacity of Lake Moeris at 3,686,667 cubic yards and the water received by it at high Nile at 465 cubic yards the second.] Several of the seven ancient mouths of the Nile are believed to be artificial channels, and Herodotus even asserts that King Menes diverted the entire course of that river from the Libyan to the Arabian side of the valley. There are traces of an ancient river-bed along the western mountains, which give eome countenance to this statement. But it is much more probable that the works of Menes were designed rather to prevent a natural, than to produce an artificial, change in the channel of the river. Two of the most celebrated cascades in Europe, those of the Teverone at Tivoli and of the Velino at Terni, owe, if not their existence, at least their position and character, to the diversion of their waters from their natural beds into new channels, in order to obviate the evils produced by their frequent floods. Remarkable works of the same sort have been executed in Switzerland, in very recent times. Until the year 1714, the Kander, which drains several large Alpine valleys, ran, for a considerable distance, parallel with the Lake of Thun, and a few miles below the city of that name emptied into the river Aar. It frequently flooded the flats along the lower part of its course, and it was determined to divert it into the Lake of Thun. For this purpose, two parallel tunnels were cut through the intervening rock, and the river turned into them. The violence of the current burst up the roof of the tunnels, and, in a very short time, wore the new channel down not less than one hundred feet, and even deepened the former bed at least fifty feet, for a distance of two or three miles above the tunnel. The lake was two hundred feet deep at the point where the river was conducted into it, but the gravel and sand carried down by the Kander has formed at its mouth a delta containing more than a hundred acres, which is still advancing at the rate of several yards a year. The Linth, which formerly sent its waters directly to the Lake of Zurich, and often produced very destructive inundations, was turned into the Wallensee about fifty years ago, and in both these cases a great quantity of valuable land was rescued both from flood and from insalubrity. Glacier Lakes. In Switzerland, the most terrible inundations often result from the damming up of deep valleys by ice-slips or by the gradual advance of glaciers, and the accumulation of great masses of water above the obstructions. The ice is finally dissolved by the heat of summer or the flow of warm waters, and when it bursts, the lake formed above is discharged almost in an instant, and all below is swept down to certain destruction. In 1595, about a hundred and fifty lives and a great amount of property were lost by the eruption of a lake formed by the descent of a glacier into the valley of the Drance, and a similar calamity laid waste a considerable extent of soil in the year 1818. On this latter occasion, the barrier of ice and snow was 3,000 feet long, 600 thick, and 400 high, and the lake which had formed above it contained not less than 800,000,000 cubic feet. A tunnel was driven through the ice, and about 300,000,000 cubic feet of water safely drawn off by it, but the thawing of the walls of the tunnel rapidly enlarged it, and before the lake was half drained, the barrier gave way and the remaining 500,000,000 cubic feet of water were discharged in half an hour. The recurrence of these floods has since been prevented by directing streams of water, warmed by the sun, upon the ice in the bed of the valley, and thus thawing it before it accumulates in sufficient mass to form a new barrier and threaten serious danger. [Footnote: In 1845 a similar lake was formed by the extension of the Vernagt glacier. When the ice barrier gave way, 3,000,000 cubic yards of water were discharged in an hour.--Sonklar, Die Oetzthaler Gebirgsgruppe, section 167.] In the cases of diversion of streams above mentioned, important geographical changes have been directly produced by those operations. By the rarer process of draining glacier lakes, natural eruptions of water, which would have occasioned not less important changes in the face of the earth, have been prevented by human agency. River Embankments. The most obvious and doubtless earliest method of preventing the escape of river-waters from their natural channels, and the overflow of fields and towns by their spread, is that of raised embankments along their course. [Footnote: Riparian embankments are a real, if not a conscious, imitation of a natural process. The waters of rivers which flow down planes of gentle inclination deposit, in their inundations, the largest proportion of their sediment as soon as, by overflowing their banks, they escape from the swift current of the channel. The immediate borders of such rivers consequently become higher than the grounds lying further from the stream, and constitute, of themselves, a sort of natural dike of small elevation. In the "intervales" or "bottoms" of the great North American rivers the alluvial banks are elevated and dry, the flats more remote from the river lower and swampy. This is generally observable in Egypt (see Figari Bey, Studi Scientifici sull' Egitto, i, p. 87), though less so than in the valley of the Mississippi, where the alluvial banks form natural glacis, descending as you recede from the river, and in some places, as below Cape Girardeau, at the rate of seven feet in the first mile. Humphreys and Abbott, Report, pp. 96, 97. In fact, rivers, like mountain torrents, often run for a long distance on the summit of a ridge built up by their own deposits. The delta of the Mississippi is a regular cone, or rather mountain, of dejection, extending far out into the Gulf of Mexico, along the crest of which the river flows, sending off here and there, as it approaches the sea, a system of lateral streams resembling the fan-shaped discharge of a torrent.] The necessity of such embankments usually arises from the gradual elevation of the bed of running streams in consequence of the deposit of the earth and gravel they are charged with in high water; and, as we have seen, this elevation is rapidly accelerated when the highlands around the headwaters of rivers are cleared of their forests. When a river is embanked at a given point, and, consequently, the water of its floods, which would otherwise spread over a wide surface, is confined within narrow limits, the velocity of the current and its transporting power are augmented, and its burden of sand and gravel is deposited at some lower point, where the rapidity of its flow is checked by a dam or other artificial obstruction, by a diminution in the inclination of the bed, by a wider channel, or finally by a lacustrine or marine basin which receives its waters. Wherever it lets fall solid material, its channel is raised in consequence, and the declivity of the whole bed between the head of the embankment and the slack of the stream is reduced. Hence the current, at first accelerated by confinement, is afterwards checked by the mechanical resistance of the matter deposited, and by the diminished inclination of its channel, and then begins again to let fall the earth it holds in suspension, and to raise its bed at the point where its overflow had been before prevented by embankment. [Footnote: In proportion as the dikes are improved, and breaches and the escape of the water through them are less frequent, the height of the annual inundations is increased. Some towns on the banks of the Po, and of course within the system of parallel embankments, were formerly secure from flood by the height of the artificial mounds on which they were built; but they have recently been obliged to construct ring-dikes for their protection. Lombardini lays down the following general statement of the effects of river embankments: "The immediate effect of embanking a river is generally an increase in the height of its floods, but, at the same time, a depression of its bed, by reason of the increased force, and consequently excavating action, of the current. "It is true that coarser material may hence be carried further, and at the same time deposit itself on a reduced slope. "The embankment of the upper branches of a river increases the volume, and therefore the height of the floods in the lower course, in consequence of the more rapid discharge of its affluents into it. "When, in consequence of the flow of a river channel through an alluvial soil not yet REGULATED, or, in other words, which has not acquired its normal inclination, the course of the river has not become established, it is natural that its bed should rise more rapidly after its embankment. ... "The embankment of the lower course of a river, near its discharge into the sea, causes the elevation of the bed of the next reach above, both because the swelling of the current, in consequence of its lateral confinement, occasions eddies, and of course deposits, and because the prolongation of the course of the stream, or the advance of its delta into the sea, is accelerated."--Dei congiamenti cia soggiacque l'idraulica condizione del Po, etc., pp. 41, 42. Del Noce states that in the levellings for the proposed Leopolda railway, he found that the bed of the Sieue had been permanently elevated two yards between 1708 and 1844, and that of the Fosso di San Gaudenzio more than a yard and a half between 1752 and 1845. Those, indeed, are not rivers of the rank of the Po; but neither are they what are technically called torrents or mountain streams, whose flow is only an occasional effect of heavy rains or melting snow.--Trattato delle Macchie e Foreste di Tuscana, Firenze, 1857, p. 29.] The bank must now be raised in proportion, and these processes would be repeated and repeated indefinitely, had not nature provided a remedy in floods, which sweep out recent deposits, burst the bonds of the river and overwhelm the adjacent country with final desolation, or divert the current into a new channel, destined to become, in its turn, the scene of a similar struggle between man and the waters. [Footnote: The Noang-ho has repeatedly burst its dikes and changed the channel of its lower course, sometimes delivering its waters into the sea to the north, sometimes to the south of the peninsula of Chan-tung, thus varying its point of discharge by a distance of 220 miles.--Elisee Reclus, La Terre, t. i, p. 477. Sec interesting notices of the lower course of the Noang-ho in Nature, Nov. 25, 1869. The frequent changes of channel and mouth in the deltas of great rivers are by no means always an effect of diking. The mere accumulation of deposits in the beds of rivers which transport much sediment compels them continually to seek new outlets, and it is only by great effort that art can keep their points of discharge pproximately constant. The common delta of the Ganges and the Brahmapootra is in a state of incessant change, and the latter river is said to have shifted its main channel 200 miles to the west since 1785, the revolution having been principally accomplished between 1810 and 1830.] But here, as in so many other fields where nature is brought into conflict with man, she first resists his attempts at interference with her operations, then, finding him the stronger, quietly submits to his rule, and ends by contributing her aid to strengthen the walls and shackles by which he essays to confine her. If, by assiduous repair of his dikes, he, for a considerable time, restrains the floods of a river within new bounds, nature, by a series of ingenious compensations, brings the fluctuating bed of the stream to a substantially constant level, and when his ramparts have been, by his toil, raised to a certain height and widened to a certain thickness, she, by her laws of gravitation and cohesion, consolidates their material until it becomes almost as hard, as indissoluble, and as impervious as the rock. But, though man may press the forces of nature into his service, there is a limit to the extent of his dominion over them, and unless future generations shall discover new modes of controlling those forces, or new remedies against their action, he must at last succumb in the struggle. When the marine estuaries and other basins of reception shall be filled up with the sedimentary debris of the mountains, or when the lower course of the rivers shall be raised or prolonged by their own deposits until they have, no longer, such a descent that gravitation and the momentum of the current can overcome the frictional resistance of the bed and banks, the water will, in spite of all obstacles, diffuse itself laterally and for a time raise the level of the champaign land upon its borders, and at last convert it into morasses. It is for this reason that Lombardini advises that a considerable space along the lower course of rivers be left undiked, and the water allowed to spread itself over its banks and gradually raise them by its deposits. [Footnote: This method has been adopted on the lower course of the Lamone, and a considerable extent of low ground adjacent to that river has been raised by spontaneous deposit to a sufficient height to admit of profitable cultivation.] This would, indeed, be a palliative, but only a palliative. For the present, however, we have nothing better, and here, as often in political economy, we must content ourselves with "apres nous le deluge," allowing posterity to suffer the penalty of our improvidence and our ignorance, or to devise means for itself to ward off the consequences of them. The deposit of slime by rivers upon the flats along their banks not only contributes greatly to the fertility of the soil thus flowed, but it subserves a still more important purpose in the general economy of nature. All running streams begin with excavating channels for themselves, or deepening the natural depressions in which they flow; [Footnote: I do not mean to say that all rivers excavate their own valleys, for I have no doubt that in the majority of cases such depressions of the surface originate in higher geological causes, such as the fissures and other irregularities of surface which could not fail to accompany upheaval, and hence the valley makes the river, not the river the valley. But even if we suppose a basin of the hardest rock to be elevated at once, completely formed, from the submarine abyss where it was fashioned, the first shower of rain that falls upon it, after it rises to the air, will discharge its waters along the lowest lines of the surface, and cut those lines deeper, and so on with every successive rain. The disintegrated rock from the upper part of the basin forms the lower by alluvial deposit, which is constantly transported farther and farther until the resistance of gravitation and cohesion balances the mechanical force of the running water. Thus plains, more or less steeply inclined, are formed, in which the river is constantly changing its bed, according to the perpetually varying force and direction of its currents, modified as they are by ever-fluctuating conditions. Thus the Po is said to have long inclined to move its channel southwards, at certain points, in consequence of the mechanical force of its northern affluents. A diversion of these tributaries from their present beds, so that they should enter the main stream at other points and in different directions, might modify the whole course of that great river. But the mechanical force of the tributary is not the only element of its influence on the course of the principal stream. The deposits it lodges in the bed of the latter, acting as simple obstructions or causes of diversion, are not less important agents of change.] but in proportion as their outlets are raised by the solid material transported by their currents, their velocity is diminished, they deposit gravel and sand at constantly higher and higher points, and so at last elevate, in the middle and lower part of their course, the beds they had previously scooped out. [Footnote: The distance to which a new obstruction to the flow of a river, whether by a dam or by a deposit in its channel, will retard its current, or, in popular phrase, "set back the water," is a problem of more difficult practical solution than almost any other in hydraulics. The elements--such as straightness or crookedness of channel, character of bottom and banks, volume and previous velocity of current, mass of water far above the obstruction, extraordinary drought or humidity of seasons, relative extent to which the river may be affected by the precipitation in its own basin, and by supplies received through subterranean channels from sources so distant as to be exposed to very different meteorological influences, effects of clearing and other improvements always going on in new countries--are all extremely difficult, and some of them impossible, to be known and measured. In the American States, very numerous water-mills have been erected within a few years, and there is scarcely a stream in the settled portion of the country which has not several mill-dams upon it. When a dam is raised--a process which the gradual diminution of the summer currents renders frequently necessary--or when a new dam is built, it often happens that the meadows above are flowed, or that the retardation of the stream extends back to the dam next above. This leads to frequent law-suits. From the great uncertainty of the facts, the testimony is more conflicting in these than in any other class of cases, and the obstinacy with which "water causes" are disputed has become proverbial.] The raising of the channels is compensated in part by the simultaneous elevation of their banks and the flats adjoining them, from the deposit of the finer particles of earth and vegetable mould brought down from the mountains, without which elevation the low grounds bordering all rivers would be, as in many cases they in fact are, mere morasses. All arrangements which tend to obstruct this process of raising the flats adjacent to the channel, whether consisting in dikes which confine the waters, and, at the same time, augment the velocity of the current, or in other means of producing the last-mentioned effect, interfere with the restorative economy of nature, and at last occasion the formation of marshes where, if left to herself, she might have accumulated inexhaustible stores of the richest soil, and spread them out in plains above the reach of ordinary floods. [Footnote: The sediment of the Po has filled up some lagoons and swamps in its delta, and converted them into comparatively dry land; but, on the other hand, the retardation of the current from the lengthening of its course, and the diminution of its velocity by the deposits at its mouth, have forced its waters at some higher points to spread in spite of embankments, and thus fertile fields have been turned into unhealthy and unproductive marshes.--See Botter, Sulla condizione dei Terreni Maremmani nel Ferraress. Annali di Agricoltura, etc., Fasc. v., 1863.] Dikes, which, as we have seen, are the means most frequently employed to prevent damage by inundation, are generally parallel to each other and separated by a distance not very much greater than the natural width of the bed. [Footnote: In the case of rivers flowing through wide alluvial plains and much inclined to shift their beds, like the Po, the embankments often leave a very wide space between them. The dikes of the Po are sometimes three or four miles apart.] If such walls are high enough to confine the water and strong enough to resist its pressure, they secure the lands behind them from all the evils of inundation except those resulting from filtration; but such ramparts are enormously costly in original construction and in maintenance, and, as has been already shown, the filling up of the bed of the river in its lower course, by sand and gravel, often involves the necessity of incurring new expenditures in increasing the height of the banks. [Footnote: It appears from the investigations of Lombardini that the rate of elevation of the bed of the Po has been much exaggerated by earlier writers, and in some parts of its course the change is so slow that its level may be regarded as nearly constant. Observation has established a similar constancy in the bed of the Rhone and of many other important rivers, while, on the other hand, the beds of the Adige and the Brenta, streams of a more torrential character, are raised considerably above the level of the adjacent fields. The length of the lower course of the Po having been considerably increased by the filling up of the Adriatic with its deposits, the velocity of the current ought, prima facie, to have been diminished and its bed raised in proportion. There are abundant grounds for believing that this has happened in the case of the Nile, and one reason why the same effect has not been more sensibly perceptible in the Po is, that the confinement of the current by continuous embankements gives it a high-water velocity sufficient to sweep out deposits let fall at lower stages and slower movements of the water. Torrential streams tend to excavate or to raise their beds according to the inclination, and to the character of the material they transport. No general law on this point can be laid down in relation to the middle and lower courses of rivers. The conditions which determine the question of the depression or elevation of a river-bed are too multifarious, variable, and complex, to be subjected to formulae, and they can scarcely even be enumerated. The following observation, however, though apparently too unconditionally stated, is too important to be omitted. Rivers which transport sand, gravel, pebbles, heavy mineral matter in short, tend to raise their own beds; those charged only with fine, light earth, to cut them deeper. The prairie rivers of the western United States have deep channels, because the mineral matter they carry down is not heavy enough to resist the impulse of even a moderate current, and those tributaries of the Po which deposit their sediment in the lakes--the Ticino, the Adda, the Oglio, and the Mincio--flow in deep cuts, for the same reason.--Baumgarten, p. 132. In regard to the level of the bed of the Po, there is another weighty consideration which does not seem to have received the attention it deserves. refer to the secular depression of the western coast of the Adriatic, which is computed at the rate of fifteen or twenty centimetres in a century, and which of course increases the inclination of the bed, and the velocity and transporting power of the current of the Po, UNLESS we assume that the whole course of the river, from the sea to its sources, shares in the depression. Of this assumption there is no proof, and the probability is to the contrary. For the evidence, though not conclusive, perhaps, tends to show an elevation of the Tuscan coast, and even of the Ligurian shore at points lying farther west than the sources of the Po. The level of certain parts of the bed of the river referred to by Lombardini as constant, is not their elevation as compared with points nearer the sea, but relatively to the adjacent plains, and there is every reason to believe that the depression of the Adriatic coast, whether, as is conceivable, occasioned by the mere weight of the fluviatile deposits or by more general geological causes, has increased the slope of the bed of the river between the points in question and the sea. In this instance, then, the relative permanency of the river level at certain points may be, not the ordinary case of a natural equilibrium, but the negative effect of an increased velocity of current which prevents deposits where they would otherwise have happened.] They are attended, too, with some collateral disadvantages. They deprive the earth of the fertilizing deposits of the waters, which are powerful natural restoratives of soils exhausted by cultivation; they accelerate the rapidity and transporting power of the current at high water by confining it to a narrower channel, and it consequently conveys to the sea the earthy matter it holds in suspension, and chokes up harbors with a deposit which it would otherwise have spread over a wider surface; they interfere with roads and the convenience of river navigation, and no amount of cost or care can secure them from occasional rupture, in case of which the rush of the waters through the breach is more destructive than the natural flow of the highest inundation. [Footnote: To secure the city of Sacramento, in California, from the inundations to which it is subject, a dike or levee was built upon the bank of the river and raised to an elevation above that of the highest known floods, and it was connected, below the town, with grounds lying considerably above the river. On one occasion a breach in the dike occurred above the town at a very high stage of the flood. The water poured in behind it, and overflowed the lower part of the city, which remained submerged for some time after the river had retired to its ordinary level, because the dike, which had been built to keep the water OUT, now kept it IN. According to Arthur Young, on the lower Po, where the surface of the river at high water has been elevated considerably above the level of the adjacent fields by diking, the peasants in his time frequently endeavored to secure their grounds against threatened devastation through the bursting of the dikes, by crossing the river when the danger became imminent and opening a cut in the opposite bank, thus saving their own property by flooding their neighbors'. He adds, that at high water the navigation of the river was absolutely interdicted, except to mail and passenger boats, and that the guards fired upon all others; the object of the prohibition being to prevent the peasants from resorting to this measure of self-defence.--Travels in Italy and Spain, Nov. 7, 1789. In a flood of the Po in 1839, a breach of the embankment took place at Bonizzo. The water poured through and inundated 116,000 acres, or 181 square miles, of the plain to the depth of from twenty to twenty-three feet, in the lower parts. The inundation of May, 1872, a giant breach occurred in the dike near Ferrara, and 170,000 acres of cultivated land were overflowed, and a population of 30,000 souls driven from their homes. In the flood of October in the same year, in consequence of a breach of the dike at Revere, 250,000 acres of cultivated soil were overflowed, and 60,000 persons were made homeless. The dikes were seriously injured at more than forty points. See page 279, ante. In the flood of 1856, the Loire made seventy-three breaches in its dikes, and thus, instead of a comparatively gradual rise and gentle expansion of its waters, it created seventy-three impetuous torrents, which inflicted infinitely greater mischief than a simply natural overflow would have done. The dikes or levees of the Mississippi, being of more recent construction than those of the Po, are not yet well consolidated and fortified, and for this reason crevasses which occasion destructive inundations are of very frequent occurrence.] For these reasons, many experienced engineers are of opinion that the system of longitudinal dikes is fundamentally wrong, and it has been argued that if the Po, the Adige, and the Brenta had been left unconfined, as the Nile formerly was, and allowed to spread their muddy waters at will, according to the laws of nature, the sediment they have carried to the coast would have been chiefly distributed over the plains of Lombardy. Their banks, it is supposed, would have risen as fast as their beds, the coast-line would not have been extended so far into the Adriatic, and, the current of the streams being consequently shorter, the inclination of their channel and the rapidity of their flow would not have been so greatly diminished. Had man, too, spared a reasonable proportion of the forests of the Alps, and not attempted to control the natural drainage of the surface, the Po, it has been said, would resemble the Nile in all its essential characteristics, and, in spite of the difference of climate, perhaps be regarded as the friend and ally, not the enemy and the invader, of the population which dwells upon its banks. But it has been shown by Humphreys and Abbot that the system of longitudinal dikes is the only one susceptible of advantageous application to the Mississippi, and if we knew the primitive geography and hydrography of the basin of the Po as well as wo do those of the valley of the great American river, we should very probably find that the condemnation of the plan pursued by the ancient inhabitants of Lombardy is a too hasty generalization, and that the case of the Nile is an exception, not an example of the normal regime and condition of a great river. [Footnote: Embankments have been employed on the lower course of the Po for at least two thousand years, and for some centuries they have been connected in a continuous chain from the sea to the vicinity of Cremona. From early ages the Italian hydrographers have stood in the front rank of their profession, and the Italian literature of this branch of material improvement is exceedingly voluminous, exhaustive, and complete. "The science of rivers after the barbarous ages," says Mengotti, "may be said to have been born and perfected in Italy." The eminent Italian engineer Lombardini published in 1870, under the title of Guida allo studio dell' idrologia fluviale e dell' Idraulica practica, which serves both as a summary of the recent progress of that science and as an index to the literature of the subject. The professional student, therefore, as well as the geographer, will have very frequent occasion to consult Italian authorities, and in the very valuable Report of Humphreys and Abbot on the Mississippi, America has lately made a contribution to our potamological knowledge, which, in scientific interest and practical utility, does not fall short of the ablest European productions in the same branch of inquiry.] But in any event, these theoretical objections are counsels apres coup. The dikes of the Po and probably of some of its tributaries were begun before we have any trustworthy physical or political annals of the provinces they water. The civilization of the valley has accommodated itself to these arrangements, and the interests which might be sacrificed by a change of system are too vast to be hazarded by what, in the present state of our knowledge, can be only considered as a doubtful experiment. [Footnote: Dupenchel advised a resort to the "heroic remedy" of sacrificing, or converting into cellars, the lower storeys of houses in cities exposed to river inundation, filling up the streets, and admitting the water of floods freely over the adjacent country, and thus allowing it to raise the level of the soil to that of the highest inundations.--Traite d'Hydraulique et de Geologie Agricole, Paris, 1868, p. 241.] The embankments of the Po, though they are of vast extent and have employed centuries in their construction, are inferior in magnitude to the dikes or levees of the Mississippi, which are the work of scarcely a hundred years, and of a comparatively sparse population. On the right or western bank of the river, the levee extends, with only occasional interruptions from high bluffs and the mouths of rivers, for a distance of more than eleven hundred miles. The left bank is, in general, higher than the right, and upon that side a continuous embankment is not needed; but the total length of the dikes of the Mississippi, including those of the lower course of its tributaries and of its bayous or natural emissaries, is not less than 2,500 miles. They constitute, therefore, not only one of the greatest material achievements of the American people, but one of the most remarkable systems of physical improvement which has been anywhere accomplished in modern times. Those who condemn the system of longitudinal embankments have often advised that, in cases where that system cannot be abandoned without involving too great a sacrifice of existing interests, the elevation of the dikes should be much reduced, so as to present no obstruction to the lateral spread of extraordinary floods, and that they should be provided with sluices to admit the water without violence whenever they are likely to be overflowed. Where dikes have not been erected, or where they have been reduced in height, it is proposed to construct, at convenient intervals, transverse embankments of moderate height running from the banks of the river across the plains to the hills which bound them. These measures, it is argued, will diminish the violence of inundations by permitting the waters to extend themselves over a greater surface, and by thus retarding the flow of the river currents, will, at the same time, secure the deposit of fertilizing slime upon all the soil covered by the flood. [Footnote: The system described in the text is substantially the Egyptian method, the ancient Nile dikes having been constructed rather to retain than to exclude the water.] Rozet, an eminent French engineer, has proposed a method of diminishing the ravages of inundations, which aims to combine the advantages of all other systems, and at the same time to obviate the objections to which they are all more or less liable. [Footnote: Moyens de forcer les Torrents de rendre une partie du sol qu'ils ravagent, et d'empecher les grandes Inondations.] The plan of Rozet is recommended by its simplicity and cheapness as well as its facility and rapidity of execution, and is looked upon with favor by many persons very competent to judge in such matters. It is, however, by no means capable of universal application, though it would often doubtless prove highly useful in connection with the measures now employed in South-eastern France. He proposes to commence with the amphitheatres in which mountain torrents so often rise, by covering their slopes and filling their beds with loose blocks of rock, and by constructing at their outlets, and at other narrow points in the channels of the torrents, permeable barriers of the same material promiscuously heaped up, much according to the method employed by the ancient Romans in their northern provinces for a similar purpose. By this means, he supposes, the rapidity of the current would be checked, and the quantity of transported pebbles and gravel--which, by increasing the mechanical force of the water, greatly aggravate the damage by floods--much diminished. When the stream has reached that part of its course where it is bordered by soil capable of cultivation, and worth the expense of protection, he proposes to place along one or both banks, according to circumstances, a line of cubical blocks of stone or pillars of masonry three or four feet high and wide, and at the distance of about eleven yards from each other. The space between the two lines, or between a line and the opposite high bank, would, of course, be determined by observation of the width of the swift-water current at high floods. As an auxiliary measure, small ditches and banks, or low walls of pebbles, should be constructed from the line of blocks across the grounds to be protected, nearly at right angles to the current, but slightly inclining downwards, and at convenient distances from each other. Rozet thinks the proper interval would be 300 yards, and it is evident that, if he is right in his main principle, hedges, rows of trees, or even common fences, would in many cases answer as good a purpose as banks and trenches or low walls. The blocks or pillars of stone would, he contends, check the lateral currents so as to compel them to let fall all their pebbles and gravel in the main channel--where they would be rolled along until ground down to sand or silt--and the transverse obstructions would detain the water upon the soil long enough to secure the deposit of its fertilizing slime. Numerous facts are cited in support of the author's views, and I imagine there are few residents of rural districts whose own observation will not furnish testimony confirmatory of their soundness. [Footnote: The effect of trees and other detached obstructions in checking the flow of water is particularly noticed by Palissy in his essay on Waters and Fountains, p. 173, edition of 1844. "There be," says he, "in divers parts of France, and specially at Nantes, wooden bridges, where, to break the force of the waters and of the floating ice, which might endamage the piers of the said bridges, they have driven upright timbers into the bed of the rivers above the said piers, without the which they should abide but little. And in like wise, the trees which be planted along the mountains do much deaden the violence of the waters that flow from them." Lombardini attaches great importance to the planting of rows of trees transversely to the current on grounds subject to overflow.--Esame degli Studi sul Tevere, Section 53, and Appendice, Sections 33, 34.] Removal of Obstructions. The removal of obstructions in the beds of rivers dredging the bottom or blasting rocks, the washing out of deposits and locally increasing the depth of water by narrowing the channel by moans of spurs or other constructions projecting from the banks, and, finally, the cutting off of bends and thus shortening the course of the stream, diminishing the resistance of its shores and bottom and giving the bed a more rapid declivity, have all been employed not only to facilitate navigation, but as auxiliaries to more effectual modes of preventing inundations. But a bar removed from one point is almost sure to re-form at the same or another, spurs occasion injurious eddies and unforeseen diversions of the current, [Footnote: The introduction of a new system of spurs with parabolic curves has been attended with giant advantage in France.--Annales du Genie Civil, Mai, 1863.] and the cutting off of bends, though occasionally effected by nature herself, and sometimes advantageous in torrential streams whose banks are secured by solid walls of stone or other artificial constructions, seldom establishes a permanent channel, and besides, the increased rapidity of the flow through the new cut often injuriously affects the regime of the river for a considerable distance below. [Footnote: This practice has sometimes been resorted to on the Mississippi with advantage to navigation, but it is quite another question whether that advantage has not been too dearly purchased by the injury to the banks at lower points. If we suppose a river to have a navigable course of 1,600 miles as measured by its natural channel, with a descent of 800 feet, we shall have a fall of six inches to the mile. If the length of channel be reduced to 1,200 miles by cutting off bends, the fall is increased to eight inches per mile. The augmentation of velocity consequent upon this increase of inclination is not computable without taking into account other elements, such as depth and volume of water, diminution of direct resistance, and the like, but in almost any supposable case, it would be sufficient to produce great effects on the height of floods, the deposit of sediment in the channel, on the shores, and at the outlet, the erosion of banks and other points of much geographical importance. The Po, in those parts of its course where the embankments leave a wide space between, often cuts off bends in its channel and straightens its course. These short cuts are called salti, or leaps, and sometimes abridge the distance between their termini by several miles. In 1777, the salto of Cottaro shortened a distance of 7,000 metres by 5,000, or, in other words, reduced the length of the river by five kilometres, or about three miles, and in 1807 and 1810 the two salti of Mozzanone effected a still greater reduction.] Combination of Methods. Upon the whole, it is obvious that no one of the methods heretofore practised or proposed for averting the evils resulting from river inundations is capable of universal application. Each of them is specially suited to a special case. But the hydrography of almost every considerable river and its tributaries will be found to embrace most special cases, most known forms of superficial fluid circulation. For rivers, in general, begin in the mountains, traverse the plains, and end in the sea; they are torrents at their sources, swelling streams in their middle course, placid currents, flowing molli flumine, at their termination. Hence in the different parts of their course the different methods of controlling and utilizing them may successively find application, and there is every reason to believe that by a judicious application of all, every great river may, in a considerable degree, be deprived of its powers of evil and rendered subservient to the use, the convenience, and the dominion of man. [Footnote: On the remedies against inundation, see the valuable paper of Lombardini, Sulle Inondazioni avvenute in questi ultimi tempi in Francia. Milano, 1858. There can be no doubt that in the case of rivers which receive their supply in a large measure from mountain streams, the methods described in a former chapter as recently employed in South-eastern France to arrest the formation and lessen the force of torrents, would prove equally useful as a preventive remedy against inundations. They would both retard the delivery of surface-water and diminish the discharge of sediment into rivers, thus operating at once against the two most efficient causes of destructive floods. See Chapter III., pp. 316 at seqq.] Dikes of the Nile. "History tells us," says Mengotti, "that the Nile became terrible and destructive to ancient Egypt, in consequence of being confined within elevated dikes, from the borders of Nubia to the sea. It being impossible for these barriers to resist the pressure of its waters at such a height, its floods burst its ramparts, sometimes on one side, sometimes on the other, and deluged the plains, which lay far below the level of its current. . . . In one of its formidable inundations the Nile overwhelmed and drowned a large part of the population. The Egyptians then perceived that they were struggling against nature in vain, and they resolved to remove the dikes, and permit the river to expand itself laterally and raise by its deposits the surface of the fields which border its channel." [Footnote: Idraulica Fisica e Sperimentale. 2d edizione, vol. i., pp. 131, 133.] The original texts of the passages cited by Mengotti, from Latin translations of Diodorus Siculus and Plutarch and from Pliny the Elder, do not by any means confirm this statement, though the most important of them, that from Diodorus Siculus, is, perhaps, not irreconcilable with it. Not one of them speaks of the removal of the dikes, and I understand them all as relating to the mixed system of embankments, reservoirs, and canals which have been employed in Egypt through the whole period concerning which we have clear information. I suppose that the disastrous inundations referred to by the authors in question were simply extraordinary floods of the same character as those which have been frequent at later periods of Egyptian history, and I find nothing in support of the proposition that continuous embankments along the banks of the Nile ever existed until such were constructed by Mehemet Ali. [Footnote: The gradual elevation of the bed of the Nile from sedimentary deposit, from the prolongation of the Delta and consequent reduction of the inclination of the river-bed, or, as has been supposed by some, though without probability, from a secular rise of the coast, rendered necessary some change in the hydraulic arrangements of Egypt. Mehemet Ali was advised to adopt a system of longitudinal levees, and he embanked the river from Jebel Silsileh to the sea with dikes six or seven feet high and twenty feet thick. Similar embankments were made around the Delta. These dikes are provided with transverse embankments, with sluices for admitting and canals for distributing the water, and they serve rather to retain the water and control its flow than to exclude it. Clot Bey, Apercu sur l'Egypte, ii., 437.] The object of the dikes of the Po, and, with few exceptions, of those of other European rivers, has always been to confine the waters of floods and the solid material transported by them within as narrow a channel as possible, and entirely to prevent them from flowing over the adjacent plains. The object of the Egyptian dikes and canals is the reverse, namely, to diffuse the swelling waters and their sediment over as wide a surface as possible, to store them up until the soil they cover has them thoroughly saturated and enriched, and then to conduct them over other grounds requiring a longer or a second submersion, and, in general, to suffer none of the precious fluid to escape except by evaporation and infiltration. Lake Moeris, whether wholly an artificial excavation, or a natural basin converted by embankments into a reservoir, was designed chiefly for the same purpose as the barrage built by Mougel Bey across the two great arms which enclose the Delta, namely, as a magazine to furnish a perennial supply of water to the thirsty soil. But these artificial arrangements alone did not suffice. Canals were dug to receive the water at lower stages of the river and conduct it far into the interior, and as all this was still not enough, hundreds of thousands of wells were sunk to bring up from the subsoil, and spread over the surface, the water which, by means of infiltration from the river-bed, pervades the inferior strata of the whole valley. [Footnote: It is said that in the Delta alone 50,000 wells are employed for irrigation.] If a system of lofty continuous dikes, like those of the Po, had really been adopted in Egypt, in the early dynasties when the power and the will to undertake the most stupendous material enterprises were so eminently characteristic of the government of that country, and persevered in through later ages, and the waters of the annual inundation had thus been permanently prevented from flooding the land, it is conceivable that the productiveness of the small area of cultivable soil in the Nile valley might have been long kept up by artificial irrigation and the application of manures. But nature would have rebelled at last, and centuries before our time the mighty river would have burst the fetters by which impotent man had vainly striven to bind his swelling floods, the fertile fields of Egypt would have been converted into dank morasses, and then, perhaps, in some distant future, when the expulsion of man should have allowed the gradual restoration of the primitive equilibrium, would be again transformed into luxuriant garden and plough land. Fortunately, the sapientia AEgyptiorum, the wisdom of the Egyptians, taught them better things. They invited and welcomed, not repulsed, the slimy embraces of Nilus, and his favors have been, from the hoariest antiquity, the greatest material blessing that nature ever bestowed upon a people. [Footnote: Deep borings have not detected any essential difference in the quantity or quality of the deposits of the Nile for forty or fifty, or, as some compute, for a hundred centuries. From what vast store of rich earth does this river derive the three or four inches of fertilizing material which it spreads over the soil of Egypt every hundred years Not from the White Nile, for that river drops nearly all its suspended matter in the broad expansions and slow current of its channel south of the tenth degree of north latitude. Nor does it appear that much sediment is contributed by the Bahr-el-Azrek, which flows through forests for a great part of its course. I have been informed by an old European resident of Egypt who is very familiar with the Upper Nile, that almost the whole of the earth with which its waters are charged is brought down by the Takazze.] Deposits of the Nile. The Nile is larger than all the rivers of Lombardy together, [Footnote: From daily measurements during a period of fourteen years--1827 to 1840--the mean delivery of the Po at Ponte Lagoscuro, below the entrance of its last tributary, is found to be 1,720 cubic metres, or 60,745 cubic feet, per second. Its smallest delivery is 186 cubic metres, or 6,569 cubic feet, its greatest 5,156 cubic metres, or 152,094 cubic feet. The average delivery of the Nile being 101,000 cubic feet per second, it follows that the Po contributes to the Adriatic rather more than six-tenths as much water as the Nile to the Mediterranean--a result which will surprise most readers. It is worth remembering that the mean delivery of the Rhone is almost identical with that of the Po, and that of the Rhine is very nearly the same. Though the Po receives four-tenths of its water from lakes, in which the streams that empty into them let fall the solid material they bring down from the mountains, its deposits in the Adriatic are at least sixty or seventy per cent. greater than those transported to the Mediterranean by the Rhone, which derives most of its supply from mountain and torrential tributaries. Those tributaries lodge much sediment in the Lake of Geneva and the Lac de Bourget, but the total erosion of the Po and its affluents must be considerably greater than that of the Rhone system. The Rhine conveys to the sea much less sediment than either of the other two rivers.--Lombardini, Cargiamenti nella condizione del Po, pp. 29, 39. The mean discharge of the Mississippi is 675,000 cubic feet per second, and, accordingly, that river contributes to the sea about eleven times as much water as the Po, and more than six and a half times as much as the Nile. The discharge of the Mississippi is estimated at one-fourth of the precipitation in its basin--certainly a very large proportion, when we consider the rapidity of evaporation in many parts of the basin, and the probable loss by infiltration.--Humphreys and Abbott'S Report, p. 93. The basin of the Mississippi has an area forty-six times as large as that of the Po, with a mean annual precipitation of thirty inches, while that of the Po, at least according to official statistics, has a precipitation of forty inches. Hence the down-fall in the former is one-fourth less than in the latter. Besides this, the Mississippi loses little or nothing by the diversion of its waters for irrigation. Consequently the measured discharge of the Mississippi is proportionally much less than that of the Po, and we are authorized to conclude that the difference is partly due to the escape of water from the bed, or at least the basin of the Mississippi, by subterranean channels. These comparisons are interesting in reference to the supply received by the sea directly from great rivers, but they fail to give a true idea of the real volume of the latter. To take the case of the Nile and the Po: we have reason to suppose that comparatively little water is diverted from the tributaries of the former for irrigation, but enormous quantities are drawn from its main trunk for that purpose, below the point where it receives its last affluent. This quantity is now increasing in so rapid a proportion, that Elisee Reclus foresees the day when the entire low-water current will be absorbed by new arrangements to meet the needs of extended and improved agriculture. On the other hand, while the affluents of the Po send off a great quantity of water into canals of irrigation, the main trunk loses little or nothing in that way except at Chivasso. Trustworthy data are wanting to enable us to estimate how far these different modes of utilizing the water balance each other in the case under consideration. Perhaps the Canal Cavour, and other irrigating canals now proposed, may one day intercept as large a proportion of the supply of the lower Po as Egyptian dikes, canals, shadoofs, and steam-pumps do of that of the Nile. Another circumstance is important to be considered in comparing the character of these three rivers. The Po runs nearly east and west, and it and its tributaries are exposed to no other difference of meterological conditions than those which always subsist between the mountains and the plains. The course of the Nile and the Mississippi is mainly north and south. The sources of the Nile are in a very humid region, its lower course for many hundred miles in almost rainless latitudes with enormous evaporating power, while the precipitation is large throughout the Mississippi system, except in the basins of some of its western affluents.] it drains a basin fifty, possibly even a hundred, times as extensive, its banks have been occupied by man probably twice as long. But its geographical character has not been much changed in the whole period of recorded history, and, though its outlets have somewhat fluctuated in number and position, its historically known encroachments upon the sea are trifling compared with those of the Po and the neighboring streams. The deposits of the Nile are naturally greater in Upper than in Lower Egypt. They are found to have raised the soil at Thebes about seven feet within the last seventeen hundred years, and in the Delta the rise has been certainly more than half as great. We shall, therefore, probably not exceed the truth if we suppose the annually inundated surface of Egypt to have been elevated, upon an average, ten feet, [Footnote: Fraas and Eyth maintain that we have no trustworthy data for calculating the annual or secular elevation of the soil of Egypt by the sediment of the Nile. The deposit, they say, is variable from irregularity of current, and especially from the interference of man with the operations of nature, to a degree which renders any probable computation of the amount quite impossible.--Fraas, Aus dem Orient, pp. 212, 213. The sedimentary matter transported by the Nile might doubtless be estimated with approximate precision by careful observation of the proportion of suspended slime and water at different stations and seasons for a few successive years. Figari Bey states that at low stages the water of the Nile contains little or no sediment, and that the greatest proportion occurs about the end of July, and of course, while the river is still rising. Experiments at Khartum at that season showed solid matter in the proportion of one to a thousand by weight. The quantity is relatively greater at Cairo, a fact which shows that the river receives more earth from the erosion of its banks than it deposits at its own bottom, and it must consequently widen its channel unless we suppose a secular depression of the coast at the mouth of the Nile which produces an increased inclination of the bed of the river, and consequently an augmented velocity of flow sufficient to sweep out earth from the bottom and mix it with the current. Herschell states the Nile sediment at 1 in 633 by weight, and computes the entire annual quantity at 140 millions of tons.--Physical Geography, p. 231. The mean proportion of sedimentary material in the waters of the Mississippi is calculated at 1 to 1,500 by weight, and 1 to 2,900 in volume, and the total annual quantity at 812,500,000,000 pounds, which would cover one square mile to the depth of 214 feet.--Humphreys and Abbott, Report, p. 140.] within the last 5,000 years, or twice and a half the period during which the history of the Po is known to us. [Footnote: We are quite safe in supposing that the valley of the Nile has been occupied by man at least 5,000 years. The dates of Egyptian chronology are uncertain, but I believe no inquirer estimates the age of the great pyramids at less than forty centuries, and the construction of such works implies an already ancient civilization. It is an interesting fact that the old Egyptian system of embankments and canals is probably more ancient than the geological changes which have converted the Mississippi from a limpid to a turbid stream, and occasioned the formation of the vast delta at the mouth of that river. Humphreys and Abbot conclude that the delta of the Mississippi began its encroachments on the Gulf of Mexico not more than 4,400 years ago, before which period they suppose the Mississippi to have been "a comparatively clear stream," conveying very little sediment to the sea. The present rate of advance of the delta is 262 feet a year, and there are reasons for thinking that the amount of deposit has long been approximately constant.--Report, pp. 435, 436.] As I have observed, the area of cultivated soil is much less extensive now than under the dynasties of the Pharaohs and the Ptolemies; for--though, in consequence of the elevation of the river-bed, the inundations now have a wider NATURAL spread--the industry of the ancient Egyptians conducted the Nile water over a great surface which it does not now reach. Had the Nile been banked in, like the Po, all this deposit, except that contained in the water diverted by canals or otherwise drawn from the river for irrigation and other purposes, would have soon carried out to sea. This would have been a considerable quantity; for the Nile holds some earth in suspension at all seasons except at the very lowest water, a much larger proportion during the flood, and irrigation must have been carried on during the whole year. The precise amount of sediment which would have been thus distributed over the soil is matter of conjecture, but though large, it would have been much less than the inundations have deposited, and continuous longitudinal embankments would have compelled the Nile to transport to the Mediterranean an immense quantity over and above what it has actually deposited in that sea. The Mediterranean is shoal for some miles out to sea along the whole coast of the Delta, and the large bays or lagoons within the coast-line, which communicate both with the river and the sea, have little depth of water. These lagoons the river deposits would have filled up, and there would still have been surplus earth enough to extend the Delta far into the Mediterranean. [Footnote: The present annual extension of the Delta is, if perceptible, at all events very small. According to some authorities, a few hectares are added every year at each Nile mouth. Others, among whom I may mention Fraas, deny that there is any extension at all, the deposit being balanced by a secular depression of the coast. Elisee Reclus states that the Delta advances about 40 inches per year.--La Terre, i., p. 500.] Obstruction of River Mouths. The mouths of a large proportion of the streams known to ancient navigation are already blocked up by sand-bars or fluviatile deposits, and the maritime approaches to river harbors frequented by the ships of Phenicia and Carthage and Greece and Rome are shoaled to a considerable distance out to sea. The inclination of the lower course of almost every known river bed has been considerably reduced within the historical period, and nothing but great volume of water, or exceptional rapidity of flow, now enables a few large streams like the Amazon, the La Plata, the Ganges, and, in a loss degree, the Mississippi, to carry their own deposits far enough out into deep water to prevent the formation of serious obstructions to navigation. But the degradation of their banks, and the transportation of earthy matter to the sea by their currents, are gradually filling up the estuaries even of those mighty floods, and unless the threatened evil shall be averted by the action of geological forces, or by artificial contrivances more efficient than dredging-machines, the destruction of every harbor in the world which receives a considerable river must inevitably take place at no very distant date. This result would, perhaps, have followed in some incalculably distant future, if man had not come to inhabit the earth as soon as the natural forces which had formed its surface had arrived at such an approximate equilibrium that his existence on the globe was possible; but the general effect of his industrial operations has been to accelerate it immensely. Rivers, in countries planted by nature with forests and never inhabited by man, employ the little earth and gravel they transport chiefly to raise their own beds and to form plains in their basins. In their upper course, where the current is swiftest, they are most heavily charged with coarse rolled or suspended matter, and this, in floods, they deposit on their shores in the mountain valleys where they rise; in their middle course, a lighter earth is spread over the bottom of their widening basins, and forms plains of moderate extent; the fine silt which floats farther is deposited over a still broader area, or, if carried out to sea, is in great part quickly swept far off by marine currents and dropped at last in deep water. Man's "improvement" of the soil increased the erosion from its surface; his arrangements for confining the lateral spread of the water in floods compel the rivers to transport to their mouths the earth derived from that erosion even in their upper course; and, consequently, the sediment they deposit at their outlets is not only much larger in quantity, but composed of heavier materials, which sink more readily to the bottom of the sea and are less easily removed by marine currents. The tidal movement of the ocean, deep-sea currents, and the agitation of inland waters by the wind, lift up the sands strewn over the bottom by diluvial streams or sent down by mountain torrents, and throw them up on dry land, or deposit them in sheltered bays and nooks of the coast--for the flowing is stronger than the ebbing tide, the affluent than the refluent wave. This cause of injury to harbors it is not in man's power to resist by any means at present available; but, as we have seen, something can be done to prevent the degradation of high grounds, and to diminish the quantity of earth which is annually abstracted from the mountains, from table-lands, and from river-banks, to raise the bottom of the sea. This latter cause of harbor obstruction, though an active agent, is, nevertheless, in many cases, the less powerful of the two. The earth suspended in the lower course of fluviatile currents is lighter than sea-sand, river water lighter than sea water, and hence, if a land stream enters the sea with a considerable volume, its water flows over that of the sea, and bears its slime with it until it lets it fall far from shore, or, as is more frequently the case, mingles with some marine current and transports its sediment to a remote point of deposit. The earth borne out of the mouths of the Nile is in part carried over the waves which throw up sea-sand on the beach, and deposited in deep water, in part drifted by the current, which sweeps east and north along the coasts of Egypt and Syria, and lodged in every nook along the shore--and among others, to the great detriment of the Suez Canal, in the artificial harbor at its northern terminus--and in part borne along until it finds a final resting-place in the north-eastern angle of the Mediterranean. [Footnote: "The stream carries this mud, etc., at first farther to the east, and only lets it fall where the force of the current becomes weakened. This explains the continual advance of the land seaward along the Syrian coast, in consequence of which Tyre and Sideon no longer lie on the shore, but some distance inland. That the Nile contributes to this deposit may easily be seen, even by the unscientific observer, from the stained and turbid character of the water for many miles from its mouths. Ships often encounter floating masses of Nile mud, and Dr. Clarke thus describes a case of this sort: "While we were at table, we heard the sailors who were throwing the lead suddenly cry out: 'Three and a half!' The ship slackened her way, and veered about. As she came round, the whole surface of the water was seen to be covered with thick, black mud, which extended so far that it appeared like an island. At the same time, actual land was nowhere to be seen--not even from the mast-head--nor was any notice of such a shoal to be found or any chart on board. The fact is, as we learned afterwards, that a stratum of mud, stretching from the mouths of the Nile for many miles out into the open sea, forms a movable deposit along the Egyptian coast. If this deposit is driven forwards by powerful currents, it sometimes rises to the surface, and disturbs the mariner by the sudden appearance of shoals where the charts lead him to expect a considerable depth of water. But these strata of mud are, in reality, not in the least dangerous. As soon as a ship strikes them they break up at once, and a frigate may hold her course in perfect safety where an inexperienced pilot, misled by his soundings, would every moment expect to be stranded."--Bottger, Das Mittchneer, pp. 188, 189. This phenomenon is not peculiar to the locality in question, and it is frequently observed in the Gulf of Bengal, and other great marine estuaries.] Thus the earth loosened by the rude Abyssinian ploughshare, and washed down by the rain from the hills of Ethiopia which man has stripped of their protecting forests, contributes to raise the plains of Egypt, to shoal the maritime channels which lead to the city built by Alexander near the mouth of the Nile, to obstruct the artificial communication between the Mediterranean and the Red Sea, and to fill up the harbors made famous by Phenician commerce. Deposits of the Tuscan Rivers. The Arno, and all the rivers rising on the western slopes and spurs of the Apennines, carry down immense quantities of mud to the Mediterranean. There can be no doubt that the volume of earth so transported is very much greater than it would have been had the soil about the headwaters of those rivers continued to be protected from wash by forests; and there is as little question that the quantity borne out to sea by the rivers of Western Italy is much increased by artificial embankments, because they are thereby prevented from spreading over the surface the sedimentary matter with which they are charged. The western coast of Tuscany has advanced some miles seawards within a very few centuries. The bed of the sea, for a long distance, has been raised, and of course the relative elevation of the land above it lessened; harbors have been filled up and destroyed; long lines of coast dunes have been formed, and the diminished inclination of the beds of the rivers near their outlets has caused their waters to overflow their banks and convert them into pestilential marshes. The territorial extent of Western Italy has thus been considerably increased, but the amount of soil habitable and cultivable by man has been, in a still higher proportion, diminished. The coast of ancient Etruria was filled with great commercial towns, and their rural environs were occupied by a large and prosperous population. But maritime Tuscany has long been one of the most unhealthy districts in Christendom; the famous Etruscan mart of Populonia has scarcely an inhabitant; the coast is almost absolutely depopulated, and the malarious fevers have extended their ravages far into the interior. These results are certainly not to be ascribed wholly to human action. They are, in a large proportion, due to geological causes over which man has no control. The soil of much of Tuscany becomes pasty, almost fluid even, as soon as it is moistened, and when thoroughly saturated with water, it flows like a river. Such a soil as this would not be completely protected by woods, and, indeed, it would now be difficult to confine it long enough to allow it to cover itself with forest vegetation. Nevertheless, it certainly was once chiefly wooded, and the rivers which flow through it must then have been much less charged with earthy matter than at present, and they must have carried into the sea a smaller proportion of their sediment when they were free to deposit it on their banks than since they have been confined by dikes. It is, in general, true, that the intervention of man has hitherto seemed to insure the final exhaustion, ruin, and desolation of every province of nature which he has reduced to his dominion. Attila was only giving an energetic and picturesque expression to the tendencies of human action, as personified in himself, when he said that "no grass grew where his horse's hoofs had trod." The instances are few, where a second civilization has flourished upon the ruins of an ancient culture, and lands once rendered uninhabitable by human acts or neglect have generally been forever abandoned as hopelessly irreclaimable. It is, as I have before remarked, a question of vast importance, how far it is practicable to restore the garden we have wasted, and it is a problem on which experience throws little light, because few deliberate attempts have yet been made at the work of physical regeneration, on a scale large enough to warrant general conclusions in any one class of cases. The valleys and shores of Tuscany form, however, a striking exception to this remark. The succcess with which human guidance has made the operations of nature herself available for the restoration of her disturbed harmonies, in the Val di Chiana and the Tuscan Maremma, is among the noblest, if not the most brilliant achievements of modern engineering, and, regarded in all its bearings on the great question of which I have just spoken, it is, as an example, of more importance to the general interests of humanity than the proudest work of internal improvement that mechanical means have yet constructed. The operations in the Val di Chiana have consisted chiefly in so regulating the flow of the surface-waters into and through it, as to compel them to deposit their sedimentary matter at the will of the engineers, and thereby to raise grounds rendered insalubrious and unfit for agricultural use by stagnating water; the improvements in the Maremma have embraced both this method of elevating the level of the soil, and the prevention of the mixture of salt-water with fresh in the coast marshes and shallow bays, which is regarded as a very active cause of the development of malarious influences. [Footnote: The fact that the mixing of salt and fresh water in coast marshes and lagoons is deleterious to the sanitary condition of the vicinity, has been generally admitted, though the precise reason why a mixture of both should be more injurious than either alone, is not altogether clear. It has been suggested that the admission of salt-water to the lagoons and rivers kills many fresh-water plants and animals, while the fresh water is equally fatal to many marine organisms, and that the decomposition of the remains originates poisonous minsmata. Other theories, however, have been proposed. The whole subject is fully and ably discussed by Dr. Salvagnoli Marchetti in the appendix to his valuable Rapporto aul Bonificamento delle Maremme Toscane. See also the Memorie Economico-Statistiche sulle Maremme Toscane, of the same author. A different view of this subject is taken by Raffanini and Orlandini in Analisi, Storico-Fisico-Economica sulli insolubrita nelle Maremme Toscane, Firenze, 1869. See also the important memoir of D. Pantaleoni, Del miasma vegetale e delle Malattie Miasmatiche, in which the views of Salvagnoli on this point are combated.] Improvements in the Tuscan Maremma. In the improvements of the Tuscan Maremma, formidable difficulties have been encountered. The territory to be reclaimed was extensive; the salubrious places of retreat for laborers and inspectors were remote; the courses of the rivers to be controlled were long and their natural inclination not rapid; some of them, rising in wooded regions, transported comparatively little earthy matter, [Footnote: This difficulty has been remedied--though with doubtful general advantage--as to one important river of the Maremma, the Pecora, by clearings recently executed along its upper course. "The condition of this marsh and of its affluents are now, November, 1859, much changed, and it is advisable to prosecute its improvement by deposits. In consequence of the extensive felling of the woods upon the plains, hills, and mountains of the territory of Massa and Scarlino, within the last ten years, the Pecora and other affluents of the marsh receive, during the rains, water abundantly charged with slime, so that the deposits within the first division of the marsh are already considerable, and we may now hope to see the whole marsh and pond filled up in a much shorter time than we had a right to expect before 1850. This circumstance totally changes the terms of the question, because the filling of the marsh and pond, which then seemed almost impossible on account of the small amount of sediment deposited by the Pecora, has now become practicable."--Salvagnoli, Rapporto sul Bonificamento delle Maremme Toscane, pp.li., lii. Between 1830 and 1859 more than 36,000,000 cubic yards of sediment were deposited in the marsh and shoal-water lake of Castiglione alone.--Salvagnoli, Raccolta di Documenti, pp. 74, 75.] and above all, the coast, which is a recent deposit of the waters, is little elevated above the sea, and admits into its lagoons and the mouths of its rivers floods of salt-water with every western wind, every rising tide. [Footnote: The tide rises ten inches on the coast of Tuscany. See Memoir by Fantoni, in the appendix to Salvagnoli, Rapporto, p. 189. On the tides of the Mediterranean, see Bottger, Das Mittelmeer, p. 190.] The western coast of Tuscany is not supposed to have been an unhealthy region before the conquest of Etruria by the Romans, but it certainly became so within a few centuries after that event. This was a natural consequence of the neglect or wanton destruction of the public improvements, and especially the hydraulic works in which the Etruscans were so skilful, and of the felling of the upland forests, to satisfy the demand for wood at Rome for domestic, industrial, and military purposes. After the downfall of the Roman empire, the incursions of the barbarians, and then feudalism, foreign domination, intestine wars, and temporal and spiritual tyrannies, aggravated still more cruelly the moral and physical evils which Tuscany and the other Italian States were doomed to suffer, and from which they have enjoyed but brief respites during the whole period of modern history. The Maremma was already proverbially unhealthy in the time of Dante, who refers to the fact in several familiar passages, and the petty tyrants upon its borders often sent criminals to places of confinement in its territory, as a slow but certain mode of execution. Ignorance of the causes of the insalubrity, and often the interference of private rights, [Footnote: In Catholic countries, the discipline of the church requires a meagre diet at certain seasons, and as fish is not flesh, there is a great demand for that article of food at those periods. For the convenience of monasteries and their patrons, and as a source of pecuniary emolument to ecclesiastical establishments and sometimes to lay proprietors, great numbers of artificial fish-ponds were created during the Middle Ages. They were generally shallow pools formed by damming up the outlet of marshes, and they were among the most fruitful sources of endemic disease, and of the peculiar malignity of the epidemics which so often ravaged Europe in those centuries. These ponds, in religious hands, were too sacred to be infringed upon for sanitary purposes, and when belonging to powerful lay lords they were almost an inviolable. The rights of fishery were a standing obstacle to every proposal of hydralic improvement, and to this day large and fertile districts in Southern Europe remain sickly and almost unimproved and uninhabited, because the draining of the ponds upon them would reduce the income of proprietors who derive large profits by supplying the faithful, in Lent, with fish, and with various species of waterfowl which, though very fat, are, ecclesiastically speaking, meagre.]prevented the adoption of measures to remove it, and the growing political and commercial importance of the large towns in more healthful localities absorbed the attention of Government, and deprived the Maremma of its just share in the systems of physical improvement which were successfully adopted in interior and Northern Italy. Before any serious attempts were made to drain or fill up the marshes of the Maremma, various other sanitary experiments were tried. It was generally believed that the insalubrity of the province was the consequence, not the cause, of its depopulation, and that, if it were once densely inhabited, the ordinary operations of agriculture, and especially the maintenance of numerous domestic fires, would restore it to its ancient healthfulness. [Footnote: Macchiavelli advised the Government of Tuscany "to provide that men should restore the wholesomeness of the soil by cultivation, and purify the air by fires."--Salvagnoli, Memorie, p. 111.] In accordance with these views, settlers were invited from various parts of Italy, from Greece, and, after the accession of the Lorraine princes, from that country also, and colonized in the Maremma. To strangers coming from soils and skies so unlike those of the Tuscan marshes, the climate was more fatal than to the inhabitants of the neighboring districts, whose constitutions had become in some degree inured to the local influences, or who at least knew better how to guard against them. The consequence very naturally was that the experiment totally failed to produce the desired effects, and was attended with a great sacrifice of life and a heavy loss to the treasury of the state. The territory known as the Tuscan Maremma, ora maritime, or Maremme--for the plural form is most generally used--lies upon and near the western coast of Tuscany, and comprises about 1,900 square miles English, of which 500 square miles, or 320,000 acres, are plain and marsh including 45,500 acres of water surface, and about 290,000 acres are forest. One of the mountain peaks, that of Mount Amiata, rises to the height of 6,280 feet. The mountains of the Maremma are healthy, the lower hills much less so, as the malaria is felt at some points at the height of 1,000 feet, and the plains, with the exception of a few localities favorably situated on the seacoast, are in a high degree pestilential. The fixed population is about 80,000, of whom one-sixth live on the plains in the winter and about one-tenth in the summer. Nine or ten thousand laborers come down from the mountains of the Maremma and the neighboring provinces into the plain, during the latter season, to cultivate and gather the crops. Out of this small number of inhabitants and strangers, 35,619 were ill enough to require medical treatment between the 1st of June, 1840, and the 1st of June, 1841, and more than one-half the cases were of intermittent, malignant, gastric, or catarrhal fever. Very few agricultural laborers escaped fever, though the disease did not always manifest itself until they had returned to the mountains. In the province of Grosseto, which embraces nearly the whole of the Maremma, the annual mortality was 3.92 per cent., the average duration of life but 23.18 years, and 75 per cent. of the deaths were among persons engaged in agriculture. The filling up of the low grounds and the partial separation of the waters of the sea and the land, which had been in progress since the year 1827, now began to show very decided effects upon the sanitary condition of the population. In the year ending June 1st, 1842, the number of the sick was reduced by more than 2,000, and the cases of fever by more than 4,000. The next year the cases of fever fell to 10,500, and in that ending June 1st, 1844, to 9,200. The political events of 1848, and the preceding and following years, occasioned the suspension of the works of improvement in the Maremma, but they were resumed after the revolution of 1859. I have spoken with some detail of the improvements in the Tuscan Maremma, because of their great relative importance, and because their history is well known; but like operations have been executed in the territory of Pisa and upon the coast of the duchy of Lucca. In the latter case they were confined principally to prevention of the intermixing of fresh water with that of the sea. In 1741 sluices or lock-gates were constructed for this purpose, and the following year the fevers, which had been destructive to the coast population for a long time previous, disappeared altogether. In 1768 and 1769, the works having fallen to decay, the fevers returned in a very malignant form, but the rebuilding of the gates again restored the healthfulness of the shore. Similar facts recurred in 1784 and 1785, and again from 1804 to 1821. This long and repeated experience has at last impressed upon the people the necessity of vigilant attention to the sluices, which are now kept in constant repair. The health of the coast is uninterrupted, and Viareggio, the capital town of the district, is now much frequented for its sea-baths and its general salubrity, at a season when formerly it was justly shunned as the abode of disease and death. [Footnote: Giorgini, Sur les causes de l'Insalubrite de l'air dans le voisinage des marais, etc., lue a l'Academie des Sciences a Paris, le 12 Juillet, 1825. Reprinted in Salvagnoli, Rapporto, etc., appendice, p. 5, et seqq.] Improvements in the Val di Chiana. For twenty miles or more after the remotest headwaters of the Arno have united to form a considerable stream, this river flows south-eastwards to the vicinity of Arezzo. It here sweeps round to the north-west, and follows that course to near its junction with the Sieve, a few miles above Florence, from which point its general direction is westward to the sea. From the bend at Arezzo, a depression called the Val di Chiana runs south-eastwards until it strikes into the valley of the Paglia, a tributary of the Tiber, and thus connects the basin of the latter river with that of the Arno. In the Middle Ages, and down to the eighteenth century, the Val di Chiana was often overflowed and devastated by the torrents which poured down from the highlands, transporting great quantities of slime with their currents, stagnating upon its surface, and gradually converting it into a marshy and unhealthy district, which was at last very greatly reduced in population and productiveness. It had, in fact, become so desolate that even the swallow had deserted it. [Footnote: This curious fact is thus stated in the preface to Fossombroni (Memorie sopra la Val di Chiana, edition of 1835, p. xiii.), from which also I borrow most of the data hereafter given with respect to that valley: "It is perhaps not universally known, that the swallows, which come from the north [south] to spend the summer in our climate, do not frequent marshy districts with a malarious atmosphere. A proof of the restoration of salubrity in the Val di Chiana is furnished by these aerial visitors, which had never before been seen in those low grounds, but which have appeared within a few years at Forano and other points similarly situated." Is the air of swamps destructive to the swallows, or is their absence in such localities merely due to the want of human habitations, near which this half-domestic bird loves to breed, perhaps because the house-fly and other insects which follow man are found only in the vicinity of his dwellings In almoust all European countries the swallow is protected, by popular opinion or superstition, from the persecution to which almost all other birds are subject. It is possible that this respect for the swallow is founded upon ancient observation of the fact just stated on the authority of Fossombroni. Ignorance mistakes the effect for the cause, and the absence of this bird may have been supposed to be the occasion, not the consequence, of the unhealthiness of particular localities. This opinion once adopted, the swallow would become a sacred bird, and in process of time fables and legends would be invented to give additional sanction to the prejudices which protected it. The Romans considered the swallow as consecrated to the Penates, or household gods, and according to Peretti (Le Serate del Villaggio, p. 168) the Lombard peasantry think it a sin to kill them, because they are le gallinelle del Signore, the chickens of the Lord.] The bed of the Arno near Arezzo and that of the Paglia at the southern extremity of the Val di Chiana did not differ much in level. The general inclination of the valley was therefore small; it does not appear to have ever been divided into opposite slopes by a true watershed, and the position of the summit seems to have shifted according to the varying amount and place of deposit of the sediment brought down by the lateral streams which emptied into it. The length of its principal channel of drainage, and even the direction of its flow at any given point, were therefore fluctuating. Hence, much difference of opinion was entertained at different times with regard to the normal course of this stream, and, consequently, to the question whether it was to be regarded as properly an affluent of the Tiber or of the Arno. The bed of the latter river at the bend has been eroded to the depth of thirty or forty feet, and that, apparently, at no very remote period. [Footnote: Able geologists infer from recent investigations, that, although the Arno flowed to the south within the pliocenic period, the direction of its course was changed at an earlier epoch than that supposed in the text.] If it were elevated to what was evidently original height, the current of the Arno would be so much above that of the Paglia as to allow of a regular flow from its channel to the latter stream, through the Val di Chiana, provided the bed of the valley had remained at the level which excavations prove it to have had a few centuries ago, before it was raised by the deposits I have mentioned. These facts, together with the testimony of ancient geographers which scarcely admits of any other explanation, are thought to prove that all the waters of the Upper Arno were originally discharged through the Val di Chiana into the Tiber, and that a part of them still continued to flow, at least occasionally, in that direction down to the days of the Roman empire, and perhaps for some time later. The depression of the bed of the Arno, and the raising of that of the valley by the deposits of the lateral torrents, finally cut off the branch of the river which had flowed to the Tiber, and all its waters were turned into its present channel, though the drainage of the principal part of the Val di Chiana appears to have been in a south-eastwardly direction until within a comparatively recent period. In the sixteenth century the elevation of the bed of the valley had become so considerable, that in 1551, at a point about ten miles south of the Arno, it was found to be not less than one hundred and thirty feet above that river; then followed a level of ten miles, and then a continuous descent to the Paglia. Along the level portion of the valley was a boatable channel, and lakes, sometimes a mile or even two miles in breadth, had formed at various points farther south. At this period the drainage of the summit level might easily have been determined in either direction, and the opposite descents of the valley made to culminate at the north or at the south end of the level. In the former case, the watershed would have been ten miles south of the Arno; in the latter, twenty miles, and the division of the valley into two opposite slopes would have been not very unequal. Various schemes were suggested at this time for drawing off the stagnant waters, as well as for the future regular drainage of the valley, and small operations for those purposes were undertaken with partial success; but it was feared that the discharge of the accumulated waters into the Tiber would produce a dangerous inundation, while the diversion of the drainage into the Arno would increase the violence of the floods to which that river was very subject, and no decisive steps were taken. In 1606 an engineer, whose name has not been preserved, proposed, as the only possible method of improvement, the piercing of a tunnel through the hills bounding the valley on the west to convey its waters to the Ombrone, but the expense and other objections prevented the adoption of this scheme. [Footnote: Morozzi, Dello stato dell' Arno, ii., pp. 39, 40.] The fears of the Roman Government for the safety of the basin of the Tiber had induced it to construct embankments across the portion of the valley lying within its territory, and these obstructions, though not specifically intended for that purpose, naturally promoted the deposit of sediment and the elevation of the bed of the valley in their neighborhood. The effect of this measure and of the continued spontaneous action of the torrents was, that the northern slope, which in 1551 had commenced at the distance of ten miles from the Arno, was found in 1605 to begin nearly thirty miles south of that river, and in 1645 it had been removed about six miles farther in the same direction. [Footnote: Morozzi, Dello stato, etc., dell' Arno, ii., pp. 39, 40.] In the seventeenth century the Tuscan and Papal Governments consulted Galileo, Torricelli, Castelli, Cassini, Viviani, and other distinguished philosophers and engineers, on the possibility of reclaiming the valley by a regular artificial drainage. Most of these eminent physicists were of opinion that the measure was impracticable, though not altogether for the same reasons; but they seem to have agreed in thinking that the opening of such channels, in either direction, as would give the current a flow sufficiently rapid to drain the lands properly, would dangerously augment the inundations of the river--whether the Tiber or the Arno--into which the waters should be turned. The general improvement of the valley was now for a long time abandoned, and the waters were allowed to spread and stagnate until carried off by partial drainage, infiltration, and evaporation. Torricelli had contended that the slope of a large part of the valley was too small to allow it to be drained by ordinary methods, and that no practicable depth and width of canal would suffice for that purpose. It could be laid dry, he thought, only by converting its surface into an inclined plane, and he suggested that this might be accomplished by controlling the flow of the numerous torrents which pour into it, so as to force them to deposit their sediment at the pleasure of the engineer, and, consequently, to elevate the level of the area over which it should be spread. [Footnote: Torricelli thus expressed himself on this point: "If we content ourselves with what nature has made practicable to human industry, we shall endeavor to control, as far as possible, the outlets of these streams, which, by raising the bed of the valley with their deposits, will realize the fable of the Tagus and the Pactolus, and truly roll golden sands for him that is wise enough to avail himself of them."--Fossombroni, Memoris sopra la Val di China, p. 219.] This plan did not meet with immediate general acceptance, but it was soon adopted for local purposes at some points in the southern part of the valley, and it gradually grew in public favor and was extended in application until its final triumph a hundred years later. In spite of these encouraging successes, however, the fear of danger to the valley of the Arno and the Tiber, and the difficulty of an agreement between Tuscany and Rome--the boundary between which states crossed the Val di Chiana not far from the half-way point between the two rivers--and of reconciling other conflicting interests, prevented the resumption of the projects for the general drainage of the valley until after the middle of the eighteenth century. In the meantime the science of hydraulics had become better understood, and the establishment of the natural law according to which the velocity of a current of water, and of course the proportional quantity discharged by it in a given time, are increased by increasing its mass, had diminished if not dissipated the fear of exposing the banks of the Arno to greater danger from inundations by draining the Val di China into it. The suggestion of Torricelli was finally adopted as the basis of a comprehensive system of improvement, and it was decided to continue and extend the inversion of the original flow of the waters, and to turn them into the Arno from a point as far to the south as should be found practicable. The conduct of the works was committed to a succession of able engineers who, for a long series of years, were under the general direction of the celebrated philosopher and statesman Fossombroni, and the success has fully justified the expectations of the most sanguine advocates of the scheme. The plan of improvement embraced two branches: the one, the removal of obstructions in the bed of the Arno, and, consequently, the further depression of the channel of that river, in certain places, with the view of increasing the rapidity of its current; the other, the gradual filling up of the ponds and swamps, and raising of the lower grounds of the Val di Chiana, by directing to convenient points the flow of the streams which pour down into it, and there confining their waters by temporary dams until the sediment was deposited where it was needed. The economical result of these operations has been, that in 1835 an area of more than four hundred and fifty square miles of pond, marsh, and damp, sickly low grounds had been converted into fertile, healthy, and well-drained soil, and, consequently, that so much territory has been added to the agricultural domain of Tuscany. But in our present view of the subject, the geographical revolution which has been accomplished is still more interesting. The climatic influence of the elevation and draining of the soil must have been considerable, though I do not know that an increase or a diminution of the mean temperature or precipitation in the valley has been established by meteorological observation. There is, however, in the improvement of the sanitary condition of the Val di Chiana, which was formerly extremely unhealthy, satisfactory proof of a beneficial climatic change. The fevers, which not only decimated the population of the low grounds but infested the adjacent hills, have ceased their ravages, and are now not more frequent than in other parts of Tuscany. The strictly topographical effect of the operations in question, besides the conversion of marsh into dry surface, has been the inversion of the inclination of the valley for a distance of thirty-five miles, so that this great plain which, within a comparatively short period, sloped and drained its waters to the south, now inclines and sends its drainage to the north. The reversal of the currents of the valley has added to the Arno a new tributary equal to the largest of its former affluents, and a most important circumstance connected with this latter fact is, that the increase of the volume of its waters has accelerated their velocity in a still greater proportion, and, instead of augmenting the danger from its inundations, has almost wholly obviated that source of apprehension. [Footnote: Arrian observes that at the junction of the Hydaspes and the Acesines, both of which are described as wide streams, "one very narrow river is formed of two confluents, and its current is very swift."--Arrian, Alex. Anab., vi., 4. A like example is observed in the Anapus near Syracuse, which, below the junction of its two branches, is narrower, though swifter than either of them, and such cases are by no means unfrequent. The immediate effect of the confluence of two rivers upon the current below depends upon local circumstances, and especially upon the angle of incidence. If the two nearly coincide in direction, so as to include a small angle, the join current will have a greater velocity than the slower confluent, perhaps even than either of them. If the two rivers run in transverse, still more if they flow in more or less opposite, directions, the velocity of the principal branch will be retarded both above and below the junction, and at high water it may even set back the current of the affluent. On the other hand, the diversion of a considerable branch from a river retards its velocity below the point of separation, and here a deposit of earth in its channel immediately begins, which has a tendency to turn the whole stream into the new bed. "Theory and the authority of all hydrographical writers combine to show that the channels of rivers undergo an elevation of bed below a canal of diversion."--Letter of Fossombroni, in Salvagnoli, Raccolta di Documenti, p. 32. See the early authorities and discussions on the principle stated in the text, in Frisi, Del modo di regolare i Fiumi e i Torrenti, libro iii., capit. i., and Mongotti, Idraulica, ii., pp. 88 et seqq., and see p. 498, note, ante. In my account of these improvements I have chiefly followed Fossombroni, under whose direction they were principally executed. Many of Fossombroni's statements and opinions have been controverted, and in comparatively unimportant particulars they have been shown to be erroneous.--See Lombardini, Guida allo studio dell' Idrologia, cap. xviii., and same author, Esame degli Studi sul Tevere, Section 33.] Between the beginning of the fifteenth century and the year 1761, thirty-one destructive floods of the Arno are recorded; between 1761, when the principal streams of the Val di Chiana were diverted into that river, and 1835, not one. [Footnote: Fossombroni, Memorie Idraulico-storiche, Introduzione, p. xvi. Between the years 1700 and 1799 the chroniclers record seventeen floods of the Arno, and twenty between 1800 and 1870, but none of these were of a properly destructive character except those in 1844, 1864, and 1870, and the ravages of this latter were chiefly confined to Pisa, and were occasioned by the bursting of a dike or wall. They are all three generally ascribed to extraordinary, if not unprecedented, rains and snows, but many inquirers attribute them to the felling of the woods in the valleys of the upper tributaries of the Arno since 1835. See a paper by Griffini, in the Italia Nuova, 18 Marzo, 1871.] Results of Operations. It is now a hundred years since the commencement of the improvements in the Val di Chiana, and those of the Maremma have been in more or less continued operation for above a generation. They have, as we have seen, produced important geographical changes in the surface of the earth and in the flow of considerable rivers, and their effects have been not less conspicuous in preventing other changes, of a more or less deleterious character, which would infallibly have taken place if they had not been arrested by the improvements in question. The sediment washed into the marshes of the Maremma is not less than 12,000,000 cubic yards per annum. The escape of this quantity into the sea, which, is now almost wholly prevented, would be sufficient to advance the coast-line fourteen yards per year, for a distance of forty miles, computing the mean depth of the sea near the shore at twelve yards. It is true that in this case, as well as in that of other rivers, the sedimentary matter would not be distributed equally along the shore, and much of it would be carried out into deep water, or perhaps transported by the currents to distant coasts. The immediate effects of the deposit in the sea, therefore, would not be so palpable as they appear in this numerical form, but they would be equally certain, and would infallibly manifest themselves, first, perhaps, at some remote point, and afterwards more energetically at or near the outlets of the rivers which produced them. The elevation of the bottom of the sea would diminish the inclination of the beds of the rivers discharging themselves into it on that coast, and of course their tendency to overflow their banks and extend still further the domain of the marshes which border them would be increased in proportion. It has been already stated that, in order to prevent the overflow of the valley of the Tiber by freely draining the Val di Chiana into it, the Papal authorities, long before the commencement of the Tuscan works, constructed strong barriers near the southern end of the valley, which detained the waters of the wet season until they could be gradually drawn off into the Paglia. They consequently deposited most of their sediment in the Val di Chiana and carried down comparatively little earth to the Tiber. The lateral streams contributing the largest quantities of sedimentary matter to the Val di Chiana originally flowed into that valley near its northern end; and the change of their channels and outlets in a southern direction, so as to raise that part of the valley by their deposits and thereby reverse its drainage, was one of the principal steps in the process of improvement. We have seen that the north end of the Val di Chiana near the Arno had been raised by spontaneous deposit of sediment to such a height as to interpose a sufficient obstacle to all flow in that direction. If, then, the Roman dam had not been erected, or the works of the Tuscan Government undertaken, the whole of the earth, which has been arrested by those works and employed to raise the bed and reverse the declivity of the valley, would have been carried down to the Tiber and thence into the sea. The deposit thus created would, of course, have contributed to increase the advance of the shore at the mouth of that river, which has long been going on at the rate of three metres and nine-tenths (twelve feet and nine inches) per annum. [Footnote: See the careful estimates of Rozet, Moyens de forcer les Torrents, etc., pp. 42, 44.] It is evident that a quantity of earth, sufficient to effect the immense changes I have described in a wide valley more than thirty miles long, if deposited at the outlet of the Tiber, would have very considerably modified the outline of the coast, and have exerted no unimportant influence on the flow of that river, by raising its point of discharge and lengthening its channel. The Coast of the Netherlands. It has been shown in a former section that the dikes of the Netherlands and the adjacent states have protected a considerable extent of coast from the encroachments of the sea, an have won a large tract of cultivable land from the dominion of the ocean waters. The immense results obtained from the operations of the Tuscan engineers in the Val di Chiana, and the Maremma have suggested the question, whether a different method of accomplishing these objects might not have been adopted with advantage. It has been argued, as in the case of the Po, that a system of transverse inland dikes and canals, upon the principle of those which have been so successfully employed in the Val di Chiana and in Egypt, might have elevated the low grounds above the ocean tides, by spreading over them the sediment brought down by the Rhine, the Maes, and the Scheld. If this process had been introduced in the Middle Ages, and constantly pursued to our times, the superficial and coast geography, as well as the hydrography of the countries in question, would undoubtedly have presented an aspect very different from their present condition; and by combining the process with a system of maritime dikes, which would have been necessary, both to resist the advance of the sea and to retain the slime deposited by river overflows, it is, indeed, possible that the territory of those states would have been as extensive as it now is, and, at the same time, somewhat elevated above its natural level. The argument in favor of that method rests on the assumption that all the sea-washed earth, which the tides have let fall upon the shallow coast of the Netherlands, has been brought down by the rivers which empty upon those shores, and could have been secured by allowing those rivers to spread over the flats and deposit their sediment in still-water pools formed by cross-dikes like those of Egypt. But we are ignorant of the proportions in which the marine deposits that form the soil of the polders have been derived from materials brought down by these rivers, or from other more remote sources. Much of the river slime has, no doubt, been transported by marine currents quite beyond the reach of returning streams, and it is uncertain how far this loss has been balanced by earth washed by the sea from distant shores and let fall on the coasts of the Netherlands and other neighboring countries. We know little or nothing of the quantity of solid matter brought down by the rivers of Western Europe in early ages, but, as the banks of those rivers are now generally better secured against wash and abrasion than in former centuries, the sediment transported by them must be less than at periods nearer the removal of the primitive forests of their valleys, though certainly greater than it was before those forests were felled. Kladen informs us that the sedimentary matter transported to the sea by the Rhine would amount to a cubic geographical mile in five thousand years. [Footnote: Erdhunde, vol. i, p. 384. The Mississippi--a river "undercharged with sediment"--with a mean discharge of about ten times that of the Rhine, deposits a cubic geographical mile in thirty-three years.] The proportion of this suspended matter which, with our present means, could be arrested and precipitated upon the ground, is almost infinitesimal, for only the surface-water, which carries much less sediment than that at the bottom of the channel, would flow over the banks, and as the movement of this water, if not checked altogether, would be greatly retarded by the proposed cross-dikes, the quantity of solid matter which would be conveyed to a given portion of land during a single inundation would be extremely small. Inundations of the Rhine occur but once or twice a year, and high water continues but a few days, or even hours; the flood-tide of the sea happens seven hundred times in a year, and at the turn of the tide the water is brought to almost absolute rest. Hence, small as is the proportion of suspended matter in the tide-water, the deposit probably amounts to far more in a year than would be let fall upon the same area by the Rhine. This argument, except as to the comparison between river and tide water, applies to the Mississippi, the Po, and most other great rivers. Hence, until that distant day when man shall devise means of extracting from rivers at flood, the whole volume of their suspended material and of depositing it at the same time on their banks, the system of cross-dikes and COLMATAGE must be limited to torrential streams transporting large proportions of sediment, and to the rivers of hot countries, like the Nile, where the saturation of the soil with water, and the securing of a supply for irrigation afterwards, are the main objects, while raising the level of the banks is a secondary consideration. CHAPTER V. THE SANDS. Origin of Sand--Sand now Carried to the Sea--Beach Sands of Northern Africa--Sands of Egypt--Sand Dunes and Sand Plains--Coast Dunes--Sand Banks--Character of Dune Sand--Interior Structure of Dunes--Geological Importance of Dunes--Dunes on American Coasts--Dunes of Western Europe--Age, Character, and Permanence of Dunes--Dunes as a Barrier against the Sea--Encroachments of the Sea--Liimfjord--Coasts of Schleswig-Holstein, Netherlands, and France--Movement of Dunes--Control of Dunes by Man--Inland Dunes--Inland Sand Plains. Origin of Sand. Sand, which is found in beds or strata at the bottom of the sea or in the channels of rivers, as well as in extensive deposits upon or beneath the surface of the dry land, appears to consist essentially of the detritus of rocks. It is not always by any means clear through what agency the solid rock has been reduced to a granular condition; for there are beds of quartzose sand, where the sharp, angular shape of the particles renders it highly improbable that they have been formed by gradual abrasion and attrition, and where the supposition of a crushing mechanical force seems equally inadmissible. In common sand, the quartz grains are the most numerous; but this is not a proof that the rocks from which these particles were derived were wholly, or even chiefly, quartzose in character; for, in many composite rocks, as, for example, in the granitic group, the mica, feldspar, and hornblende are more easily decomposed by chemical action, or disintegrated, comminuted, and reduced to an impalpable state by mechanical force, than the quartz. In the destruction of such rocks, therefore, the quartz would survive the other ingredients, and remain unmixed, when they had been decomposed and recomposed into new mineralogical or chemical combinations, or been ground to slime and washed away by water currents. The greater or less specific gravity of the different constituents of rock doubtless aids in separating them into distinct masses when once disintegrated, though there are veined and stratified beds of sand where the difference between the upper and lower layers, in this respect, is too slight to be supposed capable of effecting a complete separation. [Footnote: In the curiously variegated sandstone of Arabia Petraea--which is certainly a reaggregation of loose sand derived from disaggregation of older rocks--the continuous veins frequently differ very widely in color, but not sensibly in specific gravity or in texture; and the singular way in which they are now alternated, now confusedly intermixed, must be explained otherwise than by the weight of the respective grains which compose them. They seem, in fact, to have been let fall by water in violent ebullition or tumultuous mechanical agitation, or deposited by a succession of sudden aquatic or aerial currents flowing in different directions and charged with differently colored matter.] In cases where rock has been reduced to sandy fragments by heat, or by obscure chemical and other molecular forces, the sand-beds may remain undisturbed, and represent, in the series of geological strata, the solid formations from which they were derived. The large masses of sand not found in place have been transported and accumulated by water or by wind, the former being generally considered the most important of these agencies; for the extensive deposits of the Sahara, of the Arabian peninsulas, of the Llano Estacado and other North and South American deserts, of the deserts of Persia, and of that of Gobi, are supposed to have been swept together or distributed by marine currents, and to have been elevated above the ocean by the same means as other upheaved strata. Meteoric and mechanical influences are still active in the reduction of rocks to a fragmentary state; [Footnote: A good account of the agencies now operative in the reduction of rock to sand will be found in Winkler, Zand en Duinen, Dockarm, 1865, pp. 4-20. I take this occasion to acknowledge my obligations to this author for assuming the responsibility of many of the errors I may have committed in this chapter, by translating a large part of it from a former edition of the present work and publishing it as his own.] but the quantity of sand now transported to the sea seems to be comparatively inconsiderable, because--not to speak of the absence of diluvial action--the number of torrents emptying directly into the sea is much less than it was at earlier periods. The formation of alluvial plains in maritime bays, by the sedimentary matter brought down from the mountains, has lengthened the flow of such streams and converted them very generally into rivers, or rather affluents of rivers of later geographical origin than themselves. The filling up of the estuaries has so reduced the slope of all large and many small rivers, and, consequently, so checked the current of what the Germans call their Unterlauf, or lower course, that they are much less able to transport heavy material than at earlier epochs. The slime deposited by rivers at their junction with the sea, is usually found to be composed of material too finely ground and too light to be denominated sand, and it can be abundantly shown that the sand-banks at the outlet of most large streams are of tidal, not of fluviatile, accumulation, or, in lakes and tideless seas, a result of the concurrent action of waves and of wind. Large deposits of sand, therefore, must in general be considered as of ancient, not of recent formation, and many eminent geologists ascribe them to diluvial action. Staring has discussed this question very fully, with special reference to the sands of the North Sea, the Zuiderzee, and the bays and channels of the Dutch coast. [Footnote: De Bodem van Nederland, i., pp. 243, 246-377, et seqq. See also the arguments of Bremontier as to the origin of the dune-sands of Gascony, Annales des Ponts et Chaussees, 1833, 1er semestre, pp. 158, 161. Bremontier estimates the sand anually thrown up on that coast at five cubic toises and two feet to the running toise (ubi supra, p. 162), or rather more than two hundred and twenty cubic feet to the running foot. Laval, upon observations continued through seven years, found the quantity to be twenty-five metres per running metre, which is equal to two hundred and sixty-eight cubic feet to the running foot.--Annales des Ponts et Chaussees, 1842, 2me semestre, p. 229. These computations make the proportion of sand deposited on the coast of Gascony three or four times as great as that observed by Andresen on the shores of Jutland. Laval estimates the total quantity of sand annually thrown up on the coast of Gascony at 6,000,000 cubic metres, or more than 7,800,000 cubic yards.] His general conclusion is, that the rivers of the Netherlands "move sand only by a very slow displacement of sand-banks, and do not carry it with them as a suspended or floating material." The sands of the German Ocean he holds to be a product of the "great North German drift," deposited where they now lie before the commencement of the present geological period, and he maintains similar opinions with regard to the sands thrown up by the Mediterranean at the mouths of the Nile and on the Barbary coast. [Footnote: De Bodem van Nederland, i., p. 339.] Sand now carried to the Sea. There are, however, cases where mountain streams still bear to the sea perhaps relatively small, but certainly absolutely large, amounts of disintegrated rock. [Footnote: The conditions favorable to the production of sand from disintegrated rock, by causes now in action, are perhaps nowhere more perfectly realized than in the Sinaitic Peninsula. The mountains are steep and lofty, unprotected by vegetation or even by a coating of earth, and the rocks which compose them are in a shattered and fragmentary condition. They are furrowed by deep and precipitous ravines, with beds sufficiently inclined for the rapid flow of water, and generally without basins in which the larger blocks of stone rolled by the torrents can be dropped and left in repose; there are severe frosts and much snow on the higher summits and ridges, and the winter rains are abundant and heavy. The mountains are principally of igneous formation, but many of the less elevated peaks are capped with sandstone, and on the eastern slope of the peninsula you may sometimes see, at a single glance, several lofty pyramids of granite, separated by considerable intervals, and all surmounted by horizontally stratified deposits of sandstone often only a few yards square, which correspond to each other in height, are evidently contemporaneous in origin, and were once connected in continuous beds. The degradation of the rock on which this formation rests is constantly bringing down masses of it, and mingling them with the basaltic, porphyritic, granitic, and calcareous fragments which the torrents carry down to the valleys, and, through them, in a state of greater or less disintegration, to the sea. The quantity of sand annually washed into the Red Sea by the larger torrents of the Lesser Peninsula, is probably at least equal to that contributed to the ocean by any streams draining basins of no greater extent. Absolutely considered, then, the mass may be said to be large, but it is apparently very small as compared with the sand thrown up by the German Ocean and the Atlantic on the coasts of Denmark and of France. There are, indeed, in Arabia Petraea, many torrents with very short courses, for the sea-waves in many parts of the peninsular coast wash the base of the mountains. In these cases, the debris of the rocks do not reach the sea in a sufficiently comminuted condition to be entitled to the appellation of sand, or even in the form of well-rounded pebbles. The fragments retain their annular shape, and, at some points on the coast, they become cemented together by lime or other binding substances held in solution or mechanical suspension in the sea-water, and are so rapidly converted into a singularly heterogeneous conglomerate, that one deposit seems to be consolidated into a breccia before the next winter's torrents cover it with another. In the northern part of the peninsula there are extensive deposits of sand intermingled with agate pebbles and petrified wood, but these are evidently neither derived from the Sinaitic group, nor products of local causes known to be now in action. I may here notice the often repeated but mistaken assertion, that the petrified wood of the Western Arabian desert consists wholly of the stems of palms, or at least of endogenous vegetables. This is an error. I have myself picked up in that desert, within the space of a very few square yards, fragments apparently of fossil palms, and of at least two petrified trees distinctly marked as of exogenous growth both by annular structure and by knots. In ligneous character, one of these almost precisely resembles the grain of the extant beech, and this specimen was worm-eaten before it was converted into silex.] The quantity of sand and gravel carried into the Mediterranean by the torrents of the Maritime Alps, the Ligurian Apennines, the islands of Corsica, Sardinia, and Sicily, and the mountains of Calabria, is apparently great. In mere mass, it is possible, if not probable, that as much rocky material, more or less comminuted, is contributed to the basin of the Mediterranean by Europe, even excluding the shores of the Adriatic and the Euxine, as is washed up from it upon the coasts of Northern Africa and Syria. A great part of this material is thrown out again by the waves on the European shores of that sea. The harbors of Luni, Albenga, San Remo, and Savona west of Genoa, and of Porto Fino on the other side, are filling up, and the coast near Carrara and Massa is said to have advanced upon the sea to a distance of 475 feet in thirty-three years. [Footnote: Bottger, Das Mittelmeer, p. 128.] Besides this, we have no evidence of the existence of deep-water currents in the Mediterranean, extensive enough and strong enough to transport quartzose sand across the sea. It may be added that much of the rock from which the torrent sands of Southern Europe are derived contains little quartz, and hence the general character of these sands is such that they must be decomposed or ground down to an impalpable slime, long before they could be swept over to the African shore. Sands of Northern Africa. The torrents of Europe, then, do not at present furnish the material which composes the beach sands of Northern Africa, and it is equally certain that those sands are not brought down by the rivers of the latter continent. They belong to a remote geological period, and have been accumulated by causes which we cannot at present assign. The wind does not stir water to great depths with sufficient force to disturb the bottom, [Footnote: The testimony of divers and of other observers on this point is conflicting, as might be expected from the infinite variety of conditions by which the movement of water is affected. It is generally believed that the action of the wind upon the water is not perceptible at greater depths than from fifteen feet in ordinary to eighty or ninety in extreme cases; but these estimates are probably very considerably below the truth. Andresen quotes Bremontier as stating that the movement of the waves sometimes extends to the depth of five hundred feet, and he adds that others think it may reach to six or even seven hundred feet below the surface.--Andresen, Om Klitformationen, p. 20. Many physicists now suppose that the undulations of great bodies of water reach even deeper. But a movement of undulation is not necessarily a movement of translation, and besides, there is very frequently an undertow, which tends to carry suspended bodies out to sea as powerfully as the superficial waves to throw them on shore. Sand-banks sometimes recede from the coast, instead of rolling towards it. Reclus informs us that the Mauvaise, a sand-bank near the Point de Grave, on the Atlantic coast of France, has moved five miles to the west in less than a century.--Revue des Deux Mondes for December, 1862, p. 905. The action of currents may, in some cases, have been confounded with that of the waves. Sea-currents, strong enough, possibly, to transport sand for some distance, flow far below the surface in parts of the open ocean, and in narrow straits they have great force and velocity. The divers employed at Constantinople in 1853 found in the Bosphorus, at the depth of twenty-five fathoms and at a point much exposed to the wash from Galata and Pera, a number of bronze guns supposed to have belonged to a ship-of-war blown up about a hundred and fifty years before. These guns were not covered by sand or slime, though a crust of earthy matter, an inch in thickness, adhered to their upper surfaces, and the bottom of the strait appeared to be wholly free from sediment. The current was so powerful at this depth that the divers were hardly able to stand, and a keg of nails, purposely dropped into the water, in order that its movements might serve as a guide in the search for a bag of coin accidentally lost overboard from a ship in the harbor, was rolled by the stream several hundred yards before it stopped.] and the sand thrown upon the coast in question must be derived from a narrow belt of sea. It must hence, in time, become exhausted, and the formation of new sand-banks and dunes upon the southern shores of the Mediterranean will cease at last for want of material. [Footnote: Few seas have thrown up so much sand as the shallow German Ocean; but there is some reason to think that the amount of this material now cast upon its northern shores is less than at some former periods, though no extensive series of observations on this subject has been recorded. On the Spit of Agger, at the present outlet of the Liimfjord, Andresen found the quantity during ten years, on a beach about five hundred and seventy feet broad, equal to an annual deposit of an inch and a half over the whole surface.--Om Klitformationen, p. 56. This gives seventy-one and a quarter cubic feet to the running foot--a quantity certainly much smaller than that cast up by the same sea on the shores of the Dano-German duchies and of Holland, and, as we have seen, scarcely one-fourth of that deposited by the Atlantic on the coast of Gascony.] But even in the cases where the accumulations of sand in extensive deserts appear to be of marine formation, or rather aggregation, and to have been brought to their present position by upheaval, they are not wholly composed of material collected or distributed by the currents of the sea; for, in all such regions, they continue to receive some small contributions from the disintegration of the rocks which underlie, or crop out through, the superficial deposits. [Footnote: See, on this subject, an article in Aus der Natur, vol. xxx., p. 590. The Florentine Frescobaldi, who visited the Sinaitic peninsula five hundred years ago, observed the powerful action of the solar heat in the disintegration of the desert rocks. "This place," says he, "was a ridge of rocks burnt to powder by the sun, and this powder is blown away from the rock by the wind and is the sand of the desert; and there be many hills which are pure bare rock, and when the sun parcheth them, the wind carries off the dust, and other sand is there none in that land,"--Viaggio, pp. 69, 70. In Arabia Petraea, when a wind, powerful enough to scour down below the ordinary surface of the desert and lay bare a fresh bed of stones, is followed by a sudden burst of sunshine, the dark agate pebbles are often cracked and broken by the heat; and this is the true explanation of the occurrence of the fragments in situations where the action of fire is not probable. If the fragments are small enough to be rolled by the winds, they are in time ground down to sand and contribute to the stock of that material which covers the face of the desert, though the sand thus formed is but an infinitesimal proportion of the whole.] In some instances, too, as in Northern Africa, additions are constantly made to the mass by the prevalence of sea-winds, which transport, or, to speak more precisely, roll the finer beach-sand to considerable distances into the interior. But this is a very slow process, and the exaggerations of travellers have diffused a vast deal of popular error on the subject. Sands of Egypt. In the narrow valley of the Nile--which, above its bifurcation near Cairo, is, throughout Egypt and Nubia, generally bounded by precipitous cliffs--wherever a ravine or other considerable depression occurs in the wall of rock, one sees what seems a stream of desert sand pouring down, and common observers have hence concluded that the whole valley is in danger of being buried under a stratum of infertile soil. The ancient Egyptians apprehended this, and erected walls, often of unburnt brick, across the outlet of gorges and lateral valleys, to check the flow of the sand-streams. In later ages, these walls have mostly fallen into decay, and no preventive measures against such encroachments are now resorted to. But the extent of the mischief to the soil of Egypt, and the future danger from this source, have been much overrated. The sand on the borders of the Nile is neither elevated so high by the wind, nor transported by that agency in so great masses, as is popularly supposed; and of that which is actually lifted or rolled and finally deposited by air-currents, a considerable proportion is either calcareous, and, therefore, readily decomposable, or in the state of a very fine dust, and so, in neither case, injurious to the soil. There are, indeed, both in Africa and in Arabia, considerable tracts of fine, silicious sand, which may be carried far by high winds, but these are exceptional cases, and in general the progress of the desert sand is by a rolling motion along the surface. [Footnote: Sand heaps, three and even six hundred feet high, are indeed formed by the wind, but this is effected by driving the particles up an inclined plane, not by lifting them. Bremontier, speaking of the sand-hills on the western coast of France, says: "The particles of sand composing them are not large enough to resist wind of a certain force, nor small enough to be taken up by it, like dust; they only roll along the surface from which they are detached, and, though moving with great velocity, they rarely rise to a greater height than three or four inches."--Memoirs sur les Dunes, Annales des Ponts et Chaussecs, 1833, ler semestre, p, 148. Andresen says that a wind, having a velocity of forty feet per second, is strong enough to raise particles of sand as high as the face and eyes of a man, but that, in general, it rolls along the ground, and is scarcely ever thrown more than to the height of a couple of yards from the surface. Even in these cases, it is carried forward by a hopping, not a continuous, motion; for a very narrow sheet or channel of water stops the drift entirely, all the sand dropping into it until it is filled up. Blake observes, Pacific Railroad Report, vol. v., p. 242, that the sand of the Colorado desert does not rise high in the air, but bounds along on the surface or only a few inches above it. The character of the motion of sand drifts is well illustrated by an interesting fact not much noticed hitherto by travellers in the East. In situations where the sand is driven through depressions in rock-beds, or over deposits of silicious pebbles, the surface of the stone is worn and smoothed much more effectually than it could be by running water, and I have picked up, in such localities, rounded, irregularly broken fragments of agate, which had received from the attrition of the sand as fine a polish as could be given them by the wheel of the lapidary. Very interesting observations, by Blake, on the polishing of hard stones by drifting sand will be found in the Pacific Railroad Report, vol. v., pp. 92, 230, 231. The grinding and polishing power of sand has lately received a new and most ingenious application in America. Jets of sand, and even of small particles of softer substances, thrown with a certain force, are found capable of cutting the hardest minerals and metals. A block of corundum, some inches thick, has been bored through in a few minutes by this process, and it promises to be highly useful in glass-cutting and other similar operations.] So little is it lifted, and so inconsiderable is the quantity yet remaining on the borders of Egypt, that a wall four or five feet high suffices for centuries to check its encroachments. This is obvious to the eye of every observer who prefers the true to the marvellous; but the old-world fable of the overwhelming of caravans by the fearful simoom--which even the Arabs no longer repeat, if indeed they are the authors of it--is so thoroughly rooted in the imagination of Christendom that most desert travellers, of the tourist class, think they shall disappoint the readers of their journals if they do not recount the particulars of their escape from being buried alive by a sand-storm, and the popular demand for a "sensation" must be gratified accordingly. [Footnote: Wilkinson says that, in much experience in the most sandy parts of the Libyan desert, and much inquiry of the best native sources, he never saw or heard of any instance of danger to man or beast from the mere accumulation of sand transported by the wind. Chesney's observations in Arabia, and the testimony of the Bedouins he consulted, are to the same purpose. The dangers of the simoom are of a different character, though they are certainly aggravated by the blinding effects of the light particles of dust and sand borne along by it, and by that of the inhalation of them upon the respiration. ] Another circumstance is necessary to be considered in estimating the danger to which the arable lands of Egypt are exposed. The prevailing wind in the valley of the Nile and its borders is from the north, and it may be said without exaggeration that the north wind blows for three-quarters of the year. [Footnote: In the narrow valley of the Nile, bounded as it is, above the Delta, by high cliffs, all air-currents from the northern quarter become north winds, though of course varying in partial direction, in conformity with the sinuosities of the valley. Upon the desert plateau they incline westwards, and have already borne into the valley the sands of the eastern banks, and driven those of the western quite out of the Egyptian portion of the Nile basin.] The effect of winds blowing up the valley is to drive the sands of the desert plateau which border it, in a direction parallel with the axis of the valley, not transversely to it; and if it ran in a straight line, the north wind would carry no desert sand into it. There are, however, both curves and angles in its course, and hence, wherever its direction deviates from that of the wind, it might receive sand-drifts from the desert plain through which it runs. But, in the course of ages, the winds have, in a great measure, bared the projecting points of their ancient deposits, and no great accumulations remain in situations from which either a north or a south wind would carry them into the valley. [Footnote: These considerations apply, with equal force, to the supposed danger of the obstruction of the Suez Canal by the drifting of the desert sands. The winds across the isthmus are almost uniformly from the north, and they swept it comparatively clean of flying sands long ages since. The traces of the ancient canal between the Red Sea and the Nile are easily followed for a considerable distance from Suez. Had the drifts upon the isthmus been as formidable as some have feared and others have hoped, those traces would have been obliterated, and Lake Timsah and the Bitter Lakes filled up, many centuries ago. The few particles driven by the rare east and west winds towards the line of the canal, will easily be arrested by plantations or other simple methods, or removed by dredging. The real dangers and difficulties of this magnificent enterprise--and they have been great--consisted in the nature of the soil to be removed in order to form the line, and especially in the constantly increasing accumulation of sea-sand at the southern terminus by the tides of the Red Sea, and of sand and Nile slime at the northern, by the action of the winds and currents. Both seas are shallow for miles from the shore, and the excavation and maintenance of deep channels, and of capacious harbors with easy and secure entrances, in such localities, is doubtless one of the hardest problems offered to modern engineers for practical solution. See post, Geological Importance of Dunes, note.] The sand let fall in Egypt by the north wind is derived, not from the desert, but from a very different source--the sea. Considerable quantities of sand are thrown up by the Mediterranean, at and between the mouths of the Nile, and indeed along almost the whole southern coast of that sea, and drifted into the interior to distances varying according to the force of the wind and the abundance and quality of the material. The sand so transported contributes to the gradual elevation of the Delta, and of the banks and bed of the river itself. But just in proportion as the bed of the stream is elevated, the height of the water in the annual inundations is increased also, and as the inclination of the channel is diminished, the rapidity of the current is checked, and the deposition of the slime it holds in suspension consequently promoted. Thus the winds and the water, moving in contrary directions, join in producing a common effect. The sand, blown over the Delta and the cultivated land higher up the stream during the inundation, is covered or mixed with the fertile earth brought down by the river, and no serious injury is sustained from it. That spread over the same ground after the water has subsided, and during the short period when the soil is not stirred by cultivation or covered by the flood, forms a thin pellicle over the surface as far as it extends, and serves to divide and distinguish the successive layers of slime deposited by the annual inundations. The particles taken up by the wind on the sea-beach are borne onward, by a hopping motion, or rolled along the surface, until they are arrested by the temporary cessation of the wind, by vegetation, or by some other obstruction, and they may, in process of time, accumulate in large masses, under the lee of rocky projections, buildings, or other barriers which break the force of the wind. In these facts we find an important element in the explanation of the sand drifts, which have half buried the Sphinx and so many other ancient monuments in that part of Egypt. These drifts, as I have said, are not wholly from the desert, but in largo proportion from the sea; and, as might be supposed from the distance they have travelled, they have been long in gathering. While Egypt was a great and flourishing kingdom, measures were taken to protect its territory against the encroachment of sand, whether from the desert or from the Mediterranean; but the foreign conquerors, who destroyed so many of its religious monuments, did not spare its public works, and the process of physical degradation undoubtedly began as early as the Persian invasion. The urgent necessity, which has compelled all the successive tyrannies of Egypt to keep up some of the canals and other arrangements for irrigation, was not felt with respect to the advancement of the sands; for their progress was so slow as hardly to be perceptible in the course of a single reign, and long experience has shown that, from the natural effect of the inundations, the cultivable soil of the valley is, on the whole, trenching upon the domain of the desert, not retreating before it. The oases of the Libyan, as well as of many Asiatic deserts, have no such safeguards. The sands are fast encroaching upon them, and threaten soon to engulf them, unless man shall resort to artesian wells and plantations, or to some other efficient means of checking the advance of this formidable enemy, in time to save these islands of the waste from final destruction. Accumulations of sand are, in certain cases, beneficial as a protection against the ravages of the sea; but, in general, the vicinity, and especially the shifting of bodies of this material, are destructive to human industry, and hence, in civilized countries, measures are taken to prevent its spread. This, however, can be done only where the population is large and enlightened, and the value of the soil, or of the artificial erections and improvements upon it, is considerable. Hence in the deserts of Africa and of Asia, and thee inhabited lands which border on them, no pains are usually taken to check the drifts, and when once the fields, the houses, the springs, or the canals of irrigation are covered or choked, the district is abandoned without a struggle, and surrendered to perpetual desolation. [Footnote: In parts of the Algerian desert, some efforts are made to retard the advance of sand dunes which threaten to overwhelm villages. "At Debila," says Laurent, "the lower parts of the lofty dunes are planted with palms, ... but they are constantly menaced with burial by the sands. The only remedy employed by the natives consists in little dry walls of crystallized gypsum, built on the crests of the dunes, together with hedges of dead palm-leaves. These defensive measures are aided by incessant labor; for every day the people take up in baskets the sand blown over to them the night before and carry it back to the other side of the dune."--Memoires sur le Sahara, p. 14.] Sand Dunes and Sand Plains. Two forms of sand deposit are specially important in European and American geography. The one is that of dune or shifting hillock upon the coast, the other that of barren plain in the interior. The coast-dunes are composed of sand washed up from the depths of the sea by the waves, and heaped in more or less rounded knolls and undulating ridges by the winds. The sand with which many plains are covered appears sometimes to have been deposited upon them while they were yet submerged beneath the sea, sometimes to have been drifted from the seacoast, and scattered over them by wind-currents, sometimes to have been washed upon them by running water. In these latter cases, the deposit, though in itself considerable, is comparatively narrow in extent and irregular in distribution, while, in the former, it is often evenly spread over a very wide surface. In all great bodies of either sort, the silicious grains are the principal constituent, though, when not resulting from the disintegration of silicious rock and still remaining in place, they are generally accompanied with a greater or less admixture of other mineral particles, and of animal and vegetable remains, [Footnote: Organic constituents, such as comminuted shells, and silicious and calcareous exuviae of infusorial animals and plants, are sometimes found mingled in considerable quantities with mineral sands. These are usually the remains of aquatic vegetables or animals, but not uniformly so, for the microscopic organisms, whose flinty cases enter so largely into the sand-beds of the Mark of Brandenburg, are still living and prolific in the dry earth. See Wittwer, Physikalische Geographic, p. 142. The desert on both sides of the Nile is inhabited by a land-snail--of which I have counted eighty, in estimation, on a single shrub barely a foot high--and thousands of its shells are swept along and finally buried in the drifts by every wind. Every handful of the sand contains fragments of them. Forchhammer, in Leonhard und Bronn s Jahrbuch, 1841, p. 8, says of the sand-hills of the Danish coast: "It is not rare to find, high in the knolls, marine shells, and especially those of the oyster. They are due to the oyster-eater [Haemalopus ostralegus], which carries his prey to the top of the dunes to devour it." See also Staring, De Bodem van Nederland, i., p. 821.] and they are also, usually somewhat changed in consistence by the ever-varying conditions of temperature and moisture to which they have been exposed since their deposit. Unless the proportion of these latter ingredients is so large as to create a considerable adhesiveness in the mass--in which case it can no longer properly be called sand--it is infertile, and, if not charged with water, partially agglutinated by iron, lime, or other cement, or confined by alluvion resting upon it, it is much inclined to drift, whenever, by any chance, the vegetable network which, in most cases, thinly clothes and at the same time confines it, is broken. Human industry has not only fixed the flying dunes by plantations, but, by mixing clay and other tenacious earths with the superficial stratum of extensive sand plains, and by the application of fertilizing substances, it has made them abundantly productive of vegetable life. These latter processes belong to agriculture and not to geography, and, therefore, are not embraced within the scope of the present subject. But the preliminary steps, whereby wastes of loose, drifting barren sands are transformed into wooded knolls and plains, and finally, through the accummulation of vegetable mould, into arable ground, constitute a conquest over nature which precedes agriculture--a geographical revolution--and, therefore, an account of the means by which the change has been effected belongs properly to the history of man's influence on the great features of terrestrial surface. I proceed, then, to examine the structure of dunes, and to describe the warfare man wages with the sand-hills, striving on the one hand to maintain and even extend them, as a natural barrier against encroachments of the sea, and, on the other, to check their moving and wandering propensities, and prevent them from trespassing upon the fields he has planted and the habitations in which he dwells. COAST DUNES. Coast dunes are oblong ridges or round hillocks, formed by the action of the wind upon sands thrown up by the waves on the low beaches of seas, and sometimes of fresh-water lakes. On most coasts, the supply of sand for the formation of dunes is derived from tidal waves. The flow of the tide is more rapid, and consequently its transporting power greater, than that of the ebb; the momentum, acquired by the heavy particles in rolling in with the water, tends to carry them even beyond the flow of the waves; and at the turn of the tide, the water is in a state of repose long enough to allow it to let fall much of the solid matter it holds in suspension. Hence, on all low, tide-washed coasts of seas with sandy bottoms, there exist several conditions favorable to the formation of sand deposits along high-water mark. [Footnote: There are various reasons why the formation of dunes is confined to low shores, and this law is so universal, that when bluffs are surmounted by them, there is always cause to suspect upheaval, or the removal of a sloping beach in front of the bluff, after the dunes were formed. Bold shores are usually without a sufficient beach for the accumulation of large deposits; they are commonly washed by a sea too deep to bring up sand from its bottom; their abrupt elevation, even if moderate in amount, would still be too great to allow ordinary winds to lift the sand above them; and their influence in deadening the wind which blows towards them would even more effectually prevent the raising of sand from the beach at their foot. Forchhammer, describing the coast of Jutland, says that, in high winds, "one can hardly stand upon the dunes, except when they are near the water line and have been cut down perpendicularly by the waves. Then the wind is little or not at all felt--a fact of experience very common on our coasts, observed on all the steep shore bluffs of 200 feet height, and, in the Faroe Islands, on precipices 2,000 feet high. In heavy gales in those islands, the cattle fly to the very edge of the cliffs for shelter, and frequently fall over. The wind, impinging against the vertical wall, creates an ascending current which shoots somewhat past the crest of the rock, and thus the observer or the animal is protected against the tempest by a barrier of air."-Leonhard und Bronn, Jahrbuch, 1841, p. 3. The calming, or rather diversion, of the wind by cliffs extends to a considerable distance in front of them, and no wind would have sufficient force to raise the sand vertically, parallel to the face of a bluff, even to the height of twenty feet.] If the land-winds are of greater frequency, duration, or strength than the sea-winds, the sands left by the retreating wave will be constantly blown back into the water; but if the prevailing air-currents are in the opposite direction, the sands will soon be carried out of the reach of the highest waves, and transported continually farther and farther into the interior of the land, unless obstructed by high grounds, vegetation, or other obstacles. The laws which govern the formation of dunes are substantially these. We have seen that, under certain conditions, sand is accumulated above high-water mark on low sea and lake shores. So long as the sand is kept wet by the spray or by capillary attraction, it is not disturbed by air-currents, but as soon as the waves retire sufficiently to allow it to dry, it becomes the sport of the wind, and is driven up the gently sloping beach until it is arrested by stones, vegetables, or other obstructions, and thus an accumulation is formed which constitutes the foundation of a dune. However slight the elevation thus created, it serves to stop or retard the progress of the sand-grains which are driven against its shoreward face, and to protect from the further influence of the wind the particles which are borne beyond it, or rolled over its crest, and fall down behind it. If the shore above the beach line were perfectly level and straight, the grass or bushes upon it of equal height, the sand thrown up by the waves uniform in size and weight of particles as well as in distribution, and if the action of the wind were steady and regular, a continuous bank would be formed, everywhere alike in height and cross section. But no such constant conditions anywhere exist. The banks are curved, broken, unequal in elevation; they are sometimes bare, sometimes clothed with vegetables of different structure and dimensions; the sand thrown up is variable in quantity and character; and the winds are shifting, gusty, vertical, and often blowing in very narrow currents. From all these causes, instead of uniform hills, there rise irregular rows of sand-heaps, and these, as would naturally be expected, are of a pyramidal, or rather conical shape, and connected at bottom by more or less continuous ridges of the same material. Elisee Reclus, in describing the coast dunes of Gascony, observes that when, as sometimes happens, the sands are not heaped in a continuous, irregular bulwark, but deposited in isolated hillocks, they have a tendency to assume a crescent shape, the convexity being turned seawards, or towards the direction from which the prevailing winds proceed. This fact, the geological bearing of which is obvious, is not noticed by previous French writers or even by Andresen, though a semi-lunar outline has been long generally ascribed to inland dunes. It is, however evident that such a form would naturally be produced by the action of a wind blowing long in a given direction upon a mass of loose sand with a fixed centre--such as is constituted by the shrub or stone around which the sand is first deposited--and free extremities. On a receding coast, dunes will not attain so great a height as on more secure shores, because they are undermined and carried off before they have time to reach their greatest dimensions. Hence, while at sheltered points in South-western France, there are dunes three hundred feet or more in height, those on the Frisic Islands and the exposed parts of the coast of Schleswig-Holstein range only from twenty to one hundred feet. On the western shores of Africa, it is said that they sometimes attain an elevation of six hundred feet. This is one of the very few points known to geographers where desert sands are advancing seawards, [Footnote: "On the west coast of Africa the dunes are drifting seawards, and always receiving new accessions from the Sahara. They are constantly advancing out into the sea."--Naumann, Geognosie, ii., p.1172.] and here they rise to the greatest altitude to which sand-grains can be carried by the wind. The hillocks, once deposited, are held together and kept in shape, partly by mere gravity, and partly by the slight cohesion of the lime, clay, and organic matter mixed with the sand; and it is observed that, from capillary attraction, evaporation from lower strata, and retention of rain-water, they are always moist a little below the surface. [Footnote: "Dunes are always full of water, from the action of capillary attraction. Upon the summits, one seldom needs to dig more than a foot to find the sand moist, and in the depressions, fresh water is met with near the surface."--Forchhammer, in Leonhard and Bronx, for 1841, p.5, note. On the other hand, Andresen, who has very carefully investigated this as well as all other dune phenomena, maintains that the humidity of the sand ridges cannot be derived from capillary attraction. He found by experiment that a heap of drift-sand was not moistened to a greater height than eight and a half inches, after standing with its base a whole night in water. He states the minimum of water contained by the sand of the dunes, one foot below the surface, after a long drought, at two per cent, the maximum, after a rainy month, at four per cent. At greater depths the quantity is larger. The hygroscopicity of the sand of the coast of Jutland he found to be thirty-three per cent, by measure, or 21.5 by weight. The annual precipitation on that coast is twenty-seven inches, and as the evaporation is about the same, he argues that rain-water does not penetrate far beneath the surface of the dunes, and concludes that their humidity can be explained only by evaporation from below.--Om Klitformationen, pp. 106-110. In the dunes of Algeria, water in so abundant that wells are constantly dug in them at high points on their surface. They are sunk to the depth of three or four inches only, and the water rises to the height of a metre in them.--Laurent, Memoire sur le Sahara, pp. 11, 12, 13. The same writer observes (p. 14) that the 'hollows in the dunes are planted with palms which find moisture enough a little below the surface. It would hence seem that proposal to fix the dunes which are supposed to threaten the Suez Canal, by planting the maratime pine and other trees upon them, is not altogether so absurd as it has been thought to be by some of those disinterested philanthropists of other nations who were distressed with fears that French capitalists would lose the money they had invested in that great undertaking. Ponds of water are often found in the depression between the sand-hills of the dune chains in the North American desert.] By successive accumulations, they gradually rise to the height of thirty, fifty, sixty, or a hundred feet, and sometimes even much higher. Strong winds, instead of adding to their elevation, sweep off loose particles from their surface, and these, with others blown over or between them, build up a second row of dunes, and so on according to the character of the wind, the supply and consistence of the sand, and the face of the country. In this way is formed a belt of sand-dunes, irregularly dispersed and varying much in height and dimensions, and sometimes many miles in breadth. On the Island of Sylt, in the German Sea, where there are several rows, the width of the belt is from half a mile to a mile. There are similar ranges on the coast of Holland, exceeding two miles in breadth, while at the mouths of the Nile they form a zone not less than ten miles wide. The base of some of the dunes in the Delta of the Nile is reached by the river during the annual inundation, and the infiltration of the water, which contains lime, has converted the lower strata into a silicious limestone, or rather a calcarous sandstone, and thus afforded an opportunity of studying the structure of that rock in a locality where its origin and mode of aggregation and solidification are known. The tide, though a usual, is by no means a necessary condition for the accumulations of sand out of which dunes are formed. The Baltic and the Mediterranean are almost tideless seas, but there are vast ranges of dunes on the Russian and Prussian coasts of the Baltic and at the mouths of the Nile and many other points on the shores of the Mediterranean. The vast shoals in the latter sea, known to the ancients as the Greater and Lesser Syrtis, are of marine origin. They are still filling up with sand, washed up from greater depths, or sometimes drifted from the coast in small quantities, and will probably be converted, at some future period, into dry land covered with sand-hills. There are also extensive ranges of dunes upon the eastern shores of the Caspian, and at the southern, or rather south-eastern, extremity of Lake Michigan. [Footnote: The careful observations of Colonel J. D. Graham, of the United States Army, show a tide of about three inches in Lake Michigan. See "A Lunar Tidal Wave in the North American Lakes," demonstrated by Lieut.-Colonel J. D. Graham, in the fourteenth volume of the Proceedings of the American Association for the Advancement of Science.] There is no doubt that this latter lake formerly extended much farther in that direction, but its southern portion has gradually shoaled and at last been converted into solid land, in consequence of the prevalence of the north-west winds. These blow over the lake a large part of the year, and create a southwardly set of the currents, which wash up sand from the bed of the lake and throw it on shore. Sand is taken up from the beach at Michigan City by every wind from that quarter, and, after a heavy blow of some hours' duration, sand ridges may be observed on the north side of the fences, like the snow wreaths deposited by a drifting wind in winter. Some of the particles are carried back by contrary winds, but most of them lodge on or behind the dunes, or in the moist soil near the lake, or are entangled by vegetables, and tend permanently to elevate the level. Like effects are produced by constant sea-winds, and dunes will generally be formed on all low coasts where such prevail, whether in tideless or in tidal waters. Jobard thus describes the modus operandi, under ordinary circumstances, at the mouths of the Nile, where a tide can scarcely be detected: "When a wave breaks, it deposits an almost imperceptible line of fine sand. The next wave brings also its contribution, and shoves the preceding line a little higher. As soon as the particles are fairly out of the reach of the water they are dried by the heat of the burning sun, and immediately seized by the wind and rolled or borne farther inland. The gravel is not thrown out by the waves, but rolls backwards and forwards until it is worn down to the state of fine sand, when it, in its turn, is cast upon the land and taken up by the wind." [Footnote: Staring, De Bodun van Nederland, i., p. 327, note.] This description applies only to the common every-day action of wind and water; but just in proportion to the increasing force of the wind and the waves, there is an increase in the quantity of sand, and in the magnitude of the particles carried off from the beach by it, and, of course, every storm in a landward direction adds sensibly to the accumulation upon the shore. Sand Banks. Although dunes, properly so called, are found only on dry land and above ordinary high-water mark, and owe their elevation and structure to the action of the wind, yet, upon many shelving coasts, accumulations of sand much resembling dunes are formed under water at some distance from the shore by the oscillations of the waves, and are well known by the name of sand banks. They are usually rather ridges than banks, of moderate inclination, and with the steepest slope seawards, [Footnote: Kohl, Inseln und Marschen Schleswig Holsteins, ii., p. 33. From a drawing in Andresen, Om Klitformationen, p. 24, it would appear that on the Schleswig coast the surf-formed banks have the steepest slope landwards, those farther from the shore, as stated in the text.] and their form differs little from that of dunes except in this last particular and in being lower and more continuous. Upon the western coast of the island of Amrum, for example, there are three rows of such banks, the summits of which are at a distance of perhaps a couple of miles from each other; so that, including the width of the banks themselves, the spaces between them, and the breadth of the zone of dunes upon the land, the belt of moving sands on that coast is probably not less than eight miles wide. Under ordinary circumstances, sand banks are always rolling, landwards, and they compose the magazine from which the material for the dunes is derived. [Footnote: Sand banks sometimes connect themselves with the coast at both ends, and thus cut off a portion of the sea. In this case, as well as when salt water is enclosed by sea-dikes, the water thus separated from the ocean gradually becomes fresh, or at least brackish. The Haffs, or large expanses of fresh water in Eastern Prussia--which are divided from the Baltic by narrow sand banks called Nehrungen, or, at sheltered points of the coast, by fluviatile deposits called Werders--all have one or more open passages, through which the water of the rivers that supply them at last finds its way to the sea.] The dunes, in fact, are but aquatic sand banks transferred to dry land. The laws of their formation are closely analogous, because the action of the two fluids, by which they are respectively accumulated and built up, is very similar when brought to bear upon loose particles of solid matter. It would, indeed, seem that the slow and comparatively regular movements of the heavy, unelastic water ought to affect such particles very differently from the sudden and fitful impulses of the light and elastic air. But the velocity of the wind currents gives them a mechanical force approximating to that of the slower waves, and, however difficult it may be to explain all the phenomena that characterize the structure of the dunes, observation has proved that it is nearly identical with that of submerged sand banks. [Footnote: Forchhammer ascribes the resemblance between the furrowing of the dune sands and the beach ripples, not to the similarity of the effect of wind and water upon sand, but wholly to the action of the wind; in the first instance, directly, in the latter, through the water. "The wind-ripples on the surface of the dunes precisely resemble the water-ripples of sand flats occasionally overflowed by the sea; and with the closest scrutiny, I have never been able to detect the slightest difference between them. This is easily explained by the fact, that the water-ripples are produced by the action of light wind on the water which only transmits the air-waves to the sand."--Leonhard und Bronn, 1841, pp. 7, 8.] The differences of form are generally ascribable to the greater number and variety of surface accidents of the ground on which the sand hills of the land are built up, and to the more frequent changes, and wider variety of direction, in the courses of the wind. CHARACTER OF DUNE SAND. "Dune sand," says Staring, "consists of well-rounded grains of quartz, more or less colored by iron, and often mingled with fragments of shells, small indeed, but still visible to the naked eye. [Footnote: According to the French authorities, the dunes of France are not always composed of quartzose sand. "The dune sands" of different characters, says Bremontier, "partake of the nature of the different materials which compose them. At certain points on the coast of Normandy they are found to be purely calcareous; they are of mixed composition on the shores of Brittany and Saintonge, and generally quartzose between the mouth of the Gironde and that of the Adour."--Memoire sur les Dunes, Annales des Ponts et Chaussees, t. vii., 1833, 1er semestre, p. 146. In the dunes of Long Island and of Jutland, there are considerable veins composed almost wholly of garnet. For a very full examination of the mechanical and chemical composition of the dune sands of Jutland, see Andresen, Om Klitformationen, p. 110. Fraas informs us, Aus dem Orient, pp. 176, 177, that the dune sands of the Egyptian coast arise from the disintegration of the calcareous sandstone of the same region. This sandstone, composed in a large proportion of detritus of both land and sea shells mingled with quartz sand, appears to have been consolidated under water during an ancient period of subsidence. A later upheaval brought it to or near the surface, when it was more or less disintegrated by the action of the waves and by meteoric influences--a process still going on--and it is now again subsiding with the coast it rests on. The calcareous sand arising from the comminution of corals forms dunes on some of the West India Islands.--Agassiz, Bulletin of the Museum of Comparative Zoology, vol. i.] These fragments are not constant constituents of dune sand. They are sometimes found at the very summits of the hillocks, as at Overveen; in the King's Dune, near Egmond, they form a coarse, calcareous gravel very largely distributed through the sand, while the interior dunes between Haarlem and Warmond exhibit no trace of them. It is yet undecided whether the presence or absence of these fragments is determined by the period of the formation of the dunes, or whether it depends on a difference in the process by which different dunes have been accumulated. Land shells, such as snails, for example, are found on the surface of the dunes in abundance, and many of the shelly fragments in the interior of the hillocks may be derived from the same source." [Footnote: De Bodem van Nederland, i., p. 323.] Sand concretions form within the dunes and especially in the depressions between them. These are sometimes so extensive and impervious as to retain a sufficient supply of water to feed perennial springs, and to form small permanent ponds, and they are a great impediment to the penetration of roots, and consequently to the growth of trees planted, or germinating from self-sown seeds, upon the dunes. [Footnote: Staring, De Bodem van Nederland, i., p.317. See also Bergsoe, Reventlov's Virksomhed, ii., p. 11. "In the sand-hill ponds mentioned in the text, there is a vigourous growth of bog plants accompanied with the formation of peat, which goes on regularly as long as the dune sand does not drift. But if the surface of the dunes is broken, the sand blows into the ponds, covers the peat, and puts and end to its formation. When, in the course of time, marine currents cut away the coast, the dunes move landwards and fill up the ponds and thus are formed the remarkable strata of fossile peat called Martorv, which appears to be unknown to the geologists of other parts of Europe." -- Forchhammer, in Leonhard und Bronn, 1841, p. 18. Martorv has a specific gravity thrice as great as that of ordinary peat in consequence of the pressure of the sand.--Asbjornsen, Torv og Torvdrift, p.26.] Interior Structure of Dunes. The interior structure of the dunes, the arrangement of their particles, is not, as might be expected, that of an unorganized, confused heap, but they show a strong tendency to stratification. This is a point of much geological interest, because it indicates that sandstone may owe its stratified character to the action of other forces as well as of water. The origin and peculiar character of these layers are due to a variety of causes. For example, a south-west wind and current may deposit upon a dune a stratum of a given color and mineral composition, and this may be succeeded by a north-west wind and current, bringing with them particles of a different hue, constitution, and origin. Again, if we suppose a violent tempest to strew the beach with sand-grains very different in magnitude and specific gravity, and, after the sand is dry, to be succeeded by a gentle breeze, it is evident that only the lighter particles will be taken up and carried to the dunes. If, after some time, the wind freshens, heavier grains will be transported and deposited on the former, and a still stronger succeeding gale will roll up yet larger kernels. Each of these deposits will form a stratum. If we suppose the tempest to be followed, after the sand is dry, not by a gentle breeze, but by a wind powerful enough to lift at the same time particles of very various magnitudes and weights, the heaviest will often lodge on the dune while the lighter will be carried farther. This would produce a stratum of coarse sand, and the same effect might result from the blowing away of light particles out of a mixed layer, while the heavier remained undisturbed. [Footnote: The lower strata must be older than the superficial layers, and the particles which compose them may in time become more disintegrated, and therefore finer than those deposited later and above them. Hull ingeniously suggests that, besides other changes, fine sand intermixed with or deposited above a coarser stratum, as well as the minute particles resulting from the disintegration of the grains of the latter, may be carried by rain in the case of dunes, or by the ordinary action or sea-water in that of sand-banks, down through the interstices in the coarser layer, and thus the relative position of sand and gravel may be changed.--Oorsprong der Hollandsche Duinen, p. 103.] Still another cause of apparent stratification may be found in the occasional interposition of a thin layer of leaves or other vegetable remains between successive deposits, and this I imagine to be more frequent than has been generally supposed. Some geologists have thought that the sand strata of dunes are of annual formation; [Footnote: Schomann, Geologische Wanderungen durch die Preussischen Ost-See Provinzen, 1869, p. 81.] but the autumnal deposit of foliage from neighboring trees and shrubs furnishes a more probable explanation of the division of the sand-heaps into regular layers. A late distinguished American admiral communicated to me an interesting observation made by him at San Francisco, which has an important bearing on the arrangement of the particles of sand in dunes and other irregular accumulations of that substance. In laying out a navy-yard at that port, a large quantity of earthy material was removed from the dunes and other hillocks and carted to a low piece of ground which required filling up. Sand of various characters, fine and coarse gravel, and common earth were dropped promiscuously by the carts as accident or convenience dictated, and of course they were all confusedly intermixed. Some time after, when the new ground was consolidated, various excavations were made in it, and the different materials of which the filling was composed were found to be stratified with considerable regularity, according to their specific gravity. Two explanations of this remarkable fact suggest themselves to me, which, however, do not perhaps exclude others. San Francisco is subject to earthquakes, and though violent or even sensible shocks are not very frequent, it is highly probable that, as is shown to be the case in many other countries, by late seismological observations, there are, in the course of the year, a great number of slight shocks which escape unscientific observation. A frequent repetition of slight tremblings of the earth would, like any other moderate mechanical agitation, probably produce the separation of a miscellaneous mass, like that described, into distinct layers. Again, the Pacific coast, like all others upon an open sea, is exposed to incessant concussion from the shock of the waves, which is repeated many thousand times a day. This concussion is often sensibly felt by the observer, and it seems not in the least improbable that the agitation may have tended to produce a stratified arrangement in the case at San Francisco, as well as in all coast dunes and other accumulations of loose mineral material in similar situations. Kohl observes that the shore on the landward side of the files of dunes often trembles from the shock of the waves on the beach, [Footnote: Inseln und Marschen, etc., ii., p. 34.] and Villeneuve established by careful experiment that at Dunkerque the ground is sensibly agitated by the same cause, in stormy weather, to a distance of more than a mile from the sea. The eddies of strong winds between the hillocks must also occasion disturbances and re-arrangements of the sand layers, and it seems possible that the irregular thickness and the strange contortions of the strata of the sandstone at Petra may be due to some such cause. A curious observation of Professor Forchhammer suggests an explanation of another peculiarity in the structure of the sandstone of Mount Seir. He describes dunes in Jutland, composed of yellow quartzose sand intermixed with black titanian iron. When the wind blows over the surface of the dunes, it furrows the sand with alternate ridges and depressions, ripples, in short, like those of water. The swells, the dividing ridges of the system of sand ripples, are composed of the light grains of quartz, while the heavier iron rolls into the depressions between, and thus the whole surface of the dune appears as if covered with a fine black network. The sea side of dunes, being more exposed to the caprices of the wind, is more irregular in form than the lee or land side, where the arrangement of the particles is affected by fewer disturbing and conflicting influences. Hence, the stratification of the windward slope is somewhat confused, while the sand on the lee side is found to be disposed in more regular beds, inclining landwards, and with the largest particles lowest, where their greater weight would naturally carry them. The lee side of the dunes, being thus formed of sand deposited according to the laws of gravity, is very uniform in its slope, which, according to Forchhammer, varies little from an angle of 30 degrees with the horizon, while the more exposed and irregular weather side lies at an inclination of from 5 degrees to 10 degrees. When, however, the outer tier of dunes is formed so near the waterline as to be exposed to the immediate action of the waves, it is undermined, and the face of the hill is very steep and sometimes nearly perpendicular. Geological Importance of Dunes. These observations, and other facts which a more attentive study on the spot would detect, might furnish the means of determining interesting and important questions concerning geological formations in localities very unlike those where dunes are now thrown up. For example, Studer supposes that the drifting sand-hills of the African desert were originally coast dunes, and that they have been transported to their present position far in the interior, by the rolling and shifting leeward movement to which all dunes not covered with vegetation are subject. The present general drift of the sands of that desert appears to be to the south-west and west, the prevailing winds blowing from the north-east and east; but it has been doubted whether the shoals of the western coast of Northern Africa, and the sands upon that shore, are derived from the bottom of the Atlantic, in the usual manner, or, by an inverse process, from those of the Sahara. The latter, as has been before remarked, is probably the truth, though observations are wanting to decide the question. [Footnote: "The North African desert falls into two divisions: the Sahel, or western, and the Sahar, or eastern. The sands of the Sahar were, at a remote period, drifted to the west. In the Sahel, the prevailing east winds drive the sand-ocean with a progressive westward motion. The eastern half of the desert is swept clean."--Naumann, Geognosie, ii., p. 1173.] There would be nothing violently improbable in the a priori supposition that they may have been in part first thrown up by the Mediterranean on its Libyan coast, and thence blown south and west over the vast space they now cover. But inasmuch as it is now geologically certain that the Sahara is an uplifted bed of an ancient sea, we may suppose that, while submerged, it was, like other sea-bottoms, strewn with sand, and that its present supply of that material was, in great proportion, brought up with it. Laurent observed, some years ago, that marine shells of still extinct species were found in the Sahara, far from the sea, and even at considerable depths below the surface. [Footnote: Memoires sur le Sahara Oriental p. 62] These observations have been confirmed past all question by Desor, Martins, and others, and the facts and the obvious conclusion they suggest are at present not disputed. But whatever has been the source and movement of these sands, they can hardly fail to have left on their route some sandstone monuments to mark their progress, such, for example, as we have seen are formed from the dune sand at the mouth of the Nile; and it is conceivable that the character of the drifting sands themselves, and of the conglomerates and sandstones to whose formation they have contributed, might furnish satisfactory evidence as to their origin, their starting-point, and the course by which they have wandered so far from the sea. [Footnote: Forchhammer, after pointing out the coincidence between the inclined stratification of dunes and the structure of ancient tilted rocks, says: "But I am not able to point out a sandstone formation corresponding to the dunes. Probably most ancient dunes have been destroyed by submersion before the loose sand became cemented to solid stone, but we may suppose that circumstances have existed somewhere which have preserved the characteristics of this formation."--Leonhard und Bronn, 1841, p. 8, 9. Such formations, however, certainly exist. Laurent (Memoire sur le Sahara, etc., p. 12) tells us that in the Algerian desert there are "sandstone formation" not only "corresponding to the dunes," but, actually consolidated within them. "A place called El-Mouia-Tadjer presents a repetition of what we saw at El-Baya; one of the funnels formed in the middle of the dunes contains wells from two metres to two and a half in depth, dug in a sand which pressure, and probably the presence of certain salts, have cemented so as to form true sandstone, soft indeed, but which does not yield except to the pickaxe. These sandstones exhibit an inclination which seems to be the effect of wind; for they conform to the direction of the sands which roll down a scarp occasioned by the primitive obstacle." "At New Quay the dune sands are converted to stone by an oxide of iron held in solution by the water which pervades them. This stone, which is formed, so to speak, under our eye, has been found solid enough to be employed for building."-Esquiros, L'Angleterre, etc., in Revue des Deux Mondes, 1864, pp. 44, 45. The dunes near the mouth of the Nile, the lower sands of which have been cemented together by the infiltration of Nile water, would probably show a similar stratification in the sandstone which now forms their base. Dana describes a laminated rook often formed by the infiltration of water into the sand dunes on the Hawaian islands.--Corals and Coral Islands, 1872, p.155.] If the sand of coast dunes is, as Staring describes it, composed chiefly of well-rounded, quartzose grains, fragments of shells, and other constant ingredients, it would often be recognizable as coast sand, in its agglutinate state of sandstone. The texture of this rock varies from an almost imperceptible fineness of grain to great coarseness, and affords good facilities for microscopic observation of its structure. There are sandstones, such, for example, as are used for grindstones, where the grit, as it is called, is of exceeding sharpness; others where the angles of the grains are so obtuse that they scarcely act at all on hard metals. The former may be composed of grains of rock, disintegrated indeed, and re-cemented together, but not, in the meanwhile, much rolled; the latter, of sands long washed by the sea, and drifted by land-winds. There is, indeed, so much resemblance between the effects of driving winds and of rolling water upon light bodies, that there might be difficulty in distinguishing them; but after all, it is not probable that sandstone, composed of grains thrown up from the salt sea, and long tossed by the winds, would be identical in its structure with that formed from fragments of rock crushed by mechanical force, or disintegrated by heat, and again agglutinated without much exposure to the action of moving water. Dunes of American Coasts. Upon the Atlantic coast of the United States, the prevalence of western or off-shore winds is unfavorable to the formation of dunes, and, though marine currents lodge vast quantities of sand, in the form of banks, on that coast, its shores are proportionally more free from sand-hills than some others of lesser extent. There are, however, very important exceptions. The action of the tide throws much sand upon some points of the New England coast, as well as upon the Beaches of Long Island and other more southern shores, and here dunes resembling those of Europe are formed. There are also extensive ranges of dunes on the Pacific coast of the United States, and at San Francisco they border some of the streets of the city. The dunes of America are far older than her civilization, and the soil they threaten or protect possesses, in general, too little value to justify any great expenditure in measures for arresting their progress or preventing their destruction. Hence, great as is their extent and their geographical importance, they have, at present, no such intimate relations to human life as to render them objects of special interest in the point of view I am taking, and I do not know that the laws of their formation and motion have been made a subject of original investigation by any American observer. Dunes of Western Europe. Upon the western coast of Europe, on the contrary, the ravages occasioned by the movement of sand dunes, and the serious consequences often resulting from the destruction of them, have long engaged the earnest attention of Governments and of scientific men, and for nearly a century persevering and systematic effort has been made to bring them under human control. The subject has been carefully studied in Denmark and the adjacent duchies, in Western Prussia, in the Netherlands, and in France; and the experiments in the way of arresting the drifting of the dunes, and of securing them, and the lands they shelter, from the encroachments of the sea, have resulted in the adoption of a system of coast improvement substantially the same in all these countries. The sands, like the forests, have now their special literature, and the volumes and memoirs, which describe them and the processes employed to subdue them, are full of scientific interest and of practical instruction. Dunes of Gascony. In the small kingdom of Denmark, inclusive of the duchies of Schleswig and Holstein, the dunes cover an area of more than two hundred and sixty square miles. The breadth of the chain is very various, and in some places it consists only of a single row of sand-hills, while in others, it is more than six miles wide. [Footnote: Andersen, Om Klitformationen, pp. 78, 202, 275.] The dunes of the Prussian coast are vaguely estimated to cover from eighty-five to one hundred and ten thousand acres; those of Holland one hundred and forty thousand acres; and those of Gascony more than two hundred thousand acres. I do not find any estimate of their extent in other provinces of France, or in the Baltic provinces of Russia, but it is probable that the entire quantity of dune land upon the Atlantic and Baltic shores of Europe does not fall much short of a million of acres. [Footnote: In an article on the dunes of Europe, in vol. 29 (1864) of Aus der Natur, p. 590, the dunes are estimated to cover, on the islands and coasts of Schleswig Holstein, in North-west Germany, Denmark, Holland, and France, one hundred and eighty-one German, or nearly four thousand English square miles; in Scotland, about ten German, or two hundred and ten English miles; in Ireland, twenty German, or four hundred and twenty English miles; and in England, one hundred and twenty German, or more than twenty-five hundred English miles. Pannewitz (Anleitung zum Anbau der Sandfluchen), as cited by Andresen (Om Klitformationen, p. 45), states that the drifting sands of Europe, including, of course, sand plains as well as dunes, cover an extent of 21,000 square miles. This is, perhaps, an exaggeration, though there is, undoubtedly, much more desert-land of this description on the European continent than has been generally supposed. There is no question that most of this waste is capable of reclamation by simple planting, and no mode of physical improvement is better worth the attention of civilized Governments than this. There are often serious objections to extensive forest planting on soils capable of being otherwise made productive, but they do not apply to sand wastes, which, until covered by woods, are not only a useless incumbrance, but a source of serious danger to all human improvements in the neighborhood of them.] This vast deposit of sea-sand extends along the coasts for a distance of several hundred miles, and from the time of the destruction of the forests which covered it, to the year 1789, the whole line was rolling inwards and burying the soil beneath it, or rendering the fields unproductive by the sand which drifted from it. At the same time, as the sand-hills moved landwards, the ocean was closely following their retreat and swallowing up the ground they had covered, as fast as their movement left it bare. Age, Character, and Permanence of Dunes. The origin of most great lines of dunes goes back past all history. There are on many coasts several distinct ranges of sand-hills which seem to be of very different ages, and to have been formed under different relative conditions of land and water. [Footnote: Krause, speaking of the dunes on the coast of Prussia, says: "Their origin belongs to three different periods, in which important changes in the relative level of sea and land have unquestionably taken place.... Except in the deep depressions between them, the dunes are everywhere sprinkled, to a considerable height, with brown oxydulated iron, which has penetrated into the sand to the depth of from three to eighteen inches, and colored it red. ... Above the iron is a stratum of sand differing in composition from ordinary sea-sand, and on this, growing woods are always found.... The gradually accumulated forest soil occurs in beds of from one to three feet thick, and changes, proceeding upward, from gray sand to black humus." Even on the third or seaward range, the sand grasses appear and thrive luxuriantly, at least on the west coast, though Krause doubts whether the dunes of the east coast were ever thus protected.--Der Dunenbau, pp. 8, 11.] In some cases there has been an upheaval of the coast line since the formation of the oldest hillocks, and these have become inland dunes, while younger rows have been thrown up on the new beach laid bare by elevation of the sea-bed. Our knowledge of the mode of their first accumulation is derived from observation of the action of wind and water in the few instances where, with or without the aid of man, new coast dunes have been accumulated, and of the influence of wind alone in elevating new sand-heaps inland of the coast tier, when the outer rows are destroyed by the sea, as also when the sodded surface of ancient sands has been broken, and the subjacent strata laid open to the air. It is a question of much interest, in what degree the naked condition of most dunes is to be ascribed to the improvidence and indiscretion of man. There are, in Western France, extensive ranges of dunes covered with ancient and dense forests, while the recently formed sand-hills between them and the sea are bare of vegetation, and in some cases are rapidly advancing upon the wooded dunes, which they threaten to bury beneath their drifts. Between the old dunes and the new there is no discoverable difference in material or in structure; but the modern sand-hills are naked and shifting, the ancient, clothed with vegetation and fixed. It has been conjectured that artificial methods of confinement and plantation were employed by the primitive inhabitants of Gaul; and Laval, basing his calculations on the rate of annual movement of the shifting dunes, assigns the fifth century of the Christian era as the period when those processes wore abandoned. [Footnote: Laval, Memoire sur les Dunes de Gascogne, Annales des Ponts et Chaussees, 1847, 2me semestre, p. 231. The same opinion had been expressed by Bremontier, Annales des Ponts et Chaussees, 1833, 1er semestre, p. 185.] There is no historical evidence that the Gauls were acquainted with artificial methods of fixing the sands of the coast, and we have little reason to suppose that they were advanced enough in civilization to be likely to resort to such processes, especially at a period when land could have had but a moderate value. In other countries, dunes have spontaneously clothed themselves with forests, and the rapidity with which their surface is covered by various species of sand-plants, and finally by trees, where man and cattle and burrowing animals are excluded from them, renders it highly probable that they would, as a general rule, protect themselves, if left to the undisturbed action of natural causes. The sand-hills of the Frische Nehrung, on the coast of Prussia, were formerly wooded down to the water's edge, and it was only in the last century that, in consequence of the destruction of their forests, they became moving sands. [Footnote: "In the Middle Ages," says Willibald Alexis, as quoted by Muller, Das Buch der Pflanzenwelt, i., p. 16, "the Nebrung was extending itself further, and the narrow opening near Lochstadt had filled itself up with sand. A great pine forest bound with its roots the dune sand and the heath uninterruptedly from Danzig to Pillau. King Frederick William I. was once in want of money. A certain Herr von Korff promised to procure it for him, without loan or taxes, if he could be allowed to remove something quite useless. He thinned out the forests of Prussia, which then, indeed, possessed little pecuniary value; but he felled the entire woods of the Frische Nebrung, so far as they lay within the Prussian territory. The financial operation was a success. The king had money, but in the material effects which resulted from it, the state received irreparable injury. The sea-winds rush over the bared hills; the Frische Haff is half-choked with sand; the channel between Elbing, the sea, and Konigsberg is endangered, and the fisheries in the Haff injured. The operation of Herr von Korff brought the king 200,000 thalers. The state would now willingly expend millions to restore the forests again."] There is every reason to believe that the dunes of the Netherlands were clothed with trees until after the Roman invasion. The old geographers, in describing these countries, speak of vast forests extending to the very brink of the sea; but drifting coast dunes are first mentioned by the chroniclers of the Middle Ages, and so far as we know they have assumed a destructive character in consequence of the improvidence of man. [Footnote: Staring, Voormaals en Thans, p. 231. Had the dunes of the Netherlandish and French coasts, at the period of the Roman invasion, resembled the moving sand-hills of the present day, it is inconceivable that they could have escaped the notice of so acute a physical geographer as Strabo; and the absolute silence of Caesar, Ptolemy, and the encyclopaedic Pliny, respecting them, would be not less inexplicable.] The history of the dunes of Michigan, so far as I have been able to learn from my own observation, or that of others, is the same. Thirty years ago, when that region was scarcely inhabited, they were generally covered with a thick growth of trees, chiefly pines, and underwood, and there was little appearance of undermining and wash on the lake side, or of shifting of the sands, except where the trees had been cut or turned up by the roots. [Footnote: The sands of Cape Cod were partially, if not completely, covered with vegetation by nature. Dr. Dwight, describing the dunes as they were in 1800, says: "Some of them are covered with beach grass; some fringed with whortleberry bushes; and some tufted with a small and singular growth of oaks. ... The parts of this barrier which are covered with whortleberry bushes and with oaks, have been either not at all or very little blown. The oaks, particularly, appear to be the continuation of the forests originally formed on this spot. ... They wore all the marks of extreme age; were, in some instances, already decayed, and in others decaying; were hoary with moss and were deformed by branches, broken and wasted, not by violence, but by time."--Travels, iii., p. 91] Nature, as she builds up dunes for the protection of the seashore, provides, with similar conservatism, for the preservation of the dunes themselves; so that, without the interference of man, these hillocks would be, not perhaps absolutely perpetual, but very lasting in duration, and very slowly altered in form or position. When once covered with the trees, shrubs, and herbaceous growths adapted to such localities, dunes undergo no apparent change, except the slow occasional undermining of the outer tier, and accidental destruction by the exposure of the interior, from the burrowing of animals, or the upturning of trees with their roots, and all these causes of displacement are very much less destructive when a vegetable covering exists in the immediate neighborhood of the breach. Protection of Dunes. Before the occupation of the coasts by man, dunes, at all points where they have been observed, seem to have been protected in their rear by forests, which served to break the force of the winds in both directions, [Footnote: Bergsoe (Reventlovs Virksomhed, ii., 3) states that the dunes on the west coast of Jutland were stationary before the destruction of the forests to the east of them. The felling of the tall trees removed the resistance to the lower currents of the westerly winds, and the sands have since buried a great extent of fertile soil. See also same work, ii., p. 124.] and to have spontaneously clothed themselves with a dense growth of the various plants, grasses, shrubs, and trees, which nature has assigned to such soils. It is observed in Europe that dunes, though now without the shelter of a forest country behind them, begin to protect themselves as soon as human trespassers are excluded, and grazing animals denied access to them. Herbaceous and arborescent plants spring up almost at once, first in the depressions, and then upon the surface of the sand-hills. Every seed that sprouts, binds together a certain amount of sand by its roots, shades a little ground with its leaves, and furnishes food and shelter for still younger or smaller growths. A succession of a very few favorable seasons suffices to bind the whole surface together with a vegetable network, and the power of resistance possessed by the dunes themselves, and the protection they afford to the fields behind them, are just in proportion to the abundance and density of the plants they support. The growth of the vegetable covering can, of course, be much accelerated by judicious planting and watchful care, and this species of improvement is now carried on upon a vast scale on the sandy coasts of Western Europe, wherever the value of land is considerable and the population dense. Use of Dunes as a Barrier against the Sea. Although the sea throws up large quantities of sand on flat lee-shores, there are many cases where it continually encroaches on those same shores and washes them away. At all points of the shallow North Sea where the agitation of the waves extends to the bottom, banks are forming and rolling eastwards. Hence the sea-sand tends to accumulate upon the coast of Schleswig-Holstein and Jutland, and were there no conflicting influences, the shore would rapidly extend itself westwards. But the same waves which wash the sand to the coast undermine the beach they cover, and still more rapidly degrade the shore at points where it is too high to receive partial protection by the formation of dunes upon it. The earth of the coast is generally composed of particles finer, lighter, and more transportable by water than the sea-sand. While, therefore, the billows raised by a heavy west wind may roll up and deposit along the beach thousands of tons of sand, the same waves may swallow up even a larger quantity of fine shore-earth. This earth, with a portion of the sand, is swept off by northwardly and southwardly currents, and let fall at other points of the coast, or carried off, altogether, out of the reach of causes which might bring it back to its former position. Although, then, the eastern shore of the German Ocean here and there advances into the sea, it in general retreats before it, and but for the protection afforded it by natural arrangements seconded by the art and industry of man, whole provinces would soon be engulfed by the waters. This protection consists in an almost unbroken chain of sand banks and dunes, extending from the northernmost point of Jutland to the Elbe, a distance of not much less than three hundred miles, and from the Elbe again, though with more frequent and wider interruptions, to the Atlantic borders of France and Spain. So long as the dunes are maintained by nature or by human art, they serve, like any other embankment or dike, as a partial or a complete protection against the encroachments of the sea; and on the other hand, when their drifts are not checked by natural processes, or by the industry of man, they become a cause of as certain, if not of as sudden, destruction as the ocean itself whose advance they retard. On the whole, the dunes on the coast of the German Sea, notwithstanding the great quantity of often fertile land they cover, and the evils which result from their movement, are a protective and beneficial agent, and their maintenance is an object of solicitude with the Governments and people of the shores they defend. [Footnote: "We must, therefore, not be surprised to see the people here deal as gingerly with their dunes as if treading among eggs. He who is lucky enough to own a molehill of dune pets it affectionately, and spends his substance in cherishing and fattening it. That fair, fertile, rich province, the peninsula of Eiderstadt in the south of Friesland, has, on the point towards the sea, only a tiny row of dunes, some six miles long or so; but the people talk of their fringe of sand hills, as if it were a border set with pearls. They look upon it as their best defence against Neptune. They have connected it with their system of dikes, and for years have kept sentries posted to protect it against wanton injury."--J. G. Kohl, Die Inseln u. Marschen Schleswig-Holsteins, ii., p. 115.] The eastward progress of the sea on the Danish, Netherlandish, and French coasts depends so much on local geological structure, on the force and direction of tidal and other marine currents, on the volume and rapidity of coast rivers, on the contingencies of the weather and on other varying circumstances, that no general rate can be assigned to it. At Agger, near the western end of the Liimfjord, in Jutland, the coast was washed away, between the years 1815 and 1839, at the rate of more than eighteen feet a year. The advance of the sea appears to have been something less rapid for a century before; but from 1840 to 1857, it gained upon the land no less than thirty feet a year. At other points of the shore of Jutland the loss is smaller, but the sea is encroaching generally upon the whole line of the coast. [Footnote: Andersen, "Om Klitformationen," pp. 68-72.] The Liimfjord. The irruption of the sea into the fresh-water lagoon of Liimfjord in Jutland, in 1825--one of the most remarkable encroachments of the ocean in modern times--is expressly ascribed to "mismanagement of the dunes" on the narrow neck of land which separated the fjord from the North Sea. At earlier periods the sea had swept across the isthmus, and even burst through it, but the channel had been filled up again, sometimes by artificial means, sometimes by the operation of natural causes, and on all these occasions effects were produced very similar to those resulting from the formation of the new channel in 1825, which still remains open. [Footnote: Id., pp. 231, 232. Andresen's work, though printed in 1861, was finished in 1859. Lyell (Antiquity of Man, 1863, p. 14) says: "Even in the course of the present century, the salt-waters have made one eruption into the Baltic by the Liimfjord, although they have been now again excluded."] Within comparatively recent historical ages, the Liimfjord has thus been several times alternately filled with fresh and with salt water, and man has produced, by neglecting the dunes, or at least might have prevented by maintaining them, changes identical with those which are usually ascribed to the action of great geological causes, and sometimes supposed to have required vast periods of time for their accomplishment. "This breach," says Forchhammer, "which converted the Liimfjord into a sound, and the northern part of Jutland into an island, occasioned remarkable changes. The first and most striking phenomenon was the sudden destruction of almost all the fresh-water fish previously inhabiting this lagoon, which was famous for its abundant fisheries. Millions of fresh-water fish were thrown on shore, partly dead and partly dying, and were carted off by the people. A few only survived, and still frequent the shores at the mouth of the brooks. The eel, however, has gradually accommodated itself to the change of circumstances, and is found in all parts of the fjord, while to all other fresh-water fish, the salt-water of the ocean seems to have been fatal. It is more than probable that the sand washed in by the irruption covers, in many places, a layer of dead fish, and has thus prepared the way for a petrified stratum similar to those observed in so many older formations. "As it seems to be a law of nature that animals whose life is suddenly extinguished while yet in full vigor, are the most likely to be preserved by petrification, we find here one of the conditions favorable to the formation of such a petrified stratum. The bottom of the Liimfjord was covered with a vigorous growth of aquatic plants, belonging both to fresh and to salt water, especially Zostera marina. This vegetation totally disappeared after the irruption, and, in some instances, was buried by the sand; and here again we have a familiar phenomenon often observed in ancient strata--the indication of a given formation by a particular vegetable species--and when the strata deposited at the time of the breach shall be accessible by upheaval, the period of eruption will be marked by a stratum of Zostera, and probably by impressions of fresh-water fishes. "It is very remarkable that the Zostera marina, a sea-plant, was destroyed even where no sand was deposited. This was probably in consequence of the sudden change from brackish to salt water ... It is well established that the Liimfjord communicated with the German Ocean at some former period. To that era belong the deep beds of oyster shells and Cardium edule, which are still found at the bottom of the fjord. And now, after an interval of centuries, during which the lagoon contained no salt-water shell fish, it again produces great numbers of Mytilus edulis. Could we obtain a deep section of the bottom, we should find beds of Ostrea edulis and Cardium edule, then a layer of Zostera marina with fresh-water fish, and then a bed of Mytilus edulis. If, in course of time, the new channel should be closed, the brooks would fill the lagoon again with fresh water; fresh-water fish and shell fish would reappear, and thus we should have a repeated alternation of organic inhabitants of the sea and of the waters of the land. "These events have been accompanied with but a comparatively insignificant change of land surface, while the formations in the bed of this inland sea have been totally revolutionized in character." [Footnote: Forchhammer, Geognostiche Studien am Meeres-Ufer, Leonhard und Bronn, Jahrbuch, 1841, pp. 11, 13.] Coasts of Schleswig-Holstein, Holland, and France. On the islands on the coast of Schleswig-Holstein, the advance of the sea has been more unequivocal and more rapid. Near the beginning of the last century, the dunes which had protected the western coast of the island of Sylt began to roll to the east, and the sea followed closely as they retired. In 1757, the church of Rantum, a village upon that island, was obliged to be taken down in consequence of the advance of the sand-hills; in 1791, these hills had passed beyond its site, the waves had swallowed up its foundations, and the sea gained so rapidly, that, fifty years later, the spot where they lay was seven hundred feet from the shore. [Footnote: Andresen, Om Klitformationen, pp. 68, 72.] The most prominent geological landmark on the coast of Holland is the Huis te Britten, Arx Britannica, a fortress built by the Romans, in the time of Caligula, on the main land near the mouth of the Rhine. At the close of the seventeenth century, the sea had advanced sixteen hundred paces beyond it. The older Dutch annalists record, with much parade of numerical accuracy, frequent encroachments of the sea upon many parts of the Netherlandish coast. But though the general fact of an advance of the ocean upon the land is established beyond dispute, the precision of the measurements which have been given is open to question. Staring, however, who thinks the erosion of the coast much exaggerated by popular geographers, admits a loss of more than a million and a half acres, chiefly worthless morass; [Footnote: Voormaals en Thans, pp. 126, 170.] and it is certain that but for the resistance of man, but for his erection of dikes and protection of dunes, there would now be left of Holland little but the name. It is, as has been already seen, still a debated question among geologists whether the coast of Holland now is, and for centuries has been, subsiding. I believe most investigators maintain the affirmative; and if the fact is so, the advance of the sea upon the land is, in part, due to this cause. But the rate of subsidence is at all events very small, and therefore the encroachments of the ocean upon the coast are mainly to be ascribed to the erosion and transportation of the soil by marine waves and currents. The sea is fast advancing at several points of the western coast of France, and unknown causes have given a new impulse to its ravages since the commencement of the present century. Between 1830 and 1842, the Point de Grave, on the north side of the Girondo, retreated one hundred and eighty metres, or fifty feet per year; from the latter year to 1846, the rate was increased to more than three times that quantity, and the loss in those four years was about six hundred feet. All the buildings at the extremity of the peninsula have been taken down and rebuilt farther landwards, and the lighthouse of the Grave now occupies its third position. The sea attacked the base of the peninsula also, and the Point de Grave and the adjacent coasts have been for thirty years the scene of one of the most obstinately contested struggles between man and the ocean recorded in the annals of modern engineering. Movement of Dunes. Besides their importance as a barrier against the inroads of the ocean, dunes are useful by sheltering the cultivated ground behind them from the violence of the sea-wind, from salt spray, and from the drifts of beach sand which would otherwise overwhelm them. But the dunes themselves, unless their surface sands are kept moist, and confined by the growth of plants, or at least by a crust of vegetable earth, are constantly rolling inwards, and thus, while, on one side, they lay bare the traces of ancient human habitations or other evidences of the social life of primitive man, they are, on the other, burying fields, houses, churches, and converting populous districts into barren and deserted wastes. Especially destructive are they when, by any accident, a cavity is opened into them to a considerable depth, thereby giving the wind access to the interior, where the sand is thus first dried, and then scooped out and scattered far over the neighboring soil. The dune is now a magazine of sand, no longer a rampart against it, and mischief from this source seems more difficult to resist than from almost any other drift, because the supply of material at the command of the wind is more abundant and more concentrated than in its original thin and widespread deposits on the beach. The burrowing of conies in the dunes is, in this way, not unfreqnently a cause of their destruction and of great injury to the fields behind them. Drifts, and even inland sand-hills, sometimes result from breaking the surface of more level sand deposits, far within the range of the coast dunes. Thus we learn from Staring, that one of the highest inland dunes in Friesland owes its origin to the opening of the drift sand by the uprooting of a large Oak. [Footnote: De Bodem van Nederland, i. p. 425.] Great as are the ravages produced by the encroachment of the sea upon the western shores of continental Europe, they have been in some degree compensated by spontaneous marine deposits at other points of the coast, and we have seen in a former chapter that the industry of man has reclaimed a large territory from the bosom of the ocean. These latter triumphs are not of recent origin, and the incipient victories which paved the way for them date back perhaps as far as ten centuries. In the meantime, the dunes had been left to the operation of the laws of nature, or rather freed, by human imprudence, from the fetters with which nature had bound them, and it is scarcely three generations since man first attempted to check their destructive movements. As they advanced, he unresistingly yielded and retreated before them, and they have buried under their sandy billows many hundreds of square miles of luxuriant cornfields and vineyards and forests. On the west coast of France a belt of dunes, varying in width from a quarter of a mile to five miles, extends from the Adour to the estuary of the Gironde, and covers an area of nine hundred and seventy square kilometres, or two hundred and forty thousand acres. When not fixed by vegetable growths, these dunes advance eastwards at a mean rate of about one rod, or sixteen and a half feet, a year. Wo do not know historically when they began to drift, but if we suppose their motion to have been always the same as at present, they would have passed over the space between the sea coast and their present eastern border, and covered the large area above mentioned, in fourteen hundred years. We know, from written records, that they have buried extensive fields and forests and thriving villages, and changed the courses of rivers, and that the lighter particles carried from them by the winds, even where not transported in sufficient quantities to form sand-hills, have rendered sterile much land formerly fertile. [Footnote: The movement of the dunes has been hardly less destructive on the north side of the Gironde. See the valuable articles of Elisee Reclus in the Revue des Deux Mondes for December 1862, and several later numbers, entitled "Le Littoral de la France."] They have also injuriously obstructed the natural drainage of the maritime districts by choking up the beds of the streams, and forming lakes and pestilential swamps of no inconsiderable extent. In fact, so completely do they embank the coast, that between the Gironde and the village of Mimizan, a distance of one hundred miles, there are but two outlets for the discharge of all the waters which flow from the land to the sea; and the eastern front of the dunes is bordered by a succession of stagnant pools, some of which are more than six miles in length and breadth. [Footnote: Laval, Memoire sur les Dunes du Golfe de Gascongne, Annales des Ponte et Chaussees, 1847, p. 223. The author adds, as a curious and unexplained fact, that some of these pools, though evidently not original formations but mere accumulations of water dammed up by the dunes, have, along their western shore, near the base of the sand-hills, a depth of more than one hundred and thirty feet, and hence their bottoms are not less than eighty feet below the level of the lowest tides. Their western banks descend steeply, conforming nearly to the slope of the dunes, while on the north-east and south the inclination of their beds is very gradual. The greatest depth of these pools corresponds to that of the sea ten miles from the shore. Is it possible that the weight of the sands has pressed together the soil on which they rest, and thus occasioned a subsidence of the surface extending beyond their base? A more probable explanation of the fact stated in the note is suggested by Elisee Reclus, in an article entitled Le Littoral de la France, in the Revue des Deux Mondes for September 1, 1864, pp. 193, 194. This able writer believes such pools to be the remains of ancient maritime bays, which have been cut off from the ocean by gradually accumulated sand banks raised by the waves and winds to the character of dunes.] A range of dunes extends along the whole western coast of Jutland and Schleswig-Holstein, and the movement of these sand-hills was formerly, and at some points still is, very destructive. The rate of eastward movement of the drifting dunes varies from three to twenty-four feet per annum. If we adopt the mean of thirteen feet and a half for the annual motion, these dunes have traversed the widest part of the belt in about twenty-five hundred years. Historical data are wanting as to the period of the formation of these dunes and of the commencement of their drifting; but there is recorded evidence that they have buried a vast extent of valuable land within three or four centuries, and further proof is found in the fact that the movement of the sands is constantly uncovering ruins of ancient buildings, and other evidences of human occupation, at points far within the present limits of the uninhabitable desert. Andresen estimates the average depth of the sand deposited over this area at thirty feet, which would give a cubic mile and a half for the total quantity. [Footnote: Andresen, On Klitformationen, pp. 56, 79, 82] The drifting of the dunes on the coast of Prussia commenced not much more than a hundred years ago. The Frische Nehrung is separated from the mainland by the Frische Haff, and there is but a narrow strip of arable land along its eastern borders. Hence its rolling sands have covered a comparatively small extent of dry land, but fields and villages have been buried and valuable forests laid waste by them. The loose coast-row has drifted over the inland ranges, which, as was noticed in the description of these dunes on a former page, were protected by a surface of different composition, and the sand has thus been raised to a height which it could not have reached upon level ground. This elevation has enabled it to advance upon and overwhelm woods, which, upon a plain, would have checked its progress, and, in one instance, a forest of many hundred acres of tall pines was destroyed by the drifts between 1804 and 1827. Control of Dunes by Man. There are three principal modes in which the industry of man is brought to bear upon the dunes. First, the creation of them, at points where, from changes in the currents or other causes, new encroachments of the sea are threatened; second, the maintenance and protection of them where they have been naturally formed; and third, the removal of the inner rows where the belt is so broad that no danger is to be apprehended from the loss of them. In describing the natural formation of dunes, it was said that they began with an accumulation of sand around some vegetable or other accidental obstruction to the drifting of the particles. A high, perpendicular cliff, which deadens the wind altogether, prevents all accumulation of sand; but, up to a certain point, the higher and broader the obstruction, the more sand will heap up in front of it, and the more will that which falls behind it be protected from drifting further. This familiar observation has taught the inhabitants of the coast that an artificial wall or dike will, in many situations, give rise to a broad belt of dunes. Thus a sand dike or wall, of three or four miles in length, thrown in 1610 across the Koegras, a tide-washed flat between the Zuiderzee and the North Sea, has occasioned the formation of rows of dunes a mile in breadth, and thus excluded the sea altogether from the Koegras. A similar dike, called the Zijperzeedijk, has produced another scarcely less extensive belt in the course of two centuries. A few years since, the sea was threatening to cut through the island of Ameland, and, by encroachment on the southern side and the blowing off of the sand from a low flat which connected the two higher parts of the island, it had made such progress, that in heavy storms the waves sometimes rolled quite across the isthmus. The construction of a breakwater and a sand dike have already checked the advance of the sea, and a large number of sand-hills has been formed, the rapid growth of which promises complete future security against both wind and wave. Similar effects have been produced by the erection of plank fences, and even of simple screens of wattling and reeds. [Footnote: Staring, De Bodem van Nederland, i., pp. 329-331. Id., Voormaals en Thans, p. 163. Andresen, Om Klitformationen, pp. 280, 295. The creation of new dunes, by the processes mentioned in the text, seems to be much older in Europe than the adoption of measures for securing them by planting. Dr. Dwight mentions a case in Massachusetts, where a beach was restored, and new dunes formed, by planting beach grass. "Within the memory of my informant, the sea broke over the beach which connects Truro with Province Town, and swept the body of it away for some distance. The beach grass was immediately planted on the spot; in consequence of which the beach was again raised to a sufficient height, and in various places into hills."--Travels, iii., p. 93.] The dunes of Holland are sometimes protected from the dashing of the waves by a revetement of stone, or by piles; and the lateral high-water currents, which wash away their base, are occasionally checked by transverse walls running from the foot of the dunes to low-water mark; but the great expense of such constructions has prevented their adoption on a large scale. [Footnote: Staring, i., pp. 310, 332.] The principal means relied on for the protection of the sand-hills are the planting of their surfaces and the exclusion of burrowing and grazing animals. There are grasses, creeping plants, and shrubs of spontaneous growth, which flourish in loose sand, and, if protected, spread over considerable tracts, and finally convert their face into a soil capable of cultivation, or, at least, of producing forest trees. Krause enumerates one hundred and seventy-one plants as native to the coast sands of Prussia, and the observations of Andresen in Jutland carry the number of these vegetables up to two hundred and thirty-four. Some of these plants, especially the Arundo arenaria or arenosa, or Psamma or Psammophila arenaria--Klittetag, or Hjelme in Danish, helm in Dutch, Dunenhalm, Sandschilf, or Hugelrohr in German, gourbet in French, and marram in English--are exclusively confined to sandy soils, and thrive well only in a saline atmosphere. [Footnote: There is some confusion in the popular use of these names, and in the scientific designations of sand-plants, and they are possibly applied to different plants in different places. Some writers style the gourbet Calamagrostis arenaria, and distinguish it from the Danish Klittetag or Hjelme.] The arundo grows to the height of about twenty-four inches, but sends its strong roots with their many rootlets to a distance of forty or fifty feet. It has the peculiar property of flourishing best in the loosest soil, and a sand-shower seems to refresh it as the rain revives the thirsty plants of the common earth. Its roots bind together the dunes, and its leaves protect their surface. When the sand ceases to drift, the arundo dies, its decaying roots fertilizing the sand, and the decomposition of its leaves forming a layer of vegetable earth over it. Then follows a succession of other plants which gradually fit the sand-hills by growth and decay, for forest planting, for pasturage, and sometimes for ordinary agricultural use. But the protection and gradual transformation of the dunes is not the only service rendered by this valuable plant. Its leaves are nutritious food for sheep and cattle, its seeds for poultry; [Footnote: Bread, not indeed very palatable, has been made of the seeds of the arundo, but the quantity which can be gathered is not sufficient to form an important economical resource.--Andresen, Om Klitformationen, p. 160.] cordage and netting twine are manufactured from its fibres, it makes a good material for thatching, and its dried roots furnish excellent fuel. These useful qualities, unfortunately, are too often prejudicial to its growth. The peasants feed it down with their cattle, cut it for rope-making, or dig if up for fuel, and it has been found necessary to resort to severe legislation to prevent them from bringing ruin upon themselves by thus improvidently sacrificing their most effectual safeguard against the drifting of the sands. [Footnote: Bergsoe, Reventlovs Virksomhed, ii., p. 4.] In 1539 a decree of Christian III., king of Denmark, imposed a fine upon persons convicted of destroying certain species of sand-plants upon the west coast of Jutland. This ordinance was renewed and made more comprehensive in 1558, and in 1569 the inhabitants of several districts were required, by royal rescript, to do their best to check the sand-drifts, though the specific measures to be adopted for that purpose are not indicated. Various laws against stripping the dunes of their vegetation were enacted in the following century, but no active measures were taken for the subjugation of the sand-drifts until 1779, when a preliminary system of operation for that purpose was adopted. This consisted in little more than the planting of the Arundo arenaria, and other sand-plants, and the exclusion of animals destructive to those vegetables. [Footnote: Measures were taken for the protection of the dunes of Cape Cod, in Massachusetts, during the colonial period, though I believe they are now substantially abandoned. A hundred years ago, before the valley of the Mississippi, or even the rich plains of Central and Western New York, were opened to the white settler, the value of land was relatively much greater in New England than it is at present, and consequently some rural improvements were then worth making, which would not now yield sufficient returns to tempt the investment of capital. The money and the time required to subdue and render productive twenty acres of sea-sand on Cape Cod, would buy a "section" and rear a family in Illinois. The son of the Pilgrim, therefore, abandons the sea-hills, and seeks a better fortune on the fertile prairies of the West. See Dwight, Travels, i., pp. 92, 93.] Ten years later, plantations of forest trees, which have since proved so valuable a means of fixing the dunes and rendering them productive, were commenced, and have been continued ever since. [Footnote: Andresen, Om Klitformationen, pp. 237, 240.] During this latter period, Bremontier, without any knowledge of what was doing in Denmark, experimented upon the cultivation of forest trees on the dunes of Gascony, and perfected a system, which, with some improvements in matters of detail, is still largely pursued on those shores. The example of Denmark was soon followed in the neighboring kingdom of Prussia, and in the Netherlands; and, as we shall see hereafter, these improvements have been everywhere crowned with most flattering success. Under the administration of Reventlov, a little before the close of the last century, the Danish Government organized a regular system of improvement in the economy of the dunes. They were planted with the arundo and other vegetables of similar habits, protected against trespassers, and at last partly covered with forest trees. By these means much waste soil has been converted into arable ground, a large growth of valuable timber obtained, and the further spread of the drifts, which threatened to lay waste the whole peninsula of Jutland, to a considerable extent arrested. In France, the operations for fixing and reclaiming the dunes--which began under the direction of Bremontier about the same time as in Denmark, and which are, in principle and in many of their details, similar to those employed in the latter kingdom--have been conducted on a far larger scale, and with greater success, than in any other country. This is partly owing to a climate more favorable to the growth of suitable forest trees than that of Northern Europe, and partly to the liberality of the Government, which, having more important landed interests to protect, has put larger means at the disposal of the engineers than Denmark and Prussia have found it convenient to appropriate to that purpose. The area of the dunes already secured from drifting, and planted by the processes invented by Bremontier and perfected by his successors, is about 100,000 acres. [Footnote: "These plantations, perseveringly continued from the time of Bremontier, now cover more than 40,000 hectares, and compose forests which are not only the salvation of the department, but constitute its wealth." --Clave, Etudes Forestieres, p. 254. Other authors have stated the plantations of the French dunes to be much more extensive.] This amount of productive soil, then, has been added to the resources of France, and a still greater quantity of valuable land has been thereby rescued from the otherwise certain destruction with which it was threatened by the advance of the rolling sand-hills. The improvements of the dunes on the coast of West Prussia began in 1795, under Soren Bjorn, a native of Denmark, and, with the exception of the ten years between 1807 and 1817, they have been prosecuted ever since. The methods do not differ essentially from those employed in Denmark and France, though they are modified by local circumstances, and, with respect to the trees selected for planting, by climate. In 1850, between the mouth of the Vistula and Kahlberg, 6,300 acres, including about 1,900 acres planted with pines and birches, had been secured from drifting; between Kahlberg and the eastern boundary of West Prussia, 8,000 acres; and important preliminary operations had been carried on for subduing the dunes on the west coast. [Footnote: Kruse, Dunenbau, pp. 34, 38, 40.] The tree which has been fonnd to thrive best upon the sand-hills of the French coast, and at the same time to confine the sand most firmly and yield the largest pecuniary returns, is the maritime pine, Pinus maritima, a species valuable both for its timber and for its resinous products. It is always grown from seed, and the young shoots require to be protected for several seasons, by the branches of other trees, planted in rows, or spread over the surface and staked down, by the growth of the Arundo arenaria and other small sand-plants, or by wattled hedges. The beach, from which the sand is derived, has been generally planted with the arundo, because the pine does not thrive well so near the sea; but it is thought that a species of tamarisk is likely to succeed in that latitude even better than the arundo. The shade and the protection offered by the branching top of this pine are favorable to the growth of deciduous trees, and, while still young, of shrubs and smaller plants, which contribute more rapidly to the formation of vegetable mould, and thus, when the pine has once taken root, the redemption of the waste is considered as effectually secured. In France, the maritime pine is planted on the sands of the interior as well as on the dunes of the seacoast, and with equal advantage. This tree resembles the pitch pine of the Southern American States in its habits, and is applied to the same uses. The extraction of turpentine from it begins at the age of about twenty years, or when it has attained a diameter of from nine to twelve inches. Incisions are made up and down the trunk, to the depth of about half an inch in the wood, and it is insisted that if not more than two such slits are cut, the tree is not sensibly injured by the process. The growth, indeed, is somewhat checked, but the wood becomes superior to that of trees from which the turpentine is not extracted. Thus treated, the pine continues to flourish to the age of one hundred or one hundred and twenty years, and up to this age the trees on an acre yield annually 300 pounds of essence of turpentine, and 250 pounds of resin, worth together not far from ten dollars. The expense of extraction and distillation is calculated at about four dollars, and a clear profit of more than five dollars per acre is left. [Footnote: These processes are substantially similar to those employed in the pineries of the Carolinas, but they are better systematized and more economically conducted in France. In the latter country, all the products of the pine, even to the cones, find a remunerating market, while, in America, the price of resin is so low, that in the fierce steamboat races on the great rivers, large quantities of it are thrown into the furnaces to increase the intensity of the fires. In a carefully prepared article on the Southern pineries published in an American magazine--I think Harper's--a few years ago, it was stated that the resin from the turpentine distilleries was sometimes allowed to run to waste; and the writer, in one instance, observed a mass, thus rejected as rubbish, which was estimated to amount to two thousand barrels. Olmsted saw, near a distillery which had been in operation but a single year, a pool of resin estimated to contain three thousand barrels, which had been allowed to run off as waste.--A Journey in the seaboard Slave States, 1863, p. 345.] This is exclusive of the value of the timber, when finally cut, which, of course, amounts to a very considerable sum. In Denmark, where the climate is much colder, hardier conifers, as well as the birch and other northern trees, are found to answer a better purpose than the maritime pine, and it is doubtful whether this tree would be able to resist the winter on the dunes of Massachusetts. Probably the pitch-pine of the Northern States, in conjunction with some of the American oaks, birches, and poplars, and especially the robinia or locust, would prove very suitable to be employed on the sand-hills of Cape Cod and Long Island. The ailanthus, now coming into notice as a sand-loving tree, some species of tamarisk, and perhaps the Aspressus macrocarpa, already found useful on the dunes in California, may prove valuable auxiliaries in resisting the encroachment of drifting sands, whether in America or in Europe, and the intermixing of different species would doubtless be attended with as valuable results in this as in other branches of forest economy. It cannot, indeed, be affirmed that human power is able to arrest altogether the incursions of the waves on sandy coasts, by planting the beach, and clothing the dunes with wood. On the contrary, both in Holland and on the French coast, it has been found necessary to protect the dunes themselves by piling and by piers and sea-walls of heavy masonry. But experience has amply shown that the processes referred to are entirely successful in preventing the movement of the dunes, and the drifting of their sands over cultivated lands behind them; and that, at the same time, the plantations very much retard the landward progress of the waters. [Footnote: See a very interesting article entitled "Le Littoral de la France," by Elisee Reclus, in the Revue des Deux Mondes for December, 1862, pp. 901, 936.] Besides the special office of dune plantations already noticed, these forests have the same general uses as other woods, and they have sometimes formed by their droppings so thick a layer of vegetable mould that the sand beneath has become sufficiently secured to allow the wood to be felled, and the surface to be ploughed and cultivated with ordinary field crops. In some cases it has been found possible to confine and cultivate coast sand-hills, even without preliminary forestal plantation. Thus, in the vicinity of Cap Breton in France, a peculiar process is successfully employed, both for preventing the drifting of dunes, and for rendering the sands themselves immediately productive; but this method is applicable only in exceptional cases of favorable climate and exposure. It consists in planting vineyards upon the dunes, and protecting them by hedges of broom, Erica scoparia, so disposed as to form rectangles about thirty feet by forty. The vines planted in these enclosures thrive admirably, and the grapes produced by them are among the best grown in France. The dunes are so far from being an unfavorable soil for the vine, that fresh sea-sand is regularly employed as a fertilizer for it, alternating every other season with ordinary manure. The quantity of sand thus applied every second year, raises the surface of the vineyard about four or five inches. The vines are cut down every year to three or four shoots, and the raising of the soil rapidly covers the old stocks. As fast as buried, they send out new roots near the surface, and thus the vineyard is constantly renewed, and has always a youthful appearance, though it may have been already planted a couple of generations. This practice is ascertained to have been followed for two centuries, and is among the oldest well-authenticated attempts of man to resist and vanquish the dunes. [Footnote: Boitel, Mise en valeur des Terres pauvres, pp. 212, 218.] The artificial removal of dunes, no longer necessary as a protection, does not appear to have been practiced upon a large scale except in the Netherlands, where the numerous canals furnish an easy and economical means of transporting the sand, and where the construction and maintenance of sea and river dikes, and of causeways and other embankments and fillings, create a great demand for that material. Sand is also employed in Holland, in large quantities, for improving the consistence of the tough clay bordering upon or underlying diluvial deposits, and for forming an artificial soil for the growth of certain garden and ornamental vegetables. When the dunes are removed, the ground they covered is restored to the domain of industry; and the quantity of land recovered in the Netherlands by the removal of the barren sands which encumbered it, amounts to hundreds and perhaps thousands of acres. Inland Dunes. Vast deposits of sand, both in the form of dunes and of plains, are found far in the interior of continents, in the Old World and in the New. The deserts of Gobi, of Arabia, and of Africa have been rendered familiar by the narratives of travellers, but the sandy wilderness of America, and even of Europe, have not yet been generally recognized as important elements in the geography of the regions where they occur. There are immense wastes of drifting sands in Poland and other interior parts of Europe, in Peru, and in the less known regions of our own Western territory, where their extent is greater than that of all the coast dunes together which have hitherto been described by European and American geographers. [Footnote: On the Niobrara river alone, the dunes cover a surface of twenty thousand square miles.--Hayden, Report on Geological Survey of Wyoming, 1870, p. 108.] The inland sand-hills of both hemispheres are composed of substantially the same material and aggregated by the action of the same natural forces as the dunes of the coast. There is, therefore, a general resemblance between them, but they appear, nevertheless, to be distinguished by certain differences which a more attentive study may perhaps enable geologists to recognize in the sandstone formed by them. The sand of which they are composed comes in both principally from the bed of the sea being brought to the surface in one case by the action of the wind and the waves, in the other by geological upheaval. [Footnote: American observers do not agree in their descriptions of the form and character of the sand-grains which compose the interior dunes of the North American desert. C. C. Parry, geologist to the Mexican Boundary Commission, in describing the dunes near the station at a spring thirty-two miles west from the Rio Grande at El Paso, says: "The separate grains of the sand composing the sand-hills are seen under a lens to be angular, and not rounded, as would be the case in regular beach deposits."--U. S. Mexican Boundary Survey, Report of, vol i., Geological Report of C. C. Parry, p. 10. In the general description of the country traversed, same volume, p. 47, Colonel Emory says that on an "examination of the sand with a microscope of sufficient power," the grains are seen to be angular, not rounded by rolling in water. On the other hand, Blake, in Geological Report, Pacific Railroad Rep., vol. v., p. 119, observes that the grains of the dune sand, consisting of quartz, chalcedony, carnelian, agate, rose quartz, and probably chrysolite, were much rounded; and on page 241, he says that many of the sand grains of the Colorado desert are perfect spheres. On page 20 of a report in vol. ii. of the Pacific Railroad Report, by the same observer, it is said that an examination of dunes brought from the Llano Estacado by Captain Pope, showed the grains to be "much rounded by attrition." The sands described by Mr. Parry and Colonel Emory are not from the same localities as those examined by Mr. Blake, and the difference in their character may be due to a difference of origin or of age. In New Mexico, sixty miles south of Fort Stanton, there are island dunes composed of finely granulated gypsum.--American Naturalist, Jan. 1871, p. 695.] The sand of the coast dunes is rendered, to a certain extent, cohesive by moisture and by the saline and other binding ingredients of sea-water, while long exposure to meteoric influences has in a great measure deprived the inland sands of these constituents, though there are not wanting examples of large accumulations of sand far from the sea, and yet agglutinated by saline material. Hence, as might be expected, inland dunes, when not confined by a fixed nucleus, are generally more movable than those of the coast, and the form of such dunes is more or less modified by their want of consistence. Thus, the crescent or falciform shape is described by all observers as more constant and conspicuous in these sandhills than in those of littoral origin; they tend less to unite in continuous ridges, and they rarely attain the height or other dimensions of the dunes of the seashore. Meyer describes the sand-hills of the Peruvian desert as perfectly falciform in shape and from seven to fifteen feet high, the chord of their arc measuring from twenty to seventy paces. The slope of the convex face is described as very small, that of the concave as high as 70 degrees or 80 degrees, and their surfaces were rippled. No smaller dunes were observed, nor any in the process of formation. The concave side uniformly faced the north-west, except towards the centre of the desert, where, for a distance of one or two hundred paces, they gradually opened to the west, and then again gradually resumed the former position. Tschudi observed, in the same desert, two species of dunes, fixed and movable, and he ascribes a falciform shape to the movable, a conical to the fixed dunes, or medanos. "The medanos," he observes, "are hillock-like elevations of sand, some having a firm, others a loose base. The former [latter], which are always crescent-shaped, are from ten to twenty feet high, and have an acute crest. The inner side is perpendicular, and the outer or bow side forms an angle with a steep inclination downwards. [Footnote: The dunes of the plains between Bokhara and the Oxus are all horse-shoe shaped, convex towards the north, from which the prevailing wind blows. On this side they are sloping, inside precipitous, and from fifteen to twenty feet high.--Burnes, Journal in Bokhara, ii., pp. 1, 2.] When driven by violent winds, the medanos pass rapidly over the plains. The smaller and lighter ones move quickly forward, before the larger; but the latter soon overtake and crush them, whilst they are themselves shivered by the collision. These medanos assume all sorts of extraordinary figures, and sometimes move along the plain in rows forming most intricate labyrinths.... A plain often appears to be covered with a row of medanos, and some days afterwards it is again restored to its level and uniform aspect.... "The medanos with immovable bases are formed on the blocks of rocks which are scattered about the plain. The sand is driven against them by the wind, and as soon as it reaches the top point, it descends on the other side until that is likewise covered; thus gradually arises a conical-formed hill. [Footnote: The sand-hills observed by Desor in the Algerian desert were fixed, changing their form only on the surface as sand was blown to and from them.--Sahara und Atlas, 1865, p. 21.] Entire hillock chains with acute crests are formed in a similar manner.... On their southern declivities are found vast masses of sand, drifted thither by the mid-day gales. The northern declivity, though not steeper than the southern, is only sparingly covered with sand. If a hillock chain somewhat distant from the sea extends in a line parallel with the Andes, namely, from S. S. E. to N. N. W., the western declivity is almost entirely free of sand, as it is driven to the plain below by the south-east wind, which constantly alternates with the wind from the south." [Footnote: Travels in Peru, New York, 1848, chap. ix.] It is difficult to reconcile this description with that of Meyen, but if confidence is to be reposed in the accuracy of either observer, the formation of the sand-hills in question must be governed by very different laws from those which determine the structure of coast dunes. Captain Gilliss, of the American navy, found the sand-hills of the Peruvian desert to be in general crescent-shaped, as described by Meyen, and a similar structure is said to characterize the inland dunes of the Llano Estacado and other plateaus of the North American desert, though those latter are of greater height and other dimensions than those described by Meyen. There is no very obvious explanation of this difference in form between maritime and inland sand-hills, and the subject merits investigation. It is, however, probable that the great mobility of the flying dunes of the Peruvian desert is an effect of their dryness, no rain falling in that desert, and of the want of salt or other binding material to hold their particles together. Inland Sand Plains. The inland sand plains of Europe are either derived from the drifting of dunes or other beach sands, or consist of diluvial deposits, or are ancient sea-beds uplifted by geological upheaval. As we have seen, when once the interior of a dune is laid open to the wind, its contents ars soon scattered far and wide over the adjacent country, and the beach sands, no longer checked by the rampart which nature had constrained them to build against their own encroachments, are also carried to considerable distances from the coast. Few regions have suffered so much from this cause, in proportion to their extent, as the peninsula of Jutland. So long as the woods, with which nature had planted the Danish dunes, were spared, they seem to have been stationary, and we have no historical evidence, of an earlier date than the sixteenth century, that they had become in any way injurious. From that period there are frequent notices of the invasions of cultivated grounds by the sands; and excavations are constantly bringing to light proof of human habitation and of agricultural industry, in former ages, on soils now buried beneath deep drifts from the dunes and beaches of the seacoast. [Footnote: For details, consult Andresen, Om Klitformationen, pp. 223, 236.] Extensive tracts of valuable plain land in the Netherlands and in France have been covered in the same way with a layer of sand deep enough to render them infertile, and they can be restored to cultivation only by processes analogous to those employed for fixing and improving the dunes. [Footnote: When the deposit is not very deep, and the adjacent land lying to the leeward of the prevailing winds is covered with water, or otherwise worthless, the surface is sometimes freed from the drifts by repeated harrowings, which loosen the sand, so that the wind takes it up and transports it to grounds where accumulations of it are less injurious.] Diluvial sand plains, also, have been reclaimed by these methods in the Duchy of Austria, between Vienna and the Semmering ridge, in Jutland, and in the great champaign country of Northern Germany, especially the Mark Brandenburg, where artificial forests can be propagated with great ease, and where, consequently, this branch of industry has been pursued on a great scale, and with highly beneficial results, both as respects the supply of forest products and the preparation of the soil for agricultural use. As has been already observed, inland sands are generally looser, dryer, and more inclined to drift, than those of the seacoast, where the moist and saline atmosphere of the ocean keeps them always more or less humid and cohesive. The sands of the valley of the Lower Euphrates--themselves probably of submarine origin, and not derived from dunes are advancing to the north-west with a rapidity which seems fabulous when compared with the slow movement of the sand-hills of Gascony and the Low German coasts. Loftus, speaking of Niliyya, an old Arab town a few miles east of the ruins of Babylon, says that, "in 1848, the sand began to accumulate around it, and in six years, the desert, within a radius of six miles, was covered with little, undulating domes, while the ruins of the city were so buried that it is now impossible to trace their original form or extent." [Footnote: Travels and Researchs in Chaldaea, chap. ix. Dwight mentions (Travels, vol. iii, p. 101) an instance of great mischief from the depasturing of the beach grass which had been planted on a sand plain in Cape Cod: "Here, about one thousand acres were entirely blown away to the depth, in many places, of ten feet.... Not a green thing was visible except the whortleberries, which tufted a few lonely hillocks rising to the height of the original surface and prevented by this defence from being blown away also. These, although they varied the prospect, added to the gloom by their strongly picturesque appearance, by marking exactly the original level of the plain, and by showing us in this manner the immensity of the mass which had been thus carried away by the wind. The beach grass had been planted here, and the ground had been formerly enclosed; but the gates had been left open, and the cattle had destroyed this invaluable plant."] Loftus considers this sand-flood as the "vanguard of those vast drifts which advancing from the south-east, threaten eventually to overwhelm Babylon and Baghdad." An observation of Layard, cited by Loftus, appears to me to furnish a possible explanation of this irruption. He "passed two or three places where the sand, issuing from the earth like water, is called 'Aioun-er-rummal,' sand springs." These "springs" are very probably merely the drifting of sand from the ancient subsoil, where the protecting crust of aquatic deposit and vegetable earth has been broken through, as in the case of the drift which arose from the upturning of an oak mentioned on a former page. When the valley of the Euphrates was regularly irrigated and cultivated, the underlying sands were bound by moisture, alluvial slime, and vegetation; but now, that all improvement is neglected, and the surface, no longer watered, has become parched, powdery, and naked, a mere accidental fissure in the superficial stratum may soon be enlarged to a wide opening, that will let loose sand enongh to overwhelm a province. The Landes of Gascony. The most remarkable sand plain of France lies at the south-western extremity of the empire, and is generally known as the Landes, or heaths, of Gascony. Clave thus describes it: "Composed of pure sand, resting on an impermeable stratum called alios, the soil of the Landes was, for centuries, considered incapable of cultivation. [Footnote: The alios, which from its color and consistence was supposed to be a ferruginous formation, appears from recent observations to contain little iron and to owe most of its peculiar properties to vegetable elements carried down into the soil by the percolation of rain-water. See Revue des Eaux et Forets for 1870, p. 801.] Parched in summer, drowned in winter, it produced only ferns, rushes, and heath, and scarcely furnished pasturage for a few half-starved flocks. To crown its miseries, this plain was continually threatened by the encroachments of the dunes. Vast ridges of sand, thrown up by the waves, for a distance of more than fifty leagues along the coast, and continually renewed, were driven inland by the west wind, and, as they rolled over the plain, they buried the soil and the hamlets, overcame all resistance, and advanced with fearful regularity. The whole province seemed devoted to certain destruction, when Bremontier invented his method of fixing the dunes by plantations of the maritime pine." [Footnote: Etudes Forestieres, p. 250. See, also, Reclus, La Terre, i., 105, 106.] Although the Landes had been almost abandoned for ages, they show numerous traces of ancient cultivation and prosperity, and it is principally by means of the encroachments of the sands that they have become reduced to their present desolate condition. The destruction of the coast towns and harbors, which furnished markets for the products of the plains, the damming up of the rivers, and the obstruction of the smaller channels of natural drainage by the advance of the dunes, were no doubt very influential causes; and if we add the drifting of the sea-sand over the soil, we have at least a partial explanation of the decayed agriculture and diminished population of this great waste. When the dunes were once arrested, and the soil to the east of them was felt to be secure against invasion by them, experiments, in the way of agricultural improvement, by drainage and plantation, were commenced, and they have been attended with such signal success, that the complete recovery of one of the dreariest and most extensive wastes in Europe may be considered as both a probable and a near event. [Footnote: Lavergne, Economie Rurale de la France, p. 300, estimates the area of the Landes of Gascony at 700,000 hectares, or about 1,700,000 acres. The same author states (p. 301), that when the Moors were driven from Spain by the blind cupidity and brutal intolerance of the age, they demanded permission to establish themselves in this desert; but political and religious prejudices prevented the granting of this liberty. At this period the Moors were a far more cultivated people than their Christian persecutors, and they had carried many arts, that of agriculttire especially, to a higher pitch than any other European nation. But France was not wise enough to accept what Spain had cast out, and the Landes remained a waste for three centuries longer. For a brilliant account of the improvement of the Landes, see Edmond About, Le Progres, chap. vii. The forest of Fontainebleau, which contains above 40,000 acres, is not a plain, but its soil is composed almost wholly of sand, interspersed with ledges of rock. The sand forms not less than ninety-eight per cent of the earth, and, as it is almost without water, it would be a drifting desert but for the artificial propagation of forest trees upon it. The Landes of Sologne and of Brenne are less known than those of Gascony, because they are not upon the old great lines of communication. They once compoaed a forest of 1,200,000 acres, but by clearing the woods have relapsed into their primitive condition of a barren sand waste. Active efforts are now in progress to reclaim them.] In the northern part of Belgium, and extending across the confines of Holland, is another very similar heath plain, called the Campine. This is a vast sand flat, interspersed with marshes and inland dunes, and, until recently, considered almost wholly incapable of cultivation. Enormous sums had been expended in reclaiming it by draining and other familiar agricultural processes, but without results at all proportional to the capital invested. In 1849, the unimproved portion of the Campine was estimated at little less than three hundred and fifty thousand acres. The example of France prompted experiments in the planting of trees, especially the maritime pine, upon this barren waste, and the results have now been such as to show that its sands may both be fixed and made productive, not only without loss, but with positive pecuniary advantage. [Footnote: Economie Rurale de la Belgique, par Emile De Laveleye, Revue des Deux Mondes, Juin, 1861, pp. 6l7-644. The quantity of land annually reclaimed on the Campine is stated at about 4,000 acres. Canals for navigation and irrigation have been constructed through the Campine, and it is said that its barren sands, improved at an expense of one hundred dollars per acre, yield, from the second year, a return of twenty-five dollars to the acre.] There are still unsubdued sand wastes in many parts of interior Europe not familiarly known to tourists or even geographers. "Olkuez and Schiewier in Poland," says Naumann, "lie in true sand deserts, and a boundless plain of sand stretches around Ozenstockau, on which there grows neither tree nor shrub. In heavy winds, this plain resembles a rolling sea, and the sand-hills rise and disappear like the waves of the ocean. The heaps of waste from the Olkuez mines are covered with sand to the depth of four fathoms." [Footnote: Geognosie, ii., p. 1173.] No attempts have yet been made to subdue the sands of Poland, but when peace and prosperity shall be restored to that unhappy country, there is no reasonable doubt that the measures, which have proved so successful on similar formations in Germany and near Odessa, may be employed with advantage in the Polish deserts. [Footnote: "Sixteen years ago," says an Odessa landholder, "I attempted to fix the sand of the steppes, which covers the rocky ground to the depth of a foot, and forms moving hillocks with every change of wind. I tried acacias and pines in vain; nothing would grow in such a soil. At length I planted the varnish tree, or ailanthus, which succeeded completely in binding the sand." This result encouraged the proprietor to extend his plantations over both dunes and sand steppes, and in the course ot sixteen years this rapidly growing tree had formed real forests. Other landholders have imitated his example with great advantage.--Rentsch, Der Wald, pp. 44, 45.] CHAPTER VI. GREAT PROJECTS OF PHYSICAL CHANGE ACCOMPLISHED OR PROPOSED BY MAN. Cutting of Isthmuses--Canal of Suez--Maritime Canals in Greece--Canals to Dead Sea--Canals to Libyan Desert--Maritime Canals in Europe--Cape Cod Canal--Changes in Caspian--Diversion of the Nile--Diversion of the Rhine--Improvements in North American Hydrography--Soil below Rock--Covering Rock with Earth--Desert Valleys--Effects of Mining--Duponchel's Plans of Improvement--Action of Man on the Weather--Resistance to Great Natural Forces--Incidental Effects of Human Action--Nothing small in Nature. In a former chapter I spoke of the influence of human action on the surface of the globe as immensely superior in degree to that exerted by brute animals, if not essentially different from it in kind. The eminent Italian geologist, Stoppani, goes further than I had ventured to do, and treats the action of man as a new physical clement altogether sui generis. According to him, the existence of man constitutes a geological period which he designates as the ANTHROPOZOIC ERA. "The creation of man," says he, "was the introduction of a new element into nature, of a force wholly unknown to earlier periods." "It is a new telluric force which in power and universality may be compared to the greater forces of the earth." [Foonote: Corso Di Geologia, Milano, 1873, vol ii., cap. xxxi., section 1327.] It has already been abundantly shown that, though the undesigned and unforeseen results of man's action on the geographical conditions of the earth have perhaps been hitherto greater and more revolutionary than the effects specially aimed at by him, yet there is scarcely any assignable limit to his present and prospective voluntary controlling power over terrestrial nature. Cutting of Marine Isthmuses. Besides the great enterprises of physical transformation of which I have already spoken, other works of internal improvement or change have been projected in ancient and modern times, the execution of which would produce considerable, and, in some cases, extremely important, revolutions in the face of the earth. Some of the schemes to which I refer are evidently chimerical; others are difficult, indeed, but cannot be said to be impracticable, though discouraged by the apprehension of disastrous consequences from the disturbance of existing natural or artificial arrangements; and there are still others, the accomplishment of which is ultimately certain, though for the present forbidden by economical considerations. Nature sometimes mocks the cunning and the power of man by spontaneously performing, for his benefit, works which he shrinks from undertaking, and the execution of which by him she would resist with unconquerable obstinacy. A dangerous sand bank, that all the enginery of the world could not dredge out in a generation, may be carried off in a night by a strong river-flood, or by a current impelled by a violent wind from an unusual quarter, and a passage scarcely navigable by fishing-boats may be thus converted into a commodious channel for the largest ship that floats upon the ocean. In the remarkable gulf of Liimfjord in Jutland, referred to in the preceding chapter, nature has given a singular example of a canal which she alternately opens as a marine strait, and, by abutting again, converts into a fresh-water lagoon. The Liimfjord was doubtless originally an open channel from the Atlantic to the Baltic between two islands, but the sand washed up by the sea blocked up the western entrance, and built a wall of dunes to close it more firmly. This natural dike, as we have seen, has been more than once broken through, and it is perhaps in the power of man, either permanently to maintain the barrier, or to remove it and keep a navigable channel constantly open. If the Liimfjord becomes an open strait, the washing of sea-sand through it would perhaps block some of the belts and small channels now important for the navigation of the Baltic, and the direct introduction of a tidal current might produce very perceptible effects on the hydrography of the Cattegat. When we consider the number of narrow necks or isthmuses which separate gulfs and bays of the sea from each other, or from the main ocean, and take into account the time and cost, and risks of navigation which would be saved by executing channels to connect such waters, and thus avoiding the necessity of doubling long capes and promontories, or even continents, it seems strange that more of the enterprise and money which have been so lavishly expended in forming artificial rivers for internal navigation should not have been bestowed upon the construction of maritime canals. Many such have been projected in early and in recent ages, and some trifling cuts between marine waters had been actually made; but before the construction of the Suez Canal, no work of this sort, possessing real geographical or even commercial importance, had been effected. These enterprises are attended with difficulties and open to objections which are not, at first sight, obvious. Nature guards well the chains by which she connects promontories with mainlands, and binds continents together. Isthmuses are usually composed of adamantine rock or of shifting sands--the latter being much the more refractory material to deal with. In all such works there is a necessity for deep excavation below low-water mark--always a matter of great difficulty; the dimensions of channels for sea-going ships must be much greater than those of canals of inland navigation; the height of the masts or smokepipes of that class of vessels would often render bridging impossible, and thus a ship-canal might obstruct a communication more important than that which it was intended to promote; the securing of the entrances of marine canals and the construction of ports at their termini would in general be difficult and expensive, and the harbors and the channel which connected them would be extremely liable to fill up by deposits washed in from sea and shore. Besides all this there is, in many cases, an alarming uncertainty as to the effects of joining together waters which nature has put asunder. A new channel may deflect strong currents from safe courses, and thus occasion destructive erosion of shores otherwise secure, or promote the transportation of sand or slime to block up important harbors, or it may furnish a powerful enemy with dangerous facilities for hostile operations along the coast. The most colossal project of canalization ever suggested, whether we consider the physical difficulties of its execution, the magnitude and importance of the waters proposed to be united, or the distance which would be saved in navigation, is that of a channel between the Gulf of Mexico and the Pacific, across the Isthmus of Darien. I do not now speak of a lock-canal, by way of the Lake of Nicaragua or any other route--for such a work would not differ essentially from other canals, and would scarcely possess a geographical character--but of an open cut between the two seas. The late survey by Captain Selfridge, showing that the lowest point on the dividing ridge is 763 feet above the sea-level, must be considered as determining in the negative the question of the possibility of such a cut, by any means now at the control of man; and both the sanguine expectations of benefits, and the dreary suggestions of danger, from the realization of this great dream, may now be dismissed as equally chimerical. Suez Canal. The cutting of the Isthmus of Suez--the grandest and most truly cosmopolite physical improvement ever undertaken by man--threatens none of these dangers, and its only immediate geographical effect will probably be that interchange between the aquatic animal and vegetable life of two seas and two zones to which I alluded in a former chapter. [Footnote: According to an article by Ascherson, in Petermann's Mitthielungen, vol. xvii., p. 247, the sea-grass floras of the opposite sides of the Isthmus of Suez are as different as possible. It does not appear whether they have yet intermixed.] A collateral feature of this great enterprise deserves notice as possessing no inconsiderable geographical importance. I refer to the conduit or conduits constructed from the Nile to the isthmus, primarily to supply fresh water to the laborers on the great canal, and ultimately to serve as aqueducts for the city of Suez and other towns on the line of the canal, and for the irrigation and reclamation of a large extent of desert soil. In the flourishing days of the Egyptian empire, the waters of the Nile were carried over important districts cast of the river. In later ages, most of this territory relapsed into a desert, from the decay of the canals which once fertilized it. There is no difficulty in restoring the ancient channels, or in constructing new, and thus watering not only all the soil that the wisdom of the Pharaohs had improved, but much additional land. Hundreds of square miles of arid sand waste would thus be converted into fields of perennial verdure, and the geography of Lower Egypt would be thereby sensibly changed. Considerable towns are growing up at both ends of the channel, and at intermediate points, all depending on the maintenance of aqueducts from the Nile, both for water and for the irrigation of the neighboring fields which are to supply them with bread. Important interests will thus be created, which will secure the permanence of the hydraulic works and of the geographical changes produced by them, and Suez, or Port Said, or Ismailieh, may become the capital of the government which has been so long established at Cairo. Maritime Canals in Greece. A maritime canal executed and another projected in ancient times, the latter of which is again beginning to excite attention, deserve some notice, though their importance is of a commercial rather than a geographical character. The first of those is the cut made by Xerxes through the rock which connects the promontory of Mount Athos with the mainland; the other, a navigable canal through the Isthmus of Corinth. In spite of the testimony of Herodotus and Thucydides, the Romans classed the canal of Xerxes among the fables of "mendacious Greece," and yet traces of it are perfectly distinct at the present day through its whole extent, except at a single point where, after it had become so choked as to be no longer navigable, it was probably filled up to facilitate communication by land between the promontory and the country in the rear of it. The emperor Nero commenced the construction of a canal across the Isthmus of Corinth, solely to facilitate the importation of grain from the East for distribution among the citizens of Rome--for the encouragement of general commerce was no part of the policy either of the republic or the empire, and though the avidity of traders, chiefly foreigners, secured to the luxury of the imperial city an abundant supply of far-fetched wares, yet Rome had nothing to export in return. The line of Nero's excavations is still traceable for three-quarters of a mile, or more than a fifth of the total distance between gulf and gulf. If the fancy kingdom of Greece shall ever become a sober reality, escape from its tutelage and acquire such a moral as well as political status that its own capitalists--who now prefer to establish themselves and employ their funds anywhere else rather than in their native land--have any confidence in the permanency of its institutions, a navigable channel may be opened between the gulfs of Lepanto and AEgina. The annexation of the Ionian Islands to Greece will make such a work almost a political necessity, and it would not only furnish valuable facilities for domestic intercourse, but become an important channel of communication between the Levant and the countries bordering on the Adriatic, or conducting their trade through that sea. SHort as is the distance, the work would be a somewhat formidable undertaking, for the lowest point of the summit ridge of the isthmus is stated to be 246 feet above the water, and consequently the depth of excavation must be not less than 275 feet. As I have said, the importance of this latter canal and of a navigable channel between Mount Athos and the continent would be chiefly commercial, but both of them would be conspicuous instances of the control of man over nature in a field where he has thus far done little to interfere with her spontaneous arrangements. If they were constructed upon such a scale as to admit of the free passage of the water through them, in either direction, as the prevailing winds should impel it, they would exercise a certain influence on the coast currents, which are important as hydrographical elements, and also as producing abrasion of the coast and a drift at the bottom of seas, and hence they would be entitled to rank higher than simply as artificial means of transit. It has been thought practicable to cut a canal across the peninsula of Gallipoli from the outlet of the Sea of Marmora into the Gulf of Saros. It may be doubted whether the mechanical difficulties of such a work would not be found insuperable; but when Constantinople shall recover the important political and commercial rank which naturally belongs to her, the execution of such a canal will be recommended by strong reasons of military expediency, as well as by the interests of trade. An open channel across the peninsula would divert a portion of the water which now flows through the Dardanelles, diminishing the rapidity of that powerful current, and thus in part remove the difficulties which obstruct the navigation of the strait. It would considerably abridge the distance by water between Constantinople and the northern coast of the AEgean, and it would have the important advantage of obliging an enemy to maintain two blockading fleets instead of one. Canals Communicating with Dead Sea. The project of Captain Allen for opening a new route to India by cuts between the Mediterranean and the Dead Sea, and between the Dead Sea and the Red Sea, presents many interesting considerations. [Footnote: The Dead Sea a new Route to India. 2 vols. 12mo, London, 1855.] The hypsometrical observations of Bertou, Roth, and others, render it highly probable, if not certain, that the watershed in the Wadi-el-Araba between the Dead Sea and the Red Sea is not less than three hundred feet above the main level of the latter, and if this is so, the execution of a canal from the one sea to the other is quite out of the question. But the summit level between the Mediterranean and the Jordan, near Jezreel, is believed to be little, if at all, more than one hundred feet above the sea, and the distance is so short that the cutting of a channel through the dividing ridge would probably be found by no means an impracticable undertaking. Although, therefore, we have no reason to believe it possible to open a navigable channel to India by way of the Dead Sea, there is not much doubt that the basin of the latter might be made accessible from the Mediterranean. The level of the Dead Sea lies 1,316.7 feet below that of the ocean. It is bounded east and west by mountain ridges, rising to the height of from 2,000 to 4,000 feet above the ocean. From its southern end, a depression called the Wadi-el-Araba extends to the Gulf of Akaba, the eastern arm of the Red Sea. The Jordan empties into the northern extremity of the Dead Sea, after having passed through the Lake of Tiberias at an elevation of 663.4 feet above the Dead Sea, or 653.3 below the Mediterranean, and drains a considerable valley north of the lake, as well as the plain of Jericho, which lies between the lake and the sea. If the waters of the Mediterranean were admitted freely into the basin of the Dead Sea, they would raise its surface to the general level of the ocean, and consequently flood all the dry land below that level within the basin. I do not know that accurate levels have been taken in the valley of the Jordan above the Lake of Tiberias, and our information is very vague as to the hypsometry of the northern part of the Wadi-el-Araba. As little do we know where a contour line, carried around the basin at the level of the Mediterranean, would strike its eastern and western borders. We cannot, therefore, accurately compute the extent of now dry land which would be covered by the admission of the waters of the Mediterranean, or the area of the inland sea which would be thus created. Its length, however, would certainly exceed one hundred and fifty miles, and its mean breadth, including its gulfs and bays, could scarcely be less than fifteen, perhaps even twenty. It would cover very little ground now occupied by civilized or even uncivilized man, though some of the soil which would be submerged--for instance, that watered by the Fountain of Elisha and other neighboring sources--is of great fertility, and, under a wiser government and better civil institutions, might rise to importance, because, from its depression, it possesses a very warm climate, and might supply South-eastern Europe with tropical products more readily than they can be obtained from any other source. Such a canal and sea would be of no present commercial importance, because they would give access to no new markets or sources of supply; but when the fertile valleys and the deserted plains cast of the Jordan shall be reclaimed to agriculture and civilization, these waters would furnish a channel of communication which might become the medium of a very extensive trade. Whatever might be the economical results of the opening and filling of the Dead Sea basin, the creation of a new evaporable area, adding not less than 2,000 or perhaps 3,000 square miles to the present fluid surface of Syria, could not fail to produce important meteorological effects. The climate of Syria would probably be tempered, its precipitation and its fertility increased, the courses of its winds and the electrical condition of its atmosphere modified. The present organic life of the valley would be extinguished, and many tribes of plants and animals would emigrate from the Mediterranean to the new home which human art had prepared for them. It is possible, too, that the addition of 1,300 feet, or forty atmospheres, of hydrostatic pressure upon the bottom of the basin might disturb the equilibrium between the internal and the external forces of the crust of the earth at this point of abnormal configuration, and thus produce geological convulsions the intensity of which cannot be even conjectured. It is now established by the observations of Rohlf and others that Strabo was right in asserting that a considerable part of the Libyan desert, or Sahara, lay below the level of the Mediterranean. At some points the depression exceeds 325 feet, and at Siwah, in the oasis of Jupiter Ammon, it is not less than 130 feet. It has been proposed to cut a canal through the coast dunes, on the shore south of the Syrtis Major, or Dschnn el Kebrit of the Arabs, and another project is to reopen the communication which appears to have once existed between the Palus Tritonis, or Sebcha el Nandid, and the Syrtis Parva. As we do not know the southern or eastern limits of this depression, we cannot determine the area which would thus be covered with water, but it would certainly be many thousands of square miles in extent, and the climatic effects would doubtless be sensible through a considerable part of Northern Africa, and possibly even in Europe. The rapid evaporation would require a constant influx of water from the Mediterranean, which might perhaps perceptibly influence the current through the Straits of Gibraltar. Maritime Canals in Europe. A great navigable cut across the peninsula of Jutland, forming a new and short route between the North Sea and the Baltic, if not actually commenced, is determined upon. The motives for opening such a communication are perhaps rather to be found in political than in geographical or even commercial considerations, but it will not be without an important bearing on the material interests of all the countries to whose peoples it will furnish new facilities for communication and traffic. The North Holland canal between the Helder and the port of Amsterdam, a distance of fifty miles, executed a few years since at a cost of $5,000,000, and with dimensions admitting the passage of a frigate, was a magnificent enterprise, but it is thrown quite into the shade by the shorter channel now in process of construction for bringing that important city into almost direct communication with the North Sea, and thus restoring to it something at least of its ancient commercial importance. The work involves some of the heaviest hydraulic operations yet undertaken, including the construction of great dams, locks, dikes, embankments, and the execution of draining works and deep cutting under circumstances of extreme difficulty. In the course of these labors many novel problems have presented themselves for practical solution by the ingenuity of modern engineers, and the now inventions and processes thus necessitated are valuable contributions to our means of physical improvement. Cape Cod Canal. The opening of a navigable cut through the narrow neck which separates the southern part of Cape Cod Bay in Massachusetts from the Atlantic, was long ago suggested, and there are few coast improvements on the Atlantic shores of the United States which are recommended by higher considerations of utility. It would save the most important coasting trade of the United States the long and dangerous navigation around Cape Cod, afford a new and safer entrance to Boston harbor for vessels from Southern ports, secure a choice of passages, thus permitting arrivals upon the coast and departures from it at periods when wind and weather might otherwise prevent them, and furnish a most valuable internal communication in case of coast blockade by a foreign power. The difficulties of the undertaking are no doubt formidable, but the expense of maintenance and the uncertainty of the effects of currents getting through the new strait are still more serious objections. [Footnote: The opening of a channel across Cape Cod would have, though perhaps to a smaller extent, the same effects in interchanging the animal life of the southern and northern shores of the isthmus, as in the case of the Suez Canal; for although the breadth of Cape Cod does not anywhere exceed twenty miles, and is in some places reduced to one, it appears from the official reports on the Natural History of Massachusetts, that the population of the opposite waters differs widely in species. Not having the original documents at hand, I quote an extract from the Report on the Invertebrate Animals of Mass., given by Thoreau, Excursions, p. 69: "The distribution of the marine shells is well worthy of notice as a geological fact. Cape Cod, the right arm of the Commonwealth, reaches out into the ocean some fifty or sixty miles. It is nowhere many miles wide; but this narrow point of land has hitherto proved a barrier to the migration of many species of mollusca. Several genera and numerous species, which are separated by the intervention of only a few miles of land, are effectually prevented from mingling by the Cape, and do not pass from one side to the other. ... Of the one hundred and ninety-seven marine species, eighty-three do not pass to the south shore, and fifty are not found on the north shore of the Cape." Probably the distribution of the species of mollusks is affected by unknown local conditions, and therefore an open canal across the Cape might not make every species that inhabits the waters on one side common to those of the other; but there can be no doubt that there would be a considerable migration in both directions. The fact stated in the report may suggest an important caution in drawing conclusions upon the relative age of formations from the character of their fossils. Had a geological movement or movements upheaved to different levels the bottoms of waters thus separated by a narrow isthmus, and dislocated the connection between those bottoms, naturalists, in after ages, reasoning from the character of the fossil faunas, might have assigned them to different, and perhaps very widely distant, periods.] Changes in the Caspian. The Russian Government has contemplated the establishment of a nearly direct water communication between the Caspian Sea and the Sea of Azoff, partly by natural and partly by artificial channels, and there are now navigable canals between the Don and the Volga; but these works, though not wanting in commercial and political interest, do not possess any geographical importance. It is, however, very possible to produce appreciable geographical changes in the basin of the Caspian by the diversion of the great rivers which flow from Central Russia. The surface of the Caspian is eighty-three feet below the level of the Sea of Azoff, and its depression has been explained upon the hypothesis that the evaporation exceeds the supply derived, directly and indirectly, from precipitation, though able physicists now maintain that the sinking of this sea is due to a subsidence of its bottom from geological causes. At Tsaritsin, the Don, which empties into the Sea of Azoff, and the Volga, which pours into the Caspian, approach each other within ten miles. Near this point, by means of open or subterranean canals, the Don might be turned into the Volga, or the Volga into the Don. If we suppose the whole or a large proportion of the waters of the Don to be thus diverted from their natural outlet and sent down to the Caspian, the equilibrium between the evaporation from that sea and its supply of water might be restored, or its level even raised above its ancient limits. If the Volga were turned into the Sea of Azoff, the Caspian would be reduced in dimensions until the balance between loss and gain should be re-established, and it would occupy a much smaller area than at present. Such changes in the proportion of solid and fluid surface would have some climatic effects in the territory which drains into the Caspian, and on the other hand, the introduction of a greater quantity of fresh water into the Sea of Azoff would render that gulf less saline, affect the character and numbers of its fish, and perhaps be not wholly without sensible influence on the water of the Black Sea. Diversion of the Nile. Perhaps the most remarkable project of great physical change, proposed or threatened in earlier ages, is that of the diversion of the Nile from its natural channel, and the turning of its current into either the Libyan Desert or the Red Sea. The Ethiopian or Abyssinian princes more than once menaced the Memlouk sultans with the execution of this alarming project, and the fear of so serious an evil is said to have induced the Moslems to conciliate the Abyssinian kings by large presents, and by some concessions to the oppressed Christians of Egypt. Indeed, Arabian historians affirm that in the tenth century the Ethiopians dammed the river, and, for a whole year, cut off its waters from Egypt. [Footnote: "Some haue writte, that by certain kings inhabiting aboue, the Nilus should there be stopped; & at a time prefixt, let loose vpon a certaine tribute payd them by the Aegyptians. The error springing perhaps fro a truth (as all wandring reports for the most part doe) in that the Sultan doth pay a certaine annuall summe to the Abissin Emperour for not diuerting the course of the Riuer, which (they say) he may, or impouerish it at the least."--George Sandys, A Relation of a Journey, etc., p. 98. See, also, Vansles, Voyage en Egypte, p. 61.] The probable explanation of this story is to be found in a season of extreme drought, such as have sometimes occurred in the valley of the Nile. The Libyan Desert, above the junction of the two principal branches of the Nile at Khartum, is so much higher than the level of the river below that point, that there is no reason to believe a new channel for the united waters of the two streams could be found in that direction; but the Bahr-el-Abiad flows through, if it does not rise in, a great table-land, and some of its tributaries are supposed to communicate in the rainy season with branches of great rivers flowing in quite another direction. Hence it is probable that a portion at least of the waters of this great arm of the Nile--and perhaps a quantity the abstraction of which would be sensibly felt in Egypt--might be sent to the Atlantic by the Congo or Niger, lost in inland lakes and marshes in Central Africa, or employed to fertilize the Libyan sand wastes. About the beginning of the sixteenth century, Albuquerque the "Terrible" revived the scheme of turning the Nile into the Red Sea, with the hope of destroying the transit trade through Egypt by way of Kosseir. In 1525 the King of Portugal was requested by the Emperor of Abyssinia to send him engineers for that purpose; a successor of that prince threatened to attempt the project about the year 1700, and even as late as the French occupation of Egypt, the possibility of driving out the intruder by this means was suggested in England. It cannot be positively affirmed that the diversion of the waters of the Nile to the Red Sea is impossible. In the chain of mountains which separates the two valleys, Brown found a deep depression or wadi, extending from the one to the other, apparently at no great elevation above the bed of the river, but the height of the summit level was not measured. Admitting the possibility of turning the whole river into the Red Sea, let us consider the probable effect of the change. First and most obvious is the total destruction of the fertility of Middle and Lower Egypt, the conversion of that part of the valley into a desert, and the extinction of its imperfect civilization, if not the absolute extirpation of its inhabitants. This is the calamity threatened by the Abyssinian princes and the ferocious Portuguese warrior, and feared by the Sultans of Egypt. Beyond these immediate and palpable consequences neither party then looked; but a far wider geographical area, and far more extensive and various human interests, would be affected by the measure. The spread of the Nile during the annual inundation covers, for many weeks, several thousand square miles with water, and at other seasons of the year pervades the same and even a larger area with moisture by infiltration. The abstraction of so large an evaporating surface from the southern shores of the Mediterranean could not but produce important effects on many meteorological phenomena, and the humidity, the temperature, the electrical condition and the atmospheric currents of North-eastern Africa might be modified to a degree that would sensibly affect the climate of Europe. The Mediterranean, deprived of the contributions of the Nile, would require a larger supply, and of course a stronger current, of water from the Atlantic through the Straits of Gibraltar; the proportion of salt it contains would be increased, and the animal life of at least its southern borders would be consequently modified; the current which winds along its southern, eastern, and north-eastern shores would be diminished in force and volume, if not destroyed altogether, and its basin and its harbors would be shoaled by no new deposits from the highlands of inner Africa. In the much smaller Red Sea, more immediately perceptible, if not greater, effects, would be produced. The deposits of slime would reduce its depth, and perhaps, in the course of ages, divide it into an inland and an open sea, the former of which, receiving no supply from rivers, would, as in the case of the northern part of the Gulf of California, soon be dried up by evaporation, and its whole area added to the Africo-Arabian desert; the waters of the latter would be more or less freshened, and their immensely rich marine fauna and flora changed in character and proportion, and, near the mouth of the river, perhaps even destroyed altogether; its navigable channels would be altered in position and often quite obstructed; the flow of its tides would be modified by the new geographical conditions; the sediment of the river would form new coast-lines and lowlands, which would be covered with vegetation, and probably thereby produce sensible climatic changes. Diversion of the Rhine. The interference of physical improvements with vested rights and ancient arrangements, is a more formidable obstacle in old countries than in new, to enterprises involving anything approaching to a geographical revolution. Hence such projects meet with stronger opposition in Europe than in America, and the number of probable changes in the face of nature in the former continent is proportionally less. I have noticed some important hydraulic improvements as already executed or in progress in Europe, and I may refer to some others as contemplated or suggested. One of these is the diversion of the Rhine from its present channel below Ragatz, by a cut through the narrow ridge near Sargans, and the consequent turning of its current into the Lake of Wallenstadt. This would be an extremely easy undertaking, for the ridge is but twenty feet above the level of the Rhine, and hardly two hundred yards wide. There is no present adequate motive for this diversion, but it is easy to suppose that it may become advisable within no long period. The navigation of the Lake of Constance is rapidly increasing in importance, and the shoaling of the eastern end of that lake by the deposits of the Rhine may require a remedy which can be found by no other so ready means as the discharge of that river into the Lake of Wallenstadt. The navigation of this latter lake is not important, nor is it ever likely to become so, because the rocky and precipitous character of its shores renders their cultivation impossible. It is of great depth, and its basin is capacious enough to receive and retain all the sediment which the Rhine would carry into it for thousands of years. [Footnote: Many geographers suppose that the dividing ridge between the Lake of Wallenstadt and the bed of the Rhine at Sargans is a fluviatile deposit, which has closed a channel through which the Rhine anciently discharged a part or the whole of its waters into the lake. In the flood of 1868, the water of the Rhine rose to the level of the railway station at Sargans, and for some days there was fear of the giving way of the barrier and the diversion of the current of the river into the lake.] Improvements in North American Hydrography. We are not yet well enough acquainted with the geography of Central Africa, or of the interior of South America, to conjecture what hydrographical revolutions might there be wrought; but from the fact that many important rivers in both continents drain extensive table-lands, of moderate elevation and inclination, there is reason to suppose that important changes in the course of those rivers might be accomplished. Our knowledge of the drainage of North America is much more complete, and it is certain that there are numerous points within our territory where the courses of great rivers, or the discharge of considerable lakes, might be completely diverted, or at least partially directed into different channels. The surface of Lake Erie is 565 feet above that of the Hudson at Albany, and it is so near the level of the great plain lying east of it, that it was found practicable to supply the western section of the canal, which unites it with the Hudson, with water from the lake, or rather from the Niagara which flows out of it. The greatest depth of water yet sounded in Lake Erie is but two hundred and seventy feet, the mean depth one hundred and twenty. Open canals parallel with the Niagara, or directly towards the Genesee, might be executed upon a scale which would exercise an important influence on the drainage of the lake, if there were any adequate motive for such an undertaking. Still easier would it be to enlarge the outlet for the waters of Lake Superior at the Saut St. Mary--where the river which drains the lake descends twenty-two feet in a single mile--and thus to produce incalculable effects, both upon that lake and upon the great chain of inland waters which communicate with it. The summit level between the surface of Lake Michigan at its mean height and that of the River Des Plaines, a tributary of the Illinois, at a point some ten miles west of Chicago, is but ten and a half feet above the lake. The lake once discharged a part or the whole of its waters into the valley of the Des Plaines. A slight upheaval, at an unknown period, elevated the bed of the Des Plaines, and the prairie between it and the lake, to their present level, and the outflow of the lake was turned into a new direction. The bed of the Des Plaines is higher than the surface of the lake, and in recent times the Des Plaines, when at flood, has sent more or less of its waters across the ridge into the bed of the South Branch of Chicago River, and so into Lake Michigan. A navigable channel has now been cut, admitting a constant flow of water from the lake, by the valley of the Des Plaines, into the Illinois. The mean discharge by this channel does not much exceed 23,000 cubic feet per minute, but it would be quite practicable to enlarge its cross-section indefinitely, and the flow through it might be so regulated as to keep the Illinois and the Mississippi at flood at all seasons of the year. The increase in the volume of these rivers would augment their velocity and their transporting power, and, consequently, the erosion of their banks and the deposit of slime in the Gulf of Mexico, while the opening of a communication between the lake and the affluents of the Mississippi, unobstructed except by locks, and the introduction of a large body of colder water into the latter, would very probably produce a considerable effect on the animal life that peoples them. The diversion of water from the common basin of the great lakes through a new channel, in a direction opposite to their present discharge, would not be absolutely without influence on the St. Lawrence, though probably this effect might be too small to be readily perceptible. [Footnote: From Reports of the Canal Commissioners of the State of Illinois, and especially from a very interesting private letter from William Gooding, Esq., an eminent engineer, which I regret I have not space to print in full, I learn that the length of the present canal, from the lake to the River Illinois, is 101 miles, with a total descent of a trifle more than 145 feet, and that it is proposed to enlarge this channel to the width of one hundred and sixty feet, with a minimum depth of seven, and to create a slack-water navigation in the Illinois by the construction of five dams, one of which is already completed. The descent for the outlet of the canal at La Salle on the Illinois to the Mississippi is twenty-eight feet, the distance being 230 miles. The canal thus enlarged would cost about $16,000,000, and it would establish a navigation for vessels of 1,200 to 1,500 tons burden between Lake Michigan and the Mississippi, and consequently, by means of the great lakes and the Welland canal, between the St. Lawrence and the Gulf of Mexico.] In an able and interesting article in a California magazine, Dr. Widney has suggested a probable cause and a possible remedy for the desiccation of south-eastern California referred to in a former chapter. The Colorado Desert which lies considerably below the level of the waters of the Gulf of California, and has an area of about 4,000 square miles, evidently once formed a part of that gulf. This northern extension of the gulf appears to have been cut off from the main body by deposits brought down by the great river Colorado, at no very distant period. These deposits at the same time turned the course of the river to the south, and it now enters the gulf at a point twenty miles distant from its original outlet. When this northern arm of the gulf was cut off from the sea, and the river which once discharged itself into it was diverted, it was speedily laid dry by evaporation, and now yields no vapor to be condensed into fog, rain, and snow on the neighboring mountains, which are now parched and almost bare of vegetation. The ancient bed of the river may still be traced, and in floods the Colorado still sends a part of its overflowing supply into its old channel, and for a time waters a portion of the desert. It is believed that the river might easily be turned back into its original course, and indeed nature herself seems to be now tending, by various spontaneous processes, to accomplish that object. The waters of the Colorado, though perhaps not sufficient to fill the basin and keep it at the sea-level in spite of the rapid evaporation in that climate, [Footnote: The thermometer sometimes rises to 120 degrees F. at Fort Yuma, at the S. E. angle of California in N. L. 33 degrees.] would at least create a permanent lake in the lower part of the depression, the evaporation from which, Dr. Widney suggests, might sensibly increase the humidity and lower the temperature of an extensive region which is now an arid and desolate wilderness. Soil below Rock. One of the most singular changes of natural surface effected by man is that observed by Beechey and by Barth at Lin Tefla, and near Gebel Genunes, in the district of Ben Gasi, in Northern Africa. In this region the superficial stratum originally consisted of a thin sheet of rock covering a layer of fertile earth. This rock has been broken up, and, when not practicable to find use for it in fences, fortresses, or dwellings, heaped together in high piles, and the soil, thus bared of its stony shell, has been employed for agricultural purposes. [Footnote: Barth, Wanderungen durch die Kusten des Mittelmeeres, i., p. 853. In a note on page 380, of the same volume, Barth cites Strabo as asserting that a similar practice prevailed in Iapygia; but the epithet [word in Greek: traxeia], applied by Strabo to the original surface, does not neceasarily imply that it was covered with a continuous stratum of rock.] If we remember that gunpowder was unknown at the period when these remarkable improvements were executed, and of course that the rock could have been broken only with the chisel and wedge, we must infer that land had at that time a very great pecuniary value, and, of course, that the province, though now exhausted, and almost entirely deserted by man, had once a dense population. Covering Rock with Earth. If man has, in some cases, broken up rock to reach productive ground beneath, he has, in many other instances, covered bare ledges, and sometimes extensive surfaces of solid stone, with fruitful earth, brought from no inconsiderable distance. Not to speak of the Campo Santo at Pisa, filled, or at least coated, with earth from the Holy Land, for quite a different purpose, it is affirmed that the garden of the monastery of St. Catherine at Mount Sinai is composed of Nile mud, transported on the backs of camels from the banks of that river. Parthey and older authors state that all the productive soil of the Island of Malta was brought over from Sicily. [Footnote: Parthey, Wanderungen durch Sicilen und die Levante, i., p. 404.] The accuracy of the information may be questioned in both cases, but similar practices, on a smaller scale, are matter of daily observation in many parts of Southern Europe. Much of the wine of the Moselle is derived from grapes grown on earth carried high up the cliffs on the shoulders of men, and the steep terraced slopes of the Island of Teneriffe are covered with soil painfully scooped out from fissures in and between the rocks which have been laid bare by the destruction of the native forests. [Footnote: Mantegazza, Rio de la Plata e Teneriffa, p. 567.] In China, too, rock has been artificially covered with earth to an extent which gives such operations a real geographical importance, and the accounts of the importation of earth at Malta, and the fertilization of the rocks on Mount Sinai with slime from the Nile, may be not wholly without foundation. Valleys in Deserts. In the latter case, indeed, river sediment might be very useful as a manure, but it could hardly be needed as a soil; for the growth of vegetation in the wadies of the Sinaitic Peninsula shows that the disintegrated rock of its mountains requires only water to stimulate it to considerable productiveness. The wadies present, not unfrequently, narrow gorges, which might easily be closed, and thus accumulations of earth, and reservoirs of water to irrigate it, might be formed which would convert many a square mile of desert into flourishing date gardens and cornfields. For example, not far from Wadi Feiran, on the most direct route to Wadi Esh-Sheikh, is a very narrow pass called by the Arabs El Bueb (El Bab) or, The Gate, which might be securely closed to a very considerable height, with little labor or expense. Above this pass is a wide and nearly level expanse, filled up to a certain regular level with deposits brought down by torrents before the Gate, or Bueb, was broken through, and they have now worn down a channel in the deposits to the bed of the wadi. If a dam were constructed at the pass, and reservoirs built to retain the winter rains, a great extent of valley might be rendered cultivable. Effects of Mining. The excavations made by man, for mining and other purposes, may occasion disturbance of the surface by the subsidence of the strata above them, as in the case of the mine of Fahlun, in Sweden, but such accidents have generally been too inconsiderable in extent to deserve notice in a geographical point of view. [Footnote: In March, 1873, the imprudent extension of the excavations in a slate mine near Morzine, in Savoy, occasioned the fall of a mass of rock measuring more than 700,000 yards in cubical contents. A forest of firs was destroyed, and a hamlet of twelve houses crushed and buried by the slide.] It is said, however, that in many places in the mining regions of England alarming indications of a tendency to a wide dislocation of the superficial strata have manifested themselves. Indeed, when we consider the measure of the underground cavities which miners have excavated, we cannot but be surprised that grave catastrophes have not often resulted from the removal of the foundations on which the crust of our earth is laid. The 100,000,000 tons of coal yearly extracted from British mines require the withdrawal of subterranean strata equal to an area of 20,000 acres one yard deep, or 2,000 acres ten yards deep. These excavations have gone on for several years at this rate, and in smaller proportions for centuries. Hence, it cannot be doubted that by these and other like operations the earth has been undermined and honey-combed in many countries to an extent that may well excite serious apprehensions as to the stability of the surface. In any event such excavations may interfere materially with the course of subterranean waters, and it has even been conjectured that the removal of large bodies of metallic ore from their original deposits might, at least locally, affect in a sensible degree the magnetic and electrical condition of the earth's crust. [Footnote: The exhaustion of the more accessible deposits of coal and other minerals has compelled the miners in Belgium, England, and other countries, to carry their operations to great depths below the surface. At the colliery Des Viviers, at Cilly near Charleroi, in Belgium, coal is worked at the depth of 2,820 feet, and one pit has been sunk to the depth of 3,411 feet. It is supposed that the internal heat of the earth will render mining impossible below 4,000 feet. At Clifford Amalgamated Mines, in Cornwall, the temperature at 1,590 feet stood at 100 degrees, but after the shaft had remained a year open it fell to 83 degrees. In another Cornish mine men work at from 110 degrees to 120 degrees, but only twenty minutes at a time, and with cold water thrown frequently over them.--The last Thirty Years in Mining Districts, p. 95. Stopponi mentions an abandoned mine at Huttenberg, in Bohemia, of the depth of 3,775 feet.--Corso di Geologia, i., p. 258.] Hydraulic Mining. What is called hydraulic mining--a system substantially identical with that described in an interesting way by Pliny the elder, in Book XXXV. of his Natural History, as practised in his time in the gold mines of Spain [Footnote: I have little doubt that the hydraulic mining in Gaul, alluded to by Diodorus Siculus, Bibliotheca Historica, v. 27, as merely a mode of utilizing the effects of water flowing in its natural channels, was really the artificial method described by Pliny.]--is producing important geographical effects in California. Artificially directed currents of water have been long employed for washing down and removing masses of earth, but in the Californian mining the process is resorted to on a vastly greater scale than in any other modern engineering operations, and with results proportioned to the means. Brooks of considerable volume are diverted from their natural channels and conducted to great distances in canals or wooden aqueducts, [Footnote: In 1867 there were 6,000 miles (including branches) of artificial water-courses employed for mining purposes in California. The flumes of these canals are often of sheet-iron, and in some places are carried considerable distances at a height of 250 feet above the ground.--Raymond, Mineral Statistics west of the Rocky Mountains, 1870, p. 476.] and then directed against hills and large level surfaces of ground which it is necessary to remove to reach the gold-bearing strata, or which themselves contain deposits of the precious mineral. [Footnote: The water is sometimes driven through iron tubes under a hydrostatic pressure of several hundred feet, with a force which cuts away rock of considerable solidity almost as easily as hard earth. In this way of using water, the cutting force might, doubtless, be greatly augmented by introducing sand or gravel into the current.] Naked hills and fertile soils are alike washed away by the artificial torrent, and the material removed--vegetable mould, sand, gravel, pebbles--is carried down by the current and often spread over ground lying quite out of the reach of natural inundations, and burying it to the depth sometimes of twenty-five feet. An orchard valued at $60,000, and another estimated at not less than $200,000, are stated to have been thus sacrificed, and a report from the Agricultural Bureau at Washington computes the annual damage done by this mode of mining at the incredible sum of $12,000,000. Accidental fires in mines of coal or lignite sometimes lead to consequences not only destructive to large quantities of valuable material, but which may, directly or indirectly, produce results important in geography. The coal is occasionally ignited by the miners' lights or other fires used by them, and certain kinds of this mineral, if long exposed to air in deserted galleries, may be spontaneously kindled. Under favorable circumstances, a stratum of coal will burn until it is exhausted, and a cavity may be burnt out in a few months which human labor could not excavate in many years. Wittwer informs us that a coal mine at St. Etienne in Dauphiny has been burning ever since the fourteenth century, and that a mine near Duttweiler, another near Epterode, and a third at Zwickau, have been on fire for two hundred years. Such conflagrations not only produce cavities in the earth, but communicate a perceptible degree of heat to the surface, and the author just quoted cites cases where this heat has ben advantageously employed in forcing vegetation. Projects of Agricultural Improvements by Duponchel. Duponchel's schemes of agricultural improvement are so grandiose in their nature, so vast in their sphere of operation, and so important in their possible effects upon immense tracts of the earth's surface, that they must be considered as projects of geographical revolution, and they therefore merit more than a passing notice. In a memoir already quoted, and in a later work, [Footnote: Traite d'Hydraulique et de Geologie Agricole, 1868.] this engineer proposes to construct artificial torrents for the purpose of grinding up calcareous rock, by rolling and attrition along their beds, and thus reducing it into a fine slime; and at the same time these torrents are to transport an argillaceous deposit which is to be mingled with the calcareous slime, and distributed over the Landes by watercourses constructed for the purpose. By this means, he supposes that a very fertile soil may be formed, and so graded in depositing as to secure for it a good drainage. In order that nothing may be wanting to recommend the project, Duponchel suggests that, as some rivers of Western France are gold-bearing, it is probable that gold enough may be collected by washing the sands to reduce materially the expense of such operations. In the Landes of Gascony alone, he believes that 3,000,000 acres, now barren, might be made productive at a moderate expense, and that similar methods might be advantageously employed in France over an extent of not less than 30,000,000 acres now almost wholly valueless. The successful execution of the plan would increase the fertile territory of France by an area of four or five times the extent of Sicily or of Sardinia. There seems to be no reason why the same method, applied for such different purposes, should necessarily be destructive in the one case while it is so advantageous in the other. A wiser economy might bring about a harmony of action between the miners and the agriculturists of California, and the soil which is removed by the former as an incumbrance, judiciously deposited, might become for the latter a source of wealth more solid and enduring than the gold now obtained by such a sacrifice of agricultural interests. Action of Man on the Weather. Espy's well-known suggestion of the possibility of causing rain artificially, by kindling great fires, is not likely to be turned to practical account, but the speculations of this able meteorologist are not, for that reason, to be rejected as worthless. His labors exhibit great industry in the collection of facts, much ingenuity in dealing with them, remarkable insight into the laws of nature, and a ready perception of analogies and relations not obvious to minds less philosophically constituted. They have unquestionably contributed essentially to the advancement of meteorological science. The possibility that the distribution and action of electricity may be considerably modified by long lines of iron railways and telegraph wires, is a kindred thought, and in fact rests much on the same foundation as the belief in the utility of lightning-rods, but such influence is too obscure and too uncertain to have been yet demonstrated, though many intelligent observers believe that sensible meteorological effects have been produced by it. It is affirmed that battles and heavy cannonades are generally followed by rain and thunder-storms, and Powers has collected much evidence on this subject, [Footnote: War and the Weather, or the Artificial Production of Rain, Chicago, 1871. Paifer proposed, as early as 1814, arrangements for producing rain by firing cannon and exploding shells in the air. Ein wunderbarer Traum die Frucht, barkeit durch willkurlichen Regen zu befordern, Metz, 1814. See, on the question of the possibility of influencing the weather by artificial means, London Quarterly Journal of Science, xxix., p. 126, and Nature, Feb. 16, 1871, p. 306.] but the proposition does not seem to be by any means established. Resistance to Great Natural Forces. I have often spoken of the greater and more subtile natural forces, and especially of geological agencies, as powers beyond human guidance or resistance. This is no doubt at present true in the main, but man has shown that he is not altogether impotent to struggle with even these mighty servants of nature, and his unconscious as well as his deliberate action may in some cases have increased or diminished the intensity of their energies. It is a very ancient belief that earthquakes are more destructive in districts where the crust of the earth is solid and homogeneous, than where it is of a looser and more interrupted structure. Aristotle, Pliny the elder, and Seneca believed that not only natural ravines and caves, but quarries, wells, and other human excavations, which break the continuity of the terrestrial strata and facilitate the escape of elastic vapors, have a sensible influence in diminishing the violence and preventing the propagation of the earth-waves. In all countries subject to earthquakes this opinion is still maintained, and it is asserted that, both in ancient and in modern times, buildings protected by deep wells under or near them have suffered less from earthquakes than those the architects of which have neglected this precaution. [Footnote: Landgrebe, Geschichte der Vulkane, ii., pp. 19, 20.] If the commonly received theory of the cause of earthquakes is true--that, namely, which ascribes them to the elastic force of gases accumulated or generated in subterranean reservoirs--it is evident that open channels of communication between such reservoirs and the atmosphere might serve as a harmless discharge of gases that would otherwise acquire destructive energy. The doubt is whether artificial excavations can be carried deep enough to reach the laboratory where the elastic fluids are distilled. There are, in many places, small natural crevices through which such fluids escape, and the source of them sometimes lies at so moderate a depth that they pervade the superficial soil and, as it were, transpire from it, over a considerable area. When the borer of an ordinary artesian well strikes into a cavity in the earth, imprisoned air often rushes out with great violence, and this has been still more frequently observed, in sinking mineral-oil wells. In this latter case, the discharge of a vehement current of inflammable fluid sometimes continues for hours and even longer periods. These facts seem to render it not wholly improbable that the popular belief of the efficacy of deep wells in mitigating the violence of earthquakes is well founded. In general, light, wooden buildings are less injured by earthquakes than more solid structures of stone or brick, and it is commonly supposed that the power put forth by the earth-wave is too great to be resisted by any amount of weight or solidity of mass that man can pile up upon the surface. But the fact that in countries subject to earthquakes many very large and strongly constructed palaces, temples, and other monuments have stood for centuries, comparatively uninjured, suggests a doubt whether this opinion is sound. The earthquake of the first of November, 1755, which is asserted, though upon doubtful evidence, to have been felt over a twelfth part of the earth's surface, was among the most violent of which we have any clear and distinct account, and it seems to have exerted its most destructive force at Lisbon. It has often been noticed as a remarkable fact, that the mint, a building of great solidity, was almost wholly unaffected by the shock which shattered every house and church in the city, and its escape from the common ruin can hardly be accounted for except upon the supposition that its weight, compactness, and strength of material enabled it to resist an agitation of the earth which overthrew all weaker structures. On the other hand, a stone pier in the harbor of Lisbon, on which thousands of people had taken refuge, sank with its foundations to a great depth during the same earthquake; and it is plain that where subterranean cavities exist, at moderate depths, the erection of heavy masses upon them would tend to promote the breaking down of the strata which roof them over. No physicist, I believe, has supposed that man can avert the eruption of a volcano or diminish the quantity of melted rock which it pours out of the bowels of the earth; but it is not always impossible to divert the course of even a large current of lava. "The smaller streams of lava near Catania," says Ferrara, in describing the great eruption of 1669, "were turned from their course by building dry walls of stone as a barrier against them. ... It was proposed to divert the main current from Catania, and fifty men, protected by hides, were sent with hooks and iron bars to break the flank of the stream near Belpasso. [Footnote: Soon after the current issues from the volcano, it is covered above and at its sides, and finally in front, with scoriae, formed by the cooling of the exposed surface, which bury and conceal the fluid mass. The stream rolls on under the coating, and between the walls of scoriae, and it was the lateral crust which was broken through by the workmen mentioned in the text. The distance to which lava flows, before its surface begns to solidify, depends on its volume, its composition, its temperature and that of the air, the force with which it is ejected, and the inclination of the declivity over which it runs. In most cases it is difficult to approach the current at points where it is still entirely fluid, and hence opportunities of observing it in that condition are not very frequent. In the eruption of February, 1850, on the east side of Vesuvius, I went quite up to one of the outlets. The lava shot out of the orifice upwards with great velocity, like the water from a fountain, in a stream eight or ten feet in diameter, throwing up occasionally volcanic bombs three or four feet in diameter, which exploded at the height of eight or ten yards, but it immediately spread out on the declivity down which it flowed, to the width of several yards. It continued red-hot in broad daylight, and without a particle of scoriae on its surface, for a course of at least one hundred yards. At this distance, the suffocating, sulphurous vapors became so dense that I could follow the current no farther. The undulations of the surface were like those of a brook swollen by rain. I estimated the height of the waves at five or six inches by a breadth of eighteen or twenty. To the eye, the fluidity of the lava seemed as perfect as that of water, but masses of cold lava weighing ten or fifteen pounds floated upon it like cork. The heat emitted by lava currents seems extremely small when we consider the temperature required to fuse such materials and the great length of time they take in cooling. I saw at Nicolosi ancient oil-jars, holding a hundred gallons or more, which had been dug out from under a stream of old lava above that town. They had been very slightly covered with volcanic ashes before the lava flowed over them, but the lead with which holes in them had been plugged was not melted. The current that buried Mompiliere in 1669 was thirty-five feet thick, but marble statues, in a church over which the lava formed an arch, were found uncalcined and uninjured in 1704, See Scrope, Volcanoes, chap. vi. Section 6.] When the opening was made, fluid lava poured forth and flowed rapidly towards Paterno; but the inhabitants of that place, not caring to sacrifice their own town to save Catania, rushed out in arms and put a stop to the operation." [Footnote: Ferrara, Descrizione dell' Etna, p. 108.] In the eruption of Vesuvius in 1794, the viceroy saved from impending destruction the town of Portici, and the valuable collection of antiquities then deposited there but since removed to Naples, by employing several thousand men to dig a ditch above the town, by which the lava current was carried off in another direction. [Footnote: Landgrebe, Naturgeschichte der Vulkane, ii., p. 82.] Incidental Effects of Human Action. I have more than once alluded to the collateral and unsought consequences of human action as being often more momentous than the direct and desired results. There are cases where such incidental, or, in popular speech, accidental, consequences, though of minor importance in themselves, serve to illustrate natural processes; others, where, by the magnitude and character of the material traces they leave behind them, they prove that man, in primary or in more advanced stages of social life, must have occupied particular districts for a longer period than has been supposed by popular chronology. "On the coast of Jutland," says Forchhammer, "wherever a bolt from a wreck or any other fragment of iron is deposited in the beach sand, the particles are cemented together, and form a very solid mass around the iron. A remarkable formation of this sort was observed a few years ago in constructing the sea-wall of the harbor of Elsineur. This stratum, which seldom exceeded a foot in thickness, rested upon common beach sand, and was found at various depths, less near the shore, greater at some distance from it. It was composed of pebbles and sand, and contained a great quantity of pins, and some coins of the reign of Christian IV., between the beginning and the middle of the seventeenth century. Here and there, a coating of metallic copper had been deposited by galvanic action, and the presence of completely oxydized metallic iron was often detected. Investigation made it in the highest degree probable that this formation owed its origin to the street sweepings of the town, which had been thrown upon the beach, and carried off and distributed by the waves over the bottom of the harbor." [Footnote: Geognostische Studien am Meeres Ufer, Leonhard und Bronn, 1841, pp. 25, 26.] These and other familiar observations of the like sort show that a sandstone reef, of no inconsiderable magnitude, might originate from the stranding of a ship with a cargo of iron, [Footnote: Kohl, Schleswig-Holstein, ii., p. 45.] or from throwing the waste of an establishment for working metals into running water which might carry it to the sea. Parthey records a singular instance of unforeseen mischief from an interference with the arrangements of nature. A landowner at Malta possessed a rocky plateau sloping gradually towards the sea, and terminating in a precipice forty or fifty feet high, through natural openings in which the sea-water flowed into a large cave under the rock. The proprietor attempted to establish salt-works on the surface, and cut shallow pools in the rock for the evaporation of the water. In order to fill the salt-pans more readily, he sank a well down to the cave beneath, through which he drew up water by a windlass and buckets. The speculation proved a failure, because the water filtered through the porous bottom of the pans, leaving little salt behind. But this was a small evil, compared with other destructive consequences that followed. When the sea was driven into the cave by violent west or north-west winds, it shot a jet d'eau through the well to the height of sixty feet, the spray of which was scattered far and wide over the neighboring gardens and blasted the crops. The well was now closed with stones, but the next winter's storms hurled them out again, and spread the salt spray over the grounds in the vicinity as before. Repeated attempts were made to stop the orifice, but at the time of Parthey's visit the sea had thrice burst through, and it was feared that the evil was without remedy. [Footnote: Wanderungen durch Sicilien und die Levante, i., p. 406.] I have mentioned the great extent of the heaps of oyster and other shells left by the American Indians on the Atlantic coast of the United States. Some of the Danish kitchen-middens, which closely resemble them, are a thousand feet long, from one hundred and fifty to two hundred wide, and from six to ten high. These piles have an importance as geological witnesses, independent of their bearing upon human history. Wherever the coast line appears, from other evidence, to have remained unchanged in outline and elevation since they were accumulated, they are found near the sea, and not more than about ten feet above its level. In some cases they are at a considerable distance from the beach, and in these instances, so far as yet examined, there are proofs that the coast has advanced in consequence of upheaval or of fluviatile or marine deposit. Where they are altogether wanting, the coast seems to have sunk or been washed away by the sea. The constancy of these observations justifies geologists in arguing, where other evidence is wanting, the advance of land or sea respectively, or the elevation or depression of the former, from the position or the absence of these heaps alone. Every traveller in Italy is familiar with Monte Testaccio, the mountain of potsherds, at Rome; [Footnote: Untill recently this hillock was supposed to consist of shards of household pottery broken in using, but it now appears to be ascertained that it is composed of fragments of earthenware broken in transportation from the place of manufacture to the emporium on the Tiber where such articles were landed.] but this deposit, large as it is, shrinks into insignificance when compared with masses of similar origin in the neighborhood of older cities. The castaway pottery of ancient towns in Magna Grecia composes strata of such extent and thickness that they have been dignified with the appellation of the ceramic formation. The Nile, as it slowly changes its bed, exposes in its banks masses of the same material, so vast that the population of the world during the whole historical period would seem to have chosen this valley as a general deposit for its broken vessels. The fertility imparted to the banks of the Nile by the water and the slime of the inundations, is such that manures are little employed. Hence much domestic waste, which would elsewhere be employed to enrich the soil, is thrown out into vacant places near the town. Hills of rubbish are thus piled up which astonish the traveller almost as much as the solid pyramids themselves. The heaps of ashes and other household refuse collected on the borders and within the limits of Cairo were so large, that the removal of them by Ibrahim Pacha has been looked upon as one of the great works of the age. These heaps formed almost a complete rampart around the city, and impeded both the circulation of the air and the communication between Cairo and its suburbs. At two points these accumulations are said to have risen to the incredible height of between six and seven hundred feet; and these two heaps covered two hundred and fifty acres. [Footnote: Clot Bey, Egypte, i., p. 277.] During the occupation of Cairo by the French, the invaders constructed redoubts on these hillocks which commanded the city. They were removed by Mehemet Ali, and the material was employed in raising the level of low grounds in the environs. [Footnote: Egypt manufactures annually about 1,200,000 pounds of nitre, by lixiviating the ancient and modern rubbish-heaps around the towns.] In European and American cities, street sweepings and other town refuse are used as manure and spread over the neighboring fields, the surface of which is perceptibly raised by them, by vegetable deposit, and by other effects of human industry, and in spite of all efforts to remove the waste, the level of the ground on which large towns stand is constantly elevated. The present streets of Rome are twenty feet, and in many places much more, above those of the ancient city. The Appian Way between Rome and Albano, when cleared out a few years ago, was found buried four or five feet deep, and the fields along the road were elevated nearly or quite as much. The floors of many churches in Italy, not more than six or seven centuries old, are now three or four feet below the adjacent streets, though it is proved by excavations that they were built as many feet above them. [Footnote: Rafinesque maintained many years ago that there was a continual deposition of dust on the surface of the earth from the atmosphere, or from cosmical space, sufficient in quantity to explain no small part of the elevation referred to in the text. Observations during the eclipse of Dec. 22, 1870, led some astronomers to believe that the appearance of the corona was dependent upon or modified by cosmical dust or matter in a very attenuated form diffused through space. Tyndall has shown by optical tests that the proportion of solid matter suspended or floating in common air is very considerable, and there is abundant other evidence to the name purpose. Ehrenberg has found African and even American infusoria in dust transplanted by winds and let fall in Europe, and Schliemann offers that the quantity of dust brought by the scirocco from Africa is so great, that by cutting holes in the naked rocks of Malta enough of Libyan transported earth can be caught and retained, in the course of fourteen years, to form a soil fit for cultivation.--Beilage zur Allgemeinen Zeitung, Mar. 24, 1870.] Nothing Small in Nature. It is a legal maxim that "the law concerneth not itself with trifles," de minimis non curat lex; but in the vocabulary of nature, little and great are terms of comparison only; she knows no trifles, and her laws are as inflexible in dealing with an atom as with a continent or a planet. [Footnote: One of the sublimest, and at the same time most fearful suggestions that have been prompted by the researches of modern science, was made by Babbage in the ninth chapter of his Ninth Bridgewater Treatise. I have not the volume at hand, but the following explanation will recall to the reader, if it does not otherwise make intelligible, the suggestion I refer to: No atom can be disturbed in place, or undergo any change of temperature, of electrical state, or other material condition, without affecting, by attraction or repulsion or other communication, the surrounding atoms. These, again, by the same law, transmit the influence to other atoms, and the impulse thus given extends through the whole material universe. Every human movement, every organic act, every volition, passion, or emotion, every intellectual process, is accompanied with atomic disturbance, and hence every such movement, every such act or process, affects all the atoms of universal matter. Though action and reaction are equal, yet reaction does not restore disturbed atoms to their former place and condition, and consequently the effects of the least material change are never cancelled, but in some way perpetuated, so that no action can take place in physical, moral, or intellectual nature, without leaving all matter in a different state from what it would have been if such action had not occurred. Hence, to use language which I have employed on another occasion: there exists, not alone in the human conscience or in the omniscience of the Creator, but in external nature, an ineffaceable, imperishable record, possibly legible even to created intelligence, of every act done, every word uttered, nay, of every wish and purpose and thought conceived, by mortal man, from the birth of our first parent to the final extinction of our race; so that the physical traces of our most secret sins shall last until time shall be merged in that eternity of which not science, but religion alone assumes to take cognisance.] The human operations mentioned in the last few paragraphs, therefore, do act in the ways ascribed to them, though our limited faculties are at present, perhaps forever, incapable of weighing their immediate, still more their ultimate consequences. But our inability to assign definite values to these causes of the disturbance of natural arrangements is not a reason for ignoring the existence of such causes in any general view of the relations between man and nature, and we are never justified in assuming a force to be insignificant because its measure is unknown, or even because no physical effect can now be traced to it as its origin. The collection of phenomena must precede the analysis of them, and every new fact, illustrative of the action and reaction between humanity and the material world around it, is another step towards the determination of the great question, whether man is of material nature or above her. THE END